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Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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, IL-1ß,
and IFN-
as well as membrane molecules such as LFA-1, CD40 ligand,
and membrane bound TNF-. Finally, chemotactic bioassays of T
cell/RTEC coculture supernatants demonstrated 80% reduction of
monocyte migration following MCP-1 neutralization, indicating a
dominant role for this chemokine. In summary, activation of renal
tubular cells by infiltrating T cells can amplify and perpetuate local
inflammatory responses through chemokine production differentially
mediated by soluble and cell contact-dependent factors. Recognition of
this regulatory diversity has important implications in the choice of
potential therapeutic targets in GN. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Recruitment of circulating leukocytes to inflammatory sites is directed
by a multistep cascade of molecular interactions coordinated by locally
expressed chemoattractant and adhesion molecules (6). The
8- to 11-kDa chemokines, produced by a wide variety of stimulated cell
types, including leukocytes and resident renal cells (7),
play a central role in this process. They activate leukocyte-integrin
molecules to facilitate firm endothelial adhesion (8) and
provide a chemotactic gradient for trans- and subendothelial leukocyte
migration (9). Recent studies have shown that
chemokine functions extend to include activation of mononuclear cells
(10, 11), modulation of collagen synthesis, and fibrosis
(12, 13). Chemokines are subdivided into four major
classes, based on cysteine motifs (14). Members of
individual subgroups direct chemotaxis and activation of specific
leukocyte subsets, such that differential expression at sites of
inflammation dictates the profiles of tissue-infiltrating leukocytes
(7, 15). The C-C chemokines, monocyte chemoattractant
protein-1 (MCP-1),2
RANTES, and macrophage inflammatory protein-1 and -ß (MIP-1 and
MIP-1ß), and the C-X-C chemokine IFN-inducible protein-10 (IP-10) are
predominantly involved in the recruitment of macrophages and T cells
(16).
Both in vitro and in vivo studies have demonstrated that RTEC represent
a prominent source for the production of inflammatory mediators. Thus,
upon stimulation by proinflammatory cytokines, cultured human RTEC
produce MCP-1 and RANTES (17, 18). In a murine model of
interstitial nephritis, up-regulation of interstitial expression of
IP-10 correlates with the extent of mononuclear cell infiltration
(19). Studies in humans demonstrated interstitial
expression of MCP-1, RANTES, MIP-1, and MIP-1ß in a variety of
glomerulonephritides (GN) (20).
Direct evidence implicating chemokines in renal interstitial injury has come from animal studies. In a murine model of crescentic nephritis, neutralization of MCP-1 decreased both glomerular crescent formation and interstitial fibrosis, while neutralization of RANTES only decreased glomerular injury (12). In the same model a paucity of MCP-1 resulted in a dramatic reduction of tubular damage (21). Ectopic expression of RANTES in renal tubular epithelial cells in a murine model of lupus enhanced interstitial mononuclear cell infiltration (22).
As chemokine production by RTEC can be an important regulatory mechanism for interstitial infiltration by mononuclear cells, a major question is how this is regulated. Previous investigations have suggested a potential role of T cells in this process (17, 18, 23). T cells may stimulate RTEC either via soluble factors or by direct cell-to-cell contact. Cell-to-cell contact mediates important biologic effects of T cells that, in some cases, are distinct from those mediated by soluble factors (24, 25, 26, 27). In this study we sought to identify the soluble factors and the cell surface molecules and their relative contributions to chemokine production by RTEC. We employed a cell culture system that uses a semipermeable membrane to physically separate T cells from RTEC (and thereby delineate the relative contribution of cell-to-cell contact) in combination with chemotaxis assays. Our data demonstrate that T cells stimulate RTEC to secrete chemokines through both soluble inflammatory cytokines and cell-to-cell contact-dependent pathways, and identify key molecules involved in this interaction.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The following Abs, recombinant cytokines, and proteins were used
in these experiments: monoclonal mouse anti-human TNF- (R&D
Systems, Minneapolis, MN), monoclonal mouse anti-human IL-1ß
(Genzyme, Cambridge, MA), monoclonal mouse anti-human IFN- (R&D
Systems), monoclonal mouse anti-human CD11a/LFA-1 (PharMingen, San
Diego, CA), monoclonal mouse anti-human CD40L (Ancell, Bayport,
MN), monoclonal mouse anti-human MCP-1 (PharMingen), monoclonal
mouse anti-human RANTES (R&D Systems), recombinant human TNF-
and IL-1ß (R&D Systems), recombinant human IFN- (Genzyme), and
trimeric human CD40 ligand/leucine zipper fusion protein (a gift from
Immunex, Seattle, WA).
