Novel Opioid-Neurotensin-Based Hybrid Peptide with Spinal Long-Lasting Antinociceptive Activity and a Propensity to Delay Tolerance Development

The behavioral responses exerted by spinal administration of the opioid-neurotensin hybrid peptide, PK23, were studied in adult male rats. The antinociceptive effect upon exposure to a thermal stimulus, as well as tolerance development, was assessed in an acute pain model. The PK23 chimera at a dose of 10 nmol/rat produced a potent pain-relieving effect, especially after its intrathecal administration. Compared with intrathecal morphine, this novel compound was found to possess a favourable side effect profile characterized by a reduced scratch reflex, delayed development of analgesic tolerance or an absence of motor impairments when given in the same manner, though some animals died following barrel rotation as a result of its i.c.v. administration (in particular at doses higher than 10 nmol/rat). Nonetheless, these results suggest the potential use of hybrid compounds encompassing both opioid and neurotensin structural fragments in pain management. This highlights the enormous potential of synthetic neurotensin analogues as promising future analgesics

Treating Parkinson’s disease : a matter of density?

Dopamine agonists constitute the main first-line therapeutic option for Parkinson’s disease (PD). These compounds exert their beneficial effect on locomotion by activating the D2 receptor and thereby compensating for the declining dopaminergic transmission in the striatum. Brain imaging studies have highlighted that the density of dopamine D2 receptors markedly fluctuates across the stages of PD and its pharmacological treatment. Since receptor density constitutes a molecular determinant for the signalling profile of D2 receptors ligands, we hypothesized that variations in receptor expression could influence the response to antiparkinsonian drugs mediated by D2 receptors, most notably relying on Gi1 and β-arrestin2 proteins. The recruitment bias of dopamine, pramipexole, ropinirole, and rotigotine was examined using a live-cell nanoluciferase-based biosensor capable of monitoring the interactions between the D2L receptor and either Gi1 or β-arrestin2. The characterization of the functional selectivity of these D2 agonists was performed at two distinct D2L receptor densities by taking advantage of an engineered cellular model enabling the overexpression of the D2L receptor when exposed to doxycycline. A high receptor density oriented the signalling profile of dopamine towards a preferential recruitment of Gi1. It also moderated the marked Gi1 and β-arrestin2 biases of pramipexole and rotigotine, respectively. The Gi1 bias of ropinirole appeared as not being influenced by D2L receptor density. Given that D2 receptor density was also demonstrated to be significantly elevated in schizophrenic patients, and being exacerbated by antipsychotic treatments, we wondered whether the observed influence of receptor density on the pharmacological profile of antiparkinsonian agents could be also observed for dopamine partial agonists commonly prescribed as antipsychotics. Hence, we extended our experimental paradigm to measure the recruitment bias of aripiprazole, brexpiprazole and cariprazine at both low and high receptor densities. Increasing the dopamine D2 receptor density reoriented aripiprazole’s preferential recruitment from Gi1 to β-arrestin2. Brexpiprazole showed inverse agonism for β-arrestin2 recruitment at the lower receptor density tested, and as an inverse agonism for Gi1 recruitment when tested at a high receptor expression level. At variance, cariprazine evoked a potent partial agonism for β-arrestin2 recruitment only, in all tested conditions. Observing that receptor density was capable of influencing D2 receptor pharmacology with a considerable breadth prompted us to investigate a putative biochemical mechanism underlying our results. Since D2L receptors are known to assemble in homodimers, and that this biochemical feature was demonstrated to be influenced by receptor density and ligand binding, we explored the influence that the D2 receptor ligands exert on D2L homodimeric assembly at distinct receptor densities. By applying a D2L homodimerization assay relying upon a nanoluciferase-based biosensor to a cell model enabling the tetracycline-inducible expression of D2L receptors, we were able to show that increasing receptor density promoted constitutive dopamine D2L receptor homodimerization. Receptor full agonists promoted homodimerization, while antagonists and partial agonists disrupted dopamine D2L receptor homodimers. High receptor densities enhanced this inhibitory effect only for receptor antagonists. Taken together, these observations highlight receptor density as a key driver of both signal transducer recruitment and homodimerization evoked by dopamine agonists, either employed as antiparkinsonian or antipsychotic agents. Importantly, the effect of receptor density on both biochemical phenomena appeared as ligand specific, without any strict correlation with ligands’ intrinsic activity. Finally, this study provides molecular insights positioning rotigotine as the putative most beneficial D2 receptor agonist for the treatment of early and late Parkinson’s disease, while depicting brexpiprazole as the most beneficial option for the management of antipsychotic switches.(BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 202

The complex molecular pharmacology of the dopamine D receptor: Implications for pramipexole, ropinirole, and rotigotine.

