Association between Citrullinated Histone H3 and White Matter Lesions Burden in Patients with Ischemic Stroke.

INTRODUCTION: Neutrophil extracellular traps play a role in the pathophysiology of stroke and are associated with severity and mortality. We aimed to investigate whether the citrullinated histone H3 (CitH3), a biomarker for neutrophil extracellular traps formation, is associated with the white matter lesion (WML) burden in ischemic stroke patients. METHODS: Between September 2021 and April 2022, 322 patients were enrolled in this prospective observational cohort study. Serum CitH3 levels were measured after admission using an enzyme-linked immunosorbent assay. WMLs severity was graded according to the Fazekas scale and conceptually defined as mild (total Fazekas score 0-2) and severe (total Fazekas score 3-6). We used multivariable regression models to determine the relationship between CitH3 concentrations and the severity of WMLs burden. RESULTS: One-hundred and forty-eight (46.0%) patients were diagnosed with severe WMLs burden after admission. Increased CitH3 levels (first quartile vs. fourth quartile of H3Cit, odds ratio, 3.311, 95% confidence interval, 1.336-8.027; p = 0.011) were independently associated with a greater WML burden in the fully adjusted multivariable model. Similar results were found when the H3Cit was analyzed as a continuous variable. Furthermore, the multiple-adjusted spline regression model showed a linear association between H3Cit levels and severe WMLs (P = 0.001 for linearity). CONCLUSIONS: In the present study, increased CitH3 levels were positively associated with extensive WMLs in ischemic stroke patients, indicating a role of neutrophil extracellular traps formation in the pathogenesis of WMLs.

Astrocytic purinergic signalling contributes to the development and maintenance of neuropathic pain via modulation of glutamate release.

Although activation of astrocytes is critical in developing neuropathic pain (NP) following nerve injury, the underlying mechanisms of NP and therapeutic management for NP are still vague. Importantly, the decreases in the levels of astrocytic glutamate transporter-1 (GLT-1) in the spinal dorsal horn result in enhanced excitatory transmission and cause persistent pain. P2Y1 purinergic receptor (P2Y1R) has been shown to enhance many inflammatory processes. The up-regulated expression of astrocytic P2Y1R is crucial to participate in pain transduction under conditions of nerve injury and peripheral inflammation considering that P2Y1R is potentially involved in glutamate release and synaptic transmission. This study indicates that the expression of P2Y1R in the spinal cord was increased accompanied by the activation of A1 phenotype astrocytes in the rat model of spinal nerve ligation (SNL). Astrocyte-specific knockdown of P2Y1R alleviated SNL-induced nociceptive responses and mitigated A1 reactive astrocytes, which subsequently increased GLT-1 expression. Conversely, in naïve rats, P2Y1R over-expression induced a canonical NP-like phenotype and spontaneous hypernociceptive responses and increased the concentration of glutamate in the spinal dorsal horn. Besides, our in vitro data showed that the proinflammatory cytokine tumour necrosis factor-alpha contributes to A1/A2 astrocyte reactivity and Ca2+ -dependent release of glutamate. Conclusively, our results provide novel insights that as a significant regulator of astrocytic A1/A2 polarization and neuroinflammation, P2Y1R may represent a potential target for the treatment of SNL-induced NP.

Rescuers from the Other Shore: Intercellular Mitochondrial Transfer and Its Implications in Central Nervous System Injury and Diseases.

As the powerhouse and core of cellular metabolism and survival, mitochondria are the essential organelle in mammalian cells and maintain cellular homeostasis by changing their content and morphology to meet demands through mitochondrial quality control. It has been observed that mitochondria can move between cells under physiological and pathophysiological conditions, which provides a novel strategy for preserving mitochondrial homeostasis and also a therapeutic target for applications in clinical settings. Therefore, in this review, we will summarize currently known mechanisms of intercellular mitochondrial transfer, including modes, triggers, and functions. Due to the highly demanded energy and indispensable intercellular linkages of the central nervous system (CNS), we highlight the mitochondrial transfer in CNS. We also discuss future application possibilities and difficulties that need to be addressed in the treatment of CNS injury and diseases. This clarification should shed light on its potential clinical applications as a promising therapeutic target in neurological diseases. Intercellular mitochondrial transfer maintains the homeostasis of central nervous system (CNS), and its alteration is related to several neurological diseases. Supplementing exogenous mitochondrial donor cells and mitochondria, or utilizing some medications to regulate the process of transfer might mitigate the disease and injury.

