Significance and Recent Advances: Ischemic stroke is the leading cause of disability and third in mortality in industrialized nations. Immediate restoration of cerebral blood flow is crucial to ...salvage brain tissue, but only few patients are eligible for recanalization therapy. Thus, the need for alternative neuroprotective strategies is huge, and antioxidant interventions have long been studied in this context. Reactive oxygen species (ROS) physiologically serve as signaling molecules, but excessive amounts of ROS, as generated during ischemia/reperfusion (I/R), contribute to tissue injury.
Nevertheless and despite a strong rational of ROS being a pharmacological target, all antioxidant interventions failed to improve functional outcome in human clinical trials. Antioxidants may interfere with physiological functions of ROS or do not reach the crucial target structures of ROS-induced injury effectively.
Thus, a potentially more promising approach is the inhibition of the source of disease-promoting ROS. Within recent years, NADPH oxidases (Nox) of the Nox family have been identified as mediators of neuronal pathology. As, however, several Nox homologs are expressed in neuronal tissue, and as many of the pharmacological inhibitors employed are rather unspecific, the concept of Nox as mediators of brain damage is far from being settled. In this review, we will discuss the contribution of Nox homologs to I/R injury at large as well as to neuronal damage in particular. We will illustrate that the current data provide evidence for Nox2 as the most important NADPH oxidase mediating cerebral injury.
Cerebral ischemia–reperfusion increases intraneuronal levels of ubiquitinated proteins, but the factors driving ubiquitination and whether it results from altered proteostasis remain unclear. To ...address these questions, we used in vivo and in vitro models of cerebral ischemia–reperfusion, in which hippocampal slices were transiently deprived of oxygen and glucose to simulate ischemia followed by reperfusion, or the middle cerebral artery was temporarily occluded in mice. We found that post-ischemic ubiquitination results from two key steps: restoration of ATP at reperfusion, which allows initiation of protein ubiquitination, and free radical production, which, in the presence of sufficient ATP, increases ubiquitination above pre-ischemic levels. Surprisingly, free radicals did not augment ubiquitination through inhibition of the proteasome as previously believed. Although reduced proteasomal activity was detected after ischemia, this was neither caused by free radicals nor sufficient in magnitude to induce appreciable accumulation of proteasomal target proteins or ubiquitin–proteasome reporters. Instead, we found that ischemia-derived free radicals inhibit deubiquitinases, a class of proteases that cleaves ubiquitin chains from proteins, which was sufficient to elevate ubiquitination after ischemia. Our data provide evidence that free radical-dependent deubiquitinase inactivation rather than proteasomal inhibition drives ubiquitination following ischemia–reperfusion, and as such call for a reevaluation of the mechanisms of post-ischemic ubiquitination, previously attributed to altered proteostasis. Since deubiquitinase inhibition is considered an endogenous neuroprotective mechanism to shield proteins from oxidative damage, modulation of deubiquitinase activity may be of therapeutic value to maintain protein integrity after an ischemic insult.
