Modulation of Cutaneous Inflammation by Angiotensin-Converting Enzyme

Thomas E. Scholzen, Sonja Ständer, Helge Riemann, Thomas Brzoska and Thomas A. Luger
J Immunol April 1, 2003, 170 (7) 3866-3873; DOI: https://doi.org/10.4049/jimmunol.170.7.3866

Abstract

Cutaneous neurogenic inflammation is a complex biological response of the host immune system to noxious stimuli. Present evidence suggests that zinc metalloproteases may play an important role in the regulation of neurogenic inflammation by controlling the local availability of neuropeptides, such as substance P (SP), that are capable of initiating or amplifying cutaneous inflammation after release from sensory nerves. To address the hypothesis that the dipeptidyl carboxypeptidase angiotensin-converting enzyme (ACE) is capable of modulating skin inflammation, we have analyzed murine allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) using wild-type C57BL/6J (ACE+/+) or genetically engineered mice with a heterozygous deletion of somatic ACE (ACE+/−). In 2,4-dinitro-1-fluorobenzene-sensitized ACE+/− mice, ACD was significantly augmented in comparison to ACE+/+ controls as determined by the degree of ear swelling after exposure to hapten. Likewise, systemic treatment of ACE+/+ mice with the ACE inhibitor captopril before sensitization or elicitation of ACD significantly augmented the ACD response. In contrast, local damage and neuropeptide depletion of sensory nerves following capsaicin, injection of a bradykinin B2, or a SP receptor antagonist before sensitization significantly inhibited the augmented effector phase of ACD in mice with functionally absent ACE. However, in contrast to ACD, the response to the irritant croton oil was not significantly altered in ACE+/− compared with ACE+/+ mice. Thus, ACE by degrading bradykinin and SP significantly controls cutaneous inflammatory responses to allergens but not to irritants, which may explain the frequently observed exacerbation of inflammatory skin disease in patients under medication with ACE inhibitors.

The biological functions of a number of neuropeptide mediators are terminated by proteolytic enzymes such as the zinc metalloproteases neutral endopeptidase (NEP3; CD10) or angiotensin-converting enzyme (ACE) (1). The dipeptidyl carboxypeptidase ACE, also known as kininase II (EC 3.4.15.1; CD143), is a 150-to 180-kDa polypeptide chain containing two homologous extracellular domains bound to the cell membrane by a carboxyl-terminal hydrophobic anchor, each with an independent catalytic site. The main somatic ACE activity is associated with tissues such as the luminal side of the vascular endothelium or the renal epithelium. A soluble form of the enzyme that circulates in the plasma is also released after proteolytic cleavage of extracellular ACE (2, 3, 4). In addition to somatic ACE, a smaller testicular form of ACE also exists that is exclusively expressed by developing male germ cells (5) and appears to be of importance for male fertility (6). The main function of tissue ACE is the regulation of the local renin-angiotensin (Ang) system with the cleavage of Ang I into the vasoconstricting, aldosterone-releasing and blood pressure-rising peptide Ang II as most prominent conversion (7). In addition to NEP, ACE is the major proteolytic peptidase for the metabolism of kinins and tachykinins. ACE is capable of degrading the vasodilating and SP-inducing oligopeptide bradykinin (BK) to BK1–7 and further to the inactive molecule BK (1, 2, 3, 4, 5). Likewise, ACE degrades tachykinins such as substance P (SP) and other peptide mediators such as gastrin (1).

The neuropeptide SP is widely distributed in the central and peripheral nervous system, including the skin (8, 9). By activating neurokinin 1 receptors (NK-1R), SP is capable of inducing or augmenting a number of inflammatory responses including plasma extravasation, leukocyte activation, endothelial cell adhesion molecule expression, cytokine production, and mast cell activation (10, 11, 12). In the skin, neuropeptides such as SP are released from sensory nerves in response to noxious stimuli such as chemical, electrical, thermal, mechanical injury, and UV irradiation (13). In addition, BK is a powerful mediator capable of promoting symptoms of inflammation, including vasodilation, plasma extravasation, and pain by activating bradykinin receptors (B-R), in particular the B2-R (14, 15). Activation of B2-R on sensory nerves triggers the release of neuropeptides such as SP and calcitonin gene-related peptide, which results in the amplification of neurogenic inflammation (16).

The importance of ACE for the maintenance of blood pressure and renal function has been recently confirmed by the generation of mice with homozygous-targeted deletions of either somatic (tissue-bound and soluble) and testicular ACE (17) or by mice having only soluble ACE activity (6). In the ACE−/− animals, the lack of ACE resulted in a dramatic reduction of the blood pressure, indicating the absence of a mechanism that is capable of compensating for the loss of ACE. In addition, these mice had severely impaired renal functions and the loss of testicular ACE resulted in a reduced fertility of male mice compared with wild-type animals (6, 17). Likewise, transient experimental NEP and ACE inhibition has been demonstrated to enhance the effects of exogenously applied or endogenously released kinins and tachykinins (18).

ACE inhibitors are widely used for the treatment of hypertension and myocardial infarction (19). However, a considerable number of patients experience adverse side effects such as dry cough and angioedema (20). In the skin, side effects include skin irritations, urticaria or angioedema, and exacerbation of inflammatory skin diseases such psoriasis as well as of type I and type IV allergies (21). Little is known about a possible contribution of ACE to these inflammatory skin diseases. Therefore, in this study, we have tested the hypothesis whether the absence or short-term inhibition of ACE results in a dysregulated inflammatory skin response. Our results indicate that the acute or permanent inhibition of ACE results in an increased cutaneous inflammatory response to allergens but not to irritants. These results implicate the BK- and SP-proteolytic enzyme ACE as an important modulator of ACD inflammatory responses in the skin.

Materials and Methods

Animals

C57BL/6J mice were obtained from Harlan Winkelmann (Borchen, Germany). C57BL/6J-ACEtm2Unc mice were obtained from The Jackson Laboratory (Bar Harbor, ME) and bred as heterozygous animals. The ACEtm2Unc targeted mutation knocks out only the somatic form of the ACE gene (22). Since homozygous mice showed a reduced postnatal viability, heterozygous animals (C57BL/6J-ACE+/−) were used in all experiments; wild-type littermates (C57BL/6J-ACE+/+) served as controls. Mice were housed in a barrier facility with free access to water and food according to local and state regulations. Males and females were studied at 10–14 wk with five to seven mice per experimental condition.

