A less stressful alternative to oral gavage for pharmacological and toxicological studies in mice

Fluoxetine attenuates the anxiolytic effects of the probiotic VSL#3 in a stress-vulnerable genetic line of aves in the chick social-separation stress test, a dual screening assay

Anxiety disorders represent one of the most common and debilitating illnesses worldwide. However, the development of novel therapeutics for anxiety disorders has lagged compared to other mental illnesses. A growing body of research suggests the gut microbiota plays a role in the etiopathology of anxiety disorders and may, therefore, serve as a novel target for their treatment through the use of probiotics. The use of dietary supplements like probiotics is increasing and their interaction with pharmacotherapies is not well understood. Utilizing the chick social-separation stress test, the primary aim of this study was to evaluate the commercially-available multi-strain probiotic found in VSL#3 for potential anxiolytic-like and/or antidepressant-like effects in the stress-vulnerable Black Australorp genetic line. A secondary aim was to evaluate the interaction between probiotics and the SSRI fluoxetine. Animals were treated with either saline, probiotics, fluoxetine, or probiotics + fluoxetine for 8 days prior to exposure to a 90-min isolation stressor that produces both a panic-like (i.e., anxiety-like) state followed by a state of behavioral despair (i.e., depression-like). The 8-day probiotic regimen produced anxiolytic-like effects but did not attenuate behavioral despair. Fluoxetine failed to significantly alter behavior in either of the two phases. Moreover, the combination of fluoxetine with probiotics attenuated the anxiolytic-like effects of probiotics. The fluoxetine + probiotics combination had no effect on behavioral despair. The results of the current study align with other preclinical studies and some clinical trials suggesting probiotics may offer beneficial effects on anxiety. Investigations examining the anxiolytic-like mechanism of probiotics are needed before any conclusions can be made. Additionally, as the use of probiotics becomes more popular, research on the interactions between probiotic-microbiota and psychotropic medications is necessary.

Repercussions of Long-Term Naproxen Administration on LPS-Induced Periodontitis in Male Mice

AIMS

Chronic periodontitis is the sixth most prevalent disease worldwide and the leading cause of tooth loss in adults. With growing attention on the role of inflammatory and immune responses in its pathogenesis, there is an urgent need to evaluate host-modulatory agents. Non-steroidal anti-inflammatory drugs (NSAIDs) drugs play a crucial role in managing inflammatory conditions. This study examined the repercussions of long-term naproxen use in a periodontal inflammation model known for causing significant inflammation, disrupting epithelial and connective tissue attachment and leading to alveolar bone destruction.

METHODS

Thirty BALB/c mice were treated with naproxen for 60 days or left untreated. From Day 30, an LPS solution was injected into gingival tissues three times per week for four weeks. This model enables LPS control over the inflammatory stimulus intensity throughout the experimental period, leading to chronic inflammation development involving both innate and adaptive immunity. The liver, stomach and maxillae were submitted to histological analysis. The oxidative damage was determined by measuring lipid peroxidation (LPO) in plasma and gingiva. The activities of myeloperoxidase (MPO), eosinophil peroxidase (EPO), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and levels of leukotriene B4, the interleukin (IL)-1β, TNF-α, IL-4, IL-5, IL-10, the chemokine CCL11 were also assessed in the gingival tissues.

RESULTS

The results indicated that none of the groups displayed any indications of liver damage or alterations; however, the NPx treatment led to severe gastric damage. In contrast, the treatment alleviated periodontal inflammation, resulting in a reduction of chronic and acute inflammatory cell infiltration and prevention of connective tissue loss in the gingival tissue. Additionally, the treatment increased the activities of endogenous antioxidant enzymes SOD, CAT and GPx, as well as the IL-10 cytokine, while decreasing the levels of leukotriene B4, TNF-α, IL-4 and IL-5. Furthermore, the activities of MPO, EPO and LPO were reduced in the treated groups.

CONCLUSION

These results suggest that NPx effectively inhibits periodontal inflammation in an inflammatory periodontal model. However, the harmful gastric effects dramatically limit its long-term use.

Validation of a triiodothyronine (T3) ELISA for mouse fecal samples

Acquiring sufficient blood for hormone analysis in mice can be a limiting step. Hormone analysis techniques using non-invasive sample collection have been vigorously developed for endangered species, from whom blood sampling is prohibited, or from species that are otherwise difficult to handle in a laboratory setting. Because there are interactions between glucocorticoids and thyroid hormones (T3 and T4), reducing the animal's "distress" during sample collection is imperative. Measurement of fecal T3 provides less sensitive, baseline information regarding thyroid function while permitting a non-invasive technique for more frequent sampling. We demonstrated that using a methanol extraction protocol produced the most reliable fecal T3 measurement in an enzyme-linked immunosorbent assay (ELISA). We found that during a thyroid hormone-treated state, fecal and plasma T3 measurements from mice are directly related, while during a methimazole-treated state, fecal and plasma T3 measurements from mice are inversely related. Fecal samples are a useful way to monitor thyroid hormone function in laboratory mice.

The effect of vortioxetine on faecal microbiota in high-fat diet-exposed mice-A link to weight protection

OBJECTIVE

Weight gain is a common side effect of antidepressive treatment, causing distress among patients and caretakers as it can lead to treatment discontinuation and complications such as diabetes type II and cardiovascular disease. Vortioxetine is one of the newer antidepressants and the pharmacodynamics differ from the selective serotonin reuptake inhibitors. It is marketed as being weight neutral; however, there is little evidence as to why. In recent years, there has been an increased focus on the faecal microbiota and its impact on body weight and mental and physical health. In the current work, we examine the effect of vortioxetine on weight gain and faecal microbiota composition.

METHODS

Forty male C57BL/6NTac mice were primed for 8 weeks with a high-fat diet (Hfd) or control diet (Cd), followed by a 4-week period on the same diet and additional +/- vortioxetine 10 mg/kg/daily.

RESULTS

Vortioxetine reduced Hfd-induced weight gain (Hfd + V: 8.2%, Hfd - V: 12.7%; p = 0.0374) but did not affect weight gain of the control group (Cd + V: 7.54%, Cd - V: 7.56%; p = 0.4944). Significant differences in faecal microbiota were observed in mice who received vortioxetine.

CONCLUSION

Vortioxetine caused significant changes to the faecal microbiota composition and appeared to limit Hfd-induced weight gain.

Unveiling Niaprazine's Potential: Behavioral Insights into a Re-Emerging Anxiolytic Agent

Ongoing global research actions seek to comprehensively understand the adverse impact of stress and anxiety on the physical and mental health of both human beings and animals. Niaprazine (NIA) is a chemical compound that belongs to the class of piperazine derivatives. This compound has recently gained renewed attention due to its potential therapeutic properties for treating certain conditions such as anxiety. Despite its potential benefits, the behavioral effects of NIA have not been thoroughly investigated. This study aimed to examine NIA's potential as an anti-anxiety and anti-stress agent. After administering either vehicle or NIA in their drinking water to mice for 14 days, we conducted behavioral analyses using the Marble Burying Test and the Elevated Plus Maze test. NIA-treated mice spend more time in the open arms and bury fewer marbles. Moreover, a stability study confirmed the linear relationship between NIA concentration and its response across concentrations encompassing the NIA mother solution and the NIA solutions administered to mice. Also, a preliminary synaptic toxicity analysis showed no direct damage to cortical nerve endings. Here, we show that NIA can modulate anxiety-related behaviors without significantly impacting exploratory activity or adverse effects. Our work describes new findings that contribute to the research on safer and more tolerable anxiety management options.

Lockbox enrichment facilitates manipulative and cognitive activities for mice

Background

Due to the lack of complexity and variety of stimuli, conventional housing conditions of laboratory mice do not allow these animals to fully express their behavioral repertoire, including manipulative and cognitive activities. Therefore, we designed mechanical puzzles, so-called lockboxes, for mice that can be provided in their home cages. We investigated the impact of the lockbox enrichment on their phenotype and affective state when compared to conventional housing (CH) and super-environmental enrichment (SEE).

Methods

Young adult female C57BL/6JCrl mice were examined before and after 2-month exposure to the different types of enrichment in a phenotyping test battery, including tests for trait and state anxiety-related behavior, calorimetric measurements, body weight measurements, the analysis of stress hormone metabolite concentrations, and sequential problem-solving abilities with a novel lockbox. At the end of the study, adrenal gland weights were determined and pathohistological evaluation was performed. For all continuous variables, the relative variability was calculated.

