Rapamycin protects against paraquat‑induced pulmonary epithelial‑mesenchymal transition via the Wnt/β‑catenin signaling pathway

Abstract

Abstract. Paraquat (PQ) is a herbicide that is widely used in developing countries, and pulmonary fibrosisis one of the most typical features of PQ poisoning. The molecular mechanism underlying PQ toxicity is largely unknown, which makes it difficult to treat. In the present study, western blot analysis, reverse transcription-quantitative polymerase chain reaction and fluorescent immunostaining were used to analyze the effects of rapamycin on PQ-induced epithelial-mesenchymal transition (EMT) in A549 and MRC-5 cells. It was revealed that rapamycin significantly downregulated the mesenchymal cell marker, α-smooth muscle actin, and significantly upregulated the epithelial cell marker, E-cadherin, at mRNA and protein expression levels compared with the PQ group. Treatment with PQ significantly increased Wnt1, low-density lipoprotein receptor-related protein (LRP)5, LRP6 and β-catenin expression levels in A549 cells, while rapamycin significantly inhibited these effects of PQ. Activation of the Wnt signaling pathway using lithium chloride attenuated the inhibitory effects of rapamycin on PQ-induced EMT. In conclusion, rapamycin protects against PQ-induced pulmonary EMT via the Wnt/β-catenin signaling pathway. IntroductionParaquat (PQ; 1,1'-dimethyl-4,4'-bipyridinium) is a herbicide that is widely used in developing countries worldwide, which may cause severe toxicity in animals and humans (1). PQ poisoning was reported to account for up to a third of all suicides around the world (2). PQ poisoning may cause patients to develop acute multi-organ failure, pulmonary fibrosis and finally mortality due to respiratory failure (3). Pulmonary fibrosis is a typical feature of PQ poisoning, the onset of which may be several days or weeks following ingestion of PQ (4). Although PQ-induced pulmonary fibrosis has a high mortality rate, the molecular mechanisms underlying its toxicity are largely unknown, which makes it particularly hard to treat.Epithelial-mesenchymal transition (EMT) has been reported to be associated with pulmonary fibrosis following PQ exposure (3). It has also been reported that factors, including epithelial growth factor, transforming growth factor-β1 (TGF-β1), insulin-like growth factor and interleukin-17, may induce EMT (5). Myofibroblasts are key mediators in fibrosis. In murine models of hepatic and renal fibrosis, ~40% of α-smooth muscle actin (SMA)-positive myofibroblasts were derived from epithelial cells via EMT (6). However, to the best of our knowledge, the roles and mechanisms of rapamycin in the EMT process of A549 and MRC-5 cells remain unknown.In the present study, the roles and mechanisms of rapamycin on PQ-induced pulmonary fibrosis were investigated. It was revealed that rapamycin alleviated PQ-induced EMT in A549 and MRC-5 cells, and PQ activated the Wnt signaling pathway. Rapamycin inhibited the effects of PQ, and the activation of the Wnt signaling pathway attenuated the inhibitory effects of rapamycin on PQ-induced EMT. Materials and methodsReagents. PQ, rapamycin and lithium chloride (...

The Ameliorative Effects of Allopurinol on Paraquat-Induced Pulmonary Fibrosis in Rats

“…However, pulmonary fibrosis and lung damage are recognized as the most common causes of mortality and injury. [9][10][11][12][13] In the mid 1950's, allopurinol (Allo) was synthesized for the production of new antineoplastic agents. Nevertheless, its inhibitory effects on xanthine oxidase (XO) were reported, reducing both serum uric acid and urinary contents.…”

Role of epithelial-to-mesenchymal transition in the pulmonary fibrosis induced by paraquat in rats

“…The TGF-β1-β-catenin signaling pathway might join in the early PF process in PQ-poisoned rats. [14] Moreover, the lysyl oxidase (LOX) [21] or Wnt1 [29,30] could regulate the PQ-induced EMT by activating β-catenin that participated in the development of PF process in cell models. Our study showed that the mRNA expression of Wnt2 and β-catenin in rat lung dramatically increased with a peak on day 21 after PQ injection.…”