Vitamin E forms inhibit IL-13/STAT6-induced eotaxin-3 secretion by up-regulation of PAR4, an endogenous inhibitor of atypical PKC in human lung epithelial cells

Natural Products for the Management of Asthma and COPD

Chronic airway inflammatory diseases like asthma, chronic obstructive pulmonary disease (COPD), and their associated exacerbations cause significant socioeconomic burden. There are still major obstacles to effective therapy for controlling severe asthma and COPD progression. Advances in understanding the pathogenesis of the two diseases at the cellular and molecular levels are essential for the development of novel therapies. In recent years, significant efforts have been made to identify natural products as potential drug leads for treatment of human diseases and to investigate their efficacy, safety, and underlying mechanisms of action. Many major active components from various natural products have been extracted, isolated, and evaluated for their pharmacological efficacy and safety. For the treatment of asthma and COPD, many promising natural products have been discovered and extensively investigated. In this chapter, we will review a range of natural compounds from different chemical classes, including terpenes, polyphenols, alkaloids, fatty acids, polyketides, and vitamin E, that have been demonstrated effective against asthma and/or COPD and their exacerbations in preclinical models and clinical trials. We will also elaborate in detail their underlying mechanisms of action unraveled by these studies and discuss new opportunities and potential challenges for these natural products in managing asthma and COPD.

Evolution of Vitamin E Production: From Chemical Synthesis and Plant Extraction to Microbial Cell Factories

Vitamin E, comprising tocopherols and tocotrienols, is an essential antioxidant known for its numerous health benefits. This review traces the evolution of vitamin E production, from traditional chemical synthesis and plant extraction methods to cutting-edge microbial cell factories. Chemical synthesis, while well-established, fails to produce specific stereoisomers, and its application is limited to animal feed due to concerns about chemical residues and limited bioactivity. Plant extraction, although yielding natural vitamin E, is constrained by resource availability and high cultivation costs. Recent advancements in metabolic engineering and synthetic biology have revolutionized vitamin E bioproduction, particularly through the use of engineered microbial cell factories. This review highlights the progress of vitamin E biosynthesis in plants and microorganisms and the key metabolic engineering strategies adopted. We also discuss the existing challenges and future perspectives. When these challenges are overcome, microbial cell factories present a sustainable and effective method to fulfill the increasing demand for high-quality vitamin E.

Interactions between Dietary Antioxidants, Dietary Fiber and the Gut Microbiome: Their Putative Role in Inflammation and Cancer

The intricate relationship between the gastrointestinal (GI) microbiome and the progression of chronic non-communicable diseases underscores the significance of developing strategies to modulate the GI microbiota for promoting human health. The administration of probiotics and prebiotics represents a good strategy that enhances the population of beneficial bacteria in the intestinal lumen post-consumption, which has a positive impact on human health. In addition, dietary fibers serve as a significant energy source for bacteria inhabiting the cecum and colon. Research articles and reviews sourced from various global databases were systematically analyzed using specific phrases and keywords to investigate these relationships. There is a clear association between dietary fiber intake and improved colon function, gut motility, and reduced colorectal cancer (CRC) risk. Moreover, the state of health is reflected in the reciprocal and bidirectional relationships among food, dietary antioxidants, inflammation, and body composition. They are known for their antioxidant properties and their ability to inhibit angiogenesis, metastasis, and cell proliferation. Additionally, they promote cell survival, modulate immune and inflammatory responses, and inactivate pro-carcinogens. These actions collectively contribute to their role in cancer prevention. In different investigations, antioxidant supplements containing vitamins have been shown to lower the risk of specific cancer types. In contrast, some evidence suggests that taking antioxidant supplements can increase the risk of developing cancer. Ultimately, collaborative efforts among immunologists, clinicians, nutritionists, and dietitians are imperative for designing well-structured nutritional trials to corroborate the clinical efficacy of dietary therapy in managing inflammation and preventing carcinogenesis. This review seeks to explore the interrelationships among dietary antioxidants, dietary fiber, and the gut microbiome, with a particular focus on their potential implications in inflammation and cancer.

Vitamin D3 improved hypoxia-induced lung injury by inhibiting the complement and coagulation cascade and autophagy pathway

BACKGROUND

Pulmonary metabolic dysfunction can cause lung tissue injury. There is still no ideal drug to protect against hypoxia-induced lung injury, therefore, the development of new drugs to prevent and treat hypoxia-induced lung injury is urgently needed. We aimed to explore the ameliorative effects and molecular mechanisms of vitamin D3 (VD3) on hypoxia-induced lung tissue injury.

