Complete overlap of interleukin-31 receptor A and oncostatin M receptor beta in the adult dorsal root ganglia with distinct developmental expression patterns

Interleukin-31 does not induce immediate itch in atopic dermatitis patients and healthy controls after skin challenge

BACKGROUND

The most intriguing function attributed to interleukin-31 (IL-31) is its ability to induce pruritus in pathologic conditions, such as atopic dermatitis (AD). As of today, this feature of IL-31 was tested in vivo only in animal models.

METHODS

Ten patients with AD and 10 healthy controls were challenged with IL-31 and NaCl (negative control) by skin prick testing. Twenty additional healthy controls were subjected to skin prick testing with histamine. Itch and local inflammatory responses of the skin were assessed for up to 72 h.

RESULTS

All of the histamine-challenged subjects developed immediate pruritus (i.e. within the first 5 min). In contrast, only one IL-31- and two of the NaCl-challenged subjects reported immediate itch at the provocation site (short lasting, for 2-6 min). Nine subjects (five patients with AD) reported late itch responses to IL-31 challenges with a mean delay of 143 min. No subject reported late itch responses to histamine or NaCl testing. There was no significant difference in IL-31-induced itch start time, duration and intensity between patients with AD and healthy volunteers.

CONCLUSION

IL-31 does not induce immediate itch responses in humans. The late onset of IL-31-induced itch supports the notion that IL-31 exerts its pruritic effect indirectly via keratinocytes and secondary mediators, rather than through its receptors on cutaneous nerves.

PCR detects bands consistent with the expression of receptors associated with pruritus in canine dorsal root ganglia

BACKGROUND

Various mediators are involved in the induction of itch, i.e. pruritus; however, the in vivo pharmacology of pruritus seems to be different in distinct species, and little is known about receptors that are involved in the induction of itch in dogs. The species differences in the mediation of pruritus might be explained by species differences in receptor expression in the sensory nerves, including the dorsal root ganglia (DRG).

HYPOTHESIS/OBJECTIVES

The aim of the study was to analyse the expression of receptors for various mediators of pruritus in canine DRG.

METHODS

Dorsal root ganglia of 14 dogs, which were euthanized for reasons not related to this study, were analysed. Multiple DRG per dog were dissected and, after homogenization of the DRG tissues, total RNA was isolated, reverse transcribed to complementary DNA and amplified with custom-synthesized primers.

RESULTS

The following receptors were found in canine DRG: transient receptor potential cation channel subfamily V member 1, tachykinin receptor 1, Toll-like receptor 7, endothelin receptor type A, opioid receptors μ1 and κ1, histamine H1 -H4 receptors and the interleukin-31 receptor complex.

CONCLUSIONS AND CLINICAL IMPORTANCE

PCR analysis detected bands consistent with the expression of receptors associated with pruritus in canine DRG.

Allergen-induced production of IL-31 by canine Th2 cells and identification of immune, skin, and neuronal target cells

The canine cytokine IL-31 induces pruritus in dogs and can be detected in dogs with atopic dermatitis; however very little is understood around its interactions with specific canine cells. We hypothesize that IL-31 is involved in the progression of allergic skin disease by coordinating the interaction between the immune system with skin and neuronal systems. The goal of the following work was to identify cells that produce IL-31 as well as cells that may respond to this cytokine. Peripheral blood mononuclear cells (PBMCs) were collected from naïve and house dust mite (HDM) allergen-sensitized beagle dogs and used for ex vivo characterization of cytokine production assessed using ELISpot and quantitative immunoassay. Sensitization to HDM allergen induced a T-helper type 2 (Th2) cell phenotype characterized by an increase in the production of IL-4 protein. Interestingly, repeated allergen challenge over time also resulted in an increase in IFN-γ. Further evaluation showed that co-stimulation of Th2 polarized cells with antigen and the bacterial component Staphylococcus enterotoxin B (SEB) produced higher levels of IL-31 compared to either stimulant alone. Production of IL-31 when PBMCs were stimulated by T cell mitogens suggests T cells as a source of IL-31. Quantitative real-time PCR was utilized to determine expression of the IL-31 receptor alpha chain in canine cell lines and tissue. Canine monocytic cells, keratinocytes, and dorsal root ganglia were shown to express the IL-31 receptor alpha chain mRNA. In a multifaceted disease such as canine atopic dermatitis, the combination of Th2 polarization and microbial presence may lead to IL-31 mediated effects driving inflammation and pruritus by immune cells, keratinocytes, and direct neuronal stimulation.

