The role of degenerative pathways in the development of irreversible consequences after brain ischemia

Methionine Diet Evoked Hyperhomocysteinemia Causes Hippocampal Alterations, Metabolomics Plasma Changes and Behavioral Pattern in Wild Type Rats

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons' vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in "methylation index" of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.

Myricetin as a Promising Molecule for the Treatment of Post-Ischemic Brain Neurodegeneration

The available drug therapy for post-ischemic neurodegeneration of the brain is symptomatic. This review provides an evaluation of possible dietary therapy for post-ischemic neurodegeneration with myricetin. The purpose of this review was to provide a comprehensive overview of what scientists have done regarding the benefits of myricetin in post-ischemic neurodegeneration. The data in this article contribute to a better understanding of the potential benefits of myricetin in the treatment of post-ischemic brain neurodegeneration, and inform physicians, scientists and patients, as well as their caregivers, about treatment options. Due to the pleiotropic properties of myricetin, including anti-amyloid, anti-phosphorylation of tau protein, anti-inflammatory, anti-oxidant and autophagous, as well as increasing acetylcholine, myricetin is a promising candidate for treatment after ischemia brain neurodegeneration with full-blown dementia. In this way, it may gain interest as a potential substance for the prophylaxis of the development of post-ischemic brain neurodegeneration. It is a safe substance, commercially available, inexpensive and registered as a pro-health product in the US and Europe. Taken together, the evidence available in the review on the therapeutic potential of myricetin provides helpful insight into the potential clinical utility of myricetin in treating neurodegenerative disorders with full-blown dementia. Therefore, myricetin may be a promising complementary agent in the future against the development of post-ischemic brain neurodegeneration. Indeed, there is a scientific rationale for the use of myricetin in the prevention and treatment of brain neurodegeneration caused by ischemia.

Participation of Amyloid and Tau Protein in Neuronal Death and Neurodegeneration after Brain Ischemia

Current evidence indicates that postischemic brain injury is associated with the accumulation of folding proteins, such as amyloid and tau protein, in the intra- and extracellular spaces of neuronal cells. In this review, we summarize protein changes associated with Alzheimer’s disease and their gene expression (amyloid protein precursor and tau protein) after brain ischemia, and their roles in the postischemic period. Recent advances in understanding the postischemic mechanisms in development of neurodegeneration have revealed dysregulation of amyloid protein precursor, α-, β- and γ-secretase and tau protein genes. Reduced expression of the α-secretase gene after brain ischemia with recirculation causes neuronal cells to be less resistant to injury. We present the latest data that Alzheimer’s disease-related proteins and their genes play a crucial role in postischemic neurodegeneration. Understanding the underlying processes of linking Alzheimer’s disease-related proteins and their genes in development of postischemic neurodegeneration will provide the most significant goals to date for therapeutic development.

Shared Genomic and Proteomic Contribution of Amyloid and Tau Protein Characteristic of Alzheimer's Disease to Brain Ischemia

Post-ischemic brain damage is associated with the deposition of folding proteins such as the amyloid and tau protein in the intra- and extracellular spaces of brain tissue. In this review, we summarize the protein changes associated with Alzheimer's disease and their gene expression (amyloid protein precursor and tau protein) after ischemia-reperfusion brain injury and their role in the post-ischemic injury. Recent advances in understanding the post-ischemic neuropathology have revealed dysregulation of amyloid protein precursor, α-secretase, β-secretase, presenilin 1 and 2, and tau protein genes after ischemic brain injury. However, reduced expression of the α-secretase in post-ischemic brain causes neurons to be less resistant to injury. In this review, we present the latest evidence that proteins associated with Alzheimer's disease and their genes play a key role in progressive brain damage due to ischemia and reperfusion, and that an ischemic episode is an essential and leading supplier of proteins and genes associated with Alzheimer's disease in post-ischemic brain. Understanding the underlying processes of linking Alzheimer's disease-related proteins and their genes in post-ischemic brain injury with the risk of developing Alzheimer's disease will provide the most significant goals for therapeutic development to date.