Impact of miR-200b and miR-495 variants on the risk of large-artery atherosclerosis stroke.

Single-nucleotide polymorphisms (SNPs) of microRNAs (miRNAs) may alter miRNA transcription, maturation and target specificity, thus affecting stroke susceptibility. We aimed to investigate whether miR-200b and miR-495 SNPs may be associated with ischemic stroke (IS) risk and further explore underlying mechanisms including related genes and pathways. MiR-200b rs7549819 and miR-495 rs2281611 polymorphisms were genotyped among 712 large-artery atherosclerosis (LAA) stroke patients and 1,076 controls in a case-control study. Bioinformatic analyses were performed to explore potential association of miR-200b/495 with IS and to examine the effects of these two SNPs on miR-200b/495. Furthermore, we evaluated the association between these two SNPs and stroke using the public GWAS datasets. In our case-control study, rs7549819 was significantly associated with a decreased risk of LAA stroke (OR = 0.73, 95% CI = 0.58-0.92; p = 0.007), while rs2281611 had no significant association with LAA stroke risk. These results were consistent with the findings in East Asians from the GIGASTROKE study. Combined effects analysis revealed that individuals with 2-4 protective alleles (miR-200bC and miR-495 T) exhibited lower risk of LAA stroke than those with 0-1 variants (OR = 0.76, 95% CI = 0.61-0.96; p = 0.021). Bioinformatic analyses showed that miR-200b and miR-495 were significantly associated with genes and pathways related to IS pathogenesis, and rs7549819 and rs2281611 markedly influenced miRNA expression and structure. MiR-200b rs7549819 polymorphism and the combined genotypes of miR-200b rs7549819 and miR-495 rs2281611 polymorphisms were associated with decreased risk of LAA stroke in Chinese population.

Vascular endothelium deploys caveolin-1 to regulate oligodendrogenesis after chronic cerebral ischemia in mice.

Oligovascular coupling contributes to white matter vascular homeostasis. However, little is known about the effects of oligovascular interaction on oligodendrocyte precursor cell (OPC) changes in chronic cerebral ischemia. Here, using a mouse of bilateral carotid artery stenosis, we show a gradual accumulation of OPCs on vasculature with impaired oligodendrogenesis. Mechanistically, chronic ischemia induces a substantial loss of endothelial caveolin-1 (Cav-1), leading to vascular secretion of heat shock protein 90α (HSP90α). Endothelial-specific over-expression of Cav-1 or genetic knockdown of vascular HSP90α restores normal vascular-OPC interaction, promotes oligodendrogenesis and attenuates ischemic myelin damage. miR-3074(-1)-3p is identified as a direct inducer of Cav-1 reduction in mice and humans. Endothelial uptake of nanoparticle-antagomir improves myelin damage and cognitive deficits dependent on Cav-1. In summary, our findings demonstrate that vascular abnormality may compromise oligodendrogenesis and myelin regeneration through endothelial Cav-1, which may provide an intercellular mechanism in ischemic demyelination.

Endothelial caveolin-1 regulates cerebral thrombo-inflammation in acute ischemia/reperfusion injury.

