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Agonists1
Departments of
*
Medicine,
Pharmacology, and
Physiology, Medical University of South Carolina, Charleston, SC 29403;
§
Medical Research Service, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29403; and
¶
Vanderbilt University School of Medicine, Nashville, TN 37232
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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. In contrast to the 2- to 3-fold increase in
PGJ2 production by stimulated BALB/c mesangial cells,
supernatant PGJ2 did not increase in MRL/lpr
mesangial cell cultures. NO production in stimulated
MRL/lpr and BALB/c mesangial cells, was blocked by
PGJ2 and pioglitazone. These studies suggest that
abnormalities in PGJ2 production are present in
MRL/lpr mice and may be linked to the heightened
activation state of mesangial cells in these
mice. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Alterations in PG production are known to occur in human and murine lupus nephritis. PGE2 and PGI2, vasodilators that increase glomerular filtration rate (GFR), are decreased in lupus nephritis, whereas thromboxane A2, which reduces GFR, is elevated (10, 11, 12, 13, 14). PGE2, when exogenously administered in murine lupus, attenuates disease progression primarily by systemic immune suppression (15). PGE2, however, has minimal to no effect on NO production (16). The mechanisms for the alterations of eicosanoid production in lupus are not well understood.
PGJ2, a recently described cyclopentenone PG
formed from the dehydration of PGD2, has been
shown in vitro to inhibit activation of normal rat macrophages
(17). Additional investigations demonstrated
antiproliferative effects on macrophages and proapoptotic effects in
tumor cells lines (18, 19, 20, 21, 22). Ricote et al.
(17) recently reported that PGJ2
inhibited NO production by activated peritoneal macrophages derived
from normal rats primarily through stimulation of the peroxisomal
proliferator activation receptor- (PPAR-). Once activated,
PPAR- blocks NF-
B binding to the promoter regions of specific
genes including the gene for inducible NO synthase, thus inhibiting
gene activation. PGJ2 appears to be a natural
ligand for PPAR- and as such may serve as a key negative regulator
of macrophage-derived inflammatory responses.
Based on these observations and the known abnormalities in eicosanoid
production in lupus, we hypothesized that the prolonged heightened
state of mesangial cell activation in MRL/lpr mice may be
secondary to a lack of a key negative regulator of macrophage function
(i.e., PGJ2). To address this hypothesis, we
measured PGJ2 production by MRL/lpr
mesangial cells and assessed the effects of PGJ2
and a PPAR- agonist on mesangial cell NO production.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Eight-week-old female MRL/lpr and BALB/c mice were purchased from The Jackson Laboratory (Bar Harbor, ME), housed under specific pathogen-free conditions at the Ralph H. Johnson Veterans Affairs Medical Center Animal Facility and provided autoclaved food and sterile water ad libitum. Mice were randomly tested and were serologically negative for common murine pathogens.
Reagents
PGJ2 was purchased from Biomol (Plymouth
Meeting, PA), 15-deoxy-
12,14PGJ2,
12-PGJ2, and
PGD2 from Cayman Chemicals (Ann Arbor, MI),
IFN- from PharMingen (San Diego, CA),
L-N6-(1-iminoethyl)lysine
(L-NIL) from Calbiochem, FCS, DMEM, and RPMI 1640
from Life Technologies (Gaithersburg, MD), and the protein assay kit
from Bio-Rad (Hercules, CA). Anti-nitric oxide synthase (NOS) 2 Ab was
purchased from Transduction Laboratories (Lexington, KY). All other
reagents, including LPS, were purchased from Sigma (St. Louis, MO).
Pioglitazone was a gift from Dr. Thomas Gettys (Medical University of
South Carolina).
