Jingwei Shang

Dissociation and protection of the neurovascular unit after thrombolysis and reperfusion in ischemic rat brain

In the ischemic brain, reperfusion with tissue plasminogen activator (tPA) sometimes causes catastrophic hemorrhagic transformation (HT); however, the mechanism remains elusive. Here, we show that the basement membrane, and not the endothelial cells, is vulnerable to ischemic/reperfusion injury with tPA treatment. We treated a spontaneously hypertensive rat model of middle cerebral artery occlusion (MCAO) with vehicle alone, tPA alone, or a free radical scavenger, edaravone, plus tPA. Light and electron microscopic analyses of each microvascular component revealed that the basement membrane disintegrated and became detached from the astrocyte endfeet in tPA-treated animals that showed HT. On the other hand, edaravone prevented the dissociation of the neurovascular unit, dramatically decreased the HT, and improved the neurologic score and survival rate of the tPA-treated rats. These results suggest that the basement membrane that underlies the endothelial cells is a key structure for maintaining the integrity of the neurovascular unit, and a free-radical scavenger can be a viable agent for inhibiting tPA-induced HT.

In vivo imaging of autophagy in a mouse stroke model

Recent studies have suggested that autophagy is involved in a neural death pathway following cerebral ischemia. In vivo detection of autophagy could be important for evaluating ischemic neural cell damage for human stroke patients. Using novel green fluorescent protein (GFP)-fused microtubule-associated protein 1 light chain 3 (LC3) transgenic (Tg) mice, in vivo imaging of autophagy was performed at 1, 3 and 6 d after 60 min transient middle cerebral artery occlusion (tMCAO). Ex vivo imaging of autophagy, testing of the autophagy inhibitor 3-methyladenine (3-MA), estern blot analysis, immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) and fluorescent analyses were performed on brain sections following tMCAO. In vivo fluorescent signals were detected above the ischemic hemisphere through the skull bone at 1, 3 and 6 d after tMCAO, with a peak at 1 d. Similar results were obtained with ex vivo fluorescence imaging. western blot analysis revealed maximum LC3-I and LC3-II expression at 1 d after tMCAO and fluorescence immunohistochemistry demonstrated that GFP-LC3-positive cells were primarily neuronal, not astroglial or microglial, cells. The number of GFP-LC3/TUNEL double-positive cells was greater in the periischemic area than in the core. These results provided evidence of in vivo autophagy detection, with a peak at 1 d, in a live animal model following cerebral ischemia. This novel technique could be valuable for monitoring autophagic processes in vivo in live stroke patients, as well as for clarifying the detailed role of autophagy in the ischemic brain, as well as in other neurological diseases.

Expression of Keap1-Nrf2 system and antioxidative proteins in mouse brain after transient middle cerebral artery occlusion

Reactive oxygen species and their detrimental effects on the brain after transient ischemia have been implicated in the pathogenesis of the ischemic injury. The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) system is currently recognized as the major cellular defense mechanism under oxidative stress, but the involvement of the Keap1-Nrf2 system in the ischemic brain injuries has not been fully investigated to date. In the present study, we investigated temporal changes of Keap1, Nrf2, and their downstream antioxidative proteins in post-ischemic mice brains with respect to spacial differences between the peri-infarct regions and the regions destined to infarct. In the peri-infarct regions, a steady level of Keap1 showed a decremental expression started at 2h of reperfusion after 60 min of transient middle cerebral artery occlusion (tMCAO). In contrast, Nrf2 began to show a significant increase at 2h with a peak at 8h of reperfusion after tMCAO. Both Keap1 and Nrf2 are mainly expressed in neuronal cells but not in glial cells. In the same peri-infarct region, downstream antioxidative proteins such as thioredoxin, glutathione, and heme oxygenase-1 showed significant increases at later time-points of 24-72 h of reperfusion after tMCAO. In the regions destined to infarct, a similar trend of expression changes to those in the peri-infarct regions was observed in Keap1, Nrf2, and 3 downstream antioxidative proteins with much less reactions. The changes found in this study suggest that the induced antioxidative stress proteins after cerebral ischemia may play an important endogenous neuroprotective response under oxidative stress after ischemic stroke.