BACKGROUND: Thrombo-inflammation is an important checkpoint that orchestrates infarct development in ischemic stroke. However, the underlying mechanism remains largely unknown. Here, we explored the role of endothelial Caveolin-1 (Cav-1) in cerebral thrombo-inflammation. METHODS: The correlation between serum Cav-1 level and clinical outcome was analyzed in acute ischemic stroke patients with successful recanalization. Genetic manipulations by endothelial-specific adeno-associated virus (AAV) and siRNA were applied to investigate the effects of Cav-1 in thrombo-inflammation in a transient middle cerebral artery occlusion (tMCAO) model. Thrombo-inflammation was analyzed by microthrombosis formation, myeloid cell infiltration, and endothelial expression of adhesion molecules as well as inflammatory factors. FINDINGS: Reduced circulating Cav-1, with the potential to predict microembolic signals, was more frequently detected in recanalized stroke patients without early neurological improvement. At 24 h after tMCAO, serum Cav-1 was consistently reduced in mice. Endothelial Cav-1 was decreased in the peri-infarct region. Cav-1-/- endothelium, with prominent barrier disruption, displayed extensive microthrombosis, accompanied by increased myeloid cell inflammatory infiltration after tMCAO. Specific enhanced expression of endothelial Cav-1 by AAV-Tie1-Cav-1 remarkably reduced infarct volume, attenuated vascular hyper-permeability and alleviated thrombo-inflammation in both wild-type and Cav-1-/- tMCAO mice. Transcriptome analysis after tMCAO further designated Rxrg as the most significantly changed molecule resulting from the knockdown of Cav-1. Supplementation of RXR-γ siRNA reversed AAV-Tie1-Cav-1-induced amelioration of thrombo-inflammation without affecting endothelial tight junction. INTERPRETATION: Endothelial Cav-1/RXR-γ may regulate infarct volume and neurological impairment, possibly through selectively controlling thrombo-inflammation coupling, in cerebral ischemia/reperfusion. FUNDING: This work was supported by National Natural Science Foundation of China.

Extracellular vesicles carrying proinflammatory factors may spread atherosclerosis to remote locations.

Most cells involved in atherosclerosis release extracellular vesicles (EVs), which can carry bioactive substances to downstream tissues via circulation. We hypothesized that EVs derived from atherosclerotic plaques could promote atherogenesis in remote locations, a mechanism that mimics the blood metastasis of cancer. Ldlr gene knockout (Ldlr KO) rats were fed on a high cholesterol diet and underwent partial carotid ligation to induce local atherosclerosis. EVs were separated from carotid artery tissues and downstream blood of carotid ligation by centrifugation. MiRNA sequencing and qPCR were then performed to detect miRNA differences in EVs from rats with and without induced carotid atherosclerosis. Biochemical analyses demonstrated that EVs derived from atherosclerosis could increase the expression of ICAM-1, VCAM-1, and E-selectin in endothelial cells in vitro. EVs derived from atherosclerosis contained a higher level of miR-23a-3p than those derived from controls. MiR-23a-3p could promote endothelial inflammation by targeting Dusp5 and maintaining ERK1/2 phosphorylation in vitro. Inhibiting EV release could attenuate atherogenesis and reduce macrophage infiltration in vivo. Intravenously administrating atherosclerotic plaque-derived EVs could induce intimal inflammation, arterial wall thickening and lumen narrowing in the carotids of Ldlr KO rats, while simultaneous injection of miR-23a-3p antagomir could reverse this reaction. The results suggested that EVs may transfer atherosclerosis to remote locations by carrying proinflammatory factors, particularly miR-23a-3p.

Aberrant oligodendroglial LDL receptor orchestrates demyelination in chronic cerebral ischemia.

