Different forms of vitamin E and metabolite 13'-carboxychromanols inhibit cyclooxygenase-1 and its catalyzed thromboxane in platelets, and tocotrienols and 13'-carboxychromanols are competitive inhibitors of 5-lipoxygenase.

Cyclooxygenase (COX-1 and COX-2)- and 5-lipoxygenase (5-LOX)-catalyzed biosynthesis of eicosanoids play important roles in inflammation and chronic diseases. The vitamin E family has four tocopherols and tocotrienols. We have shown that the metabolites of δ-tocopherol (δT) and δ-tocotrienol (δTE), i.e., δT-13'-carboxychromanol (COOH) and δTE-13'-COOH, respectively, inhibit COX-1/-2 and 5-LOX activity, but the nature of how they inhibit 5-LOX is not clear. Further, the impact of tocopherols and tocotrienols on COX-1/-2 or 5-LOX activity has not been fully delineated. In this study, we found that tocopherols and tocotrienols inhibited human recombinant COX-1 with IC50s of 1-12 µM, and suppressed COX-1-mediated formation of thromboxane in collagen-stimulated rat's platelets with IC50s of 8-50 µM. None of the vitamin E forms directly inhibited COX-2 activity. 13'-COOHs inhibited COX-1 and COX-2 enzyme activity with IC50s of 3-4 and 4-10 µM, respectively, blocked thromboxane formation in collagen- and ionophore-stimulated rats' platelets with IC50s of 1.5-2.5 µM, and also inhibited COX-2-mediated prostaglandins in stimulated cells. Using enzyme kinetics, we observed that δT-13'-COOH, δTE-13'-COOH and δTE competitively inhibited 5-LOX activity with Ki of 1.6, 0.8 and 2.2 µM, respectively. These compounds decreased leukotriene B4 from stimulated neutrophil-like cells without affecting translocation of 5-LOX from cytosol to the nucleus. Our study reveals inhibitory effects of vitamin E forms and 13'-COOHs on COX-1 activity and thromboxane formation in platelets, and elucidates mechanisms underlying their inhibition of 5-LOX. These observations are useful for understanding the role of these compounds in disease prevention and therapy.

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 delta-tocotrienol and metabolite 13'-carboxychromanol inhibit colitis-associated colon tumorigenesis and modulate gut microbiota in mice.

The gut microbiota play important roles in colon cancer. Vitamin E δ-tocotrienol (δTE) and its metabolite δTE-13'-carboxychromanol (δTE-13') are known to have cancer-preventive effects, but their impact on gut flora during tumorigenesis and the role of the metabolite in δTE's beneficial effects remain to be determined. In the murine colitis-associated colon cancer (CAC) induced by azoxymethane (AOM) and dextran sulfate sodium (DSS), we show that δTE and δTE-13' inhibited the multiplicity of large adenomas (>2 mm2) by 34% (P<.05) and 55% (P<.01), respectively, compared to the control diet. δTE-13' diminished AOM/DSS-increased GM-CSF and MCP-1, and δTE decreased IL-1ß. Using 16S rRNA gene sequencing of fecal DNAs, we observe that δTE and δTE-13' modulated the composition but not the richness of gut microbes compared to the control. Both δTE and δTE-13' enhanced potentially beneficial Lactococcus and Bacteroides. The elevation of Lactococcus positively correlated with fecal concentrations of δTE-13' and its hydrogenated metabolite, suggesting that the metabolite may contribute to δTE's modulation of gut microbes. Furthermore, δTE-13' counteracted AOM/DSS-induced depletion of Roseburia that is known to be decreased in patients with inflammatory bowel diseases. δTE uniquely elevated (Eubacterium) coprostanoloigenes. Our study demonstrates that δTE and δTE-13' inhibited tumorigenesis, suppressed pro-inflammatory cytokines and modulated gut microbiota in a murine CAC model. These findings uncover new and distinct activities of δTE and δTE-13' and support the notion that the metabolite may play a role in δTE's anticancer and modulation of gut microbes.

RARα supports the development of Langerhans cells and langerin-expressing conventional dendritic cells.

