Considering sex as a biological variable in preclinical research

DHEA: a neglected biological signal that may affect fetal and child development

BACKGROUND

The stress-sensitive maternal hypothalamic-pituitary-adrenal (HPA) axis through the end-product cortisol, represents a primary pathway through which maternal experience shapes fetal development with long-term consequences for child neurodevelopment. However, there is another HPA axis end-product that has been widely ignored in the study of human pregnancy. The synthesis and release of dehydroepiandosterone (DHEA) is similar to cortisol, so it is a plausible, but neglected, biological signal that may influence fetal neurodevelopment. DHEA also may interact with cortisol to determine developmental outcomes. Surprisingly, there is virtually nothing known about human fetal exposure to prenatal maternal DHEA and offspring neurodevelopment. The current study examined, for the first time, the joint impact of fetal exposure to prenatal maternal DHEA and cortisol on infant emotional reactivity.

METHODS

Participants were 124 mother-infant dyads. DHEA and cortisol were measured from maternal hair at 15 weeks (early gestation) and 35 weeks (late gestation). Observational assessments of positive and negative emotional reactivity were obtained in the laboratory when the infants were 6 months old. Pearson correlations were used to examine the associations between prenatal maternal cortisol, prenatal maternal DHEA, and infant positive and negative emotional reactivity. Moderation analyses were conducted to investigate whether DHEA might modify the association between cortisol and emotional reactivity.

RESULTS

Higher levels of both early and late gestation maternal DHEA were linked to greater infant positive emotional reactivity. Elevated late gestation maternal cortisol was associated with greater negative emotional reactivity. Finally, the association between fetal cortisol exposure and infant emotional reactivity was only observed when DHEA was low.

CONCLUSIONS

These new observations indicate that DHEA is a potential maternal biological signal involved in prenatal programming. It appears to act both independently and jointly with cortisol to determine a child's emotional reactivity. Its role as a primary end-product of the HPA axis, coupled with the newly documented associations with prenatal development shown here, strongly calls for the inclusion of DHEA in future investigations of fetal programming.

STRAIGHT-IN: a platform for rapidly generating panels of genetically modified human pluripotent stem cell lines

Targeted integration of large DNA cargoes (>10 kb) or genomic replacements in mammalian cells, such as human pluripotent stem cells (hPS cells), remains challenging. Here we describe a platform termed serine and tyrosine recombinase-assisted integration of genes for high-throughput investigation (STRAIGHT-IN) to circumvent this. First, a landing pad cassette is precisely inserted or used to replace specific genomic regions. The site-specific integrase Bxb1 then enables DNA constructs, including those >50 kb, to be integrated into the genome, while Cre recombinase excises auxiliary DNA sequences to prevent postintegrative silencing. Using a strategy whereby the positive selection marker is only expressed if the donor plasmid carrying the payload is correctly targeted, we can obtain 100% enrichment for cells containing the DNA payload. Procedures for expressing Cre efficiently also mean that a clonal isolation step is no longer essential to derive the required genetically modified hPS cells containing the integrated DNA, potentially reducing clonal variability. Furthermore, STRAIGHT-IN facilitates rapid and multiplexed generation of genetically matched hPS cells when multiple donor plasmids are delivered simultaneously. STRAIGHT-IN has various applications, which include integrating complex genetic circuits for synthetic biology, as well as creating panels of hPS cells lines containing, as necessary, hundreds of disease-linked variants for disease modeling and drug discovery. After establishing the hPS cell line containing the landing pad, the entire procedure, including donor plasmid synthesis, takes 1.5-3 months, depending on whether single or multiple DNA payloads are integrated. This protocol only requires the researcher to be skilled in molecular biology and standard cell culture techniques.

Prefrontal cortex-nucleus reuniens-hippocampus network exhibits sex-differentiated responses to stress and antidepressant treatment in rats

RATIONALE

Depression is a serious psychiatric disease, which is diagnosed twice as frequently in women than men. We have recently shown that lesioning or inactivation of the nucleus reuniens (RE), which interconnects the prefrontal cortex (PFC) and hippocampus, promoted resilience to stress in males, exerts an antidepressant effect in the Forced Swim Test (FST) and prevents the development of behavioral and neurobiological alterations induced by the chronic mild stress model of depression.

OBJECTIVES

In this study, we expand our findings on the FST in female rats and we investigate whether RE lesion presents sex differences following treatment with two distinct antidepressants, a selective serotonin reuptake inhibitor, i.e. sertraline and a tricyclic antidepressant, i.e. clomipramine.

METHODS

Male and female rats received either a surgical lesion of the RE or sham operation, then treated with vehicle, sertraline (10mg/kg) or clomipramine (10mg/kg) and were subjected to the FST. Activation of key brain areas of interest (PFC, Hippocampus and RE) were measured by c-Fos immunoreactivity.

RESULTS

RE lesion induced an antidepressant-like phenotype in both female and male rats, confirming its crucial role in the stress response. Similarly to RE lesion, sertraline treatment resulted in increased swimming and decreased immobility duration, as well as enhanced head shake frequency, in both sexes. Notably, climbing behavior was increased only following clomipramine treatment. RE area was less active in females compared to male rats and in clomipramine-treated males compared to their corresponding vehicle-group. Activation of the PFC and the CA1 hippocampal area was reduced in clomipramine-treated females, in comparison to vehicle-treated female rats. This effect was not evident in males, which exhibited less activation in the PFC and the hippocampus than females.

CONCLUSION

Re lesion proves equally effective in female and male rats, but sex is highlighted as a pivotal factor in behavioral and treatment response in FST, as well as in related circuit connectivity and activation.

Effects of Repeated Treatment with the Monoacylglycerol Lipase Inhibitor MJN110 on Pain-Related Depression of Nesting and Cannabinoid 1 Receptor Function in Male and Female Mice

MJN110 inhibits the enzyme monoacylglycerol lipase (MAGL) to increase levels of the endocannabinoid 2-arachidonoylglycerol , an endogenous high-efficacy agonist of cannabinoid 1 and 2 receptors (CB1/2R). MAGL inhibitors are under consideration as candidate analgesics, and we reported previously that acute MJN110 produced partial antinociception in an assay of pain-related behavioral depression in mice. Given the need for repeated analgesic administration in many pain patients and the potential for analgesic tolerance during repeated treatment, this study examined antinociceptive effects of repeated MJN110 on pain-related behavioral depression and CB1R-mediated G-protein function. Male and female ICR mice were treated daily for 7 days in a 2 × 2 design with (a) 1.0 mg/kg/d MJN110 or its vehicle followed by (b) intraperitoneal injection of dilute lactic acid (IP acid) or its vehicle as a visceral noxious stimulus to depress nesting behavior. After behavioral testing, G-protein activity was assessed in lumbar spinal cord (LSC) and five brain regions using an assay of CP55,940-stimulated [35S]GTPɣS activation. As reported previously, acute MJN110 produced partial but significant relief of IP acid-induced nesting depression on day 1. After 7 days, MJN110 continued to produce significant but partial antinociception in males, while antinociceptive tolerance developed in females. Repeated MJN110 also produced modest decreases in maximum levels of CP55,940-induced [35S]GTPɣS binding in spinal cord and most brain regions. These results indicate that repeated treatment with a relatively low antinociceptive MJN110 dose produces only partial and sex-dependent transient antinociception associated with the emergence of CB1R desensitization in this model of IP acid-induced nesting depression. SIGNIFICANCE STATEMENT: The drug MJN110 inhibits monoacylglycerol lipase (MAGL) to increase levels of the endogenous cannabinoid 2-arachidonoylglycerol and produce potentially useful therapeutic effects including analgesia. This study used an assay of pain-related behavioral depression in mice to show that repeated MJN110 treatment produced (1) weak but sustained antinociception in male mice, (2) antinociceptive tolerance in females, and (3) modest cannabinoid-receptor desensitization that varied by region and sex. Antinociceptive tolerance may limit the utility of MJN110 for treatment of pain.

Development of a Bmi1+ Cardiac Mouse Progenitor Immortalized Model to Unravel the Relationship with Its Protective Vascular Endothelial Niche

The adult mammalian heart has been demonstrated to be endowed with low but real turnover capacity, especially for cardiomyocytes, the key functional cell type. The source, however, of that turnover capacity remains controversial. In this regard, we have defined and characterized a resident multipotent cardiac mouse progenitor population, Bmi1+DR (for Bmi1+ Damage-Responsive cells). Bmi1+DR is one of the cell types with the lowest ROS (Reactive Oxygen Species) levels in the adult heart, being particularly characterized by their close relationship with cardiac vessels, most probably involved in the regulation of proliferation/maintenance of Bmi1+DR. This was proposed to work as their endothelial niche. Due to the scarcity of Bmi1+DR cells in the adult mouse heart, we have generated an immortalization/dis-immortalization model using Simian Vacuolating Virus 40-Large Antigen T (SV40-T) to facilitate their in vitro characterization. We have obtained a heterogeneous population of immortalized Bmi1+DR cells (Bmi1+DRIMM) that was validated attending to different criteria, also showing a comparable sensitivity to strong oxidative damage. Then, we concluded that the Bmi1-DRIMM population is an appropriate model for primary Bmi1+DR in vitro studies. The co-culture of Bmi1+DRIMM cells with endothelial cells protects them against oxidative damage, showing a moderate depletion in non-canonical autophagy and also contributing with a modest metabolic regulation.

