Post-ischemic estradiol treatment reduced glial response and triggers distinct cortical and hippocampal signaling in a rat model of cerebral ischemia

Gender-specific prognosis models reveal differences in subarachnoid hemorrhage patients between sexes

BACKGROUND

Subarachnoid hemorrhage (SAH) represents a severe stroke subtype. Our study aims to develop gender-specific prognostic prediction models derived from distinct prognostic factors observed among different-gender patients.

METHODS

Inclusion comprised SAH-diagnosed patients from January 2014 to March 2016 in our institution. Collected data encompassed patients' demographics, admission severity, treatments, imaging findings, and complications. Three-month post-discharge prognoses were obtained via follow-ups. Analyses assessed gender-based differences in patient information. Key factors underwent subgroup analysis, followed by univariate and multivariate analyses to identify gender-specific prognostic factors and establish/validate gender-specific prognostic models.

RESULTS

A total of 929 patients, with a median age of 57 (16) years, were analyzed; 372 (40%) were male, and 557 (60%) were female. Differences in age, smoking history, hypertension, aneurysm presence, and treatment interventions existed between genders (p < 0.01), yet no disparity in prognosis was noted. Subgroup analysis explored hypertension history, aneurysm presence, and treatment impact, revealing gender-specific variations in these factors' influence on the disease. Screening identified independent prognostic factors: age, SEBES score, admission GCS score, and complications for males; and age, admission GCS score, intraventricular hemorrhage, treatment interventions, symptomatic vasospasm, hydrocephalus, delayed cerebral ischemia, and seizures for females. Evaluation and validation of gender-specific models yielded an AUC of 0.916 (95% CI: 0.878-0.954) for males and 0.914 (95% CI: 0.885-0.944) for females in the ROC curve. Gender-specific prognostic models didn't significantly differ from the overall population-based model (model 3) but exhibited robust discriminative ability and clinical utility.

CONCLUSION

Variations in baseline and treatment-related factors among genders contribute partly to gender-based prognosis differences. Independent prognostic factors vary by gender. Gender-specific prognostic models exhibit favorable prognostic performance.

Acute Combined Cerebrolysin and Nicotinamide Administration Promote Cognitive Recovery Through Neuronal Changes in the Hippocampus of Rats with Permanent Middle Cerebral Artery Occlusion

Stroke is one of the leading causes of disability worldwide, where the Hippocampus (HPC) is affected. HPC organizes memory, which is a cognitive domain compromised after a stroke, where cerebrolysin (CBL) and Nicotinamide (NAM) have been recognized as potentially therapeutic. In this study, we aimed to evaluate the efficacy of a combined administration of CBL and NAM in a rat stroke model. Male Sprague-Dawley rats (n = 36) were divided into four groups: saline (pMCAO - Saline), CBL (pMCAO + CBL), NAM (pMCAO + NAM), and experimental (pMCAO + CBL-NAM) (n = 9 per group). A permanent middle cerebral artery occlusion (pMCAO) was induced through electrocauterization of the middle cerebral artery, followed by the administration of CBL (2.5 ml/kg), NAM (500 mg/kg) or combined immediately after skin suture, as well as at 24, 48, and 72 h post-surgery. The rats were evaluated in the novel object recognition test; hippocampal infarct area measurement; reconstruction of neurons from CA1 for Sholl analysis; and, measurement of brain-derived neurotrophic factor (BDNF) levels near the infarct zone. Our findings revealed that the administration of CBL or NAM induced infarct reduction, improved cognition, and increased BDNF levels. Moreover, a combination of CBL and NAM increased dendritic intersection in CA1 pyramidal neurons. Thus, the combined administration of CBL and NAM can promote cognitive recovery after a stroke, with infarct reduction, cytoarchitectural changes in HPC CA1 neurons, and BDNF increase. Our findings suggest that this combination therapy could be a promising intervention strategy for stroke.

Pharmacological inhibition of mTORC1 reduces neural death and damage volume after MCAO by modulating microglial reactivity

Ischemic stroke is a sudden and acute disease characterized by neuronal death, increment of reactive gliosis (reactive microglia and astrocytes), and a severe inflammatory process. Neuroinflammation is an early event after cerebral ischemia, with microglia playing a leading role. Reactive microglia involve functional and morphological changes that drive a wide variety of phenotypes. In this context, deciphering the molecular mechanisms underlying such reactive microglial is essential to devise strategies to protect neurons and maintain certain brain functions affected by early neuroinflammation after ischemia. Here, we studied the role of mammalian target of rapamycin (mTOR) activity in the microglial response using a murine model of cerebral ischemia in the acute phase. We also determined the therapeutic relevance of the pharmacological administration of rapamycin, a mTOR inhibitor, before and after ischemic injury. Our data show that rapamycin, administered before or after brain ischemia induction, reduced the volume of brain damage and neuronal loss by attenuating the microglial response. Therefore, our findings indicate that the pharmacological inhibition of mTORC1 in the acute phase of ischemia may provide an alternative strategy to reduce neuronal damage through attenuation of the associated neuroinflammation.

Sex biology in amyotrophic lateral sclerosis

Although sex differences in amyotrophic lateral sclerosis (ALS) have not been studied systematically, numerous clinical and preclinical studies have shown sex to be influential in disease prognosis. Moreover, with the development of advanced imaging tools, the difference between male and female brain in structure and function and their response to neurodegeneration are more definitive. As discussed in this review, ALS patients exhibit a sex bias pertaining to the features of the disease, and their clinical, pathological, (and pathophysiological) phenotypes. Several epidemiological studies have indicated that this sex disparity stems from various aetiologies, including sex-specific brain structure and neural functioning, genetic predisposition, age, gonadal hormones, susceptibility to traumatic brain injury (TBI)/head trauma and lifestyle factors.

