Therapeutic potential of topically administered γ-AlOOH on 2,4-dinitrochlorobenzene-induced atopic dermatitis-like lesions in Balb/c mice

Characterization of Different Inflammatory Skin Conditions in a Mouse Model of DNCB-Induced Atopic Dermatitis

The mouse model of 2,4-dinitrochlorbenzene (DNCB)-induced human-like atopic dermatitis (hlAD) has been widely used to test novel treatment strategies and compounds. However, the study designs and methods are highly diverse, presenting different hlAD disease patterns that occur after sensitization and repeated challenge with DNCB on dorsal skin. In addition, there is a lack of information about the progression of the disease during the experiment and the achieved pheno- and endotypes, especially at the timepoint when therapeutic treatment is initiated. We here examine hlAD in a DNCB-induced BALB/cJRj model at different timepoints: (i) before starting treatment with dexamethasone, representing a standard drug control (day 12) and (ii) at the end of the experiment (day 22). Both timepoints display typical AD-associated characteristics: skin thickening, spongiosis, hyper- and parakeratosis, altered cytokine and gene expression, increased lipid mediator formation, barrier protein and antimicrobial peptide abnormalities, as well as lymphoid organ hypertrophy. Increased mast cell infiltration into the skin and elevated immunoglobulin E plasma concentrations indicate a type I allergy response. The DNCB-treated skin showed an extrinsic moderate sub-acute hlAD lesion at day 12 and an extrinsic mild sub-acute to chronic pheno- and endotype at day 22 with a dominating Th2 response. A dependency of the filaggrin formation and expression in correlation to the disease severity in the DNCB-treated skin was found. In conclusion, our study reveals a detailed classification of a hlAD at two timepoints with different inflammatory skin conditions and pheno- and endotypes, thereby providing a better understanding of the DNCB-induced hlAD model in BALB/cJRj mice.

Establishment and Characterization of Mild Atopic Dermatitis in the DNCB-Induced Mouse Model

In dermatological research, 2,4-dinitrochlorbenzene (DNCB)-induced atopic dermatitis (AD) is a standard model as it displays many disease-associated characteristics of human AD. However, the reproducibility of the model is challenging due to the lack of information regarding the methodology and the description of the phenotype and endotype of the mimicked disease. In this study, a DNCB-induced mouse model was established with a detailed procedure description and classification of the AD human-like skin type. The disease was induced with 1% DNCB in the sensitization phase and repeated applications of 0.3% and 0.5% DNCB in the challenging phase which led to a mild phenotype of AD eczema. Pathophysiological changes of the dorsal skin were measured: thickening of the epidermis and dermis, altered skin barrier proteins, increased TH1 and TH2 cytokine expression, a shift in polyunsaturated fatty acids, increased pro-resolving and inflammatory mediator formation, and dysregulated inflammation-associated gene expression. A link to type I allergy reactions was evaluated by increased mast cell infiltration into the skin accompanied by elevated IgE and histamine levels in plasma. As expected for mild AD, no systemic inflammation was observed. In conclusion, this experimental setup demonstrates many features of a mild human-like extrinsic AD in murine skin.

Galactomyces Ferment Filtrate Potentiates an Anti-Inflammaging System in Keratinocytes

Skincare products play a crucial role in preventing the dry skin induced by various causes. Certain ingredients can help to improve the efficacy of skincare products. Galactomyces ferment filtrate (GFF) is such a functional ingredient. Its use originated from the empirical observation that the hands of sake brewers who deal with yeast fermentation retain a beautiful and youthful appearance. Consequently, skincare products based on GFF are widely used throughout the world. Recent studies have demonstrated that GFF activates an aryl hydrocarbon receptor (AHR) and upregulates the expression of filaggrin, a pivotal endogenous source of natural moisturizing factors, in epidermal keratinocytes. It also activates nuclear factor erythroid-2-related factor 2 (NRF2), the antioxidative master transcription factor, and exhibits potent antioxidative activity against oxidative stress induced by ultraviolet irradiation and proinflammatory cytokines, which also accelerate inflammaging. GFF-mediated NRF2 activation downregulates the expression of CDKN2A, which is known to be overexpressed in senescent keratinocytes. Moreover, GFF enhances epidermal terminal differentiation by upregulating the expression of caspase-14, claudin-1, and claudin-4. It also promotes the synthesis of the antiinflammatory cytokine IL-37 and downregulates the expression of proallergic cytokine IL-33 in keratinocytes. In addition, GFF downregulates the expression of the CXCL14 and IL6R genes, which are involved in inflammaging. These beneficial properties might underpin the potent barrier-protecting and anti-inflammaging effects of GFF-containing skin formulae.

