KCa3.1 Channel-Blockade Attenuates Airway Pathophysiology in a Sheep Model of Chronic Asthma

Abstract

BackgroundThe Ca2+-activated K+ channel KCa3.1 is expressed in several structural and inflammatory airway cell types and is proposed to play an important role in the pathophysiology of asthma. The aim of the current study was to determine whether inhibition of KCa3.1 modifies experimental asthma in sheep.Methodology and Principal FindingsAtopic sheep were administered either 30 mg/kg Senicapoc (ICA-17073), a selective inhibitor of the KCa3.1-channel, or vehicle alone (0.5% methylcellulose) twice daily (orally). Both groups received fortnightly aerosol challenges with house dust mite allergen for fourteen weeks. A separate sheep group received no allergen challenges or drug treatment. In the vehicle-control group, twelve weeks of allergen challenges resulted in a 60±19% increase in resting airway resistance, and this was completely attenuated by treatment with Senicapoc (0.25±12%; n = 10, P = 0.0147). The vehicle-control group had a peak-early phase increase in lung resistance of 82±21%, and this was reduced by 58% with Senicapoc treatment (24±14%; n = 10, P = 0.0288). Senicapoc-treated sheep also demonstrated reduced airway hyperresponsiveness, requiring a significantly higher dose of carbachol to increase resistance by 100% compared to allergen-challenged vehicle-control sheep (20±5 vs. 52±18 breath-units of carbachol; n = 10, P = 0.0340). Senicapoc also significantly reduced eosinophil numbers in bronchoalveolar lavage taken 48 hours post-allergen challenge, and reduced vascular remodelling.ConclusionsThese findings suggest that KCa3.1-activity contributes to allergen-induced airway responses, inflammation and vascular remodelling in a sheep model of asthma, and that inhibition of KCa3.1 may be an effective strategy for blocking allergen-induced airway inflammation and hyperresponsiveness in humans.

Ion Channels in Innate and Adaptive Immunity

“…Inhibiting K Ca 3.1 genetically or pharmacologically reduces FcɛRI-mediated Ca 2+ influx and degranulation (344). Moreover, KCa3.1 − / − mice showed reduced passive cutaneous and systemic anaphylaxis (344), and K Ca 3.1 inhibitors attenuated airway remodeling and eosinophilia in murine and sheep asthma models (345, 346). However, while inhibition of mast cell function probably contributed to these effects, K Ca 3.1 is also expressed in T cells, fibroblasts, and proliferative airway smooth muscle cells.…”

“…In addition, K Ca 3.1 also contributes to the activation of several other immune cells, including macrophages, microglia, DCs, and many nonimmune cells such as dedifferentiated vascular smooth muscle cells and fibroblasts. The ability of K Ca 3.1 blockers to simultaneously affect all these cell types probably contributes to the beneficial effects of K Ca 3.1 blockers in mouse and sheep asthma models (345, 346), prevention of atherosclerosis in ApoE − / − mice (277), and transplant vasculopathy (278). Several K Ca 3.1 blockers have been developed by pharmaceutical companies, including Senicapoc, a small-molecule K Ca 3.1 blocker that entered Phase 3 clinical trials for sickle cell anemia (375).…”

A novel segmental challenge model for bleomycin-induced pulmonary fibrosis in sheep

“…Immunohistochemistry was performed on frozen tissue sections as previously described [27,28]. Sections were fixed with 100% cold ethanol for 10 minutes and were simultaneously blocked for endogenous peroxidase with 3% H 2 O 2 (Univar, Knoxville, Vic, Australia).…”

Development of a QPatch Automated Electrophysiology Assay for Identifying KCa3.1 Inhibitors and Activators

“…12,13 KCa3.1 is similarly involved in the activation and proliferation of B cells, fibroblasts, and dedifferentiated vascular smooth muscle cells, making KCa3.1 blockers attractive potential drugs for restenosis, asthma, and immunosuppression. 5,[14][15][16][17][18] Based on the role of KCa3.1 in erythrocyte volume regulation and intestinal fluid and electrolyte secretion, 6,19 KCa3.1 blockers have also been suggested for the treatment of sickle cell anemia and diarrhea in humans and farm animals. 20,21 In vascular endothelium, KCa3.1 is expressed together with the small-conductance KCa2.3 channel, and both channels are involved in generating endothelium-derived hyperpolarization (EDH), which then spreads to the underlying vascular smooth muscle cell layer, closes voltage-gated calcium channels, and finally produces relaxation and vasodilation.…”