MiR-126 Affects Brain-Heart Interaction after Cerebral Ischemic Stroke

Exosomes - beyond stem cells for restorative therapy in stroke and neurological injury

Stroke is a leading cause of disability worldwide, and brain injuries devastate patients and their families, but currently no drugs on the market promote neurological recovery. Limited spontaneous recovery of function as a result of brain remodelling after stroke or injury does occur, and cell-based therapies have been used to promote these endogenous processes. Increasing evidence is demonstrating that the positive effects of such cell-based therapy are mediated by exosomes released from the administered cells and that the microRNA cargo in these exosomes is largely responsible for the therapeutic effects. This evidence raises the possibility that isolated exosomes could be used alone as a neurorestorative therapy and that these exosomes could be tailored to maximize clinical benefit. The potential of exosomes as a therapy for brain disorders is therefore being actively investigated. In this Review, we discuss the current knowledge of exosomes and advances in our knowledge of their effects on endogenous neurovascular remodelling events. We also consider the opportunities for exosome-based approaches to therapeutic amplification of brain repair and improvement of recovery after stroke, traumatic brain injury and other diseases in which neurorestoration could be a viable treatment strategy.

MicroRNAs and the Genetic Nexus of Brain Aging, Neuroinflammation, Neurodegeneration, and Brain Trauma

Aging is a complex and integrated gradual deterioration of cellular activities in specific organs of the body, which is associated with increased mortality. This deterioration is the primary risk factor for major human pathologies, including cancer, diabetes, cardiovascular disorders, neurovascular disorders, and neurodegenerative diseases. There are nine tentative hallmarks of aging. In addition, several of these hallmarks are increasingly being associated with acute brain injury conditions. In this review, we consider the genes and their functional pathways involved in brain aging as a means of developing new strategies for therapies targeted to the neuropathological processes themselves, but also as targets for many age-related brain diseases. A single microRNA (miR), which is a short, non-coding RNA species, has the potential for targeting many genes simultaneously and, like practically all other cellular processes, genes associated with many features of brain aging and injury are regulated by miRs. We highlight how certain miRs can mediate deregulation of genes involved in neuroinflammation, acute neuronal injury and chronic neurodegenerative diseases. Finally, we review the recent progress in the development of effective strategies to block specific miR functions and discuss future approaches with the prediction that anti-miR drugs may soon be used in the clinic.

Correlations of C-Reactive Protein (CRP), Interleukin-6 (IL-6), and Insulin Resistance with Cerebral Infarction in Hypertensive Patients

Background

The aim of this study was to investigate the correlations of C-reactive protein (CRP), interleukin-6 (IL-6), and insulin resistance (IR) with cerebral infarction in hypertensive patients.

Material/Methods

A total of 80 patients with cerebral infarction admitted to our hospital from March 2016 to November 2017 were selected and divided into 2 groups according to the diameter of cerebral infarction, namely, lacunar cerebral infarction group (n=40) and cerebral infarction group (n=40). The levels of high-sensitivity CRP (hs-CRP) and IL-6, homeostasis model assessment of IR (HOMA-IR) index and blood pressure level were compared between the 2 groups. The correlations of hs-CRP level, IL-6 level, and IR with the diameter of cerebral infarction, as well as the relationships of hs-CRP level and IR with the neurological function score after cerebral infarction were analyzed.

Results

The levels of hs-CRP and IL-6 in the cerebral infarction group were significantly higher than those in the lacunar cerebral infarction group (P<0.05). The cerebral infarction group had a markedly higher HOMA-IR index than the lacunar cerebral infarction group (P<0.05), but it had remarkably decreased systolic blood pressure and diastolic blood pressure compared with those in the lacunar cerebral infarction group (P<0.05). There were positive correlations of hs-CRP level, IL-6 level, and IR with the diameter of cerebral infarction (P<0.05). The hs-CRP level and IR had positive correlations with the neurological function score after cerebral infarction (P<0.05).

Conclusions

In hypertensive patients complicated with cerebral infarction, the body’s inflammatory factors, and IR are positively correlated with the diameter of cerebral infarction, as well as the neurological prognosis of the patients.

