Nitration and inactivation of tyrosine hydroxylase by peroxynitrite

Gene Therapy Targeting GD3 Synthase Protects Against MPTP-Induced Parkinsonism and Executive Dysfunction

More than half of Parkinson's patients exhibit fronto-striatally mediated executive dysfunction, including deficits in sustained attention, judgment, and impulse control. We have previously shown that modification of brain gangliosides by targeted deletion of GD3 synthase (GD3S) is neuroprotective in vivo and in vitro. The objective of the present study was to determine whether GD3S knockdown will protect neurons and prevent executive dysfunction following a subchronic regimen of 25-mg/kg 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). C57BL/6N wild-type mice were assessed on a battery of sensorimotor tasks and a reaction-time task that included measures of sustained attention and impulse control. Sustained attention was measured by response accuracy and reaction time; impulsivity was measured by premature responding in the response holes or the food well during the precue period. After reaching stable performance, mice received intrastriatal injections of a recombinant adeno-associated viral (AAV) vector expressing a short-hairpin RNA (shRNA) construct targeting St8sia1, the gene that codes for GD3S, or a scrambled-sequence control (scrRNA). After 4 weeks, mice received MPTP or saline injections. MPTP-lesioned mice in the scrRNA control group exhibited loss of impulse control in the sessions following MPTP injections, compared to the other three groups. These deficits abated with extended training but re-emerged on challenge sessions with shorter cue durations or longer precue durations. GD3S knockdown partially protected nigrostriatal neurons from MPTP neurotoxicity and prevented the motor impairments (coordination, bradykinesia, fine motor skills) and loss of impulse control. Our data suggest that inhibition of GD3S warrants further investigation as a novel therapeutic strategy for Parkinson's disease.

Nitric oxide and peroxynitrite as new biomarkers for early diagnosis of autism

Autism spectrum disorder, or autism, is a neurodevelopmental disorder of the developing child's brain with a genetic causality. It can be diagnosed at about three years after birth when it begins to present itself via a range of neuropsychiatric symptoms. Nitric oxide is a crucial small molecule of life synthesized within cells of our body systems, including cells of our brain. Peroxynitrite is the product of reaction between superoxide anion and nitric oxide. It normally isomerizes into harmless nitrates or nitrites. However, when excessive superoxide anion is present, the cellular concentration of peroxynitrite can increase to a toxic level. Autism has been suggested to cause oxidative damage to brain cells. Until now, it is impossible to sample tissue from a live brain. Instead, stem cells can be derived (from an autism patient's somatic cells) which can then be differentiated and chemically directed to grow into miniature 3-dimensional tissue masses resembling specific brain regions (e.g., the cortex) called brain organoids. This review discusses utilizing nitric oxide and peroxynitrite as biomarkers and comparing their relative concentrations in stem cells and stem cell derived brain organoids of healthy and autistic individuals to develop a bioanalytical process for early diagnosis of autism.

O-GlcNAcylation regulates tyrosine hydroxylase serine 40 phosphorylation and l-DOPA levels

β-O-linked-N-acetylglucosamine (O-GlcNAcylation) is a post-translational modification (PTM) characterized by the covalent attachment of a single moiety of N-acetylglucosamine (GlcNAc) on serine/threonine residues in proteins. Tyrosine hydroxylase (TH), the rate-limiting step enzyme in the catecholamine synthesis pathway and responsible for the production of the dopamine precursor, l-3,4-dihydroxyphenylalanine (l-DOPA), has its activity regulated by phosphorylation. Here, we show an inverse feedback mechanism between O-GlcNAcylation and phosphorylation of TH at serine 40 (TH pSer40). First, we showed that, during PC12 cells neuritogenesis, TH O-GlcNAcylation decreases concurrently with the increase of pSer40. In addition, an increase in O-GlcNAcylation induces a decrease in TH pSer40 only in undifferentiated PC12 cells, whereas the decrease in O-GlcNAcylation leads to an increase in TH pSer40 levels in both undifferentiated and differentiated PC12 cells. We further show that this feedback culminates on the regulation of l-DOPA intracellular levels. Interestingly, it is noteworthy that decreasing O-GlcNAcylation is much more effective on TH pSer40 regulation than increasing its levels. Finally, ex vivo analysis confirmed the upregulation of TH pSer40 when O-GlcNAcylation levels are reduced in dopaminergic neurons from C57Bl/6 mice. Taken together, these findings demonstrate a dynamic control of l-DOPA production by a molecular cross talk between O-GlcNAcylation and phosphorylation at Ser40 in TH.NEW & NOTEWORTHY This study shows how β-O-linked-N-acetylglucosamine (O-GlcNAcylation) modulates tyrosine hydroxylase (TH) activity, revealing a negative feedback loop with Ser40 phosphorylation both in vitro and ex vivo, which directly influences on l-3,4-dihydroxyphenylalanine (l-DOPA) production. These findings offer insights into neurotransmitter homeostasis regulation, with implications for understanding and potentially treating disorders linked to aberrant catecholamine signaling.

Protein Oxidative Modifications in Neurodegenerative Diseases: From Advances in Detection and Modelling to Their Use as Disease Biomarkers

Oxidation-reduction post-translational modifications (redox-PTMs) are chemical alterations to amino acids of proteins. Redox-PTMs participate in the regulation of protein conformation, localization and function, acting as signalling effectors that impact many essential biochemical processes in the cells. Crucially, the dysregulation of redox-PTMs of proteins has been implicated in the pathophysiology of numerous human diseases, including neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. This review aims to highlight the current gaps in knowledge in the field of redox-PTMs biology and to explore new methodological advances in proteomics and computational modelling that will pave the way for a better understanding of the role and therapeutic potential of redox-PTMs of proteins in neurodegenerative diseases. Here, we summarize the main types of redox-PTMs of proteins while providing examples of their occurrence in neurodegenerative diseases and an overview of the state-of-the-art methods used for their detection. We explore the potential of novel computational modelling approaches as essential tools to obtain insights into the precise role of redox-PTMs in regulating protein structure and function. We also discuss the complex crosstalk between various PTMs that occur in living cells. Finally, we argue that redox-PTMs of proteins could be used in the future as diagnosis and prognosis biomarkers for neurodegenerative diseases.

Nitroproteomics is instrumental for stratification and targeted treatments of astrocytoma patients: expert recommendations for advanced 3PM approach with improved individual outcomes

