The Role of Heme and Copper in Alzheimer's Disease and Type 2 Diabetes Mellitus

Hemoglobin in the brain frontal lobe tissue of patients with Alzheimer's disease is susceptible to reactive nitrogen species-mediated oxidative damage

Brain inflammation in Alzheimer's disease (AD) involves reactive nitrogen species (RNS) generation. Protein contents of 3-nitrotyrosine, a product of RNS generation, were assessed in frontal lobe brain homogenates from patients with AD, patients with vascular dementia (VaD) and non-dementia (ND) controls. Western blotting revealed a dominant 15 kDa nitrated protein band in both dementia (AD/VaD) and ND frontal lobe brain tissue. Surprisingly, this protein band was identified by mass spectrometry as hemoglobin, an erythrocytic protein. The same band stained positively when western blotted using an anti-hemoglobin antibody. On western blots, the median (IQR) normalized staining intensity for 3-nitrotyrosine in hemoglobin was increased in both AD [1.71 (1.20-3.05) AU] and VaD [1.50 (0.59-3.04) AU] brain tissue compared to ND controls [0.41 (0.09-0.75) AU] (Mann-Whitney U test: AD v ND, P < 0.0005; VaD v ND, P < 0.05; n = 11). The median normalized staining of the nitrated hemoglobin band was higher in advanced AD patients compared with early-stage AD (P < 0.005). The median brain tissue NO2- levels (nmol/mg protein) were significantly higher in AD samples than in ND controls (P < 0.05). Image analysis of western blots of lysates from peripheral blood erythrocytes suggested that hemoglobin nitration was increased in AD compared to ND (P < 0.05; n = 4 in each group). Total protein-associated 3-nitrotyrosine was measured by an electrochemiluminescence-based immunosorbent assay, but showed no statistically significant differences between AD, VaD and ND. Females showed larger increases in hemoglobin nitration and NO2- levels between disease and control groups compared to males, although the group sizes in these sub-analyses were small. In conclusion, the extent of hemoglobin nitration was increased in AD and VaD brain frontal lobe tissue compared with ND. We propose that reactive nitrogen species-mediated damage to hemoglobin may be involved in the pathogenesis of AD.

Heme-Aβ compound 0: a common intermediate in ROS generation and peroxidase activity

Oxidative stress is a key factor in neurodegenerative diseases, particularly in Alzheimer's disease (AD) which is the leading cause of dementia. A hallmark of AD is the accumulation of amyloid β (Aβ) peptides, along with redox-active metal ions and heme cofactors, all of which significantly contribute to disease progression. When heme binds to Aβ, it can drive oxidative stress through two primary pathways: firstly, reduced high-spin ferrous heme-Aβ active sites may generate H2O2 through oxygen reduction, leading to the oxidation of biomolecules and lipid membranes; secondly, this H2O2 can react with the oxidised form of high-spin ferric heme-Aβ, initiating peroxidase-like activity that can catalyse the oxidation of neurotransmitters. These pathways converge at a crucial intermediate i.e. the heme-Aβ-peroxo complex, which serves as the final intermediate in the ROS cycle and the first in the peroxidase cycle. Although, we have previously characterized other intermediates in these pathways, compound 0 resulting from the reaction of a high-spin heme-Aβ species with peroxides has remained elusive due to its rapid hydrolysis in an aqueous environment. In this study, we report the oxidation of dopamine by peroxides catalyzed by ferric heme-Aβ species and successfully stabilised and characterized compound 0 of high-spin heme-Aβ in dimethylformamide, an organic aprotic solvent. This stabilization enables detection through stopped-flow, EPR and resonance Raman spectroscopy, thereby facilitating a deeper understanding of the oxidative stress caused by high-spin heme-Aβ.

