Platelet Activating Factor Case Study

Platelet-activating factor (PAF) or phospholipid, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine is a phospholipid activator and mediator of leukocyte functions that has many physiological actions. It was discovered and many studies have been done to characterize its messenger functions as a phospholipid.1 PAF is produced by many different cell types such as leukocytes, platelets, mast cells and vascular endothelial cells. PAF amplifies inflammatory responses by promoting leukocyte activation and platelet aggregation.4 PAF is regulated by an enzyme, PAF-acetylhydrolase (PAF-AH), which hydrolyzes PAF rendering it biologically inactive.2 It is important to study PAF regulation by researching the enzymes involved in its degradation to understand

It binds to receptors on the plasma membranes of other cells and then activates them, changing their phenotypes.1 PAF transmits signals between cells acting as a hormone, cytokine, or other signaling type molecule and this can trigger inflammatory and thrombotic cascades. If left unregulated by a deficiency in the PAF-AH enzyme used to regulate it, PAF signaling can cause inflammation. Rheumatoid arthritis is a disease where the fluid between joints becomes inflamed and this disease may have PAF involved.3

PAF is synthesized (Fig. 2) through one of two enzymatic pathways, one pathway that substitutes an acetyl group for the long-chain fatty acyl group of cellular phospholipids. (Remodeling) The other is de novo pathway to form PAF parallels phospholipid synthesis, in which a phosphocholine function is transferred to alkyl acetyl glycerol.5 The second step in the synthesis of PAF through the remodeling pathway is performed by the acetyl-CoA-lyso PAF acetyltransferase. Unfortunately not enough is known about this activity because the enzyme is unstable and has not been purified or

The test used was Enzyme-linked immunosorbent assay (ELISA) which is a test that uses antibodies to see a change in color to identify an antigen. Fresh venous blood samples were drawn into pyogen-free blood collection tubes without additives, immersed in ice, and allowed to clot before centrifugation. All serum samples were stored at -70°C. Serum PAF-AH levels were measured with ELISA kits. The detection limit of this assay was 0.074 ng/ml.2

The results for this study were that Serum PAF-AH levels were significantly higher in SSc patients (130.4± 69.5 ng/ml) than in healthy individuals (81.6 ± 34.8 ng/ml; P < 0.05 ;). Concerning SSc subgroups, PAF-AH levels in both patients with (diffuse) dSSc (135.5 ± 79.3 ng/ml) and those with (limited) lSSc (125.1 ± 58.6 ng/ml) patients were also increased compared with those in healthy individuals (P < 0.05 for