Deleterious effects of combination of lead and β-amyloid peptides in inducing apoptosis and altering cell cycle in human neuroblastoma cells.

Lead (Pb) is a toxic pollutant known to cause several abnormalities related to the brain, including cognitive dysfunction, and it is ubiquitous in nature. β-amyloid peptides (AP) are crucially involved in Alzheimer's disease (AD). It has been reported that there is a connection between lead and amyloid peptides in exerting similar kinds of altered functions in the brain and long-term exposure to lead leads ultimately to increased beta amyloid formation in the brain, lethal to human brain cells. There is still a lack of information on the mechanism by which Pb affects AP formation, exerting combined toxicity in AD patients. To fill the gap, we have systematically analyzed the toxicity individually and in combination of Pb and AP in human brain cells. We found that the combination of Pb and AP exerted a higher toxicity than individual exposures in human neuroblastoma cells. The lower inhibitory concentration values were determined by both time and concentration dependent manner on using MTT assay. The data resulted in the development of enhanced toxicity on exposure to Pb with both the combinations of AP(1-40) or (25-35) and with all combinations in human brain cells compared to individual exposures to Pb (1-40) or AP(25-35). The severe apoptotic effect and alteration in cell cycle by arresting at the S-phase evidenced the increased toxicity of combinational exposure to Pb and AP on human neuroblastoma cells. Furthermore, the quantitative determination of LDH and caspase-3 activity indicated the induction of severe toxicity. We conclude that both are synergistically associated with effects such as arresting the cell cycle and triggering apoptosis during the progression of Alzheimer's disease.