Intravenous administration of pravastatin immediately after middle cerebral artery occlusion reduces cerebral oedema in spontaneously hypertensive rats

Changes in Brain Electrical Activity after Transient Middle Cerebral Artery Occlusion in Rats

Objectives. Ischemic stroke is a leading cause of death and disability worldwide. To search for new therapeutic and pharmacotherapeutic strategies, numerous models of this disease have been proposed, the most popular being transient middle cerebral artery occlusion. Behavioral and sensorimotor testing, biochemical, and histological methods are traditionally used in conjunction with this model to assess the effectiveness of potential treatment options. Despite its wide overall popularity, electroencephalography/electrocorticography is quite rarely used in such studies. Materials and methods. In the present work, we explored the changes in brain electrical activity at days 3 and 7 after 30- and 45-min of transient middle cerebral artery occlusion in rats. Results. Cerebral ischemia altered the amplitude and spectral electrocorticogram characteristics, and led to a reorganization of inter- and intrahemispheric functional connections. Ischemia duration affected the severity as well as the nature of the observed changes. Conclusions. The dynamics of changes in brain electrical activity may indicate a spontaneous partial recovery of impaired cerebral functions at post-surgery day 7. Our results suggest that electrocorticography can be used successfully to assess the functional status of the brain following ischemic stroke in rats as well as to investigate the dynamics of functional recovery.

Post-ischemic administration of pravastatin reduces neuronal injury by inhibiting Bax protein expression after transient forebrain ischemia in rats

This study investigated the neuroprotective effect of pravastatin administration after forebrain ischemia in rats. Forebrain ischemia was induced by bilateral common carotid artery occlusion and systemic hypotension for 8min. Pravastatin at 1mg/kg (pravastatin group, n=10), or an identical volume of normal saline (control group, n=10), was injected 10min, and 1-4 days after reperfusion. Arterial blood gas was analyzed 10min before ischemia onset and 10min after ischemia completion. Viable and apoptotic neuronal cells were evaluated 7 days after ischemia by hematoxylin and eosin (H&E) staining and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuracil triphosphate biotin in situ nick-end labeling (TUNEL) staining of the hippocampal Cornu Ammonis area (CA1). Expression of Bcl-2 and Bax proteins was quantified by Western blot analysis. The proportion of viable neuronal cells after ischemia was greater in the pravastatin vs. control group (p<0.01), with greater expression of apoptotic cells in the control vs. pravastatin group (p<0.05). Bax protein expression was significantly decreased in the pravastatin group (p<0.05), whereas, Bcl-2 expression was increased, but not significantly (p>0.05). Our findings suggest that pravastatin administration after forebrain ischemia confers neuroprotection in rats by inhibiting Bax protein expression.

Molecular contributions to neurovascular unit dysfunctions after brain injuries: lessons for target-specific drug development

The revised 'expanded' neurovascular unit (eNVU) is a physiological and functional unit encompassing endothelial cells, pericytes, smooth muscle cells, astrocytes and neurons. Ischemic stroke and traumatic brain injury are acute brain injuries directly affecting the eNVU with secondary damage, such as blood-brain barrier (BBB) disruption, edema formation and hypoperfusion. BBB dysfunctions are observed at an early postinjury time point, and are associated with eNVU activation of proteases, such as tissue plasminogen activator and matrix metalloproteinases. BBB opening is accompanied by edema formation using astrocytic AQP4 as a key protein regulating water movement. Finally, nitric oxide dysfunction plays a dual role in association with BBB injury and dysregulation of cerebral blood flow. These mechanisms are discussed including all targets of eNVU encompassing endothelium, glial cells and neurons, as well as larger blood vessels with smooth muscle. In fact, the feeding blood vessels should also be considered to treat stroke and traumatic brain injury. This review underlines the importance of the eNVU in drug development aimed at improving clinical outcome after stroke and traumatic brain injury.

Genistein attenuates ischemic oxidative damage and behavioral deficits via eNOS/Nrf2/HO-1 signaling

