Oxidative stress and mitochondrial dysfunction in neurodegeneration; cardiolipin a critical target?

Mitochondrial Dysfunction is a Crucial Immune Checkpoint for Neuroinflammation and Neurodegeneration: mtDAMPs in Focus

Neuroinflammation is a pivotal factor in the progression of both age-related and acute neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and stroke. Mitochondria, essential for neuronal health due to their roles in energy production, calcium buffering, and oxidative stress regulation, become increasingly susceptible to dysfunction under conditions of metabolic stress, aging, or injury. Impaired mitophagy in aged or injured neurons leads to the accumulation of dysfunctional mitochondria, which release mitochondrial-derived damage-associated molecular patterns (mtDAMPs). These mtDAMPs act as immune checkpoints, activating pattern recognition receptors (PRRs) and triggering innate immune signaling pathways. This activation initiates inflammatory responses in neurons and brain-resident immune cells, releasing cytokines and chemokines that damage adjacent healthy neurons and recruit peripheral immune cells, further amplifying neuroinflammation and neurodegeneration. Long-term mitochondrial dysfunction perpetuates a chronic inflammatory state, exacerbating neuronal injury and contributing additional immunogenic components to the extracellular environment. Emerging evidence highlights the critical role of mtDAMPs in initiating and sustaining neuroinflammation, with circulating levels of these molecules potentially serving as biomarkers for disease progression. This review explores the mechanisms of mtDAMP release due to mitochondrial dysfunction, their interaction with PRRs, and the subsequent activation of inflammatory pathways. We also discuss the role of mtDAMP-triggered innate immune responses in exacerbating both acute and chronic neuroinflammation and neurodegeneration. Targeting dysfunctional mitochondria and mtDAMPs with pharmacological agents presents a promising strategy for mitigating the initiation and progression of neuropathological conditions.

Neuroprotection vs. Neurotoxicity: The Dual Impact of Brain Lipids in Depression

Growing neurochemical evidence highlights cerebral lipid dysregulation as a key factor in the pathophysiology of major depressive disorder (MDD). This review systematically explores the dual roles of lipid species in both normal behavioral regulation and MDD development. By critically examining the recent literature, we classify these lipid species into two functional categories based on their functional neuroactivity: (1) neuroprotective lipids (sphingomyelin, cholesterol, cardiolipin, sphingosine, phosphatidic acid, and phosphatidylserine), which exert neuroprotective effects by modulating membrane fluidity and supporting synaptic vesicle trafficking; and (2) neurotoxic lipids (ceramides, phosphatidylinositol, phosphocholine, and phosphatidylethanolamine), which promote apoptotic signaling cascades and disrupt mitochondrial bioenergetics. An unresolved but critical question pertains to the maintenance of homeostatic equilibrium between these opposing lipid classes. This balance is essential, given their significant impact on membrane protein localization and function, monoaminergic neurotransmitter metabolism, energy homeostasis, and redox balance in neural circuits involved in mood regulation. This emerging framework positions cerebral lipidomics as a promising avenue for identifying novel therapeutic targets and developing biomarker-based diagnostic approaches for MDD treatment.

Dysfunctional copper homeostasis in Caenorhabditis elegans affects genomic and neuronal stability

While copper (Cu) is an essential trace element for biological systems due to its redox properties, excess levels may lead to adverse effects partly due to overproduction of reactive species. Thus, a tightly regulated Cu homeostasis is crucial for health. Cu dyshomeostasis and elevated labile Cu levels are associated with oxidative stress and neurodegenerative disorders, but the underlying mechanisms have yet to be fully characterized. Here, we used Caenorhabditis elegans loss-of-function mutants of the Cu chaperone ortholog atox-1 and the Cu binding protein ortholog ceruloplasmin to model Cu dyshomeostasis, as they display a shifted ratio of total Cu towards labile Cu. We applied highly selective and sensitive techniques to quantify metabolites associated to oxidative stress with focus on mitochondrial integrity, oxidative DNA damage and neurodegeneration all in the context of a disrupted Cu homeostasis. Our novel data reveal elevated oxidative stress, compromised mitochondria displaying reduced ATP levels and cardiolipin content. Cu dyshomeostasis further induced oxidative DNA damage and impaired DNA damage response as well as neurodegeneration characterized by behavior and neurotransmitter analysis. Our study underscores the essentiality of a tightly regulated Cu homeostasis as well as mitochondrial integrity for both genomic and neuronal stability.

Role of Oxidative Stress in Blood-Brain Barrier Disruption and Neurodegenerative Diseases

Upregulation of reactive oxygen species (ROS) levels is a principal feature observed in the brains of neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD). In these diseases, oxidative stress can disrupt the blood-brain barrier (BBB). This disruption allows neurotoxic plasma components, blood cells, and pathogens to enter the brain, leading to increased ROS production, mitochondrial dysfunction, and inflammation. Collectively, these factors result in protein modification, lipid peroxidation, DNA damage, and, ultimately, neural cell damage. In this review article, we present the mechanisms by which oxidative damage leads to BBB breakdown in brain diseases. Additionally, we summarize potential therapeutic approaches aimed at reducing oxidative damage that contributes to BBB disruption in neurodegenerative diseases.

Lycopene as a Therapeutic Agent against Aflatoxin B1-Related Toxicity: Mechanistic Insights and Future Directions

Aflatoxin (AFT) contamination poses a significant global public health and safety concern, prompting widespread apprehension. Of the various AFTs, aflatoxin B1 (AFB1) stands out for its pronounced toxicity and its association with a spectrum of chronic ailments, including cardiovascular disease, neurodegenerative disorders, and cancer. Lycopene, a lipid-soluble natural carotenoid, has emerged as a potential mitigator of the deleterious effects induced by AFB1 exposure, spanning cardiac injury, hepatotoxicity, nephrotoxicity, intestinal damage, and reproductive impairment. This protective mechanism operates by reducing oxidative stress, inflammation, and lipid peroxidation, and activating the mitochondrial apoptotic pathway, facilitating the activation of mitochondrial biogenesis, the endogenous antioxidant system, and the nuclear factor erythroid 2-related factor 2 (Nrf2)/kelch-like ECH-associated protein 1 (KEAP1) and peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) pathways, as well as regulating the activities of cytochrome P450 (CYP450) enzymes. This review provides an overview of the protective effects of lycopene against AFB1 exposure-induced toxicity and the underlying molecular mechanisms. Furthermore, it explores the safety profile and potential clinical applications of lycopene. The present review underscores lycopene's potential as a promising detoxification agent against AFB1 exposure, with the intent to stimulate further research and practical utilization in this domain.

Anticancer potency of Egyptian venom snakes on MCF-7 and HepG2 carcinoma cells

Breast and hepatic cancers are the leading incidences in the globe occurring of the human sufferings from various cancers. Snake venoms have been reported to provide effective therapeutic agents. The current study investigates the anticancer potency of Egyptian venoms snakes on two cells: breast cancer cells (MCF-7) and hepato-cancer cells (HepG2) (In vitro assay). The examined venoms were more potent on MCF-7 than HepG2 cells. Their inhibition % on MCF-7 ranged from 71.47 to 99.02% with medium inhibition concentrations (IC50s): 3.48, 3.60, 3.70, 4.33, and 4.49 μg/ml for venoms: Echis pyramid (E.H), Cerastes vipera (C.V), Naja haje (N.H), Echis coloratus (E.C), and Cerastes cerastes (C.C), respectively. The values of IC50s on HepG2 were 4.32, 17.77, 59.72, 63.75, and 217.90 μg/ml for toxins: E.C, E.P, C.V, C.C, and N.H, respectively. Some biomarkers were conducted to investigate the apoptotic effects of toxins into the cells. Increasing profiles of lactate dehydrogenase (LDH) activity and levels of glutathione content (GSH) and malodialdhyde (MDA) as well as repairment of DNA indicated such these actions. So, more reliable investigations on these venoms were needed to provide intelligent therapeutic agent for cancer treatment.

