The emerging role of epigenetics in stroke: II. RNA regulatory circuitry

microRNA-27c negatively regulates NF-κB and IRF3 signaling pathway via targeting MITA in miiuy croaker

As a non-coding RNA with regulatory functions, microRNAs(miRNAs) can regulate gene expression and participate in a variety of physiological and pathological processes. In recent years, although there have been many studies on miRNA, the regulation mechanisms of miRNA in teleost fish have not been fully elucidated. In this study, it was first predicted that MITA is the target of miR-27c through bioinformatics, and it was confirmed by dual fluorescence experiments. Then we found that miR-27c can inhibit the expression of MITA at the mRNA and protein levels, thereby promoting the NF-κB or IRF3 pathway. It is speculated that miR-27c plays an important role in the innate immunity of teleost fish. This study will help to further understand miRNAs regulatory mechanism in teleost fish.

Genetics and Epigenetics of Spontaneous Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a complex and heterogeneous disease, and there is no effective treatment. Spontaneous ICH represents the final manifestation of different types of cerebral small vessel disease, usually categorized as: lobar (mostly related to cerebral amyloid angiopathy) and nonlobar (hypertension-related vasculopathy) ICH. Accurate phenotyping aims to reflect these biological differences in the underlying mechanisms and has been demonstrated to be crucial to the success of genetic studies in this field. This review summarizes how current knowledge on genetics and epigenetics of this devastating stroke subtype are contributing to improve the understanding of ICH pathophysiology and their potential role in developing therapeutic strategies.

Coding and non-coding nucleotides': The future of stroke gene therapeutics

Stroke is the foremost cause of death ranked after heart disease and cancer. It is the fatal life-threatening event that requires immediate medical admissions to overcome following morbidity and mortality. The therapeutic advances in stroke therapy have been manipulated with diverse paths for last 5 years. Recent research and clinical trials have investigated a variety of anti-stroke agents including anti-coagulants, cerebro-protective agents, antiplatelet therapy, stem-cell therapy, and specified gene therapy. In recent advanced studies, genetic therapies including noncoding RNAs (ncRNAs), long non-coding RNAs (LncRNAs), small interfering RNAs (siRNAs), microRNAs (miRNAs), Piwi interacting RNAs (PiWi RNAs) have shown better potential as targeted future therapeutics with a better outcome than conventional stroke therapeutics. The potential of targeted gene therapy is much more advanced in not only the induction of neuroprotection but also safer non-toxic targeted therapeutics. In the current state of the art review, we have focused on the recent advancements made towards the stroke with RNA modifications and targeted gene therapeutics.

Evolutionary concept of inflammatory response and stroke

The immune system plays an important role under both physiological and pathological conditions. Immune surveillance as well as defense and healing processes are crucial for the organism, but the immune system has a natural tendency to act aggressively when excessively stimulated. We may assume that the immune system is not designed to deal with severe conditions, such as polytrauma or severe stroke, because these are not compatible with life in the wilderness and evolution has no chance to act in such cases. These conditions are associated with exaggerated/deregulated inflammatory response, which may cause more damage than initial pathology. In this article, we would like to sketch a basic concept of the immune system-brain interactions from the evolutionary point of view and to discuss some implications related to stroke.

Racial and Ethnic Disparities in Hospital Mortality among Ischemic Stroke Patients in Hawaii

BACKGROUND

We evaluated disparities in in-hospital mortality rates among whites, Native Hawaiians and other Pacific Islanders (NHOPI), Filipinos, and other Asian groups in Hawaii who were hospitalized for acute ischemic stroke.

MATERIALS AND METHODS

Using a statewide hospital claims database, we performed a retrospective study including sequential acute ischemic stroke patients between 2010 and 2015. We compared in-hospital mortality rates among whites, NHOPI, Filipinos, other Asian groups excluding Filipinos, and other races (Blacks, Hispanics, Native Americans, mixed race).

RESULTS

A total of 13,030 patient discharges were included in this study. The mean (±SD) age in years at the time of stroke was 63.5 ± 14.3 for NHOPI, 69.6 ± 14.4 for Filipinos, 67.8 ± 14.2 for other race, 71.4 ± 13.8 for whites, and 76.1 ± 13.5 for other Asians (P < .001). NHOPI patients had higher rates of diabetes (48.8%), obesity (18.4%), and tobacco use (31.3%) compared with patients in other racial-ethnic categories. Filipino patients had the highest rate of hemorrhagic transformation (9.7%). Age-adjusted stroke mortality rates were highest among Filipinos (15.9%; 95% confidence interval [CI] = 14.3%-17.6%), followed by other Asian groups (15.1%; 95% CI = 14.0%-16.2%), NHOPI (14.8%; 95% CI = 12.8%-16.8%), other race (14.4%; 95% CI = 11.3%-17.4%), and lowest among whites (12.8%; 11.5%-14.2%). After adjusting for other confounding variables, Filipinos had higher mortality (odds ratio = 1.22, 95% CI = 1.03-1.45), whereas other Asian groups, NHOPI, and other race patients had mortality rates that were similar to whites.