Protein tyrosine nitration is a selectively and reversible important post-translational modification, which is closely related to oxidative stress. Astrocytoma is the most common neuroepithelial tumor with heterogeneity and complexity. In the past, the diagnosis of astrocytoma was based on the histological and clinical features, and the treatment methods were nothing more than surgery-assisted radiotherapy and chemotherapy. Obviously, traditional methods short falls an effective treatment for astrocytoma. In late 2021, the World Health Organization (WHO) adopted molecular biomarkers in the comprehensive diagnosis of astrocytoma, such as IDH-mutant and DNA methylation, which enabled the risk stratification, classification, and clinical prognosis prediction of astrocytoma to be more correct. Protein tyrosine nitration is closely related to the pathogenesis of astrocytoma. We hypothesize that nitroproteome is significantly different in astrocytoma relative to controls, which leads to establishment of nitroprotein biomarkers for patient stratification, diagnostics, and prediction of disease stages and severity grade, targeted prevention in secondary care, treatment algorithms tailored to individualized patient profile in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine). Nitroproteomics based on gel electrophoresis and tandem mass spectrometry is an effective tool to identify the nitroproteins and effective biomarkers in human astrocytomas, clarifying the biological roles of oxidative/nitrative stress in the pathophysiology of astrocytomas, functional characteristics of nitroproteins in astrocytomas, nitration-mediated signal pathway network, and early diagnosis and treatment of astrocytomas. The results finds that these nitroproteins are enriched in mitotic cell components, which are related to transcription regulation, signal transduction, controlling subcellular organelle events, cell perception, maintaining cell homeostasis, and immune activity. Eleven statistically significant signal pathways are identified in astrocytoma, including remodeling of epithelial adherens junctions, germ cell-sertoli cell junction signaling, 14-3-3-mediated signaling, phagosome maturation, gap junction signaling, axonal guidance signaling, assembly of RNA polymerase III complex, and TREM1 signaling. Furthermore, protein tyrosine nitration is closely associated with the therapeutic effects of protein drugs, and molecular mechanism and drug targets of cancer. It provides valuable data for studying the protein nitration biomarkers, molecular mechanisms, and therapeutic targets of astrocytoma towards PPPM (3P medicine) practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00348-y.

Neuronal Nitric Oxide Synthase and Post-Translational Modifications in the Development of Central Nervous System Diseases: Implications and Regulation

In the Central Nervous System (CNS), Nitric Oxide (NO) is mainly biosynthesized by neuronal Nitric Oxide Synthase (nNOS). The dysregulated activation of nNOS in neurons is critical in the development of different conditions affecting the CNS. The excessive production of NO by nNOS is responsible for a number of proteins' post-translational modifications (PTMs), which can lead to aberrant biochemical pathways, impairing CNS functions. In this review, we briefly revise the main implications of dysregulated nNOS in the progression of the most prevalent CNS neurodegenerative disorders, i.e., Alzheimer's disease (AD) and Parkinson's disease, as well as in the development of neuronal disorders. Moreover, a specific focus on compounds able to modulate nNOS activity as promising therapeutics to tackle different neuronal diseases is presented.

Role of cytokines and reactive oxygen species in brain aging

Aging is a complex process that produces profound effects on the brain. Although a number of external factors can promote the initiation and progression of brain aging, peripheral and central changes in the immune cells with time, also play an important role. Immunosenescence, which is an age-associated decline in immune function and Inflammaging, a low-grade inflammatory state in the aging brain contribute to an elevation in cytokine and reactive oxygen species production. In this review, we focus on the pro-inflammatory state that is established in the brain as a consequence of these two phenomena and the resulting detrimental changes in brain structure, function and repair that lead to a decline in central and neuroendocrine function.

The interplay between lncRNA NR_030777 and SF3B3 in neuronal damage caused by paraquat

Paraquat (PQ) has been widely acknowledged as an environmental risk factor for Parkinson's disease (PD). However, the interaction between splicing factor and long non-coding RNA (lncRNA) in the process of PQ-induced PD has rarely been studied. Based on previous research, this study focused on splicing factor 3 subunit 3 (SF3B3) and lncRNA NR_030777. After changing the target gene expression level by lentiviral transfection technology, the related gene expression was detected by western blot and qRT-PCR. The expression of SF3B3 protein was reduced in Neuro-2a cells after PQ exposure, and the reactive oxygen species (ROS) scavenger N-acetylcysteine prevented this decline. Knockdown of SF3B3 reduced the PQ-triggered NR_030777 expression increase, and overexpression of NR_030777 reduced the transcriptional and translational level of Sf3b3. Then, knockdown of SF3B3 exacerbated the PQ-induced decrease in cell viability and aggravated the reduction of tyrosine hydroxylase (TH) protein expression. Overexpressing SF3B3 reversed the reduction of TH expression caused by PQ. Moreover, after intervention with the autophagy inhibitor Bafilomycin A1, LC3B-II protein expression was further increased in Neuro-2a cells with the knockdown of SF3B3, indicating that autophagy was enhanced. In conclusion, PQ modulated the interplay between NR_030777 and SF3B3 through ROS production, thereby impairing autophagic flux and causing neuronal damage.

Exploring the Epigenetic Regulated Modulation of Fibroblast Growth Factor 21 Involvement in High-Fat Diet Associated Parkinson's Disease in Rats

Imbalance in brain glucose metabolism and epigenetic modulation during the disease course of insulin resistance (IR) associated with Parkinson's disease (PD) risk remains a prime concern. Fibroblast growth factor 21 (FGF21), the metabolic hormone, improves insulin sensitivity and elicits anti-diabetic properties. Chronic stress during brain IR may modulate the FGF21 expression and its dynamic release via epigenetic modifications. Metformin regulates and increases the expression of FGF21 which can be modulating in obesity, diabetes, and IR. Hence, this study was designed to investigate the FGF21 expression modulation via an epigenetic mechanism in PD and whether metformin (MF), an autophagy activator, and sodium butyrate (NaB), a pan histone deacetylase inhibitor, alone and in combination, exert any therapeutic benefit in PD pathology exacerbated by high-fat diet (HFD). Our results portray that the combination treatment with MF and NaB potentially attenuated the abnormal lipid profile and increased motor performance for the rats fed with HFD for 8 weeks followed by intrastriatal 6-hydroxy dopamine administration. The enzyme-linked immunosorbent assay (ELISA) estimations of C-reactive protein, tumor necrosis factor-α, interleukin-1 beta and 6, and FGF21 exhibited extensive downregulation after treatment with the combination. Lastly, mRNA, western blot, histological, and cresyl violet staining depicted that the combination treatment can restore degenerated neuronal density and increase the protein level compared to the disease group. The findings from the study effectively conclude that the epigenetic mechanism involved in FGF21 mediated functional abnormalities in IR-linked PD pathology. Hence, combined treatment with MF and NaB may prove to be a novel combination in ameliorating IR-associated PD in rats, probably via the upregulation of FGF21 expression.

The Role of the Thioredoxin System in Brain Diseases

The thioredoxin system, consisting of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, plays a fundamental role in the control of antioxidant defenses, cell proliferation, redox states, and apoptosis. Aberrations in the Trx system may lead to increased oxidative stress toxicity and neurodegenerative processes. This study reviews the role of the Trx system in the pathophysiology and treatment of Alzheimer's, Parkinson's and Huntington's diseases, brain stroke, and multiple sclerosis. Trx system plays an important role in the pathophysiology of those disorders via multiple interactions through oxidative stress, apoptotic, neuro-immune, and pro-survival pathways. Multiple aberrations in Trx and TrxR systems related to other redox systems and their multiple reciprocal relationships with the neurodegenerative, neuro-inflammatory, and neuro-oxidative pathways are here analyzed. Genetic and environmental factors (nutrition, metals, and toxins) may impact the function of the Trx system, thereby contributing to neuropsychiatric disease. Aberrations in the Trx and TrxR systems could be a promising drug target to prevent and treat neurodegenerative, neuro-inflammatory, neuro-oxidative stress processes, and related brain disorders.

Is there a halo-enzymopathy in Parkinson's disease?