IMPORTANCE: Predicting the duration of poststroke dysphagia is important to guide therapeutic decisions. Guidelines recommend nasogastric tube (NGT) feeding if swallowing impairment persists for 7 ...days or longer and percutaneous endoscopic gastrostomy (PEG) placement if dysphagia does not recover within 30 days, but, to our knowledge, a systematic prediction method does not exist. OBJECTIVE: To develop and validate a prognostic model predicting swallowing recovery and the need for enteral tube feeding. DESIGN, SETTING, AND PARTICIPANTS: We enrolled participants with consecutive admissions for acute ischemic stroke and initially severe dysphagia in a prospective single-center derivation (2011-2014) and a multicenter validation (July 2015-March 2018) cohort study in 5 tertiary stroke referral centers in Switzerland. EXPOSURES: Severely impaired oral intake at admission (Functional Oral Intake Scale score <5). MAIN OUTCOMES AND MEASURES: Recovery of oral intake (primary end point, Functional Oral Intake Scale ≥5) or return to prestroke diet (secondary end point) measured 7 (indication for NGT feeding) and 30 (indication for PEG feeding) days after stroke. RESULTS: In total, 279 participants (131 women 47.0%; median age, 77 years interquartile range, 67-84 years) were enrolled (153 54.8% in the derivation study; 126 45.2% in the validation cohort). Overall, 64% (95% CI, 59-71) participants failed to recover functional oral intake within 7 days and 30% (95% CI, 24-37) within 30 days. Prolonged swallowing recovery was independently associated with poor outcomes after stroke. The final prognostic model, the Predictive Swallowing Score, included 5 variables: age, stroke severity on admission, lesion location, initial risk of aspiration, and initial impairment of oral intake. Predictive Swallowing Score prediction estimates ranged from 5% (score, 0) to 96% (score, 10) for a persistent impairment of oral intake on day 7 and from 2% to 62% on day 30. Model performance in the validation cohort showed a discrimination (C statistic) of 0.84 (95% CI, 0.76-0.91; P < .001) for predicting the recovery of oral intake on day 7 and 0.77 (95% CI, 0.67-0.87; P < .001) on day 30, and a discrimination for a return to prestroke diet of 0.94 (day 7; 95% CI, 0.87-1.00; P < .001) and 0.71 (day 30; 95% CI, 0.61-0.82; P < .001). Calibration plots showed high agreement between the predicted and observed outcomes. CONCLUSIONS AND RELEVANCE: The Predictive Swallowing Score, available as a smartphone application, is an easily applied prognostic instrument that reliably predicts swallowing recovery. It will support decision making for NGT or PEG insertion after ischemic stroke and is a step toward personalized medicine.
Cerebral ischemia/reperfusion is associated with reactive oxygen species (ROS) generation, and NADPH oxidases are important sources of ROS. We hypothesized that NADPH oxidases mediate blood-brain ...barrier (BBB) disruption and contribute to tissue damage in ischemia/reperfusion.
Ischemia was induced by filament occlusion of the middle cerebral artery in mice for 2 hours followed by reperfusion. BBB permeability was measured by Evans blue extravasation. Monolayer permeability was determined from transendothelial electrical resistance of cultured porcine brain capillary endothelial cells.
BBB permeability was increased in the ischemic hemisphere 1 hour after reperfusion. In NADPH oxidase-knockout (gp91phox(-/-)) mice, middle cerebral artery occlusion-induced BBB disruption and lesion volume were largely attenuated compared with those in wild-type mice. Inhibition of NADPH oxidase by apocynin prevented BBB damage. In porcine brain capillary endothelial cells, hypoxia/reoxygenation induced translocation of the NADPH oxidase activator Rac-1 to the membrane. In vivo inhibition of Rac-1 by the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor atorvastatin or Clostridium difficile lethal toxin B also prevented the ischemia/reperfusion-induced BBB disruption. Stimulation of porcine brain capillary endothelial cells with H(2)O(2) increased permeability, an effect attenuated by inhibition of phosphatidyl inositol 3-kinase or c-Jun N-terminal kinase but not blockade of extracellular signal-regulated kinase-1/2 or p38 mitogen-activated protein kinase. Inhibition of Rho kinase completely prevented the ROS-induced increase in permeability and the ROS-induced polymerization of the actin cytoskeleton.
Activation of Rac and subsequently of the gp91phox containing NADPH oxidase promotes cerebral ROS formation, which then leads to Rho kinase-mediated endothelial cell contraction and disruption of the BBB. Inhibition of NADPH oxidase is a promising approach to reduce brain injury after stroke.
