Table 6.
Characteristics of preclinical cells studies.
| Reference | Study Design, Human Disease Modelled and Population | Intervention | Comparator | Outcomes | |
|---|---|---|---|---|---|
| Primary | Secondary | ||||
| [25] | ●Glutamate induced-neurotoxicity model for 12, 24 or 36 h ●Mouse hippocampal HT4 cells line |
●5-min pre-treatment with 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant time-dependent enhancement of cellular viability | ●Direct inhibition of inducible 12-lipoxygenase enzyme. ●Morphological changes indicated the prevention of neurodegeneration with the maintenance of neuronal growth. |
| [25] | ●Glutamate or L-homocysteic acid neurotoxicity for 24 h ●Immature primary cortical neurons of Sprague-Dawley rats (17th day of gestation) |
●5-min pre-treatment with 25, 50, 100 and 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement of cellular viability | |
| [25] | ●L-buthionine (S,R)-sulfoximine or L-buthionine (S,R)-sulfoximine +arachidonic acid neurotoxicity for 24 h using immature primary cortical neurons of Sprague-Dawley rats (17th day of gestation) | ●5-min pre-treatment with 100 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement cellular viability | |
| [25] | ●L-buthionine (S,R)-sulfoximine neurotoxicity for 24 h using immature primary cortical neurons of Sprague-Dawley rats (17th day of gestation) | ●5-min pre-treatment with 100 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement of cellular viability, but loss of the cellular reduced glutathione | |
| [25] | ●Glutamate, L-buthionine (S,R)-sulfoximine or L-buthionine (S,R)-sulfoximine + arachidonic acid neurotoxicity for 24 h using cerebral cortex neurons of mouse fetuses (C57BL/6) mice, (14th day of gestation) | ●5-min pre-treatment with 100 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement of cellular viability | |
| [25] | ●Glutamate, L-buthionine (S,R)-sulfoximine or L-buthionine (S,R)-sulfoximine + arachidonic acid for 24 h using cerebral cortex neurons of the fetuses of B6.129S2-Alox15tm1Fun mice | ●5-min pre-treatment with 100 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement of cellular viability | |
| [27] | ●Hydrogen peroxide neurotoxicity for 24 h using primary cells of anterior striatum of fetal Wistar rats (17th–19th day of gestation). | ●Simultaneous treatment with 0.1, 1 or 10 µM of TRF in 0.1% DMSO (TRF: 90% pure contains 14.5. mg α-TCT, 2.5 mg β-TCT, 26 mg γ-TCT and 7.2 δ-TCT) | ●0.1% DMSO | ●A significant enhancement of cellular viability. | |
| [27] | ●Hydrogen peroxide neurotoxicity for 24 h using primary cells of anterior striatum of fetal Wistar rats (17th–19th day of gestation) | ●Simultaneous treatment with 0.1, 1 or 10 µM of either α-, γ- or δ-TCT in 0.1% DMSO | ●0.1% DMSO | ●α-TCT [0.1, 1 and 10 µM], γ-TCT [1 and 10 µM] and δ-TCT [10 µM] significantly enhanced cellular viability | |
| [27] | ●Parquet neurotoxicity with for 24 h using primary cells of anterior striatum of foetal Wistar rats on the 17th–19th day of gestation | ●Simultaneous treatment with 0.1, 1 and 10 µM of either α-, γ- or δ-TCT in 0.1% DMSO | ●0.1% DMSO | ●α-, γ- or δ-TCT [0.1, 1 and 10 µM] significantly enhanced cellular viability | |
| [27] | ●S-nitrosocysteine neurotoxicity for 24 h using primary cells of anterior striatum of foetal Wistar rats on the 17th–19th day of gestation | ●Simultaneous treatment with 0.1, 1 and 10 µM of either α-, γ- or δ-TCT in 0.1% DMSO | ●0.1% DMSO | ●α- and γ-TCT [0.1, 1 and 10 µM] as well as δ-TCT [1 and 10 µM] significantly enhanced cellular viability. | |
| [27] | ●3-morpholinosydnonimine neurotoxicity for 24 h using primary cells of anterior striatum of foetal Wistar rats on the 17th–19th day of gestation | ●Simultaneous treatment with 0.1, 1 and 10 µM of either α-, γ- or δ-TCT in 0.1% DMSO | ●0.1% DMSO | ●α-TCT [0.1, 1 and 10 µM], γ-TCT [1 and 10 µM] and δ-TCT [1 and 10 µM] significantly enhanced cellular viability. | |
