The cerebrovascular endothelium exerts a profound influence on cerebral vessels and cerebral blood flow. This review summarizes current knowledge of various dilator and constrictor mechanisms intrinsic to the cerebrovascular endothelium. The endothelium contributes to the resting tone of cerebral arteries and arterioles by tonically releasing nitric oxide (NO*). Dilations can occur by stimulated release of NO*, endothelium-derived hyperpolarization factor, or prostanoids. During pathological conditions, the dilator influence of the endothelium can turn to that of constriction by a variety of mechanisms, including decreased NO* bioavailability and release of endothelin-1. The endothelium may participate in neurovascular coupling by conducting local dilations to upstream arteries. Further study of the cerebrovascular endothelium is critical for understanding the pathogenesis of a number of pathological conditions, including stroke, traumatic brain injury, and subarachnoid hemorrhage.

MJ. FGF23 directly impairs endothelium-dependent vasorelaxation by increasing superoxide levels and reducing nitric oxide bioavailability. Am J Physiol Endocrinol Metab 307: E426 -E436, 2014. First published July 15, 2014 doi:10.1152/ajpendo.00264.2014.-Fibroblast growth factor 23 (FGF23) is secreted primarily by osteocytes and regulates phosphate and vitamin D metabolism. Elevated levels of FGF23 are clinically associated with endothelial dysfunction and arterial stiffness in chronic kidney disease (CKD) patients; however, the direct effects of FGF23 on endothelial function are unknown. We hypothesized that FGF23 directly impairs endothelial vasorelaxation by hindering nitric oxide (NO) bioavailability. We detected expression of all four subtypes of FGF receptors (Fgfr1-4) in male mouse aortas. Exogenous FGF23 (90 -9,000 pg/ml) did not induce contraction of aortic rings and did not relax rings precontracted with PGF 2␣. However, preincubation with FGF23 (9,000 pg/ml) caused a ϳ36% inhibition of endothelium-dependent relaxation elicited by acetylcholine (ACh) in precontracted aortic rings, which was prevented by the FGFR antagonist PD166866 (50 nM). Furthermore, in FGF23-pretreated (9,000 pg/ml) aortic rings, we found reductions in NO levels. We also investigated an animal model of CKD (Col4a3 Ϫ/Ϫ mice) that displays highly elevated serum FGF23 levels and found they had impaired endothelium-dependent vascular relaxation and reduced nitrate production compared with age-matched wild types. To elucidate a mechanism for the FGF23-induced impairment, we measured superoxide levels in endothelial cells and aortic rings and found that they were increased following FGF23 treatment. Crucially, treatment with the superoxide scavenger tiron reduced superoxide levels and also restored aortic relaxation to ACh. Therefore, our data suggest that FGF23 increases superoxide, inhibits NO bioavailability, and causes endothelial dysfunction in mouse aorta. Together, these data provide evidence that high levels of FGF23 contribute to cardiovascular dysfunction. fibroblast growth factor 23; chronic kidney disease; nitric oxide; superoxide; and cardiovascular disease IT IS WELL KNOWN THAT PATIENTS with chronic kidney disease (CKD) have an increased risk of cardiovascular disease (CVD). Modification of the traditional risk factors for CVD (e.g., dyslipidemia, hypertension, anemia, and hyperhomocysteinemia) does not improve cardiovascular function in patients with CKD (32), suggesting that other factors may be responsible. Fibroblast growth factor 23 (FGF23) is a hormone secreted by osteocytes that serves as an important regulator of serum phosphate and vitamin D via direct actions on the kidney and parathyroid (6,8). Recently, high circulating levels of FGF23 have been clinically associated with the development of CVD (3,9,33,47,55,72) especially during CKD where serum FGF23 is substantially increased 10-to 1,000-fold (30, 37). Nevertheless, despite these clinical associations, there have been relatively few studies to determine whethe...

