The inhibitor of volume‐regulated anion channels DCPIB activates TREK potassium channels in cultured astrocytes

Abstract

Background and PurposeThe ethacrynic acid derivative, 4‐(2‐butyl‐6,7‐dichlor‐2‐cyclopentylindan‐1‐on‐5‐yl) oxobutyric acid (DCPIB) is considered to be a specific and potent inhibitor of volume‐regulated anion channels (VRACs). In the CNS, DCPIB was shown to be neuroprotective through mechanisms principally associated to its action on VRACs. We hypothesized that DCPIB could also regulate the activity of other astroglial channels involved in cell volume homeostasis.Experimental ApproachExperiments were performed in rat cortical astrocytes in primary culture and in hippocampal astrocytes in situ. The effect of DCPIB was evaluated by patch‐clamp electrophysiology and immunocytochemical techniques. Results were verified by comparative analysis with recombinant channels expressed in COS‐7 cells.Key ResultsIn cultured astrocytes, DCPIB promoted the activation of a K+ conductance mediated by two‐pore‐domain K+ (K2P) channels. The DCPIB effect occluded that of arachidonic acid, which activates K2P channels K2P 2.1 (TREK‐1) and K2P 10.1 (TREK‐2) in cultured astrocytes. Immunocytochemical analysis suggests that cultured astrocytes express K2P 2.1 and K2P 10.1 proteins. Moreover, DCPIB opened recombinant K2P 2.1 and K2P 10.1 expressed in heterologous system. In brain slices, DCPIB did not augment the large background K+ conductance in hippocampal astrocytes, but caused an increment in basal K+ current of neurons.Conclusion and ImplicationsOur results indicate that the neuroprotective effect of DCPIB could be due, at least in part, to activation of TREK channels. DCPIB could be used as template to build new pharmacological tools able to increase background K+ conductance in astroglia and neuronal cells.

Volume-regulated anion channel—a frenemy within the brain

“…Although not anticipated, these effects certainly follow the pattern of cross-inhibition of VRAC and astrocytic connexin hemichannels with numerous “VRAC” and “connexin” blockers, such as NPPB, tamoxifen, carbenoxolone, and others [21, 213]. Even more peculiar, DCPIB was found to enhance the activity of the two-pore domain K + channels TREK-1 and TREK-2, in their native environment and after recombinant expression [128]. The effects of DCPIB on glutamate release via connexins and activation of K + channels will have to be taken into consideration while interpreting effects of DCPIB on cellular and tissue functions and stroke outcomes.…”

Characterization of Human Dermal Fibroblasts in Fabry Disease

“…The reversal potential of the hypotonicity‐activated current derived by the membrane potential value of the intercept between control and the current activated upon hypotonic challenge was at ∼0 mV, strongly suggesting that hypotonicity activated a Cl − current. To corroborate this view application of DCPIB (10 μM), a selective inhibitor of VRAC (Bourke et al, ; Decher et al, ; Minieri et al, ) caused a strong decrease of the hypotonicity‐induced currents in both cell types. Quantitative analysis indicates that both the increase in current magnitude and the pharmacologic inhibition by DCPIB were significant at negative (Fig.…”

Two-pore Domain Potassium Channels in Astrocytes

“…Furthermore, K 2P channels play critical roles in the induction of passive conductance, in glutamate release, and in neuroprotection from hypoxia. Recently, the K 2P channels have been reported to be involved in hippocampal epilepsy and cellular volume regulation [118119120121122]. These findings suggest that the K 2P channels can be new therapeutic targets for treatment of neurodegenerative and psychiatric diseases in astrocytes.…”