Development of skin diseases following systemic exposure: example of dioxins.

Most skin manifestations of exposure to toxic compounds are a consequence of a direct contact with the toxicants. However, some toxicants may reach the skin following systemic exposure, and promote skin diseases. Good examples of such chemicals are dioxin-like compounds. This family of lipophilic molecules comprises polychlorinated (dibenzodioxins, dibenzofurans and biphenyls). The most potent member of this family is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Following oral ingestion of as little as a few mg TCDD, skin lesions appear in a couple of weeks, starting from the face and diffuse then on the trunk and limbs. This syndrome was historically called "chloracne" and the skin lesions have now been shown to be skin hamartoma induced by TCDD. Sweat glands release their lipid content on the surface of the skin by a holocrine secretion, and so any lost sebocyte should be transmitted to progenitor cells to differentiate and migrate to the sebaceous gland to replace the lost sebocyte. TCDD acts by inducing a switch in this signal and skin hamartoma develop in place of new sebocytes.

Corrigendum: Development of skin diseases following systemic exposure: example of dioxins.

[This corrects the article DOI: 10.3389/ftox.2023.1243192.].

Lipid Droplet Proteins in Acne Skin: A Sound Target for the Maintenance of Low Comedogenic Sebum and Acne-Prone Skin Health.

In adipocytes and sebocytes, lipid droplet proteins control the storage of lipids in organized droplets and their release on demand. The contribution of lipid droplet proteins to the pathogenesis of acne is plausible because they control the levels of comedogenic free fatty acids. The expression of two lipid droplet proteins, CIDEA and PLIN2, was analyzed in the skin of patients with acne by immunohistochemistry and western blotting. The design of clinical protocols allowed correlating the expression of CIDEA and PLIN2 with both comedogenesis and the release of free fatty acids. Both proteins were detected by immunohistochemistry in the sebaceous glands of patients with acne, with a disturbed expression pattern of PLIN2 compared with that in the controls. Higher levels of PLIN2 and CIDEA, as detected by western blotting in the infundibulum, significantly correlated with lower ongoing comedogenesis over 48 weeks of Silybum marianum fruit extract application. Accordingly, free fatty acid release from sebum triglycerides was significantly decreased, as shown with two distinct methods. The data are consistent with the expected role of PLIN2 and CIDEA in the prevention of comedogenic free fatty acid release. Modulation of PLIN2 and CIDEA expression appears as a sound target for the maintenance of low comedogenic sebum and acne-prone skin health.

Cytochrome P450 1A2 activity and incidence of thyroid disease and cancer after chronic or acute exposure to dioxins.

BACKGROUND: Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD) is the most toxic congener of a family of structurally and mechanistically related persistent organic pollutants whose effects are mediated through the aryl hydrocarbon receptor (AhR). Induction of CYP1A1/2 by TCDD through the AhR depends on the magnitude and the duration of exposure. We aimed to assess CYP1A2 activity after acute and chronic exposure to TCDD. The Maincy cohort is a sample population from Melun in the Val-de-Seine region in France that lived for at least 5 years close to a waste incinerator emitting polluted vapours (1974-2002) with high concentrations of dioxins (up to 2000 times the maximal recommended values). Acute exposure to TCDD (Viktor Yushchenko) has been described elsewhere by Sorg et al (Toxicol. Sci. 2012; 125:310-317). Both are rare cases of well-identified source of chronic and acute exposure to TCDD. METHODS: All subjects underwent a full medical history and physical examination and had a cutaneous examination, and a retro-auricular skin biopsy was taken. A questionnaire was designed and used regarding demographic, personal, environmental and occupational characteristics. CYP1A2 activity was assessed 2 hours after the ingestion of a drink containing caffeine through measurement of the metabolic ratio of paraxanthine (17X) over caffeine (137X) by LC-MS/MS or LC-UV. CYP1A1 expression in skin biopsies was determined by immunohistochemical analysis. RESULTS: Forty-seven exposed subjects (age 11-78) and 31 controls were included in the study. Eleven exposed subjects had a history of thyroid disease (23.4%), and 7 (14.8%) had a cancer vs none and 1, respectively, in controls. Nodular skin lesions were found in 13 exposed subjects (27.7%) vs none in controls. Mean CYP1A2 activity of the exposed population was modestly elevated as compared to controls (17X/137X metabolic ratio of 0.475 vs 0.374, P = .051). CYP1A2 was, however, induced (17X/137X, metabolic ratio >0.5) in 27.6% of the exposed cases vs 6.4% of the controls. In contrast, acute dioxin exposure was associated with a strong induction (mean 17X/137X, metabolic ratio of 1.9) still present 29 months after the acute exposure. CYP1A1 was expressed in 59.6% of the skin biopsies (highly expressed in 31.9%) of the Maincy cohort. No correlation between CYP1A2 activity, CYP1A1 expression and clinical manifestations (thyroid disease, cancer, skin lesions) could be demonstrated. CONCLUSION: Higher frequencies of dysthyroidism and cancer were detected in the population exposed chronically to dioxins from a waste incinerator. CYP1A2 was induced in 27.6% of the exposed population, while the magnitude of induction was fourfold higher after acute exposure in the case of Yushchenko.

