Rotenone model of Parkinson disease: multiple brain mitochondria dysfunctions after short term systemic rotenone intoxication

Orientin Modulates Nrf2-ARE, PI3K/Akt, JNK-ERK1/2, and TLR4/NF-kB Pathways to Produce Neuroprotective Benefits in Parkinson's Disease

Parkinson's disease (PD) is characterized by oxidative stress and neuroinflammation as key pathological features. Emerging evidence suggests that nuclear factor erythroid 2 related factor 2-antioxidant response element (Nrf2-ARE), phosphatidylinositol 3‑kinase-protein kinase B (PI3K-Akt), c-Jun N-terminal kinase-extracellular signal-regulated kinase 1/2 (JNK-ERK1/2), and toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-kB) pathways play pivotal roles in PD pathogenesis. Orientin, a phenolic phytoconstituent, has demonstrated modulatory potential on these pathways in various experimental conditions other than PD. In this study, we aimed to evaluate the neuroprotective effects of Orientin against rotenone-induced neurodegeneration in SH-SY5Y cell lines and the Swiss albino mice model of PD. Orientin was administered at doses 10 and 20 µM in cell lines and 10 and 20 mg/kg in mice, and its effects on rotenone-induced neurodegeneration were investigated. Oxidative stress markers including mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as inflammatory markers including interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), were measured. The expression levels of genes related to Nrf2-ARE (Nrf2), PI3K/Akt (Akt), JNK-ERK1/2 (TNF-α), and TLR4/NF-kB (TNF-α) pathways were measured to understand the modulatory effect of Orientin on these pathways. Additionally, behavioral studies assessing locomotor activity, muscle coordination, and muscle rigidity were conducted with mice. Our results indicate that Orientin dose-dependently attenuated rotenone-induced changes in oxidative stress markers, inflammatory markers, gene expression levels, and behavioral parameters. Therefore, our study concludes that Orientin exhibits significant neuroprotective benefits against rotenone-induced PD by modulating Nrf2-ARE, PI3K-Akt, JNK-ERK1/2, and TLR4/NF-kB pathways.

Activation of cyclic AMP signaling pathway in dopaminergic neurons rescues locomotion defects in a Drosophila larval model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease showing uncontrollable motor symptoms that are primarily caused by the progressive loss of dopaminergic neurons in the brain. Currently no treatment exists to prevent PD progression. Therefore, discovery of new neuroprotective strategies still has great potential to benefit PD patients. A handful of studies show that activation of cAMP pathways is neuroprotective against PD progression. However, the neuroprotective role of this signaling cascade specifically in DA neurons has not been explored. In this study, fruit fly Drosophila melanogaster was used because of its sophisticated and powerful genetic approaches, especially with related to cAMP signaling pathway. We have investigated molecular mechanisms of neuroprotection in a fly larval model of PD by administering an environmental PD toxin rotenone. Increased cAMP signaling in the dunce mutant fly carrying defects in phosphodiesterase (PDE) gene, is neuroprotective against rotenone-induced locomotion deficits. Furthermore, the neuroprotective role of cAMP signaling specifically in DA neurons has been studied as it has not been explored. By using transgenic flies expressing designer receptors exclusively activated by designer drugs (DREADDs), we have shown that an increase of cAMP levels in DA neurons rescues rotenone-induced locomotion deficits. We also showed that this neuroprotection is mediated by activation of Gαs and PKA-C1 subunits. The results provide novel findings that expand our knowledge of neuroprotective mechanisms in DA neurons affecting PD progression, which could contribute to the development of new therapeutic treatments against PD. An important future study will explore downstream targets of cAMP-PKA signaling.

High Mobility Group Box 1 Protein: A Plausible Therapeutic Molecular Target in Parkinson's Disease

Parkinson's disease (PD) is a widespread neurodegenerative disorder that exerts a broad variety of detrimental effects on people's health. Accumulating evidence suggests that mitochondrial dysfunction, neuroinflammation, α-synuclein aggregation and autophagy dysfunction may all play a role in the development of PD. However, the molecular mechanisms behind these pathophysiological processes remain unknown. Currently, research in PD has focussed on high mobility group box 1 (HMGB1), and different laboratory approaches have shown promising outcomes to some level for blocking HMGB1. Given that HMGB1 regulates mitochondrial dysfunction, participates in neuroinflammation, and modulates autophagy and apoptosis, it is hypothesised that HMGB1 has significance in the onset of PD. In the current review, research targeting multiple roles of HMGB1 in PD pathology was integrated, and the issues that need future attention for targeted therapeutic approaches are mentioned.

Kynurenine attenuates mitochondrial depolarization and neuronal cell death induced by rotenone exposure independently of AhR-mediated parkin induction in SH-SY5Y differentiated cells

Rotenone is a pesticide commonly used in agriculture that is associated with the risk of developing Parkinson's disease (PD) by inducing mitochondrial damage. As a protective cell response to different challenges, they activate mitophagy, which involves parkin activity. Parkin is an E3 ubiquitin ligase necessary in the initial steps of mitophagy, and its overexpression protects against parkinsonian effects in different models. Recent studies have reported that the aryl hydrocarbon receptor (AHR), a ligand-dependent transcription factor, induces parkin expression. Kynurenine, an endogenous AHR ligand, promotes neuroprotection in chronic neurodegenerative disorders, such as PD, although its neuroprotective mechanism needs to be fully understood. Therefore, we evaluated whether the overexpression of parkin by AHR activation with kynurenine promotes autophagy and reduces the neurotoxicity induced by rotenone in SH-SY5Y cells differentiated to dopaminergic neurons. SH-SY5Y neurons were treated with rotenone or pretreated with kynurenine or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and parkin levels, apoptosis, mitochondrial potential membrane, and autophagy were determined. The results showed that kynurenine and TCDD treatments induced parkin expression in an AHR-dependent manner. Kynurenine pretreatment inhibited rotenone-induced neuronal apoptosis in 17%, and the loss of mitochondrial membrane potential in 30% when compare to rotenone alone, together with a decrease in autophagy. By contrast, although TCDD treatment increased parkin levels, non-neuroprotective effects were observed. The kynurenine protective activity was AHR independent, suggesting that parkin induction might not be related to this effect. On the other hand, kynurenine treatment inhibited alpha amine-3-hydroxy-5-methyl-4-isoxazol propionic acid and N-methyl-D-aspartate receptors, which are well-known excitotoxicity mediators activated by rotenone exposure.

Effect of Fusidic Acid and Some Nitrogen-Containing Derivatives on Liposomal and Mitochondrial Membranes

The paper assesses the membranotropic action of the natural antibiotic fusidic acid (FA) and its derivatives. It was found that a FA analogue with ethylenediamine moiety (derivative 2), in contrast to native FA and 3,11-dioxime analogue (derivative 1), is able to increase the mobility of the lipid bilayer in the zone of lipid headgroups, as well as to induce permeabilization of lecithin liposome membranes. A similar effect of derivative 2 is also observed in the case of rat liver mitochondrial membranes. We noted a decrease in the microviscosity of the mitochondrial membrane and nonspecific permeabilization of organelle membranes in the presence of this agent, which was accompanied by a decrease in mitochondrial Δψ and OXPHOS efficiency. This led to a reduction in mitochondrial calcium retention capacity. The derivatives also reduced the production of H2O2 by mitochondria. The paper considers the relationship between the structure of the tested compounds and the observed effects.

