Cancer-associated point mutations within the extracellular domain of PTPRD affect protein stability and HSPG interaction.

PTPRD, a well-established tumor suppressor gene, encodes the protein tyrosine phosphatase-type D. This protein consists of three immunoglobulin-like (Ig) domains, four to eight fibronectin type 3 (FN) domains, a single transmembrane segment, and two cytoplasmic tandem tyrosine phosphatase domains. PTPRD is known to harbor various cancer-associated point mutations. While it is assumed that PTPRD regulates cellular functions as a tumor suppressor through the tyrosine phosphatase activity in the intracellular region, the function of its extracellular domain (ECD) in cancer is not well understood. In this study, we systematically examined the impact of 92 cancer-associated point mutations within the ECD. We found that 69.6% (64 out of 92) of these mutations suppressed total protein expression and/or plasma membrane localization. Notably, almost all mutations (20 out of 21) within the region between the last FN domain and transmembrane segment affected protein expression and/or localization, highlighting the importance of this region for protein stability. We further found that some mutations within the Ig domains adjacent to the glycosaminoglycan-binding pocket enhanced PTPRD's binding ability to heparan sulfate proteoglycans (HSPGs). This interaction is proposed to suppress phosphatase activity. Our findings therefore suggest that HSPG-mediated attenuation of phosphatase activity may be involved in tumorigenic processes through PTPRD dysregulation.

Ultraviolet B irradiation increases the expression of cornulin and retepin in human skin xenotransplants.

Cornulin (CRNN) and repetin (RPTN) belong to the fused-type S100 protein family. Although these proteins have been reported to be expressed in the granular layer of the epidermis and have been suggested to be associated with barrier formation in the epidermis, their exact function remains unclear. This study examined the effects of ultraviolet B (UVB) irradiation on CRNN and RPTN expression in human skin xenotransplantation. The CRNN expression increased in the granular layer of UVB-irradiated skin 2 days after UVB irradiation compared to that in sham-irradiated skin. Interestingly, CRNN signals were observed not only in the cytoplasm, but also in the peripheral regions of granular keratinocytes. In contrast, RPTN was rarely expressed in sham-irradiated skin; however, RPTN signals were markedly increased in the granular layer of the UVB-irradiated skin. In addition, activation of ERK1/2 and STAT3 was observed in UVB-irradiated skin. Accordingly, the present study demonstrated that CRNN and RPTN are novel proteins whose expression can be increased by UVB irradiation. The activation of ERK1/2 and STAT3 may be associated with the regeneration of a UVB-damaged epidermis, and CRNN and RPTN may be induced to repair any dysfunction in the epidermal barrier during this regeneration process.

Expression of hornerin in skin lesions of atopic dermatitis and skin diseases.

We have previously identified the filaggrin (FLG)-like protein, hornerin (HRNR). Recently, there have been several reports regarding the relationship between HRNR and atopic dermatitis (AD). In the present study, we examined HRNR expression in the skin lesions of seven unrelated patients with AD to clarify the role of HRNR in the pathogenesis of AD. HRNR was detected in chronic AD lesions (n = 4), whereas no HRNR signals were observed in acute AD lesions (n = 3). HRNR was detected in the cytokeratin 6-expressing epidermis, and Ki67-positive keratinocytes were more abundant in the HRNR-positive epidermis. These findings suggest that HRNR may be associated with epidermal hyperproliferation in AD lesions. Next, we examined HRNR expression in skin diseases associated with hyperkeratosis. HRNR signals were irregularly observed in different cells from those expressing FLG in epidermolytic ichthyosis and actinic keratosis. Therefore, HRNR may play a unique role in the molecular process of cornification.

Dysregulation of Amphiregulin stimulates the pathogenesis of cystic lymphangioma.

