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Junctional membrane complexes facilitate excitation-contraction coupling in skeletal and cardiac muscle cells by forming subcellular invaginations that maintain close (≤20 nm) proximity of ryanodine receptors (RyRs) on the sarcoplasmic reticulum (SR) with voltage-dependent Ca2+ channels in the plasma membrane. In fully differentiated smooth muscle cells, junctional membrane complexes occur as distributed sites of peripheral coupling. We investigated the role of the cytoskeleton in maintaining peripheral coupling and associated Ca2+ signaling networks within native smooth muscle cells of mouse and rat cerebral arteries. Using live-cell confocal and superresolution microscopy, we found that the tight interactions between the SR and the plasma membrane in these cells relied on arching microtubule structures present at the periphery of smooth muscle cells and were independent of the actin cytoskeleton. Loss of peripheral coupling associated with microtubule depolymerization altered the spatiotemporal properties of localized Ca2+ sparks generated by the release of Ca2+ through type 2 RyRs (RyR2s) on the SR and decreased the number of sites of colocalization between RyR2s and large-conductance Ca2+-activated K+ (BK) channels. The reduced BK channel activity associated with the loss of SR-plasma membrane interactions was accompanied by increased pressure-induced constriction of cerebral resistance arteries. We conclude that microtubule structures maintain peripheral coupling in contractile smooth muscle cells, which is crucial for the regulation of contractility and cerebral vascular tone.

Objective Midlife obesity is a risk factor for dementia development. Obesity has also been linked to hyperaldosteronism, and this can be modeled in rats by high fat (HF) feeding from weaning. Aldosterone, or activation of the mineralocorticoid receptor (MR) causes cerebrovascular injury in lean hypertensive rats. We hypothesized that rats fed a HF diet would show inward middle cerebral artery (MCA) remodeling that could be prevented by MR antagonism. We further proposed that the cerebral artery remodeling would be associated with white mater injury. Methods Three-week-old male Sprague-Dawley rats were fed a HF diet ± the MR antagonist canrenoic acid (Canr) for 17 weeks. Control rats received normal chow (control NC). MCA structure was assessed by pressure myography. Results The MCAs from HF fed rats had smaller lumens and thicker walls when compared to arteries from control NC rats; Canr prevented the MCA remodeling associated with HF feeding. HF feeding increased the mRNA expression of markers of cell proliferation and vascular inflammation in cerebral arteries and Canr treatment prevented this. White mater injury was increased in the rats fed the HF diet and this was reduced by Canr treatment. The expression of doublecortin, a marker of new and immature neurons was reduced in HF fed rats, and MR antagonism normalized this. Conclusions These data suggest that HF feeding leads to MR dependent remodeling of the MCA and this is associated with markers of dementia development.

Objective Chronic hypertension induces detrimental changes in the structure and function of surface cerebral arteries. Very little is known about parenchymal arterioles (PAs), which perfuse distinct neuronal populations in the cortex and may play a role in cerebrovascular disorders. We investigated the effect of deoxycorticosterone acetate (DOCA)-salt induced hypertension on endothelial function and artery structure in PAs and middle cerebral arteries (MCAs). Methods Uninephrectomized male Sprague-Dawley rats were implanted with a subcutaneous pellet containing DOCA (150 mg/kg b.w.) and drank salt-water (1% NaCl and 0.2% KCl) for 4 weeks. Sham rats were uninephrectomized and drank tap water. Vasoreactivity and passive structure in the MCAs and the PAs were assessed by pressure myography. Results Both MCAs and PAs from DOCA-salt rats exhibited impaired endothelium dependent dilation (p

Angiotensin II type 1 receptors (AT1R) have been linked to mechanosensivity in cardiomyocytes, mainly through activation of a β2-arrestin signaling pathway. AT1Rs are also involved in sensation of intraluminal pressure by vascular smooth muscle cells. However, it is not known if the AT1R is a mechanosensor in cerebral parenchymal arterioles (PA), a highly specialized vasculature in which small alterations in myogenic reactivity can have profound effects on blood flow and neurovascular coupling. We hypothesized that AT1Rs are mechanosensors in cerebral arteries and arterioles, acting through β-arrestin signaling to cause myogenic constriction. Anterior cerebellar arteries (ACA) from C57Bl/6J mice were isolated and pressurized. Myogenic reactivity was reduced after exposure to the AT1R antagonist losartan. The biased AT1R agonist peptide TRV120023, a selective activator of the β-arrestin pathway, caused a small yet significant constriction (-5.9±2.9 μm, p

In cerebral artery myocytes, proximity of the sarcoplasmic reticulum (SR) and plasma membrane (PM) creates microdomains where Ca2+ released from the SR attains a concentration sufficient to activat...

