Pressure Myography Research Articles

Periadventitial β-aminopropionitrile-loaded nanofibers reduce fibrosis and improve arteriovenous fistula remodeling in rats.

Arteriovenous fistula (AVF) postoperative stenosis is a persistent healthcare problem for hemodialysis patients. We have previously demonstrated that fibrotic remodeling contributes to AVF non-maturation and lysyl oxidase (LOX) is upregulated in failed AVFs compared to matured. Herein, we developed a nanofiber scaffold for the periadventitial delivery of β-aminopropionitrile (BAPN) to determine whether unidirectional periadventitial LOX inhibition is a suitable strategy to promote adaptive AVF remodeling in a rat model of AVF remodeling. Bilayer poly (lactic acid) ([PLA)-]- poly (lactic-co-glycolic acid) ([PLGA)] scaffolds were fabricated with using a two-step electrospinning process to confer directionality. BAPN-loaded and vehicle control scaffolds were wrapped around the venous limb of a rat femoral-epigastric AVF during surgery. AVF patency and lumen diameter were followed monitored using Doppler ultrasound surveillance and flow was measured before euthanasia. AVFs were harvested after 21 days for histomorphometry and immunohistochemistry. AVF compliance was measured using pressure myography. RNA from AVF veins was sequenced to analyze changes in gene expression due to LOX inhibition. Bilayer periadventitial nanofiber scaffolds extended BAPN release compared to the monolayer design (p < 0.005) and only released BAPN in one direction. Periadventitial LOX inhibition led to significant increases in AVF dilation and flow after 21 days. Histologically, BAPN trended toward increased lumen and significantly reduced fibrosis compared to control scaffolds (p < 0.01). Periadventitial BAPN reduced downregulated markers associated with myofibroblast differentiation including SMA, FSP-1, LOX, and TGF-β while increasing the contractile marker MYH11. RNA sequencing revealed differential expression of matrisome genes. Periadventitial BAPN treatment reduces fibrosis and promotes AVF compliance. Interestingly, the inhibition of LOX leads to increased accumulation of contractile VSMC while reducing myofibroblast-like cells. Periadventitial LOX inhibition alters the matrisome to improve AVF vascular remodeling.

Vascular Smooth Muscle TRPV4 (Transient Receptor Potential Vanilloid Family Member 4) Channels Regulate Vasoconstriction and Blood Pressure in Obesity.

Vascular endothelium and smooth muscle work together to keep the balance of vasomotor tone and jointly maintain vascular homeostasis. Ca2+-permeable ion channel TRPV4 (transient receptor potential vanilloid family member 4) in endothelial cells regulates endothelium-dependent vasodilation and contraction in various states. However, how vascular smooth muscle cell TRPV4 (TRPV4SMC) contributes to vascular function and blood pressure regulation in physiological and pathologically obese condition has not been fully studied. We generated smooth muscle TRPV4-deficient mice and developed diet-induced obese mice model and analyzed the role of TRPV4SMC in intracellular Ca2+ ([Ca2+]i) regulation and vasoconstriction. Vasomotor changes of mouse mesenteric artery were measured by wire, and pressure myography. [Ca2+]i were measured by fluo-4 staining. Blood pressure was recorded by telemetric device. Vascular TRPV4SMC played different roles in regulating vasomotor tone than endothelial TRPV4 due to their different features of [Ca2+]i regulation. Loss of TRPV4SMC attenuated U46619- and phenylephrine-induced contraction, suggesting its involvement in regulating vascular contractility. Mesenteric arteries from obese mice showed SMC hyperplasia, suggesting an increased level of TRPV4SMC. Loss of TRPV4SMC did not influence the development of obesity but protected mice from obesity-induced vasoconstriction and hypertension. In arteries deficient in SMC TRPV4, SMCs F-actin polymerization and RhoA dephosphorylation were attenuated under contractile stimuli. Moreover, SMC-dependent vasoconstriction was inhibited in human resistance arteries with TRPV4 inhibitor application. Our data identify TRPV4SMC as a regulator of vascular contraction in both physiological states and pathologically obese mice. TRPV4SMC contributes to the ontogeny of vasoconstriction and hypertension induced by TRPV4SMC over-expression in obese mice mesenteric artery.

Targeting M2 Macrophages with a Novel NADPH Oxidase Inhibitor

ROS in cancer cells play a key role in pathways regulating cell death, stemness maintenance, and metabolic reprogramming, all of which have been implicated in resistance to chemo/ immunotherapy. Adjusting ROS levels to reverse the resistance of cancer cells without impairing normal cell functions is a new therapeutic avenue. In this paper, we describe new inhibitors of NADPH oxidase (NOX), a key enzyme in many cells of the tumor microenvironment. The first inhibitor, called Nanoshutter-1, NS1, decreased the level of tumor-promoting "M2" macrophages differentiated from human blood monocytes. NS1 disrupted the active NADPH oxidase-2 (NOX2) complex at the membrane and in the mitochondria of the macrophages, as shown by confocal microscopy. As one of the characteristics of tumor invasion is hypoxia, we tested whether NS1 would affect vascular reactivity by reducing ROS or NO levels in wire and pressure myograph experiments on isolated blood vessels. The results show that NS1 vasodilated blood vessels and would likely reduce hypoxia. Finally, as both NOX2 and NOX4 are key proteins in tumors and their microenvironment, we investigated whether NS1 would probe these proteins differently. Models of NOX2 and NOX4 were generated by homology modeling, showing structural differences at their C-terminal NADPH site, in particular in their last Phe. Thus, the NADPH site presents an unexploited chemical space for addressing ligand specificity, which we exploited to design a novel NOX2-specific inhibitor targeting variable NOX2 residues. With the proper smart vehicle to target specific cells of the microenvironment as TAMs, NOX2-specific inhibitors could open the way to new precision therapies.

