Fish Oil Prevents Lipopolysaccharide-Induced Depressive-Like Behavior by Inhibiting Neuroinflammation

Pre-clinical studies comparing the anti-inflammatory potential of artemisinic compounds by targeting NFκB/TNF-α/NLRP3 and Nrf2/TRX pathways in Balb/C mice

Artemisinin, artemether, artesunate, and dihydroartemisinin are renowned for their antimalarial potential. The current study aims to repurpose the above-mentioned artemisinic compounds (ACs) by conducting an intercomparison to evaluate their antiinflammatory potential (AIP). In order to develop potential candidates for the evaluation of AIP of ACs (50 and 100 mg/kg BW), carbon tetrachloride (1ml/kg body weight (BW)) was administered intraperitoneally to BALB/c mice. Alterations in animal behavior were assessed weekly through tail suspension test, force swim test, open field test, Y-maze test, inverted screen analysis, and weight lifting test. Aberrations in hematological, serological, endogenous antioxidants, and oxidative stress marker profiles were assessed in all twelve groups. Histological alterations were read using hematoxylin and eosin staining. Levels of inflammatory markers including nuclear factor kappa B (NF-κB), tumor necrosis factor alpha (TNF-α), and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), were determined using immunohistochemical analysis (IHCA). Antioxidant markers i.e., nuclear factor erythroid-2-related factor (Nrf-2) and thioredoxin (TRX) were also quantified through IHCA. Comet assay was performed to quantify DNA damage. Oral administration of ACs to mice significantly alleviated the carbon tetrachloride induced inflammation in comparison with silymarin. Reduced levels of several inflammatory markers including nitric oxide, thiobarbituric acid reactive substances, interleukin-1 beta, NF-κB, TNF-α, and NLRP3, underscore the substantial AIP of ACs. IHCA depicted the revitalized percent relative expression of Nrf-2 and TRX in groups treated with ACs. Behavioral analysis revealed that ACs-treated groups significantly (p<0.05) attenuated the memory deficit, anxiety, and depressive-like behavior. Moreover, histopathological, hematological, serological, and endogenous antioxidant profiles indicated substantial AIP of ACs. Findings of comet assay further bolstered the compelling evidence as DNA damage was significantly (p<0.05) curbed down after ACs (100 mg/kg) treatment. All these outcomes implied that ACs exhibited AIP in a dose-dependent manner with maximal AIP imparted by artemisinin (100 mg/kg). This pre-clinical investigation avers the tremendous AIP of ACs targeting key molecular pathways. The current study divulges artemisinin as the most potent antiinflammatory agent among the tested compounds.

Hemerocallis citrina Baroni ameliorates chronic sleep deprivation-induced cognitive deficits and depressive-like behaviours in mice

Sleep deprivation (SD) is common during spaceflight. SD is known to cause cognitive deficits and depression, requiring treatment and prevention. Hemerocallis citrina Baroni (Liliaceae) is a perennial herb with antidepressant, antioxidant, antitumor, anti-inflammatory, and neuroprotective effects.The aim of our study was to investigate the effects of H. citrina extract (HCE) on SD-induced cognitive decline and depression-like behavior and possible neuroinflammation-related mechanisms. HCE (2 g/kg/day, i.g.) or vortioxetine (10 mg/kg/day, i.g.) were given to mice by oral gavage for a total of 28 days during the SD process. HCE treatment was found to ameliorate SD-induced impairment of short- and long-term spatial and nonspatial memory, measured using Y-maze, object recognition, and Morris water maze tests, as well as mitigating SD-induced depression-like behaviors, measured by tail suspension and forced swimming tests. HCE also reduced the levels of inflammatory cytokines (IL-1β, IL-18, and IL-6) in the serum and hippocampus. Furthermore, HCE suppressed SD-induced microglial activation in the prefrontal cortex (PFC) and the CA1 and dentate gyrus (DG) regions of the hippocampus. HCE also inhibited the expression of phosphorylated NF-κB and activation of the NLRP3 inflammasome. In summary, our findings indicated that HCE attenuated SD-induced cognitive impairment and depression-like behavior and that this effect may be mediated by the inhibition of inflammatory progression and microglial activation in the hippocampus, as well as the down-regulation of NF-κB and NLRP3 signaling. The findings of these studies showingTthese results indicate that HCE exerts neuroprotective effects and are consistent with the findings of previous studies, suggesting that HCE is beneficial for the prevention and treatment of cognitive decline and depression in SD.

Ginsenoside Rg1 Attenuates Chronic Sleep Deprivation-Induced Hippocampal Mitochondrial Dysfunction and Improves Memory by the AMPK-SIRT3 Pathway

Ginsenoside Rg1 (Rg1) is the main bioactive ginseng component. This study investigates the effects of Rg1 on cognitive deficits triggered by chronic sleep deprivation stress (CSDS) and explores its underlying mechanisms. Rg1 effectively improved spatial working and recognition memory, as evidenced by various behavioral tests. RNA-sequence analysis revealed differential gene expression in the metabolic pathway. Treatment with Rg1 abrogated reductions in SOD and CAT activity, lowered MDA content, and increased Nrf2 and HO-1 protein levels. Rg1 administration alleviated hippocampal mitochondrial dysfunction by restoring normal ultrastructure and enhancing ATP activities and Mfn2 expression while regulating Drp-1 expression. Rg1 mitigated neuronal apoptosis by reducing the Bax/Bcl-2 ratio and the levels of cleaved caspase-3. Additionally, Rg1 upregulated AMPK and SIRT3 protein expressions. These findings suggest that Rg1 has potential as a robust intervention for cognitive dysfunction associated with sleep deprivation, acting through the modulation of mitochondrial function, oxidative stress, apoptosis, and the AMPK-SIRT3 axis.

Gut Microbiota in Ischemic Stroke: Role of Gut Bacteria-Derived Metabolites

Ischemic stroke (IS) remains a leading cause of death and long-term disability globally. Several mechanisms including glutamate excitotoxicity, calcium overload, neuroinflammation, oxidative stress, mitochondrial damage, and apoptosis are known to be involved in the pathogenesis of IS, but the underlying pathophysiology mechanisms of IS are not fully clarified. During the past decade, gut microbiota were recognized as a key regulator to affect the health of the host either directly or via their metabolites. Recent studies indicate that gut bacterial dysbiosis is closely related to hypertension, diabetes, obesity, dyslipidemia, and metabolic syndrome, which are the main risk factors for cardiovascular diseases. Increasing evidence indicates that IS can lead to perturbation in gut microbiota and increased permeability of the gut mucosa, known as "leaky gut," resulting in endotoxemia and bacterial translocation. In turn, gut dysbiosis and impaired intestinal permeability can alter gut bacterial metabolite signaling profile from the gut to the brain. Microbiota-derived products and metabolites, such as short-chain fatty acids (SCFAs), bile acids (BAs), trimethylamine N-oxide (TMAO), lipopolysaccharides (LPS), and phenylacetylglutamine (PAGln) can exert beneficial or detrimental effects on various extraintestinal organs, including the brain, liver, and heart. These metabolites have been increasingly acknowledged as biomarkers and mediators of IS. However, the specific role of the gut bacterial metabolites in the context of stroke remains incompletely understood. In-depth studies on these products and metabolites may provide new insight for the development of novel therapeutics for IS.

