Lipoxin A4 methyl ester ameliorates cognitive deficits induced by chronic cerebral hypoperfusion through activating ERK/Nrf2 signaling pathway in rats

A signaling network map of Lipoxin (LXA4): an anti-inflammatory molecule

Lipoxins (LXs) are a class of endogenous bioactive lipid mediators that are involved in the regulation of inflammation. They exert immunomodulatory effects by regulating the behaviour of various immune cells, including neutrophils, macrophages, and T and B cells, by promoting the clearance of apoptotic neutrophils. This helps to dampen inflammation and promote tissue repair. LXs regulate the expression of many inflammatory genes by modulating the levels of transcription factors, such as nuclear factor κB (NF-κB), activator protein-1 (AP-1), nerve growth factor-regulated factor 1A binding protein 1 (NGF), and peroxisome proliferator activated receptor γ (PPAR-γ), which are elevated in various diseases, such as respiratory tract diseases, renal diseases, cancer, neurodegenerative diseases, and viral infections. Lipoxin-mediated signaling is involved in chronic inflammation, cancer, diabetes-associated kidney disease, lung injury, liver injury, endometriosis, respiratory tract diseases, neurodegenerative diseases, chronic cerebral hypoperfusion, and retinal degeneration. In this study, we systematically investigated the intricate network of lipoxin signaling by analyzing the relevant literature. The resulting map comprised 467 molecules categorized as activation/inhibition, enzyme catalysis, gene and protein expression, molecular associations, and translocation events. This map serves as a valuable resource for understanding the complexity of lipoxin signaling and its impact on various cellular functions.

Tangeretin confers neuroprotection, cognitive and memory enhancement in global cerebral ischemia in rats

Global cerebral ischemia is commonly associated with neurological deficits, including cognitive and memory impairments. The present study aims to investigate the neuroprotective, cognitive, and memory enhancement effects of Tangeretin, a flavonoid against global cerebral ischemia in rats. Bilateral common carotid artery occlusion (BCCAO) and reperfusion injury method was used to induce global cerebral ischemia in rats. Motor, cognitive, and memory functions were evaluated using rotarod, grip strength, Y-maze, and Morris water maze. Further, acetylcholine esterase (AchE) enzyme activity, acetylcholine (Ach), oxidative stress markers (ROS, SOD, MDA, and CAT), inflammation (IL-6 and TNF-α), and apoptotic markers (cytochrome C, caspase 9, and caspase 3) in BCCAO rats were measured following Tangeretin (5,10, and 20 mg/kg, oral) treatment. Our findings show that Tangeretin treatment significantly improved cognition and memory by enhancing Ach levels through the amelioration of AchE enzyme activity in BCCAO rats. Moreover, Tangeretin exhibited neuroprotective effects through the mitigation of oxidative stress, inflammation, and apoptosis in the BCCAO rats. In summary, the current findings suggested that Tangeretin exhibited neuroprotection, cognitive and memory enhancement against global cerebral ischemia.

Therapeutic activity of lipoxin A4 in TiO2-induced arthritis in mice: NF-κB and Nrf2 in synovial fluid leukocytes and neuronal TRPV1 mechanisms

Background

Lipoxin A4 (LXA4) has anti-inflammatory and pro-resolutive roles in inflammation. We evaluated the effects and mechanisms of action of LXA4 in titanium dioxide (TiO2) arthritis, a model of prosthesis-induced joint inflammation and pain.

Methods

Mice were stimulated with TiO2 (3mg) in the knee joint followed by LXA4 (0.1, 1, or 10ng/animal) or vehicle (ethanol 3.2% in saline) administration. Pain-like behavior, inflammation, and dosages were performed to assess the effects of LXA4 in vivo.

Results

LXA4 reduced mechanical and thermal hyperalgesia, histopathological damage, edema, and recruitment of leukocytes without liver, kidney, or stomach toxicity. LXA4 reduced leukocyte migration and modulated cytokine production. These effects were explained by reduced nuclear factor kappa B (NFκB) activation in recruited macrophages. LXA4 improved antioxidant parameters [reduced glutathione (GSH) and 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonate (ABTS) levels, nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA and Nrf2 protein expression], reducing reactive oxygen species (ROS) fluorescent detection induced by TiO2 in synovial fluid leukocytes. We observed an increase of lipoxin receptor (ALX/FPR2) in transient receptor potential cation channel subfamily V member 1 (TRPV1)+ DRG nociceptive neurons upon TiO2 inflammation. LXA4 reduced TiO2-induced TRPV1 mRNA expression and protein detection, as well TRPV1 co-staining with p-NFκB, indicating reduction of neuronal activation. LXA4 down-modulated neuronal activation and response to capsaicin (a TRPV1 agonist) and AITC [a transient receptor potential ankyrin 1 (TRPA1) agonist] of DRG neurons.

Conclusion

LXA4 might target recruited leukocytes and primary afferent nociceptive neurons to exert analgesic and anti-inflammatory activities in a model resembling what is observed in patients with prosthesis inflammation.

Lipoxin A4 methyl ester attenuated ketamine-induced neurotoxicity in SH-SY5Y cells via regulating leptin pathway

Ketamine, the widely used intravenous anesthetic, has been reported to cause neurotoxicity and disturbs normal neurogenesis. However, the efficacy of current treatment strategies targeting ketamine's neurotoxicity remains limited. Lipoxin A4 methyl ester (LXA4 ME) is relatively stable lipoxin analog, which serves an important role in protecting against early brain injury. The purpose of this study was to investigate the protective effect of LXA4 ME on ketamine-caused cytotoxicity in SH-SY5Y cells, as well as the underlying mechanisms. Cell viability, apoptosis and endoplasmic reticulum stress (ER stress) were detected by adopting experimental techniques including CCK-8 assay, flow cytometry, western blotting and transmission electron microscope. Furthermore, examining the expression of leptin and its receptor (LepRb), we also measured the levels of activation of the leptin signaling pathway. Our results showed that LXA4 ME intervention promoted the cell viability, inhibited cell apoptosis, and reduced the expression of ER stress related protein and morphological changes induced by ketamine. In addition, inhibition of leptin signaling pathway caused by ketamine could be reversed by LXA4 ME. However, as the specific inhibitor of leptin pathway, leptin antagonist triple mutant human recombinant (leptin tA) attenuated the cytoprotective effect of LXA4 ME against ketamine-induced neurotoxicity. In conclusion, our findings demonstrated LXA4 ME could exert a neuroprotective effect on ketamine-induced neuronal injury via activation of the leptin signaling pathway.

