Fernando D. Testai

Neurogenesis and Inflammation after Ischemic Stroke: What is Known and Where We Go from Here

This review covers the pathogenesis of ischemic stroke and future directions regarding therapeutic options after injury. Ischemic stroke is a devastating disease process affecting millions of people worldwide every year. The mechanisms underlying the pathophysiology of stroke are not fully understood but there is increasing evidence demonstrating the contribution of inflammation to the drastic changes after cerebral ischemia. This inflammation not only immediately affects the infarcted tissue but also causes long-term damage in the ischemic penumbra. Furthermore, the interaction between inflammation and subsequent neurogenesis is not well understood but the close relationship between these two processes has garnered significant interest in the last decade or so. Current approved therapy for stroke involving pharmacological thrombolysis is limited in its efficacy and new treatment strategies need to be investigated. Research aimed at new therapies is largely about transplantation of neural stem cells and using endogenous progenitor cells to promote brain repair. By understanding the interaction between inflammation and neurogenesis, new potential therapies could be developed to further establish brain repair mechanisms.

Inherited Metabolic Disorders and Stroke Part 2: Homocystinuria, Organic Acidurias, and Urea Cycle Disorders

Several inherited metabolic disorders have been associated with stroke particularly in newborns, children, and young adults. In part 1, we discussed the genetics, stroke pathophysiology, clinical presentation, diagnosis, and treatment of Fabry disease and mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes. In part 2, we overview homocystinuria, organic acidurias, and urea cycle disorders.

Inherited Metabolic Disorders and Stroke Part 1: Fabry Disease and Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Strokelike Episodes

Inherited metabolic disorders are single-gene genetic diseases associated with multiorgan damage. Some of these conditions increase the risk of stroke through a variety of mechanisms, and there is evidence that early recognition and initiation of appropriate treatment may improve prognosis. In this 2-part review we provide an update of the genetics, stroke pathophysiology, clinical manifestations, diagnosis, and treatment of metabolic disorders associated with stroke. In part 1, we concentrate on Fabry disease and mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes. In part 2 we will review homocystinuria, organic acidurias, and urea cycle disorders.

Ceramide in rafts (detergent-insoluble fraction) mediates cell death in neurotumor cell lines

Detergent‐resistant lipid microdomains (Rafts) were isolated from human oligodendroglioma (HOG), human neuroblastoma (LA‐N‐5), and immortalized dorsal root ganglion (F‐11) cell lines by sucrose‐density gradient ultracentrifugation and shown to be enriched in cholesterol, sphingomyelin, and ceramide. [3H]palmitate labeling allowed the Raft fraction to be easily identified as a sharp peak of 3H radioactivity in the 5–30% sucrose interphase. Treatment of [3H]palmitate‐labeled cells with staurosporine (to activate caspase 8 and induce apoptosis) or exogenous sphingomyelinase specifically increased the [3H]ceramide content of the Raft fraction. Depletion of cholesterol with β‐methylcyclodextran decreased Raft formation and partially blocked staurosporine‐induced apoptosis. Similarly, treatment of cells with Fumonisin B1 to inhibit de novo sphingolipid synthesis by 50% reduced the labeling of the Raft fraction and partially blocked staurosporine‐induced apoptosis. Staurosporine treatment activated neutral sphingomyelinase but had no effect on acid sphingomyelinase activity or on other lysosomal hydrolases, such as α‐L‐fucosidase. Most of the neutral sphingomyelinase activity is in the Raft fraction, suggesting that the conversion of sphingomyelin to ceramide in Rafts is an important event in neural cell apoptosis.

The Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) Study Protocol

Background and Purpose— Epidemiological studies of intracerebral hemorrhage (ICH) have consistently demonstrated variation in incidence, location, age at presentation, and outcomes among non-Hispanic white, black, and Hispanic populations. We report here the design and methods for this large, prospective, multi-center case–control study of ICH. Methods— The Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study is a multi-center, prospective case–control study of ICH. Cases are identified by hot-pursuit and enrolled using standard phenotype and risk factor information and include neuroimaging and blood sample collection. Controls are centrally identified by random digit dialing to match cases by age (±5 years), race, ethnicity, sex, and metropolitan region. Results— As of March 22, 2013, 1655 cases of ICH had been recruited into the study, which is 101.5% of the target for that date, and 851 controls had been recruited, which is 67.2% of the target for that date (1267 controls) for a total of 2506 subjects, which is 86.5% of the target for that date (2897 subjects). Of the 1655 cases enrolled, 1640 cases had the case interview entered into the database, of which 628 (38%) were non-Hispanic black, 458 (28%) were non-Hispanic white, and 554 (34%) were Hispanic. Of the 1197 cases with imaging submitted, 876 (73.2%) had a 24 hour follow-up CT available. In addition to CT imaging, 607 cases have had MRI evaluation. Conclusions— The ERICH study is a large, case–control study of ICH with particular emphasis on recruitment of minority populations for the identification of genetic and epidemiological risk factors for ICH and outcomes after ICH.

