A novel neuroprotective strategy for ischemic stroke: transient mild acidosis treatment by CO2 inhalation at reperfusion

Acidosis is one of the key components in cerebral ischemic postconditioning that has emerged recently as an endogenous strategy for neuroprotection. We set out to test whether acidosis treatment at reperfusion can protect against cerebral ischemia/reperfusion injury. Adult male C57BL/6 J mice were subjected to 60-minute middle cerebral arterial occlusion followed by 24-hour reperfusion. Acidosis treatment by inhaling 10%, 20%, or 30% CO₂ for 5 or 10 minutes at 5, 50, or 100 minutes after reperfusion was applied. Our results showed that inhaling 20% CO₂ for 5 minutes at 5 minutes after reperfusion-induced optimal neuroprotection, as revealed by reduced infarct volume. Attenuating brain acidosis with NaHCO₃ significantly compromised the acidosis or ischemic postconditioning-induced neuroprotection. Consistently, both acidosis-treated primary cultured cortical neurons and acute corticostriatal slices were more resistant to oxygen–glucose deprivation/reperfusion insult. In addition, acidosis inhibited ischemia/reperfusion-induced apoptosis, caspase-3 expression, cytochrome c release to cytoplasm, and mitochondrial permeability transition pore (mPTP) opening. The neuroprotection of acidosis was inhibited by the mPTP opener atractyloside both in vivo and in vitro. Taken together, these findings indicate that transient mild acidosis treatment at reperfusion protects against cerebral ischemia/reperfusion injury. This neuroprotection is likely achieved, at least partly, by inhibiting mPTP opening and mitochondria-dependent apoptosis.     

Long-lasting protection in brain trauma by endotoxin preconditioning

We investigated the occurrence of endotoxin (lipopolysaccharide, LPS) preconditioning in traumatic brain injury (TBI), evaluating the time window of LPS-induced protection, its persistence, and the associated molecular mechanisms. Mice received 0.1 mg/kg LPS or saline intraperitoneally and subsequently TBI (by controlled cortical impact brain injury) at various time intervals. Mice receiving LPS 3, 5, or 7 days before TBI showed attenuated motor deficits at 1 week after injury compared with mice receiving saline. Those receiving LPS 5 days before injury had also a reduced contusion volume (7.9±1.3 versus 12±2.3 mm³) and decreased cell death. One month after injury, the protective effect of LPS on contusion volume (14.5±1.2 versus 18.2±1.2 mm³) and neurologic function was still present. Traumatic brain injury increased glial fibrillary acidic protein, CD11b, CD68, tumor necrosis factor-α, interleukin (IL)-10, and IL-6 mRNA expression 24 hours after injury. Lipopolysaccharide administered 5 (but not 9) days before injury increased the expression of CD11b (233%) and of interferon β (500%) in uninjured mice, while it reduced the expression of CD68 (by 46%) and increased that of IL-6 (by 52%) in injured mice. Lipopolysaccharide preconditioning conferred a long-lasting neuroprotection after TBI, which was associated with a modulation of microglia/macrophages activity and cytokine production.     

Deficiency of PAR4 attenuates cerebral ischemia/reperfusion injury in mice

Stroke is the third leading cause of death in the USA. Antithrombotic therapy targeting platelet activation is one of the treatments for ischemic stroke. Here we investigate the role of one of the thrombin receptors, protease-activated receptor 4 (PAR4), in a mouse transient middle cerebral artery occlusion (MCAO) model. After a 60 min MCAO and 23 h reperfusion, leukocyte and platelet rolling and adhesion on cerebral venules, blood–brain barrier (BBB) permeability, and cerebral edema were compared in PAR4-deficient mice and wild-type mice. Cerebral infarction volume and neuronal death were also measured. PAR4−/− mice had more than an 80% reduction of infarct volume and significantly improved neurologic and motor function compared with wild-type mice after MCAO. Furthermore, deficiency of PAR4 significantly inhibits the rolling and adhesion of both platelets and leukocytes after MCAO. BBB disruption and cerebral edema were also attenuated in PAR4−/− mice compared with wild-type animals. The results of this investigation indicate that deficiency of PAR4 protects mice from cerebral ischemia/reperfusion (I/R) injury, partially through inhibition of platelet activation and attenuation of microvascular inflammation.     

