Microglia and Reactive Oxygen Species Are Required for Behavioral Susceptibility to Chronic Social Defeat Stress

Basal forebrain cholinergic systems as circuits through which traumatic stress disrupts emotional memory regulation

Contextual and spatial systems facilitate changes in emotional memory regulation brought on by traumatic stress. Cholinergic basal forebrain (chBF) neurons provide input to contextual/spatial systems and although chBF neurons are important for emotional memory, it is unknown how they contribute to the traumatic stress effects on emotional memory. Clusters of chBF neurons that project to the prefrontal cortex (PFC) modulate fear conditioned suppression and passive avoidance, while clusters of chBF neurons that project to the hippocampus (Hipp) and PFC (i.e. cholinergic medial septum and diagonal bands of Broca (chMS/DBB neurons) are critical for fear extinction. Interestingly, neither Hipp nor PFC projecting chMS/DBB neurons are critical for fear extinction. The retrosplenial cortex (RSC) is a contextual/spatial memory system that receives input from chMS/DBB neurons, but whether this chMS/DBB-RSC circuit facilitates traumatic stress effects on emotional memory remain unexplored. Traumatic stress leads to neuroinflammation and the buildup of reactive oxygen species. These two molecular processes may converge to disrupt chBF circuits enhancing the impact of traumatic stress on emotional memory.

Diosgenin alleviates alcohol-mediated escalation of social defeat stress and the neurobiological sequalae

RATIONALE

Emerging evidence indicates that persistent alcohol consumption escalates psychosocial trauma achieved by social defeat stress (SDS)-induced neurobiological changes and behavioral outcomes. Treatment with compounds with neuroprotective functions is believed to reverse ethanol (EtOH)-aggravated SDS-induced behavioral impairments.

OBJECTIVES

We investigated the outcomes of diosgenin treatment, a phytosteroidal sapogenin in mice co-exposed to repeated SDS and EtOH administration.

METHODS

During a period of 14 days, SDS male mice were repeatedly administered EtOH (20%, 10 mL/kg) orally from days 8-14 (n = 9). Within days 1-14, SDS mice fed with EtOH were simultaneously treated with diosgenin (25 and 50 mg/kg) or fluoxetine (10 mg/kg) by oral gavage. Locomotor, cognitive-, depressive-, and anxiety-like behaviors were assessed. Adrenal weight, serum glucose, and corticosterone levels were assayed. Brain markers of oxido-inflammatory, neurochemical levels, monoamine oxidase-B, and acetylcholinesterase activities were measured in the striatum, prefrontal cortex, and hippocampus.

RESULTS

The anxiety-like behavior, depression, low stress resilience, social, and spatial/non-spatial memory decline exhibited by SDS mice exposed to repeated EtOH administration were alleviated by diosgenin (25 and 50 mg/kg) and fluoxetine, illustrated by increased dopamine and serotonin concentrations and reduced monoamine oxidase-B and acetylcholinesterase activities in the prefrontal cortex, hippocampus, and striatum. Diosgenin attenuated SDS + EtOH interaction induced corticosterone release and adrenal hypertrophy, accompanied by reduced TNF-α, IL-6, malondialdehyde, and nitrite levels in the striatum, prefrontal cortex, and hippocampus. Diosgenin increased glutathione, superoxide dismutase, and catalase levels in SDS + EtOH-exposed mice.

CONCLUSIONS

Our data suggest that diosgenin reverses SDS + EtOH interaction-induced behavioral changes via normalization of hypothalamic-pituitary-adrenal axis, neurochemical neurotransmissions, and inhibition of oxidative and inflammatory mediators in mice brains.

