Anti-inflammatory lymphokine mRNA expression in antibody-induced glomerulonephritis

Expansion of regulatory T cells using low-dose interleukin-2 attenuates hypertension in an experimental model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disorder that is characterized by prevalent hypertension, renal injury, and cardiovascular disease. Numerous studies have reported a low prevalence and/or impaired function of regulatory T (T_REG) cells in both patients with SLE and murine models of the disease. Evidence suggests that T_REG cell dysfunction in SLE results from a deficiency in IL-2. Recent studies have reported that low-dose IL-2 therapy expands T_REG cells in mouse models of SLE, but whether expanding T_REG cells protects against hypertension and renal injury during SLE is unclear. To examine this question, female SLE (NZBWF1) and control (NZW) mice were injected with vehicle or recombinant mouse IL-2 three times in 24 h followed by single maintenance doses every 5 days for 4 wk. Treatment with IL-2 effectively expanded T_REG cell populations in the peripheral blood, spleen, and kidneys. Circulating levels of anti-dsDNA IgG autoantibodies, a marker of SLE disease activity, were higher in SLE mice compared with control mice but were unaffected by IL-2 treatment. As previously reported by our laboratory, mean arterial pressure, measured in conscious mice by a carotid catheter, was higher in SLE mice than in control mice. Mean arterial pressure was significantly lower in IL-2-treated SLE mice compared with vehicle-treated SLE mice, suggesting that expanding T_REG cells using low-dose IL-2 attenuates the development of hypertension. While the mechanism for the protection against hypertension is unclear, it does not appear to be related to the delay of SLE disease progression.

Hepatotoxic effect of subacute vincristine administration activates necrosis and intrinsic apoptosis in rats: protective roles of broccoli and Indian mustard

This study investigated the hepatotoxic effect of long-term vincristine (VCR) administration in rats and to assess if an individual or combined therapy with Indian mustard and broccoli afforded protection. Signs of hepatotoxicity, including altered liver architecture and higher serum levels of ALT and AST, were seen in VCR-treated rats. Concomitantly, the impaired antioxidant potential and higher mRNA levels of IL-12 and IL-4, which are markers of apoptosis, were seen in rat livers. VCR treatment induced hepatocyte apoptosis, shown by the up-regulation of mRNA and protein levels of 53, increased protein levels of cleaved caspase-3 and Bax, and reduced levels of intracellular ATP and BCl-2mRNA and protein. Although individual administration of mustard or broccoli partially ameliorated all these responses, the combined therapy of both extracts resulted in the maximum improvement. Thus, the long-term administration of VCR is hepatotoxic and induces apoptosis; however, the combined therapy of both extracts mitigated these effects.

IL10 haplotypes are associated with diabetic nephropathy susceptibility in patients from western Mexico

INTRODUCTION

Diabetic Nephropathy (DN) is the main cause of chronic kidney disease (CKD) in diabetic patients. An IL-10 imbalance could be related to renal hypertrophy and trigger to nephropathy. Three promoter polymorphisms (-1082G>A, -819C>T, and -592C>A) at IL10 gene have been associated with changes in the IL-10 expression and DN susceptibility. Therefore, the aim of this study was to analyze this association in Mexican patients with DN.

METHODS

We conducted a case-control study on 128 patients with DN and 150 control subjects (CS) from western Mexico. All patients were tested for IL10 polymorphisms by PCR-RFLP. Allele frequencies, genotypes, and haplotypes were compared between groups. The significant haplotypes were correlated with patient clinical features.

RESULTS

IL10 gene ATC haplotype (-1082A/-819T/-592C) was found significantly more frequent in DN patients than in CS (P < 0.001; OR = 3.6, 95% CI: 1.7-7.4). Similarly GTA (-1082G/-819T/-592A) haplotype was more frequent in DN patients than CS with significant differences (P < 0.05; OR = 4.02, 95% CI: 1.10-14.78). There were no correlations between IL10 haplotypes and clinical parameters in patients with DN. However, that there is a trend of higher serum urea levels and lower eGFR in ATC haplotype carriers compared to carriers of the other haplotypes (P < 0.05).

CONCLUSIONS

These results indicate that IL10 promoter haplotypes ATC and GTA carriers have a higher risk factor to develop DN in the western Mexican population.

