Early activation of matrix metalloproteinase-9 is associated with blood-brain barrier disruption after photothrombotic cerebral ischemia in rats

Correlation Tensor MRI deciphers underlying kurtosis sources in stroke

Noninvasively detecting and characterizing modulations in cellular scale micro-architecture remains a desideratum for contemporary neuroimaging. Diffusion MRI (dMRI) has become the mainstay methodology for probing microstructure, and, in ischemia, its contrasts have revolutionized stroke management. Diffusion kurtosis imaging (DKI) has been shown to significantly enhance the sensitivity of stroke detection compared to its diffusion tensor imaging (DTI) counterparts. However, the interpretation of DKI remains ambiguous as its contrast may arise from competing kurtosis sources related to the anisotropy of tissue components, diffusivity variance across components, and microscopic kurtosis (e.g., arising from cross-sectional variance, structural disorder, and restriction). Resolving these sources may be fundamental for developing more specific imaging techniques for stroke management, prognosis, and understanding its pathophysiology. In this study, we apply Correlation Tensor MRI (CTI) - a double diffusion encoding (DDE) methodology recently introduced for deciphering kurtosis sources based on the unique information captured in DDE's diffusion correlation tensors - to investigate the underpinnings of kurtosis measurements in acute ischemic lesions. Simulations for the different kurtosis sources revealed specific signatures for cross-sectional variance (representing neurite beading), edema, and cell swelling. Ex vivo CTI experiments at 16.4 T were then performed in an experimental photothrombotic stroke model 3 h post-stroke (N = 10), and successfully separated anisotropic, isotropic, and microscopic non-Gaussian diffusion sources in the ischemic lesions. Each of these kurtosis sources provided unique contrasts in the stroked area. Particularly, microscopic kurtosis was shown to be a primary "driver" of total kurtosis upon ischemia; its large increases, coupled with decreases in anisotropic kurtosis, are consistent with the expected elevation in cross-sectional variance, likely linked to beading effects in small objects such as neurites. In vivo experiments at 9.4 T at the same time point (3 h post ischemia, N = 5) demonstrated the stability and relevance of the findings and showed that fixation is not a dominant confounder in our findings. In future studies, the different CTI contrasts may be useful to address current limitations of stroke imaging, e.g., penumbra characterization, distinguishing lesion progression form tissue recovery, and elucidating pathophysiological correlates.

Development of a photochemical thrombosis investigation system to obtain a rabbit ischemic stroke model

Photochemical thrombosis is a method for the induction of ischemic stroke in the cerebral cortex. It can generate localized ischemic infarcts in the desired region; therefore, it has been actively employed in establishing an ischemic stroke animal model and in vivo assays of diagnostic and therapeutic techniques for stroke. To establish a rabbit ischemic stroke model and overcome the shortcoming of previous studies that were difficult to build a standardized photothrombotic rabbit model, we developed a photochemical thrombosis induction system that can produce consistent brain damage on a specific area. To verify the generation of photothrombotic brain damage using the system, longitudinal magnetic resonance imaging, 2,3,5-triphenyltetrazolium chloride staining, and histological staining were applied. These analytical methods have a high correlation for ischemic infarction and are appropriate for analyzing photothrombotic brain damage in the rabbit brain. The results indicated that the photothrombosis induction system has a main advantage of being accurately controlled a targeted region of photothrombosis and can produce cerebral hemisphere lesions on the target region of the rabbit brain. In conjugation with brain atlas, it can induce photochemical ischemic stroke locally in the part of the brain that is responsible for a particular brain function and the system can be used to develop animal models with degraded specific functions. Also, the photochemical thrombosis induction system and a standardized rabbit ischemic stroke model that uses this system have the potential to be used for verifications of biomedical techniques for ischemic stroke at a preclinical stage in parallel with further performance improvements.

