TY - JOUR
T1 - Sodium valproate induces mitochondrial respiration dysfunction in HepG2 in vitro cell model
AU - Komulainen, Tuomas
AU - Lodge, Tiffany
AU - Hinttala, Reetta
AU - Bolszak, Maija
AU - Pietilä, Mika
AU - Koivunen, Peppi
AU - Hakkola, Jukka
AU - Poulton, Joanna
AU - Morten, Karl J.
AU - Uusimaa, Johanna
N1 - Publisher Copyright:
© 2015 Elsevier Ireland Ltd.
PY - 2015/5/4
Y1 - 2015/5/4
N2 - Sodium valproate (VPA) is a potentially hepatotoxic antiepileptic drug. Risk of VPA-induced hepatotoxicity is increased in patients with mitochondrial diseases and especially in patients with POLG1 gene mutations. We used a HepG2 cell in vitro model to investigate the effect of VPA on mitochondrial activity. Cells were incubated in glucose medium and mitochondrial respiration-inducing medium supplemented with galactose and pyruvate. VPA treatments were carried out at concentrations of 0-2.0. mM for 24-72. h. In both media, VPA caused decrease in oxygen consumption rates and mitochondrial membrane potential. VPA exposure led to depleted ATP levels in HepG2 cells incubated in galactose medium suggesting dysfunction in mitochondrial ATP production. In addition, VPA exposure for 72. h increased levels of mitochondrial reactive oxygen species (ROS), but adversely decreased protein levels of mitochondrial superoxide dismutase SOD2, suggesting oxidative stress caused by impaired elimination of mitochondrial ROS and a novel pathomechanism related to VPA toxicity. Increased cell death and decrease in cell number was detected under both metabolic conditions. However, immunoblotting did not show any changes in the protein levels of the catalytic subunit A of mitochondrial DNA polymerase γ, the mitochondrial respiratory chain complexes I, II and IV, ATP synthase, E3 subunit dihydrolipoyl dehydrogenase of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase and glutathione peroxidase. Our results show that VPA inhibits mitochondrial respiration and leads to mitochondrial dysfunction, oxidative stress and increased cell death, thus suggesting an essential role of mitochondria in VPA-induced hepatotoxicity.
AB - Sodium valproate (VPA) is a potentially hepatotoxic antiepileptic drug. Risk of VPA-induced hepatotoxicity is increased in patients with mitochondrial diseases and especially in patients with POLG1 gene mutations. We used a HepG2 cell in vitro model to investigate the effect of VPA on mitochondrial activity. Cells were incubated in glucose medium and mitochondrial respiration-inducing medium supplemented with galactose and pyruvate. VPA treatments were carried out at concentrations of 0-2.0. mM for 24-72. h. In both media, VPA caused decrease in oxygen consumption rates and mitochondrial membrane potential. VPA exposure led to depleted ATP levels in HepG2 cells incubated in galactose medium suggesting dysfunction in mitochondrial ATP production. In addition, VPA exposure for 72. h increased levels of mitochondrial reactive oxygen species (ROS), but adversely decreased protein levels of mitochondrial superoxide dismutase SOD2, suggesting oxidative stress caused by impaired elimination of mitochondrial ROS and a novel pathomechanism related to VPA toxicity. Increased cell death and decrease in cell number was detected under both metabolic conditions. However, immunoblotting did not show any changes in the protein levels of the catalytic subunit A of mitochondrial DNA polymerase γ, the mitochondrial respiratory chain complexes I, II and IV, ATP synthase, E3 subunit dihydrolipoyl dehydrogenase of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase and glutathione peroxidase. Our results show that VPA inhibits mitochondrial respiration and leads to mitochondrial dysfunction, oxidative stress and increased cell death, thus suggesting an essential role of mitochondria in VPA-induced hepatotoxicity.
KW - Hepatotoxicity
KW - HepG2
KW - Mitochondrial respiration
KW - Mitochondrial toxicity
KW - Reactive oxygen species
KW - Sodium valproate
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U2 - 10.1016/j.tox.2015.03.001
DO - 10.1016/j.tox.2015.03.001
M3 - Article
C2 - 25745980
AN - SCOPUS:84925233499
SN - 0300-483X
VL - 331
SP - 47
EP - 56
JO - Toxicology
JF - Toxicology
ER -