Major depressive disorder as a neuro-immune disorder: Origin, mechanisms, and therapeutic opportunities

Notwithstanding advances in understanding the pathophysiology of major depressive disorder (MDD), no single mechanism can explain all facets of this disorder. An expanding body of evidence indicates a putative role for the inflammatory response. Several meta-analyses showed an increase in systemic peripheral inflammatory markers in individuals with MDD. Numerous conditions and circumstances in the modern world may promote chronic systemic inflammation through mechanisms, including alterations in the gut microbiota. Peripheral cytokines may reach the brain and contribute to neuroinflammation through cellular, humoral, and neural pathways. On the other hand, antidepressant drugs may decrease peripheral levels of inflammatory markers. Anti-inflammatory drugs and nutritional strategies that reduce inflammation also could improve depressive symptoms. The present study provides a critical review of recent advances in the role of inflammation in the pathophysiology of MDD. Furthermore, this review discusses the role of glial cells and the main drivers of changes associated with neuroinflammation. Finally, we highlight possible novel neurotherapeutic targets for MDD that could exert antidepressant effects by modulating inflammation.

Dietary Flaxseed and Flaxseed Oil Differentially Modulate Aspects of the Microbiota Gut-Brain Axis Following an Acute Lipopolysaccharide Challenge in Male C57Bl/6 Mice

The microbiota gut-brain axis (mGBA) is an important contributor to mental health and neurological and mood disorders. Lipopolysaccharides (LPS) are endotoxins that are components of Gram-negative bacteria cell walls and have been widely shown to induce both systemic and neuro-inflammation. Flaxseed (Linum usitatissimum) is an oilseed rich in fibre, n3-poly-unsaturated fatty acid (alpha-linolenic acid (ALA)), and lignan, secoisolariciresinol diglucoside, which all can induce beneficial effects across varying aspects of the mGBA. The objective of this study was to determine the potential for dietary supplementation with flaxseed or flaxseed oil to attenuate LPS-induced inflammation through modulation of the mGBA. In this study, 72 5-week-old male C57Bl/6 mice were fed one of three isocaloric diets for 3 weeks: (1) AIN-93G basal diet (BD), (2) BD + 10% flaxseed (FS), or (3) BD + 4% FS oil (FO). Mice were then injected with LPS (1 mg/kg i.p) or saline (n = 12/group) and samples were collected 24 h post-injection. Dietary supplementation with FS, but not FO, partially attenuated LPS-induced systemic (serum TNF-α and IL-10) and neuro-inflammation (hippocampal and/or medial prefrontal cortex IL-10, TNF-α, IL-1β mRNA expression), but had no effect on sickness and nest-building behaviours. FS-fed mice had enhanced fecal microbial diversity with increased relative abundance of beneficial microbial groups (i.e., Lachnospiraceae, Bifidobacterium, Coriobacteriaceae), reduced Akkermansia muciniphila, and increased production of short-chain fatty acids (SCFAs), which may play a role in its anti-inflammatory response. Overall, this study highlights the potential for flaxseed to attenuate LPS-induced inflammation, in part through modulation of the intestinal microbiota, an effect which may not be solely driven by its ALA-rich oil component.

The Effect of Increasing Concentrations of Omega-3 Fatty Acids from either Flaxseed Oil or Preformed Docosahexaenoic Acid on Fatty Acid Composition, Plasma Oxylipin, and Immune Response of Laying Hens

BACKGROUND

There is a lack of nutrition guidelines for the feeding of omega-3 polyunsaturated fatty acids (PUFA) to laying hens. Knowledge as to whether the type and concentrations of α-linolenic acid (ALA) and/or docosahexaenoic acid (DHA) in the diet can make a difference to the birds' immune responses when subjected to a lipopolysaccharide (LPS) challenge is limited.

OBJECTIVES

The study was designed to determine the potential nutritional and health benefits to laying hens when receiving dietary omega-3 PUFA from either ALA or DHA.

METHODS

A total of 80 Lohmann LSL-Classic (white egg layer, 20 wk old) were randomly assigned to 1 of 8 treatment diets (10 hens/treatment), provided 0.2%, 0.4%, 0.6%, or 0.8% of total dietary omega-3 PUFA, provided as either ALA-rich flaxseed oil or DHA-enriched algal biomass. After an 8-wk feeding period, the birds were challenged with Escherichia coli-derived LPS (8 mg/kg; i.v. injection), with terminal sample collection 4 h after challenge. Egg yolk, plasma, liver, and spleen samples were collected for subsequent analyses.

RESULTS

Increasing dietary omega-3 supplementation yielded predictable responses in egg yolk, plasma, and liver fatty acid concentrations. Dietary intake of ALA contributed mainly to ALA-derived oxylipins. Meanwhile, eicosapentaenoic acid- and DHA-derived oxylipins were primarily influenced by DHA dietary intake. LPS increased the concentrations of almost all the omega-6 PUFA-, ALA-, and DHA-derived oxylipins in plasma and decreased hepatic mRNA expression of COX-2 and 5-LOX (P < 0.001) involved in the biosynthesis of oxylipins. LPS also increased mRNA expression of proinflammatory cytokine IFN-γ and receptor TLR-4 (P < 0.001) in the spleen.

CONCLUSIONS

These results revealed that dietary intake of ALA and DHA had unique impacts on fatty acid deposition and their derived oxylipins and inflammatory responses under the administration of LPS in laying hens.

Protective effects of ginsenosides Rg1 and Rb1 against cognitive impairment induced by simulated microgravity in rats

Microgravity experienced during space flight is known to exert several negative effects on the learning ability and memory of astronauts. Few effective strategies are currently available to counteract these effects. Rg1 and Rb1, the major steroidal components of ginseng, have shown potent neuroprotective effects with a high safety profile. The present study aimed to investigate the effects of Rg1 and Rb1 on simulated microgravity-induced learning and memory dysfunction and its underlying mechanism in the hindlimb suspension (HLS) rat model. Administration of Rg1 (30 and 60 μmol/kg) and Rb1 (30 and 60 μmol/kg) for 2 weeks resulted in a significant amelioration of impaired spatial and associative learning and memory caused by 4-week HLS exposure, measured using the Morris water maze and Reward operating conditioning reflex (ROCR) tests, respectively. Furthermore, Rg1 and Rb1 administration alleviated reactive oxygen species production and enhanced antioxidant enzyme activities in the prefrontal cortex (PFC). Rg1 and Rb1 also assisted in the recovery of mitochondrial complex I (NADH dehydrogenase) activities, increased the expression of Mfn2 and decreased the fission marker dynamin-related protein (Drp)-1expression. Additionally, Rg1 and Rb1 treatment increased the SYN, and PSD95 protein expressions and decreased the ratio of Bax:Bcl-2 and reduced the expression of cleaved caspase-3 and cytochrome C. Besides these, the BDNF-TrkB/PI3K-Akt pathway was also activated by Rg1 and Rb1 treatment. Altogether, Rg1 and Rb1 treatment attenuated cognitive deficits induced by HLS, mitigated mitochondrial dysfunction, attenuated oxidative stress, inhibited apoptosis, increased synaptic plasticity, and restored BDNF-TrkB/PI3K-Akt signaling.