CONCLUSION

In Hawaii, Filipino ethnicity is an independent risk factor for higher in-hospital stroke mortality compared with whites.

The Challenge of microRNA as a Biomarker of Epilepsy

BACKGROUND

Epilepsy is one of chronic severe neurological disorders possess to recurring seizures. And now anti-epileptic drugs are only effective in less than one third of epilepsy patients, and biomarkers predicting are not available when the specific antiepileptic drugs treated. Advanced studies have showed that miRNA may be a key in the pathogenesis of epilepsy beginning in the early 2000 years. Several target genes and pathways of miRNA which related to the therapeutic methods to epilepsy.

METHOD

We searched PubMed from Jan 1,2000 to Jan 1, 2017, using the terms "epilepsy AND microRNA AND biomarker" and "seizure AND microRNA AND biomarker". We selected articles that featured novel miRNAs in vivo epilepsy models and patients. We then selected the most relevant articles based on a subjective appraisal of their quality and mechanistic insight that could be relevant to epilepsy.

RESULTS

Decrease the expression of has-miR134 could be a potential non-invasive biomarker to use in diagnosis for the epilepsy patients for using hsa-miR-134 also be identified to distinguish patients with and without epilepsy. miR-181a show significant downregulation in the acute stage, but up regulation in the chronic stage and in the latent stage there is no changing and how about this phenomenon appearance in different stage still should be discussed in the future. Besides that, miR- 146a can down-regulated in the patients using genome-wide for serum in circulating miRNAs.miR- 124, miR-199a, and miR-128 etc. could be a candidate for the biomarker in future. miR-15a-5p and -194-5p down-regulated in epilepsy patients, in the future, it may be used as a novel biomarker for improve diagnosis.

CONCLUSION

These observations give a chance that new development for diagnosis and treatment of epilepsy patients. Advanced technique and miRNA combination may product more effective roles in epilepsy and other disease. These reports will be available to solve the application of miRNAs as biomarkers and novel therapy approaches for epilepsy. In summary, researcher who focus on miRNAs should be understanding of the causes, treatment, and diagnosis of epilepsy. exploration of any of these effects on the efficacy of these drugs is worthwhile.

Epigenetic interventions for epileptogenesis: A new frontier for curing epilepsy

This article highlights the emerging therapeutic potential of specific epigenetic modulators as promising antiepileptogenic or disease-modifying agents for curing epilepsy. Currently, there is an unmet need for antiepileptogenic agents that truly prevent the development of epilepsy in people at risk. There is strong evidence that epigenetic signaling, which exerts high fidelity regulation of gene expression, plays a crucial role in the pathophysiology of epileptogenesis and chronic epilepsy. These modifications are not hard-wired into the genome and are constantly reprogrammed by environmental influences. The potential epigenetic mechanisms, including histone modifications, DNA methylation, microRNA-based transcriptional control, and bromodomain reading activity, can drastically alter the neuronal gene expression profile by exerting their summative effects in a coordinated fashion. Such an epigenetic intervention appears more rational strategy for preventing epilepsy because it targets the primary pathway that initially triggers the numerous downstream cellular and molecular events mediating epileptogenesis. Among currently approved epigenetic drugs, the majority are anticancer drugs with well-established profiles in clinical trials and practice. Evidence from preclinical studies supports the premise that these drugs may be applied to a wide range of brain disorders. Targeting histone deacetylation by inhibiting histone deacetylase enzymes appears to be one promising epigenetic therapy since certain inhibitors have been shown to prevent epileptogenesis in animal models. However, developing neuronal specific epigenetic modulators requires rational, pathophysiology-based optimization to efficiently intercept the upstream pathways in epileptogenesis. Overall, epigenetic agents have been well positioned as new frontier tools towards the national goal of curing epilepsy.

Protective role of microRNA-126 in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a disease associated with high mortality and morbidity. MicroRNAs (miRNAs) are important regulators of translation and have been reported to be associated with the pathogenesis of numerous cerebrovascular diseases, including ICH. The present study explored the role of miRNA (miR)‑126 in ICH. Adult male Wistar rats were randomly assigned to ICH model and sham groups. ICH was induced by intracerebral injection of collagenase. The mRNA expression levels of miR‑126 in the two groups were determined. The miR‑126 lentivirus expression vector pWPXL‑miR‑126 or negative control vector was then constructed and delivered via intraparenchymal injection. Following transduction, behavioral testing (rotarod and limb placement tests), relative hemorrhagic lesion size, apoptotic cells and protein levels of vascular endothelial growth factor (VEGF)‑A and caspase‑3 were determined. The relative expression levels of miR‑126 were significantly decreased in the ICH group compared to the sham group (P=0.026). Overexpression of miR‑126 significantly improved the relative duration of stay on the rotarod at day 2 (P=0.029) and 3 (P=0.033), and statistically reduced the deficit score (P=0.036), the relative size of hemorrhagic lesion (P=0.019) and the number of apoptotic cortical neurons (P=0.024) compared with the sham group. Additionally, the protein levels of VEGF‑A were significantly elevated, however levels of caspase‑3 were downregulated by overexpression of miR‑126 compared with the negative control group. MiR‑126 therefore exhibits a protective role in ICH. Overexpression of miR‑126 protects against ICH, and may be involved in the process of angiogenesis and exhibit an anti-apoptotic effect.

