ROS quenching potential of the epidermal cornified cell envelope

Development-Associated Genes of the Epidermal Differentiation Complex (EDC)

The epidermal differentiation complex (EDC) is a cluster of genes that encode protein components of the outermost layers of the epidermis in mammals, reptiles and birds. The development of the stratified epidermis from a single-layered ectoderm involves an embryo-specific superficial cell layer, the periderm. An additional layer, the subperiderm, develops in crocodilians and over scutate scales of birds. Here, we review the expression of EDC genes during embryonic development. Several EDC genes are expressed predominantly or exclusively in embryo-specific cell layers, whereas others are confined to the epidermal layers that are maintained in postnatal skin. The S100 fused-type proteins scaffoldin and trichohyalin are expressed in the avian and mammalian periderm, respectively. Scaffoldin forms the so-called periderm granules, which are histological markers of the periderm in birds. Epidermal differentiation cysteine-rich protein (EDCRP) and epidermal differentiation protein containing DPCC motifs (EDDM) are expressed in the avian subperiderm where they are supposed to undergo cross-linking via disulfide bonds. Furthermore, a histidine-rich epidermal differentiation protein and feather-type corneous beta-proteins, also known as beta-keratins, are expressed in the subperiderm. The accumulating evidence for roles of EDC genes in the development of the epidermis has implications on the evolutionary diversification of the skin in amniotes.

Environmental pro-oxidants induce altered envelope protein profiles in human keratinocytes

Cornified envelopes (CEs) of human epidermis ordinarily consist of transglutaminase-mediated cross-linked proteins and are essential for skin barrier function. However, in addition to enzyme-mediated isopeptide bonding, protein cross-linking could also arise from oxidative damage. Our group recently demonstrated abnormal incorporation of cellular proteins into CEs by pro-oxidants in woodsmoke. In this study, we focused on 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), mesquite liquid smoke (MLS), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), to further understand the mechanisms through which environmental pro-oxidants induce CE formation and alter the CE proteome. CEs induced by the ionophore X537A were used for comparison. Similar to X537A, DMNQ- and MLS-induced CE formation was associated with membrane permeabilization. However, since DMNQ is non-adduct forming, its CEs were similar in protein profile to those from X537A. By contrast, MLS, rich in reactive carbonyls that can form protein adducts, caused a dramatic change in the CE proteome. TCDD-CEs were found to contain many CE precursors, such as small proline-rich proteins and late cornified envelope proteins, encoded by the epidermal differentiation complex. Since expression of these proteins is mediated by the aryl hydrocarbon receptor (AhR), and its well-known downstream protein, CYP1A1, was exclusively present in the TCDD group, we suggest that TCDD alters the CE proteome through persistent AhR activation. This study demonstrates the potential of environmental pro-oxidants to alter the epidermal CE proteome and indicates that the cellular redox state has an important role in CE formation.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

Loricrin at the Boundary between Inside and Outside

Cornification is a specialized mode of the cell-death program exclusively allowed for terrestrial amniotes. Recent investigations suggest that loricrin (LOR) is an important cornification effector. As the connotation of its name (“lorica” meaning an armor in Latin) suggests, the keratin-associated protein LOR promotes the maturation of the epidermal structure through organizing covalent cross-linkages, endowing the epidermis with the protection against oxidative injuries. By reviewing cornification mechanisms, we seek to classify ichthyosiform dermatoses based on their function, rather than clinical manifestations. We also reviewed recent mechanistic insights into the Kelch-like erythroid cell-derived protein with the cap “n” collar homology-associated protein 1/nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway in skin health and diseases, as LOR and NRF2 coordinate the epidermis-intrinsic xenobiotic metabolism. Finally, we refine the theoretical framework of cross-talking between keratinocytes and epidermal resident leukocytes, dissecting an LOR immunomodulatory function.

Loricrin and NRF2 Coordinate Cornification

Cornification involves cytoskeletal cross-linkages in corneocytes (the brick) and the secretion of lipids/adhesion structures to the interstitial space (the mortar). Because the assembly of lipid envelopes precedes corneocyte maturation, loricrin is supposed to be dispensable for the protection against desiccation. Although the phenotypes of Lor knockout (LKO) mice are obscure, the antioxidative response on the KEAP1/NRF2 signaling pathway compensates for the structural defect in utero. In this study, we asked how the compensatory response is evoked after the defects are repaired. To this end, the postnatal phenotypes of LKO mice were analyzed with particular attention to the permeability barrier function primarily maintained by the mortar. Ultrastructural analysis revealed substantially thinner cornified cell envelopes and increased numbers of lamellar granules in LKO mice. Superficial epidermal damages triggered the adaptive repairing responses that evoke the NRF2-dependent upregulation of genes associated with lamellar granule secretion in LKO mice. We also found that corneodesmosomes are less degraded in LKO mice. The observation suggests that loricrin and NRF2 are important effectors of cornification, in which proteins need to be secreted, cross-linked, and degraded in a coordinated manner.

The Interactions of Small Proline-Rich Proteins with Late Cornified Envelope Proteins are Involved in the Pathogenesis of Psoriasis

Purpose

Psoriasis is a common cutaneous disease with multiple characteristics including inflammation and aberrant keratinocyte proliferation. However, the pathogenesis of psoriasis is not completely clear yet. The objective of this study is to perform an in-depth analysis of the association between SPRR and LCE in the pathogenesis of psoriasis.

Methods

In this study, we explore the differentially expressed genes (DEGs) in psoriasis by analyzing different gene expression profiles obtained from the Gene Expression Omnibus (GEO) database. The DEGs were examined using gene ontology (GO) functional enrichment analysis and protein–protein interactions (PPI) network. Correlation analysis in R studio software was used to analyze the association between SPRR and LCE genes. Further, potential direct protein–protein interactions between SPRR proteins and LCE3D were verified by co-localization observations and co-immunoprecipitation (CO-IP) assays in 293T cells. Also, the expression levels of SPRR and LCE genes were detected in lesional skin of the IMQ-induced psoriasiform dermatitis mice using RT-PCR.