Dermatoporosis, a prevalent skin condition affecting the elderly: current situation and potential treatments.

The term "dermatoporosis" was introduced a decade ago to highlight the need to pay attention to the problems posed by premature skin aging beyond esthetic considerations. People with this condition have a thinner skin that becomes fragile, tends to tear, and may lead to deep dissecting hematomas-as a final stage-corresponding to a medical emergency. Various studies have demonstrated a high prevalence of dermatoporosis in the elderly, with women being more exposed than men. We have developed a scoring system for dermatoporosis, providing different strategies to treat and prevent this skin condition, as well as a followup of patients treated at the University Hospital of Geneva.

From the Cover: High Susceptibility of Lrig1 Sebaceous Stem Cells to TCDD in Mice.

We have previously shown that cytochrome P450 1A1 (CYP1A1) was highly induced for a long period of time in a patient who had been poisoned by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a compound known to activate the aryl hydrocarbon receptor (AhR). During that period of time, no sebaceous glands could be observed in the skin of this patient. In this study, starting from observations in the patient exposed to TCDD, we analyzed the seboatrophy induced by dioxins in mice. We observed a very different pattern of AhR and CYP1A1 immunostaining in skin biopsies of the patient. When applying TCDD and beta-naphthoflavone, another AhR agonist, on the ears of C57BL/6J mice, we reproduced (1) an atrophy of sebaceous glands, (2) a strong induction of CYP1A1 within the glands, and (3) a dramatic repression of the genes encoding the sebogenic enzymes AWAT1, ELOVL3, and SCD1. These effects were reversible. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) expressing progenitor cells, found in the vicinity of sebaceous glands, were shown to be the initial skin cellular targets of AhR agonists. These cells retained the DNA label BrdU and colocalized with the CYP1A1 protein for at least 30 days. A downregulation of LRIG1 by siRNA in cultured sebocytes significantly decreased the CYP1A1 response to TCDD, indicating that LRIG1 contributes to a higher susceptibility of AhR agonists. In conclusion, these observations provide for the first time a strong experimental support to the concept that dioxin-induced skin pathology may be driven by a molecular switch in progenitor cells involved in the physiological turnover of sebaceous glands.

Evaluation and identification of dioxin exposure biomarkers in human urine by high-resolution metabolomics, multivariate analysis and in vitro synthesis.

A previous high-resolution metabolomic study pointed out a dysregulation of urinary steroids and bile acids in human cases of acute dioxin exposure. A subset of 24 compounds was highlighted as putative biomarkers. The aim of the current study was (i) to evaluate the 24 biomarkers in an independent human cohort exposed to dioxins released from the incineration fumes of a municipal waste incinerator and; (ii) to identify them by comparison with authentic chemical standards and biosynthesised products obtained with in vitro metabolic reactions. An orthogonal projection to latent structures discriminant analysis built on biomarker profiles measured in the intoxicated cohort and the controls separated both groups with reported values of 93.8%; 100% and 87.5% for global accuracy; sensitivity and specificity; respectively. These results corroborated the 24 compounds as exposure biomarkers; but a definite identification was necessary for a better understanding of dioxin toxicity. Dehydroepiandrosterone 3ß-sulfate, androsterone 3α-glucuronide, androsterone 3α-sulfate, pregnanediol 3α-glucuronide and 11-ketoetiocholanolone 3α-glucuronide were identified by authentic standards. Metabolic reactions characterised four biomarkers: glucuronide conjugates of 11ß-hydroxyandrosterone; glycochenodeoxycholic acid and glycocholic acid produced in human liver microsomes and glycoursodeoxycholic acid sulfate generated in cytosol fraction. The combination of metabolomics by high-resolution mass spectrometry with in vitro metabolic syntheses confirmed a perturbed profile of steroids and bile acids in human cases of dioxin exposure.

