Mitochondrial calcium, oxidative stress and apoptosis in a neurodegenerative disease model induced by 3-nitropropionic acid

An Update of Kaempferol Protection against Brain Damage Induced by Ischemia-Reperfusion and by 3-Nitropropionic Acid

Kaempferol, a flavonoid present in many food products, has chemical and cellular antioxidant properties that are beneficial for protection against the oxidative stress caused by reactive oxygen and nitrogen species. Kaempferol administration to model experimental animals can provide extensive protection against brain damage of the striatum and proximal cortical areas induced by transient brain cerebral ischemic stroke and by 3-nitropropionic acid. This article is an updated review of the molecular and cellular mechanisms of protection by kaempferol administration against brain damage induced by these insults, integrated with an overview of the contributions of the work performed in our laboratories during the past years. Kaempferol administration at doses that prevent neurological dysfunctions inhibit the critical molecular events that underlie the initial and delayed brain damage induced by ischemic stroke and by 3-nitropropionic acid. It is highlighted that the protection afforded by kaempferol against the initial mitochondrial dysfunction can largely account for its protection against the reported delayed spreading of brain damage, which can develop from many hours to several days. This allows us to conclude that kaempferol administration can be beneficial not only in preventive treatments, but also in post-insult therapeutic treatments.

SIRTUINS MODULATORS COUNTERACT MITOCHONDRIAL DYSFUNCTION IN CELLULAR MODELS OF HYPOXIA: RELEVANCE TO SCHIZOPHRENIA

Schizophrenia (SZ) is a neurodevelopmental-associated disorder strongly related to environmental factors, such as hypoxia. Because there is no cure for SZ or any pharmacological approach that could revert hypoxia-induced cellular damages, we evaluated whether modulators of sirtuins could abrogate hypoxia-induced mitochondrial deregulation as a neuroprotective strategy. Firstly, astrocytes from control (Wistar) and Spontaneously Hypertensive Rats (SHR), a model of both SZ and neonatal hypoxia, were submitted to chemical hypoxia. Then, cells were exposed to different concentrations of Nicotinamide (NAM), Resveratrol (Resv), and Sirtinol (Sir) for 48hrs. Our data indicate that sirtuins modulation reduces cell death increasing the acetylation of histone 3. This outcome is related to the rescue of loss of mitochondrial membrane potential, changes in mitochondrial calcium buffering capacity, decreased O₂^-• levels and increased expression of metabolic regulators (Nrf-1 and Nfe2l2) and mitochondrial content. Such findings are relevant not only for hypoxia-associated conditions, named pre-eclampsia but also for SZ since prenatal hypoxia is a relevant environmental factor related to this burdensome neuropsychiatric disorder.

Nrf2 Pathway in Huntington's Disease (HD): What Is Its Role?

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease that occurs worldwide. Despite some progress in understanding the onset of HD, drugs that block or delay symptoms are still not available. In recent years, many treatments have been proposed; among them, nuclear transcriptional factor-2 (Nrf2) enhancer compounds have been proposed as potential therapeutic agents to treat HD. Nrf2 triggers an endogenous antioxidant pathway activated in different neurodegenerative disorders. Probably, the stimulation of Nrf2 during either the early phase or before HD symptoms' onset, could slow or prevent striatum degeneration. In this review, we present the scientific literature supporting the role of Nrf2 in HD and the potential prophylactic and therapeutic role of this compound.

Neuroprotective Effects of the Psychoactive Compound Biatractylolide (BD) in Alzheimer's Disease

Mitochondria play a central role in the survival or death of neuronal cells, and they are regulators of energy metabolism and cell death pathways. Many studies support the role of mitochondrial dysfunction and oxidative damage in the pathogenesis of Alzheimer's disease. Biatractylolide (BD) is a kind of internal symmetry double sesquiterpene novel ester compound isolated from the Chinese medicinal plant Baizhu, has neuroprotective effects in Alzheimer's disease. We developed a systematic pharmacological model based on chemical pharmacokinetic and pharmacological data to identify potential compounds and targets of Baizhu. The neuroprotective effects of BD in PC12 (rat adrenal pheochromocytoma cells) and SH-SY5Y (human bone marrow neuroblastoma cells) were evaluated by in vitro experiments. Based on the predicted results, we selected 18 active compounds, which were associated with 20 potential targets and 22 signaling pathways. Compound-target, target-disease and target-pathway networks were constructed using Cytoscape 3.2.1. And verified by in vitro experiments that BD could inhibit Aβ by reducing oxidative stress and decreasing CytC release induced mPTP opening. This study provides a theoretical basis for the development of BD as an anti-Alzheimer's disease drug.

Kaempferol prevents the activation of complement C3 protein and the generation of reactive A1 astrocytes that mediate rat brain degeneration induced by 3-nitropropionic acid

Kaempferol is a natural antioxidant present in vegetables and fruits used in human nutrition. In previous work, we showed that intraperitoneal (i.p.) kaempferol administration strongly protects against striatum neurodegeneration induced by i.p. injections of 3-nitropropionic acid (NPA), an animal model of Huntington's disease. Recently, we have shown that reactive A1 astrocytes generation is an early event in the neurodegeneration induced by NPA i.p. injections. In the present work, we have experimentally evaluated the hypothesis that kaempferol protects both against the activation of complement C3 protein and the generation of reactive A1 astrocytes in rat brain striatum and hippocampus. To this end, we have administered NPA and kaempferol i.p. injections to adult Wistar rats following the protocol described in previous work. Kaempferol administration prevents proteolytic activation of complement C3 protein and generation of reactive A1 astrocytes NPA-induced in the striatum and hippocampus. Also, it blocked the NPA-induced increase of NF-κB expression and enhanced secretion of cytokines IL-1α, TNFα, and C1q, which have been linked to the generation of reactive A1 astrocytes. In addition, kaempferol administration prevented the enhanced production of amyloid β peptides in the striatum and hippocampus, a novel finding in NPA-induced brain degeneration found in this work.

Analysis of Mitochondrial Dysfunction by Microplate Reader in hiPSC-Derived Neuronal Cell Models of Neurodegenerative Disorders

Mitochondria are responsible for many vital pathways governing cellular homeostasis, including cellular energy management, heme biosynthesis, lipid metabolism, cellular proliferation and differentiation, cell cycle regulation, and cellular viability. Electron transport and ADP phosphorylation coupled with proton pumping through the mitochondrial complexes contribute to the preservation of mitochondrial membrane potential (ΔΨ_m). Importantly, mitochondrial polarization is essential for reactive oxygen species (ROS) production and cytosolic calcium (Ca²⁺) handling. Thus, changes in mitochondrial oxidative phosphorylation (OXPHOS), ΔΨ_m, and ATP/ADP may occur in parallel or stimulate each other. Brain cells like neurons are heavily reliant on mitochondrial OXPHOS for its high-energy demands, and hence improper mitochondrial function is detrimental for neuronal survival. Indeed, several neurodegenerative disorders are associated with mitochondrial dysfunction. Modeling this disease-relevant phenotype in neuronal cells differentiated from patient-derived human induced pluripotent stem cells (hiPSCs) provide an appropriate cellular platform for studying the disease pathology and drug discovery. In this review, we describe high-throughput analysis of crucial parameters related to mitochondrial function in hiPSC-derived neurons. These methodologies include measurement of ΔΨ_m, intracellular Ca²⁺, oxidative stress, and ATP/ADP levels using fluorescence probes via a microplate reader. Benefits of such an approach include analysis of mitochondrial parameters on a large population of cells, simultaneous analysis of different cell lines and experimental conditions, and for drug screening to identify compounds restoring mitochondrial function.

