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*
Renal Section, Imperial College School of Medicine, Hammersmith Hospital,
London, United Kingdom
Department of Histopathology, Imperial College School of Medicine,
Hammersmith Hospital, London, United Kingdom
Department of Immunology and Hemostasis, Discovery Research,
Wyeth/Genetics Institute Inc., Andover, Massachusetts.
Correspondence to Dr. Frederick W. K. Tam, Renal Section, Department of Medicine, Imperial College, School of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom. Phone: 44-20 8383 3936; Fax: 44-20 8383 2062; E-mail: f.tam{at}ic.ac.uk
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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-chain sequence, it was also shown that rat mesangial cells and
macrophages expressed IL-11 receptor -chain, demonstrating that they
were capable of responding to IL-11. In this model of necrotizing
glomerulonephritis, high-dose IL-11 treatment markedly reduced both
proteinuria and fibrinoid necrosis. At the lower dose, there was a reduction
in glomerular injury and macrophage sialoadhesin expression, but without an
alteration of macrophage numbers, suggesting that IL-11 may be acting in part
to reduce macrophage activation. |
Introduction |
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), and interleukin-1ß
(IL-1ß) appears to play a central role in macrophage-mediated injury
(1). There is evidence that the
transcription factor NF-
B is a key intermediate in macrophage
activation
(2,3,4)
and is involved in transcriptional activation of a variety of genes expressed
during glomerular inflammation, such as TNF-, IL-1ß, and IL-12 p40
(4,5).
Mediators that are able to reduce macrophage activation are therefore
potential therapeutic agents in glomerulonephritis.
IL-11 is a multifunctional cytokine involved in hematopoiesis and
regulation of inflammation
(6,7).
Recent studies have demonstrated that IL-11 has significant effects on
macrophage activation. In vitro, IL-11 inhibits the
lipopolysaccharide (LPS)-induced synthesis of TNF-, IL-1ß, IL-12,
and nitric oxide by murine peritoneal macrophages
(8). This is accompanied by a
reduction in mRNA for TNF- and IL-1ß
(9). In human macrophages,
IL-11 is a potent inhibitor of IL-12 production and reduces accumulation of
the p35 and p40 subunits of IL-12
(10). These effects of IL-11
are independent of other anti-inflammatory molecules such as IL-10, IL-6, and
TGF-ß. In an in vivo model of endotoxemia, IL-11 downregulated
serum levels of the LPS-induced proinflammatory cytokines TNF-,
IL-1ß, and interferon gamma (IFN-
)
(8). The effect on macrophages
is mediated, at least in part, by inhibition of NF-B activity
(9). Recently, inhibition of
NF-B binding by administration of decoy oligonucleotides complexed with
hemagglutinating virus of Japan liposomes has been shown to ameliorate
proteinuria and to improve renal histology in glomerulonephritis
(11). These results suggest
that IL-11 may have a potential therapeutic role in diseases characterized by
macrophage activation and synthesis of proinflammatory cytokines.
IL-11 has been shown to be effective in treating a number of experimental models of inflammation, including colitis (12), collagen-induced arthritis (13), graft-versus-host disease (14), and endotoxin-induced lung injury (15). In humans, IL-11 was effective in reducing expression of proinflammatory cytokines and ameliorating disease in a phase 1 trial of psoriasis (16). IL-11 has not been assessed for the treatment of renal inflammation, and, therefore, we have studied the effect of IL-11 in a florid model of macrophage-dependent, focal and segmental necrotizing glomerulonephritis in the Wistar Kyoto (WKY) rat (17).
