MECHANISMS OF OXIDANT REGULATION OF MONOCYTE CHEMOTACTIC PROTEIN 1 PRODUCTION IN HUMAN WHOLE BLOOD AND ISOLATED MONONUCLEAR CELLS

Abstract

Previous work has demonstrated that reactive oxygen intermediates (ROIs) play an important regulatory role in the induction of monocyte chemotactic protein 1 (MCP-1) in certain cells. This study investigated the mechanisms of ROI regulation of MCP-1 gene expression in whole blood and isolated peripheral blood mononuclear cells (PBMCs). The antioxidants dimethyl sulfoxide (DMSO), N-acetyl cysteine, and dimethyl thiourea significantly inhibited lipopolysaccharide (LPS)-induced MCP-1 production in either whole blood or isolated blood cells. In contrast, interleukin 6 and tumor necrosis factor production were not affected and interleukin-1beta levels were actually increased with DMSO treatment. Exogenous ROI (either hydrogen peroxide or O2 generated by xanthine/xanthine oxidase) stimulated MCP-1 production, which was also inhibited by DMSO. To confirm the biological relevance of these findings in vivo, mice treated with DMSO before LPS challenge had significantly lower plasma levels of MCP-1. The level of inhibition was addressed in experiments which demonstrated that DMSO significantly decreased MCP-1 mRNA induced by LPS in whole blood and PBMCs. Cycloheximide treatment did not abolish the DMSO inhibition of MCP-1 mRNA, demonstrating that de novo protein synthesis is not required. Treatment with actinomycin D showed that DMSO did not increase the decay rate of MCP-1 mRNA, indicating that ROI did not change the stability of MCP-1 mRNA. These results provide evidence that in whole blood and PBMCs, DMSO regulates MCP-1 gene expression by decreasing the induction of MCP-1 mRNA.