Mechanisms involved in activation of human eosinophil exocytosis by substance P: an in vitro model of sensory neuroimmunomodulation.
Substance P (SP), a tachykinin with a wide range of biological activities including a priming effect on human eosinophil chemotaxis, was investigated for its influence on eosinophil cytotoxic function measured as degranulation of eosinophil-derived neurotoxin (EDN). Peripheral blood was obtained from healthy volunteers and the degranulation assays were performed using radioimmunoassay (RIA). SP and its C-terminal elicited EDN release in a time-dependent mode at a narrow range of doses with optimal activity of 10(-6) M. FK888 (NK-1 receptor antagonist) inhibited EDN release stimulated by SP in dose dependency, also a complete inhibition was observed when eosinophils were preincubated with 1000 ng/ml pertussis toxin (PTX). Pre-exposure of eosinophils to staurosporine resulted in blockage of SP-induced EDN release in a dose-dependent mode. On the other hand, SP at 10(-7) M and 10(-8) M primed eosinophils to suboptimal dose (10(-8) M) of Platelet activating factor (PAF) resulting into significant enhancement of EDN release. SP(4-11) fragment showed a similar activity while SP(1-4) fragment was not active. SP priming of eosinophils was not affected by Ca2+ depletion, however, it caused a change in the pattern of the intracellular calcium influx against the suboptimal dose of PAF. These results suggest that SP i) may induced human eosinophil matrix protein degranulation through a receptor mediated mechanism coupled to PTX sensitive G protein(s) with the probability of linkage to phospholipase C activation, and, ii) primes human eosinophils for an exalted inflammatory response through a Ca2+ independent pathway.
el-Shazly
A E
AE
Department of Otorhinolaryngology, School of Medicine, Kumamoto Univesity, Japan.
Masuyama
K
K
Ishikawa
T
T
D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D047208:Eosinophil-Derived Neurotoxin; D004804:Eosinophils / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D018448:Models, Immunological; D015213:Neuroimmunomodulation; D064729:Neurokinin-1 Receptor Antagonists; D009498:Neurotoxins / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D012260:Ribonucleases; D015398:Signal Transduction; D013373:Substance P / Q000494:pharmacology*
D004151:Dipeptides; D007211:Indoles; D064729:Neurokinin-1 Receptor Antagonists; D009498:Neurotoxins; D010972:Platelet Activating Factor; C078949:FK 888; D013373:Substance P; D047208:Eosinophil-Derived Neurotoxin; D012260:Ribonucleases; D002118:Calcium