Role of redox signaling in neuroinflammation and neurodegenerative diseases

Alcohol impairs hippocampal function: From NMDA receptor synaptic transmission to mitochondrial function

Many studies have reported that alcohol produces harmful effects on several brain structures, including the hippocampus, in both rodents and humans. The hippocampus is one of the most studied areas of the brain due to its function in learning and memory, and a lot of evidence suggests that hippocampal failure is responsible for the cognitive loss present in individuals with recurrent alcohol consumption. Mitochondria are organelles that generate the energy needed for the brain to maintain neuronal communication, and their functional failure is considered a mediator of the synaptic dysfunction induced by alcohol. In this review, we discuss the mechanisms of how alcohol exposure affects neuronal communication through the impairment of glutamate receptor (NMDAR) activity, neuroinflammatory events and oxidative damage observed after alcohol exposure, all processes under the umbrella of mitochondrial function. Finally, we discuss the direct role of mitochondrial dysfunction mediating cognitive and memory decline produced by alcohol exposure and their consequences associated with neurodegeneration.

Small-Molecule Lysophosphatidic Acid Receptor 5 (LPAR5) Antagonists: Versatile Pharmacological Tools to Regulate Inflammatory Signaling in BV-2 Microglia Cells

Lysophosphatidic acid (LPA) species in the extracellular environment induce downstream signaling via six different G protein-coupled receptors (LPAR1–6). These signaling cascades are essential for normal brain development and function of the nervous system. However, in response to acute or chronic central nervous system (CNS) damage, LPA levels increase and aberrant signaling events can counteract brain function. Under neuro-inflammatory conditions signaling along the LPA/LPAR5 axis induces a potentially neurotoxic microglia phenotype indicating the need for new pharmacological intervention strategies. Therefore, we compared the effects of two novel small-molecule LPAR5 antagonists on LPA-induced polarization parameters of the BV-2 microglia cell line. AS2717638 is a selective piperidine-based LPAR5 antagonist (IC₅₀ 0.038 μM) while compound 3 is a diphenylpyrazole derivative with an IC₅₀ concentration of 0.7 μM in BV-2 cells. Both antagonists compromised cell viability, however, at concentrations above their IC₅₀ concentrations. Both inhibitors blunted LPA-induced phosphorylation of STAT1 and STAT3, p65, and c-Jun and consequently reduced the secretion of pro-inflammatory cyto-/chemokines (IL-6, TNFα, IL-1β, CXCL10, CXCL2, and CCL5) at non-toxic concentrations. Both compounds modulated the expression of intracellular (COX-2 and Arg1) and plasma membrane-located (CD40, CD86, and CD206) polarization markers yet only AS2717638 attenuated the neurotoxic potential of LPA-activated BV-2 cell-conditioned medium towards CATH.a neurons. Our findings from the present in vitro study suggest that the two LPAR5 antagonists represent valuable pharmacological tools to interfere with LPA-induced pro-inflammatory signaling cascades in microglia.

Dietary Supplementation of the Antioxidant Curcumin Halts Systemic LPS-Induced Neuroinflammation-Associated Neurodegeneration and Memory/Synaptic Impairment via the JNK/NF-κB/Akt Signaling Pathway in Adult Rats

Curcumin is a natural polyphenolic compound widely known to have antioxidant, anti-inflammatory, and antiapoptotic properties. In the present study, we explored the neuroprotective effect of curcumin against lipopolysaccharide- (LPS-) induced reactive oxygen species- (ROS-) mediated neuroinflammation, neurodegeneration, and memory deficits in the adult rat hippocampus via regulation of the JNK/NF-κB/Akt signaling pathway. Adult rats were treated intraperitoneally with LPS at a dose of 250 μg/kg for 7 days and curcumin at a dose of 300 mg/kg for 14 days. After 14 days, the rats were sacrificed, and western blotting and ROS and lipid peroxidation assays were performed. For immunohistochemistry and confocal microscopy, the rats were perfused transcardially with 4% paraformaldehyde. In order to verify the JNK-dependent neuroprotective effect of curcumin and to confirm the in vivo results, HT-22 neuronal and BV2 microglial cells were exposed to LPS at a dose of 1 μg/ml, curcumin 100 μg/ml, and SP600125 (a specific JNK inhibitor) 20 μM. Our immunohistochemical, immunofluorescence, and biochemical results revealed that curcumin inhibited LPS-induced oxidative stress by reducing malondialdehyde and 2,7-dichlorofluorescein levels and ameliorating neuroinflammation and neuronal cell death via regulation of the JNK/NF-κB/Akt signaling pathway both in vivo (adult rat hippocampus) and in vitro (HT-22/BV2 cell lines). Moreover, curcumin markedly improved LPS-induced memory impairment in the Morris water maze and Y-maze tasks. Taken together, our results suggest that curcumin may be a potential preventive and therapeutic candidate for LPS-induced ROS-mediated neurotoxicity and memory deficits in an adult rat model.

LPS-Induced Systemic Neonatal Inflammation: Blockage of P2X7R by BBG Decreases Mortality on Rat Pups and Oxidative Stress in Hippocampus of Adult Rats

Neonatal lipopolysaccharide (LPS) exposure-induced brain inflammation has been associated to neuronal injury and facilitates the development of models of neurological disorders in adult rats. The P2X7 receptor (P2X7R) plays a fundamental role in the onset and maintenance of the inflammatory cascade. Brilliant blue G (BBG), a P2X7R antagonist, has been shown to effectively promote neuroinflammatory protection. Here, we have investigated the long-term effects of the neonatal systemic inflammation on hippocampal oxidative stress, anxiety behavior and pain sensitivity in adulthood. We hypothesized that P2X7R blockade is able to modulate the effects of inflammation on these variables. Male and female rat pups received LPS and/or BBG solution intraperitoneally on the 1st, 3rd, 5th and 7th postnatal days. The survival rate and body weight were evaluated during the experimental procedures. The animals were submitted to behavioral tests for anxiety (elevated plus maze, EPM) and nociception (hot-plate and tail-flick) and the oxidative stress was measured by superoxide production in the dentate gyrus of the hippocampus using dihydroethidium (DHE) probe. BBG increased the survival rate in LPS-treated rats. No significant differences were found regarding anxiety behavior and pain sensitivity between the experimental groups. Systemic neonatal inflammation leads to a higher production of superoxide anion in the dentate gyrus of the hippocampus in adulthood and BBG inhibited that effect. Our data suggest that blocking the activation of the P2X7R during neonatal systemic inflammation may have a potential neuroprotective effect in adulthood.

Greater Circulating Copper Concentrations and Copper/Zinc Ratios are Associated with Lower Psychological Distress, But Not Cognitive Performance, in a Sample of Australian Older Adults

Dyshomeostasis of copper and zinc is linked to neurodegeneration. This study investigated the relationship between circulating copper and zinc and copper/zinc ratios and cognitive function, symptoms of depression and anxiety, and neurotrophic factors in older Australian adults. In this cross-sectional study (n = 139), plasma copper, serum zinc, and neurotrophic factors (brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor, and insulin-like growth factor-1) were assessed. Cognition was assessed using the Cogstate battery and the Behavior Rating Inventory (BRI) of Executive Function (Adult version). Symptoms of anxiety and depression were assessed with the Hospital Anxiety and Depression Scale. Copper (β = −0.024; 95% CI = −0.044, −0.004; p = 0.019) and copper/zinc ratio (β = −1.99; 95% CI = −3.41, −0.57; p = 0.006) were associated with lower depressive symptoms, but not cognition. Plasma copper had a modest positive association with BDNF (β = −0.004; 95% CI = 0.000, 0.007; p = 0.021). Zinc was not associated with any of the outcomes. In conclusion, greater circulating copper concentrations and higher copper/zinc ratios were associated with lower depressive symptoms (but not cognition), with copper also positively associated with BDNF concentration, in a sample of community-dwelling older adults.

