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International Journal of Molecular... 2012The life of any living organism can be defined as a hurdle due to different kind of stresses. As with all living organisms, plants are exposed to various abiotic... (Review)
Review
The life of any living organism can be defined as a hurdle due to different kind of stresses. As with all living organisms, plants are exposed to various abiotic stresses, such as drought, salinity, extreme temperatures and chemical toxicity. These primary stresses are often interconnected, and lead to the overproduction of reactive oxygen species (ROS) in plants, which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA, which ultimately results in oxidative stress. Stress-induced ROS accumulation is counteracted by enzymatic antioxidant systems and non-enzymatic low molecular weight metabolites, such as ascorbate, glutathione and α-tocopherol. The above mentioned low molecular weight antioxidants are also capable of chelating metal ions, reducing thus their catalytic activity to form ROS and also scavenge them. Hence, in plant cells, this triad of low molecular weight antioxidants (ascorbate, glutathione and α-tocopherol) form an important part of abiotic stress response. In this work we are presenting a review of abiotic stress responses connected to these antioxidants.
Topics: Adaptation, Physiological; Antioxidants; Ascorbic Acid; DNA Damage; DNA, Plant; Glutathione; Oxidative Stress; Plant Cells; Plants; Reactive Oxygen Species; alpha-Tocopherol
PubMed: 22605990
DOI: 10.3390/ijms13044458 -
European Journal of Clinical Nutrition Aug 2005The bioavailability of gamma-tocopherol and metabolites of vitamin E after gamma-tocopherol administration is not well understood. We investigated the effect of...
BACKGROUND
The bioavailability of gamma-tocopherol and metabolites of vitamin E after gamma-tocopherol administration is not well understood. We investigated the effect of gamma-tocopherol administration on the levels and metabolism of alpha- and gamma-tocopherol in healthy volunteers.
METHODS
We measured two metabolites of vitamin E (2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC) and 2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC)) in plasma and urine by high-performance liquid chromatography with electrochemical detection (HPLC-ECD) during administration of gamma-tocopherol. Two groups of volunteers were enrolled. The gamma-tocopherol group received two gamma-tocopherol capsules (each containing 186.4 mg of gamma-tocopherol and 5 mg of alpha-tocopherol) for 28 days, while the control group received d-alpha-tocopherol at 5 mg/day, which was the same dose as that given to the gamma-tocopherol group. Blood and urine samples were obtained on days 0, 14, 28, 35, 42, and 56 after the initiation of gamma-tocopherol administration.
RESULTS
The plasma gamma-tocopherol concentration increased markedly during administration of gamma-tocopherol and the plasma gamma-CEHC concentration increased along with that of gamma-tocopherol. The plasma alpha-tocopherol concentration decreased significantly during gamma-tocopherol administration. The plasma concentration of alpha-CEHC decreased significantly and urinary excretion of alpha-CEHC tended to increase in the gamma-tocopherol group. Urinary sodium secretion was significantly increased at 1 week after the cessation of gamma-tocopherol administration, but there was no significant difference of urine volume between the two groups.
CONCLUSION
Metabolism of alpha-tocopherol is accelerated and the plasma alpha-tocopherol concentration is decreased during gamma-tocopherol administration.
Topics: Adult; Antioxidants; Biological Availability; Chromans; Chromatography, High Pressure Liquid; Humans; Male; Propionates; Sodium; Vitamin E; alpha-Tocopherol; gamma-Tocopherol
PubMed: 15928686
DOI: 10.1038/sj.ejcn.1602154 -
Nature Plants Aug 2023The heart of oxygenic photosynthesis is the water-splitting photosystem II (PSII), which forms supercomplexes with a variable amount of peripheral trimeric...
