Figure 5

Possible pathways for the synthesis of bioactive stress mediators from the arachidonic acid (AA) cascade in the immune tissues of chickens. In response to E. coli LPS stimuli, AA is released from membrane phospholipids. It is then converted to biologically active series of prostaglandins (PGs) including prostaglandin E2 (PGE2), by the action of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzymes, which evoke the acute phase of inflammation (A). The stress mediator synthesis pathway differs in the presence of acetylsalicylic acid (ASA) and vitamin E (vE) (B); COX-1 is inhibited while, COX-2 is irreversibly acetylated and switches from producing PGs. In such circumstances, AA is metabolized to a greater extent by lipoxygenase-12 (LOX-12) and cytochrome P450 (CYP450) pathways. This mechanism, in turn, may lead to the generation of novel biologically active resolvins via pathways other than those mediated by COX-1. The generation of these and related compounds represents a novel mechanism for the therapeutic benefits of dietary supplementation with ASA and vE, which may be important in controlling inflammation in birds.