Onychiol B attenuates lipopolysaccharide-induced inflammation via MAPK/NF-κB pathways and acute lung injury in vivo

Acute lung injury (ALI) is a devastating respiratory disorder characterized by rapid alveolar injury, uncontrolled inflammatory response, etc. Onychiol B is a cyathane diterpene originally isolated from fern plants. In this study, onychiol B can inhibit the production and secretion of pro-inflammatory cytokines such as NO, iNOS, IL-6 and TNF-α in LPS-stimulated RAW264.7 cells by restraining the NF-κB and the p38 MAPK pathway. In addition, it prevents the production of ROS and reduces the loss of mitochondrial membrane potential in LPS-stimulated RAW264.7 cells. Furthermore, in the acute lung injury mouse model induced by LPS injected into the trachea, onychiol B alleviates pulmonary edema, reverses inflammatory mediator TNF-α, IL-6, and IL-β secretion in lung. In general, our data show that significant anti-ALI effects of onychiol B would render it a potential candidate for the treatment of inflammatory diseases.

Anti-inflammatory Quinoline Alkaloids from the Roots of Waltheria indica

Sixteen new quinoline alkaloids (1a-7, 8a, 9, 10, 13-15, 17, and 21) and 10 known analogs (8b, 11, 12, 16, 18-20, and 22-24), along with three known cyclopeptide alkaloids (25-27), were isolated from the roots of Waltheria indica. The structures of the new compounds were elucidated by detailed NMR and circular dichroism with computational support and mass spectrometry data interpretation. Anti-inflammatory potential of isolates was evaluated based on inhibition of lipopolysaccharide (LPS)-induced nitric oxide (NO) production and tumor necrosis factor-alpha (TNF-α)-induced nuclear factor kappa B (NF-κB) activity with cell culture models. In the absence of cell growth inhibition, compounds 6, 8a, 9-11, 13, 21, and 24 reduced TNF-α-induced NF-κB activity with IC₅₀ values ranging from 7.1 to 12.1 μM, comparable to the positive control (BAY 11-7082, IC₅₀ = 9.7 μM). Compounds 6, 8a, 8b, and 11 showed significant NO-inhibitory activity with IC₅₀ values ranging from 11.0 to 12.8 μM, being more active than the positive control (l-NMMA, IC₅₀ = 22.7 μM). Structure-activity relationships indicated that NO inhibitory activity was significantly affected by C-8 substitution. Inhibition of LPS-induced nitric oxide synthase (iNOS) by 8b [(5S)-waltherione M, IC₅₀ 11.7 ± 0.8 μM] correlated with inhibition of iNOS mRNA expression. The biological potential of W. indica metabolites supports the traditional use of this plant for the treatment of inflammatory-related disorders.

Specialized Pro-Resolving Mediators in Neuroinflammation: Overview of Studies and Perspectives of Clinical Applications

Specialized pro-resolving mediators (SPMs) are lipid mediators derived from poly-unsaturated fatty acids (PUFAs) which have been demonstrated to have an important role in the inflammation environment, preventing an overreaction of the organism and promoting the resolution of inflammation. Our purpose was to point out the current evidence for specialized pro-resolving mediators, focusing on their role in neuroinflammation and in major neurological diseases.

microRNA-140-3p protects hippocampal neuron against pyroptosis to attenuate sevoflurane inhalation-induced post-operative cognitive dysfunction in rats via activation of HTR2A/ERK/Nrf2 axis by targeting DNMT1

The incidence of post-operative cognitive dysfunction (POCD) remains a relatively prevalent complication in the elderly after surgery, especially in those receiving sevoflurane (Sevo) anesthesia. microRNA (miR)-140-3p has been demonstrated to orchestrate neuroinflammation and neuron apoptosis. However, the role of miR-140-3p in POCD remains largely unknown. In this context, this research was designed to explore whether miR-140-3p mediated Sevo inhalation-induced POCD in rats. A POCD rat model was established by Sevo inhalation, and a Sevo cell model was constructed in primary hippocampal neurons isolated from rats, followed by detection of miR-140-30 and HTR2A expression. Then, gain- and loss-of-function assays were implemented in rats and neurons. In rats, the cognitive function was evaluated by Water maze test and step-through test, and neuron apoptosis by TUNEL staining. In neurons, cell viability, apoptosis, and pyroptosis-related factors were tested by MTT, flow cytometry, and Western blot analysis respectively. Interaction between HTR2A and DNMT1 was assessed by MSP, and ChIP assay, and interaction between miR-140-3p and DNMT1 by dual-luciferase reporter assay, RIP and RNA pull-down. HTR2A and miR-140-3p were downregulated in POCD rats and Sevo-treated hippocampal neurons. Mechanistically, miR-140-3p negatively targeted DNMT1 to decrease HTR2A promoter methylation, thus upregulation HTR2A to activate ERK/Nrf2 pathway. miR-140-3p or HTR2A overexpression or activation of ERK/Nrf2 pathway elevated neuron viability and diminished their apoptosis and pyroptosis while alleviating Sevo-induced POCD in rats. Collectively, miR-140-3p might repress neuron pyroptosis to alleviate Sevo inhalation-induced POCD in rats via DNMT1/HTR2A/ERK/Nrf2 axis.

