MitoTempo protects against nε-carboxymethyl lysine-induced mitochondrial dyshomeostasis and neuronal cells injury

Abstract

Enhanced formation of advanced glycation end products (AGEs) is a pivotal factor in diabetes pathophysiology, increasing the risk of diabetic complications. Nε-carboxy-methyl-lysine (CML) is one of the most relevant AGEs found in several tissues including the peripheral blood of diabetic subjects. Despite recognizing diabetes as a risk factor for neurodegenerative diseases and the documented role of mitochondrial abnormalities in this connection, the impact of CML on neuronal mitochondria and its contribution to diabetes-related neurodegeneration remain uncertain. Here, we evaluated the effects of CML in differentiated SH-SY5Y human neuroblastoma cells. Due to the association between mitochondrial dysfunction and increased production of reactive oxygen species (ROS), the possible protective effects of MitoTempo, a mitochondria-targeted antioxidant, were also evaluated. Several parameters were assessed namely cells viability, mitochondrial respiration and membrane potential, ATP and ROS production, Ca2+ levels, mitochondrial biogenesis and dynamics, mito/autophagy, endoplasmic reticulum (ER) stress and amyloidogenic and synaptic integrity markers. CML caused pronounced mitochondrial defects characterized by a significant decrease in mitochondrial respiration, membrane potential, and ATP production and an increase in ROS production. An accumulation of individual mitochondria associated with disrupted mitochondrial networks was also observed. Furthermore, CML caused mitochondrial fusion and a decrease in mitochondrial mass and induced ER stress associated with altered unfolded protein response and Ca2+ dyshomeostasis. Moreover, CML increased the protein levels of β-secretase-1 and amyloid precursor protein, key proteins involved in Alzheimer's Disease pathophysiology. All these effects contributed to the decline in neuronal cells viability. Notable, MitoTempo was able to counteract most of CML-mediated mitochondrial defects and neuronal cells injury and death. Overall, these findings suggest that CML induces pronounced defects in neuronal mitochondria and ER stress, predisposing to neurodegenerative events. More, our observations suggest that MitoTempo holds therapeutic promise in mitigating CML-induced mitochondrial imbalance and neuronal damage and death.