Glomeruli and mesangial cell isolation
Since glomerulonephritis occurs in MRL/lpr mice beginning by 14 wk of age, glomeruli were isolated before disease onset at 8–10 wk of age. To accomplish this, mice were anesthetized with metofane and sacrificed by cervical dislocation. Renal tissue was surgically removed and kept on ice in sterile DMEM with 1% FCS. The kidneys were minced and glomeruli were separated from the remaining renal tissue by sequential mechanical sieving (23). Glomeruli were incubated for 30 min at 37°C with collagenase and then plated in 75-cm2 culture flasks in RPMI 1640 medium containing 15% FCS, streptomycin (100 µg/ml), penicillin (100 U/ml), and L-glutamine (2 mM). Media were replaced every 48 h, while adherent mesangial cells were retained. After cells reached confluence (about 2 wk), they were passaged using trypsin/EDTA. The cells exhibited typical morphologic characteristics of mesangial cells and tested uniformly positive for smooth muscle actin staining. Cells between passages 3 and 7 were used for subsequent experimental procedures.
Experimental conditions
Confluent cells in triplicate 6-well cell culture dishes were washed twice with DMEM devoid of phenol red, since phenol red interferes with nitrate/nitrite (N/N) measurements. After the final wash, DMEM plus 10% FCS without phenol red was added containing various reagents described for each experiment. At the end of each incubation, supernatants were collected and analyzed for N/N production. Cellular protein was isolated for Western blot analysis (see below).
Mass spectrometric procedure for analysis of PGJ2 and PGE2
Confluent mesangial cell cultures were serum starved (0.1% FCS) for 48 h before addition of either IL-1ß or serotonin. Media were collected for 24 h and served for the measurement of PGE2 and PGJ2 using mass spectrometry. PGE2 was quantified by gas chromatography (GC)/negative ion chemical ionization mass spectrometry (MS) using stable isotope dilution techniques as described (24). PGJ2 was analyzed using a modification of methods developed for PGE2. Briefly, PGJ2 in media from cell incubations was converted to an O-methyloxime trimethylsilyl ether pentafluorobenzyl ester derivative and purified by TLC (Silica LKD60 plates; Waters, Maidstone, U.K.) using a solvent system of hexane/acetone (70:30, v/v). Material migrating with an Rf identical to chemically pure PGJ2 (Rf = 0.31) was scraped from the plate and analyzed by GC/negative ion chemical ionization MS. GC was performed using a DB1701-fused silica capillary column (J & W Scientific, Folsom CA). MS was performed using a Nermag R10-10C (Paris, France) instrument interfaced with an IBM Pentium computer.
Thromboxane B2 (TXB2) assay
TXB2 levels were measured in supernatants of mesangial cells by RIA as described previously (25). Known concentrations of TXB2 were used to derive a standard curve.
N/N analysis
NO is metabolized rapidly to N/N; these stable catabolites are accepted measures of in vivo and in vitro NO production and were measured in 50 µl of supernatant as described (26). Briefly, supernatants were filtered using Centricon ultrafiltration tubes (Amicon, Beverly, MA). Nitrate was converted to nitrite using nitrate reductase (Boehringer Mannheim, Indianapolis, IN), and total N/N was determined by measuring nitrite via the Greiss reaction. Known amounts of N/N in PBS were used to generate a standard curve.
Western blot analysis
Immunoblots were performed as described previously (4). Briefly, mesangial cells were lysed with distilled water containing proteinase inhibitors (PharMingen) and then sonicated. After using a Bio-Rad rapid Coomassie blue kit to determine total protein concentration, 20 µg of protein was loaded into each well. The proteins were transferred onto a polyvinylidene difluoride membrane, blocked with 5% milk solids, and incubated with a monoclonal mouse anti-NOS2 (1:2500 dilution) or anti-cyclooxygenase (COX)-2 (1:250 dilution) Ab, washed, and then exposed to a secondary goat anti-mouse HRP conjugate. Chemiluminescence (enhanced chemiluminescence; Amersham, Arlington Heights, IL) in conjunction with video densitometry (National Institutes of Health Images) were used to quantitate NOS2 protein.
