Neuroprotective effects of aldehyde dehydrogenase 2 activation in rotenone-induced cellular and animal models of parkinsonism

Understanding role of pesticides in development of Parkinson's disease: Insights from Drosophila and rodent models

Parkinson's disease is a neurodegenerative illness linked to ageing, marked by the gradual decline of dopaminergic neurons in the midbrain. The exact aetiology of Parkinson's disease (PD) remains uncertain, with genetic predisposition and environmental variables playing significant roles in the disease's frequency. Epidemiological data indicates a possible connection between pesticide exposure and brain degeneration. Specific pesticides have been associated with important characteristics of Parkinson's disease, such as mitochondrial dysfunction, oxidative stress, and α-synuclein aggregation, which are crucial for the advancement of the disease. Recently, many animal models have been developed for Parkinson's disease study. Although these models do not perfectly replicate the disease's pathology, they provide valuable insights that improve our understanding of the condition and the limitations of current treatment methods. Drosophila, in particular, has been useful in studying Parkinson's disease induced by toxins or genetic factors. The review thoroughly analyses many animal models utilised in Parkinson's research, with an emphasis on issues including pesticides, genetic and epigenetic changes, proteasome failure, oxidative damage, α-synuclein inoculation, and mitochondrial dysfunction. The text highlights the important impact of pesticides on the onset of Parkinson's disease (PD) and stresses the need for more research on genetic and mechanistic alterations linked to the condition.

Detection of early proteomic alterations in 5xFAD Alzheimer's disease neonatal mouse model via MALDI-MSI

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder, characterized by memory deficit and dementia. AD is considered a multifactorial disorder where multiple processes like amyloid-beta and tau accumulation, axonal degeneration, synaptic plasticity, and autophagic processes plays an important role. In this study, the spatial proteomic differences in the neonatal 5xFAD brain tissue were investigated using MALDI-MSI coupled to LC-MS/MS, and the statistically significantly altered proteins were associated with AD. Thirty-five differentially expressed proteins (DEPs) between the brain tissues of neonatal 5xFAD and their littermate mice were detected via MALDI-MSI technique. Among the 35 proteins identified, 26 of them were directly associated with AD. Our results indicated a remarkable resemblance in the protein expression profiles of neonatal 5xFAD brain when compared to AD patient specimens or AD mouse models. These findings showed that the molecular alterations in the AD brain existed even at birth and that some proteins are neurodegenerative presages in neonatal AD brain. HIGHLIGHTS: Spatial proteomic alterations in the 5xFAD mouse brain compared to the littermate. 26 out of 35 differentially expressed proteins associated with Alzheimer's disease (AD). Molecular alterations and neurodegenerative presages in neonatal AD brain. Alterations in the synaptic function an early and common neurobiological thread.

Acetaldehyde dehydrogenase 2 activation attenuates sepsis-induced brain injury through NLRP3 inflammasome regulation

OBJECTIVE

Acetaldehyde dehydrogenase 2 (ALDH2) plays an important part in neuroprotection; however, its effect on sepsis-induced brain injury is nuclear. Our aim is to investigate the potential effect and mechanism of ALDH2 in this condition.

METHODS

We established an animal model using cecal ligation and perforation (CLP). Twenty-four rats were divided into sham group (n = 6), CLP group (n = 6), CLP + Alda-1 group (n = 6) and CLP + Cyanamide (CYA) group (n = 6). Vital signs were monitored, and arterial blood gas analysis, hippocampal histological staining and ALDH2 activity analysis were conducted. Western blot analysis and enzyme-linked immunosorbent assays were also carried out. Lipopolysaccharide (LPS)-treated HT22 cells were employed as an in vitro model of sepsis-induced brain injury, with and without pretreatment with Alda-1 or CYA, to further examine the potential mechanisms. Real-time quantitative polymerase chain reaction and western blot were used to determine the levels of pyrin domain-containing 3 (NLRP3) inflammasome.

RESULTS

We found hippocampal cell injury in the CLP group (p < 0.05), with decreased ALDH2 activity (p < 0.05) and suspected overexpression of NLRP3/caspase-1 axis (p < 0.05). In the group pretreated with Alda-1, there were increased ALDH2 activity (p < 0.05), decreased hippocampal cell damage (p < 0.05), and reduced protein levels of NLRP3, apoptosis-associated speck like protein containing a caspase recruitment domain (ASC), cleaved caspase-1 and Gasdermin D (GSDMD) (p < 0.05). The levels of interleukin 18 (IL-18) and interleukin 1β (IL-1β) were also reduced (p < 0.05). In the group pretreated with CYA, ALDH2 activity was further declined, the cell injury grade increased, and the elevated levels of pyroptosis-related proteins aggravated (p < 0.05). LPS treatment decreased the cell viability and ALDH2 activity of the HT22 cells (p < 0.05), along with increased mRNA levels of the NLRP3 inflammasome, as well as IL-1β and IL-18 (p < 0.05). Western blot further revealed elevated levels of NLRP3, ASC, cleaved caspase-1 and GSDMD (p < 0.05). In the LPS+Alda-1 group, there were increased cell viability (p < 0.05), elevated ALDH2 activity (p < 0.05), and reduced levels of NLRP3 inflammasome and pyroptosis-related proteins (p < 0.05). In the CYA+LPS group, cell viability and ALDH2 activity were further declined (p < 0.05), while levels of NLRP3 /caspase-1 axis were increased (p < 0.05).

CONCLUSIONS

The activation of ALDH2 can attenuate sepsis-induced brain injury, hypothetically through regulation of the NLRP3/caspase-1 signaling pathway. Therefore, ALDH2 could potentially be considered as a new therapeutic target for the treatment of sepsis-induced brain injury.

Disruption of the Molecular Regulation of Mitochondrial Metabolism in Airway and Lung Epithelial Cells by Cigarette Smoke: Are Aldehydes the Culprit?

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease for which cigarette smoking is the main risk factor. Acetaldehyde, acrolein, and formaldehyde are short-chain aldehydes known to be formed during pyrolysis and combustion of tobacco and have been linked to respiratory toxicity. Mitochondrial dysfunction is suggested to be mechanistically and causally involved in the pathogenesis of smoking-associated lung diseases such as COPD. Cigarette smoke (CS) has been shown to impair the molecular regulation of mitochondrial metabolism and content in epithelial cells of the airways and lungs. Although it is unknown which specific chemicals present in CS are responsible for this, it has been suggested that aldehydes may be involved. Therefore, it has been proposed by the World Health Organization to regulate aldehydes in commercially-available cigarettes. In this review, we comprehensively describe and discuss the impact of acetaldehyde, acrolein, and formaldehyde on mitochondrial function and content and the molecular pathways controlling this (biogenesis versus mitophagy) in epithelial cells of the airways and lungs. In addition, potential therapeutic applications targeting (aldehyde-induced) mitochondrial dysfunction, as well as regulatory implications, and the necessary required future studies to provide scientific support for this regulation, have been covered in this review.

Integrated Brain Metabolomics and Network Pharmacology Analysis to Reveal the Improvement Effect of Bai Chan Ting on Parkinson's Disease

BACKGROUND

Baichanting (BCT),a traditional Chinese medicine prescription, is a combination of Acanthopanax senticosus, Paeonia lactiflora, and Uncaria three herbs, which has the effect of benefiting the kidney and calming the liver. The study was aimed at investigating the protective effect of BCT against Parkinson's disease using an integrated strategy of network pharmacology and brain metabolomics.

MATERIALS AND METHODS

By integrating network pharmacology with metabolomic research, the protective effect of BCT against PD was investigated using a transgenic mouse model for α-synuclein. The metabolite level and gene level components of BCT that might be anti-PD were separated out. Indicators of behavior and pharmacodynamics were employed to gauge the effectiveness of BCT on PD in the preliminary stages. Network pharmacology, which may be the target of BCT, screened the active substances and target genes. The use of metabolomics to identify potential biomarkers of PD, and then through network pharmacology and metabolic pathways to determine their regulatory enzymes and regulatory genes, improve the pathway mechanism of the disease, has important guiding significance for the in-depth study of the pathogenesis of PD.

RESULTS

101 putative target genes were identified by the network pharmacology analysis in relation to the treatment of PD with BCT. According to the functional enrichment analysis, the proposed mechanism was primarily related to the transport of neurotransmitters, the metabolism of arachidonic acid, dopamine, and alpha-amino acids, as well as the transport of dopamine and the negative regulation of amino acid transport. 25 distinct endogenous metabolites were shown to be potential biomarkers for the BCT for treating PD based on metabolomics. These metabolites were mostly implicated in the important methionine and cysteine, tyrosine, histidine, and arginine and proline metabolic pathways. These results somewhat agreed with those of the network pharmacology analysis.

CONCLUSIONS

In conclusion, this study showed that BCT could delay the occurrence and development of PD by improving the brain metabolic disorder of α-Syn mice, which revealed the mechanism of BCT through multitarget and multipathway treatment, and provided a new explanation for the mechanism of anti-PD action. Our research, on the other hand, demonstrated that the network pharmacology-integrated metabolomics approach was a potent tool for discovering the active ingredients and mechanisms underlying the pharmacological effects of traditional Chinese medicine.