Endothelial cell TRPA1 activity exacerbates cerebral hemorrhage during severe hypertension.

Introduction: Hypoxia-induced dilation of cerebral arteries orchestrated by Ca2+-permeable transient receptor potential ankyrin 1 (TRPA1) cation channels on endothelial cells is neuroprotective during ischemic stroke, but it is unknown if the channel has a similar impact during hemorrhagic stroke. TRPA1 channels are endogenously activated by lipid peroxide metabolites generated by reactive oxygen species (ROS). Uncontrolled hypertension, a primary risk factor for the development of hemorrhagic stroke, is associated with increased ROS production and oxidative stress. Therefore, we hypothesized that TRPA1 channel activity is increased during hemorrhagic stroke. Methods: Severe, chronic hypertension was induced in control (Trpa1 fl/fl) and endothelial cell-specific TRPA1 knockout (Trpa1-ecKO) mice using a combination of chronic angiotensin II administration, a high-salt diet, and the addition of a nitric oxide synthase inhibitor to drinking water. Blood pressure was measured in awake, freely-moving mice using surgically placed radiotelemetry transmitters. TRPA1-dependent cerebral artery dilation was evaluated with pressure myography, and expression of TRPA1 and NADPH oxidase (NOX) isoforms in arteries from both groups was determined using PCR and Western blotting techniques. In addition, ROS generation capacity was evaluated using a lucigenin assay. Histology was performed to examine intracerebral hemorrhage lesion size and location. Results: All animals became hypertensive, and a majority developed intracerebral hemorrhages or died of unknown causes. Baseline blood pressure and responses to the hypertensive stimulus did not differ between groups. Expression of TRPA1 in cerebral arteries from control mice was not altered after 28 days of treatment, but expression of three NOX isoforms and the capacity for ROS generation was increased in hypertensive animals. NOX-dependent activation of TRPA1 channels dilated cerebral arteries from hypertensive animals to a greater extent compared with controls. The number of intracerebral hemorrhage lesions in hypertensive animals did not differ between control and Trpa1-ecKO animals but were significantly smaller in Trpa1-ecKO mice. Morbidity and mortality did not differ between groups. Discussion: We conclude that endothelial cell TRPA1 channel activity increases cerebral blood flow during hypertension resulting in increased extravasation of blood during intracerebral hemorrhage events; however, this effect does not impact overall survival. Our data suggest that blocking TRPA1 channels may not be helpful for treating hypertension-associated hemorrhagic stroke in a clinical setting.

Tracking endothelium-dependent NO release in pressurized arteries.

Background: Endothelial cell (EC) dysfunction is an early hallmark of cardiovascular disease associated with the reduced bioavailability of nitric oxide (NO) resulting in over-constriction of arteries. Despite the clear need to assess NO availability, current techniques do not reliably allow this in intact arteries. Methods: Confocal fluorescence microscopy was used to compare two NO-sensitive fluorescent dyes (NO-dyes), Cu2FL2E and DAR-4M AM, in both cell-free chambers and isolated, intact arteries. Intact rat mesenteric arteries were studied using pressure myography or en face imaging to visualize vascular smooth muscle cells (SMCs) and endothelial cells (ECs) under physiological conditions. Both NO-dyes irreversibly bind NO, so the time course of accumulated fluorescence during basal, EC-agonist (ACh, 1µM), and NO donor (SNAP, 10µM) responses were assessed and compared in all experimental conditions. To avoid motion artefact, we introduced the additional step of labelling the arterial elastin with AF-633 hydrazide (AF) and calculated the fluorescence ratio (FR) of NO-dye/elastin over time to provide data as FR/FR0. Results: In cell-free chambers using either Cu2FL2E or DAR-4M AM, the addition of SNAP caused a time-dependent and significant increase in fluorescence compared to baseline. Next, using pressure myography we demonstrate that both Cu2FL2E and DAR-4M AM could be loaded into arterial cells, but found each also labelled the elastin. However, despite the use of different approaches and the clear observation of NO-dye in SMCs or ECs, we were unable to measure increases in fluorescence in response to either ACh or SNAP when cells were loaded with Cu2FL2E. We then turned our attention to DAR-4M AM and observed increases in FR/FR0 following stimulation with either ACh or SNAP. The addition of each agent evoked an accumulating, time-dependent, and statistically significant increase in fluorescence within 30min compared to time controls. These experiments were repeated in the presence of L-NAME, an NO synthase inhibitor, which blocked the increase in fluorescence on addition of ACh but not to SNAP. Conclusion: These data advance our understanding of vascular function and in the future will potentially allow us to establish whether ECs continuously release NO, even under basal conditions.