Results

Interestingly, the small proline-rich (SPRR) and late cornified envelope (LCE) genes were identified as a module in the constructed PPI network. And the analysis of the gene expression profile GSE63684 showed that both SPRR family and LCE family genes were significantly upregulated in imiquimod (IMQ) induced psoriasiform dermatitis mice. Also, the correlation analysis in R studio software recognized the association of SPRR and LCE genes, which were further verified by co-localization and co-immunoprecipitation (CO-IP) assays in 293T cells, and the results show that the direct interactions between SPRR2 and LCE3D. Notably, we also found that the expression levels of SPRR and LCE genes were significantly increased in the IMQ-induced psoriasiform dermatitis mice, while specifically decreased under the tazarotene cream treatment, indicating that the SPRR and LCEs were regulated simultaneously in psoriasis.

Conclusion

In summary, our study found that interactions between SPRR proteins and LCE proteins may provide new insights into the pathogenesis of psoriasis.

The Keratinocyte as a Crucial Cell in the Predisposition, Onset, Progression, Therapy and Study of the Atopic Dermatitis

The keratinocyte (KC) is the main functional and structural component of the epidermis, the most external layer of the skin that is highly specialized in defense against external agents, prevention of leakage of body fluids and retention of internal water within the cells. Altered epidermal barrier and aberrant KC differentiation are involved in the pathophysiology of several skin diseases, such as atopic dermatitis (AD). AD is a chronic inflammatory disease characterized by cutaneous and systemic immune dysregulation and skin microbiota dysbiosis. Nevertheless, the pathological mechanisms of this complex disease remain largely unknown. In this review, we summarize current knowledge about the participation of the KC in different aspects of the AD. We provide an overview of the genetic predisposing and environmental factors, inflammatory molecules and signaling pathways of the KC that participate in the physiopathology of the AD. We also analyze the link among the KC, the microbiota and the inflammatory response underlying acute and chronic skin AD lesions.

Gene duplications and gene loss in the epidermal differentiation complex during the evolutionary land-to-water transition of cetaceans

Major protein components of the mammalian skin barrier are encoded by genes clustered in the Epidermal Differentiation Complex (EDC). The skin of cetaceans, i.e. whales, porpoises and dolphins, differs histologically from that of terrestrial mammals. However, the genetic regulation of their epidermal barrier is only incompletely known. Here, we investigated the EDC of cetaceans by comparative genomics. We found that important epidermal cornification proteins, such as loricrin and involucrin are conserved and subtypes of small proline-rich proteins (SPRRs) are even expanded in numbers in cetaceans. By contrast, keratinocyte proline rich protein (KPRP), skin-specific protein 32 (XP32) and late-cornified envelope (LCE) genes with the notable exception of LCE7A have been lost in cetaceans. Genes encoding proline rich 9 (PRR9) and late cornified envelope like proline rich 1 (LELP1) have degenerated in subgroups of cetaceans. These data suggest that the evolution of an aquatic lifestyle was accompanied by amplification of SPRR genes and loss of specific other epidermal differentiation genes in the phylogenetic lineage leading to cetaceans.

Single-cell analysis reveals urothelial cell heterogeneity and regenerative cues following cyclophosphamide-induced bladder injury

Cyclophosphamide is a commonly used chemotherapeutic drug to treat cancer with side effects that trigger bladder injury and hemorrhagic cystitis. Although previous studies have demonstrated that certain cell subsets and communications are activated to drive the repair and regeneration of bladder, it is not well understood how distinct bladder cell subsets function synergistically in this process. Here, we used droplet-based single-cell RNA sequencing (scRNA-seq) to profile the cell types within the murine bladder mucous layer under normal and injured conditions. Our analysis showed that superficial cells are directly repaired by cycling intermediate cells. We further identified two resident mesenchymal lineages (Acta2⁺ myofibroblasts and Cd34⁺ fibroblasts). The delineation of cell-cell communications revealed that Acta2⁺ myofibroblasts upregulated Fgf7 expression during acute injury, which activated Fgfr signaling in progenitor cells within the basal/intermediate layers to promote urothelial cell growth and repair. Overall, our study contributes to a more comprehensive understanding of the cellular dynamics during cyclophosphamide-induced bladder injury and may help identify important niche factors contributing to the regeneration of injured bladders.

Detoxification of ionic liquids using glutathione, cysteine, and NADH: Toxicity evaluation by Tetrahymena pyriformis

Ionic liquids (ILs), also known as green solvents, are widely acknowledged in several fields, such as chemical separation, synthesis, and electrochemistry, owing to their excellent physiochemical properties. However, their poor biodegradability may lead to environmental and health risks, posing a severe threat to humans, thus requiring further research. In this study, the biotoxicities of the imidazolium-based ILs were evaluated in Tetrahymena pyriformis. Moreover, IL detoxification was investigated by addition of glutathione (GSH), cysteine, and nicotinamide adenine dinucleotide (NADH). Reactive oxygen species (ROS) initiated by different IL types caused damage to Tetrahymena, while glutathione, cysteine, and NADH eliminated ROS, achieving the detoxification purposes. Detoxification results showed that NADH exhibited the best detoxification ability, followed by glutathione and cysteine. Finally, RT-PCR results suggested that metallothionein might have participated in IL detoxification.

