Co-operative effect of glutathione depletion and selenium induced oxidative stress on API and NFkB expression in testicular cells in vitro: insights to regulation of spermatogenesis

Previous studies have shown that transcription factors, API and NFkB exert important roles in the process by which selenium regulates spermatogenesis. Glutathione, an intracellular thiol, acts as a source of reducing power and aids in maintenance of the cellular redox status. The activities of selenium are closely related to the availability of glutathione. Presently, mouse testicular cells were cultured in the presence of BSO, a known glutathione depletor, to generate oxidative stress. Selenium (Se) was added as sodium selenite to these cells at concentrations of 0.5 µM and 1.5 µM. It was observed that at 1.5 µM, Se acted as a pro-oxidant and significantly decreased the redox ratio. RT PCR analysis revealed that cjun, cfos expression increased in testicular cells cultured with Se compared to control. However, the major outcome was that the combined effect of Se supplementation and GSH depletion resulted in reduced expression of cjun and cfos while p65 expression increased. This suggests that selenium affects both these transcription factors differently. Our study indicates that though low levels of oxidative stress generated by moderate doses of selenium augments the expression of cjun and cfos, a robust increase in the ROS generation caused by the dual effect high levels of selenium and glutathione depletion leads to decrease in the expression of these genes. The present work substantiates our in vivo experiments and indicates the detrimental effect of excess selenium supplementation on male fertility.

Hypercholesterolemia and tissue-specific differential mRNA expression of type-1 5'-iodothyronine deiodinase under different selenium status in rats

Type-1 5'-iodothyronine deiodinase (5'-DI) is responsible for conversion of T4 to T3. Selenium (Se) is an integral part of this enzyme. Keeping in view the strong association between atherosclerosis and hypothyroidism, the present study examined the behavior of 5'-DI in liver, aorta and thyroid during hypercholesterolemia following different Se status, i.e., Se deficiency (0.02ppm), adequate (0.2ppm) and excess dose (1ppm) in SD male rats. Animals were fed a control or high-cholesterol diet (2%) for 1 and 2 months. 5'-DI activity and mRNA expression was measured by RIA and RT-PCR respectively. In liver and aorta, 5'-DI expression significantly decreased with the Se-deficient and the high-cholesterol diet. The trend was opposite in thyroid, i.e., mRNA expression increased significantly during selenium deficiency and with a high-cholesterol feeding. But with 1ppm Se supplementation, the 5'-DI expression increased in all the three tissues. The present study indicates that hypercholesterolemia along with selenium deficiency is co-responsible for differential regulation of 5'-DI enzyme in thyroidal vs. extrathyroidal tissues. Distinct regulation of 5'-DI in the thyroid reflects the clinical importance of this selenoprotein during hypercholesterolemia as this enzyme is essential for T3 production, which further has a vital role in the maintenance of lipid metabolism.