Kazunori Urabe

A second tyrosinase-related protein, TRP-2, is a melanogenic enzyme termed DOPAchrome tautomerase.

The production of melanin pigment in mammals requires tyrosinase, an enzyme which hydroxylates the amino acid tyrosine to DOPA (3,4‐dihydroxyphenylalanine), thus allowing the cascade of reactions necessary to synthesize that biopolymer. However, there are other regulatory steps that follow the action of tyrosinase and modulate the quantity and quality of the melanin produced. DOPAchrome tautomerase is one such melanogenic enzyme that isomerizes the pigmented intermediate DOPAchrome to DHICA (5,6‐dihydroxyindole‐2‐carboxylic acid) rather than to DHI (5,6‐dihydroxyindole), which would be generated spontaneously. This enzyme thus regulates a switch that controls the proportion of carboxylated subunits in the melanin biopolymer. Efforts to clone the gene for tyrosinase have resulted in the isolation of a family of tyrosinase related genes which have significant homology and encode proteins with similar predicted structural characteristics. Using specific antibodies generated against synthetic peptides encoded by unique areas of several of those proteins, we have immuno‐affinity purified them and studied their melanogenic catalytic functions. We now report that TRP‐2 (tyrosinase related protein‐2), which maps to and is mutated at the slaty locus in mice, encodes a protein with DOPAchrome tautomerase activity.

Tyrosinase related protein 1 (TRP1) functions as a DHICA oxidase in melanin biosynthesis.

Several genes critical to the enzymatic regulation of melanin production in mammals have recently been cloned and mapped to the albino, brown and slaty loci in mice. All three genes encode proteins with similar structures and features, but with distinct catalytic capacities; the functions of two of those gene products have previously been identified. The albino locus encodes tyrosinase, an enzyme with three distinct melanogenic functions, while the slaty locus encodes tyrosinase‐related protein 2 (TRP2), an enzyme with a single specific, but distinct, function as DOPAchrome tautomerase. Although the brown locus, encoding TRP1, was actually the first member of the tyrosinase gene family to be cloned, its catalytic function (which results in the production of black rather than brown melanin) has been in general dispute. In this study we have used two different techniques (expression of TRP1 in transfected fibroblasts and immunoaffinity purification of TRP1 from melanocytes) to examine the enzymatic function(s) of TRP1. The data demonstrate that the specific melanogenic function of TRP1 is the oxidation of 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA) to a carboxylated indole‐quinone at a down‐stream point in the melanin biosynthetic pathway. This enzyme activity appears to be essential to the further metabolism of DHICA to a high molecular weight pigmented biopolymer.

The inherent cytotoxicity of melanin precursors: A revision

The potential cytotoxicity of the melanogenic intermediates DOPA, (L-3,4-dihydroxyphenylalanine) and DHI (5,6-dihydroxyindole) has long been recognized and exploited as a targeting concept in experimental melanoma therapy. In recent years, however, a novel branchpoint in the melanin biosynthetic pathway has been shown to divert the metabolism of DOPAchrome to a carboxylated derivative termed DHICA (DHI-2-carboxylic acid) rather than to DHI. In order to evaluate the biological implications of this regulatory control, we have reexamined the inherent cytotoxicity of DHICA versus DHI on different cell lines. We found that under the usual conditions of the biological assay, the apparent cytotoxicity of the two indoles reflect their instability in the culture medium, the less stable DHI being generally more toxic than DHICA to melanoma cells and nonmelanocytic cells. Moreover, the observed cytotoxic effects increased with the time of incubation and were markedly reduced by the addition of catalase to the medium, suggesting that they were probably due to the generation of reactive oxygen species (particularly H2O2) during the autoxidation of the melanin precursors outside the cells. To circumvent this problem, we then tested the diacetylated derivatives of DHI and DHICA (DAI and DAICA) which are sufficiently stable until taken up into the cells whereupon they may be converted by endogenous esterases back to the parent indoles. Although DAI proved to be cytotoxic for nonmelanocytic cells, it had no detectable activity on melanoma cells, whereas DAICA showed no effect on any of the cells examined. These results, when combined with other studies, point to a reconsideration of the inherent cytotoxicity of the 5,6-dihydroxyindoles, as well as DOPA, to melanin producing cells.