METHODS

Sprague-Dawley (SD) rats were randomly divided into three groups: normoxia, hypoxia, and hypoxia + VD3. The rat model of hypoxia was established by placing the rats in a hypobaric chamber. The degree of lung injury was determined using hematoxylin and eosin (H&E) staining, lung water content, and lung permeability index. Transcriptome data were subjected to differential gene expression and pathway analyses. In vitro, type II alveolar epithelial cells were co-cultured with hepatocytes and then exposed to hypoxic conditions for 24 h. For VD3 treatment, the cells were treated with low and high concentrations of VD3.

RESULTS

Transcriptome and KEGG analyses revealed that VD3 affects the complement and coagulation cascade pathways in hypoxia-induced rats, and the genes enriched in this pathway were Fgb/Fga/LOC100910418. Hypoxia can cause increases in lung edema, inflammation, and lung permeability disruption, which are attenuated by VD3 treatment. VD3 weakened the complement and coagulation cascade in the lung and liver of hypoxia-induced rats, characterized by lower expression of fibrinogen alpha chain (Fga), fibrinogen beta chain (Fgb), protease-activated receptor 1 (PAR1), protease-activated receptor 3 (PAR3), protease-activated receptor 4 (PAR4), complement (C) 3, C3a, and C5. In addition, VD3 improved hypoxic-induced type II alveolar epithelial cell damage and inflammation by inhibiting the complement and coagulation cascades. Furthermore, VD3 inhibited hypoxia-induced autophagy in vivo and in vitro, which was abolished by the mitophagy inducer, carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

CONCLUSION

VD3 alleviated hypoxia-induced pulmonary edema by inhibiting the complement and coagulation cascades and autophagy pathways.

From genes to systems: The role of food supplementation in the regulation of sepsis-induced inflammation

Systemic inflammation includes a widespread immune response to a harmful stimulus that results in extensive systemic damage. One common example of systemic inflammation is sepsis, which is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Under the pro-inflammatory environment of sepsis, oxidative stress contributes to tissue damage due to dysfunctional microcirculation that progressively causes the failure of multiple organs that ultimately triggers death. To address the underlying inflammatory condition in critically ill patients, progress has been made to assess the beneficial effects of dietary supplements, which include polyphenols, amino acids, fatty acids, vitamins, and minerals that are recognized for their immuno-modulating, anticoagulating, and analgesic properties. Therefore, we aimed to review and discuss the contribution of food-derived supplementation in the regulation of inflammation from gene expression to physiological responses and summarize the precedented potential of current therapeutic approaches during systemic inflammation.

A pilot randomized clinical trial of γ-tocopherol supplementation on wood smoke-induced neutrophilic and eosinophilic airway inflammation

Background

Air pollutants, including particulates from wood smoke, are a significant cause of exacerbation of lung disease. γ-Tocopherol is an anti-inflammatory isoform of vitamin E that has been shown to reduce allergen-, ozone-, and endotoxin-induced inflammation.

Objective

The objective of this study was to determine whether γ-tocopherol would prevent experimental wood smoke-induced airway inflammation in humans.

Methods

This was a randomized, placebo-controlled clinical trial testing the effect of a short course of γ-tocopherol-enriched supplementation on airway inflammation following a controlled exposure to wood smoke particulates.

Results

Short-course γ-tocopherol intervention did not reduce wood smoke-induced neutrophilic airway inflammation, but it did prevent wood smoke-induced eosinophilic airway inflammation.

Conclusion

γ-Tocopherol is a potential intervention for exacerbation of allergic airway inflammation, but further study examining longer dosing periods is required.

Countercurrent chromatography separation of vitamin E isomers in a co-current mode

Vitamin E represents a group of lipophilic phenolic compounds, including α-tocopherol, β-tocopherol, γ-tocopherol, and δ-tocopherol, and α-tocotrienol, β-tocotrienol, γ-tocotrienol, and δ-tocotrienol isomers. Different forms of vitamin E have been proven to exhibit varying biological activities. However, due to their structural similarities, the separation of vitamin E isomers is a challenging task. Therefore, it is crucial to establish an efficient method for isolating individual isomers. In this study, co-current countercurrent chromatography was employed to isolate vitamin E isomers from commercial capsules using a n-heptane-methanol-water (10:9.5:0.5, v/v) solvent system. The partition coefficients of the main constituents in the capsules ranged from 0.94 to 6.23, requiring over 450 min for a complete separation. To improve separation efficiency, a co-current elution mode was implemented and the flow rates of the two liquid phases as well as sample amount were examined. The results suggested that increasing the flow rate of the stationary phase and sample size could result in more effective separation, shorter separation time, and higher yield. It proved that co-current countercurrent chromatography was an effective method for the separation of vitamin E isomers.