The contribution of mouse models to understanding atopic dermatitis

Atopic dermatitis (AD) is a dermatological disease accompanied by dry and cracked skin with severe pruritus. Although various therapeutic strategies have been introduced to alleviate AD, it remains challenging to cure the disorder. To achieve such a goal, understanding the pathophysiological mechanisms of AD is a prerequisite, requiring mouse models that properly reflect the AD phenotypes. Currently, numerous AD mouse models have been established, but each model has its own advantages and weaknesses. In this review, we categorized and summarized mouse models of AD and described their characteristics from a researcher's perspective.

The protective effects of NE 52-QQ57 against interleukin-33-induced inflammatory response in activated synovial mast cells

Cytokines-mediated immunity is essential for the pathological development of rheumatoid arthritis (RA). Inhibition of signaling has suggested a potential remedial approach to RA. G protein-coupled receptor 4 (GPR4) has been proven to possess a broad range of physiological functions, but its function in synovial mast cells and RA is less reported. In this study, the protective effects of NE 52-QQ57, a GPR4 antagonist, against interleukin (IL)-33-challenged inflammatory response in activated synovial mast cells were investigated. We report that IL-33 amplified GPR4 expression in HMC-1 mast cells. The GPR4 antagonist NE 52-QQ57 alleviated IL-33-caused secretions of IL-17, interferon-γ, and tumor necrosis factor-α in HMC-1 mast cells. Furthermore, we note that NE 52-QQ57 reduced IL-33-induced expressions of matrix metalloproteinase-2 (MMP-2) and MMP-9. Also, NE 52-QQ57 inhibited cyclooxygenase 2 and prostaglandin E2 expression in IL-33-challenged cells. Also, NE 52-QQ57 ameliorated IL-33-induced oxidative stress by reducing mitochondrial reactive oxygen species and 4-hydroxynonenal. Mechanistically, NE 52-QQ57 mitigated IL-33-induced activation of the p38/nuclear factor-κB signaling pathway. We conclude that targeting GPR4 might be a promising strategy for RA treatment.

CoO Nanozymes with Multiple Catalytic Activities Regulate Atopic Dermatitis

Herein, we prepared CoO nanozymes with three types of enzyme catalytic activities for the first time, which have SOD-like, CAT-like, and POD-like catalytic activities. This is the first study to report the preparation of CoO nanoparticles with three types of enzyme catalytic activities by the one-pot method. By modifying the surface of CoO nanozymes with a carboxyl group, its biocompatibility enhanced, so it can be used in the field of life sciences. In vitro cytotoxicity and anti-H2O2-induced ROS experiments proved that CoO nanozymes can protect HaCaT cells against ROS and cytotoxicity induced by H2O2. In addition, an atopic dermatitis (AD) mouse model was established by topical application of MC903, which verified the anti-inflammatory effect of CoO nanozymes on the AD mouse model. Traditional drugs for the treatment of AD, such as dexamethasone, have significant side-effects. The side-effects include skin burns, telangiectasias, and even serious drug dependence. CoO nano-enzymes have a low cytotoxicity and its multiple enzyme-like catalytic activities can effectively protect cells and tissues in ROS environments, which proves that CoO nano-enzymes have high application potential in the field of anti-inflammation.

