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In vitro PUVA radiation abolishes fluorescent staining with epidermal cell and basement membrane zone markers
Abstract:
The purpose of this study was to investigate whether 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet (UV-A) light irradiation (PUVA) had a direct effect on the expression of epidermal cell and basement membrane zone (BMZ) markers without altering intracellular metabolic pathways. Cryostat sections of guinea-pig skin were covered with an 8-MOP solution and irradiated in vitro with UV-A light. Treated sections were stained subsequently with various membrane markers including pemphigus sera, pemphigoid sera (BMZ marker) and a group of biotin-labelled lectins (Concanavalin-A, peanut agglutinin, soybean agglutinin, Ulex europeus agglutinin (UEA) and wheat germ agglutinin). Fluorescent staining with all reagents except for UEA was reduced appreciably in intensity by PUVA radiation at higher energy doses (20 micrograms/ml of 8-MOP plus 20-30 J/cm2 of UV-A). Radiation with lower energy doses did not affect membrane marker staining. Weakened or abolished marker staining was restored to normal when scavengers of oxygen intermediates such as superoxide dismutase (540-5400 units/ml) or sodium azide (10-200 mM) were added to the 8-MOP solution during UV-A irradiation. UEA staining was negative in both PUVA-irradiated and untreated guinea-pig skin. PUVA at higher energy doses appeared to cause tissue damage by photodynamic reactions, resulting in decrease in membrane marker staining.
Insights
Photochemotherapy with 8-methoxypsoralen (8-MOP) and ultraviolet A (UV-A) light reduces skin cell and basement membrane markers. This effect is mediated by photodynamic reactions and can be mitigated by antioxidants.
Area of Science:
- Dermatology
- Photobiology
- Cell Biology
Background:
- Psoralen plus ultraviolet A (PUVA) therapy is a common dermatological treatment.
- The precise mechanisms by which PUVA affects cellular markers in the skin are not fully understood.
- Investigating direct effects on epidermal and basement membrane zone markers is crucial for understanding PUVA's action.
Purpose of the Study:
- To determine if 8-methoxypsoralen (8-MOP) plus ultraviolet A (UV-A) light (PUVA) directly impacts epidermal cell and basement membrane zone (BMZ) marker expression.
- To ascertain whether these effects occur independently of alterations in intracellular metabolic pathways.
Main Methods:
- In vitro irradiation of guinea-pig skin cryostat sections with UV-A light after 8-MOP application.
- Staining of treated skin sections with pemphigus sera, pemphigoid sera (BMZ marker), and various biotin-labelled lectins.
- Assessment of fluorescent staining intensity changes post-PUVA treatment.
- Evaluation of the protective effects of oxygen radical scavengers (superoxide dismutase, sodium azide).
Main Results:
- High-dose PUVA (20 µg/ml 8-MOP + 20-30 J/cm² UV-A) significantly reduced the intensity of most membrane marker fluorescent staining, except for Ulex europeus agglutinin (UEA).
- Lower energy doses of PUVA did not affect membrane marker staining.
- The reduction in marker staining was restored to normal levels when oxygen intermediate scavengers were included during irradiation.
- UEA staining remained negative in both treated and untreated skin.
- Higher PUVA doses induced photodynamic reactions, leading to tissue damage and decreased marker staining.
Conclusions:
- PUVA, at higher energy doses, directly affects the expression of epidermal cell and basement membrane zone markers in guinea-pig skin.
- The observed decrease in marker staining is likely due to photodynamic reactions and oxidative stress, rather than direct metabolic pathway alterations.
- Antioxidants can prevent PUVA-induced reduction in marker expression, highlighting the role of oxygen intermediates.