Pannexin 1 (Panx1), an ATP-efflux pathway, has been linked with inflammation in pulmonary capillaries. However, the physiological roles of endothelial Panx1 in the pulmonary vasculature are unknown. Endothelial transient receptor potential vanilloid 4 (TRPV4) channels lower pulmonary artery (PA) contractility and exogenous ATP activates of endothelial TRPV4 channels. We hypothesized that endothelial Panx1-ATP-TRPV4 channel signaling promotes vasodilation and lowers pulmonary arterial pressure (PAP). Endothelial, but not smooth muscle, knockout of Panx1 increased PA contractility and raised PAP in mice. Flow/shear stress increased ATP efflux through endothelial Panx1 in PAs. Panx1-effluxed extracellular ATP signaled through purinergic P2Y2 receptor (P2Y2R) to activate protein kinase Ca (PKCa), which in turn activated endothelial TRPV4 channels. Finally, caveolin-1 provided a signaling scaffold for endothelial Panx1, P2Y2R, PKCa, and TRPV4 channels in PAs, promoting their spatial proximity and enabling signaling interactions. These results indicate that endothelial Panx1-P2Y2R-TRPV4 channel signaling, facilitated by caveolin-1, reduces PA contractility and lowers PAP in mice.

Congenital obstructive nephropathy is a major cause of chronic kidney disease in children. The contribution of changes in the identity of renal cells to the pathology of obstructive nephropathy is poorly understood. Using a partial unilateral ureteral obstruction model in genetically modified neonatal mice, we traced the fate of cells derived from the renal stroma, cap mesenchyme, ureteric bud epithelium and podocytes using Foxd1Cre, Six2Cre, HoxB7Cre and Podocyte.Cre mice respectively, crossed with double fluorescent reporter (mT/mG) mice. Persistent obstruction leads to a significant loss of tubular epithelium, rarefaction of the renal vasculature and decreased renal blood flow. In addition, Foxd1-derived pericytes significantly expanded in the interstitial space, acquiring a myofibroblast phenotype. Degeneration of Six2 and HoxB7-derived cells resulted in significant loss of glomeruli, nephron tubules and collecting ducts. Surgical release of obstruction resulted in striking regeneration of tubules, arterioles, interstitium accompanied by an increase in blood flow to the level of sham animals. Contra-lateral kidneys with remarkable compensatory response to kidney injury showed an increase in density of arteriolar branches. Deciphering the mechanisms involved in kidney repair and regeneration post relief of obstruction has potential therapeutic implications for infants and children and the growing number of adults suffering from chronic kidney disease.

Background: Ca 2+ signals in smooth muscle cells (SMCs) contribute to vascular resistance and control blood pressure. Increased vascular resistance in hypertension has been attributed to impaired SMC Ca 2+ signaling mechanisms. In this regard, transient receptor potential vanilloid 4 (TRPV4 SMC ) ion channels are a crucial Ca 2+ entry pathway in SMCs. However, their role in blood pressure regulation has not been identified. Methods: We used SMC-specific TRPV4 −/− (TRPV4 SMC −/− ) mice to assess the role of TRPV4 SMC channels in blood pressure regulation. We determined the contribution of TRPV4 SMC channels to the constrictor effect of α1 adrenergic receptor (α1AR) stimulation and elevated intraluminal pressure: 2 main physiologic stimuli that constrict resistance-sized arteries. The contribution of spatially separated TRPV4 SMC channel subpopulations to elevated blood pressure in hypertension was evaluated in angiotensin II–infused mice and patients with hypertension. Results: We provide first evidence that TRPV4 SMC channel activity elevates resting blood pressure in normal mice. α1AR stimulation activated TRPV4 SMC channels through PKCα (protein kinase Cα) signaling, which contributed significantly to vasoconstriction and blood pressure elevation. Intraluminal pressure–induced TRPV4 SMC channel activity opposed vasoconstriction through activation of Ca 2+ -sensitive K + (BK) channels, indicating functionally opposite pools of TRPV4 SMC channels. Superresolution imaging of SMCs revealed spatially separated α1AR:TRPV4 and TRPV4:BK nanodomains in SMCs. These data suggest that spatially separated α1AR–TRPV4 SMC and intraluminal pressure–TRPV4 SMC –BK channel signaling have opposite effects on blood pressure, with α1AR–TRPV4 SMC signaling dominating under resting conditions. Furthermore, in patients with hypertension and a mouse model of hypertension, constrictor α1AR–PKCα–TRPV4 signaling was upregulated, whereas dilator pressure–TRPV4–BK channel signaling was disrupted, thereby increasing vasoconstriction and elevating blood pressure. Conclusions: Our data identify novel smooth muscle Ca 2+ -signaling nanodomains that regulate blood pressure and demonstrate their impairment in hypertension.

BackgroundIn vivo imaging of oxidative stress can facilitate the understanding and treatment of cardiovascular diseases. We evaluated nitroxide‐enhanced MRI with 3‐carbamoyl‐proxyl (3CP) for the detection of myocardial oxidative stress.MethodsThree mouse models of cardiac oxidative stress were imaged, namely angiotensin II (Ang II) infusion, myocardial infarction (MI), and high‐fat high‐sucrose (HFHS) diet‐induced obesity (DIO). For the Ang II model, mice underwent MRI at baseline and after 7 days of Ang II (n = 8) or saline infusion (n = 8). For the MI model, mice underwent MRI at baseline (n = 10) and at 1 (n = 8), 4 (n = 9), and 21 (n = 8) days after MI. For the HFHS‐DIO model, mice underwent MRI at baseline (n = 20) and 18 weeks (n = 13) after diet initiation. The 3CP reduction rate, Kred, computed using a tracer kinetic model, was used as a metric of oxidative stress. Dihydroethidium (DHE) staining of tissue sections was performed on Day 1 after MI.ResultsFor the Ang II model, Kred was higher after 7 days of Ang II versus other groups (p < 0.05). For the MI model, Kred, in the infarct region was significantly elevated on Days 1 and 4 after MI (p < 0.05), whereas Kred in the noninfarcted region did not change after MI. DHE confirmed elevated oxidative stress in the infarct zone on Day 1 after MI. After 18 weeks of HFHS diet, Kred was higher in mice after diet versus baseline (p < 0.05).ConclusionsNitroxide‐enhanced MRI noninvasively quantifies tissue oxidative stress as one component of a multiparametric preclinical MRI examination. These methods may facilitate investigations of oxidative stress in cardiovascular disease and related therapies.

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