Laboratory studies identified changes in the metabolism of halogens in the serum and cerebrospinal fluid (CSF) of patients with Parkinson's disease, which indicates the presence of «accelerated self-halogenation» of CSF and/or an increase in haloperoxidases, specifically serum thyroperoxidase and CSF lactoperoxidase. Furthermore, an excess of some halogenated derivatives, such as advanced oxygenation protein products (AOPP), has been detected in the CSF and serum. «Accelerated self-halogenation» and increased levels of haloperoxidases and AOPP proteins indicate that halogenative stress is present in Parkinson's disease. In addition, 3-iodo-L-tyrosine, a halogenated derivative, shows «parkinsonian» toxicity in experimental models, since it has been observed to induce α-synuclein aggregation and damage to dopaminergic neurons in the mouse brain and intestine. The hypothesis is that patients with Parkinson's disease display halogenative stress related to a haloenzymatic alteration of the synthesis or degradation of oxyacid of halogens and their halogenated derivatives. This halogenative stress would be related to nervous system damage.

Neuroprotective Effects of Oligosaccharides From Periplaneta Americana on Parkinson’s Disease Models In Vitro and In Vivo

Parkinson’s disease (PD) is one of the neurodegenerative diseases that is characterized by obvious motor and some nonmotor symptoms. Various therapeutics failed in the effective treatment of PD because of impaired neurological function in the brain and various complications. Periplaneta Americana oligosaccharides (OPA), the main active ingredients extracted from the medicine residues of Periplaneta Americana (P. Americana), have been reported to exert anti-inflammatory effects. The purpose of this study was to evaluate the possible mechanisms of OPA against 1-methyl-4-phenylpyridinium (MPP⁺)-induced apotosis in SH-SY5Y cells and its potential neuroprotective effects in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD subacute model mice. The data demonstrated that OPA significantly reversed the MPP⁺-induced decrease in SH-SY5Y cell viability, reduced the proportion of apoptotic cells, and protected SH-SY5Y cells from apoptosis in a dose-dependent manner by regulating the expression of apoptosis-related genes. Furthermore, OPA also alleviated the motor dysfunction of PD model mice, prevented the loss of tyrosine hydroxylase positive cells, suppressed the apoptosis of substantia nigra cells, and improved the dysbiosis of gut microbiota in vivo, suggesting that OPA demonstrated a significantly neuroprotective effect on PD model mice. These results indicated that OPA might be the possibility of PD therapeutics with economic utility and high safety.

An integrated systems-level model of the toxicity of brevetoxin based on high-resolution magic-angle spinning nuclear magnetic resonance (HRMAS NMR) metabolic profiling of zebrafish embryos

Brevetoxins (PbTx) are a well-recognized group of neurotoxins associated with harmful algal blooms, and specifically recurrent "Florida Red Tides," in marine waters that are linked to impacts on both human and ecosystem health including well-documented "fish kills" and marine mammal mortalities in affected coastal waters. Understanding mechanisms and pathways of PbTx toxicity enables identification of relevant biomarkers to better understand these environmental impacts, and improve monitoring efforts, in relation to this toxin. Toward a systems-level understanding of toxicity, and identification of potential biomarkers, high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) was utilized for metabolic profiling of zebrafish (Danio rerio) embryos, as an established toxicological model, exposed to PbTx-2 (the most common congener in marine waters). Metabolomics studies were, furthermore, complemented by an assessment of the toxicity of PbTx-2 in embryonic stages of zebrafish and mahi-mahi (Coryphaena hippurus), the latter representing an ecologically and geographically relevant marine species of fish, which identified acute embryotoxicity at environmentally relevant (i.e., parts-per-billion) concentrations in both species. HRMAS NMR analysis of intact zebrafish embryos exposed to sub-lethal concentrations of PbTx-2 afforded well-resolved spectra, and in turn, identification of 38 metabolites of which 28 were found to be significantly altered, relative to controls. Metabolites altered by PbTx-2 exposure specifically included those associated with (1) neuronal excitotoxicity, as well as associated neural homeostasis, and (2) interrelated pathways of carbohydrate and energy metabolism. Metabolomics studies, thereby, enabled a systems-level model of PbTx toxicity which integrated multiple metabolic, molecular and cellular pathways, in relation to environmentally relevant concentrations of the toxin, providing insight to not only targets and mechanisms, but potential biomarkers pertinent to environmental risk assessment and monitoring strategies.

Molecular Features of Parkinson's Disease in Patient-Derived Midbrain Dopaminergic Neurons

BACKGROUND

Despite intense efforts to develop an objective diagnostic test for Parkinson's disease, there is still no consensus on biomarkers that can accurately diagnose the disease.

OBJECTIVE

Identification of biomarkers for idiopathic Parkinson's disease (PD) may enable accurate diagnosis of the disease. We tried to find molecular and cellular differences in dopaminergic (DA) neurons derived from healthy subjects and idiopathic PD patients with or without rest tremor at onset.

METHODS

We measured the expression of genes controlling dopamine synthesis, sequestration, and catabolism as well as the levels of corresponding metabolites and reactive oxygen species in midbrain DA neurons differentiated from induced pluripotent stem cells (iPSCs) of healthy subjects and PD patients with or without rest tremor.

RESULTS

Significant differences in DA-related gene expression, metabolites, and oxidative stress were found between midbrain DA neurons derived from healthy subjects and patients with PD. DA neurons derived from PD patients with or without rest tremor at onset exhibited significant differences in the levels of some of these transcripts, metabolites, and oxidative stress.

CONCLUSION

The unique combination of these quantifiable molecular and cellular traits in iPSC-derived midbrain DA neurons can distinguish healthy subjects from idiopathic PD patients and segregate PD patients with or without rest tremor at onset. The strategy may be used to develop an objective diagnostic test for PD.

Neuroprotective Effects of Trehalose and Sodium Butyrate on Preformed Fibrillar Form of α-Synuclein-Induced Rat Model of Parkinson's Disease

Therapeutic options for Parkinson's disease (PD) are limited to a symptomatic approach, making it a global threat. Targeting aggregated alpha-synuclein (α-syn) clearance is a gold standard for ameliorating PD pathology, bringing autophagy into the limelight. Expression of autophagy related genes are under the regulation by histone modifications, however, its relevance in PD is yet to be established. Here, preformed fibrillar form (PFF) of α-syn was used to induce PD in wistar rats, which were thereafter subjected to treatment with trehalose (tre, 4g/kg, orally), a potent autophagy inducer and sodium butyrate (SB, 300 mg/kg, orally), a pan histone deacetylase inhibitor alone as well as in combination. The combination treatment significantly reduced motor deficits as evidenced after rotarod, narrow beam walk, and open field tests. Novel object location and recognition tests were performed to govern cognitive abnormality associated with advanced stage PD, which was overcome by the combination treatment. Additionally, with the combination, the level of pro-inflammatory cytokines were significantly reduced, along with elevated levels of dopamine and histone H3 acetylation. Further, mRNA analysis revealed that levels of certain autophagy related genes and proteins implicated in PD pathogenesis significantly improved after administration of both tre and SB. Immunofluorescence and H&E staining in the substantia nigra region mirrored a potential improvement after treatment with both tre and SB. Therefore, outcomes of the present study were adequate to prove that combinatorial efficacy with tre and SB may prove to be a formidable insight into ameliorating PD exacerbated by PFF α-syn as compared to its individual efficacy.

