Pronounced α-Synuclein Pathology in a Seeding-Based Mouse Model Is Not Sufficient to Induce Mitochondrial Respiration Deficits in the Striatum and Amygdala.

Increasing evidence suggests that cross talk between α-synuclein pathology formation and mitochondrial dysfunction plays a central role in the pathogenesis of Parkinson's disease (PD) and related synucleinopathies. While mitochondrial dysfunction is a well-studied phenomenon in the substantia nigra, which is selectively vulnerable in PD and some models thereof, less information is available in other brain regions that are also affected by synuclein pathology. Therefore, we sought to test the hypothesis that early α-synuclein pathology causes mitochondrial dysfunction and that this effect might be exacerbated in conditions of increased vulnerability in affected brain regions, such as the amygdala. We combined a model of intracerebral α-synuclein pathology seeding with chronic glucocorticoid treatment, which models non-motor symptoms of PD and affects amygdala physiology. We measured mitochondrial respiration, reactive oxygen species (ROS) generation and protein abundance as well as α-synuclein pathology in male mice. Chronic corticosterone administration induced mitochondrial hyperactivity in the amygdala. Although injection of α-synuclein preformed fibrils (PFFs) into the striatum resulted in pronounced α-synuclein pathology in both striatum and amygdala, mitochondrial respiration in these brain regions was not compromised, regardless of corticosterone treatment. Our results suggest that early stage α-synuclein pathology does not influence mitochondrial respiration in the striatum and amygdala, even in corticosterone-induced respirational hyperactivity. We discuss our findings in light of relevant literature, warn of a potential publication bias and encourage scientists to report their negative results within the framework of this model.

Chronic corticosterone aggravates behavioral and neuronal symptomatology in a mouse model of alpha-synuclein pathology.

Debilitating, yet underinvestigated nonmotor symptoms related to mood/emotion, such as depression, are common in Parkinson's disease. Here, we explore the role of depression and of the amygdala, a brain region robustly linked to mood/emotion, in synucleinopathy. We hypothesized that mood/emotional deficits might accelerate Parkinson's disease-linked symptomatology, including the formation of α-synuclein pathology. We combined elevated corticosterone treatment, modeling chronic stress and depression, with a model of seeded α-synuclein pathology in mouse striatum and assessed behavioral parameters with a focus on mood/emotion, and neuropathology. We report behavioral resilience against α-synuclein proteinopathy in the absence of additional insults, potentially based on hormesis/conditioning mechanisms. Elevated corticosterone, however, reversed α-synuclein pathology-induced behavioral adaptations and was associated with increased dopaminergic cell loss as well as aggravated α-synuclein pathology in specific brain regions, such as the entorhinal cortex. These findings point to elevated glucocorticoids as a risk factor for Parkinson's disease progression and highlight the potential of glucocorticoid level reducing strategies to slow down disease progression in synucleinopathy.

Impact of propofol anaesthesia on cytokine expression profiles in the developing rat brain: a randomised placebo-controlled experimental in-vivo study.