Results

While the different types of enrichment affected trait anxiety-related behavior, neither state anxiety-related behavior nor physiological variables (i.e., bodyweight, resting metabolic rate, stress hormone metabolite concentrations, adrenal gland weights) were influenced. LE improved sequential problem-solving (i.e., solving novel lockboxes) when compared to SEE. Regardless of the housing condition, the relative variability increased in most variables over time, although the coefficient of variation decreased for some variables, especially in animals with access to LE. There was no evidence of toxicopathological effects associated with the material from which the lockboxes were made.

Conclusions

All lockboxes are available as open-source tool. LE revealed beneficial effects on the affective state of laboratory mice and their performance in solving novel lockboxes. Neither relevant phenotype of the mice nor reproducibility of the data were compromised by LE, similar to SEE. The lockboxes may also be used as novel approach for assessing cognition in mice.

Refined tamoxifen administration in mice by encouraging voluntary consumption of palatable formulations

Drug administration in preclinical rodent models is essential for research and the development of novel therapies. Compassionate administration methods have been developed, but these are mostly incompatible with water-insoluble drugs such as tamoxifen or do not allow for precise timing or dosing of the drugs. For more than two decades, tamoxifen has been administered by oral gavage or injection to CreERT2-loxP gene-modified mouse models to spatiotemporally control gene expression, with the numbers of such inducible models steadily increasing in recent years. Animal-friendly procedures for accurately administering tamoxifen or other water-insoluble drugs would, therefore, have an important impact on animal welfare. On the basis of a previously published micropipette feeding protocol, we developed palatable formulations to encourage voluntary consumption of tamoxifen. We evaluated the acceptance of the new formulations by mice during training and treatment and assessed the efficacy of tamoxifen-mediated induction of CreERT2-loxP-dependent reporter genes. Both sweetened milk and syrup-based formulations encouraged mice to consume tamoxifen voluntarily, but only sweetened milk formulations were statistically noninferior to oral gavage or intraperitoneal injections in inducing CreERT2-mediated gene expression. Serum concentrations of tamoxifen metabolites, quantified using an in-house-developed cell assay, confirmed the lower efficacy of syrup- as compared to sweetened milk-based formulations. We found dosing with a micropipette to be more accurate than oral gavage or injection, with the added advantage that the method requires little training for the experimenter. The new palatable solutions encourage voluntary consumption of tamoxifen without loss of efficacy compared to oral gavage or injections and thus represent a refined administration method.

Optimization of lipid nanoparticles for gene editing of the liver via intraduodenal delivery

Lipid nanoparticles (LNPs) have recently emerged as successful gene delivery platforms for a diverse array of disease treatments. Efforts to optimize their design for common administration methods such as intravenous injection, intramuscular injection, or inhalation, revolve primarily around the addition of targeting ligands or the choice of ionizable lipid. Here, we employed a multi-step screening method to optimize the type of helper lipid and component ratios in a plasmid DNA (pDNA) LNP library to efficiently deliver pDNA through intraduodenal delivery as an indicative route for oral administration. By addressing different physiological barriers in a stepwise manner, we down-selected effective LNP candidates from a library of over 1000 formulations. Beyond reporter protein expression, we assessed the efficiency in non-viral gene editing in mouse liver mediated by LNPs to knockdown PCSK9 and ANGPTL3 expression, thereby lowering low-density lipoprotein (LDL) cholesterol levels. Utilizing an all-in-one pDNA construct with Strep. pyogenes Cas9 and gRNAs, our results showcased that intraduodenal administration of selected LNPs facilitated targeted gene knockdown in the liver, resulting in a 27% reduction in the serum LDL cholesterol level. This LNP-based all-in-one pDNA-mediated gene editing strategy highlights its potential as an oral therapeutic approach for hypercholesterolemia, opening up new possibilities for DNA-based gene medicine applications.

Intrathecal delivery of a bicistronic AAV9 vector expressing β-hexosaminidase A corrects Sandhoff disease in a murine model: A dosage study

The pathological accumulation of GM2 ganglioside associated with Tay-Sachs disease (TSD) and Sandhoff disease (SD) occurs in individuals who possess mutant forms of the heterodimer β-hexosaminidase A (Hex A) because of mutation of the HEXA and HEXB genes, respectively. With a lack of approved therapies, patients experience rapid neurological decline resulting in early death. A novel bicistronic vector carrying both HEXA and HEXB previously demonstrated promising results in mouse models of SD following neonatal intravenous administration, including significant reduction in GM2 accumulation, increased levels of Hex A, and a 2-fold extension of survival. The aim of the present study was to identify an optimal dose of the bicistronic vector in 6-week-old SD mice by an intrathecal route of administration along with transient immunosuppression, to inform possible clinical translation. Three doses of the bicistronic vector were tested: 2.5e11, 1.25e11, and 0.625e11 vector genomes per mouse. The highest dose provided the greatest increase in biochemical and behavioral parameters, such that treated mice lived to a median age of 56 weeks (>3 times the lifespan of the SD controls). These results have direct implications in deciding a human equivalent dose for TSD/SD and have informed the approval of a clinical trial application (NCT04798235).

Pre-clinical safety assessment of biotechnologically produced lacto-N-tetraose (LNT)

Lacto-N-tetraose (LNT) is a human milk oligosaccharide with average concentrations ranging from 0.74 to 1.07 g/L in breastmilk, depending on the lactation stage. In this study, the preclinical safety of LNT produced by the Escherichia coli K-12 E2083 production strain was assessed. LNT was negative in both the bacterial reverse mutation assay and the in vitro micronucleus assay, demonstrating the absence of genotoxic potential for this substance. In the OECD 408 guideline compliant 90-day oral toxicity study rat, LNT did not induce any adverse effects in any treatment group up to and including the highest dose tested, and no LOAEL could be determined. Therefore, the no-observed-adverse effect level (NOAEL) is set at the highest dose level tested, i.e. a dietary level of 5 % (w/w), corresponding to ≥2856 mg/kg bw/day and ≥3253 mg/kg bw/day for males and females, respectively. This might be an underestimation of the NOAEL, caused by the range of dose levels tested. The results obtained in the current study are in good agreement with available data generated using other biotechnologically produced LNT batches and therefore support its safe use as a food ingredient.

Δ9-Tetrahydrocannabinol Effects on Respiration and Heart Rate Across Route of Administration in Female and Male Mice

The physiological impact of cannabinoid receptor agonists is of great public health interest due to their increased use in recreational and therapeutic contexts. However, the body of literature on cannabinoid receptor agonists includes multiple confounding variables that complicate comparisons across studies, including route of administration, timeline across which phenotypes are observed, agonist dose, and sex of the study cohort. In this study, we characterized the impact of sex and route of administration on Δ9-tetrahydrocannabinol (THC)-induced changes in cardiopulmonary phenotypes in mice. Using noninvasive plethysmography and telemetry, we monitored heart rate and respiration in the same cohort of animals across aerosol, oral gavage, subcutaneous, and intraperitoneal administrations of THC (0-30 mg/kg THC for oral gavage, subcutaneous, and intraperitoneal, and 0-300 mg/ml THC for aerosol). All routes of THC administration altered respiratory minute volume and heart rate, with the direction of effects typically being consistent across dependent measures. THC primarily decreased respiration and heart rate, but females given oral gavage THC showed increased heart rate. Intraperitoneal and subcutaneous THC produced the longest-lasting effects, including THC-induced alterations in physiological parameters for up to 10 h, whereas effects of aerosolized THC were short lived. The fastest onset of effects of THC occurred for aerosolized and intraperitoneal THC. Altogether, the work herein establishes the impact of dosing route on THC-induced heart rate and respiratory alteration in male and female mice. This study highlights important differences in the timeline of cardiopulmonary response to THC following the most common preclinical routes of administration.

Machine learning reveals common transcriptomic signatures across rat brain and placenta following developmental organophosphate ester exposure

Toxicogenomics is a critical area of inquiry for hazard identification and to identify both mechanisms of action and potential markers of exposure to toxic compounds. However, data generated by these experiments are highly dimensional and present challenges to standard statistical approaches, requiring strict correction for multiple comparisons. This stringency often fails to detect meaningful changes to low expression genes and/or eliminate genes with small but consistent changes particularly in tissues where slight changes in expression can have important functional differences, such as brain. Machine learning offers an alternative analytical approach for "omics" data that effectively sidesteps the challenges of analyzing highly dimensional data. Using 3 rat RNA transcriptome sets, we utilized an ensemble machine learning approach to predict developmental exposure to a mixture of organophosphate esters (OPEs) in brain (newborn cortex and day 10 hippocampus) and late gestation placenta of male and female rats, and identified genes that informed predictor performance. OPE exposure had sex specific effects on hippocampal transcriptome, and significantly impacted genes associated with mitochondrial transcriptional regulation and cation transport in females, including voltage-gated potassium and calcium channels and subunits. To establish if this holds for other tissues, RNAseq data from cortex and placenta, both previously published and analyzed via a more traditional pipeline, were reanalyzed with the ensemble machine learning methodology. Significant enrichment for pathways of oxidative phosphorylation and electron transport chain was found, suggesting a transcriptomic signature of OPE exposure impacting mitochondrial metabolism across tissue types and developmental epoch. Here we show how machine learning can complement more traditional analytical approaches to identify vulnerable "signature" pathways disrupted by chemical exposures and biomarkers of exposure.