"Structural imprinting" of the cutaneous immune effector function

Keratinization provides tolerance to desiccation and mechanical durability. Loricrin, which is an epidermal thiol-rich protein, efficiently stabilizes terminally differentiated keratinocytes and maintains redox homeostasis. The discovery of the largely asymptomatic loricrin knockout (LKO) phenotype decades ago was rather unpredicted. Nevertheless, when including redox-driven, NF-E2-related factor 2-mediated backup responses, LKO mice provide opportunities for the observation of altered or "quasi-normal" homeostasis. Specifically, given that the tissue structure, as well as the local metabolism, transmits immunological signals, we sought to dissect the consequence of truncated epidermal differentiation program from immunological perspectives. Through a review of the aggregated evidence, we have attempted to generate an integrated view of the regulation of the peripheral immune system, which possibly occurs within the squamous epithelial tissue with truncated differentiation. This synthesis might not only provide insights into keratinization but also lead to the identification of factors intrinsic to the epidermis that imprint the immune effector function.

[Functional integrity of aging skin, from cutaneous biology to anti-aging strategies]

The skin is a sentinel organ making easily visible the passing of time. Chronological and environmental aging weakens skin structure and functions. The skin barrier, the elastic and mechanical properties of the cutaneous tissue as well as its vascular reactivity are impacted by aging. The barrier dysfunction in aged skin is caused by defects in epidermal keratinocytes renewal and differentiation notably linked to abnormal expression of microRNAs regulating cell death and autophagy. An abnormal balance between synthesis and degradation of matrix proteins modifies the mechanical properties of the dermis in aged skin. Finally, a reduction of the vascular reactivity linked to endothelial dysfunctions is observed in elderly people. These biological processes can be targeted by therapeutic approaches either topical or systemic, especially using anti-oxydants or senolytics. These anti-aging strategies might contribute to restore, at least in part, the functional integrity of aged skin.

Isosorbide Di-(Linoleate/Oleate) Stimulates Prodifferentiation Gene Expression to Restore the Epidermal Barrier and Improve Skin Hydration

The breakdown of the epidermal barrier and consequent loss of skin hydration is a feature of skin aging and eczematous dermatitis. Few treatments, however, resolve these underlying processes to provide full symptomatic relief. In this study, we evaluated isosorbide di-(linoleate/oleate) (IDL), which was generated by esterifying isosorbide with sunflower fatty acids. Topical effects of IDL in skin were compared with those of ethyl linoleate/oleate, which has previously been shown to improve skin barrier function. Both IDL and ethyl linoleate/oleate downregulated inflammatory gene expression, but IDL more effectively upregulated the expression of genes associated with keratinocyte differentiation (e.g., KRT1, GRHL2, SPRR4). Consistent with this, IDL increased the abundance of epidermal barrier proteins (FLG and involucrin) and prevented cytokine-mediated stratum corneum degradation. IDL also downregulated the expression of unhealthy skin signature genes linked to the loss of epidermal homeostasis and uniquely repressed an IFN-inducible coexpression module activated in multiple skin diseases, including psoriasis. In a double-blind, placebo-controlled trial enrolling females with dry skin, 2% IDL lotion applied over 2 weeks significantly improved skin hydration and decreased transepidermal water loss (NCT04253704). These results demonstrate mechanisms by which IDL improves skin hydration and epidermal barrier function, supporting IDL as an effective intervention for the treatment of xerotic pruritic skin.

Impact of cigarette smoke on physical-chemical and molecular proprieties of human skin in an ex vivo model

BACKGROUND

This is a study about the skin ageing exposome, focusing on the effect of cigarette smoke. Human living skin explants (HSE) were exposed to cigarette smoke (CS) of two cigarettes for 2 hours using a custom-made exposure chamber, the Pollubox^® . Effects on the surface physico-chemistry and molecular properties of the skin were analyzed and reported for the first time.

BASIC PROCEDURES

To this end, transcriptomic study followed by immunohistochemistry, MDA (Malondialdehyde Dosage), and surface physio-chemistry data: surface free energy determination, TEWL (Trans Epidermal Water Loss), skin pH and FT-IR (Fourier Transform-Infrared) spectroscopy of the explant were collected from untreated and treated HSE.

MAIN FINDINGS

Results showed a decrease of the total surface free energy of the treated HSE. This decrease reflected higher interactions with polar compounds from the environment and consequently a decrease of the surface hydrophobicity. Additionally, an increase of TEWL and skin pH was observed after treatment. The transcriptomic analysis showed downregulation of mitochondrial genes (PON2-NDUFA4L2-ATP1A1-ALDH2-PRODH) combined with an increase of MDA in CS-treated HSE.

CONCLUSIONS

CS-induced oxidation of lipids at HSE surface alters the skin barrier: interactions with polar products are enhanced and the lipid chain packing at the surface is modified. Consequently, skin permeability could increase which correlated with repression of CA9 and AQP1 genes. Beside activation of AHR-NRF2 pathway in CS-exposed HSE, our results suggested that mitochondrial functions were strongly impacted and oxidized lipids failed to be eliminated promoting skin barrier alteration. A mitophagy activity was suggested through the confirmation of PINK1 accumulation in the epidermis by immunostaining.

The KEAP1/NRF2 Signaling Pathway in Keratinization

Keratinization is a tissue adaptation, but aberrant keratinization is associated with skin disorders such as ichthyoses, atopic dermatitis, psoriasis, and acne. The disease phenotype stems from the interaction between genes and the environment; therefore, an understanding of the adaptation machinery may lead to a new appreciation of pathomechanisms. The KEAP1/NRF2 signaling pathway mediates the environmental responses of squamous epithelial tissue. The unpredicted outcome of the Keap1-null mutation in mice allowed us to revisit the basic principle of the biological process of keratinization: sulfur metabolism establishes unparalleled cytoprotection in the body wall of terrestrial mammals. We summarize the recent understanding of the KEAP1/NRF2 signaling pathway, which is a thiol-based sensor-effector apparatus, with particular focuses on epidermal differentiation in the context of the gene-environment interaction, the structure/function principles involved in KEAP1/NRF2 signaling, lessons from mouse models, and their pathological implications. This synthesis may provide insights into keratinization, which provides physical insulation and constitutes an essential innate integumentary defense system.

