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*
Laboratory of Rheumatology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland;
Department of Pathology, School of Medicine, Geneva, Switzerland; and
Division of Rheumatology, University Hospital of Geneva, Geneva, Switzerland
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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and TNF-
mRNA in the
synovium of arthritic knees were lower in ob/ob than in
+/? mice. In vitro Ag-specific T cell proliferative responses were
significantly decreased in ob/ob mice with lower IFN-
and higher IL-10 production, suggesting a shift toward a Th2-type
response in ob/ob mice. The serum levels of
anti-methylated BSA Abs of any isotype were significantly decreased
in arthritic ob/ob mice compared with controls.
Essentially identical results were obtained in db/db
mice, which lack the expression of the long isoform of leptin receptor.
By RT-PCR, we observed that B lymphocytes express leptin receptor mRNA,
indicating that in addition to its effect on the cellular response,
leptin may exert a direct effect on B cell function. In conclusion,
leptin contributes to the mechanisms of joint inflammation in
Ag-induced arthritis by regulating both humoral and cell-mediated
immune responses. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The role of leptin in vivo has been examined in different experimental
models using either ob/ob mice or mice with a deletion in
the Ob-Rb (db/db mice). The results of these studies
demonstrated that leptin possesses both anti- and pro-inflammatory
effects according to the disease model. Leptin deficiency enhanced the
sensitivity to LPS- and TNF--induced mortality, with a protective
effect of exogenously administered recombinant leptin in
ob/ob mice, suggesting that leptin plays an important role
in modulating the host response to inflammation (9, 10).
In contrast, ob/ob and db/db mice were protected
from T cell-mediated hepatotoxicity induced by the injection of Con A,
and replacement of leptin was able to restore the responsiveness of
ob/ob mice to Con A (11).
Rheumatoid arthritis (RA) is a systemic chronic inflammatory disease characterized by synovial hyperplasia, inflammatory cell recruitment, and, in its later stages, cartilage and bone destruction. Several studies have demonstrated that the Th1/Th2 balance plays an important role in RA, with Th1 and Th2 cytokines exerting pro- and anti-inflammatory effects, respectively (12). Fasting patients with RA exhibit an improvement in different clinical and biological parameters of disease activity associated with a marked decrease in serum levels of leptin and a shift toward Th2 cytokine production (13). These features closely resemble those observed in ob/ob mice, suggesting that leptin may play a role in the inflammatory mechanisms of arthritis through the induction of Th1 responses.
The potential role of leptin in RA needs to be assessed in vivo. Using a murine model (Ag-induced arthritis (AIA)) that is T and B cell dependent and that recapitulates some of the histologic and functional alterations of RA, we have explored the phenotype of leptin-deficient mice. Moreover, mice deficient for the long isoform of the leptin receptor (db/db mice) provided an opportunity to evaluate the role of leptin signaling during AIA.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Leptin-deficient mice (ob/ob), control (+/?) littermates, and wild-type (+/+) mice, all in a C57BL/6 background, were purchased from Janvier (Le Genest St. Isle, France). Leptin receptor-deficient mice (db/db) and +/? littermates in C57BLKs were purchased from Harlan Nederland (Horst, The Netherlands).
Induction of arthritis
AIA was established as previously described (14). Briefly, mice were immunized on days 0 and 7 with 100 µg methylated BSA (mBSA; Sigma, Buchs, Switzerland) emulsified in 0.1 ml CFA containing 200 µg mycobacterial strain H37RA (Difco, Basel, Switzerland) by intradermal injection at the base of the tail. On the same days 0.2 x 109 heat-killed Bordetella pertussis organisms (Berna, Bern, Switzerland) were injected i.p. as an additional adjuvant. Arthritis was induced on day 21 by intra-articular injection of 100 µg mBSA in 10 µl sterile PBS into the right knee; the left knee was injected with sterile PBS alone. Institutional approval was obtained for these experiments.
Isotopic quantification of joint inflammation
Joint inflammation was measured by 99mTc-technetium (99mTc) uptake in the knee joint, as previously described (14). Briefly, mice were first anesthetized by methoxyflurane and then injected s.c. in the neck region with 10 µCi 99mTc. The accumulation of the isotope in the knee was determined by external gamma counting after 15 min. The ratio of 99mTc uptake in the inflamed arthritic knee vs 99mTc uptake in the contralateral control knee was calculated. A ratio of >1.1 indicated joint inflammation.
