Julian Cahill

Subarachnoid Hemorrhage: Is It Time for a New Direction?

Background and Purpose— Despite recent advances in the treatment of patients after subarachnoid hemorrhage, morbidity and mortality rates have failed to improve significantly. Although this was often blamed on vasospasm, is it time to consider alternative etiologies? Summary of Review— Early brain injury (EBI) is a recently described term that describes the immediate injury to the brain after subarachnoid hemorrhage. A number of pathways have been recognized as having a role in the etiology of EBI. This review provides a brief synopsis of EBI and its implications for the future. Conclusions— EBI may be responsible for the detrimental effects seen in patients after subarachnoid hemorrhage. Additional studies are needed to determine the pathophysiology of EBI and to explore potential therapeutic options.

Anti-apoptotic effect of granulocyte-colony stimulating factor after focal cerebral ischemia in the rat.

We investigated the molecular mechanisms of the anti-apoptotic properties of granulocyte-colony stimulating factor (G-CSF) on neurons and whether G-CSF affects glial cell survival following focal cerebral ischemia in rats. Sprague-Dawley rats were subjected to a transient 90 min middle cerebral artery occlusion (MCAO) by the intraluminal occlusion technique. Rats were treated with either a single dose of G-CSF (50 microg/kg, s.c.) at the onset of reperfusion or G-CSF (50 microg/kg body weight, s.c.) was administered starting at the onset of reperfusion and followed by the administration of the same dose per day for an additional 2 days. Brains were harvested either 24 h, 72 h or 2 weeks after reperfusion for assays of infarct volume, immunohistological studies and Western blot analysis for phosphorylated signal transducer and activator of transcription 3 (pSTAT3), Pim-1, bcl-2, Bax, cytochrome c, cellular inhibitor of apoptosis protein 2 (cIAP2), and cleaved caspase-3 levels. G-CSF significantly reduced infarct volume and ameliorated the early neurological outcome. G-CSF treatment significantly up-regulated pSTAT3, Pim-1, bcl-2 expression, and down-regulated cytochrome c release to the cytosol, Bax translocation to the mitochondria, and cleaved caspase-3 levels in neurons. The activation of the STAT3 pathway was accompanied by increased cIAP2 expression in glial cells. After MCAO, G-CSF treatment increased both neuronal and glial survival by effecting different anti-apoptotic pathways which reflects the multifactorial actions of this drug. These changes were associated with remarkable improvement in tissue preservation and behavioral outcome.

A Novel Neuroprotectant Granulocyte-Colony Stimulating Factor

Background and Purpose— Granulocyte-colony stimulating factor (G-CSF) is a growth factor that orchestrates the proliferation, differentiation, and survival of hematopoietic progenitor cells. It has been used for many years in clinical practice to accelerate the recovery of patients from neutropenia after cytotoxic therapy. However, there is a growing body of evidence from experimental studies suggesting that G-CSF also has important nonhematopoietic functions in the central nervous system. Summary of Review— The presence of the G-CSF/G-CSF–receptor system in the brain and its role in neuroprotection and neural tissue repair has been investigated in many recent studies. The neuroprotective actions of G-CSF have mainly been attributed to its anti-inflammatory and antiapoptotic effects. Furthermore, it induces neurogenesis and angiogenesis and improves functional recovery. In this review, we summarize the role of G-CSF and the corresponding signal transduction pathways regulated by G-CSF in neuroprotection. Conclusions— Much additional work is needed to better understand the precise mechanisms of G-CSF–induced neuroprotection. However, there is emerging data suggesting that G-CSF is a potential new agent for neuroprotection.

