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With the recent market approval of Pitolisant (Wakix®), the interest in clinical application for novel multifunctional histamine H3 receptor antagonists has clearly increased. Several combinations of different H3R pharmacophores with pharmacophoric elements of other G-protein coupled receptors, transporters, or enzymes have been synthesized by numerous pharmaceutical companies and academic institutions. Since central nervous system disorders are characterized by diverse physiological dysfunctions and deregulations of a complex network of signaling pathways, optimal multipotent drugs should simultaneously and peculiarly modulate selected groups of biological targets. Interestingly, very recent studies have shown that some clinically evaluated histamine H3 receptor antagonists possess a nanomolar affinity for sigma-1 receptor binding sites, suggesting that this property might play a role in their overall efficacy. The sigma-1 receptor, unusual and yet obscure protein, is supposed to be involved in numerous CNS pathologies through neuroprotection and neuroplasticity. These two different biological structures, histamine H3 and sigma-1 receptors, combined, can represent a potential fruitful target for therapeutic developments in tackling numerous human diseases.

Aims One of the therapeutic approaches in the treatment of obesity is the use of histamine H3 receptor ligands. Histamine plays a significant role in eating behavior because it causes a loss of appetite and is considered to be a satiety signal released during food intake. Material and methods Histamine ligands were selected based on the preliminary studies which included determination of intrinsic activity and selected pharmacokinetic parameters. Female Wistar rats were fed palatable feed for 28 days and simultaneously the tested compounds were administered intraperitoneally at a dose of 10 mg/kg b.w./day. Rats’ weight was evaluated daily and calories intake was evaluated once per week. At the end of experiment insulin and glucose tolerance tests was performed. Plasma levels of cholesterol, triglycerides, leptin, insulin, glucose, C-peptide and CRP were also determined. In order to rule out false-positive results the influence of tested compounds on spontaneous activity of rats was monitored. Results Animals fed palatable feed and treated with KSK-61 or KSK-63 compounds showed the slowest weight gain which was comparable to the one observed in control animals. Both compounds with the highest pharmacological activity have also similar pharmacokinetic properties with quite long half-life and high volume of distribution indicating that they can freely cross most biological barriers. Some compounds, especially KSK-63, compensated for metabolic disorders. Conclusion The presented study proves that search among the active histamine H3 receptor ligands for the new therapeutic agents to treat obesity is justified. Compounds KSK-61 and KSK-63 can be considered as the leading structures.

The environmental issue has become a global problem that needs to be examined frequently, motivating researchers to investigate it. Thus, the present study has investigated the asymmetric impact of globalization, economic growth and natural resources on the ecological footprint in the presence of environmental Kuznets curve (EKC) in Thailand. The study has used annual time series data from 1970 to 2018. The study applied a novel method of nonlinear autoregressive distributive lag (ARDL). In particular, the current study has investigated the effect of positive and negative shocks on the independent variable on the dependent variable. The findings have confirmed that the effect of globalization and natural resources are significant and nonlinear. However, the effect of negative shocks of globalization and natural resources is more dominant on the ecological footprint in Thailand than the positive shocks of both variables. Moreover, the present study has also tested the presence of EKC in Thailand, and the findings confirm the presence of an inverted U-shape curve in the Thailand economy.

In an attempt to find new dual acting histamine H3 receptor (H3R) ligands, we designed a series of compounds, structurally based on previously described in our group, a highly active and selective human histamine H3 receptor (hH3R) ligand KSK63. As a result, 15 obtained compounds show moderate hH3R affinity, the best being the compound 17 (hH3R Ki = 518 nM). Docking to the histamine H3R homology model revealed two possible binding modes, with key interactions retained in both cases. In an attempt to find possible dual acting ligands, selected compounds were tested for antioxidant properties. Compound 16 (hH3R Ki = 592 nM) showed the strongest antioxidant properties at the concentration of 10−4 mol/L. It significantly reduced the amount of free radicals presenting 50–60% of ascorbic acid activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, as well as showed antioxidative properties in the ferric reducing antioxidant power (FRAP) assay. Despite the yet unknown antioxidation mechanism and moderate hH3R affinity, 16 (QD13) constitutes a starting point for the search of potential dual acting H3R ligands-promising tools for the treatment of neurological disorders associated with increased neuronal oxidative stress.