Haloperidol rescues the schizophrenia-like phenotype in adulthood after rotenone administration in neonatal rats

Neuropsychiatric disorders are multifactorial disturbances that encompass several hypotheses, including changes in neurodevelopment. It is known that brain development disturbances during early life can predict psychosis in adulthood. As we have previously demonstrated, rotenone, a mitochondrial complex I inhibitor, could induce psychiatric-like behavior in 60-day-old rats after intraperitoneal injections from the 5th to the 11th postnatal day. Because mitochondrial deregulation is related to psychiatric disorders and the establishment of animal models is a high-value preclinical tool, we investigated the responsiveness of the rotenone (Rot)-treated newborn rats to pharmacological agents used in clinical practice, haloperidol (Hal), and methylphenidate (MPD). Taken together, our data show that Rot-treated animals exhibit hyperlocomotion, decreased social interaction, and diminished contextual fear conditioning response at P60, consistent with positive, negative, and cognitive deficits of schizophrenia (SZ), respectively, that were reverted by Hal, but not MPD. Rot-treated rodents also display a prodromal-related phenotype at P35. Overall, our results seem to present a new SZ animal model as a consequence of mitochondrial inhibition during a critical neurodevelopmental period. Therefore, our study is crucial not only to elucidate the relevance of mitochondrial function in the etiology of SZ but also to fulfill the need for new and trustworthy experimentation models and, likewise, provide possibilities to new therapeutic avenues for this burdensome disorder.

Targeting cellular batteries for the therapy of neurological diseases

The mitochondria, apart from being known as the cell's "powerhouse," are crucial in the viability of nerve cells. Any damage to these cellular organelles can result in their cellular level dysfunction which includes rapidly multiplying reactive oxygen species (ROS) from the mitochondrial membrane, impaired calcium ion homeostasis, and disturbed mitochondrial dynamics by the formation of permeability transition pore in mitochondria. All these impaired biochemical changes lead to various neurological disorders such as progressive supranuclear palsy (PSP), Parkinson's disease (PD), and Alzheimer's disease (AD). Moreover, impaired mitochondrial functions are particularly prone to damage owing to prolonged lifespan and stretched length of the neurons. At the same time, neurons are highly dependent on ATP, and thus, the mitochondria play a central role in the pathogenesis pertaining to neuronal disorders. Dysfunction in the mitochondria is an early pathological hallmark of neurological disorders, and its early detection with the help of suitable biomarkers can lead to promising treatment in this area. Thus, the drugs which are targeting mitochondrial dysfunctions are the emerging area of research in connection with neurological disorders. This can be evidenced by the great opportunities for mitigation, diagnosis, and treatment of numerous human disorders that entail mitochondrial dysfunction at the nexus of their pathogenesis. Here, we throw light at the mitochondrial pathologies and indications of dysfunctional mitochondria in PD, AD, and PSP. There is also an insight into the possible therapeutic strategies highlighting the need for mitochondria-based medicine and made an attempt for claiming the prerequisite for the therapy of neurological diseases.

Increased acute blood flow induced by the aqueous extract of Euterpe oleracea Mart. fruit pulp in rats in vivo is not related to the direct activation of endothelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

Scientific evidence supports the antioxidant, anti-inflammatory and anti-lipidemic properties of Euterpe oleracea Mart. (açaí), which all converge to reduce cardiovascular risks. Macerating the pulp of açaí fruit produces a viscous aqueous extract (AE) rich in flavonoids that is commonly used in food production. In addition to nutritional aspects, cardiovascular benefits are attributed to AE by traditional medicine.

AIM OF THE STUDY

Evaluation of AE impact on blood flow in vivo in rats and investigation of the mechanism underlying this response in vitro in rat endothelial cells (RECs).

MATERIALS AND METHODS

For the measurement of acute blood flow, a perivascular ultrasound probe was used in Wistar rats. The in vitro assays employed REC to evaluate: concentration (1-1000 μg/mL) and time response (2-180 min) of AE in MTT cell viability assays; nitric oxide (NO) levels measurement and intracellular calcium handling using DAF-2DA and Fluo-4-AM, respectively; cellular biopterin content by HPLC; activation of Akt pathway using western blot analysis. For the chemical analyses of AE, stock solutions of the standards (+)catechin and quercetin were used for obtaining linear calibration curves. Identification and quantification of flavonoids in AE were based on comparisons with the retention times, increase in peak area determine by co-injection of AE with standards, UV-Vis scan and standard curves of known spectra. Results were expressed as mean ± standard deviation and data were analyzed using ANOVA followed by Tukey's post-test (p < 0.05).

RESULTS

Although in vivo data have revealed the participation of NO in increasing of acute blood flow on abdominal aorta, in vitro analysis demonstrated that vasodilatation AE-induced is not related to its direct action on endothelial cells inducing eNOS activation. Besides, we demonstrated in isolated endothelial cells that highest concentrations of AE caused a reduction in NO levels, effect that could be partly justified by inhibition of Akt phosphorylation which, in turn, could decrease NOS activation. The involvement of cell transduction pathways involving variations in intracellular calcium and biopterins concentration were discarded. The participation of catechin and quercetin, identified in AE, was postulated to induce the responses of AE in REC.

CONCLUSIONS

Despite the responses in vitro, vasodilation prevailed in vivo, probably by activating intermediate pathways, validating a potential beneficial effect of AE in reducing cardiovascular risks.

Oxygen Consumption Evaluation: An Important Indicator of Metabolic State, Cellular Function, and Cell Fate Along Neural Deregulation

Depletion of oxygen (O₂) levels and reduction in the ATP synthesis (or even its complete blockage) are important characteristics of mitochondrial dysfunction; features that are often correlated with neurodegeneration. The measurement of oxygen consumption rate (OCR) is thus essential to evaluate cellular metabolism, survival, and neuroprotective strategies. In the present chapter, we describe the oxygen consumption assay using a Clark-type oxygen electrode in different types of samples named cells suspension (from primary and established cell culture), brain slices (ex vivo), and fresh brain tissues. In addition, we demonstrate herein how the program Oxygraph can be used in order to analyze the data and different approaches to normalize it.

Mitochondrial and Redox-Based Therapeutic Strategies in Huntington's Disease

Significance: The molecular processes that determine Huntington's disease (HD) pathogenesis are not yet fully understood, and until now no effective neuroprotective therapeutic strategies have been developed. Mitochondria are one of most important organelles required for neuronal homeostasis, by providing metabolic pathways relevant for energy production, regulating calcium homeostasis, or controlling free radical generation and cell death. Because augmented reactive oxygen species (ROS) accompanied by mitochondrial dysfunction are relevant early HD mechanisms, targeting these cellular mechanisms may constitute relevant therapeutic approaches. Recent Advances: Previous findings point toward a close relationship between mitochondrial dysfunction and redox changes in HD. Mutant huntingtin (mHTT) can directly interact with mitochondrial proteins, as translocase of the inner membrane 23 (TIM23), disrupting mitochondrial proteostasis and favoring ROS production and HD progression. Furthermore, abnormal brain and muscle redox signaling contributes to altered proteostasis and motor impairment in HD, which can be improved with the mitochondria-targeted antioxidant mitoquinone or resveratrol, an SIRT1 activator that ameliorates mitochondrial biogenesis and function. Critical Issues: Various antioxidants and metabolic enhancers have been studied in HD; however, the real outcome of these molecules is still debatable. New compounds have proven to ameliorate mitochondrial and redox-based signaling pathways in early stages of HD, potentially precluding selective neurodegeneration. Future Directions: Unraveling the molecular etiology of deregulated mitochondrial function and dynamics, and oxidative stress opens new prospects for HD therapeutics. In this review, we explore the role of redox unbalance and mitochondrial dysfunction in HD progression, and further describe advances on clinical trials in HD based on mitochondrial and redox-based therapeutic strategies.

