Epidermal TSLP: a trigger factor for pathogenesis of atopic dermatitis

TNF-α counters skin inflammation by restraining mast cell-dependent thymic stromal lymphopoietin production

BACKGROUND

TNF-α is an important proinflammatory cytokine, but its neutralization in the management of inflammatory skin disorders like psoriasis may trigger eczematous skin lesions as an adverse reaction.

OBJECTIVES

This study aimed to elucidate whether TNF-α may protect from skin inflammation and to identify in detail the underlying mechanisms.

METHODS

Wild-type, TNF-α-deficient, thymic stromal lymphopoietin (TSLP) receptor-deficient, mast cell (MC)-deficient, TNF-α-TSLP receptor double-deficient, and TNF-α-MC double-deficient mice were subjected to a skin inflammation model and inspected by physical, clinical, histologic, immunohistochemical, and bioanalytic techniques.

RESULTS

TNF-α deficiency promoted skin inflammation. This was accompanied by MC hyperplasia and potent TSLP production in lesional skin and serum of TNF-α-deficient mice. Specifically, MCs were found to be responsible for inducing high levels of TSLP in the epidermis, compromising barrier function and initiating inflammation. In contrast, the production of immunoglobulins, including IgE, was reduced in mice lacking TNF-α.

CONCLUSIONS

TNF-α restrains MC-dependent TSLP production and the onset of eczema.

Pinewood VOC emissions protect from oxazolone-induced inflammation and dysbiosis in a mouse model of atopic dermatitis

Pinewood, increasingly used in construction and interior fittings, emits high amounts of volatile organic compounds (VOCs), which tend to accumulate in indoor air. Whether indoor VOCs affect the development of atopic dermatitis (AD) is a matter of debate. We aimed to evaluate the effects of pinewood VOCs on the development of AD-like inflammatory phenotype and linked microbiome alterations, both hallmarks of AD. An oxazolone-induced mouse model of AD was exposed to three different VOC concentrations emitted by pinewood plates throughout the experiment. The disease course and associated immunological and microbiological changes were evaluated. To validate and translate our results to humans, human keratinocytes were exposed to a synthetic pinewood VOCs mixture in an AD environment. Pinewood emitted mainly terpenes, which at a total concentration of 5 mg/m3 significantly improved oxazolone-induced key AD parameters, such as serum total IgE, transepidermal water loss, barrier gene alteration, inflammation, and dysbiosis. Notably, exposure to pinewood VOCs restored the loss of microbial richness and inhibit Staphylococci expansion characteristic of the oxazolone-induced mouse AD model. Most beneficial effects of pinewood VOCs were dose-dependent. In fact, lower (<3 mg/m3) or higher (>10 mg/m3) pinewood VOC levels maintained only limited beneficial effects, such as preserving the microbiome richness or impeding Staphylococci expansion, respectively. In the human in-vitro model, exposure of keratinocytes grown in an AD environment to a pinewood VOCs mixture reduced the release of inflammatory markers. In conclusion, our results indicate that airborne phytochemicals emitted from pinewood have beneficial effects on an AD-like phenotype and associated dysbiosis. These investigations highlight the effects of terpenes as environmental compounds in the prevention and/or control of atopic skin disease.

Staphylococcus aureus-specific skin resident memory T cells protect against bacteria colonization but exacerbate atopic dermatitis-like flares in mice

BACKGROUND

The contribution of Staphylococcus aureus to the exacerbation of atopic dermatitis (AD) is widely documented, but its role as a primary trigger of AD skin symptoms remains poorly explored.

OBJECTIVES

This study sought to reappraise the main bacterial factors and underlying immune mechanisms by which S aureus triggers AD-like inflammation.

METHODS

This study capitalized on a preclinical model, in which different clinical isolates were applied in the absence of any prior experimental skin injury.

RESULTS

The development of S aureus-induced dermatitis depended on the nature of the S aureus strain, its viability, the concentration of the applied bacterial suspension, the production of secreted and nonsecreted factors, as well as the activation of accessory gene regulatory quorum sensing system. In addition, the rising dermatitis, which exhibited the well-documented AD cytokine signature, was significantly inhibited in inflammasome adaptor apoptosis-associated speck-like protein containing a CARD domain- and monocyte/macrophage-deficient animals, but not in T- and B-cell-deficient mice, suggesting a major role for the innate response in the induction of skin inflammation. However, bacterial exposure generated a robust adaptive immune response against S aureus, and an accumulation of S aureus-specific γδ and CD4+ tissue resident memory T cells at the site of previous dermatitis. The latter both contributed to worsen the flares of AD-like dermatitis on new bacteria exposures, but also, protected the mice from persistent bacterial colonization.

CONCLUSIONS

These data highlight the induction of unique AD-like inflammation, with the generation of proinflammatory but protective tissue resident memory T cells in a context of natural exposure to pathogenic S aureus strains.

Ursodeoxycholic acid alleviates atopic dermatitis-associated inflammatory responses in HaCaT and RBL-2H3 cells and DNCB/DFE-treated mice

AIMS

Ursodeoxycholic acid (UDCA) is a hydrophilic dihydroxy bile acid used for cholestatic liver disease and exhibits antioxidant, antitumor, and anti-inflammatory effects. However, its potential effects on atopic dermatitis (AD) have not been elucidated. This study aimed to evaluate the efficacy of UDCA in inhibiting the inflammatory response and alleviating lesions in AD-like mice.

MAIN METHODS

To investigate the efficacy of UDCA in AD-like inflammatory responses, tumor necrosis factor-alpha (TNF-α)- and interferon-gamma (IFN-γ)-stimulated HaCaT cells and anti-dinitrophenyl immunoglobulin E (DNP-IgE)- and human serum albumin (HSA)-stimulated RBL-2H3 cells were used to investigate the levels of inflammatory factors and their mechanisms. AD-like lesions were induced by applying DNCB/DFE to mice. The effect of UDCA administration in AD-like mice was analyzed by assessing organ weight, serum IgE and inflammatory cytokine levels, and histopathological changes using immunohistochemical and immunofluorescent staining.

KEY FINDINGS

In HaCaT cells, UDCA significantly diminished TARC, MDC, MCP-1, and IL-6 expression by inhibiting the phosphorylation of nuclear NF-κB and cytoplasmic IκB, and also increased the levels of skin barrier protein. In RBL-2H3 cells, UDCA reduced β-hexosaminidase and IL-4 levels. In AD-like mice, UDCA suppressed organ hypertrophy, ear edema, SCORAD index, DFE-specific IgE levels, inflammatory cytokine levels, skin hypertrophy, mast cell invasion, skin barrier loss, and thymic stromal lymphopoietin-positive areas.

SIGNIFICANCE

UDCA suppressed the expression of pro-inflammatory cytokines by keratinocytes and mast cells. It also alleviated atopy by suppressing symptoms without organ toxicity in AD-like mice. UDCA may be an effective and safe treatment for AD.

