Chronic Psychosocial Stress Causes Increased Anxiety-Like Behavior and Alters Endocannabinoid Levels in the Brain of C57Bl/6J Mice

Social stress-induced depressive-like symptoms and changes in gut microbial and lipidomic profiles are prevented by pharmacological inhibition of FAAH activity in male rats

Pharmacological inhibition of fatty acid amide hydrolase (FAAH) activity has antidepressant-like effects in preclinical models of stress. In this study, we investigated whether the antidepressant-like effects of FAAH inhibition are associated with corresponding changes in gut microbial and lipidomic profiles, which are emerging as critical components in the pathophysiology of depression. Adult male Wistar rats experienced five weeks of repeated social defeat or control procedure and were treated with the FAAH inhibitor URB694 (0.3 mg/kg/day, i.p.) or vehicle starting from the third week. Repeated social defeat induced the emergence of depressive-like behavioral (sucrose preference reduction and passive coping behaviors in the forced swim test) and neuroendocrine (increased corticosterone levels) changes, which were prevented by URB694 treatment. Repeated social defeat also provoked a significant variation in gut microbiota (changes in the relative abundance of 14 bacterial taxa) and lipidic (e.g., glycerophospholipids) composition. These stress-induced changes were prevented by URB694 treatment. These findings indicate that inhibition of FAAH activity with URB694 blocks the co-occurrence of depressive-like behavioral and neuroendocrine changes and alterations in gut microbial and lipid composition in rats exposed to repeated social defeat. In conclusion, these results suggest that the gut microbiota-lipid crosstalk may represent a novel biological target for FAAH inhibitors to enhance stress resilience.

Anxiogenic doses of rapamycin prevent URB597-induced anti-stress effects in socially defeated mice

Repeated exposure to psychosocial stress modulates the endocannabinoid system, particularly anandamide (AEA) signaling in brain regions associated with emotional distress. The mTOR protein regulates various neuroplastic processes in the brain disrupted by stress, including adult hippocampal neurogenesis. This kinase has been implicated in multiple effects of cannabinoid drugs and the anti-stress behavioral effects of psychoactive drugs. Therefore, our hypothesis is that enhancing AEA signaling via pharmacological inhibition of the fatty acid amide hydrolase (FAAH) enzyme induces an anti-stress behavioral effect through an mTOR-dependent mechanism. To test this hypothesis, male C57Bl6 mice were exposed to social defeat stress (SDS) for 7 days and received daily treatment with either vehicle or different doses of the FAAH inhibitor, URB597 (0.1; 0.3; 1 mg/Kg), alone or combined with rapamycin. The results suggested that URB597 induced an inverted U-shaped dose-response curve in mice subjected to SDS (with the intermediate dose of 0.3 mg/kg being anxiolytic, and the higher tested dose of 1 mg/Kg being anxiogenic). In a second independent experiment, rapamycin treatment induced an anxiogenic-like response in control mice. However, in the presence of rapamycin, the anxiolytic dose of URB597 treatment failed to reduce stress-induced anxiety behaviors in mice. SDS exposure altered the hippocampal expression of the mTOR scaffold protein Raptor. Furthermore, the anxiogenic dose of URB597 decreased the absolute number of migrating doublecortin (DCX)-positive cells in the dentate gyrus, suggesting an anti-anxiety effect independent of newly generated/immature neurons. Therefore, our results indicate that in mice exposed to repeated psychosocial stress, URB597 fails to counteract the anxiogenic-like response induced by the pharmacological dampening of mTOR signaling.

Wistar-Kyoto rats and chronically stressed Wistar rats present similar depression- and anxiety-like behaviors but different corticosterone and endocannabinoid system modulation

The interplay of social, psychological, and biological stresses can trigger mental health conditions such as major depressive disorder (MDD), adjustment disorder, and posttraumatic stress disorder (PTSD). The endocannabinoid system (ECS), comprising endocannabinoids and cannabinoid receptors, is the critical pathway that mediates responses to stress stimuli. This study aimed to investigate the ECS's impact on responding to chronic social instability stress (SIS). Wistar (WIS) rats and an endogenously depressed rat model, Wistar-Kyoto (WKY), were used to evaluate depression- and anxiety-like behavioral responses, cognitive function, hormone levels, and ECS function. The animals in the stress group (WIS-STS and WKY-STS) were exposed to TMT (predator odor) for 10 mins (two exposures in total: one in light cycle and one in dark cycle) and daily roommate changes (30 days in total), while the control group (CTL) rats were exposed to a sham odor stimulus (distilled water) and did not undergo roommate changes. The results in the open field test suggest that WKY rats had significantly lower locomotor activity than WIS rats. In contrast, WKY rats and chronically stressed WIS rats presented similar depression- and anxiety-like behaviors and impaired cognitive function in the elevated plus maze, forced swimming test, and novel objective recognition test. However, chronic SIS did not exacerbate these behavioral changes in WKY rats. ELISA and Western blot analysis indicated that chronic SIS did not induce further upregulation of endocannabinoids and CB1R downregulation in WKY rats compared to WIS rats. In addition, the Luminex assay revealed that WKY rats showed a higher resilience on the HPA-axis modulation towards chronic SIS, distinguished by the hyperactivity of the HPA-axis modulation in WIS rats. Overall, the study revealed that the chronic SIS animal model (stressed WIS rats) and an animal model of endogenous depression (WKY rats) can generate similar behavioral changes in anxious behavior, behavioral despair, and cognitive impairment. Both animal models present hyperactivity of the ACTH modulation and ECS activity, while WKY rats are more resilient on CORT modulation towards chronic SIS.

