New mechanism underlying IL-31-induced atopic dermatitis.

TH2 cell-released IL-31 is a critical mediator in patients with atopic dermatitis (AD), a prevalent and debilitating chronic skin disorder. Brain-derived natriuretic peptide (BNP) has been described as a central itch mediator. The importance of BNP in peripheral (skin-derived) itch and its functional link to IL-31 within the neuroimmune axis of the skin is unknown. We sought to investigate the function of BNP in the peripheral sensory system and skin in IL-31-induced itch and neuroepidermal communication in patients with AD. Ca2+ imaging, immunohistochemistry, quantitative real-time PCR, RNA sequencing, knockdown, cytokine/phosphokinase arrays, enzyme immune assay, and pharmacologic inhibition were performed to examine the cellular basis of the IL-31-stimulated, BNP-related itch signaling in dorsal root ganglionic neurons (DRGs) and skin cells, transgenic AD-like mouse models, and human skin of patients with AD and healthy subjects. In human DRGs we confirmed expression and co-occurrence of oncostatin M receptor β subunit and IL-31 receptor A in a small subset of the neuronal population. Furthermore, IL-31 activated approximately 50% of endothelin-1-responsive neurons, and half of the latter also responded to histamine. In murine DRGs IL-31 upregulated Nppb and induced soluble N-ethylmaleimide-sensitive factor activating protein receptor-dependent BNP release. In Grhl3PAR2/+ mice house dust mite-induced severe AD-like dermatitis was associated with Nppb upregulation. Lesional IL-31 transgenic mice also exhibited increased Nppb transcripts in DRGs and the skin; accordingly, skin BNP receptor levels were increased. Importantly, expression of BNP and its receptor were increased in the skin of patients with AD. In human skin cells BNP stimulated a proinflammatory and itch-promoting phenotype. For the first time, our findings show that BNP is implicated in AD and that IL-31 regulates BNP in both DRGs and the skin. IL-31 enhances BNP release and synthesis and orchestrates cytokine and chemokine release from skin cells, thereby coordinating the signaling pathways involved in itch. Inhibiting peripheral BNP function might be a novel therapeutic strategy for AD and pruritic conditions.

Meng J ，Moriyama M ，Feld M ，Buddenkotte J ，Buhl T ，Szöllösi A ，Zhang J ，Miller P ，Ghetti A ，Fischer M ，Reeh PW ，Shan C ，Wang J ，Steinhoff M ... -  《-》

A sensory neuron-expressed IL-31 receptor mediates T helper cell-dependent itch: Involvement of TRPV1 and TRPA1.

Although the cytokine IL-31 has been implicated in inflammatory and lymphoma-associated itch, the cellular basis for its pruritic action is yet unclear. We sought to determine whether immune cell-derived IL-31 directly stimulates sensory neurons and to identify the molecular basis of IL-31-induced itch. We used immunohistochemistry and quantitative real-time PCR to determine IL-31 expression levels in mice and human subjects. Immunohistochemistry, immunofluorescence, quantitative real-time PCR, in vivo pharmacology, Western blotting, single-cell calcium imaging, and electrophysiology were used to examine the distribution, functionality, and cellular basis of the neuronal IL-31 receptor α in mice and human subjects. Among all immune and resident skin cells examined, IL-31 was predominantly produced by TH2 and, to a significantly lesser extent, mature dendritic cells. Cutaneous and intrathecal injections of IL-31 evoked intense itch, and its concentrations increased significantly in murine atopy-like dermatitis skin. Both human and mouse dorsal root ganglia neurons express IL-31RA, largely in neurons that coexpress transient receptor potential cation channel vanilloid subtype 1 (TRPV1). IL-31-induced itch was significantly reduced in TRPV1-deficient and transient receptor channel potential cation channel ankyrin subtype 1 (TRPA1)-deficient mice but not in c-kit or proteinase-activated receptor 2 mice. In cultured primary sensory neurons IL-31 triggered Ca(2+) release and extracellular signal-regulated kinase 1/2 phosphorylation, inhibition of which blocked IL-31 signaling in vitro and reduced IL-31-induced scratching in vivo. IL-31RA is a functional receptor expressed by a small subpopulation of IL-31RA(+)/TRPV1(+)/TRPA1(+) neurons and is a critical neuroimmune link between TH2 cells and sensory nerves for the generation of T cell-mediated itch. Thus targeting neuronal IL-31RA might be effective in the management of TH2-mediated itch, including atopic dermatitis and cutaneous T-cell lymphoma.

Cevikbas F ，Wang X ，Akiyama T ，Kempkes C ，Savinko T ，Antal A ，Kukova G ，Buhl T ，Ikoma A ，Buddenkotte J ，Soumelis V ，Feld M ，Alenius H ，Dillon SR ，Carstens E ，Homey B ，Basbaum A ，Steinhoff M ... -  《-》