TNFα increases tyrosine hydroxylase expression in human monocytes

Most, if not all, peripheral immune cells in humans and animals express tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. Since TH is typically studied in the context of brain catecholamine signaling, little is known about changes in TH production and function in peripheral immune cells. This knowledge gap is due, in part, to the lack of an adequately sensitive assay to measure TH in immune cells expressing lower TH levels compared to other TH expressing cells. Here, we report the development of a highly sensitive and reproducible Bio-ELISA to quantify picogram levels of TH in multiple model systems. We have applied this assay to monocytes isolated from blood of persons with Parkinson's disease (PD) and to age-matched, healthy controls. Our study unexpectedly revealed that PD patients' monocytes express significantly higher levels of TH protein in peripheral monocytes relative to healthy controls. Tumor necrosis factor (TNFα), a pro-inflammatory cytokine, has also been shown to be increased in the brains and peripheral circulation in human PD, as well as in animal models of PD. Therefore, we investigated a possible connection between higher levels of TH protein and the known increase in circulating TNFα in PD. Monocytes isolated from healthy donors were treated with TNFα or with TNFα in the presence of an inhibitor. Tissue plasminogen activator (TPA) was used as a positive control. We observed that TNFα stimulation increased both the number of TH+ monocytes and the quantity of TH per monocyte, without increasing the total numbers of monocytes. These results revealed that TNFα could potentially modify monocytic TH production and serve a regulatory role in peripheral immune function. The development and application of a highly sensitive assay to quantify TH in both human and animal cells will provide a novel tool for further investigating possible PD immune regulatory pathways between brain and periphery.

Effect of ginsenoside-Rg1 on experimental Parkinson's disease: A systematic review and meta-analysis of animal studies

Previous studies have reported that ginsenoside-Rg1 (G-Rg1) was able to mitigate the loss of dopaminergic neurons in animal models of Parkinson's disease (PD). The present study provided a systematic review and meta-analysis of preclinical studies to pool current evidence on the effect of G-Rg1 on neurogenesis in the treatment of PD. Eligible studies were identified through a search from six databases: PubMed, EMBASE, Web of Science, VIP, Chinese National Knowledge Infrastructure and the Wanfang database. Primary outcomes were tyrosine hydroxylase (TH)-positive cells in the nigra, Nissl staining-positive cells in the nigra, pole test time and dopamine (DA) levels in the striatum. A total of 18 eligible studies were identified, involving 343 animals. Of these, 13 reported a significant relationship between G-Rg1 and improved TH-positive cells in the nigra compared with the control group (P<0.00001). Furthermore, 3 studies reported a significant relationship between G-Rg1 and improved Nissl-positive cells in the nigra compared with the control group (P<0.00001). In addition, 4 studies reported a significant effect of G-Rg1 to reduce the total pole test time compared with that in the control group (P=0.001). A total of 3 studies indicated a significant association between G-Rg1 and improved DA levels in the striatum compared with the control group (P<0.00001). These results suggested that G-Rg1 has positive effects in attenuating damage in models of PD, and thus, it is a potential candidate neuroprotective drug for human PD.

Therapeutic effects of Wharton's jelly-derived Mesenchymal Stromal Cells on behaviors, EEG changes and NGF-1 in rat model of the Parkinson's disease

Human Wharton's jelly-derived Mesenchymal Stromal Cells (hWJ-MSCs) have shown beneficial effects in improving the dopaminergic cells in the Parkinson's disease (PD). In the present study, the effects of hWJ-MSCs on hyperalgesia, anxiety deficiency and Pallidal local electroencephalogram (EEG) impairment, alone and combined with L-dopa, were examined in a rat model of PD. Adult male Wistar rats were divided into five groups: 1) sham, 2) PD, 3) PD + C (Cell therapy), 4) PD + C+D (Drug), and 5) PD + D. PD was induced by injection of 6-OHDA (16 μg/2 μl into medial forebrain bundle (MFB)). PD + C group received hWJ-MSCs (1 × 10⁶ cells, intravenous (i.v.)) twice post PD induction. PD + C+D groups received hWJ-MSCs combined with L-Dopa/Carbidopa, (10/30 mg/kg, intraperitoneally (i.p.)). PD + D group received L-Dopa/Carbidopa alone. Four months later, analgesia, anxiety-like behaviors, were evaluated and Pallidal local EEG was recorded. Level of insulin-like growth factor 1 (IGF-1) was measured in the striatum and dopaminergic neurons were counted in substantia nigra (SNc). According to data, MFB-lesioned rats showed hyperalgesia in tail flick, anxiety-like symptoms in cognitive tests, impairment of electrical power of pallidal local EEG as field potential, count of dopaminergic neurons in SNc and level of IGF-1 in striatum. These complications restored significantly by MSCs treatment (p < 0.001). Our findings confirm that chronic treatment with hWJ-MSC, alone and in combination with L-Dopa, improved nociception and cognitive deficit in PD rats which may be the result of increasing IGF-1 and protect the viability of dopaminergic neurons.

β-Methylphenylalanine exerts neuroprotective effects in a Parkinson's disease model by protecting against tyrosine hydroxylase depletion

We evaluated the neuroprotective effects of β-methylphenylalanine in an experimental model of rotenone-induced Parkinson's disease (PD) in SH-SY5Y cells and rats. Cells were pre-treated with rotenone (2.5 µg/mL) for 24 hours followed by β-methylphenylalanine (1, 10 and 100 mg/L) for 72 hours. Cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), mitochondrial fragmentation, apoptosis, and mRNA and protein levels of tyrosine hydroxylase were determined. In a rat model of PD, dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels, bradykinesia and tyrosine hydroxylase expression were determined. In rotenone-pre-treated cells, β-methylphenylalanine significantly increased cell viability and MMP, whereas ROS levels, apoptosis and fragmented mitochondria were reduced. β-Methylphenylalanine significantly increased the mRNA and protein levels of tyrosine hydroxylase in SH-SY5Y cells. In the rotenone-induced rat model of PD, oral administration of β-methylphenylalanine recovered DA and DOPAC levels and bradykinesia. β-Methylphenylalanine significantly increased the protein expression of tyrosine hydroxylase in the striatum and substantia nigra of rats. In addition, in silico molecular docking confirmed binding between tyrosine hydroxylase and β-methylphenylalanine. Our experimental results show neuroprotective effects of β-methylphenylalanine via the recovery of mitochondrial damage and protection against the depletion of tyrosine hydroxylase. We propose that β-methylphenylalanine may be useful in the treatment of PD.

Perillyl Alcohol Mitigates Behavioural Changes and Limits Cell Death and Mitochondrial Changes in Unilateral 6-OHDA Lesion Model of Parkinson's Disease Through Alleviation of Oxidative Stress

In this study, we aim to assess the phytomedicinal potential of perillyl alcohol (PA), a dietary monoterpenoid, in a unilateral 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease (PD). We observed that PA supplementation alleviated behavioural abnormalities such as loss of coordination, reduced rearing and motor asymmetry in lesioned animals. We also observed that PA-treated animals exhibited reduced oxidative stress, DNA fragmentation and caspase 3 activity indicating alleviation of apoptotic cell death. We found reduced mRNA levels of pro-apoptotic regulator BAX and pro-inflammatory mediators IL18 and TNFα in PA-treated animals. Further, PA treatment successfully increased mRNA and protein levels of Bcl2, mitochondrial biogenesis regulator PGC1α and tyrosine hydroxylase (TH) in lesioned animals. We observed that PA treatment blocked BAX and Drp1 translocation to mitochondria, an event often associated with the inception of apoptosis. Further, 6-OHDA exposure reduced expression of electron transport chain complexes I and IV, thereby disturbing energy metabolism. Conversely, expression levels of both complexes were upregulated with PA treatment in lesioned rats. Finally, we found that protein levels of Nrf2, the transcription factor responsible for antioxidant gene expression, were markedly reduced in cytosolic and nuclear fraction on 6-OHDA exposure, and PA increased expression of Nrf2 in both fractions. We believe that our data hints towards PA having the ability to provide cytoprotection in a hemiparkinsonian rat model through alleviation of motor deficits, oxidative stress, mitochondrial dysfunction and apoptosis.

