M. Watanabe et al., PHARMACOLOGICAL ANALYSIS OF NEUTROPHIL CHEMOTACTIC FACTOR PRODUCTION BY LEUKOCYTES AND ROLES OF PAF IN ALLERGIC INFLAMMATION IN RATS, British Journal of Pharmacology, 111(1), 1994, pp. 123-130
1 The role of platelet activating factor (PAF) in neutrophil infiltrat
ion in air pouch type allergic inflammation in rats was investigated.
2 Neutrophil infiltration into the pouch fluid 8 h after injection of
the antigen (azobenzenearsonate-conjugated acetyl bovine serum albumin
) solution into the air pouch of immunized rats was inhibited dose-dep
endently by treatment with PAF antagonists (CV-3988, L-652,731 and Y-2
4,180) in parallel with the decrease in neutrophil chemotactic activit
y in the pouch fluid. 3 Four hours after injection of the antigen solu
tion into the air pouch of immunized and nonimmunized rats, there was
no significant difference between the two groups in the number of tota
l leucocytes, neutrophils, mononuclear cells and eosinophils in the po
uch fluid. However, when the infiltrated leucocytes were incubated in
medium, chemotactic factor production by leucocytes from immunized rat
s was greater than that from non-immunized rats. 4 When leucocytes fro
m non-immunized rats were preincubated for various periods in the medi
um containing 10 or 50 nM of PAF, washed, and further incubated in the
medium containing no PAF, chemotactic factor production was not stimu
lated. 5 The increase in the chemotactic activity in the conditioned m
edium was not suppressed by the 5-lipoxygenase inhibitor, AA861. In ad
dition, the chemotactic activity in the conditioned medium was not inh
ibited by the PAF antagonists. 6 Incubation of the infiltrated leucocy
tes in the medium containing the protein synthesis inhibitor, cyclohex
imide, inhibited chemotactic factor production in a concentration-depe
ndent manner in parallel with the decrease in uptake of [H-3]-leucine
into the acid-insoluble fraction of leucocytes. 7 Separation of the ch
emotactic activity in the conditioned medium by isoelectric focusing r
evealed that the leucocyte infiltrated into the pouch fluid produce tw
o kinds of factors, viz. leucocyte-derived neutrophil chemotactic fact
or-1 (LDNCF-1) and LDNCF-2 of which pI values are 4-5 and above 8, res
pectively. 8 The results indicate that PAF has no significant role in
leucocyte activation to produce chemotactic factors, and that neutroph
il chemotactic factors produced by infiltrated leucocytes are not PAF
or leukotriene B4 but are produced through a protein synthesis mechani
sm. 9 The mechanism of action of PAF antagonists on neutrophil infiltr
ation into the inflammatory locus is discussed.