Oligodendrocytes express low-density lipoprotein receptor (LDLR) to endocytose cholesterol for the maintenance of adulthood myelination. However, the potential role of LDLR in chronic cerebral ischemia-related demyelination remains unclear. We used bilateral carotid artery stenosis (BCAS) to induce sustained cerebral ischemia in mice. This hypoxic-ischemic injury caused a remarkable decrease in oligodendroglial LDLR, with impaired oligodendroglial differentiation and survival. Oligodendroglial cholesterol levels, however, remained unchanged. Mouse miR-344e-3p and the human homolog miR-410-3p, 2 miRNAs directly targeting Ldlr, were identified in experimental and clinical leukoaraiosis and were thus implicated in the LDLR reduction. Lentiviral delivery of LDLR ameliorated demyelination following chronic cerebral ischemia. By contrast, Ldlr-/- mice displayed inadequate myelination in the corpus callosum. Ldlr-/- oligodendrocyte progenitor cells (OPCs) exhibited reduced ability to differentiate and myelinate axons in vitro. Transplantation with Ldlr-/- OPCs could not rescue the BCAS-induced demyelination. Such LDLR-dependent myelin restoration might involve a physical interaction of the Asn-Pro-Val-Tyr (NPVY) motif with the phosphotyrosine binding domain of Shc, which subsequently activated the MEK/ERK pathway. Together, our findings demonstrate that the aberrant oligodendroglial LDLR in chronic cerebral ischemia impairs myelination through intracellular signal transduction. Preservation of oligodendroglial LDLR may provide a promising approach to treat ischemic demyelination.

Symptomatic Intracranial Hemorrhage After Mechanical Thrombectomy in Chinese Ischemic Stroke Patients: The ASIAN Score.

BACKGROUND AND PURPOSE: Symptomatic intracranial hemorrhage (sICH), potentially associated with poor prognosis, is a major complication of endovascular thrombectomy (EVT) for ischemic stroke patients. We aimed to develop and validate a risk model for predicting sICH after EVT in Chinese patients due to large-artery occlusions in the anterior circulation. METHODS: The derivation cohort recruited patients with EVT from the Endovascular Treatment for Acute Anterior Circulation Ischemic Stroke Registry in China. sICH was diagnosed according to the Heidelberg Bleeding Classification within 24 hours of EVT. Stepwise logistic regression was performed to derive the predictive model. The discrimination and calibration of the risk model were assessed using the C index and the calibration plot. An additional cohort of 503 patients from 2 stroke centers was prospectively enrolled to validate the new model. RESULTS: We enrolled 629 patients who underwent EVT as the derivation cohort, among whom 87 developed sICH (13.8%). In the multivariate adjustment, Alberta Stroke Program Early CT Score (odds ratio [OR], 0.85; P=0.005), baseline glucose (OR, 1.13; P=0.001), poor collateral circulation (OR, 3.06; P=0.001), passes with retriever (OR, 1.52; P=0.001), and onset-to-groin puncture time (OR, 1.79; P=0.024) were independent factors of sICH and were incorporated as the Alberta Stroke Program Early CT Score, Baseline Glucose, Poor Collateral Circulation, Passes With Retriever, and Onset-to-Groin Puncture Time (ASIAN) score. The ASIAN score demonstrated good discrimination in the derivation cohort (C index, 0.771 [95% CI, 0.716-0.826]), as well as the validation cohort (C index, 0.758 [95% CI, 0.691-0.825]). CONCLUSIONS: The ASIAN score reliably predicts the risk of sICH in Chinese ischemic stroke patients treated by EVT.

