carbocyanines and Diabetes-Mellitus--Type-1

Both innate and adaptive immune cells are critical players in autoimmune destruction of insulin-producing β cells in type 1 diabetes. However, the early pathogenic events triggering the recruitment and activation of innate immune cells in islets remain obscure. Here we show that circulating fatty acid binding protein 4 (FABP4) level was significantly elevated in patients with type 1 diabetes and their first-degree relatives and positively correlated with the titers of several islet autoantibodies. In nonobese diabetic (NOD) mice, increased FABP4 expression in islet macrophages started from the neonatal period, well before the occurrence of overt diabetes. Furthermore, the spontaneous development of autoimmune diabetes in NOD mice was markedly reduced by pharmacological inhibition or genetic ablation of FABP4 or adoptive transfer of FABP4-deficient bone marrow cells. Mechanistically, FABP4 activated innate immune responses in islets by enhancing the infiltration and polarization of macrophages to proinflammatory M1 subtype, thus creating an inflammatory milieu required for activation of diabetogenic CD8+ T cells and shift of CD4+ helper T cells toward Th1 subtypes. These findings demonstrate FABP4 as a possible early mediator for β cell autoimmunity by facilitating crosstalk between innate and adaptive immune cells, suggesting that pharmacological inhibition of FABP4 may represent a promising therapeutic strategy for autoimmune diabetes.

Topics: Adult; Animals; Autoantibodies; Benzothiazoles; Bone Marrow Transplantation; Carbocyanines; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Fatty Acid-Binding Proteins; Female; Humans; Islets of Langerhans; Macrophages; Male; Mice, Inbred NOD; Mice, Mutant Strains; Middle Aged; T-Lymphocytes

T lymphocytes constitute a major effector cell population in autoimmune type 1 diabetes. Despite essential functions of mitochondria in regulating activation, proliferation, and apoptosis of T cells, little is known regarding T cell metabolism in the progression of human type 1 diabetes. In this study, we report, using two independent cohorts, that T cells from patients with type 1 diabetes exhibited mitochondrial inner-membrane hyperpolarization (MHP). Increased MHP was a general phenotype observed in T cell subsets irrespective of prior antigen exposure, and was not correlated with HbA1C levels, subject age, or duration of diabetes. Elevated T cell MHP was not detected in subjects with type 2 diabetes. T cell MHP was associated with increased activation-induced IFNγ production, and activation-induced IFNγ was linked to mitochondria-specific ROS production. T cells from subjects with type 1 diabetes also exhibited lower intracellular ATP levels. In conclusion, intrinsic mitochondrial dysfunction observed in type 1 diabetes alters mitochondrial ATP and IFNγ production; the latter is correlated with ROS generation. These changes impact T cell bioenergetics and function.

Topics: Adenosine Triphosphate; Apoptosis; Biomarkers; Carbocyanines; Diabetes Mellitus, Type 1; Glycolysis; Humans; Immunophenotyping; Lymphocyte Activation; Membrane Potential, Mitochondrial; Microscopy, Confocal; Mitochondria; T-Lymphocyte Subsets

Pancreatic islet transplantation is a promising therapeutic approach for type 1 diabetes.However, recent advances in islet transplantation are limited by significant graft loss after transplantation. Multiple immunological and nonimmunological factors contribute to this loss. Novel therapies that could target the core reasons for the islet graft loss are desperately needed. Small interfering RNA can be used to inhibit the expression of virtually any gene with single-nucleotide specificity including genes responsible for islet damage. Applying adequate delivery of siRNA molecules to pancreatic islets prior to transplantation holds a great potential for improving the survival of islet grafts. Noninvasive imaging provides means for monitoring the survival of transplanted islets in real time. Here, we summarize the approach that has been developed to deliver siRNA to pancreatic islets in conjunction with tracking of the graft outcome by in vivo magnetic resonance imaging (MRI). We synthesize a nano-sized theranostic agent consisting of magnetic nanoparticles (MN), a reporter for MRI, labeled with Cy5.5 dye for near-infrared fluorescence (NIRF) imaging, and conjugated to siRNA molecule targeting genes that are harmful to islet grafts. Pre-labeling of islets by MN-Cy5.5-siRNA allowed us to monitor the survival of transplanted islet grafts by MRI and NIRF imaging and resulted in efficient silencing of the target genes in vivo. This novel approach combines a therapeutic effect provided by RNA interference technology with in vivo MR imaging and is expected to significantly improve the outcome of islet transplantation in patients with type 1 diabetes.

