IL-33 potentiates histaminergic itch.

BACKGROUND: Itch is a common symptom that can greatly diminish quality of life. Histamine is a potent endogenous pruritogen, and while antihistamines are often the first-line treatment for itch, in conditions like chronic spontaneous urticaria (CSU), many patients remain symptomatic while receiving maximal doses. Mechanisms that drive resistance to antihistamines are poorly defined. OBJECTIVES: Signaling of the alarmin cytokine IL-33 in sensory neurons is postulated to drive chronic itch by inducing neuronal sensitization to pruritogens. Thus, we sought to determine if IL-33 can augment histamine-induced (histaminergic) itch. METHODS: Itch behavior was assessed in response to histamine after IL-33 or saline administration. Various stimuli and conditional and global knockout mice were utilized to dissect cellular mechanisms. Multiple existing transcriptomic data sets were evaluated, including single-cell RNA sequencing of human and mouse skin, microarrays of isolated mouse mast cells at steady state and after stimulation with IL-33, and microarrays of skin biopsy samples from subjects with CSU and healthy controls. RESULTS: IL-33 amplifies histaminergic itch independent of IL-33 signaling in sensory neurons. Mast cells are the top expressors of the IL-33 receptor in both human and mouse skin. When stimulated by IL-33, mouse mast cells significantly increase IL-13 levels. Enhancement of histaminergic itch by IL-33 relies on a mast cell- and IL-13-dependent mechanism. IL-33 receptor expression is increased in lesional skin of subjects with CSU compared to healthy controls. CONCLUSIONS: Our findings suggest that IL-33 signaling may be a key driver of histaminergic itch in mast cell-associated pruritic conditions such as CSU.

Sensory neurons promote immune homeostasis in the lung.

Cytokines employ downstream Janus kinases (JAKs) to promote chronic inflammatory diseases. JAK1-dependent type 2 cytokines drive allergic inflammation, and patients with JAK1 gain-of-function (GoF) variants develop atopic dermatitis (AD) and asthma. To explore tissue-specific functions, we inserted a human JAK1 GoF variant (JAK1GoF) into mice and observed the development of spontaneous AD-like skin disease but unexpected resistance to lung inflammation when JAK1GoF expression was restricted to the stroma. We identified a previously unrecognized role for JAK1 in vagal sensory neurons in suppressing airway inflammation. Additionally, expression of Calcb/CGRPß was dependent on JAK1 in the vagus nerve, and CGRPß suppressed group 2 innate lymphoid cell function and allergic airway inflammation. Our findings reveal evolutionarily conserved but distinct functions of JAK1 in sensory neurons across tissues. This biology raises the possibility that therapeutic JAK inhibitors may be further optimized for tissue-specific efficacy to enhance precision medicine in the future.

Clinical Management of Neuropathic Itch.

This JAMA Network Insight reviews the underlying mechanisms and management of peripheral sensory itch conditions.

Emerging concepts in neuropathic and neurogenic itch.

Chronic pruritus has multiple etiologies, ranging from inflammatory to metabolic and neuropathic processes. However, recent advances in itch biology have shed light on potential mechanisms that explain the molecular and cellular basis of these pathologies. Furthermore, new understanding of neuroimmune itch circuits necessitates clarification of terminologies such as "neuropathic" and "neurogenic." This review provides an overview of ways new concepts may better explain the pathophysiology of a variety of chronic pruritic disorders and the rationale for directing emerging novel therapeutic strategies toward them.

Two-Year Experience With Latanoprostene Bunod in Clinical Practice.

PRECIS: We retrospectively reviewed records of patients prescribed latanoprostene bunod 0.024% (LBN) to assess its efficacy and safety in a real-world clinical setting. LBN was efficacious in lowering intraocular pressure (IOP) and had a favorable safety profile. PURPOSE: The aim of this study was to evaluate the usage of LBN, the first topical nitric oxide-donating prostaglandin analog (PGA) for reducing IOP, in clinical practice. PATIENTS AND METHODS: Retrospective review identified patients prescribed LBN by 5 glaucoma specialists at an academic center from January 2018 to November 2019. Fifty-six patients (102 eyes) met inclusion criteria of an IOP measured at the visit LBN was prescribed and at 2 visits ≥7 days after beginning treatment, with no surgeries, lasers or medication changes during follow-up. Main outcome measures were IOP, number of ocular medications, and adverse effects. RESULTS: IOP (mean±SD, mm Hg) at the visit LBN was prescribed was 16.2±4.3 on 3.2±1.5 glaucoma medications. IOP at most recent visit was 13.7±3.8 on 3.2±1.6 medications. Mean IOP reduction was 2.1±3.5 (P<0.0001) at first follow-up, after 38.7±36.5 days, and 2.5±3.3 (P<0.0001) at last follow-up, after 235.9±160.8 days. Pressure decreased ≥2 mm Hg in 60%, ≥3 mm Hg in 46%, and ≥4 mm Hg in 34% of eyes. All patients received LBN as replacement for a PGA or latanoprost/netarsudil fixed-dose combination. Forty-three patients remained on LBN throughout the follow-up period. Seven were discontinued for insufficient pressure control, 4 for adverse effects including pain and itching, and 2 for financial reasons. CONCLUSIONS: In 2 years of clinical use of LBN, patients exhibited IOP reductions that were statistically significant overall and clinically meaningful in 60% of patients. LBN was well-tolerated and may be more efficacious than traditional PGAs.

Cross-sectional study of blood biomarkers of patients with moderate to severe alopecia areata reveals systemic immune and cardiovascular biomarker dysregulation.

BACKGROUND: Although there is increased understanding of the alopecia areata (AA) pathogenesis based on studies in scalp tissues, little is known about its systemic profile. OBJECTIVE: To evaluate the blood proteomic signature of AA and determine biomarkers associated with increased disease severity. METHODS: In a cross-sectional study, we assessed 350 inflammatory and cardiovascular proteins using OLINK high-throughput proteomics in patients with moderate to severe AA (n = 35), as compared with healthy individuals (n = 36), patients with moderate to severe psoriasis (n = 19), and those with atopic dermatitis (n = 49). RESULTS: Seventy-four proteins were significantly differentially expressed between AA and control individuals (false discovery rate, <.05) including innate immunity (interleukin [IL] 6/IL-8), T helper (Th) type 1 (interferon [IFN] γ/CXCL9/CXCL10/CXCL11), Th2 (CCL13/CCL17/CCL7), Th17 (CCL20/PI3/S100A12), and cardiovascular-risk proteins (OLR1/OSM/MPO/PRTN3). Eighty-six biomarkers correlated with AA clinical severity (P < .05), including Th1/Th2, and cardiovascular/atherosclerosis-related proteins, including SELP/PGLYRP1/MPO/IL-18/OSM (P < .05). Patients with AA totalis/universalis showed the highest systemic inflammatory tone, including cardiovascular risk biomarkers, compared to control individuals and even to patients with atopic dermatitis and those with psoriasis. The AA profile showed some Th1/Th2 differences in the setting of concomitant atopy. LIMITATIONS: Our analysis was limited to 350 proteins. CONCLUSION: This study defined the abnormalities of moderate to severe AA and associated circulatory biomarkers. It shows that AA has systemic immune, cardiovascular, and atherosclerosis biomarker dysregulation, suggesting the need for systemic treatment approaches.