RIP4 upregulates CCL20 expression through STAT3 signalling in cultured keratinocytes

p38α deficiency ameliorates psoriasis development by downregulating STAT3-mediated keratinocyte proliferation and cytokine production

Psoriasis is characterized by keratinocyte (KC) hyperproliferation and inflammatory cell infiltration, but the mechanisms remain unclear. In an imiquimod-induced mouse psoriasiform model, p38 activity is significantly elevated in KCs and p38α specific deletion in KCs ameliorates skin inflammation. p38α signaling promotes KC proliferation and psoriasis-related proinflammatory gene expression during psoriasis development. Mechanistically, p38α enhances KC proliferation and production of inflammatory cytokines and chemokines by activating STAT3. While p38α signaling in KCs does not affect the expression of IL-23 and IL-17, it substantially amplifies the IL-23/IL-17 pathogenic axis in psoriasis. The therapeutic effect of IL-17 neutralization is associated with decreased p38 and STAT3 activities in KCs and targeting the p38α-STAT3 axis in KCs ameliorates the severity of psoriasis. As IL-17 also highly activates p38 and STAT3 in KCs, our findings reveal a sustained signaling circuit important for psoriasis development, highlighting p38α-STAT3 axis as an important target for psoriasis treatment.

Unraveling CCL20's role by regulating Th17 cell chemotaxis in experimental autoimmune prostatitis

Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS), a prevalent urological ailment, exerts a profound influence upon the well-being of the males. Autoimmunity driven by Th17 cells has been postulated as a potential factor in CP/CPPS pathogenesis. Nonetheless, elucidating the precise mechanisms governing Th17 cell recruitment to the prostate, triggering inflammation, remained an urgent inquiry. This study illuminated that CCL20 played a pivotal role in attracting Th17 cells to the prostate, thereby contributing to prostatitis development. Furthermore, it identified prostate stromal cells and immune cells as likely sources of CCL20. Additionally, this research unveiled that IL-17A, released by Th17 cells, could stimulate macrophages to produce CCL20 through the NF-κB/MAPK/PI3K pathway. The interplay between IL-17A and CCL20 establishes a positive feedback loop, which might serve as a critical mechanism underpinning the development of chronic prostatitis, thus adding complexity to its treatment challenges.

miR-26a-5p inhibits the proliferation of psoriasis-like keratinocytes in vitro and in vivo by dual interference with the CDC6/CCNE1 axis

Psoriasis is a chronic inflammatory proliferative dermatological ailment that currently lacks a definitive cure. Employing data mining techniques, this study identified a collection of substantially downregulated miRNAs (top 10). Notably, 32 targets were implicated in both the activation of the IL-17 signaling pathway and cell cycle dysregulation. In silico analysis revealed that one of these miRNAs, miR-26a-5p, is a highly conserved cross-species miRNA. Strikingly, the miR-26a-5p sequences in humans and mice are identical, and mmu-miR-26a-5p was found to target the same 7 cell cycle targets as its human counterpart, hsa-miR-26a-5p. Among these targets, CDC6 and CCNE1 were the most effective targets of miR-26a-5p, which was further validated in vitro using a dual luciferase reporter system and qPCR assay. The therapeutic assessment of miR-26a-5p revealed its remarkable efficacy in inhibiting the proliferation and G1/S transition of keratinocytes (HaCaT and HEKs) in vitro. In vivo experiments corroborated these findings, demonstrating that miR-26a-5p effectively suppressed imiquimod (IMQ)-induced psoriasis-like skin lesions in mice over an 8-day treatment period. Histological analysis via H&E staining revealed that miR-26a-5p treatment resulted in reduced keratinocyte thickness and immune cell infiltration into the spleens of IMQ-treated mice. Mechanistic investigations revealed that miR-26a-5p induced a cascade of downregulated genes associated with the IL-23/IL-17A axis, which is known to be critical in psoriasis pathogenesis, while concomitantly suppressing CDC6 and CCNE1 expression. These findings were corroborated by qPCR and Western blot analyses. Collectively, our study provides compelling evidence supporting the therapeutic potential of miR-26a-5p as a safe and reliable endogenous small nucleic acid for the treatment of psoriasis.

Functions of the RIP kinase family members in the skin

The receptor interacting protein kinases (RIPK) are a family of serine/threonine kinases that are involved in the integration of various stress signals. In response to several extracellular and/or intracellular stimuli, RIP kinases engage signaling cascades leading to the activation of NF-κB and mitogen-activated protein kinases, cell death, inflammation, differentiation and Wnt signaling and can have kinase-dependent and kinase-independent functions. Although it was previously suggested that seven RIPKs are part of the RIPK family, phylogenetic analysis indicates that there are only five genuine RIPKs. RIPK1 and RIPK3 are mainly involved in controlling and executing necroptosis in keratinocytes, while RIPK4 controls proliferation and differentiation of keratinocytes and thereby can act as a tumor suppressor in skin. Therefore, in this review we summarize and discuss the functions of RIPKs in skin homeostasis as well as the signaling pathways involved.