Berberine protects against chronic cerebral hypoperfusion-induced cognitive impairment and hippocampal damage via regulation of the ERK/Nrf2 pathway

Vascular cognitive impairment caused by chronic cerebral hypoperfusion (CCH) seriously affects the quality of life of elderly patients and places a great burden on society and family. With the development of traditional Chinese medicine (TCM), TCM approaches to the prevention and treatment of senile ischemic cerebrovascular disease has received increasing attention. In this study, rats with bilateral common carotid artery occlusion (BCCAO) were treated with berberine (BBR). Their learning and memory function, neuronal injury and repair, the extracellular regulatory protein kinase (ERK)/nuclear factor-E2-related factor 2 (Nrf2) signaling pathway, and impairment and improvement of the blood-brain barrier (BBB) were evaluated. This study found that BBR can alleviate the pathological injury to the brain, reduce neuronal loss and promote neuronal cell survival after CCH by interfering with the ERK/Nrf2 signaling pathway. BBR can reduce BBB injury in CCH rats by inhibiting the expression of VEGF-A and MMP-9 in plasma, which reveals a protective effect of BBR on vascular cognitive impairment. This study provides a new research direction for BBR in the treatment of ischemic cerebrovascular disease.

Design, Synthesis, Biological Evaluation, and Computational Studies of Novel Ureidopropanamides as Formyl Peptide Receptor 2 (FPR2) Agonists to Target the Resolution of Inflammation in Central Nervous System Disorders

Formyl peptide receptor 2 (FPR2) agonists can boost the resolution of inflammation and can offer alternative approaches for the treatment of pathologies with underlying chronic neuroinflammation, including neurodegenerative disorders. Starting from the FPR2 agonist 2 previously identified in our laboratory and through fine-tuning of FPR2 potency and metabolic stability, we have identified a new series of ureidopropanamide derivatives endowed with a balanced combination of such properties. Computational studies provided insights into the key interactions of the new compounds for FPR2 activation. In mouse microglial N9 cells and in rat primary microglial cells stimulated with lipopolysaccharide, selected compounds inhibited the production of pro-inflammatory cytokines, counterbalanced the changes in mitochondrial function, and inhibited caspase-3 activity. Among the new agonists, (S)-11l stands out also for the ability to permeate the blood-brain barrier and to accumulate in the mouse brain in vivo, thus representing a valuable pharmacological tool for studies in vivo.

Lipoxins in the Nervous System: Brighter Prospects for Neuroprotection

Lipoxins (LXs) are generated from arachidonic acid and are involved in the resolution of inflammation and confer protection in a variety of pathological processes. In the nervous system, LXs exert an array of protective effects against neurological diseases, including ischemic or hemorrhagic stroke, neonatal hypoxia-ischemia encephalopathy, brain and spinal cord injury, Alzheimer's disease, multiple sclerosis, and neuropathic pain. Lipoxin administration is a potential therapeutic strategy in neurological diseases due to its notable efficiency and unique superiority regarding safety. Here, we provide an overview of LXs in terms of their synthesis, signaling pathways and neuroprotective evidence. Overall, we believe that, along with advances in lipoxin-related drug design, LXs will bring brighter prospects for neuroprotection.

Lipoxin A4 methyl ester protects PC12 cells from ketamine-induced neurotoxicity via the miR-22/BAG5 pathway

OBJECTIVE

Ketamine is an anesthetic that induces neurotoxicity when administered at high doses. In this work, we explored the protective effects of lipoxin A₄ methyl ester (LXA₄ ME) against ketamine-induced neurotoxicity and the underlying protective mechanism in pheochromocytoma (PC12) cells.

METHODS

PC12 cells were treated with 50 μM of ketamine and different LXA₄ ME concentrations of LXA4 ME (5-50 nM) for 24 h, and their viability, apoptosis, and oxidative status were assessed.

RESULTS

Quantitative real-time polymerase chain reaction experiments showed that ketamine downregulated miR-22 expression and upregulated Bcl-2-associated athanogene 5 (BAG5) in PC12 cells in a concentration-dependent manner. LXA₄ ME induced the opposite effects, thus attenuating ketamine-induced neurotoxicity. Further in vitro assays showed that miR-22 directly targeted BAG5, thus promoting cell viability by suppressing cell apoptosis and oxidative stress. Under expression miR-22 or upregulation of BAG5 antagonized the effects of LXA₄ ME.

CONCLUSION

LXA₄ ME can protect PC12 cells from ketamine-induced neurotoxicity by activating the miR-22/BAG5 signaling pathway. Thus, LXA₄ ME can be used as a protective drug against ketamine-induced neural damage.

Role of polyunsaturated fatty acids in ischemic stroke - A perspective of specialized pro-resolving mediators

Polyunsaturated fatty acids (PUFAs) have been proposed as beneficial for cardiovascular health. However, results from both epidemiological studies and clinical trials have been inconsistent, whereas most of the animal studies showed promising benefits of PUFAs in the prevention and treatment of ischemic stroke. In recent years, it has become clear that PUFAs are metabolized into various types of bioactive derivatives, including the specialized pro-resolving mediators (SPMs). SPMs exert multiple biofunctions, such as to limit excessive inflammatory responses, regulate lipid metabolism and immune cell functions, decrease production of pro-inflammatory factors, increase anti-inflammatory mediators, as well as to promote tissue repair and homeostasis. Inflammation has been recognised as a key contributor to the pathophysiology of acute ischemic stroke. Owing to their potent pro-resolving actions, SPMs are potential for development of novel anti-stroke therapy. In this review, we will summarize current knowledge of epidemiological studies, basic research and clinical trials concerning PUFAs in stroke prevention and treatment, with special attention to SPMs as the unsung heroes behind PUFAs.

Crosstalk Between the Gut Microbiome and Bioactive Lipids: Therapeutic Targets in Cognitive Frailty

Cognitive frailty is a geriatric condition defined by the coexistence of cognitive impairment and physical frailty. This "composite" aging phenotype is associated with a higher risk of several adverse health-related outcomes, including dementia. In the last decade, cognitive frailty has gained increased attention from the scientific community that has focused on understanding the clinical impact and the physiological and pathological mechanisms of development and on identifying preventive and/or rehabilitative therapeutic interventions. The emergence of gut microbiome in neural signaling increased the interest in targeting the gut-brain axis as a modulation strategy. Multiple studies on gastroenteric, metabolic, and neurodegenerative diseases support the existence of a wide bidirectional communication network of signaling mediators, e.g., bioactive lipids, that can modulate inflammation, gut permeability, microbiota composition, and the gut-brain axis. This crosstalk between the gut-brain axis, microbiome, and bioactive lipids may emerge as the basis of a promising therapeutic strategy to counteract cognitive frailty. In this review, we summarize the evidence in the literature regarding the link between the gut microbiome, brain, and several families of bioactive lipids. In addition, we also explore the applicability of several bioactive lipid members as a potential routes for therapeutic interventions to combat cognitive frailty.