S-40-4: ANGIOTENSIN II-INDUCED BLOOD PRESSURE ELEVATION WAS POTENTIATED TOGETHER WITH INCREASES IN INTERFERON-GAMMA PRODUCING T CELLS IN INTERLEUKIN-23 RECEPTOR-DEFICIENT MICE

Objectives: We previously demonstrated a role for γδ T cells in hypertension and vascular injury. In inflammatory conditions γδT17 are a prominent producer of IL-17A, which has been shown to contribute to hypertension. The development and expansion of γδT17 cells is regulated in part through IL-23 receptors (IL-23R). We hypothesized that angiotensin (Ang) II-induced blood pressure (BP) elevation and vascular injury would be blunted in mice with dysfunctional IL-23R. Design and method: Wild-type (WT) and Il23r knock-in (Il23r gfp/gfp) mice were infused or not with Ang II (490ng/kg/min, SC) for 7 or 14 days. BP was monitored via telemetry, mesenteric artery function and remodeling using pressurized myography, and T cell profiling in mesenteric artery perivascular adipose tissue (PVAT) by flow cytometry. Results: Il23r gfp/gfp mice exhibited a greater BP elevation in response to Ang II than WT by day 3 (152 ± 5 vs 144 ± 7 mm Hg, P &lt; 0.05), which was sustained through day 9 (169 ± 2 vs 155 ± 5 mm Hg, P &lt; 0.05), but eventually similar to that of WT mice by the end of the Ang II infusion (167 ± 2 vs 167 ± 4 mm Hg). Il23r gfp/gfp mice were not protected from vascular dysfunction and remodeling after 14 days of Ang II. Il23r gfp/gfp mice had less γδT17 cells in PVAT than WT mice (40 ± 8 vs 108 ± 15 cells/PVAT, P &lt; 0.05). Ang II increased interferon-γ producing γδ T cells in WT (13 ± 3 vs 5 ± 1 cells/PVAT, P &lt; 0.05) and Il23r gfp/gfp mice (14 ± 3 vs 3 ± 1 cells/PVAT, P &lt; 0.05), and interferon-γ producing CD4+ (125 ± 27 vs 38 ± 13 cells/PVA, P &lt; 0.05) and CD8+ T cells (76 ± 13 vs 33 ± 8 cells/PVA, P &lt; 0.05) only in Il23r gfp/gfp mice. Conclusion: Functional IL-23R deficiency exaggerated BP elevation during the initiation of Ang II-induced hypertension, potentially due to the increased number of interferon-γ producing T cells.

PS-BPB04-2: P2RX7 DEFICIENCY OR P2RX7 ANTAGONISM BLUNTS ANGIOTENSIN II-INDUCED HYPERTENSION, VASCULAR INJURY AND CD8+ T CELL ACTIVATION

Objectives: Innate and adaptive immune cells contribute to hypertension and end-organ damage. High blood pressure (BP) causes cardiovascular injury and the release of damage-associated molecule patterns such as adenosine triphosphate (ATP). ATP can bind to the purinergic receptor P2X7 (P2RX7) on innate immune cells triggering interleukin-1β; release, which drives further immune activation. Elevated plasma ATP levels was observed in hypertensive patients. We hypothesized that P2rx7 knockout or P2RX7 antagonism would blunt angiotensin II (AngII)-induced BP elevation and cardiovascular injury through decreased immune activation. Design and method: Ten-to-12-week-old male C57BL/6J wild-type (WT) and P2rx7-/- mice were infused or not with AngII (1000 ng/kg/min) for 14 days. A second group of AngII-infused WT mice was also infused with the P2RX7 antagonist AZ10606120 (694 ng/kg/min) or vehicle. BP was determined by telemetry, plasma ATP using a bioluminescence assay, mesenteric artery function using pressurized myography, cardiac left ventricle (LV) function and mass by ultrasound and activated immune T cell infiltration in aortic perivascular adipose tissue (PVAT) by flow cytometry. Results: Plasma ATP was 2.2 fold higher in AngII-infused compared to sham-treated mice (P &lt; 0.05). AngII-induced systolic BP elevation was reduced by P2rx7 deficiency (12 mm Hg, P &lt; 0.05) or P2RX7 antagonism (27 mm Hg, P &lt; 0.01). AngII induced a 26% decrease in LV fractional shortening (FS, P &lt; 0.05) and a 1.5 fold increase in LV mass/body weight (BW) in WT mice (P &lt; 0.001), which were exaggerated in P2rx7-/- mice (FS: 38% lower and LVmass/BW: 1.14 fold higher, P &lt; 0.05), but not in mice receiving AZ10606120. AngII treatment caused a 26% reduction in the dilatation response of mesenteric arteries to acetylcholine in WT mice (P &lt; 0.05), but not in P2rx7-/- or AZ10606120-treated mice. AngII promoted a 3.8 fold increase in CD69+CD8+ T cell infiltration in aortic PVAT of WT mice (P &lt; 0.001), but not in P2rx7-/- or AZ10606120-treated mice. Conclusion: P2rx7 knockout or antagonism attenuates AngII-induced BP elevation, vascular injury, and infiltration of activated CD8+ T cells into aortic PVAT. P2rx7 knockout exacerbated AngII-induced cardiac dysfunction and hypertrophy, whereas P2RX7 antagonism did not.

