Transformation and degradation of leukotriene B4, 12-hydroxyeicosatetraenoic acid and 5-hydroxyeicosatetraenoic acid induced by ultraviolet radiation.

To reveal the underlying mechanisms in the therapeutic effectiveness of ultraviolet (UBV)- and psoralen plus UVA phototherapy, the photostability of leukotriene B4 (LTB4), 12-hydroxyeicosatetraenoic acid (12-HETE) and 5-HETE was investigated in the presence and absence of photosensitizers (8-methoxypsoralen and 5-methoxypsoralen). Arachidonic lipoxygenase products were irradiated with doses of narrow-band UVB (311 nm) ranging from 0.5-3.2 J/cm2, UVB and UVA (305-400 nm) ranging from 0.6-6.3 J/cm2 and UVA ranging from 5.0-60.0 J/cm2, respectively. High-performance liquid chromatography demonstrated a dose-dependent decrease of LTB4, 12-HETE, and 5-HETE. The photostability of 12-HETE was much higher than that of LTB4 and 5-HETE. Two products of transformation of LTB4 were identified as 5(S), 12(R)-dihydroxy-(6E, 8E, 10E, 14Z)-eicosatetraenoic acid [6-trans-LTB4] and 5(S), 12(R)-dihydroxy-(6E, 8Z, 10E, 14Z)-eicosatetraenoic acid [5(S), 12(R)-DiHETE]. There was no significant increase in photodegradation after addition of photosensitizing psoralens.