Sex: A change in our guidelines to authors to ensure that this is no longer an ignored experimental variable

Genetic deficiency or pharmacological inhibition of cGAS-STING signalling suppresses kidney inflammation and fibrosis

BACKGROUND AND PURPOSE

Chronic kidney disease (CKD) is characterised by inflammation, which can lead to tubular atrophy and fibrosis. The molecular mechanisms are not well understood. In this study, we investigated the functional role of the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) signalling in renal inflammation and fibrosis.

EXPERIMENTAL APPROACH

Mice with global cGAS deficiency or global or myeloid cell-specific STING deficiency or wild-type mice treated with RU.521, a selective cGAS inhibitor, were used to examine the role of cGAS-STING signalling in renal inflammation and fibrosis in a preclinical model of obstructive nephropathy in vivo. Bone marrow-derived macrophages were used to determine whether tubular epithelial cell-derived DNA can activate cGAS-STING signalling in vitro.

KEY RESULTS

Following obstructive injury, cGAS-STING signalling was activated in the kidneys during the development of renal fibrosis. Mice with deficiency of cGAS or STING exhibited significantly less macrophage proinflammatory activation, myofibroblast formation, total collagen deposition, and extracellular matrix (ECM) protein production in the kidneys following obstructive injury. Pharmacological inhibition of cGAS with RU.521 reduced macrophage proinflammatory activation, suppressed myofibroblast formation, and attenuated kidney fibrosis following obstructive injury. Mechanistically, cGAS-STING signalling in macrophages is activated by double-stranded DNA released from damaged tubular epithelial cells, which induces inflammatory responses.

CONCLUSIONS AND IMPLICATIONS

Our study identifies the cGAS-STING signalling pathway as a critical regulator of macrophage proinflammatory activation during the development of renal fibrosis. Therefore, inhibition of cGAS-STING signalling may represent a novel therapeutic strategy for CKD.

Disruption of survivin protein expression by treatment with YM155 accelerates the resolution of neutrophilic inflammation

BACKGROUND AND PURPOSE

Prolonged survival of neutrophils is essential for determining the progression and severity of inflammatory and immune-mediated disorders, including gouty arthritis. Survivin, an anti-apoptotic molecule, has been described as a regulator of cell survival. This study aims to examine the effects of YM155 treatment, a survivin selective suppressant, in maintaining neutrophil survival in vitro and in vivo experimental settings of neutrophilic inflammation.

EXPERIMENTAL APPROACH

BALB/c mice were injected with monosodium urate (MSU) crystals and treated with YM155 (intra-articularly) at the peak of inflammatory response. Leukocyte recruitment, apoptosis neutrophil and efferocytosis were determined by knee joint wash cell morphology counting and flow cytometry. Resolution interval (Ri) was quantified by neutrophil infiltration, monitoring the amplitude and duration of the inflammation. Cytokine production was measured by ELISA. Mechanical hypernociception was assessed using an electronic von Frey aesthesiometer. Efferocytosis was evaluated in zymosan-induced neutrophilic peritonitis. Survivin and cleaved caspase-3 expression was determined in human neutrophils by flow cytometry.

KEY RESULTS

Survivin was expressed in neutrophils during MSU-induced gout, and the treatment with YM155 reduced survivin expression and shortened Ri from ∼8 h observed in vehicle-treated mice to ∼5.5 h, effect accompanied by increased neutrophil apoptosis and efferocytosis, both crucial for the inflammation resolution. Reduced IL-1β and CXCL1 levels were also observed in periarticular tissue. YM155 reduced histopathological score and hypernociceptive response. In human neutrophils, lipopolysaccharide (LPS) increased survivin expression, whereas survivin inhibition with YM155 induced neutrophil apoptosis, with activation of caspase-3.

CONCLUSIONS AND IMPLICATIONS

Survivin may be a promising therapeutic target to control neutrophilic inflammation.

Unraveling morphine tolerance: CCL2 induces spinal cord apoptosis via inhibition of Nrf2 signaling pathway and PGC-1α-mediated mitochondrial biogenesis

BACKGROUND

Morphine effectively relieves severe pain but leads to analgesic tolerance with long-term use.The molecular mechanisms underlying morphine tolerance remain incompletely understood. Existing literature suggests that chemokine CCL2, present in the spinal cord, plays a role in central nervous system inflammation, including neuropathic pain. Nevertheless, the precise mechanism through which CCL2 mediates morphine tolerance has yet to be elucidated. Consequently, this study aims to investigate the molecular pathways by which CCL2 contributes to the development of morphine analgesic tolerance.

METHODS

Rats were administered intrathecal morphine (10 μg/5 μl) twice a day for seven consecutive days to induce a model of morphine nociceptive tolerance. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were used to detect the expression levels of CCL2 and its related mechanism molecules. Immunofluorescence was used to detect the localization of CCL2 in the spinal cord. Intrathecal injections of inhibitors or agonists to artificially regulate the expression of relevant molecules. The thermal tail-flick experiment was performed to evaluate morphine tolerance in rats.

RESULTS

Morphine-induced CCL2 expression was significantly increased in spinal cord, while conversely, the expressions of Nrf2 and PGC-1a were downregulated. Immunofluorescence showed that the enhanced immune response of CCL2 mainly co-localized with neurons. In vivo, we confirmed that intrathecally injection of CCL2 inhibitor Bindarit could effectively alleviate the occurrence of apoptosis and alleviate morphine tolerance. Similarly, pretreatment with Nrf2 signaling pathway agonist Oltipraz and PGC-1α agonist ZLN005 also achieved similar results, respectively. ROS Fluorescence Assay Kit indicated that increasing the expression of PGC-1α could alleviate the occurrence of apoptosis by reducing the level of ROS.

CONCLUSION

Our data emphasize that chemokine CCL2 inhibited the Nrf2 signaling pathway and PGC-1α-mediated mitochondrial biogenesis, alleviating the occurrence of apoptosis in spinal cord, thereby participating in morphine tolerance. This may provide new targets for the treatment of morphine tolerance.

mSphere of Influence: Venturing outside the biology canon with sex and gender

Victoria Prieto-Echagüe works in the field of signaling by primary cilia, adipogenesis, and obesity. In this mShpere of Influence article, she reflects on how gender studies, feminism, and societal movements such as #metoo may inform all areas of biomedical and health research. She describes how they inspired her to incorporate sex as a biological variable (SABV) principle to her research exploring sex-specific mechanisms in obesity and metabolic diseases and argues that incorporating SABV is crucial for advancing precision medicine and addressing healthcare inequities.

Peptide-Purified Anti-N-methyl-D-aspartate Receptor (NMDAR) Autoantibodies Have Inhibitory Effect on Long-Term Synaptic Plasticity

Background/Objectives: Recent studies, typically using patient cerebrospinal fluid (CSF), have suggested that different autoantibodies (Aabs) acting on their respective receptors, may underlie neuropsychiatric disorders. The GluN1 (NR1) subunit of the N-methyl-D-aspartate receptor (NMDAR) has been identified as a target of anti-NMDAR Aabs in a number of central nervous system (CNS) diseases, including encephalitis and autoimmune epilepsy. However, the role or the nature of Aabs responsible for effects on neuronal excitability and synaptic plasticity is yet to be established fully. Methods: Peptide immunisation was used to generate Aabs against selected specific GluN1 extracellular sequences based on patient-derived anti-NMDAR Aabs that have been shown to bind to specific regions within the GluN1 subunit. 'Protein A' purification was used to obtain the total IgG, and further peptide purification was used to obtain a greater percentage of NMDAR-target specific IgG Aabs. The binding and specificity of these anti-NMDAR Aabs were determined using a range of methodologies including enzyme-linked immunosorbent assays, immunocytochemistry and immunoblotting. Functional effects were determined using different in vitro electrophysiology techniques: two-electrode voltage-clamps in Xenopus oocytes and measures of long-term potentiation (LTP) in ex vivo hippocampal brain slices using multi-electrode arrays (MEAs). Results: We show that anti-NMDAR Aabs generated from peptide immunisation had specificity for GluN1 immunisation peptides as well as target-specific binding to the native protein. Anti-NMDAR Aabs had no clear effect on isolated NMDARs in an oocyte expression system. However, peptide-purified anti-NMDAR Aabs prevented the induction of LTP at Schaffer collateral-CA1 synapses in ex vivo brain slices, consistent with causing synaptic NMDAR hypofunction at a network level. Conclusions: This work provides a solid basis to address outstanding questions regarding anti-NMDAR Aab mechanisms of action and, potentially, the development of therapies against CNS diseases.