Human IL-31 is induced by IL-4 and promotes TH2-driven inflammation

BACKGROUND

The pruritic cytokine IL-31 has been shown to be expressed by murine activated effector T Lymphocytes of a TH2 phenotype. Like IL-17 and IL-22, IL-31 is a tissue-signaling cytokine the receptor of which is mainly found on nonimmune cells. An overabundance of IL-31 has been shown in patients with atopic disorders, including dermatitis, as well as asthma, and therefore represents a promising drug target, although its regulation in the context of the human TH2 clusters is not yet known.

OBJECTIVE

We sought to address the gene regulation of human IL-31 and to test whether IL-31 possesses a similar proallergic function as members of the human TH2 cytokine family, such as IL-4, IL-5, and IL-13.

METHODS

Polyclonal and purified protein derivative of tuburculin-specific T-cell clones were generated. TH phenotype was determined, and IL-31 was measured by means of ELISA. Gene expression of primary bronchial epithelial cells treated with IL-31 was also measured.

RESULTS

IL-31 was expressed by all of the TH2 clones and not by TH1, TH17, or TH22. This expression was dependent on autocrine IL-4 expression from these clones because it could be reduced if blocking antibodies to IL-4 were present. Interestingly, TH1 clones were able to express IL-31 if IL-4 was added to culture. This IL-31 expression was transient and did not affect the phenotype of the TH1 clones. IL-31 was able to induce proinflammatory genes, such as CCL2 and granulocyte colony-stimulating factor.

CONCLUSION

IL-31 is not a TH2 cytokine in the classical sense but is likely to be expressed by a number of cells in an allergic situation in which IL-4 is present and possibly contribute to the allergic reaction.

New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms?

Itch and pain are closely related but distinct sensations. They share largely overlapping mediators and receptors, and itch-responding neurons are also sensitive to pain stimuli. Itch-mediating primary sensory neurons are equipped with distinct receptors and ion channels for itch transduction, including Mas-related G protein-coupled receptors (Mrgprs), protease-activated receptors, histamine receptors, bile acid receptor, toll-like receptors, and transient receptor potential subfamily V1/A1 (TRPV1/A1). Recent progress has indicated the existence of an itch-specific neuronal circuitry. The MrgprA3-expressing primary sensory neurons exclusively innervate the epidermis of skin, and their central axons connect with gastrin-releasing peptide receptor (GRPR)-expressing neurons in the superficial spinal cord. Notably, ablation of MrgprA3-expressing primary sensory neurons or GRPR-expressing spinal cord neurons results in selective reduction in itch but not pain. Chronic itch results from dysfunction of the immune and nervous system and can manifest as neural plasticity despite the fact that chronic itch is often treated by dermatologists. While differences between acute pain and acute itch are striking, chronic itch and chronic pain share many similar mechanisms, including peripheral sensitization (increased responses of primary sensory neurons to itch and pain mediators), central sensitization (hyperactivity of spinal projection neurons and excitatory interneurons), loss of inhibitory control in the spinal cord, and neuro-immune and neuro-glial interactions. Notably, painful stimuli can elicit itch in some chronic conditions (e.g., atopic dermatitis), and some drugs for treating chronic pain are also effective in chronic itch. Thus, itch and pain have more similarities in pathological and chronic conditions.

Topical application of Taglisodog-eum inhibits the development of experimental atopic dermatitis

AIM OF STUDY

Taglisodog-eum (Tuo Li Xiao Du Yin), a standardized herbal formula, has been widely used to modulate diverse carbuncles in oriental medicine. However, it is still unclear whether Taglisodog-eum (TSE) can exert a beneficial role in dermatological disease. In this study, we examined the effect of topical application of TSE on experimental atopic dermatitis (AD) and elucidated its action mechanism.