A Silyl Ether Based Fluorescent Probe for Rapid Monitoring of Endogenous Peroxynitrite Concentration and Imaging in Living Cells through Multicolor Emission

The peroxynitrite ion (ONOO^- ) has important roles in many biological processes. We have developed a multicolor ONOO^- -sensing probe (SiONNOH) that undergoes deprotonation and desilylation processes, which result in several changes in the emission wavelengths. In response to different concentrations of ONOO^- , the probe exhibits fluorescence changes from pink (595 nm at 2 eq. ONOO^- ) to green (540 nm at 6 eq. ONOO^- ) via orange (3 eq. ONOO^- ) and yellow (4 eq. ONOO^- ) under physiological conditions until no fluorescence signal is observed after ONOO^- is completely eliminated by lipoic acid. The probe shows the high selectivity for ONOO^- and the limit of detection is calculated to be 1.27 μM. Moreover, the probe shows the capacity to monitor the concentration ranges of ONOO^- through multicolor fluorescence in living cells, which will greatly facilitate the rapid detection of ONOO^- concentration ranges by the naked eye under a UV light without any precision instrumentation.

Oral L-Tyrosine Supplementation Improves Core Temperature Maintenance in Older Adults

INTRODUCTION

During cold exposure, an increase in sympathetic nerve activity evokes vasoconstriction (VC) of cutaneous vessels to minimize heat loss. In older adults, this reflex VC response is impaired thereby increasing their susceptibility to excess heat loss and hypothermia. Because L-tyrosine, the amino acid substrate necessary for catecholamine production, has been shown to augment reflex VC in age skin, we hypothesize that oral ingestion of L-tyrosine will attenuate the decline in core temperature (Tc) during whole-body cooling in older adults.

METHODS

In a randomized, double-blind design, nine young (25 ± 3 yr) and nine older (72 ± 8 yr) participants ingested either 150 mg·kg of L-tyrosine or placebo before commencing 90 min of whole-body cooling to decrease skin temperature to approximately 29.5°C. Esophageal temperature and forearm laser Doppler flux (LDF) were measured continuously throughout the protocol to provide an index of Tc and skin blood flow, respectively. The change in esophageal temperature (ΔTES) was the difference in temperature at the end of cooling subtracted from baseline. Cutaneous vascular conductance (CVC) was calculated as CVC = LDF/mean arterial pressure and expressed as a percent change from baseline (%ΔCVCBASELINE).

RESULTS

Oral tyrosine ingestion augmented the cutaneous VC response to cooling in older adults (placebo, 14.4 ± 2.0; tyrosine, 32.7% ± 1.7% ΔCVCBASELINE; P < 0.05). Additionally, tyrosine improved Tc maintenance throughout cooling in older adults (placebo, -0.29 ± 0.07; tyrosine, -0.07 ± 0.07 ΔTES; P < 0.05). Both the cutaneous VC and Tc during cooling were similar between young and older adults supplemented with tyrosine (P > 0.05).

CONCLUSIONS

These results indicate that L-tyrosine supplementation improves Tc maintenance in response to acute cold exposure in an older population.

Neuroprotection in Oxidative Stress-Related Neurodegenerative Diseases: Role of Endocannabinoid System Modulation

SIGNIFICANCE

Redox imbalance may lead to overproduction of reactive oxygen and nitrogen species (ROS/RNS) and subsequent oxidative tissue damage, which is a critical event in the course of neurodegenerative diseases. It is still not fully elucidated, however, whether oxidative stress is the primary trigger or a consequence in the process of neurodegeneration. Recent Advances: Increasing evidence suggests that oxidative stress is involved in the propagation of neuronal injury and consequent inflammatory response, which in concert promote development of pathological alterations characteristic of most common neurodegenerative diseases.

CRITICAL ISSUES

Accumulating recent evidence also suggests that there is an important interplay between the lipid endocannabinoid system [ECS; comprising the main cannabinoid 1 and 2 receptors (CB1 and CB2), endocannabinoids, and their synthetic and metabolizing enzymes] and various key inflammatory and redox-dependent processes.

FUTURE DIRECTIONS

Targeting the ECS to modulate redox state-dependent cell death and to decrease consequent or preceding inflammatory response holds therapeutic potential in a multitude of oxidative stress-related acute or chronic neurodegenerative disorders from stroke and traumatic brain injury to Alzheimer's and Parkinson's diseases and multiple sclerosis, just to name a few, which will be discussed in this overview. Antioxid. Redox Signal. 29, 75-108.

Redox Signaling in Neurotransmission and Cognition During Aging

SIGNIFICANCE

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

CRITICAL ISSUES

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

FUTURE DIRECTIONS

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

Copper sulfate pretreatment prevents mitochondrial electron transport chain damage and apoptosis against MPP+-induced neurotoxicity

Intrastriatal injection of 1-methyl-4-phenylpyridinium (MPP⁺) is considered a model to reproduce some biochemical alterations observed in Parkinson's disease (PD) patients. Among those alterations, inhibition of mitochondrial complex I activity, increased free radical production and reduced antioxidant responses have been reported. Copper (Cu) plays an important role in the metabolism and antioxidative responses through its participation as a cofactor in the cytochrome c oxidase enzyme (COX), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), and metallothioneins. We tested the effect of copper sulfate (CuSO₄) pretreatment on the mitochondrial electron transport chain (METC) in the striatum after MPP⁺ toxicity in rats. The results showed that the MPP⁺ intrastriatal injection reduced mitochondrial complex I, II, IV and V activities; while 10 μmol of CuSO₄ pretreatment counteracted this damage. Activities of complexes I, II and IV, were coincident with ATP recovery. Moreover, Cu/Zn-SOD activity was reduced as a consequence of MPP⁺ damage; however, copper pre-treatment kept the striatal Cu/Zn-SOD activity unchanged in MPP⁺-damaged animals. We observed that MPP⁺ also reduced the metallothionein (MT) content and that CuSO₄ pretreatment maintained baseline values. CuSO₄ pretreatment also reduced the striatal caspase-3 and caspase-9 activities that were increased three days after MPP⁺-induced damage. The present study provided evidence that copper pretreatment reduced MPP⁺-induced apoptotic damage, probably through direct action on copper-dependent proteins or indirectly on proteins in the apoptotic pathway.

Pre-clinical therapeutic development of a series of metalloporphyrins for Parkinson's disease

Reactive oxygen species are a well-defined therapeutic target for Parkinson's disease (PD) and pharmacological agents that catalytically scavenge reactive species are promising neuroprotective strategies for treatment. Metalloporphyrins are synthetic catalytic antioxidants that mimic the body's own antioxidant enzymes i.e. superoxide dismutases and catalase. The goal of this study was to determine if newly designed metalloporphyrins have enhanced pharmacodynamics including oral bioavailability, longer plasma elimination half-lives, penetrate the blood brain barrier, and show promise for PD treatment. Three metalloporphyrins (AEOL 11216, AEOL 11203 and AEOL 11114) were identified in this study as potential candidates for further pre-clinical development. Each of these compounds demonstrated blood brain barrier permeability by the i.p. route and two of three compounds (AEOL 11203 and AEOL 11114) were orally bioavailable. All of these compounds protected against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity, including dopamine depletion in the striatum, dopaminergic neuronal loss in the substantial nigra, and increased oxidative/nitrative stress indices (glutathione disulfide and 3-nitrotyrosine) in the ventral midbrain of the mice without inhibiting MPTP metabolism. Daily therapeutic dosing of these metalloporphyrins were well tolerated without accumulation of brain manganese levels or behavioral alterations assessed by open field and rotarod tests. The study identified two orally active metalloporphyrins and one injectable metalloporphyrin as clinical candidates for further development in PD.

