IL-1-BETA INCREASES LAMININ B2 CHAIN MESSENGER-RNA LEVELS AND ACTIVATES NF-KAPPA-B IN RAT GLOMERULAR EPITHELIAL-CELLS

The amount and distribution of laminin in the glomerular basement membrane (GEM) change in the course of many types of glomerular disease. Because interleukin-1 (IL-1) is thought to play a role in the pathogenesis of glomerulonephritis, it raises the possibility that this and other cytokines might regulate laminin gene expression. To determine whether laminin B2 chain mRNA levels change in response to cytokines, total mRNA from rat glomerular epithelial cells (GEC) grown in culture was analyzed by Northern blots. These studies showed an increase in laminin B2 chain mRNA levels in GEC treated with IL-1 beta. Nuclear factor kappa B (NF-kappa B) is a cytokine-responsive factor that regulates transcription of many genes from the cognate kappa B enhancer element. The mouse laminin B2 chain promoter contains several kappa B-like motifs, suggesting that NF-kappa B might be involved in IL-1-induced laminin B2 chain gene expression. Nuclear extracts from IL-1 beta-treated GEC showed increased binding to the immunoglobulin kappa B enhancer element and to a kappa B consensus sequence from the murine laminin B2 chain promoter in an electrophoretic mobility-shift assay (EMSA). The immunoglobulin kappa B and the laminin B2 chain kappa B-like motifs competed for the same DNA binding activity in nuclear extracts from IL-1 beta-treated GEC. Pretreatment of these nuclear extracts with antibodies to either the p50 or p65 subunits of NF-kappa B abrogated the DNA binding activity recognized by either of the two DNA motifs. These results demonstrate that treatment of GEC with IL-1 beta activates an NF-kappa B complex, which is recognized by one of the kappa B-like motifs from the laminin B2 chain promoter. This observation may reflect involvement of NF-kappa B in the IL-1 beta-induced increase in laminin B2 chain mRNA levels in GEC.