Tocotrienol in Pre-Eclampsia Prevention: A Mechanistic Analysis in Relation to the Pathophysiological Framework

The pathophysiology of pre-eclampsia involves two major pathways, namely systemic oxidative stress and subsequent generalised inflammatory response, which eventually culminates in endothelial cell injury and the syndrome of pre-eclampsia with multi-organ dysfunction. Aspirin has been used to reduce the risk of pre-eclampsia, but it only possesses anti-inflammatory properties without any antioxidant effect. Hence, it can only partially alleviate the problem. Tocotrienols are a unique form of vitamin E with strong antioxidant and anti-inflammatory properties that can be exploited as a preventive agent for pre-eclampsia. Many preclinical models showed that tocotrienol can also prevent hypertension and ischaemic/reperfusion injury, which are the two main features in pre-eclampsia. This review explores the mechanism of action of tocotrienol in relation to the pathophysiology of pre-eclampsia. In conclusion, the study provides sufficient justification for the establishment of a large clinical trial to thoroughly assess the capability of tocotrienol in preventing pre-eclampsia.

Gamma-tocopherol, a major form of vitamin E in diets: Insights into antioxidant and anti-inflammatory effects, mechanisms, and roles in disease management

γ-Tocopherol (γT) is a major form of vitamin E in the US diet and the second most abundant vitamin E in the blood and tissues, while α-tocopherol (αT) is the predominant vitamin E in tissues. During the last >25 years, research has revealed that γT has unique antioxidant and anti-inflammatory activities relevant to disease prevention compared to αT. While both compounds are potent lipophilic antioxidants, γT but not αT can trap reactive nitrogen species by forming 5-nitro-γT, and appears to show superior protection of mitochondrial function. γT inhibits ionophore-stimulated leukotrienes by blocking 5-lipoxygenase (5-LOX) translocation in leukocytes, decreases cyclooxygenase-2 (COX-2)-catalyzed prostaglandins in macrophages and blocks the growth of cancer cells but not healthy cells. For these activities, γT is stronger than αT. Moreover, γT is more extensively metabolized than αT via cytochrome P-450 (CYP4F2)-initiated side-chain oxidation, which leads to formation of metabolites including 13'-carboxychromanol (13'-COOH) and carboxyethyl-hydroxychroman (γ-CEHC). 13'-COOH and γ-CEHC are shown to be the predominant metabolites found in feces and urine, respectively. Interestingly, γ-CEHC has natriuretic activity and 13'-COOH inhibits both COX-1/-2 and 5-LOX activity. Consistent with these mechanistic findings of γT and metabolites, studies show that supplementation of γT mitigates inflammation and disease symptoms in animal models with induced inflammation, asthma and cancer. In addition, supplementation of γT decreased inflammation markers in patients with kidney diseases and mild asthma. These observations support that γT may be useful against inflammation-associated diseases.

Vitamin E beyond Its Antioxidant Label

Vitamin E, comprising tocopherols and tocotrienols, is mainly known as an antioxidant. The aim of this review is to summarize the molecular mechanisms and signaling pathways linked to inflammation and malignancy modulated by its vitamers. Preclinical reports highlighted a myriad of cellular effects like modulating the synthesis of pro-inflammatory molecules and oxidative stress response, inhibiting the NF-κB pathway, regulating cell cycle, and apoptosis. Furthermore, animal-based models have shown that these molecules affect the activity of various enzymes and signaling pathways, such as MAPK, PI3K/Akt/mTOR, JAK/STAT, and NF-κB, acting as the underlying mechanisms of their reported anti-inflammatory, neuroprotective, and anti-cancer effects. In clinical settings, not all of these were proven, with reports varying considerably. Nonetheless, vitamin E was shown to improve redox and inflammatory status in healthy, diabetic, and metabolic syndrome subjects. The anti-cancer effects were inconsistent, with both pro- and anti-malignant being reported. Regarding its neuroprotective properties, several studies have shown protective effects suggesting vitamin E as a potential prevention and therapeutic (as adjuvant) tool. However, source and dosage greatly influence the observed effects, with bioavailability seemingly a key factor in obtaining the preferred outcome. We conclude that this group of molecules presents exciting potential for the prevention and treatment of diseases with an inflammatory, redox, or malignant component.