PS-B10-7: A VASCULAR SMOOTH MUSCLE POTASSIUM CHANNEL DYSFUNCTION UNDERLIES SMALL VESSEL DISEASE OF THE BRAIN IN BOTH HYPERTENSION AND ALZHEIMER'S DISEASE

Alzheimer's disease (AD) and hypertension-related vascular dementia share many common clinical and radiological features. Indeed, at post-mortem the majority of patients diagnosed with either disorder show extensive small vessel disease (SVD) of the brain. One phenotypic character of SVD is a reduction in cerebral blood flow (CBF). The large-conductance calcium-activated potassium (BK) channel reduces arterial contractility through hyperpolarisation of the vascular smooth muscle cell membrane. The BK channel is activated via small, localised calcium release events from ryanodine receptors (RyR), known as calcium sparks. We wished to examine whether defects in calcium spark to BK channel coupling contributes to the SVD phenotype in these diseases, which could suggest new avenues for therapy based on improvement of brain vascular health. Male spontaneously hypertensive (BPH/2) mice and normotensive controls (BPN/3) were used at 8 months of age to study hypertension-induced cSVD. To study AD we used 18–20 month old male APP23 mice that have a 7-fold increased expression of amyloid precursor protein, which results in significant amyloid-beta accumulation as is seen in human AD. During this study we used a range of physiological techniques; mainly pressure myography, patch clamp electrophysiology and high-speed spinning disc confocal microscopy, to investigate in depth, vascular ion channel function within the cerebral microvasculature of these mice. Pressure-induced constriction from cerebral pial arteries was significantly greater in both the BPH/2 and APP23 animals compared to controls. Pressure myography studies revealed that in both models there was a reduction in BK channel activity. This was confirmed with electrophysiology data that showed a decrease in spontaneous transient outward currents, which represent BK channel openings in response to calcium sparks. In the APP23 model, this reduction in BK channel function was due to a decrease in calcium spark frequency. However in the BPH/2 mice, spark frequency was equal between hypertensive individuals and controls. In this model separation of the BK channel and RyR resulted in BK channel dysfunction. Overall our data indicates that vascular BK channel dysfunction is a common mechanism underpinning reduced CBF in SVD. Therefore, therapies aimed at improving vascular BK channel function could provide new therapeutic targets for the treatment of both AD and hypertension-induced vascular dementia.

Extracellular vesicles and insulin-mediated vascular function in metabolic syndrome.

Metabolic Syndrome (MetS) raises cardiovascular disease risk. Extracellular vesicles (EVs) have emerged as important mediators of insulin sensitivity, although few studies on vascular function exist in humans. We determined the effect of insulin on EVs in relation to vascular function. Adults with MetS (n=51, n=9M, 54.8 ± 1.0 years, 36.4 ± 0.7kg/m2 , ATPIII: 3.5 ± 0.1a.u., VO2 max: 22.1 ± 0.6ml/kg/min) were enrolled in this cross-sectional study. Peripheral insulin sensitivity (M-value) was determined during a euglycemic clamp (40 mU/m2 /min, 90 mg/dl), and blood was collected for EVs (CD105+, CD45+, CD41+, TX+, and CD31+; spectral flow cytometry), inflammation, insulin, and substrates. Central hemodynamics (applanation tonometry) was determined at 0 and 120 min via aortic waveforms. Pressure myography was used to assess insulin-induced arterial vasodilation from mouse 3rd order mesenteric arteries (100-200 μm in diameter) at 0.2, 2 and 20 nM of insulin with EVs from healthy and MetS adults. Adults with MetS had low peripheral insulin sensitivity (2.6 ± 0.2 mg/kg/min) and high HOMA-IR (4.7 ± 0.4 a.u.) plus Adipose-IR (13.0 ± 1.3 a.u.). Insulin decreased total/particle counts (p < 0.001), CD45+ EVs (p=0.002), AIx75 (p=0.005) and Pb (p=0.04), FFA (p < 0.001), total adiponectin (p=0.006), ICAM (p=0.002), and VCAM (p=0.03). Higher M-value related to lower fasted total EVs (r=-0.40, p=0.004) while higher Adipose-IR associated with higher fasted EVs (r=0.42, p=0.004) independent of VAT. Fasting CD105+ and CD45+ derived total EVs correlated with fasting AIx75 (r=0.29, p < 0.05) and Pb (r=0.30, p < 0.05). EVs from MetS participants blunted insulin-induced vasodilation in mesenteric arteries compared with increases from healthy controls across insulin doses (all p < 0.005). These data highlight EVs as potentially novel mediators of vascular insulin sensitivity and disease risk.

PS-B10-6: CAPILLARY-TO-ARTERIOLAR SIGNALLING, INFLAMMATION AND SMALL VESSEL DISEASE OF THE BRAIN

Objective: Chronic cerebral inflammation is thought to be a mechanism by which hypertension causes small vessel disease of the brain, leading to dementia. Mouse studies have demonstrated enhanced small resistance artery constriction and neurovascular uncoupling in hypertension. We wished to examine whether acute exposure to the predominant inflammatory driver in hypertension, interleukin-1β; (IL-1β;) could account for this dual vascular deficit. Design and method: Pressure myography of freshly isolated mouse posterior cerebellar pial arteries was used to assess contributions of the inwardly rectifying K+ 2.1 (KIR2.1) channel to vasodilation. In order to assess neurovascular coupling from a vascular perspective, we adopted a recently described approach: the Capillary to Parenchymal Arteriole (CaPA) preparation. In the CaPA preparation, penetrating arterioles (&lt; 40ums) with attached capillary branches are isolated and pressurised. The capillary branch and arteriole are independently stimulated via a micropipette and arteriole diameter is recorded. This approach enables the retrograde hyperpolarising signal from the KIR2.1 channel, which propagates against the flow of blood in the brain, to be assessed both in terms of the extent of arteriole vasodilation and the speed of communication (video). In order to assess the effects of perivascular inflammation on cerebrovascular function, we incubated (in culture medium) small pial arteries with IL-1β; for 24 hours prior to study on a pressure myograph rig. KIR2.1 function was assessed using 10 mM exogenous K+. Cerebral arterioles with attached capillaries were incubated with IL-1β; for 2 hours prior to CaPA study. We then examined the capillary-to-arteriolar signalling mechanism via application of 10 mM K+ to the capillary. We also assessed arteriolar tone and reaction to directly applied K+, NS309 and U46619. Results: Preliminary data suggests that sub-acute incubation with exogenous IL-1β; had no effects on the degree of pressure induced constriction of either the pial artery or the arteriole. CaPA preparation showed that the KIR2.1 capillary-to-arteriolar signalling was preserved as well as arteriolar responses to direct K+, NS309 and U46619 following IL-1β; exposure. Conclusions: Whilst chronic cerebral inflammation in the setting of hypertension results in cerebrovascular deficits, sub-acute exposure with IL-1β; does not appear to significantly impair cerebral microvascular function. Precisely how chronic exposure to inflammation in hypertension induces neurovascular uncoupling is the subject of ongoing investigation.

