RESUMO
Axonal damage is an early step in traumatic and neurodegenerative disorders of the central nervous system (CNS). Damaged axons are not able to regenerate sufficiently in the adult mammalian CNS, leading to permanent neurological deficits. Recently, we showed that inhibition of the autophagic protein ULK1 promotes neuroprotection in different models of neurodegeneration. Moreover, we demonstrated previously that axonal protection improves regeneration of lesioned axons. However, whether axonal protection mediated by ULK1 inhibition could also improve axonal regeneration is unknown. Here, we used an adeno-associated viral (AAV) vector to express a dominant-negative form of ULK1 (AAV.ULK1.DN) and investigated its effects on axonal regeneration in the CNS. We show that AAV.ULK1.DN fosters axonal regeneration and enhances neurite outgrowth in vitro. In addition, AAV.ULK1.DN increases neuronal survival and enhances axonal regeneration after optic nerve lesion, and promotes long-term axonal protection after spinal cord injury (SCI) in vivo. Interestingly, AAV.ULK1.DN also increases serotonergic and dopaminergic axon sprouting after SCI. Mechanistically, AAV.ULK1.DN leads to increased ERK1 activation and reduced expression of RhoA and ROCK2. Our findings outline ULK1 as a key regulator of axonal degeneration and regeneration, and define ULK1 as a promising target to promote neuroprotection and regeneration in the CNS.
Assuntos
Proteína Homóloga à Proteína-1 Relacionada à Autofagia/metabolismo , Axônios/metabolismo , Dependovirus/genética , Técnicas de Transferência de Genes , Vetores Genéticos , Regeneração Nervosa , Traumatismos do Nervo Óptico/terapia , Nervo Óptico/metabolismo , Traumatismos da Medula Espinal/terapia , Medula Espinal/metabolismo , Animais , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/genética , Axônios/patologia , Células Cultivadas , Modelos Animais de Doenças , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Regulação para Baixo , Feminino , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Crescimento Neuronal , Nervo Óptico/patologia , Traumatismos do Nervo Óptico/genética , Traumatismos do Nervo Óptico/metabolismo , Traumatismos do Nervo Óptico/patologia , Ratos Wistar , Neurônios Serotoninérgicos/metabolismo , Neurônios Serotoninérgicos/patologia , Medula Espinal/patologia , Traumatismos da Medula Espinal/genética , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/patologia , Fatores de Tempo , Proteínas rho de Ligação ao GTP/metabolismo , Quinases Associadas a rho/metabolismoRESUMO
Adult rat retinal ganglion cells undergo degeneration after optic nerve transection. Repeated intraocular injection of glial cell-line derived neurotrophic factor (GDNF) has been shown to be efficient in enhancing retinal ganglion cell survival following optic nerve axotomy. In the present study we evaluated the potential survival-promoting effect of adenovirally administered GDNF on axotomized retinal ganglion cells. A single intravitreal injection [7 x 107 plaque-forming units (pfu) or 7 x 108 pfu] of an adenoviral vector expressing the rat GDNF gene from a cytomegalovirus promoter enhanced retinal ganglion cell survival 14 days after axotomy by 67 and 125%, respectively, when compared to control animals. Intraocular administration of the vector rescued 12.6 and 23%, respectively, of the retinal ganglion cells which would otherwise have died after axotomy. An increase in retinal GDNF protein and specific virally transduced GDNF mRNA expression was detected following intraocular vector application. Our data support previous findings showing that adenoviral delivery of neurotrophic factors to the vitreous body is a feasible approach for the prevention of axotomy-induced retinal ganglion cell death in vivo and may constitute a relevant strategy for future treatment in traumatic brain injury and ensuing neurodegeneration.