Early-life stress and dietary fatty acids impact the brain lipid/oxylipin profile into adulthood, basally and in response to LPS

Brain lipid dysregulation is a hallmark of depression and Alzheimer's disease, also marked by chronic inflammation. Early-life stress (ELS) and dietary intake of polyunsaturated fatty acids (PUFAs) are risk factors for these pathologies and are known to impact inflammatory processes. However, if these early-life factors alter brain lipid homeostasis on the long-term and thereby contribute to this risk remains to be elucidated. We have recently shown that an early diet enriched in omega(ω)-3 PUFAs protected against the long-term negative effects of ELS on cognition and neuroinflammation. Here, we aim to understand if modulation of brain lipid and oxylipin profiles contributes to the detrimental effects of ELS and the protective ones of the diet. We therefore studied if and how ELS and early dietary PUFAs modulate the brain lipid and oxylipin profile, basally as well as in response to an inflammatory challenge, to unmask possible latent effects. Male mice were exposed to ELS via the limited bedding and nesting paradigm, received an early diet with high or low ω6/ω3 ratio (HRD and LRD) and were injected with saline or lipopolysaccharide (LPS) in adulthood. Twenty-four hours later plasma cytokines (Multiplex) and hypothalamic lipids and oxylipins (liquid chromatography tandem mass spectrometry) were measured. ELS exacerbated the LPS-induced increase in IL-6, CXCL1 and CCL2. Both ELS and diet affected the lipid/oxylipin profile long-term. For example, ELS increased diacylglycerol and LRD reduced triacylglycerol, free fatty acids and ceramides. Importantly, the ELS-induced alterations were strongly influenced by the early diet. For example, the ELS-induced decrease in eicosapentaenoic acid was reversed when fed LRD. Similarly, the majority of the LPS-induced alterations were distinct for control and ELS exposed mice and unique for mice fed with LRD or HRD. LPS decreased ceramides and lysophosphotidylcholine, increased hexosylceramides and prostaglandin E₂, reduced triacylglycerol species and ω6-derived oxylipins only in mice fed LRD and ELS reduced the LPS-induced increase in phosphatidylcholine. These data give further insights into the alterations in brain lipids and oxylipins that might contribute to the detrimental effects of ELS, to the protective ones of LRD and the possible early-origin of brain lipid dyshomeostasis characterizing ELS-related psychopathologies.

The Relationship between Stress, Inflammation, and Depression

A narrative review about the relationship between stress, inflammation, and depression is made as follows: Chronic stress leads to various stress-related diseases such as depression. Although most human diseases are related to stress exposure, the common pathways between stress and pathophysiological processes of different disorders are still debatable. Chronic inflammation is a crucial component of chronic diseases, including depression. Both experimental and clinical studies have demonstrated that an increase in the levels of pro-inflammatory cytokines and stress hormones, such as glucocorticoids, substantially contributes to the behavioral alterations associated with depression. Evidence suggests that inflammation plays a key role in the pathology of stress-related diseases; however, this link has not yet been completely explored. In this study, we aimed to determine the role of inflammation in stress-induced diseases and whether a common pathway for depression exists. Recent studies support pharmacological and non-pharmacological treatment approaches significantly associated with ameliorating depression-related inflammation. In addition, major depression can be associated with an activated immune system, whereas antidepressants can exert immunomodulatory effects. Moreover, non-pharmacological treatments for major depression (i.e., exercise) may be mediated by anti-inflammatory actions. This narrative review highlights the mechanisms underlying inflammation and provides new insights into the prevention and treatment of stress-related diseases, particularly depression.

Chronic stress-induced depression requires the recruitment of peripheral Th17 cells into the brain

Background

Depression is a recurrent and devastating mental disease that is highly prevalent worldwide. Prolonged exposure to stressful events or a stressful environment is detrimental to mental health. In recent years, an inflammatory hypothesis has been implicated in the pathogenesis of stress-induced depression. However, less attention has been given to the initial phases, when a series of stress reactions and immune responses are initiated. Peripheral CD4⁺ T cells have been reported as the major contributors to the occurrence of mental disorders. Chronic stress exposure-evoked release of cytokines can promote the differentiation of peripheral CD4⁺ cells into various phenotypes. Among them, Th17 cells have attracted much attention due to their high pathogenic potential in central nervous system (CNS) diseases. Thus, we intended to determine the crucial role of CD4⁺ Th17 cells in the development of specific subtypes of depression and unravel the underpinnings of their pathogenetic effect.

Methods

In the present research, a daily 6-h restraint stress paradigm was employed in rats for 28 successive days to mimic the repeated mild and predictable, but inevitable environmental stress in our daily lives. Then, depressive-like symptoms, brain–blood barrier (BBB) permeability, neuroinflammation, and the differentiation and functional changes of CD4⁺ cells were investigated.

Results

We noticed that restrained rats showed significant depressive-like symptoms, concomitant BBB disruption and neuroinflammation in the dorsal striatum (DS). We further observed a time-dependent increase in thymus- and spleen-derived naïve CD4⁺ T cells, as well as the aggregation of inflammatory Th17 cells in the DS during the period of chronic restraint stress (CRS) exposure. Moreover, increased Th17-derived cytokines in the brain can further impair the BBB integrity, thus allowing more immune cells and cytokines to gain easy access to the CNS. Our findings suggested that, through a complex cascade of events, peripheral immune responses were propagated to the CNS, and gradually exacerbated depressive-like symptoms. Furthermore, inhibiting the differentiation and function of CD4⁺ T cells with SR1001 in the early stages of CRS exposure ameliorated CRS-induced depressive-like behaviour and the inflammatory response.

Conclusions

Our data demonstrated that inflammatory Th17 cells were pivotal in accelerating the onset and exacerbation of depressive symptoms in CRS-exposed rats. This subtype of CD4⁺ T cells may be a promising therapeutic target for the early treatment of stress-induced depression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02543-6.

Dietary Fish Hydrolysate Improves Memory Performance Through Microglial Signature Remodeling During Aging

Brain aging is characterized by a chronic low-grade inflammation, which significantly impairs cognitive function. Microglial cells, the immunocompetent cells of the brain, present a different phenotype, switching from a homeostatic signature (M0) to a more reactive phenotype called “MGnD” (microglial neurodegenerative phenotype), leading to a high production of pro-inflammatory cytokines. Furthermore, microglial cells can be activated by age-induced gut dysbiosis through the vagus nerve or the modulation of the peripheral immune system. Nutrients, in particular n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides, display powerful immunomodulatory properties, and can thus prevent age-related cognitive decline. The objective of this study was to investigate the effects of n-3 LC-PUFAs and low molecular weight peptides contained in a marine by-product-derived hydrolysate on microglial phenotypes and intestinal permeability and their consequences on cognition in mice. We demonstrated that the hydrolysate supplementation for 8 weeks prevented short- and long-term memory decline during aging. These observations were linked to the modulation of microglial signature. Indeed, the hydrolysate supplementation promoted homeostatic microglial phenotype by increasing TGF-β1 expression and stimulated phagocytosis by increasing Clec7a expression. Moreover, the hydrolysate supplementation promoted anti-inflammatory intestinal pathway and tended to prevent intestinal permeability alteration occurring during aging. Therefore, the fish hydrolysate appears as an interesting candidate to prevent cognitive decline during aging.

