Study On The Effects Of Cadmium Inhalation Exposure On Pulmonary Microenvironments And Respiratory Movements Of Mice

Cadmium as a toxic heavy metal widely exists in the natural environment and can enter the human body through a variety of ways.The relationship between inhalation exposure and human health has attracted more and more attention.Lung,as a respiratory organ of mammals,is the most vulnerable to the toxicity of cadmium aerosols.Both respiratory model study in vitro and epidemiological investigation show that the size distribution and exposure concentration of atmospheric particulates are correlated with their lung deposition,and the changes of lung microenvironment have also been proved to be closely related to the occurrence of lung diseases.However,the effects of cadmium inhalation exposure on the pulmonary microbial diversity,the formation of lung injury and the process of pulmonary microenvironment remodeling,and the changes of respiratory movement accompanied by respiratory compensation after lung injury are still unclear.Moreover,the traditional methods of lung histology evaluation often lead to deviations in the evaluation results due to the operator's experience differences.Based on this,the following research work has been carried out in this paper:?1?First,a two-stage atomization method combining ultrasonic atomization and aerodynamic atomization has been established to realize the preparation of liquid aerosols containing cadmium with different particle size distributions,and particle size effect in lung deposition and lung injury has been confirmed by cadmium inhalation exposure experiments in mice;?2?A machine vision-based lung tissue section analysis method was established to characterize the lung tissue structure,combined with the sequencing of pulmonary microbial diversity and the correlation analysis of pulmonary microenvironment factors,the pulmonary microenvironments of mice before and after cadmium inhalation exposure were characterized;?3?Based on the body characteristics of mice,a method of regional optical tracing of respiratory movement was established to explore the effects of cadmium inhalation exposure on respiratory movement in mice.The results were as follows:1.Inhalation exposure based on two-stage atomization and size effect of inhalable particulate matter containing cadmium.The results showed that the deposition of particulate matters containing cadmium in the lungs were more under the two-stage atomization condition producing more PM_2.5,which resulted in more significant increases in lung coefficient,MDA in lung tissues,i.e.increased levels of oxidative stress,pulmonary parenchyma,the expression of ATF-6 and CHOP genes related to endoplasmic reticulum stress,and the expression of TNF-?and IL-6 genes related to inflammation.The results showed that particulate matters containing cadmium had significant size effect on particle deposition in lung and lung injury in mice,and PM_2.5 had a higher correlation with pulmonary cadmium concentration and lung injury than PM₁₀.2.Machine vision analysis of lung tissue structure changes in mice exposed to cadmium inhalation.The results showed that:?1?the fitting curve between the structural element number in closed operation and the defined pulmonary aperture count was single-peak in machine vision analysis on binary lung tissue section stained images,and its peak value could be used as an appropriate parameter for the calculation of pulmonary aperture;?2?the fitting curve between the structural element number in dilation operation and the defined pulmonary aperture coefficient was logistic growth,and conformed to the simplified simulation of pulmonary aperture with circular hole.Mathematical tests of expansion operation showed that the pulmonary aperture coefficient defined in this study could be used as an effective index for describing the geometric characteristics of lung tissue;?3?with the increase of CdCl₂ exposure dose?0,1,3,5 mM?,the area of pulmonary aperture space,the pulmonary aperture count and the pulmonary aperture coefficient on the stained images of lung tissue sections in mice decreased,while the area of alveolar tissue,euler number and mean area of aperture space,the levels of pulmonary fibrosis and mucus increased,while the group treated by low dose CdCl₂?1 mM?had relatively high levels of pulmonary inflammation,suggesting that different doses of cadmium inhalation exposure could induce pathological changes of lung tissue structure and presented changes in pulmonary microenvironment;?4?interstitial pneumonia,reduced pulmonary volume and alveoli could promote pulmonary gas diffusion barrier in mice after cadmium inhalation exposure,pulmonary fibrosis increased elastic resistance,these pulmonary pathological