Increased Glucose-6-phosphate Dehydrogenase Activity Research Articles

Glucose-6-phosphate dehydrogenase and abscisic acid mediate programmed cell death induced by aluminum toxicity in soybean root tips

Programmed cell death (PCD) induced by aluminum (Al) is considered an important reason of Al phytotoxicity. However, the underlying mechanism of how Al induces PCD remains largely unknown in plants. The roles of glucose-6-phosphate dehydrogenase (G6PDH) and abscisic acid (ABA) in regulating Al-induced PCD were investigated in soybean roots. Al treatment increased G6PDH activity, while inhibition of G6PDH activity alleviated PCD occurrence and reactive oxygen species (ROS) accumulation under Al stress. Overexpression of cytosolic G6PDH1 enhanced G6PDH activity, thus promoting ROS production and cell death under Al exposure. Inhibition of NADPH oxidase activity mitigated ROS generation and cell death under Al stress. Further investigation demonstrated that G6PDH positively regulated the activity of NADPH oxidase under Al treatment using pharmacological and transgenic approach. Furthermore, Al stress increased ABA production, while inhibition of ABA biosynthesis alleviated PCD occurrence and ROS accumulation under Al stress. Interestingly, ABA upregulated G6PDH1 expression and G6PDH activity under Al stress. These results suggest that G6PDH mediates Al-induced PCD occurrence through the activation of NADPH oxidase-dependent ROS production, and ABA acts upstream of G6PDH in this process. This study will provide novel clues for the improvement of Al phytotoxicity in acidic soils.

Induced expression of the zwf gene in the presence of glucose contributes to lowering of glucose 6-phosphate level and consequently reduction of growth rate of Mycobacterium smegmatis.

In Mycobacterium smegmatis (renamed Mycolicibacterium smegmatis), glucose 6-phosphate (G6P) level is exceptionally high as compared to other bacteria, E. coli for example. Earlier investigations have indicated that G6P protects M. smegmatis (Msm) against oxidative stress-inducing agents. G6P is a glycolytic intermediate formed either directly through the phosphorylation of glucose or indirectly via the gluconeogenic pathway. Its consumption is catalysed by several enzymes, one of which being the NADPH dependent G6P dehydrogenase (G6PDH) encoded by zwf (msmeg_0314). While investigating the extent to which the carbon sources glucose and glycerol influence Msm growth, we observed that intracellular concentration of G6P was lower in the former's presence than the latter. We could correlate this difference with that in the growth rate, which was higher in glycerol than glucose. We also found that lowering of G6P content in glucose-grown cells was triggered by the induced expression of zwf and the resultant increase in G6PDH activity. When we silenced zwf using CRISPR-Cas9 technology, we observed a significant rise in the growth rate of Msm. Therefore, we have found that depletion of G6P in glucose-grown cells due to increased G6PDH activity is at least one reason why the growth rate of Msm in glucose is less than glycerol. However, we could not establish a similar link-up between slow growth in glucose and lowering of G6P level in the case of Mycobacterium tuberculosis (Mtb). Mycobacteria, therefore, may have evolved diverse mechanisms to ensure that they use glycerol preferentially over glucose for their growth.

Comparative responses of Sinopotamon henanense to acute and sub-chronic Cd exposure.

Studies on the freshwater crab Sinopotamon henanense have shown that acute and sub-chronic Cd2+ exposure induced differential alterations in the respiratory physiology and gill morphology. To elucidate Cd2+ toxicity under these two exposure conditions, crabs were acutely exposed to 7.14, 14.28, and 28.55 mg/L Cd2+ for 96 h and sub-chronically exposed to 0.71, 1.43, and 2.86 mg/L Cd2+ for 3 weeks. The Cd2+ accumulation, total metallothionein (MT), superoxide dismutase, and malondialdehyde (MDA) contents in the gill tissues were detected. Moreover, the glucose-6-phosphate dehydrogenase (G6PDH) activity, NADPH content, reduced glutathione (GSH), oxidized glutathione (GSSG), and GSH/GSSG ratio in the hepatopancreas were determined. The morphology of the X-organ-sinus gland complex was also observed. The results showed that sub-chronical Cd2+ exposure induced lower MT content and higher MDA level in the gills than in the acute exposure. In the hepatopancreas, acute Cd2+ exposure decreased the pentose phosphate pathway activity and NADPH content; however, an increased G6PDH activity and NADPH content were detected in sub-chronic Cd2+ exposure (2.86 mg/L). Morphological changes occurred in the sinus gland in crabs exposed to 2.86 mg/L Cd2+ for 3 weeks. The tightly packed structure composed by the axons, enlarged terminals, and glial cells, became loose and porous. Ultra-structurally, a large number of vacuoles and few neurosecretory granules were observed in the axon terminal. These effects added to our understanding of the toxic effects of Cd2+ and provide biochemical and histopathological evidence for S. henanense as a biomarker of acute or long-term waterborne Cd2+ pollution.