Evaluation of Anti-inflammatory Nutraceuticals in LPS-induced Mouse Neuroinflammation Model: An Update

It is known that peripheral infections, accompanied by inflammation, represent significant risk factors for the development of neurological disorders by modifying brain development or affecting normal brain aging. The acute effects of systemic inflammation on progressive and persistent brain damage and cognitive impairment are well documented. Anti-inflammatory therapies may have beneficial effects on the brain, and the protective properties of a wide range of synthetic and natural compounds have been extensively explored in recent years. In our previous review, we provided an extensive analysis of one of the most important and widely-used animal models of peripherally induced neuroinflammation and neurodegeneration - lipopolysaccharide (LPS)-treated mice. We addressed the data reproducibility in published research and summarized basic features and data on the therapeutic potential of various natural products, nutraceuticals, with known anti-inflammatory effects, for reducing neuroinflammation in this model. Here, recent data on the suitability of the LPS-induced murine neuroinflammation model for preclinical assessment of a large number of nutraceuticals belonging to different groups of natural products such as flavonoids, terpenes, non-flavonoid polyphenols, glycosides, heterocyclic compounds, organic acids, organosulfur compounds and xanthophylls, are summarized. Also, the proposed mechanisms of action of these molecules are discussed.

The antidepressant-like effects of Shen Yuan: Dependence on hippocampal BDNF-TrkB signaling activation in chronic social defeat depression-like mice

The Shen Yuan prescription (SY) comprises Panax ginseng (GT) and Polygala tenuifolia (YT), elicited superior antidepressant activity compared with that of GT or YT alone. The aim of this paper is to elucidate the effects of SY treatment on chronic social defeat stress (CSDS)-induced depression-like symptoms and the related mechanism. Our results indicated that SY treatment reverses the depressive-like behaviors induced by CSDS as measured by the social interaction test, sucrose preference test, forced swim test, and tail suspension test. SY decreased the serum levels of CORT and increased hippocampal neurotransmitters (5-HT, DA, and NE) in CSDS mice. Meanwhile, SY upregulated the brain-derived neurotrophic factor (BDNF) signaling pathway and reversed the decreased hippocampal neurogenesis caused by CSDS. In addition, we found that the TrkB antagonist K252a fully blocked the SY effects on behavioral improvement and eliminated the promoting effects of SY on hippocampal neurogenesis and BDNF-TrkB signaling (including the downstream ERK and Akt pathways) activation, thus further demonstrating that BDNF-TrkB signaling was necessary for the SY effects. In conclusion, our study showed that SY acted as an antidepressant in mice exhibiting CSDS-induced depression-like symptoms, and its effect was facilitated by promoting hippocampal neurogenesis and BDNF signaling pathway activation.

Fish Hydrolysate Supplementation Containing n-3 Long Chain Polyunsaturated Fatty Acids and Peptides Prevents LPS-Induced Neuroinflammation

Neuroinflammation constitutes a normal part of the brain immune response orchestrated by microglial cells. However, a sustained and uncontrolled production of proinflammatory factors together with microglial activation contribute to the onset of a chronic low-grade inflammation, leading to neuronal damage and cognitive as well as behavioral impairments. Hence, limiting brain inflammatory response and improving the resolution of inflammation could be particularly of interest to prevent these alterations. Dietary n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides are good candidates because of their immunomodulatory and proresolutive properties. These compounds are present in a fish hydrolysate derived from marine-derived byproducts. In this study, we compared the effect of an 18-day supplementation with this fish hydrolysate to a supplementation with docosahexaenoic acid (DHA) on lipopolysaccharide (LPS)-induced inflammation in mice. In response to peripherally injected LPS, the fish hydrolysate supplementation decreased the hippocampal mRNA expression of the proinflammatory cytokines IL-6 (p < 0.001), IL-1β (p = 0.0008) and TNF-α (p < 0.0001), whereas the DHA supplementation reduced only the expression of IL-6 (p = 0.004). This decline in proinflammatory cytokine expressions was associated with an increase in the protein expression of IκB (p = 0.014 and p = 0.0054 as compared to the DHA supplementation and control groups, respectively) and to a modulation of microglial activation markers in the hippocampus. The beneficial effects of the fish hydrolysate could be due in part to the switch of the hippocampal oxylipin profile towards a more anti-inflammatory profile as compared to the DHA supplementation. Thus, the valorization of fish byproducts seems very attractive to prevent and counteract neuroinflammation.

The antidepressant-like effects of the water extract of Panax ginseng and Polygala tenuifolia are mediated via the BDNF-TrkB signaling pathway and neurogenesis in the hippocampus

ETHNOPHARMACOLOGY RELEVANCE

The water extract of Panax ginseng (GT) and Polygala tenuifolia (YT), the main constituents of the commonly used kai-xin-san formula of traditional Chinese medicine, represents SY. It possesses strong neuroprotective effects. Using behavioural tests, we have previously established that the SY formulation exerts superior antidepressant activity than that of GT or YT.

AIM

To elucidate the impact of SY treatment on chronic unpredictable mild stress (CUMS)-induced depressive-like behaviours and the prospective mechanism related to hippocampal neurogenesis and the BDNF signaling pathway.

METHODS

We exposed Sprague-Dawley rats (male; 180-200 g) to CUMS for 35 days. The rats in the experimental treatment groups were daily treated with either fluoxetine (10 mg kg-1d-1) or SY (67.5, 135, or 270 mg kg-1d-1) orally until the behavioural tests (tail suspension test [TST], novelty-suppressed feeding test [NSFT], sucrose preference test [SPT], and forced swim test [FST]) were completed. We assessed the modifications in the hippocampal neurogenesis and the BDNF signaling pathway post-treatment with CUMS and SY. Additionally, K252a, a tyrosine protein kinase inhibitor, was utilized to evaluate the antidepressant mechanisms of SY.

RESULT

s: The results of SPT, NSFT, FST, and TST in CUMS-exposed rats confirmed the antidepressant actions of SY. Additionally, SY treatment induced the BDNF signaling pathway and reversed the hippocampal neurogenesis caused by CUMS. Moreover, we found that the TrkB antagonist K252a blocked SY effects on behavioural improvement, inhibited the incremental effects of SY on hippocampal neurogenesis, and eliminated the impact of SY on BDNF-TrkB signaling activation. Thus, the impact of SY treatment on BDNF signaling molecules (pAkt, pERK1/2, and pCREB) were significantly inhibited by K252a.

CONCLUSIONS

This study showed that SY acted as an antidepressant in rats exhibiting CUMS-induced depressive-like behaviours, and was facilitated by promoting hippocampal neurogenesis and the BDNF signaling pathway activation. Thus, SY could act as a potential novel supplement or adjuvant to prevent or treat clinical depressive disorders.

Inflammatory Depression-Mechanisms and Non-Pharmacological Interventions

Treatment of depression is hampered by the failure to identify distinct symptom profiles with distinct pathophysiologies that differentially respond to distinct treatments. We posit that inflammatory depression is a meaningful depression subtype associated with specific symptoms and biological abnormalities. We review several upstream, potentially causative, mechanisms driving low-grade inflammation in this subtype of depression. We also discuss downstream mechanisms mediating the link between inflammation and symptoms of depression, including alterations in dopaminergic neurotransmission and tryptophan metabolism. Finally, we review evidence for several non-pharmacological interventions for inflammatory depression, including probiotics, omega-3 fatty acids, and physical exercise interventions. While some evidence suggests that these interventions may be efficacious in inflammatory depression, future clinical trials should consider enriching patient populations for inflammatory markers, or stratify patients by inflammatory status, to confirm or refute this hypothesis.