Strong neurogenesis, angiogenesis, synaptogenesis, and antifibrosis of hepatocyte growth factor in rats brain after transient middle cerebral artery occlusion.

Hepatocyte growth factor (HGF) and glial cell line‐derived neurotrophic factor (GDNF) are strong neurotrophic factors. However, their potentials in neurogenesis, angiogenesis, synaptogenesis, and antifibrosis have not been compared. Therefore, we investigated these effects of HGF and GDNF in cerebral ischemia in the rat. Wistar rats were subjected to 90 min of transient middle cerebral artery occlusion (tMCAO). Immediately after reperfusion, HGF or GDNF was given by topical application. BrdU was injected intraperitoneally twice daily 1, 2, and 3 days after tMCAO. On 14 day, we histologically evaluated infarct volume, antiapoptotic effect, neurogenesis, angiogenesis, synaptogenesis, and antifibrosis. Both HGF and GDNF significantly reduced infarct size and the number of TUNEL‐positive cells, but only HGF significantly increased the number of BrdU‐positive cells in the subventricular zone, and 5′‐bromo‐2′‐deoxyuridine ‐positive cells differentiated into mature neurons on the ischemic side. Enhancement of angiogenesis and synaptogenesis at the ischemic boundary zone was also observed only in HGF‐treated rats. HGF significantly decreased the glial scar formation and scar thickness of the brain pia mater after tMCAO, but GDNF did not. Our study shows that both HGF and GDNF had significant neurotrophic effects, but only HGF can promote the neurogenesis, angiogenesis, and synaptogenesis and inhibit fibrotic change in brains after tMCAO.

Antiapoptotic and antiautophagic effects of glial cell line‐derived neurotrophic factor and hepatocyte growth factor after transient middle cerebral artery occlusion in rats

Glial cell line‐derived neurotrophic factor (GDNF) and hepatocyte growth factor (HGF) are strong neurotrophic factors, which function as antiapoptotic factors. However, the neuroprotective effect of GDNF and HGF in ameliorating ischemic brain injury via an antiautophagic effect has not been examined. Therefore, we investigated GDNF and HGF for changes of infarct size and antiapoptotic and antiautophagic effects after transient middle cerebral artery occlusion (tMCAO) in rats. For the estimation of ischemic brain injury, the infarct size was calculated at 24 hr after tMCAO by HE staining. Terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin in situ nick end labeling (TUNEL) was performed for evaluating the antiapoptotic effect. Western blot analysis of microtubule‐associated protein 1 light chain 3 (LC3) and immunofluorescence analysis of LC3 and phosphorylated mTOR/Ser2448 (p‐mTOR) were performed for evaluating the antiautophagic effect. GDNF and HGF significantly reduced infarct size after cerebral ischemia. The amounts of LC3‐I plus LC3‐II (relative to β‐tubulin) were significantly increased after tMCAO, and GDNF and HGF significantly decreased them. GDNF and HGF significantly increased p‐mTOR‐positive cells. GDNF and HGF significantly decreased the numbers of TUNEL‐, LC3‐, and LC3/TUNEL double‐positive cells. LC3/TUNEL double‐positive cells accounted for about 34.3% of LC3 plus TUNEL‐positive cells. This study suggests that the protective effects of GDNF and HGF were greatly associated with not only the antiapoptotic but also the antiautophagic effects; maybe two types of cell death can occur in the same cell at the same time, and GDNF and HGF are capable of ameliorating these two pathways.

