Enriched Endogenous Omega-3 Polyunsaturated Fatty Acids Protect Cortical Neurons from Experimental Ischemic Injury

Large-Scale Population-Based Studies of Blood Metabolome and Brain Health

Metabolomics technologies enable the quantification of multiple metabolomic measures simultaneously, which provides novel insights into molecular aspects of human health and disease. In large-scale, population-based studies, blood is often the preferred biospecimen. Circulating metabolome may relate to brain health either by affecting or reflecting brain metabolism. Peripheral metabolites may act at or cross the blood-brain barrier and, subsequently, influence brain metabolism, or they may reflect brain metabolism if similar pathways are engaged. Peripheral metabolites may also include those penetrating the circulation from the brain, indicating, for example, brain damage. Most brain health-related metabolomics studies have been conducted in the context of neurodegenerative disorders and cognition, but some studies have also focused on neuroimaging markers of these disorders. Moreover, several metabolomics studies of neurodevelopmental disorders have been performed. Here, we provide a brief background on the types of blood metabolites commonly assessed, and we review the literature describing the relationships between human blood metabolome (n > 50 metabolites) and brain health reported in large-scale studies (n > 500 individuals).

Unraveling the impact of Omega-3 polyunsaturated fatty acids on blood-brain barrier (BBB) integrity and glymphatic function

Alzheimer's disease (AD) and other forms of dementia represent major public health challenges but effective therapeutic options are limited. Pathological brain aging is associated with microvascular changes and impaired clearance systems. The application of omega-3 polyunsaturated fatty acids (n-3 or omega-3 PUFAs) is one of the most promising nutritional interventions in neurodegenerative disorders from epidemiological data, clinical and pre-clinical studies. As essential components of neuronal membranes, n-3 PUFAs have shown neuroprotection and anti-inflammatory effects, as well as modulatory effects through microvascular pathophysiology, amyloid-beta (Aβ) clearance and glymphatic pathways. This review meticulously explores these underlying mechanisms that contribute to the beneficial effects of n-3 PUFAs against AD and dementia, synthesizing evidence from both animal and interventional studies.

Effects of food-borne docosahexaenoic acid supplementation on bone lead mobilisation, mitochondrial function and serum metabolomics in pre-pregnancy lead-exposed lactating rats

Large bone lead (Pb) resulting from high environmental exposure during childhood is an important source of endogenous Pb during pregnancy and lactation. Docosahexaenoic acid (DHA) attenuates Pb toxicity, however, the effect of DHA on bone Pb mobilisation during lactation has not been investigated. We aimed to study the effects of DHA supplementation during pregnancy and lactation on bone Pb mobilisation during lactation and its potential mechanisms. Weaning female rats were randomly divided into control (0.05% sodium acetate) and Pb-exposed (0.05% Pb acetate) groups, after a 4-week exposure by ad libitum drinking and a subsequent 4-week washout period, all female rats were mated with healthy males until pregnancy. Then exposed rats were randomly divided into Pb and Pb + DHA groups, and the latter was given a 0.14% DHA diet, while the remaining groups were given normal feed until the end of lactation. Pb and calcium levels, bone microarchitecture, bone turnover markers, mitochondrial function and serum metabolomics were analyzed. The results showed that higher blood and bone Pb levels were observed in the Pb group compared to the control, and there was a significant negative correlation between blood and bone Pb. Also, Pb increased trabecular bone loss along with slightly elevated serum C-telopeptide of type I collagen (CTX-I) levels. However, DHA reduced CTX-I levels and improved trabecular bone microarchitecture. Metabolomics showed that Pb affected mitochondrial function, which was further demonstrated in bone tissue by significant reductions in ATP levels, Na+-K+-ATPase, Ca2+-Mg2+-ATPase and CAT activities, and elevated levels of MDA, IL-1β and IL-18. However, these alterations were partially mitigated by DHA. In conclusion, DHA supplementation during pregnancy and lactation improved bone Pb mobilisation and mitochondrial dysfunction in lactating rats induced by pre-pregnancy Pb exposure, providing potential means of mitigating bone Pb mobilisation levels during lactation, but the mechanism still needs further study.

Docosahexaenoic Acid Alleviates Brain Damage by Promoting Mitophagy in Mice with Ischaemic Stroke

Mitophagy, the selective removal of damaged mitochondria through autophagy, is crucial for mitochondrial turnover and quality control. Docosahexaenoic acid (DHA), an essential omega-3 fatty acid, protects mitochondria in various diseases. This study aimed to investigate the neuroprotective role of DHA in ischaemic stroke models in vitro and in vivo and its involvement in mitophagy and mitochondrial dysfunction. A mouse model of ischaemic stroke was established through middle cerebral artery occlusion (MCAO). To simulate ischaemic stroke in vitro, PC12 cells were subjected to oxygen–glucose deprivation (OGD). Immunofluorescence analysis, western blotting (WB), electron microscopy (EM), functional behavioural tests, and Seahorse assay were used for analysis. DHA treatment significantly alleviated the brain infarction volume, neuronal apoptosis, and behavioural dysfunction in mice with ischaemic stroke. In addition, DHA enhanced mitophagy by significantly increasing the number of autophagosomes and LC3-positive mitochondria in neurons. The Seahorse assay revealed that DHA increased glutamate and succinate metabolism in neurons after ischaemic stroke. JC-1 and MitoSox staining, and evaluation of ATP levels indicated that DHA-induced mitophagy alleviated reactive oxygen species (ROS) accumulation and mitochondrial injury. Mechanistically, DHA improved mitochondrial dynamics by increasing the expression of dynamin-related protein 1 (Drp1), LC3, and the mitophagy clearance protein Pink1/Parkin. Mdivi-1, a specific mitophagy inhibitor, abrogated the neuroprotective effects of DHA, indicating that DHA protected neurons by enhancing mitophagy. Therefore, DHA can protect against neuronal apoptosis after stroke by clearing the damaged mitochondria through Pink1/Parkin-mediated mitophagy and by alleviating mitochondrial dysfunction.