BACKGROUND: Recent experimental data indicate that volatile anaesthetics can induce a neuroinflammatory response in the central nervous system. The questions of to what extent this occurs in the developing brain and whether nonvolatile anaesthetics are also involved remain unanswered. OBJECTIVES: The objective of this study is to investigate the impact of propofol anaesthesia on cytokine mRNA expression profiles in the neonatal brain at defined stages of the brain growth spurt. DESIGN: A randomised placebo-controlled experimental in-vivo study. SETTING: Translational research laboratories at the University of Geneva Medical School. METHODS: Wistar rats received 6-h propofol anaesthesia at postnatal day 10 or 20. A quantitative real-time PCR was used to evaluate the impact of this treatment paradigm on mRNA expression profiles of selected members of the cytokine family in the prefrontal cortex and hippocampus. RESULTS: Propofol anaesthesia induced a transient 1.8-fold (interquartile range, IQR 1.7 to 2.2) increase (P = 0.004) in prefrontal but not hippocampal tumour necrosis factor mRNA concentrations in 10-day-old animals. No such effect was detected in 20-day-old animals. No changes in mRNA concentrations of two other pro-inflammatory cytokines, interleukins IL-6 and IL-1ß, were detected following drug exposure at any developmental stages or in any studied brain regions. In contrast, propofol anaesthesia at postnatal day 10 induced a transient increase in the mRNA expression patterns of two chemokines: Ccl2 and Ccl3 [for Ccl2 mRNA: 4.4-fold (3.8 to 5.6) increase in the prefrontal cortex, P = 0.0002 and a 3.5-fold (2.8 to 5.3) increase in the hippocampus, P = 0.0001; for Ccl3 mRNA: 2.9-fold (2.6 to 4.31) increase in the prefrontal cortex, P = 0.0001, and a 2.7-fold (2.2 to 3.6) increase in the hippocampus, P = 0.0003]. Propofol did not affect Ccl2 and Ccl3 mRNA concentrations in 20-day-old animals. In addition, it did not impact on two other members of the chemokine family, Cxcl1 and Cx3cl1, at any time points or in any brain regions investigated. CONCLUSION: This study suggests that propofol anaesthesia does not have a major impact on pro-inflammatory cytokine expression profiles in the developing central nervous system during the brain growth spurt. These results raise arguments against the involvement of neuroinflammatory pathways in propofol-related neurotoxicity observed following the administration of this drug in the early postnatal period.

Recombinant tissue plasminogen activator enhances microglial cell recruitment after stroke in mice.

The effect of recombinant human tissue plasminogen activator (rtPA) on neuroinflammation after stroke remains largely unknown. Here, we tested the effect of rtPA on expression of cellular adhesion molecules, chemokines, and cytokines, and compared those with levels of inflammatory cell recruitment, brain injury, and mortality over 3 days after transient middle cerebral artery occlusion (MCAO) in mice. Mortality was dramatically increased after rtPA treatment compared with saline treatment during the first day of reperfusion. Among the animals that survived, rtPA significantly increased CCL3 expression, microglia recruitment, and cerebral infarction 6 hours after MCAO. In contrast, the extent of neutrophils and macrophages infiltration in the brain was similar in both saline- and rtPA-treated animals. Recombinant human tissue plasminogen activator induced Il1b and Tnf expression, 6 and 72 hours after MCAO, respectively, and dramatically reduced interleukin 6 (IL-6) level 24 hours after reperfusion. A dose response study confirmed the effect of rtPA on CCL3 and Il1b expressions. The effect was similar at the doses of 1 and 10 mg/kg. In conclusion, we report for the first time that rtPA amplified microglia recruitment early after stroke in association with a rapid CCL3 production. This early response may take part in the higher susceptibility of rtPA-treated animals to reperfusion injury.

The prognostic significance of the serum biomarker heart-fatty acidic binding protein in comparison with s100b in severe traumatic brain injury.

The outcome after severe traumatic brain injury (TBI) is largely unfavorable, with approximately two thirds of patients suffering from severe disabilities or dying during the first 6 months. Existing predictive models displayed only limited utility for outcome prediction in individual patients. Time courses of heart-fatty acidic binding protein (H-FABP) and their association with outcome were investigated and compared with S100b. Forty-nine consecutive patients with severe TBI (sTBI; Head component of the Abbreviated Injury Scale [HAIS] >3) with mono and multiple trauma were enrolled in this study. Enzyme-linked immunosorbent assay measured blood concentrations of H-FABP and S100b at 6, 12, 24, and 48 h after TBI. Outcome measures were conscious state at 14 days (Glasgow Coma Scale), disability (Glasgow Outcome Scale Extended; GOSE), and mortality at 3 months. Univariate logistic regression analysis and receiver operating characteristic curves analysis were carried out. Maximal H-FABP and S100b concentrations were observed at 6 h after TBI (34.4±34.0 and 0.64±0.99 ng/mL, respectively). Patients with multi-trauma had significantly higher H-FABP concentrations at 24 and 48 h (22.6±25.6 and 12.4±18.2 ng/mL, respectively), compared to patients with mono trauma (6.9±5.1 and 3.7±4.2 ng/mL, respectively). In the first 48 h, H-FABP and S100b were inversely correlated with the GOSE at 3 months; H-FABP at 48 h predicted mortality with 75% sensitivity and 93% specificity. Early blood levels of H-FABP after sTBI have prognostic significance for survival and disability.

