title: Homocysteine induces COX-2 expression in macrophages through ROS generated by NMDA receptor-calcium signaling pathways.
abstract: Homocysteine (Hcy) at elevated levels is a putative risk factor for many cardiovascular disorders including atherosclerosis. In the present study, we investigated the effect of Hcy on the expression of cyclooxygenase (COX)-2 in murine macrophages and the mechanisms involved. Hcy increased the expression of COX-2 mRNA and protein in dose- and time-dependent manners, but did not affect COX-1 expression. Hcy-induced COX-2 expression was attenuated not only by the calcium chelators, EGTA and BAPTA-AM, but also by an antioxidant, N-acetylcysteine. Calcium chelators also attenuated Hcy-induced reactive oxygen species (ROS) production in macrophages, indicating that Hcy-induced COX-2 expression might be mediated through ROS generated by calcium-dependent signaling pathways. In another series of experiments, Hcy increased the intracellular concentration of calcium in a dose-dependent manner, which was attenuated by MK-801, an N-methyl-D-aspartate (NMDA) receptor inhibitor, but not by bicuculline, a gamma-aminobutyric acid receptor inhibitor. Molecular inhibition of NMDA receptor using small interfering RNA also attenuated Hcy-induced increases in intracellular calcium. Furthermore, both ROS production and Hcy-induced COX-2 expression were also inhibited by MK-801 as well as by molecular inhibition of NMDA receptor. Taken together, these findings suggest that Hcy enhances COX-2 expression in murine macrophages by ROS generated via NMDA receptor-mediated calcium signaling pathways.
authors.affiliation: Department of Pharmacology, School of Medicine, Pusan National University, Yangsan, Gyeongnam, Korea.
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: S J
authors.initials: SJ
authors.lastname: Lee
authors.forename: K W
authors.initials: KW
authors.lastname: Seo
authors.forename: J U
authors.initials: JU
authors.lastname: Bae
authors.forename: S Y
authors.initials: SY
authors.lastname: Park
authors.forename: C D
authors.initials: CD
authors.lastname: Kim
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004533:Egtazic Acid; D005786:Gene Expression Regulation / Q000187:drug effects*; D006710:Homocysteine / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D017382:Reactive Oxygen Species / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000975:Antioxidants; D002118:Calcium; D051546:Cyclooxygenase 2; D004533:Egtazic Acid; D006710:Homocysteine; D017382:Reactive Oxygen Species; D016194:Receptors, N-Methyl-D-Aspartate; C077623:Ptgs2 protein, mouse