Changes in rat alveolar macrophageal antioxidant defense and reactive oxygen species release by high dietary vitamin...

For the past decade there has been emphasis on the immunomodulatory effects of vitamin E apart from its established role as a free radical scavenger. In alveolar macrophages (AMs), the role of vitamin E supplementation has not yet been investigated sufficiently. In the present study we have evaluated the effects of high vitamin E (DL-alpha-tocopheryl acetate, alpha-TA) supplementation for 10 d on rat-alveolar macrophageal antioxidant defense and reactive oxygen species (ROS) release. There was an increase in plasma vitamin E content from 5.22 +/- 1.30, at 50 mg to 12.23 +/- 1.06 and 22.32 +/- 2.02 micrograms/mL at 250 and 1,250 mg alpha-TA/kg dietary supplementation. Alveolar macrophage-vitamin E content enhanced by 56 to 75% at 250 and 1,250 mg alpha-TA diet as compared with control diet. Superoxide dismutase activity decreased and catalase and glutathione peroxidase activities increased significantly in AMs of 250 and 1,250 mg alpha-TA diet-fed rats. Reduced glutathione, total glutathione, and glutathione-S-transferase activity in AMs did not change significantly at any of the high doses of alpha-TA supplementation. On stimulation of AMs by phorbol-12-myristate-13-acetate (PMA), there was 2.8- and 3.5-fold enhancement in superoxide (O2-.) and H2O2 production, respectively, at 50 mg alpha-TA dose. But this increase by PMA could not take place in AMs from animals supplemented with 250 and 1,250 mg alpha-TA. It may therefore be concluded that high alpha-TA supplementation in diet may equip the AMs with a stronger defense against oxygen-free radical mediated damage to them.