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Materials and Methods |
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Nephrotoxic Nephritis
Male WKY rats weighing 200 to 230 g were given 0.1 ml of nephrotoxic serum
intravenously (17). Urine was
collected by housing the rats in metabolic cages for 24-h periods with free
access to food and water. Urinary protein was measured by the sulfosalicylic
acid method (20). At the end
of the experiment, rats were killed while under general anesthesia induced by
isoflurane. Samples of kidney, liver, lung, and spleen were placed in 10%
formal saline, and samples of kidney were snap-frozen in optimal cutting
temperature compound by means of isopentane cooled in liquid nitrogen. All
animal experiments were conducted in accordance with the UK Animals
(Scientific Procedures) Act.
Experimental Design
Experiment 1. In experiment 1, rats (n = 10) were treated
with intraperitoneally administered IL-11 1360 µg in 0.2 ml of 0.1% bovine
serum albumin in saline once daily for 6 d. Control rats (n = 8) were
given 0.2 ml of vehicle once daily. The first injection was given 2 h before
induction of nephritis. Rats were placed in metabolic cages from day 5 to day
6 and killed on day 6.
Experiment 2. Experiment 2 used a lower dose of IL-11 with either once-daily or twice-daily dosing. In experiment 2a, WKY rats (n = 6) were treated with IL-11 400 µg intraperitoneally twice daily for 6 d. In experiment 2b, another set of WKY rats (n = 6) were treated with IL-11 800 µg intraperitoneally once a day for 6 d. Control rats (n = 6) in each experiment received intraperitoneal vehicle injections on the same schedule. The first injection was given 2 h before induction of nephritis. Rats were placed in metabolic cages from day 5 to day 6 and killed on day 6.
Experiment 3. Experiment 3 was designed to study the effect of IL-11 on IL-1ß mRNA expression. Rats (n = 3) were treated with IL-11 400 µg intraperitoneally twice daily for 2 d. Control rats (n = 3) were given 0.4 ml of vehicle twice daily. The first injection was given 2 h before induction of nephritis. Rats were killed 48 h after induction of glomerulonephritis. Glomeruli were purified from the kidneys of each rat by differential sieving (21). Total RNA was extracted from glomeruli of each rat by RNAzol B (Biogenesis, Poole, UK) according to the manufacturer's protocol. Reverse transcription was performed immediately after RNA extraction. The enzyme used to synthesize first strand cDNA was RNaseH- reverse transcriptase from MMLV (SuperScript II, Life Technologies, Paisley, UK). Oligo (dT)12-18 primer (Life Technologies) was used to prime the reaction. The reaction mixture was incubated for 50 min at 42°C, then heat-treated at 70°C for 15 min to inactivate the reverse transcriptase. Samples were stored at -20°C for subsequent competitive polymerase chain reaction (PCR) assay.
Histology and Immunohistochemistry
Glomerular fibrinoid necrosis was assessed in
hematoxylin-and-eosin—stained sections and was quantified by scoring the
number of quadrants of each glomerulus involved. Fifty glomeruli were counted
in blinded, randomized sections, and a mean score of quadrants per glomerular
cross section (gcs) was calculated
(21). Apoptosis was identified
by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling
method (ApopTag, Intergen, Purchase, NY) in paraffin sections. Paraffin
sections were used for immunohistochemistry for macrophages (monoclonal
antibody [mAb] ED1; Serotec, Oxford, UK), inducible nitric oxide synthase
(iNOS; mouse anti-iNOS mAb; Affiniti, Exeter, UK), proliferating cell nuclear
antigen (PCNA; mAb PC10; Dako, Ely, UK), and CD8+ cells (MRC OX-8
mAb; Serotec). For all antibodies except PCNA, sections were pretreated by
microwaving for 3 x 5 min. The primary antibodies were used at the
following concentrations: ED1, 1:500; iNOS, 1:50; PCNA, 1:50; and MRC OX-8,
1:200. ED1 was detected with an indirect peroxidase technique that used
peroxidase-labeled rabbit anti-mouse immunoglobulin (Ig; Dako), and iNOS,
PCNA, and OX-8 were detected by use of biotinylated rabbit anti-mouse antibody
(Dako) and streptavidin-biotin-peroxidase complex (Dako). Macrophages
expressing sialoadhesin were detected by staining with mAb ED3 (Serotec)
(22) in frozen sections by
means of the streptavidin-biotin-peroxidase technique. For each antibody,
cells were counted in blinded, randomized sections, and 50 glomeruli were
counted per section.