Exosomes from miRNA-126-modified ADSCs promotes functional recovery after stroke in rats by improving neurogenesis and suppressing microglia activation

Although adipose derived stem cells (ADSCs) exert their therapeutic potential in ischemic stroke, the migration of ADSCs in injured area is not apparently observed after intravenous administration. ADSCs are an important source of exosomes which hold great promise as an endogenous drug delivery system for the treatment of cerebral ischemia given their ability to cross the blood-brain barrier. Here we investigated whether ADSCs-derived exosomes mediated miRNAs transfer and thus promoted neurological recovery after stroke. We first proved that miR-126 levels were reduced in patients' plasma with acute ischemic stroke and in rat plasma and brain tissue after ischemia. To test the effect of exosomal miR-126, we employed overexpression and knock-down technologies to up-regulate or inhibit miR-126 level in ADSCs and thus acquired miR-126⁺ exosomes and miR-126^- exosomes, respectively. Compared with control, systemic administration of ADSCs-derived exosomes significantly increased the expression of von Willebrand factor (an endothelia cell marker) and doublecortin (a neuroblasts marker) and improved functional recovery in stroke rats. ADSCs-derived exosomes also resulted in a decrease of neuron cell death and an increase of cell proliferation compared with control. Importantly, these outcomes were further enhanced with miR-126⁺ exosomes treatment and were significantly decreased with miR-126^- exosomes treatment, compared to naïve exosomes treatment. MiR-126⁺ exosomes also inhibited microglial activation and the expression of inflammatory factors in vivo and in vitro. Our results suggest that intravenous administration of miR-126⁺ exosomes post stroke improves functional recovery, enhances neurogenesis, inhibits neuroinflammation, and represents a novel treatment for stroke.

Experimental ischaemic stroke induces transient cardiac atrophy and dysfunction

BACKGROUND

Stroke can lead to cardiac dysfunction in patients, but the mechanisms underlying the interaction between the injured brain and the heart are poorly understood. The objective of the study is to investigate the effects of experimental murine stroke on cardiac function and molecular signalling in the heart.

METHODS AND RESULTS

Mice were subjected to filament-induced left middle cerebral artery occlusion for 30 or 60 min or sham surgery and underwent repetitive micro-echocardiography. Left ventricular contractility was reduced early (24-72 h) but not late (2 months) after brain ischaemia. Cardiac dysfunction was accompanied by a release of high-sensitive cardiac troponin (hsTNT (ng/ml): d1: 7.0 ± 1.0 vs. 25.0 ± 3.2*; d3: 7.3 ± 1.1 vs. 52.2 ± 16.7*; d14: 5.7 ± 0.8 vs. 5.2 ± 0.3; sham vs. 60 min. MCAO; mean ± SEM; *p < 0.05); reduced heart weight (heart weight/tibia length ratio: d1: 6.9 ± 0.2 vs. 6.4 ± 0.1*; d3: 6.7 ± 0.2 vs. 5.8 ± 0.1*; d14: 6.7 ± 0.2 vs. 6.4 ± 03; sham vs. 60 min. MCAO; mean ± SEM; *p < 0.05); resulting from cardiomyocyte atrophy (cardiomyocyte size: d1: 12.8% ± 0.002**; d3: 13.5% ± 0.002**; 14d: 6.3% ± 0.003*; 60 min. MCAO vs. sham; mean ± SEM; **p < 0.01; *p < 0.05), accompanied by increased atrogin-1 and the E3 ubiquitin ligase murf-1. Net norepinephrine but not synthesis was increased, suggesting a reduced norepinephrine release or an increase of norepinephrine re-uptake, resulting in a functional denervation. Transcriptome analysis in cardiac tissue identified the transcription factor peroxisome proliferator-activated receptor gamma as a potential mediator of stroke-induced transcriptional dysregulation involved in cardiac atrophy.

CONCLUSIONS

Stroke induces a complex molecular response in the heart muscle with immediate but transient cardiac atrophy and dysfunction.