Pro-Oxidative and Inflammatory Actions of Extracellular Hemoglobin and Heme: Molecular Events and Implications for Alzheimer's and Parkinson Disease

Hemoglobin (Hb) and heme, which are typically confined within red blood cells (RBCs), are essential for intravascular transport of gases and nutrients. However, these molecules acquire secondary functions upon exposure to the extracellular environment. Hb and heme generate reactive oxygen species (ROS), which are potent pro-inflammatory agents that contribute to oxidative stress and cellular damage. These events are relevant to neurodegenerative processes, where oxidative stress, irregular deposition of protein aggregates, and chronic inflammation are key pathological features. Extracellular Hb, heme, and oxidative stress derived from hemorrhagic events or RBC lysis may contribute to increased blood-brain barrier (BBB) permeability. These events allow Hb and heme to interact with neuroimmune cells and pathological protein aggregates, further amplifying pro-inflammatory signaling and the progression of Alzheimer's disease (AD) and Parkinson disease (PD). Chronic neuroinflammation, oxidative stress, and mitochondrial dysfunction lead to neuronal degeneration. Here, we sought to elucidate the pro-oxidative and inflammatory actions of extracellular Hb and heme, emphasizing their potential impact on AD and PD development.

MicroRNAs: pioneering regulators in Alzheimer's disease pathogenesis, diagnosis, and therapy

This article delves into Alzheimer's disease (AD), a prevalent neurodegenerative condition primarily affecting the elderly. It is characterized by progressive memory and cognitive impairments, severely disrupting daily life. Recent research highlights the potential involvement of microRNAs in the pathogenesis of AD. MicroRNAs (MiRNAs), short non-coding RNAs comprising 20-24 nucleotides, significantly influence gene regulation by hindering translation or promoting degradation of target genes. This review explores the role of specific miRNAs in AD progression, focusing on their impact on β-amyloid (Aβ) peptide accumulation, intracellular aggregation of hyperphosphorylated tau proteins, mitochondrial dysfunction, neuroinflammation, oxidative stress, and the expression of the APOE4 gene. Our insights contribute to understanding AD's pathology, offering new avenues for identifying diagnostic markers and developing novel therapeutic targets.

Association Between Type 2 Diabetes Mellitus and Alzheimer's Disease: Common Molecular Mechanism and Therapeutic Targets

Diabetes mellitus (DM) and Alzheimer's disease (AD) rates are rising, mirroring the global trend of an aging population. Numerous epidemiological studies have shown that those with Type 2 diabetes (T2DM) have an increased risk of developing dementia. These degenerative and progressive diseases share some risk factors. To a large extent, the amyloid cascade is responsible for AD development. Neurofibrillary tangles induce neurodegeneration and brain atrophy; this chain reaction begins with hyperphosphorylation of tau proteins caused by progressive amyloid beta (Aβ) accumulation. In addition to these processes, it seems that alterations in brain glucose metabolism and insulin signalling lead to cell death and reduced synaptic plasticity in AD, before the onset of symptoms, which may be years away. Due to the substantial evidence linking insulin resistance in the brain with AD, researchers have coined the name "Type 3 diabetes" to characterize the condition. We still know little about the processes involved, even though current animal models have helped illuminate the links between T2DM and AD. This brief overview discusses insulin and IGF-1 signalling disorders and the primary molecular pathways that may connect them. The presence of GSK-3β in AD is intriguing. These proteins' association with T2DM and pancreatic β-cell failure suggests they might be therapeutic targets for both disorders.

Correction: Addressing the gaps in homeostatic mechanisms of copper and copper dithiocarbamate complexes in cancer therapy: a shift from classical platinum-drug mechanisms

Correction for 'Addressing the gaps in homeostatic mechanisms of copper and copper dithiocarbamate complexes in cancer therapy: a shift from classical platinum-drug mechanisms' by Lydia W. Njenga et al., Dalton Trans., 2023, 52, 5823-5847, https://doi.org/10.1039/D3DT00366C.