Competitive PCR Assay
A multispecific rat competitor DNA fragment was a gift from Dr. H.-D. Volk
(Institute for Medical Immunology, Berlin, Germany)
(23). To quantify cDNA,
competitive PCR was performed with a range of competitor fragment
concentrations. In the first step, serial 10-fold dilutions of competitor
fragment, ranging from 25 pg/µl to 0.25 fg/µl, were coamplified with a
constant amount of glomerular cDNA. On the basis of the results of these
reactions, serial twofold dilutions of competitor, spanning from 10- to
0.1-fold of the predicted cDNA amount, were coamplified with constant amounts
of glomerular cDNA. ß-Actin was used as a control housekeeping gene. The
images of competitive PCR were captured with CCTV Camera and Imager (version
2.0.4, Appligene Inc., Harefield, UK). The results then were analyzed with
Image-Pro Plus (version 4 for Windows, Media Cybernetics, Silver Spring, MA).
The amount of cDNA for each cytokine was divided by the amount of cDNA for the
housekeeping gene. The resulting ratios were compared between control and
treated animals.
Direct Immunofluorescence Microscopy
Direct immunofluorescence microscopic studies to assess deposition of rat
and rabbit IgG in glomeruli were carried out on frozen sections. Sections were
air-dried for 20 min, then washed in phosphate-buffered saline (PBS). Sections
were incubated with either fluorescein isothiocyanate—labeled goat
anti-rabbit IgG (1:80, Sigma, Poole, UK) or fluorescein
isothiocyanate—labeled rabbit anti-rat IgG (1:20, Dako). For
quantitation of fluorescence staining, images were captured with a color
CoolView camera (Photonic Science, Roberts-bridge, UK) and analyzed by
Image-Pro Plus software (Media Cybernetics). Images were converted to gray
scale, and the average pixel intensity of individual glomeruli was recorded.
Results are shown as arbitrary units of intensity. Twenty glomeruli were
evaluated in each section.
Enzyme-Linked Immunosorbent Assay
Circulating rat anti-rabbit antibodies were measured in sera from WKY rats
by a sandwich enzyme-linked immunosorbent assay
(24). Rabbit IgG was coated
onto 96-well polystyrene microtiter plates (ImmunoPlate, NUNC, Nalge NUNC
International, Paisley, UK), at 50 µl/well of 10 µg/ml rabbit IgG in
0.015 M carbonate buffer, pH 9.6 (British Drug House, Poole, UK), by
incubation at 4°C overnight. Coated plates were washed three times with
0.1% PBS/Tween. The plates were then blocked with 1% bovine serum albumin
(Sigma) at 37°C for 1 h. After further washing in PBS/Tween, 50-µl
aliquots of an optimal dilution of control or test rat serum (1/200 as
determined previously by a dilution curve) in PBS/Tween were added to rabbit
IgG—coated wells in triplicate and incubated at 37°C for 1 h. The
solution was then decanted, and the plates were washed three times with
PBS/Tween and drained. Bound rat anti-rabbit IgG antibody was detected by
incubating wells with 50 µl of alkaline phosphatase conjugated rabbit
anti-rat IgG (Sigma) at a dilution of 1 in 1000 for 1 h at 37°C. Excess
conjugate was washed off, and 50 µl of the substrate
p-intro-phenylphosphate disodium (Sigma 104, Sigma) in 0.015 M
carbonate buffer (British Drug House), pH 9.6, was added for 40 min at
37°C. The absorbance for each well was read at 405 nm with an Anthos HII
enzyme-linked immunosorbent assay plate reader (Lab Tech International,
Ringmer, UK).
