c-Rel and p65 trans-activate the monocyte chemoattractant protein-1 gene in interleukin-1 stimulated mesangial cells

Background. The chemokine monocyte chemoattractant protein-1 (MCP-1) is secreted by human glomerular mesangial cells in response to interleukin-l (IL-I) and has a central role in amplifying the inflammatory response during glomerulonephritis. However, the mechanism by which IL-1 regulates its transcription is not understood. Specific members of the nuclear factor kappa B/rel (NF-kappa B) proteins may regulate MCP-1 expression in a stimulus- and tissue-specific manner. Methods. Electrophoretic mobility shift assays and Western blot analysis characterized the members of the NF-kappa B family that bound the two NF-kappa B sites of the MCP-1 enhancer (Al and A2) in vitro. Trans-activation of the MCP-1 gene was investigated by transfer of the MCP-1 enhancer DNA to mesangial cells. Result. Primary human mesangial cells contained in addition to p50 (NF-kappa B1) and p65 (Rel A) NF-kappa B proteins. the oncoprotein c-rel, and Rel B, but not p52 (NF-kappa B2). IL-1 induced c-rel to form a complex with p65, which bound the MCP-1 A2 site but not the Al Or IL-6 NF-kappa B sites in vitro. IL-1 up-regulated transfected MCP-1 enhancer activity. Cotransfer of the MCP-1 enhancer together with individual members of the NF-kappa B family showed that the heterodimer c-relp65 or (p65)(2) can selectively trans-activate the MCP-1 gene via its Al and A2 sites in mesangial cells. Conclusions. This study demonstrates for the first time that the c-rel oncoprotein can enhance MCP-1 transcription in mesangial cells and suggests that it may have an important role in amplifying gene expression in the inflamed glomerulus.