Epigenetic Signature of Chronic Cerebral Hypoperfusion and Beneficial Effects of S-adenosylmethionine in Rats

Neuroprotective Effect of Platinum Nanoparticles Is Not Associated with Their Accumulation in the Brain of Rats

Platinum nanoparticles (nPts) have neuroprotective/antioxidant properties, but the mechanisms of their action in cerebrovascular disease remain unclear. We investigated the brain bioavailability of nPts and their effects on brain damage, cerebral blood flow (CBF), and development of brain and systemic oxidative stress (OS) in a model of cerebral ischemia (hemorrhage + temporary bilateral common carotid artery occlusion, tBCAO) in rats. The nPts (0.04 g/L, 3 ± 1 nm diameter) were administered to rats (N = 19) intraperitoneally at the start of blood reperfusion. Measurement of CBF via laser Doppler flowmetry revealed that the nPts caused a rapid attenuation of postischemic hypoperfusion. The nPts attenuated the apoptosis of hippocampal neurons, the decrease in reduced aminothiols level in plasma, and the glutathione redox status in the brain, which were induced by tBCAO. The content of Pt in the brain was extremely low (≤1 ng/g). Thus, nPts, despite the extremely low brain bioavailability, can attenuate the development of brain OS, CBF dysregulation, and neuronal apoptosis. This may indicate that the neuroprotective effects of nPts are due to indirect mechanisms rather than direct activity in the brain tissue. Research on such mechanisms may offer a promising trend in the treatment of acute disorders of CBF.

The effect of platelet lysate on mouse ovarian structure, function and epigenetic modifications after autotransplantation

RESEARCH QUESTION

What are the effects of platelet lysate on structure, function and epigenetic modifications of heterotopically transplanted mouse ovarian tissues?

DESIGN

Mice were divided into three groups (n = 17 per group): control (mice with no ovariectomy, grafting or treatment), autograft and autograft plus platelet lysate (3 ml/kg at the graft sites). Inflammatory markers, serum malondialdehyde (MDA) concentration and total antioxidant capacity were assessed on day 7 after transplantation. Twenty-eight days after transplantation, stereological and hormonal analyses were conducted. Chromatin immunoprecipitation and quantitative real-time polymerase chain reaction were also used to quantify the epigenetic modifications of maturation genes, parallel to their expression.

RESULTS

The total volume of the ovary, cortex and medulla, and the number of different types of follicles, the concentration of interleukin (IL)-10, progesterone and oestradiol and total antioxidant capacity significantly decreased in the autograft group compared with the control group (P < 0.001); these parameters significantly increased in the autograft plus platelet lysate group compared with the autograft group (P < 0.001). The concentrations of tumour necrosis factor alpha, IL-6 and MDA increased significantly in the autograft group compared with the control group (P < 0.001); in the autograft plus platelet lysate group, these parameters significantly decreased compared with the autograft group (P < 0.001). In the autograft plus platelet lysate group, the expression levels of Gdf-9 (P < 0.0021), Igf-1 (P < 0.0048) and Igf-2 (P < 0.0063) genes also increased along with a lower incorporation of MeCP2 in the promoter regions (P < 0.001) compared with the autograft group.

CONCLUSIONS

Platelet lysate can contribute to follicular survival by improving folliculogenesis and increasing the expression of oocyte maturation genes.

Preservation of spatial memory and neuroprotection by the fatty acid amide hydrolase inhibitor URB597 in a rat model of vascular dementia

Background

Chronic cerebral hypoperfusion (CCH) is a major risk factor for vascular dementia (VaD). There are currently no broadly effective prevention or treatment strategies for VaD, but recent studies have reported promising results following vascular bypass surgery and pharmacomodulation of the brain endocannabinoid system (ECS). In this study, early effects of encephalomyosynangiosis (EMS) bypass surgery and augmented endocannabinoid signaling on CCH-induced cognitive dysfunction and neuronal damage were investigated.

Methods

An animal model of VaD was established by bilateral common carotid artery occlusion (BCCAO). Cannabinoid signaling was upregulated by treatment with the fatty acid amide hydrolase inhibitor URB597 (URB). Spatial learning and memory, cerebral blood flow (CBF), revascularization, brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling, and apoptosis were compared among Sham, BCCAO, BCCAO + EMS, BCCAO + URB, and BCCAO + URB + EMS groups. Spatial learning and memory were evaluated using the Morris water maze (MWM). The CBF in cortex and hippocampus was evaluated by 3-dimensional arterial spin labeling. The neovascularization was visualized by CD34 immunofluorescence staining, and BDNF-TrkB signaling protein expression levels were assessed by Western blotting.