Sex differences in the metabolic activation of and platelet response to vicagrel in mice: Androgen as a key player

As a biological variable, sex influences the metabolism of and/or response to certain drugs. Vicagrel is being developed as an investigational new drug in China; however, it is unknown whether sex could affect its metabolic activation and platelet responsiveness. This study aimed to determine whether such differences could exist, and to elucidate the mechanisms involved. Orchiectomized (ORX) or ovariectomized (OVX) mouse models were used to investigate the effects of androgens or estrogens on the metabolic activation of and platelet response to vicagrel. Plasma vicagrel active metabolite H4 concentrations, platelet inhibition of vicagrel, and protein levels of intestinal hydrolases Aadac and Ces2 were measured, respectively. Further, p38-MAPK signaling pathway was enriched, whose role was determined using SB202190. Results showed that female mice exhibited significantly elevated systemic exposure of H4 and enhanced platelet responses to vicagrel than males, and that protein expression levels of Aadac and Ces2 differed by sex. OVX mice exhibited less changes than sham mice. ORX mice exhibited increases in protein levels of intestinal hydrolases, systemic exposure of H4, and platelet inhibition of vicagrel, but dihydrotestosterone (DHT) reversed these changes in ORX mice and suppressed these changes in OVX mice. Phosphorylated p38 levels were reduced in female or ORX mice but increased in ORX mice by DHT. SB202190 reversed DHT-induced changes observed in ORX mice. We concluded that sex differences exist in metabolic activation of and platelet response to vicagrel in mice through elevation of p38 phosphorylation by androgens, suggesting sex-based vicagrel dosage adjustments for patient care.

Psilocybin as a novel treatment for chronic pain

Psychedelic drugs are under active consideration for clinical use and have generated significant interest for their potential as anti-nociceptive treatments for chronic pain, and for addressing conditions like depression, frequently co-morbid with pain. This review primarily explores the utility of preclinical animal models in investigating the potential of psilocybin as an anti-nociceptive agent. Initial studies involving psilocybin in animal models of neuropathic and inflammatory pain are summarised, alongside areas where further research is needed. The potential mechanisms of action, including targeting serotonergic pathways through the activation of 5-HT2A receptors at both spinal and central levels, as well as neuroplastic actions that improve functional connectivity in brain regions involved in chronic pain, are considered. Current clinical aspects and the translational potential of psilocybin from animal models to chronic pain patients are reviewed. Also discussed is psilocybin's profile as an ideal anti-nociceptive agent, with a wide range of effects against chronic pain and its associated inflammatory or emotional components.

Sex-Related Differences in Pancreatic Ductal Adenocarcinoma Progression and Response to Therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly malignancies with an increasing incidence rate and limited therapeutic options. Biological sex has an impact on many aspects of PDAC development and response to therapy, yet it is highly unappreciated in both basic and translational research, and worryingly in PDAC clinical trials. In this review, we summarize how biological sex influences PDAC incidence and mortality, genetic and epigenetic landscapes, anti-tumor immunity, responses to hormones, cachexia, and the efficacy of therapy. We highlight the importance of sex as a variable and discuss how to implement it into preclinical and clinical research. These considerations should be of use to researchers aiming at improving understanding of PDAC biology and developing precision medicine therapeutic strategies.

Bruton's tyrosine kinase inhibition suppresses pathological retinal angiogenesis

BACKGROUND AND PURPOSE

Pathological retinal angiogenesis is a typical manifestation of vision-threatening ocular diseases. Many patients exhibit poor response or resistance to anti-vascular endothelial growth factor (VEGF) agents. Bruton's tyrosine kinase (BTK) controls the proliferation and function of immune cells. Therefore, we examined the anti-inflammatory and anti-angiogenic effects of BTK inhibition on retinal angiogenesis.

EXPERIMENTAL APPROACH

Retinal neovascularisation and vascular leakage in oxygen-induced retinopathy in C57/BL6J mice were assessed by whole-mount retinal immunofluorescence. PLX5622 was used to deplete microglia and Rag1-knockout mice were used to test the contribution of lymphocytes to the effects of BTK inhibition. The cytokines, activation markers, inflammatory and immune-regulatory activities of retinal microglia/macrophages were detected using qRT-PCR and immunofluorescence. NLRP3 was detected by western blotting, and the effects of BTK inhibition on the co-culture of microglia and human retinal microvascular endothelial cells (HRMECs) were examined.

KEY RESULTS

BTK inhibition suppressed pathological angiogenesis and vascular leakage, and significantly reduced retinal inflammation, which involved microglia/macrophages but not lymphocytes. BTK inhibition increased anti-inflammatory factors and reduced pro-inflammatory cytokines that resulted from NLRP3 inflammasome activation. BTK inhibition suppressed the inflammatory activity of microglia/macrophages, and acted synergistically with anti-VEGF without retinal toxicity. Moreover, the supernatant of microglia incubated with BTK-inhibitor reduced the proliferation, tube formation and sprouting of HRMECs.

CONCLUSION AND IMPLICATIONS

BTK inhibition suppressed retinal neovascularisation and vascular leakage by modulating the inflammatory activity of microglia and macrophages. Our study suggests BTK inhibition as a novel and promising approach for alleviating pathological retinal angiogenesis.

Sex Dependence in Control of Renal Haemodynamics and Excretion in Streptozotocin Diabetic Rats-Role of Adenosine System and Nitric Oxide

Recently, we compared an interplay of the adenosine system and nitric oxide (NO) in the regulation of renal function between male normoglycaemic (NG) and streptozotocin-induced diabetic rats (DM). Considering the between-sex functional differences, e.g., in the NO status, we present similar studies performed in female rats. We examined if the theophylline effects (non-selective adenosine antagonist) in NG and DM females with or without active NO synthases differed from the earlier findings. In anaesthetised female Sprague Dawley rats, both NG and DM, untreated or after NO synthesis blockade with L-NAME, theophylline effects, on blood pressure, renal hemodynamics and excretion, and renal tissue NO were investigated. Renal artery blood flow (Transonic probe), cortical, outer-, and inner-medullary flows (laser-Doppler technique), and renal tissue NO signal (selective electrode) were measured. In contrast to males, in female NG and DM rats, theophylline induced renal vasodilation. In NO-deficient females, theophylline induced comparable renal vasodilatation, confirming the vasoconstrictor influence of the renal adenosine. In NG and DM females with intact NO synthesis, adenosine inhibition diminished kidney tissue NO, contrasting with an increase reported in males. Lowered baseline renal excretion in DM females suggested stimulation of renal tubular reabsorption due to the prevalence of antinatriuretic over natriuretic tubular action of adenosine receptors. An opposite inter-receptor balance pattern emerged previously from male studies. The study exposed between-sex functional differences in the interrelation of adenosine and NO in rats with normoglycaemia and streptozotocin diabetes. The findings also suggest that in diabetes mellitus, the abundance of individual receptor types can distinctly differ between females and males.