Reactive oxygen species (ROS) can have divergent effects in cerebral and peripheral circulations. We found that Ca(2+)-permeable transient receptor potential ankyrin 1 (TRPA1) channels were present and colocalized with NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase 2 (NOX2), a major source of ROS, in the endothelium of cerebral arteries but not in other vascular beds. We recorded and characterized ROS-triggered Ca(2+) signals representing Ca(2+) influx through single TRPA1 channels, which we called "TRPA1 sparklets." TRPA1 sparklet activity was low under basal conditions but was stimulated by NOX-generated ROS. Ca(2+) entry during a single TRPA1 sparklet was twice that of a TRPV4 sparklet and ~200 times that of an L-type Ca(2+) channel sparklet. TRPA1 sparklets representing the simultaneous opening of two TRPA1 channels were more common in endothelial cells than in human embryonic kidney (HEK) 293 cells expressing TRPA1. The NOX-induced TRPA1 sparklets activated intermediate-conductance, Ca(2+)-sensitive K(+) channels, resulting in smooth muscle hyperpolarization and vasodilation. NOX-induced activation of TRPA1 sparklets and vasodilation required generation of hydrogen peroxide and lipid-peroxidizing hydroxyl radicals as intermediates. 4-Hydroxy-nonenal, a metabolite of lipid peroxidation, also increased TRPA1 sparklet frequency and dilated cerebral arteries. These data suggest that in the cerebral circulation, lipid peroxidation metabolites generated by ROS activate Ca(2+) influx through TRPA1 channels in the endothelium of cerebral arteries to cause dilation.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important mediators of signaling pathways in the endothelium. Specific members of the transient receptor potential (TRP) superfamily of cation channels act as important Ca2+ influx pathways in endothelial cells, and are involved in endothelium-dependent vasodilation, regulation of barrier permeability, and angiogenesis. ROS and RNS can modulate the activity of certain TRP channels mainly by modifying specific cysteine residues or by stimulating the production of second messengers. In this review we highlight the recent literature describing in redox regulation of TRP channel activity in endothelial cells as well as the physiological importance of these pathways and implication for cardiovascular diseases.

Hypertension impairs neurovascular coupling, possibly by altering the structure and function of cerebral penetrating arterioles (PenA). We hypothesized that an antihypertensive therapy (AhT) would ...

Background Inflammation is involved in the pathogenesis of hypertension. Hypertensive animals have an increased number of perivascular macrophages in cerebral arteries. Macrophages might be involved in remodeling of the cerebral vasculature. We hypothesized that peripheral macrophage depletion would improve MCA structure and function in hypertensive rats. Methods For macrophage depletion, six-week-old stroke-prone spontaneously hypertensive rats (SHRSP) were treated with CLOD, 10 mL/kg every three or four days, i.p., or vehicle (PBS lipo). MCA structure and function were analyzed by pressure and wire myography. Results Blood pressure was not affected by CLOD. The number of perivascular CD163-positive cells per microscopic field was reduced in the brain of SHRSP+CLOD. CLOD treatment caused an improvement in endothelium-dependent dilation after intralumenal perfusion of ADP and incubation with Ach. Inhibition of NO production blunted the Ach response, and endothelium-independent dilation was not altered. At an intralumenal pressure of 80 mmHg, MCA from SHRSP+CLOD showed increased lumen diameter, decreased wall thickness, and wall-to-lumen ratio. Cross-sectional area of pial arterioles from SHRSP+CLOD was higher than PBS lipo. Conclusions These results suggest that macrophage depletion attenuates MCA remodeling and improves MCA endothelial function in SHRSP.