Sigma-1 receptor activation ameliorates LPS-induced NO production and ROS formation through the Nrf2/HO-1 signaling pathway in cultured astrocytes

Accumulating evidence has shown that astrocytes play a critical role in neuroinflammation and protection against oxidative stress. In this study, we investigated the effects of sigma-1 receptor (Sig-1R) activation on lipopolysaccharide (LPS)-induced inflammatory reactions and oxidative/nitrosative stress in cultured astrocytes. We found that SA4503, a selective Sig-1R agonist, attenuated LPS-induced inflammatory reactions and oxidative/nitrosative stress by downregulating the expression of iNOS and tumor necrosis factor α (TNF-α) and upregulating glutathione (GSH) in cultured astrocytes. To investigate the mechanism by which SA4503 caused these effects, we then examined the expression of nuclear factor erythroid-derived 2-like 2 (Nrf2) and heme oxygenase-1 (HO-1) through western blotting. The results revealed that SA4503 treatment increased Nrf2 and HO-1 expression significantly. These results suggested that the antioxidative/nitrosative stress and anti-inflammatory effects of Sig-1R activation in astrocytes were partially mediated by Nrf2 and HO-1 activation.

Synthesis of Novel Baicalein Amino Acid Derivatives and Biological Evaluation as Neuroprotective Agents

Baicalein, a famously effective component of the traditional Chinese medicine Rhizoma Huang Qin (Scutellaria altissima L.), has been proved to have potent neuroprotection and anti-platelet aggregation effects with few side effects. Meanwhile, recent studies have revealed that the introduction of amino acid to baicalein could improve its neuroprotective activity. In the present study, a series of novel baicalein amino acid derivatives were designed, synthesized, and screened for their neuroprotective effect against tert-butyl, hydroperoxide-induced, SH-SY5Y neurotoxicity cells and toxicity on the normal H9C2 cell line by standard methylthiazol tetrazolium (MTT) assay. In addition, all of the newly synthesized compounds were characterized by ¹H-NMR, ¹³C-NMR, and high resolution mass spectrometry (HR-MS). The results showed that most of the compounds provided more potent neuroprotection than baicalein, and were equivalent to the positive drug edaravin. They showed no obvious cytotoxicity on normal H9C2 cells. Notably, the most active compound 8 displayed the highest protective effect (50% effective concentration (EC₅₀) = 4.31 μM) against tert-butyl, hydroperoxide-induced, SH-SY5Y neurotoxicity cells, which was much better than the baicalein (EC₅₀ = 24.77 μM) and edaravin (EC₅₀ = 5.62 μM). Further research on the chick chorioallantoic membrane (CAM) model indicated that compound 8 could significantly increase angiogenesis, which might promote neurovascular proliferation. The detection of apoptosis analysis showed that compound 8 could dramatically alleviate morphological manifestations of cell damage. Moreover, the benzyloxycarbonyl (cbz)-protected baicalein amino acid derivatives showed better neuroprotective activity than the t-Butyloxy carbonyl (boc)-protected derivatives.

N6-(2-hydroxyethyl)-adenosine from Cordyceps cicadae attenuates hydrogen peroxide induced oxidative toxicity in PC12 cells

N⁶-(2-hydroxyethyl)-adenosine (HEA), is one of the active molecule found in Cordyceps cicadae. The protective effect of HEA against H₂O₂ induced oxidative damage in PC12 cells and the mechanism of action was investigated. The cells were exposed to varying concentrations of HEA (5-40 μM) for a period of 24 h and further incubated with 100 μM of H₂O₂ for an another 12 h. Cell viability, LDH release, MMP collapse, Ca²⁺ overload, antioxidant parameters (reactive oxygen species generation (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), inflammatory mediators (interleukins 6 and 1β (IL-6 and IL-1β), tumor necrosis factor alpha (TNF-α) and NF-kB were evaluated. The results obtained showed that cells exposed to H₂O₂ toxicity showed reduced cell viability, increased LDH, ROS and Ca²⁺ overload. However, prior treatment of PC12 cells with HEA increased cell viability, reduced LDH release, MMP collapse, Ca²⁺ overload and ROS generation induced by H₂O₂ toxicity. Furthermore, HEA also increased the activities of antioxidant enzymes and inhibited lipid peroxidation as well as reduced IL-6, IL-1β, TNF-α and NF-kB. Thus, our results provided insight into the attenuative effect of HEA against H₂O₂ induced cell death through its antioxidant action by reducing ROS generation, oxidative stress and protecting mitochondrial function.

Brain-Immune Alterations and Mitochondrial Dysfunctions in a Mouse Model of Paediatric Autoimmune Disorder Associated with Streptococcus: Exacerbation by Chronic Psychosocial Stress

Adverse psychosocial experiences have been shown to modulate individual responses to immune challenges and affect mitochondrial functions. The aim of this study was to investigate inflammation and immune responses as well as mitochondrial bioenergetics in an experimental model of Paediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus (PANDAS). Starting in adolescence (postnatal day 28), male SJL/J mice were exposed to five injections (interspaced by two weeks) with Group-A beta-haemolytic streptococcus (GAS) homogenate. Mice were exposed to chronic psychosocial stress, in the form of protracted visual exposure to an aggressive conspecific, for four weeks. Our results indicate that psychosocial stress exacerbated individual response to GAS administrations whereby mice exposed to both treatments exhibited altered cytokine and immune-related enzyme expression in the hippocampus and hypothalamus. Additionally, they showed impaired mitochondrial respiratory chain complexes IV and V, and reduced adenosine triphosphate (ATP) production by mitochondria and ATP content. These brain abnormalities, observed in GAS-Stress mice, were associated with blunted titers of plasma corticosterone. Present data support the hypothesis that challenging environmental conditions, in terms of chronic psychosocial stress, may exacerbate the long-term consequences of exposure to GAS processes through the promotion of central immunomodulatory and oxidative stress.

The Neuromodulatory Effects of ω-3 Fatty Acids and Nano-Curcumin on the COX-2/ iNOS Network in Migraines: A Clinical Trial Study from Gene Expression to Clinical Symptoms

Background:

Migraine is a common neuroinflammatory disorder characterized by recurrent attacks of pain. Human and experimental models of migraine studies have demonstrated the role played by COX-2/ iNOS in migraine’s neuroinflammatory pathogenesis. COX-2 and iNOS are closely linked and both contribute to inflammation and neurogenic pain in the central nervous system. Omega- 3 fatty acids and curcumin, an active polyphenol of turmeric, have anti-inflammatory and neuroprotective effects through several mechanisms, including the suppression of COX-2 and iNOS gene expression, as well as their serum levels. The aim of the present study is to evaluate the nutrigenomic effects of ω-3 fatty acids, nano-curcumin, and a combination of the two, on neuroinflammation and clinical symptoms in migraine patients.

Methods:

This study reports the results of a clinical trial over a 2-month period, involving 74 episodic migraine patients who received ω-3 fatty acids, nano-curcumin, a combination of them, or a placebo. At the start and end of the study, the expression of COX-2/iNOS (in peripheral mononuclear blood cells isolated from patients) and COX-2/iNOS serum levels were measured, using real-time PCR and ELISA respectively. The frequency, severity and duration of pain attacks were also recorded.

Results:

The results of the present trial showed that ω-3 fatty acids and nano-curcumin can reinforce each other’s effects in the downregulation of COX-2/iNOS mRNA, as well as reduce their serum levels. In addition, the combination of ω-3 and nano-curcumin significantly reduced the frequency, severity and duration of headaches (P<0.05).

Conclusion:

These findings indicate that combination therapy of ω-3 fatty acids and nano-curcumin can be considered as a promising new approach in migraine prevention.

Neuroinflammatory Reactions in the Brain of 1,2-DCE-Intoxicated Mice during Brain Edema

We previously reported that expression of matrix metalloproteinase-9 (MMP-9) mRNA and protein was upregulated during 1,2-dichloroethane (1,2-DCE) induced brain edema in mice. We also found that the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway resulted in MMP-9 overexpression and nuclear factor-κB (NF-κB) activation in mice treated with 1,2-DCE. In this study, we further hypothesized that inflammatory reactions mediated by the p38 MAPK/ NF-κB signaling pathway might be involved in MMP-9 overexpression, blood–brain barrier (BBB) disruption and edema formation in the brain of 1,2-DCE-intoxicated mice. Our results revealed that subacute poisoning by 1,2-DCE upregulates protein levels of glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba-1), interleukin-1β (IL-1β), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and p-p65 in mouse brains. Pretreatment with an inhibitor against p38 MAPK attenuates these changes. Moreover, pretreatment with an inhibitor against NF-κB attenuates alterations in brain water content, pathological indications notable in brain edema, as well as mRNA and protein expression on levels of MMP-9, VCAM-1, ICAM-1, iNOS, and IL-1β, tight junction proteins (TJs), GFAP and Iba-1 in the brain of 1,2-DCE-intoxicated mice. Furthermore, pretreatment with an inhibitor against MMP-9 obstructs the decrease of TJs in the brain of 1,2-DCE-intoxicated mice. Lastly, pretreatment with an antagonist against the IL-1β receptor also attenuates changes in protein levels of p-p38 MAPK, p-p65, p-IκB, VCAM -1, ICAM-1, IL-1β, and Iba-1 in the brain of 1,2-DCE-intoxicated-mice. Taken together, findings from the current study indicate that the p38 MAPK/ NF-κB signaling pathway might be involved in the activation of glial cells, and the overproduction of proinflammatory factors, which might induce inflammatory reactions in the brain of 1,2-DCE-intoxicated mice that leads to brain edema.