T cell purification and culture
PBMC were isolated from normal donors by density gradient centrifugation. T cells were enriched by adherence on culture flask for 16 h at 37oC. T cell purity was assessed by FACS analysis using fluoresceinated mAb (Becton Dickinson, Mountain View, CA) with specificity for the following cell surface markers: CD14 (monocytes), CD3 (T cells), CD19 (B cells), and CD56 (NK cell). The T cell fraction routinely consisted of >80% CD3-expressing cells, <0.5% CD19-expressing cells, 3% CD14-expressing cells, and 10% CD56-expressing cells. In some experiments, CD4+ or CD8+ cells were positively selected from PBMC using anti-CD4 mAb- or anti-CD8 mAb-coupled magnetic beads (Dynal, Oslo, Norway) and then detached from beads by use of DETACHABEAD CD4/CD8 (Dynal), following the manufacturer’s manual. The purity of selected CD4+ or CD8+ cells was routinely >96%, as judged as CD4- or CD8-positive cells by FACS analysis. T cells were cultured in RPMI 1640 (Life Technologies, Gaithersburg, MD) supplemented with 10% heat-inactivated FBS (HyClone, Logan, UT), 2 mM L-glutamine, 100 IU/ml penicillin, and 100 µg/ml streptomycin (all from Life Technologies).
RTEC culture
Normal human RTEC were purchased from Clonetics (San Diego, CA). RTEC were cultured in renal epithelial basal medium (REBM), supplemented with 0.5% FBS, 10 ng/ml of recombinant human epidermal growth factor, 5 µg/ml of insulin, 0.5 µg/ml of hydrocortisone, 50 µg/ml of gentamicin, 50 ng/ml of amphotericin B, 0.5 µg/ml of epinephrine, 6.5 ng/ml triiodothyronine, and 10 µg/ml of transferrin (all from Clonetics). For these experiments we used RTEC passages 3–5.
T cells/RTEC coculture
T cells were cultured at 2 x 106/ml for 6 or 24 h in 10% FBS RPMI medium in the presence or the absence of 10 nM PMA (Sigma, St. Louis, MO) and 1 µM Ionomycin (Calbiochem, La Jolla, CA). T cells were washed three times and resuspended to a final concentration of 1 x 105/ml in supplemented REBM. RTEC were harvested at 80% confluence and cultured in 24-well plates at 6 x 104 cell/0.6 ml/well in triplicate for 16 h. In preliminary experiments serial 2-fold increments (T cells:RTEC; 0.5:1 to 2:1) were examined. A dose response was observed, with higher ratios resulting in more stimulation. Although stimulation was detected at a ratio of 0.5:1, we elected to use the ratio of 1:1 because at this ratio an adequate amount of chemokine was induced to allow meaningful comparisons without using an excess of T cells. Subsequently, 6 x 104 of prepared T cells were added to 6 x 104 RTEC. In some experiments identical parallel cultures were established in which T cells were separated from RTEC by a 0.4-µm pore size semipermeable membrane (Biocoat, Falcon, Becton Dickinson Labware, Bedford, MA) while sharing the same medium. After 24-h incubation at 37oC supernatants were harvested and stored at -20oC for chemokine determination and chemotaxis assays.
Membrane preparations from T cells
Crude plasma membrane was prepared as described previously (25). Briefly, T cells were disrupted by sonication (five 5-s bursts of 90 W each) in PBS containing 0.68 M sucrose, 200 µM PMSF, and 5 mM EDTA. The lysate was centrifuged for 15 min at 4,000 x g to discard nuclei and unbroken cells. The supernatant was centrifuged for 45 min at 100,000 x g, and the pellet containing the membrane fraction was resuspended at the theoretical concentration of 10 x 106 cell equivalent/ml in supplemented REBM.
Inhibition of cytokine synthesis by neutralizing Abs
Abs against CD11a/LFA-1, CD40L, TNF-, IL-1ß, IFN-, or
IgG1 of irrelevant specificity (Sigma) were incubated at 10 µg/ml
with T cells or membrane preparations of T cells for 30 min at room
temperature and were added without washing to RTEC as described above.