Long COVID and long chain fatty acids (LCFAs): Psychoneuroimmunity implication of omega-3 LCFAs in delayed consequences of COVID-19

The global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the lasting pandemic of coronavirus disease 2019 (COVID-19) and the post-acute phase sequelae of heterogeneous negative impacts in multiple systems known as the "long COVID." The mechanisms of neuropsychiatric complications of long COVID are multifactorial, including long-term tissue damages from direct CNS viral involvement, unresolved systemic inflammation and oxidative stress, maladaptation of the renin-angiotensin-aldosterone system and coagulation system, dysregulated immunity, the dysfunction of neurotransmitters and hypothalamus-pituitaryadrenal (HPA) axis, and the psychosocial stress imposed by societal changes in response to this pandemic. The strength of safety, well-acceptance, and accumulating scientific evidence has now afforded nutritional medicine a place in the mainstream of neuropsychiatric intervention and prophylaxis. Long chain omega-3 polyunsaturated fatty acids (omega-3 or n-3 PUFAs) might have favorable effects on immunity, inflammation, oxidative stress and psychoneuroimmunity at different stages of SARS-CoV-2 infection. Omega-3 PUFAs, particularly EPA, have shown effects in treating mood and neurocognitive disorders by reducing pro-inflammatory cytokines, altering the HPA axis, and modulating neurotransmission via lipid rafts. In addition, omega-3 PUFAs and their metabolites, including specialized pro-resolvin mediators, accelerate the process of cleansing chronic inflammation and restoring tissue homeostasis, and therefore offer a promising strategy for Long COVID. In this article, we explore in a systematic review the putative molecular mechanisms by which omega-3 PUFAs and their metabolites counteract the negative effects of long COVID on the brain, behavior, and immunity.

Systemic Elevation of n-3 Polyunsaturated Fatty Acids (n-3-PUFA) Is Associated with Protection against Visual, Motor, and Emotional Deficits in Mice following Closed-Head Mild Traumatic Brain Injury

Traumatic brain injury (TBI) causes neuroinflammation and neurodegeneration leading to various pathological complications such as motor and sensory (visual) deficits, cognitive impairment, and depression. N-3 polyunsaturated fatty acid (n-3 PUFA) containing lipids are known to be anti-inflammatory, whereas the sphingolipid, ceramide (Cer), is an inducer of neuroinflammation and degeneration. Using Fat1⁺-transgenic mice that contain elevated levels of systemic n-3 PUFA, we tested whether they are resistant to mild TBI-mediated sensory-motor and emotional deficits by subjecting Fat1-transgenic mice and their WT littermates to focal cranial air blast (50 psi) or sham blast (0 psi, control). We observed that visual function in WT mice was reduced significantly following TBI but not in Fat1⁺-blast animals. We also found Fat1⁺-blast mice were resistant to the decline in motor functions, depression, and fear-producing effects of blast, as well as the reduction in the area of oculomotor nucleus and increase in activated microglia in the optic tract in brain sections seen following blast in WT mice. Lipid and gene expression analyses confirmed an elevated level of the n-3 PUFA eicosapentaenoic acid (EPA) in the plasma and brain, blocking of TBI-mediated increase of Cer in the brain, and decrease in TBI-mediated induction of Cer biosynthetic and inflammatory gene expression in the brain of the Fat1⁺ mice. Our results demonstrate that suppression of ceramide biosynthesis and inflammatory factors in Fat1⁺-transgenic mice is associated with significant protection against the visual, motor, and emotional deficits caused by mild TBI. This study suggests that n-3 PUFA (especially, EPA) has a promising therapeutic role in preventing neurodegeneration after TBI.

Neuroprotection of N-benzyl Eicosapentaenamide in Neonatal Mice Following Hypoxic-Ischemic Brain Injury

Maca (Lepidium meyenii) has emerged as a popular functional plant food because of its medicinal properties and nutritional value. Macamides, as the exclusively active ingredients found in maca, are a unique series of non-polar, long-chain fatty acid N-benzylamides with multiple bioactivities such as antifatigue characteristics and improving reproductive health. In this study, a new kind of macamide, N-benzyl eicosapentaenamide (NB-EPA), was identified from maca. We further explore its potential neuroprotective role in hypoxic–ischemic brain injury. Our findings indicated that treatment with biosynthesized NB-EPA significantly alleviates the size of cerebral infarction and improves neurobehavioral disorders after hypoxic–ischemic brain damage in neonatal mice. NB-EPA inhibited the apoptosis of neuronal cells after ischemic challenge. NB-EPA improved neuronal cell survival and proliferation through the activation of phosphorylated AKT signaling. Of note, the protective property of NB-EPA against ischemic neuronal damage was dependent on suppression of the p53–PUMA pathway. Taken together, these findings suggest that NB-EPA may represent a new neuroprotectant for newborns with hypoxic–ischemic encephalopathy.