Epigenetic Regulation of Oxidative Stress in Ischemic Stroke

The prevalence and incidence of stroke rises with life expectancy. However, except for the use of recombinant tissue-type plasminogen activator, the translation of new therapies for acute stroke from animal models into humans has been relatively unsuccessful. Oxidative DNA and protein damage following stroke is typically associated with cell death. Cause-effect relationships between reactive oxygen species and epigenetic modifications have been established in aging, cancer, acute pancreatitis, and fatty liver disease. In addition, epigenetic regulatory mechanisms during stroke recovery have been reviewed, with focuses mainly on neural apoptosis, necrosis, and neuroplasticity. However, oxidative stress-induced epigenetic regulation in vascular neural networks following stroke has not been sufficiently explored. Improved understanding of the epigenetic regulatory network upon oxidative stress may provide effective antioxidant approaches for treating stroke. In this review, we summarize the epigenetic events, including DNA methylation, histone modification, and microRNAs, that result from oxidative stress following experimental stroke in animal and cell models, and the ways in which epigenetic changes and their crosstalk influence the redox state in neurons, glia, and vascular endothelial cells, helping us to understand the foregone and vicious epigenetic regulation of oxidative stress in the vascular neural network following stroke.

Effects of intracerebral hemorrhage on 5-hydroxymethylcytosine modification in mouse brains

The past decade has resulted in an increase in the knowledge of molecular mechanisms underlying brain injury induced by intracerebral hemorrhage (ICH). Recent advances have provided a link between epigenetic modification and the regulation of gene expression. 5-hydroxymethylcytosine (5hmC) converted from 5-methylcytosine by the ten-eleven translocation (TET) family of proteins has emerged as a new epigenetic modification. While the dynamics of 5hmC during cerebral ischemia have recently been reported, whether 5hmC is involved in ICH remains unexplored. In this study, we investigated the effects of ICH on DNA hydroxymethylation. We showed that the global level of 5hmC rapidly decreased as early as 24 hours after ICH and persisted until 72 hours. Furthermore, the level of 5hmC in the CpG-rich regions of Akt2, Pdpk1 and Vegf genes was significantly decreased with a minimum level observed at 48 hours or 72 hours. Decreased 5hmC was observed in parallel with an increase in 5-methylcytosine over this time course, and mRNA levels of Akt2, Pdpk1 and Vegf were downregulated upon ICH injury. Finally, Tet1, Tet2 and Tet3 mRNA levels were dramatically decreased in the ICH brain. Our study for the first time established the correlation between DNA hydroxymethylation and ICH injury. Further investigations should examine whether 5hmC modification could be a therapeutic target for the treatment of ICH injury.

Promoting brain remodeling to aid in stroke recovery

Endogenous brain repair after stroke involves a set of highly interactive processes, such as angiogenesis, neurogenesis, oligodendrogenesis, synaptogenesis, and axonal outgrowth, which together orchestrate neurological recovery. During the past several years, there have been advances in our understanding of miRNAs and histone deacetylases (HDACs) in brain repair processes after stroke. Emerging data indicate the important role of exosomes for intercellular communication in promoting coupled brain remodeling processes. These advances will likely have a major impact on the development of restorative therapies for ischemic brain repair, consequently leading to improvement of neurological function. In this review, we provide an update on our current understanding of cellular and molecular mechanisms of miRNAs, exosomes, and HDACs in brain restorative processes after stroke.

Moyamoya Biomarkers

Moyamoya disease (MMD) is an arteriopathy of the intracranial circulation predominantly affecting the branches of the internal carotid arteries. Heterogeneity in presentation, progression and response to therapy has prompted intense study to improve the diagnosis and prognosis of this disease. Recent progress in the development of moyamoya-related biomarkers has stimulated marked interest in this field. Biomarkers can be defined as biologically derived agents-such as specific molecules or unique patterns on imaging-that can identify the presence of disease or help to predict its course. This article reviews the current categories of biomarkers relevant to MMD-including proteins, cells and genes-along with potential limitations and applications for their use.

