The Subtype Selectivity in Search of Potent Hypotensive Agents among 5,5-Dimethylhydantoin Derived α1-Adrenoceptors Antagonists.

In order to find new hypotensive drugs possessing higher activity and better selectivity, a new series of fifteen 5,5-dimethylhydantoin derivatives (1-15) was designed. Three-step syntheses, consisting of N-alkylations using standard procedures as well as microwaves, were carried out. Crystal structures were determined for compounds 7-9. All of the synthesized 5,5-dimethylhydantoins were tested for their affinity to α1-adrenergic receptors (α1-AR) using both in vitro and in silico methods. Most of them displayed higher affinity (Ki < 127.9 nM) to α1-adrenoceptor than urapidil in radioligand binding assay. Docking to two subtypes of adrenergic receptors, α1A and α1B, was conducted. Selected compounds were tested for their activity towards two α1-AR subtypes. All of them showed intrinsic antagonistic activity. Moreover, for two compounds (1 and 5), which possess o-methoxyphenylpiperazine fragments, strong activity (IC50 < 100 nM) was observed. Some representatives (3 and 5), which contain alkyl linker, proved selectivity towards α1A-AR, while two compounds with 2-hydroxypropyl linker (11 and 13) to α1B-AR. Finally, hypotensive activity was examined in rats. The most active compound (5) proved not only a lower effective dose than urapidil but also a stronger effect than prazosin.

Anti-Inflammatory Activities of 8-Benzylaminoxanthines Showing High Adenosine A2A and Dual A1/A2A Receptor Affinity.

Chronic inflammation plays an important role in the development of neurodegenerative diseases, such as Parkinson's disease (PD). In the present study, we synthesized 25 novel xanthine derivatives with variable substituents at the N1-, N3- and C8-position as adenosine receptor antagonists with potential anti-inflammatory activity. The compounds were investigated in radioligand binding studies at all four human adenosine receptor subtypes, A1, A2A, A2B and A3. Compounds showing nanomolar A2A and dual A1/A2A affinities were obtained. Three compounds, 19, 22 and 24, were selected for further studies. Docking and molecular dynamics simulation studies indicated binding poses and interactions within the orthosteric site of adenosine A1 and A2A receptors. In vitro studies confirmed the high metabolic stability of the compounds, and the absence of toxicity at concentrations of up to 12.5 µM in various cell lines (SH-SY5Y, HepG2 and BV2). Compounds 19 and 22 showed anti-inflammatory activity in vitro. In vivo studies in mice investigating carrageenan- and formalin-induced inflammation identified compound 24 as the most potent anti-inflammatory derivative. Future studies are warranted to further optimize the compounds and to explore their therapeutic potential in neurodegenerative diseases.

Evaluation of analgesic and anti-inflammatory activity of purine-2,6-dione-based TRPA1 antagonists with PDE4/7 inhibitory activity.

BACKGROUND: To verify the validity of the proposed pain treatment approach, which is based on concomitant blocking of the Transient Receptor Potential Ankyrin 1 (TRPA1) channel and phosphodiesterases (PDEs) 4B/7A activity, we continued our pharmacological studies on 8-alkoxypurine-2,6-diones selected based on previous in vitro screening. METHODS: Derivatives 17, 31, and 36 were pharmacologically evaluated in vivo using the formalin test and oxaliplatin-induced neuropathic pain: the von Frey and the cold plate tests, and in the carrageenan-induced edema model. Compound 36, which turned out to be the most promising, was further evaluated in the collagen-induced arthritis model. The pharmacokinetic parameters of this compound were also estimated. RESULTS: All the tested compounds exhibited significant analgesic and anti-inflammatory activities. Compound 36 was additionally characterized by an antiarthritic effect and showed a favorable pharmacokinetic profile in rats. CONCLUSION: The compounds evaluated in this study represent a new class of derivatives with analgesic and anti-inflammatory activities that involve TRPA1 antagonism and PDE4/7 inhibition.