Effects of Deacetylasperulosidic Acid on Atopic Dermatitis through Modulating Immune Balance and Skin Barrier Function in HaCaT, HMC-1, and EOL-1 Cells

The medicinal plant noni (Morinda citrifolia) is widely dispersed throughout Southeast Asia, the Caribbean, and Australia. We previously reported that fermented Noni could alleviate atopic dermatitis (AD) by recovering Th1/Th2 immune balance and enhancing skin barrier function induced by 2,4-dinitrochlorobenzene. Noni has a high deacetylasperulosidic acid (DAA) content, whose concentration further increased in fermented noni as an iridoid constituent. This study aimed to determine the anti-AD effects and mechanisms of DAA on HaCaT, HMC-1, and EOL-1 cells. DAA inhibited the gene expression and secretion of AD-related cytokines and chemokines including interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-25, IL-33, thymic stromal lymphopoietin, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, thymus and activation-regulated chemokine, macrophage-derived chemokine, and regulated upon activation, normal T cell expressed and secreted, in all cells, and inhibited histamine release in HMC-1 cells. DAA controlled mitogen-activated protein kinase phosphorylation levels and the translocation of nuclear factor-kappa light chain enhancer of activated B cells into the nucleus by inhibiting IκBα decomposition in all the cells. Furthermore, DAA increased the expression of proteins involved in skin barrier functions such as filaggrin and involucrin in HaCaT cells. These results confirmed that DAA could relieve AD by controlling immune balance and recovering skin barrier function.

Cytokines Stimulated by IL-33 in Human Skin Mast Cells: Involvement of NF-κB and p38 at Distinct Levels and Potent Co-Operation with FcεRI and MRGPRX2

The IL-1 family cytokine IL-33 activates and re-shapes mast cells (MCs), but whether and by what mechanisms it elicits cytokines in MCs from human skin remains poorly understood. The current study found that IL-33 activates CCL1, CCL2, IL-5, IL-8, IL-13, and TNF-α, while IL-1β, IL-6, IL-31, and VEGFA remain unaffected in cutaneous MCs, highlighting that each MC subset responds to IL-33 with a unique cytokine profile. Mechanistically, IL-33 induced the rapid (1–2 min) and durable (2 h) phosphorylation of p38, whereas the phosphorylation of JNK was weaker and more transient. Moreover, the NF-κB pathway was potently activated, as revealed by IκB degradation, increased nuclear abundance of p50/p65, and vigorous phosphorylation of p65. The activation of NF-κB occurred independently of p38 or JNK. The induced transcription of the cytokines selected for further study (CCL1, CCL2, IL-8, TNF-α) was abolished by interference with NF-κB, while p38/JNK had only some cytokine-selective effects. Surprisingly, at the level of the secreted protein products, p38 was nearly as effective as NF-κB for all entities, suggesting post-transcriptional involvement. IL-33 did not only instruct skin MCs to produce selected cytokines, but it also efficiently co-operated with the allergic and pseudo-allergic/neurogenic activation networks in the production of IL-8, TNF-α, CCL1, and CCL2. Synergism was more pronounced at the protein than at the mRNA level and appeared stronger for MRGPRX2 ligands than for FcεRI. Our results underscore the pro-inflammatory nature of an acute IL-33 stimulus and imply that especially in combination with allergens or MRGPRX2 agonists, IL-33 will efficiently amplify skin inflammation and thereby aggravate inflammatory dermatoses.

Mouse models of atopic dermatitis: a critical reappraisal

Mouse models for atopic dermatitis (AD) are an indispensable preclinical research tool for testing new candidate AD therapeutics and for interrogating AD pathobiology in vivo. In this Viewpoint, we delineate why, unfortunately, none of the currently available so-called "AD" mouse models satisfactorily reflect the clinical complexity of human AD, but imitate more "allergic" or "irriant" contact dermatitis conditions. This limits the predictive value of AD models for clinical outcomes of new tested candidate AD therapeutics and the instructiveness of mouse models for human AD pathophysiology research. Here, we propose to initiate a rational debate on the minimal criteria that a mouse model should meet in order to be considered relevant for human AD. We suggest that valid AD models should at least meet the following criteria: (a) an AD-like epidermal barrier defect with reduced filaggrin expression along with hyperproliferation, hyperplasia; (b) increased epidermal expression of thymic stromal lymphopoietin (TSLP), periostin and/or chemokines such as TARC (CCL17); (c) a characteristic dermal immune cell infiltrate with overexpression of some key cytokines such as IL-4, IL-13, IL-31 and IL-33; (d) distinctive "neurodermatitis" features (sensory skin hyperinnervation, defective beta-adrenergic signalling, neurogenic skin inflammation and triggering or aggravation of AD-like skin lesions by perceived stress); and (e) response of experimentally induced skin lesions to standard AD therapy. Finally, we delineate why humanized AD mouse models (human skin xenotransplants on SCID mice) offer a particularly promising preclinical research alternative to the currently available "AD" mouse models.