Potential of Exosomes for the Treatment of Stroke

Stroke is the result of blockage or rupture of blood vessels in the brain and is the leading cause of death and disability in the world. Currently only a very limited number of therapeutic approaches are available for treatment of stroke patients, and the vast majority of neuroprotective agents that tested positively in pre-clinical studies failed in clinical trials. In recent years, the clinical value of the use of exosomes for stroke treatment has received widespread attention due their unique characteristics such as low immunogenicity, low toxicity and biodegradability, ability to cross the blood–brain barrier (BBB), and their important role in communication between cells. More and more evidence suggests that the secretion of exosomes is the mechanism underlying the protection induced by mesenchymal stromal cells (MSCs) after stroke. Exosomes are thought to support brain restoration and induce repairing effects, including neurovascular remodeling, and anti-apoptosis and anti-inflammatory effects. Recent reports have focused on the clinical application of exosomes as a potential drug delivery approach. This review focuses on the ability of exosomes to interrupt the stroke-induced pathologic processes of stroke, and on publications describing how to achieve more effective treatment of stroke with exosomes.

Exosome-mediated amplification of endogenous brain repair mechanisms and brain and systemic organ interaction in modulating neurological outcome after stroke

Ischemic stroke is caused by a regional interruption of cerebral blood flow to the brain. Rigorous pre-clinical and clinical research has made landmark progress in stroke treatment using thrombolytics and endovascular thrombectomy. Although numerous successful neuroprotective therapeutic agents for ischemic stroke have been reported in pre-clinical studies, most of them failed in clinical testing. Persistent pre-clinical research has demonstrated that the ischemic brain is not only passively dying but is also actively recovering. Within the neurovascular niche in the peri-infarct tissue, repair mechanisms thrive on the interactions between the neural and vascular compartments. In this review, we discuss exogenous therapy using mesenchymal stromal cell-derived exosomes to amplify endogenous brain repair mechanisms and to induce neurorestorative effects after stroke. Emerging evidence indicates that multiple communication axes between the various organs such as the brain, heart, kidney and gut, and whole body immune response mediated by the spleen can also affect stroke outcome. Therefore, in this review, we summarize this evidence and initiate a discussion on the potential to improve stroke outcome by amplifying multiple brain repair mechanisms after stroke, and by targeting peripheral organs and downstream events to enhance recovery in the injured brain and promote over all well being.

Intracerebral Hemorrhage Induces Cardiac Dysfunction in Mice Without Primary Cardiac Disease

Background: Intracerebral hemorrhage (ICH) is a life threatening stroke subtype and a worldwide health problem. In this study, we investigate brain-heart interaction after ICH in mice and test whether ICH induces cardiac dysfunction in the absence of primary cardiac disease. We also investigate underlying mechanisms such as oxidative stress and inflammatory responses in mediating cardiac dysfunction post-ICH in mice.

Methods: Male, adult (3–4 m) C57BL/6J mice were subjected to sham surgery or ICH using an autologous blood injection model (n = 16/group). Cardiac function was evaluated at 7 and 28 days after ICH using echocardiography (n = 8/group per time point). Western blot and immunostaining analysis were employed to assess oxidative stress and inflammatory responses in the heart.

Results: Mice subjected to ICH exhibited significantly decreased cardiac contractile function measured by left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) at 7 and 28 days after ICH compared to sham-control mice (p < 0.05). ICH induced cardiac dysfunction was significantly worse at 28 days than at 7 days after ICH (p < 0.05). ICH in mice significantly increased cardiomyocyte apoptosis, inflammatory factor expression and inflammatory cell infiltration in heart tissue, and induced cardiac oxidative stress at 7 days post-ICH compared to sham-control mice. Compared to sham-control mice, ICH-mice also exhibited significantly increased (p < 0.05) cardiomyocyte hypertrophy and cardiac fibrosis at 28 days after ICH.

Conclusions: ICH induces significant and progressive cardiac dysfunction in mice. ICH increases cardiac oxidative stress and inflammatory factor expression in heart tissue which may play key roles in ICH-induced cardiac dysfunction.