Corticosterone administration immediately after peripuberty stress exposure does not prevent protracted stress-induced behavioral alterations

Stress-related disorders are commonly associated with abnormalities in hypothalamic-pituitary-adrenal (HPA) axis activity. Preliminary studies with cortisol administration in the aftermath of trauma suggest that this HPA axis hormone can potentially prevent maladaptive behavioral and biological stress responses. However, the efficacy of glucocorticoid administration during the peripuberty period has not been tested yet, although this lifetime is a critical time window in brain development and is highly sensitive to the harmful effects of stress. To further examine the short and long-lasting impact of glucocorticoids treatment given during the post-peripubertal stress period, the present study utilized a rat model of peripubertal stress-induced psychopathology and animals were subjected to a battery of tests to assess anxiety-like behaviors, exploratory behavior and reactivity to novelty at late adolescence and sociability, anhedonia and stress coping behaviors at adulthood. All the experiments were performed in males and females to evaluate the potential behavioral sex differences. Overall, our results demonstrated that rats exposed to peripubertal stress show decreased sociability in adulthood without differences in anxiety and depression-like behaviors. Moreover, this study shows that the administration of corticosterone after stress exposure at peripuberty does not prevent stress-induced behavioral alterations. However, we observed that some stress-induced behavioural alterations and corticosterone responses are sex-specific. Thus, the data obtained highlight that delineating sex differences in stress-related studies may ultimately contribute to the development of effective therapeutic interventions for each sex.

Strategies for measuring non-evoked pain in preclinical models of neuropathic pain: Systematic review

The development of new analgesics for neuropathic pain treatment is crucial. The failure of promising drugs in clinical trials may be related to the over-reliance on reflex-based responses (evoked pain) in preclinical drug testing, which may not fully represent clinical neuropathic pain, characterized by spontaneous non-evoked pain (NEP). Hence, strategies for assessing NEP in preclinical studies emerged. This systematic review identified 443 articles evaluating NEP in neuropathic pain models (mainly traumatic nerve injuries in male rodents). An exponential growth in NEP evaluation was observed, which was assessed using 48 different tests classified in 12 NEP-related outcomes: anxiety, exploration/locomotion, paw lifting, depression, conditioned place preference, gait, autotomy, wellbeing, facial grooming, cognitive impairment, facial pain expressions and vocalizations. Although most of these outcomes showed clear limitations, our analysis suggests that conditioning-associated outcomes, pain-related comorbidities, and gait evaluation may be the most effective strategies. Moreover, a minimal part of the studies evaluated standard analgesics. The greater emphasis on evaluating NEP aligning with clinical pain symptoms may enhance analgesic drug development, improving clinical translation.

Autophagic signaling promotes systems-wide remodeling in skeletal muscle upon oncometabolic stress by D2-HG

OBJECTIVES

Cachexia is a metabolic disorder and comorbidity with cancer and heart failure. The syndrome impacts more than thirty million people worldwide, accounting for 20% of all cancer deaths. In acute myeloid leukemia, somatic mutations of the metabolic enzyme isocitrate dehydrogenase 1 and 2 cause the production of the oncometabolite D2-hydroxyglutarate (D2-HG). Increased production of D2-HG is associated with heart and skeletal muscle atrophy, but the mechanistic links between metabolic and proteomic remodeling remain poorly understood. Therefore, we assessed how oncometabolic stress by D2-HG activates autophagy and drives skeletal muscle loss.

METHODS

We quantified genomic, metabolomic, and proteomic changes in cultured skeletal muscle cells and mouse models of IDH-mutant leukemia using RNA sequencing, mass spectrometry, and computational modeling.

RESULTS

D2-HG impairs NADH redox homeostasis in myotubes. Increased NAD+ levels drive activation of nuclear deacetylase Sirt1, which causes deacetylation and activation of LC3, a key regulator of autophagy. Using LC3 mutants, we confirm that deacetylation of LC3 by Sirt1 shifts its distribution from the nucleus into the cytosol, where it can undergo lipidation at pre-autophagic membranes. Sirt1 silencing or p300 overexpression attenuated autophagy activation in myotubes. In vivo, we identified increased muscle atrophy and reduced grip strength in response to D2-HG in male vs. female mice. In male mice, glycolytic intermediates accumulated, and protein expression of oxidative phosphorylation machinery was reduced. In contrast, female animals upregulated the same proteins, attenuating the phenotype in vivo. Network modeling and machine learning algorithms allowed us to identify candidate proteins essential for regulating oncometabolic adaptation in mouse skeletal muscle.

CONCLUSIONS

Our multi-omics approach exposes new metabolic vulnerabilities in response to D2-HG in skeletal muscle and provides a conceptual framework for identifying therapeutic targets in cachexia.

Behavioral neuroscience's inevitable SABV growing pains

The field of rodent behavioral neuroscience is undergoing two major sea changes: an ever-growing technological revolution, and worldwide calls to consider sex as a biological variable (SABV) in experimental design. Both have enormous potential to improve the precision and rigor with which the brain can be studied, but the convergence of these shifts in scientific practice has exposed critical limitations in classic and widely used behavioral paradigms. While our tools have advanced, our behavioral metrics - mostly developed in males and often allowing for only binary outcomes - have not. This opinion article explores how this disconnect has presented challenges for the accurate depiction and interpretation of sex differences in brain function, arguing for the expansion of current behavioral constructs to better account for behavioral diversity.

Sex differences in the social motivation of rats: Insights from social operant conditioning, behavioural economics, and video tracking

BACKGROUND

Social behaviour plays a key role in mental health and wellbeing, and developing greater understanding of mechanisms underlying social interaction-particularly social motivation-holds substantial transdiagnostic impact. Common rodent behavioural assays used to assess social behaviour are limited in their assessment of social motivation, whereas the social operant conditioning model can provide unique and valuable insights into social motivation. Further characterisation of common experimental parameters that may influence social motivation within the social operant model, as well as complementary methodological and analytical approaches, are warranted.

METHODS

This study investigated the effects of biological sex, housing condition, and time-of-day, on social motivation using the social operant model. This involved training rats to lever press (FR1) for 60-s access to a social reward (same-sex conspecific stimulus). Subjects were male and female Wistar rats, housed under individual or paired conditions, and sessions were conducted either in the mid-late light phase (ZT6-10) or early-mid dark phase (ZT13-17). A behavioural economics approach was implemented to measure social demand and the influence of stimulus partner sex (same- vs. opposite-sex stimulus) on social operant responding. Additionally, video tracking analyses were conducted to assess the degree of convergence between social appetitive and consummatory behaviours.

RESULTS

Biological sex, housing conditions, the interaction between sex and housing, and stimulus partner sex potently influenced social motivation, whereas time-of-day did not. Behavioural economics demonstrated that sex, housing, and their interaction influence both the hedonic set-point and elasticity of social demand. Video analysis of social interaction during social operant sessions revealed that social appetitive and consummatory behaviours are not necessarily convergent, and indicate potential social satiety. Lastly, oestrus phase of female experimental and stimulus rats did not impact social motivation within the model.

CONCLUSIONS

Social isolation-dependent sex differences exist in social motivation for rats, as assessed by social operant conditioning. The social operant model represents an optimal preclinical assay that comprehensively evaluates social motivation and offers a platform for future investigations of neurobiological mechanisms underlying sex differences in social motivation. These findings highlight the importance of continued consideration and inclusion of sex as a biological variable in future social operant conditioning studies. Humans are social creatures-our everyday interactions with others and the support this provides play a key role in our wellbeing. For those experiencing mental health conditions, people's motivation to engage with others can wane, which can lead them to withdraw from those who support them. Therefore, to develop better treatment strategies for these conditions, we need to gain a deeper understanding of social motivation. Studying social behaviour in animals can facilitate this investigation of social motivation as it allows for a causal understanding of underlying neurobiology that is not possible in human experiments. An optimal way to study social motivation in animals is using the social operant conditioning model, where rats learn to press a lever that opens a door and allows them to interact with another rat for a short time. This study characterised the social operant model by testing whether sex, housing conditions, time-of-day, and the sex of the stimulus partner influence rats' motivation to seek interaction with another rat. We found that female rats were more socially motivated than males, and that rats living alone were more motivated than those living with another rat; interestingly, this effect of housing affected females more than males. Regardless of sex, rats were more motivated to interact with a rat of the opposite sex. These findings provide insights into sex differences in social motivation in rats and new insights into the social operant model which will help guide future research into social motivation and other mental health conditions.