An Insight into the Stages of Ion Leakage during Red Blood Cell Storage.

Packed red blood cells (pRBCs), the most commonly transfused blood product, are exposed to environmental disruptions during storage in blood banks. In this study, temporal sequence of changes in the ion exchange in pRBCs was analyzed. Standard techniques commonly used in electrolyte measurements were implemented. The relationship between ion exchange and red blood cells (RBCs) morphology was assessed with use of atomic force microscopy with reference to morphological parameters. Variations observed in the Na+, K+, Cl-, H+, HCO3-, and lactate ions concentration show a complete picture of singly-charged ion changes in pRBCs during storage. Correlation between the rate of ion changes and blood group type, regarding the limitations of our research, suggested, that group 0 is the most sensitive to the time-dependent ionic changes. Additionally, the impact of irreversible changes in ion exchange on the RBCs membrane was observed in nanoscale. Results demonstrate that the level of ion leakage that leads to destructive alterations in biochemical and morphological properties of pRBCs depend on the storage timepoint.

8-Benzylaminoxanthine scaffold variations for selective ligands acting on adenosine A2A receptors. Design, synthesis and biological evaluation.

A library of 34 novel compounds based on a xanthine scaffold was explored in biological studies for interaction with adenosine receptors (ARs). Structural modifications of the xanthine core were introduced in the 8-position (benzylamino and benzyloxy substitution) as well as at N1, N3, and N7 (small alkyl residues), thereby improving affinity and selectivity for the A2A AR. The compounds were characterized by radioligand binding assays, and our study resulted in the development of the potent A2A AR ligands including 8-((6-chloro-2-fluoro-3-methoxybenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12d; Ki human A2AAR: 68.5 nM) and 8-((2-chlorobenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12h; Ki human A2AAR: 71.1 nM). Moreover, dual A1/A2AAR ligands were identified in the group of 1,3-diethyl-7-methylxanthine derivatives. Compound 14b displayed Ki values of 52.2 nM for the A1AR and 167 nM for the A2AAR. Selected A2AAR ligands were further evaluated as inactive for inhibition of monoamine oxidase A, B and isoforms of phosphodiesterase-4B1, -10A, which represent classical targets for xanthine derivatives. Therefore, the developed 8-benzylaminoxanthine scaffold seems to be highly selective for AR activity and relevant for potent and selective A2A ligands. Compound 12d with high selectivity for ARs, especially for the A2AAR subtype, evaluated in animal models of inflammation has shown anti-inflammatory activity. Investigated compounds were found to display high selectivity and may therefore be of high interest for further development as drugs for treating cancer or neurodegenerative diseases.

KD-64-A new selective A2A adenosine receptor antagonist has anti-inflammatory activity but contrary to the non-selective antagonist-Caffeine does not reduce diet-induced obesity in mice.

The A2 adenosine receptors play an important role, among others, in the regulation of inflammatory process and glucose homeostasis in diabetes and obesity. Thus, the presented project evaluated of influence of the selective antagonist of A2A adenosine receptor-KD-64 as compared to the known non-selective antagonist-caffeine on these two particular processes. Two different inflammation models were induced namely local and systemic inflammation. Obesity was induced in mice by high-fat diet and the tested compounds (KD-64 and caffeine) were administrated for 21 days. KD-64 showed anti-inflammatory effect in both tested inflammation models and administered at the same dose as ketoprofen exerted stronger effect than this reference compound. Elevated levels of IL-6 and TNF-α observed in obese control mice were significantly lowered by the administration of KD-64 and were similar to the values observed in control non-obese mice. Interestingly, caffeine increased the levels of these parameters. In contrast to caffeine which had no influence on AlaT activity, KD-64 administration significantly lowered AlaT activity in the obese mice. Although, contrary to caffeine, KD-64 did not reduce diet-induced obesity in mice, it improved glucose tolerance. Thus, the activity of the selective adenosine A2A receptor antagonist was quite different from that of the non-selective.

