Lipoxygenases (LOs) are iron-containing enzymes that catalyze the conversion of arachidonic acid into hydroperoxyeicosatetraenoic acids (HPETEs) and other bioactive lipid mediators. In mammals, 5-LO, 15-LO and 12-LO enzymes appear to have distinct roles in pathophysiological contexts, which has emphasized the need for selective inhibitors. Cinnamyl-3,4-dihydroxy-α-cyanocinnamate (CDC) has been proposed as potent and selective inhibitor of platelet type 12-LO (p12-LO). Here we re-evaluated the selectivity profile of CDC on LOs and we show that CDC is a potent and direct inhibitor of 5-LO. CDC reduced 5-LO activity in cell-free assays (purified human recombinant enzyme or leukocyte homogenates) with IC50 values in the low nanomolar range (9-25 nM) and a selectivity index of about 35 and 15 over p12-LO and 15-LO1, respectively. Similarly, CDC inhibited 5-LO product formation in intact human polymorphonuclear leukocytes and monocytes (IC50 = 0.45-0.8 μM). A lower potency was observed for 15-LO1, while p12-LO activity in platelets was hardly affected. In human whole blood, CDC efficiently reduced formation of 5-LO products and similar effects were observed for 12(S)-H(P)ETE and 15(S)-H(P)ETE. Finally, CDC (3.5 and 7 mg/kg, i.p.) was effective in vivo in the platelet-activating factor-induced shock in mice and reduced formation of the 5-LO product leukotriene B4 in the rat carrageenan-induced pleurisy after a single oral dose of 10 mg/kg. Together, our data demonstrate that CDC is a potent inhibitor of 5-LO with efficacy in vivo and encourage further development of CDC as lead compound.
- arachidonic acid
- Received February 18, 2011.
- Revision received March 18, 2011.
- Accepted March 28, 2011.
- The American Society for Pharmacology and Experimental Therapeutics