Manifestations of Liver Impairment and the Effects of MH-76, a Non-Quinazoline α1-Adrenoceptor Antagonist, and Prazosin on Liver Tissue in Fructose-Induced Metabolic Syndrome

Excessive fructose consumption may lead to metabolic syndrome, metabolic dysfunction-associated fatty liver disease (MAFLD) and hypertension. α1-adrenoceptors antagonists are antihypertensive agents that exert mild beneficial effects on the metabolic profile in hypertensive patients. However, they are no longer used as a first-line therapy for hypertension based on Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) outcomes. Later studies have shown that quinazoline-based α1-adrenolytics (prazosin, doxazosin) induce apoptosis; however, this effect was independent of α1-adrenoceptor blockade and was associated with the presence of quinazoline moiety. Recent studies showed that α1-adrenoceptors antagonists may reduce mortality in COVID-19 patients due to anti-inflammatory properties. MH-76 (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride)) is a non-quinazoline α1-adrenoceptor antagonist which, in fructose-fed rats, exerted anti-inflammatory, antihypertensive properties and reduced insulin resistance and visceral adiposity. In this study, we aimed to evaluate the effect of fructose consumption and treatment with α1-adrenoceptor antagonists of different classes (MH-76 and prazosin) on liver tissue of fructose-fed rats. Livers were collected from four groups (Control, Fructose, Fructose + MH-76 and Fructose + Prazosin) and subjected to biochemical and histopathological studies. Both α1-adrenolytics reduced macrovesicular steatosis and triglycerides content of liver tissue and improved its antioxidant capacity. Treatment with MH-76, contrary to prazosin, reduced leucocytes infiltration as well as decreased elevated IL-6 and leptin concentrations. Moreover, the MH-76 hepatotoxicity in hepatoma HepG2 cells was less than that of prazosin. The use of α1-adrenolytics with anti-inflammatory properties may be an interesting option for treatment of hypertension with metabolic complications.

Efficacy of the Multi-Target Compound E153 in Relieving Pain and Pruritus of Different Origins

Itch and pain are closely related but distinct sensations that share largely overlapping mediators and receptors. We hypothesized that the novel, multi-target compound E153 has the potential to attenuate pain and pruritus of different origins. After the evaluation of sigma receptor affinity and pharmacokinetic studies, we tested the compound using different procedures and models of pain and pruritus. Additionally, we used pharmacological tools, such as PRE-084, RAMH, JNJ 5207852, and S1RA, to precisely determine the role of histamine H3 and sigma 1 receptors in the analgesic and antipruritic effects of the compound. In vitro studies revealed that the test compound had potent affinity for sigma 1 and sigma 2 receptors, moderate affinity for opioid kappa receptors, and no affinity for delta or μ receptors. Pharmacokinetic studies showed that after intraperitoneal administration, the compound was present at high concentrations in both the peripheral tissues and the central nervous system. The blood-brain barrier-penetrating properties indicate its ability to act centrally at the levels of the brain and spinal cord. Furthermore, the test compound attenuated different types of pain, including acute, inflammatory, and neuropathic. It also showed a broad spectrum of antipruritic activity, attenuating histamine-dependent and histamine-independent itching. Finally, we proved that antagonism of both sigma 1 and histamine H3 receptors is involved in the analgesic activity of the compound, while the antipruritic effect to a greater extent depends on sigma 1 antagonism.

Antiplatelet Effects of Selected Xanthine-Based Adenosine A2A and A2B Receptor Antagonists Determined in Rat Blood

The platelet aggregation inhibitory activity of selected xanthine-based adenosine A2A and A2B receptor antagonists was investigated, and attempts were made to explain the observed effects. The selective A2B receptor antagonist PSB-603 and the A2A receptor antagonist TB-42 inhibited platelet aggregation induced by collagen or ADP. In addition to adenosine receptor blockade, the compounds were found to act as moderately potent non-selective inhibitors of phosphodiesterases (PDEs). TB-42 showed the highest inhibitory activity against PDE3A along with moderate activity against PDE2A and PDE5A. The antiplatelet activity of PSB-603 and TB-42 may be due to inhibition of PDEs, which induces an increase in cAMP and/or cGMP concentrations in platelets. The xanthine-based adenosine receptor antagonists were found to be non-cytotoxic for platelets. Some of the compounds showed anti-oxidative properties reducing lipid peroxidation. These results may provide a basis for the future development of multi-target xanthine derivatives for the treatment of inflammation and atherosclerosis and the prevention of heart infarction and stroke.

Dual Piperidine-Based Histamine H3 and Sigma-1 Receptor Ligands in the Treatment of Nociceptive and Neuropathic Pain

In search of new dual-acting histamine H₃/sigma-1 receptor ligands, we designed a series of compounds structurally based on highly active in vivo ligands previously studied and described by our team. However, we kept in mind that within the previous series, a pair of closely related compounds, KSK67 and KSK68, differing only in the piperazine/piperidine moiety in the structural core showed a significantly different affinity at sigma-1 receptors (σ₁Rs). Therefore, we first focused on an in-depth analysis of the protonation states of piperazine and piperidine derivatives in the studied compounds. In a series of 16 new ligands, mainly based on the piperidine core, we selected three lead structures (3, 7, and 12) for further biological evaluation. Compound 12 showed a broad spectrum of analgesic activity in both nociceptive and neuropathic pain models based on the novel molecular mechanism.