| [27] | ●L-buthionine (S,R)-sulfoximine neurotoxicity for 48 h using primary cells of anterior striatum of foetal Wistar rats on the 17th–19th day of gestation | ●Simultaneous treatment with 0.01, 0.1 and 1 µM of either α-, γ- or δ-TCT in 0.1% DMSO | ●0.1% DMSO | ●α-TCT [0.1 and 1 µM], γ-TCT [1 µM] and δ-TCT [1 µM] significantly enhanced cellular viability. α-, γ- and δ-TCT [1 µM] exerted antiapoptotic effects, however, the antiapoptotic effect of α-TCT was superior to that of either γ- or δ-TCT | ●Antiapoptotic effect involved the prevention of DNA fragmentation. |
| [27] | ●Staurosporine neurotoxicity for 24 h using primary cells of anterior striatum of foetal Wistar rats on the 17th–19th day of gestation. | ●Simultaneous treatment with 10 µM of either α-, γ- or δ-TCT 0.1% DMSO | ●0.1% DMSO | ●Only 10 µM of α-TCT exerted a significant antiapoptotic effect, while γ- or δ-TCT field to exert a significant antiapoptotic effect. | ●Antiapoptotic effect involved a significant prevention of DNA fragmentation. |
| [29] | ●Glutamate neurotoxicity for 24 h using mouse Hippocampal HT4 Neurons | ●5-min pre-treatment with 250 nm of TRF in 1% ethanol (TRF: 90% pure contains 14.5. mg α-TCT, 2.5 mg β-TCT, 26 mg γ-TCT and 7.2 δ-TCT) | ●1% ethanol | ●A significant enhancement of cellular viability | ●Inhibiting the tyrosine phosphorylation of inducible 12-lipoxignase enzyme and direct inhibition of inducible 12-lipoxignase enzyme |
| [29] | ●Glutamate neurotoxicity for 24 h using cerebral cortex neurons of foetuses of Sprague-Dawley rats, (17th day of gestation) | ●5-min pre-treatment with 250 nm of TRF in 1% ethanol (TRF: 90% pure contains 14.5. mg α-TCT, 2.5 mg β-TCT, 26 mg γ-TCT and 7.2 δ-TCT) | ●1% ethanol | ●A significant enhancement of cellular viability | ●Inhibiting the tyrosine phosphorylation of inducible 12-lipoxignase enzyme and direct inhibition of inducible 12-lipoxignase enzyme |
| [29] | ●L-buthionine (S,R)-sulfoximine neurotoxicity for 24 h using mouse Hippocampal HT4 Neurons | ●5-min pre-treatment with 0.25 µM of α-TCT in 1% ethanol | ●1% ethanol | ●A relative (nonsignificant) enhancement of cellular viability | |
| [29] | ●L-buthionine (S,R)-sulfoximine + arachidonic acid neurotoxicity for 24 h using mouse Hippocampal HT4 Neurons | ●5-min pre-treatment with 0.25 µM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant loss of cellular viability | |
| [29] | ●L- arachidonic acid neurotoxicity for 24 h using mouse Hippocampal HT4 Neurons | ●5-min pre-treatment with 0.25 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Inhibiting tyrosine phosphorylation of inducible 12-lipoxignase enzyme and direct inhibition of inducible 12-lipoxignase enzyme | |
| [13] | ●Homocysteic acid neurotoxicity for 24 h using mouse hippocampal HT4 neural cells | ●5 min pre- or 8 h post-treatment with 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●Pre-treatment significantly enhanced cellular viability, while post-treatment failed to enhance cellular viability | |
| [13] | ●Homocysteic acid neurotoxicity for 24 h using mouse hippocampal HT4 neural cells | ●5-min pre- or 8 h post-treatment with 0.25, 2.5 and 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Pre- and post-treatment significantly enhanced cellular viability. | |
| [13] | ●Homocysteic acid neurotoxicity for 2 or 6 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●Provided a significant antioxidant activity through enhancing the ratio of cellular levels of reduced glutathione/oxidized glutathione | |
