Effect of lead on lipid peroxidation, phospholipids composition, and methylation in erythrocyte of human.

Lead (Pb) is one of the most abundant heavy metals on earth considered as number one environmental persistent toxin and health hazard affecting millions of people in all age groups. After entering bloodstream, 99% of Pb is accumulated in erythrocytes and causes poisoning. Toxic Pb effects on erythrocytes membrane's composition of phosphatidyl serine (PS), phosphatidyl ethanolamine (PE), phosphatidyl choline (PC), and sphingomyelin (SM), and phospholipids transmethylation were determined. Lipid peroxidation in Pb-exposed erythrocytes was evaluated as malondialdehyde (MDA) formation in presence of Fe and vitamin E to understand severity of Pb toxicity and its mitigation. Pb (0.5-5.0 μM) degraded PS (12 to 31%, P < 0.05-0.001) and elevated SM (19-51%, P < 0.05-0.001). Composition of PC and PE were diminished (22%) and elevated (29%), respectively, with higher Pb exposure (5.0 μM, P < 0.001). Pb toxicity suppressed (P < 0.001) transmethylation of phospholipids in membranes (34, 41, and 50%, respectively, with 0.5, 2.5, and 5.0 μM). Pb-induced dose-related MDA production (P < 0.05-0.001) in erythrocytes was obtained, which was accentuated in presence of Fe (P < 0.05-0.001). The vitamin E mitigated (P < 0.05-0.01) the severity of Pb-induced lipid peroxidation. The ratio PS/SM showed maximum change of -27 (P < 0.01), -30 (P < 0.01), and -54% (P < 0.001), respectively at 0.5, 2.5, and 5.0 μM Pb exposures. Ratios PC/SM and PS/PE were at the second, whereas PE/PS at the third order. The study suggests that the mechanisms underlying distortion of compositional phospholipids, inhibition of transmethylation, and exasperated phospholipid peroxidative damage are the active phenomena of Pb toxicity in erythrocytes.