Effects of Onion Extract on Endogenous Vascular H2S and Adrenomedulin in Rat Atherosclerosis

Objective: This study aimed to explore the effect of onion extract on endogenous hydrogen sulfide (H2S) and adrenomedulin (ADM) and on atherosclerotic progression in rats with atherosclerosis (AS). Methods And Results: Male Sprague-Dawley rats were randomly divided into control, AS and AS+onion groups. Ultrastructure of aorta and atherosclerotic lesions both in aorta and in coronary artery were detected. Plasma and aortic H2S were detected by using a sulfide- sensitive electrode. Plasma and aortic ADM was determined with radioimmunoassay. Cystathionine-γ-lyase (CSE), calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein (RAMP1, RAMP2 and RAMP3) mRNA expressions were analysed. Glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO) and NO synthase (NOS) contents in plasma, SOD1, SOD2 and ICAM-1 expressions in aorta were detected. Rats in the AS group showed marked atherosclerotic lesions both in aorta and in coronary artery but decreased aortic H2S production. Decreased plasma and aortic ADM content, but increased levels of aortic CRLR, RAMP2 and RAMP3 mRNAs were observed. Plasma GSH-PX and SOD were reduced but MDA elevated. Plasma ICAM-1 and NO contents and iNOS activity were increased. Onion extract, however, lessened atherosclerotic lesions and increased endogenous aortic H2S production, but decreased plasma ADM content, aortic ADM content and aortic CRLR, RAMP2 and RAMP3 mRNAs. In addition, it increased plasma GSH-PX level and SOD activities but reduced MDA; it decreased inflammatory response but increased plasma eNOS activity and NO content. Conclusions: Onion extract exerted a marked antiatherogenic effect in association with the up-regulation of the endogenous CSE/H2S pathway but down-regulation of the ADM/CRLR family in atherosclerotic rats.