A new role for caveolin-1: regulation of guanosine triphosphate cyclohydrolase I and tetrahydrobiopterin in endothelial cells

Flavin adenine dinucleotide ameliorates hypertensive vascular remodeling via activating short chain acyl-CoA dehydrogenase

AIMS

Flavin adenine dinucleotide (FAD), participates in fatty acid β oxidation as a cofactor, which has been confirmed to enhance SCAD activity and expression. However, the role of FAD on hypertensive vascular remodeling is unclear. In this study, we investigated the underlying mechanisms of FAD on vascular remodeling and endothelial homeostasis.

MAIN METHODS

Morphological examination of vascular remodeling were analyzed with hematoxylin and eosin (HE) staining, Verhoeff's Van Gieson (EVG) staing, Dihydroethidium (DHE) staining and Sirius red staining. HUVECs apoptotic rate was detected by flow cytometry and HUVECs reactive oxygen species (ROS) was detected by DHE-probe. Enzymatic reactions were used to detect SCAD enzyme activity. The protein level was detected by Western Blots, the mRNA level was detected by quantitative real-time PCR.

KEY FINDINGS

In vivo experiments, FAD significantly decreased blood pressure and ameliorated vascular remodeling by increasing SCAD expression, Nitric Oxide (NO) production and reducing ROS production. In vitro experiments, FAD protected against the tBHP induced injury in HUVEC, by increasing the activity of SCAD, increasing the elimination of free fatty acid (FFA), scavenging ROS, reducing apoptotic rate, thereby improving endothelial cell function.

SIGNIFICANCE

FAD has a new possibility for preventing and treating hypertensive vascular remodeling.

Pharmacological inhibition of guanosine triphosphate cyclohydrolase1 elevates tyrosine phosphorylation of caveolin1 and cellular senescence

The role of 2,4-diamino-6-hydroxypyrimidine (DAHP), on cellular-senescence remains unclear as differential effects of DAHP have been reported in cardiovascular and cerebrovascular systems. We investigated the effect of pharmacologically-induced guanosine-triphosphate-cyclohydrolase1 (GTPCH1)-inhibition, through DAHP, on cellular-senescence in experimentally-induced diabetic and non-diabetic Wistar rats. Cellular-senescence was evaluated through senescence-associated events, namely, cell-cycle-arrest of peripheral blood mononuclear cells (PBMNCs); myocardial DNA fragmentation, total antioxidant capacity (TAC), telomerase-activity, nicotinamide adenine dinucleotide (NAD⁺)-content and tyrosine14-phosphorylation of caveolin1 (pY14) in similarly-aged, pubertal Wistar rats with streptozotocin (STZ) and/or DAHP. Oxidative stress (OS) indices such as myocardial biopterin concentrations (tetrahydrobiopterin-BH₄ and dihydrobiopterin-BH₂) and plasma total nitrite and nitrate (NOx) were determined. DAHP, per se, exhibited distinct senescence; in addition, in STZ+DAHP (the cardiomyopathy model), there was a marked accumulation of cells in G0G1 phase, as evidenced through flow-cytometry analysis, as-well-as fragmented DNA, than the respective controls suggesting the DAHP-mediated onset of senescence in circulating cells and the myocardium, with or without STZ. Concentrations of BH4 and BH2, and NOx were impaired in STZ and/or DAHP, indicating elevated OS in the treatment groups. In the independent treatment groups or the combination treatment, typical senescence indicators including myocardial telomerase-activity, NAD⁺-content and TAC were significantly reduced, while there was a marked elevation in the concentrations of pY14 as compared to the respective controls, reinforcing the occurrence of senescence in PBMNCs and the myocardium. We postulate that DAHP promotes early onset of cellular-senescence, potentially through OS-mediated cellular events in diabetic or non-diabetic models.

Importance of mechanical signals in promoting exercise-induced improvements in vasomotor function of aged skeletal muscle resistance arteries

Current research indicates that vasomotor responses are altered with aging in skeletal muscle resistance arteries. The changes in vasomotor function are characterized by impaired vasodilator and vasoconstrictor responses. The detrimental effects of aging on vasomotor function are attenuated in some vascular beds after a program of endurance exercise training. The signals associated with exercise responsible for inducing improvements in vasomotor function have been proposed to involve short-duration increases in intraluminal shear stress and/or pressure during individual bouts of exercise. Here, we review evidence that increases in shear stress and pressure, within a range believed to present in these arteries during exercise, promote healthy vasomotor function in aged resistance arteries. We conclude that available research is consistent with the interpretation that short-duration mechanical stimulation, through increases in shear stress and pressure, contributes to the beneficial effects of exercise on vasomotor function in aged skeletal muscle resistance arteries.

ATRA improves endothelial dysfunction in atherosclerotic rabbits by decreasing CAV‑1 expression and enhancing eNOS activity

The aim of the present study was to explore the protective effects and possible mechanisms of all‑trans‑retinoic acid (ATRA) against atherosclerosis (AS). Rabbits were randomly allocated for standard or high‑fat diet with or without ATRA. After 12 weeks, the aortic rings of the rabbits were removed. Endothelium‑dependent relaxation (EDR) induced by acetylcholine and non‑endothelium‑dependent relaxation induced by sodium nitroprusside in the thoracic aorta were evaluated. NO level and eNOS activity were measured according to the protocol of NO and eNOS ELISA kits. The permeability and morphology of the arterial walls were identified by immunofluorescence and H&E staining respectively. The expression of caveolin‑1 (CAV‑1) and occludin was analyzed using western blotting and immunohistochemistry. The EDR function was significantly reduced in the AS rabbits compared with the normal group, however it was elevated following treatment with ATRA. The eNOS activity and NO level were reduced in the AS group, however were notably increased following oral administration of ATRA. There was an enhancement of endothelial permeability in the AS group compared with the normal group, which decreased following ATRA treatment. Western blot analysis and immunohistochemical analysis identified an increase in occludin expression after treatment with ATRA, in contrast to CAV‑1 expression under the same conditions. ATRA is able to ameliorate high‑fat‑induced AS in rabbits, which is mediated through the activation of eNOS and downregulating CAV‑1 expression.

Caveolae: a regulatory platform for nutritional modulation of inflammatory diseases

Dietary intervention strategies have proven to be an effective means of decreasing several risk factors associated with the development of atherosclerosis. Endothelial cell dysfunction influences vascular inflammation and is involved in promoting the earliest stages of lesion formation. Caveolae are lipid raft microdomains abundant within the plasma membrane of endothelial cells and are responsible for modulating receptor-mediated signal transduction, thus influencing endothelial activation. Caveolae have been implicated in the regulation of enzymes associated with several key signaling pathways capable of determining intracellular redox status. Diet and plasma-derived nutrients may modulate an inflammatory outcome by interacting with and altering caveolae-associated cellular signaling. For example, omega-3 fatty acids and several polyphenolics have been shown to improve endothelial cell function by decreasing the formation of ROS and increasing NO bioavailability, events associated with altered caveolae composition. Thus, nutritional modulation of caveolae-mediated signaling events may provide an opportunity to ameliorate inflammatory signaling pathways capable of promoting the formation of vascular diseases, including atherosclerosis.