Reverse cholesterol transport and lipid peroxidation biomarkers in major depression and bipolar disorder: A systematic review and meta-analysis

BACKGROUND

Major depression (MDD) and bipolar disorder (BD) are linked to immune activation, increased oxidative stress, and lower antioxidant defenses.

OBJECTIVES

To systematically review and meta-analyze all data concerning biomarkers of reverse cholesterol transport (RCT), lipid-associated antioxidants, lipid peroxidation products, and autoimmune responses to oxidatively modified lipid epitopes in MDD and BD.

METHODS

Databases including PubMed, Google scholar and SciFinder were searched to identify eligible studies from inception to January 10th, 2023. Guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed.

RESULTS

The current meta-analysis included 176 studies (60 BD and 116 MDD) and examined 34,051 participants, namely 17,094 with affective disorders and 16,957 healthy controls. Patients with MDD and BD showed a) significantly decreased RCT (mainly lowered high-density lipoprotein cholesterol and paraoxonase 1); b) lowered lipid soluble vitamins (including vitamin A, D, and coenzyme Q10); c) increased lipid peroxidation and aldehyde formation, mainly increased malondialdehyde (MDA), 4-hydroxynonenal, peroxides, and 8-isoprostanes; and d) Immunoglobulin (Ig)G responses to oxidized low-density lipoprotein and IgM responses to MDA. The ratio of all lipid peroxidation biomarkers/all lipid-associated antioxidant defenses was significantly increased in MDD (standardized mean difference or SMD = 0.433; 95% confidence intervals (CI): 0.312; 0.554) and BD (SMD = 0.653; CI: 0.501-0.806). This ratio was significantly greater in BD than MDD (p = 0.027).

CONCLUSION

In MDD/BD, lowered RCT, a key antioxidant and anti-inflammatory pathway, may drive increased lipid peroxidation, aldehyde formation, and autoimmune responses to oxidative specific epitopes, which all together cause increased immune-inflammatory responses and neuro-affective toxicity.

Unsaturated fatty acids uniquely alter aggregation rate of α-synuclein and insulin and change the secondary structure and toxicity of amyloid aggregates formed in their presence

Docosahexaenoic (DHA) and arachidonic acids (ARA) are omega-3 and omega-6 long-chain polyunsaturated fatty acids (LCPUFAs). These molecules constitute a substantial portion of phospholipids in plasma membranes. Therefore, both DHA and ARA are essential diet components. Once consumed, DHA and ARA can interact with a large variety of biomolecules, including proteins such as insulin and α-synuclein (α-Syn). Under pathological conditions known as injection amyloidosis and Parkinson's disease, these proteins aggregate forming amyloid oligomers and fibrils, toxic species that exert high cell toxicity. In this study, we investigate the role of DHA and ARA in the aggregation properties of α-Syn and insulin. We found that the presence of both DHA and ARA at the equimolar concentrations strongly accelerated aggregation rates of α-Syn and insulin. Furthermore, LCPUFAs substantially altered the secondary structure of protein aggregates, whereas no noticeable changes in the fibril morphology were observed. Nanoscale Infrared analysis of α-Syn and insulin fibrils grown in the presence of both DHA and ARA revealed the presence of LCPUFAs in these aggregates. We also found that such LCPUFAs-rich α-Syn and insulin fibrils exerted significantly greater toxicities compared to the aggregates grown in the LCPUFAs-free environment. These findings show that interactions between amyloid-associated proteins and LCPUFAs can be the underlying molecular cause of neurodegenerative diseases.

Lipids uniquely alter the secondary structure and toxicity of amyloid beta 1-42 aggregates

Abrupt aggregation of amyloid β1-42 (Aβ) peptide is a hallmark of Alzheimer's disease (AD), a severe pathology that affects more than 44 million people worldwide. A growing body of evidence suggests that lipids can uniquely alter rates of Aβ1-42 aggregation. However, it remains unclear whether lipids only alter rates of protein aggregation or also uniquely modify the secondary structure and toxicity of Aβ1-42 oligomers and fibrils. In this study, we investigated the effect of phosphatidylcholine (PC), cardiolipin (CL), and cholesterol (Chol) on Aβ1-42 aggregation. We found that PC, CL and Chol strongly accelerated the rate of fibril formation compared to the rate of Aβ1-42 aggregation in the lipid-free environment. Furthermore, anionic CL enabled the strongest acceleration of Aβ1-42 aggregation compared to zwitterionic PC and uncharged Chol. We also found that PC, CL and Chol uniquely altered the secondary structure of early-, middle- and late-stage Aβ1-42 aggregates. Specifically, CL and Chol drastically increased the amount of parallel β-sheet in Aβ1-42 oligomers and fibrils grown in the presence of these lipids. This caused a significant increase in the toxicity of Aβ : CL and Aβ : Chol compared to the toxicity of Aβ : PC and Aβ1-42 aggregates formed in the lipid-free environment. These results demonstrate that toxicity of Aβ aggregates correlates with the amount of their β-sheet content, which, in turn, is determined by the chemical structure of lipids present at the stage of Aβ1-42 aggregation.

LRP1 Deficiency Promotes Mitostasis in Response to Oxidative Stress: Implications for Mitochondrial Targeting after Traumatic Brain Injury

The brain undergoes oxidative stress and mitochondrial dysfunction following physiological insults such as Traumatic brain injury (TBI), ischemia-reperfusion, and stroke. Pharmacotherapeutics targeting mitochondria (mitoceuticals) against oxidative stress include antioxidants, mild uncouplers, and enhancers of mitochondrial biogenesis, which have been shown to improve pathophysiological outcomes after TBI. However, to date, there is no effective treatment for TBI. Studies have suggested that the deletion of LDL receptor-related protein 1 (LRP1) in adult neurons or glial cells could be beneficial and promote neuronal health. In this study, we used WT and LRP1 knockout (LKO) mouse embryonic fibroblast cells to examine mitochondrial outcomes following exogenous oxidative stress. Furthermore, we developed a novel technique to measure mitochondrial morphometric dynamics using transgenic mitochondrial reporter mice mtD2g (mitochondrial-specific Dendra2 green) in a TBI model. We found that oxidative stress increased the quantity of fragmented and spherical-shaped mitochondria in the injury core of the ipsilateral cortex following TBI, whereas rod-like elongated mitochondria were seen in the corresponding contralateral cortex. Critically, LRP1 deficiency significantly decreased mitochondrial fragmentation, preserving mitochondrial function and cell growth following exogenous oxidative stress. Collectively, our results show that targeting LRP1 to improve mitochondrial function is a potential pharmacotherapeutic strategy against oxidative damage in TBI and other neurodegenerative diseases.

