title: Effects of rapamycin against paraquat-induced pulmonary fibrosis in mice.
abstract: OBJECTIVE
  Ingestion of paraquat (PQ), a widely used herbicide, can cause severe toxicity in humans, leading to a poor survival rate and prognosis. One of the main causes of death by PQ is PQ-induced pulmonary fibrosis, for which there are no effective therapies. The aim of this study was to evaluate the effects of rapamycin (RAPA) on inhibiting PQ-induced pulmonary fibrosis in mice and to explore its possible mechanisms.
  
  
  METHODS
  Male C57BL/6J mice were exposed to either saline (control group) or PQ (10 mg/kg body weight, intraperitoneally; test group). The test group was divided into four subgroups: a PQ group (PQ-exposed, non-treated), a PQ+RAPA group (PQ-exposed, treated with RAPA at 1 mg/kg intragastrically), a PQ+MP group (PQ-exposed, treated with methylprednisolone (MP) at 30 mg/kg intraperitoneally), and a PQ+MP+RAPA group (PQ-exposed, treated with MP at 30 mg/kg intraperitoneally and with RAPA at 1 mg/kg intragastrically). The survival rate and body weight of all the mice were recorded every day. Three mice in each group were sacrificed at 14 d and the rest at 28 d after intoxication. Lung tissues were excised and stained with hematoxylin-eosin (H&E) and Masson's trichrome stain for histopathological analysis. The hydroxyproline (HYP) content in lung tissues was detected using an enzyme-linked immunosorbent assay (ELISA) kit. The expression of transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) in lung tissues was detected by immunohistochemical staining and Western blotting.
  
  
  RESULTS
  A mice model of PQ-induced pulmonary fibrosis was established. Histological examination of lung tissues showed that RAPA treatment moderated the pathological changes of pulmonary fibrosis, including alveolar collapse and interstitial collagen deposition. HYP content in lung tissues increased soon after PQ intoxication but had decreased significantly by the 28th day after RAPA treatment. Immunohistochemical staining and Western blotting showed that RAPA treatment significantly down-regulated the enhanced levels of TGF-β1 and α-SMA in lung tissues caused by PQ exposure. However, RAPA treatment alone could not significantly ameliorate the lower survival rate and weight loss of treated mice. MP treatment enhanced the survival rate, but had no significant effects on attenuating PQ-induced pulmonary fibrosis or reducing the expression of TGF-β1 and α-SMA.
  
  
  CONCLUSIONS
  This study demonstrates that RAPA treatment effectively suppresses PQ-induced alveolar collapse and collagen deposition in lung tissues through reducing the expression of TGF-β1 and α-SMA. Thus, RAPA has potential value in the treatment of PQ-induced pulmonary fibrosis.
authors.affiliation: Kidney Disease Center, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Shao
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.forename: Chong
authors.initials: C
authors.lastname: Luo
authors.forename: Ying-ying
authors.initials: YY
authors.lastname: Wang
authors.forename: Ying-ying
authors.initials: YY
authors.lastname: Lu
authors.forename: Shi
authors.initials: S
authors.lastname: Feng
authors.forename: Heng
authors.initials: H
authors.lastname: Li
authors.forename: Xia-Bing
authors.initials: XB
authors.lastname: Lang
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Wang
authors.forename: Chuan
authors.initials: C
authors.lastname: Lin
authors.forename: Xiu-jin
authors.initials: XJ
authors.lastname: Shen
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.forename: Hong
authors.initials: H
authors.lastname: Jiang
authors.forename: Jiang-hua
authors.initials: JH
authors.lastname: Chen
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D003094:Collagen / Q000737:chemistry; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D006540:Herbicides / Q000009:adverse effects; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008168:Lung / Q000187:drug effects / Q000473:pathology; D008297:Male; D008775:Methylprednisolone / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D010269:Paraquat / Q000009:adverse effects; D011379:Prognosis; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology*; D020123:Sirolimus / Q000627:therapeutic use*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D016896:Treatment Outcome
chemical_list: D000199:Actins; D006540:Herbicides; D007166:Immunosuppressive Agents; D053773:Transforming Growth Factor beta1; D003094:Collagen; D010269:Paraquat; D020123:Sirolimus; D008775:Methylprednisolone
keywords: Methylprednisolone; Paraquat; Pulmonary fibrosis; Rapamycin; Transforming growth factor-β1; α-Smooth muscle actin