Matrix metalloproteinase-9 contributes to the increase of tau protein in serum during acute ischemic stroke

Total Tau Protein Mediates the Association of Ischemic Cerebrovascular Disease with Cognitive Decline

Background

Patients with transient ischemic attack (TIA) or ischemic stroke demonstrate an increased risk of cognitive dysfunction. Accumulating evidence indicates that ischemic cerebrovascular disease (ICVD) may interact with the amyloid/tau/neurodegeneration (AT[N]) biomarkers to promote dementia. However, the precise pathological mechanisms remain to be fully characterized.

Objective

To elucidate the interrelationships among ICVD, ATN biomarkers in cerebrospinal fluid (CSF), and cognition.

Methods

A total of 2524 participants were recruited from the CABLE study. ICVD referred to TIA/ischemic stroke. Cognitive performance was assessed by China Modified Mini-Mental State Examination (CM-MMSE) and Montreal Cognitive Assessment-b (MoCA-b). Multivariate linear regression analyses were performed to evaluate the associations of ICVD with CSF ATN biomarkers and cognition. Causal mediation analyses were used to identify whether the association was mediated by ATN biomarkers.

Results

ICVD was associated with higher total-tau (t-tau) (p = 2.828×10-2) and poorer cognition (CM-MMSE: p = 1.539×10-5, MoCA-b: p = 4.552×10-6). Additionally, no discernible correlation surfaced between ICVD and amyloid-β (Aβ) 42 (p = 6.910×10-1) or phosphorylated tau (p-tau) (p = 4.324×10-1). The influence of ICVD on cognitive function was partially mediated by CSF t-tau (CM-MMSE: proportion: 2.74%, MoCA-b: proportion: 2.51%). Subgroup analyses revealed the influences of t-tau were especially evident in male (CM-MMSE: proportion: 5.45%, MoCA-b: proportion: 5.38%) and mid-life group (CM-MMSE: proportion: 9.83%, MoCA-b: proportion: 5.31%).

Conclusions

These results delineated t-tau as a potential mediator for the influence of ICVD on cognition. Targeting brain ischemia and alleviating neuronal injury induced by ischemia may be a promising approach for preventing cognitive decline.

Apitherapy in Post-Ischemic Brain Neurodegeneration of Alzheimer's Disease Proteinopathy: Focus on Honey and Its Flavonoids and Phenolic Acids

Neurodegeneration of the brain after ischemia is a major cause of severe, long-term disability, dementia, and mortality, which is a global problem. These phenomena are attributed to excitotoxicity, changes in the blood-brain barrier, neuroinflammation, oxidative stress, vasoconstriction, cerebral amyloid angiopathy, amyloid plaques, neurofibrillary tangles, and ultimately neuronal death. In addition, genetic factors such as post-ischemic changes in genetic programming in the expression of amyloid protein precursor, β-secretase, presenilin-1 and -2, and tau protein play an important role in the irreversible progression of post-ischemic neurodegeneration. Since current treatment is aimed at preventing symptoms such as dementia and disability, the search for causative therapy that would be helpful in preventing and treating post-ischemic neurodegeneration of Alzheimer's disease proteinopathy is ongoing. Numerous studies have shown that the high contents of flavonoids and phenolic acids in honey have antioxidant, anti-inflammatory, anti-apoptotic, anti-amyloid, anti-tau protein, anticholinesterase, serotonergic, and AMPAK activities, influencing signal transmission and neuroprotective effects. Notably, in many preclinical studies, flavonoids and phenolic acids, the main components of honey, were also effective when administered after ischemia, suggesting their possible use in promoting recovery in stroke patients. This review provides new insight into honey's potential to prevent brain ischemia as well as to ameliorate damage in advanced post-ischemic brain neurodegeneration.

Neurodegeneration and convergent factors contributing to the deterioration of the cytoskeleton in Alzheimer's disease, cerebral ischemia and multiple sclerosis (Review)

The cytoskeleton is the main intracellular structure that determines the morphology of neurons and maintains their integrity. Therefore, disruption of its structure and function may underlie several neurodegenerative diseases. This review summarizes the current literature on the tau protein, microtubule-associated protein 2 (MAP2) and neurofilaments as common denominators in pathological conditions such as Alzheimer's disease (AD), cerebral ischemia, and multiple sclerosis (MS). Insights obtained from experimental models using biochemical and immunocytochemical techniques highlight that changes in these proteins may be potentially used as protein targets in clinical settings, which provides novel opportunities for the detection, monitoring and treatment of patients with these neurodegenerative diseases.

Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer's Disease Proteinopathy: Possible Therapeutic Role of Curcumin

For thousands of years, mankind has been using plant extracts or plants themselves as medicinal herbs. Currently, there is a great deal of public interest in naturally occurring medicinal substances that are virtually non-toxic, readily available, and have an impact on well-being and health. It has been noted that dietary curcumin is one of the regulators that may positively influence changes in the brain after ischemia. Curcumin is a natural polyphenolic compound with pleiotropic biological properties. The observed death of pyramidal neurons in the CA1 region of the hippocampus and its atrophy are considered to be typical changes for post-ischemic brain neurodegeneration and for Alzheimer’s disease. Additionally, it has been shown that one of the potential mechanisms of severe neuronal death is the accumulation of neurotoxic amyloid and dysfunctional tau protein after cerebral ischemia. Post-ischemic studies of human and animal brains have shown the presence of amyloid plaques and neurofibrillary tangles. The significant therapeutic feature of curcumin is that it can affect the aging-related cellular proteins, i.e., amyloid and tau protein, preventing their aggregation and insolubility after ischemia. Curcumin also decreases the neurotoxicity of amyloid and tau protein by affecting their structure. Studies in animal models of cerebral ischemia have shown that curcumin reduces infarct volume, brain edema, blood-brain barrier permeability, apoptosis, neuroinflammation, glutamate neurotoxicity, inhibits autophagy and oxidative stress, and improves neurological and behavioral deficits. The available data suggest that curcumin may be a new therapeutic substance in both regenerative medicine and the treatment of neurodegenerative disorders such as post-ischemic neurodegeneration.

Post-Ischemic Neurodegeneration of the Hippocampus Resembling Alzheimer's Disease Proteinopathy

In this review, we summarize, inter alia, the protein and gene changes associated with Alzheimer’s disease and their role in post-ischemic hippocampal neurodegeneration. In the hippocampus, studies have revealed dysregulation of the genes for the amyloid protein precursor metabolism and tau protein that is identical in nature to Alzheimer’s disease. Data indicate that amyloid and tau protein, derived from brain tissue and blood due to increased permeability of the blood–brain barrier after ischemia, play a key role in post-ischemic neurodegeneration of the hippocampus, with concomitant development of full-blown dementia. Thus, the knowledge of new neurodegenerative mechanisms that cause neurodegeneration of the hippocampus after ischemia, resembling Alzheimer’s disease proteinopathy, will provide the most important therapeutic development goals to date.

The Many Faces of Post-Ischemic Tau Protein in Brain Neurodegeneration of the Alzheimer's Disease Type

Recent data suggest that post-ischemic brain neurodegeneration in humans and animals is associated with the modified tau protein in a manner typical of Alzheimer’s disease neuropathology. Pathological changes in the tau protein, at the gene and protein level due to cerebral ischemia, can lead to the development of Alzheimer’s disease-type neuropathology and dementia. Some studies have shown increased tau protein staining and gene expression in neurons following ischemia-reperfusion brain injury. Recent studies have found the tau protein to be associated with oxidative stress, apoptosis, autophagy, excitotoxicity, neuroinflammation, blood-brain barrier permeability, mitochondrial dysfunction, and impaired neuronal function. In this review, we discuss the interrelationship of these phenomena with post-ischemic changes in the tau protein in the brain. The tau protein may be at the intersection of many pathological mechanisms due to severe neuropathological changes in the brain following ischemia. The data indicate that an episode of cerebral ischemia activates the damage and death of neurons in the hippocampus in a tau protein-dependent manner, thus determining a novel and important mechanism for the survival and/or death of neuronal cells following ischemia. In this review, we update our understanding of proteomic and genomic changes in the tau protein in post-ischemic brain injury and present the relationship between the modified tau protein and post-ischemic neuropathology and present a positive correlation between the modified tau protein and a post-ischemic neuropathology that has characteristics of Alzheimer’s disease-type neurodegeneration.