In situ High-Throughput Single-Cell Analysis Reveals the Crosstalk between Nanoparticle-Induced Cell Responses

Nanomaterials are widely used in a variety of industrial, biological, and medical applications. Therefore, high concerns about their possible impact on human and environmental health have been raised. Here, we describe a high-throughput single-cell imaging method to reveal the crosstalk among quantum dot (QDot)-induced ROS generation, apoptosis, and changes in nucleus size in macrophages. In triple marker combinations, we assessed the correlations of three QDot-induced cellular responses via divided subsets based on single-cell analysis. In contrast to the results obtained from the cell population, we demonstrated that the change in nucleus size was positively correlated with ROS generation. We found that QDot exposure induced ROS generation, which led to cell apoptosis, followed by a change in nucleus size. In general, these observations on crosstalk of cellular responses provide detailed insights into the heterogeneity of nanoparticle exposure.

A 16-week randomized placebo-controlled trial investigating the effects of omega-3 polyunsaturated fatty acid treatment on white matter microstructure in recent-onset psychosis patients concurrently treated with risperidone

We examined the impact of treatment with fish oil (FO), a rich source of omega-3 polyunsaturated fatty acids (n-3 PUFA), on white matter in 37 recent-onset psychosis patients receiving risperidone in a double-blind placebo-controlled randomized clinical trial. Patients were scanned at baseline and randomly assigned to receive 16-weeks of treatment with risperidone + FO or risperidone + placebo. Eighteen patients received follow-up MRIs (FO, n = 10/Placebo, n = 8). Erythrocyte levels of n-3 PUFAs eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA) were obtained at both time points. We employed Free Water Imaging metrics representing the extracellular free water fraction (FW) and fractional anisotropy of the tissue (FA-t). Analyses were conducted using Tract-Based-Spatial-Statistics and nonparametric permutation-based tests with family-wise error correction. There were significant positive correlations of FA-t with DHA and DPA among all patients at baseline. Patients treated with risperidone + placebo demonstrated reductions in FA-t and increases in FW, whereas patients treated with risperidone + FO exhibited no significant changes in FW and FA-t reductions were largely attenuated. The correlations of DPA and DHA with baseline FA-t support the hypothesis that n-3 PUFA intake or biosynthesis are associated with white matter abnormalities in psychosis. Adjuvant FO treatment may partially mitigate against white matter alterations observed in recent-onset psychosis patients following risperidone treatment.

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.

Xanomeline Protects Cortical Cells From Oxygen-Glucose Deprivation via Inhibiting Oxidative Stress and Apoptosis

Xanomeline, a muscarinic acetylcholine receptor agonist, is one of the first compounds that was found to be effective in the treatment of schizophrenics and attenuating behavioral disturbances of patients with Alzheimer's disease (AD). However, its role in ischemia-induced injury due to oxygen and glucose deprivation (OGD) remains unclear. Primary rat neuronal cells were exposed to OGD and treated with xanomeline. The effects of xanomeline on apoptosis, cell viability, lactate dehydrogenase (LDH) levels, and reactive oxygen species (ROS) were determined using an Annexin V Apoptosis Detection Kit, a non-radioactive cell counting kit-8 (CCK-8) assay, colorimetric LDH cytotoxicity assay kit, and a dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay, respectively, and the expressions of Sirtuin 1, haem oxygenase-1 (HO-1), B-cell lymphoma 2 (Bcl-2), poly ADP-ribose polymerase (PARP), and hypoxia-inducible factor α (HIF-1α) as well as the level of phosphorylated kinase B (p-Akt) were determined by Western blotting. Compared with the control, xanomeline pretreatment increased the viability of isolated cortical neurons and decreased the LDH release induced by OGD. Compared with OGD-treated cells, xanomeline inhibited apoptosis, reduced ROS production, attenuated the OGD-induced HIF-1α increase and partially reversed the reduction of HO-1, Sirtuin-1, Bcl-2, PARP, and p-Akt induced by OGD. In conclusion, xanomeline treatment protects cortical neuronal cells possibly through the inhibition of apoptosis after OGD.

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.

A novel biscoumarin compound ameliorates cerebral ischemia reperfusion-induced mitochondrial oxidative injury via Nrf2/Keap1/ARE signaling

Some phytochemical-derived synthetic compounds have been shown to improve neurological disorders, especially in ischemic stroke. In this study, we identified a novel biscoumarin compound, known as COM 3, which had substantial antioxidant effects in neurons. Next, we found that COM 3 occupies a critical binding site between the Nrf2 and Keap1 dipolymer, impairing the inhibitory effects of Keap1 on Nrf2, both of which play central roles in increasing endogenous antioxidant activity. We verified that COM 3 could increase the survival of neurons experiencing oxygen and glucose deprivation (OGD) from 51.1% to 77.2% when exposure to 2.5 and 10 μg/mL of COM 3, respectively. In addition, the same concentrations of COM 3 could reduce brain infarct volumes by 33.8%to13.7%, respectively, while also reducing the neurobehavioral score from 3.3 to 1.4 on average in mice with a middle cerebral artery occlusion (MCAO). COM 3 reduced neuronal death from 36.5% to 13.9% and apoptosis from 35.1% to 18.2%. In addition, COM 3 could improve the neuronal mitochondrial energy metabolism after experiencing oxidative stress caused by OGD or MCAO. The present study suggests that COM 3 protects against OGD in neurons and MCAO in mice by interfering with the structure of Keap1 to activate the nuclear transcription of Nrf2, which balances endogenous redox activity and restores mitochondrial function. Hence, COM 3 might be a potential therapeutic agent for ischemic stroke in the clinic.