High-frequency repetitive transcranial magnetic stimulation improves functional recovery by inhibiting neurotoxic polarization of astrocytes in ischemic rats.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive treatment for ischemic stroke. Astrocytes regulation has been suggested as one mechanism for rTMS effectiveness. But how rTMS regulates astrocytes remains largely undetermined. There were neurotoxic and neuroprotective phenotypes of astrocytes (also denoted as classically and alternatively activated astrocytes or A1 and A2 astrocytes) pertaining to pro- or anti-inflammatory gene expression. Pro-inflammatory or neurotoxic polarized astrocytes were induced during cerebral ischemic stroke. The present study aimed to investigate the effects of rTMS on astrocytic polarization during cerebral ischemic/reperfusion injury. METHODS: Three rTMS protocols were applied to primary astrocytes under normal and oxygen-glucose deprivation/reoxygenation (OGD/R) conditions. Cell survival, proliferation, and phenotypic changes were assessed after 2-day treatment. Astrocytes culture medium (ACM) from control, OGD/R, and OGD/R + rTMS groups were mixed with neuronal medium to culture neurons for 48 h and 7 days, in order to explore the influence on neuronal survival and synaptic plasticity. In vivo, rats were subjected to middle cerebral artery occlusion (MCAO), and received posterior orbital intravenous injection of ACM collected from different groups at reperfusion, and at 3 days post reperfusion. The apoptosis in the ischemic penumbra, infarct volumes, and the modified Neurological Severity Score (mNSS) were evaluated at 1 week after reperfusion, and cognitive functions were evaluated using the Morris Water Maze (MWM) tests. Finally, the 10 Hz rTMS was directly applied to MCAO rats to verify the rTMS effects on astrocytic polarization. RESULTS: Among these three frequencies, the 10 Hz protocol exerted the greatest potential to modulate astrocytic polarization after OGD/R injury. Classically activated and A1 markers were significantly inhibited by rTMS treatment. In OGD/R model, the concentration of pro-inflammatory mediator TNF-α decreased from 57.7 to 23.0 Ñ€g/mL, while anti-inflammatory mediator IL-10 increased from 99.0 to 555.1 Ñ€g/mL in the ACM after rTMS treatment. The ACM collected from rTMS-treated astrocytes significantly alleviated neuronal apoptosis induced by OGD/R injury, and promoted neuronal plasticity. In MCAO rat model, the ACM collected from rTMS treatment decreased neuronal apoptosis and infarct volumes, and improved cognitive functions. The neurotoxic astrocytes were simultaneously inhibited after rTMS treatment. CONCLUSION: Inhibition of neurotoxic astrocytic polarization is a potential mechanism for the effectiveness of high-frequency rTMS in cerebral ischemic stroke.

CD99 mediates neutrophil transmigration through the bEnd.3 monolayer via the induction of oxygen-glucose deprivation.

AIM/BACKGROUND: CD99 participate in neutrophil infiltration after inflammatory events; however, despite the important role of inflammation in ischemic stroke, the role of CD99 in ischemic stroke remains unclear. METHOD: In the present study, we detected the protein expression of CD99, ICAM-1, and CD31 (PECAM-1) in oxygen-glucose deprivation (OGD)-induced bEnd.3 cells and neutrophils and explored the influence of HIF-1α and IL-1ß on their expression. We also explored the role of CD99 in the OGD-induced transmigration of neutrophils. RESULTS: Our results showed that OGD induction upregulated CD99 in bEnd.3 cells and that this effect could be abolished by the preadministration of IL-1ß and was not mediated by HIF-1α. However, the activation of ICAM-1 by OGD remained activated with IL-1ß treatment. No significant influence of IL-1ß on OGD-induced CD31. Finally, we found a significant increase in infiltrated neutrophils after OGD induction compared with the control and OGD + anti-CD99 groups. CONCLUSION: Our results indicated that CD99 mediates neutrophil infiltration and transmigration via OGD induction and thus constitutes a potential therapeutic target for anti-inflammatory treatment after ischemic stroke.

A droplet-based microfluidic viscometer for the measurement of blood coagulation.

A continuous microfluidic viscometer is used to measure blood coagulation. The viscometer operates by flowing oil and blood into a cross section where droplets are generated. At a set pressure, the length of the droplets is inversely proportional to the viscosity of the blood sample being delivered. Because blood viscosity increases during coagulation as the blood changes from a liquid to a solid gel, the device allows to monitor coagulation by simply measuring the drop length. Experiments with swine blood were carried out in its native state and with the addition of coagulation activators and inhibitors. The microfluidic viscometer detected an earlier initiation of the coagulation process with the activator and a later initiation with the inhibitor compared to their corresponding controls. The results from the viscometer were also compared with the clinical method of thromboelastography (TEG), which was performed concurrently for the same samples. The time to initiation of coagulation in the microfluidic viscometer was correlated with the reaction time in TEG. Additionally, the total time for the measurement of clot strengthening in TEG correlated with the time for the maximum viscosity observed in the microfluidic viscometer. The microfluidic viscometer measured changes in viscosity due to coagulation faster than TEG detected the clot formation. The present viscometer is a simple technology that can be used to further study the entire coagulation process.