Epigenetic impact of curcumin on stroke prevention

The epigenetic impact of curcumin in stroke and neurodegenerative disorders is curiosity-arousing. It is derived from Curcuma longa (spice), possesses anti-oxidative, anti-inflammatory, anti-lipidemic, neuro-protective and recently shown to exhibit epigenetic modulatory properties. Epigenetic studies include DNA methylation, histone modifications and RNA-based mechanisms which regulate gene expression without altering nucleotide sequences. Curcumin has been shown to affect cancer by altering epigenetic changes but its role as an epigenetic agent in cerebral stroke has not been much explored. Although curcumin possesses remarkable medicinal properties, the bioavailability of curcumin has limited its success in epigenetic studies and clinical trials. The present review is therefore designed to look into epigenetic mechanisms that could be induced with curcumin during stroke, along with its molecular designing with different moieties that may increase its bioavailability. Curcumin has been shown to be encapsulated in exosomes, nano-vesicles (<200 nm), thereby showing its therapeutic effects in brain diseases. Curcumin delivered through nanoparticles has been shown to be neuroregenerative but the use of nanoparticles in brain has limitations. Hence, curcumin-encapsulated exosomes along with curcumin-primed exosomes (exosomes released by curcumin-treated cells) are much needed to be explored to broadly look into their use as a novel therapy for stroke.

Comprehensive analysis of neonatal versus adult unilateral decortication in a mouse model using behavioral, neuroanatomical, and DNA microarray approaches

Previously, studying the development, especially of corticospinal neurons, it was concluded that the main compensatory mechanism after unilateral brain injury in rat at the neonatal stage was due in part to non-lesioned ipsilateral corticospinal neurons that escaped selection by axonal elimination or neuronal apoptosis. However, previous results suggesting compensatory mechanism in neonate brain were not correlated with high functional recovery. Therefore, what is the difference among neonate and adult in the context of functional recovery and potential mechanism(s) therein? Here, we utilized a brain unilateral decortication mouse model and compared motor functional recovery mechanism post-neonatal brain hemisuction (NBH) with adult brain hemisuction (ABH). Three analyses were performed: (1) Quantitative behavioral analysis of forelimb movements using ladder walking test; (2) neuroanatomical retrograde tracing analysis of unlesioned side corticospinal neurons; and (3) differential global gene expressions profiling in unlesioned-side neocortex (rostral from bregma) in NBH and ABH on a 8 × 60 K mouse whole genome Agilent DNA chip. Behavioral data confirmed higher recovery ability in NBH over ABH is related to non-lesional frontal neocortex including rostral caudal forelimb area. A first inventory of differentially expressed genes genome-wide in the NBH and ABH mouse model is provided as a resource for the scientific community.

Stroke genetics: a review and update

Stroke genetics includes several topics of clinical interest, including (1) molecular genetic variations affecting risk of monogenic stroke syndromes; (2) molecular genetic variations affecting risk of common stroke syndromes, sometimes with specific effects on risk of specific main types of stroke or subtypes of ischemic and hemorrhagic stroke; (3) genetics of conditions associated with stroke risk e.g. white matter hyperintensities, atrial fibrillation and hypertension; (4) hereditary causes of familial aggregation of stroke; (5) epigenetic impact on protein expression during acute brain injury; (6) genetic influence on stroke recovery; and (7) pharmacogenetics. Genetic research methods include candidate gene studies; Genome Wide Association Studies; family studies; RNA and protein analyses; and advanced computer-aided analytical methods to detect statistically significant associations. Several methods that could improve our knowledge of stroke genetics are being developed e.g.: Exome content analysis; Next-generation sequencing; Whole genome sequencing; and Epigenetics. During 2012-2014, several Single Nucleotide Polymorphisms (SNPs) have been related to common ischemic stroke risk. Certain SNPs have been associated with risk of specific ischemic stroke subtypes such as large vessel disease and cardiac embolism, particular subtypes of intracerebral hemorrhage (ICH), especially lobar ICH, and with prognosis after ICH. Large international studies on stroke recovery and exome content are ongoing. Advanced mathematical models have been used to study how several SNPs can act together and increase stroke risk burden. Such efforts require large numbers of patients and controls, which is achieved by co-operation in large international consortia such as the International Stroke Genetics Consortium. This overview includes an introduction to genetics, stroke genetics in general, and different genetic variations that may influence stroke risk. It presents some of the latest reports on stroke genetics published in high impact journals. The role of pharmacogenetics, the current clinical situation, and future prospects will also be discussed.

Epigenetic mechanisms of neuroplasticity and the implications for stroke recovery

Ischemic stroke is a devastating brain injury and an important cause of neurologic disability worldwide and across the lifespan. Despite the physical, social, and economic burdens of this disease there is only a single approved medicine for the treatment of acute stroke, and its use is unfortunately limited to the small fraction of patients presenting within the narrow therapeutic window. Following stroke, there is a period of plasticity involving cell genesis, axon growth, and synaptic modulation that is essential to spontaneous recovery. Treatments focusing on neuroprotection and enhancing recovery have been the focus of intense preclinical studies, but translation of these treatments into clinical use has been disappointing thus far. The important role of epigenetic mechanisms in disease states is becoming increasingly apparent, including in ischemic stroke. These regulators of gene expression are poised to be critical mediators of recovery following stroke. In this review we discuss evidence for the role of epigenetics in neuroplasticity and the implications for stroke recovery.

