RESUMO
Spinal cord injury (SCI) is a major cause of paralysis, and involves multiple cellular and tissular responses including demyelination, inflammation, cell death and axonal degeneration. Recent evidence suggests that perturbation on the homeostasis of the endoplasmic reticulum (ER) is observed in different SCI models; however, the functional contribution of this pathway to this pathology is not known. Here we demonstrate that SCI triggers a fast ER stress reaction (1-3 h) involving the upregulation of key components of the unfolded protein response (UPR), a process that propagates through the spinal cord. Ablation of X-box-binding protein 1 (XBP1) or activating transcription factor 4 (ATF4) expression, two major UPR transcription factors, leads to a reduced locomotor recovery after experimental SCI. The effects of UPR inactivation were associated with a significant increase in the number of damaged axons and reduced amount of oligodendrocytes surrounding the injury zone. In addition, altered microglial activation and pro-inflammatory cytokine expression were observed in ATF4 deficient mice after SCI. Local expression of active XBP1 into the spinal cord using adeno-associated viruses enhanced locomotor recovery after SCI, and was associated with an increased number of oligodendrocytes. Altogether, our results demonstrate a functional role of the UPR in SCI, offering novel therapeutic targets to treat this invalidating condition.
Assuntos
Fator 4 Ativador da Transcrição/genética , Proteínas de Ligação a DNA/genética , Traumatismos da Medula Espinal/genética , Medula Espinal/metabolismo , Fatores de Transcrição/genética , Ativação Transcricional/genética , Resposta a Proteínas não Dobradas/genética , Fator 4 Ativador da Transcrição/deficiência , Animais , Axônios/patologia , Contagem de Células , Proteínas de Ligação a DNA/deficiência , Dependovirus , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Vetores Genéticos , Injeções Espinhais , Locomoção , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oligodendroglia/patologia , Fatores de Transcrição de Fator Regulador X , Transdução de Sinais/genética , Medula Espinal/patologia , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/patologia , Fatores de Transcrição/deficiência , Proteína 1 de Ligação a X-BoxRESUMO
Glucagon-like peptide 1 (GLP-1) is a promising candidate for the treatment of type II diabetes. However, the short in vivo half-life of GLP-1 has made peptide-based treatments challenging. Gene therapy aimed at achieving continuous GLP-1 expression presents one way to circumvent the rapid turnover of GLP-1. We have created a GLP-1 minigene that can direct the secretion of active GLP-1 (amino acids 7-37). Plasmid and adenoviral expression vectors encoding the 31-amino-acid peptide linked to leader sequences required for secretion of GLP-1 yielded sustained levels of active GLP-1 that were significantly greater than endogenous levels. Systemic administration of expression vectors to animals using two diabetic rodent models, db/db mice and Zucker Diabetic Fatty (ZDF) rats, yielded elevated GLP-1 levels that lowered both the fasting and random-fed hyperglycemia present in these animals. Because the insulinotropic actions of GLP-1 are glucose dependent, no evidence of hypoglycemia was observed. Improved glucose homeostasis was demonstrated by improvements in %HbA1c (glycated hemoglobin) and in glucose tolerance tests. GLP-1-treated animals had higher circulating insulin levels and increased insulin immunostaining of pancreatic sections. GLP-1-treated ZDF rats showed diminished food intake and, in the first few weeks following vector administration, a diminished weight gain. These results demonstrate the feasibility of gene therapy for type II diabetes using GLP-1 expression vectors.