Defective Treg response in acute kidney injury was caused by a reduction in TIM-3+ Treg cells

BACKGROUND

Despite years of research, the treatment of acute kidney injury (AKI) remains a significant challenge. Animal studies presented causal links between elevated regulatory T cell (Treg) response and better prognosis in AKI. Previous studies in mice and humans showed that TIM-3+ Treg cells were more potent than TIM-3- Treg cells. In this study, we investigated the role of TIM-3 in Treg in AKI patients.

METHODS

Peripheral blood from AKI patients and healthy controls were gathered, and TIM-3+ Treg subset was examined.

RESULTS

Compared to healthy controls, the AKI patients presented a significant upregulation in the frequency of circulating CD4+CD25+ T cells; however, the majority of this increase was from the CD4+CD25+TIM-3- subset, and the frequency of CD4+CD25+TIM-3+ T cells was downregulated in AKI patients. In both healthy controls and AKI patients, the CD4+CD25+TIM-3+ T cells expressed higher levels of Foxp3, and were more potent at expressing LFA-1, LAG-3, CTLA-4, IL-10 and TGF-β. In addition, the CD4+CD25+TIM-3+ T cells from both healthy controls and AKI patients presented higher capacity to suppress CD4+CD25- T cell proliferation than the CD4+CD25+TIM-3- T cells. Interestingly, the total CD4+CD25+ T cells from AKI patients presented significantly lower inhibitory capacity than those from healthy controls, indicating that the low frequency of CD4+CD25+TIM-3+ T cells was restricting the efficacy of the Treg responses in AKI patients.

CONCLUSIONS

We demonstrated that TIM-3 downregulation impaired the function of Treg cells in AKI. The therapeutic potential of CD4+CD25+TIM-3+ T cells in AKI should be investigated in future studies.

Overexpression of Heme Oxygenase-1 Prevents Renal Interstitial Inflammation and Fibrosis Induced by Unilateral Ureter Obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases. Many studies have demonstrated that heme oxygenase-1 (HO-1) is involved in diverse biological processes as a cytoprotective molecule, including anti-inflammatory, anti-oxidant, anti-apoptotic, antiproliferative, and immunomodulatory effects. However, the mechanisms of HO-1 prevention in renal interstitial fibrosis remain unknown. In this study, HO-1 transgenic (TG) mice were employed to investigate the effect of HO-1 on renal fibrosis using a unilateral ureter obstruction (UUO) model and to explore the potential mechanisms. We found that HO-1 was adaptively upregulated in kidneys of both TG and wild type (WT) mice after UUO. The levels of HO-1 mRNA and protein were increased in TG mice compared with WT mice under normal conditions. HO-1 expression was further enhanced after UUO and remained high during the entire experimental process. Renal interstitial fibrosis in the TG group was significantly attenuated compared with that in the WT group after UUO. Moreover, overexpression of HO-1 inhibited the loss of peritubular capillaries. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by HO-1 overexpression. Furthermore, HO-1 restrained tubulointerstitial infiltration of macrophages and regulated the secretion of inflammatory cytokines in UUO mice. We also found that high expression of HO-1 inhibited reactivation of Wnt/β-catenin signaling, which could play a crucial role in attenuating renal fibrosis. In conclusion, these data suggest that HO-1 prevents renal tubulointerstitial fibrosis possibly by regulating the inflammatory response and Wnt/β-catenin signaling. This study provides evidence that augmentation of HO-1 levels may be a therapeutic strategy against renal interstitial fibrosis.

5-Lypoxygenase products are involved in renal tubulointerstitial injury induced by albumin overload in proximal tubules in mice

The role of albumin overload in proximal tubules (PT) in the development of tubulointerstitial injury and, consequently, in the progression of renal disease has become more relevant in recent years. Despite the importance of leukotrienes (LTs) in renal disease, little is known about their role in tubulointerstitial injury. The aim of the present work was to investigate the possible role of LTs on tubulointerstitial injury induced by albumin overload. An animal model of tubulointerstitial injury challenged by bovine serum albumin was developed in SV129 mice (wild-type) and 5-lipoxygenase-deficient mice (5-LO^–/–). The changes in glomerular morphology and nestin expression observed in wild-type mice subjected to kidney insult were also observed in 5-LO^–/– mice. The levels of urinary protein observed in the 5-LO^–/– mice subjected or not to kidney insult were lower than those observed in respective wild-type mice. Furthermore, the increase in lactate dehydrogenase activity, a marker of tubule damage, observed in wild-type mice subjected to kidney insult did not occur in 5-LO^–/– mice. LTB₄ and LTD₄, 5-LO products, decreased the uptake of albumin in LLC-PK1 cells, a well-characterized porcine PT cell line. This effect correlated with activation of protein kinase C and inhibition of protein kinase B. The level of proinflammatory cytokines, tumor necrosis factor-α and interleukin (IL)-6, increased in mice subjected to kidney insult but this effect was not modified in 5-LO^–/– mice. However, 5-LO^–/– mice subjected to kidney insult presented lower macrophage infiltration and higher levels of IL-10 than wild-type mice. Our results reveal that LTs have an important role in tubulointerstitial disease induced by albumin overload.

