| In recent years,the air quality in China is still very severe,the concentration of air pollutants is still relatively high,and the health problems caused by air pollution have received more and more attention.Studies have shown that air pollution has an impact on cardiovascular diseases.However,the etiology of cardiovascular diseases is complex.It is necessary to choose an appropriate model to study the mechanism of air pollution on the cardiovascular.Due to the heavy burden on the heart and the more susceptible myocardium,patients with basic cardiovascular diseases such as hypertension are more susceptible to air pollution.Therefore,we can further explore the mechanism of myocardial injury caused by air pollution by observing the changes in genes related to myocardial tissue damage in hypertensive patients.Recent studies have found that the composition of intestinal flora,F/B ratio(Firmicutes/Bacteroidetes ratio)are closely related to hypertension and coronary heart disease.There is also evidence that intestinal microbial dysfunction may contribute to a variety of diseases including hypertension and arteriosclerosis.Do the changes in the intestinal flora caused by air pollution further affect the cardiovascular system? At present,there is no research on this issue.Based on the above background,the spontaneously hypertensive rats(SHR)model was selected as experimental animals.The 16 S rDNA sequencing and transcriptome sequencing technology were used to study the effects of inhaled air pollutants on the intestinal flora and cardiovascular system of SHR.Then the data was used to analyze the relationship between changes in the intestinal flora and host cardiovascular system.On this basis,the influence of air pollutant exposure on the expression profile of myocardial tissue injury-related genes was analyzed,and the molecular mechanisms of the changes in blood pressure and myocardial injury in SHR caused by air pollution are explored,and finally provide a theoretical basis for elucidating the linkage toxic effects of air pollutants on the intestinal micro-ecosystem and cardiovascular system.It also provides more comprehensive recommendations for patients with hypertension to deal with air pollution,in the hope that microecological agents will intervene in the intestinal flora to combat cardiovascular diseases caused by air pollution.Methods1.In this study,atmospheric PM2.5 particulate matter collected in the autumn and winter seasons of Shenyang and artificially mixed gas pollutants were used as experimental air pollutants,and spontaneously hypertension rats(SHR)were used as animal models.SHR were exposed to PM2.5 pollution and mixed gas pollutants through tracheal instillation dust and dynamic poisoning systems.The effects of air pollutants on cardiovascular disease-related indicators such as body weight,blood pressure,and blood lipid of SHR were examined under the conditions of low,medium,and high exposure doses and 1-90 days exposure time.2.Stool samples of SHR were collected,and 16 S rDNA sequencing technology was used to detect the impact of air pollution on the intestinal flora of SHR.Bioinformatics methods,including Alpha diversity analysis(richness,evenness,diversity analysis,etc.),Beta diversity analysis(PCo A analysis,hierarchical clustering,etc.),microbial community composition analysis,and gut microbial function prediction were applied to analyze the changes in the intestinal microbial community structure caused by air pollution and the relatedness between these changes and the host cardiovascular system.3.Transcriptome sequencing technology and the QPCR method were used to detect gene expression profiles of myocardial tissues in SHR.Data quality control,sequence alignment,gene expression level quantification,differential gene expression analysis,and differential gene enrichment(GO and KEGG enrichment)analysis were applied to analyze the impact of air pollutants on the cardiovascular system.Further,the Western Blot and immunofluorescence methods were used to analyze the upstream and downstream proteins of the cardiovascular system-related signaling pathways where the differentially expressed genes are involved.Results1.The composition of air pollutants(PM2.5)in Shenyang include 16 polycyclic aromatic hydrocarbons,21 metal elements,and inorganic ions such as nitrate,sulfate,and ammonium ions.Inhalation air pollution exposure can slow down the growth and development of SHR,prolong the time required for SHR to reach adult body weight,and can further significantly increase the blood pressure of SHR,and there is a certain dose-effect relationship between the increase in blood pressure and air pollutant concentration.Moreover,medium or high doses of air pollutants cause significant acute changes in levels of serum triglyceride(TG),total cholesterol(TC),and low-density lipoprotein cholesterol(LDL-C)in SHR.2.In a short period of inhalation of air pollution(1-30 days),the richness of gut microbial community in SHR significantly decreased,and the ratio of Firmicutes to Bacteroidetes(F/B ratio)significantly increased,the abundance of some short-chain fatty acid(SCFA)producing bacteria(such as Faecalibacterium and Anaerostipes)significantly reduced,the abundance of Firmicutes that produces trimethylamine significantly increased.The intestinal microbial community was significantly disturbed.Functional analysis showed that air pollution exposure significantly reduced the propionic acid and acetic acid production capacity of intestinal microbiota in SHR,and these changes were related to the increase in damages in the host cardiovascular system.3.Inhalation of air pollution significantly affected the gene expression levels of myocardial tissue in SHR.GO enrichment analysis shows that differentially expressed genes are mainly enriched in cellular processes such as immune response and cellular components such as MHC protein complexes.KEGG pathway enrichment analysis showed that differentially expressed genes are mainly involved in viral myocarditis,T cell receptor signaling pathway,phagosomes,intestinal immune network,endocytosis,cell adhesion molecules,asthma,antigen processing and presentation,and other myocardial damage and immune response-related signal pathways.In cardiovascular disease-related signaling pathways,the expression levels of Ace(angiotensin-converting enzyme)gene and Agtr1a(angiotensin Ⅱ 1A receptor)gene that involved in blood pressure regulation,Atp2a2(sarcoplasmic/endoplasmic reticulum calcium transport ATPase A2)gene that involved in the regulation of calcium levels,and Atp2a2(sarcoplasmic/endoplasmic reticulum Calcium transport ATPase A2),Actc1(cardiac actin alpha1),Myh6(myosin heavy chain 6),Tnni3(cardiac troponin I)and Tnnt2(cardiac troponin T)that involved in myocardial contraction were significantly up-regulated.Western Blot analysis found that the protein expression of ACE,AGTR1 A,ATP2A2,TNNI3,and TPM3 in the renin-angiotensin system,vascular smooth muscle contraction pathway,myocardial contraction pathway,calcium ion signal pathway increased,while ACTC1,CALD1,CALM1,and TNNC1 decreased.Conclusions1.Air pollution has a significant impact on the body weight,blood pressure,and blood lipids of spontaneously hypertensive rats,and can significantly delay weight gain,raise blood pressure,cause blood lipid metabolism disorders,and other effects that damage the cardiovascular system.2.Inhalation of air pollution can significantly affect the diversity,community composition,and metabolic profile of the intestinal microbiota of SHR,and these changes in intestinal flora can affect the cardiovascular system through metabolites such as SCFA.3.The air pollutants damage the cardiovascular system of SHR through the immune response-related signaling pathways,the renin-angiotensin system,and calcium ion signaling pathways of myocardial tissue.It provides the research direction and experimental basis for understanding the intestinal microflora pathway of blood pressure rising of SHR and heart damage caused by air pollution. |
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