Reperfusion injury after focal cerebral ischemia: the role of inflammation and the therapeutic horizon

Fluid shear stress induced-endothelial phenotypic transition contributes to cerebral ischemia-reperfusion injury and repair

Long-term ischemia leads to insufficient cerebral microvascular perfusion and dysfunction. Reperfusion restores physiological fluid shear stress (FSS) but leads to serious injury. The mechanism underlying FSS-induced endothelial injury in ischemia-reperfusion injury (IRI) remains poorly understood. In this study, a rat model of middle cerebral artery occlusion was constructed to explore cerebrovascular endothelial function and inflammation in vivo. Additionally, the rat brain microvascular endothelial cells (rBMECs) were exposed to a laminar FSS of 0.5 dyn/cm2 for 6 h and subsequently restored to physiological fluid shear stress level (2 dyn/cm2) for 2 and 12 h, respectively. We found that reperfusion induced endothelial-to-mesenchymal transition (EndMT) in endothelial cells, leading to serious blood-brain barrier dysfunction and endothelial inflammation, accompanied by the nuclear accumulation of Yes-associated protein (YAP). During the later stage of reperfusion, cerebral endothelium was restored to the endothelial phenotype with a distinct change in mesenchymal-to-endothelial transition (MEndT), while YAP was translocated and phosphorylated in the cytoplasm. Knockdown of YAP or inhibition of actin polymerization markedly impaired the EndMT in rBMECs. These findings suggest that ischemia-reperfusion increased intensity of FSS triggered an EndMT process and, thus, led to endothelial inflammation and tissue injury, whereas continuous FSS induced a time-dependent reversal MEndT event contributing to the endothelial repair. This study provides valuable insight for therapeutic strategies targeting IRI.

miR-181a targets PTEN to mediate the neuronal injury caused by oxygen-glucose deprivation and reoxygenation

Evidence suggests that the microRNA-181 (miR-181) family performs various roles in the pathophysiology of cerebral ischemia and reperfusion injury (CIRI). MiR-181a has been identified as a critical determinant of neuronal survival. Moreover, the significance of miR-181a in controlling neuronal death after CIRI has received little attention. The objective of this study was to assess the role of miR-181a in neuronal cell injury after CIRI. To mimic the in-vitro and in-vivo CIRI, we developed an oxygen-glucose deficiency/reoxygenation (OGD/R) model in SH-SY5Y cells and a transient middle cerebral artery occlusion model in rats. MiR-181a expression was significantly higher in both in-vivo and in-vitro CIRI models. The overexpression of miR-181a increased cell damage and oxidative stress caused by OGD/R, whereas inhibition of miR-181a reduced both. PTEN has also been found to be a direct miR-181a target. PTEN overexpression reduced cell apoptosis and oxidative stress induced by miR-181a upregulation under an OGD/R condition. Furthermore, we found that the rs322931 A allele was related to increased miR-181a levels in IS peripheral blood and higher susceptibility to IS. The current results offer new insights into the understanding of the molecular pathophysiology of CIRI, as well as possible new treatment candidates.

Incidence and association of seizures in stroke patients following endovascular treatment: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Post-stroke seizures (PSSs) are some of the most common complications of stroke and are associated with poor outcomes in patients. Endovascular treatment (EVT) is the standard of care for patients with acute ischaemic stroke related large-vessel occlusion. However, whether EVT increases the risk of PSSs remains controversial; the association between PSSs and EVT is poorly understood.

METHODS

PubMed, Embase and the Cochrane Library were searched for relevant studies published from 1995 to 6 December 2021. The overall incidence of PSSs in patients treated with EVT and the separate incidence for all included studies in each subgroup, stratified by the type of treatment or time of onset, were calculated. The pooled odds ratio and confidence interval were calculated to quantify the effects of EVT on PSS occurrence.

RESULTS

In all, 946 studies were screened and 16 articles were included, with a total sample size of 12,664 patients; 7836 patients received EVT, of whom 460 had PSS. The pooled incidence of PSS after EVT was 5.8%, which was similar to patients treated with mechanical thrombectomy (5.3%), intra-arterial thrombolysis (6.8%) or bridging therapy (5.4%). The cumulative incidence of post-stroke epilepsy (6.0%) was almost twice that of acute symptomatic seizures (3.6%). The pooled odds ratio for the relationship between EVT and PSS was 1.91 (95% confidence interval 0.98-3.73).

CONCLUSIONS

The cumulative incidence of stroke patients treated with EVT who developed seizures was 5.8%, and EVT was non-significantly associated with the occurrence of seizures after stroke.

Effect of FKBP12-Derived Intracellular Peptides on Rapamycin-Induced FKBP-FRB Interaction and Autophagy

Intracellular peptides (InPeps) generated by proteasomes were previously suggested as putative natural regulators of protein-protein interactions (PPI). Here, the main aim was to investigate the intracellular effects of intracellular peptide VFDVELL (VFD7) and related peptides on PPI. The internalization of the peptides was achieved using a C-terminus covalently bound cell-penetrating peptide (cpp; YGRKKRRQRRR). The possible inhibition of PPI was investigated using a NanoBiT^® luciferase structural complementation reporter system, with a pair of plasmids vectors each encoding, simultaneously, either FK506-binding protein (FKBP) or FKBP-binding domain (FRB) of mechanistic target of rapamycin complex 1 (mTORC1). The interaction of FKBP-FRB within cells occurs under rapamycin induction. Results shown that rapamycin-induced interaction between FKBP-FRB within human embryonic kidney 293 (HEK293) cells was inhibited by VFD7-cpp (10-500 nM) and FDVELLYGRKKRRQRRR (VFD6-cpp; 1-500 nM); additional VFD7-cpp derivatives were either less or not effective in inhibiting FKBP-FRB interaction induced by rapamycin. Molecular dynamics simulations suggested that selected peptides, such as VFD7-cpp, VFD6-cpp, VFAVELLYGRKKKRRQRRR (VFA7-cpp), and VFEVELLYGRKKKRRQRRR (VFA7-cpp), bind to FKBP and to FRB protein surfaces. However, only VFD7-cpp and VFD6-cpp induced changes on FKBP structure, which could help with understanding their mechanism of PPI inhibition. InPeps extracted from HEK293 cells were found mainly associated with macromolecular components (i.e., proteins and/or nucleic acids), contributing to understanding InPeps' intracellular proteolytic stability and mechanism of action-inhibiting PPI within cells. In a model of cell death induced by hypoxia-reoxygenation, VFD6-cpp (1 µM) increased the viability of mouse embryonic fibroblasts cells (MEF) expressing mTORC1-regulated autophagy-related gene 5 (Atg5), but not in autophagy-deficient MEF cells lacking the expression of Atg5. These data suggest that VFD6-cpp could have therapeutic applications reducing undesired side effects of rapamycin long-term treatments. In summary, the present report provides further evidence that InPeps have biological significance and could be valuable tools for the rational design of therapeutic molecules targeting intracellular PPI.

Protective Effect of Low-Dose Alcohol Consumption against Post-Ischemic Neuronal Apoptosis: Role of L-PGDS

Ischemic stroke is one of the leading causes of permanent disability and death in adults worldwide. Apoptosis is a major element contributing to post-ischemic neuronal death. We previously found that low-dose alcohol consumption (LAC) protects against neuronal apoptosis in the peri-infarct cortex following transient focal cerebral ischemia. Lipocalin-type prostaglandin D2 synthase (L-PGDS), which is mainly localized in the central nervous system (CNS), was previously shown to inhibit neuronal apoptosis. Therefore, we determined whether L-PGDS is involved in the protective effect of LAC against post-ischemic neuronal apoptosis. Wild-type (WT), CaMKIIα^CreERT2/+/L-PGDS^+/+, and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice on a C57BL/6J background were gavage fed with ethanol or volume-matched water once a day for 8 weeks. Tamoxifen (2 mg/day) was given intraperitoneally to CaMKIIα^CreERT2/+/L-PGDS^+/+ and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice for 5 days during the fourth week. AT-56 (30 mg/kg/day), a selective inhibitor of L-PGDS, was given orally to AT-56-treated WT mice from the fifth week for four weeks. Cerebral ischemia/reperfusion (I/R) injury, TUNEL-positive neurons, and cleaved caspase-3-positive neurons were measured at 24 h of reperfusion after a 90 min unilateral middle cerebral artery occlusion (MCAO). We found that 0.7 g/kg/day but not 2.8 g/kg/day ethanol significantly upregulated L-PGDS in the cerebral cortex. In addition, 0.7 g/kg/day ethanol diminished cerebral ischemia/reperfusion (I/R) injury and TUNEL-positive and cleaved caspase-3-positive neurons in the peri-infarct cortex in WT and CaMKIIα^CreERT2/+/L-PGDS^+/+ mice. Furthermore, the neuroprotective effect of 0.7 g/kg/day ethanol was alleviated in AT-56-treated WT and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice. Our findings suggest that LAC may protect against cerebral I/R injury by suppressing post-ischemic neuronal apoptosis via an upregulated L-PGDS.

Neuroinflammation in Cerebral Ischemia and Ischemia/Reperfusion Injuries: From Pathophysiology to Therapeutic Strategies

Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood-brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.