Aggression repeatability in stressed fish in response to an environmental concentration of sertraline and lunar cycle as evidenced by brain metabolomics

Sertraline is an environmental pollutant which received magnified scientific attention due to its global presence in waters. Adverse effects on feeding, reproduction and other traits were observed mostly in unstressed aquatic organisms. Chronic stress, however, induces significant physiological changes, and the effects of sertraline in stressed fish may differ from those observed in non-stressed individuals. The current laboratory study addresses this gap by repeatedly monitoring the individual aggression of chronically stressed juvenile chub (Squalius cephalus L.) using the non-reversing mirror test at an environmental sertraline concentration of 0.022 g/L every three to four days for a period of 39 days. Specifically, it was hypothesized that the level and repeatability of aggressiveness would be (i) correlated with the concentration of sertraline/norsertraline in the fish brain; (ii) linked to the individual brain metabolomic profile described by LC-HRMS analyses; (iii) related to the lunar cycle. Sertraline led to an increase in fish aggression and more repeatable/consistent behaviour compared to control fish. While the level of sertraline in the brain did not correlate with aggressiveness, aggressive responses increased with higher norsertraline concentration. The observed aggressive behaviour also varied depending on the individual metabolomic profile of the brain. The behavioural outcome and metabolic change in fish brain may indicate that sertraline has demonstrated neuroprotective effects by reducing cortisol release. It is possible that fish exposed to sertraline could suffer a blunted stress response under the chronic stressors in the wild. Aggressiveness of both treatments evolved in time, revealing a sinusoid-like pattern corresponding to a lunar cycle with a peak of the aggressiveness during the new moon. There is a need for future studies to focus on this relationship to reveal its details and general validity. Our results emphasize that long-term behavioural variability should generally be taken into account in laboratory behavioural studies.

Betaine-The dark knight of the brain

The role of betaine in the liver and kidney has been well documented, even from the cellular and molecular point of view. Despite literature reporting positive effects of betaine supplementation in Alzheimer's, Parkinson's and schizophrenia, the role and function of betaine in the brain are little studied and reviewed. Beneficial effects of betaine in neurodegeneration, excitatory and inhibitory imbalance and against oxidative stress in the central nervous system (CNS) have been collected and analysed to understand the main role of betaine in the brain. There are many 'dark' aspects needed to complete the picture. The understanding of how this osmolyte is transported across neuron and glial cells is also controversial, as the expression levels and functioning of the known protein capable to transport betaine expressed in the brain, betaine-GABA transporter 1 (BGT-1), is itself not well clarified. The reported actions of betaine beyond BGT-1 related to neuronal degeneration and memory impairment are the focus of this work. With this review, we underline the scarcity of detailed molecular and cellular information about betaine action. Consequently, the requirement of detailed focus on and study of the interaction of this molecule with CNS components to sustain the therapeutic use of betaine.

Oleoylethanolamide attenuates the stress-mediated potentiation of rewarding properties of cocaine associated with an increased TLR4 proinflammatory response

The lipid-derived messenger oleoylethanolamide (OEA) has been involved in multiple physiological functions including metabolism and the immune response. More recently, OEA has been observed to affect reward-related behavior. Stress is a major risk factor for drug use and a predictor of drug relapse. In the laboratory, social stress has been largely studied using the social defeat (SD) model. Here, we explored the effects of different OEA administration schedules on the increased rewarding properties of cocaine induced by SD. In addition, we evaluated the anti-inflammatory action of OEA pretreatment in TLR4 expression caused by SD in the cerebellum, a novel brain structure that has been involved in the development of cocaine addiction. Adult OF1 mice were assigned to an experimental group according to the stress condition (exploration or SD) and treatment (OEA before SD, OEA before conditioning or subchronic OEA treatment). Mice were administered with OEA i.p (10 mg/kg) 10 min previously to the corresponding event. Three weeks after the last SD encounter, conditioned place preference (CPP) was induced by a subthreshold cocaine dose (1 mg/kg). As expected, socially defeated mice presented greater vulnerability to the cocaine reinforcing effects and expressed CPP. Conversely, this effect was not observed under a non-stressed condition. Most importantly, we observed that OEA pretreatment before SD or before conditioning prevented cocaine CPP in defeated mice. Biochemical analysis showed that OEA administration before SD decreased proinflammatory TLR4 upregulation in the cerebellum caused by social stress. In summary, our results suggest that OEA may have a protective effect on stress-induced increased cocaine sensitivity by exerting an anti-inflammatory action.

