Neuroprotective Effect of Epalrestat on Hydrogen Peroxide-Induced Neurodegeneration in SH-SY5Y Cellular Model.

Epalrestat (EPS) is a brain penetrant aldose reductase inhibitor, an approved drug currently used for the treatment of diabetic neuropathy. At near-plasma concentration, EPS induces glutathione biosynthesis, which in turn reduces oxidative stress in the neuronal cells. In this study, we found that EPS reduces neurodegeneration by inhibiting reactive oxygen species (ROS)-induced oxidative injury, mitochondrial membrane damage, apoptosis and tauopathy. EPS treatment up to 50 µM did not show any toxic effect on SH-SY5Y cell line (neuroblastoma cells). However, we observed toxic effect at a concentration of 100 µM and above. At 50 µM concentration, EPS showed better antioxidant activity against H2O2 (100 µM)-induced cytotoxicity, ROS formation and mitochondrial membrane damage in retinoic acid-differentiated SH-SY5Y cell line. Furthermore, our study revealed that 50 µM of EPS concentration reduced the glycogen synthase kinase-3 ß (GSK3-ß) expression and total tau protein level in H2O2 (100 µM)-treated cells. Findings from this study confirms the therapeutic efficacy of EPS on regulating Alzheimer's disease (AD) by regulating GSK3-ß and total tau proteins phosphorylation, which helped to restore the cellular viability. This process could also reduce toxic fibrillary tangle formation and disease progression of AD. Therefore, it is our view that an optimal concentration of EPS therapy could decrease AD pathology by reducing tau phosphorylation through regulating the expression level of GSK3-ß.

Correction to: Escin, a Novel Triterpene, Mitigates Chronic MPTP/P-Induced Dopaminergic Toxicity by Attenuating Mitochondrial Dysfunction, Oxidative Stress, and Apoptosis.

The original version of this article unfortunately contains an error in Figs. 8 and 9.

Role of Oxidative Stress and Antioxidants in Autism.

Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders with poorly understood etiology that are defined exclusively on the basis of behavioral observations. This disorder has been linked to increased levels of oxidative stress and lower antioxidant capacity. Oxidative stress in autism has been studied at the membrane level and also by measuring products of lipid peroxidation, detoxifying agents (such as glutathione), and antioxidants involved in the defense system against reactive oxygen species (ROS). Several studies have suggested alterations in the activities of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and catalase in autism. Additionally, altered glutathione levels and homocysteine/methionine metabolism, increased inflammation, excitotoxicity, as well as mitochondrial and immune dysfunction have been suggested in autism. Moreover, environmental and genetic risk factors may intensify vulnerability to oxidative stress in autism. Collectively, these studies suggest increased oxidative stress in autism that may contribute to the development of this disease both in terms of pathogenesis and clinical symptoms. Antioxidant supplementation, or ways to improve the altered metabolite levels in the interconnected transmethylation and transsulfuration pathways, has been associated with decreased autistic behaviors and severity. This chapter provides a conceptual framework on oxidative stress and antioxidants utility. These types of interventions should be further studied in order to determine their effectiveness at improving metabolic imbalances.

Natural Products and Their Therapeutic Effect on Autism Spectrum Disorder.

Autism is a complex neurodevelopmental disorder that is evident in early childhood and can persist throughout the entire life. The disease is basically characterized by hurdles in social interaction where the individuals demonstrate repetitive and stereotyped interests or patterns of behavior. A wide number of neuroanatomical studies with autistic patients revealed alterations in brain development which lead to diverse cellular and anatomical processes including atypical neurogenesis, neuronal migration, maturation, differentiation, and degeneration. Special education programs, speech and language therapy, have been employed for the amelioration of behavioral deficits in autism. Although commonly prescribed antidepressants, antipsychotics, anticonvulsants, and stimulants have revealed satisfactory responses in autistic individuals, adverse side effects and increased risk of several other complications including obesity, dyslipidemia, diabetes mellitus, thyroid disorders, etc. have compelled the researchers to turn their attention toward herbal remedies. Alternative approaches with natural compounds are on continuous clinical trial to confirm their efficacy and to understand their potential in autism treatment. This chapter aims to cover the major plant-based natural products which hold promising outcomes in the field of reliable therapeutic interventions for autism.