Oxygen therapy reduces secondary hemorrhage after thrombolysis in thromboembolic cerebral ischemia

Hyperbaric oxygen (HBO) and normobaric hyperoxia (NBO) protect the brain parenchyma and the cerebral microcirculation against ischemia. We studied their effect on secondary hemorrhage after thrombolysis in two thromboembolic middle cerebral artery occlusion (MCAO) (tMCAO) models. Beginning 60 minutes after tMCAO with either thrombin-induced thromboemboli (TT) or calcium-induced thromboemboli (CT), spontaneously hypertensive rats (n=96) breathed either air, 100% O₂ (NBO), or 100% O₂ at 3 bar (HBO) for 1 hour. Immediately thereafter, recombinant tissue plasminogen activator (rt-PA, 9 mg/kg) was injected. Although significant reperfusion was observed after thrombolysis in TT-tMCAO, vascular occlusion persisted in CT-tMCAO. In TT-tMCAO, NBO and HBO significantly reduced diffusion-weighted imaging–magnetic resonance imaging (MRI) lesion volume and postischemic blood–brain barrier (BBB) permeability on postcontrast T1-weighted images. NBO and, significantly more potently, HBO reduced macroscopic hemorrhage on T2^* MRI and on corresponding postmortem cryosections. Oxygen therapy lowered hemoglobin content and attenuated activation of matrix metalloproteinases in the ischemic hemisphere. In contrast, NBO and HBO failed to reduce infarct size in CT but both decreased BBB damage and microscopic hemorrhagic transformation. Only HBO reduced hemoglobin extravasation in the ischemic hemisphere. In conclusion, NBO and HBO decrease infarct size after thromboembolic ischemia only if recanalization is successful. As NBO and HBO also reduce postthrombolytic intracerebral hemorrhage, combining the two with thrombolysis seems promising.     

Mild hypoxemia during initial reperfusion alleviates the severity of secondary energy failure and protects brain in neonatal mice with hypoxic-ischemic injury

Reperfusion triggers an oxidative stress. We hypothesized that mild hypoxemia in reperfusion attenuates oxidative brain injury following hypoxia-ischemia (HI). In neonatal HI-mice, the reperfusion was initiated by reoxygenation with room air (RA) followed by the exposure to 100%, 21%, 18%, 15% oxygen for 60 minutes. Systemic oxygen saturation (SaO₂), cerebral blood flow (CBF), brain mitochondrial respiration and permeability transition pore (mPTP) opening, markers of oxidative injury, and cerebral infarcts were assessed. Compared with RA-littermates, HI-mice exposed to 18% oxygen exhibited significantly decreased infarct volume, oxidative injury in the brain mitochondria and tissue. This was coupled with improved mitochondrial tolerance to mPTP opening. Oxygen saturation maintained during reperfusion at 85% to 95% was associated (r=0.57) with the best neurologic outcome. Exposure to 100% or 15% oxygen significantly exacerbated brain injury and oxidative stress. Compared with RA-mice, hyperoxia dramatically increased reperfusion CBF, but exposure to 15% oxygen significantly reduced CBF to values observed during the HI-insult. Mild hypoxemia during initial reperfusion alleviates the severity of HI-brain injury by limiting the reperfusion-driven oxidative stress to the mitochondria and mPTP opening. This suggests that at the initial stage of reperfusion, a slightly decreased systemic oxygenation (SaO₂ 85% to 95%) may be beneficial for infants with birth asphyxia.     