IL-11 Receptor -Chain PCR and Sequencing
IL-11 receptor -chain primers, which were a gift from Wyeth/Genetic
Institute Inc., were designed from mouse IL-11 receptor -chain sequence
because the rat IL-11 receptor -chain sequence was unknown. Primers
were designed to span over introns to distinguish amplicons of cDNA from those
of genomic DNA. The primer sequences used in this experiment were as follows:
sense primer: 5'-TTGGGGTCCTCCAGGGGTCCAGTATG-3'; antisense primer:
5'-GGAAGTAAGGTAGCGGGTGGGCAAAC-3'. Reverse transcriptase—PCR
(RT-PCR) was carried out by means of mRNA extracted from normal glomeruli,
from day 7 nephritic glomeruli, and from primary cultured mesangial cells and
thioglycollate-elicited peritoneal macrophages
(25). The predicted product
size was 350 bp. To verify the sequence of the products, bands of the right
size from PCR reaction were cut from 1% agarose gel under ultraviolet light
and purified with Geneclean Kit II (Bio101, Harefield, UK). These purified
products were then redissolved in water. Sequencing reactions were performed
with either sense or antisense primer by adding 5 µl of purified PCR
product into 4 µl of terminator mix (BigDye V2.0, Applied Biosystems,
Warrington, UK) and 1 µl of water. The reaction products were then
column-purified with AutoSeq96 plates (Amersham Pharmacia Biotech, Little
Chalfont, UK) and dried in a speed vacuum. These samples were resuspended in
10 µl of HiDi (Applied Biosystems). By use of an ABI 3700 DNA sequencer
(Applied Biosystems), these solutions were run on a 50 cm capillary array in
POP6 polymer (Applied Biosystems). The results were analyzed by Genetyx-Mac
(version 9, Tokyo, Japan) and compared with the mouse sequence.
Statistical Analyses
Results are presented as mean ± SEM. Comparisons between groups are
by the Mann-Whitney U test (two-tailed).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Experiment 2
When we used a lower dose of IL-11, we still found a protective effect with
either twice-daily or once-daily dosing. With 400 µg IL-11 twice daily,
glomerular fibrinoid necrosis and proteinuria were decreased by 74 and 86%,
respectively (P < 0.01). Once-daily treatment with 800 µg of
IL-11 achieved a similar therapeutic effect: fibrinoid necrosis decreased by
65% and proteinuria decreased by 64% (P < 0.01). Interestingly, at
this dose, there was no reduction in the number of macrophages within
glomeruli. However, activated macrophages as assessed by the expression of
sialoadhesin (ED3+) were significantly reduced by 71% in the twice-daily
experiment and 35% in the once-daily experiment (P < 0.05)
(Figures 1 and
2). The number of iNOS-positive
cells was higher in the glomeruli of IL-11—treated rats, and the
difference reached statistical significance in the 800 µg once-daily
experiment. The number of CD8+ cells in glomeruli was similar in
the two groups (Table 2).
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Enzyme-linked immunosorbent assay for circulating rat anti-rabbit antibodies was carried out on the rats treated once daily and showed that IL-11—treated rats had significantly higher levels (P < 0.05; Figure 3). However, direct immunofluorescence staining showed no difference in glomerular deposition of either rat or rabbit Ig (Figure 4).
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Experiment 3
To explore further the mechanism of this renal protective effect, we
examined the effect of IL-11 on the expression of the proinflammatory
cytokine, IL-1ß, before the onset of tissue injury. To avoid the
confounding effect of an alteration in macrophage numbers, we chose the lower
dose of IL-11 (used in experiment 2) because we had found that this did not
affect glomerular macrophage infiltration. Forty-eight hours after induction
of glomerulonephritis, glomerular RNA was extracted. Expression of IL-1ß
and ß-actin mRNA were quantified from this RNA by means of competitive
RT-PCR. Figure 5 shows an
example of the plot obtained in a representative competitive PCR reaction,
comparing the ratio of the intensity of bands amplified from the control
fragment and the glomerular sample to the starting concentration of the
control fragment. To control for variation in RNA amount, the level of
IL-1ß mRNA was normalized to the level of ß-actin mRNA level. The
results showed that the ratio of IL-1ß/ß-actin mRNA in the
IL-11—treated rats was reduced when compared with the control group
(Figure 6).