The Synthetic Flavonoid Hidrosmin Improves Endothelial Dysfunction and Atherosclerotic Lesions in Diabetic Mice.

In diabetes, chronic hyperglycemia, dyslipidemia, inflammation and oxidative stress contribute to the progression of macro/microvascular complications. Recently, benefits of the use of flavonoids in these conditions have been established. This study investigates, in two different mouse models of diabetes, the vasculoprotective effects of the synthetic flavonoid hidrosmin on endothelial dysfunction and atherogenesis. In a type 2 diabetes model of leptin-receptor-deficient (db/db) mice, orally administered hidrosmin (600 mg/kg/day) for 16 weeks markedly improved vascular function in aorta and mesenteric arteries without affecting vascular structural properties, as assessed by wire and pressure myography. In streptozotocin-induced type 1 diabetic apolipoprotein E-deficient mice, hidrosmin treatment for 7 weeks reduced atherosclerotic plaque size and lipid content; increased markers of plaque stability; and decreased markers of inflammation, senescence and oxidative stress in aorta. Hidrosmin showed cardiovascular safety, as neither functional nor structural abnormalities were noted in diabetic hearts. Ex vivo, hidrosmin induced vascular relaxation that was blocked by nitric oxide synthase (NOS) inhibition. In vitro, hidrosmin stimulated endothelial NOS activity and NO production and downregulated hyperglycemia-induced inflammatory and oxidant genes in vascular smooth muscle cells. Our results highlight hidrosmin as a potential add-on therapy in the treatment of macrovascular complications of diabetes.

Neurovascular Uncoupling in TgF344‐AD Rats is Associated with Reduced Cerebral Capillary Endothelial Kir2.1 Expression

AbstractBackgroundAlzheimer’s disease (AD) is an emerging global health care crisis. Although reduced cerebral blood flow (CBF) is an early and persistent symptom in developing cognitive deficits, the underlying molecular and cellular mechanisms remain unclear. Recent studies suggested that restoration of capillary endothelial cells (ECs) inward‐rectifier potassium channels (Kir2.1) currents reversed cerebral hypoperfusion and enhanced neurovascular coupling in AD mice. The present study aims to investigate whether capillary ECs Kir2.1 expression is reduced in TgF344‐AD rats and whether it contributes to neurovascular uncoupling and cognitive deficits.MethodThree to six months old TgF‐344 AD rats expressing mutant human APP and PS1 and their age‐matched wildtype (WT) rats were studied. An eight‐arm water maze was used to test spatial learning and short and long‐term memory. Brain perfusion was mapped with a laser speckle imaging system. Whisker stimulation‐induced functional hyperemia was measured using laser Doppler flowmetry in vivo. Brain Kir2.1 expression was compared using western blot. Cerebral parenchymal arterioles (PAs) with attached capillaries were freshly isolated from AD and WT rats and mounted in a pressure myography. PAs response to capillaries focally injected KCL (10 mM) and Kir2.1 inhibitor (ML133) was compared.ResultAD rats exhibited learning and memory dysfunction at 6‐month of age compared with WT controls. However, cerebral hypoperfusion was observed in AD rats starting from 4‐month of age. Similarly, impaired functional hyperemia in AD rats started at 4‐month of age, which was exacerbated in 6‐month old AD rats. The expression of Kir2.1 in 6‐month AD brain tissue was significantly lower than in WT rats. AD PAs displayed less vasodilation (110.96 ± 3.92 % vs. 122.93 ± 1.97 %) and vasoconstriction (92.16 ± 3.47 % vs. 78.04 ± 2.96 %) in response to capillary administered KCL and ML133, respectively, compared to WT vessels.ConclusionReduced brain hypoperfusion precedes cognitive impairment in AD rats, associated with attenuated capillary EC Kir2.1 expression and neurovascular uncoupling.

Psychosocial Stress‐Accelerates Alzheimer’s Disease Progression via the Xanthine Oxidase Pathway

