4-phenyl-2-propionamidotetraline and Disease-Models--Animal

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

Melatonin can be synthesized and secreted not only by the pineal gland but also by many extra-pineal tissues. It has been shown that many ovarian functions are regulated by melatonin locally. Ovarian hyperstimulation syndrome (OHSS) is a serious complication during ovulation induction of the in vitro fertilization treatment. To date, the etiology of OHSS is not fully understood. However, vascular endothelial growth factor (VEGF) is recognized as a critical mediator for the pathogenesis of OHSS. High expression of melatonin has been detected in the follicular fluid of OHSS patients. However, whether VEGF expression can be regulated by melatonin in human granulosa cells and further contributes to the pathogenesis of OHSS remain unknown. In this study, we show that melatonin stimulates VEGF expression in human granulosa-lutein (hGL) cells. Our results reveal that the MT2 receptor and activation of AKT are involved in melatonin-induced VEGF expression. Using a rat OHSS model, we report that the VEGF levels are up-regulated in the ovaries of OHSS rats. Blocking the melatonin system by administrating MT2 receptor antagonist, 4-P-PDOT, alleviates OHSS symptoms by decreasing the expression of VEGF. In addition, the expression levels of melatonin and VEGF in the follicular fluid of OHSS patients are up-regulated and positively correlated. This study demonstrates an important role for melatonin in regulating the pathogenesis of OHSS.

Topics: Animals; Cells, Cultured; Disease Models, Animal; Female; Humans; Luteal Cells; Melatonin; Ovarian Hyperstimulation Syndrome; Primary Cell Culture; Proto-Oncogene Proteins c-akt; Rats; Receptor, Melatonin, MT2; Signal Transduction; Tetrahydronaphthalenes; Up-Regulation; Vascular Endothelial Growth Factor A

Melatonin is a neurohormone involved in the regulation of both acute and chronic pain whose mechanism is still not completely understood. We have recently demonstrated that selective MT2 melatonin receptor partial agonists have antiallodynic properties in animal models of chronic neuropathic pain by modulating ON/OFF cells of the descending antinociceptive system. Here, we examined the antinociceptive properties of the selective MT2 melatonin receptor partial agonists N-{2-[(3-methoxyphenyl)phenylamino]ethyl}acetamide (UCM765) and N-{2-[(3-bromophenyl)-(4-fluorophenyl)amino]ethyl}acetamide (UCM924) in two animal models of acute and inflammatory pain: the hot-plate and formalin tests. UCM765 and UCM924 (5-40 mg/kg, s.c.) dose-dependently increased the temperature of the first hind paw lick in the hot-plate test, and decreased the total time spent licking the injected hind paw in the formalin test. Antinociceptive effects of UCM765 and UCM924 were maximal at the dose of 20mg/kg. At this dose, the effects of UCM765 and UCM924 were similar to those produced by 200 mg/kg acetaminophen in the hot-plate test, and by 3 mg/kg ketorolac or 150 mg/kg MLT in the formalin test. Notably, antinociceptive effects of the two MT2 partial agonists were blocked by the pre-treatment with the MT2 antagonist 4-phenyl-2-propionamidotetralin (4P-PDOT, 10 mg/kg) in both paradigms. These results demonstrate the antinociceptive properties of UCM765 and UCM924 in acute and inflammatory pain models and corroborate the concept that MT2 melatonin receptor may be a novel target for analgesic drug development.