Chemokine synthesis after 24 h was determined by ELISA.
Chemotaxis assay
Chemotaxis assay was performed as previously described (28). Supernatants of 24-h-stimulated (24h-S) T cells alone, RTEC alone, or coculture of 24h-S T cells/RTEC were centrifuged at 10,000 x g for 10 min to remove the contamination of cells and were diluted with supplemented REBM. Human PBMC (5 x 105) in 100 µl of supplemented REBM were added to the upper chamber of a 6.5-mm diameter, 5-µm pore size polycarbonate Transwell culture insert (Costar, Cambridge, MA) and incubated in duplicate with 500 µl of supplemented REBM or prepared supernatants in the lower chamber for 2 h at 37oC. For the neutralizing experiments, undiluted supernatants obtained from cocultures were preincubated with Abs against MCP-1, RANTES, or IgG of irrelevant specificity at 10 µg/ml for 30 min at room temperature. Cells that transmigrated into the lower chamber were vigorously suspended and counted with a FACScan (Becton Dickinson, San Jose, CA) for 30 s at 60 µl/min, gating on the forward and side scatter of monocytes or lymphocytes. A 1/20 dilution of input PBMC was similarly counted, which was considered to be 100% migration.
Determination of chemokine production
MCP-1, RANTES, IP-10, MIP-1, and MIP-1ß were measured by
ELISA (R&D Systems and Endogen, Woburn, MA).
Statistical analysis
All experiments were repeated at least three times. Results are presented as the mean ± SE from three separate experiments. Statistical significance was determined by Student’s t test. A value of p < 0.05 was considered to represent a statistically significant difference between group means.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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MCP-1, RANTES, MIP-1, MIP-1ß, and IP-10 are major mononuclear
cell-directed chemokines expressed in the interstitium of a variety of
glomerulonephritides (19, 20). We first examined whether
stimulated T cells induced the production of these chemokines by RTEC.
After determining the optimal T cell/RTEC ratio and duration of
coculture (see Materials and Methods), we stimulated T cells
with PMA and ionomycin for both 6 and 24 h. This
assures maximum expression of molecules such as TNF- and CD40L,
which are known to peak 6–8 h after stimulation and decrease 24 h
later (29). T cells washed extensively were cocultured
with RTEC at a ratio of 1:1 for 24 h. At the same time, identical
parallel cultures were established in which T cells were separated from
RTEC by a 0.4-µm pore size semipermeable membrane while sharing the
same medium. In this coculture system separated T cells stimulate RTEC
exclusively through soluble molecules, thus enabling determination of
the contribution of cell-to-cell contact.
As shown in Fig. 1
, T cells induced
up-regulation of MCP-1, IP-10, and RANTES production, but failed to
induce up-regulation of MIP-1 and MIP-1ß (data not shown). Because
in the absence of RTEC stimulated T cells alone produced negligible
amounts of MCP-1 and IP-10 and small amounts of RANTES (Fig. 1), we
assumed that the major source of chemokine production in these
cocultures was RTEC. This was corroborated by subsequent experiments
using plasma membrane preparations from stimulated T cells (see below).
Production of these chemokines was T cell contact dependent, because
separation of T cells from RTEC significantly decreased their levels,
although soluble factors alone induced significant amounts of MCP-1 and
IP-10. Notably, RANTES synthesis was exclusively cell-to-cell contact
dependent, as separation of T cells decreased it to levels comparable
to those obtained with T cells alone. In summary, activated T cells
induce MCP-1, RANTES, and IP-10 (but not MIP-1 or MIP-1ß)
production by RTEC through both soluble factors and cell-to-cell
contact-dependent mechanisms.
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In chronic renal diseases T cells infiltrating the renal
interstitium consist of both CD4+ and
CD8+ cells (4, 5).
CD4+ or CD8+ cells were
positively selected from PBMC using anti-CD4 or anti-CD8
mAb-coupled magnetic beads and stimulated with PMA and ionomycin for 6
or 24 h. Stimulated cells were next cocultured both in contact
with and separated from RTEC as described before. Both
CD4+ and CD8+ cells induced
comparable chemokine production. This property was better sustained in
CD8+ cells, because chemokine production at
24 h was higher in this subset (Fig. 2).
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We next sought to identify the cytokines and cell surface
molecules involved in this interaction. TNF-, IL-1ß, and IFN-
are major proinflammatory cytokines produced by activated T cells.
