Effects of estrogen on oxidative stress of the lung tissue induced by acute paraquat poisoning

Abstract

Objective To explore the effects of estrogen on oxidative stress of the lung tissue induced by acute paraquat (PQ) poisoning. Methods Thirty-two male adult New Zealand rabbits were randomly divided into model group and estrogen intervention group, 16 rabbits in each group. The model of lung injury induced by PQ poisoning was reproduced by feeding 16 mg/kg of 20% PQ through gastric tube. The rabbits in estrogen intervention group received intravenous infusion of 5 mg/kg estrogen after PQ challenge for 7 days, and the rabbits in model group received an equal volume of normal saline. Three rabbits in each group were sacrificed at 1, 2 and 3 days respectively after exposure. The lung tissue was harvested, the levels of reactive oxygen species (ROS) was determined by 2',7'-dichlorofluorescin diacetate (DCFH-DA), malondialdehyde (MDA) was determined by thiobarbituric acid (TBA), the mRNA expression of manganese-containing superoxide dismutase (MnSOD) was determined by reverse transcription-polymerase chain reaction (RT-PCR), and adenosine triphosphatase (ATP) content in mitochondrion was determined by enzyme linked immunosorbent assay (ELISA). The pathological changes in lung were observed under light microscopy using hematoxylin and eosin (HE) staining, and the lung injury was evaluated with lung injury score. Results The contents of ROS and MDA in lung within 3 days after PQ poisoning were gradually increased, and MnSOD mRNA expression and ATP content were gradually decreased. Estrogen intervention could significantly reduce the production of ROS and MDA after PQ poisoning [3-day ROS (fluorescence intensity): 161.05±30.04 vs. 188.30±31.80, 3-day MDA (mmol/L): 98.71±0.92 vs. 122.12±1.24], up-regulate MnSOD mRNA expression (integral A value: 3.05±0.90 vs. 1.22±0.24), and increase ATP content in mitochondrion (ng/L: 3.75±0.92 vs. 2.28±0.29) with statistically significant differences (all P < 0.01). In lung tissue after PQ poisoning, congestion, edema, focal pulmonary consolidation, pulmonary interstitial and alveolar space were infiltrated by a large number of neutrophil, alveolar interval were thickened obviously and the above phenomenon were most serious at 3 days after poisoning as shown under optical microscope. Estrogen intervention could significantly improve lung injury as compared with that of model group, and the lung injury score at 3 days was significantly lower than that of model group (11.8±0.7 vs. 13.5±1.0, P < 0.01). Conclusions The oxidative stress indicators in the lung tissue after PQ poisoning were obviously abnormal, the pathological damage was serious with time dependence. The administration of estrogen can reduce acute lung injury after PQ poisoning by reducing the oxidative stress. Key words: Paraquat; Acute poisoning; Estrogen; Acute lung injury; Oxidative stress; Mitochondria