Membrane-stabilizing and protective effects of curcumin in a rotenone-induced rat model of Parkinson disease

Parkinson disease (PD) is a chronic progressive neurodegenerative disease characterized by both motor and non-motor features. Numerous risk factors (oxidative stress, free radical formation, and several environmental toxins) have been associated with PD. The experimental studies were carried out under in vivo conditions. Biochemical data analysis indicated that compared with the parameters of control (C) rats, rotenone-induced PD rats showed a significant decrease in the specific content of the total fraction of isoforms of O2--producing, heat-stable, NADPH-containing associates (NLP-Nox) from membrane formations of tissues (brain, liver, lung, and small intestine). Compared with the C group indices, in the PD and PD + curcumin (PD + CU) groups there is some change in the shape of the optical absorption spectra of isoforms associated with a change in the amount of Nox in the isoform composition of the total fraction of the NLP-Nox associate. Thus, daily administration of CU (200 mg/kg, i.p.) to PD rats for 63 days had a regulatory effect, bringing the specific content and O2--producing activity of the total fraction of NLP-Nox isoforms closer to the norm. CU has membrane-stabilizing effects in rotenone-induced PD.

Rotenone-Induced Model of Parkinson's Disease: Beyond Mitochondrial Complex I Inhibition

Parkinson's disease (PD) is usually diagnosed through motor symptoms that make the patient incapable of carrying out daily activities; however, numerous non-motor symptoms include olfactory disturbances, constipation, depression, excessive daytime sleepiness, and rapid eye movement at sleep; they begin years before motor symptoms. Therefore, several experimental models have been studied to reproduce several PD functional and neurochemical characteristics; however, no model mimics all the PD motor and non-motor symptoms to date, which becomes a limitation for PD study. It has become increasingly relevant to find ways to study the disease from its slowly progressive nature. The experimental models most frequently used to reproduce PD are based on administering toxic chemical compounds, which aim to imitate dopamine deficiency. The most used toxic compounds to model PD have been 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which inhibit the complex I of the electron transport chain but have some limitations. Another toxic compound that has drawn attention recently is rotenone, the classical inhibitor of mitochondrial complex I. Rotenone triggers the progressive death of dopaminergic neurons and α-synuclein inclusions formation in rats; also, rotenone induces microtubule destabilization. This review presents information about the experimental model of PD induced by rotenone, emphasizing its molecular characteristics beyond the inhibition of mitochondrial complex I.

Metabolic dysfunctions in the intranigral rotenone model of Parkinson's disease

Parkinson disease (PD) is a chronic neurodegenerative disorder characterized by a progressive loss of dopamine neurons in the substantia nigra pars compacta (SNpc). In the last years, a growing interest to study the relationship between metabolic dysfunction and neurodegenerative disease like PD has emerged. This study aimed to evaluate the occurrence of possible changes in metabolic homeostasis due to intranigral rotenone administration, a neurotoxin that damages dopaminergic neurons leading to motor impairments mimicking those that happen in PD. Male Wistar rats were distributed into two groups: sham (n = 10) or rotenone (n = 10). Sham group received, bilaterally, within the SNpc, 1 µL of vehicle dimethyl-sulfoxide (DMSO) and the experimental group was bilaterally injected with 1 µL of rotenone (12 µg/µL). Twenty-four hours after the stereotaxic surgeries, the animals underwent the open field test followed by subsequent peripheral blood and cerebrospinal fluid (CSF) samples collection for biochemical testing. The results showed that rotenone was able to replicate the typical motor behavior impairment seen in the disease, i.e., decrease in locomotion (P = 0.05) and increase in immobility (P = 0.01) with a strong correlation (r = - 0.85; P < 0.0001) between them. In addition, it was demonstrated that this model is able to decrease plasmatic total-cholesterol (P = 0.04) and HDL-cholesterol (P = 0.007) potentially impacting peripheral metabolism. Hence, it was revealed a potential ability to reproduce relevant metabolic dysfunctions like hyperglycemia which could be explained by acute and systemic mitochondrial rotenone toxicity and SNpc nigral toxicity. Such mechanisms may still be responsible for the potential occurrence of CSF-hyperglycemia (d = 0.7). Since intranigral rotenone is an early phase model of PD, the present results open a new road for studies aiming to investigate metabolic changes in PD.

Signaling pathways in Parkinson's disease: molecular mechanisms and therapeutic interventions

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and its treatment remains a big challenge. The pathogenesis of PD may be related to environmental and genetic factors, and exposure to toxins and gene mutations may be the beginning of brain lesions. The identified mechanisms of PD include α-synuclein aggregation, oxidative stress, ferroptosis, mitochondrial dysfunction, neuroinflammation, and gut dysbiosis. The interactions among these molecular mechanisms complicate the pathogenesis of PD and pose great challenges to drug development. At the same time, the diagnosis and detection of PD are also one of obstacles to the treatment of PD due to its long latency and complex mechanism. Most conventional therapeutic interventions for PD possess limited effects and have serious side effects, heightening the need to develop novel treatments for this disease. In this review, we systematically summarized the pathogenesis, especially the molecular mechanisms of PD, the classical research models, clinical diagnostic criteria, and the reported drug therapy strategies, as well as the newly reported drug candidates in clinical trials. We also shed light on the components derived from medicinal plants that are newly identified for their effects in PD treatment, with the expectation to provide the summary and outlook for developing the next generation of drugs and preparations for PD therapy.

Garcinia morella extract confers dopaminergic neuroprotection by mitigating mitochondrial dysfunctions and inflammation in mouse model of Parkinson's disease

Dopaminergic neuroprotection is the main interest in designing novel therapeutics against Parkinson's disease (PD). In the process of dopaminergic degeneration, mitochondrial dysfunctions and inflammation are significant. While the existing drugs provide symptomatic relief against PD, a therapy conferring total neuroprotection by targeting multiple degenerative pathways is still lacking. Garcinia morella is a common constituent of Ayurvedic medication and has been used for the treatment of inflammatory disorders. The present study investigates whether administration of G. morella fruit extract (GME) in MPTP mouse model of PD protects against dopaminergic neurodegeneration, including the underlying pathophysiologies, and reverses the motor behavioural abnormalities. Administration of GME prevented the loss of dopaminergic cell bodies in the substantia nigra and its terminals in the corpus striatum of PD mice. Subsequently, reversal of parkinsonian behavioural abnormalities, viz. akinesia, catalepsy, and rearing, was observed along with the recovery of striatal dopamine and its metabolites in the experimental model. Furthermore, reduced activity of the mitochondrial complex II in the nigrostriatal pathway of brain of the mice was restored after the administration of GME. Also, MPTP-induced enhanced activation of Glial fibrillary acidic protein (GFAP) and neuronal nitric oxide synthase (nNOS) in the nigrostriatal pathway, which are the markers of inflammatory stress, were found to be ameliorated on GME treatment. Thus, our study presented a novel mode of dopaminergic neuroprotection by G. morella in PD by targeting the mitochondrial dysfunctions and neuroinflammation, which are considered to be intricately associated with the loss of dopaminergic neurons.

