A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice.

Surawee Chuaiphichai,Gillian Douglas,Eileen Mcneill,Keith M Channon,Mark J Crabtree,Ashley B Hale,Lucy Trelfa

doi:10.1111/bph.13728

Surawee Chuaiphichai, Gillian Douglas + Show 5 more

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https://doi.org/10.1111/bph.13728

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Abstract

Background and PurposeThe cofactor tetrahydrobiopterin (BH4) is a critical regulator of endothelial NOS (eNOS) function, eNOS‐derived NO and ROS signalling in vascular physiology. To determine the physiological requirement for de novo endothelial cell BH4 synthesis for the vasomotor function of resistance arteries, we have generated a mouse model with endothelial cell‐specific deletion of Gch1, encoding GTP cyclohydrolase 1 (GTPCH), an essential enzyme for BH4 biosynthesis, and evaluated BH4‐dependent eNOS regulation, eNOS‐derived NO and ROS generation.Experimental ApproachThe reactivity of mouse second‐order mesenteric arteries was assessed by wire myography. High performance liquid chromatography was used to determine BH4, BH2 and biopterin. Western blotting was used for expression analysis.Key Results Gch1 fl/flTie2cre mice demonstrated reduced GTPCH protein and BH4 levels in mesenteric arteries. Deficiency in endothelial cell BH4 leads to eNOS uncoupling, increased ROS production and loss of NO generation in mesenteric arteries of Gch1 fl/flTie2cre mice. Gch1 fl/flTie2cre mesenteric arteries had enhanced vasoconstriction to U46619 and phenylephrine, which was abolished by L‐NAME. Endothelium‐dependent vasodilatations to ACh and SLIGRL were impaired in mesenteric arteries from Gch1 fl/flTie2cre mice, compared with those from wild‐type littermates. Loss of eNOS‐derived NO‐mediated vasodilatation was associated with increased eNOS‐derived H2O2 and cyclooxygenase‐derived vasodilator in Gch1 fl/flTie2cre mesenteric arteries.Conclusions and ImplicationsEndothelial cell Gch1 and BH4‐dependent eNOS regulation play pivotal roles in maintaining vascular homeostasis in resistance arteries. Therefore, targeting vascular Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of microvascular dysfunction in patients with cardiovascular disease.

Highlights

Hypertension affects more than one in four adults in the UK and is a major risk factor for heart failure, kidney disease and stroke
Biosynthesis of BH4 is catalysed by GTP cyclohydrolase 1 (GTPCH), a rate limiting enzyme for de novo BH4 biosynthesis, which is encoded by Gch1
Western blot analysis showed that GTPCH protein was barely detectable in mesenteric arteries from Gch1fl/flTie2cre mice, whereas this protein was readily detected in wild-type mesenteric arteries (Figure 1A)

Summary

Introduction

Hypertension affects more than one in four adults in the UK and is a major risk factor for heart failure, kidney disease and stroke. Tetrahydrobiopterin (BH4) is a critical regulator of endothelial NOS (eNOS) function, and eNOS-derived NO and ROS signalling in vascular physiology. Studies of a haplotype defined by three single nucleotide polymorphisms in GCH1 have shown that the X haplotype is associated with lower vascular levels of GCH1 mRNA and decreased levels of BH4 in the vasculature This attenuation of BH4 was associated with increased vascular superoxide production and reduced endothelial-dependent vasodilatation in arterial and venous segments from patients. To determine the physiological requirement for de novo endothelial cell BH4 synthesis for the vasomotor function of resistance arteries, we have generated a mouse model with endothelial cell-specific deletion of Gch, encoding GTP cyclohydrolase 1 (GTPCH), an essential enzyme for BH4 biosynthesis, and evaluated BH4-dependent eNOS regulation, eNOS-derived NO and ROS generation.

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