Vortioxetine Prevents Lipopolysaccharide-Induced Memory Impairment Without Inhibiting the Initial Inflammatory Cascade

Vortioxetine is a novel multimodal antidepressant that modulates a wide range of neurotransmitters throughout the brain. Preclinical and clinical studies have shown that vortioxetine exerts positive effects on different cognitive domains and neuroprotective effects. Considering the key role of microglial cells in brain plasticity and cognition, we aimed at investigating the effects of pretreatment with vortioxetine in modulating behavioral and molecular effects induced by an immune challenge: peripheral injection of lipopolysaccharide (LPS). To this purpose, C57BL/6J male mice were first exposed to a 28-day standard diet or vortioxetine-enriched diet, which was followed by an acute immune challenge with LPS. Sickness symptoms and depressive-like behaviors (anhedonia and memory impairment) were tested 6 and 24 h after exposure to LPS, respectively. Moreover, the expressions of markers of immune activation and M1/M2 markers of microglia polarization were measured in the dorsal and ventral parts of the hippocampus. The pretreatment with vortioxetine did not affect both LPS-induced sickness behavior and anhedonia but prevented the deficit in the recognition memory induced by the immune challenge. At the transcriptional level, chronic exposure to vortioxetine did not prevent LPS-induced upregulation of proinflammatory cytokines 6 h after the immune challenge but rather seemed to potentiate the immune response to the challenge also by affecting the levels of expression of markers of microglia M1 phenotype, like cluster of differentiation (CD)14 and CD86, in an area-dependent manner. However, at the same time point, LPS injection significantly increased the expression of the M2 polarization inducer, interleukin 4, only in the hippocampus of animals chronically exposed to vortioxetine. These results demonstrate that a chronic administration of vortioxetine specifically prevents LPS-induced memory impairment, without affecting acute sickness behavior and anhedonia, and suggest that hippocampal microglia may represent a cellular target of this novel antidepressant medication. Moreover, we provide a useful model to further explore the molecular mechanisms specifically underlying cognitive impairments following an immune challenge.

Human torpor: translating insights from nature into manned deep space expedition

During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (T_b ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.

Targeting neuroinflammation: The therapeutic potential of ω-3 PUFAs in substance abuse

Substance abuse is a chronic relapsing disorder that results in serious health and socioeconomic issues worldwide. Addictive drugs induce long-lasting morphologic and functional changes in brain circuits and account for the formation of compulsive drug-seeking and drug-taking behaviors. Yet, there remains a lack of reliable therapy. In recent years, accumulating evidence indicated that neuroinflammation was implicated in the development of drug addiction. Findings from both our and other laboratories suggest that ω-3 polyunsaturated fatty acids (PUFAs) are effective in treating neuroinflammation-related mental diseases, and indicate that they could exert positive effects in treating drug addiction. Thus, in the present review, we summarized and evaluated recently published articles reporting the neuroinflammation mechanism in drug addiction and the immune regulatory ability of ω-3 PUFAs. We also sought to identify some of the challenges ahead in the translation of ω-3 PUFAs into addiction treatment.

Fish oil alleviates LPS-induced inflammation and depressive-like behavior in mice via restoration of metabolic impairments

Our previous study revealed that fish oil (FO) pre-treatment could improve the lipopolysaccharides (LPS)-induced depressive-like behavior in mice but did not alter the expression of stress hormones associated with the hypothalamic-pituitary-adrenal (HPA) axis. The exact mechanisms underlying the protective effects of FO remain elusive. Here we applied the metabolomic technique to investigate the potential involvement of FO metabolites in ameliorating depressive-like behaviors in LPS-injected mice. It revealed that LPS-injection stimulated systemic inflammation, exhausted the nicotinamide adenine dinucleotide (NAD) level in the brain, decreased energy metabolism and impaired neuronal function, which collectively contributed to depressive-like behaviors in mice. FO treatment enhanced the production of neuroprotective metabolites including taurine, hypotaurine and tyramine, decreased the generation of neurotoxic agents such as ADPR, glutamate accumulation and oxidized glutathione, and prevented the NAD exhaustion in the brain, which might underlie the beneficial effects of FO against LPS-induced inflammation and depressive-like behaviors.

Antidepressant-Like Properties of Fish Oil on Postpartum Depression-Like Rats Model: Involvement of Serotonergic System

Pathophysiology of postpartum depression (PPD) has been associated with many factors, such as neuroendocrine, neuroinflammation and neurotransmitter changes. Fish oil (FO) improves PPD both in humans and animals. However, little is known with regards to its pharmacology on a PPD-like rat model. Hence, the current study aimed at investigating the effects of FO on a PPD-like rat model. Female rats were induced with PPD-like symptoms and then randomly divided into six groups (n = 6) for two experimental protocols. Protocol 1 consisted of PPD-like rats (2 mL distilled water), PPD-like + FO (9 g/kg/d) and PPD-like + Fluoxetine (FLX) (15 mg/kg/d) groups of rats, whereas Protocol 2 consisted of PPD-like rats (2 mL distilled water) + PCPA (p-chlorophenylalanine) 150 mg/kg, PPD-like + FO (9 g/kg/d) + PCPA 150 mg/kg and PPD-like + FLX (15 mg/d) + PCPA 150 mg/kg groups of rats, respectively. All treatments were administered orally for 10 days postpartum, except PCPA, which was given intraperitoneally. Prior to euthanasia, the antidepressant-like effect of the FO was evaluated using the forced swimming test (FST) and open field test (OFT) on day 10 postpartum. Biochemical analysis of serotonin, serotonin metabolite and serotonin turnover from their prefrontal cortex and hippocampus were also measured. The results showed that FO decreased immobility time and increased swimming time significantly, but not climbing time in FST. Further, it also decreased serotonin metabolite and turnover significantly in the hippocampus of the PPD-like rats. In contrast, administration with PCPA reversed all the outcomes. The antidepressant-like effects of FO were found to be similar with that of FLX. Thus, it can be concluded that FO exerts its antidepressant-like effects in PPD-like rats through modulation of serotonergic system.

Xiaoyao Pills Attenuate Inflammation and Nerve Injury Induced by Lipopolysaccharide in Hippocampal Neurons In Vitro

Lipopolysaccharides (LPS) are proinflammation mediators that can induce the inflammatory model of the hippocampal neuron, and neuroinflammation participates in the pathophysiology of depression. Xiaoyao Pill is a classical Chinese medicine formula that has been used for the treatment of mental disorders such as depression in China since the Song dynasty. We established a hippocampal neuronal cell inflammation model by LPS and investigate the intervention effect and mechanism of Xiaoyao Pills. The expression levels of IL-6, TNF-α, IDO, 5-HT, brain-derived neurotrophic factor, and β-nerve growth factor were detected by enzyme-linked immunosorbent assay. mRNA levels of IL-6, TNF-α, 5-HT1A, IDO-1, brain-derived neurotrophic factor, nerve growth factor, tropomyosin receptor kinase B, tropomyosin receptor kinase A, and cAMP response element-binding protein were detected by reverse transcription-polymerase chain reaction. To further validate, protein expression was determined by western blot and immunofluorescence. Lipopolysaccharide-induced neuroinflammatory state resulted in the release of IL-6, TNF-α, and IDO and a decrease of BDNF, NGF, TrkB, TrkA, CREB, p-CREB, p-CREB/CREB, and SYP and inhibited hippocampal neurogenesis in the hippocampal neuron. Xiaoyao Pills significantly decreased the levels of IL-6, TNF-α, and IDO in cell supernatant and increased the expression of BDNF, NGF, TrkB, TrkA, CREB, p-CREB, p-CREB/CREB, and SYP as well as the average optical density of BrdU/NeuN double-labelled positive cells. Our study shows that lipopolysaccharides induce inflammation and nerve damage in hippocampal neurons, which are closely related to the pathological mechanism of depression. Xiaoyao Pills (XYW) play an important neuroprotective effect, which is related to its inhibition of neuronal inflammation and promoting the recovery of nerve injury. These results provide a pharmacologic basis for the treatment of depression of XYW in clinical application.

