RESUMO
Transition metals like iron and copper, present inside the body system play a key role in the production of reactive oxygen radicals. These free radicals, causative agents of lipid peroxidation, not only damage proteins and DNA but also gradually changes the cellular membrane structure and ultimately leads to the loss of function and integrity. Uncontrolled lipid peroxidation results in various age related diseases, malignancy, infective diseases and injuries. Antioxidants and other phytochemical constituents present in the various plants are known to protect cells from such reactive oxygen species (ROS)-mediated damages. Here, we evaluated the effect of certain phytoconstituents present in the well-known medicinal plants on ROS scavenging using rat liver homogenate. The basal lipid peroxidation was found to be 0.1625±0.0095 ngMDA/min/mg protein, which got induced to 0.7938±0.0478 ngMDA/min/mg protein in the presence of Fe2+/ascorbate system. In this context, acteoside, berberine, catechin, 3´5-dihydroxyflavone7-o-ß-D-galacturonide-4-o-ß-D-glucopyranoside (a flavonoid glycoside from cumin), silibin and tetrahydrocurcumin decreased both basal and Fe2+/ascorbate induced lipid peroxidation as determined by thiobarbituric acid reaction. On the other hand, agnuside, andrographolide, picroside-I, negunoside, oleanolic acid, and glycerrihizin, showed enhancement in both basal and induced lipid peroxidation. Phytoconstituents which have decreased both basal and Fe2+/ascorbate induced lipid peroxidation may act as defensive against the deadly effects of ROS, causative agents of lipid peroxidation and other diseases either alone or in combination with diet/nutritional supplements.
RESUMO
Hypoxia-inducible factor 1alpha (HIF-1alpha), which transactivates a variety of hypoxia-induced genes, is rapidly degraded under nomoxia through the hydroxylation-ubiquitination-proteasome pathway. In this study, we addressed how HIF-1alpha is stabilized by proteasome inhibitors. The ubiquitin pool was rapidly reduced after proteasome inhibition, followed by the accumulation of non-ubiquitinated HIF-1alpha. The poly-ubiquitination of HIF-1alpha was resumed by restoration of free ubiquitin, which suggests that the HIF-1alpha stabilization under proteasome inhibition is attributed to depletion of the free ubiquitin pool. Ni2+ and Zn2+ also stabilized HIF-1alpha with depletion of the free ubiquitin pool and these effects of metal ions were attenuated by restoration of free ubiquitin. Ni2+ and Zn2+ may disturb the recycling of free ubiquitin, as MG132 does. Based on these results, the state of the ubiquitin pool seems to be another critical factor determining the cellular level of HIF-1alpha.