The genetic alterations identified in melanomas at different sites and with different levels of sun exposure indicate that there are distinct genetic pathways in the development of melanoma and implicate CDK4 and CCND1 as independent oncogenes in melanomas without mutations in BRAF or N-RAS.

A synthetic Nod2 agonist, muramyldipeptide (MDP), and two Nod1 agonists, FK565 and FK156, mimic the bacterial peptidoglycan moiety and are powerful adjuvants that induce cell-mediated immunity, especially delayed-type hypersensitivity. In this study, we used human dendritic cell ( Freund's complete adjuvant (10), which contains killed mycobacterial cells, has been widely used as a powerful adjuvant to induce cell-mediated immunity, represented by delayed-type hypersensitivity, as well as to enhance humoral immunity against test antigens in laboratory animals. A series of studies on the mycobacterial component responsible for the unique adjuvant activity of Freund's complete adjuvant revealed that Wax D is the active entity, being composed of peptidoglycan (PGN), arabinogalactan, and mycolic acid, and thereafter the PGN moieties of various bacteria were revealed to also be active in this respect (37). In the mid-1970s, the minimal essential structure of PGN for adjuvant activity was demonstrated to be muramyldipeptide (MDP; N-acetylmuramyl-Lalanyl-D-isoglutamine) by use of a chemically synthesized compound (8,24). MDP reproduced various bioactivities of PGN (39,40), although the activities of MDP were generally weaker than those of PGN and MDP was scarcely active in some experiments. PGN activates macrophages via Toll-like receptor 2 (TLR2) (35,42,51), whereas MDP lacks TLR2-agonistic activity (41,46,49,51).Fleck et al. (9) reported that desmuramylpeptide (DMP)containing meso-diaminopimelic acid (meso-DAP) was also active as an adjuvant to induce cell-mediated immunity. meso-DAP-type PGN is found in most gram-negative bacteria and in some gram-positive bacteria, including mycobacteria, while most gram-positive bacteria such as Staphylococcus and Streptococcus strains possess L-lysine (Lys)-type PGN (34). In their report, Fleck et al. (9) suggested by mistake that Lys-type DMPs were similarly active to meso-DAP-type DMPs in this respect. Thereafter, French and Japanese investigators chemically synthesized adjuvant-active meso-DAP-type DMPs (1).In the course of the study, the Fujisawa Pharmaceutical Company generated a DMP, D-lactyl-L-alanyl-␥-D-glutamyl-meso-DAP-glycine, by chemically mimicking a counterpart purified from fermentation broths of Streptomyces strains, and this DMP was designated FK156; the company then synthesized various derivatives of FK156, among which the leading compound was FK565, or heptanoyl-D-glutamyl-meso-DAP-␥-Dalanine (13). Recently, an intracellular molecule carrying nucleotidebinding oligomerization domain 2 (Nod2) was revealed to be a receptor for MDP (12,17). Thereafter, another Nod family molecule, Nod1, was demonstrated to recognize a PGN motif containing meso-DAP (7, 11). We found that FK156 and FK565 were Nod1 agonists similar to ␥-D-glutamyl-meso-DAP (45), which is the minimal active structure of a Nod1 agonist (7,22).

Atopic dermatitis is increasing worldwide in correlation with air pollution. Various organic components of pollutants activate the transcription factor AhR (aryl hydrocarbon receptor). Through the use of AhR-CA mice, whose keratinocytes express constitutively active AhR and that develop atopic-dermatitis-like phenotypes, we identified Artn as a keratinocyte-specific AhR target gene whose product (the neurotrophic factor artemin) was responsible for epidermal hyper-innervation that led to hypersensitivity to pruritus. The activation of AhR via air pollutants induced expression of artemin, alloknesis, epidermal hyper-innervation and inflammation. AhR activation and ARTN expression were positively correlated in the epidermis of patients with atopic dermatitis. Thus, AhR in keratinocytes senses environmental stimuli and elicits an atopic-dermatitis pathology. We propose a mechanism of air-pollution-induced atopic dermatitis via activation of AhR.

