White Matter Injury After Subarachnoid Hemorrhage: Role of Blood-Brain Barrier Disruption and Matrix Metalloproteinase-9

MST1 Suppression Reduces Early Brain Injury by Inhibiting the NF-κB/MMP-9 Pathway after Subarachnoid Hemorrhage in Mice

Background

Mammalian sterile 20-like kinase 1 (MST1), the key component of the Hippo-YAP pathway, exhibits an important role in the pathophysiological process of various neurological disorders, including ischemic stroke and spinal cord injury. However, during subarachnoid hemorrhage, the involvement of MST1 in the pathophysiology of early brain injury remains unknown.

Methods

We employed intravascular filament perforation to establish the subarachnoid hemorrhage (SAH) mouse model. The MST1 inhibitor XMU-MP-1 was intraperitoneally injected at 1 h after SAH, followed by daily injections. MST1 in vivo knockdown was performed 3 weeks prior to SAH via intracerebroventricular injection of adeno-associated virus (AAV) packaged with MST1 shRNA. The SAH grade, behavioral deficits, TUNEL staining, Evans blue dye extravasation and fluorescence, brain water content, protein and cytokine expressions by Western blotting, immunofluorescence, and proteome cytokine array were evaluated.

Results

Following SAH, the phosphorylation level of MST1 was upregulated at 12 h, with a peak at 72 h after SAH. It was colocalized with the microglial marker Iba1. Both XMU-MP-1 and MST1 shRNA alleviated the neurological deficits, blood-brain barrier (BBB) disruption, brain edema, neuroinflammation, and white matter injury, which were induced by SAH in association with nuclear factor- (NF-) κB p65 and matrix metallopeptidase-9 (MMP-9) activation and downregulated endothelial junction protein expression.

Conclusions

The current findings indicate that MST1 participates in SAH-induced BBB disruption and white matter fiber damage via the downstream NF-κB-MMP-9 signaling pathway. Therefore, MST1 antagonists may serve as a novel therapeutic target to prevent early brain injury in SAH patients.

A Comparison of Pathophysiology in Humans and Rodent Models of Subarachnoid Hemorrhage

Non-traumatic subarachnoid hemorrhage (SAH) affects an estimated 30,000 people each year in the United States, with an overall mortality of ~30%. Most cases of SAH result from a ruptured intracranial aneurysm, require long hospital stays, and result in significant disability and high fatality. Early brain injury (EBI) and delayed cerebral vasospasm (CV) have been implicated as leading causes of morbidity and mortality in these patients, necessitating intense focus on developing preclinical animal models that replicate clinical SAH complete with delayed CV. Despite the variety of animal models currently available, translation of findings from rodent models to clinical trials has proven especially difficult. While the explanation for this lack of translation is unclear, possibilities include the lack of standardized practices and poor replication of human pathophysiology, such as delayed cerebral vasospasm and ischemia, in rodent models of SAH. In this review, we summarize the different approaches to simulating SAH in rodents, in particular elucidating the key pathophysiology of the various methods and models. Ultimately, we suggest the development of standardized model of rodent SAH that better replicates human pathophysiology for moving forward with translational research.

Peli1 Contributions in Microglial Activation, Neuroinflammatory Responses and Neurological Deficits Following Experimental Subarachnoid Hemorrhage