Size-distribution-based assessment of human inhalation and dermal exposure to airborne parent, oxygenated and chlorinated PAHs during a regional heavy haze episode.

The adverse health effects of haze and particle-bound contaminants in China have recently caused increasing concern, and particle size plays a significant role in affecting human exposure to haze-correlated pollutants. To this background, size-segregated particulate samples (nine size fractions (<0.4, 0.4-0.7, 0.7-1.1, 1.1-2.1, 2.1-3.3, 3.3-4.7, 4.7-5.8, 5.8-9.0 and > 9.0 µm) were collected in three scale-gradient cities in northern China and analysed for a series of parent, oxygenated and chlorinated polycyclic aromatic hydrocarbons (PAHs, O-PAHs and Cl-PAHs). The total geometric mean concentrations of PAHs and O-PAHs for Beijing, Zhengzhou and Xinxiang were 98.1 and 27.2, 77.9 and 77.5, 41.0 and 30.7 ng m-3, respectively, which were 50-200 times higher than those for Cl-PAHs (0.5, 0.7 and 0.4 ng m-3). Though unimodal size-distribution patterns were found for all these contaminants for these three cities, PAHs represented distinctly higher concentration levels around the peak fraction (0.7-2.1 µm) than O-PAHs and Cl-PAHs. With 4-6 ring PAHs as dominant components in all samples, the percentage proportion of 2-3 ring PAHs (ranging from 1% to 26%) generally increased with particle size increasing, implying the sources of these compounds varied little among the 9 size fractions in all three cities. The International Commission on Radiological Protection (ICRP) model and permeability coefficient method were synchronously applied to the size-segregated data for inhalation and dermal exposure assessment to intensively estimate the human exposure doses to airborne PAHs. Further, the incremental lifetime cancer risk (ILCR) was calculated and it's found that ILCR from inhalation was higher than that from dermal uptake for children and adults in Beijing and Zhengzhou, while the ILCR for Xinxiang presented a contrary pattern, revealing dermal uptake to be an equally significant exposure pathway to airborne PAHs compared to inhalation.

Microglial TREM-1 receptor mediates neuroinflammatory injury via interaction with SYK in experimental ischemic stroke.

Neuroinflammation is initiated in response to ischemic stroke, generally with the hallmarks of microglial activation and collateral brain injury contributed by robust inflammatory effects. Triggering receptor expressed on myeloid cells (TREM)-1, an amplifier of the innate immune response, is a critical regulator of inflammation. This study identified that microglial TREM-1 expression was upregulated following cerebral ischemic injury. After pharmacologic inhibition of TREM-1 with synthetic peptide LP17, ischemia-induced infarction and neuronal injury were substantially alleviated. Moreover, blockade of TREM-1 can potentiate cellular proliferation and synaptic plasticity in hippocampus, resulting in long-term functional improvement. Microglial M1 polarization and neutrophil recruitment were remarkably abrogated as mRNA levels of M1 markers, chemokines, and protein levels of myeloperoxidase and intracellular adhesion molecule-1 (ICAM-1) were decreased by LP17. Mechanistically, both in vivo and in vitro, we delineated that TREM-1 can activate downstream pro-inflammatory pathways, CARD9/NF-κB, and NLRP3/caspase-1, through interacting with spleen tyrosine kinase (SYK). In addition, TREM-1-induced SYK initiation was responsible for microglial pyroptosis by elevating levels of gasdermin D (GSDMD), N-terminal fragment of GSDMD (GSDMD-N), and forming GSDMD pores, which can facilitate the release of intracellular inflammatory factors, in microglia. In summary, microglial TREM-1 receptor yielded post-stroke neuroinflammatory damage via associating with SYK.