Along with blood vessels, lymphatic vessels play an important role in the circulation of body fluid and recruitment of immune cells. Postnatal lymphangiogenesis commonly occurs from preexisting lymphatic vessels by sprouting, which is induced by lymphangiogenic factors such as vascular endothelial growth factor C (VEGF-C). However, the key signals and cell types that stimulate pathological lymphangiogenesis, such as human cystic lymphangioma, are less well known. Here, we found that mouse dermal fibroblasts that infiltrate to sponges subcutaneously implanted express VEGF-D and sushi, Von Willebrand factor type A, EGF, and pentraxin domain containing 1 (SVEP1) in response to PDGFRß signal. In vitro, Pdgfrb knockout (ß-KO) fibroblasts had reduced expression of VEGF-D and SVEP1 and overproduced Amphiregulin. Dysregulation of these three factors was involved in the cyst-like and uneven distribution of lymphatic vessels observed in the ß-KO mice. Similarly, in human cystic lymphangioma, which is one of the intractable diseases and mostly occurs in childhood, fibroblasts surrounding cystic lymphatics highly expressed Amphiregulin. Moreover, fibroblast-derived Amphiregulin could induce the expression of Amphiregulin in lymphatic endothelial cells. The dual source of Amphiregulin activated EGFR expressed on the lymphatic endothelial cells. This exacerbation cascade induced proliferation of lymphatic endothelial cells to form cystic lymphangioma. Ultimately, excessive Amphiregulin produced by fibroblasts surrounding lymphatics and by lymphatic endothelial cells per se results in pathogenesis of cystic lymphangioma and will be a fascinating therapeutic target of cystic lymphangioma.

Altered expression of S100 fused-type proteins in an atopic dermatitis skin model.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with elevated interleukin (IL)-4 and IL-13 signatures and extensive barrier dysfunction, which is correlated with the downregulation of filaggrin (FLG). FLG is a member of the S100 fused-type protein family and this family also includes cornulin (CRNN), filaggrin-2 (FLG2), hornerin (HRNR) repetin (RPTN), trichohyalin (TCHH) and trichohyalin-like 1 (TCHHL1). The present study aimed to examine the effects of IL-4 and IL-13 and the downregulation of FLG on the expression of S100 fused-type proteins using a three-dimensional (3D) AD skin model by immunohistochemical study and quantitative polymerase chain reaction. In the 3D AD skin model, which was generated by a stimulation of recombinant IL-4 and IL-13, the expression of FLG, FLG2, HRNR and TCHH was decreased, while that of RPTN was increased in comparison to the 3D control skin. In the FLG knockdown (KD) 3D skin model, which was generated using FLG siRNA, the expression of HRNR was increased. The expression of the other proteins did not differ to a statistically significant extent. The expression of fused-S100 type protein family members may differ in AD skin. This suggests that these proteins play different roles in the pathogenesis of AD.

The second nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan.

The present study compared trends in antimicrobial resistance patterns in pathogens isolated from skin and soft-tissue infections (SSTIs) in Japan with those of a nationwide survey conducted in 2013. Three organisms that caused most of the SSTIs were collected from 12 dermatology departments in medical centers and 12 dermatology clinics across Japan between April 2019 and August 2020. A total of 390 strains, including 267 Staphylococcus aureus, 109 coagulase-negative staphylococci (CNS), and 14 Streptococcus pyogenes strains were submitted to a central laboratory for antimicrobial susceptibility testing. Patient demographic and clinical information was collated. Methicillin-resistant S. aureus (MRSA) was detected in 25.8% (69/267) of the S. aureus strains. The prevalence of MRSA between the present study and the 2013 survey did not differ significantly. Furthermore, there were no significant differences in MIC values and susceptibility patterns of the MRSA strains to other agents, regardless of a history of hospitalization within 1 year or invasive medical procedures. Methicillin-resistant CNS (MRCNS) was detected in 48.6% (53/109) of CNS isolates, higher than the 35.4% prevalence in the 2013 survey. This difference could be attributed to the heterogeneity in the members of the MRCNS, which comprises multiple staphylococci species, between the 2013 and 2019 surveys. However, it was noted that the susceptibility profiles of the MRCNS to each antibiotic were not significantly different from those identified in the 2013 survey. Most strains of S. pyogenes were susceptible to each antibiotic, similar to the 2013 survey. Continuous monitoring of trends in pathogen and susceptibility profiles is important to advise local public health efforts regarding the appropriate treatment of SSTIs.

Detection of FIP1L1-PDGFRA fusion gene-positive cells in the skin lesion of a patient with hypereosinophilic syndrome.

