Laboratory of Cardiovascular Diseases, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu 610041, PR China.
Department of Cardiology, West China Hospital, Sichuan University, Chengdu, PR China.
Biomed Pharmacother. 2018 Aug;104:193-203. doi: 10.1016/j.biopha.2018.05.039. Epub 2018 May 15.
Nogo-B is a key endoplasmic reticulum (ER) protein that regulates ER stress signaling. However, its role in cardiac hypertrophy remains poorly understood. ER stress is interrelated with autophagy in the process of cardiac hypertrophy. Therefore, we aimed to test the hypothesis that both ER stress and autophagy signaling mediate the function of Nogo-B in cardiac hypertrophy.
Rat models of transverse aortic constriction (TAC), neonatal rat cardiomyocytes (NRCMs) stimulated with norepinephrine (Ne) and primary cardiac fibroblasts treated with transforming growth factor β1 (TGF-β1) were used in this study. The expression of Nogo-B and markers of ER stress were determined by quantitative RT-PCR, western blotting and immunofluorescence. Autophagy was measured by monitoring autophagic flux. Specific small interfering RNA (siRNA) of Nogo-B was transfected to investigate the role of Nogo-B in regulating cardiac hypertrophy.
In TAC-induced hypertrophic heart tissues, Ne-treated hypertrophic cardiomyocytes and TGF-β1-stimulated cardiac fibroblasts, the expression of Nogo-B, and markers of ER stress were significantly elevated. Impairment of autophagic flux was observed in the activated cardiac fibroblasts. Down-regulation of Nogo-B by siRNA further exacerbated Ne-induced cardiomyocyte hypertrophy and TGF-β1-induced cardiac fibroblast activation. Gene silencing of Nogo-B promoted the activation of the ER stress pathway and the impairment of autophagic flux. Moreover, inhibition of Nogo-B activated the protein kinase RNA-like ER kinase (PERK)/activating transcriptional factor 4 (ATF4) and activating transcriptional factor 6 (ATF6) branches of ER stress pathways.
These findings suggest that inhibition of Nogo-B promotes cardiomyocyte hypertrophy and cardiac fibroblast activation by activating the PERK/ATF4 signaling pathway and defects of autophagic flux.
Nogo-B 是一种关键的内质网（ER）蛋白，可调节 ER 应激信号。然而，其在心肌肥厚中的作用仍知之甚少。在心肌肥厚过程中，ER 应激与自噬密切相关。因此，我们旨在验证以下假说，即 ER 应激和自噬信号均介导 Nogo-B 在心肌肥厚中的功能。
本研究使用了腹主动脉缩窄（TAC）大鼠模型、去甲肾上腺素（Ne）刺激的新生大鼠心肌细胞（NRCMs）和转化生长因子β1（TGF-β1）处理的原代心肌成纤维细胞。通过定量 RT-PCR、Western blot 和免疫荧光测定 Nogo-B 和 ER 应激标志物的表达。通过监测自噬流来测量自噬。转染 Nogo-B 的特异性小干扰 RNA（siRNA），以研究 Nogo-B 在调节心肌肥厚中的作用。
在 TAC 诱导的肥厚心脏组织、Ne 处理的肥厚心肌细胞和 TGF-β1 刺激的心肌成纤维细胞中，Nogo-B 的表达和 ER 应激标志物显著升高。在激活的心肌成纤维细胞中观察到自噬流受损。siRNA 下调 Nogo-B 进一步加重了 Ne 诱导的心肌细胞肥大和 TGF-β1 诱导的心肌成纤维细胞激活。Nogo-B 的基因沉默促进了 ER 应激通路的激活和自噬流的损伤。此外，抑制 Nogo-B 激活了蛋白激酶 RNA 样内质网激酶（PERK）/激活转录因子 4（ATF4）和激活转录因子 6（ATF6）分支的 ER 应激通路。
这些发现表明，抑制 Nogo-B 通过激活 PERK/ATF4 信号通路和自噬流缺陷促进心肌细胞肥大和心肌成纤维细胞激活。
