Department of Pharmacology, Wakayama Medical University, 811-1 Kimiidera, Wakayama City, Wakayama 641-0012, Japan.
Faculty of Wakayama Health Care Sciences, Takarazuka University of Medical and Health Care, Wakayama City, 2252 Nakanoshima, Wakayama 640-8392, Japan.
Cells. 2021 Apr 12;10(4):874. doi: 10.3390/cells10040874.
It is important to investigate the sex-dependent roles of microglia in pain hypersensitivity as reactive microglia within the spinal dorsal horn (DH) have been reported to be pivotal in neuropathic pain induction in male rodents upon nerve injury. Here, we aimed at determining the role of sex differences in the behavioral and functional outcomes of the chemogenetic activation of spinal microglia using Gq-designer receptors exclusively activated by designer drugs (Gq-DREADD) driven by the microglia-specific Cx3cr1 promoter. CAG-LSL-human Gq-coupled M3 muscarinic receptors (hM3Dq)-DREADD mice were crossed with CX3C chemokine receptor 1 (CX3CR1)-Cre mice, and immunohistochemistry images revealed that hM3Dq was selectively expressed on Iba1 microglia, but not on astrocytes and neurons. Intrathecal (i.t.) administration of clozapine-N-oxide (CNO) elicited mechanical allodynia exclusively in male mice. Furthermore, the reactive microglia-dominant molecules that contributed to pain hypersensitivity in CX3CR1-hM3Dq were upregulated in mice of both sexes. The degree of upregulation was greater in male than in female mice. Depletion of spinal microglia using pexidartinib (PLX3397), a colony stimulating factor-1 receptor inhibitor, alleviated the male CX3CR1-hM3Dq mice from pain hypersensitivity and compromised the expression of inflammatory molecules. Thus, the chemogenetic activation of spinal microglia resulted in pain hypersensitivity in male mice, suggesting the sex-dependent molecular aspects of spinal microglia in the regulation of pain.
研究小胶质细胞在痛觉过敏中的性别依赖性作用非常重要，因为有报道称，神经损伤后雄性啮齿动物背角中的反应性小胶质细胞在神经病理性疼痛的诱导中起着关键作用。在这里，我们旨在确定使用 Gq 设计受体（Gq-DREADD）通过小胶质细胞特异性 Cx3cr1 启动子驱动对化学遗传激活脊髓小胶质细胞的行为和功能结果的性别差异的作用，Gq 设计受体仅被设计药物激活。CAG-LSL-人 Gq 偶联 M3 毒蕈碱受体（hM3Dq）-DREADD 小鼠与 CX3C 趋化因子受体 1（CX3CR1）-Cre 小鼠杂交，免疫组织化学图像显示 hM3Dq 选择性地表达在 Iba1 小胶质细胞上，但不在星形胶质细胞和神经元上。鞘内（i.t.）给予氯氮平-N-氧化物（CNO）仅在雄性小鼠中引起机械性痛觉过敏。此外，在雌雄小鼠中，导致 CX3CR1-hM3Dq 痛觉过敏的反应性小胶质细胞主导分子均上调。雄性小鼠中的上调程度大于雌性小鼠。使用集落刺激因子-1 受体抑制剂培昔达替尼（PLX3397）耗尽脊髓小胶质细胞可缓解雄性 CX3CR1-hM3Dq 小鼠的痛觉过敏，并削弱炎症分子的表达。因此，脊髓小胶质细胞的化学遗传激活导致雄性小鼠出现痛觉过敏，表明脊髓小胶质细胞在调节疼痛中存在性别依赖性分子方面。