Statistical analysis
The unpaired Student’s t test (see Table I
and Figs. 1 and 3) or ANOVA (see Fig. 2) followed by post hoc analysis was used
to test for significant differences between groups.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Abnormalities in eicosanoid production are known to occur in
MRL/lpr mice. To evaluate whether these alterations affect
PGJ2 production, mesangial cells were isolated
from MRL/lpr and BALB/c mice at 8–10 wk of age before
immune complex deposition, onset of elevated NO production, and/or
proteinuria. Confluent cell cultures were stimulated with serotonin or
IL-1ß, both known stimulators of COX-2 and subsequent PG production.
After 24 h in culture, supernatants were collected and the levels
of PGJ2 and PGE2 in the
media were determined. The results demonstrated that the levels of
PGJ2 and PGE2 produced by
stimulated MRL/lpr mesangial cell cultures were
significantly less than control BALB/c mesangial cells (Table I
). In contrast to BALB/c mesangial
cells, the MRL/lpr mesangial cells did not significantly
increase PGJ2 production in response to either
serotonin or IL-1ß stimulation.
To determine production of other COX products by MRL/lpr vs
BALB/c mesangial cells, we measured TXB2 levels
in supernatants of IL-1ß- and serotonin-stimulated cells. As shown in
Table I, there were no significant differences in induced mesangial
cell TXB2 production between the two strains,
indicating that MRL/lpr mesangial cells can respond to
immune stimulation and that there is not a global suppression of COX
products in MRL/lpr mesangial cells.
Effects of PG J2 on N/N production in mesangial cells
Combining the observations that compared with normal mice there is
decreased production of PGJ2 by
MRL/lpr mesangial cells, that PGJ2 is
a potent inhibitor of NO production by macrophages, and that stimulated
MRL/lpr mesangial cells produce more NO than mesangial cells
from normal mice, we determined whether the production of NO by
mesangial cells from MRL/lpr mice can be modulated by
PGJ2. We measured supernatant N/N from mesangial
cells of MRL/lpr and BALB/c mice cultured with and without
added PGJ2 (Fig. 1). Supernatants from MRL/lpr
mesangial cells, cultured with LPS and IFN-, contained greater
amounts of N/N than supernatants from BALB/c mesangial cells cultured
under the same conditions, indicating increased NO production by
MRL/lpr mesangial cells in response to immune stimuli. The
addition of PGJ2 significantly inhibited LPS- and
IFN--induced N/N production by mesangial cells from both strains.
The addition of PGJ2 to unstimulated mesangial
cells had no effect on supernatant N/N levels in either BALB/c or
MRL/lpr mice.
Having established that PGJ2 decreased NO
production by mesangial cells, we next sought to determine at what
concentration PGJ2 exerts its inhibitory effect.
PGJ2 was added at 2 x
10-6, 10-7,
10-8, and 10-9 M
concentrations to MRL/lpr and BALB/c mesangial cell cultures
(Fig. 2). The addition of
PGJ2 resulted in a concentration-dependent
decrease in N/N production by MRL/lpr mesangial cells with a
significant inhibitory effect at 2 x 10-7
M. There was no significant inhibition of NO production by BALB/c
mesangial cells below a PGJ2 concentration of
2 x 10-6 M. These results indicate a
significant difference in the responsiveness of BALB/c and
MRL/lpr mesangial cells to inhibition of NO production by
PGJ2. The BALB/c mesangial cells produced less NO
in response to LPS stimulation and were less sensitive to
PGJ2 inhibition of NO production than the
MRL/lpr mesangial cells. These differences may reflect the
intrinsic PGJ2 production by the two strains;
BALB/c mesangial cells increase PGJ2 production
when stimulated, thus produce less NO and are less sensitive to
extrinsic PGJ2.