MATERIALS AND METHODS

To test the effect of TSE treatment on IgE production in vitro, U266B1 cells and primary CD19(+) B cells isolated from AD-induced mice were treated with TSE under LPS/IL-4 stimulation and then IgE level in the culture supernatant was measured by ELISA. To evaluate the effect of TSE treatment on the production of AD related pathogenic cytokines, CD4(+) T cells isolated from AD-induced mice were treated with TSE under PMA/ionomycin stimulation, then the level of cytokine expression was analyzed by quantitative RT-PCR and ELISA. The effects of TSE on the NFκB promoter activity in T cells and on the expression level of Aicda (activation-induced cytidine deaminase) in B cells were examined. To further examine the in vivo efficacy of TSE on AD progression, TSE was topically applied to ears of mice with atopic dermatitis induced by painting of DNCB and house dust mite extract. AD Progression was estimated by following criteria: (a) ear thickness, clinical score, (b) serum total IgE and mite specific IgE level by ELISA, (c) histological examination of ear tissue by H&E staining and (d) cytokine profile of total ear cells and draining lymph node CD4(+) T cells by quantitative real time PCR and ELISA.

RESULTS

Treatment of TSE to the U266B1 cell line and primary CD19(+) B cells isolated from AD-induced mice inhibited IgE production. Treatment of TSE down-regulated the expression of several cytokines (IL-4, IL-10, IL-13, IL-17, TNF-α and IFN-γ) in CD4(+) T cells isolated from AD-induced mice. Topical application of TSE on the ears of AD-induced mice decreased the severity and progression of disease by reducing ear thickness, clinical scores including dryness, edema. TSE treatment reduced the infiltration of lymphocytes to the inflamed site analyzed by histological evaluation. TSE treatment also decreased serum IgE level and expression of AD-associated pathogenic cytokines (IL-4, IL-5 and IL-13) in total ear cells and dLN CD4(+) T cells by inhibiting the translocation of NFκB into nucleus.

CONCLUSIONS

Our study indicates that protective effect of Taglisodog-eum (TSE) in experimental atopic dermatitis is mediated by inhibiting IgE production and the levels of Th2 type cytokines, suggesting the beneficial effect of TSE on modulating atopic dermatitis.

Peripheral mechanisms of itch

Detection of environmental stimuli that provoke an aversive response has been shown to involve many receptors in the periphery. Probably the least-studied of these stimuli are those that induce the perception of itch (pruritus), an often-experienced unpleasant stimulus. This review covers the ligands and their receptors which are known to cause primary sensory neuron activation and initiate itch sensation. Also covered are several itch-inducing substances which may act indirectly by activating other cell types in the periphery which then signal to primary neurons. Finally, progress in identifying candidate neurotransmitters that sensory neurons use to propagate the itch signal is discussed.

Pruritus in cutaneous T-cell lymphoma: a review

BACKGROUND

Pruritus can be a distressing and even debilitating symptom for patients with cutaneous T-cell lymphoma (CTCL). To date, few studies have evaluated the pathophysiology of this symptom. Because of this, therapy for pruritus in CTCL has mainly relied on those therapies that target and treat the lymphoma. For patients living with CTCL that relapses or becomes refractory to treatment, and who continue to experience severe itch, this lymphoma-targeted treatment may not be enough to combat their pruritus. Therefore, other itch-targeted therapies are needed for use in this disease.

OBJECTIVE

We sought to evaluate the current evidence regarding the mechanism of action and treatments for pruritus associated with CTCL.

METHODS

An explicit and thorough search was restricted to all peer-reviewed literature available through MEDLINE (1950 to September 2011) and PubMed. Search terms used were "pruritus," "cutaneous T-cell lymphoma," "CTCL," "mycosis fungoides," "MF," and "Sézary syndrome." All studies that involved pruritus in CTCL, mycosis fungoides, or Sézary syndrome were evaluated by all 3 authors.

RESULTS

The current literature helps to identify therapies and possible mechanisms for treating patients with CTCL-associated pruritus.

LIMITATION

Most studies were preclinical. Only studies involving mechanisms of action or treatment were included.

CONCLUSION

A guideline is necessary to assist in the treatment of pruritus in CTCL and additional studies are necessary to uncover the exact mechanism or mechanisms of action.

gp130 cytokines are positive signals triggering changes in gene expression and axon outgrowth in peripheral neurons following injury