Pioglitazone Prevents Hemorrhagic Infarction After Transient Focal Ischemia in Type 2 Diabetes

Pioglitazone (PGZ), a PPARγ agonist, has been used for diabetic patients as an insulin-sensitizing agent. Recent studies have demonstrated that PGZ increases adiponectin (APN) levels and provides vascular protection in ischemic conditions. This study was designed to assess the neuroprotective effects of PGZ against cerebral ischemia-reperfusion injury via an APN-related mechanism. Type 2 diabetic leptin-deficient mice (db/db) were administered PGZ for 1 week, and plasma insulin and APN levels were measured. These mice received a middle cerebral artery occlusion and reperfusion injury, and they were evaluated for the infarct volume and by immunohistochemistry and western blotting analysis at several time points after ischemia. PGZ-administered db/db mice showed improved insulin sensitivity, and the hemorrhagic rate and infarct volume were decreased (P < 0.05). In the PGZ-administered group, plasma APN levels increased compared with the vehicle group. In the db/db group, PGZ administration significantly suppressed inflammatory reactions and oxidative stress after reperfusion (P < 0.05). PGZ may be applicable for acute cerebral ischemia treatment in metabolic syndrome patients as well as antidiabetic agents.

MicroRNA-124-loaded nanoparticles increase survival and neuronal differentiation of neural stem cells in vitro but do not contribute to stroke outcome in vivo

There is a high quest for novel therapeutic strategies to enhance recovery after stroke. MicroRNA-124 (miR-124) has been described as neuroprotective and anti-inflammatory molecule. Moreover, miR-124 is a well described enhancer of adult neurogenesis that could offer potentially beneficial effects. Herein, we used miR-124-loaded nanoparticles (miR-124 NPs) to evaluate their therapeutic potential in an in vitro and in vivo model of stroke. For that, neuroprotective and neurogenic responses were assessed in an in vitro model of stroke. Here, we found that miR-124 NPs decreased cell death and improved neuronal differentiation of subventricular zone (SVZ) neural stem cell cultures after oxygen and glucose deprivation. In contrast, intravenous injection of miR-124 NPs immediately after permanent focal ischemia induced by photothrombosis (PT) did not provide a better neurological outcome. In addition, treatment did not affect the number of 5-bromo-2'-deoxyuridine (BrdU)- and doublecortin/BrdU- positive cells in the SVZ at the study endpoint of 14 days after PT. Likewise, the ischemic insult did not affect the numbers of neuronal progenitors in the SVZ. However, in PT mice miR-124 NPs were able to specifically augment interleukin-6 levels at day 2 post-stroke. Furthermore, we also showed that NPs reached the brain parenchyma and were internalized by brain resident cells. Although, promising in vitro data could not be verified in vivo as miR-124 NPs treatment did not improve functional outcome nor presented beneficial actions on neurogenesis or post-stroke inflammation, we showed that our NP formulation can be a safe alternative for drug delivery into the brain.

Effect of ulinastatin on the permeability of the blood-brain barrier on rats with global cerebral ischemia/reperfusion injury as assessed by MRI

The study was designed to evaluate the effect of ulinastatin on the permeability of the blood-brain barrier in rats with global cerebral ischemia/reperfusion injury using MRI. A total of 108 Wistar rats (240 g-280g) were randomly divided into three groups (n=36): sham group (S group), global cerebral ischemia/reperfusion model group (GCI/R group) and 10,000U/kg ulinastatin intervention group (U group). Fifty-four Wistar rats were used for MRI, and the rest were used for Evans Blue(EB)analysis. We used the Pulsinelli four-vessel occlusion (4-VO) model of global cerebral ischemia/reperfusion to investigate the integrity of the blood-brain barrier with Evans Blue (EB) staining at 15min after ischemia and at 6h (n=6), 24h (n=6), and 48h (n=6) after reperfusion to assess blood-brain barrier permeability with MRI. In the ulinastatin treatment group, the area of EB staining was significantly smaller, the exudation of EB decreased significantly after cerebral ischemia/reperfusion at 6h, 24h, 48h, compared to the model group at corresponding time points (P<0.05) but increased compared to the sham group. The model group exhibited significantly highlighted regions of Gd-DTPA after post-contrast at the corresponding areas and time points compared with the sham group (P<0.05). The highlighted regions of Gd-DTPA in the ulinastatin treatment group were significantly higher compared with those of the sham group but lower when compared with those of the model group (P<0.05). The integrity of the blood-brain barrier after cerebral ischemia/reperfusion injury was damaged. Ulinastatin could significantly improve the permeability of the blood-brain barrier after cerebral ischemia/reperfusion injury in rats.