Effect of PGD2 and PGJ2 metabolites on NOS2 activity
PGD2 is the precursor to
PGJ2, whereas PGJ2 can be
metabolized further to
12-PGJ2 and ultimately
to 15-deoxy-12,14-PGJ2.
To determine whether the precursor and/or metabolites of
PGJ2 also possess inhibitory effects on
stimulated mesangial cells, we investigated these eicosanoids for their
ability to inhibit NO production. The addition of
PGD2 did not decrease LPS- plus IFN--induced
NO production by MRL/lpr mesangial cells (Fig. 3A). However, both
12 and
15-deoxy-12,14-PGJ2
significantly decreased cellular production of NO. Concentrations that
inhibit induced mesangial cell NO production are similar between
PGJ2 and its metabolites (data not shown).
L- NIL, a competitive inhibitor of NOS2, blocked
NO production to a similar level as 2 x
10-6 M PGJ2. The lack of
an effect of either PGJ2 or
L-NIL on baseline NO production and the similar
effect of L-NIL and PGJ2 on
induced NO production suggests that the majority of induced mesangial
cell NO production inhibited by PGJ2 is NOS2
derived.
We next assessed the inhibitory effect of PGJ2 on
IL-1ß-induced NO production by MRL/lpr mesangial cells.
IL-1ß and LPS both induce NO production via NF-B-mediated
mechanisms. As shown in Fig. 3B, IL-1ß and LPS induced
similar increases in NO production by MRL/lpr mesangial
cells; the addition of PGJ2 blocked both IL-1ß-
and LPS-induced increases in NO production.
Effect of a specific PPAR- agonist on induced mesangial cell
production of NO
Like PGJ2, a new class of antidiabetic
compounds (thiazolidinediones) block NO production by binding to
PPAR- and inhibiting NF-B transcriptional activation
(16). To determine whether a specific PPAR- agonist
blocks induced NO production, we cultured mesangial cells from
MRL/lpr mice with pioglitazone. As shown in Fig. 3B, pioglitazone, similar to PGJ2,
blocked NO production induced by either LPS or IL-1ß. These results
suggest that mesangial cells contain PPAR- and the inhibitory
effects of PGJ2 on NO production are at least
partially mediated via its PPAR- agonist activity.
Effects of PGJ2 and pioglitazone on NOS2 expression
To determine whether the inhibitory effect of
PGJ2 was blocking NOS2 enzymatic activity or
decreased production of NOS2 protein, we performed Western blot
analysis on mesangial cells from stimulated MRL/lpr and
BALB/c mice (Fig. 4). Western blot
analysis of protein lysates from mesangial cells showed that NOS2
protein levels were increased in both BALB/c and MRL/lpr
mice when stimulated for 24 h with LPS and IFN-. The expression
of NOS2 protein was increased by mesangial cells from
MRL/lpr mice compared with the BALB/c mice paralleling the
increased NO production by stimulated MRL/lpr mesangial
cells. The addition of 2 x 10-6 M
PGJ2 to the stimulated cells completely blocked
the expression of NOS2. The addition of 2 x
10-7 M PGJ2 partially
blocked NOS2 expression in both the MRL/lpr and BALB/c
mesangial cells, whereas 2 x 10-8 M and
2 x 10-9 M PGJ2 had
little effect on NOS2 expression after 24 h in either strain.
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12-PGJ2 and
15-deoxy-12,14-PGJ2)
were added to stimulated MRL/lpr cell cultures, they also
blocked the expression of NOS2 protein. In contrast, the addition of
PGD2 had little effect on NOS2 protein expression
(Fig. 5A). The addition of
L-NIL to stimulated mesangial cells did not
reduce NOS2 protein expression, since L-NIL acts
to inhibit enzyme action and not NOS2 protein synthesis.
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agonist
pioglitazone would decrease NOS2 expression similar to
PGJ2 in MRL/lpr mesangial cells.
