High-fat diet exacerbates imiquimod-induced psoriasis-like dermatitis in mice.

Psoriasis, a chronic inflammatory skin disease, is closely related to systemic metabolism. An elevated body mass index (BMI) is a risk factor for psoriasis; inflammasomes are activated by adipose tissue macrophages in obese subjects. We hypothesized that hyperlipidaemia is involved in the pathogenesis of psoriasis and examined the role of a high-fat diet (HFD) in the development of psoriasis in imiquimod (IMQ)-treated mice. The body weight and serum level of cholesterol were significantly higher in mice fed an HFD than in a regular diet (RD). HFD mice had higher psoriasis skin scores, and the number of neutrophils infiltrating into the lesional skin was elevated. IL-17A mRNA expression was significantly increased in the skin of IMQ-treated HFD mice; the expression of IL-22, IL-23 and TNF-α mRNA was not enhanced. Caspase-1 and IL-1ß were activated in the skin of IMQ-treated HFD mice, and their serum level of IL-17A, TNF-α and IL-1ß was significantly upregulated. Our findings strongly suggest that hyperlipidaemia is involved in the development and progression of psoriasis via systemic inflammation and inflammasome activation.

TCR signaling and cellular metabolism regulate the capacity of murine epidermal γδ T cells to rapidly produce IL-13 but not IFN-γ.

Resident epidermal T cells of murine skin, called dendritic epidermal T cells (DETCs), express an invariant γδ TCR that recognizes an unidentified self-ligand expressed on epidermal keratinocytes. Although their fetal thymic precursors are preprogrammed to produce IFN-γ, DETCs in the adult epidermis rapidly produce IL-13 but not IFN-γ early after activation. Here, we show that preprogrammed IFN-γ-producing DETC precursors differentiate into rapid IL-13 producers in the perinatal epidermis. The addition of various inhibitors of signaling pathways downstream of TCR to the in vitro differentiation model of neonatal DETCs revealed that TCR signaling through the p38 MAPK pathway is essential for the functional differentiation of neonatal DETCs. Constitutive TCR signaling at steady state was also shown to be needed for the maintenance of the rapid IL-13-producing capacity of adult DETCs because in vivo treatment with the p38 MAPK inhibitor decreased adult DETCs with the rapid IL-13-producing capacity. Adult DETCs under steady-state conditions had lower glycolytic capacity than proliferating neonatal DETCs. TCR stimulation of adult DETCs induced high glycolytic capacity and IFN-γ production during the late phase of activation. Inhibition of glycolysis decreased IFN-γ but not IL-13 production by adult DETCs during the late phase of activation. These results demonstrate that TCR signaling promotes the differentiation of IL-13-producing DETCs in the perinatal epidermis and is needed for maintaining the rapid IL-13-producing capacity of adult DETCs. The low glycolytic capacity of adult DETCs at steady state also regulates the rapid IL-13 response and delayed IFN-γ production after activation.

Neutrophil-Derived MicroRNA-1290 Promotes Keratinocyte Proliferation in Psoriasis.

The pathological hallmark of psoriasis is the infiltration of neutrophils into the skin. Some neutrophil-derived microRNAs (miRNAs) serve as biomarkers for various diseases, but none have been reported for psoriasis. In this study, we investigated the involvement of miRNAs released from neutrophils in psoriasis pathogenesis. We compared the expression of miRNAs in the sera of patients with psoriasis with that in healthy individuals and found that the expression of 2 miRNAs-miR-223 and miR-1290-was significantly upregulated in the sera of patients with psoriasis. The serum levels of these miRNAs positively correlated with the PASI and CRP levels. We used all-trans retinoic acid to induce the differentiation of human promyelocytic leukemia HL-60 cells into neutrophil-like cells and found that the release of both miRNAs increased during differentiation. Furthermore, the release of miR-1290 was increased by TNF-α in neutrophil-like cells and human neutrophils. Treatment with the miR-1290 precursor promoted the proliferation of human keratinocytes, increased the proportion of S-phase cells, and upregulated the phosphorylation of extracellular signal-regulated kinase 1/2. These results suggest that miR-1290 plays a vital role in regulating neutrophil differentiation and keratinocyte proliferation and could be a serum marker of psoriasis severity.