CHIP ameliorates cerebral ischemia-reperfusion injury by attenuating necroptosis and inflammation

Blood reperfusion of ischemic cerebral tissue may cause cerebral ischemia-reperfusion (CIR) injury. Necroptosis and inflammation have been demonstrated to be involved in the disease-related process of CIR injury. The E3 ubiquitin ligase carboxyl terminus of Hsp70-interacting protein (CHIP) can modulate multiple cellular signaling processes, including necroptosis and inflammation. Numerous studies have demonstrated the neuroprotective effects of CHIP on multiple central nervous system (CNS) diseases. However, the effects of CHIP on CIR injury have not been fully explored. We hypothesize that CHIP can exert neuroprotective effects by attenuating necroptosis and inflammation during CIR injury. In the present study, adult wild-type (WT) C57BL/6 mice and CHIP knock-in (KI) mice with a C57BL/6 background and CHIP overexpression in neural tissue underwent middle cerebral artery occlusion (MCAO) surgery to simulate CIR onset. Our data indicated that CHIP expression in the peri-infarct tissue was markedly increased after MCAO surgery. Compared with WT mice, CHIP KI mice significantly improved neurological deficit scores, decreased cerebral infarct volume, and attenuated brain edema and neuronal damage. Meanwhile, CHIP overexpression attenuated necroptosis and inflammation induced by MCAO surgery. These findings indicated that overexpression of CHIP might exert neuroprotective effects by attenuating necroptosis and inflammation during CIR injury, and increasing CHIP levels may be a potential strategy in cerebrovascular disease therapy.

Chronic Low-Dose Alcohol Consumption Promotes Cerebral Angiogenesis in Mice

Chronic alcohol consumption dose-dependently affects the incidence and prognosis of ischemic stroke. We determined the influence of chronic alcohol consumption on cerebral angiogenesis under physiological conditions and following ischemic stroke. In in vitro studies, acute exposure to low-concentration ethanol significantly increased angiogenic capability and upregulated vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs). The increased angiogenic capability was abolished in the presence of a VEGFR2 inhibitor. In addition, the increased angiogenic capability and upregulated VEGF-A and VEGFR2 remained in chronically low-concentration ethanol-exposed MBMVECs. In in vivo studies, 8-week gavage feeding with low-dose ethanol significantly increased vessel density and vessel branches and upregulated VEGF-A and VEGFR2 in the cerebral cortex under physiological conditions. Furthermore, vessel density, vessel branches, and expression of VEGF-A and VEGFR2 in the peri-infarct cortex were significantly greater in low-dose ethanol-fed mice at 72 h of reperfusion. Although low-dose ethanol did not alter cerebral vasoreactivity and regional cerebral blood flow (rCBF) either before or during ischemia, it significantly augmented post-ischemic hyperemia during reperfusion. In contrast, exposure to high-concentration ethanol and 8-week gavage feeding with high-dose ethanol only had a mild inhibitory effect on angiogenic capability and cerebral angiogenesis, respectively. We conclude that heavy alcohol consumption may not dramatically alter cerebral angiogenesis, whereas light alcohol consumption significantly promotes cerebral angiogenesis.

Research Progress on the Ability of Astragaloside IV to Protect the Brain Against Ischemia-Reperfusion Injury

Stroke, a disease with a sudden onset and high morbidity and mortality rates, is difficult to treat in the clinic. Traditional Chinese medicine has become increasingly widely used in clinical practice. Modern pharmacological studies have found that Radix Astragali has a variety of medicinal properties, i.e., immunoregulatory, antioxidative, anti-cancer, anti-diabetes, myocardial protective, hepatoprotective, and antiviral functions. This article reviews the protective effect and mechanism of astragaloside IV, which is extracted from Radix Astragali, on stroke, discusses the cerebroprotective effect of astragaloside IV against ischemia-reperfusion-related complications, offers insight into research prospects, and expands the idea of integrating traditional Chinese and Western medicine treatment strategies and drugs to provide a theoretical reference for the clinical treatment of cerebral ischemia-reperfusion injury and the improvement of stroke prognosis.

QKI 6 ameliorates CIRI through promoting synthesis of triglyceride in neuron and inhibiting neuronal apoptosis associated with SIRT1-PPARγ-PGC-1α axis

BACKGROUND

The stroke induced by ischemia of brain remains high incidence and death rate. The study wanted to confirm the effects of Quaking 6 (QKI 6) on the protection role in neurons of rat model of cerebral ischemia/reperfusion injury (CIRI).

MATERIAL AND METHODS

The rat model with CIRI induced by middle cerebral artery occlusion was well established and rat neurons were isolated to characterize the effects of QKI 6 mediated by sirtuin 1 (SIRT1) on synthesis of triglyceride in neuron and neuronal apoptosis via activation of SIRT1-peroxisome proliferater-activated receptor (PPAR)γ- peroxisome proliferator-activated receptor coactivator (PGC)-1α signaling pathway.

RESULTS

The expression levels of SIRT1 or QKI 6, and acetylation level of QKI 6 were decreased in neurons of rat model with CIRI. QKI 6 deacetylated and mediated by SIRT1 that contributed to suppressing the progression of neuronal apoptosis in rat through promoting synthesis of triglyceride in vivo and in vitro via SIRT1-PPARγ-PGC-1α signaling pathway, then inhibiting CIRI.

CONCLUSIONS

Our results demonstrated SIRT1 deacetylates QKI 6, the RNA-binding protein, that affects significantly the synthesis of triglyceride in neurons of CIRI rat model. Moreover, it activated transcription factor peroxisome proliferator-activated receptorγ coactivator-1α (PGC-1α) through post-transcriptional regulation of the expression of PPARγ, and further enhanced synthesis of triglyceride, thereby restrained the progression of neural apoptosis and CIRI.

Value of Dual-Energy Dual-Layer CT After Mechanical Recanalization for the Quantification of Ischemic Brain Edema

Background and Purpose: Ischemic brain edema can be measured in computed tomography (CT) using quantitative net water uptake (NWU), a recently established imaging biomarker. NWU determined in follow-up CT after mechanical thrombectomy (MT) has shown to be a strong predictor of functional outcome. However, disruption of the blood-brain barrier after MT may also lead to contrast staining, increasing the density on CT scans, and hence, directly impairing measurements of NWU. The purpose of this study was to determine whether dual-energy dual-layer CT (DDCT) after MT can improve the quantification of NWU by measuring NWU in conventional polychromatic CT images (CP-I) and virtual non-contrast images (VNC-I). We hypothesized that VNC-based NWU (vNWU) differs from NWU in conventional CT (cNWU). Methods: Ten patients with middle cerebral artery occlusion who received a DDCT follow-up scan after MT were included. NWU was quantified in conventional and VNC images as previously published and was compared using paired sample t-tests. Results: The mean cNWU was 3.3% (95%CI: 0-0.41%), and vNWU was 11% (95%CI: 1.3-23.4), which was not statistically different (p = 0.09). Two patients showed significant differences between cNWU and vNWU (Δ = 24% and Δ = 36%), while the agreement of cNWU/vNWU in 8/10 patients was high (difference 2.3%, p = 0.23). Conclusion: NWU may be quantified precisely on conventional CT images, as the underestimation of ischemic edema due to contrast staining was low. However, a proportion of patients after MT might show significant contrast leakage resulting in edema underestimation. Further research is needed to validate these findings and investigate clinical implications.

Chronic Low-Dose Alcohol Consumption Attenuates Post-Ischemic Inflammation via PPARγ in Mice

Ischemic stroke is one of the leading causes of death and permanent disability in adults. Recently, we found that light alcohol consumption (LAC) suppresses post-ischemic inflammatory response, which plays an important role in ischemic brain damage. Our goal was to determine the role of peroxisome proliferator-activated receptor-gamma (PPARγ) in the anti-inflammatory effect of LAC against transient focal cerebral ischemia. In in vivo study, male C57BL/6J wild type (WT) and endothelial-specific conditional PPARγ knockout mice were gavage fed with 0.7 g/kg/day ethanol or volume-matched water daily for 8 weeks. From the 7th week, 3 mg/kg/day GW9662 (a selective PPARγ antagonist) was intraperitoneally given for two weeks. Cerebral ischemia/reperfusion (I/R) injury and expression of manganese superoxide dismutase (MnSOD) and adhesion molecules, neutrophil infiltration, and microglial activation in the cerebral cortex before and following a 90 min unilateral middle cerebral artery occlusion (MCAO)/24 h reperfusion were evaluated. In in vitro study, the impact of chronic alcohol exposure on expression of PPARγ and MnSOD in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs) was measured. PPARγ and MnSOD were significantly upregulated in the cerebral cortex of ethanol-fed WT mice and low-concentration ethanol-exposed C57BL/6J MBMVECs. GW9662 significantly inhibited alcohol-induced upregulation of MnSOD. Eight-week ethanol feeding significantly reduced cerebral I/R injury and alleviated the post-ischemic inflammatory response (upregulation of intercellular adhesion molecule-1 (ICAM-1) and E-selectin, microglial activation, and neutrophil infiltration). Treatment with GW9662 and endothelial-specific conditional knockout of PPARγ did not alter cerebral I/R injury and the inflammatory response in the control mice but abolish the neuroprotective effect in ethanol-fed mice. In addition, GW9662 and endothelial-specific conditional knockout of PPARγ diminished the inhibitory effect of LAC on the post-ischemic expression of adhesion molecules and neutrophil infiltration. Our findings suggest that LAC may protect against cerebral I/R injury by suppressing the post-ischemic inflammation via activation of PPARγ.