Prebiotic Supplementation during Lactation Affects Microbial Colonization in Postnatal-Growth-Restricted Mice

BACKGROUND

An inadequate perinatal nutritional environment can alter the maturation of the intestinal barrier and promote long-term pathologies such as metabolic syndrome or chronic intestinal diseases. The intestinal microbiota seems to play a determining role in the development of the intestinal barrier. In the present study, we investigated the impact of consuming an early postnatal prebiotic fiber (PF) on growth, intestinal morphology and the microbiota at weaning in postnatal-growth-restricted mice (PNGR).

METHODS

Large litters (15 pups/mother) were generated from FVB/NRj mice to induce PNGR at postnatal day 4 (PN4) and compared to control litters (CTRL, 8 pups/mother). PF (a resistant dextrin) or water was orally administered once daily to the pups from PN8 to PN20 (3.5 g/kg/day). Intestinal morphology was evaluated at weaning (PN21) using the ileum and colon. Microbial colonization and short-chain fatty acid (SCFA) production were investigated using fecal and cecal contents.

RESULTS

At weaning, the PNGR mice showed decreased body weight and ileal crypt depth compared to the CTRL. The PNGR microbiota was associated with decreased proportions of the Lachnospiraceae and Oscillospiraceae families and the presence of the Akkermansia family and Enterococcus genus compared to the CTRL pups. The propionate concentrations were also increased with PNGR. While PF supplementation did not impact intestinal morphology in the PNGR pups, the proportions of the Bacteroides and Parabacteroides genera were enriched, but the proportion of the Proteobacteria phylum was reduced. In the CTRL pups, the Akkermansia genus (Verrucomicrobiota phylum) was present in the PF-supplemented CTRL pups compared to the water-supplemented ones.

CONCLUSIONS

PNGR alters intestinal crypt maturation in the ileum at weaning and gut microbiota colonization. Our data support the notion that PF supplementation might improve gut microbiota establishment during the early postnatal period.

Attenuating effects of selenium and zinc against hexavalent chromium-induced oxidative stress, hormonal instability, and placenta damage in preimplanted rats

As a toxic metal, hexavalent chromium (CrVI) has effects on both the reproductive and endocrine systems. This study aimed to evaluate the protective effects of selenium (Se) and zinc (Zn) against the toxicity of chromium on the placenta in pregnant Wistar albino rats. Thirty pregnant Wistar rats were divided into control and four treated groups, receiving subcutaneously (s.c) on the 3rd day of pregnancy, K₂Cr₂O₇ (10 mg/kg body weight (bw)) alone, or in association with Se (0.3 mg/kg bw), ZnCl₂ (20 mg/kg bw), or both of them simultaneously. Plasma steroid hormones, placenta histoarchitecture, oxidative stress profile, and developmental parameters were investigated. These results showed that K₂Cr₂O₇ exposure induced a significant increase in the levels of both plasma estradiol (E₂) and placenta malondialdehyde (MDA), the number of fetal resorptions, and percent of post-implantation loss. On the other hand, K₂Cr₂O₇ significantly reduced developmental parameters, maternal body and placenta weight, and plasma progesterone (P) and chorionic gonadotropin hormone (β HCG) levels. However, K₂Cr₂O₇ significantly decreased the placenta activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), and nonprotein sulfhydryl (NPSH). These changes have been reinforced by histopathological evaluation of the placenta. Se and/or ZnCl₂ supplementation provoked a significant improvement in most indices. These results suggest that the co-treatment with Se or ZnCl₂ strongly opposes the placenta cytotoxicity induced by K₂Cr₂O₇ through its antioxidant action.

Armour G, Horman BM, Rock KD, Witchey SK, Greenbaum A, Patisaul HB. Maternal organophosphate flame retardant exposure alters the developing mesencephalic dopamine system in fetal rat

Organophosphate flame retardants (OPFRs) have become the predominant substitution for legacy brominated flame retardants but there is concern about their potential developmental neurotoxicity (DNT). OPFRs readily dissociate from the fireproofed substrate to the environment, and they (or their metabolites) have been detected in diverse matrices including air, water, soil, and biota, including human urine and breastmilk. Given this ubiquitous contamination, it becomes increasingly important to understand the potential effects of OPFRs on the developing nervous system. We have previously shown that maternal exposure to OPFRs results in neuroendocrine disruption, alterations to developmental metabolism of serotonin (5-HT) and axonal extension in male fetal rats, and potentiates adult anxiety-like behaviors. The development of the serotonin and dopamine systems occur in parallel and interact, therefore, we first sought to enhance our prior 5-HT work by first examining the ascending 5-HT system on embryonic day 14 using whole mount clearing of fetal heads and 3-dimensional (3D) brain imaging. We also investigated the effects of maternal OPFR exposure on the development of the mesocortical dopamine system in the same animals through 2-dimensional and 3D analysis following immunohistochemistry for tyrosine hydroxylase (TH). Maternal OPFR exposure induced morphological changes to the putative ventral tegmental area and substantia nigra in both sexes and reduced the overall volume of this structure in males, whereas 5-HT nuclei were unchanged. Additionally, dopaminergic axogenesis was disrupted in OPFR exposed animals, as the dorsoventral spread of ventral telencephalic TH afferents were greater at embryonic day 14, while sparing 5-HT fibers. These results indicate maternal exposure to OPFRs alters the development trajectory of the embryonic dopaminergic system and adds to growing evidence of OPFR DNT.

Antiepileptic Effect of Neuroaid® on Strychnine-Induced Convulsions in Mice

NeuroAid II, a folk Chinese Medicine, is currently used in Asia for the treatment of stroke. An experimental study demonstrated that NeuroAid enables neuronal cells to be more resistant to glutamate toxicity. This research was constructed to evaluate the efficacy of NeuroAid in the prevention of epilepsy (EP). Forty healthy adult male mice were used and divided into four groups (10 mice/group): normal control group; positive control group; NeuroAid-treated group (10 mg/kg); topiramate-treated group (10 mg/kg). The treatment continued for 7 days, and on the last day, EP was induced using strychnine at a dose of 2 mg/kg via intraperitoneal (ip) administration. Seizure severity, latency to the seizure onset, the number of seizures, and the duration of each seizure episode were observed for one hour. The death and protection rates over the next twenty-four hours were recorded. Brain specimens from surviving animals were extracted and examined pathologically for quantification of glutamate receptor (GluR) gene expression in the isolated hippocampus employing real-time PCR analysis. Treatment with NeuroAid resulted in a significant reduction in seizure severity, prolonged the onset of seizures, decreased the number and duration of episodes, reduced brain insult, and decreased mortality rate. Reductions in the gene expression of GluRs in the hippocampus with minor histopathological changes were observed in the NeruoAid- and topiramate-treated groups. It is concluded that NeuroAid has a potential antiepileptic effect (EP) with the ability to prevent convulsion through its effect on the glutamate receptor.

Modeling hormonal contraception in female rats: A framework for studies in behavioral neurobiology

Research on hormonal contraceptives (HC) in animal models is lacking, and as a result, so is our understanding of the impact of HC on the brain and behavior. Here, we provide a review of the pharmacology of HC, as well as the methodology and best practices for designing a model of HC in female rats. We outline specific methodological considerations regarding dosing, route of administration, exposure time/timing, and selecting a control group. We also provide a framework outlining important levels of analysis for thinking about the impact of HC on behavioral and neurobiological outcomes. The purpose of this review is to equip researchers with foundational knowledge, and some basic elements of experimental design for future studies investigating the impact of HC on the brain and behavior of female rats.

Co-administration of ursodeoxycholic acid with rosuvastatin/ezetimibe in a non-alcoholic fatty liver disease model

Background

Ursodeoxycholic acid (UDCA), statins, and ezetimibe (EZE) have demonstrated beneficial effects against non-alcoholic fatty liver disease (NAFLD). We investigated the efficacy of the combination of UDCA and the mix of rosuvastatin (RSV)/EZE in the treatment of NAFLD.

Methods

NAFLD mouse models were developed by injecting thioacetamide, fasting, and high-carbohydrate refeeding, high-fat diet, and choline-deficient L-amino acid-defined high-fat diet (CDAHFD). Low-dose UDCA (L-UDCA; 15 mg/kg) or high-dose UDCA (H-UDCA; 30 mg/kg) was administered with RSV/EZE. We also employed an in vitro model of NAFLD developed using palmitic acid-treated Hepa1c1c7 cells.