Neonatal Rotenone Administration Induces Psychiatric Disorder-Like Behavior and Changes in Mitochondrial Biogenesis and Synaptic Proteins in Adulthood

Since psychiatric disorders are associated with changes in the development of the nervous system, an energy-dependent mechanism, we investigated whether mitochondrial inhibition during the critical neurodevelopment window in rodents would be able to induce metabolic alterations culminating in psychiatric-like behavior. We treated male Wistar rat puppies (P) with rotenone (Rot), an inhibitor of mitochondrial complex I, from postnatal days 5 to 11 (P5-P11). We demonstrated that at P60 and P120, Rot-treated animals showed hyperlocomotion and deficits in social interaction and aversive contextual memory, features observed in animal models of schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder. During adulthood, Rot-treated rodents also presented modifications in CBP and CREB levels in addition to a decrease in mitochondrial biogenesis and Nrf1 expression. Additionally, NFE2L2-activation was not altered in Rot-treated P60 and P120 animals; an upregulation of pNFE2L2/ NFE2L2 was only observed in P12 cortices. Curiously, ATP/ADP levels did not change in all ages evaluated. Rot administration in newborn rodents also promoted modification in Rest and Mecp2 expression, and in synaptic protein levels, named PSD-95, Synaptotagmin-1, and Synaptophysin in the adult rats. Altogether, our data indicate that behavioral abnormalities and changes in synaptic proteins in adulthood induced by neonatal Rot administration might be a result of adjustments in CREB pathways and alterations in mitochondrial biogenesis and Nrf1 expression, rather than a direct deficiency of energy supply, as previously speculated. Consequently, Rot-induced psychiatric-like behavior would be an outcome of alterations in neuronal paths due to mitochondrial deregulation.

Decreased Mitochondrial Function, Biogenesis, and Degradation in Peripheral Blood Mononuclear Cells from Amyotrophic Lateral Sclerosis Patients as a Potential Tool for Biomarker Research

Amyotrophic lateral sclerosis (ALS) is a multifactorial and progressive neurodegenerative disease of unknown etiology. Due to ALS’s unpredictable onset and progression rate, the search for biomarkers that allow the detection and tracking of its development and therapeutic efficacy would be of significant medical value. Considering that alterations of energy supply are one of ALS’s main hallmarks and that a correlation has been established between gene expression in human brain tissue and peripheral blood mononuclear cells (PBMCs), the present work investigates whether changes in mitochondrial function could be used to monitor ALS. To achieve this goal, PBMCs from ALS patients and control subjects were used; blood sampling is a quite non-invasive method and is cost-effective. Different parameters were evaluated, namely cytosolic calcium levels, mitochondrial membrane potential, oxidative stress, and metabolic compounds levels, as well as mitochondrial dynamics and degradation. Altogether, we observed lower mitochondrial calcium uptake/retention, mitochondria depolarization, and redox homeostasis deregulation, in addition to a decrease in critical metabolic genes, a diminishment in mitochondrial biogenesis, and an augmentation in mitochondrial fission and autophagy-related gene expression. All of these changes can contribute to the decreased ATP and pyruvate levels observed in ALS PBMCs. Our data indicate that PBMCs from ALS patients show a significant mitochondrial dysfunction, resembling several findings from ALS’ neural cells/models, which could be exploited as a powerful tool in ALS research. Our findings can also guide future studies on new pharmacological interventions for ALS since assessments of brain samples are challenging and represent a relevant limited strategy.

Mitochondrial Dysfunction, Neurogenesis, and Epigenetics: Putative Implications for Amyotrophic Lateral Sclerosis Neurodegeneration and Treatment

Amyotrophic lateral sclerosis (ALS) is a progressive and devastating multifactorial neurodegenerative disorder. Although the pathogenesis of ALS is still not completely understood, numerous studies suggest that mitochondrial deregulation may be implicated in its onset and progression. Interestingly, mitochondrial deregulation has also been associated with changes in neural stem cells (NSC) proliferation, differentiation, and migration. In this review, we highlight the importance of mitochondrial function for neurogenesis, and how both processes are correlated and may contribute to the pathogenesis of ALS; we have focused primarily on preclinical data from animal models of ALS, since to date no studies have evaluated this link using human samples. As there is currently no cure and no effective therapy to counteract ALS, we have also discussed how improving neurogenic function by epigenetic modulation could benefit ALS. In support of this hypothesis, changes in histone deacetylation can alter mitochondrial function, which in turn might ameliorate cellular proliferation as well as neuronal differentiation and migration. We propose that modulation of epigenetics, mitochondrial function, and neurogenesis might provide new hope for ALS patients, and studies exploring these new territories are warranted in the near future.

Early Reactive A1 Astrocytes Induction by the Neurotoxin 3-Nitropropionic Acid in Rat Brain

3-Nitropropionic acid (NPA) administration to rodents produces degeneration of the striatum, accompanied by neurological disturbances that mimic Huntington’s disease (HD) motor neurological dysfunctions. It has been shown that inflammation mediates NPA-induced brain degeneration, and activated microglia secreting cytokines interleukin-1α (IL-1α) and tumor necrosis factor α (TNFα) can induce a specific type of reactive neurotoxic astrocytes, named A1, which have been detected in post-mortem brain samples of Huntington’s, Alzheimer’s, and Parkinson’s diseases. In this work we used an experimental model based on the intraperitoneal (i.p.) administration of NPA to adult Wistar rats at doses that can elicit extensive brain degeneration, and brain samples were taken before and after extensive brain damage monitored using 2,3,5-triphenyltetrazolium chloride (TTC) staining. Western blots and immunohistochemistry of brain slices show that i.p. NPA injections elicit significant increase in the expression levels of C3α subunit, a marker of generation of neurotoxic A1 astrocytes, and of cytokines IL-1α, TNFα, and C1q within the striatum, hippocampus, and cerebellum before the appearance of the HD-related neurological dysfunctions and neuronal death induced by NPA. Noteworthy, NPA administration primarily induces the generation of A1 astrocytes in the more recent phylogenetic area of the rat cerebellum. We conclude that the activation of complement C3 protein in the brain from Wistar rats is an early event in NPA-induced brain neurodegeneration.

Oxidative Stress in DNA Repeat Expansion Disorders: A Focus on NRF2 Signaling Involvement

DNA repeat expansion disorders are a group of neuromuscular and neurodegenerative diseases that arise from the inheritance of long tracts of nucleotide repetitions, located in the regulatory region, introns, or inside the coding sequence of a gene. Although loss of protein expression and/or the gain of function of its transcribed mRNA or translated product represent the major pathogenic effect of these pathologies, mitochondrial dysfunction and imbalance in redox homeostasis are reported as common features in these disorders, deeply affecting their severity and progression. In this review, we examine the role that the redox imbalance plays in the pathological mechanisms of DNA expansion disorders and the recent advances on antioxidant treatments, particularly focusing on the expression and the activity of the transcription factor NRF2, the main cellular regulator of the antioxidant response.

Mitochondrial Dysfunction and Changes in High-Energy Compounds in Different Cellular Models Associated to Hypoxia: Implication to Schizophrenia

Schizophrenia (SZ) is a multifactorial mental disorder, which has been associated with a number of environmental factors, such as hypoxia. Considering that numerous neural mechanisms depends on energetic supply (ATP synthesis), the maintenance of mitochondrial metabolism is essential to keep cellular balance and survival. Therefore, in the present work, we evaluated functional parameters related to mitochondrial function, namely calcium levels, mitochondrial membrane potential, redox homeostasis, high-energy compounds levels and oxygen consumption, in astrocytes from control (Wistar) and Spontaneously Hypertensive Rats (SHR) animals exposed both to chemical and gaseous hypoxia. We show that astrocytes after hypoxia presented depolarized mitochondria, disturbances in Ca²⁺ handling, destabilization in redox system and alterations in ATP, ADP, Pyruvate and Lactate levels, in addition to modification in NAD⁺/NADH ratio, and Nfe2l2 and Nrf1 expression. Interestingly, intrauterine hypoxia also induced augmentation in mitochondrial biogenesis and content. Altogether, our data suggest that hypoxia can induce mitochondrial deregulation and a decrease in energy metabolism in the most prevalent cell type in the brain, astrocytes. Since SHR are also considered an animal model of SZ, our results can likewise be related to their phenotypic alterations and, therefore, our work also allow an increase in the knowledge of this burdensome disorder.

