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Activation of volume-sensitive outwardly rectifying chloride channel by ROS contributes to ER stress and cardiac contractile dysfunction: involvement of CHOP through Wnt.

Shen M, Wang L, Wang B, Wang T, Yang G, Shen L, Wang T, Guo X, Liu Y, Xia Y, Jia L, Wang X - Cell Death Dis (2014)

Bottom Line: Tunicamycin activates volume-sensitive outward rectifying Cl(-) currents.Blockade of the volume-sensitive outwardly rectifying (VSOR) Cl(-) channel by 4,4'-diisothiocya-natostilbene-2,2'-disulfonic acid (DIDS), a non-selective Cl(-) channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl) oxybutyric acid (DCPIB), a selective VSOR Cl(-) channel blocker, improves cardiac contractility, which correlates with suppressed ER stress through inhibiting the canonical GRP78/eIF2α/ATF4 and XBP1 pathways, and promotes survival of cardiomyocytes by inverting tunicamycin-induced decrease of Wnt through the CHOP pathway.VSOR activation of tunicamycin-treated cardiomyocytes is attributed to increased intracellular levels of reactive oxygen species (ROS).

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, China [2] Department of Cardiology, Hainan Branch of PLA General Hospital, Sanya, China.

ABSTRACT
Endoplasmic reticulum (ER) stress occurring in stringent conditions is critically involved in cardiomyocytes apoptosis and cardiac contractile dysfunction (CCD). However, the molecular machinery that mediates cardiac ER stress and subsequent cell death remains to be fully deciphered, which will hopefully provide novel therapeutic targets for these disorders. Here, we establish tunicamycin-induced model of cardiomyocyte ER stress, which effectively mimicks pathological stimuli to trigger CCD. Tunicamycin activates volume-sensitive outward rectifying Cl(-) currents. Blockade of the volume-sensitive outwardly rectifying (VSOR) Cl(-) channel by 4,4'-diisothiocya-natostilbene-2,2'-disulfonic acid (DIDS), a non-selective Cl(-) channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl) oxybutyric acid (DCPIB), a selective VSOR Cl(-) channel blocker, improves cardiac contractility, which correlates with suppressed ER stress through inhibiting the canonical GRP78/eIF2α/ATF4 and XBP1 pathways, and promotes survival of cardiomyocytes by inverting tunicamycin-induced decrease of Wnt through the CHOP pathway. VSOR activation of tunicamycin-treated cardiomyocytes is attributed to increased intracellular levels of reactive oxygen species (ROS). Our study demonstrates a pivotal role of ROS/VSOR in mediating ER stress and functional impairment of cardiomyocytes via the CHOP-Wnt pathway, and suggests the therapeutic values of VSOR Cl(-) channel blockers against ER stress-associated cardiac anomalies.

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ROS induce VSOR Cl− currents in cardiomyocytes. (a) Background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting phenotypic properties of ICl,Vol (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DIDS (500 μM); n=5 for each group. (b) Corresponding current-voltage (I-V) relationship for the mean current densities of isosmotic (▴), H2O2 (▪) and H2O2 with DIDS (●) conditions. (c) Current densities at +100 mV from B. *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5. (d) Negligible background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting representative properties of VSOR Cl− currents (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DCPIB (10 μM). n=5 for each group. (e) Corresponding current-voltage (I-V) relationship for the mean current densities of Ctrl (▴), Tm (▪) and Tm with DIDS (●) conditions. (f) Current densities at +100 mV from (e). *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5
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fig6: ROS induce VSOR Cl− currents in cardiomyocytes. (a) Background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting phenotypic properties of ICl,Vol (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DIDS (500 μM); n=5 for each group. (b) Corresponding current-voltage (I-V) relationship for the mean current densities of isosmotic (▴), H2O2 (▪) and H2O2 with DIDS (●) conditions. (c) Current densities at +100 mV from B. *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5. (d) Negligible background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting representative properties of VSOR Cl− currents (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DCPIB (10 μM). n=5 for each group. (e) Corresponding current-voltage (I-V) relationship for the mean current densities of Ctrl (▴), Tm (▪) and Tm with DIDS (●) conditions. (f) Current densities at +100 mV from (e). *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5

Mentions: Next, we explored whether ROS mediate VSOR Cl− currents in tunicamycin-exposed cardiomyocytes. Hydrogen peroxide (H2O2) and ROS scavenger NAC were used to mimic ROS and block ROS production in cardiomyocytes, respectively. Extracellular application of H2O2 (500 μM, 7–10 min) directly elicited VSOR Cl− currents, which could be inhibited by DIDS (500 μM, 5–7 min, 77.49±3.11%, n=5, P<0.05) and DCPIB (10 μM, 6-7 min, 88.74±4.86%, n=5, P<0.05) (Figure 6). In addition, tunicamycin-induced activation of VSOR Cl− currents was almost completely abolished through scavenging ROS with NAC (10 mM, 5–10 min, 99.07±5.86% n=5, P<0.05) (Figure 7). Therefore, ROS production is pivotally involved in VSOR Cl− channel activation.


Activation of volume-sensitive outwardly rectifying chloride channel by ROS contributes to ER stress and cardiac contractile dysfunction: involvement of CHOP through Wnt.