Results

Co-administration of RSV/EZE with UDCA significantly decreased the collagen accumulation, serum alanine aminotransferase (ALT) levels, and mRNA levels of fibrosis-related markers than those observed in the vehicle group in thioacetamide-treated mice (all P < 0.01). In addition, in the group fasted and refed with a high-carbohydrate diet, UDCA/RSV/EZE treatment decreased the number of apoptotic cells and serum ALT levels compared with those observed in the vehicle group (all P < 0.05). Subsequently, H-UDCA/RSV/EZE treatment decreased the number of ballooned hepatocytes and stearoyl-CoA desaturase 1 (SCD-1) mRNA levels (P = 0.027) in the liver of high-fat diet-fed mice compared with those observed in the vehicle group. In the CDAHFD-fed mouse model, UDCA/RSV/EZE significantly attenuated collagen accumulation and fibrosis-related markers compared to those observed in the vehicle group (all P < 0.05). In addition, UDCA/RSV/EZE treatment significantly restored cell survival and decreased the protein levels of apoptosis-related markers compared to RSV/EZE treatment in palmitic acid-treated Hepa1c1c7 cells (all P < 0.05).

Conclusion

Combination therapy involving UDCA and RSV/EZE may be a novel strategy for potent inhibition of NAFLD progression.

Effects of adolescent alcohol exposure via oral gavage on adult alcohol drinking and co-use of alcohol and nicotine in Sprague Dawley rats

BACKGROUND

Preclinical models simulating adolescent substance use leading to increased vulnerability for substance use disorders in adulthood are needed. Here, we utilized a model of alcohol and nicotine co-use to assess adult addiction vulnerability following adolescent alcohol exposure.

METHODS

In Experiment 1, adolescent (PND30) male and female Sprague-Dawley rats received 25% ethanol (EtOH) or a control solution via oral gavage every 8 h, for 2 days. In young adulthood, animals were tested with a 2-bottle choice between H20% and 15% EtOH or 0.2% saccharin/15% EtOH, followed by co-use of oral Sacc/EtOH and operant-based i.v. nicotine (0.03 mg/kg/infusion) self-administration. In Experiment 2, adolescents received control gavage, EtOH gavage, or no-gavage, and were tested in young adulthood in a 2-bottle choice between H20% and 15% EtOH, Sacc/EtOH, or 0.2% saccharin.

RESULTS

In Experiment 1, the adolescent EtOH gavage reduced adult EtOH consumption in the 2-bottle choice, but not during the co-use phase. During co-use, Sacc/EtOH served as an economic substitute for nicotine. In Experiment 2, the control gavage increased adult EtOH drinking relative to the no-gavage control group, an effect that was mitigated in the EtOH gavage group. In both experiments, treatment group differences in EtOH consumption were largely driven by males.

CONCLUSIONS

EtOH administration via oral gavage in adolescence decreased EtOH consumption in adulthood without affecting EtOH and nicotine co-use. Inclusion of a no-gavage control in Experiment 2 revealed that the gavage procedure increased adult EtOH intake and that including EtOH in the gavage buffered against the effect.

Comparison of Gelatin Flavors for Oral Dosing of C57BL/6J and FVB/N Mice

Precise oral dosing in rodents is usually achieved by intragastric gavage. If performed incorrectly due to technical difficulties, inexperience, or animal resistance, oral gavage may have animal welfare implications such as esophageal and gastric rupture and aspiration. The stress that is induced by this procedure can also lead to confounding results. In several animal models, drug vehicles must be sugar-free, deliver drugs in a specific formulation, and sometimes supply water. Gelatin has all of these properties. The current study aimed to evaluate the use of gelatin vehicles with different sensory features as an alternative to oral gavage. We investigated the time taken by 2 different inbred mouse strains, FVB/N and C57BL/6J, to ingest sugar-free gelatin pellets of varying flavors. Results showed that FVB/N mice took more time to eat the unflavored, strawberry and diet-flavored gelatin pellets than did C57BL/6J mice. Both strains showed low preference for lemon flavor, with the same ingestion times after the second day. This study showed that the C57BL/6J mice are more likely to eat gelatin than are FVB/N mice, and that the 2 strains of mice show a lower preference for lemon flavoring as compared with other flavors. This method of voluntarily oral administration offers an alternative to gavage for studies that use oral dosing studies.

Development of a 3D-Printed High Temperature Resin Cecal Fistula Implant for Long-Term and Minimally Invasive Access to the Gut Microbiome

Microbiota dysbiosis has been associated with chronic diseases ranging from gastrointestinal inflammatory and metabolic conditions to neurological changes affecting the gut-brain neural axis, mental health, and general well-being. However, current animal studies using oral gavage and gnotobiotic animals do not allow for non-invasive long-term access to gut microbiome. The purpose of the present study was to evaluate the feasibility of 3D-printed fistula implants through the body wall and into the cecum of rats to obtain long-term access to gut microbiome. Cecal fistulas were designed and 3D-printed using a high temperature resin (Formlabs; acrylic and methacrylic mixture). Nine male Sprague-Dawley rats underwent the fistula implantation. Food intake, body weight, and body fat were measured to determine the impact of fistula manipulation. Gut microbiome, vagal afferents in the hindbrain, and microglia activation were analyzed to determine if fistula implantation disrupted the gut-brain neural axis. We found that the procedure induced a transient decrease in microbial diversity in the gut that resolved within a few weeks. Fistula implantation had no impact on food intake, body weight, fat mass, or microglia activation. Our study shows that 3D-printed cecal fistula implantation is an effective procedure that allows long-term and minimally invasive access to gut microbiome.

Alternative method for oral administration of insoluble toxins to rats. A prenatal study of L-mimosine

L-mimosine is a compound found in Leucaena leucocephala, that is used as animal feed due to its high protein content, but it can also cause intoxication. Due to its low solubility in organic and aqueous solvents, its administration in laboratory animals is difficult, especially in delicate periods such as pregnancy. Thus, to circumvent such problems, this study proposes a stress-free form of oral administration with gelatin tablets with flavoring (meat broth) for 14 consecutive days of the gestational period (GD06 to GD20). For that, 17 pregnant Wistar rats divided into 3 groups were used: control (CO; n = 5) not treated; gelatin (GEL; n = 6), which received a gelatin tablet with flavoring; and gelatin with flavoring added 140 mg/kg of L-mimosine (GM; n = 6). All animals received feed and water ad libitum. The parameters analyzed were body weight gain, water and feed consumption, serum biochemistry, blood count and reproductive indices. Among these, only the real and total weight gains of dams showed statistically significant differences, with a decrease in the group GM. Thus, we could observe that flavored gelatin was an efficient and effective administration method to insoluble compounds and long-term administration to pregnant rats, with quick adaptation and without refusal by the animals. In addition, we could observe a direct effect of L-mimosine on the animals' weight gain; however, the dose administered was not sufficient to confer maternal and fetal toxicity.

Late Inflammation Induced by Asbestiform Fibers in Mice Is Ameliorated by a Small Molecule Synthetic Lignan

Exposure to Libby amphibole (LA) asbestos-like fibers is associated with increased risk of asbestosis, mesothelioma, pulmonary disease, and systemic autoimmune disease. LGM2605 is a small molecule antioxidant and free radical scavenger, with anti-inflammatory effects in various disease models. The current study aimed to determine whether the protective effects of LGM2605 persist during the late inflammatory phase post-LA exposure. Male and female C57BL/6 mice were administered daily LGM2605 (100 mg/kg) via gel cups for 3 days before and 14 days after a 200 µg LA given via intraperitoneal (i.p.) injection. Control mice were given unsupplemented gel cups and an equivalent dose of i.p. saline. On day 14 post-LA treatment, peritoneal lavage was assessed for immune cell influx, cytokine concentrations, oxidative stress biomarkers, and immunoglobulins. During the late inflammatory phase post-LA exposure, we noted an alteration in trafficking of both innate and adaptive immune cells, increased pro-inflammatory cytokine concentrations, induction of immunoglobulin isotype switching, and increased oxidized guanine species. LGM2605 countered these changes similarly among male and female mice, ameliorating late inflammation and altering immune responses in late post-LA exposure. These data support possible efficacy of LGM2605 in the prolonged treatment of LA-associated disease and other inflammatory conditions.

