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Inhibitory effect of 8-methoxypsoralen plus ultraviolet-A on interleukin-1 production by murine keratinocytes
Y Tokura1, J Yagi, R L Edelson
1Department of Dermatology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510.
Abstract:
We report the effects of 8-methoxypsoralen (8-MOP) plus ultraviolet-A (UV-A) irradiation on interleukin-1 (IL-1) production by murine epidermal keratinocytes, correlating its effect on IL-1 with cell viability, DNA synthesis, and 8-MOP-DNA photoadduct formation. Freshly isolated murine keratinocytes were treated with various doses of 8-MOP (5-100 ng/mL; incubation time, 30 min) plus 1 J/cm2 UV-A and cultured for 1-3 days. The IL-1/epidermal cell-derived thymocyte-activating factor (ETAF) activity in both supernatant and cell extract was reduced proportionately with increasing doses of 8-MOP/UV-A. Interleukin-1 inhibitors induced by 8-MOP plus UV-A were not detected in either supernatant or cell extract. A clear reduction of the IL-1 production was induced by the treatment as low as 15 ng/mL 8-MOP plus 1 J/cm2 UV-A, which led to the formation of 0.52 8-MOP photoadducts per million DNa bases and affected neither cell viability nor DNA synthesis of the treated cells. Cells treated with 100 ng/mL 8-MOP and 1 J/cm2 UV-A exhibited 57% suppression of IL-1 production in both 2- and 3-day culture samples. This treatment resulted in the formation of 3.8 photoadducts per million bases as well as significant abrogation of DNA synthesis although cell viability was unchanged. These observations provide some insights into the phototoxicity mechanisms of 8-MOP and the effect of PUVA therapy on the cytokine regulation in keratinocytes.
Insights
8-methoxypsoralen (8-MOP) plus ultraviolet-A (UV-A) irradiation significantly reduces interleukin-1 (IL-1) production in mouse skin cells. This photochemotherapy effect on IL-1 correlates with DNA damage, not cell death.
Area of Science:
- Dermatology
- Photobiology
- Immunology
Background:
- Psoralen plus ultraviolet A (PUVA) therapy is a common dermatological treatment.
- The precise mechanisms by which PUVA affects cytokine production in skin cells remain incompletely understood.
- Interleukin-1 (IL-1) is a key cytokine involved in inflammation and immune responses within the skin.
Purpose of the Study:
- To investigate the impact of 8-methoxypsoralen (8-MOP) and UV-A irradiation on IL-1 production in murine epidermal keratinocytes.
- To correlate the observed effects on IL-1 with keratinocyte viability, DNA synthesis, and the formation of 8-MOP-DNA photoadducts.
- To gain insights into the phototoxicity mechanisms of 8-MOP and its influence on cytokine regulation.
Main Methods:
- Murine keratinocytes were treated with varying doses of 8-MOP (5-100 ng/mL) followed by UV-A irradiation (1 J/cm²).
- Interleukin-1 (IL-1) activity was measured in cell supernatants and extracts after 1-3 days of culture.
- Cell viability, DNA synthesis, and 8-MOP-DNA photoadduct formation were assessed to correlate with IL-1 levels.
Main Results:
- A dose-dependent reduction in IL-1/epidermal cell-derived thymocyte-activating factor (ETAF) activity was observed with increasing 8-MOP/UV-A doses.
- Significant suppression of IL-1 production (up to 57%) was noted at higher 8-MOP/UV-A concentrations, accompanied by DNA synthesis inhibition.
- The reduction in IL-1 occurred even at low 8-MOP/UV-A doses that did not affect cell viability or DNA synthesis, but did form photoadducts.
Conclusions:
- 8-MOP plus UV-A irradiation effectively suppresses IL-1 production in keratinocytes.
- The phototoxic effects on IL-1 production are linked to 8-MOP-DNA photoadduct formation and can occur independently of significant cell death or impaired DNA synthesis.
- These findings elucidate aspects of PUVA therapy's phototoxicity and its impact on keratinocyte cytokine regulation.