MRL/lpr mesangial cells were stimulated with LPS and
cultured with pioglitazone. Western blot analysis revealed that
pioglitazone blocked NOS2 protein expression induced by LPS and IFN-
stimulation from 4 to 24 h (Fig. 5B). Both
PGJ2 and pioglitazone blocked the expression of
NOS2 following IL-1ß stimulation of MRL/lpr mesangial
cells (Fig. 6).
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We sought to determine whether the decrease in
PGJ2 production in stimulated MRL/lpr
mesangial cells compared with BALB/c controls was secondary to
alterations in COX-2 expression. Western blot analysis of protein
lysates of mesangial cells stimulated with LPS showed that detectable
levels of COX-2 were present at 1 and 4 h (Fig. 7). By 24 h, however, the expression
of COX-2 was decreased in the MRL/lpr mesangial cell
cultures whereas in the BALB/c control cells, COX-2 expression was
maintained. Treating the stimulated mesangial cell cultures with
PGJ2 had little effect on COX-2 expression in the
BALB/c controls over 24 h. However, in the stimulated
MRL/lpr mesangial cells with the addition of
PGJ2, COX-2 expression was slightly increased at
8 h and maintained for 24 h. Although in Fig. 7 there appears
to be differences in the amount of COX-2 protein expressed between
MRL/lpr and BALB/c mice at 1 and 4 h, this difference
was not always present on repetition of the experiment. The lack of
COX-2 expression at 24 h with maintenance of expression with
additional PGJ2 by the MRL/lpr
mesangial cells, however, was evident in all experiments.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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agonist pioglitazone, inhibited stimulated, but not
baseline, NO production by mesangial cells from MRL/lpr and
BALB/c mice. PGJ2 and pioglitazone blocked
induced NO production by decreasing protein synthesis of the NOS2
enzyme. Alterations in COX-2 expression by mesangial cells from
MRL/lpr mice compared with BALB/c controls were demonstrated
and perhaps explain the decreased production of
PGJ2 by mesangial cells from these mice. Thus,
these results support our hypothesis that decreased production of
PGJ2, an intrinsic PPAR- agonist, is a feature
of disease in MRL/lpr mice resulting in a heightened and
prolonged inflammatory response to immune stimuli. Together these
results suggest that decreased mesangial cell
PGJ2 production is of pathogenic significance in
MRL/lpr renal disease. Alterations in eicosanoid production in both human and murine lupus nephritis were first described a number of years ago. These alterations in TXA2 and PGE2/PGI2 were considered primarily in the context of their effects on glomerular filtration and renal blood flow (10, 15, 27). Plotz and Kimberly (28) first suggested that inhibiting PG production may result in significant alterations in renal function. Our findings of alterations in PGJ2 production in MRL/lpr mice expand the effects of PGs in lupus nephritis to include control of the local inflammatory response.
The presence of these abnormalities in PG production in young
(prediseased) MRL/lpr mice suggests that the abnormality in
PGJ2 production is a primary or at least a very
early manifestation of disease, rather than a result of disease.
MRL/lpr mice have a number of known immune abnormalities.
Both T cells and B cells are activated early in disease development and
contribute to pathogenesis. Indeed, in animal models of systemic lupus
erythematosus, autoantibody production is associated with polyclonal T
and B cell activation (29). Recently, Kelley and coworkers
reported that MRL/lpr mice deficient in the IFN- receptor
were protected from kidney disease compared with control
MRL/lpr mice (30, 31). This protection included
a lack of infiltrating T cells and activated macrophages into the
kidney. IFN- up-regulates the expression of MHC class II molecules
on APCs and induces macrophage and mesangial cell activation in
MRL/lpr mice. Others have shown defects in various other
cytokines in prediseased lupus mice and a heightened response of
MRL/lpr mesangial cells to stimulatory cytokines. These
defects include decreased production of IL-1 following LPS stimulation
in macrophages (32), but increased IL-1ß gene expression
in different organs (33). Thus, it is clear renal disease
in MRL/lpr mice is multifactorial. Expression of disease is
controlled by the MRL background with the lpr gene
accelerating and accentuating disease expression.