Hallmarks and Molecular Tools for the Study of Mitophagy in Parkinson’s Disease

The best-known hallmarks of Parkinson’s disease (PD) are the motor deficits that result from the degeneration of dopaminergic neurons in the substantia nigra. Dopaminergic neurons are thought to be particularly susceptible to mitochondrial dysfunction. As such, for their survival, they rely on the elaborate quality control mechanisms that have evolved in mammalian cells to monitor mitochondrial function and eliminate dysfunctional mitochondria. Mitophagy is a specialized type of autophagy that mediates the selective removal of damaged mitochondria from cells, with the net effect of dampening the toxicity arising from these dysfunctional organelles. Despite an increasing understanding of the molecular mechanisms that regulate the removal of damaged mitochondria, the detailed molecular link to PD pathophysiology is still not entirely clear. Herein, we review the fundamental molecular pathways involved in PINK1/Parkin-mediated and receptor-mediated mitophagy, the evidence for the dysfunction of these pathways in PD, and recently-developed state-of-the art assays for measuring mitophagy in vitro and in vivo.

Embelin and levodopa combination therapy for improved Parkinson's disease treatment

Parkinson’s disease (PD), a progressive neurodegenerative disorder, affects dopaminergic neurons. Oxidative stress and gut damage play critical roles in PD pathogenesis. Inhibition of oxidative stress and gut damage can prevent neuronal death and delay PD progression. The objective of this study was to evaluate the therapeutic effect of embelin or the combination with levodopa (LD) in a rotenone-induced PD mouse model. At the end of experimentation, the mice were sacrificed and the midbrain was used to evaluate various biochemical parameters, such as nitric oxide, peroxynitrite, urea, and lipid peroxidation. In the substantia nigra (midbrain), tyrosine hydroxylase (TH) expression was examined by immunohistochemistry, and Nurr1 expression was evaluated by western blotting. Gut histopathology was evaluated on tissue sections stained with hematoxylin and eosin. In silico molecular docking studies of embelin and α-synuclein (α-syn) fibrils were also performed. Embelin alone or in combination with LD ameliorated oxidative stress and gut damage. TH and Nurr1 protein levels were also significantly restored. Docking studies confirmed the affinity of embelin toward α-syn. Taken together, embelin could be a promising drug for the treatment of PD, especially when combined with LD.

Mitochondrial function influences expression of methamphetamine-induced behavioral sensitization

Repeated methamphetamine use leads to long lasting brain and behavioral changes in humans and laboratory rats. These changes have high energy requirements, implicating a role for mitochondria. We explored whether mitochondrial function underpins behaviors that occur in rats months after stopping methamphetamine self-administration. Accordingly, rats self-administered intravenous methamphetamine for 3 h/day for 14 days. The mitochondrial toxin rotenone was administered as (1 mg/kg/day for 6 days) via an osmotic minipump starting at 0, 14 or 28 days of abstinence abstinence. On abstinence day 61, expression of methamphetamine-induced behavioral sensitization was obtained with an acute methamphetamine challenge in rotenone-free rats. Rotenone impeded the expression of sensitization, with the most robust effects obtained with later abstinence exposure. These findings verified that self-titration of moderate methamphetamine doses results in behavioral (and thus brain) changes that can be revealed months after exposure termination, and that the meth-initiated processes progressed during abstinence so that longer abstinence periods were more susceptible to the consequences of exposure to a mitochondrial toxin.

Avocado Oil Prevents Kidney Injury and Normalizes Renal Vasodilation after Adrenergic Stimulation in Hypertensive Rats: Probable Role of Improvement in Mitochondrial Dysfunction and Oxidative Stress

Hypertension impairs the function of the kidney and its vasculature. Adrenergic activation is involved in these processes by promoting oxidative stress and mitochondrial dysfunction. Thus, the targeting of mitochondrial function and mitochondrial oxidative stress may be an approach to alleviate hypertensive kidney damage. Avocado oil, a source of oleic acid and antioxidants, improves mitochondrial dysfunction, decreases mitochondrial oxidative stress, and enhances vascular function in hypertensive rats. However, whether avocado oil improves the function of renal vasculature during the adrenergic stimulation, and if this is related to improvement in renal damage and enhancement of mitochondrial activity is unknown. Thus, the effects of avocado oil on renal vascular responses to adrenergic stimulation, mitochondrial dysfunction, oxidative stress, and renal damage were compared with prazosin, an antagonist of α₁-adrenoceptors, in hypertensive rats induced by L-NAME. Avocado oil or prazosin decreased blood pressure, improved endothelium-dependent renal vasodilation, prevented mitochondrial dysfunction and kidney damage in hypertensive rats. However, avocado oil, but not prazosin, decreased mitochondrial ROS generation and improved the redox state of mitochondrial glutathione. These results suggest that avocado oil and prazosin prevented hypertensive renal damage due to the improvement in mitochondrial function.

Reactive Oxygen Species: Not Omnipresent but Important in Many Locations

Reactive oxygen species (ROS), such as the superoxide anion or hydrogen peroxide, have been established over decades of research as, on the one hand, important and versatile molecules involved in a plethora of homeostatic processes and, on the other hand, as inducers of damage, pathologies and diseases. Which effects ROS induce, strongly depends on the cell type and the source, amount, duration and location of ROS production. Similar to cellular pH and calcium levels, which are both strictly regulated and only altered by the cell when necessary, the redox balance of the cell is also tightly regulated, not only on the level of the whole cell but in every cellular compartment. However, a still widespread view present in the scientific community is that the location of ROS production is of no major importance and that ROS randomly diffuse from their cellular source of production throughout the whole cell and hit their redox-sensitive targets when passing by. Yet, evidence is growing that cells regulate ROS production and therefore their redox balance by strictly controlling ROS source activation as well as localization, amount and duration of ROS production. Hopefully, future studies in the field of redox biology will consider these factors and analyze cellular ROS more specifically in order to revise the view of ROS as freely flowing through the cell.