AbstractBackgroundVascular contributions to cognitive impairment and dementia are a key pathology associated with Alzheimer’s disease (AD). We have shown that chronic stress induces cerebrovascular dysfunction due to a pro‐oxidative environment, a phenotype similar to that noted with AD. Epidemiological studies also suggest a link between chronic stress and dementia. We tested the hypothesis that chronic stress accelerates the AD pathology via the xanthine oxidase (XO) pathway.MethodsWild type (WT) and Triple transgenic (AD) mice were separated into 1) WT control, 2) WT+UCMS, 3) AD control, 4) AD control+Feb, 5) AD+UCMS, 6) AD+UCMS+Feb. At 4 months‐of‐age, dependent upon group, the unpredicted chronic mild stress (UCMS) model with or without Febuxostat (Feb) treated water (50mg/L) began for 8 weeks. Mice were either euthanized at 6 or 9 months‐of‐age. The middle cerebral artery (MCA) was removed for pressure myography. Brains were homogenized to extract soluble and insoluble fractions of tau proteins using Western blot normalized to GAPDH or B‐actin.ResultsAt 6 months‐of‐age, AD mice displayed a 72% impaired MCA dilation to acetylcholine compared to WT control mice (p&lt;0.05). WT and AD mice that underwent UCMS displayed similar MCA dysfunction compared to AD control mice. UCMS accelerated total and phosphorylated tau protein expression by 83% (p&lt;0.05) and 350% (p&lt;0.001), respectively, compared to AD controls. Treatment with Feb prevented MCA dysfunction in AD control mice, WT UCMS mice, and AD UCMS mice. Feb prevented the increased expression of phosphorylated tau and lowered the total tau protein expression in the AD‐UCMS group. However, total tau protein expression remained higher compared to AD control levels. At 9 months‐of‐age, the majority of these trends persisted with the one exception being a significant impairment in the AD UCMS group compared to both AD control or WT UCMS mice. Tau levels have yet to be processed for 9‐months.ConclusionOverall, these data suggest that chronic stress accelerates cerebrovascular pathology with AD and via a pro‐oxidative state driven by activation of the XO pathway. We will further explore Aβ1‐42 and XO in 3xTg brain homogenates at 6 and 9 months‐of‐age, to better understand how stress accelerates AD pathology.

Increased Ca2+-dependent intrinsic tone and arterial stiffness in mesenteric microvessels of hypertensive pregnant rats

Preeclampsia is a pregnancy-related hypertensive disorder (HTN-Preg) with unclear mechanisms. We have shown increased vascular reactivity to extrinsic vasoconstrictors in HTN-Preg rats. Here, we test whether microvascular intrinsic tone and arterial stiffness could contribute to HTN-Preg, and examined the underlying cellular mechanisms. On gestational day 19, BP was recorded in normal pregnant (Preg) rats and Preg rats with reduced uterine perfusion pressure (RUPP), and mesenteric microvessels were mounted on a pressure myograph for measurement of intrinsic tone, simultaneous changes in [Ca2+]i (fura-2 340/380 ratio), and arterial stiffness. Arteries were incubated in Ca2+-containing and 0 Ca2+ (2 mM EGTA) Krebs, pressurized at 10 to 110 mmHg in 10 mmHg increments, and the % change in vessel diameter from initial diameter at 10 mmHg was analyzed for measurement of total (active + passive) intrinsic tone and passive intrinsic response, respectively. The passive response was then subtracted from the total intrinsic tone to determine the active myogenic tone. The strain–stress relationship was also constructed as a measure of arterial stiffness. BP was higher in RUPP vs Preg rats. In Ca2+-containing Krebs, increases in intraluminal pressure caused smaller increases in diameter and greater increases in [Ca2+]i in microvessels of RUPP vs Preg rats, suggesting increased Ca2+-dependent myogenic tone. In 0 Ca2+ Krebs, increases in pressure also caused less increases in diameter in microvessels of RUPP vs Preg rats, but with no changes in [Ca2+]i, suggesting changes in the structure and mechanics of the arterial wall. The total and passive strain–stress relationship was shifted to the left in microvessels of RUPP vs Preg rats, suggesting increased arterial wall stiffness. Histology and immunohistochemistry showed greater vascular wall thickness and collagen-I staining in RUPP vs Preg rats, supporting changes in the wall architecture and structural proteins. The increased active myogenic tone and underlying increases in Ca2+ signaling as well as the increased passive intrinsic response, arterial stiffness and collagen-I in the mesenteric microvessels could play a role in the regulation of blood flow to the splanchnic region and the increased vascular resistance and BP in HTN-Preg.

Disrupting circadian control of peripheral myogenic reactivity mitigates cardiac injury following myocardial infarction.

Circadian rhythms orchestrate important functions in the cardiovascular system: the contribution of microvascular rhythms to cardiovascular disease progression/severity is unknown. This study hypothesized that (i) myogenic reactivity in skeletal muscle resistance arteries is rhythmic and (ii) disrupting this rhythmicity would alter cardiac injury post-myocardial infarction (MI). Cremaster skeletal muscle resistance arteries were isolated and assessed using standard pressure myography. Circadian rhythmicity was globally disrupted with the ClockΔ19/Δ19 mutation or discretely through smooth muscle cell-specific Bmal1 deletion (Sm-Bmal1 KO). Cardiac structure and function were determined by echocardiographic, hemodynamic and histological assessments. Myogenic reactivity in cremaster muscle resistance arteries is rhythmic. This rhythm is putatively mediated by the circadian modulation of a mechanosensitive signalosome incorporating tumour necrosis factor and casein kinase 1. Following left anterior descending coronary artery ligation, myogenic responsiveness is locked at the circadian maximum, although circadian molecular clock gene expression cycles normally. Disrupting the molecular clock abolishes myogenic rhythmicity: myogenic tone is suspended at the circadian minimum and is no longer augmented by MI. The reduced myogenic tone in ClockΔ19/Δ19 mice and Sm-Bmal1 KO mice associates with reduced total peripheral resistance (TPR), improved cardiac function and reduced infarct expansion post-MI. Augmented microvascular constriction aggravates cardiac injury post-MI. Following MI, skeletal muscle resistance artery myogenic reactivity increases specifically within the rest phase, when TPR would normally decline. Disrupting the circadian clock interrupts the MI-induced augmentation in myogenic reactivity: therapeutics targeting the molecular clock, therefore, may be useful for improving MI outcomes.