Results

Treatment with URB597 but not EMS alone reversed the spatial learning and memory deficits induced by BCCAO. Neovascularization was enhanced after EMS surgery but not by URB597. Alternatively, there were no significant differences in CBF among treatment groups. Expression levels of BDNF and TrkB were significantly reduced by CCH compared to Sham treatment, and downregulation of both proteins was reversed by URB597 treatment but not EMS. BCCAO enhanced neuronal apoptosis, which was also reversed by URB597.

Conclusions

Augmentation of endogenous cannabinoid signaling but not EMS protects against CCH-induced neurodegeneration and preserves spatial learning and memory, possibly by activating BDNF-TrkB signaling.

DNA Methylation in Neurodegenerative and Cerebrovascular Disorders

DNA methylation is an epigenetic mechanism by which methyl groups are added to DNA, playing a crucial role in gene expression regulation. The aim of the present study is to compare methylation status of healthy subjects with that of patients with Alzheimer’s, Parkinson’s or Cerebrovascular diseases. We also analyze methylation status of a transgenic Alzheimer’s disease mouse model (3xTg-AD). Our results show that both global methylation (n = 141) and hydroxymethylation (n = 131) levels are reduced in DNA samples from buffy coats of patients with neurodegenerative disorders and age-related cerebrovascular disease. The importance of methylation and hydroxymethylation reduction is stressed by the finding that DNMT3a mRNA levels are also downregulated in buffy coats of patients with Dementia (n = 25). Global methylation is also reduced in brain, liver and serum samples of 3xTg-AD vs. wild type mice, such as DNMT3a mRNA levels that are also decreased in the brain of 3xTg-AD (n = 10). These results suggest that the use of global methylation and hydroxymethylation levels, together with the study of DNMT3a expression, could be useful as a new diagnostic biomarker for these prevalent disorders.

Regulation Is in the Air: The Relationship between Hypoxia and Epigenetics in Cancer

Hypoxia is an inherent condition of tumors and contributes to cancer development and progression. Hypoxia-inducible factors (HIFs) are the major transcription factors involved in response to low O₂ levels, orchestrating the expression of hundreds of genes involved in cancer hallmarks’ acquisition and modulation of epigenetic mechanisms. Epigenetics refers to inheritable mechanisms responsible for regulating gene expression, including genes involved in the hypoxia response, without altering the sequence of DNA bases. The main epigenetic mechanisms are DNA methylation, non-coding RNAs, and histone modifications. These mechanisms are highly influenced by cell microenvironment, such as O₂ levels. The balance and interaction between these pathways is essential for homeostasis and is directly linked to cellular metabolism. Some of the major players in the regulation of HIFs, such as prolyl hydroxylases, DNA methylation regulators, and histone modifiers require oxygen as a substrate, or have metabolic intermediates as cofactors, whose levels are altered during hypoxia. Furthermore, during pathological hypoxia, HIFs’ targets as well as alterations in epigenetic patterns impact several pathways linked to tumorigenesis, such as proliferation and apoptosis, among other hallmarks. Therefore, this review aims to elucidate the intricate relationship between hypoxia and epigenetic mechanisms, and its crucial impact on the acquisition of cancer hallmarks.

Gene Expression Profiling of Two Epilepsy Models Reveals the ECM/Integrin signaling Pathway is Involved in Epiletogenesis

The molecular mechanisms underlying the development of epilepsy, i.e., epileptogenesis, are due to altered expression of a series of genes. Global expression profiling of temporal lobe epilepsy is confounded by a number of factors, including the variability among animal species, animal models, and tissue sampling time-points. In this study, we pooled two microarray datasets of the most used pilocarpine and kainic acid epilepsy models from the Gene Expression Omnibus database. A total of 567 known and novel genes were commonly differentially expressed across the two models. Pathway analyses demonstrated that the dysregulated genes were involved in 46 pathways. Real-time PCR and western blot analysis confirmed the activation of extracellular matrix (ECM)/integrin signaling pathways. Moreover, targeting ECM/integrin signaling inhibits astrocyte activation and promotes neuron injury in the hippocampus of epileptic mice. This study may provide a "gene/pathway database" that with further investigation can determine the mechanisms underlining epileptogenesis and the possible targets for neuron protection in the hippocampus after status epilepticus.