Molecular and Cellular Interactions in Pathogenesis of Sporadic Parkinson Disease

An increasing number of the population all around the world suffer from age-associated neurodegenerative diseases including Parkinson’s disease (PD). This disorder presents different signs of genetic, epigenetic and environmental origin, and molecular, cellular and intracellular dysfunction. At the molecular level, α-synuclein (αSyn) was identified as the principal molecule constituting the Lewy bodies (LB). The gut microbiota participates in the pathogenesis of PD and may contribute to the loss of dopaminergic neurons through mitochondrial dysfunction. The most important pathogenetic link is an imbalance of Ca²⁺ ions, which is associated with redox imbalance in the cells and increased generation of reactive oxygen species (ROS). In this review, genetic, epigenetic and environmental factors that cause these disorders and their cause-and-effect relationships are considered. As a constituent of environmental factors, the example of organophosphates (OPs) is also reviewed. The role of endothelial damage in the pathogenesis of PD is discussed, and a ‘triple hit hypothesis’ is proposed as a modification of Braak’s dual hit one. In the absence of effective therapies for neurodegenerative diseases, more and more evidence is emerging about the positive impact of nutritional structure and healthy lifestyle on the state of blood vessels and the risk of developing these diseases.

Neurotoxicity of pesticides - A link to neurodegeneration

Parkinson's disease (PD) is a neurodegenerative disorder which mainly targets motor symptoms such as tremor, rigidity, bradykinesia and postural instability. The physiological changes occur due to dopamine depletion in basal ganglia region of the brain. PD aetiology is not yet elucidated clearly but genetic and environmental factors play a prominent role in disease occurrence. Despite of various environmental factors, pesticides exposure has been convicted as major candidate in PD pathogenesis. Among various pesticides 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been widely investigated in PD following with paraquat (PQ), maneb (MB), organochlorines (OC) and rotenone. Effect of these pesticides has been suggested to be involved in oxidative stress, alterations in dopamine transporters, mitochondrial dysfunction, α-synuclein (αSyn) fibrillation, and neuroinflammation in PD. The present review discusses the influence of pesticides in neurodegeneration and its related epidemiological studies conducted in PD. Furthermore, we have deliberated the common pesticides involved in PD and its associated genetic alterations and the probable mechanism of them behind PD pathogenesis. Hence, we conclude that pesticides play a prominent role in PD pathogenesis and advance research is needed to investigate the alterations in genetic and mechanistic aspects of PD.

The ALDH2 rs671 polymorphism is associated with athletic status and muscle strength in a Japanese population

Aldehyde dehydrogenase 2 (ALDH2) catalyses aldehyde species, including alcohol metabolites, mainly in the liver. We recently observed that ALDH2 is also expressed in skeletal muscle mitochondria; thus, we hypothesize that rs671 polymorphism-promoted functional loss of ALDH2 may induce deleterious effects in human skeletal muscle. We aimed to clarify the association of the ALDH2 rs671 polymorphism with muscle phenotypes and athletic capacity in a large Japanese cohort. A total of 3,055 subjects, comprising 1,714 athletes and 1,341 healthy control subjects (non-athletes), participated in this study. Non-athletes completed a questionnaire regarding their exercise habits, and were subjected to grip strength, 30-s chair stand, and 8-ft walking tests to assess muscle function. The ALDH2 GG, GA, and AA genotypes were detected at a frequency of 56%, 37%, and 7% among athletes, and of 54%, 37%, and 9% among non-athletes, respectively. The minor allele frequency was 25% in athletes and 28% in controls. Notably, ALDH2 genotype frequencies differed significantly between athletes and non-athletes (genotype: p = 0.048, allele: p = 0.021), with the AA genotype occurring at a significantly lower frequency among mixed-event athletes compared to non-athletes (p = 0.010). Furthermore, non-athletes who harboured GG and GA genotypes exhibited better muscle strength than those who carried the AA genotype (after adjustments for age, sex, body mass index, and exercise habits). The AA genotype and A allele of the ALDH2 rs671 polymorphism were associated with a reduced athletic capacity and poorer muscle phenotypes in the analysed Japanese cohort; thus, impaired ALDH2 activity may attenuate muscle function.

Multifactoriality of Parkinson's Disease as Explored Through Human Neural Stem Cells and Their Transplantation in Middle-Aged Parkinsonian Mice

Parkinson's disease (PD) is an age-associated neurodegenerative disorder for which there is currently no cure. Cell replacement therapy is a potential treatment for PD; however, this therapy has more clinically beneficial outcomes in younger patients with less advanced PD. In this study, hVM1 clone 32 cells, a line of human neural stem cells, were characterized and subsequently transplanted in middle-aged Parkinsonian mice in order to examine cell replacement therapy as a treatment for PD. In vitro analyses revealed that these cells express standard dopamine-centered markers as well as others associated with mitochondrial and peroxisome function, as well as glucose and lipid metabolism. Four months after the transplantation of the hVM1 clone 32 cells, striatal expression of tyrosine hydroxylase was minimally reduced in all Parkinsonian mice but that of dopamine transporter was decreased to a greater extent in buffer compared to cell-treated mice. Behavioral tests showed marked differences between experimental groups, and cell transplant improved hyperactivity and gait alterations, while in the striatum, astroglial populations were increased in all groups due to age and a higher amount of microglia were found in Parkinsonian mice. In the motor cortex, nonphosphorylated neurofilament heavy was increased in all Parkinsonian mice. Overall, these findings demonstrate that hVM1 clone 32 cell transplant prevented motor and non-motor impairments and that PD is a complex disorder with many influencing factors, thus reinforcing the idea of novel targets for PD treatment that tend to be focused on dopamine and nigrostriatal damage.

The NRF2-Dependent Transcriptional Regulation of Antioxidant Defense Pathways: Relevance for Cell Type-Specific Vulnerability to Neurodegeneration and Therapeutic Intervention

Oxidative stress has been implicated in the etiology and pathobiology of various neurodegenerative diseases. At baseline, the cells of the nervous system have the capability to regulate the genes for antioxidant defenses by engaging nuclear factor erythroid 2 (NFE2/NRF)-dependent transcriptional mechanisms, and a number of strategies have been proposed to activate these pathways to promote neuroprotection. Here, we briefly review the biology of the transcription factors of the NFE2/NRF family in the brain and provide evidence for the differential cellular localization of NFE2/NRF family members in the cells of the nervous system. We then discuss these findings in the context of the oxidative stress observed in two neurodegenerative diseases, Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), and present current strategies for activating NFE2/NRF-dependent transcription. Based on the expression of the NFE2/NRF family members in restricted populations of neurons and glia, we propose that, when designing strategies to engage these pathways for neuroprotection, the relative contributions of neuronal and non-neuronal cell types to the overall oxidative state of tissue should be considered, as well as the cell types which have the greatest intrinsic capacity for producing antioxidant enzymes.

The rat rotenone model reproduces the abnormal pattern of central catecholamine metabolism found in Parkinson's disease

Recent reports indicate that Parkinson's disease (PD) involves specific functional abnormalities in residual neurons – decreased vesicular sequestration of cytoplasmic catecholamines via the vesicular monoamine transporter (VMAT) and decreased aldehyde dehydrogenase (ALDH) activity. This double hit builds up the autotoxic metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), the focus of the catecholaldehyde hypothesis for the pathogenesis of PD. An animal model is needed that reproduces this abnormal catecholamine neurochemical pattern. Adult rats received subcutaneous vehicle or the mitochondrial complex 1 inhibitor rotenone (2 mg/kg/day via a minipump) for 10 days. Locomotor activity was recorded, and striatal tissue sampled for catechol contents and catechol ratios that indicate the above abnormalities. Compared to vehicle, rotenone reduced locomotor activity (P=0.002), decreased tissue dopamine concentrations (P=0.00001), reduced indices of vesicular sequestration (3,4-dihydroxyphenylacetic acid (DOPAC)/dopamine) and ALDH activity (DOPAC/DOPAL) (P=0.0025, P=0.036), and increased DOPAL levels (P=0.04). The rat rotenone model involves functional abnormalities in catecholaminergic neurons that replicate the pattern found in PD putamen. These include a vesicular storage defect, decreased ALDH activity and DOPAL build-up. The rat rotenone model provides a suitable in vivo platform for studying the catecholaldehyde hypothesis.

Summary: This study presents an animal model that reflects the neurochemical pattern found in Parkinson's patients, the basis of the new and evolving catecholaldehyde hypothesis for the disease.

Early Cognitive Impairment Behind Nigrostriatal Circuit Neurotoxicity: Are Astrocytes Involved?