Dual Target Ligands with 4-tert-Butylphenoxy Scaffold as Histamine H3 Receptor Antagonists and Monoamine Oxidase B Inhibitors.

Dual target ligands are a promising concept for the treatment of Parkinson's disease (PD). A combination of monoamine oxidase B (MAO B) inhibition with histamine H3 receptor (H3R) antagonism could have positive effects on dopamine regulation. Thus, a series of twenty-seven 4-tert-butylphenoxyalkoxyamines were designed as potential dual-target ligands for PD based on the structure of 1-(3-(4-tert-butylphenoxy)propyl)piperidine (DL76). Probed modifications included the introduction of different cyclic amines and elongation of the alkyl chain. Synthesized compounds were investigated for human H3R (hH3R) affinity and human MAO B (hMAO B) inhibitory activity. Most compounds showed good hH3R affinities with Ki values below 400 nM, and some of them showed potent inhibitory activity for hMAO B with IC50 values below 50 nM. However, the most balanced activity against both biological targets showed DL76 (hH3R: Ki = 38 nM and hMAO B: IC50 = 48 nM). Thus, DL76 was chosen for further studies, revealing the nontoxic nature of DL76 in HEK293 and neuroblastoma SH-SY5Ycells. However, no neuroprotective effect was observed for DL76 in hydrogen peroxide-treated neuroblastoma SH-SY5Y cells. Furthermore, in vivo studies showed antiparkinsonian activity of DL76 in haloperidol-induced catalepsy (Cross Leg Position Test) at a dose of 50 mg/kg body weight.

Anti-Alzheimer's multitarget-directed ligands with serotonin 5-HT6 antagonist, butyrylcholinesterase inhibitory, and antioxidant activity.

Serotonin 5-HT6 receptors, butyrylcholinesterase (BuChE) and oxidative stress are related to the pathophysiology of Alzheimer's disease. Inhibition of BuChE provides symptomatic treatment of the disease and the same effect was demonstrated for 5-HT 6 antagonists in clinical trials. Oxidative stress is regarded as a major and primary factor contributing to the development of Alzheimer's disease; therefore, antioxidant agents may provide a disease-modifying effect. Combining BuChE inhibition, 5-HT 6 antagonism, and antioxidant properties may result in multitarget-directed ligands providing cognition-enhancing properties with neuroprotective activity. On the basis of the screening of the library of 5-HT 6 antagonists against BuChE, we selected two compounds and designed their structural modifications that could lead to improved BuChE inhibitory activity. We synthesized two series of compounds and tested their affinity and functional activity at 5-HT 6 receptors, BuChE inhibitory activity and antioxidant properties. Compound 12 with K i and K b values against 5-HT 6 receptors of 41.8 and 74 nM, respectively, an IC 50 value of 5 µM against BuChE and antioxidant properties exceeding the activity of ascorbic acid is a promising lead structure for further development of anti-Alzheimer's agents.

Novel multi-target directed ligands based on annelated xanthine scaffold with aromatic substituents acting on adenosine receptor and monoamine oxidase B. Synthesis, in vitro and in silico studies.

N9-Benzyl-substituted imidazo-, pyrimido- and 1,3-diazepino[2,1-f]purinediones were designed as dual-target-directed ligands combining A2A adenosine receptor (AR) antagonistic activity with blockade of monoamine oxidase B (MAO-B). A library of 37 novel compounds was synthesized and biologically evaluated in radioligand binding studies at AR subtypes and for their ability to inhibit MAO-B. A systematic modification of the tricyclic structures based on a xanthine core by enlargement of the third heterocyclic ring or attachment of various substituted benzyl moieties resulted in the development of 9-(2-chloro-6-fluorobenzyl)-1,3-dimethyl-6,7,8,9-tetrahydropyrimido[2,1-f]purine-2,4(1H,3H)-dione (9u; Ki human A2AAR: 189 nM and IC50 human MAO-B: 570 nM) as the most potent dual acting ligand of the series displaying high selectivity versus related targets. Moreover, some potent, selective MAO-B inhibitors were identified in the group of pyrimido- and 1,3-diazepino[2,1-f]purinediones. Compound 10d (10-(3,4-dichlorobenzyl)-1,3-dimethyl-7,8,9,10-tetrahydro-1H-[1,3]diazepino[2,1-f]purine-2,4(3H,6H)-dione) displayed an IC50 value at human MAO-B of 83 nM. Analysis of structure-activity relationships was complemented by molecular docking studies based on previously published X-ray structures of the protein targets. An extended biological profile was determined for selected compounds including in vitro evaluation of potential hepatotoxicity calculated in silico and antioxidant properties as an additional desirable activity. The new molecules acting as dual target drugs may provide symptomatic relief as well as disease-modifying effects for neurodegenerative diseases, in particular Parkinson's disease.

