Formation of Antigenic Quinolone Photoadducts on Langerhans Cells Initiates Photoallergy to Systemically Administered Quinolone in Mice

Quinolone antibacterial agents are well known to cause photoallergy as a side-effect. Murine photoallergy to fluoroquinolones is a T cell-mediated immune response, evoked either by systemic fluoroquinolone and subsequent exposure of skin to ultraviolet A light or by subcutaneous injection of fluoroquinolone-photomodified epidermal cells. In this photosensitivity, epidermal Langerhans cells may be photomodified initially with the drug and thus present photohaptenic moieties to sensitize and restimulate T cells. Although we have shown that Langerhans cells photocoupled in vitro with fluoroquinolones are capable of stimulating sensitized T cells, it remains unclear whether systemically given fluoroquinolone photomodifies Langerhans cells upon ultraviolet A irradiation of the skin and the Langerhans cells become photohapten-bearing, T cell-stimulatory cells. In a murine model of fleroxacin photoallergy induced by intraperitoneal injection of the drugs plus ultraviolet A irradiation of skin, we found that Langerhans cells as well as keratinocytes are photoderivatized with fleroxacin as demonstrated with a fluoroquinolone-specific monoclonal antibody. Langerhans-cell-enriched epidermal cells prepared from mice treated with fleroxacin and ultraviolet A induced proliferation of sensitized T cells, indicating that photomodified Langerhans cells are functional. There was an optimal range of ultraviolet A dose to quantitatively and qualitatively form fleroxacin-photomodified Langerhans cells, as excess ultraviolet A rather reduced the photoantigen-presenting capacity of Langerhans cells presumably because of drug phototoxicity. Our study suggests that Langerhans cells serve as photoantigen-presenting cells in drug photoallergy

Th2 Suppressor Cells Are More Susceptible to Sphingosine Than Th1 Cells in Murine Contact Photosensitivity

Murine contact photosensitivity (CPS) to 3,3',4',5-tetrachlorosalicylanilide (TCSA) is a cutaneous delayed-type hypersensitivity reaction in which both positive and negative regulatory pathways exist. The latter pathway is mediated by antigen-specific, CD4+ suppressor T cells (CPS-Ts) that are Th2 cells. We examined the effects of sphingosine and synthetic cell-permeable analogs of ceramide on the cellular kinetics of CPS-Ts and immune lymph node cells from TCSA-photosensitized mice (CPS-LNC), along with other murine T-cell populations. The addition of sphingosine at 10 or 3 μM to in vitro cultures suppressed DNA synthesis of CPS-Ts and Th2 clones, including D10 cells and 24-2 cells, but not that of CPS-LNC or Th1 clones, including 23-1-8 and 28-4 cells. This suggested that sphingosine exerts its inhibitory effects preferentially on the proliferation of Th2 cells. Although suppressing DNA synthesis, sphingosine augmented the production and mRNA expression of interleukin-4 (IL-4) and enhanced the expression of the IL-4 receptor in CPS-Ts. In addition, the ability of sphingosine to induce signal transduction of CPS-Ts was confirmed by elevation of the intracellular free Ca++ concentration. Because CPS-Ts exposed to sphingosine exhibited a lower G2M/G1 ratio than control, these seemingly ambivalent phenomena may be caused by retardation of the G1 to S phase progression, a cell-cycle dysregulation known to augment cytokine production. In contrast to sphingosine, cell-permeable ceramide did not affect the proliferation of these cells when stimulated with mitogen/antigen and did not augment IL-4 production by CPS-Ts. Our study suggests that sphingosine modifies the Th1/Th2 balance by preferentially affecting the cellular kinetics of Th2

Treatment of T Lymphocytes with 8-Methoxypsoralen Plus Ultraviolet A Induces Transient but Biologically Active Th1-Skewing Cytokine Production