Early brain injury (EBI) following subarachnoid hemorrhage (SAH) is closely associated with neuroinflammation. Microglial activation is an early event that leads to neuroinflammation after SAH. Peli1 is an E3 ubiquitin ligase that mediates the induction of pro-inflammatory cytokines in microglia. Here we report Peli1 contributions in SAH mediated brain pathology. An SAH model was induced by endovascular perforation in adult male C57BL/6J mice. Peli1 was markedly induced in mice brains in a time-dependent manner and was predominantly expressed in CD16/32-positive microglia after SAH. Using genetic approaches, we demonstrated that decreased Peli1 significantly improved neurological deficits, attenuated brain edema, reduced over-expression of pro-inflammatory cytokine IL-6 and modified apoptotic/antiapoptotic biomarkers. In addition, Peli1 downregulation suppressed ERK and JNK phosphorylation levels via the downregulation of cIAP1/2 expression, subsequently reducing inducible nitric oxide synthase (iNOS) expression after SAH. Therefore, these findings demonstrate that Peli1 contributes to microglia-mediated neuroinflammation in EBI by mediating cIAP1/2 activation, thus promoting the activation of MyD88-dependent MAPK pathway after experimental SAH. Our findings also showed that Peli1 could promote the expression of M1 microglia polarization biomarker CD16/32 and iNOS after SAH. Targeting Peli1 exerts neuroprotective effects during EBI after SAH, thus could provide potential option for prevention-therapy in high-risk individuals.

Expression of MMP-9 and IL-6 in patients with subarachnoid hemorrhage and the clinical significance

The purpose of the present study was to investigate the expression of matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6) in patients with subarachnoid hemorrhage (SAH) and the clinical significance thereof. Forty-three patients with SAH and 23 healthy individuals were enrolled in this study. Patients were divided into the cerebral vasospasm (CVS) and non-cerebral vasospasm (non-CVS) groups, or the good and poor prognosis groups. Serum levels of MMP-9 and IL-6 were detected by ELISA. Expression levels of MMP-9 and IL-6 mRNAs were detected by RT-qPCR. Expression levels of MMP-9 and IL-6 were elevated with the increase of grades as determined by the Hunt-Hess grading method. Serum levels of MMP-9 and IL-6 in the CVS and poor prognosis groups were significantly higher than those in the control group. Expression levels of MMP-9 and IL-6 in the CVS group were significantly higher than those in the non-CVS group (P<0.05). Compared with the good prognosis group, the expression levels of MMP-9 and IL-6 were significantly increased in the poor prognosis group at 1, 4, 7 and 10 days after SAH (P<0.05). Additionally, the expression level of MMP-9 was significantly positively correlated with that of IL-6 (P<0.05). Expression levels of MMP-9 and IL-6 were significantly increased in patients with SAH, and the expression level of MMP-9 was positively correlated with that of IL-6. Thus, MMP-9 and IL-6 are involved in the development of SAH.

Mechanisms of Global Cerebral Edema Formation in Aneurysmal Subarachnoid Hemorrhage

A growing body of clinical literature emphasizes the impact of cerebral edema in early brain injury following aneurysmal subarachnoid hemorrhage (aSAH). Aneurysm rupture itself initiates global cerebral edema in up to two thirds of cases. Although cerebral edema is not a universal feature of aSAH, it portends a poor clinical course, with quantitative analysis revealing a direct correlation between cerebral edema and poor outcome, including mortality and cognitive deficits. Mechanistically, global cerebral edema has been linked to global ischemia at the time of aneurysm rupture, dysfunction of autoregulation, blood breakdown products, neuroinflammation, and hyponatremia/endocrine abnormalities. At a molecular level, several culprits have been identified, including aquaporin-4, matrix metalloproteinase-9, SUR1-TRPM4 cation channels, vascular endothelial growth factor, bradykinin, and others. Here, we review these cellular and molecular mechanisms of global cerebral edema formation in aSAH. Given the importance of edema to the outcome of patients with aSAH and its status as a highly modifiable pathological process, a better understanding of cerebral edema in aSAH promises to hasten the development of medical therapies to improve outcomes in this frequently devastating disease.

Minocycline protects against delayed cerebral ischemia after subarachnoid hemorrhage via matrix metalloproteinase-9 inhibition

Objective

Delayed cerebral ischemia (DCI) is an independent risk factor for poor outcome after aneurysmal subarachnoid hemorrhage (SAH) and is multifactorial in etiology. While prior studies have suggested a role for matrix metalloproteinase-9 (MMP-9) in early brain injury after SAH, its contribution to the pathophysiology of DCI is unclear.