Trisubstituted 1,3,5-Triazines as Histamine H4 Receptor Antagonists with Promising Activity In Vivo

Pain is a very unpleasant experience that makes life extremely uncomfortable. The histamine H₄ receptor (H₄R) is a promising target for the treatment of inflammatory and immune diseases, as well as pain. H₄R ligands have demonstrated analgesic effects in a variety of pain models, including inflammatory pain. Continuing the search for active H₄R ligands among the alkyl derivatives of 1,3,5-triazine, we obtained 19 new compounds in two series: acyclic (I) and aliphatic (II). In vitro pharmacological evaluation showed their variable affinity for H₄R. The majority of compounds showed a moderate affinity for this receptor (K_i > 100 nM), while all compounds tested in ß-arrestin and cAMP assays showed antagonistic activity. The most promising, compound 6, (4-(cyclopentylmethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine; K_i = 63 nM) was selected for further in vitro evaluation: blood-brain barrier permeability (PAMPA assay; P_e = 12.26 × 10^-6 cm/s) and toxicity tests (HepG2 and SH-5YSY cells; no toxicity up to 50 µM). Next, compound 6 tested in vivo in a carrageenan-induced inflammatory pain model showed anti-inflammatory and analgesic effects (strongest at 50 mg/kg i.p.). Furthermore, in a histamine- and chloroquine-induced pruritus model, compound 6 at a dose of 25 mg/kg i.p. and 50 mg/kg i.p., respectively, reduced the number of scratch bouts. Thus, compound 6 is a promising ligand for further studies.

Benzophenone Derivatives with Histamine H3 Receptor Affinity and Cholinesterase Inhibitory Potency as Multitarget-Directed Ligands for Possible Therapy of Alzheimer's Disease

The multitarget-directed ligands demonstrating affinity to histamine H₃ receptor and additional cholinesterase inhibitory potency represent a promising strategy for research into the effective treatment of Alzheimer's disease. In this study, a novel series of benzophenone derivatives was designed and synthesized. Among these derivatives, we identified compound 6 with a high affinity for H₃R (K_i = 8 nM) and significant inhibitory activity toward BuChE (IC₅₀ = 172 nM and 1.16 µM for eqBuChE and hBuChE, respectively). Further in vitro studies revealed that compound 6 (4-fluorophenyl) (4-((5-(piperidin-1-yl)pentyl)oxy)phenyl)methanone) displays moderate metabolic stability in mouse liver microsomes, good permeability with a permeability coefficient value (P_e) of 6.3 × 10^-6 cm/s, and its safety was confirmed in terms of hepatotoxicity in the HepG2 cell line. Therefore, we investigated the in vivo activity of compound 6 in the Passive Avoidance Test and the Formalin Test. While compound 6 did not show a statistically significant influence on memory and learning, it showed analgesic properties in both acute (ED₅₀ = 20.9 mg/kg) and inflammatory (ED₅₀ = 17.5 mg/kg) pain.

Discovery of (R)-N-Benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamide [], a Novel Orally Bioavailable EAAT2 Modulator with Drug-like Properties and Potent Antiseizure Activity In Vivo

(R)-7 [(R)-AS-1] showed broad-spectrum antiseizure activity across in vivo mouse seizure models: maximal electroshock (MES), 6 Hz (32/44 mA), acute pentylenetetrazol (PTZ), and PTZ-kindling. A remarkable separation between antiseizure activity and CNS-related adverse effects was also observed. In vitro studies with primary glia cultures and COS-7 cells expressing the glutamate transporter EAAT2 showed enhancement of glutamate uptake, revealing a stereoselective positive allosteric modulator (PAM) effect, further supported by molecular docking simulations. (R)-7 [(R)-AS-1] was not active in EAAT1 and EAAT3 assays and did not show significant off-target activity, including interactions with targets reported for marketed antiseizure drugs, indicative of a novel and unprecedented mechanism of action. Both in vivo pharmacokinetic and in vitro absorption, distribution, metabolism, excretion, toxicity (ADME-Tox) profiles confirmed the favorable drug-like potential of the compound. Thus, (R)-7 [(R)-AS-1] may be considered as the first-in-class small-molecule PAM of EAAT2 with potential for further preclinical and clinical development in epilepsy and possibly other CNS disorders.

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.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00397-6.

Identification of New Compounds with Anticonvulsant and Antinociceptive Properties in a Group of 3-substituted (2,5-dioxo-pyrrolidin-1-yl)(phenyl)-Acetamides

We report herein a series of water-soluble analogues of previously described anticonvulsants and their detailed in vivo and in vitro characterization. The majority of these compounds demonstrated broad-spectrum anticonvulsant properties in animal seizure models, including the maximal electroshock (MES) test, the pentylenetetrazole-induced seizure model (scPTZ), and the psychomotor 6 Hz (32 mA) seizure model in mice. Compound 14 showed the most robust anticonvulsant activity (ED₅₀ MES = 49.6 mg/kg, ED₅₀ 6 Hz (32 mA) = 31.3 mg/kg, ED₅₀scPTZ = 67.4 mg/kg). Notably, it was also effective in the 6 Hz (44 mA) model of drug-resistant epilepsy (ED₅₀ = 63.2 mg/kg). Apart from favorable anticonvulsant properties, compound 14 revealed a high efficacy against pain responses in the formalin-induced tonic pain, the capsaicin-induced neurogenic pain, as well as in the oxaliplatin-induced neuropathic pain in mice. Moreover, compound 14 showed distinct anti-inflammatory activity in the model of carrageenan-induced aseptic inflammation. The mechanism of action of compound 14 is likely complex and may result from the inhibition of peripheral and central sodium and calcium currents, as well as the TRPV1 receptor antagonism as observed in the in vitro studies. This lead compound also revealed beneficial in vitro ADME-Tox properties and an in vivo pharmacokinetic profile, making it a potential candidate for future preclinical development. Interestingly, the in vitro studies also showed a favorable induction effect of compound 14 on the viability of neuroblastoma SH-SY5Y cells.

