The formation of intracellular glyceraldehyde-derived advanced glycation end-products and cytotoxicity

Abstract

Nonalcoholic steatohepatitis (NASH) is a feature of metabolic syndrome. Advanced glycation end-products (AGEs) are formed by the Maillard reaction, which contributes to aging and to certain pathological complications of diabetes. A recent study has suggested that glyceraldehyde-derived AGEs (Glycer-AGEs) are elevated in the sera of patients with NASH. Furthermore, immunohistochemistry of Glycer-AGEs showed intense staining in the livers of patients with NASH. The present study aimed to examine the effect of intracellular Glycer-AGEs on hepatocellular carcinoma (Hep3B) cells. Cell viability was determined by the WST-1 assay. The slot blot and Western blot were used to detect intracellular Glycer-AGEs, and their localization was analyzed by confocal microscopy. Real-time reverse transcription-polymerase chain reaction was used to quantify the mRNA for the acute phase reactant C-reactive protein (CRP). Glyceraldehyde (GA), which is the precursor of Glycer-AGEs, induced a concentration- and time-dependent increase in cell death, which was associated with an increase in intracellular Glycer-AGEs formation. Aminoguanidine (AG), which prevents AGEs formation, inhibited the formation of intracellular Glycer-AGEs and prevented cell death. Among the intracellular Glycer-AGEs that were formed, heat shock cognate 70 (Hsc70) was identified as a GA-modified protein, and its modification reduced the activity of Hsc70. Furthermore, intracellular Glycer-AGEs increased the CRP mRNA concentration. These results suggest that intracellular Glycer-AGEs play important roles in promoting inflammation and hepatocellular death.