Anti-allergic effects of vitamin E in allergic diseases: An updated review

Allergic diseases are caused by the immune system's response to innocent antigens called allergens. Recent decades have seen a significant increase in the prevalence of allergic diseases worldwide, which has imposed various socio-economic effects in different countries. Various factors, including genetic factors, industrialization, improved hygiene, and climate change contribute to the development of allergic diseases in many parts of the world. Moreover, changes in lifestyle and diet habits play pivotal roles in the prevalence of allergic diseases. Dietary changes caused by decreased intake of antioxidants such as vitamin E lead to the generation of oxidative stress, which is central to the development of allergic diseases. It has been reported in many articles that oxidative stress diverts immune responses to the cells associated with the pathogenesis of allergic diseases. The aim of this short review was to summarize current knowledge about the anti-allergic properties of vitamin E.

MFHAS1 promotes colorectal cancer progress by regulating polarization of tumor-associated macrophages via STAT6 signaling pathway

Malignant fibrous histiocytoma amplified sequence 1 (MFHAS1) is a predicted oncoprotein that demonstrates tumorigenic activity in vivo; however, the mechanisms involved are unknown. Macrophages are divided into the pro-inflammatory M1 and anti-inflammatory/protumoral M2 subtypes. Tumor cells can induce M2 polarization of tumor-associated macrophages (TAMs) to promote metastasis; but the underlying pathways require to be elucidated. In this study, we detected a positive association between MFHAS1 expression in TAMs and human colorectal cancer (CRC) TNM stage. Supernatant of CT26 murine CRC cells induced MFHAS1 expression in RAW264.7 murine macrophages. Additionally, CT26 supernatant induced the M2 marker CD206 and activated the pro-M2 STAT6 and KLF4 signaling in control but not MFHAS1-silenced RAW264.7 macrophages. Moreover, supernatant of control, but not MFHAS1-silenced macrophages promoted CT26 cell proliferation, migration and epithelial-mesenchymal transition. Compared with control macrophages, MFHAS1-silenced macrophages showed significantly reduced protumoral effects in vivo. Together, these results suggested that CRC cells induce M2 polarization of TAMs through MFHAS1 induction and subsequent STAT6 and KLF4 activation to promote CRC progress. Finally, similar to CT26 supernatant stimulation, peroxisome proliferator-activated receptor-γ (PPARγ) activation by rosiglitazone induced M2 polarization of RAW264.7 macrophages through MFHAS1-dependent pathway. Our results highlight the role of MFHAS1 as a regulator of macrophages polarization and CRC progress.

1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) reduces hepatic injury in concanavalin A-treated mice

1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), a chemically synthesized monoacetyldiaglyceride, is one of the constituents in Sika deer antlers and has been known traditionally as having immunomodulatory effects. However, the mechanism by which PLAG controls neutrophil migration, which evokes liver injury in the hepatitis animal model, remains largely unknown. This study was designed to evaluate the immunomodulatory effects of PLAG on cytokine secretion and neutrophil migration in vivo and in vitro. Concanavalin A (Con A) induced leukocyte infiltration in the liver and increased plasma cytokine levels. Pretreatment with PLAG reduced the levels of interleukin (IL)-4, IL-6, IL-10, and CXCL2, but maintained interferon (IFN)-γ levels and modulated neutrophil recruitment toward the liver. Furthermore, the mRNA and protein levels of IL-4 and CXCL2 in liver tissue were also decreased in the Con A-treated mice. Liver histology analyses showed that PLAG reduced Con A-induced hepatic necrosis, which was accompanied by leukocyte infiltration. The in vitro studies revealed that PLAG reduced IL-4 secretion in Con A stimulated T cell and blocked signal transducer and activator of transcription 6 (STAT6) Con A induced hepatocyte. PLAG attenuated IL-4 induced activation of atypical protein kinase C (PKC)/STAT6 in hepatocytes and inhibited neutrophil migration toward the liver tissue through suppression of IL-8/vascular cell adhesion molecule (VCAM) expression. These results suggest that PLAG could mitigate excess neutrophil migration into liver tissue and potentially have a therapeutic effect on immune-mediated liver injury.

Gamma tocopherol-enriched supplement reduces sputum eosinophilia and endotoxin-induced sputum neutrophilia in volunteers with asthma

BACKGROUND

We and others have shown that the gamma tocopherol (γT) isoform of vitamin E has multiple anti-inflammatory and antioxidant actions and that γT supplementation reduces eosinophilic and endotoxin (LPS)-induced neutrophilic airway inflammation in animal models and healthy human volunteers.