Novel enhancement mechanism of tyrosine hydroxylase enzymatic activity by nitric oxide through S-nitrosylation

Tyrosine hydroxylase (TH) is a rate-limiting step enzyme in the synthesis of catecholamines. Catecholamines function both as hormone and neurotransmitters in the peripheral and central nervous systems, therefore TH’s expression and enzymatic activity is tightly regulated by various mechanisms. Several post-translational modifications have been shown to regulate TH’s enzymatic activity such as phosphorylation, nitration and S-glutathionylation. While phosphorylation at N-terminal of TH can activate its enzymatic activity, nitration and S-glutathionylation can inactivate TH. In this study, we found that TH can also be S-nitrosylated by nitric oxide (NO). S-nitrosylation is a reversible modification of cysteine (cys) residue in protein and is known to be an emerging signaling mechanism mediated by NO. We found that TH can be S-nitrosylated at cys 279 and TH S-nitrosylation enhances its enzymatic activity both in vitro and in vivo. These results provide a novel mechanism of how NO can modulate TH’s enzymatic activity through S-nitrosylation.

FeTPPS Reduces Secondary Damage and Improves Neurobehavioral Functions after Traumatic Brain Injury

Traumatic brain injury (TBI) determinate a cascade of events that rapidly lead to neuron's damage and death. We already reported that administration of FeTPPS, a 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrin iron III chloride peroxynitrite decomposition catalyst, possessed evident neuroprotective effects in a experimental model of spinal cord damage. The present study evaluated the neuroprotective property of FeTPPS in TBI, using a clinically validated model of TBI, the controlled cortical impact injury (CCI). We observe that treatment with FeTPPS (30 mg/kg, i.p.) reduced: the state of brain inflammation and the tissue hurt (histological score), myeloperoxidase activity, nitric oxide production, glial fibrillary acidic protein (GFAP) and pro-inflammatory cytokines expression and apoptosis process. Moreover, treatment with FeTPPS re-established motor-cognitive function after CCI and it resulted in a reduction of lesion volumes. Our results established that FeTPPS treatment decreases the growth of inflammatory process and the tissue injury associated with TBI. Thus our study confirmed the neuroprotective role of FeTPPS treatment on TBI.

Targeting nitrative stress for attenuating cisplatin-induced downregulation of cochlear LIM domain only 4 and ototoxicity

Cisplatin-induced ototoxicity remains a primary dose-limiting adverse effect of this highly effective anticancer drug. The clinical utility of cisplatin could be enhanced if the signaling pathways that regulate the toxic side-effects are delineated. In previous studies, we reported cisplatin-induced nitration of cochlear proteins and provided the first evidence for nitration and downregulation of cochlear LIM domain only 4 (LMO4) in cisplatin ototoxicity. Here, we extend these findings to define the critical role of nitrative stress in cisplatin-induced downregulation of LMO4 and its consequent ototoxic effects in UBOC1 cell cultures derived from sensory epithelial cells of the inner ear and in CBA/J mice. Cisplatin treatment increased the levels of nitrotyrosine and active caspase 3 in UBOC1 cells, which was detected by immunocytochemical and flow cytometry analysis, respectively. The cisplatin-induced nitrative stress and apoptosis were attenuated by co-treatment with SRI110, a peroxynitrite decomposition catalyst (PNDC), which also attenuated the cisplatin-induced downregulation of LMO4 in a dose-dependent manner. Furthermore, transient overexpression of LMO4 in UBOC1 cells prevented cisplatin-induced cytotoxicity while repression of LMO4 exacerbated cisplatin-induced cell death, indicating a direct link between LMO4 protein levels and cisplatin ototoxicity. Finally, auditory brainstem responses (ABR) recorded from CBA/J mice indicated that co-treatment with SRI110 mitigated cisplatin-induced hearing loss. Together, these results suggest that cisplatin-induced nitrative stress leads to a decrease in the levels of LMO4, downregulation of LMO4 is a critical determinant in cisplatin-induced ototoxicity, and targeting peroxynitrite could be a promising strategy for mitigating cisplatin-induced hearing loss.

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Cisplatin-induced nitrative stress leads to a decrease in the levels of LMO4.

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Downregulation of LMO4 is a critical factor in cisplatin-induced ototoxicity.

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SRI110 appears to be a promising candidate for preventing cisplatin ototoxicity.

Inhibition and conformational change of SERCA3b induced by Bcl-2

An interaction of Bcl-2 with SERCA had been documented in vitro using the SERCA1a isoform isolated from rat skeletal muscle [Dremina, E. S., Sharov, V. S., Kumar, K., Azidi, A., Michaelis, E. K., Schöneich, C. (2004) Biochem. J. 383 (361-370)]. Here, we demonstrate the interaction of Bcl-2 with the SERCA3b isoform both in vitro and in cell culture. In vitro, the interaction of Bcl-2 with SERCA3b was studied using Bcl-2∆21, a truncated form of human Bcl-2, and microsomes isolated from SERCA3b-overexpressing HEK-293 cells. For these experiments, SERCA3b was quantified by a combination of amino acid analysis and Western blotting. We observed that Bcl-2∆21 both inactivates SERCA3b and co-immunoprecipitates with SERCA3b. The incubation with Bcl-2∆21 changes the distribution of SERCA3b during sucrose density gradient centrifugation, likely as the result of Bcl-2∆21-induced conformational change of SERCA3b. When SERCA3b-overexpressing HEK-293 cells were co-transfected with Bcl-2, Bcl-2-dependent SERCA3b inactivation was observed. In these cells, Bcl-2 interaction with SERCA3b was demonstrated by co-immunoprecipitation. Furthermore, overexpression of Bcl-2 reduced fluorescein isothiocyanate (FITC) labeling of SERCA3b. Together, our data provide evidence for the interaction of Bcl-2 with SERCA3b in vitro and in cell culture, and for Bcl-2-dependent conformational and functional changes of SERCA3b.