Methods

In the first experiment, wild-type (WT) and MMP-9^-/- mice were subjected to sham or endovascular perforation SAH surgery. In separate experiments, WT and MMP-9^-/-mice were administered vehicle or minocycline either pre- or post-SAH. All mice underwent assessment of multiple components of DCI including vasospasm, neurobehavioral function, and microvessel thrombosis. In another experiment, rabbits were subjected to sham or cisterna magna injection SAH surgery, and administered vehicle or minocycline followed by vasospasm assessment.

Results

MMP-9 expression and activity was increased after SAH. Genetic (MMP-9^-/- mice) and pharmacological (pre-SAH minocycline administration) inhibition of MMP-9 resulted in decreased vasospasm and neurobehavioral deficits. A therapeutically feasible strategy of post-SAH administration of minocycline resulted in attenuation of multiple components of DCI. Minocycline administration to MMP-9^-/- mice did not yield additional protection. Consistent with experiments in mice, both pre- and post-SAH administration of minocycline attenuated SAH-induced vasospasm in rabbits.

Interpretation

MMP-9 is a key player in the pathogenesis of DCI. The consistent attenuation of multiple components of DCI with both pre- and post-SAH administration of minocycline across different species and experimental models of SAH, combined with the excellent safety profile of minocycline in humans suggest that a clinical trial in SAH patients is warranted.

Heparin and Heparin-Derivatives in Post-Subarachnoid Hemorrhage Brain Injury: A Multimodal Therapy for a Multimodal Disease

Pharmacologic efforts to improve outcomes following aneurysmal subarachnoid hemorrhage (aSAH) remain disappointing, likely owing to the complex nature of post-hemorrhage brain injury. Previous work suggests that heparin, due to the multimodal nature of its actions, reduces the incidence of clinical vasospasm and delayed cerebral ischemia that accompany the disease. This narrative review examines how heparin may mitigate the non-vasospastic pathological aspects of aSAH, particularly those related to neuroinflammation. Following a brief review of early brain injury in aSAH and heparin’s general pharmacology, we discuss potential mechanistic roles of heparin therapy in treating post-aSAH inflammatory injury. These roles include reducing ischemia-reperfusion injury, preventing leukocyte extravasation, modulating phagocyte activation, countering oxidative stress, and correcting blood-brain barrier dysfunction. Following a discussion of evidence to support these mechanistic roles, we provide a brief discussion of potential complications of heparin usage in aSAH. Our review suggests that heparin’s use in aSAH is not only safe, but effectively addresses a number of pathologies initiated by aSAH.

Apolipoprotein E ε4: A Possible Risk Factor of Intracranial Pressure and White Matter Perfusion in Good-Grade Aneurysmal Subarachnoid Hemorrhage Patients at Early Stage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating and complicated disease with significant morbidity and mortality. Previous studies have shown that genetic susceptibility may play an important role in the outcome of a given individual with aSAH. This study evaluates the potential association in effects of the APOE allele on the early brain injury (EBI) in light of elevated intracranial pressure (ICP) and cerebral perfusion disorders in a consecutive series of non-comatose Chinese patients with aSAH. A total of 122 patients with aSAH (54 males and 68 females) were enrolled in this study. Demographic and clinical data were collected. We measured ICP before microsurgical clipping or endovascular coiling during the first 72 h after aneurysm rupture. Computed tomography perfusion (CTP) examination in patients was performed before treatment. The distributions of APOE genotypes and alleles matched Hardy–Weinberg law (p > 0.05). In this study, 68 patients (55.7%) had a normal ICP, whereas 54 (44.3%) had an elevated ICP. Fourteen of 21 patients with APOE ε4 had an elevated ICP, which was significantly different from those without APOE ε4 (p = 0.03). The patients with the ε4 allele had a higher incidence of elevated ICP [p = 0.009, 95% confidence interval (CI) = 1.481–15.432, odds ratio = 4.780] than those without this allele. For CTP measurements, a lower mean cerebral blood flow (difference, −4.74; 95% CI, 0.53–8.94 s, p = 0.03), longer mean transit time (difference, 0.47; 95% CI, −0.87 to −0.78, p = 0.02), and time-to-peak (difference, 2.29; 95% CI, −3.64 to −0.93 s, p = 0.02) were observed in patients with ε4 allele than in those without in the internal capsule regions. In conclusion, the APOE ε4 allele predisposes patients to elevated ICP and perfusion disorders in white matter regions during the first 72 h after aSAH. The presence of an APOE ε4 allele plays an important role in the EBI response to aSAH.

