Exploration of Metabolite Biomarkers to Predict the Efficacy of Dupilumab Treatment for Atopic Dermatitis.

Dupilumab (DUP) is the first biological agent used treating atopic dermatitis (AD). Notwithstanding its high cost, the type of patient group for which the drug is effective remains unclear. In this retrospective study, we aimed to identify novel and reliable biomarkers which can be measured before DUP administration and to predict the efficacy of DUP. Serum samples from 19 patients with AD treated with DUP were analysed by metabolome analysis using gas chromatography-mass spectrometry. Total 148 metabolites were detected, and the relative values of the metabolites were compared between the patient group that achieved 75% improvement in Eczema Area and Severity Index 16 weeks after administration of DUP (high responders: HR; n = 11) and that did not (low responders: LR; n = 8). The HR and LR groups had significant differences in the relative values of the eight metabolites (lactic acid, alanine, glyceric acid, fumaric acid, nonanoic acid, ribose, sorbitol, and ornithine), with ribose emerging as the best. Furthermore, we evaluated the serum concentrations of ribose and found that ribose may be a useful metabolite biomarker for predicting the efficacy of DUP in AD.

IL-33-induced keratoconjunctivitis is mediated by group 2 innate lymphoid cells in mice.

BACKGROUND: Interleukin-33 (IL-33) is involved in type 2 innate immunity by inducing type 2 cytokines, such as IL-5 and IL-13, through the activation of group 2 innate lymphoid cells (ILC2s) or T helper 2 (Th2) cells. We previously reported that mice overexpressing IL-33 (IL-33Tg) in the cornea and conjunctiva spontaneously develop atopic keratoconjunctivitis-like inflammation. Despite previous studies, it is not fully understood what types of immune cells contribute to the disease process of IL-33-induced keratoconjunctivitis. METHODS: To defect Th2 cells, IL-33Tg mice were crossed with Rag2KO mice. To defect ILC2s, IL-33Tg mice received bone marrow transplantations from B6.C3(Cg)-Rorasg/J mice that lacked ILC2. Immunostaining techniques were used to determine where ILC2 is distributed in the cornea and conjunctiva. We analyzed the transcriptomes of ILC2 from the conjunctiva by using single-cell RNA-seq analysis. To investigate whether tacrolimus reduces type 2 cytokine production by ILC2, ILC2 was cultured with tacrolimus, and the percentage of cytokine-producing ILC2 was examined. To investigate whether tacrolimus can inhibit IL-33-induced keratoconjunctivitis in vivo, IL-33Tg mice were treated with tacrolimus eye drops. RESULTS: ILC2 infiltrated the conjunctival epithelium and subepithelial tissue. Keratoconjunctivitis developed spontaneously in Rag2KO/IL-33Tg mice, but keratoconjunctivitis was abolished in IL-33Tg mice lacking ILC2. ILC2 was not a uniform cluster but a heterogeneous cluster. Tacrolimus inhibited cytokine production from ILC2s in vitro, and tacrolimus eye drops inhibited keratoconjunctivitis in IL-33Tg mice in vivo. CONCLUSIONS: ILC2 plays a pivotal role in IL-33-induced keratoconjunctivitis in mice.

Arteriosclerosis Derived from Cutaneous Inflammation Is Ameliorated by the Deletion of IL-17A and IL-17F.