Loss-of-function mutations of progranulin (PGRN) have been linked to frontotemporal dementia, but little is known about the effects of PGRN deficiency on the brain in health and disease. PGRN has ...been implicated in neurovascular development, inflammation, and Wnt signaling, a pathway involved in the formation of the blood-brain barrier (BBB). Because BBB alterations and inflammation contribute to ischemic brain injury, we examined the role of PGRN in the brain damage produced by ischemia-reperfusion. PGRN(+/-) and PGRN(-/-) mice underwent middle cerebral artery occlusion (MCAO) with monitoring of cerebral blood flow. Infarct volume and motor deficits were assessed 72 h later. Post-ischemic inflammation was examined by expression of inflammatory genes and flow cytometry. BBB structure and permeability were examined by electron microscopy (EM) and Evans blue (EB) extravasation, respectively. MCAO resulted in ~60% larger infarcts in PGRN(+/-) and PGRN(-/-) mice, an effect independent of hemodynamic factors or post-ischemic inflammation. Rather, massive hemorrhages and post-ischemic BBB disruption were observed, unrelated to degradation of tight junction (TJ) proteins or matrix metalloproteinases (MMPs). By EM, TJ were 30-52% shorter, fewer, and less interlocking, suggesting a weaker seal between endothelial cells. Intracerebral injection of platelet-derived growth factor-CC (PDGF-CC), which increases BBB permeability, resulted in a more severe BBB breakdown in PGRN(+/-) and PGRN(-/-) than wild-type mice. We describe a previously unrecognized involvement of PGRN in the expression of key ultrastructural features of the BBB. Such a novel vasoprotective role of PGRN may contribute to brain dysfunction and damage in conditions associated with reduced PGRN function.
Background:
Natalizumab significantly reduces the disease activity in patients with relapsing-remitting multiple sclerosis but due to the risk of progressive multifocal leukoencephalopathy it is ...often discontinued. Fingolimod is seen as an alternative, but there are no long-term analyses of the efficacy of fingolimod in this setting using the no evidence of disease activity (NEDA)-3 criteria. We provide an assessment of patients who discontinued natalizumab and switched to fingolimod or other treatments by evaluating the proportion of patients who fulfil NEDA-3 criteria after prolonged follow-up periods.
Methods:
We conducted a retrospective observational study of multiple sclerosis patients, who were treated with continuous natalizumab or who had switched to fingolimod or other treatments after natalizumab discontinuation. We assessed NEDA-3 status, annual relapse rate and determined the odds ratio between disease course after treatment switch and other patient and treatment characteristics.
Results:
A total of 61 patients on continuous natalizumab treatment and 53 patients who switched from natalizumab to fingolimod or other treatments were accompanied for up to 5 years. While the proportion of natalizumab patients fulfilling NEDA-3 criteria remained stable at 90% during the entire follow-up period, the proportion of patients switching to fingolimod or other therapies dropped to 76.7% in the first year after discontinuation, and to 50% in the years thereafter. While the median Expanded Disability Status Scale remained stable and the percentage of relapsing patients did not change significantly, recurring magnetic resonance imaging activity was found in up to 42% of the patients after switching from natalizumab to other treatments. New disease activity was significantly correlated with extended treatment gap between natalizumab discontinuation and the start of a new therapy.
Discussion:
Patients remain clinically stable after discontinuing natalizumab and switching to other therapies. However, when considering NEDA-3 criteria, a considerable proportion of patients show disease reactivation. Careful monitoring and early evaluation of alternatives is necessary after switching from natalizumab to other treatments.
Cerebral ischemia is accompanied by fulminant cellular and humoral inflammatory changes in the brain which contribute to lesion development after stroke. A tight interplay between the brain and the ...peripheral immune system leads to a biphasic immune response to stroke consisting of an early activation of peripheral immune cells with massive production of proinflammatory cytokines followed by a systemic immunosuppression within days of cerebral ischemia that is characterized by massive immune cell loss in spleen and thymus. Recent work has documented the importance of T lymphocytes in the early exacerbation of ischemic injury. The lipid signaling mediator sphingosine 1-phosphate-derived stable analog FTY720 (fingolimod) acts as an immunosuppressant and induces lymphopenia by preventing the egress of lymphocytes, especially T cells, from lymph nodes. We found that treatment with FTY720 (1
mg/kg) reduced lesion size and improved neurological function after experimental stroke in mice, decreased the numbers of infiltrating neutrophils, activated microglia/macrophages in the ischemic lesion and reduced immunohistochemical features of apoptotic cell death in the lesion.
