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A vast amount of investigation has centered on how the endothelium and smooth muscle communicate. From this evidence, myoendothelial junctions have emerged as critical anatomical structures to regulate heterocellular cross talk. Indeed, there is now evidence that the myoendothelial junction serves as a signaling microdomain to organize proteins used to facilitate vascular heterocellular communication. This review highlights the evolving role of myoendothelial junctions in the context of vascular cell-cell communication. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is one of the critical components of the vasculature, regulating key signaling pathways in health. In macrovessels, NO functions to suppress cell inflammation as well as adhesion. In this way, it inhibits thrombosis and promotes blood flow. It also functions to limit vessel constriction and vessel wall remodeling. In microvessels and particularly capillaries, NO, along with growth factors, is important in promoting new vessel formation, a process termed angiogenesis. With age and cardiovascular disease, animal and human studies confirm that NO is dysregulated at multiple levels including decreased production, decreased tissue half-life, and decreased potency. NO has also been implicated in diseases that are related to neurotransmission and cancer although it is likely that these processes involve NO at higher concentrations and from nonvascular cell sources. Conversely, NO and drugs that directly or indirectly increase NO signaling have found clinical applications in both age-related diseases and in younger individuals. This focused review considers recently reported advances being made in the field of NO signaling regulation at several levels including enzymatic production, receptor function, interacting partners, localization of signaling, matrix-cellular and cell-to-cell cross talk, as well as the possible impact these newly described mechanisms have on health and disease. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) binds soluble guanylyl cyclase β (sGCβ) to produce cGMP and relax vascular smooth muscle cells (SMCs) needed for vasodilation. Although the regulation of NO-stimulated sGC activity has been well characterized at the posttranslational level, the mechanisms that govern sGC transcription remain incompletely understood. Recently, we identified Forkhead box subclass O (FoxO) transcription factors as essential for expression of sGC; however, the specific FoxO family member responsible for the expression of sGCb in SMC remains unknown. Using FoxO shRNA knockdown adenovirus treatment in rat aortic SMCs, we show that FoxO1 or FoxO3 knockdown causes greater than twofold increases in Gucy1a3 and Gucy1b3 mRNA expression, without changes in NO-dependent cGMP production or cGMP-dependent phosphorylation. FoxO4 knockdown produced a 50% decrease in Gucy1a3 and Gucy1b3 mRNA with 70% loss of sGCa and 50% loss of sGCb protein expression. Knockdown of FoxO4 expression decreased cGMP production and downstream protein kinase G-dependent phosphorylation more than 50%. Triple FoxO knockdown exacerbated loss of sGC-dependent function, phenocopying previous FoxO inhibition studies. Using promoter luciferase and chromatin immunoprecipitation assays, we find that FoxO4 acts as a transcriptional activator by directly binding several FoxO DNA motifs in the promoter regions of GUCY1B3 in human aortic SMCs. Collectively, our data show FoxO4 is a critical transcriptional regulator of sGCb expression in SMC. [ABSTRACT FROM AUTHOR]

The small conductance calcium-activated potassium channel (KCa2.3) has long been recognized for its role in mediating vasorelaxation through the endothelium-derived hyperpolarization (EDH) response. Histone deacetylases (HDACs) have been implicated as potential modulators of blood pressure and histone deacetylase inhibitors (HDACi) are being explored as therapeutics for hypertension. Herein, we show that HDACi increase KCa2.3 expression when heterologously expressed in HEK cells and endogenously expressed in primary cultures of human umbilical vein endothelial cells (HUVECs) and human intestinal microvascular endothelial cells (HIMECs). When primary endothelial cells were exposed to HDACi, KCa2.3 transcripts, subunits, and functional current are increased. Quantitative RT-PCR (qPCR) demonstrated increased KCa2.3 mRNA following HDACi, confirming transcriptional regulation of KCa2.3 by HDACs. By using pharmacological agents selective for different classes of HDACs, we discriminated between cytoplasmic and epigenetic modulation of KCa2.3. Biochemical analysis revealed an association between the cytoplasmic HDAC6 and KCa2.3 in immunoprecipitation studies. Specifically inhibiting HDAC6 increases expression of KCa2.3. In addition to increasing the expression of KCa2.3, we show that nonspecific inhibition of HDACs causes an increase in the expression of the molecular chaperone Hsp70 in endothelial cells. When Hsp70 is inhibited in the presence of HDACi, the magnitude of the increase in KCa2.3 expression is diminished. Finally, we show a slower rate of endocytosis of KCa2.3 as a result of exposure of primary endothelial cells to HDACi. These data provide the first demonstrated approach to increase KCa2.3 channel number in endothelial cells and may partially account for the mechanism by which HDACi induce vasorelaxation. [ABSTRACT FROM AUTHOR]

