Schizophrenia remains a sizable socioeconomic burden that continues to be treated with therapeutics based on 70-year old science. All currently approved therapeutics primarily target the dopamine D2 receptor to achieve their efficacy. Whilst dopaminergic dysregulation is a key feature in this disorder, the targeting of dopaminergic machinery has yielded limited efficacy and an appreciable side effect burden. Over the recent decades, numerous drugs that engage non-dopaminergic GPCRs have yielded a promise of efficacy without the deleterious side effect profile, yet none have successfully completed clinical studies and progressed to the market. More recently, there has been increased attention around non-dopaminergic GPCR-targeting drugs, notably KarXT, which demonstrated efficacy in some schizophrenia symptom domains. This provides renewed hope that effective schizophrenia may lay outside of the dopaminergic space. Despite the potential for muscarinic receptor- (and other well-characterised GPCR families) targeting drugs to treat schizophrenia, they are often plagued with complications such as lack of receptor subtype selectivity and peripheral on-target side-effects. Orphan GPCR studies have opened a new avenue of exploration with many demonstrating schizophrenia-relevant mechanisms and a favourable expression profile, thus offering potential for novel drug development. This review discusses centrally-expressed orphan G protein-coupled receptors: GPR3, GPR6, GPR12, GPR52, GPR85, GPR88 and GPR139 and their relationship to schizophrenia. We review their expression, signalling mechanisms and cellular function, in conjunction with small molecule development and structural insights. We seek to provide a snapshot of the growing evidence and development potential of new classes of schizophrenia therapeutics.
Background and Purpose Vancomycin is one of the most common antibiotics administered in the hospital setting, yet acute kidney injury is a major limiting factor. Common combinations of antibiotics with vancomycin have been reported to worsen and improve vancomycin-induced kidney injury. We aimed to study the impact of flucloxacillin and imipenem-cilastatin on kidney injury when combined with vancomycin in our translational rat model. Experimental Approach Male Sprague-Dawley rats received allometrically scaled (1) vancomycin (2) flucloxacillin, (3) vancomycin+flucloxacillin, (4) vancomycin+imipenem-cilastatin, or (5) saline for 4 days. Vancomycin was administered intravenously and flucloxacillin or imipenem-cilastatin were administered intraperitoneally. Kidney injury was evaluated via drug accumulation and urinary biomarkers including urinary output, kidney injury molecule-1 (KIM-1), clusterin, and osteopontin. Relationships between vancomycin accumulation in the kidney and urinary kidney injury biomarkers were explored. Key Results Urinary output increased every study day for vancomycin+flucloxacillin; whereas in the vancomycin group it was elevated after the first dose only. In the vancomycin+flucloxacillin group, urinary KIM-1/24h increased on all days compared to vancomycin. In the vancomycin+imipenem-cilastatin group, urinary KIM-1/24h was decreased on days 1 and 2 compared to vancomycin. Similar trends were observed for clusterin. More vancomycin accumulated in the kidney with vancomycin+flucloxacillin compared to vancomycin and vancomycin+imipenem-cilastatin. The accumulation of vancomycin in the kidney tissue correlated with increasing urinary KIM-1 (4-parameter Hill Slope, R2=0.7985). Conclusion and Implications Vancomycin+flucloxacillin caused more kidney injury compared to vancomycin alone and vancomycin+imipenem-cilastatin in a translational rat model as determined by multiple kidney injury biomarkers. The combination of vancomycin+imipenem-cilastatin was nephroprotective.
Ageing is the main risk factor common to most primary neurodegenerative disorders. Indeed, age-related brain alterations have been long considered to predispose to neurodegeneration. Although protein misfolding and the accumulation of toxic protein aggregates have been contemplated as causative events in neurodegeneration, several biological pathways affected by brain ageing are also contributing to pathogenesis. Here, we discuss the evidence showing the involvement of the mechanisms controlling neuronal structure, gene expression, autophagy, cell metabolism, and neuroinflammation in the onset and progression of neurodegenerative disorders. Furthermore, we review the therapeutic strategies currently under development or as future approaches designed to normalize these pathways, which may then boost brain resilience to cope with toxic protein species. Therefore, in addition to therapies targeting the insoluble protein aggregates specifically associated with each neurodegenerative disorder, these novel pharmacological approaches may be part of combined therapies designed to rescue brain function.