Novel amide derivatives of 1,3-dimethyl-2,6-dioxopurin-7-yl-alkylcarboxylic acids as multifunctional TRPA1 antagonists and PDE4/7 inhibitors: A new approach for the treatment of pain.

A series of novel amide derivatives of 1,3-dimethyl-2,6-dioxopurin-7-yl-alkylcarboxylic acids designed using a structure-based computational approach was synthesized and assayed to evaluate their ability to block human TRPA1 channel and inhibit PDE4B/7A activity. We identified compounds 16 and 27 which showed higher potency against TRPA1 compared to HC-030031. In turn, compound 36 was the most promising multifunctional TRPA1 antagonist and PDE4B/7A dual inhibitor with IC50 values in the range of that of the reference rolipram and BRL-50481, respectively. Compound 36 as a combined TRPA1/PDE4B/PDE7A ligand was characterized by a distinct binding mode in comparison to 16 and 27, in the given protein targets. The inhibition of both cAMP-specific PDE isoenzymes resulted in a strong anti-TNF-α effect of 36in vivo. Moreover, the potent anti-inflammatory and analgesic efficacy of 36 was observed in animal models of pain and inflammation (formalin test in mice and carrageenan-induced paw edema in rats). This compound also displayed significant antiallodynic properties in the early phase of chemotherapy-induced peripheral neuropathy in mice. In turn, the pure TRPA1 antagonists 16 and 27 revealed a statistically significant antiallodynic effect in the formalin test and in the von Frey test performed in both phases of oxaliplatin-induced allodynia. Antiallodynic activity of the test compounds 16, 27 and 36 was observed at a dose range comparable to that of the reference drug - pregabalin. In conclusion, the proposed approach of pain treatment based on the concomitant blocking of TRPA1 channel and PDE4B/7A inhibitory activity appears to be interesting research direction for the future search for novel analgesics.

Synthesis and Pharmacological Evaluation of Novel Silodosin-Based Arylsulfonamide Derivatives as α1A/α1D-Adrenergic Receptor Antagonist with Potential Uroselective Profile.

Benign prostatic hyperplasia (BPH) is the most common male clinical problem impacting the quality of life of older men. Clinical studies have indicated that the inhibition of α1A-/α1D adrenoceptors might offer effective therapy in lower urinary tract symptoms. Herein, a limited series of arylsulfonamide derivatives of (aryloxy)ethyl alicyclic amines was designed, synthesized, and biologically evaluated as potent α1-adrenoceptor antagonists with uroselective profile. Among them, compound 9 (3-chloro-2-fluoro-N-([1-(2-(2-(2,2,2-trifluoroethoxy)phenoxy]ethyl)piperidin-4-yl)methyl)benzenesulfonamide) behaved as an α1A-/α1D-adrenoceptor antagonist (Ki(α1) = 50 nM, EC50(α1A) = 0.8 nM, EC50(α1D) = 1.1 nM), displayed selectivity over α2-adrenoceptors (Ki(α2) = 858 nM), and a 5-fold functional preference over the α1B subtype. Compound 9 showed adequate metabolic stability in rat-liver microsome assay similar to the reference drug tamsulosin (Clint = 67 and 41 µL/min/mg, respectively). Compound 9 did not decrease systolic and diastolic blood pressure in normotensive anesthetized rats in the dose of 2 mg/kg, i.v. These data support development of uroselective agents in the group of arylsulfonamides of alicyclic amines with potential efficacy in the treatment of lower urinary tract symptoms associated to benign prostatic hyperplasia.

