Vitamin E activates CRABP-II gene expression in cultured human fibroblasts, role of protein kinase C

α-Tocopherol Stereoisomer Profiles in Matched Human Maternal and Umbilical Cord Plasma

BACKGROUND

α-Tocopherol (αT) is essential for fetal development. One study has shown that the human placenta preferentially transfers the natural stereoisomer, RRR-αT. But prenatal supplements generally contain synthetic αT (S-αT).

OBJECTIVES

We aimed to determine if umbilical cord plasma is enriched for RRR-αT in racially diverse neonates from both uncomplicated and complicated pregnancies and if cord RRR-αT enrichment is impacted by maternal αT stereoisomer profile.

METHODS

We measured αT and αT stereoisomers in plasma from a randomly selected subset of 66 predominantly black and Hispanic maternal-fetal pairs from the Camden Study involving control (n = 28) and complicated pregnancies (n = 38). We collected maternal plasma at study entry (week 16 gestation; w16) and week 28 gestation (w28) and cord plasma at birth.

RESULTS

RRR-αT was the predominant stereoisomer in all maternal and cord plasma samples, but S-αT stereoisomers were found in most samples and comprised a high percentage of αT in some maternal-neonate pairs. Cord plasma had a higher percentage RRR-αT (P < 0.05) and lower percentage S-αT (P < 0.0001) than w28 plasma. Pregnancy status did not impact maternal or cord plasma concentrations of αT, RRR-αT, or S-αT; except plasma from complicated pregnancies was higher in S-αT at w28 than at w16 (P < 0.05). Maternal w28 αT did not correlate with cord αT. However, both maternal w28 αT and S-αT positively correlated with both cord S-αT (r = 0.340, P = 0.0049; r = 0.538, P < 0.00001) and percentage S-αT (r = 0.399, P = 0.001; r = 0.786, P < 0.00001) but negatively correlated with cord percentage RRR-αT (r = -0.399, P = 0.0009; r = -0.786, P < 0.00001).

CONCLUSIONS

The proportion of RRR-αT was higher in cord compared with maternal plasma in both uncomplicated and complicated pregnancies. Our data suggest that maternal S-αT raises cord S-αT and decreases the proportion of RRR-αT in the neonatal circulation. Because the bioactivities of RRR-αT and S-αT differ, this warrants future research to determine the importance of our observations to neonatal αT status.

Vitamin A Deficiency and the Lung

Vitamin A (all-trans-retinol) is a fat-soluble micronutrient which together with its natural derivatives and synthetic analogues constitutes the group of retinoids. They are involved in a wide range of physiological processes such as embryonic development, vision, immunity and cellular differentiation and proliferation. Retinoic acid (RA) is the main active form of vitamin A and multiple genes respond to RA signalling through transcriptional and non-transcriptional mechanisms. Vitamin A deficiency (VAD) is a remarkable public health problem. An adequate vitamin A intake is required in early lung development, alveolar formation, tissue maintenance and regeneration. In fact, chronic VAD has been associated with histopathological changes in the pulmonary epithelial lining that disrupt the normal lung physiology predisposing to severe tissue dysfunction and respiratory diseases. In addition, there are important alterations of the structure and composition of extracellular matrix with thickening of the alveolar basement membrane and ectopic deposition of collagen I. In this review, we show our recent findings on the modification of cell-junction proteins in VAD lungs, summarize up-to-date information related to the effects of chronic VAD in the impairment of lung physiology and pulmonary disease which represent a major global health problem and provide an overview of possible pathways involved.

