Calcium Spark Activity is Modulated by Perfusion Pressure in Vascular Smooth Muscle of Afferent Arterioles

Myogenic contraction is the principal component of renal autoregulation that protects the kidney from hypertensive barotrauma. Contractions are initiated by a rise in perfusion pressure that signals a reduction in membrane potential ( Em) of vascular smooth muscle cells to activate voltage-operated Ca2+ channels. Since ROS have variable effects on myogenic tone, we investigated the hypothesis that superoxide (O2·−) and H2O2 differentially impact myogenic contractions. The myogenic contractions of mouse isolated and perfused single afferent arterioles were assessed from changes in luminal diameter with increasing perfusion pressure (40–80 mmHg). O2·−, H2O2, and Em were assessed by fluorescence microscopy during incubation with paraquat to increase O2·− or with H2O2. Paraquat enhanced O2·− generation and myogenic contractions (−42 ± 4% vs. −19 ± 4%, P < 0.005) that were blocked by SOD but not by catalase and signaled via PKC. In contrast, H2O2 inhibited the effects of paraquat and reduced myogenic contractions (−10 ± 1% vs. −19 ± 2%, P < 0.005) and signaled via PKG. O2·− activated Ca2+-activated Cl− channels that reduced Em, whereas H2O2 activated Ca2+-activated and voltage-gated K+ channels that increased Em. Blockade of voltage-operated Ca2+ channels prevented the enhanced myogenic contractions with paraquat without preventing the reduction in Em. Myogenic contractions were independent of the endothelium and largely independent of nitric oxide. We conclude that O2·− and H2O2 activate different signaling pathways in vascular smooth muscle cells linked to discreet membrane channels with opposite effects on Em and voltage-operated Ca2+ channels and therefore have opposite effects on myogenic contractions.

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Influence of connexin45 on renal autoregulation

AJP Renal Physiology ◽

10.1152/ajprenal.00185.2019 ◽

2020 ◽

Vol 318 (3) ◽

pp. F732-F740 ◽

Cited By ~ 3

Author(s):

Sophie Møller ◽

Jens Christian Brings Jacobsen ◽

Thomas H. Braunstein ◽

Niels-Henrik Holstein-Rathlou ◽

Charlotte M. Sorensen

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Perfusion Pressure ◽

Vascular Wall ◽

Renal Perfusion ◽

Renal Autoregulation ◽

Renal Perfusion Pressure ◽

Afferent Arterioles

Renal autoregulation is mediated by the myogenic response and tubuloglomerular feedback (TGF) working in concert to maintain renal blood flow and glomerular filtration rate despite fluctuations in renal perfusion pressure. Intercellular communication through gap junctions may play a role in renal autoregulation. We examine if one of the building blocks in gap junctions, connexin45 (Cx45), which is expressed in vascular smooth muscle cells, has an influence on renal autoregulatory efficiency. The isolated perfused juxtamedullary nephron preparation was used to measure afferent arteriolar diameter changes in response to acute changes in renal perfusion pressure. In segmental arteries, pressure myography was used to study diameter changes in response to pressure changes. Wire myography was used to study vasoconstrictor and vasodilator responses. A mathematical model of the vascular wall was applied to interpret experimental data. We found a significant reduction in the afferent arteriolar constriction in response to acute pressure increases in Cx45 knockout (KO) mice compared with wild-type (WT) mice. Abolition of TGF caused a parallel upward shift in the autoregulation curve of WT animals but had no effect in KO animals, which is compatible with TGF providing a basal tonic contribution in afferent arterioles whereas Cx45 KO animals were functionally papillectomized. Analysis showed a shift toward lower stress sensitivity in afferent arterioles from Cx45 KO animals, indicating that the absence of Cx45 may also affect myogenic properties. Finally, loss of Cx45 in vascular smooth muscle cells appeared to associate with a change in both structure and passive properties of the vascular wall.