The functional role of long non-coding RNAs and epigenetics

Long non-coding RNAs (lncRNAs) are non-protein coding transcripts longer than 200 nucleotides. The post-transcriptional regulation is influenced by these lncRNAs by interfering with the microRNA pathways, involving in diverse cellular processes. The regulation of gene expression by lncRNAs at the epigenetic level, transcriptional and post-transcriptional level have been well known and widely studied. Recent recognition that lncRNAs make effects in many biological and pathological processes such as stem cell pluripotency, neurogenesis, oncogenesis and etc. This review will focus on the functional roles of lncRNAs in epigenetics and related research progress will be summarized.

Psychological stress as a modulator of functional recovery following spinal cord injury

There is strong evidence indicating that the social environment triggers changes to the psychological stress response and glucocorticoid receptor function. Considerable literature links the subsequent changes in stress resiliency to physical health. Here, converging evidence for the modulatory role of chronic psychological stress in the recovery process following spinal cord injury (SCI) is presented. Despite the considerable advances in SCI research, we are still unable to identify the causes of variability in patients' recovery following injury. We propose that individuals' past and present life experiences (in the form of stress exposure) may significantly modulate patients' outcome post-SCI. We propose a theoretical model to explain the negative impact of chronic psychological stress on physical and psychological recovery. The stress experienced in life prior to SCI and also as a result of the traumatic injury, could compromise glucocorticoid receptor sensitivity and function, and contribute to high levels of inflammation and apoptosis post-SCI, decreasing the tissue remaining at the injury site and undermining recovery of function. Both stress-induced glucocorticoid resistance and stress-induced epigenetic changes to the glucocorticoid receptor can modulate the nuclear factor-kappa B regulated inflammatory pathways and the Bcl-2 regulated apoptosis pathways. This model not only contributes to the theoretical understanding of the recovery process following injury, but also provides concrete testable hypotheses for future studies.

Xuezhikang therapy increases miR-33 expression in patients with low HDL-C levels

Background. MicroRNA-33a and -b (miR-33a/b) have been revealed to be posttranscriptional regulators of HDL metabolism. Xuezhikang (XZK) is a marked natural HDL-raising polypill. We aim to evaluate the effects of XZK on the expression of circulating miR-33a/b in patients with low plasma HDL-C levels. Methods. A total of 42 participating patients with low baseline levels of HDL cholesterol were assigned to receive an XZK capsule, 600 mg twice daily for 6 months. The expression of circulating miR-33a/b was detected at baseline and after XZK therapy measured with quantitative reverse-transcription (RT) polymerase chain reaction (PCR). Results. The mean (SD) HDL-C level after XZK treatment was 1.19 (0.13) mmol/L, representing an increase of 11.2% from baseline (P < 0.001). Q-PCR analysis of plasma miRNAs revealed an increase in relative miR-33a/b expression with XZK treatment. The miR-33a expression was raised from 0.81 to 1.73 (P = 0.012); miR-33b expression was increased from 1.2 to 2.75 (P < 0.001). The changes of miR-33a and miR-33b were inversely related to the posttreatment LDL-C levels (r = −0.37, P = 0.019; r = −0.33, P = 0.035, resp.). Conclusion. In patients with low HDL-C levels, XZK therapy raised plasma levels of miR-33a and miR-33b, which may inhibit cellular cholesterol export and limit the HDL-raising effect of XZK.

Convergent and divergent pathways decoding hierarchical additive mechanisms in treating cerebral ischemia-reperfusion injury

INTRODUCTION

Cerebral ischemia is considered to be a highly complex disease resulting from the complicated interplay of multiple pathways. Disappointedly, most of the previous studies were limited to a single gene or a single pathway. The extent to which all involved pathways are translated into fusing mechanisms of a combination therapy is of fundamental importance.

AIMS

We report an integrative strategy to reveal the additive mechanism that a combination (BJ) of compound baicalin (BA) and jasminoidin (JA) fights against cerebral ischemia based on variation of pathways and functional communities.

RESULTS

We identified six pathways of BJ group that shared diverse additive index from 0.09 to 1, which assembled broad cross talks from seven pathways of BA and 16 pathways of JA both at horizontal and vertical levels. Besides a total of 60 overlapping functions as a robust integration background among the three groups based on significantly differential subnetworks, additive mechanism with strong confidence by networks altered functions.

CONCLUSIONS

These results provide strong evidence that the additive mechanism is more complex than previously appreciated, and an integrative analysis of pathways may suggest an important paradigm for revealing pharmacological mechanisms underlying drug combinations.