Microdevice Platform for In Vitro Nervous System and Its Disease Model

The development of precise microdevices can be applied to the reconstruction of in vitro human microenvironmental systems with biomimetic physiological conditions that have highly tunable spatial and temporal features. Organ-on-a-chip can emulate human physiological functions, particularly at the organ level, as well as its specific roles in the body. Due to the complexity of the structure of the central nervous system and its intercellular interaction, there remains an urgent need for the development of human brain or nervous system models. Thus, various microdevice models have been proposed to mimic actual human brain physiology, which can be categorized as nervous system-on-a-chip. Nervous system-on-a-chip platforms can prove to be promising technologies, through the application of their biomimetic features to the etiology of neurodegenerative diseases. This article reviews the microdevices for nervous system-on-a-chip platform incorporated with neurobiology and microtechnology, including microfluidic designs that are biomimetic to the entire nervous system. The emulation of both neurodegenerative disorders and neural stem cell behavior patterns in micro-platforms is also provided, which can be used as a basis to construct nervous system-on-a-chip.

The beneficial role of Naringin- a citrus bioflavonoid, against oxidative stress-induced neurobehavioral disorders and cognitive dysfunction in rodents: A systematic review and meta-analysis

OBJECTIVES

Naringin is a bioflavonoid, very abundantly found in citrus species. In literature, naringin has been scientifically well documented for its beneficial effects in various neurological disorders. In this systematic review and meta-analysis, we have made an attempt to correlate the protective role of naringin against oxidative stress-induced neurological disorders in rodents.

METHODS

The systematic search was performed using electronic databases; the search was mainly focused on the role of naringin in oxidative stress-induced neuropathological conditions in rodents. While, the meta-analysis was performed on the effect of naringin on oxidative stress markers [superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), reduced glutathione (GSH), lipid peroxidation (LPO)], nitrite, mitochondrial complexes (I to IV) and enzymes (acetylcholinesterase, Na⁺-K⁺-ATPase, Ca²⁺-ATPase, and Mg²⁺-ATPase) in the rodent brain. The data was analyzed using Review Manager Software.

THE RESULTS

Based on the inclusion and exclusion criteria, twenty studies were selected. The meta-analysis revealed that, naringin could significantly inhibit various physical and chemical stimuli- induced neurological perturbances in the rodent brain, mediated through oxidative stress. Further, naringin also significantly restored the levels of all the oxidative stress markers (oxidative, nitrosative, enzymes, and mitochondrial complexes) in different parts of the rodent brain.

SUMMARY

This systematic review and meta-analysis supports the available scientific evidence on the beneficial role of naringin in the management of various neurological ailments. However, further studies involving human subjects is recommended to establish the safety and therapeutic efficacy in humans.

Mevalonolactone disrupts mitochondrial functions and induces permeability transition pore opening in rat brain mitochondria: Implications for the pathogenesis of mevalonic aciduria

Mevalonic aciduria (MVA) is caused by severe deficiency of mevalonic kinase activity leading to tissue accumulation and high urinary excretion of mevalonic acid (MA) and mevalonolactone (ML). Patients usually present severe neurologic symptoms whose pathophysiology is poorly known. Here, we tested the hypothesis that the major accumulating metabolites are toxic by investigating the in vitro effects of MA and ML on important mitochondrial functions in rat brain and liver mitochondria. ML, but not MA, markedly decreased mitochondrial membrane potential (ΔΨm), NAD(P)H content and the capacity to retain Ca²⁺ in the brain, besides inducing mitochondrial swelling. These biochemical alterations were totally prevented by the classical inhibitors of mitochondrial permeability transition (MPT) cyclosporine A and ADP, as well as by ruthenium red in Ca²⁺-loaded mitochondria, indicating the involvement of MPT and an important role for mitochondrial Ca²⁺ in these effects. ML also induced lipid peroxidation and markedly inhibited aconitase activity, an enzyme that is highly susceptible to free radical attack, in brain mitochondrial fractions, indicating that lipid and protein oxidative damage may underlie some of ML-induced deleterious effects including MTP induction. In contrast, ML and MA did not compromise oxidative phosphorylation in the brain and all mitochondrial functions evaluated in the liver, evidencing a selective toxicity of ML towards the central nervous system. Our present study provides for the first time evidence that ML impairs essential brain mitochondrial functions with the involvement of MPT pore opening. It is therefore presumed that disturbance of brain mitochondrial homeostasis possibly contributes to the neurologic symptoms in MVA.

Cell-based technologies for Huntington's disease

Huntington's disease (HD) is a fatal genetic disorder, which causes the progressive breakdown of neurons in the human brain. HD deteriorates human physical and mental abilities over time and has no cure. Stem cell-based technologies are promising novel treatments, and in HD, they aim to replace lost neurons and/or to prevent neural cell death. Herein we discuss the use of human fetal tissue (hFT), neural stem cells (NSCs) of hFT origin or embryonic stem cells (ESCs) and induced pluripotent stem cells (IPSCs), in clinical and pre-clinical studies. The in vivo use of mesenchymal stem cells (MSCs), which are derived from non-neural tissues, will also be discussed. All these studies prove the potential of stem cells for transplantation therapy in HD, demonstrating cell grafting and the ability to differentiate into mature neurons, resulting in behavioral improvements. We claim that there are still many problems to overcome before these technologies become available for HD patient treatment, such as:

a) safety regarding the use of NSCs and pluripotent stem cells, which are potentially teratogenic;

b) safety regarding the transplantation procedure itself, which represents a risk and needs to be better studied; and finally

c) technical and ethical issues regarding cells of fetal and embryonic origin.

Dihydromyricetin Ameliorates 3NP-induced Behavioral Deficits and Striatal Injury in Rats

Oxidative stress is closely involved in neurodegenerative diseases. The present study aimed to examine the effect of anti-oxidant DHM (dihydromyricetin) on 3NP (3-nitropropionic acid) -induced behavioral deficits of experimental rats and striatal histopathological injury by using behavioral, imaging, biochemistry, histochemistry and molecular biology technologies. The experimental results showed that both motor dysfunctions and learning and memory impairments induced by 3NP were significantly reduced after DHM treatment. 3NP-induced striatal metabolic abnormality was also remarkably improved by DHM treatment, showed as the increased glucose metabolism in PET/CT scan, decreased MDA (malondialdehyde) and increased SOD (superoxide dismutase) activity in enzyme histochemical staining. In addition, the cell apoptosis was evidently detected in the striatum of the 3NP group, while in the 3NP + DHM group, the number of apoptotic cells was remarkably reduced. 3NP treatment obviously induced down-regulation of Bcl-2, and up-regulations of Bax and Cleaved Caspase-3, while these changes were significantly reversed by DHM treatment. The present results suggested that DHM showed its protective effect by anti-oxidant and anti-apoptosis mechanisms.

Genistein improves sensorimotor gating: Mechanisms related to its neuroprotective effects on the striatum

Huntington's disease (HD) is a neurodegenerative disorder, characterized by selective atrophy in the striatum, particularly the medium spiny GABAergic efferent neurons. This results in striatal sensorimotor gating deficits. Systemic administration of 3-nitropropionic acid (3-NPA) produces selective lesions mimicking those of HD. Males were found to be more susceptible to 3-NPA-induced neurotoxicity than females, suggesting neuroprotective effects of estrogens. Phytoestrogens, including genistein, are good estrogenic alternatives that keep their beneficial effects on non-reproductive organs and lack the potential hazardous side effects. The current study was designed to investigate the potential beneficial effects of genistein in 3-NPA-induced HD in ovariectomized rats. Results showed that 3-NPA (20 mg/kg) administration caused significant disruption of the rats' locomotor activity and prepulse inhibition. In addition, it decreased striatal ATP levels and increased oxidative stress, inflammatory and apoptotic markers with striatal focal hemorrhage and gliosis. Pretreatment with 17β-estradiol (2.5 mg/kg) or genistein (20 mg/kg) led to a significant improvement of behavioral parameters, increased ATP production, decreased oxidative stress, attenuated inflammation and apoptosis. Therefore, this study suggests potential neuroprotective effects of genistein in ovariectomized rats challenged with 3-NPA.