Global cerebral ischemia, such as occurs following cardiac arrest, can lead to oxidative stress, hippocampal neuronal cell death, and cognitive defects. The current study examined the potential beneficial effect and underlying mechanisms of post-treatment with the naturally occurring isoflavonic phytoestrogen, genistein, which has been implicated to attenuate oxidative stress. Genistein (1 mg kg(-1)) was administered i.v. 5 min after reperfusion in rats subjected to four-vessel global cerebral ischemia (GCI). The results revealed that genistein exerted significant neuroprotection of hippocampal CA1 neurons following GCI, as evidenced by an increase in NeuN-positive neurons and the decrease in TUNEL-positive neurons. Furthermore, genistein treatment also resulted in significantly improved spatial learning and memory as compared to vehicle control animals. The beneficial effects of genistein appear to be mediated by an increase of phosphorylation/activation of eNOS, with subsequent activation of the antioxidant/detoxification Nrf2/Keap1 transcription system. Along these lines, genistein increased keap1 S-nitrosylation, with a corresponding nuclear accumulation and enhanced DNA binding activity of Nrf2. Genistein also enhanced levels of the Nrf2 downstream antioxidant protein, heme oxygenase (HO)-1, as compared to vehicle control groups. In accordance with its induction of Nrf2 activation, genistein exerted a robust attenuation of oxidative DNA damage and lipid peroxidative damage in hippocampal CA1 neurons after GCI, as measured by immunofluorescence staining of the oxidative stress markers, 8-hydroxy-2-deoxyguanosine (8-OHdG) and 4-Hydroxynonenal (4-HNE). Interestingly, the aforementioned effects of genistein were abolished by pretreatment with L-NAME, an inhibitor of eNOS activation. In conclusion, the results of the study demonstrate that low dose genistein can exert significant antioxidant, neuroprotective, and cognitive-enhancing effects in the hippocampal CA1 region following GCI. Mechanistically, the beneficial effects of genistein appear to be mediated by enhanced eNOS phosphorylation/activation and nitric oxide (NO)-mediated thiol modification of Keap1, with subsequent upregulation of the Nrf2/HO-1 antioxidative signaling pathway and a resultant attenuation of oxidative stress.

The immune system in stroke: clinical challenges and their translation to experimental research

Stroke represents an unresolved challenge for both developed and developing countries and has a huge socio-economic impact. Although considerable effort has been made to limit stroke incidence and improve outcome, strategies aimed at protecting injured neurons in the brain have all failed. This failure is likely to be due to both the incompleteness of modelling the disease and its causes in experimental research, and also the lack of understanding of how systemic mechanisms lead to an acute cerebrovascular event or contribute to outcome. Inflammation has been implicated in all forms of brain injury and it is now clear that immune mechanisms profoundly influence (and are responsible for the development of) risk and causation of stroke, and the outcome following the onset of cerebral ischemia. Until very recently, systemic inflammatory mechanisms, with respect to common comorbidities in stroke, have largely been ignored in experimental studies. The main aim is therefore to understand interactions between the immune system and brain injury in order to develop novel therapeutic approaches. Recent data from clinical and experimental research clearly show that systemic inflammatory diseases -such as atherosclerosis, obesity, diabetes or infection - similar to stress and advanced age, are associated with dysregulated immune responses which can profoundly contribute to cerebrovascular inflammation and injury in the central nervous system. In this review, we summarize recent advances in the field of inflammation and stroke, focusing on the challenges of translation between pre-clinical and clinical studies, and potential anti-inflammatory/immunomodulatory therapeutic approaches.

Method parameters' impact on mortality and variability in rat stroke experiments: a meta-analysis

Background

Even though more than 600 stroke treatments have been shown effective in preclinical studies, clinically proven treatment alternatives for cerebral infarction remain scarce. Amongst the reasons for the discrepancy may be methodological shortcomings, such as high mortality and outcome variability, in the preclinical studies. A common approach in animal stroke experiments is that A) focal cerebral ischemia is inflicted, B) some type of treatment is administered and C) the infarct sizes are assessed. However, within this paradigm, the researcher has to make numerous methodological decisions, including choosing rat strain and type of surgical procedure. Even though a few studies have attempted to address the questions experimentally, a lack of consensus regarding the optimal methodology remains.

Methods

We therefore meta-analyzed data from 502 control groups described in 346 articles to find out how rat strain, procedure for causing focal cerebral ischemia and the type of filament coating affected mortality and infarct size variability.

Results

The Wistar strain and intraluminal filament procedure using a silicone coated filament was found optimal in lowering infarct size variability. The direct and endothelin methods rendered lower mortality rate, whereas the embolus method increased it compared to the filament method.

Conclusions

The current article provides means for researchers to adjust their middle cerebral artery occlusion (MCAo) protocols to minimize infarct size variability and mortality.

Nitric oxide: considerations for the treatment of ischemic stroke

Some 40 years ago it was recognized by Furchgott and colleagues that the endothelium releases a vasodilator, endothelium-derived relaxing factor (EDRF). Later on, several groups identified EDRF to be a gas, nitric oxide (NO). Since then, NO was identified as one of the most versatile and unique molecules in animal and human biology. Nitric oxide mediates a plethora of physiological functions, for example, maintenance of vascular tone and inflammation. Apart from these physiological functions, NO is also involved in the pathophysiology of various disorders, specifically those in which regulation of blood flow and inflammation has a key role. The aim of the current review is to summarize the role of NO in cerebral ischemia, the most common cause of stroke.