Dong Daosong, Yu Xue, Tao Xueshu, Wang Qian, Zhao Lin
Department of Pain, The First Hospital of China Medical University, Shenyang, China.
Key Laboratory of Precision Diagnosis and Treatment of Gastrointestinal Tumors (China Medical University), Department of Surgical Oncology and General Surgery, The First Hospital of China Medical University, Ministry of Education, Shenyang, China.
Front Pharmacol. 2024 Jul 9;15:1407347. doi: 10.3389/fphar.2024.1407347. eCollection 2024.
Pain is a complex perception involving unpleasant somatosensory and emotional experiences. However, the underlying mechanisms that mediate its different components remain unclear. Sphingosine-1-phosphate (S1P), a metabolite of sphingomyelin and a potent lipid mediator, initiates signaling via G protein-coupled receptors (S1PRs) on cell surfaces. It serves as a second messenger in cellular processes such as proliferation and apoptosis. Nevertheless, the neuropharmacology of sphingolipid signaling in pain conditions within the central nervous system remains largely unexplored and controversial.
Chronic nociceptive pain models were induced in vivo by intraplantar injection of 20 μL complete Freund's adjuvant (CFA) into the left hind paws. We assessed S1P and S1PR1 expression in the spinal cords of CFA model mice. Functional antagonists of S1PR1 or S1PR1-specific siRNA were administered daily following CFA model establishment. Paw withdrawal response frequency (PWF) and paw withdrawal latency (PWL) were measured to evaluate mechanical allodynia and thermal hyperalgesia, respectively. RT-PCR assessed interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α levels. Western blotting and immunofluorescence were used to analyze glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule (Iba1), STAT3, ERK, and p38 MAPK protein expression.
In the chronic nociceptive pain model induced by CFA, S1P and S1PR1 expression levels were significantly elevated, leading to activation of spinal cord glial cells. S1PR1 activation also promoted MMP2-mediated cleavage of mature IL-1β. Additionally, S1PR1 activation upregulated phosphorylation of STAT3, ERK, and p38 MAPK in glial cells, profoundly impacting downstream signaling pathways and contributing to chronic nociceptive pain.
The S1P/S1PR1 axis plays a pivotal role in the cellular and molecular mechanisms underlying nociceptive pain. This signaling pathway modulates glial cell activation and the expression of pain-related genes (STAT3, ERK, p38 MAPK) and inflammatory factors in the spinal dorsal horn. These findings underscore the potential of targeting the S1P system for developing novel analgesic therapies.
疼痛是一种复杂的感知，涉及不愉快的躯体感觉和情感体验。然而，介导其不同成分的潜在机制仍不清楚。鞘氨醇-1-磷酸（S1P）是鞘磷脂的一种代谢产物，也是一种强效脂质介质，通过细胞表面的G蛋白偶联受体（S1PRs）启动信号传导。它在细胞增殖和凋亡等细胞过程中作为第二信使发挥作用。然而，中枢神经系统疼痛状态下鞘脂信号传导的神经药理学在很大程度上仍未被探索且存在争议。
通过将20 μL完全弗氏佐剂（CFA）注射到左后爪足底内，在体内诱导慢性伤害性疼痛模型。我们评估了CFA模型小鼠脊髓中S1P和S1PR1的表达。在建立CFA模型后，每天给予S1PR1的功能性拮抗剂或S1PR1特异性小干扰RNA（siRNA）。测量爪退缩反应频率（PWF）和爪退缩潜伏期（PWL），分别评估机械性异常性疼痛和热痛觉过敏。逆转录-聚合酶链反应（RT-PCR）评估白细胞介素（IL）-1β、IL-6和肿瘤坏死因子（TNF）-α水平。蛋白质免疫印迹法和免疫荧光法用于分析胶质纤维酸性蛋白（GFAP）、离子钙结合衔接分子（Iba1）、信号转导和转录激活因子3（STAT3）、细胞外信号调节激酶（ERK）和p38丝裂原活化蛋白激酶（p38 MAPK）的蛋白表达。
在由CFA诱导的慢性伤害性疼痛模型中，S1P和S1PR1的表达水平显著升高，导致脊髓胶质细胞活化。S1PR1的激活还促进了基质金属蛋白酶2（MMP2）介导的成熟IL-1β的裂解。此外，S1PR1的激活上调了胶质细胞中STAT3、ERK和p38 MAPK的磷酸化，深刻影响下游信号通路并导致慢性伤害性疼痛。
S1P/S1PR1轴在伤害性疼痛的细胞和分子机制中起关键作用。该信号通路调节胶质细胞活化以及脊髓背角中疼痛相关基因（STAT3、ERK、p38 MAPK）和炎性因子的表达。这些发现强调了靶向S1P系统开发新型镇痛疗法的潜力。