Characterization of age-dependent changes in the striatum: Response to the mitochondrial toxin 3-nitropropionic acid

Neurodegenerative phenomena are associated with mitochondrial dysfunction and this could be exacerbated by aging. Age-dependence of mitochondrial response to toxins could help understand these mechanisms and evolve novel therapeutics. 3-Nitropropionic acid (3-NPA) is a mitochondrial toxin that induces neurotoxicity in the striatum via inhibition of complex II. We investigated the age-related events that contribute to 3-NPA toxicity. 3-NPA induced neuronal death, oxidative stress and altered mitochondrial structure in neuronal cells. 3-NPA injection in vivo caused motor impairment, mitochondrial dysfunction and oxidative damage with different trend in young and adult mice. To understand the age-dependent mechanisms, we carried out proteomic analysis of the striatal protein extract from young mice (control: YC vs. 3-NPA treated: YT) and adult mice (control: AC vs. 3-NPA treated: AT). Among the 3752 identified proteins, 33 differentially expressed proteins (mitochondrial, synaptic and microsomal proteins) were unique either to YT or AT. Interestingly, comparison of the proteomic profile in AC and YC indicated that 161 proteins (linked with cytoskeletal structure, neuronal development, axogenesis, protein transport, cell adhesion and synaptic function) were down-regulated in AC compared to YC. We surmise that aging contributes to the cellular and molecular architecture in the mouse striatum with implications for neurodegeneration.

Phytochemical analysis of hydroethanolic extract of Turnera diffusa Willd and evaluation of its effects on astrocyte cell death

OBJECTIVE

To evaluate the phytochemical composition of hydroethanolic extracts from powdered aerial parts of Turnera diffusa Willd (Turneraceae; T. diffusa), as well as its toxicity in astrocytes.

METHODS

Chemical analyses of hydroethanolic extract from powdered aerial parts ofT. diffusa were carried out using HPLC-DAD-ESI-MS/MS.In vitro assays using astrocytes culture were performed to evaluate cell death.

RESULTS

Flavone-C, O-diglycosides, such as, luteolin-8-C-[6-deoxy-2-O-rhamnosyl]-xylo-hexos-3-uloside, apigenin-8-C-[6-deoxy-2-O-rhamnosyl]-xylo-hexos-3-uloside and apigenin-7-O-6"-p-coumaroylglucoside were the main compounds found in this hydroethanolic extract. Concentration time-effect demonstrated the toxicity of this extract at a concentration of 1,000µg/mL in astrocyte culture, after 6 and 24 hours of incubation.

CONCLUSION

In phytochemical analyses, important antioxidants (mainly flavonoids) were observed. T. diffusa extracts presented cytotoxic effect in high concentrations, leading to increased cell death in astrocyte culture.

Increased Expression of Osteopontin in the Degenerating Striatum of Rats Treated with Mitochondrial Toxin 3-Nitropropionic Acid: A Light and Electron Microscopy Study

The mycotoxin 3-nitropropionic acid (3NP) is an irreversible inhibitor that induces neuronal damage by inhibiting mitochondrial complex II. Neurodegeneration induced by 3NP, which is preferentially induced in the striatum, is caused by an excess influx and accumulation of calcium in mitochondria. Osteopontin (OPN) is a glycosylated phosphoprotein and plays a role in the regulation of calcium precipitation in the injured brain. The present study was designed to examine whether induction of OPN protein is implicated in the pathogenesis of 3NP-induced striatal neurodegeneration. We observed overlapping regional expression of OPN, the neurodegeneration marker Fluoro-Jade B, and the microglial marker ionized calcium-binding adaptor molecule 1 (Iba1) in the 3NP-lesioned striatum. OPN expression was closely associated with the mitochondrial marker NADH dehydrogenase (ubiquinone) flavoprotein 2 in the damaged striatum. In addition, immunoelectron microscopy demonstrated that OPN protein was specifically localized to the inner membrane and matrix of the mitochondria in degenerating striatal neurons, and cell fragments containing OPN-labeled mitochondria were also present within activated brain macrophages. Thus, our study revealed that OPN expression is associated with mitochondrial dysfunction produced by 3NP-induced alteration of mitochondrial calcium homeostasis, suggesting that OPN is involved in the pathogenesis of striatal degeneration by 3NP administration.

Deregulation of mitochondrial functions provoked by long-chain fatty acid accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase and mitochondrial permeability transition deficiencies in rat heart--mitochondrial permeability transition pore opening as a potential contributing pathomechanism of cardiac alterations in these disorders

Mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies are fatty acid oxidation disorders biochemically characterized by tissue accumulation of long-chain fatty acids and derivatives, including the monocarboxylic long-chain 3-hydroxy fatty acids (LCHFAs) 3-hydroxytetradecanoic acid (3HTA) and 3-hydroxypalmitic acid (3HPA). Patients commonly present severe cardiomyopathy for which the pathogenesis is still poorly established. We investigated the effects of 3HTA and 3HPA, the major metabolites accumulating in these disorders, on important parameters of mitochondrial homeostasis in Ca(2+) -loaded heart mitochondria. 3HTA and 3HPA significantly decreased mitochondrial membrane potential, the matrix NAD(P)H pool and Ca(2+) retention capacity, and also induced mitochondrial swelling. These fatty acids also provoked a marked decrease of ATP production reflecting severe energy dysfunction. Furthermore, 3HTA-induced mitochondrial alterations were completely prevented by the classical mitochondrial permeability transition (mPT) inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca(2+) uptake blocker, indicating that LCHFAs induced Ca(2+)-dependent mPT pore opening. Milder effects only achieved at higher doses of LCHFAs were observed in brain mitochondria, implying a higher vulnerability of heart to these fatty acids. By contrast, 3HTA and docosanoic acids did not change mitochondrial homeostasis, indicating selective effects for monocarboxylic LCHFAs. The present data indicate that the major LCHFAs accumulating in mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies induce mPT pore opening, compromising Ca(2+) homeostasis and oxidative phosphorylation more intensely in the heart. It is proposed that these pathomechanisms may contribute at least in part to the severe cardiac alterations characteristic of patients affected by these diseases.

Neuroprotective efficacy of naringin on 3-nitropropionic acid-induced mitochondrial dysfunction through the modulation of Nrf2 signaling pathway in PC12 cells

Oxidative stress and mitochondrial dysfunction are implicated in neuronal apoptosis associated with Huntington's disease. Naringin is the flavanone present in grapefruit and related citrus species possess diverse pharmacological and therapeutic properties including antioxidant, anti-apoptotic, and neuroprotective properties. The aim of this study was to investigate the protective effect of naringin on 3-nitropropionic acid (3-NP)-induced neurotoxicity in pheochromocytoma cells (PC12) cells and to explore its mechanism of action. Naringin protects PC12 cells from 3-NP neurotoxicity, as evaluated the by cell viability assays. The lactate dehydrogenase release was decreased upon naringin treatment in 3-NP-induced PC12 cells. Naringin treatment enhances the antioxidant defense by increasing the activities of enzymatic antioxidants and the level of reduced glutathione. The increase in levels of reactive oxygen species and lipid peroxidation induced by 3-NP were significantly decreased by naringin. PC12 cells induced with 3-NP showed decrease in the mitochondrial membrane potential and mitochondrial respiratory complex enzymes, succinate dehydrogenase and cytochrome c oxidase activities, and it was significantly altered to near normal upon naringin treatment. Naringin reduced the 3-NP-induced apoptosis through the modulation in expressions of B-cell lymphoma 2 and Bcl-2-associated X protein. Further, naringin enhances the nuclear translocation of Nrf2 and induces the

NAD(P)H

quinone oxidoreductase-1 and Heme oxygenase-1 expressions through the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway. Taken together, the above findings suggest that naringin augments cellular antioxidant defense capacity and reduces the 3-NP-induced neurotoxicity in PC12 cells through the PI-3K/Akt-dependent Nrf2 activation in PC12 cells.

