Plasma Levels of Bioactive Vitamin D and A5 Ligands Positively Correlate with Clinical Atopic Dermatitis Markers.

BACKGROUND: Over the past decade, several controversial studies described a relationship between vitamin D and atopic diseases. Low plasma vitamin D levels or even vitamin D deficiency was associated with an increased incidence of atopic disease, postulating that a higher dietary intake of vitamin D may be a beneficial strategy against atopic diseases such as atopic dermatitis (AD). OBJECTIVE: Our aim was to determine the relationship between plasma 25-hydroxyvitamin D3 (25(OH)D3) levels, the levels of the ligand of the vitamin D receptor (VDR) heterodimerization partner as well as the retinoid X receptor (RXR) and the active vitamin A5 derivative 9-cis-13,14-dihydroretinoic acid (9CDHRA) and AD severity. METHODS/RESULTS: Samples from AD patients (n = 20) and healthy volunteers (n = 20) were assessed. In our study, the frequently measured VDR ligand precursor 25(OH)D3 in addition to the VDR-ligand 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 9CDHRA displayed no different levels when compared with the plasma of AD patients and healthy volunteers. When performing further correlation studies focusing on AD patients, plasma 25(OH)D3 levels showed a negative correlation with eosinophils in blood (EOS) and SCORing Atopic Dermatitis (SCORAD) values, while 1,25(OH)2D3 and 9CDHRA levels correlated positively with plasma IgE, EOS, and SCORAD values. CONCLUSION: In consequence, the metabolic activation of vitamin D from 25(OH)D3 towards 1,25(OH)2D3 as well as the co-liganding of the RXR by 9CDHRA may be an important signalling mechanism, an important marker for AD development and severity as well as the basis for novel nutritional and pharmaceutical AD treatment options.

Saturated and monounsaturated fatty acids in membranes are determined by the gene expression of their metabolizing enzymes SCD1 and ELOVL6 regulated by the intake of dietary fat.

PURPOSE: We investigated the effect of dietary fats on the incorporation of saturated (SAFAs) and monounsaturated dietary fatty acids (MUFAs) into plasma phospholipids and the regulation of the expression of lipid-metabolizing enzymes in the liver. METHODS: Mice were fed different diets containing commonly used dietary fats/oils (coconut fat, margarine, fish oil, sunflower oil, or olive oil) for 4 weeks (n = 6 per diet group). In a second experiment, mice (n = 6 per group) were treated for 7 days with synthetic ligands to activate specific nuclear hormone receptors (NHRs) and the hepatic gene expression of CYP26A1 was investigated. Hepatic gene expression of stearoyl-coenzyme A desaturase 1 (SCD1), elongase 6 (ELOVL6), and CYP26A1 was examined using quantitative real-time PCR (QRT-PCR). Fatty acid composition in mouse plasma phospholipids was analyzed by gas chromatography (GC). RESULTS: We found significantly reduced hepatic gene expression of SCD1 and ELOVL6 after the fish oil diet compared with the other diets. This resulted in reduced enzyme-specific fatty acid ratios, e.g., 18:1n9/18:0 for SCD1 and 18:0/16:0 and 18:1n7/16:1n7 for ELOVL6 in plasma phospholipids. Furthermore, CYP26A1 a retinoic acid receptor-specific target was revealed as a new player mediating the suppressive effect of fish oil-supplemented diet on SCD1 and ELOVL6 hepatic gene expression. CONCLUSION: Plasma levels of MUFAs and SAFAs strongly reflect an altered hepatic fatty acid-metabolizing enzyme expression after supplementation with different dietary fats/oils.

9-cis-13,14-Dihydroretinoic Acid Is an Endogenous Retinoid Acting as RXR Ligand in Mice.

