MRL-Fas Lpr Mice Research Articles

Gene transfer of RANTES elicits autoimmune renal injury in MRL-Faslpr mice

We report that the beta-chemokine RANTES, a chemoattractant for macrophages and T cells, is up-regulated in the MRL-Fas(1pr) kidney prior to injury, but not normal kidneys (MRL-++, C3H-++) and increases with progressive injury. Furthermore, we establish an association between RANTES expression in the kidney and renal damage using a gene transfer approach. Tubular epithelial cells genetically modified to secrete RANTES infused under the renal capsule incites interstitial nephritis in MRL-Fas(1pr), but not MRL-++ or C3H-++ mice. RANTES recruits predominantly macrophages (M phi) and CD4+ and CD8+ T cells. In contrast, gene transfer of CSF-1, another molecule up-regulated simultaneously with RANTES in MRL-Fas(1pr) kidneys, promotes the influx of M phi, CD4+ T cells and the unique double-negative (DN) T cells (CD4-, CD8-), which are prominent in diseased MRL-Fas(1pr) kidneys. Thus, RANTES and CSF-1 recruit distinct T cell populations into the MRL-Fas(1pr) kidney. In addition, delivery of RANTES and CSF-1 into the kidney of MRL-Fas(1pr) mice causes an additive increase in pathology. We suggest that the complementary recruitment of T cell populations by RANTES (CD4, CD8) and CSF-1 (CD4, DN) promotes autoimmune nephritis in MRL-Fas(1pr) mice.

IFN-γ Limits Macrophage Expansion in MRL-FaslprAutoimmune Interstitial Nephritis: A Negative Regulatory Pathway

AbstractIFN-γ is capable of enhancing and limiting inflammation. Therefore, an increase in IFN-γ in autoimmune MRL-Faslpr mice could exacerbate or thwart renal injury. We have established a retroviral gene transfer approach to incite interstitial nephritis in MRL-Faslpr mice that is rapid, enduring, and circumscribed. Renal tubular epithelial cells (TEC) were genetically modified to secrete macrophage (Mφ) growth factors (CSF-1-TEC, GM-CSF-1-TEC) and infused under the renal capsule. To determine the impact of IFN-γ in Mφ growth factor-incited renal injury, we constructed a MRL-Faslpr IFN-γ-receptor (IFN-γR)-deficient strain. Gene transfer of CSF-1 or GM-CSF incited more severe interstitial nephritis in IFN-γR-deficient than in IFN-γR-intact MRL-Faslpr mice, consisting of an increase of Mφ. To determine the mechanism responsible for the increase in Mφ in IFN-γR-deficient MRL-Faslpr mice, we evaluated Mφ proliferation, apoptosis, and recruitment. Proliferation of bone marrow Mφ from IFN-γR-intact MRL-Faslpr costimulated with CSF-1 or GM-CSF and IFN-γ was reduced twofold, while the IFN-γR-deficient MRL-Faslpr bone marrow Mφ remained stable. Furthermore, we detected more proliferating and fewer apoptotic Mφ within the interstitium in IFN-γR-deficient MRL-Faslpr mice. Using unilateral ureteral ligation we established that IFN-γR signaling does not alter Mφ recruitment into the kidney. Thus, the increase in Mφ elicited by Mφ growth factors in IFN-γR-deficient MRL-Faslpr mice is a result of enhanced proliferation and decreased apoptosis, and is independent of recruitment. Taken together, we suggest that IFN-γ provides a negative regulatory pathway capable of limiting Mφ-mediated renal inflammation.

Enhanced Osteopontin Expression and Macrophage Infiltration in MRL-Fas lpr Mice with Lupus Nephritis

MRL-Fas lpr mice spontaneously develop a chronic lupus-like renal disease, characterized by immune complex-mediated glomerulonephritis and abundant mononuclear cell infiltration in the interstitium. In the present study we have examined whether the macrophage chemoattractant osteopontin (Opn) could be important in the recruitment of macrophages in this murine model of autoimmune renal injury. We have examined the expression of Opn in the kidney of MRL-Fas lpr mice and have correlated Opn synthesis with the degree of macrophage infiltration. Immunofluorescence staining revealed prominent expression of Opn by proximal tubules in MRL-Fas lpr mice but not in MRL-++ control mice. Northern blot analysis demonstrated that steady-state transcript levels for Opn mRNA were also significantly increased in MRL-Fas lpr kidneys compared with control kidneys. Furthermore, in situ hybridization showed massive Opn mRNA transcripts in proximal tubules in MRL-Fas lpr mice but not in controls. The diffuse macrophage infiltration in the kidney of MKL-Fas lpr correlated with the enhanced Opn expression. Opn secretion in vitro by cultured renal tubular epithelial cells was upregulated by TNF-α and l,25(OH)2-vitamin D3, whereas no regulation was observed in a control macrophage cell line. We conclude that the enhanced expression of the chemotactic molecule Opn by tubular cells is a prominent feature of murine lupus nephritis and might be promoted by the proinflammatory cytokine environment in MRL-Fas lpr . The chronic upregulation of Opn could participate in the recruitment of monocytes in the kidney of MRL-Fas lpr mice, thereby contributing to the pathogenesis of autoimmune renal disease.

