The effect of lipoic acid on SP-A and SP-B during acute paraquat poisoning

Abstract

Objective To observe the changes in concentrations of pulmonary surfactant SP-A/B in lung tissue during acute lung injury (ALI) /acute respiratory distress syndrome (ARDS) induced by acute paraquat poisoning (PQP) after the treatment with metabolic antioxidant,lipoic acid,and to explore the potential involvement of TNF-α in ALI/ARDS as well as to discuss the assumed protective mechanisms of lipoic acid against acute lung injury.Methods Sixty-six male Sprage-Dawley rats were randomly (random number) divided into 3 groups,namely control group (NS,n =6),paraquat poisoning group (PQ,n =30),paraquat + lipoic acid treatment group (LA,n =30).Then both group PQ and group LA were further divided separately into five subgroups,namely 3,6,12,24 and 48 h subgroups (n =6 in each subgroup).After rats sacrificed,the lung tissues were selected,and after HE staining,histological changes were observed under light microscope.Histopathological changes were inflammation and fibrosis in models successfully established.The lung tissues were also taken for tests of SOD and MDA levels.Specimens of whole blood 0.8 mL without anticoagulant were taken from tail vein of rats for determining the TNF-α level.The expressions of SP-A mRNA and SP-B mRNA were measured with RT-PCR from total RNA of the lung tissue.Results ① HE staining showed that the histopathological changes were milder in LA group than that in PQ group.② There were significant differences in MDA and SOD levels between different intervals both in intergroups and intragroup except the groups of 3 hours (P ＜ 0.01).③ Likewise,the significant differences in the levels of TNF-α were also present between three groups and between different intervals (P＜0.01).④ The significant differences in SP-A mRNA and SP-B mRNA amplification ratio existed between three groups at the same interval (P ＜ 0.01),but those differences between different intervals in group PQ were of statistical significance (P ＜ 0.05).And those differences between diffirent intervals in group LA were statistically significant (P ＜0.01).Conclusions Lipoic acid in acute paraquat poisoning could lessen lung tissue damage,which might be directly dominated by the levels of tumor necrosis factor,and in turn indirectly affect the content of pulmonary surfactant,thereby reducing pulmonary edema and improving lung compliance,then protecting the lung tissues. Key words: Lipoic acid ; Paraquat; Acute lung injury ; Surfactant protein ; Tumor necrosis factor-α; Oxygen free radical; Superoxide dimutase; Malonaldehyde