Non-ischemic Hemisphere Research Articles

Gasdermin D could be lost in the brain parenchyma infarct core and a pyroptosis-autophagy inhibition effect of Jie-Du-Huo-Xue decoction after stroke.

The Chinese ethnic medicine Jie-Du-Huo-Xue Decoction (JDHXD) is used to alleviate neuroinflammation in cerebral ischemia (CI). Our previous studies have confirmed that JDHXD can inhibit microglial pyroptosis in CI. However, the pharmacological mechanism of JDHXD in alleviating neuroinflammation and pyroptosis needs to be further elucidated. New research points out that there is an interaction between autophagy and inflammasome NLRP3, and autophagy can help clear NLRP3. The NLRP3 is a key initiator of pyroptosis and autophagy. The effect of JDHXD promoting autophagy to clear NLRP3 to inhibit pyroptosis on cerebral ischemia-reperfusion inflammatory injury is currently unknown. We speculate that JDHXD can inhibit pyroptosis in CI by promoting autophagy to clear NLRP3. Chemical characterization of JDHXD was performed using LC-MS. Model of middle cerebral artery occlusion/reperfusion (MCAO/R) was established in SD rats. Neurological deficits, neuron damage, and cerebral infarct volume were evaluated. Western Blot and immunofluorescence were used to detect neuronal pyroptosis and autophagy. 30 possible substance metabolites in JDHXD medicated serum were analyzed by LC-MS (Composite Score > 0.98). Furthermore, JDHXD protects rat neurological function and cerebral infarct size after CI. JDHXD inhibited the expression of pyroptosis and autophagy after CI. Our western blot and immunofluorescence results showed that JDHXD treatment can reduce the expression of autophagy-related factors ULK1, beclin1, and LC3-Ⅱ. The expression of NLRP3 protein was lower in the JDHXD group than in the I/R group. Compared with the I/R group, the expressions of pyroptosis-related factors caspase-1 P 10, GSDMD-NT, IL-18, and IL-1β decreased in the JDHXD group. Furthermore, we observed an unexpected result: immunofluorescence demonstrated that Gasdermin D (GSDMD) was significantly absent in the infarct core, and highly expressed in the peri-infarct and contralateral cerebral hemispheres. This finding challenges the prevailing view that GSDMD is elevated in the ischemic cerebral hemisphere. JDHXD inhibited pyroptosis and autophagy after MCAO/R. JDHXD suppressed pyroptosis and autophagy by inhibiting NLRP3, thereby alleviating CI. In addition, we present a different observation from previous studies that the expression of GSDMD in the infarct core was lower than that in the peri-infarct and contralateral non-ischemic hemispheres on day 3 of CI.

Long-Term Region-Specific Mitochondrial Functionality Changes in Both Cerebral Hemispheres after fMCAo Model of Ischemic Stroke.

Cerebral ischemia/reperfusion (I/R) refers to a secondary brain injury that results in mitochondrial dysfunction of variable extent, leading to neuronal cell damage. The impact of this process has mainly been studied in the short term, from the early hours up to one week after blood flow reperfusion, and in the ischemic hemisphere only. The focus of this study was to assess the long-term impacts of I/R on mitochondrial functionality using high-resolution fluorespirometry to evaluate state-dependent activities in both ischemic (ipsilateral) and non-ischemic (contralateral) hemispheres of male mice 60, 90, 120, and 180 days after I/R caused by 60-min-long filament-induced middle cerebral artery occlusion (fMCAo). Our results indicate that in cortical tissues, succinate-supported oxygen flux (Complex I&II OXPHOS state) and H2O2 production (Complex II LEAK state) were significantly decreased in the fMCAo (stroke) group ipsilateral hemisphere compared to measurements in the contralateral hemisphere 60 and 90 days after stroke. In hippocampal tissues, during the Complex I&II ET state, mitochondrial respiration was generally lower in the ipsilateral compared to the contralateral hemisphere 90 days following stroke. An aging-dependent impact on mitochondria oxygen consumption following I/R injury was observed 180 days after surgery, wherein Complex I&II activities were lowest in both hemispheres. The obtained results highlight the importance of long-term studies in the field of ischemic stroke, particularly when evaluating mitochondrial bioenergetics in specific brain regions within and between separately affected cerebral hemispheres.

