Enhanced activation of NAD(P)H:quinone oxidoreductase 1 attenuates spontaneous hypertension by improvement of endothelial nitric oxide synthase coupling via tumor suppressor kinase liver kinase B1/adenosine 5 '-monophosphate-activated protein kinase-mediated guanosine 5 '-triphosphate cyclohydrolase 1 preservation

Abstract

Aims:Guanosine 5-triphosphate cyclohydrolase-1 (GTPCH-1) is a rate-limiting enzyme in de-novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for endothelial nitric oxide synthase (eNOS) coupling. Adenosine 5-monophosphate-activated protein kinase (AMPK) is crucial for GTPCH-1 preservation, and tumor suppressor kinase liver kinase B1 (LKB1), an upstream kinase of AMPK, is activated by NAD(+)-dependent class III histone deacetylase sirtuin 1 (SIRT1)-mediated deacetylation. -Lapachone has been shown to increase cellular NAD(+)/NADH ratio via NAD(P)H:quinone oxidoreductase 1 (NQO1) activation. In this study, we have evaluated whether -lapachone-induced NQO1 activation modulates blood pressure (BP) through preservation of GTPCH-1 in a hypertensive animal model.Methods and results:Spontaneously hypertensive rats (SHRs), primary aortic endothelial cells, and endothelial cell line were used to investigate the hypotensive effect of -lapachone and its action mechanism. -Lapachone treatment dramatically lowered BP and vascular tension in SHRs and induced eNOS activation in endothelial cells. Consistent with these effects, -lapachone treatment also elevated levels of both aortic cGMP and plasma nitric oxide in SHRs. Meanwhile, -lapachone-treated SHRs showed significantly increased levels of aortic NAD(+), LKB1 deacetylation, and AMPK Thr(172) phosphorylation followed by increased GTPCH-1 and tetrahydrobiopterin/dihydrobiopterin ratio. In-vitro study revealed that AMPK inhibition by overexpression of dominant-negative AMPK nearly abolished GTPCH-1 protein conservation. Enhanced LKB1 deacetylation and AMPK activation were also elicited by -lapachone in endothelial cells. However, inhibition of LKB1 deacetylation by blocking of NQO1 or SIRT1 blunted AMPK activation by -lapachone.Conclusion:This is the first study demonstrating that eNOS coupling can be regulated by NQO1 activation via LKB1/AMPK/GTPCH-1 modulation, which is possibly correlated with relieving hypertension. These findings provide strong evidence to suggest that NQO1 might be a new therapeutic target for hypertension.