Topics in transcriptional control of lipid metabolism: from transcription factors to gene-promoter polymorphisms

The central dogma of biology (DNA>>RNA>>Protein) has remained as an extremely useful scaffold to guide the study of molecular regulation of cellular metabolism. Molecular regulation of cellular metabolism has been pursued from an individual enzyme to a global assessment of protein function at the genomic (DNA), transcriptomic (RNA) and translation (Protein) levels. Details of a key role by inhibitory small RNAs and post-translational processing of cellular proteins on a whole cell/global basis are now just emerging. Below we emphasize the role of transcription factors (TF) in regulation of adipogenesis and lipogenesis. Additionally we have also focused on emerging additional TF that may also have hitherto unrecognized roles in adipogenesis and lipogenesis as compared to our present understanding. It is generally recognized that SNPs in structural genes can affect the final structure/function of a given protein. The implications of SNPs located in the non-transcribed promoter region on transcription have not been examined as extensively at this time. Here we have also summarized some emerging results on promoter SNPs for lipid metabolism and related cellular processes.

Circulating microRNAs as potential non-invasive biomarkers for the early detection of hypertension-related stroke

Hypertension is one of the most important risk and modifiable factors for stroke. Crucial in managing the cerebrovascular damage caused by long-lasting and inadequately treated hypertension is not only lowering arterial blood pressure but also early predicting subtypes of hypertension-related stroke and applying more effective interventions. Accumulating evidence suggested that circulating microRNAs (miRNAs) could be developed as biomarkers for early recognition of the onset of a variety of diseases. The role of miRNAs has been extensively reviewed, involving cardiac hypertrophy, hypertensive heart failure, kidney failure and renal fibrosis. miRNA research in stroke is still in its infancy, although there are few literatures reviewing the role of miRNAs in the processes of hypertension-related stroke. This review summarizes current advances in miRNAs regulation of critical pathogenic process underlying hypertension, ischemic stroke and hemorrhagic stroke, and highlights the potential of using circulating miRNAs as noninvasive biomarkers for the early detection of hypertension-related stroke.

Novel protective effects of histone deacetylase inhibition on stroke and white matter ischemic injury

Understanding how epigenetics influences the process and progress of a stroke could yield new targets and therapeutics for use in the clinic. Experimental evidence suggests that inhibitors of zinc-dependent histone deacetylases can protect neurons, axons, and associated glia from the devastating effects of oxygen and glucose deprivation. While the specific enzymes involved have yet to be clearly identified, there are hints from somewhat selective chemical inhibitors and also from the use of specific small hairpin RNAs to transiently knockdown protein expression. Neuroprotective mechanisms implicated thus far include the upregulation of extracellular glutamate clearance, inhibition of p53-mediated cell death, and maintenance of mitochondrial integrity. The histone deacetylases have distinct cellular and subcellular localizations, and discrete substrates. As a number of chemical inhibitors are already in clinical use for the treatment of cancer, repurposing for the stroke clinic should be expedited.

Folate and epigenetic mechanisms in neural tube development and defects

INTRODUCTION

Multiple genetic and epigenetic factors involved in central nervous system (CNS) development influence the incidence of neural tube defects (NTDs).

DISCUSSION

The beneficial effect of periconceptional folic acid on NTD prevention denotes a vital role for the single-carbon biochemical pathway in NTD genesis. Indeed, NTDs are associated with polymorphisms in a diversity of genes that encode folate pathway enzymes. Recent evidence suggests that CNS development and function, and consequently NTDs, are also associated with epigenetic mechanisms, many of which participate in the folate cycle and its input and output pathways. We provide an overview with select examples drawn from the authors' research.

Non-Coding RNAs as Potential Neuroprotectants against Ischemic Brain Injury

Over the past decade, scientific discoveries have highlighted new roles for a unique class of non-coding RNAs. Transcribed from the genome, these non-coding RNAs have been implicated in determining the biological complexity seen in mammals by acting as transcriptional and translational regulators. Non-coding RNAs, which can be sub-classified into long non-coding RNAs, microRNAs, PIWI-interacting RNAs and several others, are widely expressed in the nervous system with roles in neurogenesis, development and maintenance of the neuronal phenotype. Perturbations of these non-coding transcripts have been observed in ischemic preconditioning as well as ischemic brain injury with characterization of the mechanisms by which they confer toxicity. Their dysregulation may also confer pathogenic conditions in neurovascular diseases. A better understanding of their expression patterns and functions has uncovered the potential use of these riboregulators as neuroprotectants to antagonize the detrimental molecular events taking place upon ischemic-reperfusion injury. In this review, we discuss the various roles of non-coding RNAs in brain development and their mechanisms of gene regulation in relation to ischemic brain injury. We will also address the future directions and open questions for identifying promising non-coding RNAs that could eventually serve as potential neuroprotectants against ischemic brain injury.