Identification of epidermal differentiation genes of the tuatara provides insights into the early evolution of lepidosaurian skin

The tuatara (Sphenodon punctatus) is the phylogenetically closest relative of squamates (including lizards and snakes) from which it diverged around 250 million years ago. Together, they constitute the clade Lepidosauria. Fully terrestrial vertebrates (amniotes) form their skin barrier to the environment under the control of a gene cluster, termed the epidermal differentiation complex (EDC). Here we identified EDC genes in the genome of the tuatara and compared them to those of other amniotes. The organization of the EDC and proteins encoded by EDC genes are most similar in the tuatara and squamates. A subcluster of lepidosaurian EDC genes encodes corneous beta-proteins (CBPs) of which three different types are conserved in the tuatara. Small proline-rich proteins have undergone independent expansions in the tuatara and some, but not all subgroups of squamates. Two genes encoding S100 filaggrin-type proteins (SFTPs) are expressed during embryonic skin development of the tuatara whereas SFTP numbers vary between 1 and 3 in squamates. Our comparative analysis of the EDC in the tuatara genome suggests that many molecular features of the skin that were previously identified in squamates have evolved prior to their divergence from the lineage leading to the tuatara.

Impact of airborne particulate matter on skin: a systematic review from epidemiology to in vitro studies

BACKGROUND

Air pollution is killing close to 5 million people a year, and harming billions more. Air pollution levels remain extremely high in many parts of the world, and air pollution-associated premature deaths have been reported for urbanized areas, particularly linked to the presence of airborne nano-sized and ultrafine particles.

MAIN TEXT

To date, most of the research studies did focus on the adverse effects of air pollution on the human cardiovascular and respiratory systems. Although the skin is in direct contact with air pollutants, their damaging effects on the skin are still under investigation. Epidemiological data suggested a correlation between exposure to air pollutants and aggravation of symptoms of chronic immunological skin diseases. In this study, a systematic literature review was conducted to understand the current knowledge on the effects of airborne particulate matter on human skin. It aims at providing a deeper understanding of the interactions between air pollutants and skin to further assess their potential risks for human health.

CONCLUSION

Particulate matter was shown to induce a skin barrier dysfunction and provoke the formation of reactive oxygen species through direct and indirect mechanisms, leading to oxidative stress and induced activation of the inflammatory cascade in human skin. Moreover, a positive correlation was reported between extrinsic aging and atopic eczema relative risk with increasing particulate matter exposure.

Loricrin: Past, Present, and Future

The terminal differentiation of the epidermis is a complex physiological process. During the past few decades, medical genetics has shown that defects in the stratum corneum (SC) permeability barrier cause a myriad of pathological conditions, ranging from common dry skin to lethal ichthyoses. Contrarily, molecular phylogenetics has revealed that amniotes have acquired a specialized form of cytoprotection cornification that provides mechanical resilience to the SC. This superior biochemical property, along with desiccation tolerance, is attributable to the proper formation of the macromolecular protein-lipid complex termed cornified cell envelopes (CE). Cornification largely depends on the peculiar biochemical and biophysical properties of loricrin, which is a major CE component. Despite its quantitative significance, loricrin knockout (LKO) mice have revealed it to be dispensable for the SC permeability barrier. Nevertheless, LKO mice have brought us valuable lessons. It is also becoming evident that absent loricrin affects skin homeostasis more profoundly in many more aspects than previously expected. Through an extensive review of aggregate evidence, we discuss herein the functional significance of the thiol-rich protein loricrin from a biochemical, genetic, pathological, metabolic, or immunological aspect with some theoretical and speculative perspectives.

DNA damage in human skin and the capacities of natural compounds to modulate the bystander signalling

Human skin is a stratified organ frequently exposed to sun-generated ultraviolet radiation (UVR), which is considered one of the major factors responsible for DNA damage. Such damage can be direct, through interactions of DNA with UV photons, or indirect, mainly through enhanced production of reactive oxygen species that introduce oxidative changes to the DNA. Oxidative stress and DNA damage also associate with profound changes at the cellular and molecular level involving several cell cycle and signal transduction factors responsible for DNA repair or irreversible changes linked to ageing. Crucially, some of these factors constitute part of the signalling known for the induction of biological changes in non-irradiated, neighbouring cells and defined as the bystander effect. Network interactions with a number of natural compounds, based on their known activity towards these biomarkers in the skin, reveal the capacity to inhibit both the bystander signalling and cell cycle/DNA damage molecules while increasing expression of the anti-oxidant enzymes. Based on this information, we discuss the likely polypharmacology applications of the natural compounds and next-generation screening technologies in improving the anti-oxidant and DNA repair capacities of the skin.

Xenobiotic Receptors and Their Mates in Atopic Dermatitis

Atopic dermatitis (AD) is the most common inflammatory skin disease worldwide. It is a chronic, relapsing and pruritic skin disorder which results from epidermal barrier abnormalities and immune dysregulation, both modulated by environmental factors. AD is strongly associated with asthma and allergic rhinitis in the so-called 'atopic march.' Xenobiotic receptors and their mates are ligand-activated transcription factors expressed in the skin where they control cellular detoxification pathways. Moreover, they regulate the expression of genes in pathways involved in AD in epithelial cells and immune cells. Activation or overexpression of xenobiotic receptors in the skin can be deleterious or beneficial, depending on context, ligand and activation duration. Moreover, their impact on skin might be amplified by crosstalk among xenobiotic receptors and their mates. Because they are activated by a broad range of endogenous molecules, drugs and pollutants owing to their promiscuous ligand affinity, they have recently crystalized the attention of researchers, including in dermatology and especially in the AD field. This review examines the putative roles of these receptors in AD by critically evaluating the conditions under which the proteins and their ligands have been studied. This information should provide new insights into AD pathogenesis and ways to develop new therapeutic interventions.