Mitochondria Have Made a Long Evolutionary Path from Ancient Bacteria Immigrants within Eukaryotic Cells to Essential Cellular Hosts and Key Players in Human Health and Disease

Mitochondria have made a long evolutionary path from ancient bacteria immigrants within the eukaryotic cell to become key players for the cell, assuming crucial multitasking skills critical for human health and disease. Traditionally identified as the powerhouses of eukaryotic cells due to their central role in energy metabolism, these chemiosmotic machines that synthesize ATP are known as the only maternally inherited organelles with their own genome, where mutations can cause diseases, opening up the field of mitochondrial medicine. More recently, the omics era has highlighted mitochondria as biosynthetic and signaling organelles influencing the behaviors of cells and organisms, making mitochondria the most studied organelles in the biomedical sciences. In this review, we will especially focus on certain 'novelties' in mitochondrial biology "left in the shadows" because, although they have been discovered for some time, they are still not taken with due consideration. We will focus on certain particularities of these organelles, for example, those relating to their metabolism and energy efficiency. In particular, some of their functions that reflect the type of cell in which they reside will be critically discussed, for example, the role of some carriers that are strictly functional to the typical metabolism of the cell or to the tissue specialization. Furthermore, some diseases in whose pathogenesis, surprisingly, mitochondria are involved will be mentioned.

Protein-to-lipid ratio uniquely changes the rate of lysozyme aggregation but does not significantly alter toxicity of mature protein aggregates

Irreversible aggregation of misfolded proteins is the underlying molecular cause of numerous pathologies, including diabetes type 2, Alzheimer's, and Parkinson's diseases. Such an abrupt protein aggregation results in the formation of small oligomers that can propagate into amyloid fibrils. A growing body of evidence suggests that protein aggregation can be uniquely altered by lipids. However, the role of the protein-to-lipid (P:L) ratio on the rate of protein aggregation, as well as the structure and toxicity of corresponding protein aggregates remains poorly understood. In this study, we investigate the role of the P:L ratio of five different phospho- and sphingolipids on the rate of lysozyme aggregation. We observed significantly different rates of lysozyme aggregation at 1:1, 1:5, and 1:10 P:L ratios of all analyzed lipids except phosphatidylcholine (PC). However, we found that at those P:L ratios, structurally and morphologically similar fibrils were formed. As a result, for all studies of lipids except PC, mature lysozyme aggregates exerted insignificantly different cell toxicity. These results demonstrate that the P:L ratio directly determines the rate of protein aggregation, however, has very little if any effect on the secondary structure of mature lysozyme aggregates. Furthermore, our results point to the lack of a direct relationship between the rate of protein aggregation, secondary structure, and toxicity of mature fibrils.

Elucidation of the Effect of Phospholipid Charge on the Rate of Insulin Aggregation and Structure and Toxicity of Amyloid Fibrils

The plasma membrane is a dynamic structure that separates the cell interior from the extracellular space. The fluidity and plasticity of the membrane determines a large number of physiologically important processes ranging from cell division to signal transduction. In turn, membrane fluidity is determined by phospholipids that possess different charges, lengths, and saturation states of fatty acids. A growing body of evidence suggests that phospholipids may play an important role in the aggregation of misfolded proteins, which causes pathological conditions that lead to severe neurodegenerative diseases. In this study, we investigate the role of the charge of the most abundant phospholipids in the plasma membrane: phosphatidylcholine and phosphatidylethanolamine, zwitterions: phosphatidylserine and phosphatidylglycerol, lipids that possess a negative charge, and cardiolipin that has double negative charge on its polar head. Our results show that both zwitterions strongly inhibit insulin aggregation, whereas negatively charged lipids accelerate fibril formation. We also found that in the equimolar presence of zwitterions insulin yields oligomers that exert significantly lower cell toxicity compared to fibrils that were grown in the lipid-free environment. Such aggregates were not formed in the presence of negatively charged lipids. Instead, long insulin fibrils that had strong cell toxicity were grown in the presence of such negatively charged lipids. However, our results showed no correlation between the charge of the lipid and secondary structure and toxicity of the aggregates formed in its presence. These findings show that the secondary structure and toxicity are determined by the chemical structure of the lipid rather than by the charge of the phospholipid polar head.

Restoring mitochondrial cardiolipin homeostasis reduces cell death and promotes recovery after spinal cord injury

Alterations in phospholipids have long been associated with spinal cord injury (SCI). However, their specific roles and signaling cascades in mediating cell death and tissue repair remain unclear. Here we investigated whether alterations of cardiolipin (CL), a family of mitochondrion-specific phospholipids, play a crucial role in mitochondrial dysfunction and neuronal death following SCI. Lipidomic analysis was used to determine the profile of CL alteration in the adult rat spinal cord following a moderate contusive SCI at the 10th thoracic (T10) level. Cellular, molecular, and genetic assessments were performed to determine whether CL alterations mediate mitochondrial dysfunction and neuronal death after SCI, and, if so, whether reversing CL alteration leads to neuroprotection after SCI. Using lipidomic analysis, we uncovered CL alterations at an early stage of SCI. Over 50 distinct CL species were identified, of which 50% showed significantly decreased abundance after SCI. The decreased CL species contained mainly polyunsaturated fatty acids that are highly susceptible to peroxidation. In parallel, 4-HNE, a lipid peroxidation marker, significantly increased after SCI. We found that mitochondrial oxidative stress not only induced CL oxidation, but also resulted in CL loss by activating cPLA2 to hydrolyze CL. CL alterations induced mitochondrial dysfunction and neuronal death. Remarkably, pharmacologic inhibition of CL alterations with XJB-5-131, a novel mitochondria-targeted electron and reactive oxygen species scavenger, reduced cell death, tissue damage and ameliorated motor deficits after SCI in adult rats. These findings suggest that CL alteration could be a novel mechanism that mediates injury-induced neuronal death, and a potential therapeutic target for ameliorating secondary SCI.

Lipids uniquely alter secondary structure and toxicity of lysozyme aggregates

Abrupt aggregation of misfolded proteins is a hallmark of the large group of amyloid pathologies that include diabetes type 2, Alzheimer and Parkinson's diseases. Protein aggregation yields oligomers and fibrils, β-sheet-rich structures that exert cell toxicity. Microscopic examination of amyloid deposits reveals the presence of lipids membranes, which suggests that lipids can be involved in the process of pathogenic protein assembly. In this study, we show that lipids can uniquely alter the aggregation rates of lysozyme, a protein that is associated with systemic amyloidosis. Specifically, cardiolipin (CL), ceramide (CER), and sphingomyelin (SM) accelerate, phosphatidylcholine (PC) strongly inhibits, whereas phosphatidylserine (PS) has no effect on the rate of protein aggregation. Furthermore, lipids uniquely alter the secondary structure of lysozyme aggregates. Furthermore, we found that lysozyme aggregates grown in the presence of CL, CER, SM, PS, and CL:PC mixtures exert significantly lower production of reactive oxygen species and mitochondrial dysfunction compared to lysozyme:PC aggregates and lysozyme fibrils grown in the lipid-free environment. These findings suggest that a change in the lipid composition of cell membranes, which is taken place upon neurodegeneration, may trigger the formation of toxic protein species that otherwise would not be formed.

