Ambivalent aspects of interleukin-6 in cerebral ischemia: inflammatory versus neurotrophic aspects

J Cereb Blood Flow Metab. 2009 Mar;29(3):464-79. doi: 10.1038/jcbfm.2008.141. Epub 2008 Nov 19.

Abstract

Interleukin-6 (IL-6) is pleiotropic cytokine involved in many central nervous system disorders including stroke, and elevated serum IL-6 has been found in acute stroke patients. IL-6 is implicated in the inflammation, which contributes to both injury and repair process after cerebral ischemia. However, IL-6 is one of the neurotrophic cytokines sharing a common receptor subunit, gp130, with other neurotrophic cytokines, such as leukemia inhibitory factor (LIF) and ciliary neurotrophic factor. The expression of IL-6 is most prominently identified in neurons in the peri-ischemic regions, and LIF expression shows a similar pattern. The direct injection of these cytokines into the brain after ischemia can reduce ischemic brain injury. The cytokine receptors are localized on the neuron surface, suggesting that neurons are the cytokine target. The major IL-6 downstream signaling pathway is JAK-STAT, and Stat3 activation occurs mainly in neurons during postischemic reperfusion. Further investigation is necessary to clarify the exact role of Stat3 signaling in neuroprotection. Taken together, the information suggests that IL-6 plays a double role in cerebral ischemia, as an inflammatory mediator during the acute phase and as a neurotrophic mediator between the subacute and prolonged phases.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Brain Ischemia / immunology*
  • Brain Ischemia / metabolism
  • Ciliary Neurotrophic Factor / metabolism
  • Ciliary Neurotrophic Factor / physiology*
  • Humans
  • Interleukin-6 / blood
  • Interleukin-6 / genetics
  • Interleukin-6 / immunology
  • Interleukin-6 / physiology*
  • Leukemia Inhibitory Factor / metabolism
  • Leukemia Inhibitory Factor / physiology*
  • Neurons / immunology*
  • Neurons / metabolism
  • Phosphorylation
  • Polymorphism, Genetic
  • STAT3 Transcription Factor / metabolism
  • STAT3 Transcription Factor / physiology

Substances

  • Ciliary Neurotrophic Factor
  • Interleukin-6
  • Leukemia Inhibitory Factor
  • STAT3 Transcription Factor