Mitofusin 2-deficiency suppresses cell proliferation through disturbance of autophagy

Mitofusin2 (Mfn2), a mitochondrial outer membrane protein serving primarily as a mitochondrial fusion protein, has multiple functions in regulating cell biological processes. Defects of Mfn2 were found in diabetes, obesity, and neurodegenerative diseases. In the present study, we found that knockdown of Mfn2 by shRNA led to impaired autophagic degradation, inhibited mitochondrial oxygen consumption rate and cell glycolysis, reduced ATP production, and suppressed cell proliferation. Inhibition of autophagic degradation mimicked Mfn2-deficiency mediated cell proliferation suppression, while enhancement of autophagosome maturation restored the suppressed cell proliferation by Mfn2-deficiency. Thus, our findings revealed the role of Mfn2 in regulating cell proliferation and mitochondrial metabolism, and shed new light on understanding the mechanisms of Mfn2 deficiency related diseases.

Mitochondrial permeability transition pore is a potential drug target for neurodegeneration

Mitochondrial permeability transition pore (mPTP) plays a central role in alterations of mitochondrial structure and function leading to neuronal injury relevant to aging and neurodegenerative diseases including Alzheimer's disease (AD). mPTP putatively consists of the voltage-dependent anion channel (VDAC), the adenine nucleotide translocator (ANT) and cyclophilin D (CypD). Reactive oxygen species (ROS) increase intra-cellular calcium and enhance the formation of mPTP that leads to neuronal cell death in AD. CypD-dependent mPTP can play a crucial role in ischemia/reperfusion injury. The interaction of amyloid beta peptide (Aβ) with CypD potentiates mitochondrial and neuronal perturbation. This interaction triggers the formation of mPTP, resulting in decreased mitochondrial membrane potential, impaired mitochondrial respiration function, increased oxidative stress, release of cytochrome c, and impaired axonal mitochondrial transport. Thus, the CypD-dependent mPTP is directly linked to the cellular and synaptic perturbations observed in the pathogenesis of AD. Designing small molecules to block this interaction would lessen the effects of Aβ neurotoxicity. This review summarizes the recent progress on mPTP and its potential therapeutic target for neurodegenerative diseases including AD.

Mitochondrial bioenergetics deregulation caused by long-chain 3-hydroxy fatty acids accumulating in LCHAD and MTP deficiencies in rat brain: a possible role of mPTP opening as a pathomechanism in these disorders?

Long-chain 3-hydroxylated fatty acids (LCHFA) accumulate in long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiencies. Affected patients usually present severe neonatal symptoms involving cardiac and hepatic functions, although long-term neurological abnormalities are also commonly observed. Since the underlying mechanisms of brain damage are practically unknown and have not been properly investigated, we studied the effects of LCHFA on important parameters of mitochondrial homeostasis in isolated mitochondria from cerebral cortex of developing rats. 3-Hydroxytetradecanoic acid (3 HTA) reduced mitochondrial membrane potential, NAD(P)H levels, Ca(2+) retention capacity and ATP content, besides inducing swelling, cytochrome c release and H2O2 production in Ca(2+)-loaded mitochondrial preparations. We also found that cyclosporine A plus ADP, as well as ruthenium red, a Ca(2+) uptake blocker, prevented these effects, suggesting the involvement of the mitochondrial permeability transition pore (mPTP) and an important role for Ca(2+), respectively. 3-Hydroxydodecanoic and 3-hydroxypalmitic acids, that also accumulate in LCHAD and MTP deficiencies, similarly induced mitochondrial swelling and decreased ATP content, but to a variable degree pending on the size of their carbon chain. It is proposed that mPTP opening induced by LCHFA disrupts brain bioenergetics and may contribute at least partly to explain the neurologic dysfunction observed in patients affected by LCHAD and MTP deficiencies.

Sulfite disrupts brain mitochondrial energy homeostasis and induces mitochondrial permeability transition pore opening via thiol group modification

Sulfite oxidase (SO) deficiency is biochemically characterized by the accumulation of sulfite, thiosulfate and S-sulfocysteine in tissues and biological fluids of the affected patients. The main clinical symptoms include severe neurological dysfunction and brain abnormalities, whose pathophysiology is still unknown. The present study investigated the in vitro effects of sulfite and thiosulfate on mitochondrial homeostasis in rat brain mitochondria. It was verified that sulfite per se, but not thiosulfate, decreased state 3, CCCP-stimulated state and respiratory control ratio in mitochondria respiring with glutamate plus malate. In line with this, we found that sulfite inhibited the activities of glutamate and malate (MDH) dehydrogenases. In addition, sulfite decreased the activity of a commercial solution of MDH, that was prevented by antioxidants and dithiothreitol. Sulfite also induced mitochondrial swelling and reduced mitochondrial membrane potential, Ca(2+) retention capacity, NAD(P)H pool and cytochrome c immunocontent when Ca(2+) was present in the medium. These alterations were prevented by ruthenium red, cyclosporine A (CsA) and ADP, supporting the involvement of mitochondrial permeability transition (MPT) in these effects. We further observed that N-ethylmaleimide prevented the sulfite-elicited swelling and that sulfite decreased free thiol group content in brain mitochondria. These findings indicate that sulfite acts directly on MPT pore containing thiol groups. Finally, we verified that sulfite reduced cell viability in cerebral cortex slices and that this effect was prevented by CsA. Therefore, it may be presumed that disturbance of mitochondrial energy homeostasis and MPT induced by sulfite could be involved in the neuronal damage characteristic of SO deficiency.

Effects of Panax ginseng, Turnera diffusa and Heteropterys tomentosa extracts on hippocampal apoptosis of aged rats

Objective:

To verify if the medicinal plants Panax ginseng C.A. Mey, Turnera diffusa Willd. ex Schult., and Heteropterys tomentosa O. Mach., which are amply used by the population as tonics and cognition enhancers, could have a protective effect on cell death by apoptosis, since this could be one of the mechanisms of action of these substances.

Methods:

Aged male Wistar rats (n=24) were divided into four groups. Over 30 days, three groups received treatments with hydroalcoholic extracts of the plants, and one group received saline solution. A fifth group with young adult male Wistar rats (n=4) received saline solution during the same period. Using the TUNEL technique, the percentage of apoptosis in the hippocampus of these animals was evaluated.

Results:

No differences were observed between the percentage of apoptotic cells in the hippocampus of aged animals and of young control animals. The percentage of apoptosis in the hippocampus of aged animals treated chronically with the extracts from the three plants also did not differ from the percentage of apoptosis in the hippocampus of the control group of aged animals.

Conclusion:

Treatment with the hydroalcoholic extracts of Panax ginseng, Turnera diffusa, and Heteropterys tomentosa did not influence the apoptosis of the hippocampal cells of aged rats.

The anti-apoptotic and anti-inflammatory properties of puerarin attenuate 3-nitropropionic-acid induced neurotoxicity in rats

Puerarin (Pur), an isoflavonoid extracted from the dried roots of Pueraria lobata, has been reported to be useful in the treatment of various diseases. This study was designed to evaluate the anti-apoptotic and anti-inflammatory activities of Pur against 3-nitropropionic acid (3-NP) induced neurotoxicity. For 5 consecutive days, male Wistar rats were given Pur (200 mg/kg body mass) 30 min before treatment with 20 mg/kg body mass of 3-NP. The striata, hippocampi, and cortices of the 3-NP treated group showed apoptotic damage, inflammation, and energy deficit as well as histopathological lesions. The 3-NP-induced alteration in apoptotic biomarkers (caspase-3 activity/level, cytosolic cytochrome c, Bax/Bcl-2 levels) were significantly ameliorated by Pur treatment. Moreover, Pur pretreatment blocked 3-NP-induced inflammatory biomarkers (NF-κB, TNF-α, and iNOS) and prevented the energy deficit (ATP reduction). Nissl staining further confirmed Pur's neuroprotective effect. These results indicate that Pur may be a useful preventive approach to various neurodegenerative diseases with underlying apoptosis and neuroinflammation.