Charge of Phospholipids Determines the Rate of Lysozyme Aggregation but Not the Structure and Toxicity of Amyloid Aggregates

Biophysical properties of plasma membranes are determined by a chemical structure of phospholipids, including saturation of fatty acids and charge of polar heads of these molecules. Phospholipids not only determine fluidity and plasticity of membranes but also play an important role in abrupt aggregation of misfolded proteins. In this study, we investigate the role of the charge of the most abundant phospholipids in the plasma membrane on the aggregation properties of the lysozyme. We found that the charge of phospholipids determines the aggregation rate of lysozyme and the morphology of the protein aggregates. However, the secondary structure and toxicity of these protein specimens are determined by the chemical nature rather than the charge of phospholipids. These findings show that the charge of phospholipids can be a key factor that determines the stability and aggregation mechanism of amyloidogenic proteins.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Length and Unsaturation of Fatty Acids of Phosphatidic Acid Determines the Aggregation Rate of Insulin and Modifies the Structure and Toxicity of Insulin Aggregates

Phosphatidic acid (PA) is a unique plasma membrane lipid that contains fatty acids (FAs) with different lengths and degrees of unsaturation. Under physiological conditions, PA acts as a second messenger regulating a wide variety of cellular processes. At the same time, the role of PA under pathological conditions, which are caused by an abrupt aggregation of amyloid proteins, remains unclear. In this study, we investigated the effect of PA with different lengths and unsaturation of FAs on insulin aggregation. We found that PA with C16:0 FAs strongly inhibited insulin aggregation, whereas PA with C18:0 FAs accelerated it. Furthermore, PA with unsaturated (C18:1) FAs made the insulin form extremely long and thick fibrils that were not observed for PAs with saturated FAs. We also found that the presence of PA with C16:0 FAs resulted in the formation of aggregates that exerted significantly lower cell toxicity compared to the aggregates formed in the presence of PAs with C18:0 and C18:1 FAs. These results suggest that PA may play a key role in neurodegeneration.

Unsaturation in the Fatty Acids of Phospholipids Drastically Alters the Structure and Toxicity of Insulin Aggregates Grown in Their Presence

Lipid bilayers play an important role in the pathological assembly of amyloidogenic proteins and peptides. This assembly yields oligomers and fibrils, which are highly toxic protein aggregates. In this study, we investigated the role of saturation in fatty acids of two phospholipids that are present in cell membranes. We found that unsaturated cardiolipin (CL) drastically shortened the lag phase of insulin aggregation. Furthermore, structurally and morphologically different aggregates were formed in the presence of unsaturated CL vs saturated CL. These aggregates exerted drastically different cell toxicity. Both saturated and unsaturated phosphatidylcholine (PC) were able to inhibit insulin aggregation equally efficiently. Similar to CL, structurally different aggregates were formed in the presence of saturated and unsaturated PC. These aggregates exerted different cell toxicities. These results show that unsaturated phospholipids catalyze the formation of more toxic amyloid aggregates comparing to those formed in the presence of saturated lipids.

A review on neurodegenerative diseases associated with oxidative stress and mitochondria

Alzheimer's disease, Parkinson's disease, and other neurological diseases afflict people of all ages. Neuronal loss and cognitive dysfunction are common symptoms of these disorders. Overproduction of reactive oxygen species has been demonstrated to aggravate disease progression in previous investigations (ROS). Because of the large quantities of polyunsaturated fatty acids in their membranes and their fast oxygen consumption rate, neurons are especially susceptible to oxidative damage. The molecular aetiology of neurodegeneration produced by changes in redox balance has not yet been established. New antioxidants have shown considerable potential in modifying disease characteristics. For the treatment of Alzheimer's disease and other neurodegenerative illnesses such as Parkinson's disease, ALS and spinocerebellar ataxia and Huntington's disease, antioxidant-based therapies are examined extensively in the literature.

Fat and Protein Combat Triggers Immunological Weapons of Innate and Adaptive Immune Systems to Launch Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is the second-most common neurodegenerative disease in the world, affecting up to 10 million people. This disease mainly happens due to the loss of dopaminergic neurons accountable for memory and motor function. Partial glucocerebrosidase enzyme deficiency and the resultant excess accumulation of glycosphingolipids and alpha-synuclein (α-syn) aggregation have been linked to predominant risk factors that lead to neurodegeneration and memory and motor defects in PD, with known and unknown causes. An increasing body of evidence uncovers the role of several other lipids and their association with α-syn aggregation, which activates the innate and adaptive immune system and sparks brain inflammation in PD. Here, we review the emerging role of a number of lipids, i.e., triglyceride (TG), diglycerides (DG), glycerophosphoethanolamines (GPE), polyunsaturated fatty acids (PUFA), sphingolipids, gangliosides, glycerophospholipids (GPL), and cholesterols, and their connection with α-syn aggregation as well as the induction of innate and adaptive immune reactions that trigger neuroinflammation in PD.

Protective effects of sciadopitysin against methylglyoxal-induced degeneration in neuronal SK-N-MC cells

The accumulation of advanced glycation end products (AGEs) causes metabolic dysfunction and neuronal cell damage. Methylglyoxal (MG) is a major glycating agent that reacts with basic residues present in proteins and promotes the formation of AGEs. Sciadopitysin, a type of biflavonoid, exerts protective effects against neuronal cell damage; however, the underlying mechanisms have not been studied. This study aimed to investigate the mechanisms underlying the protective effects of sciadopitysin against MG-mediated cytotoxicity in SK-N-MC neuroblastoma cells. Our results demonstrated that pretreatment of SK-N-MC cells with sciadopitysin improved the cell viability that was inhibited by MG and inhibited the apoptosis induced by MG. Sciadopitysin attenuated intracellular Ca²⁺ , NOX4 levels, oxidative stress, and MG-protein adduct levels, and increased nuclear Nrf2 and glyoxalase 1 levels in the presence of MG. These results suggest that sciadopitysin exerts neuroprotective effects against MG-induced death of human SK-N-MC cells via its antioxidative action. This study highlights sciadopitysin as a promising candidate for antioxidant therapy and designing natural drugs against AGE-induced neurodegenerative disorders.

Mitophagy and Oxidative Stress: The Role of Aging

Mitochondrial dysfunction is a hallmark of aging. Dysfunctional mitochondria are recognized and degraded by a selective type of macroautophagy, named mitophagy. One of the main factors contributing to aging is oxidative stress, and one of the early responses to excessive reactive oxygen species (ROS) production is the induction of mitophagy to remove damaged mitochondria. However, mitochondrial damage caused at least in part by chronic oxidative stress can accumulate, and autophagic and mitophagic pathways can become overwhelmed. The imbalance of the delicate equilibrium among mitophagy, ROS production and mitochondrial damage can start, drive, or accelerate the aging process, either in physiological aging, or in pathological age-related conditions, such as Alzheimer’s and Parkinson’s diseases. It remains to be determined which is the prime mover of this imbalance, i.e., whether it is the mitochondrial damage caused by ROS that initiates the dysregulation of mitophagy, thus activating a vicious circle that leads to the reduced ability to remove damaged mitochondria, or an alteration in the regulation of mitophagy leading to the excessive production of ROS by damaged mitochondria.

Unraveling the Link Between Mitochondrial Dynamics and Neuroinflammation

Neuroinflammatory and neurodegenerative diseases are a major public health problem worldwide, especially with the increase of life-expectancy observed during the last decades. For many of these diseases, we still lack a full understanding of their etiology and pathophysiology. Nonetheless their association with mitochondrial dysfunction highlights this organelle as an important player during CNS homeostasis and disease. Markers of Parkinson (PD) and Alzheimer (AD) diseases are able to induce innate immune pathways induced by alterations in mitochondrial Ca2+ homeostasis leading to neuroinflammation. Additionally, exacerbated type I IFN responses triggered by mitochondrial DNA (mtDNA), failures in mitophagy, ER-mitochondria communication and mtROS production promote neurodegeneration. On the other hand, regulation of mitochondrial dynamics is essential for CNS health maintenance and leading to the induction of IL-10 and reduction of TNF-α secretion, increased cell viability and diminished cell injury in addition to reduced oxidative stress. Thus, although previously solely seen as power suppliers to organelles and molecular processes, it is now well established that mitochondria have many other important roles, including during immune responses. Here, we discuss the importance of these mitochondrial dynamics during neuroinflammation, and how they correlate either with the amelioration or worsening of CNS disease.