Carnosine Decreases PMA-Induced Oxidative Stress and Inflammation in Murine Macrophages

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine. This naturally occurring molecule is present at high concentrations in several mammalian excitable tissues such as muscles and brain, while it can be found at low concentrations in a few invertebrates. Carnosine has been shown to be involved in different cellular defense mechanisms including the inhibition of protein cross-linking, reactive oxygen and nitrogen species detoxification as well as the counteraction of inflammation. As a part of the immune response, macrophages are the primary cell type that is activated. These cells play a crucial role in many diseases associated with oxidative stress and inflammation, including atherosclerosis, diabetes, and neurodegenerative diseases. In the present study, carnosine was first tested for its ability to counteract oxidative stress. In our experimental model, represented by RAW 264.7 macrophages challenged with phorbol 12-myristate 13-acetate (PMA) and superoxide dismutase (SOD) inhibitors, carnosine was able to decrease the intracellular concentration of superoxide anions (O2-•) as well as the expression of Nox1 and Nox2 enzyme genes. This carnosine antioxidant activity was accompanied by the attenuation of the PMA-induced Akt phosphorylation, the down-regulation of TNF-α and IL-6 mRNAs, and the up-regulation of the expression of the anti-inflammatory mediators IL-4, IL-10, and TGF-β1. Additionally, when carnosine was used at the highest dose (20 mM), there was a generalized amelioration of the macrophage energy state, evaluated through the increase both in the total nucleoside triphosphate concentrations and the sum of the pool of intracellular nicotinic coenzymes. Finally, carnosine was able to decrease the oxidized (NADP+)/reduced (NADPH) ratio of nicotinamide adenine dinucleotide phosphate in a concentration dependent manner, indicating a strong inhibitory effect of this molecule towards the main source of reactive oxygen species in macrophages. Our data suggest a multimodal mechanism of action of carnosine underlying its beneficial effects on macrophage cells under oxidative stress and inflammation conditions.

Targeting oxidative stress improves disease outcomes in a rat model of acquired epilepsy

Epilepsy therapy is based on antiseizure drugs that treat the symptom, seizures, rather than the disease and are ineffective in up to 30% of patients. There are no treatments for modifying the disease-preventing seizure onset, reducing severity or improving prognosis. Among the potential molecular targets for attaining these unmet therapeutic needs, we focused on oxidative stress since it is a pathophysiological process commonly occurring in experimental epileptogenesis and observed in human epilepsy. Using a rat model of acquired epilepsy induced by electrical status epilepticus, we show that oxidative stress occurs in both neurons and astrocytes during epileptogenesis, as assessed by measuring biochemical and histological markers. This evidence was validated in the hippocampus of humans who died following status epilepticus. Oxidative stress was reduced in animals undergoing epileptogenesis by a transient treatment with N-acetylcysteine and sulforaphane, which act to increase glutathione levels through complementary mechanisms. These antioxidant drugs are already used in humans for other therapeutic indications. This drug combination transiently administered for 2 weeks during epileptogenesis inhibited oxidative stress more efficiently than either drug alone. The drug combination significantly delayed the onset of epilepsy, blocked disease progression between 2 and 5 months post-status epilepticus and drastically reduced the frequency of spontaneous seizures measured at 5 months without modifying the average seizure duration or the incidence of epilepsy in animals. Treatment also decreased hippocampal neuron loss and rescued cognitive deficits. Oxidative stress during epileptogenesis was associated with de novo brain and blood generation of high mobility group box 1 (HMGB1), a neuroinflammatory molecule implicated in seizure mechanisms. Drug-induced reduction of oxidative stress prevented HMGB1 generation, thus highlighting a potential novel mechanism contributing to therapeutic effects. Our data show that targeting oxidative stress with clinically used drugs for a limited time window starting early after injury significantly improves long-term disease outcomes. This intervention may be considered for patients exposed to potential epileptogenic insults.

Astrocyte alterations in neurodegenerative pathologies and their modeling in human induced pluripotent stem cell platforms

Astrocytes are the most abundant cell type in the brain. They were long considered only as passive support for neuronal cells. However, recent data have revealed many active roles for these cells both in maintenance of the normal physiological homeostasis in the brain as well as in neurodegeneration and disease. Moreover, human astrocytes have been found to be much more complex than their rodent counterparts, and to date, astrocytes are known to actively participate in a multitude of processes such as neurotransmitter uptake and recycling, gliotransmitter release, neuroenergetics, inflammation, modulation of synaptic activity, ionic balance, maintenance of the blood-brain barrier, and many other crucial functions of the brain. This review focuses on the role of astrocytes in human neurodegenerative disease and the potential of the novel stem cell-based platforms in modeling astrocytic functions in health and in disease.

Protein pathway analysis to study development-dependent effects of acute and repeated trimethyltin (TMT) treatments in 3D rat brain cell cultures

Trimethyltin is an organometallic compound, described to be neurotoxic and to trigger neuroinflammation and oxidative stress. Previous studies associated TMT with the perturbation of mitochondrial function, or neurotransmission. However, the mechanisms of toxicity may differ depending on the duration of exposure and on the stage of maturation of brain cells. This study aim at elucidating whether the toxicity pathways triggered by a known neurotoxicant (TMT) differs depending on cell maturation stage or duration of exposure. To this end omics profiling of immature and differentiated 3D rat brain cell cultures exposed for 24 h or 10 days (10-d) to 0.5 and 1 μM of TMT was performed to better understand the underlying mechanisms of TMT associated toxicity. Proteomics identified 55 and 17 proteins affected by acute TMT treatment in immature and differentiated cultures respectively, while 10-day treatment altered 96 proteins in immature cultures versus 353 in differentiated. The results suggest different sensitivity to TMT depending on treatment duration and cell maturation. In accordance with known TMT mechanisms oxidative stress and neuroinflammation was observed after 10-d treatment at both maturation stages, whereas the neuroinflammatory process was more prominent in differentiated cultures than in the immature, no development-dependent difference could be detected for oxidative stress or synaptic neurodegeneration. Pathway analysis revealed that both vesicular trafficking and the synaptic machinery were strongly affected by 10-d TMT treatment in both maturation stages, as was GABAergic and glutamatergic neurotransmission. This study shows that omics approaches combined with pathway analysis constitutes an improved tool-set in elucidating toxicity mechanisms.

Caffeine Modulates Cadmium-Induced Oxidative Stress, Neuroinflammation, and Cognitive Impairments by Regulating Nrf-2/HO-1 In Vivo and In Vitro

Cadmium (Cd), a nonbiodegradable heavy metal and one of the most neurotoxic environmental and industrial pollutants, promotes disturbances in major organs and tissues following both acute and chronic exposure. In this study, we assessed the neuroprotective potential of caffeine (30 mg/kg) against Cd (5 mg/kg)-induced oxidative stress-mediated neuroinflammation, neuronal apoptosis, and cognitive deficits in male C57BL/6N mice in vivo and in HT-22 and BV-2 cell lines in vitro. Interestingly, our findings indicate that caffeine markedly reduced reactive oxygen species (ROS) and lipid peroxidation (LPO) levels and enhanced the expression of nuclear factor-2 erythroid-2 (Nrf-2) and hemeoxygenase-1 (HO-1), which act as endogenous antioxidant regulators. Also, 8-dihydro-8-oxoguanine (8-OXO-G) expression was considerably reduced in the caffeine-treated group as compared to the Cd-treated group. Similarly, caffeine ameliorated Cd-mediated glial activation by reducing the expression of glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba-1), and other inflammatory mediators in the cortical and hippocampal regions of the mouse brain. Moreover, caffeine markedly attenuated Cd-induced neuronal loss, synaptic dysfunction, and learning and cognitive deficits. Of note, nuclear factor-2 erythroid-2 (Nrf-2) gene silencing and nuclear factor-κB (NF-κB) inhibition studies revealed that caffeine exerted neuroprotection via regulation of Nrf-2- and NF-κB-dependent mechanisms in the HT-22 and BV-2 cell lines, respectively. On the whole, these findings reveal that caffeine rescues Cd-induced oxidative stress-mediated neuroinflammation, neurodegeneration, and memory impairment. The present study suggests that caffeine might be a potential antioxidant and neuroprotective agent against Cd-induced neurodegeneration.

