Radiation from ultraviolet phototherapy sources results in photodegradation of 12(R) and 12(S)-hydroxy-eicosatetraenoic acid: high-performance liquid chromatography and polymorph migration studies.

The effect of irradiation from Sylvania PUVA lamps (emitting predominantly in the ultraviolet (UVA) region) and broadband Philips TL-12 lamps (peaking in the UVB region) on two inflammatory mediators, 12(R)- and 12(S)-hydroxy-eicosatetraenoic acid (HETE) was studied. A high-performance liquid chromatography study showed significant photodegradation of both enantiomers at a concentration of 5 micrograms/ml in phosphate-buffered saline following irradiation with 10 J.cm-2 UVA or 0.375 J.cm-2 UVB. The in vitro chemokinetic microdroplet migration response of human peripheral polymorphonuclear leukocytes from normal and psoriatic subjects was significantly reduced following irradiation of 12(R)-HETE at a concentration of 1 micrograms/ml in medium with 40 J.cm-2 UVA and 1.5 J.cm-2 UVB respectively. No such effect was seen with 12(S)-HETE. The effect of ultraviolet on skin physiology, and in particular in the successful phototherapy of a range of inflammatory skin disorders, is not fully understood. The photodegradation of inflammatory mediators such as 12-HETE, as shown in this study, provides another factor of possible therapeutic significance.