Investigation of cardiolipin oxidation products as a new endpoint for oxidative stress in C. elegans by means of online two-dimensional liquid chromatography and high-resolution mass spectrometry

The investigation of neurodegenerative and age-related diseases is a highly relevant topic in current research. Especially oxidative stress is thought to be the common underlying mechanism in diseases such as Parkinson's or Alzheimer's disease. The nematode Caenorhabditis elegans (C. elegans) is a prominent model organism, which is often used for such investigations and has gained extensive recognition in research regarding the linkage of reactive oxygen species (ROS) and neurodegeneration. Not only studies regarding genomics and proteomics have been increasingly conducted, also the number of studies based on the lipidome is rising. The phospholipid class of cardiolipin (CL) is a unique lipid class, which is exclusively located in mitochondria and is therefore of great relevance regarding oxidative stress and associated diseases. CL oxidation products have become a prominent marker for oxidative stress in various organisms. However, the CL distribution in the nematode C. elegans is still scarcely known on the molecular level and oxidation products have not yet been identified. In this work, we demonstrate the importance of CL distribution and the applicability of CL oxidation products as a sensitive marker for oxidative stress in C. elegans. For this reason, the CL distribution was determined by means of online two-dimensional liquid chromatography hyphenated with high-resolution mass spectrometry (2D-LC/HRMS). Subsequently, worms were treated with tert-butyl hydroperoxide (tBOOH) in order to provoke oxidative stress and induce the artificial formation of oxidized CL. We were able to detect increasing amounts of CL oxidation products of highly unsaturated CL species in a concentration-dependent manner. This finding emphasizes the great potential of CL oxidation products as a sensitive marker substance of oxidative stress in C. elegans, which is not only directly linked to mitochondria function but also favourable to other oxidative stress markers in terms of the needed sample material, relative substance stability and specificity of the oxidation site.

Cytotoxicity and Oxidative Stress Responses of Imidacloprid and Glyphosate in Human Prostate Epithelial WPM-Y.1 Cell Line

Insecticide imidacloprid and herbicide glyphosate have a broad spectrum of applicable use in the agricultural sector of Egypt. Their ability to induce in vitro cytotoxic and oxidative stress on normal human cells (prostate epithelial WPM-Y.1 cell line) was evaluated with the methyl tetrazolium test (MTT) and histopathological investigation. Cell viability was evaluated with an MTT test for 24 h. The median inhibition concentration (IC50) values were 0.023 and 0.025 mM for imidacloprid and glyphosate, respectively. Sublethal concentrations: 1/10 and 1/50 of IC50 and IC50 levels significantly induced an increase in the lactate dehydrogenase (LDH) activity and malondialdehyde (MDA) level compared with the untreated cells. Rapid decrease in the glutathione (GSH) content and glutathione-S-transferase (GST) activity was induced. Significant increases were recorded in activities of catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR), respectively, compared with the control group. Transmission electron microscopic (TEM) investigation showed significant defects in the cells following pesticide treatments for 24 h. Therefore, it is concluded that imidacloprid and glyphosate are very toxic in vitro assays and able to induce apoptotic effects as well as oxidative stress. So, these findings provide a scenario of multibiomarkers to achieve the imposed risks of pesticides at low doses.

Hydroperoxylated vs Dihydroxylated Lipids: Differentiation of Isomeric Cardiolipin Oxidation Products by Multidimensional Separation Techniques

In recent years, cardiolipin (CL) oxidation products were recognized as potential markers for mitochondrial dysfunction in conjunction with age related diseases. The analysis of oxidized CL requires powerful analysis techniques due to high structural diversity. In addition, low concentrations of partly labile compounds pose a special challenge, supplemented by the occurrence of isomeric compounds, e.g., hydroperoxylated vs dihydroxylated products. Therefore, we present a hyphenated method based on liquid chromatography coupled to trapped ion mobility spectrometry (TIMS) for separation and tandem mass spectrometry (MS/MS) for structural characterization. This enables comprehensive analysis of an artificially oxidized CL extract of bovine heart. Isomeric oxidation products could be differentiated by mobility-resolved MS/MS fragmentation experiments. Our developed method could help to better understand the physiological role of oxidized CL.

The interplay between oxidative stress and bioenergetic failure in neuropsychiatric illnesses: can we explain it and can we treat it?

Nitro-oxidative stress and lowered antioxidant defences play a key role in neuropsychiatric disorders such as major depression, bipolar disorder and schizophrenia. The first part of this paper details mitochondrial antioxidant mechanisms and their importance in reactive oxygen species (ROS) detoxification, including details of NO networks, the roles of H₂O₂ and the thioredoxin/peroxiredoxin system, and the relationship between mitochondrial respiration and NADPH production. The second part highlights and identifies the causes of the multiple pathological sequelae arising from self-amplifying increases in mitochondrial ROS production and bioenergetic failure. Particular attention is paid to NAD⁺ depletion as a core cause of pathology; detrimental effects of raised ROS and reactive nitrogen species on ATP and NADPH generation; detrimental effects of oxidative and nitrosative stress on the glutathione and thioredoxin systems; and the NAD⁺-induced signalling cascade, including the roles of SIRT1, SIRT3, PGC-1α, the FOXO family of transcription factors, Nrf1 and Nrf2. The third part discusses proposed therapeutic interventions aimed at mitigating such pathology, including the use of the NAD⁺ precursors nicotinamide mononucleotide and nicotinamide riboside, both of which rapidly elevate levels of NAD⁺ in the brain and periphery following oral administration; coenzyme Q₁₀ which, when given with the aim of improving mitochondrial function and reducing nitro-oxidative stress in the brain, may be administered via the use of mitoquinone, which is in essence ubiquinone with an attached triphenylphosphonium cation; and N-acetylcysteine, which is associated with improved mitochondrial function in the brain and produces significant decreases in oxidative and nitrosative stress in a dose-dependent manner.

Incidence of Antithrombin Deficiency and Anti-Cardiolipin Antibodies After Severe Traumatic Brain Injury: A Prospective Cohort Study

BACKGROUND

Animal studies suggested that cerebral mitochondrial cardiolipin phospholipids were released after severe traumatic brain injury (TBI), contributing to the pathogenesis of thromboembolism.

OBJECTIVES

To determine the incidence of anti-cardiolipin antibodies after severe TBI and whether this was related to the severity of TBI and development of venous thromboembolism.

METHODS

Serial anti-cardiolipin antibodies, antithrombin levels, viscoelastic testing, and coagulation parameters were measured on admission, day-1, and between day-5 and day-7 in patients with severe TBI requiring intracranial pressure monitoring.

RESULTS

Of the 40 patients included (85% male and median age 42 years), 7 (18%) had a raised Ig-G or Ig-M anti-cardiolipin antibody titer after TBI. Antithrombin levels were below the normal level-especially on day-0 and day-1-in 15 patients (38%), and 14 patients (38%) developed an increase in maximum clot firmness on the viscoelastic test in conjunction with elevations in fibrinogen concentration and platelet count. Four patients (10%) developed deep vein thrombosis, and 10 patients (25%) died, both of which were not significantly related to the presence of anti-cardiolipin antibodies (P = 0.619 and P = 0.638, respectively).

