Multiple actions of fenamates and other nonsteroidal anti-inflammatory drugs on GABAA receptors

Mechanisms of Glioblastoma Replication: Ca2+ Flares and Cl- Currents

Glioblastoma (GBM) is amongst the deadliest types of cancers, with no resolutive cure currently available. GBM cell proliferation in the patient's brain is a complex phenomenon controlled by multiple mechanisms. The aim of this study was to determine whether the ionic fluxes controlling cell duplication could represent a target for GBM therapy. In this work, we combined multi-channel Ca2+ and Cl- imaging, optical tweezers, electrophysiology, and immunohistochemistry to describe the role of ion fluxes in mediating the cell volume changes that accompany mitosis of U87 GBM cells. We identified three main steps: (i) in round GBM cells undergoing mitosis, during the transition from anaphase to telophase and cytokinesis, large Ca2+ flares occur, reaching values of 0.5 to 1 μmol/L; (ii) these Ca2+ flares activate Ca2+-dependent Cl- channels, allowing the entry of Cl- ions; and (iii) to maintain osmotic balance, GBM cells swell to complete mitosis. This sequence of steps was validated by electrophysiological experiments showing that Cl- channels are activated either directly or indirectly by Ca2+, and by additional live-cell imaging experiments. Cl- channel blockers with different molecular structures, such as niflumic acid and carbenoxolone, blocked GBM replication by arresting GBM cells in a round configuration. These results describe the central role of Ca2+ flares and Cl- fluxes during mitosis and show that inhibition of Ca2+-activated Cl- channels blocks GBM replication, opening the way to new approaches for the clinical treatment of GBM. Implications: Our work identifies ionic fluxes occurring during cell division as targets for devising novel therapies for glioblastoma treatment.

Antiseizure properties of fenamate NSAIDs determined in mature human stem-cell derived neuroglial circuits

Repeated and uncontrolled seizures in epilepsy result in brain cell loss and neural inflammation. Current anticonvulsants primarily target ion channels and receptors implicated in seizure activity. Identification of neurotherapeutics that can inhibit epileptiform activity and reduce inflammation in the brain may offer significant benefits in the long-term management of epilepsy. Fenamates are unique because they are both non-steroidal anti-inflammatory drugs (NSAIDs) and highly subunit selective modulators of GABAA receptors. In the current study we have investigated the hypothesis that fenamates have antiseizure properties using mature human stem cell-derived neuro-glia cell cultures, maintained in long-term culture, and previously shown to be sensitive to first, second and third generation antiepileptics. Mefenamic acid, flufenamic acid, meclofenamic acid, niflumic acid, and tolfenamic acid (each tested at 10-100 μM) attenuated 4-aminopyridine (4-AP, 100 μM) evoked epileptiform activity in a dose-dependent fashion. These actions were as effective diazepam (3-30 μM) and up to 200 times more potent than phenobarbital (300-1,000 μM). The low (micromolar) concentrations of fenamates that inhibited 4-AP evoked epileptiform activity correspond to those reported to potentiate GABAA receptor function. In contrast, the fenamates had no effect on neural spike amplitudes, indicating that their antiseizure actions did not result from inhibition of sodium-channels. The antiseizure actions of fenamates were also not replicated by either of the two non-fenamate NSAIDs, ibuprofen (10-100 μM) or indomethacin (10-100 μM), indicating that inhibition of cyclooxygenases is not the mechanism through which fenamates have anticonvulsant properties. This study therefore shows for the first time, using functionally mature human stem cell-derived neuroglial circuits, that fenamate NSAIDs have powerful antiseizure actions independent of, and in addition to their well-established anti-inflammatory properties, suggesting these drugs may provide a novel insight and new approach to the treatment of epilepsy in the future.