In vitro comparison between α-tocopheryl acetate and α-tocopheryl phosphate against bacteria responsible of prosthetic and joint infections

Biofilm-related infections represent a recurrent problem in the orthopaedic setting. In recent years, great interest was directed towards the identification of novel molecules capable to interfere with pathogens adhesion and biofilm formation on implant surfaces. In this study, two stable forms of α-tocopherol, the hydrophobic acetate ester and the water-soluble phosphate ester, were tested in vitro as coating for titanium prosthesis. Antimicrobial activity against microorganisms responsible of prosthetic and joints infections was assessed by broth microdilution method. In addition, α-tocopherol esters were evaluated for both their ability to hamper bacterial adhesion to and biofilm formation on sandblasted titanium surfaces. Results showed that only α-tocopheryl phosphate displayed antimicrobial activity against the tested strains. Both esters were able to significantly interfere with bacterial adhesion and to prevent biofilm formation, especially by Staphylococcus aureus and Staphylococcus epidermidis. The activity of α-tocopheryl phosphate was greater than that of α-tocopheryl acetate. Alterations at membrane levels have been reported in literature and may be likely responsible for the interference on bacterial adhesion and biofilm formation shown by α-tocopherol esters. Although further studies are needed to better investigate the mechanisms of action and the spectrum of activity of α-tocopherol esters, these characteristics together with the positive effect on wound healing and immune response, make these molecules promising candidate for coating in order to prevent implant-associated infections.

Protective role of vitamin E preconditioning of human dermal fibroblasts against thermal stress in vitro

AIMS

Oxidative microenvironment of burnt skin restricts the outcome of cell based therapies of thermal skin injuries. The aim of this study was to precondition human dermal fibroblasts with an antioxidant such as vitamin E to improve their survival and therapeutic abilities in heat induced oxidative in vitro environment.

MAIN METHODS

Fibroblasts were treated with 100μM vitamin E for 24h at 37°C followed by heat shock for 10min at 51°C in fresh serum free medium.

KEY FINDINGS

Preconditioning with vitamin E reduced cell injury as demonstrated by decreased expression of annexin-V, cytochrome p450 (CYP450) mediated oxidative reactions, senescence and release of lactate dehydrogenase (LDH) accomplished by down-regulated expression of pro-apoptotic BAX gene. Vitamin E preconditioned cells exhibited remarkable improvement in cell viability, release of paracrine factors such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), stromal derived factor-1alpha (SDF-1α) and also showed significantly up-regulated levels of PCNA, VEGF, BCL-XL, FGF7, FGF23, FLNβ and Col7α genes presumably through activation of phosphatidylinositol 3-kinase (PI3-K)/Akt pathway.

SIGNIFICANCE

The results suggest that pretreatment of fibroblasts with vitamin E prior to transplantation in burnt skin speeds up the wound healing process by improving the antioxidant scavenging responses in oxidative environment of transplanted burn wounds.

Exposure of okadaic acid alters the angiogenesis in developing chick embryos

Okadaic acid (OA) is a common phycotoxin, which concerns diarrheic shellfish poisoning (DSP) in human being. It has been known that OA can induce disorganization in cytoskeletal architecture and cell-cell contact, cause chromosome loss, apoptosis, DNA damage and inhibit phosphatases, suggesting its potential embryotoxicity. In this paper, we found that low concentration of OA (50 nM, 100 nM and 200 nM) significantly reduced the density of vascular plexus in yolk-sac membrane (YSM) of chick embryo, while high concentration of OA (500 nM) distinctly depressed the blood vessel density in chorioallantoic membrane (CAM). After exposed to OA, MDA level and SOD activity increased significantly in CAM tissues. However, addition of vitamin C could rescue OA-suppressed angiogenesis in CAM of chick embryo. After exposure of OA, Ang-2 expression was down-regulated in CAM tissues. Taking together, we proposed that OA interfered with angiogenesis in developing chick embryo, through, at least partly, the induction of excessive ROS generation.