Since mammalian skin expresses the enzymatic apparatus for melatonin synthesis, it may be an extrapineal site of melatonin synthesis. However, evidence is still lacking that this is really the case in situ. Here, we demonstrate melatonin-like immunoreactivity (IR) in the outer root sheath (ORS) of mouse and human hair follicles (HFs), which corresponds to melatonin, as shown by radioimmunoassay and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The melatonin concentration in organ-cultured mouse skin, mouse vibrissae follicles, and human scalp HFs far exceeds the respective melatonin serum level and is significantly increased ex vivo by stimulation with norepinephrine (NE), the key stimulus for pineal melatonin synthesis. By real-time PCR, transcripts for the melatonin membrane receptor MT2 and for the nuclear mediator of melatonin signaling, retinoid orphan receptor alpha (ROR)alpha, are detectable in murine back skin. Transcript levels for these receptors fluctuate in a hair cycle-dependent manner, and are maximal during apoptosis-driven HF regression (catagen). Melatonin may play a role in hair cycle regulation, since its receptors (MT2 and RORalpha) are expressed in murine skin in a hair cycle-dependent manner, and because it inhibits keratinocyte apoptosis and down-regulates ERalpha expression. Therefore, the HF is both, a prominent extrapineal melatonin source, and an important peripheral melatonin target tissue. Regulated intrafollicular melatonin synthesis and signaling may play a previously unrecognized role in the endogenous controls of hair growth, for example, by modulating keratinocyte apoptosis during catagen and by desensitizing the HF to estrogen signaling. As a prototypic neuroectodermal-mesodermal interaction model, the HF can be exploited for dissecting the obscure role of melatonin in such interactions in peripheral tissues.

After application of haptens to the skin, Langerhans cells (LC), i.e. immature dendritic cells (DC) in the skin, move to secondary lymphoid organs to sensitize naive T cells. During this process, LC become mature DC with augmented expression of various co-stimulatory molecules and MHC class II antigens. In this scenario, however, critical questions remain as to what kind of chemicals can induce this maturation process through what kind of mechanisms. To clarify these questions, we used monocyte-derived CD1a+ DC instead of LC since LC maturated spontaneously in vitro culture. After we confirmed that monocyte-derived DC showed at least phenotypic characteristics and a response to TNF-alpha similar to LC, we added various chemicals, i.e., dinitrochlorobenzene (DNCB), trinitrochlorobenzene (TNCB), NiCl2, ZnCl2, sodium dodecyl sulfate (SDS), or benzalkonium chloride (BC), to a culture of purified monocyte-derived CD1a+ DC. Of these chemicals, only NiCl2 and DNCB significantly increased the surface expression of CD54, CD86, HLA-DR antigen, and interleukin (IL)-1 beta production, while SDS, BC, or ZnCl2 could not augment them, except for weak augmentation of CD86 expression by SDS. The increase in the expression of CD86 induced by NiCl2 or DNCB was most remarkable, being observed in DC from almost all the subjects we examined. TNCB could also induce responses similar to those induced with DNCB, but the number of subjects whose DC responded to it was far less than that of subjects whose DC responded to NiCl2 or DNCB. In spite of the augmented CD86 expression on DC treated with DNCB or NiCl2, these chemicals induced different responses of DC in their expression of CD54 and HLA-DR and the production of IL-6 and tumor necrosis factor (TNF)-alpha. In addition, the up-regulation of CD86 expression on DC treated with DNCB was significantly suppressed by either anti-IL-1 beta or anti-TNF-alpha antibody, while that by NiCl2 was relatively insensitive to these antibody treatments. Finally, the protein kinase C inhibitor, H7, but not staurosporine, could suppress the augmentation of CD86 expression on DC induced either by NiCl2 or by DNCB. These data suggest that DC respond to some haptens by changing their expression of several co-stimulatory molecules and their production of cytokines with a resultant change in antigen-presenting function. They also suggest that these chemicals stimulate DC by different mechanisms. By these responses, DC may modulate the final immune response to chemicals.