A quick and low-intensity method for oral administration to large numbers of mice: A possible alternative to oral gavage

Oral administration of medication to experimental animals is a cause of significant stress. When coupled to animals who are already under strenuous circumstances due to the disease being modelled, there is a significant risk for increased morbidity and mortality, thus influencing the results. Faced with these constraints, a low-intensity method for oral administration was developed, based solely on the natural behaviour of the animals and minimal conditioning, in which precise doses of medication were administered in a locally available, standard wheat cookie fragment, providing both a palatable vehicle and an absorbent matrix for the medication. Fast administration to large numbers of animals was thus achieved, safeguarding the animals' welfare and ensuring ease of handling. This method is a promising alternative to oral gavage in pre-clinical drug studies with laboratory mice.

Global cerebral ischemia in adolescent male Long Evans rats: Effects of vanillic acid supplementation on stress response, emotionality, and visuospatial memory

The developmental period is critical in delineating plastic response to internal and external events. However, neurobehavioural effects of global cerebral ischemia (GCI) in the maturing brain remain largely unknown. This study characterised the effects of GCI experienced at puberty on adulthood (1) hippocampus CA1 neuronal damage, (2) cognitive and emotional impairments, and (3) glucocorticoid receptor (GR) expression. Effects of adolescent exposure to the phenol vanillic acid (VA) on post-ischemic outcomes were also determined. Male Long Evans rats (n = 35) were supplemented for 21 consecutive days (postnatal days 33-53) with VA (91 mg/kg) or nut paste vehicle (control) prior to a 10-min GCI or sham surgery. As adults, rats were tested in the Open Field Test (OFT), Elevated-Plus Maze (EPM), and Barnes Maze (BM). GR expression was determined in the basolateral amygdala (BLA), CA1, and paraventricular nucleus (PVN), and brain injury assessed via CA1 neuronal density. Adolescent GCI exposure induced extensive hippocampal CA1 injury, which was not prevented by VA supplementation. Behaviourally, GCI increased EPM exploration while having no impact on spatial memory. VA intake increased OFT peripheral exploration. Notably, while no delayed changes in CA1 and PVN GR immunoreactivity were noted, both treatments separately increased BLA GR expression when compared with sham-nut paste rats. Age at GCI occurrence plays a critical role on post-ischemic impairments. The observation of minimal functional impairments despite important CA1 neuronal damage supports use of compensatory mechanisms. Our findings also show daily VA supplementation during adolescence to have no protective effects on post-ischemic outcomes, contrasting adult intake.

A novel small molecule approach for the treatment of propionic and methylmalonic acidemias

Propionic Acidemia (PA) and Methylmalonic Acidemia (MMA) are inborn errors of metabolism affecting the catabolism of valine, isoleucine, methionine, threonine and odd-chain fatty acids. These are multi-organ disorders caused by the enzymatic deficiency of propionyl-CoA carboxylase (PCC) or methylmalonyl-CoA mutase (MUT), resulting in the accumulation of propionyl-coenzyme A (P-CoA) and methylmalonyl-CoA (M-CoA in MMA only). Primary metabolites of these CoA esters include 2-methylcitric acid (MCA), propionyl-carnitine (C3), and 3-hydroxypropionic acid, which are detectable in both PA and MMA, and methylmalonic acid, which is detectable in MMA patients only (Chapman et al., 2012). We deployed liver cell-based models that utilized PA and MMA patient-derived primary hepatocytes to validate a small molecule therapy for PA and MMA patients. The small molecule, HST5040, resulted in a dose-dependent reduction in the levels of P-CoA, M-CoA (in MMA) and the disease-relevant biomarkers C3, MCA, and methylmalonic acid (in MMA). A putative working model of how HST5040 reduces the P-CoA and its derived metabolites involves the conversion of HST5040 to HST5040-CoA driving the redistribution of free and conjugated CoA pools, resulting in the differential reduction of the aberrantly high P-CoA and M-CoA. The reduction of P-CoA and M-CoA, either by slowing production (due to increased demands on the free CoA (CoASH) pool) or enhancing clearance (to replenish the CoASH pool), results in a net decrease in the CoA-derived metabolites (C3, MCA and MMA (MMA only)). A Phase 2 study in PA and MMA patients will be initiated in the United States.

Sensitivity of turtles to anticoagulant rodenticides: Risk assessment for green sea turtles (Chelonia mydas) in the Ogasawara Islands and comparison of warfarin sensitivity among turtle species

Although anticoagulant rodenticides (ARs) are effectively used for the control of invasive rodents, nontarget species are also frequently exposed to ARs and secondary poisonings occur widely. However, little data is available on the effects of ARs, especially on marine organisms. To evaluate the effects of ARs on marine wildlife, we chose green sea turtles (Chelonia mydas), which are one of the most common marine organisms around the Ogasawara islands, as our primary study species. The sensitivity of these turtles to ARs was assessed using both in vivo and in vitro approaches. We administered 4 mg/kg of warfarin sodium either orally or intravenously to juvenile green sea turtles. The turtles exhibited slow pharmacokinetics, and prolongation of prothrombin time (PT) was observed only with intravenous warfarin administration. We also conducted an in vitro investigation using liver microsomes from green sea turtles, and two other turtle species (softshell turtle and red-eared slider) and rats. The cytochrome P450 metabolic activity in the liver of green sea turtles was lower than in rats. Additionally, vitamin K epoxide reductase (VKOR), which is the target enzyme of ARs, was inhibited by warfarin in the turtles at lower concentration levels than in rats. These data indicate that turtles may be more sensitive to ARs than rats. We expect that these findings will be helpful for sea turtle conservation following accidental AR-broadcast incidents.

Sex, species and age: Effects of rodent demographics on the pharmacology of ∆9-tetrahydrocanabinol

Cannabis edibles are becoming more common in an increasingly diverse population of users, and the impact of first pass metabolism on cannabis's pharmacological profile across age and sex is not well understood. The present study examined the impact of age, sex and rodent species on the effects of intraperitoneal (i.p.) delta-9-tetrahydrocannabinol (THC) and its primary psychoactive metabolite, 11-OH-THC, in rodent models of psychoactivity and molecular assays of cannabinoid receptor type-1 (CB₁) pharmacology. Like oral THC, i.p. THC also undergoes first pass metabolism. In both species and sexes, 11-OH-THC exhibited marginally higher affinity (~1.5 fold) than THC and both served as partial agonists in [³⁵S]GTPγS binding with equivalent potency; 11-OH-THC exhibited slightly greater efficacy in rat brain tissue. In ICR mice, 11-OH-THC exhibited greater potency than THC in assays of catalepsy (7- to 15-fold) and hypothermia (7- to 31-fold). Further, 11-OH-THC was more potent in THC drug discrimination (7- to 9-fold) in C57Bl/6 J mice, with THC-like discriminative stimulus effects being CB₁-, but not CB₂-, mediated. THC's discriminative stimulus also was stable across age in mice, as its potency did not change over the course of the experiment (~17 months). While sex differences in THC's effects were not revealed in mice, THC was significantly more potent in females Sprague-Dawley rats than in males trained to discriminate THC from vehicle. This study demonstrates a cross-species in the psychoactive effects of i.p. THC across sex that may be related to differential metabolism of THC into its psychoactive metabolite 11-OH-THC, suggesting that species is a crucial design consideration in the preclinical study of phytocannabinoids.

Rats exposed to intermittent ethanol during late adolescence exhibit enhanced habitual behavior following reward devaluation

The brain undergoes substantial maturation during adolescence, and repeated exposure to ethanol at this time has been shown to result in long-lasting behavioral and neural consequences. During the broad period of adolescence, different neuronal populations and circuits are refined between early and late adolescence, suggesting the possibility that ethanol exposure at these differing times may lead to differential outcomes. The goal of the current study was to evaluate the impact of adolescent intermittent ethanol (AIE) during early and late adolescence on the formation of goal-directed and habitual behavior in adulthood. Male and female Sprague-Dawley rats were exposed to ethanol via intragastric gavage (4.0 g/kg, 25% v/v) every other day from postnatal day (P) 25-45 or P45-65, considered early and late adolescence, respectively. In adulthood (~P70 early or ~ P90 late), rats were gradually food-restricted and began operant training on a fixed ratio 1 schedule. Rats were then transitioned onto random interval schedules and eventually underwent a sensory-specific satiation procedure as a model of reward devaluation. Few differences as a result of adolescent ethanol exposure were found during instrumental training. Following reward devaluation, rats exposed to water and ethanol during early adolescence exhibited reductions in lever pressing, suggestive of a goal-directed response pattern. In contrast, late AIE males and females demonstrated persistent responding following both devalued and non-devalued trials, findings representative of a habitual behavior pattern. The shifts from goal-directed to habitual behavior noted only following late AIE contribute to the growing literature identifying specific behavioral consequences as a result of ethanol exposure during distinct developmental periods within adolescence. More work is needed to determine whether the greater habit formation following late AIE is also associated with elevated habitual ethanol consumption.