The retinoid X receptors (RXRs) are ligand-activated transcription factors which heterodimerize with a number of nuclear hormone receptors, thereby controlling a variety of (patho)-physiological processes. Although synthetic RXR ligands are developed for the treatment of various diseases, endogenous ligand(s) for these receptors have not been conclusively identified. We show here that mice lacking cellular retinol binding protein (Rbp1-/-) display memory deficits reflecting compromised RXR signaling. Using HPLC-MS and chemical synthesis we identified in Rbp1-/- mice reduced levels of 9-cis-13,14-dihydroretinoic acid (9CDHRA), which acts as an RXR ligand since it binds and transactivates RXR in various assays. 9CDHRA rescues the Rbp1-/- phenotype similarly to a synthetic RXR ligand and displays similar transcriptional activity in cultured human dendritic cells. High endogenous levels of 9CDHRA in mice indicate physiological relevance of these data and that 9CDHRA acts as an endogenous RXR ligand.

Eicosanoids and docosanoids in plasma and aorta of healthy and atherosclerotic rabbits.

Eicosanoids and docosanoids have been shown to be involved in atherosclerosis. Polyunsaturated fatty acids (PUFAs) are important nutrients that are metabolized by lipoxygenases and cyclooxygenases to various mono-hydroxy metabolites which can be further metabolized by specific enzymes to more complex eicosanoids and docosanoids. In this study a high-performance liquid chromatography methodology was established and rabbits were fed with a control or a high-cholesterol diet to induce atherosclerotic lesions to determine pro- or anti-inflammatory lipid mediators in atherosclerotic vessels. In aortic samples from atherosclerotic rabbits we determined for the first time various eicosanoids/docosanoids and observed an increased concentration of 12-lipoxygenase metabolites. Increased levels of 12-hydroxyeicosatetraenoic acid (12-HETE) in high-cholesterol versus control animals as well as increased ratios of 12-HETE/arachidonic acid ratios indicate that 12-lipoxygenase metabolites may have importance in atherosclerosis. In addition, decreased concentrations of the 5-lipoxygenase metabolite leukotriene B4 levels were detected in high-cholesterol animals. A positive correlation of total plaque area with plasma levels of 12-HETE and a negative correlation with aortic levels of endogenous PPARγ-ligand 13-oxo-octadecadienoic acid were found. This study let us conclude that the cholesterol content in the diet might influence atherosclerosis via increased 12-lipoxygenase- and cyclooxygenase-mediated pathways and reduced 5-lipoxygenase pathways.

An immune-shift induced by lycopene; from an eosinophil-dominant type towards an eosinophil/neutrophil-co-dominant type of airway inflammation.

Lycopene as the main carotenoid from tomatoes is known to have beneficial effects on various inflammatory diseases. In mice, lycopene ameliorates asthma symptoms and in human asthmatic patients serum lycopene levels are reduced. To further investigate the immunomodulatory effect of lycopene, first, we used a ragweed pollen extract (RWE)-induced asthma model in mice. In a second approach, we established a RWE-induced asthma model in gerbils, because of a more human-like carotenoid absorption in these animals. In RWE-sensitized/RWE-challenged gerbils (C+) following a basal diet, mainly the number of eosinophils in the broncho-alveolar lavage (BAL) significantly increased, comparable to RWE-sensitized/PBS-challenged gerbils (C-). In RWE-sensitized/PBS-challenged gerbils with lycopene-supplementation (L-), an elevated number of mainly neutrophils, in addition to eosinophils, was detected compared to C-, whereas in RWE-sensitized/RWE-challenged animals with lycopene-supplementation (L+), mainly increased neutrophil numbers in BAL were detected compared to C+. Furthermore, using LC-MS, we determined an array of eicosanoids/docosanoids in the lungs and observed that 5-, 8-lipoxygenase (LOX) and cyclooxygenase (COX) pathways were significantly increased after intranasal RWE-challenge in sensitized mice and just by tendency in gerbils. In PBS- and RWE-challenged animals, lycopene-supplementation significantly raised COX-pathway metabolites. In conclusion, we found that lycopene-supplementation resulted in an increased inflammatory influx of neutrophils in combination with increased COX-pathways metabolites. This pro-inflammatory, pro-neutrophil activity induced by lycopene might be an important shift from allergic asthma towards an inflammatory symptomatic asthma type, though with the potential for resolution.