Piceatannol protects against cerebral ischemia/reperfusion‑induced apoptosis and oxidative stress via the Sirt1/FoxO1 signaling pathway

Reperfusion is a critical therapeutic intervention used following acute ischemic stroke; however, it may cause cerebral ischemia/reperfusion injury (CIRI) and aggravate brain damage. Piceatannol (Pic), a hydroxylated analog of resveratrol, has been reported to exhibit anti‑inflammatory effects. However, the detailed molecular mechanisms and its effects on CIRI have not been sufficiently assessed, and, to the best of our knowledge, current methods of prevention of CIRI are limited. The aim of the present study was to investigate the effects of Pic on improving neurological function in a mouse model of CIRI. For the animal experiments, 8‑week‑old C57BL/6 mice were raised and randomly grouped, and an in vivo model of CIRI was established. Mice were administered a low (10 mg/kg/day) or high‑dose (20 mg/kg/d) of Pic 1 h after CIRI orally and once daily for the next 6 days. Neurological dysfunction was assessed using a modified neurological severity score and a rotarod test 1 week after CIRI establishment, and the cognitive status of the mice was assessed using a Morris water maze. Hematoxylin and eosin staining was used to evaluate the histopathological changes. The expression levels of sirtuin 1 (Sirt1), FoxO1, cleaved caspase‑3 (CC‑3), Bax and Bcl‑2 were measured using western blotting. Intracellular reactive oxygen species (ROS) generation, antioxidant enzymes [superoxide dismutase, glutathione (GSH) peroxidase and catalase] and non‑enzymatic antioxidants (GSH) were also detected using spectrophotometry. After inhibition of the Sirt1/FoxO1 pathway, a TUNEL assay was used for the detection of apoptotic cells in vitro and in vivo. The co‑localization of neuron‑specific nuclear protein and CC‑3 was assessing using immunofluorescent staining. Pic improved neurological functions and ameliorated hippocampal neuronal pathology following CIRI. In addition, the expression levels of CC‑3 and Bax and intracellular ROS levels were increased, while levels of antioxidant and non‑enzymatic enzymes were decreased in the mouse model of CIRI. Low and high doses of Pic significantly decreased ROS production and the expression levels of apoptosis‑related proteins, but increased antioxidant enzyme levels. However, a high‑dose of Pic did not result in increased levels of non‑enzymatic enzymes. Furthermore, low and high doses of Pic treatment significantly activated the Sirt1/FoxO1 pathway. Following inhibition of the Sirt1/FoxO1 pathway, the percentage of TUNEL‑positive cells and expression of CC‑3 were increased, and CC‑3 was enriched in neurons. The antioxidant effects of Pic were blocked by inhibition of Sirt1 in vitro and in vivo. In conclusion, these results suggested that Pic may exert a neuroprotective effect against in hippocampal neurons via the Sirt1/FoxO1 pathway.

Lack of sphingomyelin synthase 2 reduces cerebral ischemia/reperfusion injury by inhibiting microglial inflammation in mice

Recanalization of blood flow after ischemia can lead to ischemia/reperfusion injury, and inflammation plays an important role in the mechanisms behind cerebral ischemia/reperfusion injury. Sphingomyelin synthase 2 (SMS2) deficiency reduces inflammation; however, the effect and mechanism of action of SMS2 on the inflammatory response after cerebral ischemia/reperfusion injury are still unclear. Wild-type (WT) and SMS2 knockout C57BL/6 mice were used to establish a model of cerebral ischemia/reperfusion. The neurological deficit score was evaluated with Longa's method, and infarct volume was evaluated by magnetic resonance imaging and 2,3,5-triphenyltetrazolium chloride staining. Neurological deficit and infarct volume were used to evaluate the degree of cerebral ischemia/reperfusion injury in mice. Western blotting, reverse transcription-quantitative PCR and immunofluorescence were used to detect the expression profiles. The neurological deficit score of SMS2^-/- mice was significantly lower than that of WT mice at 72 h after cerebral ischemia/reperfusion injury (P=0.027), but not significantly different at 24 h (P=0.064). Compared with WT mice at 24 and 72 h after cerebral ischemia/reperfusion, the infarct volume of SMS2^-/- mice was decreased, the expression of pro-inflammatory cytokines galectin 3 and interleukin-1β were decreased, the activation of microglia was decreased, and the nuclear translocation of NF-κB p65 was decreased, but the expression of the anti-inflammatory factor arginase 1 was increased. Lack of SMS2 in mice can help to reduce the inflammatory reaction by inhibiting the activation of NF-κB signaling pathway, further attenuating cerebral ischemia/reperfusion injury in mice.

Beneficial consequences of Lupeol on middle cerebral artery-induced cerebral ischemia in the rat involves Nrf2 and P38 MAPK modulation

Lupeol has been reported to exhibit anti-inflammatory and anti-tumor activities in many diseases, but its potential effects in cerebral ischemia injury have not been studied to date. In this work we present evidence for a beneficial effect of lupeol in a rat model of middle cerebral artery occlusion (MCAO) followed by reperfusion (MCAO/R) injury and provide some histological and biochemical evidence for its mechanism of action. A cerebral MCAO rat model was established by vascular occlusion for 2 h, followed by 24 h reperfusion period. The infarct volume, neurological deficits, and brain water content were compared with animals treated during reperfusion with different concentrations of lupeol. Macroscopic parameters, cell viability, pro-inflammatory factors generation, as well as oxidative stress parameters and associated apoptotic signaling cascades were evaluated. Treatment with lupeol significantly reduced the cerebral infarct volume and water content and recovered neuro behavioral functions in affected rats. Lupeol treatment down-regulated the expression of oxidative stress and inflammation factors. In addition, lupeol activated Nrf2, suppressed caspase-3 activity, reduced BAX/Bcl-2 ratio and inhibited phosphorylation of p38 MAPK. The data suggest that lupeol may exert protective effects against cerebral ischemia by suppressing oxidative stress and reduction of inflammation factors possible via activation of nuclear transcription factors and inhibition of cell death pathways.

LncRNA MALAT1 silencing protects against cerebral ischemia-reperfusion injury through miR-145 to regulate AQP4

BACKGROUND

The present study aimed to verify whether long noncoding RNA (lncRNA) MALAT1 is involved in brain tissue damage induced by ischemia-reperfusion injury, and to explore the mechanism by which MALAT1 regulates aquaporin 4 (AQP4).

METHODS

In this study, we established glucose deprivation (OGD)/reoxygenation (RX) astrocyte cell model and middle cerebral artery occlusion (MCAO)/reperfusion mouse model in vitro and in vivo. Then cell counting kit-8 assay, flow cytometry analysis, Triphenyltetrazolium chloride (TTC) staining, and western blotting were used to determine cell viability, cell apoptosis, cerebral infarction volume, and the abundance of AQP4, respectively.

RESULTS

We found that the level of MALAT1 was significantly upregulated in both the MCAO/reperfusion model and OGD/RX model. Knockdown of MALAT1 increased cell viability and reduced cell apoptosis in MA-C cells, while an AQP4 siRNA combined with a siRNA targeting MALAT1 could not enhance this effect. Further experiments showed that MALAT1 positively regulated AQP4 expression via miR-145. The MALAT1 siRNA did not alleviate the exacerbation of damage after miR-145 inhibitor action. However, an miR-145 inhibitor reversed the protection effects of MALAT1, indicating that MALAT1 silencing protects against cerebral ischemia-reperfusion injury through miR-145. TTC staining showed that the infracted area of whole brain was significantly attenuated in treated with sh-MALAT1 group in vivo.

CONCLUSION

Taken together, our study confirmed that MALAT1 promotes cerebral ischemia-reperfusion injury by affecting AQP4 expression through competitively binding miR-145, indicating that MALAT1 might be a new therapeutic target for treatment cerebral ischemic stroke.

Knockdown of IL-32 protects PC12 cells against oxygen-glucose deprivation/reoxygenation-induced injury via activation of Nrf2/NF-κB pathway

Cerebral ischemia/reperfusion injury (IRI) is one of major causes of ischemic organ damage. It is well established that inflammatory cytokines serve as regulatory factors in cerebral oxygen glucose deprivation/reoxygenation (OGD/R). However, the involving mechanism is not clear enough. OGD/R PC12 cells were used as a hypoxia/reoxygenation model. IL-32 expression and cell viability were detected by qRT-PCR and CCK-8 assay, respectively. Cell apoptosis were determined by flow cytometry and western blotting. Protein levels of inflammatory factors, and the activity of MPO, MDA and SOD were analyzed. Furthermore, western blot assay was carried out to assess protein levels of Nrf2, keap1, NQO-1, p-p65, p-IκBα, p65 and IκBα. The results revealed that IL-32 expression was significantly upregulated in PC12 cells induced by OGD/R. Nrf2, keap1 and NQO-1 level was reduced while phosphorylation level of p65 and IκBα was up-regulated in OGD/R-induced PC12 cells. Mechanism investigations found that IL-32 silence elevated the level of Nrf2, Keap1 and NQO-1, reduced p-p65 and p-IκBα level, and regulated the contents of TNF-a, IL-1β, IL-6 and MCP-1 in OGD/R PC12 cells. In addition, knockdown of IL-32 suppressed production of intracellular ROS, elevated SOD activity, reduced MPO and MDA content, and enhanced cell viability. Furthermore, cell apoptosis was induced in OGD/R PC12 cells with IL-32 silence. However, Nrf2 inhibitor reversed the effects of IL-32 knockdown on OGD/R PC12 cells. This research suggests that IL-32 silence may alleviate OGD/R and Nrf2 plays an important role in the protection by IL-32 silence on PC12 cells induced by OGD/R.