SIRT5 reduces the inflammatory response and barrier dysfunction in IL-17A-induced epidermal keratinocytes

Psoriasis is a chronic multisystemic inflammatory disease with inflammatory cell infiltration, hyperproliferation of keratinocytes in skin lesions, and epidermal barrier dysfunction. Normal human epidermal keratinocytes (NHEKs) were stimulated with interleukin 17A (IL-17A). The expression levels of sirtuin-5 (SIRT5) were analyzed by RT-qPCR and western blot assay. The proliferation levels of NHEKs were assessed by EdU staining. The expression of ELOVL1 and ELOVL4 was analyzed by RT-Qpcr, and the expression levels of filaggrin, loricrin, and aquaporin-3 were analyzed by RT-qPCR and western blot. Extracellular signal-regulated kinase 1/2 (ERK1/2) activator t-butylhydroquinone was used to activate ERK1/2. Here, we show that SIRT5 overexpression reduces cell viability and cell proliferation, and improves barrier dysfunction in IL-17A-treated human epidermal keratinocytes, this effect of which is significantly blunted by the ERK1/2 activator. In epidermal keratinocytes, SIRT5 decreases cell proliferation and inflammation and improves barrier dysfunction via ERK/STAT3. This study reveals the role of SIRT5 in the pathogenesis of psoriasis, epidermal hyperplasia, keratinocyte-mediated inflammatory responses, and barrier dysfunction, the role of which is mediated by ERK/STAT3.

Chemokine expression in human 3-dimensional cultured epidermis exposed to PM2.5 collected by cyclonic separation

Fine particulate matter (PM2.5) exposure has a risk of inducing several health problems, especially in the respiratory tract. The skin is the largest organ of the human body and is therefore the primary target of PM2.5. In this study, we examined the effects of PM2.5 on the skin using a human 3-dimensional cultured epidermis model. PM2.5 was collected by cyclonic separation in Yokohama, Japan. Global analysis of 34 proteins released from the epidermis revealed that the chemokines, chemokine C-X-C motif ligand 1 (CXCL1) and interleukin 8 (IL-8), were significantly increased in response to PM2.5 exposure. These chemokines stimulated neutrophil chemotaxis in a C-X-C motif chemokine receptor 2-dependent manner. The oxidative stress and signal transducer and activator of transcription 3 pathways may be involved in the increased expression of CXCL1 and IL-8 in the human epidermis model. Interestingly, in the HaCaT human keratinocyte cell line, PM2.5 did not affect chemokine expression but did induce IL-6 expression, suggesting a different effect of PM2.5 between the epidermis model and HaCaT cells. Overall, PM2.5 could induce the epidermis to release chemokines, followed by neutrophil activation, which might cause an unregulated inflammatory reaction in the skin.

Five Rutaceae family ethanol extracts alleviate H2O2 and LPS-induced inflammation via NF-κB and JAK-STAT3 pathway in HaCaT cells

This study was designed to investigate the effects of five Rutaceae family ethanol extracts (FRFEE): Citrus medica Linn (CML), Citrus aurantium L. Cv. Daidai (CAD), Citrus medica Linn. var. sarcodactylis (Noot.) Swingle (CMS),Citrus sinensis L. Osbeck (CSO) and Zanthoxylum bungeanum Maxim (ZBM) on retarding the progression of H₂O₂ and LPS-induced HaCaT cells. Cell inflammatory injury model was established by H₂O₂ and LPS. The alleviative effects of FRFEE were evaluated by detecting the activity of superoxide dismutase (SOD), glutathione (GSH) and the generation of reactive oxygen species (ROS). The inflammatory signaling pathways of NF-κB and JAK-STAT3 were detected by Western blotting, the mRNA expression levels of inflammatory factors and skin barrier factors were detected by RT-PCR. 50% ethanol extracts of five medicinal and food homologous herbs of Rutaceae family showed different levels of anti-oxidant and anti-inflammatory activities. The FRFEE effectively improved SOD and GSH content and decreased ROS levels. Meanwhile, FRFEE strongly suppressed two inflammatory signaling pathways NF-κB and JAK-STAT3. The RT-PCR examination of inflammatory factors and skin barrier factor revealed significant anti-inflammatory effects of FRFEE. It was worth noting that among the five extracts, Zanthoxylum bungeanum Maxim extract had the best anti-inflammatory and anti-oxidation effects. In addition, it could strongly inhibit the expression of psoriasis factor CCL20. In summary, these results suggested that Zanthoxylum bungeanum Maxim extract could be used as an anti-psoriatic agent in the treatment of psoriasis among FRFEE.