Multimodality MRI assessment of grey and white matter injury and blood-brain barrier disruption after intracerebral haemorrhage in mice

In this study, we examined injury progression after intracerebral haemorrhage (ICH) induced by collagenase in mice using a preclinical 11.7 Tesla MRI system. On T2-weighted MRI, lesion and striatal volumes were increased on day 3 and then decreased from days 7 to 28. On day 3, with an increase in striatal water content, vasogenic oedema in the perihaematomal region presented as increased T2 and increased apparent diffusion coefficient (ADC) signal. With a synchronous change in T2 and ADC signals, microglial activation peaked on day 3 in the same region and decreased over time. Iron deposition appeared on day 3 around the haematoma border but did not change synchronously with ADC signals. Vascular permeability measured by Evans blue extravasation on days 1, 3, and 7 correlated with the T1-gadolinium results, both of which peaked on day 3. On diffusion tensor imaging, white matter injury was prominent in the corpus callosum and internal capsule on day 3 and then partially recovered over time. Our results indicate that the evolution of grey/white matter injury and blood-brain barrier disruption after ICH can be assessed with multimodal MRI, and that perihaematomal vasogenic oedema might be attributable to microglial activation, iron deposition, and blood-brain barrier breakdown.

Traumatic brain injury induced matrix metalloproteinase2 cleaves CXCL12α (stromal cell derived factor 1α) and causes neurodegeneration

Traumatic brain injury (TBI), even at mild levels, can activate matrix metalloproteinases (MMPs) and the induction of neuroinflammation that can result in blood brain barrier breakdown and neurodegeneration. MMP2 has a significant role in neuroinflammation and neurodegeneration by modulating the chemokine CXCL12α (stromal cell derived factor SDF-1α) signaling pathway and the induction of apoptosis. SDF-1α is responsible for cell proliferation and differentiation throughout the nervous system and is also implicated in various neurodegenerative illnesses. We hypothesized that TBI leads to MMP2 activation and cleavage of the N-terminal 4 amino acid residues of CXCL12α with generation of the highly neurotoxic fragment SDF-1(5-67). Using an in vitro stretch-injury model of rat neuronal cultures and the in vivo fluid percussion injury (FPI) model in rats, we found that oxidative stress has a significant role in the activation of MMP2. This is initiated by the induction of free radical generating enzyme NADPH oxidase 1 (NOX1). Induction of NOX1 correlated well with the signatures of oxidative stress marker, 4HNE in the injured neuronal cultures and cerebral cortex of rats. Further, using MMP2 siRNA and pharmacological MMP2 inhibitor, ARP100, we established the neurodegenerative role of MMP2 in cleaving SDF-1α to a neurotoxic fragment SDF-1(5-67). By immunofluorescence, western blotting and TUNEL experiments, we show the cleaved form of SDF leads to apoptotic cell death in neurons. This work identifies a new potential therapeutic target to reduce the complications of brain damage in TBI.

Angiopoietin-1 and Angiopoietin-2 Expression Imbalance Influence in Early Period After Subarachnoid Hemorrhage

Purpose

Microvascular endothelial integrity is important for maintaining the blood-brain barrier (BBB). However, subarachnoid hemorrhage (SAH) disrupts this integrity, making the BBB dysfunctional—an important pathophysiological change after SAH. Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) regulate microvascular permeability by balancing each other’s expression.

