Barbara Chruścicka

Is the mGlu5 receptor a possible target for new antidepressant drugs

The current treatment of depression, based on conventional antidepressant drugs that influence monoaminergic systems, is not satisfactory, and innovative antidepressant drugs are still needed. The next generation of treatments needs to be more effective, faster-acting and better tolerated than currently used antidepressants. A growing body of evidence indicates that compounds that modulate the glutamatergic system may be a group of novel and mechanistically distinct agents for the treatment of depression. Both preclinical and clinical data show strong, rapid and sustained effects of the NMDA receptor antagonist ketamine in treatment-resistant depression. However, ketamine cannot be considered as a novel antidepressant drug because of its side-effects and abuse potential. Because glutamatergic transmission is controlled not only by ionotropic but also by metabotropic glutamate receptors, their involvement in the etiology and the therapy of depression has also been postulated. Here, we review data supporting the potential antidepressant activity of mGlu5 receptor antagonists as well as the involvement of mGlu5 receptors in the pathophysiology of depression.

Tetracycline-Based System for Controlled Inducible Expression of Group III Metabotropic Glutamate Receptors

A stable and inducible expression of metabotropic glutamate receptor type 4, 7, and 8 was obtained in T-REx 293 cells using the tetracycline system. Tetracycline administration to the cell medium resulted in rapid induction and time-dependent expression of mGlu receptors, which also correlates with its functionality in a cAMP accumulation assay. The pharmacological properties of recombinant mGlu receptors were verified using orthosteric and allosteric ligands. Data suggest that the Tet-on inducible system is suitable for functional mGlu receptors’ expression and characterization by means of the cAMP accumulation assay. It makes this system a precise, reproducible, and large-scale screening method, as well as a reasonable tool to study signaling properties of mGlu receptors.

Expression of group III metabotropic glutamate receptors in the reproductive system of male mice

Although the presence of metabotropic glutamate (mGlu) receptors in the central nervous system is well documented, they have recently been found in peripheral and non-neuronal tissues. In the present study we investigated the expression of group III mGlu receptors in the reproductive system of male mice. Reverse transcription-polymerase chain reaction analysis revealed the presence of mGlu6, mGlu7 and mGlu8 (but not mGlu4) receptor transcripts in testes and epididymides from adult mice. In addition, expression of mGlu6 (Grm6) and mGlu8 receptor (Grm8) mRNA was detected in spermatozoa isolated from the vas deferens. The vas deferens was found to contain only mGlu7 receptor (Grm7) mRNA, which was particularly intense in 21-day-old male mice. In penile homogenates, only the mGlu7 receptor signal was detected. Genetic ablation of the mGlu7 receptor in males led to fertility disorders manifested by decreased insemination capability as well as deterioration of sperm parameters, particularly sperm motility, vitality, sperm membrane integrity and morphology, with a simultaneous increase in sperm concentration. These results indicate that constitutively expressed mGlu receptors in the male reproductive system may play an important role in ejaculation and/or erection processes, as well as in the formation and maturation of spermatozoa.

Expression of metabotropic glutamate receptors in mammalian cells as a method for identification of new chemical compounds with drug-like activity

Background The metabotropic glutamate receptors (mGluRs) play important neuromodulatory role throughout the brain. Intervention in glutamatergic neurotransmission through mGluRs has been investigated in the treatment of many psychiatric and neurological disorders like anxiety, depression, schizophrenia, Parkinsons disease. Expression of mGluRs in heterologous mammalian cells is a method for their functional characterization, and tool to study the agonist, antagonist and allosteric effects, which might be very attractive target for therapeutic intervention. The constitutive expression of mGluRs seems to have a toxic effect on the HEK293 cells. Thus, an inducible expression system is used. Aim Our goal was to obtain a mammalian cell lines with stable expression of mGlu receptors. Furthermore, we try to improve pharmacological characterization of new chemical compounds by implementation of the newest molecular methods and hi-tech instruments, which lead to higher throughput and cost reduction. Methods cDNA fragments encoding mGluRs (mGluR2, 3, 4, 7, 8) were cloned into a pcDNA5/ FRT/TO vector under the control of a tetracycline regulated promoter (Invitrogen). The screening study was determined using forskolin-induced cAMP production in a HEK293 T-REx cell line stably expressing mGluRs (HTRF cAMP detection kit, Cisbio). Results Stably transfected HEK293 T-REx cells with inducible expression of mGluR 2, 3, 4, 7 and 8 were obtained. Functionality of mGluRs cell lines was verified by means of endogenous orthosteric agonist L-Glutamine (L-Glu). Furthermore, the references compounds (orthosteric agonists: L-AP4, LY379268 and allosteric modulators: VU0155041, MMPIP, AZ 12216052) activity was confirmed. The results were consistent with literature data. Conclusions We have created precise and high throughput screening platform as a tool for identification of new chemical compounds with drug-like activity.