Hypereosinophilic syndrome (HES) is a heterogeneous group of diseases, characterized by persistent hypereosinophilia and end-organ damage. The FIP1L1-PDGFRA (F/P) fusion gene is found in 3-25% of patients with HES and is an oncogenic driver of myeloid neoplasms with clonal eosinophilia. Although cutaneous symptoms are the most common type of symptom in patients who have F/P fusion gene-positive HES (F/P HES), histological reports are limited. We herein present the case of a 78-year-old man with erythematous macules and severe pruritus on his trunk and extremities. Laboratory investigations revealed marked eosinophilia and elevated serum vitamin B12. A histological examination showed massive infiltration of eosinophils and mast cells around the vessels in the upper dermis. Fluorescence in situ hybridization revealed F/P fusion genes in nuclei in the peripheral blood and the skin lesion. The patient was diagnosed with F/P HES, and showed an excellent clinical and haematological response to imatinib.

Overexpression of D-dopachrome tautomerase increases ultraviolet B irradiation-induced skin tumorigenesis in mice.

Ultraviolet irradiation (UV) exposure is the leading factor underlying the development of skin malignancies. D-dopachrome tautomerase (D-DT), a functional homolog of macrophage migration inhibitory factor (MIF), has functional similarities to MIF. However, its role, unlike the role of MIF in photocarcinogenesis, is unknown. We therefore explored the role of D-DT in photocarcinogenesis by developing D-DT transgenic (D-DT Tg) mice and provided a research model for future studies targeting D-DT. Chronic UVB exposure accelerated tumor development in D-DT Tg mice compared with wild-type (WT) mice, with a higher incidence of tumors observed in D-DT Tg mice than in WT mice. In D-DT Tg irradiated mouse keratinocytes, the p53, PUMA, and Bax expression was lower than that in WT mice. These results indicate that D-DT Tg overexpression confers prevention against UVB-induced apoptosis in keratinocytes. Taken together, these findings support D-DT as a functionally important cytokine in photocarcinogenesis and potential therapeutic target for the prevention of photocarcinogenesis.

Non-canonical Regulation of EGFR by the Air Pollutant 9,10-Phenanthrenequinone.

9,10-Phenanthrenequinone (9,10-PQ), a polycyclic aromatic hydrocarbon that is present in air pollutants, such as diesel exhaust gas and PM2.5, causes the production of excess reactive oxygen species. 9,10-PQ was recently shown to induce the activation of epidermal growth factor receptor (EGFR) by inhibiting protein tyrosine phosphatase 1B. In the present study, we focused on the non-canonical regulation of EGFR, including negative feedback and internalization. In contrast to previous findings, 9,10-PQ inhibited the constitutive tyrosine phosphorylation of EGFR via the mitogen-activated protein extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK)-mediated phosphorylation of Thr-669 in EGFR-overexpressing A431 and MDA-MB-468 cells. In addition, 9,10-PQ induced the clathrin-mediated endocytosis of EGFR via the p38 phosphorylation of Ser-1015 in HeLa and A549 cells. These results revealed that 9,10-PQ strongly induced the non-canonical regulation of EGFR by activating mitogen-activated protein kinase (MAPK).

Identification of a de novo mutation of the elastin gene by targeted exome sequencing in autosomal dominant cutis laxa.

Cutis laxa (CL) comprises a heterogeneous group of entities mainly classified as X-linked, autosomal dominant and recessive forms, which differ in severity. We encountered a CL baby with no familial history. We performed targeted exome sequencing, and detected a de novo heterozygous frameshift mutation in the elastin gene of the baby.

Involvement of α-Melanocyte-Stimulating Hormone-Thromboxane A2 System on Itching in Atopic Dermatitis.

α-Melanocyte-stimulating hormone (α-MSH) is an endogenous peptide hormone involved in cutaneous pigmentation in atopic dermatitis (AD) with severe itching. α-MSH elicits itch-related responses in mice. We, therefore, investigated whether α-MSH was involved in itching in AD. In the skin of AD patients and mice with atopy-like dermatitis, α-MSH and the prohormone convertase 2, which is the key processing enzyme for the production of α-MSH, were distributed mainly in keratinocytes. In the skin of mice with dermatitis, melanocortin receptors (MC1R and MC5R) were expressed at the mRNA level and were distributed in the dermis. In the dorsal root ganglion of mice with dermatitis, mRNAs encoding MC1R, MC3R, and MC5R were also expressed. MC1R antagonist agouti-signaling protein inhibited spontaneous scratching in mice with dermatitis. In healthy mice, intradermal α-MSH elicited itch-associated responses, which were inhibited by thromboxane (TX) A2 receptor antagonist ONO-3708. In mouse keratinocytes, α-MSH increased the production of TXA2, which was inhibited by adenylyl cyclase inhibitor SQ-22536 and Ca2+ chelator EGTA. In mouse keratinocytes treated with siRNA for MC1R and/or MC5R, α-MSH-induced TXA2 production was decreased. α-MSH increased intracellular Ca2+ ion concentration in dorsal root ganglion neurons and keratinocytes. These results suggest that α-MSH is involved in itching during AD and may elicit itching through the direct action of primary afferents and TXA2 production by keratinocytes.