Geranylgeranylacetone attenuates cerebral ischemia\u2013reperfusion injury in rats through the augmentation of HSP 27 phosphorylation: a preliminary study

BackgroundWe previously reported that heat shock protein 27 (HSP27) phosphorylation plays an important role in the activation of glucose-6-phosphate dehydrogenase (G6PD), resulting in the upregulation of the pentose phosphate pathway and antioxidant effects against cerebral ischemia–reperfusion injury. The present study investigated the effect of geranylgeranylacetone, an inducer of HSP27, on ischemia–reperfusion injury in male rats as a preliminary study to see if further research of the effects of geranylgeranylacetone on the ischemic stroke was warranted.MethodsIn all experiments, male Wistar rats were used. First, we conducted pathway activity profiling based on a gas chromatography–mass spectrometry to identify ischemia–reperfusion-related metabolic pathways. Next, we investigated the effects of geranylgeranylacetone on the pentose phosphate pathway and ischemia–reperfusion injury by real-time polymerase chain reaction (RT-PCR), immunoblotting, and G6PD activity, protein carbonylation and infarct volume analysis. Geranylgeranylacetone or vehicle was injected intracerebroventricularly 3 h prior to middle cerebral artery occlusion or sham operation.ResultsPathway activity profiling demonstrated that changes in the metabolic state depended on reperfusion time and that the pentose phosphate pathway and taurine-hypotaurine metabolism pathway were the most strongly related to reperfusion among 137 metabolic pathways. RT-PCR demonstrated that geranylgeranylacetone did not significantly affect the increase in HSP27 transcript levels after ischemia–reperfusion. Immunoblotting showed that geranylgeranylacetone did not significantly affect the elevation of HSP27 protein levels. However, geranylgeranylacetone significantly increase the elevation of phosphorylation of HSP27 after ischemia–reperfusion. In addition, geranylgeranylacetone significantly affected the increase in G6PD activity, and reduced the increase in protein carbonylation after ischemia–reperfusion. Accordingly, geranylgeranylacetone significantly reduced the infarct size (median 31.3% vs 19.9%, p = 0.0013).ConclusionsAs a preliminary study, these findings suggest that geranylgeranylacetone may be a promising agent for the treatment of ischemic stroke and would be worthy of further study. Further studies are required to clearly delineate the mechanism of geranylgeranylacetone-induced HSP27 phosphorylation in antioxidant effects, which may guide the development of new approaches for minimizing the impact of cerebral ischemia–reperfusion injury.

Enzymatic Changes in Red Blood Cells of Diamond-Blackfan Anemia

Diamond-Blackfan anemia is a congenital bone marrow failure syndrome characterized by red blood cell (RBC) aplasia with varied malformations in infants. Elevated activity of adenosine deaminase (ADA) has been considered as a useful biomarker of Diamond-Blackfan anemia, and ADA assay has been shown to be more sensitive than genetic diagnosis. Approximately, 80% of the examined patients showed elevated ADA activity, whereas genetic tests of ribosome subunit genes identified mutations in approximately 60% of the patients. We previously reported that reduced glutathione (GSH) levels in RBCs may serve as a biomarker of Diamond-Blackfan anemia. In this study, to confirm the universality of our data, we extended the analysis to seven RBC enzymes and GSH of 14 patients with Diamond-Blackfan anemia and performed a cross-analysis study using enzyme activity assay and recently reported proteome data. Statistical analysis revealed that both data exhibited high similarity, upregulation in the hexokinase and pentose-phosphate pathway, and downregulation in glycolytic enzymes such as phosphofructokinase and pyruvate kinase, in the RBCs obtained from the subjects with Diamond-Blackfan anemia. The only discrepancy between enzyme activity and proteome data was observed in glucose-6-phosphate dehydrogenase (G6PD), as increased G6PD activity showed no relation with the significant elevation in protein levels. These results suggest that our enzymatic activity data of Diamond-Blackfan anemia are universal and that the enzymatic activation of G6PD via a hitherto-unveiled mechanism is another metabolic feature of RBCs of Diamond-Blackfan anemia.

