Brain mitochondrial alterations after chronic alcohol consumption

Fermented Protaetia brevitarsis Larvae Improves Neurotoxicity in Chronic Ethanol-Induced-Dementia Mice via Suppressing AKT and NF-κB Signaling Pathway

This study was investigated to examine the neuroprotective effect of fermented Protaetia brevitarsis larvae (FPB) in ethanol-induced-dementia mice. Consumption of FPB by mice resulted in improved memory dysfunction in the Y-maze, passive avoidance, and Morris water maze tests. FPB significantly decreased oxidative stress by regulating levels of malondialdehyde (MDA), superoxide dismutase (SOD), and reduced glutathione (GSH) in brain tissues. In addition, FPB restored cerebral mitochondrial dysfunction by modulating levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP. In addition, FPB enhanced the cholinergic system via the regulation of acetylcholine (ACh) content, acetylcholinesterase (AChE) activity, and expressions of AChE and choline acetyltransferase (ChAT) in brain tissues. FPB ameliorated neuronal apoptosis through modulation of the protein kinase B (AKT)/B-cell lymphoma (BCL)-2 signaling pathway. Also, FPB improved inflammation response by down-regulating the toll-like receptor (TLR)-4/nuclear factor (NF)-κB pathway. Additionally, FPB ameliorated synaptic plasticity via the increase of the expressions of synaptophysin (SYP), postsynaptic density protein (PSD)-95, and growth-associated protein (GAP)-43. Treatment with FPB also reinforced the blood-brain barrier by increasing tight junctions including zonula occludens (ZO)-1, occludin, and claudin-1. In conclusion, these results show that FPB can improve cognitive impairment via AKT/NF-κB pathways in ethanol-induced-dementia mice.

Molecular Imaging Studies of Alcohol Use Disorder

Alcohol use disorder (AUD) is a serious public health problem in many countries, bringing a gamut of health risks and impairments to individuals and a great burden to society. Despite the prevalence of a disease model of AUD, the current pharmacopeia does not present reliable treatments for AUD; approved treatments are confined to a narrow spectrum of medications engaging inhibitory γ-aminobutyric acid (GABA) neurotransmission and possibly excitatory N-methyl-D-aspartate (NMDA) receptors, and opioid receptor antagonists. Molecular imaging with positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can open a window into the living brain and has provided diverse insights into the pathology of AUD. In this narrative review, we summarize the state of molecular imaging findings on the pharmacological action of ethanol and the neuropathological changes associated with AUD. Laboratory and preclinical imaging results highlight the interactions between ethanol and GABA A-type receptors (GABAAR), but the interpretation of such results is complicated by subtype specificity. An abundance of studies with the glucose metabolism tracer fluorodeoxyglucose (FDG) concur in showing cerebral hypometabolism after ethanol challenge, but there is relatively little data on long-term changes in AUD. Alcohol toxicity evokes neuroinflammation, which can be tracked using PET with ligands for the microglial marker translocator protein (TSPO). Several PET studies show reversible increases in TSPO binding in AUD individuals, and preclinical results suggest that opioid-antagonists can rescue from these inflammatory responses. There are numerous PET/SPECT studies showing changes in dopaminergic markers, generally consistent with an impairment in dopamine synthesis and release among AUD patients, as seen in a number of other addictions; this may reflect the composite of an underlying deficiency in reward mechanisms that predisposes to AUD, in conjunction with acquired alterations in dopamine signaling. There is little evidence for altered serotonin markers in AUD, but studies with opioid receptor ligands suggest a specific up-regulation of the μ-opioid receptor subtype. Considerable heterogeneity in drinking patterns, gender differences, and the variable contributions of genetics and pre-existing vulnerability traits present great challenges for charting the landscape of molecular imaging in AUD.

Alcohol-Induced Neuroinflammatory Response and Mitochondrial Dysfunction on Aging and Alzheimer's Disease

Mitochondria are essential organelles central to various cellular functions such as energy production, metabolic pathways, signaling transduction, lipid biogenesis, and apoptosis. In the central nervous system, neurons depend on mitochondria for energy homeostasis to maintain optimal synaptic transmission and integrity. Deficiencies in mitochondrial function, including perturbations in energy homeostasis and mitochondrial dynamics, contribute to aging, and Alzheimer's disease. Chronic and heavy alcohol use is associated with accelerated brain aging, and increased risk for dementia, especially Alzheimer's disease. Furthermore, through neuroimmune responses, including pro-inflammatory cytokines, excessive alcohol use induces mitochondrial dysfunction. The direct and indirect alcohol-induced neuroimmune responses, including pro-inflammatory cytokines, are critical for the relationship between alcohol-induced mitochondrial dysfunction. In the brain, alcohol activates microglia and increases inflammatory mediators that can impair mitochondrial energy production, dynamics, and initiate cell death pathways. Also, alcohol-induced cytokines in the peripheral organs indirectly, but synergistically exacerbate alcohol's effects on brain function. This review will provide recent and advanced findings focusing on how alcohol alters the aging process and aggravates Alzheimer's disease with a focus on mitochondrial function. Finally, we will contextualize these findings to inform clinical and therapeutic approaches towards Alzheimer's disease.