Bioactive Metabolites from Marine Ascidians: Future Treatment for Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a developmental disorder that influences communication and behavior. Numerous researches propose that genes can act together with manipulations from the environment to affect development in ways that lead to ASD. The broad range of issues facing people with ASD means that there is no single proper drug and treatment for ASD. Numerous shortcomings associated with the present conventional therapeutic strategies have forced researchers to venture into alternative natural sources for effective compounds. The marine environment has emerged as an alternate search environment due to its versatile conditions where organisms employ various biodefense mechanisms for their survival. Ascidians are an excellent source for unique bioactive compounds with nutritive and therapeutic content and it still holds credit for being an underused source from marine animals. Bioactive compounds isolated from ascidians have various commendable biomedical applications due to their unique chemical structures. The present chapter will focus on the potential of bioactive compounds derived from ascidians for the treatment of the neurologic disorder-ASD.

Cocoa beans improve mitochondrial biogenesis via PPARγ/PGC1α dependent signalling pathway in MPP+ intoxicated human neuroblastoma cells (SH-SY5Y).

Polyphenols are shown to protect from or delay the progression of chronic neurodegenerative diseases. Mitochondrial dysfunction plays a key role in the pathogenesis of Parkinson's disease (PD). This study was aims to gain insight into the role of ahydroalcoholic extract of cocoa (standardised for epicatechin content) on mitochondrial biogenesis in MPP+ intoxicated human neuroblastoma cells (SHSY5Y). The effects of cocoa on PPARγ, PGC1α, Nrf2 and TFAM protein expression and mitochondrial membrane potential were evaluated. A pre-exposure to cocoa extract decreased reactive oxygen species formation and restored mitochondrial membrane potential. The cocoa extract was found to up-regulate the expression of PPARγ and the downstream signalling proteins PGC1α, Nrf2 and TFAM. It increased the expression of the anti-apoptotic protein BCl2 and increased superoxide dismutase activity. Further, the cocoa extract down-regulated the expression of mitochondria fission 1 (Fis1) and up-regulated the expression of mitochondria fusion 2 (Mfn2) proteins, suggesting an improvement in mitochondrial functions in MPP+ intoxicated cells upon treatment with cocoa. Interestingly, cocoa up-regulates the expression of tyrosine hydroxylase, the rate limiting enzyme in dopamine synthesis. No change in the expression of PPARγ on treatment with cocoa extract was observed when the cells were pre-treated with PPARγ antagonist GW9662. This data suggests that cocoa mediates mitochondrial biogenesis via a PPARγ/PGC1α dependent signalling pathway and also has the ability to improve dopaminergic functions by increasing tyrosine hydroxylase expression. Based on our data, we propose that a cocoa bean extract and products thereof could be used as potential nutritional supplements for neuroprotection in PD.

Correction to: Dietary Supplementation of Walnut Partially Reverses 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine Induced Neurodegeneration in a Mouse Model of Parkinson's Disease.

The original version of this article unfortunately contains an error in Fig. 2a (4th image for walnut). This has been corrected by publishing this erratum.

Neuroprotective attributes of L-theanine, a bioactive amino acid of tea, and its potential role in Parkinson's disease therapeutics.

Meta-analyses of tea consumption and reduced risk of Parkinson's disease have thrown light in the pathway of exploring beneficial properties of tea components. On the basis of dry mass, a typical black or green tea beverage contains approximately 6% of free amino acids, which impart high quality, taste and distinctive aroma to the tea infusion. L-theanine (chemically known as γ-glutamylethylamide) is a non-proteinogenic amino acid of tea that takes part in the biosynthesis of its polyphenols. Recently discovered neuroprotective effects of L-theanine can be attributed to its structural analogy with glutamate, the principal excitatory neurotransmitter in brain. This unique amino acid also bears a potential to ameliorate the pathophysiological changes associated with Parkinson's disease as it displays antioxidant and anti-inflammatory properties, improves motor behavioral abnormalities, increases dopamine availability and may cause a favorable downshift in neurodegeneration due to glutamate excitotoxicity. To gain an explicit understanding of the role of L-theanine, this review article is the first one to focus on its mechanism of neuromodulatory action and to critically evaluate the possibilities of employing this bioactive amide in the forage of anti-Parkinsonian medication. We also hypothesize the idea of L-theanine being a potent natural agent against L-DOPA induced dyskinesia, since long-term reliance on dopamine replacement therapy is linked with elevation in glutamate receptor activity.