Cathepsin and Calpain Inhibitor E64d Attenuates Matrix Metalloproteinase-9 Activity After Focal Cerebral Ischemia in Rats

Background and Purpose— Matrix metalloproteinases (MMPs) and cysteine proteases (calpain and cathepsin B) play an important role in cell death and are upregulated after focal cerebral ischemia. Because there is a significant interaction between MMP-9 with calpain and cathepsin B, we investigated the role of E64d (a calpain and cathepsin B inhibitor) on MMP-9 activation in the rat focal ischemia model. Methods— Male Sprague-Dawley rats were subjected to 2 hours of middle cerebral artery occlusion by using the suture insertion method followed by 22 hours of reperfusion. In the treatment group, a single dose of E64d (5 mg/kg IP) was administrated 30 minutes before the induction of focal ischemia, whereas the nontreatment group received dimethyl sulfoxide only. The neurological deficits, infarct volumes, Evans blue extravasation, brain edema, and MMP-9 activation in the brain were determined. Results— Pretreatment with E64d produced a significant reduction in the cerebral infarction volume (353.1±19.8 versus 210.3±23.7 mm3) and the neurological deficits. Immunofluorescence studies showed MMP-9, calpain, and cathepsin B activation colocalized to both neurons and the neurovascular endothelial cells after ischemia, which was reduced by E64d. Conclusion— These results suggest that E64d treatment provides a neuroprotective effect to rats after transient focal cerebral ischemia by inhibiting the upregulation of MMP-9.

Vasospasm and p53-Induced Apoptosis in an Experimental Model of Subarachnoid Hemorrhage

Background and Purpose— Despite intensive research efforts, the etiology of vasospasm (sustained constriction of the cerebral vessels) remains unknown. In this study, we investigated the role of p53-induced apoptosis in the vasculature at 24 and 72 hours. To completely examine the apoptotic cascades, key proteins of the caspase-dependent, -independent and mitochondrial pathways were examined. Methods— In this study, adult rats were divided into 3 groups: sham (n=21), nontreatment (subarachnoid hemorrhage [SAH]+dimethyl sulfoxide; n=42), and treatment (SAH+pifithrin-α) (n=42) groups. Each animal in the SAH group underwent a surgical procedure to induce SAH, and the basilar artery was harvested at 24 and 72 hours for analysis. Results— We found severe vasospasm at the 24-hour time point, which persisted to 72 hours. Furthermore, we found that the markers of the apoptotic cascades rose significantly at the 24-hour time point but had dissipated by 72 hours. However, the neurological outcome and mortality scores improved at the 72-hour time point. Conclusions— Apoptosis, and in particular p53, may play an important role in the etiology of vasospasm with relation to SAH, and in this model, vasospasm persisted to 72 hours, despite the fact that apoptosis does not.

Granulocyte colony-stimulating factor protects the brain against experimental stroke via inhibition of apoptosis and inflammation

Abstract Objectives: The molecular mechanisms of the anti-apoptotic and anti-inflammatory properties of granulocyte-colony stimulating factor (G-CSF) following focal cerebral ischemia in rats were examined in this study. Methods: Sprague–Dawley rats were randomly divided into three groups: sham, middle cerebral artery occlusion (MCAO) non-treatment and MCAO with G-CSF treatment. Focal ischemia was induced with the suture occlusion method for 90 minutes, and treatment was given at the onset of reperfusion. All animals were killed 24 hours after reperfusion. Assessment included neurological scores, infarction volumes, histology, immunofluorescent staining and Western blotting. Results: G-CSF significantly reduced the infarct volume and ameliorated the early neurological outcome scores. Western blot analysis showed that G-CSF treatment significantly elevated the cIAP2 levels and decreased the activation of caspase 3 in the ischemic cortex compared with the non-treated rats. Immunofluorescent works also showed that G-CSF treatment inhibited both neuronal and glial tumor necrosis factor α and interleukin 1β expressions. Discussion: The neuronal anti-apoptotic action of G-CSF may be mediated in part by the anti-apoptotic protein cIAP2. G-CSF also exerts anti-inflammatory actions after focal cerebral ischemia by preventing both neuronal and glial pro-inflammatory cytokine expressions.

Hyperbaric oxygen and cerebral physiology

Abstract Hyperbaric oxygen (HBO) therapy is defined by the Undersea and Hyperbaric Medical Society (UHMS) as a treatment in which a patient intermittingly breathes 100% oxygen under a pressure that is greater than the pressure at sea level [a pressure greater than 1 atmosphere absolute (ATA)]. HBO has been shown to be a potent means to increase the oxygen content of blood and has been advocated for the treatment of various ailments, including air embolism, carbon monoxide poisoning, wound healing and ischemic stroke. However, definitive established mechanisms of action are still lacking. This has led to uncertainty among clinicians, who have understandingly become hesitant in regard to using HBO therapy, even in situations where it could prove beneficial. Therefore, this review will summarize the literature regarding the effects of HBO on brain oxygenation, cerebral blood flow and intracranial pressure in both the healthy and injured brains, as well as discuss how changes in these three factors can impart protection.

