Contributions of multiple proteases to neurotoxicity in a mouse model of intracerebral haemorrhage

Crosstalk Between Matrix Metalloproteinases and Their Inducer EMMPRIN/CD147: a Promising Therapeutic Target for Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is characterized by the disruption of cerebrovascular integrity, resulting in hematoma enlargement, edema formation, and physical damage in the brain parenchyma. Primary ICH also leads to secondary brain injury contributed by oxidative stress, dysregulated immune responses, and proteolysis. In this context, matrix metalloproteinases (MMPs) represent a ubiquitous superfamily of structurally related zinc-dependent endopeptidases capable of degrading all components of the extracellular matrix. They disrupt the blood-brain barrier and promote neuroinflammation. Importantly, several MMP members are upregulated following ICH, and members may have different functions at specific periods in ICH. Hence, the modulation and function of MMPs are more complex than expected. Extracellular matrix metalloproteinase inducer (EMMPRIN, CD147) is a transmembrane glycoprotein that induces the production of MMPs. In this review, we systematically discuss the biology and functions of MMPs and EMMPRIN/CD147 in ICH and the complex crosstalk between them.

Naringenin mitigates nanoparticulate-aluminium induced neuronal degeneration in brain cortex and hippocampus through downregulation of oxidative stress and neuroinflammation

Alumunium usage and toxicity has been a global concern especially an increased use of nanoparticulated aluminum (Al-NPs) products from the environment and the workplace. Al degrades in to nanoparticulate form in the environment due to the routine process of bioremediation in human body. Al-NPs toxicity plays key role in the pathophysiology of neurodegeneration which is characterised by the development of neurofibrillary tangles and neuritic plaques which correlates to the Alzheimer's disease. This study evaluated the Al-NPs induced neurodegeneration and causative behavioral alterations due to oxidative stress, inflammation, DNA damage, β-amyloid aggregation, and histopathological changes in mice. Furthermore, the preventive effect of naringenin (NAR) as a potent neuroprotective flavonoid against Al-NPs induced neurodegeneration was assessed. Al-NPs were synthesized and examined using FTIR, XRD, TEM, and particle size analyzer. Mice were orally administered with Al-NPs (6 mg/kg b.w.) followed by NAR treatment (10 mg/kg b.w. per day) for 66 days. The spatial working memory was determined by novel object recognition, T-maze, Y-maze, and Morris Water Maze tests. We measured nitric oxide, advanced oxidation of protein products, protein carbonylation, lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, reduced glutathione, oxidised glutathione, and acetylcholine esterase, as well as cytokines analysis, immunohistochemistry, and DNA damage. Al-NPs significantly reduced the learning memory power, increased oxidative stress, reduced antioxidant enzymatic activity, increased DNA damage, altered the levels of cytokines, and increased β-amyloid aggregation in the cortex and hippocampus regions of the mice brain. These neurobehavioral impairments, neuronal oxidative stress, and histopathological alterations were significantly attenuated by NAR supplementation. In conclusion, Al-NPs may be potent neurotoxic upon exposure and that NAR could serve as a potential preventive measure in the treatment and management of neuronal degeneration.

Hemorrhagic stroke-induced subtype of inflammatory reactive astrocytes disrupts blood-brain barrier

Astrocytes undergo disease-specific transcriptomic changes upon brain injury. However, phenotypic changes of astrocytes and their functions remain unclear after hemorrhagic stroke. Here we reported hemorrhagic stroke induced a group of inflammatory reactive astrocytes with high expression of Gfap and Vimentin, as well as inflammation-related genes lipocalin-2 (Lcn2), Complement component 3 (C3), and Serpina3n. In addition, we demonstrated that depletion of microglia but not macrophages inhibited the expression of inflammation-related genes in inflammatory reactive astrocytes. RNA sequencing showed that blood-brain barrier (BBB) disruption-related gene matrix metalloproteinase-3 (MMP3) was highly upregulated in inflammatory reactive astrocytes. Pharmacological inhibition of MMP3 in astrocytes or specific deletion of astrocytic MMP3 reduced BBB disruption and improved neurological outcomes of hemorrhagic stroke mice. Our study demonstrated that hemorrhagic stroke induced a group of inflammatory reactive astrocytes that were actively involved in disrupting BBB through MMP3, highlighting a specific group of inflammatory reactive astrocytes as a critical driver for BBB disruption in neurological diseases.

The hallmark and crosstalk of immune cells after intracerebral hemorrhage: Immunotherapy perspectives

Intracerebral hemorrhage (ICH) is one of the most dangerous types of strokes with a high morbidity and mortality rate. Currently, the treatment of ICH is not well developed, mainly because its mechanisms are still unclear. Inflammation is one of the main types of secondary injury after ICH and catalyzes the adverse consequences of ICH. A large number of immune cells are involved in neuroinflammation, such as microglia, astrocytes, oligodendrocytes, lymphocytes, macrophages, and neutrophils. Nevertheless, the characteristics and crosstalk of immune cells have not been fully elucidated. In this review, we endeavor to delve into the respective characteristics of immune cells and their interactions in neuroimmune inflammation, and further elucidate favorable immunotherapeutic approaches regarding ICH, and finally present an outlook.

Neurokinin Receptor 1 (NK1R) Antagonist Aprepitant Enhances Hematoma Clearance by Regulating Microglial Polarization via PKC/p38MAPK/NFκB Pathway After Experimental Intracerebral Hemorrhage in Mice

Hematoma clearance is an important therapeutic target to improve outcome following intracerebral hemorrhage (ICH). Recent studies showed that Neurokinin receptor-1 (NK1R) inhibition exerts protective effects in various neurological disease models, but its role in ICH has not been explored. The objective of this study was to investigate the role of NK1R and its relation to hematoma clearance after ICH using an autologous blood injection mouse model. A total of 332 adult male CD1 mice were used. We found that the expression levels of NK1R and its endogenous ligand, substance P (SP), were significantly upregulated after ICH. Intraperitoneal administration of the NK1R selective antagonist, Aprepitant, significantly improved neurobehavior, reduced hematoma volume and hemoglobin levels after ICH, and promoted microglia polarization towards M2 phenotype. Aprepitant decreased phosphorylated PKC, p38MAPK, and NFκB p65, and downregulated M1 markers while upregulating M2 markers after ICH. Intracerebroventricular administration of the NK1R agonist, GR73632 or PKC agonist, phorbol 12-myristate 13-acetate (PMA) reversed the effects of Aprepitant. To demonstrate the upstream mediator of NK1R activation, we performed thrombin injection and found that it increased SP. Inhibiting thrombin suppressed SP and decreased M1 markers while increasing M2 microglia polarization. Thus, NK1R inhibition promoted hematoma clearance after ICH by increasing M2 microglial polarization via downregulating PKC/p38MAPK/NFκB signaling pathway, and thrombin may be a key upstream mediator of NK1R activation. Therapeutic interventions inhibiting NK1R signaling may be a new target for the treatment of ICH.

Role of Thrombin in Central Nervous System Injury and Disease

Thrombin is a Na+-activated allosteric serine protease of the chymotrypsin family involved in coagulation, inflammation, cell protection, and apoptosis. Increasingly, the role of thrombin in the brain has been explored. Low concentrations of thrombin are neuroprotective, while high concentrations exert pathological effects. However, greater attention regarding the involvement of thrombin in normal and pathological processes in the central nervous system is warranted. In this review, we explore the mechanisms of thrombin action, localization, and functions in the central nervous system and describe the involvement of thrombin in stroke and intracerebral hemorrhage, neurodegenerative diseases, epilepsy, traumatic brain injury, and primary central nervous system tumors. We aim to comprehensively characterize the role of thrombin in neurological disease and injury.

