Curcumin confers neuroprotection against alcohol-induced hippocampal neurodegeneration via CREB-BDNF pathway in rats

Alcohol Consumption During Adolescence Alters the Cognitive Function in Adult Male Mice by Persistently Increasing Levels of DUSP6

Binge alcohol drinking during adolescence has long-term effects on the adult brain that alter brain structure and behaviors, but the underlying mechanisms remain poorly understood. Extracellular signal-regulated kinase (ERK) is involved in the synaptic plasticity and pathological brain injury by regulating the expression of cyclic adenosine monophosphate response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF). Dual-specificity phosphatase 6 (DUSP6) is a critical effector that dephosphorylates ERK1/2 to control the basal tone, amplitude, and duration of ERK signaling. To explore DUSP6 as a regulator of ERK signaling in the mPFC and its impact on long-term effects of alcohol, a male mouse model of adolescent intermittent alcohol (AIA) exposure was established. Behavioral experiments showed that AIA did not affect anxiety-like behavior or sociability in adulthood, but significantly damaged new object recognition and social recognition memory. Molecular studies further found that AIA reduced the levels of pERK-pCREB-BDNF-PSD95/NR2A involved in synaptic plasticity, while DUSP6 was significantly increased. Intra-mPFC infusion of AAV-DUSP6-shRNA restored the dendritic spine density and postsynaptic density thickness by reversing the level of p-ERK and its downstream molecular expression, and ultimately repaired adult cognitive impairment caused by chronic alcohol exposure during adolescence. These findings indicate that AIA exposure inhibits ERK-CREB-BDNF-PSD95/NR2A by increasing DUSP6 in the mPFC in adulthood that may be associated with long-lasting cognitive deficits.

Unraveling the protective effects of curcumin against drugs of abuse

Curcumin, a natural compound derived from the turmeric plant (Curcuma longa), has garnered significant attention for its diverse neuroprotective properties. Curcumin has been widely recognized for its remarkable anti-inflammatory, antioxidant, and anti-apoptotic effects, which have shown great potential in the treatment of various disorders, encompassing psychiatric and neurodegenerative diseases. In this review, we delve into the protective effects of curcumin against drugs of abuse, including morphine, methamphetamine, cocaine, nicotine, and alcohol, with a particular focus on the underlying mechanisms from a neuroscience perspective. Overall, curcumin demonstrates promising effects against the neurotoxicity induced by abused drugs through a wide range of mechanisms. These include the modulation of inflammatory cytokines, maintenance of ion homeostasis, epigenetic regulation, enhancement of antioxidant capacity, as well as the activation of the cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) signaling pathways. These findings suggest that curcumin emerges as a promising therapeutic agent in combatting the detrimental effects induced by drugs of abuse, and further research is warranted to fully comprehend the molecular pathways and optimize its utilization for the prevention and treatment of substance abuse-related neurotoxicity.

A low dose of curcumin-PDA nanoparticles improves viability and proliferation in endoneurial fibroblasts and Schwann cell cultures

Curcumin is a polyphenol extracted from Curcuma longa's roots. Low doses of curcumin are related to anti-inflammatory, antioxidant, and neuroprotective effects, while high doses are used for their lethality. This diversity of behaviors allows us to understand curcumin as a compound with hormetic action. Due to its strongly hydrophobic character, curcumin is often solubilized in organic compounds. In this way, we have recently reported the undesirable and occasionally irreversible effects of alcohol and DMSO on the viability of primary Schwann cell cultures. In this scenario, the use of nanoparticles as delivery systems has become a successful alternative strategy for these compounds. In the present work, we describe the structure of Polydopamine (PDA) nanoparticles, loaded with a low dose of curcumin (Curc-PDA) without the use of additional organic solvents. We analyzed the curcumin released, and we found two different forms of curcumin. Small increased cell viability and proliferation were observed in endoneurial fibroblast and Schwann cell primary cultures when Curc-PDA was steadily supplied for 5 days. The increased bioavailability of this natural compound and the impact on cells in culture not only confirm the properties of curcumin at very low doses but also provide a glimpse of a possible therapeutic alternative for PNS conditions in which SCs are involved.

The ameliorative effect of turmeric (Curcuma longa Linn) extract and its major constituent, curcumin, and its analogs on ethanol toxicity

Ethanol toxicity is a major public health problem that can cause damage to various organs in the body by several mechanisms inducing oxidative stress, inflammation, and apoptosis. Recently, there has been a growing interest in the potential of herbal medicines as therapeutic agents for the prevention and treatment of various disorders. Turmeric (Curcuma longa) extracts and its main components including curcumin have antioxidant, anti-inflammatory, and anti-apoptotic properties. This review aims to evaluate the literature on the ameliorative effects of turmeric extracts and their main components on ethanol toxicity. The relevant studies were identified through searches of Google Scholar, PubMed, and Scopus without any time limitation. The underlying mechanisms of turmeric and curcumin were also discussed. The findings suggest that turmeric and curcumin ameliorate ethanol-induced organ damage by suppressing oxidative stress, inflammation, apoptosis, MAPK activation, TGF-β/Smad signaling pathway, hyperlipidemia, regulating hepatic enzymes, expression of SREBP-1c and PPAR-α. However, the limited clinical evidence suggests that further research is needed to determine the efficacy and safety of turmeric and curcumin in human subjects. In conclusion, the available evidence supports the potential use of turmeric and curcumin as alternative treatments for ethanol toxicity, but further high-quality studies are needed to firmly establish the clinical efficacy of the plant.

Curcumin-ZnO conjugated nanoparticles confer neuroprotection against ketamine-induced neurotoxicity

BACKGROUND

Nanotechnology and its application to manipulate herbal compounds to design new neuroprotective agents to manage neurotoxicity has recently increased. Cur-ZnO conjugated nanoparticles were synthesized and used in an experimental model of ketamine-induced neurotoxicity.

METHODS

Cur-ZnO conjugated nanoparticles were chemically characterized, and the average crystalline size was determined. Forty-nine adult mice were divided into seven groups of seven animals each. Normal saline was given to control mice (group 1). Ketamine (25 mg/kg) was given to a second group. A third group of mice was given ketamine (25 mg/kg) in combination with curcumin (40 mg/kg), while mice in groups 4, 5, and 6 received ketamine (25 mg/kg) plus Cur-ZnO nanoparticles (10, 20, and 40 mg/kg). Group 7 received only ZnO (5 mg/kg). All doses were ip for 14 days. Hippocampal mitochondrial quadruple complex enzymes, oxidative stress, inflammation, and apoptotic characteristics were assessed.

RESULTS

Cur-ZnO nanoparticles and curcumin decreased lipid peroxidation, GSSG content, IL-1β, TNF-α, and Bax levels while increasing GSH and antioxidant enzymes like GPx, GR, and SOD while increasing Bcl-2 level and mitochondrial quadruple complex enzymes in ketamine treatment groups.

CONCLUSION

The neuroprotective properties of Cur-ZnO nanoparticles were efficient in preventing ketamine-induced neurotoxicity in the mouse brain. The nanoparticle form of curcumin (Cur-ZnO) required lower doses to produce neuroprotective effects against ketamine-induced toxicity than conventional curcumin.

Silymarin pretreatment protects against ethanol-induced memory impairment: Biochemical and histopathological evidence

BACKGROUND

Ethanol (Eth.) abuse induces memory impairment. Oxidative damage and apoptosis are considered the likely causes of memory impairment. Silymarin (Sil.) is a flavonoid isolated from the plant Silymarin marianum (milk thistle). While studies have reported the neuroprotective effect of Sil. against neurodegenerative processes, the precise mechanism of action of Sil. in Eth.-induced memory impairment remains unclear.

METHODS

Twenty-eight rats were equally divided into four groups: Control (saline 1 ml/rat); Sil. (200 mg/kg for 30 days); Eth. (2 g/kg/day for 30 days); and Sil. + Eth. Behavioral tests including inhibitory avoidance and open field were used to investigate memory and locomotion. Brain antioxidant parameters, including catalase, superoxide dismutase, total antioxidant capacity and total thiol group, plus oxidative parameters, including malondialdehyde and total oxidant status, followed by hippocampal apoptosis (Bax/Bcl2, cleaved caspase) and histopathological changes were evaluated in the groups.

