European Journal of Pharmacology, 218 (1992)369-372 369 © 1992 Elsevier Science Publishers B.V. All rights reserved 0014-2999/92/$05.00 EJP 21100 Short communication 13-Hydroxyoctadecadienoic acid attenuates oedema formation induced by leukotriene B 4 in vivo in rabbit skin Theresa L. Buckley, Marco J. Van de Velde, Paul A.J. Henricks, Ferdi Engels and Frans P. Nijkamp Department of Pharmacology, Faculty of Pharmacy, Universityof Utrecht, P.O. Box 80.082, 3508 TB Utrecht, Netherlands Received 16 April 1992,revised MS received 12 June 1992,accepted 16 June 1992 Intradermal 13-hydroxyoctadecadienoic acid (13-HODE; 10-11-10 -9 mol/site) inhibited oedema formation induced by the neutrophil-dependent mediator leukotriene B 4 (LTB 4) in the presence of calcitonin gene-related peptide (CGRP; 10 -11 tool/site) in rabbit skin. In contrast, the responses to the direct acting mediators bradykinin and histamine were unaffected by 13-HODE. 13-HODE failed to induce oedema formation in rabbit skin when injected alone or in the presence of the potent vasodilator CGRP. These results present a novel interaction between 13-HODE and LTB4 that could have important implications in the pathogenesis of inflammation. 13-HODE (13-hydroxyoctadecadienoic acid); Oedema formation; Leukotriene B4; Skin (rabbit) 1. Introduction Studies investigating the role of fatty acids in inflam- mation have focussed predominantly on arachidonic acid and its metabolites. However, recently there is increasing awareness of the importance of linoleic acid (and its metabolites) which is also present in plasma membranes. Linoleic acid is metabolised into various products including 13-hydroxyoctadecadienoic acid (13-HODE) by endothelial cells (Buchanan et al., 1985b), epithelial cells (Oosthuizen et al., 1990) and leukocytes (Claeys et al., 1982; Engels et al., 1991). 13-HODE, which is continuously synthesised by en- dothelial cells under basal conditions, has been re- ported to inhibit the adhesion of platelets to endothe- lial cells in vitro (Buchanan et al., 1985a). However, 13-HODE induced chemotaxis of bovine and human leukocytes in vitro (Henricks et al., 1991). Oedema formation and neutrophil accumulation are prominent features of inflammation. Mediators such as the arachidonate metabolite leukotriene B 4 (LTB 4) can induce neutrophil-dependent oedema formation in rabbit skin whereas histamine and bradykinin induce oedema by acting directly on the endothelium (Wedmore and Williams, 1981). In contrast vasodila- tors, including calcitonin gene-related peptide (CGRP) Correspondence to: T.L. Buckley, Department of Pharmacology, Faculty of Pharmacy, University of Utrecht, P.O. Box 80.082, 3508 TB Utrecht, Netherlands. Tel. 31.30.537 352, fax 31.30.537 420. and prostaglandin 12 (PGI2), do not induce oedema formation but as a consequence of their vasodilator activities they can synergistically potentiate oedema induced by mediators of increased microvascular per- meability (Brain and Williams, 1985; Buckley et al., 1991). The possible role of 13-HODE in inflammation has been the subject of limited studies most of which have investigated the 'chemorepellent' effects of 13-HODE against platelet adhesion. In this study, we investigated whether 13-HODE could induce or modulate oedema formation in rabbit skin. 2. Materials and methods 2.1. Preparation of 13-HODE 13-HODE was prepared as described in Engels et al. (1991). Briefly, linoleic acid was incubated with lipoxidase-1 enzyme (type IV) at 4°C. The formation of the linoleic acid intermediate 13-hydroperoxyocta- decadienoic acid (13-HPODE) was followed by mea- suring samples of the incubation mixture at appropri- ate intervals in a spectrophotometer (235 nm). After the linoleic acid had been metabolised the incubation was stopped by adding HCI to obtain a pH of 4. 13-HPODE was separated from non-metabolised linoleic acid using thin layer chromatography and re- duced with sodium borohydrate. After reduction the purity of 13-HODE was measured by reverse phase