Punicalagin from pomegranate ameliorates TNF-α/IFN-γ-induced inflammatory responses in HaCaT cells via regulation of SIRT1/STAT3 axis and Nrf2/HO-1 signaling pathway

Punicalagin (PUN) was isolated from the peel of pomegranate (Punica granatum L.), is a polyphenol with anti-inflammatory, hepatoprotective, and antioxidant activities. However, it remains unclear whether PUN alleviates the inflammation and anti-inflammatory mechanisms in pro-inflammatory cytokines-induced human keratinocyte HaCaT cells. Here, we investigated that tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) mixture-stimulated HaCaT cells were treated with various concentrations of PUN, followed by analyzed the expression of inflammation-related mediators and evaluate anti-inflammatory-related pathways. Our results demonstrated that PUN ≤ 100 μM did not reduce HaCaT cell viability, and PUN ≥ 3 μM was sufficient to decrease interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein-1 (MCP-1), chemokine ligand 5 (CCL5), CCL17 and CCL20 concentrations. We found that PUN ≥ 10 μM and ≥ 3 μM significantly increased sirtuin 1 (SIRT1) expression and inhibited signal transducer and activator of transcription 3 (STAT3) phosphorylation, respectively. PUN downregulated inflammation-related proteins cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), enhanced nuclear factor erythroid-2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1) expression. Moreover, PUN decreased intercellular adhesion molecule-1 (ICAM-1) expression and inhibited monocyte adhesion to inflamed HaCaT cells. PUN also suppressed inflammatory-related pathways, including mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways in TNF-α/IFN-γ- stimulated HaCat cells. Collectively, there is significant evidence that PUN has effective protective defenses against TNF-α/IFN-γ-induced skin inflammation by enhancing SIRT1 to mediate STAT3 and Nrf2/HO-1 signaling pathway.

Unraveling the skin; a comprehensive review of atopic dermatitis, current understanding, and approaches

Atopic dermatitis, also known as atopic eczema, is a chronic inflammatory skin disease characterized by red pruritic skin lesions, xerosis, ichthyosis, and skin pain. Among the social impacts of atopic dermatitis are difficulties and detachment in relationships and social stigmatization. Additionally, atopic dermatitis is known to cause sleep disturbance, anxiety, hyperactivity, and depression. Although the pathological process behind atopic dermatitis is not fully known, it appears to be a combination of epidermal barrier dysfunction and immune dysregulation. Skin is the largest organ of the human body which acts as a mechanical barrier to toxins and UV light and a natural barrier against water loss. Both functions face significant challenges due to atopic dermatitis. The list of factors that can potentially trigger or contribute to atopic dermatitis is extensive, ranging from genetic factors, family history, dietary choices, immune triggers, and environmental factors. Consequently, prevention, early clinical diagnosis, and effective treatment may be the only resolutions to combat this burdensome disease. Ensuring safe and targeted drug delivery to the skin layers, without reaching the systemic circulation is a promising option raised by nano-delivery systems in dermatology. In this review, we explored the current understanding and approaches of atopic dermatitis and outlined a range of the most recent therapeutics and dosage forms brought by nanotechnology. This review was conducted using PubMed, Google Scholar, and ScienceDirect databases.

Age-dependent topic modeling of comorbidities in UK Biobank identifies disease subtypes with differential genetic risk

The analysis of longitudinal data from electronic health records (EHRs) has the potential to improve clinical diagnoses and enable personalized medicine, motivating efforts to identify disease subtypes from patient comorbidity information. Here we introduce an age-dependent topic modeling (ATM) method that provides a low-rank representation of longitudinal records of hundreds of distinct diseases in large EHR datasets. We applied ATM to 282,957 UK Biobank samples, identifying 52 diseases with heterogeneous comorbidity profiles; analyses of 211,908 All of Us samples produced concordant results. We defined subtypes of the 52 heterogeneous diseases based on their comorbidity profiles and compared genetic risk across disease subtypes using polygenic risk scores (PRSs), identifying 18 disease subtypes whose PRS differed significantly from other subtypes of the same disease. We further identified specific genetic variants with subtype-dependent effects on disease risk. In conclusion, ATM identifies disease subtypes with differential genome-wide and locus-specific genetic risk profiles.

Zhenxin Anshen formula ameliorates atopic der-matitis-like skin dysfunction in mice and regulation of transient receptor potential vanilloid 1 and transient receptor potential ankyrin 1 in Neural pathways

OBJECTIVE

To investigate the efficacy of Zhenxin Anshen formula (, ZXAS) on atopic dermatitis (AD) by transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) signalling pathway in mice and .

METHODS

AD-like lesions were induced by 1-chloro-2,4-dinitrobenzene (DNCB) to the shaved dorsal skin of BALB/c mice. BALB/c mice were divided into five groups: normal control, model control, cetirizine, low-, medium-, and high-dose of ZXAS. After ZXAS in-tervention, the skin lesions and blood samples were collected for hematoxylin and eosin-stained and measuring the concentrations of inflammatory cytokines. Immun-oglobulin E (IgE), interleukin (IL)-4, IL-5, IL-13, and thymic stromal lymphopoietin (TSLP) were de-tected by Enzyme-linked immunosorbent assay (ELISA). The spinal cords were collected for measuring the expression of gastrin-releasing peptide receptor (GRPR), TRPV1, and TRPA1 by using immunohistochemistry, western blotting, and quantitative real-time polymerase chain reaction (qRT-PCR) analyses. In addition, 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, ELISA, and Western blotting were conducted for analysis of primary dorsal root ganglia (DRG) neurons .

RESULTS

ZXAS treatment improved DNCB-induced AD-like lesions through reducing dermatitis score, number of scratching and epidermal thickness, accompanied by the de-creased IgE and Th2 inflammatory cytokines. ZXAS also supressed the mRNA and protein expression of GRPR, TRPV1, and TRPA1 in the spinal cord. The medicated sera of ZXAS decreased capsaicin-induced Ca influx and downregulated the expression of TRPV1, TRPA1, and phospholipase C in DRG neurons.

CONCLUSIONS

The therapeutic effect of ZXAS on AD may be related to the regulation of TRPV1 and TRPA1 and inhibition of Ca2+ signals in neurons.

Skin Microbiome in Prurigo Nodularis

Prurigo nodularis (PN) is a chronic condition characterized by the presence of nodular lesions accompanied by intense pruritus. The disease has been linked to several infectious factors, but data on the direct presence of microorganisms in the lesions of PN are scarce. The aim of this study was to evaluate the diversity and composition of the bacterial microbiome in PN lesions by targeting the region V3-V4 of 16S rRNA. Skin swabs were obtained from active nodules in 24 patients with PN, inflammatory patches of 14 patients with atopic dermatitis (AD) and corresponding skin areas of 9 healthy volunteers (HV). After DNA extraction, the V3-V4 region of the bacterial 16S rRNA gene was amplified. Sequencing was performed using the Illumina platform on the MiSeq instrument. Operational taxonomic units (OTU) were identified. The identification of taxa was carried out using the Silva v.138 database. There was no statistically significant difference in the alpha-diversity (intra-sample diversity) between the PN, AD and HV groups. The beta-diversity (inter-sample diversity) showed statistically significant differences between the three groups on a global level and in paired analyses. Staphylococcus was significantly more abundant in samples from PN and AD patients than in controls. The difference was maintained across all taxonomic levels. The PN microbiome is highly similar to that of AD. It remains unclear whether the disturbed composition of the microbiome and the domination of Staphylococcus in PN lesions may be the trigger factor of pruritus and lead to the development of cutaneous changes or is a secondary phenomenon. Our preliminary results support the theory that the composition of the skin microbiome in PN is altered and justify further research on the role of the microbiome in this debilitating condition.