CONCLUSIONS

A reduction in antithrombin level and development of anti-cardiolipin antibodies were not rare immediately after severe TBI; these abnormalities were followed by an increase in in vitro clot strength due to elevations in fibrinogen concentration and platelet count. The quantitative relationships between the development of anti-cardiolipin antibodies and severity of TBI or clinical thromboembolic events deserve further investigation.

Novel Fluorescent Mitochondria-Targeted Probe MitoCLox Reports Lipid Peroxidation in Response to Oxidative Stress In Vivo

A new mitochondria-targeted probe MitoCLox was designed as a starting compound for a series of probes sensitive to cardiolipin (CL) peroxidation. Fluorescence microscopy reported selective accumulation of MitoCLox in mitochondria of diverse living cell cultures and its oxidation under stress conditions, particularly those known to cause a selective cardiolipin oxidation. Ratiometric fluorescence measurements using flow cytometry showed a remarkable dependence of the MitoCLox dynamic range on the oxidation of the sample. Specifically, MitoCLox oxidation was induced by low doses of hydrogen peroxide or organic hydroperoxide. The mitochondria-targeted antioxidant 10-(6'-plastoquinonyl)decyltriphenyl-phosphonium (SkQ1), which was shown earlier to selectively protect cardiolipin from oxidation, prevented hydrogen peroxide-induced MitoCLox oxidation in the cells. Concurrent tracing of MitoCLox oxidation and membrane potential changes in response to hydrogen peroxide addition showed that the oxidation of MitoCLox started without a delay and was complete during the first hour, whereas the membrane potential started to decay after 40 minutes of incubation. Hence, MitoCLox could be used for splitting the cell response to oxidative stress into separate steps. Application of MitoCLox revealed heterogeneity of the mitochondrial population; in living endothelial cells, a fraction of small, rounded mitochondria with an increased level of lipid peroxidation were detected near the nucleus. In addition, the MitoCLox staining revealed a specific fraction of cells with an increased level of oxidized lipids also in the culture of human myoblasts. The fraction of such cells increased in high-density cultures. These specific conditions correspond to the initiation of spontaneous myogenesis in vitro, which indicates that oxidation may precede the onset of myogenic differentiation. These data point to a possible participation of oxidized CL in cell signalling and differentiation.

Impact of Intravenous Iron on Oxidative Stress and Mitochondrial Function in Experimental Chronic Kidney Disease

Background: Mitochondrial dysfunction is observed in chronic kidney disease (CKD). Iron deficiency anaemia (IDA), a common complication in CKD, is associated with poor clinical outcomes affecting mitochondrial function and exacerbating oxidative stress. Intravenous (iv) iron, that is used to treat anaemia, may lead to acute systemic oxidative stress. This study evaluated the impact of iv iron on mitochondrial function and oxidative stress. Methods: Uraemia was induced surgically in male Sprague-Dawley rats and studies were carried out 12 weeks later in two groups sham operated and uraemic (5/6 nephrectomy) rats not exposed to i.v. iron versus sham operated and uraemic rats with iv iron. Results: Induction of uraemia resulted in reduced iron availability (serum iron: 31.1 ± 1.8 versus 46.4 ± 1.4 µM), low total iron binding capacity (26.4 ± 0.7 versus 29.5 ± 0.8 µM), anaemia (haematocrit: 42.5 ± 3.0 versus 55.0 ± 3.0%), cardiac hypertrophy, reduced systemic glutathione peroxidase activity (1.12 ± 0.11 versus 1.48 ± 0.12 U/mL), tissue oxidative stress (oxidised glutathione: 0.50 ± 0.03 versus 0.36 ± 0.04 nmol/mg of tissue), renal mitochondrial dysfunction (proton/electron leak: 61.8 ± 8.0 versus 22.7 ± 5.77) and complex I respiration (134.6 ± 31.4 versus 267.6 ± 26.4 pmol/min/µg). Iron therapy had no effect on renal function and cardiac hypertrophy but improved anaemia and systemic glutathione peroxidase (GPx) activity. There was increased renal iron content and complex II and complex IV dysfunction. Conclusion: Iron therapy improved iron deficiency anaemia in CKD without significant impact on renal function or oxidant status.

The mitochondria-targeted antioxidant MitoQ inhibits memory loss, neuropathology, and extends lifespan in aged 3xTg-AD mice

Oxidative stress, likely stemming from dysfunctional mitochondria, occurs before major cognitive deficits and neuropathologies become apparent in Alzheimer's disease (AD) patients and in mouse models of the disease. We previously reported that treating 2- to 7-month-old 3xTg-AD mice with the mitochondria-targeted antioxidant MitoQ (mitoquinone mesylate: [10-(4,5-Dimethoxy-2-methyl-3,6-dioxo-1,4-cyclohexadien-1-yl)decyl](triphenyl)phosphonium methanesulfonate), a period when AD-like pathologies first manifest in them, prevents AD-like symptoms from developing. To elucidate further a role for mitochondria-derived oxidative stress in AD progression, we examined the ability of MitoQ to inhibit AD-like pathologies in these mice at an age in which cognitive and neuropathological symptoms have fully developed. 3xTg-AD female mice received MitoQ in their drinking water for five months beginning at twelve months after birth. Untreated 18-month-old 3xTg-AD mice exhibited significant learning deficits and extensive AD-like neuropathologies. MitoQ-treated mice showed improved memory retention compared to untreated 3xTg-AD mice as well as reduced brain oxidative stress, synapse loss, astrogliosis, microglial cell proliferation, Aβ accumulation, caspase activation, and tau hyperphosphorylation. Additionally, MitoQ treatment significantly increased the abbreviated lifespan of the 3xTg-AD mice. These findings support a role for the involvement of mitochondria-derived oxidative stress in the etiology of AD and suggest that mitochondria-targeted antioxidants may lessen symptoms in AD patients.

Naja mossambica mossambica Cobra Cardiotoxin Targets Mitochondria to Disrupt Mitochondrial Membrane Structure and Function

Cobra venom cardiotoxins (CVCs) can translocate to mitochondria to promote apoptosis by eliciting mitochondrial dysfunction. However, the molecular mechanism(s) by which CVCs are selectively targeted to the mitochondrion to disrupt mitochondrial function remains to be elucidated. By studying cardiotoxin from Naja mossambica mossambica cobra (cardiotoxin VII4), a basic three-fingered S-type cardiotoxin, we hypothesized that cardiotoxin VII4 binds to cardiolipin (CL) in mitochondria to alter mitochondrial structure/function and promote neurotoxicity. By performing confocal analysis, we observed that red-fluorescently tagged cardiotoxin rapidly translocates to mitochondria in mouse primary cortical neurons and in human SH-SY5Y neuroblastoma cells to promote aberrant mitochondrial fragmentation, a decline in oxidative phosphorylation, and decreased energy production. In addition, by employing electron paramagnetic resonance (EPR) and protein nuclear magnetic resonance (¹H-NMR) spectroscopy and phosphorescence quenching of erythrosine in model membranes, our compiled biophysical data show that cardiotoxin VII4 binds to anionic CL, but not to zwitterionic phosphatidylcholine (PC), to increase the permeability and formation of non-bilayer structures in CL-enriched membranes that biochemically mimic the outer and inner mitochondrial membranes. Finally, molecular dynamics simulations and in silico docking studies identified CL binding sites in cardiotoxin VII4 and revealed a molecular mechanism by which cardiotoxin VII4 interacts with CL and PC to bind and penetrate mitochondrial membranes.