Shank3 ameliorates neuronal injury after cerebral ischemia/reperfusion via inhibiting oxidative stress and inflammation

Shank3, a key molecule related to the development and deterioration of autism, has recently been found to downregulate in the murine brain after ischemia/reperfusion (I/R). Despite this discovery, however, its effects on neuronal injury and the mechanism underlying the effects remain to be clarified. To address this, in this study, based on genetically modified mice models, we revealed that the expression of Shank3 showed a time-dependent change in murine hippocampal neurons after I/R, and that conditional knockout (cko) of Shank3 in neurons resulted in aggravated neuronal injuries. The protective effects of Shank3 against oxidative stress and inflammation after I/R were achieved through direct binding STIM1 and subsequent proteasome-mediated degradation of STIM1. The STIM1 downregulation induced the phosphorylation of downstream Nrf2 Ser40, which subsequently translocated to the nucleus, and further increased the expression of antioxidant genes such as NQO1 and HO-1 in HT22 cells. In vivo, the study has further confirmed that double knockout of Shank3 and Stim1 alleviated oxidative stress and inflammation after I/R in Shank3cko mice. In conclusion, the present study has demonstrated that Shank3 interacts with STIM1 and inhibits post-I/R neuronal oxidative stress and inflammatory response via the Nrf2 pathway. This interaction can potentially contribute to the development of a promising method for I/R treatment.

Subsecond Codetection of Dopamine and Estradiol at a Modified Sharkfin Waveform

17β-Estradiol (E2) is a ubiquitously expressed hormone that is active in a wide range of neuroprotective and regenerative roles throughout the brain. In particular, it is a well-known dopamine (DA) regulator and is responsible for modulating the expression of dopaminergic receptors and transporters. Recent studies point to E2 release occurring on a rapid time scale and having impacts on DA activity within seconds to minutes. As such, tools capable of monitoring the release of both E2 and DA in real time are essential for developing an accurate understanding of their interactive roles in neurotransmission and regulation. Currently, no analytical techniques capable of codetection of both analytes with high sensitivity, spatiotemporal resolution, extended monitoring, and minimal tissue damage exist. We describe a modified waveform using fast-scan cyclic voltammetry that is capable of low nanomolar detection of both DA and E2 on a subsecond time scale. Both analytes have limits of detection at or below 30 nM and high sensitivity: 11.31 ± 0.55 nA/μM for DA and 9.47 ± 0.36 nA/μM for E2. The waveform is validated in a tissue matrix, confirming its viability for measurement in a biologically relevant setting. This is the first method capable of codetection of fluctuations in DA and E2 with the temporal, spatial, and sensitivity requirements necessary for studying real-time neurochemical signaling.

Female mice are protected from impaired parenchymal arteriolar TRPV4 function and impaired cognition in hypertension

Hypertension is a leading modifiable risk factor for cerebral small vessel disease. Our laboratory has shown that endothelium-dependent dilation in cerebral parenchymal arterioles (PAs) is dependent on transient receptor potential vanilloid 4 (TRPV4) activation, and this pathway is impaired in hypertension. This impaired dilation is associated with cognitive deficits and neuroinflammation. Epidemiological evidence suggests that women with midlife hypertension have an increased dementia risk that does not exist in age-matched men, though the mechanisms responsible for this are unclear. This study aimed to determine the sex differences in young, hypertensive mice to serve as a foundation for future determination of sex differences at midlife. We tested the hypothesis that young hypertensive female mice would be protected from the impaired TRPV4-mediated PA dilation and cognitive dysfunction observed in male mice. Angiotensin II (ANG II)-filled osmotic minipumps (800 ng/kg/min, 4 wk) were implanted in 16- to 19-wk-old male C56BL/6 mice. Age-matched female mice received either 800 ng/kg/min or 1,200 ng/kg/min ANG II. Sham-operated mice served as controls. Systolic blood pressure was elevated in ANG II-treated male mice and in 1,200 ng ANG II-treated female mice versus sex-matched shams. PA dilation in response to the TRPV4 agonist GSK1016790A (10-9-10-5 M) was impaired in hypertensive male mice, which was associated with cognitive dysfunction and neuroinflammation, reproducing our previous findings. Hypertensive female mice exhibited normal TRPV4-mediated PA dilation and were cognitively intact. Female mice also showed fewer signs of neuroinflammation than male mice. Determining the sex differences in cerebrovascular health in hypertension is critical for developing effective therapeutic strategies for women.NEW & NOTEWORTHY Vascular dementia is a significant public health concern, and the effect of biological sex on dementia development is not well understood. TRPV4 channels are essential regulators of cerebral parenchymal arteriolar function and cognition. Hypertension impairs TRPV4-mediated dilation and memory in male rodents. Data presented here suggest female sex protects against impaired TRPV4 dilation and cognitive dysfunction during hypertension. These data advance our understanding of the influence of biological sex on cerebrovascular health in hypertension.

Immune regulation based on sex differences in ischemic stroke pathology

Ischemic stroke is one of the world's leading causes of death and disability. It has been established that gender differences in stroke outcomes prevail, and the immune response after stroke is an important factor affecting patient outcomes. However, gender disparities lead to different immune metabolic tendencies closely related to immune regulation after stroke. The present review provides a comprehensive overview of the role and mechanism of immune regulation based on sex differences in ischemic stroke pathology.

Sex-biased autophagy as a potential mechanism mediating sex differences in ischemic stroke outcome

Stroke is the second leading cause of death and a major cause of disability worldwide, and biological sex is an important determining factor in stroke incidence and pathology. From childhood through adulthood, men have a higher incidence of stroke compared with women. Abundant research has confirmed the beneficial effects of estrogen in experimental ischemic stroke but genetic factors such as the X-chromosome complement can also play an important role in determining sex differences in stroke. Autophagy is a self-degrading cellular process orchestrated by multiple core proteins, which leads to the engulfment of cytoplasmic material and degradation of cargo after autophagy vesicles fuse with lysosomes or endosomes. The levels and the activity of components of these signaling pathways and of autophagy-related proteins can be altered during ischemic insults. Ischemic stroke activates autophagy, however, whether inhibiting autophagy after stroke is beneficial in the brain is still under a debate. Autophagy is a potential mechanism that may contribute to differences in stroke progression between the sexes. Furthermore, the effects of manipulating autophagy may also differ between the sexes. Mechanisms that regulate autophagy in a sex-dependent manner in ischemic stroke remain unexplored. In this review, we summarize clinical and pre-clinical evidence for sex differences in stroke. We briefly introduce the autophagy process and summarize the effects of gonadal hormones in autophagy in the brain and discuss X-linked genes that could potentially regulate brain autophagy. Finally, we review pre-clinical studies that address the mechanisms that could mediate sex differences in brain autophagy after stroke.

