Methylglyoxal increases cardiomyocyte ischemia-reperfusion injury via glycative inhibition of thioredoxin activity

Abstract

Diabetes mellitus (DM) is closely related to cardiovascular morbidity and mortality, but the specific molecular basis linking DM with increased vulnerability to cardiovascular injury remains incompletely understood. Methylglyoxal (MG), a precursor to advanced glycation end products (AGEs), is increased in diabetic patient plasma, but its role in diabetic cardiovascular complications is unclear. Thioredoxin (Trx), a cytoprotective molecule with antiapoptotic function, has been demonstrated to be vulnerable to glycative inhibition, but whether Trx is glycatively inhibited by MG, thus contributing to increased cardiac injury, has never been investigated. Cultured H9c2 cardiomyocytes were treated with MG (200 muM) for 6 days. The following were determined pre- and post-simulated ischemia-reperfusion (SI-R; 8 h of hypoxia followed by 3 h of reoxygenation): cardiomyocyte death/apoptosis, Trx expression and activity, AGE formation, Trx-apoptosis-regulating kinase-1 (Trx-ASK1) complex formation, and p38 mitogen-activated protein kinase (MAPK) phosphorylation and activity. Compared with vehicle, MG significantly increased SI-R-induced cardiomyocyte LDH release and apoptosis (P < 0.01). Prior to SI-R, Trx activity was reduced in MG-treated cells, but Trx expression was increased moderately. Moreover, Trx-ASK1 complex formation was reduced, and both p38 MAPK activity and phosphorylation were increased. To investigate the effects of MG on Trx directly, recombinant human Trx (hTrx) was incubated with MG in vitro. Compared with vehicle, MG incubation markedly increased CML formation (a glycation footprint) and inhibited Trx activity. Finally, glycation inhibitor aminoguanidine administration during MG treatment of cultured cells reduced AGE formation, increased Trx activity, restored Trx-ASK1 interaction, and reduced p38 MAPK phosphorylation and activity, caspase-3 activation, and LDH release (P < 0.01). We demonstrated for the first time that methylglyoxal sensitized cultured cardiomyocytes to SI-R injury by posttranslational modification of Trx via glycation. Therapeutic interventions scavenging AGE precursors may attenuate ischemic-reperfusion injury in hyperglycemic state diseases such as diabetes.

Transcriptional control of glyoxalase 1 by Nrf2 provides a stress-responsive defence against dicarbonyl glycation

“…Glo1 transgenic rats were resistant to renal reperfusion injury, showing decreased AGE accumulation, oxidative stress and renal tubular cell apoptosis [38]. Similar evidence is currently unavailable for myocardial reperfusion injury after acute myocardial infarction but MG has been found to induce increases cardiomyocyte ischemia-reperfusion in vitro [56]. Glo1 inducers are also likely to find benefit in renal failure, countering the increased exposure to MG and thereby countering the potential for increased formation of atherogenic MG-modified LDL [51;57].…”

Loss of thioredoxin function in retinas of mice overexpressing amyloid β

“…Of interest, these effects were associated with increased phosphorylation of the stress-related kinases ASK-1 and p38MAPK [42]. Phosphorylation/ activation of ASK-1 is due to decreased activity of the TrxS [43,44]. Reduced, active, Trx1 binds ASK-1 and prevents its phosphorylation, thus blocking downstream events including phosphorylation/activation of p38MAPK [43].…”

Thioredoxin Superfamily and Its Effects on Cardiac Physiology and Pathology

“…In a model of ischemia reperfusion in H9c2 cardiomyoblasts, cells preincubated with methylglyoxal have lower Trx1 activity accompanied by reduced binding of Trx1 to ASK1 and by enhanced p38-MAP kinase activation (190). The Trx1 activity is reduced in the aging heart due to the posttranslational nitrative modification, which leads to a decreased Trx1-ASK1 binding (209).…”

“…Hyperglycemia induces nitrative inactivation of Trx1 and sensitizes the heart to ischemia reperfusion injury by promoting the ASK1-p38 MAP kinase signaling to induce cardiomyocyte apoptosis (102,206). Another interesting mechanistic possibility in diabetic hearts is glycative inactivation of Trx1 activity (190). Posttranslational modification of Trx1 by glycation sensitizes cultured cardiomyocytes to ischemia reperfusion injury (190).…”

“…Another interesting mechanistic possibility in diabetic hearts is glycative inactivation of Trx1 activity (190). Posttranslational modification of Trx1 by glycation sensitizes cultured cardiomyocytes to ischemia reperfusion injury (190). In addition, the receptor for advanced glycation endproducts (RAGE) can be causative of Trx1 inactivation in diabetic mouse hearts, and modulates myocardial ischemia reperfusion injury (100).…”