The heart of oxygenic photosynthesis is the water-splitting photosystem II (PSII), which forms supercomplexes with a variable amount of peripheral trimeric light-harvesting complexes (LHCII). Our knowledge of the structure of green plant PSII supercomplex is based on findings obtained from several representatives of green algae and flowering plants; however, data from a non-flowering plant are currently missing. Here we report a cryo-electron microscopy structure of PSII supercomplex from spruce, a representative of non-flowering land plants, at 2.8 Å resolution. Compared with flowering plants, PSII supercomplex in spruce contains an additional Ycf12 subunit, Lhcb4 protein is replaced by Lhcb8, and trimeric LHCII is present as a homotrimer of Lhcb1. Unexpectedly, we have found α-tocopherol (α-Toc)/α-tocopherolquinone (α-TQ) at the boundary between the LHCII trimer and the inner antenna CP43. The molecule of α-Toc/α-TQ is located close to chlorophyll a614 of one of the Lhcb1 proteins and its chromanol/quinone head is exposed to the thylakoid lumen. The position of α-Toc in PSII supercomplex makes it an ideal candidate for the sensor of excessive light, as α-Toc can be oxidized to α-TQ by high-light-induced singlet oxygen at low lumenal pH. The molecule of α-TQ appears to shift slightly into the PSII supercomplex, which could trigger important structure-functional modifications in PSII supercomplex. Inspection of the previously reported cryo-electron microscopy maps of PSII supercomplexes indicates that α-Toc/α-TQ can be present at the same site also in PSII supercomplexes from flowering plants, but its identification in the previous studies has been hindered by insufficient resolution.
Topics: Photosystem II Protein Complex; Cryoelectron Microscopy; alpha-Tocopherol; Thylakoids; Photosynthesis; Plants
PubMed: 37550369
DOI: 10.1038/s41477-023-01483-0 -
Journal of Plant Physiology Jul 2005Environmental stresses trigger a wide variety of plant responses, ranging from altered gene expression to changes in cellular metabolism and growth. A plethora of plant... (Review)
Review
Environmental stresses trigger a wide variety of plant responses, ranging from altered gene expression to changes in cellular metabolism and growth. A plethora of plant reactions exist to circumvent the potentially harmful effects caused by light, drought, salinity, extreme temperatures, pathogen infections and other stresses. Alpha-tocopherol is the major vitamin E compound found in leaf chloroplasts, where it is located in the chloroplast envelope, thylakoid membranes and plastoglobuli. This antioxidant deactivates photosynthesis-derived reactive oxygen species (mainly 1O2 and OH), and prevents the propagation of lipid peroxidation by scavenging lipid peroxyl radicals in thylakoid membranes. Alpha-tocopherol levels change differentially in response to environmental constraints, depending on the magnitude of the stress and species-sensitivity to stress. Changes in alpha-tocopherol levels result from altered expression of pathway-related genes, degradation and recycling, and it is generally assumed that increases of alpha-tocopherol contribute to plant stress tolerance, while decreased levels favor oxidative damage. Recent studies indicate that compensatory mechanisms exist to afford adequate protection to the photosynthetic apparatus in the absence of alpha-tocopherol, and provide further evidence that it is the whole set of antioxidant defenses (ascorbate, glutathione, carotenoids, tocopherols and other isoprenoids, flavonoids and enzymatic antioxidants) rather than a single antioxidant, which helps plants to withstand environmental stress.
Topics: Antioxidants; Environment; Oxidative Stress; Plants; alpha-Tocopherol
PubMed: 16008098
DOI: 10.1016/j.jplph.2005.04.022 -
The Journal of Nutrition Oct 2015Studies examining vitamin E intake and the percentage of the population meeting dietary guidelines do not distinguish between natural (RRR-α-tocopherol) and synthetic...
BACKGROUND
Studies examining vitamin E intake and the percentage of the population meeting dietary guidelines do not distinguish between natural (RRR-α-tocopherol) and synthetic (all-rac-α-tocopherol) intake, even though these different isomeric forms differ in bioactivity.
OBJECTIVE
This study aimed to determine the effect of RRR-α-tocopherol vs. all-rac-α-tocopherol intake on the percentage of the population meeting the vitamin E recommendation and on plasma α-tocopherol stereoisomer distribution.