Advances in Current Drugs and Formulations for the Management of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease with a complex pathophysiology. Treatment of AD remains challenging owing to the presence of a wide spectrum of clinical phenotypes and limited response to existing therapies. However, recent genetic, immunological, and pathophysiological insights into the disease mechanism resulted in the invention of novel therapeutic drug candidates. This review provides a comprehensive overview of current therapies and assesses various novel drug delivery strategies currently under clinical investigation. Further, this review majorly emphasizes on various topical treatments including emollient therapies, barrier repair agents, topical corticosteroids (TCS), phosphodiesterase 4 (PDE4) inhibitors, calcineurin inhibitors, and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway inhibitors. It also discusses biological and systemic therapies, upcoming treatments based on ongoing clinical trials. Additionally, this review scrutinized the use of pharmaceutical inactive ingredients in the approved topical dosage forms for AD treatment.

Current Biologics in Asthma Treatment

Uncontrolled asthma and/or severe asthma causes significant impairments in quality of life and is often a huge health care burden. Monoclonal antibodies have been an important addition to the therapeutic management of patients with moderate to severe asthma who do not respond to conventional asthma management. Currently the majority of Food and Drug Administration (FDA) approved biologics target T2 high inflammation. However, with the expanding knowledge of asthma pathogenesis, novel therapeutics targeting T2 low inflammation are in development. In this article we will focus on the current understanding of T2 inflammation and approved biologics for moderate to severe asthma.

Lobelia chinensis Extract and Its Active Compound, Diosmetin, Improve Atopic Dermatitis by Reinforcing Skin Barrier Function through SPINK5/LEKTI Regulation

The skin acts as a mechanical barrier that protects the body from the exterior environment, and skin barrier function is attributed to the stratum corneum (SC), which is composed of keratinocytes and skin lipids. Skin barrier homeostasis is maintained by a delicate balance between the differentiation and exfoliation of keratinocytes, and keratinocyte desquamation is regulated by members of the serine protease kalikrein (KLK) family and their endogenous inhibitor SPINK5/LEKTI (serine protease inhibitor Kazal type 5/lympho-epithelial Kazal-type-related inhibitor). Furthermore, SPINK5/LEKTI deficiency is involved in impaired skin barrier function caused by KLK over-activation. We sought to determine whether increased SPINK5/LEKTI expression ameliorates atopic dermatitis (AD) by strengthening skin barrier function using the ethanol extract of Lobelia chinensis (LCE) and its active compound, diosmetin, by treating human keratinocytes with UVB and using a DNCB-induced murine model of atopic dermatitis. LCE or diosmetin dose-dependently increased the transcriptional activation of SPINK5 promoter and prevented DNCB-induced skin barrier damage by modulating events downstream of SPINK5, that is, KLK, PAR2 (protease activated receptor 2), and TSLP (thymic stromal lymphopoietin). LCE or diosmetin normalized immune response in DNCB treated SKH-1 hairless mice as determined by reductions in serum immunoglobulin E and interleukin-4 levels and numbers of lesion-infiltrating mast cells. Our results suggest that LCE and diosmetin are good candidates for the treatment of skin barrier-disrupting diseases such as Netherton syndrome or AD, and that they do so by regulating SPINK5/LEKTI.

Probiotics: Protecting Our Health from the Gut

The gut microbiota (GM) comprises billions of microorganisms in the human gastrointestinal tract. This microbial community exerts numerous physiological functions. Prominent among these functions is the effect on host immunity through the uptake of nutrients that strengthen intestinal cells and cells involved in the immune response. The physiological functions of the GM are not limited to the gut, but bidirectional interactions between the gut microbiota and various extraintestinal organs have been identified. These interactions have been termed interorganic axes by several authors, among which the gut-brain, gut-skin, gut-lung, gut-heart, and gut-metabolism axes stand out. It has been shown that an organism is healthy or in homeostasis when the GM is in balance. However, altered GM or dysbiosis represents a critical factor in the pathogenesis of many local and systemic diseases. Therefore, probiotics intervene in this context, which, according to various published studies, allows balance to be maintained in the GM, leading to an individual's good health.

Break on through: The role of innate immunity and barrier defence in atopic dermatitis and psoriasis

The human skin can be affected by a multitude of diseases including inflammatory conditions such as atopic dermatitis and psoriasis. Here, we describe how skin barrier integrity and immunity become dysregulated during these two most common inflammatory skin conditions. We summarise recent advances made in the field of the skin innate immune system and its interaction with adaptive immunity. We review gene variants associated with atopic dermatitis and psoriasis that affect innate immune mechanisms and skin barrier integrity. Finally, we discuss how current and future therapies may affect innate immune responses and skin barrier integrity in a generalized or more targeted approach in order to ameliorate disease in patients.

Saikosaponin A and Saikosaponin C Reduce TNF-α-Induced TSLP Expression through Inhibition of MAPK-Mediated EGR1 Expression in HaCaT Keratinocytes

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases worldwide, characterized by intense pruritus and eczematous lesions. Aberrant expression of thymic stromal lymphopoietin (TSLP) in keratinocytes is associated with the pathogenesis of AD and is considered a therapeutic target for the treatment of this disease. Saikosaponin A (SSA) and saikosaponin C (SSC), identified from Radix Bupleuri, exert anti-inflammatory effects. However, the topical effects of SSA and SSC on chronic inflammatory skin diseases are unclear. In this study, we investigated the effects of SSA and SSC on TSLP suppression in an AD-like inflammatory environment. We observed that SSA and SSC suppressed tumor necrosis factor-α-induced TSLP expression by downregulating the expression of the transcription factor early growth response 1 (EGR1) via inhibition of the extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase 1/2, and p38 mitogen-activated protein kinase pathways. We also confirmed that topical application of SSA or SSC reduced AD-like skin lesions in BALB/c mice challenged with 2,4-dinitrochlorobenzene. Our findings suggest that suppression of EGR1-regulated TSLP expression in keratinocytes might be attributable to the anti-inflammatory effects of SSA and SSC in AD-like skin lesions.

Immunomodulatory Role of Staphylococcus aureus in Atopic Dermatitis

Staphylococcus aureus is a gram-positive bacterium commonly found on humans, and it constitutes the skin microbiota. Presence of S. aureus in healthy individuals usually does not pose any threat, as the human body is equipped with many mechanisms to prevent pathogen invasion and infection. However, colonization of S. aureus has been correlated with many healthcare-associated infections, and has been found in people with atopic diseases. In atopic dermatitis, constant fluctuations due to inflammation of the epidermal and mucosal barriers can cause structural changes and allow foreign antigens and pathogens to bypass the first line of defense of the innate system. As they persist, S. aureus can secrete various virulence factors to enhance their survival by host invasion and evasion mechanisms. In response, epithelial cells can release damage-associated molecular patterns, or alarmins such as TSLP, IL-25, IL-33, and chemokines, to recruit innate and adaptive immune cells to cause inflammation. Until recently, IL-36 had been found to play an important role in modulating atopic dermatitis. Secretion of IL-36 from keratinocytes can activate a Th2 independent pathway to trigger symptoms of allergic reaction resulting in clinical manifestations. This mini review aims to summarize the immunomodulatory roles of S. aureus virulence factors and how they contribute to the pathogenesis of atopic diseases.

Mast cells instruct keratinocytes to produce TSLP - relevance of the tryptase/PAR-2 axis

BACKGROUND

Thymic stromal lymphopoietin (TSLP) promotes Th2 inflammation and is deeply intertwined with inflammatory dermatoses like atopic dermatitis. The mechanisms regulating TSLP are poorly defined.