Abstract WP323: Late-Stage Degeneration Due to Middle-Cerebral Artery Occlusion Observed in White Matter Tracts and Specific Forebrain Regions in Middle-Aged Female Rats is Attenuated by mir20a-3p Treatment: A Magnetic Resonance-Diffusion Tensor Imaging and Conventional Morphometry Study

Introduction: Our earlier studies show that the small non-coding RNA, mir20a-3p, is neuroprotective after stroke, and reduces sensory-motor impairments in the acute phase and cognitive decline in the long-term in female rats. Cognitive decline due to vascular diseases, such as stroke, is associated with volume loss in the cortex, the limbic structures and white matter tracts. In this study, we examined the volume of forebrain white matter tracts, cortical and limbic structures in animals with characterized cognitive impairment due to stroke, and the efficacy of microRNA treatment. Methodology: Middle-aged females were subjected to ischemic stroke using endothelin 1, injected adjacent to the left middle cerebral artery (MCA). Mir-20a-3p mimic (n=10) or scrambled oligo (n=8) was administered i.v. 4h, 24h and 70d post stroke. Animals were assessed periodically for cognitive performance up to 100d after stroke using both the cued fear conditioning test and the novel object recognition test (NORT). After perfusion fixation, T2 and diffusion tensor imaging (DTI) magnetic resonance imaging of the brain was performed. Thereafter, brains were processed for Weil myelin staining, followed by quantification of the corpus callosum and internal capsule. Results: Stroke resulted in impairment in both the cued fear conditioning test and the NORT, which was attenuated by mir-20a-3p treatment. Compared to sham (no-stroke) animals, volumetric analysis of DTI scans showed a significant reduction in the volume of substantia nigra (p<0.02) and the entorhinal cortex (P=0.0402) in stroke +scrambled group, but not in Stroke+ Mir20 treated group. White matter tracts showed a significant reduction in the corpus callosum and internal capsule volume in the ischemic hemisphere as compared to non-ischemic hemisphere in MCAo animals treated with the scrambled oligo. In contrast, sham and MCAo+Mir-20a-3p animals displayed no hemispheric differences in volume in either tract. Conclusion: Cognitive changes measured with remote fear memory retrieval and NORT were associated with volume reductions in the substantia nigra, the entorhinal cortex, and the major forebrain white matter tracts due to stroke. These stroke-induced deficits were attenuated in Mir-20-3p treated animals.

Therapeutic efficacy of intravenous infusion of mesenchymal stem cells in rat perinatal brain injury.

Perinatal brain injury is multifactorial and primarily associated with brain prematurity, inflammation, and hypoxia-ischemia. Although recent advances in perinatal medicine have improved the survival rates of preterm infants, neurodevelopmental disorders remain a significant complication. We tested whether the intravenous infusion of mesenchymal stem cells (MSCs) had therapeutic efficacy against perinatal brain injury in rats. Pregnant rats at embryonic day (E) 18 received lipopolysaccharide and the pups were born at E21. On postnatal day (PND) 7, the left common carotid artery of each pup was ligated, and they were exposed to 8% oxygen for 2 h. They were randomized on PND10, and MSCs or vehicle were intravenously infused. We performed behavioral assessments, measured brain volume using MRI, and performed histological analyses on PND49. Infused MSCs showed functional improvements in our model. In vivo MRI revealed that MSC infusion increased non-ischemic brain volume compared to the vehicle group. Histological analyses showed that cortical thickness, the number of NeuN+ and GAD67+ cells, and synaptophysin density in the non-ischemic hemisphere in the MSC group were greater than the vehicle group, but less than the control group. Infused MSCs improve sensorimotor and cognitive functions in perinatal brain injury and enhance neuronal growth. Intravenous infusion of MSCs improved neurological function in rats with perinatal brain injury, including motor, sensorimotor, cognitive, spatial, and learning memory. Infused MSCs increased residual (non-ischemic) tissue volume, number of neuronal cells, GABAergic cells, and cortical synapses in the contralesional (right) hemisphere. Intravenous administration of MSC might be suitable for the treatment of perinatal brain injury.

Head down tilt 15° to preserve salvageable brain tissue in acute ischemic stroke: A pre-clinical pooled analysis, with focus on cerebral hemodynamics.

Neurological outcome after ischemic stroke depends on residual salvageable brain tissue at the time of recanalization. Head down tilt 15° (HDT15) was proven effective in reducing infarct size and improving functional outcome in rats with transient middle cerebral artery occlusion (t-MCAO) by increasing cerebral perfusion within the ischemic penumbra. In this pooled analysis, individual animal-level data from three experimental series were combined in a study population of 104 t-MCAO rats (45 in HDT15 group and 59 in flat position group). Co-primary outcomes were infarct size and functional outcome at 24 h in both groups. The secondary outcome was hemodynamic change induced by HDT15 in ischemic and non-ischemic hemispheres in a subgroup of animals. Infarct size at 24 h was smaller in HDT15 group than in flat position group (absolute mean difference 31.69 mm3 , 95% CI 9.1-54.2, Cohen's d 0.56, p = 0.006). Functional outcome at 24 h was better in HDT15 group than in flat position group (median [IQR]: 13[10-16] vs. 11), with a shift in the distribution of the neurobehavioural scores in favour of HDT15. Mean cerebral perfusion in the ischemic hemisphere was higher during HDT15 than before its application (Perfusion Unit [P.U.], mean ± SD: 52.5 ± 19.52 P.U. vs. 41.25 ± 14.54 P.U., mean of differences 13.36, 95% CI 7.5-19.18, p = 0.0002). Mean cerebral perfusion in the non-ischemic hemisphere before and during HDT15 was unchanged (P.U., mean ± SD: 94.1 ± 33.8 P.U. vs. 100.25 ± 25.34 P.U., mean of differences 3.95, 95%, CI -1.9 to 9.6, p = 0.1576). This study confirmed that HDT15 improves the outcome in t-MCAO rats by promoting cerebral perfusion in the ischemic territory, without disrupting hemodynamics in non-ischemic areas.

