Pharmacological analysis of neutrophil chemotactic factor production by leucocytes and roles of PAF in allergic inflammation in rats

Abstract

1 The role of platelet activating factor (PAF) in neutrophil infiltration in air pouch type allergic inflammation in rats was investigated. 2 Neutrophil infiltration into the pouch fluid 8 h after injection of the antigen (azobenzenearsonateconjugated acetyl bovine serum albumin) solution into the air pouch of immunized rats was inhibited dose-dependently by treatment with PAF antagonists 180) in parallel with the decrease in neutrophil chemotactic activity in the pouch fluid. 3 Four hours after injection of the antigen solution into the air pouch of immunized and nonimmunized rats, there was no significant difference between the two groups in the number of total leucocytes, neutrophils, mononuclear cells and eosinophils in the pouch fluid. However, when the infiltrated leucocytes were incubated in medium, chemotactic factor production by leucocytes from immunized rats was greater than that from non-immunized rats. 4 When leucocytes from non-immunized rats were preincubated for various periods in the medium containing 10 or 50 nM of PAF, washed, and further incubated in the medium containing no PAF, chemotactic factor production was not stimulated. 5The increase in the chemotactic activity in the conditioned medium was not suppressed by the 5-lipoxygenase inhibitor, AA861. In addition, the chemotactic activity in the conditioned medium was not inhibited by the PAF antagonists. 6 Incubation of the infiltrated leucocytes in the medium containing the protein synthesis inhibitor, cycloheximide, inhibited chemotactic factor production in a concentration-dependent manner in parallel with the decrease in uptake of [3H]-leucine into the acid-insoluble fraction of leucocytes. 7 Separation of the chemotactic activity in the conditioned medium by isoelectric focusing revealed that the leucocyte infiltrated into the pouch fluid produce two kinds of factors, viz. leucocyte-derived neutrophil chemotactic factor-i (LDNCF-1) and LDNCF-2 of which pI values are 4-5 and above 8, respectively. 8 The results indicate that PAF has no significant role in leucocyte activation to produce chemotactic factors, and that neutrophil chemotactic factors produced by infiltrated leucocytes are not PAF or leukotriene B4 but are produced through a protein synthesis mechanism. 9 The mechanism of action of PAF antagonists on neutrophil infiltration into the inflammatory locus is discussed.

Possible roles of protein kinases in neutrophil chemotactic factor production by leucocytes in allergic inflammation in rats

“…Neutrophil chemotactic activity in the diluted supernatant fraction of the conditioned medium was assayed using modified Boyden chambers as described previously (Watanabe et al, 1994).…”

“…infiltrated into the pouch fluid in the allergic inflammation model are much more active than those in the non-allergic inflammation model with respect to neutrophil chemotactic factor production. When the infiltrated leucocytes in the pouch fluid were collected 4 h after injection of the antigen solution and incubated, leucocytes from the immunized rats produced a larger amount of neutrophil chemotactic factors than did leucocytes from the non-immunized rats, thereby suggesting that the leucocytes infiltrated into the pouch fluid in the immunized rats are much more active than those in the non-immunized rats (Watanabe et al, 1994). Our present investigation was intended to clarify pharmacologically the mechanism of activation of leucocytes for the production of neutrophil chemotactic factors in the allergic inflammation.…”

“…During the course of experiments to identify the difference between allergic and non-allergic inflammation employing an air pouch-type inflammation model in rats 1985;Tsurufuji et al, 1982;Hirasawa et al, 1986;Watanabe et al,1987;1990), focused especially on the qualitative difference in the function of infiltrated leucocytes, we found (Watanabe et al, 1994) that the leucocytes ' Author for correspondence. infiltrated into the pouch fluid in the allergic inflammation model are much more active than those in the non-allergic inflammation model with respect to neutrophil chemotactic factor production.…”

“…We have reported that the leucocytes infiltrated into the pouch fluid produce two neutrophil chemotactic proteins, leucocyte-derived neutrophil chemotactic factor (LDNCF) 1 and LDNCF-2 (Watanabe et al, 1994). It is possible that the production of the two chemotactic proteins by the infiltrated leucocytes is induced after activation of leucocytes at the inflammatory sites.…”

Enhancement by cyclo‐oxygenase inhibitors of platelet‐activating factor production in thapsigargin‐stimulated macrophages

“…Therefore, PAF has been implicated as a potent chemical mediator of inflammation and allergy. We reported (Watanabe et al, 1990;1994) that several PAF antagonists inhibit neutrophil infiltration in the allergic inflammation model in rats and suggested that PAF plays a significant role in neutrophil infiltration.…”