RESULTS

While the administration of Eth. impaired memory, Sil. significantly reversed Eth-induced memory deficits. Eth. administration also augmented brain oxidative and hippocampal apoptosis parameters. In contrast, a marked reduction in brain antioxidant and anti-apoptotic parameters was observed in the Eth. group. At the tissue level, hippocampal sections from Eth.-treated animals revealed severe neuronal damage. The administration of Sil. to Eth.-treated rats remarkably alleviated all the said Eth.-induced biochemical and histopathological effects. On the contrary, Sil. alone did not change the behavior and biochemical/molecular parameters.

CONCLUSION

The memory-enhancing effect of Sil. in Eth.-induced demented rats may be partly mediated by the augmented antioxidant effects and amelioration of apoptotic and histopathological changes.

Mitochondrial dysfunction and type I interferon signaling induce anxiodepressive-like behaviors in mice with neuropathic pain

Clinical evidence indicates that major depression is a common comorbidity of chronic pain, including neuropathic pain; however, the cellular basis for chronic pain-mediated major depression remains unclear. Mitochondrial dysfunction induces neuroinflammation and has been implicated in various neurological diseases, including depression. Nevertheless, the relationship between mitochondrial dysfunction and anxiodepressive-like behaviors in the neuropathic pain state remains unclear. The current study examined whether hippocampal mitochondrial dysfunction and downstream neuroinflammation are involved in anxiodepressive-like behaviors in mice with neuropathic pain, which was induced by partial sciatic nerve ligation (PSNL). At 8 weeks after surgery, there was decreased levels of mitochondrial damage-associated molecular patterns, such as cytochrome c and mitochondrial transcription factor A, and increased level of cytosolic mitochondrial DNA in the contralateral hippocampus, suggesting the development of mitochondrial dysfunction. Type I interferon (IFN) mRNA expression in the hippocampus was also increased at 8 weeks after PSNL surgery. The restoration of mitochondrial function by curcumin blocked the increased cytosolic mitochondrial DNA and type I IFN expression in PSNL mice and improved anxiodepressive-like behaviors. Blockade of type I IFN signaling by anti-IFN alpha/beta receptor 1 antibody also improved anxiodepressive-like behaviors in PSNL mice. Together, these findings suggest that neuropathic pain induces hippocampal mitochondrial dysfunction followed by neuroinflammation, which may contribute to anxiodepressive-behaviors in the neuropathic pain state. Improving mitochondrial dysfunction and inhibiting type I IFN signaling in the hippocampus might be a novel approach to reducing comorbidities associated with neuropathic pain, such as depression and anxiety.

Fisetin provides neuroprotection in pentylenetetrazole-induced cognition impairment by upregulating CREB/BDNF

OBJECTIVES

Fisetin is a flavonoid molecule known to be neuroprotective by its multiple mechanisms. The present study was designed to explore the effect of fisetin in the pentylenetetrazole (PTZ) kindling-induced cognitive dysfunction in mice.

METHODS

Kindling was established by the intraperitoneal administration of PTZ in a subconvulsive dose (25 mg/kg). Mice were administered fisetin (5, 10, and 20 mg/kg, p.o.) to study its probable cognition-enhancing effect. The kindled mice were evaluated for cognition using behavioral tests-elevated plus maze and passive avoidance response. Then, the oxidative stress markers, gene expressions and neurotransmitters levels were estimated in the hippocampus and cortex of mice.

RESULTS

Passive avoidance response and elevated plus maze paradigms showed that fisetin administration improved the cognitive function in kindled mice. The increased levels of lipid peroxidation and protein carbonyl were modulated upon fisetin administration through increasing the levels of antioxidants (reduced glutathione, glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase) in the hippocampus and cortex of kindled mice. Upregulated gene expressions of cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) were observed in the hippocampus and cortex of fisetin-administered mice which play a crucial role in cognitive function. Furthermore, alterations of neurotransmitter levels (dopamine, GABA, and glutamate) and acetylcholinesterase (AchE) were ameliorated by fisetin administration in the hippocampus and cortex of kindled mice.

CONCLUSION

Our findings suggest a therapeutic potential of fisetin against cognitive dysfunction associated with PTZ-induced kindling.

Schizophrenia, Curcumin and Minimizing Side Effects of Antipsychotic Drugs: Possible Mechanisms

Schizophrenia is a mental disorder characterized by episodes of psychosis; major symptoms include hallucinations, delusions, and disorganized thinking. More recent theories focus on particular disorders of interneurons, dysfunctions in the immune system, abnormalities in the formation of myelin, and augmented oxidative stress that lead to alterations in brain structure. Decreased dopaminergic activity and increased phospholipid metabolism in the prefrontal cortex might be involved in schizophrenia. Antipsychotic drugs used to treat schizophrenia have many side effects. Alternative therapy such as curcumin (CUR) can reduce the severity of symptoms without significant side effects. CUR has important therapeutic properties such as antioxidant, anti-mutagenic, anti-inflammatory, and antimicrobial functions and protection of the nervous system. Also, the ability of CUR to pass the blood-brain barrier raises new hopes for neuroprotection. CUR can improve and prevent further probable neurological and behavioral disorders in patients with schizophrenia. It decreases the side effects of neuroleptics and retains lipid homeostasis. CUR increases the level of brain-derived neurotrophic factor and improves hyperkinetic movement disorders. CUR may act as an added counteraction mechanism to retain cell integrity and defense against free radical injury. Thus it appears to have therapeutic potential for improvement of schizophrenia. In this study, we review several properties of CUR and its ability to improve schizophrenia and minimize the side effects of antipsychotic drugs, and we explore the underlying mechanisms by which CUR affects schizophrenia and its symptoms.

Multiple mechanisms of curcumin targeting spinal cord injury

Spinal cord injury (SCI) is an irreversible disease process with a high disability and mortality rate. After primary spinal cord injury, the secondary injury may occur in sequence, which is composed of ischemia and hypoxia, excitotoxicity, calcium overload, oxidative stress and inflammation, resulting in massive death of parenchymal cells in the injured area, followed by the formation of syringomyelia. Effectively curbing the process of secondary injury can promote nerve repair and improve functional prognosis. As the main active ingredient in turmeric, curcumin can play an important role in reducing inflammation and oxidation, protecting the neurons, and ultimately reducing spinal cord injury. This article reviews the effects of curcumin on the repair of nerve injury, with emphasis on the various mechanisms by which curcumin promotes the treatment of spinal cord injury.

Natural Phytochemicals for the Treatment of Major Depressive Disorder: A Mini-Review of Pre- and Clinical Studies

Major Depressive Disorder (MDD) is a common mental illness that causes significant disability and declining quality of life. An overlap of multiple factors can be involved in the pathophysiology of this mood disorder, including increased inflammation and oxidative stress, change in neurotransmitters, decreased brain-derived neurotrophic factor (BDNF), activation of the hypothalamicpituitary- adrenal (HPA) axis, and changes in the microbiota-gut-brain axis. Although the classic treatment for MDD is safe, it is far from ideal, with delay to start the best clinic, side effects, and a large number of non-responses or partial-responses. Therefore, other alternatives are being studied to improve depressive symptoms, and, among them, the role of phytochemicals in food stands out. This mini-review will discuss the main phytochemicals present in foods with clinical and preclinical studies showing benefits for MDD treatment. In addition, the main mechanisms of action that are being proposed for each of these compounds will be addressed.

