Tong Lei, Chen Gaojun, Liu Tianfeng, Wang Linping, Zhang Haili, Chen Fuxue, Zhang Shuai, Du Dongshu
College of Life Sciences, Shanghai University, Shanghai.
College of Agriculture and Bioengineering, Heze University, Heze.
J Hypertens. 2023 Aug 1;41(8):1323-1332. doi: 10.1097/HJH.0000000000003470. Epub 2023 May 23.
Dysfunctional neurons and microglia in the rostral ventrolateral medulla (RVLM) have been implicated in the pathogenesis of stress-induced hypertension (SIH). Functional perturbation of microglial synaptic engulfment can induce aberrant brain circuit activity. IFN-γ is a pleiotropic cytokine that plays a role in regulating neuronal activity. However, existing research on the exploration of the effects of microglia on synapses in the RVLM is lacking, particularly on the function of IFN-γ in microglial synaptic engulfment involved in SIH.
A SIH rat model was established by electric foot shocks combined with noise stimulation. The underlying mechanism of IFN-γ on synaptic density and microglial synaptic engulfment was investigated through in-vivo and in-vitro experiments involving gain of function, immunofluorescence, quantitative real-time PCR, western blot, and morphometric analysis. Furthermore, the function of IFN-γ in neuronal activity, renal sympathetic nerve activity (RSNA), and blood pressure (BP) regulation was determined through in-vivo and in-vitro experiments involving Ca 2+ imaging, immunofluorescence, platinum-iridium electrode recording, ELISA, the femoral artery cannulation test, and the tail-cuff method.
The BP, heart rate, RSNA, plasma norepinephrine, and the number of c-Fos-positive neurons in SIH rats increased compared with those in control rats. Pre and postsynaptic densities in the RVLM also increased in SIH rats. IFN-γ and CCL2 expression levels were significantly reduced in the RVLM of the SIH group, whose microglia also exhibited an impaired capacity for synapse engulfment. IFN-γ elevation increased CCL2 expression and microglial synaptic engulfment and decreased synaptic density in vivo and in vitro . However, CCL2 inhibition reversed these effects. Moreover, the reduction of neuronal excitability, RSNA, plasma norepinephrine, and BP by IFN-γ was abrogated through CCL2 expression.
IFN-γ deficiency in the RVLM impaired the microglial engulfment of synapses by inhibiting CCL2 expression and increasing synaptic density and neuronal excitability, thereby contributing to SIH progression. Targeting IFN-γ may be considered a potential strategy to combat SIH.
延髓头端腹外侧区（RVLM）功能失调的神经元和小胶质细胞与应激性高血压（SIH）的发病机制有关。小胶质细胞突触吞噬功能的扰动可诱导异常的脑回路活动。干扰素-γ（IFN-γ）是一种多效性细胞因子，在调节神经元活动中发挥作用。然而，目前缺乏关于小胶质细胞对RVLM中突触影响的研究，特别是关于IFN-γ在SIH相关的小胶质细胞突触吞噬功能中的作用。
通过电足击结合噪声刺激建立SIH大鼠模型。通过体内和体外实验，包括功能增强、免疫荧光、定量实时聚合酶链反应、蛋白质免疫印迹和形态计量分析，研究IFN-γ对突触密度和小胶质细胞突触吞噬的潜在机制。此外，通过体内和体外实验，包括钙离子成像、免疫荧光、铂铱电极记录、酶联免疫吸附测定、股动脉插管试验和尾套法，确定IFN-γ在神经元活动、肾交感神经活动（RSNA）和血压（BP）调节中的作用。
与对照组大鼠相比，SIH大鼠的血压、心率、RSNA、血浆去甲肾上腺素和c-Fos阳性神经元数量增加。SIH大鼠RVLM中的突触前和突触后密度也增加。SIH组RVLM中IFN-γ和CCL2表达水平显著降低，其小胶质细胞的突触吞噬能力也受损。IFN-γ升高可增加CCL2表达和小胶质细胞突触吞噬，并在体内和体外降低突触密度。然而，CCL2抑制可逆转这些作用。此外，通过CCL2表达可消除IFN-γ对神经元兴奋性、RSNA、血浆去甲肾上腺素和血压的降低作用。
RVLM中IFN-γ缺乏通过抑制CCL2表达、增加突触密度和神经元兴奋性，损害小胶质细胞对突触的吞噬作用，从而促进SIH进展。靶向IFN-γ可能被认为是对抗SIH的潜在策略。