The Role of Twist1 in Chronic Pancreatitis-Associated Pancreatic Stellate Cells

In a healthy pancreas, pancreatic stellate cells (PaSCs) synthesize the basement membrane, which is mainly composed of type IV collagen and laminin. In chronic pancreatitis (CP), PaSCs are responsible for the production of a rigid extracellular matrix (ECM) that is mainly composed of fibronectin and type I/III collagen. Reactive oxygen species evoke the formation of the rigid ECM by PaSCs. One source of reactive oxygen species is NADPH oxidase (Nox) enzymes. Nox1 up-regulates the expression of Twist1 and matrix metalloproteinase-9 (MMP-9) in PaSCs from mice with CP. This study determined the functional relationship between Twist1 and MMP-9, and other PaSC-produced proteins, and the extent to which Twist1 regulates digestion of ECM proteins in CP. Twist1 induced the expression of MMP-9 in mouse PaSCs. The action of Twist1 was not selective to MMP-9 because Twist1 induced the expression of types I and IV collagen, fibronectin, transforming growth factor, and α-smooth muscle actin. Using luciferase assay, Twist1 in human primary PaSCs increased the expression of MMP-9 at the transcriptional level in an NF-κB dependent manner. The digestion of type I/III collagen by MMP-9 secreted by PaSCs from mice with CP depended on Twist1. Thus, Twist1 in PaSCs from mice with CP induces rigid ECM production and MMP-9 transcription in an NF-κB-dependent mechanism that selectively displays proteolytic activity toward type I/III collagen.

Cyclosorus Terminans Extract Alleviates Neuroinflammation in Insulin Resistant Rats

High-fat diet consumption for an extended period causes obesity, systemic metabolic disturbance, and brain insulin resistance, resulting in neuroinflammation. Although the beneficial effect of Cyclosorus terminans extract on obesity-related insulin resistance has been demonstrated, little is known about how it affects neuroinflammation and brain insulin resistance in obese rats. Male Wistar rats were given either a normal diet (ND, n = 6) or a high-fat diet (HFD, n = 24) for a total of 14 weeks. At the beginning of the week, 13 rats in the ND group were given vehicle orally for 2 weeks, while rats on HFD diets were randomized to one of four groups and given either vehicle, 100 mg/kg/day of Cyclosorus terminans extract, 200 mg/kg/day of Cyclosorus terminans extract, or 20 mg/kg/day of pioglitazone orally for 2 weeks. After the experimental period, blood and brain samples were taken to assess metabolic and brain parameters. HFD-fed rats had obesity, systemic and brain insulin resistance, brain inflammation, microglial and astrocyte hyperactivity, and brain necroptosis. Treatment with 200 mg/kg/day of Cyclosorus terminans extract and pioglitazone equally attenuated obesity, insulin resistance, brain insulin dysfunction, and neuroinflammation in insulin resistant rats. Our findings suggest that Cyclosorus terminans extract may hold promise as a therapeutic agent for insulin resistance and neuroinflammation in obese conditions.

Comparison of Implant-Retained Overdenture and Conventional Complete Denture: A Survey Study to Measure Patients' Satisfaction and Quality of Life in Dental School Clinics

Patient satisfaction and quality of life are integral to assessing oral health care quality. For many Americans still using conventional complete dentures (CDs) or implant-retained mandibular overdentures (IODs), it remains essential to consider improving their oral health outcomes and quality of life. Due to inexperienced student dentists providing dental care to dental school patients, patient grievances are generally considered a problem. Patient feedback and satisfaction have proven valuable resources for monitoring and improving patient safety. While CDs and IODs are the 2 leading treatment options for edentulism, more comparative studies in the literature need to compare their outcomes in a school setting. The research question that guided this comparative analysis was, "Is patient satisfaction and quality of life affected by the type of prostheses and provider?" A validated questionnaire was mailed to 520 individuals selected from records of patients who had received treatment for edentulous mandible at a student prosthodontic clinic at the University of Kentucky College of Dentistry from 2014 to 2016 with at least 1 year of follow-up time. A validated questionnaire for edentulous patients based on the Oral Health Impact Profile (OHIP-19) was used. In addition, information on patients' oral health-related quality of life, including questions related to the edentulous patients' satisfaction with their dentures, was collected. The response rate was 33% (N = 171). The study's findings confirm previous findings, suggesting that IODs may significantly impact oral health-related quality of life. Data show that 76% of the IOD group reported improvement in experience when using the implants to retain the mandibular denture. However, there were no statistically significant differences in the OHIP scores between overall CD and IOD patient groups. Males with IODs had lower physical pain, limitations, and disability scores than males with CD. However, females with IODs reported more significant concerns associated with a social disability and handicap domains. Comparing users who had experiences with both treatment options, this study discerned essential characteristics that contribute to increased patient satisfaction with IODs and identified significance in outcomes by gender. These findings guide prosthodontic practitioners' patient care practices and identify a continuing need to discuss CD and IOD treatment protocols within dental school curricula.

A systematic evidence map and bibliometric analysis of the behavioural impacts of pesticide exposure on zebrafish

Pesticides are indispensable in agriculture and have become ubiquitous in aquatic environments. Pesticides in natural environments can cause many negative impacts on aquatic species, ranging from mortality to sub-lethal physiological and behavioural changes. The complex sub-lethal impacts of pesticides are routinely tested on model species, with zebrafish (Danio rerio) being regularly used as a behavioural model. Although behavioural ecotoxicology research using zebrafish is increasing rapidly, we lack quantitative evidence to support which pesticides have been tested and how study designs are carried out. This shortcoming not only limits the deliberate planning for future primary studies to fill the knowledge gaps but also hinders evidence synthesis. To provide quantitative evidence of what pesticides are currently studied and what study designs are used, we combined a systematic evidence map approach and bibliometric analysis. This novel method has been coined research weaving and allows us to elicit gaps and clusters in our evidence base, whilst showing connections between authors and institutions. The methodology can be summarised in five primary steps: literature searching, screening, extraction, data analysis and bibliometric analysis. We identified four areas where research on the sub-lethal effects of pesticide exposure on zebrafish is lacking. First, some widely used pesticides, such as neonicotinoids, are understudied. Second, most studies do not report important elements of the study design, namely the sex and the life-stage of the zebrafish. Third, some behaviours, such as impacts of pesticide exposure on zebrafish cognition, are underexplored. And last, we revealed through the bibliometric analysis that most of the research is conducted in developed countries and there is limited cross country co-authorships. Upon identifying these gaps, we offer solutions for each limitation, emphasizing the importance of diverse global research output and cross-country co-authorships. Our systematic evidence map and bibliometric analysis provide valuable insights for helping to guide future research, which can be used to help support evidence-based policy decisions.

Neural correlates of novelty detection in the primary auditory cortex of behaving monkeys

The neural mechanisms underlying novelty detection are not well understood, especially in relation to behavior. Here, we present single-unit responses from the primary auditory cortex (A1) from two monkeys trained to detect deviant tones amid repetitive ones. Results show that monkeys can detect deviant sounds, and there is a strong correlation between late neuronal responses (250-350 ms after deviant onset) and the monkeys' perceptual decisions. The magnitude and timing of both neuronal and behavioral responses are increased by larger frequency differences between the deviant and standard tones and by increasing the number of standard tones preceding the deviant. This suggests that A1 neurons encode novelty detection in behaving monkeys, influenced by stimulus relevance and expectations. This study provides evidence supporting aspects of predictive coding in the sensory cortex.

A review of animal models for burning mouth syndrome: Mechanistic insights and knowledge gaps

OBJECTIVES

The underlying mechanisms of burning mouth syndrome (BMS) remain unclear leading to challenges and unsatisfactory management. Current treatments focus primarily on symptom relief, with few consistently achieving a 50% reduction in pain. This review aims to explore animal models of BMS to gain a better understanding of the underlying mechanisms and to discuss potential and existing knowledge gaps.

METHODS

A comprehensive review of PubMed® , Google Scholar, and Scopus was performed to assess advances and significant gaps of existing rodent models that mimic BMS-related symptoms.

RESULTS

Rodent models of BMS involve reproduction of dry-tongue, chorda tympani transection, or overexpression of artemin protein. Existing preclinical models tend to highlight one specific etiopathogenesis and often overlook sex- and hormone-specific factors.