Histological grading of arthritis
At least six mice per group were sacrificed, and the knees were dissected and fixed in 10% buffered formalin for 7 days. Fixed tissues were decalcified for 3 wk in 15% EDTA, dehydrated, and embedded in paraffin. Sagittal sections (5 µm) of the whole knee joint were stained with Safranin-O and counterstained with Fast Green/iron hematoxylin. Histological sections were graded independently by two observers who were unaware of the animal genotype using the following parameters. Synovial membrane thickness, which reflects the degree of synovial inflammation and hyperplasia, was scored on a scale of 0 to 6 (0 = normal thickness; 6 = maximum of thickness). Cartilage proteoglycan depletion, reflected by loss of Safranin-O staining intensity, was scored on a scale of 0 (fully stained cartilage) to 6 (totally unstained cartilage) in proportion to severity. For each histopathologic parameter, the score (mean ± SEM) of all slides was calculated.
Synovial IL-1 and TNF- mRNA levels
The right knee joints of arthritic ob/ob and +/? mice
(day 8 of arthritis) were dissected, and the synovial membranes were
prepared and snap-frozen. Total RNA was extracted with TRIzol (Life
Technologies, Paisley, U.K.). RNA was quantitated using
OD260 determination, and the integrity was
verified on a 1% Tris-borate EDTA agarose gel. Riboprobes
complementary to murine IL-1 and GAPDH mRNA were created as recently
described (15). The riboprobe for TNF- mRNA was created
using the following primers: 5'TNF-, GCA GAA TTC ACA AGC CTG TAG CCC
ACG TCG; and 3'TNF-, GCA AAG CTT TGT CCC TTG AAG AGA ACC TG. The PCR
products were cleaved with EcoRI and HindIII,
gel-purified, and cloned into pBluescript SK+
(Stratagene, San Diego, CA). The plasmids containing the probes were
linearized with EcoRI and transcribed with T7 RNA polymerase
and 32P-labeled CTP. RNase protection assays were
performed as recently described (16), and quantification
of cytokine and GAPDH mRNA fragments was performed by PhosphorImager
(ImageQuant, Molecular Dynamics, Sunnyvale, CA).
T cell proliferation assay
Mice were sacrificed according to the experimental protocol.
Inguinal lymph nodes were removed, and single-cell suspensions were
incubated in RPMI supplemented with -ME, penicillin, streptomycin,
and 1% autologous serum. Lymph node cells (LNC) (4 x
105/200 µl/well) were plated in 96-well
flat-bottom plates and stimulated with 50 µg/ml mBSA (Sigma). The
cells were incubated at 37°C in 5% CO2 for
48 h, then 1 µCi/well [3H]thymidine was
added to the cultures for 18 h. The cells were harvested, and
[3H]thymidine uptake was measured using a beta
scintillation counter.
Determination of cytokine production in vitro
LNC were isolated and cultured with or without 50 µg/ml mBSA.
The culture supernatants were harvested after 72 h for
determination of IFN-, IL-4, and IL-10 levels. Quantification of
cytokine production was performed by ELISA kits specific for murine
IFN- (Amersham Pharmacia, Dubendorf, Switzerland), IL-4, and IL-10
(Quantikine, R&D Systems, Abingdon, U.K.).
Measurement of serum levels of anti-mBSA Abs
For determination of anti-mBSA IgG, 96-wells plates (Maxisorp-Nunc, Life Technologies, Basel, Switzerland) were coated overnight at 4°C with 1% BSA in PBS. After four washings with TTBS (50 mM Tris (pH 7.4) and 140 mM NaCl containing 0.05% Tween 20), 100 µl serum, serially diluted in 1% gelatin/PBS (final dilutions, 1/100, 1/200, and 1/400), were incubated for 2 h at room temperature. Wells were washed four times. Then, 100 µl/well alkaline phosphatase-conjugated goat anti-mouse IgG (Sigma) diluted 1/500 in TTBS was added for 30 min. After four washings with TTBS, color was developed with 100 µl/well p-nitrophenylphosphate (Sigma), and the reaction was stopped by adding 25 µl/well 3 M NaOH. Plate reading was performed at 405 nm, and results were calculated according to a standard curve with a reference serum. For determination of anti-mBSA-specific Ig isotypes, 50 µl/well of serum diluted 1/200 in 1% gelatin/PBS was incubated for 2 h at room temperature. After four washings in TTBS, 50 µl/well of a rat anti-mouse Ig isotype (from BD PharMingen, Allschwill, Switzerland), five different mAb, (each specific for murine IgG1, IgG2a, IgG2b, IgG3, IgM, and IgA, respectively) diluted 1/20 in 1% gelatin/PBS were incubated for 2 h at room temperature. Alkaline phosphatase-conjugated secondary Ab (100 µl/well; BD PharMingen) was added, and color was developed as described above. Plate reading was performed at 405 nm, and results were calculated according to a standard curve constructed with purified murine IgG1, IgG2a, IgG2b, or IgM or with a reference mouse serum for IgG3 and IgA.