Cyclo-(Phe-Tyr) as a novel cyclic dipeptide compound alleviated ischemic stroke reperfusion brain injury via JUNB/JNK/NF-κB and SOX5/PI3K/AKT pathways

Ischemic stroke reperfusion (IR) can cause adverse reactions including apoptosis, oxidative stress, and inflammation, but the existing therapeutic strategies have been limited. Moreover, the regulation of microglia plays an important role in brain injury after reperfusion. Hence, it is imperative to find new and effective drugs for modulating microglia to treat IR brain injury. Cyclic peptide compound cyclo-(Phe-Tyr) (Sparganin C, SC) is a compound isolated from Sparganii Rhizoma. However, the protective effects of SC on the central nervous system are rather unclear. In an attempt to elucidate the protective effects and mechanism of SC on cerebral damage induced by the IR, we used a middle cerebral artery occlusion reperfusion (MCAO/R) model in rats and discovered that SC significantly decreased the size of cerebral infarcts, improved neurological scores, and blocked inflammatory and oxidative factor release. Using RNA-Seq and metabolomics association analyses, SC was shown to have a protective impact through the JUNB and SOX5-related pathways. Metabolomic analysis revealed twenty-eight differentially expressed biomarkers. In addition, the detection of SC content in brain tissue using LC/MS revealed that SC had blood-brain barrier penetration. To investigate the mechanism, we established an in vitro BV2 cell oxygen-glucose deprived re-oxygenation (OGD/R) model and used siRNA as well as an inhibitor. The protective effects of SC were dependent on the JUNB and SOX5 to inhibit inflammation and apoptosis in microglia. Our findings revealed for the first that SC against IR injury by reducing inflammation and apoptosis while simultaneously acting as potential therapeutic lead compound for ischemic stroke.

Sex-Associated Differences in Neurovascular Dysfunction During Ischemic Stroke

Neurovascular units (NVUs) are basic functional units in the central nervous system and include neurons, astrocytes and vascular compartments. Ischemic stroke triggers not only neuronal damage, but also dissonance of intercellular crosstalk within the NVU. Stroke is sexually dimorphic, but the sex-associated differences involved in stroke-induced neurovascular dysfunction are studied in a limited extend. Preclinical studies have found that in rodent models of stroke, females have less neuronal loss, stronger repairing potential of astrocytes and more stable vascular conjunction; these properties are highly related to the cerebroprotective effects of female hormones. However, in humans, these research findings may be applicable only to premenopausal stroke patients. Women who have had a stroke usually have poorer outcomes compared to men, and because stoke is age-related, hormone replacement therapy for postmenopausal women may exacerbate stroke symptoms, which contradicts the findings of most preclinical studies. This stark contrast between clinical and laboratory findings suggests that understanding of neurovascular differences between the sexes is limited. Actually, apart from gonadal hormones, differences in neuroinflammation as well as genetics and epigenetics promote the sexual dimorphism of NVU functions. In this review, we summarize the confirmed sex-associated differences in NVUs during ischemic stroke and the possible contributing mechanisms. We also describe the gap between clinical and preclinical studies in terms of sexual dimorphism.

Dysregulation of mTOR Signaling after Brain Ischemia

In this review, we provide recent data on the role of mTOR kinase in the brain under physiological conditions and after damage, with a particular focus on cerebral ischemia. We cover the upstream and downstream pathways that regulate the activation state of mTOR complexes. Furthermore, we summarize recent advances in our understanding of mTORC1 and mTORC2 status in ischemia–hypoxia at tissue and cellular levels and analyze the existing evidence related to two types of neural cells, namely glia and neurons. Finally, we discuss the potential use of mTORC1 and mTORC2 as therapeutic targets after stroke.

Protective Effects of Estrogen via Nanoparticle Delivery to Attenuate Myelin Loss and Neuronal Death after Spinal Cord Injury

Spinal cord injury (SCI) is associated with devastating neurological deficits affecting more than 11,000 Americans each year. Although several therapeutic agents have been proposed and tested, no FDA-approved pharmacotherapy is available for SCI treatment. We have recently demonstrated that estrogen (E2) acts as an antioxidant and anti-inflammatory agent, attenuating gliosis in SCI. We have also demonstrated that nanoparticle-mediated focal delivery of E2 to the injured spinal cord decreases lesion size, reactive gliosis, and glial scar formation. The current study tested in vitro effects of E2 on reactive oxygen species (ROS) and calpain activity in microglia, astroglia, macrophages, and fibroblasts, which are believed to participate in the inflammatory events and glial scar formation after SCI. E2 treatment decreased ROS production and calpain activity in these glial cells, macrophages, and fibroblast cells in vitro. This study also tested the efficacy of fast- and slow-release nanoparticle-E2 constructs in a rat model of SCI. Focal delivery of E2 via nanoparticles increased tissue distribution of E2 over time, attenuated cell death, and improved myelin preservation in injured spinal cord. Specifically, the fast-release nanoparticle-E2 construct reduced the Bax/Bcl-2 ratio in injured spinal cord tissues, and the slow-release nanoparticle-E2 construct prevented gliosis and penumbral demyelination distal to the lesion site. These data suggest this novel E2 delivery strategy to the lesion site may decrease inflammation and improve functional outcomes following SCI.

G-Protein-Coupled Receptors and Ischemic Stroke: a Focus on Molecular Function and Therapeutic Potential

In ischemic stroke, there is only one approved drug, tissue plasminogen activator, to be used in clinical conditions for thrombolysis. New neuroprotective therapies for ischemic stroke are desperately needed. Several targets and pathways have been shown to confer neuroprotective effects in ischemic stroke. G-protein-coupled receptors (GPCRs) are one of the most frequently targeted receptors for developing novel therapeutics for central nervous system disorders. GPCRs are a large family of cell surface receptors that response to a wide variety of extracellular stimuli. GPCRs are involved in a wide range of physiological and pathological processes. More than 90% of the identified non-sensory GPCRs are expressed in the brain, where they play important roles in regulating mood, pain, vision, immune responses, cognition, and synaptic transmission. There is also good evidence that GPCRs are implicated in the pathogenesis of stroke. This review narrates the pathophysiological role and possible targeted therapy of GPCRs in ischemic stroke.

