Methylglyoxal upregulates Dictyostelium discoideum slug migration by triggering glutathione reductase and methylglyoxal reductase activity

Role of the Glyoxalase System in Breast Cancer and Gynecological Cancer-Implications for Therapeutic Intervention: a Review

Methyglyoxal (MGO), an essential endogenous dicarbonyl metabolite, can lead to multiple physiological problems including hyperglycemia, kidney diseases, malignant tumors, beyond its normal concentration range. The glyoxalase system, making MGO maintained at a low level, links glycation to carcinogenesis, growth, metastasis, and cancer chemotherapy. The glyoxalase system comprises glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2), which is often overexpressed in various tumor tissues. However, very little is known about the glyoxalase system in breast cancer and gynecological cancer. In this review, we introduce the role of the glyoxalase system in breast cancer, endometrial cancer, ovarian cancer and cervical cancer, and highlight the potential of the glyoxalase system to be both as a marker for diagnosis and a novel target for antitumor therapy. However, the intrinsic molecular biology and mechanisms of the glyoxalase system in breast cancer and gynecological cancer need further exploration.

Alcohol dehydrogenase 1 and NAD(H)-linked methylglyoxal oxidoreductase reciprocally regulate glutathione-dependent enzyme activities in Candida albicans

Glutathione reductase (Glr1) activity controls cellular glutathione and reactive oxygen species (ROS). We previously demonstrated two predominant methylglyoxal scavengers-NAD(H)-linked methylglyoxal oxidoreductase (Mgd1) and alcohol dehydrogenase 1 (Adh1)-in glutathione-depleted γ-glutamyl cysteinyl synthetase-disrupted Candida albicans. However, experimental evidence for Candida pathophysiology lacking the enzyme activities of Mgd1 and Adh1 on glutathione-dependent redox regulation remains unclear. Herein, we have aimed to demonstrate that glutathione-dependent enzyme activities coupled with cellular ROS changes is regulated by methylglyoxal accumulation in Δmgd1/Δadh1 double disruptants. Δmgd1/Δadh1 showed severe growth defects and G1-phase cell cycle arrest. The observed complementary and reciprocal methylglyoxal-oxidizing and methylglyoxalreducing activities between Δmgd1 and Δadh1 were not always exhibited in Δmgd1/Δadh1. Although intracellular accumulation of methylglyoxal and pyruvate was shown in all disruptants, to a greater or lesser degree, methylglyoxal was particularly accumulated in the Δmgd1/Δadh1 double disruptant. While cellular ROS significantly increased in Δmgd1 and Δadh1 as compared to the wild-type, Δmgd1/Δadh1 underwent a decrease in ROS in contrast to Δadh1. Despite the experimental findings underlining the importance of the undergoing unbalanced redox state of Δmgd1/Δadh1, glutathione-independent antioxidative enzyme activities did not change during proliferation and filamentation. Contrary to the significantly lowered glutathione content and Glr1 enzyme activity, the activity staining-based glutathione peroxidase activities concomitantly increased in this mutant. Additionally, the enhanced GLR1 transcript supported our results in Δmgd1/Δadh1, indicating that deficiencies of both Adh1 and Mgd1 activities stimulate specific glutathione-dependent enzyme activities. This suggests that glutathione-dependent redox regulation is evidently linked to C. albicans pathogenicity under the control of methylglyoxal-scavenging activities.

Glyoxalases in Urological Malignancies

Urological cancers include a spectrum of malignancies affecting organs of the reproductive and/or urinary systems, such as prostate, kidney, bladder, and testis. Despite improved primary prevention, detection and treatment, urological cancers are still characterized by an increasing incidence and mortality worldwide. While advances have been made towards understanding the molecular bases of these diseases, a complete understanding of the pathological mechanisms remains an unmet research goal that is essential for defining safer pharmacological therapies and prognostic factors, especially for the metastatic stage of these malignancies for which no effective therapies are currently being used. Glyoxalases, consisting of glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2), are enzymes that catalyze the glutathione-dependent metabolism of cytotoxic methylglyoxal (MG), thus protecting against cellular damage and apoptosis. They are generally overexpressed in numerous cancers as a survival strategy by providing a safeguard through enhancement of MG detoxification. Increasing evidence suggests that glyoxalases, especially Glo1, play an important role in the initiation and progression of urological malignancies. In this review, we highlight the critical role of glyoxalases as regulators of tumorigenesis in the prostate through modulation of various critical signaling pathways, and provide an overview of the current knowledge on glyoxalases in bladder, kidney and testis cancers. We also discuss the promise and challenges for Glo1 inhibitors as future anti-prostate cancer (PCa) therapeutics and the potential of glyoxalases as biomarkers for PCa diagnosis.