DL-3-n-butylphthalide protects the blood-brain barrier against ischemia/hypoxia injury via upregulation of tight junction proteins

BACKGROUND

The increased permeability of the blood-brain barrier (BBB) induced by ischemia/hypoxia is generally correlated with alteration of tight junctions (TJs). DL-3-n-butylphthalide (NBP) has been shown to exert neuroprotective effects after ischemic injury. However, few studies have assessed the correlation between NBP and TJs. This study aimed to investigate the potential effect of NBP on the TJ proteins claudin-5, zonula occludens-1 (ZO-1), and occludin during brain ischemia.

METHODS

A chronic cerebral hypoperfusion (CCH) Sprague-Dawley rat model was established, and NBP (20, 40, or 80 mg/kg, gavage, once a day) treatment was performed for 14 days. NBP (0.1 or 1.0 μmol/L) pre-treatment was applied to an in vitro hypoxia microvascular endothelial cell model (1% O2, 24 h). BBB permeability was assessed by performing the Evans blue assay. The expressions and localization of claudin-5, ZO-1, occludin, phosphorylated/total protein kinase B (p-Akt/Akt), phosphorylated/total glycogen synthase kinase 3β (GSK-3β)/GSK-3β, and β-catenin/β-actin were evaluated by Western blotting or immunofluorescence. Reactive oxygen species (ROS) generation was measured by flow cytometry analysis. TJ ultrastructure was observed by transmission electron microscopy.

RESULTS

In CCH rats, treatment with 40 and 80 mg/kg NBP decreased the Evans blue content in brain tissue (9.0 ± 0.9 μg/g vs. 12.3 ± 1.9 μg/g, P = 0.005; 6.7 ± 0.6 μg/g vs. 12.3 ± 1.9 μg/g, P < 0.01), increased the expression of claudin-5 (0.79 ± 0.08 vs. 0.41 ± 0.06, P < 0.01; 0.97 ± 0.07 vs. 0.41 ± 0.06, P < 0.01), and elevated the ZO-1 protein level (P < 0.05) in brain microvascular segments in a dose-dependent manner in comparison with the corresponding values in the model group. There was no significant difference in occludin expression (P > 0.05). In the hypoxia cell model, NBP pre-treatment improved TJ ultrastructure, decreased intracellular ROS level, and increased the expression of claudin-5 (P < 0.01) and ZO-1 (P < 0.01) in comparison with the corresponding values in the hypoxia group. NBP treatment also elevated the relative expression levels of p-Akt/Akt, p-GSK-3β/GSK-3β, and β-catenin/β-actin in comparison with the corresponding values in the hypoxia group (all P < 0.05).

CONCLUSION

NBP improves the barrier function of BBB against ischemic injury by upregulating the expression of TJ proteins, possibly by reducing oxidative stress and activating the Akt/GSK-3β/β-catenin signaling pathway.

Anti-inflammatory effects of Aureusidin in LPS-stimulated RAW264.7 macrophages via suppressing NF-κB and activating ROS- and MAPKs-dependent Nrf2/HO-1 signaling pathways

Aureusidin, a naturally-occurring flavonoid, is found in various plants of Cyperaceae such as Heleocharis dulcis (Burm. f.) Trin., but its pharmacological effect and active mechanism are rarely reported. This study aimed to investigate the anti-inflammatory effect and action mechanism of Aureusidin in LPS-induced mouse macrophage RAW264.7 cells. The results suggested that lipopolysaccharide (LPS)-induced nitric oxide (NO), tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2) production were obviously inhibited by Aureusidin. Moreover, Aureusidin also significantly decreased the mRNA expression of various inflammatory factors in LPS-stimulated RAW264.7 cells. Furthermore, mechanistic studies showed that Aureusidin significantly inhibited nuclear transfer of nuclear factor-κB (NF-κB), while increasing the nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) as well as expression of Nrf2 target genes such as heme oxygenase (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1), but the addition of the HO-1 inhibitor Sn-protoporphyrin (Snpp) significantly abolished the anti-inflammatory effect of Aureusidin in LPS-stimulated RAW264.7 cells, confirming the view that HO-1 was involved in the anti-inflammatory effect. In addition, Aureusidin increased the levels of reactive oxygen species (ROS) and mitogen-activated protein kinase (MAPK) phosphorylation in RAW264.7 cells. Antioxidant N-acetylcysteine (NAC) or three MAPK inhibitors blocked the nuclear translocation of Nrf2 and HO-1 expression induced by Aureusidin, indicating that Aureusidin activated the Nrf2/HO-1 signaling pathway through ROS and MAPKs pathways. At the same time, co-treatment with the NAC blocked the phosphorylation of MAPKs. Results from molecular docking indicated that Aureusidin inhibited the NF-κB pathway by covalently binding to NF-κB. Thus, Aureusidin exerted the anti-inflammatory activity through blocking the NF-κB signaling pathways and activating the MAPKs and Nrf2/HO-1 signaling pathways. Based on the above results, Aureusidin may be an attractive therapeutic candidate for the inflammation-related diseases.

Oxiracetam ameliorates cognitive deficits in vascular dementia rats by regulating the expression of neuronal apoptosis/autophagy-related genes associated with the activation of the Akt/mTOR signaling pathway

Oxiracetam (ORC) is a commonly used nootropic drug for improving cognition and memory impairments. The therapeutic effect and underlying mechanism of ORC in vascular dementia (VaD) treatment remain unknown. In this study, 3-month-old male Sprague-Dawley rats with permanent bilateral common carotid artery occlusion-induced VaD were treated orally with low (100 mg/kg) or high (200 mg/kg) dose ORC once a day for 4 weeks. The results of the Morris water maze test and Nissl staining showed that ORC treatment significantly alleviated learning and memory deficits and neuronal damage in rats with VaD. Mechanistically, the protein levels of a panel of genes associated with neuronal apoptosis (Bcl-2, Bax) and autophagy (microtubule-associated protein 1 chain 3, Beclin1, p62) were significantly altered by ORC treatment compared with VaD, suggesting a protective role of ORC against VaD-induced neuronal apoptosis and autophagy. Moreover, the Akt/mTOR pathway, which is known to be the upstream signaling governing apoptosis and autophagy, was found to be activated in ORC-treated rats, suggesting an involvement of Akt/mTOR activation in ORC-rendered protection in VaD rats. Taken together, this study demonstrated that ORC may alleviate learning and memory impairments and neuronal damage in VaD rats by altering the expression of apoptosis/autophagy-related genes and activation of the Akt/mTOR signaling pathway in neurons.

