CYP4F2 repression and a modified alpha-tocopherol (vitamin E) metabolism are two independent consequences of ethanol toxicity in human hepatocytes.

Russo A, Bartolini D, Torquato P, Giusepponi D, Barola C, Galarini R, Birringer M, Lorkowski S, Galli F.

Toxicol In Vitro. 2017 Apr;40:124-133. doi: 10.1016/j.tiv.2016.12.014. Epub 2017 Jan 3.

Abstract

The expression of CYP4F2, a form of cytochrome P-450 with proposed role in α-tocopherol and long-chain fatty acid metabolism, was explored in HepG2 and HepaRG human hepatocytes during ethanol toxicity. Cytotoxicity, ROS production, and JNK and ERK1/2 kinase signaling increased in a dose and time-dependent manner during ethanol treatments; CYP4F2 gene expression decreased, while other CYP4F forms, namely 4F11 and 12, increased along with 3A4 and 2E1 isoforms. α-Tocopherol antagonized the cytotoxicity and CYP4F2 gene repression effect of ethanol in HepG2 cells. Ethanol stimulated the tocopherol-ω-hydroxylase activity and the other steps of vitamin E metabolism, which points to a minor role of CYP4F2 in this metabolism of human hepatocytes. PPAR-γ and SREBP-1c followed the same expression pattern of CYP4F2 in response to ethanol and α-tocopherol treatments. Moreover, the pharmacological inhibition of PPAR-γ synergized with ethanol in decreasing CYP4F2 protein expression, which suggests a role of this nuclear receptor in CYP4F2 transcriptional regulation. In conclusion, ethanol toxicity modifies the CYP expression pattern of human hepatic cells impairing CYP4F2 transcription and protein expression. These changes were associated with a lowered expression of the fatty acid biosynthesis regulators PPAR-γ and SREBP-1c, and with an increased enzymatic catabolism of vitamin E. CYP4F2 gene repression and a sustained vitamin E metabolism appear to be independent effects of ethanol toxicity in human hepatocytes.

Banini BA, Sanyal AJ.

Curr Opin Gastroenterol. 2017 Mar 24. doi: 10.1097/MOG.0000000000000356. [Epub ahead of print]

Abstract

Nonalcoholic steatohepatitis (NASH), the aggressive form of nonalcoholic fatty liver disease (NAFLD), can progress to cirrhosis and hepatocellular cancer in 5-15% of patients and is rapidly becoming the leading cause for end-stage liver disease. Dietary caloric restriction and exercise, currently the cornerstone of therapy for NAFLD, can be difficult to achieve and maintain, underscoring the dire need for pharmacotherapy. This review presents the agents currently used in managing NAFLD and their pharmacologic targets. It also provides an overview of NAFLD agents currently under development. Therapies for NASH can be broadly classified into agents that target the metabolic perturbations driving disease pathogenesis (such as insulin resistance and de novo lipogenesis) and agents that target downstream processes including cell stress, apoptosis, inflammation, and fibrosis. Modulation of peroxisome proliferator-activator receptors, farnesoid-X-receptors, and the glucagon-like peptide 1 pathway have been shown to improve liver histology. The intestinal microbiome and metabolic endotoxemia are novel targets that are currently under review. Antioxidants such as vitamin E, and more recently anti-inflammatory agents such as apoptosis signal-regulating kinase 1 inhibitors show promise as therapy for NASH. Several antifibrotic agents including cysteine-cysteine motif chemokine receptor type 2 and type 5 antagonists have been shown to inhibit the progression of fibrosis toward cirrhosis. There are currently several agents in the drug pipeline for NASH. Within the next few years, the availability of therapeutic options for NAFLD will hopefully curb the rising trend of NAFLD-related end stage liver disease.

Fiorino S, Bacchi-Reggiani ML, Leandri P, Loggi E, Andreone P.

World J Hepatol. 2017 Feb 28;9(6):333-342. doi: 10.4254/wjh.v9.i6.333.

Abstract

To assess vitamin E efficacy, defined as its ability to induce hepatitis B e antigen (HBeAg) seroconversion, in children with HBeAg-positive persistent hepatitis. In July 2016, we extracted articles published in MEDLINE and the Cochrane Library using the following search terms: “chronic hepatitis B”, “children”, “childhood”, “therapy”, “treatment”, “vitamin E”, “tocopherols”, “tocotrienols“. Only randomized controlled trials (RCTs) published in English language were collected. Three RCTs met inclusion criteria and were considered in the present meta-analysis. Overall, 23/122 children in the treatment group underwent HBeAg seroconversion vs 3/74 in the control group (OR = 3.96, 95%CI: 1.18-13.25, P = 0.025). Although our meta-analysis has several limits, including the very small number of available studies and enrolled children with HBeAg positivity-related hepatitis, it suggests that vitamin E use may enhance the probability to induce HBeAg seroconversion in these patients. Further well designed and adequately sized trials are required to confirm or deny these very preliminary results.