OBJECTIVE

To investigate whether and by what mechanisms mast cells (MCs) foster TSLP responses in the cutaneous environment.

METHODS

Ex vivo and in vivo skin MC degranulation was induced by compound 48/80 in wildtype, PAR-2- and MC-deficient mice in the presence/absence of neutralizing antibodies, antagonists or exogenous mMCP6. Primary human keratinocytes (hKCs) and murine skin explants (mSEs) were stimulated with lysates/supernatants of human skin MCs, purified tryptase or MC-lysate diminished of tryptase. Chymase and histamine were also used. TSLP was quantified by ELISA, RT-qPCR and immunofluorescence staining.

RESULTS

Mrgprb2-activation elicited TSLP in intact skin, mainly in the epidermis. Responses were strictly MC-dependent and relied on PAR-2. Complementarily, TSLP was elicited by tryptase in mSEs. Exogenous mMCP6 could fully restore responsiveness in MC-deficient mSEs. Conversely, PAR-2-knockout mice were unresponsive to mMCP6, while displaying increased responsiveness to other inflammatory pathways, e.g. IL-1α. Indeed, IL-1α acted in concert with tryptase. In hKCs, MC-elicited TSLP generation was likewise abolished by tryptase inhibition or elimination. Chymase and histamine did not impact TSLP production, but histamine triggered IL-6, IL-8, and SCF.

CONCLUSION

MCs communicate with KCs more broadly than hitherto suspected. The tryptase-PAR-2 axis is a crucial component of this crosstalk, underlying MC-dependent stimulation of TSLP in neighboring KCs. Interference specifically with MC tryptase may offer a treatment option for disorders initiated or perpetuated by aberrant TSLP, such as atopic dermatitis.

CLINICAL IMPLICATIONS

Awareness of the crosstalk between MCs and KCs may permit improved management of skin disorders, e.g. by selective targeting of tryptase.

Baicalin ameliorates 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin lesions in mice through modulating skin barrier function, gut microbiota and JAK/STAT pathway

Baicalin has distinct therapeutic effects in various skin diseases animal models such as atopic dermatitis (AD) and psoriasis. In this study, we aimed to investigate the anti-atopic dermatitis (AD) effects of baicalin in 2,4-dinitrochlorobenzene (DNCB)-treated mice. Female BALB/c mice treated with DNCB to induce AD-like skin lesions and orally administrated with baicalin daily for 14 consecutive days. Baicalin significantly inhibited dorsal skin thickness and trans-epidermal water loss and epidermal thickness in dorsal skin. In addition, baicalin also significantly up-regulated the protein expressions of filaggrin, involucrin, and loricrin, but inhibited the inflammatory response and the activation of NF-κB and JAK/STAT pathways in the dorsal skin of the DNCB-treated mice. Furthermore, baicalin significantly restored the abundance of probiotics in the gut microbiota of the DNCB-treated mice. Pseudo germ-free (GF) DNCB-treated mice receiving fecal microbiota from baicalin donors reduced the dorsal skin thickness and skin EASI score, and inhibited the release of IgE, histamine, TNF-α and IL-4 in serum of mice. In summary, baicalin ameliorates AD-like skin lesions induced by DNCB in mice via regulation of the Th1/Th2 balance, improvement of skin barrier function and modulation of gut dysbiosis, and inhibition of inflammation through suppressing the activation of NF-κB and JAK/STAT pathways.

A Cornflower Extract Containing N-Feruloylserotonin Reduces Inflammation in Human Skin by Neutralizing CCL17 and CCL22 and Inhibiting COX-2 and 5-LOX

Thymus and Activation-Regulated Chemokine (TARC/CCL17) and Macrophage-Derived Chemokine (MDC/CCL22) are two key chemokines exerting their biological effect via binding and activating a common receptor CCR4, expressed at the surface of type 2 helper T (Th2) cells. By recruiting Th2 cells in the dermis, CCL17 and CCL22 promote the development of inflammation in atopic skin. The aim of this research was to develop a plant extract whose biological properties, when applied topically, could be beneficial for people with atopic-prone skin. The strategy which was followed consisted in identifying ligands able to neutralize the biological activity of CCL17 and CCL22. Thus, an in silico molecular modeling and a generic screening assay were developed to screen natural molecules binding and blocking these two chemokines. N-Feruloylserotonin was identified as a neutraligand of CCL22 in these experiments. A cornflower extract containing N-feruloylserotonin was selected for further in vitro tests: the gene expression modulation of inflammation biomarkers induced by CCL17 or CCL22 in the presence or absence of this extract was assessed in the HaCaT keratinocyte cell line. Additionally, the same cornflower extract in another vehicle was evaluated in parallel with N-feruloylserotonin for cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzymatic cellular inhibition. The cornflower extract was shown to neutralize the two chemokines in vitro, inhibited COX-2 and 5-LOX, and demonstrated anti-inflammatory activities due mainly to the presence of N-feruloylserotonin. Although these findings would need to be confirmed in an in vivo study, the in vitro studies lay the foundation to explain the benefits of the cornflower extract when applied topically to individuals with atopic-prone skin.

Itch in Hymenoptera Sting Reactions

Insect stings and the resulting itch are a ubiquitous problem. Stings by members of the insect order Hymenoptera, which includes sawflies, wasps, bees and ants, and especially by bees and wasps are extremely common, with 56–94% of the population being stung at least once in their lifetime. The complex process of venom activity and inflammation causes local reactions with pain and pruritus, sometimes anaphylactic reactions and more seldomly, as in case of numerous stings, systemic intoxication. We reviewed the literature regarding itch experienced after Hymenoptera stings, but found no study that placed a specific focus on this topic. Hymenoptera venoms are composed of many biologically active substances, including peptide toxins and proteinaceous toxins. Peptide toxins from bee venom cause cell lysis and ion channel modulation in the peripheral and central nervous systems, while toxins from wasp venom induce mast cell degranulation and chemotaxis of polymorphonuclear leukocytes in the skin. The proteinaceous toxins cause a disruption of the cell membranes and necrotic cell death, degradation of hyaluronan (an extracellular matrix glycosaminoglycan), increased vascular permeability, hemolysis, as well as activated platelet aggregation. Mediators which could be directly involved in the venom-induced pruritus include histamine and tryptase released from mast cells, interleukin-4 and interleukin-13 from Th2 lymphocytes, as well as leukotriene C4. We postulate that a pruriceptive itch is induced due to the pharmacological properties of Hymenoptera venoms.

Atopic dermatitis is associated with hidradenitis suppurativa diagnosis: A single institution retrospective cohort study

Background

Hidradenitis suppurativa (HS) and atopic dermatitis (AD) are both chronic inflammatory skin diseases. An association between these 2 conditions can have important potential implications for elucidating pathogenesis, disease course, and treatment.

Objective

To investigate the association between AD and HS.

Methods

We performed a retrospective cohort study of patients seen at Duke University Medical Center from 2007 to 2017 who had AD compared with a control group without an AD diagnosis. The association of AD and HS was evaluated using a logistic regression model after adjusting for other confounders including age, sex, and race.

Results

Of 28,780 patients with an AD diagnosis, 325 (1.1%) were diagnosed with HS compared with 76 (0.2%) within the 48,383 patients in the non-AD group. An adjusted logistic regression model demonstrated an increased odds ratio of having HS diagnosis in the AD group as compared with the control non-AD group (odds ratio: 5.57, 95% confidence interval: 4.30-7.21, P < .001).