Indole-3 acetic acid increased risk of impaired cognitive function in patients receiving hemodialysis

Patients receiving hemodialysis (HD) have a higher risk of cognitive impairment and dementia than the general population. The accumulation of uremic toxins in the brain causes uremic encephalopathy, however, limited data exists to elucidate the effect of protein-bound uremic toxins on cognitive function. Here we investigate the effect of indole-3 acetic acid (IAA) and hippuric acid (HA), two different protein-bound uremic toxins from amino acid derivatives, on cognitive function by Silico and in a clinical study. Prevalent HD patients were enrolled in two independent hospitals. Serum IAA and HA were measured using mass spectrometry. Cognitive performance was measured using Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Cognitive Abilities Screening Instrument (CASI) by trained psychologists. Using silico data to predict the effect of blood-brain barrier penetration was performed. The silico data demonstrated that IAA and HA had positive blood-brain barrier penetration ability. Amongst the 230 HD patients, serum IAA was associated with poor MMSE score (β= -0.90, 95% CI -1.61 to -0.19) and poor CASI score (β= -3.29, 95% CI -5.69 to -0.88) in stepwise multiple linear regression analysis. In logistic regression model, Serum IAA was also associated with cognitive impairment based on MMSE definition (OR, 1.96, 95% CI 1.10, 3.5) and CASI definition (OR, 2.09, 95% CI 1.21, 3.61). There was no correlation between Serum HA levels and cognitive function status. In conclusion, IAA, not HA, was associated with cognitive impairment in HD patients. Further large scale and prospective studies are needed to confirm our findings.

Effect of the Lipid Peroxidation Product 4-Hydroxynonenal on Neuroinflammation in Microglial Cells: Protective Role of Quercetin and Monochloropivaloylquercetin

Objectives

The lipid peroxidation-derived aldehyde 4-hydroxynonenal (HNE) has been implicated in a number of oxidative stress-induced inflammatory pathologies such as neurodegenerative diseases and aging. In this regard, we investigated the effects of HNE on neuroinflammatory responses by measuring cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) induction with cytokine production. In addition, we measured nuclear factor erythroid 2-related factor 2 (Nrf-2)/Kelch-like ECH-associated protein 1 (Keap1) signaling proteins, and antioxidant enzymes heme oxygenase-1 (HO-1) and nicotinamide adenine dinucleotide phosphate dehydrogenase, quinone 1 (NQO1), and compared the results with quercetin and monochloropivaloylquercetin (MPQ) pretreated microglial cells.

Materials and Methods

Cytotoxicity was determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and production of cytokines was determined by cytokine array. Furthermore, intracellular Nfr2/Keap1 signaling proteins, HO-1, NQO1, and COX-2 expression were analyzed by western blot in 2.5 μM HNE treated BV-2 cells.

Results

Inducible nitric oxide synthase (iNOS) and COX-2 mRNA levels were measured with reverse transcription-quantitative polymerase chain reaction. HNE induced both COX-2 mRNA and protein levels, iNOS mRNA expression, and cytokine production. In addition, HNE markedly increased Keap1 levels and decreased cytoplasmic Nrf-2 expression with antioxidant enzyme HO-1 levels. Quercetin and monochloropivaloylquercetin treatment alleviated neuroinflammatory responses in microglial cells, by decreasing COX-2 mRNA expression. Monochloropivaloylquercetin decreased cytoplasmic Keap1 levels and increased nuclear translocation of Nrf-2 resulted in induction of HO-1 and NQO1 expression.

Conclusion

These results suggest that HNE could be a link between oxidative stress and inflammation in BV-2 microglia cells. In particular, monochloropivaloylquercetin alleviated inflammation, probably by decreasing the expression of proinflammatory genes and strengthening the antioxidant defense system.

When safeguarding goes wrong: Impact of oxidative stress on protein homeostasis in health and neurodegenerative disorders

Cellular redox status is an established player in many different cellular functions. The buildup of oxidants within the cell is tightly regulated to maintain a balance between the positive and negative outcomes of cellular oxidants. Proteins are highly sensitive to oxidation, since modification can cause widespread unfolding and the formation of toxic aggregates. In response, cells have developed highly regulated systems that contribute to the maintenance of both the global redox status and protein homeostasis at large. Changes to these systems have been found to correlate with aging and age-related disorders, such as neurodegenerative pathologies. This raises intriguing questions as to the source of the imbalance in the redox and protein homeostasis systems, their interconnectivity, and their role in disease progression. Here we focus on the crosstalk between the redox and protein homeostasis systems in neurodegenerative diseases, specifically in Alzheimer's, Parkinson's, and ALS. We elaborate on some of the main players of the stress response systems, including the master regulators of oxidative stress and the heat shock response, Nrf2 and Hsf1, which are essential features of protein folding, and mediators of protein turnover. We illustrate the elegant mechanisms used by these components to provide an immediate response, including protein plasticity controlled by redox-sensing cysteines and the recruitment of naive proteins to the redox homeostasis array that act as chaperons in an ATP-independent manner.

Pharmacological targeting of brain inflammation in epilepsy: Therapeutic perspectives from experimental and clinical studies

Increasing evidence supports a pathogenic role of unabated neuroinflammation in various central nervous system (CNS) diseases, including epilepsy. Neuroinflammation is not a bystander phenomenon of the diseased brain tissue, but it may contribute to neuronal hyperexcitability underlying seizure generation, cell loss, and neurologic comorbidities. Several molecules, which constitute the inflammatory milieu in the epileptogenic area, activate signaling pathways in neurons and glia resulting in pathologic modifications of cell function, which ultimately lead to alterations in synaptic transmission and plasticity. Herein we report the up-to-date experimental and clinical evidence that supports the neuromodulatory role of inflammatory mediators, their related signaling pathways, and involvement in epilepsy. We discuss how these mechanisms can be harnessed to discover and validate targets for novel therapeutics, which may prevent or control pharmacoresistant epilepsies.

The Role of NADPH Oxidases and Oxidative Stress in Neurodegenerative Disorders

For a number of years, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) was synonymous with NOX2/gp91^phox and was considered to be a peculiarity of professional phagocytic cells. Over the last decade, several more homologs have been identified and based on current research, the NOX family consists of NOX1, NOX2, NOX3, NOX4, NOX5, DUOX1 and DUOX2 enzymes. NOXs are electron transporting membrane proteins that are responsible for reactive oxygen species (ROS) generation-primarily superoxide anion (O₂^●-), although hydrogen peroxide (H₂O₂) can also be generated. Elevated ROS leads to oxidative stress (OS), which has been associated with a myriad of inflammatory and degenerative pathologies. Interestingly, OS is also the commonality in the pathophysiology of neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). NOX enzymes are expressed in neurons, glial cells and cerebrovascular endothelial cells. NOX-mediated OS is identified as one of the main causes of cerebrovascular damage in neurodegenerative diseases. In this review, we will discuss recent developments in our understanding of the mechanisms linking NOX activity, OS and neurodegenerative diseases, with particular focus on the neurovascular component of these conditions. We conclude highlighting current challenges and future opportunities to combat age-related neurodegenerative disorders by targeting NOXs.

Enhancement of neuroprotective activity of Sagunja-tang by fermentation with lactobacillus strains

BACKGROUND

Sagunja-tang (SGT) is widely used in traditional herbal medicine to treat immune system and gastrointestinal disorders and reportedly has protective effects against inflammation, cancer, and osteoporosis. In this study, we fermented SGT with different Latobacillus strains and investigated the change in phytochemical compositions in SGT and enhancement of it neuroprotective effects in SH-SY5Y human neuroblastoma.