Treatment with Evasin-3 reduces atherosclerotic vulnerability for ischemic stroke, but not brain injury in mice.

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactivity and related neutrophilic inflammation in two mouse models of carotid atherosclerosis and ischemic stroke, respectively. In the first model, the chronic treatment with Evasin-3 as compared with Vehicle (phosphate-buffered saline (PBS)) was investigated in apolipoprotein E-deficient mice implanted of a 'cast' carotid device. In the second model, acute Evasin-3 treatment (5 minutes after cerebral ischemia onset) was assessed in mice subjected to transient left middle cerebral artery occlusion. Although CXCL1 and CXCL2 were upregulated in both atherosclerotic plaques and infarcted brain, only CXCL1 was detectable in serum. In carotid atherosclerosis, treatment with Evasin-3 was associated with reduction in intraplaque neutrophil and matrix metalloproteinase-9 content and weak increase in collagen as compared with Vehicle. In ischemic stroke, treatment with Evasin-3 was associated with reduction in ischemic brain neutrophil infiltration and protective oxidants. No other effects in clinical and histological outcomes were observed. We concluded that Evasin-3 treatment was associated with reduction in neutrophilic inflammation in both mouse models. However, Evasin-3 administration after cerebral ischemia onset failed to improve poststroke outcomes.

Matrix metalloproteinase 9 and cellular fibronectin plasma concentrations are predictors of the composite endpoint of length of stay and death in the intensive care unit after severe traumatic brain injury.

BACKGROUND: The relationship between severe traumatic brain injury (TBI) and blood levels of matrix metalloproteinase-9 (MMP-9) or cellular fibronectin (c-Fn) has never been reported. In this study, we aimed to assess whether plasma concentrations of MMP-9 and c-Fn could have predictive values for the composite endpoint of intensive care unit (ICU) length of stay (LOS) of survivors and mortality after severe TBI. Secondary outcomes were the state of consciousness measured with the Glasgow Coma Scale (GCS) of survivors at 14 days and Glasgow Outcome Scale Extended (GOSE) at 3 months. METHODS: Forty-nine patients with abbreviated injury scores of the head region ≥ 4 were included. Blood was sampled at 6, 12, 24 and 48 hours after injury. MMP-9 and c-Fn concentrations were measured by ELISA. The values of MMP-9 and c-Fn, and, for comparison, the value of the GCS on the field of the accident (fGCS), as predictors of the composite outcome of ICU LOS and death were assessed by logistic regression. RESULTS: There was a linear relationship between maximal MMP-9 concentration, measured during the 6-12-hour period, and maximal c-Fn concentration, measured during the 24-48-hour period. The risk of staying longer than 9 days in the ICU or of dying was increased in patients with a maximal early MMP-9 concentration ≥ 21.6 ng/ml (OR = 5.0; 95% CI: 1.3 to 18.6; p = 0.02) or with a maximal late c-Fn concentration ≥ 7.7 µg/ml (OR = 5.4; 95% CI: 1.4 to 20.8; p = 0.01). A similar risk association was observed with fGCS ≤8 (OR, 4.4; 95% CI, 1.2-15.8; p = 0.02). No relationship was observed between MMP-9, c-Fn concentrations or fGCS and the GCS at 14 days of survivors and GOSE at 3 months. CONCLUSIONS: Plasma MMP-9 and c-Fn concentrations in the first 48 hours after injury are predictive for the composite endpoint of ICU LOS and death after severe TBI but not for consciousness at 14 days and outcome at 3 months.

Increase of arginase activity in old apolipoprotein-E deficient mice under Western diet associated with changes in neurovascular unit.