| [13] | ●Homocysteic acid neurotoxicity for 8 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 2.5 and 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Blue fluorescence imaging indicated a completely elimination of ROS | |
| [13] | ●Linoleic acid neurotoxicity for 4 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 0.25, 1, 2.5 and 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●1, 2.5 and 10 µM of α-TCT significantly attenuated lipid peroxidation | ●Fluorescence imaging indicated the attenuation of the build-up of ROS |
| [13] | ●Linoleic acid neurotoxicity for 24 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 0.25, 1, 2.5 and 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Significantly enhanced cellular viability [2.5 and 10 µM] | |
| [13] | ●Homocysteic acid neurotoxicity for 12 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●A significant enhancement of cellular viability | ●Prevented overexpression of c-Src and 2-lipoxigenase |
| [13] | ●Homocysteic acid neurotoxicity for 6 h using mouse hippocampal HT4 neural cells | ●5-min pre-treatment with 0.25, 1, 2.5 and 10 µM of α-TCT 1% ethanol | ●1% ethanol | ●Provided a significant antioxidant activity [2.5 and 10 µM] through enhancing the ratio of cellular levels of reduced glutathione/oxidized glutathione | |
| [13] | ●Homocysteic acid neurotoxicity for 24 h using primary cortical neurons of foetuses of Sprague–Dawley (17th day of gestation) | ●5-min pre-treatment with 250 nM of α-TCT in 1% ethanol | ●1% ethanol | ●Significantly enhanced cellular viability | |
| [13] | ●Homocysteic acid neurotoxicity for 24 h using primary cortical neurons of foetuses of Sprague–Dawley (17th day of gestation) | ●5-min pre-treatment with 0.25, 1, 2.5 and 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Significantly enhanced cellular viability | |
| [24] | ●Glutamate neurotoxicity for 30 min using murine hippocampal HT4 neuronal cells | ●10-min pre-treatment with 250 µM α-TCT in ethanol 1% | ●1% ethanol | ●A significant enhancement of cellular viability | ●Decreasing significantly the release of arachidonic and docosahexaenoic acids from cell membrane through attenuating the hydrolysis activity of cytosolic phospholipase A2 on cell membrane due to inhibiting: ●Translocation of cytosolic phospholipase A2 to cell membrane, ●Ser505 phosphorylation of cytosolic phospholipase A2 ●Phospholipase A2 activity |
| [24] | ●Glutamate neurotoxicity for 24 h using murine hippocampal HT4 neuronal cells | ●2-h pre-treatment with 250 µM α-TCT in ethanol 1% | ●1% ethanol | ●A significant enhancement of cellular viability | ●Direct inhibition of phospholipase A2. |
| [28] | ●Glutamate neurotoxicity for 24 h using human neuroblastoma cells line (SK-N-SH) | ●5-min pre-treatment with 100, 200, or 300 ng/mL of TRF in DMSO (TRF: 25% tocopherol and 75% tocotrienols) | ●DMSO | ●A significant enhancement of cellular viability particularly 200 ng/mL ●A significant dose-dependent attenuation of lipid peroxidation through reducing the levels of MDA |
●Annexin V-FITC/PI staining indicated that 200 mg/kg was significantly the highest against necrosis as well as early and late stage apoptosis |
| [28] | ●Glutamate neurotoxicity for 24 h using human neuroblastoma cells line (SK-N-SH) | ●30-min post-treatment with 100, 200, or 300 ng/mL TRF in DMSO (TRF: 25% tocopherol and 75% tocotrienols) | ●DMSO | ●A significant enhancement of cellular viability particularly 200 mg/kg. ●A significant attenuation of lipid peroxidation through reducing the levels of MDA particularly 300 mg/kg |
●Annexin V-FITC/PI staining indicated slight (nonsignificant) antiapoptotic effect against necrosis as well as early and late stage apoptosis ●Electronic microscope scanning for cellular morphology indicated that only 200 mg/kg could provide a little improvement to the cell membrane integrity. |
