Tocopherol suppresses 24(S)-hydroxycholesterol-induced cell death via inhibition of CaMKII phosphorylation

Kimura Y, Asa M, Urano Y, Saito Y, Nishikawa K, Noguchi N

Biochimie. 2018 Oct;153:203-209. doi: 10.1016/j.biochi.2018.07.004. Epub 2018 Jul 7.

Abstract

Although 24(S)-hydroxycholesterol (24S-OHC) plays an important role to maintain homeostasis of cholesterol in the brain, it induces neuronal cell death at high concentrations. 24S-OHC-induced cell death was suppressed by γ-tocopherol (γ-Toc) but not by γ-tocotrienol (γ-Toc3) in a similar way to α-tocopherol (α-Toc) and α-tocotrienol (α-Toc3) in human neuroblastoma SH-SY5Y cells. Both γ-Toc and γ-Toc3 significantly inhibited cumene hydroperoxide-induced cell death, as previously shown in the case of α-Toc and α-Toc3. Lipid droplet-like structure formation induced by 24S-OHC was suppressed by neither γ-Toc nor γ-Toc3. The phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII) was induced by 24S-OHC, which was suppressed by CaMKII phosphorylation-site inhibitor mM3 but not by calmodulin-binding-site inhibitor KN62. A calcium chelator, BAPTA-AM, inhibited calcium ionophore A23187-induced CaMKII phosphorylation but not 24S-OHC-induced CaMKII phosphorylation. Receptor-interacting protein kinase 1 (RIPK1) phosphorylation induced by 24S-OHC was not inhibited by either mM3 or KN62, suggesting that CaMKII activation does not affect RIPK1 phosphorylation. Knockdown of RIPK1 using siRNA induced not only inhibition of CaMKII phosphorylation but also reduction of total CaMKII protein levels, suggesting that RIPK1 may regulate CaMKII signalling. 24S-OHC-induced RIPK1 phosphorylation was inhibited by neither α-Toc nor α-Toc3. In contrast, CaMKII phosphorylation induced by 24S-OHC was significantly suppressed by α-Toc but not by α-Toc3. These results suggest that CaMKII activation is involved in the mechanism of 24S-OHC-induced cell death and that Toc inhibits the cell death via inhibition of CaMKII activation through a RIPK1 phosphorylation-independent pathway.

Hinman A, Holst CR, Latham JC, Bruegger JJ, Ulas G, McCusker KP, Amagata A, Davis D, Hoff KG, Kahn-Kirby AH, Kim V, Kosaka Y, Lee E, Malone SA, Mei JJ, Richards SJ, Rivera V, Miller G, Trimmer JK, Shrader WD

PLoS One. 2018 Aug 15;13(8):e0201369. doi: 10.1371/journal.pone.0201369. eCollection 2018.

Abstract

Ferroptosis is a form of programmed cell death associated with inflammation, neurodegeneration, and ischemia. Vitamin E (alpha-tocopherol) has been reported to prevent ferroptosis, but the mechanism by which this occurs is controversial. To elucidate the biochemical mechanism of vitamin E activity, we systematically investigated the effects of its major vitamers and metabolites on lipid oxidation and ferroptosis in a striatal cell model. We found that a specific endogenous metabolite of vitamin E, alpha-tocopherol hydroquinone, was a dramatically more potent inhibitor of ferroptosis than its parent compound, and inhibits 15-lipoxygenase via reduction of the enzyme’s non-heme iron from its active Fe3+ state to an inactive Fe2+ state. Furthermore, a non-metabolizable isosteric analog of vitamin E which retains antioxidant activity neither inhibited 15-lipoxygenase nor prevented ferroptosis. These results call into question the prevailing model that vitamin E acts predominantly as a non-specific lipophilic antioxidant. We propose that, similar to the other lipophilic vitamins A, D and K, vitamin E is instead a pro-vitamin, with its quinone/hydroquinone metabolites responsible for its anti-ferroptotic cytoprotective activity.

Guan JZ, Guan WP, Maeda T

Can J Physiol Pharmacol. 2018 Aug 9. doi: 10.1139/cjpp-2018-0246. [Epub ahead of print]

Abstract

Systemic peroxidation status has been reported as a pathogenic factor for multiple sclerosis (MS). Systemically elevated oxidation levels are associated with serum lipid peroxidation and somatic telomere length (TL) shortening. We investigated whether vitamin E (VE) administration suppresses peroxidation and improves clinical symptoms in 34 MS patients. We analyzed serum lipid peroxidation and degree of TL in circulating leukocytes of MS patients before and after VE treatment. The oxidation level was enhanced and TL was shortened in MS. The MS population treated with VE 400 mg/day for 3 months showed significantly reduced serum lipid oxidation level with maintenance of TL. These findings showed that systemic peroxidation is associated with the development of MS. Antioxidants such as vitamin E can be candidates for supplementary therapeutic agents for MS.