METHODS

Marker components, including ginsenoside Rg₁, glycyrrhizin, liquiritin, liquiritigenin, atractylenolide I, atractylenolide II, atractylenolide III, and pachymic acid, in SGT, were qualitatively and quantitatively analyzed using high-performance liquid chromatography-diode array detection and liquid chromatography-mass spectrometry. SGT was fermented with eight different Lactobacillus strains to yield eight fermented SGTs (FSGTs). The conversion efficiencies of SGT marker components were determined in each FSGT. To detect the protective effect of SGT and FSGT, reactive oxygen species (ROS) assay and mitochondrial membrane potentials (MMPs) assay were performed in SH-SY5Y cells.

RESULTS

Compared with the other FSGTs, SGT166, i.e., SGT fermented with L. plantarum 166, had high conversion efficiency, as indicated by increased amounts of glycyrrhizin, liquiritigenin, and atractylenolides I-III. In SH-SY5Y cells, protection against cell death induced by H₂O₂ and etoposide was high using SGT166 and very low using SGT. Furthermore, ROS production and mitochondrial membrane potential disruption in SH-SY5Y cells were markedly suppressed by SGT166 treatment, which demonstrated that inhibition of ROS generation may be one of the neuroprotective mechanisms of SGT166.

CONCLUSIONS

This study demonstrated that fermentation of SGT with L. plantarum 166 enhanced suppression of oxidative stress and MMP loss. This enhanced neuroprotective effect was thought to be caused by the conversion of SGT phytochemicals by fermentation. SGT166 shows potential for treating neurological damage-related diseases.

Palm Fruit Bioactives modulate human astrocyte activity in vitro altering the cytokine secretome reducing levels of TNFα, RANTES and IP-10

Neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, are becoming more prevalent and an increasing burden on society. Neurodegenerative diseases often arise in the milieu of neuro-inflammation of the brain. Reactive astrocytes are key regulators in the development of neuro-inflammation. This study describes the effects of Palm Fruit Bioactives (PFB) on the behavior of human astrocytes which have been activated by IL-1β. When activated, the astrocytes proliferate, release numerous cytokines/chemokines including TNFα, RANTES (CCL5), IP-10 (CXCL10), generate reactive oxygen species (ROS), and express specific cell surface biomarkers such as the Intercellular Adhesion Molecule (ICAM), Vascular Cellular Adhesion Molecule (VCAM) and the Neuronal Cellular Adhesion Molecule (NCAM). Interleukin 1-beta (IL-1β) causes activation of human astrocytes with marked upregulation of pro-inflammatory genes. We show significant inhibition of these pro-inflammatory processes when IL-1β-activated astrocytes are exposed to PFB. PFB causes a dose-dependent and time-dependent reduction in specific cytokines: TNFα, RANTES, and IP-10. We also show that PFB significantly reduces ROS production by IL-1β-activated astrocytes. Furthermore, PFB also reduces the expression of ICAM and VCAM, both in activated and naïve human astrocytes in vitro. Since reactive astrocytes play an essential role in the neuroinflammatory state preceding neurodegenerative diseases, this study suggests that PFB may have a potential role in their prevention and/or treatment.

Developmental Neurotoxicity of Arsenic: Involvement of Oxidative Stress and Mitochondrial Functions

Over the last decade, there has been an increased concern about the health risks from exposure to arsenic at low doses, because of their neurotoxic effects on the developing brain. The exact mechanism underlying arsenic-induced neurotoxicity during sensitive periods of brain development remains unclear, although enhanced oxidative stresses, leading to mitochondrial dysfunctions might be involved. Here, we highlight the generation of reactive oxygen species (ROS) and oxidative stress which leads to mitochondrial dysfunctions and apoptosis in arsenic-induced developmental neurotoxicity. Here, the administration of sodium arsenite at doses of 2 or 4 mg/kg body weight in female rats from gestational to lactational (GD6-PD21) resulted to increased ROS, led to oxidative stress, and increased the apoptosis in the frontal cortex, hippocampus, and corpus striatum of developing rats on PD22, compared to controls. Enhanced levels of ROS were associated with decreased mitochondrial membrane potential and the activity of mitochondrial complexes, and hampered antioxidant levels. Further, neuronal apoptosis, as measured by changes in the expression of pro-apoptotic (Bax, Caspase-3), anti-apoptotic (Bcl2), and stress marker proteins (p-p38, pJNK) in arsenic-exposed rats, was discussed. The severities of changes were found to more persist in the corpus striatum than in other brain regions of arsenic-exposed rats even after the withdrawal of exposure on PD45 as compared to controls. Therefore, our results indicate that perinatal arsenic exposure leads to abrupt changes in ROS, oxidative stress, and mitochondrial functions and that apoptotic factor in different brain regions of rats might contribute to this arsenic-induced developmental neurotoxicity.

A novel therapeutic potential of cysteinyl leukotrienes and their receptors modulation in the neurological complications associated with Alzheimer's disease

Cysteinyl leukotrienes (cysLTs) are member of eicosanoid inflammatory lipid mediators family produced by oxidation of arachidonic acid by action of the enzyme 5-lipoxygenase (5-LOX). 5-LOX is activated by enzyme 5-Lipoxygenase-activating protein (FLAP), which further lead to production of cysLTs i.e. leukotriene C4 (LTC4), leukotriene D4 (LTD4) and leukotriene E4 (LTE4). CysLTs then produce their potent inflammatory actions by activating CysLT1 and CysLT2 receptors. Inhibitors of cysLTs are indicated in asthma, allergic rhinitis and other inflammatory disorders. Earlier studies have associated cysLTs and their receptors in several neurodegenerative disorders diseases like, multiple sclerosis, Parkinson's disease, Huntington's disease, epilepsy and Alzheimer's disease (AD). These inflammatory lipid mediators have previously shown effects on various aggravating factors of AD. However, not much data has been elucidated to test their role against AD clinically. Herein, through this review, we have provided the current and emerging information on the role of cysLTs and their receptors in various neurological complications responsible for the development of AD. In addition, literature evidences for the effect of cysLT inhibitors on distinct aspects of abnormalities in AD has also been reviewed. Promising advancement in understanding on the role of cysLTs on the various neuromodulatory processes and mechanisms may contribute to the development of newer and safer therapy for the treatment of AD in future.

AST-120 Reduces Neuroinflammation Induced by Indoxyl Sulfate in Glial Cells

Chronic kidney disease (CKD) involves multiple organ dysfunction, and the neurological complications that are often present in CKD patients support the idea of a crosstalk between the kidneys and the brain. Evidence suggests a possible role for products accumulating in these patients as uremic toxins in various CKD complications, including neurodegeneration. Indoxyl sulfate (IS), derived from tryptophan metabolism, is well-known as a uremic nephron-vascular toxin, and recent evidence suggests it also has a role in the immune response and in neurodegeneration. Inflammation has been associated with neurodegenerative diseases, as well as with CKD. In this study, we demonstrated that sera of CKD patients induced a significant inflammation in astrocyte cells which was proportional to IS sera concentrations, and that the IS adsorbent, AST-120, reduced this inflammatory response. These results indicated that, among the uremic toxins accumulating in serum of CKD patients, IS significantly contributed to astrocyte inflammation. Moreover, being also chronic inflammation associated with CKD, here we reported that IS further increased inflammation and oxidative stress in primary central nervous system (CNS) cells, via Nuclear Factor-κB (NF-κB) and Aryl hydrocarbon Receptor (AhR) activation, and induced neuron death. This study is a step towards elucidating IS as a potential pharmacological target in CKD patients.

Donepezil-based multi-functional cholinesterase inhibitors for treatment of Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders in elderly people. Considering the multifactorial nature of AD, the concept of multi-target-directed ligands (MTDLs) has recently emerged as a new strategy for designing therapeutic agents on AD. MTDLs are confirmed to simultaneously affect diverse targets which contribute to etiology of AD. As the most potent approved drug, donepezil affects various events of AD, like inhibiting cholinesterases activities, anti-Aβ aggregation, anti-oxidative stress et al. Modifications of donepezil or hybrids with pharmacophores of donepezil in recent five years are summarized in this article. On the basis of case studies, our concerns and opinions about development of donepezil derivatives, designing of MTDLs, and perspectives for AD treatments are discussed in final part.