Methods

This study investigated the dynamics of Ang-1 and Ang-2 expression after SAH and the protective effect of Ang-1 on BBB functioning using an endovascular puncture model of rat SAH. The Ang-1 and Ang-2 expression in brain tissue was determined by immunohistochemistry. In addition, Western blotting was used to estimate Ang-1 and Ang-2 concentration and to compare them at 6–72 hours post-SAH cortex and hippocampus. Evans blue viability assay was used to evaluate BBB permeability, and neurological testing was implemented to evaluate neurological impairment during SAH.

Results

It was found that following SAH, Ang-1 expression decreases and Ang-2 expression increases in the cortex, hippocampus, and microvessels. The Ang-1/Ang-2 ratio decreased as quickly as 6 hours after SAH and reached its lowest 1 day after SAH. Finally, it was found that exogenous Ang-1 reduces SAH-associated BBB leakage and improves neurological function in post-SAH rats.

Conclusions

Our findings suggest that the equilibrium between Ang-1 and Ang-2 is broken in a period shortly after SAH, and the treatment of exogenous Ang-1 injection alleviates neurological dysfunctions through decreasing BBB destruction.

Inhibition of Blood-Brain Barrier Disruption by an Apolipoprotein E-Mimetic Peptide Ameliorates Early Brain Injury in Experimental Subarachnoid Hemorrhage

Apolipoprotein E (ApoE)-mimetic peptides have been demonstrated to be beneficial in secondary brain injury following experimental subarachnoid hemorrhage (SAH). However, the molecular mechanisms underlying these benefits in SAH models have not been clearly identified. This study investigated whether an ApoE-mimetic peptide affords neuroprotection in early brain injury (EBI) following SAH by attenuating BBB disruption. SAH was induced by an endovascular perforation in young, healthy, male wild-type (WT) C57BL/6J mice. Multiple techniques, including MRI with T2-weighted imaging, ¹⁸ FDG PET-CT scanning and histological studies, were used to examine BBB integrity and neurological dysfunction in EBI following SAH. We found that SAH induced a significant increase of BBB permeability and neuron apoptosis, whereas ApoE-mimetic peptide treatment significantly reduced the degradation of tight junction proteins and endothelial cell apoptosis. These effects reduced brain edema and neuron apoptosis, increased cerebral glucose uptake, and improved neurological functions. Further investigation revealed that the ApoE-mimetic peptide inhibited the proinflammatory activators of MMP-9, including CypA, NF-κB, IL-6, TNF-α, and IL-1β, thereby ameliorating BBB disruption at the acute stage of SAH. Together, these data indicate that ApoE-mimetic peptide may be a novel and promising therapeutic strategy for EBI amelioration after SAH that are worthy of further study.

Measuring serum matrix metalloproteinase-9 levels in peripheral blood after subarachnoid hemorrhage to predict cerebral vasospasm

Purpose

We aimed to investigate serum levels of matrix metalloproteinase-9 in both subarachnoid hemorrhage and control groups for prediction of cerebral vasospasm in this study.

Methods

Venous serum matrix metalloproteinase-9 levels were prospectively measured four times (days 1, 3, 7, and 14) for 34 consecutive patients with subarachnoidal hemorrhage (n = 27) and for elective aneurysm clipping (control, n = 7).

Results

Vasospasm developed in 11/34 (32.4 %) patients between 3 and 10 days after subarachnoid hemorrhage (median 5.58 days), mean peak serum matrix metalloproteinase-9 compared with the non-vasospasm cohort. Matrix metalloproteinase-9 levels were higher in subarachnoid hemorrhage patients than in the controls.

Conclusion

Increased serum matrix metalloproteinase-9 could be an accurate biomarker to predict the onset of cerebral vasospasm after subarachnoid hemorrhage.

Combination of Ligusticum chuanxiong and Radix Paeoniae ameliorate focal cerebral ischemic in MCAO rats via endoplasmic reticulum stress-dependent apoptotic signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Combination of Ligusticum chuanxiong and Radix Paeoniae (XS) is highly effective in the treatment for focal cerebral ischemic, but the underlying mechanism is not clear. This study was conducted to evaluate the combinative effects of XS on MCAO rats and explore the underlying mechanisms.