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Complex interactions of NO/cGMP/PKG systems on Ca2+ signaling in afferent arteriolar vascular smooth muscle

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00485.2009 ◽

2010 ◽

Vol 298 (1) ◽

pp. H144-H151 ◽

Cited By ~ 21

Author(s):

Susan K. Fellner ◽

William J. Arendshorst

Keyword(s):

Nitric Oxide ◽

Smooth Muscle ◽

Vascular Smooth Muscle ◽

No Production ◽

No Donor ◽

Complex Interactions ◽

Resistance Vessels ◽

Microsphere Method ◽

Afferent Arterioles ◽

Oxide Synthase

Little is known about the effects of nitric oxide (NO) and the cyclic GMP (cGMP)/protein kinase G (PKG) system on Ca2+ signaling in vascular smooth muscle cells (VSMC) of resistance vessels in general and afferent arterioles in particular. We tested the hypotheses that cGMP-, Ca2+-dependent big potassium channels (BKCa2+) buffer the Ca2+ response to depolarization by high extracellular KCl and that NO inhibits adenosine diphosphoribose (ADPR) cyclase, thereby reducing the Ca2+-induced Ca2+ release. We isolated rat afferent arterioles, utilizing the magnetized microsphere method, and measured cytosolic Ca2+ concentration ([Ca2+]i) with fura-2, a preparation in which endothelial cells do not participate in [Ca2+]i responses. KCl (50 mM)-induced depolarization causes an immediate increase in [Ca2+]i of 151 nM. The blockers Nω-nitro-l-arginine methyl ester (of nitric oxide synthase), 1,2,4-oxodiazolo-[4,3- a]quinoxalin-1-one (ODQ, of guanylyl cyclase), KT-5823 (of PKG activation), and iberiotoxin (IBX, of BKCa2+ activity) do not alter the [Ca2+]i response to KCl, suggesting no discernible endogenous NO production under basal conditions. The NO donor sodium nitroprusside (SNP) reduces the [Ca2+]i response to 77 nM; IBX restores the response to control values. These data show that activation of BKCa2+ in the presence of NO/cGMP provides a brake on KCl-induced [Ca2+]i responses. Experiments with the inhibitor of cyclic ADPR 8-bromo-cyclic ADPR (8-Br-cADPR) and SNP + downstream inhibitors of PKG and BKCa2+ suggest that NO inhibits ADPR cyclase in intact arterioles. When we pretreat afferent arterioles with 8-bromoguanosine 3′,5′-cyclic monophosphate (8-Br-cGMP; 10 μM), the response to KCl is 143 nM. However, in the presence of both IBX and 8-Br-cGMP, we observe a surprising doubling of the [Ca2+]i response to KCl. In summary, we present evidence for effects of the NO/cGMP/PKG system to reduce [Ca2+]i, via activation of BKCa2+ and possibly by inhibition of ADPR cyclase, and to increase [Ca2+]i, by a mechanism(s) yet to be defined.

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Vascular mechanisms of increased arterial pressure in preeclampsia: lessons from animal models

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00762.2001 ◽

2002 ◽

Vol 283 (1) ◽

pp. R29-R45 ◽

Cited By ~ 136

Author(s):

Raouf A. Khalil ◽

Joey P. Granger

Keyword(s):

