HSP20 phosphorylation and interstitial metabolites in hypoxia-induced dilation of swine coronary arteries.
OBJECTIVE
Hypoxia induces coronary artery dilation, but the responsible mechanism is largely unknown. Many stimuli induce arterial smooth muscle relaxation by reducing ser19-myosin regulatory light chain (MLC) phosphorylation. Other stimuli can induce smooth muscle relaxation without reductions in ser19-MLC phosphorylation. This form of relaxation has been termed force suppression and appears to be associated with heat shock protein 20 (HSP20) phosphorylation on ser16. We investigated whether hypoxia-induced sustained dilation in swine coronary arteries was promoted without ser19-MLC dephosphorylation and associated with ser16-HSP20 phosphorylation. Nitroglycerin vasodilation served as control.


METHODS
In a pressure myograph, the tunica media of intact pre-contracted (PGF(2alpha); 10(-5) m) porcine coronary artery segments were cannulated using a microdialysis catheter. Diameter responses and interstitial lactate/pyruvate ratios were studied during 90 min hypoxia, hypoxia + reoxygenation (60 min), nitroglycerin (100 microm, 90 min), and nitroglycerin + wash-out (60 min). The arterial segments were snap-frozen and analysed for ser16-HSP20 phosphorylation and ser19-MLC phosphorylation.


RESULTS
The normalized diameter responses to hypoxia (6.1 +/- 4.3%) and nitroglycerin (12.6 +/- 1.6%) were both significantly greater than normoxic control arteries (-10.5 +/- 1.8%, anova, P < 0.05). Ser16-HSP20 phosphorylation was increased with hypoxia and nitroglycerin treatment and ser16-HSP20 phosphorylation correlated with changes in diameters (n = 29, r2 = 0.64, P < 0.001). Ser19-MLC phosphorylation was not significantly altered by hypoxia. The lactate/pyruvate ratio was significantly increased in hypoxic arteries but did not correlate with diameters or ser16-HSP20 phosphorylation.


CONCLUSIONS
Ser16-HSP20 phosphorylation is a potential regulator of hypoxia-induced dilation in coronary arteries.
Frøbert
O
O
Department of Cardiology S, Center for Cardiovascular Research, Aalborg Hospital, Aarhus University Hospital, Aarhus, Denmark. frobert@dadlnet.dk
Buus
C L
CL
Rembold
C M
CM
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D004108:Dilatation, Pathologic; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism; D007773:Lactates / Q000097:blood; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D005996:Nitroglycerin / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019289:Pyruvic Acid / Q000097:blood; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology
D001786:Blood Glucose; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007773:Lactates; D018994:Myosin Light Chains; D010750:Phosphoproteins; D014665:Vasodilator Agents; D019289:Pyruvic Acid; D005996:Nitroglycerin