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Rat IL-11 Receptor -Chain
By using PCR primers designed from the mouse IL-11 receptor -chain
sequence, we showed that rat glomeruli, primary cultured mesangial cells, and
macrophages contained mRNA that produced a PCR product of the expected size
(Figure 7). The PCR product was
sequenced and compared with mouse sequence by the Blast test. This result
showed that the rat sequence shared 91% homology with mouse IL-11 receptor
-chain (Figure 8).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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in glomeruli as early as 1 h after induction of disease, with
levels of mRNA increasing to day 3
(27). Activated NF-B is
detectable from day 1 until at least day 14
(28). We studied this model
for the following reasons: (1) it is a reproducible model of severe
necrotizing glomerulonephritis, histologically resembling human focal and
segmental necrotizing glomerulonephritis; (2) there is infiltration
of glomeruli by activated macrophages and the glomerular injury is macrophage
dependent (29); and
(3) there is upregulation of IL-1ß and TNF- and
activation of NF-B, all of which have been reported to be downregulated
by IL-11. We chose to study the acute phase of the model, in the first
instance, to test the anti-inflammatory effect of IL-11.
IL-11 is a pleiotropic cytokine that was first identified in 1990. Human
IL-11 cDNA encodes a protein of 199 amino acids, with a leader sequence of 21
amino acids and a molecular mass of 19 kD (reviewed in Schwertschlag et
al. [7]). It is expressed
in multiple tissues, including the central nervous system, lung, bone,
connective tissue, skin, and kidney
(6,7),
but the cells responsible for its synthesis in the kidney are unknown. It is a
member of a family of cytokines that use the gp 130 receptor subunit for
signal transduction. The other members of the family are IL-6, ciliary
neurotropic factor, leukemia inhibitory factor, oncostatin M, and
cardiotropin-1. IL-11 was initially identified as a hemopoietic factor and has
a marked stimulatory effect on megakaryocyte and platelet production in
particular, although it has no effects on peripheral leukocyte counts when
administered to normal rodents
(30). It is currently approved
for the treatment of chemotherapy-induced thrombocytopenia. Of most interest
in the context of glomerulonephritis is its role as an anti-inflammatory
cytokine with the ability to reduce macrophage secretion of proinflammatory
cytokines through inhibition of NF-B activation. In LPS-stimulated
macrophages, IL-11 inhibited NF-B nuclear translocation, and this was
associated with an increase in the levels of IB proteins that bind and
sequester NF-B in the cytosol, thus preventing its nuclear
translocation and transcriptional activity
(9). We therefore hypothesized
that IL-11 would reduce glomerular inflammation in immune-mediated
glomerulonephritis.
We found that IL-11 did reduce glomerular damage as assessed by proteinuria and by segmental glomerular fibrinoid necrosis in the model of nephrotoxic nephritis in the WKY rat. At the higher dose, this was associated with a reduction in glomerular macrophage infiltration, but importantly, at the lower dose, there was no reduction in macrophage infiltration, although there was still a reduction in injury. We therefore asked whether we could detect any change in macrophage activation that could account for the reduced injury. We studied macrophage expression of sialoadhesin, which is a well recognized marker of activation in tissue macrophages (22,31), and found that there was a reduction in the number of macrophages expressing sialoadhesin in the IL-11—treated animals. This is similar to the results we have previously published that used the unrelated anti-inflammatory cytokine IL-4, which, if given after the onset of macrophage infiltration, reduced injury and macrophage sialoadhesin expression without an effect on glomerular macrophage numbers (21). Because this model is dependent on CD8+ cells (26), we also quantified glomerular CD8 cells in glomeruli but found that IL-11 had no effect, excluding this as a mechanism in the reduction of injury.