Noting the worldwide rapid increase in the prevalence of overweight and obesity new effective drugs are now being sought to combat these diseases. Histamine H3 receptor antagonists may represent an effective therapy as they have been shown to modulate histamine synthesis and release and affect a number of other neurotransmitters (norepinephrine, acetylcholine, γ-aminobutyric acid, serotonin, substance P) thus influencing the food intake. Based on the preliminary studies determining affinity, intrinsic activity, and selected pharmacokinetic parameters, two histamine H3 receptor ligands were selected. Female rats were fed palatable food for 28 days and simultaneously administered the tested compounds intraperitoneally (i.p.) at a dose of 10 or 1 mg/kg b.w./day. Weight was evaluated daily and calorie intake was evaluated once per week. The plasma levels of cholesterol, triglycerides, leptin, adiponectin, ghrelin, corticosterone, CRP and IL-6 were determined at the end of experiment. The glucose tolerance test was also performed. To exclude false positives, the effect of tested compounds on spontaneous activity was monitored during the treatment, as well as the amount of consumed kaolin clay was studied as a reflection of possible gastrointestinal disturbances comparable to nausea. The histamine H3 receptor antagonists KSK-59 and KSK-73 administered i.p. at a dose of 10 mg/kg b.w. prevented weight gain in a rat model of excessive eating. They reduced adipose tissue deposits and improved glucose tolerance. Both compounds showed satisfying ability to penetrate through biological membranes determined in in vitro studies. Compound KSK-73 also reduced the caloric intake of the experimental animals what indicates its anorectic effect. These results show the pharmacological properties of histamine H3 receptor antagonists, (4-pyridyl)piperazine derivatives, as the compounds causing not only slower weight gain but also ameliorating some metabolic disorders in rats having the opportunity to overeat.

The pharmacological profile of pitolisant, a histamine H3 receptor antagonist/inverse agonist, indicates that this compound might reduce body weight and metabolic disturbances. Therefore, we studied the influence of pitolisant on body weight, water and sucrose intake as well as metabolic disturbances in the high-fat and high-sugar diet-induced obesity model in mice. To induce obesity, male CD-1 mice were fed a high-fat diet consisting of 40% fat blend for 14 weeks, water and 30% sucrose solution available ad libitum. Glucose tolerance test was performed at the beginning of week 15. Insulin tolerance was tested the day after. At the end of study, plasma levels of triglycerides and cholesterol were determined. Pitolisant at dose of 10 mg/kg bw (ip) was administrated during 14 days, starting from the beginning of week 13. Metformin at dose of 100 mg/kg bw (ip) was used as reference drug. Mice fed with high-fat diet and sucrose solution showed more weight gain throughout the 12-week period of inducing obesity. Animals fed with high-fat diet and treated with pitolisant (for the next 14 days) showed significantly less weight gain than mice from the control group consuming a high-fat feed. In the group treated with pitolisant, glucose levels were significantly lower than glucose levels of control obese mice after glucose load. The plasma triglyceride levels in pitolisant-treated mice were significantly lower compared with those in control obese group. In conclusion, pitolisant has a favorable influence of body weight and improves glucose tolerance and the lipid profile in obese mice.