Aryl Hydrocarbon Receptor Activation in Acne Vulgaris Skin: A Case Series from the Region of Naples, Italy.

BACKGROUND: Dioxins are persistent organic pollutants present in the environment. They exert their biological effects by binding to an intracellular receptor, the aryl hydrocarbon receptor (AhR). Activation of AhR leads to the induction of cytochrome p450 1A1 (CYP1A1). Expression of CYP1A1 in human skin is a key marker for AhR activation, and it may induce comedogenesis resulting in acne-like lesions known as chloracne/metabolising acquired dioxin-induced skin hamartomas (MADISH). The contribution of this pathway in patients seen in a busy acne clinic is unknown. MATERIALS AND METHODS: We explored the expression of CYP1A1 by immunohistochemistry in the acne lesions of 16 patients living in the region of Naples, Italy, where epidemiological studies have suggested a possibly increased exposure to environmental dioxins. A composite score to outline potential components of the chloracne/MADISH histological pattern was used. RESULTS: CYP1A1 expression was observed in 11 lesions (69%) and was distributed in sebaceous glands, follicular epithelium, cystic wall and endothelial cells. The histological score for chloracne/MADISH was 'likely' in 3 cases and 'possible' in 11 cases. Compared to current data on CYP1A1 expression in the skin of 67 patients with proven exposure to AhR agonists, these data indicate a high incidence of AhR activation in this series. CONCLUSION: This is the first study analysing AhR activation in skin in a series of patients from a hospital-based acne clinic. It provides information for future controlled prospective studies. The significance of CYP1A1 expression in terms of AhR ligand exposure is discussed.

L-Tryptophan as a Novel Potential Pharmacological Treatment for Wound Healing via Aryl Hydrocarbon Receptor Activation.

BACKGROUND: The aryl hydrocarbon receptor has been shown to be involved in wound healing. OBJECTIVE: The aim of this study was to assess the effect of tryptophan on wound healing in vitro and in a clinical trial. METHODS: The ability of tryptophan and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to increase wound healing was assessed in an in vitro scratch wound model in human keratinocytes. Topical tryptophan and vehicle were assessed for 12 weeks in 51 patients with lower limb ulcers that were resistant to conventional therapies. RESULTS: TCDD 0.1 nM and tryptophan 1 µM increased the rate of scratch recovery in a culture model. Topical tryptophan induced stronger pain relief and faster re-epithelialization than its vehicle in patients with lower limb ulcers. CONCLUSION: Tryptophan shows promising potential as a novel topical treatment for wound healing.

Topical retinoids in skin ageing: a focused update with reference to sun-induced epidermal vitamin A deficiency.

Vitamin A is an important constituent of the epidermis, where it plays a crucial role in epidermal turnover. A deficiency of epidermal vitamin A may be the consequence of nutritional vitamin A deficiency, exposure to sunlight or any UV source, oxidative stress or chronological ageing. As a consequence, any treatment aiming at increasing epidermal vitamin A would exert a protective effect against these deleterious conditions. Retinoids may counteract some deleterious actions of UV radiation by physical and biological mechanisms. Topical natural retinoic acid precursors such as retinaldehyde or retinol are less irritant than acidic retinoids and may prevent epidermal vitamin A deficiency due to nutritional deficiency, exposure to sunlight or any condition leading to free radical production. Retinoids may be combined with other compounds with complementary actions against ageing, nutritional deficiency and cancer, such as antioxidants, to potentiate their beneficial effects in the skin.

Activation of Nrf2 in keratinocytes causes chloracne (MADISH)-like skin disease in mice.