Background and Purpose: Overexpression of astrocytic lactoferrin (Lf) was observed in the brains of Alzheimer’s disease (AD) patients, whereas the role of astrocytic Lf in AD progression remains unexplored. In this study, we aimed to evaluate the effects of astrocytic Lf on AD progression. Experimental Approach: The APP/PS1 mice with astrocytes overexpressing human Lf were developed to evaluate the effects of astrocytic Lf on AD progression, and the N2a-sw cells were employed to further uncover the mechanism of astrocytic Lf on β-amyloid (Aβ) production. Key Results: Astrocytic Lf overexpression increased protein phosphatase 2A (PP2A) activity, and reduced amyloid precursor protein (APP) phosphorylation, Aβ burden and tau hyperphosphorylation in APP/PS1 mice. Mechanistically, astrocytic Lf overexpression promoted the astrocytic Lf secretion into neurons in APP/PS1 mice, and the conditional medium from astrocytes overexpressing Lf inhibited the p-APP(Thr668) expression in N2a-sw cells. Furthermore, the recombinant human Lf (hLf) also significantly enhanced PP2A activity and inhibited p-APP expression, while inhibitions of p38 or PP2A activities abrogated the hLf-induced p-APP downregulation in N2a-sw cells. Additionally, hLf promoted the interaction of p38 and PP2A via p38 activation, thereby enhancing PP2A activity; and low-density lipoprotein receptor-related protein 1 (LRP1) knockdown significantly reversed the hLf-induced p38 activation and p-APP downregulation. Conclusions and Implications: Our data suggested that astrocytic Lf promoted neuronal p38 activation via targeting to LRP1, subsequently promoting p38 binds to PP2A to enhance PP2A activity, which finally inhibited Aβ production via APP dephosphorylation. Therefore, promoting astrocytic Lf expression may be a potential strategy against AD.
Background and Purpose: Cardiovascular disease (CVD) affects up to half of the patients with chronic obstructive pulmonary disease (COPD), which exerts deleterious impact on health outcomes and survivability. Vascular endothelial dysfunction marks the onset of cardiovascular disease. The present study examined the effect of a potent NADPH Oxidase (NOX) inhibitor and free-radical scavenger, apocynin, on COPD-related CVD. Experimental Approach: Male BALB/c mice were exposed to either room air (Sham) or cigarette smoke (CS) generated from 9 cigarettes per day, 5 days a week for up to 24 weeks with or without apocynin treatment (5 mg·kg-1·day-1, intraperitoneal injection). Key Results: Eight-weeks of apocynin treatment reduced airway neutrophil infiltration (by 42%) and completely preserved endothelial function and endothelial nitric oxide synthase (eNOS) activity against the oxidative insults of CS exposure. These preservative effects were maintained up until the 24-week time point. 24-week of apocynin treatment exhibited marked benefits on airway inflammation (reduced infiltration of macrophage, neutrophil and lymphocyte) and lung function decline (hyperinflation), and prevented airway collagen deposition by CS exposure. Conclusion and Implications: Limiting NOX activity may slow COPD progression and lower CVD risk, particularly when signs of oxidative stress become evident.
Background and Purpose: How to prevent the damage of ionizing radiation to testis has become an urgent problem to be solved. The present aim is to investigate whether inhibition of p38MAPK signaling can alleviate radiation-induced testicular damage. Experimental Approaches: HE staining was used to measure the morphological changes of epididymis and testis. Immunohistochemistry staining was used to assess the expression of PLZF, SOX9, p-p38MAPK. RNA-Seq was used to profile gene expression. The expression of Mapk14, Atf2, Ddit3 and Ap1m1 genes was detected by qPCR. Western blotting was used to detect the protein expression of p38MAPK and p-p38MAPK. Key Results: There was a dose-response relationship between testicular injury and ionizing radiation. The sperm quality was significantly decreased at 6 and 8 weeks after 6Gy of radiation. Radiation led to the decrease of PLZF+ cells and increase of SOX9+ cells in testis. RNA-Seq data showed radiation induced 969 genes changed in the testis. The expression of genes related to p38MAPK signal pathway enriched by GO was significantly increased by qPCR. The expression of p-p38MAPK in testis was significantly increased at 4 weeks after irradiation. SB203580 treatment increased numbers of spermatozoa, the area and diameter of seminiferous tubules and numbers of SOX9+ cells in irradiated mice, which were consistent with the increased sperm movement rate and density under radiation with SB203580 administration. Conclusions and Implications: Ionizing radiation significantly changes testicular gene expression, in which p38MAPK signal pathway is activated. p38MAPK inhibitor SB203580 partially alleviates the testicular damage caused by radiation and accelerate the recovery of sperm quality.
