Redox imbalance and mutagenesis in spleens of mice harboring a hypomorphic allele of Gpdx(a) encoding glucose 6-phosphate dehydrogenase

Mice harboring the activity-attenuated Gpdx(a-m2Neu) allele and also harboring a chromosomally integrated lacZ reporter gene to study mutagenesis (pUR288) were used to demonstrate that moderate glucose 6-phosphate dehydrogenase (G6PD) deficiency causes elevated mutagenesis and endogenous oxidative stress in the spleen. G6PD-deficient spleens with a residual enzyme activity of 22% exhibited a dramatic shift in the mutational pattern of lacZ (4.6-fold increase in the prevalence of recombination mutations of lacZ) together with a 1.8-fold increase in mutant frequencies in lacZ. A concomitant 3-fold reduction in catalase activity (dependent upon NADPH) indicated that the in vivo supply of G6PD-generated NADPH was insufficient. An additional 3-fold increase in oxidized glutathione suggested that redox control was disturbed in G6PD-deficient spleens. These findings indicate that G6PD is required for limiting oxidative mutagenesis in the mouse spleen. Gpdx(a-m2Neu) is the first hypomorphic allele of a mouse housekeeping gene associated with elevated somatic mutagenesis in vivo.     

Elevated presence of retrotransposons at sites of DNA double strand break repair in mouse models of metabolic oxidative stress and MYC-induced lymphoma

The chromosomally integrated shuttle vector pUR288 contains a lacZ reporter gene to study mutagenesis in vivo. We used pUR288 to compare patterns of genomic instability in two mouse models, lymphoma resulting from deregulated c-MYC expression (lambda-MYC), and endogenous oxidative stress caused by partial glucose 6-phosphate dehydrogenase (G6PD) deficiency. We found previously that spontaneous mutations in both models were predominantly genomic rearrangements of lacZ with mouse sequences, while most mutations in controls were point mutations. Here, we characterized the fine structure of 68 lacZ/mouse rearrangements from lambda-MYC lymphomas and G6PD deficient mice by sequencing breakpoint junctions and determining the origin of recombining mouse sequences. Fifty-eight of 68 (85%) recombination partners were identified. The structure of rearrangements from both lambda-MYC and G6PD deficient mice were remarkably alike. Intra-chromosomal deletions and inversions were common, occurring in 41% (24/58) of rearrangements, while 59% (34/58) were random translocations between lacZ and other chromosomes. Signatures of double strand break repair by nonhomologous end joining were observed at breakpoint junctions; 37% (25/68) contained 1-4 bp microhomologies, while the remaining breakpoints had no sequence homology. Long interspersed nuclear element-1 (LINE-1 or L1) retrotransposons, which constitute approximately 10% of the mouse genome, were present at 25% (17/68) of breakpoints, suggesting their participation in rearrangements. The similarity in the structure of rearrangements is consistent with the hypothesis that genetic rearrangements in lambda-MYC lymphomas and G6PD deficient mice result from the same mechanism, mutagenic repair of DNA double strand breaks arising from oxidative damage.     

Inducible mutagenesis in TEPC 2372, a mouse plasmacytoma cell line that harbors the transgenic shuttle vector lambdaLIZ

The plasmacytoma cell line, TEPC 2372, was derived from a malignant plasma cell tumor that developed in the peritoneal cavity of a BALB/c mouse that harbored the transgenic shuttle vector for the assessment of mutagenesis in vivo, lambdaLIZ. TEPC 2372 was found to display the typical features of a BALB/c plasmacytoma. It consisted of pleomorphic plasma cells that secreted a monoclonal immunoglobulin (IgG2b/lambda), was initially dependent on the presence of IL-6 to grow in cell culture, contained a hyperdiploid chromosome complement with a tendency to undergo tetraploidization, and harbored a constitutively active c-myc gene by virtue of a T(6;15) chromosomal translocation. TEPC 2372 was further characterized by the ability to respond to in vitro exposure with 4-NQO (4-nitroquinoline-1-oxide), an oxidative model mutagen, with a vigorous dose-dependent increase in mutagenesis that peaked at a 7.85-fold elevation of mutant rates in lambdaLIZ when compared to background mutant rates in untreated controls. Cotreatment with 4-NQO and BSO (buthionine sulfoximine), a glutathione-depleting compound that causes endogenous oxidative stress, resulted in a 9.03-fold increase in the mutant frequency in lambdaLIZ. These results demonstrated that TEPC 2372, the malignant plasma cell counterpart of the lambdaLIZ-based in vivo mutagenesis assay, may be useful as an in vitro reference point for the further elucidation of oxidative mutagenesis in lymphoid tissues.     