NADPH-oxidases as potential pharmacological targets for thrombosis and depression comorbidity

There is a complex interrelationship between the nervous system and the cardiovascular system. Comorbidities of cardiovascular diseases (CVD) with mental disorders, and vice versa, are prevalent. Adults with mental disorders such as anxiety and depression have a higher risk of developing CVD, and people with CVD have an increased risk of being diagnosed with mental disorders. Oxidative stress is one of the many pathways associated with the pathophysiology of brain and cardiovascular disease. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is one of the major generators of reactive oxygen species (ROS) in mammalian cells, as it is the enzyme that specifically produces superoxide. This review summarizes recent findings on the consequences of NOX activation in thrombosis and depression. It also discusses the therapeutic effects and pharmacological strategies of NOX inhibitors in CVD and brain disorders. A better comprehension of these processes could facilitate the development of new therapeutic approaches for the prevention and treatment of the comorbidity of thrombosis and depression.

Stress and traumatic brain injury: An inherent bi-directional relationship with temporal and synergistic complexities

Traumatic brain injury (TBI) and stress are prevalent worldwide and can both result in life-altering health problems. While stress often occurs in the absence of TBI, TBI inherently involves some element of stress. Furthermore, because there is pathophysiological overlap between stress and TBI, it is likely that stress influences TBI outcomes. However, there are temporal complexities in this relationship (e.g., when the stress occurs) that have been understudied despite their potential importance. This paper begins by introducing TBI and stress and highlighting some of their possible synergistic mechanisms including inflammation, excitotoxicity, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, and autonomic nervous system dysfunction. We next describe different temporal scenarios involving TBI and stress and review the available literature on this topic. In doing so we find initial evidence that in some contexts stress is a highly influential factor in TBI pathophysiology and recovery, and vice versa. We also identify important knowledge gaps and suggest future research avenues that will increase our understanding of this inherent bidirectional relationship and could one day result in improved patient care.

Antidepressant and Anxiolytic Effects of Fermented Huauzontle, a Prehispanic Mexican Pseudocereal

This study aimed to assess the potential antidepressant- and anxiolytic-like effects of huauzontle fermented by Lactiplantibacillus plantarum Lp22. The possible association between oxidative stress/inflammation biomarkers and unconditional behavioural tests was also evaluated. Red light-induced stress mice C57Bl/6 (n = 5 per group) received orally either fermented or unfermented huauzontle, diazepam or fluoxetine. A non-stressed group which received saline solution was also included. Then, anxiety-related and depression-related behaviour tests were performed; after that, blood and tissues samples were collected to determine oxidative stress/inflammation biomarkers. The mice receiving both fermented and unfermented huauzontle spent more time (94 s) in open arms in the elevated plus maze test p < 0.05; besides, travelled longer distance (p < 0.05) and increased by more than 50% the exploration time for the open field, as well as the time spent in the illuminated zone (197 s) in the light/dark test. Furthermore, reduced immobility time in the tail suspension and forced swim tests (23.1 and 15.85, respectively), and anhedonia was no detected in the sucrose preference test. The oxidative stress index was lower in the liver of fermented huauzontle-treated mice, while enhanced levels of IL-10, MCP-1 and BDNF in plasma, and lipoxygenase (LOX) activity in the hippocampus were found. Finally, PCA revealed a positive correlation among LOX and BDNF and parameters determined in the anxiety tests, as between catalase activity and immobility time in the depression test. These findings indicate the novel potential therapeutic applications of fermented huauzontle on depression and anxiety-like behaviours possibly mediated by antioxidant and anti-inflammatory mechanisms.

Inhibition of Microbiota-dependent Trimethylamine N-Oxide Production Ameliorates High Salt Diet-Induced Sympathetic Excitation and Hypertension in Rats by Attenuating Central Neuroinflammation and Oxidative Stress