8-Methoxypsoralen plus ultraviolet A light is suggested to shift T lymphocytes from Th2 to Th1 cells. To clarify this issue, we examined the effects of 8-methoxypsoralen/ultraviolet A on the expression/production of cytokines in peripheral blood mononuclear cells from normal subjects and a Sézary syndrome patient. 8-Methoxypsoralen/ultraviolet A augmented the expression of mRNAs for interferon-γ and interleukin-2 and reduced those for interleukin-4 and interleukin-10. It seems that this enhancement of Th1 cytokines is caused by increment of cytokine production by Th1 cells but not by conversion of Th2 cells to produce Th1 cytokines. The number of interferon-γ-secreting lymphocytes was markedly increased in 8-methoxypsoralen/ultraviolet A-treated peripheral blood mononuclear cells 20 h after treatment, whereas that of Th2 cytokine-producing cells was decreased. Accordingly, the amount of interferon-γ was elevated in culture supernatants from 8-methoxypsoralen-phototreated peripheral blood mononuclear cells, whereas interleukin-4 was significantly reduced. This enhanced production of interferon-γ, however, was found only until 3 d after 8-methoxypsoralen phototreatment and was declined by 5 d after treatment. Finally, 8-methoxypsoralen/ultraviolet A treatment of T cells regulated their ability to induce keratinocyte CD54 expression. Our results show that 8-methoxypsoralen/ultraviolet A has a transient but biologically active Th1-skewing action in human T cells, suggesting that 8-methoxypsoralen/ultraviolet A exerts a beneficial therapeutic effect on Th2-mediated or Th2-malignant diseases

Inhibition of Epidermal Growth Factor Receptor and PI3K/Akt Signaling Suppresses Cell Proliferation and Survival through Regulation of Stat3 Activation in Human Cutaneous Squamous Cell Carcinoma

Recent studies have emphasized the important role of Stat3 activation in a number of human tumors from the viewpoint of its oncogenic and antiapoptotic activity. In this study, we examined the role and related signaling molecules of Stat3 in the carcinogenesis of human cutaneous squamous cell carcinoma (SCC). In 35 human cutaneous SCC samples, 86% showed overexpression of phosphorylated (p)-Stat3, and most of those simultaneously overexpressed p-EGFR or p-Akt. Constitutive activation of EGFR and Stat3 was observed in three SCC cell lines and four of five SCC tissues. AG1478, an inhibitor of the EGFR, downregulated Stat3 activation in HSC-1 human SCC cells. AG1478 inhibited cell proliferation and induced apoptosis of HSC-1 cells but did not inhibit the growth of normal human epidermal keratinocytes that did not show Stat3 activation. Furthermore, a PI3K inhibitor also suppressed Stat3 activation in HSC-1 cells to some degree. Combined treatment with the PI3K inhibitor and AG1478 strongly suppressed Stat3 activity and dramatically induced apoptosis of HSC-1 cells. These data suggest that Stat3 activation through EGFR and/or PI3K/Akt activation plays a critical role in the proliferation and survival of human cutaneous SCC

A Phenotypic Analysis of Involucrin-Membrane-Bound Ovalbumin Mice after Adoptive Transfer of Ovalbumin-Specific CD8⁺ T Cells

To investigate the mechanism of autoimmunity and peripheral tolerance in the skin, several transgenic mouse strains expressing membrane-bound ovalbumin (mOVA) as an epidermal self-antigen under the control of keratinocyte-specific promotors, such as keratin 5 and keratin 14, were employed in combination with adoptive transfer of CD8⁺ T cells from OT-I mice (OT-I T cells) that recognize an ovalbumin-derived peptide. However, these strains showed bodyweight loss and required additional inflammatory stimuli, such as γ-irradiation and tape-stripping, to induce skin inflammation. In this study, we generated a mouse strain expressing mOVA under the control of human involucrin promoter (involucrin-mOVA mice). In contrast to previous strains, involucrin-mOVA mice spontaneously developed skin inflammation after the transfer of OT-I T cells in the absence of external stimuli without significant bodyweight loss. We focused on the skin infiltration process of OT-I T cells and found that transferred OT-I T cells accumulated around the hair follicles in the early phase of skin inflammation, and in the later phase, the skin inflammation spontaneously resolved despite the remaining OT-I T cells in the skin. Our involucrin-mOVA mice will provide a promising tool to investigate the pathogenesis and the tolerance mechanisms of cytotoxic skin autoimmunity