Long non-coding RNA H19 contributes to apoptosis of hippocampal neurons by inhibiting let-7b in a rat model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is one of the most common types of intractable epilepsy, characterized by hippocampal neuron damage and hippocampal sclerosis. Long noncoding RNAs (lncRNAs) have been increasingly recognized as posttranscriptional regulators. However, their expression levels and functions in TLE remain largely unknown. In the present study, TLE rat model is used to explore the expression profiles of lncRNAs in the hippocampus of epileptic rats using microarray analysis. Our results demonstrate that H19 is the most pronouncedly differentiated lncRNA, significantly upregulated in the latent period of TLE. Moreover, the in vivo studies using gain- and loss-of-function approaches reveal that the overexpression of H19 aggravates SE-induced neuron apoptosis in the hippocampus, while inhibition of H19 protects the rats from SE-induced cellular injury. Finally, we show that H19 might function as a competing endogenous RNA to sponge microRNA let-7b in the regulation of cellular apoptosis. Overall, our study reveals a novel lncRNA H19-mediated mechanism in seizure-induced neural damage and provides a new target in developing lncRNA-based strategies to reduce seizure-induced brain injury.

LncRNA H19 contributes to hippocampal glial cell activation via JAK/STAT signaling in a rat model of temporal lobe epilepsy

Background

Astrocyte and microglia activation are well-known features of temporal lobe epilepsy that may contribute to epileptogenesis. However, the mechanisms underlying glia activation are not well understood. Long non-coding RNA (lncRNA) H19 has diverse functions depending on physiological or pathological state, and its role in epilepsy is unknown. We previously demonstrated that H19 was significantly upregulated in the latent period of epilepsy and may be associated with cell proliferation and immune and inflammatory responses. We therefore speculated that H19 is involved in the hippocampal glial cell activation during epileptogenesis.

Methods

H19 was overexpressed or knocked down using an adeno-associated viral vector delivery system. A rat status epilepticus model was induced by intra-amygdala kainic acid injection. Astrocyte and microglia activation were assessed by immunofluorescence and western blot analyses. Expression of proinflammatory cytokines and components of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways were evaluated with western blotting.

Results

H19 overexpression induced the activation of astrocytes and microglia and the release of proinflammatory cytokines (interleukin-1β and interleukin-6 and tumor necrosis factor-α) in the hippocampus, whereas H19 knockdown inhibited status epilepticus-induced glial cell activation. Moreover, H19 activated JAK/STAT signaling by promoting the expression of Stat3 and c-Myc, which is thought to be involved in astrocyte activation.

Conclusions

LncRNA H19 contributes to hippocampal glial cell activation via modulation of the JAK/STAT pathway and could be a therapeutic tool to prevent the development of epilepsy.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1139-z) contains supplementary material, which is available to authorized users.

MicroRNA-181c Ameliorates Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion in Rats

Chronic cerebral hypoperfusion (CCH) characterized by global cerebral ischemia is an important risk factor contributing to the development of dementia. MicroRNAs (miRNAs) play important roles in the cellular adaptation to long-term ischemia/hypoxia by turning off or on the expression of target genes. MiR-181c is widely expressed in the nervous system, and tripartite motif 2 (TRIM2) is one of its target genes. In this work, we had identified that progressive spatial memory deficiency was induced in the bilateral common carotid artery occlusion (2-VO) rat models. Meanwhile, inhibition of miR-181c expression and upregulation of TRIM2 in the hippocampus of 2-VO rats were found accompanying with reduction in the dendritic branching and dendrite spine density of the hippocampal neurons. Viral vector-mediated miR-181c delivery might improve the cognitive deficiency via TRIM2 on neurofilament light (NF-L) ubiquitination resulting in remodeling of the hippocampal neurons as well as increase in N-methyl-D-aspartate receptor 1 (NR1) subunit cell surface expression. Meanwhile, miR-181c might rescue the cellular activity from ischemia/hypoxia. These results indicated a novel miRNA-mediated mechanism involving miR-181c and TRIM2 in the cognitive impairment induced by CCH and provided a rationale for the development of miRNA-based strategies for prevention of dementia.