Kinetics of adaptive immunity to cationic bovine serum albumin-induced membranous nephropathy

Membranous nephropathy is an autoimmune-mediated glomerulonephritis and a major cause of nephrotic syndrome. We studied the kinetics of adaptive immunity in the pathogenesis of membranous nephropathy in T1/T2 double transgenic mice (T1/T2 TG mice) that express human Thy1 protein under the control of interferon-gamma (INF-gamma) and mouse Thy1.1 protein under the control of interleukin (IL)-4. Nephropathy was induced by cationic bovine serum albumin. We found that splenocytes expressed a progressive Th2 response and a subsequent compensatory T-helper 1 (Th1) response, with a gradual augmentation of IL-4-producing Th2 cells and INF-gamma-producing Th1 cells. Increased Th2 marker expression was seen in peripheral blood and kidney cells, with the immunoglobulin G1 (IgG1) antibody isotype predominant in the serum and kidneys. We found that CD8+ T cells contribute more to the augmented INF-gamma production than CD4+ T cells. Moreover, CD19+ B cells demonstrated a greater production of IL-4 than the CD4+ T cells. Cytokine-related gene expression in kidneys and splenocytes showed an upregulation of proinflammatory Th1 and Th2 cytokines. Th2 cells but not Th1 cells were significantly correlated with serum cholesterol and proteinuria. Our study shows that both peripheral and renal immune reactions are strongly polarized toward Th2-type immune responses during the course of membranous nephropathy. The T1/T2 mouse model may help decipher the kinetic changes of adaptive immunity in glomerulonephritis.

Mesangial cells initiate compensatory renal tubular hypertrophy via IL-10-induced TGF-β secretion: effect of the immunomodulator AS101 on this process

The present study investigated the role of IL-10 produced by the mesangial cells in postnephrectomy compensatory renal growth and the effect of the immunomodulator AS101 on this process. One hundred forty unilateral nephrectomized and sham-operated male Sprague-Dawley rats were treated by AS101 or PBS before and after surgery. The results show that secretion of IL-10 and TGF-β by mesangial cells isolated from the remaining kidneys was increased significantly, compared with those of control and sham animals. Moreover, TGF-β secretion by mesangial cells was increased after the addition of exogenous recombinant IL-10 and inhibited in the presence of neutralizing anti-IL-10 antibodies. In vivo, compensatory growth of the remaining kidneys was associated with significant increase in IL-10 content in renal tissues and plasma. Immunohistochemical studies show that IL-10 was produced by mesangial cells. Elevated IL-10 levels were followed by the rise in TGF-β content in plasma and renal tissue. AS101 treatment decreased IL-10 and TGF-β expression in plasma and kidney tissues and results in 25% reduction in the fresh and fractional kidney weight and decreased hypertrophy of tubular cells (protein/DNA ratio, morphometric analysis). Taken together, these data demonstrate that TGF-β production by mesangial cells is IL-10 dependent. Mesangial cells are the major source of IL-10 in kidneys. AS101, by inhibiting the activity of IL-10, decreases TGF-β production by mesangial cells, thus limiting compensatory tubular cell hypertrophy.

IL-18 translational inhibition restricts IFN-gamma expression in crescentic glomerulonephritis

BACKGROUND

Interleukin-18 (IL-18), a potent inducer of interferon gamma (IFN-gamma) production, is a cytokine involved in the cell-mediated immune response that is expressed during inflammatory and pathologic conditions. IFN-gamma plays a role in the development of some models of glomerulonephritis (GN); however, the role of IL-18 in the production of IFN-gamma during these pathologies has not been studied.