Experimentally induced allergic contact dermatitis (ACD) and administration of neuromodulating agents

ACD was induced as previously described (23). Mice (C57BL/6J-ACE+/− or wild-type littermate controls) were sensitized on day 0 by painting 25 μl of 0.5% 2,4-dinitro-1-fluorobenzene (DNFB; Sigma-Aldrich, St. Louis, MO) in 4:1 acetone:olive oil on the shaved abdomen. Mice were challenged on day 5 by epicutaneous application of 10 μl of 0.2% DNFB in 4:1 acetone:olive oil on the dorsal surface of the right ear. The left ears were treated with vehicle alone (acetone:olive oil, 4:1) and served as an internal control for these studies. The ear swelling induced by the carrier alone was negligible. To detect any potential irritant effects of the hapten, some mice were challenged with 10 μl of 0.2% DNFB on the right ear without previous sensitization. The ACD response was determined by the degree of ear swelling of the hapten-exposed ear compared with that of the vehicle-treated contralateral ear before DNFB challenge and at 0–72 h after challenge as measured with a micrometer.

Ears were obtained from euthanized mice and processed for histological examination. In some experiments, the effect of neuropeptide depletion on ACD was determined by application of the sensory neurotoxin capsaicin in an ointment containing 0.075% trans-8-methyl-N-vanillyl-6-nonenamide (capsaicin) to the shaved abdomen (area 2 × 2 cm) of unsensitized ACE+/+ mice twice a day for 5 days before Ag sensitization. In a separate study, mice were treated with ointment vehicle only, which was prepared according to the formula prepared by the Central Clinical Pharmacy (University of Münster). To determine the effect of acute ACE inhibition on ACD in wild-type animals, the ACE inhibitor captopril ([2S]-N-[3-mercapto-2-methyl-propionyl]-l-proline; Calbiochem, La Jolla, CA) was injected into the intraperitoneum of anesthetized C57BL/6J mice at a dose of 2.5 mg/kg in 0.9% NaCl either 30 min before Ag sensitization or challenge with Ag. In some experiments, the effect of B-R blockage on ACD induction was measured by systemic administration of the B2-R antagonist Hoe140 (d-Arg [Hyp3,Thi5,d-Tic7,Oic8]-BK, 0.1 nmol/kg i.p.; Calbiochem) to anesthetized and sensitized C57BL/6J-ACE+/+ mice 60 min before Ag sensitization with or without injection of captopril 30 min before sensitization. The effect of SP receptor blockage on ACD sensitization in C57BL/6J-ACE+/− mice was measured by administration of the NK-1R antagonist SR140333 ((S)-1-(2-[3-{3,4-dichlorophenyl}-1-{3-isopropoxyphenylacetyl}piperidin-3yl]ethyl)-4-phenyl-l-azoniabcyclo(2.2.2), 1.0 μmol/kgi.p., kindly provided by Dr. Emonds-Alt, Sanofi-Synthélabo, Montpellier, France). All studies were conducted three times to verify reproducibility of results.

Induction of irritant contact dermatitis (ICD)

After measurement of the ear thickness of untreated animals, mice (C57BL/6J-ACE+/− and C57BL/6J-ACE+/+ wild-type littermate controls, n = 10/group) were injected i.p. with 2.5 mg/kg captopril in 0.9% NaCl or 0.9% NaCl alone (control) 30 min before ICD induction by croton oil (0.8% in acetone; Sigma-Aldrich) as previously described (24). The left ear was treated with vehicle only. The ICD response was determined by the degree of ear swelling of the irritant-exposed ear compared with that of the vehicle-treated contralateral ear before irritant challenge and at 0–24 h after challenge as measured with a micrometer. From some mice of each group ears were harvested after 6 h and processed for histological evaluation. Experiments were performed twice to verify reproducibility of the results.

Histology

Ears of three to four mice from each group were fixed in 10% PBS-buffered Formalin and 3- to 5-μm paraffin sections were stained with H&E and examined by light microscopy to assess histological changes and immune cell infiltration.

Electron microscopy

Biopsies from the abdominal skin of four mice treated with capsaicin or vehicle, respectively, were fixed in Karnovsky’s fixative, postfixed in 1% osmium tetraoxide, dehydrated, and embedded in Epon. Ultrathin sections were cut on an ultramicrotome (OMU3; Reichert-Jung, Wien, Austria) with diamond knives, mounted on copper grids, and stained with uranyl acetate and lead citrate. All of the ultrathin preparations were examined in a Philips CM10 electron microscope (Kassel, Germany).

Immunohistochemistry and immunofluorescence

Ears from three to four mice in each group were snap frozen, embedded in OCT compound (Miles, Elkhart, IN), cryostat sectioned, and fixed in acetone for 20 min. Sections were processed for immunohistochemistry as described elsewhere (25). Slides were incubated with monoclonal rat anti-mouse CD4 or rat anti-mouse CD8 mAbs (BD PharMingen, Heidelberg, Germany). Subsequently, slides were incubated with a secondary goat anti-rat Ab conjugated to peroxidase (BD PharMingen, Heidelberg, Germany) and stained with 3-amino-9-ethylcarbazole substrate. Abs and irrelevant IgG (control) were diluted in PBS/1% BSA. For immunofluorescence technique, frozen sections (3–5 μm) of abdominal murine skin treated with capsaicin or vehicle, respectively, were preincubated for 30 min with 2% BSA. Specimens were then incubated overnight at 4°C with rabbit polyclonal Abs against SP (1:100; Chemicon, Hofheim, Germany) and calcitonin gene-related peptide (1:200; Genosys, Bad Homburg, Germany). After three 10-min washes in 0.1 M TBS/0.2% Triton X-100, sections were incubated with a pork FITC-labeled anti-rabbit Ab (1:50; DAKO, Hamburg, Germany). After final rinsing with TBS, sections were coverslipped with Vectashield (Vector Laboratories, Burlingame, CA) and immediately investigated with a fluorescence microscope (Axioplan; Zeiss, Köln, Germany).

Statistical analysis

Results are expressed as mean ± SE. Differences between multiple groups were examined using an ANOVA and Bonferroni t test. Mean differences with p < 0.05 were considered to be significant.

Results

Enhanced ACD responses in mice after transient inhibition of ACE

To assess the role of ACE in modulating cutaneous inflammation, we compared the ACD response in normal mice (C57BL/6J) to that in mice subjected to treatment with the ACE inhibitor captopril before sensitization. In DNFB-sensitized mice, application of DNFB to the right ear induced marked swelling in both untreated and captopril-treated animals (Fig. 1⇓a). Notably, the response was significantly higher (50–65%) in mice subjected to captopril treatment before sensitization compared with mice not treated with the inhibitor. DNFB challenge in nonsensitized animals failed to induce a significant ear swelling in either the captopril-treated or vehicle-treated mice, indicating that the reaction to DNFB was allergic and not due to an irritant effect of the DNFB solution (data not shown). Likewise, inhibition of ACE by captopril treatment of sensitized animals before DNFB challenge also significantly increased the ACD response compared with animals not treated with the ACE inhibitor (Fig. 1⇓b). Thus, transient inhibition of ACE by captopril enhances hapten sensitization and expression of ACD.

FIGURE 1.
FIGURE 1.