OBJECTIVE

We sought to determine whether γT supplementation reduces eosinophilic airway inflammation and acute neutrophilic response to inhaled LPS challenge in volunteers with asthma.

METHODS

Participants with mild asthma were enrolled in a double-blinded, placebo-controlled crossover study to assess the effect of 1200 mg of γT daily for 14 days on sputum eosinophils, mucins, and cytokines. We also assessed the effect on acute inflammatory response to inhaled LPS challenge following γT treatment, focusing on changes in sputum neutrophilia, mucins, and cytokines. Mucociliary clearance was measured using gamma scintigraphy.

RESULTS

Fifteen subjects with mild asthma completed both arms of the study. Compared with placebo, γT notably reduced pre-LPS challenge sputum eosinophils and mucins, including mucin 5AC and reduced LPS-induced airway neutrophil recruitment 6 and 24 hours after challenge. Mucociliary clearance was slowed 4 hours postchallenge in the placebo group but not in the γT treatment group. Total sputum mucins (but not mucin 5AC) were reduced at 24 hours postchallenge during γT treatment compared with placebo.

CONCLUSIONS

When compared with placebo, γT supplementation for 14 days reduced inflammatory features of asthma, including sputum eosinophils and mucins, as well as acute airway response to inhaled LPS challenge. Larger scale clinical trials are needed to assess the efficacy of γT supplements as a complementary or steroid-sparing treatment for asthma.

PLAG (1-Palmitoyl-2-Linoleoyl-3-Acetyl-rac-Glycerol) Modulates Eosinophil Chemotaxis by Regulating CCL26 Expression from Epithelial Cells

Increased number of eosinophils in the circulation and sputum is associated with the severity of asthma. The respiratory epithelium produces chemokine (C-C motif) ligands (CCL) which recruits and activates eosinophils. A chemically synthesized monoacetyl-diglyceride, PLAG (1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol) is a major constituent in the antlers of Sika deer (Cervus nippon Temminck) which has been used in oriental medicine. This study was aimed to investigate the molecular mechanism of PLAG effect on the alleviation of asthma phenotypes. A549, a human alveolar basal epithelial cell, and HaCaT, a human keratinocyte, were activated by the treatment of interleukin-4 (IL-4), and the expression of chemokines, known to be effective on the induction of eosinophil migration was analyzed by RT-PCR. The expression of IL-4 induced genes was modulated by the co-treatment of PLAG. Especially, CCL26 expression from the stimulated epithelial cells was significantly blocked by PLAG, which was confirmed by ELISA. The transcriptional activity of signal transducer and activator of transcription 6 (STAT6), activated by IL-4 mediated phosphorylation and nuclear translocation, was down-regulated by PLAG in a concentration-dependent manner. In ovalbumin-induced mouse model, the infiltration of immune cells into the respiratory tract was decreased by PLAG administration. Cytological analysis of the isolated bronchoalveolar lavage fluid (BALF) cells proved the infiltration of eosinophils was significantly reduced by PLAG. In addition, PLAG inhibited the migration of murine bone marrow-derived eosinophils, and human eosinophil cell line, EoL-1, which was induced by the addition of A549 culture medium.

Phloretin inhibits interleukin-1β-induced COX-2 and ICAM-1 expression through inhibition of MAPK, Akt, and NF-κB signaling in human lung epithelial cells

Phloretin, a flavonoid isolated from the apple tree, is reported to have anti-inflammatory, anti-oxidant, and anti-adiposity effects. In this study, we evaluated the suppressive effects of phloretin on intercellular adhesion molecule 1 (ICAM-1) and cyclooxygenase (COX)-2 expression in IL-1β-stimulated human lung epithelial A549 cells. The cells were pretreated with various concentrations of phloretin (3-100 μM), followed by induced inflammation by IL-1β. Phloretin inhibited levels of prostaglandin E2, decreased COX-2 expression, and suppressed IL-8, monocyte chemotactic protein 1, and IL-6 production. It also decreased ICAM-1 gene and protein expression and suppressed monocyte adhesion to inflammatory A549 cells. Phloretin also significantly inhibited Akt and mitogen-activated protein kinase (MAPK) phosphorylation and decreased nuclear transcription factor kappa-B (NF-κB) subunit p65 protein translocation into the nucleus. In addition, ICAM-1 and COX-2 expression was suppressed by pretreatment with both MAPK inhibitors and phloretin in inflammatory A549 cells. However, phlorizin, a derivative of phloretin, did not suppress the inflammatory response in IL-1β-stimulated A549 cells. These results suggest that phloretin might have an anti-inflammatory effect by inhibiting proinflammatory cytokine, COX-2, and ICAM-1 expression via blocked NF-κB and MAPK signaling pathways.