The effect of female sex hormones on Hsp27 phosphorylation and histological changes in prefrontal cortex after tMCAO

BACKGROUND

Female sex hormones are protective factors against many neurological disorders such as brain ischemia. Heat shock protein like HSP27 is activated after tissue injury. The main purpose of the present study is to determine the effect of a combined estrogen / progesterone cocktail on the morphology of astrocytes, neurons and Hsp27 phosphorylation after cerebral ischemia.

METHODS

One hour after the MCAO induction, a single dose of estrogen and progesterone was injected. The infarct volume was calculated by TTC staining 24 h after ischemia. Immunohistochemistry was used to show the effects of estrogen and progesterone on astrocyte and neuron morphology, as well as the Western blot technique used for the quantitation of phosphorylated Hsp27.

RESULTS

The combined dose of estrogen and progesterone significantly decreased astrocytosis after ischemia and increased neuron survival. There was a large increase in Hsp27 phosphorylation in the penumbra ischemic region after stroke, which was significantly reduced by hormone therapy.

CONCLUSION

Our results indicate that the neuroprotective effect of neurosteroids in the brain may be due to the modulation of heat shock proteins.

Energy-Sensing Pathways in Ischemia: The Counterbalance Between AMPK and mTORC

Stroke is an important cause of death and disability, and it is the second leading cause of death worldwide. In humans, middle cerebral artery occlusion (MCAO) is the most common cause of ischemic stroke. The damage occurs due to the lack of nutrients and oxygen contributed by the blood flow. The present review aims to analyze to what extent the lack of each of the elements of the system leads to damage and which mechanisms are unaffected by this deficiency. We believe that the specific analysis of the effect of lack of each component could lead to the emergence of new therapeutic targets for this important brain pathology.

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.

ERK activation by zeranol has neuroprotective effect in cerebral ischemia reperfusion

AIMS

Incidence of stroke increases in postmenopausal women with dangerous consequences. In this study we used zeranol to protect ovariectomized (OVX) rats against cerebral I/R damage and our target is to identify the mechanism of its protection, in addition to investigating whether this mechanism inhibits inflammation (by preventing glial cell activation) and apoptosis.

MAIN METHODS

First 18 ovariectomized rats were allocated into 3 groups: I/R group, zeranol+ I/R group and U0126, MEK1/2 inhibitor + zeranol+ I/R group. After 24 h reperfusion, protein expression of total extracellular signal-regulated protein kinase (t-ERK1/2), phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2), Bcl-2, and Bax were quantified. Second 36 female rats were allocated into 3 groups: sham group, I/R group (after ovariectomy by 7 weeks, rats exposed to cerebral I/R) and zeranol group (after ovariectomy by 2 weeks, rats received zeranol for 5 weeks). After 24 h of reperfusion, the following parameters were measured; total nitrate/nitrite, interleukin-10, myeloperoxidase, caspase-3, and finally immunohistochemistry analysis of glial fibrillary acidic protein, cyclooxygenase-2 in cortex and hippocampus (CA1) regions were performed.

KEY FINDINGS

U-0126 administration reversed the neuroprotective effect induced by zeranol through decreasing ratio of p-ERK1/2:ERK1/2 and Bcl-2/Bax in brain tissue. Activation of ERK signaling pathway by zeranol caused reduction in brain apoptosis and inflammation.

SIGNIFICANCE

Zeranol showed protective effect in OVX rats that were exposed to cerebral I/R by activation of ERK signaling pathway which was blocked by U0126. This protective effect in turns led to decrease inflammation and apoptosis.

WWOX Phosphorylation, Signaling, and Role in Neurodegeneration

Homozygous null mutation of tumor suppressor WWOX/Wwox gene leads to severe neural diseases, metabolic disorders and early death in the newborns of humans, mice and rats. WWOX is frequently downregulated in the hippocampi of patients with Alzheimer’s disease (AD). In vitro analysis revealed that knockdown of WWOX protein in neuroblastoma cells results in aggregation of TRAPPC6AΔ, TIAF1, amyloid β, and Tau in a sequential manner. Indeed, TRAPPC6AΔ and TIAF1, but not tau and amyloid β, aggregates are present in the brains of healthy mid-aged individuals. It is reasonable to assume that very slow activation of a protein aggregation cascade starts sequentially with TRAPPC6AΔ and TIAF1 aggregation at mid-ages, then caspase activation and APP de-phosphorylation and degradation, and final accumulation of amyloid β and Tau aggregates in the brains at greater than 70 years old. WWOX binds Tau-hyperphosphorylating enzymes (e.g., GSK-3β) and blocks their functions, thereby supporting neuronal survival and differentiation. As a neuronal protective hormone, 17β-estradiol (E2) binds WWOX at an NSYK motif in the C-terminal SDR (short-chain alcohol dehydrogenase/reductase) domain. In this review, we discuss how WWOX and E2 block protein aggregation during neurodegeneration, and how a 31-amino-acid zinc finger-like Zfra peptide restores memory loss in mice.

Invasion of Peripheral Immune Cells into Brain Parenchyma after Cardiac Arrest and Resuscitation

Although a direct link has long been suspected between systemic immune responses and neuronal injuries after stroke, it is unclear which immune cells play an important role. A question remains as to whether the blood brain barrier (BBB) is transiently disrupted after circulatory arrest to allow peripheral immune cells to enter brain parenchyma. Here, we developed a clinically relevant cardiac arrest and resuscitation model in mice to investigate the BBB integrity using noninvasive magnetic resonance imaging. Changes in immune signals in the brain and periphery were assayed by immunohistochemistry and flow cytometry. Quantitative variance maps from T1-weighted difference images before and after blood-pool contrast clearance revealed BBB disruptions immediately after resuscitation and one day after reperfusion. Time profiles of hippocampal CA1 neuronal injuries correlated with the morphological changes of microglia activation. Cytotoxic T cells, CD11b⁺CD11c⁺ dendritic cells, and CD11b⁺CD45^+hi monocytes and macrophages were significantly increased in the brain three days after cardiac arrest and resuscitation, suggesting direct infiltration of these cells following the BBB disruption. Importantly, these immune cell changes were coupled with a parallel increase in the same subset of immune cell populations in the bone marrow and blood. We conclude that neurovascular breakdown during the initial reperfusion phase contributes to the systemic immune cell invasion and subsequent neuropathogenesis affecting the long-term outcome after cardiac arrest and resuscitation.