Effect of selected drugs on zinc accumulation in teeth of laboratory animals.

BACKGROUND: Zinc (Zn) is a micronutrient and essential element of life and its deficiency causes severe disorders of numerous body systems, such as immune, reproductive and central nervous system. Zinc supplementation affects wound healing and sexual development. The interactions between drugs administration and Zn level in tissues are not fully understood. The aim of the study was to demonstrate differences in Zn content in teeth of laboratory animals that have undergone pharmacological tests. METHODS: The teeth were extracted from laboratory animals after chronic administration of a non-steroidal anti-inflammatory drug (8-[4-[4-(4-chlorophenyl) piperazine-1-sulfonylphenyl]]-1-propylxanthine), a steroid anti-inflammatory drug (deoxycorticosterone) and an anti-cancer drug (oxaliplatin used acutely). The method of flame atomic absorption spectrometry was used to determine the Zn content in the teeth of the laboratory animals. RESULTS: Based on the studies conducted, the administration of the anti-inflammatory drug PSB-603 and deoxycorticosterone results in an increase in Zn accumulation in the teeth of laboratory animals, which may be indicative of the effect of anti-inflammatory drugs on the metabolism of this bioelement. Oxaliplatin has the opposite effect, after which the level of the measured bioelement in the teeth of mice depended on the administered dose. This level was on average 21.0-28.1% lower than the Zn level in the teeth of the control group. Anti-cancer drugs may interfere with Zn accumulation in the teeth and cause the removal of this metal from bone tissue. CONCLUSION: It can be assumed that the Zn content in teeth can be markedly affected by the drugs that were administrated to animals.

The effect of NaCl on the level of reduced sulfur compounds in rat liver. Implications for blood pressure increase.

BACKGROUND: It is commonly known that excessive salt intake is a risk factor of hypertension. Currently, there is an increasing interest in reduced reactive sulfur species (RSS), mainly H2S and sulfane sulfur (SS) as new gasotransmitters showing vasorelaxant properties. The aim of the present study was to determine the effect of repeated administration of low sodium chloride dose included in physiological saline on blood pressure, on the level of RSS and activity of enzymes involved in their biosynthesis in the rat. METHODS: Two separate experiments were carried out on male Wistar rats: one with intravenous injections of saline and the second one with intraperitoneal saline injections. Blood pressure was measured during the experiment. The level of RSS and other biochemical assays were conducted in the rat liver, because of an intense cysteine metabolism to RSS in this organ. RESULTS: Intravenous administration of saline induced a significant increase in systolic blood pressure while intraperitoneal injections showed only a tendency towards increasing blood pressure. The RSS (H2S and SS) level as well as the activity of the main enzyme responsible for their production in the liver of animals after iv saline injections were decreased. Animals injected with physiological saline by ip route did not reveal any statistically significant differences in SS, H2S, and activities of sulfurtransferases, although a tendency to decrease in the RSS was observed. CONCLUSIONS: The repeated iv saline injection induced a slight hypertension accompanied by disturbances in anaerobic cysteine metabolism in the rat liver.

Nicotine affects hydrogen sulfide concentrations in mouse kidney and heart but not in brain and liver tissues.

