[Effects of small RNA interference targeting mammalian target of rapamycin on paraquat-induced pulmonary fibrosis in rats]

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

Background: Pulmonary fibrosis is described as a chronic idiopathic inflammatory disease of the interstitial lungs. It is associated with a potentially fatal prognosis, and patients show insignificant response to treatment. To treat paraquat (PQ)-induced pulmonary injury and fibrosis, multiple approaches have been used. We aimed to determine the effects of allopurinol (Allo), a xanthine oxidase inhibitor, on PQ-induced pulmonary fibrosis in rats. Methods: A total of 30 female Sprague-Dawley rats were divided randomly into five groups (200±20 g). Group 1 (control) and group 2 (PQ group) were intraperitoneally administered PQ (20 mg/kg) once on day seven without any treatment, while groups 3–5 orally received 50, 100, and 200 mg/kg of Allo seven days before and three weeks following the administration of PQ, respectively. The animals were sacrificed three weeks after PQ administration. For the histopathological analysis and assessment of serum malondialdehyde (MDA) and hydroxyproline (HP) contents, the animals’ blood and lungs were collected. Results: The PQ group showed significantly higher lung HP, serum MDA, and lung index in comparison with the control. Treatment with Allo, especially at 100 and 200 mg/kg, decreased HP, MDA, and lung index significantly, compared to the PQ group. Allo could prevent inflammatory cell infiltration, presence of fibroblasts, and PQ-related alveolar thickening. Conclusion: The results revealed that Allo has potential protective effects on PQ-related pulmonary fibrosis, and the role of xanthine oxidase in the exacerbation of PQ-induced pulmonary fibrosis was confirmed.

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

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.