Valproate Sodium Protects Blood Brain Barrier Integrity in Intracerebral Hemorrhage Mice

Valproate sodium (VPA) is a traditional antiepileptic drug with a neuroprotective role in cerebrovascular disease. After intracerebral hemorrhage (ICH), mechanical compression by hematoma, neuroinflammation, oxidative stress, and cytotoxicity of hematoma lysates caused the destruction of the blood brain barrier (BBB). Targeting BBB is a major therapeutic method for patients with ICH. The purpose of the present study was to explore the role of VPA in preserving BBB integrity in the ICH model and investigate the underlying molecular mechanisms. One hundred and thirty-six adult male CD1 mice were randomly divided into five groups in the study. Mice subjected to ICH were administered intraperitoneally with VPA at 3, 24, and 48 h post-ICH, respectively. Neurobehavioral assessments, BBB permeability, Evans blue fluorescence, hematoma volume, and protein expression were evaluated. The administration of VPA reduced BBB permeability and improved the neurobehavior significantly post-ICH. VPA administration significantly decreased the expression of phosphorylated nuclear factor-kappa B (p-NFκB), matrix metalloproteinases 9 (MMP9), tumor necrosis factorα (TNFα), and interleukin-6 (IL-6), while it enhanced the expression of claudin 5 and occludin in the brain. In conclusion, VPA administration maintained the integrity of BBB after experimental ICH, thus reducing brain edema and improving the neurological outcomes. Therefore, VPA administration might be a new therapeutic method to protect BBB integrity for patients with ICH.

Matrix Metalloproteinases in Acute Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 10-30% of all strokes and affects more than one million people every year worldwide, and it is the stroke subtype associated with the highest rates of mortality and residual disability. So far, clinical trials have mainly targeted primary cerebral injury and have substantially failed to improve clinical outcomes. The understanding of the pathophysiology of early and delayed injury after ICH is, hence, of paramount importance to identify potential targets of intervention and develop effective therapeutic strategies. Matrix metalloproteinases (MMPs) represent a ubiquitous superfamily of structurally related zinc-dependent endopeptidases able to degrade any component of the extracellular matrix. They are upregulated after ICH, in which different cell types, including leukocytes, activated microglia, neurons, and endothelial cells, are involved in their synthesis and secretion. The aim of this review is to summarize the available experimental and clinical evidence about the role of MMPs in brain injury following spontaneous ICH and provide critical insights into the underlying mechanisms.

Microglia and macrophage phenotypes in intracerebral haemorrhage injury: therapeutic opportunities

The prognosis of intracerebral haemorrhage continues to be devastating despite much research into this condition. A prominent feature of intracerebral haemorrhage is neuroinflammation, particularly the excessive representation of pro-inflammatory CNS-intrinsic microglia and monocyte-derived macrophages that infiltrate from the circulation. The pro-inflammatory microglia/macrophages produce injury-enhancing factors, including inflammatory cytokines, matrix metalloproteinases and reactive oxygen species. Conversely, the regulatory microglia/macrophages with potential reparative and anti-inflammatory roles are outcompeted in the early stages after intracerebral haemorrhage, and their beneficial roles appear to be overwhelmed by pro-inflammatory microglia/macrophages. In this review, we describe the activation of microglia/macrophages following intracerebral haemorrhage in animal models and clinical subjects, and consider their multiple mechanisms of cellular injury after haemorrhage. We review strategies and medications aimed at suppressing the pro-inflammatory activities of microglia/macrophages, and those directed at elevating the regulatory properties of these myeloid cells after intracerebral haemorrhage. We consider the translational potential of these medications from preclinical models to clinical use after intracerebral haemorrhage injury, and suggest that several approaches still lack the experimental support necessary for use in humans. Nonetheless, the preclinical data support the use of deactivator or inhibitor of pro-inflammatory microglia/macrophages, whilst enhancing the regulatory phenotype, as part of the therapeutic approach to improve the prognosis of intracerebral haemorrhage.

Neonatal cerebral hypoxia-ischemia in mice triggers age-dependent vascular effects and disabilities in adults; implication of tissue plasminogen activator (tPA)

Neonatal encephalopathy frequently results from hypoxia-ischemia (HI) or inflammation in preterm or term neonates. Neuropathology depends on cerebral development at insult time, but the poor correlation of neuromotor, cognitive, and behavioral disabilities in infancy with initial imaging and clinical records precludes early prognosis. The Rice-Vannucci HI procedure was applied to wild type and tissue plasminogen activator knockout (tPA-KO) mice as surrogates for human preterm (with five-day-old postnatal (P5) mice) or human term (with ten-day-old postnatal (P10) mice). Acute and delayed T2-magnetic resonance imaging (T2-MRI) signals and cognitive deficits in adulthood (spatial memory and social interaction) were investigated in the same animals. Early vascular tPA and matrix metalloproteinase-9 (MMP-9) activities, blood-brain barrier permeability to water or IgG, and microglial activation were assessed separately. HI in P5 or P10 mice induced early hemisphere swelling in T2-MRI scans, and a delayed atrophy of the cortex and hippocampus, but affected white matter in the P5 group only, irrespective of the wild type or tPA-KO genotype. Adults had no motor disabilities, but we did find HI-induced age-dependent deficits, preferentially social interaction and activity in P5 mice, and spatial learning in P10 mice. In P5 mice, tPA-KO prevented MMP-9 activation, IgG extravasation, microglial activation, and behavior impairments. In P10 mice, MMP-9 activation and inflammatory processes remained in the hippocampus of the tPA-KO group, and also contributed to persistent spatial learning deficits. Perinatal HI in mice mimicked the unpredictability of outcomes from imaging in human clinics. Delayed deficits appeared associated to vascular dysfunction-induced inflammation, which recalls our previous work showing major vascular maturation between P5 and P10 stages. Using omics to explore neural, glial, or brain vessel markers in neonate blood may be a promising perspective to identify pertinent prognostic tools.

The p35/CDK5 signaling is regulated by p75NTR in neuronal apoptosis after intracerebral hemorrhage

The p75 neurotrophin receptor (p75NTR), a member of tumor necrosis factor receptor superfamily, involves in neuronal apoptosis after intracerebral hemorrhage (ICH). It has been previously demonstrated that phosphorylation of p35 is a crucial factor for fighting against the proapoptotic p25/CDK5 signaling in neuronal apoptosis. Then, in ICH models of rats and primary cortical neurons, we found that the expressions of p75NTR, p-histone H1 (the kinase activity of CDK5), p25, Fas-associated phosphatase-1 (FAP-1), and phosphorylated myocyte enhancer factor 2D (p-MEF2D) were enhanced after ICH, whereas the expression of p35-Thr(138) was attenuated. Coimmunoprecipitation analysis indicated several interactions as follows: p35/p25 and CKD5, p75NTR and p35, as well as p75NTR and FAP-1. After p75NTR or FAP-1 depletion with double-stranded RNA interference in PC12 cells, the levels of p25 and p-histone H1 were attenuated, whereas p35-Thr(138) was elevated. Considering p75NTR has no effect of dephosphorylation, our results suggested that p75NTR might promote the dephosphorylation of p35-Thr(138) via interaction with FAP-1, and the p75NTR/p35 complex upregulated p25/CDK5 signaling to facilitate the neuronal apoptosis following ICH. So, in the study, we aimed to provide a theoretical and experimental basis that p75NTR could be regulated to reduce neuronal apoptosis following ICH for potential clinical treatment.

Matrix metalloproteinases and ADAMs in stroke

Stroke is a leading cause of death and disability worldwide. However, after years of in-depth research, the pathophysiology of stroke is still not fully understood. Increasing evidence shows that matrix metalloproteinases (MMPs) and "a disintegrin and metalloproteinase" (ADAMs) participate in the neuro-inflammatory cascade that is triggered during stroke but also in recovery phases of the disease. This review covers the involvement of these proteins in brain injury following cerebral ischemia which has been widely studied in recent years, with efforts to modulate this group of proteins in neuroprotective therapies, together with their implication in neurorepair mechanisms. Moreover, the review also discusses the role of these proteins in specific forms of neurovascular disease, such as small vessel diseases and intracerebral hemorrhage. Finally, the potential use of MMPs and ADAMs as guiding biomarkers of brain injury and repair for decision-making in cases of stroke is also discussed.

