MmLDL Upregulate ET_AR Through Class Ⅲ PI3K/Beclin-1 Signal Pathway

Purpose and background Minimally modified low-density lipoprotein(mmLDL)as a seminal factor,takes part in many cardiovascular diseases.This study was designed to examine the role of autophagy in mmLDL-associated endothelin type A(ET_A)receptors and contractile regulation in mice mesenteric arteries.Methods Intravenous tail injection of mmLDL in the experimental group,which is mmLDL group,and mmLDL+3-MA group.Then mice were subjective to an intraperitoneal injection of the autophagic inhibitor3-Methyladenine(3-MA)(mmLDL+U0126 group).Mice were injected with normal saline(NS group),the autophagic protein level and contractile properties of mesenteric arteries were evaluated in mice.The dose-response curve of mesenteric artery contraction induced by endothelin-1(ET-1),the ET_A receptor agonist,was measured using a sensitive myograph system.ELISA were used to determine the serum concentrations of mouse oxidized low density lipoprotein(oxLDL).The expression of ET_A receptor was detected by RT-PCR and Western blot.Results The expression of autophagy relative protein was detected by Western blot.Compared with the NS group,the mmLDL group exhibited a noticeably enhanced ET-1-induced dose–response curve and a significantly increased Emax value(P<0.01).3-MA(the autophagic inhibitor)caused a noticeable right shift of the dose–response curve.3-MA inhibited the autophagy and abolished the ET-1-induced dose–response curve caused by mmLDL,as observed by a significantly decreased Emax value(P<0.01).It inhibited the increased ET_A receptors expression caused by mmLDL.3-MA inhibited the mmLDL-induced the ClassⅢPI3K、beclin-1and LC3-II/I protein level increased and p62protein level reduced in the vessel wall.3-MA also attenuated mmLDL increased the protein expression of p-NF-κB.Conclusions mmLDL increased the protein level of NF-κB in vivo by activating the autophagy pathway,which resulted in ET_A receptor-mediated vasoconstriction and an increase in the expression of ET_A receptor.The results of this study may provide new ideas for the prevention and cure of cardiovascular diseases in the future.