Embelin Improves the Spatial Memory and Hippocampal Long-Term Potentiation in a Rat Model of Chronic Cerebral Hypoperfusion

Alzheimer's disease (AD) is the second most occurring neurological disorder after stroke and is associated with cerebral hypoperfusion, possibly contributing to cognitive impairment. In the present study, neuroprotective and anti-AD effects of embelin were evaluated in chronic cerebral hypoperfusion (CCH) rat model using permanent bilateral common carotid artery occlusion (BCCAO) method. Rats were administered with embelin at doses of 0.3, 0.6 or 1.2 mg/kg (i.p) on day 14 post-surgery and tested in Morris water maze (MWM) followed by electrophysiological recordings to access cognitive abilities and synaptic plasticity. The hippocampal brain regions were extracted for gene expression and neurotransmitters analysis. Treatment with embelin at the doses of 0.3 and 0.6 mg/kg significantly reversed the spatial memory impairment induced by CCH in rats. Embelin treatment has significantly protected synaptic plasticity impairment as assessed by hippocampal long-term potentiation (LTP) test. The mechanism of this study demonstrated that embelin treatment alleviated the decreased expression of BDNF, CREB1, APP, Mapt, SOD1 and NFκB mRNA levels caused by CCH rats. Furthermore, treatment with embelin demonstrated neuromodulatory activity by its ability to restore hippocampal neurotransmitters. Overall these data suggest that embelin improve memory and synaptic plasticity impairment in CCH rats and can be a potential drug candidate for neurodegenerative disease-related cognitive disorders.

Iron dysregulation in vascular dementia: Focused on the AMPK/autophagy pathway

Recent researches suggested that iron dysregulation play an important role in the pathogenesis of vascular dementia (VD). Iron deposition had been found in hippocampus in vascular dementia model in recent research. Nevertheless, the underlying mechanisms of iron deposition and its neurotoxicity in vascular dementia was still unclear. Thus, our research was aimed at whether the neurotoxicity of iron was associated with autophagy regulation. We established a chronic cerebral hypoperfusion model in the rat brain in order to mimic the vascular dementia using permanent bilateral common carotid artery occlusion (2VO). The preparation of iron overloaded rats model by intraperitoneal injection of iron dextran. Following, we tested the learning and memory function of each group using Morris Water Maze. Consequently, we analyzed the iron content and iron transport related molecules (TFR1, DMT1) in hippocampus. Furthermore, we examined the effect of iron deposition on autophagy-related molecules including AMPK, Beclin1 and LC3 and the number of autophagosomes in hippocampus. Last, we tested the apoptosis of neurons in hippocampus. We found that iron deposition in hippocampus in model groups which accompanied the decline of learning and memory function. And the expression of TFR1 and DMT1 were up-regulated in model groups. Moreover, iron deposition up-regulated the expression of AMPK, Beclin1 and LC3 and increase the number of autophagosomes in hippocampus. And the expression of Bax was up-regulated and Bcl-2 was down-regulated in iron deposition groups. To sum up, our data suggested that iron deposition increased AMPK/autophagy pathway associated molecules in the hippocampus and promoted neuronal apoptosis, which might be a new pathogenesis in vascular dementia.

Direct and indirect effects of lipids on microglia function

Microglia are key players in brain function by maintaining brain homeostasis across lifetime. They participate to brain development and maturation through their ability to release neurotrophic factors, to remove immature synapses or unnecessary neural progenitors. They modulate neuronal activity in healthy adult brains and they also orchestrate the neuroinflammatory response in various pathophysiological contexts such as aging and neurodegenerative diseases. One of the main features of microglia is their high sensitivity to environmental factors, partly via the expression of a wide range of receptors. Recent data pinpoint that dietary fatty acids modulate microglia function. Both the quantity and the type of fatty acid are potent modulators of microglia physiology. The present review aims at dissecting the current knowledge on the direct and indirect mechanisms (focus on gut microbiota and hormones) through which fatty acids influence microglial physiology. We summarize main discoveries from in vitro and in vivo models on fatty acid-mediated microglial modulation. All these studies represent a promising field of research that could promote using nutrition as a novel therapeutic or preventive tool in diseases involving microglia dysfunctions.

Lipoxin A4 Methyl Ester Reduces Early Brain Injury by Inhibition of the Nuclear Factor Kappa B (NF-κB)-Dependent Matrix Metallopeptidase 9 (MMP-9) Pathway in a Rat Model of Intracerebral Hemorrhage

Background

Intracerebral hemorrhage (ICH) is associated with inflammation and disruption of the blood-brain barrier (BBB). Lipoxin A4 methyl ester (LXA4 ME), is a stable synthetic analog of lipoxin with anti-inflammatory properties. This study aimed to investigate the effects of LXA4 ME in a rat model of ICH.

Material/Methods

Male Sprague-Dawley rats (n=120), between 12–13 weeks of age, were divided into the sham group (sham-operated), the vehicle-treated group (ICH+vehicle), the LXA4 ME-L group (ICH+low-dose LXA4 ME, 10 ng/d), and the LXA4 ME-H group (ICH+high-dose LXA4 ME, 100 ng/d). The ICH model was created by injection of autologous blood into the right basal ganglia. LXA4 ME was injected into the ventricle 10 min after the development of ICH. A modified neurological severity score (mNSS), rotarod latencies, and brain water content were used to evaluate the rats. The TUNEL assay measured neuronal cell death. Western blot was used to measure protein expression of nuclear factor kappa B (NF-κB), matrix metalloproteinase-9 (MMP-9), zonula occludens-1 (ZO-1), and claudin-5.