神经生长因子对兔局灶性脑缺血再灌注损伤的治疗时间窗及MR影像学评价

目的研究神经生长因子(NGF)对脑缺血再灌注损伤保护作用的有效时间窗,同时利用MR成像技术对其进行评价。方法采用兔大脑中动脉阻断(MCAO)局灶性脑缺血2 h再灌注72 h模型,分别于缺血再灌注0、1、36、h应用微量进样器将NGF立体定向导入梗死灶周,并于再灌注不同时间点应用MR影像学、TTC染色和流式细胞术评价家兔梗死体积、神经功能缺损和凋亡状态。结果缺血再灌注0、13、h组梗死灶周注射NGF后,经MRI检查所测梗死体积分别为(229.9±17.1)(、260.7±24.2)、(314.6±25.3)mm3,与对照组[(468.6±29.7)mm3]比较差异有统计学意义(均P<0.01);缺血再灌注6 h组梗死体积为(441.1±14.8)mm3,与对照组比较差异无统计学意义(P>0.05)。采用TTC染色所测梗死体积与MRI检查结果一致。脑缺血再灌注3 h内注射NGF,其神经功能缺损评分明显降低,凋亡率明显下降;再灌注6 h后注射NGF则无明显作用。结论NGF对兔局灶性脑缺血再灌注损伤的有效时间窗为再灌注损伤3 h内,MR影像学检查可作为定量评价基因疗效的可靠指标。     

SirT1 mediates hyperbaric oxygen preconditioning-induced ischemic tolerance in rat brain

Our previous studies have shown that hyperbaric oxygen preconditioning (HBO-PC) induces tolerance to cerebral ischemia/reperfusion (I/R). This study aimed to investigate whether SirT1, a class III histone deacetylase, is involved in neuroprotection elicited by HBO-PC in animal and cell culture models of ischemia. Rats were subjected to middle cerebral artery occlusion for 120 minutes after HBO-PC (once a day for 5 days). Primary cultured cortical neurons were exposed to 2 hours of HBO-PC after 2 hours of oxygen–glucose deprivation (OGD). We showed that HBO-PC increased SirT1 protein and mRNA expression, promoted neurobehavioral score, reduced infarct volume, and improved morphology at 24 hours and 7 days after cerebral I/R. Neuroprotection of HBO-PC was attenuated by SirT1 inhibitor EX527 and SirT1 knockdown by short interfering RNA (siRNA), whereas it was mimicked by SirT1 activator resveratrol. Furthermore, HBO-PC enhanced SirT1 expression and cell viability and reduced lactate dehydrogenase release 24 hours after OGD/re-oxygenation. The neuroprotective effect of HBO-PC was emulated through upregulating SirT1 and, reversely, attenuated through downregulating SirT1. The modulation of SirT1 was made by adenovirus infection carrying SirT1 or SirT1 siRNA. Besides, SirT1 increased B-cell lymphoma 2 (Bcl-2) expression and decrease cleaved caspase 3. These results indicate that SirT1 mediates HBO-PC-induced tolerance to cerebral I/R through inhibition of apoptosis.     

Low Doses of Carbon Monoxide Protect Against Experimental Focal Brain Ischemia

Carbon monoxide (CO) is associated with central nervous system toxicity. However, evidence also indicates that CO can be protective, depending on its concentration. To determine if CO can be neuroprotective after ischemic brain injury, we subjected mice to transient middle cerebral artery occlusion and exposed them to different concentrations of CO. We found that in mice, low CO levels protected the brain from injury following 90-min transient focal ischemia and 48 h of reperfusion. When inhalation of 125 or 250 ppm CO began immediately at the onset of reperfusion, total hemispheric infarct volume was reduced by 32.1 ± 8.9% and 62.2 ± 14.4%, respectively; with an extended therapeutic window of 1–3 h after ischemia, CO inhalation also attenuated infarct volume significantly. Furthermore, early CO exposure limited brain edema formation by 3.2 ± 0.8% (125 ppm) and 2.6 ± 0.3% (250 ppm). Finally, CO inhalation significantly improved neurological deficit scores at 48 h of survival time after ischemia. Transient elevation of carboxyhemoglobin levels returned rapidly to baseline when CO exposure was stopped. These findings suggest a potential application of CO to treat brain ischemic stroke.     

