Key Points Closed head trauma sequentially releases tPA followed by uPA from injured brain. Increased uPA is responsible for delayed intracerebral hemorrhage, which is prevented by a tPA variant that inhibits uPA activity.

Approximately one-half of the patients who develop clinical atherosclerosis have normal or only modest elevations in plasma lipids, indicating that additional mechanisms contribute to pathogenesis. In view of increasing evidence that inflammation contributes to atherogenesis, we studied the effect of human neutrophil ␣-defensins on low density lipoprotein (LDL) trafficking, metabolism, vascular deposition, and atherogenesis using transgenic mice expressing human ␣-defensins in their polymorphonuclear leukocytes (Def ؉/؉ ). Accelerated Def Atherosclerosis and its thrombotic sequel, "atherothrombosis," are likely to remain the predominant cause of death in "developed" countries for decades to come. The etiology of this syndrome is multifactorial, and current predictors provide an incomplete estimate of the risk and opportunity for intervention. In a pooled analysis of over 87,000 persons with diagnosed coronary heart disease, one in five lacked any of the conventional risk factors: hypertension, smoking, high cholesterol, or diabetes (1). Furthermore, half of all cardiovascular events occur in patients with normal lipid levels (2). These data reveal the need to identify and mitigate as yet undescribed, but clinically relevant, risk factors for cardiovascular disease beyond those targeted in current practice.This problem is compounded by the lack of animal models that closely simulate human disease. Animal models used to study atherosclerosis, including its hyperlipidemic (3, 4) and inflammatory (5) components, are often characterized by striking elevations in plasma cholesterol, reaching plasma concentrations of 1500 -2200 mg/dl in LDLR Ϫ/Ϫ and 400 -450 mg/dl in ApoE Ϫ/Ϫ mice fed a high fat diet (3, 4), and most of the cholesterol is found in the VLDL fraction (3, 4). Neither these levels of lipids nor this distribution of lipoproteins is representative of findings in the vast majority of patients with atherosclerosis. Thus, there continues to be a need for new models to identify novel risk factors and novel approaches to intervention.We have identified human ␣-defensins 1-4, also known as human neutrophil peptides (HNPs), 2 as potentially having a role in the development of atherosclerosis. ␣-Defensins are antimicrobial proteins that constitute ϳ5% of the total protein in polymorphonuclear leukocytes (PMNs). ␣-Defensins are released from a subset of azurophilic granules when the PMNs are activated by a variety of agonists (6, 7). ␣-Defensins are abundant in human atherosclerotic coronary and carotid arteries (8, 9), and there is a significant correlation between the deposition of ␣-defensins in skin tissue and the severity of coronary artery disease (10). ␣-Defensins inhibit the degradation of low density lipoprotein (LDL) and Lp(a) by vascular cells (11), increase their binding and retention in extracellular matrix (12), and inhibit tissue-type plasminogen activator (tPA)-mediated fibrinolysis (13, 14).These observations have been confirmed and extended by others. Increased plasma levels of ␣-defensins are assoc...

Glucagon exerts a marked neuroprotective effect post-TBI by decreasing CNS glutamate. Glucagon was beneficial despite increasing blood glucose. Favorable effects also occurred when glucagon was given prior to TBI, suggesting its involvement in the preconditioning process. Thus, glucagon may be of value in providing neuroprotection when administered after TBI or prior to certain neurosurgical or cardiac interventions in which the incidence of perioperative ischemia is high.

Abu Fanne R, Nassar T, Heyman SN, Hijazi N, Higazi AA. Insulin and glucagon share the same mechanism of neuroprotection in diabetic rats: role of glutamate. Am J Physiol Regul Integr Comp Physiol 301: R668 -R673, 2011. First published June 15, 2011 doi:10.1152/ajpregu.00058.2011In patients with acute ischemic stroke, diabetes and hyperglycemia are associated with increased infarct size, more profound neurologic deficits and higher mortality. Notwithstanding extensive clinical and experimental data, treatment of stroke-associated hyperglycemia with insulin is controversial. In addition to hyperglycemia, diabetes and even early prediabetic insulin resistance are associated with increased levels of amino acids, including the neurotoxic glutamate, in the circulation. The pleiotropic metabolic effects of insulin include a reduction in the concentration of amino acids in the circulation. In this article, we show that in diabetic rats exposed to transient middle cerebral artery occlusion, a decrease of plasma glutamate by insulin or glucagon reduces CSF glutamate, improves brain histology, and preserves neurologic function. The neuroprotective effect of insulin and glucagon was similar, notwithstanding their opposite effects on blood glucose. The therapeutic window of both hormones overlapped with the short duration (ϳ30 min) of elevated brain glutamate following brain trauma in rodents. Similar neuroprotective effects were found after administration of the glutamate scavenger oxaloacetate, which does not affect glucose metabolism. These data indicate that insulin and glucagon exert a neuroprotective effect within a very brief therapeutic window that correlates with their capacity to reduce glutamate, rather than by modifying glucose levels. stroke; brain damage; glutamate IN ϳ30 -40% OF PATIENTS WITH acute ischemic stroke, diabetes is found at presentation (5, 24), ϳ70% have elevated blood glucose levels (27), and about 25% develop persistent hyperglycemia (21). Hyperglycemia is associated with increased infarct size (5,9,12,21,36,44), as well as with a ϳ3-fold higher risk of death (15), and survivors have more profound neurologic deficits and disability (26). Hyperglycemia is also associated with aggravated postischemic brain damage in animal models. In cats, acute hyperglycemia is associated with a ϳ3-fold increase in the volume of hemispheric infarcts induced by cerebrovascular occlusion (19), and in dogs, even moderate hyperglycemia has been shown to increase brain damage and mortality induced by ischemia (33). Consistent with these findings, treatment of hyperglycemia with insulin in these models, improves the outcome (10, 29, 45). Notwithstanding extensive clinical and experimental data indicating that hyperglycemia exacerbates poststroke brain damage and evidence from animal models that reversal of hyperglycemia with insulin attenuates injury (10, 29, 45), in clinical practice, this approach is controversial (8,23,25,31,35,37). This disconcerting lack of clinical success is not entirely surprising, since insu...