Reduction of the neuroprotective transcription factor Npas4 results in increased neuronal necrosis, inflammation and brain lesion size following ischaemia

Stroke is the second leading cause of death and the most frequent cause of adult disability. Neuronal Per-Arnt-Sim domain protein 4 (Npas4) is an activity-dependent transcription factor whose expression is induced in various brain insults, including cerebral ischaemia. Although previous studies have demonstrated that Npas4 plays a critical role in protecting neurons against neurodegenerative insults, the neuroprotective effect of Npas4 in response to ischaemic brain injury remains unknown. In this study, we used a loss-of-function approach to examine the neuroprotective potential of Npas4 in the context of ischaemic damage. Using oxygen and glucose deprivation, we demonstrated that the knockdown of Npas4 in mouse cortical neurons resulted in increased susceptibility to cell death. The protective effect of Npas4 was further investigated in vivo using a photochemically-induced stroke model in mice. We found a significantly larger lesion size and increased neurodegeneration in Npas4 knockout mice as compared to wild-type mice. Moreover, we also showed that ablation of Npas4 caused an increase in activated astrocytes and microglia, pro-inflammatory cytokines interleukin-6 and tumour necrosis factor alpha levels and a switch from apoptotic to necrotic cell death. Taken together, these data suggest that Npas4 plays a neuroprotective role in ischaemic stroke by limiting progressive neurodegeneration and neuroinflammation.

Expression of adhesion molecules, chemokines and matrix metallo- proteinases (MMPs) in viable and degenerating stage of Taenia solium metacestode in swine neurocysticercosis

Neurocysticercosis (NCC) is a parasitic infection of central nervous system (CNS). Expression of adhesion molecules, chemokines and matrix metalloproteinases (MMPs) were investigated on brain tissues surrounding viable (n=15) and degenerating cysticerci (n=15) of Taenia solium in swine by real-time RT-PCR and ELISA. Gelatin gel zymography was performed for MMPs activity. ICAM-1 (intercellular adhesion molecule-1), E-selectin, MIP-1α (macrophage inflammatory protein-1α), Eotaxin-1 and RANTES (regulated on activation, normal T cell expressed and secreted) were associated with degenerating cysticerci (cysts). However, VCAM-1 (vascular cell adhesion molecule-1), MCP-1 (monocyte chemotactic protein-1), MMP-2 and MMP-9 were associated with both viable and degenerating cysts. In conclusion, viable and degenerating cysticerci have different immune molecule profiles and role of these molecules in disease pathogenesis needs to be investigated.

Correlation of matrix metalloproteinase-2 single nucleotide polymorphisms with the risk of small vessel disease (SVD)

BACKGROUND

Maladjustment of matrix metalloproteinases (MMPs) results in cerebral vasculature and blood-brain barrier dysfunction, which is associated with small vessel disease (SVD). This study was to aim at evaluating correlations between matrix metalloproteinase-2 and 9 single nucleotide polymorphisms and the risk of SVD.

METHODS

A total of 178 patients with SVD were enrolled into this study via Nanjing Stroke Registry Program (NSRP) from January 2010 to November 2011. SVD patients were further subtyped as isolated lacunar infarction (ILI, absent or with mild leukoaraiosis) and ischemic leukoaraiosis (ILA, with moderate or severe leukoaraiosis) according to the Fazekas scale. 100 age- and gender-matched individuals from outpatient medical examination were recruited as the control group. The genotypes of MMP-2-1306 T/C and MMP-9-1562 C/T were determined by the TaqMan method.

RESULTS

Of 178 SVD patients, 86 and 92 patients were classified as ILI and ILA, respectively. Comparison analysis between SVD patients and controls revealed a significant correlation between SVD and hypertension, as well as a prevalence of hypertension in ILA. Further genotype analysis showed that the frequency of MMP-2-1306 CC genotype was higher in ILA patients than in controls (P=0.009, χ(2) test; P=0.027, the multiple test with Bonferroni correction). Finally, logistic regression analysis with adjustment of age, sex and vascular risk factors showed that the MMP-2-1306 T/C polymorphism was an independent predictor for ILA (OR: 2.605; 95% confidence interval [CI], 1.067-6.364; P=0.036).

CONCLUSION

Our findings suggest that the MMP-2-1306 T/C polymorphism is a direct risk factor for ILA.