Rapid effects of olopatadine hydrochloride on the histamine-induced skin responses.

Olopatadine hydrochloride is one of the second‐generation nonsedating antihistamines that are used for treating allergic disorders such as urticaria, rhinitis, and atopic dermatitis. We examined the inhibitory effects of this drug on the flare and wheal responses induced by histamine iontophoresis at 30, 60, and 90 min after oral administration in a double‐blind, cross‐over, and placebo‐controlled study. Olopatadine hydrochloride significantly inhibited the histamine‐induced flare and wheal responses as early as 60 min after oral administration when compared with placebo. Significant inihibitory effects of olopatadine hydrochloride on the itch responses were seen at 90 min after administration. Thus, olopatadine hydrochloride exhibited a very rapid and potent antihistamine effect on the histamine‐induced skin responses.

Migration of keratinocytes is impaired on glycated collagen I

Advanced glycation end products are the chemical modification of proteins induced by sugars in a hyperglycemic condition. Extracellular matrix proteins are prominent targets of nonenzymatic glycation because of their slow turnover rates. The aim of this study was to investigate the influence of nonenzymatic glycation of type I collagen on the migration of keratinocytes. The migration of keratinocytes was dramatically promoted on native type I collagen‐coated dishes compared with that on uncoated dishes. When type I collagen was glycated with glycolaldehyde, large amounts of advanced glycation end products were produced; the glycated collagen I‐coated dishes did not promote the migration of keratinocytes. Glycated collagen I did not affect the proliferative capacity of keratinocytes. However, the adhesion of keratinocytes to glycated collagen I was profoundly diminished in a glycation intensity‐dependent manner. α2β1 integrin is responsible for the migration and adhesion of keratinocytes to type I collagen. Pretreatment with glycated collagen I did not affect the expression level or functional activity of α2β1 integrin on keratinocytes. These findings suggest that in the presence of glycated collagen I, keratinocytes lose their adhesive and migratory abilities. As the glycation did not modify the α2β1 integrin on keratinocytes, it is suggested that glycation may diminish the binding capacity of type I collagen.

Activated and mature CD83-positive dendritic cells and interferon-γ-positive cells in skin eruptions of secondary syphilis

Dendritic cells are considered to be the most potent antigen-presenting cells, and CD83 is expressed at a high level in immunocompetent, activated and mature dendritic cells. Various pathogens can activate and modulate the function of dendritic cells. The presence of activated and mature dendritic cells in skin lesions of secondary syphilis has never been reported. In the present study, an immunohistochemical technique was used to determine the exact tissue distributions of CD83+ dendritic cells and interferon-gamma+ cells in skin lesions of patients with secondary syphilis. Immunohistochemical staining was performed by using formalin-fixed, paraffin-embedded sections. A small but significant subpopulation of CD83+ dendritic cells was found in the dermis. CD83+ dendritic cells were in close contact with lymphocytes. High-intensity staining of CD83 antigens was detected not only on the surface but also in the cytoplasm of dendritic cells. Infiltrating mononuclear cells were stained positively for CD4 or CD8, with CD8+ cells always being in the majority. A small number of interferon-gamma+ cells resembling mononuclear lymphoid cells were detected in all samples. These results provide in vivo support for the hypothesis that dendritic cells are activated by Treponema pallidum and that thus activated and mature CD83+ dendritic cells may play a role in the Th1 response in secondary syphilis.