Excessive dietary salt intake induces neuroinflammation and oxidative stress in the brain, which lead to sympathetic excitation, contributing to hypertension. However, the underlying mechanisms remain elusive. Accumulating evidence reveals that trimethylamine-N-oxide (TMAO), a gut microbiota-derived metabolite, is implicated in the pathogenesis of multiple cardiovascular diseases. The present study sought to determine whether central TMAO is elevated and associated with neuroinflammation and oxidative stress in the brain after long-term high salt (HS) diet intake and, if so, whether inhibition of TMAO generation ameliorates HS-induced sympathetic excitation and hypertension. Sprague-Dawley rats were fed either a HS diet or a normal salt (NS) diet and simultaneously treated with vehicle (VEH) or 1.0% 3,3-Dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) for 8 weeks. HS + VEH rats, compared with NS + VEH rats, had elevated TMAO in plasma and cerebrospinal fluid (CSF), increased blood pressure (BP), and increased sympathetic drive as indicated by the BP response to ganglionic blockade and plasma norepinephrine levels. HS-induced these changes were attenuated by DMB, which significantly reduced TMAO in plasma and CSF. Neuroinflammation as assessed by proinflammatory cytokine expression and NF-κB activity and microglial activity, and oxidative stress as measured by NAD(P)H oxidase subunit expression and NAD(P)H activity and reactive oxygen species (ROS) production in the hypothalamic paraventricular nucleus (PVN) were increased in HS + VEH rats but were decreased by DMB. DMB had no effects on above measured parameters in NS rats. The results suggest that long-term HS diet intake causes elevation in TMAO in the circulation and brain, which is associated with increased neuroinflammation and oxidative stress in the PVN, an important cardiovascular regulatory center. Inhibition of TMAO generation ameliorates HS-induced sympathetic excitation and hypertension by reducing neuroinflammation and oxidative stress in the PVN.

Treatment With the CSF1R Antagonist GW2580, Sensitizes Microglia to Reactive Oxygen Species

Microglia activation and proliferation are hallmarks of many neurodegenerative disorders and may contribute to disease pathogenesis. Neurons actively regulate microglia survival and function, in part by secreting the microglia mitogen interleukin (IL)-34. Both IL-34 and colony stimulating factor (CSF)-1 bind colony stimulating factor receptor (CSFR)1 expressed on microglia. Systemic treatment with central nervous system (CNS) penetrant, CSFR1 antagonists, results in microglia death in a dose dependent matter, while others, such as GW2580, suppress activation during disease states without altering viability. However, it is not known how treatment with non-penetrant CSF1R antagonists, such as GW2580, affect the normal physiology of microglia. To determine how GW2580 affects microglia function, C57BL/6J mice were orally gavaged with vehicle or GW2580 (80mg/kg/d) for 8 days. Body weights and burrowing behavior were measured throughout the experiment. The effects of GW2580 on circulating leukocyte populations, brain microglia morphology, and the transcriptome of magnetically isolated adult brain microglia were determined. Body weights, burrowing behavior, and circulating leukocytes were not affected by treatment. Analysis of Iba-1 stained brain microglia indicated that GW2580 treatment altered morphology, but not cell number. Analysis of RNA-sequencing data indicated that genes related to reactive oxygen species (ROS) regulation and survival were suppressed by treatment. Treatment of primary microglia cultures with GW2580 resulted in a dose-dependent reduction in viability only when the cells were concurrently treated with LPS, an inducer of ROS. Pre-treatment with the ROS inhibitor, YCG063, blocked treatment induced reductions in viability. Finally, GW2580 sensitized microglia to hydrogen peroxide induced cell death. Together, these data suggest that partial CSF1R antagonism may render microglia more susceptible to reactive oxygen and nitrogen species.

Gut microbiota and neuropsychiatric disorders: Implications for neuroendocrine-immune regulation

Recently, increasing evidence has shown gut microbiota dysbiosis might be implicated in the physiological mechanisms of neuropsychiatric disorders. Altered microbial community composition, diversity and distribution traits have been reported in neuropsychiatric disorders. However, the exact pathways by which the intestinal microbiota contribute to neuropsychiatric disorders remain largely unknown. Given that the onset and progression of neuropsychiatric disorders are characterized with complicated alterations of neuroendocrine and immunology, both of which can be continually affected by gut microbiota via "microbiome-gut-brain axis". Thus, we assess the complicated crosstalk between neuroendocrine and immunological regulation might underlie the mechanisms of gut microbiota associated with neuropsychiatric disorders. In this review, we summarized clinical and preclinical evidence on the role of the gut microbiota in neuropsychiatry disorders, especially in mood disorders and neurodevelopmental disorders. This review may elaborate the potential mechanisms of gut microbiota implicating in neuroendocrine-immune regulation and provide a comprehensive understanding of physiological mechanisms for neuropsychiatric disorders.