Cognitive dysfunction is one of the most severe nonmotor symptoms of nigrostriatal impairment. This occurs as a result of profound functional and morphological changes of different neuronal circuits, including modifications in the plasticity and architecture of hippocampal synapses. Such alterations can be implicated in the genesis and progression of dementia associated with neurodegenerative diseases including Parkinson-like symptoms. There are few studies regarding cognitive changes in nigrostriatal animal models. The aim of this study was to characterize the onset of memory deficit after induction of neurotoxicity with 6-hydroxydopamine (6-OHDA) and its correlation with hippocampal dysfunction. For this, we bilaterally microinjected 6-OHDA in dorsolateral Caudate-Putamen unit (CPu) and then, animals were tested weekly for working memory, spatial short-term memory, and motor performance. We evaluated tyrosine hydroxylase (TH) as a dopamine marker, aldehyde dehydrogenase 2 (ALDH2), a mitochondria detoxification enzyme and astrocyte glial fibrillar acid protein (GFAP) an immunoreactivity marker involved in different areas: CPu, substantia nigra, prefrontal cortex, and hippocampus. We observed a specific prefrontal cortex and nigrostriatal pathway TH reduction while ALDH2 showed a decrease-positive area in all the studied regions. Moreover, GFAP showed a specific CPu decrease and hippocampus increase of positively stained area on the third week after toxicity. We also evaluated the threshold to induce long-term potentiation in hippocampal excitability. Our findings showed that reduced hippocampal synaptic transmission was accompanied by deficits in memory processes, without affecting motor performance on the third-week post 6-OHDA administration. Our results suggest that 3 weeks after neurotoxic administration, astrocytes and ALDH2 mitochondrial enzyme modifications participate in altering the properties that negatively affect hippocampal function and consequently cognitive behavior.

The epigenetic mechanisms involved in mitochondrial dysfunction: Implication for Parkinson's disease

Mitochondrial dysfunction is one of the crucial factors involved in PD’s pathogenicity, which emerges from a combination of genetic and environmental factors. These factors cause differential molecular expression in neurons, such as varied transcriptional regulation of genes, elevated oxidative stress, α‐synuclein aggregation and endogenous neurotoxins release, which induces epigenetic modifications and triggers energy crisis by damaging mitochondria of the dopaminergic neurons (DN). So far, these events establish a complicated relationship with underlying mechanisms of mitochondrial anomalies in PD, which has remained unclear for years and made PD diagnosis and treatment extremely difficult. Therefore, in this review, we endeavored to discuss the complex association of epigenetic modifications and other associated vital factors in mitochondrial dysfunction. We propose a hypothesis that describes a vicious cycle in which mitochondrial dysfunction and oxidative stress act as a hub for regulating DA neuron's fate in PD. Oxidative stress triggers the release of endogenous neurotoxins (CTIQs) that lead to mitochondrial dysfunction along with abnormal α‐synuclein aggregation and epigenetic modifications. These disturbances further intensify oxidative stress and mitochondrial damage, amplifying the synthesis of CTIQs and works vice versa. This vicious cycle may result in the degeneration of DN to hallmark Parkinsonism. Furthermore, we have also highlighted various endogenous compounds and epigenetic marks (neurotoxic and neuroprotective), which may help for devising future diagnostic biomarkers and target specific drugs using novel PD management strategies.

The Catecholaldehyde Hypothesis for the Pathogenesis of Catecholaminergic Neurodegeneration: What We Know and What We Do Not Know

3,4-Dihydroxyphenylacetaldehyde (DOPAL) is the focus of the catecholaldehyde hypothesis for the pathogenesis of Parkinson’s disease and other Lewy body diseases. The catecholaldehyde is produced via oxidative deamination catalyzed by monoamine oxidase (MAO) acting on cytoplasmic dopamine. DOPAL is autotoxic, in that it can harm the same cells in which it is produced. Normally, DOPAL is detoxified by aldehyde dehydrogenase (ALDH)-mediated conversion to 3,4-dihydroxyphenylacetic acid (DOPAC), which rapidly exits the neurons. Genetic, environmental, or drug-induced manipulations of ALDH that build up DOPAL promote catecholaminergic neurodegeneration. A concept derived from the catecholaldehyde hypothesis imputes deleterious interactions between DOPAL and the protein alpha-synuclein (αS), a major component of Lewy bodies. DOPAL potently oligomerizes αS, and αS oligomers impede vesicular and mitochondrial functions, shifting the fate of cytoplasmic dopamine toward the MAO-catalyzed formation of DOPAL—destabilizing vicious cycles. Direct and indirect effects of DOPAL and of DOPAL-induced misfolded proteins could “freeze” intraneuronal reactions, plasticity of which is required for neuronal homeostasis. The extent to which DOPAL toxicity is mediated by interactions with αS, and vice versa, is poorly understood. Because of numerous secondary effects such as augmented spontaneous oxidation of dopamine by MAO inhibition, there has been insufficient testing of the catecholaldehyde hypothesis in animal models. The clinical pathophysiological significance of genetics, emotional stress, environmental agents, and interactions with numerous proteins relevant to the catecholaldehyde hypothesis are matters for future research. The imposing complexity of intraneuronal catecholamine metabolism seems to require a computational modeling approach to elucidate clinical pathogenetic mechanisms and devise pathophysiology-based, individualized treatments.

Neurotoxin-Induced Rodent Models of Parkinson's Disease: Benefits and Drawbacks

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by cardinal motor impairments, including akinesia and tremor, as well as by a host of non-motor symptoms, including both autonomic and cognitive dysfunction. PD is associated with a death of nigral dopaminergic neurons, as well as the pathological spread of Lewy bodies, consisting predominantly of the misfolded protein alpha-synuclein. To date, only symptomatic treatments, such as levodopa, are available, and trials aiming to cure the disease, or at least halt its progression, have not been successful. Wong et al. (2019) suggested that the lack of effective therapy against neurodegeneration in PD might be attributed to the fact that the molecular mechanisms standing behind the dopaminergic neuronal vulnerability are still a major scientific challenge. Understanding these molecular mechanisms is critical for developing effective therapy. Thirty-five years ago, Calne and William Langston (1983) raised the question of whether biological or environmental factors precipitate the development of PD. In spite of great advances in technology and medicine, this question still lacks a clear answer. Only 5-15% of PD cases are attributed to a genetic mutation, with the majority of cases classified as idiopathic, which could be linked to exposure to environmental contaminants. Rodent models play a crucial role in understanding the risk factors and pathogenesis of PD. Additionally, well-validated rodent models are critical for driving the preclinical development of clinically translatable treatment options. In this review, we discuss the mechanisms, similarities and differences, as well as advantages and limitations of different neurotoxin-induced rat models of PD. In the second part of this review, we will discuss the potential future of neurotoxin-induced models of PD. Finally, we will briefly demonstrate the crucial role of gene-environment interactions in PD and discuss fusion or dual PD models. We argue that these models have the potential to significantly further our understanding of PD.

Alda-1 Attenuates Hyperoxia-Induced Acute Lung Injury in Mice

Acute lung injury (ALI), a milder form of acute respiratory distress syndrome (ARDS), is a leading cause of mortality in older adults with an increasing prevalence. Oxygen therapy, is a common treatment for ALI, involving exposure to a high concentration of oxygen. Unfortunately, hyperoxia induces the formation of reactive oxygen species which can cause an increase in 4-HNE (4-hydroxy 2 nonenal), a toxic byproduct of lipid peroxidation. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as an endogenous shield against oxidative stress-mediated damage by clearing 4-HNE. Alda-1 [(N-(1, 3 benzodioxol-5-ylmethyl)-2, 6- dichloro-benzamide)], a small molecular activator of ALDH2, protects against reactive oxygen species-mediated oxidative stress by promoting ALDH2 activity. As a result, Alda-1 shields against ischemic reperfusion injury, heart failure, stroke, and myocardial infarction. However, the mechanisms of Alda-1 in hyperoxia-induced ALI remains unclear. C57BL/6 mice implanted with Alzet pumps received Alda-1 in a sustained fashion while being exposed to hyperoxia for 48 h. The mice displayed suppressed immune cell infiltration, decreased protein leakage and alveolar permeability compared to controls. Mechanistic analysis shows that mice pretreated with Alda-1 also experience decreased oxidative stress and enhanced levels of p-Akt and mTOR pathway associated proteins. These results show that continuous delivery of Alda-1 protects against hyperoxia-induced lung injury in mice.

"Sick-but-not-dead": multiple paths to catecholamine deficiency in Lewy body diseases

Profound depletion of the catecholamines dopamine (DA) and norepinephrine in the brain, heart, or both characterizes Lewy body diseases such as Parkinson disease, dementia with Lewy bodies, and pure autonomic failure. Although one might presume that catecholamine deficiency in these disorders results directly and solely from loss of catecholaminergic neurons, there is increasing evidence that functional abnormalities in extant residual neurons contribute to the neurotransmitter deficiencies-the "sick-but-not-dead" phenomenon. This brief review highlights two such functional abnormalities-decreased vesicular sequestration of cytoplasmic catecholamines and decreased catecholamine biosynthesis. Another abnormality, decreased activity of aldehyde dehydrogenase, may have pathogenetic significance and contribute indirectly to the loss of catecholamine stores via interactions between the autotoxic catecholaldehyde 3,4-dihydroxyphenylacetaldehyde and the protein alpha-synuclein, which is a major component of Lewy bodies. Theoretically, chronically repeated stress responses could accelerate these abnormalities, via increased exocytosis and neuronal reuptake, which indirectly shifts tissue catecholamines from vesicular stores into the cytoplasm, and via increased tyrosine hydroxylation, which augments intra-cytoplasmic DA production. The discovery of specific paths mediating the sick-but-not-dead phenomenon offers novel targets for multi-pronged therapeutic approaches.