Contribution of TSPO imaging in the understanding of the state of gliosis in substance use disorders

PURPOSE

Recent research in last years in substance use disorders (SUD) synthesized a proinflammatory hypothesis of SUD based on reported pieces of evidence of non-neuronal central immune signalling pathways modulated by drug of abuse and that contribute to their pharmacodynamic actions. Positron emission tomography has been shown to be a precious imaging technique to study in vivo neurochemical processes involved in SUD and to highlight the central immune signalling actions of drugs of abuse.

METHODS

In this review, we investigate the contribution of the central immune system, with a particular focus on translocator protein 18 kDa (TSPO) imaging, associated with a series of drugs involved in substance use disorders (SUD) specifically alcohol, opioids, tobacco, methamphetamine, cocaine, and cannabis.

RESULTS

The large majority of preclinical and clinical studies presented in this review converges towards SUD modulation of the neuroimmune responses and TSPO expression and speculated a pivotal positioning in the pathogenesis of SUD. However, some contradictions concerning the same drug or between preclinical and clinical studies make it difficult to draw a clear picture about the significance of glial state in SUD.

DISCUSSION

Significant disparities in clinical and biological characteristics are present between investigated populations among studies. Heterogeneity in genetic factors and other clinical co-morbidities, difficult to be reproduced in animal models, may affect findings. On the other hand, technical aspects including study designs, radioligand limitations, or PET imaging quantification methods could impact the study results and should be considered to explain discrepancies in outcomes.

CONCLUSION

The supposed neuroimmune component of SUD provides new therapeutic approaches in the prediction and treatment of SUD pointing to the central immune signalling.

NADPH oxidase contributes to oxidative damage and mitochondrial impairment induced by acute ethanol treatment in rat hippocampal neurons

Acute ethanol treatment induces neurodegeneration in cultured neurons and can lead to brain damage in animal models. Neuronal cells exposed to ethanol showed an increase in reactive oxygen species (ROS), oxidative damage and mitochondrial impairment contributing to synaptic failure. However, the underlying mechanisms of these events are not well understood. Here, we studied the contribution of NADPH oxidase, as a relevant source of ROS production in the brain, to mitochondrial impairment and oxidative stress induced by ethanol. We used primary hippocampal neurons subjected to an acute treatment of ethanol at increasing concentrations (25, 50, and 75 mM, 24 h), and we evaluated ROS production, mitochondrial function, and synaptic vesicle activity. Our studies showed that after ethanol administration, hippocampal neurons presented an increase in ROS levels, mitochondrial dysfunction, calcium handling defects, and synaptic impairment. Interestingly, treatment with the NADPH inhibitor, apocynin, significantly prevented oxidative stress, mitochondrial dysfunction, and the impairment of synaptic vesicle activity induced by ethanol treatment. These results indicate that NADPH oxidase could be a key participant in the molecular mechanism by which alcohol affects the brain.

Alcohol impairs hippocampal function: From NMDA receptor synaptic transmission to mitochondrial function

Many studies have reported that alcohol produces harmful effects on several brain structures, including the hippocampus, in both rodents and humans. The hippocampus is one of the most studied areas of the brain due to its function in learning and memory, and a lot of evidence suggests that hippocampal failure is responsible for the cognitive loss present in individuals with recurrent alcohol consumption. Mitochondria are organelles that generate the energy needed for the brain to maintain neuronal communication, and their functional failure is considered a mediator of the synaptic dysfunction induced by alcohol. In this review, we discuss the mechanisms of how alcohol exposure affects neuronal communication through the impairment of glutamate receptor (NMDAR) activity, neuroinflammatory events and oxidative damage observed after alcohol exposure, all processes under the umbrella of mitochondrial function. Finally, we discuss the direct role of mitochondrial dysfunction mediating cognitive and memory decline produced by alcohol exposure and their consequences associated with neurodegeneration.