METHODS

Rat IL-18 cDNA was isolated and the regulation of IL-18 gene expression was studied. IFN-gamma and IL-18 expression were determined in anti-glomerular basement membrane (GBM) antibody (Ab)-induced GN. Recombinant active IL-18 (rIL-18) was used to further identify its effect on IFN-gamma production during this GN. Glomerular injury and levels of IFN-gamma were assayed in Wistar Kyoto (WKY) rats with anti-GBM GN in the presence or absence of rIL-18.

RESULTS

Rat IL-18, similar to the mouse clone, requires processing by the IL-1beta converting enzyme to become activated. A rat IL-18 5'-untranslated region (UTR) translational inhibitor was identified that strongly inhibited the synthesis of IL-18. This translational inhibitor with different lengths (180 and 130 bp) was highly expressed during GN and correlated with minimal IFN-gamma mRNA expression. Injection of recombinant active IL-18 in WKY rats with anti-GBM GN was associated with an increase of glomerular IFN-gamma levels, proliferating cell nuclear antigen (PCNA)-ED1+ cells, and PCNA-CD8+ cells, with worsening of glomerular injury.

CONCLUSION

These data suggest that the translational control of IL-18 expression by its 5'-UTR limits the production of IL-18, resulting in restricted expression of mRNA and protein IFN-gamma in this model of GN. Furthermore, it was suggested that possible IL-18/IFN-gamma induction of local proliferation of macrophages and CD8+ cells might be an important mechanism for amplifying CD8+-mediated macrophage-dependent GN.

Interleukin-10 inhibits experimental mesangial proliferative glomerulonephritis

Conflicting reports exist regarding the effects of interleukin-10 (IL-10) on mesangial cells. There have been reports of both proliferative and antiproliferative effects, and both proinflammatory and anti-inflammatory effects of IL-10 on mesangial cells. However, the potential for IL-10 to affect glomerulonephritis characterized by mesangial proliferation is not known. To test the hypothesis that IL-10 would limit experimental mesangial proliferative glomerulonephritis, IL-10 was administered to rats in which mesangial proliferative glomerulonephritis was induced by administration of anti-Thy 1 antibody. Compared to control treated rats, IL-10 treated rats showed less proliferation, with fewer cells in glomeruli. Glomerular cellular proliferation was reduced, assessed by the numbers of cells within glomeruli expressing either proliferating cell nuclear antigen (PCNA) or bromodeoxyuridine. Glomerular macrophage influx (but not the proportion of glomerular macrophages that were PCNA positive) was reduced by IL-10 administration. There was no significant reduction in glomerular alpha-smooth muscle actin staining. IL-10 treatment resulted in reduced renal IL-1beta mRNA expression and reduced glomerular ICAM-1 expression, but renal expression of MCP-1 and osteopontin mRNA was unaltered. This study demonstrates that in experimental mesangial proliferative glomerulonephritis IL-10 diminishes inflammatory cell recruitment and mesangial cell proliferation. The effects of IL-10 in inhibiting mesangial cell proliferation are likely to be due to a combination of direct effects of IL-10 on mesangial cells and effects mediated by macrophages.

Posttranscriptional regulation of human iNOS by the NO/cGMP pathway

Nitric oxide (NO) and cGMP may exert positive or negative effects on inducible NO synthase (iNOS) expression. We have explored the influence of the NO/cGMP pathway on iNOS levels in human mesangial cells. Inhibition of NOS activity during an 8-h stimulation with IL-1beta plus tumor necrosis factor (TNF)-alpha reduced iNOS levels, while NO donors amplified iNOS induction threefold. However, time-course studies revealed a subsequent inhibitory effect of NO donors on iNOS protein and mRNA levels. This suggests that NO may contribute both to iNOS induction and downregulation. Soluble guanylyl cyclase (sGC) activation may be involved in these effects. Inhibition of sGC attenuated IL-1beta/TNF-alpha-elicited iNOS induction and reduced NO-driven amplification. Interestingly, cGMP analogs also modulated iNOS protein and mRNA levels in a biphasic manner. Inhibition of transcription unveiled a negative posttranscriptional modulation of the iNOS transcript by NO and cGMP at late times of induction. Supplementation with 8-bromo-cGMP (8-BrcGMP) reduced iNOS mRNA stability by 50%. These observations evidence a complex feedback regulation of iNOS expression, in which posttranscriptional mechanisms may play an important role.

