Injury Length and Arteriole Constriction Shape Clot Growth and Blood-Flow Acceleration in a Mouse Model of Thrombosis.Arteriosclerosis, Thrombosis, and... Sep 2020Quantitative relationships between the extent of injury and thrombus formation in vivo are not well understood. Moreover, it has not been investigated how increased...
Quantitative relationships between the extent of injury and thrombus formation in vivo are not well understood. Moreover, it has not been investigated how increased injury severity translates to blood-flow modulation. Here, we investigated interconnections between injury length, clot growth, and blood flow in a mouse model of laser-induced thrombosis. Approach and Results: Using intravital microscopy, we analyzed 59 clotting events collected from the cremaster arteriole of 14 adult mice. We regarded injury length as a measure of injury severity. The injury caused transient constriction upstream and downstream of the injury site resulting in a 50% reduction in arteriole diameter. The amount of platelet accumulation and fibrin formation did not depend on arteriole diameter or deformation but displayed an exponentially increasing dependence on injury length. The height of the platelet clot depended linearly on injury length and the arteriole diameter. Upstream arteriolar constriction correlated with delayed upstream velocity increase, which, in turn, determined downstream velocity. Before clot formation, flow velocity positively correlated with the arteriole diameter. After the onset of thrombus growth, flow velocity at the injury site negatively correlated with the arteriole diameter and with the size of the above-clot lumen.
Injury severity increased platelet accumulation and fibrin formation in a persistently steep fashion and, together with arteriole diameter, defined clot height. Arterial constriction and clot formation were characterized by a dynamic change in the blood flow, associated with increased flow velocity.
Topics: Abdominal Muscles; Animals; Arterioles; Blood Coagulation; Blood Flow Velocity; Blood Platelets; Constriction, Pathologic; Disease Models, Animal; Fibrin; Intravital Microscopy; Male; Mice; Microscopy, Fluorescence; Severity of Illness Index; Thrombosis; Time Factors; Vascular System Injuries
IUBMB Life Oct 2019Vascular smooth muscle cells of the renal afferent arteriole are unusual in that they must be able to contract very rapidly in response to a sudden increase in systemic...
Vascular smooth muscle cells of the renal afferent arteriole are unusual in that they must be able to contract very rapidly in response to a sudden increase in systemic blood pressure in order to protect the downstream glomerular capillaries from catastrophic damage. We showed that this could be accounted for, in part, by exclusive expression, at the protein level, of the "fast" (B) isoforms of smooth muscle myosin II heavy chains in the afferent arteriole, in contrast to other vascular smooth muscle cells such as the rat aorta and efferent arteriole which express exclusively the "slow" (A) isoforms (Shiraishi et al. (2003) FASEB. J. 17, 2284-2286). As contraction of the more rapidly contracting striated (skeletal and cardiac) muscles is regulated by the thin filament-associated troponin (Tn) system, we hypothesized that Tn or a Tn-like system may exist in afferent arteriolar cells and contribute to the unusually rapid contraction of this tissue in response to increased intraluminal pressure. We examined the expression of TnC (Ca -binding subunit), TnI (inhibitory subunit), and TnT (tropomyosin-binding subunit) in vascular smooth muscle cells of the rat renal afferent arteriole at the mRNA level. Fast-twitch skeletal muscle and slow-twitch skeletal muscle/cardiac TnC isoforms and slow-twitch skeletal muscle and cardiac TnI isoforms were detected by reverse transcription-polymerase chain reaction (RT-PCR) and confirmed by cDNA sequencing. Furthermore, cardiac and slow-twitch skeletal muscle TnI isoforms, but not fast-twitch skeletal muscle TnI, were detected in isolated afferent arterioles at the protein level by proximity ligation assay. Finally, striated muscle myosin II heavy chain expression was identified in isolated rat afferent arterioles by RT-PCR. We conclude that, in addition to Ca -mediated phosphorylation of myosin II regulatory light chains, contraction of the afferent arteriole may be regulated by a mechanism normally associated with the much more rapidly contracting cardiac and skeletal muscles, which involves Ca binding to TnC, leading to alleviation of inhibition of the actomyosin MgATPase by TnI and tropomyosin and rapid contraction of the vessel.
Topics: Actin Cytoskeleton; Adenosine Triphosphatases; Animals; Arterioles; Calcium; Gene Expression Regulation; Humans; Kidney; Muscle Contraction; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Myosin Type II; Phosphorylation; Protein Isoforms; Rats; Tropomyosin; Troponin
Biology of Sex Differences Jan 2019The pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of...
The pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of hypertension. ET-1 participates in blood pressure regulation through activation of endothelin A (ET) and endothelin B (ET) receptors including those in the vasculature. Previous studies demonstrated that sex and sex hormones evoke discrepancies in ET-1-mediated control of vascular tone in different vascular beds. However, little is known about sex- and sex hormone-related differences in ET-1-dependent renal microvascular reactivity. Accordingly, we hypothesized that loss of sex hormones impairs afferent arteriole reactivity to ET-1.
Male and female Sprague Dawley rats were subjected to gonadectomy or sham surgery (n = 6/group). After 3 weeks, kidneys from those rats were prepared for assessment of renal microvascular responses to ET-1 (ET and ET agonist, 10 to 10 M) and sarafotoxin 6c (S6c, ET agonist, 10 to 10 M) using the blood-perfused juxtamedullary nephron preparation.
Control afferent arteriole diameters at 100 mmHg were similar between sham male and female rats averaging 14.6 ± 0.3 and 15.3 ± 0.3 μm, respectively. Gonadectomy had no significant effect on control arteriole diameter. In sham males, ET-1 produced significant concentration-dependent decreases in afferent arteriole diameter, with 10 M ET-1 decreasing diameter by 84 ± 1%. ET-1 induced similar concentration-dependent vasoconstrictor responses in sham female rats, with 10 M ET-1 decreasing the diameter by 82 ± 1%. The afferent arteriolar vasoconstrictor responses to ET-1 were unchanged by ovariectomy or orchiectomy. Selective ET receptor activation by S6c induced a concentration-dependent decline in afferent arteriole diameter, with 10 M S6c decreasing diameter by 77 ± 3 and 76 ± 3% in sham male and female rats, respectively. Notably, ovariectomy augmented the vasoconstrictor response to S6c (10 to 10 M), whereas orchiectomy had no significant impact on the responsiveness to ET receptor activation.
These data demonstrate that sex does not significantly influence afferent arteriole reactivity to ET receptor activation. Gonadectomy potentiated the responsiveness of the afferent arteriole to ET-induced vasoconstriction in females, but not males, suggesting that female sex hormones influence ET-mediated vasoconstriction in the renal microcirculation.
Topics: Animals; Arterioles; Castration; Endothelin-1; Female; Male; Microcirculation; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Sex Characteristics; Vasoconstriction; Vasoconstrictor Agents; Viper Venoms
Correlation between Arteriole Membrane Potential and Cerebral Vasospasm after Subarachnoid Hemorrhage in Rats.Neurology IndiaMicrovessel constriction plays an important role in delayed cerebral ischemia after aneurismal subarachnoid hemorrhage (SAH). This constriction has been demonstrated in...
Microvessel constriction plays an important role in delayed cerebral ischemia after aneurismal subarachnoid hemorrhage (SAH). This constriction has been demonstrated in both animal model and clinical operation. The present study examined the time-related membrane potential (Em) alteration of arterioles isolated from SAH model rats and the correlation between the potential alteration of arterioles and the diameter of basilar artery.
MATERIALS AND METHODS
Sprague-Dawley rats (n = 90), weighing 300 g to 350 g, were divided into t control, sham, and SAH groups. In the SAH group, blood was injected into the prechiasmatic cistern of the rats. The Em of arterioles and basilar artery diameter was measured using whole-cell clamp recordings and pressure myograph, respectively, 1, 3, 5, 7, and 14 days after SAH. The correlation was evaluated using Pearson correlation coefficients.
The Em of arterioles in the SAH group depolarized on days 3, 5, and 7, and peaked on day 7. The diameters significantly decreased on days 1, 3, 5, 7, and 14, and the smallest diameter was observed on day 7. A significant correlation between potential alteration of arterioles and diameter of basilar artery was found.
Similar to the artery, arteriole constriction is also involved in the pathophysiological events of delayed cerebral ischemia.
Topics: Animals; Arterioles; Basilar Artery; Disease Models, Animal; Membrane Potentials; Muscle, Smooth, Vascular; Patch-Clamp Techniques; Rats; Subarachnoid Hemorrhage; Vasospasm, Intracranial
Aortic stiffness is associated with changes in retinal arteriole flow pulsatility mediated by local vasodilation in healthy young/middle-age adults.Journal of Applied Physiology... Jul 2020Aortic stiffness is associated with augmented pressure pulsatility in large conduit arteries and remodeling of the microcirculation. However, studies in humans examining...