Enhanced ACD mice after acute inhibition of ACE. C57BL/6J-ACE+/+ mice were sensitized (s) with 0.5% DNFB on the shaved abdomen at day 0 and challenged (c) with 0.2% DNFB on the right ear at day 5. Mice were treated with the ACE inhibitor captopril (2.5 mg/kg i.p.) either 30 min before Ag sensitization (a) or challenge with Ag (b). In some experiments, the effect of neuropeptide depletion by repeated application of capsaicin or the effect of the B2-R blocking by injection of a B2-R antagonist (Hoe140, 0.1 nmol/kg i.p.) before captopril injection and sensitization was examined (a). The ACD response was determined by the degree of ear swelling of the hapten-exposed ear compared with that of the vehicle-treated contralateral ear before DNFB challenge and at 24, 48, and 72 h after challenge. Ear swelling values are given in micrometers as mean ± SEM, n = 7. ∗, p < 0.05; ∗∗, p < 0.01; ∗∗∗, p < 0.001for captopril-treated vs untreated mice. #, p < 0.05; ##, p < 0.01; ###, p < 0.001 for capsaicin/captopril-treated vs captopril-treated mice. +++, p < 0.001 for B2-R antagonist/captopril-treated vs captopril-treated mice.

Modulation of ACD response in captopril-treated mice by a B-2R antagonist or capsaicin

BK via the activation of B2-R is capable of triggering the release of neuropeptides such as SP from sensory nerves. To test the possibility that this kinin is involved in augmented ACD responses, mice were treated with physiological concentrations of the specific B2-R antagonist Hoe140. Intraperitoneal injection of Hoe140 before captopril treatment and DNFB sensitization significantly inhibited cutaneous inflammation 24, 48, and 72 h after challenge with DNFB (Fig. 1⇑a). Likewise, depending on the time point analyzed, Hoe140 injection of mice without captopril also resulted in a reduction of the ACD ear swelling response by 31.5, 41.6, and 21.5% at 24, 48, and 72 h, respectively, after elicitation of ACD (p < 0.05 at 48 h, n = 5). These results indicate that the elevated ACD expression observed after inhibition of ACE during the sensitization phase also involves BK activation of B2-Rs. Repeated application of the neurotoxin capsaicin that activates vanniloid receptor 1 expressed on sensory c-fibers results in release and subsequent depletion of neuropeptides, including SP from sensory nerves (26). Therefore, we examined whether capsaicin is capable of inhibiting the enhancing effect of captopril on the ACD sensitization phase. An ointment containing 0.075% capsaicin was applied to the mouse abdominal skin twice daily over 5 days before systemic captopril treatment and DNFB sensitization. After Ag challenge, a profound reduction of the cutaneous inflammatory response in mice treated with capsaicin compared with animals not treated with this neurotoxin was observed (Fig. 1⇑a). In animals treated with vehicle alone (ointment without capsaicin), no reduction in the augmented inflammatory response induced by captopril injection was detectable (data not shown). To elucidate the possibility that capsaicin treatment may interfere with DNFB sensitization involving a mechanism other than neuropeptide depletion, abdominal skin from mice treated multiple times with capsaicin was harvested and prepared for electron microscopy (Fig. 2⇓). Examination of cutaneous nerves in these biopsies revealed that unmyelinated nerve fibers lose their intra-axonal structures, i.e., mitochondria and neuropeptide-containing vesicles were destroyed in the skin of capsaicin-treated mice (Fig. 2⇓b), but not in the skin of vehicle-treated control animals (Fig. 2⇓a). Surrounding Schwann cells and large myelinated nerve fibers were unaffected. In addition, as determined by immunofluorescence, SP and calcitonin gene-related peptide were significantly less abundant when present in small subepidermal nerve fibers in the skin of mice subjected to capsaicin treatment (data not shown). Thus, capsaicin treatment of murine skin damages cutaneous unmyelinated nerves and depletes them of SP and other neuropeptides which may impair sensitization, resulting in reduced ACD inflammatory responses.

FIGURE 2.
FIGURE 2.

Effect of topical capsaicin on sensory nerve morphology in murine skin. Mice were subjected to epicutaneous treatment with an ointment containing 0.075% capsaicin on the shaved abdomen (2 × 2 cm) twice a day over a period of 5 days. As a control, mouse skin was treated with ointment vehicle only. Skin was harvested as described in Materials and Methods and processed for transmission electron microscopy. Bold arrows designate either intact (a; no capsaicin) or destroyed (b; after capsaicin) vesicular structures in cross-sections of unmyelinated nerve fibers (AU, axon, unmyelinated nerve fiber). Larger myelinated nerve fibers (AM, axon, myelinated nerve fiber) or Schwann cells (S) were unaffected. Small arrow (a) designates dermal collagen fibers (CF). Data are representative of two different experiments with identical results. Scale bar = 640 nm (a); 580 nm (b).

Cutaneous changes during ACD in mice subjected to ACE inhibition

The effect of ACE inhibition before sensitization on allergic skin inflammation was also investigated by histological examination of mouse ears after hapten challenge (Fig. 3⇓). No significant differences were observed in the skin of sensitized animals treated with vehicle only (Fig. 3⇓, a and b). Likewise, no differences were observed between DNFB-challenged ears of nonsensitized, untreated, or captopril-treated mice (data not shown). However, in sensitized, captopril-treated animals, severe dermal edema, an intense inflammatory infiltration consisting predominantly of neutrophils and mononuclear cells, and some epidermal hyperplasia were detected 72 h after Ag challenge (Fig. 3⇓c). Notably, edema, cellular infiltrate, and epidermal hyperplasia were clearly less prominent in sensitized but not captopril-treated C57BL/6J mice (Fig. 3⇓d). Treatment of mice with either capsaicin or the B2-R antagonist before DNFB sensitization resulted in a reduction of cutaneous edema and leukocyte infiltration (data not shown). In addition, staining of ear tissue with Abs against CD4 or CD8 (Fig. 4⇓) revealed a clear increase of CD4+ and CD8+ cells in the ears of sensitized and challenged C57BL/6J mice (Fig. 4⇓, e and f) in comparison to control ears of mice not subjected to ACD elicitation (Fig. 4⇓, b and c). Importantly, in ears from captopril-treated, sensitized, and challenged mice a higher density of CD4+ and of CD8+ T cells could be detected 72 h after Ag challenge (Fig. 4⇓, h and i) in comparison to animals not treated with the ACE inhibitor before sensitization (Fig. 4⇓, e and f). Moreover, capsaicin treatment before ACE inhibition and sensitization resulted in a reduction in the density of both CD4+ and CD8+ cells (Fig. 4⇓, k and l). These results indicate that ACE inhibition before sensitization results in an enhanced recruitment of CD4+CD8+ T cells after Ag challenge during the effector phase of ACD.