Erythrocyte glucose-6-phosphate dehydrogenase activity and risk of gestational diabetes.

Glucose-6-phosphate dehydrogenase (G6PD) is the regulating enzyme in the pentose phosphate pathway. A link between the activity of G6PD and diabetes mellitus has previously been reported. The association of G6PD activity with the pathogenesis of gestational diabetes mellitus (GDM) has not yet been investigated. The aim of the present study was to investigate the association of erythrocyte G6PD activity with major characteristics of GDM. This case-control study was conducted at Hafez Hospital, Shiraz University of Medical Sciences, Shiraz, Iran from March to November 2017. Eighty-four age-matched pregnant women including GDM (n = 33), impaired glucose tolerance (IGT; n = 7), and normal glucose tolerance (NGT; n = 44) subjects were enrolled in this study. The levels of erythrocyte G6PD activity, fasting plasma glucose (FPG), insulin, malondialdehyde (MDA), and ferric reducing power (FRAP) of serum were measured. The level of homeostasis model for the assessment of insulin resistance (HOMA-IR) was calculated. The data were analyzed using SPSS software. P < 0.05 was considered statistically significant. The values of FPG, insulin, HOMA-IR, G6PD activity, and FRAP were significantly higher in GDM patients compared to NGT subjects. G6PD activity was correlated with FPG ((r = 0.224; P = 0.041). Binary logistic regression analysis revealed independent association of body mass index >25.88 [OR = 3.23, 95% CI 1.071-9.75, P = 0.037], HOMA- IR >2.33 [OR = 7.15, 95% CI 2.26-22.56, P < 0.001], and G6PD activity>21.17U/g Hb [OR = 4.63, 95% CI 1.49-14.38, P = 0.008] with an increased risk of GDM. No significant change was observed among serum MDA levels in the three groups. The findings demonstrate that increased G6PD activity is positively associated with the risk of GDM.

Glucose-6-phosphate dehydrogenase (G6PD) activity can modulate macrophage response to Leishmania major infection

Glucose-6-phosphate dehydrogenase (G6PDH) ultimately plays a critical role in macrophage functions used against infectious agents. The present study investigated whether changes in G6PDH activity could influence the resistance of infected macrophages against Leishmania major infection. Mouse peritoneal and J774 macrophages were infected, respectively, ex vivo and in vitro, with L. major and then exposed to an inhibitor (6-aminonicotinamide) or activator (LPS + melatonin) of G6PDH activity for 24 h. Cell viability [using MTT assay] was measured to assess any direct toxicity from the doses of inhibitor/activator used for the macrophage treatments. Nitric oxide (NO) produced by the cells and released into culture supernatants was measured (Griess method) and cell G6PDH activity was also determined. Moreover, the number of amastigotes form Leishmania in macrophages that developed over a 7-d period was evaluated. The results showed that an increase in G6PDH activity after treatment of both types of macrophages with a combination of LPS + melatonin caused significant increases in NO production and cell resistance against L. major amastigote formation/survival. However, exposure to 6-aminonicotinamide led to remarkable suppression of G6PDH activity and NO production, events that were associated with a deterioration in cell resistance against (and an increase in cell levels of) the parasites. The results suggested that activation or suppression of G6PDH activity could affect leishmanicidal function of both mouse peritoneal and J774 macrophages. Thus, regulation of macrophages via modulation of G6PDH activity appears to provide a novel window for those seeking to develop alternative therapies for the treatment of leishmaniasis.