Phenol glycosides extract of Fructus Ligustri Lucidi attenuated depressive-like behaviors by suppressing neuroinflammation in hypothalamus of mice

Depression is partially caused by inflammation in central nervous system. This study investigated the ameliorative effects of phenol glycosides (PG) from Ligustrum lucidum Ait. (Oleaceae) on neuroinflammation and depressive-like behavior in mice hypothalamus as well as the molecular mechanism. Mice were administered with PG extract for 2 weeks prior to treatment with LPS. The mice treated with PG extract showed resistance to LPS-induced reduction in body weight and LPS-induced depressive-like behaviors shown by sucrose preference, tail suspension test, forced swimming test and open field test. LPS-induced activation of microglial cells and elevation in protein expression of inflammatory cytokines including IL-1β, RANTES and MCP-1 in hypothalamus of mice were abrogated by pre-treatment with PG extract. This extract down-regulated expression of TLR4, MyD88, NLRP3, renin and angiotensin II and decreased proportional area of Iba-1⁺ microglias in hypothalamus. Pre-treatment with PG extract inhibited LPS-triggered activation of CaSR/G_α11 signaling, stimulated 1-OHase expression in hypothalamus, and enhanced circulating 1,25(OH)₂ D₃ level. Overall, pre-treatment with PG extract ameliorated LPS-induced depressive-like behaviors by repressing neuroinflammation in mice hypothalamus which was attributed to its suppression on activation of microglia and production of inflammatory cytokines via acting on TLR4 pathway, CaSR and RAS cascade associated with improving vitamin D metabolism.

Ginsenoside Rg1 ameliorates chronic social defeat stress-induced depressive-like behaviors and hippocampal neuroinflammation

Chronic social defeat stress (CSDS) is an ethologically relevant psychosocial stress animal model and has been widely used in depression studies. Ginsenoside Rg1 (Rg1) is the major active ingredients of ginseng with low toxicity and neuroprotective effects. The present study aims to investigate the antidepressant effects of Rg1 in CSDS mice and explore its molecular mechanism. We found that Rg1 (20 or 40 mg/kg, i.g.) administration significantly alleviated depressive-like behaviors caused by 4-week CSDS exposure, as measured by social interaction test and sucrose preference test, tail suspension test and forced swim test. Additionally, Rg1 treatment inhibited CSDS-induced production of IL-6, TNF-α and IL-1β, decreased the expression of iNOS, COX2, and caspase-9 and -3, and inhibited microglial activation (Iba1) in the hippocampus. Rg1 was found to significantly downregulate p-JNK1/2 and p-P38 MAPK levels, upregulate p-ERK1/2 levels and inhibit the expression of phosphorylated NF-κB in the hippocampus. Meanwhile, Rg1 regulated SIRT1 and decreased the levels of acetylated p65 (ac-p65) in the hippocampus. Moreover, the reduction in adult hippocampal neurogenesis in CSDS mice was reversed by Rg1 treatment. In conclusion, our findings suggest that Rg1 prevents depressive-like behavior in CSDS-exposed mice, partially through the downregulation of hippocampal neuroinflammation and the upregulation of adult hippocampal neurogenesis and that these changes presumably occur through increased anti-inflammatory effects and the inhibition of proinflammatory cytokine and neurotoxic mediator expression and microglial activation, which is partly mediated by the regulation of the MAPK and SIRT1 signaling pathways and results in the inhibition of NF-κB transcriptional activity.

Fish oil protects the blood-brain barrier integrity in a mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is ranked as the most prevalent neurodegenerative disease. However, the exact molecular mechanisms underlying pathophysiological alterations in AD remain unclear, especially at the prodromal stage. The decreased proteolytic degradation of Aβ, blood-brain barrier (BBB) disruption, and neuroinflammation are considered to play key roles in the course of AD.

METHODS

Male APPswe/PS1dE9 C57BL/6 J double-transgenic (APP/PS1) mice in the age range from 1 month to 6 months and age-matched wild type mice were used in this study, intending to investigate the expression profiles of Aβ-degrading enzymes for Aβ degradation activities and zonula occludens-1 (zo-1) for BBB integrity at the prodromal stage.

RESULTS

Our results showed that there were no significant genotype-related alterations in mRNA expression levels of 4 well-characterized Aβ-degrading enzymes in APP/PS1 mice within the ages of 6 months. Interestingly, a significant decrease in zo-1 expression was observed in APP/PS1 mice starting from the age of 5 months, suggesting that BBB disrupt occurs at an early stage. Moreover, treatment of fish oil (FO) for 4 weeks remarkably increased zo-1 expression and significantly inhibited the glial activation and NF-κB activation in APP/PS1 mice.

CONCLUSION

The results of our study suggest that FO supplement could be a potential therapeutic early intervention for AD through protecting the BBB integrity and suppressing glial and NF-κB activation.

Omega-3 polyunsaturated fatty acids promote brain-to-blood clearance of β-Amyloid in a mouse model with Alzheimer's disease

Amyloid-β (Aβ) plaques is one of the typical pathological hallmark of Alzheimer disease (AD). Accumulating evidence suggests that the imbalance between Aβ production and clearance leads to extracellular Aβ accumulation in the brain. It is reported that the blood-brain barrier (BBB) transport plays a predominant role in Aβ clearance from brain to blood. In the present study, we investigated dynamic alterations of BBB transport function in the early disease stage of AD using APPswe/PS1dE9 C57BL/6J (APP/PS1) transgenic mice. Our results showed that the expression of lipoprotein receptor-related protein 1 (LRP-1), a main efflux transporter of BBB, started to decrease at the age of 4 months old. Interestingly, supplementing with fish oil which is rich in omega-3 polyunsaturated fatty acids (PUFAs) significantly enhanced the expression level of LRP-1 and promoted Aβ clearance from the bran to circulation, as revealed by reduced soluble/insoluble Aβ levels and senile plaques in the brain parenchyma and a corresponding increase of Aβ levels in plasma. Besides, fish oil supplement significantly inhibited the NF-κB activation, reduced the expression of interleukin-1β and tumor necrosis factor-α, and suppressed the glial activation in APP/PS1 mice. The results of the study provide evidence that BBB transport function could be impaired at a very early disease stage, which might contribute to Aβ pathological accumulation in AD, and omega-3 PUFAs intervention could be an effective strategy for the prevention of the progression of AD through promoting Aβ clearance from brain-to-blood.