Smooth Muscle ◽

Arterial Pressure ◽

Vascular Smooth Muscle ◽

Vascular Resistance ◽

Vascular Reactivity ◽

Perfusion Pressure ◽

Smooth Muscle Contraction ◽

Vascular Relaxation ◽

Cell Dysfunction ◽

Placental Ischemia

Normal pregnancy is associated with reductions in total vascular resistance and arterial pressure possibly due to enhanced endothelium-dependent vascular relaxation and decreased vascular reactivity to vasoconstrictor agonists. These beneficial hemodynamic and vascular changes do not occur in women who develop preeclampsia; instead, severe increases in vascular resistance and arterial pressure are observed. Although preeclampsia represents a major cause of maternal and fetal morbidity and mortality, the vascular and cellular mechanisms underlying this disorder have not been clearly identified. Studies in hypertensive pregnant women and experimental animal models suggested that reduction in uteroplacental perfusion pressure and the ensuing placental ischemia/hypoxia during late pregnancy may trigger the release of placental factors that initiate a cascade of cellular and molecular events leading to endothelial and vascular smooth muscle cell dysfunction and thereby increased vascular resistance and arterial pressure. The reduction in uterine perfusion pressure and the ensuing placental ischemia are possibly caused by inadequate cytotrophoblast invasion of the uterine spiral arteries. Placental ischemia may promote the release of a variety of biologically active factors, including cytokines such as tumor necrosis factor-α and reactive oxygen species. Threshold increases in the plasma levels of placental factors may lead to endothelial cell dysfunction, alterations in the release of vasodilator substances such as nitric oxide (NO), prostacyclin (PGI2), and endothelium-derived hyperpolarizing factor, and thereby reductions of the NO-cGMP, PGI2-cAMP, and hyperpolarizing factor vascular relaxation pathways. The placental factors may also increase the release of or the vascular reactivity to endothelium-derived contracting factors such as endothelin, thromboxane, and ANG II. These contracting factors could increase intracellular Ca2+concentrations ([Ca2+]i) and stimulate Ca2+-dependent contraction pathways in vascular smooth muscle. The contracting factors could also increase the activity of vascular protein kinases such as protein kinase C, leading to increased myofilament force sensitivity to [Ca2+]i and enhancement of smooth muscle contraction. The decreased endothelium-dependent mechanisms of vascular relaxation and the enhanced mechanisms of vascular smooth muscle contraction represent plausible causes of the increased vascular resistance and arterial pressure associated with preeclampsia.

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Abstract 34: Diminished Contractile Capability In Cerebral Vascular Smooth Muscle Cells In The TgF344-AD Rat Model Of Alzheimer's Disease

Hypertension ◽

10.1161/hyp.78.suppl_1.34 ◽

2021 ◽

Vol 78 (Suppl_1) ◽

Author(s):

Xing Fang ◽

Huawei Zhang ◽

Yedan Liu ◽

Shaoxun Wang ◽

Baoying Zheng ◽

...

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Rat Model ◽

Perfusion Pressure ◽

Vascular Dysfunction ◽

Muscle Cells ◽

Model Of Alzheimer’S Disease ◽

Cerebral Vascular

We recently reported that cerebral vascular dysfunction leads to impaired autoregulation of cerebral blood flow (CBF), neurovascular coupling (NVC), and blood-brain barrier (BBB) leakage. The present study examined if cerebral vascular dysfunction precedes cognitive impairment in the TgF344-AD (AD) rat model of Alzheimer's disease. In the present study, we confirmed that the AD rats develop learning and memory deficits beginning at 24-week of age using an eight-arm water maze. AD rats (n = 11) took a longer time to escape and displayed more errors than age-matched wildtype (WT) rats (n = 6). We also completed a longitudinal comparison of the myogenic response (MR) of the middle cerebral artery (MCA) and found that the MR was similar in AD and WT rats at 8- to 12-week of age when perfusion pressure was increased from 40 to 180 mmHg. However, the MR was significantly reduced in 16-week old AD rats (n = 6) as the inner diameter of the MCA only decreased by 8.2 ± 2.4% when perfusion pressure was increased from 40 to 180 mmHg compared with 14.5% ± 2.0% in age-matched WT rats (n = 6). The impaired MR of the MCA was exacerbated in AD rats with aging. Autoregulation of CBF AD rats (n = 4) in vivo was impaired in the surface and deep cortex at 24-week of age compared to age-matched WT rats (n = 4). Furthermore, we found the contractile capability of the cerebral vascular smooth muscle cells (VSMCs) isolated from AD rats (n = 4) was significantly reduced compared with WT rats (n = 4), detected by the reduction in size of 15.7 ± 0.9% vs. 25.4 ± 1.0% using a collagen gel-based assay kit. These results provide evidence that cerebral VSMC dysfunction, impaired MR, and autoregulation of CBF precede the development of memory and learning deficits in the TgF344-AD rat model. However, the underlying mechanisms for the loss of VSMCs contractility in this AD model overexpressing mutant human amyloid precursor protein ( APPsw ) and presenilin 1 ( PS1ΔE9 ) genes remain to be determined. Nevertheless, these results provide novel insight into the vascular contribution to AD.