Decreased cortical muscarinic M1 receptors in schizophrenia are associated with changes in gene promoter methylation, mRNA and gene targeting microRNA

Many studies have shown decreased cortical muscarinic M1 receptors (CHRM1) in schizophrenia (Sz), with one study showing Sz can be separated into two populations based on a marked loss of CHRM1 (-75%) in -25% of people (Def-Sz) with the disorder. To better understand the mechanism contributing to the loss of CHRM1 in Def-Sz, we measured specific markers of gene expression in the cortex of people with Sz as a whole, people differentiated into Def-Sz and people with Sz that do not have a deficit in cortical CHRM1 (Non-Def-Sz) and health controls. We now report that cortical CHRM1 gene promoter methylation and CHRM1 mRNA are decrease in Sz, Def-Sz and Non-Def-Sz but levels of the micro RNA (miR)-107, a CHRM1 targeting miR, are increased only in Def-Sz. We also report in vitro data strongly supporting the notion that miR-107 levels regulate CHRM1 expression. These data suggest there is a reversal of the expected inverse relationship between gene promoter methylation and CHRM1 mRNA in people with Sz and that a breakdown in gene promoter methylation control of CHRM1 expression is contributing to the global pathophysiology of the syndrome. In addition, our data argues that increased levels of at least one miR, miR-107, is contributing to the marked loss of cortical CHRM1 in Def-Sz and this may be a differentiating pathophysiology. These latter data continue to support the hypothesis that microRNAs (miRNA) have a role in the underlying neurobiology of Sz but argue they are differentially affected in subsets of people within that syndrome.

Emerging molecular targets for brain repair after stroke

The field of neuroprotection generated consistent preclinical findings of mechanisms of cell death but these failed to be translated into clinics. The approaches that combine the modulation of the inhibitory environment together with the promotion of intrinsic axonal outgrowth needs further work before combined therapeutic strategies will be transferable to clinic trials. It is likely that only when some answers have been found to these issues will our therapeutic efforts meet our expectations. Stroke is a clinically heterogeneous disease and combinatorial treatments require much greater work in pharmacological and toxicological testing. Advances in genetics and results of the Whole Human Genome Project (HGP) provided new unknown information in relation to stroke. Genetic factors are not the only determinants of responses to some diseases. It was recognized early on that "epigenetic" factors were major players in the aetiology and progression of many diseases like stroke. The major players are microRNAs that represent the best-characterized subclass of noncoding RNAs. Epigenetic mechanisms convert environmental conditions and physiological stresses into long-term changes in gene expression and translation. Epigenetics in stroke are in their infancy but offer great promise for better understanding of stroke pathology and the potential viability of new strategies for its treatment.

Epigenetics and the environment: in search of the "toleroasome" vital to execution of ischemic preconditioning

Activation and repression of gene expression are key features of ischemic tolerance. Converging lines of inquiry from several groups suggests that epigenetic proteins may transduce sublethal stresses, including bioenergetic or oxidative stress into durable (2-3 days) changes in gene expression that mediate ischemic tolerance. Here we discuss the potential mechanisms by which changes in cell state (e.g., ATP, NAD+, and oxygen) can modify specific targets including polycomb complexes, jumonji domain histone demethylases, and zinc and NAD-dependent histone decetylases and thus trigger an adaptive program. A major unanswered question is whether these proteins work in parallel or convergently as part of a "tolerosome" (tolero is the Latin word for tolerance), a multiprotein complex recruited to promoters or enhancers of specific genes, to mediate preconditioning. Whatever the case may be, epigenetic proteins are fertile targets for the treatment of stroke.

The effects of estrogen in ischemic stroke

Stroke is a leading cause of death and the most common cause of long-term disability in the USA. Women have a lower incidence of stroke compared with men throughout most of the lifespan which has been ascribed to protective effects of gonadal steroids, most notably estrogen. Due to the lower stroke incidence observed in pre-menopausal women and robust preclinical evidence of neuroprotective and anti-inflammatory properties of estrogen, researchers have focused on the potential benefits of hormones to reduce ischemic brain injury. However, as women age, they are disproportionately affected by stroke, coincident with the loss of estrogen with menopause. The risk of stroke in elderly women exceeds that of men and it is clear that in some settings estrogen can have pro-inflammatory effects. This review will focus on estrogen and inflammation and its interaction with aging.

Cardiovascular epigenetics: from DNA methylation to microRNAs

Epigenetic phenomena are defined as heritable mechanisms that establish and maintain mitotically stable patterns of gene expression without modifying the base sequence of DNA. The major epigenetic features of mammalian cells include DNA methylation, post-translational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (miRNAs). The impact of epigenetic mechanisms in cardiovascular pathophysiology is now emerging as a major player in the interface between genotype to phenotype variability. This topic of research has strict implications on disease development and progression, and opens up possible novel preventive strategies in cardiovascular disease. An important aspect of epigenetic mechanisms is that they are potentially reversible and may be influenced by nutritional-environmental factors and through gene-environment interactions, all of which have an important role in complex, multifactorial diseases such as those affecting the cardiovascular system. Gene expression regulation through the interplay of DNA methylation and histone modifications is well-established, although the knowledge about the function of epigenetic signatures in cardiovascular disease is still largely unexplored. The study of epigenetic markers is, therefore, a very promising frontier of science which may aid in a deeper understanding of molecular mechanisms underlying the modulation of gene expression in the biomolecule pathways linked to cardiovascular diseases. This review focuses on up-to-date knowledge pertaining to the role of epigenetics, from DNA methylation to miRNAs, in major cardiovascular diseases such as ischemic heart disease, hypertension, heart failure and stroke.