A mitochondrial basis for Huntington's disease: therapeutic prospects

Huntington's disease (HD) is an autosomal dominant disease, with overt movement dysfunctions. Despite focused research on the basis of neurodegeneration in HD for last few decades, the mechanism for the site-specific lesion of neurons in the brain is not clear. All the explanations that partially clarify the phenomenon of neurodegeneration leads to one organelle, mitochondrion, which is severely affected in HD at the level of electron transport chain, Ca(2+) buffering efficiency and morphology. But, with the existing knowledge, it is not clear whether the cell death processes in HD initiate from mitochondria, though the Huntingtin (Htt) aggregates show close proximity to this organelle, or do some extracellular stimuli like TNFα or FasL trigger the process. Mainly because of the disparity in the different available experimental models, the results are quite confusing or at least inconsistent to a great extent. The fact remains that the mutant Htt protein was seen to be associated with mitochondria directly, and as the striatum is highly enriched with dopamine and glutamate, it may make the striatal mitochondria more vulnerable because of the presence of dopa-quinones, and due to an imbalance in Ca(2+). The current therapeutic strategies are based on symptomatic relief, and, therefore, mainly target neurotransmitter(s) and their receptors to modulate behavioral outputs, but none of them targets mitochondria or try to address the basic molecular events that cause neurons to die in discrete regions of the brain, which could probably be resulting from grave mitochondrial dysfunctions. Therefore, targeting mitochondria for their protection, while addressing symptomatic recovery, holds a great potential to tone down the progression of the disease, and to provide better relief to the patients and caretakers.

Infrared laser pulse triggers increased singlet oxygen production in tumour cells

Photodynamic therapy (PDT) is a technique developed to treat the ever-increasing global incidence of cancer. This technique utilises singlet oxygen (¹O₂) generation via a laser excited photosensitiser (PS) to kill cancer cells. However, prolonged sensitivity to intensive light (6–8 weeks for lung cancer), relatively low tissue penetration by activating light (630 nm up to 4 mm), and the cost of PS administration can limit progressive PDT applications. The development of quantum-dot laser diodes emitting in the highest absorption region (1268 nm) of triplet oxygen (³O₂) presents the possibility of inducing apoptosis in tumour cells through direct ³O₂ → ¹O₂ transition. Here we demonstrate that a single laser pulse triggers dose-dependent ¹O₂ generation in both normal keratinocytes and tumour cells and show that tumour cells yield the highest ¹O₂ far beyond the initial laser pulse exposure. Our modelling and experimental results support the development of direct infrared (IR) laser-induced tumour treatment as a promising approach in tumour PDT.

Assessing competence of broccoli consumption on inflammatory and antioxidant pathways in restraint-induced models: estimation in rat hippocampus and prefrontal cortex

A growing body of evidence advocated the protective and therapeutic potential of natural compounds and phytochemicals used in diets against pathological conditions. Herein, the outcome of dietary whole broccoli consumption prior to restraint stress has been investigated in the hippocampus and prefrontal cortex of male rats, two important regions involved in the processing of responses to stressful events. Interestingly, a region-specific effect was detected regarding some of antioxidant defense system factors: nuclear factor erythroid-derived 2-related factor 2 (Nrf-2) antioxidant pathway, mitochondrial prosurvival proteins involved in mitochondrial biogenesis, and apoptotic cell death proteins. Dietary broccoli supplementation modulated the restraint-induced changes towards a consistent overall protection in the hippocampus. In the prefrontal cortex, however, despite activation of most of the protective factors, presumably as an attempt to save the system against the stress insult, some detrimental outcomes such as induced malate dehydrogenase (MDA) level and cleaved form of caspase-3 were detectable. Such diversity may be attributed in one hand to the different basic levels and/or availability of defensive mechanisms within the two studied cerebral regions, and on the other hand to the probable dose-dependent and hormetic effects of whole broccoli. More experiments are essential to demonstrate these assumptions.

Naringin modulates oxidative stress and inflammation in 3-nitropropionic acid-induced neurodegeneration through the activation of nuclear factor-erythroid 2-related factor-2 signalling pathway

Nuclear factor-erythroid 2-related factor-2 (Nrf2) mediated regulation of cellular antioxidant production and the anti-inflammatory mechanism play an important role in neuroprotection against neurodegenerative diseases. Naringin a citrus flavonone, has been reported to possess neuroprotective effect against Huntington's disease, and other neurodegenerative disorders, however the mechanisms underlying its beneficial effects on 3-nitropropionic acid (3-NP)-induced neurodegeneration are poorly defined. The objective of the present study was to investigate the neuroprotective role of naringin and delineate the mechanism of action on 3-NP-induced neurodegeneration. Rats were injected with 3-NP (10mg/kg body weight/day, i.p.) for 2 weeks to develop neurodegeneration, while naringin (80 mg/kg body weight/day, orally) was administered throughout the experimental period, 1h prior to 3-NP exposure. Thereafter rats were euthanized for biochemical, histological, and molecular studies. Treatment with naringin ameliorated the reduced glutathione/oxidized glutathione ratio with concomitant decrease in the levels of hydroxyl radical, hydroperoxide and nitrite in 3-NP-induced rats. Nissl staining and transmission electron microscopic studies showed that naringin modulated 3-NP-induced histological changes. Naringin induces NAD(P)H:quinone oxidoreductase-1, heme oxygenase-1, glutathione S-transferase P1 and gamma-glutamylcysteine ligase mRNA expressions through the activation of Nrf2 and decreased the expressions of pro-inflammatory mediators like tumour necrosis factor-alpha, cyclooxygenase-2 and inducible nitric oxide synthase. These results indicate that naringin might be beneficial in mitigating 3-NP-induced neurodegeneration through the enhancement of phase II and antioxidant gene expressions via Nrf2 activation; thereby modulating the oxidative stress and inflammatory responses.

Hesperidin and naringin attenuate hyperglycemia-mediated oxidative stress and proinflammatory cytokine production in high fat fed/streptozotocin-induced type 2 diabetic rats

Abnormal regulation of glucose and impaired carbohydrate utilization that result from a defective or deficient insulin are the key pathogenic events in type 2 diabetes mellitus (T2DM). The present study was hypothesized to investigate the beneficial effects of hesperidin and naringin on hyperglycemia-induced oxidative damage in HFD/STZ-induced diabetic rats. Diabetes was induced by feeding rats with an HFD for 2 weeks followed by an intraperitoneal injection of STZ (35 mg/kg body weight). An oral dose of 50mg/kg hesperidin or naringin was daily given for 4 weeks after diabetes induction. At the end of the experimental period, blood was obtained from jugular vein and livers were rapidly excised and homogenized for biochemical assays. In the diabetic control group, levels of glucose, glycosylated hemoglobin (HbA1c%), MDA, NO, TNF-α and IL-6 were significantly increased, while serum insulin, GSH, vitamin C, and vitamin E levels were decreased. Both hesperidin and naringin administration significantly reversed these alterations. Moreover, supplementation with either compound significantly ameliorated serum and liver MDA, NO and glutathione, and liver antioxidant enzymes. Although detailed studies are required for the evaluation of the exact mechanism of the ameliorative effects of hesperidin and naringin against diabetic complications, these preliminary experimental findings demonstrate that both hesperidin and naringin exhibit antidiabetic effects in a rat model of T2DM by potentiating the antioxidant defense system and suppressing proinflammatory cytokine production.