Vitamin E therapy beyond cancer: Tocopherol versus tocotrienol

The discovery of vitamin E (α-tocopherol) began in 1922 as a vital component required in reproduction. Today, there are eight naturally occurring vitamin E isoforms, namely α-, β-, γ- and δ-tocopherol and α-, β-, γ- and δ-tocotrienol. Vitamin E is potent antioxidants, capable of neutralizing free radicals directly by donating hydrogen from its chromanol ring. α-Tocopherol is regarded the dominant form in vitamin E as the α-tocopherol transfer protein in the liver binds mainly α-tocopherol, thus preventing its degradation. That contributed to the oversight of tocotrienols and resulted in less than 3% of all vitamin E publications studying tocotrienols. Nevertheless, tocotrienols have been shown to possess superior antioxidant and anti-inflammatory properties over α-tocopherol. In particular, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase to lower cholesterol, attenuating inflammation via downregulation of transcription factor NF-κB activation, and potent radioprotectant against radiation damage are some properties unique to tocotrienols, not tocopherols. Aside from cancer, vitamin E has also been shown protective in bone, cardiovascular, eye, nephrological and neurological diseases. In light of the different pharmacological properties of tocopherols and tocotrienols, it becomes critical to specify which vitamin E isoform(s) are being studied in any future vitamin E publications. This review provides an update on vitamin E therapeutic potentials, protective effects and modes of action beyond cancer, with comparison of tocopherols against tocotrienols. With the concerted efforts in synthesizing novel vitamin E analogs and clinical pharmacology of vitamin E, it is likely that certain vitamin E isoform(s) will be therapeutic agents against human diseases besides cancer.

Vitamin E γ-Tocotrienol Inhibits Cytokine-Stimulated NF-κB Activation by Induction of Anti-Inflammatory A20 via Stress Adaptive Response Due to Modulation of Sphingolipids

NF-κB plays a central role in pathogenesis of inflammation and cancer. Many phytochemicals, including γ-tocotrienol (γTE), a natural form of vitamin E, have been shown to inhibit NF-κB activation, but the underlying mechanism has not been identified. In this study, we show that γTE inhibited cytokine-triggered activation of NF-κB and its upstream regulator TGF-β-activated kinase-1 in murine RAW 264.7 macrophages and primary bone marrow-derived macrophages. In these cells, γTE induced upregulation of A20, an inhibitor of NF-κB. Knockout of A20 partially diminished γTE's anti-NF-κB effect, but γTE increased another NF-κB inhibitor, Cezanne, in A20(-/-) cells. In search of the reason for A20 upregulation, we found that γTE treatment increased phosphorylation of translation initiation factor 2, IκBα, and JNK, indicating induction of endoplasmic reticulum stress. Liquid chromatography-tandem mass spectrometry analyses revealed that γTE modulated sphingolipids, including enhancement of intracellular dihydroceramides, sphingoid bases in de novo synthesis of the sphingolipid pathway. Chemical inhibition of de novo sphingolipid synthesis partially reversed γTE's induction of A20 and the anti-NF-κB effect. The importance of dihydroceramide increase is further supported by the observation that C8-dihydroceramide mimicked γTE in upregulating A20, enhancing endoplasmic reticulum stress, and attenuating TNF-triggered NF-κB activation. Our study identifies a novel anti-NF-κB mechanism where A20 is induced by stress-induced adaptive response as a result of modulation of sphingolipids, and it demonstrates an immunomodulatory role of dihydrocermides.

γ-Tocotrienol reduces human airway smooth muscle cell proliferation and migration

AIMS

Vitamin E is an antioxidant that occurs in 8 different forms (α, β, γ, and δ tocopherol and tocotrienol). Clinical trials of tocopherol supplementation to assess the impact of antioxidant activity in asthma have yielded equivocal results. Tocotrienol exhibits greater antioxidant activity than tocopherol in several biological phenomena in vivo and in vitro. We tested the effect of tocotrienol on human airway smooth muscle (ASM) cell growth and migration, both of which mediate airway remodeling in asthma.

MAIN METHODS

We measured platelet-derived growth factor-BB (PDGF-BB)-induced ASM cell proliferation and migration by colorimetric and Transwell migration assays in the presence and absence of γ-tocotrienol (an isoform of tocotrienol).