Vitamin A5/X, a New Food to Lipid Hormone Concept for a Nutritional Ligand to Control RXR-Mediated Signaling.

Vitamin A is a family of derivatives synthesized from carotenoids acquired from the diet and can be converted in animals to bioactive forms essential for life. Vitamin A1 (all-trans-retinol/ATROL) and provitamin A1 (all-trans-ß,ß-carotene/ATBC) are precursors of all-trans-retinoic acid acting as a ligand for the retinoic acid receptors. The contribution of ATROL and ATBC to formation of 9-cis-13,14-dihydroretinoic acid (9CDHRA), the only endogenous retinoid acting as retinoid X receptor (RXR) ligand, remains unknown. To address this point novel and already known retinoids and carotenoids were stereoselectively synthesized and administered in vitro to oligodendrocyte cell culture and supplemented in vivo (orally) to mice with a following high-performance liquid chromatography-mass spectrometry (HPLC-MS)/UV-Vis based metabolic profiling. In this study, we show that ATROL and ATBC are at best only weak and non-selective precursors of 9CDHRA. Instead, we identify 9-cis-13,14-dihydroretinol (9CDHROL) and 9-cis-13,14-dihydro-ß,ß-carotene (9CDHBC) as novel direct nutritional precursors of 9CDHRA, which are present endogenously in humans and the human food chain matrix. Furthermore, 9CDHROL displayed RXR-dependent promnemonic activity in working memory test similar to that reported for 9CDHRA. We also propose that the endogenous carotenoid 9-cis-ß,ß-carotene (9CBC) can act as weak, indirect precursor of 9CDHRA via hydrogenation to 9CDHBC and further metabolism to 9CDHROL and/or 9CDHRA. In summary, since classical vitamin A1 is not an efficient 9CDHRA precursor, we conclude that this group of molecules constitutes a new class of vitamin or a new independent member of the vitamin A family, named "Vitamin A5/X".

Reduced Carotenoid and Retinoid Concentrations and Altered Lycopene Isomer Ratio in Plasma of Atopic Dermatitis Patients.

Carotenoids and retinoids are known to alter the allergic response with important physiological roles in the skin and the immune system. In the human organism various carotenoids are present, some of which are retinoid precursors. The bioactive derivatives of these retinoids are the retinoic acids, which can potently activate nuclear hormone receptors such as the retinoic acid receptor and the retinoid X receptor. In this study, we aimed to assess how plasma carotenoid and retinoid concentrations along with the ratio of their isomers are altered in atopic dermatitis (AD) patients (n = 20) compared to healthy volunteers (HV, n = 20). The study indicated that plasma levels of the carotenoids lutein (HV 198 ± 14 ng/mL, AD 158 ± 12 ng/mL, p = 0.02; all values in mean ± SEM), zeaxanthin (HV 349 ± 30 ng/mL, AD 236 ± 18 ng/mL, p ≤ 0.01), as well as the retinoids retinol (HV 216 ± 20 ng/mL, AD 167 ± 17 ng/mL, p = 0.04) and all-trans-retinoic acid (HV 1.1 ± 0.1 ng/mL, AD 0.7 ± 0.1 ng/mL, p = 0.04) were significantly lower in the AD-patients, while lycopene isomers, α-carotene, and ß-carotene levels were comparable to that determined in the healthy volunteers. In addition, the ratios of 13-cis- vs. all-trans-lycopene (HV 0.31 ± 0.01, AD 0.45 ± 0.07, p = 0.03) as well as 13-cis- vs. all-trans-retinoic acid (HV 1.4 ± 0.2, AD 2.6 ± 0.6, p = 0.03) were increased in the plasma of AD-patients indicating an AD-specific 13-cis-isomerisation. A positive correlation with SCORAD was calculated with 13-cis- vs. all-trans-lycopene ratio (r = 0.40, p = 0.01), while a negative correlation was observed with zeaxanthin plasma levels (r = -0.42, p = 0.01). Based on our results, we conclude that in the plasma of AD-patients various carotenoids and retinoids are present at lower concentrations, while the ratio of selected lycopene isomers also differed in the AD-patient group. An increase in plasma isomers of both lycopene and retinoic acid may cause an altered activation of nuclear hormone receptor signaling pathways and thus may be partly responsible for the AD-phenotype.

