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

Discriminative stimulus properties of α-ethyltryptamine (α-ET) in rats: α-ET-like effects of MDMA, MDA and aryl-monomethoxy substituted derivatives of α-ET

Rationale α-ET (α-ethyltryptamine), a homolog of the classical hallucinogen α-methyltryptamine, was once prescribed clinically as an antidepressant. Classical psychedelic drugs are currently of interest as potential pharmacotherapy for psychiatric disorders. Objectives Drug discrimination was used to (a) determine if α-ET-like stimulus effects could be engendered by the prototypical phenylalkylamines MDMA ("Ecstasy") or MDA ("Love Drug") and (b) evaluate the α-ET-like stimulus effects of four synthesized aryl-substituted monomethoxy analogs of α-ET (4-OMe-, 5-OMe-, 6-OMe- and 7-OMe-α-ET). Methods Rats were trained to discriminate α-ET (2.5 mg/kg) from saline using a two-lever operant task. Results The α-ET (ED50 = 1.04 mg/kg) stimulus generalized to MDMA (ED50 = 0.72 mg/kg) and MDA (ED50 = 0.48 mg/kg). The four α-ET derivatives produced various results; 4-OMe α-ET yielded negligible (20% maximum) α-ET-like responding; 5-OMe α-ET occasioned a modest level (40% maximum) of α-ET-like substitution; 6-OMe α-ET (ED50 = 6.26 mg/kg) generalized completely, but in a narrow dose range and in an inverted U-shaped manner; 7-OMe α-ET (ED50 = 2.78 mg/kg) generalized completely. Conclusions α-ET stimulus effects are similar to those of MDMA, but appear more closely aligned to those of MDA and are produced by its stereoisomers which, when combined, exert MDA/MDMA-, hallucinogen- and some stimulant-like stimulus actions. Thus, α-ET exerts a complex (compound) stimulus and appears to be a tryptamine counterpart of these prototypic phenylalkylamines. The monomethoxy analogs of α-ET produced an assortment of α-ET-like outcomes such that future investigations of these agents will likely need to be performed on an individual basis; extrapolations of α-ET-like effects to these analogs should be done judiciously.

Intrapericardial Administration of Human Pericardial Fluid Cells Improves Cardiac Functions in Rats with Heart Failure

Heart failure (HF) is still the main cause of mortality worldwide. This study investigated the characteristics of human pericardial fluid-derived cells (hPFCs) and their effects in treating doxorubicin (DOX)-induced HF rats through intrapericardial injection. hPFCs were isolated from patients who underwent heart transplantation (N = 5). These cells that primarily expressed SCA-1, NANOG, and mesenchymal markers, CD90, CD105, and CD73, were able to form adipocytes, osteoblasts, and cardiomyocytes in vitro. Passage 3 hPFCs (2.5 × 105 cells/heart) were injected into the pericardial cavity of the DOX-injured rat hearts, significantly improving cardiac functions after 4 weeks. The tracked and engrafted red fluorescent protein-tagged hPFCs coexpressed cardiac troponin T and connexin 43 after 4 weeks in the host myocardium. This observation was also coupled with a significant reduction in cardiac fibrosis following hPFC treatment (P < 0.0001 vs. untreated). The elevated inflammatory cytokines interleukin (IL)-6, IL-10, and tumor necrosis factor-α in the DOX-treated hearts were found to be significantly reduced (P < 0.001 vs. untreated), while the regional proangiogenic vascular endothelial growth factor A (VEGFA) level was increased in the hPFC-treated group after 4 weeks (P < 0.05 vs. untreated). hPFCs possess stem cell characteristics and can improve the cardiac functions of DOX-induced HF rats after 4 weeks through pericardial administration. The improvements were attributed to a significant reduction in cardiac fibrosis, inflammation, and elevated regional proangiogenesis factor VEGFA, with evidence of cellular engraftment and differentiation in the host myocardium.