The epigenetic landscape related to reactive oxygen species formation in the cardiovascular system

Cardiovascular diseases are among the leading causes of death worldwide. Reactive oxygen species (ROS) can act as damaging molecules but also represent central hubs in cellular signalling networks. Increasing evidence indicates that ROS play an important role in the pathogenesis of cardiovascular diseases, although the underlying mechanisms and consequences of pathophysiologically elevated ROS in the cardiovascular system are still not completely resolved. More recently, alterations of the epigenetic landscape, which can affect DNA methylation, post-translational histone modifications, ATP-dependent alterations to chromatin and non-coding RNA transcripts, have been considered to be of increasing importance in the pathogenesis of cardiovascular diseases. While it has long been accepted that epigenetic changes are imprinted during development or even inherited and are not changed after reaching the lineage-specific expression profile, it becomes more and more clear that epigenetic modifications are highly dynamic. Thus, they might provide an important link between the actions of ROS and cardiovascular diseases. This review will provide an overview of the role of ROS in modulating the epigenetic landscape in the context of the cardiovascular system.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Molecular targeting of hypoxia in radiotherapy

Hypoxia (low O₂) is an essential microenvironmental driver of phenotypic diversity in human solid cancers. Hypoxic cancer cells hijack evolutionarily conserved, O₂- sensitive pathways eliciting molecular adaptations that impact responses to radiotherapy, tumor recurrence and patient survival. In this review, we summarize the radiobiological, genetic, epigenetic and metabolic mechanisms orchestrating oncogenic responses to hypoxia. In addition, we outline emerging hypoxia- targeting strategies that hold promise for individualized cancer therapy in the context of radiotherapy and drug delivery.

Molecular Mechanisms of Vascular Dementia: What Can Be Learned from Animal Models of Chronic Cerebral Hypoperfusion?

Vascular dementia (VD) is defined as a progressive neurodegenerative disease of cognitive decline, attributable to cerebrovascular factors. Numerous studies have demonstrated that chronic cerebral hypoperfusion (CCH) is associated with the initiation and progression of VD and Alzheimer's disease (AD). Suitable animal models were established to replicate such pathological condition in experimental research, which contributes largely to comprehending causal relationships between CCH and cognitive impairment. The most widely used experimental model of VD and CCH is permanent bilateral common carotid artery occlusion in rats. In CCH models, changes of learning and memory, cerebral blood flow (CBF), energy metabolism, and neuropathology initiated by ischemia were revealed. However, in order to achieve potential therapeutic targets, particular mechanisms in cognitive and neuropathological changes from CCH to dementia should be investigated. Recent studies have shown that hypoperfusion resulted in a chain of disruption of homeostatic interactions, including oxidative stress, neuroinflammation, neurotransmitter system dysfunction, mitochondrial dysfunction, disturbance of lipid metabolism, and alterations of growth factors. Evidence from experimental studies that elucidate the damaging effects of such imbalances suggests their critical roles in the pathogenesis of VD. The present review provides a summary of the achievements in mechanisms made with the CCH models, permits an understanding of the causative role played by CCH in VD, and highlights preventative and therapeutic prospects.

S-adenosylmethionine Administration Attenuates Low Brain-Derived Neurotrophic Factor Expression Induced by Chronic Cerebrovascular Hypoperfusion or Beta Amyloid Treatment

Chronic cerebrovascular hypoperfusion is a high-risk factor for Alzheimer's disease (AD) as it is conducive to beta amyloid (Aβ) over-production. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family widely expressed in the central nervous system. The structure of the rat BDNF gene is complex, consisting of eight non-coding exons (I-VIII) and one coding exon (IX). The BDNF gene is transcribed from multiple promoters located upstream of different 5' non-coding exons to produce a heterogeneous population of BDNF mRNAs. S-adenosylmethionine (SAM) produced in the methionine cycle is the primary methyl donor and the precursor of glutathione. In this study, a cerebrovascular hypoperfusion rat model and an Aβ intrahippocampal injection rat model were used to explore the expression profiles of all BDNF transcripts in the hippocampus with chronic cerebrovascular hypoperfusion or Aβ injection as well as with SAM treatment. We found that the BDNF mRNAs and protein were down-regulated in the hippocampus undergoing chronic cerebrovascular hypoperfusion as well as Aβ treatment, and BDNF exons IV and VI played key roles. SAM improved the low BDNF expression following these insults mainly through exons IV and VI. These results suggest that SAM plays a neuroprotective role by increasing the expression of endogenous BDNF and could be a potential target for AD therapy.

