An antagomir to microRNA Let7f promotes neuroprotection in an ischemic stroke model

Downregulation of miR-337-3p in hypoxia/reoxygenation neuroblastoma cells increases KCTD11 expression

Neurodegeneration is linked to the progressive loss of neural function and is associated with several diseases. Hypoxia is a hallmark in many of these diseases, and several therapies have been developed to treat this disease, including gene expression therapies that should be tightly controlled to avoid side effects. Cells experiencing hypoxia undergo a series of physiological responses that are induced by the activation of various transcription factors. Modulation of microRNA (miRNA) expression to alter transcriptional regulation has been demonstrated to be beneficial in treating multiple diseases, and in this study, we therefore explored potential miRNA candidates that could influence hypoxia-induced nerve cell death. Our data suggest that in mouse neuroblasts Neuro-2a cells with hypoxia/reoxygenation (H/R), miR-337-3p is downregulated to increase the expression of Potassium channel tetramerization domain containing 11 (KCTD11) and subsequently promote apoptosis. Here, we demonstrate for the first time that KCTD11 plays a role in the cellular response to hypoxia, and we also provide a possible regulatory mechanism by identifying the axis of miR-337-3p/KCTD11 as a promising candidate modulator of nerve cell survival after H/R exposure.

Brain-derived neuerotrophic factor and related mechanisms that mediate and influence progesterone-induced neuroprotection

Historically, progesterone has been studied significantly within the context of reproductive biology. However, there is now an abundance of evidence for its role in regions of the central nervous system (CNS) associated with such non-reproductive functions that include cognition and affect. Here, we describe mechanisms of progesterone action that support its brain-protective effects, and focus particularly on the role of neurotrophins (such as brain-derived neurotrophic factor, BDNF), the receptors that are critical for their regulation, and the role of certain microRNA in influencing the brain-protective effects of progesterone. In addition, we describe evidence to support the particular importance of glia in mediating the neuroprotective effects of progesterone. Through this review of these mechanisms and our own prior published work, we offer insight into why the effects of a progestin on brain protection may be dependent on the type of progestin (e.g., progesterone versus the synthetic, medroxyprogesterone acetate) used, and age, and as such, we offer insight into the future clinical implication of progesterone treatment for such disorders that include Alzheimer's disease, stroke, and traumatic brain injury.

Growth-suppressor microRNAs mediate synaptic overgrowth and behavioral deficits in Fragile X mental retardation protein deficiency

Abnormal neuronal and synapse growth is a core pathology resulting from deficiency of the Fragile X mental retardation protein (FMRP), but molecular links underlying the excessive synthesis of key synaptic proteins remain incompletely defined. We find that basal brain levels of the growth suppressor let-7 microRNA (miRNA) family are selectively lowered in FMRP-deficient mice and activity-dependent let-7 downregulation is abrogated. Primary let-7 miRNA transcripts are not altered in FMRP-deficiency and posttranscriptional misregulation occurs downstream of MAPK pathway induction and elevation of Lin28a, a let-7 biogenesis inhibitor. Neonatal restoration of brain let-7 miRNAs corrects hallmarks of FMRP-deficiency, including dendritic spine overgrowth and social and cognitive behavioral deficits, in adult mice. Blockade of MAPK hyperactivation normalizes let-7 miRNA levels in both brain and peripheral blood plasma from Fmr1 KO mice. These results implicate dysregulated let-7 miRNA biogenesis in the pathogenesis of FMRP-deficiency, and highlight let-7 miRNA-based strategies for future biomarker and therapeutic development.

miRNAs as modulators of neuroinflammation and excitotoxicity: Implications for stroke therapeutics

Stroke is a widespread neurological disorder associated with physical disabilities, mortality, and economic burden. In recent decades, substantial progress has been achieved in reducing the impact of this public health problem. However, further understanding of the pathophysiology of stroke and the underlying genetic pathways is required. The pathological mechanisms of stroke comprise multifaceted molecular cascades regulated by various microRNAs (miRNAs). An increasing number of studies have highlighted the role of miRNAs, which have received much attention during the last decades as an important class of post-transcriptional regulators. It was shown that miRNAs exert their role in the etiology of stroke via mediating excitotoxicity and neuroinflammation. Additionally, miRNAs could be helpful as non-invasive or minimally invasive biomarkers and therapeutic agents. Thus, the current review focused on the interplay of these miRNAs in stroke pathology to upgrade the existing therapeutic strategies.

Prenatal alcohol alters inflammatory signatures in enteric portal tissues following adult-onset cerebrovascular ischemic stroke

Prenatal alcohol exposure (PAE) impairs recovery from cerebrovascular ischemic stroke in adult rodents. Since the gut becomes dysbiotic following stroke, we assessed links between PAE and enteric portal inflammation. Adult control and PAE rat offspring received a unilateral endothelin-1-induced occlusion of the middle cerebral artery. Post-stroke behavioral disabilities and brain cytokines were assessed. Mesenteric adipose and liver transcriptomes were assessed from stroke-exposed and stroke-naive offspring. We identified, in the liver of stroke-naive animals, a moderate correlation between PAE and a gene network for inflammatory necroptosis. PAE inhibited the acute-phase brain inflammatory cytokine response to stroke. Post-stroke neurological function was correlated with an adipose gene network associated with B-lymphocyte differentiation and nuclear factor κB (NF-κB) signaling and with a liver pro-inflammatory gene network. Collectively, PAE inhibits brain inflammation but results in an inflammatory signature in enteric portal tissues after stroke, suggesting that PAE persistently and adversely impacts the gut-brain axis following adult-onset disease.

The aging ovary impairs acute stroke outcomes

In experimental stroke, ovariectomized (OVX) adult rats have larger infarct volumes and greater sensory-motor impairment as compared to ovary-intact females and is usually interpreted to indicate that ovarian hormones are neuroprotective for stroke. Previous work from our lab shows that middle-aged, acyclic reproductively senescent (RS) females have worse stroke outcomes as compared to adult (normally cycling) females. We hypothesized that if loss of ovarian estrogen is the critical determinant of stroke outcomes, then ovary-intact middle-aged acyclic females, who have reduced levels of estradiol, should have similar stroke outcomes as age-matched OVX. Instead, the data demonstrated that OVX RS animals showed better sensory-motor function after stroke and reduced infarct volume as compared to ovary-intact females. Inflammatory cytokines were decreased in the aging ovary after stroke as compared to non-stroke shams, which led to the hypothesis that immune cells may be extravasated from the ovaries post-stroke. Flow cytometry indicated reduced overall T cell populations in the aging ovary after middle cerebral artery occlusion (MCAo), with a paradoxical increase in regulatory T cells (Tregs) and M2-like macrophages. Moreover, in the brain, OVX RS animals showed increased Tregs, increased M2-like macrophages, and increased MHC II + cells as compared to intact RS animals, which have all been shown to be correlated with better prognosis after stroke. Depletion of ovary-resident immune cells after stroke suggests that there may be an exaggerated response to ischemia and possible increased burden of the inflammatory response via extravasation of these cells into circulation. Increased anti-inflammatory cells in the brain of OVX RS animals further supports this hypothesis. These data suggest that stroke severity in aging females may be exacerbated by the aging ovary and underscore the need to assess immunological changes in this organ after stroke.