The clinical impact of glucose-6-phosphate dehydrogenase deficiency in patients with sickle cell disease.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency and sickle cell disease (SCD) cause hemolysis, often occurring in individuals of African descent. These disorders co-occur frequently, and possibly interact, altering clinical outcomes in SCD. However, epidemiological investigations of SCD with G6PD deficiency have produced variable results. This contribution reviews the available data about the interaction of G6PD deficiency and SCD. Overall, G6PD deficiency contributes few, if any, effects to laboratory values and clinical outcomes in SCD patients, but may impact transfusion efficacy. This observation is most likely because of the relatively increased G6PD activity in the young red blood cell (RBC) population seen in SCD patients with or without G6PD deficiency. In addition, G6PD deficiency possibly interacts with other genetic modifiers, such as α thalassemia, hemoglobin F levels and SCD haplotype. Although G6PD deficiency is relatively common, it does not appear to clinically impact patients with SCD. Nonetheless, it is important to evaluate G6PD status in patients with SCD to avoid the use of medications that may cause hemolysis. Future studies evaluating the clinical impact of transfusions from G6PD-deficient RBC donors would be of the greatest benefit to the current literature.

Loss of cytosolic glucose-6-phosphate dehydrogenase increases the susceptibility of Arabidopsis thaliana to root-knot nematode infection.

Root knot nematodes (RKNs, Meloidogyne spp.) are microscopic roundworms with a wide host range causing great economic losses worldwide. Understanding how metabolic pathways function within the plant upon RKN infection will provide insight into the molecular aspects of plant-RKN interactions. Glucose-6-phosphate dehydrogenase (G6PDH), the key regulatory enzyme of the oxidative pentose phosphate pathway (OPPP), is involved in plant responses to abiotic stresses and pathogenesis. In this study, the roles of Arabidopsis cytosolic G6PDH in plant-RKN interactions were investigated. Enzyme assays and western blotting were used to characterize changes in total G6PDH activity and protein abundance in wild-type Arabidopsis in response to RKN infection. The susceptibility of wild-type plants and the double mutant g6pd5/6 to RKNs was analysed and the expression of genes associated with the basal defence response was tested after RKN infection using quantitative reverse transcription PCR. RKN infection caused a marked increase in total G6PDH activity and protein abundance in wild-type Arabidopsis roots. However, the transcript levels of G6PDH genes except G6PD6 were not significantly induced following RKN infection, suggesting that the increase in G6PDH activity may occur at the post-transcriptional level. The double mutant g6pd5/6 with loss-of-function of the two cytosolic isoforms G6PD5 and G6PD6 displayed enhanced susceptibility to RKNs. Moreover, reactive oxygen species (ROS) production and gene expression involved in the defence response including jasmonic acid and salicylic acid pathways were suppressed in the g6pd5/6 mutant at the early stage of RKN infection when compared to the wild-type plants. The results demonstrated that the G6PDH-mediated OPPP plays an important role in the plant-RKN interaction. In addition, a new aspect of G6PDH activity involving NADPH production by the OPPP in plant basal defence against RKNs is defined, which may be involved in ROS signalling.

Abstract 502: Glucose-6-Phosphate Dehydrogenase Regulates MYH11 and MYOCD Expression in HDAC and miR-1 Dependent Manner

Vascular smooth muscle cell (VSMC) phenotype and function is altered in diabetic and obese patients and animals. Increased activity of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in Pentose Phosphate Pathway, in diabetic and obese animals is associated with decreased expression of MYOCD and MYOCD-dependent genes in the arteries of these animals. Therefore, we hypothesize that reprogrammed metabolism and increased G6PD activity is critical in switching the VSMC from a differentiated to a dedifferentiated phenotype. Our results demonstrated metabolic reprogramming and decrease in MYOCD and MYOCD-driven MYH11 in the aorta of normal chow- and high fat diet (HFD)-fed diabetic Goto-Kakizaki (GK) as compared to control rats. Up regulated G6PD activity in the aorta of these animals positively correlated with increased arterial elastance (R 2 = 0.8322) and total peripheral resistance (R 2 = 0.8364). In vitro , VSMCs (A7r5) treated with Ad-shRNA for G6PD, epiandrosterone (Epi), G6PD inhibitor, and PD2958, a selective inhibitor of G6PD activity, increased (P&lt;0.05) Myocd and Myh11 levels and MYOCD-regulated MYH11 and CNN1 expressions as compared to untreated cells. Furthermore, we found that G6PD-mediated expression of MYOCD and MYH11 expressions was regulated at transcriptional and post transcriptional level. Inhibition of G6PD by PD2958 or Epi decreased histone deacetylase (HDAC) activity by 70-80% (P&lt;0.05), and concomitantly, PD2958 and Ad-shRNA-G6PD up regulated H3K9Ac expression in A7r5 cells as compared to their respective controls. Next, we compared the expression of VSMC-restricted MYH11 in A7r5 cells treated with HDAC inhibitor, Trichostatin (TSA), and PD2958+TSA. Our results demonstrated that MYH11 expression increased by TSA and PD2958 was not further potentiated by PD2958+TSA, suggesting that G6PD inhibition up regulated MYH11 via HDAC inhibition. We also found that G6PD inhibition increased miR-1 levels, which post-transcriptionally regulates MYOCD and MYOCD-dependent gene expression. Therefore, our results collectively suggest that increased G6PD activity is associated with switching of VSMCs from a differentiated to a dedifferentiated phenotype in HDAC and miR-1 dependent manner.

