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Dermatitis encompasses a spectrum of inflammatory skin disorders with aberrant immune responses classified as type 1, type 2, and/or type 3. Major advances in the understanding of the pathogenesis of atopic dermatitis (AD) have shed new light on how innate immune responses critically regulate type 2 inflammation and itch. This article highlights the diverse ways by which type 2 immune cells regulate diseases beyond AD. The discovery of human Mas-related G protein-coupled receptor X2 on mast cells has revealed novel T cell-independent and immunoglobulin E-independent mechanisms of allergic contact dermatitis-associated and urticarial itch, respectively.
Learn More >Dupilumab, a fully human monoclonal antibody targeting the alpha subunit of IL-4 was recently approved for the treatment of moderate-to-severe atopic dermatitis (AD) in adult patients. To assess dupilumab effectiveness and safety in adults with moderate-to-severe AD in a real-life Italian multicentre retrospective cohort. Adult moderate-to-severe AD patients, referring to 39 Italian centres, received dupilumab in the context of a national patient access program. Disease assessment was performed at baseline, after 4 and 16 weeks of treatment using Eczema-Area-and-Severity-Index (EASI) score, itch and sleep numerical-rating-score (itch-NRS, sleep-NRS) and Dermatology-Life-Quality-Index (DLQI). A total of 109 (71M/38F) patients was studied. There was a significant reduction in EASI score, itch-NRS, sleep-NRS and DLQI from baseline to week 4 and a further significant decline to week 16. EASI 50, EASI75 and EASI90 were achieved by 59.6%, 28.4% and 9.3% of patients at 4 weeks and by 87.2%, 60.6% and 32.4% of them at 16 weeks, respectively. Adverse events were experienced by 19.2% (21/109) of the patients and they were all mild in intensity, being conjunctivitis the most common side effect. Dupilumab significantly improved disease severity, pruritus, sleep loss and quality of life with an acceptable safety profile.
Learn More >Allergic inflammation is often the result of a dysregulated Th2 immune response, IgE production, and the release of allergic mediators such as histamine or leukotrienes (LTs) by basophils and mast cells (MCs). Allergic diseases can manifest as acute allergic reactions (anaphylaxis), or as chronic allergic inflammation in chronic urticaria, allergic rhinitis, allergic asthma, and atopic dermatitis (AD). Common allergic symptoms such as sneezing, airway mucus secretion, and chronic itch are caused by interactions between immune cells and sensory neurons in the inflamed tissue.
Learn More >Patients with psoriasis have an impaired quality of life and higher use of analgesics than the general population. Whether such use is due to skin pain or a consequence of joint pain resulting from psoriatic arthritis (PsA) is unclear.
Learn More >Skin pain (described as discomfort or soreness) is increasingly recognized as a symptom of atopic dermatitis which impacts patient quality of life. This analysis examined the effect of baricitinib on skin pain in atopic dermatitis in three phase 3 studies (BREEZE-AD1, -AD2, and -AD7).
Learn More >The present study focused on lithocholic acid (LCA), a secondary bile acid that contributes to cholestatic pruritus. Although recent studies have found that LCA acts on MAS-related G protein-coupled receptor family member X4 (MRGPRX4) in humans, it is unclear which subtypes of MRGPRs are activated by LCA in mice since there is no precise ortholog of human MRGPRX4 in the mouse genome. Using calcium imaging, we found that LCA could activate mouse Mrgpra1 when transiently expressed in HEK293T cells. Moreover, LCA similarly activates mouse Mrgprb2. Importantly, LCA-induced responses showed dose-dependent effects through Mrgpra1 and Mrgprb2. Moreover, treatment with QWF (an antagonist of Mrgpra1 and Mrgprb2), YM254890 (Gα inhibitor), and U73122 (an inhibitor of phospholipase C) significantly suppressed the LCA-induced responses, implying that the LCA-induced responses are indeed mediated by Mrgpra1 and Mrgprb2. Furthermore, LCA activated primary cultures of mouse sensory neurons and peritoneal mast cells, suggesting that Mrgpra1 and Mrgprb2 contribute to LCA-induced pruritus. However, acute injection of LCA did not induce noticeable differences in scratching behavior, implying that the pruritogenic role of LCA may be marginal in non-cholestatic conditions. In summary, the present study identified for the first time that LCA can activate Mrgpra1 and Mrgprb2. The current findings provide further insight into the similarities and differences between human and mouse MRGPR families, paving a way to understand the complex roles of these pruriceptors.
Learn More >Itch severity in chronic itch patients is influenced by mental state. However, the brain network mediating this nuisance relationship remains unknown. The medial parietal cortex (MPC) is a key hub of the default mode network (DMN) that regulates the mental state and also a brain region selective for itch (i.e., itch, but not pain, activates the MPC). Moreover, antidepressants are used in the treatment of chronic itch and are well known to alter activity in DMN.
Learn More >Chronic pruritus (itch lasting ≥6 weeks) is a bothersome chief complaint that may present in a broad variety of diseases. Most itch-causing diagnoses fit into 1 of 5 categories (inflammatory, secondary to systemic disease, neuropathic, chronic pruritus of undetermined origin, and psychogenic itch) and this broad differential can be narrowed using key findings in the history and physical. In this article, we discuss which key findings are most pertinent for narrowing this differential and guiding further workup and treatment, as well as how to treat many itchy conditions.
Learn More >Alloknesis, an abnormal itch sensation induced by innocuous stimuli, is a key phenomenon in the vicious itch-scratch cycle in patients with atopic dermatitis. Dry skin and pruritus, including alloknesis, are major health problems in peri- and post-menopausal women. We recently reported permeability barrier dysfunction in ovariectomised (OVX) mice-a model of menopause-and found that the dysfunction was related to dry skin. However, the mechanism of the itch remains unknown. Therefore, we examined touch- and pruritogen-evoked alloknesis and epidermal innervation in OVX mice and acetone, diethyl ether, and water (AEW)-treated mice, for the experimental dry skin model. Both alloknesis and epidermal innervation were comparable in OVX and AEW mice. Neutralising antibodies against IL-4 and IL-13 inhibited alloknesis in both OVX and AEW mice as early as 30 min after intradermal administration. Comparable values close to the measurement limit of IL-4 were found in the skin of HRT and Sham mice as well as AEW and the control mice, but the levels of IL-4 were within the measurement limit in OVX mice. We could not detect mRNAs of IL-4 or IL-13 in any groups of mice. On the other hand, the number of eosinophils and basophils was increased in OVX and AEW mice. These results suggest that impaired barrier function in cooperation with type 2 cytokines derived from eosinophils and basophils in the skin or with endogenous type 2 cytokine may trigger the development of alloknesis, and thus, these cytokines could be a therapeutic target for sensitive skin.
Learn More >Baricitinib previously demonstrated improvements in itch and sleep disturbance versus placebo in adults with moderate-to-severe atopic dermatitis (AD).
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