Structure-Based Design and Optimization of FPPQ, a Dual-Acting 5-HT3 and 5-HT6 Receptor Antagonist with Antipsychotic and Procognitive Properties

In line with recent clinical trials demonstrating that ondansetron, a 5-HT₃ receptor (5-HT₃R) antagonist, ameliorates cognitive deficits of schizophrenia and the known procognitive effects of 5-HT₆ receptor (5-HT₆R) antagonists, we applied the hybridization strategy to design dual-acting 5-HT₃/5-HT₆R antagonists. We identified the first-in-class compound FPPQ, which behaves as a 5-HT₃R antagonist and a neutral antagonist 5-HT₆R of the Gs pathway. FPPQ shows selectivity over 87 targets and decent brain penetration. Likewise, FPPQ inhibits phencyclidine (PCP)-induced hyperactivity and displays procognitive properties in the novel object recognition task. In contrast to FPPQ, neither 5-HT₆R inverse agonist SB399885 nor neutral 5-HT₆R antagonist CPPQ reversed (PCP)-induced hyperactivity. Thus, combination of 5-HT₃R antagonism and 5-HT₆R antagonism, exemplified by FPPQ, contributes to alleviating the positive-like symptoms. Present findings reveal critical structural features useful in a rational polypharmacological approach to target 5-HT₃/5-HT₆ receptors and encourage further studies on dual-acting 5-HT₃/5-HT₆R antagonists for the treatment of psychiatric disorders.

Cyanobiphenyls: Novel H3 receptor ligands with cholinesterase and MAO B inhibitory activity as multitarget compounds for potential treatment of Alzheimer's disease

Alzheimer's disease (AD) is a complex and incurable illness that requires the urgent approval of new effective drugs. However, since 2003, no new molecules have shown successful results in clinical trials, thereby making the common "one compound - one target" paradigm questionable. Recently, the multitarget-directed ligand (MTDL) approach has gained popularity, as compounds targeting at least two biological targets may be potentially more effective in treating AD. On the basis of these findings, we designed, synthesized, and evaluated through biological assays a series of derivatives of alicyclic amines linked by an alkoxy bridge to an aromatic lipophilic moiety of [1,1'-biphenyl]-4-carbonitrile. The research results revealed promising biological activity of the obtained compounds toward the chosen targets involved in AD pathophysiology; the compounds showed high affinity (mostly low nanomolar range of K_i values) for human histamine H₃ receptors (hH₃R) and good nonselective inhibitory potency (micromolar range of IC₅₀ values) against acetylcholinesterase from electric eel (eeAChE) and equine serum butyrylcholinesterase (eqBuChE). Moreover, micromolar/submicromolar potency against human monoamine oxidase B (hMAO B) was detected for some compounds. The study identified compound 5 as a multiple hH₃R/eeAChE/eqBuChE/hMAO B ligand (5: hH₃R K_i = 9.2 nM; eeAChE IC₅₀ = 2.63 µM; eqBuChE IC₅₀ = 1.30 µM; hMAO B IC₅₀ = 0.60 µM). Further in vitro studies revealed that compound 5 exhibits a mixed type of eeAChE and eqBuChE inhibition, good metabolic stability, and moderate hepatotoxicity effect on HepG2 cells. Finally, compound 5 showed a beneficial effect on scopolamine-induced memory impairments, as assessed by the passive avoidance test, thus revealing the potential of this compound as a promising agent for further optimization for AD treatment.

Bioresearch of New 1H-pyrrolo[3,4-c]pyridine-1,3(2H)-diones

The subject of the work was the synthesis of new derivatives of1H-pyrrolo[3,4-c]pyridine-1,3(2H)-dione with potential analgesic and sedative activity. Eight compounds werereceived. The analgesic activity of the new compounds was confirmed in the “hot plate” test and in the “writhing” test. All tested imides 8–15 were more active in the “writhing” test than aspirin, and two of them, 9 and 11, were similar to morphine. In addition, all of the new imides inhibited the locomotor activity in mice to a statistically significant extent, and two of them also prolonged the duration of thiopental sleep.On the basis of the results obtained for the previously synthesized imides and the results presented in this paper, an attempt was madeto determine the relationship between thechemical structure of imides and their analgesic and sedativeproperties.

KA-104, a new multitargeted anticonvulsant with potent antinociceptive activity in preclinical models

OBJECTIVE

The main objective of the present work was to assess the utility of KA-104 as potential therapy for drug-resistant seizures and neuropathic pain, and to characterize its druglike properties in a series of absorption, distribution, metabolism, excretion and toxicity (ADME-Tox) studies. We also aimed to establish its mechanism of action in electrophysiological studies.

METHODS

The activity of KA-104 against drug-resistant seizures was tested in the mouse 6-Hz (44-mA) model, whereas the antinociceptive activity was assessed with the capsaicin- and oxaliplatin-induced pain models in mice. The patch-clamp technique was used to study the influence of KA-104 on fast voltage-gated sodium currents in rat prefrontal cortex pyramidal neurons. The pharmacokinetic profile was determined after intraperitoneal (ip) injection in mice. The in vitro ADME-Tox properties were studied by applying routine testing procedures.

RESULTS

KA-104 was effective in the 6-Hz (44-mA) model (median effective dose [ED₅₀ ] = 73.2 mg/kg) and revealed high efficacy in capsaicin-induced neurogenic pain as well as in oxaliplatin-induced neuropathic pain in mice. Patch-clamp technique showed that KA-104 reversibly inhibits voltage-gated sodium currents. KA-104 was rapidly absorbed after the ip injection and showed relatively good penetration through the blood-brain barrier. This molecule was also characterized by high passive permeability, moderate influence on CYP2C9, and negligible hepatotoxicity on HepG2 cells.

SIGNIFICANCE

The results reported herein indicate that KA-104 is a new wide-spectrum multitargeted anticonvulsant with favorable in vitro ADME-Tox properties. Importantly, this compound may also prove to become an interesting and hopefully more effective therapeutic option for treatment of neuropathic pain.