L-Cysteine in vitro can restore cellular glutathione and inhibits the expression of cell adhesion molecules in G6PD-deficient monocytes.

L-Cysteine is a precursor of glutathione (GSH), a potent physiological antioxidant. Excess glucose-6-phosphate dehydrogenase (G6PD) deficiency in African Americans and low levels of L-cysteine diet in Hispanics can contributes to GSH deficiency and oxidative stress. Oxidative stress and monocyte adhesion was considered to be an initial event in the progression of vascular dysfunction and atherosclerosis. However, no previous study has investigated the contribution of GSH/G6PD deficiency to the expression of monocyte adhesion molecules. Using human U937 monocytes, this study examined the effect of GSH/G6PD deficiency and L-cysteine supplementation on monocyte adhesion molecules. G6PD/GSH deficiency induced by either siRNA or inhibitors (6AN/BSO, respectively) significantly (p < 0.005) increased the levels of cell adhesion molecules (ICAM-1, VCAM-1, SELL, ITGB1 and 2); NADPH oxidase (NOX), reactive oxygen species (ROS) and MCP-1 were upregulated, and decreases in levels of GSH, and nitric oxide were observed. The expression of ICAM-1 and VCAM-1 mRNA levels increased in high glucose, MCP-1 or TNF-α-treated G6PD-deficient compared to G6PD-normal cells. L-Cysteine treatment significantly (p < 0.005) increased G6PD activity and levels of GSH, and decreased NOX, ROS, and adhesion molecules. Thus, GSH/G6PD deficiency increases susceptibility to monocyte adhesion processes, whereas L-cysteine supplementation can restore cellular GSH/G6PD and attenuates NOX activity and expression of cell adhesion molecules.

Glucose-6-phosphate dehydrogenase inhibition attenuates acute lung injury through reduction in NADPH oxidase-derived reactive oxygen species.

Acute lung injury (ALI) is a heterogeneous disease with the hallmarks of alveolar capillary membrane injury, increased pulmonary oedema and pulmonary inflammation. The most common direct aetiological factor for ALI is usually parenchymal lung infection or haemorrhage. Reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX2) are thought to play an important role in the pathophysiology of ALI. Glucose-6-phosphate dehydrogenase (G6PD) plays an important role both in production of ROS as well as their removal through the supply of NADPH. However, how G6PD modulation affects NOX2-mediated ROS in the airway epithelial cells (AECs) during acute lung injury has not been explored previously. Therefore, we investigated the effect of G6PD inhibitor, 6-aminonicotinamide on G6PD activity, NOX2 expression, ROS production and enzymatic anti-oxidants in AECs in a mouse model of ALI induced by lipopolysaccharide (LPS). ALI led to increased G6PD activity in the AECs with concomitant elevation of NOX2, ROS, SOD1 and nitrotyrosine. G6PD inhibitor led to reduction of LPS-induced airway inflammation, bronchoalveolar lavage fluid protein concentration as well as NOX2-derived ROS and subsequent oxidative stress. Conversely, ALI led to decreased glutathione reductase activity in AECs, which was normalized by G6PD inhibitor. These data show that activation of G6PD is associated with enhancement of oxidative inflammation in during ALI. Therefore, inhibition of G6PD might be a beneficial strategy during ALI to limit oxidative damage and ameliorate airway inflammation.