Neurochemical mechanisms underlying acute and chronic ethanol-mediated responses in zebrafish: The role of mitochondrial bioenergetics

Ethanol (EtOH) is a socially-accepted drug, whose consumption is a risk factor for non-intentional injuries, development of pathologies, and addiction. In the brain, EtOH affects redox signaling and increases reactive oxygen species (ROS) production after acute and chronic exposures. Here, using a high-resolution respirometry assay, we investigated whether changes in mitochondrial bioenergetics play a role in both acute and chronic EtOH-mediated neurochemical responses in zebrafish. For the first time, we showed that acute and chronic EtOH exposures differently affect brain mitochondrial function. Acutely, EtOH stimulated mitochondrial respiration through increased baseline state, CI-mediated OXPHOS, OXPHOS capacity, OXPHOS coupling efficiency, bioenergetic efficiency, and ROX/ETS ratio. Conversely, EtOH chronically decreased baseline respiration, complex I- and II-mediated ETS, as well as increased ROX state and ROX/ETS ratio, which are associated with ROS formation. Overall, we observed that changes in mitochondrial bioenergetics play a role, at least partially, in both acute and chronic effects of EtOH in the zebrafish brain. Moreover, our findings reinforce the face, predictive, and construct validities of zebrafish models to explore the neurochemical bases involved in alcohol abuse and alcoholism.

Effects of Acute Ethanol Administration on Brain Oxidative Status: The Role of Acetaldehyde

BACKGROUND

Ethanol (EtOH), one of the most widely consumed substances of abuse, can induce brain damage and neurodegeneration. EtOH is centrally metabolized into acetaldehyde, which has been shown to be responsible for some of the neurophysiological and cellular effects of EtOH. Although some of the consequences of chronic EtOH administration on cell oxidative status have been described, the mechanisms by which acute EtOH administration affects the brain's cellular oxidative status and the role of acetaldehyde remain to be elucidated in detail.

METHODS

Swiss CD-I mice were pretreated with the acetaldehyde-sequestering agent d-penicillamine (DP; 75 mg/kg, i.p.) or the antioxidant lipoic acid (LA; 50 mg/kg, i.p.) 30 minutes before EtOH (2.5 g/kg, i.p.) administration. Animals were sacrificed 30 minutes after EtOH injection. Glutathione peroxidase (GPx) mRNA levels; GPx and glutathione reductase (GR) enzymatic activities; reduced glutathione (GSH), glutathione disulfide (GSSG), glutamate, g-L-glutamyl-L-cysteine (Glut-Cys), and malondialdehyde (MDA) concentrations; and protein carbonyl group (CG) content were determined in whole-brain samples.

RESULTS

Acute EtOH administration enhanced GPx activity and the GSH/GSSG ratio, while it decreased GR activity and GSSG concentration. Pretreatment with DP or LA only prevented GPx activity changes induced by EtOH.

CONCLUSIONS

Altogether, these results show the capacity of a single dose of EtOH to unbalance cellular oxidative homeostasis.

Matching Diabetes and Alcoholism: Oxidative Stress, Inflammation, and Neurogenesis Are Commonly Involved

Diabetes and alcohol misuse are two of the major challenges in health systems worldwide. These two diseases finally affect several organs and systems including the central nervous system. Hippocampus is one of the most relevant structures due to neurogenesis and memory-related processing among other functions. The present review focuses on the common profile of diabetes and ethanol exposure in terms of oxidative stress and proinflammatory and prosurvival recruiting transcription factors affecting hippocampal neurogenesis. Some aspects around antioxidant strategies are also included. As a global conclusion, the present review points out some common hits on both diseases giving support to the relations between alcohol intake and diabetes.

Autophagy and mitochondrial alterations in human retinal pigment epithelial cells induced by ethanol: implications of 4-hydroxy-nonenal

Retinal pigment epithelium has a crucial role in the physiology and pathophysiology of the retina due to its location and metabolism. Oxidative damage has been demonstrated as a pathogenic mechanism in several retinal diseases, and reactive oxygen species are certainly important by-products of ethanol (EtOH) metabolism. Autophagy has been shown to exert a protective effect in different cellular and animal models. Thus, in our model, EtOH treatment increases autophagy flux, in a concentration-dependent manner. Mitochondrial morphology seems to be clearly altered under EtOH exposure, leading to an apparent increase in mitochondrial fission. An increase in 2',7'-dichlorofluorescein fluorescence and accumulation of lipid peroxidation products, such as 4-hydroxy-nonenal (4-HNE), among others were confirmed. The characterization of these structures confirmed their nature as aggresomes. Hence, autophagy seems to have a cytoprotective role in ARPE-19 cells under EtOH damage, by degrading fragmented mitochondria and 4-HNE aggresomes. Herein, we describe the central implication of autophagy in human retinal pigment epithelial cells upon oxidative stress induced by EtOH, with possible implications for other conditions and diseases.