METHODS
With the use of data from the Irish National Adult Nutrition Survey (NANS), this study examined the percentage of the Irish population meeting the European Union (EU) RDA for vitamin E of 12 mg/d, correcting for a bioactivity difference in all-rac- vs. RRR-α-tocopherol, where 1 mg of all-rac-α-tocopherol is considered to be equivalent to 1:1.36 (0.74) mg in the EU RDA. In a subcohort of supplement users and nonusers, plasma α- and γ-tocopherol concentrations and α-tocopherol stereoisomer distribution were measured. Receiver operating characteristic (ROC) curve analysis was conducted to determine ability to discriminate supplement user types.
RESULTS
Analysis of the NANS showed that 100% of participants still met the recommended intake of 12 mg/d, after all-rac-α-tocopherol intake was corrected for α-tocopherol equivalent bioactivity. In the subcohort analysis, the percentage of plasma RRR-α-tocopherol was significantly lower in high all-rac-α-tocopherol supplement (>11 mg/d) users (82%) compared with nonusers and with high RRR-α-tocopherol supplement (>35 mg/d) users (91% and 93% respectively, P < 0.01). High RRR-α-tocopherol supplement users had a significantly higher plasma α-tocopherol than low all-rac-α-tocopherol supplement (<2.5 mg/d) users (34 vs. 25 μmol/L, P = 0.01). ROC analysis demonstrated an ability to distinguish between RRR- and all-rac-α-tocopherol consumers, which may be useful in investigating the potential effect of RRR- and all-rac-α-tocopherol intake on health.
CONCLUSIONS
This study demonstrated that the percentage of the population meeting the vitamin E recommendation was unaffected when all-rac-α-tocopherol intake was corrected for α-tocopherol equivalent bioactivity. all-rac-α-Tocopherol intake led to a decrease in the percentage of plasma RRR-α-tocopherol relative to RRR-α-tocopherol intake.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Cohort Studies; Cross-Sectional Studies; Diet; Dietary Supplements; European Union; Female; Humans; Ireland; Male; Middle Aged; Nutrition Surveys; Nutritive Value; Patient Compliance; ROC Curve; Recommended Dietary Allowances; Stereoisomerism; Vitamin E; Young Adult; alpha-Tocopherol; gamma-Tocopherol
PubMed: 26290004
DOI: 10.3945/jn.115.213280 -
Food Chemistry Apr 2017α-Tocopherol-loaded niosome was developed using modified heating method. The influence of surfactants (Span60 and Tween60) in different mole ratios, presence or absence...
α-Tocopherol-loaded niosome was developed using modified heating method. The influence of surfactants (Span60 and Tween60) in different mole ratios, presence or absence of cholesterol (Chol) and dicetyl phosphate (DCP) as well as different concentration of α-tocopherol (α-TOC) on mean size, polydispersity index, zeta potential and entrapment efficiency (EE) was evaluated. The results showed that α-TOC loaded niosomes exhibited a small mean size (73.85±0.6-186±0.58nm), narrow size distribution and high EE (61.13±0.52-98.92±0.92). By decreasing the HLB, the EE and stability of the niosomes increased. The DCP and Chol improved the physicochemical properties of niosomes. 3:1 mole ratio of Span 60:Tween 60, 4mg/ml of α-TOC and 25:12.5:2.5 mole ratio of surfactant:Chol:DCP was the optimum formulation in the encapsulation of α-TOC applying niosome system. The niosomes had sustained release profile in the simulated gastric and intestinal fluid.
Topics: Heating; Liposomes; alpha-Tocopherol
PubMed: 27979250
DOI: 10.1016/j.foodchem.2016.11.129 -
Journal of the College of Physicians... Jul 2023To evaluate the histomorphological response of alpha-tocopherol co-administration with carboplatin chemotherapy.
OBJECTIVE
To evaluate the histomorphological response of alpha-tocopherol co-administration with carboplatin chemotherapy.