Asiatic Acid Attenuated Aluminum Chloride-Induced Tau Pathology, Oxidative Stress and Apoptosis Via AKT/GSK-3ß Signaling Pathway in Wistar Rats.

Asiatic acid (AA), a triterpenoid present in Centella asiatica, possesses the ability to cross blood brain barrier and received considerable attention for its neuroprotective role. We have reported the benefit of AA against aluminum chloride (AlCl3)-induced amyloid pathology, enhanced acetylcholine esterase (AChE) activity, and inflammation in Alzheimer's disease (AD) like model rats. Based on that, to find the exact mechanism of action of AA, the present study was designed to evaluate the oxidative stress, tau pathology, apoptosis, and Akt/GSK3ß signaling pathway on AlCl3-induced neurotoxicity in Wistar rats. AD-like pathology was induced by oral administration of AlCl3 (100 mg/kg b.w.) for 6 weeks, which demonstrated a significant reduction in spatial memory performance, anxiety, and motor dysfunction and diminished the expression of cyclin-dependent kinase 5 (CDK 5-enzyme implicated in the phosphorylation of tau proteins), pTau, oxidative stress, and apoptosis, whereas oral ingestion of AA (75 mg/kg b.w.) for 7 weeks attenuated the above-said indices, which could be by activating Akt/GSK3ß pathway. Current results suggested that AA could be able to modulate various pathological features of AD and could hold promise in AD treatment.

Dendritic spines: Revisiting the physiological role.

Dendritic spines are small, thin, specialized protrusions from neuronal dendrites, primarily localized in the excitatory synapses. Sophisticated imaging techniques revealed that dendritic spines are complex structures consisting of a dense network of cytoskeletal, transmembrane and scaffolding molecules, and numerous surface receptors. Molecular signaling pathways, mainly Rho and Ras family small GTPases pathways that converge on actin cytoskeleton, regulate the spine morphology and dynamics bi-directionally during synaptic activity. During synaptic plasticity the number and shapes of dendritic spines undergo radical reorganizations. Long-term potentiation (LTP) induction promote spine head enlargement and the formation and stabilization of new spines. Long-term depression (LTD) results in their shrinkage and retraction. Reports indicate increased spine density in the pyramidal neurons of autism and Fragile X syndrome patients and reduced density in the temporal gyrus loci of schizophrenic patients. Post-mortem reports of Alzheimer's brains showed reduced spine number in the hippocampus and cortex. This review highlights the spine morphogenesis process, the activity-dependent structural plasticity and mechanisms by which synaptic activity sculpts the dendritic spines, the structural and functional changes in spines during learning and memory using LTP and LTD processes. It also discusses on spine status in neurodegenerative diseases and the impact of nootropics and neuroprotective agents on the functional restoration of dendritic spines.

Protective Effects of Antioxidants in Huntington's Disease: an Extensive Review.

Huntington's disease (HD) is a hereditary neurodegenerative disease of the central nervous system (CNS). Onset of HD occurs between the ages of 30 and 50 years, although few cases are reported among children and elderly. HD appears to be less common in some populations such as those of Japanese, Chinese, and African descent. Clinical features of HD include motor dysfunction (involuntary movements of the face and body, abnormalities in gait, posture and balance), cognitive impairment (obsessive-compulsive disorder), and psychiatric disorders (dementia). Mutation in either of the two copies of a gene called huntingtin (HTT), which codes genetic information for a protein called "huntingtin (Htt)", precipitates the disease in an individual. Expansion of cytosine-adenine-guanine (CAG) triplet repeats in the HTT gene results in an abnormal Htt protein. Intracellular neuronal accumulation of the mutated Htt protein (mHtt) causes distinctive erratic movements associated with HD. Further, excessive accumulation of the HTT gene repeats causes abnormal production of reactive oxygen species (ROS) and the ensuing mitochondrial (MT) oxidative stress in neurons. Since there is neither a cure nor a promising strategy to delay onset or progression of HD currently available, therapeutics are mainly focusing only on symptomatic management. Several studies have shown that MT dysfunction-mediated oxidative stress is a key factor for the neurodegeneration observed in HD. Supplementation of antioxidants and nutraceuticals has been widely studied in the management of oxidative damage, an associated complication in HD. Therefore, various antioxidants are used as therapeutics for managing and/or treating HD. The present review aimed at delving into the abnormal cellular changes and energy kinetics of the neurons expressing the mHtt gene and the therapeutic roles of antioxidants in HD.

