Ira Weinryb

Population distribution and effects on drug metabolism of a genetic variant in the 5′ promotor region of CYP3A4

There are large interindividual differences in CYP3A4 expression and in the metabolism of drug substrates for this enzyme. We and others have identified a polymorphism in the 5′ promotor region of the CYP3A4 gene; however, its functional significance is not currently known. This study was conducted to determine whether this polymorphism plays a clinically important role in determining CYP3A4 phenotype.

Potent magnesium-dependent inhibition of adenylate cyclase activity from guinea pig lung by adenosine and other 9-substituted adenines

Abstract The inhibition of adenylate cyclase activity (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) from guinea pig lung by adenosine and a number of 9-substituted adenines was Mg 2+ -dependent, the compounds being up to 13 times more potent at saturating or near saturating Mg 2+ concentrations (11.8 mM) than at limiting (1.8 mM) concentrations. Inhibition by adenine and 6-mercaptopurine did not show a Mg 2+ dependence. The most potent inhibitors of cyclase activity at 11.8 mM Mg 2+ of the 9-substituted adenines tested were: 9-(tetrahydro-5-methyl-2-furyl)adenine ( I 50 = 8 μ M), 9-(tetrahydro-2-furyl)adenine ( I 50 = 10 μ M), 9-cyclopentyladine I 50 = 20 μ M), and 9-furfuryadenine I 50 = 26 μ M). The inhibition of lung cyclase activity by 9-(tetrahydro-2-furyl)adenine was deduced to be hyperbolic non-competitive at 1.8 mM ( K 1 = 1.2·10 −4 M) and 11.8 mM ( K 1 = 2.5·10 −6 M) Mg + from analysis of double-reciprocal plots; these plots showed a concave downward non-linearity in the presence of inhibitor at both Mg 2+ concentrations. This non-linearity was eliminated under conditions where Mg 2+ levels were never in excess of those of ATP. Hill plots of the inhibition by 9-(tetrahydro-2-furyl)adenine (and by adenosine) suggested that negative co-operativity is involved in binding to the enzyme. The possibility that the Mg 2+ -dependence of inhibitory potency of adenosine and its analogs functions as a cellular control mechanism is discussed.

Dihydro- and tetrahydroisoquinolines as inhibitors of cyclic nucleotide phosphodiesterases from dog heart: Structure-activity relationships

Abstract A series of nineteen closely related dihydro- and tetrahydroisoquinolines was examined for inhibitory effects on soluble and particulate preparations of cyclic AMP and cyclic GMP phosphodiesterases from dog heart. Dose-response curves for all the compounds were approximately parallel. 6, 7-Dimethoxy-1 [3-(trifluoromethyl)phenyl]-3, 4-dihydroisoquinoline hydrochloride (USV 2776), the most potent inhibitor in this series, was a competitive inhibitor of all preparations tested, with K i values of 2–3 μM for membrane cyclic AMP and cyclic GMP phosphodiesterases and 1, 10 and 5μM for soluble “low K m ” cyclic AMP, “high K m ” cyclic AMP and cyclic GMP phosphodiesterases respectively. 6-Methoxy-7-benzyloxy-I-phenyl-3, 4 dihydroisoquinoline hydrochloride (USV 2469) was about equipotent to USV 2776; both 2776 and 2469 were two to four times more potent than papaverine and 1-methyl-3-isobutylxanthine. Each dihydroisoquinoline was much more potent than its tetrahydroisoquinoline counterpart. Inhibitory potency was influenced by 6, 7-substitutions. e.g. at the C-6 position, benzyloxy > methoxy > hydroxy > hydrogen or methyl. These compounds represent a group of phosphodiesterase inhibitors spanning a 3000-fold activity range, which are related to each other by single structural modifications; they are potentially useful in denning the role of phosphodiesterase inhibition in the various pharmacologic effects elicited by isoquinolines, including papaverine.