Poly(ADP) ribose polymerase-1 ablation alters eicosanoid and docosanoid signaling and metabolism in a murine model of contact hypersensitivity.

Poly(ADP­ribose) polymerase (PARP)­1 is a pro­inflammatory protein. The inhibition of PARP­1 reduces the activity of numerous pro­inflammatory transcription factors, which results in the reduced production of pro­inflammatory cytokines, chemokines, matrix metalloproteinases and inducible nitric oxide synthase, culminating in reduced inflammation of the skin and other organs. The aim of the present study was to investigate the effects of the deletion of PARP­1 expression on polyunsaturated fatty acids (PUFA), and PUFA metabolite composition, in mice under control conditions or undergoing an oxazolone (OXA)­induced contact hypersensitivity reaction (CHS). CHS was elicited using OXA in both the PARP­1+/+ and PARP­1/ mice, and the concentration of PUFAs and PUFA metabolites in the diseased skin were assessed using lipidomics experiments. The levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were shown to be increased in the PARP­1/ mice, as compared with the control, unsensitized PARP­1+/+ mice. In addition, higher expression levels of fatty acid binding protein 7 (FABP7) were detected in the PARP­1/ mice. FABP7 is considered to be a specific carrier of DHA and EPA. Furthermore, the levels of the metabolites of DHA and EPA (considered mainly as anti­inflammatory or pro­resolving factors) were higher, as compared with the metabolites of arachidonic acid (considered mainly pro­inflammatory), both in the unsensitized control and OXA­sensitized PARP­1/ mice. The results of the present study suggest that the genetic deletion of PARP­1 may affect the PUFA­homeostasis of the skin, resulting in an anti­inflammatory milieu, including increased DHA and EPA levels, and DHA and EPA metabolite levels. This may be an important component of the anti­inflammatory action of PARP­1 inhibition.

Ratio of pro-resolving and pro-inflammatory lipid mediator precursors as potential markers for aggressive periodontitis.

Aggressive periodontitis (AgP) is a rapidly progressing type of periodontal disease in otherwise healthy individuals which causes destruction of the supporting tissues of the teeth. The disease is initiated by pathogenic bacteria in the dental biofilm, and the severity of inflammation and attachment loss varies with the host response. Recently, there has been an increased interest in determining the role of lipid mediators in inflammatory events and the concept of pro-inflammatory and pro-resolution lipid mediators has been brought into focus also in periodontal disease. The present study aimed to determine the profile of omega-3 or n3- as well as omega-6 or n6- polyunsaturated fatty acids (PUFAs) and PUFA-metabolites of linoleic acid, arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in gingival crevicular fluid (GCF), saliva and serum in AgP patients and healthy controls. In total, 60 selected n3- and n6-PUFAs and various PUFA metabolites were measured using high performance liquid chromatography-tandem electrospray ionisation mass spectrometry (HPLC-ESI-MS-MS). Of these, 51 could be quantified in this study. The concentrations of the majority were low in saliva samples compared with serum and GCF, but were mainly higher in AgP patients compared with healthy controls in all three kinds of sample. Ratios of n3- to n6-PUFAs (DHA + EPA)/AA were significantly lower in the GCF of AgP patients than in the healthy controls. Furthermore, various ratios of the direct precursors of the pro-resolution lipid mediators (precursors of resolvins and protectins) were calculated against the precursors of mainly pro-inflammatory lipid mediators. These ratios were mainly lower in GCF and saliva of AgP patients, compared with healthy controls, but only reached significance in GCF (P<0.05). To conclude, the ratios of precursors of pro-resolution/pro-inflammatory lipid mediators seem to be more relevant for describing the disease status of AgP than the concentration of specific lipid mediators.