The skin is one of the major immune organs producing large amounts of proinflammatory and inflammatory cytokines in response to internal or exogenous stimuli, inducing systemic inflammation in various internal organs. In recent years, organ damage associated with inflammatory skin diseases such as psoriasis and atopic dermatitis has received increasing attention, and vascular disorder such as arteriosclerosis is one of the serious complications of chronic inflammatory skin diseases. However, the detailed mechanism of arteriosclerosis in dermatitis and the role of cytokines have not been clarified so far. In the current study, using a spontaneous dermatitis model, we investigated the pathophysiology of arteriosclerosis and the treatment option for inflammatory skin conditions. We employed spontaneous dermatitis model mice overexpressing human caspase-1 in the epidermal keratinocyte (Kcasp1Tg). The thoracic and abdominal aorta was investigated histologically. GeneChip and RT-PCR analysis were performed to measure the changes in mRNA levels in the aorta. To elucidate the direct effect on the artery by major inflammatory cytokines, endothelial cells, vascular smooth muscle cells, and fibroblast cells were co-cultured with several cytokines, and mRNA expression levels were measured. In order to observe the efficacy of IL-17A/F in arteriosclerosis, cross-mating with IL-17A, IL-17F, and IL-17A/F deficient mice was performed. Finally, we also measured snap tension in the abdominal aorta in WT, Kcasp1Tg, and IL17A/F-deficient mice. Kcasp1Tg showed a decrease in the diameter of the abdominal aorta compared to wild-type mice. mRNA levels for six genes including Apol11b, Camp, Chil3, S100a8, S100a9, and Spta1 were increased in the abdominal aorta of Kcasp1Tg. Some of the above mRNA levels were also increased in the co-culture with major inflammatory cytokines, IL-17A/F, IL-1ß, and TNF-α. Dermatitis improved and mRNA levels were partially ameliorated in Kcasp1Tg with IL-17A/F deletion. Arterial fragility was also evidenced in the inflammatory model, but arterial flexibility was revealed in the IL-17A/F deletion model. Severe dermatitis is closely related to secondary arteriosclerosis caused by the persistent release of inflammatory cytokines. The results also proved that treatment against IL-17A and F may ameliorate arteriosclerosis.

ILC2s in skin disorders.

The activation of group 2 innate lymphoid cells (ILC2s) is controlled by various tissue-derived factors, including cytokines, whereas T cells respond to foreign antigens. This review discusses the tissue-specific properties of ILC2s in skin and their involvement in human skin diseases. In a steady state, cutaneous ILC2s contribute to tissue homeostasis. In the keratinocytes of patients with atopic dermatitis (AD), the inflammatory cytokine interleukin-33 (IL-33) is overexpressed. ILC2s are stimulated by IL-33-stimulated basophils through IL-4 to produce type 2 cytokines, such as IL-5 and IL-13. According to several studies, ILC2 expression is upregulated in human AD skin lesions, and it is involved in AD pathogenesis. Dupilumab, an antibody against IL-4 receptor α, lowered the number and percentage of ILC2s in the peripheral blood of patients with AD. Cutaneous ILC2s are divided into two subgroups: circulating and skin-resident ILC2s. However, ILC2s are homogeneous cell populations that are highly diverse and plastic, and there is no consensus on the classification that should be used. The variations in the definition for cutaneous ILC2s in different studies make comparisons among studies difficult, and in particular, the weak expression of the IL-33 receptor ST2 in cutaneous ILC2s and its lack of markers have posed a great challenge to researchers. Therefore, further comprehensive analytical studies are warranted.

The Interplay of Type 1, Type 2, and Type 3 Lymphocytes and Cytokines in Atopic Dermatitis.

Atopic dermatitis (AD) is classified as a type 2 disease owing to the majority of type 2 lymphocytes that constitute the skin-infiltrating leukocytes. However, all of the type 1-3 lymphocytes intermingle in inflamed skin lesions. Here, using an AD mouse model where caspase-1 was specifically amplified under keratin-14 induction, we analyzed the sequential changes in type 1-3 inflammatory cytokines in lymphocytes purified from the cervical lymph nodes. Cells were cultured and stained for CD4, CD8, and γδTCR, followed by intracellular cytokines. Cytokine production in innate lymphocyte cells (ILCs) and the protein expression of type 2 cytokine IL-17E (IL-25) were investigated. We observed that, as inflammation progresses, the cytokine-producing T cells increased and abundant IL-13 but low levels of IL-4 are produced in CD4-positive T cells and ILCs. TNF-α and IFN-γ levels increased continuously. The total number of T cells and ILCs peaked at 4 months and decreased in the chronic phase. In addition, IL-25 may be simultaneously produced by IL-17F-producing cells. IL-25-producing cells increased in a time-dependent manner during the chronic phase and may work specifically for the prolongation of type 2 inflammation. Altogether, these findings suggest that inhibition of IL-25 may be a potential target in the treatment of inflammation.

IL-17A Is the Critical Cytokine for Liver and Spleen Amyloidosis in Inflammatory Skin Disease.

