Does inhibition of aldose reductase contribute to the anti-inflammatory action of setipiprant?

The aim of this study was to investigate aldose reductase inhibitory action of setipiprant as a potential additional mechanism contributing to its anti-inflammatory action. Aldose reductase activity was determined by spectrophotometric measuring of NADPH consumption. Setipiprant was found to inhibit aldose reductase/NADPH-mediated reduction of 4-hydroxynonenal, 4-hydroxynonenal glutathione and prostaglandin H2 substrates, all relevant to the process of inflammation. Molecular modeling simulations into the aldose reductase inhibitor binding site revealed an interaction pattern of setipiprant. Considering multifactorial etiology of inflammatory pathologies, it is suggested that, in addition to the antagonizing prostaglandin D2 receptor, inhibition of aldose reductase may contribute to the reported anti-inflammatory action of setipiprant.

Development of the new group of indole-derived neuroprotective drugs affecting oxidative stress.

1. The role of oxidative stress, and accordingly uncontrolled reactive oxygen species generation/action, have been widely documented in a number of different neuronal pathologies. However, the concept of pharmacological interventions in prevention and therapy of oxidative stress-related diseases has not found adequate application in clinical practice. This may be due to the insufficient efficacy of drugs available, their unsuitable pharmacokinetics, side effects, toxicity, etc. 2. Based on stobadine, (--)-cis-2,8-dimethyl-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4,3-b]indole, a well-known antioxidant, free radical scavenger, and neuroprotectant, it was attempted to develop new stobadine derivatives with improved pharmacodynamic and toxicity profiles, on applying molecular design, synthesis and adequate tests. Stobadine molecule was modified mostly by electron donating substitution on the benzene ring and by alkoxycarbonyl substitution at N-2 position. A total of >70 derivatives were prepared. 3. In a mice model of head trauma, some of the new stobadine derivatives administered i.v. immediately after the trauma, significantly improved sensomotoric outcome in the animals assessed 1 h later. Accordingly, decrease in brain edema was proved histologically as well as by brain wet weight assessment. 4. Putative neuroprotective action of the compounds was confirmed on rat hippocampal slices exposed to reversible 6 min hypoxia/low glucose by analysis of synaptic transmission in CA1 region neurons. Irreversible impairment of neurotransmission resulting from the hypoxia was significantly reduced by the presence of SMe1EC2, one of the new compounds, in concentration range 0.03-10.0x10(-6) mol l(-1). Both the neuroprotective and antioxidant effect of the compound closely resembled those of stobadine, melatonin, 21-aminosteroids, alpha-phenyl-tert-butylnitrone and others, all well-established antioxidants, except the range of effective concentrations was by 1-2 orders lower in SMe1EC2. 5. A remarkable antioxidant efficacy was observed in the new compounds in rat brain homogenates exposed to iron/ascorbate system by protection of lipids and creatine kinase against the oxidative impairment. A link between the neuroprotective and antioxidant/ scavenger properties in the compounds can be assumed. 6. Acute toxicity of some of the new pyridoindoles was diminished compared to stobadine. That might be due to the virtually full elimination of stobadine's undesired alpha (1)-adrenolytic activity attained by appropriate modifications of its molecule. 7. The new pyridoindoles extend the range of available neuroprotectants interfering with oxidative stress in neuronal tissue.

Carvedilol--a beta-blocker with considerable antiaggregatory effect on human blood platelets.

BACKGROUND: Activated blood platelets play a key role in the genesis of many pathological states. Several studies have documented that beta-blockers can influence platelet aggregation. Carvedilol, a third generation non-selective agent with vasodilatory properties, is successfully used in pathological states accompanied with platelet hyperreactivity, however information on its antiplatelet activity is lacking. OBJECTIVES: The aim of this study was to analyse the in vitro effect of carvedilol on aggregation of human blood platelets, to compare this effect with the effect of propranolol and atenolol, and to determine whether its suggested antiaggregatory effect was accompanied with reduced thromboxane B2 formation. Moreover, some physico-chemical parameters of the drugs tested were calculated and compared. METHODS: Platelets were isolated by differential centrifugation and platelet aggregation was measured by the turbidimetric method. The amount of thromboxane B2 was measured by the radioimmunoassay method. Physico-chemical parameters of the drugs tested were calculated using the computer programme Hyperchem. RESULTS: Carvedilol and propranolol inhibited platelet aggregation in the rank order of stimuli: PMA > thrombin > A23187 > epinephrine. The reduction was accompanied by inhibition of thromboxane B2 formation. In comparison to propranolol, carvedilol was more effective, with the exception for aggregation stimulated with ADP. Atenolol did not affect any platelet function tested. From the drugs studied, the molecule of carvedilol was found to possess the highest partition coefficient, the highest index of molar refractivity, and the lowest dipole moment. CONCLUSION: Our study found carvedilol to be more potent than propranolol and atenolol in inhibiting platelet aggregation and thromboxane B2 production. This may be due to the different structure and more convenient physico-chemical parameters of the carvedilol molecule.

Antiplatelet activity of carvedilol in comparison to propranolol.