Regulation of sphingomyelinases in cells of the oligodendrocyte lineage

Controversy exists regarding the nature of the “executioner” sphingomyelinase (SMase) in cells and its subcellular localization. A new fluorescence‐based assay with the substrate 6‐hexadecanoylamino‐4‐methylumbelliferyl‐phosphorylcholine allowed rapid and reliable microassays of neutral (N) and acid (A) SMase activity in cell extracts from primary cultures of neonatal rat oligodendrocytes (OPC) and a human oligodendroglioma cell line (HOG). Total SMase activity was much higher in OPC than in HOG cells. Both staurosporine and tumor necrosis factor‐α (TNF‐α) induced apoptosis and activated NSMase in a multiphasic manner in both OPC and HOG cells. The increase in caspase 8 activity preceded the 1 hr peak of NSMase activation, which was followed by caspase 3 activation. In contrast, ASMase activity, which constituted >90% of the total SMase activity, was unresponsive to proapoptotic drugs. Neither reducing ASMase levels by 50% by pretreatment with desipramine nor inhibiting sphingolipid synthesis by 50% with fumonisin B1 had any effect on cell death. Isolation of sphingolipid‐rich plasma membrane microdomains (rafts) from the cells by sucrose density gradient ultracentrifugation revealed an enrichment of sphingomyelin, ceramide, and caspase 8. Proapoptotic drugs such as staurosporine promoted the translocation of NSMase to the raft fraction. In contrast, ASMase, other lysosomal hydrolases, and caspase 3 remained absent from rafts even after staurosporine treatment. The staurosporine‐induced concomitant increase of ceramide in the raft fraction and caspase 3 in the cytosol could be mimicked by the addition of exogenous bacterial SMase. We conclude that caspase 8 activates NSMase in rafts in oligodendrocytes and that the downstream apoptotic signal is via caspase 3.

Acid sphingomyelinase and inhibition by phosphate ion: role of inhibition by phosphatidyl‐myo‐inositol 3,4,5‐triphosphate in oligodendrocyte cell signaling

There is ample evidence that both acid (ASMase) and neutral (NSMase) sphingomyelinases play a role in cell death so inhibitors of either enzyme could have significant value as protectors against neurodegeneration. We used a fluorogenic sphingomyelinase substrate, 6‐hexadecanoylamino‐4‐methylumbelliferyl‐phosphorylcholine, and a [14C]choline‐labeled sphingomyelin substrate to screen large numbers of phosphocompounds for inhibition of ASMase in extracts of human oligodendroglioma cells (HOG) and neonatal rat oligodendrocytes. Non‐competitive inhibition was observed with inorganic phosphate and AMP, which was a more potent inhibitor of ASMase than cyclic AMP, ADP or ATP. However, other nucleotide phosphates, sugar phosphates, nucleotide sugars and glycerol phosphate did not inhibit ASMase. Our key finding was that phosphatidyl‐myo‐inositol 3,4,5‐triphosphate [PtdIns (3,4,5)P3] was a much more potent inhibitor of ASMase than lysophosphatidic acid or phosphatidyl‐myo‐inositol 4,5‐diphosphate [PtdIns(4,5)P2]. When PtdIns(3,4,5)P3 was added to cultured cells we observed 50% inhibition of ASMase but no inhibition of other lysosomal hydrolases. After transfection of HOG cells with the tumor supressor phosphatase and tensin homolog protein (PTEN), which hydrolyses PtdIns(3,4,5)P3 to PtdIns(4,5)P2, we observed a two‐fold increase in ASMase activity. Furthermore, the phosphatidylinositol‐3‐kinase inhibitor wortmannin (which reduces PtdIns(3,4,5)P3 levels) also resulted in activation of ASMase. We propose that the small amount of ASMase activity associated with detergent‐resistant cell membranes (Rafts) is regulated by PtdIns(3,4,5)P3 and is most likely involved in receptor clustering and capping.

Correction of coagulopathy in warfarin associated cerebral hemorrhage

Purpose of reviewWarfarin is the most commonly used oral anticoagulant. Intracranial hemorrhage is the most serious complication of anticoagulation and the anticoagulant effect of warfarin has to be urgently reversed in this situation. Traditional methods of reversal of the anticoagulant effect of warfarin involving the use of vitamin K and fresh frozen plasma are slow and relatively ineffective and there is a need for alternative treatment approaches. Recent findingsAgents such as prothrombin complex conjugates and recombinant activated factor VII are being increasingly used to emergently correct warfarin-associated coagulopathy. Over the last decade, several small case series have suggested that these agents may lead to more rapid correction of the INR, however, improved clinical outcome is yet to be proven. A recent small prospective trial has also demonstrated the safety of a prothrombin complex conjugate and its efficacy in rapidly correcting an elevated INR in these patients. SummaryThere is a need for well designed randomized clinical trials aimed at evaluating the efficacy of these agents in improving the outcome of patients with anticoagulant associated intracranial hemorrhage.

Acute hemorrhagic stroke pathophysiology and medical interventions: blood pressure control, management of anticoagulant-associated brain hemorrhage and general management principles.

Nontraumatic intracerebral hemorrhage is a neurologic emergency that accounts for about 10% to 20% of all strokes. Few patients suffering from intracerebral hemorrhage are expected to be independent 6 months after the event. This article reviews the pathophysiology and general medical management principles of spontaneous intracerebral hemorrhage, including the acute management of elevated blood pressure and management of anticoagulant-associated intracerebral hemorrhage.

The dementia of cardiac disease.

Cardiovascular disease and dementia are common in the elderly and are major causes of disability in the general population. The public health burden of dementia is projected to increase as life expectancy increases in the United States and elsewhere. Epidemiological studies suggest that these once believed unrelated conditions, heart disease and dementia, may be linked by shared common risks and pathogenic elements. These observations have sparked the notion that prevention or modification of certain vascular risk factors and proper management of cardiovascular disease may prevent the development or progression of dementia including Alzheimer’s disease. In this article, the authors discuss the association between cognitive impairment and atrial fibrillation, coronary artery disease, congestive heart failure, and cardiovascular procedures.