Brain Cell Senescence: A New Therapeutic Target for the Acute Treatment of Ischemic Stroke.

Aging is a major risk factor for cerebral infarction. Since cellular senescence is intrinsic to aging, we postulated that stroke-induced cellular senescence might contribute to neural dysfunction. Adult male Wistar rats underwent 60-minute middle cerebral artery occlusion and were grouped according to 3 reperfusion times: 24 hours, 3, and 7 days. The major biomarkers of senescence: 1) accumulation of the lysosomal pigment, lipofuscin; 2) expression of the cell cycle arrest markers p21, p53, and p16INK4a; and 3) expression of the senescence-associated secretory phenotype cytokines interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), and interleukin-1β (IL-1β) were investigated in brain samples. Lipofuscin accumulation was scarce at the initial stage of brain damage (24 hours), but progressively increased until it reached massive distribution at 7 days post-ischemia. Lipofuscin granules (aggresomes) were mainly confined to the infarcted areas, that is parietal cortex and adjacent caudate-putamen, which were equally affected. The expression of p21, p53, and p16INK4a, and that of IL-6, TNF-α, and IL-1β, was significantly higher in the ischemic hemisphere than in the non-ischemic hemisphere. These data indicate that brain cell senescence develops during acute ischemic infarction and suggest that the acute treatment of ischemic stroke might be enhanced using senolytic drugs.

Effects of amantadine and topiramate on neuronal damage in rats with experimental cerebral ischemia-reperfusion.

Ischemia-reperfusion models are used to evaluate treatment options that may minimize cellular damage after ischemia. To investigate the effects of amantadine and topiramate on apoptosis and cellular oxidative damage. This experiment was performed using 30 male Wistar albino rats. The right internal carotid artery was identified and clamped with an aneurysm clip under general anesthesia, except for animals in the control group. After 10 min of occlusion, the aneurysm clip was removed, allowing reperfusion. After reperfusion and a waiting period of 12 h, the test and control groups were intraperitoneally administered the following solutions: the sham group received 10 mg/kg of isotonic solution, the amantadine group received 20 mg/kg of amantadine, the topiramate group received 40 mg/kg of topiramate, and the amantadine-topiramate group received 20 mg/kg of amantadine and 40 mg/kg of topiramate. After 24 h, the rats were euthanized. Apoptosis was evaluated using the TUNEL method. Total antioxidant status (TAS), total oxidant status (TOS), total thiol, and ischemia-modified albumin (IMA) levels were measured in both brain tissue and serum samples. The rate of apoptosis in the sham and amantadine groups increased significantly compared to the control group and the non-ischemic counter hemisphere. In the amantadine-topiramate group, both serum TAS and tissue thiol levels decreased. Tissue TOS levels were significantly higher in the topiramate group compared to all other test groups. Tissue TAS levels were significantly higher in the amantadine group compared to all other test groups. This experimental ischemia-reperfusion model revealed that topiramate reduces apoptosis in the early period after ischemia and that its combination with amantadine does not provide additional benefits against cell death. However, topiramate did not have an inhibitory effect on the oxidative stress biomarkers used in our study (TAS, TOS, IMA, and thiol). Studies that reveal the neuroprotective mechanism of action and long-term effects of topiramate are needed to complement this study.

Study of the activation of the RISK and SAFE signaling pathways by cyclosporin A pre- and post-conditioning in a mouse model of cerebral infarction

Cyclosporin A (CsA) has been shown to be useful in preventing ischemia-reperfusion injury in basic models of myocardial or cerebral infarction. CsA limits the opening of the mitochondrial transition pore (mPTP) through its direct interaction with cyclophilin D. However, recent studies in cardioprotection and neuroprotection suggest a role of CsA on the classic RISK and SAFE pathways, upstream of mitochondria. We aim to study the effect of CsA in ischemic pre- and post-conditioning on the RISK and SAFE pathways in a mouse model of stroke. Mice underwent 60 min ischemia and 30 min or 24 h reperfusion and received either no treatment (IR), a bolus of CsA (10 mg/kg) 10 min before the ischemia (pre-CsA) or 10 min after the reperfusion (post-CsA). Infarction of the middle cerebral artery was performed with a microfilament placed intra-arterially for the desired duration. Surgery was performed on Sham mice, but the filament was not occlusive. mPTP opening was evaluated by calcium retention capacity (CRC) on isolated mitochondria from ischemic right hemisphere and non-ischemic left hemisphere. Activation of the RISK and SAFE pathways was evaluated by determining the phosphorylation state of key proteins by Western blots: STAT3, GSK3-β, Akt and Erk. As expected, CRC was significantly reduced in the mitochondria from the right hemisphere in the IR group (Sham, 103 ± 21 vs. IR, 57 ± 18 nmol Ca2+/mg, n = 12/gp, P < 0.05). There was a slight increase in PTP resistance in the ischemic mitochondria from the pre-CsA and post-CsA groups. Experiments are ongoing to measure infarct size after 24 h of reperfusion. There was no significant change in protein phosphorylation in the left hemisphere. In the right ischemic hemisphere, there was a trend of activation of GSK3-β in post-CsA mice and STAT3 in pre-CsA mice. Our results suggest an effect of CsA upstream of the mPTP during stroke, which could correspond to a positive feedback loop.