Inhalation bioaccessibility of PAHs in PM2.5: Implications for risk assessment and toxicity prediction.

In this study, 46 PM2.5 samples collected from Nanjing, China were analyzed for total PAH concentration, with 14 samples assessed for PAH inhalation bioaccessibility and dioxin toxicity. The concentration of 19 PAH compounds in PM2.5 ranged from 4.03 to 102 ng m-3. When PAH inhalation bioaccessibility was assessed using simulated epithelial lung fluid, mean bioaccessibility values ranged from 3.21% (Benzo(c)fluorene) to 44.2% (Acenaphthylene). Benzo(a)pyrene concentration in 50% of the PM2.5 samples exceeded the Chinese air quality standard of 2.5 ng m-3, however, when bioaccessibility was considered, all samples were below the criterion. Similarly, the cancer risk probability for all PM2.5 samples was >10-4 incidences on the basis of total PAH concentration, while only 37% of samples posed a risk >10-4 after incorporation of bioaccessibility. Dioxin toxicity of PM2.5-bound PAHs was also investigated by characterizing mRNA expression of cytochrome P450 superfamily members in human lung cells (A549 cell). Compared to total PAH concentration, the use of bioaccessible concentration was better at predicting dioxin toxicity of PM2.5-associated PAHs (correlation coefficient R2 = 0.40-0.83 with p < 0.05). This study indicates that PAH inhalation bioaccessibility is an important consideration when assessing and predicting the risk posed by PM2.5 particles, which is particularly important for countries with deteriorating air quality.

Breast cancer susceptibility protein 1 (BRCA1) rescues neurons from cerebral ischemia/reperfusion injury through NRF2-mediated antioxidant pathway.

Cellular oxidative stress plays a vital role in the pathological process of neural damage in cerebral ischemia/reperfusion (I/R). The breast cancer susceptibility protein 1 (BRCA1), a tumor suppressor, can modulate cellular antioxidant response and DNA repair. Yet the role of BRCA1 in cerebral I/R injury has not been explored. In this study, we observed that BRCA1 was mainly expressed in neurons and was up-regulated in response to I/R insult. Overexpression of BRCA1 attenuated reactive oxygen species production and lipid peroxidation. Enhanced BRCA1 expression promoted DNA double strand break repair through non-homologous end joining pathway. These effects consequently led to neuronal cell survival and neurological recovery. Mechanically, BRCA1 can interact with the nuclear factor (erythroid-derived 2)-like 2 (NRF2) through BRCA1 C-terminal (BRCT) domain. The cross-talk between BRCT and NRF2 activated the NRF2/Antioxidant Response Element signaling pathway and thus protected injured neurons during cerebral I/R. In conclusion, enhanced BRCA1 after cerebral I/R injury may attenuate or prevent neural damage from I/R via NRF2-mediated antioxidant pathway. The finding may provide a potential therapeutic target against ischemic stroke.

GRP78 Promotes Neural Stem Cell Antiapoptosis and Survival in Response to Oxygen-Glucose Deprivation (OGD)/Reoxygenation through PI3K/Akt, ERK1/2, and NF-κB/p65 Pathways.

When brain injury happens, endogenous neural stem cells (NSCs) located in the adult subventricular zone (SVZ) and subgranular zone (SGZ) are attacked by ischemia/reperfusion to undergo cellular apoptosis and death before being induced to migrate to the lesion point and differentiate into mature neural cells for damaged cell replacement. Although promoting antiapoptosis and NSC survival are critical to neuroregeneration, the mechanism has yet been elucidated clearly. Here in this study, we established an in vitro oxygen-glucose deprivation (OGD)/reoxygenation model on NSCs and detected glucose-regulated protein 78 (GRP78) involved in apoptosis, while in the absence of GRP78 by siRNA transfection, OGD/reoxygenation triggered PI3K/Akt, ERK1/2, and NF-κB/p65 activation, and induced NSC apoptosis was attenuated. Further investigation, respectively, with the inhibitor of PI3K/Akt or ERK1/2 demonstrated a blockage on GRP78 upregulation, while the inhibition of NF-κB rarely affected GRP78 induction by OGD/reoxygenation. The results indicated the bidirectional regulations of GRP78-PI3K/Akt and GRP78-ERK1/2 and the one-way signalling transduction through GRP78 to NF-κB/p65 on NSC survival from OGD/reoxygenation. In conclusion, we found that GRP78 mediated the signalling cross talk through PI3K/Akt, ERK1/2, and NF-κB/p65, which leads to antiapoptosis and NSC survival from ischemic stroke. Our finding gives a new evidence of GRP78 in NSCs as well as a new piece of signalling mechanism elucidation to NSC survival from ischemic stroke.

