The xanthine derivative KMUP-1 inhibits models of pulmonary artery hypertension via increased NO and cGMP-dependent inhibition of RhoA/Rho kinase.
OBJECTIVE
KMUP-1 is known to increase cGMP, enhance endothelial nitric oxide synthase (eNOS) and suppress Rho kinase (ROCK) expression in smooth muscle. Here, we investigated the mechanism of action of KMUP-1 on acute and chronic pulmonary artery hypertension (PAH) in rats.


METHODS
We measured pulmonary vascular contractility, wall thickening, eNOS immunostaining, expressions of ROCK II, RhoA activation, myosin phosphatase target subunit 1 (MYPT1) phosphorylation, eNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG) and phosphodiesterase 5A (PDE-5A), blood oxygenation and cGMP/cAMP, and right ventricular hypertrophy (RVH) in rats.


RESULTS
In rings of intact pulmonary artery (PA), KMUP-1 relaxed the vasoconstriction induced by phenylephrine (10 microM) or the thromboxane A(2)-mimetic U46619 (0.5 microM). In endothelium-denuded PA rings, this relaxation was reduced. In acute PAH induced by U46619 (2.5 microg x kg(-1) x min(-1), 30 min), KMUP-1 relaxed vasoconstriction by enhancing levels of eNOS, sGC and PKG, suppressing those of PDE-5A, RhoA/ROCK II activation and MYPT1 phosphorylation, and restoring oxygenation in blood and cGMP/cAMP in plasma. Incubating smooth muscle cells from PA (PASMCs) with KMUP-1 inhibited thapsigargin-induced Ca(2+) efflux and angiotensin II-induced Ca(2+) influx. In chronic PAH model induced by monocrotaline, KMUP-1 increased eNOS and reduced RhoA/ROCK II activation/expression, PA wall thickening, eNOS immunostaining and RVH. KMUP-1 and sildenafil did not inhibit monocrotaline-induced PDE-5A expression.


CONCLUSIONS
KMUP-1 decreased PAH by enhancing NO synthesis by eNOS, with consequent cGMP-dependent inhibition of RhoA/ROCK II and Ca(2+) desensitization in PASMCs. KMUP-1 has the potential to reduce vascular resistance, remodelling and RVH in PAH.
Chung
Hui-Hsuan
HH
Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Dai
Zen-Kong
ZK
Wu
Bin-Nan
BN
Yeh
Jwu-Lai
JL
Chai
Chee-Yin
CY
Chu
Koung-Shing
KS
Liu
Chung-Pin
CP
Chen
Ing-Jun
IJ
D000818:Animals; D000959:Antihypertensive Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000627:therapeutic use*; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006976:Hypertension, Pulmonary / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism / Q000517:prevention & control; D017380:Hypertrophy, Right Ventricular / Q000517:prevention & control; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009712:Nucleotides, Cyclic / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010880:Piperidines / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000627:therapeutic use*; D054645:Protein Phosphatase 1 / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects; D014970:Xanthines / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000627:therapeutic use*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000959:Antihypertensive Agents; D004791:Enzyme Inhibitors; D009712:Nucleotides, Cyclic; D010880:Piperidines; D014970:Xanthines; C439304:KMUP 1; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D054460:rho-Associated Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D020742:rhoA GTP-Binding Protein