Subendothelial retention of apolipoprotein B100-containing lipoprotein, such as low-density lipoprotein (LDL), is the initial step of atherogenesis. Activation of autophagy exhibits beneficial effects for the treatment of atherosclerosis. In our previous study, we demonstrated that hyperglycemia suppressed autophagic degradation of caveolin-1, which in turn resulted in acceleration of caveolae-mediated LDL transcytosis across endothelial cells and lipid retention. Therefore, targeting the crossed pathway in autophagy activation and LDL transcytosis interruption may be a promising antiatherosclerotic strategy. In metabolic diseases, including atherosclerosis, salidroside, a phenylpropanoid glycoside compound (3,5-dimethoxyphenyl) methyl-β-glucopyranoside), is the most important compound responsible for the therapeutic activities of Rhodiola. However, whether salidroside suppresses LDL transcytosis to alleviate atherosclerosis has not yet been elucidated. In the present study, we demonstrated that salidroside significantly decreased LDL transcytosis across endothelial cells. Salidroside-induced effects were dramatically blocked by AMPK (adenosine monophosphate-activated protein kinase) inhibitor (compound c, AMPKα siRNA) and by overexpression of exogenous tyrosine-phosphorylated caveolin-1 using transfected cells with phosphomimicking caveolin-1 on tyrosine 14 mutant plasmids (Y14D). Furthermore, we observed that salidroside promoted autophagosome formation via activating AMPK. Meanwhile, the interaction between caveolin-1 and LC3B-II, as well as the interaction between active Src (indicated by the phosphorylation of Src on tyrosine 416) and LC3B-II, was significantly increased, upon stimulation with salidroside. In addition, both bafilomycin A₁ (a lysosome inhibitor) and an AMPK inhibitor (compound c) markedly prevented salidroside-induced autophagic degradation of p-Src and caveolin-1. Moreover, the phosphorylation of caveolin-1 on tyrosine 14 was disrupted due to the downregulation of p-Src and caveolin-1, thereby directly decreasing LDL transcytosis by attenuating the number of caveolae on the cell membrane and by preventing caveolae-mediated LDL endocytosis released from the cell membrane. In ApoE^-/- mice, salidroside significantly delayed the formation of atherosclerotic lesions. Meanwhile, a significant increase in LC3B, accompanied by attenuated accumulation of the autophagy substrate SQSTM1, was observed in aortic endothelium of ApoE^-/- mice. Taken together, our findings demonstrated that salidroside protected against atherosclerosis by inhibiting LDL transcytosis through enhancing the autophagic degradation of active Src and caveolin-1.

中文翻译：

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红景天苷介导的主动Src和Caveolin-1自噬靶向抑制跨内皮细胞的低密度脂蛋白转胞吞作用。

含载脂蛋白B100的脂蛋白（如低密度脂蛋白（LDL））在内皮下的保留是动脉粥样硬化的第一步。自噬的激活表现出对动脉粥样硬化治疗的有益作用。在我们之前的研究中，我们证明了高血糖抑制了caveolin-1的自噬降解，进而导致了caveolae介导的LDL跨细胞内皮细胞LDL转胞吞的加速和脂质的滞留。因此，在自噬激活和LDL转胞吞作用中断中靶向交叉途径可能是一种有前途的抗动脉粥样硬化策略。在包括动脉粥样硬化在内的代谢疾病中，红景天苷，一种苯丙烷类糖苷化合物（3,5-二甲氧基苯基）甲基-β-吡喃葡萄糖苷）是负责红景天治疗活性的最重要化合物。然而，尚未阐明红景天苷是否抑制LDL转胞作用以减轻动脉粥样硬化。在本研究中，我们证明了红景天苷显着降低了跨内皮细胞的LDL转胞作用。红景天苷诱导的作用被AMPK（单磷酸腺苷激活的蛋白激酶）抑制剂（化合物c，AMPKαsiRNA），并使用转染细胞并在小酪氨酸14突变质粒（Y14D）上模拟小窝-1磷酸化转染细胞，从而过表达外源性酪氨酸磷酸化小窝-1。此外，我们观察到红景天苷通过激活AMPK促进了自噬体的形成。同时，在红景天苷刺激下，caveolin-1与LC3B-II之间的相互作用以及活性Src（由酪氨酸416上的Src磷酸化指示）与LC3B-II之间的相互作用显着增加。此外，两种bafilomycin A ₁（溶酶体抑制剂）和AMPK抑制剂（化合物c）明显预防了红景天苷诱导的p-Src和小窝蛋白1的自噬降解。此外，由于p-Src和caveolin-1的下调，破坏了酪氨酸14上caveolin-1的磷酸化，从而通过减弱细胞膜上caveolae的数量并防止caveolae介导的LDL内吞作用释放而直接降低了LDL转胞吞作用。从细胞膜。在ApoE ^-/-小鼠中，红景天苷显着延迟了动脉粥样硬化病变的形成。同时，在ApoE的主动脉内皮中观察到LC3B的显着增加，伴随着自噬底物SQSTM1的积累减少^。老鼠。两者合计，我们的研究结果表明，红景天苷通过增强活性Src和Caveolin-1的自噬降解来抑制LDL转胞吞作用，从而预防动脉粥样硬化。