Binge-like mephedrone treatment induces memory impairment concomitant with brain kynurenic acid reduction in mice.

While mephedrone (4-methylmethcathinone), a synthetic cathinone derivative, is widely abused by adolescents and young adults, the knowledge about its long-term effects on memory processes is limited. Kynurenic acid (KYNA) is a neuroactive metabolite of the kynurenine pathway of tryptophan degradation. KYNA is considered an important endogenous modulator influencing physiological and pathological processes, including learning and memory processes. The aim of this study was to determine whether (A) binge-like mephedrone administration (10.0 and 30.0 mg/kg, intraperitoneally, in 4 doses separated by 2 h) induces memory impairments, assessed 2, 8 and 15 days after mephedrone cessation in the passive avoidance test in mice, and whether (B) KYNA is involved in these memory processes. To clarify the role of KYNA in the mephedrone effects, its production in the murine brain in vivo, and in cortical slices in vitro, as well as the activities of kynurenine aminotransferases (KATs) I and II were assessed. Furthermore, cell line experiments were conducted to investigate the effects of mephedrone on normal human brain cells. Our results showed memory impairments 8 and 15 days after binge-like mephedrone administration. At the same time, reduction in the KYNA level in the murine brain was noted. In vitro studies showed no effect of mephedrone on the production of KYNA in cortical slices or on the activity of the KAT I and II enzymes. Finally, exposure of normal cells to mephedrone in vitro resulted in a modest reduction of cell viability and proliferation.

Effect of Tryptophan-Derived AhR Ligands, Kynurenine, Kynurenic Acid and FICZ, on Proliferation, Cell Cycle Regulation and Cell Death of Melanoma Cells-In Vitro Studies.

Tryptophan metabolites: kynurenine (KYN), kynurenic acid (KYNA) and 6-formylindolo[3,2-b]carbazole (FICZ) are considered aryl hydrocarbon receptor (AhR) ligands. AhR is mainly expressed in barrier tissues, including skin, and is involved in various physiological and pathological processes in skin. We studied the effect of KYN, KYNA and FICZ on melanocyte and melanoma A375 and RPMI7951 cell toxicity, proliferation and cell death. KYN and FICZ inhibited DNA synthesis in both melanoma cell lines, but RPMI7951 cells were more resistant to pharmacological treatment. Tested compounds were toxic to melanoma cells but not to normal human adult melanocytes. Changes in the protein level of cyclin D1, CDK4 and retinoblastoma tumor suppressor protein (Rb) phosphorylation revealed different mechanisms of action of individual AhR ligands. Importantly, all tryptophan metabolites induced necrosis, but only KYNA and FICZ promoted apoptosis in melanoma A375 cells. This effect was not observed in RPMI7951 cells. KYN, KYNA and FICZ in higher concentrations inhibited the protein level of AhR but did not affect the gene expression. To conclude, despite belonging to the group of AhR ligands, KYN, KYNA and FICZ exerted different effects on proliferation, toxicity and induction of cell death in melanoma cells in vitro.

Development of the 1,2,4-triazole-based anticonvulsant drug candidates acting on the voltage-gated sodium channels. Insights from in-vivo, in-vitro, and in-silico studies.

The treatment of epilepsy remains difficult mostly since almost 30% of patients suffer from pharmacoresistant forms of the disease. Therefore, there is an urgent need to search for new antiepileptic drug candidates. Previously, it has been shown that 4-alkyl-5-substituted-1,2,4-triazole-3-thione derivativatives possessed strong anticonvulsant activity in a maximal electroshock-induced seizure model of epilepsy. In this work, we examined the effect of the chemical structure of the 1,2,4-triazole-3-thione-based molecules on the anticonvulsant activity and the binding to voltage-gated sodium channels (VGSCs) and GABAA receptors. Docking simulations allowed us to determine the mode of interactions between the investigated compounds and binding cavity of the human VGSC. Selected compounds were also investigated in a panel of ADME-Tox assays, including parallel artificial membrane permeability assay (PAMPA), single cell gel electrophoresis (SCGE) and cytotoxicity evaluation in HepG2 cells. The obtained results indicated that unbranched alkyl chains, from butyl to hexyl, attached to 1,2,4-triazole core are essential both for good anticonvulsant activity and strong interactions with VGSCs. The combined in-vivo, in-vitro and in-silico studies emphasize 4-alkyl-5-substituted-1,2,4-triazole-3-thiones as promising agents in the development of new anticonvulsants.

