Reactive oxygen species (ROS) are generated as by-products of cellular metabolism, primarily in the mitochondria. When the cellular production of ROS exceeds the cell's antioxidant capacity, cellular macromolecules such as lipids, proteins and DNA can be damaged. Because of this, 'oxidative stress' is thought to contribute to aging and pathogenesis of a variety of human diseases. However, in the last 10-15 years, a considerable body of evidence has accumulated that ROS serve as subcellular messengers, and play a role in gene regulation and signal transduction pathways, which may be involved in defensive mechanisms against oxidative stress. This review focuses on oxidative stress caused by the inactivation of glutathione peroxidase (GPx), a major peroxide scavenging enzyme. GPx is inactivated by a variety of physiological substances, including nitric oxide and carbonyl compounds in vitro and in cell culture. Decreased GPx activity has also been reported in tissues where oxidative stress occurs in several pathological animal models. The accumulation of increased levels of peroxide resulting from inactivation of GPx may act as a second messenger and regulate expression of anti-apoptotic genes and the GPx itself to protect against cell damage. These findings suggest that GPx undergoes inactivation under various conditions such as nitroxidative stress and glycoxidative stress, and that these changes are a common feature of various types of oxidative stress which may be associated with the modification of redox regulation and cellular function.

Objective-Acrolein, a known toxin in tobacco smoke, might be involved in atherogenesis. This study examined the effect of acrolein on expression of cyclooxygenase-2(COX-2) and prostaglandin (PG) production in endothelial cells. Methods and Results-Cyclooxygenase (COX)-2 induction by acrolein and signal pathways were measured using Western blots, Northern blots, immunoflouresence, ELISA, gene silencing, and promoter assay. Colocalization of COX2 and acrolein-adduct was determined by immunohistochemistry. Here we report that the levels of COX-2 mRNA and protein are increased in human umbilical vein endothelial cells (HUVECs) after acrolein exposure. COX-2 was found to colocalize with acrolein-lysine adducts in human atherosclerotic lesions. Inhibition of p38 MAPK activity abolished the induction of COX-2 protein and PGE 2 accumulation by acrolein, while suppression of extracellular signal-regulated kinase (ERK) and JNK activity had no effect on the induction of COX-2 expression in experiments using inhibitors and siRNA. Furthermore, rottlerin, an inhibitor of protein kinase C␦ (PKC␦), abrogated the upregulation of COX-2 at both protein and mRNA levels. Conclusion-These results provide that acrolein may play a role in progression of atherosclerosis and new information on the signaling pathways involved in COX-2 upregulation in response to acrolein and provide evidence that PKC␦ and p38 MAPK are required for transcriptional activation of COX-2. Key Words: acrolein Ⅲ COX-2 Ⅲ p38 MAPK Ⅲ atherosclerosis Ⅲ endothelial cells A ctivation of endothelial cells by proinflammatory stimuli has been established as an important link between risk factors and the pathologic mechanisms underlying atherosclerosis. 1 Thus, control of the inflammatory status of endothelial cells, which is achieved by a balance of pro-and antiinflammatory signals, is crucial to limiting the disease. Tobacco smoking induces inflammatory reactions 2 and promotes atherosclerosis 3 ; however, the mechanism that links cigarette smoking to an increased incidence of atherosclerosis is poorly understood.Acrolein (CH 2 ϭCH-CHO), a major product of organic combustion, including tobacco smoking, is the most reactive ␣, ␤-unsaturated aldehyde found widely in the environmol/ Lent. Acrolein is highly reactive and is hazardous to human health. 4 Acrolein is produced by a wide variety of both natural and synthetic processes, including the incomplete combustion of organic materials. Acrolein also has been found to be formed from threonine by neutrophil myeloperoxidase at sites of inflammation 5 and has been identified as both a product and initiator of lipid peroxidation. 6 Recent studies have shown that acrolein levels are increased in many diseases such as atherosclerosis, Alzheimer disease, and diabetes, and is possibly related to pathogenesis in these conditions. 7-9 We and others have reported that acrolein elevates intracellular reactive oxygen species (ROS) levels, which leads to cell dysfunction. 8,10 ROS-mediated cell damage is an important etiologic factor ...

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