Sex differences in cognitive impairment after focal ischemia in middle-aged rats and the effect of iv miR-20a-3p treatment

Stroke is a major cause of death and disability worldwide and is also a leading cause of vascular dementia and Alzheimer's disease, with older women experiencing accelerated decline. Our previous studies show that intravenous (iv) injections of miR-20a-3p, a small noncoding RNA (miRNA) delivered after stroke improves acute stroke outcomes in middle-aged male and female rats. The present study tested whether mir-20a-3p treatment would also ameliorate stroke-induced cognitive decline in the chronic phase. Acyclic middle-aged females and age-matched male Sprague Dawley rats were subjected to middle cerebral artery occlusion using endothelin-1 or sham surgery, and treated iv with miR-20a-3p mimics or scrambled oligos at 4 hours, 24 hours, and 70 days post-stroke. Stroke resulted in a significant sensory motor deficit, while miR-20a-3p treatment reduced these deficits in both sexes. Cognitive impairment was assessed periodically for 3 months after stroke using contextual fear conditioning and the novel object recognition task. Overall, the tests of associative and episodic memory were affected by focal ischemia only in female rats, and miR-20a-3p ameliorated the rate of decline.

Genetic polymorphisms of pri-let-7f, gene-environment and gene-gene interactions, and associations with ischemic stroke risk in Liaoning Province

OBJECTIVE

The incidence of stroke has been rising annually and investigations into traditional risk factors have led to increased attention on genetic factors. In this study, we focused on the pri-let-7f gene, and investigated the association between pri-let-7f gene polymorphisms and ischemic stroke (IS).

METHODS

This case-control study included 1803 patients and 1456 healthy controls of Han ethnicity living in Liaoning Province. We carried out genotyping analysis of two loci, pri-let-7f-1 rs10739971 and pri-let-7f-2 rs17276588, and performed statistical analysis controlling for confounding factors by logistic regression.

RESULTS

The A alleles and AA genotypes of both loci were significantly associated with an increased risk of IS. Variant genotypes of rs17276588 may also increase the risk of IS in females with alcohol intake. Gene-gene interaction analysis showed combined effects of mutations in both these single nucleotide polymorphisms (SNPs).

CONCLUSIONS

This study demonstrated an association between pri-let-7f SNPs and IS, providing potential latent biomarkers for the risk of IS. However, more detailed studies are needed to clarify these results.

Genetic variants in the promoters of let-7 are associated with the risk and age at onset of ischemic stroke: A case control study

PURPOSE

Let-7 family members serve as crucial regulatory molecules in the pathogenesis of ischemic stroke. We predicted that genetic variations in the let-7 family's promoters may be linked to the risk of ischemic stroke. The connection of rs10877887 and rs13293512 in the let-7 family promoters with liability to ischemic stroke was explored in this study.

PATIENTS AND METHODS

Clinical data and peripheral blood samples were collected from 914 ischemic stroke patients and 836 controls in this case-control study. All statistical analyses were carried out using SPSS.

RESULTS

Our analysis results reveal that the rs10877887 TC+CC genotype in the dominant model is associated with a lower risk of ischemic stroke than the TT genotype. Individuals with heterozygous TC or homozygous CC genotypes in the male population showed higher odds of ischemic stroke than those with the wild TT genotype in rs13293512 analysis. Furthermore, there existed a multiplicative interaction between the rs10877887 C allele and the rs13293512 T allele. In the presence of the rs13293512 T allele, the effect of the rs10877887 C allele on ischemic stroke risk was increased. Similarly, in the presence of the rs10877887 C allele, the outcome of the rs13293512 T allele on ischemic stroke risk was elevated. In addition, the rs13293512 CC genotype seemed to lead to an earlier onset of ischemic stroke.

CONCLUSION

Our findings indicated that these two SNPs might have a joint role in IS and could potentially act as risk markers. Detecting let-7 promoter polymorphisms could raise awareness of the risk of IS, which directed individuals with risk alleles to have regular checks at an appropriate frequency to avoid developing the disease.

Internal m7G methylation: A novel epitranscriptomic contributor in brain development and diseases

In recent years, N7-methylguanosine (m7G) methylation, originally considered as messenger RNA (mRNA) 5' caps modifications, has been identified at defined internal positions within multiple types of RNAs, including transfer RNAs, ribosomal RNAs, miRNA, and mRNAs. Scientists have put substantial efforts to discover m7G methyltransferases and methylated sites in RNAs to unveil the essential roles of m7G modifications in the regulation of gene expression and determine the association of m7G dysregulation in various diseases, including neurological disorders. Here, we review recent findings regarding the distribution, abundance, biogenesis, modifiers, and functions of m7G modifications. We also provide an up-to-date summary of m7G detection and profile mapping techniques, databases for validated and predicted m7G RNA sites, and web servers for m7G methylation prediction. Furthermore, we discuss the pathological roles of METTL1/WDR-driven m7G methylation in neurological disorders. Last, we outline a roadmap for future directions and trends of m7G modification research, particularly in the central nervous system.

Genetic variation within the pri-let-7f-2 in the X chromosome predicting stroke risk in a Chinese Han population from Liaoning, China: From a case-control study to a new predictive nomogram

Background and objectives

Stroke is the most common cause of disability and the second cause of death worldwide. Therefore, there is a need to identify patients at risk of developing stroke. This case-control study aimed to create and verify a gender-specific genetic signature-based nomogram to facilitate the prediction of ischemic stroke (IS) risk using only easily available clinical variables.

Materials and methods

A total of 1,803 IS patients and 1,456 healthy controls from the Liaoning province in China (Han population) were included which randomly divided into training cohort (70%) and validation cohort (30%) using the sample function in R software. The distribution of the pri-let-7f-2 rs17276588 variant genotype was analyzed. Following genotyping analysis, statistical analysis was used to identify relevant features. The features identified from the multivariate logistic regression, the least absolute shrinkage and selection operator (LASSO) regression, and univariate regression were used to create a multivariate prediction nomogram model. A calibration curve was used to determine the discrimination accuracy of the model in the training and validation cohorts. External validity was also performed.

Results

The genotyping analysis identified the A allele as a potential risk factor for IS in both men and women. The nomogram identified the rs17276588 variant genotype and several clinical parameters, including age, diabetes mellitus, body mass index (BMI), hypertension, history of alcohol use, history of smoking, and hyperlipidemia as risk factors for developing IS. The calibration curves for the male and female models showed good consistency and applicability.

Conclusion

The pri-let-7f-2 rs17276588 variant genotype is highly linked to the incidence of IS in the northern Chinese Han population. The nomogram we devised, which combines genetic fingerprints and clinical data, has a lot of promise for predicting the risk of IS within the Chinese Han population.

Cerebral edema after ischemic stroke: Pathophysiology and underlying mechanisms

Ischemic stroke is associated with increasing morbidity and has become the main cause of death and disability worldwide. Cerebral edema is a serious complication arising from ischemic stroke. It causes an increase in intracranial pressure, rapid deterioration of neurological symptoms, and formation of cerebral hernia, and is an important risk factor for adverse outcomes after stroke. To date, the detailed mechanism of cerebral edema after stroke remains unclear. This limits advances in prevention and treatment strategies as well as drug development. This review discusses the classification and pathological characteristics of cerebral edema, the possible relationship of the development of cerebral edema after ischemic stroke with aquaporin 4, the SUR1-TRPM4 channel, matrix metalloproteinase 9, microRNA, cerebral venous reflux, inflammatory reactions, and cerebral ischemia/reperfusion injury. It also summarizes research on new therapeutic drugs for post-stroke cerebral edema. Thus, this review provides a reference for further studies and for clinical treatment of cerebral edema after ischemic stroke.

Some miRNA expressions and their targets in ischemic stroke

Ischemic stroke (IS) is a global health challenge leading to life-long disabilities or the deaths of patients. IS is a complex disease where genetic and environmental factors are both concerned with the pathophysiology of the condition. Here, we aimed to investigate various microRNA (miRNA) expressions and their targets in IS. A rapid and accurate diagnosis of acute IS is important to perform appropriate treatment. Therefore, there is a need for a more rapid and simple tool to carry out an acute diagnosis of IS. miRNAs are small RNA molecules serving as precious biomarkers due to their easy detection and stability in blood samples. The present systematic review aimed to summarize previous studies investigating several miRNA expressions and their targets in IS.