The R-enantiomer of ketorolac reduces ovarian cancer tumor burden in vivo

BACKGROUND

Rho-family GTPases, including Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42), are important modulators of cancer-relevant cell functions and are viewed as promising therapeutic targets. Based on high-throughput screening and cheminformatics we identified the R-enantiomer of an FDA-approved drug (ketorolac) as an inhibitor of Rac1 and Cdc42. The corresponding S-enantiomer is a non-steroidal anti-inflammatory drug (NSAID) with selective activity against cyclooxygenases. We reported previously that R-ketorolac, but not the S-enantiomer, inhibited Rac1 and Cdc42-dependent downstream signaling, growth factor stimulated actin cytoskeleton rearrangements, cell adhesion, migration and invasion in ovarian cancer cell lines and patient-derived tumor cells.

METHODS

In this study we treated mice with R-ketorolac and measured engraftment of tumor cells to the omentum, tumor burden, and target GTPase activity. In order to gain insights into the actions of R-ketorolac, we also performed global RNA-sequencing (RNA-seq) analysis on tumor samples.

RESULTS

Treatment of mice with R-ketorolac decreased omental engraftment of ovarian tumor cells at 18 h post tumor cell injection and tumor burden after 2 weeks of tumor growth. R-ketorolac treatment inhibited tumor Rac1 and Cdc42 activity with little impact on mRNA or protein expression of these GTPase targets. RNA-seq analysis revealed that R-ketorolac decreased expression of genes in the HIF-1 signaling pathway. R-ketorolac treatment also reduced expression of additional genes associated with poor prognosis in ovarian cancer.

CONCLUSION

These findings suggest that R-ketorolac may represent a novel therapeutic approach for ovarian cancer based on its pharmacologic activity as a Rac1 and Cdc42 inhibitor. R-ketorolac modulates relevant pathways and genes associated with disease progression and worse outcome.

Peanut butter as an alternative dose delivery method to prevent strain-dependent orogastric gavage-induced stress in mouse teratogenicity studies

INTRODUCTION

Animal-based studies are essential for assessing toxicity to environmental pollutants, especially when the potential targets are specific developmental time points, teratogenic, or multi-organ systems that cannot be modeled in vitro. Orogastric gavage is a widely used technique for exposure because of its increased accuracy of dose administration over free feeding. However, repeated use of this method has been reported to cause physiological stress on the exposed animals that could interfere with interpretation of results. Previous studies have shown that genetic background also contributes to the level of stress and can affect individual response.

METHODS

To evaluate the impact of stress on repeated orogastric gavage, we exposed C67BL/6J and 129S1/SvImJ inbred mouse strains to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), a potent xenobiotic that has been extensively studied in vivo. Pregnant females were dosed for ten days after mating using orogastric gavage with olive oil as vehicle or through diet using peanut butter as vehicle. Serum corticosterone levels, body weight, and reproduction endpoints were measured to evaluate levels of stress induced by the dosing technique.

RESULTS

The levels of stress caused by orogastric gavage was strongly dependent on strain background and on the phenotypic endpoint. Orogastric gavage-induced stress was more detrimental in 129S1/SvlmJ pregnant female mice than in C57BL/6J.

CONCLUSION

These results show that administration of xenobiotics via controlled diet can improve the reproducibility and rigor of exposure studies requiring orogastric delivery.

An alternative method for oral drug administration by voluntary intake in male and female mice

Drug administration to experimental rodents is often invasive and stressful, thus reducing animal welfare and potentially confounding experimental results. Methods of oral drug delivery in which rodents cooperate voluntarily minimize stress, pain and morbidity. We herein describe a method for oral administration through voluntary intake of strawberry jam, developed for C57BL/6J mice. During a 3-day habituation period, animals were placed in individual cages once daily and presented with a drop of jam. Five days later, the jam was again offered with admixed drug. Mice ingested it in less than 5 min, with latency times below 1 min, confirming the suitability of the administration method.

PiDose: an open-source system for accurate and automated oral drug administration to group-housed mice

Drug treatment studies in laboratory mice typically employ manual administration methods such as injection or gavage, which can be time-consuming to perform over long periods and cause substantial stress in animals. These stress responses may mask or enhance treatment effects, increasing the risk of false positive or negative results and decreasing reliability. To address the lack of an automated method for drug treatment in group-housed mice, we have developed PiDose, a home-cage attached device that weighs individual animals and administers a daily dosage of drug solution based on each animal’s bodyweight through their drinking water. Group housed mice are identified through the use of RFID tagging and receive both regular water and drug solution drops by licking at a spout within the PiDose module. This system allows animals to be treated over long periods (weeks to months) in a fully automated fashion, with high accuracy and minimal experimenter interaction. PiDose is low-cost and fully open-source and should prove useful for researchers in both translational and basic research.

Institutional protocols for the oral administration (gavage) of chemicals and microscopic microbial communities to mice: Analytical consensus

IMPACT STATEMENT

Institutional protocols designed for the oral administration of live microbial communities, either complex or microscopic (microcosmic), to mice do not exist. However, this approach is increasingly employed by investigators focusing on the gut microbiome in experimental research. Herein, we propose two analytically Kappa-based consensus protocols to promote reproducibility and standardization in research practices and describe biologically relevant factors in achieving optimal microbial engraftment of communities in germ-free mice.

Distinct actions of the fermented beverage kefir on host behaviour, immunity and microbiome gut-brain modules in the mouse

BACKGROUND

Mounting evidence suggests a role for the gut microbiota in modulating brain physiology and behaviour, through bi-directional communication, along the gut-brain axis. As such, the gut microbiota represents a potential therapeutic target for influencing centrally mediated events and host behaviour. It is thus notable that the fermented milk beverage kefir has recently been shown to modulate the composition of the gut microbiota in mice. It is unclear whether kefirs have differential effects on microbiota-gut-brain axis and whether they can modulate host behaviour per se.

METHODS

To address this, two distinct kefirs (Fr1 and UK4), or unfermented milk control, were administered to mice that underwent a battery of tests to characterise their behavioural phenotype. In addition, shotgun metagenomic sequencing of ileal, caecal and faecal matter was performed, as was faecal metabolome analysis. Finally, systemic immunity measures and gut serotonin levels were assessed. Statistical analyses were performed by ANOVA followed by Dunnett's post hoc test or Kruskal-Wallis test followed by Mann-Whitney U test.

RESULTS

Fr1 ameliorated the stress-induced decrease in serotonergic signalling in the colon and reward-seeking behaviour in the saccharin preference test. On the other hand, UK4 decreased repetitive behaviour and ameliorated stress-induced deficits in reward-seeking behaviour. Furthermore, UK4 increased fear-dependent contextual memory, yet decreased milk gavage-induced improvements in long-term spatial learning. In the peripheral immune system, UK4 increased the prevalence of Treg cells and interleukin 10 levels, whereas Fr1 ameliorated the milk gavage stress-induced elevation in neutrophil levels and CXCL1 levels. Analysis of the gut microbiota revealed that both kefirs significantly changed the composition and functional capacity of the host microbiota, where specific bacterial species were changed in a kefir-dependent manner. Furthermore, both kefirs increased the capacity of the gut microbiota to produce GABA, which was linked to an increased prevalence in Lactobacillus reuteri.

CONCLUSIONS

Altogether, these data show that kefir can signal through the microbiota-gut-immune-brain axis and modulate host behaviour. In addition, different kefirs may direct the microbiota toward distinct immunological and behavioural modulatory effects. These results indicate that kefir can positively modulate specific aspects of the microbiota-gut-brain axis and support the broadening of the definition of psychobiotic to include kefir fermented foods. Video abstract.

2,3,7,8-Tetrachlorodibenzo-p-dioxin Induces Vascular Dysfunction That is Dependent on Perivascular Adipose and Cytochrome P4501A1 Expression

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is associated with hypertension in humans and animals, and studies suggest that cytochrome P4501A1 (Cyp1a1) induction and vascular dysfunction may contribute. We investigated the role of perivascular adipose tissue (PVAT) and Cyp1a1 in TCDD-induced vascular dysfunction. Cyp1a1 wild-type (WT) and knockout (KO) male mice were fed a dough pill containing 1,4-p-dioxane (TCDD vehicle control) on days 0 and 7, or 1000 ng/kg TCDD on day 0 and 250 ng/kg TCDD on day 7. mRNA expression of Cyp1a1 was assessed on days 3, 7, and 14, and of Cyp1b1, 1a2, angiotensinogen, and phosphodiesterase 5a on day 14. Dose-dependent vasoconstriction to a thromboxane A₂ mimetic (U46619), and vasorelaxation to acetylcholine and a nitric oxide donor (S-nitroso-N-acetyl-DL-penicillamine, SNAP), were investigated in the aorta with and without PVAT. Cyp1a1 and 1a2 mRNA was induced in aorta of WT mice only with PVAT, and Cyp1a1 induction was sustained through day 14. TCDD significantly enhanced constriction to U46619 in WT mice and inhibited relaxation to both acetylcholine and SNAP, but only in the presence of PVAT. The effects of TCDD on U46619 constriction and SNAP relaxation were not observed in Cyp1a1 KO mice. Finally, in aorta + PVAT of WT mice TCDD significantly induced expression of angiotensinogen and phosphodiesterase 5a both of which could contribute to the TCDD-induced vascular dysfunction. These data establish PVAT as a TCDD target which is critically involved in mediating vascular dysfunction. TCDD enhances vasoconstriction via the thromboxane/prostanoid (TP) receptor and inhibits vasorelaxation via nitric oxide (NO) signaling. This TCDD-induced vascular dysfunction requires perivascular adipose (PVAT) and cytochrome P4501a1 (CYP1a1) induction.