Amelioration of oxidative stress in differentiated neuronal cells by rutin regulated by a concentration switch

Increasing studies have implicated superfluous production of reactive oxygen species (ROS) as a significant factor in the progress of neurodegenerative disorders ranging from ischemic stroke to amyotrophic lateral sclerosis. The possible mechanisms relating to oxidative stress and neurodegeneration are yet to be thoroughly understood. Rutin, a flavonoid, has been well documented for its beneficial and pharmacological activities against diverse targets. However, the mechanism involved in the beneficial effects of rutin against neurodegeneration still remains unclear. Our study investigates the concentration switch effects of rutin on differentiated human neuroblastoma cells (IMR32) in vitro to unveil the possible mechanism of its action. IMR32 cells were differentiated using retinoic acid and challenged with different doses of rutin for 24 h duration to study the influence of ROS on differentiated neuronal cells and ROS-mediated apoptosis. The study showed that the high (100 μM) and low (100 nM and 10μM) rutin concentrations significantly avert ROS generation by two different mechanisms, by enhancing apoptosis through the modulation of levels of Bcl2, Caspase-3, survivin and its antioxidant activity via stress-related proteins, JNK and p38 MAPK. Our study suggests that rutin is a multi-targeted therapeutic and preventive agent that may act as an adjuvant complementary therapeutic molecule to treat oxidative stress-mediated neurodegeneration.

Walnut Protein Hydrolysates Play a Protective Role on Neurotoxicity Induced by d-Galactose and Aluminum Chloride in Mice

In recent years, with an increase in the aging population, neurodegenerative diseases have attracted more and more attention. This study aimed to investigate the potential neuroprotective effect of defatted walnut meal protein hydrolysates (DWMPH) on neurotoxicity induced by d-galactose (d-gal) and aluminum chloride (AlCl₃) in mice. The animal models were established by combining treatments with d-gal (200 mg/kg/day, subcutaneously) and AlCl₃ (100 mg/kg in drinking water) for 90 days. During the 90 days, 1 g/kg of DWMPH was administrated orally every day. The results indicated that DWMPH treatment alleviated oxidative stress, reversed cholinergic dysfunction, and suppressed the release of proinflammatory cytokines in the brains of d-gal + AlCl₃-treated mice, and thus improving the learning and memory functions of these mice, which was closely correlated with the strong antioxidant activity of DWMPH. This finding suggests that DWMPH might be a promising dietary supplement in improving neuronal dysfunctions of the brain.

The Sources of Reactive Oxygen Species and Its Possible Role in the Pathogenesis of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by progressive loss of dopaminergic neurons in the substantia nigra. The precise mechanism underlying pathogenesis of PD is not fully understood, but it has been widely accepted that excessive reactive oxygen species (ROS) are the key mediator of PD pathogenesis. The causative factors of PD such as gene mutation, neuroinflammation, and iron accumulation all could induce ROS generation, and the later would mediate the dopaminergic neuron death by causing oxidation protein, lipids, and other macromolecules in the cells. Obviously, it is of mechanistic and therapeutic significance to understand where ROS are derived and how ROS induce dopaminergic neuron damage. In the present review, we try to summarize and discuss the main source of ROS in PD and the key pathways through which ROS mediate DA neuron death.

The role of inflammation and potential use of sex steroids in intracranial aneurysms and subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (aSAH) continues to be a devastating neurological condition with a high risk of associated morbidity and mortality. Inflammation has been shown to increase the risk of complications associated with aSAH such as vasospasm and brain injury in animal models and humans. The goal of this review is to discuss the inflammatory mechanisms of aneurysm formation, rupture and vasospasm and explore the role of sex hormones in the inflammatory response to aSAH.

Methods

A literature review was performed using PubMed using the following search terms: "intracranial aneurysm," "cerebral aneurysm," "dihydroepiandrosterone sulfate" "estrogen," "hormone replacement therapy," "inflammation," "oral contraceptive," "progesterone," "sex steroids," "sex hormones" "subarachnoid hemorrhage," "testosterone." Only studies published in English language were included in the review.

Results

Studies have shown that administration of sex hormones such as progesterone and estrogen at early stages in the inflammatory cascade can lower the risk and magnitude of subsequent complications. The exact mechanism by which these hormones act on the brain, as well as their role in the inflammatory cascade is not fully understood. Moreover, conflicting results have been published on the effect of hormone replacement therapy in humans. This review will scrutinize the variations in these studies to provide a more detailed understanding of sex hormones as potential therapeutic agents for intracranial aneurysms and aSAH.

Conclusion

Inflammation may play a role in the pathogenesis of intracranial aneurysm formation and subarachnoid hemorrhage, and administration of sex hormones as anti-inflammatory agents has been associated with improved functional outcome in experimental models. Further studies are needed to determine the therapeutic role of these hormones in the intracranial aneurysms and aSAH.

The Impact of Uremic Toxins on Cerebrovascular and Cognitive Disorders

Individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia. Stroke is also highly prevalent in this population and is associated with a higher risk of neurological deterioration, in-hospital mortality, and poor functional outcomes. Evidence from in vitro studies and in vivo animal experiments suggests that accumulation of uremic toxins may contribute to the pathogenesis of stroke and amplify vascular damage, leading to cognitive disorders and dementia. This review summarizes current evidence on the mechanisms by which uremic toxins may favour the occurrence of cerebrovascular diseases and neurological complications in CKD.

Berberine Protects Secondary Injury in Mice with Traumatic Brain Injury Through Anti-oxidative and Anti-inflammatory Modulation

Traumatic brain injury (TBI) is one of the major causes of death and disability worldwide. Novel and effective therapy is needed to prevent the secondary spread of damage beyond the initial injury. The aim of this study was to investigate whether berberine has a neuroprotective effect on secondary injury post-TBI, and to explore its potential mechanism in this protection. The mice were randomly divided into Sham-saline, TBI-saline and TBI-Berberine (50 mg/kg). TBI was induced by Feeney's weight-drop technique. Saline or berberine was administered via oral gavage starting 1 h post-TBI and continuously for 21 days. Motor coordination, spatial learning and memory were assessed using beam-walking test and Morris water maze test, respectively. Brain sections were processed for lesion volume assessment, and expression of neuronal nuclei (NeuN), cyclooxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS), 8-hydroxy-2-deoxyguanosine (8-OHdG), ionized calcium-binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) were detected via immunohistochemistry and immunofluorescence. There were statistically significant improvement in motor coordination, spatial learning and memory in the TBI-Berberine group, compared to the TBI-saline group. Treatment with berberine significantly reduced cortical lesion volume, neuronal loss, COX-2, iNOS and 8-OHdG expression in both the cortical lesion border zone (LBZ) and ipsilateral hippocampal CA1 region (CA1), compared to TBI-saline. Berberine treatment also significantly decreased Iba1- and GFAP-positive cell number in both the cortical LBZ and ipsilateral CA1, relative to saline controls. These results indicated that berberine exerted neuroprotective effects on secondary injury in mice with TBI probably through anti-oxidative and anti-inflammatory properties.

The p53 Family in Brain Disease

SIGNIFICANCE

The p53 family of transcription factors, including p53, p63, and p73, plays key roles in both biological and pathological processes, including cancer and neural development. Recent Advances: In recent years, a growing body of evidence has indicated that the entire p53 family is involved in the regulation of the central nervous system (CNS) functions as well as in the pathogenesis of several neurological disorders. Mechanistically, the p53 proteins control neuronal cell fate, terminal differentiation, and survival, via a complex interplay among the family members.

CRITICAL ISSUES

In this article, we discuss the involvement of the p53 family in neurobiology and in pathological conditions affecting the CNS, including neuroinflammation.

FUTURE DIRECTIONS

Understanding the molecular mechanism(s) underlying the function of the p53 family could improve our general knowledge of the pathogenesis of brain disorders and potentially pave the road for new therapeutic intervention. Antioxid. Redox Signal. 29, 1-14.

Essential Dietary Bioactive Lipids in Neuroinflammatory Diseases

SIGNIFICANCE

Under physiological conditions, neurons and glia are in a healthy, redox-balanced environment; when injury perturbs this equilibrium, a neuroinflammatory state is established by activated microglia that triggers pro-inflammatory responses and alters the oxidant/antioxidant balance, thus leading to neuronal loss and neurodegeneration. In neurodegenerative diseases (such as Alzheimer's disease, Parkinson's disease, amyothrophic lateral sclerosis, and multiple sclerosis), the brain is in a constitutively self-sustaining cycle of inflammation and oxidative stress that prompts and amplifies brain damage. Recent Advances: Recently, an increasing amount of scientific data highlight the ability of specific nutrients to cross the blood-brain barrier, and to modulate inflammatory and oxidative pathways. Therefore, nutritional approaches may contribute to restore the lost equilibrium among factors accounting for neurodegeneration.

