Methylglyoxal-induced AMPK activation leads to autophagic degradation of thioredoxin 1 and glyoxalase 2 in HT22 nerve cells

Abstract

Methylglyoxal (MGO) is a major glycating agent that reacts with basic residues of proteins and promotes the formation of advanced glycation end products which are believed to play key roles in a number of pathologies, such as diabetes, Alzheimer’s disease, and inflammation. We previously showed that MGO treatment targets the thioredoxin and the glyoxalase systems, leading to a decrease in Trx1 and Glo2 proteins in immortalized mouse hippocampal HT22 nerve cells. Here, we propose that autophagy is the underlying mechanism leading to Glo2 and Trx1 loss induced by MGO. The autophagic markers p62, and the lipidated and active form of LC3, were increased by MGO (0.5 mM). Autophagy inhibition with bafilomycin or chloroquine prevented the decrease in Trx1 and Glo2 at 6 and 18 h after MGO treatment. Proteasome inhibition by MG132 exacerbated the effect of MGO on Trx1 and Glo2 degradation (18 h), further suggesting a role for autophagy. ATG5 small interfering RNA protected Trx1 and Glo2 from MGO-induced degradation, confirming Trx1 and Glo2 loss is mediated by autophagy. In the search for the signals that control autophagy, we found that AMPK activation, a known autophagy inducer, was markedly increased by MGO treatment. AMPK activation was confirmed by increased acetyl coenzyme A carboxylase phosphorylation, a direct AMPK substrate and by decreased mTOR phosphorylation, an indirect marker of AMPK activation. To confirm that MGO-mediated Trx1 and Glo2 degradation was AMPK-dependent, AMPK-deficient mouse embryonic fibroblasts (MEFs) were treated with MGO. Wildtype MEFs presented the expected decrease in Trx1 and Glo2, while MGO was ineffective in decreasing these proteins in AMPK-deficient cells. Overall, the data indicate that MGO activates autophagy in an AMPK-dependent manner, and that autophagy was responsible for Trx1 and Glo2 degradation, confirming that Trx1 and Glo2 are molecular targets of MGO.

Methylglyoxal-Induced Dysfunction in Brain Endothelial Cells via the Suppression of Akt/HIF-1α Pathway and Activation of Mitophagy Associated with Increased Reactive Oxygen Species

“…Accumulating evidence indicates that mitophagy is activated as an adaptive response to oxidative stress and mitochondria damage [ 33 , 34 , 35 ], and we investigated the activation of mitophagy in MG-exposed brain ECs. The formation of autophagosomes was increased following MG treatment, as measured by immunostaining of microtubule-associated proteins 1B light chain 3B (LC3B).…”

“…Interestingly, Zhang et al [35] demonstrated that HIF-1 negatively regulated the gene expression of Glo-1 in leukemia stem cells. Dafre et al [33] demonstrated that autophagy inhibitors (bafilomycin A and chloroquine) reversed Glo-2 degradation induced by MG. Since we have shown that MG treatment induces HIF-1 degradation and autophagy activation, these mechanisms might affect the expression levels of Glo-1 and Glo-2 in ECs.…”

Methylglyoxal down-regulates the expression of cell cycle associated genes and activates the p53 pathway in human umbilical vein endothelial cells

“…Compatible with this suggestion is the finding that knockdown of glyoxalase-1 in non-diabetic mice results in renal lesions indistinguishable from those of diabetic mice, while overexpression of glyoxalase-1 in diabetic mice prevents the development of nephropathy 18 . Other studies have shown that MGO impairs HIF-1α degradation and signaling 19,20 and activates AMPK mediated autophagic degradation of thioredoxin 1 21 , thus emphasizing its influence on redox homeostasis 22 . Despite the clear association between reactive carbonyl species and diabetic complications, their mode of action on endothelial cells is discussed ambiguously 23–27 .…”

Function prediction and network analysis to investigate the response of microbial communities to a single environmental factor

“…In addition, we have noticed that the functional abundance of Thioredoxin (Trx) is not elevated (supplementary material, Table S2), which may be that aldehydes restrict the activity of Thioredoxin (Trx). Indeed (Dafre et al 2017), some aldehyde molecules including malondialdehyde (MDA), trans-2-hexenal and 4-hydroxynonenal were proved to function as powerful gene activators despite their potential toxicity. Our research shows that changes in salinity on the structure of bacterial communities are obvious, but the impact on bacterial function is limited.…”