Eicosapentaenoic acid alleviates fibromyalgia-like pain by modulating microglia, astrocytes, and toll-Like receptor 4 signaling in the mice cerebellum

Fibromyalgia (FM) is a widespread systemic pain disorder often accompanied by symptoms such as insomnia, mania, obesity, and depression. FM is difficult to diagnose and, therefore, cannot be effectively treated with current medical approaches. After prolonged suffering, FM patients frequently seek help from chronic pain physicians and psychiatrists. Eicosapentaenoic acid (EPA), derived from fish oil, is a common nutritional therapy for pain. While EPA is a documented fatty acid for depression treatment, its role in FM management is less established. In this study, we investigated the effects of EPA on FM pain and its potential mechanisms involving microglia/astrocytes and toll-like receptor 4 (TLR4) pathways in the cerebellum of mice. We found that intermittent cold stress (ICS) effectively induced FM-like pain in mice. Pain was evaluated using von Frey and Hargraves' tests to assess mechanical (2.01 ± 0.11 g) and thermal (4.09 ± 0.34 s) sensitivity. Nociceptive responses were alleviated by oral EPA administration (3.68 ± 0.13 g and 7.89 ± 0.3 s). EPA levels were lower in FM mice but increased following oral intake. Our findings revealed elevated levels of microglia/astrocyte markers and neurotransmitters such as HMGB1 and S100B in the cerebellum 5-7 (CB5-7) of FM mice. Similarly, TLR4 and related nociceptive signals were upregulated in the FM group. Notably, oral EPA effectively reduced these pain-related substances in CB5-7. Our results suggest that EPA can treat FM by modulating microglia/astrocyte activity and TLR4 signaling, highlighting its potential as a therapeutic target in FM management.