Adult peripheral neurons, in contrast to adult central neurons, are capable of regeneration after axonal damage. Much attention has focused on the changes that accompany this regeneration in two places, the distal nerve segment (where phagocytosis of axonal debris, changes in the surface properties of Schwann cells, and induction of growth factors and cytokines occur) and the neuronal cell body (where dramatic changes in cell morphology and gene expression occur). The changes in the axotomized cell body are often referred to as the "cell body response." The focus of the current review is a family of cytokines, the glycoprotein 130 (gp130) cytokines, which produce their actions through a common gp130 signaling receptor and which function as injury signals for axotomized peripheral neurons, triggering changes in gene expression and in neurite outgrowth. These cytokines play important roles in the responses of sympathetic, sensory, and motor neurons to injury. The best studied of these cytokines in this context are leukemia inhibitory factor (LIF) and interleukin (IL)-6, but experiments with conditional gp130 knockout animals suggest that other members of this family, not yet determined, are also involved. The primary gp130 signaling pathway shown to be involved is the activation of Janus kinase (JAK) and the transcription factors Signal Transducers and Activators of Transcription (STAT), though other downstream pathways such as mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) may also play a role. gp130 signaling may involve paracrine, retrograde, and autocrine actions of these cytokines. Recent studies suggest that manipulation of this cytokine system can also stimulate regeneration by injured central neurons.

Basic mechanisms of itch

Chronic itch represents a burdensome clinical problem that can originate from a variety of aetiologies. Pruriceptive itch originates following the activation of peripheral sensory nerve endings following damage or exposure to inflammatory mediators and ascends to the brain through the spinal thalamic tract. Much insight has been gained into the understanding of the mechanisms underlying pruriceptive itch through studies using humans and experimental animals. More than one sensory nerve subtype is thought to subserve pruriceptive itch which includes both unmyelinated C-fibres and thinly myelinated Aδ nerve fibres. There are a myriad of mediators capable of stimulating these afferent nerves leading to itch, including biogenic amines, proteases, cytokines, and peptides. Some of these mediators can also evoke sensations of pain and the sensory processing underlying both sensations overlaps in complex ways. Studies have demonstrated that both peripheral and central sensitization to pruritogenic stimuli occur during chronic itch.

Signaling by IL-31 and functional consequences

Cytokines are key to control cellular communication. Interleukin-31 (IL-31) was recently discovered as a new member of the IL-6 family of cytokines. IL-31 signals through a heterodimeric receptor composed of OSMR and IL-31RA, a complex that stimulates the JAK-STAT, the RAS/ERK and the PI3K/AKT signal transduction pathways. The available data suggests that IL-31 is important for both innate and adaptive immunity in tissues that are in close contact with the environment, i.e. the skin, the airways and the lung, and the lining of the intestine. Enhanced expression of IL-31 is associated with a number of diseases, including pruritic diseases such as atopic dermatitis, but also in allergy and inflammatory bowel disease. In these tissues IL-31 coordinates the interaction of different immune cells, including T-cells, mast cells, and eosinophils, with epithelial cells. In this review we have summarized the available data on IL-31 and its receptor, their expression pattern and how they are regulated. We describe the current state of knowledge of the involvement of IL-31 in diseases, both in humans and in mouse models. From these studies it is becoming clear that IL-31 plays an important role in the proper functioning of the skin and of airway and intestinal epithelia. The findings available suggest that IL-31 might be an interesting target for directed drug therapy.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

The molecular skin pathology of familial primary localized cutaneous amyloidosis

Familial primary localized cutaneous amyloidosis (FPLCA) is an autosomal dominant disorder associated with chronic itching and skin lichenification. In lesional skin, there are apoptotic basal keratinocytes and deposits of amyloid material on degenerate keratin filaments in the upper dermis. The genetic basis of FPLCA involves mutations in the OSMR and IL31RA genes but the disease pathophysiology is not fully understood. In this study, we identified new pathogenic heterozygous missense mutations in the OSMR gene (p.Val631Leu and p.Asp647Tyr) in two Dutch FPLCA families. We then compared gene expression profiles between FPLCA lesional skin (n = 4) and site-matched control skin (n = 6). There was twofold or greater upregulation of 34 genes and downregulation of 43 genes. Most changes in gene expression (verified by quantitative RT-PCR) reflected alterations in epidermal differentiation and proliferation consistent with lichenification, but we also noted a reduction in several interfollicular keratinocyte stem cell markers in FPLCA skin. Differences in gene expression were also noted for proteins involved in apoptosis and nerve conduction. Collectively, this study expands the molecular basis of FPLCA and provides new insight into the skin pathology of this condition.