Sex steroid hormones as neuroprotective elements in ischemia models

Among sex steroid hormones, progesterone and estradiol have a wide diversity of physiological activities that target the nervous system. Not only are they carried by the blood stream, but also they are locally synthesized in the brain and for this reason, estradiol and progesterone are considered 'neurosteroids'. The physiological actions of both hormones range from brain development and neurotransmission to aging, illustrating the importance of a deep understanding of their mechanisms of action. In this review, we summarize key roles that estradiol and progesterone play in the brain. As numerous reports have confirmed a substantial neuroprotective role for estradiol in models of neurodegenerative disease, we focus this review on traumatic brain injury and stroke models. We describe updated data from receptor and signaling events triggered by both hormones, with an emphasis on the mechanisms that have been reported as 'rapid' or 'cytoplasmic actions'. Data showing the therapeutic effects of the hormones, used alone or in combination, are also summarized, with a focus on rodent models of middle cerebral artery occlusion (MCAO). Finally, we draw attention to evidence that neuroprotection by both hormones might be due to a combination of 'cytoplasmic' and 'nuclear' signaling.

The Synthetic Steroid Tibolone Decreases Reactive Gliosis and Neuronal Death in the Cerebral Cortex of Female Mice After a Stab Wound Injury

Previous studies have shown that estradiol reduces reactive gliosis after a stab wound injury in the cerebral cortex. Since the therapeutic use of estradiol is limited by its peripheral hormonal effects, it is of interest to determine whether synthetic estrogenic compounds with tissue-specific actions regulate reactive gliosis. Tibolone is a synthetic steroid that is widely used for the treatment of climacteric symptoms and/or the prevention of osteoporosis. In this study, we have assessed the effect of tibolone on reactive gliosis in the cerebral cortex after a stab wound brain injury in ovariectomized adult female mice. By 7 days after brain injury, tibolone reduced the number of glial fibrillary acidic protein (GFAP) immunoreactive astrocytes, the number of ionized calcium binding adaptor molecule 1 (Iba1) immunoreactive microglia, and the number of microglial cells with a reactive phenotype in comparison to vehicle-injected animals. These effects on gliosis were associated with a reduction in neuronal loss in the proximity to the wound, suggesting that tibolone exerts beneficial homeostatic actions in the cerebral cortex after an acute brain injury.

Role of mTORC1 Controlling Proteostasis after Brain Ischemia

Intense efforts are being undertaken to understand the pathophysiological mechanisms triggered after brain ischemia and to develop effective pharmacological treatments. However, the underlying molecular mechanisms are complex and not completely understood. One of the main problems is the fact that the ischemic damage is time-dependent and ranges from negligible to massive, involving different cell types such as neurons, astrocytes, microglia, endothelial cells, and some blood-derived cells (neutrophils, lymphocytes, etc.). Thus, approaching such a complicated cellular response generates a more complex combination of molecular mechanisms, in which cell death, cellular damage, stress and repair are intermixed. For this reason, animal and cellular model systems are needed in order to dissect and clarify which molecular mechanisms have to be promoted and/or blocked. Brain ischemia may be analyzed from two different perspectives: that of oxygen deprivation (hypoxic damage per se) and that of deprivation of glucose/serum factors. For investigations of ischemic stroke, middle cerebral artery occlusion (MCAO) is the preferred in vivo model, and uses two different approaches: transient (tMCAO), where reperfusion is permitted; or permanent (pMCAO). As a complement to this model, many laboratories expose different primary cortical neuron or neuronal cell lines to oxygen-glucose deprivation (OGD). This ex vivo model permits the analysis of the impact of hypoxic damage and the specific response of different cell types implicated in vivo, such as neurons, glia or endothelial cells. Using in vivo and neuronal OGD models, it was recently established that mTORC1 (mammalian Target of Rapamycin Complex-1), a protein complex downstream of PI3K-Akt pathway, is one of the players deregulated after ischemia and OGD. In addition, neuroprotective intervention either by estradiol or by specific AT2R agonists shows an important regulatory role for the mTORC1 activity, for instance regulating vascular endothelial growth factor (VEGF) levels. This evidence highlights the importance of understanding the role of mTORC1 in neuronal death/survival processes, as it could be a potential therapeutic target. This review summarizes the state-of-the-art of the complex kinase mTORC1 focusing in upstream and downstream pathways, their role in central nervous system and their relationship with autophagy, apoptosis and neuroprotection/neurodegeneration after ischemia/hypoxia.

Pre-treated Populus tomentiglandulosa extract inhibits neuronal loss and alleviates gliosis in the gerbil hippocampal CA1 area induced by transient global cerebral ischemia

The genus Populus (poplar) belonging to the Salicaceae family has been used in traditional medicine, and its several species show various pharmacological properties including antioxidant and anti-inflammatory effects. No study regarding protective effects of Populus species against cerebral ischemia has been reported. Therefore, in the present study, we examined neuroprotective effects of ethanol extract from Populus tomentiglandulosa (Korea poplar) in the hippocampal cornu ammonis (CA1) area of gerbils subjected to 5 minutes of transient global cerebral ischemia. Pretreatment with 200 mg/kg of P. tomentiglandulosa extract effectively protected CA1 pyramidal neurons from transient global cerebral ischemia. In addition, glial fibrillary acidic protein immunoreactive astrocytes and ionized calcium binding adapter molecule 1 immunoreactive microglia were significantly diminished in the ischemic CA1 area by pretreatment with 200 mg/kg of P. tomentiglandulosa extract. Briefly, our results indicate that pretreatment with P. tomentiglandulosa extract protects neurons from transient cerebral ischemic injury and diminish cerebral ischemia-induced reactive gliosis in ischemic CA1 area. Based on these results, we suggest that P. tomentiglandulosa can be used as a potential candidate for prevention of ischemic injury.