The relationship between gender and pharmacology

The part of sexuality in pharmacology research was not acknowledged, and it was not thought-out to be a determinant that could impact strength and disease. For decades research has mainly contained male, women and animals, leading to a lack of news about syndromes in females. Still, it is critical to guarantee equal likeness so that determine the security, influence, and resistance of healing agents for all individuals. The underrepresentation of female models in preclinical studies over various decades has surpassed to disparities in the understanding, disease, and treatment of ailments 'tween genders. The closeness of sexuality bias has happened recognized as a contributing determinant to the restricted interpretation and replicability of preclinical research. Many demands operation have stressed the significance of including sexuality as a organic changeable, and this view is acquire growing support. Regardless of important progress in incorporating more female models into preclinical studies, differences prevail contemporary. The current review focuses on the part of sexuality and common in biomedical research and, therefore, their potential function in pharmacology and analyze the potential risks guide.

Intravenous recombinant cerebellin 1 treatment restores signalling by spinal glutamate delta 1 receptors and mitigates chronic pain

BACKGROUND AND PURPOSE

Chronic pain remains a major clinical problem that needs effective therapeutic agents. Glutamate delta 1 (GluD1) receptors and the protein cerebellin 1 (Cbln1) are down-regulated in the central amygdala (CeA) in models of inflammatory and neuropathic pain. One treatment with Cbln1, intracerebroventricularly (ICV) or in CeA, normalized GluD1 and reduced AMPA receptor expression, resulting in lasting (7-10 days) pain relief. Unlike many CNS-targeting biological agents, the structure of Cbln1 suggests potential blood-brain barrier penetration. Here, we have tested whether systemic administration of Cbln1 provides analgesic effects via action in the CNS.

EXPERIMENTAL APPROACH

Analgesic effects of intravenous recombinant Cbln1 was assessed in complete Freund's adjuvant inflammatory pain model in mice. GluD1 knockout and a mutant form of Cbln1 were used.

KEY RESULTS

A single intravenous injection of Cbln1 mitigated nocifensive and averse behaviour in both inflammatory and neuropathic pain models. This effect of Cbln1 was dependent on GluD1 receptors and required binding to the amino terminal domain of GluD1. Time course of analgesic effect was similar to previously reported ICV and intra-CeA injection. GluD1 in both spinal cord and CeA was down -regulated in the inflammatory pain model, whereas GluD1 expression in spinal cord but not in CeA, was partly normalized by intravenous Cbln1. Importantly, recombinant Cbln1 was detected in the synaptoneurosomes in spinal cord but not in the CeA.

CONCLUSIONS AND IMPLICATIONS

Our results describe a novel mechanism by which systemic Cbln1 induces analgesia potentially by central actions involving normalization of signalling by spinal cord GluD1 receptors.

Novel rapid treatment options for adolescent depression

There is an urgent need for novel fast-acting antidepressants for adolescent treatment-resistant depression and/or suicidal risk, since the selective serotonin reuptake inhibitors that are clinically approved for that age (i.e., fluoxetine or escitalopram) take weeks to work. In this context, one of the main research lines of our group is to characterize at the preclinical level novel approaches for rapid-acting antidepressants for adolescence. The present review summarizes the potential use in adolescence of non-pharmacological options, such as neuromodulators (electroconvulsive therapy and other innovative types of brain stimulation), as well as pharmacological options, including consciousness-altering drugs (mainly ketamine but also classical psychedelics) and cannabinoids (i.e., cannabidiol), with promising fast-acting responses. Following a brief analytical explanation of adolescent depression, we present a general introduction for each therapeutical approach together with the clinical evidence supporting its potential beneficial use in adolescence (mainly extrapolated from prior successful examples for adults), to then report recent and/or ongoing preclinical studies that will aid in improving the inclusion of these therapies in the clinic, by considering potential sex-, age-, and dose-related differences, and/or other factors that might affect efficacy or long-term safety. Finally, we conclude the review by providing future avenues to maximize treatment response, including the need for more clinical studies and the importance of designing and/or testing novel treatment options that are safe and fast-acting for adolescent depression.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Methodological approach: using a within-subjects design in the marble burying assay

In 2016, the National Institutes of Health mandated the use of both male and female mice in funded research. The use of both sexes is an important variable to consider; however, it comes with negative consequences such as increased animal expenses. One way to combat these negatives is to explore the option of using a within-subjects design (repeated measures) in behavioral assays that historically use a between-subjects design. Our study aimed to determine if a within-subjects design can be utilized in the marble burying assay. The marble burying assay is used as a tool for screening putative anxiolytic compounds as the assay is thought to measure obsessive-compulsive disorder- or anxiety-like behaviors. First, we compared the effects of sex and digging medium (corn cob or Sani Chip) on the number of marbles buried using CD-1 mice. Second, we determined if mice would continue to bury marbles after repeated exposures to the test arena. Lastly, we tested three positive controls (buspirone, ketamine, and fluoxetine). We found that mice buried significantly more marbles within Sani Chip digging medium, and no sex differences were observed. Next, the number of marbles buried and locomotor activity remained consistent across four test sessions. The positive controls buspirone (3.2-10 mg/kg) ketamine (32 mg/kg), and fluoxetine (10 mg/kg) decreased the number of marbles buried using the within-subjects design. These data suggest that a within-subjects design is optimal for the marble burying assay as it will reduce the number of animals and increase statistical power.

Rat models of diet-induced obesity and metabolic dysregulation: Current trends, shortcomings and considerations for future research

Rat diet-induced obesity and metabolic dysregulation (DIO/DIMD) is widely used as a pre-clinical model for human obesity and for testing weight-loss interventions. The aim of this review was to utilise a systematic literature survey of rat DIO/DIMD studies as a tool to document trends around study design and metabolic outcomes of these studies, and to consider ways in which the design of these studies may be improved to enhance the relevance thereof for human obesity research. In total, 110 comparisons between control and obesogenic dietary groups were included in the survey. Young male rats were found to be the model of choice, but fewer than 50% of studies provided comprehensive information about diet composition and energy intake. In addition, it was found that the majority of expected DIO/DIMD responses (hyperglycemia, hyperinsulinemia, dyslipidemia, hypoadiponectinemia) occurred at < 80% frequency, drawing into question the concept of a "typical" or "appropriate" response. We discuss the impact of differences in diet composition and energy intake on metabolic outcomes against the context of large heterogeneity of obesogenic diets employed in rat DIO/DIMD studies, and provide recommendations for the improvement of reporting standards around diet composition and dietary intake. In addition, we highlight the lack of data from female and older rats and describe considerations around the inclusion of sex and age as a variable in rat DIO/DIMD studies, aiming towards improving the applicability of these studies as a model of human obesity, which is most prevalent in women and older individuals.

Aromatase inhibition and ketamine in rats: sex-differences in antidepressant-like efficacy

BACKGROUND

Ketamine has been recently approved to treat resistant depression; however preclinical studies showed sex differences in its efficacy. Sex steroids, such as estrogens and testosterone, both in the periphery and locally in the brain, are regarded as important modulators of these sex differences. Therefore, the present study evaluated how inhibiting the biosynthesis of estrogens with letrozole (an aromatase inhibitor) could affect the observed sex differences in ketamine's antidepressant-like-response.

METHODS

We performed several consecutive studies in adult Sprague-Dawley rats to evaluate potential sex differences in the antidepressant-like effects of ketamine (5 mg/kg, 7 days, i.p.), letrozole (1 mg/kg, 8 days, i.p.) and their combination (letrozole pre-treatment 3 h before ketamine). Acute and repeated antidepressant-like responses were ascertained in a series of behavioral tests (forced-swim, novelty-suppressed feeding, two-bottle choice for sucrose preference).

