ALDH2 inhibition by Lead and Ethanol co-exposure: impact on bioenergetics and oxidative stress biomarkers in SH-SY5Y cells.

DEZA-PONZIO, R; EICHWALD, T; GARAY, YC; IRAZOQUI FJ; LATINI, A; VIRGOLINI, M

Congreso; Neurotoxicity Society; 2021

We have previously reported that perinatally-Pb-exposed rats showed elevated ethanol (EtOH) intake, which seems to be mediated by brain acetaldehyde (ACD) accumulation, a highly reactive metabolite Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial oxidoreductase that metabolizes ACD to acetate during EtOH metabolism, with NAD+ as the limiting factor of the reaction, a cofactor that is recycled within the mitochondria. Based on a reduced brain ALDH2 activity and expression observed in the Pb-exposed rats, in vitro experiments were performed in SH-SY5Y cells to elucidate the mechanisms underlying ALDH2 defective function in the presence of Pb and EtOH. Thus, whole intact neuroblastoma cells exposed for 24 h to Pb (10 µM), EtOH (200 mM), or their combination were analyzed in an Oxygraph Oroboros 2K for oxygen consumption rates. In addition, to evaluate their redox status, cells were harvested, homogenized and the supernatant was used for the measurement of ALDH2 activity and expression as well as total ROS, TBARS generation and catalase activity and expression. The results in these cells replicated the in vivo data in terms of ALDH2 inhibition after Pb, EtOH, or the combination. High-resolution respirometry shows that Pb and EtOH co-exposure decreased routine and maximal respiratory capacity in addition to the mitochondrial oxygen reserve capacity. On the other hand, Pb and EtOH exposure increase ROS levels, lipid peroxidation and catalase activity and expression, probably as a compensatory mechanism in order to reestablish the oxidative balance in the cell. It can be concluded that Pb and EtOH cause mitochondrial toxicity by altering bioenergetics in SH-SY5Y cells, with possible consequences on NAD+ availability and thereby ALDH2 functionality. This mitochondrial dysfunction may be responsible for the excess in oxidant products that in turn, affect the mitochondrial functionality and leads to an inhibition of ALDH2 activity due to cofactor depletion as previously showed in other experiments. Thus, whether oxidative stress follows mitochondrial dysfunction or the opposite is a fact that deserves consideration in the context of a low-functional ALDH2 enzyme.