CONCLUSION

Combining aspects from various BMS models could prove beneficial in developing comprehensive experimental designs and outcomes encompassing the multifaceted nature of BMS.

Errors elicit frontoparietal theta-gamma coupling that is modulated by endogenous estradiol levels

Cognitive control-related error monitoring is intimately involved in behavioral adaptation, learning, and individual differences in a variety of psychological traits and disorders. Accumulating evidence suggests that a focus on women's health and ovarian hormones is critical to the study of such cognitive brain functions. Here we sought to identify a novel index of error monitoring using a time-frequency based phase amplitude coupling (t-f PAC) measure and examine its modulation by endogenous levels of estradiol in females. Forty-three healthy, naturally cycling young adult females completed a flanker task while continuous electroencephalogram was recorded on four occasions across the menstrual cycle. Results revealed significant error-related t-f PAC between theta phase generated in fronto-central areas and gamma amplitude generated in parietal-occipital areas. Moreover, this error-related theta-gamma coupling was enhanced by endogenous levels of estradiol both within females across the cycle as well as between females with higher levels of average circulating estradiol. While the role of frontal midline theta in error processing is well documented, this paper extends the extant literature by illustrating that error monitoring involves the coordination between multiple distributed systems with the slow midline theta activity modulating the power of gamma-band oscillatory activity in parietal regions. They further show enhancement of inter-regional coupling by endogenous estradiol levels, consistent with research indicating modulation of cognitive control neural functions by the endocrine system in females. Together, this work identifies a novel neurophysiological marker of cognitive control-related error monitoring in females that has implications for neuroscience and women's health.

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.

Neuroimmune Activation and Microglia Reactivity in Female Rats Following Alcohol Dependence

The rates of alcohol use disorder among women are growing, yet little is known about how the female brain is affected by alcohol. The neuroimmune system, and specifically microglia, have been implicated in mediating alcohol neurotoxicity, but most preclinical studies have focused on males. Further, few studies have considered changes to the microglial phenotype when examining the effects of ethanol on brain structure and function. Therefore, we quantified microglial reactivity in female rats using a binge model of alcohol dependence, assessed through morphological and phenotypic marker expression, coupled with regional cytokine levels. In a time- and region-dependent manner, alcohol altered the microglial number and morphology, including the soma and process area, and the overall complexity within the corticolimbic regions examined, but no significant increases in the proinflammatory markers MHCII or CD68 were observed. The majority of cytokine and growth factor levels examined were similarly unchanged. However, the expression of the proinflammatory cytokine TNFα was increased, and the anti-inflammatory IL-10, decreased. Thus, female rats showed subtle differences in neuroimmune reactivity compared to past work in males, consistent with reports of enhanced neuroimmune responses in females across the literature. These data suggest that specific neuroimmune reactions in females may impact their susceptibility to alcohol neurotoxicity and other neurodegenerative events with microglial contributions.

Anticoagulation use is associated with lower fetal fraction and more indeterminate results

BACKGROUND

Maternal anticoagulation use may increase indeterminate result rates on cell-free DNA-based screening, but existing studies are confounded by inclusion of individuals with autoimmune disease, which alone is associated with indeterminate results. Changes in chromosome level Z-scores are proposed by others as a reason for indeterminate results, but the etiology of this is uncertain.

OBJECTIVE

This study aimed to evaluate differences in fetal fraction, indeterminate result rate, and total cell-free DNA concentration in individuals on anticoagulation without autoimmune disease compared with controls undergoing noninvasive prenatal screening. Secondly, using a nested case-control design, we evaluated differences in fragment size, GC-content, and Z-scores to evaluate laboratory-level test characteristics.

STUDY DESIGN

This was a retrospective single-institution study of pregnant individuals undergoing cell-free DNA-based noninvasive prenatal screening using low-pass whole-genome sequencing between 2017 and 2021. Individuals with autoimmune disease, suspected aneuploidy, and cases where fetal fraction was not reported were excluded. Anticoagulation included heparin-derived products (unfractionated heparin, low-molecular-weight heparin), clopidogrel, and fondaparinux, with a separate group for those on aspirin alone. An indeterminate result was defined as fetal fraction <4%. We evaluated the association between maternal anticoagulation or aspirin use, and fetal fraction, indeterminate results, and total cell-free DNA concentration using univariate and multivariate analyses, controlling for body mass index, gestational age at sample collection, and fetal sex. For the anticoagulation cohort, we compared laboratory-level test characteristics among cases (on anticoagulation) and a subset of controls. Lastly, we evaluated for differences in chromosome level Z-scores among those on anticoagulation with and without indeterminate results.

RESULTS

A total of 1707 pregnant individuals met the inclusion criteria. Of those, 29 were on anticoagulation and 81 were on aspirin alone. For those on anticoagulation, the fetal fraction was significantly lower (9.3% vs 11.7%; P<.01), the indeterminate result rate was significantly higher (17.2% vs 2.7%; P<.001), and the total cell-free DNA concentration was significantly higher (218 pg/μL vs 83.7 pg/μL; P<.001). Among those on aspirin alone, the fetal fraction was lower (10.6% vs 11.8%; P=.04); however, there were no differences in the rate of indeterminate results (3.7% vs 2.7%; P=.57) or total cell-free DNA concentration (90.1 pg/μL vs 83.8 pg/μL; P=.31). After controlling for maternal body mass index, gestational age at sample collection, and fetal sex, anticoagulation was associated with an >8-fold increase in the likelihood of an indeterminate result (adjusted odds ratio, 8.7; 95% confidence interval, 3.1-24.9; P<.001), but not aspirin (adjusted odds ratio, 1.2; 95% confidence interval, 0.3-4.1; P=.8). Anticoagulation was not associated with appreciable differences in cell-free DNA fragment size or GC-content. Although differences in chromosome 13 Z-scores were observed, none were observed for chromosomes 18 or 21, and this difference did not contribute to the indeterminate result call.

CONCLUSION

In the absence of autoimmune disease, anticoagulation use, but not aspirin, is associated with lower fetal fraction, higher total cell-free DNA concentration, and higher rates of indeterminate results. Anticoagulation use was not accompanied by differences in cell-free DNA fragment size or GC-content. Statistical differences in chromosome level Z-scores did not clinically affect aneuploidy detection. This suggests a likely dilutional effect by anticoagulation on cell-free DNA-based noninvasive prenatal screening assays contributing to low fetal fraction and indeterminate results, and not laboratory or sequencing-level changes.

Desmarestia anceps Montagne modulates inflammatory response in experimental periodontitis in male Wistar rats

OBJECTIVE

Desmarestia anceps Montagne (D. anceps) seaweed has been shown to play a range of biologic activities, such as anti-inflammatory and antioxidant properties. The purpose of this study was to investigate the effects of D. anceps on pathogenesis of ligature-induced experimental periodontitis in rats.

DESIGN

Fifty-four male Wistar rats were randomly divided into six groups. Doses of D. anceps (100 and 200 mg/kg) were administered for 14 days to animals with or without ligature-induced periodontitis, in order to compare to control groups (vehicle solution). Morphometric registration of alveolar bone loss and histological analysis were conducted. Inflammatory cells were counted on hematoxylin-eosin-stained slides. Immunohistochemical expressions for interleukin-1 beta (IL-1β), tumor necrosis factor (TNF-α), receptor activator of nuclear factor kappa-Β ligand (RANKL) and bone morphogenetic protein 2 (BMP-2) were evaluated.

RESULTS

Alveolar bone loss was higher in groups exposed to ligature-induced periodontitis, but no significant differences were observed comparing different treatment and control groups. Animals that received D. anceps extracts showed significant lower counts of inflammatory cells. D. anceps promoted increased expression of BMP-2 and inhibited IL-1β, TNF-α and RANKL.

CONCLUSION

D. anceps modulates inflammatory response in experimental periodontitis in rats. Further pharmacological and immunological analyses are warranted.

