The immunological effect of 8-methoxypsoralen and UVA treatment on murine T-cell leukemia

Quantitative echographic analysis of photochemotherapy on systemic sclerosis skin

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, in which development of fibrosis, vascular insufficiency and inflammatory processes are prominent in the skin as well as in other organs. We studied the effect of photochemotherapy with quantitative echography in SSc. Dermal echo intensity and dermal thickness was measured using high-frequency dermal echography before and after therapy. The dermal echo intensity after photochemotherapy (33.51+/-9.34) significantly increased than that before therapy (21.23+/-6.00) (P < 0.01), while dermal thickness (1.20+/-0.20) significantly decreased than that before therapy (1.38+/-0.18) (P < 0.05). Photochemotherapy was more likely to improve dermal edema, not fibrosis, because echo intensity after treatment was significantly elevated with that before treatment in patients with edema. Quantitative echographic analysis was concluded to be a reliable method in evaluating the change of skin edema in SSc.

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-gamma 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-gamma-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-gamma was elevated in culture supernatants from 8-methoxypsoralen-phototreated peripheral blood mononuclear cells, whereas interleukin-4 was significantly reduced. This enhanced production of interferon-gamma, 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.

Modulation of cytokine production by 8-methoxypsoralen and UVA

Modulatory effects on cytokine expression of 8-MOP in conjunction with UVA have been investigated in different systems using different cell types, including keratinocytes, lymphocytes, monocytes and endothelial cells. The vast majority of data have exhibited reduced production of cytokines in 8-MOP/UVA-treated cells and skin, reflecting its simplistic cellular damage. However, 8-MOP/UVA at modest doses stimulate T lymphocytes to produce Thl cytokines such as interferon-gamma, suggesting that some activational events may occur in certain types of cells phototreated with 8-MOP. Both the inhibitory and augmentative effects of 8-MOP/UVA on cytokine production appear to participate in the mechanisms underlying the therapeutic efficacy of PUVA and extracorporeal photochemotherapy (photopheresis). In particular, photopheresis may exert beneficial effects on cutaneous T-cell lymphoma as a cytokine modifier.

Photoactivated 8-methoxypsoralen treatment causes a peptide-dependent increase in antigen display by transformed lymphocytes

Ex vivo exposure of malignant human T cells to photoactivated 8-methoxypsoralen (8-MOPa), followed by their i.v. return, appears to vaccinate patients against tumor-associated antigens of cutaneous T cell lymphoma in a procedure termed photopheresis. The molecular basis of this Food and Drug Administration-approved therapy, administered in 100 centers worldwide, is unclear. Most of the attention to the mechanism of action of the drug has focused on its capacity to form covalent cross-links with pyrimidine bases of DNA, thereby inhibiting cellular proliferation. Because immunologic factors appear to be important in the clinical response and could potentially serve as a model for immunotherapy of other malignancies, we explored the possibility that 8-MOP-treated cells display increased quantities of antigenic peptides at their cell surface. In this work, human B-lymphoblastoid tissue culture lines were exposed to 8-MOPa and expression of cell surface class I major histocompatibility complex proteins assessed, since CD8 T cells recognize antigenic moieties in the context of class I molecules. A peak 200-300% increase in MHC class I expression in 8-MOPa-treated cells occurred at 20 hr. 8-MOPa was far more effective in inducing this increase in class I MHC than other modalities, including mitomycin C, gamma-irradiation, ultraviolet B or heat or cold shock. This increase in surface class I MHC molecules appears to be driven by the degradation of cytoplasmic proteins into small peptides, followed by the transport of these peptides to MHC class I molecules in the endoplasmic reticulum. The data suggest that 8-MOPa treatment may augment the immunogenicity of tumor and/or antigen-presenting cells by enhancing processing and transport of class I MHC antigenic peptides.