Free Radical Scavenger Edaravone Administration Protects against Tissue Plasminogen Activator Induced Oxidative Stress and Blood Brain Barrier Damage

One of the therapeutics for acute cerebral ischemia is tissue plasminogen activator (t-PA). Using t-PA after 3 hour time window increases the chances of hemorrhage, involving multiple mechanisms. In order to show possible mechanisms of t-PA toxicity and the effect of the free radical scavenger edaravone, we administered vehicle, plasmin, and t-PA into intact rat cortex, and edaravone intravenously. Plasmin and t-PA damaged rat brain with the most prominent injury in t-PA group on 4-HNE, HEL, and 8-OHdG immunostainings. Such brain damage was strongly decreased in t-PA plus edaravone group. For the neurovascular unit immunostainings, occludin and collagen IV expression was decreased in single plasmin or t-PA group, which was recovered in t-PA plus edaravone group. In contrast, matrix metalloproteinase-9 intensity was the strongest in t-PA group, less in plasmin, and was the least prominent in t-PA plus edaravone group. In vitro data showed a strong damage to tight junctions for occludin and claudin 5 in both administration groups, while there were no changes for endothelial (NAGO) and perivascular (GFAP) stainings. Such damage to tight junctions was recovered in t-PA plus edaravone group with similar recovery in Sodium-Fluorescein permeability assay. Administration of t-PA caused oxidative stress damage to lipids, proteins and DNA, and led to disruption of outer parts of neurovascular unit, greater than the effect in plasmin administration. Additive edaravone ameliorated such an oxidative damage by t-PA with protecting outer layers of blood-brain barrier (in vivo) and tight junctions (in vitro).

In vivo optical imaging for evaluating the efficacy of edaravone after transient cerebral ischemia in mice

Detection and protection of apoptosis, autophagy and neurovascular unit (NVU) are essentially important in understanding and treatment for ischemic stroke patients. In this study, we have conducted an in vivo optical imaging for detecting apoptosis and activation of matrix metalloproteinases (MMPs), then evaluated the protective effect of 2 package types of free radical scavenger edaravone (A and B) on apoptosis, autophagy and NVU in mice after transient middle cerebral artery occlusion (tMCAO). As compared to vehicle treatment, edaravones A and B showed a significant improvement of clinical scores and infarct size at 48 h after 90 min of tMCAO with great reductions of in vivo fluorescent signal for MMPs and early apoptotic annexin V activations. Ex vivo imaging of MMPSense 680 or annexin V-Cy5.5 showed a fluorescent signal, while which was remarkably different between vehicle and edaravone groups, and colocalized with antibody for MMP-9 or annexin V. Edaravone A and B ameliorated the apoptotic neuronal cell death in immunohistochemistry, and activations of MMP-9 and aquaporin 4 with reducing autophagic activations of microtubule-associated protein 1 light chain 3 (LC3) in Western blot. In this study, edaravone in both packages showed a similar strong neuroprotection after cerebral ischemia, which was confirmed with in vivo and ex vivo optical imagings for MMPs and annexin V as well as reducing cerebral infarct, inhibiting apoptotic/autophagic mechanisms, and protecting a part of neurovascular unit.

Temporal and spatial differences of multiple protein expression in the ischemic penumbra after transient MCAO in rats

Temporal and spatial differences and relationships of proteins relating to the ischemic penumbra were examined at 1, 3, 12, 24, and 48 h after 90 min of transient middle cerebral artery occlusion (tMCAO) in rats. 2, 3, 5-triphenyltetrazolium chloride (TTC) staining showed that the apparent infarction focus first appeared at 1h after tMCAO, which then largely matured at 24h. Immunohistochemistry and Western blot indicated no or trace levels of c-fos, hypoxia inducible factor-1 alpha (HIF-1 alpha), heat shock protein 70 (HSP70), and annexin V (A5) positive cells in the sham control brain. Expression of c-fos increased quickly and widely within and outside of the affected arterial territory (peak at 1h), and that of HIF-1 alpha reached the maximum at 12h in a smaller area than c-fos. HSP70 began to be induced during the first few hours after tMCAO, peaked at 24h, then decreased within 48 h, while A5 was slightly expressed at 3h, then gradually increased until 48 h. Double immunofluorescent analyses showed that the colocalization rates of c-fos/HIF-1 alpha, HIF-1 alpha/HSP70, HSP70/A5, and A5/TUNEL were 40.6%, 58.4%, 42.1% and 61.0%, respectively. These data suggest that multiple molecular penumbra exist after 90 min of tMCAO in the rat brain where several different proteins participate in different temporal and spatial expression patterns. Thus, there is a window for rescue of ischemic neural cells from 12 to 48 h after injury.