Aging and atherosclerosis are well-recognized risk factors for cardiac and neurovascular diseases. The Apolipoprotein E deficient (ApoE-/-) mouse on a high-fat diet is a classical model of atherosclerosis, characterized by the presence of atherosclerotic plaques in extracranial vessels but not in cerebral arteries. Increase in arginase activity was shown to participate in vascular dysfunction in the peripheral arteries of atherosclerotic mice by changing the level of nitric oxide (NO). NO plays a key role in the physiological functions of the neurovascular unit (NVU). However, the regulation of arginase expression and activity in the brain was never investigated in association with changes in the NVU, ApoE deficiency and high fat diet.Fourteen-month-old ApoE-/- mice on high-fat diet exhibited deposition of lipids in the NVU, impairment of blood-brain barrier properties, astrogliosis and an increase of aquaporin 4 staining. In association with these changes, brain arginase activity was significantly increased in the old ApoE-/- mice as compared to old wild type mice, with an increase in the level of arginase type I in the blood vessels.In conclusion, aging in this classical mouse model of atherosclerosis induces an increase in the level and activity of arginase I that may impair NO synthesis and contribute to changes in the NVU leading to blood-brain barrier leakage and inflammation.

Matrix metalloproteinase-9 concentration in the cerebral extracellular fluid of patients during the acute phase of aneurysmal subarachnoid hemorrhage.

OBJECTIVES: The pathogenesis of delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH) is multi-factorial and not completely elucidated. Matrix metalloproteinase-9 (MMP-9) might participate in wall remodeling leading to luminal narrowing. The authors investigated MMP-9 concentration in brain extracellular fluid of aSAH patients and assessed whether this enzyme could have a predictive value for the risk of DCI. METHODS: Patients were classified according to the grading of the World Federation of Neurological Surgeons (WFNS) in low- and high-grade patients (WFNS = 1-3, n = 9 and WFNS = 4-5, n = 12, respectively). Cerebral microdialysis probes were placed in brain parenchyma of the respective vascular territory of the aneurysm in 21 consecutive aSAH patients, enrolled in a prospective study on inflammation. Microdialysis samples, collected daily from day 0 until day 8 after aSAH, were retrospectively analyzed for MMP-9 by zymography. RESULTS: Initial concentration of the MMP-9 proform (pro-MMP-9) was significantly higher in high-grade patients as compared to low-grade patients. Furthermore, initial pro-MMP-9 concentration in patients with DCI was seven-fold higher than in asymptomatic patients. Pro-MMP-9 values greater than or equal to 0·27 pg/µl showed 83% sensitivity and 63% specificity in predicting vasospasm. The mature form of the MMP-9 could be preferentially detected in patients with DCI but was usually low. DISCUSSION: The pro and mature forms of MMP-9 were released locally in the brain after aSAH. Pro-MMP-9 release was related to WFNS grade severity. This protease, considered as playing a critical role in endothelial basal membrane damage, may contribute to the inflammatory processes leading to arterial narrowing.

Recombinant tissue plasminogen activator induces blood-brain barrier breakdown by a matrix metalloproteinase-9-independent pathway after transient focal cerebral ischemia in mouse.

The role of the inducible matrix metalloproteinase (MMP)-9 in blood-brain barrier (BBB) disruption after ischemic stroke is well accepted. Recombinant tissue plasminogen activator (r-tPA) is the only approved thrombolytic treatment of ischemic stroke but r-tPA is potentially neurotoxic. Vasogenic edema after r-tPA treatment has been linked with an increase in cerebral MMP-9. However, because cerebral ischemia clearly increases the levels of endogenous tPA, the consequence of additional r-tPA may be questionable. In this study, wild type and MMP-9 knockout mice were subjected to 90 min transient middle cerebral artery occlusion and treated with 10 mg/kg r-tPA. At 24 h after occlusion, BBB permeability, hemispheric enlargement, collagen and laminin degradation as well as cerebral infarction were increased in both wild type and MMP-9 knockout treated animals as compared with non-treated animals. Mortality was increased in wild type but reduced in knockout treated mice. Cerebral MMP-9 concentration was not modified by r-tPA. However, pre-treatment with p-aminobenzoyl-gly-pro-D-leu-D-ala-hydroxamate, a broad-spectrum MMP inhibitor, counteracted the effects of r-tPA on the neurovascular unit and decreased mortality in both wild type and knockout mice. MMP inhibition did not modify cerebral infarction in r-tPA-treated animals. Our results suggest that r-tPA toxicity is mainly independent of MMP-9 after transient middle cerebral artery occlusion but could involve some other MMPs. Additionally, our results support the hypothesis of a dissociation between r-tPA-dependent mechanisms of BBB breakdown and cerebral infarction. Due to the importance of r-tPA in thrombolytic treatment of ischemic stroke patients, the MMPs that could participate in r-tPA-induced BBB disruption should be further characterized.