Relationship between serum insulin-like growth factor 1 levels and ischaemic stroke: a systematic review and meta-analysis

OBJECTIVE

To assess the association of insulin-like growth factor 1 (IGF-1) with the risk of incident ischaemic stroke and outcome after ischaemic stroke.

DESIGN

A systematic review of primary studies.

SETTING

Hospitals in Western Sweden, Italy, China and Denmark.

METHODS

A search was carried out in eligible studies in electronic databases (PubMed, Scopus, Embase, China National Knowledge Infrastructure and Web of Science) updated to 29 December 2020. The relevant data were extracted in order to conduct the meta-analysis. Review Manager V.5.2 was used to pool data and calculate the mean difference (MD) and its 95% CI. Heterogeneity, subgroup analysis, sensitivity analysis and publication bias were also performed in this meta-analysis.

RESULTS

A total of 2277 patients were included in 17 studies. This meta-analysis indicated that higher serum IGF-1 levels were significantly correlated with less risk of ischaemic stroke (MD=-45.32 95% CI -63.70 to -26.94], p < 0.00001, I²=99%) and better improvement of outcome after ischaemic stroke (MD=27.52, 95% CI 3.89 to 51.14, p=0.02, I²=96%). According to subgroup analysis, heterogeneity comes from country, sample size, male and the time from symptom onset to blood collection. Sensitivity analysis showed that there was no significant influence of any individual study on the pooled MD. The effect of high heterogeneity on result credibility was eliminated when four included studies were merged (MD=-30.32, 95% CI -36.52 to -24.11, p< 0.00001, I²=0%). Moreover, no potential publication bias was discovered in this meta-analysis.

CONCLUSION

Higher serum IGF-1 was significantly correlated with a lower risk of ischaemic stroke. In view of the high degree of heterogeneity, it may need more studies to confirm the prognostic value of serum IGF-1 levels in ischaemic stroke and explore the sources of heterogeneity.

Systematic review: Association between circulating microRNA expression & stroke

This systematic review aimed to establish the range and quality of clinical and preclinical evidence supporting the association of individual microRNAs, and the use of microRNA expression in the diagnosis and prognosis of ischaemic or haemorrhagic stroke. Electronic databases were searched from 1993 to October 2021, using key words relevant to concepts of stroke and microRNA. Studies that met specific inclusion and exclusion criteria were selected for data extraction. To minimise erroneous associations, findings were restricted to microRNAs reported to change in more than two independent studies. Of the papers assessed, 155 papers reported a change in microRNA expression observed in more than two independent studies. In ischaemic studies, two microRNAs were consistently differentially expressed in clinical samples (miR-29b & miR-146a) and four were altered in preclinical samples (miR-137, miR-146a, miR-181b & miR-223-3p). Across clinical and preclinical haemorrhagic studies, four microRNAs were downregulated consistently (miR-26a, miR-126, miR-146a & miR-155). Across included studies, miR-126 and miR-146a were the only two microRNAs to be differentially expressed in clinical and preclinical cohorts following ischaemic or haemorrhagic stroke. Further studies, employing larger populations with consistent methodologies, are required to validate the true clinical value of circulating microRNAs as biomarkers of ischaemic and haemorrhagic stroke.

Functional Assessment of Stroke-Induced Regulation of miR-20a-3p and Its Role as a Neuroprotectant

MicroRNAs have gained popularity as a potential treatment for many diseases, including stroke. This study identifies and characterizes a specific member of the miR-17-92 cluster, miR-20a-3p, as a possible stroke therapeutic. A comprehensive microRNA screening showed that miR-20a-3p was significantly upregulated in astrocytes of adult female rats, which typically have better stroke outcomes, while it was profoundly downregulated in astrocytes of middle-aged females and adult and middle-aged males, groups that typically have more severe stroke outcomes. Assays using primary human astrocytes and neurons show that miR-20a-3p treatment alters mitochondrial dynamics in both cell types. To assess whether stroke outcomes could be improved by elevating astrocytic miR-20a-3p, we created a tetracycline (Tet)-induced recombinant adeno-associated virus (rAAV) construct where miR-20a-3p was located downstream a glial fibrillary acidic protein promoter. Treatment with doxycycline induced miR-20-3p expression in astrocytes, reducing mortality and modestly improving sensory motor behavior. A second Tet-induced rAAV construct was created in which miR-20a-3p was located downstream of a neuron-specific enolase (NSE) promoter. These experiments demonstrate that neuronal expression of miR-20a-3p is vastly more neuroprotective than astrocytic expression, with animals receiving the miR-20a-3p vector showing reduced infarction and sensory motor improvement. Intravenous injections, which are a therapeutically tractable treatment route, with miR-20a-3p mimic 4 h after middle cerebral artery occlusion (MCAo) significantly improved stroke outcomes including infarct volume and sensory motor performance. Improvement was not observed when miR-20a-3p was given immediately or 24 h after MCAo, identifying a unique delayed therapeutic window. Overall, this study identifies a novel neuroprotective microRNA and characterizes several key pathways by which it can improve stroke outcomes.

The Role of miR-20 in Health and Disease of the Central Nervous System

Current understanding of the mechanisms underlying central nervous system (CNS) injury is limited, and traditional therapeutic methods lack a molecular approach either to prevent acute phase or secondary damage, or to support restorative mechanisms in the nervous tissue. microRNAs (miRNAs) are endogenous, non-coding RNA molecules that have recently been discovered as fundamental and post-transcriptional regulators of gene expression. The capacity of microRNAs to regulate the cell state and function through post-transcriptionally silencing hundreds of genes are being acknowledged as an important factor in the pathophysiology of both acute and chronic CNS injuries. In this study, we have summarized the knowledge concerning the pathophysiology of several neurological disorders, and the role of most canonical miRNAs in their development. We have focused on the miR-20, the miR-17~92 family to which miR-20 belongs, and their function in the normal development and disease of the CNS.

Noncoding RNA as Diagnostic and Prognostic Biomarkers in Cerebrovascular Disease

Noncoding RNAs (ncRNAs), such as microRNAs, long noncoding RNAs, and circular RNAs, play an important role in the pathophysiology of cerebrovascular diseases (CVDs). They are effectively detectable in body fluids, potentially suggesting new biomarkers for the early detection and prognosis of CVDs. In this review, the physiological functions of circulating ncRNAs and their potential role as diagnostic and prognostic markers in patients with cerebrovascular diseases are discussed, especially in acute ischemic stroke, subarachnoid hemorrhage, and moyamoya disease.

Interactions of Glutamate and Gamma Amino Butyric Acid with the Insulin-like growth factor system in Traumatic Brain Injury (TBI) and/or Cardiovascular Accidents (CVA or stroke): A systematic review

The brain maintains homeostasis of neural excitation in part through the receptor-mediated signaling of Glutamate (Glu) and Gamma Amino Butyric Acid (GABA), but localized injuries cause cellular release of excess Glu leading to neurotoxicity. The literature strongly supports the role of Insulin-like growth factor-1 (IGF-1) in adult brain neuroprotection and repair, and research supporting the existence of molecular interactions between Glu, GABA, and IGF-1 in vitro and in normal animals raises the question of whether and/or how the Glu/GABA system interacts with IGF-1 post-injury. This systematic review was undertaken to explore works addressing this question among adults with a history of traumatic brain injury (TBI) and/or cerebrovascular accident (CVA; stroke). The literature was searched for human and animal studies and only four animal papers met inclusion criteria. The SYRCLE criteria was used to evaluate risk of bias; results varied between categories and papers. All the included studies, one on TBI and three on stroke, supported the molecular relationship between the excitatory and IGF-1 systems; two studies provided direct, detailed molecular evidence. The results point to the importance of research on the role of this protective system in pathological brain injury; a hypothetical proposal for future studies is presented.

