Electroacupuncture Attenuates Chronic Inflammatory Pain And Depression Comorbidity by Inhibiting Hippocampal Neuronal Apoptosis via the PI3K/Akt Signaling Pathway

we hypothesized that the potential mechanism of EA for chronic inflammatory pain and depression comorbidity is related to reducing apoptosis of hippocampal neurons by activating the PI3K/Akt signal pathway. Rats received plantar injections of complete Freund’s adjuvant (CFA) on days 0 and 14. They were then divided into groups: sham operation, model, EA, and duloxetine. EA was administered at Hegu (LI4) and Taichong (LR3) from days 15 to 28, while the duloxetine group received duloxetine and distilled water daily (0.1 mg/ml). Pain behavior was assessed using the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. Depression-like behavior was evaluated through the sucrose preference test (SPT), open-field test (OFT), and forced swim test (FST). Hematoxylin and eosin (HE) staining was employed to assess pathological changes in the hippocampus. Nerve cell apoptosis was determined using TUNEL fluorescence staining. Western blot analysis was conducted to measure the protein expression of Bcl-2, Bax, p-PI3K/PI3K, and p-Akt/Akt. EA demonstrated significant pain intensity reduction and alleviation of pain-related depressive symptoms. Our findings from the HE staining confirmed that CIP induced by CFA led to morphological changes in the hippocampus, while EA effectively reversed these pathological alterations. Moreover, EA intervention remarkably reduced neuronal apoptosis and exhibited an upregulation of Bcl-2 protein expression accompanied by a decrease in Bax expression. Additionally, EA activated the PI3K/Akt signaling pathway. Overall, our study suggests that EA holds the potential to improve pain and depressive behaviors in rats with CIP and depression comorbidity, potentially mediated through the activation of the PI3K/Akt pathway, leading to a reduction in hippocampal neuronal apoptosis.我们提出假设，电针（Electroacupuncture, EA）用于治疗慢性炎症痛（Chronic Inflammatory Pain, CIP）与抑郁共病的潜在机制，可能通过激活PI3K/Akt信号通路，减少海马神经元凋亡而实现。本研究中，研究者于第0天和第14天对大鼠足底注射完全弗氏佐剂（Complete Freund’s Adjuvant, CFA）构建疾病模型，随后将大鼠分为假手术组、模型组、电针组与度洛西汀组。电针组于第15天至第28天选取合谷（LI4）与太冲（LR3）穴位进行电针干预；度洛西汀组每日给予浓度为0.1 mg/ml的度洛西汀与蒸馏水混合溶液灌胃。采用机械缩足反射阈值（Mechanical Withdrawal Threshold, MWT）与热缩足潜伏期（Thermal Withdrawal Latency, TWL）实验评估大鼠痛觉行为；通过糖水偏好实验（Sucrose Preference Test, SPT）、旷场实验（Open-Field Test, OFT）与强迫游泳实验（Forced Swim Test, FST）评价大鼠抑郁样行为。采用苏木精-伊红（Hematoxylin and Eosin, HE）染色观察海马组织的病理形态变化；采用TUNEL荧光染色检测神经细胞凋亡情况；通过蛋白质印迹法（Western Blot）检测Bcl-2、Bax、p-PI3K/PI3K及p-Akt/Akt的蛋白表达水平。实验结果显示，电针可显著降低大鼠痛觉敏感性，并缓解痛觉相关抑郁症状。苏木精-伊红染色结果证实，完全弗氏佐剂诱导的CIP与抑郁共病模型大鼠海马组织出现形态学异常，而电针干预可有效逆转上述病理改变。此外，电针干预可显著减少神经元凋亡，上调Bcl-2蛋白表达并下调Bax蛋白表达；同时，电针可激活PI3K/Akt信号通路。综上，本研究表明电针可改善CIP与抑郁共病模型大鼠的痛觉与抑郁样行为，其潜在作用机制可能通过激活PI3K/Akt信号通路，减少海马神经元凋亡而实现。