Jgr. Elferink et Bm. De Koster, Inhibition of interleukin-8-activated human neutrophil chemotaxis by thapsigargin in a calcium- and cyclic AMP-dependent way, BIOCH PHARM, 59(4), 2000, pp. 369-375
Chemotactic migration of human neutrophils, induced by interleukin-8 (IL-8)
or other activators, was inhibited by thapsigargin in the high nanomolar r
ange. The degree of inhibition depended on the type of activator. Other inh
ibitors of Ca2+-ATPases associated with intracellular calcium stores, such
as cyclopiazonic acid and 2,5-di-(tert-butyl)-1,4-benzohydroquinone, equall
y inhibited IL-8-activated migration. Inhibition of migration by thapsigarg
in and the other ATPase inhibitors occurred only in the presence of extrace
llular Ca2+; migration was not inhibited in the presence of EGTA. La3+ reve
rsed thapsigargin-induced inhibition to a large degree; other calcium chann
el blockers gave a partial reversal (econazole, verapamil, and SK&F 96365)
or had no effect (gadolinium chloride and Ni2+). Using electroporated cells
and Ca buffers, it was shown that inhibition started at about 0.2 mu M and
was complete at a cytosolic Ca concentration of about 2 mu M. it appears t
hat under certain conditions the thapsigargin-induced influx of extracellul
ar calcium, causing relatively high local calcium concentrations, initiates
or permits a process which may be detrimental to chemotactic migration. Cy
clic AMP (cAMP; adenosine 3',5'-cyclic monophosphate) is probably involved
in this process, because thapsigargin increased the cAMP level and cAMP inh
ibited IL-8-activated migration in a calcium-dependent way. The hypothesis
that cAMP is involved in the effect of thapsigargin on migration is support
ed by the finding that very low concentrations of thapsigargin stimulate ne
utrophil migration in the absence of other chemoattractants. The results su
ggest that thapsigargin causes a (compartmentalized) increase in cAMP, whic
h results in a calcium-dependent modulation of migration. BIOCHEM PHARMACOL
59;4:369-375, 2000. (C) 2000 Elsevier Science Inc.