The Protect Effect Of Vitamin C In PM2.5 Induced Lung Oxidative Injury:up-regulated Nrf2/HO-1 Pathway

Objective: A rat model with chronic PM2.5 intoxication was created to explore the protective effects of vitamin C on the oxidative damage in lung tissue and its possible mechanism.Methods: Forty healthy adult male wistar rats were selected.Using random number table method divided into five groups(n=8): control group,normal saline group,PM2.5 group,low-dose and high-dose vitamin C groups.Control group was not given any intervention;normal saline group was given trachea instillation of 0.9% sodium chloride solution(1ml/kg)weekly for four weeks;PM2.5 group,low-dose and high-dose vitamin C groups were given trachea instillation of 1ml/kg PM2.5(7.5mg/ml)suspension liquid once a week for four weeks;low-dose and high-dose vitamin C groups were respectively given vitamin C(1ml/kg)with 10mg/ml and 30mg/ml every day during the experiment.The rats were killed 24 hours later after the last time of trachea instillation.Pathological morphologic changes were observed under light microscope,protein content in BALF and the levels of vitamin C,MDA,LDH,8-OHdG,bilirubin,Hcy in serum were examined.The expression of Nrf2 and HO-1 in the lung tissue were detected by immunohistochemical staining,Western blotting and RT-PCR.Results:1 No abnormal manifestations in lung tissue slices were observed under light microscope in control group and normal saline group.Infiltration of inflammatory cells,distroyed alveolars,thickened alveoli septum were noted in PM2.5 group.In low-dose and high-dose vitamin C groups,we found that the exudation of inflammatory cells in alveolar space and impairment of lung tissue reduced.And the change in high dose group was more obvious;2 The differences of indexs in serum and BALF between control group and normal saline group were not statistically significant.The content of protein in BALF,the levels of LDH、Hcy、MDA、8-OHdG in serum increased in PM2.5 group compared with the control group and normal saline group.The levels of vitamin C,total bilirubin and indirect bilirubin decreased in PM2.5group compared with the control group and normal saline group.The intervention of vitamin C achieved the effect of an antioxidative.The protein content in BALF,the levels of LDH 、 Hcy 、 MDA and 8-OHdG in serum decreased in vitamin C high-dose and low-dose groups.The levels of antioxident substances increased in vitamin C high-dose and low-dose groups.However,there was no significant difference between the two groups except the level of LDH;3 The results of western blotting showed that HO-1,total Nrf2 and nuclear Nrf2 in lung tissue of rats exposed to PM2.5 were decreased significantly.The decrease of expression of Nrf2 and HO-1 can be reversed by vitamin C.The results of immunohistochemical were consistent with the results of western blotting.Real-time PCR further confirmed the effect of vitamin C on the expression of HO-1 in lung tissue of rats exposed to PM2.5.PM2.5 could reduce the HO-1 mRNA in lung tissue,and vitamin C could reverse this effect.There was no significant difference in the expression of HO-1,Nrf2 and HO-1 mRNA between the low and high dose groups of vitamin C.Conclusions:1 Vitamin C played an antioxidant role in rat lung injury models exposured to PM2.5.However,the increase of vitamin C concentration did not significantly improve the antioxidant effect.2 The expression of Nrf2/HO-1 pathway in lung tissue decreased in PM2.5 exposed rat models.And the expression of Nrf2,HO-1 and HO-1mRNA increased in rats with vitamin C intervention.