TGFβ1 induces resistance of human lung myofibroblasts to cell death via down-regulation of TRPA1 channels

Background and purpose: TGFβ1-mediated myofibroblast activation contributes to pathological fibrosis in many diseases including idiopathic pulmonary fibrosis (IPF), where myofibroblast resistance to oxidant-mediated Apoptosis is also evident. We therefore investigated the involvement of redox-sensitive TRPA1 ion channels on human lung myofibroblasts (HLMFs) cell death and TGFβ1-mediated pro-fibrotic responses.

Experimental approach: The effects of TGFβ1 stimulation on TRPA1 expression and cell viability was studied in HLMFs derived from IPF patients and non-fibrotic patients. We also examined a model of TGFβ1-dependent fibrogenesis in human lung. We used qRT-PCR, immunofluorescent assays, overexpression with lentiviral vectors and electrophysiological methods.

Key results: TRPA1 mRNA, protein and ion currents were expressed in HLMFs derived from both non-fibrotic patient controls and IPF patients, and expression was reduced by TGFβ1. TRPA1 mRNA was also down-regulated by TGFβ1 in a model of lung fibrogenesis in human lung. TRPA1 over-expression or activation induced HLMF Apoptosis, and activation of TRPA1 channel activation by H₂ O₂ induced necrosis. TRPA1 inhibition following TGFβ1 down-regulation or pharmacological inhibition, protected HLMFs from both Apoptosis and necrosis. Lentiviral vector mediated TRPA1 expression was also found to induce sensitivity to H₂ O₂ induced cell death in a TRPA1-negative HEK293T cell line.

Conclusion and implications: TGFβ1 induces resistance of HLMFs to TRPA1 agonist- and H₂ O₂ -mediated cell death via down-regulation of TRPA1 channels. Our data suggest that therapeutic strategies which prevent TGFβ1-dependent down-regulation of TRPA1 may reduce myofibroblast survival in IPF and therefore improve clinical outcomes.

IPF; TGFβ1; TRPA1; apoptosis; fibrosis; myofibroblast; oxidative stress.