Previous investigations have demonstrated that rTNF- and rIL-1
induce MCP-1 by RTEC in vitro (17). CD40L, a costimulatory
molecule expressed on activated T cells, and the LFA-1/ICAM-1 pathway
have also been shown to be critical in many T cell-mediated
inflammatory responses (30, 31, 32). Therefore, we
blocked these molecules using neutralizing Abs by preincubating
activated T cells with neutralizing Abs (or IgG of irrelevant
specificity) for 30 min and adding them to RTEC. Twenty-four hours
later, chemokine production was determined by ELISA. The percent
inhibition relative to cocultures without Abs was calculated as
described in Fig. 3.
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A, blockade of TNF-, IL-1ß, or
IFN- alone significantly reduced RTEC MCP-1 synthesis in cocultures
of 6h-S T cells, but had no effect in cocultures of 24h-S T cells. In
contrast, simultaneous blockade of TNF-, IL-1ß, and IFN-
decreased RTEC MCP-1 production in cocultures of both 6h-S and 24h-S T
cells (Fig. 3A), suggesting that different mechanisms
operate through sequential T cell activation. Similarly, blockade of
TNF-, IL-1ß, or IFN- separately decreased RANTES synthesis in
cocultures of 6h-S T cells, while only simultaneous blockade
significantly reduced it in cocultures of 24h-S T cells. Interestingly,
blockade of LFA-1 or CD40L resulted in dramatic reduction of RANTES
(Fig. 3B), but not MCP-1 or IP-10 (data not shown),
synthesis induced by 6h-S T cells. T cell induction of IP-10 by RTEC
was IFN- dependent. Blockade of IFN- alone achieved a >60%
decrease in IP-10 synthesis by RTEC in cocultures of both 6h-S and
24h-S T cells. Thus, chemokines manifest differential requirements for
cell and soluble effector pathways that we sought to better define in
subsequent experiments. Role of membrane-bound cytokines
Several studies have suggested a significant role for T cell
membrane-bound TNF- and IFN- in inflammatory responses (25, 33). To address the role of membrane-bound TNF- and IFN-
in the interactions between RTEC and activated T cells, we next
examined whether plasma membrane preparations from stimulated T cells
could induce chemokine production by RTEC. Crude plasma membrane
fractions from T cells were cocultured with RTEC at the theoretical
ratio of 10:1 (T cells:RTEC). Membrane preparation from 6h-S or 24h-S T
cells induced MCP-1 and IP-10 (Fig. 4A), but not RANTES (data not
shown). Simultaneous blockade of TNF- and IFN- by specific
neutralizing Abs decreased MCP-1 synthesis by 50% (Fig. 4B). These results suggest that in addition to the soluble
form, the membrane form of TNF- and IFN- may be involved in T
cell induction of chemokines by RTEC.
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Since their cooperative effects on production of a panel of
chemokines by RTEC have not previously defined, we next characterized
in more details the role of cytokines and CD40L. In preliminary
experiments we determined the optimal concentrations of cytokines to
induce maximum response by RTEC. RTEC were cultured for 24 h in
the presence or the absence of rTNF- (10 ng/ml), rIL-1ß (2 ng/ml),
rIFN- (500 IU/ml), or combinations of these cytokines and soluble
CD40L, and chemokine synthesis was determined by ELISA. As shown in
Fig. 5A, IL-1ß induced a
higher level of MCP-1 compared with TNF-. IFN- in combination
with TNF- or IL-1ß, but not alone, enhanced MCP-1 synthesis. The
production of RANTES required multiple cytokines, as neither TNF-,
IL-1ß, nor IFN- alone induced significant RANTES synthesis; it
required the combination of all these cytokines. Of interest, although
IP-10 synthesis was IFN- dependent, IFN- alone could not induce
significant IP-10 synthesis. IFN- in combination with TNF- or
IL-1ß (but not combination of TNF- with IL-1ß) induced a high
level of IP-10. These data demonstrate that IFN- is necessary, but
not sufficient, to induce IP-10 synthesis.