Analysis of the Relationship Between Metalloprotease-9 and Tau Protein in Alzheimer's Disease

BACKGROUND

Neurofibrillary tangles (NFTs) and amyloid plaques are the neuropathological hallmarks in brains with Alzheimer's disease (AD). Post-translational modifications of tau, such as phosphorylation and truncation, have been proposed as initiators in the assembly of the abnormal paired helical filaments that constitute the NFTs. Neurons and NFTs are sites of matrix metalloproteinases (MMPs).

OBJECTIVE

The aim of this study was to analyze the relationship of MMP-9 and tau protein in brain samples with AD.

METHODS

This study was performed on brain tissue samples from patients with early, moderate, and late AD. MMPs and tau levels were analyzed by western blot and gelatin-substrate zymography. Immunofluorescence techniques and confocal microscopy were used to analyze the presence of both proteins in NFTs. Further, molecular dynamics simulations (MDS) and protein-protein docking were conducted to predict interaction between MMP-9 and tau protein.

RESULTS

MMP-9 expression was greatest in moderate and late AD, whereas MMP-2 expression was only increased in late-stage AD. Interestingly, confocal microscopy revealed NFTs in which there was co-localization of MMP-9 and tau protein. MDS and protein-protein docking predictions indicate that a high-affinity complex can be formed between MMP-9 and full-length tau protein.

CONCLUSION

These observations provide preliminary evidence of an interaction between these two proteins. Post-translational modifications of tau protein, such as C-terminal truncation or phosphorylation of amino acid residues in the MMP-9 recognition site and conformational changes in the protein, such as folding of the N-terminal sequence over the three-repeat domain, could preclude the interaction between MMP-9 and tau protein during stages of NFT development.

Brain Ischemia as a Prelude to Alzheimer's Disease

Transient ischemic brain injury causes massive neuronal death in the hippocampus of both humans and animals. This was accompanied by progressive atrophy of the hippocampus, brain cortex, and white matter lesions. Furthermore, it has been noted that neurodegenerative processes after an episode of ischemia-reperfusion in the brain can continue well-beyond the acute stage. Rarefaction of white matter was significantly increased in animals at 2 years following ischemia. Some rats that survived 2 years after ischemia developed severe brain atrophy with dementia. The profile of post-ischemic brain neurodegeneration shares a commonality with neurodegeneration in Alzheimer's disease. Furthermore, post-ischemic brain injury is associated with the deposition of folding proteins, such as amyloid and tau protein, in the intracellular and extracellular space. Recent studies on post-ischemic brain neurodegeneration have revealed the dysregulation of Alzheimer's disease-associated genes such as amyloid protein precursor, α-secretase, β-secretase, presenilin 1, presenilin 2, and tau protein. The latest data demonstrate that Alzheimer's disease-related proteins and their genes play a key role in the development of post-ischemic brain neurodegeneration with full-blown dementia in disease types such as Alzheimer's. Ongoing interest in the study of brain ischemia has provided evidence showing that ischemia may be involved in the development of the genotype and phenotype of Alzheimer's disease, suggesting that brain ischemia can be considered as a useful model for understanding the mechanisms responsible for the initiation of Alzheimer's disease.

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.

Tau as a potential therapeutic target for ischemic stroke

Tau is a protein mainly expressed in adult human brain. It plays important roles both in neurodegenerative diseases and stroke. Stroke is an important cause of adult death and disability, ischemic stroke almost account for 80% in all cases. Abundant studies have proven that the increase of dysfunctional tau may act as a vital factor in pathological changes after ischemic stroke. However, the relationship between tau and ischemic stroke remains ununified. Based on present studies, we firstly introduced the structure and biological function of tau protein. Secondly, we summarized the potential regulatory mechanisms of tau protein in the process of ischemic stroke. Thirdly, we discussed about the findings in therapeutic researches of ischemic stroke. This review may be helpful in implementing new therapies for ischemic stroke and may be beneficial for the clinical and experimental studies.

Highly glycosylated CD147 promotes hemorrhagic transformation after rt-PA treatment in diabetes: a novel therapeutic target?

Background

Diabetes is known to be a main risk factor of post-stroke hemorrhagic transformation following recombinant tissue plasminogen activator (rt-PA) therapy. However, the mechanism through which diabetes exacerbates hemorrhagic transformation is insufficiently understood. We aimed to verify that CD147, the extracellular matrix metalloproteinase (MMP) inducer, played a vital role in the progress.