Topics: Acetamides; Acetaminophen; Analgesics; Aniline Compounds; Animals; Behavior, Animal; Brain; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Partial Agonism; Formaldehyde; Ketorolac; Male; Nociception; Nociceptive Pain; Protein Binding; Rats, Wistar; Receptor, Melatonin, MT2; Signal Transduction; Tetrahydronaphthalenes; Time Factors

It has been observed that the secretion pattern of melatonin is modified in Parkinson's disease (PD). Hence, it is hypothesized that dysregulations of melatonin MT2 receptors may be involved in the installation of depression in PD patients. Together with recent evidence based on the use of the intranigral rotenone model of PD, have led to the hypothesis that modulating the striatal MT2 receptor could provide a more comprehensive understanding of the antidepressant properties triggered. To further investigate this issue, male Wistar rats were infused with intranigral rotenone (12μg/μL) and seven days later subjected to a rapid eye movement sleep deprivation (REMSD) for 24h. After, we injected within the striatum the MT2 selective agonist, 8-M-PDOT (10μg/μL), the MT2 selective antagonist, 4-P-PDOT (5μg/μL) or vehicle. Subsequently, they were tested in the forced swimming test and were allowed to perform the sleep rebound (REB). Then, the rats were re-tested, and the striatum, hippocampus and substantia nigra pars compacta (SNpc) were collected for neurochemical purposes. Results indicated substantial antidepressant effects promoted by the blockade of striatal MT2 receptors that were potentiated by REMSD. MT2 activation increased DA levels in the striatum and hippocampus, while MT2 blockade increase DA in the SNpc. 4-P-PDOT treatment of the rotenone REMSD group generated a decrement in 5-HT levels within the striatum, hippocampus and SNpc. However, increased 5-HT turnover was observed among these structures. Therefore, we demonstrated the neurochemical antidepressant effect induced by striatal MT2 blockage associated with REMSD in the rotenone model of PD.

Topics: Animals; Biogenic Monoamines; Corpus Striatum; Depression; Disease Models, Animal; Insecticides; Male; Rats; Rats, Wistar; Receptors, Melatonin; Rotenone; Sleep Deprivation; Statistics as Topic; Swimming; Tetrahydronaphthalenes

Melatonin has been shown to modulate glucose metabolism by influencing insulin secretion. Recent investigations have also indicated a regulatory function of melatonin on the pancreatic α-cells. The present in vitro and in vivo studies evaluated whether melatonin mediates its effects via melatonin receptors and which signaling cascade is involved. Incubation experiments using the glucagon-producing mouse pancreatic α-cell line αTC1 clone 9 (αTC1.9) as well as isolated pancreatic islets of rats and mice revealed that melatonin increases glucagon secretion. Preincubation of αTC1.9 cells with the melatonin receptor antagonists luzindole and 4P-PDOT abolished the glucagon-stimulatory effect of melatonin. In addition, glucagon secretion was lower in the pancreatic islets of melatonin receptor knockout mice than in the islets of the wild-type (WT) control animals. Investigations of melatonin receptor knockout mice revealed decreased plasma glucagon concentrations and elevated mRNA expression levels of the hepatic glucagon receptor when compared to WT mice. Furthermore, studies using pertussis toxin, as well as measurements of cAMP concentrations, ruled out the involvement of Gαi- and Gαs-coupled signaling cascades in mediating the glucagon increase induced by melatonin. In contrast, inhibition of phospholipase C in αTC1.9 cells prevented the melatonin-induced effect, indicating the physiological relevance of the Gαq-coupled pathway. Our data point to the involvement of the phosphatidylinositol 3-kinase signaling cascade in mediating melatonin effects in pancreatic α-cells. In conclusion, these findings provide evidence that the glucagon-stimulatory effect of melatonin in pancreatic α-cells is melatonin receptor mediated, thus supporting the concept of melatonin-modulated and diurnal glucagon release.