Cytokines and hormones with anti-inflammatory effects: new tools for therapeutic intervention

The inflammation that is involved in the development of glomerulonephritis is tightly regulated by the expression of anti-inflammatory factors. These include circulating hormones, such as glucocorticoids, and mediators that are produced by intrinsic cells and infiltrating leucocytes. The present review focuses on these anti-inflammatory factors, summarizing in particular their activities in existing models of glomerulonephritis. In addition, experimental evidence is presented that anti-inflammatory mediators are able to increase glucocorticoid binding or signalling in target cells. These data help to explain the in-vivo efficacy of anti-inflammatory mediators, and offer a promising new avenue for therapeutic intervention.

An anti-CD5 monoclonal antibody ameliorates proteinuria and glomerular lesions in rat mesangioproliferative glomerulonephritis

BACKGROUND

Increased numbers of lymphocytes have been identified in biopsy specimens of human mesangial proliferative glomerulonephritis (GN). However, the causal relationship between infiltrating T lymphocytes and mesangial changes in mesangial proliferative GN has not been previously evaluated. In this study, we elucidated the role of lymphocytes in the development of mesangial proliferative GN.

METHOD

Immunohistological and flow cytometric analyses as well as a reverse transcription-polymerase chain reaction (RT-PCR) studies were performed in monoclonal antibody (mAb) 1-22-3-induced Thy 1.1 GN. To elucidate the role of these lymphocytes, depletion studies were carried out using anti-CD8 mAb (OX-8), which depletes both CD8+ T lymphocytes and natural killer (NK) cells and anti-CD5 mAb (OX-19), which depletes both CD4+ and CD8+ T lymphocytes.

RESULTS

Immunofluorescence (IF) studies revealed that NK cells and CD4+ T lymphocytes were recruited into glomeruli. Glomerular mRNA expression for interferon-gamma, interleukin-2 (IL-2), IL-10, and perforin increased after induction of GN. Increased expressions of several chemokines, which have the potential to attract lymphocytes, were also detected. Anti-CD8 mAb treatment completely prevented the recruitment of NK cells; however, it had no protective effect on proteinuria and mesangial injury. By contrast, anti-CD5 mAb treatment suppressed the recruitment of CD4+ T lymphocytes into glomeruli and reduced proteinuria (60.4 +/- 25.7 vs. 120.0 +/- 32.3 mg/day, P < 0.05) and mesangial changes evaluated by total number of cells in glomeruli (63.2 +/- 6.0 vs. 81.4 +/- 5.9, P < 0.01) and alpha-smooth muscle actin staining score (1.4 +/- 0.2 vs. 2.2 +/- 0. 4, cf2eth P < 0.01) on day 14 after induction of GN. mRNA expression for IL-2 was significantly reduced by OX-19 treatment.

CONCLUSION

T lymphocytes participate in the development of mesangial proliferative GN.

Endogenous interleukin-10 regulates Th1 responses that induce crescentic glomerulonephritis

BACKGROUND

Interleukin (IL)-10 plays a pivotal role in regulating the Th1/Th2 predominance of immune responses. Exogenously administered IL-10 suppresses nephritogenic Th1 responses, inhibits macrophage function, and attenuates crescentic glomerulonephritis (GN). To determine the role of endogenous IL-10, the development of the nephritogenic immune response and crescentic GN was compared in IL-10-deficient (IL-10-/-) and normal (IL-10+/+) C57BL/6 mice.

METHODS

GN was initiated in sensitized mice by the intravenous administration of sheep antimouse glomerular basement membrane globulin. Renal injury was evaluated 21 days later.