RESULTS

The main results proved clear sex differences in the antidepressant-like response induced by ketamine, which was observed following a repeated paradigm in adult male rats, but rendered inefficacious in female rats. Moreover, decreasing estrogens production with letrozole induced on itself an antidepressant-like response in female rats, while also increased ketamine's response in male rats (i.e., quicker response observed after only a single dose). Interestingly, both the antidepressant-like effects induced by ketamine in male rats or letrozole in female rats persisted over time up to 65 days post-treatment, suggesting long-term sex-directed benefits for these drugs.

CONCLUSIONS

The present results demonstrated a sex-specific role for aromatase inhibition with letrozole in the antidepressant-like response induced by ketamine in male rats. Moreover, letrozole itself presented as a potential antidepressant for females with persistent effects over time. Clearly, the production of estrogens is key in modulating, in a sex-specific manner, affective-like responses and thus deserve further studies.

Pharmacologic hyperreactivity of kappa opioid receptors in periaqueductal gray matter during alcohol withdrawal syndrome in rats

BACKGROUND

Periaqueductal gray matter (PAG) is a brain region rich in kappa-opioid receptors (KOR). KOR in PAG mediates behavioral responses related to pain integration, and panic response, among others. Its participation in the addiction phenomena has been poorly studied. Hence, this preliminary study explored the pharmacological effects of KOR stimulation/blockade in dorsal-PAG (D-PAG) during alcohol withdrawal on anxiety-type behaviors and alcohol intake/preference.

METHODS

Juvenile male Wistar rats were unexposed (A-naïve group) or exposed to alcohol for 5 weeks and then restricted (A-withdrawal group). Posteriorly, animals received intra D-PAG injections of vehicle (10% DMSO), salvinorin A (SAL-A; a selective KOR agonist), or 2-Methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine (PF-04455242; a highly selective KOR-antagonist). Subsequently, the defensive burying behavior (DBB) and alcohol intake/preference paradigms were evaluated.

RESULTS

SAL-A markedly increased burying time, the height of bedding, and alcohol consumption/preference in A-withdrawal, while slightly increased the height of bedding in A-näive rats. PF-04455242 decreased both burying and immobility duration, whereas increases latency to burying, frequency of rearing, and the number of stretches attempts with no action on alcohol intake/preference in A-withdrawal rats.

CONCLUSIONS

In general, stimulation/blockade of KOR in A-withdrawal animals exert higher responses compared to A-naïve ones. SAL-A produced anxiety-like behaviors and increased alcohol consumption/preference, especially/solely in the alcohol-withdrawal condition, while PF-04455242 augmented exploration with no effects on alcohol intake/preference. Our findings suggest a possible pharmacologic hyperreactivity of the KOR in PAG during alcohol withdrawal.

Aromatase Inhibition and Electroconvulsive Seizures in Adolescent Rats: Antidepressant and Long-Term Cognitive Sex Differences

BACKGROUND

We recently showed sex differences in the antidepressant-like potential of electroconvulsive seizures (ECS) in adolescent rats; whereas it worked for male rats, it was inefficacious in females. Because sex steroids might be important modulators of these sex disparities, we evaluated the role of estrogens in the differential response induced by adolescent ECS. Moreover, given the literature suggesting certain cognitive sequelae from ECS exposure, we aimed at evaluating its long-term safety profile in adulthood.

METHODS

Adolescent Sprague-Dawley rats were pretreated with letrozole (1 mg/kg/day) or vehicle (1 mL/kg/day) for 8 days (i.p.) and treated during the last 5 days (3 hours later) with ECS (95 mA, 0.6 s, 100 Hz) or SHAM. Antidepressant-like responses were measured in the forced swim test, and long-term cognitive performance was assessed in the Barnes maze.

RESULTS

During adolescence, whereas ECS alone exerted an antidepressant-like response in male rats, its combination with letrozole permitted ECS to also induce efficacy in females. Moreover, adolescent ECS treatment improved cognitive performance in adulthood although exclusively in male rats.

CONCLUSIONS

Adolescent ECS demonstrated an antidepressant-like potential together with certain long-term beneficial cognitive effects but exclusively in male rats. For females, efficacy was restricted to a situation in which the biosynthesis of estrogens was reduced. Therefore, estrogens and/or testosterone levels play a crucial role in the sex disparities induced by ECS in Sprague-Dawley rats. Based on this study and on the literature supporting its safety, ECS should be encouraged for use in cases of treatment-resistant depression during adolescence, while adhering to sex-specific considerations.

Unmasking the Adverse Impacts of Sex Bias on Science and Research Animal Welfare

Sex bias in biomedical and natural science research has been prevalent for decades. In many cases, the female estrous cycle was thought to be too complex an issue to model for, and it was thought to be simpler to only use males in studies. At times, particularly when studying efficacy and safety of new therapeutics, this sex bias has resulted in over- and under-medication with associated deleterious side effects in women. Many sex differences have been recognized that are unrelated to hormonal variation occurring during the estrous cycle. Sex bias also creates animal welfare challenges related to animal over-production and wastage, insufficient consideration of welfare (and scientific) impact related to differential housing of male vs female animals within research facilities, and a lack of understanding regarding differential requirements for pain recognition and alleviation in male versus female animals. Although many funding and government agencies require both sexes to be studied in biomedical research, many disparities remain in practice. This requires further enforcement of expectations by the Institutional Animal Care and Use Committee when reviewing protocols, research groups when writing grants, planning studies, and conducting research, and scientific journals and reviewers to ensure that sex bias policies are enforced.

Evaluation of Sex Differences in Preclinical Pharmacology Research: How Far Is Left to Go?

Until the last quarter of the 20th century, sex was not recognized as a variable in health research, nor was it believed to be a factor that could affect health and illness. Researchers preferred studying male models for a variety of reasons, such as simplicity, lower costs, hormone confounding effects, and fear of liability from perinatal exposure in case of pregnancy. Equitable representation is imperative for determining the safety, effectiveness, and tolerance of therapeutic agents for all consumers. Decades of female models' underrepresentation in preclinical studies has resulted in inequality in the understanding, diagnosis, and treatment of disease between the sexes. Sex bias has been highlighted as one of the contributing factors to the poor translation and replicability of preclinical research. There have been multiple calls for action, and the inclusion of sex as a biological variable is increasingly supported. However, although there has been substantial progress in the efforts to include more female models in preclinical studies, disparities today remain. In the present review, we consider the current standard practice of the preclinical research setting, why the sex bias exists, why there is the need to include female models, and what risks may arise from continuing this exclusion from experimental design.

Sex differences: From preclinical pharmacology to clinical pharmacology

Sex is a crucial variable to take into account in medical research. In this review, we attempted to present its importance at all stages of research and even during drug's post-marketing surveillance. Most preclinical research studies do not take sex into account while many diseases are known to present sexual dimorphism. However, a shift in thinking occurred since the January 2016 implementation of the US Institutes of Health recommendations to take sex into account in research. Nevertheless, in preclinical studies, the lack of sex-based statistical analyses persists. Moreover, in humans, women are often under-represented in some clinical trials, despite well-identified sexual dimorphism. In addition, some pathologies are subject to social representations of diseases considered "male" or "female" which can also lead to a delay in diagnosis and management for both sexes. Finally, many drug classes may be subject to sex differences in efficacy and safety. For example, women present more adverse events than men, mainly because of different pharmacokinetic parameters. Accounting sex as a variable from the preclinical phase is essential to improve the transposition of observed results and move towards personalized medicine.

