Effects And Mechanisms Of Histone Deacetylase 9 Inhibitor On Atherosclerosis In Mice

BackgroundA report on cardiovascular health and disease in China showed that the prevalence of coronary heart disease is still increasing year by year,and as we know atherosclerosis is its main pathogenesis.The lipid metabolism disorders is the prominent risk factor,as well as the most significant therapeutic target.However,there is still an insufficient rate of lipid attainment with the current treatment strategy based on statins.Exploring new means of lipid lowering is necessary.Most of the existing treatments target hepatic lipid metabolism,especially the process of cholesterol synthesis and absorption.With the maturaity of second generation sequencing technology,intestinal flora has been found to be closely related to as in recent years.By taking part in nutritional digestion in the intestine and secreting compounds that impact steroid,bile acid,and glucose metabolism,the flora contributes to the development and occurrence of atherosclerosis.The intestinal flora may become another important target for the treatment of AS and the regulation of blood lipid metabolism.Recently,several clinical studies have identified an association between histone deacetylase 9(HDAC9)polymorphisms and arteriosclerosis.HDAC9 has also been implicated in lipid metabolism and the direction of the inflammatory response.What’s more,a previous study by our group found that proline/serine rich coiled coil 1(PSRC11)is protective for AS.ApoE-/-mice with knockout of PSRC1 gene showed increased blood lipids and aggravated as lesions,along with disturbed intestinal flora.Further liver transcriptome sequencing found that its HDAC9 transcript level was upregulated.The above studies suggest that HDAC9 may be involved in lipid metabolism disorders and inflammatory responses during the progression of AS.ObjectiveThe aim of the study was to explore the possible effect and mechanism of the HDAC9 inhibitor TMP195 on atherosclerosis.Methods18 male ApoE-/-mice aged 8 weeks,after being fed with high fat for 12 weeks to construct AS model,were apportioned into three groups at random and given drug interventions for 4 weeks:Control group,TMP195 group,atorvastatin group.After intervention,tissue samples were collected.The hepatic steatosis area and the aorta gross plaque area were assessed by oil red O staining.Four items of mouse lipid,and hepatic lipid transporter expression were detected and validated in vitro.Transcription levels of peritoneal macrophage inflammatory factor were detected and experimentally verified in vitro.Untargeted metabolomics was applied to identify gut flora compounds,and 16srRNA sequencing was performed to assess differences in gut flora abundance between groups.ResultInhibition of HDAC9 reduced plaque area,total cholesterol,triglyceride,and LDL-C levels in high-fat fed ApoE-/-mice.Protein levels of cholesterol transporters include of ABCG5,LXR,LDLR and SRB1 in mouse liver were significantly upregulated.After intervention of TMP195,peritoneal macrophages from ApoE-/-mice as well as raw264.7 cell line inflammatory cytokines IL-6,TNF-α mRNA levels were significantly downregulated.Inhibition of HDAC9 altered the composition of the gut microbiota in mice,in which Lactobacillus abundance was significantly increased.Untargeted metabolomics identified significantly increased riboflavin-5-phosphate and L-ascorbic acid levels in serum.ConclusionsThe HDAC9 inhibitor TMP195 can slow the progression of atherosclerotic lesions,mainly by activating the LXR pathway to upregulate ABCG5 expression to increase cholesterol efflux,upregulating LDLR and SRB1 to increase blood cholesterol uptake by the liver,increasing abundance of Lactobacillus to reduce blood lipids and alleviating macrophage inflammatory responses.