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 xenobiotic

Hyaluronate Fragments Reverse Skin Atrophy by a CD44-Dependent Mechanism

BACKGROUND: Skin atrophy is a common manifestation of aging and is frequently accompanied by ulceration and delayed wound healing. With an increasingly aging patient population, management of skin atrophy is becoming a major challenge in the clinic, particularly in light of the fact that there are no effective therapeutic options at present. METHODS AND FINDINGS: Atrophic skin displays a decreased hyaluronate (HA) content and expression of the major cell-surface hyaluronate receptor, CD44. In an effort to develop a therapeutic strategy for skin atrophy, we addressed the effect of topical administration of defined-size HA fragments (HAF) on skin trophicity. Treatment of primary keratinocyte cultures with intermediate-size HAF (HAFi; 50,000–400,000 Da) but not with small-size HAF (HAFs; <50,000 Da) or large-size HAF (HAFl; >400,000 Da) induced wild-type (wt) but not CD44-deficient (CD44(−/−)) keratinocyte proliferation. Topical application of HAFi caused marked epidermal hyperplasia in wt but not in CD44(−/−) mice, and significant skin thickening in patients with age- or corticosteroid-related skin atrophy. The effect of HAFi on keratinocyte proliferation was abrogated by antibodies against heparin-binding epidermal growth factor (HB-EGF) and its receptor, erbB1, which form a complex with a particular isoform of CD44 (CD44v3), and by tissue inhibitor of metalloproteinase-3 (TIMP-3). CONCLUSIONS: Our observations provide a novel CD44-dependent mechanism for HA oligosaccharide-induced keratinocyte proliferation and suggest that topical HAFi application may provide an attractive therapeutic option in human skin atrophy

Synergistic Effect of Hyaluronate Fragments in Retinaldehyde-Induced Skin Hyperplasia Which Is a Cd44-Dependent Phenomenon

BACKGROUND: CD44 is a polymorphic proteoglycan and functions as the principal cell-surface receptor for hyaluronate (HA). Heparin-binding epidermal growth factor (HB-EGF) activation of keratinocyte erbB receptors has been proposed to mediate retinoid-induced epidermal hyperplasia. We have recently shown that intermediate size HA fragments (HAFi) reverse skin atrophy by a CD44-dependent mechanism. METHODOLOGY AND PRINCIPAL FINDINGS: Treatment of primary mouse keratinocyte cultures with retinaldehyde (RAL) resulted in the most significant increase in keratinocyte proliferation when compared with other retinoids, retinoic acid, retinol or retinoyl palmitate. RAL and HAFi showed a more significant increase in keratinocyte proliferation than RAL or HAFi alone. No proliferation with RAL was observed in CD44-/- keratinocytes. HA synthesis inhibitor, 4-methylumbelliferone inhibited the proliferative effect of RAL. HB-EGF, erbB1, and tissue inhibitor of MMP-3 blocking antibodies abrogated the RAL- or RAL- and HAFi-induced keratinocyte proliferation. Topical application of RAL or RAL and HAFi for 3 days caused a significant epidermal hyperplasia in the back skin of wild-type mice but not in CD44-/- mice. Topical RAL and HAFi increased epidermal CD44 expression, and the epidermal and dermal HA. RAL induced the expression of active HB-EGF and erbB1. However, treatment with RAL and HAFi showed a more significant increase in pro-HB-EGF when compared to RAL or HAFi treatments alone. We then topically applied RAL and HAFi twice a day to the forearm skin of elderly dermatoporosis patients. After 1 month of treatment, we observed a significant clinical improvement. CONCLUSIONS AND SIGNIFICANCE: Our results indicate that (i) RAL-induced in vitro and in vivo keratinocyte proliferation is a CD44-dependent phenomenon and requires the presence of HA, HB-EGF, erbB1 and MMPs, (ii) RAL and HAFi show a synergy in vitro and in vivo in mouse skin, and (iii) the combination of RAL and HAFi seems to have an important therapeutic effect in dermatoporosis

In vivo Bio-Integration of Three Hyaluronic Acid Fillers in Human Skin: A Histological Study

&lt;b&gt;&lt;i&gt;Background:&lt;/i&gt;&lt;/b&gt; Hyaluronic acid (HA) formulations are used for aesthetic applications. Different cross-linking technologies result in HA dermal fillers with specific characteristic visco-elastic properties. &lt;b&gt;&lt;i&gt;Objective:&lt;/i&gt;&lt;/b&gt; Bio-integration of three CE-marked HA dermal fillers, a cohesive (monophasic) polydensified, a cohesive (monophasic) monodensified and a non-cohesive (biphasic) filler, was analysed with a follow-up of 114 days after injection. Our aim was to study the tolerability and inflammatory response of these fillers, their patterns of distribution in the dermis, and influence on tissue integrity. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; Three HA formulations were injected intradermally into the iliac crest region in 15 subjects. Tissue samples were analysed after 8 and 114 days by histology and immunohistochemistry, and visualized using optical and transmission electron microscopy. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; Histological results demonstrated that the tested HA fillers showed specific characteristic bio-integration patterns in the reticular dermis. Observations under the optical and electron microscopes revealed morphological conservation of cutaneous structures. Immunohistochemical results confirmed absence of inflammation, immune response and granuloma. &lt;b&gt;&lt;i&gt;Conclusion:&lt;/i&gt;&lt;/b&gt; The three tested dermal fillers show an excellent tolerability and preservation of the dermal cells and matrix components. Their tissue integration was dependent on their visco-elastic properties. The cohesive polydensified filler showed the most homogeneous integration with an optimal spreading within the reticular dermis, which is achieved by filling even the smallest spaces between collagen bundles and elastin fibrils, while preserving the structural integrity of the latter. Absence of adverse reactions confirms safety of the tested HA dermal fillers.</jats:p