The Possible Role of Naringenin in the Prevention of Alcohol-Induced Neurochemical and Neurobehavioral Deficits

Chronic alcohol consumption is associated with progressive/irreversible neurodegeneration. However, there is not a clear understanding of its discrete pathophysiology or therapeutic intervention. The present study aimed to investigate the protective effect of the natural citrus flavonoid, naringenin (NAG), against alcohol-induced neurodegeneration in the brain cerebral cortex. Thirty-two male albino rats were randomly divided into four equal groups (eight rats each): control group (I); NAG-treated group (II); alcohol-intoxicated group (III) and alcohol + NAG co-treated group (IV). Brain nuclear factor erythroid 2-related factor 2 and receptor-interacting protein kinase 3 expression were assessed by real-time polymerase chain reaction. NAD(P)H quinone oxidoreductase 1 activity and malondialdehyde, reduced glutathione, mixed lineage kinase-like protein, phosphorylated glycogen synthase kinase 3 beta, and ciliary neurotrophic factor levels were all measured biochemically. B-cell lymphoma 2 expression was assessed by immunohistochemistry. A histopathological examination and neurobehavioral tests were performed. The alcohol-treated group showed a significant increase in oxidative stress and necroptosis biomarkers with a significant reduction in neuroprotective proteins. NAG co-administration effectively ameliorated cognitive dysfunction with an apparent neuroprotective effect by targeting various signaling pathways, including nuclear factor erythroid 2-related factor/NAD(P)H quinone oxidoreductase 1, anti-oxidant capacity, attenuated necroptosis, and upregulated neuroprotective ciliary neurotrophic factor. The study findings suggest NAG as a possible management strategy for alcohol-induced neurodegeneration.

Exploring the Neuroprotective Mechanism of Curcumin Inhibition of Intestinal Inflammation against Parkinson's Disease Based on the Gut-Brain Axis

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease commonly seen in aged people, in which gastrointestinal dysfunction is the most common nonmotor symptom and the activation of the gut-brain axis by intestinal inflammation may contribute to the pathogenesis of PD. In a previous study, curcumin was considered neuroprotective in PD, and this neuroprotective mechanism may act by inhibiting intestinal inflammation. Therefore, the aim of this study was to evaluate the effect of curcumin on motor dysfunction and the loss of dopaminergic neurons in a PD mouse model, induced by N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) using open field test and pole test behavioral assessments and the immunofluorescence and Western blot methods. Moreover, the effects of curcumin on gastrointestinal dysfunction, gastric barrier function, pro-inflammatory cytokines, and the SIRT1/NRF2 pathway in intestinal tissues in a PD mouse model were assessed using fecal parameters and intestinal dynamics, immunofluorescence, ELISA, and Western blot. A motor impairment study of an MPTP-induced mouse group prior to treatment with curcumin had a lower total movement distance and a slow average speed, while there was no statistical difference in the curcumin group. After treatment with curcumin, the total movement distance and average speed improved, the tyrosine hydroxylase (TH) rate in the substantia nigra pars compacta (SNpc) and striatum were reduced, the pyroptosis of AIM2 and caspase-1 activations were inhibited, and intestinal inflammatory factors and intestinal inflammation were reduced. Curcumin improved gastrointestinal disorders and gastrointestinal barrier function in the MPTP-induced mice and reversed MPTP-induced motor dysfunction and dopaminergic neuron loss in mice. The above effects may be partly dependent on curcumin activation of the SIRT1/NRF2 pathway in the colon. This study provides a potential opportunity to develop new preventive measures and novel therapeutic approaches that could target the gut-brain axis in the context of PD and provide a new intervention in the treatment of Parkinson's disease.

The effects of curcumin in learning and memory impairment associated with hypothyroidism in juvenile rats: the role of nitric oxide, oxidative stress, and brain-derived neurotrophic factor

The effect of curcumin (Cur) on cognitive impairment and the possible role of brain tissue oxidative stress, nitric oxide (NO) levels, and brain-derived neurotrophic factor (BDNF) were investigated in juvenile hypothyroid rats. The juvenile rats (21 days old) were allocated into the following groups: (1) control; (2) hypothyroid (0.05% propylthiouracil (PTU) in drinking water); (3-5) hypothyroid-Cur 50, 100, and 150, which in these groups 50, 100, or 150 mg/kg, Cur was orally administered by gavage during 6 weeks. In the hypothyroid rats, the time elapsed and the traveled distance to locate the hidden platform in the learning trials of Morris water maze (MWM) increased, and on the probe day, the amount of time spent in the target quadrant and the distance traveled in there was decreased. Hypothyroidism also decreased the latency and increased the time spent in the darkroom of the passive avoidance (PA) test. Compared with the hypothyroid group, Cur enhanced the performance of the rats in both MWM and PA tests. In addition, Cur reduced malondialdehyde concentration and NO metabolites; however, it increased thiol content as well as the activity of catalase (CAT) and superoxide dismutase enzymes in both the cortex and hippocampus. Cur also increased hippocampal synthesis of BDNF in hypothyroid rats. The beneficial effects of Cur cognitive function in juvenile hypothyroid rats might be attributed to its protective effect against oxidative stress and potentiation of BDNF production.

Biological Potential, Gastrointestinal Digestion, Absorption, and Bioavailability of Algae-Derived Compounds with Neuroprotective Activity: A Comprehensive Review

Currently, there is no known cure for neurodegenerative disease. However, the available therapies aim to manage some of the symptoms of the disease. Human neurodegenerative diseases are a heterogeneous group of illnesses characterized by progressive loss of neuronal cells and nervous system dysfunction related to several mechanisms such as protein aggregation, neuroinflammation, oxidative stress, and neurotransmission dysfunction. Neuroprotective compounds are essential in the prevention and management of neurodegenerative diseases. This review will focus on the neurodegeneration mechanisms and the compounds (proteins, polyunsaturated fatty acids (PUFAs), polysaccharides, carotenoids, phycobiliproteins, phenolic compounds, among others) present in seaweeds that have shown in vivo and in vitro neuroprotective activity. Additionally, it will cover the recent findings on the neuroprotective effects of bioactive compounds from macroalgae, with a focus on their biological potential and possible mechanism of action, including microbiota modulation. Furthermore, gastrointestinal digestion, absorption, and bioavailability will be discussed. Moreover, the clinical trials using seaweed-based drugs or extracts to treat neurodegenerative disorders will be presented, showing the real potential and limitations that a specific metabolite or extract may have as a new therapeutic agent considering the recent approval of a seaweed-based drug to treat Alzheimer’s disease.

Curcumin can improve Parkinson's disease via activating BDNF/PI3k/Akt signaling pathways

Parkinson's disease is a common progressive neurodegenerative disease, and presently has no curative agent. Curcumin, as one of the natural polyphenols, has great potential in neurodegenerative diseases and other different pathological settings. The brain-derived neurotrophic factor (BDNF) and phosphatidylinositol 3 kinase (PI3k)/protein kinase B (Akt) signaling pathways are significantly involved nerve regeneration and anti-apoptotic activities. Currently, relevant studies have confirmed that curcumin has an optimistic impact on neuroprotection via regulating BDNF and PI3k/Akt signaling pathways in neurodegenerative disease. Here, we summarized the relationship between BDNF and PI3k/Akt signaling pathway, the main biological functions and neuroprotective effects of curcumin via activating BDNF and PI3k/Akt signaling pathways in Parkinson's disease. This paper illustrates that curcumin, as a neuroprotective agent, can delay the progression of Parkinson's disease by protecting nerve cells.

The effects of Gum Arabic, curcumin (Curcuma longa) and Garcinia kola on the rat hippocampus after electromagnetic field exposure: A stereological and histological study

The present study was designed to focus on the potential effects of the electromagnetic field (EMF) emitted by mobile phones on hippocampal pyramidal neurons and to investigate the role of curcumin (Cur), Garcinia kola (GK) and Gum Arabic (GA) in reducing these adverse effects. Fifty-four 12-week-old male Wistar albino rats were used. These were randomly divided into nine groups of six rats each. The control, Cur, GK and GA groups were not exposed to EMF, while the sham group was kept in the EMF exposure system without being exposed to EMF. The EMF+Cur, EMF+GK, EMF+GA and EMF groups were exposed to 900 MHz EMF for one hour a day for 28 days. The number of the pyramidal neurons in the cornu ammonis (CA) of the hippocampus was estimated using the optical fractionator technique. Histopathological changes were evaluated under light and electron microscopes. The activities of the superoxide dismutase (SOD) and catalase (CAT) enzymes were also evaluated from serum samples. Significant levels of CAT and SOD activities were observed in the EMF group compared to the control group (p = 0.000; p = 0.001) respectively. Microscopic observations showed that dark-coloured nuclei with unclear neuron boundaries were frequently observed in the EMF group. Stereological data analysis revealed a significant decrease in the CA's total number of pyramidal neurons in the EMF group compared to the control and sham groups (p = 0.000; p = 0.000) respectively. Cur and GK were observed to provide significant protection in the EMF+Cur and EMF+GK groups compared to the EMF group (p = 0.000; p = 0.000) respectively. No significant difference was observed between the EMF+GA group and EMF group (p = 0.989). Exposure to 900 MHz EMF causes severe alterations in the number and structure of hippocampal pyramidal neurons. Cur and GK exhibit a protective effect against these deleterious effects, but GA showed no protective effect.