P53 MAY PLAY AN ORCHESTRATING ROLE IN APOPTOTIC CELL DEATH AFTER EXPERIMENTAL SUBARACHNOID HEMORRHAGE

OBJECTIVESecondary brain injury after subarachnoid hemorrhage (SAH) is poorly understood. As a result, there are few treatment options. Consequently, SAH is associated with a high rate of morbidity and mortality. In an effort to combat these problems, the role of apoptosis was examined in the whole brain after SAH. In particular, the role of p53 and the three major apoptotic cascades were studied, the caspase-dependent and caspase-independent cascades and the mitochondrial pathway. METHODSIn this study, 195 Sprague-Dawley rats were divided into three groups, including sham, nontreatment, and treatment (Pifithrin-α; BIOMOL, Inc., Plymouth Meeting, PA) groups. The monofilament puncture model was used to induce SAH and the animals were subsequently sacrificed at 24 and 72 hours. Western blot analysis, histology, physiological parameters, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling, and immunohistological techniques were used to demonstrate the role of p53 and the apoptotic cascades in the rat brain after SAH. In addition, outcome was determined based on mortality rates and neurological outcome scores. RESULTSWe found that p53 and associated apoptotic proteins were up-regulated after SAH and that downstream mediators of apoptosis were negatively influenced by the inhibition of p53 by Pifithrin-α. Furthermore, we found that apoptotic inhibition resulted in less cell death and an overall favorable outcome in the treated animals. CONCLUSIONThese results suggest that apoptosis may be an important cause of cell death in the brain after SAH and that p53 may play an orchestrating role regarding apoptosis in SAH.

Early brain injury following aneurysmal subarachnoid hemorrhage: emphasis on cellular apoptosis.

Subarachnoid hemorrhage (SAH) due to intracranial aneurysm rupture is a complex clinical disease with high mortality and morbidity. Recent studies suggest that early brain injury (EBI) rather than vasospasm might be responsible for morbidity and mortality within 24-72 hours after SAH. The rise in intracranial pressure following SAH causes a significant drop in cerebral perfusion pressure that leads to global cerebral ischemia and initiates the acute injury cascade. Various molecular mechanisms have been shown to involve in the pathophysiology of EBI including cellular apoptosis. In this review, we summarize apoptotic molecular mechanisms involved in the etiology of EBI and its potential as a target for future therapeutic intervention.

Inhibition of c-Jun N-terminal kinase pathway attenuates cerebral vasospasm after experimental subarachnoid hemorrhage through the suppression of apoptosis

BACKGROUND Recent studies have demonstrated that apoptosis in cerebral arteries could play an essential role in cerebral vasospasm after subarachnoid hemorrhage (SAH) and that SP600125, an inhibitor of c-Jun N-terminal kinase (JNK) could suppress apoptosis. The present study examined whether SP600125 could reduce cerebral vasospasm through the suppression of apoptosis. METHOD Fifteen dogs were assigned to 3 groups: control, SAH, and SAH + SP600125 (30 micromol/l). SAH was induced by the injection of autologous blood into the cisterna magna on day 0 and day 2. Angiograms were evaluated on day 0 and day 7. The activation of the JNK pathway and caspase-3 were also evaluated using Western blot. To determine the distribution, TUNEL staining and immunohistochemistry for phosphorylated c-jun and cleaved caspase-3 were performed. FINDINGS Severe vasospasm was observed in the basilar artery of the SAH dogs. SP600125 reduced angiographic and morphological vasospasm and reduced the expression of cleaved caspase-3, thereby suppressing apoptosis. CONCLUSIONS These results demonstrate that SP600125 attenuates cerebral vasospasm through the suppression of apoptosis, which may provide a novel therapeutic target for cerebral vasospasm.