Generation and actions of electrophilic nitro-fatty acids

BONACCI G

Kagoshima

Congreso; 5th Biennial Meeting of Society for Free Radical Research-Asia(SFRR-Asia), 8th Conference of Asian Society for Mitochondrial Research and Medicine(ASMRM) 11th Conference of Japanese Society of Mitochondrial Research and Medicine(J-mit; 2011

Society for Free Radical Research-Asia (SFRR-Asia), Asian Society for Mitochondrial Research and Medicine (ASMRM) and Japanese Society of Mitochondrial Research and Medicine (J-mit)

Nitro-fatty acids (NO2-FA) are generated by reactions of unsaturated fatty acids with NO, nitrite and secondary reactive species. Studies in animal models of ischemic preconditioning (IPC) in rat heart and focal cardiac ischemia/reperfusion (I/R) in mice, show that NO2-FA are formed in oxidative environments after hypoxia and acidosis. They possess unique chemical reactivities exerting cytoprotective effects by virtue of their electrophilic properties that facilitate covalent adduct formation with cellular nucleophiles such as cysteine and histidine residues of protein as well as small molecules as reduced glutathione (GSH). In terms of cell signaling, a variety of protein targets of nitroalkylation have been described, including activation of PPAR and the antioxidant pathway Keap1/Nrf2 and inhibition of the pro-inflammatory transcription factor NK-kB. Despite the multiple signaling pathways that are responsive to NO2-FA, the mechanisms of formation of these mediators still remains elusive. Several mechanisms have been proposed including radical reactions involving nitric oxide (•NO), nitrogen dioxide (•NO2) and acidic nitration. We now report that mitochondria in the presence of NO2- and mild acidic condition are a key source of NO2-FA. The principal nitration product generated by mitochondria was structurally identical to NO2-FA generated by cardiac ischemia/reperfusion. The structural characterization of these species by HPLC-MS revealed that conjugated-linoleic acid (conj-LA) is a highly susceptible nitration substrate. Experimental observations from activated macrophages, H2O2/nitrite/myeloperoxidase and peroxynitrite (ONOO-) reinforced that a conjugated double bond system (octadeca-9,11-dienoic acid) is more susceptible to nitration than the bis-allylic double bond on octadeca-9,12-dienoic acid. The conj-LNO2 species are electrophilic, reactive with GSH and protein targets, and modulate mitochondrial homeostasis and respiration.