DDR1 may play a key role in destruction of the blood-brain barrier after cerebral ischemia-reperfusion

Discoidin domain receptor 1 (DDR1) has been shown to mediate matrix metalloproteinase-9 (MMP-9) secretions and degrade all extracellular matrix compounds in mammalian tumor cells. We hypothesized that DDR1 expression will be elevated and the blood-brain barrier (BBB) will be damaged after focal cerebral ischemia in rats. Inhibiting DDR1 expression can alleviate BBB disruption and cerebral ischemic damage via down-regulation of MMP-9 expression and activity. To test our hypothesis, we injected specific DDR1 siRNA into ipsilateral ischemic lateral ventricles in a focal ischemic model. Our results showed that phospho-DDR1 expression increased after ischemia/reperfusion (I/R) injury (p < 0.01). Inactivation of DDR1 by specific siRNA caused a decrease in phospho-DDR1 and MMP-9 expression in the ischemic cortex, reduced stroke-induced infarct volume, and alleviated BBB disruption in rat brain following I/R injury (p < 0.01). Our results suggested that DDR1-siRNA attenuates phospho-DDR1 and MMP-9 upregulation, which was followed by a reduction in infarction and BBB disruption in the ischemic brain after I/R injury. DDR1 may represent a molecular target for the prevention of BBB disruption after cerebral I/R injury.

Baicalin attenuates brain edema in a rat model of intracerebral hemorrhage

Baicalin is a flavonoid compound purified from the roots of Scutellaria baicalensis, which possesses multiple biological activities. Previous studies have shown that baicalin is protective in ischemic cerebral diseases. The aim of the present study was to examine the effects of baicalin on brain injury in a rat model of intracerebral hemorrhage (ICH) and to explore the possible mechanisms. Intracerebral hemorrhage was induced in male Wistar rats by injection of 0.5 U collagenaseVII to the caudate nucleus. Sham operation rats were injected with equal volume of saline. After the induction of ICH, the rats were randomly divided into four groups and administered with different dose of baicalin (0, 25, 50, or 100 mg/kg in saline) through peritoneal injection. The brain tissues around the hemorrhage areas were collected on days 1, 3, and 5 after treatment. Brain edema was analyzed by desiccation method; the metalloproteinase-9 (MMP-9) protein and mRNA expression were determined by western blotting and real time RT-PCR, respectively. Nuclear factor-κB (NF-κB) protein expression was analyzed by western blotting. IL-1β and IL-6 levels were determined by enzyme-linked immunosorbent assay. Blood-brain barrier permeability was determined by Evans blue leakage method. The results showed that baicalin reduced brain edema following ICH in a dose-dependent manner, with concomitant inhibition of NF-κB activation and suppression of MMP-9 expression. In addition, baicalin also reduced IL-1β and IL-6 production, as well as blood-brain barrier permeability. The above results indicated that baicalin prevents against perihematomal edema development after intracerebral hemorrhage possibly through an anti-inflammatory mechanism.

Rutin improves functional outcome via reducing the elevated matrix metalloproteinase-9 level in a photothrombotic focal ischemic model of rats

BACKGROUND

Blood-brain barrier (BBB) disruption mediated by proteases plays a pivotal role in neural tissue damage after acute ischemic stroke. In an animal stroke model, the activation of matrix metalloproteinases (MMPs), especially MMP-9, was significantly increased and it showed potential association with blood-brain barrier (BBB) disruption and cerebral edema. Theoretically, it is expected that early blockade of expression and activation of MMP-9 after ischemic stroke provides neuroprotective effects from secondary neural tissue damage. This study was aimed to determine the ability of rutin to influence MMP-9 expression, activity and BBB disruption using a photothrombotic focal ischemic model in rats.

METHODS

Adult male Sprague-Dawley rats, weighing between 250 and 300 g (aged 8 weeks) received focal cerebral ischemia by photothrombosis using Rose Bengal (RB) and cold light. Injured animals were divided into two groups; one group received 50mg/kg of rutin intraperitoneally, starting 1h after injury and at 12h intervals for 3 days, while animals in the control group received weight-adjusted doses of saline vehicle over the same period. In each group, the expressions and activities of MMP-9 were assessed by Western blot and gelatin zymography at 6, 24, 48, and 72 h after photothrombotic insult. The effects of rutin on BBB disruption and functional outcomes were also determined.