Adenylate cyclase from guinea pig lung: Further characterization and inhibitory effects of substrate analogs and cyclic nucleotides

Abstract A potent ( K i = 0.01 mM ), competitive inhibition of adenylate cyclase activity in particulate fractions of guinea pig lung by 2′ O -palmitoyl cyclic AMP has been observed, in striking contrast to the inactivity of cyclic AMP and N 6 ,2′ O -dibutyryl cyclic AMP at concentrations of up to 1 m m or more. The possibility that 2′ O -palmitoyl cyclic AMP or similar compounds might function as endogenous regulators of the hormonal stimulation of adenylate cyclase activity is discussed. Several 6- and 8- substituted purine 3′,5′-cyclic ribotides also inhibit, probably by direct interaction with enzymatic sulfhydryl groups. A study of the inhibition by purine bases, nucleosides, and 5′ nucleotides suggests that most of the substrate (ATP) binding determinants reside in the nucleoside. The particulate enzyme fractions were found to have lower ATPase activity relative to cyclase activity than cyclase preparations from either guinea pig heart or bronchial smooth muscle. Lung cyclase fractions were maximally stimulated by 5–15 m m Mg 2+ in the presence of 1.2 m m ATP as substrate. The percentage of stimulation of cyclase activity by 0.01 m m isoproterenol is dependent on the Mg 2+ concentration. Cyclase activity was significantly stimulated not only by the catecholamines (isoproterenol, epinephrine, and norepinephrine) and fluoride ion, but also by prostaglandins E 1 , E 2 , and F 2α , histamine, and glucagon.

Arylmethyl Phenyl Ethers

Oxidative metabolites of arachidonic acid produced by the 5-lipoxygenase pathway are potent mediators of hypersensitivity and inflammation (see O’Flaherty, 1982; Lewis and Austen, 1984 for reviews). Their proposed roles in the pathophysiology of asthma, chronic inflammation, and psoriasis have prompted an intense search for specific inhibitors of their biosynthesis (Bach, 1984). Three years ago a program was initiated at Revlon Health Care Group to find compounds that would modulate the biosynthesis of leukotrienes or antagonize their spasmogenic actions on smooth muscle. In particular, we sought specific and stable inhibitors of the 5-lipoxygenase (5-LOX) enzyme, utilizing a cellular assay as our primary screening tool.

Divergent effects of theophylline on adenylate cyclase preparations from guinea-pig heart and lung

Theophyllin verringert die Aktivität der Adenyl-Cyclase (AC) in der plasmamembranreichen Fraktion der Meerschweinchenlunge in Konzentrationen von 6–10 mM; es hat dagegen keinen Einfluss auf die Aktivität der AC in Meerschweinchenherzen. Diese Resultate weisen darauf hin, dass in verschiedenen Geweben geringe Unterschiede in der Enzym-Katalyse bestehen können.

Interactions of α-methylfluorene-2-acetic acid with adenylate cyclase☆

Abstract α-Methylfluorene-2-acetic acid (MFA), a new anti-inflammatory agent, enhanced the stimulation of adenylate cyclase activity from guinea pig heart by isoproterenol, epinephrine and norepinephrine, but did not cause increases in either basal or histamine-stimulated activity. Propranolol blocked the effects of isoproterenol plus MFA on heart cyclase activity. MFA did not enhance PGE 1 - or PGE 2 -stimulated cyclase activity from guinea pig lung; effects of MFA on isoproterenol-stimulated activity were obscured by a marked inhibition of basal activity. d -MFA and l -MFA were equipotent enhancers of isoproterenol-responsive heart cyclase activity. Increases in isoproterenol-stimulated cyclase activity from heart in the presence of MFA appeared reversible; decreases in basal activity were irreversible. The action of MFA was not due to inhibition of cyclic nueleotide phosphodiesterase activity, nor did MFA appear either to affect catecholamine degradation or to antagonize an endogenous cytoplasmic inhibitor of catecholamine action. It is possible that MFA perturbed the membrane milieu of the cyclase complex so as to have enhanced catecholamine binding to hormone receptors or coupling of the binding event to cyclic AMP synthesis.

