Interleukin‐17 (IL‐17) is considered a proinflammatory cytokine, but whether neuronal IL‐17 receptors contribute to the generation of arthritic pain is unknown. This study was undertaken to explore whether IL‐17A acts on neurons, whether it sensitizes joint nociceptors, and whether neutralization of IL‐17 is antinociceptive.

We recorded action potentials from rat joint nociceptors after intraarticular injection of IL‐17A. We studied the expression of the IL‐17A receptor in the rat dorsal root ganglia (DRG), explored the effect of IL‐17A on signaling pathways in cultured rat DRG neurons, and using patch clamp recordings, monitored changes of excitability by IL‐17A. We tested whether an antibody to IL‐17 influences pain behaviors in mice with antigen‐induced arthritis (AIA).

A single injection of IL‐17A into the rat knee joint elicited a slowly developing and long‐lasting sensitization of nociceptive C fibers of the joint to mechanical stimuli, which was not attenuated by neutralizing tumor necrosis factor α or IL‐6. The IL‐17A receptor was visualized in most rat DRG neurons, the cell bodies of primary sensory neurons. In isolated and cultured rat DRG neurons, IL‐17A caused rapid phosphorylation of protein kinase B and ERK, and it rapidly enhanced excitability. In mice with unilateral AIA in the knee, an antibody against IL‐17 improved the guarding score and reduced secondary mechanical hyperalgesia at the ipsilateral paw.

Our findings indicate that IL‐17A has the potential to act as a pain mediator by targeting IL‐17 receptors in nociceptive neurons, and these receptors are particularly involved in inflammation‐evoked mechanical hyperalgesia.