Role of a redox-based methylation switch in mRNA life cycle (pre- and post-transcriptional maturation) and protein turnover: implications in neurological disorders

Homeostatic synaptic scaling in response to neuronal stimulus or activation, and due to changes in cellular niche, is an important phenomenon for memory consolidation, retrieval, and other similar cognitive functions (Turrigiano and Nelson, 2004). Neurological disorders and cognitive disabilities in autism, Rett syndrome, schizophrenia, dementia, etc., are strongly correlated to alterations in protein expression (both synaptic and cytoplasmic; Cajigas et al., 2010). This correlation suggests that efficient temporal regulation of synaptic protein expression is important for synaptic plasticity. In addition, equilibrium between mRNA processing, protein translation, and protein turnover is a critical sensor/trigger for recording synaptic information, normal cognition, and behavior (Cajigas et al., 2010). Thus a regulatory switch, which controls the lifespan, maturation, and processing of mRNA, might influence cognition and adaptive behavior. Here, we propose a two part novel hypothesis that methylation might act as this suggested coordinating switch to critically regulate mRNA maturation at (1) the pre-transcription level, by regulating precursor-RNA processing into mRNA, via other non-coding RNAs and their influence on splicing phenomenon, and (2) the post-transcription level by modulating the regulatory functions of ribonucleoproteins and RNA binding proteins in mRNA translation, dendritic translocation as well as protein synthesis and synaptic turnover. DNA methylation changes are well recognized and highly correlated to gene expression levels as well as, learning and memory; however, RNA methylation changes are recently characterized and yet their functional implications are not established. This review article provides some insight on the intriguing consequences of changes in methylation levels on mRNA life-cycle. We also suggest that, since methylation is under the control of glutathione anti-oxidant levels (Lertratanangkoon et al., 1997), the redox status of neurons might be the central regulatory switch for methylation-based changes in mRNA processing, protein expression, and turnover. Lastly, we also describe experimental methods and techniques which might help researchers to evaluate the suggested hypothesis.

Genomic, transcriptomic, and epigenomic approaches to recovery after acquired brain injury

Genomics and its related fields have expanded rapidly, primarily because of the potential utility for clinical decision making and improving our understanding of the pathophysiology of complex conditions. The state of the science and technology associated with this field is such that current and future health care providers, when consulting with new patients about their acquired brain injury and options for rehabilitation, will use genetic information as a routine part of the process, which may include information received from a laboratory report that uses transcriptomic data, informs regarding patient prognosis, and makes recommendations for individualized therapeutic approaches to optimize recovery. This may sound like science fiction, but, in the field of oncology, it is the norm for breast cancer and, more recently, for colon cancer, with expansion to other types of cancer on the horizon as research data continue to contribute to the understanding of the pathophysiology of these conditions. Something similar for rehabilitation after acquired brain injury is much further off on the horizon. However, it is a possibility that will never be realized if the community of scientists and health care providers who work with these patients do not have the knowledge or expertise to embrace genomics and related approaches. This article discusses these approaches, some practical considerations for using such approaches, and what is currently published in this area with regard to brain injury.

Circulating microRNA-26a: potential predictors and therapeutic targets for non-hypertensive intracerebral hemorrhage

The mechanisms of non-hypertensive intracerebral hemorrhages (ICH), which may have different pathologies, mechanisms and genetic background from hypertensive ICH, are not clear. MicroRNAs are a new class of endogenous small RNAs that negatively regulate gene expression at the posttranscriptional level. Previous studies indicate that vascular smooth muscle cell (VSMC) function places important role in non-hypertensive ICH. MiRNA-26a, a pivotal regulator of VSMC function, is one of the cell-free miRNAs that could be detected in healthy humans. Therefore, we get the hypotheses that circulating miR-26a is a potential predictors and therapeutic targets for non-hypertensive ICH.

Non-coding RNA networks underlying cognitive disorders across the lifespan

Non-coding RNAs (ncRNAs) and their associated regulatory networks are increasingly being implicated in mediating a complex repertoire of neurobiological functions. Cognitive and behavioral processes are proving to be no exception. In this review, we discuss the emergence of many novel, diverse and rapidly expanding classes and subclasses of short and long ncRNAs. We briefly review the life cycles and molecular functions of these ncRNAs. We also examine how ncRNA circuitry mediates brain development, plasticity, stress responses and aging, and highlight its potential roles in the pathophysiology of cognitive disorders, including neural developmental and age-associated neurodegenerative diseases, as well as those that manifest throughout the lifespan.