This paper describes the methodology of inductively coupled plasma optical emission spectrometry for determining the total phosphorus content in bottom sediment samples. Homogenized samples subjected to a microwave-assisted aqua regia digestion, and next analyzed for total phosphorus content using the inductively coupled plasma optical emission spectrometer. The method was optimized and its validation parameters were determined. Assessing the selectivity of the method, found the spectral interferences of other elements (especially copper) on P can be partially eliminated by using the optimal operating conditions. The method exhibited excellent linearity (r>0.999) in the entire measurement range (25-5000 mg Pkg-1) and very good recovery (99%). It was also characterized by high repeatability (relative standard deviation of 1%) and reproducibility (reproducibility standard deviation of 10%). The relative expanded uncertainty of the method was estimated at 21.2%.

Taking into account that multidrug resistance (MDR) is the main cause for chemotherapeutic failure in cancer treatment, the ability of novel histamine H3 receptor ligands to reverse the cancer MDR was evaluated, using the ABCB1 efflux pump inhibition assay in mouse MDR T-lymphoma cells. The most active compounds displayed significant cytotoxic and antiproliferative effects as well as a very potent MDR efflux pump inhibitory action, 3-5-fold stronger than that of reference inhibitor verapamil. Although these compounds possess weak antagonistic properties against histamine H3 receptors, they are valuable pharmacological tools in the search for novel anticancer molecules. Furthermore, for the most active compounds, an insight into mechanisms of action using either, the luminescent Pgp-Glo™ Assay in vitro or docking studies to human Pgp, was performed.

A series of 4-pyridylpiperazine derivatives with varying regulatory region substituents proved to be potent histamine H3 receptor (H3R) ligands in the nanomolar concentration range. The most influential modification that affected the affinity toward the H3R appeared by introducing electron-withdrawing moieties into the distal aromatic ring. In order to finally discuss the influence of the characteristic 4-pyridylpiperazine moiety on H3R affinity, two Ciproxifan analogues 2 and 3 with a slight modification in their basic part were obtained. The replacement of piperazine in 3 with piperidine in compound 2, led to slightly reduced affinity towards the H3R (Ki = 3.17 and 7.70 nM, respectively). In fact, 3 showed the highest antagonistic properties among all compounds in this series, hence affirming our previous assumptions, that the 4-pyridylpiperazine moiety is the key element for suitable interaction with the human histamine H3 receptor. While its structural replacement to piperidine is also tolerated for H3R binding, the heteroaromatic 4-pyridyl moiety seems to be essential for proper ligand-receptor interaction. The putative protein-ligand interactions responsible for their high affinity were demonstrated using molecular modeling techniques. Furthermore, selectivity, intrinsic activity at the H3R, as well as drug-like properties of ligands were evaluated using in vitro methods. Moreover, pharmacological in vivo test results of compound 9 (structural analogue of Abbott’s A-331440) clearly indicate that it may affect the amount of calories consumed, thus act as an anorectic compound.

Aims Histamine H3 receptors ligands act anorectic by blocking the H3 autoreceptors in the CNS, that results in increased synthesis and disinhibition of histamine release. Histamine further influencing H1 receptors participates in the leptin-dependent inhibition of food intake. It also affects the peripheral metabolism by increasing white adipose tissue lipolysis. Thus, ligands such as KSK19 with significant antagonistic properties at the H3 receptor might serve as an useful treatment for obesity. Materials and methods To induce obesity, female CD-1 mice were fed a high-fat diet for 14 weeks. The test compound at the doses of 10 or 15 mg/kg, i.p. was administrated for 21 days. Glucose and insulin tolerance tests was performed at the beginning of week 15. At the end of study, amount of intraperitoneal fat pads, AlAT, IL-6 and TNF-α plasma levels were determined. Results Animals fed with high-fat diet and treated with test compound at the dose of 15 mg/kg showed significantly less weight gain, than mice from the control group. The use of KSK19 for 21 days in obese mice also significantly improved glucose tolerance and insulin resistance. In the tested doses KSK19 did not affect locomotor activity neither in lean nor in obese mice after single i.p. administration, but spontaneous activity increased during three hour after twentieth administrations. Conclusion KSK19 is a strong, selective histamine H3 receptor antagonist with a favorable influence on body weight after multiple administration at the dose of 15 mg/kg. Moreover it significantly improves glucose tolerance.

