ABSTRACT
Fatty acids are important constituents of membrane phospholipids and when fatty acids are released by cellular phospholipases and lipases, or made available to the cell from the extracellular environment, they serve as important cellular signaling molecules. These released fatty acids can serve as second messengers for transduction of internal and external signals. Furthermore, they function as cellular modulators, because their action can be reversed at a precise intra-and extracellular location; they can serve to amplify, attenuate, or alter a cellular signal. Among their many actions fatty acids can modify the action of protein kinases, G-proteins, adenylate and guanylate cyclases, and phospholipases, as well as modulate ion channels and events involved in stimulus-response coupling mechanisms. Many of the cellular signaling events related to fatty acids are via their conversion to eicosanoids, which are potent bioactive lipid molecules and these are reviewed in Chapter 28. Furthermore, the recently discovered lipid mediators lipoxins (LPX) and the two new families of lipid mediators, resolvins (resolution phase interaction products) and protectins, which derive from omega-3 polyunsaturated fatty acid (PUFA) provide for better understanding of the cellular signaling in the in, ammatory process (see Chapter 28) (Schwab and Serhan, 2006). These resolution-active lipid mediators are small molecules that derive from essential n-6 and n-3 eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA) PUFAs in the diet. Among the n-6 PUFAs, arachidonic acid (AA)-derived LXA4 and aspirin-triggered LXA4 (ATL) evoke anti-in, ammatory protective actions in physiologic and pathophysiologic processes. These two molecular series have emerged as prototypic members of the 4 rst class of endogenous lipid/chemical mediators that are “switched on” in the resolution phase of an in, ammatory response, thus acting as “braking signals” in in, ammation (see Chapter 28).