Although we have centered our studies on mesangial cells, infiltrating
macrophages are also prominent immune cells in lupus nephritis. Both
mesangial cells and macrophages are able to synthesize PGs, TXBs, and
NO (6, 9, 34, 35). The interplay of these two cell types
is likely a deciding factor in the overall inflammatory response to an
immune stimulus. Previous reports suggest that the infiltrating
macrophage in lupus nephritis is the primary producer of both NO and
TXA2, both of which are overall detrimental in
the setting of lupus nephritis (4, 10, 35).
PGJ2 is a potent inhibitor of macrophage function
and NO production (17, 22). Production of
PGJ2 to limit the inflammatory response and
down-regulate macrophage activation may be a primary function of the
mesangial cell, although macrophages are also able to produce
PGJ2 (36).
15-Deoxy-12,14-PG J2 has
been shown to decrease the activation of microglia and affect cellular
function independent of PPAR- (37).
The mechanisms underlying the altered PG production in lupus nephritis are incompletely understood; there are, however, multiple potential mechanisms to explain the differential regulation of TXA2, PGE2, PGI2, and PGJ2 production in nephritis in MRL/lpr mice. These differences could reflect the possibility that TXA2 is a product of COX-1 enzymatic pathways, whereas PGJ2 is produced by COX-2. Alternatively, arachidonic acid may be differentially sequestered for subsequent metabolism to PGJ2, PGE2, and TXA2 in the MRL/lpr mesangial cell vs the BALB/c mesangial cell (38). To explain why TXA2 production is increased while PGJ2 is underproduced in lupus nephritis, recent observations by Covell-Nash et al. (39) may provide important insight. In the carrageenan pleurisy model of inflammation, these investigators found a bimodal expression of COX-2. Early expression of COX-2 was associated with the production of proinflammatory PGs. The later peak in COX-2 expression was hypothesized, though not proven, to result in the production of PGs that terminate inflammation. Although highly speculative, the decreased expression of COX-2 protein by MRL/lpr mesangial cells at 24 h following immune stimulation may fit within this model. Indeed, if prolonged COX-2 activation leads to increased PGJ2 production then sustained COX-2 enzyme expression could result in modulation of the inflammatory response. The key to understanding the effects of COX-2 expression on the local inflammatory response lies in identifying its products at various time points and the synthases/isomerases responsible for synthesis of the metabolically active COX products.
The decreased expression of COX-2 by MRL/lpr mesangial cells at 24 h may be linked to enhanced NO production. Several reports have shown a relationship between the expression of NOS2 and COX-2 protein and their biologically active products. In rat peritoneal macrophages, the addition of exogenous NO decreased COX-2 expression. Inhibition of NOS2 activity by a NOS2 inhibitor increased PG formation and COX-2 expression following immune stimulation (40). Alternately, Salvemini et al. (41) showed that in the hydronephritic kidney, NO release by NOS2 resulted in increased COX-2 expression and the production of proinflammatory PGs. These studies illustrate that depending on the model used, NOS2 and COX-2 may work synergistically or antagonistically in their effects on coexpression. NO production may alter further PG production by affecting the intracellular localization of COX-2 (42).
The maintenance of COX-2 expression by MRL/lpr mesangial
cells at 24 h following the addition of LPS and
PGJ2 seems paradoxical. Recently, Callejas et
al., (43) reported that PPAR- agonists inhibited
production of COX-2 mRNA in LPS-stimulated macrophages; however, COX-2
protein expression was enhanced. These results suggest that stimulation
of PPAR- prevents the breakdown of the COX-2 protein. Our results
are perhaps demonstrating the same phenomenon in mesangial cells; the
addition of PGJ2 to mesangial cells stabilized
the levels of COX-2 enzyme. The protein stabilizing effect of activated
PPAR- appears independent of NO effects on the COX-2 protein because
adding L-NIL, a NOS2-specific inhibitor, to
stimulated MRL/lpr mesangial cells did not affect COX-2
protein expression at 24 h (data not shown).