REV 2871 (CHBZ): A novel inhibitor of histamine release

CHBZ is a novel, non-disodium cromoglycate (DSCG)-like, antiallergic drugin vitro. Whereas DSCG loses anti-secretory activity with increasing time of preincubation with rat mast cells (RMC) before antigen challenge, and does not inhibit non-immunologically mediated release from human leukocytes, CHBZ exerts long-lived inhibition of both types of release from both types of cells. CHBZ is taken up by RMC in a saturable and time-dependent manner. It is enzymatically converted inside RMC to a DSCG-like metabolite, REV 3579, which, because of its ionic character, accumulates inside the cell. CHBZ, presumably through the action of the REV 3579 generated intracellularly, may mediate long-lived phosphorylation of the same 78 K protein which is transiently phosphorylated upon exposure of RMC to DSCG.

RHC 3288 [1-methyl-2(1,3,4-oxadiazol-2(3H)-one-5-yl) benzimidazole] and related compounds: Novel inhibitors of histamine release from rat mast cells and human basophils

RHC 3288 [1-methyl-2(1,3,4-oxadiazol-2(3H)-one-5-yl) benzimidazole] and twenty-five related 5-substituted oxadiazolones have been investigated for their antiallergic activities in three in vitro models of anaphylaxis. Sixteen compounds were potent (I50 less than or equal to 50 microM) inhibitors of antigen-induced release of histamine (AIR) from rat mast cells (RMC), and seven compounds inhibited anti-IgE-induced release of histamine from human basophils (I50 less than or equal to 100 microM). The antiallergic activity profiles of RHC 3288 and three other compounds in these models have been compared with that of disodium cromoglycate (DSCG). As inhibitors of AIR from RMC, RHC 3288, 3334, 3354 and 3380 were 3 to 10 times more potent than DSCG. In the same model (AIR from RMC), activity profiles of all four RHC compounds were identical to that of DSCG in the following respects: loss of inhibitory activity with increasing preincubation time, tachyphylaxis and cross-tachyphylaxis to each other, and inability to inhibit histamine release stimulated by Ca2+ ionophore, dextran + phosphatidyl serine and compound 48/80. RHC 3288, 3334, 3354 and DSCG had no effect in the other two models, histamine release from guinea pig lung mediated predominantly by IgG1 class of antibodies and anti-IgE-induced histamine release from human basophils. We conclude that RHC 3288 is a potent inhibitor of mediator release with a mechanism of action similar to that of DSCG.

REV 2871 (CHBZ): A potent antiallergic agent with a novel mechanism of action: I. Activity profile as an inhibitor of mediator release☆☆☆

REV 2871 (CHBZ) and its putative metabolite REV 3579-Z (also designated in the literature as RHC 3579-Z) were shown to be potent and orally effective inhibitors of passive cutaneous anaphylaxis (PCA) in the rat (ED50 = 12 mg/kg). The activity profiles of CHBZ, REV 3579-Z and disodium cromoglycate (DSCG) were compared as inhibitors of histamine release (HR) in vitro from rat mast cells, human basophils, and guinea pig lung slices. CHBZ was a potent inhibitor of both immunologic and non-immunologic HR (I50 2-20 microM from rat mast cells). The activity profile of CHBZ as an inhibitor of HR from rat mast cells differed from that of DSCG and REV 3579-Z in the following respects: increasing inhibition of HR with increasing preincubation time; irreversibility of the inhibition; lack of tachyphylaxis and cross-tachyphylaxis to DSCG; potentiation of the inhibition of antigen-induced release of histamine (AIR) by DSCG; and inhibition of HR induced by dextran + phosphatidyl serine, compound 48/80, ionophore A23187 and platelet activating factor (PAF). In the human basophil model, CHBZ was: a potent inhibitor (I50 = 25 microM) of anti-IgE-induced release (AbIR), whereas DSCG and REV 3579-Z had no effect on AbIR; more potent as an inhibitor of AbIR than ionophore-induced release, whereas the reverse was true for proxicromil; an inhibitor of PAF-induced release, whereas proximcromil stimulated it; and potentiative with proxicromil for inhibition of AbIR. In the guinea pig lung slice model, CHBZ inhibited AIR (I50 = 800 microM) whereas DSCG and REV 3579-Z did not (I50 greater than 300 microM). We conclude that CHBZ is an orally effective antiallergic agent whose mechanism of action as an inhibitor of mediator release is different from DSCG and proxicromil.