Massimo Giossi

The involvement of the release of nitric oxide in the pharmacological activity of the new furoxan derivative CHF 2363

1 The mechanism of action and the pharmacological effects of the new furoxan derivative, CHF 2363 (4‐ethoxy‐3‐phenylsulphonylfuroxan), were investigated. 2 Pre‐incubation of CHF 2363 with human platelet‐rich plasma produced a concentration‐dependent inhibition of the platelet aggregation induced by collagen, adenosine diphosphate (ADP) and platelet activating factor (PAF). The test compound was about 5 times more potent than sodium nitroprusside. 3‐Isobutyl‐1‐methyl‐xanthine (IBMX) potentiated the antiaggregating effect of CHF 2363. 3 CHF 2363 was a potent inhibitor of rubbed endothelium rabbit aortic ring contraction induced by noradrenaline. Comparison of IC50 values showed that CHF 2363 was as potent as glyceryl trinitrate (GTN). 4 Increasing concentrations of CHF 2363 elevated platelet guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) levels. Adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) levels were unaffected. 5 Oxyhaemoglobin reduced all the pharmacological actions of the test compound. Moreover, CHF 2363 concentration‐dependently released nitric oxide (NO) in platelet‐rich plasma. The NO release was correlated to its ability to increase platelet cyclic GMP levels. 6 After exposure of rat aortic strips to supramaximal concentrations of GTN (550 μm), the vasorelaxant activity of CHF 2363 did not change, although that of GTN decreased about 55 fold. 7 It has been concluded that the new furoxan derivative CHF 2363 exerts a potent antiaggregating and vasorelaxant activity via NO release and increase of cyclic GMP levels. No in vitro cross tolerance between GTN and CHF 2363 was observed.

INHIBITION OF PARATHYROID HORMONE-STIMULATED RESORPTION IN CULTURED FETAL RAT LONG BONES BY THE MAIN METABOLITES OF IPRIFLAVONE

Ipriflavone is an isoflavone derivative used in the prevention and treatment of postmenopausal and senile osteoporosis in humans. To assess the potential contribution of the mainin vivo ipriflavone metabolites (M1, M2, M3, and M5) on the pharmacological properties of the drug, we investigated their effect on osteoclastic resorption induced by the well-known stimulator of bone resorption bovine parathyroid hormone fragment 1–34 (bPTH 1–34). The study was carried out using fetal rat long bones in stationary cultures. The amount of osteoclastic resorption was determined by assaying for 5 days the release from bones in the media of previously incorporated45Ca. All metabolites were effective at inhibiting osteoclastic resorption. Maximal potency was shown by M3, characterized by a significant effect at 10 μM (P<0.01) and by an IC50 value of 17 μM. M2 was about threefold less potent than M3 (IC50=46 μM). M1 and m5 were the least active compounds with an IC50 value of 117 and 200 μM, respectively. The present evidence indicates that metabolites of ipriflavone, in particular M3 and M2, inhibit bPTH 1–34-induced bone resorption in fetal rat long bones. Accordingly, they may play an important role in the pharmacological effects of the drug.

Modulation of arachidonic acid metabolism by orally administered morniflumate in man

Unlike other classic NSAIDs, some fenamates given at therapeutic concentrations, have been shown to inhibit, bothin vitro andin vivo, the 5-lipoxygenase pathway of arachidonic acid cascade as well as the synthesis of cyclooxygenase products. This dual inhibitory property might represent an improvement in anti-inflammatory therapy. The aim of this work was to characterize the effect of morniflumate, admistered at therapeutic dosages to normal human volunteers, on leukotriene B4 (LTB4) and thromboxane (TXB2) synthesis, both in purified PMNs and in whole blood. PMNs, isolated two hours after a single oral administration of morniflumate and at steady-state condition, fully retain their capacity to release LTB4 and TXB2. Since intracellular concentrations of the drug were undetectable, in spite of its elevated concentrations in platelet poor plasma, the results obtained using PMNs suggest a drug loss during the cells purification procedure. In whole blood experiments, morniflumate reduced blood LTB4 synthesis induced by Ca-ionophore A23187 Bx approximately 50%, both after single dose and at steady state; the degree of inhibition showed a pattern similar to the plasma levels of the bioactive metabolite of morniflumate (M1). The inhibition of serum TXB2 levels was higher than 85%. Hence, morniflumate is capable of reducing arachidonic acid metabolism acting both on cyclooxygenase and 5-lipoxygenase. This characteristic might provide a better approach in anti-inflammatory therapy.

Comparative analysis of isolated human bronchi contraction and biosynthesis of cysteinyl leukotrienes using a direct 5-lipoxygenase inhibitor

Quantitation of cysteinyl leukotriene production and smooth muscle contraction upon immunological challenge of isolated human bronchi was evaluated. Analysis of picomole amounts of leukotriene C4, D4, and E4 was achieved using HPLC separation and enzyme immunoassay quantitative determination. The aim of the study was to correlate the contraction of airway smooth muscle and cysteinyl leukotriene production with and without 5-lipoxygenase inhibition. In human isolated bronchial tissue treated with indomethacin and pyrilamine to make their contractile responses leukotriene dependent only, the novel 5-lipoxygenase inhibitor 5,6-Dihydroxy-2-(N,N-Dimethylhydrazino)-1,2,3,4-tetrahydro-naph talene bromide (CHF 1909) caused a concentration-dependent inhibition of the immunologically induced contraction, showing an IC50 value of 13 +/- 2.2 microM (mean +/- CV). At the concentration of 30 microM, this compound caused more than 90% inhibition of the maximal bronchoconstriction in vitro, and inhibited cysteinyl leukotriene production by 90% as well. Contemporary measurement of immunologically induced contraction and production of cysteinyl leukotrienes in isolated human bronchi provided a direct correlation between smooth muscle contraction and synthesis of leukotriene C4, D4, and E4.