Apolipoprotein E Exerts a Whole-Brain Protective Property by Promoting M1? Microglia Quiescence After Experimental Subarachnoid Hemorrhage in Mice

Subarachnoid hemorrhage (SAH) is a neurologically destructive stroke in which early brain injury (EBI) plays a pivotal role in poor patient outcomes. Expanding upon our previous work, multiple techniques and methods were used in this preclinical study to further elucidate the mechanisms underlying the beneficial effects of apolipoprotein E (ApoE) against EBI after SAH in murine apolipoprotein E gene-knockout mice (Apoe^-/-, KO) and wild-type mice (WT) on a C57BL/6J background. We reported that Apoe deficiency resulted in a more extensive EBI at 48 h after SAH in mice demonstrated by MRI scanning and immunohistochemical staining and exhibited more extensive white matter injury and neuronal apoptosis than WT mice. These changes were associated with an increase in NADPH oxidase 2 (NOX2) expression, an important regulator of both oxidative stress and inflammatory cytokines. Furthermore, immunohistochemical analysis revealed that NOX2 was abundantly expressed in activated M1 microglia. The JAK2/STAT3 signaling pathway, an upstream regulator of NOX2, was increased in WT mice and activated to an even greater extent in Apoe^-/- mice; whereas, the JAK2-specific inhibitor, AG490, reduced NOX2 expression, oxidative stress, and inflammation in Apoe-deficient mice. Also, apoE-mimetic peptide COG1410 suppressed the JAK2/STAT3 signaling pathway and significantly reduced M1 microglia activation with subsequent attenuation of oxidative stress and inflammation after SAH. Taken together, apoE and apoE-mimetic peptide have whole-brain protective effects that may reduce EBI after SAH via M1 microglial quiescence through the attenuation of the JAK2/STAT3/NOX2 signaling pathway axis.

Post-stroke DHA Treatment Protects Against Acute Ischemic Brain Injury by Skewing Macrophage Polarity Toward the M2 Phenotype

Systemic docosahexaenoic acid (DHA) has been explored as a clinically feasible protectant in stroke models. However, the mechanism for DHA-afforded neuroprotection remains elusive. Transient middle cerebral artery occlusion (tMCAO) was induced for 1 h. DHA (i.p., 10 mg/kg) was administered immediately after reperfusion and repeated daily for 3 days. Stroke outcomes, systemic inflammatory status, and microglia/macrophage phenotypic alterations were assessed 3 days after stroke. Macrophage depletion was induced by clodronate liposomes injection. Primary macrophage cultures were used to evaluate the direct effect of DHA on macrophages. We demonstrated that post-stroke DHA injection efficiently reduced brain infarct and ameliorated neurological deficits 3 days after tMCAO. Systemic DHA treatment significantly inhibited immune cell infiltration (macrophages, neutrophils, T lymphocytes, and B lymphocytes) and promoted macrophage polarization toward an anti-inflammatory M2 phenotype in the ischemic brain. Meanwhile, systemic DHA administration inhibited the otherwise elevated pro-inflammatory factors in blood and shifted circulating macrophage polarity toward M2 phenotype after ischemic stroke. The numbers of circulating immune cells in blood and spleen, however, were equivalent between DHA- and vehicle-treated groups. The protective effects of DHA were macrophage-dependent, as macrophage depletion abolished DHA-afforded neuroprotection. In vitro studies confirmed that DHA suppressed production of chemokines and pro-inflammatory cytokines from macrophages under inflammatory stimulation. These data indicate that post-stroke DHA treatment ameliorated acute ischemic brain injury in a macrophage-dependent manner and DHA enhanced macrophage phenotypic shift toward an anti-inflammatory phenotype to reduced central and peripheral inflammation after stroke.