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 Ki = 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 22 vs. 4 and 10; hH3R Ki = 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.

As a continuation of our search for novel histamine H3 receptor ligands, a series of twenty four new tert-butyl and tert-pentyl phenoxyalkylamine derivatives (2−25) was synthesized. Compounds with three to four carbon atoms alkyl chain spacer were evaluated for their binding properties at human histamine H3 receptor (hH3R). The highest affinities were observed for 4-pyridyl derivatives 4, 10, 16 and 22 (Ki = 16.0–120 nM). As it has been shown in docking studies, those specific heteroaromatic 4-N piperazine substituents might interact with one of the key receptor interacting amino acids. Moreover, the most promising compounds exhibited anticonvulsant activity in the maximal electroshock-induced seizure (MES) model in mice. Furthermore, the blood-brain barrier penetration, the functional H3R antagonist potency as well as the pro-cognitive properties in the passive avoidance test were demonstrated for compound 10. In order to estimate drug-likeness of compound 10, in silico and experimental evaluation of metabolic stability in human liver microsomes was performed. In addition, paying attention to the results obtained within this study, the 4-pyridyl-piperazino moiety has been established as a new bioisosteric piperidine replacement in H3R ligands.

Since its discovery in 1983, followed by gene cloning in 1999, the histamine H3 receptor served as an outstanding target for drug discovery. The wide spectrum of possible therapeutic implications makes H3R's one of the most researched areas in the vast GPCR ligands field - started from imidazole containing ligands, through various successful imidazole replacements, with recent introduction of Wakix® to pharmaceutical market. One such replacement is piperazine moiety, a significant versatile scaffold in rational drug design for most of the GPCR ligands. Therefore, herein, we review ligands built on piperazine, as well as its seven membered analogue azepine, that target H3R’s and their potential therapeutical applications, in order to elucidate the current state of the art in this vast field. Due to a high level of structural divergence among compounds described herein, we decided to divide them into groups, where the key division element was the position of nitrogen basicity decreasing moieties in (homo)piperazine ring. Paying attention to a number of published structures and their overall high biological activity, one can realize that the (homo)piperazine scaffold bids a versatile template also for histamine H3 receptor ligands. With two possible substitution sites and therefore a number of possible structural combinations, piperazine derivatives stand as one of the largest group of high importance among H3R ligands.

In order to map out molecular determinants for the competitive blockade of AMPA receptor subtypes, a series of racemic aryl-substituted phenylalanines was synthesized and pharmacologically characterized in vitro at native rat ionotropic glutamate receptors. Most of the compounds showed micromolar affinity and preference for AMPA receptors. Individual stereoisomers of selected compounds were further evaluated at recombinant homomeric rat GluA2 and GluA3 receptors. The most potent compound, (-)-2-amino-3-(6-chloro-2',5'-dihydroxy-5-nitro-[1,1'-biphenyl]-3-yl)propanoic acid, the expected R-isomer showing Ki of 1.71 μM at the GluA2 subtype, was found to competitively antagonize GluA2(Q)i receptors in TEVC electrophysiological experiments (Kb = 2.13 μM). Molecular docking experiments allowed us to compare two alternative antagonist binding modes for the synthesized phenylalanines at the GluA2 binding core, showing the direction for further structural modifications.

A novel series of 4-pyridylpiperazine derivatives with varying alkyl linker length and eastern part substituents proved to be potent histamine H 3 receptor (hH 3 R) ligands in the nanomolar concentration range. While paying attention to their alkyl linker length, derivatives with a six methylene linker tend to be more potent than their five methylene homologues. Moreover, in the case of both phenoxyacetyl- and phenoxypropionyl- derivatives, an eight methylene linkers possess lower activity than their seven methylene homologues. However, in global analysis of collected data on the influence of alkyl linker length, a three methylene homologues appeared to be of highest hH 3 R affinity among all described 4-pyridylpiperazine derivatives from our group up to date. In the case of biphenyl and benzophenone derivatives, compounds with para- substituted second aromatic ring were of higher affinity than their meta analogues. Interestingly, benzophenone derivative 18 showed the highest affinity among all tested compounds (hH 3 R K i = 3.12 nM). The likely protein-ligand interactions, responsible for their high affinity were demonstrated using molecular modeling techniques. Furthermore, selectivity, intrinsic activity at H 3 R, as well as drug-like properties of selected ligands were evaluated using in vitro methods.

