The K+ Channel KCa3.1 as a Novel Target for Idiopathic Pulmonary Fibrosis

Abstract

BackgroundIdiopathic pulmonary fibrosis (IPF) is a common, progressive and invariably lethal interstitial lung disease with no effective therapy. We hypothesised that KCa3.1 K+ channel-dependent cell processes contribute to IPF pathophysiology. MethodsKCa3.1 expression in primary human lung myofibroblasts was examined using RT-PCR, western blot, immunofluorescence and patch-clamp electrophysiology. The role of KCa3.1 channels in myofibroblast proliferation, wound healing, collagen secretion and contraction was examined using two specific and distinct KCa3.1 blockers (TRAM-34 and ICA-17043 [Senicapoc]). ResultsBoth healthy non fibrotic control and IPF-derived human lung myofibroblasts expressed KCa3.1 channel mRNA and protein. KCa3.1 ion currents were elicited more frequently and were larger in IPF-derived myofibroblasts compared to controls. KCa3.1 currents were increased in myofibroblasts by TGFβ1 and basic FGF. KCa3.1 was expressed strongly in IPF tissue. KCa3.1 pharmacological blockade attenuated human myofibroblast proliferation, wound healing, collagen secretion and contractility in vitro, and this was associated with inhibition of TGFβ1-dependent increases in intracellular free Ca2+.ConclusionsKCa3.1 activity promotes pro-fibrotic human lung myofibroblast function. Blocking KCa3.1 may offer a novel approach to treating IPF with the potential for rapid translation to the clinic.

Ca2+ signalling in fibroblasts and the therapeutic potential of KCa3.1 channel blockers in fibrotic diseases

“…Ca 2+ -activated K + channels BK Ca , IK CA /K Ca 3.1, SK Ca Human lung fibroblasts (Roach et al, 2013) Human cardiac fibroblasts (Wang et al, 2006) Renal interstitial fibroblasts (Huang, Shen, et al, 2014) Hepatic stellate cells (Freise et al, 2015) Voltage-gated Na + channels INa.TTX, INa.TTXR, INa.TTXR Na V 1.2, Na V 1.9…”

“…Human cardiac fibroblasts (Chatelier et al, 2012;Koivumaki et al, 2014;Li et al, 2009;Zhan et al, 2016) Voltage-gated K + channels Transient outward K + current, I to Delayed rectified K + currents: I K , I Kf Human and rat cardiac fibroblast Rook et al, 1992; Neonatal rat cardiac fibroblasts (Rook et al, 1992;Walsh & Zhang, 2008) Inward-rectifier K + channels K ir , IK v Human lung fibroblasts (Roach et al, 2013) Human cardiac fibroblasts (Aguilar et al, 2014;Li et al, 2009) Canine atrial fibroblasts (Benamer et al, 2009) ATP-activated K + channels K ATP Rat ventricular fibroblasts (Benamer et al, 2009) Human dermal fibroblasts (Bednarczyk et al, 2018) TRP channels TRPA1, TRPC1, TRPC3, TRPC4, TRPC6, TRPV4, TRPM2, TRPM7 Human and mouse lung fibroblasts (Hofmann et al, 2017;Rahaman et al, 2014;Wei et al, 2009;Yonezawa et al, 2016) Mouse proximal tubular cells (Mannaa et al, 2018) Human and rat hepatic stellate cells (Song et al, 2014) Human, rat, and mouse kidney fibroblasts (Saliba et al, 2015) Rat ventricular fibroblasts (Rose et al, 2007) Human, rat, and mouse cardiac fibroblasts (Chen et al, 2010;Du et al, 2010;Li et al, 2019;Mannaa et al, 2018;Oguri et al, 2014;Rahaman et al, 2014;Runnels et al, 2002;Saliba et al, 2015;Song et al, 2014) Cl − channels I Cl-swell , ClC-3, I Cl Human cardiac fibroblasts (Li et al, 2009;…”

“…These are likely to be encoded by α-subunits of K v proteins, such as K v 1.2, K v 1.4, K v 1.5 and K v 2.1. Functional K ir currents have also been recorded in human lung fibroblasts (Roach et al, 2013) and canine (Benamer et al, 2009) and human cardiac fibroblasts (Aguilar et al, 2014). In a canine model of congestive heart failure, K ir channels were reported to play a role in atrial remodelling (Benamer et al, 2009).…”

“…The K Ca 3.1 IC 50 values of clotrimazole are in the 25-to 387-nM range, whileTRAM-34 is more potent with an IC 50 value of 20 nM(Wulff et al, 2000). The inactive analogues of TRAM-34, TRAM-7 and TRAM-85 have no blocking activity and are often used as structural controls for TRAM-34 specificity(Grgic et al, 2005; Grgic, Kiss, et al, 2009;Roach et al, 2013;Wulff et al, 2000).2. Senicapoc (ICA-17043) has been developed more recently and is even more potent than TRAM-34 and clotrimazole with an IC 50 of around 6-11 nM(McNaughton-Smith et al, 2008).…”

Blockade of KCa3.1 Attenuates Left Ventricular Remodeling after Experimental Myocardial Infarction

“…KCa3.1 has been shown to play an important role in proliferation, migration, and activation of fibroblasts [11,12,13]. Additionally, selectively targeting KCa3.1 in fibroblasts ameliorates the progression of unilateral ureteral obstruction-induced renal fibrosis and may be a novel approach in treating idiopathic pulmonary fibrosis [11,14]. …”