Extracellular acidosis activates ASIC-like channels in freshly isolated cerebral artery smooth muscle cells

Chung, Wen-Shuo; Farley, Jerry M.; Swenson, Alyssa; Barnard, John M.; Hamilton, Gina; Chiposi, Rumbidzayi; Drummond, Heather A.

doi:10.1152/ajpcell.00511.2009

Cited by 37 publications

(42 citation statements)

References 30 publications

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“…Prolonged acidification affects vascular smooth muscles and contributes to baseline blood pressure and vascular disease (74). In rodents, ASIC1b is expressed in these cells and may mediate a depolarizing response to acidosis (73). We did observe some hVariant 3 expression in non-neuronal tissues (supplementary data and Fig.…”

Section: Discussionmentioning

confidence: 72%

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Identification of a Calcium Permeable Human Acid-sensing Ion Channel 1 Transcript Variant

Hoagland

Sherwood

Lee

et al. 2010

Journal of Biological Chemistry

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The acid-sensing ion channels (ASICs) are proton-gated cation channels activated when extracellular pH declines. In rodents, the Accn2 gene encodes transcript variants ASIC1a and ASIC1b, which differ in the first third of the protein and display distinct channel properties. In humans, ACCN2 transcript variant 2 (hVariant 2) is homologous to mouse ASIC1a. In this article, we study two other human ACCN2 transcript variants. Human ACCN2 transcript variant 1 (hVariant 1) is not present in rodents and contains an additional 46 amino acids directly preceding the proposed channel gate. We report that hVariant 1 does not produce proton-gated currents under normal conditions when expressed in heterologous systems. We also describe a third human ACCN2 transcript variant (hVariant 3) that is similar to rodent ASIC1b. hVariant 3 is more abundantly expressed in dorsal root ganglion compared with brain and shows basic channel properties analogous to rodent ASIC1b. Yet, proton-gated currents from hVariant 3 are significantly more permeable to calcium than either hVariant 2 or rodent ASIC1b, which shows negligible calcium permeability. hVariant 3 also displays a small acid-dependent sustained current. Such a sustained current is particularly intriguing as ASIC1b is thought to play a role in sensory transduction in rodents. In human DRG neurons, hVariant 3 could induce sustained calcium influx in response to acidic pH and make a major contribution to acid-dependent sensations, such as pain.The acid-sensing ion channels (ASICs) 4 are a family of proton-gated cation channels expressed in neurons throughout the central and peripheral nervous system (1). There are four ASIC genes (Accn1-4) that produce at least six individual ASIC subunits in rodents (ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3, and ASIC4). ASIC subunits have a characteristic topology with two transmembrane domains separated by a large cysteine-rich extracellular region (2, 3). Three individual ASIC subunits associate to form functional cation channels that are activated by decreases in extracellular pH (4, 5). ASIC currents are typically transient, inactivate even in the continued presence of acidic pH, and (except for ASIC1a) are not substantially permeable to calcium (6). The specific properties of an ASIC current, such as the pH necessary for activation and the kinetics of inactivation, are defined by the subunit composition of the channel (7). In the central nervous system, the ASIC1a subunit plays an important role (8). Genetic disruption or pharmacological inhibition of ASIC1a affects learning and memory, fear-related behaviors, pain, depression, and seizure duration in rodents (9 -15). ASIC1a also contributes to neuronal damage after cerebral ischemia in mice and mediates neuronal death following prolonged acidosis (16 -19). ASIC1a is thought to play a prominent role in neuronal death because it is uniquely permeable to calcium compared with other ASICs (16,20,21).In rodents, the Accn2 gene encodes both ASIC1a and ASIC1b. ASIC1b is a transcript variant expressed...

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Section: Discussionmentioning

confidence: 72%

“…Interestingly, ASIC1b has been implicated in vascular smooth muscle cell physiology (73). Prolonged acidification affects vascular smooth muscles and contributes to baseline blood pressure and vascular disease (74).…”

Section: Discussionmentioning

confidence: 99%

Identification of a Calcium Permeable Human Acid-sensing Ion Channel 1 Transcript Variant

Hoagland

Sherwood

Lee

et al. 2010

Journal of Biological Chemistry

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“…Whole cell currents were recorded using conventional patch-clamp techniques with an Axopatch 200B amplifier (Axon Instruments) interfaced to a PC through Digidata1440A digitizer (Axon Instruments) as previously described (4,5). Data were sampled at 5 kHz and filtered at 1 kHz using a low-pass Bessel filter.…”

Section: Methodsmentioning

confidence: 99%

βENaC is required for whole cell mechanically gated currents in renal vascular smooth muscle cells