The transcription factor Nrf2 is a key regulator of the cellular stress response, and pharmacological Nrf2 activation is a promising strategy for skin protection and cancer prevention. We show here that prolonged Nrf2 activation in keratinocytes causes sebaceous gland enlargement and seborrhea in mice due to upregulation of the growth factor epigen, which we identified as a novel Nrf2 target. This was accompanied by thickening and hyperkeratosis of hair follicle infundibula. These abnormalities caused dilatation of infundibula, hair loss, and cyst development upon aging. Upregulation of epigen, secretory leukocyte peptidase inhibitor (Slpi), and small proline-rich protein 2d (Sprr2d) in hair follicles was identified as the likely cause of infundibular acanthosis, hyperkeratosis, and cyst formation. These alterations were highly reminiscent to the phenotype of chloracne/"metabolizing acquired dioxin-induced skin hamartomas" (MADISH) patients. Indeed, SLPI, SPRR2, and epigen were strongly expressed in cysts of MADISH patients and upregulated by dioxin in human keratinocytes in an NRF2-dependent manner. These results identify novel Nrf2 activities in the pilosebaceous unit and point to a role of NRF2 in MADISH pathogenesis.

Human urinary biomarkers of dioxin exposure: analysis by metabolomics and biologically driven data dimensionality reduction.

Untargeted metabolomic approaches offer new opportunities for a deeper understanding of the molecular events related to toxic exposure. This study proposes a metabolomic investigation of biochemical alterations occurring in urine as a result of dioxin toxicity. Urine samples were collected from Czech chemical workers submitted to severe dioxin occupational exposure in a herbicide production plant in the late 1960s. Experiments were carried out with ultra-high pressure liquid chromatography (UHPLC) coupled to high-resolution quadrupole time-of-flight (QTOF) mass spectrometry. A chemistry-driven feature selection was applied to focus on steroid-related metabolites. Supervised multivariate data analysis allowed biomarkers, mainly related to bile acids, to be highlighted. These results supported the hypothesis of liver damage and oxidative stress for long-term dioxin toxicity. As a second step of data analysis, the information gained from the urine analysis of Victor Yushchenko after his poisoning was examined. A subset of relevant urinary markers of acute dioxin toxicity from this extreme phenotype, including glucuro- and sulfo-conjugated endogenous steroid metabolites and bile acids, was assessed for its ability to detect long-term effects of exposure. The metabolomic strategy presented in this work allowed the determination of metabolic patterns related to dioxin effects in human and the discovery of highly predictive subsets of biologically meaningful and clinically relevant compounds. These results are expected to provide valuable information for a deeper understanding of the molecular events related to dioxin toxicity. Furthermore, it presents an original methodology of data dimensionality reduction by using extreme phenotype as a guide to select relevant features prior to data modeling (biologically driven data reduction).

AhR signalling and dioxin toxicity.

Dioxins are a family of molecules associated to several industrial accidents such as Ludwigshafen in 1953 or Seveso in 1976, to the Agent Orange used during the war of Vietnam, and more recently to the poisoning of the former president of Ukraine, Victor Yushchenko. These persistent organic pollutants are by-products of industrial activity and bind to an intracellular receptor, AhR, with a high potency. In humans, exposure to dioxins, in particular 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces a cutaneous syndrome known as chloracne, consisting in the development of many small skin lesions (hamartoma), lasting for 2-5 years. Although TCDD has been classified by the WHO as a human carcinogen, its carcinogenic potential to humans is not clearly demonstrated. It was first believed that AhR activation accounted for most, if not all, biological properties of dioxins. However, certain AhR agonists found in vegetables do not induce chloracne, and other chemicals, in particular certain therapeutic agents, may induce a chloracne-like syndrome without activating AhR. It is time to rethink the mechanism of dioxin toxicity and analyse in more details the biological events following exposure to these compounds and other AhR agonists, some of which have a very different chemical structure than TCDD. In particular various food-containing AhR agonists are non-toxic and may on the contrary have beneficial properties to human health.

Interaction of ω-3 polyunsaturated fatty acids with radiation therapy in two different colorectal cancer cell lines.