Amlodipine and atorvastatin exert protective and additive effects via antiapoptotic and antiautophagic mechanisms after transient middle cerebral artery occlusion in Zucker metabolic syndrome rats.

We examined the neuroprotective effects amlodipine and/or atorvastatin in metabolic syndrome (MetS) Zucker fatty rats against transient (90 min) middle cerebral artery occlusion (MCAO). The rats were pretreated with vehicle, amlodipine, atorvastatin, or amlodipine plus atorvastatin for 28 days, and 24 hr after transient MCAO the infarct size was assessed via hematoxylin and eosin staining, and terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin in situ nick end labeling (TUNEL) and microtubule‐associated protein 1 light chain 3 (LC3) expression were examined by immunohistochemistry to evaluate apoptosis and autophagy, respectively. Compared with the vehicle group, rats treated with amlodipine or atorvastatin alone showed a significant decrease in infarct volume (P < 0.01), which was further decreased in the amlodipine plus atorvastatin group (P < 0.001). Compared with the vehicle group, the numbers of TUNEL‐ and LC3‐positive cells were markedly reduced by amlodipine or atorvastatin alone (P < 0.01) and further decreased by amlodipine plus atorvastatin (P < 0.001). The number of apoptotic TUNEL/autophagic LC3 double‐positive cells was also significantly decreased with amlodipine or atorvastatin alone compared with vehicle (P < 0.01) and was further decreased by amlodipine plus atorvastatin (P < 0.001). These data suggest additive neuroprotective effects of combination amlodipine and atorvastatin treatment after acute ischemic stroke in MetS model Zucker rats. These effects are mediated, at least in part, via antiapoptotic and antiautophagic mechanisms. Further studies are now needed to expand these preliminary results to understand fully the mechanisms involved in the protective effects of amlodipine and atorvastatin against ischemic stroke.

Time-dependent profiles of microRNA expression induced by ischemic preconditioning in the gerbil hippocampus.

MicroRNAs (miRNAs) are critically important in both normal neuronal development and neurological diseases. Although cerebral ischemia has been shown to alter the miRNA profiles of rats, the role of miRNA in the cornu ammonis 1 region of the gerbil hippocampus under ischemic tolerance has not been studied. In the present study, Mongolian gerbils were subjected to one or three times the nonlethal dose of 2-min transient common carotid artery occlusion (tCCAO). miRNA microarray technology detected 251 miRNAs and the expression of seven of these in terms of ischemic tolerance. They were compared at different time points: 1 day, 7 days, 1 month, and 6 months. mmu-miR-15a-5p, related to neurogenesis, showed increased expression after one dose of 2-min tCCAO and was much higher after three doses. An increase in sha-miR-24 and oan-let-7b-3p, related to transactivation response DNA-binding protein (TDP43), was observed after one dose of 2-min tCCAO, but the peak was accelerated to an earlier period of reperfusion after three doses. In contrast, mmu-miR-125b-5p and mmu-miR-132–5p, related to fused in sarcoma/translocated in liposarcoma (FUS/TLS), showed similar increases at both doses. mmu-miR-181c-5p and mmu-miR-378a-5p, related to heat shock protein 70 (HSP70), also showed accelerated expression after three doses. This data set provides new insight about miRNA expression during neurogenesis, and related to TDP43, FUS/TLS, and HSP70, which may be useful when pursuing further studies on the possible use of miRNAs as biomarkers in cerebral ischemic tolerance and neuroregeneration.