Determination of serum levels of total Ig isotypes
Ninety-six-well plates (Maxisorp-Nunc) were coated overnight at 4°C h with 50 µl of one of each isotype-specific rat anti-mouse Ig (as described above) diluted 1/5 in PBS. After four washings in TTBS, each well was incubated with 200 µl blocking solution (1% BSA in PBS) for 30 min at room temperature. After four washings, 100 µl of the appropriate dilution of serum to be tested (1/2,000 for IgG3 and IgA, 1/10,000 for IgG1 and IgM, 1/50,000 for IgG2a, and 1/100,000 for IgG2b) were incubated for 2 h at room temperature. Then, alkaline phosphatase-labeled rat anti-mouse Ig mAb was added, and wells were processed as described above. Results were calculated according to a standard curve constructed with purified murine IgG1, IgG2a, IgG2b, and IgM or with a reference serum for IgG3 and IgA.
B lymphocyte purification and Ob-Rb identification by RT-PCR
Spleens from C57BL/6 mice were removed and disrupted. Erythrocytes from spleens were lysed, and the remaining cells were washed three times and counted. Splenocytes (50 x 106) were incubated for 30 min on ice with PE-conjugated B-220 (RA3-6B2) Ab (BD PharMingen) in a final volume of 1 ml. After three washes splenocytes were resuspended in serum-free DMEM at a concentration of 106 cells/ml. Sorting was performed on a FACStar+ cell sorter (BD Biosciences, San Jose, CA). Sorted B220-positive cells as well as B220-stained but unsorted splenocytes were stained with either FITC-conjugated anti-Mac-1 (M1/70) or anti-Thy-1.2 (TIB107) Abs, which specifically recognize monocytes and T lymphocytes, respectively. Double-stained cells were then analyzed using a FACSCalibur flow cytometer (BD Biosciences).
Total RNA from purified spleen B lymphocytes was extracted using TRIzol
(Life Technologies). One microgram of total RNA was treated with
Ampgrade DNase I (Life Technologies) and reverse transcribed, and PCR
was performed for 40 cycles at 94°C for 15 s, 57°C for 30
s, and 72°C for 90 s, using specific primers for Ob-Rb (long
isoform): 5'-ATT ATT TCC TCT TGT GTC CTA and 3'-GTC TGA TAA AAG GAA AAA
TGT (17). The integrity of the cDNA was determined by
assessing the relative levels of murine GAPDH as previously described
(18). Total spleen RNA was used as a control. The
amplified products were electrophoresed within a 1% agarose gel. The
amplified products of murine Ob-Rb and GAPDH were 587 and 211 bp in
size, respectively. The purity of B cell preparation was confirmed by
the absence of markers of T cells (IL-18R mRNA) or
monocytes/macrophages (FcR -chain mRNA) as assessed by RT-PCR.
Statistical analysis
The Wilcoxon/Kruskal-Wallis (rank-sum test) for unpaired variables was used to compare differences between groups with non-Gaussian distribution. The unpaired Student t test was used to compare the groups with normally distributed values. A level of p < 0.05 was considered statistically significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To explore whether leptin deficiency had an effect on the course
of AIA, we measured the levels of knee joint inflammation according to
the ratio of 99mTc uptake in the arthritic joint
over that in the nonarthritic contralateral knee joint at different
time points up to day 7 after the onset of arthritis (Fig. 1
). Three groups of mice were included in
these experiments, leptin-deficient ob/ob mice,
+/? Mice, and wild-type C57BL/6 mice (+/+). The results
showed that the levels of 99mTc uptake on days 1
and 3 were significantly lower in ob/ob mice than in
+/? and +/+ mice (on day 1, 1.44 ± 0.05 vs 1.9 ±
0.1 (p < 0.0002) and 1.86 ± 0.05
(p < 0.0005); on day 3, 1.33 ± 0.08 vs
1.52 ± 0.07 (p < 0.13) and 1.58 ±
0.07 (p < 0.04)). The levels of
99mTc uptake declined on day 7, and no
significant difference was observed between the different strains of
mice at this time point.