Salvianolic acid A alleviated inflammatory response mediated by microglia through inhibiting the activation of TLR2/4 in acute cerebral ischemia-reperfusion

BackgroundToll-like receptor 2 and Toll-like receptor 4 (TLR2/4) on microglia have been found as important regulators in the inflammatory response during cerebral ischemia/reperfusion (I/R). In China, traditional Chinese medicine Salvia miltiorrhiza (danshen) and its some components are considered to be effective in rescuing cerebral I/R injury through clinical practice. Hypothesis/PurposeHere we examined the effect of Salvianolic acid A (SAA), a monomer compound in the water extract of Salvia miltiorrhiza, on TLR2/4 of microglia and its mediated inflammatory injury during cerebral I/R in vivo and in vitro. Study DesignFor exploring the effect of SAA on cerebral I/R and TLR2/4, classic middle cerebral artery occlusion (MCAO) model and oxygen glucose deprivation / reoxygenation (OGD/R) model of co-culture with primary hippocampal neurons and microglia in vitro were used. Signal pathway research and gene knockout have been applied to further explain its mechanism. MethodsThe evaluation indexes of I/R injury included infarct size, edema degree and pathology as well as primary hippocampal neurons and microglia culture, ELISA, western, RT-PCR, HE staining, immunofluorescence, flow cytometry, siRNA gene knockout were also employed. ResultsSAA significantly improved the degree of brain edema and ischemic area in I/R rats accompanied by decreases in levels of interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α). Pathological staining revealed that SAA could reduce inflammatory cell infiltration and mcirogila activation after reperfusion. Both protein and gene expression of TLR2 and TLR4 in ischemic hemisphere were obviously inhibited by SAA treatment while changes were not found in the non-ischemic hemisphere. In order to further study its mechanism, OGD/R model was used to mimic inflammatory damage of ischemic tissue by co-culturing primary rat hippocampal neurons and microglial cells. It was found that SAA also inhibited the protein and gene expression of TLR2 and TLR4 after OGD/R injury in microglia. After TLR2/4 knockout, the inhibitory effect of SAA on IL-1β and TNF-α levels in cell supernatant and neuron apoptosis were significantly weakened in each dose group. Moreover, expression levels of myeloid differentiation factor 88 (MyD88), NFκB, IL-1β and IL-6 in TLR2/4 mediated inflammatory pathway were reduced with SAA treatment. ConclusionSAA could significantly reduce the inflammatory response and injury in cerebral ischemia-reperfusion in vivo and in vitro, and its mechanism may be through the inhibition of TLR2/4 and its related signal pathway.

Matrix Metalloproteinase-9 Expression is Enhanced by Ischemia and Tissue Plasminogen Activator and Induces Hemorrhage, Disability and Mortality in Experimental Stroke

Matrix metalloproteinase-9 (MMP-9) degrades collagen and other cellular matrix proteins. After acute ischemic stroke, increased MMP-9 levels are correlated with hemorrhage, lack of reperfusion and stroke severity. Nevertheless, definitive data that MMP-9 itself causes poor outcomes in ischemic stroke are limited. In a model of experimental ischemic stroke with reperfusion, we examined whether ischemia and recombinant tissue plasminogen activator (r-tPA) therapy affected MMP-9 expression, and we used specific inhibitors to test if MMP-9 affects brain injury and recovery. After stroke, MMP-9 expression increased significantly in the ischemic vs. non-ischemic hemisphere of the brain (p < 0.001). MMP-9 expression in the ischemic, but not the non-ischemic hemisphere, was further increased by r-tPA treatment (p < 0.001). To determine whether MMP-9 expression contributed to stroke outcomes after r-tPA treatment, we tested three different antibody MMP-9 inhibitors. When compared to treatment with r-tPA and saline, treatment with r-tPA and MMP-9 antibody inhibitors significantly reduced brain hemorrhage by 11.3 to 38.6-fold (p < 0.01), brain swelling by 2.8 to 4.3-fold (p < 0.001) and brain infarction by 2.5 to 3.9-fold (p < 0.0001). Similarly, when compared to treatment with r-tPA and saline, treatment with r-tPA and an MMP-9 antibody inhibitor significantly improved neurobehavioral outcomes (p < 0.001), decreased weight loss (p < 0.001) and prolonged survival (p < 0.01). In summary, both prolonged ischemia and r-tPA selectively enhanced MMP-9 expression in the ischemic hemisphere. When administered with r-tPA, specific MMP-9 inhibitors markedly reduced brain hemorrhage, swelling, infarction, disability and death, which suggests that blocking the deleterious effects of MMP-9 may improve outcomes after ischemic stroke.