Macrophages are the major effector cells in human and experimental
glomerulonephritis (1).
Glomerular macrophage accumulation can occur through several mechanisms,
including humoral and cellular immunity
(32,33).
In immune complex disease, ligation of Fc receptors of macrophages and
possibly mesangial cells appears to play a central role, with subsequent
induction of adhesion molecule expression and chemokine secretion. The
macrophage response can be divided in two phases: the induction phase of
chemotaxis, adhesion, and migration; and the effector phase of cytokine
secretion, phagocytosis, tissue modeling, and destruction. Currently, most
studies in glomerulonephritis have focused on reagents that work on the
induction phase of inflammation, where the reduction of glomerular injury is
often accompanied by reduction of infiltrating macrophages. This has made
interpretation of the role of macrophage function in glomerulonephritis
difficult. To address this question clearly, in our study, we reduced the dose
of IL-11 in experiment 2 and found that even with a similar number of
glomerular macrophages in treated and control rats, IL-11—treated
animals still had significantly less proteinuria and fibrinoid necrosis. These
results showed that IL-11 exerted its renal protective effect not only by
reducting glomerular macrophage infiltration, but also through inactivating
macrophage function.
One possible way in which IL-11 could exert its effect is by reducing the glomerular binding of rabbit or rat Ig. We excluded this possibility by performing quantitative immunofluorescence. Interestingly, however, we found that IL-11 treatment led to an increase in circulating rat anti-rabbit Ig. This is consistent with the findings of a previous study that showed that IL-11 enhanced antibody synthesis in a primary immune response in mice (34).
We also examined macrophage expression of iNOS. iNOS is expressed by
macrophages in inflamed glomeruli, and isolated glomeruli synthesize NO in
vitro
(35,36,37,38).
However, the role of NO in the inflamed glomerulus is not clear. It has been
suggested that NO may have a damaging effect either directly or after
conversion to peroxynitrite, or alternatively, that it may have beneficial
effects by inhibiting glomerular thrombosis, adhesion molecule expression, and
inflammatory cytokine production
(39). IL-11 in vitro
has been shown to reduce NO synthesis by LPS or IFN-—treated
murine macrophages (8) but did
not reduce iNOS mRNA levels, suggesting that the control of NO synthesis was
at the translational or post-translational level
(9). In experimental murine
Lyme disease, iNOS mRNA was higher in the spleens of IL-11—treated mice
(40). We therefore assessed
the effect of IL-11 on macrophage iNOS expression in our model. By
immunohistochemistry, we found that there was a significant increase in
macrophages expressing iNOS. Further experiments will be necessary to
determine how this is related to levels of iNOS mRNA and the synthesis of NO,
which is critically dependent on substrate and cofactor availability. Our
results illustrate the complex nature of the relationship between glomerular
injury and iNOS expression.
To elucidate further the possible mechanism of action of IL-11 in this model, we examined the expression of the proinflammatory cytokine IL-1ß. We chose to study the lower dose of IL-11 because we had established that this did not affect macrophage numbers in the glomerulus, and therefore we hoped to demonstrate an effect on macrophage activation independent of an effect on glomerular infiltration. By using the method of quantitative RT-PCR, we found that at day 2 of the model, there was a marked reduction in the levels of IL-1ß mRNA in the glomeruli of the IL-11—treated animals. The importance of IL-1ß in mediating glomerular inflammation has been shown in studies that used antagonists such as IL-1 receptor antagonist (41), and we think that the downregulation of IL-1ß is likely to be an important mechanism by which IL-11 exerts its anti-inflammatory effect
In a model of combined radiation therapy and chemotherapy in mice, IL-11
was able to suppress intestinal epithelial cell apoptosis and therefore
increased survival (42). A
similar protective effect has also been shown after thoracic irradiation
(43). In our experiment, we
found that glomerular apoptosis in the IL-11—treated animals was
significantly reduced. Whether this is a direct effect of IL-11 or whether it
reflects a reduction in glomerular inflammation remains unclear. However, in
view of the known effect of TNF- and IL-1ß on apoptosis, and in
view of the fact that IL-11 can reduce production of these mediators by
downregulating macrophage function, one of the possible mechanisms of this
effect is that IL-11 reduces glomerular apoptosis indirectly through its
effect on glomerular macrophages.
