Inhibition of Kv channel expression by NSAIDs depolarizes membrane potential and inhibits cell migration by disrupting calpain signaling

Kristopher Silver,Alaina Littlejohn,Laurel Thomas,Elizabeth Marsh,James D Lillich

doi:10.1016/j.bcp.2015.10.017

Kristopher Silver, Alaina Littlejohn + Show 3 more

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https://doi.org/10.1016/j.bcp.2015.10.017

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Journal: Biochemical Pharmacology	Publication Date: Nov 7, 2015
Citations: 13	License type: cc-by

Affiliation: Kansas State University

Abstract

Clinical use of non-steroidal anti-inflammatory drugs (NSAIDs) is well known to cause gastrointestinal ulcer formation via several mechanisms that include inhibiting epithelial cell migration and mucosal restitution. The drug-affected signaling pathways that contribute to inhibition of migration by NSAIDs are poorly understood, though previous studies have shown that NSAIDs depolarize membrane potential and suppress expression of calpain proteases and voltage-gated potassium (Kv) channel subunits. Kv channels play significant roles in cell migration and are targets of NSAID activity in white blood cells, but the specific functional effects of NSAID-induced changes in Kv channel expression, particularly on cell migration, are unknown in intestinal epithelial cells. Accordingly, we investigated the effects of NSAIDs on expression of Kv1.3, 1.4, and 1.6 in vitro and/or in vivo and evaluated the functional significance of loss of Kv subunit expression. Indomethacin or NS-398 reduced total and plasma membrane protein expression of Kv1.3 in cultured intestinal epithelial cells (IEC-6). Additionally, depolarization of membrane potential with margatoxin (MgTx), 40mM K+, or silencing of Kv channel expression with siRNA significantly reduced IEC-6 cell migration and disrupted calpain activity. Furthermore, in rat small intestinal epithelia, indomethacin and NS-398 had significant, yet distinct, effects on gene and protein expression of Kv1.3, 1.4, or 1.6, suggesting that these may be clinically relevant targets. Our results show that inhibition of epithelial cell migration by NSAIDs is associated with decreased expression of Kv channel subunits, and provide a mechanism through which NSAIDs inhibit cell migration and may contribute to NSAID-induced gastrointestinal (GI) toxicity.

Highlights

non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used for their analgesic, anti-inflammatory, and anti-pyretic activities
Previous studies have shown that NSAIDs with ulcerogenic potential inhibit cell migration in cultured IEC-6 cells through several mechanisms, including depolarization of Em, disruption of calpain signaling pathways, and inhibition of growth factor expression [15,27,28]
NSAIDs suppressed the total expression of Kv1.4 and the surface expression of Kv1.4 and Kv1.6 channels, an effect which is consistent with depolarization of Em [18]

Summary

Introduction

NSAIDs are commonly used for their analgesic, anti-inflammatory, and anti-pyretic activities. Use of NSAIDs is associated with a suite of negative, off-target effects, including cardiovascular, renal, and gastrointestinal (GI) toxicity [1,2]. Whereas there is little doubt that NSAIDs inhibit COX activity and suppress prostaglandin (PG) production, there is significant evidence that COX-independent mechanisms are involved in inducing GI toxicity [5,10]. Other mechanisms that have been proposed to contribute to NSAID-induced GI toxicity include altering intestinal microflora, interfering with neutrophil recruitment, uncoupling of oxidative phosphorylation, decreasing rates of apoptosis, depolarizing membrane potential, and inhibiting cell migration or epithelial restitution [11,12,13,14,15,16,17,18]

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