Neurological deficit and cerebral infarction after temporary middle cerebral artery occlusion in unanesthetized cats

Forty-four unanesthetized cats underwent temporary middle cerebral artery (MCA) occlusion with an implanted, externally controlled balloon cuff occluder. The occlusion was reversed to allow reperfusion of the MCA after 2 min to 24 hr of ischemia. Fourteen cats had temporary occlusions lasting 2 min to 3 hr; their neurological deficits improved or resolved after reperfusion, and brain sections showed only scattered microscopic areas of necrosis. After a 4-hr occlusion, five of nine cats (55%) recovered completely within 24 hr; two had persistent deficit when sacrificed, 10 days later, and each had a circumscribed infarct. All 18 cats undergoing 5-, 6-, 8-, and 24-hr occlusions sustained permanent neurological deficits. Three 3-hr occlusions at 2-day intervals in three cats resulted in permanent deficits and infarcts that were 25% larger than those after single 8-hr occlusions. Ten cats underwent permanent MCA occlusion; three deteriorated neurologically and died, and the survivors showed no improvement. Infarcts after 5-, 6-, and 8-hr occlusions followed by reperfusion were 66% smaller (p less than 0.05) than those after permanent occlusion; reperfusion after 24 hr of occlusion did not reduce infarct size. Hemorrhagic infarction occurred after two permanent occlusions, but after only one 5-hr temporary occlusion. The results obtained with this method of temporary regional ischemia indicate that restoration of flow after 1-8 hr, but not after 24 hr, of MCA occlusion resulted in less severe neurological deficit and smaller infarcts than did permanent occlusion. The infarct size correlated with the duration of MCA occlusion (p less than 0.05) rather than with the degree of deficit during occlusion.     

Agmatine attenuates brain edema through reducing the expression of aquaporin-1 after cerebral ischemia

Brain edema is frequently shown after cerebral ischemia. It is an expansion of brain volume because of increasing water content in brain. It causes to increase mortality after stroke. Agmatine, formed by the decarboxylation of -arginine by arginine decarboxylase, has been shown to be neuroprotective in trauma and ischemia models. The purpose of this study was to investigate the effect of agmatine for brain edema in ischemic brain damage and to evaluate the expression of aquaporins (AQPs). Results showed that agmatine significantly reduced brain swelling volume 22 h after 2 h middle cerebral artery occlusion in mice. Water content in brain tissue was clearly decreased 24 h after ischemic injury by agmatine treatment. Blood–brain barrier (BBB) disruption was diminished with agmatine than without. The expressions of AQPs-1 and -9 were well correlated with brain edema as water channels, were significantly decreased by agmatine treatment. It can thus be suggested that agmatine could attenuate brain edema by limitting BBB disruption and blocking the accumulation of brain water content through lessening the expression of AQP-1 after cerebral ischemia.     

Prolonged, 24-h delayed peripheral inflammation increases short- and long-term functional impairment and histopathological damage after focal ischemia in the rat

The incidence of infection among stroke patients is alarmingly high and both acute and delayed infections increase morbidity and mortality. Experimental studies support the acute clinical data, but little attention has focused on delayed systemic infections. Here, we investigated the effects of prolonged systemic inflammation either before or 24-h after ischemia. Systemic inflammation was induced by injecting rats with three separate doses of lipopolysaccharide (LPS; 50 μg/kg, i.p.) with core temperature monitoring for 48-h after middle cerebral artery occlusion (MCAo). Lipopolysaccharide injected before MCAo increased injury by ∼30%, whereas delayed injection increased injury by ∼85% (30-day survival). Proinflammatory cytokines assessed repeatedly for 72 h were significantly and persistently elevated with inflammation. This was accompanied by increases in microglia/macrophage and infiltrating leukocyte numbers in delayed LPS-treated animals. Behavioral assessments at 7 and 30 days revealed ∼15% deficit in hindlimb function in animals treated with LPS 24-h after ischemia. Clearly, delayed and prolonged postischemic systemic inflammation has devastating effects on stroke outcome, in the absence of a prolonged febrile response. These findings, together with corroborative clinical data, emphasize the importance of early intervention to counteract the deleterious consequences of stroke-associated inflammation and infection.     