Rational design of new multitarget histamine H3 receptor ligands as potential candidates for treatment of Alzheimer's disease

Design and development of multitarget-directed ligands (MTDLs) has become a very important approach in the search of new therapies for Alzheimer's disease (AD). In our present research, a number of xanthone derivatives were first designed using a pharmacophore model for histamine H₃ receptor (H₃R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H₃R (hH₃R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH₃R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC₅₀ values in submicromolar range. Furthermore, the inhibitory effects of monoamine oxidases (MAO) A and B were investigated. The results showed low micromolar and selective human MAO B (hMAO B) inhibition. Two azepane derivatives, namely 23 (2-(5-(azepan-1-yl)pentyloxy)-9H-xanthen-9-one) and 25 (2-(5-(azepan-1-yl)pentyloxy)-7-chloro-9H-xanthen-9-one), were especially very promising and showed high affinity for hH₃R (K_i = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC₅₀ = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC₅₀ = 880 nM and 394 nM respectively) and hMAO B (IC₅₀ = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH₃R, human cholinesterases and hMAO B to describe the mode of interactions with these biological targets. Next, the two most promising compounds 23 and 25 were selected for in vivo studies. The results showed significant memory-enhancing effect of compound 23 in dizocilpine-induced amnesia in rats in two tests: step-through inhibitory avoidance paradigm (SIAP) and transfer latency paradigm time (TLPT). In addition, favourable analgesic effects of compound 23 were observed in neuropathic pain models. Therefore, compound 23 is a particularly promising structure for further design of new MTDLs for AD.

Multitargeted Compounds Derived from (2,5-Dioxopyrrolidin-1-yl)(phenyl)-Acetamides as Candidates for Effective Anticonvulsant and Antinociceptive Agents

We developed a focused set of original hybrid pyrrolidine-2,5-dione derivatives with potent anticonvulsant and antinociceptive properties. These hybrid compounds demonstrated broad-spectrum protective activity in a range of mouse models, such as the maximal electroshock (MES) test, the pentylenetetrazole-induced seizures (scPTZ), and the 6 Hz (32 mA) seizures. Compound 22 showed the most potent anticonvulsant activity (ED₅₀ MES = 23.7 mg/kg, ED₅₀ 6 Hz (32 mA) = 22.4 mg/kg, ED₅₀ scPTZ = 59.4 mg/kg). In addition, 22 revealed potent efficacy in the formalin-induced tonic pain. These in vivo activities of 22 are likely mediated by several targets and may result from the inhibition of central sodium/calcium currents and transient receptor potential vanilloid 1 (TRPV1) receptor antagonism. Finally, the lead compound 22 revealed drug-like absorption, distribution, metabolism, excretion, toxicity (ADME-Tox) properties in the in vitro assays, making it a potential candidate for further development in epilepsy and neuropathic pain indications.

Beneficial effects of non-quinazoline α1-adrenolytics on hypertension and altered metabolism in fructose-fed rats. A comparison with prazosin

BACKGROUND AND AIMS

Metabolic syndrome associated with insulin resistance and hypertension is often caused by excessive fructose consumption. Treatment of hypertension in patients with metabolic syndrome is a difficult task as many antihypertensive drugs have adverse effects on the metabolic profile. We investigated if MH-76 and MH-79, non-quinazoline α₁-adrenoceptor antagonists with an additional ability to stimulate NO/cGMP/K⁺ pathway, ameliorates metabolic syndrome in fructose-fed rats. As reference compound prazosin was used.

METHODS AND RESULTS

Male rats were divided into 5 groups (n = 8) and studied for 18 weeks: group control: standard diet and drinking water; group Fructose: high-fructose diet (20% fructose in drinking water); groups Fructose + MH-76, Fructose + MH-79, Fructose + prazosin: high-fructose diet with subsequent MH-76, MH-79 (5 mg/kg/day ip) or prazosin (0.2 mg/kg/day ip) treatment 12 weeks later. In addition to their antihypertensive effect, the studied compounds reversed endothelial dysfunction, decreased hyperglycemia and hypertriglyceridemia, as well as prevented abdominal adiposity. Moreover, MH-76 reduced insulin resistance and decreased TNF-α concentration and lipid peroxidation in adipose tissue. Prazosin treatment exerted an antihypertensive effect, reduced hyperglycemia but did not improve endothelial dysfunction, insulin resistance, and abdominal adiposity. The lower efficacy of prazosin may be the result of its short half-time and the lack of described pleiotropic effects.

CONCLUSIONS

α₁-adrenoceptor blockade, endothelial protection, TNF-α suppressing and antioxidant activity together with favorable pharmacokinetic parameters determines high efficacy of MH-76, leading to the effective improvement of hemodynamic and metabolic disturbances in metabolic syndrome. The use of non-quinazoline, multiple-targeted α₁-blockers may be an interesting option for treatment of hypertension with metabolic complications.

Reversal of cardiac, vascular, and renal dysfunction by non-quinazoline α1-adrenolytics in DOCA-salt hypertensive rats: a comparison with prazosin, a quinazoline-based α1-adrenoceptor antagonist

We investigated the therapeutic effect of MH-76 and MH-79, which are non-quinazoline α1-adrenoceptor antagonists with an additional ability to stimulate the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/K + pathway, on deoxycorticosterone acetate (DOCA)-salt induced hypertension in rats. Prazosin was used as a reference compound, as quinazoline-based α1-adrenolytics may potentially exert unfavorable proapoptotic and necrotic effects. DOCA-salt hypertension was induced by DOCA (20 mg/kg s.c., twice weekly) administration plus 1% NaCl and 0.2% KCl solutions in drinking water for 12 weeks. The studied compounds MH-76, MH-79 (10 mg/kg i.p.) or prazosin (0.4 mg/kg i.p.) were administered to the DOCA-salt-treated rats, starting from the 6th week of DOCA-salt treatment and continuing for 6 weeks. This study showed that the administration of MH-79 and, to a lesser extent, MH-76 decreased elevated systolic blood pressure and heart rate, reduced heart and kidney hypertrophy, and reversed the histopathological alterations of the heart, kidney, and vessels in DOCA-salt hypertensive rats. MH-79 reversed endothelial dysfunction, which reduced inflammatory cell infiltration, arteriosclerotic alterations in renal and coronary arteries, and tubulointerstitial fibrosis. Prazosin showed a potent hemodynamic effect and reduced cardiac and renal fibrosis but exerted detrimental effects on blood vessels, potentiating fibroplasia of the media of the intrarenal artery and causing calcification of coronary arteries. Prazosin did not reverse endothelial dysfunction. Our results show the beneficial effect of non-quinazoline α1-adrenolytics on cardiac, vascular, and renal dysfunction in DOCA-salt hypertensive rats. Our findings also support the idea that targeting endothelial protection and endothelial integrity would yield beneficial effects against cardiac, blood vessel and renal injury related to hypertension.