Endocannabinoid markers in autism spectrum disorder: A scoping review of human studies

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social communication deficits and patterns of restrictive and repetitive behavior. Although the neurological underpinnings of ASD remain elusive, the endocannabinoid system (ECS) may play a role in modulating social behavior in ASD. Preclinical studies have suggested that alterations in the ECS result in ASD-like phenotypes, but currently no reviews have examined ECS abnormalities in human studies. This scoping review investigated any evidence of ECS alterations in humans with ASD. A comprehensive literature search was conducted and five studies were eligible for review. Three studies reported a significant reduction of anandamide in ASD compared to controls. Other alterations included decreased 2-arachidonoylglycerol, oleoylethanolamide, and palmitoylethanolamide and elevated diacylglycerol lipase and monoacylglycerol lipase. Some discrepant findings were also noted, which included elevated or reduced CB2 receptor in three studies and elevated or reduced N-acyl phosphatidylethanolamine phospholipase D and fatty acid amide hydrolase in two studies. We conclude from this preliminary investigation that the ECS may be altered in humans with ASD. Potential limitations of the reviewed studies include medication use and psychiatric comorbidities. Further research, such as positron emission tomography studies, are necessary to fully understand the relationship between ECS markers and ASD.

The role of endocannabinoid system and TRPV1 receptors in the antidepressant and anxiolytic effects of dipyrone in chronic unpredictable mild stress in mice

Although dipyrone is a widely used analgesic and antipyretic, its mechanism of action is not fully clarified. Recent studies have drawn attention to its central effects and its relationship with the endocannabinoid system. The endocannabinoid system plays important roles in processes such as anxiety, depression, fear, and learning-memory. In this study, we aimed to investigate whether endocannabinoid levels change in the amygdala in chronic unpredictable mild stress model in mice and whether cannabinoid and TRPV1 receptors mediate antidepressant and anxiolytic effects of dipyrone. Mice were submitted to chronic unpredictable mild stress protocol of 6-weeks, then behavioral test were performed. In the first part of the study, dipyrone was injected at doses of 150, 300, and 600 mg/kg (i.p.) during behavioral tests. In the second part, the CB1 antagonist AM 251 (1 mg/kg, i.p.), the CB2 antagonist AM630 (1 mg/kg, i.p.), and the TRPV1 antagonist capsazepine (3 mg/kg, i.p.) were administered alone or in combination with 300 mg/kg dipyrone to observe if these receptors mediate dipyrone effects. Endocannabinoid and N-acylethanolamines levels were measured by LC-MS/MS in amygdala. Our results showed that there were no changes in AEA, 2-AG, PEA, OAE levels in the amygdala in mice exposed to chronic unpredictable mild stress model; dipyrone exerted antidepressant and anxiolytic effects at doses of 300 and 600 mg/kg; its anxiolytic effect appears to be mediated via CB1 receptors, whereas TRPV1 receptors seems to mediate its antidepressant action.

Insomnia May Mediate the Relationship Between Stress and Anxiety: A Cross-Sectional Study in University Students

BACKGROUND

High perceived stress and anxiety disorders are usually comorbid with each other, with stress often sequentially preceding the development of anxiety. While prior findings showed a causal role of sleep problems in anxiety, no study has assessed the role of insomnia as a mediator in the relationship between stress and anxiety.

METHODS

A cross-sectional study on university students (n = 475, age = 21.1+2.6 years) was conducted over 3 months. Participants completed self-report measures of Leeds Sleep Evaluation Questionnaire-Mizan (LSEQ-M), Perceived Stress Scale-10 (PSS-10), generalized anxiety disorder-7 scale (GAD-7), and a sociodemographic tool. The mediation effect model given by Baron and Kelly was used to determine the relationship.

RESULTS

The prevalence of insomnia and anxiety disorder was 43.6% and 21.9%, respectively. Stress was significantly associated with LSEQ-M (insomnia measure) (b = -.44, SE = 0.16, p<0.01), and high levels of anxiety (b = 0.25, SE = 0.03, p < 0.01). The indirect effect of stress on anxiety through LSEQ-M (insomnia measure) was significant (95% confidence interval [0.01, 0.04]). However, the indirect effect of anxiety on stress through LSEQ-M (insomnia measure) was non-significant (95% confidence interval [-.01, 0.04]).

CONCLUSIONS

Students having higher perceived stress levels and comorbid insomnia were also likely to have a higher anxiety level.