The basis for folinic acid treatment in neuro-psychiatric disorders

Multiple factors such as genetic and extraneous causes (drugs, toxins, adverse psychological events) contribute to neuro-psychiatric conditions. In a subgroup of these disorders, systemic folate deficiency has been associated with macrocytic anemia and neuropsychiatric phenotypes. In some of these, despite normal systemic levels, folate transport to the brain is impaired in the so-called cerebral folate deficiency (CFD) syndromes presenting as developmental and psychiatric disorders. These include infantile-onset CFD syndrome, infantile autism with or without neurologic deficits, a spastic-ataxic syndrome and intractable epilepsy in young children expanding to refractory schizophrenia in adolescents, and finally treatment-resistant major depression in adults. Folate receptor alpha (FRα) autoimmunity with low CSF N(5)-methyl-tetrahydrofolate (MTHF) underlies most CFD syndromes, whereas FRα gene abnormalities and mitochondrial gene defects are rarely found. The age at which FRα antibodies of the blocking type emerge, determines the clinical phenotype. Infantile CFD syndrome and autism with neurological deficits tend to be characterized by elevated FRα antibody titers and low CSF MTHF. In contrast, in infantile autism and intractable schizophrenia, abnormal behavioral signs and symptoms may wax and wane with fluctuating FRα antibody titers over time accompanied by cycling changes in CSF folate, tetrahydrobiopterin (BH4) and neurotransmitter metabolites ranging between low and normal levels. We propose a hypothetical model explaining the pathogenesis of schizophrenia. Based on findings from clinical, genetic, spinal fluid and MRI spectroscopic studies, we discuss the neurochemical changes associated with these disorders, metabolic and regulatory pathways, synthesis and catabolism of neurotransmitters, and the impact of oxidative stress on the pathogenesis of these conditions. A diagnostic algorithm and therapeutic regimens using high dose folinic acid, corticosteroids and milk-free diet is presented which has proven to be beneficial in providing adequate folate to the brain and decreasing the FRα autoantibody titer in those positive for the antibody.

Epicatechin Reduces Striatal MPP⁺-Induced Damage in Rats through Slight Increases in SOD-Cu,Zn Activity

Parkinson's disease is a neurodegenerative disorder characterized by movement alterations caused by reduced dopaminergic neurotransmission in the nigrostriatal pathway, presumably by oxidative stress (OS). MPP⁺ intrastriatal injection leads to the overproduction of free radicals (FR). The increasing formation of FR produces OS, a decline in dopamine (DA) content, and behavioral disorders. Epicatechin (EC) has shown the ability to be FR scavenger, an antioxidant enzyme inductor, a redox state modulator, and transition metal chelator. Acute administration of 100 mg/kg of EC significantly prevented (P < 0.05) the circling MPP⁺-induced behavior (10 μg/8 μL). Likewise, EC significantly (P < 0.05) reduced the formation of fluorescent lipid products caused by MPP⁺. MPP⁺ injection produced (P < 0.05) increased enzymatic activity of the constitutive nitric oxide synthase (cNOS). This effect was blocked with acute EC pretreatment. Cu/Zn-dependent superoxide dismutase (Cu/Zn-SOD) activity was significantly (P < 0.05) reduced as a consequence of MPP⁺ damage. EC produced a slight increase (≈20%) in Cu/Zn-SOD activity in the control group. Such effects persisted in animals injured with MPP⁺. The results show that EC is effective against MPP⁺-induced biochemical and behavioral damage, which is possible by an increase in Cu/Zn-SOD activity.

Peroxynitrite and fibrinolytic system-The effects of peroxynitrite on t-PA-induced plasmin activity

The aim of the present study was the investigation of peroxynitrite (ONOO(-)) effects on fibrinolysis in vitro and in silico. The exposure of human plasminogen to ONOO(-) (10-1000μM) resulted in a decrease of t-PA-induced amidolytic activity of plasmin; the inhibitory effect was associated with the increasing level of 3-nitrotyrosine in plasminogen/plasmin molecule. Furthermore, ONOO(-) displayed both the ability to impair the t-PA-induced activation of plasminogen to plasmin, and to reduce the rate of fibrin lysis by plasmin. The susceptibility of plasminogen in blood plasma to nitrative action of ONOO(-) was revealed by the immunoprecipitation technique. To confirm the hypothesis that 3-nitrotyrosine generation is crucial for the impairment of plasmin activity, (-)-epicatechin, a polyphenolic antioxidant that selectively prevents tyrosine nitration, was used both for in vitro experiments as well as for in silico studies on ONOO(-), ONOOH and (-)-epicatechin binding and plasminogen nitration. (-)-Epicatechin effectively protected plasminogen against ONOO(-)-induced inactivation and significantly reduced the level of 3-nitrotyrosine. The obtained results revealed tyrosine nitration as the most likely mechanism of the inhibitory effect of ONOO(-) on plasmin(ogen) functions. The possible role of tyrosine modifications was additionally confirmed by bioinformatics calculations with indication of nitration susceptible tyrosine residues.

Preconditioning offers cardioprotection in hyperlipidemic rat hearts: possible role of Dopamine (D2) signaling

BACKGROUND

Ischemic preconditioning (IPC) induced cardioprotection has been reported to be blunted in hyperlipidemic subjects. Dopamine, via its D2 receptor signaling, appears to mimic the signaling cascade involved in myocardial preconditioning and is also involved in the inhibition of hyperlipidemia induced mediators. The present study was designed to investigate the possible involvement of D2 receptors in IPC and to see whether dopamine preconditioning can offer cardioprotection in hyperlipidemic rat hearts.

METHODS

Wistar albino rats were divided into 8 groups and fed on normal or high fat diet for 4 weeks. Hyperlipidemia was confirmed after 4 weeks by serum lipid estimations. Isolated perfused hearts were subjected to ischemic preconditioning or dopamine induced pharmacological preconditioning followed by 30-min ischemic insult and 60-min reperfusion. Clozapine was administered as D2 antagonist. Coronary perfusate (basal and post-ischemic) was collected for the estimations of LDH (Lactate dehydrogenase) and CKMB (Creatine kinase MB). Hearts were then removed and frozen for infarct size measurement.

RESULTS

A significant increase body weight, serum lipids except HDL was noted in high fat diet fed rats, as compared to normal rats. The level of LDH, CKMB in coronary effluent and infarct size were found to be decreased in preconditioned normal hearts, as compared to hearts treated with ischemia reperfusion. This effect was found to be blunted in hyperlipidemic animals. Dopamine (10 μM) alone and in combination with ischemic preconditioning significantly reduced the levels of LDH, CKMB and infarct size in hyperlipidemic hearts, as compared to preconditioned and non-preconditioned hyperlipidemic hearts. This effect was abolished significantly by Clozapine (D2 antagonist).

CONCLUSION

The present study reveals possible involvement of D2 receptors in ischemic preconditioning and suggests that dopamine preconditioning may offer significant cardioprotection in hyperlipidemic rat hearts.

Reactive nitrogen species in cellular signaling

The transduction of cellular signals occurs through the modification of target molecules. Most of these modifications are transitory, thus the signal transduction pathways can be tightly regulated. Reactive nitrogen species are a group of compounds with different properties and reactivity. Some reactive nitrogen species are highly reactive and their interaction with macromolecules can lead to permanent modifications, which suggested they were lacking the specificity needed to participate in cell signaling events. However, the perception of reactive nitrogen species as oxidizers of macromolecules leading to general oxidative damage has recently evolved. The concept of redox signaling is now well established for a number of reactive oxygen and nitrogen species. In this context, the post-translational modifications introduced by reactive nitrogen species can be very specific and are active participants in signal transduction pathways. This review addresses the role of these oxidative modifications in the regulation of cell signaling events.