Assessment of biomarkers in the neotropical fish Brycon amazonicus exposed to cypermethrin-based insecticide.

The effects of cypermethrin-based insecticide (CBI), commonly used in aquaculture and agriculture, were evaluated in matrinxa (Brycon amazonicus) exposed to sub-lethal concentration (20% of LC50) for 96 h. Physiological and biochemical effects were studied through biomarkers: lipid peroxidation (LPO), glutathione (GSH), and ascorbic acid concentrations; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glucose-6-phosphate dehydrogenase (G6PDH) assays in the liver and gills. Besides, ions Na+, Cl-, and K+; protein and glucose concentrations were measured in the plasma. Red blood cells count (RBC), hemoglobin concentration (Hb), hematocrit (Ht), and hematimetric parameters were evaluated in the total blood. The NKA (Na+ /K+ ATPase) activity was assayed in the gills. The histopathological effects of CBI were also investigated in the gills. The liver and gill LPO increased 62 and 100%, respectively. The tripeptide GSH concentration reduced in the liver and increased in the gill of exposed fish. The SOD and CAT activities increased in the liver, whereas CAT reduced in the gill. Liver also presented an increase in G6PDH activity. Plasma Na+ and Cl- and glucose concentrations increased in the exposed fish. Levels of Ht, Hb and RBC were significantly increased. The gill NKA activity also increased. Exposed fish exhibited histological alterations in the gills such as hypertrophy and proliferation of chloride cells, blood vessels dilation, aneurysms and hemorrhage of the lamella. The histological index indicated moderate to heavy damage to the gills. CBI provokes liver and gills oxidative stress, gill structural damages, and ionic imbalance. A multi-biomarker approach allows us to see that B. amazonicus was unable to cope with CBI exposure.

PAK4 regulates G6PD activity by p53 degradation involving colon cancer cell growth

The p21-activated kinase 4 (PAK4) is overexpressed in different cancers and promotes proliferation of cancer cells. Reprogramming of glucose metabolism is found in most cancer cells which in turn supports rapid proliferation. However, the relationship between PAK4 and glucose metabolism in cancer cells has not been explored. In this study, we reported that PAK4 promoted glucose intake, NADPH production and lipid biosynthesis, leading to an increased proliferation of colon cancer cells. Mechanistically, PAK4 interacted with glucose-6-phosphate dehydrogenase (G6PD), a rate-limiting enzyme of the pentose phosphate pathway and increased G6PD activity via enhancing Mdm2-mediated p53 ubiquitination degradation. In addition, we demonstrated a close positive correlation between PAK4 and G6PD expression in colon cancer specimens. Furthermore, expression of PAK4 or G6PD was positively correlated with an aggressive phenotype of clinical colon cancer. These findings revealed a novel glucose metabolism-related mechanism of PAK4 in promoting colon cancer cell growth, suggesting that PAK4 and/or G6PD blockage might be a potential therapeutic strategy for colon cancer.

Glucose 6-phosphate dehydrogenase and the kidney.

Glucose 6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway. G6PD is the main source of the essential cellular reductant, NADPH. The purpose of this review is to describe the biochemistry of G6PD and NADPH, cellular factors that regulate G6PD, normal physiologic roles of G6PD, and the pathogenic role altered G6PD/NADPH plays in kidney disease. NADPH is required for many essential cellular processes such as the antioxidant system, nitric oxide synthase, cytochrome p450 enzymes, and NADPH oxidase. Decreased G6PD activity and, as a result, decreased NADPH level have been associated with diabetic kidney disease, altered nitric oxide production, aldosterone-mediated endothelial dysfunction, and dialysis-associated anemia. Increased G6PD activity is associated with all cancers including kidney cancer. Inherited G6PD deficiency is the most common mutation in the world that is thought to be a relatively mild disorder primarily associated with anemia. Yet, intriguing studies have shown an increased prevalence of diabetes mellitus in G6PD-deficient people. It is not known if G6PD-deficient people are at more risk for other diseases. Much more research needs to be done to determine the role of altered G6PD activity (inherited or acquired) in the pathogenesis of kidney disease.