Kynurenic Acid Protects against Thioacetamide-Induced Liver Injury in Rats.

Acute liver failure (ALF) is a life-threatening disorder of liver function. Kynurenic acid (KYNA), a tryptophan metabolite formed along the kynurenine metabolic pathway, possesses anti-inflammatory and antioxidant properties. Its presence in food and its potential role in the digestive system was recently reported. The aim of this study was to define the effect of KYNA on liver failure. The Wistar rat model of thioacetamide-induced liver injury was used. Morphological and biochemical analyses as well as the measurement of KYNA content in liver and hepatoprotective herbal remedies were conducted. The significant attenuation of morphological disturbances and aspartate and alanine transaminase activities, decrease of myeloperoxidase and tumor necrosis factor-α, and elevation of interleukin-10 levels indicating the protective effect of KYNA in thioacetamide (TAA) - induced liver injury were discovered. In conclusion, the hepatoprotective role of KYNA in an animal model of liver failure was documented and the use of KYNA in the treatment of ALF was suggested.

Cancer chemoprevention - selected molecular mechanisms.

The effect of diet on cancer formation and prevention of carcinogenesis has attracted considerable attention for years and is the subject of several studies. Some components of the daily diet, such as resveratrol, curcumin, genistein, gingerol, can significantly reduce the risk of cancer or affect the rate of tumor progression. Cancer chemoprevention assumes the use of natural or synthetic biologically active substances in order to prevent, inhibit or reverse the progression of cancer. There are many biologically active compounds in several natural products, i.e. garlic, ginger, soy, curcuma, tomatoes, cruciferous plants or green tea. Their chemopreventive activity is based on the inhibition of processes underlying carcinogenesis (inflammation, transformation and proliferation), but also affects the final phase of carcinogenesis - angiogenesis and metastasis. Despite the relatively low toxicity of chemopreventive agents, their molecular targets often coincide with the objectives of the currently used cancer therapies. The widespread use of chemopreventive agents may contribute to reduction of the rate of cancer incidence, and increase the effectiveness of conventional cancer therapies. In the present study, selected molecular mechanisms of the chemopreventive activity have been discussed, especially their involvement in the regulation of signal transduction, cell cycle regulation, apoptosis, metastasis and angiogenesis. The role of chemopreventive agents in the inflammatory process, the metabolism of xenobiotics and multidrug resistance has been also characterized.

The paraoxonase 1 (PON1), platelet-activating factor acetylohydrolase (PAF-AH) and dimethylarginine dimethylaminohydrolase (DDAH) activity in the metformin treated normal and diabetic rats.