Role and mechanisms of cytokines in the secondary brain injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common and severe cerebrovascular disease that has high mortality. Few survivors achieve self-care. Currently, patients receive only symptomatic treatment for ICH and benefit poorly from this regimen. Inflammatory cytokines are important participants in secondary injury after ICH. Increases in proinflammatory cytokines may aggravate the tissue injury, whereas increases in anti-inflammatory cytokines might be protective in the ICH brain. Inflammatory cytokines have been studied as therapeutic targets in a variety of acute and chronic brain diseases; however, studies on ICH are limited. This review summarizes the roles and functions of various pro- and anti-inflammatory cytokines in secondary brain injury after ICH and discusses pathogenic mechanisms and emerging therapeutic strategies and directions for treatment of ICH.

Basement membrane and stroke

Located at the interface of the circulation system and the CNS, the basement membrane (BM) is well positioned to regulate blood-brain barrier (BBB) integrity. Given the important roles of BBB in the development and progression of various neurological disorders, the BM has been hypothesized to contribute to the pathogenesis of these diseases. After stroke, a cerebrovascular disease caused by rupture (hemorrhagic) or occlusion (ischemic) of cerebral blood vessels, the BM undergoes constant remodeling to modulate disease progression. Although an association between BM dissolution and stroke is observed, how each individual BM component changes after stroke and how these components contribute to stroke pathogenesis are mostly unclear. In this review, I first briefly introduce the composition of the BM in the brain. Next, the functions of the BM and its major components in BBB maintenance under homeostatic conditions are summarized. Furthermore, the roles of the BM and its major components in the pathogenesis of hemorrhagic and ischemic stroke are discussed. Last, unsolved questions and potential future directions are described. This review aims to provide a comprehensive reference for future studies, stimulate the formation of new ideas, and promote the generation of new genetic tools in the field of BM/stroke research.

Striatal neurons directly converted from Huntington's disease patient fibroblasts recapitulate age-associated disease phenotypes

In Huntington's disease (HD), expansion of CAG codons in the huntingtin gene (HTT) leads to the aberrant formation of protein aggregates and the differential degeneration of striatal medium spiny neurons (MSNs). Modeling HD using patient-specific MSNs has been challenging, as neurons differentiated from induced pluripotent stem cells are free of aggregates and lack an overt cell death phenotype. Here we generated MSNs from HD patient fibroblasts through microRNA-based direct neuronal conversion, bypassing the induction of pluripotency and retaining age signatures of the original fibroblasts. We found that patient MSNs consistently exhibited mutant HTT (mHTT) aggregates, mHTT-dependent DNA damage, mitochondrial dysfunction and spontaneous degeneration in culture over time. We further provide evidence that erasure of age stored in starting fibroblasts or neuronal conversion of presymptomatic HD patient fibroblasts results in differential manifestation of cellular phenotypes associated with HD, highlighting the importance of age in modeling late-onset neurological disorders.

CM352 Reduces Brain Damage and Improves Functional Recovery in a Rat Model of Intracerebral Hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is an acute neurological disorder with high mortality and no effective treatment. In addition to the initial bleeding event, rebleeding and hematoma expansion are associated with poor outcome in these patients. We studied the effectiveness of the new antifibrinolytic agent CM352, a short-half-life matrix metalloproteinase inhibitor, for achieving early hemostasis and improving functional recovery in a rat model of collagenase-induced ICH.

METHODS AND RESULTS

ICH was induced by striatal injection of collagenase, and 1 hour later, rats received an intravenous injection of saline (n=6) or CM352 (1 mg/kg, n=6). Hematoma (basal and after 3 and 24 hours) and lesion (14 days) volumes were quantified on T2-weighted (T2) magnetic resonance images. Neurological and functional recovery was evaluated by using Bederson score and a cylinder test (basal, 24 hours, and 14 days). Early treatment (1 hour) with CM352 was efficient reducing hematoma expansion at 3 hours (P<0.01) and, more markedly, at 24 hours (P<0.01). Decreased bleeding after antifibrinolytic treatment was accompanied by reduced interleukin-6 levels at 3 hours (P<0.05) and smaller lesion volume at 14 days (P<0.01). CM352 drastically reduced sensorimotor impairment (cylinder test) after ICH in rats at 24 hours (P<0.01) and 14 days (P<0.01). Similarly, it also attenuated neurological deficit (Bederson scale) at 24 hours (P<0.01) and 14 days (P<0.01). Interestingly, late (3 hours) CM352 administration also resulted in reduced lesion size and better functional outcome.

CONCLUSIONS

CM352, a new antifibrinolytic agent and matrix metalloproteinase inhibitor, effectively prevented hematoma growth and reduced lesion size in ICH in association with improved functional and neurological recovery.

Role of thrombin-PAR1-PKCθ/δ axis in brain pericytes in thrombin-induced MMP-9 production and blood-brain barrier dysfunction in vitro

Thrombin, an essential component in the coagulation cascade, participates in the pathogenesis of brain diseases, such as ischemic stroke, intracerebral hemorrhage, Alzheimer's disease and Parkinson's disease through blood-brain barrier (BBB) dysfunction. It is thought that the thrombin-matrix metalloproteinase (MMP)-9 axis is an important process in the pathogenesis of neurovascular disease, such as BBB dysfunction. We recently reported that brain pericytes are the most MMP-9-releasing cells in response to thrombin stimulation among the BBB-constituting cells. This thrombin-induced MMP-9 release is partially due to protease-activated receptor (PAR1), one of the specific thrombin receptors. Then, we evaluated the intracellular signaling pathways involved in MMP-9 release and the contribution of thrombin-reactive brain pericytes to BBB dysfunction. PKC activator evoked MMP-9 release from brain pericytes. The thrombin-induced MMP-9 release was inhibited by U0126, LY294002, Go6976, and Go6983. However, Go6976 decreased phosphorylation levels of PKCθ and Akt, and Go6983 decreased phosphorylation levels of PKCδ and extracellular signal-regulated kinase (ERK). Additionally, treatment of pericytes with thrombin or PAR1-activating peptide stimulated PKCδ/θ signaling. These substances impaired brain endothelial barrier function in the presence of brain pericytes. Brain pericytes function through two independent downstream signaling pathways via PAR1 activation to release MMP-9 in response to thrombin - the PKCθ-Akt pathway and the PKCδ-ERK1/2 pathway. These pathways participate in PAR1-mediated MMP-9 release from pericytes, which leads to BBB dysfunction. Brain pericytes and their specific signaling pathways could provide novel therapeutic targets for thrombin-induced neurovascular diseases.

Upregulation of Thrombin/Matrix Metalloproteinase-1/Protease-Activated Receptor-1 Chain in Proliferative Diabetic Retinopathy

PURPOSE

Selective proteolytic activation of protease-activated receptor-1 (PAR1) by thrombin and matrix metalloproteinase-1 (MMP-1) plays a central role in enhancing angiogenesis. We investigated the expression levels of thrombin, MMP-1, and PAR1 and correlated these levels with vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR). In addition, we examined the expression of PAR1 and thrombin in the retinas of diabetic rats and PAR1 in human retinal microvascular endothelial cells (HRMEC) following exposure to high-glucose, the proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and the hypoxia mimetic agent cobalt chloride (CoCl₂).

METHODS

Vitreous samples from 32 PDR and 23 nondiabetic patients, epiretinal membranes from 10 patients with PDR, retinas of rats, and HRMEC were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and Western blot analysis. An assay for in vitro cell migration angiogenesis was performed in HRMEC.

RESULTS

In epiretinal membranes, PAR1 was expressed in vascular endothelial cells, CD45-expressing leukocytes, and myofibroblasts. ELISA and Western blot assays revealed significant increases in the expression levels of thrombin, MMP-1, and VEGF in vitreous samples from PDR patients compared to nondiabetic controls. Significant positive correlations were found between the levels of VEGF and the levels of thrombin (r = 0.41; p = 0.006) and MMP-1 (r = 0.66; p < 0.0001). Significant increases of cleaved PAR1 (approximately 50 kDa) and the proteolytically active thrombin (approximately 50 kDa) were detected in rat retinas after induction of diabetes. The proinflammatory cytokines IL-1β and TNF-α, but not high-glucose and CoCl₂, induced upregulation of cleaved PAR1 (approximately 30 kDa) in HRMEC. In addition, thrombin and MMP-1 induced VEGF in HRMEC and vorapaxar, a PAR1 inhibitor, inhibited thrombin-induced migration in HRMEC.

