Key result
TNF-α blockade reduces blood pressure and sympathetic outflow in stress-induced hypertension via the AMPK-Sirt3 pathway.
Why the study?
The impact of neuroinflammation on neuronal mitochondrial homeostasis and the involved signaling pathway in the RVLM during stress-induced hypertension were largely unknown.
Microglia-derived TNF-α in the RVLM contributes to stress-induced hypertension by impairing neuronal mitochondrial function via the AMPK-Sirt3 pathway, highlighting a potential therapeutic target.
May inform neuroinflammation-targeted hypertension research; leaves open translation of TNF-α blockade from rodent models to clinical use.
BACKGROUND: Neuroinflammation in the rostral ventrolateral medulla (RVLM) has been associated with the pathogenesis of stress-induced hypertension (SIH). Neuronal mitochondrial dysfunction is involved in many pathological and physiological processes. However, the impact of neuroinflammation on neuronal mitochondrial homeostasis and the involved signaling pathway in the RVLM during SIH are largely unknown. METHODS: The morphology and phenotype of microglia and the neuronal mitochondrial injury in vivo were analyzed by immunofluorescence, Western blot, RT-qPCR, transmission electron microscopy, and kit detection. The underlying mechanisms of microglia-derived tumor necrosis factor-α (TNF-α) on neuronal mitochondrial function were investigated through in vitro and in vivo experiments such as immunofluorescence and Western blot. The effect of TNF-α on blood pressure (BP) regulation was determined in vivo via intra-RVLM microinjection of TNF-α receptor antagonist R7050. RESULTS: The results demonstrated that BP, heart rate (HR), renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE), and electroencephalogram (EEG) power increased in SIH rats. Furthermore, the branching complexity of microglia in the RVLM of SIH rats decreased and polarized into M1 phenotype, accompanied by upregulation of TNF-α. Increased neuronal mitochondria injury was observed in the RVLM of SIH rats. Mechanistically, Sirtuin 3 (Sirt3) and p-AMPK expression were markedly downregulated in both SIH rats and TNF-α-treated N2a cells. AMPK activator A769662 upregulated AMPK-Sirt3 signaling pathway and consequently reversed TNF-α-induced mitochondrial dysfunction. Microinjection of TNF-α receptor antagonist R7050 into the RVLM of SIH rats significantly inhibited the biological activities of TNF-α, increased p-AMPK and Sirt3 levels, and alleviated neuronal mitochondrial injury, thereby reducing c-FOS expression, RSNA, plasma NE, and BP. CONCLUSIONS: This study revealed that microglia-derived TNF-α in the RVLM impairs neuronal mitochondrial function in SIH possibly through inhibiting the AMPK-Sirt3 pathway. Therefore, microglia-derived TNF-α in the RVLM may be a possible therapeutic target for the intervention of SIH.
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Wang et al. (2023) studied Stress-induced hypertension (n=220). TNF-α receptor antagonist R7050 vs. Vehicle (NaCl, 0.9%) was evaluated on Blood pressure, heart rate, and sympathetic outflow. Microglia-derived TNF-α in the RVLM impairs neuronal mitochondrial function in stress-induced hypertension via the AMPK–Sirt3 pathway, and its blockade reduces blood pressure and sympathetic outflow.
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