The Effect of Glyceraldehyde-Derived Advanced Glycation End Products on β-Tubulin-Inhibited Neurite Outgrowth in SH-SY5Y Human Neuroblastoma Cells

Abstract

Nutritional factors can affect the risk of developing neurological disorders and their rate of progression. In particular, abnormalities of carbohydrate metabolism in diabetes mellitus patients lead to an increased risk of neurological disorders such as Alzheimer’s disease (AD). In this study, we investigated the relationship between nervous system disorder and the pathogenesis of AD by exposing SH-SY5Y neuroblastoma cells to glyceraldehyde (GA). We previously reported that GA-derived toxic advanced glycation end products (toxic AGEs, TAGE) induce AD-like alterations including intracellular tau phosphorylation. However, the role of TAGE and their target molecules in the pathogenesis of AD remains unclear. In this study, we investigated the target protein for TAGE by performing two-dimensional immunoblot analysis with anti-TAGE antibody and mass spectrometry and identified β-tubulin as one of the targets. GA treatment induced TAGE-β-tubulin formation and abnormal aggregation of β-tubulin, and inhibited neurite outgrowth in SH-SY5Y cells. On the other hand, glucose-derived AGEs were also involved in developing AD. However, glucose did not make abnormal aggregation of β-tubulin and did not inhibit neurite outgrowth. Understanding the underlying mechanism of TAGE-β-tubulin formation by GA and its role in neurodegeneration may aid in the development of novel therapeutics and neuroprotection strategies.

Intracellular Toxic AGEs (TAGE) Triggers Numerous Types of Cell Damage

“…Previous studies on AGEs reported that the effects of AGEs were associated with their extracellular binding to RAGE or accumulation in numerous tissues; however, further research on these molecules is needed to clarify the impact of the intracellular generation of TAGE. The in vitro intracellular TAGE molecules that participate in cytotoxic effects in neuroblastoma cells [ 24 , 25 ], hepatocytes [ 26 , 27 , 28 ], pancreatic cells [ 29 ], cardiomyocytes [ 30 ], and myoblast cells [ 31 ] have been identified. These molecules are produced as intermediates during abnormal glucose and fructose metabolism in the presence of excess GA. TAGE appear to play roles in apoptotic/necrotic events, and thus, have been implicated in cell death and tissue damage.…”

“…We investigated target proteins for TAGE using two-dimensional gel electrophoresis and mass spectrometry, and the findings obtained demonstrated that β-tubulin was one of the targets of TAGE. The formation of TAGE-β-tubulin, the abnormal aggregation of β-tubulin, and the inhibition of neurite outgrowth were observed in GA-treated SH-SY5Y cells [ 25 ]. These findings implicated the formation of TAGE-β-tubulin in the generation of PHF, a component of NFT.…”

“…Therefore, TAGE may be general causative agents of the onset of neurodegenerative diseases, such as AD. Although the exact structure of TAGE-β-tubulin, the mechanisms responsible for its formation, and its downstream signaling pathway currently remain unclear, we identified β-tubulin as one of the targets of TAGE [ 25 ]. In addition, we demonstrated that GA induced the abnormal aggregation of β-tubulin and inhibited neurite outgrowth.…”

“…We demonstrated that TAGE were mainly present in the neurons of the hippocampus and parahippocampal gyrus and generally localized to the cell bodies of neurons in the brains of AD patients [ 12 ]. We also showed that a treatment with GA increased the intracellular generation of TAGE and induced cell dysfunction, including β-tubulin aggregation, tau phosphorylation, and the inhibition of glycolysis [ 24 , 25 ].…”

“…The accumulation of TAGE has been implicated in the pathogenesis of AD [ 11 , 12 , 13 ], NAFLD/NASH [ 14 , 15 , 16 , 17 ], CVD [ 18 , 19 , 20 ], and DM and diabetic microvascular complications [ 21 , 22 , 23 ]. We recently demonstrated that intracellular TAGE generation/accumulation induced not only neuronal cell damage [ 24 , 25 ], but also hepatocellular damage [ 26 , 27 , 28 ], pancreatic ductal epithelial cell damage [ 29 ], cardiomyocyte pulsation arrest and cell death [ 30 ], and myoblast cell death [ 31 ]. Therefore, the accumulation of TAGE in cells induces cell damage, resulting in their extracellular leakage into the blood, and thus, increased levels in circulating fluids [ 32 ].…”