Inhibitory Effect of Bisdemethoxycurcumin on DNCB-Induced Atopic Dermatitis in Mice

Therapeutic effects of chamomile volatile oil nanoemulsion/Bletilla striata polysaccharides gels on atopic dermatitis

Atopic dermatitis (AD) is a prevalent chronic skin condition characterized by complex immune responses. Chamomile possesses potent anti-inflammatory properties and has been widely used in treating various skin diseases. This study aimed to assess the therapeutic benefits of chamomile volatile oil nanoemulsion gels (CVO-NEGs) for the treatment of AD. Chamomile volatile oil nanoemulsions (CVO-NEs) were prepared using the phase transition method, yielding spherical nanoparticles with a particle size of 19.07 nm. Subsequently, Bletilla striata polysaccharides were employed to encapsulate CVO-NEs, resulting in the formation of CVO-NEGs. In vivo studies demonstrated that the preparation of CVO-NEGs enhanced the biological activity of volatile oil in AD therapy. Histopathological results indicated that CVO-NEGs reduced skin damage, epidermal thickness, and mast cell infiltration. CVO-NEGs suppressed IgG production and reduced the levels of cytokines, including TNF-α, IL-4, and IFN-γ, in AD mice. Furthermore, flow cytometry revealed that CVO-NEGs were involved in regulating the differentiation of CD4+ T cell subsets. The immune imbalance of Th1/Th2 in AD mice can be controlled, resulting in a reduction in the hypersensitivity reaction caused by excessive Th2 activation. In conclusion, the present study confirms that CVO-NEGs have the potential to serve as an effective alternative treatment for AD.

Role of LECT2 in exacerbating atopic dermatitis: insight from in vivo and in vitro models via NF-κB signaling pathway

Leukocyte cell-derived chemotaxin 2 (LECT2) is linked to various immune diseases. Previously, we reported that serum LECT2 levels correlate with disease severity in atopic dermatitis (AD) patients. To investigate the role of LECT2 in AD and elucidate its potential mechanisms, we used LECT2 to treat an AD mouse model induced by 1-Chloro-2,4-dinitrobenzene (DNCB) in LECT2 knockout (KO) and wild-type (WT) mice, and an AD cell model using TNF-α/IFN-γ-induced HaCaT cells. Inflammatory factors and barrier proteins were analyzed by histology, immunohistochemistry, RT-qPCR, ELISA, and Western Blot. Activation of the NF-κB signaling pathway was evaluated by Western Blot and immunofluorescence. In the AD mouse model, LECT2 treatment increased epidermal and dermal thickness, mast cell infiltration, and downregulated barrier proteins. Inflammatory factors were increased in skin lesions and serum. In the AD cell model, LECT2 decreased barrier protein levels and increased inflammatory factor levels, enhancing NF-κB P65 nuclear translocation. These results indicate that LECT2 exacerbates AD-like responses by dysregulating the NF-κB signaling pathway, highlighting its potential as a therapeutic target for AD management.

Celastrol alleviates atopic dermatitis by regulating Ezrin-mediated mitochondrial fission and fusion

