Abstract P741: Elemental Calcium Influx Through Endothelial N-Methyl-D-Aspartate Receptors is Impaired by Acute Amyloid- β (1-40) in Cerebral Arteries

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Emily C Peters ◽  
Allison M Kath ◽  
Michael T Gee ◽  
Paulo W Pires
Keyword(s):  
Calcium Influx ◽  
Cerebral Arteries ◽  
Amyloid Β ◽  
Cyclopiazonic Acid ◽  
Time Lapse ◽  
Amyloid Angiopathy ◽  
Wild Type ◽  
Pial Arteries ◽  
Intracellular Ca ◽  
Nmdar Activation

Introduction: Cerebral amyloid angiopathy (CAA), the accumulation of amyloid- β (1-40) (A β ) around cerebral arteries, impairs endothelial function. Endothelium-dependent dilation is a consequence of transient increases in intracellular [Ca 2+ ] in endothelial cells (EC). The Ca 2+ permeable N-methyl-D-aspartate receptor (NMDAR) mediates endothelium-dependent dilation, although if these effects are dependent on Ca 2+ influx and transients, or if they are impaired by A β , remains undetermined. Hypothesis: A β inhibits endothelial NMDAR-mediated Ca 2+ influx and transients in murine pial arteries. Methods: We performed Ca 2+ time-lapse imaging of en face pial arteries from cdh5-GCaMP8 mice to quantify EC Ca 2+ events induced by NMDAR activation. Data are means ± SEM. Results: Elemental Ca 2+ entry through NMDAR, hereon called NMDAR sparklets , was assessed in arteries incubated with EGTA-AM and cyclopiazonic acid (CPA) to inhibit intracellular Ca 2+ transients. NMDA (10 μM) induced an increase in NMDAR sparklets frequency when compared to vehicle, an effect inhibited by the NMDAR antagonist D-APV (in Hz: 0.12±0.01 vs 0.44±0.05 vs 0.21±0.02, vehicle vs NMDA vs NMDA+D-APV, p<0.05). Further, pial arteries exposed to NMDA without EGTA-AM and CPA showed an increase in the frequency of intracellular Ca 2+ transients, also blocked by D-APV (in Hz: 0.24±0.05 vs 0.53±0.10 vs 0.28±0.05, vehicle vs NMDA vs NMDA+D-APV, p<0.05). We then tested the effects of A β on Ca 2+ events in pial artery EC. We observed that 30 minutes exposure to A β (5 μM) caused a significant reduction in NMDAR sparklets (in Hz: 0.62±0.07 vs 0.22±0.03, NMDA vs NMDA + A β , p<0.05) but did not significantly alter intracellular Ca 2+ transients (in Hz: 0.62±0.37 vs 0.27±0.07, NMDA vs NMDA + A β ). Lastly, we performed pressure myography on pial arteries of wild-type and 5x-FAD mice, a model of familial Alzheimer’s disease with rapid amyloid accumulation. 5x-FAD mice displayed impaired vasodilation to NMDA (vasodilation (%): 9.86±0.64 vs 4.22±2.76, wild-type vs 5x-FAD , p<0.05). Conclusion: These preliminary data suggest that A β impairs endothelial NMDAR-associated Ca 2+ influx events in cerebral arteries, which can impair blood flow in CAA patients, thus contributing to cognitive impairment.