Synthesis and pharmacological evaluation of novel arylpiperazine oxicams derivatives as potent analgesics without ulcerogenicity

Gastrotoxicity continues to be a major issue in therapy with nonsteroidal anti-inflammatory drugs (NSAIDs). Medicine is yet to develop absolutely safe analgesics. Numerous strategies are employed to discover new, safer NSAIDs, for example selective inhibition of cyclooxygenase-2, new molecular targets (e.g. microsomal prostaglandin E₂ synthase-1), incorporation of cytoprotective compounds in the drug molecule or modification of the classic NSAIDs currently available on the market. The research presented in this paper is indicative of a current worldwide trend in this area of science, and is an example of the fourth strategy noted above. Two series of new arylpiperazine derivatives of the classic NSAID - piroxicam, were developed by conventional synthesis. The full range of compounds obtained proved to be between two and five times analgesically more potent than the reference drug and, most importantly, they did not show any ulcerogenic activity.

KA-11, a Novel Pyrrolidine-2,5-dione Derived Broad-Spectrum Anticonvulsant: Its Antiepileptogenic, Antinociceptive Properties and in Vitro Characterization

Recently, compound KA-11 was identified as a promising candidate for a new broad-spectrum anticonvulsant. This compound revealed wide protective activity across the most important animal models of seizures such as the maximal electroshock test (MES), the subcutaneous pentylenetetrazole test ( scPTZ), and the six-hertz test (6 Hz, 32 mA). Importantly, KA-11 was devoid of acute neurological activity, which was assessed by applying the chimney test (TD₅₀ value higher than 1500 mg/kg). The preliminary in vivo results confirmed favorable anticonvulsant and safety properties of KA-11. With the aim of further biological characterization of KA-11, in the current studies we evaluated its antiepileptogenic activity in the kindling model of epilepsy induced by repeated injection of PTZ in mice. Furthermore, we assessed the antinociceptive activity of KA-11 in several animal pain models. As a result, KA-11 (at all doses applied: 25, 50, and 100 mg/kg) significantly delayed the progression of kindling induced by repeated injection of PTZ in mice. Additionally, KA-11 revealed potent antinociceptive activity in the formalin-induced tonic pain and, importantly, in the oxaliplatin-induced neuropathic pain model in mice. Moreover, KA-11 did not induce motor deficits in the rotarod test. Patch-clamp experiments revealed that one of the mechanisms of action of KA-11 is inhibition of voltage-gated sodium currents. Compound KA-11 appeared to be safe in relation to hepatotoxic properties as no phospholipidosis induction was determined in HepG2 cells at 50 μM, and a small, statistically significant decrease of cell viability was observed only at the highest used dose of 100 μM. Moreover, KA-11 did not affect the function of CYP2D6. The aforementioned hybrid substance proved to penetrate the biological membranes in the in vitro permeability assays.

Optimization and preclinical evaluation of novel histamine H3receptor ligands: Acetyl and propionyl phenoxyalkyl piperazine derivatives

As a continuation of our search for novel histamine H₃ receptor ligands, a series of new acetyl and propionyl phenoxyalkylamine derivatives (2-25) was synthesized. Compounds with three to four carbon atoms alkyl chain spacer, composed of six various 4N-substituted piperazine moieties were evaluated for their binding properties at human histamine H₃ receptors (hH₃R). In vitro test results proved the 4-pyridylpiperazine moiety as crucial element for high hH₃R affinity (hH₃R K_i = 5.2-115 nM). Moreover introduction of carbonyl group containing residues in the lipophilic part of molecules instead of branched alkyl substituents resulted in increased affinity in correlation to previously described series, whereas propionyl derivatives showed slightly higher affinities than those of acetyl (16 and 22vs.4 and 10; hH₃R K_i = 5.2 and 15.4 nM vs. 10.2 and 115 nM, respectively). These findings were confirmed by molecular modelling studies, demonstrating multiple ligand-receptor interactions. Furthermore, pharmacological in vivo test results of compound 4 clearly indicate that it may affect the amount of calories consumed, thus act as an anorectic compound. Likewise, its protective action against hyperglycemia and the development of overweight has been shown. In order to estimate drug-likeness of compound 4, in silico and experimental evaluation of metabolic stability in human liver microsomes was performed.

Involvement of the NO/sGC/cGMP/K+ channels pathway in vascular relaxation evoked by two non-quinazoline α1-adrenoceptor antagonists

The aim of this study was to explore the α₁-adrenoceptor-independent mechanisms involved in the vasorelaxant properties of two non-quinazoline α₁-adrenoceptors antagonists (MH-76 and MH-79). Endothelium intact and endothelium denuded rat aorta was contracted with 1 μM phenylephrine to plateau, and the vasodilatory effect of MH-76 and MH-79 was examined in the absence or presence of inhibitors of the different signal transduction pathways. cGMP concetration was measured in rat aorta (enzyme immunoassay kit). In human aortic endothelial cells (HAEC) NO production was examined using a DAF-FM DA fluorescent indicator, whereas in human aortic smooth muscle cells the influence of the title compounds on K⁺ efflux was evaluated. The vasorelaxant effect of MH-76 and MH-79 was attenuated by endothelium removal, N_ω-Nitro-l-arginine methyl ester (L-NAME) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) pretreatment to the level characteristic for α₁-adrenoreceptor blocking activity. In addition, the MH-76 and MH-79 induced relaxation was reduced by K⁺ channels blockers. In endothelium intact rat aorta, MH-76 and MH-79 caused an increase in cGMP level, whereas in HAEC they increased NO generation. In contrast, the reference, quinazoline based α₁-antagonist prazosin, did not influence NO production. Our findings suggest that the mechanisms underlying the vasodilatory properties of non-quinazoline based α₁-adrenoceptors antagonists MH-76 and MH-79 involve not only α₁-adrenoceptor blocking activity but also the activation of the endothelial NO-cGMP signalling pathway and the subsequent opening of K⁺ channels. Our studies show that such double mechanism of action is superior to pure α₁-adrenoceptor blockade, and may be considered as a promising alternative for the prevention and treatment of cardiovascular diseases.