Coordinated Action of miR-146a and Parkin Gene Regulate Rotenone-induced Neurodegeneration

Mitochondrial dysfunction is a common cause in pathophysiology of different neurodegenerative diseases. Elimination of dysfunctional and damaged mitochondria is a key requirement for maintaining homeostasis and bioenergetics of degenerating neurons. Using global microRNA (miRNA) profiling in a systemic rotenone model of Parkinson's disease, we have identified miR-146a as upmost-regulated miRNA, which is known as inflammation regulatory miRNA. Here, we report the role of activated nuclear factor kappa beta (NF-kβ) in miR-146a-mediated downregulation of Parkin protein, which inhibits clearance of damaged mitochondria and induces neurodegeneration. Our studies have shown that 4-week rotenone exposure (2.5 mg/kg b.wt) induced oxidative imbalance-mediated NF-kβ activation in 1-year-old rat's brain. Activated NF-kβ binds in promoter region of miR-146a gene and induces its transcription, which downregulates levels of Parkin protein. Decreased amount of Parkin protein results in accumulation of damaged and dysfunctional mitochondria, which further promotes the generation of reactive oxygen species in degenerating neurons. In conclusion, our studies have identified direct role of NF-kβ-mediated upregulation of miR-146a in regulating mitophagy through inhibition of the Parkin gene.

Microemulsion-based gel for the transdermal delivery of rasagiline mesylate: In vitro and in vivo assessment for Parkinson's therapy

Rasagiline mesylate (RSM) is a selective and irreversible monoamine oxidase B inhibitor used for the treatment of Parkinson's disease (PD). However, its unfavorable biopharmaceutical properties, such as extensive degradation in the gastrointestinal tract and first-pass metabolism are responsible for its low oral bioavailability and suboptimal therapeutic efficacy. Here, we report the feasibility of delivering RSM via the transdermal route using RSM containing microemulsion-based gel (RSM-MEG) to achieve effective management of PD. Our in vitro skin permeation studies of RSM-MEG showed significantly higher (at least ~1.5-fold) permeation across rat skin compared to the conventional RSM hydrogel. Our skin irritation studies in rabbits showed that RSM-MEG is safe for transdermal application. Finally, using the rat model of rotenone-induced Parkinsonism, we demonstrated that the topical application of RSM-MEG was equally effective in reversing PD symptoms when compared to oral RSM therapy. Thus, our study confirmed the feasibility and potential of transdermal delivery of RSM via simple topical application of RSM-MEG, and this approach could be an alternative therapeutic intervention for the treatment of Parkinson's disease.

Beyond mitochondria: Alternative energy-producing pathways from all strata of life

It is well-established that mitochondria are the powerhouses of the cell, producing adenosine triphosphate (ATP), the universal energy currency. However, the most significant strengths of the electron transport chain (ETC), its intricacy and efficiency, are also its greatest downfalls. A reliance on metal complexes (FeS clusters, hemes), lipid moities such as cardiolipin, and cofactors including alpha-lipoic acid and quinones render oxidative phosphorylation vulnerable to environmental toxins, intracellular reactive oxygen species (ROS) and fluctuations in diet. To that effect, it is of interest to note that temporal disruptions in ETC activity in most organisms are rarely fatal, and often a redundant number of failsafes are in place to permit continued ATP production when needed. Here, we highlight the metabolic reconfigurations discovered in organisms ranging from parasitic Entamoeba to bacteria such as pseudomonads and then complex eukaryotic systems that allow these species to adapt to and occasionally thrive in harsh environments. The overarching aim of this review is to demonstrate the plasticity of metabolic networks and recognize that in times of duress, life finds a way.

Functions of ROS in Macrophages and Antimicrobial Immunity

Reactive oxygen species (ROS) are a chemically defined group of reactive molecules derived from molecular oxygen. ROS are involved in a plethora of processes in cells in all domains of life, ranging from bacteria, plants and animals, including humans. The importance of ROS for macrophage-mediated immunity is unquestioned. Their functions comprise direct antimicrobial activity against bacteria and parasites as well as redox-regulation of immune signaling and induction of inflammasome activation. However, only a few studies have performed in-depth ROS analyses and even fewer have identified the precise redox-regulated target molecules. In this review, we will give a brief introduction to ROS and their sources in macrophages, summarize the versatile roles of ROS in direct and indirect antimicrobial immune defense, and provide an overview of commonly used ROS probes, scavengers and inhibitors.

Mitochondrial function is impaired in the primary visual cortex in an experimental glaucoma model

Glaucoma is a neurodegenerative disease that affects eye structures and brain areas related to the visual system. Oxidative stress plays a key role in the development and progression of the disease. The aims of the present study were to evaluate the mitochondrial function and its participation in the brain redox metabolism in an experimental glaucoma model. 3-month-old female Wistar rats were subjected to cauterization of two episcleral veins of the left eye to elevate the intraocular pressure. Seven days after surgery, animals were sacrificed, the brain was carefully removed and the primary visual cortex was dissected. Mitochondrial bioenergetics and ROS production, and the antioxidant enzyme defenses from both mitochondrial and cytosolic fractions were evaluated. When compared to control, glaucoma decreased mitochondrial ATP production (23%, p < 0.05), with an increase in superoxide and hydrogen peroxide production (30%, p < 0.01 and 28%, p < 0.05, respectively), whereas no changes were observed in membrane potential and oxygen consumption rate. In addition, the glaucoma group displayed a decrease in complex II activity (34%, p < 0.01). Moreover, NOX4 expression was increased in glaucoma compared to the control group (27%, p < 0.05). Regarding the activity of enzymes associated with the regulation of the redox status, glaucoma showed an increase in mitochondrial SOD activity (34%, p < 0.05), mostly due to an increase in Mn-SOD (50%, p < 0.05). A decrease in mitochondrial GST activity was observed (11%, p < 0.05). GR and TrxR activity were decreased in both mitochondrial (16%, p < 0.05 and 20%, p < 0.05 respectively) and cytosolic (21%, p < 0.01 and 50%, p < 0.01 respectively) fractions in the glaucoma group. Additionally, glaucoma showed an increase in cytoplasmatic GPx (50%, p < 0.01). In this scenario, redox imbalance took place resulting in damage to mitochondrial lipids (39%, p < 0.01) and proteins (70%, p < 0.05). These results suggest that glaucoma leads to mitochondrial function impairment in brain visual targets, that is accompanied by an alteration in both mitochondrial and cytoplasmatic enzymatic defenses. As a consequence of redox imbalance, oxidative damage to macromolecules takes place and can further affect vital cellular functions. Understanding the role of the mitochondria in the development and progression of the disease could bring up new neuroprotective therapies.