The Role of BDNF on Aging-Modulation Markers

An important link between brain aging and a class of growth/survival factors called neurotrophins has recently been demonstrated. In particular, brain-derived neurotrophic factor (BDNF) plays a fundamental role during age-related synaptic loss, preventing cerebral atrophy and cognitive decline. The aim of the present study was to investigate whether the use of low dose BDNF sequentially kinetic activated (SKA) was able to counteract some mechanisms underlying the degeneration and aging of nervous tissue by increasing endogenous protection mechanisms. Both in vitro and in vivo experiments were performed to assess the ability of BDNF SKA to protect and regenerate survival-related molecular pathways, studying intestinal absorption in vitro and brain function in vivo. Our pioneering results show that BDNF SKA is able to induce the endogenous production of BDNF, using its receptor TrkB and influencing the apolipoprotein E expression. Moreover, BDNF SKA exerted effects on β-Amyloid and Sirtuin 1 proteins, confirming the hypothesis of a fine endogenous regulatory effect exerted by BDNF SKA in maintaining the health of both neurons and astrocytes. For this reason, a change in BDNF turnover is considered as a positive factor against brain aging.

Long Term Pharmacological Perturbation of Autophagy in Mice: Are HCQ Injections a Relevant Choice?

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved catabolic process whose loss-of-function has been linked to a growing list of pathologies. Knockout mouse models of key autophagy genes have been instrumental in the demonstration of the critical functions of autophagy, but they display early lethality, neurotoxicity and unwanted autophagy-independent phenotypes, limiting their applications for in vivo studies. To avoid problems encountered with autophagy-null transgenic mice, we investigated the possibility of disturbing autophagy pharmacologically in the long term. Hydroxychloroquine (HCQ) ip injections were done in juvenile and adult C57bl/6j mice, at range doses adapted from the human malaria prophylactic treatment. The impact on autophagy was assessed by western-blotting, and juvenile neurodevelopment and adult behaviours were evaluated for four months. Quite surprisingly, our results showed that HCQ treatment in conditions used in this study neither impacted autophagy in the long term in several tissues and organs nor altered neurodevelopment, adult behaviour and motor capabilities. Therefore, we recommend for future long-term in vivo studies of autophagy, to use genetic mouse models allowing conditional inhibition of selected Atg genes in appropriate lineage cells instead of HCQ treatment, until it could be successfully revisited using higher HCQ doses and/or frequencies with acceptable toxicity.

Imipramine and Venlafaxine Differentially Affect Primary Glial Cultures of Prenatally Stressed Rats

Here, we examine the effects of prenatal administration of two antidepressants—imipramine (IMI) and venlafaxine (VEN)—on morphology and activity of a primary glial culture. Microglia are targeted by antidepressants used for antenatal depression and are important regulators of central nervous system development. In this study, female Wistar rats were assigned to one of four groups: a control group that received water ad libitum (1), and groups that received additionally once daily either water (2), IMI (10 mg/kg) (3), or VEN (20 mg/kg) (4) by oral gavage from gestation day 7 to 22. Oral gavage administration induced prenatal stress. Cell cultures were obtained from the brains of 1-day-old pups. Prenatal stress caused a disturbance of sensorimotor function in pups. Prenatal stress also produced alterations in the glial cultures, specifically, an increased percentage of microglia in the mixed glial cultures and an increased percentage of dead cells. Moreover, increased levels of IL1-β, TNF-α, NO, and an increased expression of CX3CR1 mRNA were found in microglia. However, the ratio of Bax/Bcl2 mRNA was reduced. Prenatal stress increased the vulnerability of microglia to lipopolysaccharide (LPS). The mixed glial culture derived from pups exposed to IMI showed greater morphological changes and the highest percentage of microglia. Microglia were characterized by the largest increase in the production of pro-inflammatory cytokines and NO, and the greatest reduction in the expression of CX3CR1 mRNA. Exposure to IMI reduced the effects of LPS on IL-1β production and Bax/Bcl2 mRNA, and exacerbated the effects of LPS on CX3CR1 mRNA expression. Prenatal administration of VEN induced protective effects on microglia, as measured by all studied parameters. Taken together, our data suggest that, by disturbing microglia function, exposure to even mild forms of chronic prenatal stress may predispose individuals to psychiatric or neurodevelopmental disorders. These data also indicate that chronic mild stress sensitizes microglia to immune challenges, which may lead to enhanced neuronal damage in the embryonic brain. The observed detrimental effects of IMI on microglial activity under conditions of prenatal stress may help to explain the teratogenic effects of IMI reported in the literature.

Foodborne infection of mice with Salmonella Typhimurium

The bacterial pathogen Salmonella enterica serovar Typhimurium is one of the most common causes of foodborne disease in humans and is also an important model system for bacterial pathogenesis. Oral inoculation of C57Bl/6 mice, which are genetically susceptible to Salmonella, results in systemic infection but the murine intestine is not efficiently colonized unless the intestinal microbiota is disrupted. Pretreatment of C57Bl/6 mice with streptomycin, followed by oral inoculation with Salmonella Typhimurium results in colitis resembling human intestinal Salmonellosis. The predominant method of delivery of bacteria is oral gavage, during which organisms are deposited directly into the stomach via a feeding needle. Although convenient, this method can be stressful for mice, and may lead to unwanted tracheal or systemic introduction of bacteria. Here, we developed a method for oral infection of mice by voluntary consumption of regular mouse chow inoculated with bacteria. Mice readily ate chow fragments containing up to 10⁸ CFU Salmonella, allowing for a wide range of infectious doses. In mice pretreated with streptomycin, infection with inoculated chow resulted in reproducible infections with doses as low as 10³ CFU. Mice not treated with streptomycin, as well as resistant Nramp1 reconstituted C57Bl/6J mice, were also readily infected using this method. In summary, voluntary consumption of chow inoculated with Salmonella represents a natural route of infection for foodborne salmonellosis and a viable alternative to oral gavage.

Design, Synthesis, and Biological Characterization of Orally Active 17β-Hydroxysteroid Dehydrogenase Type 2 Inhibitors Targeting the Prevention of Osteoporosis

Osteoporosis is predominantly treated with drugs that inhibit further bone resorption due to estrogen deficiency. Yet, osteoporosis drugs that not only inhibit bone resorption but also stimulate bone formation, such as potentially inhibitors of 17β-hydroxysteroid dehydrogenase type 2 (17β-HSD2), may be more efficacious in the treatment of osteoporosis. Blockade of 17β-HSD2 is thought to increase intracellular estradiol and testosterone in bone, thereby inhibiting bone resorption by osteoclasts and stimulating bone formation by osteoblasts, respectively. We here describe the design, synthesis, and biological characterization of a novel bicyclic-substituted hydroxyphenylmethanone 17β-HSD2 inhibitor (compound 24). Compound 24 is a nanomolar potent inhibitor of human 17β-HSD2 (IC₅₀ of 6.1 nM) and rodent 17β-HSD2 with low in vitro cellular toxicity, devoid of detectable estrogen receptor α affinity, displays high aqueous solubility and in vitro metabolic stability, and has an excellent oral pharmacokinetic profile for testing in a rat osteoporosis model. Administration of 24 in a rat osteoporosis model demonstrates its bone-sparing efficacy.

