Mitochondrial dysfunction in animal models of PTSD: Relationships between behavioral models, neural regions, and cellular maladaptation

The Emerging Role of Brain Mitochondria in Fear and Anxiety

The functional complexity of brain circuits underlies the broad spectrum of behaviors, cognitive functions, and their associated disorders. Mitochondria, traditionally known for their role in cellular energy metabolism, are increasingly recognized as central to brain function and behavior. This review examines how mitochondria are pivotal in linking cellular energy processes with the functioning of neural circuits that govern fear and anxiety. Following an introductory section in which we summarize current knowledge about fear and anxiety neural circuits, we provide a brief summary of mitochondria fundamental roles (e.g., from energy production and calcium buffering to their involvement in reactive oxygen species (ROS) generation, mitochondrial dynamics, and signaling), particularly emphasizing their contribution to synaptic plasticity, neurodevelopment, and stress response mechanisms. The review's core focuses on the current state of knowledge regarding how mitochondrial function and dysfunction impact the neural substrates of fear and anxiety. Furthermore, we explore the implications of mitochondrial alterations in the context of posttraumatic stress disorder (PTSD) and anxiety disorders, underscoring the potential of mitochondrial pathways as new therapeutic targets. Integrating insights from genetic, biochemical, neurobiological, behavioral, and clinical studies, we propose a model in which mitochondrial function is critical for regulating the neural circuits that underpin fear and anxiety behaviors, highlighting how mitochondrial dysfunction can lead to their pathological manifestations. This integration emphasizes the potential for developing novel treatments targeting the biological roots of fear, anxiety, and related disorders. By merging mitochondrial biology with behavioral and circuit neuroscience, we enrich our neurobiological understanding of fear and anxiety, uncovering promising avenues for therapeutic intervention.

Impacts of linseed oil diet on anxiety and memory extinction after early life stress: A sex-specific analysis of mitochondrial dysfunction, astrocytic markers, and inflammation in the amygdala

Early exposure to stressors affects how the organism reacts to stimuli, its emotional state throughout life, and how it deals with emotional memories. Consequently, it may affect susceptibility to psychopathology later in life. We used an animal model of early stress by maternal separation to study its potential impact on the extinction of aversive memories and anxiety-like behavior in adulthood, as well as its effects on mitochondrial functionality, inflammatory and astrocytic markers in the amygdala. We also assessed whether a diet enriched with linseed oil, known for its high content in omega-3 fats, could be used to attenuate the behavioral and neurochemical effects of early stress. Litters of Wistar rats were divided into controls (intact) or subjected to maternal separation (MS). They were subdivided into two groups receiving isocaloric diets enriched in soy or linseed oils at weaning. In adulthood, the animals were exposed to the open field and the elevated plus maze, to evaluate exploratory activity and anxiety-like behavior. They were also trained in a context of fear conditioning, and afterward subjected to an extinction session, followed by a test session to evaluate the extinction memory. Amygdalae were evaluated for inflammatory cytokines (interleukin (IL)-1beta, IL-6, and tumor-necrose factor (TNF)-alpha), mitochondrial functionality, and astrocyte markers (glial fibrillary acidic protein - GFAP, S100B, and glutamine synthetase activity). MS induced anxiety-like behavior in the elevated plus-maze, which was reversed by a diet enriched in linseed oil offered from weaning. When testing the memory of an extinction session of fear conditioning, MS animals showed more freezing behavior. MS males receiving a linseed oil-enriched diet had lower functional mitochondria in the amygdala. In addition, MS led to increased inflammatory cytokines, particularly IL-1beta, and the diet enriched in linseed oil further increased these levels in MS animals. MS also increased S100B levels. These results point to a higher emotionality presented by MS animals, with higher levels of inflammatory cytokines and S100B. While a diet enriched in linseed oil attenuated anxiety-like behavior, it further altered amygdala IL-1beta and reduced mitochondria functionality, particularly in males. MS also increased glutamine synthetase activity in the amygdala, and this effect was higher when the animals received a diet enriched in linseed oil, particularly in females. In conclusion, these results point to MS effects on emotional behavior, and neurochemical alterations in the amygdala, with sex-specific effects. Although a diet enriched in linseed oil appears to be able to reverse some of MS behavioral effects, these results must be considered with caution, since biochemical parameters could be worsened in MS animals receiving a linseed oil-enriched diet. This knowledge is important for the understanding of mechanisms of action of strategies aiming to reverse early stress effects, and future studies are warranted to determine possible interventions to promote resilience.