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Vascular Smooth Muscle Cells Express the α 1A Subunit of a P-/Q-Type Voltage-Dependent Ca 2+ Channel, and It Is Functionally Important in Renal Afferent Arterioles

Circulation Research ◽

10.1161/01.res.87.10.896 ◽

2000 ◽

Vol 87 (10) ◽

pp. 896-902 ◽

Cited By ~ 59

Author(s):

Pernille B. Hansen ◽

Boye L. Jensen ◽

Ditte Andreasen ◽

Ulla G. Friis ◽

Ole Skøtt

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Muscle Cells ◽

Voltage Dependent ◽

Afferent Arterioles

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Effect of calcitonin, hydrocortisone, and parathyroid hormone on canine bone blood vessels

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1981.241.1.h91 ◽

1981 ◽

Vol 241 (1) ◽

pp. H91-H94 ◽

Cited By ~ 1

Author(s):

M. Driessens ◽

P. M. Vanhoutte

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Blood Vessels ◽

Vascular Smooth Muscle Cells ◽

Perfusion Pressure ◽

Muscle Cells ◽

Ringer Solution ◽

Dependent Inhibition ◽

Dose Dependent

Experiments were designed to determine whether or not calcitonin, parathormone, and glucocorticoids have direct effects on the vascular smooth muscle cells of bone blood vessels. Tibias of mongrel dogs were isolated. The arteria nutriens was cannulated and perfused at constant flow with aerated Krebs-Ringer solution (37 degrees C). The perfusion pressure was continuously recorded. In unstimulated preparations calcitonin caused dose-dependent increases in perfusion pressure, indicating that it causes constriction of bone blood vessels. Parathormone did not affect basal perfusion; it did not significantly alter vasoconstrictions caused by the injection of norepinephrine indicating that the hormone has no direct effect on the vascular smooth muscle of bone blood vessels. Hydrocortisone, at low concentrations, augmented the constrictions caused by exogenous norepinephrine and periarterial nerve stimulation; at higher concentrations, hydrocortisone caused a dose-dependent inhibition of the response to adrenergic activation. The depressant effect of hydrocortisone was antagonized by propranolol, suggesting that the glucocorticoid facilitates beta-adrenergic relaxation of the vascular smooth muscle cells by catecholamines.

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Integrin-mediated mechanotransduction in renal vascular smooth muscle cells: activation of calcium sparks

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00025.2007 ◽

2007 ◽

Vol 293 (4) ◽

pp. R1586-R1594 ◽

Cited By ~ 36

Author(s):

Lavanya Balasubramanian ◽

Abu Ahmed ◽

Chun-Min Lo ◽

James S. K. Sham ◽

Kay-Pong Yip

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Muscle Cells ◽

Mechanical Force ◽

Binding Peptide ◽

Intracellular Ca ◽

Afferent Arterioles ◽

Paramagnetic Beads

Integrins are transmembrane heterodimeric proteins that link extracellular matrix (ECM) to cytoskeleton and have been shown to function as mechanotransducers in nonmuscle cells. Synthetic integrin-binding peptide triggers Ca2+ mobilization and contraction in vascular smooth muscle cells (VSMCs) of rat afferent arteriole, indicating that interactions between the ECM and integrins modulate vascular tone. To examine whether integrins transduce extracellular mechanical stress into intracellular Ca2+ signaling events in VSMCs, unidirectional mechanical force was applied to freshly isolated renal VSMCs through paramagnetic beads coated with fibronectin (natural ligand of α5β1-integrin in VSMCs). Pulling of fibronectin-coated beads with an electromagnet triggered Ca2+ sparks, followed by global Ca2+ mobilization. Paramagnetic beads coated with low-density lipoprotein, whose receptors are not linked to cytoskeleton, were minimally effective in triggering Ca2+ sparks and global Ca2+ mobilization. Preincubation with ryanodine, cytochalasin-D, or colchicine substantially reduced the occurrence of Ca2+ sparks triggered by fibronectin-coated beads. Binding of VSMCs with antibodies specific to the extracellular domains of α5- and β1-integrins triggered Ca2+ sparks simulating the effects of fibronectin-coated beads. Preincubation of microperfused afferent arterioles with ryanodine or integrin-specific binding peptide inhibited pressure-induced myogenic constriction. In conclusion, integrins transduce mechanical force into intracellular Ca2+ signaling events in renal VSMCs. Integrin-mediated mechanotransduction is probably involved in myogenic response of afferent arterioles.