Vitamin E and wound healing: an evidence-based review

Vitamin E has been demonstrated to modulate cellular signalling, gene expression and affect wounds infected with methicillin-resistant Staphylococcus aureus (MRSA), thus influencing wound healing. This evidence-based review aimed to identify and evaluate current research assessing the properties of vitamin E in relation to wound healing, through its role as an antioxidant and its influence on connective tissue growth factor (CTGF), MRSA and gene transcription. Literature dated from 1996 to 2012, published in English, involving either animals or adult humans with an acute or chronic wound were included. The databases that contained relevant articles were narrowed down to four, and a total of 33 identified studies were included. The literature review revealed that there is a significant dearth of robust studies establishing the effects of vitamin E on wound healing, and further research is clearly warranted.

Retinaldehyde is a substrate for human aldo-keto reductases of the 1C subfamily

Human AKR (aldo-keto reductase) 1C proteins (AKR1C1-AKR1C4) exhibit relevant activity with steroids, regulating hormone signalling at the pre-receptor level. In the present study, investigate the activity of the four human AKR1C enzymes with retinol and retinaldehyde. All of the enzymes except AKR1C2 showed retinaldehyde reductase activity with low Km values (~1 μM). The kcat values were also low (0.18-0.6 min-1), except for AKR1C3 reduction of 9-cis-retinaldehyde whose kcat was remarkably higher (13 min-1). Structural modelling of the AKR1C complexes with 9-cis-retinaldehyde indicated a distinct conformation of Trp227, caused by changes in residue 226 that may contribute to the activity differences observed. This was partially supported by the kinetics of the AKR1C3 R226P mutant. Retinol/retinaldehyde conversion, combined with the use of the inhibitor flufenamic acid, indicated a relevant role for endogenous AKR1Cs in retinaldehyde reduction in MCF-7 breast cancer cells. Overexpression of AKR1C proteins depleted RA (retinoic acid) transactivation in HeLa cells treated with retinol. Thus AKR1Cs may decrease RA levels in vivo. Finally, by using lithocholic acid as an AKR1C3 inhibitor and UVI2024 as an RA receptor antagonist, we provide evidence that the pro-proliferative action of AKR1C3 in HL-60 cells involves the RA signalling pathway and that this is in part due to the retinaldehyde reductase activity of AKR1C3.

Induction of oxidative DNA damage by the marine toxin okadaic acid depends on human cell type

The marine toxin okadaic acid (OA) is the main representative of diarrhoeic shellfish poisoning (DSP) toxins. Its ingestion induces nausea, vomiting, diarrhoea and abdominal ache. It has also been found to trigger cellular and molecular effects at low concentrations. Its mechanism of action has not been described yet. Results of a previous study showed that OA can induce cytotoxic and genotoxic effects, both directly and indirectly, and modulations in DNA repair processes in three different types of human cells (leukocytes, SHSY5Y neuroblastoma and HepG2 cells). These effects varied depending on the type of cell and the concentration employed (Valdiglesias et al., 2010). On that basis, the ability of OA to induce oxidative DNA damage on the same cell types was investigated in the present study. To this end, the antioxidant enzymes catalase and N-acetylcysteine, and the human DNA- glycosylase hOGG1 were used in combination with the alkaline Comet assay. The cells were treated with a range of OA concentrations (5-1000 nM) in the presence and absence of S9 fraction. The results of this study showed that OA induces oxidative DNA damage directly in leukocytes, directly and indirectly in SHSY5Y cells, while it does not induce oxidative DNA damage in HepG2 cells. Combining the outcomes of both studies, the data showed that OA induces both cytotoxicity and genotoxicity, including DNA strand breaks and oxidative DNA damage, in the cells evaluated. However, the extent of these effects are cell type dependent.

Vitamin E: the shrew waiting to be tamed

Vitamin E is the last of all vitamins whose essentiality is not yet understood. Its widely accepted role as a lipophilic antioxidant has been questioned, since proof of its in vivo relevance remained scarce. The influence of vitamin E on biomarkers of oxidative stress in vivo is inconsistent and metabolites of vitamin E having reacted as an antioxidant are hardly detectable. Novel functions of vitamin E include the regulation of enzymes, most of which are membrane bound or activated by membrane recruitment. Also, expression of genes responds to vitamin E. The search for a transcription factor common to all regulated genes failed so far and a receptor that specifically binds vitamin E has not yet been identified. According to microarray data, pathways preferentially affected by the vitamin E status are the inflammatory response and cellular traffic. A role of vitamin E in cellular trafficking could best explain the neurological symptoms seen in vitamin E deficiency. Emerging knowledge on vitamin E is compiled here with the perspective to unravel the molecular mechanisms that could more likely explain the essentiality of the vitamin than its ability to scavenge free radicals.