Tiratricol, a thyroid hormone metabolite, has potent inhibitory activity against human dihydroorotate dehydrogenase

Human dihydroorotate dehydrogenase (hDHODH) is a promising drug target for many diseases including autoimmune diseases, cancer, and viral infection. To develop more novel and potent hDHODH inhibitors, we screened our in-house library of old drugs. We found that tiratricol (3,3',5-triiodothyroacetic acid), a thyroid hormone metabolite, has potent hDHODH inhibitory activity (IC50 : 0.754 ± 0.126 μM), and its precursor tetrac (3,3',5,5'-tetraiodothyroacetic acid) also shows a certain inhibitory activity against hDHODH (IC50 : 11.960 ± 1.453 μM). Enzyme kinetic analysis shows that tiratricol and tetrac are noncompetitive inhibitors versus CoQ0 , which is different from the positive control A771726. ThermoFMN assay, molecular docking and site-directed mutagenesis all indicate that tiratricol and tetrac interact with more key residues of hDHODH than A771726, especially some hydrophobic residues in Subsite 1. In conclusion, our experiment results indicate a potential new use for the old drug, tiratricol, and provide a novel chemical scaffold for the design of hDHODH inhibitors.

Changes in working memory induced by lipopolysaccharide administration in mice are associated with metabotropic glutamate receptors 5 and contrast with changes induced by cyclooxygenase-2: Involvement of postsynaptic density protein 95 and down syndrome cell adhesion molecule

The strength and quality of the signal propagated by the glutamate synapse (Glu) depend, among other things, on the structure of the postsynaptic part and the quality of adhesion between the interacting components of the synapse. Postsynaptic density protein 95 (PSD95), mammalian target of rapamycin (mTOR), and Down syndrome cell adhesion molecule (DSCAM) are components of the proper functioning of an excitatory synapse. PSD95 is a member of the membrane-associated guanylate kinases protein family, mainly located at the postsynaptic density of the excitatory synapse. PSD95, via direct interaction, regulates the clustering and functionality of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) receptors at a synapse. Here, the effects of treatment with an antagonist of mGluR5 (MTEP) and NS398 (cyclooxygenase-2, COX-2 inhibitor) on PSD95, mTOR, and DSCAM in the hippocampus (HC) of C57B1/6 J mice using Western blots in the context of learning were examined. Moreover, the sensitivity of selected proteins to lipopolysaccharide (LPS) was monitored. MTEP injected for seven days induced upregulation of PSD95 in HC of mice. The observed effect was regulated by a COX-2 inhibitor and concurrently by LPS. Accompanying alterations in DSCAM protein were found, suggesting changes in adhesion strength after modulation of glutamatergic (Glu) synapse via tested compounds.

Searching for new anxiolytic agents among derivatives of 11-dialkylaminoethyl-2,3,4,5-tetrahydrodiazepino[1,2-a]benzimidazole

A study on the anxiolytic activity of the new derivatives of 11-dialkylaminoethyl-2,3,4,5-tetrahydrodiazepino[1,2-a]benzimidazole, containing privileged scaffolds of benzodiazepine and benzimidazole in their structure, was conducted. The cytotoxic properties of low levels of six compounds were preliminary determined in vitro using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test. The screening of these substances for anxiolytic activity was conducted using elevated plus maze (EPM) test in vivo, and DAB-21 was found to be the most active compound. The acute toxicity of DAB-21 was determined as less toxic than that of diazepam. The dose-dependent effect of the most active compound revealed a minimum dose of 1.26 mg/kg, which resulted in the maximum counterphobic effect. The effect of DAB-21 was superior in a number of tests compared with that of diazepam, which indicated a high level of tranquilizing activity for DAB-21. The results of in silico docking analysis suggest that DAB-21 should have a slightly lower anxiolytic activity than diazepam, but should exhibit greater specific affinity for the benzodiazepine site of the GABA_A receptor, in comparison with its GABA-binding site. The interaction between DAB-21 and flumazenil in terms of EPM verifies the GABAergic mechanism of action of DAB-21. Our results highlight the potential of 11-dialkylaminomethyl-2,3,4,5-tetrahydrodiazepino[1,2-a]benzimidazoles as promising compounds in the search for new highly effective anxiolytics.