The role of "anti-inflammatory" cytokines in axon regeneration.

The injured central and peripheral nervous system (CNS and PNS) are difficult to regenerate due to the presence of growth inhibitory molecules which are upregulated around the lesion site. In addition, a strong inflammatory response triggering the production of so-called "pro"- and "anti-inflammatory" cytokines, adds to this dilemma. Both pro- and anti-inflammatory cytokines are involved in the regulation of diverse signaling pathways. One of the main aims to induce regeneration is to promote axonal outgrowth and stimulate the formation of new connections. Anti-inflammatory cytokines as modulators of neurite plasticity and outgrowth are of pivotal importance in neuroregeneration with different effects reported. Here we summarize the most relevant information about IL-4, IL-10, IL-13, LIF and TGF-β focusing on their direct and indirect role in axonal outgrowth.