Electroacupuncture Alleviates Cerebral Ischemia/Reperfusion Injury in Rats by Histone H4 Lysine 16 Acetylation-Mediated Autophagy

Background: Electroacupuncture (EA) treatment in ischemic stroke has been highlighted recently; however, the specific mechanism is still elusive. Autophagy is considered a new target for cerebral ischemia/reperfusion (I/R), but whether it plays a role of protecting or causing rapid cell apoptosis remains unclear. Studies have reported that the reduction in lysine 16 of histone H4 acetylation coheres with autophagy induction. The primary purpose of the study was to explore whether EA could alleviate I/R via autophagy-mediated histone H4 lysine 16 acetylation in the middle cerebral artery occlusion (MCAO) rat model. Methods: One hundred and twenty male Sprague-Dawley rats were divided into five groups: control group, MCAO group, MCAO+EA group, MCAO+EA+hMOF siRNA group, and MCAO+EA+Sirt1 inhibitor group. EA was applied to "Baihui" (Du20) and "Renzhong" (Du26) at 5 min after modeling and 16 h after the first EA intervention. The structure and molecular markers of the rat brain were evaluated. Results: EA significantly alleviated I/R injury by upregulating the expressions of Sirt1, Beclin1, and LC3-II and downregulating the expressions of hMOF and H4K16ac. In contrast, the Sirt1 inhibitor lowered the increase in Sirt1, Beclin1, and LC3-II and enhanced the level of hMOF and H4K16ac expressions associated with EA treatment. Besides, ChIP assay revealed that the binding of H4K16ac in the Beclin1 promoter region of the autophagy target gene was significantly raised in the MCAO+EA group and MCAO+EA+hMOF siRNA group. Conclusions: EA treatment inhibited the H4K16ac process, facilitated autophagy, and alleviated I/R injury. These findings suggested that regulating histone H4 lysine 16 acetylation-mediated autophagy may be a key mechanism of EA at Du20 and Du26 to treat I/R.

MicroRNA‑217 inhibition relieves cerebral ischemia/reperfusion injury by targeting SIRT1

MicroRNAs (miRs) have been proposed to be involved in the pathological processes of cerebral ischemia/reperfusion (CIR) injury. The present study aimed to investigate the potential role and molecular mechanisms of miR-217 in the regulation of neuronal survival in CIR injury. To perform the investigation, an in vitro cellular model of CIR injury was established by treating neurons with oxygen-glucose deprivation and reoxygenation (OGD/R). miR-217 levels in neurons were detected using reverse transcription-quantitative PCR. The association between miR-217 and sirtuin 1 (SIRT1) was identified using TargetScan and validated in a dual-luciferase reporter assay. Cell viability and apoptosis were measured using a Cell Counting Kit-8 assay and flow cytometry, respectively. The release of lactate dehydrogenase, and the production of proinflammatory factors and oxidative stress biomarkers were analyzed by ELISAs and using specific assay kits. It was revealed that miR-217 was significantly upregulated in OGD/R-treated neurons. SIRT1 was a direct target of miR-217, and was downregulated in neurons following OGD/R treatment. Downregulation of miR-217 significantly ameliorated OGD/R-induced neuronal injury, inflammatory responses and oxidative stress. The effects of miR-217 inhibitor on OGD/R treated neurons were attenuated by SIRT1 knockdown. Additionally, western blotting revealed that the SIRT1/AMP-activated protein kinase-α/NF-κB pathway was partially involved in the regulation of OGD/R-induced neuronal injury by miR-217. In conclusion, the data of the present study indicated that the downregulation of miR-217 protected neurons against OGD/R-induced injury by targeting SIRT1.

Influence of low-dose alcohol consumption on post-ischemic inflammation: Role of cystathionine γ-lyase

Low-dose alcohol consumption (LAC) has been shown to suppress post-ischemic inflammation and alleviate cerebral ischemia/reperfusion (I/R) injury. Cystathionine γ-Lyase (CSE) is one of the enzymes that endogenously produce hydrogen sulfide (H₂S), which has an anti-inflammatory property at low concentration. We determined the potential role of CSE in the protective effect of LAC. Male C57BL/6J mice were divided into two groups, an ethanol group and a control group, and gavage fed with 0.7 g/kg/day ethanol or volume-matched water once a day for 8 weeks. Transient focal cerebral ischemia was induced by unilateral middle cerebral artery occlusion (MCAO) for 90 min. CSE inhibitors were intraperitoneally given 30 min prior to the ischemia. Cerebral I/R injury, H₂S production, adhesion molecules, IL-1 receptor accessory protein (IL-1RAcP), IL-1β, microglial activation, and neutrophil infiltration were evaluated at 24 h of reperfusion. Eight-week ethanol feeding upregulated CSE in the cerebral cortex and reduced cerebral I/R injury. Moreover, ethanol increased post-ischemic H₂S production and alleviated the post-ischemic inflammatory response (expression of adhesion molecules, IL-1RAcP, IL-1β, microglial activation, and neutrophil infiltration) in the peri-infarct cerebral cortex. Both inhibitors of CSE, DL-Propargylglycine (PAG) and β-cyano-L-alanine (BCA), abolished the protective effect of ethanol on cerebral I/R injury. In addition, PAG attenuated the inhibitory effect of ethanol on the post-ischemic inflammation. Thus, LAC may protect against cerebral I/R injury by suppressing post-ischemic inflammation via an upregulated CSE.

Reduction of Leukocyte Microvascular Adherence and Preservation of Blood-Brain Barrier Function by Superoxide-Lowering Therapies in a Piglet Model of Neonatal Asphyxia

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical (O 2 ⋅ _ ) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removingO 2 ⋅ _ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical. Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously. Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition ofO 2 ⋅ _ production by oxypurinol, or elimination ofO 2 ⋅ _ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels. Conclusion: Using three different strategies to either prevent formation or enhance elimination ofO 2 ⋅ _ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lowerO 2 ⋅ _ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia.

Significance of Complement System in Ischemic Stroke: A Comprehensive Review

The complement system is an essential part of innate immunity, typically conferring protection via eliminating pathogens and accumulating debris. However, the defensive function of the complement system can exacerbate immune, inflammatory, and degenerative responses in various pathological conditions. Cumulative evidence indicates that the complement system plays a critical role in the pathogenesis of ischemic brain injury, as the depletion of certain complement components or the inhibition of complement activation could reduce ischemic brain injury. Although multiple candidates modulating or inhibiting complement activation show massive potential for the treatment of ischemic stroke, the clinical availability of complement inhibitors remains limited. The complement system is also involved in neural plasticity and neurogenesis during cerebral ischemia. Thus, unexpected side effects could be induced if the systemic complement system is inhibited. In this review, we highlighted the recent concepts and discoveries of the roles of different kinds of complement components, such as C3a, C5a, and their receptors, in both normal brain physiology and the pathophysiology of brain ischemia. In addition, we comprehensively reviewed the current development of complement-targeted therapy for ischemic stroke and discussed the challenges of bringing these therapies into the clinic. The design of future experiments was also discussed to better characterize the role of complement in both tissue injury and recovery after cerebral ischemia. More studies are needed to elucidate the molecular and cellular mechanisms of how complement components exert their functions in different stages of ischemic stroke to optimize the intervention of targeting the complement system.

Dose-Dependent Influences of Ethanol on Ischemic Stroke: Role of Inflammation

Chronic ethanol consumption dose-dependently affects both incidence and prognosis of ischemic stroke. Our goal was to determine whether the influence of chronic ethanol consumption on ischemic stroke is related to an altered inflammatory profile in the brain. Male C57BL/6J mice were divided into six groups and gavage fed with 0.175, 0.35, 0.7, 1.4, 2.8 g/kg/day ethanol or volume-matched water once a day for 8 weeks. Adhesion molecules, microglial activation, neutrophil infiltration, pro- and anti-inflammatory cytokines/chemokines, blood-brain barrier (BBB) permeability, and matrix metallopeptidases (MMPs) in the cerebral cortex before and following a 90-min unilateral middle cerebral artery occlusion (MCAO)/24-h reperfusion were evaluated. Brain ischemia/reperfusion (I/R) injury was significantly reduced in 0.7 g/kg/day ethanol group (peak blood ethanol concentration: 9 mM) and worsened in 2.8 g/kg/day ethanol group (peak blood ethanol concentration: 37 mM). Baseline E-selectin was downregulated in all ethanol groups, whereas baseline intercellular adhesion molecule-1 (ICAM-1) was only downregulated in 0.35 and 0.7 g/kg/day ethanol groups. Interestingly, baseline vascular cell adhesion molecule-1 (VCAM-1) was upregulated in 0.35, 0.7, and 1.4 g/kg/day ethanol groups. Post-ischemic upregulation of ICAM-1 and E-selectin were suppressed in all ethanol groups. Post-ischemic neutrophil infiltration and microglial activation were significantly less in the low-moderate (0.175–1.4 g/kg/day) ethanol groups but greater in the 2.8 g/kg/day ethanol group compared to the vehicle group. At basal conditions, ethanol increased one pro- and two anti-inflammatory cytokines/chemokines at the 0.7 g/kg/day dose, and 13 pro- and eight anti-inflammatory cytokines/chemokines at the 2.8 g/kg/day dose. After ischemia, 0.7 g/kg/day ethanol suppressed post-ischemic pro-inflammatory cytokines/chemokines and enhanced post-ischemic anti-inflammatory cytokines/chemokines. Moreover, 0.7 g/kg/day ethanol significantly reduced baseline MMP-9 activity and alleviated post-ischemic BBB breakdown. On the other hand, 2.8 g/kg/day ethanol worsened post-ischemic BBB breakdown. Our findings suggest that low-moderate ethanol consumption may prevent ischemic stroke and reduce brain I/R injury by suppressing inflammation, whereas heavy alcohol consumption may induce ischemic stroke and worsen brain I/R injury by aggravating inflammation.