CONCLUSIONS

Interactions among thrombin, MMP-1, PAR1, and VEGF might facilitate angiogenesis in PDR.

Distinct roles for metalloproteinases during traumatic brain injury

BACKGROUND

Significant protease activations have been reported after traumatic brain injury (TBI). These proteases are responsible for cleavage of transmembrane proteins in neurons, glial, and endothelial cells and this results in the release of their extracellular domains (ectodomains).

METHODS

Two TBI models were employed here, representing both closed head injury (CHI) and open head injury (OHI). In situ zymography, immunohistochemistry, bright field and confocal microscopy, quantification of immunopositive cells and statistical analysis were applied.

RESULTS

We found, using in situ zymography, that gelatinase activity of matrix metalloproteinases (MMP)-2 and MMP-9 was upregulated in cortex of both injury models. Using immunohistochemistry for several MPPs (Matrix metalloproteinases) and ADAMs (disintegrin and metalloproteinases), including MMP-2, -9, ADAM-10, -17, distinct patterns of induction were observed in the two TBI models. In closed head injury, an early increase in protein expression of MMP-2, -9 and ADAM-17 was found as early as 10 min post injury in cortex and peaked at 1 h for all 4 proteases examined. In contrast, after OHI the maximal expression was observed locally neighboring the impact site, at a later time-point, as long as 24 h after the injury for MMP-2 and MMP-9. Confocal microscopy revealed colocalization of the 4 proteases with the neuronal marker NeuN in CHI, but only MMP2 colocalized with NeuN in OHI.

CONCLUSIONS

The findings may lead to a trauma-induced therapeutic strategy triggered soon after a primary insult to improve survival and to reduce brain damage following TBI.

Recombinant ADAMTS 13 Attenuates Brain Injury After Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Inflammatory responses and blood-brain barrier (BBB) dysfunction play important roles in brain injury after intracerebral hemorrhage (ICH). The metalloprotease ADAMTS 13 (a disintegrin and metalloprotease with thrombospondin type I motif, member 13) was shown to limit inflammatory responses through its proteolytic effects on von Willebrand factor. In the present study, we addressed the role of ADAMTS 13 after experimental ICH.

METHODS

ICH was induced in mice by intracerebral infusion of autologous blood. The peri-hematomal inflammatory responses, levels of matrix metalloproteinase-9 and intercellular adhesion molecule-1, pericyte coverage on brain capillaries, and BBB permeability were quantified at 24 hours. Functional outcomes, cerebral edema, and hemorrhagic lesion volume were quantified at day 3.

RESULTS

Treatment with recombinant ADAMTS 13 (rADAMTS 13) reduced the levels of chemokines and cytokines, myeloperoxidase activity, and microglia activation and neutrophil recruitment after ICH. rADAMTS 13 also decreased interleukin-6 expression in brain endothelial cells stimulated by lipopolysaccharide, whereas recombinant von Willebrand factor reversed this effect. The anti-inflammatory effect of rADAMTS 13 was accompanied by reduced expression of intercellular adhesion molecule-1 and less activation of matrix metalloproteinase, enhanced pericyte coverage of brain microvessels, and attenuated BBB disruption. Furthermore, neutrophil depletion protected against BBB damage, and rADAMTS 13 treatment had no further beneficial effect. Finally, treatment of mice with rADAMTS 13 reduced cerebral edema and hemorrhagic lesion volume and improved neurological functions.

CONCLUSIONS

Our findings reveal the importance of rADAMTS 13 in regulating pathological inflammation and BBB function and suggest that rADAMTS 13 may provide a new therapeutic strategy for ICH.

Brain pericytes are the most thrombin-sensitive matrix metalloproteinase-9-releasing cell type constituting the blood-brain barrier in vitro

In the acute phase of intracerebral hemorrhage (ICH), hemorrhagic transformation and brain edema are associated with blood-brain barrier (BBB) disruption. Elevated levels of thrombin, a coagulation factor, contribute to the development of brain edema during ICH through matrix metalloproteinase (MMP)-9 production. Thrombin directly induces a variety of cellular responses through its specific receptors known as protease-activated receptors (PARs). However, it remains unclear which cell types constituting the BBB mainly produce MMP-9 in response to thrombin. Here, we compared the MMP-9 release induced by thrombin using primary cultures of rat brain microvascular endothelial cells, astrocytes, and pericytes. Brain pericytes exhibited the highest levels of MMP-9 release due to thrombin stimulation among the BBB cells. The pattern of PAR mRNA expression in pericytes was characterized by high expression of PAR1 and moderate expression of PAR4. Heat-inactivated thrombin failed to stimulate pericytes to release MMP-9. A selective PAR1 inhibitor SCH79797 blocked the thrombin-induced MMP-9 release from pericytes. These findings suggest that both PAR1 and PAR4 mediate thrombin-induced MMP-9 release from pericytes. The present study raises the possibility that brain pericytes could play a pivotal role as a highly thrombin-sensitive and MMP-9-producing cell type at the BBB in brain damage including ICH.

Toxic role of prostaglandin E2 receptor EP1 after intracerebral hemorrhage in mice

Inflammatory mechanisms mediated by prostaglandins may contribute to the progression of intracerebral hemorrhage (ICH)-induced brain injury, but they are not fully understood. In this study, we examined the effect of prostaglandin E2 receptor EP1 (EP1R) activation and inhibition on brain injury in mouse models of ICH and investigated the underlying mechanism of action. ICH was induced by injecting collagenase, autologous blood, or thrombin into the striatum of middle-aged male and female mice and aged male mice. Effects of selective EP1R agonist ONO-DI-004, antagonist SC51089, and nonspecific Src family kinase inhibitor PP2 were evaluated by a combination of histologic, magnetic resonance imaging (MRI), immunofluorescence, molecular, cellular, and behavioral assessments. EP1R was expressed primarily in neurons and axons but not in astrocytes or microglia after ICH induced by collagenase. In middle-aged male mice subjected to collagenase-induced ICH, EP1R inhibition mitigated brain injury, brain edema, cell death, neuronal degeneration, neuroinflammation, and neurobehavioral deficits, whereas its activation exacerbated these outcomes. EP1R inhibition also was protective in middle-aged female mice and aged male mice after collagenase-induced ICH and in middle-aged male mice after blood- or thrombin-induced ICH. EP1R inhibition also reduced oxidative stress, white matter injury, and brain atrophy and improved functional outcomes. Histologic results were confirmed by MRI. Src kinase phosphorylation and matrix metalloproteinase-9 activity were increased by EP1R activation and decreased by EP1R inhibition. EP1R regulated matrix metalloproteinase-9 activity through Src kinase signaling, which mediated EP1R toxicity after collagenase-induced ICH. We conclude that prostaglandin E2 EP1R activation plays a toxic role after ICH through mechanisms that involve the Src kinases and the matrix metalloproteinase-9 signaling pathway. EP1R inhibition could be a novel therapeutic strategy to improve outcomes after ICH.

Discovery and safety profiling of a potent preclinical candidate, (4-[4-[[(3R)-3-(hydroxycarbamoyl)-8-azaspiro[4.5]decan-3-yl]sulfonyl]phenoxy]-N-methylbenzamide) (CM-352), for the prevention and treatment of hemorrhage

Discovery of potent and safe therapeutics that improve upon currently available antifibrinolytics, e.g., tranexamic acid (TXA, 1) and aprotinin, has been challenging. Matrix metalloproteinases (MMPs) participate in thrombus dissolution. Then we designed a novel series of optimized MMP inhibitors that went through phenotypic screening consisting of thromboelastometry and mouse tail bleeding. Our optimized lead compound, CM-352 (2), inhibited fibrinolysis in human whole blood functional assays and was more effective than the current standard of care, 1, in the tail-bleeding model using a 30 000 times lower dose. Moreover, 2 reduced blood loss during liver hepatectomy, while 1 and aprotinin had no effect. Molecule 2 displayed optimal pharmacokinetic and safety profiles with no evidence of thrombosis or coagulation impairment. This novel mechanism of action, targeting MMP, defines a new class of antihemorrhagic agents without interfering with normal hemostatic function. Furthermore, 2 represents a preclinical candidate for the acute treatment of bleeding.