Optical Modalities for Research, Diagnosis, and Treatment of Stroke and the Consequent Brain Injuries

Stroke is the second most common cause of death and third most common cause of disability worldwide. Therefore, it is an important disease from a medical standpoint. For this reason, various studies have developed diagnostic and therapeutic techniques for stroke. Among them, developments and applications of optical modalities are being extensively studied. In this article, we explored three important optical modalities for research, diagnostic, and therapeutics for stroke and the brain injuries related to it: (1) photochemical thrombosis to investigate stroke animal models; (2) optical imaging techniques for in vivo preclinical studies on stroke; and (3) optical neurostimulation based therapy for stroke. We believe that an exploration and an analysis of previous studies will help us proceed from research to clinical applications of optical modalities for research, diagnosis, and treatment of stroke.

MicroRNA miR-21 Decreases Post-stroke Brain Damage in Rodents

Due to their role in controlling translation, microRNAs emerged as novel therapeutic targets to modulate post-stroke outcomes. We previously reported that miR-21 is the most abundantly induced microRNA in the brain of rodents subjected to preconditioning-induced cerebral ischemic tolerance. We currently show that intracerebral administration of miR-21 mimic decreased the infarct volume and promoted better motor function recovery in adult male and female C57BL/6 mice subjected to transient middle cerebral artery occlusion. The miR-21 mimic treatment is also efficacious in aged mice of both sexes subjected to focal ischemia. Mechanistically, miR-21 mimic treatment decreased the post-ischemic levels of several pro-apoptotic and pro-inflammatory RNAs, which might be responsible for the observed neuroprotection. We further observed post-ischemic neuroprotection in adult mice administered with miR-21 mimic intravenously. Overall, the results of this study implicate miR-21 as a promising candidate for therapeutic translation after stroke.

Cerebral derailment after myocardial infarct: mechanisms and effects of the signaling from the ischemic heart to brain

Myocardial infarction (MI) is the leading cause of death among ischemic heart diseases and is associated with several long-term cardiovascular complications, such as angina, re-infarction, arrhythmias, and heart failure. However, MI is frequently accompanied by non-cardiovascular multiple comorbidities, including brain disorders such as stroke, anxiety, depression, and cognitive impairment. Accumulating experimental and clinical evidence suggests a causal relationship between MI and stroke, but the precise underlying mechanisms have not yet been elucidated. Indeed, the risk of stroke remains a current challenge in patients with MI, in spite of the improvement of medical treatment among this patient population has reduced the risk of stroke. In this review, the effects of the signaling from the ischemic heart to the brain, such as neuroinflammation, neuronal apoptosis, and neurogenesis, and the possible actors mediating these effects, such as systemic inflammation, immunoresponse, extracellular vesicles, and microRNAs, are discussed.

Noncoding RNA crosstalk in brain health and diseases

The mammalian brain expresses several classes of noncoding RNAs (ncRNAs), including long ncRNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs). These ncRNAs play vital roles in regulating cellular processes by RNA/protein scaffolding, sponging and epigenetic modifications during the pathophysiological conditions, thereby controlling transcription and translation. Some of these functions are the result of crosstalk between ncRNAs to form a competitive endogenous RNA network. These intricately organized networks comprise lncRNA/miRNA, circRNA/miRNA, or lncRNA/miRNA/circRNA, leading to crosstalk between coding and ncRNAs through miRNAs. The miRNA response elements predominantly mediate the ncRNA crosstalk to buffer the miRNAs and thereby fine-tune and counterbalance the genomic changes and regulate neuronal plasticity, synaptogenesis and neuronal differentiation. The perturbed levels and interactions of the ncRNAs could lead to pathologic events like apoptosis and inflammation. Although the regulatory landscape of the ncRNA crosstalk is still evolving, some well-known examples such as lncRNA Malat1 sponging miR-145, circRNA CDR1as sponging miR-7, and lncRNA Cyrano and the circRNA CDR1as regulating miR-7, has been shown to affect brain function. The ability to manipulate these networks is crucial in determining the functional outcome of central nervous system (CNS) pathologies. The focus of this review is to highlights the interactions and crosstalk of these networks in regulating pathophysiologic CNS function.

Mice and Rats Exhibit Striking Inter-species Differences in Gene Response to Acute Stroke

Neuroprotection in acute stroke has not been successfully translated from animals to humans. Animal research on promising agents continues largely in rats and mice which are commonly available to researchers. However, controversies continue on the most suitable species to model the human situation. Generally, putative agents seem less effective in mice as compared with rats. We hypothesized that this may be due to inter-species differences in stroke response and that this might be manifest at a genetic level. Here we used whole-genome microarrays to examine the differential gene regulation in the ischemic penumbra of mice and rats at 2 and 6 h after permanent middle cerebral artery occlusion (pMCAO; Raw microarray CEL data files are available in the GEO database with an accession number GSE163654). Differentially expressed genes (adj. p ≤ 0.05) were organized by hierarchical clustering, correlation plots, Venn diagrams and pathway analyses in each species and at each time-point. Emphasis was placed on genes already known to be associated with stroke, including validation by RT-PCR. Gene expression patterns in the ischemic penumbra differed strikingly between the species at both 2 h and 6 h. Nearly 90% of significantly regulated genes and most pathways modulated by ischemia differed between mice and rats. These differences were evident globally, among stroke-associated genes, immediate early genes, genes implicated in stress response, inflammation, neuroprotection, ion channels, and signal transduction. The findings of this study may have significant implications for the choice of species for screening putative stroke therapies.

MicroRNAs and Long Noncoding RNAs as Novel Therapeutic Targets in Estrogen Receptor-Positive Breast and Ovarian Cancers

Aromatase inhibitors (AIs) such as anastrozole, letrozole, and exemestane have shown to prevent metastasis and angiogenesis in estrogen receptor (ER)-positive breast and ovarian tumors. They function primarily by reducing estrogen production in ER-positive post-menopausal breast and ovarian cancer patients. Unfortunately, current AI-based therapies often have detrimental side-effects, along with acquired resistance, with increased cancer recurrence. Thus, there is an urgent need to identify novel AIs with fewer side effects and improved therapeutic efficacies. In this regard, we and others have recently suggested noncoding RNAs (ncRNAs), specifically microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), as potential molecular targets for utilization in modulating cancer hallmarks and overcoming drug resistance in several cancers, including ER-positive breast and ovarian cancer. Herein, we describe the disruptive functions of several miRNAs and lncRNAs seen in dysregulated cancer metabolism, with a focus on the gene encoding for aromatase (CYP19A1 gene) and estrogen synthesis as a novel therapeutic approach for treating ER-positive breast and ovarian cancers. Furthermore, we discuss the oncogenic and tumor-suppressive roles of several miRNAs (oncogenic miRNAs: MIR125b, MIR155, MIR221/222, MIR128, MIR2052HG, and MIR224; tumor-suppressive miRNAs: Lethal-7f, MIR27B, MIR378, and MIR98) and an oncogenic lncRNA (MIR2052HG) in aromatase-dependent cancers via transcriptional regulation of the CYP19A1 gene. Additionally, we discuss the potential effects of dysregulated miRNAs and lncRNAs on the regulation of critical oncogenic molecules, such as signal transducer, and activator of transcription 3, β-catenin, and integrins. The overall goal of this review is to stimulate further research in this area and to facilitate the development of ncRNA-based approaches for more efficacious treatments of ER-positive breast and ovarian cancer patients, with a slight emphasis on associated treatment–delivery mechanisms.