Sex Differences in the Development of an Opioid Addiction-Like Phenotype: A Focus on the Telescoping Effect

Background

Women develop addiction and drug-related health consequences after fewer years of drug use than men; this accelerated time course, or telescoping effect, has been observed clinically for multiple drugs, including opioids. Preclinical studies indicate that this is a biologically based phenomenon; however, these studies have focused exclusively on cocaine, and none have considered health effects.

Methods

In this study, we used a rat (Sprague Dawley) model to determine sex differences in the time course for the development of an opioid addiction-like phenotype, as defined by the development of physical dependence (withdrawal-induced weight loss) and an increase in motivation for fentanyl (under a progressive-ratio schedule). Effects were determined following either 10 days (optimized, experiment 1) or 3 days (threshold, experiment 2) of extended-access fentanyl self-administration (24 hours/day, fixed ratio 1, 2- to 5-minute trials/hour) or following short-access fentanyl self-administration (subthreshold, experiment 3; fixed ratio 1, up to 40 infusions/day). Opioid-related adverse health effects were also determined (experiment 4).

Results

Motivation for fentanyl was similarly increased in males and females following 10 days of extended-access self-administration (experiment 1), was transiently increased in females, but not males, following 3 days of extended-access self-administration (experiment 2) and was not increased in either sex following short-access self-administration (experiment 3). Females developed fentanyl-associated adverse health effects more readily than males (experiment 4), with particularly robust differences during extended-access self-administration and withdrawal.

Conclusions

As with findings in humans, female rats developed opioid addiction-like features and adverse health consequences more readily than male rats. These data provide support for a biologically based telescoping effect in females for opioids, particularly for opioid-related adverse health consequences.

NK2R control of energy expenditure and feeding to treat metabolic diseases

The combination of decreasing food intake and increasing energy expenditure represents a powerful strategy for counteracting cardiometabolic diseases such as obesity and type 2 diabetes1. Yet current pharmacological approaches require conjugation of multiple receptor agonists to achieve both effects2-4, and so far, no safe energy-expending option has reached the clinic. Here we show that activation of neurokinin 2 receptor (NK2R) is sufficient to suppress appetite centrally and increase energy expenditure peripherally. We focused on NK2R after revealing its genetic links to obesity and glucose control. However, therapeutically exploiting NK2R signalling has previously been unattainable because its endogenous ligand, neurokinin A, is short-lived and lacks receptor specificity5,6. Therefore, we developed selective, long-acting NK2R agonists with potential for once-weekly administration in humans. In mice, these agonists elicit weight loss by inducing energy expenditure and non-aversive appetite suppression that circumvents canonical leptin signalling. Additionally, a hyperinsulinaemic-euglycaemic clamp reveals that NK2R agonism acutely enhances insulin sensitization. In diabetic, obese macaques, NK2R activation significantly decreases body weight, blood glucose, triglycerides and cholesterol, and ameliorates insulin resistance. These findings identify a single receptor target that leverages both energy-expending and appetite-suppressing programmes to improve energy homeostasis and reverse cardiometabolic dysfunction across species.

Review of the Influences of Sex Differences on Health and Disease: What Is the Role of Journals?

➢ Sex-based differences are understudied, which has potential consequences for the health of everyone.➢ Women's health is particularly affected given a lack of sex-specific data across many disease states.➢ Journals do not consistently require the inclusion of both sexes and the disaggregation of data by sex in cell, animal model, and human studies.➢ Instructions for investigators and journals regarding the inclusion of sex-specific data are found in guidelines such as those by the Sex and Gender Equity in Research (SAGER) group, but these guidelines are underutilized.➢ Consistency in the inclusion of both sexes in studies (except in studies on diseases affecting only 1 sex), as well as in the disaggregation and reporting of results by sex, has the potential to improve health for all people.

