PAF as a facilitator of the immune response: Its role in priming inflammatory and endothelial cells

PROSTAGLANDINS

PAF AS A FACILITATOR OF THE IMMUNE RESPONSE ITS ROLE IN PRIMING INFLAMMATORY AND ENDOTHELIAL CELLS H. S. Jacob, University

N. W. FL Wickham,

and

of Minnesota, Department Minneapolis (USA)

:

G. M. Vercellotti of Medicine,

Intravascular coagulation generates thrombin during the Adult Respiratory Distress Syndrome, sepsis and with organ graft rejection. We wondered whether thrombin might augment granulocytelendothelial cell interaction and hence amplify vascular damage by inducing endothelium to produce platelet-activating factor (PAF) (JCI 76 : 2235-2246 ; 1985). To examine this premise and the mechanisms involved, we first measured intracellular calcium [Ca*+]l in human endothelial cells (grown on glass cover slips), in a scanning spectrofluorometer at 37 OC after loading with FURA 2 (4p.M). Resting [Ca”+]l was 148 +22nM (Mean &SEM) which rapidly increased 4-fold following thrombin addition (0.5 p/ml) and returned to baseline by 5 min. Phosphatidylinositol (PI) turnover was assessed in 3H-myoinositol-loaded endothelial cells using water-soluble extracts separated by Dowex anion exchange chromatography. Within 30 s of thrombin stimulation, PI turnover markedly accelerated, with inositol, bi- and tri-phosphates increasing 5-fold. Associated with these perturbations, thrombin-treated endothelial monolayers became highly stimulatory to marginated granulocytes ; that is, this “activated” endothelium could amplify superoxide production and elastase release from apposed inflammatory cells (p
AUGUST

1987 VOL. 34 NO. 2

171