Orazipone inhibits activation of inflammatory transcription factors nuclear factor-kappa B and signal transducer and activator of transcription 1 and decreases inducible nitric-oxide synthase expression and nitric oxide production in response to inflammatory stimuli.

Orazipone [OR-1384; 3-[4-(methylsulfonyl)benzylidene]pentane-2,4-dione] is a novel sulfhydryl-modulating compound that has anti-inflammatory properties in experimental models of asthma and inflammatory bowel disease. In inflammation, inducible nitricoxide synthase (iNOS) generates NO, which modulates the immune response. Compounds that inhibit iNOS expression or iNOS activity possess anti-inflammatory effects. In the present study, we examined the effects of orazipone and its derivative OR-1958 [3-[3-chlorine-4-(methylsulfonyl)benzylidene]pentane-2,4-dione] on iNOS expression and NO production in J774 macrophages stimulated by bacterial lipopolysaccharide (LPS) and in human alveolar epithelial cells activated by proinflammatory cytokines. Protein expression and nuclear translocation of transcription factors were measured by Western blot. iNOS mRNA expression was determined by quantitative reverse transcription-polymerase chain reaction and iNOS mRNA stability by actinomycin D assay. iNOS promoter activity was studied in a cell line expressing luciferase under the control of iNOS promoter. Orazipone and its derivative OR-1958 but not its nonthiol-modulating analog inhibited iNOS expression and NO production in a concentration-dependent manner. Orazipone decreased LPS-induced iNOS mRNA expression, but the decay of iNOS mRNA was not affected. Orazipone extensively prevented LPS-induced activation of nuclear factor kappaB (NF-kappaB) and signal transducer and activator of transcription (STAT) 1, which are important transcription factors for iNOS. In agreement, human iNOS promoter activity was inhibited by orazipone. In conclusion, orazipone decreased activation of inflammatory transcription factors NF-kappaB and STAT1, and expression of iNOS in cells exposed to inflammatory stimuli. The thiolmodulating property seems to be critical in mediating the antiinflammatory effects of orazipone.

Positive inotropic effect of levosimendan is correlated to its stereoselective Ca2+-sensitizing effect but not to stereoselective phosphodiesterase inhibition.

In order to clarify the mechanisms of the positive inotropic actions of levosimendan and its optical isomer, dextrosimendan, we compared their concentration-dependent effects in intact papillary muscles, permeabilized cardiomyocytes and in purified phosphodiesterase enzyme preparations of guinea-pig hearts. In papillary muscles twitch tension increased with EC50 values of 60 nM and 2.8 microM for levosimendan and dextrosimendan, respectively. Hence, the two enantiomers exhibited a 47 times potency difference in their positive inotropic effects in a preparation where theoretically Ca2+-sensitization and phosphodiesterase inhibition could both contribute to the positive inotropic effects. In guinea-pig cardiomyocytes, levosimendan and dextrosimendan increased isometric force production (at pCa 6.2) due to Ca2+-sensitization with EC50 values of 8.4 nM and 0.64 microM, respectively, with a similar relative potency difference of 76. A major difference appeared in their relative pharmacological potencies, however, when the inhibitory effects of the two enantiomers were assayed on phosphodiesterase III, purified from guinea pig left ventricle (i.e. the phosphodiesterase isoenzyme which is dominant in that tissue). Levosimendan was a 427 times more potent phosphodiesterase inhibitor than dextrosimendan, with IC50 values of 7.5 nM, and 3.2 microM, respectively. Taken together, our data support the hypothesis that levosimendan and dextrosimendan exert their positive inotropic effects via a stereoselective Ca2+-sensitizing mechanism and not via stereoselective inhibition of phosphodiesterase III in the myocardium.

Novel sulfhydryl-reactive compounds orazipone and OR-1958 inhibit cytokine production and histamine release in rat and human mast cells.

Orazipone (OR-1384) and OR-1958 are novel anti-inflammatory sulfhydryl reactive compounds with potential applications in the treatment of chronic obstructive lung disease and colitis. Mast cells are potent immune system cells which can be found in abundant numbers in mucosa of lung and gut. We have studied whether the anti-inflammatory effect of these compounds could be mediated through inhibition of the function of mast cells and compared their effects with the glucocorticoid budesonide. Human mast cell line (HMC-1) cells were activated using a combination of a calcium ionophore and a phorbol ester and the production of cytokines was measured using ELISA assay. Tumour necrosis factor-alpha mRNA levels were assessed using a semiquantitative reverse transcriptase polymerase chain reaction assay. Histamine release was studied in rat peritoneal mast cells. Orazipone, OR-1958 and budesonide inhibited significantly and dose dependently tumour necrosis factor-alpha production in HMC-1 cells with IC50-values of 20, 10, and 0.25 microM, respectively. Polymerase chain reaction studies showed that OR-1958 attenuated the activation-induced increase of tumour necrosis factor-alpha mRNA in HMC-1 cells. OR-1958 and, to a lesser extent, orazipone inhibited dose dependently compound 48/80-induced histamine release from rat peritoneal mast cells in a reversible manner. In contrast, budesonide did not appreciably affect the histamine release. Both orazipone and OR-1958 inhibit efficiently mast cell functions and therefore could prove useful in the treatment of diseases associated with inappropriate mast cell activation.

