The Effects Of Myeloid Angiotensin Type 1 Receptor Gene Knock Out On Vascular Insulin Resistance And Vascular Injury In Salt-sensitive Hypertensive Mice

ObjectiveHypertension is often associated with the activation of renin-angiotensin system（RAS）and increased infiltration of inflammatory macrophages.We have previously shown that treatment with the angiotensin type 1 receptor（AT1R）blocker candesartan improved vascular insulin signaling pathway and vascular function,and reduced vascular inflammation and vascular damage in salt-sensitive hypertensive mice.Chemical depletion of macrophages reduces blood pressure and improves vascular function and vascular insulin resistance.Macrophages can express all components of RAS,but whether RAS in macrophages participated in impairment of vascular insulin signaling and vascular dysfunction in hypertension is still not defined.In the present study,we investigated the role of myeloid AT1R in the regulation macrophage M1function,impaired vascular insulin resistance and vascular injury in deoxycorticosterone acetate（DOCA）salt sensitive hypertensive mice,using specific myeloid AT1R knockout mice.MethodsC57BL/6J and Mye AT1R^-/-mice were randomly divided into four groups:control,DOCA-salt hypertension,Mye AT1R^-/-,and Mye AT1R^-/-/DOCA-salt hypertensive group（n=8）.The mice were treated with DOCA and high salt for 5 weeks to induce DOCA/salt hypertension.Systolic blood pressure（SBP）was measured by tail cuff method.Hematoxylin-eosin staining was used to evaluate aortic hypertrophy,Masson-Trichron staining was used to evaluate aortic fibrosis,immunofluorescence for F4/80（a marker for monocyte/macrophage）,and Real-time PCR was used to detect abdominal macrophage AT1R,macrophage M1 and M2 polarization factors.Western blot was used to detect the protein expression of abdominal macrophage AT1R,aorta and macrophage proinflammatory factors and insulin signaling pathway molecules.Acetylcholine or insulin-induced endothelium-dependent relaxation（EDR）was determined by organ bath system.ResultsDOCA mice exhibited an increase in systolic blood pressure（P<0.05）,aortic thickness（P<0.01）and aortic fibrosis（P<0.01）,and impairment of endothelium-dependent vasodilation to acetylcholine or insulin（P<0.05）.Compared with control mice,the number of F4/80 positive cells（P<0.01）,the protein expression of MCP-1,TNFα（P<0.05）and p-JNK（P<0.01）were increased in the aorta of DOCA hypertensive mice.The protein expression of AT1R（P<0.05）and m RNA expression of M1inflammatory cytokines i NOS（P<0.01）and TNFa were increased（P<0.05）in the peritoneal macrophage of DOCA hypertnsive mice,while the m RNA expression of M2macrophage markers CD163 and CD206 was decreased（P<0.01）.The protein expression of HIF1α,TLR4,p-IκB and TNFαwere increased（P<0.01）in the peritoneal macrophage of DOCA hypertnsive mice.The insulin signaling pathway protein expression of p-IRS1 was up-regulated（P<0.01）,and the insulin signaling pathway protein expression of p-e NOS and p-Akt were down-regulated（P<0.01）in the aorta of DOCA hypertensive mice.In DOCA salt sensitive hypertensive mice,specific Mye AT1R knockout reduced aortic hypertrophy（P<0.05）,aortic fibrosis（P<0.05）,the number of F4/80 positive cells（P<0.05）,the protein expression of MCP-1,TNFα（P<0.05）and p-JNK were down-regulated（P<0.01）in the aorta of Mye AT1R^-/-/DOCA hypertensive mice,improved endothelium-dependent vasodilation mediated by acetylcholine and insulin（P<0.05）,but did not significantly affect systolic blood pressure.The m RNA expression of i NOS and TNFαwere down-regulated（P<0.01）,the m RNA expression of CD163 and CD206 were up-regulated（P<0.01）in the peritoneal macrophage of Mye AT1R^-/-/DOCA hypertnsive mice.The protein expression of AT1R,HIF1α,TLR4,TNFα（P<0.05）and p-IκB was down-regulated（P<0.01）in the peritoneal macrophage of Mye AT1R^-/-/DOCA hypertnsive mice.The insulin signaling pathway protein expression of p-IRS1 was down-regulated（P<0.05）,the insulin signaling pathway expression of p-e NOS（P<0.05）and p-Akt were up-regulated（P<0.01）in the aorta of Mye AT1R^-/-/DOCA hypertensive mice.ConclusionsSpecific KO of myeloid AT1R inhibited vascular macrophage infiltration,vascular inflammation and macrophage M1 polarity induced by DOCA salt-sensitive hypertension,and improves endothelial function,vascular insulin resistance and vascular injury.Therefore,macrophage AT1R may be involved in the pathogenesis of hypertension and vascular damage as part of the activation of RAS in hypertension.