Phospholipase iPLA2β averts ferroptosis by eliminating a redox lipid death signal

Ferroptosis, triggered by discoordination of iron, thiols and lipids, leads to the accumulation of 15-hydroperoxy (Hp)-arachidonoyl-phosphatidylethanolamine (15-HpETE-PE), generated by complexes of 15-lipoxygenase (15-LOX) and a scaffold protein, phosphatidylethanolamine (PE)-binding protein (PEBP)1. As the Ca²⁺-independent phospholipase A₂β (iPLA₂β, PLA2G6 or PNPLA9 gene) can preferentially hydrolyze peroxidized phospholipids, it may eliminate the ferroptotic 15-HpETE-PE death signal. Here, we demonstrate that by hydrolyzing 15-HpETE-PE, iPLA₂β averts ferroptosis, whereas its genetic or pharmacological inactivation sensitizes cells to ferroptosis. Given that PLA2G6 mutations relate to neurodegeneration, we examined fibroblasts from a patient with a Parkinson's disease (PD)-associated mutation (fPD^R747W) and found selectively decreased 15-HpETE-PE-hydrolyzing activity, 15-HpETE-PE accumulation and elevated sensitivity to ferroptosis. CRISPR-Cas9-engineered Pnpla9^R748W/R748W mice exhibited progressive parkinsonian motor deficits and 15-HpETE-PE accumulation. Elevated 15-HpETE-PE levels were also detected in midbrains of rotenone-infused parkinsonian rats and α-synuclein-mutant Snca^A53T mice, with decreased iPLA₂β expression and a PD-relevant phenotype. Thus, iPLA₂β is a new ferroptosis regulator, and its mutations may be implicated in PD pathogenesis.

Therapeutic potential of mangiferin in the treatment of various neuropsychiatric and neurodegenerative disorders

Xanthones are important chemical class of bioactive products that confers therapeutic benefits. Of several xanthones, mangiferin is known to be distributed widely across several fruits, vegetables and medicinal plants. Mangiferin has been shown to exert neuroprotective effects in both in-vitro and in-vivo models. Mangiferin attenuates cerebral infarction, cerebral edema, lipid peroxidation (MDA), neuronal damage, etc. Mangiferin further potentiate levels of endogenous antioxidants to confer protection against the oxidative stress inside the neurons. Mangiferin is involved in the regulation of various signaling pathways that influences the production and levels of proinflammatory cytokines in brain. Mangiferin cosunteracted the neurotoxic effect of amyloid-beta, MPTP, rotenone, 6-OHDA etc and confer protection to neurons. These evidence suggested that the mangiferin may be a potential therapeutic strategy for the treatment of various neurological disorders. The present review demonstrated the pharmacodynamics-pharmacokinetics of mangiferin and neurotherapeutic potential in several neurological disorders with underlying mechanisms.

Approaches for Reactive Oxygen Species and Oxidative Stress Quantification in Epilepsy

Oxidative stress (OS) and excessive reactive oxygen species (ROS) production have been implicated in many neurological pathologies, including acute seizures and epilepsy. Seizure-induced damage has been demonstrated both in vitro and in several in vivo seizure and epilepsy models by direct determination of ROS, and by measuring indirect markers of OS. In this manuscript, we review the current reliable methods for quantifying ROS-related and OS-related markers in pre-clinical and clinical epilepsy studies. We first provide pieces of evidence for the involvement of different sources of ROS in epilepsy. We then discuss general methods and assays used for the ROS measurements, mainly superoxide anion, hydrogen peroxide, peroxynitrite, and hydroxyl radical in in vitro and in vivo studies. In addition, we discuss the role of these ROS and markers of oxidative injury in acute seizures and epilepsy pre-clinical studies. The indirect detection of secondary products of ROS such as measurements of DNA damage, lipid peroxidation, and protein oxidation will also be discussed. This review also discusses reliable methods for the assessment of ROS, OS markers, and their by-products in epilepsy clinical studies.

Age-Related Deterioration of Mitochondrial Function in the Intestine

Aging is an important and inevitable biological process in human life, associated with the onset of chronic disease and death. The mechanisms behind aging remain unclear. However, changes in mitochondrial function and structure, including reduced activity of the mitochondrial respiratory chain and increased production of reactive oxygen species—thus oxidative damage—are believed to play a major role. Mitochondria are the main source of cellular energy, producing adenosine triphosphate (ATP) via oxidative phosphorylation. Accumulation of damaged cellular components reduces a body's capacity to preserve tissue homeostasis and affects biological aging and all age-related chronic conditions. This includes the onset and progression of classic degenerative diseases such as cardiovascular disease, kidney failure, neurodegenerative diseases, and cancer. Clinical manifestations of intestinal disorders, such as mucosal barrier dysfunction, intestinal dysmotility, and chronic obstipation, are highly prevalent in the elderly population and have been shown to be associated with an age-dependent decline of mitochondrial function. This review summarizes our current understanding of the role of mitochondrial dysfunction in intestinal aging.

Novel Drosophila model for parkinsonism by targeting phosphoglycerate kinase

Patients with Parkinson's disease (PD) show a common progressive neurodegenerative movement disorder characterized by rigidity, tremors, postural instability, and bradykinesia due to the loss of dopaminergic neurons in the substantia nigra, and is often accompanied by several non-motor symptoms, called parkinsonism. Several lines of recent evidence support the hypothesis that mutations in the gene encoding phosphoglycerate kinase (PGK) play an important role in the PD mechanism. PGK is a key enzyme in the glycolytic pathway that catalyzes the reaction from 1,3-diphosphoglycerate to 3-phosphoglycerate. We herein established a parkinsonism model targeting Drosophila Pgk. Dopaminergic (DA) neuron-specific Pgk knockdown lead to locomotive defects in both young and aged adult flies and was accompanied by progressive DA neuron loss with aging. Pgk knockdown in DA neurons decreased dopamine levels in the central nervous system (CNS) of both young and aged adult flies. These phenotypes are similar to the defects observed in human PD patients, suggesting that the Pgk knockdown flies established herein are a promising model for parkinsonism. Furthermore, pan-neuron-specific Pgk knockdown induced low ATP levels and the accumulation of reactive oxygen species (ROS) in the CNS of third instar larvae. Collectively, these results indicate that a failure in the energy production system of Pgk knockdown flies causes locomotive defects accompanied by neuronal dysfunction and degeneration in DA neurons.

Mitochondrial Complex I Is an Essential Player in LPS-Induced Preconditioning in Differentiated PC12 Cells

Preconditioning (PC) as a protective strategy against noxious insults can decline cell death and apoptosis. It has been approved that mitochondria play a key role in PC mechanism. The critical role of complex I (CI) in oxidative phosphorylation machinery and intracellular ROS production, particularly in the brain, accentuates its possible role in PC-induced neuroprotection. Here, differentiated PC12 cells were preconditioned with ultra-low dose LPS (ULD, 3 μg/mL) prior to exposure to high concentration of LPS (HD, 750 μg/mL). Our results showed that HD LPS treatment reduces cell viability and CI activity, and intensifies expression of cleaved caspase 3 compared to the control group. Intriguingly, PC induction resulted in enhancement of cell viability and CI activity and reduction of caspase3 cleavage compared to HD LPS group. In order to explore the role of CI in PC, we combined the ULD LPS with rotenone, a CI inhibitor. Following rotenone administration, cell viability significantly reduced while caspase3 cleavage increased compared to PC induction group. Taken together, cell survival and reduction of apoptosis followed by PC can be at least partially attributed to the preservation of mitochondrial CI function.

