RESUMEN
Novel strategies in diabetes therapy would obviously benefit from the use of beta (beta) cell stem/progenitor cells. However, whether or not adult beta cell progenitors exist is one of the most controversial issues in today's diabetes research. Guided by the expression of Neurogenin 3 (Ngn3), the earliest islet cell-specific transcription factor in embryonic development, we show that beta cell progenitors can be activated in injured adult mouse pancreas and are located in the ductal lining. Differentiation of the adult progenitors is Ngn3 dependent and gives rise to all islet cell types, including glucose responsive beta cells that subsequently proliferate, both in situ and when cultured in embryonic pancreas explants. Multipotent progenitor cells thus exist in the pancreas of adult mice and can be activated cell autonomously to increase the functional beta cell mass by differentiation and proliferation rather than by self-duplication of pre-existing beta cells only.
Asunto(s)
Células Secretoras de Insulina/citología , Páncreas/citología , Páncreas/lesiones , Células Madre/citología , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/aislamiento & purificación , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Diferenciación Celular , Núcleo Celular/metabolismo , Proliferación Celular , Expresión Génica , Genes Reporteros , Vectores Genéticos , Proteínas Fluorescentes Verdes/metabolismo , Inmunohistoquímica , Insulina/análisis , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Queratinas/metabolismo , Lentivirus/genética , Ligadura , Ratones , Ratones Endogámicos BALB C , Ratones Transgénicos , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/aislamiento & purificación , Proteínas del Tejido Nervioso/metabolismo , Técnicas de Cultivo de Órganos , Conductos Pancreáticos/cirugía , Células Madre/metabolismo , Factores de Tiempo , beta-Galactosidasa/metabolismoRESUMEN
Perturbation of endoplasmic reticulum (ER) homeostasis impairs insulin biosynthesis, beta cell survival, and glucose homeostasis. We show that a murine model of diabetes is associated with the development of ER stress in beta cells and that treatment with the GLP-1R agonist exendin-4 significantly reduced biochemical markers of islet ER stress in vivo. Exendin-4 attenuated translational downregulation of insulin and improved cell survival in purified rat beta cells and in INS-1 cells following induction of ER stress in vitro. GLP-1R agonists significantly potentiated the induction of ATF-4 by ER stress and accelerated recovery from ER stress-mediated translational repression in INS-1 beta cells in a PKA-dependent manner. The effects of exendin-4 on the induction of ATF-4 were mediated via enhancement of ER stress-stimulated ATF-4 translation. Moreover, exendin-4 reduced ER stress-associated beta cell death in a PKA-dependent manner. These findings demonstrate that GLP-1R signaling directly modulates the ER stress response leading to promotion of beta cell adaptation and survival.
Asunto(s)
Factor de Transcripción Activador 4/farmacología , Retículo Endoplásmico/fisiología , Células Secretoras de Insulina/fisiología , Péptidos/farmacología , Receptores de Glucagón/metabolismo , Estrés Fisiológico , Ponzoñas/farmacología , eIF-2 Quinasa/fisiología , Animales , Supervivencia Celular , Células Cultivadas , Retículo Endoplásmico/efectos de los fármacos , Exenatida , Femenino , Receptor del Péptido 1 Similar al Glucagón , Glucosa/metabolismo , Homeostasis , Hipoglucemiantes/farmacología , Células Secretoras de Insulina/efectos de los fármacos , Ratones , Ratas , Ratas Wistar , Receptores de Glucagón/fisiología , Regulación hacia ArribaRESUMEN
Type 1 diabetes is a T cell-mediated autoimmune disease, and insulin is an important target of the autoimmune response associated with beta cell destruction. The mechanism of destruction is still unknown. Here, we provide evidence for CD8 T cell autoreactivity associated with recurrent autoimmunity and loss of beta cell function in type 1 diabetic islet transplant recipients. We first identified an insulin B chain peptide (insB10-18) with extraordinary binding affinity to HLA-A2(*0201) that is expressed by the majority of type 1 diabetes patients. We next demonstrated that this peptide is naturally processed by both constitutive and immuno proteasomes and translocated to the endoplasmic reticulum by the peptide transporter TAP1 to allow binding to HLA-A2 in the endoplasmic reticulum and cell surface presentation. Peripheral blood mononuclear cells from a healthy donor were primed in vitro with this peptide, and CD8 T cells were isolated that specifically recognize target cells expressing the insulin B chain peptide. HLA-A2(insB10-18) tetramer staining revealed a strong association between detection of autoreactive CD8 T cells and recurrent autoimmunity after islet transplantation and graft failure in type 1 diabetic patients. We demonstrate that CD8 T cell autoreactivity is associated with beta cell destruction in type 1 diabetes in humans.