Aldehyde dehydrogenase 2 protects against sympathetic excitation-induced cardiac fibrosis

Sympathetic stimulated-cardiac fibrosis imposes great significance on both disease progression and survival in the pathogenesis of many cardiovascular diseases. However, there are few effective therapies targeting it clinically. The cardioprotective effect of aldehyde dehydrogenase 2 (ALDH2) has been explored in many pathological conditions, whether it can exert benefit effects on chronic sympathetic stimulus-induced cardiac fibrosis remains unclear. In this study, we determined to explore the role of ALDH2 on isoproterenol (ISO)-induced cardiac fibroblasts (CF) proliferation and cardiac fibrosis. It was found that ALDH2 enzymatic activity was impaired in ISO-induced HCF proliferation and Aldh2 deficiency promoted mouse CF proliferation. Alda-1, an ALDH2 activator, exerted obvious suppressive effect on ISO-induced HCF proliferation, together with the induction of cell cycle arrest at G₀/G₁ phase and decreased expression of cyclin E1 and cyclin-dependent kinase 2 (CDK2). Mechanistically, the inhibitory role of Alda-1 on HCF proliferation was achieved by decreasing mitochondrial reactive oxygen species (ROS) production, which was partially reversed by rotenone, an inducer of ROS. In addition, wild-type mice treated with Alda-1 manifested with reduced fibrosis and better cardiac function after ISO pump. In summary, Alda-1 alleviates sympathetic excitation-induced cardiac fibrosis via decreasing mitochondrial ROS accumulation, highlighting ALDH2 activity as a promising drug target of cardiac fibrosis.

Oxidative Stress in Parkinson's Disease: Potential Benefits of Antioxidant Supplementation

Parkinson's disease (PD) occurs in approximately 1% of the population over 65 years of age and has become increasingly more common with advances in age. The number of individuals older than 60 years has been increasing in modern societies, as well as life expectancy in developing countries; therefore, PD may pose an impact on the economic, social, and health structures of these countries. Oxidative stress is highlighted as an important factor in the genesis of PD, involving several enzymes and signaling molecules in the underlying mechanisms of the disease. This review presents updated data on the involvement of oxidative stress in the disease, as well as the use of antioxidant supplements in its therapy.

α-Bisabolol, a Dietary Bioactive Phytochemical Attenuates Dopaminergic Neurodegeneration through Modulation of Oxidative Stress, Neuroinflammation and Apoptosis in Rotenone-Induced Rat Model of Parkinson's disease

Rotenone (ROT), a plant-derived pesticide is a well-known environmental neurotoxin associated with causation of Parkinson’s disease (PD). ROT impairs mitochondrial dysfunction being mitochondrial complex-I (MC-1) inhibitor and perturbs antioxidant-oxidant balance that contributes to the onset and development of neuroinflammation and neurodegeneration in PD. Due to the scarcity of agents to prevent the disease or to cure or halt the progression of symptoms of PD, the focus is on exploring agents from naturally occurring dietary phytochemicals. Among numerous phytochemicals, α-Bisabolol (BSB), natural monocyclic sesquiterpene alcohol found in many ornamental flowers and edible plants garnered attention due to its potent pharmacological properties and therapeutic potential. Therefore, the present study investigated the neuroprotective effects of BSB in a rat model of ROT-induced dopaminergic neurodegeneration, a pathogenic feature of PD and underlying mechanism targeting oxidative stress, inflammation and apoptosis. BSB treatment significantly prevented ROT-induced loss of dopaminergic neurons and fibers in the substantia nigra and striatum respectively. BSB treatment also attenuated ROT-induced oxidative stress evidenced by inhibition of MDA formation and GSH depletion as well as improvement in antioxidant enzymes, SOD and catalase. BSB treatment also attenuated ROT-induced activation of the glial cells as well as the induction and release of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and inflammatory mediators (iNOS and COX-2) in the striatum. In addition to countering oxidative stress and inflammation, BSB also attenuated apoptosis of dopaminergic neurons by attenuating downregulation of anti-apoptotic protein Bcl-2 and upregulation of pro-apoptotic proteins Bax, cleaved caspases-3 and 9. Further, BSB was observed to attenuate mitochondrial dysfunction by inhibiting mitochondrial lipid peroxidation, cytochrome-C release and reinstates the levels/activity of ATP and MC-I. The findings of the study demonstrate that BSB treatment salvaged dopaminergic neurons, attenuated microglia and astrocyte activation, induction of inflammatory mediators, proinflammatory cytokines and reduced the expression of pro-apoptotic markers. The in vitro study on ABTS radical revealed the antioxidant potential of BSB. The results of the present study are clearly suggestive of the neuroprotective effects of BSB through antioxidant, anti-inflammatory and anti-apoptotic properties in ROT-induced model of PD.

The "Sick-but-not-Dead" Phenomenon Applied to Catecholamine Deficiency in Neurodegenerative Diseases

The catecholamines dopamine and norepinephrine are key central neurotransmitters that participate in many neurobehavioral processes and disease states. Norepinephrine is also the main neurotransmitter mediating regulation of the circulation by the sympathetic nervous system. Several neurodegenerative disorders feature catecholamine deficiency. The most common is Parkinson's disease (PD), in which putamen dopamine content is drastically reduced. PD also entails severely decreased myocardial norepinephrine content, a feature that characterizes two other Lewy body diseases-pure autonomic failure and dementia with Lewy bodies. It is widely presumed that tissue catecholamine depletion in these conditions results directly from loss of catecholaminergic neurons; however, as highlighted in this review, there are also important functional abnormalities in extant residual catecholaminergic neurons. We refer to this as the "sick-but-not-dead" phenomenon. The malfunctions include diminished dopamine biosynthesis via tyrosine hydroxylase (TH) and L-aromatic-amino-acid decarboxylase (LAAAD), inefficient vesicular sequestration of cytoplasmic catecholamines, and attenuated neuronal reuptake via cell membrane catecholamine transporters. A unifying explanation for catecholaminergic neurodegeneration is autotoxicity exerted by 3,4-dihydroxyphenylacetaldehyde (DOPAL), an obligate intermediate in cytoplasmic dopamine metabolism. In PD, putamen DOPAL is built up with respect to dopamine, associated with a vesicular storage defect and decreased aldehyde dehydrogenase activity. Probably via spontaneous oxidation, DOPAL potently oligomerizes and forms quinone-protein adducts with ("quinonizes") α-synuclein (AS), a major constituent in Lewy bodies, and DOPAL-induced AS oligomers impede vesicular storage. DOPAL also quinonizes numerous intracellular proteins and inhibits enzymatic activities of TH and LAAAD. Treatments targeting DOPAL formation and oxidation therefore might rescue sick-but-not-dead catecholaminergic neurons in Lewy body diseases.

Common Protective Strategies in Neurodegenerative Disease: Focusing on Risk Factors to Target the Cellular Redox System

Neurodegenerative disease is an umbrella term for different conditions which primarily affect the neurons in the human brain. In the last century, significant research has been focused on mechanisms and risk factors relevant to the multifaceted etiopathogenesis of neurodegenerative diseases. Currently, neurodegenerative diseases are incurable, and the treatments available only control the symptoms or delay the progression of the disease. This review is aimed at characterizing the complex network of molecular mechanisms underpinning acute and chronic neurodegeneration, focusing on the disturbance in redox homeostasis, as a common mechanism behind five pivotal risk factors: aging, oxidative stress, inflammation, glycation, and vascular injury. Considering the complex multifactorial nature of neurodegenerative diseases, a preventive strategy able to simultaneously target multiple risk factors and disease mechanisms at an early stage is most likely to be effective to slow/halt the progression of neurodegenerative diseases.

Mitochondrial biogenesis as a therapeutic target for traumatic and neurodegenerative CNS diseases

Central nervous system (CNS) diseases, both traumatic and neurodegenerative, are characterized by impaired mitochondrial bioenergetics and often disturbed mitochondrial dynamics. The dysregulation observed in these pathologies leads to defective respiratory chain function and reduced ATP production, thereby promoting neuronal death. As such, attenuation of mitochondrial dysfunction through induction of mitochondrial biogenesis (MB) is a promising, though still underexplored, therapeutic strategy. MB is a multifaceted process involving the integration of highly regulated transcriptional events, lipid membrane and protein synthesis/assembly and replication of mtDNA. Several nuclear transcription factors promote the expression of genes involved in oxidative phosphorylation, mitochondrial import and export systems, antioxidant defense and mitochondrial gene transcription. Of these, the nuclear-encoded peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is the most commonly studied and is widely accepted as the 'master regulator' of MB. Several recent preclinical studies document that reestablishment of mitochondrial homeostasis through increased MB results in inhibited injury progression and increased functional recovery. This perspective will briefly review the role of mitochondrial dysfunction in the propagation of CNS diseases, while also describing current research strategies that mediate mitochondrial dysfunction and compounds that induce MB for the treatment of acute and chronic neuropathologies.