Neurovascular protection by targeting early blood–brain barrier disruption with neurotrophic factors after ischemia–reperfusion in rats

The ‘new penumbra'' concept imbues the transition between injury and repair at the neurovascular unit with profound implications for selecting the appropriate type and timing of neuroprotective interventions. In this conceptual study, we investigated the protective effects of pigment epithelium-derived factor (PEDF) and compared them with the properties of epidermal growth factor (EGF) in a rat model of ischemia–reperfusion injury. We initiated a delayed intervention 3 hours after reperfusion using equimolar amounts of PEDF and EGF. These agents were then administered intravenously for 4 hours following reperfusion after 1 hour of focal ischemia. Magnetic resonance imaging indices were characterized, and imaging was performed at multiple time points post reperfusion. PEDF and EGF reduced lesion volumes at all time points as observed on T₂-weighted images (T₂-LVs). In addition PEDF selectively attenuated lesion volume expansion at 48 hours after reperfusion and persistently modulated blood–brain barrier (BBB) permeability at all time points. Intervention with peptides is suspected to cause edema formation at distant regions. The observed T₂-LV reduction and BBB modulation by these trophic factors is probably mediated through a number of diverse mechanisms. A thorough evaluation of neurotrophins is still necessary to determine their time-dependent contributions against injury and their modulatory effects on repair after stroke.     

Neuroprotective Effect of Resveratrol on Ischemia/Reperfusion Injury in Rats Through TRPC6/CREB Pathways

Previous studies have provided evidences that resveratrol can protect the brain from ischemia/reperfusion injury; the mechanisms of its neuroprotective effects remain unknown. To investigate whether resveratrol has neuroprotective effects on ischemia and reperfusion injury and whether resveratrol exerts its neuroprotective effects through inhibition of calpain proteolysis of TRPC6, a transient middle cerebral artery occlusion (MCAO) model was employed in rats. Western blot analysis was performed to detect the protein levels of aII-spectrin, transient receptor potential canonical (subtype) 6 (TRPC6) and phosphorylated cAMP/Ca²⁺ response element-binding protein (p-CREB). The immunoreactivity of p-CREB and TRPC6 were measured by quantum dot-based immunofluorescence analysis. Our results showed that MCAO rats showed large cortical infarct volumes and neurological scores. By contrast, resveratrol, when applied for 7 days before MCAO onset, significantly reduced infarct volumes and enhanced neurological scores at 24 h after reperfusion, and these results were accompanied by elevated TRPC6 and p-CREB activity and decreased calpain activity. When MEK or CaMKIV activity was inhibited by the addition of PD98059 or KN62, the neuroprotective effects of resveratrol were attenuated, and we observed a correlated decrease in CREB activity. Our results demonstrated that resveratrol prevented the brain from ischemia/reperfusion injury through the TRPC6–MEK–CREB and TRPC6–CaMKIV–CREB pathways.     

The KCa3.1 blocker TRAM-34 reduces infarction and neurological deficit in a rat model of ischemia/reperfusion stroke

Microglia and brain infiltrating macrophages significantly contribute to the secondary inflammatory damage in the wake of ischemic stroke. Here, we investigated whether inhibition of KCa3.1 (IKCa1/KCNN4), a calcium-activated K⁺ channel that is involved in microglia and macrophage activation and expression of which increases on microglia in the infarcted area, has beneficial effects in a rat model of ischemic stroke. Using an HPLC/MS assay, we first confirmed that our small molecule KCa3.1 blocker TRAM-34 effectively penetrates into the brain and achieves micromolar plasma and brain concentrations after intraperitoneal injection. Then, we subjected male Wistar rats to 90 minutes of middle cerebral artery occlusion (MCAO) and administered either vehicle or TRAM-34 (10 or 40 mg/kg intraperitoneally twice daily) for 7 days starting 12 hours after reperfusion. Both compound doses reduced infarct area by ∼50% as determined by hematoxylin & eosin staining on day 7 and the higher dose also significantly improved neurological deficit. We further observed a significant reduction in ED1⁺-activated microglia and TUNEL-positive neurons as well as increases in NeuN⁺ neurons in the infarcted hemisphere. Our findings suggest that KCa3.1 blockade constitutes an attractive approach for the treatment of ischemic stroke because it is still effective when initiated 12 hours after the insult.     