FIGURE 3.
FIGURE 3.

Altered histological changes in ACE inhibitor-treated animals during ACD. The cutaneous histological changes in C57BL/6J mice was examined after captopril treatment before sensitization and DNFB exposure. Control ears of captopril-treated (a) or NaCl-treated (b) sensitized mice challenged with vehicle (acetone/olive oil) only. NaCl- (d) and captopril-treated (c) mice were sensitized and challenged with DNFB and mouse ears were examined histologically at 72 h. Cutaneous histological changes were examined in tissue stained with H&E. Data are representative of three different experiments with similar results Scale bars, 100 μm.

FIGURE 4.
FIGURE 4.

Altered T cell infiltrate composition in ACE inhibitor-treated animals during ACD. The cutaneous histological changes in C57BL/6J mice were examined after captopril treatment before sensitization and DNFB exposure. Control ears of sensitized mice treated with vehicle only demonstrated only weak staining with anti-CD4 (b) or anti-CD8 Abs (c). In contrast, 72 h after challenge, in captopril-treated sensitized mice staining for CD4+ (h) and CD8+ cells (i) was more pronounced in comparison to mice not treated with the ACE-inhibitor (e and f). Mice subjected to neuropeptide depletion before captopril treatment and sensitization demonstrated reduced CD4+ (k) and CD8+ cell infiltrate (l) in comparison to animals treated with captopril (h and i). Tissue stained with an isotype control Ab revealed no staining (a, d, g, and j). The tissue was counterstained with hematoxylin. Data are representative of three different experiments with similar results Scale bars, 100 μm.

ACD responses in C57BL/6J-ACE+/− and C57BL/6J-ACE+/+ mice

To verify that the effects of captopril on ACD are specific for ACE and not due to the inhibition of other peptidases, the ACD response in mice with a targeted deletion of the somatic form of ACE was examined. Due to a reduced postnatal viability of homozygous animals, heterozygous mice were used in these experiments (ACE+/−; Fig. 5⇓). When C57BL/6J-ACE+/− were sensitized and challenged with DNFB, a significant increase of the allergic ear swelling response in comparison to sensitized and challenged wild-type animals 24 h after Ag challenge was observed (Fig. 5⇓a). Importantly, this increased ACD response could be significantly reduced by injection of a highly specific nonpeptide NK-1R antagonist (SR140333) before sensitization (Fig. 5⇓b). These data indicate that temporary inhibition of ACE before sensitization or challenge as well as partial genomic deletion of ACE results in significantly increased ACD inflammatory response in mice, which require sensory nerves and involve BK-mediated B2-R and SP-mediated NK-1R activation.

FIGURE 5.
FIGURE 5.

ACD responses in ACE+/− and ACE+/+ mice. C57BL/6J-ACE+/− and C57BL/6J-ACE+/+ mice were sensitized and challenged with DNFB as described. The ACD response was determined by the degree of ear swelling of the hapten-exposed ear compared with that of the vehicle-treated contralateral ear before DNFB challenge and at 24 and 48 h after challenge (a). In some experiments, the effect of the NK-1R blocking by injection of a NK-1R antagonist (SR140333, 1.0 μmol/kg i.p.) before sensitization on ACD responses in C57BL/6J-ACE+/− mice was examined (b). Ear swelling values are given in micrometers as mean ± SEM, n = 7. ∗∗, p < 0.01 for C57BL/6J-ACE+/− vs ACE+/+ wild-type control mice. ###, p < 0.001 for NK-1R antagonist (NK-1RA)-treated C57BL/6J-ACE+/− vs C57BL/6J-ACE+/− mice.

Similar ICD responses in ACE+/− and ACE+/+ mice

When ACE+/− and ACE+/+ mice were treated with the topically applied irritant croton oil, the ear swelling response to the irritant was time-dependent increased in ACE+/− and wild-type animals, reaching a peak swelling at ∼6 h after croton oil challenge (Fig. 6⇓). However, in contrast to the results observed during ACD, the ICD response to croton oil in mice bearing a partial ACE deletion was not significantly different from that in wild-type ACE+/+ animals (Fig. 6⇓). Upon histological examination, the cellular infiltration as well as the tissue morphology in ICD was also not visibly different in ACE+/− mice compared with ACE+/+ (data not shown). Thus, ACE is an important inflammatory modulator of ACD responses, but not of ICD cutaneous inflammation.

FIGURE 6.
FIGURE 6.

ICD responses in ACE+/− and ACE+/+ mice. C57BL/6J-ACE+/− or C57BL/6J-ACE+/+ mice were treated with 0.8% croton oil on the right ear to induce irritation. The left ear was treated with vehicle only. The ICD response was determined by the degree of ear swelling of the irritant-exposed ear compared with that of the vehicle-treated contralateral ear before croton oil challenge and at 2, 4, 6, and 24 h after challenge. All ear swelling values are given in micrometers as mean ± SEM, n = 10. Differences between C57BL/6J-ACE+/− and wild-type mice were not statistically significant in this study.

Discussion

The local tissue availability and bioactivity of BK as well as those of SP appear to be tightly controlled by their release from cells and sensory nerves, the presence of B-R or NK-1R on target cells, and local expression of kinin/tachykinin-degrading enzymes such as NEP or ACE (1, 18, 27, 28). The role of NEP in modulating neuropeptide-mediated biological responses and systemic inflammation is supported by a number of recent in vivo studies demonstrating that NEP−/− animals are highly sensitive to bacterial endotoxins (29) and the absence of NEP promotes intestinal (30) as well as cutaneous inflammatory response to allergens (24). Likewise, transient inhibition of ACE was shown to promote neurogenic inflammation in mice, i.e., plasma extravasation, vasodilation (31, 32), and experimental dermatitis (33, 34, 35). Accordingly, ACE inhibition enhanced short-term (<24 h) skin inflammation induced by OVA, capsaicin, or BK injection although the extent of inflammation was dependent on the ACE inhibitor used (34, 35).