Multiple integrated social stress induces depressive-like behavioral and neural adaptations in female C57BL/6J mice

Despite women representing most of those affected by major depression, preclinical studies have focused almost exclusively on male subjects, partially due to a lack of ideal animal paradigms. As the persistent need regarding the sex balance of neuroscience research and female-specific pathology of mental disorders surges, the establishment of natural etiology-based and systematically validated animal paradigms for depression with female subjects becomes an urgent scientific problem. This study aims to establish, characterize, and validate a "Multiple Integrated Social Stress (MISS)" model of depression in female C57BL/6J mice by manipulating and integrating daily social stressors that females are experiencing. Female C57BL/6J mice randomly experienced social competition failure in tube test, modified vicarious social defeat stress, unescapable overcrowding stress followed by social isolation on each day, for ten consecutive days. Compared with their controls, female MISS mice exhibited a relatively decreased preference for social interaction and sucrose, along with increased immobility in the tail suspension test, which could last for at least one month. These MISS mice also exhibited increased levels of blood serum corticosterone, interleukin-6 L and 1β. In the pharmacological experiment, MISS-induced dysfunctions in social interaction, sucrose preference, and tail suspension tests were amended by systematically administrating a single dose of sub-anesthetic ketamine, a rapid-onset antidepressant. Compared with controls, MISS females exhibited decreased c-Fos activation in their anterior cingulate cortex, prefrontal cortex, nucleus accumbens and some other depression-related brain regions. Furthermore, 24 h after the last exposure to the paradigm, MISS mice demonstrated a decreased center zone time in the open field test and decreased open arm time in the elevated plus-maze test, indicating anxiety-like behavioral phenotypes. Interestingly, MISS mice developed an excessive nesting ability, suggesting a likely behavioral phenotype of obsessive-compulsive disorder. These data showed that the MISS paradigm was sufficient to generate pathological profiles in female mice to mimic core symptoms, serum biochemistry and neural adaptations of depression in clinical patients. The present study offers a multiple integrated natural etiology-based animal model tool for studying female stress susceptibility.

Sex diversity in the 21st century: Concepts, frameworks, and approaches for the future of neuroendocrinology

Sex is ubiquitous and variable throughout the animal kingdom. Historically, scientists have used reductionist methodologies that rely on a priori sex categorizations, in which two discrete sexes are inextricably linked with gamete type. However, this binarized operationalization does not adequately reflect the diversity of sex observed in nature. This is due, in part, to the fact that sex exists across many levels of biological analysis, including genetic, molecular, cellular, morphological, behavioral, and population levels. Furthermore, the biological mechanisms governing sex are embedded in complex networks that dynamically interact with other systems. To produce the most accurate and scientifically rigorous work examining sex in neuroendocrinology and to capture the full range of sex variability and diversity present in animal systems, we must critically assess the frameworks, experimental designs, and analytical methods used in our research. In this perspective piece, we first propose a new conceptual framework to guide the integrative study of sex. Then, we provide practical guidance on research approaches for studying sex-associated variables, including factors to consider in study design, selection of model organisms, experimental methodologies, and statistical analyses. We invite fellow scientists to conscientiously apply these modernized approaches to advance our biological understanding of sex and to encourage academically and socially responsible outcomes of our work. By expanding our conceptual frameworks and methodological approaches to the study of sex, we will gain insight into the unique ways that sex exists across levels of biological organization to produce the vast array of variability and diversity observed in nature.

Sex Differences in Stress Response: Classical Mechanisms and Beyond

Neuropsychiatric disorders, which are associated with stress hormone dysregulation, occur at different rates in men and women. Moreover, nowadays, preclinical and clinical evidence demonstrates that sex and gender can lead to differences in stress responses that predispose males and females to different expressions of similar pathologies. In this curated review, we focus on what is known about sex differences in classic mechanisms of stress response, such as glucocorticoid hormones and corticotrophin-releasing factor (CRF), which are components of the hypothalamicpituitary- adrenal (HPA) axis. Then, we present sex differences in neurotransmitter levels, such as serotonin, dopamine, glutamate and GABA, as well as indices of neurodegeneration, such as amyloid β and Tau. Gonadal hormone effects, such as estrogens and testosterone, are also discussed throughout the review. We also review in detail preclinical data investigating sex differences caused by recentlyrecognized regulators of stress and disease, such as the immune system, genetic and epigenetic mechanisms, as well neurosteroids. Finally, we discuss how understanding sex differences in stress responses, as well as in pharmacology, can be leveraged into novel, more efficacious therapeutics for all. Based on the supporting evidence, it is obvious that incorporating sex as a biological variable into preclinical research is imperative for the understanding and treatment of stress-related neuropsychiatric disorders, such as depression, anxiety and Alzheimer's disease.

Effects of naltrexone on amphetamine choice in rhesus monkeys and rats

Clinical amphetamine use is constrained by high abuse potential, and amphetamine use disorder is a persistent clinical problem with no approved medications for its treatment. The opioid antagonist naltrexone has been reported to reduce some abuse-related effects of amphetamine. This study used an amphetamine-versus-food choice procedure in rhesus monkeys and rats to test the hypothesis that naltrexone might serve as either (a) a maintenance medication for amphetamine use disorder treatment or (b) an "abuse-deterrent" adjunct to clinical amphetamine formulations. Male rhesus monkeys and male and female rats were trained to choose between increasing unit doses of intravenous amphetamine and an alternative food reinforcer during daily behavioral sessions. Experiment 1 evaluated effectiveness of continuous naltrexone maintenance to reduce amphetamine-versus-food choice in both monkeys and rats. Experiment 2 combined naltrexone with amphetamine in fixed-proportion amphetamine + naltrexone mixtures to evaluate the effectiveness of naltrexone in both species to reduce mixture choice relative to amphetamine-alone choice. Amphetamine maintained a dose-dependent increase in amphetamine choice in both monkeys and rats. Naltrexone maintenance did not significantly decrease amphetamine choice in either species. Addition of naltrexone to amphetamine reduced amphetamine choices per session in monkeys, but behavior was not reallocated to food choice, and in rats, the addition of naltrexone only decreased food choice without significantly affecting amphetamine choice. These results argue against the use of naltrexone as either (a) a maintenance medication for treatment of amphetamine use disorder or (b) an "abuse-deterrent" adjunct to amphetamine for clinical applications. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Female aging: when translational models don't translate

For many pathologies associated with aging, female patients present with higher morbidity and more frequent adverse events from treatments compared to male patients. While preclinical models are the foundation of our mechanistic understanding of age-related diseases, the most common models fail to recapitulate archetypical female aging trajectories. For example, while over 70% of the top age-related diseases are influenced by the systemic effects of reproductive senescence, we found that preclinical studies that include menopausal phenotypes modeling those seen in humans make up <1% of published aging biology research. The long-term impacts of pregnancy, birthing and breastfeeding are also typically omitted from preclinical work. In this Perspective, we summarize limitations in the most commonly used aging models, and we provide recommendations for better incorporating menopause, pregnancy and other considerations of sex in vivo and in vitro. Lastly, we outline action items for aging biology researchers, journals, funding agencies and animal providers to address this gap.

Capparis sepiaria's root bark aqueous lyophilisate shows antiamnesic properties on scopolamine induce cognitive impairment in mice

Capparis sepiaria (Capparaceae) is a plant used in African traditional medicine to treat psychiatic disorders. The aim of this study was to assess the anti-amnesic effect of aqueous lyophilisate of the root bark of Capparis sepiaria (C. sepiaria) on scopolamine-induced animal model of memory impairment using Swiss albino adult mice of both sexes. Memory integrity was assessed by Morris water Maze test, Novel Object Recognition (NOR) and Object-location memory (OLT) tasks were used to assess behavioural components of memory processes and learning. Malondialdehyde (MDA), reduced glutathione (GSH), NO levels and catalase were used to assess oxidative stress while acethylcholinesterase activity was used to evaluate acetylcholine activity in the hippocampus tissues. The quantitative phytochemistry and acute toxicity of the roots of C. sepiaria were also evaluated. The aqueous lyophilisate of C. sepiaria at doses of 10 mg/kg and 40 mg/kg significantly increased the discrimination index in the Morris Water Maze and the objet location tasks. The aqueous lyophilisate of C. sepiaria significantly increased hippocampal GSH and catalase levels and decreased hippocampal MDA, NO levels and achetylcholinesterase (AChE) activities. The aqueous lyophilisate of C. sepiaria showed no acute toxicity with a LD50 > 5000 mg/kg, and revealed a content of flavonoids, tannins and phenols. These results suggest that C. sepiaria improve memory impairment induced by scopolamine and therefore possess antiamnesic properties. These properties would result from a modulation of cholinergic neurotransmission as well as an antioxidant activity of the plant.

Knockout or inhibition of USP30 protects dopaminergic neurons in a Parkinson's disease mouse model

Mutations in SNCA, the gene encoding α-synuclein (αSyn), cause familial Parkinson's disease (PD) and aberrant αSyn is a key pathological hallmark of idiopathic PD. This α-synucleinopathy leads to mitochondrial dysfunction, which may drive dopaminergic neurodegeneration. PARKIN and PINK1, mutated in autosomal recessive PD, regulate the preferential autophagic clearance of dysfunctional mitochondria ("mitophagy") by inducing ubiquitylation of mitochondrial proteins, a process counteracted by deubiquitylation via USP30. Here we show that loss of USP30 in Usp30 knockout mice protects against behavioral deficits and leads to increased mitophagy, decreased phospho-S129 αSyn, and attenuation of SN dopaminergic neuronal loss induced by αSyn. These observations were recapitulated with a potent, selective, brain-penetrant USP30 inhibitor, MTX115325, with good drug-like properties. These data strongly support further study of USP30 inhibition as a potential disease-modifying therapy for PD.