Spatiotemporal Control of Vascular CaV1.2 by α1C S1928 Phosphorylation.

L-type CaV1.2 channels undergo cooperative gating to regulate cell function, although mechanisms are unclear. This study tests the hypothesis that phosphorylation of the CaV1.2 pore-forming subunit α1C at S1928 mediates vascular CaV1.2 cooperativity during diabetic hyperglycemia. A multiscale approach including patch-clamp electrophysiology, super-resolution nanoscopy, proximity ligation assay, calcium imaging' pressure myography, and Laser Speckle imaging was implemented to examine CaV1.2 cooperativity, α1C clustering, myogenic tone, and blood flow in human and mouse arterial myocytes/vessels. CaV1.2 activity and cooperative gating increase in arterial myocytes from patients with type 2 diabetes and type 1 diabetic mice, and in wild-type mouse arterial myocytes after elevating extracellular glucose. These changes were prevented in wild-type cells pre-exposed to a PKA inhibitor or cells from knock-in S1928A but not S1700A mice. In addition, α1C clustering at the surface membrane of wild-type, but not wild-type cells pre-exposed to PKA or P2Y11 inhibitors and S1928A arterial myocytes, was elevated upon hyperglycemia and diabetes. CaV1.2 spatial and gating remodeling correlated with enhanced arterial myocyte Ca2+ influx and contractility and in vivo reduction in arterial diameter and blood flow upon hyperglycemia and diabetes in wild-type but not S1928A cells/mice. These results suggest that PKA-dependent S1928 phosphorylation promotes the spatial reorganization of vascular α1C into "superclusters" upon hyperglycemia and diabetes. This triggers CaV1.2 activity and cooperativity, directly impacting vascular reactivity. The results may lay the foundation for developing therapeutics to correct CaV1.2 and arterial function during diabetic hyperglycemia.

Abstract 11524: Maternal Vaping Impacts on Cerebrovascular Function in Offspring

Electronic cigarettes (E-cigs) are marketed as a safer alternative to smoking even during pregnancy, but health effects of vaping are still largely unknown and under investigation. Emerging studies find cerebrovascular dysfunction in offspring with in-utero E-cig exposure, but little is known what the effect of E-cig device wattage has. We hypothesize maternal vaping at 30 watts will have a greater effect (compared to 5-watts) on cerebrovascular dysfunction in offspring. Female Sprague Dawley rats were time-mated, and the dams were randomly assigned to the following groups 1) 5-watts (N=5), 2) 30-watts (N=5), 3) and ambient air (control, N=5). Exposure was 60-puffs/day (5 days/week) beginning on gestational day (GD) 2-3 until GD21 using whole-body chambers. E-liquid was 50% vegetable glycerin, and 50% propylene glycol containing no nicotine and no flavor. One male &amp; female offspring per dam are reported at 1- and 6-months of age, where the middle cerebral artery (MCA) was isolated and reactivity assessed using dose-response (10 -9 M to 10 -4 M) to acetylcholine (ACh), serotonin (5-HT), and sodium nitroprusside (SNP) via pressure myography. 1-month offspring, maximal MCA dilation to ACh was impaired in both 5- and 30-watts compared to air (33±3%, 50±3%, respectively, p&lt;0.05). SNP-induced dilation (20±6%, 39±4%, respectively, p&lt;0.05) and 5-HT vasoconstriction (37±3%, 47±3%, respectively, p&lt;0.05) were blunted in both groups compared to controls. Compared to air, the 6-month offspring showed similar impairments in 5- and 30-watt groups (27±3% and 45±2%, respectively, p&lt;0.05). Likewise, SNP dilation (12±3% and 23±6%, p&lt;0.05) and 5-HT constriction (21±3% and 36±3%, p&lt;0.05) were impaired in 5- and 30-watt groups, respectively, compared to controls. For all conditions, 30-watt MCA impairment was significantly greater than 5-watts in 1 and 6-month offspring (p&lt;0.05). These data show (regardless of the E-cig device wattage used) that maternal vaping during pregnancy results in cerebrovascular impairment involving endothelial-dependent and -independent pathways in adolescent and adult offspring, but also shows that the magnitude of impairment is greater with maternal vaping at higher compared to lower wattage.

Abstract 15318: Global Deletion of P90 Ribosomal S6 Kinase Provides Cardiovascular Protection Against Age-Related Hypertension