With L-DOPA, dopamine agonists such as pramipexole, ropinirole and rotigotine constitute key therapeutic options for the management of motor symptoms of Parkinson's disease. These compounds exert their beneficial effect on motor behaviours by activating dopamine D-class receptors and thereby compensating for the declining dopaminergic transmission in the dorsal striatum. Despite a strong similarity in their mechanism of action, these three dopamine agonists present distinct clinical profiles, putatively underpinned by differences in their pharmacological properties. In this context, this review aims at contributing to close the gap between clinical observations and data from molecular neuropharmacology by exploring the properties of pramipexole, ropinirole and rotigotine from both the clinical and molecular perspectives. Indeed, this review first summarizes and compares the clinical features of these three dopamine agonists, and then explores their binding profiles at the different dopamine receptor subtypes. Moreover, the signalling profiles of pramipexole, ropinirole and rotigotine at the D receptor are recapitulated, with a focus on biased signalling and the potential therapeutic implications. Overall, this review aims at providing a unifying framework of interpretation for both clinicians and fundamental pharmacologists interested in a deep understanding of the pharmacological properties of pramipexole, ropinirole and rotigotine

Receptor Density Influences the Recruitment Bias of Aripiprazole and Brexpiprazole at the Dopamine D2L Receptor

Aripiprazole, brexpiprazole and cariprazine are dopamine D2 receptor ligands considered as effective and tolerable antipsychotics. Brain imaging studies showed that schizophrenia is characterized by elevated dopamine receptor density, which is exacerbated by antipsychotic treatments. Despite the complexity of translating in vitro studies to human neurobiology, overexpression experiments in transfected cells provide a proof-of-concept model of the influence of receptor density on antipsychotic treatments. Since receptor density was demonstrated to influence the signaling profile of dopaminergic ligands, we hypothesized that high dopamine D2 receptor expression levels could influence the recruitment of Gi1 and β-arrestin2 in response to partial agonists used as antipsychotics. A nanoluciferase complementation assay was used to monitor β-arrestin2 and Gi1 recruitment at the dopamine D2L receptor in response to aripiprazole, brexpiprazole and cariprazine. This was performed in transfected cells carrying a doxycycline-inducible system allowing to manipulate the expression of the dopamine D2L receptors. Increasing D2L receptor density reoriented aripiprazole’s preferential recruitment from Gi1 to β-arrestin2. With respect to brexpiprazole, which showed inverse agonism for β-arrestin2 recruitment at the lower receptor density tested, inverse agonism for Gi1 recruitment was observed when tested at a high receptor expression level. At variance, cariprazine evoked a potent partial agonism for β-arrestin2 recruitment only, in all the tested conditions. D2L receptor density appears to shape the recruitment bias of aripiprazole and brexpiprazole, but not cariprazine. This suggests that changes in receptor expression level could qualitatively influence the functional response of partial agonists used in psychiatry

Dopamine D2L receptor density influences the recruitment of β-arrestin2 and Gi1 induced by antiparkinsonian drugs.

[en] INTRODUCTION: Brain imaging studies have highlighted that the density of dopamine D2 receptors markedly fluctuates across the stages of Parkinson's disease and in response to pharmacological treatment. Moreover, receptor density constitutes a molecular determinant for the signaling profile of D2 receptor ligands. We therefore hypothesized that variations in receptor expression could influence D2 receptor response to antiparkinsonian drugs, most notably with respect to the recruitment bias between Gi1 and β-arrestin2. METHODS: The recruitment bias of dopamine, pramipexole, ropinirole, and rotigotine was examined using a nanoluciferase-based biosensor for probing the interactions of the D2L receptor with either Gi1 or β-arrestin2. The characterization of the functional selectivity of these D2 receptor agonists was performed at two distinct D2L receptor densities by taking advantage of a cell model carrying an inducible system that enables the overexpression of the D2L receptor when exposed to doxycycline. RESULTS: A high receptor density oriented the balanced signaling profile of dopamine towards a preferential recruitment of Gi1. It also moderated the marked Gi1 and β-arrestin2 biases of pramipexole and rotigotine, respectively. At variance, the Gi1 bias of ropinirole appeared as not being influenced by D2L receptor density. CONCLUSIONS: Taken together, these observations highlight receptor density as a key driver of the signaling transducer recruitment triggered by antiparkinsonian agents. Moreover, given the putative beneficial properties of β-arrestin2 in promoting locomotion, this study provides molecular insights that position the arrestin-biased ligand rotigotine as a putatively more beneficial D2 receptor agonist for the treatment of early and late Parkinson's disease

Receptor Density Influences the Recruitment Bias of Aripiprazole and Brexpiprazole at the Dopamine D2L Receptor.