The Synergistic Combination of Everolimus and Paroxetine Exerts Post-ischemic Neuroprotection In Vitro

Ischemic stroke is a debilitating multi-factorial cerebrovascular disorder, representing an area of tremendous unmet medical need. Combination treatment has been proposed as a promising therapeutic approach towards combating ischemic stroke. The present study employs in vitro oxygen glucose deprivation (OGD) model to evaluate the post-ischemic neuroprotective efficacy of Everolimus and Paroxetine, alone and in combination. Post-OGD treatment with Everolimus and Paroxetine, alone or in combination, significantly improved the cell survival (~ 80%) when compared to the cells subjected to ischemic injury alone. The individual neuroprotective doses of Everolimus and Paroxetine were found to be at 6.25 and 25 nM, respectively. Whereas, the synergistic neuroprotective dose for Everolimus:Paroxetine was 2:10 nM, calculated using the Chou-Talalay combination index and other four mathematical models. The synergistic combination dose downregulated neuroinflammatory genes (Tnf-α, Il1b, Nf-κB, and iNos) and upregulated the neuroprotective genes (Bcl-2, Bcl-xl, Hif-1, and Epo). The mitochondrial functioning and ROS neutralizing ability increased with combination treatment. Further, the active role of nitric oxide synthase and calmodulin were revealed while exploring the bio-activity of Everolimus and Paroxetine through network pharmacology. The present study for the first time demonstrates the synergistic post-ischemic neuroprotective efficacy of combination treatment with Everolimus and Paroxetine in vitro. Taken together, these findings clearly suggest that Everolimus in combination with Paroxetine may represent a promising therapeutic strategy for the treatment of ischemic stroke, further supporting the combination treatment strategy for this debilitating disorder.

Association between different acute stroke therapies and development of post stroke seizures

Background

Epilepsy is a major complication of stroke. We aimed to establish whether there is an association between intravenous thrombolysis, intra-arterial thrombolysis and post stroke seizure (PSS) development. Improved understanding of the relationship between reperfusion therapies and seizure development may improve post-stroke monitoring and follow-up.

Methods

This was a retrospective, multicentre cohort study conducted at the Royal Melbourne Hospital and Jingling Hospital Nanjing. We included patients with anterior circulation ischemic stroke admitted 2008–2015. Patients were divided into four treatment groups 1. IV-tPA only, 2. Intra-arterial therapies (IAT) only, 3. IAT + IV-tPA and 4. stroke unit care only (i.e. no IV-tPA or IAT). To assess the association between type of reperfusion treatment and seizure incidence we used multivariable logistic regression models adjusted for age, stroke severity, 3-month functional outcome and prognostic factors.

Results

There were 1375 stroke unit care-only patients, of whom 28 (2%) developed PSS. There were 363 patients who received only IV-tPA, of whom 21 (5.8%) developed PSS. There were 93 patients who received IAT only, of whom 12 (12.9%) developed PSS and 112 that received both IV-tPA + IAT, of which 5 (4.5%) developed PSS. All reperfusion treatments were associated with seizure development compared to stroke unit care-only patients: IV-tPA only adjusted odds ratio (aOR) 3.7, 95%CI 1.8–7.4, p < 0.0001; IAT aOR 5.5, 95%CI 2.1–14.3, p < 0.0001, IAT + IV-tPA aOR 3.4, 95% CI 0.98–11.8, p = 0.05. These aORs did not differ significantly between treatment groups (IV-tPA + IAT versus IV-tPA p = 0.89, IV-tPA + IAT versus IAT, p = 0.44).

Conclusions

Patients receiving thrombolytic or intra-arterial reperfusion therapies for acute ischemic stroke are at higher risk of epilepsy and may benefit from longer follow-up. No evidence for an additive or synergistic effect of treatment modality on seizure development was found.

Electronic supplementary material

The online version of this article (10.1186/s12883-018-1064-x) contains supplementary material, which is available to authorized users.

Inflammatory Responses are Sex Specific in Chronic Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is increasingly recognized as a sexually dimorphic disease. Male infants are not only more vulnerable to ischemic insult; they also suffer more long-term cognitive deficits compared with females with comparable brain damage. The innate immune response plays a fundamental role in mediating acute neonatal HIE injury. However, the mechanism underlying the sex difference in chronic HIE is still elusive. The present study investigated the sex difference in HIE outcomes and inflammatory response in the chronic stage (30 days after HIE). Postnatal day 10 (P10) male and female C57BL/6 pups were subjected to 60-min Rice-Vanucci model (RVM) to induce HIE. Brain atrophy and behavioral deficits were analyzed to measure stroke outcomes at 30 days of HIE. Flow cytometry (FC) was performed to examine central (microglial activation) and peripheral immune responses. Serum levels of cytokines and sex hormones were determined by enzyme-linked immunosorbent assay (ELISA). Neurogenesis was quantified by 5-Bromo-2'-deoxyuridine (BrdU) incorporation with neurons. Results showed males had worse HIE outcomes than females at the endpoint. Female microglia exhibited a more robust anti-inflammatory response that was corresponding to an enhanced expression of CX3C chemokine receptor 1 (CX3CR1) than males. More infiltration of peripheral lymphocytes was seen in male vs. female HIE brains. Cytokine levels of tumor necrosis factor (TNF)-α and interleukin (IL)-10 were more upregulated in males and females respectively than their counterparts. Neurogenesis was more highly induced in females vs. males. No significant difference in circulating hormonal level was found between males and females after HIE. We conclude that a sex dichotomy in pro- and anti-inflammatory response underlies the sex-specific chronic HIE outcomes, and an enhanced neurogenesis in females also contribute to the sex difference.

Phosphorylation at S153 as a Functional Switch of Phosphatidylethanolamine Binding Protein 1 in Cerebral Ischemia-Reperfusion Injury in Rats

This study aimed to estimate the role of phosphatidylethanolamine binding protein 1 (PEBP1) in cerebral ischemia-reperfusion (I/R) injury and the underlying mechanisms. Middle cerebral artery occlusion/reperfusion (MCAO/R) model in adult male Sprague Dawley rats (250-280 g) were established and cultured neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic I/R injury in vitro. Expression vectors encoding wild-type PEBP1 and PEBP1 with Ser153Ala mutation (S153A), PEBP1 specific siRNAs, and human recombinant PEBP1 (rhPEBP1) were administered intracerebroventricularly. Endogenous PEBP1 level and its phosphorylation at Ser153 were increased within penumbra tissue and cultured neurons after I/R, accompanied by decreased interaction between PEBP1 and Raf-1. There was a trend toward increased Raf-1/MEK/ERK/NF-κB signaling pathway and phosphatidylcholine-phospholipase C (PC-PLC) activity after I/R, which was enhanced by wild-type PEBP1overexpression and rhPEBP1 treatment and inhibited by PEBP1 (S153A) overexpression. And PEBP1 (S153A) overexpression increased its interaction with Raf-1, reduced infarct size, neuronal death and inflammation, and improved neurological function after I/R, while wild-type PEBP1overexpression exerted opposite effects, suggesting that phosphorylation at Ser153 may exert as a functional switch of PEBP1 by switching PEBP1 from Raf-1 inhibition to PC-PLC activation following I/R. Compared with PEBP1 knockdown, PEBP1 (S153A) overexpression exerted a better rescue effect on I/R injury, which further proved that PEBP1 may be a good protein gone bad with phosphorylation at S153 as a functional switch following I/R. Collectively, our findings suggest that PEBP1 contributed to neuronal death and inflammation after I/R. Selective inhibition of PEBP1 phosphorylation may be a novel approach to ameliorate I/R injury.

MicroRNA-93 inhibits inflammatory responses and cell apoptosis after cerebral ischemia reperfusion by targeting interleukin-1 receptor-associated kinase 4

The present study aimed to investigate changes in the expression of interleukin (IL)-1 receptor-associated kinase 4 (IRAK4) and microRNA (miRNA or miR)-93 in mice with cerebral ischemia reperfusion (CIR) injury, as well as the association and regulatory mechanism between IRAK4 and miR-93. The CIR mouse model was constructed and mouse microglia BV2 cells were transfected with miR-93 mimic or miR-93 inhibitor. Quantitative polymerase chain reaction was used to measure the expression of mRNA and miR-93. Western blotting was performed to determine protein expression. Enzyme-linked immunosorbent assays were performed to measure the concentrations pro-inflammatory factors. The expression of miR-93 in CIR mice brains was significantly reduced, while Ago-miR-93 (a type of miRNA analog) increased its expression. Ago-miR-93 alleviated neurological deficits and reduced cerebral infarction volume in the mice. Furthermore, Ago-miR-93 inhibited inflammatory responses following CIR. Ago-miR-93 decreased the rate of cell apoptosis following CIR. In addition, miR-93 downregulated IRAK4 protein expression, but did not alter its mRNA expression levels in BV2 cells. miR-93 expression reduced the expression of pro-inflammatory factors in BV2 cells. Ago-miR-93 inhibited IRAK4 expression in the brain tissues of CIR mice. The present study demonstrated that miR-93 inhibits inflammatory responses and cell apoptosis following CIR by targeting the IRAK4 signaling pathway.

