Photodegradation of folic acid during extracorporeal photopheresis.
BACKGROUND
Photodegradation of folic acid (FA) by ultraviolet (UV) radiation is a well-documented photochemical reaction, and decreased serum levels of FA have been found in patients receiving photochemotherapy (psoralen plus UVA). During extracorporeal photopheresis (ECP) leucocytes and plasma are subjected to 8-methoxypsoralen (8-MOP) plus UVA.


OBJECTIVE
To investigate whether ECP leads to the photodegradation of FA in the extracorporeal system.


METHODS
In 30 patients undergoing ECP on two consecutive days the FA levels were measured in the extracorporeal collected plasma prior to and after UVA exposure. Healthy donor plasma was exposed to 8-MOP and increasing doses of UVA in vitro. In five patients serum folate levels were determined before and after ECP.


RESULTS
We found a mean reduction of 44% and 46% on the first and second day of treatment, respectively. This effect could be reproduced in vitro: the irradiation of healthy donor plasma with UVA led to a dose-dependent reduction of FA of up to 54.75% at 16 J cm(-2). This was independent of the presence of 8-MOP and the base concentration of 5-methyltetrahydrofolate; minimal changes were observed for vitamin B(12) and homocysteine, not undergoing photodegradation. Serum folate levels did not change significantly before and after ECP.


CONCLUSIONS
We conclude that extracorporeal exposure of plasma to UVA during ECP leads to photodegradation of FA. Further investigations are required to determine the biological effects of folate photoproducts and whether clinically relevant loss of FA might be a consequence of ECP.
Der-Petrossian
M
M
Division of Special and Environmental Dermatology, Department of Dermatology, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria. manon.der-petrossian@meduniwien.ac.at
Födinger
M
M
Knobler
R
R
Hönigsmann
H
H
Trautinger
F
F
D016022:Case-Control Studies; D004307:Dose-Response Relationship, Radiation; D005492:Folic Acid / Q000097:blood*; D005494:Folic Acid Deficiency / Q000209:etiology*; D006801:Humans; D017893:Photopheresis / Q000009:adverse effects*; D012871:Skin Diseases / Q000628:therapy*; D014466:Ultraviolet Rays / Q000009:adverse effects; D014806:Vitamin B 12 Deficiency / Q000209:etiology
D005492:Folic Acid