The Role Of MAD2L1 In Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis（IPF）is a lung disease with slow onset,increased fibrosis connective tissue and extremely high mortality.After the lung is injured,the repair will be carried out,but once the repair process is abnormal,a fibrotic lesion will be formed and irreversible,and eventually the lung become stiff and result in dying due to breath difficulties.IPF is prone to occur in the elderly and its prevalence is increasing year by year worldwide.Accurate and timing separation of sister chromatids during cell mitosis is very pivotal to maintain the stability and integrity of chromosomes.The normal operation of cell mitosis is controlled by the inspection mechanism of spindle assembly checkpoint（SAC）.Mitotic arrest deficient 2 like 1（MAD2L1）is one of the main components of SAC,which can detect the correctness of right attaching the centromere to the spindle,while preventing sister chromatids from dividing prematurely before anaphase arrival until all chromosomes can be precisely aligned at the location of the metaphase plate.Thereafter,MAD2L1 activates the anaphase promoting complex（APC/C）to initiate anaphase transcription.Abnormal expression of MAD2L1 has been found in liver cancer,lung cancer,breast cancer and many other cancers now,but no association between MAD2L1 and IPF has been reported.In this study,the expression alteration of MAD2L1 in clinical samples of IPF were detected by immunohistochemistry and fluorescence quantitative PCR,and results showed that MAD2L1 is upregulated in IPF lungs and mainly located in type II alveolar epithelial cells（Type II alveolar epithelial cells）.And similarly in the bleomycin induced lung fibrosis,the results of immunohistochemistry,western blotting,and fluorescent quantitative PCR showed that the expression level of MAD2L1 was increased in the BLM group.This suggests that MAD2L1 may be involved in the occurrence of IPF.In this article,to explore the role of MAD2L1 in fibrosis,we silenced MAD2L1 gene in A549 cells and determined the cell viability,migration,and proliferation by CCK8、 cell scratch、 Ed U assays and found that MAD2L1 can improve cell viability and promote cell migration and proliferation.The effect of MAD2L1 on cell senescence was investigated by detecting the activity of β-galactosidase and the level of reactive oxygen species.The results showed that MAD2L1 could inhibit cell senescence.Furthermore,the effects of MAD2L1 on mitochondrial membrane potential and mitochondrial related proteins were investigated by Western blot and JC-1 method.The results indicated that MAD2L1 could promote the stability of mitochondrial structure and function.Finally,the effect of MAD2L1 on extracellular matrix-related proteins was detected by Western blotting and fluorescent quantitative PCR.It was found that the expression of Collagen1、N-cadherin、α-SMA and Vimentin increased at the protein level or at the gene level,while the expression of E-cadherin was reduced.These results indicate that MAD2L1 can inhibit the synthesis of extracellular matrix.In summary,MAD2L1 plays a crucial role in the process of pulmonary fibrosis and can regulate the properties of cell fibrosis.Inhibition of the expression of MAD2L1 reduces cell activity,migration,and proliferation,which leads to cell aging and accumulation of large amounts of reactive oxygen species,and causes a large accumulation of extracellular substrate-related proteins to promote the fibrotic process.