Nicotine, a potent parasympathomimetic alkaloid with stimulant effects, is contributing to addictive properties of tobacco smoking and is though used in the smoking cessation therapy. Hydrogen sulfide (H2S) is involved in physiology and pathophysiology of various systems in mammals. The interactions between nicotine and H2S are not fully recognized. The aim of the study is to assess the influence of nicotine on the H2S tissue concentrations in different mouse organs. Adult CBA male mice were administered intraperitoneally 1.5 mg/kg b.w. per day of nicotine (group D1, n = 10) or 3 mg/ kg b.w. per day of nicotine (group D2, n = 10). The control group (n = 10) received physiological saline. The measurements of the free and acid-labile H2S tissue concentrations were performed with the Siegel spectrophotometric modi ed method. ere was a significant increase in H2S concentrations in both nicotine doses groups in the kidney (D1 by 54.2%, D2 by 40.0%). In the heart the higher nicotine dose caused a marked decrease in H2S tissue level (by 65.4%), while the lower dose did not affect H2S content. Nicotine administration had no effect on H2S concentrations in the brain and liver. In conclusion, nicotine affects H2S tissue concentrations in kidney and heart but not in the liver and brain tissues.

Contribution of the nitric oxide donor molsidomine and the antiparkinsonian drug l-DOPA to the modulation of the blood pressure in unilaterally 6-OHDA-lesioned rats.

BACKGROUND: Interaction between dopaminergic and nitrergic neurotransmission in the brain plays a crucial role in the control of motor function and in the regulation of blood pressure (BP). In Parkinson's disease (PD), dopaminergic denervation of the striatum leads to disturbances in the nitrergic system in the basal ganglia. Recently, it has been demonstrated that addition of a low dose of the nitric oxide donor molsidomine to l-DOPA therapy improves dopaminergic neurotransmission in the denervated nigrostriatal system and weakens dyskinesias in rodent models of the disease. METHODS: The aim of the present study was to examine the impact of chronic administration of molsidomine (2mg/kg) and l-DOPA (25mg/kg), alone and in combination, on systolic (SBP) and diastolic (DBP) blood pressure in the anesthetized, unilaterally 6-OHDA-lesioned rats. The measurement of SBP and DBP was performed 24h after the penultimate and immediately after the last drug doses. RESULTS: In 6-OHDA-lesioned rats receiving saline, spontaneous, small decreases in SBP and DBP were observed during the measurements lasting 60min. Administration of molsidomine alone or in combination with l-DOPA distinctly decreased the BP in 6-OHDA-lesioned rats already after 10min compared to those treated with saline or l-DOPA alone, respectively. In both groups, the molsidomine-mediated declines in BP persisted till the end of measurement but they disappeared after 24h. CONCLUSIONS: Our results indicate that in this PD model molsidomine evokes a short-lasting decrease in BP in contrast to conventional antihypertensive drugs that maintain long-term effect and worsen orthostatic hypotension in parkinsonian patients.

Evaluation of antidepressant-like and anxiolytic-like activity of purinedione-derivatives with affinity for adenosine A2A receptors in mice.

BACKGROUND: It has recently been suggested that the adenosine A2A receptor plays a role in several animal models of depression. Additionally, A2A antagonists have reversed behavioral deficits and exhibited a profile similar to classical antidepressants. METHODS: In the present study, imidazo- and pyrimido[2,1-f]purinedione derivatives (KD 66, KD 167, KD 206) with affinity to A2A receptors but poor A1 affinity were evaluated for their antidepressant- and anxiolytic-like activity. The activity of these derivatives was tested using a tail suspension and forced swim test, two widely-used behavioral paradigms for the evaluation of antidepressant-like activity. In turn, the anxiolytic activity was evaluated using the four-plate test. RESULTS: The results showed the antidepressant-like activity of pyrimido- and imidazopurinedione derivatives (i.e. KD 66, KD 167 and KD 206) in acute and chronic behavioral tests in mice. KD 66 revealed an anxiolytic-like effect, while KD 167 increased anxiety behaviors. KD 206 had no effect on anxiety. Furthermore, none of the tested compounds increased locomotor activity. CONCLUSION: Available data support the proposition that the examined compounds with adenosine A2A receptor affinity may be an interesting target for the development of antidepressant and/or anxiolytic agents.

Arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines as α1-adrenergic receptor antagonist with uro-selective activity.