The regulation of protein kinase casein kinase II by apigenin is involved in the inhibition of ultraviolet B-induced macrophage migration inhibitory factor-mediated hyperpigmentation.

Ultraviolet (UV) radiation elicits melanogenesis and pigmentation in the skin. Apigenin (4',5,7-trihydroxyflavone [AGN]) is a plant flavone contained in various herbs, fruits, and vegetables. We herein investigated antimelanogenic properties of AGN and the molecular mechanisms of the action of AGN. In UVB-treated mice, AGN inhibited cutaneous hyperpigmentation and macrophage migration inhibitory factor (MIF) expression as a melanogenesis-related key factor. In mouse keratinocytes, AGN inhibited the expression of MIF and also the related factors (e.g., stem cell factor and proteinase-activated receptor 2) induced by MIF. In addition to ellagic acid as a casein kinase II (CK2) inhibitor, AGN suppressed CK2 enzymatic activity and UVB-induced CK2 expression and subsequent phosphorylation of IκB and MIF expression. These results suggest that AGN inhibits UVB-induced hyperpigmentation through the regulation of CK2-mediated MIF expression in keratinocytes.

Erythropoietic Protoporphyria in a Japanese Population.

Erythropoietic protoporphyria is caused by a partial deficiency of ferrochelatase, which is the last enzyme in the heme biosynthesis pathway. In a typical erythropoietic protoporphyria, photosensitivity initially appears, following the first exposure to the sun in early infancy or childhood. Erythropoietic protoporphyria has been reported worldwide, but there is a regional variation in its epidemiology. Approximately 20% of the Japanese patients were recognized to have symptoms of erythropoietic protoporphyria after 10 years of age. Physicians occasionally encounter Japanese patients with erythropoietic protoporphyria, mild symptoms and no FECH gene mutations. The homozygous IVS3-48C polymorphism may cause a mild phenotype of the erythropoietic protoporphyria via a slight increase in protoporphyrin. The frequency of the homozygous IVS3-48C polymorphism in the Japanese population is higher than that observed in European countries. Japanese type of erythropoietic protopor-phyria shows a characteristic phenotype of the late onset and mild symptoms compared to the Caucasian erythropoietic protoporphyria. This review describes the characteristics of erythropoietic protoporphyria in Japanese patients.

Inflammatory cytokine-mediated induction of serine racemase in atopic dermatitis.

Serine racemase (SR) is an enzyme that catalyses the synthesis of d-serine, an endogenous coagonist for N-methyl-D-aspartate (NMDA)-type glutamate receptor in the central nervous system. Our previous study demonstrated that SR was expressed in the epidermis of wild-type (WT) mice but not in SR knockout (KO) mice. In addition, SR immune-reactivity was only found in the granular and cornified layers of the epidermis in WT mice. These findings suggested that SR is involved in the differentiation of epidermal keratinocytes and the formation of the skin barrier. However, its role in skin barrier dysfunction such as atopic dermatitis (AD) remains elusive. AD is a chronic inflammatory disease of skin, and the clinical presentation of AD has been reported to be occasionally associated with psychological factors. Therefore, this study examined the content of d-serine in stratum corneum in AD patients and healthy controls using a tape-stripping method. Skin samples were collected from the cheek and upper arm skin of AD patient's lesion and healthy individuals. The d-serine content was significantly increased in the involved skin of AD in comparison with healthy individuals. An immunohistochemical analysis also revealed an increased SR expression in the epidermis of AD patients. Furthermore, the SR expression in cultured human keratinocytes was significantly increased by the stimulation with tumour necrosis factor -α or macrophage migration inhibitory factor. Taken together, these findings suggest that d-serine expressed particularly strongly in AD lesional skin and that the SR expression in the keratinocytes is linked to inflammatory cytokines.

