Effect And Mechanism Of Acute PM_2.5 Exposure On Lung Injury In Rats

Objective:To study the acute exposure of PM_2.5to rats by tracheal drip to study its pulmonary injury on rats of different sexes,and to further explore its occurrence mechanism.Methods:SPF-grade SD rats were randomly divided into normal saline control group,PM_2.5high,medium and low dose（13.5mg/kg,4.5mg/kg,1.5mg/kg）groups,and dissected after seven consecutive days of tracheal instillation to observe the general changes of lung organs.Calculation of pulmonary coefficients;Detect the changes of oxidative stress indexes MDA,SOD,GSH-PX of lung tissue;Detect the changes of pulmonary epithelial injury indexes（LDH,AKP）and pulmonary vascular permeability indexes（ALB,TP）in BALF.HE staining to observe the pathological structure of lung tissue;ELISA measured the expression levels of pyroxosis-related inflammatory factors IL-1βand IL-18 in lung tissue;RT-PCR detected the expression levels of NLRP3 and caspase-1 m RNA genes associated with pyroptosis in lung tissues.Western-Blot measured the expression levels of lung tissue pyroptosis-related proteins NLRP3 and caspase-1proteins.Results:（1）After PM_2.5tracheal instillation,the general changes of the lung organs of rats were observed by dissection,and it was found that the lung tissue structure of the saline control group was clear,the texture was soft,the color was uniform,the surface was flat,and there were no obvious black spots and dark spots.Among them,the high-dose group of male mice had obvious dark spots and texture changes.（2）The results of lung organ coefficient showed that the organ coefficient was increased in the high-dose group of female mice compared with the normal saline control group,and the difference was statistically significant（P<0.05）;compared with female mice,the lung coefficient of male mice in the low-dose group was lower and the difference was statistically significant（P<0.05）.（3）The results of oxidative stress showed that compared with the normal saline control group,female mice were high,medium and The MDA content in the low-dose group was increased（all P<0.05）,and compared with the female mice,the male mice in the high-dose group had a lower MDA content and the difference was statistically significant（P<0.05）.Compared with the control group,the content of GSH-Px in each dose group of female mice gradually decreased with the increase of dose,and the difference between the high dose group and the normal saline control group was statistically significant（P<0.05）.（4）Compared with the control group,the AKP content in the high-dose group,high-dose group and high-dose group of female mice and male mice was increased statistically significantly（all P<0.05）;the LDH content in the high-dose group,high-dose group and high-dose group of male mice was significantly higher than that in the normal saline control group,and the difference was statistically significant（P<0.01）;the TP content in the high-dose group of female mice and the low-dose group and high-dose group of male mice increased（all P<0.05）,and compared with female mice,the LDH content in the high-dose group and the low-dose group and high-dose group of male mice increased（all P<0.05）.The TP content in the high-dose group was low（P<0.05）;Compared with the control group,the ALB content of female mice in the medium and high dose groups was increased（P<0.05）,and the ALB content of male mice in the high dose group was increased（P<0.01）.（5）HE staining found that with the increase of the dose of infection,the alveolar wall gradually thickened,and a large area of alveolar consolidation appeared in the medium and high dose groups,and the lesions of female mice were more serious than those of male mice.（6）In order to further observe whether the toxic effect of lung induced by different doses of PM_2.5tracheal drip is related to pyrozoosis,ELISA was used to detect the level of pyrozois-related inflammatory factors,and it was found that the content of IL-1βincreased in the high-dose group of female mice and male mice compared with the normal saline control group of the same sex,and the difference was statistically significant（P<0.01）;the level of IL-18 in the middle and high-dose groups of female mice and the high-dose group of male mice was significantly higher than that of the corresponding control group.The difference was statistically significant（P<0.05）;（7）RT-PCR results showed that compared with the control group,the expression levels of NLRP3 and caspase-1 m RNA in the medium-dose group and high-dose group of female mice were increased（P<0.05）,and the expression level of caspase-1 m RNA in the high-dose group of male mice was increased（P<0.05）,compared with female mice in the same dose group,and caspase-1 in the medium-dose group of male mice The expression of m RNA was low and the difference was statistically significant（P<0.05）.（8）It can be seen from the band plot of Western-Blot results that NLRP3 and caspase-1 proteins as a whole show an upward trend of expression with the increase of infection dose,among which the bands of the medium-dose group and high-dose group of female mice are significantly darker than those of male mice.The grayscale value of protein was analyzed and it was found that the NLRP3 protein in the low,medium and high dose groups of female mice was upregulated and the difference was statistically significant compared with the control group（all P<0.05）,the NLRP3 protein level in the low-dose group and the medium-dose group of male mice was adjusted up and the difference was statistically significant compared with the control group（all P<0.05）,and the expression of caspase-1 protein in the medium-dose group and high-dose group of female mice was upregulated compared with the control group（P<0.05）.Conclusion:PM_2.5cause morphological and pathological damage to rat lung tissue,and cause oxidative stress response of rat lung tissue,so that rat alveolar epithelial injury,alveolar epithelial-capillary barrier is destroyed,these damage may be due to lung tissue cell pyrozis caused by the body’s inflammatory response,resulting in oxidative stress and tissue damage and a series of reactions,PM_2.5on lung tissue these toxic effects have sex differences,manifested as female rats more serious damage than male mice.