莱菔硫烷对大鼠局灶性脑缺血再灌注损伤的保护作用及机制研究

目的 探讨莱菔硫烷对大鼠局灶性脑缺血再灌注损伤的保护作用及机制.方法 采用线栓法制备大鼠大脑中动脉阻断局灶性脑缺血模型,分别于MCAO后1h腹腔注射莱菔硫烷2.5mg/kg、5mg/kg、10mg/kg.于缺血2h再灌注24h时进行神经行为缺损评分,TTC染色评价脑梗死体积,测定脑组织中超氧化物歧化酶(SOD)活力和丙二醛(MDA)含量.免疫荧光组织化学染色法检测黄核蛋白NQ01和脂质过氧化酶Prx6的表达.结果 莱菔硫烷给药组与对照组相比均能改善大鼠脑缺血再灌注后神经行为缺损评分,减少脑梗死体积.其中5mg/kg组能显著改善大鼠脑缺血再灌注后神经行为缺损评分,减少脑梗死体积,增强SOD活性,降低MDA含量.免疫荧光组织化学染色法提示NQ01和Prx6的表达明显增强.结论 莱菔硫烷对大鼠局灶性脑缺血再灌注损伤有神经保护作用,其机制可能与上调内源性抗氧化蛋白NQ01和Prx6的表达有关.     

Peripheral administration of fetuin-A attenuates early cerebral ischemic injury in rats

Cerebral ischemia-elicited inflammatory responses are driven by inflammatory mediators produced both by central (e.g., neurons and microglia) and infiltrating peripheral immune cells (e.g., macrophage/monocyte), and contribute to the evolution of tissue injury. A ubiquitous molecule, spermine, is released from injured cells, and counter-regulates release of various proinflammatory cytokines. However, the spermine-mediated anti-inflammatory activities are dependent on the availability of fetuin-A, a liver-derived negative acute-phase protein. Using an animal model of focal cerebral ischemia (i.e., permanent middle cerebral artery occlusion, MCAo), we found that levels of fetuin-A in the ischemic brain tissue were elevated in a time-dependent manner, starting between 2 and 6 h, peaking around 24 to 48 h, and returning to baseline 72 h after MCAo. When administered peripherally, exogenous fetuin-A gained entry across the BBB into the ischemic brain tissue, and dose dependently reduced brain infarct volume at 24 h after MCAo. Meanwhile, fetuin-A effectively attenuated (i) ischemia-induced HMGB1 depletion from the ischemic core; (ii) activation of centrally (e.g., microglia) and peripherally derived immune cells (e.g., macrophage/monocytes); and (iii) TNF production in ischemic brain tissue. Taken together, these experimental data suggest that fetuin-A protects against early cerebral ischemic injury partly by attenuating the brain inflammatory response.     

Chronic trigeminal ganglionectomy or topical capsaicin application to pial vessels attenuates postocclusive cortical hyperemia but does not influence postischemic hypoperfusion.