Systemic varicella zoster virus reinfection in a case of angioimmunoblastic T‐cell lymphoma

Angioimmunoblastic T‐cell lymphoma (AITL) is a rare subtype of peripheral T‐cell lymphoma that causes immunological disorders such as immunosuppression, autoimmune disease‐like symptoms and allergy. We report a case of a 67‐year‐old man with AITL who had a serious varicella zoster virus (VZV) reinfection that appeared clinically to be varicella. Forty percent of cases of AITL are associated with skin rash. A variety of cutaneous manifestations have been reported; however, the majority are macropapular eruptions that are often diagnosed as drug associated. Our study emphasizes the need to correctly diagnose opportunistic infections, such as the varicella that is documented in our patient, at early stages in AITL.

Generalised granuloma annulare associated with myelodysplastic syndrome

Granuloma annulare (GA) is a benign inflammatory dermatosis. Several systemic diseases can be associated with generalised GA, including diabetes mellitus, thyroid disease, hepatitis B and C, Borrelia infection, and neoplastic diseases. We report a patient with generalised GA which was the initial manifestation of myelodysplastic syndrome (MDS).A 62-year-old woman presented with an eight-month history of disseminated red papules with mild pruritus on the trunk and extremities (figure 1A). The papules [...]

Late onset suppurative lymphadenopathy induced by bacillus Calmette–Guérin (BCG) vaccination

1 Zonios DI, Falloon J, Bennett JE et al. Idiopathic CD4+ lymphocytopenia: natural history and prognostic factors. Blood 2008; 112: 287–294. 2 de Oliveira WR, Festa Neto C, Rady PL, Tyring SK. Clinical aspects of epidermodysplasia verruciformis. J Eur Acad Dermatol Venereol 2003; 17: 394–398. 3 Fischer LA, Norgaard A, Permin H et al. Multiple flat warts associated with idiopathic CD4-positive T lymphocytopenia. J Am Acad Dermatol 2008; 58: S37–S38. 4 Tobin E, Rohwedder A, Holland SM, Philips B, Carlson JA. Recurrent ‘sterile’ verrucous cyst abscesses and epidermodysplasia verruciformis-like eruption associated with idiopathic CD4 lymphopenia. Br J Dermatol 2003; 149: 627–633. 5 Paavonen J. Human papillomavirus infection and the development of cervical cancer and related genital neoplasias. Int J Infect Dis 2007; 11: S3–S9. 6 Minero MV, Marin M, Cercenado E, Rabadan PM, Bouza E, Munoz P. Nocardiosis at the turn of the century. Medicine (Baltimore) 2009; 88: 250–261. 7 Venzor J, Hua Q, Bressler RB, Miranda CH, Huston DP. Behcet’s-like syndrome associated with idiopathic CD4+ T-lymphocytopenia, opportunistic infections, and a large population of TCR alpha beta+ CD4CD8T cells. Am J Med Sci 1997; 313: 236–238. 8 Zaharatos GJ, Behr MA, Libman MD. Profound T-lymphocytopenia and cryptococcemia in a human immunodeficiency virus-seronegative patient with disseminated tuberculosis. Clin Infect Dis 2001; 33: E125–E128.

Molecular biological evaluation of sentinel lymph nodes of melanoma patients

当科では2001年4月～2004年8月までに, 33例のメラノーマ患者にセンチネルリンパ節生検を施行した。色素法, リンパシンチそしてガンマプローブも併用しており, センチネルリンパ節の同定率は31例 (93.9%) で, 平均個数は1.94個だった。ガンマプローブを使用することで, より高い同定率が得られた。センチネル陽性例は7例 (21.2%) であり, 7例中6例に所属リンパ節郭清を施行した。郭清しなかった1例にin-transit metastasisを認めたが, 郭清した6例には現在まで転移を認めていない。またセンチネル陰性例のうち, 術後転移を認めたのは2例だった。診断はHE染色, 複数の抗体を用いた免疫染色そしてRT-PCR法によって検討しており, 診断の精度を高めるために複数の方法を用いることは有用であると考えた。