Review and Practical Guidance on Managing Fungal Infections in Patients With Psoriasis Receiving Anti-IL-17 Therapies

The IL-17 signalling pathway is a major target in treatment of plaque psoriasis. IL-17 signalling contributes to chronic inflammation and epidermal hyperplasia seen in psoriatic lesions. Blocking the IL-17 signalling cascade is an effective method in treating this disease. However, IL-17 also plays a role in the immunological protection against fungal infections and therefore, patients on IL-17 biologics experience an increased rate of fungal infections, specifically Candida albicans. It is prudent that patients and physicians are aware of this risk and understand how to recognize and manage Candida infections. In this review, we examine the Candida infection rates associated with IL-17 biologics, both in clinical trials and real-world practice. We discuss common presentations associated with various types of candidiasis and propose a recommended management approach to treating these infections.

A Modified Hyaluronic Acid–Based Dissolving Microneedle Loaded With Daphnetin Improved the Treatment of Psoriasis

Psoriasis is a common chronic immune-inflammatory disease. Challenges exist in the present treatment of psoriasis, such as difficulties in transdermal drug administration and severe side effects. We hope to achieve a better therapeutic outcome for psoriasis treatment. By using modified soluble microneedles (MNs) loaded with daphnetin, the psoriasis symptoms of mice, the abnormal proliferation of keratinocytes, and the secretion of inflammatory factors were significantly reduced. In vitro, daphnetin is proven to inhibit the NF-κB signaling pathway and to inhibit the proliferation of HaCaT cells and the release of inflammatory factors, especially CCL20. This research showed that the modified microneedle loaded with daphnetin optimized transdermal drug delivery and relieved the symptoms of psoriasis more effectively. The novel route of Daph administration provides a future research direction for the treatment of psoriasis.

A Michael Acceptor Analogue, SKSI-0412, Down-Regulates Inflammation and Proliferation Factors through Suppressing Signal Transducer and Activator of Transcription 3 Signaling in IL-17A-Induced Human Keratinocyte

The activation of signal transducer and activator of transcription 3 (STAT3), as well as up-regulation of cytokines and growth factors to promote STAT3 activation, have been found in the epidermis of psoriatic lesions. Recently, a series of synthetic compounds possessing the Michael acceptor have been reported as STAT3 inhibitors by covalently binding to cysteine of STAT3. We synthesized a Michael acceptor analog, SKSI-0412, and confirmed the binding affinity between STAT3 and SKSI-0412. We hypothesized that the SKSI-0412 can inhibit interleukin (IL)-17A-induced inflammation in keratinocytes. The introduction of IL-17A increased the phosphorylation of STAT3 in keratinocytes, whereas the inactivation of STAT3 by SKSI-0412 reduced IL-17A-induced STAT3 phosphorylation and IκBζ expression. In addition, human β defensin-2 and S100A7, which are regulated by IκBζ, were significantly decreased with SKSI-0412 administration. We also confirmed that SKSI-0412 regulates cell proliferation, which is the major phenotype of psoriasis. Based on these results, we suggest targeting STAT3 with SKSI-0412 as a novel therapeutic strategy to regulate IL-17A-induced psoriatic inflammation in keratinocytes.

STAT3 maintains skin barrier integrity by modulating SPINK5 and KLK5 expression in keratinocytes

Skin barrier dysfunction induces skin inflammation. Signal transducer and activator of transcription 3 (STAT3) is known to be involved in Th17-mediated immune responses and barrier integrity in the cornea and intestine; however, its role in the skin barrier remains largely unknown. In this study, we elucidated the potential role of STAT3 in the skin barrier and its effect on kallikrein-related peptidase 5 (KLK5) and serine protease inhibitor Kazal-type 5 (SPINK5) expression using a mouse model with keratinocyte-specific ablation of STAT3. Keratinocyte-specific loss of STAT3 induced a cutaneous inflammatory phenotype with pruritus and intense scratching behaviour in mice. Transcriptomic analysis revealed that the genes associated with impaired skin barrier function, including KLK5, were upregulated. The effect of STAT3 on KLK5 expression in keratinocytes was not only substantiated by the increase in KLK5 expression following treatment with STAT3 siRNA but also by its decreased expression following STAT3 overexpression. Overexpression and IL-17A-mediated stimulation of STAT3 increased the expression of SPINK5, which was blocked by STAT3 siRNA. These results suggest that the expression of SPINK5 and KLK5 in keratinocytes could be dependent on STAT3 and that STAT3 might play an essential role in the maintenance of skin barrier homeostasis.