Rosiglitazone infusion therapy following minimally invasive surgery for intracerebral hemorrhage evacuation decreases matrix metalloproteinase-9 and blood-brain barrier disruption in rabbits

Background

The objective of this study was to investigate the effects of Rosiglitazone (RSG) infusion therapy following minimally invasive surgery (MIS) for intracerebral hemorrhage(ICH) evacuation on perihematomal secondary brain damage as assessed by MMP-9 levels, blood–brain barrier (BBB) permeability and neurological function.

Methods

A total of 40 male rabbits (2.8–3.4 kg) was randomly assigned to a normal control group (NC group; 10 rabbits), a model control group (MC group; 10 rabbits), a minimally invasive treatment group (MIS group; 10 rabbits) or a combined MIS and RSG group (MIS + RSG group; 10 rabbits). ICH was induced in all the animals, except for the NC group. MIS was performed to evacuate ICH 6 hours after the successful preparation of the ICH model in the MIS and MIS + RSG groups. The animals in the MC group underwent the same procedures for ICH evacuation but without hematoma aspiration, and the NC group was subjected to sham surgical procedures. The neurological deficit scores (Purdy score) and ICH volumes were determined on days 1, 3 and 7. All of the animals were sacrificed on day 7, and the perihematomal brain tissue was removed to determine the levels of PPARγ, MMP-9, BBB permeability and brain water content (BWC).

Results

The Purdy score, perihematomal PPARγ levels, BBB permeability, and BWC were all significantly increased in the MC group compared to the NC group. After performing the MIS for evacuating the ICH, the Purdy score and the ICH volume were decreased on days 1, 3 and 7 compared to the MC group. A remarkable decrease in perihematomal levels of PPARγ, MMP-9, BBB permeability and BWC were observed. The MIS + RSG group displayed a remarkable increase in PPARγ as well as significant decrease in MMP-9, BBB permeability and BWC compared with the MIS group.

Conclusions

RSG infusion therapy following MIS for ICH treatment might be more efficacious for reducing the levels of MMP-9 and secondary brain damage than MIS therapy alone.

Design, synthesis, and biological evaluation of novel matrix metalloproteinase inhibitors as potent antihemorrhagic agents: from hit identification to an optimized lead

Growing evidence suggests that matrix metalloproteinases (MMP) are involved in thrombus dissolution; then, considering that new therapeutic strategies are required for controlling hemorrhage, we hypothesized that MMP inhibition may reduce bleeding by delaying fibrinolysis. Thus, we designed and synthesized a novel series of MMP inhibitors to identify potential candidates for acute treatment of bleeding. Structure-based and knowledge-based strategies were utilized to design this novel chemical series, α-spiropiperidine hydroxamates, of potent and soluble (>75 μg/mL) pan-MMP inhibitors. The initial hit, 12, was progressed to an optimal lead 19d. Racemic 19d showed a remarkable in vitro phenotypic response and outstanding in vivo efficacy; in fact, the mouse bleeding time at 1 mg/kg was 0.85 min compared to 29.28 min using saline. In addition, 19d displayed an optimal ADME and safety profile (e.g., no thrombus formation). Its corresponding enantiomers were separated, leading to the preclinical candidate 5 (described in Drug Annotations series, J. Med. Chem. 2015, ).

PGE2 receptor agonist misoprostol protects brain against intracerebral hemorrhage in mice

Intracerebral hemorrhage (ICH) is a devastating form of stroke. Misoprostol, a synthetic prostaglandin E1 (PGE1) analog and PGE2 receptor agonist, has shown protection against cerebral ischemia. In this study, we tested the efficacy of misoprostol in the 12-month-old mice subjected to 1 of 2 complementary ICH models, the collagenase model (primary study) and blood model (secondary study, performed in an independent laboratory). We also investigated its potential mechanism of action. Misoprostol posttreatment decreased brain lesion volume, edema, and brain atrophy and improved long-term functional outcomes. In the collagenase-induced ICH model, misoprostol decreased cellular inflammatory response; attenuated oxidative brain damage and gelatinolytic activity; and decreased high-mobility group box 1 (HMGB1) expression, Src kinase activity, and interleukin-1β expression without affecting cyclooxygenase-2 expression. Furthermore, HMGB1 inhibition with glycyrrhizin decreased Src kinase activity, gelatinolytic activity, neuronal death, and brain lesion volume. Src kinase inhibition with 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) decreased gelatinolytic activity and brain edema and improved neurologic function but did not decrease HMGB1 protein level. These results indicate that misoprostol protects brain against ICH injury through mechanisms that may involve the HMGB1, Src kinase, and matrix metalloproteinase-2/9 pathways.

Effects of focal mild hypothermia on thrombin-induced brain edema formation and the expression of protease activated receptor-1, matrix metalloproteinase-9 and aquaporin 4 in rats

Hypothermia is an effective neuroprotective treatment for brain injury caused by intracerebral hemorrhage (ICH). It is reported to reduce brain edema and neuronal cell death. Thrombin, a coagulation protease released from blood clots, is critical in brain edema formation following ICH. Protease activated receptor‑1 (PAR‑1), matrix metalloproteinase‑9 (MMP‑9) and aquaporin 4 (AQP4) are edema‑associated mediators that have been implicated in ICH pathology. In the present study, thrombin was used to induce brain edema in adult male Sprague‑Dawley rats. Differences between a focal mild hypothermic group (33±0.5˚C) and a normothermic group (37˚C) were investigated. Following hypothermia, brain water content and blood‑brain barrier (BBB) disruption was assessed at 6, 24 and 48 h and subsequently at 3, 5 and 7 days. At the same time, the mRNA and protein expression of PAR‑1, MMP‑9 and AQP4 were also determined. It was identified that brain water content and BBB disruption increased at 6 h and reached a maximal level at 24 h in the normothermic group. The mRNA and protein expression levels of PAR‑1, MMP‑9 and AQP4 started to increase at 24 h and reached a maximal level at 48 h. Focal mild hypothermia tended to significantly reduce brain water content, BBB disruption and PAR‑1, MMP‑9 and AQP expression at 24 and 48 h. The present data suggest that focal mild hypothermia is an effective treatment for edema formation through moderation of the mRNA and protein expression of PAR‑1, MMP‑9 and AQP4.

Effects of minimally invasive procedures for evacuation of intracerebral hematoma in early stages on MMP-9 and BBB permeability in rabbits

BACKGROUND

The effects of performing a minimally invasive procedure at different stages after intracerebral hemorrhage on perihematomal MMP-9 expression and blood-brain barrier (BBB) permeability were evaluated.

METHODS

Sixty rabbits were randomly distributed into a model control group (MC group, 30 rabbits) or a minimally invasive group (MI group, 30 rabbits). A model of intracerebral hemorrhage was established in the MC and MI group. In the MI group, the intracerebral hematoma was evacuated by stereotactic minimally invasive procedures over 6 hours (6 rabbits), 12 hours (6 rabbits), 18 hours (6 rabbits) 24 hours or 48 hours (6 rabbits) following successful induction of intracerebral hemorrhage. The same procedure was performed in the MC group at the same time point but without evacuating the hematoma. All the animals were sacrificed within two weeks after the hematoma was surgically evacuated. A neurological deficit score was determined, and the perihematomal MMP-9 level and the BBB permeability were measured.

RESULTS

The neurological deficit score, perihematomal MMP-9 level and BBB permeability of the MI group decreased significantly compared to the MC group. Performing the MI procedure 6-12 h after intracerebral hemorrhage showed the most favorable outcome.

CONCLUSIONS

Regarding the pathophysiological changes surrounding the hematoma, the optimal time window of performing MI procedures for the intracerebral hematoma evacuation might be within 6-12 h after hemorrhage.