Topics: Animals; Carbocyanines; Diabetes Mellitus, Type 1; Gene Transfer Techniques; Heterografts; Humans; Islets of Langerhans; Islets of Langerhans Transplantation; Magnetic Resonance Imaging; Magnetite Nanoparticles; Mice; Molecular Imaging; RNA, Small Interfering; Staining and Labeling

Proper cellular function requires the maintenance of mitochondrial membrane potential (MMP) sustained by the electron transport chain. Mitochondrial dysfunction is believed to play a role in the development of diabetes and diabetic complications possibly because of the active generation of free radicals. Since MMP can be investigated in clinical settings using fluorescent probes and living whole blood cells, mitochondrial membrane alterations have been observed in some chronic disorders. We have used the mitochondrial indicator 5,5',6,6'-tetra chloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) in conjunction with flow cytometry to measure the MMP in peripheral blood granulocytes from type 1 diabetes (T1D) families. The intracellular ROS levels and the respiratory burst activity were also measured. Leukocyte MMP was elevated in 20 T1D patients and their 20 non-diabetic siblings compared with 25 healthy subjects without family history of T1D. Fasting plasma glucose was the only correlate of MMP. If confirmed by further observations, the functional implications of mitochondrial hyperpolarisation (probably different among different cells) will require extensive investigation.

Topics: Adult; Benzimidazoles; Body Mass Index; Carbocyanines; Diabetes Mellitus, Type 1; Female; Flow Cytometry; Humans; Leukocytes; Male; Membrane Potential, Mitochondrial; Middle Aged; Mitochondria; Reactive Oxygen Species; Reference Values; Respiratory Burst

Evidence exists for an essential role of beta-cell apoptosis in the pathology of type 1 and type 2 diabetes. Current methods for diabetes-associated apoptosis detection, however, suffer the drawbacks of relying on in situ-based strategies. In this study, we attempted to measure, both in vitro and ex vivo, levels of beta-cell apoptosis in diabetic mice using Cy5.5-labeled annexin V. We used streptozotocin-treated BALB/c mice and NOD mice of different ages as models of type 1 diabetes and db/db mice as a model of type 2 diabetes. With annexin V Cy5.5, we established differences in levels of apoptosis between diabetic and control animals. Intravenously administered annexin V Cy5.5 accumulated in pancreata of diabetic mice but not in nondiabetic controls. Furthermore, its localization was specific to apoptotic events within diabetic islets; its selectivity was supported by transferase-mediated dUTP nick-end labeling staining. Because annexin V defines an early marker of apoptosis and the developed probe is suitable for in vivo administration, it may provide a promising tool for real-time identification in intact animals of the earliest stages of diabetes-associated beta-cell death and for tracing the events that characterize the pathology of the disease.

Topics: Animals; Annexin A5; Apoptosis; Carbocyanines; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Infrared Rays; Islets of Langerhans; Mice; Mice, Inbred NOD

Erythrocytes of diabetic patients have abnormal membrane properties. We examined in vitro transmembrane potential and the possible effect of resorcylidene aminoguanidine (RAG) on its modulation in erythrocytes of diabetic subjects. The transmembrane potential was assessed in RAG-treated and untreated erythrocytes, respectively, using a fluorescent dye (3,3'-dipropylthiadicarbocyanine iodide [DiSC3(5)]). We confirmed earlier findings that the transmembrane potential of diabetic erythrocytes is significantly increased compared with control (P < 0.01). The membrane hyperpolarization found in diabetic cells seems to be a result of oxidative stress present in diabetes mellitus. On one hand, the RAG treatment induced decrease in abnormal transmembrane potential values in diabetic erythrocytes (P < 0.01), presumably via its antioxidant and antiglycation activity. On the other hand, RAG moderately hyperpolarized the control erythrocytes (P < 0.05). We suggest that the drug-induced transient membrane expansion leads to an intracellular potassium loss and a subsequent change of the transmembrane potential. However, if controlled by an appropriate dosage, RAG can eliminate certain types of erythrocyte membrane damage induced by diabetes mellitus.

Topics: Benzothiazoles; Carbocyanines; Diabetes Mellitus, Type 1; Erythrocyte Membrane; Fluorescent Dyes; Guanidines; Humans; Membrane Potentials

Topics: Adolescent; Adult; Biomarkers; Carbocyanines; Child; Child, Preschool; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Fluorescent Dyes; Humans; In Vitro Techniques; Lymphocyte Activation; Membrane Potentials; Reference Values; T-Lymphocytes