Topics: Animals; Cell Line; Cyclic AMP; Diabetes Mellitus, Type 2; Disease Models, Animal; Dose-Response Relationship, Drug; Gene Expression Regulation; Glucagon; Glucagon-Secreting Cells; GTP-Binding Protein alpha Subunits, Gq-G11; Liver; Male; Melanins; Mice; Mice, Knockout; Pertussis Toxin; Phosphatidylinositol 3-Kinase; Rats; Rats, Wistar; Receptor, Melatonin, MT1; Receptor, Melatonin, MT2; Receptors, Glucagon; RNA, Messenger; Signal Transduction; Tetrahydronaphthalenes; Tissue Culture Techniques; Tryptamines; Type C Phospholipases

Melatonin (MLT) is a neurohormone known to be involved in the regulation of anxiety. Most of the physiological actions of MLT in the brain are mediated by two high-affinity G-protein-coupled receptors, denoted MT(1) and MT(2). However, the particular role of these receptors in anxiety remains to be defined. Here we used a novel MT(2)-selective partial agonist, UCM765 to evaluate the involvement of MT(2) receptors in anxiety. Adult male rats were acutely injected with UCM765 (5-10-20mg/kg), MLT (20mg/kg) or diazepam (DZ, 1mg/kg). Anxiety-related behaviors were assessed in the elevated plus maze test (EPMT), novelty suppressed feeding test (NSFT) and open field test (OFT). UCM765 at the dose of 10mg/kg showed anxiolytic-like properties by increasing the time spent in the open arm of the EPMT, and by reducing the latency to eat in a novel environment in the NSFT. In the EPMT, animals treated with UCM765 (10mg/kg) or MLT (20mg/kg) spent more time in the open arms compared to vehicle-treated animals, but to a lesser extent compared to DZ (1mg/kg). In the NSFT, all treatments similarly decreased the latency to eat in a novel environment compared to vehicle. UCM765 and MLT did not affect the total time and the number of entries into the central area of the OFT, but unlike DZ, did not impair locomotion. The anxiolytic effects of UCM765 and MLT in the EPMT and the NSFT were blocked using a pre-treatment with the MT(1)/MT(2) antagonist luzindole (10mg/kg) or the MT(2) antagonist 4P-PDOT (10mg/kg). These results demonstrated, for the first time, the anxiolytic properties of UCM765 and suggest that MT(2)-receptors may be considered a novel target for the development of anxiolytic drugs.

Topics: Acetamides; Aniline Compounds; Animals; Anti-Anxiety Agents; Anxiety; Diazepam; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Drug Partial Agonism; Feeding Behavior; Male; Maze Learning; Melatonin; Motor Activity; Rats; Rats, Sprague-Dawley; Receptor, Melatonin, MT2; Tetrahydronaphthalenes; Tryptamines

The pineal hormone melatonin has been shown to enhance hippocampal excitability. We therefore investigated whether inactivation of hippocampal melatonin receptors affects behavioral seizures.. Intrahippocampal infusions were performed in rats to study the effect of different melatonin receptor antagonists on behavioral activity, EEG, and seizure susceptibility. Experiments were conducted at 2 times of the day that coincided with the peak and trough of the daily melatonin rhythm.. Local infusion of the Mel(1b) receptor antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT) into the hippocampus, but not the overlying neocortex, significantly increased seizure latency and in some cases provided complete protection against seizure development. In addition, 4-P-PDOT suppressed open field activity and hippocampal EEG amplitude. The mixed Mel(1a)/Mel(1b) receptor antagonist luzindole also increased seizure latency but to a lesser degree than 4-P-PDOT. The behavioral effects of Mel(1b) receptor inhibition were comparable to those of the gamma-aminobutyric acid (GABA)(A) receptor agonist muscimol and were observed during the dark phase (2400-0200 h) but not the light phase (1200-1400 h) of the daily photocycle. The anticonvulsant effect of intrahippocampal infusion of 4P-P-DOT was blocked by coadministration of the GABA(A) antagonist bicuculline.. Our results suggest that nocturnal activation of hippocampal Mel(1b) receptors depresses GABA(A) receptor function in the hippocampus and enhances seizure susceptibility.