Amyloid-β disrupts unitary calcium entry through endothelial NMDA receptors in mouse cerebral arteries

2021 ◽  
pp. 0271678X2110395
Author(s):  
Emily C Peters ◽  
Michael T Gee ◽  
Lukas N Pawlowski ◽  
Allison M Kath ◽  
Felipe D Polk ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cerebral Arteries ◽  
Amyloid Β ◽  
Amyloid Angiopathy ◽  
Wild Type ◽  
Pial Arteries ◽  
Aspartate Receptor ◽  
Model Of Alzheimer’S Disease ◽  
Intracellular Ca ◽  
Cerebral Amyloid

Transient increases in intracellular Ca2+ activate endothelium-dependent vasodilatory pathways. This process is impaired in cerebral amyloid angiopathy, where amyloid- β(1-40) accumulates around blood vessels. In neurons, amyloid- β impairs the Ca2+-permeable N-methyl-D-aspartate receptor (NMDAR), a mediator of endothelium-dependent dilation in arteries. We hypothesized that amyloid- β(1-40) reduces NMDAR-elicited Ca2+ signals in mouse cerebral artery endothelial cells, blunting dilation. Cerebral arteries isolated from 4-5 months-old, male and female cdh5:Gcamp8 mice were used for imaging of unitary Ca2+ influx through NMDAR ( NMDAR sparklets) and intracellular Ca2+ transients. The NMDAR agonist NMDA (10 µmol/L) increased frequency of NMDAR sparklets and intracellular Ca2+ transients in endothelial cells; these effects were prevented by NMDAR antagonists D-AP5 and MK-801. Next, we tested if amyloid- β(1-40) impairs NMDAR-elicited Ca2+ transients. Cerebral arteries incubated with amyloid- β(1-40) (5 µmol/L) exhibited reduced NMDAR sparklets and intracellular Ca2+ transients. Lastly, we observed that NMDA-induced dilation of pial arteries is reduced by acute intraluminal amyloid- β(1-40), as well as in a mouse model of Alzheimer’s disease, the 5x-FAD, linked to downregulation of Grin1 mRNA compared to wild-type littermates. These data suggest that endothelial NMDAR mediate dilation via Ca2+-dependent pathways, a process disrupted by amyloid- β(1-40) and impaired in 5x-FAD mice.

Ca2+-Induced Ca2+ Release Activates Spontaneous Miniature Outward Currents (SMOCs) in Parasympathetic Cardiac Neurons

1999 ◽  
Vol 82 (2) ◽  
pp. 540-550 ◽  
Author(s):  
Laura A. Merriam ◽  
Fabiana S. Scornik ◽  
Rodney L. Parsons
Keyword(s):  
Calcium Influx ◽  
Cyclopiazonic Acid ◽  
Bk Channels ◽  
Tetraacetic Acid ◽  
Atpase Inhibitor ◽  
Release Channel ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Whole Cell Recordings

Mudpuppy parasympathetic cardiac neurons exhibit spontaneous miniature outward currents (SMOCs) that are thought to be due to the activation of clusters of large conductance Ca2+-activated K+ channels (BK channels) by localized release of Ca2+ from internal stores close to the plasma membrane. Perforated-patch whole cell recordings were used to determine whether Ca2+-induced Ca2+ release (CICR) is involved in SMOC generation. We confirmed that BK channels are involved by showing that SMOCs are inhibited by 100 nM iberiotoxin or 500 μM tetraethylammonium (TEA), but not by 100 nM apamin. SMOC frequency is decreased in solutions that contain 0 Ca2+/3.6 mM Mg2+, and also in the presence of 1 μM nifedipine and 3 μM ω-conotoxin GVIA, suggesting that SMOC activation is dependent on calcium influx. However, Ca2+ influx alone is not sufficient; SMOC activation is also dependent on Ca2+release from the caffeine- and ryanodine-sensitive Ca2+store, because exposure to 2 mM caffeine consistently caused an increase in SMOC frequency, and 10–100 μM ryanodine altered the configuration of SMOCs and eventually inhibited SMOC activity. Depletion of intracellular Ca2+ stores by the Ca-ATPase inhibitor cyclopiazonic acid (10 μM) inhibited SMOC activity, even when Ca2+ influx was not compromised. We also tested the effects of the membrane-permeable Ca2+ chelators, bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid-AM (BAPTA-AM) and EGTA-AM. EGTA-AM (10 μM) caused no inhibition of SMOC activation, whereas 10 μM BAPTA-AM consistently inhibited SMOCs. After SMOCs were completely inhibited by BAPTA, 3 mM caffeine caused SMOC activity to resume. This effect was reversible on removal of caffeine and suggests that the source of Ca2+ that triggers the internal Ca2+ release channel is different from the source of Ca2+ that activates clusters of BK channels. We propose that influx of Ca2+ through voltage-dependent Ca2+ channels is required for SMOC generation, but that the influx of Ca2+ triggers CICR from intracellular stores, which then activates the BK channels responsible for SMOC generation.

