Chronic Paraquat Poisoning Cause Epithelial Mesenchymal Transition Through TGF-?/Twist Signal Pathway

Objective: Paraquat(PQ),a kind of herbicide widely used in developing countries,is featured by low amount of mortality but high mortality rate.After accumulating in the lung,paraquat can cause lung injuries including edema,hemorrhage,hypoxemia,inflammatory cell infiltration into the lung interstitium and alveolar space.That means patients usually end up with dyspnea and other organ failure such as liver failure and renal failure.Regardless of the amount of intake,paraquat can cause injury with low dose because of the effective absorption of paraquat by polyamine system,which leads to pulmonary fibrosis and respiratory failure.Pulmonary interstitial fibrosis is largely characterized by epithelial-mesenchymal transition(EMT),the process of epithelial cells transform into mesenchymal cells.At the microscopic level,EMT is featured by the down-regulation of epithelial markers such as E-cadherin and upregulation of interstitial markers such as ?-SMA and vimentin.Paraquat can promote epithelial mesenchymal-transition(EMT)through many signaling molecules,the most important of which is transforming growth factor ?(TGF-?).Such substance then activates Notch,Smad,Snail,HIF-1,Twist and other translation factors,and promote epithelial mesenchymal transition(EMT).At present,most researches regarding epithelial-mesenchymal transition(EMT)caused by paraquat poisoning focus on exploring the roles of signaling pathways composed by TGF-?,Notch,Smad and Snail in mediating epithelial-mesenchymal transition(EMT).However,as a downstream translation factor,studies on Twist and its effect on EMT are insufficient.As such,this paper attempts to clarify the role of signaling pathway of TGF-? / Twist in epithelial mesenchymal-transition(EMT)caused by chronic paraquat poisoning,aiming at discovering a new therapeutic approach.Methods:A549 cells are treated with different concentration of paraquat for 6 days,the morphology of them is observed under microscop and the mobility of cells is observed through wound healing assay.The expression of Twist,E-cadherin,?-SMA is tested by Western Blot.On this basis,si RNA is used to interfere the expression of Twist,and then analyse the change of E-cadherin,?-SMA.Results:(1)30umol/L concentration of parequat for a long period of time(6 days)can change the morphology of A549 cells.(2)30umol/L concentration of paraquat increased the ability of A549 cells to metastasize.(3)30umol/L concentration of paraquat for a long period of time(6 days)can induce EMT in A549 cells through TGF-?/Twist signal pathway.Conclusion:The migration ability of A549 cells at the concentration(30umol/L)of paraquat for a long period of time(6 days)shown to be enhanced in macroscopically,and the cell morphology will change.Microcosmic aspects are characterized by epithelial markers E-cadherin expression decrease,mesenchymal markers of alpha SMA expression increase,EMT induced molecular Twist expression increased,at the same time EMT is a key factor of induced pulmonary fibrosis,therefore 30unol/L concentration of paraquat for a long time(6 days)can induce EMT through the TGF-beta/Twist pathway and finally result in pulmonary fibrosis.