Stability of a metallic state in the two-orbital Hubbard model

Electron correlations in the two-orbital Hubbard model at half-filling are investigated by combining dynamical mean field theory with the exact diagonalization method. We systematically study how the interplay of the intra- and inter-band Coulomb interactions, together with the Hund coupling, affects the metal-insulator transition. It is found that if the intra- and inter-band Coulomb interactions are nearly equal, the Fermi-liquid state is stabilized due to orbital fluctuations up to fairly large interactions, while the system is immediately driven to the Mott insulating phase away from this condition. The effects of the isotropic and anisotropic Hund coupling are also addressed.Comment: 7 pages, 9 figure

Mutations in SERPINB7, Encoding a Member of the Serine Protease Inhibitor Superfamily, Cause Nagashima-type Palmoplantar Keratosis

“Nagashima-type” palmoplantar keratosis (NPPK) is an autosomal recessive nonsyndromic diffuse palmoplantar keratosis characterized by well-demarcated diffuse hyperkeratosis with redness, expanding on to the dorsal surfaces of the palms and feet and the Achilles tendon area. Hyperkeratosis in NPPK is mild and nonprogressive, differentiating NPPK clinically from Mal de Meleda. We performed whole-exome and/or Sanger sequencing analyses of 13 unrelated NPPK individuals and identified biallelic putative loss-of-function mutations in SERPINB7, which encodes a cytoplasmic member of the serine protease inhibitor superfamily. We identified a major causative mutation of c.796C>T (p.Arg266∗) as a founder mutation in Japanese and Chinese populations. SERPINB7 was specifically present in the cytoplasm of the stratum granulosum and the stratum corneum (SC) of the epidermis. All of the identified mutants are predicted to cause premature termination upstream of the reactive site, which inhibits the proteases, suggesting a complete loss of the protease inhibitory activity of SERPINB7 in NPPK skin. On exposure of NPPK lesional skin to water, we observed a whitish spongy change in the SC, suggesting enhanced water permeation into the SC due to overactivation of proteases and a resultant loss of integrity of the SC structure. These findings provide an important framework for developing pathogenesis-based therapies for NPPK

Dendritic cells promote the spread of human T-cell leukemia virus type 1 via bidirectional interactions with CD4+ T cells

Human T-cell leukemia virus type-1 (HTLV-1) propagates within and between individuals via cell-to-cell transmission, and primary infection typically occurs across juxtaposed mucosal surfaces during breastfeeding and sexual intercourse. It is therefore likely that dendritic cells (DCs) are among the first potential targets for HTLV-1. However, it remains unclear how DCs contribute to virus transmission and dissemination in the early stages of infection. We show that an HTLV-1-infected cell line (MT-2) and naturally-infected CD4+ T-cells transfer p19+ viral particles to the surface of allogeneic DCs via cell-to-cell contacts. Similarly organized cell-to-cell contacts facilitate DC-mediated transfer of HTLV-1 to autologous CD4+ T-cells. These findings shed light on the cellular structures involved in anterograde and retrograde transmission, and suggest a key role for DCs in the natural history and pathogenesis of HTLV-1 infection

Mechanisms of Contact Photosensitivity in Mice. VII. Diminished Elicitation by Reserpine and Defective Expression in Mast Cell-Deficient Mice

The involvement of mast cells in the elicitation of contact photosensitivity (CPS) was examined in mice treated with pharmacologic agents and in genetically mast cell-deficient W/Wv mice. Contact photosensitivity responses were diminished by pretreatment with reserpine, which may have been due to depletion of vasoactive amines in mast cells. This inhibition was almost reversed by the monoamine oxidase inhibitor, pargyline-HCl, which prevented reserpine-induced depletion of vasoactive amines such as serotonin. Defective CPS was also found in W/Wv mice, but not in their congenic littermates (+/+). Abnormal CPS in mast cell-deficient mice was due to a defect in the elicitation of CPS rather than a defect in the induction of effector T cells, since the ability to elicit CPS could be transferred to normal +/+ mice by photosensitized cells from mast cell-deficient mice. These findings favor the view that mast cells are involved in the elicitation of CPS