scholarly journals Thrombin-mediated increases in cytosolic [Ca2+] involve different mechanisms in human pulmonary artery smooth muscle and endothelial cells

2008 ◽  
Vol 295 (6) ◽  
pp. L1048-L1055 ◽  
Author(s):  
Richard S. Sacks ◽  
Amy L. Firth ◽  
Carmelle V. Remillard ◽  
Negin Agange ◽  
Jocelyn Yau ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Calcium Influx ◽  
Dynamic Balance ◽  
Cyclopiazonic Acid ◽  
Cell Types ◽  
Intracellular Ca ◽  
Pulmonary Artery Smooth Muscle ◽  
Human Pulmonary Artery

Thrombin is a procoagulant inflammatory agonist that can disrupt the endothelium-lumen barrier in the lung by causing contraction of endothelial cells and promote pulmonary cell proliferation. Both contraction and proliferation require increases in cytosolic Ca2+ concentration ([Ca2+]cyt). In this study, we compared the effect of thrombin on Ca2+ signaling in human pulmonary artery smooth muscle (PASMC) and endothelial (PAEC) cells. Thrombin increased the [Ca2+]cyt in both cell types; however, the transient response was significantly higher and recovered quicker in the PASMC, suggesting different mechanisms may contribute to thrombin-mediated increases in [Ca2+]cyt in these cell types. Depletion of intracellular stores with cyclopiazonic acid (CPA) in the absence of extracellular Ca2+ induced calcium transients representative of those observed in response to thrombin in both cell types. Interestingly, CPA pretreatment significantly attenuated thrombin-induced Ca2+ release in PASMC; this attenuation was not apparent in PAEC, indicating that a PAEC-specific mechanism was targeted by thrombin. Treatment with a combination of CPA, caffeine, and ryanodine also failed to abolish the thrombin-induced Ca2+ transient in PAEC. Notably, thrombin-induced receptor-mediated calcium influx was still observed in PASMC after CPA pretreatment in the presence of extracellular Ca2+. Ca2+ oscillations were triggered by thrombin in PASMC resulting from a balance of extracellular Ca2+ influx and Ca2+ reuptake by the sarcoplasmic reticulum. The data show that thrombin induces increases in intracellular calcium in PASMC and PAEC with a distinct CPA-, caffeine-, and ryanodine-insensitive release existing only in PAEC. Furthermore, a dynamic balance between Ca2+ influx, intracellular Ca2+ release, and reuptake underlie the Ca2+ transients evoked by thrombin in some PASMC. Understanding of such mechanisms will provide an important insight into thrombin-mediated vascular injury during hypertension.

Abstract 211: The Role of Vascular Amyloid β in the Formation of Microhemorrhages in Cerebral Amyloid Angiopathy

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Susanne J van Veluw ◽  
Andreas Charidimou ◽  
Anand Viswanathan ◽  
Matthew Frosch ◽  
Brian Bacskai ◽  
...  
Keyword(s):  
Cerebral Amyloid Angiopathy ◽  
Amyloid Β ◽  
Direct Consequence ◽  
Transgenic Animals ◽  
Diagnostic Feature ◽  
Amyloid Angiopathy ◽  
Wild Type ◽  
Cerebral Amyloid

