RESUMO
Intraocular administration of neurotrophic factors has been shown to delay irreversible degeneration of retinal ganglion cells (RGCs). It would be beneficial for the treatment of optic nerve (ON) injury if such neurotrophic factors could be delivered in a less-invasive manner. The dipeptide leucine-isoleucine (Leu-Ile) appears to induce the production of neurotrophic factors, including brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), in the brain. We therefore administered Leu-Ile via periocular depot injection in rats and investigated the dipeptide's ability to induce BDNF and GDNF in the retina and to delay RGC loss in an ON injury model. Poloxamer-alginate hydrogels containing Leu-Ile were injected into the subconjunctival space of intact or ON-injured rats. BDNF and GDNF levels in the retina were determined by an enzyme immunoassay. Survival of RGCs was assessed in retinal flatmounts. Activation of extracellular signal-regulated kinases (ERK) and cAMP response element binding protein (CREB) in the retina was examined by Western blotting. At 2 h after injection of fluorescein isothiocyanate-conjugated Leu-Ile, the fluorescence intensities in the retina were 4.3-fold higher than those in the saline control. Treatment with Leu-Ile significantly increased the retinal levels of BDNF at 6 h and GDNF at 6-72 h after injection. Treatment with Leu-Ile significantly increased RGC survival to 14 days after ON injury and enhanced the activation of ERK at 72 h and CREB at 48 h after injection in the ON-injured retina. These results suggest that periocular delivery of Leu-Ile induces BDNF and GDNF production in the retina, which may eventually enhance RGC survival after ON injury.
Assuntos
Alginatos/química , Dipeptídeos/administração & dosagem , Portadores de Fármacos , Hidrogéis , Fatores de Crescimento Neural/metabolismo , Fármacos Neuroprotetores/administração & dosagem , Traumatismos do Nervo Óptico/tratamento farmacológico , Poloxâmero/química , Células Ganglionares da Retina/efeitos dos fármacos , Animais , Western Blotting , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Preparações de Ação Retardada , Dipeptídeos/química , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Ativação Enzimática , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Técnicas Imunoenzimáticas , Injeções Intraoculares , Masculino , Fármacos Neuroprotetores/química , Traumatismos do Nervo Óptico/metabolismo , Traumatismos do Nervo Óptico/patologia , Ratos , Ratos Wistar , Células Ganglionares da Retina/metabolismo , Células Ganglionares da Retina/patologia , Transdução de Sinais/efeitos dos fármacos , Espectrometria de Fluorescência , Fatores de Tempo , Regulação para CimaRESUMO
The first example is presented here of an amiphiphilic block copolymer synthesized by mechanochemical solid-state polymerization and used to form polymeric micelles. A model amphiphilic block copolymer was synthesized first, possessing galactose as a hydrophilic side chain and theophylline as a hydrophobic side chain, by mechanochemical solid-state polymerization. The resulting copolymer had a narrow molecular weight distribution. Polymeric micelle formation was subsequently carried out with the copolymer by a dialysis method. To gain insight into the physicochemical properties of the polymeric micelle, dynamic light scattering (DLS) measurements were performed. A narrow distribution of diameters was observed in the polymeric micelle solution, and these micelles were disrupted by the addition of sodium dodecyl sulfate (SDS). It was also confirmed by DLS measurements that the polymeric micelles were spherical. These results suggested that the block copolymer synthesized by mechanochemical solid-state polymerization was as suitable for the preparation of polymeric micelles as materials obtained by living polymerization.
