Background: The reaction of NO with superoxide anion to form peroxynitrite has been implicated as a potential mechanism contributing to the limited NO bioavailability observed in diabetes. Furthermore, there is little evidence outlining the effects of intravenous anesthetic, propofol, on NO bioavailability in cardiomyocytes (CMs) isolated from diabetic mice. We hypothesized that propofol would act as a superoxide scavenger, thereby increasing NO bioavailability.
Methods: For NO, superoxide and peroxynitrite measurements, freshly isolated control and diabetic CMs were incubated in the presence or absence of propofol with NO, superoxide (DHE) or peroxynitrite (HKG) fluorescent probes. Fluorescence was measured using either fluorescence microscopy or a fluorescent microplate reader.
Results: NO fluorescence was decreased 34 ± 8% in diabetic CMs as compared to control. Superoxide-dismutase polyethylene-glycol (catalyzes superoxide; PEG-SOD) increased fluorescence 33 ± 6% in diabetic CMs while it had no effect on the control. Intra-nuclear DHE fluorescence was increased 41 ± 9% in diabetic CMs compared to controls. Propofol increased NO bioavailability 25 ± 7%, 32 ± 5% and 41 ± 6%, respectively, in diabetic CMs while having no effect in controls. Moreover, propofol decreased superoxide 24 ± 8% and peroxynitrite 27 ± 3% in diabetic CMs while having no effect in controls.
Conclusions: Our results indicate that NO levels are decreased in diabetic CMs due to its reaction with elevated superoxide levels, producing excessive amounts of peroxynitrite. Clinically relevant concentrations of propofol increased NO bioavailability and this is, in part, mediated by the propofol-induced decrease in superoxide in diabetic CMs.
Mr. Spencer Andrei B.S.
Dr. Derek Damron Ph.D.
A pathological mechanism underlying diabetic cardiomyopathy involves the reaction of nitric oxide (NO) with superoxide to form peroxynitrite. We hypothesized that the intravenous anesthetic, propofol, would act as a superoxide scavenger, thereby increasing NO bioavailability in diabetic cardiomyocytes (CMs). CMs were untreated or treated with clinically relevant concentrations of propofol and loaded with fluorescent probes detecting NO, superoxide or peroxynitrite. NO fluorescence was decreased, whereas superoxide and peroxynitrite was increased in diabetic CMs. Propofol administration increased NO bioavailability and returned superoxide and peroxynitrite levels to near baseline values. Our results indicate that NO levels are decreased in diabetic CMs due to its reaction with elevated superoxide levels, producing excessive amounts of peroxynitrite. Propofol treatment restored pathological NO, superoxide and peroxynitrite accumulation to near healthy levels.