Carren Sy Hau

P2Y6 Receptor Signaling Pathway Mediates Inflammatory Responses Induced by Monosodium Urate Crystals

Gout occurs in individuals with hyperuricemia when monosodium urate (MSU) crystals precipitate in tissues and induce acute inflammation via phagocytic cells such as monocytes. MSU crystals have been demonstrated in skin diseases such as tophaceous gout or psoriasis; however, the importance of MSU crystals in the skin is totally unknown. In this study, we found that MSU crystals, through P2Y6 receptors, stimulated normal human keratinocytes (NHK) to produce IL-1α, IL-8/CXCL8, and IL-6. P2Y6 receptor expression increased in MSU-stimulated NHK. Both P2Y6-specific antagonist and P2Y6 antisense oligonucleotides significantly inhibited the production of IL-1α, IL-8/CXCL8, and IL-6 by NHK. Similarly, the P2Y6-specific antagonist completely inhibited the MSU-induced production of IL-1β by THP-1 cells, a human monocytic cell line. Remarkably, the P2Y6-specific antagonist significantly reduced neutrophil influx in both mouse air pouch and peritonitis models. Thus, these results indicate that the P2Y6 receptor signaling pathway may be a potential therapeutic target for MSU-associated inflammatory diseases, such as tophaceous gout.

Adiponectin Regulates Cutaneous Wound Healing by Promoting Keratinocyte Proliferation and Migration via the ERK Signaling Pathway

Diabetic patients are at high risk of developing delayed cutaneous wound healing. Adiponectin plays a pivotal role in the pathogenesis of diabetes and is considered to be involved in various pathological conditions associated with diabetes; however, its role in wound repair is unknown. In this study, we elucidated the involvement of adiponectin in cutaneous wound healing in vitro and in vivo. Normal human keratinocytes expressed adiponectin receptors, and adiponectin enhanced proliferation and migration of keratinocytes in vitro. This proliferative and migratory effect of adiponectin was mediated via AdipoR1/AdipoR2 and the ERK signaling pathway. Consistent with in vitro results, wound closure was significantly delayed in adiponectin-deficient mice compared with wild-type mice, and more importantly, keratinocyte proliferation and migration during wound repair were also impaired in adiponectin-deficient mice. Furthermore, both systemic and topical administration of adiponectin ameliorated impaired wound healing in adiponectin-deficient and diabetic db/db mice, respectively. Collectively, these results indicate that adiponectin is a potent mediator in the regulation of cutaneous wound healing. We propose that upregulation of systemic and/or local adiponectin levels is a potential and very promising therapeutic approach for dealing with diabetic wounds.

Adiponectin as an anti-inflammatory factor in the pathogenesis of psoriasis: induction of elevated serum adiponectin levels following therapy

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Adiponectin regulates psoriasiform skin inflammation by suppressing IL-17 production from γδ-T cells

Accumulating epidemiologic evidence has revealed that metabolic syndrome is an independent risk factor for psoriasis development and is associated with more severe psoriasis. Adiponectin, primarily recognized as a metabolic mediator of insulin sensitivity, has been newly drawing attention as a mediator of immune responses. Here we demonstrate that adiponectin regulates skin inflammation, especially IL-17-related psoriasiform dermatitis. Mice with adiponectin deficiency show severe psoriasiform skin inflammation with enhanced infiltration of IL-17-producing dermal Vγ4+γδ-T cells. Adiponectin directly acts on murine dermal γδ-T cells to suppress IL-17 synthesis via AdipoR1. We furthermore demonstrate here that the adiponectin level of skin tissue as well as subcutaneous fat is decreased in psoriasis patients. IL-17 production from human CD4- or CD8-positive T cells is also suppressed by adiponectin. Our data provide a regulatory role of adiponectin in skin inflammation, which would imply a mechanism underlying the relationship between psoriasis and metabolic disorders.

Decreased serum LL-37 and vitamin D3 levels in atopic dermatitis: relationship between IL-31 and oncostatin M.