Introduction: Cerebral microhemorrhages are a key diagnostic feature of advanced cerebral amyloid angiopathy (CAA), but the underlying mechanisms remain poorly understood. We investigate the role of vascular Amyloid β (Aβ) in the formation of microhemorrhages in CAA, examining both human tissue and mouse models. Methods: First, we examined the histopathology of microhemorrhages, targeted with post-mortem MRI in humans. Brain slabs from nine cases with moderate/severe CAA were subjected to 7 T MRI. Samples were taken from representative MRI-observed microhemorrhages. On the corresponding histopathological sections we assessed the presence of Aβ in the walls of involved vessels, as well as number of Aβ-positive cortical vessels in areas (<2 mm) surrounding the rupture site. Second, to evaluate microhemorrhage formation in real-time in 3D, we performed in vivo two-photon microscopy in aged APP/PS1 mice with advanced CAA. Mice with previously installed cranial windows were injected with fluorescently labeled anti-fibrin, dextran, and methoxy-XO4 to study clot formation (i.e. microhemorrhages) and their spatial localization in relation to Aβ-positive vessels. Results: Human data: in 7/19 microhemorrhages the involved vessels were preserved. Only one of these vessels was positive for Aβ. Moreover, the density of Aβ-positive cortical vessels was lower close to the site of microhemorrhage (~1 positive vessel/mm 2 ), compared to control areas (~2 positive vessels/mm 2 ). Mouse data: we studied six transgenic ~21 month old APP/PS1 mice and two age-matched wild-type littermates. Mean number of in vivo observed microhemorrhages did not differ between groups (Tg: 1.3 / WT: 1), but the transgenic mice tended to have bigger microhemorrhages (mean size 4706 μm 3 ) than their wild-type controls (2505 μm 3 ). Interestingly, in the transgenic animals only one microhemorrhage was found in close proximity to vascular Aβ deposits. Conclusions: These findings question the widely held assumption that microhemorrhages in CAA are a direct consequence of Aβ deposition in the walls of responsible vessels. Our observations suggest that microhemorrhage formation may not be a direct consequence of more severe CAA locally, but may occur preferentially in areas of relatively low CAA.

scholarly journals Dysregulation of Ca2+ signaling in astrocytes from mice lacking amyloid precursor protein

2011 ◽  
Vol 300 (6) ◽  
pp. C1502-C1512 ◽  
Author(s):  
Cristina I. Linde ◽  
Sergey G. Baryshnikov ◽  
A. Mazzocco-Spezzia ◽  
Vera A. Golovina
Keyword(s):  
Transient Receptor Potential ◽  
Amyloid Β ◽  
Cyclopiazonic Acid ◽  
Receptor Potential ◽  
Precursor Protein ◽  
Wild Type ◽  
Atpase Inhibitor ◽  
Cultured Astrocytes ◽  
Essential Components ◽  
Transient Receptor

The relationship between altered metabolism of the amyloid-β precursor protein (APP) and Alzheimer's disease is well established but the physiological roles of APP still remain unclear. Here, we studied Ca2+ signaling in primary cultured and freshly dissociated cortical astrocytes from APP knockout (KO) mice and from Tg5469 mice overproducing by five- to sixfold wild-type APP. Resting cytosolic Ca2+ (measured with fura-2) was not altered in cultured astrocytes from APP KO mice. The stored Ca2+ evaluated by measuring peak amplitude of cyclopiazonic acid [CPA, endoplasmic reticulum (ER) Ca2+ ATPase inhibitor]-induced Ca2+ transients in Ca2+-free medium was significantly smaller in APP KO astrocytes than in wild-type cells. Store-operated Ca2+ entry (SOCE) activated by ER Ca2+ store depletion with CPA was also greatly reduced in APP KO astrocytes. This reflected a downregulated expression in APP KO astrocytes of TRPC1 (C-type transient receptor potential) and Orai1 proteins, essential components of store-operated channels (SOCs). Indeed, silencer RNA (siRNA) knockdown of Orai1 protein expression in wild-type astrocytes significantly attenuated SOCE. SOCE was also essentially reduced in freshly dissociated APP KO astrocytes. Importantly, knockdown of APP with siRNA in cultured wild-type astrocytes markedly attenuated ATP- and CPA-induced ER Ca2+ release and extracellular Ca2+ influx. The latter correlated with downregulation of TRPC1. Overproduction of APP in Tg5469 mice did not alter, however, the stored Ca2+ level, SOCE, and expression of TRPC1/4/5 in cultured astrocytes from these mice. The data demonstrate that the functional role of APP in astrocytes involves the regulation of TRPC1/Orai1-encoded SOCs critical for Ca2+ signaling.