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). In both ob/ob
and control +/? and +/+ mice, overt signs of synovitis were seen in the
joints injected with mBSA. In contrast, no signs of inflammation were
present in contralateral knees injected with PBS (data not shown).
There was a clear difference in the thickness of synovial membrane
(noted sy on the figure), which was more inflamed in +/+ and +/? mice
than in ob/ob mice. The synovial thickness was graded
independently by two observers (N.B. and V.C.-P.) who were unaware of
animal genotype. The histologic scorings from +/? and +/+ were pooled
and considered as controls. As shown in Fig. 3, synovial thickness on day 4 of
arthritis was significantly higher in controls than in ob/ob
mice (4.3 ± 0.4 in control mice (n = 7) vs
2.6 ± 0.2 in ob/ob mice (n = 6);
p < 0.01). On day 8 of AIA there was a trend toward a
lower synovial inflammation score in ob/ob mice compared
with controls, although results did not reach statistical significance
(data not shown). The effect of AIA on articular cartilage degradation
was evaluated according to the proteoglycan content, as demonstrated by
Safranin-O staining. In contrast to the results on synovial
inflammation, cartilage damage scorings were not significantly
different in ob/ob compared with control mice (Fig. 3).
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and TNF- in
leptin-deficient (ob/ob) mice
Several studies in experimental models of arthritis suggested that
TNF- and IL-1 exert different effects. TNF- plays an important
role in the induction of synovial inflammation, whereas IL-1 could be
predominantly involved in the mechanisms leading to cartilage
destruction (19). Thus, we examined whether a difference
in IL-1 and TNF- levels can contribute to the discrepancy between
synovial thickness and cartilage damage in ob/ob mice. As
shown in Fig. 4, synovial levels of
IL-1 and TNF- mRNA were significantly decreased in the arthritic
knees of ob/ob compared with +/? mice on day 8 of arthritis.
Results in wild-type C57BL/6 mice were not different from those in +/?
mice (data not shown).
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The humoral response was examined by measuring the serum levels of
total Igs and of specific anti-mBSA Abs by ELISA in naive mice and
in immunized mice on day 8 after the onset of arthritis. Anti-mBSA Abs
were undetectable in nonimmunized mice (data not shown). In arthritic
mice, the circulating levels of anti-mBSA Abs were significantly
lower in ob/ob mice than in +/? and +/+ mice
(p < 0.003; Fig. 5). The serum levels of IgG isotypes,
IgM, and IgA were not significantly different in naive ob/ob
compared with +/? mice (Fig. 6A). In contrast, the levels
of anti-mBSA IgG1, IgG2a, IgG2b, IgG3, IgM, and IgA were
significantly lower in ob/ob than in control mice (Fig. 6B).
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). We also
measured the levels of IFN- and IL-10 in LNC supernatants, as
typical Th1 and Th2 cytokines, respectively. The mBSA-induced
production of IFN- was significantly lower in ob/ob mice
than in controls, whereas opposite results were observed for IL-10
(Fig. 8). The levels of IL-4 were not
detectable by ELISA in any of the tested conditions. This finding was
not unexpected, since other investigators observed that IL-4 production
was very weak using the same experimental system (20)
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In db/db mice a point mutation in the Ob-Rb gene
creates a new splice donor site that inserts a premature stop into the
Ob-Rb 3' end, resulting in the replacement of the long Ob-Rb by a short
intracytoplasmic tail of Ob-Ra (21). This mutation results
in the inability to respond appropriately to leptin and the presence of
an obese phenotype. Arthritis was induced in mice deficient in Ob-Rb
(db/db) and their lean littermates (+/?), as described
above. The results recapitulate the arthritic phenotype of
ob/ob mice. The severity of articular inflammation as
assessed by 99mTc uptake was lower in
db/db than in +/? mice on days 1, 3, and 7 of AIA, although
only the decrease on day 1 was statistically significant (Fig. 9A). The levels of Abs against
mBSA measured after 8 days of arthritis were lower in db/db
than in +/? mice (Fig. 9B). The proliferation rate of LNC in
response to mBSA in culture was also significantly lower in
db/db than in control mice (Fig. 9C). In
addition, production of IFN- in culture was lower in
db/db mice than in lean +/? littermates, whereas opposite
results were observed for IL-10 (Fig. 9, D and E,
respectively).
