Platelet-activating factor and lyso-PAF possess direct antimicrobial properties in vitro
The effects of platelet-activating factor (PAF) and lyso-platelet-activating factor (L-PAF) at concentrations of 0.25–20 μg/ml on potassium transport and growth of gram-positive and gram-negative bacteria have been investigated in vitro and compared with those of lysophosphatidylcholine (LPC). Potassium transport was determined using 86Rb+ as tracer, while growth was measured according to the extent of uptake of radiolabeled amino acids. All of the test phospholipids caused dose-related inhibition of 86Rb+-uptake and growth of gram-positive bacteria, the order of potency being PAF>LPC>L-PAF. Gram-negative bacteria, on the other hand, were less sensitive to the inhibitory effects of the phospholipids on K+ transport and growth. Some, but not all, of the gram-positive and gram-negative bacteria were able to degrade LPC, but not PAF or L-PAF, demonstrating that enzymatic degradation of phospholipids does not explain the differential sensitivity to these agents. The bioactive phospholipids LPC, PAF and L-PAF may represent an oxygen-independent antimicrobial host defense system operative primarily against gram-positive bacteria.
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Document Type: Research Article
Affiliations: Medical Research Council Unit for Inflammation and Immunity, Department of Immunology, Institute for Pathology, University of Pretoria, Republic of South Africa
Publication date: February 1, 2002