Methylmalonic Acid Compromises Energy Metabolism and Decreases the Expression of Neuronal Differentiation Genes in SH‐SY5Y Human Neuroblastoma Cells

Abstract

Methylmalonic acidemia is an organic acidemia caused by deficient activity of L‐methylmalonyl‐CoA mutase or its cofactor cyanocobalamin and it is biochemically characterized by an accumulation of methylmalonic acid (MMA) in tissue and body fluids of patients. The main clinical manifestations of this disease are neurological and symptoms during metabolic decompensation commonly appear in newborns. Considering that the mechanisms underlying neurological alterations of this disorder are not fully understood, this study aimed to investigate the toxic effects of MMA in a neuroblastoma cell line presenting neuronal features. Undifferentiated and retinoic acid (RA)‐differentiated human neuroblastoma SH‐SY5Y cells were exposed to MMA (1–10mM) for 24 or 48 hours and cell viability, glucose consumption and mitochondrial metabolic function were analyzed. Additionally, the expression of some molecular markers of neuronal differentiation was also quantified after co‐exposition with 10 μM RA and 1 mM of MMA for 3 and 7 days.MMA significantly reduced cell viability after 48‐hour period exposition in undifferentiated and RA differentiated SH‐SY5Y cells. It was also observed an increase in glucose consumption in cells exposed to MMA. Regarding oxygen consumption, there was an increase in respiratory parameters in RA differentiated SH‐SY5Y cells when compared to undifferentiated cells. MMA significantly reduced basal, ATP‐linked and maximal respiration, as well as the reserve respiratory capacity of cells after 48‐hour exposition in both undifferentiated and RA differentiated SH‐SY5Y cells. Regarding the effects of MMA in the neuronal differentiation process, it was observed that co‐exposition to RA and MMA significantly decreased the expression of enolase 2 (ENO2) and synaptophysin (SYP) genes after 7 days of exposition.In summary, MMA cell viability and oxygen consumption in SH‐SY5Y neuronal cells, suggesting that this organic acid compromises cell respiration, at resting and reserve capacity states, which might influence the cell capacity to meet energetic demands. In addition, glucose uptake was increased after exposition to MMA, corroborating that aerobic metabolism is compromised. The expression of mature neuronal genes was also reduced, suggesting that MMA possibly compromises neuronal differentiation, which can be involved in symptoms presented by affected patients during brain development. Finally, our findings suggest that these effects could be involved in the pathophysiology of neurological dysfunction of this disease.Support or Funding InformationThis study was supported by grants from FAPESP (2015/25541‐0), CAPES and UFABC.