Smoking and increased Alzheimer's disease risk: a review of potential mechanisms

BACKGROUND

Cigarette smoking has been linked with both increased and decreased risk for Alzheimer's disease (AD). This is relevant for the US military because the prevalence of smoking in the military is approximately 11% higher than in civilians.

METHODS

A systematic review of published studies on the association between smoking and increased risk for AD and preclinical and human literature on the relationships between smoking, nicotine exposure, and AD-related neuropathology was conducted. Original data from comparisons of smoking and never-smoking cognitively normal elders on in vivo amyloid imaging are also presented.

RESULTS

Overall, literature indicates that former/active smoking is related to a significantly increased risk for AD. Cigarette smoke/smoking is associated with AD neuropathology in preclinical models and humans. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathology and increased risk for AD.

CONCLUSIONS

A reduction in the incidence of smoking will likely reduce the future prevalence of AD.

Risk marker associations with venous thrombotic events: a cross-sectional analysis

OBJECTIVE

To examine the interrelations among, and risk marker associations for, superficial and deep venous events-superficial venous thrombosis (SVT), deep venous thrombosis (DVT) and pulmonary embolism (PE).

DESIGN

Cross-sectional analysis.

SETTING

San Diego, California, USA.

PARTICIPANTS

2404 men and women aged 40-79 years from four ethnic groups: non-Hispanic White, Hispanic, African-American and Asian. The study sample was drawn from current and former staff and employees of the University of California, San Diego and their spouses/significant others.

OUTCOME MEASURES

Superficial and deep venous events, specifically SVT, DVT, PE and combined deep venous events (DVE) comprising DVT and PE.

RESULTS

Significant correlates on multivariable analysis were, for SVT: female sex, ethnicity (African-American=protective), lower educational attainment, immobility and family history of varicose veins. For DVT and DVE, significant correlates included: heavy smoking, immobility and family history of DVEs (borderline for DVE). For PE, significant predictors included immobility and, in contrast to DVT, blood pressure (BP, systolic or diastolic). In women, oestrogen use duration for hormone replacement therapy, in all and among oestrogen users, predicted PE and DVE, respectively.

CONCLUSIONS

These findings fortify evidence for known risk correlates/predictors for venous disease, such as family history, hormone use and immobility. New risk associations are shown. Striking among these is an association of PE, but not DVT, to elevated BP: we conjecture PE may serve as cause rather than consequence. Future studies should evaluate the temporal direction of this association. Oxidative stress and cell energy compromise are proposed to explain and predict many risk factors, operating through cell-death mediated triggering of coagulation activation.

Naltrexone reverses ethanol-induced rat hippocampal and serum oxidative damage

Naltrexone, an antagonist of μ-opioid receptors, is clinically used as adjuvant therapy of alcohol dishabituation. The aim of the present work was to test the effect of 1 mg/kg body weight of naltrexone to revert oxidative stress-related biochemical alterations, in the hippocampus and serum of chronic alcoholic adult rats. Malondialdehyde concentration was increased and glutathione peroxidase activity was decreased in hippocampus and serum of alcohol-treated rats. Naltrexone treatment restored these alterations. The in vitro antioxidant ability of Ntx could not justify these effects considering the doses used. Thus this apparent protective effect of Ntx can only be attributed to its pharmacological effects, as herein discussed.

Alcohol-induced oxidative/nitrosative stress alters brain mitochondrial membrane properties

Chronic alcohol consumption causes numerous biochemical and biophysical changes in the central nervous system, in which mitochondria is the primary organelle affected. In the present study, we hypothesized that alcohol alters the mitochondrial membrane properties and leads to mitochondrial dysfunction via mitochondrial reactive oxygen species (mROS) and reactive nitrogen species (RNS). Alcohol-induced hypoxia further enhances these effects. Administration of alcohol to rats significantly increased the mitochondrial lipid peroxidation and protein oxidation with decreased SOD2 mRNA and protein expression was decreased, while nitric oxide (NO) levels and expression of iNOS and nNOS in brain cortex were increased. In addition, alcohol augmented HIF-1α mRNA and protein expression in the brain cortex. Results from this study showed that alcohol administration to rats decreased mitochondrial complex I, III, IV activities, Na(+)/K(+)-ATPase activity and cardiolipin content with increased anisotropic value. Cardiolipin regulates numerous enzyme activities, especially those related to oxidative phosphorylation and coupled respiration. In the present study, decreased cardiolipin could be ascribed to ROS/RNS-induced damage. In conclusion, alcohol-induced ROS/RNS is responsible for the altered mitochondrial membrane properties, and alcohol-induced hypoxia further enhance these alterations, which ultimately leads to mitochondrial dysfunction.