Acetylation of histones in neocortex and hippocampus of rats exposed to different modes of hypobaric hypoxia: Implications for brain hypoxic injury and tolerance

Acetylation of nucleosome histones results in relaxation of DNA and its availability for the transcriptional regulators, and is generally associated with the enhancement of gene expression. Although it is well known that activation of a variety of pro-adaptive genes represents a key event in the development of brain hypoxic/ischemic tolerance, the role of epigenetic mechanisms, in particular histone acetylation, in this process is still unexplored. The aim of the present study was to investigate changes in acetylation of histones in vulnerable brain neurons using original well-standardized model of hypobaric hypoxia and preconditioning-induced tolerance of the brain. Using quantitative immunohistochemistry and Western blot, effects of severe injurious hypobaric hypoxia (SH, 180mm Hg, 3h) and neuroprotective preconditioning mode (three episodes of 360mm Hg for 2h spaced at 24h) on the levels of the acetylated proteins and acetylated H3 Lys24 (H3K24ac) in the neocortex and hippocampus of rats were studied. SH caused global repression of the acetylation processes in the neocortex (layers II-III, V) and hippocampus (CA1, CA3) by 3-24h, and this effect was prevented by the preconditioning. Moreover, hypoxic preconditioning remarkably increased the acetylation of H3K24 in response to SH in the brain areas examined. The preconditioning hypoxia without subsequent SH also stimulated acetylation processes in the neocortex and hippocampus. The moderately enhanced expression of the acetylated proteins in the preconditioned rats was maintained for 24h, whereas acetylation of H3K24 was intense but transient, peaked at 3h. The novel data obtained in the present study indicate that large activation of the acetylation processes, in particular acetylation of histones might be essential for the development of brain hypoxic tolerance.

H2S- and NO-Signaling Pathways in Alzheimer's Amyloid Vasculopathy: Synergism or Antagonism?

Alzheimer's type of neurodegeneration dramatically affects H2S and NO synthesis and interactions in the brain, which results in dysregulated vasomotor function, brain tissue hypoperfusion and hypoxia, development of perivascular inflammation, promotion of Aβ deposition, and impairment of neurogenesis/angiogenesis. H2S- and NO-signaling pathways have been described to offer protection against Alzheimer's amyloid vasculopathy and neurodegeneration. This review describes recent developments of the increasing relevance of H2S and NO in Alzheimer's disease (AD). More studies are however needed to fully determine their potential use as therapeutic targets in Alzheimer's and other forms of vascular dementia.

Acupuncture ameliorates cognitive impairment and hippocampus neuronal loss in experimental vascular dementia through Nrf2-mediated antioxidant response

Emerging evidence suggests acupuncture could exert neuroprotection in the vascular dementia via anti-oxidative effects. However, the involvement of Nrf2, a master regulator of antioxidant defense, in acupuncture-induced neuroprotection in vascular dementia remains undetermined. The goal of our study was to investigate the contribution of Nrf2 in acupuncture and its effects on vascular dementia. Morris water maze and Nissl staining were used to assess the effect of acupuncture on cognitive function and hippocampal neurodegeneration in experimental vascular dementia. The distribution of Nrf2 in neurons in hippocampus, the protein expression of Nrf2 in both cytosol and nucleus, and the protein and mRNA levels of its downstream target genes NQO1 and HO-1 were detected by double immunofluorescent staining, Western blotting and realtime PCR analysis respectively. Cognitive function and microglia activation were measured in both wild-type and Nrf2 gene knockout mice after acupuncture treatment. We found that acupuncture could remarkably reverse the cognitive deficits, neuron cell loss, reactive oxygen species production, and decreased cerebral blood flow. It was notable that acupuncture enhanced nuclear translocation of Nrf2 in neurons and up-regulate the protein and mRNA levels of Nrf2 and its target genes HO-1 and NQO1. Moreover, acupuncture could significantly down-regulated the over-activation of microglia after common carotid artery occlusion surgery. However, the reversed cognitive deficits, neuron cell loss and microglia activation by acupuncture were abolished in Nrf2 gene knockout mice. In conclusion, these findings provide evidence that the neuroprotection of acupuncture in models of vascular dementia was via the Nrf2 activation and Nrf2-dependent microglia activation.