Alda-1, an activator of ALDH2, ameliorates Achilles tendinopathy in cellular and mouse models

Achilles tendinopathy has a high re-injury rate and poor prognosis. Development of effective therapy for Achilles tendinopathy is important. Excessive accumulation of ROS and resulting oxidative stress are believed to cause tendinopathy. Overproduction of hydrogen peroxide (H₂O₂), the most common ROS, could lead to the tendinopathy by causing oxidative damage, activation of endoplasmic reticulum (ER) stress and apoptotic death of tenocytes. Activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) is expected to alleviate oxidative stress and ER stress. Alda-1 is a selective and potent activator of ALDH2. In this study, we examined the cytoprotective benefit of Alda-1, an activator of ALDH2, on H₂O₂-induced Achilles tendinopathy in cellular and mouse models. We prepared cellular and mouse models of Achilles tendinopathy by treating cultured Achilles tenocytes and Achilles tendons with oxidative stressor H₂O₂. Subsequently, we studied the protective benefit of Alda-1 on H₂O₂-induced Achilles tendinopathy. Alda-1 pretreatment attenuated H₂O₂-induced cell death of cultured Achilles tenocytes. Treatment of Alda-1 prevented H₂O₂-induced oxidative stress and depolarization of mitochondrial membrane potential in tenocytes. Application of Alda-1 attenuated H₂O₂-triggered mitochondria- and ER stress-mediated apoptotic cascades in cultured tenocytes. Alda-1 treatment ameliorated the severity of H₂O₂-induced Achilles tendinopathy in vivo by preventing H₂O₂-induced pathological histological features of Achilles tendons, apoptotic death of Achilles tenocytes and upregulated expression of inflammatory cytokines IL-1β and TNF-α. Our results provide the evidence that ALDH2 activator Alda-1 ameliorates H₂O₂-induced Achilles tendinopathy. Alda-1 could be used for preventing and treating Achilles tendinopathy.

ALDH2 Gene: Its Effects on the Neuropsychological Functions in Patients with Opioid Use Disorder Undergoing Methadone Maintenance Treatment

Objective

Patients with opioid use disorder (OUD) have impaired attention, inhibition control, and memory function. The aldehyde dehydrogenase 2(ALDH2) gene has been associated with OUD and ALDH2 gene polymorphisms may affect aldehyde metabolism and cognitive function in other substance use disorder. Therefore, we aimed to investigate whether ALDH2 genotypes have significant effects on neuropsychological functions in OUD patients undergoing methadone maintenance therapy (MMT).

Methods

OUD patients undergoing MMT were investigated and followed-up for 12 weeks. ALDH2 gene polymorphisms were genotyped. Connors' Continuous Performance Test (CPT) and the Wechsler Memory Scale-Revised (WMS-R) were administered at baseline and after 12 weeks of MMT. Multivariate linear regressions and generalized estimating equations (GEEs) were used to examine the correlation between the ALDH2 genotypes and performance on the CPTs and WMS-R.

Results

We enrolled 86 patients at baseline; 61 patients completed the end-of-study assessments. The GEE analysis showed that, after the 12 weeks of MMT, OUD patients with the ALDH2 *1/*2＋*2/*2 (ALDH2 inactive) genotypes had significantly higher commission error T-scores (p= 0.03), significantly lower hit reaction time T-scores (p= 0.04), and significantly lower WMS-R visual memory index scores (p= 0.03) than did patients with the ALDH2 1*/*1 (ALDH2 active) genotype.

Conclusion

OUD patients with the ALDH2 inactive genotypes performed worse in cognitive domains of attention, impulse control, and memory than did those with the ALDH2 active genotype. We conclude that the ALDH2 gene is important in OUD and is associated with neuropsychological performance after MMT.

Neuroprotective Effects of Pomegranate Juice against Parkinson's Disease and Presence of Ellagitannins-Derived Metabolite-Urolithin A-In the Brain

Pomegranate juice is a rich source of ellagitannins (ETs) believed to contribute to a wide range of pomegranate’s health benefits. While a lot of experimental studies have been devoted to Alzheimer disease and hypoxic-ischemic brain injury, our knowledge of pomegranate’s effects against Parkinson’s disease (PD) is very limited. It is suggested that its neuroprotective effects are mediated by ETs-derived metabolites—urolithins. In this study, we examined the capability of pomegranate juice for protection against PD in a rat model of parkinsonism induced by rotenone. To evaluate its efficiency, assessment of postural instability, visualization of neurodegeneration, determination of oxidative damage to lipids and α-synuclein level, as well as markers of antioxidant defense status, inflammation, and apoptosis, were performed in the midbrain. We also check the presence of plausible active pomegranate ETs-derived metabolite, urolithin A, in the plasma and brain. Our results indicated that pomegranate juice treatment provided neuroprotection as evidenced by the postural stability improvement, enhancement of neuronal survival, its protection against oxidative damage and α-synuclein aggregation, the increase in mitochondrial aldehyde dehydrogenase activity, and maintenance of antiapoptotic Bcl-xL protein at the control level. In addition, we have provided evidence for the distribution of urolithin A to the brain.

Activation of TGR5 with INT-777 attenuates oxidative stress and neuronal apoptosis via cAMP/PKCε/ALDH2 pathway after subarachnoid hemorrhage in rats

BACKGROUND

Oxidative stress and neuronal apoptosis play important roles in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). The activation of TGR5, a novel membrane-bound bile acid receptor, possesses anti-oxidative stress and anti-apoptotic effects in hepatobiliary disease and kidney disease. The present study aimed to explore the neuroprotective effect of TGR5 activation against EBI after SAH and the potential underlying mechanisms.

METHODS

The endovascular perforation model of SAH was performed on 199 Sprague Dawley rats to investigate the beneficial effects of TGR5 activation after SAH. INT-777, a specific synthetic TGR5 agonist, was administered intranasally at 1 h after SAH induction. TGR5 CRISPR and ALDH2 CRISPR were administered intracerebroventricularly at 48 h before SAH to illuminate potential mechanisms. The SAH grade, short-term and long-term neurobehavioral tests, TUNEL staining, Fluoro-Jade C staining, Nissl staining, immunofluorescence staining, and western blots were performed at 24 h after SAH.

RESULTS

The expressions of endogenous TGR5 and ALDH2 gradually increased and peaked at 24 h after SAH. TGR5 was expressed primarily in neurons, as well as in astrocytes and microglia. The activation of TGR5 with INT-777 significantly improved the short-term and long-term neurological deficits, accompanied by reduced the oxidative stress and neuronal apoptosis at 24 h after SAH. Moreover, INT-777 treatment significantly increased the expressions of TGR5, cAMP, phosphorylated PKCε, ALDH2, HO-1, and Bcl-2, while downregulated the expressions of 4-HNE, Bax, and Cleaved Caspase-3. TGR5 CRISPR and ALDH2 CRISPR abolished the neuroprotective effects of TGR5 activation after SAH.

CONCLUSIONS

In summary, the activation of TGR5 with INT-777 attenuated oxidative stress and neuronal apoptosis via the cAMP/PKCε/ALDH2 signaling pathway after SAH in rats. Furthermore, TGR5 may serve as a novel therapeutic target to ameliorate EBI after SAH.

Upregulated Expression of MicroRNA-204-5p Leads to the Death of Dopaminergic Cells by Targeting DYRK1A-Mediated Apoptotic Signaling Cascade

MicroRNAs (miRs) downregulate or upregulate the mRNA level by binding to the 3′-untranslated region (3′UTR) of target gene. Dysregulated miR levels can be used as biomarkers of Parkinson’s disease (PD) and could participate in the etiology of PD. In the present study, 45 brain-enriched miRs were evaluated in serum samples from 50 normal subjects and 50 sporadic PD patients. The level of miR-204-5p was upregulated in serum samples from PD patients. An upregulated level of miR-204-5p was also observed in the serum and substantia nigra (SN) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Expression of miR-204-5p increased the level of α-synuclein (α-Syn), phosphorylated (phospho)-α-Syn, tau, or phospho-tau protein and resulted in the activation of endoplasmic reticulum (ER) stress in SH-SY5Y dopaminergic cells. Expression of miR-204-5p caused autophagy impairment and activation of c-Jun N-terminal kinase (JNK)-mediated apoptotic cascade in SH-SY5Y dopaminergic cells. Our study using the bioinformatic method and dual-luciferase reporter analysis suggests that miR-204-5p positively regulates mRNA expression of dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) by directly interacting with 3′UTR of DYRK1A. The mRNA and protein levels of DYRK1A were increased in SH-SY5Y dopaminergic cells expressing miR-204-5p and SN of MPTP-induced PD mouse model. Knockdown of DYRK1A expression or treatment of the DYRK1A inhibitor harmine attenuated miR-204-5p-induced increase in protein expression of phospho-α-Syn or phospho-tau, ER stress, autophagy impairment, and activation of JNK-mediated apoptotic pathway in SH-SY5Y dopaminergic cells or primary cultured dopaminergic neurons. Our results suggest that upregulated expression of miR-204-5p leads to the death of dopaminergic cells by targeting DYRK1A-mediated ER stress and apoptotic signaling cascade.