Metabolomics study of the anti-inflammatory effects of endogenous omega-3 polyunsaturated fatty acids

Low-grade inflammation is usually defined as the chronic production and a low-grade state of inflammatory factors, it often does not have symptoms, and has been associated with neurodegenerative disease, obesity, and diabetes. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are the precursors of many anti-inflammatory metabolites, such as resolvins and neuroprotectins. It is of interest to study the metabolic profile of endogenous n-3 PUFAs in low-grade inflammatory conditions. To evaluate the protective effects of endogenous n-3 PUFAs on low-grade inflammation with the metabolomics approach, we fed fat-1 mice with an n-6 PUFAs rich diet for a long time to induce a low-grade inflammatory condition. Multi-analysis techniques, including structural analysis using quadrupole time-of-flight mass spectrometry with MS^E mode, were applied in untargeted metabolomics to search for meaningful metabolites with significant variance in fat-1 mice under low-grade inflammation. Following the untargeted metabolomics screening, several meaningful metabolites were selected which were associated with anti-inflammatory effects generated from endogenous n-3 PUFAs for further analysis. The results revealed that the purine metabolism, fatty acid metabolism and oxidative stress response pathways through insulin resistance were involved in anti-inflammatory mechanisms of n-3 PUFA in low-grade inflammatory conditions. For the first time, this study explored the highlighted pathways as contributors to the anti-inflammatory effects of endogenous n-3 PUFAs in low-grade inflammatory conditions.

Low-grade inflammation is usually defined as the chronic production and a low-grade state of inflammatory factors, it often does not have symptoms, and has been associated with neurodegenerative disease, obesity, and diabetes.

Lipid Reshaping and Lipophagy Are Induced in a Modeled Ischemia-Reperfusion Injury of Blood Brain Barrier

Ischemic-reperfusion (I/R) injury induced a remodeling of protein and lipid homeostasis, under oxidative stress and inflammatory status. Starvation occurring during I/R is a condition leading to autophagy activation, which allows abnormal material clearance or amino acid, or both, and fatty acid (FA) recycling essential for survival. This study investigated the lipid reshaping, peroxidation, and related-signaling pathways, in rat brain endothelial cells (RBE4) subjected to 3 h of oxygen and glucose deprivation (OGD) and restoration of standard condition (I/R in vitro model). Lipids and proteins were analyzed after 1 or 24 h of oxygen and nutrient restoration. Together with the oxidative stress and inflammatory status, I/R injury induced a reshaping of neutral lipids and biogenesis of lipid droplets (LD) with excessive lipid storage. The increase of LC3-II/LC3-I ratio, an autophagy marker, and LC3 co-localization with LD suggest the activation of lipophagy machinery to counteract the cell engulfment. Lipophagy leads to cholesterol ester (CE) hydrolysis, increasing free cholesterol (FC) secretion, which occurred by specific transporters or unconventional exocytosis pathways, or both. Here, we propose that an unconventional spreading of FC and other lipid metabolites may influence the neurovascular unit (NVU) cells, contributing to Blood brain barrier (BBB) alteration or adaptation, or both, to the cumulative effects of several transient ischemia.

Fish oil treatment reduces chronic alcohol exposure induced synaptic changes

Alcohol addiction is a chronic neuropsychiatric disorder that represents one of the most serious global public health problems. Yet, currently there still lacks an effective pharmacotherapy. Omega-3 polyunsaturated fatty acids (N-3 PUFAs) have exhibited beneficial effects in a variety of neurological disorders, particularly in reversing behavioral deficits and neurotoxicity induced by prenatal alcohol exposure and binge drinking. In the present study, we investigated if fish oil, which is rich in N-3 PUFAs, had beneficial effects on preventing relapse and alleviating withdrawal symptoms after chronic alcohol exposure. Our results demonstrated that fish oil significantly reduced the chronic alcohol exposure-induced aberrant dendritic morphologic changes of the medium-sized spiny neurons in the core and the shell of nucleus accumbens. This inhibited the expression of AMPAR2-lacking AMPARs and their accumulation on the post synaptic membranes of medium-sized spiny neurons and eventually alleviated withdrawal symptoms and alcohol dependence. Our study therefore suggests that N-3 PUFAs are promising for treating withdrawal symptoms and alcohol dependence.

Activation of the Omega-3 Fatty Acid Receptor GPR120 Protects against Focal Cerebral Ischemic Injury by Preventing Inflammation and Apoptosis in Mice

G protein-coupled receptor 120 (GPR120) has been shown to negatively regulate inflammation and apoptosis, but its role in cerebral ischemic injury remains unclear. Using an in vivo model of middle cerebral artery occlusion (MCAO) and an in vitro model of oxygen-glucose deprivation (OGD), we investigated the potential role and molecular mechanisms of GPR120 in focal cerebral ischemic injury. Increased GPR120 expression was observed in microglia and neurons following MCAO-induced ischemia in wild type C57BL/6 mice. Treatment with docosahexaenoic acid (DHA) inhibited OGD-induced inflammatory response in primary microglia and murine microglial BV2 cells, whereas silencing of GPR120 strongly exacerbated the inflammation induced by OGD and abolished the anti-inflammatory effects of DHA. Mechanistically, DHA inhibited OGD-induced inflammation through GPR120 interacting with β-arrestin2. In addition to its anti-inflammatory function, GPR120 also played a role in apoptosis as its knockdown impaired the antiapoptotic effect of DHA in OGD-induced rat pheochromocytoma (PC12) cells. Finally, using MCAO mouse model, we demonstrated that GPR120 activation protected against focal cerebral ischemic injury by preventing inflammation and apoptosis. Our study indicated that pharmacological targeting of GPR120 may provide a novel approach for the treatment of patients with ischemic stroke.

