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The oxidation resistance gene 1 (OXR1) prevents oxidative stress-induced cell death by an unknown pathway. Here, depletion of human OXR1 (hOXR1) sensitized several human cell lines to hydrogen peroxide-induced oxidative stress, reduced mtDNA integrity, and increased apoptosis. In contrast, depletion of hOXR1 in cells lacking mtDNA showed no significant change in ROS or viability, suggesting that OXR1 prevents intracellular hydrogen peroxide-induced increase in oxidative stress levels to avoid a vicious cycle of increased oxidative mtDNA damage and ROS formation. Furthermore, expression of p21 and the antioxidant genes GPX2 and HO-1 was reduced in hOXR1-depleted cells. In sum, these data reveal that human OXR1 upregulates the expression of antioxidant genes via the p21 signaling pathway to suppress hydrogen peroxide-induced oxidative stress and maintain mtDNA integrity.

The oxidized glutathione mimetic NOV-002, is a unique anti-tumor agent that not only has the ability to inhibit tumor cell proliferation, survival, and invasion, but in some settings can also ameliorate cytotoxic chemotherapy-induced hematopoietic and immune suppression. However, the mechanisms by which NOV-002 protects the hematopoietic and immune systems against the cytoxic effects of chemotherapy are not known. Therefore, in the present study we investigated the mechanisms of action of NOV-002 using a mouse model in which hematopoietic and immune suppression was induced by cyclophosphamide (CTX) treatment. We found that NOV-002 treatment in a clinically comparable dose regimen attenuated CTX-induced reduction in bone marrow hematopoietic stem and progenitor cells (HSPCs), and reversed the immunosuppressive activity of myeloid-derived suppressor cells (MDSCs), which led to a significant improvement in hematopoietic and immune functions. These effects of NOV-002 may be attributable to its ability to modulate cellular redox. This suggestion is supported by the finding that NOV-002 treatment upregulated the expression of superoxide dismutase 3 and glutathione peroxidase 2 in HSPCs; inhibited CTX-induced increases in reactive oxygen species production in HSPCs and MDSCs; and attenuated CTX-induced reduction of the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) in splenocytes. These findings provide a better understanding of the mechanisms whereby NOV-002 modulates chemotherapy-induced myelosuppression and immune dysfunction, and a stronger rationale for clinical utilization of NOV-002 has the potential to be utilized to reduce chemotherapy-induced hematopoietic and immune suppression.

Localization of glutathione peroxidase 2 (GPx2), the gastrointestinal form of GPx's, in the intestinal crypt epithelium points to a specific but so-far unknown function of this particular GPx. Therefore, the consequences of a GPx2 knockout were tested in mice fed a selenium-restricted, Se-adequate, or Se-supplemented diet. An unexpected increase in total GPx activity was found throughout the intestine in selenium-fed GPx2 knockout (KO) animals. Immunohistochemistry revealed a strong increase in GPx1 in the colon and ileum, especially in crypt bases where typically GPx2 is localized. GPx1 mRNA was not enhanced in GPx2 KO, indicating that up-regulation most probably occurs at the translational level. Loss of GPx2 was accompanied by an increase in apoptotic cells at colonic crypt bases, an area essential for the self-renewal of the intestinal epithelium, particularly under selenium restriction. Additionally, mitotic cells increased in the middle parts of the crypts, indicating an extension of the proliferative area. These findings corroborate a role for GPx2 in regulating mucosal homeostasis. In GPx2 KO mice, an increase in GPx1 can only partially compensate for GPx2, even under selenium supplementation, indicating that GPx2 is the major antiapoptotic GPx in the colon. These data explain why spontaneous ileocolitis becomes manifested only if both Gpx2 and Gpx1 are deleted.

In contrast to Escherichia coli and yeast thioredoxin reductases, the human placental enzyme contains an additional redox center consisting of a cysteine-selenocysteine pair that precedes the C-terminal glycine residue. This reactive selenocysteine-containing center imbues the enzyme with its unusually wide substrate specificity. For expression of the human gene in E. coli, the sequence corresponding to the SECIS element required for selenocysteine insertion in E. coli formate dehydrogenase H was inserted downstream of the TGA codon in the human thioredoxin reductase gene. Omission of this SECIS element from another construct resulted in termination at UGA. Change of the TGA codon to TGT gave a mutant enzyme form in which selenocysteine was replaced with cysteine. The three gene products were purified using a standard isolation protocol. Binding properties of the three proteins to the affinity resins used for purification and to NADPH were similar. The three proteins occurred as dimers in the native state and exhibited characteristic thiolate-flavin charge transfer spectra upon reduction. With DTNB as substrate, compared to native rat liver thioredoxin reductase, catalytic activities were 16% for the recombinant wild type enzyme, about 5% for the cysteine mutant enzyme, and negligible for the truncated enzyme form.

Dietary factors have been identified as important modulators of the risk of developing cancer. The antioxidant defense could be involved in this process. The maternal nutrition epigenetically reprograms gene expression in the mammary gland. Evaluate the effects of consumption of grape juice and/or high fat diet by pregnant and nursing dams on antioxidant profile during the pregnancy and on offspring’s mammary cancer risk. Methods: During the pregnancy, 40 pregnancy female Wistar rats received grape juice or water and control diet or high fat diet. We evaluated the weight gain during the pregnancy and lactating, three times a week. After the lactating, the female offspring were euthanized evaluated on 50th post natal day. The 4th-5th mammary gland was removed and all the analyses were performed in this tissue. SOD2 level was performed by Western Blotting. Gpx1, Gpx2 and Sod2 expression gene were performed by PCR. The epigenetic parameters, Dnmt1, Dnmt3a and Dnmt3b expression gene were performed by PCR assay. Statistically analyses were obtained by ANOVA two ways. We observed that the high fat diet induced an important reduction on Gpx1 expression (Control diet= 0.765± 0.121; High Fat Diet=1.197±0.121). On the Gpx2 expression, we observed that the grape juice increase this enzyme (Water= 5.77± 0.49; Grape juice=7.70 ± 0.51). SOD2 protein level and Sod1 expression gene didn´t change with the diet or the beverage during the pregnancy. High fat diet reduce the DNMT1 and DNMT3b expression gene, and this effect could be reduced the transcription Gpx1 expression. High fat diet reduced the transcription gene, this diet reduced the Dnmt1 (Control diet= 0.516±0.05; High Fat Diet=0.325±0.05) and Dnmt3b expression (Control diet= 0.604±0.05; High Fat Diet=0.325±0.05). Conclusion: The high fat diet increase the GPx1 expression probably by the DNA methylation reduction. However the Gpx2 expression was increased on the grape juice group. We can concluded that the pregnant diet is an important factor to modified the antioxidant defense by epigenetic way, by DNA methylation. This effect could be influence on the breast cancer risk.