Role for E-cadherin as an inhibitory receptor on epidermal gammadelta T cells.

E-cadherin is a homophilic adhesion molecule that maintains homotypic intercellular adhesion between epithelial cells such as epidermal keratinocytes. E-cadherin is also expressed on resident murine epidermal γδ T cells, known as dendritic epidermal T cells (DETCs), but they express another receptor for E-cadherin, α(E)(CD103)ß(7) integrin, as well. In this study, we analyzed functional differences between E-cadherin-mediated homophilic binding and heterophilic binding of α(E)ß(7) integrin to E-cadherin in heterotypic intercellular adhesion of DETCs to keratinocytes. E-cadherin, but not α(E)ß(7) integrin, was downregulated on activation of DETCs in vivo and in vitro. Short-term (1-h) adhesion of DETCs to keratinocytes in vitro was primarily mediated by α(E)ß(7) integrin, and blocking of the binding of α(E)ß(7) integrin to E-cadherin inhibited the lysis of keratinocytes by DETCs. Stable binding of E-cadherin on DETCs to plate-bound recombinant E-cadherin was observed only after 24-h culture in vitro. Cytokine production and degranulation by DETCs in response to suboptimal TCR cross-linking and mitogen stimulation were augmented by coligation of α(E)ß(7) integrin. In contrast, engagement of E-cadherin on DETCs with immobilized anti-E-cadherin Ab, plate-bound recombinant E-cadherin, and E-cadherin on keratinocytes inhibited DETC activation. Therefore, E-cadherin acts as an inhibitory receptor on DETCs, whereas α(E)ß(7) integrin acts as a costimulatory receptor. Differential expression of E-cadherin and α(E)ß(7) integrin on resting and activated DETCs, as well as their opposite functions in DETC activation, suggests that E-cadherin and α(E)ß(7) integrin on DETCs regulate their activation threshold through binding to E-cadherin on keratinocytes.

Granulocyte and monocyte adsorptive apheresis for pyoderma gangrenosum.

Pyoderma gangrenosum (PG), a chronic aseptic inflammatory skin disease characterized by skin ulcers with elevated and undermined borders, is resistant to conventional therapies. PG is elicited by activated neutrophils and macrophages and is often associated with systemic diseases such as inflammatory bowel disease, rheumatoid arthritis, aortitis syndrome, and hematopoietic disorders. This single-center study assessed the efficacy and safety of selectively depleting myeloid-lineage leukocytes in patients with PG. Patients with PG, aged 20 or over, received 5 or 10 treatment sessions of granulocyte and monocyte adsorption apheresis (GMA), once or twice a week. Treatment efficacy was assessed based on the rate of skin ulcer reduction, the visual analog scale of pain, and the physician's global assessment of the skin lesions. A complete response (CR) was obtained in eight patients, a nearly complete response (nCR) in three patients, and a partial response (PR) in two patients. In four of the other six, the disease remained stable (SD) and in two we observed disease progression (PD). No severe adverse events were recorded. Our results suggest that GMA is a useful and safe treatment modality for PG.

Novel AP3B1 compound heterozygous mutations in a Japanese patient with Hermansky-Pudlak syndrome type 2.