Protective Role of Fucoidan in Cerebral Ischemia-Reperfusion Injury through Inhibition of MAPK Signaling Pathway

Fucoidan has been reported to exhibit various beneficial activities ranging from to antivirus and anticancer properties. However, little information is available about the effects of fucoidan on cerebral ischemia-reperfusion injury (IRI). Our study aimed to explore the effects of fucoidan on cerebral IRI, as well as the underlying mechanisms. Sprague-Dawley (SD) rats were randomly subjected to four groups: Sham, IRI+saline (IRI+S), IRI+80 mg/kg fucoidan (IRI+F80), and IRI+160 mg/kg fucoidan (IRI+F160). Fucoidan (80 mg/kg or 160 mg/kg) was intraperitoneally injected from 7 days before the rats were induced to cerebral IRI model with middle cerebral artery occlusion (MCAO) method. At 24 h after reperfusion, neurological deficits and the total infarct volume were determined. The levels of inflammation-associated cytokines (interleukin (IL)-1β, IL-6, myeloperoxidase (MPO), and tumor necrosis factor (TNF)-α), oxidative stress-related proteins (malondialdehyde (MDA) and superoxide dismutase (SOD)) in the ischemic brain were measured by enzyme-linked immunosorbent assay (ELISA). Besides, the levels of apoptosis-related proteins (p-53, Bax, and B-cell lymphoma (Bcl)-2) and mitogen-activated protein kinase (MAPK) pathway (phosphorylation-extracellular signalregulated kinase (p-ERK), p-c-Jun N-terminal kinase (JNK), and p-p38) were measured. Results showed that administration of fucoidan significantly reduced the neurological deficits and infarct volume compared to the IRI+S group in a dose-dependent manner. Also, fucoidan statistically decreased the levels of inflammation-associated cytokines, and oxidative stress-related proteins, inhibited apoptosis, and suppressed the MAPK pathway. So, Fucoidan plays a protective role in cerebral IRI might be by inhibition of MAPK pathway.

Clinical pathophysiology of hypoxic ischemic brain injury after cardiac arrest: a "two-hit" model

Hypoxic ischemic brain injury (HIBI) after cardiac arrest (CA) is a leading cause of mortality and long-term neurologic disability in survivors. The pathophysiology of HIBI encompasses a heterogeneous cascade that culminates in secondary brain injury and neuronal cell death. This begins with primary injury to the brain caused by the immediate cessation of cerebral blood flow following CA. Thereafter, the secondary injury of HIBI takes place in the hours and days following the initial CA and reperfusion. Among factors that may be implicated in this secondary injury include reperfusion injury, microcirculatory dysfunction, impaired cerebral autoregulation, hypoxemia, hyperoxia, hyperthermia, fluctuations in arterial carbon dioxide, and concomitant anemia.Clarifying the underlying pathophysiology of HIBI is imperative and has been the focus of considerable research to identify therapeutic targets. Most notably, targeted temperature management has been studied rigorously in preventing secondary injury after HIBI and is associated with improved outcome compared with hyperthermia. Recent advances point to important roles of anemia, carbon dioxide perturbations, hypoxemia, hyperoxia, and cerebral edema as contributing to secondary injury after HIBI and adverse outcomes. Furthermore, breakthroughs in the individualization of perfusion targets for patients with HIBI using cerebral autoregulation monitoring represent an attractive area of future work with therapeutic implications.We provide an in-depth review of the pathophysiology of HIBI to critically evaluate current approaches for the early treatment of HIBI secondary to CA. Potential therapeutic targets and future research directions are summarized.

Cellular Stress Response and Immune Signaling in Retinal Ischemia-Reperfusion Injury

Ischemia–reperfusion injury is a well-known pathological hallmark associated with diabetic retinopathy, glaucoma, and other related retinopathies that ultimately can lead to visual impairment and vision loss. Retinal ischemia pathogenesis involves a cascade of detrimental events that include energy failure, excitotoxic damage, calcium imbalance, oxidative stress, and eventually cell death. Retina for a long time has been known to be an immune privileged site; however, recent investigations reveal that retina, as well as the central nervous system, elicits immunological responses during various stress cues. Stress condition, such as reperfusion of blood supply post-ischemia results in the sequestration of different immune cells, inflammatory mediators including cytokines, chemokines, etc., to the ischemic region, which in turn facilitates induction of inflammatory conditions in these tissues. The immunological activation during injury or stress per se is beneficial for repair and maintenance of cellular homeostasis, but whether the associated inflammation is good or bad, during ischemia–reperfusion injury, hitherto remains to be explored. Keeping all these notions in mind, the current review tries to address the immune response and host stress response mechanisms involved in ischemia–reperfusion injury with the focus on the retina.

Anti-inflammation Effects of Oxysophoridine on Cerebral Ischemia-Reperfusion Injury in Mice

Oxysophoridine (OSR) is a bioactive alkaloid extracted from the Sophora alopecuroides Linn. Our aim is to explore the potential anti-inflammation mechanism of OSR in cerebral ischemic injury. Mice were intraperitoneally pretreated with OSR (62.5, 125, and 250 mg/kg) or nimodipine (Nim) (6 mg/kg) for 7 days followed by cerebral ischemia. The inflammatory-related cytokines in cerebral ischemic hemisphere tissue were determined by immunohistochemistry staining, Western blot and enzyme-like immunosorbent assay (ELISA). OSR-treated groups observably suppressed the nuclear factor kappa B (NF-κB), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). OSR-treated group (250 mg/kg) markedly reduced the inflammatory-related protein prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8). Meanwhile, it dramatically increased the interleukin-10 (IL-10). Our study revealed that OSR protected neurons from ischemia-induced injury in mice by downregulating the proinflammatory cytokines and blocking the NF-κB pathway.

Critical Care of Brain Reperfusion

Over the last few decades, the management of acute ischemic stroke has undergone significant advancements with the introduction of intravenous thrombolysis and more recently punctuated by the success of endovascular mechanical thrombectomy trials for large vessel occlusion. These advancements have transformed the practice of neurocritical care. In this review, we present a case-based discussion of common brain reperfusion techniques with an emphasis on complication recognition and management. The article encompasses recent evidence-based recommendations as well as some of our own institutional protocols.

Effects of Shaoyao-Gancao Decoction on Infarcted Cerebral Cortical Neurons: Suppression of the Inflammatory Response following Cerebral Ischemia-Reperfusion in a Rat Model

The mechanisms by which Shaoyao-Gancao decoction (SGD) inhibits the production of inflammatory cytokines in serum and brain tissue after cerebral ischemia-reperfusion (CI-RP) in rats were investigated. A right middle cerebral artery occlusion was used to induce CI-RP after which the rats were divided into model (n = 39), SGD (n = 28), clopidogrel (n = 25) and sham operated (n = 34) groups. The Bederson scale was used to evaluate changes in behavioral indices. The levels of IL-1β, TNF-α, MCP-1, IL-10, RANTES, VEGF, and TGF-β1 in the serum and infarcted brain tissues were measured. Nissl body and immunohistochemical staining methods were used to detect biochemical changes in neurons, microglial cells, and astrocytes. Serum levels of VEGF, TNF-α, MCP-1, IL-1β, and IL-10 increased significantly 24 h after CI-RP. In brain tissue, levels of TNF-α and IL-1β significantly increased 24 h after CI-RP, whereas levels of TGF-β1 and MCP-1 were significantly higher 96 h after CI-RP (P < 0.05). SGD or clopidogrel after CI-RP reduced TNF-α and IL-1β levels in brain tissue and serum levels of MCP-1, IL-1β, and IL-10. SGD increased the number of NeuN-positive cells in infarcted brain tissue and reduced the number of IBA1-positive and GFAP-positive cells. The efficacy of SGD was significantly higher than that of clopidogrel.

Ischemia-reperfusion Injury in the Brain: Mechanisms and Potential Therapeutic Strategies

Ischemia-reperfusion injury is a common feature of ischemic stroke, which occurs when blood supply is restored after a period of ischemia. Reperfusion can be achieved either by thrombolysis using thrombolytic reagents such as tissue plasminogen activator (tPA), or through mechanical removal of thrombi. Spontaneous reperfusion also occurs after ischemic stroke. However, despite the beneficial effect of restored oxygen supply by reperfusion, it also causes deleterious effect compared with permanent ischemia. With the recent advancement in endovascular therapy including thrombectomy and thrombus disruption, reperfusion-injury has become an increasingly critical challenge in stroke treatment. It is therefore of extreme importance to understand the mechanisms of ischemia-reperfusion injury in the brain in order to develop effective therapeutics. Accumulating experimental evidence have suggested that the mechanisms of ischemia-reperfusion injury include oxidative stress, leukocyte infiltration, platelet adhesion and aggregation, complement activation, mitochondrial mediated mechanisms, and blood-brain-barrier (BBB) disruption, which altogether ultimately lead to edema or hemorrhagic transformation (HT) in the brain. Potential therapeutic strategies against ischemia-reperfusion injury may be developed targeting these mechanisms. In this review, we briefly discuss the pathophysiology and cellular and molecular mechanisms of cerebral ischemia-reperfusion injury, and potential therapeutic strategies.