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Our results showed that circulating levels of anti-mBSA Abs of
any isotype were strongly reduced in arthritic ob/ob and
db/db mice as opposed to arthritic controls. We hypothesized
that leptin could have a direct effect on B lymphocytes and therefore
determined whether the long isoform of Ob-R was expressed by B cells
from C57BL/6 mice. Total RNA was extracted from B lymphocytes purified
from C57BL/6 spleen, and RT-PCR was performed with primers that
specifically amplify Ob-Rb cDNA. As shown in Fig. 10, B lymphocytes express Ob-Rb mRNA,
suggesting that leptin regulates directly the B cell responses.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, a Th1 cytokine, and an
increased secretion of IL-10, a Th2 cytokine, following stimulation
with mBSA in vitro. Immunized ob/ob mice also had decreased
circulating levels of anti-mBSA Ig isotypes compared with +/? mice.
Similar results were obtained in db/db mice, indicating that
the effects of leptin in AIA are mediated through its interaction with
Ob-Rb.
The results of several studies indicate that leptin plays an important
role in the regulation of immune responses. Leptin levels are regulated
by nutritional status and fall rapidly during starvation. Thymic and
lymphoid atrophy are well-recognized consequences of food deprivation
in humans and animals (22, 23, 24). A reduced delayed-type
hypersensitivity reaction to Ags observed during fasting can be
restored with leptin replacement (25). Consistent with
these findings, mice deficient in leptin exhibit evidence of defective
cell-mediated immunity and lymphoid atrophy, analogous to those
observed in chronic undernutrition in humans (7).
Ob/ob mice have a marked reduction in the size and
cellularity of thymus with a high level of thymocyte apoptosis, which
can be rescued by the exogenous administration of leptin
(8). Leptin stimulates the proliferation of
CD4+ T cells, with a stronger effect on naive
CD4+ CD45RO+ than on memory
CD4+ CD45RA+ T cells, thus
playing an important role in primary T cell immune responses
(7). In addition, leptin has been shown to promote Th1
responses (7). Consistent with these studies we observed
that T cell proliferation and production of IFN- by isolated LNC
were significantly decreased in ob/ob mice.
Circulating levels of anti-mBSA IgG, IgM, and IgA were significantly lower in arthritic ob/ob than in control mice. This impaired humoral response can be secondary to a direct effect of leptin signaling on B cells and/or to an indirect effect of leptin on CD4+ T cell function. By RT-PCR we showed that Ob-Rb mRNA is expressed by isolated murine B cells, suggesting that leptin can act directly on B cells to regulate the production of Ig. A direct effect of leptin on B cells is also supported by previous studies showing that the number of peripheral and bone marrow B cells is decreased in db/db mice (26). Cognate interactions between B cells and Ag-specific CD4+ Th cells play an important role in the activation and maturation of the humoral response. Thus, the presence of impaired T cell responses is also likely to contribute to the decreased Ig production in ob/ob and db/db mice. In addition to these direct cell-cell interactions between B and T lymphocytes, the Ig production is modulated by CD4+ T cell-derived lymphokines. Indeed, Th1 cytokines enhance the production of IgG2a and IgG3, whereas Th2 cytokines promote the synthesis of IgG1 (27, 28, 29). However, the presence of decreased anti-mBSA IgG levels in ob/ob mice cannot be solely explained by a switch toward Th2 responses, as the levels of all IgG subtypes were lower in leptin-deficient mice.
The presence of hyperglycemia and high cortisol levels in ob/ob animals can also decrease the immune responses. However, previous experiments with food restriction showed that reduced plasma levels of cortisol and glucose did not reverse the immune defects in ob/ob mice, whereas leptin replacement restored a normal immune response in ob/ob mice (7, 8). In addition, humans with congenital leptin deficiencies secondary to mutations in the ob gene exhibit low total T cell counts, impaired cell-mediated immune responses, and an increased rate of infections in the absence of hypercortisolemia and hyperglycemia (30, 31). Taken together, these findings in rodents and humans suggest that leptin deficiency is directly responsible for the immune abnormalities in ob/ob mice.
The experimental model of arthritis used in this study required prior immunization with mBSA. As leptin-deficient and leptin receptor-deficient mice have impaired immune responses, we were not able to analyze separately the effect of leptin signaling on the inflammatory response. This question is of interest, since the results of some in vitro and in vivo studies suggested that leptin may exert anti-inflammatory actions (9, 10, 32). Studies are currently in progress in our laboratory using a model in which active immunization is not required for the development of arthritis.
