RAGE induces abnormal mitochondrial dynamics in sympathetic neurons expose to high glucose

*M. G. OTERO; XIAOFAN LU; ANDREW R. CHANDNA; YASUHIKO YAMAMOTO; TOMAS L. FALZONE; VERÓNICA A. CAMPANUCCI

Chicago

Congreso; Society for Neuroscience; 2015

Mitochondria are dynamic and tubular organelles essential for normal neuronal physiology, and their dysfunction lead to the metabolic abnormalities observed in diabetes. ATP biosynthesis by mitochondria is associated with the formation of reactive oxygen species (ROS), which are usually buffered by antioxidant enzymes. However, under hyperglycemic conditions the antioxidants defense becomes overwhelmed leading to oxidative damage. The elevated levels of glucose in diabetes lead to the formation of advanced glycation end-products (AGEs) which bind to their membrane receptor, RAGE. Since RAGE signallling is up-regulated in autonomic neurons during diabetes we hypothesized that RAGE signaling is linked to mitochondrial damage and dysfunction in diabetes. To test this hypothesis we investigated changes in mitochondrial dynamics in cultured neurons from the autonomic superior cervical ganglion (SCG) of mice and we exposed them to either control or high glucose conditions. To investigate the potential role of RAGE signaling we used SCG neurons from RAGE mice lacking the functional expression of RAGE (RAGE-/- mice). To visualize and study live mitochondria, neurons were transfected with vector containing enhanced green fluorescent protein (EGFP) fused to a mitochondrial signal peptide (MITO-EGFP). Our findings revealed that high glucoses induces morphological changes in SCG neurons. Electron micrographs obtained from ultrathin SCG sections show an abundance of damaged mitochondria cristae and mitochondrial swelling in sections from STZ-diabetic mice (2 months after onset), while control mice had preserver mitochondrial ultrastructure. Moreover, we observed that for mitochondrial along neurites, high glucose disrupted compensatory changes in mitochondrial dynamics in neurons from WT when compared to RAGE-/- mice. These changes in the WT neurons included a significant increase in the density and proportion only of mitochondria moving anterogradely, while in the RAGE-/- neurons there were significant increases in the density and proportion of mitochondria moving both anterogradely and retrogradely. In addition, we found a significant reduction in the size of stationary mitochondria in neurons from WT but not from RAGE-/- mice. We hypothesize that since mitochondria in RAGE-/- neurons do not show changes in size/morphology, the changes in dynamics may be part of a compensatory response to high glucose, a task that can be better performed in RAGE-/- cells.