P0090SPIRONOLACTONE ALLEVIATES ISCHEMIC STROKE SEVERITY IN MALE MICE WITH CHRONIC KIDNEY DISEASE

Abstract Background and Aims Ischemic stroke is highly prevalent in patients with chronic kidney disease (CKD) and has been associated with poor outcomes. In experimental studies, CKD mice display wider and more inflammatory ischemic lesions as well as poorer functional outcomes than mice with normal renal function. In rodents with normal renal function, treatment with a mineralocorticoid receptor antagonist decreases brain ischemic lesion and improves functional outcomes. The goal of this study was to investigate the impact of a treatment with spironolactone, a mineralocorticoid receptor antagonist, on stroke outcomes in CKD mice. Method Male C57BL/6J mice were randomly assigned to CKD or SHAM groups. CKD was induced through right kidney cortical electrocautery in 8 week-old mice followed 2 weeks later by left total nephrectomy. Mice received spironolactone (50 µg/kg/day) or placebo (subcutaneous tablets, Innovative Research of America) for 6 weeks until stroke induction by transient middle cerebral artery occlusion (tMCAO). Neurological deficits were monitored daily, 3 days before and 1 day after stroke induction. Mice were euthanized 24 hours after tMCAO. Total infarct volumes and apoptosis were determined by cresyl violet staining and TUNEL respectively. Immunohistochemical detection of neurons was performed using an anti-NeuN antibody. To characterize the pro-inflammatory polarization of microglia/macrophages, M1 signature genes’ expression (CD-32, IL-1β and IL-6) was analyzed by qPCR. Results Untreated CKD mice displayed wider ischemic lesions (40.3 ± 4.5 versus 23.8 ± 3.9 mm3; p &amp;lt; 0.05) and poorer neurological score, grip strength and prehensile abilities compared to untreated sham mice. Pro-inflammatory M1 signature genes’ expression (CD-32, IL-1β and IL-6) was significantly increased in the ischemic hemisphere of CKD mice compared to the non-ischemic hemisphere. Treatment with spironolactone decreased ischemic lesion (19.3 ± 5.1 mm3; p &amp;lt; 0.05) and improved neurological score, grip strength and prehensile abilities in CKD mice. Treatment with spironolactone also reduced apoptosis, neuronal loss and microglia/macrophages pro-inflammatory M1 signature genes’ expression in CKD mice. In contrast, treatment with spironolactone had no effect in sham mice. Conclusion These data demonstrate that the mineralocorticoid receptor could be a promising therapeutic target to decrease brain inflammation and improve stroke recovery in CKD.

Post-stroke inflammatory response is linked to volume loss in the contralateral hemisphere

ObjectivesThere is a delicate homeostatic balance between the central nervous system and immune system. Stroke triggers an immunodepressive state to suppress a potential immune reaction directed against neuroglial tissue; however, this supposedly protective response inadvertently results in an infection-prone, and thereby a pro-inflammatory setting. In this study, we assessed the magnitude of cerebral volume loss in the unaffected contralateral hemisphere following stroke, and determined its relationship with inflammatory cascades. MethodsThe volume of the hemisphere contralateral to the ischemic insult was measured on admission and follow-up MRI's in 50 ischemic stroke patients. Information related to clinical features, infectious complications, and markers of inflammation (erythrocyte sedimentation rate, neutrophil/lymphocyte ratio, C-reactive protein) were prospectively collected, and their relationship with hemispheric volume change was evaluated using bivariate and multivariate statistics. ResultsThe contralateral hemisphere volume decreased by a median (interquartile range) of 14 (4–32) mL after a follow-up duration of 101 (63–123) days (p < .001); the volume reduction was 0.8 (0.2–1.8) % per month with respect to baseline. Old age, atrial fibrillation, stroke severity, C-reactive protein level, neutrophil/lymphocyte ratio, and development of infections during hospitalization were significantly associated with volume loss (p < .05). Stroke severity (NIHSS score or infarct volume) and inflammation related parameters (neutrophil/lymphocyte ratio or systemic infections) remained independently and positively associated with volume loss in multivariate regression models. ConclusionsCerebral tissue changes following stroke are not limited to the ischemic hemisphere. Apart from stroke severity, a pro-inflammatory state and post-stroke infections contribute to cerebral volume loss in the non-ischemic hemisphere.

Transient ischemic stroke induces substantial leukocyte recruitment to both the ischemic and non‐ischemic cerebrovasculature as visualized through live animal imaging.