scholarly journals Impaired Glymphatic Function and Pulsation Alterations in a Mouse Model of Vascular Cognitive Impairment

2022 ◽  
Vol 13 ◽  
Author(s):  
Mosi Li ◽  
Akihiro Kitamura ◽  
Joshua Beverley ◽  
Juraj Koudelka ◽  
Jessica Duncombe ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Carotid Stenosis ◽  
Molecular Layer ◽  
Amyloid Β ◽  
Vascular Cognitive Impairment ◽  
Wild Type ◽  
Fluorescent Tracer ◽  
Pial Arteries ◽  
Dorsolateral Cortex ◽  
Large Vessel Disease

Large vessel disease and carotid stenosis are key mechanisms contributing to vascular cognitive impairment (VCI) and dementia. Our previous work, and that of others, using rodent models, demonstrated that bilateral common carotid stenosis (BCAS) leads to cognitive impairment via gradual deterioration of the neuro-glial-vascular unit and accumulation of amyloid-β (Aβ) protein. Since brain-wide drainage pathways (glymphatic) for waste clearance, including Aβ removal, have been implicated in the pathophysiology of VCI via glial mechanisms, we hypothesized that glymphatic function would be impaired in a BCAS model and exacerbated in the presence of Aβ. Male wild-type and Tg-SwDI (model of microvascular amyloid) mice were subjected to BCAS or sham surgery which led to a reduction in cerebral perfusion and impaired spatial learning acquisition and cognitive flexibility. After 3 months survival, glymphatic function was evaluated by cerebrospinal fluid (CSF) fluorescent tracer influx. We demonstrated that BCAS caused a marked regional reduction of CSF tracer influx in the dorsolateral cortex and CA1-DG molecular layer. In parallel to these changes increased reactive astrogliosis was observed post-BCAS. To further investigate the mechanisms that may lead to these changes, we measured the pulsation of cortical vessels. BCAS impaired vascular pulsation in pial arteries in WT and Tg-SwDI mice. Our findings show that BCAS influences VCI and that this is paralleled by impaired glymphatic drainage and reduced vascular pulsation. We propose that these additional targets need to be considered when treating VCI.

scholarly journals Chronic cerebral hypoperfusion alters amyloid-β peptide pools leading to cerebral amyloid angiopathy, microinfarcts and haemorrhages in Tg-SwDI mice

2017 ◽  
Vol 131 (16) ◽  
pp. 2109-2123 ◽  
Author(s):  
Natalia Salvadores ◽  
James L. Searcy ◽  
Philip R. Holland ◽  
Karen Horsburgh
Keyword(s):  
Amyloid Β ◽  
Chronic Cerebral Hypoperfusion ◽  
Cerebral Hypoperfusion ◽  
Amyloid Angiopathy ◽  
Amyloid Β Peptide ◽  
Wild Type ◽  
Aβ Peptides ◽  
Bilateral Carotid ◽  
The Brain ◽  
Bilateral Carotid Artery