Limitations

This was a retrospective study performed at a single institution with the possibility of surveillance bias being present.

Conclusions

Patients with AD are more likely to be diagnosed with HS than patients without AD. Further research is needed to understand the pathophysiologic mechanism and potential treatment implications.

Gut Microbiota, Probiotics, and Their Interactions in Prevention and Treatment of Atopic Dermatitis: A Review

Atopic dermatitis (AD) is a public health concern and is increasing in prevalence in urban areas. Recent advances in sequencing technology have demonstrated that the development of AD not only associate with the skin microbiome but gut microbiota. Gut microbiota plays an important role in allergic diseases including AD. The hypothesis of the “gut-skin” axis has been proposed and the cross-talk mechanism between them has been gradually demonstrated in the research. Probiotics contribute to the improvement of the intestinal environment, the balance of immune responses, regulation of metabolic activity. Most studies suggest that probiotic supplements may be an alternative for the prevention and treatment of AD. This study aimed to discuss the effects of probiotics on the clinical manifestation of AD based on gut microbial alterations. Here we reviewed the gut microbial alteration in patients with AD, the association between gut microbiota, epidermal barrier, and toll-like receptors, and the interaction of probiotics and gut microbiota. The potential mechanisms of probiotics on alleviating AD via upregulation of epidermal barrier and regulation of immune signaling had been discussed, and their possible effective substances on AD had been explored. This provides the supports for targeting gut microbiota to attenuate AD.

Current Insights into Immunology and Novel Therapeutics of Atopic Dermatitis

Atopic dermatitis (AD) is one of the most prevalent inflammatory disease among non-fatal skin diseases, affecting up to one fifth of the population in developed countries. AD is characterized by recurrent pruritic and localized eczema with seasonal fluctuations. AD initializes the phenomenon of atopic march, during which infant AD patients are predisposed to progressive secondary allergies such as allergic rhinitis, asthma, and food allergies. The pathophysiology of AD is complex; onset of the disease is caused by several factors, including strong genetic predisposition, disrupted epidermal barrier, and immune dysregulation. AD was initially characterized by defects in the innate immune system and a vigorous skewed adaptive Th2 response to environmental agents; there are compelling evidences that the disorder involves multiple immune pathways. Symptomatic palliative treatment is the only strategy to manage the disease and restore skin integrity. Researchers are trying to more precisely define the contribution of different AD genotypes and elucidate the role of various immune axes. In this review, we have summarized the current knowledge about the roles of innate and adaptive immune responsive cells in AD. In addition, current and novel treatment strategies for the management of AD are comprehensively described, including some ongoing clinical trials and promising therapeutic agents. This information will provide an asset towards identifying personalized targets for better therapeutic outcomes.

Biologics for Treatment of Atopic Dermatitis: Current Status and Future Prospect

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by intense pruritus and recurrent eczematous lesions that significantly impair quality of life. It is a heterogeneous disease affecting both children and adults. The treatment of moderate-to-severe forms of AD is challenging, as topical corticosteroids are often insufficient to achieve disease control or inappropriate and off-label use of immunosuppressants may have significant undesirable side effects. The development of targeted biologic therapies specifically for AD is thus highly desirable. Dupilumab is the only biologic therapy that is Food and Drug Administration approved for the treatment of moderate-to-severe AD in patients 6 years and older, with consistent long-term efficacy and safety trial data. In this article, we review the mechanisms, safety, and efficacy of dupilumab from recent clinical trials, and we review the current data, mechanism of action, clinical efficacy, and limitations of new biologics currently in phase 2 and 3 clinical trials (lebrikizumab, tralokinumab, nemolizumab, tezepelumab, and ISB 830).

A murine model of eosinophilic chronic rhinosinusitis using the topical application of a vitamin D3 analog

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a chronic inflammatory disease, characterized by eosinophilic infiltration, T-helper type 2 (Th2-type) response, and olfactory dysfunction. A master regulator of Th2-type inflammation, thymic stromal lymphopoietin (TSLP), is important for basophil activation. TSLP-elicited basophils are a key factor in the pathogenesis of ECRS.

METHODS

In order to elucidate the mechanisms of ECRS in humans, we aimed to establish a murine model of ECRS based on TSLP production in response to the topical application of MC903 (a vitamin D3 analog) and the subsequent TSLP-induced basophil activation. Histological analyses were performed to assess immune cell infiltration into the nasal mucosa and to explore the impact of eosinophilic inflammation on the olfactory epithelium. The status of Th2-type inflammation was evaluated by quantitative real-time PCR and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Eosinophils, basophils, and M2 macrophages increased significantly in the nasal mucosa of the mice treated with MC903 and ovalbumin (OVA), compared to those treated with OVA alone or the controls. Quantitative real-time PCR and ELISA revealed elevated expression of interleukin (IL)-4, IL-5, IL-13, TSLP, the chemokine CCL11, and CCL24 in the nasal mucosa of the ECRS mice. In parallel, thinned olfactory epithelium and decreased mature olfactory sensory neurons were observed in the ECRS mice.

CONCLUSIONS

Our model of ECRS displayed Th2-type inflammation in the sinonasal region, including both eosinophil infiltration and basophil infiltration. Additionally, olfactory epithelium turned out to be affected by eosinophilic inflammation. These features are consistent with the characteristics of the human ECRS.

Periostin Activation of Integrin Receptors on Sensory Neurons Induces Allergic Itch

Chronic allergic itch is a common symptom affecting millions of people and animals, but its pathogenesis is not fully explained. Herein, we show that periostin, abundantly expressed in the skin of patients with atopic dermatitis (AD), induces itch in mice, dogs, and monkeys. We identify the integrin α_Vβ3 expressed on a subset of sensory neurons as the periostin receptor. Using pharmacological and genetic approaches, we inhibited the function of neuronal integrin α_Vβ3, which significantly reduces periostin-induced itch in mice. Furthermore, we show that the cytokine TSLP, the application of AD-causing MC903 (calcipotriol), and house dust mites all induce periostin secretion. Finally, we establish that the JAK/STAT pathway is a key regulator of periostin secretion in keratinocytes. Altogether, our results identify a TSLP-periostin reciprocal activation loop that links the skin to the spinal cord via peripheral sensory neurons, and we characterize the non-canonical functional role of an integrin in itch.

Mishra et al. demonstrate periostin-induced itch in mice, dogs, and monkeys and identify the integrin α_Vβ3 as the periostin neuronal receptor. They find that keratinocytes release periostin in response to TSLP, thus identifying a possible reciprocal vicious circle implicating the cytokine TSLP and periostin in chronic allergic itch.

Effect of Cone of Pinus densiflora on DNCB-Induced Allergic Contact Dermatitis-Like Skin Lesion in Balb/c Mice

Cone of Pinus densiflora (CP), or Korean red pinecone, is a cluster of Pinus densiflora fruit. CP has also been verified in several studies to have anti-oxidation, anti-fungal, anti-bacterial, and anti-melanogenic effects. However, anti-inflammatory effects have not yet been confirmed in the inflammatory responses of pinecones to allergic contact dermatitis. The purpose of this study is to prove the anti-inflammatory effect of CP on allergic contact dermatitis (ACD) in vitro and in vivo. CP inhibited the expression of TSLP, TARC, MCP-1, TNF-α, and IL-6 in TNF-α/IFN-γ-stimulated HaCaT cells and MCP-1, GM-CSF, TNF-α, IL-6, and IL-8 in PMACI (phorbol-12-myristate-13-acetate plus A23187)-stimulated HMC-1 cells. CP inhibited the phosphorylation of mitogen-activated protein kinase (MAPKs), as well as the translocation of NF-κB on TNF-α/IFN-γ stimulated in HaCaT cells. In vivo, CP decreased major symptoms of ACD, levels of IL-6 in skin lesion, thickening of the epidermis and dermis, infiltration of eosinophils and mast cells, and the infiltration of CD4⁺ T cells and CD8⁺ T cells. This result suggests that CP represents a potential alternative medicine to ACD for diseases such as chronic skin inflammation.