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), we also examined the effect of rCD40L. Thus, we
next cultured RTEC in the presence or the absence of rCD40L (3
µg/ml), rIFN- (500 IU/ml), or their combination. CD40L in
combination with IFN-, but not alone, induced dramatic up-regulation
of MCP-1 and RANTES (Fig. 5B). MCP-1 induces significant monocyte migration
Direct evidence from animal models of GN and circumstantial
evidence from analysis of tissues obtained from patients with a variety
of GN have suggested an important role of monocyte migration in
mediating tubulointerstitial injury. Because several chemokines are
produced during T cell/RTEC interaction, it was necessary to examine
their relative contributions to monocyte migration in chemotaxis
assays. Freshly isolated human PBMC in supplemented REBM were added to
the upper chamber of a 5-µm pore size polycarbonate Transwell filter.
Supernatants of T cells alone, RTEC alone, or cocultures of 24h-S T
cells/RTEC were added to the lower chamber, either directly or after
dilution with supplemented REBM. After a 2-h incubation, monocytes or
lymphocytes that transmigrated into the lower chamber were counted by
FACScan gating on the forward and side scatters. As shown in Fig. 6A, coculture supernatants
induced significant monocyte migration in a dose-dependent fashion,
while supernatants of RTEC or T cells alone did not. Interestingly,
monocyte migration was only blocked by neutralization of MCP-1, not
that of RANTES (Fig. 6B). Moreover, although high levels of
IP-10 and RANTES were present in the coculture supernatants,
lymphocytes did not significantly migrate in response to them (data not
shown). This may be due to the low level of chemokine receptor
expression on rested lymphocytes (34, 35). We did not use
activated T cells in these chemotaxis experiments, because T cells
produce chemokines upon activation, and this may confound the
results.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Previous in vitro studies have shown that proinflammatory cytokines,
such as TNF-, IL-1ß, and IFN-, or ligation of CD40 on the
surface of RTEC induce MCP-1 and RANTES production by RTEC (17, 18, 37). These studies, however, did not address the relative
importance of these inflammatory mediators in the context of adjacent
activated T cells as would be expected in vivo. We have now
systematically examined such T cell/RTEC interactions. Our observations
indicate that MCP-1, IP-10, and RANTES are synthesized in distinct
regulatory cascades that differentially use soluble and cell
contact-dependent pathways. Functional assays indicated that MCP-1
accounted for 
80% of the chemotactic activity toward monocytes
arising from T cell/RTEC interactions. Monocyte migration in the
interstitium is important for subsequent tubular injury
(12). Moreover, animal models of GN define an important
role of MCP-1 in interstitial infiltration and tubular injury. Of
interest, MCP-1 exhibited the least stringent activation requirements
in our assay. Thus, although soluble factors and cell contact were
required to achieve maximal MCP-1 production, either mechanism alone
induced the secretion of significant amounts of MCP-1. Neutralization
of IL-1ß and TNF- in combination accounted for 60–70% of MCP-1
production. IFN-, although insufficient by itself to induce MCP-1,
further enhanced the effects of TNF-, IL-1ß, and CD40L.
Although regulation of IP-10 production resembled that of MCP-1,
important differences emerged. Compared with MCP-1 and RANTES,
synthesis of IP-10 was more dependent upon IFN-. IP-10 is
up-regulated in animal models of interstitial nephritis
(19). Our chemotaxis assay, however, suggested that IP-10
is unlikely to be involved in the migration of monocytes, consistent
with previous findings that monocytes do not posses CXCR3, the only
receptor reported to date for IP-10 (34). In contrast, it
is probable that IP-10 may be involved in the migration of activated
CXCR3+ T cells into inflamed interstitium. Such T
cell recruitment will probably further enhance IP-10 and other
chemokine expression through the pathways defined above. Resting
lymphocytes express very low levels of chemokine receptors (34, 35), and this may account for their lack of migration in our
assay.
A pathogenic role for RANTES has been proposed for glomerular injury,
interstitial mononuclear cell infiltration, and interstitial rejection
of renal allografts (12, 22, 37). Our chemotaxis assays
suggest that RANTES may play a predominant role in migration (and
activation) of T cells, rather than macrophages. In contrast to MCP-1
and IP-10, synthesis of RANTES required the simultaneous presence of
both soluble factors and cell contact. Separation of cells
significantly decreased RANTES production, and membrane preparations
from activated T cells alone failed to induce significant synthesis.