Neuroprotection by glucose-6-phosphate dehydrogenase and the pentose phosphate pathway

Glucose-6-phosphate dehydrogenase (G6PD), the rate limiting enzyme that channels glucose catabolism from glycolysis into the pentose phosphate pathway (PPP), is vital for the production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) in cells. NADPH is in turn a substrate for glutathione reductase, which reduces oxidized glutathione disulfide to sulfhydryl glutathione. Best known for inherited deficiencies underlying acute hemolytic anemia due to elevated oxidative stress by food or medication, G6PD, and PPP activation have been associated with neuroprotection. Recent works have now provided more definitive evidence for G6PD's protective role in ischemic brain injury and strengthened its links to neurodegeneration. In Drosophila models, improved proteostasis and lifespan extension result from an increased PPP flux due to G6PD induction, which is phenocopied by transgenic overexpression of G6PD in neurons. Moderate transgenic expression of G6PD was also shown to improve healthspan in mouse. Here, the deciphered and implicated roles of G6PD and PPP in protection against brain injury, neurodegenerative diseases, and in healthspan/lifespan extensions are discussed together with an important caveat, namely NADPH oxidase (NOX) activity and the oxidative stress generated by the latter. Activation of G6PD with selective inhibition of NOX activity could be a viable neuroprotective strategy for brain injury, disease, and aging.     

Bcl-2 reduces mutant rates in a transgenic lacZ reporter gene in mouse pre-B lymphocytes

To assess mutagenesis during early B-lymphocyte development in vitro, progenitor B cells (pre-B cells) were obtained from fetal livers of BALB/c mice and DBA/2N mice that harbored the transgenic shuttle vector, pUR288, with a lacZ reporter gene for the determination of mutant frequencies (MFs). Differentiation-arrested pre-B cells demonstrated a marked dose-dependent increase in lacZ mutant levels after exposure to gamma-irradiation with a peak MF of 250 x 10(-5) at 2.5 Gy. Without genotoxic treatment, pre-B cells undergoing spontaneous differentiation into surface IgM expressing immature B cells exhibited lacZ mutant levels of up to 95 x 10(-5). The mutational pattern was dominated in both experiments by illegitimate recombination mutations of lacZ, not point mutations. Likewise, in both experiments, the enforced expression of Bcl-2 resulted in a striking reduction of lacZ mutations. These findings indicated that mouse pre-B cells are prone to accumulate induced and self-inflicted mutations, particularly recombinations. Additionally, our studies revealed a heretofore unknown role of Bcl-2 in inhibiting mutagenesis during early B-cell development in mice.     

Regulation of glucose 6-phosphate dehydrogenase expression in CHO-human fibroblast somatic cell hybrids

Human--hamster somatic cell hybrids have been obtained by fusion of a CHO line (NA31) doubly deficient in hypoxanthine guanine phosphoribosyltransferase and glucose 6-phosphate dehydrogenase (G6PD) with normal G6PD(+) human fibroblasts. Analysis of NA31 extracts has revealed that, although G6PD activity is nearly absent, significant activity can be detected with 2-deoxyglucose 6-phosphate as substrate, so that the mutant and normal forms of the enzyme can both be easily detected. The cell hybrids obtained express human G6PD. The human G6PD subunits are distributed in homodimeric molecules as well as in human--hamster heterodimeric molecules. However, whereas the amount of hamster G6PD subunits present in the hybrid is similar to that in the hamster parental cells, the amount of human G6PD subunits is decreased by 3- to 10-fold when compared to the human parental cell. These results indicate that either the expression of the G6PD gene or the stability of the gene product is altered in the hybrid. By mutagenesis and selection in diamide (a substance that oxidizes intracellular glutathione), we have isolated a clone with a 3- to 5-fold increase in human G6PD activity. This derivative may have an increased rate of expression of the human G6PD structural gene.     