Nutritional Regulators of Bcl-xL in the Brain

B-cell lymphoma-extra large (Bcl-xL) is an anti-apoptotic Bcl-2 protein found in the mitochondrial membrane. Bcl-xL is reported to support normal brain development and protects neurons against toxic stimulation during pathological process via its roles in regulation of mitochondrial functions. Despite promising evidence showing neuroprotective properties of Bcl-xL, commonly applied molecular approaches such as genetic manipulation may not be readily applicable for human subjects. Therefore, findings at the bench may be slow to be translated into treatments for disease. Currently, there is no FDA approved application that specifically targets Bcl-xL and treats brain-associated pathology in humans. In this review, we will discuss naturally occurring nutrients that may exhibit regulatory effects on Bcl-xL expression or activity, thus potentially providing affordable, readily-applicable, easy, and safe strategies to protect the brain.

Post-stroke DHA Treatment Protects Against Acute Ischemic Brain Injury by Skewing Macrophage Polarity Toward the M2 Phenotype

Systemic docosahexaenoic acid (DHA) has been explored as a clinically feasible protectant in stroke models. However, the mechanism for DHA-afforded neuroprotection remains elusive. Transient middle cerebral artery occlusion (tMCAO) was induced for 1 h. DHA (i.p., 10 mg/kg) was administered immediately after reperfusion and repeated daily for 3 days. Stroke outcomes, systemic inflammatory status, and microglia/macrophage phenotypic alterations were assessed 3 days after stroke. Macrophage depletion was induced by clodronate liposomes injection. Primary macrophage cultures were used to evaluate the direct effect of DHA on macrophages. We demonstrated that post-stroke DHA injection efficiently reduced brain infarct and ameliorated neurological deficits 3 days after tMCAO. Systemic DHA treatment significantly inhibited immune cell infiltration (macrophages, neutrophils, T lymphocytes, and B lymphocytes) and promoted macrophage polarization toward an anti-inflammatory M2 phenotype in the ischemic brain. Meanwhile, systemic DHA administration inhibited the otherwise elevated pro-inflammatory factors in blood and shifted circulating macrophage polarity toward M2 phenotype after ischemic stroke. The numbers of circulating immune cells in blood and spleen, however, were equivalent between DHA- and vehicle-treated groups. The protective effects of DHA were macrophage-dependent, as macrophage depletion abolished DHA-afforded neuroprotection. In vitro studies confirmed that DHA suppressed production of chemokines and pro-inflammatory cytokines from macrophages under inflammatory stimulation. These data indicate that post-stroke DHA treatment ameliorated acute ischemic brain injury in a macrophage-dependent manner and DHA enhanced macrophage phenotypic shift toward an anti-inflammatory phenotype to reduced central and peripheral inflammation after stroke.

Inhibiting Jumoji domain containing protein 3 (JMJD3) prevent neuronal apoptosis from stroke

Control of p53 by histone methylation is closely related in the neuronal apoptosis following ischemic stroke. In mammalian cells, demethylation of methylated lysine residue of histones is catalyzed by Jumonji domain-containing proteins (JMJD) family. Among them, JMJD3 is reported to be a hypoxic target gene and expressed in all cell types of brain including neurons. However, the role of JMJD3 on process of neuronal apoptosis after ischemic stroke is still largely unknown. PCR, immunostaining and Western blotting results indicated that JMJD3 expression was upregulated in cultured neurons upon oxygen-glucose deprivation (OGD) injury. Jmjd3^-/- neurons exhibited inhibited cell apoptosis and tolerance to the OGD injury. Chromatin immunoprecipitation and promoter reporter assays showed that the underlying mechanism was through transcriptional activation of p53, thus altering the downstream Bax and Caspase-3 genes. Silencing Jmjd3 improved neurological deficit and reduced infarct volume following ischemic injury in vivo. The present study suggested that JMJD3 was a critical promoter of neuronal apoptosis by regulating the expression of Bax and Caspase-3, and inhibition of JMJD3 might provide a new therapeutic intervention for treating cerebral ischemia.

Enriched Brain Omega-3 Polyunsaturated Fatty Acids Confer Neuroprotection against Microinfarction

Cerebral microinfarcts have significant effects on the development of geriatric neurological disorders, including vascular dementia and Alzheimer's disease. However, little is known about the pathophysiological mechanisms involved in the evolution of microinfarcts and potential treatment and prevention against these microvascular ischemic lesions. In the present study, the "single cortical microinfarct model" generated via occluding a penetrating arteriole by femtosecond laser ablation and the "multiple diffuse microinfarcts model" induced by unilateral injection of cholesterol crystals through the internal carotid artery were established to investigate the pathophysiological mechanisms underlying the evolution of microinfarcts and the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on alleviating microinfarct burdens and functional deficits. The occlusion of a single penetrating arteriole led to a distinct cortical microinfarct, which manifested as neuronal loss and occupation of activated glial cells in the ischemic core. Using Fat-1 transgenic mice and fish oil supplements, we demonstrated that both endogenously-generated and exogenously-delivered ω-3 PUFAs significantly inhibited the activation of receptor-interacting serine/threonine protein kinases 1 (RIPK1) and its downstream apoptosis-associated proteins, mitigated cell apoptosis, and anatomically reduced the microinfarct size. The protective effects of ω-3 PUFAs against microinfarcts were further verified in a multiple diffuse microinfarcts model, where ω-3 PUFAs significantly attenuated cell apoptosis as revealed by TUNEL staining, alleviated the diffuse microinfarct burdens and remarkably improved the functional deficits as evidenced by reduced spontaneous anxiety, increased preference for the novel object, and improved hippocampal-based learning and short-term memory. Together, these findings demonstrate that enriched brain ω-3 PUFAs are effective for reducing microinfarct burdens and improving the function deficits, which support the clinical research and application of ω-3 PUFAs in the treatment or prophylaxis in vascular dementia.

