Inhibition of the K_Ca3.1 Channel Alleviates Established Pulmonary Fibrosis in a Large Animal Model

Abstract

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease of increasing prevalence marked by poor prognosis and limited treatment options. Ca-activated K3.1 potassium channels have been shown to play a key role in the aberrant activation and responses to injury in both epithelial cells and fibroblasts, both considered key drivers in the fibrotic process of IPF. Pharmacological inhibition of IPF-derived fibroblasts is able to somewhat prevent TGF-β- and basic fibroblast growth factor-dependent profibrotic responses. In the current study, we investigated whether blockade of the K3.1 ion channel in vivo with a selective inhibitor, Senicapoc, was able to attenuate both histological and physiological outcomes of early fibrosis in our large animal (sheep) model for pulmonary fibrosis. We also determined whether treatment was targeting the profibrotic activity of sheep lung fibroblasts. Senicapoc was administered in established fibrosis, at 2 weeks after bleomycin instillation, and drug efficacy was assessed 4 weeks after treatment. Treatment with Senicapoc improved pre-established bleomycin-induced changes compared with vehicle control, leading to improved lung compliance, reduced extracellular matrix and collagen deposition, and a reduction in both α-smooth muscle actin expression and proliferating cells, both in vivo and in vitro. These studies show that inhibiting the K3.1 ion channel is able to attenuate the early fibrogenic phase of bleomycin-dependent fibrosis and inhibits profibrotic behavior of primary sheep lung fibroblasts. This supports the previous research conducted in human IPF-derived fibroblasts and suggests that inhibiting K3.1 signaling may provide a novel therapeutic approach for IPF.

A model of human lung fibrogenesis for the assessment of anti-fibrotic strategies in idiopathic pulmonary fibrosis

“…The K Ca 3.1 ion channel promotes TGFβ1-dependent activation through the regulation of SMAD2/3 nuclear translocation and downstream transcription 20 – 22 . As a result, blocking or silencing K Ca 3.1 inhibits the pro-fibrotic activity of parenchymal human lung myofibroblasts, and prevents tissue fibrosis in several animal models 25 , 26 , including bleomycin-dependent fibrosis in sheep 23 . In our current model, K Ca 3.1 blockade using senicapoc, a drug very well tolerated in a phase 3 clinical trial of human sickle cell disease, was highly effective at inhibiting the pro-fibrotic effects of TGFβ1 both in terms of gene transcription, and tissue protein markers of fibrosis.…”

“…These Ca 2+ -activated K + channels regulate constitutive and TGFβ1-dependent pro-fibrotic activity in human lung myofibroblasts by promoting Ca 2+ influx, SMAD2/3 phosphorylation and nuclear translocation, α-smooth muscle actin (αSMA) expression/stress fibre formation, and cell contraction 20 – 22 . K Ca 3.1 channels promote bleomycin-dependent lung parenchymal fibrosis in sheep 23 , and airway fibrosis in a mouse model of asthma 24 , as well as tissue fibrosis in other organs 25 , 26 . A selective K Ca 3.1 blocker (senicapoc [ICA-17043]) administered orally was very well tolerated over 12 months in a human phase III clinical trial for sickle cell disease 27 , 28 .…”

Histone Deacetylases Enhance Ca2+-Activated K+ Channel KCa3.1 Expression in Murine Inflammatory CD4+ T Cells

“…The contribution of HDAC2 to tissue fibrosis is attracting increasing attention [ 48 , 49 ]. Recent studies showed that K Ca 3.1 inhibitors are a potential treatment option for renal, liver, kidney, corneal, and pulmonary fibrosis [ 50 , 51 , 52 , 53 , 54 ]. It currently remains unclear whether epigenetic modifications by HDAC2/3 are involved in these K Ca 3.1-related disorders; therefore, further studies are needed to clarify the therapeutic effectiveness of selective HDACis in various K Ca 3.1-related disorders.…”

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

“…These pro‐fibrotic responses were markedly attenuated by the selective K Ca 3.1 blocker senicapoc but not by dexamethasone (Roach et al, ; Figure ). In support of this, in a sheep model of bleomycin‐induced pulmonary fibrosis in separate lung segments, where each sheep acts as its own control, oral administration of senicapoc for 2 weeks after bleomycin instillation improved pre‐established bleomycin‐induced fibrosis with associated improvements in extracellular matrix and collagen deposition, α‐ smooth muscle actin expression and lung function (Organ et al, ). Importantly, senicapoc was well tolerated in this model, unlike pirfenidone (unpublished).…”

“…K Ca 3.1 knockout mice are viable, of normal appearance, produce normal litter sizes and exhibit rather mild phenotypes (Kohler et al, ; Si et al, ). High doses of TRAM‐34 administered to mice and rats over many weeks are well tolerated (Grgic, Kiss, et al, ) and the orally available K Ca 3.1 blocker senicapoc (ICA‐17043) was well tolerated when administered to sheep for several weeks (Organ et al, ).…”