Ischemic stroke is a leading cause of a death and disability worldwide. Current treatment strategies rely on early restoration of blood flow; however, injury persists despite successful reperfusion. The innate immune response plays a pivotal role in reperfusion injury, but the mechanisms and time‐course of neutrophil and monocyte recruitment to the cerebrovasculature (CBV) during ischemic stroke remain unclear. We sought to characterize the real‐time leukocyte response at the CBV in a mouse stroke model with reperfusion.To visualize leukocyte recruitment induced by ischemia, Ly6G‐tdTomato mice (which have fluorescent red neutrophils) were subjected to 90 minutes of transient middle cerebral artery occlusion (tMCAO) followed by reperfusion. Real‐time spinning‐disc confocal intravital microscopy of the CBV was performed at 24 and 72 hours following reperfusion. Intracranial windows were placed in both ischemic and non‐ischemic hemispheres; and tMCAO treated mice were compared to mice that underwent sham surgery. Neutrophil recruitment (adhesion, rolling) and extravasation were quantified in vivo on both the ischemic and contralateral non‐ischemic hemispheres. Postmortem staining with 2,3,5‐triphenyltetrazolium chloride was used to confirm induction of the stroke and to quantify infarct volume. In addition, wide‐field microscopy was used to examine neutrophil extravasation across the parenchyma.Animals subjected to sham surgery showed negligible leukocyte recruitment to the CBV. However, marked increases in leukocyte rolling, adhesion, and extravasation were observed at 24 and 72 hours following the tMCAO procedure. Interestingly, non‐ischemic hemispheres also demonstrated increased leukocyte rolling and adhesion, but not extravasation tMCAO group. Also, substantially more neutrophil extravasation was observed in the core of the infarct at 72 hours. These findings are consistent with an early recruitment of neutrophils to the cortical surface at early time points and a delayed infiltration into the core, as reported by others.These results show that a significant leukocyte response persists after reperfusion following tMCAO. This response is present both on the ischemic and, to a lesser extent, the non‐ischemic cortical CBV. Acute leukocyte recruitment observed on the non‐ischemic hemisphere suggests that ischemic stroke triggers a global inflammatory response within the CBV. Further reducing inflammation through immunomodulatory therapy in conjunction with reperfusion therapy may be beneficial in not only reducing stroke volume but potentially mitigating inflammation mediated secondary neuronal damage.Support or Funding InformationNIH R01 HL046849 and R37 HL064774 to W.A.M.

Abstract WMP80: Live Animal Imaging Reveals Delayed But Sustained Neutrophil Recruitment to Both Ischemic and Non-Ischemic Cortical Cerebrovasculature in a Mouse Transient Stroke Model

Background: Treatment for acute ischemic stroke (AIS) relies on early restoration of blood flow; however, injury persists despite reperfusion. The innate immune response plays a pivotal role in reperfusion injury, but the mechanisms and timing of neutrophil recruitment to the cerebrovasculature (CBV) during AIS remain unclear. We sought to characterize the neutrophil response in the CBV following ischemia/reperfusion using a transient middle cerebral artery occlusion (tMCAO) AIS model. Methods: Fluorescent reporter mice underwent 90-minute tMCAO confirmed with LSCI or surgery without occlusion (sham). Real-time confocal intravital microscopy of the CBV was performed at 24 and 72 hrs post-reperfusion through cranial windows in ischemic and non-ischemic hemispheres. Neutrophil recruitment (adhesion, rolling) and extravasation were quantified in vivo over both hemispheres. Neutrophil extravasation was further quantified using whole mount sections. Infarct volume was measured by 2,3,5-triphenyltetrazolium chloride staining. Results: An increase in neutrophil rolling, adhesion and extravasation was observed within the ischemic hemisphere compared to sham (p &lt; 0.01) at 24 and markedly 72 hrs. Non-ischemic hemispheres showed increased neutrophil rolling and adhesion, but not extravasation, compared to sham surgery (p &lt; 0.05). Whole mount sections demonstrated increased cortical and subcortical neutrophil extravasation in the ischemic hemisphere only (p &lt; 0.01). Conclusions: Early neutrophil recruitment to the ischemic hemisphere following tMCAO was present at both the CBV and within the infarcted parenchyma at 72 hours. Acute neutrophil recruitment at the CBV in the non-ischemic hemisphere, but not the cortex, suggests that AIS triggers a global inflammatory response within the CBV. Targeted neutrophil-specific therapies during reperfusion may reduce global inflammation at the CBV, and potentially mitigate secondary neuronal injury.

Response of distant regions affected by diaschisis commissuralis in one of the most common models of transient focal ischemia in rats

Stroke induces widespread changes in the brain. In this paper, we monitored some markers of early (2 h) and delayed events (1, 3 and 7 days of reperfusion) initiated by middle cerebral artery occlusion in core/penumbra counterparts of the non-ischemic hemisphere (i.e. contra-core and contra-penumbra).Our results showed that a profound transient drop (2 h and 3 days) of protein synthesis was measured in the contra-core, while the contra-penumbra exhibited translation over-activity at the same time. Glutamate release was detected only in the contra-core, with a peak on the first day. Degenerating neurons became visible in the striatum (day 1), followed by cortex (day 3), earlier in contra-penumbra and later in contra-core. Moreover, the loss of NADPH diaphorase-positive neurons in the non-ischemic hemisphere was detected, with the greatest drop at the first day. Total microglia also started to fall, the earliest in the contra-penumbra region of the striatum (day 1), followed by the contra-core of the striatum and both cortex regions at the seventh day.In conclusion, transient focal ischemia affects remote regions of the brain and initiates processes involved in neuronal degeneration in an order which corresponds to the tissue sensitivity to ischemia, namely earlier in the contra-penumbra, and afterwards in the contra-core. The mechanism of secondary damage would influence the progressive neuronal loss of more distant brain regions.