Celastrol, a bioactive molecule extracted from the plant Tripterygium wilfordii Hook F., possesses anti-inflammatory, anti-obesity and anti-tumour properties. Despite its efficacy in improving erythema and scaling in psoriatic mice, the specific therapeutic mechanism of celastrol in atopic dermatitis (AD) remains unknown. This study aims to examine the role and mechanism of celastrol in AD using TNF-α-stimulated HaCaT cells and DNCB-induced Balb/c mice as in vitro and in vivo AD models, respectively. Celastrol was found to inhibit the increased epidermal thickness, reduce spleen and lymph node weights, attenuate inflammatory cell infiltration and mast cell degranulation and decrease thymic stromal lymphopoietin (TSLP) as well as various inflammatory factors (IL-4, IL-13, TNF-α, IL-5, IL-31, IL-33, IgE, TSLP, IL-17, IL-23, IL-1β, CCL11 and CCL17) in AD mice. Additionally, celastrol inhibited Ezrin phosphorylation at Thr567, restored mitochondrial network structure, promoted translocation of Drp1 to the cytoplasm and reduced TNF-α-induced cellular reactive oxygen species (ROS), mitochondrial ROS (mtROS) and mitochondrial membrane potential (MMP) production. Interestingly, Mdivi-1 (a mitochondrial fission inhibitor) and Ezrin-specific siRNAs lowered inflammatory factor levels and restored mitochondrial reticular formation, as well as ROS, mtROS and MMP production. Co-immunoprecipitation revealed that Ezrin interacted with Drp1. Knocking down Ezrin reduced mitochondrial fission protein Drp1 phosphorylation and Fis1 expression while increasing the expression of fusion proteins Mfn1 and Mfn2. The regulation of mitochondrial fission and fusion by Ezrin was confirmed. Overall, celastrol may alleviate AD by regulating Ezrin-mediated mitochondrial fission and fusion, which may become a novel therapeutic reagent for alleviating AD.

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.

N-benzyl-N-methyldecan-1-amine, derived from garlic, and its derivative alleviate 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin lesions in mice

Given the intricate etiology and pathogenesis of atopic dermatitis (AD), the complete cure of AD remains challenging. This study aimed to investigate if topically applying N-benzyl-N-methyldecan-1-amine (BMDA), derived from garlic, and its derivative [decyl-(4-methoxy-benzyl)-methyl-1-amine] (DMMA) could effectively alleviate AD-like skin lesions in 2,4-dinitrochlorobenzene (DNCB)-treated mice. Administering these compounds to the irritated skin of DNCB-treated mice significantly reduced swelling, rash, and excoriation severity, alongside a corresponding decrease in inflamed epidermis and dermis. Moreover, they inhibited spleen and lymph node enlargement and showed fewer infiltrated mast cells in the epidermis and dermis through toluidine-blue staining. Additionally, they led to a lower IgE titer in mouse sera as determined by ELISA, compared to vehicle treatment. Analyzing skin tissue from the mice revealed decreased transcript levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6), IL-4, iNOS, and COX-2, compared to control mice. Simultaneously, the compounds impeded the activation of inflammation-related signaling molecules such as JNK, p38 MAPK, and NF-κB in the mouse skin. In summary, these findings suggest that BMDA and DMMA hold the potential to be developed as a novel treatment for healing inflammatory AD.

Epigenetic control of inflammation in Atopic Dermatitis

Atopic dermatitis (AD), also known as atopic eczema, is a common but also complex chronic, itchy skin condition with underlying inflammation of the skin. This skin ailment is prevalent worldwide and affects people of all ages, particularly children below five years of age. The itching and resulting rashes in AD patients are often the result of inflammatory signals, thus necessitating a closer look at the inflammation-regulating mechanisms for putative relief, care and therapy. Several chemical- as well as genetically-induced animal models have established the importance of targeting pro-inflammatory AD microenvironment. Epigenetic mechanisms are gaining attention towards a better understanding of the onset as well as the progression of inflammation. Several physiological processes with implications in pathophysiology of AD, such as, barrier dysfunction either due to reduced filaggrin / human β-defensins or altered microbiome, reprograming of Fc receptors with resulting overexpression of high affinity IgE receptors, elevated eosinophil numbers or the elevated IL-22 production by CD4 + T cells have underlying epigenetic mechanisms that include differential promoter methylation and/or regulation by non-coding RNAs. Reversing these epigenetic changes has been verified to reduce inflammatory burden through altered secretion of cytokines IL-6, IL-4, IL-13, IL-17, IL-22 etc, with benefit against AD progression in experimental models. A thorough understanding of epigenetic remodeling of inflammation in AD has the potential of opening avenues for novel diagnostic, prognostic and therapeutic options.

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.