CCL20 induced by visfatin in macrophages via the NF-κB and MKK3/6-p38 signaling pathways contributes to hepatic stellate cell activation

Chemokines interact with hepatic resident cells during inflammation and fibrosis. CC chemokine ligand (CCL) 20 has been reported to be important in inflammation and fibrosis in the liver. We hypothesized that visfatin, an adipocytokine, could play a role in hepatic fibrosis via CCL20. We investigated the effect of visfatin on CCL20 in THP-1 human promonocytic cells and examined the molecular mechanisms involved. Following treatment of THP-1 cells with visfatin, CCL20 expression and secretion were assessed. We assessed the intracellular signaling molecules IKK/NF-κB, JAK2/STAT3, MAPKs, and MKK3/6 by western blotting. We treated THP-1 cells with visfatin and signaling inhibitors, and examined CCL20 mRNA and protein levels. To investigate the effect of visfatin-induced CCL20 expression in hepatic stellate cells (HSCs), LX-2 cells were co-cultured with the culture supernatant of THP-1 cells with or without anti-CCL20 neutralizing antibodies, and fibrosis markers were examined by RT-PCR and immunoblotting. In THP-1 cells, visfatin increased the CCL20 mRNA and protein levels. visfatin increased the activities of the NF-κB, p38, and MLK3/6 signaling pathways but not those of the JAK2/STAT3 and ERK pathways. Visfatin treatment together with an NF-κB, p38, or MLK3 inhibitor reduced the mRNA and protein levels of CCL20. The visfatin-induced CCL20 increased the expression of fibrosis markers and CCR6 in HSCs. Following neutralization of CCL20, the levels of fibrosis markers and CCR6 were decreased. Visfatin increases the expression of CCL20 via the NF-κB and MKK3/6-p38 signaling pathways in macrophages, and visfatin-induced CCL20 expression promotes the fibrosis markers in HSCs.

Interleukin-17A and Keratinocytes in Psoriasis

The excellent clinical efficacy of anti-interleukin 17A (IL-17A) biologics on psoriasis indicates a crucial pathogenic role of IL-17A in this autoinflammatory skin disease. IL-17A accelerates the proliferation of epidermal keratinocytes. Keratinocytes produce a myriad of antimicrobial peptides and chemokines, such as CXCL1, CXCL2, CXCL8, and CCL20. Antimicrobial peptides enhance skin inflammation. IL-17A is capable of upregulating the production of these chemokines and antimicrobial peptides in keratinocytes. CXCL1, CXCL2, and CXCL8 recruit neutrophils and CCL20 chemoattracts IL-17A-producing CCR6⁺ immune cells, which further contributes to forming an IL-17A-rich milieu. This feed-forward pathogenic process results in characteristic histopathological features, such as epidermal hyperproliferation, intraepidermal neutrophilic microabscess, and dermal CCR6⁺ cell infiltration. In this review, we focus on IL-17A and keratinocyte interaction regarding psoriasis pathogenesis.

Immune Control by TRAF6-Mediated Pathways of Epithelial Cells in the EIME (Epithelial Immune Microenvironment)

In the protective responses of epithelial tissues, not only immune cells but also non-immune cells directly respond to external agents. Epithelial cells can be involved in the organization of immune responses through two phases. First, the exogenous harmful agents trigger the primary responses of the epithelial cells leading to various types of immune cell activation. Second, cytokines produced by the immune cells that are activated directly by the external agents and indirectly by the epithelial cell products elicit the secondary responses giving rise to further propagation of immune responses. TRAF6 is a ubiquitin E3 ligase, which intermediates between various types of receptors for exogenous agents or endogenous mediators and activation of subsequent transcriptional responses via NF-kappaB and MAPK pathways. TRAF6 ubiquitously participates in many protective responses in immune and non-immune cells. Particularly, epithelial TRAF6 has an essential role in the primary and secondary responses via driving type 17 response in psoriatic inflammation of the skin. Consistently, many psoriasis susceptibility genes encode the TRAF6 signaling players, such as ACT1 (TRAF3IP2), A20 (TNFAIP3), ABIN1 (TNIP1), IL-36Ra (IL36RN), IkappaBzeta (NFKBIZ), and CARD14. Herein, we describe the principal functions of TRAF6, especially in terms of positive and regulatory immune controls by interaction between immune cells and epithelial cells. In addition, we discuss how TRAF6 in the epithelial cells can organize the differentiation of immune responses and drive inflammatory loops in the epithelial immune microenvironment, which is termed EIME.