R e s e a R c h a R t i c l e3 4 9 2 jci.org Volume 125 Number 9 September 2015Other factors are likely involved, since over 80 genes were differentially expressed (at least 2-fold) in the TIE2-L914F endothelial cells compared with WT (30). We hypothesized that mutant TIE2 in endothelial cells is sufficient to cause VM. Here, we show that HUVECs engineered to Previous studies on mutant TIE2 showed that expression of TIE2-L914F or TIE2-R849W in HUVECs increased activation of AKT and of . Elevated AKT signaling in these cells has been linked to increased survival (29, 30) and to reduced production of PDGF-B (30), a major player in mural cell recruitment.

Summary Endothelial dysfunction is a central hallmark of diabetes. The transcriptional coactivator PGC-1α is a powerful regulator of metabolism, but its role in endothelial cells remains poorly understood. We show here that endothelial PGC-1α expression is high in diabetic rodents and humans and that PGC-1α powerfully blocks endothelial migration in cell culture and vasculogenesis in vivo. Mechanistically, PGC-1α induces Notch signaling, blunts activation of Rac/Akt/eNOS signaling, and renders endothelial cells unresponsive to established angiogenic factors. Transgenic overexpression of PGC-1α in the endothelium mimics multiple diabetic phenotypes, including aberrant re-endothelialization after carotid injury, blunted wound healing, and reduced blood flow recovery after hindlimb ischemia. Conversely, deletion of endothelial PGC-1α rescues the blunted wound healing and recovery from hindlimb ischemia seen in type 1 and type 2 diabetes. Endothelial PGC-1α thus potently inhibits endothelial function and angiogenesis, and induction of endothelial PGC-1α contributes to multiple aspects of vascular dysfunction in diabetes.

Abstract-To determine the mechanism(s) involved in vasorelaxation of small arteries from hypertensive rats, normotensive (NORM), angiotensin II-infused (ANG), high-salt (HS), ANG high-salt (ANG/HS), placebo, and deoxycorticosterone acetate-salt rats were studied. Third-order mesenteric arteries from ANG or ANG/HS displayed decreased sensitivity to acetylcholine (ACh)-induced vasorelaxation compared with NORM or HS, respectively. Maximal relaxations were comparable between groups. Blockade of Ca 2ϩ -activated K ϩ channels had no effect on ANG versus blunting relaxation in NORM (log EC 50 : Ϫ6.8Ϯ0.1 versus Ϫ7.2Ϯ0.1 mol/L). NO synthase (NOS) inhibition abolished ACh-mediated relaxation in small arteries from ANG, ANG/HS, and deoxycorticosterone acetate-salt versus blunting relaxation in NORM, HS, and placebo (% maximal relaxation: ANG: 2.7Ϯ1.8; ANG/HS: 7.2Ϯ3.2; NORM: 91Ϯ3.1; HS: 82.1Ϯ13.3; deoxycorticosterone acetate-salt: 35.2Ϯ17.7; placebo: 79.3Ϯ10.3), indicating that NOS is the primary vasorelaxation pathway in these arteries from hypertensive rats. We hypothesized that NO/cGMP signaling and NOS-dependent H 2 O 2 maintains vasorelaxation in small arteries from ANG. ACh increased NOS-dependent cGMP production, indicating that NO/cGMP signaling is present in small arteries from ANG (55.7Ϯ6.9 versus 30.5Ϯ5.1 pmol/mg), and ACh stimulated NOS-dependent H 2 O 2 production (ACh: 2.8Ϯ0.2 mol/mg; N -nitro-L-arginine methyl ester hydrochlorideϩACh: 1.8Ϯ0.1 mol/mg) in small arteries from ANG. H 2 O 2 induced vasorelaxation and catalase blunted ACh-mediated vasorelaxation. In conclusion, Ca 2ϩ -activated K ϩ channel-mediated relaxation is dysfunctional in small mesenteric arteries from hypertensive rats, and the NOS pathway compensates to maintain vasorelaxation in these arteries through NOS-mediated cGMP and H 2 O 2 production.

We previously reported that small mesenteric arteries from hypertensive rats have increased NOS-derived H(2)O(2) and reduced NO/cGMP signaling. We hypothesized that antihypertensive therapy lowers blood pressure through a tetrahydrobiopterin (BH(4))-dependent mechanism restoring NO/cGMP signaling and endothelial NOS (NOS3; eNOS) phosphorylation in small arteries. To test this hypothesis, small mesenteric arteries from normotensive rats (NORM), angiotensin II-infused rats (ANG), ANG rats with triple therapy (reserperine, hydrochlorothiazide, and hydralazine), or ANG rats with oral BH(4) therapy were studied. Both triple therapy and oral BH(4) therapy attenuated the rise in systolic blood pressure in ANG rats and restored NO/cGMP signaling in small arteries similarly. Triple therapy significantly increased vascular BH(4) levels and BH(4)-to-BH(2) ratio similar to ANG rats with BH(4) supplementation. Furthermore, triple therapy (but not oral BH(4) therapy) significantly increased GTP cyclohydrolase I (GTPCH I) activity in small arteries without a change in expression. NOS3 phosphorylation at Ser1177 was reduced in small arteries from ANG compared with NORM, while NOS3 phosphorylation at Ser633 and Thr495 were similar in ANG and NORM. NOS3 phosphorylation at Ser1177 was restored with triple therapy or oral BH(4) in ANG rats. In conclusion, antihypertensive therapy regulates NO/cGMP signaling in small arteries through increasing BH(4) levels and NOS3 phosphorylation at Ser1177.

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