Neutralizing experiments implicated TNF-, IL-1ß, IFN-, LFA-1,
and CD40L in RANTES induction by T cells early in their activation
cycle. The latter represents an important observation, because, as
expected, T cells stimulated for longer periods spontaneously
synthesized RANTES in the absence of RTEC. Our data suggest that T
cell/RTEC interactions are likely to be important during the early
phase of developing inflammatory lesions before established autocrine T
cell synthesis. How the relative contributions of T cells and RTEC to
RANTES production are regulated in established lesions remains unclear,
as does the reciprocal contribution RTEC make to T cell RANTES
production.
LFA-1/ICAM-1 is important for various hemopoietic as well as
heterotypic cell-to-cell interactions. There is increasing evidence
that ICAM-1 not only acts as an adhesion molecule, but also has
signaling functions (38, 39). Our data suggest that
LFA-1/ICAM-1 interactions are involved in RANTES production by T cells.
This may be mediated by strengthening cell contact between T cells and
RTEC. Alternatively, ligation of ICAM-1 on the surface of RTEC may
mediate signals that are essential for RANTES production. LFA-1/ICAM-1
interactions may have a more prominent role in RANTES production by T
cells early in their activation cycle (within 6 h). Although
cell-to-cell contact is clearly also essential for RANTES production by
T cells later in their activation cycle (e.g., at 24 h), our data
suggest that other cell surface molecules are likely to be involved at
that stage.
That CD4 and CD8 T cells behaved differently in our assay represents an intriguing observation. Whereas CD4 and CD8 cells encountering RTEC within 6 h of stimulation induced equivalent chemokine secretion, this capacity was further enhanced at 24 h poststimulation only in CD8 T cells. Indeed, the capacity of CD4 cells stimulated for 24 h to promote chemokine expression was significantly depressed, especially for RANTES production. These data suggest that as T cell subsets differentiate, their relative contributions to resident renal cell activation may be altered. Further studies are now required to define whether differential effects of CD4 and CD8 cells interacting with RTEC are manifest beyond chemokine synthesis.
Up-regulation of CD40 on resident renal cells and CD40L expression in
infiltrating mononuclear cells have been observed in renal biopsies of
patients with proliferative lupus nephritis (40). In
animal models of lupus nephritis, anti-CD40L Abs ameliorate
nephritis even when administered after disease onset (41).
Anti-CD40L prevents the rejection of a variety of allogeneic
transplants, including renal transplants (42, 43). We now
show that blockade of CD40/CD40L decreased RANTES production by RTEC
following T cell contact. Moreover, rCD40L in combination with IFN-
induced MCP-1 and RANTES production by RTEC. These findings raise the
possibility that the protective effect of anti-CD40L in these
diseases may partly reflect inhibition of chemokine production
following T cell/RTEC interactions. The failure of CD40L blockade to
reduce MCP-1 production in our studies does not necessarily exclude a
role for this molecule in T cell-mediated production of MCP-1 by RTEC.
Functional redundancy may exist among cell membrane molecules, with
other factors, such as mTNF-, substituting for CD40L. The clinical
consequence of our observations, however, remains that targeting CD40L
alone is unlikely to completely suppress MCP-1 activity in
vivo.
Although in many glomerulonephritides tubulointerstitial disease is
thought to represent a secondary event resulting from downstream events
that follow glomerular injury, once the latter is established, T cells
and macrophages may assume a more important role in its perpetuation. T
cells infiltrating the interstitium probably activate interstitial
macrophages that are abundant sources of TNF- and IL-1ß. T cell-
and macrophage-mediated activation of RTEC could promote a variety of
other biologic effects in RTEC including 1) increased expression of
accessory molecules and enhancement of their ability to present Ags and
activate local T cells, 2) trans-differentiation of tubular
epithelial cells to fibroblast-like cells that may promote fibrosis, 3)
production of vasoactive mediators such as endothelin-1 and nitric
oxide that exacerbate ischemia, and 4) induction of RTEC apoptosis
resulting in tubular atrophy. The net effect of such processes will be
atrophy of tubular cells, interstitial fibrosis, and loss of renal
function (44). The present study, although focussed on
chemokine and sustained leukocyte recruitment, demonstrates the
biological plausibility of these possibilities.
The availability of specific inhibitors of cytokines, such as TNF-
and IL-1, and Abs recognizing CD40L and ICAM-1 for clinical use in
humans provides unique opportunities to examine the contributions of
these molecules in human GN (45, 46, 47, 48). Our data suggest
that in addition to their well-described effects on mesangial cells
(49), these membrane-bound and secreted molecules may also
affect the biology and behavior of human RTEC, and hence pathology, in
the renal interstitium (Fig. 7). Our
studies have thus defined clear therapeutic targets, but demonstrate
significant diversity and potential redundancy, recognition of which
will be essential to logical therapeutic selection.
