Role of glyoxalases in human neuroblastoma cell

Abstract

Methylglyoxal (MG) detoxification is a significant phenomenon in cells which is related to glutathione homeostasis. The main detoxifying enzymes for MG are glyoxalase system and this is composed of glyoxalase I (GLO1) and II (GLO II, HAGH) and in case of HAGH, there are two forms which are known to localize in cytosol and mitochondria. Glyoxalase system have been studied actively for many years however the core mechanism between these two glyoxalases is not yet completely clear correlated to cell physiology. I generated knockout (KO) cells deficient in glyoxalase system in human dopaminergic neuronal cell line, SH-SY5Y, and investigated the various defects in those cells. Specially, HAGH KO cells showed increased sensitivity against MG treatment as of GLO1 KO cells as well. Thus, I observed the apparent increase of apoptosis therefore more AGEs (advanced glycation endproducts) were accumulated. Also, I established double KO cells and they tend to follow of GLO1 KO cells phenotypes and highly sensitive to MG treatment than single KO cell lines as expected. Residual MG induced the activation of cell signaling pathways related cell death and accumulation of tremendous level of ROS after long period of treatment in KO cell lines. And remarkably, the mitochondria of glyoxalases KO cells showed aberrant physiology even if without MG treatment such as decrease of cellular ATP level, and abnormal structural network. By contrast, rescue of each mutant dramatically improved those defects caused by the abnormalities. Based on the data obtained from these rescue cell lines, I figured out that GLO1 and HAGH are behave differently to present the resistance against MG. Rescue of two forms, cytosolic and mitochondrial forms, both HAGH are intimately related to oxidative stress caused by exogenous MG treatment. In other words, overexpressed HAGH removed ROS generated by MG whereas GLO1 did not inhibit MG-induced ROS accumulations. Instead, both GLO1 and HAGH increased total glutathione (GSH) level in cells and this means that GLO1 would not decrease the ROS directly but regulate the factors affecting oxidative stress. Moreover, I noticed that glyoxalases are related with autophagy and this will be applied for the next study. Here I report that the orchestra action between GLO1 and HAGH could be suggested for the new insight of the dicarbonyl stress in the aspect of the nature in mitochondrial physiology related diseases.