Effects of colchicine on cyclic AMP levels in human leukocytes

Abstract

The increase in human leukocyte adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels seen in response to various substances was markedly potentiated by colchicine and other agents that affect microtubule assembly. Addition of dI-isoproterenol (2 AiM) or prostaglandin El (10 ttM), together with the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM), caused a much greater increase in cyclic AMP in colchicine-pretreated cells tan in control cells. With isoproterenol (2 MM) plus isobutylmethylxanthine (1 mM), cyclic AMP levels rose about 3fold but, in combination with colchicine, these drugs caused a more than 15-fold increase in cyclic AMP. The effects of colchicine were both time-and dose-dependent; they could be seen'within 1 min after addition of colchichme or at concentrations as low as 10 nM. In addition to its potentiation of hormonally induced increases in cyclic AMP levels, colchicine also potentiated the effect of isobutylmethylxanthine alone on leukocyte cyclic AMP levels. Vinblastine, vincristine, podophyllotoxin, and oncodazole all had effects similar to those of colchicine but blmicolchicine did not. The data suggest that cytoplasmic nticrbtubules interact with the leukocyte plasma membrane to impose constraints on the expression of hormone-sensitive adenylate cyclase; the therapeutic effects of colchicine may depend in part upon the relaxation of such constraints. Moreover, the synergism described here between colchicine-like agents and hormones is of potential therapeutic importanceiln clinical conditions in which either alkaloid or hormone has been useful separately. IThe cyclic nucleotide levels of human leukocytes (both granulocytes and mononuclear cells) are controlled by a number of hormones and pharmacological agents (1-5). f3-Adrenergic agonists (isoproterenol, epinephrine), histamine, and prostaglandin E1 (PGE1) all raise adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels in these cells; the muscarinic cholinergic agonists (acetylcholine, carbamylcholine) raise cyclic GMP levels. In granulocytes, a functional significance of cyclic nucleotides has been suggested by experiments showing that increases in cyclic AMP inhibit the degranulation of lysosomes that normally accompanies phagocytosis, whereas increases in cyclic GMP enhance degranulation (2, 3, 5, 6). Colchicine and vinblastine, agents that cause the disappearance of cytoplasmic microtubules by preventing their assembly (7-10), also inhibit degranulation (6, 11-13); it is through this inhibition of microtubule assembly, with consequent effects on microtubuleassociated functions, that colchicine is thought to exert its therapeutic anti-inflammatory action in acute gouty arthritis and other disorders (14). We now report that colchicine and other agents that interfere with microtubule assembly increase cyclic AMP levels in human leukocytes and potentiate the effects of hormones on cyclic AMP levels in these cells. METHODSLeukocytes were obtained from freshly drawn, heparinized blood from healthy, adult donors by de...

Characterization of (-)-[3H]dihydroalprenolol binding to intact and broken cell preparations of human peripheral blood lymphocytes

“…The intact cell procedure provides the possibility for investigating the ,8-adrenergic receptor system under physiological conditions, retaining the integrity of the cell and all factors which are required for B-adrenergic receptor function. This includes in particular soluble factors such as guanine nucleotides and functional cytoskeletal elements, which may be lost in membrane preparations (Ross et al, 1977;Rudolph et al, 1977). A change in these factors may have caused the observed differences between fl-adrenergic receptor affinity for agonists and antagonists in intact and broken cell preparations.…”

Colchicine alters the quantitative and qualitative display of selectins on endothelial cells and neutrophils.

“…Indeed, colchicine, by a microtubuledependent mechanism, enhances capping of concanavalin Abinding glycoproteins ( 10) but diminishes surface expression of receptors for TNFa (6), insulin (9), and /3-adrenergic agonists ( 11). Colchicine also inhibits assembly of the leukotreineB4-forming complex at the plasma membrane (5), affects the interactions of heterotrimeric G proteins with the catalytic subunit of adenylate cyclase (13), increases intracellular cAMP (14), and enhances the synthesis of stable prostaglandins (15). Each of these effects, shared with vinblastine and nocodazole but not lumicolchicine, has been held responsible for one or another of the effects of colchicine in inflammation.…”

Cytoskeleton regulates β‐adrenergic hormonal stimulation in normal and leukemic white blood cells

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