Effect of amoxicillin/clavulanic acid in attenuating pregabalin-induced condition place preference

Substance abuse is a worldwide problem with serious repercussions for patients and the communities where they live. Pregabalin (Lyrica), is a medication commonly used to treat neuropathic pain. Like other analgesic medications there has been concern about pregabalin abuse and misuse. Although it was initially suggested that pregabalin, like other gabapentinoids, has limited abuse liability, questions still remain concerning this inquiry. Changes in glutamate system homeostasis are a hallmark of adaptations underlying drug dependence, including down-regulation of the glutamate transporter 1 (GLT-1; SLC1A2) and the cystine/glutamate antiporter (xCT; SLC7A11). In this study, it was found that pregabalin (90 mg/kg) produces a conditioned place preference (CPP), indicative of reinforcing effects that suggest a potential for abuse liability. Moreover, like other drugs of abuse, pregabalin also produced alterations in glutamate homeostasis, reducing the mRNA expression of Slc1a2 and Slc7a11 in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC). Amoxicillin clavulanic acid, a β-lactam antibiotic, blocked the reinforcing effects of pregabalin and normalized glutamate homeostasis. These results suggest that pregabalin has abuse potential that should be examined more critically, and that, moreover, the mechanisms underlying these effects are similar to those of other drugs of abuse, such as heroin and cocaine. Additionally, these results support previous findings showing normalization of glutamate homeostasis by β-lactam drugs that provides a novel potential therapeutic approach for the treatment of drug abuse and dependence.

Endothelin type A receptor blockade increases renoprotection in congestive heart failure combined with chronic kidney disease: Studies in 5/6 nephrectomized rats with aorto-caval fistula

BACKGROUND

Association of congestive heart failure (CHF) and chronic kidney disease (CKD) worsens the patient's prognosis and results in poor survival rate. The aim of this study was to examine if addition of endothelin type A (ET_A) receptor antagonist to the angiotensin-converting enzyme inhibitor (ACEi) will bring additional beneficial effects in experimental rats.

METHODS

CKD was induced by 5/6 renal mass reduction (5/6 NX) and CHF was elicited by volume overload achieved by creation of aorto-caval fistula (ACF). The follow-up was 24 weeks after the first intervention (5/6 NX). The treatment regimens were initiated 6 weeks after 5/6 NX and 2 weeks after ACF creation.

RESULTS

The final survival in untreated group was 15%. The treatment with ET_A receptor antagonist alone or ACEi alone and the combined treatment improved the survival rate to 64%, 71% and 75%, respectively, however, the difference between the combination and either single treatment regimen was not significant. The combined treatment exerted best renoprotection, causing additional reduction in albuminuria and reducing renal glomerular and tubulointerstitial injury as compared with ACE inhibition alone.

CONCLUSIONS

Our results show that treatment with ET_A receptor antagonist attenuates the CKD- and CHF-related mortality, and addition of ET_A receptor antagonist to the standard blockade of RAS by ACEi exhibits additional renoprotective actions.

Sex differences in the antidepressant-like response and molecular events induced by the imidazoline-2 receptor agonist CR4056 in rats

In searching for novel targets to design antidepressants, among the characterized imidazoline receptors (IR), I2 receptors are an innovative therapeutical approach since they are dysregulated in major depressive disorder and by classical antidepressant treatments. In fact, several I2 agonists have been characterized for their antidepressant-like potential, but the results in terms of efficacy were mixed and exclusively reported in male rodents. Since there are well-known sex differences in antidepressant-like efficacy, this study characterized the potential effects induced by two I2 drugs, CR4056 (i.e., most promising drug already in phase II clinical trial for its analgesic properties) and B06 (a compound from a new family of bicyclic α-iminophosphonates) under the stress of the forced-swim test in male and female rats exposed to early-life stress. Moreover, some hippocampal neuroplasticity markers related to the potential effects observed were also evaluated (i.e., FADD, p-ERK/ERK, mBDNF, cell proliferation: Ki-67 + cells). The main results replicated the only prior study reporting the efficacy of CR4056 in male rats, while providing new data on its efficacy in females, which was clearly dependent on prior early-life stress exposure. Moreover, B06 showed no antidepressant-like effects in male or female rats. Finally, CR4056 increased FADD content and decreased cell proliferation in hippocampus, without affecting p-ERK/t-ERK ratio and/or mBDNF content. Interestingly, these effects were exclusively observed in female rats, and independently of early-life conditions, suggesting some distinctive molecular underpinnings participating in the therapeutic response of CR4056 for both sexes. In conjunction, these results present CR4056 with an antidepressant-like potential, especially in female rats exposed to stress early in life, together with some neuronal correlates described in the context of these behavioral changes in females.

Guidance for the use and reporting of anaesthetic agents in BJP manuscripts involving work with animals

Scientists who plan to publish in the British Journal of Pharmacology (BJP) should read this article before undertaking studies utilising anaesthetics in mammalian animals. This editorial identifies certain gaps in the reporting of details on the use of anaesthetics in animal research studies published in the BJP. The editorial also provides guidance, based upon current best practices, for performing in vivo experiments that require anaesthesia. In addition, mechanisms of action and physiological impact of specific anaesthetic agents are discussed. Our goal is to identify best practices and to provide guidance on the information required for manuscripts submitted to the BJP that involve the use of anaesthetic agents in studies with experimental animals.

Marked oestrous cycle-dependent regulation of rat arterial KV 7.4 channels driven by GPER1

BACKGROUND AND PURPOSE

Kcnq-encoded KV 7 channels (termed KV 7.1-5) regulate vascular smooth muscle cell (VSMC) contractility at rest and as targets of receptor-mediated responses. However, the current data are mostly derived from males. Considering the known effects of sex, the oestrous cycle and sex hormones on vascular reactivity, here we have characterised the molecular and functional properties of KV 7 channels from renal and mesenteric arteries from female Wistar rats separated into di-oestrus and met-oestrus (F-D/M) and pro-oestrus and oestrus (F-P/E).

EXPERIMENTAL APPROACH

RT-qPCR, immunocytochemistry, proximity ligation assay and wire myography were performed in renal and mesenteric arteries. Circulating sex hormone concentrations were determined by liquid chromatography-tandem mass spectrometry. Whole-cell electrophysiology was undertaken on cells expressing KV 7.4 channels in association with G-protein-coupled oestrogen receptor 1 (GPER1).

KEY RESULTS

The KV 7.2-5 activators S-1 and ML213 and the pan-KV 7 inhibitor linopirdine were more effective in arteries from F-D/M compared with F-P/E animals. In VSMCs isolated from F-P/E rats, exploratory evidence indicates reduced membrane abundance of KV 7.4 but not KV 7.1, KV 7.5 and Kcne4 when compared with cells from F-D/M. Plasma oestradiol was higher in F-P/E compared with F-D/M, and progesterone showed the converse pattern. Oestradiol/GPER1 agonist G-1 diminished KV 7.4 encoded currents and ML213 relaxations and reduced the membrane abundance of KV 7.4 and interaction between KV 7.4 and heat shock protein 90 (HSP90), in arteries from F-D/M but not F-P/E.

CONCLUSIONS AND IMPLICATIONS

GPER1 signalling decreased KV 7.4 membrane abundance in conjunction with diminished interaction with HSP90, giving rise to a 'pro-contractile state'.