Mediation-adjusted multivariable Mendelian randomisation study identified novel metabolites related to mental health

BACKGROUND

From the pathway perspective, metabolites have the potential to improve knowledge about the aetiology of psychiatric diseases. Previous studies suggested a link between specific blood metabolites and mental disorders, but some Mendelian randomisation (MR) studies in particular are insufficient for various reasons.

OBJECTIVE

This study focused on bias assessment due to interdependencies between metabolites and psychiatric mediation effects.

METHODS

In a multistep framework containing network and multivariable MR, direct effects of 21 mutually adjusted metabolites on 8 psychiatric disorders were estimated based on summary statistics of genome-wide association studies from multiple resources. Robust inverse-variance weighted models were used in primary analyses. Several sensitivity analyses were performed to assess different patterns of pleiotropy and weak instrument bias. Estimates for the same phenotypes from different resources were pooled using fixed effect meta-analysis models.

FINDINGS

After adjusting for mediation effects, genetically predicted metabolite levels of six metabolites of lipid, amino acid and cofactors pathways were directly associated with overall six mental disorders (attention-deficit/hyperactivity disorder, bipolar disorder, anorexia nervosa, depression, post-traumatic stress disorder and schizophrenia). Point estimates ranged from -0.45 (95% CI -0.67; -0.24, p=1.0×104) to 1.78 (95% CI 0.85; 2.71, p=0.006). No associations were found with anxiety and suicide attempt.

CONCLUSIONS

This study provides insights into new metabolic pathways that seems to be causally related to certain mental disorders.

CLINICAL IMPLICATIONS

Further studies are needed to investigate whether the identified associations are effects of the metabolites itself or the biochemical pathway regulating the metabolites.

Resveratrol: A Multifaceted Guardian against Anxiety and Stress Disorders-An Overview of Experimental Evidence

The medicinal properties of resveratrol have garnered increasing attention from researchers. Extensive data have been accumulated on its use in treating cardiovascular diseases, immune system disorders, cancer, neurological diseases, and behavioral disorders. The protective mechanisms of resveratrol, particularly in anxiety-related stress disorders, have been well documented. However, less attention has been given to the side effects of resveratrol. This review explores not only the mechanisms underlying the anxiolytic effects of resveratrol but also the mechanisms that may lead to increased anxiety following resveratrol treatment. Understanding these mechanisms is crucial for enhancing the efficacy of resveratrol in managing anxiety disorders associated with stress and PTSD.

Uncertainty and anxiety: Evolution and neurobiology

Anxiety is a complex phenomenon: Its eliciting stimuli and circumstances, component behaviors, and functional consequences are only slowly coming to be understood. Here, we examine defense systems from field studies; laboratory studies focusing on experimental analyses of behavior; and, the fear conditioning literature, with a focus on the role of uncertainty in promoting an anxiety pattern that involves high rates of stimulus generalization and resistance to extinction. Respectively, these different areas provide information on evolved elicitors of defense (field studies); outline a defense system focused on obtaining information about uncertain threat (ethoexperimental analyses); and, provide a simple, well-researched, easily measured paradigm for analysis of nonassociative stress-enhanced fear conditioning (the SEFL). Results suggest that all of these-each of which is responsive to uncertainty-play multiple and interactive roles in anxiety. Brain system findings for some relevant models are reviewed, with suggestions that further analyses of current models may be capable of providing a great deal of additional information about these complex interactions and their underlying biology.

Exploring the effect of Anshen Dingzhi prescription on hippocampal mitochondrial signals in single prolonged stress mouse model

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE

Anshen Dingzhi prescription (ADP), which was first published in the masterpiece of traditional Chinese Medicine in the Qing Dynasty, "Yi Xue Xin Wu" (1732 CE), is documented to interrupt panic-related disorders. However, the mechanism of its action is still not clear.

AIM OF THE STUDY

This study aims to investigate the effects of ADP on post-traumatic stress disorder (PTSD)-like behaviors and explore the mechanism from perspective of sirtuin1 (SIRT1)-peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α)-dependent mitochondrial function.

MATERIALS AND METHODS

The changes of SIRT1-PGC-1α signal and mitochondrial function were evaluated in the hippocampus of mice receiving single prolonged stress (SPS). Later, the roles of this signaling pathway played in fear memory generalization and anxiety-like behavior in SPS mice was investigated using two agonists of this signaling pathway. On this basis, the effects of ADP (36.8 mg/kg) with definite therapeutic effects, on mitochondrial function were investigated and further confirmed by a SIRT1 inhibitor. Finally, the possible components of ADP targeting PGC-1α were monitored through bioinformatics.