RESULTS

Following the administration of anti-glomerular basement membrane globulin, normal (IL-10+/+) C57BL/6 mice developed proliferative GN with occasional crescents, glomerular CD4+ T-cell and macrophage accumulation, and fibrin deposition. Using an identical induction protocol, IL-10-/-mice developed more severe GN. Crescent formation (IL-10-/-, 23 +/- 2% of glomeruli; IL-10+/+, 5 +/- 2%), glomerular CD4+ T cells [IL-10-/-, 1. 0 +/- 0.2 cells per glomerular cross-section (c/gcs); IL-10 +/+, 0.3 +/- 0.05 c/gcs], glomerular macrophages (IL-10-/-, 4.8 +/- 0.3 c/gcs; IL-10 +/+, 1.7 +/- 0.2 c/gcs), fibrin deposition [fibrin score (range 0 to 3+); IL-10-/-, 1.10 +/- 0.04; IL-10+/+, 0.6 +/- 0. 07], and serum creatinine (IL-10-/-, 30 +/- 2 micromol/L; IL-10 +/+, 23 +/- 1 micromol/L) were all significantly increased in IL-10-/- mice (P < 0.05). Circulating antibody (IL-10-/-, 1.05 +/- 0.16 OD units; IL-10+/+, 0.63 +/- 0.08 OD units) and cutaneous delayed-type hypersensitivity (skin swelling; IL-10-/-, 0.21 +/- 0.03 mm; IL-10+/+, 0.12 +/- 0.02 mm) to the nephritogenic antigen (sheep globulin) were also increased (both P < 0.05). Interferon-gamma production by cultured splenocytes was increased (IL-10-/- 7.9 +/- 2. 5 ng/4 x 106 cells, IL-10+/+ 0.28 +/- 0.09 ng/4 x 106 cells, P < 0. 05), but IL-4 production was unchanged.

CONCLUSIONS

Endogenous IL-10 counter-regulates nephritogenic Th1 responses and attenuates crescentic GN.

Identification of soluble interleukin-4 receptor in rat glomerular epithelial cells(1)

Interleukin (IL)-4, a pleiotropic cytokine involved in many glomerular diseases, is regulated positively by membrane-bound IL-4R (mIL-4R) and negatively by soluble IL-4R (sIL-4R). Because natural sIL-4R has been documented only in mice, we undertook this study in rats to determine whether they, too, express sIL-4R, particularly in kidney cells. A pair of IL-4R primers was designed for this purpose and used in the polymerase chain reaction. As a result, sIL-4R was found not only in rats spleen cells but also in their glomerular epithelial cells (GEC). Sequence analysis revealed that the mRNA of rat sIL-4R has a 75-bp insert sequence. This insert generated a termination TGA codon upstream from the transmembrane region, resulting in formation of the sIL-4R. Subsequent screening of the kidney cDNA library enabled us to obtain the whole 3605-bp cDNA of sIL-4R; the full-length 3530-bp mIL-4R cDNA was also identified as a much longer sequence than previously published. Among the total 39 clones positive for IL-4R, two were confirmed as sIL-4R, and 37 clones were positive for mIL-4R. Next, the translated portion of sIL-4R cDNA was constructed into an expression vector, enabling us to obtain a recombinant sIL4R-myc fusion protein. By using this recombinant sIL-4R, we proved that sIL-4R can antagonize the IL-4-induced proliferation of spleen cells. Present study demonstrated that sIL-4R is expressed in kidney cells and antagonistically functional.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

Failure to induce anti-glomerular basement membrane glomerulonephritis in TNF alpha/beta deficient mice

TNF is a key proinflammatory cytokine playing a central role in the expression of endothelial adhesion molecules required for the recruitment of inflammatory cells. Proliferative glomerulonephritis induced by anti-GBM antibody is characterized by the recruitment of inflammatory cells into the glomerulus and capillary damage followed by regeneration with crescent formation. The glomerular pathology may be due to TNF induction and we therefore tested this hypothesis in TNF alpha/beta deficient mice. Anti-GBM antibody administration in sensitised wild-type mice resulted in deposition of immune complexes and complement factor 3, followed by increased ICAM-1 and VCAM-1 expression and influx of polymorphonuclear leucocytes. Distinct proteinuria precedes proliferative glomerulonephritis with glomerular crescent formation, which is fully developed at 10 days. By contrast, no glomerulonephritis developed in TNF alpha/beta deficient mice. Comparable antibody complex deposits are found, but the upregulation of ICAM-1 and VCAM-1, the influx of inflammatory cells and the subsequent tissue damage is absent in TNF alpha/beta deficient mice. Therefore, we conclude that TNF plays a key role for the recruitment of inflammatory cells by preventing the upregulation of endothelial adhesion molecule and the subsequent development of proliferative glomerulonephritis.