Cellular mechanisms of complex I-associated pathology

Mitochondria control vitally important functions in cells, including energy production, cell signalling and regulation of cell death. Considering this, any alteration in mitochondrial metabolism would lead to cellular dysfunction and the development of a disease. A large proportion of disorders associated with mitochondria are induced by mutations or chemical inhibition of the mitochondrial complex I - the entry point to the electron transport chain. Subunits of the enzyme NADH: ubiquinone oxidoreductase, are encoded by both nuclear and mitochondrial DNA and mutations in these genes lead to cardio and muscular pathologies and diseases of the central nervous system. Despite such a clear involvement of complex I deficiency in numerous disorders, the molecular and cellular mechanisms leading to the development of pathology are not very clear. In this review, we summarise how lack of activity of complex I could differentially change mitochondrial and cellular functions and how these changes could lead to a pathology, following discrete routes.

DNA damage and repair in Parkinson's disease: Recent advances and new opportunities

Parkinson's disease (PD) is the most common movement neurodegenerative disorder. Although our understanding of the underlying mechanisms of pathogenesis in PD has greatly expanded, this knowledge thus far has failed to translate into disease-modifying therapies. Therefore, it is of the utmost urgency to interrogate further the multifactorial etiology of PD. DNA repair defects cause many neurodegenerative diseases. An exciting new PD research avenue is the role that DNA damage and repair may play in neuronal death. The goal of this mini-review was to discuss the evidence for the types of DNA damage that accumulates in PD, which has provided clues for which DNA repair pathways, such as DNA double-strand break repair, are dysfunctional. We further highlight compelling data for activation of the DNA damage response in familial and idiopathic PD. The significance of DNA damage and repair is emerging in the PD field and linking these insights to PD pathogenesis may provide new insights into PD pathophysiology and consequently lead to new therapies.

Mangiferin: A multipotent natural product preventing neurodegeneration in Alzheimer's and Parkinson's disease models

Alzheimer's disease (AD) and Parkinson's disease (PD) are recognized as the universal neurodegenerative diseases, with the involvement of misfolded proteins pathology, leading to oxidative stress, glial cells activation, neuroinflammation, mitochondrial dysfunction, and cellular apoptosis. Several discoveries indicate that accumulation of pathogenic proteins, i.e. amyloid β (Aβ), the microtubule-binding protein tau, and α-synuclein, are parallel with oxidative stress, neuroinflammation, and mitochondrial dysfunction. Whether the causative factors are misfolded proteins or these pathophysiological changes, leading to neurodegeneration still remain ambiguous. Importantly, directing pharmacological researches towards the prevention of AD and PD seem a promising approach to detect these complicating mechanisms, and provide new insight into therapy for AD and PD patients. Mangiferin (MGF, 2-C-β-D-glucopyranosyl-1, 3, 6, 7-tetrahydroxyxanthone), well-known as a natural product, is detached from multiple plants, including Mangifera indica L. With the structure of C-glycosyl and phenolic moiety, MGF possesses multipotent properties starting from anti-oxidant effects, to the alleviation of mitochondrial dysfunction, neuroinflammation, and cellular apoptosis. In particular, MGF can cross the blood-brain barrier to exert neuronal protection. Different researches implicate that MGF is able to protect the central nervous system from oxidative stress, mitochondrial dysfunction, neuroinflammation, and apoptosis under in vitro and in vivo models. Additional facts support that MGF plays a role in improving the declined memory and cognition of rat models. Taken together, the neuroprotective capacity of MGF may stand out as an agent candidate for AD and PD therapy.

Soluble epoxide hydrolase inhibitor, APAU, protects dopaminergic neurons against rotenone induced neurotoxicity: Implications for Parkinson's disease

Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid, play a crucial role in cytoprotection by attenuating oxidative stress, inflammation and apoptosis. EETs are rapidly metabolised in vivo by the soluble epoxide hydrolase (sEH). Increasing the half life of EETs by inhibiting the sEH enzyme is a novel strategy for neuroprotection. In the present study, sEH inhibitors APAU was screened in silico and further evaluated for their antiparkinson activity against rotenone (ROT) induced neurodegeneration in N27 dopaminergic cell line and Drosophila melanogaster model of Parkinson disease (PD). In the in vitro study cell viability (MTT and LDH release assay), oxidative stress parameters (total intracellular ROS, hydroperoxides, protein oxidation, lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidise, glutathione reductase, glutathione, total antioxidant status, mitochondrial complex-1activity and mitochondrial membrane potential), inflammatory markers (IL-6, COX-1 and COX-2), and apoptotic markers (JNK, phospho-JNK, c-jun, phospho-c-jun, pro and active caspase-3) were assessed to study the neuroprotective effects. In vivo activity of APAU was assessed in Drosophila melanogaster by measuring survival rate, negative geotaxis, oxidative stress parameters (total intracellular ROS, hydroperoxides, glutathione levels) were measured. Dopamine and its metabolites were estimated by LC-MS/MS analysis. In the in silico study the molecule, APAU showed good binding interaction at the active site of sEH (PDB: 1VJ5). In the in vitro study, APAU significantly attenuated ROT induced changes in oxidative, pro-inflammatory and apoptotic parameters. In the in vivo study, APAU significantly attenuates ROT induced changes in survival rate, negative geotaxis, oxidative stress, dopamine and its metabolites levels (p < 0.05). Our study, therefore, concludes that the molecule APAU, has significant neuroprotection benefits against rotenone induced Parkinsonism.

Revisiting the Paraquat-Induced Sporadic Parkinson's Disease-Like Model

Parkinson's disease (PD) is a major neurodegenerative disorder that affects 1-2% of the total global population. Despite its high prevalence and publication of several studies focused on understanding its pathology, an effective treatment that stops and/or reverses the damage to dopaminergic neurons is unavailable. Similar to other neurodegenerative disorders, PD etiology may be linked to several factors, including genetic susceptibility and environmental elements. Regarding environmental factors, several neurotoxic pollutants, including 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), have been identified. Moreover, some pesticides/herbicides, such as rotenone, paraquat (PQ), maneb (MB), and mancozeb (MZ), cause neurotoxicity and induce a PD-like pathology. Based on these findings, several in vitro and in vivo PD-like models have been developed to understand the pathophysiology of PD and evaluate different therapeutic strategies to fight dopaminergic neurodegeneration. 6-OHDA and MPTP are common models used in PD research, and pesticide-based approaches have become secondary models of study. However, some herbicides, such as PQ, are commonly used by farming laborers in developing countries. Thus, the present review summarizes the relevant scientific background regarding the use and effects of chronic exposure to PQ in the context of PD. Similarly, we discuss the relevance of PD-like models developed using this agrochemical compound.