KEY FINDINGS

PDGF-BB-induced ASM cell proliferation and migration were inhibited by γ-tocotrienol. This effect was associated with inhibition of RhoA activation, but it had no effect on p42/p44 mitogen-activated protein kinase (MAPK) or Akt1 activation. We confirmed that pharmacological inhibition of Rho kinase activity was sufficient to inhibit PDGF-BB-induced ASM cell proliferation and migration.

SIGNIFICANCE

γ-Tocotrienol could impart therapeutic benefits for airway remodeling in asthma by inhibiting human ASM cell proliferation and migration.

Natural forms of vitamin E: metabolism, antioxidant, and anti-inflammatory activities and their role in disease prevention and therapy

The vitamin E family consists of four tocopherols and four tocotrienols. α-Tocopherol (αT) is the predominant form of vitamin E in tissues and its deficiency leads to ataxia in humans. However, results from many clinical studies do not support a protective role of αT in disease prevention in people with adequate nutrient status. On the other hand, recent mechanistic studies indicate that other forms of vitamin E, such as γ-tocopherol (γT), δ-tocopherol, and γ-tocotrienol, have unique antioxidant and anti-inflammatory properties that are superior to those of αT in prevention and therapy against chronic diseases. These vitamin E forms scavenge reactive nitrogen species, inhibit cyclooxygenase- and 5-lipoxygenase-catalyzed eicosanoids, and suppress proinflammatory signaling such as NF-κB and STAT3/6. Unlike αT, other vitamin E forms are significantly metabolized to carboxychromanols via cytochrome P450-initiated side-chain ω-oxidation. Long-chain carboxychromanols, especially 13'-carboxychromanols, are shown to have stronger anti-inflammatory effects than unmetabolized vitamins and may therefore contribute to the beneficial effects of vitamin E forms in vivo. Consistent with mechanistic findings, animal and human studies show that γT and tocotrienols may be useful against inflammation-associated diseases. This review focuses on non-αT forms of vitamin E with respect to their metabolism, anti-inflammatory effects and mechanisms, and in vivo efficacy in preclinical models as well as human clinical intervention studies.

Supplementation with γ-tocopherol attenuates endotoxin-induced airway neutrophil and mucous cell responses in rats

Neutrophil-mediated tissue injury is a shared pathogenesis of both chronic pulmonary diseases and acute responses to pathogens, allergens, and airborne pollutants. Interventions to minimize toxic effects of neutrophil-derived oxidants and proteases are usually limited to corticosteroids, which can have adverse side effects. We used a rodent model of endotoxin-induced lung injury to test the hypothesis that the dietary supplement γ-tocopherol (γT), a natural form of vitamin E with antioxidant and novel anti-inflammatory properties, will protect from adverse nasal and pulmonary inflammatory responses induced by endotoxin (lipopolysaccharide; LPS). Male Fisher F344 rats were intranasally (i.n.) instilled with LPS for 2 consecutive days. Beginning 2 days before i.n. LPS, the rats were gavaged daily with 30mg/kg γT. Twenty-four hours after the last i.n. LPS, bronchoalveolar lavage fluid (BALF) was collected, and pulmonary and nasal tissues were analyzed for gene expression and morphometric analyses of neutrophils and intraepithelial mucosubstances (IM). LPS caused increased BALF total cells (70% increase), neutrophils (300%), protein (35%), PGE2 (500%), and secreted mucins (75%). Robust increases in neutrophils and IM were detected in conducting airways. Pulmonary expression of MUC5AC, MIP-2, CINC-1, and MCP-1 was elevated three- to eightfold by LPS. Treatment with γT inhibited LPS-induced increases in BALF total cells, neutrophils, protein, PGE2, and secreted mucins, as well as IM and tissue neutrophil influx. Furthermore γT induced the expression of the regulatory cytokines IL-10 and IFN-γ while decreasing MUC5AC, MIP-2, CINC-1, and MCP-1. These data demonstrate novel therapeutic effects of the dietary vitamin E γT promoting anti-inflammatory pathways to protect from neutrophil-mediated lung injury.