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Impaired myogenic constriction of the renal afferent arteriole in a mouse model of reduced βENaC expression

AJP Renal Physiology ◽

10.1152/ajprenal.00638.2011 ◽

2012 ◽

Vol 302 (11) ◽

pp. F1486-F1493 ◽

Cited By ~ 16

Author(s):

Ying Ge ◽

Kimberly Gannon ◽

Monette Gousset ◽

Ruishing Liu ◽

Beau Murphey ◽

...

Keyword(s):

Smooth Muscle ◽

Mouse Model ◽

Vascular Resistance ◽

Perfusion Pressure ◽

Rate Of Change ◽

Renal Vascular Resistance ◽

Myogenic Tone ◽

Afferent Arteriole ◽

Afferent Arterioles ◽

Renal Vascular

Previous studies demonstrate a role for β epithelial Na+ channel (βENaC) protein as a mediator of myogenic constriction in renal interlobar arteries. However, the importance of βENaC as a mediator of myogenic constriction in renal afferent arterioles, the primary site of development of renal vascular resistance, has not been determined. We colocalized βENaC with smooth muscle α-actin in vascular smooth muscle cells in renal arterioles using immunofluorescence. To determine the importance of βENaC in myogenic constriction in renal afferent arterioles, we used a mouse model of reduced βENaC (βENaC m/m) and examined pressure-induced constrictor responses in the isolated afferent arteriole-attached glomerulus preparation. We found that, in response to a step increase in perfusion pressure from 60 to 120 mmHg, the myogenic tone increased from 4.5 ± 3.7 to 27.3 ± 5.2% in +/+ mice. In contrast, myogenic tone failed to increase with the pressure step in m/m mice (3.9 ± 0.8 to 6.9 ± 1.4%). To determine the importance of βENaC in myogenic renal blood flow (RBF) regulation, we examined the rate of change in renal vascular resistance following a step increase in perfusion pressure in volume-expanded animals. We found that, following a step increase in pressure, the rate of myogenic correction of RBF is inhibited by 75% in βENaC m/m mice. These findings demonstrate that myogenic constriction in afferent arterioles is dependent on normal expression of βENaC.

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Localization of P2X1 purinoceptors by autoradiography and immunohistochemistry in rat kidneys

AJP Renal Physiology ◽

10.1152/ajprenal.1998.274.4.f799 ◽

1998 ◽

Vol 274 (4) ◽

pp. F799-F804 ◽

Cited By ~ 41

Author(s):

C. M. Chan ◽

R. J. Unwin ◽

M. Bardini ◽

I. B. Oglesby ◽

A. P. D. W. Ford ◽

...

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Polyclonal Antibody ◽

Functional Significance ◽

Rat Kidney ◽

P2 Receptors ◽

Renal Tubules ◽

Vascular Control ◽

Afferent Arterioles ◽

Rat Kidneys

P2 receptors have been identified in rat kidney by autoradiography, using the radioligand [3H]α,β-methylene ATP, and by immunohistochemistry, using a polyclonal antibody to the P2X1 purinoceptor. They have been localized to the vascular smooth muscle of intrarenal arteries, including arcuate and interlobular arteries, and afferent arterioles, but not glomeruli, postglomerular efferent arterioles, or renal tubules. We conclude that at least some of the P2 receptors present on vascular smooth muscle are of the P2X1 subtype. The functional significance of these findings in the vascular control of the kidney is discussed.

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