In the present study, we have used murine models for allergic and ICD to study the relative contribution of ACE in cutaneous inflammation. Our results provide substantial evidence for a major role for ACE in ACD. Inflammatory responses to the hapten DNFB over 72 h were markedly greater in sensitized animals partially lacking ACE or in wild-type mice treated with physiological concentrations of an ACE inhibitor. This supports the hypothesis that ACE contributes to the down-regulation of neuroinflammatory responses. Importantly, in our study, the use of animals partially lacking ACE demonstrated that increased ACD inflammatory responses are truly due to the inactivation of ACE and not due to a drug-dependent nonspecific inhibition of other proteolytic peptidases. This is in accordance with recent studies demonstrating that even heterozygous mice, which only partially lacked somatic and testicular ACE, displayed significantly decreased ACE activity (22) and blood pressure responses to exogenous ACE substrates such as Ang I and BK (36). In our study, the enhanced expression of ACD observed in mice after temporary inhibition or heterozygous deletion of ACE was prevented by the local depletion of SP from cutaneous sensory nerves at the site of sensitization or by administration of B2-R or NK-1R antagonists before sensitization. We have previously demonstrated that neuropeptide depletion from sensory nerves by repeated treatment with the neurotoxin capsaicin profoundly reduces the efferent ACD response in NEP-deficient mice (24). Likewise, another study demonstrated that inhibition of ACE in mice increased plasma extravasation involving BK as an important mediator of neurogenic inflammation (31). In extension of these data, our observations support the role of an intact functional peripheral sensory nervous system in ACD sensitization and demonstrates that impaired degradation of BK and also of SP during ACD sensitization contributes to allergic inflammatory effector responses in the skin. In contrast, ICD responses appear to be less affected by the functional absence of ACE. Although initial ICD ear swelling responses in ACE+/− mice were slightly increased compared with those of wild-type animals, this difference was not significant. This confirms our previous data using NEP−/−-mice demonstrating that the lack of NEP does not affect ICD responses to croton oil or SDS (24). However, other studies also demonstrated an involvement of SP and sensory nerves in both allergic and irritant inflammation (37, 38, 39, 40, 41). The precise mechanism of this difference between nonspecific irritant inflammation and the hapten-specific ACD response in mice with functionally inactive proteolytic peptidases such as ACE or NEP compared with wild-type animals is not entirely clear. ACD responses, in contrast to ICD, require contact between APC; i.e., Ag-loaded dendritic cells (DC) and T cells in the T cell zones of secondary lymphoid organs such as draining lymph nodes resulting in the generation of Ag-specific effector and memory T cells. In the extension of previous results that focused on the effect of ACE inhibition before Ag challenge (33, 34, 35), our study directly addresses the role of ACE on the induction phase of ACD. Accordingly, functional absence of ACE before sensitization was sufficient to augment ACD responses after hapten challenge without further ACE inactivation in the elicitation phase. A comparable boosting effect on murine ACD responses could be obtained after inhibition of NEP by injection of phosphoramidon before hapten sensitization (T. E. Scholzen, unpublished data). These data suggest that the basis of an exaggerated ACD response in mice with functionally inactive BK- and SP-degrading peptidases is already set during the initial contact with hapten, strongly implying that increased SP and BK are capable of boosting not only ACD expression, but also the sensitization phase of ACD. In case of ACD induction, increased SP may directly enhance functions of epidermal or dermal APC such as Ag presentation or migration into the regional lymph nodes. In favor of this hypothesis are recent observations indicating that a NK-1R agonist promoted ACD induction and prevented or reversed hapten-specific tolerance induced by low-dose UVB radiation in vivo. This appeared to be due to a local effect, although intradermal injection of the NK-1R agonist failed to alter the density of epidermal Langerhans cells (42). Likewise, we have preliminary evidence that the functional absence of NEP promotes maturation and function of bone marrow-derived DC (43). Recently, it has been demonstrated that in addition to monocytes and macrophages (44), human and murine DC express functional NK-1R (45) and are capable of producing SP (46). Stimulation of DC with SP results in NF-κB activation, which is an important transcription factor involved in the up-regulation of molecules that are required for maturation and stimulatory activity of DC such as MHC class II, CD80, CD86, and IL-12 expression (47, 48, 49, 50, 51). Thus, it appears to be conceivable that in an environment where SP and the SP-inducing BK are prevented from degradation, SP may in an auto- or paracrine manner modulate DC functions such as Ag uptake and processing, migration into regional lymph nodes, or Ag presentation. Consequently, this may result in the generation of an increased number of Ag-specific effector and memory T cells that subsequently infiltrate peripheral tissues, including the skin.

In addition, there is increasing evidence that released neuropeptides including SP are capable of directly or indirectly acting on T lymphocytes (52). Whereas sensory neurons that innervate secondary lymphoid organs were originally thought to be the exclusive source of SP (53), there is now evidence that T lymphocytes themselves are capable of expressing pre/protachykinin A mRNA and of releasing SP (54). Moreover, human and murine lymphocytes express NK-1R (54, 55) and SP augments the mitogen- and Ag-induced proliferation and IL-2 secretion of T lymphocytes (52, 56) as well as the expression of the IL-2R α-chain (CD25) (57). In addition, SP is also capable of directly inducing T cell IFN-γ which is known to suppress IL-4 and the development of a Th2 cell phenotype (58, 59). A recent in vitro study demonstrated that the addition of a specific NK1-R antagonist partly reduced T cell proliferation during the interaction with syngeneic or allogeneic DC. Likewise, in the absence of DC, proliferation of T cells induced by direct CD3/CD28 ligation was partly dependent on signaling through NK1-R, revealing an autocrine effect of SP production by T cells (46). Importantly, T cells have been demonstrated to express ACE and in vitro captopril treatment of T cells, resulting in reduced ACE activity (60), promoted T cell proliferation induced by ConA (61). Thus, blocking of SP degradation by transient inhibition of ACE might result in the local or systemic generation of a distinct cytokine environment involving IL-12 and IFN-γ that may be capable of promoting a Th1-mediated cellular immune response. However, the precise mechanism of the increased ACD inflammatory response triggered by ACE inhibition before elicitation of ACD is not clear. As demonstrated previously, elicitation of ACD can be dissected into an hapten-specific effector cell activation and a relatively unspecific proinflammatory signal, which is due to the fact that haptens also act as irritants (62, 63, 64, 65). In this scenario, impaired neuropeptide degradation might result in both activation of Ag-specific T cells as well as in the generation of an unspecific proinflammatory skin environment at the site of Ag challenge that conditions the tissue for a full Ag-specific ACD elicitation.

In summary, our data indicate that the absence or reduced activity of ACE during sensitization leads to the development of augmented responses to allergens in a murine ACD model system which may be due to the prolonged tissue presence of released SP and BK. Our observations further support the hypothesis that the expression and regulation of proteolytic peptidases such as ACE or NEP and of SP and NK-1R play an important role in inflammatory skin diseases such as ACD. This could be of importance for the clinical use of ACE and possibly NEP inhibitors, since application of these drugs may, under certain circumstances and predispositions, promote the induction of type IV hypersensitivity reactions. In addition, it appears to be conceivable that ACE inhibition may trigger expression of allergic inflammatory responses in already sensitized individuals. These findings further suggest the notion that in addition to cytokines, neuropeptides play an important role in the regulation of immune and inflammatory responses.

Acknowledgments

We thank Michaela Fastrich, Karin Fischer, and Andrea Wissel for their expert technical assistance. The NK-1R antagonist SR140333 was kindly provided by Dr. Emonds-Alt (Sanofi-Synthélabo, Montpellier, France). We are grateful to Stephan Grabbe for carefully reading this manuscript.