Impressic Acid Ameliorates Atopic Dermatitis-Like Skin Lesions by Inhibiting ERK1/2-Mediated Phosphorylation of NF-κB and STAT1

Impressic acid (IPA), a lupane-type triterpenoid from Acanthopanax koreanum, has many pharmacological activities, including the attenuation of vascular endothelium dysfunction, cartilage destruction, and inflammatory diseases, but its influence on atopic dermatitis (AD)-like skin lesions is unknown. Therefore, we investigated the suppressive effect of IPA on 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin symptoms in mice and the underlying mechanisms in cells. IPA attenuated the DNCB-induced increase in the serum concentrations of IgE and thymic stromal lymphopoietin (TSLP), and in the mRNA levels of thymus and activation regulated chemokine (TARC), macrophage derived chemokine (MDC), interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-13 (IL-13), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) in mice. Histopathological analysis showed that IPA reduced the epidermal/dermal thickness and inflammatory and mast cell infiltration of ear tissue. In addition, IPA attenuated the phosphorylation of NF-κB and IκBα, and the degradation of IκBα in ear lesions. Furthermore, IPA treatment suppressed TNF-α/IFN-γ-induced TARC expression by inhibiting the NF-κB activation in cells. Phosphorylation of extracellular signal-regulated protein kinase (ERK1/2) and the signal transducer and activator of transcription 1 (STAT1), the upstream signaling proteins, was reduced by IPA treatment in HaCaT cells. In conclusion, IPA ameliorated AD-like skin symptoms by regulating cytokine and chemokine production and so has therapeutic potential for AD-like skin lesions.

The Wound Healing Peptide, AES16-2M, Ameliorates Atopic Dermatitis In Vivo

Peptide materials have recently been considered for use in various industrial fields. Because of their efficacy, safety, and low cost, therapeutic peptides are studied for various diseases, including atopic dermatitis (AD). AD is a common inflammatory skin disease impairing the patient's quality of life. Various therapies, such as treatments with corticosteroids, calcineurin inhibitors, and antibody drugs, have been applied, but numerous side effects have been reported, including skin atrophy, burning, and infection. In the case of antibody drugs, immunogenicity against the drugs can be a problem. To overcome these side effects, small peptides are considered therapeutic agents. We previously identified the small wound healing peptide AES16-2M with a sequence of REGRT, and examined its effects on AD in this study. Interestingly, the administration of AES16-2M downregulated the AD disease score, ear thickness, serum IgE, and thymic stromal lymphopoietin (TSLP) in AD mice. The thickness of the epidermal layer was also improved by AES16-2M treatment. In addition, quantities of IL-4-, IL-13-, and IL-17-producing CD4 T cells from peripheral lymph nodes and spleens were reduced by injection of AES16-2M. Furthermore, the expression of TSLP was significantly reduced in AES16-2M-treated human keratinocytes. Therefore, these results suggest that AES16-2M can be a novel candidate for AD treatment.

Involvement of Neuro-Immune Interactions in Pruritus With Special Focus on Receptor Expressions

Pruritus is a common, but very challenging symptom with a wide diversity of underlying causes like dermatological, systemic, neurological and psychiatric diseases. In dermatology, pruritus is the most frequent symptom both in its acute and chronic form (over 6 weeks in duration). Treatment of chronic pruritus often remains challenging. Affected patients who suffer from moderate to severe pruritus have a significantly reduced quality of life. The underlying physiology of pruritus is very complex, involving a diverse network of components in the skin including resident cells such as keratinocytes and sensory neurons as well as transiently infiltrating cells such as certain immune cells. Previous research has established that there is a significant crosstalk among the stratum corneum, nerve fibers and various immune cells, such as keratinocytes, T cells, basophils, eosinophils and mast cells. In this regard, interactions between receptors on cutaneous and spinal neurons or on different immune cells play an important role in the processing of signals which are important for the transmission of pruritus. In this review, we discuss the role of various receptors involved in pruritus and inflammation, such as TRPV1 and TRPA1, IL-31RA and OSMR, TSLPR, PAR-2, NK1R, H1R and H4R, MRGPRs as well as TrkA, with a focus on interaction between nerve fibers and different immune cells. Emerging evidence shows that neuro-immune interactions play a pivotal role in mediating pruritus-associated inflammatory skin diseases such as atopic dermatitis, psoriasis or chronic spontaneous urticaria. Targeting these bidirectional neuro-immune interactions and the involved pruritus-specific receptors is likely to contribute to novel insights into the underlying pathogenesis and targeted treatment options of pruritus.

Cytokinocytes: the diverse contribution of keratinocytes to immune responses in skin

The skin serves as the primary interface between our body and the external environment and acts as a barrier against entry of physical agents, chemicals, and microbes. Keratinocytes make up the main cellular constitute of the outermost layer of the skin, contributing to the formation of the epidermis, and they are crucial for maintaining the integrity of this barrier. Beyond serving as a physical barrier component, keratinocytes actively participate in maintaining tissue homeostasis, shaping, amplifying, and regulating immune responses in skin. Keratinocytes act as sentinels, continuously monitoring changes in the environment, and, through microbial sensing, stretch, or other physical stimuli, can initiate a broad range of inflammatory responses via secretion of various cytokines, chemokines, and growth factors. This diverse function of keratinocytes contributes to the highly variable clinical manifestation of skin immune responses. In this Review, we highlight the highly diverse functions of epidermal keratinocytes and their contribution to various immune-mediated skin diseases.

TSLP as druggable target - a silver-lining for atopic diseases?

Atopic diseases refer to common allergic inflammatory diseases such as atopic dermatitis (AD), allergic rhinitis (AR), and allergic asthma (AA). AD often develops in early childhood and may herald the onset of other allergic disorders such as food allergy (FA), AR, and AA. This progression of the disease is also known as the atopic march, and it goes hand in hand with a significantly impaired quality of life as well as a significant economic burden. Atopic diseases usually are considered as T helper type 2 (Th2) cell-mediated inflammatory diseases. Thymic stromal lymphopoietin (TSLP), an epithelium-derived pro-inflammatory cytokine, activates distinct immune and non-immune cells. It has been shown to be a master regulator of type 2 immune responses and atopic diseases. In experimental settings, the inhibition or knockout of TSLP signaling has shown great therapeutic potential. This, in conjunction with the increasing knowledge about the central role of TSLP in the pathogenesis of atopic diseases, has sparked an interest in TSLP as a druggable target. In this review, we will discuss the autocrine and paracrine effects of TSLP, how it regulates the tissue microenvironment and drives atopic diseases, which provide the rationale for the increasing interest in TSLP as a druggable target.