Differential effect of tetracaine and bupivacaine on catecholamine and 5-hydroxytryptamine turnover.

The effect of the local anesthetics, tetracaine and bupivacaine, on monoamine oxidase (MAO) activity of rat brain and on the major steps of catecholamine and 5-hydroxytryptamine (5-HT) turnover was examined. The IC50 of tetracaine for MAO-A and MAO-B inhibition was 1.2 microM and 19.5 microM, respectively. Up to 2.5 mM bupivacaine was without effect on either form of MAO. None of the following activities in rat brain or adrenal medulla were inhibited by 5-2500 microM of tetracaine or bupivacaine: catecholamine-O-methyltransferase, tyrosine hydroxylase, dopamine-beta-hydroxylase. Tetracaine caused only a moderately potent inhibition of synaptosomal uptake of norepinephrine (NE) (IC50 14 microM), dopamine (IC50 37 microM) and 5-HT (IC50 45 microM). The potent and specific MAO inhibition by tetracaine, in association with an impaired uptake of synaptosomal amines, may lead to an increase in the synaptosomal content of neurotransmitter amines, such as 5-HT and NE, with possible antinociceptive consequences.

Effects of entacapone and tolcapone on mitochondrial membrane potential.

Catechol-O-methyl transferase (COMT) inhibitors, entacapone and tolcapone, are used as an adjunctive treatment to L-dopa in Parkinson's disease. Based on their catechol structure, both inhibitors are potential uncoupling agents, but only tolcapone shows this effect in vitro at clinically relevant concentrations. This study was designed to evaluate the direct uncoupling effects of the two COMT inhibitors in vitro and in vivo. In isolated rat liver mitochondria, entacapone had no effect on the membrane potential at therapeutical concentrations, but both tolcapone and the reference compound 2,4-dinitrophenol disrupted the potential at low microM concentrations. Since protein binding is speculated to decrease the uncoupling effects in vivo, the COMT inhibitory effect of entacapone and tolcapone as a surrogate for the overall activity of these inhibitors was evaluated in vitro with or without serum. The COMT inhibitory activity of entacapone was reduced to half, while tolcapone had only about 1/10 of its activity left in the presence of serum. Further, uncoupling is known to induce an increase in the body temperature in vivo, and these effects were evaluated in the rat by a possible hyperthermic response to the treatment with entacapone or tolcapone in combination with L-dopa (10 mg/kg) and carbidopa (20 mg/kg). This combination with entacapone (400 mg/kg) had no effect on the rectal body temperature. In contrast, tolcapone (50 mg/kg) caused an elevation in the body temperature together with L-dopa and carbidopa (P < 0.01). Both in vitro and in vivo results indicate that entacapone does not impair energy metabolism related to uncoupling of oxidative phosphorylation.

Introductory remarks: Catechol-O-methyltransferase inhibition--an innovative approach to enhance L-dopa therapy in Parkinson's disease with dual enzyme inhibition.

Catechol-O-methyltransferase (COMT) enzyme and its inhibition have been closely related to the treatment of Parkinson's disease (PD) patients with motor fluctuations needing enhancement of their levodopa (L-dopa) therapy (L-dopa/dopa decarboxylase inhibitor), this indication being so far the only clinical application of COMT inhibitors. L-dopa treatment has remained the most effective therapy for PD, but its further development has been quite a challenge mainly due to the effective metabolism of L-dopa in the human body by multiple pathways, decarboxylation and O-methylation being the two most important of them. The introduction of clinically effective and safe COMT inhibitors has greatly increased the usefulness of L-dopa therapy, but how to utilize the full potential of L-dopa is still unsolved leaving a need for more potent COMT inhibitors.

Biochemistry and pharmacology of catechol-O-methyltransferase inhibitors.

Catechol-O-methyltransferase (COMT) is an important enzyme in the metabolism of catechol structured compounds such as catecholamines, catecholestrogens, and L-dopa. When combined with decarboxylase inhibitor L-dopa is the most efficacious treatment for Parkinson's disease. Bioavailability and efficacy of L-dopa treatment can be enhanced greatly by the use of COMT inhibitors. This has been the driving force for development of new selective and potent COMT inhibitors. The success in COMT inhibitor development has generated a tremendous scientific interest in the role of COMT in health and disease. COMT inhibitors have also helped to clarify the reaction mechanism of COMT, increased interest in its structural biology, and physicochemical properties in order to develop even better COMT inhibitors. New techniques, especially the transgenic mice, have revealed further new aspects about the role of COMT in periphery as well as in the brain.