Immune Response Mediates Cardiac Dysfunction after Traumatic Brain Injury

Cardiovascular complications are common after traumatic brain injury (TBI) and are associated with increased morbidity and mortality. In this study, we investigated the possible role of the immune system in mediating cardiac dysfunction post-TBI in mice. Adult male C57BL/6J mice were subjected to a TBI model of controlled cortical impact (CCI) with or without splenectomy (n = 20/group). Splenectomy was performed immediately prior to induction of TBI. Cardiac function was measured using echocardiography prior to and after TBI. Neurological and cognitive functional tests and flow cytometry and immunostaining were performed. TBI mice exhibited significant cardiac dysfunction identified by decreased left ventricular ejection fraction and fractional shortening at 3 and 30 days post-TBI. In addition, these mice exhibited significantly increased cardiomyocyte apoptosis, inflammation, and oxidative stress at 3 and 30 days post-TBI, as well as cardiac hypertrophy and fibrosis and ventricular dilatation at 30 days after TBI. TBI mice subjected to splenectomy showed significantly improved cardiac function, and decreased cardiac fibrosis, oxidative stress, cardiomyocyte apoptosis, and infiltration of immune cells and inflammatory factor expression in the heart compared with TBI control mice. TBI mice exhibited severe neurological and cognitive function deficits. However, splenectomy did not improve neurological and cognitive functional outcome after TBI compared with the TBI control group. TBI induces immune cell infiltration and inflammatory factor expression in the heart as well as cardiac dysfunction. Splenectomy decreases heart inflammation and improves cardiac function after TBI. Immune response may contribute to TBI-induced cardiac dysfunction.

Deciphering Non-coding RNAs in Cardiovascular Health and Disease

After being long considered as “junk” in the human genome, non-coding RNAs (ncRNAs) currently represent one of the newest frontiers in cardiovascular disease (CVD) since they have emerged in recent years as potential therapeutic targets. Different types of ncRNAs exist, including small ncRNAs that have fewer than 200 nucleotides, which are mostly known as microRNAs (miRNAs), and long ncRNAs that have more than 200 nucleotides. Recent discoveries on the role of ncRNAs in epigenetic and transcriptional regulation, atherosclerosis, myocardial ischemia/reperfusion (I/R) injury and infarction (MI), adverse cardiac remodeling and hypertrophy, insulin resistance, and diabetic cardiomyopathy prompted vast interest in exploring candidate ncRNAs for utilization as potential therapeutic targets and/or diagnostic/prognostic biomarkers in CVDs. This review will discuss our current knowledge concerning the roles of different types of ncRNAs in cardiovascular health and disease and provide some insight on the cardioprotective signaling pathways elicited by the non-coding genome. We will highlight important basic and clinical breakthroughs that support employing ncRNAs for treatment or early diagnosis of a variety of CVDs, and also depict the most relevant limitations that challenge this novel therapeutic approach.

The circulating non-coding RNA landscape for biomarker research: lessons and prospects from cardiovascular diseases

Pervasive transcription of the human genome is responsible for the production of a myriad of non-coding RNA molecules (ncRNAs) some of them with regulatory functions. The pivotal role of ncRNAs in cardiovascular biology has been unveiled in the last decade, starting from the characterization of the involvement of micro-RNAs in cardiovascular development and function, and followed by the use of circulating ncRNAs as biomarkers of cardiovascular diseases. The human non-coding secretome is composed by several RNA species that circulate in body fluids and could be used as biomarkers for diagnosis and outcome prediction. In cardiovascular diseases, secreted ncRNAs have been described as biomarkers of several conditions including myocardial infarction, cardiac failure, and atrial fibrillation. Among circulating ncRNAs, micro-RNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) have been proposed as biomarkers in different cardiovascular diseases. In comparison with standard biomarkers, the biochemical nature of ncRNAs offers better stability and flexible storage conditions of the samples, and increased sensitivity and specificity. In this review we describe the current trends and future prospects of the use of the ncRNA secretome components as biomarkers of cardiovascular diseases, including the opening questions related with their secretion mechanisms and regulatory actions.

Extracellular microRNAs and oxidative stress in liver injury: a systematic mini review

Recent evidence has suggested that extracellular microRNAs have crucial roles in intercellular communications and are promising as minimally invasive biomarkers for various diseases including cancers. Oxidative stress also plays an essential role in homeostasis and disease development. This systematic review aims to clarify the current evidence on the interaction between oxidative stress and extracellular microRNAs. We identified 32 studies that provided information regarding the association between oxidative stress and extracellular microRNAs: 9 focused on the central nervous system, 11 focused on cardiovascular diseases, and 4 focused on liver injury. Endothelial cell-specific miR-126-3p was the most studied extracellular miRNA associated with oxidative stress. In addition, we highlight some reports that describe the mechanisms of how oxidative stress affects extracellular microRNA profiles in liver injury. In liver injury, the levels of miR-122-5p, miR-192-5p, miR-223-3p, and miR-1224-5p were reported to be elevated in the sera. The release of miR-122-5p, miR-192-5p, and miR-1224-5p from hepatocytes may be attributed to oxidative stress. miR-223-3p could be released from neutrophils and suppress oxidative stress in the liver. Elucidation of the mechanisms of the interaction between extracellular microRNAs and oxidative stress would improve our pathophysiological understanding as well as future medical practice.