STUDY DESIGN
A laboratory-based experimental study. Place and Duration of the Study: Anatomy Department, Army Medical College / National University of Medical Sciences (NUMS), Rawalpindi, Pakistan, from January to December 2021.
METHODOLOGY
Thirty adult Sprague-Dawley rats were divided into three groups of ten rats each. Control group A received normal diet and water, experimental group B was administered single injection of carboplatin 2.5 mg/Kg intraperitoneally; and experimental group C along with carboplatin injection also received alpha-tocopherol 62.7 mg/Kg daily. At the end of 12 weeks, the euthanasia of animals was done and kidneys were dissected out. Right-sided kidneys were stained with Haematoxylin and Eosin. Micrometry was done to measure the diameters of renal cortical tubules and renal corpuscles.
RESULTS
The proximal and distal tubular and luminal diameter and transvertical diameter of renal corpuscle were increased in group B as compared to control group A. In group C, the proximal and distal tubular diameters were 5.175 ± 0.39 µm and 3.88 ± 0.364 µm, respectively; proximal and distal luminal diameters were 2.67 ± 0.35 µm and 1.64 ± 0.24 µm, respectively and transvertical diameter of renal corpuscle was 12.16 ± 0.870 µm. These values were less than experimental group B and closer to that of control group A.
CONCLUSION
Renal microscopic parameters showed improvement in the group administered with alpha-tocopherol. Therefore, alpha-tocopherol has ameliorative effects on carboplatin-induced renal damage.
KEY WORDS
Alpha-tocopherol, Carboplatin, Renal corpuscle, Tubules.
Topics: Rats; Animals; alpha-Tocopherol; Carboplatin; Rats, Sprague-Dawley; Kidney; Antioxidants
PubMed: 37401209
DOI: 10.29271/jcpsp.2023.07.722 -
International Journal of Pharmaceutics Feb 2021Vitamin E (alpha tocopherol, α-T) is an important skin antioxidant, but its penetration into the viable epidermis, where it acts, is very limited. This study...
Vitamin E (alpha tocopherol, α-T) is an important skin antioxidant, but its penetration into the viable epidermis, where it acts, is very limited. This study investigated if phosphorylating α-tocopherol (α-TP) to form a provitamin, improved its interactions with skin, its passage into the tissue, and thus its ability to protect the skin from ultraviolet radiation (UVR) damage. At pH 7.4, when the α-TPO microspecies predominated in solution, dynamic light scattering measurements showed that α-TP formed nanoaggregates with a median hydrodynamic diameter of 9 nm (Critical aggregation constant, CAC, - 4.2 mM). At 9.0 when the α-TPO microspecies predominated there was no aggregation. The passage of α-TP nanoaggregates through regenerated cellulose membranes was significantly slower than the α-TP monomers (at pH 9) suggesting that aggregation slowed diffusion. However, a lotion formulation containing the nanoaggregates delivered more α-TP into the skin compared to the formulation containing the monomers. In addition, the nanosized α-TP aggregates delivered 8-fold more active into the stratum corneum (SC) (252.2 μg/cm vs 29.5 μg/cm) and 4 fold more active into the epidermis (85.1 μg/cm vs 19 μg/cm, respectively, p < 0.05) compared to α-T. Langmuir subphase injection studies at pH 7.4 (surface pressure 10 mN m) showed that the α-TP nanoaggregates more readily fused with the SC compared to the monomers and the membrane compression studies demonstrated that α-TP fluidised the SC lipids. Together the fusion with the SC and its fluidisation were proposed as the causes of the better α-TP penetration into the skin, which enhanced potential of α-TP to protect from UVR-induced skin damage compared to α-T.