Bioactivity of vitamin E

More than 80 years after the discovery of the essentiality of vitamin E for mammals, the molecular basis of its action is still an enigma. From the eight different forms of vitamin E, only α-tocopherol is retained in the body. This is in part due to the specific selection ofRRR-α-tocopherol by the α-tocopherol transfer protein and in part by its low rate of degradation and elimination compared with the other vitamers. Since the tocopherols have comparable antioxidant properties and some tocotrienols are even more effective in scavenging radicals, the antioxidant capacity cannot be the explanation for its essentiality, at least not the only one. In the last decade, a high number of so-called novel functions of almost all forms of vitamin E have been described, including regulation of cellular signalling and gene expression. α-Tocopherol appears to be most involved in gene regulation, whereas γ-tocopherol appears to be highly effective in preventing cancer-related processes. Tocotrienols appear to be effective in amelioration of neurodegeneration. Most of the novel functions of individual forms of vitamin E have been demonstratedin vitroonly and requirein vivoconfirmation. The distinct bioactivities of the various vitamers are discussed, considering their metabolism and the potential functions of metabolites.

Increased expression of transglutaminase-1 and PPARgamma after vitamin E treatment in human keratinocytes

In skin, vitamin E acts as the predominant lipophilic antioxidant with a protective function against irradiation and oxidative stress. In addition to that, vitamin E can also modulate signal transduction and gene expression. To study whether the four natural tocopherol analogues (alpha-, beta-, gamma-, delta-tocopherol) can influence transcriptional activity by modulating the activity of nuclear receptors, a human keratinocytes cell line (NCTC 2544) was transfected with plasmids containing the luciferase reporter gene under control by direct repeat elements (DR1-DR4), representing binding sites for four different classes of nuclear receptors. In this model, the tocopherols positively modulated only the reporter construct containing a consensus element for peroxisome proliferator-activated receptors (PPARs). The induction was strongest with gamma-tocopherol and was most likely the direct consequence of stimulation of PPARgamma protein expression in keratinocytes. Vitamin E treatment also led to increased expression of a known PPARgamma target gene involved in terminal keratinocytes differentiation, the transglutaminase-1.

Vitamins E and C pretreatment prevents ovariectomy-induced memory deficits in water maze

We investigated whether the pretreatment with vitamins E (alpha-tocopherol) and C (ascorbic acid) would act on ovariectomy-induced memory deficits in Morris water maze tasks. Adult female Wistar rats were divided into three groups: (1) naive (control), (2) sham (submitted to surgery without removal of ovaries) and (3) ovariectomized. Thirty days after surgery, they were trained in the Morris water maze in order to verify ovariectomy effects both on reference and working memory tasks. Results show that ovariectomized rats presented impairment in spatial navigation in the acquisition phase, as well as in the time spent in target quadrant and in the latency to cross over the location of the platform in test session, when compared to naive and sham groups (controls), in the reference memory task. Ovariectomy did not affect performance in the working memory task. Confirming our hypothesis, ovariectomized rats pretreated for 30 days with vitamins E and C had those impairments prevented. We conclude that ovariectomy significantly impairs spatial reference learning/memory and that pretreatment with vitamins E and C prevents such effect. Assuming this experimental memory impairment might mimic, at least in part, the cognitive deficit sometimes present in the human condition of lack of reproductive hormones, our findings lend support to a novel therapeutic strategy, based on vitamins E and C, to cognitive impairments in post-menopausal women.