A comparison of the proinflammatory effects of 12(R)- and 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid in human skin.

Topical application of racemic 12-hydroxy-5,8,10,14-eicosatetraenoic acid [12(R,S)-HETE] produces erythema and leucocyte accumulation in human skin. Since 12(R)-HETE is more potent than its epimer 12(S)-HETE as a neutrophil chemoattractant in vitro, their proinflammatory effects have now been compared in vivo. 12(R)- and 12(S)-HETE (0.5 - 20 ug/site) were applied topically to the forearm skin of 5 healthy volunteers and the sites occluded for 6 h. Five ug each of the two enantiomers were also applied to the opposite forearm. At 6 and 24 h blood flow and the areas of erythematous responses were measured. The 5 ug application sites were biopsied at 24 h. Both enantiomers caused dose related erythema and increased blood flow at 6 and 24 h, which were not significantly different at either of the time points tested. In contrast, pronounced neutrophil infiltrates were seen in the epidermis (25.2 +/- 13 cells/hpf) and dermis (13.2 +/- 5.1 cells/hpf) 24 h after application of 12(R)-, but not 12(S)-HETE (0.02 +/- 0.02 and 1.02 +/- 0.7 cells/hpf in epidermis and dermis respectively). However, the numbers of dermal mononuclear cells accumulating in response to the two enantiomers were similar. 12(R)-HETE thus appears to be a more potent neutrophil chemoattractant than 12(S)-HETE in human skin in vivo and may be of potential importance as a mediator of inflammation in man.