Design, synthesis and cardiovascular evaluation of some aminoisopropanoloxy derivatives of xanthone

A series of aminoisopropanoloxy derivatives of xanthone has been synthesized and their pharmacological properties regarding the cardiovascular system has been evaluated. Radioligand binding and functional studies in isolated organs revealed that title compounds present high affinity and antagonistic potency for α₁-(compound 2 and 8), β-(compounds 1, 3, 4, 7), α₁/β-(compounds 5 and 6) adrenoceptors. Furthermore, compound 7, the structural analogue of verapamil, possesses calcium entry blocking activity. The title compounds showed hypotensive and antiarrhythmic properties due to their adrenoceptor blocking effect. Moreover, they did not affect QRS and QT intervals, and they did not have proarrhythmic potential at tested doses. In addition they exerted anti-aggregation effect. The results of this study suggest that new compounds with multidirectional activity in cardiovascular system might be found in the group of xanthone derivatives.

Biphenyloxy-alkyl-piperidine and azepane derivatives as histamine H3 receptor ligands

Novel biphenyloxy-alkyl derivatives of piperidine and azepane were synthesized and evaluated for their binding properties at the human histamine H₃ receptor. Two series of compounds were obtained with a meta- and a para-biphenyl moiety. The alkyl chain spacer contained five and six carbon atoms. The highest affinity among all compounds was shown by 1-(6-(3-phenylphenoxy)hexyl)azepane (13) with a K_i value of 18nM. Two para-biphenyl derivatives, 1-(5-(4-phenylphenoxy)pentyl)piperidine (14; K_i=25nM) and 1-(5-(4-phenylphenoxy)pentyl)azepane (16; K_i=34nM), classified as antagonists in a cAMP accumulation assay (IC₅₀=4 and 9nM, respectively), were studied in detail. Compounds 14 and 16 blocked RAMH-induced dipsogenia in rats (ED₅₀ of 2.72mg/kg and 1.75mg/kg respectively), and showed high selectivity (hH₄R vs hH₃R>600-fold) and low toxicity (hERG inhibition: IC₅₀>1.70µM; hepatotoxicity IC₅₀>12.5µM; non-mutagenic up to 10µM). Furthermore, the metabolic stability was evaluated in vitro on human liver microsomes (HLMs) and/or rat liver microsomes (RLMs). Metabolites produced were analyzed and tentatively identified by UPLC-MS techniques. The results demonstrated easy hydroxylation of the biphenyl ring.

Aryl-1,3,5-triazine ligands of histamine H4 receptor attenuate inflammatory and nociceptive response to carrageen, zymosan and lipopolysaccharide

Objective and design

Histamine H₄ receptor (H₄R) offers a great potential for new therapeutic strategies for the treatment of inflammation-based diseases. The aim of this study is to present the pharmacological profile of two recently synthesized ligands of H₄R with particular reference to their anti-inflammatory and analgesic activity.

Materials and subjects

We used mice and rats in the in vivo tests. We also used murine RAW 264.7 cells and isolated guinea-pig ileum in in vitro test.

Treatments

In the in vivo tests, animals were pre-treated with the increasing doses of investigated compounds (12.5, 25 and 50 mg/kg) and reference compounds: JNJ7777120 (25 mg/kg), indomethacin (10 mg/kg). Macrophages were pre-treated with two concentrations of tested compounds 100 and 10 µM.

Methods

We examined anti-inflammatory and analgesic effects of the new H₄R antagonists in the in vivo models of inflammation induced by carrageenan or zymosan. We assessed the level of cAMP and release of cytokines, ROS and NO in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Moreover, we assessed the affinity of the investigated compounds for histamine H₁ receptor in functional studies.

Results

Both investigated compounds reduced paw edema, mechanical and thermal hyperalgesia in the carrageenan-induced acute inflammation. Moreover, administration of the investigated compounds resulted in decreased granulocyte influx and attenuated nociceptive reaction in the zymosan-induced peritonitis model. In the same model of inflammation, the investigated compounds reduced vascular permeability; however, this effect was observed only after the highest applied dose. Furthermore, the test compounds had no impact on cell viability in the experiments on RAW 264.7 macrophages. In these cells, stimulated with LPS, the test compounds decreased reactive oxygen species (ROS) production. They increased the cellular concentration of cAMP and attenuated the production of inflammatory cytokines such as TNFα and IL-1β. All results were comparable to those obtained for the reference compound JNJ7777120 with the exception of the impact on NO production. Nevertheless, this effect was similar to that obtained for the other reference compound rolipram, which is a phosphodiesterase 4 (PDE 4) inhibitor. Further experiments revealed that both of the investigated compounds possessed relatively low affinity for histamine H₁ receptor and do not inhibit the activity of the PDE 4B1 enzyme. In addition, all the effects of the investigated compounds in in vivo experiments were observed at doses that did not cause neurologic deficits in rotarod test and did not reduce spontaneous locomotor activity.

Conclusions

Our results demonstrate the anti-inflammatory and analgesic activity of the new aryl-1,3,5-triazine derivatives, which are primarily H₄R–dependent.