Biochemical effects of fipronil and its metabolites on lipid peroxidation and enzymatic antioxidant defense in tadpoles (Eupemphix nattereri: Leiuperidae)

Amphibians are very sensitive to environmental change and pollution because they have both aquatic and terrestrial life cycle stages and high skin permeability. Particularly during the larval stages, when these animals are restricted to small, transient ponds, exposure to high concentrations of pesticides is inevitable in agricultural areas. Given that pesticide application increases during the summer, which coincides with the reproductive season and the occurrence of most neotropical tadpoles in their natural environment, strong indications exist that tadpoles are developing in contaminated ponds. Fipronil is one of the primary insecticides used in sugarcane cultivation in Brazil, and little is known about its toxic effects on non-target organisms such as tadpoles. The purpose of this study was to evaluate the effects of fipronil and its metabolites on oxidative stress in Eupemphix nattereri tadpoles after exposure in water and sediment at concentrations of 35, 120 and 180µgkg−1. We assessed the activities of the antioxidant enzymes glutathione S-transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH) and catalase (CAT) and lipid peroxidation (malondialdehyde, MDA). The results showed that fipronil has an inherent capacity to cause oxidative stress in tadpoles, as evidenced by a decrease in CAT activity and an increase in lipid peroxidation levels at all concentrations tested. Fipronil sulfone also produced elevated MDA levels at two of the tested concentrations and increased G6PDH activity in tadpoles exposed to the highest concentration of this metabolite but did not affect MDA levels. Our data showed that fipronil and its degradation products promoted oxidative stress in Eupemphix nattereri tadpoles exposed to environmentally relevant concentrations and could lead to a decrease in the long-term physiological performance of these animals, leading to detrimental effects at the population level.

G6PD protects from oxidative damage and improves healthspan in mice.

Reactive oxygen species (ROS) are constantly generated by cells and ROS-derived damage contributes to ageing. Protection against oxidative damage largely relies on the reductive power of NAPDH, whose levels are mostly determined by the enzyme glucose-6-phosphate dehydrogenase (G6PD). Here, we report a transgenic mouse model with moderate overexpression of human G6PD under its endogenous promoter. Importantly, G6PD-Tg mice have higher levels of NADPH, lower levels of ROS-derived damage, and better protection from ageing-associated functional decline, including extended median lifespan in females. The G6PD transgene has no effect on tumour development, even after combining with various tumour-prone genetic alterations. We conclude that a modest increase in G6PD activity is beneficial for healthspan through increased NADPH levels and protection from the deleterious effects of ROS.

TRAF6-Mediated SM22α K21 Ubiquitination Promotes G6PD Activation and NADPH Production, Contributing to GSH Homeostasis and VSMC Survival In Vitro and In Vivo.

Vascular smooth muscle cell (VSMC) survival under stressful conditions is integral to promoting vascular repair, but facilitates plaque stability during the development of atherosclerosis. The cytoskeleton-associated smooth muscle (SM) 22α protein is involved in the regulation of VSMC phenotypes, whereas the pentose phosphate pathway plays an essential role in cell proliferation through the production of dihydronicotinamide adenine dinucleotide phosphate. To identify the relationship between dihydronicotinamide adenine dinucleotide phosphate production and SM22α activity in the development and progression of vascular diseases. We showed that the expression and activity of glucose-6-phosphate dehydrogenase (G6PD) are promoted in platelet-derived growth factor (PDGF)-BB-induced proliferative VSMCs. PDGF-BB induced G6PD membrane translocation and activation in an SM22α K21 ubiquitination-dependent manner. Specifically, the ubiquitinated SM22α interacted with G6PD and mediated G6PD membrane translocation. Furthermore, we found that tumor necrosis factor receptor-associated factor (TRAF) 6 mediated SM22α K21 ubiquitination in a K63-linked manner on PDGF-BB stimulation. Knockdown of TRAF6 decreased the membrane translocation and activity of G6PD, in parallel with reduced SM22α K21 ubiquitination. Elevated levels of activated G6PD consequent to PDGF-BB induction led to increased dihydronicotinamide adenine dinucleotide phosphate generation through stimulation of the pentose phosphate pathway, which enhanced VSMC viability and reduced apoptosis in vivo and in vitro via glutathione homeostasis. We provide evidence that TRAF6-induced SM22α ubiquitination maintains VSMC survival through increased G6PD activity and dihydronicotinamide adenine dinucleotide phosphate production. The TRAF6-SM22α-G6PD pathway is a novel mechanism underlying the association between glucose metabolism and VSMC survival, which is beneficial for vascular repair after injury but facilitates atherosclerotic plaque stability.