Antidiabetic agents per se, apart from their glucose-lowering effect, can have an important impact on modifying the cardiovascular risk. The present study was undertaken to determine whether the known cardio-protective effects of metformin are linked to its potential ability to affect activities of HDL's paraoxonase (PON1) and platelet activating factor acetylohydrolase (PAF-AH) or via its interaction with the asymmetric dimethylarginine (ADMA)- dimethylarginine dimethylaminohydrolase (DDAH) axis. Normal and streptozotocin (STZ)-induced diabetic rats were treated with metformin (300mg/kg; 4 weeks). The activity of PON1, PAF-AH and DDAH were measured spectrophotometrically. The plasma ADMA level was determined by ELISA method. In STZ-induced diabetic rats the long-term administration of metformin normalized reduced PON1 activity assayed toward paraoxon (+42.5%, P<0.05), phenyl acetate (+22.35%, P<0.05) and γ-decanolactone (+108.0%, P<0.01), without affecting elevated PAF-AH activity in the plasma. Moreover, metformin increased DDAH activity in the renal cortex (+38.24%, P<0.01). Additionally metformin administration caused the increase in PON1 activity in the liver (+29.2%, P<0.01) accompanied by the reduction in the lipid peroxidation (-59.8%, P<0.001). Similarly, in non-diabetic treated rats the increase in liver PON1 activity was observed toward both paraoxon (+80.19%, P<0.001) and phenyl acetate (+29.3%, P<0.05), respectively. The present study has demonstrated that insulin-sensitizer metformin is important for preserving antioxidant HDL function in diabetes. Metformin might also exert its effect against diabetic complications by improving DDAH activity in the kidney and increasing PON1 activity in the liver.

Tempol, a Membrane-Permeable Radical Scavenger, Exhibits Anti-Inflammatory and Cardioprotective Effects in the Cerulein-Induced Pancreatitis Rat Model.

To date, it remains unclear whether mild form of acute pancreatitis (AP) may cause myocardial damage which may be asymptomatic for a long time. Pathogenesis of AP-related cardiac injury may be attributed in part to ROS/RNS overproduction. The aim of the present study was to evaluate the oxidative stress changes in both the pancreas and the heart and to estimate the protective effects of 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (tempol) at the early phase of AP. Cerulein-induced AP led to the development of acute edematous pancreatitis with a significant decrease in the level of sulfhydryl (-SH) groups (oxidation marker) both in heart and in pancreatic tissues as well as a substantial increase in plasma creatine kinase isoenzyme (CK-MB) activity (marker of the heart muscle lesion) which confirmed the role of oxidative stress in the pathogenesis of cardiac damage. The tempol treatment significantly reduced the intensity of inflammation and oxidative damage and decreased the morphological evidence of pancreas injury at early AP stages. Moreover, it markedly attenuated AP-induced cardiac damage revealed by normalization of the -SH group levels and CK-MB activity. On the basis of these studies, it is possible to conclude that tempol has a profound protective effect against cardiac and pancreatic damage induced by AP.

On the toxicity of kynurenic acid in vivo and in vitro.

BACKGROUND: Kynurenic acid (KYNA), a tryptophan metabolite is an antagonist of ionotropic glutamate receptors and alpha-7 nicotinic receptor. Moreover, it is an agonist of G-protein receptor GPR35. Its neuroprotective, anticonvulsant, anti-inflammatory and antioxidant activity was documented. KYNA is present in food and herbal medicines. However, the data on effects induced by a long-lasting treatment with KYNA is lacking. The aim of the study was the assessment of toxicity of a prolonged administration of KYNA in rodents. The cytotoxicity of KYNA in vitro was also examined. METHODS: Adult mice and rats were used. KYNA was administered in the drinking water in concentrations of 25 or 250mg/L for 3-21 days. The following cells were cultured in an in vitro study: mouse fibroblast (NIH/3T3), green monkey kidney cells and primary chick embryo cells (CECC). Cell viability was determined with methyl thiazol tetrazolium reduction assay, neutral red uptake assay and lactate dehydrogenase leakage assay. RESULTS: KYNA affected neither body gain nor body composition. Blood counts were also unaffected. The viability of cells in the culture was lowered at high millimolar concentrations of KYNA. An elevated viability of GMK and CECC cells was detected in the presence of KYNA in micromolar concentrations. CONCLUSIONS: The obtained results showed that a long-term application of KYNA in the drinking water is well-tolerated by rodents. No evidence of a toxic response was recorded. Achieved results indicate that diets containing a high amount of KYNA or enriched with KYNA should not cause any risk to the human health.