Probiotic-fermented Portulaca oleracea L. alleviated DNFB-induced atopic dermatitis by inhibiting the NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Probiotic fermentation is a mild and safe biological method to boost the performance of herbs. Portulaca oleracea L. (PO), with folklore records of purgative, anti-dermatological and anti-epidemic effects, has been demonstrated to possess anti-inflammatory, immunomodulatory, and antioxidant properties. However, the potential of PO for the treatment of atopic dermatitis (AD) has not been sufficiently explored.

AIM OF STUDY

This study aimed to evaluate the therapeutic benefits of PO and fermented Portulaca oleracea L. (FPO) and explore their intrinsic mechanisms.

METHODS

By utilizing 2,4-dinitrofluorobenzene-induced AD mice as a model, the histopathology of the lesions was observed using H&E and toluidine blue staining methods; the levels of immunoglobulin E (Ig E), histamine (HIS), and thymic stromal lymphopoietin (TSLP) in serum were measured using ELISA, whereas, the expression of inflammatory cytokines in skin lesion was measured using ELISA and immunohistochemistry experiments. The expression of tumor necrosis factor-α (TNF-α), IKKα, NF-κB mRNA was measured using qPCR; and the expression of TNF-α、p-IKKα, p-IκBα, p-NF-κB was measured using western blotting.

RESULTS

Both 20 mg/mL PO and FPO alleviated mast cell infiltration and lesion pathology, reduced serum levels of Ig E, HIS and TSLP, down-regulated the expression of AD-related inflammatory cytokines, such as, TNF-α, interferon-γ, and interleukin-4, and increased filaggrin expression. Furthermore, they inhibited the expression of TNF-α, IKKα, and NF-κB genes and TNF-α, p-IKKα, p-NF-κB and p-IκBα proteins associated with the NF-κB signaling pathway.

CONCLUSIONS

PO and FPO has a positive therapeutic potential on AD, indicating that it may be employed as alternative therapies for AD.

The Anti-Atopic Dermatitis Effects of Mentha arvensis Essential Oil Are Involved in the Inhibition of the NLRP3 Inflammasome in DNCB-Challenged Atopic Dermatitis BALB/c Mice

The NLRP3 inflammasome is upregulated by various agents, such as nuclear factor-kappa B (NF-κB), lipopolysaccharide (LPS), and adenosine triphosphate (ATP). The NLRP3 inflammasome facilitations the maturation of interleukin (IL)-1β, a proinflammatory cytokine that is critically involved in the pathogenesis of atopic dermatitis (AD). Although the NLRP3 inflammasome clearly exacerbates AD symptoms such as erythema and pruritus, drugs for AD patients targeting the NLRP3 inflammasome are still lacking. Based on the previous findings that Mentha arvensis essential oil (MAEO) possesses strong anti-inflammatory and anti-AD properties through its inhibition of the ERK/NF-κB signaling pathway, we postulated that MAEO might be capable of modulating the NLRP3 inflammasome in AD. The aim of this research was to investigate whether MAEO affects the inhibition of NLRP3 inflammasome activation in murine bone marrow-derived macrophages (BMDMs) stimulated with LPS + ATP in vitro and in a murine model displaying AD-like symptoms induced by 2,4-dinitrochlorobenzene (DNCB) in vivo. We found that MAEO inhibited the expression of NLRP3 and caspase-1, leading to the suppression of NLRP3 inflammasome activation and IL-1β production in BMDMs stimulated with LPS + ATP. In addition, MAEO exhibited efficacy in ameliorating AD symptoms in a murine model induced by DNCB, as indicated by the reduction in dermatitis score, ear thickness, transepidermal water loss (TEWL), epidermal thickness, and immunoglobulin E (IgE) levels. Furthermore, MAEO attenuated the recruitment of NLRP3-expressing macrophages and NLRP3 inflammasome activation in murine dorsal skin lesions induced by DNCB. Overall, we provide evidence for the anti-AD effects of MAEO via inhibition of NLRP3 inflammasome activation.