Aromatase and neuroinflammation in rat focal brain ischemia

Accumulating evidence suggests that expression of aromatase, the enzyme responsible for the conversion of androgens to estrogens, is transiently upregulated in rat stroke models. It was further suggested that increased aromatase expression is linked to neuroinflammation and that it is neuroprotective in females. Our goal was to investigate aromatase upregulation in male rats subjected to experimental stroke in relationship to neuroinflammation, infarct and response to treatment with different putative neuroprotective agents. Intact male rats were subjected to transient (90min) middle cerebral artery occlusion (MCAO) and administered selfotel (N-methyl-d-aspartic acid (NMDA) receptor competitive antagonist), TPEN (a zinc chelator), a combination of the two drugs or vehicle, injected immediately after reperfusion. Animals were killed 14days after MCAO and consecutive brain sections used to measure aromatase expression, cerebral infarct volume and neuroinflammation. Quantitative immunohistochemistry (IHC) demonstrated increased brain aromatase expression in the peri-infarct area relative to contralesional area, which was partially abrogated by neuroprotective agents. There was no correlation between aromatase expression in the peri-infarct zone and infarct volume, which was reduced by neuroprotective agents. Microglial activation, measured by quantitative autoradiography, was positively correlated with infarct and inversely correlated with aromatase expression in the peri-infarct zone. Our findings indicate that focal ischemia upregulates brain aromatase in the male rat brain at 14days post surgery, which is within the time frame documented in females. However, the lack of negative correlation between aromatase expression and infarct volume and lack of positive correlation between microgliosis and aromatase do not support a major role for aromatase as a mediator of neuroprotection or a causal relationship between microglial activation and increased aromatase expression in male focal ischemia.

Electroacupuncture Treatment Alleviates Central Poststroke Pain by Inhibiting Brain Neuronal Apoptosis and Aberrant Astrocyte Activation

Electroacupuncture (EA) is reported to effectively relieve the central poststroke pain (CPSP). However, the underlying mechanism remains unclear. The present study investigated the detailed mechanisms of action of EA treatment at different frequencies for CPSP. A CPSP model was established with a single collagenase injection to the left ventral posterolateral nucleus of the thalamus. The EA-treated groups then received EA treatment at frequency of 2, 2/15, or 15 Hz for 30 min daily for five days. The pain-related behavioral responses, neuronal apoptosis, glial activation, and the expression of pain signal transmission-related factors (β-catenin, COX-2, and NK-1R) were assessed using behavioral tests, Nissl staining, TUNEL staining, and immunohistochemical staining, respectively. The low-frequency EA treatment significantly (1) reduced brain tissue damage and hematoma sizes and (2) inhibited neuronal apoptosis, thereby exerting abirritative effects. Meanwhile, the high-frequency EA treatment induced a greater inhibition of the aberrant astrocyte activation, accompanied by the downregulation of the expressions of COX-2, β-catenin, and subsequently NK-1R, thereby alleviating inflammation and producing strong analgesic effects. Together, these findings suggest that CPSP is closely related to pathological changes of the neocortex and hippocampus. EA treatments at different frequencies may exert abirritative effects by inhibiting brain neuronal apoptosis and aberrant astrocyte activation in the brain.

The pro-resolving lipid mediator Maresin 1 protects against cerebral ischemia/reperfusion injury by attenuating the pro-inflammatory response

Inflammation plays a crucial role in acute ischemic stroke pathogenesis. Macrophage-derived Maresin 1 (MaR1) is a newly uncovered mediator with potent anti-inflammatory abilities. Here, we investigated the effect of MaR1 on acute inflammation and neuroprotection in a mouse brain ischemia reperfusion (I/R) model. Male C57 mice were subjected to 1-h middle cerebral artery occlusion (MCAO) and reperfusion. By the methods of 2,3,5-triphenyltetrazolium chloride, haematoxylin and eosin or Fluoro-Jade B staining, neurological deficits scoring, ELISA detection, immunofluorescence assay and western blot analysis, we found that intracerebroventricular injection of MaR1 significantly reduced the infarct volume and neurological defects, essentially protected the brain tissue and neurons from injury, alleviated pro-inflammatory reactions and NF-κB p65 activation and nuclear translocation. Taken together, our results suggest that MaR1 significantly protects against I/R injury probably by inhibiting pro-inflammatory reactions.

Isoflurane Is More Deleterious to Developing Brain Than Desflurane: The Role of the Akt/GSK3β Signaling Pathway

Demand is increasing for safer inhalational anesthetics for use in pediatric anesthesia. In this regard, researchers have debated whether isoflurane is more toxic to the developing brain than desflurane. In the present study, we compared the effects of postnatal exposure to isoflurane with those of desflurane on long-term cognitive performance and investigated the role of the Akt/GSK3β signaling pathway. Postnatal day 6 (P6) mice were exposed to either isoflurane or desflurane, after which the phosphorylation levels of Akt/GSK3β and learning and memory were assessed at P8 or P31. The phosphorylation levels of Akt/GSK3β and learning and memory were examined after intervention with lithium. We found that isoflurane, but not desflurane, impaired spatial learning and memory at P31. Accompanied by behavioral change, only isoflurane decreased p-Akt (ser473) and p-GSK3β (ser9) expressions, which led to GSK3β overactivation. Lithium prevented GSK3β overactivation and alleviated isoflurane-induced cognitive deficits. These results suggest that isoflurane is more likely to induce developmental neurotoxicity than desflurane in context of multiple exposures and that the Akt/GSK3β signaling pathway partly participates in this process. GSK3β inhibition might be an effective way to protect against developmental neurotoxicity.

