Effects of solubilization and vanadate/glutathione complex on inhibitor potencies against eosinophil cyclic AMP‐specific phosphodiesterase

Souness, John E.; Maslen, Christopher; Scott, Lisa C.

doi:10.1016/0014-5793(92)80435-j

Cited by 36 publications

(34 citation statements)

References 11 publications

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“…Complexing PDE4A4 with the SRC homology (SH3) domains of tyrosyl protein kinases, such as LYN, FYN, and SRC, increases its sensitivity to inhibition by rolipram (McPhee et al, 1999). Treatment of guinea pig eosinophil membranes with deoxycholate and high salt or with a vanadate/glutathione complex increases the potency of rolipram by greater than 10-fold (Souness et al, 1992). PKA-mediated phosphorylation of PDE4D3 increases its sensitivity to rolipram inhibition (Sette and Conti, 1996;Hoffmann et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Antidepressant-Induced Increase in High-Affinity Rolipram Binding Sites in Rat Brain: Dependence on Noradrenergic and Serotonergic Function

Zhao¹,

Zhang²,

O'Donnell³

2003

J Pharmacol Exp Ther

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Section: Discussionmentioning

confidence: 99%

Antidepressant-Induced Increase in High-Affinity Rolipram Binding Sites in Rat Brain: Dependence on Noradrenergic and Serotonergic Function

Zhao¹,

Zhang²,

O'Donnell³

2003

J Pharmacol Exp Ther

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“…Alternatively, the aforementioned lack of correlation may be explained by the existence of two sites (a catalytic site and a second biologically important site) on PDE IV as proposed for the guinea-pig eosinophil enzyme (Souness et al, 1992 Based on the results discussed so far, the question arises why the non-selective PDE inhibitors IBMX and theophylline are able to suppress eosinophil functions in contrast to the selective PDE IV and III/IV inhibitors. The fact that human eosinophils contain PDE IV as the exclusive PDE isoenzyme suggests that other mechanisms besides or in addition to PDE inhibition may contribute to the inhibitory action of IBMX and theophylline.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of non‐selective and selective phosphodiesterase inhibitors on human eosinophil functions

Hatzelmann

Tenor

Schudt

1995

British J Pharmacology

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1 The effect of non-selective (3-isobutyl-l-methylxanthine, IBMX; theophylline) and type IV-or tolafentrine also inhibited both cell responses in the presence of salbutamol, the potency of these two compounds in inhibiting eosinophil function in intact cells was at least two orders of magnitude lower than would have been expected from the inhibition of PDE IV activity in the cell-free system. 5 These results indicate that (i) C0a-stimulated human eosinophils are sensitive to inhibition by the non-selective PDE inhibitors theophylline and IBMX, (ii) the inhibitory effect of these non-selective PDE inhibitors cannot be mimicked by selective PDE IV or PDE III/IV inhibitors although human eosinophils almost exclusively contain PDE IV; (iii) the selective PDE inhibitors need an additional cyclic AMP trigger like a P2-adrenoceptor agonist to be effective; but (iv) under the latter conditions inhibition of cell responses in intact cells does not correspond to inhibition of PDE IV activity in the cell-free system. 6 We conclude that the non-selective PDE-inhibiting xanthines may inhibit C5a-stimulated human eosinophil responses by other action(s) in addition to PDE IV inhibition, and that inhibition of PDE IV activity in the cell-free system by the selective inhibitors may not generally represent the potency of the compounds in intact cells.

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“…Thus, under the aforementioned conditions, ibudilast is a relatively potent PDE IV inhibitor, exhibiting IC50 values which are at least 100 fold lower than those against other PDE isoenzymes. The increased potencies of some, but not all, PDE inhibitors against the eosinophil PDE IV caused by solubilization or V/GSH led us to propose the existence of a biologically important high-affinity site on the enzyme at which rolipramlike compounds can interact (Souness et al, 1992). This site was envisaged as concealed in freshly prepared membranes and exposed by solubilization or V/GSH treatment.…”

Section: Discussionmentioning

confidence: 99%

“…An increased potency of ibudilast (IC50 = 0.11 ± 0.05 EM, n = 3) was also observed under these conditions (Figure 1). Exposure of membranebound PDE IV to V/GSH, which activates PDE III (Souness et al, 1985) and PDE IV (Souness et al, 1992) through an uncertain mechanism likely to involve an active complex of a vanadyl ion and two or more electron donors (Thompson et al, 1991), similarly increased the potencies of both ibudilast (ICm = 0.11 ± 0.02 gM, n = 3) and rolipram (ICm = 0.02 ± 0.01 #IM, n = 3) (Figure 2). The 8 fold increase in ibudilast potency observed when the PDE IV was solubilized or exposed to V/GSH was slightly less than that seen with rolipram (10-16 fold).…”

