Li Xilei, Guo Qulian, Ye Zhi, Wang E, Zou Wangyuan, Sun Zhihua, He Zhenghua, Zhong Tao, Weng Yingqi, Pan Yundan
Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha, China.
National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, China.
Front Neurosci. 2021 Mar 24;15:620525. doi: 10.3389/fnins.2021.620525. eCollection 2021.
Previous studies have proved that peripheral nerve injury is involved in the pathogenesis of neuropathic pain (NP). The peripheral nerve injury primes spinal M1 microglia phenotype and produces pro-inflammatory cytokines, which are responsible for neurotoxic and neuronal hyper-excitable outcomes. Spinal peroxisome proliferator-activated receptor gamma (PPAR γ) has been shown to play an anti-inflammatory role in the development of NP. However, the role of PPAR γ in attenuating the pathological pathway of spinal microgliosis is still unknown.
Sprague-Dawley rats (male, aged 8-10 weeks) were randomly divided into three groups, i.e., a control group, a NP group, and a NP + lentivirus encoding PPAR γ (LV-PPAR γ) group. The sciatic chronic constriction injury (CCI) model was used to induce NP in rats. Pain behavior was assessed by monitoring the rat hind-paw withdrawal threshold to mechanical stimuli and withdrawal latency to radiant heat. The LV-PPAR γ was intrathecally infused 1 day before CCI. Western blot analysis and real-time qPCR were used to detect the microglia phenotypic molecules and CX3CR1 expression in the spinal cord. , BV-2 microglia cells were transfected with LV-PPAR γ and incubated with lipopolysaccharides (LPS), and the levels of M1 microglia phenotypic molecules and CX3CR1 in BV-2 microglia cells were assessed by western blot analysis, real-time qPCR, and enzyme-linked immunosorbent assay.
Preoperative intrathecal infusion of LV-PPAR γ attenuated pain in rats 7 days post-CCI. The M1-microglia marker, CX3CR1, and pro-inflammatory signaling factors were increased in the spinal cord of CCI rats, while the preoperative intrathecal infusion of LV-PPAR γ attenuated these changes and increased the expression of IL-10. , the overexpression of PPAR γ in BV-2 cells reduced LPS-induced M1 microglia polarization and the levels of CX3CR1 and pro-inflammatory cytokines.
Intrathecal infusion of LV-PPAR γ exerts a protective effect on the development of NP induced by CCI in rats. The overexpression of PPAR γ may produce both analgesic and anti-inflammatory effects due to inhibition of the M1 phenotype and CX3CR1 signaling pathway in spinal microglia.
以往研究证明，周围神经损伤参与神经性疼痛（NP）的发病机制。周围神经损伤引发脊髓M1小胶质细胞表型并产生促炎细胞因子，这些因子导致神经毒性和神经元过度兴奋的结果。脊髓过氧化物酶体增殖物激活受体γ（PPARγ）已被证明在NP的发展中发挥抗炎作用。然而，PPARγ在减轻脊髓小胶质细胞增生病理途径中的作用仍不清楚。
将8-10周龄雄性Sprague-Dawley大鼠随机分为三组，即对照组、NP组和NP + 编码PPARγ的慢病毒（LV-PPARγ）组。采用坐骨神经慢性压迫损伤（CCI）模型诱导大鼠产生NP。通过监测大鼠后爪对机械刺激的缩足阈值和对热辐射的缩足潜伏期来评估疼痛行为。在CCI前1天鞘内注射LV-PPARγ。采用蛋白质免疫印迹分析和实时定量PCR检测脊髓中小胶质细胞表型分子和CX3CR1的表达。将BV-2小胶质细胞用LV-PPARγ转染并与脂多糖（LPS）孵育，通过蛋白质免疫印迹分析、实时定量PCR和酶联免疫吸附测定评估BV-2小胶质细胞中M1小胶质细胞表型分子和CX3CR1的水平。
术前鞘内注射LV-PPARγ可减轻CCI后7天大鼠的疼痛。CCI大鼠脊髓中M1小胶质细胞标志物、CX3CR1和促炎信号因子增加，而术前鞘内注射LV-PPARγ可减轻这些变化并增加IL-10的表达。此外，BV-2细胞中PPARγ的过表达降低了LPS诱导的M1小胶质细胞极化以及CX3CR1和促炎细胞因子的水平。
鞘内注射LV-PPARγ对CCI诱导的大鼠NP发展具有保护作用。PPARγ的过表达可能由于抑制脊髓小胶质细胞中的M1表型和CX3CR1信号通路而产生镇痛和抗炎作用。