A review of behavioral methods for the evaluation of cognitive performance in animal models: Current techniques and links to human cognition

INTRODUCTION

Memory is defined as the ability to store, maintain and retrieve information. Learning is the acquisition of information that changes behavior and memory. Stress, dementia, head trauma, amnesia, Alzheimer's, Huntington, Parkinson's, Wernicke-Korsakoff syndrome (WKS) may be mentioned among the diseases in which memory and learning are affected. The task of understanding deficits in memory and learning in humans is daunting due to the complexity of neural and cognitive mechanisms in the nervous system. This job is made more difficult for clinicians and researchers by the fact that many techniques used to research memory are not ethically acceptable or technically feasible for use in humans. Thus, animal models have been necessary alternative for studying normal and disordered learning and memory. This review attempts to bridge these domains to allow biomedical researchers to have a firm grasp of "memory" and "learning" as constructs in humans whereby they may then select the proper animal cognitive test.

RESULTS AND CONCLUSION

Various tests (open field habituation test, Y-maze test, passive avoidance test, step-down inhibitory avoidance test, active avoidance test, 8-arms radial maze test, Morris water maze test, radial arm water maze, novel object recognition test and gait function test) have been designed to evaluate different kinds of memory. Each of these tests has their strengths and limits. Abnormal results obtained using these tasks in non-human animals indicate malfunctions in memory which may be due to several physiological and psychological diseases of nervous system. Further studies by using the discussed tests can be very beneficial for achieving a therapeutic answer to these diseases.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Pharmacological and Molecular Evidence of Neuroprotective Curcumin Effects Against Biochemical and Behavioral Sequels Caused by Methamphetamine: Possible Function of CREB-BDNF Signaling Pathway

INTRODUCTION

The neuroprotective impact of curcumin and the role of CREB (Cyclic AMP Response Element Binding protein)-BDNF (Brain-Derived Neurotrophic Factor) signaling pathway was evaluated in Methamphetamine (METH)-induced neurodegeneration in rats.

METHODS

Sixty adult male rats were randomly divided into 6 groups. While normal saline and 10 mg/kg METH were administered intraperitoneally in groups 1 and 2, groups 3, 4, 5, and 6 received METH (10 mg/kg) and curcumin (10, 20, 40, and 80 mg/kg, respectively) simultaneously. Morris water maze test was administered, and oxidative hippocampal, antioxidant, inflammatory, apoptotic, and CREB and BDNF were assessed.

RESULTS

We found that METH disturbs learning and memory. Concurrent curcumin therapy (40 and 80 mg/kg) decreased cognitive disturbance caused by METH. Multiple parameters, such as lipid peroxidation, the oxidized form of glutathione, interleukin 1 beta, tumor necrosis factor-alpha, and Bax were increased by METH therapy, while the reduced type of glutathione, Bcl-2, P-CREB, and BDNF concentrations in the hippocampus were decreased.

CONCLUSION

Different doses of curcumin adversely attenuated METH-induced apoptosis, oxidative stress, and inflammation but enhanced the concentrations of P-CREB and BDNF. The neuroprotection caused by curcumin against METH-induced neurodegeneration is mediated through P-CREB-BDNF signaling pathway activation.

Dichloroacetic acid-induced dysfunction in rat hippocampus and the protective effect of curcumin

The present study was designed to evaluate the role of cAMP-PKA-CREB signaling in mediating the neuroprotective effects of curcumin against DCAA-induced oxidative stress, inflammation and impaired synaptic plasticity in rats. Sixty Sprague-Dawley rats were randomly divided into five groups, and we assessed the histomorphological, behavioral and biochemical characteristics to investigate the beneficial effects of different concentrations of curcumin against DCAA-induced neurotoxicity in rat hippocampus. The results indicated that animal weight gain and food consumption were not significantly affected by DCAA. However, behavioral tests, including morris water maze and shuttle box, showed varying degrees of alterations. Additionally, we found significant changes in hippocampal neurons by histomorphological observation. DCAA exposure could increase lipid peroxidation, reactive oxygen species (ROS), inflammation factors while reducing superoxide dismutase (SOD) activity and glutathione (GSH) level accompanied by DNA damage in the hippocampus. Furthermore, we found that DCAA exposure could cause a differential modulation of mRNA and proteins (cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), cAMP-response element-binding protein (CREB), p-CREB, brain-derived neurotrophic factor (BDNF), postsynaptic density-95 (PSD-95), synaptophysin (SYP)). Conversely, various doses of curcumin attenuated DCAA-induced oxidative stress, inflammation response and impaired synaptic plasticity, while elevating cAMP, PKA, p-CREB, BDNF, PSD-95, SYP levels. Thus, curcumin could activate the cAMP-PKA-CREB signaling pathway, conferring neuroprotection against DCAA-induced neurotoxicity.

Transferrin-functionalized lipid nanoparticles for curcumin brain delivery

Curcumin is an anti-inflammatory and antioxidant compound with potent neuroprotective activity. Due to its poor water solubility, low bioavailability, rapid elimination and the challenges for crossing and transposing the blood-brain barrier (BBB), solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) loaded with curcumin were successfully produced and functionalized with transferrin, in order to mediate the transport of these particles through the BBB endothelium to the brain. The nanosystems revealed Z-averages under 200 nm, polydispersity index below 0.2 and zeta potential around -30 mV. Curcumin encapsulation around 65 % for SLNs and 80 % for NLCs was accomplished, while the functionalized nanoparticles presented a value around 70-75 %. A stability study revealed these characteristics remained unchanged for at least 3 months. hCMEC/D3 cells viability was firstly analysed by MTT and LDH assays, respectively, and a concentration of 10 μM of curcumin-loaded nanoparticles were then selected for the subsequent permeability assay. The permeability study was conducted using transwell devices with hCMEC/D3 cells monolayers and a 1.5-fold higher permeation of curcumin through the BBB was verified. Both SLNs and NLCs are promising for curcumin brain delivery, protecting the incorporated curcumin and targeting to the brain by the addition of transferrin to the nanoparticles surface.

The possible role of CREB-BDNF signaling pathway in neuroprotective effects of minocycline against alcohol-induced neurodegeneration: molecular and behavioral evidences

Abuse of alcohol triggers neurodegeneration in human brain. Minocycline has characteristics conferring neuroprotection. Current study evaluates the role of the CREB-BDNF signaling pathway in mediating minocycline's neuroprotective effects against alcohol-induced neurodegeneration. Seventy adult male rats were randomly split into groups 1 and 2 that received saline and alcohol (2 g/kg/day by gavage, once daily), respectively, and groups 3, 4, 5, and 6 were treated simultaneously with alcohol and minocycline (10, 20, 30 and 40 mg/kg I.P, respectively) for 21 days. Group 7 received minocycline alone (40 mg/kg, i.p) for 21 days. Morris water maze (MWM) has been used to assess cognitive activity. Hippocampal neurodegenerative and histological parameters as well as cyclic AMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) levels were assessed. Alcohol impaired cognition, and concurrent therapy with various minocycline doses attenuated alcohol-induced cognition disturbances. Additionally, alcohol administration boosted lipid peroxidation and levels of glutathione in oxidized form (GSSG), tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and Bax protein, while decreased reducing type of glutathione (GSH), Bcl-2 protein, phosphorylated CREB, and BDNF levels in rat hippocampus. Alcohol also decreased the activity in the hippocampus of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR). In comparison, minocycline attenuated alcohol-induced neurodegeneration; elevating expression levels of P-CREB and BDNF and inhibited alcohol induced histopathological changes in both dentate gyrus (DG) and CA1 of hippocampus. Thus, minocycline is likely to provide neuroprotection against alcohol-induced neurodegeneration through mediation of the P-CREB/BDNF signaling pathway.

