[Neutrophins in biology and medicine]

Nerve growth factor NGF was the first neurotrophic substance to be identified, isolated, and characterized. NGF is member of a class of substances which has been termed the neurotrophins familly. This family of NGF-related trophic factors includes also brain-derived neurotrophic factor--BDNF, neurotrophin-3, neurotrophin-4/5 and neurotrophin-6 and 7. Each neurotrophin is able to bind to the p75NTR and a specyfic Trk tyrosine kinase receptor. Traditional view is that trophic factors are relesed from target cells, retrogradely transported along their axons, and rapidly degraded upon arrival in cell bodies. But several trophic factors can move anterogradely along axons. NGF-responsive cells are known to belong to the hemopoetic-immune system and to populations in the brain involved in neuroendocrine function. The concentration of NGF is elevated in a number of inflammatory and autoimmune states in conjuction with increased accumulation of mast cells. Neurotrophins can also regulate adult nervous system plasticity by promoting neuronal survival and stimulating nerve regrowth following injury. The potential exists for these neurotrophic factors to be used as therapeutic agents for the treatment neurodegenerative disorders.