Carotid-cavernous sinus fistulas (CCFs) are abnormal communications between the internal carotid artery (ICA) and the cavernous sinus (CS). Direct CCFs are associated with trauma or are iatrogenic ...complications of neuroendovascular procedures. Meanwhile, mechanical endovascular thrombectomy (MT) in acute ischaemic stroke (AIS) patients with large vessel occlusion (LVO) has been established as a common treatment approach. However, MT is not without its risks of complications, and only a few reports exist on CCF occurring after MT. Here, we present a case of a 63-year-old patient with iatrogenic high-flow CCF of the right horizontal cavernous ICA segment (C4) following repeated MT due to LVO of the middle cerebral artery, and the recent literature is reviewed.
Abstract Reactive oxygen species (ROS) are mediators of brain injury in ischemia/reperfusion. An involvement of the NADPH oxidase Nox2 has been demonstrated. In contrast, only little is known about ...the contribution of the Nox1 homologue in this context. Thus, we studied the role of Nox1 in early cerebral reperfusion injury in the middle cerebral artery filament occlusion model using Nox1 knockout mice. Genetic deletion of a functional Nox1 lead to a 55% attenuation in lesion size at 24 h after induction of 1 h ischemia ( p < 0.05). This result was paralleled by a significant improvement of neurological outcome, preservation of blood–brain barrier integrity and reduced cerebral edema in Nox1y/− compared to WT mice. Interestingly, no difference in infarct size between WT and Nox1y/− was observed with an occlusion time of 2 h and longer. Apoptosis rate as measured by TUNEL staining was similar between the groups. Moreover, infusion of the antioxidant TEMPOL as well as of the unspecific NO-synthase inhibitor l -NAME elicited similar changes with respect to ischemic tissue damage between WT and Nox1-deficient mice. In conclusion, Nox1 is involved in the pathophysiology of cerebral ischemia. Our data however indicate that ROS-mediated direct cellular injury is unlikely to explain the protective effect achieved by genetic deletion of the enzyme.
In many neuroinflammatory conditions, including multiple sclerosis (MS), encephalitis, meningitis, brain tumours and cerebral
ischaemia, the matrix metalloproteinases (MMPs) play an important role in ...disrupting the bloodâbrain barrier (BBB). Normally
under tight regulation, increased MMP-9 cerebrospinal fluid levels and excessive proteolytic activity is detected in the blood
and cerebrospinal fluid in patients with acute MS. MMP-9 is a member of the type IV collagenases, which attack components
of the endothelial basal lamina, including type IV collagen. The disruption of the BBB and clinical symptoms can be reduced
with different inhibitors to MMPs including activators of tissue inhibitor of metalloproteinases-1 (TIMP-1), the cognate tissue
inhibitor of MMP-9. Since intravenous glucocorticoid (GC) treatment reduces the levels of MMP-9 markedly in patients, we hypothesized
that GC effects might be mediated by transcriptional activation of the TIMP-1 gene in addition to reported repressive effects
on MMP-9 transcription. Our results provide direct evidence that GCs increase TIMP-1 in the brain endothelial cell line cEND,
prevent alterations in microvascular integrin α1 subunit expression and help maintain endothelial barrier function in response
to pro-inflammatory stimuli (TNFα administration). GC-induced up-regulation of TIMP-1 expression by the CNS vascular endo-thelium
may thus play a role in preservation of the endothelial basal lamina and maintain integrin α1 and tight junction protein expression
important for vessel wall integrity.
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