Epigenetics Mechanisms in Ischemic Stroke: A Promising Avenue?

Stroke has emerged as the second most common cause of mortality worldwide and is a major public health problem. It is a multi-factorial disease and genetics plays an important role in its pathophysiology, however, mechanisms of genome involvement in the disease remain unclear. Both genetic and epigenetic mechanisms could play a role in the development of stroke disease. Although epigenetic characteristics may also be heritable, they can be modified during the lifetime under different environmental exposure in response to lifestyle. Recent studies provide clear evidence that epigenetic factors play an important role in the pathological mechanisms leading to an elevated risk of cardiovascular diseases and stroke. Epigenetic changes are reversible therefore; studying epigenetic factors may serve as a marker for disease progression, biomarker for disease diagnosis, and development of novel targets for therapeutic intervention. Identifying the factors which predispose the risk of stroke provides information for the mechanism of stroke and the design of new drug targets where epigenetic modifications play a significant role. Epigenetic modifications play an essential role in a large variety of multifactorial diseases. This review will focus on the evidence that epigenetic mechanisms play a crucial role in the pathophysiology of ischemic stroke.

Potential Therapies for Cerebral Edema After Ischemic Stroke: A Mini Review

Stroke is the leading cause of global mortality and disability. Cerebral edema and intracranial hypertension are common complications of cerebral infarction and the major causes of mortality. The formation of cerebral edema includes three stages (cytotoxic edema, ionic edema, and vasogenic edema), which involve multiple proteins and ion channels. A range of therapeutic agents that successfully target cerebral edema have been developed in animal studies, some of which have been assessed in clinical trials. Herein, we review the mechanisms of cerebral edema and the research progress of anti-edema therapies for use after ischemic stroke.

New Mechanistic Insights, Novel Treatment Paradigms, and Clinical Progress in Cerebrovascular Diseases

The past decade has brought tremendous progress in diagnostic and therapeutic options for cerebrovascular diseases as exemplified by the advent of thrombectomy in ischemic stroke, benefitting a steeply increasing number of stroke patients and potentially paving the way for a renaissance of neuroprotectants. Progress in basic science has been equally impressive. Based on a deeper understanding of pathomechanisms underlying cerebrovascular diseases, new therapeutic targets have been identified and novel treatment strategies such as pre- and post-conditioning methods were developed. Moreover, translationally relevant aspects are increasingly recognized in basic science studies, which is believed to increase their predictive value and the relevance of obtained findings for clinical application.This review reports key results from some of the most remarkable and encouraging achievements in neurovascular research that have been reported at the 10th International Symposium on Neuroprotection and Neurorepair. Basic science topics discussed herein focus on aspects such as neuroinflammation, extracellular vesicles, and the role of sex and age on stroke recovery. Translational reports highlighted endovascular techniques and targeted delivery methods, neurorehabilitation, advanced functional testing approaches for experimental studies, pre-and post-conditioning approaches as well as novel imaging and treatment strategies. Beyond ischemic stroke, particular emphasis was given on activities in the fields of traumatic brain injury and cerebral hemorrhage in which promising preclinical and clinical results have been reported. Although the number of neutral outcomes in clinical trials is still remarkably high when targeting cerebrovascular diseases, we begin to evidence stepwise but continuous progress towards novel treatment options. Advances in preclinical and translational research as reported herein are believed to have formed a solid foundation for this progress.

Sex differences in stroke outcome correspond to rapid and severe changes in gut permeability in adult Sprague-Dawley rats

BACKGROUND

Sex differences in experimental stroke outcomes are well documented, such that adult males have a greater infarct volume, increased stroke-induced mortality, and more severe sensory-motor impairment. Based on recent evidence that the gut is an early responder to stroke, the present study tested the hypothesis that sex differences in stroke severity will be accompanied by rapid and greater permeability of the gut-blood barrier and gut dysbiosis in males as compared to females.

METHOD

Male and female Sprague-Dawley rats (5-7 months of age) were subject to endothelin (ET)-1-induced middle cerebral artery occlusion (MCAo). Sensory-motor tests were conducted pre- and 2 days after MCAo. Gut permeability was assessed in serum samples using biomarkers of gut permeability as well as functional assays using size-graded dextrans. Histological analysis of the gut was performed with H&E staining, periodic acid-Schiff for mucus, and immunohistochemistry for the tight junction protein, ZO-1. Fecal samples obtained pre- and post-stroke were analyzed for bacterial taxa and short-chain fatty acids (SCFAs).

RESULTS

After stroke, males displayed greater mortality, worse sensory-motor deficit, and higher serum levels of proinflammatory cytokines IL-17A, MCP-1, and IL-5 as compared to females. MCAo-induced gut permeability was rapid and severe in males as indicated by dextran extravasation from the gut to the blood in the hyperacute (< 2 h) and early acute (2 days) phase of stroke. This was accompanied by dysmorphology of the gut villi and dysregulation of the tight junction protein ZO-1 in the acute phase. Fecal 16s sequencing showed no differences in bacterial diversity in the acute phase of stroke. Predictive modeling indicated that markers of gut permeability were associated with acute sensory-motor impairment and infarct volume.

CONCLUSIONS

These data show that extensive leakiness of the gut barrier is associated with severe post-stroke disability and suggest that reinforcing this barrier may improve stroke outcomes.

let7f‑5p attenuates inflammatory injury in in vitro pneumonia models by targeting MAPK6

Pneumonia accounts for ~1.3 million mortalities in children per year worldwide. MicroRNAs are implicated in several diseases, including cancer and pneumonia; however, the role of let7f-5p in pneumonia is not completely understood. In the present study, lipopolysaccharide (LPS) was used to establish an in vitro pneumonia model in A549 and WI-38 cells. The reverse transcription-quantitative PCR (RT-qPCR) and western blotting results demonstrated that let7f-5p expression levels were significantly decreased, whereas MAPK6 expression levels were significantly increased in the peripheral venous blood of patients with pneumonia and in LPS-induced A549 and WI-38 cells compared with healthy volunteers and control cells, respectively. Furthermore, the dual-luciferase reporter assay demonstrated that let7f-5p targeted the 3′-untranslated region of MAPK6. The ELISA and RT-qPCR results demonstrated that let7f-5p mimic ameliorated LPS-induced inflammatory injury in A549 and WI-38 cells, as demonstrated by decreased expression levels of proinflammatory cytokines, including TNF-α and IL-6. In addition, the Cell Counting Kit-8 assay results indicated that let7f-5p mimic ameliorated LPS-induced reductions in cell viability, and the western blotting results demonstrated that let7f-5p mimic reversed LPS-induced activation of the STAT3 signaling pathway. Notably, the aforementioned let7f-5p-mediated effects were reversed by MAPK6 overexpression. Collectively, the results of the present study suggested that let7f-5p inhibited inflammation by targeting MAPK6 in the in vitro pneumonia model, thus let7f-5p may serve as a potential novel therapeutic target for pneumonia.

Emerging roles for noncoding RNAs in female sex steroids and reproductive disease

The "central dogma" of molecular biology, that is, that DNA blueprints encode messenger RNAs which are destined for translation into protein, has been challenged in recent decades. In actuality, a significant portion of the genome encodes transcripts that are transcribed into functional RNA. These noncoding RNAs (ncRNAs), which are not transcribed into protein, play critical roles in a wide variety of biological processes. A growing body of evidence derived from mouse models and human data demonstrates that ncRNAs are dysregulated in various reproductive pathologies, and that their expression is essential for female gametogenesis and fertility. Yet in many instances it is unclear how dysregulation of ncRNA expression leads to a disease process. In this review, we highlight new observations regarding the roles of ncRNAs in the pathogenesis of disordered female steroid hormone production and disease, with an emphasis on long noncoding RNAs (lncRNAs) and microRNAs (miRNAs). We will focus our discussion in the context of three ovarian disorders which are characterized in part by altered steroid hormone biology - diminished ovarian reserve, premature ovarian insufficiency, and polycystic ovary syndrome. We will also discuss the limitations and challenges faced in studying noncoding RNAs and sex steroid hormone production. An enhanced understanding of the role of ncRNAs in sex hormone regulatory networks is essential in order to advance the development of potential diagnostic markers and therapeutic targets for diseases, including those in reproductive health. Our deepened understanding of ncRNAs has the potential to uncover new applications and therapies; however, in many cases, the next steps will involve distinguishing critical ncRNAs from those which are merely changing in response to a particular disease state, or which are altogether unrelated to disease pathophysiology.