CRITICAL ISSUES

Herein, we critically examine how essential lipids (including fatty acids, liposoluble vitamins and phytosterols) might contribute to accelerate or prevent the onset and progression of such pathologies. In particular, we highlight that experimental and clinical findings, although promising, are still inadequate to draw definitive conclusions.

FUTURE DIRECTIONS

More research is warranted in order to establish the real impact of lipid intake on brain health, especially when redox balance and inflammatory responses have been already compromised. In the future, it would be hoped to gain a detailed knowledge of chemical modifications and dynamic properties of such nutrients, before planning to exploit them as potential therapeutics. Antioxid. Redox Signal. 29, 37-60.

Lauric Acid Alleviates Neuroinflammatory Responses by Activated Microglia: Involvement of the GPR40-Dependent Pathway

In several neurodegenerative diseases such as Alzheimer's disease (AD), microglia are hyperactivated and release nitric oxide (NO) and proinflammatory cytokines, resulting its neuropathology. Mounting evidence indicates that dietary supplementation with coconut oil (CNO) reduces the cognitive deficits associated with AD; however, the precise mechanism(s) underlying the beneficial effect of CNO are unknown. In the present study, we examined the effects of lauric acid (LA), a major constituent of CNO, on microglia activated experimentally by lipopolysaccharide (LPS), using primary cultured rat microglia and the mouse microglial cell line, BV-2. LA attenuated LPS-stimulated NO production and the expression of inducible NO synthase protein without affecting cell viability. In addition, LA suppressed LPS-induced reactive oxygen species and proinflammatory cytokine production, as well as phosphorylation of p38-mitogen activated protein kinase and c-Jun N-terminal kinase. LA-induced suppression of NO production was partially but significantly reversed in the presence of GW1100, an antagonist of G protein-coupled receptor (GPR) 40, which is an LA receptor on the plasma membrane. LA also decreased LPS-induced phagocytosis, which was completely reversed by co-treatment with GW1100. Moreover, LA alleviated amyloid-β-induced enhancement of phagocytosis. These results suggest that attenuation of microglial activation by LA may occur via the GPR40-dependent pathway. Such effects of LA may reduce glial activation and the subsequent neuronal damage in AD patients who consume CNO.

Redox Signaling in Neurotransmission and Cognition During Aging

SIGNIFICANCE

Oxidative stress increases in the brain with aging and neurodegenerative diseases. Previous work emphasized irreversible oxidative damage in relation to cognitive impairment. This research has evolved to consider a continuum of alterations, from redox signaling to oxidative damage, which provides a basis for understanding the onset and progression of cognitive impairment. This review provides an update on research linking redox signaling to altered function of neural circuits involved in information processing and memory. Recent Advances: Starting in middle age, redox signaling triggers changes in nervous system physiology described as senescent physiology. Hippocampal senescent physiology involves decreased cell excitability, altered synaptic plasticity, and decreased synaptic transmission. Recent studies indicate N-methyl-d-aspartate and ryanodine receptors and Ca²⁺ signaling molecules as molecular substrates of redox-mediated senescent physiology.

CRITICAL ISSUES

We review redox homeostasis mechanisms and consider the chemical character of reactive oxygen and nitrogen species and their role in regulating different transmitter systems. In this regard, senescent physiology may represent the co-opting of pathways normally responsible for feedback regulation of synaptic transmission. Furthermore, differences across transmitter systems may underlie differential vulnerability of brain regions and neuronal circuits to aging and disease.

FUTURE DIRECTIONS

It will be important to identify the intrinsic mechanisms for the shift in oxidative/reductive processes. Intrinsic mechanism will depend on the transmitter system, oxidative stressors, and expression/activity of antioxidant enzymes. In addition, it will be important to identify how intrinsic processes interact with other aging factors, including changes in inflammatory or hormonal signals. Antioxid. Redox Signal. 28, 1724-1745.

Redox Signaling, Neuroinflammation, and Neurodegeneration

Production of pro-inflammatory and anti-inflammatory cytokines is part of the defense system that mostly microglia and macrophages display to induce normal signaling to counteract the deleterious actions of invading pathogens in the brain. Also, redox activity in the central nervous system (CNS) constitutes an integral part of the metabolic processes needed by cells to exert their normal molecular and biochemical functions. Under normal conditions, the formation of reactive oxygen and nitrogen species, and the following oxidative activity encounter a healthy balance with immunological responses to preserve cell functions in the brain. However, under different pathological conditions, inflammatory responses recruit pro-oxidant signals and vice versa. The aim of this article is to review the basic concepts about the triggering of inflammatory and oxidative responses in the CNS. Recent Advances: Diverse concurrent toxic pathways are described to provide a solid mechanistic scope for considering intervention at the experimental and clinical levels that are aimed at diminishing the harmful actions of these two contributing factors to nerve cell damage. Critical Issues and Future Directions: The main conclusion supports the existence of a narrow cross-talk between pro-inflammatory and oxidative signals that can lead to neuronal damage and subsequent neurodegeneration. Further investigation about critical pathways crosslinking oxidative stress and inflammation will strength our knowlegde on this topic. Antioxid. Redox Signal. 28, 1626-1651.

Neuroprotective and Cognitive Enhancement Potentials of Baicalin: A Review

Neurodegenerative diseases are a heterogeneous group of disorders that are characterized by the gradual loss of neurons. The development of effective neuroprotective agents to prevent and control neurodegenerative diseases is specifically important. Recently, there has been an increasing interest in selecting flavonoid compounds as potential neuroprotective agents, owing to their high effectiveness with low side effects. Baicalin is one of the important flavonoid compounds, which is mainly isolated from the root of Scutellaria baicalensis Georgi (an important Chinese medicinal herb). In recent years, a number of studies have shown that baicalin has a potent neuroprotective effect in various in vitro and in vivo models of neuronal injury. In particular, baicalin effectively prevents neurodegenerative diseases through various pharmacological mechanisms, including antioxidative stress, anti-excitotoxicity, anti-apoptotic, anti-inflammatory, stimulating neurogenesis, promoting the expression of neuronal protective factors, etc. This review mainly focuses on the neuroprotective and cognitive enhancement effects of baicalin. The aim of the present review is to compile all information in relation to the neuroprotective and cognitive enhancement effects of baicalin and its molecular mechanisms of action in various in vitro and in vivo experimental models.

Neuroprotective Effects of Dehydroepiandrosterone Sulfate Through Inhibiting Expression of Matrix Metalloproteinase-9 from Bradykinin-Challenged Astroglia

Dehydroepiandrosterone sulfate (DHEAS), one of the most important neuroactive steroids, is produced in the adrenals and the brain. DHEAS is believed to play a critical role in modulating different forms of cellular control, including processes associated with human neural systems. Its production rate and level in serum, adrenals, and brain gradually decrease with advancing age. The decline of DHEAS level was associated with age-related neuronal dysfunction and degeneration, most probably because the steroids protect the central nervous system (CNS) neurons against neurotoxic challenges. Moreover, increasing studies show that matrix metalloproteinases (MMPs), MMP-9 especially, are upregulated by proinflammatory mediators in the CNS disorders. The increased MMP-9 as an inflammatory biomarker of several CNS disorders that may participate in the CNS inflammation and neurodegeneration. Herein, we investigate the effects of DHEAS on brain inflammation by the model we have defined of bradykinin (BK)-induced MMP-9 expression in rat brain astrocyte (RBA) and its mechanism. The results showed that DHEAS significantly reduce MMP-9 induced by BK. Pretreatment with DHEAS can inhibit BK-stimulated phosphorylation of c-Src and PYK2. Moreover, DHEAS attenuated BK-stimulated NADPH oxidase (Nox)-derived reactive oxygen species (ROS) production, suggesting that DHEAS has an antioxidative effect. We further demonstrated that DHEAS blocked activation of ERK1/2, Akt, and c-Fos/AP-1 by BK. Finally, DHEAS decreased MMP-9-related events including RBA migration and neuronal apoptosis. The results will provide new insights into the anti-inflammatory action of DHEAS, supporting that DHEAS may have a neuroprotective effect in the improvement of the CNS disorders by reducing neuroinflammation.