Objective-The goal of this study was to compare vascular function, superoxide levels, and MnSOD protein expression in young (4 to 7 months) and old (22 to 24 months) MnSOD ϩ/ϩ and MnSOD-deficient (MnSOD ϩ/Ϫ ) mice. Methods and Results-Relaxation of aorta in vitro to the endothelium-dependent dilator acetylcholine (ACh) was similar in young MnSOD ϩ/ϩ (nϭ9) and young MnSOD ϩ/Ϫ (nϭ6) mice. This response was impaired in old MnSOD ϩ/ϩ (nϭ8) mice and old MnSOD ϩ/Ϫ mice (nϭ14), with dysfunction being greater in old MnSOD-deficient mice (eg, 100 mol/L ACh produced 77Ϯ3% [meanϮSE], 77Ϯ3%, 70Ϯ4%, and 57Ϯ4% relaxation in young MnSOD ϩ/ϩ , young MnSOD ϩ/Ϫ , old MnSOD ϩ/ϩ , and old MnSOD ϩ/Ϫ mice, respectively). The endothelial dysfunction was similar in mice on both C57BL/6 and CD-1 genetic backgrounds. In contrast to ACh, responses to the endothelium-independent dilator sodium nitroprusside were enhanced in old MnSOD ϩ/ϩ and MnSOD ϩ/Ϫ mice compared with both groups of young mice (PϽ0.05). Superoxide levels, as measured using lucigenin-enhanced chemiluminescence, were increased more than 2-fold in old MnSOD ϩ/Ϫ mice compared with old MnSOD ϩ/ϩ and young mice (PϽ0.05). Conclusions-These data provide the first direct evidence that MnSOD halpoinsufficiency results in increased vascular oxidative stress and endothelial dysfunction with aging. (Arterioscler Thromb Vasc

We sought to determine whether adenovirus-mediated gene transfer in vivo of calcitonin gene-related peptide (CGRP), a potent vasodilator, ameliorates cerebral vasoconstriction after experimental subarachnoid hemorrhage (SAH). Arterial blood was injected into the cisterna magna of rabbits to mimic SAH 5 days after injection of AdRSVCGRP (8x10(8) pfu), AdRSVbetagal (control virus), or vehicle. After injection of AdRSVCGRP, there was a 400-fold increase in CGRP in cerebrospinal fluid. Contraction of the basilar artery to serotonin in vitro was greater in rabbits after SAH than after injection of artificial cerebrospinal fluid (P<0.001). Contraction to serotonin was less in rabbits with SAH after AdRSVCGRP than after AdRSVbetagal or vehicle (P:<0.02). Basal diameter of the basilar artery before SAH (measured with digital subtraction angiogram) was 13% greater in rabbits treated with AdRSVCGRP than in rabbits treated with vehicle or AdRSVbetagal (P:<0.005). In rabbits treated with vehicle or AdRSVbetagal, arterial diameter after SAH was 25+/-3% smaller than before SAH (P<0.0005). In rabbits treated with AdRSVCGRP, arterial diameter was similar before and after SAH and was reduced by 19+/-3% (P<0.01) after intracisternal injection of CGRP-(8-37) (0.5 nmol/kg), a CGRP(1) receptor antagonist. To determine whether gene transfer of CGRP after SAH may prevent cerebral vasoconstriction, we constructed a virus with a cytomegalovirus (CMV) promoter, which results in rapid expression of the transgene product. Treatment of rabbits with AdCMVCGRP after experimental SAH prevented constriction of the basilar artery 2 days after SAH. Thus, gene transfer of CGRP prevents cerebral vasoconstriction in vivo after experimental SAH.

Background and Purpose-Superoxide may play an important role in cerebral vasospasm after subarachnoid hemorrhage (SAH). Our first goal was to determine the effect of gene transfer of extracellular superoxide dismutase (ECSOD) on vasospasm after experimental SAH. Our second goal was to determine whether tissue binding of ECSOD via the heparin-binding domain (HBD) is important for the effect of the enzyme. Thus, we examined effects of gene transfer of ECSOD with the HBD deleted (ECSOD⌬HBD). Methods-Adenovirus expressing human ECSOD (AdECSOD), ECSOD⌬HBD (AdECSOD⌬HBD), or no transgene (AdBglII) was injected into the cisterna magna of anesthetized rabbits 30 minutes after induction of experimental SAH. Cerebral angiography, an assay for ECSOD activity in cerebrospinal fluid (CSF), and Western blotting for human ECSOD in the basilar artery were performed. Results-Baseline diameter of the basilar artery averaged 0.77Ϯ0.01 mm (meanϮSEM) and was similar in all treatment groups. Decreases in diameter of the basilar artery 2 days after SAH were smaller after AdECSOD (11Ϯ3%; nϭ10) than after AdBglII (25Ϯ4%; nϭ7; PϽ0.05). ECSOD activity was not detected in CSF before SAH and gene transfer. Of 8 rabbits treated with AdECSOD, in which ECSOD activity in CSF was measured after SAH, 5 animals had detectable ECSOD activity in CSF (46Ϯ13 U/mL). In these 5 rabbits, the diameter decreased by only 6Ϯ3%, and ECSOD protein was detected in the basilar artery. After AdECSOD⌬HBD (nϭ4), despite high levels of ECSOD activity in CSF (91Ϯ19 U/mL), vessel diameter decreased by 20Ϯ2%, and no ECSOD⌬HBD protein was detected in the basilar artery. Conclusions-Gene