Xanthine oxidase leukocyte,human

The release of iron from ferritin can be induced by different factors. In 1984, Biemond et al. [159] have shown that stimulated leukocytes mobilize iron from human and horse ferritin. Release of iron was induced by superoxide because SOD inhibited this process. Similarly, the release of iron from ferritin can be induced by xanthine oxidase [160] this process is believed to induce ischemia and inflammation. Under anerobic conditions xanthine oxidase is also able to stimulate iron release from ferritin through superoxide-independent mechanism [161]. Another physiological free radical nitric oxide also stimulates iron release from ferritin [162],... 

Thus, the mechanism of MT antioxidant activity might be connected with the possible antioxidant effect of zinc. Zinc is a nontransition metal and therefore, its participation in redox processes is not really expected. The simplest mechanism of zinc antioxidant activity is the competition with transition metal ions capable of initiating free radical-mediated processes. For example, it has recently been shown [342] that zinc inhibited copper- and iron-initiated liposomal peroxidation but had no effect on peroxidative processes initiated by free radicals and peroxynitrite. These findings contradict the earlier results obtained by Coassin et al. [343] who found no inhibitory effects of zinc on microsomal lipid peroxidation in contrast to the inhibitory effects of manganese and cobalt. Yeomans et al. [344] showed that the zinc-histidine complex is able to inhibit copper-induced LDL oxidation, but the antioxidant effect of this complex obviously depended on histidine and not zinc because zinc sulfate was ineffective. We proposed another mode of possible antioxidant effect of zinc [345], It has been found that Zn and Mg aspartates inhibited oxygen radical production by xanthine oxidase, NADPH oxidase, and human blood leukocytes. The antioxidant effect of these salts supposedly was a consequence of the acceleration of spontaneous superoxide dismutation due to increasing medium acidity. 

One particular relevant source of free radicals is provided by the xanthine oxidase-catalysed conversion of oxygen to the superoxide radical. This process may be initiated by tumour necrosis factor (TNFoO- Arroyo et al. (1995) have shown that sulphur mustard can induce human monocytes to release TNFa thus, a link between sulphur mustard and oxygen free radical formation has been identified. Polymorphonuclear leukocytes respond to the presence of bacteria by an... 

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