The results of histology studies showed that ob/ob mice had
a lower score for synovial thickness, indicating the presence of
decreased synovial inflammation compared with control mice. In
contrast, there was no statistical difference between ob/ob
and control mice regarding cartilage degradation. This uncoupling
between synovial inflammation and cartilage destruction can be related
to the relative contribution of cytokines such as TNF- and IL-1
(19). However, the results of RNase protection assays
showed that the mRNA levels of both TNF- and IL-1 were decreased
in ob/ob mice, indicating that our results cannot be
explained by a predominant contribution of one of these cytokines.
Although other cytokines can also be involved, it is likely that the
discrepancy between synovial inflammation and tissue damage may be due
to a lack of sensitivity of Safranin-O staining to detect subtle
changes in cartilage degradation.
Several different isoforms of leptin receptor (Ob-Ra to Ob-Rf) have been cloned. They are produced from the same gene by mRNA splicing and contain a common extracellular domain (29). Ob-Rb has a long cytoplasmic tail and is considered of prime importance for leptin signaling. Ob-Ra has a shorter cytoplasmic domain and is the predominant Ob-R isoform found in most tissues and cells (33). Using transfection experiments, Ob-Ra was able to transduce intracellular signals upon binding with its ligand (34). However, no definitive demonstration of the signaling role of this short Ob-R isoform has been reported to date. The milder form of AIA in mice deficient in Ob-Rb is in accordance with the presence of defective T cell immune responses in db/db mice (35) and reproduces the results in ob/ob mice, thus indicating that the effect of leptin in AIA is mediated through its interaction with Ob-Rb.
LNC isolated from ob/ob and db/db mice produced high levels of IL-10 in the presence of mBSA. IL-10 is a Th2 cytokine that has been demonstrated to possess anti-inflammatory properties (36). Similar findings, including milder AIA, decreased LNC proliferation, and enhanced IL-10 production in vitro, were observed in IL-6 knockout mice (20), suggesting that IL-6 and leptin may have common effects. Indeed, leptin augments IL-1-induced corticosterone and IL-6 production, two effects typically observed after administration of IL-6-related cytokines (37, 38). In addition, both leptin and IL-6 are able to stimulate the production of IL-1Ra by monocytes in culture (32, 39). Finally, leptin and its receptor have structural similarities with IL-6 family members. Ob-Rb is related to class I cytokine receptors, which include gp-130, the common signal-transducing component for the IL-6-related receptor family (33). Ob-Rb has signaling activities similar to those of IL-6-type cytokine receptors, including activation of the STAT3 and ERK pathways (40, 41). Taken together, these structural and functional homologies may explain the presence of common findings in mice deficient in IL-6 and in ob/ob and db/db mice.
In conclusion, our results in leptin-deficient and leptin receptor-deficient mice indicate that leptin plays an important role in the regulation of cellular and humoral responses. Future studies should be performed to determine whether therapies interacting with leptin signaling would be of value in the treatment of patients with arthritis and other immune-mediated inflammatory disorders.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Cem Gabay, Division of Rheumatology, University Hospital of Geneva, 26 Avenue Beau-Séjour, 1211 Geneva 14, Switzerland. E-mail address: cem.gabay{at}hcuge.ch
3 Abbreviations used in this paper: Ob-R, leptin receptor; AIA, Ag-induced arthritis; db/db, leptin receptor-deficient mice; LNC, lymph node cells; mBSA, methylated BSA; Ob, leptin protein; ob/ob, leptin-deficient mice; RA, rheumatoid arthritis; 99mTc,, 99mTc-labeled technetium pertechnetate99m.