Curcumin Can be Acts as Effective agent for Prevent or Treatment of Alcohol-induced Toxicity in Hepatocytes: An Illustrated Mechanistic Review

Previous studies have shown that alcohol abuse can cause serious liver damage and cirrhosis. The main pathway for these types of hepatocellular cell neurodegeneration is mitochondrial dysfunction, which causes lipid peroxidation and dysfunction of the glutathione ring and the defect of antioxidant enzymes in alcoholic hepatic cells. Alcohol can also initiate malicious inflammatory pathways and trigger the initiation and activation of intestinal and extrinsic apoptosis pathways in hepatocellular tissues that lead to cirrhosis. Previous studies have shown that curcumin may inhibit lipid peroxidation, glutathione dysfunction and restore antioxidant enzymes. Curcumin also modulates inflammation and the production of alcohol-induced biomarkers. Curcumin has been shown to play a critical role in the survival of alcoholic hepatocellular tissue. It has been shown that curcumin can induce and trigger mitochondrial biogenesis and, by this mechanism, prevent the occurrence of both intrinsic and extrinsic apoptosis pathways in liver cells that have been impaired by alcohol. According to this mechanism, curcumin may protect hepatocellular tissue from alcohol-induced cell degeneration and may therefore survive alcoholic hepatocellular tissue. . Based on these mechanisms, the protective functions of curcumin against alcohol-induced cell degeneration due to oxidative stress, inflammation, and apoptosis events in hepatocellular tissue have been recorded. Hence, in this research, we have attempted to evaluate and analyze the main contribution mechanism of curcumin cell defense properties against alcohol-induced hepatocellular damage, according to previous experimental and clinical studies, and in this way we report findings from major studies.

Natural Products for the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases are a heterogeneous group of disorders characterized by the progressive degeneration of the structure and function of the central nervous system or peripheral nervous system. Alzheimer's Disease (AD), Parkinson's Disease (PD) and Spinal Cord Injury (SCI) are the common neurodegenerative diseases, which typically occur in people over the age of 60. With the rapid development of an aged society, over 60 million people worldwide are suffering from these uncurable diseases. Therefore, the search for new drugs and therapeutic methods has become an increasingly important research topic. Natural products especially those from the Traditional Chinese Medicines (TCMs), are the most important sources of drugs, and have received extensive interest among pharmacist. In this review, in order to facilitate further chemical modification of those useful natural products by pharmacists, we will bring together recent studies in single natural compound from TCMs with neuroprotective effect.

Neuroprotective Effects of Curcumin-Loaded Emulsomes in a Laser Axotomy-Induced CNS Injury Model

PURPOSE

Curcumin, a polyphenol isolated from the rhizomes of turmeric, holds great potential as a neuroprotective agent in addition to its anti-inflammatory and antioxidant characteristics. The poor bioavailability and low stability of curcumin are the greatest barriers to its clinical use. This study aims to investigate the neuroprotective effect of curcumin on axonal injury, by delivering the lipophilic polyphenol to a primary hippocampal neuron culture by means of a lipid-based drug delivery system, named emulsomes.

METHODS

To study neuroregeneration ex vivo, an injury model was established through single-cell laser axotomy on hippocampal neurites. Upon treatment with curcumin-loaded emulsomes (CurcuEmulsomes), curcumin and CurcuEmulsome uptake into neurons was verified by three-dimensional Z-stack images acquired with confocal microscopy. Neuron survival after axonal injury was tracked by propidium iodide (PI) and Hoechst staining. Alterations in expression levels of physiological markers, such as anti-apoptotic marker Bcl2, apoptotic marker cleaved caspase 3, neuroprotective marker Wnt3a and the neuronal survival marker mTOR, were investigated by immunocytochemistry analyses.

RESULTS

The results indicated significant improvement in the survival rate of injured neurons upon CurcuEmulsome treatment. Bcl2 expression was significantly higher for injured neurons treated with curcumin or CurcuEmulsome. Reduction in caspase 3 expression was seen in both curcumin and CurcuEmulsome treatment, whereas there were no significant changes in Wnt3a and mTOR expression.

CONCLUSION

The established laser-axotomy model was proven as a reliable methodology to study neurodegenerative models ex vivo. CurcuEmulsomes delivered curcumin to primary hippocampal neurons successfully. Treated with CurcuEmulsomes, injured hippocampal neurons benefit from the neuroprotective effects of curcumin, exhibiting a higher survival rate and increased anti-apoptotic marker levels.

Modulatory effect of simvastatin on redox status, caspase-3 expression, p-protein kinase B (p-Akt), and brain-derived neurotrophic factor (BDNF) in an ethanol-induced neurodegeneration model

Neurodegenerative diseases are a common cause of morbidity and mortality worldwide, with oxidative stress, inflammation, and protein aggregation representing the main underlying mechanisms that ultimately lead to cell death. Ethanol has shown strong neurodegenerative consequences in experimental animal brains. Statins are a class of lipid-lowering drugs with many pleotropic effects. Therefore, the aim of the present study was to explore the modulatory effect of simvastatin (10 mg·kg^-1·day^-1) before and after the development of neurodegeneration (for 55 and 25 days, respectively) on redox state, caspase-3 expression, p-protein kinase B (p-Akt), and brain-derived neurotrophic factor (BDNF) in ethanol-induced (15% ethanol solution for 55 days) neurodegeneration. Seventy female Albino Swiss mice were included and randomly divided into five groups: C, control group; E, ethanol group; ES, group treated with simvastatin from the first day of ethanol intake; E + S, group treated with simvastatin after neurodegeneration development; and S, simvastatin group. Administration of simvastatin from the first day improved the biochemical changes, suppressed apoptosis, and induced autophagy and neurogenesis; however, its administration after the development of neurodegeneration resulted in partial improvement. The histopathological findings confirmed the biochemical changes. In conclusion, simvastatin has a neuroprotective effect against the development of ethanol-induced neurodegeneration and its progression.

Obstacles against the Marketing of Curcumin as a Drug

Among the extensive public and scientific interest in the use of phytochemicals to prevent or treat human diseases in recent years, natural compounds have been highly investigated to elucidate their therapeutic effect on chronic human diseases including cancer, cardiovascular disease, and neurodegenerative disease. Curcumin, an active principle of the perennial herb Curcuma longa, has attracted an increasing research interest over the last half-century due to its diversity of molecular targets, including transcription factors, enzymes, protein kinases, growth factors, inflammatory cytokines, receptors, and it's interesting pharmacological activities. Despite that, the clinical effectiveness of the native curcumin is weak, owing to its low bioavailability and rapid metabolism. Preclinical data obtained from animal models and phase I clinical studies done in human volunteers confirmed a small amount of intestinal absorption, hepatic first pass effect, and some degree of intestinal metabolism, might explain its poor systemic availability when it is given via the oral route. During the last decade, researchers have attempted with new pharmaceutical methods such as nanoparticles, liposomes, micelles, solid dispersions, emulsions, and microspheres to improve the bioavailability of curcumin. As a result, a significant number of bioavailable curcumin-based formulations were introduced with a varying range of enhanced bioavailability. This manuscript critically reviews the available scientific evidence on the basic and clinical effects and molecular targets of curcumin. We also discuss its pharmacokinetic and problems for marketing curcumin as a drug.

Boosting the autophagy-lysosomal pathway by phytochemicals: A potential therapeutic strategy against Alzheimer's disease

The lysosome is a membrane-enclosed organelle in eukaryotic cells, which has basic pattern recognition for nutrient-dependent signal transduction. In Alzheimer's disease, the already declining autophagy-lysosomal function is exacerbated by an increased need for clearance of damaged proteins and organelles in aged cells. Recent evidence suggests that numerous diseases are linked to impaired autophagy upstream of lysosomes. In this way, a comprehensive survey on the pathophysiology of the disease seems necessary. Hence, in the first section of this review, we will discuss the ultimate findings in lysosomal signaling functions and how they affect cellular metabolism and trafficking under neurodegenerative conditions, specifically Alzheimer's disease. In the second section, we focus on how natural products and their derivatives are involved in the regulation of inflammation and lysosomal dysfunction pathways, including how these should be considered a crucial target for Alzheimer's disease therapeutics.

