Visual exposure to dim, green, light has been found to reduce pain levels in patients living with migraine, low back pain, and fibromyalgia. Preclinical studies discovered that the analgesic effect of green light was due to the central release of endogenous opioids and a reduction in inflammatory cytokines in the cerebrospinal fluid. The present study assessed the effect of green light therapy (GLT) on joint pain in a rat model of osteoarthritis (OA) and investigated the role of endolipids. Male and female Wistar rats (207-318 g) received an intra-articular injection of sodium monoiodoacetate (3 mg in 50 μL saline) into the knee to induce OA. On day 9, animals were placed in a room illuminated by either white (neutral-white 4000K; 20 lux) or green (wavelength: 525 nm; luminance: 20 lux) light for 5 days (8 hours per day). Joint nociception was assessed by von Frey hair algesiometry, dynamic weight bearing, and in vivo single unit extracellular recordings from knee joint mechanonociceptors. Compared to white light, GLT significantly reduced secondary mechanical hypersensitivity in both sexes and improved hindlimb weight bearing in females only. There was no effect of GLT on joint nociceptor activity in either sex. Serum lipidomics indicated an increase in circulating analgesic endolipids in response to GLT, particularly the N-acyl-glycines. Partial blockade of the endocannabinoid system with the G protein receptor-18/cannabinoid-1 receptor antagonist AM281 (500 μg/kg i.p.) attenuated GLT-induced analgesia. These data show for the first time that GLT acts to reduce OA pain by upregulating circulating analgesic endolipids, which then engage the endocannabinoid system.

中文翻译：

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视觉暴露于绿光疗法可减轻膝关节疼痛并改变骨关节炎大鼠的脂质组。


研究发现，将昏暗的绿色光线视觉暴露可以减轻偏头痛、腰痛和纤维肌痛患者的疼痛程度。临床前研究发现，绿光的镇痛作用是由于内源性阿片类药物的集中释放和脑脊液中炎性细胞因子的减少。本研究评估了绿光疗法 （GLT） 对骨关节炎 （OA） 大鼠模型关节疼痛的影响，并研究了内脂的作用。雄性和雌性 Wistar 大鼠 （207-318 g） 关节内注射单碘乙酸钠 （3 mg，溶于 50 μL 生理盐水） 以诱导 OA。第 9 天，将动物放置在用白色（中性白 4000K;20 勒克斯）或绿色（波长：525 nm;亮度：20 勒克斯）光照明 5 天（每天 8 小时）的房间中。通过 von Frey 头发测数法、动态负重和膝关节机械感受器的体内单单位细胞外记录评估关节伤害感受。与白光相比，GLT 显著降低了两性的继发性机械超敏反应，并仅改善了女性的后肢负重。GLT 对两性关节伤害感受器活动均无影响。血清脂质组学显示，响应 GLT 的循环镇痛药内层脂质增加，尤其是 N-酰基甘氨酸。用 G 蛋白受体-18/大麻素-1 受体拮抗剂 AM281 （500 μg/kg ip.） 部分阻断内源性大麻素系统减弱了 GLT 诱导的镇痛作用。这些数据首次表明，GLT 通过上调循环镇痛药内脂来减轻 OA 疼痛，然后内分泌系统参与其中。