Physiological and Biochemical Effects of Echium Amoenum Extract on Mn2+-Imposed Parkinson Like Disorder in Rats

Purpose: Manganism is a cognitive disorder take places in peoples are exposed to environmental manganese pollution. Overexposure to manganese ion (Mn2+) mainly influences central nervous system and causes symptoms that increase possibility of hippocampal damages. Methods: In this study rats were administrated by two different doses of MnCl2 and behavioral and physiological consequences were evaluated. We also investigated effects of E. Amoenum on Mn2+-imposed toxicity by behavioral, biochemical, immunoblotting and histological studies on hippocampus tissue. Results: Results showed metal overexposure increases oxidative stress mainly by lipid peroxidation and reactive oxygen species overproduction. Histological studies and caspase 3 analyses by immunoblotting revealed Mn2+ induced apoptosis from mitochondrial-dependent pathway in the presence of low metal dose. This study provides evidence that oral administration of E. amoenum extract inhibited manganese neurotoxicity by oxidative stress attenuation and apoptosis reduction that lead to improved depression like behavior. Plant extract also increased catecholamine content in Mn2+ treated hippocampus. Conclusion: As molecular and pathophysiological effects of E. amoenum, it could be considered as a pre-treatment for Parkinson and Parkinson like disorders in high-risk people.

Does hypothyroidism augment sun-induced skin damage?

OBJECTIVES

We investigated the mutual effects of overt hypothyroidism and prolonged sunlight exposure on free radical accumulation and oxidative skin damage.

METHODS

Free radical accumulation was evaluated by monitoring the transformation of 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) into MTT-formazan. The pro-oxidant enzymes xanthine oxidase (XO) and NADPH-diaphorase were measured in the skin. XO activity was estimated based on the yield of uric acid, while NADPH-diaphorase reactivity was monitored histochemically as an indirect marker of nitric oxide synthase and nitric oxide activity. Cellular damage was determined by malondialdehyde formation, a marker for lipid peroxidation.

RESULTS

In the skin of both euthyroid and hypothyroid animals, solar simulated ultraviolet irradiance increased the activity of XO and the NADPHdiaphorase reactivity as a protective response to formation of free radicals, such as reactive oxygen or nitrogen species. These pro-oxidant enzymes diminished in hypothyroid rats. Accumulation of the same amount of free radicals led to similar peroxidation in both hypothyroid and irradiated euthyroid rats. Hypothyroid skin after UV-exposure showed even greater lipid peroxidation.

DISCUSSION

The hypothyroid state could be a risk factor for enhanced oxidative skin damage in chronic photo-exposed skin due to oxidative stress. The lipid peroxidation is one of the major pathways by which photo-oxidative stress promotes photocarcinogenesis and photo-aging.

Vitamin E Supplementation Reduces Cellular Loss in the Brain of a Premature Aging Mouse Model

BACKGROUND

Aging is a highly complex biological process driven by multiple factors. Its progression can partially be influenced by nutritional interventions. Vitamin E is a lipid-soluble anti-oxidant that is investigated as nutritional supplement for its ability to prevent or delay the onset of specific aging pathologies, including neurodegenerative disorders.

PURPOSE

We aimed here to investigate the effect of vitamin E during aging progression in a well characterized mouse model for premature aging.

METHOD

Xpg-/- animals received diets with low (~2.5 mg/kg feed), medium (75 mg/kg feed) or high (375 mg/kg feed) vitamin E concentration and their phenotype was monitored during aging progression. Vitamin E content was analyzed in the feed, for stability reasons, and in mouse plasma, brain, and liver, for effectiveness of the treatment. Subsequent age-related changes were monitored for improvement by increased vitamin E or worsening by depletion in both liver and nervous system, organs sensitive to oxidative stress.

RESULTS

Mice supplemented with high levels of vitamin E showed a delayed onset of age-related body weight decline and appearance of tremors when compared to mice with a low dietary vitamin E intake. DNA damage resulting in liver abnormalities such as changes in polyploidy, was considerably prevented by elevated amounts of vitamin E. Additionally, immunohistochemical analyses revealed that high intake of vitamin E, when compared with low and medium levels of vitamin E in the diet, reduces the number of p53-positive cells throughout the brain, indicative of a lower number of cells dying due to DNA damage accumulated over time.

CONCLUSIONS

Our data underline a neuroprotective role of vitamin E in the premature aging animal model used in this study, likely via a reduction of oxidative stress, and implies the importance of improved nutrition to sustain health.

BRCA1 deficiency sensitizes breast cancer cells to bromodomain and extra-terminal domain (BET) inhibition

BRCA1 is a tumor suppressor frequently mutated in breast and ovarian cancer, serving it as a target for therapeutic exploitation. Here, we show that BRCA1 has a synthetic lethality interaction with an epigenetics regulator, bromodomain and extra-terminal domain (BET). BET inhibition led to gene expression changes reversing MYC-dependent transcription repression of a redox regulator, thioredoxin-interacting protein (TXNIP), via switching the promoter occupant from MYC to MondoA:MLX complex. Reversing the MYC-TXNIP axis inhibited thioredoxin activity and elevated cellular oxidative stress, causing DNA damages that are detrimental to BRCA1-deficient breast cancer cells. Tumor xenograft models and breast cancer clinical data analyses further demonstrated an in vivo synthetic lethality interaction and clinical association between BET/TXNIP and BRCA1 deficiency in the survival of breast cancer patients.