Alfaxalone population pharmacokinetics in the rat: Model application for pharmacokinetic and pharmacodynamic design in inbred and outbred strains and sexes

The translation of new injectable anesthetic drugs from rodent to humans remains slow, despite the realization that reliance on the volatile agents is unsustainable from an environmental perspective. The aim of this study was to investigate the influence of rat sex and strain on the PK and PD of the anesthetic neurosteroid alfaxalone. Forty rats had cannulas inserted under isoflurane anesthesia for drug administration and sampling. Carotid artery blood samples were collected for blood gas analysis, hematology, biochemistry, and plasma concentrations of alfaxalone. Plasma samples were assayed using liquid chromatography-mass spectrometry. Compartmental non-linear mixed effects methods (NLME) models were applied to two rat populations to determine whether body weight, sex, and strain influenced PK parameters. There were significant differences between the sexes for plasma clearance, half-life and mean residence time in Lewis rats, and mean arterial blood pressure was significantly lower in the female rats at 120 min. An initial NLME PK population model was used to design an adjusted alfaxalone infusion for SD females matching plasma concentrations in males and minimizing cardiopulmonary depression but maintaining an appropriate hypnotic effect. A final NLME population model showed that alfaxalone clearance was dependent on both bodyweight and sex, whereas volume of distribution was influenced by strain. NLME PK models offer the advantage of having a single model that describes a population and therefore shares data interpretation between animals unlike the standard deterministic PK approach. This approach can be used to propose bespoke dosing regimens for optimal use of alfaxalone.

The MEK Inhibitor Trametinib Improves Outcomes following Subarachnoid Haemorrhage in Female Rats

Aneurysmal subarachnoid haemorrhage (SAH) is a haemorrhagic stroke that causes approximately 5% of all stroke incidents. We have been working on a treatment strategy that targets changes in cerebrovascular contractile receptors, by blocking the MEK/ERK1/2 signalling pathway. Recently, a positive effect of trametinib was found in male rats, but investigations of both sexes in pre-clinical studies are an important necessity. In the current study, a SAH was induced in female rats, by autologous blood-injection into the pre-chiasmatic cistern. This produces a dramatic, transient increase in intracranial pressure (ICP) and an acute and prolonged decrease in cerebral blood flow. Rats were then treated with either vehicle or three doses of 0.5 mg/kg trametinib (specific MEK/ERK1/2 inhibitor) intraperitoneally at 3, 9, and 24 h after the SAH. The outcome was assessed by a panel of tests, including intracranial pressure (ICP), sensorimotor tests, a neurological outcome score, and myography. We observed a significant difference in arterial contractility and a reduction in subacute increases in ICP when the rats were treated with trametinib. The sensory motor and neurological outcomes in trametinib-treated rats were significantly improved, suggesting that the improved outcome in females is similar to that of males treated with trametinib.

The glucose tolerance test in mice: Sex, drugs and protocol

AIM

To establish the impact of sex, dosing route, fasting duration and acute habituation stress on glucose tolerance test (GTT) measurements used in the preclinical evaluation of potential glucose-modulating therapeutics.

METHODS

Adult male and female C57Bl/6J mice, implanted with HD-XG glucose telemetry devices, were fasted for 16 hours or 6 hours following acute habituation stress due to whole cage change, cage change with retention of used bedding or no cage change prior to intraperitoneal (IP) GTTs. To evaluate protocol refinement and sex on the ability of the GTT to detect drug effects, we administered 250 mg/kg oral metformin or 10 nmol/kg IP exendin-4 using optimized protocols.

RESULTS

Female mice were less sensitive to human intervention when initiating fasting. Following a 6-hour fast, retention of bedding whilst changing the cage base promotes quicker stabilization of basal blood glucose in both sexes. Prolonged fasting for 16 hours resulted in an exaggerated GTT response but induced pronounced basal hypoglycaemia. Following GTT protocol optimization the effect of exendin-4 and metformin was equivalent in both sexes, with females showing a more modest but more reproducible GTT response.

CONCLUSIONS

Variations in GTT protocol have profound effects on glucose homeostasis. Protocol refinement and/or the use of females still allows for detection of drug effects, providing evidence that more severe phenotypes are not an essential prerequisite when characterizing/validating new drugs.

Revisiting the antidepressant-like effects of desipramine in male and female adult rats: sex disparities in neurochemical correlates

Background

The preclinical antidepressant-like characterization of desipramine relied almost exclusively in male rodents, with only a few contradictory reports done in females. Given that most experiments assessed a single dose and/or timepoint of analysis after-treatment, this study evaluated potential sex-differences in the length of the antidepressant-like response induced by different doses of desipramine as well as the molecular underpinnings driving the different responses by sex.

Methods

Male and female Sprague–Dawley rats were treated (i.p.) with 3 pulses of desipramine (5, 10 or 20 mg/kg) or vehicle (0.9% NaCl) within 24 h. The antidepressant-like effects were evaluated in the forced-swim test 1-h, 1- and 3-day post-treatment. The rate of cell proliferation and the regulation of key neuroplasticity markers (FADD, Cdk5, p35, p25) involved in antidepressant-like responses in the hippocampus were evaluated 1-h, 1-day and 5-day post-treatment.

Results

Desipramine induced similar antidepressant-like effects in male and female rats (effective doses of 10 and 20 mg/kg, with effects that lasted up to 1-day post-treatment), without altering the rate of cell proliferation. However, some sex-differences emerged when evaluating neuroplasticity markers in the hippocampus, while no changes were observed for female rats, desipramine regulated FADD, Cdk-5 and p25 in males in a way that suggested neuroprotective actions.

Conclusions

Our findings imply that while desipramine induced similar antidepressant-like responses for male and female rats, some differences emerged in the regulation of certain neuroplasticity markers, suggesting that distinctive molecular mechanisms might be participating in the therapeutic response of desipramine for both sexes.

Exploring pharmacological options for adolescent depression: a preclinical evaluation with a sex perspective

There is an urgent need for developing novel pharmacological treatment options for adolescent depression, and to ensure an optimal translational outcome to the clinic, sex should be included as a biological variable in preclinical studies. In this context, the present study compared the antidepressant-like potential of ketamine and cannabidiol, with the clinical standard fluoxetine, in adolescent rats exposed to maternal deprivation (as a model of early-life stress), while including a sex perspective. Moreover, changes in drug efficacy over time were evaluated by re-exposing rats to the same dose regimens during adulthood. Antidepressant-like responses were scored through a battery of distinctive tests (forced-swim, novelty-suppressed feeding, and sucrose preference) across time. The main results proved an antidepressant-like potential for ketamine and cannabidiol in adolescent rats, although their efficacy was dependent on sex and prior stress exposure, as well as on treatment length and the behavioral feature analyzed. In general, while all tested antidepressants in male rats improved certain affective-like features, female rats were mainly unresponsive to the treatments performed (except for certain benefits induced by ketamine), demonstrating the need for further characterizing proper treatments for this particular sex. Moreover, when rats were re-exposed in adulthood to the same drug regimens as in adolescence, a drop in efficacy was observed. These findings may have translational ramifications in that ketamine or cannabidiol could be moved forward as antidepressants for the adolescent depressed population, but not before further characterizing their potential long-term safety and/or beneficial vs. harmful effects for both sexes.

Are we any WISER yet? Progress and contemporary need for smart trials to include women in coronary artery disease trials

Despite calls to ensure proportionate representation of both sexes in biomedical research, women continue to be underrepresented in cardiovascular disease (CVD) clinical trials. A comprehensive analysis of seven large suspected ischemic heart disease/coronary artery disease (HD/CAD) clinical trials (PROMISE, ISCHEMIA, CIAO-ISCHEMIA, ORBITA, FAME, FAME 2 and COURAGE trial) provides understanding of contributions to barriers to enrollment of women and leads to strategies to address these barriers. Specifically, in the seven trials, enrollment of women did not exceed 27%, while numerous barriers are evident. Proposed strategies to improve women´s inclusion in clinical trials, include adding reproductive stage/estrogen status, attention to study design inclusion/exclusion criteria using female thresholds, consideration of diagnostic and intervention study design to be inclusive, increasing women and minorities in leadership positions, including sex as a biological variable (SABV) in study design and statistical analysis, and addressing social and race/ethnicity barriers. Dedicated action to actualizing these steps are needed at this time to developing diagnostic and therapeutic strategies resulting in better care and improved outcomes for CVD in women.