Glucose 6-phosphate dehydrogenase deficiency enhances germ cell apoptosis and causes defective embryogenesis in Caenorhabditis elegans

Glucose 6-phosphate dehydrogenase (G6PD) deficiency, known as favism, is classically manifested by hemolytic anemia in human. More recently, it has been shown that mild G6PD deficiency moderately affects cardiac function, whereas severe G6PD deficiency leads to embryonic lethality in mice. How G6PD deficiency affects organisms has not been fully elucidated due to the lack of a suitable animal model. In this study, G6PD-deficient Caenorhabditis elegans was established by RNA interference (RNAi) knockdown to delineate the role of G6PD in animal physiology. Upon G6PD RNAi knockdown, G6PD activity was significantly hampered in C. elegans in parallel with increased oxidative stress and DNA oxidative damage. Phenotypically, G6PD-knockdown enhanced germ cell apoptosis (2-fold increase), reduced egg production (65% of mock), and hatching (10% of mock). To determine whether oxidative stress is associated with G6PD knockdown-induced reproduction defects, C. elegans was challenged with a short-term hydrogen peroxide (H₂O₂). The early phase egg production of both mock and G6PD-knockdown C. elegans were significantly affected by H₂O₂. However, H₂O₂-induced germ cell apoptosis was more dramatic in mock than that in G6PD-deficient C. elegans. To investigate the signaling pathways involved in defective oogenesis and embryogenesis caused by G6PD knockdown, mutants of p53 and mitogen-activated protein kinase (MAPK) pathways were examined. Despite the upregulation of CEP-1 (p53), cep-1 mutation did not affect egg production and hatching in G6PD-deficient C. elegans. Neither pmk-1 nor mek-1 mutation significantly affected egg production, whereas sek-1 mutation further decreased egg production in G6PD-deficient C. elegans. Intriguingly, loss of function of sek-1 or mek-1 dramatically rescued defective hatching (8.3- and 9.6-fold increase, respectively) induced by G6PD knockdown. Taken together, these findings show that G6PD knockdown reduces egg production and hatching in C. elegans, which are possibly associated with enhanced oxidative stress and altered MAPK pathways, respectively.     

Molecular identification of mutations in G6PD gene in patients with favism in Iran

Glucose 6-phosphate dehydrogenase is a highly polymorphic enzyme encoded by a human X-linked gene (Xq2.8). This enzyme catalyses the first step of pentose phosphate pathway, that converts glucose 6-phosphate to 6-phosphogluconate with production of NADPH2. G6PD deficiency is the most common human metabolic inborn error affecting more than 400 million people world wide. The main clinical manifestations are acute hemolytic anemia and jaundice, triggered by infection or ingestion of Fava beans or oxidative drugs. A predominant variant of G6PD named Mediterranean is often associated with favism. This has been evident in several countries including Northern coastal provinces of Iran. Other current variants are Chatham and Cosenza. Molecular identification of the most prevalent mutations in G6PD gene was carried out in 71 males and females with G6PD deficiency. They were from Iranian Northern province of Golestan. DNA was extracted from blood samples and analyzed for known G6PD mutation by PCR and restriction fragment length polymorphisms (RFLP) technique. Adapting this method, revealed that Mediterranean mutation at nt 563(C-->T) is predominant in the area (69%) and 26.7% of patients have Chatham mutation at nt 1003(G-->A). Findings indicate a higher prevalence of these mutations, in Golestan compared to Mazandaran (66.2% Mediterranean and 19% Chatham mutation) and Gilan (86.4% Mediterranean and 9.71% Chatham mutations). Cosenza mutation at nt 1376(G-->C), by PCR-RFLP technique was not found among other 3 samples (4.3%). The similarity of these results with mutations in Italy indicates probable existence of a common ancestral origin in the observed populations.     

