Mechanism Study Of Quaternary Ammonium Disinfectant Disrupts Respiratory Microflora Homeostasis Cause Lung Injury

The use of disinfectants has increased dramatically since the outbreak of the COVID-19 health crisis in 2019,More attention has been paid to environmental enrichment and ecological risk of disinfectants.Among them,quaternary ammonium disinfectant(QAC),as the preferred reagent against SARS-Co V-2 virus,is advocated by various governments.High concentrations of QAC have been detected in the environment,with the concentration of QAC on indoor residential dust particles reaching 531μg/g.Epidemiological studies have shown that inhaled quaternary ammonium disinfectant is associated with various lung diseases,suggesting that quaternary ammonium disinfectant may promote the occurrence and development of lung diseases by affecting the immune defense system.In addition,the microorganisms attached to the respiratory tract have complex and diverse characteristics.As the gatekeeper of human health,microorganisms are also closely related to the occurrence and development of lung diseases.However,there is a lack of animal experimental models of quaternary ammonium disinfectant exposure to support the study of the effects of quaternary ammonium disinfectant on the pulmonary immune system and the mechanism of interaction with pulmonary microorganisms.Therefore,this study established an animal exposure model of quaternary ammonium disinfectant,analyzed the lung immune response to quaternary ammonium disinfectant,combined with the dynamic changes of lung microecology,and explored the molecular mechanism of the impact of quaternary ammonium disinfectant exposure on the lung health of mice.In this study,the BAC exposure model was established with C57BL/6 mice.The exposure group was exposed to whole-body dynamic inhalation,while the control group was exposed to fresh air.The mice were anesthetized at 1,3,7,and 14 days of exposure,extracted alveolar lavage solution and collected tissue samples.The weight of mice decreased after exposure,and the viscera-body ratio was also affected.H&E pathological staining showed that the lungs of mice exposed to BAC showed inflammatory infiltration,airway wall thickening and alveolar spacing increasing in a time dependent manner.There was absence of marginal area and blurred boundary of red and white pulp in spleen.Masson staining showed a progression of fibrosis in the lungs.PCR showed that the expression levels of inflammatory and chemokines such as IL-1β,TNF-α,CXCL2,GM-CSF,LTB4,and IL-8 increased in the lung and spleen after exposure,indicating that neutrophils gathered in the injured tissue and activated the immune response and triggered systemic inflammation.Subsequently,we explored the mechanism of neutrophilic effect,and it was found that the m RNA expressions of MPO,NE and PAD4 increased after exposure,revealing that neutrophils responded to BAC exposure by releasing NETs.After that,16 S r RNA sequencing was performed on the lung microorganisms of mice.The results showed that BAC exposure disturbed the lung microecology of mice,species richness and diversity decreased with time exposure,species composition was different at the phylum and genus levels,and the relative abundance of Firmicutes and Proteobacteria increased after exposure.In addition,the biomass of pathogenic bacteria increased after exposure and was significantly correlated with inflammatory and chemokine.These results indicated that BAC exposure increased the risk of colonization of pathogenic bacteria,and finally promoted the occurrence and development of lung diseases.After the prediction of microbial phenotype and function,it was found that the phenotype of Gram-negative,aerobic and compositive anaerobes and the ability of biofilm formation,migration and bacterial toxin secretion has increased.It indicating that the lung microecology of mice changed from healthy to pathogenic after BAC exposure.In addition,through the establishment of microbial co-vision network,it also shows that the stability of lung microorganisms is reduced and the resistance to environmental changes is weakened,which may increase health risks.The joint analysis of the immune response and microbial changes caused by exposure to BAC revealed the interaction mechanism of breaking the homeostasis of lung microbial community,and activating the immune defense of mice,and triggering systemic inflammation after exposure to BAC.This study provides theoretical support for the health risk management objective of controlling the use of disinfectants under the normal epidemic situation.