TGF-β1 as an Endogenous Defender Against Macrophage-Triggered Stromelysin Gene Expression in the Glomerulus

Recent investigation has indicated that TGF-β1, the macrophage (Mφ) deactivator, may attenuate Mφ-mediated acute glomerular injury. Using stromelysin as an indicator, this study investigated whether and how endogenous TGF-β1 modulates the glomerular cell activation triggered by Mφ. Rat mesangial cells were stably transfected with a cDNA encoding the active form of TGF-β1 and a cDNA coding for a dominant-negative mutant of the TGF-βR type II. Compared with mock-transfected cells, TGF-β1 transfectants exhibited blunted expression of stromelysin in response to the Mφ-derived, inflammatory cytokine IL-1β. In contrast, mesangial cells expressing the dominant-interfering TGF-βR showed enhanced expression of stromelysin in response to IL-1β, suggesting that endogenous TGF-β functions as an autocrine inhibitor of the IL-1 response. In isolated, normal rat glomeruli, externally added TGF-β1 suppressed the induction of stromelysin by mediators that were elaborated by activated Mφ. Similarly, when isolated, nephritic glomeruli producing the active form of TGF-β1 were stimulated by IL-1β or Mφ-conditioned medium, the induction of stromelysin was dramatically suppressed as compared with normal glomeruli. To investigate whether endogenous TGF-β1 affects the glomerular cell activation triggered by Mφ, a technique for adoptive Mφ transfer was used. LPS-stimulated reporter Mφ were transferred into either normal rat glomeruli or nephritic glomeruli expressing active TGF-β1. In the normal glomeruli, stromelysin expression was markedly induced in resident cells after the transfer of activated Mφ. This induction was substantially repressed in those glomeruli producing active TGF-β1. These results reinforce the idea that TGF-β1 is an endogenous defender that attenuates certain actions of infiltrating Mφ in the glomerulus.

IL-4 Is an Endogenous Inhibitor of Neutrophil Influx and Subsequent Pathology in Acute Antibody-Mediated Inflammation

IL-4 is an immunoregulatory cytokine that has in vitro and in vivo anti-inflammatory actions. In this study we investigated whether endogenously produced IL-4 modulates inflammatory processes that occur after Abs bind to target tissue by comparing the severity of glomerulonephritis induced by heterologous anti-glomerular basement membrane Abs in wild-type (IL-4+/+) mice to that of glomerulonephritis induced in homozygous IL-4 gene knockout (IL-4−/−) mice. Two hours after Ab injection, IL-4−/− mice had significantly higher intrarenal intercellular adhesion molecule-1 mRNA expression and intraglomerular neutrophil accumulation than the IL-4+/+ group. Treatment of IL-4−/− mice with recombinant murine IL-4 at the time of disease induction reduced intercellular adhesion molecule-1 expression and neutrophil influx to levels observed in IL-4+/+ kidneys. Four days after Ab administration, untreated IL-4−/− mice developed significantly greater urinary protein excretion, intracapillary fibrinogen deposits, and glomerular hypercellularity than IL-4+/+ mice. These results demonstrate that endogenous IL-4 suppresses neutrophil influx and limits tissue damage in Ab-induced glomerulonephritis, suggesting that IL-4 is an important regulator of acute inflammatory processes.

TGF-beta1-induced cell cycle arrest in renal mesangial cells involves inhibition of cyclin E-cdk 2 activation and retinoblastoma protein phosphorylation

In glomerular disease, transforming growth factor-beta1 (TGF-beta1) has been demonstrated to exert anti-mitogenic and anti-inflammatory as well as fibrogenic effects. To better understand the TGF-beta1 action on glomerular cells at the molecular level, we investigated mechanisms of TGF-beta1-induced growth suppression in primary cultures of rat mesangial cells (MCs). TGF-beta1 (5 ng/ml) markedly inhibited proliferation of MCs incubated with PDGF, endothelin-1, bFGF, serotonin, or EGF, indicating that TGF-beta1 interferes with post-receptor signals of mitogenesis. TGF-beta1 did not affect mitogen-stimulated induction of the immediate early genes, c-fos, c-jun, and Egr-1 in MCs that occurred transiently at 30 to 120 minutes. Time-course studies revealed that TGF-beta1 inhibited DNA synthesis and MC replication when added up to six to eight hours after MC stimulation with PDGF. FACS analysis demonstrated that MCs had reached middle to late G1 phase of cell cycle progression at this timepoint. PDGF stimulation of MCs induced protein expression of the G1 phase cyclin D1 as well as the cyclin-dependent kinases cdk 4 and cdk 2. This was not significantly altered when MCs were coincubated with both, PDGF and TGF-beta1. However, TGF-beta1 prevented PDGF-elicited phosphorylation of the retinoblastoma tumor suppressor (pRb), a negative cell cycle regulator. Moreover, TGF-beta1 significantly reduced cyclin E-associated histone H1 kinase activity in the presence of PDGF. These results indicate that TGF-beta1 inhibits mitogen-stimulated MC growth by causing cell cycle arrest in late G1 phase. While TGF-beta1 does not alter the mitogen-induced expression and abundance of G1 phase cyclin D1 and cdks 4 and 2 in MCs, it inhibits cyclin E-cdk 2 activity, thus preventing mitogen-elicited phosphorylation and inactivation of pRb in G1 phase and transition to S phase.

