Oxidative Stress Augments the Production of Matrix Metalloproteinase-1, Cyclooxygenase-2, and Prostaglandin E2 through Enhancement of NF-κB Activity in Lipopolysaccharide-Activated Human Primary Monocytes

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Abstract
The excessive production of reactive oxidative species (ROS) associated with inflammation leads to a condition of oxidative stress. Cyclooxygenase-2 (COX-2), PGE2, and matrix metalloproteinases (MMPs) are important mediators during the process of inflammation. In this paper we report on studies examining how the ROS hydrogen peroxide (H2O2) affects the production of MMP-1, COX-2, and PGE2. Addition of H2O2 to LPS-activated monocytes, but not naive monocytes, caused a significant enhancement of the LPS-induced production of MMP-1, COX-2, and PGE2. The mechanism by which H2O2 increased these mediators was through enhancement of IκBα degradation, with subsequent increases in NF-κB activation and NF-κB p50 translocation to the nucleus. The effects of H2O2 on IκBα degradation, NF-κB activation, and NF-κB p50 localization to the nucleus were demonstrated through studies of coimmunoprecipitation of IκBα with p50, ELISA of NF-κB p65 activity, and Western blot analysis of the nuclear fraction extract for p50. The key role for NF-κB in this process was demonstrated by the ability of MG-132 or lactacystin (proteasome inhibitors) to block the enhanced production of MMP-1, COX-2, and PGE2. In contrast, indomethacin, which inhibited PGE2 production, partially blocked the enhanced MMP-1 production. Moreover, although PGE2 restored MMP-1 production in indomethacin-treated monocyte cultures; it failed to significantly restore MMP-1 production in proteasome inhibitor-treated cultures. Thus, in the presence of LPS and H2O2, NF-κB plays a dominate role in the regulation of MMP-1, COX-2, and PGE2 expression.

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