A series of arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines was synthesized to develop new α1-adrenoceptor antagonists with uroselective profile. Biological evaluation for α1- and α2-adrenorecepor showed that tested compounds 13-37 displayed high-to-moderate affinity for the α1-adrenoceptor (Ki=34-348nM) and moderate selectivity over α2-receptor subtype. Compounds with highest affinity and selectivity for α1-adrenoceptor were evaluated in vitro for their intrinsic activity toward α1A- and α1B-adrenoceptor subtypes. All compounds behaved as antagonists at both α1-adrenoceptor subtypes, displaying 2- to 6-fold functional preference to α1A-subtype. Among them, N-{1-[2-(2-methoxyphenoxy)ethyl]piperidin-4-yl}isoquinoline-4-sulfonamide (25) and 3-chloro-2-fluoro-N-{[1-(2-(2-isopropoxyphenoxy)ethyl)piperidin-4-yl]methyl}benzene sulfonamide (34) displayed the highest preference to α1A-adrenoceptor. Finally, compounds 25 and 34 (2-5mg/kg, iv), in contrast to tamsulosin (1-2mg/kg, iv), did not significantly decrease systolic and diastolic blood pressure in normotensive anesthetized rats to determine their influence on blood pressure.

ANTI-INFLAMMATORY AND ANTIOXIDANT ACTIVITY OF 8-METHOXY-1,3-DIMETHYL-2,6-DIOXO-PURIN-7-YL DERIVATIVES WITH TERMINAL CARBOXYLIC, ESTER OR AMIDE MOIETIES IN ANIMAL MODELS.

The previous studies in a series of 8-methoxy-1,3-dimethyl-2,6-dioxo-purin-7-yl derivatives revealed their analgesic properties. We extended the study with these compounds in aim to assess their impact on inflammatory process. For this purpose we used: the zymosan-induced peritonitis and the carrageenan-induced edema model. Furthermore, the antioxidant activity of the investigated compounds by the FRAP assay was determined. For the most active derivatives from evaluated series their influence on plasma TNF-α level was also tested in vivo. All investigated purine-2,6-dione derivatives 1-11 decreased neutrophils count and inhibited intensity of early vascular permeability. Furthermore, all evaluated compounds reduced the volume of edema caused by subcutaneous injection of carrageenan. Derivatives 1 (with ester moiety), 3 and 4 (with carboxylic group) showed the highest activity in the zymosan-induced peritonitis. In addition, a significant inhibition of plasma TNF-α level in rats with endotoxemia was observed following intraperitoneal administration of these compounds. In turn, compounds 6 and 8-11 containing amide moiety showed the greatest anti-inflammatory (antiedematous) effect in the carrageenan-induced paw edema model. All compounds did not show significant antioxidant properties. The present studies revealed that the presented purine-2,6-dione derivatives exhibit a significant anti-inflammatory activity and this effect may result from their ability to lower TNF-α level.

Chemically Homogenous Compounds with Antagonistic Properties at All α1-Adrenoceptor Subtypes but not ß1-Adrenoceptor Attenuate Adrenaline-Induced Arrhythmia in Rats.