| [23] | ●Hydrogen peroxide neurotoxicity for 24 h using human neuroblastoma cells line [SH-SY5Y wild-type] | ●Simultaneous treatment with 10 µM of α-TCT in 1% ethanol | ●1% ethanol | ●Significantly reduced the levels of ROS | ●Significant strong protection of total cholesterol and free cholesterol. |
| [23] | ●Alzheimer’s disease model using human neuroblastoma cells line [SH-SY5Y APP] overexpressing the human APP695 isoform | ●Simultaneous treatment with 10 µM of α-TCT in 1% ethanol for 24 h | ●1% ethanol | ●A nonsignificant increase in the levels of Aβ indicating early onset of AD | ●Direct activation of γ-secretase independent of gene expression |
| [23] | ●Alzheimer’s disease model using human neuroblastoma cells line [SH-SY5Y wild-type] | ●Simultaneous treatment with 10 µM of α-TCT in 1% ethanol for 24 h | ●1% ethanol | ●A significant increase in the levels of Aβ | ●Due to direct increase in β-secretase activity independent of gene transcription of BACE1 |
| [23] | ●Alzheimer’s disease model using human neuroblastoma cells line [SH-SY5Y cells] stably expressing C99 | ●Simultaneous treatment with 10 µM of α-TCT in 1% ethanol for 24 h | ●1% ethanol | ●Significantly increased levels of Aβ | ●Direct activation of γ-secretase independent of gene transcription of PSEN1, PSEN2, NCSTN, PSENEN and APH1A |
| [23] | ●Alzheimer’s disease model using mouse neuroblastoma cell line (N2a) | ●Simultaneous treatment with 10 µM of α-TCT in 1% ethanol for 24 h | ●1% ethanol | ●Significantly decreasing Aβ degradation | ●Inhibiting insulin-degrading enzyme |
| [26] | ●Glutamate neurotoxicity for 24 h using human astrocytes cell line (CRL-2020 cells) derived from glioblastoma with S100B protein | ●5-min pre-treatment with 100, 200 and 300 ng/mL of TRF in absolute ethanol (TRF: 25% tocopherol and 75% tocotrienols) | ●Absolute ethanol | ●TRF could neither promptly (significantly) enhance cellular viability nor modulate the situation of oxidative stress since the level of the reduced glutathione was still low. However, 200 and 300 ng/mL could significantly attenuate lipid peroxidation through reducing the MDA level. | ●Morphological cellular changes indicated a significantly reduction in the percentages of apoptotic and necrotic cells at higher concentrations. |
| [26] | ●Glutamate neurotoxicity for 24 h using human astrocytes cell line (CRL-2020 cells) derived from glioblastoma with S100B protein | ●30-min post-treatment with 100, 200 and 300 ng/mL of TRF in absolute ethanol (TRF: 25% tocopherol and 75% tocotrienols) | ●Absolute ethanol | ●TRF could neither promptly (significantly) enhance cellular viability nor modulate the situation of oxidative stress since the level of the reduced glutathione was still low. However, TRF could significantly attenuate lipid peroxidation through reducing the MDA level. | ●Morphological cellular changes indicated a significant reduction in the percentages of apoptotic and necrotic cells at higher concentrations. |
| [30] * | ●Alzheimer’s disease model with Aβ42 aggregates for 24 h using human neuroblastoma cell line (SH-SY5Y) | ●Simultaneous treatment with 0.00003, 0.0003, 0.003% (v/v) TRF in 0.15% ethanol (TRF: 196 mg/g α-TCT, 24 mg/g β-TCT, 255 mg/g γ-TCT,75mg/gδ-TCT and 168 mg/g α-tocopherol) | ●0.15% ethanol | ●TRF could significantly enhance cellular viability | |
AD: Alzheimer’s disease, TRF: tocotrienol-rich fraction, MDA: malondialdehyde, TCT: tocotrienol, Aβ: amyloid-β protein, ROS: reactive oxygen species. PSEN1: presenilin 1, PSEN2: presenilin 2, NCSTN: nicastrin, PSENEN: presenilin-enhancer 2, APH1A: anterior-pharynx-defective 1A, BACE1: Beta-secretase 1. * superscript: this study was a part of a preclinical animal study.