RESULTS

Western blot and zymographic analysis showed up-regulated MMP-9 expression and activity in the ischemic cortex. The expression and activity of MMP-9 were significantly elevated at 6h after photothrombotic insult, which remained up-regulated for at least until 72 h after injury. In the rutin-treated group, MMP-9 expression and activity were significantly attenuated at 6, 24, and 48 h compared to the control group. Relative to the control group, BBB permeability was significantly reduced in the rutin-treated group. The results of the rotarod test revealed that rutin treatment significantly improved functional outcomes.

CONCLUSIONS

Rutin treatment starting 1h after injury attenuated BBB disruption during photothrombotic focal ischemia, which was partly, at least, achieved through inhibitory effects on MMP-9 expression and activity. The results of this study suggest that rutin might be useful in clinical trials aimed to improve the outcome of patients suffering from acute ischemic stroke.

Green tea polyphenols alleviate early BBB damage during experimental focal cerebral ischemia through regulating tight junctions and PKCalpha signaling

Background

It has been supposed that green tea polyphenols (GTPs) have neuroprotective effects on brain damage after brain ischemia in animal experiments. Little is known regarding GTPs’ protective effects against the blood-brain barrier (BBB) disruption after ischemic stroke. We investigated the effects of GTPs on the expression of claudin-5, occludin, and ZO-1, and the corresponding cellular mechanisms involved in the early stage of cerebral ischemia.

Methods

Male Wistar rats were subjected to a middle cerebral artery occlusion (MCAO) for 0, 30, 60, and 120 min. GTPs (400 mg/kg/day) or vehicle was administered by intragastric gavage twice a day for 30 days prior to MCAO. At different time points, the expression of claudin-5, occludin, ZO-1, and PKCα signaling pathway in microvessel fragments of cerebral ischemic tissue were evaluated.

Results

GTPs reduced BBB permeability at 60 min and 120 min after ischemia as compared with the vehicle group. Transmission electron microscopy also revealed that GTPs could reverse the opening of tight junction (TJ) barrier at 60 min and 120 min after MACO. The decreased mRNA and protein expression levels of claudin-5, occludin, and ZO-1 in microvessel fragments of cerebral ischemic tissue were significantly prevented by treatment with GTPs at the same time points after ischemia in rats. Furthermore, GTPs could attenuate the increase in the expression levels of PKCα mRNA and protein caused by cerebral ischemia.

Conclusions

These results demonstrate that GTPs may act as a potential neuroprotective agent against BBB damage at the early stage of focal cerebral ischemia through the regulation of TJ and PKCα signaling.

Comparison of matrix metalloproteinase activation after focal cortical ischemia in young adult and aged mice

Matrix metalloproteinase (MMP) activity is implicated in the degradation of the extracellular matrix during cerebral ischemia. Although many studies have demonstrated spatiotemporal patterns of activation of gelatinases (MMP-9 and MMP-2) after ischemic stroke in young adult rodents, no data exist on MMP activity in old brains. In this study, we investigated the gelatinolytic activity in young adult (3-month-old) and aged (1-year-old) mice subjected to photothrombotic stroke. Using in situ zymography and gel zymography, we found that the basal gelatinolytic activity in the intact cerebral cortex was similar at both investigated ages. Similarly, after photothrombosis, the increased gelatinolytic response up to 7 days poststroke was the same in young and aged brains. At both ages, early activation of gelatinolysis in the ischemic core and the perilesional area was present in neuronal nuclei as revealed by colocalization of gelatinolytic product with NeuN immunostaining and DAPI. Additionally, application of specific antibodies against MMP-9 and MMP-2 revealed the increase in MMP-9 immunoreactivity in cell nuclei as early as 4 hr poststroke. No differences between young and aged mice were observed concerning the level and localization of MMP-9 immunoreactivity. The lack of age-related differences in the degree and pattern of activation of gelatinolysis after focal stroke and the lack of correspondence between the results of in situ and gel zymography suggest that extracellular proteolysis is not directly responsible for the more severe outcome of ischemic stroke in aged subjects.