Methods

We performed middle cerebral artery occlusion on diabetic and non-diabetic rats, with or without rt-PA treatment, and then compared the glycosylation level of CD147, caveolin-1, MMPs activities, and blood-brain barrier (BBB) permeability. In vitro, tunicamycin treatment and genetic tools were used to produce non-glycosylated and lowly glycosylated CD147. An endogenous glucagon-like peptide-1 receptor (GLP-1R) agonist was used to downregulate the glycosylation of CD147 in vivo.

Results

Compared with non-diabetic rats, diabetic rats expressed higher levels of highly glycosylated CD147 in endothelium and astrocytes following rt-PA treatment accompanied by higher activity of MMPs and BBB permeability, in the middle cerebral artery occlusion model. Caveolin-1 was also overexpressed and co-localized with CD147 in astrocytes and endothelium in diabetic rats. In vitro, advanced glycation end products increased the expression of highly glycosylated CD147 in astrocytes and endothelial cells. Downregulating the glycosylation of CD147 lowered the activity of MMPs and promoted the expression of tight junction proteins. The expression of caveolin-1 in endothelial cells and astrocytes was not inhibited by tunicamycin, which revealed that caveolin-1 was an upstream of CD147. In vivo, GLP-1R agonist downregulated the glycosylation of CD147 and further reduced the activity of MMPs and protected the BBB in diabetic rats.

Conclusion

CD147 is essential for diabetes-associated rt-PA-induced hemorrhagic transformation, and downregulation of CD147 glycosylation is a promising therapy for neurovascular-unit repair after rt-PA treatment of patients with diabetes.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1460-1) contains supplementary material, which is available to authorized users.

The peripheral immune response after stroke-A double edge sword for blood-brain barrier integrity

The blood‐brain barrier (BBB) is a highly regulated interface that separates the peripheral circulation and the brain. It plays a vital role in regulating the trafficking of solutes, fluid, and cells at the blood‐brain interface and maintaining the homeostasis of brain microenvironment for normal neuronal activity. Growing evidence has led to the realization that ischemic stroke elicits profound immune responses in the circulation and the activation of multiple subsets of immune cells, which in turn affect both the early disruption and the later repair of the BBB after stroke. Distinct phenotypes or subsets of peripheral immune cells along with diverse intracellular mechanisms contribute to the dynamic changes of BBB integrity after stroke. This review focuses on the interaction between the peripheral immune cells and the BBB after ischemic stroke. Understanding their reciprocal interaction may generate new directions for stroke research and may also drive the innovation of easy accessible immune modulatory treatment strategies targeting BBB in the pursuit of better stroke recovery.

The effect of recombinant tissue plasminogen activator on MMP-2 and MMP-9 activities in vitro

One of the most significant side effects during recombinant tissue plasminogen activator (rtPA) for acute stroke treatment is intracranial bleeding. Gelatinases [matrix metalloproteinase (MMP)-2 and MMP-9] are one of the agents involved in the blood-brain barrier destruction resulting in secondary bleeding into the ischemic area during stroke. Previous papers revealed that patients with high baseline MMP-9 serum level have higher risk of intracranial bleeding after thrombolytic therapy. Our objective was to evaluate rtPA influence on serum MMP-2 and MMP-9 activities in vitro. Nine sera obtained from healthy donors were applied for experiment. The commercially available rtPA (Actylise) were diluted with included solvent and additionally with phosphate-buffered saline (PBS) to get concentrations: 2, 4, 8, and 16 μg/ml. Next, 100 μl of serum was mixed with equal proportion with different concentrations of rtPA to obtain final rtPA concentrations: 1, 2, 4, and 8 μg/ml. The sera together with rtPA were incubated for 1 or 2 hours at 37 °C. The activity of gelatinases was estimated with zymography. The activities of MMP-9 (92 kDa) and MMP-2 (72 kDa) were increased by incubation with rtPA in a dose-dependent manner. Simultaneously, the activity of band at 200 kDa (MMP-9/MMP-9 homodimer) was decreased. The activity of gelatinases incubated for 2 hours was elevated in comparison with 1-hour incubation; however, the increase was observed even for sample without rtPA. In conclusion, this study showed that rtPA can increase the biological activity of MMP-2 and MMP-9 on posttranslational level.