Mitochondrial protective mechanism of simvastatin protects against amyloid ß peptide-induced injury in SH-SY5Y cells.

Mitochondrial dysfunction is implicated in the pathology of neuronal damage during Alzheimer's disease (AD). Previous studies suggest that simvastatin (SV) ameliorates amyloid ß (Aß)­mediated cognitive impairment in AD patients and transgenic mice; however, the mechanisms remain unknown. To investigate the potential mechanisms by which SV protects against AD neurotoxicity, the present study used a series of cellular and molecular assays to analyze the effects of SV in an in vitro model of Aß1­42-induced injury. The results demonstrated that SV protected against Aß1­42­induced SH­SY5Y cell injury by inhibiting the release of cytochrome c from the mitochondria to the cytoplasm, and reducing the production of intracellular reactive oxygen species. In addition, SV downregulated cleaved­caspase­3 protein levels, increased the ratio of B cell lymphoma 2 (Bcl-2) to Bcl-2-associated X protein, and increased the protein levels of peroxisome proliferator-activated receptor Î³ coactivator-1α in the Aß1­42­treated cells. Furthermore, SV increased the mitochondrial membrane potential and adenosine triphosphate levels, and enhanced the cell respiratory function and mitochondrial mass of the cells. In conclusion, the present study revealed that SV protected SH­SY5Y cells against Aß1­42-induced injury through regulating the mitochondrial apoptosis pathway and mitochondrial function.

Impact of particle size on distribution and human exposure of flame retardants in indoor dust.

The effect of dust particle size on the distribution and bioaccessibility of flame retardants (FRs) in indoor dust remains unclear. In this study, we analyzed 20 FRs (including 6 organophosphate flame retardants (OPFRs), 8 polybrominated diphenyl ethers (PBDEs), 4 novel brominated flame retardants (NBFRs), and 2 dechlorane plus (DPs)) in composite dust samples from offices, public microenvironments (PME), and cars in Nanjing, China. Each composite sample (one per microenvironment) was separated into 6 size fractions (F1-F6: 200-2000µm, 150-200µm, 100-150µm, 63-100µm, 43-63µm, and <43µm). FRs concentrations were the highest in car dust, being 16 and 6 times higher than those in offices and PME. The distribution of FRs in different size fractions was Kow-dependent and affected by surface area (Log Kow=1-4), total organic carbon (Log Kow=4-9), and FR migration pathways into dust (Log Kow>9). Bioaccessibility of FRs was measured by the physiologically-based extraction test, with OPFR bioaccessibility being 1.8-82% while bioaccessible PBDEs, NBFRs, and DPs were under detection limits due to their high hydrophobicity. The OPFR bioaccessibility in 200-2000µm fraction was significantly higher than that of <43µm fraction, but with no difference among the other four fractions. Risk assessment was performed for the most abundant OPFR-tris(2-chloroethyl) phosphate. The average daily dose (ADD) values were the highest for the <43µm fraction for all three types of dust using total concentrations, but no consistent trend was found among the three types of dust if based on bioaccessible concentrations. Our results indicated that dust size impacted human exposure estimation of FRs due to their variability in distribution and bioaccessibility among different fractions. For future risk assessment, size selection for dust sampling should be standardized and bioaccessibility of FRs should not be overlooked.