Aortic stiffness is associated with augmented pressure pulsatility in large conduit arteries and remodeling of the microcirculation. However, studies in humans examining the relation between aortic stiffness and end-organ microvascular flow pulsatility are limited. Therefore, we used the retinal microvasculature as an end-organ in vivo model to examine the hypothesis that aortic stiffness would be positively associated with microvascular flow pulsatility index (PI) (flow pulse amplitude/mean flow) in humans. In 40 young/middle-age healthy adults (25-60 yr old, 50% women), aortic stiffness (carotid-femoral pulse wave velocity, CFPWV) and retinal arteriole flow (laser speckle flowgraphy) were examined at rest and during metabolic vasodilation (light flicker). CFPWV and related increases in central pulse pressure (PP) were inversely correlated with arteriole lumen diameter independent of age (CFPWV: = -0.52, = 0.001; Central PP: = -0.39, = 0.014). Accordingly, microvascular resistance was positively related to CFPWV independent of age ( = 0.35, = 0.031). Multiple linear regression showed that CFPWV was not a significant determinant of resting arteriole flow PI (β = -0.10, = 0.64). However, during reduced retinal microvascular resistance using light flicker ( < 0.001), CFPWV was a significant determinant of the percent change in arteriole flow PI (β = 0.58, = 0.046), but not mean flow (β = -0.17, = 0.54), where reductions in arteriole flow PI were associated with lower CFPWV. In summary, our findings suggest that higher aortic stiffness and the related increase in central PP in healthy young/middle-age adults are associated with retinal arteriole narrowing and smaller reductions in arteriole flow pulsatility in response to dynamic conditions such as local metabolic vasodilation. By using the human retinal microvasculature as an end-organ in vivo model, we confirm that aortic stiffness and related increases in central pulse pressure are inversely correlated with retinal arteriole lumen diameter and increased microvascular resistance among heathy young/middle-age adults. Additionally, higher aortic stiffness is not associated with excessive flow pulsatility in the retinal microvasculature under tonic conditions but may be related to limited reductions in retinal arteriole flow pulsatility in response to local vasodilation.
Topics: Adult; Arterioles; Blood Pressure; Female; Humans; Male; Middle Aged; Pulse Wave Analysis; Vascular Stiffness; Vasodilation
American Journal of Physiology. Renal... Feb 2021Renal arteriolar tone depends considerably on the dilatory action of nitric oxide (NO) via activation of soluble guanylyl cyclase (sGC) and cGMP action. NO deficiency...
Renal arteriolar tone depends considerably on the dilatory action of nitric oxide (NO) via activation of soluble guanylyl cyclase (sGC) and cGMP action. NO deficiency and hypoxia/reoxygenation are important pathophysiological factors in the development of acute kidney injury. It was hypothesized that the NO-sGC-cGMP system functions differently in renal afferent arterioles (AA) compared with efferent arterioles (EA) and that the sGC activator cinaciguat differentially dilates these arterioles. Experiments were performed in isolated, perfused mouse glomerular arterioles. Hypoxia (0.1% oxygen) was achieved by using a hypoxia chamber. Phosphodiesterase 5 (PDE5) and sGC subunits were considerably expressed on the mRNA level in AA. PDE5 inhibition with sildenafil, which blocks cGMP degradation, diminished the responses to ANG II bolus application in AA, but not significantly in EA. Vasodilation induced by sildenafil in ANG II-preconstricted vessels was stronger in EA than AA. Cinaciguat, an NO- and heme-independent sGC activator, dilated EA more strongly than AA after -nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) treatment and preconstriction with ANG II. Cinaciguat-induced dilatation of l-NAME-pretreated and ANG II-preconstricted arterioles was similar to controls without l-NAME treatment. Cinaciguat also induced dilatation in iodinated contrast medium treated AA. Furthermore, it dilated EA, but not AA, after hypoxia/reoxygenation. The results reveal an important role of the NO-sGC-cGMP system for renal dilatation and that EA have a more potent sGC activated dilatory system. Furthermore, AA seem to be more sensitive to hypoxia/reoxygenation than EA under these experimental conditions.