PCNA is an accessory protein required for DNA synthesis and repair of DNA (44). In an in vitro study, Peterson et al. (45) showed that IL-11 had a cytoprotective effect by reducing the proliferation rate of a rat intestinal cell line and this growth inhibition effect correlated with delayed entry into S phase of the cell cycle. In this study, we also found that IL-11—treated rats had significantly lower PCNA in the glomeruli. This result indicates that IL-11 may also have a growth inhibitory effect on intraglomerular cells. Further study is necessary to clarify this effect.
Like other cytokines, to have its biologic effect on target cells, IL-11
has to interact with its receptor complex on the cellular surface. The
receptor for IL-11, like other members of the IL-6 family of cytokines, is
composed of a gp130 signal transduction unit together with a unique IL-11
receptor -chain (46).
Gp130 is an important signal transduction unit that is shared by many
cytokines and expressed in almost every organ, including kidney
(47). We therefore
investigated whether rat macrophages and mesangial cells expressed IL-11
receptor -chain. Because the rat IL-11 receptor -chain sequence
is still unknown, we used primer pairs designed from mouse IL-11 receptor
-chain sequence. The PCR results revealed that glomeruli, primary
cultured mesangial cells, and peritoneal macrophages of WKY rats all possessed
IL-11 receptor -chain. The PCR product was sequenced and showed 91%
homology with mouse IL-11 receptor -chain. We think that this is the
first demonstration of the rat IL-11 receptor -chain sequence.
Because IL-11 is a member of the IL-6 cytokine family, it is important to compare its effect with other members of the family. Clearly, the effects of the different members are not identical. For example, IL-11 inhibits macrophage synthesis of IL-12, whereas IL-6 does not (10). Our group has previously studied the effect of continuous infusion of IL-6 in a model of accelerated nephrotoxic nephritis in the Lewis rats and has shown a reduction of albuminuria, glomerular macrophage infiltration, and glomerular sialoadhesin expression similar to the results we have found here with IL-11 (48). Further studies will be necessary to elucidate the relative therapeutic potential of IL-11 compared with IL-6 and other potential therapeutic anti-inflammatory cytokines such as IL-4 and IL-10. One of the possible benefits of IL-11, in addition to its role in reducing macrophage activation, is its ability to divert the immune response from a Th1 to a Th2 response (14). The possible relevance of this to glomerular inflammation will require the use of different models such as experimental autoimmune glomerulonephritis in the rat (49) and Th1-dependent crescentic nephritis in the mouse (50), and this is the subject of future experiments.
To our knowledge, this is the first study to examine the effect of IL-11 in glomerulonephritis. We found that in a model of severe necrotizing glomerular injury, IL-11 reduced glomerular necrosis and proteinuria. At a higher dose, there was a reduction in glomerular macrophage infiltration. At a lower dose, macrophage numbers were unaffected, but there was evidence of a reduction in macrophage activation and in glomerular IL-1ß expression. We think IL-11 is worthy of further investigation in the treatment of glomerulonephritis.
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Acknowledgments |
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References |
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) in
anti—glomerular basement membrane (GBM) glomerulonephritis (GN) in WKY
rats [Abstract]. J Am Soc Nephrol9
: 458A,1998
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