DCPIB is a novel selective blocker of I_Cl,swell and prevents swelling‐induced shortening of guinea‐pig atrial action potential duration

Abstract

1. We identified the ethacrynic-acid derivative DCPIB as a potent inhibitor of I(Cl,swell), which blocks native I(Cl,swell) of calf bovine pulmonary artery endothelial (CPAE) cells with an IC(50) of 4.1 microM. Similarly, 10 microM DCPIB almost completely inhibited the swelling-induced chloride conductance in Xenopus oocytes and in guinea-pig atrial cardiomyocytes. Block of I(Cl,swell) by DCPIB was fully reversible and voltage independent. 2. DCPIB (10 microM) showed selectivity for I(Cl,swell) and had no significant inhibitory effects on I(Cl,Ca) in CPAE cells, on chloride currents elicited by several members of the CLC-chloride channel family or on the human cystic fibrosis transmembrane conductance regulator (hCFTR) after heterologous expression in Xenopus oocytes. DCPIB (10 microM) also showed no significant inhibition of several native anion and cation currents of guinea pig heart like I(Cl,PKA), I(Kr), I(Ks), I(K1), I(Na) and I(Ca). 3. In all atrial cardiomyocytes (n=7), osmotic swelling produced an increase in chloride current and a strong shortening of the action potential duration (APD). Both swelling-induced chloride conductance and AP shortening were inhibited by treatment of swollen cells with DCPIB (10 microM). In agreement with the selectivity for I(Cl,swell), DCPIB did not affect atrial APD under isoosmotic conditions. 4. Preincubation of atrial cardiomyocytes with DCPIB (10 microM) completely prevented both the swelling-induced chloride currents and the AP shortening but not the hypotonic cell swelling. 5. We conclude that swelling-induced AP shortening in isolated atrial cells is mainly caused by activation of I(Cl,swell). DCPIB therefore is a valuable pharmacological tool to study the role of I(Cl,swell) in cardiac excitability under pathophysiological conditions leading to cell swelling.

A fluid secretion pathway unmasked by acinar-specific Tmem16A gene ablation in the adult mouse salivary gland

“…5E). The blocked fractions of IPR-and hypotonic shock-induced macroscopic currents by DCPIB differ from those of VRAC-mediated currents reported in other cell types, which are almost fully blocked by DCPIB (23,24). The contribution of other ion channels that are insensitive to DCPIB cannot be ruled out; indeed, this possibility is supported by the finding that DCPIB dramatically inhibited IPR-induced ex vivo saliva secretion.…”

DCPIB, a specific inhibitor of volume regulated anion channels (VRACs), reduces infarct size in MCAo and the release of glutamate in the ischemic cortical penumbra

“…It reverses cell swelling-induced action potential duration shortening in atrial myocytes and inhibits astroglial swelling in vitro (Abdullaev et al, 2006;Bourke et al, 1981;Best et al, 2004). DCPIB has been shown to be a specific antagonist of volume regulated anion channels (VRAC) using cell expression systems where it was shown not to have any effect on a variety of expressed Cl − channels , but to be a very effective inhibitor of VRAC activity in swollen cells (Decher et al, 2001). This does not exclude other possible effects that could lead to the observed reduction in infarct volumes and the modestly improved behavioral scores, but there are currently no reports of any other effects of DCPIB expected to give such results.…”

“…Synthesis of these compounds was guided by the principle of increasing their efficacy in inhibiting brain edema and reducing their renal saludiuretic effects (Nelson et al, 1979;Kimelberg et al, 1987;Kimelberg et al, 1990;Bourke et al, 1979;Cragoe et al, 1982;Cragoe, Jr. et al, 1986;Cragoe, 1987). Since that time one of these compounds 4-(2-butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid and therefore given the acronym DCPIB Bourke et al, 1981;Nelson et al, 1982); and see Figure 1a), has been shown to specifically inhibit VRAC activity, but not a number of expressed chloride channels in Xenopus oocytes (Decher et al, 2001). VRACs are an important class of anion channels that are widely distributed, but whose molecular identity has so far eluded investigators' best efforts (Nilius and Droogmans, 2003;Strange, 1998;Okada, 1997).…”

Disruption of ionic and cell volume homeostasis in cerebral ischemia: The perfect storm

“…Other VRAC blockers include 1,9-dideoxyforskolin, niflumic acid, calaxarenes, and phloretin [23,24]. The most selective VRAC inhibitor identified so far is the ethacrynic-acid derivative DCPIB (IC 50 =4 μM) [63]. At the concentrations of 10-20 μM, DCPIB nearly completely blocks Cl − currents via VRAC, but does not affect other Cl − channels (CFTR, Ca 2+ -activated Cl − channels, and ClC-1, −2, −4, and −5), nor voltage gated K + , Na + and Ca 2+ channels [63].…”

“…The most selective VRAC inhibitor identified so far is the ethacrynic-acid derivative DCPIB (IC 50 =4 μM) [63]. At the concentrations of 10-20 μM, DCPIB nearly completely blocks Cl − currents via VRAC, but does not affect other Cl − channels (CFTR, Ca 2+ -activated Cl − channels, and ClC-1, −2, −4, and −5), nor voltage gated K + , Na + and Ca 2+ channels [63]. Importantly, DCPIB potently blocks swelling-activated glutamate release from cultured astroglial cells [64].…”