Systemic amyloidosis is recognized as a serious complication of rheumatoid arthritis or inflammatory bowel disease, but also of inflammatory skin disease. However, the detailed molecular mechanism of amyloidosis associated with cutaneous inflammation remains unclear, and therapeutic approaches are limited. Here, we investigated the pathophysiology of amyloidosis secondary to cutaneous inflammation and the therapeutic effects of Janus kinase (JAK) inhibitors by examining a mouse model of spontaneous dermatitis (KCASP1Tg mice). Moreover, KCASP1Tg mice were crossed with interleukin-17A (IL-17A) knockout mice to generate IL-17A-/KCASP1Tg and examine the role of IL-17A in amyloidosis under cutaneous inflammation. KCASP1Tg mice showed severe amyloid deposition in the liver and spleen. Increased serum-neutral fat levels and decreased lymphocyte production were observed in the spleen. Overproduction of amyloidosis was partially ameliorated by the administration of JAK inhibitors and was further improved in IL-17A-/KCASP1Tg mice. IL-17A-producing cells included CD4, gamma delta, and CD8 T cells. In summary, our results from the analysis of a mouse model of dermatitis revealed that skin-derived inflammatory cytokines can induce amyloid deposition in the liver and spleen, and that the administration of JAK inhibitors and, even more, IL-17A ablation, reduced amyloidosis. This study demonstrates that active control of skin inflammation is essential to prevent internal organ amyloidosis.

Single-cell RNA sequencing of mycosis fungoides reveals a cluster of actively proliferating lymphocytes.

A 70-year-old man's chronic erythematous skin lesion in the extremity had developed into a tumour one year before his first visit at our hospital. A biopsy showed atypical lymphocyte-like cells, and immunostaining identified atypical cells as CD3+, CD4+, CD5+ and FOXP3+. Single-cell RNA sequencing (scRNA-seq) analysis using BD Rhapsody revealed the higher expression of CD3, CD4, CD5 and FOXP3 genes in a group of cells that highly expressed genes, such as PCNA, in the S/M phase, which is in agreement with immunofluorescence staining results. The use of scRNA-seq analysis data is expected to promote personalised medicine for cutaneous lymphoma.

Dupilumab Effects on Innate Lymphoid Cell and Helper T Cell Populations in Patients with Atopic Dermatitis.

Group 2 innate lymphoid cells (ILCs) are thought to contribute to the pathogenesis of atopic dermatitis (AD). IL-4 stimulates T helper type 2 (Th2) cells and ILC2s to proliferate and produce cytokines. Dupilumab, an antibody against the IL-4 receptor, is used in AD therapy. We speculated that its efficacy might involve blocking the activation of Th2 cells and ILC2s via IL-4. Here, we examined circulating Th2 cells and ILC2s in 27 Japanese patients with AD before and after the administration of dupilumab. Between 0 and 4 months after dupilumab administration, the percentages of Th2 cells and ILC2s were decreased. Notably, ILC2/3 ratio was decreased after dupilumab treatment. Interestingly, ILC2/3 ratio before dupilumab treatment were significantly higher in high responders than in low responders to dupilumab. To resolve the molecular signatures of the Th2 and ILC2s in AD, we sorted CD4+ T cells and ILCs from peripheral blood and analyzed their transcriptomes using the BD Rhapsody Single-cell RNA sequencing system. Between 0 and 4 months after dupilumab administration, the Th2 and ILC2 cluster gene signatures were downregulated. Thus, dupilumab might improve dermatitis by suppressing the Th2 cell and ILC2 populations and altering the Th2 and ILC2 repertoire in patients with AD.

Monitoring Cellular Movement with Photoconvertible Fluorescent Protein and Single-Cell RNA Sequencing Reveals Cutaneous Group 2 Innate Lymphoid Cell Subtypes, Circulating ILC2 and Skin-Resident ILC2.