Peptidylarginine deiminases and deiminated proteins at the epidermal barrier

Deimination or citrullination is a post-translational modification catalysed by a family of calcium-dependent enzymes called peptidylarginine deiminases (PADs). It corresponds to the transformation of arginine residues within a peptide sequence into citrulline residues. Deimination induces a decreased net charge of targeted proteins; therefore, it alters their folding and changes intra- and intermolecular ionic interactions. Deimination is involved in several physiological processes (inflammation, gene regulation, etc.) and human diseases (rheumatoid arthritis, neurodegenerative diseases, cancer, etc.). Here, we describe the PADs expressed in the epidermis and their known substrates, focusing on their role in the epidermal barrier function.

Targeted therapy of esophageal squamous cell carcinoma: the NRF2 signaling pathway as target

Esophageal squamous cell carcinoma (ESCC) is a deadly disease that requires extensive research. Here, we review the current understanding of the functions of the nuclear factor erythroid-derived 2-like 2 (NRF2) signaling pathway in the esophagus. Genomic data suggest that gene mutations and several other mechanisms result in NRF2 hyperactivation in human ESCC. As a consequence, NRF2^high ESCC is more resistant to chemoradiotherapy and associated with poorer survival than NRF2^low ESCC. Mechanistically, we believe NRF2, functioning as a transcription factor, causes an esophageal phenotype through regulation of gene transcription. We discuss metabolism, mitochondria, proteasomes, and several signaling pathways as downstream players that may contribute to an esophageal phenotype due to NRF2 hyperactivation. Finally, strategies are proposed to target the NRF2 signaling pathway for therapy of NRF2^high ESCC.

Identification of Wheat Inflorescence Development-Related Genes Using a Comparative Transcriptomics Approach

Inflorescence represents the highly specialized plant tissue producing the grains. Although key genes regulating flower initiation and development are conserved, the mechanism regulating fertility is still not well explained. To identify genes and gene network underlying inflorescence morphology and fertility of bread wheat, expressed sequence tags (ESTs) from different tissues were analyzed using a comparative transcriptomics approach. Based on statistical comparison of EST frequencies of individual genes in EST pools representing different tissues and verification with RT-PCR and RNA-seq data, 170 genes of 59 gene sets predominantly expressed in the inflorescence were obtained. Nearly one-third of the gene sets displayed differentiated expression profiles in terms of their subgenome orthologs. The identified genes, most of which were predominantly expressed in anthers, encode proteins involved in wheat floral identity determination, anther and pollen development, pollen-pistil interaction, and others. Particularly, 25 annotated gene sets are associated with pollen wall formation, of which 18 encode enzymes or proteins participating in lipid metabolic pathway, including fatty acid ω-hydroxylation, alkane and fatty alcohol biosynthesis, and glycerophospholipid metabolism. We showed that the comparative transcriptomics approach was effective in identifying genes for reproductive development and found that lipid metabolism was particularly active in wheat anthers.

Protective role of integrin-linked kinase against oxidative stress and in maintenance of genomic integrity

The balance between the production of reactive oxygen species and activation of antioxidant pathways is essential to maintain a normal redox state in all tissues. Oxidative stress caused by excessive oxidant species generation can cause damage to DNA and other macromolecules, affecting cell function and viability. Here we show that integrin-linked kinase (ILK) plays a key role in eliciting a protective response to oxidative damage in epidermal cells. Inactivation of the Ilk gene causes elevated levels of intracellular oxidant species (IOS) and DNA damage in the absence of exogenous oxidative insults. In ILK-deficient cells, excessive IOS production can be prevented through inhibition of NADPH oxidase activity, with a concomitant reduction in DNA damage. Additionally, ILK is necessary for DNA repair processes following UVB-induced damage, as ILK-deficient cells show a significantly impaired ability to remove cyclobutane pyrimidine dimers following irradiation. Thus, ILK is essential to maintain cellular redox balance and, in its absence, epidermal cells become more susceptible to oxidative damage through mechanisms that involve IOS production by NADPH oxidase activity.

Orthogonal Array composite design to study and optimize antioxidant combinations in the prevention of UVB-induced HSF damage

Excessive exposure to ultraviolet (UV) B radiation may lead to skin damage, photosensitivity, or even tumorigenesis via induction of oxidative stress. Naturally derived antioxidants could play significant roles in cancer therapy due to their multi-targeted actions and lack of substantial toxicity. Drug combinations target at diverse pathway of cells and make cells export meticulous biological outcomes through the multifaceted signaling network. The UVB protective effects of combinations of naturally derived antioxidants- curcumin, resveratrol, proanthocyanidins, baicalein, and beta-nicotinamide adenine dinucleotide (NADH) were investigated. An oxidative cell damage model was established to study the ultraviolet irradiation system. An orthogonal array composite design (OACD) was employed in the optimization of antioxidants combinations. Combination of resveratrol (0.1μM) and baicalein in medium concentration (0.2μM), with NADH in high concentration (0.8μM) was found to be the most efficacious combination among all the 30 runs performed using OACD. The findings suggested that UVB exposure-inflicted cell apoptosis can be significantly reduced by naturally-derived antioxidant combinations. These results provide an insight into the discovery of synergistic antioxidant combinations in skin cancer, using orthogonal array composite design (OACD). The results also have practical implications in the understanding of drug mechanisms in skin cancer, which can assist clinical practice by recommending better drug combinations.

Sulphurous Mineral Waters: New Applications for Health

Sulphurous mineral waters have been traditionally used in medical hydrology as treatment for skin, respiratory, and musculoskeletal disorders. However, driven by recent intense research efforts, topical treatments are starting to show benefits for pulmonary hypertension, arterial hypertension, atherosclerosis, ischemia-reperfusion injury, heart failure, peptic ulcer, and acute and chronic inflammatory diseases. The beneficial effects of sulphurous mineral waters, sulphurous mud, or peloids made from sulphurous mineral water have been attributed to the presence of sulphur mainly in the form of hydrogen sulphide. This form is largely available in conditions of low pH when oxygen concentrations are also low. In the organism, small amounts of hydrogen sulphide are produced by some cells where they have numerous biological signalling functions. While high levels of hydrogen sulphide are extremely toxic, enzymes in the body are capable of detoxifying it by oxidation to harmless sulphate. Hence, low levels of hydrogen sulphide may be tolerated indefinitely. In this paper, we review the chemistry and actions of hydrogen sulphide in sulphurous mineral waters and its natural role in body physiology. This is followed by an update of available data on the impacts of exogenous hydrogen sulphide on the skin and internal cells and organs including new therapeutic possibilities of sulphurous mineral waters and their peloids.