Montagnani Marelli M, Marzagalli M, Fontana F, Raimondi M, Moretti RM, Limonta P

J Cell Physiol. 2018 Aug 1. doi: 10.1002/jcp.27075. [Epub ahead of print]

Abstract

Vitamin E is composed of two groups of compounds: α-, β-, γ-, and δ-tocopherols (TPs), and the corresponding unsaturated tocotrienols(TTs). TTs are found in natural sources such as red palm oil, annatto seeds, and rice bran. In the last decades, TTs (specifically, γ-TT and δ-TT) have gained interest due to their health benefits in chronic diseases, based on their antioxidant, neuroprotective, cholesterol-lowering, anti-inflammatory activities. Several in vitro and in vivo studies pointed out that TTs also exert a significant antitumor activity in a wide range of cancer cells. Specifically, TTs were shown to exert antiproliferative/proapoptotic effects and to reduce the metastatic or angiogenic properties of different cancer cells; moreover, these compounds were reported to specifically target the subpopulation of cancer stem cells, known to be deeply involved in the development of resistance to standard therapies. Interestingly, recent studies pointed out that TTs exert a synergistic antitumor effect on cancer cells when given in combination with either standard antitumor agents (i.e., chemotherapeutics, statins, “targeted” therapies) or natural compounds with anticancer activity (i.e., sesamin, epigallocatechin gallate (EGCG), resveratrol, ferulic acid). Based on these observations, different TT synthetic derivatives and formulations were recently developed and demonstrated to improve TT water solubility and to reduce TT metabolism in cancer cells, thus increasing their biological activity. These promising results, together with the safety of TT administration in healthy subjects, suggest that these compounds might represent a new chemopreventive or anticancer treatment (i.e., in combination with standard therapies) strategy. Clinical trials aimed at confirming this antitumor activity of TTs are needed.

Dong R, Yang Q, Zhang Y, Li J, Zhang L, Zhao H

Wei Sheng Yan Jiu. 2018 Jul;47(4):648-654.

Abstract

OBJECTIVE:

To systematically evaluate the levels of vitamin C, vitamin E and β-carotene in the plasma of Alzheimer’s disease( AD) patients.

METHODS:

In this study, literature of the levels of vitamin C, vitamin E and β-carotene in the plasma of AD patients were collected by retrieving the database of Pub Med, Science Direct, CNKI and Wan Fang( from they were built to July 2017).

RESULTS:

Meta-analysis result showed that, compared with the control group, the level of vitamin E in the plasma of AD patients declined significantly( SMD =-1. 49 μmol/L, 95% CI-2. 08–0. 89 μmol/L, P <0. 001). However, no differences were determined in the levels of the plasma vitamin C and β-carotene between the two groups( vitamin C: SMD =-1. 43 μmol/L, 95% CI-3. 05-0. 19 μmol/L, P = 0. 083; β-carotene: SMD =-0. 61 μmol/L, 95% CI-1. 40-0. 18 μmol/L, P = 0. 131).

CONCLUSION:

Increasing vitamin E level in the plasma through vitamin E riched diet may be useful to prevent AD. However it is not yet believed the benefical role on AD to increase vitamin C and β-carotene.

Chin KY, Tay SS

Nutrients. 2018 Jul 9;10(7). pii: E881. doi: 10.3390/nu10070881.

Abstract

Alzheimer’s disease (AD) is plaguing the aging population worldwide due to its tremendous health care and socioeconomic burden. Current treatment of AD only offers symptomatic relief to patients. Development of agents targeting specific pathologies of AD is very slow. Tocotrienol, a member of the vitamin E family, can tackle many aspects of AD, such as oxidative stress, mitochondrial dysfunction and abnormal cholesterol synthesis. This review summarizes the current evidence on the role of tocotrienol as a neuroprotective agent. Preclinical studies showed that tocotrienol could reduce oxidative stress by acting as a free-radical scavenger and promoter of mitochondrial function and cellular repair. It also prevented glutamate-induced neurotoxicity in the cells. Human epidemiological studies showed a significant inverse relationship between tocotrienol levels and the occurrence of AD. However, there is no clinical trial to support the claim that tocotrienol can delay or prevent the onset of AD. As a conclusion, tocotrienol has the potential to be developed as an AD-preventing agent but further studies are required to validate its efficacy in humans.