New insight into mechanisms of pruritus from molecular studies on familial primary localized cutaneous amyloidosis

Macular and lichen amyloidosis are common variants of primary localized cutaneous amyloidosis (PLCA) in which clinical features of pruritus and skin scratching are associated with histological findings of deposits of amyloid staining on keratinous debris in the papillary dermis. Most cases are sporadic, but an autosomal dominant family history may be present in up to 10% of cases, consistent with a genetic predisposition in some individuals. Familial PLCA has been mapped to a locus on 5p13.1-q11.2 and in 2008 pathogenic heterozygous missense mutations were identified in the OSMR gene, which encodes oncostatin M receptor beta (OSMRbeta), an interleukin (IL)-6 family cytokine receptor. OSMRbeta is expressed in various cell types, including keratinocytes, cutaneous nerves and nociceptive neurones in dorsal root ganglia; its ligands are oncostatin M and IL-31. All pathogenic mutations are clustered in the fibronectin-III repeat domains of the extracellular part of OSMRbeta, sites that are critical for receptor dimerization (with either gp130 or IL-31RA), and lead to defective signalling through Janus kinase-signal transducers and activators of transcription, extracellular signal-regulated protein kinase 1/2 and phosphoinositide 3 kinase/Akt pathways. Elucidating the molecular pathology of familial PLCA provides new insight into mechanisms of pruritus in human skin, findings that may have relevance to developing novel treatments for skin itching. This review provides a clinicopathological and molecular update on familial PLCA.

Role of stem cell factor and bone marrow-derived fibroblasts in airway remodeling

Recent evidence suggests that bone marrow-derived fibroblasts are involved in airway remodeling in asthma, but the role and mechanism of recruitment of these fibroblasts remains unclear. Stem cell factor (SCF), a key factor in the propagation of hematopoietic stem cells, is important in the process of airway remodeling as well. To test the hypothesis that SCF is involved in the recruitment and differentiation of bone marrow-derived progenitor cells, GFP-bone marrow chimeric mice were created. These mice were then sensitized and chronically challenged with cockroach antigen to induce chronic airway disease. Fluorescence microscopy revealed an influx of significant numbers of GFP-expressing fibroblasts in the airways of these mice, which was confirmed by flow cytometric analysis of cells co-expressing both GFP and collagen I. These cells preferentially expressed c-kit, interleukin-31 receptor, and telomerase reverse transcriptase when compared with control lung-derived fibroblasts. Interestingly, SCF stimulated interleukin-31 receptor expression in bone marrow cells, whereas interleukin-31 strongly induced telomerase reverse transcriptase expression in fibroblasts. Treatment with neutralizing antibodies to SCF significantly reduced airway remodeling and suppressed the recruitment of these bone marrow-derived cells to the lung. Thus SCF in conjunction with interleukin-31 may play a significant role in airway remodeling by promoting the recruitment of bone marrow-derived fibroblast precursors into the lung with the capacity to promote lung myofibroblast differentiation.

Regulated expression of the IL-31 receptor in bronchial and alveolar epithelial cells, pulmonary fibroblasts, and pulmonary macrophages

Interleukin-31 (IL-31), an IL-6 cytokine family member, is proposed to play a role in animal models of airway hyperreactivity. It is produced by activated T cells and signals via a heterodimeric receptor complex composed of IL-31Ralpha and OSMRbeta. Only low levels of IL-31Ralpha expression have been demonstrated in pulmonary epithelial cell lines, however, and little is known about the ability to regulate its expression and signaling. Therefore, primary cultures of human bronchial and alveolar epithelial cells, pulmonary fibroblasts, pulmonary macrophages, and established lines of immortalized bronchial epithelial cells (HBE) and alveolar carcinoma cells (A549) were analyzed by RT-PCR, immunoblotting, and thymidine incorporation. Distinct, cell type-specific regulation of IL-31Ralpha expression was detected. Transforming growth factor-beta (TGF-beta) enhanced IL-31Ralpha mRNA expression in primary cultures and established lines of epithelial cells, but not in macrophages. In contrast, interferon-gamma (IFN-gamma) induced IL-31Ralpha mRNA expression in macrophages. IL-31Ralpha protein expression was below detection threshold in primary epithelial cell cultures but was detectable in A549 cells and increased with TGF-beta treatment. In HBE and A549 cells, TGF-beta pretreatment increased IL-31-mediated Stat3 and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. In A549 cells, TGF-beta magnified IL-31-dependent suppression of proliferation. The data suggest that increased IL-31Ralpha expression correlates with an enhanced response to IL-31.