Cytosolic NADP(+)-dependent isocitrate dehydrogenase status modulates oxidative damage to cells

NADPH is an important cofactor in many biosynthesis pathways and the regeneration of reduced glutathione, critically important in cellular defense against oxidative damage. It is mainly produced by glucose 6-phosphate dehydrogenase (G6PD), malic enzyme, and the cytosolic form of NADP(+)-dependent isocitrate dehydrogenase (IDPc). Little information is available about the role of IDPc in antioxidant defense. In this study we investigated the role of IDPc against cytotoxicity induced by oxidative stress by comparing the relative degree of cellular responses in three different NIH3T3 cells with stable transfection with the cDNA for mouse IDPc in sense and antisense orientations, where IDPc activities were 3-4-fold higher and 35% lower, respectively, than that in the parental cells carrying the vector alone. Although the activities of other antioxidant enzymes, such as superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and G6PD, were comparable in all transformed cells, the ratio of GSSG to total glutathione was significantly higher in the cells expressing the lower level of IDPc. This finding indicates that IDPc is essential for the efficient glutathione recycling. Upon transient exposure to increasing concentrations of H(2)O(2) or menadione, an intracellular source of free radicals and reactive oxygen species, the cells with low levels of IDPc became more sensitive to oxidative damage by H(2)O(2) or menadione. Lipid peroxidation, oxidative DNA damage, and intracellular peroxide generation were higher in the cell-line expressing the lower level of IDPc. However, the cells with the highly over-expressed IDPc exhibited enhanced resistance against oxidative stress, compared to the control cells. This study provides direct evidence correlating the activities of IDPc and the maintenance of the cellular redox state, suggesting that IDPc plays an important role in cellular defense against oxidative stress.     

An embryoprotective role for glucose-6-phosphate dehydrogenase in developmental oxidative stress and chemical teratogenesis.

The primary recognized health risk from common deficiencies in glucose-6-phosphate dehydrogenase (G6PD), a cytoprotective enzyme for oxidative stress, is red blood cell hemolysis. Here we show that litters from untreated pregnant mutant mice with a hereditary G6PD deficiency had increased prenatal (fetal resorptions) and postnatal death. When treated with the anticonvulsant drug phenytoin, a human teratogen that is commonly used in pregnant women and causes embryonic oxidative stress, G6PD-deficient dams had higher embryonic DNA oxidation and more fetal death and birth defects. The reported G6PD gene mutation was confirmed and used to genotype fetal resorptions, which were primarily G6PD deficient. This is the first evidence that G6PD is a developmentally critical cytoprotective enzyme for both endogenous and xenobiotic-initiated embryopathic oxidative stress and DNA damage. G6PD deficiencies accordingly may have a broader biological relevance as important determinants of infertility, in utero and postnatal death, and teratogenesis.     

Knockdown of glucose-6-phosphate dehydrogenase (G6PD) following cerebral ischemic reperfusion: the pros and cons

NADPH derived from glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway, has been implicated not only to promote reduced glutathione (GSH) but also enhance oxidative stress in specific cellular conditions. In this study, the effects of G6PD antisense oligodeoxynucleotides (AS-ODNs) was examined on the CA1 pyramidal neurons following transient cerebral ischemia. Specifically knockdown of G6PD protein expression in hippocampus CA1 subregion at early reperfusion period (1-24 h) with a strategy to pre-treated G6PD AS-ODNs significantly reduced G6PD activity and NADPH level, an effect correlated with attenuation of NADPH oxidase activation and superoxide anion production. Concomitantly, pre-treatment of G6PD AS-ODNs markedly reduced oxidative DNA damage and the delayed neuronal cell death in rat hippocampal CA1 region induced by global cerebral ischemia. By contrast, knockdown of G6PD protein at late reperfusion period (48-96 h) increased oxidative DNA damage and exacerbated the ischemia-induced neuronal cell death in hippocampal CA1 region, an effect associated with reduced NADPH level and GSH/GSSG ratio. These findings indicate that G6PD not only plays a role in oxidative neuronal damage but also a neuroprotective role during different ischemic reperfusion period. Therefore, G6PD mediated oxidative response and redox regulation in the hippocampal CA1 act as the two sides of the same coin and may represent two potential applications of G6PD during different stage of cerebral ischemic reperfusion.     

