The Role Of KCa3.1 Induced Endoplasmic Reticulum Stress In Paraquat-Induced Pulmonary Fibrosis

Background and objective: Respiratory failure caused by irreversible pulmonary fibrosis is the main reasons of death after paraquat(PQ)poisoning.KCa3.1,a Ca2+-activated K+ channel,plays an important role in modulating calcium signaling and maintaining membrane potential during cell activation.It has been reported to promote fibroblast function in many fibrotic diseases.Meanwhile,our previous study indicated that endoplasmic reticulum stress(ERS)might participate in the progress of PQinduced pulmonary fibrosis.However,the role of KCa3.1 and ERS in the pathophysiology of pulmonary fibrosis after paraquat poisoning has not been studied.Methods: The rat model of paraquat poisoning was established and the primary pulmonary fibroblasts were extracted to establish the model of paraquat intoxication pulmonary fibroblasts.In applying KCa3.1 blocker TRAM-34 and endoplasmic reticulum stress inhibitor salubrinal,we used H&E staining and Masson staining of rat lung tissue,lung tissue hydroxyproline content,wet/dry weight ratio of lung tissue,ELISA determination of alveolar lavage fluid type I collagen to detect lung inflammation and fibrosis degree.Immunohistochemical was used to detect KCa3.1,α-SMA,GRP78 expression.Western blot was used to detect the expression of KCa3.1,α-SMA,I collagen,GRP78.The expression of KCa3.1 and GRP78 was also detected by immunofluorescence,and the proliferation level of pulmonary fibroblasts before and after the intervention was detected by MTT and Brd U.Results:1.The results showed that KCa3.1 expression was elevated after PQ poisoning.Blockade of KCa3.1 alleviated PQ-induced pulmonary inflammation and fibrosis.Blockade of KCa3.1 also attenuated the level of collagen I and α-SMA and the proliferation of fibroblasts.However,TGF-β1 expression remained unaffected by blockade of KCa3.1 in rat lung tissues after PQ poisoning.2.Blockade of KCa3.1 alleviated PQ-induced ERS in lung tissue and fibroblasts.Inhibition of endoplasmic reticulum stress alleviated KCa3.1 induced lung fibroblast proliferation after paraquat poisoning.Conclusion: The present study suggests that KCa3.1 expression increased and might promote pulmonary fibroblast proliferation in PQ-induced pulmonary fibrosis.In addition,we confirmed that TRAM-34 attenuates proliferation and collagen secretion of fibroblasts.KCa3.1 may regulate the proliferation and collagen secretion activity by inducing endoplasmic reticulum stress in pulmonary fibroblasts.Our findings indicated that blockade of KCa3.1 might inhibit PQ-induced proliferation of pulmonary fibroblasts and prevent progression of lung fibrosis.