Effect of the duration of middle cerebral artery occlusion on the risk of hemorrhagic transformation after tissue plasminogen activator injection in rats.

Thrombolysis with tissue plasminogen activator increases the risk of brain hemorrhage after ischemic stoke. However, the relationship between the duration of ischemia and the risk of hemorrhagic transformation is still unclear. In the present study, we used a rat model of thrombolysis with tissue plasminogen activator after different periods of middle cerebral artery occlusion and we analyzed the effect of the duration of ischemia on the rate of hemorrhagic transformation, the extent of cerebral infarction and the degree of neurological impairment. Most of the rats reperfused before 3 h of ischemia did not develop intracerebral hemorrhages, while 90% of the rats occluded for more than 3 h developed cerebral hemorrhages ranging from benign hemorrhagic infarctions to severe parenchymal hemorrhages. After 6-hour occlusion, the proportion of parenchymal hemorrhages, as seen in 50% of the animals, was significantly augmented compared to the 11 to 13% of parenchymal hemorrhages observed in animals occluded for less than 6 h. Meanwhile, the quantity of hemoglobin measured in the brain parenchyma of animals showing hemorrhagic infarctions was doubled (0.19 mg/hemisphere in rats reperfused after 6 h of ischemia compared to 0.08 mg/hemisphere in rats reperfused earlier). Neurological outcome did also worsen with the duration of ischemia. However, the amplitude of cerebral infarction was not statistically different in animals subjected to short or longer time of ischemia. In addition, the risk of hemorrhagic transformation and the degree of neurological impairment were not statistically different between animals occluded for less than 3 h and animals permanently occluded. Our data clearly demonstrate a progression in the risk and gravity of hemorrhagic transformation that parallels the increase in the duration of transient cerebral ischemia. The results suggest a relationship, which is independent on the duration of ischemia, between neurological deficit and hemorrhagic transformation and confirm the expected but still debated principle that early recanalization of an occluded artery reduces the hemorrhagic risk after thrombolysis with tissue plasminogen activator.

Delayed matrix metalloproteinase inhibition reduces intracerebral hemorrhage after embolic stroke in rats.

Hemorrhagic transformation (HT) and brain edema are life-threatening complications of recombinant tissue plasminogen activator (rt-PA)-induced reperfusion after ischemic stroke. The risk of HT limits the therapeutic window for reperfusion to 3 h after stroke onset. Pre-treatment with matrix metalloproteinase (MMP) inhibitors reduces HT and cerebral edema in experimental stroke. However, whether a delayed therapeutic intervention would be beneficial is unknown. In this study, 215 male Sprague-Dawley rats were subjected to embolic stroke and 75 rats were included in the final analysis. The animals were treated with the MMP inhibitor p-aminobenzoyl-gly-pro-D-leu-D-ala-hydroxamate before or after 3 or 6 h of ischemia. Animals were monitored for reperfusion and received rt-PA 6 h after ischemia onset. The results at 24 h showed that MMP inhibition 3 h after ischemia significantly decreased the degree of brain edema (17% of hemispheric enlargement in the treated group versus 24% in controls, P=0.018), reduced the risk (OR=0.163; 95% CI: 0.029 to 0.953) and gravity (0.09 versus 0.19 mg of parenchymal hemoglobin, P=0.02) of intracerebral hemorrhage, and improved neurological outcome (20% of the treated animals had a slight deficit; all of the controls had a bad outcome, P<0.05). Delaying MMP inhibition to 6 h after ischemia restricted the beneficial role of the treatment to a reduction in the risk of parenchymal hemorrhage (OR=0.242; 95% CI: 0.060 to 0.989). Our results confirm the involvement of MMPs in HT and support the possibility of extending the therapeutic window for thrombolysis in stroke by administering a broad-spectrum MMP inhibitor after the onset of ischemia.