Studies proved that among all α1-adrenoceptors, cardiac myocytes functionally express only α1A- and α1B-subtype. Scientists indicated that α1A-subtype blockade might be beneficial in restoring normal heart rhythm. Therefore, we aimed to determine the role of α1-adrenoceptors subtypes (i.e., α1A and α1B) in antiarrhythmic effect of six structurally similar derivatives of 2-methoxyphenylpiperazine. We compared the activity of studied compounds with carvedilol, which is ß1- and α1-adrenoceptors blocker with antioxidant properties. To evaluate the affinity for adrenergic receptors, we used radioligand methods. We investigated selectivity at α1-adrenoceptors subtypes using functional bioassays. We tested antiarrhythmic activity in adrenaline-induced (20 µg/kg i.v.), calcium chloride-induced (140 and 25 mg/kg i.v.) and barium chloride-induced (32 and 10 mg/kg i.v.) arrhythmia models in rats. We also evaluated the influence of studied compounds on blood pressure in rats, as well as lipid peroxidation. All studied compounds showed high affinity toward α1-adrenoceptors but no affinity for ß1 receptors. Biofunctional studies revealed that the tested compounds blocked α1A-stronger than α1B-adrenoceptors, but except for HBK-19 they antagonized α1A-adrenoceptor weaker than α1D-subtype. HBK-19 showed the greatest difference in pA2 values-it blocked α1A-adrenoceptors around seven-fold stronger than α1B subtype. All compounds showed prophylactic antiarrhythmic properties in adrenaline-induced arrhythmia, but only the activity of HBK-16, HBK-17, HBK-18, and HBK-19 (ED50 = 0.18-0.21) was comparable to that of carvedilol (ED50 = 0.36). All compounds reduced mortality in adrenaline-induced arrhythmia. HBK-16, HBK-17, HBK-18, and HBK-19 showed therapeutic antiarrhythmic properties in adrenaline-induced arrhythmia. None of the compounds showed activity in calcium chloride- or barium chloride-induced arrhythmias. HBK-16, HBK-17, HBK-18, and HBK-19 decreased heart rhythm at ED84. All compounds significantly lowered blood pressure in normotensive rats. HBK-18 showed the strongest hypotensive properties (the lowest active dose: 0.01 mg/kg). HBK-19 was the only compound in the group, which did not show hypotensive effect at antiarrhythmic doses. HBK-16, HBK-17, HBK-18, HBK-19 showed weak antioxidant properties. Our results indicate that the studied 2-methoxyphenylpiperazine derivatives that possessed stronger α1A-adrenolytic properties (i.e., HBK-16, HBK-17, HBK-18, and HBK-19) were the most active compounds in adrenaline-induced arrhythmia. Thus, we suggest that the potent blockade of α1A-receptor subtype is essential to attenuate adrenaline-induced arrhythmia.

HBK-7 - A new xanthone derivative and a 5-HT1A receptor antagonist with antidepressant-like properties.

Xanthone derivatives possess many biological properties, including neuroprotective, antioxidant or antidepressant-like. In this study we aimed to investigate antidepressant- and anxiolytic-like properties of a new xanthone derivative - 6-methoxy-4-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-7), as well as its possible mechanism of action, and the influence on cognitive and motor function. HBK-7 in our earlier studies showed high affinity for serotonergic 5-HT1A receptor. We determined the affinity of HBK-7 for CNS receptors and transporters using radioligand assays and examined its intrinsic activity towards 5-HT1A receptor. We evaluated antidepressant- and anxiolytic-like activity of HBK-7 in the mouse forced swim test, and four-plate test, respectively. We examined the influence on locomotor activity in mice to determine if the effect observed in the forced swim test was specific. We used step-through passive avoidance and rotarod tests to evaluate the influence of HBK-7 on cognitive and motor function, respectively. HBK-7 showed moderate affinity for dopaminergic D2 receptor and very low for serotonergic 5-HT2A, adrenergic α2 receptors, as well as serotonin transporter. Functional studies revealed that HBK-7 was a 5-HT1A receptor antagonist. HBK-7 (10mg/kg) decreased immobility time in the forced swim test. Combined treatment with sub-effective doses of HBK-7 and fluoxetine reduced immobility of mice in the forced swim test. Pretreatment with p-chlorophenylalanine and WAY-100,635 antagonized the antidepressant-like effect of HBK-7. Neither of the treatments influenced locomotor activity of mice. HBK-7 at antidepressant-like dose did not impair memory or motor coordination in mice. We demonstrated that HBK-7 was a 5-HT1A receptor antagonist with potent, comparable to mianserin, antidepressant-like activity. HBK-7 mediated its effect through serotonergic system and its antidepressant-like action required the activation of 5-HT1A receptors. At active dose it did not influence cognitive and motor function. Since 5-HT1A receptor antagonists may accelerate the occurrence of antidepressant effect, our findings highlight their potential as future antidepressants.