The significance of matrix metalloproteinase (MMP)-2 and MMP-9 in the ischemic stroke

There is a continuous urgent need to explore the pathogenesis and biochemical changes within the infarcted area during acute ischemic stroke (IS). Matrix metalloproteinases (MMPs), prevailing extracellular endopeptideses, can digest proteins located extracellulary, e.g. collagen, proteoglycans, elastin or fibronectin. Among MMPs, gelatinases (MMP-2 and MMP-9) are the most investigated enzymes. Gelatinases possess the ability to active numerous pro-inflammatory agents as chemokine CXCL-8, interleukin 1β or tumor necrosis factor α. Moreover, due to digestion of collagen type IV (the component of basal membranes) and tight junction proteins (TJPs) they facilitate to cross the endothelium by leukocytes. Due to the significant role of gelatinases during brain ischemia, their selective inhibition seems to be an interesting kind of treatment of acute stroke. The synthetic inhibitors of gelatineses decrease the infarct volume in animal models of IS. In clinical practice statins, the lipid-lowering drugs possess the ability to inhibit the activity of MMP-9 during acute IS. This review briefly provides the most important information about the involvement of MMP-2 and MMP-9 in the pathogenesis of brain ischemia.

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches.

Serum biomarkers of neurologic injury in cardiac operations

Assessment of subtle neurocognitive decline after surgical procedures has been hampered by heterogeneous testing techniques and a lack of reproducibility. This review summarizes the sensitivity and specificity of biomarkers of neurologic injury to determine whether they can be applied in the postoperative period to accurately predict neurocognitive decline. Creatine kinase-brain type, neuron-specific enolase, and S100B can be released into serum during operations by extracranial sources. Glial fibrillary acidic protein is a sensitive marker, and there are extracranial sources that are antigenically different from the brain-derived form. Serum levels of tau protein after acute neurologic injury do not reliability correlate with incidence.

The prognostic value of serum tau in patients with intracerebral hemorrhage

OBJECTIVES

This study aimed to investigate the relationship between serum tau concentrations and 3-month clinical outcomes in patients with intracerebral hemorrhage.

DESIGN AND METHODS

Serum tau concentrations of 176 patients were quantified by enzyme-linked immunosorbent assay. The end points were mortality and poor outcome (modified Rankin Scale score>2) after 3 months.

RESULTS

110 patients (62.5%) had a poor outcome at 3 months. The 3-month mortality rate was 36.4% (64/176). A forward stepwise logistic regression selected serum tau concentration as an independent predictor for 3-month mortality (P=0.002) and poor outcomes (P=0.009) of patients. A receiver operating characteristic curve analysis showed that serum tau concentration predicted 3-month mortality (P=0.001) and poor outcomes (P=0.001) statistically significantly. The area under curve of tau was similar to that of the National Institutes of Health Stroke Scale score for 3-month mortality (P=0.715) and poor outcomes (P=0.315). In a combined logistic-regression model, tau statistically significantly improved the area under curve of the National Institutes of Health Stroke Scale score for the prediction of 3-month poor outcome (P=0.039), but not for the prediction of 3-month mortality (P=0.106).

CONCLUSIONS

Serum tau concentration represents a novel biomarker for predicting mortality and poor outcomes at 3 months in patients with intracerebral hemorrhage.

Angiogenesis in old-aged subjects after ischemic stroke: a cautionary note for investigators

Angiogenesis represents a form of neovascularisation of exceptional importance in numerous pathological conditions including stroke. In this context it is directly related to neuroregeneration which is seen in close proximity. However, numerous experimental data have been drawn from studies that have ignored the age criterion. This is extremely important as angiogenesis is different in young versus old subjects. Extrapolating data obtained from studies performed in young subjects or "in vitro" to old-age patients could lead to inexact conclusions since the dynamics of angiogenesis is age-dependent.

The current review covers the key features of brain senescence including morphological and functional changes related to the brain parenchyma, its vascular network and blood flow which could possibly influence the process of angiogenesis. This is followed by a description of post-stroke angiogenesis and its relationship to neuroregeneration and its modulation by vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF 1), the most important factors active in old brain after ischemic injury.