Cerebral hypoperfusion is an early feature of Alzheimer’s disease (AD) that influences the progression from mild cognitive impairment to dementia. Understanding the mechanism is of critical importance in the search for new effective therapies. We hypothesized that cerebral hypoperfusion promotes the accumulation of amyloid-β (Aβ) and degenerative changes in the brain and is a potential mechanism contributing to development of dementia. To address this, we studied the effects of chronic cerebral hypoperfusion induced by bilateral carotid artery stenosis on Aβ peptide pools in a transgenic mouse model of AD (transgenic mice with Swedish, Dutch and Iowa mutations in human amyloid precursor protein (APP) (Tg-SwDI)). Cerebrovascular integrity was characterized by quantifying the occurrence of microinfarcts and haemorrhages and compared with wild-type mice without Aβ. A significant increase in soluble Aβ peptides (Aβ40/42) was detected after 1 month of hypoperfusion in the parenchyma in parallel with elevated APP and APP proteolytic products. Following 3 months, a significant increase in insoluble Aβ40/42 was determined in the parenchyma and vasculature. Microinfarct load was significantly increased in the Tg-SwDI as compared with wild-type mice and further exacerbated by hypoperfusion at 1 and 3 months. In addition, the number of Tg-SwDI hypoperfused mice with haemorrhages was increased compared with hypoperfused wild-type mice. Soluble parenchymal Aβ was associated with elevated NADPH oxidase-2 (NOX2) which was exacerbated by 1-month hypoperfusion. We suggest that in response to hypoperfusion, increased Aβ production/deposition may contribute to degenerative processes by triggering oxidative stress promoting cerebrovascular disruption and the development of microinfarcts.

scholarly journals Anti-Parallel β-Hairpin Structure in Soluble Aβ Oligomers of Aβ40-Dutch and Aβ40-Iowa

2021 ◽  
Vol 22 (3) ◽  
pp. 1225
Author(s):  
Ziao Fu ◽  
William E. Van Nostrand ◽  
Steven O. Smith
Keyword(s):  
Amyloid Β ◽  
Amyloid Angiopathy ◽  
Aβ Oligomers ◽  
Dominant Component ◽  
Fibril Structure ◽  
Predominant Component ◽  
Aβ Aggregation ◽  
Aβ Fibrils ◽  
Soluble Aβ Oligomers ◽  
Β Sheet

The amyloid-β (Aβ) peptides are associated with two prominent diseases in the brain, Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA). Aβ42 is the dominant component of cored parenchymal plaques associated with AD, while Aβ40 is the predominant component of vascular amyloid associated with CAA. There are familial CAA mutations at positions Glu22 and Asp23 that lead to aggressive Aβ aggregation, drive vascular amyloid deposition and result in degradation of vascular membranes. In this study, we compared the transition of the monomeric Aβ40-WT peptide into soluble oligomers and fibrils with the corresponding transitions of the Aβ40-Dutch (E22Q), Aβ40-Iowa (D23N) and Aβ40-Dutch, Iowa (E22Q, D23N) mutants. FTIR measurements show that in a fashion similar to Aβ40-WT, the familial CAA mutants form transient intermediates with anti-parallel β-structure. This structure appears before the formation of cross-β-sheet fibrils as determined by thioflavin T fluorescence and circular dichroism spectroscopy and occurs when AFM images reveal the presence of soluble oligomers and protofibrils. Although the anti-parallel β-hairpin is a common intermediate on the pathway to Aβ fibrils for the four peptides studied, the rate of conversion to cross-β-sheet fibril structure differs for each.

scholarly journals Blood-Brain Barrier Disruption Increases Amyloid-Related Pathology in TgSwDI Mice

2021 ◽  
Vol 22 (3) ◽  
pp. 1231
Author(s):  
Ihab M. Abdallah ◽  
Kamal M. Al-Shami ◽  
Euitaek Yang ◽  
Amal Kaddoumi
Keyword(s):  
Mouse Model ◽  
Blood Brain Barrier ◽  
High Throughput Screening ◽  
Amyloid Β ◽  
Brain Barrier ◽  
Amyloid Angiopathy ◽  
Cancer Resistance ◽  
Screening Assay ◽  
Blood Brain ◽  
High Throughput Screening Assay