Topical retinaldehyde increases skin content of retinoic acid and exerts biologic activity in mouse skin

Retinaldehyde, a natural metabolite of β-carotene and retinol, has been proposed recently for topical use in humans. Because retinaldehyde does not bind to retinoid nuclear receptors, its biologic activity should result from enzymatic transformation by epidermal keratinocytes into ligands for these receptors, such as all-trans retinoic acid and 9-cis-retinoic acid. In this study, we analyzed by high performance liquid chromatography the type and amounts of tissue retinoids as well as several biologic activities resulting from topical application of either retinaldehyde or all-trans retinoic acid on mouse tail skin. Biologic activities of all-trans retinoic acid and retinaldehyde were qualitatively identical in metaplastic parameters (induction of orthokeratosis, reduction of keratin 65-kDa mRNA, increase in filaggrin and loricrin 65-kDa mRNAs) and hyperplastic parameters (increase in epidermal thickness, increase in bromodeoxyuridine (BrdU)-positive cells, increase in keratin 50-kDa mRNA, and reduction in keratin 70-kDa mRNA). Some quantitative differences, not all in favor of all-trans retinoic acid, were found in several indices. Cellular retinoic acid-binding protein II and cellular retinol-binding protein I mRNAs were increased by both topical retinaldehyde and all-trans retinoic acid. Whereas all-trans retinoic acid, 9-cis-retinoic acid, and 13-cis-retinoic acid were not detectable (limit 5ng/g) in vehicle-treated skin, 0.05% retinaldehyde-treated skin contained 13 ± 6.9ng/g wet tissue of all-trans retinoic acid (mean ± SD), 12.6 ± 5.9ng/g 13-cis-retinoic acid, and no 9-cis-retinoic acid. In contrast, 9-cis-retinoic acid was detectable in 0.05% of all-trans retinoic acid-treated skin, which also contained 25-fold more all-trans retinoic acid and 5-fold more 13-cis-retinoic acid than retinaldehyde-treated skin. Our results show that topical retinaldehyde is transformed in vivo into all-trans retinoic acid by mouse epidermis. The small amounts of ligand for retinoic acid nuclear receptors thus produced are sufficient to induce biologic effects similar to those resulting from the topical application of the ligand itself in much higher concentration

UVA and UVB decrease the expression of CD44 and hyaluronate in mouse epidermis, which is counteracted by topical retinoids

The transmembrane glycoprotein CD44 is currently thought to be the main cell surface receptor for the glycosaminoglycan hyaluronate. We previously showed that (1) CD44 regulate keratinocyte proliferation; (2) topical retinoids dramatically increase the expression of CD44, hyaluronate and hyaluronate synthase (HAS)s in mouse epidermis; (3) topical retinaldehyde restores the epidermal thickness and CD44 expression which are correlated with clinical improvement in lichen sclerosus et atrophicus lesions; and (4) retinaldehyde-induced proliferative response of keratinocytes is a CD44-dependent phenomenon and requires the presence of HB-EGF, erbB1 and matrix metalloproteinases. In this study, we analyzed the effect of UV irradiation on the levels of epidermal hyaluronate and CD44 in mice, as well as its potential prevention by topical retinoids. UVA (10 J/cm(2)) or UVB (1 J/cm(2)) irradiation significantly decreased the expression of CD44 and hyaluronate in the epidermis of hairless mice after 2 h. Expression of both epidermal CD44 and hyaluronate was reconstituted within 24 h. Topical application of retinaldehyde for 3 days prior to UVA or UVB irradiation prevented the decrease of CD44 and hyaluronate expression. Topical retinol and retinoic acid also increased the basal levels of epidermal CD44 and hyaluronate, although their preventive effect on UV-induced decrease of these molecules was less pronounced as compared to topical retinaldehyde. These data confirm the relationships between retinoid and CD44 pathways, although the primary target(s) of UV leading to CD44 and hyaluronate degradation remain to be elucidated

Metabolism and biological activities of topical 4-oxoretinoids in mouse skin

Retinoic acid mediates most of the biological actions of vitamin A. It is oxidized by CYP26A1 to 4-oxoretinoic acid, considered as an inactive catabolite of retinoic acid. However, in the light of studies reporting the presence of 4-oxoretinal or 4-oxoretinol as the predominant retinoids during morphogenesis, we analyzed the retinoid-like biological activity of these oxoretinoids in mouse skin in vivo. Topical 4-oxoretinal and 4-oxoretinol promoted significant epidermal hyperplasia and metaplasia in mouse tail. They induced a moderate response for epidermal inflammation, compared with retinal, whereas neither 4-oxoretinal nor 4-oxoretinol prevented menadione-induced epidermal lipid peroxidation, unlike retinal and retinol. As analyzed by quantitative PCR, 4-oxoretinal and 4-oxoretinol did not reproduce the significant increased expression of genes coding for keratin 4, amphiregulin, heparin-EGF and CYP26A1, that did induce retinal and retinol. However, both retinal and 4-oxoretinal significantly inhibited the lipopolysaccharide-induced maturation of human dendritic cells in vitro. As analyzed in vivo and in vitro, 4-oxoretinal and 4-oxoretinol were not converted into retinoic acid. We conclude that 4-oxoretinal and 4-oxoretinol exert a moderate direct retinoid-like activity in vivo, thus confirming previous in vitro studies in amphibians showing 4-oxometabolites of vitamin A as bioactive agents rather than inactive catabolites