Langerhans cells (LC) are the prototype langerin-expressing dendritic cells (DC) that reside specifically in the epidermis, but langerin-expressing conventional DCs also reside in the dermis and other tissues, yet the factors that regulate their development are unclear. Because retinoic acid receptor alpha (RARα) is highly expressed by LCs, we investigate the functions of RARα and retinoic acid (RA) in regulating the langerin-expressing DCs. Here we show that the development of LCs from embryonic and bone marrow-derived progenitors and langerin+ conventional DCs is profoundly regulated by the RARα-RA axis. During LC differentiation, RARα is required for the expression of a LC-promoting transcription factor Runx3, but suppresses that of LC-inhibiting C/EBPß. RARα promotes the development of LCs and langerin+ conventional DCs only in hypo-RA conditions, a function effectively suppressed at systemic RA levels. Our findings identify positive and negative regulatory mechanisms to tightly regulate the development of the specialized DC populations.

Protective Effect of Deer Bone Oil on Cartilage Destruction in Rats with Monosodium Iodoacetate (MIA)-Induced Osteoarthritis.

The anti-osteoarthritic activity of the methanol fraction of deer bone oil extract (DBO-M) was evaluated in interleukin (IL)-1ß-inflamed primary rabbit chondrocytes and in rats with monosodium iodoacetate (MIA)-induced osteoarthritis. The active compound in DBO-M was analyzed using a direct infusion liquid chromatography quadrupole (LCQ) ion-trap electrospray ionization (ESI)-mass spectrometer (MS). DBO-M significantly suppressed the IL-1ß-induced sulfated-glycosaminoglycan (s-GAG) release from chondrocyte, and lowered mRNA levels of the collagen-degrading enzymes matrix metalloproteinase (MMP)-1 and MMP-3 in a dose-dependent manner. Upon treatment with high doses of DBO-M, the levels of IL-1ß, tumor necrosis factor (TNF)-α, and IL-6 decreased by around 40, 70, and 50%, respectively, compared to the control in the serum of rats with MIA-induced osteoarthritis. Bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) increased by over 40% in rats treated with DBO-M compared to the values reported for the MIA-treated control group, while trabecular separation (Tb.Sp) showed a significant decrease (ca. 38%), as confirmed through micro-computed tomography (CT) analysis of MIA-induced destruction of articular bones. Furthermore, direct infusion ESI-MS analysis showed that DBO-M contains gangliosides, which are glycosphingolipids with monosialic acid (GM3), as a major compound. Our results suggest that DBO-M effectively improves MIA-induced osteoarthritis by suppressing inflammatory responses, and that gangliosides could be one of the DBO-derived anti-inflammatory components.

Deer Bone Oil Extract Suppresses Lipopolysaccharide-Induced Inflammatory Responses in RAW264.7 Cells.

The aim of this study was to investigate the effect of deer bone oil extract (DBOE) on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 cells. DBOE was fractionated by liquid-liquid extraction to obtain two fractions: methanol fraction (DBO-M) and hexane fraction (DBO-H). TLC showed that DBO-M had relatively more hydrophilic lipid complexes, including unsaturated fatty acids, than DBOE and DBO-H. The relative compositions of tetradecenoyl carnitine, α-linoleic acid, and palmitoleic acid increased in the DBO-M fraction by 61, 38, and 32%, respectively, compared with DBOE. The concentration of sugar moieties was 3-fold higher in the DBO-M fraction than DBOE and DBO-H. DBO-M significantly decreased LPS-induced nitric oxide (NO) production in RAW264.7 cells in a dose-dependent manner. This DBO-M-mediated decrease in NO production was due to downregulation of mRNA and protein levels of inducible nitric oxide synthase (iNOS). In addition, mRNA expression of pro-inflammatory mediators, such as cyclooxygenase (COX-2), interleukin (IL)-1ß, and IL-12ß, was suppressed by DBO-M. Our data showed that DBO-M, which has relatively higher sugar content than DBOE and DBO-H, could play an important role in suppressing inflammatory responses by controlling pro-inflammatory cytokines and mediators.