Amelioration of Aluminum Maltolate-Induced Inflammation and Endoplasmic Reticulum Stress-Mediated Apoptosis by Tannoid Principles of Emblica officinalis in Neuronal Cellular Model.

The neuroprotective role of tannoid principles of Emblica officinalis (EoT), an Indian and Chinese traditional medicinal plant against memory loss in aluminum chloride-induced in vivo model of Alzheimer's disease through attenuating AChE activity, oxidative stress, amyloid and tau toxicity, and apoptosis, was recently reported in our lab. However, to further elucidate the mechanism of neuroprotective effect of EoT, the current study was designed to evaluate endoplasmic reticulum stress-suppressing and anti-inflammatory role of EoT in PC 12 and SH-SY 5Y cells. These cells were divided into four groups: control (aluminum maltolate (Al(mal)3), EoT + Al(mal)3, and EoT alone based on 3-(4, 5-dimethyl 2-yl)-2, and 5-diphenyltetrazolium bromide (MTT) assay. EoT significantly reduced Al(mal)3-induced cell death and attenuated ROS, mitochondrial membrane dysfunction, and apoptosis (protein expressions of Bax; Bcl-2; cleaved caspases 3, 6, 9, 12; and cytochrome c) by regulating endoplasmic reticulum stress (PKR-like ER kinase (PERK), α subunit of eukaryotic initiation factor 2 (EIF2-α), C/EBP-homologous protein (CHOP), and high-mobility group box 1 protein (HMGB1)). Moreover, inflammatory response (NF-κB, IL-1ß, IL-6, and TNF-α) and Aß toxicity (Aß1-42) triggered by Al(mal)3 was significantly normalized by EoT. Our results suggested that EoT could be a possible/promising and novel therapeutic lead against Al-induced neurotoxicity. However, further extensive research is needed to prove its efficacy in clinical studies.

Low Molecular Weight Sulfated Chitosan: Neuroprotective Effect on Rotenone-Induced In Vitro Parkinson's Disease.

The present investigation was an attempt to study the effect of low molecular weight sulfated chitosan (LMWSC) on in vitro rotenone model of Parkinson's disease (PD) by evaluating cell viability, oxidative stress, mitochondrial membrane potential, DNA fragmentation, and apoptosis. Incubation of SH-SY5Y cells with 100 nm rotenone resulted in neuronal cell death, redox imbalanced mitochondrial dysfunction, DNA fragmentation, condensation, and apoptotic cellular morphology. Rotenone exposure enhanced the expression of preapoptotic (cytochrome C (cyto c), caspase-3, -8, -9, and Bax) and down-regulated the expression of anti-apoptotic (Bcl-2) markers. Reduction of the intracellular reactive oxygen species (ROS) levels ensued due to pretreatment of LMWSC along with consequent normalization of antioxidant enzymes, mitigation of rotenone induced mitochondrial dysfunction and apoptosis. Our current findings suggested that LMWSC exhibit the pronounced neuroprotective effects, which could be due to its antioxidant, mitochondrial protection, and anti-apoptotic properties. We thus conclude that LMWSC could be developed as a novel therapeutic molecule for the benefit of reducing the consequences of PD. However, further extensive preclinical and clinical studies are warranted.

Antioxidant therapies in attention deficit hyperactivity disorder.