Systemic autoimmune nephritogenic components induce CSF-1 and TNF-α in MRL kidneys

MRL-Faslpr mice are an appealing strain to understand the importance of cytokines in the pathogenesis of autoimmune renal destruction, since injury is rapid and predictable. Colony stimulating factor 1 (CSF-1) and tumor necrosis factor alpha (TNF-alpha) are detected in the kidney and circulation prior to renal injury and continue to increase with progressive renal damage in MRL-Faslpr, Fas deficient mice, but not the congenic Fas intact MRL-(++) strain. Delivery of CSF-1, but not TNF-alpha, into the kidney via gene transfer incites local renal injury. By comparison, dual gene transfer of CSF-1 and TNF-alpha incites autoimmune renal injury that is far more severe than CSF-1 alone. The purpose of this study was to establish whether CSF-1 and TNF-alpha incites autoimmune renal injury that is far more severe than CSF-1 alone. The purpose of this study was to establish whether CSF-1 and TNF-alpha expression in the kidney of MRL-Faslpr mice induced by a circulating stimulant resulted from a primary defect in the kidney. Therefore, we transplanted (Tx) a MRL-(++) kidney without CSF-1, TNF-alpha and renal injury into an MRL-Faslpr recipient after removing nephritic kidney expressing CSF-1 and TNF-alpha. The Tx kidneys were examined after 2, 4, 5, 6, and 12 weeks. CSF-1 and TNF-alpha were rapidly induced in the MRL-(++) Tx kidney. CSF-1 and TNF-alpha were evident by two weeks and continually increased for 12 weeks post-transplantation. Within several weeks, the rapid expansion of M phi and T cells and induction of glomerulonephritis and interstitial nephritis in the MRL-(++) Tx kidney was similar to the age-matched native MRL-Faslpr kidney. In conclusion, we have constructed an experimental transplantation system that can explore whether cytokine expression in the kidney induced by a circulating stimulant is a result of a primary defect in the kidney. Using this approach, we established that the MRL-Faslpr kidney is not defective, but rather a circulating stimulant in the MRL-Faslpr mouse can induce CSF-1, TNF-alpha and renal injury in a normal MRL-(++) kidney. Thus, we exclude an intrinsic defect in the MRL-Faslpr kidney as the pathogenic mechanism responsible for tissue damage. We suggest purging the circulation of molecules that induce CSF-1 and TNF-alpha as a therapeutic strategy for autoimmune renal injury.

Upregulation of lymphoid and renal interferon-gamma mRNA in autoimmune MRL-Fas(lpr) mice with lupus nephritis.

MRL-Fas(lpr) mice develop an aggressive form of autoimmunity, characterized by immune complex-mediated glomerulonephritis and massive expansion of lymphoid tissues. Increased MHC class II expression by macrophages and renal parenchymal cells is a prominent feature of MRL-Fas(lpr) mice. Since interferon-gamma (IFN-gamma) is the major and the most potent inducer of MHC class II molecules it could play a pathogenic role in the disease process in MRL-Fas(lpr). We have analyzed IFN-gamma expression in normal and nephritic MRL-Fas(lpr) mice by examining renal and lymphoid IFN-gamma-specific mRNA production, using reverse transcription-polymerase chain reaction (RT-PCR) and Northern blotting. We detect abundant IFN-gamma mRNA expression in the kidney of nephritic MRL-Fas(lpr) by RT-PCR, whereas normal mice display absent or only very weak expression of this cytokine. By RT-PCR, IFN-gamma mRNA is detectable in normal spleen, but is overexpressed in the enlarged spleen and lymph nodes of MRL-Fas(lpr). Northern blotting using total RNA from tissues confirms abundant IFN-gamma expression in spleen and lymph node of MRL-Fas(lpr). We conclude that enhanced renal IFN-gamma mRNA expression is a prominent feature of MRL-Fas(lpr) lupus nephritis. Increased IFN-gamma produced by infiltrating T cells could lead to increased MHC class II expression by renal parenchymal cells, thereby promoting the nephritic process by augmentation of antigen presentation in the kidney of autoimmune MRL-Fas(lpr).

Up-regulation of tubular epithelial interleukin-12 in autoimmune MRL-Faslpr mice with renal injury

Phagocyte-derived interleukin-12 (IL-12) is a key cytokine that induces the development of an effective Th1 type immune response in various inflammatory and infectious disorders. To determine the importance of IL-12 in the pathogenesis of autoimmune renal injury we examined the renal production of this heterodimeric cytokine in the MRL-Fas(lpr) lupus nephritis model. Compared with normal mice RT-PCR products encoding both the p35 and p40 subunits of IL-12 were markedly increased in the kidney of MRL-Fas(lpr). Immunofluorescence staining demonstrated expression of the IL-12 p75 heterodimer on isolated infiltrating mononuclear cells and also on proximal tubular epithelial cells in MRL-Fas(lpr) but less in normal mice kidneys. The enhanced expression of IL-12 correlated with an increased intrarenal transcription of IFN-gamma. The p35 and p40 transcripts and soluble IL-12 p75 protein were also produced by cultured TEC. In addition, membrane bound IL-12 was detected on Tec. We conclude that IL-12 production is significantly up-regulated in MRL-Fas(lpr) lupus nephritis. In addition to mononuclear cells, TEC are an important source of IL-12 and could thereby participate in the development of a Th1 type immune response in autoimmune renal injury.