This multigenic effect would be expected to influence different glomerular disease models in distinct ways

This multigenic effect would be expected to influence different glomerular disease models in distinct ways. The role of MMPs in Alport glomerular pathogenesis has been explored previously. gelatinase activity using a small molecule inhibitor (BAY-12-9566) ameliorated progression of proteinuria and restored the architecture of the glomerular basement membrane in 1 integrin-null Alport mice, suggesting that elevated gelatinase activity exacerbates glomerular disease progression in these mice. The accumulation of extracellular matrix in the glomerular basement membrane (GBM) and the mesangium as a function Difloxacin HCl of renal disease progression is a feature shared by a variety of glomerular diseases. This is true for Alport syndrome, in which defects in genes encoding basement membrane collagen 3(IV), 4(IV), or 5(IV) chains result in a delayed onset, progressive glomerulonephritis characterized by mesangial matrix expansion and GBM irregularities. 1 A number of animal models for Alport syndrome exist, and most resemble human Alport syndrome with regard to renal disease.2 In earlier work, we showed that autosomal Alport [3(IV) knockout] mice that are also null for 11 integrin (double knockout, or DKO, mice) display attenuated glomerular and tubulointerstitial pathogenesis and lived nearly twice as long as strain-matched Alport mice.3 These DKO animals showed reduced mesangial expansion and improved GBM architecture. The mechanism underlying Difloxacin HCl the influence of 1 1 integrin on the progression of glomerular pathogenesis in these mice has not been elucidated. Integrin 11 is expressed at high levels on glomerular mesangial cells.4 As a collagen-binding integrin, 11 has been implicated to function in mesangial cell adhesion, migration, and proliferation.5,6 11 integrin appears to play a direct role in matrix remodeling, because neutralizing antibodies against either integrin subunit prevents collagen gel contraction by cultured rat mesangial cells.7,8 This effect is mediated via activation of the ERK 1/2 Rabbit Polyclonal to ELL branch of the mitogen-activated protein kinase (MAPK) signal transduction pathway.9 These data are in contrast to genetic studies of both fibroblasts and vascular endothelial cells, which showed elevated matrix metalloproteinase (MMP) expression in 1 integrin-null cells versus wild-type cells.10,11,12 The effect of the 1-null genotype on mesangial cell expression of MMPs has not been explored. Dysregulation of MMPs in glomerular mesangial cells has been implicated as contributing to the pathobiological mechanism for a number of glomerular diseases.13 Because glomerular disease is often associated with altered signaling of the MAPK pathway in mesangial cells,14,15 and because integrin 11-blocking studies of rat mesangial cells alter both collagen matrix remodeling and MAPK signaling,9 we surmised that the absence of 1 integrin might alter pathways that regulate matrix metabolism, and that this might help explain the reduced accumulation of glomerular matrix in the DKO Difloxacin HCl mice. Here we show that the expression of MMP-2, MMP-9, and MMP-14 (also called MT-1 MMP) are significantly elevated in both glomeruli and cultured mesangial cells from integrin 1-null mice compared to wild-type mice, whereas only MMP-9 is up-regulated in Alport glomeruli and mesangial cells. Elevated expression can be abrogated in 1 integrin-null mesangial cells by blocking the activation of the p38, but not the ERK1/2 branch of MAPK. Conversely, the same strategy shows ERK regulation of MMP-9 in mesangial cells from Alport mice. Blocking the activity of these MMPs using a small molecule inhibitor attenuates progression of albuminuria in DKO mice, suggesting Difloxacin HCl that overexpression of MMPs likely exacerbates disease progression in DKO mice. Thus, even though the net effect of the 1-null background in Alport mice is significant attenuation of glomerular disease,3 some metabolic changes (in this case, elevated gelatinase expression) occur that are actually deleterious to glomerular structure/function. Materials and Methods Administration of MMP Inhibitor to Alport Mice The Alport, integrin 1-null, and DKO mice are all on the 129 Sv background and have been described previously.3,16,17 Wild-type mice (controls) are normal for both collagen 3(IV) alleles and are.