The Role of Mitochondrial Damage-Associated Molecular Patterns in Chronic Neuroinflammation

Mitochondrial dysfunction has been established as a common feature of neurodegenerative disorders that contributes to disease pathology by causing impaired cellular energy production. Mitochondrial molecules released into the extracellular space following neuronal damage or death may also play a role in these diseases by acting as signaling molecules called damage-associated molecular patterns (DAMPs). Mitochondrial DAMPs have been shown to initiate proinflammatory immune responses from nonneuronal glial cells, including microglia and astrocytes; thereby, they have the potential to contribute to the chronic neuroinflammation present in these disorders accelerating the degeneration of neurons. In this review, we highlight the mitochondrial DAMPs cytochrome c (CytC), mitochondrial transcription factor A (TFAM), and cardiolipin and explore their potential role in the central nervous system disorders including Alzheimer's disease and Parkinson's disease, which are characterized by neurodegeneration and chronic neuroinflammation.

Stress-Induced Synaptic Dysfunction and Neurotransmitter Release in Alzheimer's Disease: Can Neurotransmitters and Neuromodulators be Potential Therapeutic Targets?

The communication between neurons at synaptic junctions is an intriguing process that monitors the transmission of various electro-chemical signals in the central nervous system. Albeit any aberration in the mechanisms associated with transmission of these signals leads to loss of synaptic contacts in both the neocortex and hippocampus thereby causing insidious cognitive decline and memory dysfunction. Compelling evidence suggests that soluble amyloid-β (Aβ) and hyperphosphorylated tau serve as toxins in the dysfunction of synaptic plasticity and aberrant neurotransmitter (NT) release at synapses consequently causing a cognitive decline in Alzheimer's disease (AD). Further, an imbalance between excitatory and inhibitory neurotransmission systems induced by impaired redox signaling and altered mitochondrial integrity is also amenable for such abnormalities. Defective NT release at the synaptic junction causes several detrimental effects associated with altered activity of synaptic proteins, transcription factors, Ca2+ homeostasis, and other molecules critical for neuronal plasticity. These detrimental effects further disrupt the normal homeostasis of neuronal cells and thereby causing synaptic loss. Moreover, the precise mechanistic role played by impaired NTs and neuromodulators (NMs) and altered redox signaling in synaptic dysfunction remains mysterious, and their possible interlink still needs to be investigated. Therefore, this review elucidates the intricate role played by both defective NTs/NMs and altered redox signaling in synaptopathy. Further, the involvement of numerous pharmacological approaches to compensate neurotransmission imbalance has also been discussed, which may be considered as a potential therapeutic approach in synaptopathy associated with AD.

SIRT3 activator Honokiol attenuates β-Amyloid by modulating amyloidogenic pathway

Honokiol (poly-phenolic lignan from Magnolia grandiflora) is a Sirtuin-3 (SIRT3) activator which exhibit antioxidant activity and augment mitochondrial functions in several experimental models. Modern evidence suggests the critical role of SIRT3 in the progression of several metabolic and neurodegenerative diseases. Amyloid beta (Aβ), the precursor to extracellular senile plaques, accumulates in the brains of patients with Alzheimer's disease (AD) and is related to the development of cognitive impairment and neuronal cell death. Aβ is generated from amyloid-β precursor protein (APP) through sequential cleavages, first by β-secretase and then by γ-secretase. Drugs modulating this pathway are believed to be one of the most promising strategies for AD treatment. In the present study, we found that Honokiol significantly enhanced SIRT3 expression, reduced reactive oxygen species generation and lipid peroxidation, enhanced antioxidant activities, and mitochondrial function thereby reducing Aβ and sAPPβ levels in Chinese Hamster Ovarian (CHO) cells (carrying the amyloid precursor protein-APP and Presenilin PS1 mutation). Mechanistic studies revealed that Honokiol affects neither protein levels of APP nor α-secretase activity. In contrast, Honokiol increased the expression of AMPK, CREB, and PGC-1α, thereby inhibiting β-secretase activity leading to reduced Aβ levels. These results suggest that Honokiol is an activator of SIRT3 capable of improving antioxidant activity, mitochondrial energy regulation, while decreasing Aβ, thereby indicating it to be a lead compound for AD drug development.

Oxidative Stress: Mechanistic Insights into Inherited Mitochondrial Disorders and Parkinson's Disease

Oxidative stress arises when cellular antioxidant defences become overwhelmed by a surplus generation of reactive oxygen species (ROS). Once this occurs, many cellular biomolecules such as DNA, lipids, and proteins become susceptible to free radical-induced oxidative damage, and this may consequently lead to cellular and ultimately tissue and organ dysfunction. Mitochondria, as well as being a source of ROS, are vulnerable to oxidative stress-induced damage with a number of key biomolecules being the target of oxidative damage by free radicals, including membrane phospholipids, respiratory chain complexes, proteins, and mitochondrial DNA (mt DNA). As a result, a deficit in cellular energy status may occur along with increased electron leakage and partial reduction of oxygen. This in turn may lead to a further increase in ROS production. Oxidative damage to certain mitochondrial biomolecules has been associated with, and implicated in the pathophysiology of a number of diseases. It is the purpose of this review to discuss the impact of such oxidative stress and subsequent damage by reviewing our current knowledge of the pathophysiology of several inherited mitochondrial disorders together with our understanding of perturbations observed in the more commonly acquired neurodegenerative disorders such as Parkinson’s disease (PD). Furthermore, the potential use and feasibility of antioxidant therapies as an adjunct to lower the accumulation of damaging oxidative species and hence slow disease progression will also be discussed.

Cardiolipin in Central Nervous System Physiology and Pathology

Cardiolipin, an anionic phospholipid found primarily in the inner mitochondrial membrane, has many well-defined roles within the peripheral tissues, including the maintenance of mitochondrial membrane fluidity and the regulation of mitochondrial functions. Within the central nervous system (CNS), cardiolipin is found within both neuronal and non-neuronal glial cells, where it regulates metabolic processes, supports mitochondrial functions, and promotes brain cell viability. Furthermore, cardiolipin has been shown to act as an elimination signal and participate in programmed cell death by apoptosis of both neurons and glia. Since cardiolipin is associated with regulating brain homeostasis, the modification of its structure, or even a decrease in the overall levels of cardiolipin, can result in mitochondrial dysfunction, which is a characteristic feature of many diseases. In this review, we outline the various functions of cardiolipin within the cells of the CNS, including neurons, astrocytes, microglia, and oligodendrocytes. In addition, we discuss the role cardiolipin may play in the pathogenesis of the neurodegenerative disorders Alzheimer's disease and Parkinson's disease, as well as traumatic brain injury.