New and Emerging Biologics for Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is characterized by complex pathophysiology involving both skin barrier dysfunction and aberrant type 2 inflammation/immune responses. AD can be a debilitating condition that drastically impairs quality of life, especially in patients with moderate-to-severe disease. Currently, topical therapies such as corticosteroids and non-steroidal immunomodulatory therapy provide limited efficacy for patients with moderate-to-severe AD; limitations include inadequate response, cutaneous toxicity from overuse, and poor tolerance due to stinging and burning. Historically, the development of targeted therapies has been challenging due to the complex and multifaceted etiology of AD. Recent progress in understanding the immunopathology of AD reinforces the development of newly targeted therapeutics. The successful launch of dupilumab, a monoclonal antibody targeting the interleukin (IL)-4α receptor subunit, for AD in 2017 spurred the development of a number of biologics targeting novel cytokine and receptor targets that are now in phase II and III of development. This review aims to explore the rationale behind these novel biological therapies and to summarize current clinical studies of these agents.

Exosomes from Human Adipose Tissue-Derived Mesenchymal Stem Cells Promote Epidermal Barrier Repair by Inducing de Novo Synthesis of Ceramides in Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial, heterogeneous disease associated with epidermal barrier disruption and intense systemic inflammation. Previously, we showed that exosomes derived from human adipose tissue-derived mesenchymal stem cells (ASC-exosomes) attenuate AD-like symptoms by reducing multiple inflammatory cytokine levels. Here, we investigated ASC-exosomes' effects on skin barrier restoration by analyzing protein and lipid contents. We found that subcutaneous injection of ASC-exosomes in an oxazolone-induced dermatitis model remarkably reduced trans-epidermal water loss, while enhancing stratum corneum (SC) hydration and markedly decreasing the levels of inflammatory cytokines such as IL-4, IL-5, IL-13, TNF-α, IFN-γ, IL-17, and TSLP, all in a dose-dependent manner. Interestingly, ASC-exosomes induced the production of ceramides and dihydroceramides. Electron microscopic analysis revealed enhanced epidermal lamellar bodies and formation of lamellar layer at the interface of the SC and stratum granulosum with ASC-exosomes treatment. Deep RNA sequencing analysis of skin lesions demonstrated that ASC-exosomes restores the expression of genes involved in skin barrier, lipid metabolism, cell cycle, and inflammatory response in the diseased area. Collectively, our results suggest that ASC-exosomes effectively restore epidermal barrier functions in AD by facilitating the de novo synthesis of ceramides, resulting in a promising cell-free therapeutic option for treating AD.

Eckol from Ecklonia cava ameliorates TNF-α/IFN-γ-induced inflammatory responses via regulating MAPKs and NF-κB signaling pathway in HaCaT cells

We investigated the protective effect of the bioactive compound eckol on inflammatory-related skin lesions in vitro. HaCaT cells were stimulated with tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) mixture, and treated with various concentration of eckol (25, 50, and 100 µg/ml). The expression of pro-inflammatory cytokines and chemokines were analyzed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR), respectively. Mitogen-activated protein kinase (MAPKs) and nuclear factor-kappa B (NF-κB) signaling pathways regulate immune and inflammation responses. Phosphorylation of MAPKs and NF-κB, indicating activation of respective signaling pathways, was examined by western blot analysis. Treatment of TNF-α and IFN-γ promoted the mRNA expression and production of pro-inflammatory cytokines and chemokines in HaCaT cells. However, eckol significantly suppressed the these mediators. Furthermore, activation of TNF-α/IFN-γ-induced MAPKs and NF-κB signaling pathway was inhibited by eckol treatment. Eckol also hampered the TNF-α/IFN-γ-mediated nuclear translocation of NF-κB p65 in HaCaT cells. Taken together, our findings demonstrate that eckol shows effective protective activity against TNF-α/IFN-γ-induced skin inflammation.

An overview of drug discovery efforts for eczema: why is this itch so difficult to scratch?

Introduction: Atopic dermatitis (AD) is a type of allergic/inflammatory dermatitis characterized by itch and an impairment in quality of life.Areas covered: Herein, the authors review drug discovery efforts for AD, highlighting the clinical efficacy of novel drugs, with a particular focus on the relief of pruritus. Topical agents include emollients, topical antihistamines, corticosteroids, calcineurin inhibitors and herbs. Recently, topical phosphodiesterase E4 (PDE4) inhibitors like crisaborole have become available and are efficacious for mild to moderate AD with few side effects. For more severe AD, monoclonal antibodies like dupilumab are considered as efficacious subcutaneous treatment options. In severe and recalcitrant AD, systemic treatment can ameliorate AD symptoms.Expert opinion: Many topical and systemic medications have demonstrated therapeutic benefits for AD. Indeed, randomized trials have shown that topical PDE4 inhibitors and subcutaneous dupilumab are safe and efficacious. Objective tools to evaluate itch and gauge treatment efficacy is important, but current methodology relies primarily on clinical scores. AD is a systemic atopic disease with a lot of complicated psychosocial issues. Suboptimal efficacy is often due to poor compliance and unrealistic expectation of curative treatment, rendering treatment difficult despite the existence of effective medications.

Galectin-9 Induced by Dietary Probiotic Mixture Regulates Immune Balance to Reduce Atopic Dermatitis Symptoms in Mice

Probiotics can be an effective treatment for atopic dermatitis (AD), while their mechanism of action is still unclear. Here, we induced AD in mice with 2,4-dinitrochlorobenzene and administrated YK4, a probiotic mixture consisting of Lactobacillus acidophilus CBT LA1, L. plantarum CBT LP3, Bifidobacterium breve CBT BR3, and B. lactis CBT BL3. Then, we have validated the underlying mechanism for the alleviation of AD by YK4 from the intestinal and systematic immunological perspectives. Administration of YK4 in AD mice alleviated the symptoms of AD by suppressing the expression of skin thymic stromal lymphopoietin and serum immunoglobulin E eliciting excessive T-helper (Th) 2 cell-mediated responses. YK4 inhibited Th2 cell population through induce the proportion of Th1 cells in spleen and Treg cells in Peyer's patches and mesenteric lymph node (mLN). CD103⁺ dendritic cells (DCs) in mLN and the spleen were significantly increased in AD mice administered with YK4 when compared to AD mice. Furthermore, galectin-9 was significantly increased in the gut of AD mice administered with YK4. In vitro experiments were performed using bone marrow-derived DCs (BMDC) and CD4⁺ T cells to confirm the immune mechanisms of YK4 and galectin-9. The expression of CD44, a receptor of galectin-9, together with programmed death-ligand 1 was significantly upregulated in BMDCs following treatment with YK4. IL-10 and IL-12 were upregulated when BMDCs were treated with YK4. Cytokines together with co-receptors from DCs play a major role in the differentiation and activation of CD4⁺ T cells. Proliferation of Tregs and Th1 cell activation were enhanced when CD4⁺T cells were co-cultured with YK4-treated BMDCs. Galectin-9 appeared to contribute at least partially to the proliferation of Tregs. The results further suggested that DCs treated with YK4 induced the differentiation of naïve T cells toward Th1 and Tregs. At the same time, YK4 alleviated AD symptoms by inhibiting Th2 response. Thus, the present study suggested a potential role of YK4 as an effective immunomodulatory agent in AD patients.

Neuroimmune interactions in chronic itch of atopic dermatitis

Itch is a defining symptom of atopic dermatitis. Crosstalk between keratinocytes, the immune system and non‐histaminergic sensory nerves is responsible for the pathophysiology of chronic itch in atopic dermatitis. An expanding understanding of the contribution of the nervous system and its interaction with immune pathways in atopic itch are helping to identify new therapeutic strategies.