Perinatal Ischemia Alters Global Expression of Synaptosomal Proteins Critical for Neural Plasticity in the Developing Mouse Brain

Ischemic perinatal stroke (IPS) affects 1 in 2,300–5,000 live births. Despite a survival rate >95%, approximately 60% of IPS infants develop motor and cognitive impairments. Given the importance of axonal growth and synaptic plasticity in neurocognitive development, our objective was to identify the molecular pathways underlying IPS-associated synaptic dysfunction using a mouse model. IPS was induced by unilateral ligation of the common carotid artery of postnatal day 10 (P10) mice. Five days after ischemia, sensorimotor and motor functions were assessed by vibrissae-evoked forepaw placement and the tail suspension test respectively, showing evidence of greater impairments in male pups than in female pups. Twenty-four hours after ischemia, both hemispheres were collected and synaptosomal proteins then prepared for quantification, using isobaric tags for relative and absolute quantitation. Seventy-two of 1,498 qualified proteins were altered in the ischemic hemisphere. Ingenuity Pathway Analysis was used to map these proteins onto molecular networks indicative of reduced neuronal proliferation, survival, and synaptic plasticity, accompanied by reduced PKCα signaling in male, but not female, pups. These effects also occurred in the non-ischemic hemisphere when compared with sham controls. The altered signaling effects may contribute to the sex-specific neurodevelopmental dysfunction following IPS, highlighting potential pathways for targeting during treatment.

Attenuation Changes in ASPECTS Regions: A Surrogate for CT Perfusion-based Ischemic Core in Acute Ischemic Stroke.

Background Recent studies have proven the effectiveness of thrombectomy up to 24 hours after stroke onset for patients with specific criteria at advanced CT or MRI. Clinical implementation of treatment in this extended time window remains a challenge, as many stroke centers do not routinely use advanced imaging. Purpose To determine whether automated cerebral x-ray attenuation measurements at noncontrast CT provide information on the presence of CT perfusion-defined ischemic core as applied in late time windows for thrombectomy. Materials and Methods In this retrospective study, patients with middle cerebral artery stroke due to proximal occlusion from 2009 to 2017 were included. All patients underwent noncontrast CT and CT perfusion. Automated software was used to calculate relative Hounsfield unit (rHU) values for Alberta Stroke Program Early CT Score (ASPECTS) regions on noncontrast CT images as the ratio of x-ray attenuation between ischemic versus non-ischemic hemispheres. Sensitivity, specificity, and diagnostic performance of rHU and composite rHU-ASPECTS, a score incorporating rHU from all regions, were analyzed for the classification of regional ischemic core and late time window thrombectomy criteria at CT perfusion. Results Data in a total of 200 patients were evaluated (105 women [mean age, 74 years ± 14 {standard deviation}] and 95 men [mean age, 76 years ± 14]). There were 121 patients in the validation cohort and 79 patients in the independent test cohort. Compared among all examined regions, rHU values yielded the best classification of ischemic core for the caudate nucleus, the lentiform nucleus, and the insula (with areas under the receiver operating characteristic curve [AUCs] ranging from 0.70 to 0.77; P < .001 for each). The composite rHU-ASPECTS score allowed classification of CT perfusion imaging selection criteria of ischemic core sizes of less than 70 mL and target mismatch of greater than 1.8 with AUCs of 0.80 (P = .001; 75% sensitivity and 83% specificity) in the test cohort and 0.74 (P < .001; 58% sensitivity and 82% specificity) in the validation cohort. Conclusion Noncontrast CT x-ray attenuation measurements identify Alberta Stroke Program Early CT Score regions classified as ischemic core at CT perfusion. This approach may serve as a selection criteria surrogate for thrombectomy in late time windows. © RSNA, 2019 Online supplemental material is available for this article.

Spreading depolarization and neuronal damage or survival in mouse neocortical brain slices immediately and 12 hours following middle cerebral artery occlusion.