MATERIALS AND METHODS

MCAO rats were used to evaluate the protective effect of Ligusticum chuanxiong (CX), Radix Paeoniae Rubra (CS) and their combination (XS) on ameliorating focal cerebral ischemic. Cerebral ischemia deficits and infarct size were performed by 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (H-E) staining. Activities of SOD, CAT and GSH-Px, as well as levels of LPO and MDA were detected by commercial kits while ELISA kits for the content of plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator (PA). Immunohistochemistry (IHC) and western blot analysis (WB) were carried out to examine the protein expressions including PKR-like endoplasmic reticulum kinase (PERK), cytoplasmic of glucose regulated protein 78 (GRP78), X box-binding protein-1 (XBP-1), activating transcription factor-6 (ATF-6), C/EBP-homologous protein (CHOP), metalloprotease-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), Bcl-2 associated X protein (Bax), and porcineB-cellleukemia/lymphoma-2 (Bcl-2) in brain tissues. Reverse transcription polymerase chain reaction (RT-PCR) and Quantitative PCR (Q-PCR) were applied to examine vascular endothelial growth factor (VEGF) and N-methyl-d-aspartate receptors (NMDAR1) mRNA levels.

RESULTS

CX, CS and their combination (XS) could reduce cerebral ischemia deficits and infarct size of MCAO rats. They increased SOD, CAT and GSH-Px activities, and reduced MDA and LPO levels in serum, markedly. A significant decrease of endoplasmic reticulum stress-related factors PERK, XBP-1, ATF-6 and CHOP protein expression levels while an increase of GRP78 and MVD expression by the treatment of CX, CS and XS. It could also be observed that their treatment could reduce apoptotic damage of brain tissues by up-regulating Bax level and down-regulating Bcl-2 level. Furthermore, the levels of MMP-9 and PAI-1 in serum and tissues of rats were down-regulated remarkably while TIMP-1 and PA levels were up-regulated. VEGF mRNA level was up-regulated dramatically whereas NMDAR1 was reduced. Importantly, the combination of CX and CS, namely XS, has a more meaningful improvement on focal cerebral ischemic than CX or CS alone.

CONCLUSION

All these revealed that the combined XS exerted more remarkable protective effects than alone. XS could inhibit neuronal apoptosis by attenuating ER-stress-dependent apoptotic signaling and protected the blood-brain barrier. These findings might supply beneficial hints for the synergy of CX and CS, and provide the basis for rationality of XS preparation and deserve further clinical investigations.

Matrix metalloproteinase-9 and vascular endothelial growth factor expression change in experimental retinal neovascularization

AIM

To investigate the signal transduction mechanism of matrix metalloproteinase-9 (MMP-9) mediated- vascular endothelial growth factor (VEGF) expression and retinal neovascularization (RNV) in oxygen-induced retinopathy (OIR) model.

METHODS

C57BL/6J mice were divided into four groups: control group, OIR group, OIR control group (phosphate-buffered saline by intravitreal injection) and treated group [tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) by intravitreal injection]. OIR model was established in C57BL/6J mice exposed to 75%±2% oxygen for 5d. mRNA level and protein expression of MMP-9, TIMP-1 and VEGF were measured by real-time polymerase chain reaction and Western blotting, and located by immunohistochemistry.

RESULTS

Levels of MMP-9 and VEGF in retina were significantly increased in animals with OIR and OIR control group. Levels of TIMP-1 in retina was significantly reduced in animals with OIR and OIR control group. Furthermore, a significant correlation was found between MMP-9 and VEGF. Intravitreal injection of TIMP-1 significantly reduced MMP-9 and VEGF expression of the OIR mouse model (all P<0.05).

CONCLUSION

These results demonstrate that MMP-9-mediated up-regulation of VEGF promotes RNV in retinopathy of prematurity (ROP). TIMP-1 may be a potential target for the prevention and treatment of ROP.