Proof-of-concept clinical trial of etokimab shows a key role for IL-33 in atopic dermatitis pathogenesis

Targeted inhibition of cytokine pathways provides opportunities to understand fundamental biology in vivo in humans. The IL-33 pathway has been implicated in the pathogenesis of atopy through genetic and functional associations. We investigated the role of IL-33 inhibition in a first-in-class phase 2a study of etokimab (ANB020), an IgG1 anti-IL-33 monoclonal antibody, in patients with atopic dermatitis (AD). Twelve adult patients with moderate to severe AD received a single systemic administration of etokimab. Rapid and sustained clinical benefit was observed, with 83% achieving Eczema Area and Severity Index 50 (EASI50), and 33% EASI75, with reduction in peripheral eosinophils at day 29 after administration. We noted significant reduction in skin neutrophil infiltration after etokimab compared with placebo upon skin challenge with house dust mite, reactivity to which has been implicated in the pathogenesis of AD. We showed that etokimab also inhibited neutrophil migration to skin interstitial fluid in vitro. Besides direct effects on neutrophil migration, etokimab revealed additional unexpected CXCR1-dependent effects on IL-8-induced neutrophil migration. These human in vivo findings confirm an IL-33 upstream role in modulating skin inflammatory cascades and define the therapeutic potential for IL-33 inhibition in human diseases, including AD.

Peripheral and Central Mechanisms of Itch

Itch is a unique sensory experience that is encoded by genetically distinguishable neurons both in the peripheral nervous system (PNS) and central nervous system (CNS) to elicit a characteristic behavioral response (scratching). Itch interacts with the other sensory modalities at multiple locations, from its initiation in a particular dermatome to its transmission to the brain where it is finally perceived. In this review, we summarize the current understanding of the molecular and neural mechanisms of itch by starting in the periphery, where itch is initiated, and discussing the circuits involved in itch processing in the CNS.

More from the Pipeline of Clinical Research on SELECTED SYSTEMIC THERAPIES FOR ATOPIC DERMATITIS

Many systemic therapies are under development for atopic dermatitis, many of which are injectable monoclonal antibodies that inhibit specific pathways involved in the pathogenesis of the disease. Most are currently under development, however, there are preliminary studies with subcutaneous omalizumab (IgE-directed therapy), and oral apremilast (phosphodiesterase-4 [PDE-4] inhibition. Further studies are needed with these agents. This article discusses various agents that address several potential therapeutic approaches, including IgE-directed therapy, anti-IL-31, anti-IL-5, anti-IL-22, PDE-4 inhibition, and thymic stromal lymphopoietin (TSLP)-directed therapy.

Direct activation of aryl hydrocarbon receptor by benzo[a]pyrene elicits T-helper 2-driven proinflammatory responses in a mouse model of allergic dermatitis

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that binds to various environmental chemicals and contributes to numerous toxicological effects. However, the direct effects of AhR on the development of allergic diseases are not fully understood. The main aim of this study was to elucidate the action of AhR in the development of cutaneous allergies. Initially, the potential for a direct relationship between AhR and the immune cells was investigated in vitro, using murine bone marrow-derived dendritic cells, human epidermal keratinocytes, and the mixed leukocyte reaction assay. Benzo[a]pyrene (BaP) and 6-formylindolo[3,2-b]carbazole were used as selective ligands for the AhR. Pretreatment with BaP and/or 6-formylindolo[3,2-b]carbazole significantly induced cytokine release by activated keratinocytes and T-cell proliferation, whereas interleukin-12 production in bone marrow-derived dendritic cells was reduced by AhR activation. To confirm the in vitro results, in vivo experiments were also performed in T-helper (Th)2-type hapten toluene-2,4-diisocyanate- and Th1-type hapten dinitrochlorobenzene-induced mouse models of allergic dermatitis. Mice were orally administered BaP at 48, 24 and 4 hours before the final allergen challenge. In the Th2 model, ear-swelling response and scratching behavior were promoted by BaP exposure, which supported the observed significant increases in local cytokine secretion. The infiltration of helper T cells, B cells and dendritic cells into the auricular lymph node was significantly enhanced by BaP administration, although Th1-type immune responses were not influenced by AhR activation. Our findings demonstrate that AhR activation directly activates keratinocytes and T cells, which leads to the exacerbation of Th2-type cutaneous allergy.

Synthesis of poly(lactide-co-glycerol) as a biodegradable and biocompatible polymer with high loading capacity for dermal drug delivery

Due to the low cutaneous bioavailability of tacrolimus (TAC), penetration enhancers are used to improve its penetration into the skin. However, poor loading capacity, non-biodegradability, toxicity, and in some cases inefficient skin penetration are challenging issues that hamper their applications for the dermal TAC delivery. Here we present poly(lactide-co-glycerol) (PLG) as a water soluble, biodegradable, and biocompatible TAC-carrier with high loading capacity (14.5% w/w for TAC) and high drug delivery efficiencies into the skin. PLG was synthesized by cationic ring-opening copolymerization of a mixture of glycidol and lactide and showed 35 nm and 300 nm average sizes in aqueous solutions before and after loading of TAC, respectively. Delivery experiments on human skin, quantified by fluorescence microscopy and LC-MS/MS, showed a high ability for PLG to deposit Nile red and TAC into the stratum corneum and viable epidermis of skin in comparison with Protopic® (0.03% w/w, TAC ointment). The cutaneous distribution profile of delivered TAC proved that 80%, 16%, and 4% of the cutaneous drug level was deposited in the stratum corneum, viable epidermis, and upper dermis, respectively. TAC delivered by PLG was able to efficiently decrease the IL-2 and TSLP expressions in human skin models. Taking advantage of the excellent physicochemical and biological properties of PLG, it can be used for efficient dermal TAC delivery and potential treatment of inflammatory skin diseases.

Toll-like receptor 4 attenuates a murine model of atopic dermatitis through inhibition of langerin-positive DCs migration

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that is often associated with skin barrier dysfunction leading to a higher frequency of bacterial and viral skin infections. Toll-like receptor (TLR) 4 on resident skin cells was involved in sensing pathogens and eliciting pathogen-specific innate and adaptive immune responses. Previous studies have demonstrated that TLR4 was linked to AD severity in context of pathogen infection. However, the immune regulatory role of TLR4 in AD remains to be defined. We here investigated the immune regulatory function of TLR4 in AD induced by repeated epicutaneous application of a hapten, 2,4-dinitrochlorobenzene (DNCB). Our results showed that TLR4-deficient (TLR4^-/- ) mice exhibited more severe AD symptoms than WT mice after DNCB challenge. The DNCB-treated TLR4^-/- mice also displayed higher expression levels of inflammatory cytokines and stronger Th2 response than WT counterparts. Moreover, the skin expression of thymic stromal lymphopoietin (TSLP), an important potential contributor to allergic inflammation, was significantly elevated in TLR4^-/- mice compared with that in WT mice upon DNCB administration. Furthermore, we demonstrated that the migration of langerin-positive dendritic cells (DCs) into draining lymph nodes was enhanced in TLR4^-/- mice following DNCB challenge, which is partially dependent on the production of pro-inflammatory cytokine TNF-α. Together, these results determined that TLR4 affected the hapten-induced skin inflammation in the absence of exogenous pathogen infection, suggesting that TLR4 not only regulates infection but also may serve as a modulator of the immune response during AD development.