Biology subjects

Feja, M.

Publications and source records attributed to Feja, M..

3 recordsLinked to original sources

bioRxiv2020

Mouse model for testing SARS-CoV-2 antivirals: Pharmacokinetics

Background and ObjectivesRemdesivir and hydroxychloroquine are or were among the most promising therapeutic options to tackle the current SARS-CoV-2 pandemic. Besides the use of the prodrug remdesivir itself, the direct administration of GS-441 524, the resulting main metabolite of remdesivir, could be advantageous and even more effective. All substances were not originally developed for the treatment of COVID-19 and especially for GS-441 524 little is known about its pharmacokinetic and physical-chemical properties. To justify the application of new or repurposed drugs in humans, pre-clinical in vivo animal models are mandatory to investigate relevant PK and PD properties and their relationship to each other. In this study, an adapted mouse model was chosen to demonstrate its suitability to provide sufficient information on the model substances GS-441 524 and HCQ regarding plasma concentration and distribution into relevant tissues a prerequisite for treatment effectiveness. MethodsGS-441 524 and HCQ were administered intravenously as a single injection to male mice. Blood and organ samples were taken at several time points and drug concentrations were quantified in plasma and tissue homogenates by two liquid chromatography/tandem mass spectrometry methods. In vitro experiments were conducted to investigate the degradation of remdesivir in human plasma and blood. All pharmacokinetic analyses were performed with R Studio using non-compartmental analysis. ResultsHigh tissue to plasma ratios for GS-441 524 and HCQ were found, indicating a significant distribution into the examined tissue, except for the central nervous system and fat. For GS-441 524, measured tissue concentrations exceeded the reported in vitro EC50 values by more than 10-fold and in consideration of its high efficacy against feline infectious peritonitis, GS-441 524 could indeed be effective against SARS-CoV-2 in vivo. For HCQ, relatively high in vitro EC50 values are reported, which were not reached in all tissues. Facing its slow tissue distribution, HCQ might not lead to sufficient tissue saturation for a reliable antiviral effect. ConclusionThe mouse model was able to characterise the PK and tissue distribution of both model substances and is a suitable tool to investigate early drug candidates against SARS-CoV-2. Furthermore, we could demonstrate a high tissue distribution of GS-441 524 even if not administered as the prodrug remdesivir.

systems biology↗

bioRxiv2020

Chemogenetic activation of mesoaccumbal Gamma-Aminobutyric Acid projections selectively tunes responses to predictive cues when reward value is unexpectedly decreased

BackgroundMesolimbic circuits regulate the attribution of motivational significance to incentive cues that predict reward, yet this network also plays a key role in adapting reward-seeking behavior when the contingencies linked to a cue unexpectedly change. Here we asked whether mesoaccumbal gamma-aminobutyric acid (GABA) projections enhance adaptive responding to incentive cues of abruptly altered reward value, and whether these effects were distinct from global activation of all ventral tegmental area (VTA) GABA circuits. MethodsWe used a viral targeting system to chemogenetically activate mesoaccumbal GABA projections in male rats during a novel cue-dependent operant Value Shifting (VS) task, in which the volume of a sucrose reward associated with a predictive cue is suddenly altered, from the beginning and throughout the session. We compared the results with global activation of VTA GABA neurons, which will activate local inhibitory circuits and long loop projections. ResultsWe found that activation of mesoaccumbal GABA projections decreases responding to incentive cues associated with smaller-than-expected rewards. This tuning of behavioral responses was specific to cues associated with smaller-than-expected rewards, but did not impact measures related to consuming the reward. In marked contrast, activating all VTA(GABA) neurons resulted in a uniform decrease in responding to incentive cues irrespective of changes in the size of the reward. ConclusionsTargeted activation of mesoaccumbal GABA neurons facilitate adaptation in reward-seeking behaviors. This suggests that these projections may play a very specific role in associative learning processes.

neuroscience↗

bioRxiv2018

Exendin-4 disrupts responding to reward predictive incentive cues in rats

Exendin-4 (EX4) is a GLP-1 receptor agonist used clinically to control glycemia in Type-2 Diabetes Mellitus (T2DM), with the additional effect of promoting weight loss. The weight loss seen with EX4 is attributable to the varied peripheral and central effects of GLP-1, with contributions from the mesolimbic dopamine pathway that are implicated in cue-induced reward seeking. GLP-1 receptor agonists reduce preference for palatable foods (i.e. sweet and fat) as well as the motivation to obtain and consume these foods. Accumulating evidence suggest that GLP-1 receptor activity can attenuate cue-induced reward seeking behaviors. In the present study, we tested the effects of EX4 (0.6, 1.2, and 2.4 {micro}g/kg i.p.) on incentive cue (IC) responding. This rat model required rats to emit a nosepoke response during an intermittent audiovisual cue to obtain a sucrose reward (10% solution). EX4 dose-dependently attenuated responding to reward predictive cues, and increased latencies of the cue response and reward cup entry to consume the sucrose reward. Moreover, EX4 dose-dependently decreased the number of nosepokes relative to the number of cue presentations during the session. There was no drug effect on the number of reward cup entries per reward earned during the session, a related reward-seeking behavior with similar locomotor demand. Interestingly, there was a dose-dependent effect of time on the responding to reward predictive cues and nosepoke response latency, such that 2.4 {micro}g/kg of EX4 delayed responding to the initial IC of the behavioral session. Together, these findings suggest that agonism of the GLP-1 receptor with EX4 modulates the incentive properties of cues attributed with motivational significance.

pharmacology and toxicology↗