Results

In the rat model of ICH, treatment with LXA4 ME reduced the levels of proinflammatory cytokines, improved neurologic function, reduced neuronal apoptosis, and reduced cerebral edema associated with damage to the BBB, and reduced the expression levels of NF-κB, MMP-9, ZO-1, and claudin-5.

Conclusions

In a rat model of ICH, treatment with LXA4 reduced early brain injury and protected the BBB by inhibiting the NF-κB-dependent MMP-9 pathway.

Is lipoxin A4 an effective treatment on fat embolism syndrome by attenuating pro-inflammatory response?

Fat embolism syndrome (FES) is characterized by high mortality and lack of effective treatment, the symptomatic therapy is most used to relieve clinical symptoms. Some studies have shown that inflammation is one of the main pathogeneses of FES. Lipoxin A4 is an endogenous-derived anti-inflammatory substance which was discovered recently. It can alleviate inflammatory response and promote inflammation resolution, and is referred as brake signal of inflammation. Therefore we hypothesize that lipoxin A4 may have a remission and therapeutic effect on FES by attenuating FES-induced inflammatory responses.

Chotosan ameliorates cognitive impairment and hippocampus neuronal loss in experimental vascular dementia via activating the Nrf2-mediated antioxidant pathway

Recent studies suggested that Chotosan has ameliorative effects on vascular dementia through antioxidative pathways. Nevertheless, no systematic pharmacological research was conducted to evaluate the contribution of nuclear factor-E2-related factor 2 (Nrf2), a crucial regulator of antioxidative system, on Chotosan-induced neuroprotection invascular dementia. The present study aimed to investigate the neuroprotective effect of Chotosan on vascular dementia and reveal the possible molecular mechanism involving Nrf2. We found that Chotosan treatment could ameliorate memory impairment and reduce neuron cell loss induced by common carotid artery occlusion surgery. Furthermore, Chotosan could significantly reverse reactive oxygen species production, neuronal apoptosis and microglia over-activation in hippocampus. In addition, Chotosan enhanced Nrf2 expression and its nuclear translocation as well as its downstream antioxidant protein expression, NAD(P)H/quinone oxidoreductase 1 and heme oxygenase-1. These findings suggest that Chotosan exert neuroprotection in an animal model of vascular dementia via activating Nrf2-mediated antioxidant pathway. Chotosan may serve as a potential candidate and promising Nrf2 activator for treating vascular dementia.

Ambiguous Effects of Autophagy Activation Following Hypoperfusion/Ischemia

Autophagy primarily works to counteract nutrient deprivation that is strongly engaged during starvation and hypoxia, which happens in hypoperfusion. Nonetheless, autophagy is slightly active even in baseline conditions, when it is useful to remove aged proteins and organelles. This is critical when the mitochondria and/or proteins are damaged by toxic stimuli. In the present review, we discuss to that extent the recruitment of autophagy is beneficial in counteracting brain hypoperfusion or, vice-versa, its overactivity may per se be detrimental for cell survival. While analyzing these opposite effects, it turns out that the autophagy activity is likely not to be simply good or bad for cell survival, but its role varies depending on the timing and amount of autophagy activation. This calls for the need for an appropriate autophagy tuning to guarantee a beneficial effect on cell survival. Therefore, the present article draws a theoretical pattern of autophagy activation, which is hypothesized to define the appropriate timing and intensity, which should mirrors the duration and severity of brain hypoperfusion. The need for a fine tuning of the autophagy activation may explain why confounding outcomes occur when autophagy is studied using a rather simplistic approach.

Astrocyte-specific overexpression of Nrf2 protects against optic tract damage and behavioural alterations in a mouse model of cerebral hypoperfusion

Mouse models have shown that cerebral hypoperfusion causes white matter disruption and memory impairment relevant to the study of vascular cognitive impairment and dementia. The associated mechanisms include inflammation and oxidative stress are proposed to drive disruption of myelinated axons within hypoperfused white matter. The aim of this study was to determine if increased endogenous anti-oxidant and anti-inflammatory signalling in astrocytes was protective in a model of mild cerebral hypoperfusion. Transgenically altered mice overexpressing the transcription factor Nrf2 (GFAP-Nrf2) and wild type littermates were subjected to bilateral carotid artery stenosis or sham surgery. Behavioural alterations were assessed using the radial arm maze and tissue was collected for pathology and transcriptome analysis six weeks post-surgery. GFAP-Nrf2 mice showed less pronounced behavioural impairments compared to wild types following hypoperfusion, paralleled by reduced optic tract white matter disruption and astrogliosis. There was no effect of hypoperfusion on anti-oxidant gene alterations albeit the levels were increased in GFAP-Nrf2 mice. Instead, pro-inflammatory gene expression was determined to be significantly upregulated in the optic tract of hypoperfused wild type mice but differentially affected in GFAP-Nrf2 mice. In particular, complement components (C4 and C1q) were increased in wild type hypoperfused mice but expressed at levels similar to controls in hypoperfused GFAP-Nrf2 mice. This study provides evidence that overexpression of Nrf2 in astrocytes exerts beneficial effects through repression of inflammation and supports the potential use of Nrf2-activators in the amelioration of cerebrovascular-related inflammation and white matter degeneration.

Neuroprotection Targeting Protein Misfolding on Chronic Cerebral Hypoperfusion in the Context of Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster of risk factors that lead to microvascular dysfunction and chronic cerebral hypoperfusion (CCH). Long-standing reduction in oxygen and energy supply leads to brain hypoxia and protein misfolding, thereby linking CCH to Alzheimer's disease. Protein misfolding results in neurodegeneration as revealed by studying different experimental models of CCH. Regulating proteostasis network through pathways like the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), chaperone-mediated autophagy (CMA), and macroautophagy emerges as a novel target for neuroprotection. Lipoxin A4 methyl ester, baclofen, URB597, N-stearoyl-L-tyrosine, and melatonin may pose potential neuroprotective agents for rebalancing the proteostasis network under CCH. Autophagy is one of the most studied pathways of proteostatic cell response against the decrease in blood supply to the brain though the role of the UPR-specific chaperones and the UPS system in CCH deserves further research. Pharmacotherapy targeting misfolded proteins at different stages in the proteostatic pathway might be promising in treating cognitive impairment following CCH.

