α-Tocopherol at Nanomolar Concentration Protects PC12 Cells from Hydrogen Peroxide-Induced Death and Modulates Protein Kinase Activities

Abstract

The aim of this work was to compare protective and anti-apoptotic effects of α-tocopherol at nanomolar and micromolar concentrations against 0.2 mM H2O2-induced toxicity in the PC12 neuronal cell line and to reveal protein kinases that contribute to α-tocopherol protective action. The protection by 100 nM α-tocopherol against H2O2-induced PC12 cell death was pronounced if the time of pre-incubation with α-tocopherol was 3–18 h. For the first time, the protective effect of α-tocopherol was shown to depend on its concentration in the nanomolar range (1 nM < 10 nM < 100 nM), if the pre-incubation time was 18 h. Nanomolar and micromolar α-tocopherol decreased the number of PC12 cells in late apoptosis induced by H2O2 to the same extent if pre-incubation time was 18 h. Immunoblotting data showed that α-tocopherol markedly diminished the time of maximal activation of extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt)-induced in PC12 cells by H2O2. Inhibitors of MEK 1/2, PI 3-kinase and protein kinase C (PKC) diminished the protective effect of α-tocopherol against H2O2-initiated toxicity if the pre-incubation time was long. The modulation of ERK 1/2, Akt and PKC activities appears to participate in the protection by α-tocopherol against H2O2-induced death of PC12 cells. The data obtained suggest that inhibition by α-tocopherol in late stage ERK 1/2 and Akt activation induced by H2O2 in PC12 cells makes contribution to its protective effect, while total inhibition of these enzymes is not protective.

α-Tocopherol at Nanomolar Concentration Protects Cortical Neurons against Oxidative Stress

“…Previously, we have shown [ 14 ] that the protective effect of α-T against H 2 O 2 -induced PC12 cell death was also higher the higher was the α-T concentration in the nanomolar range (1 nM < 10 nM < 100 nM). Numakawa and co-authors were the first to show the protective effect of nanomolar α-T, but did not reveal its dependence on the α-T concentration [ 10 ].…”

“…The protective effect of 250 nM α-T against 10 mM glutamate-induced death of immature brain cortical neurons was shown to be much less pronounced than the protective effect of 2.5 µM α-T [ 13 ]. It was also shown [ 10 , 14 ] that long preincubation (18–24 h) with α-T at nanomolar concentrations increased its protective effect in rat brain cortical neurons and PC12 cells. The protective effect of nanomolar α-T against the H 2 O 2 -induced death of brain cortical neurons [ 10 ] or PC12 cells [ 14 ] was comparable with the protective effect of micromolar α-T after preincubation for 18–24 h.…”

“…At the same time, nanomolar α-tocotrienol was found to increase the viability of both hippocampal neurons and cells of the HT4 hippocampal cell line exposed to glutamate; its effect was shown to depend on the inhibition of 12-lipoxygenase and phospholipase A 2 [ 11 , 12 ]. Data on the protective effect of α-T at nanomolar concentrations on nerve cells and cells of neuronal cell lines are not abundant [ 10 , 13 , 14 ]. The protective effect of 250 nM α-T against 10 mM glutamate-induced death of immature brain cortical neurons was shown to be much less pronounced than the protective effect of 2.5 µM α-T [ 13 ].…”

Application of nanostructured lipid carriers: the prolonged protective effects for sesamol in in vitro and in vivo models of ischemic stroke via activation of PI3K signalling pathway

“…The cellular damage was also evaluated by measuring an indicator of cell toxicity, LDH, the cytoplasmic enzyme which is rapidly released into the cell culture medium following the damage of cell plasma membrane. In general, increased LDH activity has been recognized as a marker for the ischemic processes or cell death [ 39 ]. As shown in Fig.…”

“…In treatment groups, 20, 40, 80, and 100 μM of sesamol [ 6 – 10 ], S-NLCs (containing 20, 40, 80, and 100 μM of sesamol), vehicle, or blank NLCs were added to the cell cultures 24 h before and upon the OGD onset. In the case of any effect, cells were treated with specific PI3K inhibitor, LY294002, dissolved in 0.2% dimethyl sulfoxide (DMSO) at concentrations of 10, 20, and 50 μM [ 38 , 39 ] 20 min before the application of the effective agent.…”