Dual Role of Act1 in Keratinocyte Differentiation and Host Defense: TRAF3IP2 Silencing Alters Keratinocyte Differentiation and Inhibits IL-17 Responses

TRAF3IP2 is a candidate psoriasis susceptibility gene encoding Act1, an adaptor protein with ubiquitin ligase activity that couples the IL-17 receptor to downstream signaling pathways. We investigated the role of Act1 in keratinocyte responses to IL-17 using a tetracycline inducible short hairpin RNA targeting TRAF3IP2. Tetracycline exposure for 7 days effectively silenced TRAF3IP2 mRNA and Act1 protein, resulting in 761 genes with significant changes in expression (495 down, 266 up; >1.5-fold, P < 0.05). Gene ontology analysis showed that genes affected by TRAF3IP2 silencing are involved in epidermal differentiation, with early differentiation genes (KRT1, KRT10, DSC1, DSG1) being down-regulated and late differentiation genes (SPRR2, SPRR3, LCE3) being up-regulated. AP1 binding sites were enriched upstream of genes up-regulated by TRAF3IP2 silencing. Correspondingly, nuclear expression of FosB and Fra1 was increased in TRAF3IP2-silenced cells. Many genes involved in host defense were induced by IL-17 in a TRAF3IP2-dependent fashion. Inflammatory differentiation conditions (serum addition for 4 days postconfluence) markedly amplified these IL-17 responses and increased basal levels and TRAF3IP2 silencing-dependent up-regulation of multiple late differentiation genes. These findings suggest that TRAF3IP2 may alter both epidermal homeostasis and keratinocyte defense responses to influence psoriasis risk.

The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline

Neurodegeneration, the progressive death of neurons, loss of brain function, and cognitive decline is an increasing problem for senior populations. Its causes are poorly understood and therapies are largely ineffective. Neurons, with high energy and oxygen requirements, are especially vulnerable to detrimental factors, including age-related dysregulation of biochemical pathways caused by altered expression of multiple genes. GHK (glycyl-l-histidyl-l-lysine) is a human copper-binding peptide with biological actions that appear to counter aging-associated diseases and conditions. GHK, which declines with age, has health promoting effects on many tissues such as chondrocytes, liver cells and human fibroblasts, improves wound healing and tissue regeneration (skin, hair follicles, stomach and intestinal linings, boney tissue), increases collagen, decorin, angiogenesis, and nerve outgrowth, possesses anti-oxidant, anti-inflammatory, anti-pain and anti-anxiety effects, increases cellular stemness and the secretion of trophic factors by mesenchymal stem cells. Studies using the Broad Institute Connectivity Map show that GHK peptide modulates expression of multiple genes, resetting pathological gene expression patterns back to health. GHK has been recommended as a treatment for metastatic cancer, Chronic Obstructive Lung Disease, inflammation, acute lung injury, activating stem cells, pain, and anxiety. Here, we present GHK's effects on gene expression relevant to the nervous system health and function.

Lce1 Family Members Are Nrf2-Target Genes that Are Induced to Compensate for the Loss of Loricrin

Loricrin is a major component of the cornified cell envelope, a highly insoluble structure composed of covalently cross-linked proteins. Although loricrin knockout mice only exhibit a mild transient phenotype at birth, they show a marked delay in the formation of an epidermal barrier in utero. We recently discovered that induction of a compensatory response to repair the defective barrier is initiated by amniotic fluid via activation of NF-E2-related factor 2 and identified Sprr2d and Sprr2h as direct transcriptional targets. Proteomic analysis suggested that other proteins were also incorporated into the loricrin knockout cell envelope, in addition to the small proline rich proteins. Here we present evidence suggesting that the late cornified envelope 1 proteins are also compensatory components as determined by their localization within the loricrin knockout cell envelope via immunoelectron microscopy. We also demonstrate that late cornified envelope 1 genes are upregulated at the transcriptional level in loricrin knockout mouse skin and confirm that late cornified envelope 1 genes are transcriptional targets of NRF2. Our present study further highlights the complexity and importance of a compensatory mechanism that evolved in terrestrial animals to ensure the formation of a functional epidermal barrier.

Periodic Exposure of Keratinocytes to Cold Physical Plasma: An In Vitro Model for Redox-Related Diseases of the Skin

Oxidative stress illustrates an imbalance between radical formation and removal. Frequent redox stress is critically involved in many human pathologies including cancer, psoriasis, and chronic wounds. However, reactive species pursue a dual role being involved in signaling on the one hand and oxidative damage on the other. Using a HaCaT keratinocyte cell culture model, we investigated redox regulation and inflammation to periodic, low-dose oxidative stress after two, six, eight, ten, and twelve weeks. Chronic redox stress was generated by recurrent incubation with cold physical plasma-treated cell culture medium. Using transcriptome microarray technology, we identified both acute ROS-stress responses as well as numerous adaptions after several weeks of redox challenge. We determined a differential expression (2-fold, FDR < 0.01, p < 0.05) of 260 genes that function in inflammation and redox homeostasis, such as cytokines (e.g., IL-6, IL-8, and IL-10), growth factors (e.g., CSF2, FGF, and IGF-2), and antioxidant enzymes (e.g., HMOX, NQO1, GPX, and PRDX). Apoptotic signaling was affected rather modestly, especially in p53 downstream targets (e.g., BCL2, BBC3, and GADD45). Strikingly, the cell-protective heat shock protein HSP27 was strongly upregulated (p < 0.001). These results suggested cellular adaptions to frequent redox stress and may help to better understand the inflammatory responses in redox-related diseases.

