Characteristics of the protective action of alpha-Tocopherol in vascular hypoxia

Effects of antioxidant vitamins on newborn and placental traits in gestations at high altitude: comparative study in high and low altitude native sheep

The present study evaluated the hypothesis that the effects of hypoxia on sheep pregnancies at high altitude (HA) are mediated by oxidative stress and that antioxidant vitamins may prevent these effects. Both HA native and newcomer ewes were maintained at an altitude of 3,589 m during mating and pregnancy. Control low altitude (LA) native ewes were maintained at sea level. Half of each group received daily oral supplements of vitamins C (500 mg) and E (350 IU) during mating and gestation. Near term, maternal plasma vitamin levels and oxidative stress biomarkers were measured. At delivery, lambs were weighed and measured, and placentas were recovered for macroscopic and microscopic evaluation. Vitamin concentrations in supplemented ewes were two- or threefold greater than in non-supplemented ewes. Plasma carbonyls and malondialdehyde in non-supplemented ewes were consistent with a state of oxidative stress, which was prevented by vitamin supplementation. Vitamin supplementation increased lamb birthweight and cotyledon number in both HA native and newcomer ewes, although placental weight and cotyledon surface were diminished. Placentas from vitamin-supplemented HA ewes were similar to those from ewes at sea level, making these placental traits (weight, number and diameter of cotyledons) similar to those from ewes at sea level. Vitamin supplementation had no effect on LA pregnancies. In conclusion, supplementation with vitamins C and E during pregnancy at HA prevents oxidative stress, improving pregnancy outcomes.

Protective effects of sesamin and sesamolin on hypoxic neuronal and PC12 cells

Reactive oxygen species (ROS) are important mediators of a variety of pathological processes, including inflammation and ischemic injury. The neuroprotective effects of sesame antioxidants, sesamin and sesamolin, against hypoxia or H2O2-induced cell injury were evaluated by cell viability or lactate dehydrogenase (LDH) activity. Sesamin and sesamolin reduced LDH release of PC12 cells under hypoxia or H2O2-stress in a dose-dependent manner. Dichlorofluorescein (DCF)-sensitive ROS production was induced in PC12 cells by hypoxia or H2O2-stress but was diminished in the presence of sesamin and sesamolin. We evaluated further the role of mitogen-activated protein kinases (MAPKs) and caspase-3 in hypoxia-induced PC12 cell death. Extracellular signal-regulated protein kinase (ERK) 1, c-jun N-terminal kinase (JNK), and p38 MAPKs of signaling pathways were activated during hypoxia. We found that the inhibition of MAPKs and caspase-3 by sesamin and sesamolin correlated well with the reduction in LDH release under hypoxia. Furthermore, the hypoxia-induced apoptotic-like cell death in cultured cortical cells as detected by a fluorescent DNA binding dye was reduced significantly by sesamin and sesamolin. Taken together, these results suggest that the protective effect of sesamin and sesamolin on hypoxic neuronal and PC12 cells might be related to suppression of ROS generation and MAPK activation.

Vitamin K1 attenuates hypoxia-induced relaxation of rat carotid artery

Vascular responses to hypoxia are heterogeneous and involve the release of vasodilators substances such as nitric oxide (NO) and prostacyclin (PGI(2)). In vitro studies have shown that Vitamin K(1) modulates the release of arachidonic acid (AA) in vascular cells, and thus inhibits the capacity of blood vessels to synthesise vasodilator AA metabolites. The aim of our work was to investigate the effects of Vitamin K(1) on the hypoxia-induced vasorelaxation. Hypoxia was induced by changing the gas from 95% O(2)/5% CO(2) to a mixture containing 95% N(2)/5% CO(2). Rat carotid arteries were pre-contracted with phenylephrine (Phe, 10(-8)mol/l) and when the contraction reached a plateau, the bath was bubbled with 95% N(2)/5% CO(2) for 15 min. In intact rings, there was a total relaxation after 15 min of exposure to hypoxia. Removal of the endothelium strongly reduced hypoxia-induced relaxation. In intact rings, indomethacin and L-NAME reduced the hypoxic relaxation after 5 min of exposure but not after 10 or 15 min. Exposure of endothelium-intact rings to Vitamin K(1) (5 x 10(-6) and 5 x 10(-5)mol/l), L-NAME+indomethacin as well as the combination of L-NAME+indomethacin+Vitamin K(1) reduced the hypoxic relaxation after 5 and 10 min of exposure but not after 15 min. At 5 x 10(-7)mol/l Vitamin K(1) did not attenuate hypoxia-induced relaxation. It was also found that Vitamin K(1) (5 x 10(-6) and 5 x 10(-5)mol/l) inhibited ACh-induced relaxation in normoxic conditions. These results show that the effect of Vitamin K(1) on attenuating hypoxia-induced vasorelaxation is concentration-dependent and probably related to its action on endothelial cells.