Antidepressant-like effects of penta-acetyl geniposide in chronic unpredictable mild stress-induced depression rat model: Involvement of inhibiting neuroinflammation in prefrontal cortex and regulating hypothalamic-pituitaryadrenal axis

We previously reported that penta-acetyl geniposide ((Ac)₅GP, an acetylated derivative of geniposide) exhibited better pharmacological functions than geniposide, a major active component of Gardenia jasminoides Ellis. This study demonstrated the antidepressant-like effects of (Ac)₅GP and its involved mechanisms using a rat depression model caused by chronic unpredictable mild stress (CUMS). Behavioral tests including sucrose preference, open field and forced swimming were applied to evaluate depression symptoms. IL-1β, IL-6 and TNF-α mRNA and protein levels in prefrontal cortex (PFC) were respectively measured by quantitative PCR and ELISA. The protein levels of IκBα, p-IκBα, NF-κB p65, NLRP3, pro- and mature-IL-1β in PFC were determined by western blot. The activity of hypothalamic-pituitaryadrenal (HPA) axis was also measured. (Ac)₅GP treatment alleviated the CUMS-induced depressive-like behaviors in rats, as indicated by increased sucrose intake, increased total crossing and rearing numbers, improved central activity and reduced immobility time. (Ac)₅GP reversed the CUMS-induced elevations of IL-1β, IL-6 and TNF-α mRNA and protein levels in PFC. (Ac)₅GP reduced degradation and phosphorylation of IκBα and protein level of nuclear NF-κB p65 in PFC. (Ac)₅GP also decreased the mRNA and protein levels of NLRP3 and reduced the ratio of mature-IL-1β protein over total IL-1β protein (pro-IL-1β + mature-IL-1β) in PFC. Moreover, (Ac)₅GP reduced serum levels of adrenocorticotropic hormone/corticosterone and mRNA level of hypothalamic corticotrophin-releasing hormone. In conclusion, (Ac)₅GP treatment improved the depressive-like behaviors in CUMS rats perhaps by suppressing neuroinflammation in PFC and inhibiting activations of NF-κB and NLRP3 and also attenuating HPA axis hyperactivity.

Xiaoyao Pills Prevent Lipopolysaccharide-Induced Depression by Inhibiting Inflammation and Protecting Nerves

Lipopolysaccharides are pro-inflammation mediators that can induce inflammation in the serum, hippocampus, and cortex of animals. And lipopolysaccharide-induced neuroinflammatory state resulted in significant depression-like behaviors, including reduced locomotor activity in the open field test, reduced saccharin preference, added immobility time in tail suspension test and forced swimming test, decreased comb time in the splash test, and increased latency to food in the novelty suppressed feeding test time, and reduced the levels of neurotrophic factors and synaptic proteins, and decreased Nissl bodies. Treatment with Xiaoyao Pills ameliorated the depression-like behavior, decreased the levels of inflammatory indicators, increased those of neurotrophic factors and synaptic proteins, and restored Nissl bodies. Our study suggests that lipopolysaccharides induce inflammation and nerve injury, thereby leading to depression. Xiaoyao Pills could be considered a potential therapeutic candidate for inflammation-induced depression.

Potential link between the RagA-mTOR-p70S6K axis and depressive-behaviors during bacterial liposaccharide challenge

BACKGROUND

Bacterial infection is a potential risk factor for depression. However, little is known about the mechanistic link between bacterial endotoxin and depressive-like behaviors. The aim of the present study was to clarify whether liposaccharide (LPS) could induce depressive-like behaviors in mice via sequentially activating small GTPase RagA, mammalian target of rapamycin (mTOR), and p70S6K.

METHODS

C57BL/6 N mice were treated with 0.83 mg/kg LPS by intraperitoneal injection for 24 h. The animals were assessed for depressive-like behaviors by forced swim test and tail suspension test. The expression levels of RagA, mTOR, and p70S6K were determined in mice, primary cortical neurons, neural stem cells, and PC12 cells.

RESULTS

LPS effectively induced depressive-like behaviors in mice. Biochemical examination revealed that LPS not only upregulated RagA expression but also activated mTOR/p70S6K pathway in mouse brains. LPS challenge also achieved a similar effect in primary cortical neurons, neural stem cells, and PC12 cells. Following the silencing of RagA expression with specific siRNA, LPS failed to induce mTORC1 translocation to the lysosomal membranes in PC12 cells. These results suggested that LPS might sequentially upregulate RagA and activate mTOR and p70S6K pathways in mice and neural stem cells.

CONCLUSIONS

This study for the first time demonstrated that LPS might induce depressive-like behaviors in mice via the upregulation of RagA and subsequent activation of mTOR/p70S6K pathway. Such information may highlight the RagA-mTOR-p70S6K signaling cascade as a novel therapeutic target for the development of new anti-depressant therapeutics.

Herring roe oil supplementation alters microglial cell gene expression and reduces peripheral inflammation after immune activation in a neonatal piglet model

Neonatal brain development can be disrupted by infection that results in microglial cell activation and neuroinflammation. Studies indicate that polyunsaturated fatty acids (PUFAs) and their metabolites can resolve inflammation. It is not known if dietary PUFA increases lipid metabolites in brain or reduces neuroinflammation in neonates. We hypothesized that dietary PUFAs might suppress neuroinflammation by inhibiting pro-inflammatory cytokine over-production and promoting inflammatory resolution in the periphery and brain. Piglets were obtained on postnatal day (PD) 2 and randomly assigned to herring roe oil (HRO) or control (CON) diet. HRO was included at 2 g/kg powdered diet. HRO increased DHA levels in occipital lobe and the DHA to arachidonic acid (ARA) ratio in hippocampal tissue. HRO decreased ARA metabolites in occipital lobe. HRO failed to attenuate microglial pro-inflammatory cytokine production ex vivo. HRO did not affect fever or circulating resolvin D1 levels. HRO decreased circulating neutrophils and liver inflammatory gene expression, but increased resolution marker gene expression in liver post LPS. HRO upregulated CXCL16, TGFBR1, and C1QA in microglial cells. HRO supplementation exerted beneficial effects on inflammation in the periphery, but further studies are needed to evaluate the specific effects of omega-3 supplementation on microglial cell physiology in the neonate.

N-3 Polyunsaturated Fatty Acids and the Resolution of Neuroinflammation

In the past few decades, as a result of their anti-inflammatory properties, n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs), have gained greater importance in the regulation of inflammation, especially in the central nervous system (in this case known as neuroinflammation). If sustained, neuroinflammation is a common denominator of neurological disorders, including Alzheimer’s disease and major depression, and of aging. Hence, limiting neuroinflammation is a real strategy for neuroinflammatory disease therapy and treatment. Recent data show that n-3 LC-PUFAs exert anti-inflammatory properties in part through the synthesis of specialized pro-resolving mediators (SPMs) such as resolvins, maresins and protectins. These SPMs are crucially involved in the resolution of inflammation. They could be good candidates to resolve brain inflammation and to contribute to neuroprotective functions and could lead to novel therapeutics for brain inflammatory diseases. This review presents an overview 1) of brain n-3 LC-PUFAs as precursors of SPMs with an emphasis on the effect of n-3 PUFAs on neuroinflammation, 2) of the formation and action of SPMs in the brain and their biological roles, and the possible regulation of their synthesis by environmental factors such as inflammation and nutrition and, in particular, PUFA consumption.