Most PGs exert their effects through interactions with cell surface
receptors. The major biologic actions of PGs of the J series, however,
appear mediated by binding to PPAR- located in the nucleus
(35). Our data, as well as previous reports by others,
indicate that the major mechanism by which PGJ2
inhibits macrophage/mesangial cell function is through activation of
PPAR- (17). Other biologic effects of
PGJ2 may be mediated by other mechanisms
especially at low concentrations of PGJ2.
JPGs all show affinity for PPAR- receptors (17, 18);
however, little is known about the in vivo systemic or local levels of
these eicosanoids. PGJ2 and
12-PGJ2 are known to be
formed in vivo and 12 is present in human and
monkey urine in significant quantities (
150 ng/24 h in males)
(44). Thus, it is clear that PGJ2 is
produced in vivo, the in vivo actions of this eicosanoid, however, are
incompletely understood. We hypothesize that as one of its functions,
PGJ2 is an intrinsic negative regulator of
macrophages and macrophage-like cells. Regulated production of
PGJ2 may be important to allow an initial immune
response to inflammatory stimuli, followed by negative regulation of
the immune response. PGJ2, by blocking NF-B
interactions with the promoters of genes of inflammatory mediators,
would be an ideal candidate for such a negative regulator.
In summary, our results demonstrate that mesangial cells from
prediseased MRL/lpr mice produced less
PGJ2 than cells from BALB/c mice.
PGJ2 added to mesangial cell cultures decreased
NO production in stimulated mesangial cells through effects on NOS2
protein expression. These results suggest that decreased production of
PGJ2 may be a contributing factor in the enhanced
and prolonged activation of mesangial cells in MRL/lpr mice.
Thus, PGJ2 and activated PPAR- are potential
important negative regulators of local inflammatory responses in the
kidney. Further studies of the role of PGJ2 in
the lupus kidney will likely provide insight into the mechanisms of
inflammation in lupus nephritis and perhaps provide new paradigms for
treatment.
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Gary S. Gilkeson, 912 Clinical Science Building, Medical University of South Carolina, 171 Ashley Avenue, Charleston, SC 29425. E-mail address:
3 Abbreviations used in this paper: MRL/lpr, MRL/Mp-lpr/lpr; PPAR-, proliferator activation receptor-; L-NIL, L-N6-(1-iminoethyl)lysine; N/N, nitrate/nitrite; GC, gas chromatography; MS, mass spectrometry; GFR, glomerular filtration rate; NOS, nitric oxide synthase; COX, cyclooxygenase; TXB2, thrombaxane B2.
Received for publication July 20, 1999. Accepted for publication November 10, 1999.