Substance use disorder (SUD) is a chronic condition with maintained abuse of a substance leading to physiological and psychological alterations and often changes in cognitive and social behaviours. Current therapies mainly consist of psychotherapy coupled with medication; however, alarmingly high relapse rates reveal the shortcomings of the current standard of care. The signalling and expression profile, and neurological function of the serotonin 2C receptor (5-HT2C receptor) make it an ideal candidate of interest for the treatment of SUD. This is further corroborated by pre-clinical and clinical evidence of therapeutically relevant compounds acting at the 5-HT2C receptor. Notwithstanding, drug binding at closely related serotonin receptor subtypes has impeded drug development. More recently, psychedelics, which broadly act at 5-HT2 receptors, have indicated promising potential for the treatment of SUD, implicating in part, the 5-HT2C receptor. The modern psychedelic movement has rekindled therapeutic interest in the 5-HT2C receptor, resulting in an influx of new studies, especially structural analyses. This review delves into the structural, molecular and cellular mechanisms governing the 5-HT2C receptor function, in the context of SUD. This provides the basis of the preclinical and clinical evidence for their role in SUD and highlights the potential for future exploration.
Background and Purpose Neonatal seizures are a clinical emergency. Current anti-seizure medications, however, fail to resolve seizures in ~50% of infants. The P2X7 receptor (P2X7R) is an important driver of inflammation and evidence suggest P2X7R contributing to seizures and epilepsy in adults. To date, however, no genetic proof has been provided to determine the contribution of the P2X7R to neonatal seizures, its effects on inflammatory signalling during neonatal seizures and the therapeutic potential of P2X7R-based treatments on long-lasting brain excitability. Experimental Approach Neonatal seizures were induced via global hypoxia in 7 day-old mouse pups (P7). The role of P2X7Rs during seizures was analyzed in P2X7R overexpressing and knock-out mice. Treatment of wild-type mice post-hypoxia with the P2X7R antagonist JNJ-47965567 was used to determine the effects of the P2X7R on long-lasting brain hyperexcitability. Cell type-specific P2X7R expression was analyzed via P2X7R-EGFP reporter mice. RNA sequencing was used to monitor P2X7R-dependent hippocampal down-stream signalling. Key Results P2X7R deletion reduced seizure severity whereas P2X7R overexpression exacerbated seizure severity and reduced responsiveness to anti-seizure medication. P2X7R deficiency let to an anti-inflammatory phenotype in microglia and treatment of mice with a P2X7R antagonist reduced long-lasting brain hyperexcitability. RNA sequencing identified several pathways altered in P2X7R knock-out mice after neonatal hypoxia including a down-regulation of genes implicated in inflammation and glutamatergic signalling. Conclusion and Implications Treatments based on targeting the P2X7R may represent a novel therapeutic strategy for neonatal seizures with P2X7Rs contributing to the generation of neonatal seizures, driving inflammatory processes and long-term hyperexcitability states.
Autism is a neurodevelopmental condition with a range of symptoms that vary in intensity and severity from person to person. Genetic sequencing has identified thousands of genes containing mutations in autistic individuals, which may contribute to the development of autistic symptoms. Several of these genes encode G protein-coupled receptors (GPCRs) which are cell surface expressed proteins that transduce extracellular messages to the intracellular space. Mutations in GPCRs can impact their function, resulting in aberrant signalling within cells, and across neurotransmitter systems in the brain. This review summarises the current knowledge on autism-associated single nucleotide variations encoding missense mutations in GPCRs, and the impact of these genetic mutations on GPCR function. For some autism-associated mutations, changes in GPCR expression levels, ligand affinity, potency and efficacy have been observed; however, for many the functional consequences remain unknown. Thus, further work to characterise the functional impacts of the genetically identified mutations is required.
Gastrointestinal motility is tightly regulated by the enteric nervous system (ENS). Disruption of coordinated ENS activity can result in dysmotility. Pharmacological treatment options for dysmotility include targeting of G protein-coupled receptors (GPCRs) expressed by neurons of the ENS. Current GPCR-targeting drugs for motility disorders bind to the highly conserved endogenous ligand binding site and promote indiscriminate activation or inhibition of the target receptor throughout the body. This can be associated with significant side-effect liability and a loss of physiological tone. Allosteric modulators of GPCRs bind to a distinct site from the endogenous ligand, which is typically less conserved across multiple receptor subtypes and can modulate endogenous ligand signalling. Allosteric modulation of GPCRs that are important for ENS function may provide effective relief from motility disorders while limiting side-effects. This review will focus on how allosteric modulators of GPCRs may influence gastrointestinal motility, using 5-HT, ACh, and opioid receptors as examples.
