Papers of the Week

Sphingosine-1-phosphate (S1P) receptor 1 subtype (S1PR1) activation by its ligand S1P in the dorsal horn of the spinal cord (DH-SC) causes mechano-hypersensitivity. The cellular and molecular pathways remain poorly understood. We now report that activation of S1PR1 with intrathecal injection of the highly selective S1PR1 agonist SEW2871 led to the development of mechano-allodynia by activating the nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome (increased expression of NLRP3, cleaved caspase 1 and mature interleukin (IL)-1β) in the DH-SC. The functional S1PR1 antagonist FTY720 blocked NLRP3 activation and IL-1β production. Moreover, inhibiting IL-10 signaling with an intrathecal injection of an anti-IL-10 antibody attenuated the beneficial effects exerted by FTY720. This suggests that disrupting S1PR1 signaling engages beneficial IL-10-dependent pathways. Noteworthy, we found that mice with astrocyte-specific deletions of S1pr1 did not develop mechano-allodynia following intrathecal injection of SEW2871 and exhibited reduced levels of cleaved caspase 1; identifying astrocytes as a key cellular locus for S1PR1 activity. Our findings provide novel mechanistic insights on how S1PR1 activation in the spinal cord contributes to the development of nociception while identifying the cellular substrate for these activities. PERSPECTIVE: This is the first study to link the activation of NLRP3 and IL-1β signaling in the spinal cord and S1PR1 signaling in astrocytes to the development of S1PR1-evoked mechano-allodynia. These findings provide critical basic science insights to support the development of therapies targeted toward S1PR1.