Therapeutic Effect Of Sodium Salicylate (NaSAL) On The Paraquat-induced Pulmonary Damage In Rats

Paraquat(PQ) is a non-selective contact herbicide,which is used word-widely for its high efficiency and characteristics of no residues detectable in the crops. Paraquat poisoning was particularly prevalent in the accidental or suicide.It has been extensively demonstrated that the target organ of PQ is lung. However,the exact mechanism of its toxicity still remains unclear and there are no known pharmacological antagonists for its poisoning at present.The mechanism may be involved as follows:a variety of regulatory factors,oxidative stress and apoptosis induced by paraquat and/or its metabolites,after which becomes oxidative damage of lungs at the early stage and the persistent fibrosis with fibroblast proliferation and extracellular matrix.Previous studies have shown that the pulmonary damage at early stage may be the main cause for death.Sodium salicylate is an anti-inflammatory drug widely used in the clinical,however,studies in recent years suggested that high doses of the therapeutic effect of sodium salicylate may have potential therapeutic effects on PQ-induced toxic effects.Therefore,we determined the expression of TGF-β1,TNF-α,NF-κB,caspase-3,Bcl-2,P53 and some oxidative index in the rat model of paraquat-induced pulmonary damage and evaluated their roles in this specific process.Moreover,we aimed to investigate effects of sodium salicylate(NaSAL) on the pulmonary damage induced by paraquat and to observe its potential therapeutic effects so as to provide evidence for the treatment strategy of paraquat-induced lung damage.We established rat poisoning model by intragastric administration of 80mg/kg PQ.72 male SD rats were randomly divided into 0.9%NaCl control group,PQ exposure group,PQ+NaSAL intervention group,24 rats in each group.Control group were made orally in an injection volume of 0.5 mL/100 g of body weight,after 2h an injection of equivalent 0.9%NaCl were made intraperitoneally; PQ group were made 80mg/kg PQ orally,after 2h an injection of equivalent 0.9% NaCl were made intraperitoneally;PQ+NaSAL group were given an intraperitoneal injection of 120mg/kg NASAL after an orally administrating of 80mg/kg PQ.After exposure,animals were sacrificed in batches on days 1,3,7,14.After dislodged from abdominal aorta,the blood was placed in 37℃waterbath for 2h and the supernatant was taken away and retained in eppendorf tubes.Lung tissues were obtained with routine method.Then the activities of total antioxidative capacity(T-AOC),catalase(CAT), superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),malondialdehyde (MDA) both in serum and lung homogenate of rats and the contents of hypertrophy (HYP) in lung homogenate were measured using qualified kits provided by Nanjing Institute of Bio-engineering.The level of NF-κB was assayed by electrophoresis mobility shift assay(EMSA),while the protein level of TGF-β1,TNF-αwere determined with Rat TGF-β1,TNF-αkits.And the mRNA of caspase-3,Bcl-2, P-53 was determined using real-time reverse transcription polymerase chain reaction (real-time RT PCR).It has been found that the activities of SOD,GSH-Px,T-AOC,CAT in serum and lung homogenate were decreased with positive significance(P＜0.05) and MDA level was increased in both PQ group and PQ+NaSAL group compared with the control group.So was the HYP level(P＜0.05).However,the activities of SOD, GSH-Px,T-AOC,CAT in PQ+NaSAL group were markedly higher than that of PQ treated group,and still lower than that of the control group.MDA content was lower than that of the PQ group(P＜0.05),but still higher than that of the control group(P＜0.05).HYP in PQ+NaSAL group was lower than that of the PQ group but higher than that of the control group.After 80mg/kg PQ exposure,the rat lung tissue NF-κB content,TGF-β1 and TNF-αprotein expression increased remarkebly than that of the control group(P＜0.05);apoptosis-related gene such as caspase-3,P53 mRNA increased and Bcl-2 mRNA reduced evidently compared with the control group(P＜0.05).NF-κB content,TGF-β1 and TNF-αprotein showed a low expression than that of the PQ group(P＜0.05),however,There was no significant difference compared with the control one.Meanwhile,NaSAL withstand increasing of PQ-induced caspase-3,P53 mRNA and decreasing of Bcl-2 mRNA expression to a certain extent(P＜0.05).In addition,the histological examination showed ultra-morphological changes such as alveolar edema,hemorrhage and inflammatory cell infiltration in the PQ group.Similar changes such as hyperemia,edema and hemorrhage were also found in the PQ+NaSAL group,but it was slighter than that of the PQ group.So,it can be seen that sodium salicylate can improve the PQ-induced pulmonary edema in rats evidently.In summary,we found that NaSAL significantly improved PQ-induced pulmonary damage.These findings suggested that NaSAL may exert its therapeutic effects on paraquat-induced pulmonary damage via counteracting paraquat-induced oxidative stress in rat lung and by regulating the mRNA expression of apoptosis gene and decreasing inflammatory factor releasing.However,further studies are still needed to investigate and clarify the underlying mechanisms involved in this complicated process.