Sex- and Gender-Related Differences in Obesity: From Pathophysiological Mechanisms to Clinical Implications

Obesity, primarily characterized by excessive fat accumulation, is a multifactorial chronic disease with an increasing global prevalence. Despite the well-documented epidemiology and significant advances in understanding its pathophysiology and clinical implications, the impact of sex is typically overlooked in obesity research. Worldwide, women have a higher likelihood to become obese compared to men. Although women are offered weight loss interventions more often and at earlier stages than men, they are more vulnerable to psychopathology. Men, on the other hand, are less likely to pursue weight loss intervention and are more susceptible to the metabolic implications of obesity. In this narrative review, we comprehensively explored sex- and gender-specific differences in the development of obesity, focusing on a variety of biological variables, such as body composition, fat distribution and energy partitioning, the impact of sex steroid hormones and gut microbiota diversity, chromosomal and genetic variables, and behavioural and sociocultural variables influencing obesity development in men and women. Sex differences in obesity-related comorbidities and varying effectiveness of different weight loss interventions are also extensively discussed.

Potential Differences in Psychedelic Actions Based on Biological Sex

The resurgence of interest in psychedelics as treatments for psychiatric disorders necessitates a better understanding of potential sex differences in response to these substances. Sex as a biological variable (SABV) has been historically neglected in medical research, posing limits to our understanding of treatment efficacy. Human studies have provided insights into the efficacy of psychedelics across various diagnoses and aspects of cognition, yet sex-specific effects remain unclear, making it difficult to draw strong conclusions about sex-dependent differences in response to psychedelic treatments. Compounding this further, animal studies used to understand biological mechanisms of psychedelics predominantly use one sex and present mixed neurobiological and behavioral outcomes. Studies that do include both sexes often do not investigate sex differences further, which may hinder the translation of findings to the clinic. In reviewing sex differences in responses to psychedelics, we will highlight the direct interaction between estrogen (the most extensively studied steroid hormone) and the serotonin system (central to the mechanism of action of psychedelics), and the potential that estrogen-serotonin interactions may influence the efficacy of psychedelics in female participants. Estrogen influences serotonin neurotransmission by affecting its synthesis and release, as well as modulating the sensitivity and responsiveness of serotonin receptor subtypes in the brain. This could potentially influence the efficacy of psychedelics in females by modifying their therapeutic efficacy across menstrual cycles and developmental stages. Investigating this interaction in the context of psychedelic research could aid in the advancement of therapeutic outcomes, especially for conditions with sex-specific prevalence.

Studying intramuscular fat deposition and muscle regeneration: insights from a comparative analysis of mouse strains, injury models, and sex differences

Intramuscular fat (IMAT) infiltration, pathological adipose tissue that accumulates between muscle fibers, is a shared hallmark in a diverse set of diseases including muscular dystrophies and diabetes, spinal cord and rotator cuff injuries, as well as sarcopenia. While the mouse has been an invaluable preclinical model to study skeletal muscle diseases, they are also resistant to IMAT formation. To better understand this pathological feature, an adequate pre-clinical model that recapitulates human disease is necessary. To address this gap, we conducted a comprehensive in-depth comparison between three widely used mouse strains: C57BL/6J, 129S1/SvlmJ and CD1. We evaluated the impact of strain, sex and injury type on IMAT formation, myofiber regeneration and fibrosis. We confirm and extend previous findings that a Glycerol (GLY) injury causes significantly more IMAT and fibrosis compared to Cardiotoxin (CTX). Additionally, females form more IMAT than males after a GLY injury, independent of strain. Of all strains, C57BL/6J mice, both females and males, are the most resistant to IMAT formation. In regard to injury-induced fibrosis, we found that the 129S strain formed the least amount of scar tissue. Surprisingly, C57BL/6J of both sexes demonstrated complete myofiber regeneration, while both CD1 and 129S1/SvlmJ strains still displayed smaller myofibers 21 days post injury. In addition, our data indicate that myofiber regeneration is negatively correlated with IMAT and fibrosis. Combined, our results demonstrate that careful consideration and exploration are needed to determine which injury type, mouse model/strain and sex to utilize as preclinical model especially for modeling IMAT formation.