Shen M, Wang L, Wang B, Wang T, Yang G, Shen L, Wang T, Guo X, Liu Y, Xia Y, Jia L, Wang X - Cell Death Dis (2014)

ROS induce VSOR Cl− currents in cardiomyocytes. (a) Background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting phenotypic properties of ICl,Vol (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DIDS (500 μM); n=5 for each group. (b) Corresponding current-voltage (I-V) relationship for the mean current densities of isosmotic (▴), H2O2 (▪) and H2O2 with DIDS (●) conditions. (c) Current densities at +100 mV from B. *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5. (d) Negligible background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting representative properties of VSOR Cl− currents (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DCPIB (10 μM). n=5 for each group. (e) Corresponding current-voltage (I-V) relationship for the mean current densities of Ctrl (▴), Tm (▪) and Tm with DIDS (●) conditions. (f) Current densities at +100 mV from (e). *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5
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fig6: ROS induce VSOR Cl− currents in cardiomyocytes. (a) Background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting phenotypic properties of ICl,Vol (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DIDS (500 μM); n=5 for each group. (b) Corresponding current-voltage (I-V) relationship for the mean current densities of isosmotic (▴), H2O2 (▪) and H2O2 with DIDS (●) conditions. (c) Current densities at +100 mV from B. *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5. (d) Negligible background Cl− currents recorded under isosmotic solution (Ctrl). H2O2 (500 μM)-induced Cl− currents exhibiting representative properties of VSOR Cl− currents (H2O2). H2O2-induced VSOR Cl− currents were inhibited by adding DCPIB (10 μM). n=5 for each group. (e) Corresponding current-voltage (I-V) relationship for the mean current densities of Ctrl (▴), Tm (▪) and Tm with DIDS (●) conditions. (f) Current densities at +100 mV from (e). *P<0.05 versus Ctrl; **P<0.05 versus H2O2, n=5
Mentions: Next, we explored whether ROS mediate VSOR Cl− currents in tunicamycin-exposed cardiomyocytes. Hydrogen peroxide (H2O2) and ROS scavenger NAC were used to mimic ROS and block ROS production in cardiomyocytes, respectively. Extracellular application of H2O2 (500 μM, 7–10 min) directly elicited VSOR Cl− currents, which could be inhibited by DIDS (500 μM, 5–7 min, 77.49±3.11%, n=5, P<0.05) and DCPIB (10 μM, 6-7 min, 88.74±4.86%, n=5, P<0.05) (Figure 6). In addition, tunicamycin-induced activation of VSOR Cl− currents was almost completely abolished through scavenging ROS with NAC (10 mM, 5–10 min, 99.07±5.86% n=5, P<0.05) (Figure 7). Therefore, ROS production is pivotally involved in VSOR Cl− channel activation.

Bottom Line: Tunicamycin activates volume-sensitive outward rectifying Cl(-) currents.Blockade of the volume-sensitive outwardly rectifying (VSOR) Cl(-) channel by 4,4'-diisothiocya-natostilbene-2,2'-disulfonic acid (DIDS), a non-selective Cl(-) channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl) oxybutyric acid (DCPIB), a selective VSOR Cl(-) channel blocker, improves cardiac contractility, which correlates with suppressed ER stress through inhibiting the canonical GRP78/eIF2α/ATF4 and XBP1 pathways, and promotes survival of cardiomyocytes by inverting tunicamycin-induced decrease of Wnt through the CHOP pathway.VSOR activation of tunicamycin-treated cardiomyocytes is attributed to increased intracellular levels of reactive oxygen species (ROS).

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, China [2] Department of Cardiology, Hainan Branch of PLA General Hospital, Sanya, China.

ABSTRACT
Endoplasmic reticulum (ER) stress occurring in stringent conditions is critically involved in cardiomyocytes apoptosis and cardiac contractile dysfunction (CCD). However, the molecular machinery that mediates cardiac ER stress and subsequent cell death remains to be fully deciphered, which will hopefully provide novel therapeutic targets for these disorders. Here, we establish tunicamycin-induced model of cardiomyocyte ER stress, which effectively mimicks pathological stimuli to trigger CCD. Tunicamycin activates volume-sensitive outward rectifying Cl(-) currents. Blockade of the volume-sensitive outwardly rectifying (VSOR) Cl(-) channel by 4,4'-diisothiocya-natostilbene-2,2'-disulfonic acid (DIDS), a non-selective Cl(-) channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl) oxybutyric acid (DCPIB), a selective VSOR Cl(-) channel blocker, improves cardiac contractility, which correlates with suppressed ER stress through inhibiting the canonical GRP78/eIF2α/ATF4 and XBP1 pathways, and promotes survival of cardiomyocytes by inverting tunicamycin-induced decrease of Wnt through the CHOP pathway. VSOR activation of tunicamycin-treated cardiomyocytes is attributed to increased intracellular levels of reactive oxygen species (ROS). Our study demonstrates a pivotal role of ROS/VSOR in mediating ER stress and functional impairment of cardiomyocytes via the CHOP-Wnt pathway, and suggests the therapeutic values of VSOR Cl(-) channel blockers against ER stress-associated cardiac anomalies.

Show MeSH
Related in: MedlinePlus