Nitroglycerin fails to lower blood pressure in redox-dead Cys42Ser PKG1α knock-in mouse.
BACKGROUND
Although nitroglycerin has remained in clinical use since 1879, the mechanism by which it relaxes blood vessels to lower blood pressure remains incompletely understood. Nitroglycerin undergoes metabolism that generates several reaction products, including oxidants, and this bioactivation process is essential for vasodilation. Protein kinase G (PKG) mediates classic nitric oxide-dependent vasorelaxation, but the 1α isoform is also independently activated by oxidation that involves interprotein disulfide formation within this homodimeric protein complex. We hypothesized that nitroglycerin-induced vasodilation is mediated by disulfide activation of PKG1α.


RESULTS
Treating smooth muscle cells or isolated blood vessels with nitroglycerin caused PKG1α disulfide dimerization. PKG1α disulfide formation was increased in wild-type mouse aortas by in vivo nitroglycerin treatment, but this oxidation was lost as tolerance developed. To establish whether kinase oxidation underlies nitroglycerin-induced vasodilation in vivo, we used a Cys42Ser PKG1α knock-in mouse that cannot transduce oxidant signals because it does not contain the vital redox-sensing thiol. This redox-dead knock-in mouse was substantively deficient in hypotensive response to nitroglycerin compared with wild-type littermates as measured in vivo by radiotelemetry. Resistance blood vessels from knock-ins were markedly less sensitive to nitroglycerin-induced vasodilation (EC(50)=39.2 ± 10.7 μmol/L) than wild-types (EC(50)=12.1 ± 2.9 μmol/L). Furthermore, after ≈24 hours of treatment, wild-type controls stopped vasodilating to nitroglycerin, and the vascular sensitivity to nitroglycerin was decreased, whereas this tolerance phenomenon, which routinely hampers the management of hypertensive patients, was absent in knock-ins.


CONCLUSIONS
PKG1α disulfide formation is a significant mediator of nitroglycerin-induced vasodilation, and tolerance to nitroglycerin is associated with loss of kinase oxidation.
Cardiovascular Division, King's College London, The British Heart Foundation Centre of Excellence, The Rayne Institute, St. Thomas' Hospital, United Kingdom.
Olena
O
Rudyk
Oleksandra
O
Prysyazhna
Joseph R
JR
Burgoyne
Philip
P
Eaton
D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001011:Aorta / Q000166:cytology; D001794:Blood Pressure / Q000187:drug effects* / Q000235:genetics*; D002478:Cells, Cultured; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D055879:Gene Knock-In Techniques; D006973:Hypertension / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D005996:Nitroglycerin / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013686:Telemetry; D014664:Vasodilation / Q000187:drug effects / Q000235:genetics; D014665:Vasodilator Agents / Q000494:pharmacology
D004220:Disulfides; D013438:Sulfhydryl Compounds; D014665:Vasodilator Agents; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569720:Prkg1 protein, mouse; D005996:Nitroglycerin