Marked hyperemia accompanies reperfusion after ischemia in the brain, and may account for the propensity of cerebral hemorrhage to follow embolic stroke or carotid endarterectomy, and for the morbidity that follows head injury or the ligation of large arteriovenous malformations. To evaluate the contribution of trigeminal sensory fibers to the hyperemic response, CBF was determined in 12 symmetrical brain regions, using microspheres with up to five different isotopic labels, in four groups of cats. Measurements were made at 15-min intervals for up to 2 h of reperfusion after global cerebral ischemia induced by four-vessel occlusion combined with systemic hypotension of either 10- or 20-min duration. In normal animals, hyperemia in cortical gray matter 30 min after reperfusion was significantly greater after 20 min (n = 10) than after 10 min (n = 7) of ischemia (312 ml/100 g/min versus 245 ml/100 g/min; p less than 0.01). CBF returned to preischemic levels approximately 45 min after reperfusion and was reduced to approximately 65% of basal CBF for the remaining 75 min. In cats subjected to chronic trigeminal ganglionectomy (n = 15), postocclusive hyperemia in cortical gray matter was attenuated by up to 48% on the denervated side (249 versus 150 ml/100 g/min; p less than 0.01) after 10 min of ischemia. This effect was maximal in the middle cerebral artery (MCA) territory, and was confined to regions known to receive a trigeminal innervation. In these animals, substance P (SP) levels in the MCA were reduced by 64% (p less than 0.01), and the density of nerve fibers containing calcitonin gene-related peptide (but not vasoactive intestinal polypeptide or neuropeptide Y) was decreased markedly on the lesioned side. Topical application of capsaicin (100 nM; 50 microliters) to the middle or posterior temporal branch of the MCA 10-14 days before ischemia decreased SP levels by 36%. Postocclusive hyperemia in cortical gray matter was attenuated throughout the ipsilateral hemisphere by up to 58%, but the cerebral vascular response to hypercapnia (PaCO2 = 60 mm Hg) was unimpaired. The duration of hyperemia and the severity of the delayed hypoperfusion were not influenced by trigeminalectomy, capsaicin application, or the intravenous administration of ATP. These data demonstrate the importance of neurogenic mechanisms in the development of postischemic hyperperfusion, and suggest the potential utility of strategies aimed at blocking axon reflex-like mechanisms to reduce severe cortical hyperemia.     

Albumin therapy enhances collateral perfusion after laser-induced middle cerebral artery branch occlusion: a laser speckle contrast flow study

Laser speckle contrast (LSC) was used to compare the extent of cortical ischemia in two inbred mouse strains that differed in their degree of collateral circulation, after laser occlusion of the distal middle cerebral artery, and after treatment with 25% albumin (ALB) or saline (control). Sequential LSC images acquired over ∼90 minutes were coaligned, converted to relative flow, and normalized to baseline. After 3-day survival, infarction was quantified by triphenyl tetrazolium chloride or magnetic resonance imaging. In the sparsely collateralized BALB/c strain, mean flow fell to 13% to 14% and 33% to 34% of baseline in central (core) and peripheral (penumbral) regions of interest, and ALB treatment at 30 minutes enhanced perfusion in both regions by ∼2-fold relative to saline, restoring flow to the benign-oligemic range centrally, and to the hyperemic range peripherally. The ALB-induced increment in parenchymal perfusion was disproportionate to the subtle flow increase in the occluded artery itself, suggesting that ALB improved collateral circulation. Cortical infarction in BALB/c mice was reduced 45% by ALB treatment. In contrast to BALB/c mice, the better-collateralized CD-1 strain developed milder ischemia, had smaller infarcts, and showed no differential benefit of ALB. We conclude that where native collateralization is insufficient (BALB/c strain), ALB treatment exerts a significant therapeutic effect after ischemia by augmenting collateral perfusion.     

选择性COX2抑制剂对脑缺血再灌注损伤的影响

目的 :观察脑缺血再灌注损伤中COX2的表达以及选择性COX2抑制剂SC5 812 5对脑缺血再灌注后脑梗死体积、PGE2 含量的影响。方法 :应用小鼠短暂性局灶性脑缺血模型 ;脑梗死体积的测定采用TTC染色法 ;ELISA测定PGE2 含量 ;DNA单链损伤的测定采用PANT染色。结果 :缺血前 3 0min和缺血后 2h用药组脑梗死体积显著缩小 ,缺血后 6h延迟用药组脑梗死体积无明显变化。脑缺血再灌注后PGE2 含量显著升高。SC5 812 5的治疗显著降低了PGE2 的水平。SC5 812 5并可显著抑制缺血后DNA单链损伤的程度。结论 :提示COX2参与了脑缺血再灌注损伤 ,选择性COX2抑制剂在小鼠局灶性脑缺血再灌注损伤的模型中起着重要作用