Curcumin and Baicalin ameliorate ethanol-induced liver oxidative damage via the Nrf2/HO-1 pathway

One of the key mechanisms of alcoholic liver disease is oxidative stress. Both Curcumin and Baicalin exert antioxidant effects, but the mechanism of their combined effects of ethanol-induced liver injury is still unclear. This study was conducted to evaluate the dual antioxidant activity of Curcumin combined with Baicalin against ethanol-induced liver injury in rats. Rats were divided into five groups, a control, ethanol, ethanol + Curcumin (50 mg/kg), ethanol + Baicalin (50 mg/kg), and ethanol + Curcumin +Baicalin group with ten rats per group. The effects of ethanol on liver enzymes, oxidative stress indicators and the levels of Nrf2/HO-1 pathway related proteins and mRNA were observed along with liver histopathology in rats. Our results found that the serum ALT and AKP levels were increased in ethanol-treated rats, which also showed a rising trend of 8-OHdG and LPO levels while hydroxyl radical scavenging ability, T-AOC, and the activities of SOD and GSH-Px were decreased in liver. The mRNA levels of Nrf2 and HO-1, the ratio of p-Nrf2/Nrf2, the protein level of HO-1 were decreased while NQO1 mRNA level, Nrf2, p-Nrf2, and NQO1 protein levels were increased in ethanol-treated rats. Combination treatment of Curcumin and Baicalin significantly reversed the ethanol-induced liver oxidative damage and further activate the Nrf2/HO-1 pathway, which was more effective than each drug alone. In conclusion, evidence has shown for the first time in this study that Curcumin combined with Baicalin ameliorated ethanol-induced liver oxidative damage in rats and revealed liver-protection. PRACTICAL APPLICATIONS: Many drugs for treating alcoholic liver disease are available commercially, but some adverse effects they have may cause secondary damage to the liver. At present, the combined treatment of different natural phytochemicals has attracted special attention in modern medicine. Curcumin, a kind of phytochemicals, is extracted from turmeric rhizome. Baicalin is one of the major active components of Scutellaria Baicalensis. The current research is to explore the antioxidant effect of Curcumin and Baicalin in ethanol-induced liver injury in rats. Our research proves that Curcumin combined with Baicalin on ethanol-induced liver oxidative damage is superior to single drug treatment. Therefore, the combination of Curcumin and Baicalin may provide a more prospective natural remedy to combat ethanol-induced liver injury.

Selegiline acts as neuroprotective agent against methamphetamine-prompted mood and cognitive related behavior and neurotoxicity in rats: Involvement of CREB/BDNF and Akt/GSK3 signal pathways

Objective(s):

Present study investigated the neuroprotective effects of selegiline and the molecular mechanisms involved in methamphetamine-induced neurotoxicity.

Materials and Methods:

Male wistar rats were randomly divided into six groups (10 rats in each group). Group 1 and group 2 received normal saline and methamphetamine (10 mg/kg), respectively. Groups 3, 4, 5 and 6 were treated simultaneously with methamphetamine and selegiline. From day 22 to day 28, forced swim test, elevated plus maze, and open field test were conducted to assess mood (anxiety and depression) levels, and from day 17 to day 21, Morris Water Maze was conducted for cognition assessment. On day 29, hippocampus of the animals were isolated and evaluated by ELISA method for oxidative, antioxidant, and inflammatory factors and expression levels of active (total) and inactive (phosphorylated) forms of cyclic AMP response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), Akt (Protein Kinase B) and glycogen synthase kinase 3 (GSK3) proteins.

Results:

Selegiline reduced behavioral impacts caused by methamphetamine in all doses. Methamphetamine administration may improve malondialdehyde, tumor necrosis factor-alpha, interleukin-1 beta and GSK3 (both forms). Moreover, methamphetamine reduced the activity of superoxide dismutase, glutathione peroxidase, glutathione reductase, amount of BDNF, CREB and Akt (both forms).

Conclusion:

Current research showed that selegiline can protect the brain from methamphetamine-prompted neurodegeneration, and this could be intervened by CREB -BDNF or Akt-GSK3 signaling pathways.

The Modulatory Effect of Metformin on Ethanol-Induced Anxiety, Redox Imbalance, and Extracellular Matrix Levels in the Brains of Wistar Rats

The study investigated the potential neuroprotective effects of metformin (MET) on alcohol-induced neurotoxicity in adult Wistar rats. The animals were randomized in four groups (n = 10): control, alcohol (ALC), ALC + MET, and MET. ALC (2 g/kg b.w.) and MET (200 mg/kg b.w.) were orally administered for 21 days, once daily. For the ALC + MET group, MET was administered 2 h after ALC treatment. On day 22, the open field test (OFT) and elevated plus maze (EPM) were performed. MET improved global activity and increased the time spent in unprotected open arms, decreased oxidative stress, both in the frontal lobe and in the hippocampus, and increased neuroglobin expression in the frontal cortex. Histopathologically, an increased neurosecretory activity in the frontal cortex in the ALC + MET group was noticed. Thus, our findings suggest that metformin has antioxidant and anxiolytic effects and may partially reverse the neurotoxic effects induced by ethanol.

Molecular, histological and behavioral evidences for neuroprotective effects of minocycline against nicotine-induced neurodegeneration and cognition impairment: Possible role of CREB-BDNF signaling pathway

AIM

Neurodegeneration is one of the serious adverse effects of stimulant agents such as nicotine. Minocycline possess established neuroprotective properties. The role of CREB-BDNF signaling pathway in mediating the neuroprotective effects of minocycline against nicotine-induced neurodegeneration in rats was evaluated in current study.

METHODS

Seventy adult male rats were divided randomly into seven groups. Group 1 and 2, received 0.7 ml/rat of normal saline (i.p) and nicotine (10 mg/kg, s.c) respectively. Groups 3, 4, 5 and 6, treated concurrently with nicotine (10 mg/kg) and minocycline (10, 20, 30 and 40 mg/kg, i.p, respectively) for 21 days. Group 7 received minocycline alone (40 mg/kg, i.p) for 21 days. From 17th to 21 st days of experiment, Morris water maze (MWM) was used to evaluate learning and spatial memory in rats treated in different groups. According to the critical role of hippocampus in cognitive behavior, hippocampal neurodegenerative parameters (oxidative stress and inflammatory biomarkers) and also cyclic AMP response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) levels were evaluated in isolated hippocampus in day 22 of experiment and after drug treatment. Also hippocampal cell density and tissue changes were evaluated by hematoxylin and eosin staining.

RESULT

Nicotine administration impaired the learning and spatial memory in rats and simultaneous treatment with various doses of minocycline attenuated the nicotine-induced cognition disturbances. In addition, nicotine treatment increased lipid peroxidation and the levels of oxidized form of glutathione (GSSG), interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), and Bax protein, while decreasing reduced form of glutathione (GSH), Bcl-2 protein, P-CREB and BDNF levels in the hippocampus of experimental animals. Nicotine also reduced the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) in the hippocampus. Minocycline attenuated nicotine-induced neurodegeneration and elevating CREB (both forms) and BDNF levels. Also minocycline treatment alone increases the cognitive activity and increased CREB (both forms) and BDNF levels and decreased oxidative stress, inflammation and apoptotic biomarkers. Minocycline at high doses cause inhibition of nicotine induced cell density and changes in both area of dentate gyrus (DG) and CA1 in hippocampus.

CONCLUSION

It can be concluded that minocycline, probably through activation of P-CREB/BDNF signaling pathway, confers neuroprotection against nicotine-induced neurodegeneration in rat hippocampus.

Effects of curcumin on mitochondria in neurodegenerative diseases

Neurodegenerative diseases (NDs) result from progressive deterioration of selectively susceptible neuron populations in different central nervous system (CNS) regions. NDs are classified in accordance with the primary clinical manifestations (e.g., parkinsonism, dementia, or motor neuron disease), the anatomic basis of neurodegeneration (e.g., frontotemporal degenerations, extrapyramidal disorders, or spinocerebellar degenerations), and fundamental molecular abnormalities (e.g., mutations, mitochondrial dysfunction, and its related molecular alterations). NDs include the Alzheimer disease and Parkinson disease, among others. There is a growing evidence that mitochondrial dysfunction and its related mutations in the form of oxidative/nitrosative stress and neurotoxic compounds play major roles in the pathogenesis of various NDs. Curcumin, a polyphenol and nontoxic compound, obtained from turmeric, has been shown to have a therapeutic beneficial effect in various disorders especially on the CNS cells. It has been shown that curcumin has considerable neuro- and mitochondria-protective properties against broad-spectrum neurotoxic compounds and diseases/injury-associating NDs. In this article, we have reviewed the various effects of curcumin on mitochondrial dysfunction in NDs.

