The Effectof Diammonium Glycyrrhizinate On Paraquat-induced Pulmonary Fibrosis And The Expression Of TGF-β1 And CTGF In The Lungs Of Rats

Objective:Paraquat(PQ)is a highly efficient heterocyclic herbicide used around the world.PQ poisoning may induce acute lung injury and pulmonary fibrosis.PQ can selectively accumulate in the lungs,so the lung is the main target organ for PQ poisoning.Our previous studies have confirmed that TGF-β1 plays a key role in paraquat-induced acute lung injury and pulmonary fibrosis,anddiammoniumglycyrrhizinate(DG)has protective effects on acute lung injury induced by paraquat.The study aims to explore the pathogenesis of pulmonary fibrosis in rat induced by paraquatpoisoning through observing the expression levels of transforming growth factor-β1(TGF-β1)and connective tissue growth factor(CTGF).And we investigate the effect and possible mechanisms of Diammoniumglycyrrhizinate therapy on attenuating pulmonary fibrosis by intervention of DG in rat model.Methods: Male SD rats were randomly divided into 3 groups of 10 rats each: normal control group(A),poisoning group(B),the treatment group(C).Rats in group B(the poisoning group)and group C(the treatment group)received a single dose of PQ(20mg/kg)by gavage.Group A(the control group)was given equal amount of saline by gavage.Group C(the treatment group)were given treatment of DG(75mg/kg)by intraperitoneal injection 24 hours after poisoning.Group A and group B were given equal amount of saline intraperitoneally.After 21 days after poisoning,all the animals were killed and lung tissue was harvested.Pathological HE staining and masson’s staining were made to measure lung inflammation and lung fibrosis.Hydroxyproline(HYP)in lung tissue was detected.Quantitative Real-Time PCR for TGF-β1,CTGF mRNA expression in lung was performed.Results: HE staining showed that the alveolar,bronchial,and lung tissues in the control group were structurally intact and the tissues were tightly connected.The nucleus was large and round,and the cytoplasm was abundant and uniform.There was no inflammatory cell infiltration in the lung and the structure of lung tissue was clear.Whereas in the poisoning group,The alveolar septum showed congestion,edema,thickening,narrowing of the alveolar space,extensive damage of the vascular endothelial cells,infiltration of a few lymphocytes,marked enlargement of the lung interstitial space,and obvious tissue hyperplasia,collagen proliferation and fibrosis.The degree of congestive edema and inflammatory cell infiltration in alveolar in the treatment group was lower than that in the poisoning group.Masson staining showed minimal collagen fibril deposition in the interstitium of lung in the control group.A large number of blue-stained collagen fibers can be seen in the alveolar interstitium in the poisoned group.The degree of alveolar interstitial fibrosis in the treatment group was lower than that in the poisoned group.Compared with the control group,the HYP content in the lung tissue of the poisoning group increased significantly,and the difference was statistically significant.(p<0.05).Compared with the poisoning group,the HYP content in the lung tissue of the treatment group decreased significantly,and the difference was statistically significant(p< 0.05).And results showed that compared with the control group,the expression of TGF-β1 and CTGF mRNA in the lungs of the poisoning group were significantly increased by RT-PCR,and the difference was statistically significant.Compared with the poisoning group,the expression of TGF-β1 and CTGF in the lung tissue of the treated group decreased significantly,and the difference was statistically significant.(p< 0.05).Conclusion:1.The increase of TGF-β 1 and CTGF is closely related to the pulmonary fibrosis induced by paraquat in rats.Animal experiments showed that the expression of TGF-β 1 and CTGF mRNA in lung tissue was significantly increased in rat pulmonary fibrosis induced by paraquat poisoning.These results indicate that TGF-β1 and CTGF are involved in the process of pulmonary fibrosis induced by paraquat in rats.2.Diammoniumglycyrrhizinate reduce the degree of fibrosis in rats induced by paraquat through inhibiting the overexpression of TGF-β1 and CTGF in lung tissue,thereby exerting a therapeutic effect on pulmonary fibrosis induced by paraquat-poisoning.