High glucose-mediated VPS26a downregulation dysregulates neuronal amyloid precursor protein processing and tau phosphorylation

BACKGROUND AND PURPOSE

The relationship between hyperglycaemia-induced retromer dysfunction impairing intracellular trafficking and AD remains unclear, although Diabetes mellitus (DM) is considered a risk factor for Alzheimer's disease (AD). Here, we investigated the effects of high glucose on the retromer, and defined the dysregulation of mechanisms of amyloid precursor protein (APP) processing and tau phosphorylation.

EXPERIMENTAL APPROACH

We used human induced-pluripotent stem cell-derived neuronal differentiated cells and SH-SY5Ys exposed to high glucose to identify the underlying mechanisms. Streptozotocin-induced diabetic mice were used to elucidate whether the retromer contributes to the AD-like pathology.

KEY RESULTS

We found that vacuolar protein sorting-associated protein 26a (VPS26a) was decreased in the hippocampus of diabetic mice and high glucose-treated human neuronal cells. High glucose downregulated VPS26a through ROS/NF-κB/DNA methyltransferase1-mediated promoter hypermethylation. VPS26a recovery blocked retention of APP and cation-independent mannose-6-phosphate receptor in endosomes and promoted transport to the trans-Golgi, which decreased Aβ levels, and improved Cathepsin D activity, reducing p-tau levels, respectively. Retromer enhancement ameliorated synaptic deficits, astrocyte over-activation, and cognitive impairment in diabetic mice.

CONCLUSION AND IMPLICATIONS

In conclusion, VPS26a is a promising candidate for the inhibition of DM-associated AD pathogenesis by modulating APP processing and tau phosphorylation.

Science Forum: Sex differences and sex bias in human circadian and sleep physiology research

Growing evidence shows that sex differences impact many facets of human biology. Here we review and discuss the impact of sex on human circadian and sleep physiology, and we uncover a data gap in the field investigating the non-visual effects of light in humans. A virtual workshop on the biomedical implications of sex differences in sleep and circadian physiology then led to the following imperatives for future research: (1) design research to be inclusive and accessible, (2) implement recruitment strategies that lead to a sex-balanced sample, (3) use data visualization to grasp the effect of sex, (4) implement statistical analyses that include sex as a factor and/or perform group analyses by sex, where possible, (5) make participant-level data open and available to facilitate future meta-analytic efforts.

Factors Determining Plasticity of Responses to Drugs

The plasticity of responses to drugs is an ever-present confounding factor for all aspects of pharmacology, influencing drug discovery and development, clinical use and the expectations of the patient. As an introduction to this Special Issue of the journal IJMS on pharmacological plasticity, we address the various levels at which plasticity appears and how such variability can be controlled, describing the ways in which drug responses can be affected with examples. The various levels include the molecular structures of drugs and their receptors, expression of genes for drug receptors and enzymes involved in metabolism, plasticity of cells targeted by drugs, tissues and clinical variables affected by whole body processes, changes in geography and the environment, and the influence of time and duration of changes. The article provides a rarely considered bird’s eye view of the problem and is intended to emphasize the need for increased awareness of pharmacological plasticity and to encourage further debate.

Differential sleep/wake response and sex effects following acute suvorexant, MK-1064 and zolpidem administration in the rTg4510 mouse model of tauopathy

Background and Purpose

Transgenic mouse models of tauopathy display prominent sleep/wake disturbances which manifest primarily as a hyperarousal phenotype during the active phase, suggesting that tau pathology contributes to sleep/wake changes. However, no study has yet investigated the effect of sleep‐promoting compounds in these models. Such information has implications for the use of hypnotics as potential therapeutic tools in tauopathy‐related disorders.

Experimental Approach

This study examined polysomnographic recordings in 6‐6.5‐month‐old male and female rTg4510 mice following acute administration of suvorexant (50 mg·kg⁻¹), MK‐1064 (30 mg·kg⁻¹) or zolpidem (10 mg·kg⁻¹), administered at the commencement of the active phase.

Key Results

Suvorexant, a dual OX receptor antagonist, promoted REM sleep in rTg4510 mice, without affecting wake or NREM sleep. MK‐1064, a selective OX₂ receptor antagonist, reduced wake and increased NREM and total sleep time. MK‐1064 normalised the hyperarousal phenotype of male rTg4510 mice, whereas female rTg4510 mice exhibited a more transient response. Zolpidem, a GABA_A receptor positive allosteric modulator, decreased wake and increased NREM sleep in both male and female rTg4510 mice. Of the three compounds, the OX₂ receptor antagonist MK‐1064 promoted and normalised physiologically normal sleep, especially in male rTg4510 mice.

Conclusions and Implications

Our findings indicate that hyperphosphorylated tau accumulation and associated hyperarousal does not significantly alter the responses of tauopathy mouse models to hypnotics. However, the sex differences observed in the sleep/wake response of rTg4510 mice to MK‐1064, but not suvorexant or zolpidem, raise questions about therapeutic implications for the use of OX₂ receptor antagonists in human neurodegenerative disorders.

The underestimated sex: a review on female animal models of depression

Major depression (MD) is the most common psychiatric disorder, predicted to affect around 264 million people worldwide. Although the etiology of depression remains elusive, the interplay between genetics and environmental factors, such as early life events, stress, exposure to drugs and health problems appears to underlie its development. Whereas depression is twice more prevalent in women than in men, most preclinical studies are performed in male rodents. In fact, females' physiology and reproductive experience are associated with changes to brain, behavior and endocrine profiles that may influence both stress, an important precipitating factor for depression, and response to treatment. These specificities emphasize the need to choose the most suitable models and readouts in order to better understand the pathophysiological mechanisms of depression in females. With this review, we aim to provide an overview of female animal models of depression highlighting the major differences between models, regarding behavioral, physiological, and molecular readouts, but also the major gaps in research, attending to the role of etiological factors, protocol variability and sex.

Sexual dimorphism in prostacyclin-mimetic responses within rat mesenteric arteries: A novel role for KV 7.1 in shaping IP-receptor mediated relaxation

Background and Purpose

Prostacyclin mimetics express potent vasoactive effects via prostanoid receptors that are not unequivocally defined, as to date no study has considered sex as a factor. The aim of this study was to determine the contribution of IP and EP₃ prostanoid receptors to prostacyclin mimetic iloprost‐mediated responses, whether K_V7.1–5 channels represent downstream targets of selective prostacyclin‐IP‐receptor agonist MRE‐269 and the impact of the oestrus cycle on vascular reactivity.

Experimental Approach

Within second‐order mesenteric arteries from male and female Wistar rats, we determined (1) relative mRNA transcripts for EP_1–4 (Ptger_1–4), IP (Ptgi) and TXA₂ (Tbxa) prostanoid receptors via RT‐qPCR; (2) the effect of iloprost, MRE‐269, isoprenaline and ML277 on precontracted arterial tone in the presence of inhibitors of prostanoid receptors, potassium channels and the molecular interference of K_V7.1 via wire‐myograph; (3) oestrus cycle stage via histological changes in cervical cell preparations.