Background: Hypertension (HT) is highly prevalent and associated with significant mortality and morbidity among older individuals. Aging is associated with structural and functional remodeling of the vasculature, similar to blood vessel alterations observed in HT. We previously demonstrated that young adult global Rsk2 KO mice had more dilated mesenteric arteries (MAs), with reduced vessel tone, stiffness and RLC 20 phosphorylation, and significantly lower basal blood pressure compared to WT. However, it is unknown whether RSK2 plays a role in age-related HT. Hypothesis: Loss of RSK2 signaling in aged mice inhibits age-related- and L-NAME-induced HT, arterial stiffness, and vascular remodeling. Methods: Systolic blood pressure (SBP) measurements of &gt;24-month-old global Rsk2 KO and WT males were performed daily for 2 weeks after 2 weeks of daily training using tail cuff manometry. Baseline echocardiographic (echo) parameters were measured. N(G)-Nitro-L-arginine-methyl ester (L-NAME) was administered (20 mg/kg/day) via drinking water to induce HT. Pressure myography studies assessed vascular reactivity and arterial stiffness in MAs isolated from Rsk2 KO and WT mice. Aorta and MAs were sectioned and stained to examine structural changes. Results: WT mice had a significantly higher mortality rate (63.6%) compared to Rsk2 KO (12.5%). Baseline SBP was also significantly higher in WT compared to KOs (123±10 vs. 99±12 mmHg, p &lt; 0.001, n = 9/7). L-NAME elevated SBP in WT but not in KO mice (137±2 vs. 97±8 mmHg, p &lt; 0.00001, n = 4/7). Although there were no differences in echo parameters, we observed a negative correlation between ejection fraction (EF) and SBP in WT (-0.94 %/mmHg, p = 0.046, R 2 = 0.59, n = 6), but not in Rsk2 KO mice (p = 0.15, n = 7). Functional and histological studies in aged KO mice are ongoing to examine age-related changes in vascular reactivity and remodeling. Conclusion: Loss of RSK2 reduces BP levels in aged mice akin to young adult mice. Additionally, the hypertensive effects of L-NAME are absent in aged Rsk2 KO mice. Aged Rsk2 KO mice appear to be protected from cardiovascular effects associated with age-related HT. Therapeutic targeting of RSK2 could prove beneficial for reducing risk of cardiovascular diseases associated with HT in the elderly.

Abstract 15590: Smooth Muscle Specific Deletion of P90 Ribosomal S6 Kinase Alters the Vasomotor Response of Resistance Arteries

Background: Smooth muscle (SM) contraction is triggered by Ca 2+ /calmodulin-dependent myosin light chain kinase (MLCK), which phosphorylates the regulatory light chain of myosin (RLC 20 ). However, additional regulatory mechanisms exist. We found that global Rsk2 KO mice had more dilated mesenteric arteries (MAs) with reduced myogenic tone and RLC 20 phosphorylation, and significantly lower blood pressure. Furthermore, RSK2-dependent activation of the Na + /H + exchanger resulted in an increase in pH i and increased Ca 2+ i transients. However, it is unclear whether our observations were due to developmental abnormalities observed in Rsk2 global KO mice. Hypothesis: RSK2 signaling in SM is a significant regulator of myogenic tone, arterial stiffness, and Ca 2+ signaling. Methods: To study the role of RSK2 signaling in vascular tone, we generated inducible SM-specific RSK2 KO mice. Detection of total and phospho proteins were determined by western blot. Pressure myography studies assessed vascular reactivity in 4 th - and 5 th -order MAs isolated from MYH11-Cre + Rsk2 fl/fl (RSK2 SM -/- ) and MYH11-Cre - Rsk2 fl/fl (RSK2 SM +/+ ) mice. We examined SM-specific Ca 2+ events in pressurized MAs by confocal fluorescent microscopy. Results: Western blot confirms knock down of RSK2 expression (~70%) in MAs and aorta. Intraluminal pressure-induced constriction of MAs is attenuated in RSK2 SM -/- . RSK2 SM -/- MAs display a delay in development of myogenic tone at 40 mmHg and decreased vascular stiffness, compared to RSK2 SM +/+ . Vasodilatory responses to Spermine NONOate (1-100 μM) in preconstricted (L-NNA; 10 μM) RSK2 SM -/- vessels were enhanced. RSK2 SM -/- MAs display fewer Ca 2+ events (97±19.6; n = 4) than RSK2 SM +/+ (400±24.5; n = 4) at 80 mmHg ( p = 0.0001). Additionally, Ca 2+ events are slower and longer-lasting in the RSK2 SM -/- . Decreased levels of p-RLC 20 are observed at 40 mmHg, but not 80 mmHg in RSK2 SM -/- vs. RSK2 SM +/+ mice, consistent with impeding tone development. Conclusion: RSK2 signaling contributes to myogenic tone and vessel stiffness by regulating sensitivity to NO, increasing Ca 2+ events, and RLC 20 activity. RSK2 signaling pathway is a potential therapeutic target for hypertension.

Cell contractility and Focal Adhesion Kinase control circumferential arterial stiffness.

Arterial stiffening is a hallmark of aging and cardiovascular disease. While it is well established that vascular smooth muscle cells (SMCs) contribute to arterial stiffness by synthesizing and remodeling the arterial extracellular matrix, the direct contributions of SMC contractility and mechanosensors to arterial stiffness, and particularly the arterial response to pressure, remain less well understood despite being a long-standing question of biomedical importance. Here, we have examined this issue by combining use of pressure myography of intact carotid arteries, pharmacologic inhibition of contractility, and genetic deletion of SMC focal adhesion kinase (FAK). Biaxial inflation-extension tests performed at physiological pressures showed that acute inhibition of cell contractility with blebbistatin or EGTA altered vessel geometry and preferentially reduced circumferential, as opposed to axial, arterial stiffness in wild-type mice. Similarly, genetic deletion of SMC FAK, which attenuated arterial contraction to KCl, reduced vessel wall thickness and circumferential arterial stiffness in response to pressure while having minimal effect on axial mechanics. Moreover, these effects of FAK deletion were lost by treating arteries with blebbistatin or by inhibiting myosln light chain kinase. The expression of arterial fibrillar collagens, the integrity of arterial elastin, or markers of SMC differentiation were not affected by deletion of SMC FAK. Our results connect cell contractility and SMC FAK to the regulation of arterial wall thickness and directionally-specific arterial stiffening.