peer reviewedAripiprazole, brexpiprazole and cariprazine are dopamine D2 receptor ligands considered as effective and tolerable antipsychotics. Brain imaging studies showed that schizophrenia is characterized by elevated dopamine receptor density, which is exacerbated by antipsychotic treatments. Despite the complexity of translating in vitro studies to human neurobiology, overexpression experiments in transfected cells provide a proof-of-concept model of the influence of receptor density on antipsychotic treatments. Since receptor density was demonstrated to influence the signaling profile of dopaminergic ligands, we hypothesized that high dopamine D2 receptor expression levels could influence the recruitment of Gi1 and β-arrestin2 in response to partial agonists used as antipsychotics. A nanoluciferase complementation assay was used to monitor β-arrestin2 and Gi1 recruitment at the dopamine D2L receptor in response to aripiprazole, brexpiprazole and cariprazine. This was performed in transfected cells carrying a doxycycline-inducible system allowing to manipulate the expression of the dopamine D2L receptors. Increasing D2L receptor density reoriented aripiprazole's preferential recruitment from Gi1 to β-arrestin2. With respect to brexpiprazole, which showed inverse agonism for β-arrestin2 recruitment at the lower receptor density tested, inverse agonism for Gi1 recruitment was observed when tested at a high receptor expression level. At variance, cariprazine evoked a potent partial agonism for β-arrestin2 recruitment only, in all the tested conditions. D2L receptor density appears to shape the recruitment bias of aripiprazole and brexpiprazole, but not cariprazine. This suggests that changes in receptor expression level could qualitatively influence the functional response of partial agonists used in psychiatry

Impact of a Caffeine Restriction Policy on Inpatients With Schizophrenia- A Pre-Post Comparison Using Electronic Health Records

Background/Purpose: Caffeine is the most commonly used psychostimulant worldwide. Although its large intake is suspected toworsen psychotic symptoms because of increasing dopamine neurotransmission, schizophrenic patients are heavier caffeine consumers than the general population. This study aims to assess the impact of a caffeine restriction policy in a psychiatric hospital on patient psychopathology, hospitalization characteristics, and psychotropic prescribing patterns. Methods: It is a retrospective cross-sectional study based on electronic health records of a psychiatric hospital in the French-speaking area of Belgium. Two different periodswere compared, the first (n = 142), in 2017,when caffeinewas available in the institution and the second (n = 119), between November 2018 andNovember 2019 after the restriction of access to caffeinewas implemented. Adult inpatients with schizophrenia or schizoaffective disorder admitted for an acute hospitalization were included. Antipsychotic exposure, benzodiazepine daily dose, Global Assessment of Functioning scores, length of hospital stay, and some other factors were tested for their potential association with the decaffeinated period. Results: After adjusting for potential confounders, reduced caffeine availability inside the hospital was significantly associated with higher Global Assessment of Functioning scores at discharge (adjusted odds ratio [aOR] = 2.86, 95% confidence interval [CI] = 1.77–4.62) and shorter hospital stays (aOR = 0.68, 95% CI = 0.47–0.99) but was not associated with change in antipsychotic exposure at discharge (aOR= 1.04,95%CI = 0.64–1.7) or benzodiazepine daily dose (aOR = 0.89, 95% CI = 0.61–1.29). Conclusions: Limiting access to caffeine in psychiatric hospitals is a simple and inexpensive intervention tha

β‐arrestin2 recruitment at the β2 adrenergic receptor: A luciferase complementation assay adapted for undergraduate training in pharmacology

In the context of pharmacology teaching, hands-on activities constitute an essential complement to theoretical lectures. Frequently, these activities consist in exposing fresh animal tissues or even living animals to selected drugs and qualitatively or quantitatively evaluating functional responses. However, technological advancements in pharmacological research and the growing concerns for animal experimentation support the need for innovative and flexible in vitro assays adapted for teaching purposes. We herein report the implementation of a luciferase complementation assay (LCA) enabling to dynamically monitor β-arrestin2 recruitment at the β2 adrenergic receptor in the framework of pharmacological training at the faculty of Pharmacy and Biomedical Sciences. The assay allowed students to quantitatively characterize the competitive antagonism of propranolol, and to calculate pEC50, pKB, and pA2 values after a guided data analysis session. Moreover, the newly implemented workshop delivered highly reproducible results and were generally appreciated by students. As such, we report that the luciferase complementation-based assay proved to be a straightforward, robust, and cost-effective alternative to experiments performed on animal tissues, constituting a useful and flexible tool to enhance and update current hands-on training in the context of pharmacological teaching

Receptor density influences ligand-induced dopamine D2L receptor homodimerization

Chronic treatments with dopamine D2 receptor ligands induce fluctuations in D2 receptor density. Since D2 receptors tend to assemble as homodimers, we hypothesized that receptor density might influence constitutive and ligand-induced homodimerization. Using a nanoluciferase-based complementation assay to monitor dopamine D2L receptor homodimerization in a cellular model enabling the tetracycline-controlled expression of dopamine D2L receptors, we observed that increasing receptor density promoted constitutive dopamine D2L receptor homodimerization. Receptor full agonists promoted homodimerization, while antagonists and partial agonists disrupted dopamine D2L receptor homodimers. High receptor densities enhanced this inhibitory effect only for receptor antagonists. Taken together, our findings indicate that both receptor density and receptor ligands influence dopamine D2L receptor homodimerization, albeit excluding any strict correlation with ligands’ intrinsic activity and highlighting further complexity to dopaminergic pharmacology

Clinical characteristics, management and in-hospital mortality of patients with COVID-19 In Genoa, Italy

To describe clinical characteristics, management and outcome of COVID-19 patients; and to evaluate risk factors for all-cause in-hospital mortality