changes were accompanied by the raise of hematocrit and hemoglobin concentration,which suggested that the changes of pulmonary microenvironment promoted the occurrence of hypoxic hypoxia in mice,while the pH of heart blood and bronchoalveolar lavage fluid increased,indicating that respiratory alkalosis occurred in mice after hypoxia.3.Response of pulmonary microorganisms to the pulmonary microenvironment of mice after cadmium inhalation exposure.The results showed that:?1?different doses of cadmium inhalation could induce different pulmonary microenvironment in mice.In addition to the differences of inherent cadmium stress and the lung tissue structure,there were also differences in ventilation level,pH,nutritional status,inflammatory stress and pulmonary microbial diversity;?2?the correlation between pulmonary microorganisms and other pulmonary microenvironment factors was not consistent,in the lung injury induced by cadmium inhalation exposure,pulmonary microorganisms might participate in the process of pulmonary microenvironment remodeling,such as inflammatory cell infiltration,inflammation stress was the most important microenvironment factor affecting pulmonary microorganisms rather than Cd stress,while Lactobacillus spp.was the most influential group of pulmonary microorganisms;?3?differences in the pulmonary microbial diversity in mice caused by different doses of cadmium inhalation might be directly related to the changes of pulmonary microenvironment factors,or indirectly related to the changes of pulmonary microorganisms based on the potential species correlations among pulmonary microorganisms;?4?the levels of gene function and metabolic pathway in pulmonary microorganisms had different manifestations under different doses of cadmium inhalation exposure,the control group had higher extracellular structure-related gene function level and lower ubiquitination-related metabolic pathway level.4.Analyses of respiratory movements in somatic characteristic regions of mice exposed to cadmium inhalation.The results showed that:?1?videos of respiratory movements on the ventral surfaces of mice could reflect the periodicity of respiratory movements more truthfully than that on the lateral surfaces,the relative position of diaphragm used to locate the focus of respiratory motion video was relatively stable in different individuals,in the model of thoracoabdominal distribution based on the anatomical structure of mice,the relative position of the defined thoracoabdominal boundary in different individuals was also relatively stable,when the width of the video analysis area of respiratory movement was small,the noise data of respiratory movement signals detected were less;?2?the frequency,amplitude and rhythm index of respiratory movements increased after cadmium inhalation exposure,indicating the emergence of compensatory enhancement of respiratory movement and the subsequent decline of stability,the correlations between the exposure doses or times of cadmium inhalation and the respiratory movements of mice were low at low dose and short exposure time,but with the raise of exposure doses and times,the correlations showed upward trends;?3?in normal and pathological thoracoabdominal respirations of mice,abdominal respiratory movement contributed more,after cadmium inhalation exposure,the thoracoabdominal respiratory movements of mice showed different state changes,in respiratory compensation after lung injury,abdominal respiratory movement had stronger adaptive regulation and more obvious fluctuation.In conclusion,this study originally used inhalation exposure methods of two-stage atomization,machine vision analysis on lung tissue section stained images and optical tracing of respiratory movements to explore the pulmonary microenvironments and respiratory movements of mice exposed to cadmium inhalation.The results showed that:cadmium-containing particulate matter had size effect on pulmonary cadmium deposition and lung injury in mice;after cadmium inhalation exposure,the changes of pulmonary microenvironment factors such as the lung tissue structures and pulmonary microbial diversity of mice were observed and had obvious dose effects;pulmonary microorganisms had special response to the pulmonary microenvironment exposed to cadmium inhalation and were closely related to the inflammatory reaction of lung tissue;cadmium inhalation exposure could lead to respiratory alkalosis in mice,the amplitude and the decline of stability in abdominal respiratory movements were more significant than thoracic respiration in the period of respiratory compensation.The new methods and conclusions presented in this study can provide references for the further study on toxic effects and mechanisms of inhalable particulates.