Adhesion Molecules: Master Controllers of the Circulatory System

This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

Rare complication characterized by late-onset transient neurological symptoms without hyperperfusion after carotid artery stenting: A report of three cases

We experienced a rare complication after carotid artery stenting (CAS) characterized by transient neurological symptoms with no evidence of distal emboli or hyperperfusion. Using neuroimaging, we investigated the pathogenesis of the complication that occurred after CAS in three patients who developed neurological symptoms over a period of ten hours after CAS and improved within two days. None of the three patients showed signs of fresh infarctions on diffusion-weighted imaging or hyperperfusion on single-photon emission computed tomography. However, high signal intensity was observed in the leptomeningeal zone of the cerebral hemisphere on the stent side in all three patients and in the leptomeningeal zone of the contralateral anterior cerebral artery territory in one patient. These areas were assessed using fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging without gadolinium administration. The high signal intensity in the leptomeningeal zone disappeared as the symptoms improved. Based on the transient nature of the neurological disorders and the normalization of FLAIR imaging findings in these patients, the pathogenesis of this complication might have been vasogenic edema due to vasoparalysis of the local vessels caused by the hemodynamic changes occurring after CAS.

Advances in stroke therapy

Stroke is a leading cause of death, long-term disability, and socioeconomic costs, highlighting the urgent need for more effective treatments. Intravenous administration of tissue plasminogen activator (t-PA) is the only FDA-approved therapy to re-establish cerebral blood flow. However, because of increased risk of hemorrhage beyond 3 h post stroke, few stroke patients (1-2%) benefit from t-PA; t-PA, which has neurotoxic effects, can also aggravate the extent of reperfusion injury by increasing blood-brain barrier permeability. An alternative strategy is needed to extend the window of intervention, minimize damage from reperfusion injury, and promote brain repair leading to neurological recovery. Reactive oxygen species (ROS), generated soon after ischemia and during reperfusion and thereafter, are considered the main mediators of ischemic injury. Antioxidant enzymes such as catalase, superoxide dismutase, etc. can neutralize ROS-mediated injury but their effective delivery to the brain remains a challenge. In this article, we review various therapeutic approaches including surgical interventions, and discuss the potential of nanoparticle-mediated delivery of antioxidants for stroke therapy.

17β-estradiol increases expression of the oxidative stress response and DNA repair protein apurinic endonuclease (Ape1) in the cerebral cortex of female mice following hypoxia

While it is well established that 17β-estradiol (E2) protects the rodent brain from ischemia-induced damage, it has been unclear how this neuroprotective effect is mediated. Interestingly, convincing evidence has also demonstrated that maintaining or increasing the expression of the oxidative stress response and DNA repair protein apurinic endonuclease 1 (Ape1) is instrumental in reducing ischemia-induced damage in the brain. Since E2 increases expression of the oxidative stress response proteins Cu/Zn superoxide dismutase and thioredoxin in the brain, we hypothesized that E2 may also increase Ape1 expression and that this E2-induced expression of Ape1 may help to mediate the neuroprotective effects of E2 in the brain. To test this hypothesis, we utilized three model systems including primary cortical neurons, brain slice cultures, and whole animals. Although estrogen receptor α and Ape1 were expressed in primary cortical neurons, E2 did not alter Ape1 expression in these cells. However, immunofluorescent staining and quantitative Western blot analysis demonstrated that estrogen receptor α and Ape1 were expressed in the nuclei of cortical neurons in brain slice cultures and that E2 increased Ape1 expression in the cerebral cortex of these cultures. Furthermore, Ape1 expression was increased and oxidative DNA damage was decreased in the cerebral cortices of ovariectomized female C57Bl/6J mice that had been treated with E2 and exposed to hypoxia. Taken together, our studies demonstrate that the neuronal microenvironment may be required for increased Ape1 expression and that E2 enhances expression of Ape1 and reduces oxidative DNA damage, which may in turn help to reduce ischemia-induced damage in the cerebral cortex and mediate the neuroprotective effects of E2.

The growth factor progranulin attenuates neuronal injury induced by cerebral ischemia-reperfusion through the suppression of neutrophil recruitment

Background

To improve the clinical outcome of patients who suffered ischemic stroke, cerebral ischemia-reperfusion (I/R) injury is one of the major concerns that should be conquered. Inflammatory reactions are considered a major contributor to brain injury following cerebral ischemia, and I/R exacerbates these reactions. The aim of this study was to investigate the possible ameliorative effects of progranulin (PGRN) against I/R injury in mice.

Methods

In vivo I/R was induced in four-week-old male ddY mice by 2 h of MCAO (middle cerebral artery occlusion) followed by 22 h of reperfusion. We evaluate expression of PGRN in I/R brain, efficacy of recombinant-PGRN (r-PGRN) treatment and its therapeutic time-window on I/R injury. Two hours after MCAO, 1.0 ng of r-PRGN or PBS was administered via intracerebroventricular. We assess neutrophil infiltration, expression of tumor necrosis factor (TNF)-α, matrix metalloproteinase-9 (MMP-9) and phosphorylation of nuclear factor-κB (NF-κB) by immunofluorescense staining and Western blotting. We also investigate neutrophil chemotaxis and intercellular adhesion molecule-1 (ICAM-1) expression in vitro inflammation models using isolated neutrophils and endothelial cells.

Results

We found that expression of PGRN was decreased in the I/R mouse brain. r-PGRN treatment at 2 h after MCAO resulted in a reduction in the infarct volume and decreased brain swelling; this led to an improvement in neurological scores and to a reduction of mortality rate at 24 h and 7 d after MCAO, respectively. Immunohistochemistry, Western blotting, and gelatin zymography also confirmed that r-PGRN treatment suppressed neutrophil recruitment into the I/R brain, and this led to a reduction of NF-κB and MMP-9 activation. In the in vitro inflammation models, PGRN suppressed both the neutrophil chemotaxis and ICAM-1 expression caused by TNF-α in endothelial cells.

Conclusions

PGRN exerted ameliorative effects against I/R-induced inflammation, and these effects may be due to the inhibition of neutrophil recruitment into the I/R brain.

Neuroprotective effects of ultra-low-molecular-weight heparin on cerebral ischemia/reperfusion injury in rats: involvement of apoptosis, inflammatory reaction and energy metabolism

Previous experiments showed that ultra-low-molecular-weight heparin (ULMWH) reduced the infarct and neurologic deficit in rats followed by transient cerebral ischemia, but the mechanisms of its neuroprotective effect are unclear. This study reported the effect of ULMWH on energy metabolism, inflammatory reaction and neuronal apoptosis. Male Wistar rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion for 24 h. ULMWH (0.5, 1 mg/kg, i.v.) was administered after the MCAO and reperfusion. 24 h after the reperfusion, Spectrophotometric assay was used to determine the activity of ATPase and the content of lactic acid in the brain. The ICAM-1 and Caspase-3 genes were investigated by RT-PCR. Furthermore, the apoptotic percentage of cells in hippocampus was quantified by flow cytometry. Compared with the model group, ULMWH significantly decreased lactic acid content and increased ATPase activity in ischemic brain. At the same time, ULMWH inhibited the neural apoptosis and decreased the expressions of ICAM-1 and Caspase-3 mRNA in hippocampus. These findings suggest that ULMWH exhibits a neuroprotective effect against cerebral ischemia/reperfusion injury, partly through improving energy metabolism, inhibiting apoptosis and attenuating inflammatory reaction.

Complement inhibition promotes endogenous neurogenesis and sustained anti-inflammatory neuroprotection following reperfused stroke

Background and Purpose

The restoration of blood-flow following cerebral ischemia incites a series of deleterious cascades that exacerbate neuronal injury. Pharmacologic inhibition of the C3a-receptor ameliorates cerebral injury by attenuating post-ischemic inflammation. Recent reports also implicate C3a in the modulation of tissue repair, suggesting that complement may influence both injury and recovery at later post-ischemic time-points.

Methods

To evaluate the effect of C3a-receptor antagonism on post-ischemic neurogenesis and neurological outcome in the subacute period of stroke, transient focal cerebral ischemia was induced in adult male C57BL/6 mice treated with multiple regimens of a C3a receptor antagonist (C3aRA).

Results

Low-dose C3aRA administration during the acute phase of stroke promotes neuroblast proliferation in the subventricular zone at 7 days. Additionally, the C3a receptor is expressed on T-lymphocytes within the ischemic territory at 7 days, and this cellular infiltrate is abrogated by C3aRA administration. Finally, C3aRA treatment confers robust histologic and functional neuroprotection at this delayed time-point.

Conclusions

Targeted complement inhibition through low-dose antagonism of the C3a receptor promotes post-ischemic neuroblast proliferation in the SVZ. Furthermore, C3aRA administration suppresses T-lymphocyte infiltration and improves delayed functional and histologic outcome following reperfused stroke. Post-ischemic complement activation may be pharmacologically manipulated to yield an effective therapy for stroke.

Dietary flavonoids are neuroprotective through Nrf2-coordinated induction of endogenous cytoprotective proteins

Epidemiological studies have demonstrated that the consumption of fruits and vegetables is associated with reduced risk for cardiovascular disease and stroke. Detailed investigations into the specific dietary components of these foods have revealed that many polyphenolic constituents exert anti-oxidant effects on key substrates involved in the pathogenesis and progression of ischemic injury. These data have perpetuated the belief that the protective effects of flavonoids result from direct anti-oxidant actions at the levels of the cerebral vasculature and brain parenchyma. While many in vitro studies using purified extracts support this contention, first-pass metabolism alters the bioavailability of flavonoids such that the achievable concentrations after oral consumption are not consistent with this mechanism. Importantly, oral consumption of flavonoids may promote neural protection by facilitating the expression of gene products responsible for detoxifying the ischemic microenvironment through both anti-oxidative and anti-inflammatory actions. In particular, the transcriptional factor nuclear factor erythroid 2-related factor 2 has emerged as a critical regulator of flavonoid-mediated protection through the induction of various cytoprotective genes. The pleiotropic effects associated with potent transcriptional regulation likely represent the primary mechanisms of neural protection, as the flavonoid concentrations reaching ischemic tissues in vivo are sufficient to alter intracellular signal transduction but likely preclude the one-to-one stoichiometry necessary to confer protection by direct anti-oxidation. These data reflect an exciting new direction in the study of complementary and alternative medicine that may lead to the development of novel therapies for ischemic/hemorrhagic stroke, traumatic brain injury, and other neurological disorders.