Footnotes

  • ↵1 This work was supported by the SFB293 and 87/E1 T from the Deutsche Forschungsgemeinschaft and by the Center de Recherché et Investigations Epidermiques et Sensorielles, Paris (to T.A.L.) and by Scho 629/1-1 and Scho 629/1-3 from the Deutsche Forschungsgemeinschaft (to T.E.S.).

  • ↵2 Address correspondence and reprint requests to Dr. Thomas Scholzen, Department of Dermatology, Ludwig Boltzmann Institute for Cell and Immunobiology of the Skin, University of Münster, Von-Esmarch-Strasse 58, 48149 Münster, Germany. E-mail address: thoscho{at}uni-muenster.de

  • ↵3 Abbreviations used in this paper: NEP, neutral endopeptidase; ACD, allergic contact dermatitis; ACE, angiotensin-converting enzyme; Ang, angiotensin; BK, bradykinin; B-R, BK receptor; B2-R, BK 2 receptor; DC, dendritic cell; DNFB, 2,4-dinitro-1-fluorobenzene; ICD, irritant contact dermatitis; NK-1R, neurokinin 1 receptor; SP, substance P.

  • Received October 9, 2002.
  • Accepted January 21, 2003.

References

  1. ↵
    Nadel, J. A.. 1996. Peptidase modulation of neurogenic inflammation. P. Geppetti, and P. Holzer, eds. Neurogenic Inflammation 115-127. CRC Press, Boca Raton, FL.
  2. ↵
    Corvol, P., T. A. Williams, F. Soubrier. 1995. Peptidyl dipeptidase A: angiotensin I-converting enzyme. Methods Enzymol. 248: 283
    OpenUrlCrossRefPubMed
  3. ↵
    Wei, L., F. Alhenc-Gelas, P. Corvol, E. Clauser. 1991. The two homologous domains of human angiotensin I-converting enzyme are both catalytically active. J. Biol. Chem. 266: 9002
    OpenUrlAbstract/FREE Full Text
  4. ↵
    Beldent, V., A. Michaud, L. Wei, M. T. Chauvet, P. Corvol. 1993. Proteolytic release of human angiotensin-converting enzyme: localization of the cleavage site. J. Biol. Chem. 268: 26428
    OpenUrlAbstract/FREE Full Text
  5. ↵
    Langford, K. G., Y. Zhou, L. D. Russell, J. N. Wilcox, K. E. Bernstein. 1993. Regulated expression of testis angiotensin-converting enzyme during spermatogenesis in mice. Biol. Reprod. 48: 1210
    OpenUrlAbstract
  6. ↵
    Krege, J. H., H. S. Kim, J. S. Moyer, J. C. Jennette, L. Peng, S. K. Hiller, O. Smithies. 1997. Angiotensin-converting enzyme gene mutations, blood pressures, and cardiovascular homeostasis. Hypertension 29: 150
    OpenUrlAbstract/FREE Full Text
  7. ↵
    Ng, K. K., J. R. Vane. 1967. Conversion of angiotensin I to angiotensin II. Nature 216: 762
    OpenUrlCrossRefPubMed
  8. ↵
    Fong, T. M.. 1996. Molecular biology of tachykinins. P. Geppetti, and P. Holzer, eds. Neurogenic Inflammation 3-14. CRC Press, Boca Raton, FL.
  9. ↵
    Reilly, D. M., D. Ferdinando, C. Johnston, C. Shaw, K. D. Buchanan, M. R. Green. 1997. The human epidermal nerve fibre network: characterization of nerve fibres in human skin by confocal microscopy and assessment of racial variations. Br. J. Dermatol. 137: 163
    OpenUrlCrossRefPubMed
  10. ↵
    Regoli, D., Q. T. Nguyen, G. Calo. 1996. Pharmacology of tachykinins. P. Holzer, and P. Geppetti, eds. Neurogenic Inflammation 91-99. CRC Press, Boca Raton, FL.
  11. ↵
    Quartara, L., C. A. Maggi. 1998. The tachykinin NK1 receptor. Part II: Distribution and pathophysiological roles. Neuropeptides 32: 1
    OpenUrlCrossRefPubMed
  12. ↵
    Scholzen, T., C. A. Armstrong, N. W. Bunnett, T. A. Luger, Olerud, J. C. Ansel. 1998. Neuropeptides in the skin: interactions between the neuroendocrine and the skin immune systems. Exp. Dermatol. 7: 81
    OpenUrlCrossRefPubMed
  13. ↵
    Holzer, P.. 1988. Local effector functions of capsaicin-sensitive sensory nerve endings: involvement of tachykinins, calcitonin gene-related peptide and other neuropeptides. Neuroscience 24: 739
    OpenUrlCrossRefPubMed
  14. ↵
    Bhoola, K. D., C. D. Figueroa, K. Worthy. 1992. Bioregulation of kinins: kallikreins, kininogens, and kininases. Pharmacol. Rev. 44: 1
    OpenUrlPubMed
  15. ↵
    Hall, J. M.. 1992. Bradykinin receptors: pharmacological properties and biological roles. Pharmacol. Ther. 56: 131
    OpenUrlCrossRefPubMed
  16. ↵
    Geppetti, P.. 1993. Sensory neuropeptide release by bradykinin: mechanisms and pathophysiological implications. Regul. Pept. 47: 1
    OpenUrlCrossRefPubMed
  17. ↵
    Krege, J. H., S. W. John, L. L. Langenbach, J. B. Hodgin, J. R. Hagaman, E. S. Bachman, J. C. Jennette, D. A. O’Brien, O. Smithies. 1995. Male-female differences in fertility and blood pressure in ACE-deficient mice. Nature 375: 146
    OpenUrlCrossRefPubMed
  18. ↵
    Pham, I., W. Gonzalez, J. Doucet, M. C. Fournie-Zaluski, B. P. Roques, J. B. Michel. 1996. Effects of angiotensin-converting enzyme and neutral endopeptidase inhibitors: influence of bradykinin. Eur. J. Pharmacol. 296: 267
    OpenUrlCrossRefPubMed
  19. ↵
    Linz, W., G. Wiemer, P. Gohlke, T. Unger, B. A. Scholkens. 1995. Contribution of kinins to the cardiovascular actions of angiotensin-converting enzyme inhibitors. Pharmacol. Rev. 47: 25
    OpenUrlAbstract
  20. ↵
    Israili, Z. H., W. D. Hall. 1992. Cough and angioneurotic edema associated with angiotensin-converting enzyme inhibitor therapy: a review of the literature and pathophysiology. Ann. Intern. Med. 117: 234
    OpenUrlCrossRefPubMed
  21. ↵
    Gilleaudeau, P., V. P. Vallat, D. M. Carter, A. B. Gottlieb. 1993. Angiotensin-converting enzyme inhibitors as possible exacerbating drugs in psoriasis. J. Am. Acad. Dermatol. 28: 490