Studies were conducted on samples taken from giving birth women ( n = 40) living in Poland, representing three age groups: 19–25, 26–30 and 31–38 years old. Mercury concentrations were measured with CV-AAS in placenta, umbilical cord, cord blood and amniotic fluid. The placentas weight did not exceed the 750 g value and was heavier than 310 g. Mean values of Hg concentrations in blood, placenta and umbilical cord were similar (c.a. 9 μg/g). High levels of mercury were noted in cord blood which in 75% of all observations exceeded (up to 17 μg/L) the safe dose set by US EPA (5.8 μg/L). No statistically significant differences in medium level of Hg in all the studied tissues among age groups of women were observed. Positive correlations between Hg concentrations in placenta and umbilical cord and cord blood were revealed as well as some negative ones between mercury concentrations and pregnancy parameters.

As a continuation of our search for novel histamine H3 receptor ligands a series of twenty new tert-amyl phenoxyalkylamine derivatives (2-21) was synthesized. Compounds of four to eight carbon atoms spacer alkyl chain were evaluated on their binding properties at human histamine H3 receptor (hH3R). The highest affinities were observed for pentyl derivatives 6-8 (Ki=8.8-23.4nM range) and among them piperidine derivative 6 with Ki=8.8nM. Structures 6, 7 were also classified as antagonists in cAMP accumulation assay (with EC50=157 and 164nM, respectively). Moreover, new compounds were also evaluated for anticonvulsant activity in Antiepileptic Screening Program (ASP) at National Institute of Neurological Disorders and Stroke (USA). Seven compounds (2-4, 9, 11, 12 and 20) showed anticonvulsant activity at maximal electroshock (MES) test in the dose of 30mg/kg at 0.5h. In the subcutaneous pentetrazole (scMET) test compound 4 showed protection at 100 and 300mg/kg dose at mice, however compounds showed high neurotoxicity in rotarod test at used doses. Also, molecular modeling studies were undertaken, to explain affinity of compounds at hH3R (taking into the consideration X-ray analysis of compound 18). In order to estimate "drug-likeness" of selected compounds in silico and experimental evaluation of lipophilicity, metabolic stability and cytotoxicity was performed.

The implication of select protein kinase C (PKC) isoenzymes in cytokine production by human monocytes was investigated using an isozyme-selective inhibitor of PKC, rottlerin. We found that lipopolysaccharide (LPS) triggers cytosol-to-membrane translocation of PKCα and δ isoenzymes, whereas phorbol ester (PMA) induces translocation of several PKC isoforms. Moreover, we show that in LPS- and PMA-stimulated monocytes rottlerin affects several cellular responses. (1) At low (15 μM) concentration it blocks translocation of PKCδ, diminishes DNA binding activity of AP-1 transcription factor, and attenuates cytokine production [tumor necrosis factor α (TNF-α) > interleukin-1β (IL-1β)]. (2) At high (50 μM) concentration it prevents translocation of PKCα, and subsequently inhibits ERK1/ERK2 phosphorylation, DNA binding activities of AP-1 and nuclear factor-κB transcription factors, and the production of both tested cytokines. Thus, we propose that cytosol-to-membrane translocation of PKCα and PKδ isoenzymes may represent early steps in the signaling cascades that lead to TNF-α and IL-1β production in human monocytes. J. Leukoc. Biol. 67: 249–258; 2000.