Neuro-inflammatory effects of photodegradative products of bilirubin

Phototherapy was introduced in the early 1950’s, and is the primary treatment of severe neonatal jaundice or Crigler-Najjar syndrome. Nevertheless, the potential biological effects of the products generated from the photodegradation of bilirubin during phototherapy remain unknown. This is very relevant in light of recent clinical observations demonstrating that the use of aggressive phototherapy can increase morbidity or even mortality, in extremely low birthweight (ELBW) infants. The aim of our study was to investigate the effects of bilirubin, lumirubin (LR, its major photo-oxidative product), and BOX A and B (its monopyrrolic oxidative products) on the central nervous system (CNS) using in vitro and ex vivo experimental models. The effects of bilirubin photoproducts on cell viability and expression of selected genes were tested in human fibroblasts, three human CNS cell lines (neuroblastoma SH-SY5Y, microglial HMC3, and glioblastoma U-87 cell lines), and organotypic rat hippocampal slices. Neither bilirubin nor its photo-oxidative products affected cell viability in any of our models. In contrast, LR in biologically-relevant concentrations (25 μM) significantly increased gene expression of several pro-inflammatory genes as well as production of TNF-α in organotypic rat hippocampal slices. These findings might underlie the adverse outcomes observed in ELBW infants undergoing aggressive phototherapy.

The Anti-neuroinflammatory Activity of Tectorigenin Pretreatment via Downregulated NF-κB and ERK/JNK Pathways in BV-2 Microglial and Microglia Inactivation in Mice With Lipopolysaccharide

The activation of microglia is decisively involved with the neurodegeneration observed in many neuroinflammatory pathologies, such as multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease. Tectorigenin (TEC) is an isoflavone isolated from various medicinal plants, such as Pueraria thunbergiana Benth, Belamcanda chinensis, and Iris unguicularis. In the present study, the neuroinflammatory effects of TEC were evaluated in both lipopolysaccharide (LPS)-treated BV-2 microglial and mouse models. TEC remarkably inhibited reactive oxygen species (ROS) generation. TEC also inhibits the production and expression of nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in LPS-stimulated BV-2 cells. In addition, TEC suppressed the LPS-induced activation of nuclear factor-κB (NF-κB), phosphorylation of extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) to regulate the inflammatory mediators, such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α, and IL-6. These results indicate that TEC may inhibit neuronal inflammation through the downregulation of inflammatory mediators, including iNOS, COX-2, TNF-α, and IL-6 by suppressing NF-κB/ERK/JNK-related signaling pathways. Furthermore, cotreatment with TEC and ERK inhibitor SCH772984 or JNK inhibitor SP600125 suppressed the overproduction of LPS-induced NO production in BV-2 cells. Consistent with the results of in vitro experiments, an LPS-induced brain inflammation mouse model, administration of TEC effectively decrease the levels of malondialdehyde, iNOS in hippocampus, and prevented increases in the levels of TNF-α and IL-6 in the serum. TEC showed marked attenuation of microglial activation. Finally, TEC inhibited protein expression of toll-like receptor 4 and myeloid differentiation factor 88 in LPS-activated BV-2 microglia and mouse models. Taken altogether, the cumulative findings suggested that TEC holds the potential to develop as a neuroprotective drug for the intervention of neuroinflammatory disorders.

Effect of Chronic Oxidative Stress on Neuroinflammatory Response Mediated by CD4+T Cells in Neurodegenerative Diseases

In a state of oxidative stress, there is an increase of reactive species, which induce an altered intracellular signaling, leading to dysregulation of the inflammatory response. The inability of the antioxidant defense systems to modulate the proinflammatory response is key to the onset and progression of neurodegenerative diseases. The aim of this work is to review the effect of the state of oxidative stress on the loss of regulation of the inflammatory response on the microglia and astrocytes, the induction of different CD4⁺T cell populations in neuroinflammation, as well as its role in some neurodegenerative diseases. For this purpose, an intentional search of original articles, short communications, and reviews, was carried out in the following databases: PubMed, Scopus, and Google Scholar. The articles reviewed included the period from 1997 to 2017. With the evidence obtained, we conclude that the loss of redox balance induces alterations in the differentiation and number of CD4⁺T cell subpopulations, leading to an increase in Th1 and Th17 response. This contributes to the development of neuroinflammation as well as loss of the regulation of the inflammatory response in neurodegenerative diseases such as Alzheimer's (AD), Parkinson's (PD), and Multiple Sclerosis (MS). In contrast, regulatory T cells (Tregs) and Th2 modulate the inflammatory response of effect of T cells, microglia, and astrocytes. In this respect, it has been found that the mobilization of T cells with anti-inflammatory characteristics toward damaged regions of the CNS can provide neuroprotection and become a therapeutic strategy to control inflammatory processes in neurodegeneration.

Designer exosomes produced by implanted cells intracerebrally deliver therapeutic cargo for Parkinson's disease treatment

Exosomes are cell-derived nanovesicles (50-150 nm), which mediate intercellular communication, and are candidate therapeutic agents. However, inefficiency of exosomal message transfer, such as mRNA, and lack of methods to create designer exosomes have hampered their development into therapeutic interventions. Here, we report a set of EXOsomal transfer into cells (EXOtic) devices that enable efficient, customizable production of designer exosomes in engineered mammalian cells. These genetically encoded devices in exosome producer cells enhance exosome production, specific mRNA packaging, and delivery of the mRNA into the cytosol of target cells, enabling efficient cell-to-cell communication without the need to concentrate exosomes. Further, engineered producer cells implanted in living mice could consistently deliver cargo mRNA to the brain. Therapeutic catalase mRNA delivery by designer exosomes attenuated neurotoxicity and neuroinflammation in in vitro and in vivo models of Parkinson's disease, indicating the potential usefulness of the EXOtic devices for RNA delivery-based therapeutic applications.

Transcranial magnetic stimulation as an antioxidant

In the last decades, different transcranial magnetic stimulation protocols have been developed as a therapeutic tool against neurodegenerative and psychiatric diseases, although the biochemical, molecular and cellular mechanisms underlying these effects are not well known. Recent data show that those magnetic stimulation protocols showing beneficial effects could trigger an anti-oxidant action that would favour, at least partially, their therapeutic effect. We have aimed to review the molecular effects related to oxidative damage induced by this therapeutic strategy, as well as from them addressing a broader definition of the anti-oxidant concept.

Stress-Induced Synaptic Dysfunction and Neurotransmitter Release in Alzheimer's Disease: Can Neurotransmitters and Neuromodulators be Potential Therapeutic Targets?

The communication between neurons at synaptic junctions is an intriguing process that monitors the transmission of various electro-chemical signals in the central nervous system. Albeit any aberration in the mechanisms associated with transmission of these signals leads to loss of synaptic contacts in both the neocortex and hippocampus thereby causing insidious cognitive decline and memory dysfunction. Compelling evidence suggests that soluble amyloid-β (Aβ) and hyperphosphorylated tau serve as toxins in the dysfunction of synaptic plasticity and aberrant neurotransmitter (NT) release at synapses consequently causing a cognitive decline in Alzheimer's disease (AD). Further, an imbalance between excitatory and inhibitory neurotransmission systems induced by impaired redox signaling and altered mitochondrial integrity is also amenable for such abnormalities. Defective NT release at the synaptic junction causes several detrimental effects associated with altered activity of synaptic proteins, transcription factors, Ca2+ homeostasis, and other molecules critical for neuronal plasticity. These detrimental effects further disrupt the normal homeostasis of neuronal cells and thereby causing synaptic loss. Moreover, the precise mechanistic role played by impaired NTs and neuromodulators (NMs) and altered redox signaling in synaptic dysfunction remains mysterious, and their possible interlink still needs to be investigated. Therefore, this review elucidates the intricate role played by both defective NTs/NMs and altered redox signaling in synaptopathy. Further, the involvement of numerous pharmacological approaches to compensate neurotransmission imbalance has also been discussed, which may be considered as a potential therapeutic approach in synaptopathy associated with AD.

Therapeutic Potential of Oridonin and Its Analogs: From Anticancer and Antiinflammation to Neuroprotection

Oridonin, a diterpenoid natural product commonly used in East Asian herbal medicine, is garnering increased attention in the biomedical community due to its extensive biological activities that include antitumor, anti-inflammatory, antimicrobial, hepatic fibrosis prevention, and neurological effects. Over the past decade, significant progress has been made in structure activity relationship and mechanism of action studies of oridonin for the treatment of cancer and other diseases. This review provides a brief summary on oridonin and its analogs in cancer drug discovery and antiinflammation and highlights its emerging therapeutic potential in neuroprotection applications.