Cuproptosis and Cu: a new paradigm in cellular death and their role in non-cancerous diseases

Cuproptosis, a newly characterized form of regulated cell death driven by copper accumulation, has emerged as a significant mechanism underlying various non-cancerous diseases. This review delves into the complex interplay between copper metabolism and the pathogenesis of conditions such as Wilson's disease (WD), neurodegenerative disorders, and cardiovascular pathologies. We examine the molecular mechanisms by which copper dysregulation induces cuproptosis, highlighting the pivotal roles of key copper transporters and enzymes. Additionally, we evaluate the therapeutic potential of copper chelation strategies, which have shown promise in experimental models by mitigating copper-induced cellular damage and restoring physiological homeostasis. Through a comprehensive synthesis of recent advancements and current knowledge, this review underscores the necessity of further research to translate these findings into clinical applications. The ultimate goal is to harness the therapeutic potential of targeting cuproptosis, thereby improving disease management and patient outcomes in non-cancerous conditions associated with copper dysregulation.

A critical appraisal of ferroptosis in Alzheimer's and Parkinson's disease: new insights into emerging mechanisms and therapeutic targets

Neurodegenerative diseases represent a pressing global health challenge, and the identification of novel mechanisms underlying their pathogenesis is of utmost importance. Ferroptosis, a non-apoptotic form of regulated cell death characterized by iron-dependent lipid peroxidation, has emerged as a pivotal player in the pathogenesis of neurodegenerative diseases. This review delves into the discovery of ferroptosis, the critical players involved, and their intricate role in the underlying mechanisms of neurodegeneration, with an emphasis on Alzheimer's and Parkinson's diseases. We critically appraise unsolved mechanistic links involved in the initiation and propagation of ferroptosis, such as a signaling cascade resulting in the de-repression of lipoxygenase translation and the role played by mitochondrial voltage-dependent anionic channels in iron homeostasis. Particular attention is given to the dual role of heme oxygenase in ferroptosis, which may be linked to the non-specific activity of P450 reductase in the endoplasmic reticulum. Despite the limited knowledge of ferroptosis initiation and progression in neurodegeneration, Nrf2/Bach1 target genes have emerged as crucial defenders in anti-ferroptotic pathways. The activation of Nrf2 and the inhibition of Bach1 can counteract ferroptosis and present a promising avenue for future therapeutic interventions targeting ferroptosis in neurodegenerative diseases.

Redox changes and cellular senescence in Alzheimer's disease

The redox process and cellular senescence are involved in a range of essential physiological functions. However, they are also implicated in pathological processes underlying age-related neurodegenerative disorders, including Alzheimer's disease (AD). Elevated levels of reactive oxygen species (ROS) are generated as a result of abnormal accumulation of beta-amyloid peptide (Aβ), tau protein, and heme dyshomeostasis and is further aggravated by mitochondria dysfunction and endoplasmic reticulum (ER) stress. Excessive ROS damages vital cellular components such as proteins, DNA and lipids. Such damage eventually leads to impaired neuronal function and cell death. Heightened oxidative stress can also induce cellular senescence via activation of the senescence-associated secretory phenotype to further exacerbate inflammation and tissue dysfunction. In this review, we focus on how changes in the redox system and cellular senescence contribute to AD and how they are affected by perturbations in heme metabolism and mitochondrial function. While potential therapeutic strategies targeting such changes have received some attention, more research is necessary to bring them into clinical application.

Metalloproteins and metalloproteomics in health and disease

Metalloproteins represents more than one third of human proteome, with huge variation in physiological functions and pathological implications, depending on the metal/metals involved and tissue context. Their functions range from catalysis, bioenergetics, redox, to DNA repair, cell proliferation, signaling, transport of vital elements, and immunity. The human metalloproteomic studies revealed that many families of metalloproteins along with individual metalloproteins are dysregulated under several clinical conditions. Also, several sorts of interaction between redox- active or redox- inert metalloproteins are observed in health and disease. Metalloproteins profiling shows distinct alterations in neurodegenerative diseases, cancer, inflammation, infection, diabetes mellitus, among other diseases. This makes metalloproteins -either individually or as families- a promising target for several therapeutic approaches. Inhibitors and activators of metalloenzymes, metal chelators, along with artificial metalloproteins could be versatile in diagnosis and treatment of several diseases, in addition to other biomedical and industrial applications.