Sharma A, Kshetrimayum C, Sadhu HG, Kumar S

Environ Sci Pollut Res Int. 2018 Jun 8. doi: 10.1007/s11356-018-2398-z. [Epub ahead of print]

Abstract

Arsenic toxicity becomes one of the major public health issues in several countries. Chronic and acute exposure to arsenic has been reported to be toxic to various systems of the human body and also observed in controlled experimental studies. The study was conducted to evaluate the neurotoxic effect of arsenic in Swiss albino mice and its amelioration by Vitamin E, Coenzyme Q10 and their combination. Swiss albino mice were treated with arsenic of 136 ppm for 15 days. The daily dose is 1/3 of LD 50 (acute) reported dose of arsenic. Thereafter, the animals were maintained either on drinking water or treated with Vitamin E (50 mg/kg bwt), Coenzyme Q10 (10 mg/kg bwt), and their combination by i.p.daily for 15 days. After the treatment, animals were sacrificed. The weight of the brain was marginally lower (ns), in arsenic-treated group as compared to control and antioxidant-protected groups. The LPO (lipid peroxidation) level was higher in arsenic-treated group, and this elevation was checked to some extent by the selected antioxidants which were statistically significant in combination of antioxidant-protected group. A significant reduction was found in GSH (reduced glutathione) level in the brain of arsenic-treated mice whereas GSH level was considerably higher in antioxidant-protected groups. Further, total thiol and total protein level were lower in arsenic-treated group. However, total thiol was significantly higher in antioxidant-protected groups. CAT (catalase) activity was significantly lower while SOD (superoxide dismutase) activity was marginally lowered in arsenic-treated group, and it was slightly higher in antioxidant-protected groups. Further, reduction in AChE (acetylcholinesterase) and BChE (butyrylcholinesterase) and motor coordination activity were also observed in arsenic-treated groups. Whereas, a higher AChE, BChE, and motor coordination activity was observed in antioxidant-protected group. These data indicate a positive role of selected antioxidant against the toxicity of arsenic in the brain of mice.

Jamilian M, Shojaei A, Samimi M, Afshar Ebrahimi F, Aghadavod E, Karamali M, Taghizadeh M, Jamilian H, Alaeinasab S, Jafarnejad S, Asemi Z

J Affect Disord. 2018 Mar 15;229:41-47. doi: 10.1016/j.jad.2017.12.049. Epub 2017 Dec 28.

Abstract

OBJECTIVE:

The aim of this study was to evaluate the effects of omega-3 and vitamin E co-supplementation on parameters of mental health and gene expression related to insulin and inflammation in subjects with polycystic ovary syndrome (PCOS).

METHODS:

Forty PCOS women were allocated into two groups and treated with 1000mg omega-3 fatty acids plus 400 IU vitamin Esupplements (n = 20) or placebo (n = 20) per day for 12 weeks. Parameters of mental health were recorded at baseline and after the 12-week intervention. Gene expression related to insulin and inflammation were measured in blood samples of PCOS women.

RESULTS:

After the 12-week intervention, compared with the placebo, omega-3 and vitamin E co-supplementation led to significant improvements in beck depression inventory total score (- 2.2 ± 2.0 vs. – 0.2 ± 1.3, P = 0.001), general health questionnaire scores (- 5.5 ± 4.6 vs. – 1.0 ± 2.3, P < 0.001) and depression anxiety and stress scale scores (- 7.2 ± 5.2 vs. – 1.3 ± 1.3, P < 0.001). Compared with the placebo, omega-3 and vitamin E co-supplementation could up-regulate peroxisome proliferator-activated receptor gamma (PPAR-γ) expression (P = 0.04) in peripheral blood mononuclear cells (PBMC) of PCOS women. In addition, compared with the placebo, omega-3 and vitamin E co-supplementation down-regulated interleukin-8 (IL-8) (P = 0.003) and tumor necrosis factor alpha (TNF-α) expression (P = 0.001) in PBMC of PCOS women. There were no significant difference between-group changes in glucose transporter 1 (GLUT-1), IL-6 and transforming growth factor beta (TGF-β) in PBMC of PCOS women.

CONCLUSION:

Omega-3 and vitamin E co-supplementation was effective in improving parameters of mental health, and gene expression of PPAR-γ, IL-8 and TNF-α of women with PCOS.

Abubakar IB, Lim SW, Loh HS.

