Excessive Matrix Accumulation in the Kidneys of MRL/lpr Lupus Mice Is Dependent on Complement Activation

Abstract

Abstract. Complement receptor 1-related gene/protein y (Crry) in rodents is a potent membrane complement regulator that inhibits complement C3 activation by both classical and alternative pathways. Complement inhibition with Crry as the recombinant protein Crry-Ig has been demonstrated to prevent MRL/MpJ-Tnfrsf6 lpr (MRL/lpr) mice from developing proteinuria and renal failure. Crry-Ig-treated mice also showed less glomerulosclerosis compared with control MRL/lpr mice. To clarify how complement inhibition with Crry might affect renal scarring in lupus nephritis, gene transcript profiling was performed comparing Crry-Ig-treated MRL/lpr mice to controltreated MRL/lpr mice as well as to the MRL/ϩ strain control. Altered gene expression was confirmed by quantitative PCR, and protein quantity with either immunoblotting or immunofluorescence microscopy. Collagens I, III, IV, and VI were overexpressed in control MRL/lpr mice, whereas complement inhibition with Crry reduced the overexpression of these extracellular matrix components toward normal. Plasminogen activator inhibitor 1, connective tissue growth factor, and TGF-␤1 were upregulated in MRL/lpr mice compared with MRL/ϩ mice and were normalized by Crry-Ig treatment, suggesting that the product of these genes may contribute to the progressive glomerulosclerosis in MRL/lpr mice in a complement-dependent fashion. Thus, complement inhibition with Crry has a prominent effect on matrix-related genes and proteins, which translates into improvement in functional renal disease.The MRL/MpJ-Tnfrsf6 lpr (MRL/lpr) strain is a murine model of human systemic lupus erythematosus. These mice develop many features of human systemic lupus erythematosus, including autoantibodies, hypocomplementemia, and proliferative glomerulonephritis (GN) (1,2). MRL/lpr mice differ from the lupus-prone congenic MRL/ϩ strain by the nearly complete absence of the apoptosis-promoting membrane Fas protein, which is due to a retroviral insertion in the Tnfrsf6 (Fas) gene (3,4). In contrast to MRL/lpr mice, MRL/ϩ mice develop lupus very late in life, including only mild renal disease. Renal disease in MRL/lpr mice has similar features to the human disease it models, with mesangial proliferative GN early in disease and diffuse proliferative and crescentic GN later in the course. Ultimately, glomerulosclerosis and renal failure occur in the terminal phase of disease and are believed to cause death in these mice (5). Decreased serum C3 levels and deposition of C3 activation fragments and other complement components in kidney suggest that complement is involved in the pathogenesis of murine as well as human lupus nephritis (2).Complement activation can proceed via the classical, alternative, or mannose-binding lectin pathways (6). Activation through each of the three pathways leads to cleavage of C3 with generation of the proinflammatory and regulatory fragments C3a and C3b. C3b attaches covalently to immune complexes, which is followed by C5 binding and its cleavage to C5a and C5b. The former is a potent in...

C5a promotes development of experimental lupus nephritis which can be blocked with a specific receptor antagonist

“…Blockade of C5aR with the specific C5aRa peptide significantly reduced renal disease in MRL/lpr mice, as reflected by lower BUN and albuminuria levels compared to control animals, which further translated into delayed mortality in these mice. Similar findings were observed by our group when complement activation was inhibited at the level of C3/C5 convertases in MRL/lpr mice [8,9,38], indicating that complement is involved in the pathogenesis of lupus nephritis, not only through generation of pro-inflammatory C3a and C3b, and the cell injuring/ activating C5b-9 membrane attack complex, but also through the additional product of C5 activation, the C5a anaphylatoxin. Similar findings to ours have recently been observed by backcrossing the MRL/lpr strain into the C5aR-deficient strain generated by Wetsel et al [33], including protection from functional renal disease and a delay in mortality (M. Braun et al, C5a receptor deficiency attenuates T cell function and renal disease in MRL lpr mice; submitted for publication), thereby providing further evidence for the relevance of C5a signaling through C5aR in lupus nephritis.…”

“…Total RNA from renal cortex was extracted and cDNA produced as described previously [38]. qRT-PCR was performed using QuantiTect SYBR Green RT-PCR Kit (Qiagen Inc., Valencia, CA) on an ABI 7700 Sequence Detector (Applied Biosystems, Foster City, CA).…”

Role for Nephritogenic T Cells in Lupus Glomerulonephritis: Progression to Renal Failure Is Accompanied by T Cell Activation and Expansion in Regional Lymph Nodes

“…The progression of renal disease is dependent on a variety of pathogenetic processes through FcR-mediated inflammation (13) complement system (20,21), local expression of inflammatory chemokines and cytokines (14,22,23), and molecules affecting innate immune responses (TLRs) (24,25). Clinical reports show a corelation between interstitial T cell infiltration and poor renal function.…”

C3a Is Required for the Production of CXC Chemokines by Tubular Epithelial Cells after Renal Ishemia/Reperfusion

“…For both time points, two samples each were included from sham-treated wild-type mice, postischemic wild-type mice, and postischemic fB Ϫ/Ϫ mice, for a total of 12 samples. Microarrays were performed with the murine genome expression set 430 (Affymetrix) as previously described (25). In brief, the quality of the RNA was confirmed by evaluation on an Agilent 2100 Bioanalyzer.…”