Plasma concentrations of brain-derived neurotrophic factor in patients undergoing minor surgery: a randomized controlled trial.

We measured perioperative plasma concentrations of brain-derived neurotrophic factor (BDNF), a major mediator of synaptic plasticity in the central nervous system, in males, 30-65 years old, undergoing lumbar or cervical discotomy. Patients were randomly allocated to a general anesthetic with propofol induction and maintenance or with thiopental induction and isoflurane maintenance. BDNF plasma concentrations were measured before induction (baseline), 15 min after induction but before start of surgery, at skin closure, in the post-anesthetic care unit, and 24 h postoperatively. Data from 26 patients (13 in each group) were analyzed. At each time point, BDNF plasma concentrations showed large variability. At baseline, concentrations were 631 +/- 337 (mean +/- SD) pg ml(-1) in the propofol group and were 549 +/- 512 pg ml(-1) in the thiopental-isoflurane group (P = 0.31). At 15 min, concentrations significantly decreased in the propofol group (247 +/- 219 pg ml(-1), P = 0.0012 compared with baseline) but remained unchanged in the thiopental-isoflurane group (597 +/- 471 pg ml(-1), P = 0.798 compared with baseline). At skin closure and in the post-anesthetic care unit, concentrations were not different from baseline in both groups. At 24 h, concentrations significantly decreased below baseline in both groups (propofol: 232 +/- 129 pg ml(-1), P = 0.0015; thiopental-isoflurane: 253 +/- 250 pg ml(-1), P = 0.016). In the propofol group, there was a weak but statistically significant positive correlation (R2 = 0.38, P = 0.026) between the duration of surgery and BDNF plasma concentrations at skin closure. These data suggest that in males undergoing elective minor surgery, BDNF plasma concentrations show a specific pattern that is influenced by the anesthetic technique and, possibly, by the duration of surgery.

Matrix metalloproteinase-9 deficiency has no effect on glial scar formation after transient focal cerebral ischemia in mouse.

Glial scar formation was investigated in wild-type and MMP-9 deficient mice during a period of 21 days after 45 min of focal cerebral ischemia by intraluminal thread occlusion of the middle cerebral artery. The results showed no differences in the kinetics of activation of microglia, oligodendrocyte precursors and reactive astrocytes and showed only a slight difference in the pattern of macrophage infiltration. These results suggest that a specific targeting of MMP-9, as a mean to prevent ischemia-induced blood-brain barrier disruption, would have no significant effects on the recruitment of cells involved in glial scar formation.

Persisting vasculitis after pneumococcal meningitis.

INTRODUCTION: Bacterial meningitis is associated with a high mortality and a high incidence of neurological sequelae. Parainfectious vasculitis leading to ischemic brain damage is a known complication of bacterial meningitis but its treatment is uncertain. METHODS AND RESULTS: We report the case of a 53-year-old man with pneumococcal meningitis who developed numerous ischemic lesions in the brainstem and basal ganglia caused by parainfectious vasculitis. Clinical and radiological improvement was observed after delayed corticosteroid initiation. Symptomatic vasculitis relapsed after steroid withdrawal and stabilized after reintroduction of the immunosuppressive therapy. Although the cerebrospinal fluid (CSF) contained high levels of MMP-9 at the time of symptomatic vasculitis, a significant decrease of the enzyme accompanied the introduction of corticotherapy and the regression of vasculitic symptoms. No relation between the level of MMP-9 and the white blood cell count in CSF could be found. CONCLUSION: Parainfectious vasculitis may respond to late corticosteroid treatment. MMP-9 level in CSF may be a marker of vasculitic complication in bacterial meningitis.

Matrix metalloproteinases and diseases of the central nervous system with a special emphasis on ischemic brain.

