| Background: As a kind of non-cardiogenic pulmonary edema based on the damage of endothelial-epithelial barriers, acute lung injury can be caused by a variety of direct or indirect factors of injury, such as pneumonia, trauma, poisoning, etc. The early pulmonary lesions caused by paraquat poisoning fall into the category of acute lung injury caused by poison. In the lung tissue, the toxicity of paraquat will lead to apoptosis of damaged cells. And in the acute period of destruction, Type I and Type II alveolar epithelial cells will swell, fall off, with mitochondria and endoplasmic reticulum generating cavitation and fracture damage. Following the acute period of destruction comes the fibroproliferative phase, during which the fibroblasts will be formed, leading to the formation of pulmonary fibrosis eventually. The clinical manifestations of paraquat poisoning depends on the intake of paraquat. A high intake of paraquat(> 50-100 ml, 20% concentration) may cause multiple organ failure. While the pulmonary and renal injury developed in 2-6 days are mainly caused by small doses of paraquat. The lung injury was divided largely into two stages: acute pneumonia phase from Day 1 to Day 3, and the later period of pulmonary fibrosis. However, there is no effective treatment unfortunately. Therefore, with the toxicological mechanism of paraquat and toxicokinetics as a breach, it is imminent to find a new method of effective treatment.Apigenin is a kind of natural flavonoids, abundant in a variety of fruits, vegetables, and medicinal herbs. It has been proved to have the effect of anti-oxidant, anti-inflammatory, anti-mutation, inhibition of tumor, inhibition of tumor proliferation and metastasis, and inhibition of angiogenesis etc. Moreover, the cytotoxicity of apigenin is very low, without mutagenic effect. Animal experiments show that, apigenin can play a protective role in acute lung injury induced by lipopolysaccharide. Previous researchers of apigenin, however, focused more on neoplastic diseases, autoimmune diseases, and inflammation induced by LPS, etc., while there's a lack of study reports of paraquat poisoning.Objective: This experiment mainly focuses on the effect of apigenin on acute lung injury in mice induced by paraquat poisoning, and preliminary discussion on its mechanism.Methods: 1. In vivo experiment, the experimental mice were divided into normal control group, the PQ group, PQ+API(20 mg / kg weight) group, PQ+API(50 mg / kg weight) group. Each group has 18 mice, which will be treated with apigenin or vehicle. The mice will to be put to death on the third day after induced by PQ or normal saline. Following specimens will be collected:(1) For the bronchoalveolar lavage fluid, detect the proinflammatory cytokines TNF-? and IL-6 by ELISA; conduct cell counting and classified counting by flow cytometry.(2) For the lung tissue, make HE dyeing pathological slices, and detect the tissue protein content, MDA level, SOD, GSH-Px and CAT enzyme activity with the biochemical method.(3) For the spleen, measure the change of weight, and cultivate the spleen cells induced by LPS or ConA and then detect IL-6 and IL-2 by ELISA.2. In vitro experiment, separate normal mouse spleen cells, and cultivate the cells with LPS as well as different concentration of apigenin for 24 hours. Then we collect the cells and supernatant to detect following indexes: the TNF-?, IL-6 levels of cell supernatant by ELISA, the toxicity of apigenin to spleen cells by cell counting kit-8, and the molecules(CD80,CD86 and MHC?) expressed on antigen presenting cells especially dendritic cells surface detected by flow cytometry.Results: 1. The effect of apigenin to the mice poisoned by paraquat:(1) The apigenin can reduce MDA in lung(P < 0.001), and improve the activity of SOD(P < 0.001), GSH-Px(P < 0.01) and CAT(P < 0.01);(2) Apigenin can alleviate the inflammatory cells' infiltration, lessen the level of IL-6(P < 0.01) and TNF-?(P < 0.01) in the BALF, and reduce the protein exudation in the lung tissue(P < 0.01);(3) Apigenin can reduce the spleen weight loss(P<0.05), cut down the spleen cells to secret IL-6 inducd by paraquat(P<0.05), and increase the level of IL-2(P<0.05).2. In vitro apigenin can suppress the secretion of proinflammatory cytokine IL-6(P < 0.01) and TNF-?(P < 0.05); and inhibit the expression of CD80, CD86 and MHC II on the surface of antigen presenting cells, especially dendritic cells. Besides, in certain scope, apigenin has no impact on the activity of immune cells.Conclusion: apigenin can alleviate acute lung injury in mice induced by paraquat poisoning, and the protective effect may be realized through anti-inflammatory and antioxidant mechanisms etc. Moreover, apigenin can inhibit the antigen presenting cells' maturity to achieve anti-inflammatory effect. |
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