Immunologic determinants of susceptibility to experimental glomerulonephritis: role of cellular immunity

To identify the immunologic mechanisms that influence susceptibility to GN, we compared the severity of accelerated anti-glomerular basement membrane (GBM) nephritis between Lewis (LEW) and Brown Norway (BN) rats and analyzed differences in their immune responses to the nephritogenic immunoglobulin. Lewis (LEW) rats preimmunized with sheep IgG developed proliferative GN with marked proteinuria [peak protein excretion (mean +/- SEM) = 85.3 +/- 15.3 mg/24 hr; normal = 6.4 +/- 0.8 mg/24 hr] after receiving a subnephritogenic dose of sheep anti-rat GBM antiserum. Identically treated Brown Norway (BN) rats, on the other hand, had minimal renal pathology and minimal proteinuria (peak protein excretion = 22.6 +/- 3.1 mg/24 hr; normal = 13.0 +/- 0.6 mg/24 hr). Serum titers of rat anti-sheep IgG isotypes and intraglomerular binding of sheep IgG, rat IgG, and rat complement (C3) were comparable in both strains. In contrast, only LEW rats developed a strong cellular immune response to sheep IgG represented by intrarenal T lymphocyte (OX19+) and monocyte (ED1+) accumulation [LEW vs. BN (mean +/- SEM): OX19+ = 0.60 +/- 0.10 vs. 0.14 +/- 0.01 cells/glomerulus, control = 0.02 +/- 0.01; ED1+ = 4.0 +/- 0.4 vs. 1.0 +/- 0.2 cells/glom., control = 0.8 +/- 0.3] and a significant cutaneous delayed-type hypersensitivity (DTH) reaction [LEW versus BN (mean +/- SEM): delta ear thickness = 0.22 +/- 0.02 vs. 0.05 +/- 0.03 mm; control = 0.04 +/- 0.02 mm]. Upon rechallenge with sheep IgG in vitro, LEW splenocytes expressed a T helper 1 (Th1) cytokine pattern (IFN gamma and IL-2 mRNA, but little IL-4 mRNA) which is associated with delayed-type hypersensitivity reactions. BN splenocytes, on the other hand, expressed IL-4 in addition to IL-2 and IFN gamma mRNA that is consistent with an undifferentiated (Th0) cytokine profile. These studies suggest that humoral immunity to heterologous immunoglobulin planted in the kidney is not sufficient for full expression of accelerated anti-GBM nephritis, and that additional cellular immune mechanisms are required. We conclude that susceptibility to accelerated anti-GBM nephritis is strongly influenced by the host's propensity to mount a Th1-type response and DTH reaction to the disease-inciting immunoglobulin.

Renal fibrosis: insights into pathogenesis and treatment

The progression of chronic renal failure is characterised histologically by glomerulosclerosis, tubulointerstitial fibrosis and vascular sclerosis. Recent research has identified common mechanisms underlying these fibrotic processes. In particular, the scarring process within the glomeruli and the tubulointerstitium involves the infiltration by inflammatory cells including monocytes, the activation of intrinsic renal cells as well as interactions between infiltrating and resident cells. These interactions depend, to a large extent, on the release by these cells of chemokines, cytokines and growth factors. These factors are in turn involved in the induction of cellular proliferation within the kidney and the stimulation of the synthesis and deposition of extracellular collagenous matrix. Fibrosis is believed to result from excessive synthesis of extracellular matrix and a concommitant decrease in its breakdown. This fibrotic process resulting in end stage renal insufficiency bears strong similarities to that taking place within cirrhotic livers or fibrotic lungs. The new insights in our understanding of renal fibrosis have opened the way to new interventions aimed at its prevention. This may ultimately slow the progression of chronic renal insufficiency and decrease the number of patients requiring dialysis replacement therapy.