Retinoids are potent inhibitors of the generation of rat leukocyte leukotriene B4-like activity in vitro.

Several retinoids (tretinoin, retinol, retinal, retinyl acetate, etretinate and RO 10-1670) were tested in vitro for their ability to inhibit the generation of the leukocyte chemotactic factor leukotriene B4 (LTB4) from calcium ionophore-stimulated rat PMN in vitro. LTB4 activity was measured in vitro via bioassay using rat PMN aggregation and chemokinesis. Tretinoin, retinol, RO 10-1670 and retinal were active inhibitors of LTB4 generation with ID50S (microM) of 0.55-1.5, 5.9-6.5, 4.8-5.9 and 19-28.4 respectively whilst retinyl acetate and etretinate were inactive. Inhibition of the generation of LTB4 by tretinoin was confirmed by reverse phase-high pressure liquid chromatography. These results are discussed in the context of retinoid treatment of skin diseases such as psoriasis where inhibition of neutrophil accumulation during retinoid treatment has been reported.