Nervous system injury: focus on the inflammatory cytokine 'granulocyte-macrophage colony stimulating factor'

Any lesion in the nervous system, be it infectious, immunopathological, ischemic or traumatic, is followed by an inflammatory process that induces rapid activation of glial cells and additional recruitment of granulocytes, T-cells and monocytes/macrophages from the blood stream. Neuroinflammation is a double-sided sword. It can cause neuronal damage and participate in neuropathic pain, but it also has neuroprotective and neurotrophic effects at some stages. Cytokines are the main molecular actors of this 'network of inflammation'. Among them, granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pro-inflammatory hematopoietic cytokine widely used in haematological disorders to stimulate proliferation and differentiation of neutrophilic, eosinophilic and monocytic lineages. GM-CSF and its receptor are expressed in the brain and the cytokine can cross the blood-brain barrier. It is thus likely to affect various nervous system functions. This review will focus on the role of GM-CSF in nervous system disorders and their experimental models with particular emphasis on its possible beneficial effect on axonal regeneration after PNS and CNS injury.