(-)-Epicatechin protects hemorrhagic brain via synergistic Nrf2 pathways

Objective

In the wake of intracerebral hemorrhage (ICH), a devastating stroke with no effective treatment, hemoglobin/iron-induced oxidative injury leads to neuronal loss and poor neurologic outcomes. (-)-Epicatechin (EC), a brain-permeable flavanol that modulates redox/oxidative stress via the NF-E2–related factor (Nrf) 2 pathway, has been shown to be beneficial for vascular and cognitive function in humans. Here, we examined whether EC can reduce early brain injury in ICH mouse models and investigated the underlying mechanisms.

Methods

ICH was induced by injecting collagenase, autologous blood, or thrombin into mouse striatum. EC was administered orally at 3 h after ICH and then every 24 h. Lesion volume, neurologic deficits, brain edema, reactive oxygen species, and protein expression and activity were evaluated.

Results

EC significantly reduced lesion volume and ameliorated neurologic deficits in both male and female ICH mice. Cell death and neuronal degeneration were decreased in the perihematomal area and were associated with reductions in caspase-3 activity and high-mobility group protein B1 (HMGB-1) level. These changes were accompanied by attenuation of oxidative insults, increased phase II enzyme expression, and increased Nrf2 nuclear accumulation. Interestingly, in addition to providing neuroprotection via Nrf2 signaling, EC diminished heme oxygenase-1 induction and brain iron deposition via an Nrf2-independent pathway that downregulated ICH-induced activating protein-1 activation and decreased matrix metalloproteinase 9 activity, lipocalin-2 levels, iron-dependent cell death, and ferroptosis-related gene expression.

Interpretation

Collectively, our data show that EC protects against ICH by activation of Nrf2-dependent and -independent pathways and may serve as a potential intervention for patients with ICH.

Acute and delayed protective effects of pharmacologically induced hypothermia in an intracerebral hemorrhage stroke model of mice

Hemorrhagic stroke, including intracerebral hemorrhage (ICH), is a devastating subtype of stroke; yet, effective clinical treatment is very limited. Accumulating evidence has shown that mild to moderate hypothermia is a promising intervention for ischemic stroke and ICH. Current physical cooling methods, however, are less efficient and often impractical for acute ICH patients. The present investigation tested pharmacologically induced hypothermia (PIH) using the second-generation neurotensin receptor (NTR) agonist HPI-201 (formerly known as ABS-201) in an adult mouse model with ICH. Acute or delayed administrations of HPI-201 (2mg/kg bolus injection followed by 2 injections of 1mg/kg, i.p.) were initiated at 1 or 24h after ICH. HPI-201 induced mild hypothermia within 30 min and body and brain temperatures were maintained at 32.7 ± 0.4°C for at least 6h without causing observable shivering. With the 1-h delayed treatment, HPI-201-induced PIH significantly reduced ICH-induced cell death and brain edema compared to saline-treated ICH animals. When HPI-201-induced hypothermia was initiated 24h after the onset of ICH, it still significantly attenuated brain edema, cell death and blood-brain barrier breakdown. HPI-201 significantly decreased the expression of matrix metallopeptidase-9 (MMP-9), reduced caspase-3 activation, and increased Bcl-2 expression in the ICH brain. Moreover, ICH mice received 1-h delayed HPI-201 treatment performed significantly better in the neurological behavior test 48 h after ICH. All together, these data suggest that systemic injection of HPI-201 is an effective hypothermic strategy that protects the brain from ICH injury with a wide therapeutic window. The protective effect of this PIH therapy is partially mediated through the alleviation of apoptosis and neurovascular damage. We suggest that pharmacological hypothermia using the newly developed neurotensin analogs is a promising therapeutic treatment for ICH.

Mitochondrial impairment induced by 3-nitropropionic acid is enhanced by endogenous metalloprotease activity inhibition in cultured rat striatal neurons

Metalloproteases from the metzincin family mediate molecule processing at the cell membrane termed ectodomain shedding (ES). This mechanism enables the generation of intracellular and extracellular fragments from cell membrane molecules that exert additional functions involved in cell processes including cell death, beyond those of full length molecules. Micotoxin 3-nitropropionic acid (3-NP) induces striatal neuronal degeneration in vivo and in vitro through mitochondrial complex II inhibition. In this study, we hypothesized that metalloproteases regulate mitochondrial activity in cultured rat striatal neurons undergoing degeneration. To test this idea, striatal neuronal cultures characterized by NeuN and GAD-67 expression were treated with 3-NP together with the metalloprotease inhibitor GM6001 and their mitochondrial activity was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Our results showed that metalloprotease inhibition potentiated mitochondrial activity impairment induced by 3-NP whereas the inhibitor alone had no effect. These results indicate that metalloproteases regulate and promote mitochondrial functionality in striatal neurons undergoing degeneration induced by 3-NP. Since NMDA receptor is involved in the excitotoxic neuronal death triggered by 3-NP and is known to undergo ES, we analyzed NMDAR subunit NR1 phenotypic distribution by immunofluorescence. 3-NP and GM6001 induced abnormal perinuclear NR1 accumulation that was not observed with 3-NP or GM6001 alone. This observation suggests that metalloproteases are involved in NR1 cellular reorganization induced by 3-NP, and that their inhibition results in abnormal NR1 distribution. Together results indicate that endogenous metalloproteases are activated during striatal neurodegeneration induced by 3-NP eliciting an adaptative or compensatory response that protects mitochondrial functionality.

Overcoming neurite-inhibitory chondroitin sulfate proteoglycans in the astrocyte matrix

Acute trauma to the central nervous system (CNS) can result in permanent damage and loss of function related to the poor regeneration of injured axons. Injured axons encounter several barriers to regeneration, such as the glial scar at the injury site. The glial scar contains extracellular matrix (ECM) macromolecules deposited by reactive astrocytes in response to injury. The scar ECM is rich in chondroitin sulfate proteoglycans (CSPGs), macromolecules that inhibit axonal growth. CSPGs consist of a core protein with attachment sites for glycosaminoglycan (GAG) chains. An extensive literature demonstrates that enzymatic removal of the GAG chains by chondroitinase ABC permits some axonal regrowth; however, the remaining intact core proteins also possess inhibitory domains. Because metalloproteinases can degrade core proteins of CSPGs, we have evaluated five matrix metalloproteinases (MMPs) and a related protease-a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4)-for their capacity to overcome CSPG inhibition of neuritic growth in culture. The metalloproteinases were selected for their known expression after CNS injuries. Of the MMPs, MMP-3, -7 and -8 reduced or abolished inhibition of neurite outgrowth on a purified CSPG substrate and on an astrocyte-derived ECM. ADAMTS-4 also attenuated CSPG inhibition of neurites and had the additional benefits of neither degrading laminin nor causing neurotoxicity. The efficacy of ADAMTS-4 matched that of blocking the EGFR signaling previously reported to mediate CSPG inhibition. These findings highlight ADAMTS-4 as a superior protease for overcoming CSPG inhibition of axonal regeneration in the CNS.

Early stage minimally invasive procedures reduce perihematomal MMP-9 and blood-brain barrier disruption in a rabbit model of intracerebral hemorrhage

INTRODUCTION

The effects of performing a minimally invasive procedure at different stages after intracerebral hemorrhage (ICH) on perifocal MMP-9 expression and blood-brain barrier (BBB) permeability were evaluated.

METHODS

Thirty-six rabbits were randomly distributed into a normal control group (NC group, six rabbits), a model control group (MC group, six rabbits), and a minimally invasive group (MI group, 24 rabbits). A model of ICH was established in the MC and MI groups. In the MI group, the intracerebral hematoma was evacuated by stereotactic minimally invasive procedures over 6 hours (six rabbits), 12 hours (six rabbits), 18 hours (six rabbits), and 24 hours (six rabbits), following successful induction of ICH. All animals were sacrificed within 48 hours after the hematoma was surgically evacuated. A neurological deficit score was determined, and the perihematomal MMP-9 level and the BBB permeability were measured.

RESULTS

The neurological deficit score, the perihematomal MMP-9 level, and the BBB permeability of the MI group were decreased significantly compared with the MC group. Performing the MI procedure 6-12 hours after ICH showed the most significant decrease in MMP-9, BBB permeability, and neurological deficit score.

CONCLUSION

The optimal time window of performing MI procedures for the intracerebral hematoma evacuation might be within 6-12 hours after hemorrhage.