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Footnotes |
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2 Abbreviations used in this paper: MCP-1, monocyte chemoattractant protein-1; MIP-1, macrophage inflammatory protein-1; GN, glomerulonephritis; RTEC, renal tubular epithelial cell; IP-10, IFN-inducible protein-10; REBM, renal epithelial basal medium; 24h-S, 24-h-stimulated; CD40L, CD40 ligand.
Received for publication September 15, 1999. Accepted for publication January 5, 2000.
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A. Y. Hoi, M. J. Hickey, P. Hall, J. Yamana, K. M. O'Sullivan, L. L. Santos, W. G. James, A. R. Kitching, and E. F. Morand Macrophage Migration Inhibitory Factor Deficiency Attenuates Macrophage Recruitment, Glomerulonephritis, and Lethality in MRL/lpr Mice J. Immunol., October 15, 2006; 177(8): 5687 - 5696. [Abstract] [Full Text] [PDF]
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S. Laxmanan, D. Datta, C. Geehan, D. M. Briscoe, and S. Pal CD40: A Mediator of Pro- and Anti-Inflammatory Signals in Renal Tubular Epithelial Cells J. Am. Soc. Nephrol., September 1, 2005; 16(9): 2714 - 2723. [Abstract] [Full Text] [PDF]
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G. Castellano, V. Cappiello, N. Fiore, P. Pontrelli, L. Gesualdo, F. P. Schena, and V. Montinaro CD40 Ligand Increases Complement C3 Secretion by Proximal Tubular Epithelial Cells J. Am. Soc. Nephrol., July 1, 2005; 16(7): 2003 - 2011. [Abstract] [Full Text] [PDF]
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S. de Haij, A. C. Bakker, R. N. van der Geest, G. Haegeman, W. Vanden Berghe, J. Aarbiou, M. R. Daha, and C. van Kooten NF-{kappa}B Mediated IL-6 Production by Renal Epithelial Cells Is Regulated by C-Jun NH2-Terminal Kinase J. Am. Soc. Nephrol., June 1, 2005; 16(6): 1603 - 1611. [Abstract] [Full Text] [PDF]
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 P I Sidiropoulos and D T Boumpas Lessons learned from anti-CD40L treatment in systemic lupus erythematosus patients Lupus, May 1, 2004; 13(5): 391 - 397. [Abstract] [PDF]
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A.-J. Ruth, A. R. Kitching, T. J. Semple, P. G. Tipping, and S. R. Holdsworth Intrinsic Renal Cell Expression of CD40 Directs Th1 Effectors Inducing Experimental Crescentic Glomerulonephritis J. Am. Soc. Nephrol., November 1, 2003; 14(11): 2813 - 2822. [Abstract] [Full Text] [PDF]
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T. Tanaka, T. Kuroiwa, H. Ikeuchi, F. Ota, Y. Kaneko, K. Ueki, Y. Tsukada, I. B. McInnes, D. T. Boumpas, and Y. Nojima Human Platelets Stimulate Mesangial Cells to Produce Monocyte Chemoattractant Protein-1 via the CD40/CD40 Ligand Pathway and May Amplify Glomerular Injury J. Am. Soc. Nephrol., October 1, 2002; 13(10): 2488 - 2496. [Abstract] [Full Text] [PDF]
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 N. G. Inston and P. Cockwell The evolving role of chemokines and their receptors in acute allograft rejection Nephrol. Dial. Transplant., August 1, 2002; 17(8): 1374 - 1379. [Full Text] [PDF]
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P. Cockwell, J. W. Calderwood, C. J. Brooks, S. J. Chakravorty, and C. O. S. Savage Chemoattraction of T cells expressing CCR5, CXCR3 and CX3CR1 by proximal tubular epithelial cell chemokines Nephrol. Dial. Transplant., May 1, 2002; 17(5): 734 - 744. [Abstract] [Full Text] [PDF]
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A. R. Rosenkranz and G. Mayer Proteinuria in the transplanted patient Nephrol. Dial. Transplant., September 1, 2000; 15(9): 1290 - 1292. [Full Text] [PDF]
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