    OpenUrlCrossRefPubMed
  22. ↵
    Hagaman, J. R., J. S. Moyer, E. S. Bachman, M. Sibony, P. L. Magyar, J. E. Welch, O. Smithies, J. H. Krege, D. A. O’Brien. 1998. Angiotensin-converting enzyme and male fertility. Proc. Natl. Acad. Sci. USA 95: 2552
    OpenUrlAbstract/FREE Full Text
  23. ↵
    Grabbe, S., R. S. Bhardwaj, K. Mahnke, M. M. Simon, T. Schwarz, T. A. Luger. 1996. α-Melanocyte-stimulating hormone induces hapten-specific tolerance in mice. J. Immunol. 156: 473
    OpenUrlAbstract
  24. ↵
    Scholzen, T. E., M. Steinhoff, P. Bonaccorsi, R. Klein, S. Amadesi, P. Geppetti, B. Lu, N. P. Gerard, J. E. Olerud, T. A. Luger, et al 2001. Neutral endopeptidase terminates substance P-induced inflammation in allergic contact dermatitis. J. Immunol. 166: 1285
    OpenUrlAbstract/FREE Full Text
  25. ↵
    Sunderkotter, C., S. Seeliger, F. Schönlau, J. Roth, R. Hallmann, T. A. Luger, C. Sorg, G. Kolde. 2001. Different pathways leading to leukocytoclastic vasculitis in mice. Exp. Dermatol. 10: 391
    OpenUrlCrossRefPubMed
  26. ↵
    Biro, T., G. Acs, P. Acs, S. Modarres, P. M. Blumberg. 1997. Recent advances in understanding of vanilloid receptors: a therapeutic target for treatment of pain and inflammation in skin. J. Invest. Dermatol. Symp. Proc. 2: 56
    OpenUrlCrossRef
  27. ↵
    Okamoto, A., M. Lovett, D. G. Payan, N. W. Bunnett. 1994. Interactions between neutral endopeptidase (EC 3.4.24.11) and the substance P (NK1) receptor expressed in mammalian cells. Biochem. J. 299: 683
    OpenUrlAbstract/FREE Full Text
  28. ↵
    Roques, B. P., F. Noble. 1995. Dual inhibitors of enkephalin-degrading enzymes (neutral endopeptidase 24.11 and aminopeptidase N) as potential new medications in the management of pain and opioid addiction. NIDA Res. Monogr. 147: 104
    OpenUrlPubMed
  29. ↵
    Lu, B., N. P. Gerard, L. F. Kolakowski, Jr., M. Bozza, D. Zurakowski, O. Finco, M. C. Carroll, C. Gerard. 1995. Neutral endopeptidase modulation of septic shock. J. Exp. Med. 181: 2271
    OpenUrlAbstract/FREE Full Text
  30. ↵
    Sturiale, S., G. Barbara, B. Qui, M. Figini, P. Geppetti, N. Gerard, C. Gerard, E. F. Grady, N. W. Bunnett, S. M. Collins. 1999. Neutral endopeptidase (EC 3.4.24.11) terminates colitis by degrading SP. Proc. Natl. Acad. Sci. USA 96: 11653
    OpenUrlAbstract/FREE Full Text
  31. ↵
    Emanueli, C., E. F. Grady, P. Madeddu, M. Figini, N. W. Bunnett, D. Parisi, D. Regoli, P. Geppetti. 1998. Acute ACE inhibition causes plasma extravasation in mice that is mediated by bradykinin and substance P. Hypertension 31: 1299
    OpenUrlAbstract/FREE Full Text
  32. ↵
    Baluk, P., G. Thurston, T. J. Murphy, N. W. Bunnett, D. M. McDonald. 1999. Neurogenic plasma leakage in mouse airways. Br. J. Pharmacol. 126: 522
    OpenUrlCrossRefPubMed
  33. ↵
    Ito, K., K. Ito, Y. Sawada, T. Iga. 1995. Toxicodynamic analysis of inflammatory reactions by an angiotensin converting enzyme inhibitor (lisinopril) in guinea-pig skin. J. Pharm. Pharmacol. 47: 499
    OpenUrlCrossRefPubMed
  34. ↵
    Rosenqvist, U., K. Persson, B. R. Lindgren, R. G. Andersson. 1991. Effects of cilazaprilat and enalaprilat on experimental dermatitis in guinea pigs. Pharmacol. Toxicol. 68: 404
    OpenUrlCrossRefPubMed
  35. ↵
    Lindgren, B. R., C. D. Anderson, R. G. Andersson. 1987. Potentiation of inflammatory reactions in guinea-pig skin by an angiotensin converting enzyme inhibitor (MK 422). Eur. J. Pharmacol. 135: 383
    OpenUrlCrossRefPubMed
  36. ↵
    Tian, B., Q. C. Meng, Y. F. Chen, J. H. Krege, O. Smithies, S. Oparil. 1997. Blood pressures and cardiovascular homeostasis in mice having reduced or absent angiotensin-converting enzyme gene function. Hypertension 30: 128
    OpenUrlAbstract/FREE Full Text
  37. ↵
    Payan, D. G.. 1989. Neuropeptides and inflammation: the role of substance P. Annu. Rev. Med. 40: 341
    OpenUrlCrossRefPubMed
  38. ↵
    Wallengren, J., R. Ekman, H. Moller. 1991. Capsaicin enhances allergic contact dermatitis in the guinea pig. Contact Dermatitis 24: 30
    OpenUrlCrossRefPubMed
  39. ↵
    Wallengren, J., H. Moller. 1988. Some neuropeptides as modulators of experimental contact allergy. Contact Dermatitis 19: 351
    OpenUrlCrossRefPubMed
  40. ↵
    Gutwald, J., M. Goebeler, C. Sorg. 1991. Neuropeptides enhance irritant and allergic contact dermatitis. J. Invest. Dermatol. 96: 695
    OpenUrlCrossRefPubMed
  41. ↵
    Goebeler, M., U. Henseleit, J. Roth, C. Sorg. 1994. Substance P and calcitonin gene-related peptide modulate leukocyte infiltration to mouse skin during allergic contact dermatitis. Arch. Dermatol. Res. 286: 341
    OpenUrlCrossRefPubMed
  42. ↵
    Niizeki, H., I. Kurimoto, J. W. Streilein. 1999. A substance p agonist acts as an adjuvant to promote hapten-specific skin immunity. J. Invest. Dermatol. 112: 437
    OpenUrlCrossRefPubMed
  43. ↵
    Scholzen, T. E., T. Brzoska, M. Fastrich, S. Grundmann, C. A. Armstrong, J. C. Ansel, T. A. Luger.. 2002. Genomic deletion of neutral endopeptidase in mice promotes hapten uptake, maturation and function of bone marrow-derived dendritic cells. J. Invest. Dermatol. 119: 308 (Abstr.).
    OpenUrl
  44. ↵