Pharmacological Evidences for Curcumin Neuroprotective Effects against Lead-Induced Neurodegeneration: Possible Role of Akt/GSK3 Signaling Pathway

One of main herbal compounds with neuroprotective effects is curcumin. Lead poisoning cause neurodegeneration effect but its clear mechanism remains unknown. The current study evaluates the role of Akt/GSK3 signaling pathway in mediating the neuroprotective effects of curcumin against lead -induced neurodegeneration in rats. Sixty adult male rats were divided to: Group 1 and 2 receiving normal saline and drinking water containing 0.075% of lead acetate. Groups 3, 4, 5, and 6 were treated concurrently with lead acetate (0.075% in drinking water) and Curcumin (10, 20, 40, and 80 mg/kg I.P, respectively). Morris water maze (MWM) was used to evaluate cognitive activity, Hippocampal oxidative, anti-oxidant, as well as inflammatory and apoptotic factors and also Akt and GSK3 protein levels were studied. We found that lead poisoning disturbed the learning and memory and simultaneous treatment with Curcumin reduced the lead -induced cognition disturbances. In addition, lead acetate treatment increased lipid peroxidation and the levels of IL-1β, TNF-α , Bax, GSK3 (total and phosphorylated) while reducing reduced form of GSH, Bcl-2, and Akt3 (total and phosphorylated) levels in the hippocampus. Lead also reduced the activity of SOD, GPx, and GR in the hippocampus. In contrast, various doses of Curcumin attenuated lead -induced apoptosis, oxidative stress and inflammation; while elevating P-Akt and reduced of GSK3 levels. Thus, Curcumin via mediation of Akt/GSK3 signaling pathway confers neuroprotection against lead-induced neurodegeneration in hippocampus.

Naturally Derived Polyphenols Protect Against Corticosterone-Induced Changes in Primary Cortical Neurons

BACKGROUND

Polyphenols are phytochemicals that have been associated with therapeutic effects in stress-related disorders. Indeed, studies suggest that polyphenols exert significant neuroprotection against multiple neuronal injuries, including oxidative stress and neuroinflammation, but the mechanisms are unclear. Evidence indicates that polyphenol neuroprotection may be mediated by activation of Nrf2, a transcription factor associated with antioxidant and cell survival responses. On the other hand, in stress-linked disorders, Fkbp5 is a novel molecular target for treatment because of its capacity to regulate glucocorticoid receptor sensitivity. However, it is not clear the role Fkbp5 plays in polyphenol-mediated stress modulation. In this study, the neuroprotective effects and mechanisms of the naturally derived polyphenols xanthohumol and quercetin against cytotoxicity induced by corticosterone were investigated in primary cortical cells.

METHODS

Primary cortical cells containing both neurons and astrocytes were pre-incubated with different concentrations of quercetin and xanthohumol to examine the neuroprotective effects of polyphenols on cell viability, morphology, and gene expression following corticosterone insult.

RESULTS

Both polyphenols tested prevented the reduction of cell viability and alterations of neuronal/astrocytic numbers due to corticosterone exposure. Basal levels of Bdnf mRNA were also decreased after corticosterone insult; however, this was reversed by both polyphenol treatments. Interestingly, the Nrf2 inhibitor blocked xanthohumol but not quercetin-mediated neuroprotection. In contrast, we found that Fkbp5 expression is exclusively modulated by quercetin.

CONCLUSIONS

These results suggest that naturally derived polyphenols protect cortical cells against corticosterone-induced cytotoxicity and enhance cell survival via modulation of the Nrf2 pathway and expression of Fkbp5.

Preventive Effects of Duloxetine Against Methamphetamine Induced Neurodegeneration and Motor Activity Disorder in Rat: Possible Role of CREB/BDNF Signaling Pathway

Background:

The neuroprotective effects of duloxetine and neurodegenerative effects of methamphetamine have been shown in previous studies, but their exact mechanism remain unclear. In the current study it involved molecular mechanisms of neuroprotective effects of duloxetine against methamphetamine induced neurodegeneration were clarified.

Methods:

About 40 adult male rats randomly were divided to 5 groups. Group 1 and 2, as control and methamphetamine treated, received normal saline and methamphetamine (10 mg/kg) respectively. Groups 3, 4 and 5 concurrently treated with methamphetamine and duloxetine at doses of 10, 20 and 30 mg/kg respectively. All treatments were undertaken for 21 days. On day 22 Open Field Test (OFT) were used to examine the level of motor activity disturbance and anxiety in animals. After that hippocampus was isolated from each rat and oxidative, antioxidant, inflammatory factors and also level or expression of total and phosphorylated forms of CREB and P-CREB and BDNF proteins were measured.

Results:

Duloxetine in all mentioned doses could inhibit the effects of methamphetamine induced motor activity disturbance in MWM. Chronic abuse of methamphetamine could increase malondialdehyde (MDA), tumor necrosis factor-Alpha (TNF-α) and interleukine-1beta (IL-1β) while caused decreases in superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities and decreased CREB (both forms) and BDNF proteins, while duloxetine could prevent these malicious effects of methamphetamine.

Conclusions:

We conclude that P-CREB/BDNF signaling pathways might have critical role in duloxetine neuroprotective effects against methamphetamine induced neurodegeneration.

Participation of cAMP/PKA-Mediated Signaling Pathways in Functional Activity of Regeneration-Competent Cells in the Nervous Tissue under Conditions of Ethanol-Induced Neurodegeneration

We studied the involvement of cAMP/PKA signaling in the realization of the growth potential of neural progenitors and secretion of neurotrophic growth factors by glial elements under conditions of ethanol-induced neurodegeneration in vitro and in vivo. The stimulating role of cAMP and PKA in cell cycle progression of the neural progenitor cells and in production of neurotrophins by the cells in nervous tissue under the optimal conditions to vital activity was demonstrated. Ethanol inverted the role of cAMP/PKA signaling pathways in determination of the proliferation-differentiation status of neural stem cells. Selective blockade of adenylate cyclase or PKA in neural stem cells increased the rate of their division against the background of relative decrease in differentiation rate. In addition, cAMP/PKA signaling does not longer participate in neurotrophin production by glial cells in neurodegeneration. These findings suggest that inhibitors of activity/expression of adenylate cyclase and PKA can be considered as possible drugs with regenerative activity for the treatment of nervous system pathologies provoked by alcohol.

The Therapeutic Effect of Curcumin in Quinolinic Acid-Induced Neurotoxicity in Rats is Associated with BDNF, ERK1/2, Nrf2, and Antioxidant Enzymes

In the present study we investigated the participation of brain-derived neurotropic factor (BDNF) on the activation of the mitogen activated protein kinase (MAPK) protein extracellular signal-regulated kinase-1/2 (ERK1/2) as a mechanism of curcumin (CUR) to provide an antioxidant defense system mediated by the nuclear factor erythroid 2-related factor 2 (Nrf2) in the neurotoxic model induced by quinolinic acid (QUIN). Wistar rats received CUR (400 mg/kg, intragastrically) for 6 days after intrastriatal injection with QUIN (240 nmol). CUR improved the motor deficit and morphological alterations induced by QUIN and restored BDNF, ERK1/2, and Nrf2 levels. CUR treatment avoided the decrease in the protein levels of glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamylcysteine ligase (γ-GCL), and glutathione (GSH) levels. Only, the QUIN-induced decrease in the GR activity was prevented by CUR treatment. Finally, QUIN increased superoxide dismutase 2 (SOD2) and catalase (CAT) levels, and the γGCL and CAT activities; however, this increase was major in the QUIN+CUR group for γ-GCL, CAT, and SOD activities. These data suggest that the therapeutic effect of CUR could involve BDNF action on the activation of ERK1/2 to induce increased levels of protein and enzyme activity of antioxidant proteins regulated by Nrf2 and GSH levels.

