Mitochondrial dysfunction as a possible trigger of neuroinflammation at post-traumatic stress disorder (PTSD)

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.

Vicious cycle of oxidative stress and neuroinflammation in pathophysiology of chronic vascular encephalopathy

Chronic vascular encephalopathy (CVE) is a frequent cause of vascular mild cognitive impairment and dementia, which significantly worsens the quality of life, especially in the elderly population. CVE is a result of chronic cerebral hypoperfusion, characterized by prolonged limited blood flow to the brain. This causes insufficient oxygenation of the brain leading to hypoxia. The latter can trigger a series of events associated with the development of oxidative/reductive stresses and neuroinflammation. Addressing the gap in knowledge regarding oxidative and reductive stresses in the development of vascular disorders and neuroinflammation can give a start to new directions of research in the context of CVE. In this review, we consider the hypoxia-induced molecular challenges involved in the pathophysiology of CVE, focusing on oxidative stress and neuroinflammation, which are combined in a vicious cycle of neurodegeneration. We also briefly describe therapeutic approaches to the treatment of CVE and outline the prospects for the use of sulforaphane, an isothiocyanate common in cruciferous plants, and vitamin D to break the vicious cycle and alleviate the cognitive impairments characteristic of patients with CVE.

Suvorexant improves mitochondrial dynamics with the regulation of orexinergic and mTOR activation in rats exhibiting PTSD-like symptoms

BACKGROUND

Increasing evidence suggests that mitochondrial dysfunction plays a significant role in PTSD. However, the exact mechanism is still unclear. Mitochondrial dynamics could be one of the mechanisms, as it is crucial for mitochondrial homeostasis and is widely affected in traumatic situations. Mitochondrial dynamics regulate mitochondrial homeostasis via orexinergic receptors, and it is shown that antagonism of orexinergic receptors attenuates PTSD-like symptoms. Therefore, the present study aimed to determine how orexin antagonists affect mitochondrial dynamics in rats exhibiting PTSD-like symptoms.

METHODS

Using rats, a stress-re-stress (SRS) model with PTSD-like symptoms was established. On day 2 (D-2), the animals were exposed to variable stressors including 2 h of restraint followed by brief mild foot shock and exposure to 4%halothane. Foot shock was performed as a re-stress from D-8 to D-32 at six-day intervals.

RESULTS

SRS exposure caused PTSD-like phenotype, hypothalamic-pituitary-adrenal axis dysfunction, activation of mammalian target of rapamycin (mTOR), and mitochondrial-fission-process-1 (MTFP-1). SRS-subjected rats exhibited enhanced expression of fission-regulating proteins, including dynamin-related protein-1 and mitochondrial-fission-protein-1 and reduced expression of fusion-regulating proteins, including optic-atrophy-1 and mitofusin-2, in the amygdala. TEM analysis revealed that SRS exposure further damaged the mitochondria. Treatment with suvorexant with rapamycin significantly mitigated PTSD-like symptoms and improved mitochondrial dynamics in SRS-exposed rats. However, their combination showed a more pronounced effect. Further, suvorexant in combination with rapamycin significantly mitigated mTOR and MTFP-1 activation. Sertraline attenuated PTSD-like symptoms without affecting SRS-induced activation of mTOR and disparity in mitochondrial dynamics. Suvorexant pharmacological effects on mitochondrial biogenesis also involve the mTOR pathway.

LIMITATION

The role of orexinergic pathway in SRS-induced mitochondrial mitophagy was not explored.

CONCLUSIONS

Targeting both the orexinergic and mTOR pathways might exert a beneficial synergistic effect for treating PTSD.