Hermansky-Pudlak syndrome type 2 (HPS2) is an extremely rare autosomal recessive inherited disease characterized by partial oculocutaneous albinism (OCA), bleeding diathesis due to a storage pool deficiency and immunodeficiency. The disorder is caused by disruption of the adapter protein 3 complex, which is involved in impaired intracellular vesicle transport. Here, we report the first case of a 1-year-old girl with HPS2 in Asia. She had no specific symptoms other than OCA and neutropenia. We analyzed her platelet function using transmission electron microscopy and a platelet aggregation test, cytotoxic degranulation assay of her natural killer (NK) cells and bleeding time, the results of which led to the diagnosis of HPS2. Although her NK-cell cytotoxic degranulation was impaired, she had not developed signs of hemophagocytic lymphohistiocytosis (HLH) or fibrosing lung disease. Molecular genetic analyses showed novel heterozygous mutations (c.188T>A [p.M63K] and c.2546>A [p.L849X]) in AP3B1. When examining patients with OCA, blood tests should be performed to confirm neutrophil count, bleeding time and platelet agglutination. When HPS2 is suspected, detailed immunological tests should be considered, and attention should be paid to HLH and pulmonary lesions immediately and over the long term.

Prominent dermal Langerhans cells in an Omenn syndrome patient with a novel mutation in the IL2RG gene.

Prominent dermal infiltration by Langerhans cells (LC) is a rare finding in patients with Omenn syndrome (OS). Here, we report the case study of a 7-month-old boy with OS and with prominent dermal infiltration by LC, which is a rare histological manifestation of the skin. Striking erythroderma appeared in the patient 2 weeks after birth. We also noted alopecia, lymphadenopathy, hepatosplenomegaly, eosinophilia and an elevated serum immunoglobulin E level with hypogammaglobulinemia. Peripheral blood flow cytometry showed the Tlow NK+ B+ immunophenotype and genetic analysis, a novel mutation in the IL2RG gene (c.337_339delTCT, p.Ser113del). The final diagnosis was that of OS. He responded well to an allograft umbilical cord blood transplantation that was performed when the patient was 8 months of age. We speculate that the LC accumulated in the dermis will eventually migrate to the regional lymph node, then stimulate autoreactive T cells by overpresenting antigens, thus causing OS-specific skin symptoms.

NKG2D triggers cytotoxicity in murine epidermal γδ T cells via PI3K-dependent, Syk/ZAP70-independent signaling pathway.

Murine epidermal γδ T cells, known as dendritic epidermal T cells (DETCs), survey tissue stress through the invariant T-cell receptor (TCR) and non-clonotypic receptors such as NKG2D. NKG2D signaling via the DAP10-phosphatidylinositol 3-kinase (PI3K) pathway directly stimulates cytotoxicity in natural killer (NK) cells and costimulates CD8(+) T cells to augment TCR signals. In activated murine NK cells, NKG2D signals also via the DAP12-Syk/ZAP70 pathway that triggers both cytotoxicity and cytokine production. It remains controversial whether NKG2D on DETCs is a primary activating receptor or functions only as a costimulatory receptor, and signaling pathways initiated by NKG2D ligation in DETCs have not been analyzed. We show that stimulation of short-term DETC lines with recombinant NKG2D ligands triggers degranulation (exocytosis of cytotoxic granules) via the PI3K-dependent signaling pathway, but does not induce cytokine production or Syk/ZAP70 activation. Coengagement of TCR or Syk/ZAP70 signaling was not crucial for DETC-mediated killing of NKG2D ligand-expressing target cells. Thus, NKG2D can function as a coactivating stress receptor that directly triggers cytotoxicity in DETCs, at least after priming, via the PI3K-dependent, Syk/ZAP70-independent signaling pathway.

Metastatic cutaneous squamous cell carcinoma treated successfully with surgery, radiotherapy and S-1/cisplatin chemotherapy.

Primary cutaneous squamous cell carcinoma (SCC) is a malignant tumor that arises from keratinizing cells of the epidermis or its appendages. We present a patient with cutaneous SCC on the left instep with metastases to multiple lymph nodes in the para-aortic, iliac and groin region. We chose a combination of surgery and concurrent chemoradiotherapy. The chemotherapeutic agent S-1/cisplatin was selected based on results of the histoculture drug response assay. The patient responded dramatically to this multidisciplinary treatment and complete remission was achieved.