Transplacental neurotoxicity of cypermethrin induced astrogliosis, microgliosis and depletion of let-7 miRNAs expression in the developing rat cerebral cortex

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Transplacental neurotoxicity of the pyrethroid insecticide, cypermethrin

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DNA alterations and immunohistochemical staining of astrocytes and microglia

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Cypermethrin induces astrogliosis and microgliosis in cerebral cortex

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MicroRNAs let7a, b, and c deplete in cerebral cortex of rat pups at postanal days

The use of type II pyrethroids, cypermethrin is becoming a growing concern among environmental research centers. While most studies have attempted to cover the areas of DNA damage and microglia activation following exposure to cypermethin in the adult or postnatal life, less is known about the exact degree of neurotoxicity that results from exposure to transplacental sublethal doses of cypermethrin. To study the transplacental neurotoxicity of cypermethrin, pregnant rats were orally administered 10 % of LD₅₀ (25 mg/kg body weight) cypermethrin, one dose daily for one week during the gestational days 15–21. The pups were investigated at postnatal day7, 14 and 21 after birth. In brain, DNA alterations were detected, astrocytes and microglia quantification were performed and some let7 family member miRNAs are estimated. The results show a gain of three major bands in the range of 350bp to 2100bp with high intensities in cortex exposed to cypermethrin compared with similar pattern indicating unaffected genomic regions in thalamus and hypothalamus at 21days. Moreover, increases in the percentage of GFAP positive astrocytes and IBA1 positive microglia indicate astrogliosis and microgliosis respectively due to cypermethrin treatment in cerebral cortex. For the first time, drastically reduced expression of let7a, b and c members are also associated with gliosis and DNA alterations, which are detected in cerebral cortex, following transplacental neurotoxicity of cypermethrin. Taking together, these results suggest that cypermethrin neurotoxicity may be mediated partly through let7 miRNAs.

Mir363-3p Treatment Attenuates Long-Term Cognitive Deficits Precipitated by an Ischemic Stroke in Middle-Aged Female Rats

Cognitive impairment and memory loss are commonly seen after stroke and a third of patients will develop signs of dementia a year after stroke. Despite a large number of studies on the beneficial effects of neuroprotectants, few studies have examined the effects of these compounds/interventions on long-term cognitive impairment. Our previous work showed that the microRNA mir363-3p reduced infarct volume and sensory-motor impairment in the acute stage of stroke in middle-aged females but not males. Thus, the present study determined the impact of mir363-3p treatment on stroke-induced cognitive impairment in middle-aged females. Sprague–Dawley female rats (12 months of age) were subjected to middle cerebral artery occlusion (MCAo; or sham surgery) and injected (iv) with mir363-3p mimic (MCAo + mir363-3p) or scrambled oligos (MCAo + scrambled) 4 h later. Sensory-motor performance was assessed in the acute phase (2–5 days after stroke), while all other behaviors were tested 6 months after MCAo (18 months of age). Cognitive function was assessed by the novel object recognition test (declarative memory) and the Barnes maze (spatial memory). The MCAo + scrambled group showed reduced preference for a novel object after the stroke and poor learning in the spatial memory task. In contrast, mir363-3p treated animals were similar to either their baseline performance or to the sham group. Histological analysis showed significant deterioration of specific white matter tracts due to stroke, which was attenuated in mir363-3p treated animals. The present data builds on our previous finding to show that a neuroprotectant can abrogate the long-term effects of stroke.

Intracerebral hemorrhage alters circular RNA expression profiles in the rat brain

Circular RNAs (circRNAs), formed from pre-messenger RNAs by back-splicing, are a novel class of evolutionarily-conserved endogenous non-coding RNAs. While circRNAs are involved in various diseases, the role of circRNAs in intracerebral hemorrhage (ICH) remains unknown. In the present study, we performed high-throughput sequencing to profile the expression of circRNAs in the rat brain at 24 and 48 hours after ICH onset, and utilized bioinformatics methods to make predictions about the function of dysregulated circRNAs. Compared with the sham group, 346 and 389 circRNAs changed significantly (|log2 (fold change)| > 1 and P < 0.05) at 24 and 48 hours after ICH, respectively. Bioinformatics analyses indicated that parent genes of dysregulated circRNAs were involved in biological processes, cellular component, and molecular function following ICH, and that they were enriched in the dopaminergic synapses, glutamatergic synapses, endocytosis, regulation of actin cytoskeleton, the mitogen-activated protein kinase signaling pathway, and the retrograde endocannabinoid signaling pathway. Enrichment analyses of target mRNAs showed that these mRNAs were enriched in synaptic plasticity, ion channel activity, and pathways including the phospholipase D signaling and the cGMP-PKG signaling. Our study indicates that the expression profile of circRNAs changes significantly after ICH in rat brains, and suggests that circRNAs may be crucial for the pathophysiological process following ICH.

Let-7g* and miR-98 Reduce Stroke-Induced Production of Proinflammatory Cytokines in Mouse Brain

Stroke is a debilitating illness facing healthcare today, affecting over 800,000 people and causing over 140,000 deaths each year in the United States. Despite being the third-leading cause of death, very few treatments currently exist for stroke. Often, during an ischemic attack, the blood-brain barrier (BBB) is significantly damaged, which can lead to altered interactions with the immune system, and greatly worsen the damage from a stroke. The impaired, BBB promotes the infiltration of peripheral inflammatory cells into the brain, secreting deleterious mediators (cytokines/chemokines) and resulting in permanent barrier injury. let-7 microRNAs (miRs) are critical for regulating immune responses within the BBB, particularly after ischemic stroke. We have previously shown how transient stroke decreases expression of multiple let-7 miRs, and that restoration of expression confers significant neuroprotection, reduction in brain infiltration by neutrophils, monocytes and T cells. However, the specific mechanisms of action of let-7 miRs remain unexplored, though emerging evidence implicates a range of impacts on cytokines. In the current study, we evaluate the impacts of miR-98 and let-7g* on targeting of cytokine mRNAs, cytokine release following ischemic stroke, and cell-specific changes to the neurovascular space. We determined that miR-98 specifically targets IP-10, while let-7g* specifically aims IL-8, and attenuates their levels. Both produce strong impacts on CCL2 and CCL5. Further, let-7g* strongly improves neurovascular perfusion following ischemic stroke. Together, the results of the study indicate that let-7 miRs are critical for mediating endothelial-immune reactions and improving recovery following ischemic stroke.