Astrocytic response to cerebral ischemia is influenced by sex differences and impaired by aging

Ischemic stroke occurs more often among the elderly, and within this demographic, women are at an increased risk for stroke and have poorer functional recovery than men. This is also well replicated in animal studies where aging females are shown to have more extensive brain tissue loss as compared to adult females. Astrocytes provide nutrients for neurons, regulate glutamate levels, and release neurotrophins and thus play a key role in the events that occur following ischemia. In addition, astrocytes express receptors for gonadal hormones and synthesize several neurosteroids suggesting that the sex differences in stroke outcome may be mediated through astrocytes. This review discusses key astrocytic responses to ischemia including, reactive gliosis, excitotoxicity, and neuroinflammation. In light of the age and sex differences in stroke outcomes, this review highlights how aging and gonadal hormones influence these responses. Lastly, astrocyte specific changes in gene expression and epigenetic modifications during aging and following ischemia are discussed as possible molecular mechanisms for impaired astrocytic functioning.

Proline-, glutamic acid-, and leucine-rich protein 1 mediates estrogen rapid signaling and neuroprotection in the brain

17-β estradiol (E2) has been implicated as neuroprotective in a variety of neurodegenerative disorders. However, the underlying mechanism remains unknown. Here, we provide genetic evidence, using forebrain-specific knockout (FBKO) mice, that proline-, glutamic acid-, and leucine-rich protein 1 (PELP1), an estrogen receptor coregulator protein, is essential for the extranuclear signaling and neuroprotective actions of E2 in the hippocampal CA1 region after global cerebral ischemia (GCI). E2-mediated extranuclear signaling (including activation of extracellular signal-regulated kinase and Akt) and antiapoptotic effects [such as attenuation of JNK signaling and increase in phosphorylation of glycogen synthase kinase-3β (GSK3β)] after GCI were compromised in PELP1 FBKO mice. Mechanistic studies revealed that PELP1 interacts with GSK3β, E2 modulates interaction of PELP1 with GSK3β, and PELP1 is a novel substrate for GSK3β. RNA-seq analysis of control and PELP1 FBKO mice after ischemia demonstrated alterations in several genes related to inflammation, metabolism, and survival in PELP1 FBKO mice, as well as a significant reduction in the activation of the Wnt/β-catenin signaling pathway. In addition, PELP1 FBKO studies revealed that PELP1 is required for E2-mediated neuroprotection and for E2-mediated preservation of cognitive function after GCI. Collectively, our data provide the first direct in vivo evidence, to our knowledge, of an essential role for PELP1 in E2-mediated rapid extranuclear signaling, neuroprotection, and cognitive function in the brain.

Baclofen mediates neuroprotection on hippocampal CA1 pyramidal cells through the regulation of autophagy under chronic cerebral hypoperfusion

GABA receptors play an important role in ischemic brain injury. Studies have indicated that autophagy is closely related to neurodegenerative diseases. However, during chronic cerebral hypoperfusion, the changes of autophagy in the hippocampal CA1 area, the correlation between GABA receptors and autophagy, and their influences on hippocampal neuronal apoptosis have not been well established. Here, we found that chronic cerebral hypoperfusion resulted in rat hippocampal atrophy, neuronal apoptosis, enhancement and redistribution of autophagy, down-regulation of Bcl-2/Bax ratio, elevation of cleaved caspase-3 levels, reduction of surface expression of GABAA receptor α1 subunit and an increase in surface and mitochondrial expression of connexin 43 (CX43) and CX36. Chronic administration of GABAB receptors agonist baclofen significantly alleviated neuronal damage. Meanwhile, baclofen could up-regulate the ratio of Bcl-2/Bax and increase the activation of Akt, GSK-3β and ERK which suppressed cytodestructive autophagy. The study also provided evidence that baclofen could attenuate the decrease in surface expression of GABAA receptor α1 subunit, and down-regulate surface and mitochondrial expression of CX43 and CX36, which might enhance protective autophagy. The current findings suggested that, under chronic cerebral hypoperfusion, the effects of GABAB receptors activation on autophagy regulation could reverse neuronal damage.

Nanoparticle Estrogen in Rat Spinal Cord Injury Elicits Rapid Anti-Inflammatory Effects in Plasma, Cerebrospinal Fluid, and Tissue

Persons with spinal cord injury (SCI) are in need of effective therapeutics. Estrogen (E2), as a steroid hormone, is a highly pleiotropic agent; with anti-inflammatory, anti-apoptotic, and neurotrophic properties, it is ideal for use in treatment of patients with SCI. Safety concerns around the use of high doses of E2 have limited clinical application, however. To address these concerns, low doses of E2 (25 μg and 2.5 μg) were focally delivered to the injured spinal cord using nanoparticles. A per-acute model (6 h after injury) was used to assess nanoparticle release of E2 into damaged spinal cord tissue; in addition, E2 was evaluated as a rapid anti-inflammatory. To assess inflammation, 27-plex cytokine/chemokine arrays were conducted in plasma, cerebrospinal fluid (CSF), and spinal cord tissue. A particular focus was placed on IL-6, GRO-KC, and MCP-1 as these have been identified from CSF in human studies as potential biomarkers in SCI. S100β, an additional proposed biomarker, was also assessed in spinal cord tissue only. Tissue concentrations of E2 were double those found in the plasma, indicating focal release. E2 showed rapid anti-inflammatory effects, significantly reducing interleukin (IL)-6, GRO-KC, MCP-1, and S100β in one or all compartments. Numerous additional targets of rapid E2 modulation were identified including: leptin, MIP-1α, IL-4, IL-2, IL-10, IFNγ, tumor necrosis factor-α, etc. These data further elucidate the rapid anti-inflammatory effects E2 exerts in an acute rat SCI model, have identified additional targets of estrogen efficacy, and suggest nanoparticle delivered estrogen may provide a safe and efficacious treatment option in persons with acute SCI.