Background and Purpose: Chronic pain is a devastating problem affecting 1 in 5 individuals around the globe, with neuropathic pain the most debilitating and poorly treated type of chronic pain. Advances in transcriptomics and data mining have contributed to cataloging diverse cellular pathways and transcriptomic alterations in response to peripheral nerve injury but have focused on phenomenology and classifying transcriptomic responses. Experimental approach: Here, with the goal of identifying new types of pain-relieving agents, we compared transcriptional reprogramming changes in the dorsal spinal cord after peripheral nerve injury cross-sex and cross-species and imputed commonalities, as well as differences in cellular pathways and gene regulation. Key Results: We identified 93 transcripts in the dorsal horn that were increased by peripheral nerve injury in male and female mice and rats. Following gene ontology and transcription factor analyses, we constructed a pain interactome for the proteins encoded by the differentially expressed genes, discovering new, conserved signaling nodes. We interrogated the interactome with the Drug-Gene database to predict FDA-approved medications that may modulate key nodes within the network. The top hit from the analysis was fostamatinib, the molecular target of which is the non-receptor tyrosine kinase Syk, which our analysis had identified as a key node in the interactome. Conclusions & Implications : We found that intrathecally administrating the active metabolite of fostamatinib, R406, significantly reversed pain hypersensitivity in both sexes. Thus, we have identified and shown the efficacy of an agent that could not have been previously predicted to have analgesic properties.
Background and Purpose Incubation of craving is associated with temporal changes in the activity of several structures involved in drug-seeking behavior. Hypodopaminergic activity, responsible for negative emotional states, has been reported in the ventral tegmental area (VTA) during cocaine abstinence. The neuroadaptations underlying the VTA hyperdopaminergic state after chronic cocaine is not well understood. In this work, we investigated the potential involvement of a VTA inhibiting circuit (amygdala-ventral pallidum (VP) pathway) in the hypodopaminergic state during abstinence from chronic cocaine. Experimental Approach In a model of cocaine self-administration, we performed in vivo electrophysiological recordings of DA VTA neurons and basolateral amygdala (BLA) neurons from anesthetized rats during early and protracted abstinence and evaluated the involvement of the BLA-VP pathway using a pharmacological approach. Key Results We found a significant decrease of VTA DA population activity and a significant increase of BLA activity after 30 days of abstinence from chronic cocaine but not one day. The decrease in VTA DA activity was restored by pharmacological inhibition of the activity of either the BLA or the VP. Conclusion and Implications Our study sheds new lights on neuroadaptations occurring during incubation of craving leading to relapse. In particular, we described the involvement of the BLA-VP pathway in cocaine-induced decreases of DA activity in the VTA. This study adds an important building block to the characterization of specific brain network dysfunctions underlying hypodopaminergic activity during abstinence.
Background and Purpose: In recent decades, a focus on the most critical and fundamental concepts has proven highly advantageous to students and educators in many science disciplines. Pharmacology, unlike microbiology, biochemistry or physiology, lacks a consensus list of such core concepts. Experimental approach: We sought to develop a research-based, globally relevant list of core concepts that all students completing a foundational pharmacology course should master. This two-part project consisted of exploratory and refinement phases. The exploratory phase involved empirical data mining of the introductory sections of five key textbooks, in parallel with an online survey of over 200 pharmacology educators from 17 countries across six continents. The refinement phase involved three Delphi rounds involving 24 experts from 15 countries across six continents. Key Results: The exploratory phase resulted in a consolidated list of 74 candidate core concepts. In the refinement phase, the expert group produced a consensus list of 25 core concepts of pharmacology. Conclusion and Implications: This list will allow pharmacology educators everywhere to focus their efforts on the conceptual knowledge perceived to matter most by experts within the discipline. Next steps for this project include defining and unpacking each core concept and developing resources to help pharmacology educators globally teach and assess these concepts within their educational contexts.