Sodium alendronate is an effective adjunctive therapy for treating periodontitis in male rats treated with anticancer chemotherapy

OBJECTIVES

To assess sodium alendronate as a local adjunctive therapy for treating experimental periodontitis in male rats treated with chemotherapy.

DESIGN

One-hundred-eighty male rats were randomly divided into two groups (n = 90) based on the systemic treatments: PSS, physiological saline solution; and 5-Fluorouracil, and then, subdivided into three subgroups (n = 30): NT, no treatment; scaling and root planing; and sodium alendronate. Treatments were performed 7 days after induction of experimental periodontitis. Specimens were collected at 14, 22, and 37 days after induction. Alveolar bone level, percentage of bone in the furcation, percentage of non-vital bone in the furcation, histopathologic features, and immunolabeling pattern for tartrate-resistant acid phosphatase (TRAP) and osteocalcin (OCN) were evaluated.

RESULTS

The lowest amount of alveolar bone and highest amount of non-vital bone was found in group 5-Fluorouracil when no treatment was performed. In animals receiving 5-Flurouracil and subjected to periodontal treatment, adjunctive sodium alendronate resulted in higher percentage of bone in the furcation and higher alveolar bone loss, when compared with scaling and root planing alone. Better structural and cellularity patterns were found in the periodontal tissues when sodium alendronate was used, regardless of systemic treatment. Higher TRAP-expression was found when no treatment was performed. Sodium alendronate didn't affect the immunolabeling pattern of osteocalcin in the presence of 5-Fluorouracil.

CONCLUSION

Adjunctive therapy with local sodium alendronate prevented alveolar bone loss and improved the histopathological features of the periodontal tissues following scaling and root planing in male rats with experimental periodontitis receiving anticancer chemotherapy with 5-Fluorouracil.

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.

The Aqueous Lyophilisate of Alchemilla Kiwuensis Engl. (Rosaceae) Displays Antiepileptogenic and Antiepileptic Effects on PTZ-induced Kindling in rats: Evidence of Modulation of Glutamatergic and GABAergic Pathways Coupled to Antioxidant Properties

Alchemilla kiwuensis Engl. (Rosaceae) (A. kiwuensis) is an herbaceous plant traditionally used by Cameroonians to treat epilepsy and other central nervous system disorders. The present study evaluated the antiepileptogenic and antiepileptic effects of A. kiwuensis (40 mg/kg, 80 mg/kg) following Pentylenetetrazole (PTZ)-induced kindling as well as its sub-chronic toxicity. Following an initial i.p administration of a challenge dose (70 mg/kg), Wistar rats of both sexes received sub convulsive doses (35 mg/kg) of PTZ every other day, one hour after the oral gavage of animals with treatments, until two consecutive stage 4, in all animals of negative control. Seizure progression, latency, duration, and repetition were noted. Twenty-four hours later, animals were dissected to extract their hippocampi. The resulting homogenates were used to evaluate Malondialdehyde, reduced glutathione, catalase activity, GABA, GABA-Transaminase, glutamate, glutamate transporter 2, IL-1β and TGF-1 β. Sub-chronic toxicity was conducted according to OECD 407 guidelines. The lyophilisate of A. kiwuensis significantly increased the latency of seizure appearance, delayed seizure progression and decreased seizure repetition and duration. Biochemical analysis revealed that the lyophilisate significantly increased the catalase activity, reduced glutathione, GABA, glutamate transporter 2 and TGF-1B levels. The lyophilisate equally caused a significant decreased in the GABA-Transaminase activity, malondialdehyde, and IL-1 β levels. There was no noticeable sign of toxicity. A. kiwuensis possesses antiepileptic and antiepiletogenic effects by enhancing GABAergic neurotransmission and antioxidant properties, coupled to modulation of glutamatergic and neuroinflammatory pathways and is innocuous in a sub-chronic model. These justifies its local use for the treatment of epilepsy.

A review of the historical use of sex as a biological variable in the American Journal of Physiology-Heart and Circulatory Physiology

Despite National Institute of Health (NIH) mandates requiring sex as a biological variable (SABV), female underrepresentation persists in research, driving the American Journal of Physiology-Heart and Circulatory Physiology (Am J Physiol-Heart Circ) to publish SABV expectations in 2021. To determine progress within the Am J Physiol-Heart Circ, this mini-review evaluated SABV during the first 6 mo of each decade from 1980 to 2020, and 2019, to mitigate pandemic influence. Of the 1,205 articles published, 1,087 articles were included in this review (articles without original research subjects were excluded), of which 72.9% identified subjects. There were consistently fewer female human participants than males, except within 2019 (1980: females n = 3, males n = 5; 1990: females n = 70, males n = 199; 2000: females n = 305, males n = 355; 2010: females n = 186, males n = 472; 2019: females n = 1,695, males n = 1,550; 2020: females n = 1,157, males n = 1,222) and fewer female animals than males (1980: females n = 58, males n = 1,291; 1990: females n = 447, males n = 2,628; 2000: females n = 590, males n = 3,083; 2010: females n = 663, males n = 4,517; 2019: females n = 338, males n = 1,340; 2020: females n = 1,372, males n = 1,973). Only 16 (12.3%) articles including humans discussed SABV from 1980 to 2020. There are persistent SABV disparities within Am J Physiol-Heart Circ with some improvements in recent years. It is imperative that organizations such as the American Physiological Society and NIH foster an expectation of SABV as the norm, not the exception.

Leveraging Digital Health to Improve the Cardiovascular Health of Women

Purpose of Review

In this review, we present a comprehensive discussion on the population-level implications of digital health interventions (DHIs) to improve cardiovascular health (CVH) through sex- and gender-specific prevention strategies among women.

Recent Findings

Over the past 30 years, there have been significant advancements in the diagnosis and treatment of cardiovascular diseases, a leading cause of morbidity and mortality among men and women worldwide. However, women are often underdiagnosed, undertreated, and underrepresented in cardiovascular clinical trials, which all contribute to disparities within this population. One approach to address this is through DHIs, particularly among racial and ethnic minoritized groups. Implementation of telemedicine has shown promise in increasing adherence to healthcare visits, improving BP monitoring, weight control, physical activity, and the adoption of healthy behaviors. Furthermore, the use of mobile health applications facilitated by smart devices, wearables, and other eHealth (defined as electronically delivered health services) modalities has also promoted CVH among women in general, as well as during pregnancy and the postpartum period. Overall, utilizing a digital health approach for healthcare delivery, decentralized clinical trials, and incorporation into daily lifestyle activities has the potential to improve CVH among women by mitigating geographical, structural, and financial barriers to care.

Summary

Leveraging digital technologies and strategies introduces novel methods to address sex- and gender-specific health and healthcare disparities and improve the quality of care provided to women. However, it is imperative to be mindful of the digital divide in specific populations, which may hinder accessibility to these novel technologies and inadvertently widen preexisting inequities.

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.

Electrostatically assembled wound dressings deliver pro-angiogenic anti-miRs preferentially to endothelial cells

Chronic non-healing wounds occur frequently in individuals affected by diabetes, yet standard-of-care treatment leaves many patients inadequately treated or with recurring wounds. MicroRNA (miR) expression is dysregulated in diabetic wounds and drives an anti-angiogenic phenotype, but miRs can be inhibited with short, chemically-modified RNA oligonucleotides (anti-miRs). Clinical translation of anti-miRs is hindered by delivery challenges such as rapid clearance and uptake by off-target cells, requiring repeated injections, excessively large doses, and bolus dosing mismatched to the dynamics of the wound healing process. To address these limitations, we engineered electrostatically assembled wound dressings that locally release anti-miR-92a, as miR-92a is implicated in angiogenesis and wound repair. In vitro, anti-miR-92a released from these dressings was taken up by cells and inhibited its target. An in vivo cellular biodistribution study in murine diabetic wounds revealed that endothelial cells, which play a critical role in angiogenesis, exhibit higher uptake of anti-miR eluted from coated dressings than other cell types involved in the wound healing process. In a proof-of-concept efficacy study in the same wound model, anti-miR targeting anti-angiogenic miR-92a de-repressed target genes, increased gross wound closure, and induced a sex-dependent increase in vascularization. Overall, this proof-of-concept study demonstrates a facile, translational materials approach for modulating gene expression in ulcer endothelial cells to promote angiogenesis and wound healing. Furthermore, we highlight the importance of probing cellular interactions between the drug delivery system and the target cells to drive therapeutic efficacy.