Improving asthma during pregnancy with dietary antioxidants: the current evidence

The complication of asthma during pregnancy is associated with a number of poor outcomes for the mother and fetus. This may be partially driven by increased oxidative stress induced by the combination of asthma and pregnancy. Asthma is a chronic inflammatory disease of the airways associated with systemic inflammation and oxidative stress, which contributes to worsening asthma symptoms. Pregnancy alone also intensifies oxidative stress through the systemic generation of excess reactive oxidative species (ROS). Antioxidants combat the damaging effects of ROS; yet antioxidant defenses are reduced in asthma. Diet and nutrition have been postulated as potential factors to combat the damaging effects of asthma. In particular, dietary antioxidants may play a role in alleviating the heightened oxidative stress in asthma. Although there are some observational and interventional studies that have shown protective effects of antioxidants in asthma, assessment of antioxidants in pregnancy are limited and there are no antioxidant intervention studies in asthmatic pregnancies on asthma outcomes. The aims of this paper are to (i) review the relationships between oxidative stress and dietary antioxidants in adults with asthma and asthma during pregnancy, and (ii) provide the rationale for which dietary management strategies, specifically increased dietary antioxidants, might positively impact maternal asthma outcomes. Improving asthma control through a holistic antioxidant dietary approach might be valuable in reducing asthma exacerbations and improving asthma management during pregnancy, subsequently impacting perinatal health.

Vitamin E, γ-tocopherol, reduces airway neutrophil recruitment after inhaled endotoxin challenge in rats and in healthy volunteers

Epidemiologic studies suggest that dietary vitamin E is an important candidate intervention for asthma. Our group has shown that daily consumption of vitamin E (γ-tocopherol, γT) has anti-inflammatory actions in both rodent and human phase I studies. The objective of this study was to test whether γT supplementation could mitigate a model of neutrophilic airway inflammation in rats and in healthy human volunteers. F344/N rats were randomized to oral gavage with γT versus placebo, followed by intranasal LPS (20μg) challenge. Bronchoalveolar lavage fluid and lung histology were used to assess airway neutrophil recruitment. In a phase IIa clinical study, 13 nonasthmatic subjects completed a double-blinded, placebo-controlled crossover study in which they consumed either a γT-enriched capsule or a sunflower oil placebo capsule. After 7 days of daily supplementation, they underwent an inhaled LPS challenge. Induced sputum was assessed for neutrophils 6 h after inhaled LPS. The effect of γT compared to placebo on airway neutrophils post-LPS was compared using a repeated-measures analysis of variance. In rats, oral γT supplementation significantly reduced tissue infiltration (p<0.05) and accumulation of airway neutrophils (p<0.05) that are elicited by intranasal LPS challenge compared to control rats. In human volunteers, γT treatment significantly decreased induced sputum neutrophils (p=0.03) compared to placebo. Oral supplementation with γT reduced airway neutrophil recruitment in both rat and human models of inhaled LPS challenge. These results suggest that γT is a potential therapeutic candidate for prevention or treatment of neutrophilic airway inflammation in diseased populations.

γ-Tocotrienol inhibits lipopolysaccharide-induced interlukin-6 and granulocyte colony-stimulating factor by suppressing C/EBPβ and NF-κB in macrophages

Cytokines generated from macrophages contribute to pathogenesis of inflammation-associated diseases. Here we show that γ-tocotrienol (γ-TE), a natural vitamin E form, inhibits lipopolysaccharide (LPS)-induced interleukin (IL)-6 production without affecting tumor necrosis factor α (TNF-α), IL-10 or cyclooxygenase-2 (COX-2) up-regulation in murine RAW264.7 macrophages. Mechanistic studies indicate that nuclear factor κB (NF-κB), but not c-Jun NH(2)-terminal protein kinase, p38 or extracellular signal-regulated kinase mitogen-activated protein kinases (MAPKs), is important to IL-6 production and that γ-TE treatment blocks NF-κB activation. In contrast, COX-2 appears to be regulated by p38 MAPK in RAW cells, but γ-TE has no effect on LPS-stimulated p38 phosphorylation. Despite necessary for IL-6, NF-κB activation by TNF-α or other cytokines is not sufficient for IL-6 induction with exception of LPS. CCAAT/enhancer-binding protein (C/EBP) β appears to be involved in IL-6 formation because LPS induces C/EBPβ up-regulation, which parallels IL-6 production, and knockdown of C/EBPβ with small interfering RNA results in diminished IL-6. LPS but not individual cytokines is capable of stimulating C/EBPβ and IL-6 in macrophages. Consistent with its dampening effect on IL-6, γ-TE blunts LPS-induced up-regulation of C/EBPβ without affecting C/EBPδ. γ-TE also decreases LPS-stimulated granulocyte colony-stimulating factor (G-CSF), a C/EBPβ target gene. Compared with RAW264.7 cells, γ-TE shows similar or stronger inhibitory effects on LPS-triggered activation of NF-κB, C/EPBβ and C/EBPδ and more potently suppresses IL-6 and G-CSF in bone marrow-derived macrophages. Our study demonstrates that γ-TE has antiinflammatory activities by inhibition of NF-κB and C/EBPs activation in macrophages.