The key difference is that enzymes generate a restricted number of specific products, with oxygen insertion effectively dictated by the enzyme pathway involved

The key difference is that enzymes generate a restricted number of specific products, with oxygen insertion effectively dictated by the enzyme pathway involved. innate immune function during health and disease. We also review the mass spectrometry methods used for identification of the lipids and describe how these approaches can be used for discovery of new lipid mediators in complex biologic samples. Introduction During infection and injury, circulating innate immune cells and platelets respond acutely to a variety of pathophysiologic agonists that mediate profound changes in both their function and physical state. Significant alterations in the lipid compartment, including changes to the plasma membrane and generation of potent signaling mediators occur within 2-5 minutes of stimulation.1C4 Activation of neutrophils, monocytes, and platelets leads to several common events at the plasma membrane, including shape change, flattening, adhesion, phagocytosis, microvilli, and microparticle generation.5,6 Phospholipids are the building blocks of the cell membrane, forming a permeability barrier and providing substrates for generation of important signaling mediators, including platelet-activating factor, phosphoinositides, diacylglycerides, sphingosine-derived phospholipids, Darapladib phosphatidic acids, and eicosanoids. All of these are formed acutely in immune cells through the actions of phospholipases and other enzymes, for example, phospholipase A2 (PLA2), which hydrolyzes phospholipids at tyrosine kinases, protein kinase C, and sPLA2 and calcium mobilization, and can be triggered by either protease activated receptors (PAR) 1 or 4.52 Similar to neutrophil 5-HETE-PEs, the platelet lipids are generated through PLA2 hydrolysis of phospholipid, oxidation by LOX, and then re-esterification into the plasma membrane. The time scale of generation is fast, similar to that for free 12-HETE generation, suggesting that the proteins involved may be coupled collectively in a tight complex. In support, we found that exogenously added 12-HETE-d8 does not become Darapladib integrated into PE or Personal computer during the time level of 12-HETE-PE/Personal computer synthesis.47 Platelets also generate several additional Darapladib phospholipid-esterified hydroxyl-fatty acids. These include 4 PE-esterified 14-hydroxydocosahexaenoic acids (HDOHEs), created via 12-LOX oxidation of docosahexaneoic acid-containing phospholipids55 (Number 1F). Their levels are lower than 12-HETE-PE/Personal computers, reflecting the lower amounts of unsaturated fatty acid substrate in the platelet membrane. Much like 12-HETE-PE/PC, generation of esterified HDOHEs requires calcium and phospholipases. Intriguingly, platelets do not appear to generate esterified thromboxane, although we recently recognized COX-1Cderived PE esterified PGE2 and PGD2, created on activation of platelets with thrombin (M. Aldrovandi and V.B.O., unpublished data, 2012). The mechanism of formation and proposed biologic actions of 12-HETECcontaining phospholipids generated by human being platelets are demonstrated in Number 4. Open in a separate windowpane Number 4 Summary of mechanism of formation and action of 12-HETE-PLs in human being platelets. (A) The 12-HETE-PLs are generated in response to thrombin activation of PAR1 and PAR4, via several signaling intermediates. Hydrolysis of arachidonate by cPLA2 is required. (B) Some HETE-PEs translocate to the outside of the plasma membrane and may enhance cells factor-dependent thrombin generation. sPLA2 shows secretory phospholipase A2; FACL, fatty acyl CoA USP39 ligase; and PLC, phospholipase C. New generation mass spectrometry methods for recognition of immune cell lipids The recognition of esterified eicosanoids explained in this evaluate used a mass spectrometry method termed precursor scanning that takes advantage of the facile fragmentation of these species to generate a characteristic eicosanoid carboxylate anion on collision-induced dissociation. This mode is available on standard triple quadrupole tools, and when combined with an ion capture (eg, Q-Trap), enables MS/MS to also become performed during elution, greatly aiding structural identification. By using this mode, lipid extracts were analyzed for families of lipids that contain a common practical group, specifically an eicosanoid.39,40,47,52,55 Because the mass spectrometry fragmentation patterns of both eicosanoids and phospholipids are already well known, the structural characterization of these lipids was straightforward. This approach could equally be used for lipids comprising other practical groups of interest (eg, particular fatty acids or short chain revised lipids where the fragment produces a negative ion). Where a charged species is not created on dissociation, neutral loss scanning can on the other hand be used. Our methods coupled precursor scanning to high pressure liquid chromatography. Good separation is essential for analysis of complex lipid components because artifactual adducts of HETEs with additional matrix constituents can form in the electrospray resource that behave much like esterified HETEs, when direct infusion of complex lipid extracts is performed. In our studies, an extraction method that components most lipid varieties was used, where cells or cells (homogenized in the.