Sex Matters-Insights from Testing Drug Efficacy in an Animal Model of Pancreatic Cancer

Preclinical studies rarely test the efficacy of therapies in both sexes. The field of oncology is no exception in this regard. In a model of syngeneic, orthotopic, metastasized pancreatic ductal adenocarcinoma we evaluated the impact of sex on pathological features of this disease as well as on the efficacy and possible adverse side effects of a novel, small molecule-based therapy inhibiting KRAS:SOS1, MEK1/2 and PI3K signaling in male and female C57BL/6J mice. Male mice had less tumor infiltration of CD8-positive cells, developed bigger tumors, had more lung metastasis and a lower probability of survival compared to female mice. These more severe pathological features in male animals were accompanied by higher distress at the end of the experiment. The evaluated inhibitors BI-3406, trametinib and BKM120 showed synergistic effects in vitro. This combinatorial therapy reduced tumor weight more efficiently in male animals, although the drug concentrations were similar in the tumors of both sexes. These results underline the importance of sex-specific preclinical research and at the same time provide a solid basis for future studies with the tested compounds.

Increased stress vulnerability in the offspring of socially isolated rats: Behavioural, neurochemical and redox dysfunctions

Stressful events during pregnancy impact on the progeny neurodevelopment. However, little is known about preconceptional stress effects. The rat social isolation represents an animal model of chronic stress inducing a variety of dysfunctions. Moreover, social deprivation during adolescence interferes with key neurodevelopmental processes. Here, we investigated the development of behavioural, neurochemical and redox alterations in the male offspring of socially isolated female rats before pregnancy, reared in group (GRP) or in social isolation (ISO) from weaning until young-adulthood. To this aim, females were reared in GRP or in ISO conditions, from PND21 to PND70, when they were mated. Their male offspring was housed in GRP or ISO conditions through adolescence and until PND70, when passive avoidance-PA, novel object recognition-NOR and open field-OF tests were performed. Levels of noradrenaline (NA), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), glutamate (GLU) and GABA were assessed in the prefrontal cortex (PFC). Moreover, cortical ROS levels were quantified, as well as NF-kB and the NADPH oxidase NOX2 expression, redox status (expressed as GSH:GSSG ratio) and SOD1 amount. A significant decrease of the latency time in the PA was observed in the offspring of ISO females. In the NOR test, while a significant increase in the exploratory activity towards the novel object was observed in the offspring of GRP females, no significant differences were found in the offspring of ISO females. No significant differences were found in the OF test among experimental groups. Theoffspring of ISO females showed increased NA and 5-HIAA levels, whereas in the offspring persistently housed in isolation condition from weaninguntil adulthood, we detected reduced 5-HT levels and ehnanced 5-HIAA amount. No significant changes in GLU concentrations were detected, while decreased GABA content was observed in the offspring of ISO females exposed to social isolation. Increased ROS levels as well as reduced NF-κB, NOX2 expression were detected in the offspring of ISO females. This was accompanied by reduced redox status and enhanced SOD1 levels. In conclusion, our results suggest that female exposure to chronic social stress before pregnancy might have a profound influence on the offspring neurodevelopment in terms of cognitive, neurochemical and redox-related alterations, identifying this specific time window for possible preventive and therapeutic strategies.

Therapeutic potential of stilbenes in neuropsychiatric and neurological disorders: A comprehensive review of preclinical and clinical evidence

Neuropsychiatric disorders are anticipated to be a leading health concern in the near future, emphasizing an outstanding need for the development of new effective therapeutics to treat them. Stilbenes, with resveratrol attracting the most attention, are an example of multi-target compounds with promising therapeutic potential for a broad array of neuropsychiatric and neurological conditions. This review is a comprehensive summary of the current state of research on stilbenes in several neuropsychiatric and neurological disorders such as depression, anxiety, schizophrenia, autism spectrum disorders, epilepsy, traumatic brain injury, and neurodegenerative disorders. We describe and discuss the results of both in vitro and in vivo studies. The majority of studies concentrate on resveratrol, with limited findings exploring other stilbenes such as pterostilbene, piceatannol, polydatin, tetrahydroxystilbene glucoside, or synthetic resveratrol derivatives. Overall, although extensive preclinical studies show the potential benefits of stilbenes in various central nervous system disorders, clinical evidence on their therapeutic efficacy is largely missing.