School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China; College of Life Sciences, Shanghai University, Shanghai 200444, China.
College of Life Sciences, Shanghai University, Shanghai 200444, China.
Neurobiol Dis. 2023 Jul;183:106173. doi: 10.1016/j.nbd.2023.106173. Epub 2023 May 27.
Neuronal hyperexcitation in the rostral ventrolateral medulla (RVLM) drives heightened sympathetic nerve activity and contributes to the etiology of stress-induced hypertension (SIH). Maintenance of mitochondrial functions is central to neuronal homeostasis. PDZD8, an endoplasmic reticulum (ER) transmembrane protein, tethers ER to mitochondria. However, the mechanisms of PDZD8-mediated ER-mitochondria associations regulating neuronal mitochondrial functions and thereby mediating blood pressure (BP) in the RVLM of SIH were largely unknown. SIH rats were subjected to intermittent electric foot shocks plus noise for 2 h twice daily for 15 consecutive days. The underlying mechanisms of PDZD8 were investigated through in vitro experiments by using small interfering RNA and through in vivo experiments, such as intra-RVLM microinjection and Western blot analysis. The function of PDZD8 on BP regulation in the RVLM was determined in vivo via the intra-RVLM microinjection of adeno-associated virus (AAV)2-r-Pdzd8. We found that the c-Fos-positive RVLM tyrosine hydroxylase (TH) neurons, renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE) level, BP, and heart rate (HR) were elevated in SIH rats. ER-mitochondria associations in RVLM neurons were significantly reduced in SIH rats. PDZD8 was mainly expressed in RVLM neurons, and mRNA and protein levels were markedly decreased in SIH rats. In N2a cells, PDZD8 knockdown disrupted ER-mitochondria associations and mitochondrial structure, decreased mitochondrial membrane potential (MMP) and respiratory metabolism, enhanced ROS levels, and reduced catalase (CAT) activity. These effects suggested that PDZD8 dysregulation induced mitochondrial malfunction. By contrast, PDZD8 upregulation in the RVLM of SIH rats could rescue neuronal mitochondrial function, thereby suppressing c-Fos expression in TH neurons and decreasing RSNA, plasma NE, BP, and HR. Our results indicated that the dysregulation of PDZD8-mediated ER-mitochondria associations led to the loss of the activity homeostasis of RVLM neurons by disrupting mitochondrial functions, thereby participating in the regulation of SIH pathology.
延髓头端腹外侧区（RVLM）中的神经元过度兴奋会驱动交感神经活动增加，并导致应激诱导性高血压（SIH）的发生。维持线粒体功能对于神经元的内稳态至关重要。PDZD8 是一种内质网（ER）跨膜蛋白，将 ER 与线粒体连接起来。然而，PDZD8 介导的 ER-线粒体关联调节神经元线粒体功能从而调节 SIH 中 RVLM 血压（BP）的机制在很大程度上尚不清楚。将 SIH 大鼠暴露于每天两次、每次 2 小时的间歇性足底电击加噪声，连续 15 天。通过使用小干扰 RNA 的体外实验和通过 RVLM 内微注射和 Western blot 分析等体内实验研究了 PDZD8 的潜在机制。通过 RVLM 内微注射腺相关病毒（AAV）2-r-Pdzd8 来确定 PDZD8 对 RVLM 中 BP 调节的作用。我们发现，SIH 大鼠的 RVLM 酪氨酸羟化酶（TH）神经元中的 c-Fos 阳性神经元、肾交感神经活动（RSNA）、血浆去甲肾上腺素（NE）水平、BP 和心率（HR）升高。SIH 大鼠 RVLM 神经元中的 ER-线粒体关联显著减少。PDZD8 主要在 RVLM 神经元中表达，并且 SIH 大鼠中的 mRNA 和蛋白水平明显降低。在 N2a 细胞中，PDZD8 敲低破坏了 ER-线粒体关联和线粒体结构，降低了线粒体膜电位（MMP）和呼吸代谢，增加了 ROS 水平，并降低了过氧化氢酶（CAT）活性。这些作用表明 PDZD8 失调会导致线粒体功能障碍。相比之下，在 SIH 大鼠的 RVLM 中上调 PDZD8 可以挽救神经元线粒体功能，从而抑制 TH 神经元中的 c-Fos 表达并减少 RSNA、血浆 NE、BP 和 HR。我们的结果表明，PDZD8 介导的 ER-线粒体关联的失调通过破坏线粒体功能导致 RVLM 神经元的活动稳态丧失，从而参与 SIH 病理的调节。
