Pulmonary Toxicology Of Chitosan Oligosaccharide-stearic Acid In Mice

Background and ObjectiveChitosan oligosaccharide-stearic acid(CSO-SA) is a new type of drug delivery material. A pre-experiment indicated that CSO-SA may cause acute lung injure when mice were exposed to high dose of CSO-SA. After examination of the lung of the dead mice, blutpunkte and adama were found in the lung. So it was conjected that lung might be the target organ of CSO-SA. Here we studied the possible machenism of how CSO-SA induced acute lung injury.Materials and methodsThe experiments included three parts:blood gas analysis, acute toxicity experiment and repeated toxicity experiment.1.Blood gas analysis:mice were divided into negative control(saline),treated groups(25,50,125mg/kg), positive control(LPS). After vain injection for lh, arterial blood samples were taken for analysis. The pH, PO2, PCO2and SO2were recorded for analysis.2.Acute toxicity experiment:mice were divided into negative control, treated groups(25,50,75mg/kg), positive control. The experiment were carried out by bronchoalveolar lavage analysis and lung homogenate analysis. Total cell number, protein content in lung, SOD, LDH, AKP level and MDA content were tested.3.Repeated toxicity experiment:mice were divided into6groups, negative control, treated groups(5,10,25,50mg/kg), positive control. Each mouse received tail intravenous injection of different dose of CSO-SA for five days. The experiment was carried out by bronchoalveolar lavage analysis, lung homogenate analysis, western blot. Lung histopathology was observed using HE staining and electron microscopy.Total cell number, protein content in lung, lung index, the SOD, LDH, AKP level and MDA content, the IL-1β, TNF-α level, SP-A in lung were examined. Data were analysized using Spss18.0, P<0.05was considered significant.ResultsThe pH of the blood in125mg/kg treatment group was significantly lower compared to the negative control after exposure to CSO-SA for1h. In repeated toxicity experiment,25and50mg/kg treatment can inhibit the weight gain notablely when compared to the control. At the same time, the lung index of those treatment group was increased compared to the control (P<0.05). Both acute and repeat treatments(24h,5d) significantly elevated total cell numbers in the BALF when compared to the negative group (p<0.05).Total protein concentration was increased in the75mg/kg (24h) and50mg/kg(5D) group significantly when compared to the negative control(p<0.05).The level of LDH in25,50mg/kg groups(5d) was increased compared to the control(p<0.05). The level of AKP in10,25,50mg/kg(5d) was increased when compared to the control(p<0.05).The level of IL-1β in all treatment group was increased compared to the control(p<0.05).The level of TNF-α in5,25,50mg/kg also increased compared to the control(p<0.05). The SP-A level in lung was significantly decreased after exposure to10,25,50mg/kg CSO-SA treatment compared to the negative control. CSO-SA affect the structure of pulmonary alveoli as HE staining shows in50mg/kg treatment. The electron microscopy shows exposure to CSO-SA produced necrosis of type Ⅱ alveoli, tissue thickening in50mg/kg treatment.Conclusion1. The target organ of CSO-SA is lung. Once or repeated injection of CSO-SA induce lung inflammation in mice and this maybe the main reason of acute death.2.Repeated injection of CSO-SA may induce apoptosis in lung cell and destory the structure of type II epithetium cell.CSO-SA may decreased the expression of SP-A in the lung and affect the function of breath.