Received for publication June 13, 2001. Accepted for publication November 2, 2001.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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 A. Batra, J. Pietsch, I. Fedke, R. Glauben, B. Okur, T. Stroh, M. Zeitz, and B. Siegmund Leptin-Dependent Toll-Like Receptor Expression and Responsiveness in Preadipocytes and Adipocytes Am. J. Pathol., June 1, 2007; 170(6): 1931 - 1941. [Abstract] [Full Text] [PDF]
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 M. S. Desruisseaux, Nagajyothi, M. E. Trujillo, H. B. Tanowitz, and P. E. Scherer Adipocyte, Adipose Tissue, and Infectious Disease Infect. Immun., March 1, 2007; 75(3): 1066 - 1078. [Full Text] [PDF]
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 M. J. Ryan, G. R. McLemore Jr, and S. T. Hendrix Insulin Resistance and Obesity in a Mouse Model of Systemic Lupus Erythematosus Hypertension, November 1, 2006; 48(5): 988 - 993. [Abstract] [Full Text] [PDF]
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G. Palmer, M. Aurrand-Lions, E. Contassot, D. Talabot-Ayer, D. Ducrest-Gay, C. Vesin, V. Chobaz-Peclat, N. Busso, and C. Gabay Indirect Effects of Leptin Receptor Deficiency on Lymphocyte Populations and Immune Response in db/db Mice. J. Immunol., September 1, 2006; 177(5): 2899 - 2907. [Abstract] [Full Text] [PDF]
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 A. Schaffler, U. Muller-Ladner, J. Scholmerich, and C. Buchler Role of Adipose Tissue as an Inflammatory Organ in Human Diseases Endocr. Rev., August 1, 2006; 27(5): 449 - 467. [Abstract] [Full Text] [PDF]
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M. Otero, R. Lago, R. Gomez, C. Dieguez, F. Lago, J. Gomez-Reino, and O. Gualillo Towards a pro-inflammatory and immunomodulatory emerging role of leptin Rheumatology, August 1, 2006; 45(8): 944 - 950. [Abstract] [Full Text] [PDF]
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 P. Plaisancie, R. Ducroc, M. E. Homsi, A. Tsocas, S. Guilmeau, S. Zoghbi, O. Thibaudeau, and A. Bado Luminal leptin activates mucin-secreting goblet cells in the large bowel Am J Physiol Gastrointest Liver Physiol, April 1, 2006; 290(4): G805 - G812. [Abstract] [Full Text] [PDF]
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 E. A. Oral, E. D. Javor, L. Ding, G. Uzel, E. K. Cochran, J. R. Young, A. M. DePaoli, S. M. Holland, and P. Gorden Leptin Replacement Therapy Modulates Circulating Lymphocyte Subsets and Cytokine Responsiveness in Severe Lipodystrophy J. Clin. Endocrinol. Metab., February 1, 2006; 91(2): 621 - 628. [Abstract] [Full Text] [PDF]
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 C.-H. Lee, Y.-G. Chen, J. Chen, P. C. Reifsnyder, D. V. Serreze, M. Clare-Salzler, M. Rodriguez, C. Wasserfall, M. A. Atkinson, and E. H. Leiter Novel Leptin Receptor Mutation in NOD/LtJ Mice Suppresses Type 1 Diabetes Progression: II. Immunologic Analysis Diabetes, January 1, 2006; 55(1): 171 - 178. [Abstract] [Full Text] [PDF]
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 C Popa, M G Netea, T R D S Radstake, P L van Riel, P Barrera, and J W M van der Meer Markers of inflammation are negatively correlated with serum leptin in rheumatoid arthritis Ann Rheum Dis, August 1, 2005; 64(8): 1195 - 1198. [Abstract] [Full Text] [PDF]
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B. Mattioli, E. Straface, M. G. Quaranta, L. Giordani, and M. Viora Leptin Promotes Differentiation and Survival of Human Dendritic Cells and Licenses Them for Th1 Priming J. Immunol., June 1, 2005; 174(11): 6820 - 6828. [Abstract] [Full Text] [PDF]
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 J. P. McGillis White Adipose Tissue, Inert No More! Endocrinology, May 1, 2005; 146(5): 2154 - 2156. [Full Text] [PDF]
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J. A. Sennello, R. Fayad, A. M. Morris, R. H. Eckel, E. Asilmaz, J. Montez, J. M. Friedman, C. A. Dinarello, and G. Fantuzzi Regulation of T Cell-Mediated Hepatic Inflammation by Adiponectin and Leptin Endocrinology, May 1, 2005; 146(5): 2157 - 2164. [Abstract] [Full Text] [PDF]
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G. Matarese, P. B. Carrieri, A. La Cava, F. Perna, V. Sanna, V. De Rosa, D. Aufiero, S. Fontana, and S. Zappacosta Leptin increase in multiple sclerosis associates with reduced number of CD4+CD25+ regulatory T cells PNAS, April 5, 2005; 102(14): 5150 - 5155. [Abstract] [Full Text] [PDF]
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G. Matarese, S. Moschos, and C. S. Mantzoros Leptin in Immunology J. Immunol., March 15, 2005; 174(6): 3137 - 3142. [Abstract] [Full Text] [PDF]