Distribution of glucose-6-phosphate dehydrogenase mutations in Southeast Asia

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a heterogeneous enzyme abnormality with high frequency in tropical areas. We performed population screening and molecular studies of G6PD variants to clarify their distribution and features in Southeast Asia. A total of 4317 participants (2019 males, 2298 females) from 16 ethnic groups in Myanmar, Lao in Laos, and Amboinese in Indonesia were screened with a single-step screening method. The prevalence of G6PD-deficient males ranged from 0% (the Akha) to 10.8% (the Shan). These G6PD-deficient individuals and 12 G6PD-deficient patients who had been diagnosed at hospitals in Indonesia and Malaysia were subjected to molecular analysis by a combination of polymerase-chain-reaction-based single-strand conformation polymorphism analysis and direct sequencing. Ten different missense mutations were identified in 63 G6PD-deficient individuals (50 hemizygotes, 11 heterozygotes, and 2 homozygotes) from 14 ethnic groups. One missense mutation (1291 G-->A) found in an Indonesian Chinese, viz., G6PD Surabaya, was previously unknown. The 487 G-->A (G6PD Mahidol) mutation was widely seen in Myanmar, 383 T-->C (G6PD Vanua Lava) was specifically found among Amboinese, 871 G-->A (G6PD Viangchan) was observed mainly in Lao, and 592 C-->T (G6PD Coimbra) was found in Malaysian aborigines (Orang Asli). The other five mutations, 95 A-->G (G6PD Gaohe), 1003 G-->A (G6PD Chatham), 1360 C-->T (G6PD Union), 1376 G-->T (G6PD Canton), and 1388 G-->A (G6PD Kaiping) were identified mostly in accordance with distributions reported previously.     

Prevalence and Molecular Characterization of Glucose-6-Phosphate Dehydrogenase Deficiency at the China-Myanmar Border

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked hereditary disease that predisposes red blood cells to oxidative damage. G6PD deficiency is particularly prevalent in historically malaria-endemic areas. Use of primaquine for malaria treatment may result in severe hemolysis in G6PD deficient patients. In this study, we systematically evaluated the prevalence of G6PD deficiency in the Kachin (Jingpo) ethnic group along the China-Myanmar border and determined the underlying G6PD genotypes. We surveyed G6PD deficiency in 1770 adult individuals (671 males and 1099 females) of the Kachin ethnicity using a G6PD fluorescent spot test. The overall prevalence of G6PD deficiency in the study population was 29.6% (523/1770), among which 27.9% and 30.6% were males and females, respectively. From these G6PD deficient samples, 198 unrelated individuals (147 females and 51 males) were selected for genotyping at 11 known G6PD single nucleotide polymorphisms (SNPs) in Southeast Asia (ten in exons and one in intron 11) using a multiplex SNaPshot assay. Mutations with known association to a deficient phenotype were detected in 43.9% (87/198) of cases, intronic and synonymous mutations were detected alone in 34.8% (69/198) cases and no mutation were found in 21.2% (42/198) cases. Five non-synonymous mutations, Mahidol 487G>A, Kaiping 1388G>A, Canton 1376G>T, Chinese 4 392G>T, and Viangchan 871G>A were detected. Of the 87 cases with known deficient mutations, the Mahidol variant was the most common (89.7%; 78/87), followed by the Kaiping (8.0%; 7/87) and the Viangchan (2.2%; 2/87) variants. The Canton and Chinese 4 variants were found in 1.1% of these 87 cases. Among them, two females carried the Mahidol/Viangchan and Mahidol/Kaiping double mutations, respectively. Interestingly, the silent SNPs 1311C>T and IVS11nt93T>C both occurred in the same 95 subjects with frequencies at 56.4% and 23.5% in tested females and males, respectively (P<0.05). It is noteworthy that 24 subjects carrying the Mahidol mutation and two carrying the Kaiping mutation also carried the 1311C>T/IVS11nt93T>C SNPs. Further studies are needed to determine the enzyme levels of the G6PD deficient people and presence of additional G6PD mutations in the study population.     