Impaired dopamine metabolism in Parkinson's disease pathogenesis

A full understanding of Parkinson's Disease etiopathogenesis and of the causes of the preferential vulnerability of nigrostriatal dopaminergic neurons is still an unsolved puzzle. A multiple-hit hypothesis has been proposed, which may explain the convergence of familial, environmental and idiopathic forms of the disease. Among the various determinants of the degeneration of the neurons in Substantia Nigra pars compacta, in this review we will focus on the endotoxicity associated to dopamine dyshomeostasis. In particular, we will discuss the relevance of the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) in the catechol-induced neurotoxicity. Indeed, the synergy between the catechol and the aldehyde moieties of DOPAL exacerbates its reactivity, resulting in modification of functional protein residues, protein aggregation, oxidative stress and cell death. Interestingly, αSynuclein, whose altered proteostasis is a recurrent element in Parkinson's Disease pathology, is considered a preferential target of DOPAL modification. DOPAL triggers αSynuclein oligomerization leading to synapse physiology impairment. Several factors can be responsible for DOPAL accumulation at the pre-synaptic terminals, i.e. dopamine leakage from synaptic vesicles, increased rate of dopamine conversion to DOPAL by upregulated monoamine oxidase and decreased DOPAL degradation by aldehyde dehydrogenases. Various studies report the decreased expression and activity of aldehyde dehydrogenases in parkinsonian brains, as well as genetic variants associated to increased risk in developing the pathology. Thus, we discuss how the deregulation of these enzymes might be considered a contributing element in the pathogenesis of Parkinson's Disease or a down-stream effect. Finally, we propose that a better understanding of the impaired dopamine metabolism in Parkinson's Disease would allow a more refined patients stratification and the design of more targeted and successful therapeutic strategies.

Phenothiazine normalizes the NADH/NAD+ ratio, maintains mitochondrial integrity and protects the nigrostriatal dopamine system in a chronic rotenone model of Parkinson's disease

Impaired mitochondrial function has been associated with the etiopathogenesis of Parkinson's disease (PD). Sustained inhibition of complex I produces mitochondrial dysfunction, which is related to oxidative injury and nigrostriatal dopamine (DA) neurodegeneration. This study aimed to identify disease-modifying treatments for PD. Unsubstituted phenothiazine (PTZ) is a small and uncharged aromatic imine that readily crosses the blood-brain barrier. PTZ lacks significant DA receptor-binding activity and, in the nanomolar range, exhibits protective effects via its potent free radical scavenging and anti-inflammatory activities. Given that DAergic neurons are highly vulnerable to oxidative damage and inflammation, we hypothesized that administration of PTZ might confer neuroprotection in different experimental models of PD. Our findings showed that PTZ rescues rotenone (ROT) toxicity in primary ventral midbrain neuronal cultures by preserving neuronal integrity and reducing protein thiol oxidation. Long-term treatment with PTZ improved animal weight, survival rate, and behavioral deficits in ROT-lesioned rats. PTZ protected DA content and fiber density in the striatum and DA neurons in the SN against the deleterious effects of ROT. Mitochondrial dysfunction, axonal impairment, oxidative insult, and inflammatory response were attenuated with PTZ therapy. Furthermore, we have provided a new insight into the molecular mechanism underlying the neuroprotective effects of PTZ.

Histamine-4 receptor antagonist JNJ7777120 inhibits pro-inflammatory microglia and prevents the progression of Parkinson-like pathology and behaviour in a rat model

The activation of microglial cells is presumed to play a key role in the pathogenesis of Parkinson's disease (PD). The activity of microglia is regulated by the histamine-4 receptor (H₄R), thus providing a novel target that may prevent the progression of PD. However, this putative mechanism has so far not been validated. In our previous study, we found that mRNA expression of H₄R was upregulated in PD patients. In the present study, we validated this possible mechanism using the rotenone-induced PD rat model, in which mRNA expression levels of H₄R-, and microglial markers were significantly increased in the ventral midbrain. Inhibition of H₄R in rotenone-induced PD rat model by infusion of the specific H₄R antagonist JNJ7777120 into the lateral ventricle resulted in blockade of microglial activation. In addition, pharmacological targeting of H₄R in rotenone-lesioned rats resulted in reduced apomorphine-induced rotational behaviour, prevention of dopaminergic neuron degeneration and associated decreases in striatal dopamine levels. These changes were accompanied by a reduction of Lewy body-like neuropathology. Our results provide first proof of the efficacy of an H₄R antagonist in a commonly used PD rat model, and proposes the H₄R as a promising target to clinically tackle microglial activation and thereby the progression of PD.

Combined Assessment of Serum Alpha-Synuclein and Rab35 is a Better Biomarker for Parkinson's Disease

BACKGROUND AND PURPOSE

It is essential to develop a reliable predictive serum biomarker for Parkinson's disease (PD). The accumulation of alpha-synuclein (αSyn) and up-regulated expression of Rab35 participate in the etiology of PD. The purpose of this investigation was to determine whether the combined assessment of serum αSyn and Rab35 is a useful predictive biomarker for PD.

METHODS

Serum levels of αSyn or Rab35 were determined in serum samples from 59 sporadic PD patients, 19 progressive supranuclear palsy (PSP) patients, 20 multiple system atrophy (MSA) patients, and 60 normal controls (NC). Receiver operating characteristics (ROC) curves were calculated to determine the diagnostic accuracy of αSyn or/and Rab35 in discriminating PD patients from NC or atypical parkinsonian patients.

RESULTS

The levels of αSyn and Rab35 were increased in PD patients. The serum level of Rab35 was positively correlated with that of αSyn in PD patients. Compared to analyzing αSyn or Rab35 alone, the combined analysis of αSyn and Rab35 produced a larger area under the ROC curve and performed better in discriminating PD patients from NC, MSA patients, or PSP patients. When age was dichotomized at 55, 60, 65, or 70 years, the combined assessment of αSyn and Rab35 for classifying PD was better in the group below the cutoff age than in the group above the cutoff age.

CONCLUSIONS

Combined assessment of serum αSyn and Rab35 is a better biomarker for discriminating PD patients from NC or atypical parkinsonian patients, and is a useful predictive biomarker for younger sporadic PD patients.

Alda-1, an aldehyde dehydrogenase-2 agonist, causes deterioration in renal functions following ischemia-reperfusion injury due to crystalline nephropathy

Renal ischemia-reperfusion injury (IRI) induces the production of aldehydes which are detoxified by aldehyde dehydrogenases (ALDHs). Alda-1 is a selective ALDH2 agonist and its protective effect was demonstrated in several conditions. The effect of Alda-1 on the kidney or on renal IRI was not investigated. We investigated the effect of Alda-1 on the renal dysfunction following IRI. Wistar rats underwent left IRI for 40 min. Group-Alda (n = 11) received Alda-1 starting 24 h before IRI and continued for 7 days thereafter when renal functions were measured. Group-Vx (n = 11) underwent similar protocol but received the dissolvent. Alda-1 did not affect renal blood flow or glomerular filtration rate in the left ischemic kidney in Group-Alda compared to Group-Vx (3.05 ± 0.50 vs. 3.53 ± 0.70, and 0.40 ± 0.06 vs. 0.51 ± 0.08, respectively, p > .05 for both). However, left renal fractional sodium excretion was higher in Group-Alda (2.80 ± 0.43 vs. 1.37 ± 0.36, p = .02). Alda-1 also adversely affected the gene expressions of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin (217 ± 38 vs. 99 ± 13 and 49 ± 13 vs. 20 ± 5, respectively, p < .05 for both) and the alterations in tumor necrosis factor-α, transforming growth factor-β1, plasminogen activator inhibitor-1, fibronectin 1 and p53 (4.4 ± 0.9 vs. 2.1 ± 0.3, 1.5 ± 0.1 vs. 1.1 ± 0.1, 30.0 ± 2.7 vs. 11.7 ± 2.3, 3.6 ± 0.4 vs. 2.1 ± 0.2 and 1.3 ± 0.1 vs. 0.9 ± 0.07, respectively, p ≤ .05 for all). This was associated with intratubular crystal deposition suggestive of crystalline nephropathy. Alda-1 exacerbated the IRI-induced renal tubular dysfunction and alterations in markers of acute kidney injury, biomarkers of inflammation, fibrosis and apoptosis and this was associated with intratubular crystal deposition suggestive of crystalline nephropathy.

Genetic variants in ALDH2 predict risk of ischemic stroke in a Chinese population

BACKGROUND AND PURPOSE

Genome-wide association studies discovered a novel correlation between chromosome 12q24 and ischemic stroke in European populations. This study aimed to determine whether two genetic variants (rs10744777 and rs886205) on chromosome 12q24 can modify the risk of ischemic stroke in Chinese population.

METHODS

We recruited 1195 patients with ischemic stroke and 642 healthy Chinese individuals. The rs10744777 and rs886205 polymorphisms in aldehyde dehydrogenase2 (ALDH2) was genotyped and compared using multivariate logistic regression.

