TRPV4 blockade alleviates endoplasmic reticulum stress mediated apoptosis in hypoxia-induced cardiomyocyte injury.

BACKGROUND: Hypoxia-induced myocardial injury remains to be a huge health issue worldwide. Transient receptor potential vanilloid 4 (TRPV4) is a high-flux Ca2+ channel that is involved in numerous cardiovascular diseases. However, the role of TRPV4 in myocardial hypoxic injury remains unclear. Accordingly, this study aimed to investigate the antiapoptotic activity of TRPV4 inhibition and elucidate the underlying mechanisms in myocardial hypoxic injury. METHODS: The ability of TRPV4 to modulate the endoplasmic reticulum stress (ERS) and apoptosis was assessed in vitro through the administration of the TRPV4 antagonist HC-067047 or the agonist GSK1016790A. Additionally, intracellular Ca2+ concentration was measured by Fluo-4 AM. RESULTS: TRPV4 expression was significantly upregulated in hypoxic H9c2 cells compared with that in normoxic cardiomyocytes, accompanied with increased intracellular Ca2+ levels. Conversely, TRPV4 inhibition alleviated ERS in hypoxic H9c2 cells and prevented apoptosis, whereas TRPV4 agonist exacerbated such events. Furthermore, H9c2 cell apoptosis was attenuated with the administration of 4-PBA, an ERS inhibitor. CONCLUSION: TRPV4 inhibition alleviates hypoxia-induced H9c2 cell apoptosis by mitigating ERS.

MiRNA-620 promotes TGF-ß1-induced proliferation of airway smooth muscle cell through controlling PTEN/AKT signaling pathway.

Asthma is an inflammatory syndrome characterized by airway hyperresponsiveness, bronchial inflammation, and airway remodeling. The hypertrophy and hyperplasia of airway smooth muscle cells (ASMCs) are hallmarks of bronchial remodeling in asthma. In this study, the regulatory effects of microRNA-620 (miR-620) on ASMC proliferation and apoptosis in response to transforming growth factor ß1 (TGF-ß1) stimulation was investigated. The expression of miR-620 was significantly upregulated in TGF-ß1-treated ASMCs compared with vehicle-treated cells. Downregulation of miR-620 suppressed the proliferation and increased apoptosis in TGF-ß1-stimulated ASMCs. Phosphatase and tensin homolog (PTEN) was predicted and confirmed as a downstream target of miR-620. PTEN was upregulated in miR-620-inhibitor transfected ASMCs, but decreased in cells delivered with miR-620 mimics. Moreover, knocking down miR-620 alone efficiently reduced the phosphorylation of protein kinase B (AKT), decreased TGF-ß1-induced proliferation and promoted apoptosis in ASMCs, whereas downregulation of PTEN in miR-620 inhibitor-transfected cells restored the activation of AKT, increased TGF-ß1-triggered proliferation, and partially inhibited ASMC apoptosis. Taken together, the present study provided evidence that miR-620 increased TGF-ß1-mediated proliferation and suppressed apoptosis in ASMCs via the regulation of PTEN and AKT expression. These findings suggest that miR-620/PTEN/AKT axis may be considered as a therapeutic target for asthma treatment.

Dual isoflurane-induced preconditioning improves neuroprotection in rat brain in vitro and the role of extracellular signal--regulated protein kinase.

OBJECTIVE: To test the ability of isoflurane-induced preconditioning against oxygen and glucose deprivation (OGD) injury in vitro. METHODS: Rat hippocampal slices were exposed to 1 volume percentage (vol%), 2vol% or 3vol% isoflurane respectively for 20 minutes under normoxic conditions (95% O2/5% CO2) once or twice (12 slices in each group) before OGD, with 15-minute washout after each exposure. During OGD experiments, hippocampus slices were bathed with artificial cerebrospinal fluid (ACSF) lacking glucose and perfused with 95% N2 and 5% CO2 for 14 minutes, followed by a 30-minute reperfusion in normal ACSF. The CA1 population spike (PS) was measured and used to quantify the degree of neuronal function recovery after OGD. To assess the role of mitogen-activated protein kinases (MAPKs) in isoflurane preconditioning, U0126, an inhibitor of extracellular signal-regulated protein kinase (ERK1/2), and SB203580, an inhibitor of p38 MAPK, were used before two periods of 3vol% isoflurane exposure. RESULTS: The degree of neuronal function recovery of hippocampal slices exposed to 1vol%, 2vol%, or 3vol% isoflurane once was 41.88%±9.23%, 55.05% ± 11.02%, or 63.18% ± 10.82% respectively. Moreover, neuronal function recovery of hippocampal slices exposed to 1vol%, 2vol%, or 3vol% isoflurane twice was 53.75% ± 12.04%, 63.50% ± 11.06%, or 76.25% ± 12.25%, respectively. Isoflurane preconditioning increased the neuronal function recovery in a dose-dependent manner. U0126 blocked the preconditioning induced by dual exposure to 3vol% isoflurane (6.13% ± 1.56%, P < 0.01) and ERK1/2 activities. CONCLUSIONS: Isoflurane is capable of inducing preconditioning in hippocampal slices in vitro in a dose-dependent manner, and dual exposure to isoflurane with a lower concentration is more effective in triggering preconditioning than a single exposure. Isoflurane-induced neuroprotection might be involved with ERK1/2 activities.

Duplicate preconditioning with sevoflurane in vitro improves neuroprotection in rat brain via activating the extracellular signal-regulated protein kinase.

OBJECTIVE: Sevoflurane preconditioning has been demonstrated to reduce cerebral ischemia-reperfusion (IR) injury, but the underlying mechanisms have not been fully elucidated. Besides, different protocols would usually lead to different results. The objective of this study was to determine whether dual exposure to sevoflurane improves the effect of anesthetic preconditioning against oxygen and glucose deprivation (OGD) injury in vitro. METHODS: Rat hippocampal slices under normoxic conditions (95% O2/5% CO2) were pre-exposed to sevoflurane 1, 2 and 3 minimum alveolar concentration (MAC) for 30 min, once or twice, with 15-min washout after each exposure. The slices were then subjected to 13-min OGD treatment (95% N2/5% CO2, glucose-free), followed by 30-min reoxygenation. The population spikes (PSs) were recorded in the CA1 region of rat hippocampus. The percentage of PS amplitude at the end of 30-min reoxygenation to that before OGD treatment was calculated, since it could indicate the recovery degree of neuronal function. In addition, to assess the role of mitogen-activated protein kinases (MAPKs) in preconditioning, U0126, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2, ERK1/2 MAPK), and SB203580, an inhibitor of p38 MAPK, were separately added 10 min before sevoflurane exposure. RESULTS: Preconditioning once with sevoflurane 1, 2, and 3 MAC increased the percentage of PS amplitude at the end of 30-min reoxygenation to that before OGD treatment, from (15.13+/-3.79)% (control) to (31.88+/-5.36)%, (44.00+/-5.01)%, and (49.50+/-6.25)%, respectively, and twice preconditioning with sevoflurane 1, 2, and 3 MAC increased the percentage to (38.53+/-4.36)%, (50.74+/-7.05)% and (55.86+/-6.23)%, respectively. The effect of duplicate preconditioning with sevoflurane 3 MAC was blocked by U0126 [(16.23+/-4.62)%]. CONCLUSION: Sevoflurane preconditioning can induce neuroprotection against OGD injury in vitro, and preconditioning twice enhances this effect. Besides, the activation of extracellular signal-regulated protein kinase (MEK-ERK1/2, ERK1/2 MAPK) may be involved in this process.