Toll-like receptor 4 signaling in intracerebral hemorrhage-induced inflammation and injury

Intracerebral hemorrhage (ICH) is a common type of fatal stroke, accounting for about 15% to 20% of all strokes. Hemorrhagic strokes are associated with high mortality and morbidity, and increasing evidence shows that innate immune responses and inflammatory injury play a critical role in ICH-induced neurological deficits. However, the signaling pathways involved in ICH-induced inflammatory responses remain elusive. Toll-like receptor 4 (TLR4) belongs to a large family of pattern recognition receptors that play a key role in innate immunity and inflammatory responses. In this review, we summarize recent findings concerning the involvement of TLR4 signaling in ICH-induced inflammation and brain injury. We discuss the key mechanisms associated with TLR4 signaling in ICH and explore the potential for therapeutic intervention by targeting TLR4 signaling.

Albumin induces upregulation of matrix metalloproteinase-9 in astrocytes via MAPK and reactive oxygen species-dependent pathways

BACKGROUND

Astrocytes are an integral component of the blood-brain barrier (BBB) which may be compromised by ischemic or traumatic brain injury. In response to trauma, astrocytes increase expression of the endopeptidase matrix metalloproteinase (MMP)-9. Compromise of the BBB leads to the infiltration of fluid and blood-derived proteins including albumin into the brain parenchyma. Albumin has been previously shown to activate astrocytes and induce the production of inflammatory mediators. The effect of albumin on MMP-9 activation in astrocytes is not known. We investigated the molecular mechanisms underlying the production of MMP-9 by albumin in astrocytes.

METHODS

Primary enriched astrocyte cultures were used to investigate the effects of exposure to albumin on the release of MMP-9. MMP-9 expression was analyzed by zymography. The involvement of mitogen-activated protein kinase (MAPK), reactive oxygen species (ROS) and the TGF-β receptor-dependent pathways were investigated using pharmacological inhibitors. The production of ROS was observed by dichlorodihydrofluorescein diacetate fluorescence. The level of the MMP-9 inhibitor tissue inhibitor of metalloproteinase (TIMP)-1 produced by astrocytes was measured by ELISA.

RESULTS

We found that albumin induces a time-dependent release of MMP-9 via the activation of p38 MAPK and extracellular signal regulated kinase, but not Jun kinase. Albumin-induced MMP-9 production also involves ROS production upstream of the MAPK pathways. However, albumin-induced increase in MMP-9 is independent of the TGF-β receptor, previously described as a receptor for albumin. Albumin also induces an increase in TIMP-1 via an undetermined mechanism.

CONCLUSIONS

These results link albumin (acting through ROS and the p38 MAPK) to the activation of MMP-9 in astrocytes. Numerous studies identify a role for MMP-9 in the mechanisms of compromise of the BBB, epileptogenesis, or synaptic remodeling after ischemia or traumatic brain injury. The increase in MMP-9 produced by albumin further implicates both astrocytes and albumin in the acute and long-term complications of acute CNS insults, including cerebral edema and epilepsy.

Chemokines and their receptors in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating clinical event which results in a high rate of disability and death. At present, no effective treatment is available for ICH. Accumulating evidence suggests that inflammatory responses contribute significantly to the ICH-induced secondary brain outcomes. During ICH, inflammatory cells accumulate at the ICH site attracted by gradients of chemokines. This review summarizes recent progress in ICH studies and the chemoattractants that act during the injury and focuses on and introduces the basic biology of the chemokine monocyte chemoattractant protein-1 (MCP1) and its role in the progression of ICH. Better understanding of MCP1 signaling cascade and the compensation after its inhibition could shed light on the development of effective treatments for ICH.

A critical appraisal of experimental intracerebral hemorrhage research

The likelihood of translating therapeutic interventions for stroke rests on the quality of preclinical science. Given the limited success of putative treatments for ischemic stroke and the reasons put forth to explain it, we sought to determine whether such problems hamper progress for intracerebral hemorrhage (ICH). Approximately 10% to 20% of strokes result from an ICH, which results in considerable disability and high mortality. Several animal models reproduce ICH and its underlying pathophysiology, and these models have been widely used to evaluate treatments. As yet, however, none has successfully translated. In this review, we focus on rodent models of ICH, highlighting differences among them (e.g., pathophysiology), issues with experimental design and analysis, and choice of end points. A Pub Med search for experimental ICH (years: 2007 to 31 July 2011) found 121 papers. Of these, 84% tested neuroprotectants, 11% tested stem cell therapies, and 5% tested rehabilitation therapies. We reviewed these to examine study quality (e.g., use of blinding procedures) and choice of end points (e.g., behavioral testing). Not surprisingly, the problems that have plagued the ischemia field are also prevalent in ICH literature. Based on these data, several recommendations are put forth to facilitate progress in identifying effective treatments for ICH.

PDGFR-α inhibition preserves blood-brain barrier after intracerebral hemorrhage

OBJECTIVE

Perihematomal edema results from disruption of the blood-brain barrier (BBB) by key mediators, such as thrombin, following intracerebral hemorrhage (ICH). Platelet-derived growth factor receptor alpha (PDGFR-α), a tyrosine kinase receptor, was found in previous studies to play a role in orchestrating BBB impairment. In the present study, we investigated the role of PDGFR-α following ICH-induced brain injury in mice, specifically investigating its effect on BBB disruption.

METHODS

Brain injury was induced by autologous arterial blood (30 μl) or thrombin (5 U) injection into mice brains. A PDGFR antagonist (Gleevec) or agonist (PDGF-AA) was administered following ICH. PDGF-AA was injected with a thrombin inhibitor, hirudin, in ICH mice. Thrombin-injected mice were given Gleevec or PDGF-AA neutralizing antibody. A p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, was delivered with PDGF-AA in naïve animals. Postassessment included neurological function tests, brain edema measurement, Evans blue extravasation, immunoprecipitation, western blot, and immunohistology assay.

RESULTS

PDGFR-α suppression prevented neurological deficits, brain edema, and Evans blue extravasation at 24 to 72 hours following ICH. PDGFR-α activation led to BBB impairment and this was reversed by SB203580 in naïve mice. Thrombin inhibition suppressed PDGFR-α activation and exogenous PDGF-AA increased PDGFR-α activation, regardless of thrombin inhibition. Animals receiving a PDGF-AA-neutralizing antibody or Gleevec showed minimized thrombin injection-induced BBB impairment.

INTERPRETATION

PDGFR-α signaling may contribute to BBB impairment via p38 MAPK-mediated matrix metalloproteinase (MMP) activation/expression following ICH, and thrombin may be the key upstream orchestrator. The therapeutic interventions targeting the PDGFR-α signaling may be a novel strategy to prevent thrombin-induced BBB impairment following ICH.

Efficacy of the lipid-soluble iron chelator 2,2'-dipyridyl against hemorrhagic brain injury

Previous studies have indicated that 2,2'-dipyridyl, a lipid-soluble ferrous iron chelator, can reduce brain injury after cerebral ischemia and reduce cerebral vasospasm after subarachnoid hemorrhage. In this study, we examined the efficacy of 2,2'-dipyridyl after intracerebral hemorrhage (ICH) in 12-month-old mice. ICH was modeled by intrastriatal injection of collagenase or autologous whole blood. 2,2'-Dipyridyl or vehicle was administered intraperitoneally 2h before ICH (pretreatment) or 6h after ICH (post-treatment) and then once daily for up to 3 days. Mice in the pretreatment group were sacrificed 1 or 3 days after ICH and examined for iron deposition, neuronal death, oxidative stress, microglial/astrocyte activation, neutrophil infiltration, and white matter damage. Mice in the post-treatment group were examined for brain lesion volume and edema on day 3 and for neurologic deficits on days 1, 3, and 28 after ICH. Pretreatment with 2,2'-dipyridyl decreased iron accumulation and neuronal death, attenuated production of reactive oxygen species, reduced microglial activation without affecting astrocytes or neutrophil infiltration, and attenuated white matter damage. Post-treatment reduced brain lesion volume and edema and improved neurologic function. These results indicate that the lipid-soluble ferrous iron chelator 2,2'-dipyridyl can reduce brain injury and improve functional outcome after ICH.