Interventions after acute stress prevent its delayed effects on the amygdala

Stress is known to elicit contrasting patterns of plasticity in the amygdala and hippocampus. While chronic stress leads to neuronal atrophy in the rodent hippocampus, it has the opposite effect in the basolateral amygdala (BLA). Further, even a single episode of acute stress is known to elicit delayed effects in the amygdala. For example, 2 h of immobilisation stress has been shown to cause a delayed increase in dendritic spine density on BLA principal neurons 10 days later in young rats. This is paralleled by higher anxiety-like behaviour at the same delayed time point. This temporal build-up of morphological and behavioural effects 10 days later, in turn, provides a stress-free time window of intervention after exposure to acute stress. Here, we explore this possibility by specifically testing the efficacy of an anxiolytic drug in reversing the delayed effects of acute immobilisation stress. Oral gavage of diazepam 1 h after immobilisation stress prevented the increase in anxiety-like behaviour on the elevated plus-maze 10 days later. The same post-stress intervention also prevented delayed spinogenesis in the BLA 10 days after acute stress. Surprisingly, gavage of only the vehicle also had a protective effect on both the behavioural and synaptic effects of stress 10 days later. Vehicle gavage was found to trigger a significant rise in corticosterone levels that was comparable to that elicited by acute stress. This suggests that a surge in corticosterone levels, caused by the vehicle gavage 1 h after acute stress, was capable of reversing the delayed enhancing effects of stress on anxiety-like behaviour and BLA synaptic connectivity. These findings are consistent with clinical reports on the protective effects of glucocorticoids against the development of symptoms of post-traumatic stress disorder. Taken together, these results reveal strategies, targeted 1 h after stress, which can prevent the delayed effects of a brief exposure to a severe physical stressor.

•

Acute immobilisation stress increases anxiety and BLA spinogenesis 10 days later.

•

Oral gavage of diazepam 1 h after stress prevents both these delayed effects.

•

Oral gavage of vehicle also has a similar protective effect on anxiety and spines.

•

Vehicle-gavage administration leads to an increase in levels of corticosterone.

•

This post-stress corticosterone surge may have prevented stress-effects 10 days later.

French maritime pine bark treatment decelerates plaque development and improves spatial memory in Alzheimer's disease mice

BACKGROUND

Plant extracts are increasingly investigated as potential drugs against Alzheimer's disease (AD) and dementia in general. Pycnogenol is an extract from the bark of the French maritime pine (Pinus pinaster Aiton subsp. atlantica) with known anti-oxidative and neuroprotective effects.

HYPOTHESIS/PURPOSE

Pycnogenol is thought to improve cognitive functions in elderly. We wanted to investigate and quantify these effects in a model system of cerebral ß-amyloidosis/AD.

STUDY DESIGN/METHODS

This study experimentally assessed the effects of Pycnogenol on AD-related pathology in a ß-amyloidosis mouse model. APP-transgenic mice and controls were treated orally in a pre-onset and post-onset treatment paradigm. The effects of Pycnogenol were characterized by analysing ß-amyloid (Aß) plaques, number of neurons, glia coverage, myelination pattern, and cortical coverage with axons using immunohistochemistry. Aß levels were quantified using ELISA and gene expression levels of APP-processing enzymes ADAM10, BACE1 and IDE protein levels were determined by Western blot. Behavioural changes in circadian rhythm were monitored and spatial memory / cognition was assessed using a water maze test.

RESULTS

Pycnogenol significantly decreased the number of plaques in both treatment paradigms but did not alter levels of soluble Aß or the gene expression of APP-processing enzymes. The morphological analyses revealed no changes in the number of neurons, astrocytes, microglia, the myelination pattern, or the morphology of axons. Behavioural testing revealed an improvement of the spatial memory in the pre-onset treatment paradigm only.

CONCLUSION

Our results suggest to evaluate clinically a potential use of Pycnogenol in the prevention or in early stages of mild cognitive impairment (MCI) and AD.

Aspirin pre-treatment modulates ozone-induced fetal growth restriction and alterations in uterine blood flow in rats

Prenatal exposure to ozone has been linked to low birth weight in people and fetal growth restriction in rats. Clinical recommendations suggest use of low dose aspirin to lower risk of preeclampsia and intrauterine growth restriction in high-risk pregnancies, yet its utility in mitigating the postnatal effects of gestational ozone exposure is unknown. The present study investigated the possibility of low dose aspirin to mitigate the effects of ozone exposure during pregnancy. Exposure to ozone impaired uterine arterial flow and induced growth restriction in fetuses of both sexes. Aspirin treatment induced marginal improvements in ozone-induced uterine blood flow impairment. However, this resulted in a protection of fetal weight in dams given aspirin only in early pregnancy. Aspirin administration for the entirety of gestation increased placental weight and reduced antioxidant status, suggesting that prolonged exposure to low dose aspirin may induce placental inefficiency in our model of growth restriction.

Does the Stress of Laboratory Life and Experimentation on Animals Adversely Affect Research Data? A Critical Review

Recurrent acute and/or chronic stress can affect all vertebrate species, and can have serious consequences. It is increasingly and widely appreciated that laboratory animals experience significant and repeated stress, which is unavoidable and is caused by many aspects of laboratory life, such as captivity, transport, noise, handling, restraint and other procedures, as well as the experimental procedures applied to them. Such stress is difficult to mitigate, and lack of significant desensitisation/habituation can result in considerable psychological and physiological welfare problems, which are mediated by the activation of various neuroendocrine networks that have numerous and pervasive effects. Psychological damage can be reflected in stereotypical behaviours, including repetitive pacing and circling, and even self-harm. Physical consequences include adverse effects on immune function, inflammatory responses, metabolism, and disease susceptibility and progression. Further, some of these effects are epigenetic, and are therefore potentially transgenerational: the biology of animals whose parents/grandparents were wild-caught and/or have experienced chronic stress in laboratories could be altered, as compared to free-living individuals. It is argued that these effects must have consequences for the reliability of experimental data and their extrapolation to humans, and this may not be recognised sufficiently among those who use animals in experiments.

Perinatal antibiotic exposure alters composition of murine gut microbiota and may influence later responses to peanut antigen

Background

Accumulating evidence suggests that the gut microbiota shapes developmental processes within the immune system. Early life antibiotic use is one factor which may contribute to immune dysfunction and the recent surge in allergies by virtue of its effects on gut microbiota.

Objective and methods

As a first step towards determining whether a relationship exists between perinatal antibiotic induced changes in the gut microbiota and the later development of a peanut allergy, we exposed newborn mice to either the broad-spectrum antibiotic vancomycin or to a vehicle for 6 weeks and then used a novel murine model of peanut allergy.

Results

Early-life treatment with vancomycin resulted in a significant shift in the gut microbiota community characterized by a reduction in the abundance of firmicutes and preponderance of inflammatory proteobacteria. Mice with an antibiotic-altered microbiota, showed a localized allergic-like response characterized by ear swelling and scratching following intra-dermal peanut antigen challenge. Likewise, circulating IgE levels were increased in antibiotic-treated mice, but no evidence of a systemic allergic or anaphylactic-like response was observed. Importantly, we utilized the naturally occurring pro-inflammatory cytokine, tumor necrosis factor-α (TNF-α), rather than the more commonly used cholera toxin, as an adjuvant together with the peanut antigen.

Conclusion

Our data suggest that early antibiotic exposure promotes a shift in the gut microbiota community that may in turn, influence how mice later respond to a TNF-α + antigen challenge. However, further studies verifying the capacity of microbiota restoration to protect against allergic responses will be needed to confirm a causal role of antibiotic-induced microbiota variations in promoting allergic disease phenotypes.

Impact of repeated anesthesia with ketamine and xylazine on the well-being of C57BL/6JRj mice

Within the scope of the 3Rs of Russel and Burch, the number of laboratory animals can be reduced by repeated use of an animal. This strategy only becomes relevant, if the total amount of pain, distress or harm the individual animal experiences does not exceed the severity of a single manipulation. For example, when using imaging techniques, an animal can be examined several times during a study, but it has to be anesthetized each time imaging is performed. The severity of anesthesia is thought to be mild according to the Directive 2010/63/EU. However, the Directive does not differentiate between single and repeated anesthesia, although repeated anesthesia may have a greater impact on well-being. Hence, we compared the impact of single and repeated anesthesia (six times at an interval of three to four days) by injection of ketamine and xylazine (KX) on the well-being of adult female and male C57BL/6JRj mice. After anesthesia, well-being of mice was assessed according to a protocol for systematic assessment of well-being including nesting, the Mouse Grimace Scale (MGS), a test for trait anxiety, home cage activity, and the rotarod test for motor activity, food intake, and body weight, as well as corticosterone (metabolite) analysis. Repeated anesthesia increased the MGS in mice of both sexes and caused short-term effects on well-being of female mice in the immediate post-anesthetic period, indicated by longer lasting effects on trait anxiety-related behavior. However, corticosterone metabolite concentrations suggested that mice habituated to the stress induced by repeated KX administration. Hence, the mildly negative effects on well-being of repeated KX anesthesia do not seem to accumulate over time using the respective regimen. However, further observations for severity classification are warranted in order to more specifically determine the duration of mild distress and trait anxiety.