Background and Purpose: ISX9 is a neurogenesis-promoting small molecule compound which can upregulate the expression of NeuroD1 and induce differentiation of neuronal, cardiac and islet endocrine progenitors. So far, the molecular mechanisms underlying the action of ISX9 still remain elusive. Experimental Approach: To identify a novel agonist of the Wnt/β‐catenin, a cell-based SuperTOPFlash reporter system was used to screen known-compound libraries. An activation effect of ISX9 on the Wnt/β‐catenin pathway was analysed with the SuperTOPFlash or SuperFOPFlash reporter system. Effects of ISX9 on Axin1/LRP6 interaction were examined using a mammalian two-hybrid system, co‐immunoprecipitation, microscale thermophoresis (MST), emission spectra and mass spectroscopy assays. The expression of Wnt target and stemmness marker genes were evaluated with real‐time PCR and immunoblotting. In vivo hair regeneration abilities of ISX9 were analysed by immunohistochemical staining, real‐time PCR and immunoblotting in hair regrowth model using C57BL/6J mice. Key Results: In this study, ISX9 was identified as a novel agonist of the Wnt/β‐catenin pathway. ISX9 targeted Axin1 by covalently binding to its N-terminal region and potentiated the LRP6-Axin1 interaction, thereby resulting in the stabilization of β‐catenin and upregulation of Wnt target genes and stemmness marker genes. Moreover, the topical application of ISX9 markedly promoted hair regrowth in C57BL/6J mice and induced hair follicle transition from telogen to anagen via enhancing Wnt/β‐catenin pathway. Conclusions and Implications: Taken together, our study unraveled that ISX9 could activate Wnt/β‐catenin signaling by potentiating the association between LRP6 and Axin1, and may be a promising therapeutic agent for alopecia treatment
Background and Purpose. The proalgesic transient receptor potential (TRP) ankyrin 1 (TRPA1) channel, expressed by a subpopulation of primary sensory neurons, has been implicated in various pain models in mice. However, evidence in rats indicates that TRPA1 conveys nociceptive signals elicited by channel agonists but not those associated with tissue inflammation or nerve injury. Here, in rats, we explored the TRPA1 role in mechanical allodynia associated with neurogenic inflammation and moderate (partial sciatic nerve ligation, pSNL) or severe (chronic constriction injury, CCI) sciatic nerve injury. Experimental Approach. Acute nociception and mechanical hypersensitivity associated with neurogenic inflammation and sciatic nerve injury (pSNL and CCI) were investigated in rats with TRPA1 pharmacological antagonism or genetic silencing. TRPA1 presence and function was analyzed in cultured rat Schwann cells. Key Results. Hind paw mechanical allodynia (HPMA), but not acute nociception, evoked by local injection of the TRP vanilloid 1 (TRPV1) agonist, capsaicin, or the TRPA1 agonist, allyl isothiocyanate, was mediated by calcitonin gene related peptide (CGRP) released from peripheral nerve terminals. CGRP-evoked HPMA was sustained by a reactive oxygen species (ROS)-dependent TRPA1 activation, probably in Schwann cells. HPMA evoked by pSNL, but not that evoked by CCI, was mediated by ROS and TRPA1 without the involvement of CGRP. Conclusions and Implications. As found in mice, TRPA1 mediates mechanical allodynia associated with neurogenic inflammation and moderate nerve injury in rats. The channel implication in mechanical hypersensitivity following inflammation and partial nerve damage is a common rodent feature and might be explored in humans.
Background: Ticagrelor is labelled as a reversible, direct-acting platelet P2Y12 receptor (P2Y12R) antagonist that is indicated clinically for the prevention of thrombotic events in patients with acute coronary syndrome (ACS). As with many antiplatelet drugs, ticagrelor therapy increases bleeding risk in patients which in emergency situations requires platelet transfusion although there is ongoing debate on its effectiveness following ticagrelor therapy. The aim of this study was to further examine the reversibility of ticagrelor at the P2Y12R. Methods: Studies were performed in human platelets with both P2Y12R-stimulated GTPase activity and platelet aggregation assessed. Cell-based bioluminescence resonance energy transfer (BRET) assays were also undertaken to assess G protein subunit activation downstream of P2Y12R activation. Results: Initial studies revealed a range of P2Y12R ligands including ticagrelor displayed inverse agonist activity at the P2Y12R. Of these only ticagrelor was resistant to wash-out. In both human platelets and cell-based assays, washing failed to reverse ticagrelor-dependent inhibition of ADP-stimulated P2Y12R function in contrast to other P2Y12R antagonists. The P2Y12R agonist 2MeSADP, which was also resistant to wash-out, was able to effectively compete with ticagrelor. In silico docking revealed that ticagrelor and 2MeSADP penetrated more deeply into the orthosteric binding pocket of the P2Y12R than other P2Y12R ligands. Conclusion: Ticagrelor binding to the P2Y12R is prolonged and more akin to that of an irreversible antagonist especially versus the endogenous P2Y12R agonist ADP. This study highlights the potential clinical need for novel ticagrelor reversal strategies in patients with spontaneous major bleeding and bleeding associated with urgent invasive procedures.