Inhibition of HSP90α protects cultured neurons from oxygen-glucose deprivation induced necroptosis by decreasing RIP3 expression

Heat shock protein 90α (HSP90α) maintains cell stabilization and regulates cell death, respectively. Recent studies have shown that HSP90α is involved in receptor interacting protein 3 (RIP3)-mediated necroptosis in HT29 cells. It is known that oxygen and glucose deprivation (OGD) can induce necroptosis, which is regulated by RIP3 in neurons. However, it is still unclear whether HSP90α participates in the process of OGD-induced necroptosis in cultured neurons via the regulation of RIP3. Our study found that necroptosis occurs in primary cultured cortical neurons and PC-12 cells following exposure to OGD insult. Additionally, the expression of RIP3/p-RIP3, MLKL/p-MLKL, and the RIP1/RIP3 complex (necrosome) significantly increased following OGD, as measured through immunofluorescence (IF) staining, Western blotting (WB), and immunoprecipitation (IP) assay. Additionally, data from computer simulations and IP assays showed that HSP90α interacts with RIP3. In addition, HSP90α was overexpressed following OGD in cultured neurons, as measured through WB and IF staining. Inhibition of HSP90α in cultured neurons, using the specific inhibitor, geldanamycin (GA), and siRNA/shRNA of HSP90α, protected cultured neurons from necrosis. Our study showed that the inhibitor of HSP90α, GA, rescued cultured neurons not only by decreasing the expression of total RIP3/MLKL, but also by decreasing the expression of p-RIP3/p-MLKL and the RIP1/RIP3 necrosome. In this study, we reveal that inhibition of HSP90α protects primary cultured cortical neurons and PC-12 cells from OGD-induced necroptosis through the modulation of RIP3 expression.

Houshiheisan and its components promote axon regeneration after ischemic brain injury

Houshiheisan, a classic prescription in traditional Chinese medicine, contains Flos Chrysanthemi, Radix Saposhnikoviae, Ramulus Cinnamomi, Rhizoma Chuanxiong, Radix et Rhizoma Asari, Radix Platycodonis, Rhizoma Atractylodis macrocephalae, Poria, Rhizoma Zingiberis, Radix Angelicae sinensis, Radix et Rhizoma Ginseng, Radix Scutellariae and Concha Ostreae. According to traditional Chinese medicine theory, Flos Chrysanthemi, Radix Saposhnikoviae, Ramulus Cinnamomi, Rhizoma Chuanxiong, Radix et Rhizoma Asari and Radix Platycodonis are wind-dispelling drugs; Rhizoma Atractylodis macrocephalae, Poria, Rhizoma Zingiberis, Radix Angelicae sinensis and Radix et Rhizoma Ginseng are deficiency-nourishing drugs. A large number of randomized controlled trials have shown that Houshiheisan is effective in treating stroke, but its mechanism of action is unknown. Axonal remodeling is an important mechanism in neural protection and regeneration. Therefore, this study explored the effect and mechanism of action of Houshiheisan on the repair of axons after cerebral ischemia. Rat models of focal cerebral ischemia were established by ligating the right middle cerebral artery. At 6 hours after model establishment, rats were intragastrically administered 10.5 g/kg Houshiheisan or 7.7 g/kg wind-dispelling drug or 2.59 g/kg deficiency-nourishing drug. These medicines were intragastrically administered as above every 24 hours for 7 consecutive days. Houshiheisan, and its wind-dispelling and deficiency-nourishing components reduced the neurological deficit score and ameliorated axon and neuron lesions after cerebral ischemia. Furthermore, Houshiheisan, and its wind-dispelling and deficiency-nourishing components decreased the expression of proteins that inhibit axonal remodeling: amyloid precursor protein, neurite outgrowth inhibitor protein A (Nogo-A), Rho family small GTPase A (RhoA) and Rho-associated kinase 2 (Rock2), and increased the expression of growth associated protein-43, microtubule-associated protein-2, netrin-1, Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle 42 (Cdc42). The effect of Houshiheisan was stronger than wind-dispelling drugs or deficiency-nourishing drugs alone. In conclusion, Houshiheisan, and wind-dispelling and deficiency-nourishing drugs promote the repair of axons and nerve regeneration after cerebral ischemia through Nogo-A/RhoA/Rock2 and Netrin-1/Rac1/Cdc42 signaling pathways. These effects are strongest with Houshiheisan.