Copper in Gynecological Diseases

Copper (Cu) is an essential micronutrient for the correct development of eukaryotic organisms. This metal plays a key role in many cellular and physiological activities, including enzymatic activity, oxygen transport, and cell signaling. Although the redox activity of Cu is crucial for enzymatic reactions, this property also makes it potentially toxic when found at high levels. Due to this dual action of Cu, highly regulated mechanisms are necessary to prevent both the deficiency and the accumulation of this metal since its dyshomeostasis may favor the development of multiple diseases, such as Menkes' and Wilson's diseases, neurodegenerative diseases, diabetes mellitus, and cancer. As the relationship between Cu and cancer has been the most studied, we analyze how this metal can affect three fundamental processes for tumor progression: cell proliferation, angiogenesis, and metastasis. Gynecological diseases are characterized by high prevalence, morbidity, and mortality, depending on the case, and mainly include benign and malignant tumors. The cellular processes that promote their progression are affected by Cu, and the mechanisms that occur may be similar. We analyze the crosstalk between Cu deregulation and gynecological diseases, focusing on therapeutic strategies derived from this metal.

Alzheimer's disease: The role of proteins in formation, mechanisms, and new therapeutic approaches

Alzheimer's disease (AD) is a progressive neurological disorder that affects the central nervous system (CNS), leading to memory and cognitive decline. In AD, the brain experiences three main structural changes: a significant decrease in the quantity of neurons, the development of neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein, and the formation of amyloid beta (Aβ) or senile plaques, which are protein deposits found outside cells and surrounded by dystrophic neurites. Genetic studies have identified four genes associated with autosomal dominant or familial early-onset AD (FAD): amyloid precursor protein (APP), presenilin 1 (PS1), presenilin 2 (PS2), and apolipoprotein E (ApoE). The formation of plaques primarily involves the accumulation of Aβ, which can be influenced by mutations in APP, PS1, PS2, or ApoE genes. Mutations in the APP and presenilin (PS) proteins can cause an increased amyloid β peptides production, especially the further form of amyloidogenic known as Aβ42. Apart from genetic factors, environmental factors such as cytokines and neurotoxins may also have a significant impact on the development and progression of AD by influencing the formation of amyloid plaques and intracellular tangles. Exploring the causes and implications of protein aggregation in the brain could lead to innovative therapeutic approaches. Some promising therapy strategies that have reached the clinical stage include using acetylcholinesterase inhibitors, estrogen, nonsteroidal anti-inflammatory drugs (NSAIDs), antioxidants, and antiapoptotic agents. The most hopeful therapeutic strategies involve inhibiting activity of secretase and preventing the β-amyloid oligomers and fibrils formation, which are associated with the β-amyloid fibrils accumulation in AD. Additionally, immunotherapy development holds promise as a progressive therapeutic approach for treatment of AD. Recently, the two primary categories of brain stimulation techniques that have been studied for the treatment of AD are invasive brain stimulation (IBS) and non-invasive brain stimulation (NIBS). In this article, the amyloid proteins that play a significant role in the AD formation, the mechanism of disease formation as well as new drugs utilized to treat of AD will be reviewed.

Unveiling the Effects of Copper Ions in the Aggregation of Amyloidogenic Proteins

Amyloid diseases have become a global concern due to their increasing prevalence. Transition metals, including copper, can affect the aggregation of the pathological proteins involved in these diseases. Copper ions play vital roles in organisms, but the disruption of their homeostasis can negatively impact neuronal function and contribute to amyloid diseases with toxic protein aggregates, oxidative stress, mitochondrial dysfunction, impaired cellular signaling, inflammation, and cell death. Gaining insight into the imbalance of copper ions and its impact on protein folding and aggregation is crucial for developing focused therapies. This review examines the influence of copper ions on significant amyloid proteins/peptides, offering a comprehensive overview of the current understanding in this field.