Dopamine D2 receptor-mediated neuroprotection in a G2019S Lrrk2 genetic model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder in which genetic and environmental factors synergistically lead to loss of midbrain dopamine (DA) neurons. Mutation of leucine-rich repeated kinase2 (Lrrk2) genes is responsible for the majority of inherited familial cases of PD and can also be found in sporadic cases. The pathophysiological role of this kinase has to be fully understood yet. Hyperactivation of Lrrk2 kinase domain might represent a predisposing factor for both enhanced striatal glutamatergic release and mitochondrial vulnerability to environmental factors that are observed in PD. To investigate possible alterations of striatal susceptibility to mitochondrial dysfunction, we performed electrophysiological recordings from the nucleus striatum of a G2019S Lrrk2 mouse model of PD, as well as molecular and morphological analyses of G2019S Lrrk2-expressing SH-SY5Y neuroblastoma cells. In G2019S mice, we found reduced striatal DA levels, according to the hypothesis of alteration of dopaminergic transmission, and increased loss of field potential induced by the mitochondrial complex I inhibitor rotenone. This detrimental effect is reversed by the D2 DA receptor agonist quinpirole via the inhibition of the cAMP/PKA intracellular pathway. Analysis of mitochondrial functions in G2019S Lrrk2-expressing SH-SY5Y cells revealed strong rotenone-induced oxidative stress characterized by reduced Ca2+ buffering capability and ATP synthesis, production of reactive oxygen species, and increased mitochondrial fragmentation. Importantly, quinpirole was able to prevent all these changes. We suggest that the G2019S-Lrrk2 mutation is a predisposing factor for enhanced striatal susceptibility to mitochondrial dysfunction induced by exposure to mitochondrial environmental toxins and that the D2 receptor stimulation is neuroprotective on mitochondrial function, via the inhibition of cAMP/PKA intracellular pathway. We suggest new possible neuroprotective strategies for patients carrying this genetic alteration based on drugs specifically targeting Lrrk2 kinase domain and mitochondrial functionality.

Understanding Miro GTPases: Implications in the Treatment of Neurodegenerative Disorders

The Miro GTPases represent an unusual subgroup of the Ras superfamily and have recently emerged as important mediators of mitochondrial dynamics and for maintaining neuronal health. It is now well-established that these enzymes act as essential components of a Ca²⁺-sensitive motor complex, facilitating the transport of mitochondria along microtubules in several cell types, including dopaminergic neurons. The Miros appear to be critical for both anterograde and retrograde mitochondrial transport in axons and dendrites, both of which are considered essential for neuronal health. Furthermore, the Miros may be significantly involved in the development of several serious pathological processes, including the development of neurodegenerative and psychiatric disorders. In this review, we discuss the molecular structure and known mitochondrial functions of the Miro GTPases in humans and other organisms, in the context of neurodegenerative disease. Finally, we consider the potential human Miros hold as novel therapeutic targets for the treatment of such disease.

Mitochondrial Complex I Reversible S-Nitrosation Improves Bioenergetics and Is Protective in Parkinson's Disease

AIMS

This study was designed to explore the neuroprotective potential of inorganic nitrite as a new therapeutic avenue in Parkinson's disease (PD).

RESULTS

Administration of inorganic nitrite ameliorates neuropathology in phylogenetically distinct animal models of PD. Beneficial effects are not confined to prophylactic treatment and also occur if nitrite is administered when the pathogenic cascade is already active. Mechanistically, the effect is mediated by both complex I S-nitrosation, which under nitrite administration is favored over formation of other forms of oxidation, and down-stream activation of the antioxidant Nrf2 pathway. Nitrite also rescues respiratory reserve capacity and increases proton leakage in LRRK2 PD patients' dermal fibroblasts.

INNOVATION

The study proposes an unprecedented approach based on the administration of the nitrosonium donor nitrite to contrast complex I and redox anomalies in PD. Dysfunctional mitochondrial complex I propagates oxidative stress in PD, and treatments mitigating this defect may, therefore, limit disease progression. Therapeutic complex I targeting has been successfully achieved in ischemia/reperfusion by using nitrosonium donors such as nitrite to reversibly modify its subunits and protect from oxidative damage after reperfusion. This evidence led to the innovative hypothesis that nitrite could exert protective effects also in pathological conditions where complex I dysfunction occurs in normoxia, such as in PD.

CONCLUSIONS

Overall, these results demonstrate that administration of inorganic nitrite improves mitochondrial function in PD, and it, therefore, represents an amenable intervention to hamper disease progression. Antioxid. Redox Signal. 28, 44-61.

Achyranthes bidentata polypeptide protects dopaminergic neurons from apoptosis induced by rotenone and 6-hydroxydopamine

It has been well documented that Achyranthes bidentata polypeptides (ABPPs) are potent neuroprotective agents in several types of neurons. However, whether ABPPs protect dopaminergic neurons from apoptosis induced by neurotoxins is still unknown. This study was designed to observe the effect of ABPPk, a purified fraction of ABPPs, on apoptosis of dopaminergic neurons. SH-5YHY cells and primary dopaminergic neurons were pre-treated with ABPPk (25, 50, or 100 ng/mL) for 12 hours. Cells were then exposed to 6-hydroxydopamine (50 or 150 μM) or rotenone (50 or 200 μM) for 36 hours to induce cell apoptosis. Our results demonstrate that ABPPk markedly increased viability in SH-SY5Y cells and primary dopaminergic neurons, decreased lactate dehydrogenase activity and number of apoptotic dopaminergic neurons, elevated mitochondrial membrane potential, and increased Bcl-2/Bax ratio. These findings suggest that ABPPk protects dopaminergic neurons from apoptosis, and that ABPPk treatment might be an effective intervention for treating dopaminergic neuronal loss associated with disorders such as Parkinson's disease.

Inflammasomes in CNS Diseases

Neuroinflammation is a common pathological feature in almost all neurological diseases and is a response triggered as a consequence of the chronic activation of the innate immune response in the CNS against a variety of stimuli, including infection, traumatic brain injury, toxic metabolites, aggregated proteins, or autoimmunity. Crucial mediators of this neurinflammatory process are the intracellular protein complexes known as inflammasomes which can be triggered by pathogens as well as pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). However, chronic inflammasome activation can eventually result in cellular death and tissue damage, leading to the release of DAMPs that can reactivate the inflammasome, thereby propagating a vicious cycle of inflammation. The primary cells involved in CNS inflammasome activation are the immunocompetent microglia and the infiltrating macrophages into the CNS. However, astrocytes and neurons also express inflammasomes, and the understanding of how they are engaged in the pathogenesis of a variety of neurological diseases is crucial to develop effective therapeutic approaches for CNS pathologies that are propagated by chronic inflammasome activation. This chapter covers the activation mechanisms of relevant inflammasomes in the brain and summarizes their roles in the pathogenesis and progression of different neurological conditions.

MDR1 deficiency impairs mitochondrial homeostasis and promotes intestinal inflammation

The multidrug resistance-1 (MDR1) gene encodes an ATP-dependent efflux transporter that is highly expressed in the colon. In mice, loss of MDR1 function results in colitis with similarities to human inflammatory bowel diseases (IBD). Here, we show that MDR1 has an unexpected protective role for the mitochondria where MDR1 deficiency results in mitochondrial dysfunction with increased mitochondrial reactive oxygen species (mROS) driving the development of colitis. Exogenous induction of mROS accelerates, while inhibition attenuates colitis in vivo; these effects are amplified in MDR1 deficiency. In human IBD, MDR1 is negatively correlated to SOD2 gene expression required for mROS detoxification. To provide direct evidential support, we deleted intestinal SOD2 gene in mice and showed an increased susceptibility to colitis. We exploited the genome-wide association data sets and found many (∼5%) of IBD susceptibility genes with direct roles in regulating mitochondria homeostasis. As MDR1 primarily protects against xenotoxins via its efflux function, our findings implicate a distinct mitochondrial toxin+genetic susceptibility interaction leading to mitochondrial dysfunction, a novel pathogenic mechanism that could offer many new therapeutic opportunities for IBD.