The role of parkin in the differential susceptibility of tuberoinfundibular and nigrostriatal dopamine neurons to acute toxicant exposure

Parkinson disease causes degeneration of nigrostriatal dopamine (DA) neurons, while tuberoinfundibular DA neurons remain unaffected. A similar pattern is observed following exposure to 1-methy-4-phenyl-1,2,3,6-tetrahydropyradine (MPTP). The mechanism of tuberoinfundibular neuronal recovery from MPTP is associated with up-regulation of parkin protein. Here we tested if parkin mediates tuberoinfundibular neuronal recovery from MPTP by knocking-down parkin in tuberoinfundibular neurons using recombinant adeno-associated virus (rAAV), expressing a short hairpin RNA (shRNA) directed toward parkin. Following knockdown, axon terminal DA and tyrosine hydroxylase (TH) concentrations were analyzed 24h post-MPTP administration. rAAV-shRNA-mediated knockdown of endogenous parkin rendered tuberoinfundibular neurons susceptible to MPTP induced terminal DA loss, but not TH loss, within 24h post-MPTP. To determine if the neuroprotective benefits of parkin up-regulation could be translated to nigrostriatal neurons, rAAV expressing human parkin was injected into the substantia nigra of mice and axon terminal DA and TH concentrations were analyzed 24h post-MPTP. Nigral parkin over-expression prevented loss of TH in the axon terminals and soma of nigrostriatal neurons, but had no effect on terminal DA loss within 24h post-MPTP. These data show that parkin is necessary for the recovery of terminal DA concentrations within tuberoinfundibular neurons following acute MPTP administration, and parkin can rescue MPTP-induced decreases in TH within nigrostriatal neurons.

Multimarker screening of oxidative stress in aging

Aging is a complex process of organism decline in physiological functions. There is no clear theory explaining this phenomenon, but the most accepted one is the oxidative stress theory of aging. Biomarkers of oxidative stress, substances, which are formed during oxidative damage of phospholipids, proteins, and nucleic acids, are present in body fluids of diseased people as well as the healthy ones (in a physiological concentration). 8-iso prostaglandin F_2α is the most prominent biomarker of phospholipid oxidative damage, o-tyrosine, 3-chlorotyrosine, and 3-nitrotyrosine are biomarkers of protein oxidative damage, and 8-hydroxy-2^′-deoxyguanosine and 8-hydroxyguanosine are biomarkers of oxidative damage of nucleic acids. It is thought that the concentration of biomarkers increases as the age of people increases. However, the concentration of biomarkers in body fluids is very low and, therefore, it is necessary to use a sensitive analytical method. A combination of HPLC and MS was chosen to determine biomarker concentration in three groups of healthy people of a different age (twenty, forty, and sixty years) in order to find a difference among the groups.

Oxidation and nitration in dopaminergic areas of the prefrontal cortex from patients with bipolar disorder and schizophrenia

BACKGROUND

Increased oxidative stress is strongly implicated in bipolar disorder (BD), where protein oxidation, lipid peroxidation and oxidative damage to DNA have been consistently reported. High levels of dopamine (DA) in mania are also well-recognized in patients with BD, and DA produces reactive oxygen species and electron-deficient quinones that can oxidize proteins when it is metabolized.

METHODS

Using immunohistochemistry and acceptor photobleaching Förster resonance energy transfer (FRET), we examined oxidation and nitration of areas immunoreactive for the DA transporter (DAT) and tyrosine hydroxylase (TH) in the postmortem prefrontal cortex from patients with BD, schizophrenia and major depression as well as nonpsychiatric controls.

RESULTS

We found increased oxidation of DAT-immunoreactive regions in patients with BD (F3,48 = 6.76, p = 0.001; Dunnett post hoc test p = 0.001) and decreased nitration of TH-immunoreactive regions in both patients with BD (F3,45 = 3.10, p = 0.036; Dunnett post hoc test p = 0.011) and schizophrenia (p = 0.027). On the other hand, we found increased global levels of oxidation in patients with BD (F3,44 = 6.74, p = 0.001; Dunnett post hoc test p = 0.001) and schizophrenia (p = 0.020), although nitration levels did not differ between the groups (F3,46 = 1.75; p = 0.17).

LIMITATIONS

Limitations of this study include the use of postmortem brain sections, which may have been affected by factors such as postmortem interval and antemortem agonal states, although demographic factors and postmortem interval were accounted for in our statistical analysis.

CONCLUSION

These findings suggest alterations in levels of protein oxidation and nitration in DA-rich regions of the prefrontal cortex in patients with BD and schizophrenia, but more markedly in those with BD.

Inhibition of peroxisomal hydroxypyruvate reductase (HPR1) by tyrosine nitration

BACKGROUND

Protein tyrosine nitration is a post-translational modification (PTM) mediated by nitric oxide-derived molecules. Peroxisomes are oxidative organelles in which the presence of nitric oxide (NO) has been reported.

METHODS

We studied peroxisomal nitroproteome of pea leaves by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and proteomic approaches.

RESULTS

Proteomic analysis of peroxisomes from pea leaves detected a total of four nitro-tyrosine immunopositive proteins by using an antibody against nitrotyrosine. One of these proteins was found to be the NADH-dependent hydroxypyruvate reductase (HPR). The in vitro nitration of peroxisomal samples caused a 65% inhibition of HPR activity. Analysis of recombinant peroxisomal NADH-dependent HPR1 activity from Arabidopsis in the presence of H2O2, NO, GSH and peroxynitrite showed that the ONOO(-) molecule caused the highest inhibition of activity (51% at 5mM SIN-1), with 5mM H2O2 having no inhibitory effect. Mass spectrometric analysis of the nitrated recombinant HPR1 enabled us to determine that, among the eleven tyrosine present in this enzyme, only Tyr-97, Tyr-108 and Tyr-198 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Site-directed mutagenesis confirmed Tyr198 as the primary site of nitration responsible for the inhibition on the enzymatic activity by peroxynitrite.

CONCLUSION

These findings suggest that peroxisomal HPR is a target of peroxynitrite which provokes a loss of function.

GENERAL SIGNIFICANCE

This is the first report demonstrating the peroxisomal NADH-dependent HPR activity involved in the photorespiration pathway is regulated by tyrosine nitration, indicating that peroxisomal NO metabolism may contribute to the regulation of physiological processes under no-stress conditions.

Alterations in energy metabolism, neuroprotection and visual signal transduction in the retina of Parkinsonian, MPTP-treated monkeys

Parkinson disease is mainly characterized by the degeneration of dopaminergic neurons in the central nervous system, including the retina. Different interrelated molecular mechanisms underlying Parkinson disease-associated neuronal death have been put forward in the brain, including oxidative stress and mitochondrial dysfunction. Systemic injection of the proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to monkeys elicits the appearance of a parkinsonian syndrome, including morphological and functional impairments in the retina. However, the intracellular events leading to derangement of dopaminergic and other retinal neurons in MPTP-treated animal models have not been so far investigated. Here we have used a comparative proteomics approach to identify proteins differentially expressed in the retina of MPTP-treated monkeys. Proteins were solubilized from the neural retinas of control and MPTP-treated animals, labelled separately with two different cyanine fluorophores and run pairwise on 2D DIGE gels. Out of >700 protein spots resolved and quantified, 36 were found to exhibit statistically significant differences in their expression levels, of at least ±1.4-fold, in the parkinsonian monkey retina compared with controls. Most of these spots were excised from preparative 2D gels, trypsinized and subjected to MALDI-TOF MS and LC-MS/MS analyses. Data obtained were used for protein sequence database interrogation, and 15 different proteins were successfully identified, of which 13 were underexpressed and 2 overexpressed. These proteins were involved in key cellular functional pathways such as glycolysis and mitochondrial electron transport, neuronal protection against stress and survival, and phototransduction processes. These functional categories underscore that alterations in energy metabolism, neuroprotective mechanisms and signal transduction are involved in MPTP-induced neuronal degeneration in the retina, in similarity to mechanisms thought to underlie neuronal death in the Parkinson’s diseased brain and neurodegenerative diseases of the retina proper.