Decreased Expression of the Voltage-Dependent Anion Channel in Differentiated PC-12 and SH-SY5Y Cells Following Low-Level Pb Exposure

Lead (Pb) has been shown to disrupt cellular energy metabolism, which may underlie the learning deficits and cognitive dysfunctions associated with environmental Pb exposure. The voltage-dependent anion channel (VDAC) plays a central role in regulating energy metabolism in neurons by maintaining cellular ATP levels and regulating calcium buffering, and studies have shown that VDAC expression is associated with learning in mice. In this study, we examined the effect of 5 and 10 mu M Pb on VDAC expression in vitro in order to determine whether Pb alters VDAC expression levels in neuronal cell lines. PC-12 and SH-SY5Y cells were used since they differentiate to resemble primary neuronal cells. VDAC expression levels were significantly decreased 48 h after exposure to Pb in both cell lines. In contrast, exposure to 24 h of hypoxia failed to produce a decrease in VDAC, suggesting that decreased VDAC expression is not a general cellular stress response but is a result of Pb exposure. This decreased VDAC expression was also correlated with a corresponding decrease in cellular ATP levels. Real-time reverse transcription-polymerase chain reaction demonstrated a significant decrease in messenger RNA levels for the VDAC1 isoform, indicating that Pb reduces transcription of VDAC1. These results demonstrate that exposure to 5 and 10 mu M Pb reduces VDAC transcription and expression and is associated with reduced cellular ATP levels.