Miguel FM, Schemitt EG, Colares JR, Hartmann RM, Morgan-Martins MI, Marroni NP.

Arq Gastroenterol. 2017 Feb 13:0. doi: 10.1590/S0004-2803.201700000-03. [Epub ahead of print]

Abstract

BACKGROUND:

Severe Acute Liver Failure (ALF) is a life-threatening clinical syndrome characterized by hepatocyte necrosis, loss of hepatic architecture, and impairment of liver functions. One of the main causes of ALF is hepatotoxicity from chemical agents, which damage hepatocytes and result in increase of reactive oxygen species. The vitamin E isoform is the one with the strongest biological antioxidant activity.

OBJECTIVE:

To evaluate the antioxidant effect of vitamin E in this ALF model.

METHODS:

We used 56 rats (mean weight of 300 g) divided into eight groups, four groups assessed at 24 hours and 4 assessed at 48 hours after induction: control group (CO); Vitamin E (Vit. E); Thioacetamide (TAA) and Thioacetamide + Vitamina E (TAA+Vit.E). Rats were submitted to injections of thioacetamide (400 mg/kg i.p.) at baseline and 8 hours later. Vitamin E (100 mg/kg ip) was administered 30 minutes after the second dose of thioacetamide. The 48-hour group rats received two additional doses of vitamin E (24h and 36h). At 24h or 48 hours after the administration of the first dose of TAA, rats were weighed and anesthetized and their blood sampled for evaluation of liver integrity through enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Liver tissue was sampled for assessment of lipid peroxidation (LPO) by the technique TBARS, antioxidant enzymes SOD, CAT, GPx and GST activity, levels of the NO 2 /NO 3 and histology by H&E in two times. The results were expressed as mean ± standard deviation and statistically analyzed by ANOVA followed by Student-Newman-Keuls, with P <0.05 considered as significant.

CONCLUSION:

These results suggest that vitamin E was able to protect the liver from lesions caused by thioacetamide.

Mondal R, Biswas S, Chatterjee A, Mishra R, Mukhopadhyay A, Bhadra RK, Mukhopadhyay PK.

J Basic Clin Physiol Pharmacol. 2016 Nov 1;27(6):643-652. doi: 10.1515/jbcpp-2016-0020.

Abstract

Chronic arsenic exposure via contaminated drinking water is a global environmental health problem associated with hematological, hepatic and many serious systemic disorders. This study on adult male rats evaluated the protective effects of vitamin E (VE) and vitamin C (VC) against arsenic-mediated hematological and hepatic toxicities. As a result, the present investigation offers strong evidence regarding the protective efficacy of co-administration of VC and VE against hematotoxicity and hepatotoxicity in adult male rats caused by chronic arsenic exposure.

Galli F, Azzi A, Birringer M, Cook-Mills JM, Eggersdorfer M, Frank J, Cruciani G, Lorkowski S, Özer NK.

Free Radic Biol Med. 2016 Nov 2;102:16-36. doi: 10.1016/j.freeradbiomed.2016.09.017. [Epub ahead of print]

Abstract

The discovery of vitamin E will have its 100th anniversary in 2022, but we still have more questions than answers regarding the biological functions and the essentiality of vitamin E for human health. Discovered as a factor essential for rat fertility and soon after characterized for its properties of fat-soluble antioxidant, vitamin E was identified to have signaling and gene regulation effects in the 1980s. In the same years the cytochrome P-450 dependent metabolism of vitamin E was characterized and a first series of studies on short-chain carboxyethyl metabolites in the 1990s paved the way to the hypothesis of a biological role for this metabolism alternative to vitamin E catabolism. In the last decade other physiological metabolites of vitamin E have been identified, such as α-tocopheryl phosphate and the long-chain metabolites formed by the ω-hydroxylase activity of cytochrome P-450. Recent findings are consistent with gene regulation and homeostatic roles of these metabolites in different experimental models, such as inflammatory, neuronal and hepatic cells, and in vivo in animal models of acute inflammation. Molecular mechanisms underlying these responses are under investigation in several laboratories and side-glances to research on other fat soluble vitamins may help to move faster in this direction. Other emerging aspects presented in this review paper include novel insights on the mechanisms of reduction of the cardiovascular risk, immunomodulation and antiallergic effects, neuroprotection properties in models of glutamate excitotoxicity and spino-cerebellar damage, hepatoprotection and prevention of liver toxicity by different causes and even therapeutic applications in non-alcoholic steatohepatitis. We here discuss these topics with the aim of stimulating the interest of the scientific community and further research activities that may help to celebrate this anniversary of vitamin E with an in-depth knowledge of its action as vitamin.

Burdeos GC, Ito J, Eitsuka T, Nakagawa K, Kimura F, Miyazawa T.

Food Funct. 2016 Oct 12;7(10):4170-4174.

Abstract

Tocotrienol (T3) has recently gained increasing interest due to its anti-cancer effect. Here, we investigated the modulating effect of δ and γ T3 on the Ras-Raf-MEK-ERK oncogenic upstream signaling pathway in human hepatocellular carcinoma HepG2 cells. The results indicated that T3 regulated the upstream signaling cascades of this pathway.

