Characterization of vasoconstrictor-induced relaxation in the cerebral basilar artery

Vitamin D attenuates cerebral artery remodeling through VDR/AMPK/eNOS dimer phosphorylation pathway after subarachnoid hemorrhage in rats

The role of vitamin D3 (VitD3) in the upregulation of osteopontin (OPN) and eNOS in the endothelium of cerebral arteries after subarachnoid hemorrhage (SAH) is investigated. The endovascular perforation SAH model in Sprague-Dawley rats ( n = 103) was used. The VitD3 pretreatment (30 ng/kg) increased endogenous OPN and eNOS expression in cerebral arteries compared with naïve rats ( n = 5 per group). Neurobehavioral scores were significantly improved in Pre-SAH+VitD3 group compared with the SAH group. The effects of VitD3 were attenuated by intracerebroventricular (i.c.v) injections of siRNA for the vitamin D receptor (VDR) and OPN in Pre-SAH+VitD3+VDR siRNA and Pre-SAH+VitD3+OPN siRNA rats, respectively ( n = 5 per group). The significant increase of VDR, OPN and decrease of C44 splicing in the cerebral arteries of Pre-SAH+VitD3 rats lead to an increase in basilar artery lumen. The increase in VDR expression led to an upregulation and phosphorylation of AMPK and eNOS, especially dimer form, in endothelium of cerebral artery. The results provide that VitD3 pretreatment attenuates cerebral artery remodeling and vasospasm through the upregulation of OPN and phosphorylation of AMPK (p-AMPK) and eNOS (p-eNOS) at Ser1177-Dimer in the cerebral arteries. Vitamin D may be a useful new preventive and therapeutic strategy against cerebral artery remodeling in stroke patients.

Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.

Endothelial AMP-activated protein kinase regulates blood pressure and coronary flow responses through hyperpolarization mechanism in mice

OBJECTIVE

Vascular endothelium plays an important role to maintain cardiovascular homeostasis through several mechanisms, including endothelium-dependent hyperpolarization (EDH). We have recently demonstrated that EDH is involved in endothelial metabolic regulation in mice. However, it remains to be examined whether AMP-activated protein kinase (AMPK), an important metabolic regulator, is involved in EDH and if so, whether endothelial AMPK (eAMPK) plays a role for circulatory regulation.

APPROACH AND RESULTS

We examined the role of eAMPK in EDH, using mice with endothelium-specific deficiency of α-catalytic subunit of AMPK, either α1 (eAMPKα1 (-/-)α2 (+/+)) or α2 (eAMPKα1 (+/+)α2 (-/-)) alone or both of them (eAMPKα1 (-/-)α2 (-/-)). We performed telemetry, organ chamber, electrophysiological, and Langendorff experiments to examine blood pressure, vascular responses, hyperpolarization of membrane potential, and coronary flow responses, respectively. Hypertension was noted throughout the day in eAMPKα1 (-/-)α2 (-/-) and eAMPKα1 (-/-)α2 (+/+) but not in eAMPKα1 (+/+)α2 (-/-) mice when compared with respective control. Importantly, endothelium-dependent relaxations, EDH, and coronary flow increase were all significantly reduced in eAMPKα1 (-/-)α2 (-/-) and eAMPKα1 (-/-)α2 (+/+) but not in eAMPKα1 (+/+)α2 (-/-) mice. In contrast, endothelium-independent relaxations to sodium nitroprusside (a NO donor), NS-1619 (a Ca(2+)-activated K(+) channel opener), and exogenous H2O2 were almost comparable among the groups. In eAMPKα1 (-/-)α2 (-/-) mice, antihypertensive treatment with hydralazine or long-term treatment with metformin (a stimulator of AMPK) failed to restore EDH-mediated responses.

CONCLUSIONS

These results provide the first direct evidence that α1 subunit of eAMPK substantially mediates EDH responses of microvessels and regulates blood pressure and coronary flow responses in mice in vivo, demonstrating the novel role of eAMPK in cardiovascular homeostasis.

Effects of Krill-derived phospholipid-enriched n-3 fatty acids on Ca(2+) regulation system in cerebral arteries from ovariectomized rats

AIMS

To investigate the effects of n-3 polyunsaturated fatty acids on cerebral circulation, ovariectomized (OVX) rats were administered with phospholipids in krill oil (KPL) or triglycerides in fish oil (FTG); effects on the Ca(2+) regulating system in their basilar artery (BA) were then analyzed.

MAIN METHODS

The rats were divided into 4 groups: control, OVX, OVX given KPL (OVXP), and OVX given FTG (OVXT) orally, daily for 2weeks. Time dependent relaxation (TDR) of contractile response to 5HT in BA was determined myographically, Na(+)/Ca(2+) exchanger (NCX) 1 mRNA expression was determined by real time PCR, and nucleotides were analyzed by HPLC.

KEY FINDINGS

The level of TDR in OVX that was significantly lower in the control was inhibited by l-NAME and indomethacin; TEA inhibited TDR totally in the control but only partly in OVXP and OVXT. Relaxation induced by the addition of 5mM KCl to the BA pre-contracted with 5-HT was inhibited by TEA in the controls, OVXP and OVXT, but not in OVX. Overexpression of NCX1 mRNA in the BA from OVX was significantly inhibited by FTG. The ratio of ADP/ATP in cerebral arteries from OVX was significantly inhibited by KPL and FTG. Levels of triglyceride and arachidonic acid in the plasma of OVX increased, but were significantly inhibited by KPL and FTG.

SIGNIFICANCE

Ovarian dysfunction affects Ca(2+) activated-, ATP-sensitive-K(+) channels and NCX1, which play crucial roles in the autoregulation of cerebral blood flow. Also, KPL may become as good a supplement as FTG for postmenopausal women.