Lipid peroxidation in neurodegeneration

Neurodegenerative diseases have great social and economic impact and cause millions of deaths every year. The potential molecular mechanisms in these pathologies have been widely studied and implicate lipid peroxidation as an important factor in the development of neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's diseases. Data indicates that pathologic mechanisms specifically involve ferroptosis and mitochondrial dysfunction. Here we review the molecular mechanisms related to the lipid peroxidation that involve the development of neurodegeneration, as well as the utility of some biomarkers in diagnosis, prognosis and evaluation of new therapies for neurodegenerative diseases.

Protective role of metformin against methamphetamine induced anxiety, depression, cognition impairment and neurodegeneration in rat: The role of CREB/BDNF and Akt/GSK3 signaling pathways

BACKGROUND

Methamphetamine is a neuro-stimulant with neurodegenerative effects, and ambiguous mechanism of action. Metformin is an antidiabetic agent with neuroprotective properties but not fully understood mechanisms. The present study investigated the molecular basis of metformin neuroprotection against methamphetamine-induced neurodegeneration.

BRIEF METHOD

Sixty adult male rats were randomly divided into six groups: group 1 (received normal saline), group 2 (received 10 mg/kg of methamphetamine) and groups 3, 4, 5 and 6 [received methamphetamine (10 mg/kg) plus metformin (50, 75, 100 and 150 mg/kg) respectively]. Elevated Plus Maze (EPM), Open Field Test (OFT), Forced Swim Test (FST), Tail Suspension Test (TST) and Morris Water Maze (MWM) were used to assess the level of anxiety, depression and cognition in experimental animals. Also animals' hippocampus were isolated and oxidative stress and inflammatory parameters and expression of total and phosphorylated forms of cAMP response element binding (CREB), brain-derived neurotrophic factor (BDNF), protein kinase B (Akt) and glycogen synthase kinase 3 (GSK3) proteins were evaluated by ELISA method.

RESULTS

According to the data obtained, methamphetamine caused significant depression, anxiety, motor activity disturbances and cognition impairment in experimental animals. Metformin, in all used doses, decreased methamphetamine induced behavioral disturbances. Also chronic administration of methamphetamine could increase malondialdehyde (MDA), tumor necrosis factor-Alpha (TNF-α) and interleukine-1 beta (IL-1β) in rats, while caused reduction of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities. Metformin, especially in high doses, could prevent these malicious effects of methamphetamine. Also Metformin could activate CREB (both forms), BDNF and Akt (both forms) proteins' expression and inhibited GSK3 (both forms) protein expression in methamphetamine treated rats.

SIGNIFICANCE

According to obtained data, metformin could protect the brain against methamphetamine-induced neurodegeneration probably by mediation of CREB/BDNF or Akt/GSK3 signaling pathways. These data suggested that CREB/BDNF or Akt/GSK3 signaling pathways may have a critical role in methamphetamine induced neurotoxicity and/or neuroprotective effects of metformin.

Possible Role of Cyclic AMP Response Element Binding/Brain-Derived Neurotrophic Factor Signaling Pathway in Mediating the Pharmacological Effects of Duloxetine against Methamphetamine Use-Induced Cognitive Impairment and Withdrawal-Induced Anxiety and Depression in Rats

Background:

Duloxetine is used for treating depression and anxiety. The current study evaluated the effects of duloxetine against methamphetamine withdrawal-induced anxiety, depression, and motor disturbances and methamphetamine use-induced cognitive impairments.

Materials and Methods:

Ninety-six adult male rats were used for two independent experiments. Each experiment consisted of Groups 1 and 2 which received normal saline (0.2 ml/rat) and methamphetamine (10 mg/kg) respectively, Groups 3, 4, and 5 received both methamphetamine and duloxetine at doses of 5, 10, and 15 mg/kg, respectively. Groups 6, 7, and 8 received 5, 10, and 15 mg/kg of duloxetine, respectively. All administrations were performed for 21 days. In experiment 1, elevated plus maze (EPM), open-field test (OFT), forced swim test (FST), and tail suspension test (TST) were used to examine anxiety and depression in animals during withdrawal period. In experiment 2, Morris water maze (MWM) test was used to assess the effect of methamphetamine use followed by duloxetine treatment, on learning and memory. In the experiments, the expression of cyclic AMP response element binding (CREB) and brain-derived neurotrophic factor (BDNF) proteins were evaluated using enzyme-linked immunosorbent assay.

Results:

In the first experiment, duloxetine at all doses attenuated methamphetamine withdrawal induced-depression, anxiety, and motor disturbances in FST, OFT, EPM, and TST. In the second experiment, duloxetine at all doses attenuated methamphetamine use-induced cognitive impairment in MWM. In both experiments, duloxetine activated cAMP, CREB, and BDNF proteins’ expression in methamphetamine-treated rats.

Conclusions:

Duloxetine can protect the brain against methamphetamine withdrawal-induced mood and motor disturbances and can also inhibit methamphetamine-induced cognitive impairment, possibly via cAMP/CREB/BDNF signaling pathway.

Neuroprotective Effects of Forced Exercise and Bupropion on Chronic Methamphetamine-induced Cognitive Impairment via Modulation of cAMP Response Element-binding Protein/Brain-derived Neurotrophic Factor Signaling Pathway, Oxidative Stress, and Inflammatory Biomarkers in Rats

Background

Forced exercise can act as non-pharmacologic neuroprotective agent. In current study, we tried the involved molecular mechanisms of protective effects of forced exercise against methamphetamine induced neurodegeneration.

Materials and Methods

Forty adult male rats were divided to Group 1 and 2 which received normal saline and methamphetamine (10 mg/kg) respectively for 30 days. Groups 3, 4 and 5 were treated with methamphetamine for first 15 days and then were treated by forced exercise, bupropion (20 mg/kg/day) or combination of them for the following 15 days. Between 26^th and 30^th days, Morris Water Maze (MWM) was used to evaluate the cognition. On day 31, hippocampus was isolated from each rat and oxidative, antioxidant and inflammatory factors also the level of total and phosphorylated forms of cAMP response element-binding protein (CREB) and brain derived neurotrophic factor (BDNF) proteins were also evaluated.

Results

Chronic abuse of methamphetamine could decreases cognition and increase malondialdehyde (MDA), Tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), while caused decreases in superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities all these changes was significant (P < 0.001) in compared to control group while treatment with bupropion, forced exercise and bupropion in combination with forced exercise could prevent all these malicious effects of methamphetamine (P < 0.001). Bupropion, forced exercise and bupropion in combination with forced exercise could activate CREB (both forms) and activates BDNF proteins' expression with P < 0.001 in methamphetamine treated rats.

Conclusions

P-CREB/BDNF signaling pathways might have critical role in forced exercise protective effects against methamphetamine induced neurodegeneration.

Mechanistic insights of hepatoprotective effects of curcumin: Therapeutic updates and future prospects

The liver is the most essential organ of the body performing vital functions. Hepatic disorders affect the physiological and biochemical functions of the body. These disorders include hepatitis B, hepatitis C, alcoholic liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), liver cirrhosis, hepatic failure and hepatocellular carcinoma (HCC). Drugs related hepatotoxicity is one of the major challenges facing by clinicians as it is a leading cause of liver failure. During post-marketing surveillance studies, detection and reporting of drug-induced hepatotoxicity may lead to drug withdrawal or warnings. Several mechanisms are involved in hepatotoxicity such as cell membrane disruption, initiating an immune response, alteration of cellular pathways of drug metabolism, accumulation of reactive oxygen species (ROS), lipid peroxidation and cell death. Curcumin, the active ingredient of turmeric and exhibits therapeutic potential for the treatment of diabetes, cardiovascular disorders and various types of cancers. Curcumin is strong anti-oxidant and anti-inflammatory effects and thus it possesses hepatoprotective properties. Despite its low bioavailability, its hepatoprotective effects have been studied in various protocols of hepatotoxicity including acetaminophen, alcohol, lindane, carbon tetrachloride (CCL₄), diethylnitrosamine and heavy metals induced hepatotoxicities. This report reviews the hepatoprotective effects of curcumin with a focus on its mechanistic insights in various hepatotoxic protocols.