Expression and Chromosomal Mapping of Mouse Gpx2 Gene Encoding the Gastrointestinal Form of Glutathione Peroxidase, GPX-GI

GPX-GI is a cytosolic tetrameric Se-dependent glutathione peroxidase, similar in properties to GPX-1. Unlike the almost ubiquitous GPX-1, GPX-GI is mainly expressed in the epithelium of gastrointestinal tract. GPX-GI contributes to at least fifty percent of GPX activity in rodent small intestmal epithelium. The total GPX activity consists of at least 70% of selenium-dependent GPX activity in this compartment.By analyzing a panel of mouse mterspecies DNA from the Jackson Laboratory's backcross resource,we mapped Gpx2 gene to mouse chromosome 12 between D12Mit4 and D12Mit5, near the Ccs1 locus which contains a colon cancer susceptibility gene. A pseudogene, Gpx2-ps is mapped to mouse chromosome 7.Comparison of Gpx2 gene expression in three pairs of C57BL/6Ha and ICR/Ha mice which are respectively resistant and sensitive to dimethylhydrazine-induced colon cancer, we found a higher Gpx2 mRNA level in C57BL/6Ha colon than ICR/Ha colon. Interestingly, a lower level of GPX activity is found in the resistant strain of mice. Because GPX-1 has three times higher specific activity than GPX GI, our data suggest that the decreased GPX activity may result from a higher level of Gpx2 gene expression in those cells co-express GPx1 gene

Effect of selenium on human myocardial glutathione peroxidase gene expression

To examine the role of selenium (Se) in the expression and activity of selenium-dependent cellular glutathione peroxidase (GPX-1) Methods 46 patients with atrial septal defect or ventricular septal defect were separated into two groups, a control group (23 cases) and a Se supplementation group (23 cases) The Se supplementation group received 400*!μg selenium per day for 7 days before surgery We used biochemical techniques, atomic absorption, RT-PCR and cDNA sequence testing methods to evaluate and compare the changes during ischemia/reperfussion (I/R) in myocardial melondialdehyde (MDA) level, GPX activity and gene expression level, GPX cDNA nucleotide sequence, selenium and calcium and magnesium concentration Results Before ischemia, taking selenium for 7 days did not change the selenium concentration in either plasma or blood cells in either group The GPX mean activity level in the selenium group was slightly lower than that in the control group, and the MDA level was equal in both After 30 minutes of reperfusion, the Se level in plasma and blood cells remained constant, while the myocardial Se concentration and GPX gene expression in the Se group increased significantly The MDA level in the Se group reduced 4 2%, compared to an 8 2% rise in the control group The mean level of GPX activity in the Se group was slightly lower than that in the control group Both pre- and post-myocardial reperfusion, the Se group had a higher rate of myocardial GPX gene expression, and the nucleotide sequence was normal These results indicate that supplementing Se is not likely to enhance myocardial GPX activity, but it could increase the GPX gene expression level, and thereby enhance the Se patients' myocardial antioxidant level during I/R, allowing free radicals to be scavenged as soon as they are generated Conclusion Se supplementation could increase myocardial selenium content and improve GPX gene expression during I/R, and in this way defend against free radical peroxide damage to the myocardium