Section: Inhibition Of Eosinophil Pde IVmentioning

confidence: 99%

“…Both ibudilast (IC, = 0.87 ± 0.37 JIM, n = 3) and rolipram (IC50 = 0.20 ± 0.04 pM, n = 5) were more potent inhibitors of this activity than of the partially purified PDE IV from bovine trachea (Figures 1 & 2). As previously demonstrated (Souness et al, 1992), the potency IC5o values were determined as described in the Methods section. The Ca2" PDE (I) was assayed in the presence of Ca2l (2 mM) + calmodulin (2.5 u).…”

Section: Inhibition Of Eosinophil Pde IVmentioning

confidence: 99%

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Possible role of cyclic AMP phosphodiesterases in the actions of ibudilast on eosinophil thromboxane generation and airways smooth muscle tone

Souness¹,

Villamil²,

Scott³

et al. 1994

British J Pharmacology

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1 The possible role of cyclic AMP phosphodiesterase (PDE) in the inhibitory actions of ibudilast on tracheal smooth muscle contractility and eosinophil thromboxane generation was investigated. 2 Ibudilast was a non-selective inhibitor of partially purified cyclic nucleotide PDE isoenzymes from pig aorta and bovine tracheal smooth muscle, exhibiting only moderate potency against bovine tracheal PDE IV (IC0 = 12 ± 4 AM, n = 3). Similar or slightly lower potencies were displayed against PDEs I, II, III and V. In contrast, rolipram exhibited selectivity for PDE IV (3 0.5 AM, n = 3).3 Ibudilast (IC50 = 0.87 ± 0.37 AM, n = 3), like rolipram (IC = 0.20 0.04 AM, n = 3), was a more potent inhibitor of membrane-bound PDE IV from guinea-pig eosinophils than of partially purified PDE IV from bovine tracheal smooth muscle. The potency of ibudilast increased when the eosinophil enzyme was solubilised with deoxycholate and NaCl (IC50 = 0.11 ± 0.05 JAM, n = 3) or exposed to vanadate/glutathione complex (V/GSH) (ICo=0.11 ± 0.02 JM, n = 3). The potency of rolipram was also increased by solubilization (IC50 = 0.012 0.003, n = 3) or V/GSH (IC,0 = 0.012 ± 0.003, n = 3). 4 In intact eosinophils, ibudilast (0.032 jiM-20 JM) potentiated isoprenaline-induced cyclic AMP accumulation in a concentration-dependent manner, being approximately 20 fold less potent than rolipram. Little or no effect on basal cyclic AMP levels was observed with either compound. The cyclic AMP-dependent protein kinase activity ratio was significantly increased following incubation of eosinophils with either ibudilast (20 AM) or rolipram (20 gM) in the absence or presence of isoprenaline. 5Leukotriene B4 (300 nM)-induced thromboxane generation from guinea-pig eosinophils was inhibited by ibudilast (IC50 = 11.3 ± 3.7 AM, n = 5) and rolipram (IC,0 = 0.280 ± 0.067 AM, n = 5) in a concentration-dependent manner. 6 Ibudilast (10 nM-I AM), whilst generally less potent than rolipram (1 nM-AM), produced concentration-dependent relaxation of spasmogen (methacholine, histamine, LTD4)-induced tone in the guineapig isolated tracheal strip. Ibudilast was less potent in reversing the methacholine (IC50 = 1.95 ± 0.40 JM, n = 6)-induced contraction than those of histamine (IC50 = 0.18 ± 0.70 AM, n =6) or leukotriene D4 (LTD4, IC50 = 0.12 ± 0.05 JM, n = 6). Rolipram also exhibited a similar pattern of activity, although the difference in potency against methacholine (IC50 = 0.1 ± 0.01 JAM, n = 6) compared with the other two spasmogens, histamine (IC50 = 0.034 ± 0.017 JM, n = 7) and LTD4 (IC50 = 0.026 ± 0.008 AM, n = 7), was not as great.7 These results demonstrate that ibudilast, like rolipram, has several biological actions on the eosinophil and airways smooth muscle which may be attributed to inhibition of cyclic AMP PDE. These actions may account, at least in part, for the recently reported anti-asthma effects of ibudilast.

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Effects of solubilization and vanadate/glutathione complex on inhibitor potencies against eosinophil cyclic AMP‐specific phosphodiesterase

Cited by 36 publications

References 11 publications

Antidepressant-Induced Increase in High-Affinity Rolipram Binding Sites in Rat Brain: Dependence on Noradrenergic and Serotonergic Function

Antidepressant-Induced Increase in High-Affinity Rolipram Binding Sites in Rat Brain: Dependence on Noradrenergic and Serotonergic Function

Differential effects of non‐selective and selective phosphodiesterase inhibitors on human eosinophil functions

Possible role of cyclic AMP phosphodiesterases in the actions of ibudilast on eosinophil thromboxane generation and airways smooth muscle tone

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