Therapeutic potential of omega-3 fatty acid-derived epoxyeicosanoids in cardiovascular and inflammatory diseases

Numerous benefits have been attributed to dietary long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs), including protection against cardiac arrhythmia, triglyceride-lowering, amelioration of inflammatory, and neurodegenerative disorders. This review covers recent findings indicating that a variety of these beneficial effects are mediated by "omega-3 epoxyeicosanoids", a class of novel n-3 LC-PUFA-derived lipid mediators, which are generated via the cytochrome P450 (CYP) epoxygenase pathway. CYP enzymes, previously identified as arachidonic acid (20:4n-6; AA) epoxygenases, accept eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA), the major fish oil n-3 LC-PUFAs, as efficient alternative substrates. In humans and rodents, dietary EPA/DHA supplementation causes a profound shift of the endogenous CYP-eicosanoid profile from AA- to EPA- and DHA-derived metabolites, increasing, in particular, the plasma and tissue levels of 17,18-epoxyeicosatetraenoic acid (17,18-EEQ) and 19,20-epoxydocosapentaenoic acid (19,20-EDP). Based on preclinical studies, these omega-3 epoxyeicosanoids display cardioprotective, vasodilatory, anti-inflammatory, and anti-allergic properties that contribute to the beneficial effects of n-3 LC-PUFAs in diverse disease conditions ranging from cardiac disease, bronchial disorders, and intraocular neovascularization, to allergic intestinal inflammation and inflammatory pain. Increasing evidence also suggests that background nutrition as well as genetic and disease state-related factors could limit the response to EPA/DHA-supplementation by reducing the formation and/or enhancing the degradation of omega-3 epoxyeicosanoids. Recently, metabolically robust synthetic analogs mimicking the biological activities of 17,18-EEQ have been developed. These drug candidates may overcome limitations of dietary EPA/DHA supplementation and provide novel options for the treatment of cardiovascular and inflammatory diseases.

Pretreatment with fish oil attenuates heart ischaemia consequences in rats

NEW FINDINGS

What is the central question of this study? We investigated whether pretreatment with fish oil could prevent the major consequences of ischaemic injury to the heart. What is the main finding and its importance? Fish oil pretreatment attenuated the consequences of ischaemic injury as indicated by the small infarction area and the preservation of systolic function and coronary blood flow. These findings support the use of fish oil in order to reduce the impact of heart ischaemia. ω-3 Polyunsaturated fatty acid (ω-3 PUFA)-rich fish oil supplementation has protective effects on heart ischaemic injury. Left ventricular (LV) ischaemia was induced in rats by permanent ligation of the left descending coronary artery. Saline, fish oil or soybean oil was administered daily by gavage [3 g (kg body weight)^-1 ] for 20 days before inducing ischaemia. Outcomes were assessed 24 h after left descending coronary artery ligation. Pretreatment with fish oil decreased the ω-6/ω-3 fatty acid ratio in the LV. A reduction in infarct size and in the intensity of ventricular systolic dysfunction was found in the fish oil group compared with the saline or soybean oil groups through echocardiographic evaluation. Before infarction, LV glycogen concentrations were decreased in the fish oil group compared with the saline group. Soybean oil pretreatment led to a further increase in the LV levels of CINC-2/αβ, IL-1β and TNF-α induced by the heart infarction. In heart-infarcted rats, fish oil pretreatment decreased creatine kinase and caspase-3 activities; prevented the decrease in the coronary blood flow; increased LV contents of ATP and lactate; increased the mRNA levels of iNOS, eNOS, HIF1α, GLUT1, VEGF-α and p53 in the LV as measured by RT-PCR; and did not change LV pro-inflammatory cytokine concentrations compared with the control group. Fish oil protected the heart from ischaemia, as indicated by the decrease in the heart infarction area and systolic dysfunction associated with increased LV ATP concentrations and maintenance of the coronary blood flow with no change in pro-inflammatory cytokine levels.

Hypoxia-inducible factor-1 alpha is involved in RIP-induced necroptosis caused by in vitro and in vivo ischemic brain injury

Necroptosis, a novel type of programmed cell death, is involved in stroke-induced ischemic brain injury. Although studies have sought to explore the mechanisms of necroptosis, its signaling pathway has not yet to be completely elucidated. Thus, we used oxygen-glucose deprivation (OGD) and middle cerebral artery occlusion (MCAO) models mimicking ischemic stroke (IS) conditions to investigate mechanisms of necroptosis. We found that OGD and MCAO induced cell death, local brain ischemia and neurological deficit, while zVAD-fmk (zVAD, an apoptotic inhibitor), GSK’872 (a receptor interacting protein kinase-3 (RIP3) inhibitor), and combined treatment alleviated cell death and ischemic brain injury. Moreover, OGD and MCAO upregulated protein expression of the triggers of necroptosis: receptor interacting protein kinase-1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL). The upregulation of these proteins was inhibited by GSK’872, combination treatments and RIP3 siRNA but not zVAD treatment. Intriguingly, hypoxia-inducible factor-1 alpha (HIF-1α), an important transcriptional factor under hypoxic conditions, was upregulated by OGD and MCAO. Similar to their inhibitory effects on aforementioned proteins upregulation, GSK’872, combination treatments and RIP3 siRNA decreased HIF-1α protein level. These findings indicate that necroptosis contributes to ischemic brain injury induced by OGD and MCAO and implicate HIF-1α, RIP1, RIP3, and MLKL in necroptosis.

Comparison of the effects of major fatty acids present in the Mediterranean diet (oleic acid, docosahexaenoic acid) and in hydrogenated oils (elaidic acid) on 7-ketocholesterol-induced oxiapoptophagy in microglial BV-2 cells