Regulatory function of microRNAs in microglia

Microglia are CNS-resident cells involved in immune surveillance and maintenance of intercellular homeostasis, while also contributing to neurologic pathologies. MicroRNAs (miRNAs) are a class of small (~22 nucleotides) single-stranded noncoding RNAs that participate in gene regulation at the post-transcriptional level. miRNAs typically bind to the untranslated region (3' UTR) of RNAs. It has been shown that miRNAs are important players in controlling inflammation and that their abnormal expression is linked to cancer and ageing, and to the onset and progression of neurodegenerative disease. Furthermore, miRNAs participate in intercellular trafficking. Thus, miRNAs are released from cells in a free form, bound to proteins or packaged within extracellular vesicles (EVs), exerting paracrine and long distance signaling. In this review, recent findings on the role of miRNAs as drivers of microglia phenotypic changes and their cotribution in neurological disease are addressed. MAIN POINTS: miRNAs have a key role in microglia function/dysfunction, polarization, and restoration. Microglia are both a source and recipient of extracellular vesicles (EVs) containing miRNAs. Extracellular miRNAs may be found as soluble (free and EV cargo) and protein complexes.

miR-142-3p Regulates BDNF Expression in Activated Rodent Microglia Through Its Target CAMK2A

Microglia, the innate immune effector cells of the mammalian central nervous system (CNS), are involved in the development, homeostasis, and pathology of CNS. Microglia become activated in response to various insults and injuries and protect the CNS by phagocytosing the invading pathogens, dead neurons, and other cellular debris. Recent studies have demonstrated that the epigenetic mechanisms ensure the coordinated regulation of genes involved in microglial activation. In this study, we performed a microRNA (miRNA) microarray in activated primary microglia derived from rat pup's brain and identified differentially expressed miRNAs targeting key genes involved in cell survival, apoptosis, and inflammatory responses. Interestingly, miR-142-3p, one of the highly up-regulated miRNAs in microglia upon lipopolysaccharide (LPS)-mediated activation, compared to untreated primary microglia cells was predicted to target Ca²⁺/calmodulin dependent kinase 2a (CAMK2A). Further, luciferase reporter assay confirmed that miR-142-3p targets the 3'UTR of Camk2a. CAMK2A has been implicated in regulating the expression of brain-derived neurotrophic factor (BDNF) and long-term potentiation (LTP), a cellular mechanism underlying memory and learning. Given this, this study further focused on understanding the miR-142-3p mediated regulation of the CAMK2A-BDNF pathway via Cyclic AMP-responsive element-binding protein (CREB) in activated microglia. The results revealed that CAMK2A was downregulated in activated microglia, suggesting an inverse relationship between miR-142-3p and Camk2a in activated microglia. Overexpression of miR-142-3p in microglia was found to decrease the expression of CAMK2A and subsequently BDNF through regulation of CREB phosphorylation. Functional analysis through shRNA-mediated stable knockdown of CAMK2A in microglia confirmed that the regulation of BDNF by miR-142-3p is via CAMK2A. Overall, this study provides a database of differentially expressed miRNAs in activated primary microglia and reveals that microglial miR-142-3p regulates the CAMK2A-CREB-BDNF pathway which is involved in synaptic plasticity.

Heterogeneity of Microglia Phenotypes: Developmental, Functional and Some Therapeutic Considerations

BACKGROUND

Microglia play a pivotal role in maintaining homeostasis in complex brain environment. They first exist as amoeboid microglial cells (AMCs) in the developing brain, but with brain maturation, they transform into ramified microglial cells (RMCs). In pathological conditions, microglia are activated and have been classified into M1 and M2 phenotypes. The roles of AMCs, RMCs and M1/M2 microglia phenotypes especially in pathological conditions have been the focus of many recent studies.

METHODS

Here, we review the early development of the AMCs and RMCs and discuss their specific functions with reference to their anatomic locations, immunochemical coding etc. M1 and M2 microglia phenotypes in different neuropathological conditions are also reviewed.

RESULTS

Activated microglia are engaged in phagocytosis, production of proinflammatory mediators, trophic factors and synaptogenesis etc. Prolonged microglia activation, however, can cause damage to neurons and oligodendrocytes. The M1 and M2 phenotypes featured prominently in pathological conditions are discussed in depth. Experimental evidence suggests that microglia phenotype is being modulated by multiple factors including external and internal stimuli, local demands, epigenetic regulation, and herbal compounds.

CONCLUSION

Prevailing views converge that M2 polarization is neuroprotective. Thus, proper therapeutic designs including the use of anti-inflammatory drugs, herbal agents may be beneficial in suppression of microglial activation, especially M1 phenotype, for amelioration of neuroinflammation in different neuropathological conditions. Finally, recent development of radioligands targeting 18 kDa translocator protein (TSPO) in activated microglia may hold great promises clinically for early detection of brain lesion with the positron emission tomography.

microRNA-195 attenuates neuronal apoptosis in rats with ischemic stroke through inhibiting KLF5-mediated activation of the JNK signaling pathway

BACKGROUND

Accumulating evidence has implicated the regulation of microRNAs (miRs) in ischemia stroke. The current study aimed to elucidate the role of microRNA-195 (miR-195) in neuronal apoptosis and brain plasticity in rats with ischemic stroke via the JNK signaling pathway/KLF5 axis.

METHODS

Ischemic stroke rat models were established by middle cerebral artery occlusion (MCAO), and oxygen deprivation (OGD) models were constructed in rat neuronal cells, followed by gain- or loss-of-function of miR-195 and/or KLF5 in rats and cells. Infarct volume, neuronal loss and ultrastructure, the expression of GAP-43, SYP and KLF5 protein as well as cell apoptosis were determined in the rats. Caspase-3 activity as well as the expression of miR-195, KLF5, GAP-43, SYP, JNK, phosphorylated JNK, Bax and Bcl-2 was measured in the cells.

RESULTS

The infarct size, expression of GAP-43 and SYP protein and apoptotic cells were increased in the miR-195^-/- MCAO rats, while reductions were detected in the miR-195 mimic MCAO and KLF5^-/- MCAO rats. Bcl-2 expression was increased, Bax and Caspase-3 expression as well as the ratio of phosphorylated JNK/JNK was decreased in response to miR-195 overexpression or KLF5 knockdown. Interestingly, the silencing of KLF5 reversed the effects exerted by the miR-195 inhibitor on the expression of Bcl-2, phosphorylated JNK/JNK, Bax and Caspase-3.

CONCLUSIONS

Collectively, our study unraveled that miR-195 could down-regulate KLF5 and block the JNK signaling pathway, ultimately inhibiting neuronal apoptosis in rats with ischemic stroke.

[MicroRNA and their potential role in the pathogenesis of hemorrhagic stroke]

Spontaneous (non-traumatic) intracerebral hemorrhage (ICH), or hemorrhagic stroke, is a common and serious disease with high morbidity and mortality. Current methods of treating hemorrhagic stroke, from conservative to surgical, are insufficient, which justifies the continuation of the study of this condition, including cellular and molecular changes that occur during a stroke. MicroRNAs (miRNAs) are a class of small non-coding RNAs that play an important role in post-transcriptional regulation of gene expression. MicroRNAs are involved in almost all biological processes, including cell proliferation, apoptosis and cell differentiation, and are also key substances in pathophysiological processes in many diseases, and therefore they can be both potential biomarkers and new therapeutic targets in cancer, degenerative and cardiovascular disease. In recent years, a number of studies have been aimed at studying the role of microRNAs in pathophysiological processes in hemorrhagic stroke, such as apoptosis, inflammation, oxidative stress, violation of the blood-brain barrier (BBB) and cerebral edema. The results of the studies demonstrated that changes in miRNA expression may be associated with the prognosis of ICH. In this article, we consider studies related to miRNAs and hemorrhagic stroke, and clarify the complex relationship between them.

MicroRNA-206 Regulation of Skin Pigmentation in Koi Carp (Cyprinus carpio L.)

