FTY720 is an immunomodulating drug, approved for treating multiple sclerosis

by Selleckchem | Jun 03 2013

There is much evidence FTY720 to suggest a role for uncontrolled neutrophil activation in the pathophysiology of various chronic and acute diseases . Among the mediators capable of activating neutrophils, the chemokine IL-8 appears to be of particular importance, not only because it is a potent neutrophil chemoattractant and activating factor but also because neutrophils themselves can produce considerable amounts of IL-8 . In the present study, we have evaluated the e.ects of phosphodiesterase inhibitors and other cyclic AMP-elevating agents on the ability of neutrophils to release IL-8 in response to activation with zymosan particles. Three classes of compounds known to induce an elevation of cyclic AMP in neutrophils were used PDE4 inhibitors, prostaglandins of the E series, and a b2-adrenoceptor agonist . PDE4 inhibitors such as rolipram increase cyclic AMP levels by inhibiting the metabolism of cyclic AMP. Prostaglandins and the b2-adrenoceptor agonist increase cyclic AMP levels by activating surface receptors which are Gs protein coupled to the cyclic AMP-generating enzyme adenylate cyclase . Rolipram, when used alone, had little e.ect on the production of VEGFR IL-8 by zymosan-activated neutrophils. This is in agreement with the lack of e.ect of rolipram when used alone on various neutrophil functions, including the respira- tory burst . In contrast, two newly described PDE4 inhibitors, RP 73401 and SB 207499, dose-dependently and completely inhibited IL-8 generation by neutrophils when used alone at concentrations of 1077M and 1075M, respectively. RP 73401 was approxi-T0070907 mately 100 times more potent than SB 207499. The rank order of potencies of the PDE4 inhibitors in modulating IL-8 generation when used in combination with PGE2 is in good agreement with their rank order of potency at inhibiting the catalytic site of purired neutrophil PDE4 . The signi?cant synergism between PDE4 inhibitors and PGE2, or rolipram and salbutamol is in good agreement with other observation of synergistic interactions between agents which activate adenylate cyclase and suppress other neutrophil functions in vitro . In contrast to the e.ect of PDE4 inhibitors, a PDE3 and PDE5inhibitor had no inhibitory e.ect on zymosan-induced IL- 8 production alone or in combination withPGE2. This correlates with the lack of expression of PDE3 and PDE5 in neutrophils and suggests that PDE4 is the main isoenzyme responsible for the regulation of cyclic AMP and the generation of IL-8 in human neutrophils. Recently, Zurbonsen et al. showed that the antiproliferative e.ects of some PDE4 inhibitors on the Dami cell line was due to their cytotoxic e.ect rather than their e.ects on cyclicAMPlevels. Quizartinib However, since we failed to observe any signi?cant e.ect of PDE4 inhibitors on neutrophil viability, this could not account for the inhibitory e.ect of these drugs on IL-8 production from neutrophils. We evaluated the potential role of a cyclic AMP/PKA pathway in regulating IL-8 production by using two structurally distinct PKA inhibitors, H 89 and KT 5720 . Preincubating neutrophils with rolipram and PGE2 blocked the zymosan-induced IL-8 release and this inhibition was dose-dependently reversed by the PKA inhibitors. This indicates that activation of the cyclic AMP/protein kinase A cascade is an e.ective means of preventing Sodium valproate the production of IL-8 by zymosan-activated neutrophils. In this respect, the 5'-ranking region of the IL-8 gene isolated from monocytes has a cyclic AMP responsive element that is potentially the site of cyclic AMP regulation of monocyte-derived IL-8 . However, PGE2 does not inhibit the generation of IL-8 by neutrophils activated with LPS , suggesting that a direct e.ect on the IL-8 gene may not explain in full the inhibitory e.ects of cyclic AMP elevating agents observed in the present study.