Topics: Angiotensin II; Animals; Arterioles; Cyclic Nucleotide Phosphodiesterases, Type 5; Gene Expression Regulation, Enzymologic; Kidney; Male; Mice; Mice, Inbred C57BL; NG-Nitroarginine Methyl Ester; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Soluble Guanylyl Cyclase
Enhanced parenchymal arteriole tone and astrocyte signaling protect neurovascular coupling mediated parenchymal arteriole vasodilation in the spontaneously hypertensive...Journal of Cerebral Blood Flow and... Jul 2015Functional hyperemia is the regional increase in cerebral blood flow upon increases in neuronal activity which ensures that the metabolic demands of the neurons are met....
Enhanced parenchymal arteriole tone and astrocyte signaling protect neurovascular coupling mediated parenchymal arteriole vasodilation in the spontaneously hypertensive rat.
Functional hyperemia is the regional increase in cerebral blood flow upon increases in neuronal activity which ensures that the metabolic demands of the neurons are met. Hypertension is known to impair the hyperemic response; however, the neurovascular coupling mechanisms by which this cerebrovascular dysfunction occurs have yet to be fully elucidated. To determine whether altered cortical parenchymal arteriole function or astrocyte signaling contribute to blunted neurovascular coupling in hypertension, we measured parenchymal arteriole reactivity and vascular smooth muscle cell Ca(2+) dynamics in cortical brain slices from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. We found that vasoconstriction in response to the thromboxane A2 receptor agonist U46619 and basal vascular smooth muscle cell Ca(2+) oscillation frequency were significantly increased in parenchymal arterioles from SHR. In perfused and pressurized parenchymal arterioles, myogenic tone was significantly increased in SHR. Although K(+)-induced parenchymal arteriole dilations were similar in WKY and SHR, metabotropic glutamate receptor activation-induced parenchymal arteriole dilations were enhanced in SHR. Further, neuronal stimulation-evoked parenchymal arteriole dilations were similar in SHR and WKY. Our data indicate that neurovascular coupling is not impaired in SHR, at least at the level of the parenchymal arterioles.
Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Arterioles; Astrocytes; Brain; Calcium; Hypertension; Male; Muscle, Smooth, Vascular; Potassium; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Metabotropic Glutamate; Signal Transduction; Vascular Remodeling; Vasoconstriction; Vasodilation
Intraluminal pressure triggers myogenic response via activation of calcium spark and calcium-activated chloride channel in rat renal afferent arteriole.American Journal of Physiology. Renal... Dec 2018Myogenic contraction of renal arterioles is an important regulatory mechanism for renal blood flow autoregulation. We have previously demonstrated that integrin-mediated...
Myogenic contraction of renal arterioles is an important regulatory mechanism for renal blood flow autoregulation. We have previously demonstrated that integrin-mediated mechanical force increases the occurrence of Ca sparks in freshly isolated renal vascular smooth muscle cells (VSMCs). To further test whether the generation of Ca sparks is a downstream signal of mechanotransduction in pressure-induced myogenic constriction, the relationship between Ca sparks and transmural perfusion pressure was investigated in intact VSMCs of pressurized rat afferent arterioles. Spontaneous Ca sparks were found in VSMCs when afferent arterioles were perfused at 80 mmHg. The spark frequency was significantly increased when perfusion pressure was increased to 120 mmHg. A similar increase of spark frequency was also observed in arterioles stimulated with β-integrin-activating antibody. Moreover, spark frequency was significantly higher in arterioles of spontaneous hypertensive rats at 80 and 120 mmHg. Spontaneous membrane current recorded using whole cell perforated patch in renal VSMCs showed predominant activity of spontaneous transient inward currents instead of spontaneous transient outward currents when holding potential was set close to physiological resting membrane potential. Real-time PCR and immunohistochemistry confirmed the expression of Ca-activated Cl channel (Cl) TMEM16A in renal VSMCs. Inhibition of TMEM16A with T16Ainh-A01 impaired the pressure-induced myogenic contraction in perfused afferent arterioles. Our study, for the first time to our knowledge, detected Ca sparks in VSMCs of intact afferent arterioles, and their frequencies were positively modulated by the perfusion pressure. Our results suggest that Ca sparks may couple to Cl channels and trigger pressure-induced myogenic constriction via membrane depolarization.
Topics: Animals; Anoctamin-1; Arterial Pressure; Arterioles; Calcium Signaling; Disease Models, Animal; Hypertension; Kidney; Male; Mechanotransduction, Cellular; Membrane Potentials; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Rats, Inbred SHR; Rats, Sprague-Dawley; Vasoconstriction
Cell Reports Aug 2021Very-low-frequency oscillations in microvascular diameter cause fluctuations in oxygen delivery that are important for fueling the brain and for functional imaging....