Hypoxia-induced glucose-6-phosphate dehydrogenase overexpression and -activation in pulmonary artery smooth muscle cells: implication in pulmonary hypertension.

Severe pulmonary hypertension is a debilitating disease with an alarmingly low 5-yr life expectancy. Hypoxia, one of the causes of pulmonary hypertension, elicits constriction and remodeling of the pulmonary arteries. We now know that pulmonary arterial remodeling is a consequence of hyperplasia and hypertrophy of pulmonary artery smooth muscle (PASM), endothelial, myofibroblast, and stem cells. However, our knowledge about the mechanisms that cause these cells to proliferate and hypertrophy in response to hypoxic stimuli is still incomplete, and, hence, the treatment for severe pulmonary arterial hypertension is inadequate. Here we demonstrate that the activity and expression of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway, are increased in hypoxic PASM cells and in lungs of chronic hypoxic rats. G6PD overexpression and -activation is stimulated by H2O2. Increased G6PD activity contributes to PASM cell proliferation by increasing Sp1 and hypoxia-inducible factor 1α (HIF-1α), which directs the cells to synthesize less contractile (myocardin and SM22α) and more proliferative (cyclin A and phospho-histone H3) proteins. G6PD inhibition with dehydroepiandrosterone increased myocardin expression in remodeled pulmonary arteries of moderate and severe pulmonary hypertensive rats. These observations suggest that altered glucose metabolism and G6PD overactivation play a key role in switching the PASM cells from the contractile to synthetic phenotype by increasing Sp1 and HIF-1α, which suppresses myocardin, a key cofactor that maintains smooth muscle cell in contractile state, and increasing hypoxia-induced PASM cell growth, and hence contribute to pulmonary arterial remodeling and pathogenesis of pulmonary hypertension.

Glucose-6-phosphate dehydrogenase plays a critical role in hypoxia-induced CD133+ progenitor cells self-renewal and stimulates their accumulation in the lungs of pulmonary hypertensive rats.

Although hypoxia is detrimental to most cell types, it aids survival of progenitor cells and is associated with diseases like cancer and pulmonary hypertension in humans. Therefore, understanding the underlying mechanisms that promote survival of progenitor cells in hypoxia and then developing novel therapies to stop their growth in hypoxia-associated human diseases is important. Here we demonstrate that the proliferation and growth of human CD133(+) progenitor cells, which contribute to tumorigenesis and the development of pulmonary hypertension, are increased when cultured under hypoxic conditions. Furthermore, glucose-6-phosphate dehydrogenase (G6PD) activity was increased threefold in hypoxic CD133(+) cells. The increased G6PD activity was required for CD133(+) cell proliferation, and their growth was arrested by G6PD inhibition or knockdown. G6PD activity upregulated expression of HIF1α, cyclin A, and phospho-histone H3, thereby promoting CD133(+) cell dedifferentiation and self-renewal and altering cell cycle regulation. When CD133(+) cells were cocultured across a porous membrane from pulmonary artery smooth muscle cells (PASMCs), G6PD-dependent H2O2 production and release by PASMCs recruited CD133(+) cells to the membrane, where they attached and expressed smooth muscle markers (α-actin and SM22α). Inhibition of G6PD reduced smooth muscle marker expression in CD133(+) cells under normoxia but not hypoxia. In vivo, CD133(+) cells colocalized with G6PD(+) cells in the perivascular region of lungs from rats with hypoxia-induced pulmonary hypertension. Finally, inhibition of G6PD by dehydroepiandrosterone in pulmonary arterial hypertensive rats nearly abolished CD133(+) cell accumulation around pulmonary arteries and the formation of occlusive lesions. These observations suggest G6PD plays a key role in increasing hypoxia-induced CD133(+) cell survival in hypertensive lungs that differentiate to smooth muscle cells and contribute to pulmonary arterial remodeling during development of pulmonary hypertension.