Glucose 6-phosphate dehydrogenase deficiency: a protection against malaria and a risk for hemolytic accidents

Glucose 6-phosphate dehydrogenase (G6PD) catalyses the first step of the pentose phosphate pathway, which in the RBC leads to the formation of NADPH, essential to prevent the cell from an oxidative stress. Worldwide, more than 400 million people (90% being males) are affected by G6PD deficiency, in regions that are, or have been, endemic for malaria and in populations originating from these regions. RBCs with low G6PD activity offer a hostile environment to parasite growth and thus an advantage to G6PD deficiency carriers. The counterpart of this protective effect is an increased susceptibility to oxidants such as some foods (fava beans), drugs (anti-malarial or sulphonamides), or various chemicals. In the case of G6PD deficiency, the hypothesis of a convergent evolution between parasite, protecting mutation, and cultural traditions (food, skin painting...) has been proposed. Near to 150 different G6PD variants have been described, which are classified into four types, according to their clinical effects. Several variants, such as the G6PD A- or the Mediterranean variant, reach the polymorphism level in endemic regions. The recent determination of the three-dimensional structure of this enzyme allows one to explain now the mechanisms of the disorders in terms of structure-function relationship.     

High somatic mutation frequencies in a LacZ transgene integrated on the mouse X-chromosome

To study spontaneous and induced mutagenesis in vivo we recently constructed a series of transgenic mice harboring different numbers of bacteriophage lambda shuttle vectors, provided with a LacZ mutational target gene, integrated in their genome. The transgenic mice enabled analysis of spontaneous and induced mutation frequencies in postmitotic tissues like liver and brain. The obtained data indicated spontaneous mutation frequencies in the order of ⁻⁵ - 10⁻⁶. Here we report a 25–100 times higher spontaneous mutation frequency in liver and brain DNA of mice from strain 35.5, with the lambda-gt10LacZ concatemer integrated on the X-chromosome. These results indicate the presence of a mutational ‘hot spot’ in the mammalian somatic genome in vivo.     

Augmented resistance to oxidative stress in fatty rat livers induced by a short-term sucrose-rich diet

Hepatic steatosis and the accompanying oxidative stress have been associated with a variety of liver diseases. It is not known if fat accumulation per se plays a direct role in the oxidative stress of the organ. This study tested if steatosis induced by a short-term carbohydrate-rich diet results in an increased hepatic sensitivity to oxidative stress. Antioxidant status was determined in a liver perfusion system and in isolated parenchymal, endothelial and Kupffer cells from rats kept on sucrose-rich diet or on regular diet for 48 h. t-Butyl hydroperoxide addition (2 mM) to the perfusion fluid resulted in a release of alanine aminotransferase (ALT) in livers from controls, whereas no ALT release was observed in fatty livers. After t-butyl hydroperoxide addition, oxidized glutathione release was 40% less in fatty than in control livers, whereas reduced glutathione (GSH) release was not different. Sinusoidal oxidant stress was mimicked by the addition of lipopolysaccharide (LPS) from Escherichia coli (10 microg/ml) followed by the addition of opsonized zymosan (8 mg/ml) to the perfusion medium. LPS plus zymosan treatments resulted in the release of ALT in control but not in fatty livers. At the end of perfusion, liver glutathione content was 3-fold elevated, and the tissue content of lipid peroxidation products was approx. 40% less in fatty livers compared to controls. GSH content was doubled and glucose-6-phosphate dehydrogenase (G6PD) expression was elevated by 3- and 10-fold in sinusoidal endothelial and parenchymal cells form fatty livers compared to cells from control animals. Following H(2)O(2) administration in vitro (0.2-1 mM), GSH remained elevated in endothelial and parenchymal cells from fatty livers compared to cells from controls. In contrast, G6PD activity and GSH content were similar in Kupffer cells isolated from fatty or control livers. The study shows that hepatic fat accumulation caused by a short-term sucrose diet is not accompanied by elevated hepatic lipid peroxidation, and an elevated hepatic antioxidant activity can be manifested in the presence of prominent steatosis. The diet-induced increase in G6PD expression and, thus, the efficient maintenance of reduced glutathione in endothelial and parenchymal cells are a supportive mechanism in the observed hepatic resistance against intracellular or sinusoidal oxidative stress.     