Proteomic and Genomic Changes in Tau Protein, Which Are Associated with Alzheimer's Disease after Ischemia-Reperfusion Brain Injury

Recent evidence suggests that transient ischemia of the brain with reperfusion in humans and animals is associated with the neuronal accumulation of neurotoxic molecules associated with Alzheimer’s disease, such as all parts of the amyloid protein precursor and modified tau protein. Pathological changes in the amyloid protein precursor and tau protein at the protein and gene level due to ischemia may lead to dementia of the Alzheimer’s disease type after ischemic brain injury. Some studies have demonstrated increased tau protein immunoreactivity in neuronal cells after brain ischemia-reperfusion injury. Recent research has presented many new tau protein functions, such as neural activity control, iron export, protection of genomic DNA integrity, neurogenesis and long-term depression. This review discusses the potential mechanisms of tau protein in the brain after ischemia, including oxidative stress, apoptosis, autophagy, excitotoxicity, neurological inflammation, endothelium, angiogenesis and mitochondrial dysfunction. In addition, attention was paid to the role of tau protein in damage to the neurovascular unit. Tau protein may be at the intersection of many regulatory mechanisms in the event of major neuropathological changes in ischemic stroke. Data show that brain ischemia activates neuronal changes and death in the hippocampus in a manner dependent on tau protein, thus determining a new and important way to regulate the survival and/or death of post-ischemic neurons. Meanwhile, the association between tau protein and ischemic stroke has not been well discussed. In this review, we aim to update the knowledge about the proteomic and genomic changes in tau protein following ischemia-reperfusion injury and the connection between dysfunctional tau protein and ischemic stroke pathology. Finally we present the positive correlation between tau protein dysfunction and the development of sporadic Alzheimer’s disease type of neurodegeneration.

Expression of the Tau Protein and Amyloid Protein Precursor Processing Genes in the CA3 Area of the Hippocampus in the Ischemic Model of Alzheimer's Disease in the Rat

Understanding the mechanisms underlying the selective susceptibility to ischemia of the CA3 region is very important to explain the neuropathology of memory loss after brain ischemia. We used a rat model to study changes in gene expression of the amyloid protein precursor and its cleaving enzymes and tau protein in the hippocampal CA3 sector, after transient 10-min global brain ischemia with survival times of 2, 7, and 30 days. The expression of the α-secretase gene was below control values at all times studied. But, the expression of the β-secretase gene was below the control values at 2-7 days after ischemia and the maximal increase in its expression was observed on day 30. Expression of the presenilin 1 gene was significantly elevated above the control values at 2-7 days after ischemia and decreased below the control values at day 30. Expression of the presenilin 2 gene showed an opposite trend to the expression of presenilin 1. Expression of the amyloid protein precursor gene after ischemia was at all times above the control values with a huge significant overexpression on day 7. Additionally, the expression of the tau protein gene was below the control values 2 days after ischemia, but the significant increase in its expression was observed on days 7-30. Data show that brain ischemia activates neuronal changes and death in the CA3 region of the hippocampus in a manner dependent on amyloid and tau protein, thus determining a new and important way to regulate the survival and/or death of ischemic neurons.

Neuroprotective and Neurological/Cognitive Enhancement Effects of Curcumin after Brain Ischemia Injury with Alzheimer's Disease Phenotype

In recent years, ongoing interest in ischemic brain injury research has provided data showing that ischemic episodes are involved in the development of Alzheimer's disease-like neuropathology. Brain ischemia is the second naturally occurring neuropathology, such as Alzheimer's disease, which causes the death of neurons in the CA1 region of the hippocampus. In addition, brain ischemia was considered the most effective predictor of the development of full-blown dementia of Alzheimer's disease phenotype with a debilitating effect on the patient. Recent knowledge on the activation of Alzheimer's disease-related genes and proteins-e.g., amyloid protein precursor and tau protein-as well as brain ischemia and Alzheimer's disease neuropathology indicate that similar processes contribute to neuronal death and disintegration of brain tissue in both disorders. Although brain ischemia is one of the main causes of death in the world, there is no effective therapy to improve the structural and functional outcomes of this disorder. In this review, we consider the promising role of the protective action of curcumin after ischemic brain injury. Studies of the pharmacological properties of curcumin after brain ischemia have shown that curcumin has several therapeutic properties that include anti-excitotoxic, anti-oxidant, anti-apoptotic, anti-hyperhomocysteinemia and anti-inflammatory effects, mitochondrial protection, as well as increasing neuronal lifespan and promoting neurogenesis. In addition, curcumin also exerts anti-amyloidogenic effects and affects the brain's tau protein. These results suggest that curcumin may be able to serve as a potential preventive and therapeutic agent in neurodegenerative brain disorders.