Colchicine inhibits arachidonate release and 5-lipoxygenase action
in alveolar macrophages.
Peters-Golden, Marc, Robert W. McNish, Julie A. Davis, R. Alexander
Blackwood, and Thomas G. Brock.
Division of Pulmonary and Critical Care Medicine and the Division
of Nephrology, Department of Internal Medicine, and #the Department
of Pediatrics, University of Michigan and Veterans Affairs Medical
Centers, Ann Arbor, MI 48109-0652
APStracts 3:0147L, 1996.
Although colchicine is known to inhibit leukotriene synthesis in
neutrophils, its effect on other aspects of arachidonic acid (AA)
metabolism, as well as its mechanism of action, is unknown. To
address these questions, we investigated the effects of colchicine on
resident rat alveolar macrophages (AM), cells that generate a variety
of lipoxygenase and cyclooxygenase products following stimulation.
Pretreatment of AM with 10 [mu]M colchicine for 1 h dramatically
inhibited the synthesis of all 5-lipoxygenase (5-LO) metabolites from
endogenous AA in ionophore A23187-stimulated cells. In addition,
colchicine inhibited the total release of AA as well as prostanoids
to a lesser extent. Similar effects were observed with the other
microtubule-disruptive agents nocodazole and vinblastine, and 5-LO
product formation stimulated by the particulate agonist zymosan was
inhibited as well. A selective inhibitory effect of colchicine on the
5-LO pathway was demonstrated by monitoring the synthesis of 5-LO
products from exogenously supplied AA. Cell-free enzyme assays showed
that this effect was not through a direct inhibition of the 5-LO
enzyme. Moreover, colchicine did not affect the translocation of 5-LO
to the nuclear envelope. We next evaluated the effect of colchicine
on the levels of the two 5-LO cofactors, ATP and calcium. While
colchicine did not affect ATP levels, it did abrogate the ionophore
-induced increase in intracellular Ca2+ concentration; the inhibitory
effect of colchicine on 5-LO metabolism in AM was partially overcome
by stimulation with higher doses of A23187. We conclude that
microtubular disruption inhibits agonist-induced increases in
intracellular Ca2+ concentration, with multiple consequences for AA
metabolism. These include a reduction in the liberation of AA from
membrane phospholipids as well as the selective inhibition of
processing of AA by 5-LO.
Received 30 November 1995; accepted in final form 22 June 1996.
APS Manuscript Number L347-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996