Human alpha B-crystallin mutation causes oxido-reductive stress and protein aggregation cardiomyopathy in mice

The autosomal dominant mutation in the human alphaB-crystallin gene inducing a R120G amino acid exchange causes a multisystem, protein aggregation disease including cardiomyopathy. The pathogenesis of cardiomyopathy in this mutant (hR120GCryAB) is poorly understood. Here, we show that transgenic mice overexpressing cardiac-specific hR120GCryAB recapitulate the cardiomyopathy in humans and find that the mice are under reductive stress. The myopathic hearts show an increased recycling of oxidized glutathione (GSSG) to reduced glutathione (GSH), which is due to the augmented expression and enzymatic activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase, and glutathione peroxidase. The intercross of hR120GCryAB cardiomyopathic animals with mice with reduced G6PD levels rescues the progeny from cardiac hypertrophy and protein aggregation. These findings demonstrate that dysregulation of G6PD activity is necessary and sufficient for maladaptive reductive stress and suggest a novel therapeutic target for abrogating R120GCryAB cardiomyopathy and heart failure in humans.     

Frequency of glutathione reductase, pyruvate kinase and glucose-6-phosphate dehydrogenase deficiency in a Spanish population.

The frequencies of deficiencies of glutathione reductase (GSSG-R), pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G6PD) in a Spanish sample are presented. A total of 2,129 individuals was analyzed for GSSG-R, 1,636 for PK, and 1,066 (629 males and 437 females) for G6PD. Beutler's method was used. The frequencies obtained for these deficiencies were: GSSG-R, 0.09%; PK, 0.24%; and G6PD, 0.79%. The results are discussed.     

Evaluation of DNA damage in leukocytes of G6PD-deficient Iranian newborns (Mediterranean variant) using comet assay

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited disease, which causes neonatal hemolytic anemia and jaundice. Recent studies of our group showed that the Mediterranean variant of this enzyme (Gd-Md) is the predominant G6PD in Iranian male infants suffering from jaundice; this variant is classified as severe G6PD deficiency. Considering the importance of G6PD reaction and its products NADPH and glutathione (GSH) against oxidative stress, we hypothesized the failure of detoxification of H(2)O(2) in G6PD-deficient white blood cells that could probably induce primary DNA damage. For the evaluation of DNA damage, we analyzed mononuclear leukocytes of 36 males suffering from the Gd-Md deficiency using alkaline single cell gel electrophoresis (SCGE) or comet assay. The level of DNA damage was compared with the level of basal DNA damage in control group represented by healthy male infant donors (of the same age group). Visual scoring was used for the evaluation of DNA damages. The results showed that the mean level of the DNA strand breakage in mononuclear leukocytes of 36 male G6PD-deficient (Gd-Md) infants was significantly higher (P < 0.001) than those observed in the normal lymphocytes. In conclusion, this investigation indicates that the mononuclear leukocytes of the Gd-Md samples may be exposed to DNA damage due to oxidative stress. This is the first report using comet assay for evaluation of DNA damage in severe G6PD deficiency samples.