The Neuroprotective Effect of Genetic Mannose-binding Lectin Deficiency is not Sustained in the Sub-acute Phase of Stroke

INTRODUCTION

The complement cascade is a critical mediator of the inflammatory response following cerebral ischemia. Recent work has demonstrated that genetic-deficiency of Mannose-binding lectin(MBL) ameliorates reperfusion injury and improves outcome in the acute phase of stroke. The present study sought to further delineate the pathogenic role of MBL in stroke and to examine whether the neuroprotection associated with MBL-deficiency is sustained beyond the acute phase. We hypothesized that genetic MBL deficiency would suppress complement activation and ameliorate reperfusion injury in the acute phase, but that persistent inhibition of complement into the sub-acute phase would serve to abrogate this neuroprotective effect.

METHODS

The time-course and localization of post-ischemic cerebral MBL and C3 deposition were characterized using both Western-blot and immunohistochemistry. MBL-a/c null(MBL-KO) mice subjected to transient middle cerebral artery occlusion(MCAO) were then employed to investigate the histologic injury and functional outcome associated with genetic MBL deletion at both 24 hours and 7 days.

RESULTS

MBL-a/c rapidly deposit on ischemic endothelium and trigger downstream complement activation in the acute phase. Genetic deficiency of MBL abrogates C3 cleavage as well as the sub-acute accumulation of mononuclear cells in the ischemic region. Although MBL-KO mice demonstrate significantly improved outcome at 24 hours, the neuroprotective effect associated with genetic MBL deletion is not sustained.

CONCLUSIONS

Development of a successful anti-complement neuroprotective strategy will require carefully-tailored inhibition coupled with a greater understanding of the functional effects of complement activation during later phases of stroke recovery.

Inhibition of protein kinase Cβ reverses increased blood-brain barrier permeability during hyperglycemic stroke and prevents edema formation in vivo

BACKGROUND AND PURPOSE

We investigated the effect of circulating factors and protein kinase Cβ on blood-brain barrier permeability and edema during hyperglycemic stroke.

METHODS

Male Wistar rats that were hyperglycemic by streptozotocin (50 mg/kg) for 5 to 6 days underwent middle cerebral artery occlusion (MCAO) for 2 hours with 2 hours of reperfusion. Blood-brain barrier permeability was measured in middle cerebral arteries that were ischemic (MCAO) or nonischemic (CTL) and perfused with plasma (20% in buffer) from MCAO or CTL animals. A separate set of MCAO vessels was perfused with the protein kinase Cβ inhibitor CGP53353 (0.5 μmol/L) and permeability measured. Lastly, hyperglycemic rats were treated intravenously with CGP53353 (10 or 100 μg/kg or vehicle 15 minutes before reperfusion and edema formation measured by wet:dry weights (n=6/group).

RESULTS

MCAO vessels had increased permeability compared with controls regardless of the plasma perfusate. Permeability (water flux, μm(3)×10(8)) of CTL vessel/CTL plasma (n=8), CTL vessel/MCAO plasma (n=7), MCAO vessel/CTL plasma (n=6), and MCAO vessel/MCAO plasma (n=6) was 0.98±0.11, 1.13±0.07, 1.36±0.02, and 1.34±0.06; P<0.01). Inhibition of protein kinase Cβ in MCAO vessels (n=6) reversed the increase in permeability (0.92±0.1; P<0.01). In vivo, hyperglycemia increased edema versus normoglycemia after MCAO (water content=78.84%±0.11% versus 81.38%±0.21%; P<0.01). Inhibition of protein kinase Cβ with 10 or 100 μg/kg CGP53353 during reperfusion prevented the increased edema in hyperglycemic animals (water content=79.54%±0.56% and 79.99%±0.43%; P<0.01 versus vehicle).

CONCLUSIONS

These results suggest that the pronounced vasogenic edema that occurs during hyperglycemic stroke is mediated in large part by activation of protein kinase Cβ.

Cyanine dyes attenuate cerebral ischemia and reperfusion injury in rats

Some photosensitizing cyanine dyes act on the immune system to enhance the phagocytic capacity of macrophages. In this study, we examined whether these dyes have neurotrophin-like activities and neuroprotective effects in vitro and in vivo. By screening more than 250 cyanine dyes, we found that NK-4 and NK-150, which belong to a group of pentamethine trinuclear cyanine dyes, significantly potentiated nerve growth factor (NGF)-primed neurite outgrowth of PC12HS cells in nanomolar to micromolar concentrations. Both NK-4 and NK-150 showed a remarkable hydroxyl radical-scavenging activity using an in vitro electron spin resonance (ESR)-based technique. They also effectively scavenged peroxy radicals, and in addition, NK-4 acted on superoxides to a similar extent as ascorbate. In vivo, NK-4 and NK-150 prevented cerebral ischemic injury induced by 2 h middle cerebral artery occlusion (MCAO) and 24 h reperfusion in rats. Dyes were intravenously administrated twice 1 h after the occlusion and immediately after the start of reperfusion. NK-4 and NK-150 (100 µg/kg) reduced cerebral infarct volumes by 57.0% and 46.0%, respectively. Those dyes also decreased brain swelling in the ischemic semispheres. As a result, administration of NK-4 and NK-150 provided substantial improvements in MCAO-induced neurological deficits in a dose-dependent manner. These results suggest that NK-4 and NK-150 effectively prevented ischemia-induced brain injury through their potent neurotrophin-like activity as well as antioxidative activity.

The splenic response to ischemic stroke: what have we learned from rodent models?

The majority of promising experimental compounds have failed in clinical trials, highlighting the need for novel approaches to treat stroke. Much research has been devoted to elucidating the signaling pathways involved in delayed neuroinflammation that can be targeted at clinically relevant time points. The field of stroke research has benefited from experiments characterizing the temporal expression profiles of candidate cytokines, chemokines, matrix metalloproteinases, and other putative pro-inflammatory molecules. Yet, these data have offered only a glimpse into the complex pathological sequelae and have not advanced the treatment of neuropathies. Upon recognition that peripheral immune cell activation is involved in penumbral expansion, the spleen has emerged as a novel target that mediates the peripheral immune response and promotes pro-inflammatory injury. Although the precise mechanisms have yet to be elucidated, accumulated evidence demonstrates that focal cerebral ischemia alters cytokine, chemokine, and immune cell profiles in the spleen. Additionally, removal of this peripheral lymphoid organ is neuroprotective, and the efficacy of several protective therapies has been linked to actions at the level of the spleen. Future experiments aimed at identifying the splenic lymphocyte populations that respond to ischemic stroke, as well as their signaling mechanisms, are critical in developing novel therapies.

Therapeutic time window for the neuroprotective effects of NGF when administered after focal cerebral ischemia

In the present study, we evaluated the neuroprotection time window for nerve growth factor (NGF) after ischemia/reperfusion brain injury in rabbits as related to this anti-apoptosis mechanism. Male New Zealand rabbits were subjected to 2 h of middle cerebral artery occlusion (MCAO), followed by 70 h of reperfusion. NGF was administered after injury to evaluate the time window. Neurological deficits, infarct volume, neural cell apoptosis and expressions of caspase-3 and Bcl-2 were measured. Compared to saline-treated control, NGF treatment at 2, 3 and 5 h after MCAO significantly reduced infarct volume, neural cell apoptosis and expression of caspase-3 (P < 0.01), up-regulated the expression of Bcl-2 and improved functional recovery (P < 0.01). However, treatment at latter time points did not produce significant neuroprotection. Neuroprotection treatment with NGF provides an extended time window of up to 5 h after ischemia/reperfusion brain injury, in part by attenuating the apoptosis.

The paradox of the neutrophil's role in tissue injury

The neutrophil is an essential component of the innate immune system, and its function is vital to human life. Its production increases in response to virtually all forms of inflammation, and subsequently, it can accumulate in blood and tissue to varying degrees. Although its participation in the inflammatory response is often salutary by nature of its normal interaction with vascular endothelium and its capability to enter tissues and respond to chemotactic gradients and to phagocytize and kill microrganisms, it can contribute to processes that impair vascular integrity and blood flow. The mechanisms that the neutrophil uses to kill microorganisms also have the potential to injure normal tissue under special circumstances. Its paradoxical role in the pathophysiology of disease is particularly, but not exclusively, notable in seven circumstances: 1) diabetic retinopathy, 2) sickle cell disease, 3) TRALI, 4) ARDS, 5) renal microvasculopathy, 6) stroke, and 7) acute coronary artery syndrome. The activated neutrophil's capability to become adhesive to endothelium, to generate highly ROS, and to secrete proteases gives it the potential to induce local vascular and tissue injury. In this review, we summarize the evidence for its role as a mediator of tissue injury in these seven conditions, making it or its products potential therapeutic targets.