Pulmonary arterial hypertension (PAH) is a fatal cardiopulmonary disease characterized by increased vascular cell proliferation with apoptosis resistance and occlusive remodeling of the small pulmonary arteries. The Notch family of proteins subserves proximal signaling of an evolutionarily conserved pathway that effects cell proliferation, fate determination, and development. In endothelial cells (ECs), Notch receptor 2 (Notch2) was shown to promote endothelial apoptosis. However, a pro- or antiproliferative role for Notch2 in pulmonary endothelial proliferation and ensuing PAH is unknown. We postulated that suppressed Notch2 signaling drives pulmonary endothelial proliferation in the context of PAH. We observed that levels of Notch2 are ablated in lungs from PAH subjects compared with non-PAH controls. Notch2 expression was attenuated in human pulmonary artery endothelial cells (hPAECs) exposed to vasoactive stimuli including hypoxia, TGF-b, ET-1, and IGF-1. Notch2-deficient hPAECs activated Akt, Erk1/2, and antiapoptotic protein Bcl-2 and reduced levels of p21cip and Bax associated with increased EC proliferation and reduced apoptosis. In addition, Notch2 suppression elicited a paradoxical activation of Notch1 and canonical Notch target gene Hes1, Hey1, and Hey2 transcription. Furthermore, reduction in Rb and increased E2F1 binding to the Notch1 promoter appear to explain the Notch1 upregulation. Yet, when Notch1 was decreased in Notch2-suppressed cells, the wound injury response was augmented. In aggregate, our results demonstrate that loss of Notch2 in hPAECs derepresses Notch1 and elicits EC hallmarks of PAH. Augmented EC proliferation upon Notch1 knockdown points to a context-dependent role for Notch1 and 2 in endothelial cell homeostasis. [ABSTRACT FROM AUTHOR]

Renovascular hypertension is characterized by activation of the renin-angiotensinaldosterone system, blunted natriuretic responses, and elevated sympathetic nerve activity. Excess dietary salt intake exaggerates arterial blood pressure (ABP) in multiple models of experimental hypertension. The present study tested whether a high-salt diet exaggerated ABP and vascular dysfunction in a 2-kidney, 1-clip (2K1C) murine model. Male C57BL/6J mice (8 –12 wk) were randomly assigned, and fed a 0.1% or 4.0% NaCl diet, and instrumented with telemetry units to measure ABP. Then, the 2K1C model was produced by placing a cuff around the right renal artery. Systolic, diastolic, and mean ABP were significantly higher in mice fed 4.0% vs. 0.1% NaCl at 1 wk but not after 3 wk. Interestingly, 2K1C hypertension progressively increased arterial pulse pressure in both groups; however, the magnitude was significantly greater in mice fed 4.0% vs. 0.1% NaCl at 3 wk. Moreover, pulse wave velocity was significantly greater in 2K1C mice fed 4.0% vs. 0.1% NaCl diet or sham-operated mice fed either diet. Histological assessment of aortas indicated no structural differences among groups. Finally, endothelium-dependent vasodilation was significantly and selectively attenuated in the aorta but not mesenteric arteries of 2K1C mice fed 4.0% NaCl vs. 0.1% NaCl or shamoperated control mice. The findings suggest that dietary salt loading transiently exaggerates 2K1C renovascular hypertension but promotes chronic aortic stiffness and selective aortic vascular dysfunction. [ABSTRACT FROM AUTHOR]