Serum IL-6 levels and oxidation rate of LDL cholesterol were related to depressive symptoms independent of omega-3 fatty acids among female hospital and nursing home workers in Japan

BACKGROUND

Chronic low-grade inflammation and oxidative stress are commonly observed in persons with depression or depressive symptoms. We explored the degree of depressive symptoms under psychological stress in relation to serum LDL oxidation, inflammatory markers, and fatty acid (FA) distribution among female population. The purpose of this study was to identify peripheral factors that are related to depressive symptoms, and to assess how each factor is related to depressive symptoms.

METHODS

133 female workers in a hospital and nursing homes were recruited in Japan. Depressive symptoms were assessed using the Japanese version of the Centre for Epidemiologic Studies Depression Scale (CES-D), and perceived stress was assessed using the visual analogue scale. Cytokine levels and oxidation rate of LDL cholesterol (ox-LDL/LDL) were measured as indices of inflammation and oxidation. Omega-3 FA distribution was also measured. Path analysis and hierarchical regression analysis were used to determine if each factor was predictive of depressive symptoms.

RESULTS

It was identified that serum ox-LDL/LDL was positively connected with depressive symptoms, but was more strongly related to perceived psychological stress. Elevated serum IL-6 was positively correlated with depressive symptoms, though the effect was partly transmitted via ox-LDL/LDL. Additionally, serum ω3 PUFAs were inversely associated with depressive symptoms independently of IL-6 or ox-LDL/LDL.

CONCLUSION

Although this study is unlikely to fully explain the causes of depressive symptoms, it suggests that psychological stress and somatic factors such as inflammation, oxidation and nutrition are related to depressive symptoms. These findings suggest the therapeutic potential of lifestyle targets to alleviate the identified depression risk factors, anti-oxidative therapies, anti-inflammatory therapies and nutritional interventions to prevent depression.

Omega-3 Polyunsaturated Fatty Acid Deficiency and Progressive Neuropathology in Psychiatric Disorders: A Review of Translational Evidence and Candidate Mechanisms

Meta-analytic evidence indicates that mood and psychotic disorders are associated with both omega-3 polyunsaturated fatty acid (omega-3 PUFA) deficits and progressive regional gray and white matter pathology. Although the association between omega-3 PUFA insufficiency and progressive neuropathological processes remains speculative, evidence from translational research suggests that omega-3 PUFA insufficiency may represent a plausible and modifiable risk factor not only for enduring neurodevelopmental abnormalities in brain structure and function, but also for increased vulnerability to neurodegenerative processes. Recent evidence from human neuroimaging studies suggests that lower omega-3 PUFA intake/status is associated with accelerated gray matter atrophy in healthy middle-aged and elderly adults, particularly in brain regions consistently implicated in mood and psychotic disorders, including the amygdala, anterior cingulate, hippocampus, prefrontal cortex, and temporal cortex. Human neuroimaging evidence also suggests that both low omega-3 PUFA intake/status and psychiatric disorders are associated with reductions in white matter microstructural integrity and increased rates of white matter hyperintensities. Preliminary evidence suggests that increasing omega-3 PUFA status is protective against gray matter atrophy and deficits in white matter microstructural integrity in patients with mood and psychotic disorders. Plausible mechanisms mediating this relationship include elevated pro-inflammatory signaling, increased synaptic regression, and reductions in cerebral perfusion. Together these associations encourage additional neuroimaging research to directly investigate whether increasing omega-3 PUFA status can mitigate neuropathological processes in patients with, or at high risk for, psychiatric disorders.

Acyl-CoA synthetase 6 enriches the neuroprotective omega-3 fatty acid DHA in the brain

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is highly abundant in the brain and confers protection against numerous neurological diseases, yet the fundamental mechanisms regulating the enrichment of DHA in the brain remain unknown. Here, we have discovered that a member of the long-chain acyl-CoA synthetase family, Acsl6, is required for the enrichment of DHA in the brain by generating an Acsl6-deficient mouse (Acsl6^-/-). Acsl6 is highly enriched in the brain and lipid profiling of Acsl6^-/- tissues reveals consistent reductions in DHA-containing lipids in tissues highly abundant with Acsl6. Acsl6^-/- mice demonstrate motor impairments, altered glutamate metabolism, and increased astrogliosis and microglia activation. In response to a neuroinflammatory lipopolysaccharide injection, Acsl6^-/- brains show similar increases in molecular and pathological indices of astrogliosis compared with controls. These data demonstrate that Acsl6 is a key mediator of neuroprotective DHA enrichment in the brain.

Food for Mood: Relevance of Nutritional Omega-3 Fatty Acids for Depression and Anxiety

The central nervous system (CNS) has the highest concentration of lipids in the organism after adipose tissue. Among these lipids, the brain is particularly enriched with polyunsaturated fatty acids (PUFAs) represented by the omega-6 (ω6) and omega-3 (ω3) series. These PUFAs include arachidonic acid (AA) and docosahexaenoic acid (DHA), respectively. PUFAs have received substantial attention as being relevant to many brain diseases, including anxiety and depression. This review addresses an important question in the area of nutritional neuroscience regarding the importance of ω3 PUFAs in the prevention and/or treatment of neuropsychiatric diseases, mainly depression and anxiety. In particular, it focuses on clinical and experimental data linking dietary intake of ω3 PUFAs and depression or anxiety. In particular, we will discuss recent experimental data highlighting how ω3 PUFAs can modulate neurobiological processes involved in the pathophysiology of anxiety and depression. Potential mechanisms involved in the neuroprotective and corrective activity of ω3 PUFAs in the brain are discussed, in particular the sensing activity of free fatty acid receptors and the activity of the PUFAs-derived endocannabinoid system and the hypothalamic-pituitary-adrenal axis.

NLRP3 inflammasome activation contributes to long-term behavioral alterations in mice injected with lipopolysaccharide

Lipopolysaccharide (LPS) might affect the central nervous system by causing neuroinflammation, which subsequently leads to brain damage and dysfunction. In this study, we evaluated the role of nod-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation in long-term behavioral alterations of 8-week-old male C57BL/6 mice injected intraperitoneally with LPS (5mg/kg). At different time points after injection, we assessed locomotor function with a 24-point neurologic deficit scoring system and the rotarod test; assessed recognition memory with the novel object recognition test; and assessed emotional abnormality (anhedonia and behavioral despair) with the tail suspension test, forced swim test, and sucrose preference test. We also assessed protein expression of NLRP3, apoptosis-associated speck-like protein (ASC), and caspase-1 p10 in hippocampus by Western blotting; measured levels of interleukin (IL)-1β, IL-18, tumor necrosis factor α (TNFα), and IL-10 in hippocampus; measured TNFα and IL-1β in serum by ELISA; and evaluated microglial activity in hippocampus by Iba1 immunofluorescence. We found that LPS-injected mice displayed long-term depression-like behaviors and recognition memory deficit; elevated expression of NLRP3, ASC, and caspase-1 p10; increased levels of IL-1β, IL-18, and TNFα; decreased levels of IL-10; and increased microglial activation. These effects were blocked by the NLRP3 inflammasome inhibitor Ac-Tyr-Val-Ala-Asp-chloromethylketone. The results demonstrate proof of concept that NLRP3 inflammasome activation contributes to long-term behavioral alterations in LPS-exposed mice, probably through enhanced inflammation, and that NLRP3 inflammasome inhibition might alleviate peripheral and brain inflammation and thereby ameliorate long-term behavioral alterations in LPS-exposed mice.