Cytokine regulation in animal models of neuropathic pain and in human diseases.

Cytokines are soluble proteins secreted mainly by immune cells and are key players in the induction and maintenance of pain. Pro-inflammatory cytokines are mostly algesic, while anti-inflammatory cytokines have analgesic properties. After the role of cytokines was shown in diverse animal models of pain, interest arose in the systemic and local regulation of cytokines in human pain states. Most clinical studies give evidence for an imbalance between pro- and anti-inflammatory cytokines in neuropathic and other pain states with pronounced pro-inflammatory cytokine profiles. Anti-cytokine treatment gives encouraging preliminary results and supports the notion of a crucial role of cytokines also in human pain states. Further research is needed for a better understanding of the mechanisms linking altered cytokine profiles to the sensation of pain.