Identification of a Serum Component That Regulates Cyclooxygenase-2 Gene Expression in Cooperation with 4-Hydroxy-2-nonenal

Abstract

Atherosclerosis is a disorder of lipid metabolism as well as a chronic inflammatory disease. Cyclooxygenase-2 (COX-2), an inducible isoform responsible for high levels of prostaglandin production during inflammation and immune responses, mediates a variety of biological actions involved in vascular pathophysiology. We have previously shown that COX-2 gene expression is dramatically induced by a lipid-derived endogenous electrophile, 4-hydroxy-2-nonenal (HNE) (Kumagai, T., Matsukawa, N., Kaneko, Y., Kusumi, Y., Mitsumata, M., and Uchida, K. (2004) J. Biol. Chem. 279, 48389 -48396). In the present study, based on the finding that HNE induced COX-2 expression only in the serum-containing media, we characterized a serum component essential for the HNE-induced COX-2 induction and found that low density lipoprotein (LDL) that had been denatured by freeze-thawing or oxidized LDL might be involved in the COX-2 induction. Moreover, we characterized the cellular events triggered by the combined stimulus of HNE and oxidized LDL and established that COX-2 induction is regulated by two sets of signaling mechanisms, one for the up-regulation of the scavenger receptor CD36 by HNE and one for the CD36-mediated COX induction by oxidized LDL. These findings represent a demonstration of a link between lipoprotein modification and activation of the inflammatory potential of macrophages.Atherosclerosis is a disorder of lipid metabolism as well as a chronic inflammatory disease. Monocyte-derived macrophages play a prominent role in the formation and progression of atherosclerotic plaque, particularly after their transformation into foam cells. When activated by inflammatory stimuli, the macrophages synthesize and secrete various mediators, including cytokines, prothrombotic substances, and eicosanoids, which cause the clinical manifestations and acute clinical complications of atherosclerosis. The eicosanoids derived from the metabolism of arachidonate have been extensively investigated because several studies have focused on their close relation to atherogenesis (1, 2). In macrophages as well as in other cell types arachidonate metabolites are synthesized by the cyclooxygenase enzyme. Presently, two isoforms of cyclooxygenase have been identified; cyclooxygenase-1 (COX-1), 2 which is the constitutive form, and cyclooxygenase-2 (COX-2), which is the inducible form. COX-1 is present under normal conditions in most tissues and is responsible for housekeeping functions. On the other hand, COX-2 is not normally present under basal conditions or is present in very low amounts. COX-2 is rapidly induced by various stimuli, including proinflammatory cytokines, such as interleukin-1␤ and tumor necrosis factor-␣, growth factors, and tumor promoters, to result in prostaglandin synthesis associated with inflammation and carcinogenesis (3). Substantial evidence indicates that unregulated COX-2 expression and prostaglandin synthesis influence chronic inflammatory conditions, including atherosclerosis and its complications (3-5).Various lines of ev...

Proinflammatory Effects of Advanced Lipoxidation End Products in Monocytes

“…However, unlike MDALys, HNE did not activate NF-B or induce iNOS. Kanayama et al (37) showed that HNE upregulates CD36 expression, whereas our data show that MDA-Lys had no effect on CD36 mRNA. Thus, MDA-Lys and HNE may act via different signaling mechanisms.…”

Interleukin-6 plays a protective role in development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors

“…4-HNE also has been reported to increase cox-2 mRNA and protein expression in a dosedependent manner in tissue injury (Kanayama et al, 2007). Overexpression of 4-HNE was thought to contribute to acceleration of cisplatin-induced acute renal failure in IL-6 −/− mice.…”

Fatty Acid and Peptide Profiles in Plasma Membrane and Membrane Rafts of PUFA Supplemented RAW264.7 Macrophages

“…Total protein in each fraction was determined using the Roti ® Quant assay kit (Roth, Karlsruhe, Germany). Fractions were analyzed by Western blot for the presence of the raft marker EGF receptor [4], [48], [50]–[52] (using anti-EGFR antibody, Biolegend, Diego, USA) as well as the plasma membrane marker transferrin receptor [8], [12], [48] (using anti-TFRC antibody, GeneTex, Irvine, USA). EGF receptor was found to be enriched in fraction 1 ( =  membrane raft fraction), transferrin receptor was found to be enriched in fraction 7 ( =  plasma membrane fraction).…”