RESULTS

The genotype of rs10744777 (CT/TT) was associated with risk of ischemic stroke in males (OR = 1.99, 95% CI = 1.15-3.42, P = 0.013). In contrast, no significant correlation was found in females. Haplotype analysis indicated that haplotype "TA" was associated with increased ischemic stroke risk (OR = 1.85, 95% CI = 1.10-3.12, P = 0.042). Further subtype analysis demonstrated that the rs10744777 (CT/TT) genotype was strongly associated with large artery atherosclerosis subtype in males (OR = 2.27, 95% CI = 1.30-3.95, P = 0.004). After three months follow-up, we found a poorer functional outcome of ischemic stroke associated with the rs886205 GA genotype (OR = 1.76, 95% CI 1.03-3.00, P = 0.057) in males.

CONCLUSIONS

Genetic polymorphisms in ALDH2 modified ischemic stroke risk and outcome in Chinese males, but not in females.

Aldehyde dehydrogenase 2 in the spotlight: The link between mitochondria and neurodegeneration

Growing body of evidence suggests that mitochondrial dysfunctions and resultant oxidative stress are likely responsible for many neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Aldehyde dehydrogenase (ALDH) superfamily plays a crucial role in several biological processes including development and detoxification pathways in the organism. In particular, ALDH2 is crucial in the oxidative metabolism of toxic aldehydes in the brain, such as catecholaminergic metabolites (DOPAL and DOPEGAL) and the principal product of lipid peroxidation process 4-HNE. This review aims to deepen the current knowledge regarding to ALDH2 function and its relation with brain-damaging processes that increase the risk to develop neurodegenerative disorders. We focused on relevant literature of what is currently known at molecular and cellular levels in experimental models of these pathologies. The understanding of ALDH2 contributions could be a potential target in new therapeutic approaches for PD and AD due to its crucial role in mitochondrial normal function maintenance that protects against neurotoxicity.

3,4-Dihydroxyphenylacetaldehyde-Induced Protein Modifications and Their Mitigation by N-Acetylcysteine

The catecholaldehyde hypothesis posits that 3,4-dihydroxyphenylacetaldehyde (DOPAL), an obligate intermediary metabolite of dopamine, is an autotoxin that challenges neuronal homeostasis in catecholaminergic neurons. DOPAL toxicity may involve protein modifications, such as oligomerization of α-synuclein (AS). Potential interactions between DOPAL and other proteins related to catecholaminergic neurodegeneration, however, have not been systemically explored. This study examined DOPAL-induced protein-quinone adduct formation ("quinonization") and protein oligomerization, ubiquitination, and aggregation in cultured MO3.13 human oligodendrocytes and PC12 rat pheochromocytoma cells and in test tube experiments. Using near-infrared fluorescence spectroscopy, we detected spontaneous DOPAL oxidation to DOPAL-quinone, DOPAL-induced quinonization of intracellular proteins in both cell lines, and DOPAL-induced quinonization of several proteins related to catecholaminergic neurodegeneration, including AS, the type 2 vesicular monoamine transporter, glucocerebrosidase, ubiquitin, and l-aromatic-amino-acid decarboxylase (LAAAD). DOPAL also oligomerized AS, ubiquitin, and LAAAD; inactivated LAAAD (IC₅₀ 54 μM); evoked substantial intracellular protein ubiquitination; and aggregated intracellular AS. Remarkably, N-acetylcysteine, which decreases DOPAL-quinone formation, attenuated or prevented all of these protein modifications and functional changes. The results fit with the proposal that treatments based on decreasing the formation and oxidation of DOPAL may slow or prevent catecholaminergic neurodegeneration.

The potential of aldehyde dehydrogenase 2 as a therapeutic target in cardiovascular disease

INTRODUCTION

Mitochondrial aldehyde dehydrogenase (ALDH-2) plays a major role in the ethanol detoxification pathway by removing acetaldehyde. Therefore, ALDH-2 inhibitors such as disulfiram represent the first therapeutic targeting of ALDH-2 for alcoholism therapy. Areas covered: Recently, ALDH-2 was identified as an essential bioactivating enzyme of the anti-ischemic organic nitrate nitroglycerin, bringing ALDH-2 again into the focus of clinical interest. Mechanistic studies on the nitroglycerin bioactivation process revealed that during bioconversion of nitroglycerin and in the presence of reactive oxygen and nitrogen species the active site thiols of ALDH-2 are oxidized and the enzyme activity is lost. Thus, ALDH-2 activity represents a useful marker for cardiovascular oxidative stress, a concept, which has been meanwhile supported by a number of animal disease models. Mechanistic studies on the protective role of ALDH-2 in different disease processes identified the detoxification of 4-hydroxynonenal by ALDH-2 as a fundamental process of cardiovascular, cerebral and antioxidant protection. Expert opinion: The most recent therapeutic exploitation of ALDH-2 includes activators of the enzyme such as Alda-1 but also cell-based therapies (ALDH-bright cells) that deserve further clinical characterization in the future.

Neurotoxin-Induced Animal Models of Parkinson Disease: Pathogenic Mechanism and Assessment

Parkinson disease (PD) is the second most common neurodegenerative movement disorder. Pharmacological animal models are invaluable tools to study the pathological mechanisms of PD. Currently, invertebrate and vertebrate animal models have been developed by using several main neurotoxins, such as 6-hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, paraquat, and rotenone. These models achieve to some extent to reproduce the key features of PD, including motor defects, progressive loss of dopaminergic neurons in substantia nigra pars compacta, and the formation of Lewy bodies. In this review, we will highlight the pathogenic mechanisms of those neurotoxins and summarize different neurotoxic animal models with the hope to help researchers choose among them accurately and to promote the development of modeling PD.

Linking lipid peroxidation and neuropsychiatric disorders: focus on 4-hydroxy-2-nonenal

4-hydroxy-2-nonenal (HNE) is considered to be a strong marker of oxidative stress; the interaction between HNE and cellular proteins leads to the formation of HNE-protein adducts able to alter cellular homeostasis and cause the development of a pathological state. By virtue of its high lipid concentration, oxygen utilization, and the presence of metal ions participating to redox reactions, the brain is highly susceptible to the formation of free radicals and HNE-related compounds. A variety of neuropsychiatric disorders have been associated with elevations of HNE concentration. For example, increased levels of HNE were found in the cortex of bipolar and schizophrenic patients, while HNE plasma concentrations resulted high in patients with major depression. On the same line, high brain concentrations of HNE were found associated with Huntington's inclusions. The incidence of high HNE levels is relevant also in the brain and cerebrospinal fluid of patients suffering from Parkinson's disease. Intriguingly, in this case the increase of HNE was associated with an accumulation of iron in the substantia nigra, a brain region highly affected by the pathology. In the present review we recapitulate the findings supporting the role of HNE in the pathogenesis of different neuropsychiatric disorders to highlight the pathogenic mechanisms ascribed to HNE accumulation. The aim of this review is to offer novel perspectives both for the understanding of etiopathogenetic mechanisms that remain still unclear and for the identification of new useful biological markers. We conclude suggesting that targeting HNE-driven cellular processes may represent a new more efficacious therapeutical intervention.

PARK14 PLA2G6 mutants are defective in preventing rotenone-induced mitochondrial dysfunction, ROS generation and activation of mitochondrial apoptotic pathway

Mutations in the gene encoding Ca²⁺-independent phospholipase A₂ group 6 (PLA2G6) cause the recessive familial type 14 of Parkinson’s disease (PARK14). Mitochondrial dysfunction is involved in the pathogenesis of Parkinson’s disease (PD). PLA2G6 is believed to be required for maintaining mitochondrial function. In the present study, rotenone-induced cellular model of PD was used to investigate possible molecular pathogenic mechanism of PARK14 mutant PLA2G6-induced PD. Overexpression of wild-type (WT) PLA2G6 ameliorated rotenone-induced apoptotic death of SH-SY5Y dopaminergic cells. PARK14 mutant (D331Y), (G517C), (T572I), (R632W), (N659S) or (R741Q) PLA2G6 failed to prevent rotenone-induced activation of mitochondrial apoptotic pathway and exert a neuroprotective effect. WT PLA2G6, but not PARK14 mutant PLA2G6, prevented rotenone-induced mitophagy impairment. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 was ineffective in attenuating rotenone-induced decrease in mitochondrial membrane potential and increase in the level of mitochondrial superoxide. WT PLA2G6, but not PARK14 PLA2G6 mutants, restored enzyme activity of mitochondrial complex I and cellular ATP content in rotenone-treated SH-SY5Y dopaminergic cells. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 failed to prevent rotenone-induced mitochondrial lipid peroxidation and cytochrome c release. These results suggest that PARK14 PLA2G6 mutants lose their ability to maintain mitochondrial function and are defective inpreventing mitochondrial dysfunction, ROS production and activation of mitochondrial apoptotic pathway in rotenone-induced cellular model of PD.