Very-low-frequency oscillations in microvascular diameter cause fluctuations in oxygen delivery that are important for fueling the brain and for functional imaging. However, little is known about how the brain regulates ongoing oscillations in cerebral blood flow. In mouse and rat cortical brain slice arterioles, we find that selectively enhancing tone is sufficient to recruit a TRPV4-mediated Ca elevation in adjacent astrocyte endfeet. This endfoot Ca signal triggers COX-1-mediated "feedback vasodilators" that limit the extent of evoked vasoconstriction, as well as constrain fictive vasomotion in slices. Astrocyte-Ptgs1 knockdown in vivo increases the power of arteriole oscillations across a broad range of very low frequencies (0.01-0.3 Hz), including ultra-slow vasomotion (∼0.1 Hz). Conversely, clamping astrocyte Cain vivo reduces the power of vasomotion. These data demonstrate bidirectional communication between arterioles and astrocyte endfeet to regulate oscillatory microvasculature activity.
Topics: Animals; Arterioles; Astrocytes; Calcium; Cyclooxygenase 1; Feedback, Physiological; Female; Male; Mice, Inbred C57BL; Rats, Sprague-Dawley; Stress, Mechanical; TRPV Cation Channels; Vasoconstriction; Vasodilation
Mineralocorticoid receptor antagonism improves parenchymal arteriole dilation via a TRPV4-dependent mechanism and prevents cognitive dysfunction in hypertension.American Journal of Physiology. Heart... Nov 2018Hypertension and mineralocorticoid receptor activation cause cerebral parenchymal arteriole remodeling; this can limit cerebral perfusion and contribute to cognitive...
Hypertension and mineralocorticoid receptor activation cause cerebral parenchymal arteriole remodeling; this can limit cerebral perfusion and contribute to cognitive dysfunction. We used a mouse model of angiotensin II-induced hypertension to test the hypothesis that mineralocorticoid receptor activation impairs both transient receptor potential vanilloid (TRPV)4-mediated dilation of cerebral parenchymal arterioles and cognitive function. Mice (16-18 wk old, male, C57Bl/6) were treated with angiotensin II (800 ng·kg·min) with or without the mineralocorticoid receptor antagonist eplerenone (100 mg·kg·day) for 4 wk; sham mice served as controls. Data are presented as means ± SE; n = 5-14 mice/group. Eplerenone prevented the increased parenchymal arteriole myogenic tone and impaired carbachol-induced (10-10 mol/l) dilation observed during hypertension. The carbachol-induced dilation was endothelium-derived hyperpolarization mediated because it could not be blocked by N-nitro-l-arginine methyl ester (10 mol/l) and indomethacin (10 mol/l). We used GSK2193874 (10 mol/l) to confirm that in all groups this dilation was dependent on TRPV4 activation. Dilation in response to the TRPV4 agonist GSK1016790A (10-10 mol/l) was also reduced in hypertensive mice, and this defect was corrected by eplerenone. In hypertensive and eplerenone-treated animals, TRPV4 inhibition reduced myogenic tone, an effect that was not observed in arterioles from control animals. Eplerenone treatment also improved cognitive function and reduced microglia density in hypertensive mice. These data suggest that the mineralocorticoid receptor is a potential therapeutic target to improve cerebrovascular function and cognition during hypertension. NEW & NOTEWORTHY Vascular dementia is a growing public health issue that lacks effective treatments. Transient receptor potential vanilloid (TRPV)4 channels are important regulators of parenchymal arteriole dilation, and they modulate myogenic tone. The data presented here suggest that TRPV4 channel expression is regulated by the mineralocorticoid receptor (MR). MR blockade also improves cognitive function during hypertension. MR blockade might be a potential therapeutic approach to improve cerebrovascular function and cognition in patients with hypertension.
Topics: Angiotensin II; Animals; Antihypertensive Agents; Arterioles; Behavior, Animal; Brain; Cognition; Cognition Disorders; Disease Models, Animal; Eplerenone; Hypertension; Male; Maze Learning; Mice, Inbred C57BL; Mineralocorticoid Receptor Antagonists; Nesting Behavior; Recognition, Psychology; Signal Transduction; TRPV Cation Channels; Vasodilation