In Alzheimer’s disease (AD), several studies have reported blood-brain barrier (BBB) breakdown with compromised function. P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are transport proteins localized at the BBB luminal membrane and play an important role in the clearance of amyloid-β (Aβ). The purpose of this study was to investigate the effect of pharmacological inhibition of Aβ efflux transporters on BBB function and Aβ accumulation and related pathology. Recently, we have developed an in vitro high-throughput screening assay to screen for compounds that modulate the integrity of a cell-based BBB model, which identified elacridar as a disruptor of the monolayer integrity. Elacridar, an investigational compound known for its P-gp and BCRP inhibitory effect and widely used in cancer research. Therefore, it was used as a model compound for further evaluation in a mouse model of AD, namely TgSwDI. TgSwDI mouse is also used as a model for cerebral amyloid angiopathy (CAA). Results showed that P-gp and BCRP inhibition by elacridar disrupted the BBB integrity as measured by increased IgG extravasation and reduced expression of tight junction proteins, increased amyloid deposition due to P-gp, and BCRP downregulation and receptor for advanced glycation end products (RAGE) upregulation, increased CAA and astrogliosis. Further studies revealed the effect was mediated by activation of NF-κB pathway. In conclusion, results suggest that BBB disruption by inhibiting P-gp and BCRP exacerbates AD pathology in a mouse model of AD, and indicate that therapeutic drugs that inhibit P-gp and BCRP could increase the risk for AD.

Role of iPLA2 and store-operated channels in agonist-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries

2008 ◽  
Vol 294 (3) ◽  
pp. H1183-H1187 ◽  
Author(s):  
Kristen M. Park ◽  
Mario Trucillo ◽  
Nicolas Serban ◽  
Richard A. Cohen ◽  
Victoria M. Bolotina
Keyword(s):  
Carotid Arteries ◽  
Cerebral Arteries ◽  
Present Evidence ◽  
Voltage Gated ◽  
Functional Inhibition ◽  
Intracellular Ca ◽  
Dependent Pathway ◽  
Secondary Activation

Store-operated channels (SOC) and store-operated Ca2+ entry are known to play a major role in agonist-induced constriction of smooth muscle cells (SMC) in conduit vessels. In microvessels the role of SOC remains uncertain, in as much as voltage-gated L-type Ca2+ (CaL2+) channels are thought to be fully responsible for agonist-induced Ca2+ influx and vasoconstriction. We present evidence that SOC and their activation via a Ca2+-independent phospholipase A2 (iPLA2)-mediated pathway play a crucial role in agonist-induced constriction of cerebral, mesenteric, and carotid arteries. Intracellular Ca2+ in SMC and intraluminal diameter were measured simultaneously in intact pressurized vessels in vitro. We demonstrated that 1) Ca2+ and contractile responses to phenylephrine (PE) in cerebral and carotid arteries were equally abolished by nimodipine (a CaL2+ inhibitor) and 2-aminoethyl diphenylborinate (an inhibitor of SOC), suggesting that SOC and CaL2+ channels may be involved in agonist-induced constriction of cerebral arteries, and 2) functional inhibition of iPLA2β totally inhibited PE-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries, whereas K+-induced Ca2+ influx and vasoconstriction mediated by CaL2+ channels were not affected. Thus iPLA2-dependent activation of SOC is crucial for agonist-induced Ca2+ influx and vasoconstriction in cerebral, mesenteric, and carotid arteries. We propose that, on PE-induced depletion of Ca2+ stores, nonselective SOC are activated via an iPLA2-dependent pathway and may produce a depolarization of SMC, which could trigger a secondary activation of CaL2+ channels and lead to Ca2+ entry and vasoconstriction.

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