The effect of aluminum on the vanadium-mediated oxidation of NADH

An in vitro study on reproductive toxicity of aluminium chloride on rabbit sperm: The protective role of some antioxidants

An in vitro study using rabbit sperm was designed to evaluate the cytotoxic effects of different concentrations of aluminium chloride (AlCl(3)) at 0, 2 and 4h of incubation on sperm motility and viability, oxidative status and the activities of some antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), transaminases and acid phosphatase. The role of vitamin C (1 mM) or vitamin E (2 mM) was also investigated in counteracting deterioration caused by AlCl(3) on the tested parameters. Rabbit sperm was incubated with different concentrations of AlCl(3) (0, 1, 5, 10, 15 and 20 mM) with or without vitamin C or vitamin E for 2 and 4 h. Results revealed that the percentage of motile and viable sperm decreased significantly after AlCl(3) treatment at 10, 15 and 20 mM and the response was both concentration and time dependent. Aluminium chloride at concentrations of 10, 15 and 20 mM caused significant induction of oxidative stress as evidenced by increased thiobarbituric acid reactive substances (TBARS) levels and inhibition in the activities of SOD and CAT. Increase in the activities of aspartate transaminase (AST) and alanine transaminase (ALT) and decline in the activity of acid phosphatase (ACP) were also observed at AlCl(3) concentrations of 15 and 20 mM. Co-incubation with either vitamin C or vitamin E resulted in marked degrees of protection against AlCl(3)-induced cytotoxic effects, represented in decreased TBARS levels and restoration of enzymes activities near control. On the other hand, no significant effect was exerted from vitamin C or vitamin E on motility and viability. The present study demonstrated that AlCl(3) caused deterioration in sperm motility and viability, enhancement of free radicals and alterations in enzymes activities. The antioxidants revealed protective effects against the cytotoxicity of AlCl(3).

The pro-oxidant activity of aluminum

Aluminum, a non-redox-active metal is, nevertheless, a pro-oxidant both in in vitro preparations and in vivo. It facilitates both superoxide- and iron-driven biological oxidation by mechanisms that remain to be resolved. More than 10 years ago Fridovich and colleagues suggested that the facilitation of superoxide-driven biological oxidation by aluminum was due to an interaction between the metal and the superoxide radical anion (Free Radic. Biol. Med. 13: 79-81; 1992). This thesis has been examined herein and it is concluded that much, if not all, of the pro-oxidant activity of aluminum might be explained by the formation of an aluminum superoxide semireduced radical ion.

A molecular mechanism of aluminium-induced Alzheimer's disease?

An abundance of research has continued to link aluminium (Al) with Alzheimer's disease (AD) (Strong et al., J. Toxicol. Environ. Health 48 (1996) 599; Savory et al., J. Toxicol. Environ. Health 48 (1996) 615). Animals loaded with Al develop both symptoms and brain lesions that are similar to those found in AD. However, these animal models of Al intoxication are not representative of human exposure to Al. They have not addressed the significance of a truly chronic exposure to Al. If Al is a cause of AD it is effective at the level of our everyday exposure to the metal and AD will be one possible outcome of the life-long presence of a low, though burgeoning, brain Al burden. Individual susceptibility to AD will be as much to do with differences in brain physiology as with changes in our everyday exposure to the metal. There will be a chemical response and indeed biochemical/physiological response in the brain to Al. The question is whether brain Al homeostasis could impact upon brain function. In reviewing the recent literature covering the neurotoxicity of Al and, in particular, of the known and probable mechanisms involved in brain Al homeostasis I have identified a mechanism through which a truly chronic exposure to Al would bring about subtle and persistent changes in neurotransmission which, in time, could instigate the cascade of events known collectively as AD. This mechanism involves the potentiation of the activities of neurotransmitters by the action of Al-ATP at adenosine 5'-triphosphate (ATP) receptors in the brain.

Oxidative stress of vanadium-mediated oxygen free radical generation stimulated by aluminium on human erythrocytes

It has been suggested that aluminium stimulates vanadium-mediated superoxide radical generation. The oxidative stress of generated superoxide radicals on antioxidant enzyme activity, oxidation of NADH and NADPH, membrane lipid peroxidation and osmotic fragility in human red blood cells (RBC) was investigated. RBC were incubated with varying concentrations of vanadium and aluminium ions at 37 degrees C for 2 h. RBC incubated with vanadium ions showed significantly increased superoxide dismutase and catalase activities, and oxidized NADH and NADPH concentrations compared with control RBC preparations. Erythrocyte lipid peroxidation was assessed by measuring thiobarbituric acid reactivity. RBC incubated with elevated levels of vanadium showed significantly increased membrane lipid peroxidation when compared with control RBC; it increased further on addition of aluminium. A significant positive correlation was observed between the extent of vanadium induced membrane lipid peroxidation and the osmotic fragility of treated RBC. In the presence of vanadium, aluminium stimulates superoxide dismutase and catalase activities. NADH and NADPH oxidation and membrane lipid peroxidation, as well as increasing osmotic fragility of human erythrocytes. The stimulatory effect of aluminium was dependent on concentration. These results may have implications for the mechanism of toxicity of aluminium and vanadium in haemodialysis patients.

Vanadium-mediated oxidation of NADH is enhanced by aluminium and inhibited by vitamin E and some copper (II) complexes

The effect of aluminium on vanadium-mediated oxidation of NADH was examined. The oxidation of NADH was enhanced in the presence of aluminium. The effect was concentration dependent. Vitamin E and copper (II) complexes with superoxide dismutase (SOD)-like activities containing isobutyric acid hydrazine were tested for their effect on the vanadium-mediated oxidation of NADH. The stimulatory effect of aluminium was decreased upon addition of different concentrations of vitamin E and copper (II) complexes. These results indicate that the biological toxicity of aluminium may be attributed to its enhancement of the production of superoxide radicals (O2.-) in association with the accumulation of other trace elements such as vanadium.