    Ho, W. Z., J. P. Lai, X. H. Zhu, M. Uvaydova, S. D. Douglas. 1997. Human monocytes and macrophages express substance P and neurokinin-1 receptor. J. Immunol. 159: 5654
    OpenUrlAbstract
  45. ↵
    Marriott, I., K. L. Bost. 2001. Expression of authentic substance P receptors in murine and human dendritic cells. J. Neuroimmunol. 114: 131
    OpenUrlCrossRefPubMed
  46. ↵
    Lambrecht, B. N., P. R. Germonpre, E. G. Everaert, I. Carro-Muino, M. De Veerman, C. De Felipe, S. P. Hunt, K. Thielemans, G. F. Joos, R. A. Pauwels. 1999. Endogenously produced substance P contributes to lymphocyte proliferation induced by dendritic cells and direct TCR ligation. Eur. J. Immunol. 29: 3815
    OpenUrlCrossRefPubMed
  47. ↵
    Marriott, I., M. J. Mason, A. Elhofy, K. L. Bost. 2000. Substance P activates NF-κB independent of elevations in intracellular calcium in murine macrophages and dendritic cells. J. Neuroimmunol. 102: 163
    OpenUrlCrossRefPubMed
  48. ↵
    Cruz, M. T., C. B. Duarte, M. Goncalo, A. P. Carvalho, M. C. Lopes. 2001. LPS induction of IκB-α degradation and iNOS expression in a skin dendritic cell line is prevented by the Janus kinase 2 inhibitor, Tyrphostin b42. Nitric Oxide 5: 53
    OpenUrlCrossRefPubMed
  49. ↵
    Rescigno, M., M. Martino, C. L. Sutherland, M. R. Gold, P. Ricciardi-Castagnoli. 1998. Dendritic cell survival and maturation are regulated by different signaling pathways. J. Exp. Med. 188: 2175
    OpenUrlAbstract/FREE Full Text
  50. ↵
    Yoshimura, S., J. Bondeson, B. M. Foxwell, F. M. Brennan, M. Feldmann. 2001. Effective antigen presentation by dendritic cells is NF-κB dependent: coordinate regulation of MHC, co-stimulatory molecules and cytokines. Int. Immunol. 13: 675
    OpenUrlAbstract/FREE Full Text
  51. ↵
    Grohmann, U., M. L. Belladonna, R. Bianchi, C. Orabona, E. Ayroldi, M. C. Fioretti, P. Puccetti. 1998. IL-12 acts directly on DC to promote nuclear localization of NF-κB and primes DC for IL-12 production. Immunity 9: 315
    OpenUrlCrossRefPubMed
  52. ↵
    Payan, D. G., D. R. Brewster, A. Missirian-Bastian, E. J. Goetzl. 1984. Substance P recognition by a subset of human T lymphocytes. J. Clin. Invest. 74: 1532
    OpenUrlCrossRefPubMed
  53. ↵
    Lorton, D., D. L. Bellinger, S. Y. Felten, D. L. Felten. 1991. Substance P innervation of spleen in rats: nerve fibers associate with lymphocytes and macrophages in specific compartments of the spleen. Brain Behav. Immun. 5: 29
    OpenUrlCrossRefPubMed
  54. ↵
    Lai, J. P., S. D. Douglas, W. Z. Ho. 1998. Human lymphocytes express substance P and its receptor. J. Neuroimmunol. 86: 80
    OpenUrlCrossRefPubMed
  55. ↵
    Stanisz, A. M., R. Scicchitano, P. Dazin, J. Bienenstock, D. G. Payan. 1987. Distribution of substance P receptors on murine spleen and Peyer’s patch T and B cells. J. Immunol. 139: 749
    OpenUrlAbstract
  56. ↵
    Calvo, C. F., G. Chavanel, A. Senik. 1992. Substance P enhances IL-2 expression in activated human T cells. J. Immunol. 148: 3498
    OpenUrlAbstract
  57. ↵
    Santoni, G., M. C. Perfumi, E. Spreghini, S. Romagnoli, M. Piccoli. 1999. Neurokinin type-1 receptor antagonist inhibits enhancement of T cell functions by substance P in normal and neuromanipulated capsaicin-treated rats. J. Neuroimmunol. 93: 15
    OpenUrlCrossRefPubMed
  58. ↵
    Weinstock, J. V., D. Elliott. 1998. The substance P and somatostatin interferon-γ immunoregulatory circuit. Ann. NY Acad. Sci. 840: 532
    OpenUrlCrossRefPubMed
  59. ↵
    Wagner, F., R. Fink, R. Hart, H. Dancygier. 1987. Substance P enhances interferon-γ production by human peripheral blood mononuclear cells. Regul. Pept. 19: 355
    OpenUrlCrossRefPubMed
  60. ↵
    Petrov, V., R. Fagard, P. Lijnen. 2000. Effect of protease inhibitors on angiotensin-converting enzyme activity in human T-lymphocytes. Am. J Hypertens. 13: 535
    OpenUrlCrossRefPubMed
  61. ↵
    Yeung, J. H.. 1994. A comparison of the effects of angiotensin-converting enzyme inhibitors with bradykinin, angiotensin II and their specific antagonists on concanavalin A-induced proliferation of mouse T-lymphocytes. Methods Find. Exp. Clin. Pharmacol. 16: 163
    OpenUrlPubMed
  62. ↵
    Grabbe, S., M. Steinert, K. Mahnke, A. Schwartz, T. A. Luger, T. Schwarz. 1996. Dissection of antigenic and irritative effects of epicutaneously applied haptens in mice: evidence that not the antigenic component but nonspecific proinflammatory effects of haptens determine the concentration-dependent elicitation of allergic contact dermatitis. J. Clin. Invest. 98: 1158
    OpenUrlCrossRefPubMed
  63. ↵
    Grabbe, S., T. Schwarz. 1996. Immunoregulatory mechanisms involved in elicitation of allergic contact hypersensitivity. Am. J. Contact Dermat. 7: 238
    OpenUrlCrossRefPubMed
  64. ↵
    McLelland, J., S. Shuster, J. N. Matthews. 1991. ’Irritants’ increase the response to an allergen in allergic contact dermatitis. Arch. Dermatol. 127: 1016
    OpenUrlCrossRefPubMed
  65. ↵
    Kondo, S., S. Pastore, G. M. Shivji, R. C. McKenzie, D. N. Sauder. 1994. Characterization of epidermal cytokine profiles in sensitization and elicitation phases of allergic contact dermatitis as well as irritant contact dermatitis in mouse skin. Lymphokine Cytokine Res. 13: 367
    OpenUrlPubMed
Back to top

In this issue

Print
Download PDF
Article Alerts
Email Article
Citation Tools

Jump to section