Melatonin protects against behavioral deficits, dopamine loss and oxidative stress in homocysteine model of Parkinson's disease

AIM

Hyperhomocysteinemia and homocysteine (Hcy) mediated dopaminergic neurotoxicity is a matter of concern in the pathophysiology of Parkinson's disease (PD). Our previous study established the involvement of oxidative stress in the substantia nigra (SN) of Hcy rat model of PD; however, the role of antioxidants, such as melatonin, was not tested in this model.

MAIN METHODS

Melatonin (10, 20 and 30mg/kg, i.p.) was administered to rats injected with Hcy in right SN (1.0μmol in 2μl saline) to investigate its potency in attenuating the behavioral abnormalities, dopamine depletion and oxidative stress prompted by Hcy.

KEY FINDINGS

Treatment of melatonin protected against nigral dopamine loss and replenished the striatal dopamine loss that resulted in amelioration of rotational behavioral bias in Hcy denervated animals. Melatonin administration significantly improved mitochondrial complex-I activity and protected the SN neurons from the toxic insults of oxidative stress induced by Hcy. Amelioration of oxidative stress by melatonin in Hcy-infused SN was bought by dose-dependently scavenging of hydroxyl radicals, restoration of glutathione level and elevation in the activity of antioxidant enzymes.

SIGNIFICANCE

The observations bring into light the significant neuroprotective potentials of melatonin in Hcy model of PD which is attributed to the attenuation of oxidative stress in SN.

Physiological Levels of Nitric Oxide Diminish Mitochondrial Superoxide. Potential Role of Mitochondrial Dinitrosyl Iron Complexes and Nitrosothiols

Mitochondria are the major source of superoxide radicals and superoxide overproduction contributes to cardiovascular diseases and metabolic disorders. Endothelial dysfunction and diminished nitric oxide levels are early steps in the development of these pathological conditions. It is known that physiological production of nitric oxide reduces oxidative stress and inflammation, however, the precise mechanism of “antioxidant” effect of nitric oxide is not clear. In this work we tested the hypothesis that physiological levels of nitric oxide diminish mitochondrial superoxide production without inhibition of mitochondrial respiration. In order to test this hypothesis we analyzed effect of low physiological fluxes of nitric oxide (20 nM/min) on superoxide and hydrogen peroxide production by ESR spin probes and Amplex Red in isolated rat brain mitochondria. Indeed, low levels of nitric oxide substantially attenuated both basal and antimycin A-stimulated production of reactive oxygen species in the presence of succinate or glutamate/malate as mitochondrial substrates. Furthermore, slow releasing NO donor DPTA-NONOate (100 μM) did not change oxygen consumption in State 4 and State 3. However, the NO-donor strongly inhibited oxygen consumption in the presence of uncoupling agent CCCP, which is likely associated with inhibition of the over-reduced complex IV in uncoupled mitochondria. We have examined accumulation of dinitrosyl iron complexes and nitrosothiols in mitochondria treated with fast-releasing NO donor MAHMA NONOate (10 μM) for 30 min until complete release of NO. Following treatment with NO donor, mitochondria were frozen for direct detection of dinitrosyl iron complexes using Electron Spin Resonance (ESR) while accumulation of nitrosothiols was measured by ferrous-N-Methyl-D-glucamine dithiocarbamate complex, Fe(MGD)₂, in lysed mitochondria. Treatment of mitochondria with NO-donor gave rise to ESR signal of dinitrosyl iron complexes while ESR spectra of Fe(MGD)₂ supplemented mitochondrial lysates showed presence of both dinitrosyl iron complexes and nitrosothiols. We suggest that nitric oxide attenuates production of mitochondrial superoxide by post-translational modifications by nitrosylation of protein cysteine residues and formation of protein dinitrosyl iron complexes with thiol-containing ligands and, therefore, nitric oxide reduction in pathological conditions associated with endothelial dysfunction may increase mitochondrial oxidative stress.

Neuroprotective effects of phloretin and its glycosylated derivative on rotenone-induced toxicity in human SH-SY5Y neuronal-like cells

Phloretin and phlorizin are the two strong natural antioxidants whose biological and pharmacological applications are rapidly growing in different human pathological conditions. The neuroprotective activity of the two flavonoids has been analyzed on cell culture of neuroblastoma cells. The neuroprotective activity of the two flavonoids has been analyzed on cell culture of neuroblastoma cells and evaluated by testing cell vitality, mitochondrial transmembrane potential and ROS production, antioxidant enzymes detection, activation of caspase 3, DNA damage, protein carbonylation, lipid peroxidation, and superoxide anion scavenging activity. Incubation of cells with rotenone caused cell death and significant increase in intracellular reactive oxygen species, activation of caspase 3, and variation in mitochondrial transmembrane potential. Although, rotenone exposure caused a significant increase of antioxidant enzymes, high levels of lipid peroxidation were also observed. Phloretin or phlorizin, at micromolar concentration, reduced rotenone-induced cell death by scavenging ability against superoxide anion radical, one of the main effectors of rotenone toxicity at level of mitochondrial respiratory chain complex I. Under our experimental conditions, a reduction of the intracellular ROS levels with consequent normalization of the aforementioned antioxidant enzymes occurred. Concomitantly, we observed the inhibition of caspase 3 activity and DNA damage. This study shows the promising neuroprotective ability of the two dihydrochalcones able to protect human differentiated neuroblastoma cells (commonly used as model of Parkinson's disease) from injury induced by rotenone, actively scavenging ROS, normalizing mitochondrial transmembrane potential and consequently avoiding energy depletion. © 2017 BioFactors, 43(4):549-557, 2017.

Neural Repair Strategies for Parkinson's Disease: Insights from Primate Models

Nonhuman primate models of Parkinson's disease (PD) have been invaluable to our understanding of the human disease and in the advancement of novel therapies for its treatment. In this review, we attempt to give a brief overview of the animal models of PD currently used, with a more comprehensive focus on the advantages and disadvantages presented by their use in the nonhuman primate. In particular, discussion addresses the 6-hydroxydopamine (6-OHDA), 1-methyl-1,2,3,6-tetrahydopyridine (MPTP), rotenone, paraquat, and maneb parkinsonian models. Additionally, the role of primate PD models in the development of novel therapies, such as trophic factor delivery, grafting, and deep brain stimulation, are described. Finally, the contribution of primate PD models to our understanding of the etiology and pathology of human PD is discussed.