Nerve alterations showing autophagy in 2 patients with lichen aureus.

Lichen aureus is a rare, chronic, persistent purpuric dermatosis clinically characterized by striking yellow- to bronze-colored lesions. Histologically, lichen aureus differs from other pigmented purpuric dermatoses in containing dense, band-like infiltrates closely associated with the epidermis. This report describes 2 patients with lichen aureus, a 20-year-old woman with a lesion on her right arm and a 51-year-old man with a lesion on the right side of his groin. Skin biopsy specimens revealed almost identical findings in both patients, including dense band-like infiltrates containing lymphocytes, histiocytes with hemosiderin deposits scattered extravasated red blood cells and nerve alterations at the dermo-epidermal interface. The nerves within the lesions were filled with granules, which stained positive with antibody to microtubule-associated protein 1A/1B-light chain 3, suggesting autophagy within the nerves. These altered nerves were present only in areas of band-like dermal lymphocytic infiltration. Electron microscopy of the lesions showed the accumulation of autophagosomes in Schwann cells.

Role of macrophage migration inhibitory factor in heat-induced apoptosis in keratinocytes.

In human skin, keratinocytes are constantly challenged by adverse influences, such as hot and cold temperatures; however, the effects of heat on apoptosis induction in keratinocytes are not well understood. Macrophage migration inhibitory factor (MIF) is a potent cytokine that overcomes p53 function by suppressing its transcriptional activity. Here, we evaluated the effects of MIF on hyperthermia (HT)-induced apoptosis in MIF-deficient [knockout (KO)] and MIF-transgenic (Tg) mouse keratinocytes. Cells were exposed to HT at 44°C, and increased apoptosis was observed in MIF-KO and wild-type (WT) cells compared with MIF-Tg cells. To determine the mechanism, MIF-mediated changes in the cellular p53 level and its effects on p53-dependent death signaling (Bax and p21) and JNK signaling (p-JNK, JNK, p-Bad, and Bad) were investigated. MIF-Tg cells exhibited substantially decreased levels of p53 after HT treatment compared with WT and MIF-KO cells. In addition, HT treatment caused decreased expression of p-JNK and p-Bad in MIF-Tg cells; however, no such changes were observed in MIF-KO and WT cells. These results showed that the activation of JNK (p-JNK and p-Bad) and p53 may be involved in HT-induced apoptosis in keratinocytes and that enhanced endogenous MIF expression suppressed apoptosis.-Yoshihisa, Y., Rehman, M. U., Kondo, T., Shimizu, T. Role of macrophage migration inhibitory factor in heat-induced apoptosis in keratinocytes.

The first nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan.

To investigate the trends of antimicrobial resistance in pathogens isolated from skin and soft-tissue infections (SSTI) at dermatology departments in Japan, a Japanese surveillance committee conducted the first nationwide survey in 2013. Three main organisms were collected from SSTI at 30 dermatology departments in medical centers and 10 dermatology clinics. A total of 860 strains - 579 of Staphylococcus aureus, 240 of coagulase-negative Staphylococci, and 41 of Streptococcus pyogenes - were collected and shipped to a central laboratory for antimicrobial susceptibility testing. The patient profiles were also studied. Among all 579 strains of S. aureus, 141 (24.4%) were methicillin-resistant (MRSA). Among 97 Staphylococcus epidermidis strains, 54 (55.7%) were methicillin-resistant (MRSE). MRSA and MRSE were more frequently isolated from inpatients than from outpatients. Furthermore, these methicillin-resistant strains were also isolated more frequently from patients with histories of taking antibiotics within 4 weeks and hospitalization within 1 year compared to those without. However, there were no significant differences in MIC values and susceptibility patterns of the MRSA strains between patients with a history of hospitalization within 1 year and those without. Therefore, most of the isolated MRSA cases at dermatology departments are not healthcare-acquired, but community-acquired MRSA. S. pyogenes strains were susceptible to most antibiotics except macrolides. The information in this study is not only important in terms of local public health but will also contribute to an understanding of epidemic clones of pathogens from SSTI.