A. S. Hackam

Regulation of Neurotrophin Expression and Activity in the Retina

Growth factors and their receptors are upregulated during retinal degeneration as an intrinsic tissue response that may protect remaining photoreceptors (Harada et al., 2002; Wen et al., 1995; Yu et al., 2004). Growth factor delivery to animal models of retinal degeneration leads to various degrees of preservation of photoreceptor morphology and function (Chaum, 2003). A major class of neuroprotective growth factors in the retina are the neurotrophins NGF, BDNF, NT3 and NT4/5. Therapeutic use of these molecules is complicated by their ability to activate pro-death as well as pro-survival pathways. Understanding mechanisms that induce neurotrophin upregulation during injury and controlling the cellular response to exogenous growth factors will be essential for taking full advantage of their neuroprotective activity while minimizing deleterious side-effects. This review summarizes the complex regulation of neurotrophin ligands and receptors that together promote neuronal survival.