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Effects of 8-methoxypsoralen (8-MOP) and UVA on human lymphocytes
Abstract:
Peripheral lymphocytes of 37 psoriatic patients are tested before and under PUVA treatment using as parameter the non specific stimulation effect of HgCl2 (10 microgram/ml) in culture, measuring the 3H-thymidine incorporation after the last 16 h of a 5-days culture. Oral 8-MOP in therapeutic doses is decreasing the lymphocyte stimulation as well as 8-MOP together with UVA irradiation during the first week of treatment. After 1 week, the stimulation is, on the contrary, significantly enhanced after irradiation. Lymphocytes isolated by centrifugation over Lymphoprep are submitted to PUVA conditions in petri dishes (Hank's solution 8-MOP 1 microgram/ml, irradiation with 350 nm, 93-372 mJ/cm2). The total cell number, the E-rosette formation (as marker for T-lymphocytes) and the EAC-rosette formation (as marker for B-lymphocytes) are determined. PUVA conditions have an energy dependent decreasing effect on the cell number, while the T- and B-cell proportions remain constant. UVA irradiation alone has such an effect only with high energies. 8-MOP without UVA has no significant influence on the cell number.
Insights
PUVA therapy, involving psoralen (8-MOP) and UVA light, initially decreases lymphocyte stimulation in psoriasis patients. However, after one week, PUVA significantly enhances lymphocyte stimulation, impacting T- and B-cell numbers.
Area of Science:
- Dermatology
- Immunology
- Photomedicine
Background:
- Psoriasis is a chronic inflammatory skin condition.
- PUVA therapy (psoralen plus UVA) is a common treatment for psoriasis.
- The immunomodulatory effects of PUVA on peripheral lymphocytes require further elucidation.
Purpose of the Study:
- To investigate the impact of PUVA treatment on the in vitro stimulation of peripheral lymphocytes from psoriatic patients.
- To assess the effects of 8-methoxypsoralen (8-MOP) and UVA irradiation on lymphocyte proliferation and cell counts.
Main Methods:
- Peripheral blood lymphocytes from 37 psoriatic patients were cultured with HgCl2 to measure 3H-thymidine incorporation.
- Lymphocytes were exposed to PUVA conditions in vitro (8-MOP and UVA irradiation).
- Cell counts, T-lymphocyte (E-rosette), and B-lymphocyte (EAC-rosette) proportions were determined.
Main Results:
- In vivo, oral 8-MOP and initial PUVA treatment decreased lymphocyte stimulation.
- After one week of PUVA, lymphocyte stimulation was significantly enhanced.
- In vitro PUVA exposure reduced total cell number in an energy-dependent manner, without altering T- and B-cell proportions.
- UVA alone affected cell number only at high energies; 8-MOP alone had no significant effect.
Conclusions:
- PUVA therapy exhibits biphasic immunomodulatory effects on psoriatic lymphocytes, initially suppressing and later enhancing stimulation.
- The observed changes in lymphocyte stimulation may contribute to the therapeutic efficacy of PUVA in psoriasis.
- PUVA treatment impacts lymphocyte viability in a dose-dependent manner, with implications for treatment protocols.