Linking Stress, Catecholamine Autotoxicity, and Allostatic Load with Neurodegenerative Diseases: A Focused Review in Memory of Richard Kvetnansky

In this Focused Review, we provide an update about evolving concepts that may link chronic stress and catecholamine autotoxicity with neurodegenerative diseases such as Parkinson's disease. Richard Kvetnansky's contributions to the field of stress and catecholamine systems inspired some of the ideas presented here. We propose that coordination of catecholaminergic systems mediates adjustments maintaining health and that senescence-related disintegration of these systems leads to disorders of regulation and to neurodegenerative diseases such as Parkinson's disease. Chronically repeated episodes of stress-related catecholamine release and reuptake, with attendant increases in formation of the toxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde, might accelerate this process.

Pretreatment with the ALDH2 agonist Alda-1 reduces intestinal injury induced by ischaemia and reperfusion in mice

Many studies demonstrate that activation of aldehyde dehydrogenase 2 (ALDH2) protects against oxidative stress via detoxification of cytotoxic aldehydes, and could attenuate cardiac, cerebral, lung and renal ischaemia-reperfusion (I/R) injuries. However, the effect of ALDH2 in intestinal I/R is unknown. The present study was set up to determine whether an ALDH2 agonist, Alda-1, could alleviate intestinal injury after gut I/R. In a mouse model of intestinal I/R injury, histological grading, proinflammatory cytokines, oxidative stress, cellular apoptosis, chemokine contents, ALDH2 activity, 4-hydroxy-trans-2-nonenal (4-HNE) and malondialdehyde (MDA) were evaluated. The results indicated that I/R treatment conferred elevation in pathological scores, proinflammatory cytokines, oxidative stress, cellular apoptosis and chemokine levels, accompanied by accumulated 4-HNE and MDA. No significant changes in ALDH2 activity were observed after I/R. However, Alda-1 pretreatment significantly decreased these injurious indicators, concomitant with up-regulated ALDH2 activity, and lessened 4-HNE and MDA accumulation. Taken together, our results implicate activation of ALDH2 by Alda-1 in the significant abatement intestinal I/R injury.

Proteomic Analysis of Mitochondria-Enriched Fraction Isolated from the Frontal Cortex and Hippocampus of Apolipoprotein E Knockout Mice Treated with Alda-1, an Activator of Mitochondrial Aldehyde Dehydrogenase (ALDH2)

The role of different genotypes of apolipoprotein E (apoE) in the etiology of Alzheimer’s disease is widely recognized. It has been shown that altered functioning of apoE may promote 4-hydroxynonenal modification of mitochondrial proteins, which may result in mitochondrial dysfunction, aggravation of oxidative stress, and neurodegeneration. Mitochondrial aldehyde dehydrogenase (ALDH2) is an enzyme considered to perform protective function in mitochondria by the detoxification of the end products of lipid peroxidation, such as 4-hydroxynonenal and other reactive aldehydes. The goal of our study was to apply a differential proteomics approach in concert with molecular and morphological techniques to elucidate the changes in the frontal cortex and hippocampus of apolipoprotein E knockout (apoE^−/−) mice upon treatment with Alda-1—a small molecular weight activator of ALDH2. Despite the lack of significant morphological changes in the brain of apoE^−/− mice as compared to age-matched wild type animals, the proteomic and molecular approach revealed many changes in the expression of genes and proteins, indicating the impairment of energy metabolism, neuroplasticity, and neurogenesis in brains of apoE^−/− mice. Importantly, prolonged treatment of apoE^−/− mice with Alda-1 led to the beneficial changes in the expression of genes and proteins related to neuroplasticity and mitochondrial function. The pattern of alterations implies mitoprotective action of Alda-1, however, the accurate functional consequences of the revealed changes require further research.

Of Pesticides and Men: a California Story of Genes and Environment in Parkinson's Disease

At the start of the postgenomics era, most Parkinson's disease (PD) etiology cannot be explained by our knowledge of genetic or environmental factors alone. For more than a decade, we have explored gene-environment (GxE) interactions possibly responsible for the heterogeneity of genetic as well as environmental results across populations. We developed three pesticide exposure measures (ambient due to agricultural applications, home and garden use, and occupational use) in a large population-based case-control study of incident PD in central California. Specifically, we assessed interactions with genes responsible for pesticide metabolism (PON1); transport across the blood-brain barrier (ABCB1); pesticides interfering with or depending on dopamine transporter activity (DAT/SLC6A3) and dopamine metabolism (ALDH2); impacting mitochondrial function via oxidative/nitrosative stress (NOS1) or proteasome inhibition (SKP1); and contributing to immune dysregulation (HLA-DR). These studies established some specificity for pesticides' neurodegenerative actions, contributed biologic plausibility to epidemiologic findings, and identified genetically susceptible populations.

Hydrogen Sulfide Ameliorates Homocysteine-Induced Cognitive Dysfunction by Inhibition of Reactive Aldehydes Involving Upregulation of ALDH2

BACKGROUND

Homocysteine, a risk factor for Alzheimer's disease, induces cognitive dysfunction. Reactive aldehydes play an important role in cognitive dysfunction. Aldehyde-dehydrogenase 2 detoxifies reactive aldehydes. Hydrogen sulfide, a novel neuromodulator, has neuroprotective effects and regulates learning and memory. Our previous work confirmed that the disturbance of hydrogen sulfide synthesis is invovled in homocysteine-induced defects in learning and memory. Therefore, the present work was to explore whether hydrogen sulfide ameliorates homocysteine-generated cognitive dysfunction and to investigate whether its underlying mechanism is related to attenuating accumulation of reactive aldehydes by upregulation of aldehyde-dehydrogenase 2.

METHODS

The cognitive function of rats was assessed by the Morris water maze test and the novel object recognition test. The levels of malondialdehyde, 4-hydroxynonenal, and glutathione as well as the activity of aldehyde-dehydrogenase 2 were determined by enzyme linked immunosorbent assay; the expression of aldehyde-dehydrogenase 2 was detected by western blot.

RESULTS

The behavior experiments, Morris water maze test and novel objects recognition test, showed that homocysteine induced deficiency in learning and memory in rats, and this deficiency was reversed by treatment of NaHS (a donor of hydrogen sulfide). We demonstrated that NaHS inhibited homocysteine-induced increases in generations of MDA and 4-HNE in the hippocampus of rats and that hydrogen sulfide reversed homocysteine-induced decreases in the level of glutathione as well as the activity and expression of aldehyde-dehydrogenase 2 in the hippocampus of rats.

CONCLUSION

Hydrogen sulfide ameliorates homocysteine-induced impairment in cognitive function by decreasing accumulation of reactive aldehydes as a result of upregulations of glutathione and aldehyde-dehydrogenase 2.

The Role of Mitochondrial Aldehyde Dehydrogenase 2 (ALDH2) in Neuropathology and Neurodegeneration

Aldehydes-induced toxicity has been implicated in many neurodegenerative diseases. Exposure to reactive aldehydes from (1) alcohol and food metabolism; (2) environmental pollutants, including car, factory exhausts, smog, pesticides, herbicides; (3) metabolism of neurotransmitters, amino acids and (4) lipid peroxidation of biological membrane from excessive ROS, all contribute to 'aldehydic load' that has been linked to the pathology of neurodegenerative diseases. In particular, the α, β-unsaturated aldehydes derived from lipid peroxidation, 4-hydroxynonenal (4-HNE), DOPAL (MAO product of dopamine), malondialdehyde, acrolein and acetaldehyde, all readily form chemical adductions with proteins, DNA and lipids, thus causing neurotoxicity. Mitochondrial aldehyde dehydrogenase 2 (ALDH 2) is a major aldehyde metabolizing enzyme that protects against deleterious aldehyde buildup in brain, a tissue that has a particularly high mitochondrial content. In this review, we highlight the deleterious effects of increased aldehydic load in the neuropathology of ischemic stroke, Alzheimer's disease and Parkinson's disease. We also discuss evidence for the association between ALDH2 deficiency, a common East Asianspecific mutation, and these neuropathologies. A novel class of small molecule aldehyde dehydrogenase activators (Aldas), represented by Alda-1, reduces neuronal cell death in models of ischemic stroke, Alzheimer's disease and Parkinson's disease. Together, these data suggest that reducing aldeydic load by enhancing the activity of aldehyde dehydrogenases, such as ALDH2, represents as a therapeutic strategy for neurodegenerative diseases.

Integrated High-Content Quantification of Intracellular ROS Levels and Mitochondrial Morphofunction

Oxidative stress arises from an imbalance between the production of reactive oxygen species (ROS) and their removal by cellular antioxidant systems. Especially under pathological conditions, mitochondria constitute a relevant source of cellular ROS. These organelles harbor the electron transport chain, bringing electrons in close vicinity to molecular oxygen. Although a full understanding is still lacking, intracellular ROS generation and mitochondrial function are also linked to changes in mitochondrial morphology. To study the intricate relationships between the different factors that govern cellular redox balance in living cells, we have developed a high-content microscopy-based strategy for simultaneous quantification of intracellular ROS levels and mitochondrial morphofunction. Here, we summarize the principles of intracellular ROS generation and removal, and we explain the major considerations for performing quantitative microscopy analyses of ROS and mitochondrial morphofunction in living cells. Next, we describe our workflow, and finally, we illustrate that a multiparametric readout enables the unambiguous classification of chemically perturbed cells as well as laminopathy patient cells.