Whereas many studies have examined the properties of the compromised neocortex in the first several days following ischemia, there is less information regarding the initial 12 h poststroke. In this study we examined live mouse neocortical slices harvested immediately and 12 h after a 30-min middle cerebral artery occlusion (MCAo). We compared nonischemic and ischemic hemispheres with regard to the propensity for tissue swelling and for generating spreading depolarization (SD), as well as evoked synaptic responses and single pyramidal neuron electrophysiological properties. We observed spontaneous SD in 7% of slices on the nonstroked side and 25% in the stroked side following the 30-min MCAo. Spontaneous SD was rare in 12-h recovery slices. The region of the ischemic core and surround in slices was not susceptible to SD induced by oxygen and glucose deprivation. At the neuronal level, neocortical gray matter is surprisingly unaltered in brain slices harvested immediately poststroke. However, by 12 h, the fields of pyramidal and striatal neurons that comprise the infarcted core are electrophysiologically silent because the majority are morphologically devastated. Yet, there remains a subset of diffusely distributed "healthy" pyramidal neurons in the core at 12 h post-MCAo that persist for days poststroke. Their intact electrophysiology and dendritic morphology indicate a surprisingly selective resilience to stroke at the neuronal level. NEW & NOTEWORTHY It is generally accepted that the injured core region of the brain resulting from a focal stroke contains no functioning neurons. Our study shows that some neurons, although surrounded by devastated neighbors, can maintain their structure and electrical activity. This surprising finding raises the possibility of discovering how these neurons are protected to pinpoint new strategies for reducing stroke injury.

Abstract TMP38: Dysregulated Post-Stroke Immune Response is Associated With Cerebral Volume Loss in the Contralateral Non-Ischemic Hemisphere

Background: There is delicate homeostatic balance between the central nervous system and immune system. Cerebral insults, like ischemia, trigger an immune-depressive state to suppress a potential immune response directed against the neuroglial tissue; however, this supposedly protective reaction inadvertently creates an infection-prone state in the peri-stroke setting. In this study, we assessed the magnitude of cerebral volume loss in the unaffected contralateral hemisphere following stroke, and determined its relationship with the intimate cascades of inflammation, immune-depression and infection. Methods: The change in contralateral hemisphere volume was determined by voxel-based morphometry on admission and follow-up MRI’s in a consecutive series of 50 patients with ischemic stroke involving the MCA territory. Information related to clinical features, infectious complications, and markers of inflammation (erythrocyte sedimentation rate, neutrophil/lymphocyte ratio, C-reactive protein) and immunodepression (plasma high mobility group box 1 protein level; HMGB-1) were prospectively collected. Results: The contralateral hemisphere volume decreased by a median (interquartile range) of 2.80% (0.70-5.64) after a follow-up duration of 101 (63-123) days (p&lt;0.001); the monthly volume reduction was 0.82% (0.18-1.79). Old age, stroke severity, neutrophil/lymphocyte ratio, and development of infections during hospitalization were significantly associated with monthly volume loss (p&lt;0.05). Stroke severity (NIHSS score or infarct volume) and inflammation related parameters (neutrophil/lymphocyte ratio or systemic infections) remained independently and positively associated with monthly volume loss when assessed in multivariate regression models, while plasma HMGB-1 levels were inversely related to this loss. Conclusions: Cerebral tissue damage following stroke is not limited to the ischemic hemisphere. Apart from stroke severity, a pro-inflammatory state and an impaired immune-depressive response contribute to cerebral volume loss in the non-ischemic hemisphere.

Abstract WMP23: Automated Regional Density Measurements on Baseline Non-Contrast CT Predict Final Infarction in Acute Ischemic Stroke Patients

Introduction: Early ischemic changes on non-contrast CT (NCCT) can be visually assessed using the Alberta Stroke Program Early CT Score (ASPECTS). We sought to determine if automated regional density quantification provides additional information on the development of final infarction. Methods: We selected 121 patients with middle cerebral artery stroke due to large vessel occlusion out of a consecutive cohort. Densities in ASPECTS regions were quantified as average Hounsfield Unit (HU) values using automated segmentation (Fig. 1). Relative HU (rHU) values were calculated dividing absolute regional densities of ischemic by non-ischemic hemispheres. Final infarction was quantified semi-automatically as total volume and was defined visually per ASPECTS region in a dichotomized fashion. A composite rHU score incorporating values from all ASPECTS regions weighted by regional relevance was calculated. ROC analysis was performed to calculate AUC values. Linear regression analysis was used for multivariable adjustment. Results: Median visual ASPECTS on NCCT was 8 (IQR: 6-9). Automated density measurements were feasible in all 121 patients within one minute of post-processing time. rHU values yielded significant regional classification of final infarction in ROC analyses for all ASPECTS regions except M3 and M6. Best classifications were achieved for lentiform nucleus (AUC=0.810, p&lt;0.001), caudate nucleus (AUC=0.777, p&lt;0.001), and insula (AUC=0.764, p&lt;0.001). The composite rHU score was independently associated with final infarction volume (β=-0.353, p&lt;0.001), outperforming visual ASPECTS assessment (β=-0.190, p=0.062) in multivariable regression analysis. Conclusions: Automated NCCT density changes identify ASPECTS regions that develop final infarction in stroke patients. The composite rHU score outperformed visual ASPECTS interpretation in the prediction of final infarction volumes and may serve as an observer-independent imaging biomarker.