Lipoxin A4 inhibits UV radiation-induced skin inflammation and oxidative stress in mice

BACKGROUND

Lipoxin A4 (LXA4) is a metabolic product of arachidonic acid. Despite potent anti-inflammatory and pro-resolution activities, it remains to be determined if LXA4 has effect on ultraviolet (UV) radiation-induced skin inflammation.

OBJECTIVE

To investigate the effects of systemic administration with LXA4 on UV radiation-induced inflammation and oxidative damage in the skin of mice.

METHODS

Varied parameters of inflammation and oxidative stress in the skin of mice were evaluated after UV radiation (4.14 J/cm2).

RESULTS

Pretreatment with LXA4 significantly inhibited UV radiation-induced skin edema and myeloperoxidase activity. LXA4 efficacy was enhanced by increasing the time of pre-treatment to up to 72 h. LXA4 reduced UV radiation-induced skin edema, neutrophil recruitment (myeloperoxidase activity and LysM-eGFP+ cells), MMP-9 activity, deposition of collagen fibers, epidermal thickness, sunburn cell counts, and production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-33). Depending on the time point, LXA4 increased the levels of anti-inflammatory cytokines (TGF-β and IL-10). LXA4 significantly attenuated UV radiation-induced oxidative damage returning the oxidative status to baseline levels in parameters such as ferric reducing ability, scavenging of free radicals, GSH levels, catalase activity and superoxide anion production. LXA4 also reduced UV radiation-induced gp91phox [nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) subunit] mRNA expression and enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream target enzyme nicotinamide adenine dinucleotide (phosphate) quinone oxidoreductase (Nqo1) mRNA expression.

CONCLUSION

LXA4 inhibited UV radiation-induced skin inflammation by diminishing pro-inflammatory cytokine production and oxidative stress as well as inducing anti-inflammatory cytokines and Nrf2.

Pro-apoptotic effects of lipid oxidation products: HNE at the crossroads of NF-κB pathway and anti-apoptotic Bcl-2

The axis between lipid oxidation products and cell death is explicitly linked. 4-Hydroxynonenal (HNE), as well as other lipid oxidation products was also established to induce apoptosis in various experimental settings. Yet, the decision leading to apoptotic execution not only includes upregulation of pro-apoptotic signals but also involves a downregulation of anti-apoptotic signals. Within the frames of this paradigm, HNE acts significantly different from other lipid oxidation products in the regulation of two widely known anti-apoptotic elements, Nuclear Factor-κB (NF-κB) transcription factors and its target anti-apoptotic B-Cell Lymphoma-2 (Bcl-2) protein. Even so, a review inclusively linking these anti-apoptotic factors and their crosstalk upon HNE exposure is still at demand. In order to elucidate presence of such crosstalk, reports on the link between HNE and NF-κB pathway, on the link between HNE and anti-apoptotic Bcl-2 and on the crossroad of these links during HNE exposure were summarized and discussed. IKK, the upstream kinase of NF-κB, has been shown to regulate HNE mediated phosphorylation and inactivation of Bcl-2 by our group. Based on this observation and other studies reporting on HNE-NF-κB pathway interaction, IKK was proposed to mediate the crosstalk of NF-κB pathway and anti-apoptotic Bcl-2 protein, when HNE is present. These reports further suggested that HNE based inhibition of NF-κB pathway is highly likely. Besides, evidence on the HNE-anti-apoptotic Bcl-2 axis supported the deduction of HNE mediated NF-κB pathway inhibition and IKK mediated Bcl-2 inactivation. In conclusion, through combining all evidences, three possible scenarios intervening the HNE mediated crosstalk between NF-κB pathway and anti-apoptotic Bcl-2 protein, was extrapolated.

Nimodipine activates neuroprotective signaling events and inactivates autophages in the VCID rat hippocampus

BACKGROUND

Autophagy and phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathways are implicated in cognitive decline associated with cerebrovascular lesions. This decline is reflected in the concept of vascular cognitive impairment and dementia (VCID). However, the underlying molecular mechanism and specific details regarding these types of cognitive deficits induced by chronic brain hypoperfusion have not been elucidated.

METHODS

We designed a method to evaluate these mechanisms. Adult male Sprague-Dawley rats were subjected to permanent bilateral occlusion of the common carotid artery (2VO) and randomly divided into three groups: Sham, Vehicle (2VO), and Nimodipine10 (2VO + nimodipine 10 mg/kg). Each group was studied for 4 weeks postoperatively and assessed by the Morris water maze.

RESULTS

The results of this study show that chronic brain hypoperfusion significantly increased the number of autophagic vacuoles with high LC3 II levels, but it decreased p-Akt and p-CREB levels, which were involved in the PI3K/Akt kinase pathway in the hippocampi of rats. Additionally, significant cognitive losses were observed following 2VO. Further analysis showed that, in VCID rats subjected to 2VO, nimodipine administration decreased autophagy, increased the Akt/CREB signaling pathway and significantly reduced brain damage.

CONCLUSIONS

We concluded that neuronal pathology and activation of the autophagic and Akt/CREB signaling pathway caused by chronic brain hypoperfusion could suppress cognitive behavior, which may provide a novel way for the prevention of VCID. The results of this study indicate that nimodipine protected the brain from chronic brain hypoperfusion damage by suppressing autophagy and activating the Akt/CREB signaling pathway.

