| Air pollution has become increasingly fearful with the rapid development of world economy for many developing countries.Cardiovascular disease,the world’s leading cause of death,has a gradual increase in the number of new cases and death rates due to air pollution.It is urgent to explore the mechanism of air pollution affecting cardiovascular disease and trace the role of air pollutant components in it.Based on basic medical research,this study is horizontally combined with myocardial biomechanics,and vertically explored the mechanism from the perspectives of histology and molecular biology,aiming to comprehensively and deeply explain the scientific problem that how ultrafine zinc particles in air pollutants to affect the progression of myocardial infarction.Based on Wistar rat models of myocardial infarction,physiological and functional indexes were measured after inhalation of ultrafine zinc particles for 4 and 6 weeks,respectively.The results showed that inhalation of ultrafine zinc particles for four weeks could retard the rate of deterioration of cardiac systolic-diastolic function and decrease the degree of ventricular wall thinning and enlargement,while at postoperative 6 weeks,cardiac function deteriorated sharply and the performance of thin-walled spherical heart rapidly became highlights.The results of factorial analysis showed that whether or not ultrafine zinc particles were inhaled and the time of inhalation had a significant interaction,suggesting that ultrafine zinc particles had a time-dependent cumulative effect on the deterioration of myocardial infarction.Myocardial strain and strain rate were measured by speckle tracking echocardiography.A three-dimensional model of left ventricular end-diastolic was constructed by myocardial finite element software from ultrasound images.Then the zero-pressure configuration was obtained by the method of inversion of the deformation gradient tensor.The nonlinear transect isotropic myocardial material hypothesis proposed by Mr.Feng was adopted.The end-diastolic pressure in left ventricle was loaded into the zero-pressure configuration to complete the diastolic simulation and achieve the Cauchy stress distribution in the ventricular wall.The results showed that strain and strain rate of LV decreased significantly after myocardial infarction,myocardial compliance weakened,diastolic stress increased significantly,and myocardial stiffness increased.The biomechanical characterization of MIZn4 group(myocardial infarctional rats inhaled ultrafine zinc particle for 4 weeks)was better than MI4 group,while there was an opposite result after 6 weeks.All these indicated that the effect of ultrafine zinc particles on the myocardial biomechanics after myocardial infarction also had a time-dependent cumulative effect.The vascular compliance and peripheral impedance of common carotid artery were calculated based on Windkessel model.Flow velocity profiles and associated hemodynamic parameters in carotid arteries were calculated using Womersley analysis.The results showed that the peripheral blood flow mechanical environment of the zinc inhalation group for 4 weeks was better than that of the group without zinc inhalation,while the hemodynamic parameters of the zinc inhalation group for 6 weeks were reversed and deteriorated.The effect of ultrafine zinc particles on peripheral hemodynamics also had time accumulation effect.Finally,the results of quantitative detection of serum zinc and tissue zinc,histological staining of myocardial samples and detection of various molecular markers showed that ultrafine zinc particles interfered with biological pathways such as inflammatory response,apoptosis and myocardium fibrosis after myocardial infarction by affecting zinc homeostasis.Furthermore,the interaction between inhalation of ultrafine zinc particles and further deterioration in functional,morphological and biomechanical characteristics after myocardial infarction was explained,and the time cumulative effect of inhalation of ultrafine zinc particles was explained from the perspective of molecular biology.In this paper,the mechanism of ultrafine zinc particles,regarded as the main metal component in air pollution particles,on the development of myocardial infarction was explored,which not only has positive social value for the precise governing of air pollution,but also provides a new idea for clinical detecting and evaluating biomechanical indexes and making precise treatment plans for myocardial infarction. |
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