We previously generated a transgenic mouse line expressing skin-specific IL-33 (IL33tg mice) and showed that IL-33 elicits group 2 innate lymphoid cell (ILC2)-dependent atopic dermatitis-like skin inflammation. ILC2s are believed to be tissue-resident cells under steady-state conditions, but the dynamics of ILC2 migration are not fully understood. We sorted ILC2s from the skin and draining lymph nodes of IL33tg mice and analyzed their transcriptomes using the single-cell RNA sequencing technique, which revealed that the skin ILC2s had split into two clusters: circulating ILC2 and skin-resident ILC2. The circulating ILC2s expressed H2-related major histocompatibility complex class II genes. Conversely, the skin-resident ILC2s demonstrated increased mRNA expression of the ICOS, IL-5, and IL-13. Next, we tracked ILC2 migration using IL33tg-Kikume Green-Red mice. Exposing the IL33tg-Kikume Green-Red mice's inflamed skin to violet light allowed us to label the circulating ILC2s in their skin and track the ILC2 migration from the skin to the draining lymph nodes. Cutaneous local innate responses could transition to systemic type 2 responses by migrating the activated ILC2s from the skin into the draining lymph node. Conversely, the skin-resident ILC2s produced a large number of cytokines. Thus, the skin ILC2s turned out to be a heterogeneous cell population.

Alarmins/stressorins and immune dysregulation in intractable skin disorders.

Unlike other barrier epithelia of internal organs, the stratified squamous epithelium of the skin is always exposed to the external environment. However, the robust barrier structure and function of the skin are highly resistant against external insults so as to not easily allow foreign invasions. Upon sensing danger signals, the innate immunity system is promptly activated. This process is mediated by alarmins, which are released passively from damaged cells. Nuclear alarmins or stressorins are actively released from intact cells in response to various cellular stresses. Alarmins/stressorins are deeply involved in the disease processes of chronic skin disorders of an unknown cause, such as rosacea, psoriasis, and atopic dermatitis. Furthermore, alarmins/stressorins are also induced in the congenital skin disorders of ichthyosis and keratoderma due to defective keratinization. Studies on alarmin activation and its downstream pathways may help develop novel therapeutic agents for intractable skin disorders.

Effectiveness and safety of tacrolimus ointment combined with dupilumab for patients with atopic dermatitis in real-world clinical practice.

Atopic dermatitis (AD) is the most common inflammatory skin disease affecting people of all age groups worldwide. To our knowledge, there are currently no studies estimating the effectiveness of tacrolimus ointment and dupilumab as a combination therapy for AD. Thus, here we describe the effectiveness and safety of tacrolimus ointment in combination with dupilumab for facial rashes in patients with AD. Overall, we included 109 patients who newly received dupilumab from April 2018 to July 2020 in the Dermatology Department of Hyogo College of Medicine Hospital. Of them, 60 patients were treated with tacrolimus ointment. Specifically, of the 60 patients, 40 were treated with dupilumab in combination with tacrolimus ointment and topical steroids, whereas the remaining 20 were prescribed tacrolimus ointment alone and were further analyzed. The analysis showed that the combination does not cause serious side-effects at high frequency. The patients showed rapid improvement of facial dermatitis along with systemic dermatitis, and the rate of improvement of head/neck Eczema Area and Severity Index (EASI) score significantly correlated with the rate of improvement of overall EASI score. In addition, there was no complication of herpes simplex observed in these 20 patients. Thus, tacrolimus ointment combined with dupilumab is an effective and safe treatment option for facial AD.

Comprehensive stratum corneum ceramide profiling reveals reduced acylceramides in ichthyosis patient with CERS3 mutations.

The stratum corneum (SC) of the epidermis acts as a skin permeability barrier, and abnormalities in SC formation lead to several skin disorders. Lipids, especially the epidermis-specific ceramide classes ω-O-acylceramides (acylceramides) and protein-bound ceramides, are essential for skin barrier formation. Ceramide synthase 3 (CERS3) is involved in the synthesis of acylceramides and protein-bound ceramides, and CERS3 mutations cause autosomal recessive congenital ichthyosis. In the present study, we measured ceramide synthase activity and performed comprehensive SC ceramide profiling in an ichthyosis patient with compound heterozygous CERS3 mutations: nonsense mutation p.Arg75* and missense mutation p.Arg229His. The activity of p.Arg75* and p.Arg229His mutant CERS3 proteins was reduced to 4% and 56%, respectively, of the wild-type protein. In the patient's SC, acylceramide levels were greatly reduced, but the levels of protein-bound ceramides remained almost unchanged. Non-acylated ceramide levels were also affected in the patient; in particular, the levels of ceramides composed of sphingosine and non-hydroxy or α-hydroxy fatty acid were substantially higher than in healthy controls. These results suggest that a reduction in acylceramide levels alone leads to ichthyosis. Although protein-bound ceramides are synthesized from acylceramides, levels of acylceramides and protein-bound ceramides are not necessarily correlated.