Topics: Animals; Behavior, Animal; Cerebral Cortex; Disease Models, Animal; Electroencephalography; Epilepsy, Temporal Lobe; Exploratory Behavior; Functional Laterality; GABA Antagonists; Hippocampus; Locomotion; Male; Muscimol; Pilocarpine; Rats; Rats, Wistar; Receptors, Melatonin; Seizures; Tetrahydronaphthalenes; Tryptamines

Melatonin, its agonists/antagonists were administered intrathecally (i.t.) before/after intradermal injection of capsaicin. Capsaicin produced an increase in the paw withdrawal frequency (PWF) in the presumed area of secondary mechanical allodynia and hyperalgesia. Melatonin agonists in the absence of a capsaicin injection decreased the PWF significantly, whereas melatonin antagonists given intrathecally alone were ineffective in the absence of a capsaicin injection. Pre-treatment with a melatonin agonist i.t. caused a reduction in the PWF after capsaicin. In contrast, the PWF increased after capsaicin with pre-administration of a melatonin antagonist i.t. Combined pre-treatment with melatonin and a melatonin antagonist i.t. prevented the change in PWF induced by melatonin alone after capsaicin. Intrathecal post-treatment with a melatonin agonist reduced the enhanced PWF that followed an injection of capsaicin, but treatment with a combination of a melatonin agonist and its antagonist did not alter the responses. The PWF was unaffected when melatonin analogs were applied i.t. at the T6 level or were injected intramuscularly adjacent to the L4 vertebra. In spinal rats, the data showed comparable effects of melatonin analogs on capsaicin-induced secondary mechanical hyperalgesia. Animal motor function tested by 'activity box' showed that motion activity was not affected by i.t. melatonin or its antagonist. These results suggest that activation of the endogenous melatonin system in the spinal cord can reduce the generation, development and maintenance of central sensitization, with a resultant inhibition of capsaicin-induced secondary mechanical allodynia and hyperalgesia.

Topics: Administration, Topical; Afferent Pathways; Animals; Capsaicin; Disease Models, Animal; Drug Interactions; Hyperalgesia; Injections, Intramuscular; Injections, Spinal; Male; Melatonin; Neural Inhibition; Pain; Physical Stimulation; Rats; Rats, Sprague-Dawley; Reflex; Skin; Spinal Cord; Spinal Cord Injuries; Tetrahydronaphthalenes; Tryptamines

Periventricular leukomalacia is one of the main causes of cerebral palsy. Perinatal white matter lesions associated with cerebral palsy appears to involve glutamate excitotoxicity and excess free radical production. When injected intracerebrally into newborn mice, the glutamatergic analog ibotenate induces white matter cysts mimicking human periventricular leukomalacia. Melatonin acts on specific receptors. It also exhibits intrinsic free radical scavenging properties. The goal of the present study is to determine whether melatonin can protect against excitotoxic lesions induced by ibotenate in newborn mice. Mice that received intraperitoneal melatonin had an 82% reduction in size of ibotenate-induced white matter cysts when compared with controls. Although melatonin did not prevent the initial appearance of white matter lesions, it did promote secondary lesion repair. Axonal markers supported the hypothesis that melatonin induced axonal regrowth or sprouting. The protective effects of melatonin were suppressed by coadministration of luzindole, a melatonin receptor antagonist. Forskolin, an adenylate cyclase activator, prevented the protective effects of melatonin; inhibitors of protein kinase C and mitogen-associated protein kinase had no detectable effect. Melatonin and derivatives that block cAMP production through activation of melatonin receptors could represent new avenues for treating human periventricular leukomalacia.

Topics: Animals; Animals, Newborn; Antioxidants; Cell Death; Cerebral Palsy; Cystine; Denervation; Disease Models, Animal; Excitatory Amino Acid Agonists; Free Radical Scavengers; Humans; Hypothermia, Induced; Ibotenic Acid; Infant, Newborn; Leukomalacia, Periventricular; Melatonin; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neocortex; Neuroprotective Agents; Neurotoxins; Receptors, Cell Surface; Receptors, Cytoplasmic and Nuclear; Receptors, Melatonin; RNA, Messenger; Tetrahydronaphthalenes; Tryptamines