Iron toxicity in mice with collagenase-induced intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating form of stroke. In this study, we examined the efficacy of deferoxamine (DFX), an iron chelator, after collagenase-induced ICH in 12-month-old mice. Intracerebral hemorrhage was induced by intrastriatal injection of collagenase. Deferoxamine (200  mg/kg, intraperitoneal) or vehicle was administrated 6  hours after ICH and then every 12  hours for up to 3 days. Neurologic deficits were examined on days 1 and 3 after ICH. Mice were killed after 1 or 3 days of DFX treatment for examination of iron deposition, neuronal death, oxidative stress, microglia/astrocyte activation, neutrophil infiltration, brain injury volume, and brain edema and swelling. Collagenase-induced ICH resulted in iron overload in the perihematomal region on day 3. Systemic administration of DFX decreased iron accumulation and neuronal death, attenuated production of reactive oxygen species, and reduced microglial activation and neutrophil infiltration without affecting astrocytes. Although DFX did not reduce brain injury volume, edema, or swelling, it improved neurologic function. Results of our study indicate that iron toxicity contributes to collagenase-induced hemorrhagic brain injury and that reducing iron accumulation can reduce neuronal death and modestly improve functional outcome after ICH in mice.

Mesenchymal stem cells support dorsal root ganglion neurons survival by inhibiting the metalloproteinase pathway

The positive effect of adult undifferentiated mesenchymal stem cells (MSCs) on neuronal survival has already been reported, although the mechanisms by which MSCs exert their effect are still a matter of debate. Here we have demonstrated that MSCs are able to prolong the survival of dorsal root ganglion (DRG) neurons mainly by inhibiting some proteolytic enzymes, and in particular the pathway of metalloproteinases (MMPs), a family of proteins that are involved in many neuronal processes, including survival. The inhibition of MMPs was both direct, by acting on MT-MMP1, and indirect, by acting on those proteins that regulate MMPs' activation, such as Timp-1 and Sparc. The importance of the MMPs' down-regulation for neuronal survival was also demonstrated by using N-isobutyl-N-(4-methoxyphenylsulfonyl)-glycyl hydroxamic acid (NNGH), a wide range inhibitor of metalloproteinases, which was able to increase the survival of DRG neurons in a significant manner. The down-regulation of MMPs, obtained both by MSC contact and by chemical inhibition, led to the inactivation of caspase 3, the executor of apoptotic death in DRG neurons cultured alone, while caspase 7 was found to be irrelevant for the apoptotic process. The capacity of MSCs to prevent apoptosis mainly by inactivating the metalloproteinase pathway is an important finding that sheds light on MSCs' mechanism of action, making undifferentiated MSCs a promising tool for the treatment of many different neurodegenerative pathologies.

Inflammation in neurological disorders: a help or a hindrance?

Inflammation of the central nervous system (CNS) (neuroinflammation) is now recognized to be a feature of all neurological disorders. In multiple sclerosis, there is prominent infiltration of various leukocyte subsets into the CNS. Even when there is no significant inflammatory infiltrates, such as in Parkinson or Alzheimer disease, there is intense activation of microglia with resultant elevation of many inflammatory mediators within the CNS. An extensive dataset describes neuroinflammation to have detrimental consequences, but results emerging largely over the past decade have indicated that aspects of the inflammatory response are beneficial for CNS outcomes. Benefits of neuroinflammation now include neuroprotection, the mobilization of neural precursors for repair, remyelination, and even axonal regeneration. The findings that neuroinflammation can be beneficial should not be surprising as a properly directed inflammatory response in other tissues is a natural healing process after an insult. In this article, we review the data that highlight the dual aspects of neuroinflammation in being a hindrance on the one hand but also a significant help for recovery of the CNS on the other. We consider how the inflammatory response may be beneficial or injurious, and we describe strategies to harness the beneficial aspects of neuroinflammation.

Exploring neuroprotective drug therapies for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating neurological disorder with high mortality and poor prognosis, for which virtually no effective drug therapies are available at present. Experimental animal models, based on intrastriatal injection of collagenase or autologous blood, have enabled great advances in elucidation of cellular/molecular events contributing to brain pathogenesis associated with ICH. Many lines of evidence indicate that blood constituents, including hemoglobin-derived products as well as proteases such as thrombin, play important roles in the pathogenic events. Inflammatory reactions involving neutrophils, activated microglia, and production of proinflammatory cytokines also constitute a critical aspect of pathology leading to neurodegeneration and tissue damage. Efforts are continuing to find drugs that potentially alleviate pathological and neurological outcomes of ICH. Various drugs that possess antioxidative, anti-inflammatory or neurotrophic/neuroprotective properties have been demonstrated to produce therapeutic effects on ICH animal models. Drugs already in clinical use such as minocycline, statins, and several nuclear receptor ligands are among the list of effective drugs, but whether they also show therapeutic efficacy in human ICH patients remains unproven. Here, current knowledge of ICH pathogenesis and problems arising with respect to exploration of new drug candidates are discussed.

Matrix metalloproteinases are modifiers of huntingtin proteolysis and toxicity in Huntington's disease

Proteolytic cleavage of huntingtin (Htt) is known to be a key event in the pathogenesis of Huntington's disease (HD). Our understanding of proteolytic processing of Htt has thus far focused on the protease families-caspases and calpains. Identifying critical proteases involved in Htt proteolysis and toxicity using an unbiased approach has not been reported. To accomplish this, we designed a high-throughput western blot-based screen to examine the generation of the smallest N-terminal polyglutamine-containing Htt fragment. We screened 514 siRNAs targeting the repertoire of human protease genes. This screen identified 11 proteases that, when inhibited, reduced Htt fragment accumulation. Three of these belonged to the matrix metalloproteinase (MMP) family. One family member, MMP-10, directly cleaves Htt and prevents cell death when knocked down in striatal Hdh(111Q/111Q) cells. Correspondingly, MMPs are activated in HD mouse models, and loss of function of Drosophila homologs of MMPs suppresses Htt-induced neuronal dysfunction in vivo.

Effects of minimally invasive procedures for removal of intracranial hematoma on matrix metalloproteinase expression and blood-brain barrier permeability in perihematomal brain tissues

OBJECTIVE

To observe the effects of minimally invasive removal of intracerebral hematoma on perihematomal matrix metalloproteinase (MMP)-9 expressions and permeability of blood-brain barrier (BBB).

METHODS

Twenty-four rabbits of 2.8-3.4 kg body weight (regardless of male and female) were selected and randomly divided into a control group and a minimally invasive group, and the model of intracranial hemorrhage (ICH) was established in the two groups by injecting fresh autologous non-anticoagulant blood into the brain basal ganglia of rabbits. The minimally invasive procedures for removal of intracranial hematoma were performed 6 hours after the model of ICH was established successfully. All the animals were killed on the first, third, and seventh days after the model of ICH was established, and the perihematomal brain tissues were extracted to observe MMP-9 expressions by immunohistochemical methods. The permeability of BBB was detected by Evans blue (EB) as a tracer.

RESULTS

The numbers of neurons with expression of MMP-9 in perihematomal brain tissues on the first, third, and seventh days after minimally invasive removal of hematoma were 5.00±2.94, 13.75±7.89, and 8±6.98 respectively, while in model control group were 25.25±6.85, 39.01±10.68, and 23.12±5.72 respectively. Expression of MMP-9 in the minimally invasive group decreased significantly as compared with that of model control group, and a significant difference was observed. The content of EB in perihematomal brain tissues on the first, third and seventh days was 28.41±0.72, 34.04±1.48, and 26.30±0.78 μg respectively in minimally invasive group, and 31.24±1.02, 37.13±1.57, and 28.72±0.23 μg in the control group. A significant decrease in EB content in minimally invasive group was observed in the brain tissue around the hematoma as compared with that of control group, suggesting that the BBB permeability was reduced.

CONCLUSIONS

The minimally invasive procedure for removal of intracranial hematoma could decrease the MMP-9 expression and BBB permeability in perihematomal brain tissues. It might be helpful in reducing secondary brain damages after intracerebral hemorrhage.