Attention Deficit Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder among children and adults. Impulsivity, inattention, and hyperactivity are hallmark of ADHD. While ADHD is not on the autism spectrum, they are related in several ways as they have some overlapping symptoms. The pathogenesis of ADHD has so far remained enigmatic, however, there is some evidence suggesting critical association among ADHD and the level of oxidative stress which trigger cell membrane damage, changes in inner structure and function of proteins, as well as structural damage to DNA which eventually culminate into development of ADHD. Although stimulants as well as some classes of non-stimulants are used to ameliorate symptom of ADHD, various adverse effects have been associated with such compounds. To date, treatment of ADHD is done with a combination of medications, behavior modifications, psycho-education, family therapy and life-style changes. The American Academy of Pediatrics officially promote stimulant medications and/or behavior therapy as 'first line of therapy'. In addition to the presently therapeutic armamentarium, evidences are emerging on relevancy of natural products. There has been an interest on the therapeutic role of antioxidants in the treatment of ADHD. The present review aims to highlight the beneficiary role played by different antioxidants in mitigating the symptoms of ADHD.

Accumulation of Cholesterol and Homocysteine in the Nigrostriatal Pathway of Brain Contributes to the Dopaminergic Neurodegeneration in Mice.

Elevated levels of cholesterol (hypercholesterolemia) and homocysteine (hyperhomocysteinemia, HHcy) in blood have been linked with the pathology of Parkinson's disease. However, the impact of their combined effect on brain is unknown. The present study aims to investigate the effect of HHcy on dopaminergic neurons in brain of mice with hypercholesterolemia. Mice were subjected to a high-cholesterol diet for 12 weeks to develop hypercholesterolemia, and were administered with homocysteine (250 mg/kg, b.w., i.p., 60 days) daily starting from 24th day of the high-cholesterol diet for induction of HHcy. The animals were subjected to Parkinsonian motor behavioral tests and sacrificed to estimate the levels of cholesterol, homocysteine and dopamine in brain, and to assess dopaminergic neuronal status. There occurred elevation in cholesterol and homocysteine levels in nigrostriatum of hypercholesterolemic animals with HHcy. Injection of homocysteine in hypercholesterolemic mice exacerbated the motor abnormalities as well as caused depletion of striatal dopamine level significantly, which was supported by a significant decrease in tyrosine hydroxylase (TH) immunoreactivity in striatum. While neither hypercholesterolemia nor HHcy caused significant changes in the number of TH-positive neurons, hypercholesterolemia in combination with HHcy resulted in a significant loss of nigral TH-positive neurons. The results highlighted the involvement of mitochondrial complex-I dysfunction with subsequent generation of hydroxyl radicals for the observed loss of midbrain dopamine neurons in animals receiving the combined treatment. Thus, the findings of the present study pointed out the combined effect of homocysteine and cholesterol toward dopamine neuronal dysfunctions, which has substantial relevance to Parkinson's disease.

Telmisartan Ameliorates Astroglial and Dopaminergic Functions in a Mouse Model of Chronic Parkinsonism.

Many studies reported the neuroprotective effects of angiotensin II type 1 receptor (AT1R) antagonists in Parkinson's disease (PD). However, the role of AT1R blockade on astroglial, in turn, dopaminergic functions in chronic PD is still to be studied. In the present study, telmisartan (TEL; 3 and 10 mg/kg/day; p.o), was used to study the effects AT1R blockade on astrocytic and dopaminergic functions in a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinsonism (250 mg/kg, i.p, in 10 equally divided doses at 3.5 days interval) in C57BL/6 J mice. TEL significantly downregulated glial fibrillary acidic protein (GFAP), inducible nitric oxide synthase (iNOS), TNFα and IL1ß expressions and nitric oxide (NO) content. Significant upregulation glial cell derived neurotrophic factor (GDNF) expression and increased glutathione (GSH) content reveal the ameliorating effects of TEL on astroglial functions. On the other hand, TEL upregulated tyrosine hydroxylase (TH), dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT2) expressions. Finally, TEL improved dopamine and its turnover and restored locomotor performance. Present experiment reveals that TEL has the potential to alleviate astroglial functions, apart from restoring dopaminergic functions, at least in part. To conclude, TEL may be a better disease-modifying therapeutic regimen in the management of Parkinsonism, acting primarily via astroglial-dopaminergic functions.