The non-selective vasodilating beta-blocker carvedilol was found to inhibit platelet aggregation as well as thromboxane B(2) formation more effectively than propranolol. The antiaggregatory activity of carvedilol decreased, depending on the stimulus used, in the following rank order of potency (in parentheses the respective mean inhibitory concentrations of carvedilol and propranolol are given in micromol/l): PMA (19 and 34) > thrombin (55 and 77) > Ca(2+)-ionophore A23187 (58 and 81) > epinephrine (86 and 118). However, aggregation of platelets activated with ADP was not affected by carvedilol in concentrations up to 100 micromol/l. In platelets stimulated with thrombin, carvedilol (10 micromol/l) reduced thromboxane B(2) formation by 64%, whereas propranolol was ineffective at this concentration. Moreover, A23187-induced formation of thromboxane B(2), not affected by propranolol, was completely blocked by 100 micromol/l carvedilol. In comparison to propranolol, the molecule of carvedilol is more lipophilic and possesses lower dipole moment and higher molar refractivity, thus penetrating into platelet membranes readily and in large quantities. The antiplatelet effect was assumed to result from interactions of carvedilol with membrane macromolecules (phospholipids, ion channels, enzymes, etc.) rather than from blockade of alpha- and beta-adrenergic receptors.

Structural aspects of antioxidant activity of substituted pyridoindoles.

Stobadine and its two structural analogues, dehydrostobadine and N-acetylated stobadine were used to examine how structural alteration in the close proximity of the indolic nitrogen would influence the antioxidant activity of the substituted pyridoindoles. The compounds were tested for their efficiency to scavenge stable free radicals of alpha,alpha'-diphenyl-beta-picrylhydrazyl as well as for their ability to prevent 2,2'-azobis-(2-amidinopropane)hydrochloride induced peroxidation of dioleoyl phosphatidylcholine liposomes. The results proved that the substituted pyridoindoles can act as potent scavengers of peroxyl radicals both in aqueous and lipid phases, the antioxidant activity being comparable with that of Trolox. Structural changes in the proximity of the indolic nitrogen were found crucial for the radical scavenging efficiency: aromatisation of the pyridoindole skeleton in dehydrostobadine lowered the antioxidant activity, while acetylation of the indolic nitrogen completely abolished the ability to scavenge peroxyl radicals. The results are in agreement with the notion that the antioxidant activity of stobadine and of the related pyridoindoles may be mediated via the indolic nitrogen centre. When stobadine and Trolox were present simultaneously in liposomal incubations, Trolox spared stobadine in a dose-dependent manner; a direct interaction of Trolox with stobadinyl radical appears to be a plausible explanation with possible consequences for the antioxidant capacity of stobadine under in vivo conditions, where re-cycling of stobadine by vitamin E might occur.

Theoretical study of the reactivity properties of two forms of stobadine.

The cardio- and neuroprotective effect of the pyridoindole stobadine (S) is conditioned mainly by its good radical scavenging properties. It has been showed by EPR experiment, that the ultimate product of the reaction of stobadine with hydroxyl radical is the nitroxyl radical. However, for the unsaturated dehydrostobadine (DHS) the ultimate product was not experimentally determined, although its reactivity with a hydroxyl radical has been detected. Using the quantum chemical method AM1 we calculated the physico-chemical properties of S, DHS and their radicals. For the stobadine alone, the corresponding radical was formed by removing the H* from the NH group of indol, while in the case of DHS we removed the CH3* from the nitrogen in pyridine ring. For S and DHS we calculated the differences in the energies between the parent molecules and the corresponding radicals as well as the spin distributions for the radicals. The results confirmed the differences in the reactivities of S and DHS.

Binding modes of PCBs to a degrading enzyme: a receptor-mapping study.

The binding site of a PCB-degrading enzyme was mapped using the published data on biodegradation rates of individual PCB congeners by the Acinetobacter P6 strain. For this purpose an approach allowing for multiple binding modes of individual congeners, resulting from the symmetry of the biphenyl skeleton, was used. The effect of substitution patterns and conformational flexibility of individual congeners on their binding to a protein were investigated. The resulting map of the binding site is described by three parameters that indicate the importance of positions 4, 5', 5, 2' in a basic substitution pattern, the first two being favourable while the other two unfavourable for binding. An incorporation of conformational energy dependences of individual ligands into the model showed that ligand's conformation is either not a limiting factor for binding or that ligands bind in their relaxed conformations.

Inhibition of blood platelet functions by cationic amphiphilic drugs in relation to their physico-chemical properties.

The effects of bromadryl, dithiaden, chloroquine and propranolol on thrombin-stimulated rat platelet aggregation (measured turbidimetrically) and thromboxane B2 generation (detected by an RIA method) were compared with four selected physico-chemical parameters of these drugs. Platelet aggregation was inhibited in the rank order of potency: bromadryl > dithiaden > propranolol > chloroquine, which corresponded with the decrease in the net charge of the terminal methyl-(or ethyl-) groups in the side chain and with the increase of the dipole moment of drug molecules. On the other hand, the rank order of potency in which the drugs tested inhibited thromboxane B2 formation (chloroquine > dithiaden > bromadryl > propranolol) correlated well with the decline in molar refractivity of the drugs. No relationship was found between inhibitory effects of drugs and their partition coefficients. The results presented indicate that inhibition of platelet functions might consist of several types of drug-cell interactions, depend on the structure and physico-chemical properties of the drugs and cannot be estimated simply on the basis of partition coefficients.