Oncostatin M suppresses IL31RA expression in dorsal root ganglia and interleukin-31-induced itching.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by intermittent itchy rash. Type 2 inflammatory cytokines such as interleukin (IL)-4, IL-13, and IL-31 are strongly implicated in AD pathogenesis. Stimulation of IL-31 cognate receptors on C-fiber nerve endings is believed to activate neurons in the dorsal root ganglion (DRG), causing itch. The IL-31 receptor is a heterodimer of OSMRβ and IL31RA subunits, and OSMRβ can also bind oncostatin M (OSM), a pro-inflammatory cytokine released by monocytes/macrophages, dendritic cells, and T lymphocytes. Further, OSM expression is enhanced in the skin lesions of AD and psoriasis vulgaris patients. The current study aimed to examine the contributions of OSM to AD pathogenesis and symptom expression. The expression levels of the OSM gene (OSM) and various cytokine receptor genes were measured in human patient skin samples, isolated human monocytes, mouse skin samples, and mouse DRG by RT-qPCR. Itching responses to various pruritogens were measured in mice by counting scratching episodes. We confirmed overexpression of OSM in skin lesions of patients with AD and psoriasis vulgaris. Monocytes isolated from the blood of healthy subjects overexpressed OSM upon stimulation with IL-4 or GM-CSF. Systemic administration of OSM suppressed IL31RA expression in the mouse DRG and IL-31-stimulated scratching behavior. In contrast, systemic administration of OSM increased the expression of IL-4- and IL-13-related receptors in the DRG. These results suggest that OSM is an important cytokine in the regulation of skin monocytes, promoting the actions of IL-4 and IL-13 in the DRG and suppressing the action of IL-31. It is speculated that OSM released from monocytes in skin modulates the sensitivity of DRG neurons to type 2 inflammatory cytokines and thereby the severity of AD-associated skin itch.

Suehiro M ，Numata T ，Saito R ，Yanagida N ，Ishikawa C ，Uchida K ，Kawaguchi T ，Yanase Y ，Ishiuji Y ，McGrath J ，Tanaka A ... -  《Frontiers in Immunology》

BNP facilitates NMB-encoded histaminergic itch via NPRC-NMBR crosstalk.

Histamine-dependent and -independent itch is conveyed by parallel peripheral neural pathways that express gastrin-releasing peptide (GRP) and neuromedin B (NMB), respectively, to the spinal cord of mice. B-type natriuretic peptide (BNP) has been proposed to transmit both types of itch via its receptor NPRA encoded by Npr1. However, BNP also binds to its cognate receptor, NPRC encoded by Npr3 with equal potency. Moreover, natriuretic peptides (NP) signal through the Gi-couped inhibitory cGMP pathway that is supposed to inhibit neuronal activity, raising the question of how BNP may transmit itch information. Here, we report that Npr3 expression in laminae I-II of the dorsal horn partially overlaps with NMB receptor (NMBR) that transmits histaminergic itch via Gq-couped PLCβ-Ca2+ signaling pathway. Functional studies indicate that NPRC is required for itch evoked by histamine but not chloroquine (CQ), a nonhistaminergic pruritogen. Importantly, BNP significantly facilitates scratching behaviors mediated by NMB, but not GRP. Consistently, BNP evoked Ca2+ responses in NMBR/NPRC HEK 293 cells and NMBR/NPRC dorsal horn neurons. These results reveal a previously unknown mechanism by which BNP facilitates NMB-encoded itch through a novel NPRC-NMBR cross-signaling in mice. Our studies uncover distinct modes of action for neuropeptides in transmission and modulation of itch in mice.

Meng QT ，Liu XY ，Liu XT ，Liu J ，Munanairi A ，Barry DM ，Liu B ，Jin H ，Sun Y ，Yang Q ，Gao F ，Wan L ，Peng J ，Jin JH ，Shen KF ，Kim R ，Yin J ，Tao A ，Chen ZF ... -  《eLife》

IL-20 promotes cutaneous inflammation and peripheral itch sensation in atopic dermatitis.

Atopic dermatitis (AD) is a chronic skin disease, which is associated with intense itch, skin barrier dysfunction and eczematous lesions. Aberrant IL-20 expression has been implicated in numerous inflammatory diseases, including psoriasis. However, the role of IL-20 in AD remains unknown. Here, RNA-seq, Q-PCR, and immunocytochemistry were utilized to examine disease-driven changes of IL-20 and its cognate receptor subunits in skin from healthy human subjects, AD patients and murine AD-models. Calcium imaging, knockdown and cytokine array were used to investigate IL-20-evoked responses in keratinocytes and sensory neurons. The murine cheek model and behavioral scoring were employed to evaluate IL-20-elicited sensations in vivo. We found that transcripts and protein of IL-20 were upregulated in skin from human AD and murine AD-like models. Topical MC903 treatment in mice ear enhanced IL-20R1 expression in the trigeminal sensory ganglia, suggesting a lesion-associated and epidermal-driven mechanism for sensitization of sensory IL-20 signaling. IL-20 triggered calcium influx in both keratinocytes and sensory neurons, and promoted their AD-related molecule release and transcription of itch-related genes. In sensory neurons, IL-20 application increased TLR2 transcripts, implicating a link between innate immune response and IL-20. In a murine cheek model of acute itch, intradermal injection IL-20 and IL-13 elicited significant itch-like behavior, though only when co-injected. Our findings provide novel insights into IL-20 function in peripheral (skin-derived) itch and clinically relevant intercellular neuron-epidermal communication, highlighting a role of IL-20 signaling in the pathophysiology of AD, thus forming a new basis for the development of a novel antipruritic strategy via interrupting IL-20 epidermal pathways.

Lu Z ，Xiao S ，Chen W ，Zhu R ，Yang H ，Steinhoff M ，Li Y ，Cheng W ，Yan X ，Li L ，Xue S ，Larkin C ，Zhang W ，Fan Q ，Wang R ，Wang J ，Meng J ... -  《-》