Matrix metalloproteinases (MMPs) are involved in the pathogenesis of several diseases of the CNS, that share common pathophysiological processes, such as blood-brain barrier (BBB) disruption, oxidative stress, remodeling of the extracellular matrix (ECM) and inflammation. In ischemic brain injury, MMPs are implicated in various stages of the disease. Early after the onset of ischemia, MMPs contribute to the disruption of the BBB leading to vasogenic edema and to the influx of leucocytes into the CNS. The ability of MMPs to digest the basal lamina of capillaries increases the risk of hemorrhagic transformation of the ischemic tissue. During the acute ischemic phase, maintenance of the ECM is essential for neuronal survival. However, ECM degradation and its reconstitution are critical to tissue recovery. MMPs as a key modulator of ECM homeostasis play a role in the cascades leading to neuronal cell death and tissue regeneration. This pleiotropic implication of MMPs in brain injury has open new areas of investigation, which should lead to innovative therapeutic strategies. Yet MMPs may have a detrimental or beneficial role depending on the stage of brain injury. Simple therapeutic strategies based on MMP inhibition have thus little chance to favorably alter prognosis.

Role of matrix metalloproteinases in apoptosis after transient focal cerebral ischemia in rats and mice.

The involvement of matrix metalloproteinases (MMPs) in cerebral ischemia-induced apoptosis was investigated in a model of transient focal cerebral ischemia in rats treated intracerebroventricularly (i.c.v.) with 4-((3-(4-phenoxylphenoxy)propylsulfonyl)methyl)-tetrahydropyran-4-carboxylic acid N-hydroxy amide, a broad spectrum non-peptidic hydroxamic acid MMP inhibitor, and in MMP-9-deficient mice. Our results showed that MMP inhibition reduced DNA fragmentation by 51% (P < 0.001) and cerebral infarct by 60% (P < 0.05) after ischemia. This protection was concomitant with a 29% reduction of cytochrome c release into the cytosol (P < 0.005) and a 54% reduction of calpain-related alpha-spectrin degradation (P < 0.05), as well as with an 84% increase in the immunoreactive signal of the native form of poly(ADP) ribose polymerase (P < 0.01). By contrast, specific targeting of the mmp9 gene in mice did reduce cerebral damage by 34% (P < 0.05) but did not modify the apoptotic response after cerebral ischemia. However, i.c.v. injection of MMP-9-deficient mice with the same broad-spectrum inhibitor used in rats significantly reduced DNA degradation by 32% (P < 0.05) and contributed even further to the protection of the ischemic brain. Together, our pharmacological and genetic results indicate that MMPs other than MMP-9 are actively involved in cerebral ischemia-induced apoptosis.

Neurodegeneration in striatum induced by the mitochondrial toxin 3-nitropropionic acid: role of matrix metalloproteinase-9 in early blood-brain barrier disruption?

Blood-brain barrier (BBB) dysfunction is a potential mechanism involved in progressive striatal damage induced by the mitochondrial excitotoxin, 3-nitropropionic acid (3-NP). After activation by proteases and free radicals, matrix metalloproteinases (MMPs), particularly MMP-9 and -2, can digest the endothelial basal lamina leading to BBB opening. Using CD-1 mice, we show that MMP-9 expression by zymography is increased in the injured striatum compared with the contralateral striatum 2 hr after 3-NP injection [133.50 +/- 57.17 vs 50.25 +/- 13.56; mean +/- SD of optical densities in arbitrary units (A.U.); p < 0.005] and remains elevated until 24 hr (179.33 +/- 78.24 A.U.). After 4 hr, MMP-9 expression and activation are accompanied by an increase in BBB permeability. MMP inhibition attenuates BBB disruption, swelling, and lesion volume compared with vehicle-treated controls. There is a clear spatial relationship between MMP-9 expression and oxidized hydroethidine, indicating reactive oxygen species (ROS) production. Furthermore, transgenic mice that overexpress copper/zinc-superoxide dismutase (SOD1) show decreased lesion size and edema along with decreased immunoreactivity for MMP-9, compared with wild-type littermates (lesion: 38.8 +/- 15.1 and 53.3 +/- 10.3, respectively, p < or = 0.05; edema: 21.8 +/- 11.2 and 35.28 +/- 11, respectively, p < or = 0.05; MMP-9-positive cells: 352 +/- 57 and 510 +/- 45, respectively, p < or = 0.005), whereas knock-out mice deficient in SOD1 display significantly greater swelling (48.65 +/- 17; p < or = 0.05). We conclude that early expression and activation of MMP-9 by ROS may be involved in early BBB disruption and progressive striatal damage after 3-NP treatment.