Deciphering the Potential Neuroprotective Effects of Luteolin against Aβ1-42-Induced Alzheimer's Disease

The current study was undertaken to unveil the protective effects of Luteolin, a natural flavonoid, against amyloid-beta (Aβ₁–₄₂)-induced neuroinflammation, amyloidogenesis, and synaptic dysfunction in mice. For the development of an AD mouse model, amyloid-beta (Aβ₁–₄₂, 5 μL/5 min/mouse) oligomers were injected intracerebroventricularly (i.c.v.) into mice’s brain by using a stereotaxic frame. After that, the mice were treated with Luteolin for two weeks at a dose of 80 mg/kg/day. To monitor the biochemical changes, we conducted western blotting and immunofluorescence analysis. According to our findings, the infusion of amyloid-beta activated c-Jun N-terminal kinases (p-JNK), p38 mitogen-activated protein kinases, glial fibrillary acidic protein (GFAP), and ionized calcium adaptor molecule 1 (Iba-1) in the cortex and hippocampus of the experimental mice; these changes were significantly inhibited in Aβ₁–₄₂ + Luteolin-treated mice. Likewise, we also checked the expression of inflammatory markers, such as p-nuclear factor-kB p65 (p-NF-kB p65 (Ser536), tissue necrosis factor (TNF-α), and Interleukin1-β (IL-1β), in Aβ₁–₄₂-injected mice brain, which was attenuated in Aβ₁–₄₂ + Luteolin-treated mice brains. Further, we investigated the expression of pro- and anti-apoptotic cell death markers such as Bax, Bcl-2, Caspase-3, and Cox-2, which was significantly reduced in Aβ₁–₄₂ + Lut-treated mice brains compared to the brains of the Aβ-injected group. The results also indicated that with the administration of Aβ₁–₄₂, the expression levels of β-site amyloid precursor protein cleaving enzyme (BACE-1) and amyloid-beta (Aβ₁–₄₂) were significantly enhanced, while they were reduced in Aβ₁–₄₂ + Luteolin-treated mice. We also checked the expression of synaptic markers such as PSD-95 and SNAP-25, which was significantly enhanced in Aβ₁–₄₂ + Lut-treated mice. To unveil the underlying factors responsible for the protective effects of Luteolin against AD, we used a specific JNK inhibitor, which suggested that Luteolin reduced Aβ-associated neuroinflammation and neurodegeneration via inhibition of JNK. Collectively, our results indicate that Luteolin could serve as a novel therapeutic agent against AD-like pathological changes in mice.

Sleep, Narcolepsy, and Sodium Oxybate

Sodium oxybate (SO) has been in use for many decades to treat narcolepsy with cataplexy. It functions as a weak GABAB agonist but also as an energy source for the brain as a result of its metabolism to succinate and as a powerful antioxidant because of its capacity to induce the formation of NADPH. Its actions at thalamic GABAB receptors can induce slow-wave activity, while its actions at GABAB receptors on monoaminergic neurons can induce or delay REM sleep. By altering the balance between monoaminergic and cholinergic neuronal activity, SO uniquely can induce and prevent cataplexy. The formation of NADPH may enhance sleep’s restorative process by accelerating the removal of the reactive oxygen species (ROS), which accumulate during wakefulness. SO improves alertness in normal subjects and in patients with narcolepsy. SO may allay severe psychological stress - an inflammatory state triggered by increased levels of ROS and characterized by cholinergic supersensitivity and monoaminergic deficiency. SO may be able to eliminate the inflammatory state and correct the cholinergic/ monoaminergic imbalance.