New drugs targeting Th2 lymphocytes in asthma

Asthma represents a profound worldwide public health problem. The most effective anti-asthmatic drugs currently available include inhaled beta2-agonists and glucocorticoids and control asthma in about 90-95% of patients. The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term therapy. Although glucocorticoids are highly effective in controlling the inflammatory process in asthma, they appear to have little effect on the lower airway remodelling processes that appear to play a role in the pathophysiology of asthma at currently prescribed doses. The development of novel drugs may allow resolution of these changes. In addition, severe glucocorticoid-dependent and resistant asthma presents a great clinical burden and reducing the side-effects of glucocorticoids using novel steroid-sparing agents is needed. Furthermore, the mechanisms involved in the persistence of inflammation are poorly understood and the reasons why some patients have severe life threatening asthma and others have very mild disease are still unknown. Drug development for asthma has been directed at improving currently available drugs and findings new compounds that usually target the Th2-driven airway inflammatory response. Considering the apparently central role of T lymphocytes in the pathogenesis of asthma, drugs targeting disease-inducing Th2 cells are promising therapeutic strategies. However, although animal models of asthma suggest that this is feasible, the translation of these types of studies for the treatment of human asthma remains poor due to the limitations of the models currently used. The myriad of new compounds that are in development directed to modulate Th2 cells recruitment and/or activation will clarify in the near future the relative importance of these cells and their mediators in the complex interactions with the other pro-inflammatory/anti-inflammatory cells and mediators responsible of the different asthmatic phenotypes. Some of these new Th2-oriented strategies may in the future not only control symptoms and modify the natural course of asthma, but also potentially prevent or cure the disease.

Oncostatin M receptor-beta mutations underlie familial primary localized cutaneous amyloidosis

Familial primary localized cutaneous amyloidosis (FPLCA) is an autosomal-dominant disorder associated with chronic skin itching and deposition of epidermal keratin filament-associated amyloid material in the dermis. FPLCA has been mapped to 5p13.1-q11.2, and by candidate gene analysis, we identified missense mutations in the OSMR gene, encoding oncostatin M-specific receptor beta (OSMRbeta), in three families. OSMRbeta is a component of the oncostatin M (OSM) type II receptor and the interleukin (IL)-31 receptor, and cultured FPLCA keratinocytes showed reduced activation of Jak/STAT, MAPK, and PI3K/Akt pathways after OSM or IL-31 cytokine stimulation. The pathogenic amino acid substitutions are located within the extracellular fibronectin type III-like (FNIII) domains, regions critical for receptor dimerization and function. OSM and IL-31 signaling have been implicated in keratinocyte cell proliferation, differentiation, apoptosis, and inflammation, but our OSMR data in individuals with FPLCA represent the first human germline mutations in this cytokine receptor complex and provide new insight into mechanisms of skin itching.

Interleukin-31 and oncostatin-M mediate distinct signaling reactions and response patterns in lung epithelial cells

Lung epithelial cells are primary targets of oncostatin M (OSM) and, to a lower degree, of interleukin (IL)-6 and IL-31, all members of the IL-6 cytokine family. The OSM receptor (OSMR) signals through activation of STAT and mitogen-activated protein kinase pathways to induce genes encoding differentiated cell functions, reduce cell-cell interaction, and suppress cell proliferation. IL-31 functions through the heteromeric IL-31 receptor, which shares with OSMR the OSMRbeta subunit, but does not engage gp130, the common subunit of all other IL-6 cytokine receptors. Because the response of epithelial cells to IL-31 is unknown, the action of IL-31 was characterized in the human alveolar epithelial cell line A549 in which the expression of the ligand-binding IL-31Ralpha subunit was increased. IL-31 initiated signaling that differed from other IL-6 cytokines by the particularly strong recruitment of the STAT3, ERK, JNK, and Akt pathways. IL-31 was highly effective in suppressing proliferation by altering expression of cell cycle proteins, including up-regulation of p27(Kip1) and down-regulation of cyclin B1, CDC2, CDK6, MCM4, and retinoblastoma. A single STAT3 recruitment site (Tyr-721) in the cytoplasmic domain of IL-31Ralpha exerts a dominant function in the entire receptor complex and is critical for gene induction, morphological changes, and growth inhibition. The data suggest that inflammatory and immune reactions involving activated T-cells regulate functions of epithelial cells by IL-6 cytokines through receptor-defined signaling reactions.