Skin lesions with atopic dermatitis (AD) are associated with dysregulated expression of LL‐37 and enhanced expression of IL‐22, thymic stromal lymphopoietin (TSLP), IL‐25, IL‐31, and oncostatin M. Vitamin D3 enhances LL‐37 production in keratinocytes. This study aimed to examine the serum levels of LL‐37 and vitamin D3 and their regulation of cytokine production in patients with AD.

Histamine induces human β-defensin-3 production in human keratinocytes

BACKGROUND The antimicrobial peptide human beta-defensin-3 (hBD-3) is produced by epidermal keratinocytes, and promotes cutaneous antimicrobial defense, inflammation, and wound repair. hBD-3 induces histamine release from mast cells. We previously showed that histamine enhanced transcriptional activity of activator protein-1 (AP-1) in human keratinocytes by inducing the expression of AP-1 component c-Fos via the activation of extracellular signal-regulated kinase (ERK) through H1 receptors. OBJECTIVE To examine in vitro effects of histamine on hBD-3 production in normal human keratinocytes. METHODS The hBD-3 production was examined by enzyme-linked immunosorbent assays and reverse transcription-polymerase chain reaction. The transcriptional activities were analyzed by dual luciferase assays. The phosphorylation of proteins was examined by Western blotting. RESULTS Histamine enhanced hBD-3 secretion and mRNA expression in keratinocytes. The histamine-induced hBD-3 production was suppressed by H1 antagonist pyrilamine and antisense oligonucleotides against signal transducer and activator of transcription 3 (STAT3) and AP-1 components c-Jun and c-Fos. Histamine enhanced STAT3 transcriptional activity and induced tyrosine and serine phosphorylation of STAT3. The former was suppressed by Janus kinase 2 (JAK2) inhibitor AG490, while the latter was suppressed by mitogen-activated protein kinase kinase (MEK) inhibitor PD98059; both were suppressed by pyrilamine. AG490 and PD98059 suppressed histamine-induced hBD-3 production and STAT3 activity. Histamine induced tyrosine phosphorylation of JAK2, and pyrilamine suppressed the phosphorylation. CONCLUSION It is suggested that histamine induces hBD-3 production in human keratinocytes through H1 receptors by activating STAT3 and AP-1 via JAK2 and MEK/ERK. Histamine may promote cutaneous antimicrobial defense, inflammation, and wound repair through hBD-3.

Visfatin Enhances CXCL8, CXCL10, and CCL20 Production in Human Keratinocytes

Psoriasis patients are frequently associated with metabolic syndromes. Such associations are possibly mediated by adipokines. We investigated the in vitro effects of visfatin (an adipokine) on chemokine expression in human keratinocytes. Normal human keratinocytes were incubated with visfatin, and their chemokine production was analyzed by ELISA and RT-PCR. Visfatin enhanced TNF-α-induced CXC chemokine ligand (CXCL) 8, CXCL10, and CC chemokine ligand (CCL) 20 secretion and mRNA expression in keratinocytes, although visfatin alone was ineffective. A small interfering RNA against nuclear factor-κB (NF-κB) p65 suppressed the visfatin-induced production of CXCL8, CXCL10, and CCL20 whereas a small interfering RNA against signal transducer and activator of transcription (STAT) 3 suppressed CXCL8 induction. This indicates the involvement of NF-κB in CXCL8, CXCL10, and CCL20 induction by visfatin and the involvement of STAT3 in CXCL8 induction. Visfatin alone increased the transcriptional activity and tyrosine phosphorylation of STAT3, which was suppressed by Janus kinase (JAK) 2 inhibitor. Visfatin enhanced basal and TNF-α-induced NF-κB activity and inhibitory κB (IκB) α phosphorylation, which was suppressed by IκB kinase inhibitor. Visfatin induced the tyrosine and serine phosphorylation of JAK2 and IκB kinase α/β, respectively. Intraperitoneal injection of visfatin elevated mRNA and protein levels of CXCL1, CXCL10, and CCL20 in murine skin. These results suggest that visfatin enhances CXCL8, CXCL10, and CCL20 production in human keratinocytes and homologous chemokine production in murine skin. Visfatin may induce the infiltration of type 1 or type 17 helper T cells or neutrophils to the skin via chemokine induction and thus link metabolic syndromes to psoriasis.

