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Lysophosphatidic acid (LPA) and LPA1 receptor signaling play a crucial role in the initiation of peripheral nerve injury-induced neuropathic pain through the alternation of pain-related genes/proteins expression and demyelination. However, LPA and its signaling in the brain are still poorly understood. In the present study, we revealed that the LPA5 receptor expression in corpus callosum elevated after the initiation of demyelination, and the hyperalgesia through Aδ-fibers following cuprizone-induced demyelination was mediated by LPA5 signaling. These data suggest that LPA5 signaling may play a key role in the mechanisms underlying neuropathic pain following demyelination in the brain. Keywords: LPA5, Neuropathic pain, Multiple sclerosis

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator that contains a unique cyclic phosphate ring at the sn-2 and sn-3 positions of its glycerol backbone. Using mouse models for multiple sclerosis (cuprizone-induced demyelination and experimental autoimmune encephalomyelitis) and traumatic brain injury, we revealed that cPA and its metabolically stabilized cPA derivative, 2-carba-cPA (2ccPA), have potential to protect against neuroinflammation. In this study, we investigated whether 2ccPA has anti-inflammatory effect on peripheral immune function or not using inflammation-induced macrophages-like cell line, THP-1 monocytes differentiated by phorbol 12-myristate 13-acetate (PMA). Lipopolysaccharide (LPS)-stimulated THP-1 cells were found to have higher expression of the mRNAs of several inflammation-related cytokines and of the enzyme cyclooxygenase-2 (Cox-2); however, when THP-1 cells were stimulated by LPS in the presence of 2ccPA, the increase in the expression of pro-inflammatory cytokine and Cox-2 mRNA was attenuated. 2ccPA treatment also decreased the amount of prostaglandin E2 (PGE2) produced by LPS-stimulated THP-1 cells and decreased expression of the mRNA of prostaglandin E receptor 2 (EP2, PTGER2), a PGE2 receptor that mediates inflammation. These results indicate that 2ccPA has anti-inflammatory properties. Keywords: 2ccPA, Prostaglandin E2, Anti-inflammatory, THP-1 monocytes