4-Phenylbutyric Acid (4-PBA) and Lithium Cooperatively Attenuate Cell Death during Oxygen-Glucose Deprivation (OGD) and Reoxygenation

Hypoxia is an important cause of brain injury in ischemic stroke. It is known that endoplasmic reticulum (ER) stress is an important determinant of cell survival or death during hypoxia. However, the signaling pathways and molecular mechanisms involved remain to be studied in more detail. To investigate whether inhibition of ER stress promotes neuroprotection pathways, we applied an in vitro oxygen-glucose deprivation (OGD) followed by reoxygenation model of human SK-N-MC neuronal cell cultures in this study. Our results showed that neuronal cell death was induced in this model during the OGD reoxygenation by the sustained ER stress, but not during OGD phase. However, treatment of the cultures with lithium with the OGD reoxygenation insult did not result in neuroprotection, whereas concomitant treatment of chemical chaperon 4-phenylbutyric acid (4-PBA) provides protective effects in ER stress-exposed cells. Moreover, 4-PBA rescued ER stress-suppressed Akt protein biosynthesis, which works cooperatively with lithium in the activation of Akt downstream signaling by inhibition of autophagy-induced cell death. Taken together, our finding provides a possible mechanism by which 4-PBA and lithium contribute to mediate neuroprotection cooperatively. This result may potentially be a useful therapeutic strategy for ischemic stroke.

Damage effect of interleukin (IL)-23 on oxygen-glucose-deprived cells of the neurovascular unit via IL-23 receptor

Interleukin-23/interleukin-23 receptor (IL-23/IL-23R) has been implicated in many inflammatory diseases. Previous research mainly focused on its ability to induce IL-17 production from T cells. However, few studies have investigated its role in cerebral ischemic injury. The aim of our study was to explore the potential effect of IL-23 on cells of the neurovascular unit (NVU) under an oxygen-glucose deprivation (OGD) condition and the role of IL-23R in IL-23-mediated effect. OGD of primary cells of the NVU and permanent middle cerebral artery occlusion (pMCAO) were used to produce experimental stroke in vitro and in vivo, respectively. IL-23 and IL-23R were detected by immunohistochemistry and western blot in pMCAO mice. Metabolic viability of cultured cells was assessed by MTT assay. The cell-associated proteins (Bcl-2, AQP4 and ET-1) were determined by western blot and enzyme-linked immunosorbent assay (ELISA). Immunofluorescence staining and western blot were used to detect the IL-23R expression. The results showed that the expression of IL-23/IL-23R was elevated in pMCAO mice. IL-23 could aggravate neuron damage, astrocyte swelling, and further impair the integrity of blood-brain barrier induced by OGD. In addition, the effect of IL-23 on cells of the NVU is mediated by IL-23R and is likely IL-23R-expression-level dependent. However, there are no such biological properties for the IL-23p19 subunit alone. Our study provides the first evidence that IL-23 has a toxic effect on cells of the NVU under OGD stress, which is mediated by IL-23R. These results not only help us better understand the role of IL-23/IL-23R in brain ischemia, but also provide a potential therapeutic target in stroke.

The neuroprotective actions of oestradiol and oestrogen receptors

Hormones regulate homeostasis by communicating through the bloodstream to the body's organs, including the brain. As homeostatic regulators of brain function, some hormones exert neuroprotective actions. This is the case for the ovarian hormone 17β-oestradiol, which signals through oestrogen receptors (ERs) that are widely distributed in the male and female brain. Recent discoveries have shown that oestradiol is not only a reproductive hormone but also a brain-derived neuroprotective factor in males and females and that ERs coordinate multiple signalling mechanisms that protect the brain from neurodegenerative diseases, affective disorders and cognitive decline.

Perillaldehyde attenuates cerebral ischemia-reperfusion injury-triggered overexpression of inflammatory cytokines via modulating Akt/JNK pathway in the rat brain cortex

Perillaldehyde (PAH), one of the major oil components in Perilla frutescens, has anti-inflammatory effects. Few studies have examined the neuroprotective effect of PAH on stroke. So the aim of our study is to investigate the effect of PAH on ischemia-reperfusion-induced injury in the rat brain cortex. Middle cerebral artery occlusion (MCAO) model was selected to make cerebral ischemia-reperfusion injury. Rats were assigned randomly to groups of sham, MCAO, and two treatment groups by PAH at 36.0, 72.0mg/kg. Disease model was set up after intragastrically (i.g.) administering for 7 consecutive days. The neurological deficit, the cerebral infarct size, biochemical parameters and the relative mRNA and protein levels were examined. The results showed that the NO level, the iNOS activity, the neurological deficit scores, the cerebral infarct size and the expression of inflammatory cytokines including interleukin (IL)-1β, interleukin (IL)-6 and tumor necrosis factor (TNF)-α were significantly decreased by PAH treatment. PAH also increased the Phospho-Akt level and decrease the Phospho-JNK level by Western blot analysis. Meanwhile, the PAH groups exhibited a dramatically decrease of apoptosis-related mRNA expression such as Bax and caspase-3. Our findings shown that PAH attenuates cerebral ischemia/reperfusion injury in the rat brain cortex, and suggest its neuroprotective effect is relate to regulating the inflammatory response through Akt /JNK pathway. The activation of this signalling pathway eventually inhibits apoptotic cell death induced by cerebral ischemia-reperfusion.

Neuroprotective effects of rhynchophylline against ischemic brain injury via regulation of the Akt/mTOR and TLRs signaling pathways

Rhynchophylline (Rhy) is an alkaloid isolated from Uncaria which has long been recommended for the treatment of central nervous diseases. In our study, the neuroprotective effect of Rhy was investigated in a stroke model, namely permanent middle cerebral artery occlusion (pMCAO). Rats were injected intraperitoneally once daily for four consecutive days before surgery and then received one more injection after surgery. The protein and mRNA levels of p-Akt, p-mTOR, apoptosis-related proteins (p-BAD and cleaved caspase-3), TLR2/4/9, NF-κB, MyD88, BDNF and claudin-5 were examined. Following pMCAO, Rhy treatment not only ameliorated neurological deficits, infarct volume and brain edema, but also increased claudin-5 and BDNF expressions (p < 0.05). Moreover, Rhy could activate PI3K/Akt/mTOR signaling while inhibiting TLRs/NF-κB pathway. Wortmannin, a selective PI3K inhibitor, could abolish the neuroprotective effect of Rhy and reverse the increment in p-Akt, p-mTOR and p-BAD levels. In conclusion, we hypothesize that Rhy protected against ischemic damage, probably via regulating the Akt/mTOR pathway.