Trop Life Sci Res. 2018 Mar;29(1):229-238. doi: 10.21315/tlsr2018.29.1.15. Epub 2018 Mar 2.

Abstract

Kajian terbaru mencadangkan bahawa pendekatan gabungan rawatan boleh digunakan untuk meningkatkan potensi antikanser dan menghindari batasan pemberian tocotrienol dos tinggi. Acalypha wilkesiana adalah tumbuhan ubatan yang telah digunakan sebagai rawatan tambahan untuk kanser dalam perubatan tradisional. Di sini, kesan rawatan tunggal dan gabungan β-, γ-dan δ-tocotrienols dan ekstrak etil asetat (9EA) daripada Acalypha wilkesiana pada paru-paru (A549) dan sel-sel kanser otak (U87MG) telah disiasat. γ-dan δ-tocotrienols menunjukkan kesan antiproliferatif yang lebih tinggi terhadap A549 (12.1 μg/ml dan 13.6 μg/ml) dan sel U87MG (3.3 μg/ml dan 5.2 μg/ml) berbanding β-tocotrienols (9.4 μg/ml), masing-masing. Sedangkan, 9EA merangsang kesan antiproliferatif yang kuat terhadap sel U87MG sahaja (2.0 μg/ml). Rawatan terapi tocotrienols dan 9EA mencetuskan perencatan pertumbuhan sinergis sehingga pengurangan 8.4 kali ganda dalam dos yang kuat dari β-, γ-dan δ-tocotrienols pada sel A549. Ciri-ciri apoptotik juga dibuktikan pada sel-sel A549 yang menerima rawatan tunggal dan gabungan. Sinergi ini boleh meningkatkan hasil terapeutik untuk kanser paru-paru.

Recent studies suggested that combined treatment approaches can be used to improve anticancer potency and circumvent the limitations of high-dose tocotrienols administration. Acalypha wilkesiana is a medicinal plant that has been used as an adjunct treatment for cancers in traditional medicine. Herein, the effects of single and combined treatments of β-, γ- and δ-tocotrienols and ethyl acetate extract (9EA) of Acalypha wilkesiana on lung (A549) and brain (U87MG) cancer cells were investigated. γ- and δ-tocotrienols exhibited higher potent antiproliferative effects against A549 (12.1 μg/ml and 13.6 μg/ml) and U87MG cells (3.3 μg/ml and 5.2 μg/ml) compared to β-tocotrienols (9.4 μg/ml and 92.4 μg/ml), respectively. Whereas, 9EA induced potent antiproliferative effects against U87MG cells only (2.0 μg/ml). Combined treatments of tocotrienols and 9EA induced a synergistic growth inhibition with up to 8.4-fold reduction in potent doses of β-, γ- and δ-tocotrienols on A549 cells. Apoptotic features were also evidenced on A549 cells receiving single and combined treatments. The synergism may greatly improve the therapeutic outcome for lung cancer.

KEYWORDS:

Acalypha wilkesiana; Apoptosis; Synergism; Tocotrienol

Kumar MR, Reddy GR

Hum Exp Toxicol. 2018 Mar;37(3):295-308. doi: 10.1177/0960327117698540. Epub 2017 Mar 23.

Abstract

This study was planned to determine arsenic (As) (10 mg/kg body weight given through oral gavage) induced behavioral and cholinergic perturbations in three different age groups of rats; young (postnatal day 21), adult (3 months), and aged (18 months) at 7 days post-acute exposure ( n = 6 for each of the four groups of all three age points). Further, we also evaluated the ameliorative effect of essential metal zinc (Zn; 0.02% through drinking water) and an antioxidant, α-tocopherol (vitamin E; 125 mg/kg body weight through oral gavage) against As-induced neurotoxicity. As exposure showed significant alterations in behavioral functions (open-field behavior, total locomotor activity, grip strength, exploratory behavior, and water maze learning). Cholinergic studies in three brain regions (cerebral cortex, cerebellum, and hippocampus) of different age groups also showed significant increase in acetylcholine levels and a decrease in acetylcholinesterase activity. These effects were more pronounced in hippocampus followed by cerebral cortex and cerebellum. Among the three different age points, aged animals were found to be more vulnerable to the As-induced toxicity as compared to young and adult animals suggesting that As neurotoxicity is age dependent. These As-induced alterations were significantly reversed following supplementation with Zn or vitamin E. However, vitamin E was found to elicit greater protection as compared to Zn in restoring the altered behavioral and cholinergic perturbations, providing evidence for As-induced oxidative damage.