Autophagy and Akt/CREB signalling play an important role in the neuroprotective effect of nimodipine in a rat model of vascular dementia

The Akt/CREB signalling pathway is involved in neuronal survival and protection. Autophagy is also likely to be involved in survival mechanisms. Nimodipine is an L-type calcium channel antagonist that reduces excessive calcium influx during pathological conditions (contributing to its neuroprotective properties). However, the potential role of nimodipine in autophagic and Akt/CREB signalling is not well understood. In addition, little is known about the relationship between autophagic and Akt/CREB signalling. Here, we designed a way to evaluate these issues. Adult male Sprague-Dawley rats were subjected to permanent bilateral occlusion of the common carotid artery (2VO) and randomly divided into three groups: the Vehicle (2VO), Nimodipine10 (2VO+nimodipine 10mg/kg), and Nimodipine20 (2VO+nimodipine 20mg/kg) groups. A fourth group of animals served as Sham controls. Each group was investigated at 4 and 8 weeks post-operatively and assessed using the Morris water maze. Nimodipine significantly alleviated spatial learning and memory impairments and inhibited the loss of neurons in the CA1 region of the hippocampus. These drug effects were more pronounced at 8 weeks than at 4 weeks. The activities of LC3 II p-Akt and p-CREB were examined using immunohistochemistry and western blotting. Suppressing autophagy induced pyramidal cell death without affecting increased pro-survival signalling induced by nimodipine. Nimodipine protected the brain from chronic cerebral hypoperfusion by activating the Akt/CREB signalling pathway. Autophagy has a neuroprotective effect on rats after 2VO. Autophagy is likely part of an integrated survival signalling network involving the Akt/CREB pathway.

Mechanical evaluation of lipid accumulation in atherosclerotic tissues by photoacoustic viscoelasticity imaging

Photoacoustic viscoelasticity imaging (PAVEI) is a technique that directly provides the morphology of biological tissues with correlative mechanical information. In this Letter, we demonstrate the use of PAVEI to successfully characterize early-stage atherosclerotic plaques. Lipid, as the main material in early plaque lesions, embedded in gelatin was imaged to test the feasibility of PAVEI. Atherosclerosis of rabbits was studied ex vivo, and the rabbit arteries were imaged to show the intrinsic contrast of PAVEI. Our results demonstrate that PAVEI can provide valuable viscoelasticity information for early detection of atherosclerotic plaques, which yields new insights into biomechanical diagnosis of cardiovascular diseases.

Molecular Mechanisms of Vascular Dementia: What Can Be Learned from Animal Models of Chronic Cerebral Hypoperfusion?

Vascular dementia (VD) is defined as a progressive neurodegenerative disease of cognitive decline, attributable to cerebrovascular factors. Numerous studies have demonstrated that chronic cerebral hypoperfusion (CCH) is associated with the initiation and progression of VD and Alzheimer's disease (AD). Suitable animal models were established to replicate such pathological condition in experimental research, which contributes largely to comprehending causal relationships between CCH and cognitive impairment. The most widely used experimental model of VD and CCH is permanent bilateral common carotid artery occlusion in rats. In CCH models, changes of learning and memory, cerebral blood flow (CBF), energy metabolism, and neuropathology initiated by ischemia were revealed. However, in order to achieve potential therapeutic targets, particular mechanisms in cognitive and neuropathological changes from CCH to dementia should be investigated. Recent studies have shown that hypoperfusion resulted in a chain of disruption of homeostatic interactions, including oxidative stress, neuroinflammation, neurotransmitter system dysfunction, mitochondrial dysfunction, disturbance of lipid metabolism, and alterations of growth factors. Evidence from experimental studies that elucidate the damaging effects of such imbalances suggests their critical roles in the pathogenesis of VD. The present review provides a summary of the achievements in mechanisms made with the CCH models, permits an understanding of the causative role played by CCH in VD, and highlights preventative and therapeutic prospects.

Flupirtine attenuates chronic restraint stress-induced cognitive deficits and hippocampal apoptosis in male mice

Chronic restraint stress (CRS) causes hippocampal neurodegeneration and hippocampus-dependent cognitive deficits. Flupirtine represents neuroprotective effects and we have previously shown that flupirtine can protect against memory impairment induced by acute stress. The present study aimed to investigate whether flupirtine could alleviate spatial learning and memory impairment and hippocampal apoptosis induced by CRS. CRS mice were restrained in well-ventilated Plexiglass tubes for 6h daily beginning from 10:00 to 16:00 for 21 consecutive days. Mice were injected with flupirtine (10mg/kg and 25mg/kg) or vehicle (10% DMSO) 30min before restraint stress for 21 days. After stressor cessation, the spatial learning and memory, dendritic spine density, injured neurons and the levels of Bcl-2, Bax, p-Akt, p-GSK-3β, p-Erk1/2 and synaptophysin of hippocampal tissues were examined. Our results showed that flupirtine significantly prevented spatial learning and memory impairment induced by CRS in the Morris water maze. In addition, flupirtine (10mg/kg and 25mg/kg) treatment alleviated neuronal apoptosis and the reduction of dendritic spine density and synaptophysin expression in the hippocampal CA1 region of CRS mice. Furthermore, flupirtine (10mg/kg and 25mg/kg) treatment significantly decreased the expression of Bax and increased the p-Akt and p-GSK-3β, and flupirtine (25mg/kg) treatment up-regulated the p-Erk1/2 in the hippocampus of CRS mice. These results suggested that flupirtine exerted protective effects on the CRS-induced cognitive impairment and hippocampal neuronal apoptosis, which is possibly associated with the activation of Akt/GSK-3β and Erk1/2 signaling pathways.

Salidroside prevents cognitive impairment induced by chronic cerebral hypoperfusion in rats

OBJECTIVE

To investigate the effects of salidroside on cognitive dysfunction induced by chronic cerebral hypoperfusion in rats.

METHODS

Male Sprague-Dawley rats (n = 36) were divided into three groups (n = 12 per group): sham operation; bilateral permanent occlusion of the common carotid arteries (2-VO); 2-VO + salidroside. Rats received 20 mg/kg per day salidroside or vehicle intraperitoneal injection beginning the day before surgery and continuing until 34 days postoperatively. Cognitive function was evaluated by Morris water maze test and hippocampal long-term potentiation (LTP) measurement. Hippocampal neuronal apoptosis was evaluated via immunofluorescence.

RESULTS

Chronic cerebral hypoperfusion caused marked cognitive deficit and LTP inhibition. These effects were largely ameliorated by salidroside administration. Salidroside prevented caspase-3 activation, increased the ratio of Bax/Bcl-2, and reversed hippocampal neuronal loss induced by chronic cerebral hypoperfusion.

CONCLUSIONS

Salidroside prevents cognitive deficits caused by chronic cerebral hypoperfusion in rats, and alleviates apoptosis in the hippocampal CA1 area.