Key Results

Iloprost evoked a biphasic response in male mesenteric arteries, at concentrations ≤100 nmol·L⁻¹ relaxing, then contracting the vessel at concentration ≥300 nmol·L⁻¹, a process attributed to IP and EP₃ receptors respectively. Secondary contraction was absent in the females, which was associated with a reduction in Ptger3. Pharmacological inhibition and molecular interference of K_V7.1 significantly attenuated relaxations produced by the selective IP receptor agonist MRE‐269 in male and female Wistar in dioestrus/metoestrus, but not pro‐oestrus/oestrus.

Conclusions and Implications

Stark sexual dimorphisms in iloprost‐mediated vasoactive responses are present within mesenteric arteries. K_V7.1 is implicated in IP receptor‐mediated vasorelaxation and is impaired by the oestrus cycle.

Sex bias in alcohol research: A 20-year comparative study

We aimed to assess the sex-inclusive and sex-based analysis bias in alcohol research for the past 20 years. Data were abstracted from 2988 original research articles published from 2000 through 2019 in 51 representative journals across 9 biomedical disciplines. An analysis in 5-year intervals revealed that the percentage of studies using participants of both sexes was significantly higher between 2015 and 2019 than between 2000 and 2014. When stratified, clinical studies showed a higher percentage of both-sex studies compared to basic studies using animals. The reasons for the use of single-sex cohorts mainly included insufficient participant numbers and misconceptions surrounding the hormonal variability of females. Implementation of the NIH SABV policy promoted the ratio of NIH-funded papers with sex-based analyses. In conclusion, sex bias in alcohol-related biomedical studies has improved over the past 20 years, particularly after the implementation of the SABV policy. Although clinical studies increasingly included sex-based analysis, basic studies were biased towards the use of males.

Interaction between α1B - and other α1 - and α2 -adrenoceptors in producing contractions of mouse spleen

We have investigated the interaction of α₁ - and α₂ -adrenoceptor subtypes in producing isometric contractions to NA in mouse whole spleen. The α₁ -adrenoceptor antagonist prazosin (10^-8 M) or the α₂ -adrenoceptor antagonist yohimbine (10^-6 M) alone produced only small shifts in NA potency in wild type (WT) mice, but the combination produced a large shift in NA potency. In spleen from α_1A/D -KO mice, the effects of prazosin and the combination of prazosin and yohimbine were similar to their effects in WT mice. Hence, in α_1A/D -KO mice, in which the only α₁ -adrenoceptor present is the α_1B -adrenoceptor, prazosin still antagonized contractions to NA. The α_1A -adrenoceptor antagonist RS100329 (3x10^-9 M) produced significant shifts in the effects of higher concentrations of NA (EC₅₀ and EC₇₅ levels) and the α_1D -adrenoceptor antagonist BMY7378 (3x10^-8 M) produced significant shifts in the effects of lower concentrations of NA (EC₂₅ and EC₅₀ levels). The effects of BMY7378 and RS00329 demonstrate α_1D -adrenoceptor and α_1A -adrenoceptor components, and suggest that the α_1B -adrenoceptor interacts with an α_1D -adrenoceptor, and to a lesser extent an α_1A -adrenoceptor, at low, and an α_1A -adrenoceptor at high, NA concentrations. This study demonstrates the complex interaction between α₁ - and α₂ -adrenoceptor subtypes in producing contractions of mouse spleen and may have general implications for α-adrenoceptor mediated control of smooth muscle.

Let's talk about sex: Differences in drug therapy in males and females

Professor Henry Higgins in My Fair Lady said, 'Why can't a woman be more like a man?' Perhaps unintended, such narration extends to the reality of current drug development. A clear sex-gap exists in pharmaceutical research spanning from preclinical studies, clinical trials to post-marketing surveillance with a bias towards males. Consequently, women experience adverse drug reactions from approved drug products more often than men. Distinct differences in pharmaceutical response across drug classes and the lack of understanding of disease pathophysiology also exists between the sexes, often leading to suboptimal drug therapy in women. This review explores the influence of sex as a biological variable in drug delivery, pharmacokinetic response and overall efficacy in the context of pharmaceutical research and practice in the clinic. Prospective recommendations are provided to guide researchers towards the consideration of sex differences in methodologies and analyses. The promotion of disaggregating data according to sex to strengthen scientific rigour, encouraging innovation through the personalisation of medicines and adopting machine learning algorithms is vital for optimised drug development in the sexes and population health equity.

Beneficial effects of atorvastatin on sex-specific cognitive impairment induced by a cerebral microhaemorrhage in mice

BACKGROUND AND PURPOSES

Cerebral microhaemorrhages (CMHs) are associated with cognitive decline in humans. In rodents, CMHs induces cognitive impairment in male mice along with sex-specific cortical and hippocampal changes affecting neural, glial and vascular functions. Statins, have been proposed to prevent cognitive decline. We tested here the action of atorvastatin on CMH-induced cognitive impairment in a murine model of CMH.

EXPERIMENTAL APPROACH

Using a multimodal approach combining behavioural tests, in vivo imaging, biochemistry and molecular biology, the effects of oral administration of atorvastatin on the sex-specific changes induced by a cortical CMH were studied in male and female mice (C57BL/6J) at 6-week post-induction using a collagenase-induced model.

KEY RESULTS

Atorvastatin caused specific effects according to the sex-specific CMH-induced changes. In males, atorvastatin improved the visuospatial memory, induced a local modulation of microglial response and enhanced brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (trkB) and vascular endothelial growth factor (VEGF) expression in the cortex. In the hippocampus, atorvastatin increased glucose metabolism and modulated astrocytes morphology. In females, atorvastatin did not modulate visuospatial memory despite the increased expression of cortical BDNF and the decrease in the number of hippocampal astrocytes. Atorvastatin also induced a decrease in the expression of cortical oestrogen receptors but did not modify body weight nor serum cholesterol levels in both sexes.

CONCLUSION AND IMPLICATIONS

Atorvastatin modulated the sex-specific cognitive impairment induced by the CMH with a pathophysiological impact mainly within the cortical area. It could represent a promising candidate for future sex-stratified clinical trials in patients with CMH.

Adolescent cocaine induced persistent negative affect in female rats exposed to early-life stress

RATIONALE

The combination of several risk factors (sex, a prior underlying psychiatric condition, or early drug initiation) could induce the emergence of negative affect during cocaine abstinence and increase the risk of developing addiction. However, most prior preclinical studies have been centered in male rodents, traditionally excluding females from these analyses.

OBJECTIVES

To ascertain the behavioral and neurochemical consequences of adolescent cocaine exposure when the combination of several risk factors is present (female, early-life stress).

METHODS

Whole litters of Sprague-Dawley rats were exposed to maternal deprivation for 24 h on postnatal day (PND) 9. Cocaine was administered in adolescence (15 mg/kg/day, i.p., PND 33-39). Negative affect was assessed by several behavioral tests (forced swim, open field, novelty-suppressed feeding, sucrose preference). Hippocampal cell fate markers were evaluated by western blot (FADD, Bax, cytochrome c) or immunohistochemistry (Ki-67; cell proliferation).

RESULTS

Maternal deprivation is a suitable model of psychiatric vulnerability in which to study the impact of adolescent cocaine in female rats. While adolescent cocaine did not alter affective-like behavior during adolescence, a pro-depressive-like state emerged during adulthood, exclusively in rats re-exposed to cocaine during abstinence. FADD regulation by cocaine in early-life stressed female rats might contribute to certain hippocampal neuroadaptations with some significance to the observed induced negative affect.

CONCLUSIONS

Adolescent cocaine induced persistent negative affect in female rats exposed to early-life stress, highlighting the risk of early drug initiation during adolescence for the emergence of negative reinforcement during abstinence likely driving cocaine addiction vulnerability, also in female rats.