Beneficial effect of (-)schisandrin B against 3-nitropropionic acid-induced cell death in PC12 cells

Huntington's disease (HD) is characterized by the dysfunction of mitochondrial energy metabolism, which is associated with the functional impairment of succinate dehydrogenase (mitochondrial complex II), and pyruvate dehydrogenase (PDH). Treatment with 3-nitropropionic acid (3-NP), a potent irreversible inhibitor of succinate dehydrogenase, replicates most of the pathophysiological features of HD. In the present study, we investigated the effect of (-)schisandrin B [(-)Sch B, a potent enantiomer of schisandrin B] on 3-NP-induced cell injury in rat differentiated neuronal PC12 cells. The 3-NP caused cell necrosis, as assessed by lactate dehydrogenase (LDH) leakage, and mitochondrion-dependent cell apoptosis, as assessed by caspase-3 and caspase-9 activation, in differentiated PC12 cells. The cytotoxicity induced by 3-NP was associated with a depletion of cellular reduced glutathione (GSH) as well as the activation of redox-sensitive c-Jun N-terminal kinase (JNK) pathway and the inhibition of PDH. (-)Sch B pretreatment (5 and 15 μM) significantly reduced the extent of necrotic and apoptotic cell death in 3-NP-challenged cells. The cytoprotection afforded by (-)Sch B pretreatment was associated with the attenuation of 3-NP-induced GSH depletion as well as JNK activation and PDH inhibition. (-)Sch B pretreatment enhanced cellular glutathione redox status and ameliorated the 3-NP-induced cellular energy crisis, presumably by suppressing the activated JNK-mediated PDH inhibition, thereby protecting against necrotic and apoptotic cell death in differentiated PC12 cells.

N-Acetylcysteine reverses mitochondrial dysfunctions and behavioral abnormalities in 3-nitropropionic acid-induced Huntington's disease

Mitochondrial dysfunction is a major event involved in the pathogenesis of Huntington's disease (HD). The present study evaluates the role of N-acetyl-L-cysteine (NAC) in preventing mitochondrial dysfunctions in a 3-nitropropionic acid (3-NP)-induced model of HD. Administration of 3-NP to rats (Wistar strain) resulted in significant inhibition of mitochondrial complexes II, IV and V in the striatum. However, no significant effect on complex I was observed. Increased generation of reactive oxygen species and lipid peroxidation was observed in mitochondria of 3-NP-treated animals. Endogenous antioxidants (thiols and manganese-superoxide dismutase) were lowered in mitochondria of 3-NP-treated animals. 3-NP-treated animals showed increased cytosolic cytochrome c levels and mitochondrial swelling. Increased expressions of caspase-3 and p53 were also observed in 3-NP-treated animals. Histopathological examination of the striata of 3-NP-treated animals revealed increased neural space, neurodegeneration and gliosis. This was accompanied by cognitive and motor deficits. NAC treatment, on the other hand, was found to be effective in reversing 3-NP-induced mitochondrial dysfunctions and neurobehavioral deficits. Our findings suggest a beneficial effect of NAC in HD.

Aerobic production and utilization of lactate satisfy increased energy demands upon neuronal activation in hippocampal slices and provide neuroprotection against oxidative stress

Ever since it was shown for the first time that lactate can support neuronal function in vitro as a sole oxidative energy substrate, investigators in the field of neuroenergetics have been debating the role, if any, of this glycolytic product in cerebral energy metabolism. Our experiments employed the rat hippocampal slice preparation with electrophysiological and biochemical methodologies. The data generated by these experiments (a) support the hypothesis that lactate, not pyruvate, is the end-product of cerebral aerobic glycolysis; (b) indicate that lactate plays a major and crucial role in affording neural tissue to respond adequately to glutamate excitation and to recover unscathed post-excitation; (c) suggest that neural tissue activation is accompanied by aerobic lactate and NADH production, the latter being produced when the former is converted to pyruvate by mitochondrial lactate dehydrogenase (mLDH); (d) imply that NADH can be utilized as an endogenous scavenger of reactive oxygen species (ROS) to provide neuroprotection against ROS-induced neuronal damage.

Neuroprotective effect of naringin, a dietary flavonoid against 3-nitropropionic acid-induced neuronal apoptosis

The aim of this study was to investigate the protective effect of naringin, a flavonoid on 3-Nitropropionic acid (3-NP)-induced neurodegeneration through the modulation of intrinsic apoptotic cascade in Wistar rats. 3-NP is an irreversible inhibitor of complex II in the mitochondria. 3-NP-induced neurodegeneration has been widely used as an animal model of Huntington's disease (HD). Increased oxidative stress is one of the major deleterious events in 3-NP-induced neuronal apoptosis. Rats administered with 3-NP showed increase in the levels of lipid peroxidation and protein carbonyl, which was significantly decreased upon naringin treatment (80 mg/kg body weight). 3-NP-induced rats showed decrease in the activities of enzymic antioxidants and reduced levels of non-enzymic antioxidants. Naringin treatment ameliorated the antioxidant status by increasing the activities of enzymic antioxidants and the levels of non-enzymatic antioxidants. 3-NP-induced rats showed decrease in the activities of ATPases in striatum, which was restored to normal level upon naringin treatment. Histopathological observation of the striatal tissue showed protective role of naringin in 3-NP-induced rats. Naringin also reduced the 3-NP-induced apoptosis via decrease in the cytochrome c release from mitochondria and caspase 3 activation as revealed by Western blot. Naringin treatment also decreased the expressions of pro-apoptotic markers like Bad and Bax. Further, naringin antagonized 3-NP-induced decrease in Bcl-2 mRNA expression. The results of this study show evidence on the neuroprotective effect of naringin against 3-NP-induced neuronal apoptosis through its antioxidant and anti-apoptotic effects.

FK506 ameliorates cell death features in Huntington's disease striatal cell models

Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by striatal neurodegeneration, involving apoptosis. FK506, an inhibitor of calcineurin (or protein phosphatase 3, formerly known as protein phosphatase 2B), has shown neuroprotective effects in several cellular and animal models of HD. In the present study, we show the protective effects of FK506 in two striatal HD models, primary rat striatal neurons treated with 3-nitropropionic acid (3-NP) and immortalized striatal STHdh cells derived from HD knock-in mice expressing normal (STHdh(7/7)) or full-length mutant huntingtin (FL-mHtt) with 111 glutamines (STHdh(111/111)), under basal conditions and after exposure to 3-NP or staurosporine (STS). In rat striatal neurons, FK506 abolished 3-NP-induced increase in caspase-3 activation, DNA fragmentation/condensation and necrosis. Nevertheless, in STHdh(111/111) cells under basal conditions, FK506 did not prevent, in a significant manner, the release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria, or alter Bax/Bcl-2 ratio, but significantly reverted caspase-3 activation. In STHdh(111/111) cells treated with 0.3mM 3-NP or 25 nM STS, linked to high necrosis, exposure to FK506 exerted no significant effects on caspase-3 activation. However, treatment of STHdh(111/111) cells exposed to 10nM STS with FK506 effectively prevented cell death by apoptosis and moderate necrosis. The results suggest that FK506 may be neuroprotective against apoptosis and necrosis under mild cell death stimulus in the presence of FLmHtt.

Glutamate-induced alterations in Ca2+ signaling are modulated by mitochondrial Ca2+ handling capacity in brain slices of R6/1 transgenic mice

Huntington's disease is a neurodegenerative disorder caused by an expansion of CAGs repeats and characterized by alterations in mitochondrial functions. Although changes in Ca(2+) handling have been suggested, the mechanisms involved are not completely understood. The aim of this study was to investigate the possible alterations in Ca(2+) handling capacity and the relationship with mitochondrial dysfunction evaluated by NAD(P)H fluorescence, reactive oxygen species levels, mitochondrial membrane potential (DeltaPsi(m)) measurements and respiration in whole brain slices from R6/1 mice of different ages, evaluated in situ by real-time real-space microscopy. We show that the cortex and striatum of the 9-month-old R6/1 transgenic mice present a significant sustained increase in cytosolic Ca(2+) induced by glutamate (Glu). This difference in Glu response was partially reduced in R6/1 when in the absence of extracellular Ca(2+), indicating that N-methyl-D-aspartate receptors participation in this response is more important in transgenic mice. In addition, Glu also lead to a decrease in NAD(P)H fluorescence, a loss in DeltaPsi(m) and a further increase in respiration, which may have evoked a decrease in mitochondrial Ca(2+) Ca(2+)(m) uptake capacity. Taken together, these results show that alterations in Ca(2+) homeostasis in transgenic mice are associated with a decrease in Ca(2+)(m) uptake mechanism with a diminished Ca(2+) handling ability that ultimately causes dysfunctions and worsening of the neurodegenerative and the disease processes.