Increased levels of 7-ketocholesterol (7KC), which results mainly from cholesterol auto-oxidation, are often found in the plasma and/or cerebrospinal fluid of patients with neurodegenerative diseases and might contribute to activation of microglial cells involved in neurodegeneration. As major cellular dysfunctions are induced by 7KC, it is important to identify molecules able to impair its side effects. Since consumption of olive and argan oils, and fish is important in the Mediterranean diet, the aim of the study was to determine the ability of oleic acid (OA), a major compound of olive and argan oil, and docosahexaenoic acid (DHA) present in fatty fishes, such as sardines, to attenuate 7KC-induced cytotoxic effects. Since elaidic acid (EA), the trans isomer of OA, can be found in hydrogenated cooking oils and fried foods, its effects on 7KC-induced cytotoxicity were also determined. In murine microglial BV-2 cells, 7KC induces cell growth inhibition, mitochondrial dysfunctions, reactive oxygen species overproduction and lipid peroxidation, increased plasma membrane permeability and fluidity, nuclei condensation and/or fragmentation and caspase-3 activation, which are apoptotic characteristics, and an increased LC3-II/LC3-I ratio, which is a criterion of autophagy. 7KC is therefore a potent inducer of oxiapoptophagy (OXIdation+APOPTOsis+autoPHAGY) on BV-2 cells. OA and EA, but not DHA, also favor the accumulation of lipid droplets revealed with Masson's trichrome, Oil Red O, and Nile Red staining. The cytotoxicity of 7KC was strongly attenuated by OA and DHA. Protective effects were also observed with EA. However, 7KC-induced caspase-3 activation was less attenuated with EA. Different effects of OA and EA on autophagy were also observed. In addition, EA (but not OA) increased plasma membrane fluidity, and only OA (but not EA) was able to prevent the 7KC-induced increase in plasma membrane fluidity. Thus, in BV-2 microglial cells, the principal fatty acids of the Mediterranean diet (OA, DHA) were able to attenuate the major toxic effects of 7KC, thus reinforcing the interest of natural compounds present in the Mediterranean diet to prevent the development of neurodegenerative diseases.

Anatomical mechanism of spontaneous recovery in regions caudal to thoracic spinal cord injury lesions in rats

Background

The nerve fibre circuits around a lesion play a major role in the spontaneous recovery process after spinal cord hemisection in rats. The aim of the present study was to answer the following question: in the re-control process, do all spinal cord nerves below the lesion site participate, or do the spinal cord nerves of only one vertebral segment have a role in repair?

Methods

First we made a T7 spinal cord hemisection in 50 rats. Eight weeks later, they were divided into three groups based on distinct second operations at T7: ipsilateral hemisection operation, contralateral hemisection, or transection. We then tested recovery of hindlimbs for another eight weeks. The first step was to confirm the lesion had role or not in the spontaneous recovery process. Secondly, we performed T7 spinal cord hemisections in 125 rats. Eight weeks later, we performed a second single hemisection on the ipsilateral side at T8–T12 and then tested hindlimb recovery for another six weeks.

Results

In the first part, the Basso, Beattie, Bresnahan (BBB) scores and the electrophysiology tests of both hindlimbs weren’t significantly different after the second hemisection of the ipsilateral side. In the second part, the closer the second hemisection was to T12, the more substantial the resulting impairment in BBB score tests and prolonged latency periods.

Conclusions

The nerve regeneration from the lesion area after hemisection has no effect on spontaneous recovery of the spinal cord. Repair is carried out by all vertebrae caudal and ipsilateral to the lesion, with T12 being most important.

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

Depression is associated with somatic immune changes, and neuroinflammation is now recognized as hallmark for depressive disorders. N-3 (or omega-3) polyunsaturated fatty acids (PUFAs) are well known to suppress neuroinflammation, reduce oxidative stress, and protect neuron from injury. We pretreated animals with fish oil and induced acute depression-like behaviors with systemic lipopolysaccharide (LPS) injection. The levels of cytokines and stress hormones were determined from plasma and different brain areas. The results showed that fish oil treatment prevent LPS-induce depressive behavior by suppression of neuroinflammation. LPS induced acute neuroinflammation in different brain regions, which were prevented in fish oil fed mice. However, neither LPS administration nor fish oil treatment has strong effect on stress hormone secretion in the hypothalamus and adrenal. Fish oil might provide a useful therapy against inflammation-associated depression.

Delayed Docosahexaenoic Acid Treatment Combined with Dietary Supplementation of Omega-3 Fatty Acids Promotes Long-Term Neurovascular Restoration After Ischemic Stroke

Prophylactic dietary intake of omega-3 polyunsaturated fatty acids (n-3 PUFAs) has been shown to remarkably ameliorate ischemic brain injury. However, the therapeutic efficacy of n-3 PUFA administration post-stroke, especially its impact on neurovascular remodeling and long-term neurological recovery, has not been fully characterized thus far. In this study, we investigated the effect of n-3 PUFA supplementation, as well as in combination with docosahexaenoic acid (DHA) injections, on long-term stroke outcomes. Mice were subjected to transient middle cerebral artery occlusion (MCAO) before randomly assigned to four groups to receive the following: (1) low dose of n-3 PUFAs as the vehicle control, (2) intraperitoneal DHA injections, (3) n-3 PUFA dietary supplement, or (4) combined treatment of (2) and (3). Neurological deficits and brain atrophy, neurogenesis, angiogenesis, and glial scar formation were assessed up to 28 days after MCAO. Results revealed that groups 2 and 3 showed only marginal reduction in post-stroke tissue loss and attenuation of cognitive deficits. Interestingly, group 4 exhibited significantly reduced tissue atrophy and improved cognitive functions compared to groups 2 and 3 with just a single treatment. Mechanistically, the combined treatment promoted post-stroke neurogenesis and angiogenesis, as well as reduced glial scar formation, all of which significantly correlated with the improved spatial memory in the Morris water maze. These results demonstrate an effective therapeutic regimen to enhance neurovascular restoration and long-term cognitive recovery in the mouse model of MCAO. Combined post-stroke DHA treatment and n-3 PUFA dietary supplementation thus may be a potential clinically translatable therapy for stroke or related brain disorders.