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 M. B. Crosby, J. L. Svenson, J. Zhang, C. J. Nicol, F. J. Gonzalez, and G. S. Gilkeson Peroxisome Proliferation-Activated Receptor (PPAR){gamma} Is Not Necessary for Synthetic PPAR{gamma} Agonist Inhibition of Inducible Nitric-Oxide Synthase and Nitric Oxide J. Pharmacol. Exp. Ther., January 1, 2005; 312(1): 69 - 76. [Abstract] [Full Text] [PDF]
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C. M. Reilly, N. Mishra, J. M. Miller, D. Joshi, P. Ruiz, V. M. Richon, P. A. Marks, and G. S. Gilkeson Modulation of Renal Disease in MRL/lpr Mice by Suberoylanilide Hydroxamic Acid J. Immunol., September 15, 2004; 173(6): 4171 - 4178. [Abstract] [Full Text] [PDF]
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 S. Cheng, H. Afif, J. Martel-Pelletier, J.-P. Pelletier, X. Li, K. Farrajota, M. Lavigne, and H. Fahmi Activation of Peroxisome Proliferator-activated Receptor {gamma} Inhibits Interleukin-1{beta}-induced Membrane-associated Prostaglandin E2 Synthase-1 Expression in Human Synovial Fibroblasts by Interfering with Egr-1 J. Biol. Chem., May 21, 2004; 279(21): 22057 - 22065. [Abstract] [Full Text] [PDF]
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 P. K. Chatterjee, N. S.A Patel, S. Cuzzocrea, P. A.J Brown, K. N Stewart, H. Mota-Filipe, D. Britti, W. Eberhardt, J. Pfeilschifter, and C. Thiemermann The cyclopentenone prostaglandin 15-deoxy-{Delta}12,14-prostaglandin J2 ameliorates ischemic acute renal failure Cardiovasc Res, February 15, 2004; 61(3): 630 - 643. [Abstract] [Full Text] [PDF]
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D. Perez-Sala, E. Cernuda-Morollon, and F. J. Canada Molecular Basis for the Direct Inhibition of AP-1 DNA Binding by 15-Deoxy-{Delta}12,14-prostaglandin J2 J. Biol. Chem., December 19, 2003; 278(51): 51251 - 51260. [Abstract] [Full Text] [PDF]
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 M. Masuya, C. J. Drake, P. A. Fleming, C. M. Reilly, H. Zeng, W. D. Hill, A. Martin-Studdard, D. C. Hess, and M. Ogawa Hematopoietic origin of glomerular mesangial cells Blood, March 15, 2003; 101(6): 2215 - 2218. [Abstract] [Full Text] [PDF]
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 R. B. Clark The role of PPARs in inflammation and immunity J. Leukoc. Biol., March 1, 2002; 71(3): 388 - 400. [Abstract] [Full Text] [PDF]
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 K. Scholz-Pedretti, A. Gans, K.-F. Beck, J. Pfeilschifter, and M. Kaszkin Potentiation of TNF-{alpha}-Stimulated Group IIA Phospholipase A2 Expression by Peroxisome Proliferator-Activated Receptor {alpha} Activators in Rat Mesangial Cells J. Am. Soc. Nephrol., March 1, 2002; 13(3): 611 - 620. [Abstract] [Full Text] [PDF]
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B. H. ROVIN, L. LU, and A. COSIO Cyclopentenone Prostaglandins Inhibit Cytokine-Induced NF-{kappa}B Activation and Chemokine Production by Human Mesangial Cells J. Am. Soc. Nephrol., August 1, 2001; 12(8): 1659 - 1667. [Abstract] [Full Text] [PDF]
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H. Sekine, C. M. Reilly, I. D. Molano, G. Garnier, A. Circolo, P. Ruiz, V. M. Holers, S. A. Boackle, and G. S. Gilkeson Complement Component C3 Is Not Required for Full Expression of Immune Complex Glomerulonephritis in MRL/lpr Mice J. Immunol., May 15, 2001; 166(10): 6444 - 6451. [Abstract] [Full Text] [PDF]
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K. Guyton, R. Bond, C. Reilly, G. Gilkeson, P. Halushka, and J. Cook Differential effects of 15-deoxy-{Delta}12,14-prostaglandin J2 and a peroxisome proliferator-activated receptor {gamma} agonist on macrophage activation J. Leukoc. Biol., April 1, 2001; 69(4): 631 - 638. [Abstract] [Full Text]
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 S. B. Nicholas, Y. Kawano, S. Wakino, A. R. Collins, and W. A. Hsueh Expression and Function of Peroxisome Proliferator-Activated Receptor-{{gamma}} in Mesangial Cells Hypertension, February 1, 2001; 37(2): 722 - 727. [Abstract] [Full Text] [PDF]
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