Interferon-␤ (IFN-␤) is a multifunctional cytokine with immunomodulatory properties. We examined the effect of IFN-␤ in three separate rat models of glomerular injury and in cultured human glomerular endothelial cells and podocytes. In nephrotoxic nephritis in WKY rats, recombinant rat IFN-␤ started either at induction or after establishment of disease significantly reduced 24-h proteinuria by up to 73% and 51%, respectively, but did not affect serum creatinine. There was a slight reduction in numbers of glomerular macrophages, but no difference in glomerular or tubulointerstitial scarring. In Thy-1 nephritis in Lewis rats, IFN-␤ started at induction of disease reduced proteinuria by up to 66% with no effect on numbers of glomerular macrophages, but a reduced number of proliferating cells. In puromycin nephropathy in Wistar rats, IFN-␤ started at induction of disease reduced proteinuria by up to 93%, but had no effect on glomerular histology. In cultured cells, human IFN-␤-1a had a dramatic effect on barrier properties, increasing electrical resistance across monolayers of either glomerular endothelial cells or podocytes and decreasing trans-monolayer passage of albumin. In conclusion, these results show that IFN-␤ reduces proteinuria in three different rat models of glomerular injury and that its anti-proteinuric action may result from direct effects on cells that comprise the glomerular filtration barrier. These data indicate that IFN-␤ may have potential as a therapeutic agent in proteinuric renal disease.

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