TGFß1-induces resistance to apoptosis in human lung myofibroblasts via TRPA1 downregulation

Background: Idiopathic pulmonary fibrosis (IPF) is driven by failure of the normal wound healing response to tissue injury, leading to the inappropriate accumulation of human lung myofibroblasts (HLMF) and the development of fibroblastic foci. Targeting the failure of HLMF apoptosis in IPF is emerging as a therapeutic strategy. TGFβ1 is a key pro-fibrotic cytokine driving IPF, and has dual roles in both promoting and inhibiting apoptosis. Redox-sensitive transient receptor potential (TRP) ion channels are implicated in the regulation of cell apoptosis induced by oxidants. We explored the role of TRPA1, the most abundant TRP channel in HLMFs, in HLMF apoptosis and death. Methods: Flow cytometry was used to detect IPF-derived and non-fibrotic control (NFC) HLMF cell death (apoptosis and necrosis). The contribution of TRPA1 activation was studied using the agonists allyl-isothiocyanate and JT010, the specific antagonist A967079, and lentiviral-mediated overexpression of TRPA1. Results: TRPA1 agonists induced HLMF death by apoptosis that was inhibited by A967079, in both NFC and IPF donors. Agonist induced death correlated strongly with TRPA1 expression and was increased following TRPA1 overexpression. TGFβ1 reduced expression of TRPA1 resulting in reduced sensitivity of HLMFs to cell death by TRPA1 agonists and H2O2, an effect that was recapitulated with A967079. Furthermore, A967079 was less effective at inhibiting death responses following TGFβ1 treatment. Conclusion: Our data suggest that the downregulation of TRPA1 by TGFβ1 may protect HLMFs from apoptosis, promoting their persistence in IPF. Therapies that prevent this downregulation may have the potential to stop IPF progression.