Association of MMP-2 and MMP-9 with clinical outcome of neurocysticercosis

Matrix metalloproteinases (MMPs) are the major endopeptidases involved in proteolysis of blood brain barrier (BBB) during central nervous system (CNS) infections. The present study detected serum levels and activities of MMP-2 and MMP-9 in patients with neurocysticercosis (NCC) and their association with symptomatic disease. In total, 68 individuals with NCC (36 symptomatic patients with active seizures and 32 asymptomatic individuals) and 37 healthy controls were enrolled for the study. Serum MMP-2 and MMP-9 levels and their activities were measured by ELISA and gel zymography respectively. Mean serum MMP-2 levels (ng/ml) were higher both in asymptomatic and symptomatic NCC cases compared to healthy controls. However, significantly higher levels of serum MMP-9 (ng/ml) were detected only in symptomatic NCC patients compared to asymptomatic NCC cases and healthy controls. Levels of both MMPs positively correlated with symptomatic NCC. Serum MMP-2 activities were significantly higher in symptomatic and asymptomatic NCC compared to healthy controls whereas serum MMP-9 activity was significantly associated with symptomatic NCC compared to healthy controls and asymptomatic NCC. In conclusion, the elevated level of MMP-9 in serum appears to play an important role in the development of symptoms i.e. active seizures in patients with NCC. However, further studies are needed to elucidate its precise role in disease pathogenesis.

Effect of baicalin on matrix metalloproteinase-9 expression and blood-brain barrier permeability following focal cerebral ischemia in rats

Focal cerebral ischemia results in an increased expression of matrix metalloproteinase-9 (MMP-9), which induces vasogenic brain edema via disrupting the blood-brain barrier (BBB) integrity. Recent studies from our laboratory showed that baicalin reduces ischemic brain damage by inhibiting inflammatory reaction and neuronal apoptosis in a rat model of focal cerebral ischemia. In the present study, we first explored the effect of baicalin on the neuronal damage, brain edema and BBB permeability, then further investigated its potential mechanisms. Sprague-Dawley rats underwent permanent middle cerebral artery occlusion (MCAO). Baicalin was administrated by intraperitoneally injected twice at 2 and 12 h after the onset of MCAO. Neuronal damage, brain edema and BBB permeability were measured 24 h following MCAO. Expression of MMP-9 protein and mRNA were determined by western blot and RT-PCR, respectively. Expression of tight junction protein (TJP) occludin was detected by western blot. Neuronal damage, brain edema and BBB permeability were significantly reduced by baicalin administration following focal cerebral ischemia. Elevated expression of MMP-9 protein and mRNA were significantly down-regulated by baicalin administration. In addition, MCAO caused the decreased expression of occludin, which was significantly up-regulated by baicalin administration. Our study suggested that baicalin reduces MCAO-induced neuronal damage, brain edema and BBB permeability, which might be associated with the inhibition of MMP-9 expression and MMP-9-mediated occludin degradation.

Quercetin reduces the elevated matrix metalloproteinases-9 level and improves functional outcome after cerebral focal ischemia in rats

BACKGROUND

Blood-brain barrier (BBB) disruption mediated by matrix metalloproteinase (MMPs) activation is a critical event during cerebral ischemia. The inhibition of MMP might be a potential approach to protect against secondary injury. The present study was designed to determine the effects of quercetin on BBB disruption and MMP activity, in a focal ischemia model induced by photothrombosis, in rats.

METHODS

Adult male Sprague-Dawley rats received focal ischemia by photothrombosis. The injured animals were divided into two groups: one group received 25 μmol/kg of quercetin intraperitoneally, starting 1 h after injury with continued treatment at 12-h intervals for 3 days, while animals in the control group received weight-adjusted doses of a saline vehicle. The effects of quercetin on BBB disruption, brain edema, MMP activities, and neurological deficits were determined.

FINDINGS

Quercetin treatment markedly reduced ischemia-induced up-regulation of MMP-9 at 24 and 48 h after ischemic injury. No significant change in MMP-2 activity was observed throughout the experimental period. Post-ischemic increase in BBB permeability and brain edema were significantly reduced in the quercetin-treated group compared to the vehicle-treated ischemia control. Quercetin treatment significantly improved the functional outcomes assessed by the accelerating rotarod test.

CONCLUSIONS

The results of this study demonstrated that quercetin attenuated BBB disruption during focal ischemia through inhibitory effects on MMP-9 activity. These results suggest that quercetin might have a potential role in the protection against neuronal injury in patients with focal ischemic stroke.