Synthesis and activity of newly designed aroxyalkyl or aroxyethoxyethyl derivatives of piperazine on the cardiovascular and the central nervous systems

In the search for new hypotensive agents some new aroxyalkyl or aroxyethoxyethyl derivatives of piperazine have been synthesized and evaluated for their pharmacological properties. Pharmacological tests included receptor binding assays toward adrenergic receptors α₁, α₂ and β₁, additionally 5-HT_1A, functional bioassay and in vivo evaluation of hypotensive activity as well as antidepressant-like potential. All the tested compounds exhibited α₁-antagonistic properties, three of them possessed also hypotensive activity in rats. The most promising compound 3 1-[4-(2,6-dimethylphenoxy)butyl]-4-(2-methoxyphenyl)piperazine hydrochloride was a selective α₁ receptor antagonist (K_i=23.5±1.3, α₁/α₂=15.77, pK_B=8.538±0.109). It was active in all tested doses in vivo (1, 0.5, and 0.1mg/kg) and it reduced blood pressure by 10-13% at the dose of 1mg/kg (rats, i.v.). Compound 5 1-[2-(2,3-dimethylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine dihydrochloride exhibited the lowest dose for antidepressant-like activity 5mg/kgb.w. (mice, i.p.) without influence on spontaneous activity (mice, i.p.).

Chemically Homogenous Compounds with Antagonistic Properties at All α1-Adrenoceptor Subtypes but not β1-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 β1- 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 β1 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.

Antidepressant-like activity of aroxyalkyl derivatives of 2-methoxyphenylpiperazine and evidence for the involvement of serotonin receptor subtypes in their mechanism of action

Since serotonin (5-HT) is strongly involved in the etiology and pathophysiology of depression, the development of new antidepressants is still based on the serotonergic system. The complexity of serotonergic system provides an opportunity for the development of compounds with multiple and complementary mechanism of action. This study describes serotonin receptor profile, functional characterization, and pharmacological in vivo evaluation of new aroxyalkyl derivatives of 2-methoxyphenylpiperazine. The obtained results allowed for the identification of compound 3, (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride), a partial 5-HT1A receptor agonist, and 5-HT2A receptor antagonist, with high affinity toward 5-HT7 receptors, showing antidepressant- and anxiolytic-like properties. Moreover, 5-HT1A receptor activation is crucial for the antidepressant-like activity of compound 3. The rest of the compounds (except compounds 1 and 9) showed antidepressant but not anxiolytic-like properties, which did not result from 5-HT1A receptors activation. Furthermore, the compounds are 5-HT1A and weak 5-HT3 receptors antagonists, and some of them 5-HT2A antagonists. Moreover, none of the studied compounds impaired motor coordination at antidepressant-like doses. Since the studied compounds exhibited activity in behavioral assays and interacted with various receptors, the results of our experiments are very promising and require further studies.

Antinociceptive, anti-inflammatory and smooth muscle relaxant activities of the pyrrolo[3,4-d]pyridazinone derivatives: Possible mechanisms of action

The aim of this study was to evaluate the analgesic as well as anti-inflammatory activities of the new pyrrolo[3,4-d]pyridazinone derivatives. Moreover, the present study attempted to assess some of the mechanisms involved in the pharmacological activity of these compounds. In the previous studies it was shown that these compounds were highly active in the phenylbenzoquinone-induced 'writhing syndrome' test and had much lower activity in the hot plate, which indicates that mainly peripheral mechanisms of analgesia are involved in their effects. In these extended studies the analgesic activity of two tested compounds (4c, 4f) was confirmed in some animal models of pain. The studied compounds showed a significant and dose-related antinociceptive effect in the models of pain induced by formalin, capsaicin and glutamic acid. Both compounds decreased the edema formation and one of them (4c) attenuated mechanical hyperalgesia in carrageenan-induced paw inflammation in rats. Furthermore, both compounds inhibited cell migration, plasma exudation and nociceptive reaction in zymosan A-induced mouse peritonitis. In the subsequent studies, including experiments on isolated organs (ileum, trachea, aorta), radioligand assays and biochemical tests, it was demonstrated that analgesic and anti-inflammatory effects of the investigated structures are largely due to their competitive antagonism for histamine H1 receptor. The influence on the level of cAMP in inflammatory cells (shown in RAW 264.7 macrophages) and subsequent inhibition of cytokine (TNFα, IL-1β) release can also be one of the important mechanisms of their action. Moreover some additional mechanisms may also be involved in the eventual analgesic effect of tested pyrrolo[3,4-d]pyridazinone derivatives.

Relaxant effects of selected sildenafil analogues in the rat aorta

A new series of sulfonamide derivatives of pyrazolo[4,3-e][1,2,4]triazine with chiral amino group has been synthesized and characterized. The compounds were tested for their relaxant effects in the rat aorta. Evaluation of prepared derivatives demonstrated that compound (8a) is probably a non-selective phosphodiesterase (PDE) inhibitor, as it induced aortic relaxation through endothelium-independent mechanism.

The nitric oxide/soluble cyclic guanylase/cyclic guanosine monophosphate pathway is involved in the cardiovascular effects of a novel α1- and β-adrenoceptor antagonist

The compound MH-78 ((+/-)-1-(2,6-dimethylphenoxy)-3-{4-[2-(2-methoxyphenoxy)ethyl]-piperazin-1-yl}propan-2-ol dihydrochloride) contains structural elements that are typical for α1- and β-blockers. This study aimed to investigate the hypotensive activity as well as the in vitro and in vivo cardiovascular effects of a novel α1- and β-adrenoceptor antagonist (MH-78) and compare it with carvedilol and urapidil. The procedures were performed on aortic rings of normotensive anesthetized rats. MH-78 decreased the blood pressure and heart rate after intravenous and oral administration. MH-78 possesses both α1- and β-adrenoceptor blocking activity, which was confirmed in the in vivo study. In biofunctional assays, MH-78 displayed vasorelaxant activity due to α1-adrenoceptor antagonism and calcium channel blocking properties. Moreover, in endothelium-intact aortic rings, pretreatment with Nω-nitro-L-arginine methyl ester (L-NAME) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) reduced the MH-78-induced vasorelaxation to a level that is characteristic for MH-78 affinity to α1-adrenoceptors. Our results demonstrated that MH-78 possesses α1- and β-adrenoceptor blocking properties and induces potent hypotensive and vasorelaxant effects. Moreover, it relaxes vascular smooth muscle not only due to α1-adrenoceptor blocking activity, but also via the endothelium-dependent nitric oxide/soluble guanylyl cyclase/cyclic guanosine monophosphate signalling pathway.