MicroRNAs (miRNAs) are ∼22 nucleotide non-coding RNA molecules that act as crucial roles in plenty of biological processes. However, the molecular and cellular mechanisms of miRNAs to regulate skin color differentiation and pigmentation in fish have not been fully understood. Herein, we revealed that miR-206, a skin-enriched miRNA, regulates melanocortin 1 receptor (Mc1r, a key regulator of melanogenesis) expression by binding to its 3'-untranslated (UTR) region through bioinformatics and luciferase reporter assay in koi carp (Cyprinus carpio L.). The analysis of spatial and temporal expression patterns suggested that miR-206 is a potential regulator in the skin pigmentation process. Then, we silenced it in vivo with an antagomir method. The result showed a substantial increase of Mc1r mRNA expression and protein level, and also its downstream genes: tyrosinase (Tyr) and dopachrome tautomerase (Dct) that encoding key enzymes involved in melanin synthesis. Moreover, we constructed the miRNA-206 sponge lentivirus vector to transfect koi carp melanocytes in vitro, further checked the functions of melanocytes using Cck-8 and Transwell assays. As a result, inhibition of miR-206 significantly up-regulated Mc1r mRNA expression and protein level and accelerated the melanocyte proliferation and migration ability compared with the scrambled-sequence negative control group (miR-NC). Overall, these findings provide the evidence that miR-206 plays a regulatory role in the skin color pigmentation through targeting the Mc1r gene and would facilitate understanding the molecular regulatory mechanisms underlying miRNA-mediated skin color pigmentation in koi carp.

The Role of Circular RNAs in Brain Injury

Circular RNAs are an increasingly important topic in non-coding RNA biology, drawing considerable attention in recent years. Accumulating evidence suggests a critical role for circular RNAs in both early and latent stages of disease pathogenesis. Circular RNAs are abundantly expressed in brain tissue, with significant implications for neural development and disease progression. Disruption of these processes, including those seen in response to brain injury, can have serious consequences such as hemiplegia, aphasia, coma, and death. In this review, we describe the role of circular RNAs in the context of brain injury and explore the potential connection between circular RNAs, brain hypoxic ischemic injury, ischemia-reperfusion injury, and traumatic injury.

Design, Synthesis and Biological Evaluation of Diosgenin-Amino Acid Derivatives with Dual Functions of Neuroprotection and Angiogenesis

Diosgenin, a natural product with steroidal structure, has a wide range of clinical applications in China. It also shows great potential in the treatment of blood clots and nerve damage. To enhance the bioavailability as well as efficacy of diosgenin, eighteen diosgenin-amino acid derivatives were designed and synthesized. The neuroprotective effects of these compounds were evaluated by SH-SY5Y cell line and the biosafety was evaluated by H9c2 cell line. The results displayed that part of the derivatives' activities (EC₅₀ < 20 μM) were higher than positive control edaravone (EC₅₀ = 21.60 ± 3.04 μM), among which, DG-15 (EC₅₀ = 6.86 ± 0.69 μM) exhibited the best neuroprotection. Meanwhile, biosafety evaluation showed that DG-15 had no cytotoxicity on H9c2 cell lines. Interestingly, combined neuroprotective and cytotoxic results, part of the derivatives without their protecting group were superior to compounds with protecting group. Subsequently, Giemsa staining and DAPI (4',6-diamidino-2-phenylindole) staining indicated that DG-15 had a protective effect on damaged SH-SY5Y cells by reducing apoptosis. Moreover, DG-15 showed a higher role in promoting angiogenesis at high concentrations (4 mg/mL) on the chorioallantoic membrane model. This finding displayed that DG-15 had dual functions of neuroprotection and angiogenesis, which provided further insight into designing agent for the application in treatment of ischemic stroke.

Age and sex differences in the pathophysiology of acute CNS injury

Despite the immeasurable burden on patients and families, no effective therapies to protect the CNS after an acute injury are available yet. Furthermore, the underlying mechanisms that promote neuronal death and functional deficits after injury remain to be poorly understood. The prevalence, age of onset, pathophysiology, and symptomatology of many CNS insults differ significantly between males and females. In the case of stroke, younger males tend to show a higher risk than younger females, while this trend reverses with age. Accumulating evidence from preclinical studies have shown that sex hormones play a crucial role in providing neuroprotection following ischemic stroke and other acute CNS injuries. Estrogen, in particular, exerts a neuroprotective effect by modulating the immune responses after injury. In addition, there exists a sexual dimorphism in cell death pathways between males and females that are independent of hormones. Meanwhile, recent studies suggest that microRNAs are critically involved in the sex-specific mechanisms of cell death. This review discusses the current knowledge on the contribution of sex and age to outcome after stroke. Implication of the interplay between these two factors on other CNS injuries (spinal cord injury and traumatic brain injury) from the experimental evidence were also discussed.

Sex differences in Alzheimer's disease: Understanding the molecular impact

Alzheimer's disease (AD) is a common neurodegenerative disorder that presents with cognitive impairment and behavioral disturbance. Approximately 5.5 million people in the United States live with AD, most of whom are over the age of 65 with two-thirds being woman. There have been major advancements over the last decade or so in the understanding of AD neuropathological changes and genetic involvement. However, studies of sex impact in AD have not been adequately integrated into the investigation of disease development and progression. It becomes indispensable to acknowledge in both basic science and clinical research studies the importance of understanding sex-specific differences in AD pathophysiology and pathogenesis, which could guide future effort in the discovery of novel targets for AD. Here, we review the latest and most relevant literature on this topic, highlighting the importance of understanding sex dimorphism from a molecular perspective and its association to clinical trial design and development in AD research field.

Tackling Aging by Using miRNA as a Target and a Tool

miRNA is a class of short noncoding RNA that regulates gene expression at the post-transcriptional level. Evidence of age-associated changes in miRNA expression has been collected in models ranging from nematodes to humans; however, there has been little discussion of how to turn our knowledge of miRNA biology into antiaging therapy. This opinion article provides a snapshot of our current understanding of the roles of miRNA in modulating the aging process. We discuss major chemical techniques for modifying the miRNA structure as well as developing delivery systems for intervention. Finally, technical needs to be met for bench-to-clinic translation of miRNA-based interventions are highlighted for future research.

Sex as a biological variable in the pathology and pharmacology of neurodegenerative and neurovascular diseases

The incidence of dementia, most commonly caused by cerebrovascular and neurodegenerative diseases, continues to grow as our population ages. Alzheimer disease (AD) and vascular cognitive impairment (VCI) are responsible for more than 80% of all cases of dementia. There are few effective, long-term treatments for AD and VCI-related conditions (e.g., stroke and cerebral amyloid angiopathy (CAA)). This review focuses on AD (as the most common "neurodegenerative" cause of dementia), CAA (as an "emerging" cause of dementia), and stroke (as the most common cause of "vascular" dementia). We will discuss the available literature on the pharmacological therapies that demonstrate sex differences, which refer to any combination of structural, chromosomal, gonadal, or hormonal differences between males and females. We will emphasize the importance of considering sex as a biological variable in the design of preclinical and clinical studies that investigate underlying pathologies or response to pharmacological interventions in dementia. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Precise closure of single blood vessels via multiphoton absorption-based photothermolysis

We report a novel approach to selectively close single blood vessels within tissue using multiphoton absorption-based photothermolysis (multiphoton photothermolysis) without the need of exogenous agents. The treatment process is monitored by in vivo reflectance confocal microscopy in real time. Closure of single targeted vessels of varying sizes ranging from capillaries to venules was demonstrated. We also demonstrated that deeply situated blood vessels could be closed precisely while preserving adjacent overlying superficial blood vessels. In vivo confocal Raman spectroscopy of the treatment sites confirmed vessel closure as being mediated by local coagulative damage. Partial vessel occlusion could be achieved, and it is accompanied by increased intravascular blood cell speed. Multiphoton photothermolysis under real-time reflectance confocal imaging guidance provides a novel precision medicine approach for noninvasive, precise microsurgery treatment of vascular diseases on a per-vessel/per-lesion basis. The method could also be used for building ischemic stroke models for basic biology study.