Transdermal Drug Delivery for Hair Regrowth

Today, about 50% of men and 15-30% of women suffer from hair loss as well as the associated psychological impact. Drug therapy, especially through topical administration, is the main treatment strategy for stimulating hair regrowth. However, challenges exist due to the skin barrier that hinders drug penetration. To this end, many efforts have been made to enhance drug penetration efficiency. This review focuses on the advancement of the transdermal drug delivery strategies for hair loss therapy reported in the last five years, especially those via nanoformulations for topical administration and microneedles for transdermal delivery. In addition, physical or chemical penetration enhancers are also introduced, which are often applied with the drug delivery systems to achieve a synergy effect.

Salidroside inhibits MAPK, NF-κB, and STAT3 pathways in psoriasis-associated oxidative stress via SIRT1 activation

Objectives: To unveil the role of SIRT1 in limiting oxidative stress in psoriasis and to further discuss the therapeutic prospects of salidroside in psoriasis.

Methods: Literature from 2002 to 2019 was searched with “psoriasis”, “oxidative stress”, “SIRT1”, “salidroside” as the key words. Then, Oxidative stress in psoriasis and the role of SIRT1 were summarized and the potential role of salidroside in the disease was speculated.

Results: Oxidative stress might contribute to the pathogenesis of psoriasis. High levels of ROS produced during oxidative stress lead to the release of inflammatory mediators, that, in turn, induce angiogenesis and excessive proliferation of keratinocytes. SIRT1 is a member of the sirtuin family, of which the activation lead to the inhibition of such oxidative stress signaling pathways MAPK, NF-κB, and STAT3, down-regulation of inflammatory factors, suppression of inflammation and keratinocyte hyperproliferation, and inhibition of angiogenesis. Salidroside, the main ingredient of Rhodiola, is known to exert antioxidant roles, which has been attributed to SIRT1 activation.

Conclusion: Salidroside might inhibit oxidative stress singling pathways via SIRT1 activation, and could be as an ideal candidate for management of psoriasis.

IL-33 and MRGPRX2-Triggered Activation of Human Skin Mast Cells-Elimination of Receptor Expression on Chronic Exposure, but Reinforced Degranulation on Acute Priming

Clinically relevant exocytosis of mast cell (MC) mediators can be triggered by high-affinity IgE receptor (FcεRI)-aggregation (allergic route) or by the so-called pseudo-allergic pathway elicited via MAS-related G protein-coupled receptor-X2 (MRGPRX2). The latter is activated by drugs and endogenous neuropeptides. We recently reported that FcεRI-triggered degranulation is attenuated when human skin mast cells are chronically exposed to IL-33. Here, we were interested in the regulation of the MRGPRX2-route. Chronic exposure of skin MCs to IL-33 basically eliminated the pseudo-allergic/neurogenic route as a result of massive MRGPRX2 reduction. This downregulation seemed to partially require c-Jun N-terminal Kinase (JNK), but not p38, the two kinases activated by IL-33 in skin MCs. Surprisingly, however, JNK had a positive effect on MRGPRX2 expression in the absence of IL-33. This was evidenced by Accell^®-mediated JNK knockdown and JNK inhibition. In stark contrast to the dampening effect upon prolonged exposure, IL-33 was able to prime for increased degranulation by MRGPRX2 ligands when administered directly before stimulation. This supportive effect depended on p38, but not on JNK activity. Our data reinforce the concept that exposure length dictates whether IL-33 will enhance or attenuate secretion. IL-33 is, thus, the first factor to acutely enhance MRGPRX2-triggered degranulation. Finally, we reveal that p38, rarely associated with MC degranulation, can positively affect exocytosis in a context-dependent manner.