Antieosinophilic activity of simendans.

Simendans are novel agents used in the treatment of decompensated heart failure. They sensitize troponin C to calcium and open ATP-sensitive potassium channels and have been shown to reduce cardiac myocyte apoptosis. The aim of the present study was to evaluate whether simendans reduce pulmonary eosinophilia and regulate eosinophil apoptosis. Bronchoalveolar lavage (BAL) eosinophilia was evaluated in ovalbumin-sensitized mice. Effects of simendans on apoptosis in isolated human eosinophils were assessed by relative DNA fragmentation assay, annexin V-binding, and morphological analysis. Dextrosimendan [(+)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)phenyl)hydrazono]propanedinitrile] reduced ovalbumin-induced BAL-eosinophilia in sensitized mice. Levosimendan [(-)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)phenyl]hydrazono]propanedinitrile] and dextrosimendan reversed interleukin (IL)-5-afforded survival of human eosinophils by inducing apoptosis in vitro. Even high concentrations of IL-5 were not able to overcome the effect of dextrosimendan. Dextrosimendan further enhanced spontaneous apoptosis as well as that induced by CD95 ligation, without inducing primary necrosis. Dextrosimendan-induced DNA fragmentation was shown to be dependent on caspase and c-Jun NH2-terminal kinase activation, whereas extracellular signal-regulated kinase, p38 mitogen-activated kinase, and ATP-sensitive potassium channels seemed to play no role in its actions. Taken together, our results show that simendans possess antieosinophilic activity and may be useful for the treatment of eosinophilic inflammation.

Antieosinophilic activity of orazipone.

Orazipone is a novel sulfhydryl-reactive compound that has been previously shown to reduce lung eosinophilia in guinea pigs and rats and to inhibit degranulation in mast cells and cytokine production in monocytes and T-cells. However, the effects of orazipone on granulocyte longevity are unknown. Orazipone and its derivative 3-(4-chloro-3-nitro-benzylidene)-pentane-2,4-dione (OR-2370) reversed interleukin-5-afforded survival of human eosinophils by inducing apoptosis. In contrast, orazipone did not affect granulocyte macrophage-colony-stimulating factor-induced survival of human neutrophils. The effect of orazipone on eosinophil apoptosis is different from that of glucocorticoids in that even high con-centrations of interleukin-5 were not able to overcome the effect of orazipone. Orazipone further enhanced spontaneous apoptosis as well as that induced by CD95 ligation without inducing primary necrosis. OR-2370-induced DNA fragmentation was shown to be dependent on caspases 3 and 6 and c-jun-N-terminal kinase, whereas extracellular regulated kinase, p38 mitogen-activated protein kinase, and phosphatidylinositol 3-kinase as well as caspases 4, 8, and 9 seem not to mediate its actions. Our results suggest that orazipone and its derivative OR-2370 possess strong antieosinophilic activity and thus may have anti-inflammatory efficacy in the treatment of asthma and/or allergic conditions.

Tissue histopathology, clinical chemistry and behaviour of adult Comt-gene-disrupted mice.

Catechol-O-methyltransferase (COMT) enzyme is a widely distributed enzyme that catalyses O-methylation of catecholamines and other compounds having a catechol structure. Because there has been some concern about the consequences of a low COMT activity in the development of oestrogen-dependent cancers and because one of the COMT inhibitors, tolcapone, has caused serious liver injuries in Parkinsonian patients, the histopathology and clinical chemistry of Comt-gene-disrupted mice were studied at the age of 12 months. Owing to the high COMT activities in liver and kidney and the role of COMT in the metabolism of catechol oestrogens, special emphasis was given to the histology of the liver, kidney and oestrogen-dependent organs such as mammary glands and uterus. The mice of both heterozygous and homozygous genotypes appear to be physically healthy and fertile. Diurnal motility rhythm and behaviour in measuring anxiety and depression were equal in all genotypes. At the age of 12 months, the body weight of homozygous mice was 7-9% lower than that of the other groups. This was reflected in histology as a diminished incidence of vacuolation of liver cells (fatty change). Macroscopic pathology and histopathology revealed no abnormal findings in any COMT genotype. The values of some clinical chemistry parameters, such as alkaline phosphatase, alanine aminotransferase, urea, glucose, calcium and proteins, were at a higher level in homozygous animals compared with the wild-type mice. However, all the values remained within the normal physiological range, and the differences in enzyme levels between genotypes were not reflected as histopathological findings in the relevant organs. No changes in haematological parameters or plasma catecholamine concentrations were noted but plasma 3,4-dihydroxyphenylethylene glycol levels were high in COMT null mice. The results suggest that the full or 50% lack of Comt gene as such is not associated with any toxic consequences.