Chung S, Ghelfi M, Atkinson J, Parker R, Qian J, Carlin C, Manor D.

J Biol Chem. 2016 Aug 12;291(33):17028-39. doi: 10.1074/jbc.M116.734210.

Abstract

α-Tocopherol (vitamin E) is an essential nutrient for all vertebrates. From the eight naturally occurring members of the vitamin E family, α-tocopherol is the most biologically active species and is selectively retained in tissues. The hepatic α-tocopherol transfer protein (TTP) preferentially selects dietary α-tocopherol and facilitates its transport through the hepatocyte and its secretion to the circulation. In doing so, TTP regulates body-wide levels of α-tocopherol. The mechanisms by which TTP facilitates α-tocopherol trafficking in hepatocytes are poorly understood. We found that the intracellular localization of TTP in hepatocytes is dynamic and responds to the presence of α-tocopherol. In the absence of the vitamin, TTP is localized to perinuclear vesicles that harbor CD71, transferrin, and Rab8, markers of the recycling endosomes. Upon treatment with α-tocopherol, TTP- and α-tocopherol-containing vesicles translocate to the plasma membrane, prior to secretion of the vitamin to the exterior of the cells. The change in TTP localization is specific to α-tocopherol and is time- and dose-dependent. The aberrant intracellular localization patterns of lipid binding-defective TTP mutants highlight the importance of protein-lipid interaction in the transport of α-tocopherol. These findings provide the basis for a proposed mechanistic model that describes TTP-facilitated trafficking of α-tocopherol through hepatocytes.

Araoud M, Neffeti F, Douki W, Khaled L, Najjar MF, Kenani A, Houas Z.

Environ Toxicol. 2016 Jul;31(7):842-54. doi: 10.1002/tox.22095.

Abstract

The role of alpha-tocopherol on nephrotoxicity and hepatotoxicity induced by methamidophos (MT) was investigated in wistar rats. Animals were given via gavage, for four weeks, a low dose of MT (MT1), a high dose of MT (MT2), vitamin E (200 mg/kg of bw) or both MT2 plus vitamin E (Vit E) and control group was given distillate water. MT treatment resulted in a significant decrease in the body weight of MT2-treated group. Moreover, MT-treated groups had significantly lower butyrylcholinesterase (p < 0.01) and paraoxonase 1 (PON1) activities compared with the control group (p < 0.05). However, MT2-treated group had significantly higher alkaline phosphatase activity compared with untreated rats (p < 0.05). Both MT-treated groups had significantly higher urea (p < 0.01) and uric acid levels (p < 0.05) compared with the control group. However, significant low uric acid level (p < 0.05) was noted in MT2 plus vit E-treated rats compared with MT2-treated group. Histopathological changes in organ tissues were observed in both MT-treated groups and MT2 plus vit E-treated rats. However, the damage was reduced in MT2 plus vit E-treated rats. Therefore, this study deduces that alpha-tocopherol administration may ameliorate the adverse effects of subacute exposure to MT on rat liver and kidney and this antioxidant can protect PON1 from oxidative stress induced by this organophosphorus pesticide.

Miyazaki H, Takitani K, Koh M, Inoue A, Tamai H.

J Clin Biochem Nutr. 2016 May;58(3):223-31. doi: 10.3164/jcbn.15-133.

Abstract

In humans, dehydroepiandrosterone and its sulfate ester metabolite DHEA-S are secreted predominantly from the adrenal cortex, and dehydroepiandrosterone is converted to steroid hormones, including androgens and estrogens, and neurosteroid. Dehydroepiandrosterone exerts protective effects against several pathological conditions. Although there are reports on the association between dehydroepiandrosterone and vitamins, the exact relationship between dehydroepiandrosterone and vitamin Eremains to be determined. Therefore, we attempted to elucidate the effect of dehydroepiandrosterone on vitamin E status and the expression of various vitamin E-related proteins, including binding proteins, transporters, and cytochrome P450, in vitamin E-deficient rats. Plasma α-tocopherol levels in vitamin E-deficient rats increased in response to dehydroepiandrosterone administration. The expression of hepatic α-tocopherol transfer protein was repressed in vitamin E-deficient rats compared to that in control rats; however, dehydroepiandrosterone administration significantly upregulated this expression. Hepatic expression of CYP4F2, an α-tocopherolmetabolizing enzyme, in vitamin E-deficient rats was decreased by dehydroepiandrosterone administration, whereas hepatic expression of ATP-binding cassette transporter A1, an α-tocopherol transporter, was not altered following dehydroepiandrosterone administration. Dehydroepiandrosterone repressed lipid peroxidation in the liver of vitamin E-deficient rats. Therefore, adequate dehydroepiandrosterone supplementation may improve lipid peroxidation under several pathological conditions, and dehydroepiandrosterone may modulate α-tocopherol levels through altered expression of vitamin E-related proteins.