Impact of sex on ventral hernia repair outcomes: A systematic review and meta-analysis

BACKGROUND

Given the variability in abdominal physiology and hernia presentation between sexes, better comprehension of sex-related differences in outcomes would tailor surgical approach and counseling regarding postoperative outcomes. This meta-analysis aims to appraise the effect of sex on the outcomes of ventral hernia repair.

METHODS

A literature search in PubMed, EMBASE and Cochrane selected studies comparing outcomes of ventral hernia repair between sexes. Postoperative outcomes were assessed by pooled and meta-analysis. Statistical analysis was performed using RevMan 5.4.

RESULTS

We screened 3128 studies, reviewed 133, and included 18 observational studies, which encompassed 220,799 patients following ventral hernia repair. Postoperative chronic pain was significantly higher in female (OR 1,9; 95% CI 1,64-2,2; p ​< ​0,001). There were no significant differences in complications, readmission, or recurrence rates between females and males.

CONCLUSION

Female sex is associated with a higher risk of postoperative chronic pain following ventral hernia repair.

Sex-Specific Reliability of Lower-Limb Corticospinal Excitability and Silent Periods

ABSTRACT

Pagan, JI, Harmon, KK, Girts, RM, MacLennan, RJ, Beausejour, JP, Hernandez-Sarabia, JA, Coker, NA, Carr, JC, Ye, X, DeFreitas, JM, and Stock, MS. Sex-specific reliability of lower-limb corticospinal excitability and silent periods. J Strength Cond Res 37(9): 1882-1887, 2023-Transcranial magnetic stimulation (TMS) is a research tool that has potential to provide new insights into strength training-induced adaptations. However, using TMS to study the lower limbs is challenging, and sex-specific reliability has yet to be reported. We examined the reliability of corticospinal excitability and silent periods for the rectus femoris, vastus lateralis, and biceps femoris in both sexes. Thirteen males and 14 females reported to the laboratory twice. During both trials, a double cone coil was used to deliver 20 pulses to the rectus femoris hotspot with a stimulator output of 130% of active motor threshold. Motor-evoked potential peak-to-peak amplitude, which reflects corticospinal excitability, and silent period duration were quantified. Our results offer 4 novel findings. First, corticospinal excitability and silent period demonstrated higher reliability for the females. Second, regardless of sex and muscle, the silent period was more reliable than corticospinal excitability. Third, reliability was highest for our target muscle (rectus femoris), with lower reliability for the vastus lateralis and biceps femoris, suggesting that these methods cannot be used to study coactivation. Fourth, active motor threshold showed less variability than corticospinal excitability and silent period but increased at trial 2 in females. Many of the intraclass correlation coefficients were excellent (≥0.90), although we attribute this finding to variability between subjects. Reliability of lower-limb TMS measures may be sex, muscle, and variable dependent. Our findings suggest that both males and females should be included in lower-limb TMS research, although combining data between sexes should be approached cautiously.

Establishment of a Private Foundation-Academic Partnership to Promote Careers of Early-Stage Investigators Examining the Influence of Sex and Gender on Health and Health Care

Biological sex and gender-based constructs contribute significantly to the diversity of disease outcomes and treatment responses across the life course. To promote research considering sex and gender, the National Institutes of Health (NIH) Office of Research on Women's Health (ORWH) launched the Specialized Centers of Research Excellence (SCORE) on sex differences program. The Career Enhancement Core (CEC) of the Johns Hopkins SCORE on Sex and Age Differences in Immunity to Influenza (SADII) partnered with the Foundation for Gender-Specific Medicine, which matched NIH funding to support seed grants. Over 3 years we awarded 12 (10 were women faculty) seed grants to early-stage investigators. One year after the award, the seed grant awardees highlighted their progress, including publications, grant applications, and abstracts. All awardees noted challenges with their progress related to the COVID-19 pandemic and supply chain delays and shared suggestions for improving the programming of the CEC. They also highlighted the multiple ways the awards had helped them gain pilot data toward larger grants, build collaborative relationships, and present at the annual SCORE symposium. We describe a model and evidence supporting a private-academic collaboration to support the careers of early-stage investigators conducting research related to sex and gender.

Gender Differences in a Mouse Model of Hepatocellular Carcinoma Revealed Using Multi-Modal Imaging

The worldwide incidence of hepatocellular carcinoma (HCC) continues to rise, in part due to poor diet, limited exercise, and alcohol abuse. Numerous studies have suggested that the loss or mutation of PTEN plays a critical role in HCC tumorigenesis through the activation of the PI3K/Akt signaling axis. The homozygous knockout of PTEN in the livers of mice results in the accumulation of fat (steatosis), inflammation, fibrosis, and eventually progression to HCC. This phenotype bears a striking similarity to non-alcoholic steatohepatitis (NASH) which is thought to occupy an intermediate stage between non-alcoholic fatty liver disease (NAFLD), fibrosis, and HCC. The molecular and physiological phenotypes that manifest during the transition to HCC suggest that molecular imaging could provide a non-invasive screening platform to identify the hallmarks of HCC initiation prior to the presentation of clinical disease. We have carried out longitudinal imaging studies on the liver-specific PTEN knockout mouse model using CT, MRI, and multi-tracer PET to interrogate liver size, steatosis, inflammation, and apoptosis. In male PTEN knockout mice, significant steatosis was observed as early as 3 months using both magnetic resonance spectroscopy (MRS) and computed tomography (CT). Enhanced uptake of the apoptosis tracer 18F-TBD was also observed in the livers of male PTEN homozygous knockout mice between 3 and 4 months of age relative to heterozygous knockout controls. Liver uptake of the inflammation tracer [18F]4FN remained relatively low and constant over 7 months in male PTEN homozygous knockout mice, suggesting the suppression of high-energy ROS/RNS with PTEN deletion relative to heterozygous males where the [18F]4FN liver uptake was elevated at early and late time points. All male PTEN homozygous mice developed HCC lesions by month 10. In contrast to the male cohort, only 20% (2 out of 10) of female PTEN homozygous knockout mice developed HCC lesions by month 10. Steatosis was significantly less pronounced in the female PTEN homozygous knockout mice relative to males and could not accurately predict the eventual occurrence of HCC. As with the males, the [18F]4FN uptake in female PTEN homozygous knockout mice was low and constant throughout the time course. The liver uptake of 18F-TBD at 3 and 4.5 months was higher in the two female PTEN knockout mice that would eventually develop HCC and was the most predictive imaging biomarker for HCC in the female cohort. These studies demonstrate the diagnostic and prognostic role of multi-modal imaging in HCC mouse models and provide compelling evidence that disease progression in the PTEN knockout model is highly dependent on gender.

Sex and gender as critical and distinct contributors to the human brain-gut-microbiome axis

The brain-gut-microbiome axis (BGMA) is a pivotal contributor to human health. A large body of research, especially from animal models, has revealed bidirectional, causal relationships between the BGMA and sex. In particular, sex steroids appear to be affected by the BGMA, to influence the BGMA, and to moderate environmental effects on the BGMA. However, animal research on the relationship between sex and the BGMA has not translated well to human models. We contend that this is due in part to an oversimplified approach to sex: although BGMA researchers have traditionally approached sex as a unidimensional, dichotomous variable, it is in fact multidimensional and is comprised of both multi-categorical and continuous dimensions. We also contend that research on the BGMA in humans should approach gender as a variable that is distinct from sex and that gender may influence the BGMA through pathways that are independent from the effects of sex alone. Research practices that consider the complexity and distinctiveness of sex and gender in relation to the human BGMA will not only yield improved understanding of this consequential system, but will also enhance the development of treatments for adverse health outcomes with BGMA-related etiologies. We conclude with recommendations for the implementation of such practices.

Mapping strategies towards improved external validity in preclinical translational research

INTRODUCTION

Translation is about successfully bringing findings from preclinical contexts into the clinic. This transfer is challenging as clinical trials frequently fail despite positive preclinical results. Limited robustness of preclinical research has been marked as one of the drivers of such failures. One suggested solution is to improve the external validity of in vitro and in vivo experiments via a suite of complementary strategies.

AREAS COVERED

In this review, the authors summarize the literature available on different strategies to improve external validity in in vivo, in vitro, or ex vivo experiments; systematic heterogenization; generalizability tests; and multi-batch and multicenter experiments. Articles that tested or discussed sources of variability in systematically heterogenized experiments were identified, and the most prevalent sources of variability are reviewed further. Special considerations in sample size planning, analysis options, and practical feasibility associated with each strategy are also reviewed.

EXPERT OPINION

The strategies reviewed differentially influence variation in experiments. Different research projects, with their unique goals, can leverage the strengths and limitations of each strategy. Applying a combination of these approaches in confirmatory stages of preclinical research putatively increases the chances of success in clinical studies.