Administration of Protocatechuic Acid Reduces Traumatic Brain Injury-Induced Neuronal Death

Protocatechuic acid (PCA) was first purified from green tea and has shown numerous biological activities, including anti-apoptotic, anti-inflammatory, and anti-atherosclerotic effects. The effect of PCA on traumatic brain injury (TBI)-induced neuronal death has not previously been evaluated. TBI is defined as damage to the brain resulting from external mechanical force, such as rapid acceleration or deceleration, impact, blast waves, or penetration by a projectile. TBI causes neuronal death in the hippocampus and cerebral cortex. The present study aimed to evaluate the therapeutic potential of PCA on TBI-induced neuronal death. Here, TBI was induced by a controlled cortical impact model using rats. PCA (30 mg/kg) was injected into the intraperitoneal (ip) space immediately after TBI. Neuronal death was evaluated with Fluoro Jade-B (FJB) staining at 24 h after TBI. Oxidative injury was detected by 4-hydroxy-2-nonenal (4HNE), glutathione (GSH) concentration was analyzed by glutathione adduct with N-ethylmaleimide (GS-NEM) staining at 24 h after TBI, and microglial activation in the hippocampus was detected by CD11b immunohistochemistry at one week after TBI. We found that the proportion of degenerating neurons, oxidative injury, GSH depletion, and microglia activation in the hippocampus and cortex were all reduced by PCA treatment following TBI. Therefore, our study suggests that PCA may have therapeutic potential in preventing TBI-induced neuronal death.

Cytochrome c peroxidase regulates intracellular reactive oxygen species and methylglyoxal via enzyme activities of erythroascorbate peroxidase and glutathione-related enzymes in Candida albicans

D-erythroascorbate peroxidase (EAPX1) deficiency causes glutathione deprivation, leading to the accumulation of methylglyoxal and reactive oxygen species (ROS), and especially, induction of cytochrome c peroxidase (Ccp1) in Candida albicans. Nevertheless, reciprocal effects between changes in Ccp1 activity and the antioxidative D-erythroascorbic acid- and glutathione-dependent redox status, which reflects methylglyoxal biosynthesis altering pathophysiology are unclear in eukaryotes. To elucidate the effect of CCP1 expression on EAPX1 and glutathione reductase (Glr1) activity-mediated D-erythroascorbic acid biosynthesis and redox homeostasis, the CCP1 gene was disrupted and overexpressed. First, we demonstrated both glutathione-independent and-dependent metabolite contents and their corresponding gene transcripts and enzyme activities (i.e., Ccp1, catalase-peroxidase [KatG], superoxide dismutase [Sod], Eapx1, and Glr1) in CCP1 mutants. Second, methylglyoxal-oxidizing alcohol dehydrogenase (Adh1) and methylglyoxal-reducing oxidoreductase activity on glycolytic methylglyoxal and pyruvate production and NAD(P)H content were determined in these mutants. Contrary to our expectation, CCP1 disruption (42.19±3.22nmolO₂h^-1mgwetcell^-1) failed to affect cell respiration compared to the wild-type strain (41.62±7.11nmolO₂h^-1mgwetcell^-1) under cyanide treatment, and in contrast to hydrogen peroxide (H₂O₂) treatment (21.74±1.03nmol O₂h^-1mgwetcell^-1). Additionally, Ccp1 predominantly detoxified H₂O₂ rather than negligible scavenging activities towards methylglyoxal and other oxidants. CCP1 deficiency stimulated Sod and Adh1 activity but downregulated Glr1, Eapx1, catalase, and peroxidase activity while enhancing KatG, EAPX1, and GLR1 transcription by decreasing glutathione and D-erythroascorbic acid and increasing pyruvate. Noticeably, the ROS-accumulating CCP1-deficient mutant maintained steady-state levels of methylglyoxal, which was revealed to be regulated by methylglyoxal-oxidizing and -reducing activity with drastic changes in NAD(P)H. We confirmed and clarified our results by showing that CCP1/EAPX1 double disruptants underwent severe growth defects due to the D-erythroascorbic acid and glutathione depletion because of pyruvate overaccumulation. These observations were made in both budding and hyphal-growing CCP1 mutants. The revealed metabolic network involving Ccp1 and other redox regulators affected ROS and methylglyoxal through D-erythroascorbic acid and glutathione-dependent metabolites, thereby influencing dimorphism. This is the first report of the Ccp1-mediated D-erythroascorbic acid and glutathione biosynthesis accompanying methylglyoxal scavengers for full fungal virulence.