Biofunctional studies of new 2-methoxyphenylpiperazine xanthone derivatives with α₁-adrenolytic properties

BACKGROUND

The aim of this study was to assess the selectivity of the studied xanthone derivatives for α1-adrenoceptor subtypes (α1A, α1B, α1D, α1L) in functional experiments in order to verify if they possess any selectivity for a distinct subtype of α1-adrenoceptor. Moreover, several pharmacological tests were carried out to assess whether they reveal other than α1-adrenoceptor blocking properties such as: antagonistic for 5-HT2 receptors, vasorelaxant or spasmolytic.

METHODS

The influence on α1A-adrenoceptors was examined in biofunctional studies employing isolated rat vas deferens, on α1B-adrenoceptors in guinea-pig spleen, on α1D-adrenoceptors in rat aorta, and on α1L-adrenoceptors in rabbit spleen. Affinity for 5-HT2 receptors was measured in radioligand binding assay, whereas antagonistic potency for 5-HT2 receptors was studied on isolated rat aorta. Vasorelaxant effect of tested compounds was assessed in functional study employing rat aorta, whereas direct spasmolytic activity was investigated using the isolated rabbit small intestine.

RESULTS

The present study provides evidences that the tested 2-methoxyphenylpiperazine xanthone derivatives are non-selective α1-adrenoceptor blockers. However, at higher concentrations the direct spasmolytic effect could enhance their hypotensive activity. The obtained results indicate that the studied xanthones possessed weak calcium entry blocking activity, as well as antagonistic properties for 5-HT2A receptors.

CONCLUSIONS

The results of the present study support the idea that the hypotensive activity of the studied compounds is related to their α1-adrenolytic properties.

Anti-inflammatory activity of lipoic acid in mice peritonitis model

This work aimed to investigate the effect of lipoic acid (LA) on sulfane sulfur (S*) level, infiltration of neutrophils and vascular permeability in a model of zymosan-induced peritonitis. The study showed that lipoic acid increased the sulfane sulfur level. Also, it decreased count of neutrophils and inhibition of intensity of early vascular permeability compared to the control group. These studies indicated that LA exhibits antiinflammatory activity. LA serves as a sulfane sulfur acceptor and releases sulfane sulfur in the form of hydrogen sulfide (H2S), which is probably responsible for its anti-inflammatory activity.

The hypotensive activity and alpha1-adrenoceptor antagonistic properties of some aroxyalkyl derivatives of 2-methoxyphenylpiperazine

In the search for new hypotesive agents a series of aroxyalkyl derivatives of 2-methoxyphenylpiperazine was obtained. The aim of the present study was to examine their hypotensive properties and to evaluate their mechanism of action. In the study their hypotensive activity after i.v. and p.o. administration, influence on the pressor responses to adrenaline, noradrenaline and methoxamine, direct spasmolytic and vasorelaxant effects were assessed. In the next step two compounds which were the most active and selective for α(1)-adrenoceptors were evaluated for their α(1)-adrenoreceptor subtypes selectivity in functional bioassays. The data from our experiments indicate that the hypotensive activity of tested aroxyalkyl derivatives of 2-methoxyphenylpiperazine is mainly a result of their α(1)- or α(1)/α(2)-adrenoceptor blocking properties. The two most active compounds showed to be the competitive antagonists of α(1)-adrenoceptors with stronger activity at α(1D)-, α(1A)- and α(1L)- and weaker at α(1B)-subtype.

Synthesis, alpha 1-adrenoceptor antagonist activity, and SAR study of novel arylpiperazine derivatives of phenytoin

In the search for new antiarrhythmic agents, some active 2-methoxyphenylpiperazine derivatives of phenytoin were obtained as a chemical modification of compound AZ-99 (3-ethyl-1-[2-hydroxy-3-(4-phenylpiperazin-1-yl)-propyl]-2,4-dioxo-5,5-diphenylimidazolidine). These compounds possessed structural properties similar to those of alpha(1)-adrenoceptor antagonists. In the present study, the affinities of the 2-methoxyphenylpiperazine derivatives (1a-3a) for alpha(1)- and alpha(2)-adrenoceptors were evaluated using radioligand ([(3)H]prazosin, [(3)H]clonidine) binding assays. In the next step, a new series of phenylpiperazine derivatives of phenytoin (4a-16a) containing 2-methoxyphenyl-, 2-ethoxyphenyl-, 2-pyridyl- or 2-furoylpiperazine moiety, as well as, various ester or alkyl substituents at 3-position of hydantoin ring were synthesized. The newly synthesized compounds were tested for their affinity to alpha(1)- and alpha(2)-adrenoceptors. They have shown affinities for alpha(1)-adrenoceptors at nanomolar to submicromolar range. Some compounds were moderately selective ligands of alpha(1)-adrenoceptors. Selected compounds (3a-5a, 7a, 13a, 14a) were also evaluated for their alpha(1)-adrenoceptor antagonistic properties in functional bioassays. A SAR study indicated that the most active compounds contain 2-alkoxyphenylpiperazine moieties and methyl or 2-methylpropionate substituent at 3-N position in hydantoin. The exchange of 2-alkoxyphenyl moiety into 2-furoyl or 2-pyridyl group significantly decreased affinities for alpha(1)-adrenoceptors. Molecular modelling results obtained using conformational analysis CONFLEX and PM5 method for geometry optimization, allowed for comparison of the spatial properties of tested compounds with pharmacophore model created by Barbaro et al. for the ideal alpha(1)-adrenoceptor antagonist.