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J. L. Chan, S. J. Moschos, J. Bullen, K. Heist, X. Li, Y.-B. Kim, B. B. Kahn, and C. S. Mantzoros Recombinant Methionyl Human Leptin Administration Activates Signal Transducer and Activator of Transcription 3 Signaling in Peripheral Blood Mononuclear Cells in Vivo and Regulates Soluble Tumor Necrosis Factor-{alpha} Receptor Levels in Humans with Relative Leptin Deficiency J. Clin. Endocrinol. Metab., March 1, 2005; 90(3): 1625 - 1631. [Abstract] [Full Text] [PDF]
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 M. Granado, T. Priego, A. I. Martin, M. A. Villanua, and A. Lopez-Calderon Anti-inflammatory effect of the ghrelin agonist growth hormone-releasing peptide-2 (GHRP-2) in arthritic rats Am J Physiol Endocrinol Metab, March 1, 2005; 288(3): E486 - E492. [Abstract] [Full Text] [PDF]
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S. Ikejima, S. Sasaki, H. Sashinami, F. Mori, Y. Ogawa, T. Nakamura, Y. Abe, K. Wakabayashi, T. Suda, and A. Nakane Impairment of Host Resistance to Listeria monocytogenes Infection in Liver of db/db and ob/ob Mice Diabetes, January 1, 2005; 54(1): 182 - 189. [Abstract] [Full Text] [PDF]
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 B. Siegmund, J. A. Sennello, H. A. Lehr, A. Batra, I. Fedke, M. Zeitz, and G. Fantuzzi Development of intestinal inflammation in double IL-10- and leptin-deficient mice J. Leukoc. Biol., October 1, 2004; 76(4): 782 - 786. [Abstract] [Full Text] [PDF]
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F. Peelman, K. Van Beneden, L. Zabeau, H. Iserentant, P. Ulrichts, D. Defeau, A. Verhee, D. Catteeuw, D. Elewaut, and J. Tavernier Mapping of the Leptin Binding Sites and Design of a Leptin Antagonist J. Biol. Chem., September 24, 2004; 279(39): 41038 - 41046. [Abstract] [Full Text] [PDF]
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 G Matarese and R I Lechler Leptin in intestinal inflammation: good and bad gut feelings Gut, July 1, 2004; 53(7): 921 - 922. [Full Text] [PDF]
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B Siegmund, J A Sennello, J Jones-Carson, F Gamboni-Robertson, H A Lehr, A Batra, I Fedke, M Zeitz, and G Fantuzzi Leptin receptor expression on T lymphocytes modulates chronic intestinal inflammation in mice Gut, July 1, 2004; 53(7): 965 - 972. [Abstract] [Full Text] [PDF]
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 T. E. Weber and M. E. Spurlock Leptin alters antibody isotype in the pig in vivo, but does not regulate cytokine expression or stimulate STAT3 signaling in peripheral blood monocytes in vitro J Anim Sci, June 1, 2004; 82(6): 1630 - 1640. [Abstract] [Full Text] [PDF]
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 A. S.M. Shamsuzzaman, M. Winnicki, R. Wolk, A. Svatikova, B. G. Phillips, D. E. Davison, P. B. Berger, and V. K. Somers Independent Association Between Plasma Leptin and C-Reactive Protein in Healthy Humans Circulation, May 11, 2004; 109(18): 2181 - 2185. [Abstract] [Full Text] [PDF]
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R. M. Tarzi, H. T. Cook, I. Jackson, C. D. Pusey, and G. M. Lord Leptin-Deficient Mice Are Protected from Accelerated Nephrotoxic Nephritis Am. J. Pathol., February 1, 2004; 164(2): 385 - 390. [Abstract] [Full Text] [PDF]
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 L. M. Gaetke, H. S. Oz, R. C. Frederich, and C. J. McClain Anti-TNF-{alpha} Antibody Normalizes Serum Leptin in IL-2 Deficient Mice J. Am. Coll. Nutr., October 1, 2003; 22(5): 415 - 420. [Abstract] [Full Text] [PDF]
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G Palmer and C Gabay A role for leptin in rheumatic diseases? Ann Rheum Dis, October 1, 2003; 62(10): 913 - 915. [Full Text]
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M Bokarewa, D Bokarew, O Hultgren, and A Tarkowski Leptin consumption in the inflamed joints of patients with rheumatoid arthritis Ann Rheum Dis, October 1, 2003; 62(10): 952 - 956. [Abstract] [Full Text]
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 G. K. Bhat, M. L. Hamm, J. U. Igietseme, and D. R. Mann Does Leptin Mediate the Effect of Photoperiod on Immune Function in Mice? Biol Reprod, July 1, 2003; 69(1): 30 - 36. [Abstract] [Full Text] [PDF]
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 A. M. Madiehe, T. D. Mitchell, and R. B. S. Harris Hyperleptinemia and reduced TNF-alpha secretion cause resistance of db/db mice to endotoxin Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2003; 284(3): R763 - R770. [Abstract] [Full Text] [PDF]
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