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Nicotinamide N ‐methyltransferase expression in SH‐SY5Y human neuroblastoma cells decreases oxidative stress
Author(s) -
Mistry Rakhee J.,
Klamt Fábio,
Ramsden David B.,
Parsons Richard B.
Publication year - 2020
Publication title -
journal of biochemical and molecular toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.526
H-Index - 58
eISSN - 1099-0461
pISSN - 1095-6670
DOI - 10.1002/jbt.22439
Subject(s) - uncoupling protein , oxidative stress , sh sy5y , reactive oxygen species , chemistry , lipid peroxidation , oxidative phosphorylation , cell culture , nicotinamide , glutathione , biochemistry , mitochondrion , biology , enzyme , neuroblastoma , adipose tissue , brown adipose tissue , genetics
Nicotinamide N ‐methyltransferase (NNMT) plays a central role in cellular metabolism, regulating pathways including epigenetic regulation, cell signalling, and energy production. Our previous studies have shown that the expression of NNMT in the human neuroblastoma cell line SH‐SY5Y increased complex I activity and subsequent ATP synthesis. This increase in ATP synthesis was lower than the increase in complex I activity, suggesting uncoupling of the mitochondrial respiratory chain. We, therefore, hypothesised that pathways that reduce oxidative stress are also increased in NNMT‐expressing SH‐Y5Y cells. The expression of uncoupling protein‐2 messenger RNA and protein were significantly increased in NNMT‐expressing cells (57% ± 5.2% and 20.1% ± 1.5%, respectively; P = .001 for both). Total GSH (22 ± 0.3 vs 35.6 ± 1.1 nmol/mg protein), free GSH (21.9 ± 0.2 vs 33.5 ± 1 nmol/mg protein), and GSSG (0.6 ± 0.02 vs 1 ± 0.05 nmol/mg protein; P = .001 for all) concentrations were significantly increased in NNMT‐expressing cells, whereas the GSH:GSSG ratio was decreased (39.4 ± 1.8 vs 32.3 ± 2.5; P = .02). Finally, reactive oxygen species (ROS) content was decreased in NNMT‐expressing cells (0.3 ± 0.08 vs 0.12 ± 0.03; P = .039), as was the concentration of 8‐isoprostane F2α (200 ± 11.5 vs 45 ± 2.6 pg/mg protein; P = .0012). Taken together, these results suggest that NNMT expression reduced ROS generation and subsequent lipid peroxidation by uncoupling the mitochondrial membrane potential and increasing GSH buffering capacity, most likely to compensate for increased complex I activity and ATP production.