Chung

Weissman

Farley

et al. 2013

American Journal of Physiology-Renal Physiology

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Chung WS, Weissman JL, Farley J, Drummond HA. ␤ENaC is required for whole cell mechanically gated currents in renal vascular smooth muscle cells. Am J Physiol Renal Physiol 304: F1428 -F1437, 2013. First published April 3, 2013 doi:10.1152/ajprenal.00444.2012.-Myogenic constrictor responses in small renal arteries and afferent arterioles are suppressed in mice with reduced levels of ␤-epithelial Na ϩ channel (␤ENaC m/m ). The underlying mechanism is unclear. Decreased activity of voltage-gated calcium channels (VGCC) or mechanically gated ion channels and increased activity of large conductance calcium-activated potassium (BK) channels are a few possible mechanisms. The purpose of this study was to determine if VGCC, BK, or mechanically gated ion channel activity was altered in renal vascular smooth muscle cell (VSMC) from ␤ENaC m/m mice. To address this, we used whole cell patch-clamp electrophysiological approaches in freshly isolated renal VSMCs. Compared with ␤ENaC ϩ/ϩ controls, the current-voltage relationships for VGCC and BK activity are similar in ␤ENaC m/m mice. These findings suggest neither VGCC nor BK channel dysfunction accounts for reduced myogenic constriction in ␤ENaC m/m mice. We then examined mechanically gated currents using a novel in vitro assay where VSMCs are mechanically activated by stretching an underlying elastomer. We found the mechanically gated currents, predominantly carried by Na ϩ , are observed with less frequency (87 vs. 43%) and have smaller magnitude (Ϫ54.1 Ϯ 12.5 vs. Ϫ20.9 Ϯ 4.9 pA) in renal VSMCs from ␤ENaC m/m mice. Residual currents are expected in this model since VSMC ␤ENaC expression is reduced by 50%. These findings suggest ␤ENaC is required for normal mechanically gated currents in renal VSMCs and their disruption may account for the reduced myogenic constriction in the ␤ENaC m/m model. Our findings are consistent with the role of ␤ENaC as a VSMC mechanosensor and function of evolutionarily related nematode degenerin proteins.epithelial Na ϩ channel; ion channel; degenerin; myogenic constriction THE MYOGENIC RESPONSE IS AN inherent property of small arteries and arterioles in certain organs, including the kidney. The myogenic response is characterized by vasoconstriction following an increase in intraluminal pressure and vasodilation following a decrease in intraluminal pressure. Myogenic constriction is a physiologically relevant response. In the kidney, it is an important mechanism of renal autoregulation, critical for maintaining normal renal blood flow and glomerular filtration rate with changes in perfusion pressure. Recent studies also suggest myogenic constriction plays an important role in protecting against pressure-related renal injury by preventing transmission of systemic pressure swings to delicate renal microvasculature (28,29,42).There are at least three ion channels that play important roles in the myogenic response; mechanically gated ion channels, voltage-gated calcium channels (VGCC), and large conductance calcium activated potassium (BK) channels...

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“…In a previous study, we showed ASIC-like channels in cerebral VSMCs tend to be electrically silent although the underlying reason is unclear [10]. Recent reports suggest ASIC currents are modulated by oxidationreduction; reducing agents potentiate and oxidizing agents inhibit certain ASIC currents [11][12][13].…”

Section: Introductionmentioning

confidence: 90%

“…Cerebral arteries were dissected from the brain and collected into an ice-cold cell isolation solution containing (in mM) 140 NaCl, 5 KCl, 0.15 CaCl 2 , 1 MgCl 2 , 10 HEPES, and 5.5 D-glucose, pH 7.4. To isolate VSMCs appropriate for evaluating the effect of reducing agents, we modified our previous cell isolation method by replacing papain, which requires the reducing agent DTT for activation, with protease Type XIV [10]. Briefly, cells were first incubated with 1 mg/ml Protease Type XIV (Sigma-Aldrich, St. Louis, MO) and 2 mg/ml Collagenase Type IV (Worthington) for 5 min, followed by 2 mg/ml Collagenase Type IV for 5 min at room temperature.…”

Section: Preparation Of Vsmcsmentioning

confidence: 99%

ASIC-like Currents in Freshly Isolated Cerebral Artery Smooth Muscle Cells are Inhibited by Endogenous Oxidase Activity

Chung

Farley²,

Drummond³

2011

Cell Physiol Biochem

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Background/Aims: The aim of this study was to determine if VSMC ASIC-like currents are regulated by oxidative state. Methods: We used whole-cell patch clamp of isolated mouse cerebral VSMCs to determine if 1) reducing agents, such as DTT and GSH, and 2) inhibition of endogenous oxidase activity from NADPH and Xanthine oxidases potentiate active currents and activate electrically silent currents. Results: Pretreatment with 2 mM DTT or GSH, increased the mean peak amplitude of ASIC-like currents evoked by pH 6.0 from 0.4 ± 0.1 to 14.9 ± 3.6 pA/pF, and from 0.9 ± 0.3 to 11.3 ± 2.4 pA/pF, respectively. Pretreatment with apocynin, a NADPH oxidase inhibitor, mimics the effect of the reducing agents, with the mean peak current amplitude increased from 0.9 ± 0.5 to 7.0 ± 2.6 pA/pF and from 0.5 ± 0.2 to 26.4 ± 6.8 pA/pF by 50 and 200 µM apocynin, respectively. Pretreatment with allopurinol, a xanthine oxidase inhibitor, also potentiates the VSMC ASIC-like activity. Conclusion: These findings suggest that VSMC ASIC-like channels are regulated by oxidative state and may be inhibited by basal endogenous oxidative sources such as NADPH and xanthine oxidase.

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Extracellular acidosis activates ASIC-like channels in freshly isolated cerebral artery smooth muscle cells

Cited by 37 publications

References 30 publications

Identification of a Calcium Permeable Human Acid-sensing Ion Channel 1 Transcript Variant

Identification of a Calcium Permeable Human Acid-sensing Ion Channel 1 Transcript Variant

βENaC is required for whole cell mechanically gated currents in renal vascular smooth muscle cells

ASIC-like Currents in Freshly Isolated Cerebral Artery Smooth Muscle Cells are Inhibited by Endogenous Oxidase Activity

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