Topics: Epidermis; Nanostructures; Skin; Ultraviolet Rays; alpha-Tocopherol
PubMed: 33166585
DOI: 10.1016/j.ijpharm.2020.120000 -
Free Radical Research Jun 2002alpha-Tocopherol is a lipophilic vitamin that exhibits an antioxidative activity. The purpose of this study was to clarify the roles of alpha-tocopherol in the...
alpha-Tocopherol is a lipophilic vitamin that exhibits an antioxidative activity. The purpose of this study was to clarify the roles of alpha-tocopherol in the regulation of intracellular glutathione (GSH) levels in HaCaT keratinocytes. When HaCaT keratinocytes were cultivated with alpha-tocopherol for 24 h, the intracellular GSH was increased at every concentration of alpha-tocopherol tested. Furthermore, the HaCaT keratinocytes cultured with alpha-tocopherol at 50 microM for 24 h exhibited resistance against H2O2. However, a short exposure of HaCaT keratinocytes to alpha-tocopherol for 1 h did not influence either the GSH level or the resistance to H2O2. These findings suggest that GSH, which is inductively synthesized by alpha-tocopherol, effectively reduces exogenous oxidative stress. To evaluate the effect of alpha-tocopherol on the GSH level, BSO, which is a typical inhibitor of gamma-glutamylcysteine synthetase (gamma-GCS), was used. When BSO was added to HaCaT keratinocytes, no action of alpha-tocopherol on the GSH level was observed. On the other hand, alpha-tocopherol resulted in the up-regulation of gamma-GCS-HS (heavy subunit) mRNA. In addition, water soluble alpha-tocopherol derivatives (alpha-tocopherol phosphate and trolox) caused no changes in GSH level. From these results, it was concluded that alpha-tocopherol increases the intracellular GSH level of HaCaT keratinocytes through the up-regulation of gamma-GCS-HS mRNA.
Topics: Antioxidants; Buthionine Sulfoximine; Cells, Cultured; Chromans; Enzyme Inhibitors; Glutamate-Cysteine Ligase; Glutathione; Humans; Keratinocytes; RNA, Messenger; Up-Regulation; alpha-Tocopherol
PubMed: 12180196
DOI: 10.1080/10715760210873 -
Free Radical Biology & Medicine Nov 2011α-Tocopherol (α-TOH), a dietary component of vitamin E, is well known for its antioxidant capacity. Nevertheless, recent studies have pointed out non-anti-radical...
α-Tocopherol (α-TOH), a dietary component of vitamin E, is well known for its antioxidant capacity. Nevertheless, recent studies have pointed out non-anti-radical properties including cellular and genomic actions. Decreased levels of α-tocopherol in the brain are associated with neuronal dysfunctions ranging from mood disorders to neurodegeneration. All these behavioral effects of α-tocopherol deficiency probably do not rely simply on its anti-radical properties, but could also be reminiscent of a not-yet characterized neuromodulatory action. We have thus measured the direct actions of α-tocopherol and of its natural phosphate derivative, α-tocopheryl phosphate (α-TP), on synaptic transmission in rodent hippocampus. These compounds had opposite actions on both glutamatergic and GABAergic transmission: whereas α-TOH potentiated these transmissions, α-TP inhibited them. Interestingly, these effects were both mediated by cannabinoid receptors (CB1Rs), because they were blocked by the CB1R antagonist AM251. Although α-tocopherol and α-tocopheryl phosphate did not directly bind CB1R, both α-TP and CB1R agonists inhibited forskolin-evoked Erk1/2 phosphorylation in a nonadditive manner. Furthermore, both α-tocopherol and α-tocopheryl phosphate attenuated depolarization-induced suppression of excitation and CB1R agonist-mediated hypothermia. Therefore, we identify α-tocopherol as new lipid modulator of the cannabinoid system in the rodent hippocampus, i.e., a novel "non-anti-radical" action of vitamin E, which may have some preeminent impact in neuronal disorders associated with vitamin E deficiency.
Topics: Animals; Antioxidants; Cannabinoid Receptor Agonists; Cannabinoids; Cells, Cultured; Hippocampus; Neurons; Rats; Receptors, Cannabinoid; alpha-Tocopherol
PubMed: 21843633
DOI: 10.1016/j.freeradbiomed.2011.07.012