Extracellular microRNAs as messengers in the central and peripheral nervous system

MicroRNAs are small post-transcriptional regulators that play an important role in nervous system development, function and disease. More recently, microRNAs have been detected extracellularly and circulating in blood and other body fluids, where they are protected from degradation by encapsulation in vesicles, such as exosomes, or by association with proteins. These microRNAs are thought to be released from cells selectively through active processes and taken up by specific target cells within the same or in remote tissues where they are able to exert their repressive function. These characteristics make extracellular microRNAs ideal candidates for intercellular communication over short and long distances. This review aims to explore the potential mechanisms underlying microRNA communication within the nervous system and between the nervous system and other tissues. The suggested roles of extracellular microRNAs in the healthy and the diseased nervous system will be reviewed.

Brain-Heart Interaction: Cardiac Complications After Stroke

Neurocardiology is an emerging specialty that addresses the interaction between the brain and the heart, that is, the effects of cardiac injury on the brain and the effects of brain injury on the heart. This review article focuses on cardiac dysfunction in the setting of stroke such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage. The majority of post-stroke deaths are attributed to neurological damage, and cardiovascular complications are the second leading cause of post-stroke mortality. Accumulating clinical and experimental evidence suggests a causal relationship between brain damage and heart dysfunction. Thus, it is important to determine whether cardiac dysfunction is triggered by stroke, is an unrelated complication, or is the underlying cause of stroke. Stroke-induced cardiac damage may lead to fatality or potentially lifelong cardiac problems (such as heart failure), or to mild and recoverable damage such as neurogenic stress cardiomyopathy and Takotsubo cardiomyopathy. The role of location and lateralization of brain lesions after stroke in brain-heart interaction; clinical biomarkers and manifestations of cardiac complications; and underlying mechanisms of brain-heart interaction after stroke, such as the hypothalamic-pituitary-adrenal axis; catecholamine surge; sympathetic and parasympathetic regulation; microvesicles; microRNAs; gut microbiome, immunoresponse, and systemic inflammation, are discussed.

The Involvement of miRNA in Carotid-Related Stroke

Cardiovascular disease is the leading cause of morbidity and mortality in developed countries. Stroke is associated with a marked disability burden and has a major economic impact; this is especially true for carotid artery stroke. Major advances in primary and secondary prevention during the last few decades have helped to tackle this public health problem. However, better knowledge of the physiopathology of stroke and its underlying genetic mechanisms is needed to improve diagnosis and therapy. miRNAs are an important, recently identified class of post-transcriptional regulators of gene expression and are known to be involved in cerebrovascular disease. These endogenous, small, noncoding RNAs may have applications as noninvasive biomarkers and therapeutic tools in practice. Here, we review the involvement of several miRNAs in cell-based and whole-animal models of stroke, with a focus on human miRNA profiling studies of carotid artery stroke. Lastly, we describe the miRNAs' potential role as a biomarker of stroke.

Advances in molecular mechanism of cardioprotection induced by helium

Helium has been classified as a kind of inert gas that is not effortless to spark chemical reactions with other substances in the past decades. Nevertheless, the cognition of scientists has gradually changed accompanied with a variety of studies revealing the potential molecular mechanism underlying organ-protection induced by helium. Especially, as a non-anesthetic gas which is deficient of relevant cardiopulmonary side effects, helium conditioning is recognized as an emerging and promising approach to exert favorable effects by mimicking the cardioprotection of anesthetic gases or xenon. In this review we will summarize advances in the underlying biological mechanisms and clinical applicability with regards to the cardioprotective effects of helium.