Platelet-Activating Factor Potentiates the Activity of Respiratory Burst and Interleukin-1 in Rat Alveolar Macrophages

Platelet-Activating Factor Potentiates the Activity of Respiratory Burst and Interleukin-1 in Rat Alveolar Macrophages

The objective of the present study was to test the effect of platelet-activating factor (PAF) on rat alveolar macrophages. PAF alone did not stimulate superoxide secretion from alveolar macrophages. However, PAF (10^-5 M) significantly enhanced phagocytic activator zymosan-induced superoxide secretion from alveolar macrophages. This enhancement of PAF plus zymosan was 30% above the sum of the separate effects of PAF and zymosan. Similarly, PAF 1.3 X (10^-5 M) was not a direct stimulant of alveolar macrophages, as it had no stimulatory effect on chemiluminescence generation, but potentiated zymosan-induced activation of chemiluminescence, i.e., 162% above the separate effects of each stimulant. PAF 10^-16±10^-6 M also failed to stimulate IL-1 production from alveolar macrophages. In contrast, when both PAF 10^-10 M and lipopolysaccharide(LPS) (1 μg/ml) were added together at the initiation of the culture, IL-1 production was significantly increased indicating the potentiative effects of PAF on IL-1 production by alveolar macrophages. Collectively, these data suggest that PAF alone does not activate the release of bioactive products from alveolar macrophages. However, PAF appears to act as a priming mediator that potentiates stimuli-induced macrophage activity. These novel actions of PAF prove its role as a potent mediator of inflammatory and immune responses in the lung.