Measurement of Mitochondrial Mass by Flow Cytometry during Oxidative Stress

Properly assessing mitochondrial health is crucial to understand their role in disease. MitoTracker green (MTG) and nonylacridine orange (NAO) are fluorescent probes which have been commonly used to assess mitochondrial mass. This is based on the assumption that both MTG and NAO accumulate in mitochondria regardless of the mitochondrial transmembrane potential (ΔΨ_m). Here, we utilized flow cytometry to evaluate the performance of these probes for assessment of mitochondrial mass relative to forward (FSC) and side scatter (SSC) in human peripheral blood lymphocytes (PBL). In isolated mitochondria, two subpopulations were identified by FSC and SSC measurements which were matched to subpopulations stained by MTG and NAO. The performance of these dyes was examined under oxidative and nitrosative stress induced by rotenone and NOC-18 while N-acetylcysteine (NAC) was employed as an antioxidant. Production of reactive oxygen species (ROS) and ΔΨ_m were monitored in parallel. With respect to representation of mitochondrial mass, neither MTG nor NAO was affected by ΔΨ_m. However, MTG showed significant correlation with cytosolic and mitochondrial ROS production and nitrosative stress. Our data suggest that NAO may be more suitable than MTG for assessment of mitochondrial mass by flow cytometry during oxidative stress.

Epigallocatechin-3-gallate induces oxidative phosphorylation by activating cytochrome c oxidase in human cultured neurons and astrocytes

Mitochondrial dysfunction and resulting energy impairment have been identified as features of many neurodegenerative diseases. Whether this energy impairment is the cause of the disease or the consequence of preceding impairment(s) is still under discussion, however a recovery of cellular bioenergetics would plausibly prevent or improve the pathology. In this study, we screened different natural molecules for their ability to increase intracellular adenine triphosphate purine (ATP). Among them, epigallocatechin-3-gallate (EGCG), a polyphenol from green tea, presented the most striking results. We found that it increases ATP production in both human cultured astrocytes and neurons with different kinetic parameters and without toxicity.

Specifically, we showed that oxidative phosphorylation in human cultured astrocytes and neurons increased at the level of the routine respiration on the cells pre-treated with the natural molecule. Furthermore, EGCG-induced ATP production was only blocked by sodium azide (NaN₃) and oligomycin, inhibitors of cytochrome c oxidase (CcO; complex IV) and ATP synthase (complex V) respectively. These findings suggest that the EGCG modulates CcO activity, as confirmed by its enzymatic activity. CcO is known to be regulated differently in neurons and astrocytes. Accordingly, EGCG treatment is acting differently on the kinetic parameters of the two cell types. To our knowledge, this is the first study showing that EGCG promotes CcO activity in human cultured neurons and astrocytes. Considering that CcO dysfunction has been reported in patients having neurodegenerative diseases such as Alzheimer's disease (AD), we therefore suggest that EGCG could restore mitochondrial function and prevent subsequent loss of synaptic function.

Thrombomodulin-dependent protein C activation is required for mitochondrial function and myelination in the central nervous system

Essentials The role of protein C (PC) activation in experimental autoimmune encephalitis (EAE) is unknown. PC activation is required for mitochondrial function in the central nervous system. Impaired PC activation aggravates EAE, which can be compensated for by soluble thrombomodulin. Protection of myelin by activated PC or solulin is partially independent of immune-modulation.

SUMMARY

Background Studies with human samples and in rodents established a function of coagulation proteases in neuro-inflammatory demyelinating diseases (e.g. in multiple sclerosis [MS] and experimental autoimmune encephalitis [EAE]). Surprisingly, approaches to increase activated protein C (aPC) plasma levels as well as antibody-mediated inhibition of PC/aPC ameliorated EAE in mice. Hence, the role of aPC generation in demyelinating diseases and potential mechanisms involved remain controversial. Furthermore, it is not known whether loss of aPC has pathological consequences at baseline (e.g. in the absence of disease). Objective To explore the role of thrombomodulin (TM)-dependent aPC generation at baseline and in immunological and non-immunological demyelinating disease models. Methods Myelination and reactive oxygen species (ROS) generation were evaluated in mice with genetically reduced TM-mediated protein C activation (TMPro/Pro ) and in wild-type (WT) mice under control conditions or following induction of EAE. Non-immunological demyelination was analyzed in the cuprizone-diet model. Results Impaired TM-dependent aPC generation already disturbs myelination and mitochondrial function at baseline. This basal phenotype is linked with increased mitochondrial ROS and aggravates EAE. Reducing mitochondrial ROS (p66Shc deficiency), restoring aPC plasma levels or injecting soluble TM (solulin) ameliorates EAE in TMPro/Pro mice. Soluble TM additionally conveyed protection in WT-EAE mice. Furthermore, soluble TM dampened demyelination in the cuprizone-diet model, demonstrating that its myelin-protective effect is partially independent of an immune-driven process. Conclusion These results uncover a novel physiological function of TM-dependent aPC generation within the CNS. Loss of TM-dependent aPC generation causes a neurological defect in healthy mice and aggravates EAE, which can be therapeutically corrected.

Influence of tissue, diet, and enzymatic remodeling on cardiolipin fatty acyl profile

Cardiolipin is a specialized phospholipid found primarily in the inner mitochondrial membrane. Because of its unique dimeric structure, cardiolipin plays an important role in mitochondrial function, stability, and membrane fluidity. As such, cardiolipin is subject to a high degree of remodeling by phospholipases, acyltransferases, and transacylases that create a fatty acyl profile that tends to be highly tissue-specific. Despite this overarching regulation, the molecular species of cardiolipin produced are also influenced by dietary lipid composition. A number of studies have characterized the tissue-specific profile of cardiolipin species and have investigated the specific nature of cardiolipin remodeling, including the role of both enzymes and diet. The aim of this review is to highlight tissue specific differences in cardiolipin composition and, collectively, the enzymatic and dietary factors that contribute to these differences. Consequences of aberrant cardiolipin fatty acyl remodeling are also discussed.

Loss of PLA2G6 leads to elevated mitochondrial lipid peroxidation and mitochondrial dysfunction

The PLA2G6 gene encodes a group VIA calcium-independent phospholipase A2 beta enzyme that selectively hydrolyses glycerophospholipids to release free fatty acids. Mutations in PLA2G6 have been associated with disorders such as infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation type II and Karak syndrome. More recently, PLA2G6 was identified as the causative gene in a subgroup of patients with autosomal recessive early-onset dystonia-parkinsonism. Neuropathological examination revealed widespread Lewy body pathology and the accumulation of hyperphosphorylated tau, supporting a link between PLA2G6 mutations and parkinsonian disorders. Here we show that knockout of the Drosophila homologue of the PLA2G6 gene, iPLA2-VIA, results in reduced survival, locomotor deficits and organismal hypersensitivity to oxidative stress. Furthermore, we demonstrate that loss of iPLA2-VIA function leads to a number of mitochondrial abnormalities, including mitochondrial respiratory chain dysfunction, reduced ATP synthesis and abnormal mitochondrial morphology. Moreover, we show that loss of iPLA2-VIA is strongly associated with increased lipid peroxidation levels. We confirmed our findings using cultured fibroblasts taken from two patients with mutations in the PLA2G6 gene. Similar abnormalities were seen including elevated mitochondrial lipid peroxidation and mitochondrial membrane defects, as well as raised levels of cytoplasmic and mitochondrial reactive oxygen species. Finally, we demonstrated that deuterated polyunsaturated fatty acids, which inhibit lipid peroxidation, were able to partially rescue the locomotor abnormalities seen in aged flies lacking iPLA2-VIA gene function, and restore mitochondrial membrane potential in fibroblasts from patients with PLA2G6 mutations. Taken together, our findings demonstrate that loss of normal PLA2G6 gene activity leads to lipid peroxidation, mitochondrial dysfunction and subsequent mitochondrial membrane abnormalities. Furthermore we show that the iPLA2-VIA knockout fly model provides a useful platform for the further study of PLA2G6-associated neurodegeneration.