Prolactin induces the production of Th17 and Th1 cytokines/chemokines in murine Imiquimod‐induced psoriasiform skin

Prolactin (PRL) is a pituitary‐derived neuropeptide hormone that has been suggested to promote the development of psoriasis, a Th17/Th1‐mediated inflammatory dermatosis. PRL increases the expression of Th1 cytokines; however, its effects on Th17 responses are unknown.

Visfatin Enhances the Production of Cathelicidin Antimicrobial Peptide, Human β-Defensin-2, Human β-Defensin-3, and S100A7 in Human Keratinocytes and Their Orthologs in Murine Imiquimod-Induced Psoriatic Skin

Psoriasis, a chronic inflammatory dermatosis, is frequently associated with metabolic disorders, suggesting that adipokines are involved in its pathogenesis. We recently reported that the adipokine visfatin activates NF-κB and STAT3 in keratinocytes. Antimicrobial peptide expression is enhanced in psoriatic lesions and may promote disease development. Here, we investigated the effects of visfatin on antimicrobial peptide expression. In vitro, visfatin enhanced basal and tumor necrosis factor-α (TNF-α)-induced mRNA expression and secretion of cathelicidin antimicrobial peptide (CAMP), and enhanced TNF-α-induced human β-defensin-2 (hBD-2), hBD-3, and S100A7 mRNA expression and secretion in human keratinocytes. siRNAs targeting CCAAT/enhancer-binding protein-α (C/EBPα) suppressed visfatin-induced and visfatin plus TNF-α-induced CAMP production. siRNAs targeting NF-κB p65 and STAT3 suppressed visfatin plus TNF-α-induced hBD-2 and S100A7 production. siRNAs targeting c-Jun and STAT3 suppressed visfatin plus TNF-α-induced hBD-3 production. Visfatin and/or TNF-α enhanced C/EBP transcriptional activity and C/EBPα phosphorylation, which were suppressed by p38 mitogen-activated protein kinase (MAPK) inhibition. Visfatin and/or TNF-α induced p38 MAPK phosphorylation. Visfatin increased mRNA and protein expression of CAMP, hBD-2, hBD-3, and S100A7 orthologs in murine imiquimod-treated skin, mimicking psoriasis. In conclusion, visfatin enhances CAMP, hBD-2, hBD-3, and S100A7 production in human keratinocytes and their orthologs in murine imiquimod-treated psoriatic skin. Visfatin may potentiate the development of psoriasis via antimicrobial peptides.

Lipocalin-2 exacerbates psoriasiform skin inflammation by augmenting T-helper 17 response.

Lipocalin‐2 (LCN2) is an antimicrobial protein and adipokine associated with insulin resistance, obesity and atherosclerotic disease. Psoriasis is a T‐helper (Th)1/Th17‐mediated, chronic inflammatory dermatosis related to metabolic syndromes and serum LCN2 levels are elevated in psoriatic patients. We examined the in vivo effects of LCN2 on topical imiquimod (IMQ)‐induced psoriasiform skin in BALB/c mice and in vitro on human keratinocytes (KC). Clinically, i.p. injected LCN2 exacerbated erythema and scaling in IMQ‐treated murine skin compared with phosphate‐buffered saline injection alone, and it augmented interleukin (IL)‐17A, IL‐17F, IL‐22, IL‐23p19, IL‐12p40, CCL20, tumor necrosis factor‐α, chemokine (C‐X‐C motif) ligand (CXCL)1, CXCL2, DEFB4, DEFB14, LCN2 and S100A7 mRNA levels of IMQ‐treated murine skin while it did not increase the mRNA levels of interferon‐γ, IL‐12p35 or CXCL10. LCN2 in synergy with IL‐17 increased mRNA levels of CCL20, LCN2 and DEFB4A but not of CXCL10 in human KC in vitro. These results suggest that LCN2 enhances the expression of Th17 cytokines/chemokines and antimicrobial peptides in murine IMQ‐treated psoriatic skin and KC. LCN2 may potentiate the development of psoriasis via the enhancement of Th17‐ and antimicrobial peptide‐mediated inflammation.