Lead: As in drug toxicities, Spirulina or its bioactive constituent, phycocyanin, has been found to protect from heavy metal poisoning. Again, this protection seems to be mediated mostly by the prevention of oxidative damage through direct antioxidant actions and through induction of endogenous antioxidant enzymes. For example, in rats treated with lead acetate, dietary S.fusiformis (1500 mg/kg) reversed the lead-induced inhibition of SOD and catalase activity in liver, lung, heart, and kidney to levels that were only slightly, but not significantly, lower than those of untreated controls.23 Lead did not induce significant decreases in the activities of these anti-oxidant enzymes in the brain, and Spirulina did not markedly alter them either. Interestingly, brain was the only tissue in which Spirulina feeding resulted in a significant reduction in lead concentrations compared to the lead-treated unsupplemented group. Dietary S. fusiformis was also associated with a pronounced decrease in the levels of lipid peroxidation in liver, lung, heart, and kidney, although they remained higher than in control animals that had not received lead acetate.
Mercury: When mice were given S. fusiformis orally for 10 days before and 30 days after mercury chloride administration, they exhibited significantly decreased levels of lipid peroxidation in the liver, reduced histological damage, and lower liver enzyme activities than animals that received only mercury chloride.24 In mice treated according to the same protocol, kidney tissue of Spirulina-treated animals also showed markedly fewer and less severe lesion in association with reduced lipid peroxidation. In addition, Spirulina partially inhibited mercury-induced changes in the activities of several kidney enzymes.
Arsenic poisoning: In a recent randomized placebo-controlled study, the efficacy of an ethanol extract of Spirulina in combination with zinc against chronic arsenic poisoning was examined in a total of 41 patients.25 Filtered water was provided to all the patients and resulted in decreased urinary excretion of arsenic. Between second week and sixth week of treatment, the urinary arsenic concentration rose sharply in the group treated with Spirulina plus zinc, but not in the placebo group. This strongly suggests that Spirulina plus zinc enhanced the urinary excretion of this toxin. It is not immediately obvious why this effect was no longer evident after 4-6 weeks of treatment. From that time until the end of the study after 16 weeks, the urinary excretion remained slightly and nonsignificantly higher in the group treated with Spirulina plus zinc compared to the placebo group. At the end of 16 weeks of treatment, arsenic concentrations in hair of patients in the placebo group had decreased only slightly. In contrast, a marked decline (47%) occurred in the Spirulina plus zinc-treated group. Significant clinical improvements in the skin manifestations of arsenic poisoning, that is, hyperpigmentation primarily of the upper chest and arms and keratosis, were seen only in patients treated with Spirulina plus zinc, but not in the placebo group.
Once absorbed, arsenic is enzymatically or nonenzymatically reduced to arsenite and then methylated. Note that, while methylation enhances arsenic excretion, the resulting metabolites exhibit significant toxicities of their own.26 Approximately 6080% of ingested arsenic is excreted in urine, while the remainder is secreted into bile, which results in fecal elimination. It has been shown that glutathione plays an important role in biliary arsenic excretion.27 Arsenic triglutathione and methylarsenic diglutathione have also been detected in urine of mice and these two species were found to represent ~60-70% of urinary arsenic.28 This suggests that the ability of Spirulina to restore drug- or chemical-induced levels of reduced glutathione may be a factor in the enhanced arsenic excretion in the above study. It is as yet unknown whether the glutathione conjugation of arsenic metabolites is catalyzed by GST or occurs nonenzymatically. If mediated by GST, the ability of Spirulina to upregulate GST activity—as seen in liver,3,4 though not in kidney1—may also have contributed to the observed higher urinary excretion of arsenic and the significant reduction in hair arsenic levels and presumably body burden.
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