Interleukin-33 in atopic dermatitis.

Atopic dermatitis (AD) is characterized by pruritus, barrier disruption, and inflammationincluding type 2 cytokine production. Interleukin-33 (IL-33) is an inflammatory cytokine that is over-expressed in the keratinocytes of patients with AD. IL-33 transgenic mice, which express IL-33 specifically in keratinocytes, spontaneously develop AD-like eczema, suggesting that IL-33 is sufficient for the development of AD. IL-33 stimulates various cells, including group 2 innate lymphoid cells (ILC2s), to produce type 2 cytokines, such as IL-5 and IL-13, and IL-33-stimulated basophils activate ILC2s via IL-4. ILC2s are enriched in human AD skin lesions, and ILC2 isolated from AD lesions, are activated by IL-33, not by thymic stromal lymphopoietin (TSLP). IL-33 induces IL-31, thereby promoting pruritus and scratching behavior. Conversely, scratching the skin promotes IL-33 release from keratinocytes. IL-33 reduces the expression of filaggrin and claudin-1; it also reduces the skin barrier function. However, barrier destruction causes percutaneous exposure to allergens or IL-33 release. Thus, IL-33 is a common point of entry into the itch-scratch cycle of AD. These new findings can facilitate the development of novel therapeutic drugs targeting IL-33.

IL-33-Induced Atopic Dermatitis-Like Inflammation in Mice Is Mediated by Group 2 Innate Lymphoid Cells in Concert with Basophils.

IL-33 is a proinflammatory cytokine that plays a pivotal role in allergic disorders. In a transgenic mouse expressing IL-33 driven by a keratin-14 promoter (IL33tg), atopic dermatitis (AD)-like inflammation develops spontaneously with the activation of group 2 innate lymphoid cells (ILC2s). However, it remains unknown how effector cells, such as T helper type 2 cells, ILC2s, and basophils, contribute to the inflammatory process induced by IL-33. To address the question, we examined the phenotype of IL33tg mice lacking each of these cells. AD-like inflammation still developed in Rag2KO IL33tg mice lacking T and B cells; in contrast, when ILC2s were depleted in IL33tg mice via bone marrow transplantation from ILC2-lacking, RAR-related orphan receptor alpha-deficient mice, the development of AD-like inflammation was almost completely suppressed. Basophils were accumulated in the inflamed skin of IL33tg mice, and AD-like inflammation was alleviated by the conditional depletion of basophils using anti-FcεRIα antibodies or a Bas-TRECK transgenic mouse system. In these basophil-depleted IL33tg skins, ILC2s were decreased, and cytokines and chemokines such as IL-5, IL-13, and CCL5 were reduced. From these results, we suggest that IL-33-induced AD-like inflammation is dependent on innate immune responses that are mediated by ILC2s in concert with basophils.

Relationship between YKL-40 and pulmonary arterial hypertension in systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc) is an intractable connective tissue disease that causes skin and organ fibrosis. Interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) affect its prognosis. YKL-40 protein impacts inflammation and tissue remodeling. Therefore, we evaluated the utility of YKL-40 blood levels in identifying patients with SSc complicated by PAH, as confirmed by immunohistochemistry (IHC) examination. METHODS: We retrospectively analyzed 78 patients with SSc and performed IHC on 7 normal and 7 SSc skin samples in the Japanese population. Age-adjusted YKL-40 serum levels were analyzed. RESULTS: YKL-40 age percentile was significantly elevated in SSc patients. There was no difference between patients with SSc with and without ILD and PAH. YKL-40 age percentile was greater in patients with PAH complication. YKL-40 immunostaining was negative in normal skin and prominent in the subcutaneous vascular wall of all SSc samples. Receiver operating characteristic (ROC) curve analysis indicated that YKL-40 age percentile correctly differentiated between patients with and without PAH with a sensitivity of 80% and a specificity of 94.1%. CONCLUSION: A higher YKL-40 level with PAH may be reflective of angiogenesis due to capillary injury in SSc. YKL-40 may offer a useful and easily applicable diagnostic biomarker of SSc complicated with PAH.