BACKGROUND & AIMS: This study aims at evaluating if docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) increases the efficacy of radiation therapy (RT) on two human colorectal cancer cell lines with different radio-sensitivity. METHODS: LS174T and HT-29 cells were treated with 20 or 50 µmol/L EPA or DHA followed by single X-ray RT of 0, 2 or 4 Gy, to evaluate cell survival, apoptosis, peroxide and malondialdehyde productions. Inflammation- and apoptosis-related proteins were analyzed by Western Blot. ANOVAs were used for statistical analysis. RESULTS: LS174T was more sensitive to RT than HT-29. DHA and to a lesser extent EPA increased cell death, apoptosis and peroxide production after RT in LS174T and to a lesser extent in HT-29 (p < 0.05). This was associated with increased expression of heat shock protein 70, decreased expression of NF-kB p65, COX-2 and Bcl-2 proteins. CONCLUSIONS: The effect of RT combination with DHA and to a lesser extent EPA was synergistic in the radio-sensitive LS174T cells, but additive in the radio-resistant HT-29 cells. This enhanced cytotoxicity was provoked at least partly by lipid peroxidation, which consequently modulated inflammatory response and induced apoptosis.

Vitamin E content in fish oil emulsion does not prevent lipoperoxidative effects on human colorectal tumors.

OBJECTIVE: The anticancer action exerted by polyunsaturated fatty acid peroxidation may not be reproduced by commercially available lipid emulsions rich in vitamin E. Therefore, we evaluated the effects of fish oil (FO) emulsion containing α-tocopherol 0.19 g/L on human colorectal adenocarcinoma cells and tumors. METHODS: HT-29 cell growth, survival, apoptosis, and lipid peroxidation were analyzed after a 24-h incubation with FO 18 to 80 mg/L. Soybean oil (SO) emulsion was used as an isocaloric and isolipidic control. In vivo, nude mice bearing HT-29 tumors were sacrificed 7 d after an 11-d treatment with intravenous injections of FO or SO 0.2 g ∙ kg(-1) ∙ d(-1) FO or SO to evaluate tumor growth, necrosis, and lipid peroxidation. RESULTS: The FO inhibited cell viability and clonogenicity in a dose-dependent manner, whereas SO showed no significant effect compared with untreated controls. Lipid peroxidation and cell apoptosis after treatment with FO 45 mg/L were increased 2.0-fold (P < 0.01) and 1.6-fold (P = 0.04), respectively. In vivo, FO treatment did not significantly affect tumor growth. However, immunohistochemical analyses of tumor tissue sections showed a decrease of 0.6-fold (P < 0.01) in the cell proliferation marker Ki-67 and an increase of 2.3-fold (P = 0.03) in the necrotic area, whereas malondialdehyde and total peroxides were increased by 1.9-fold (P = 0.09) and 7.0-fold (P < 0.01), respectively, in tumors of FO-treated compared with untreated mice. CONCLUSION: These results suggest that FO but not SO has an antitumor effect that can be correlated with lipid peroxidation, despite its vitamin E content.

The cutaneous lesions of dioxin exposure: lessons from the poisoning of Victor Yushchenko.

Several million people are exposed to dioxin and dioxin-like compounds, primarily through food consumption. Skin lesions historically called "chloracne" are the most specific sign of abnormal dioxin exposure and classically used as a key marker in humans. We followed for 5 years a man who had been exposed to the most toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), at a single oral dose of 5 million-fold more than the accepted daily exposure in the general population. We adopted a molecular medicine approach, aimed at identifying appropriate therapy. Skin lesions, which progressively covered up to 40% of the body surface, were found to be hamartomas, which developed parallel to a complete and sustained involution of sebaceous glands, with concurrent transcriptomic alterations pointing to the inhibition of lipid metabolism and the involvement of bone morphogenetic proteins signaling. Hamartomas created a new compartment that concentrated TCDD up to 10-fold compared with serum and strongly expressed the TCDD-metabolizing enzyme cytochrome P450 1A1, thus representing a potentially significant source of enzymatic activity, which may add to the xenobiotic metabolism potential of the classical organs such as the liver. This historical case provides a unique set of data on the human tissue response to dioxin for the identification of new markers of exposure in human populations. The herein discovered adaptive cutaneous response to TCDD also points to the potential role of the skin in the metabolism of food xenobiotics.