Redox-dependent coronary metabolic dilation

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 293; no. 6; pp. H3720 - H3725
• Main Authors: Saitoh, Shu-ichi, Kiyooka, Takahiko, Rocic, Petra, Rogers, Paul A, Zhang, Cuihua, Swafford, Albert, Dick, Gregory M, Viswanathan, Chandrasekar, Park, Yoonjung, Chilian, William M
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.12.2007
• Subjects: Acetylcysteine - pharmacology; Animals; Antioxidants - pharmacology; Cells; Coronary vessels; Coronary Vessels - drug effects; Coronary Vessels - enzymology; Coronary Vessels - metabolism; Culture Media, Conditioned - metabolism; Dithiothreitol - pharmacology; Enzyme Activation; Hydrogen; Hydrogen Peroxide - metabolism; Imidazoles - pharmacology; In Vitro Techniques; Kinases; Metabolism; Microscopy, Fluorescence; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - metabolism; Nitroprusside - pharmacology; Oxidation; Oxidation-Reduction; p38 Mitogen-Activated Protein Kinases - antagonists & inhibitors; p38 Mitogen-Activated Protein Kinases - metabolism; Paracrine Communication; Phosphorylation; Protein Kinase Inhibitors - pharmacology; Pyridines - pharmacology; Rats; Rats, Wistar; Reactive Oxygen Species - metabolism; Reducing Agents - pharmacology; Sulfhydryl Compounds - metabolism; Vasodilation - drug effects; Vasodilator Agents - pharmacology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00436.2007

1 Departments of Integrative Medical Sciences, Northeastern Ohio University College of Medicine, Rootstown, Ohio; 2 Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, Louisiana; and 3 Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas Submitted 10 April 2007 ; accepted in final form 16 October 2007 We have observed that hydrogen peroxide (H 2 O 2 ), the dismutated product of superoxide, is a coronary metabolic dilator and couples myocardial oxygen consumption to coronary blood flow. Because the chemical activity of H 2 O 2 favors its role as an oxidant, and thiol groups are susceptible to oxidation, we hypothesized that coronary metabolic dilation occurs via a redox mechanism involving thiol oxidation. To test this hypothesis, we studied the mechanisms of dilation of isolated coronary arterioles to metabolites released by metabolically active (paced at 400 min) isolated cardiac myocytes and directly compared these responses with authentic H 2 O 2 . Studies were performed under control conditions and using interventions designed to reduce oxidized thiols [0.1 µM dithiothreitol (DTT) and 10 mM N -acetyl- L -cysteine (NAC)]. Aliquots of the conditioned buffer from paced myocytes produced vasodilation of isolated arterioles (peak response, 71% ± 6% of maximal dilation), whereas H 2 O 2 produced complete dilation (92% ± 7%). Dilation to either the conditioned buffer or to H 2 O 2 was significantly reduced by the administration of either NAC or DTT. The location of the thiols oxidized by the conditioned buffer or of H 2 O 2 was determined by the administration of the fluorochromes monochlorobimane (20 µM) or monobromotrimethylammoniobimane (20 µM), which covalently label the reduced total or extracellular-reduced thiols, respectively. H 2 O 2 or the conditioned buffer predominately oxidized intracellular thiols since the fluorescent signal from monochlorobimane was reduced more than that of monobromotrimethylammoniobimane. To determine whether one of the intracellular targets of thiol oxidation that leads to dilation is the redox-sensitive kinase p38 mitogen-activated protein (MAP) kinase, we evaluated dilation following the administration of the p38 inhibitor SB-203580 (10 µM). The inhibition of p38 attenuated dilation to either H 2 O 2 or to the conditioned buffer from stimulated myocytes by a similar degree, but SB-203580 did not attenuate dilation to nitroprusside. Western blot analysis for the activated form of p38 (phospho-p38) in the isolated aortae revealed robust activation of this enzyme by H 2 O 2 . Taken together, our results show that an active component of cardiac metabolic dilation, like that of H 2 O 2 , produces dilation by the oxidation of thiols, which are predominately intracellular and dependent activation on the p38 MAP kinase. Thus coronary metabolic dilation appears to be mediated by redox-dependent signals. coronary circulation; coronary microcirculation; reactive oxygen species; vasodilatation Address for reprint requests and other correspondence: W. M. Chilian, Dept. of Integrative Medical Sciences, Northeastern Ohio Universities College of Medicine, 4209 State Rte. 44, Rootstown, OH 44272-0095 (e-mail: WChilian{at}neoucom.edu )