Activation of K(+) current plays a critical role in the control of programmed cell death. In the present study, whole-cell patch-clamp recording, a caspase-3 activity assay, and flow cytometric analysis were used to examine the effects of the MT2 melatonin receptor agonist 2-iodomelatonin on the delayed-rectifier K(+) current (IK) and the prevention of apoptosis. It was found that apoptosis of cerebellar granular neurons induced by low-K(+) (5 mm) incubation was associated with an increase in IK amplitude and caspase-3 activity. After 6 hr of low-K(+) treatment, IK was increased by 45% (n = 86). Flow cytometry showed that the apoptosis rate increased by 333% compared with the control neurons. In addition, exposure of cultured granule cells to low K(+) also resulted in a significant activation of caspase-3, by 466%. 2-Iodomelatonin (10 microm in injection pipette) inhibited the IK amplitude recorded from control cells and from cells undergoing apoptosis. However, 2-iodomelatonin only modified the IK-channel activation kinetics of cells under both conditions. Furthermore, 2-iodomelatonin reduced the rate of apoptosis and caspase-3 activation, by 66 and 64%, respectively. The melatonin receptor antagonist, 4P-PDOT, abrogated the effect of 2-iodomelatonin on the IK augmentation, caspase-3 activity, and apoptosis. These results suggest that the neuroprotective effects of melatonin are not only because of its function as a powerful antioxidant, but also to its interactions with specific receptors. The effect of 2-iodomelatonin against apoptosis may be mediated by activating a melatonin receptor, which modulates IK channels and reduces K(+) efflux.

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

BACKGROUND AND PURPOSEThe molecular identity of calcium-activated chloride channels (CaCCs) in vascular endothelial cells remains unknown. This study sought to identify whether anoctamin-1 (Ano1, also known as TMEM16A) functions as a CaCC and whether hypoxia alters the biophysical properties of Ano1 in mouse cardiac vascular endothelial cells (CVECs).EXPERIMENTAL APPROACHWestern blot, quantitative real-time PCR, confocal imaging analysis and patch-clamp analysis combined with pharmacological approaches were used to determine whether Ano1 was expressed and functioned as CaCC in CVECs.KEY RESULTSAno1 was expressed in CVECs. The biophysical properties of the current generated in the CVECs, including the Ca2+ and voltage dependence, outward rectification, anion selectivity and the pharmacological profile, are similar to those described for CaCCs. The density of ICl(Ca) detected in CVECs was significantly inhibited by T16Ainh-A01, an Ano1 inhibitor, and a pore-targeting, specific anti-Ano1 antibody, and was markedly decreased in Ano1 gene knockdown CVECs. The density of ICl(Ca) was significantly potentiated in CVECs exposed to hypoxia, and this hypoxia-induced increase in the density of ICl(Ca) was inhibited by T16Ainh-A01 or anti-Ano1 antibody. Hypoxia also increased the current density of ICl(Ca) in Ano1 gene knockdown CVECs.CONCLUSIONS AND IMPLICATIONSAno1 formed CaCC in CVECs of neonatal mice. Hypoxia enhances Ano1-mediated ICl(Ca) density via increasing its expression, altering the ratio of its splicing variants, sensitivity to membrane voltage and to Ca2+. Ano1 may play a role in the pathophysiological processes during ischaemia in heart, and therefore, Ano1 might be a potential therapeutic target to prevent ischaemic damage.

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Abstract. Recent studies have implicated the acid-sensing ion channel 1 (ASIC1), a proton-gated cation channel that belongs to the epithelial sodium channel (ENaC)/Degenerin family, plays an important role in glioma cell migration. Among the ASIC subunits, only ASIC1a has been found be calcium permeable. However, it has not been determined whether Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) regulates ASIC1 in glioblastoma multiforme (GBM). Herein, we report that ASIC1 and CaMKII assemble to form a functional complex at the plasma membrane of GBM cells. We found that migration ability was significantly attenuated in GBM cells that were pre-treated with autocamtide-2-related inhibitory peptide (AIP), a CaMKII-specific inhibitor, or psalmotoxin 1 (PcTX-1), a selective ASIC1 blocker. Furthermore, the inhibitory effect of AIP or PcTX-1 on migration was diminished when ASIC1 was knocked down in GBM cells; when ASIC1 knockdown GBM cells were concurrently treated with these two inhibitors, cell migration was slightly but significantly decreased. Using whole-cell patch-clamp recordings, we detected an amiloride-sensitive current in GBM cells, and this current was significantly inhibited by both PcTX-1 and AIP. Moreover, the magnitude of this current was dramatically decreased when ASIC1 was knocked down in GBM cells. The addition of AIP failed to further decrease the amplitude of this current. Taken together, these data suggest that ASIC1 and CaMKII form a functional complex in GBM cells. Furthermore, it can be concluded that CaMKII regulates the activity of ASIC1, which is associated with the ability of GBM cells to migrate.