RESULTS

Compared with control mice, SIRT1-PGC-1α signal in the hippocampus was impaired in SPS mice, accompanied with dysfunction of mitochondria and abnormal expression of synaptic proteins. The agonists of SIRT1-PGC-1α signal, ZLN005, as well as resveratrol improved the behavioral changes of mice caused by SPS, reversed the decline of proteins in SIRT1-PGC-1α signal, mitochondrial dysfunction, and the abnormal expression of synaptic proteins. The fingerprint was established for the quality control of ADP. At a dose of 36.8 mg/kg, ADP could prevent fear memory generalization and anxiety-like behavior in SPS mice. Mechanically, ADP promoted SIRT1-PGC-1α signal and repaired mitochondrial function. Importantly, SIRT1 inhibitor, selisistat eliminated the ameliorative effects of ADP on behavioral and mitochondrial function. Through molecular docking simulation, the brain-entering components of ADP, including malkangunin, Rg5, fumarine, frutinone A, celabenzine, and inermin had high binding energy with PGC-1α.

CONCLUSION

Dysfunction of SIRT1-PGC-1α-dependent mitochondrial function is attributed to SPS-triggered fear generalization and anxiety-like behavior, and ADP could improve PTSD-like behaviors likely through activating this signaling pathway.

Potential oxidative stress related targets of mitochondria-focused therapy of PTSD

Post-traumatic stress disorder (PTSD) remains a highly prevalent, under-diagnosed, and under-treated psychiatric disorder that often deteriorates over time, and is highly comorbid with major depressive disorder, suicidality, and substance use disorder. Several biomarkers have been proposed but have yet to be implemented into clinical practice. Treatments, including selective serotonin reuptake inhibitors, are efficacious in only a small number of patients, which underscores the need to develop novel, efficient treatments. Mitochondrial dysfunction resulting from chronic oxidative stress has been linked with both altered neurotransmitter signaling and the inflammatory response. Hereinafter, we discuss mechanisms by which mitochondrial dysfunction may contribute to the development of PTSD symptoms, and how these may even increase PTSD susceptibility. We also highlight possible therapeutic targets to reduce oxidative stress to prevent or treat PTSD symptoms.

Unveiling the Link: Exploring Mitochondrial Dysfunction as a Probable Mechanism of Hepatic Damage in Post-Traumatic Stress Syndrome

PTSD is associated with disturbed hepatic morphology and metabolism. Neuronal mitochondrial dysfunction is considered a subcellular determinant of PTSD, but a link between hepatic mitochondrial dysfunction and hepatic damage in PTSD has not been demonstrated. Thus, the effects of experimental PTSD on the livers of high anxiety (HA) and low anxiety (LA) rats were compared, and mitochondrial determinants underlying the difference in their hepatic damage were investigated. Rats were exposed to predator stress for 10 days. Then, 14 days post-stress, the rats were evaluated with an elevated plus maze and assigned to HA and LA groups according to their anxiety index. Experimental PTSD caused dystrophic changes in hepatocytes of HA rats and hepatocellular damage evident by increased plasma ALT and AST activities. Mitochondrial dysfunction was evident as a predominance of small-size mitochondria in HA rats, which was positively correlated with anxiety index, activities of plasma transaminases, hepatic lipids, and negatively correlated with hepatic glycogen. In contrast, LA rats had a predominance of medium-sized mitochondria. Thus, we show links between mitochondrial dysfunction, hepatic damage, and heightened anxiety in PTSD rats. These results will provide a foundation for future research on the role of hepatic dysfunction in PTSD pathogenesis.

Sodium aescinate improve behavioral performance by inhibiting dorsal raphe nucleus NLRP3 inflammasome in Post-traumatic stress disorder Rat Model

Growing evidence suggest that NLRP3 inflammasome activation in hippocampus and amygdala is involved in the pathophysiology of PTSD. Our previous studies have demonstrated that apoptosis of dorsal raphe nucleus (DRN) contributes to the pathological progression of PTSD. Recent studies by others have shown that in brain injury sodium aescinate (SA) has a protective effect on neurons by inhibiting inflammatory response pathways, thereby relieving symptoms. Here, we extend the therapeutic effects of SA to PTSD rats. We found that PTSD was associated with significant activation of the NLRP3 inflammasome in DRN, whereas administration of SA significantly inhibited DRN NLRP3 inflammasome activation and reduced DRN apoptosis level. SA also improved learning and memory ability and reduced anxiety and depression level in PTSD rats. In addition, NLRP3 inflammasome activation in DRN of PTSD rats impaired mitochondria function by inhibiting ATP synthesis and increasing ROS production, whereas SA can effectively reverse the pathological progression of mitochondria. We recommend SA as a new candidate for the pharmacological treatment of PTSD.