Nrf2--A regulator of keratinocyte redox signaling

The skin is frequently exposed to environmental challenges, such as UV irradiation, toxic chemicals, and mechanical wounding. These insults cause an increase in the levels of reactive oxygen species, resulting in oxidative stress and concomitant inflammation, skin aging, and even cancer development. Therefore, an efficient antioxidant defense strategy is of major importance in this tissue. Since the Nrf2 transcription factor regulates a battery of genes involved in the defense against reactive oxygen species and in compound metabolism, it plays a key role in skin homeostasis, repair, and disease. In this review we summarize current knowledge on the expression and function of Nrf2 in normal skin and its role in the acute and chronic UV response as well as in the pathogenesis of epithelial skin cancer and of different inflammatory skin diseases. Finally, we discuss the potential of Nrf2-activating compounds for skin protection under stress conditions and for the treatment of major human skin disorders.

Oxidative stress in aging human skin

Oxidative stress in skin plays a major role in the aging process. This is true for intrinsic aging and even more for extrinsic aging. Although the results are quite different in dermis and epidermis, extrinsic aging is driven to a large extent by oxidative stress caused by UV irradiation. In this review the overall effects of oxidative stress are discussed as well as the sources of ROS including the mitochondrial ETC, peroxisomal and ER localized proteins, the Fenton reaction, and such enzymes as cyclooxygenases, lipoxygenases, xanthine oxidases, and NADPH oxidases. Furthermore, the defense mechanisms against oxidative stress ranging from enzymes like superoxide dismutases, catalases, peroxiredoxins, and GSH peroxidases to organic compounds such as L-ascorbate, α-tocopherol, beta-carotene, uric acid, CoQ10, and glutathione are described in more detail. In addition the oxidative stress induced modifications caused to proteins, lipids and DNA are discussed. Finally age-related changes of the skin are also a topic of this review. They include a disruption of the epidermal calcium gradient in old skin with an accompanying change in the composition of the cornified envelope. This modified cornified envelope also leads to an altered anti-oxidative capacity and a reduced barrier function of the epidermis.

GHK and DNA: resetting the human genome to health

During human aging there is an increase in the activity of inflammatory, cancer promoting, and tissue destructive genes plus a decrease in the activity of regenerative and reparative genes. The human blood tripeptide GHK possesses many positive effects but declines with age. It improves wound healing and tissue regeneration (skin, hair follicles, stomach and intestinal linings, and boney tissue), increases collagen and glycosaminoglycans, stimulates synthesis of decorin, increases angiogenesis, and nerve outgrowth, possesses antioxidant and anti-inflammatory effects, and increases cellular stemness and the secretion of trophic factors by mesenchymal stem cells. Recently, GHK has been found to reset genes of diseased cells from patients with cancer or COPD to a more healthy state. Cancer cells reset their programmed cell death system while COPD patients' cells shut down tissue destructive genes and stimulate repair and remodeling activities. In this paper, we discuss GHK's effect on genes that suppress fibrinogen synthesis, the insulin/insulin-like system, and cancer growth plus activation of genes that increase the ubiquitin-proteasome system, DNA repair, antioxidant systems, and healing by the TGF beta superfamily. A variety of methods and dosages to effectively use GHK to reset genes to a healthier state are also discussed.

Fetal inhibition of inflammation improves disease phenotypes in harlequin ichthyosis

Harlequin ichthyosis (HI) is a severe skin disease which leads to neonatal death in ∼50% of cases. It is the result of mutations in ABCA12, a protein that transports lipids required to establish the protective skin barrier needed after birth. To better understand the life-threatening newborn HI phenotype, we analysed the developing epidermis for consequences of lipid dysregulation in mouse models. We observed a pro-inflammatory signature which was characterized by chemokine upregulation in embryonic skin which is distinct from that seen in other types of ichthyosis. Inflammation also persisted in grafted HI skin. To examine the contribution of inflammation to disease development, we overexpressed interleukin-37b to globally suppress fetal inflammation, observing considerable improvements in keratinocyte differentiation. These studies highlight inflammation as an unexpected contributor to HI disease development in utero, and suggest that inhibiting inflammation may reduce disease severity.

Topical hesperidin prevents glucocorticoid-induced abnormalities in epidermal barrier function in murine skin

Systemic and topical glucocorticoids (GC) can cause significant adverse effects not only on the dermis, but also on epidermal structure and function. In epidermis, a striking GC-induced alteration in permeability barrier function occurs that can be attributed to an inhibition of epidermal mitogenesis, differentiation and lipid production. As prior studies in normal hairless mice demonstrated that topical applications of a flavonoid ingredient found in citrus, hesperidin, improve epidermal barrier function by stimulating epidermal proliferation and differentiation, we assessed here whether its topical applications could prevent GC-induced changes in epidermal function in murine skin and the basis for such effects. When hairless mice were co-treated topically with GC and 2% hesperidin twice-daily for 9 days, hesperidin co-applications prevented the expected GC-induced impairments of epidermal permeability barrier homoeostasis and stratum corneum (SC) acidification. These preventive effects could be attributed to a significant increase in filaggrin expression, enhanced epidermal β-glucocerebrosidase activity and accelerated lamellar bilayer maturation, the last two likely attributable to a hesperidin-induced reduction in stratum corneum pH. Furthermore, co-applications of hesperidin with GC largely prevented the expected GC-induced inhibition of epidermal proliferation. Finally, topical hesperidin increased epidermal glutathione reductase mRNA expression, which could counteract multiple functional negative effects of GC on epidermis. Together, these results show that topical hesperidin prevents GC-induced epidermal side effects by divergent mechanisms.