Lipoxygenase metabolism of arachidonic acid in ischemic preconditioning and PKC-induced protection in heart

Lipoxygenase metabolism of arachidonic acid in ischemic preconditioning and PKC-induced protection in heart. Am. J. Physiol. 276 (Heart Circ. Physiol. 45): H2094-H2101, 1999.-We tested the hypothesis that activation of the 12 -lipoxygenase (12-LO) pathway of arachidonic acid metabolism contributes to the protective effect of protein kinase C (PKC) activation and ischemic pr econditioning (PC), and we report, in perfused rat heart, that both PC and the PKC activator 1,2-dioctanoyl-sn-glycerol (DOG;) confer a similar protec tive effect and stimulate a comparable accumulation of 12-LO metabolites. T he 12-LO product, 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], was incr eased in DOG-treated (22.8 +/- 4.4 ng/g wet wt) and PC hearts (26.8 +/- 5.5 ng/g wet wt) compared with control (13.8 +/- 2.1 ng/g wet wt, P < 0.05), a nd this increase was blocked by 12-LO or PKC inhibitors. Both DOG pretreatm ent and PC improved recovery of left ventricular developed pressure (LVDP) nearly twofold after 20 min of ischemia; this improvement was blocked by 12 -LO inhibitors and was mimicked by infusion of 12-hydroperoxyeicosatetraeno ic acid [12(S)-HpETE; 67 +/- 6% recovery of LVDP vs. 35 +/- 3% for untreate d hearts]. Also, the protection afforded by 12(S)-HpETE, as well as by PC, was attenuated by the K+-channel blocker 5-hydroxydecanoate, suggesting tha t the downstream mechanisms of 12(S)-HpETE-mediated protection are similar to PC. Furthermore, PC stimulates 12-LO metabolism in perfused rabbit heart , and 12-LO inhibition blocks PC-induced cardioprotection. Thus the data su ggest that 12-LO metabolism plays an important role in cardioprotection.