Attenuation of apoptosis in enterocytes by blockade of potassium channels

Abstract

Apoptosis plays an important role in maintaining the balance between proliferation and cell loss in the intestinal epithelium. Apoptosis rates may increase in intestinal pathologies such as inflammatory bowel disease and necrotizing enterocolitis, suggesting pharmacological prevention of apoptosis as a therapy for these conditions. Here, we explore the feasibility of this approach using the rat epithelial cell line IEC-6 as a model. On the basis of the known role of K+ efflux in apoptosis in various cell types, we hypothesized that K+ efflux is essential for apoptosis in enterocytes and that pharmacological blockade of this efflux would inhibit apoptosis. By probing intracellular [K+] with the K+-sensitive fluorescent dye and measuring the efflux of 86Rb+, we found that apoptosis-inducing treatment with the proteasome inhibitor MG-132 leads to a twofold increase in K+ efflux from IEC-6 cells. Blockade of K+ efflux with tetraethylammonium, 4-aminopyridine, stromatoxin, chromanol 293B, and the recently described K+ channel inhibitor 48F10 prevents DNA fragmentation, caspase activation, release of cytochrome c from mitochondria, and loss of mitochondrial membrane potential. Thus K+ efflux occurs early in the apoptotic program and is required for the execution of later events. Apoptotic K+ efflux critically depends on activation of p38 MAPK. These results demonstrate for the first time the requirement of K+ channel-mediated K+ efflux for progression of apoptosis in enterocytes and suggest the use of K+ channel blockers to prevent apoptotic cell loss occurring in intestinal pathologies.

Human Lactoferrin Induces Apoptosis-Like Cell Death inCandida albicans: Critical Role of K+-Channel-Mediated K+Efflux

“…It has been previously demonstrated that K ϩ efflux is one of the earliest events of the apoptotic process in metazoan cells and is presumed to be necessary for activation of the biochemical apoptotic pathways (4,8,15,21,41,48). However, a similar role for the intracytoplasmic loss of potassium ions has not been reported in fungi.…”

“…Changes in the mitochondrial transmembrane potential (⌬⌿ m ) have been considered as a hallmark of apoptosis (28). To determine the ability of rhLf to induce mitochondrial depolarization, the ⌬⌿ m was quantified by Rh-123 uptake, using suspensions of cells treated for different periods of time with rhLf (15,30,60,120, and 180 min). As Fig.…”

Channels and Volume Changes in the Life and Death of the Cell

“…The two phases of AVD are accomplished by the same mechanism that includes outward fluxes of K 1 and Cl -moving across specific channels and a decrease in osmolyte intracellular concentration and water outflow resulting in AVD (Kondratskyi et al, 2015). It has yet to be determined whether this decrease in cell volume is a passive factor or an active signal in the induction of apoptosis, but evidence does exist that points to an explicit role for volume decrease in the apoptotic process; blockade of the main osmolyte pathways that reduce AVD impairs the progression of apoptosis (Yu and Choi, 2000;Grishin et al, 2005).…”

Cell shrinkage and monovalent cation fluxes: Role in apoptosis

“…In rat epithelial cells, potassium channels blockers such as TEA, 4-AP, stromatoxin, chromanol 293B, and 48F10 were shown to prevent AVD and apoptosis [28]. Early studies on neuronal cell death also demonstrated the importance of potassium as a key regulator of apoptosis [29][30][31].…”