Achieving Equity in Emergency Medicine Quality Measures Requires a Sex and Gender Lens

BACKGROUND

Quality measures within Emergency Medicine (EM) were developed to standardize and improve care. Their development has been limited by lack of consideration of sex- and gender-based differences. Research has suggested that sex and gender can impact clinical care and treatment. Inclusion of sex and gender differences is needed to create EM quality measures that are equitable to all.

OBJECTIVE

The aim of the review is to provide a brief history of EM quality measures and the value of considering sex- and gender-based evidence in their development to ensure equity, using acute myocardial infarction (AMI) as an example.

DISCUSSION

Current quality measures related to AMI, such as time-to-electrocardiogram and door-to-balloon time in percutaneous coronary intervention, may have important and modifiable disparities when stratified by sex. Even when presenting with signs and symptoms of AMI, women experience delayed time to diagnosis and treatment. Few studies have considered interventions to mitigate these differences. However, the data available suggest that sex-based disparities can be minimized by implementation of strategies such as a quality control checklist.

CONCLUSIONS

Quality measures were created to deliver high-quality, evidence-based, and standardized care, but without the inclusion of sex and gender metrics, they may not advance care to an equitable level.

Steroid hormones: risk and resilience in women's Alzheimer disease

More women have Alzheimer disease (AD) than men, but the reasons for this phenomenon are still unknown. Including women in clinical research and studying their biology is key to understand not just their increased risk but also their resilience against the disease. In this sense, women are more affected by AD than men, but their reserve or resilience mechanisms might delay symptom onset. The aim of this review was to explore what is known about mechanisms underlying women's risk and resilience in AD and identify emerging themes in this area that merit further research. We conducted a review of studies analyzing molecular mechanisms that may induce neuroplasticity in women, as well as cognitive and brain reserve. We also analyzed how the loss of steroid hormones in aging may be linked to AD. We included empirical studies with human and animal models, literature reviews as well as meta-analyses. Our search identified the importance of 17-b-estradiol (E2) as a mechanism driving cognitive and brain reserve in women. More broadly, our analysis revealed the following emerging perspectives: (1) the importance of steroid hormones and their effects on both neurons and glia for the study of risk and resilience in AD, (2) E2's crucial role in women's brain reserve, (3) women's verbal memory advantage as a cognitive reserve factor, and (4) E2's potential role in linguistic experiences such as multilingualism and hearing loss. Future directions for research include analyzing the reserve mechanisms of steroid hormones on neuronal and glial plasticity, as well as identifying the links between steroid hormone loss in aging and risk for AD.

Phase Angle in Head and Neck Cancer: A Sex-Differential Analysis from Biological and Clinical Behavior to Health-Related Quality of Life

Head and neck cancer (H&NC) is a diverse category of tumors related to malignancies in the common aerodigestive pathway, with high metabolic rate, poor nutritional and treatment outcomes, and elevated mortality despite the best standard treatment. Herein, we focus on determining how the phase angle (PA) differs across sex as a predictor of poor prognosis, low quality-of-life (QoL) scores, and mortality in patients with head and neck cancer. This follow-up study presents a sex-differential analysis in a prospective cohort of 139 head and neck cancer patients categorized by sex as male (n = 107) and female (n = 32). Patients were compared in terms of nutritional, biochemical, and quality-of-life indicators between low and normal PA in women (<3.9° (n = 14, 43.75%) and ≥3.9°) and men (<4.5° (n = 62, 57.9%) and ≥4.5°). Our results show that most patients were in locally advanced clinical stages (women: n = 21 (65.7%); men: n = 67 (62.6%)) and that patients with low PA had a lower punctuation in parameters such as handgrip strength, four-meter walking speed, albumin, C-reactive protein (CRP), and CRP/albumin ratio (CAR), as well as the worst QoL scores in functional and symptomatic scales in both the male and female groups. A comparison between sexes revealed significant disparities; malnourishment and tumor cachexia related to an inflammatory state was more evident in the women's group.

Statistical simulations show that scientists need not increase overall sample size by default when including both sexes in in vivo studies

In recent years, there has been a strong drive to improve the inclusion of animals of both sexes in the design of in vivo research studies, driven by a need to increase sex representation in fundamental biology and drug development. This has resulted in inclusion mandates by funding bodies and journals, alongside numerous published manuscripts highlighting the issue and providing guidance to scientists. However, progress is slow and barriers to the routine use of both sexes remain. A frequent, major concern is the perceived need for a higher overall sample size to achieve an equivalent level of statistical power, which would result in an increased ethical and resource burden. This perception arises from either the belief that sex inclusion will increase variability in the data (either through a baseline difference or a treatment effect that depends on sex), thus reducing the sensitivity of statistical tests, or from misapprehensions about the correct way to analyse the data, including disaggregation or pooling by sex. Here, we conduct an in-depth examination of the consequences of including both sexes on statistical power. We performed simulations by constructing artificial datasets that encompass a range of outcomes that may occur in studies studying a treatment effect in the context of both sexes. This includes both baseline sex differences and situations in which the size of the treatment effect depends on sex in both the same and opposite directions. The data were then analysed using either a factorial analysis approach, which is appropriate for the design, or a t test approach following pooling or disaggregation of the data, which are common but erroneous strategies. The results demonstrate that there is no loss of power to detect treatment effects when splitting the sample size across sexes in most scenarios, providing that the data are analysed using an appropriate factorial analysis method (e.g., two-way ANOVA). In the rare situations where power is lost, the benefit of understanding the role of sex outweighs the power considerations. Additionally, use of the inappropriate analysis pipelines results in a loss of statistical power. Therefore, we recommend analysing data collected from both sexes using factorial analysis and splitting the sample size across male and female mice as a standard strategy.

Sex differences in pharmacological interventions and their effects on lifespan and healthspan outcomes: a systematic review

With an increasing aging population, the burden of age-related diseases magnifies. To alleviate this burden, geroprotection has been an area of intense research focus with the development of pharmacological interventions that target lifespan and/or healthspan. However, there are often sex differences, with compounds mostly tested in male animals. Given the importance of considering both sexes in preclinical research, this neglects potential benefits for the female population, as interventions tested in both sexes often show clear sexual dimorphisms in their biological responses. To further understand the prevalence of sex differences in pharmacological geroprotective intervention studies, we performed a systematic review of the literature according to the PRISMA guidelines. Seventy-two studies met our inclusion criteria and were classified into one of five subclasses: FDA-repurposed drugs, novel small molecules, probiotics, traditional Chinese medicine, and antioxidants, vitamins, or other dietary supplements. Interventions were analyzed for their effects on median and maximal lifespan and healthspan markers, including frailty, muscle function and coordination, cognitive function and learning, metabolism, and cancer. With our systematic review, we found that twenty-two out of sixty-four compounds tested were able to prolong both lifespan and healthspan measures. Focusing on the use of female and male mice, and on comparing their outcomes, we found that 40% of studies only used male mice or did not clarify the sex. Notably, of the 36% of pharmacologic interventions that did use both male and female mice, 73% of these studies showed sex-specific outcomes on healthspan and/or lifespan. These data highlight the importance of studying both sexes in the search for geroprotectors, as the biology of aging is not the same in male and female mice. Systematic Review Registration: [website], identifier [registration number].

Male and female C57BL/6 mice display drug-induced aversion and reward in the combined conditioned taste avoidance/conditioned place preference procedure

BACKGROUND

Drugs of abuse have rewarding and aversive effects that, in balance, impact abuse potential. Although such effects are generally examined in independent assays (e.g., CPP and CTA, respectively), a number of studies have examined these effects concurrently in rats in a combined CTA/CPP design. The present study assessed if similar effects can be produced in mice which would allow for determining how each is affected by subject and experiential factors relevant to drug use and abuse and the relationship between these affective properties.

METHODS

Male and female C57BL/6 mice were exposed to a novel saccharin solution, injected (IP) with saline or 5.6, 10 or 18 mg/kg of the synthetic cathinone, methylone, and placed on one side of the place conditioning apparatus. The following day, they were injected with saline, given access to water and placed on the other side of the apparatus. After four conditioning cycles, saccharin avoidance and place preferences were assessed in a final two-bottle CTA test and a CPP Post-Test, respectively.

RESULTS

In the combined CTA/CPP design, mice acquired a significant dose-dependent CTA (p = 0.003) and a significant CPP (p = 0.002). These effects were independent of sex (all p's > 0.05). Further, there was no significant relationship between the degree of taste avoidance and place preference (p > 0.05).

CONCLUSIONS

Similar to rats, mice displayed significant CTA and CPP in the combined design. It will be important to extend this design in mice to other drugs and to examine the impact of different subject and experiential factors on these effects to facilitate predictions of abuse liability.