4-Hydroxynonenal Induces Endothelial Cell Apoptosis via ROS and Peroxynitrite Generation

Abstract

The formation of reactive lipid aldehydes, 4-hydroxynonenal (HNE) is shown to be derived from fatty acid hydroperoxides through the oxidative process. Among its known effects in cytotoxicity, HNE has been implicated in apoptotic cell death. To delineate its putative role as a potential mediator, we investigated the mechanism by which HNE induces apoptosis of endothelial cells (ECs). The anti-proliferative effects of HNE were tested through MTT assay after exposure to various concentrations (5~15 μM) of HNE. We observed apoptotic bodies with propidium iodide staining, and measured the HNE induction of endothelial apoptosis by flow cytometry assay. We observed that cells exposed to HNE for 24 hr resulted in increased poly(ADP-ribose) polymerase cleavage and up-regulation of Bax. Data on the HNE action strongly indicated the involvement of reactive species, namely, intracellular ROS, nitrite, and peroxynitrite. To obtain evidence on the implication of ROS and peroxynitrite in HNE-induced apoptosis, a ROS scavenger, N-acetylcysteine (NAC), and a peroxynitrite scavenger, penicillamine, were tested. Results clearly indicate that the induction of apoptosis by HNE was effectively inhibited by NAC and penicillamine. Based on the present data, we conclude that the endothelial apoptosis induced by HNE involves both ROS generation and peroxynitrite activity. Our new data could lead to a redefinition of HNE action on apoptosis in ECs.Key words : 4-Hydroxynonenal, apoptosis, ROS, peroxynitrite, endothelial cells *Corresponding author *Tel：+82-51-510-2801, Fax：+82-51-513-6754 *E-mail : nadkim@pusan.ac.kr ISSN : 1225-9918 Journal of Life Science 2011 Vol. 21. No. 7. 961~968 DOI : 10.5352/JLS.2011 Introduction In recent years, many studies presented evidence pointing to the involvement of reactive aldehydes and other lipid peroxidative byproducts in various pathophysiological processes, including aging, diabetes mellitus, atherosclerosis, and cancer [16,29]. Among the major reactive aldehydes, 4-hydroxynonenal (HNE) derived from lipid peroxidation process from arachidonic acids, linoleic acids, or their hydroperoxides can be accumulated in relatively large amounts under oxidatively stressed conditions, namely it has shown to be largely responsible for the cytotoxic effects associated with oxidative stress [8,32], as detected in several diseases, such as, atherosclerosis, diabetes, and Parkinson's disease [17,35]. The formation of HNE and HNE-protein conjugates could be important biological deleterious instigators, as oxidative stress-induced apoptosis is believed to be involved in those chronic diseases. In fact, HNE has been shown to be a potential inducer of apoptotic cell death [23].Apoptosis, a form of cell death characterized by cell shrinkage, chromatin condensation, and DNA fragmentation, can be induced by a variety of stimuli. The role of radicals in apoptosis become apparent with the following evidence: (a) reactive intermediates influence the cellular redox status [3], therefore, apoptosis [27], and (b) antioxidan...