FSAP aggravated endothelial dysfunction and neurological deficits in acute ischemic stroke due to large vessel occlusion.

Revascularization and angiogenesis, as substrates of sustained collateral circulation, play a crucial role in determining the severity and clinical outcome of acute ischemic stroke (AIS) due to large vessel occlusion (LVO). Developing an adjunct biomarker to help identify and monitor collateral status would aid stroke diagnosis and prognosis. To screen the potential biomarkers, proteomic analysis was performed in this study to identify those distinct plasma protein profiles in AIS due to LVO with different collateral status. Interestingly, we found that levels of Plasma Factor VII Activating Protease (FSAP) significantly increased in those AIS patients with poor collaterals, and were correlated with worse neurological outcome. Furtherly, both in vitro and in vivo models of ischemic stroke were used to explore pathological mechanisms of FSAP in endothelial dysfunction. We demonstrated that the FSAP inhibitor, high-molecular-weight hyaluronan (HMW-HA), enhanced the pro-angiogenic vascular factors, improved the integrity of brain blood barrier, and promoted newly formed cerebral microvessels in the ischemic penumbra, consequently improving neurological function. To elucidate the pathways that might contribute to revascularization during LVO, we applied transcriptomic analysis via unbiased RNA sequencing and showed that Wnt signaling was highly involved in FSAP mediated endothelial dysfunction. Notably, inhibition of Wnt5a largely reversed the protective effects from HMW-HA treatment, implying that FSAP might aggravate endothelial dysfunction and neurological deficits by regulating Wnt5a signaling. Therefore, FSAP may represent a potential biomarker for collateral status after LVO and a promising therapeutic target to be explored in the treatment of stroke.

Mitochondrial Metabolism behind Region-Specific Resistance to Ischemia-Reperfusion Injury in Gerbil Hippocampus. Role of PKCßII and Phosphate-Activated Glutaminase.

Ischemic episodes are a leading cause of death worldwide with limited therapeutic interventions. The current study explored mitochondrial phosphate-activated glutaminase (GLS1) activity modulation by PKCßII through GC-MS untargeted metabolomics approach. Mitochondria were used to elucidate the endogenous resistance of hippocampal CA2-4 and dentate gyrus (DG) to transient ischemia and reperfusion in a model of ischemic episode in gerbils. In the present investigation, male gerbils were subjected to bilateral carotids occlusion for 5 min followed by reperfusion (IR). Gerbils were randomly divided into three groups as vehicle-treated sham control, vehicle-treated IR and PKCßII specific inhibitor peptide ßIIV5-3-treated IR. Vehicle or ßIIV5-3 (3 mg/kg, i.v.) were administered at the moment of reperfusion. The gerbils hippocampal tissue were isolated at various time of reperfusion and cell lysates or mitochondria were isolated from CA1 and CA2-4,DG hippocampal regions. Recombinant proteins PKCßII and GLS1 were used in in vitro phosphorylation reaction and organotypic hippocampal cultures (OHC) transiently exposed to NMDA (25 µM) to evaluate the inhibition of GLS1 on neuronal viability. PKCßII co-precipitates with GAC (GLS1 isoform) in CA2-4,DG mitochondria and phosphorylates GLS1 in vitro. Cell death was dose dependently increased when GLS1 was inhibited by BPTA while inhibition of mitochondrial pyruvate carrier (MPC) attenuated cell death in NMDA-challenged OHC. Fumarate and malate were increased after IR 1h in CA2-4,DG and this was reversed by ßIIV5-3 what correlated with GLS1 activity increases and earlier showed elevation of neuronal death (Krupska et al., 2017). The present study illustrates that CA2-4,DG resistance to ischemic episode at least partially rely on glutamine and glutamate utilization in mitochondria as a source of carbon to tricarboxylic acid cycle. This phenomenon depends on modulation of GLS1 activity by PKCßII and remodeling of MPC: all these do not occur in ischemia-vulnerable CA1.

Glutathione Peroxidase Activity Is Altered in Vascular Cognitive Impairment-No Dementia and Is a Potential Marker for Verbal Memory Performance.

BACKGROUND: Coronary artery disease (CAD) increases risk for vascular cognitive impairment-no dementia (VCIND), a precursor to dementia, potentially through persistent oxidative stress. OBJECTIVE: This study assessed peripheral glutathione peroxidase activity (GPX), which is protective against oxidative stress, in VCIND versus cognitively normal CAD controls (CN). GPX activity was also evaluated as a biomarker of cognition, particularly verbal memory. METHODS: 120 CAD patients with VCIND (1SD below norms on executive function or verbal memory (VM)) or without (CN) participated in exercise rehabilitation for 24 weeks. Neurocognitive and cardiopulmonary fitness (VO2peak) assessments and plasma were collected at baseline and 24-weeks. RESULTS: GPX was higher in VCIND compared to CN (F1,119 = 3.996, p = 0.048). Higher GPX was associated with poorer baseline VM (ß= -0.182, p = 0.048), and longitudinally with VM decline controlling for sex, body mass index, VO2peak, and education (b[SE] = -0.02[0.01], p = 0.004). Only CN participants showed improved VM performance with increased fitness (b[SE] = 1.30[0.15], p < 0.005). CONCLUSION: GPX was elevated in VCIND consistent with a compensatory response to persistent oxidative stress. Increased GPX predicted poorer cognitive outcomes (verbal memory) in VCIND patients despite improved fitness.

A cannabinoid type 2 (CB2) receptor agonist augments NOS-dependent responses of cerebral arterioles during type 1 diabetes.

While activation of cannabinoid (CB2) receptors has been shown to be neuroprotective, no studies have examined whether this neuroprotection is directed at cerebral arterioles and no studies have examined whether activation of CB2 receptors can rescue cerebrovascular dysfunction during a chronic disease state such as type 1 diabetes (T1D). Our goal was to test the hypothesis that administration of a CB2 agonist (JWH-133) would improve impaired endothelial (eNOS)- and neuronal (nNOS)-dependent dilation of cerebral arterioles during T1D. In vivo diameter of cerebral arterioles in nondiabetic and T1D rats was measured in response to an eNOS-dependent agonist (adenosine 5'-diphosphate; ADP), an nNOS-dependent agonist (N-methyl-d-aspartate; NMDA), and an NOS-independent agonist (nitroglycerin) before and 1 h following JWH-133 (1 mg/kg IP). Dilation of cerebral arterioles to ADP and NMDA was greater in nondiabetic than in T1D rats. Treatment with JWH-133 increased responses of cerebral arterioles to ADP and NMDA in both nondiabetic and T1D rats. Responses of cerebral arterioles to nitroglycerin were similar between nondiabetic and T1D rats, and JWH-133 did not influence responses to nitroglycerin in either group. The restoration in responses to the agonists by JWH-133 could be inhibited by treatment with a specific inhibitor of CB2 receptors (AM-630; 3 mg/kg IP). Thus, activation of CB2 receptors can potentiate reactivity of cerebral arterioles during physiologic and pathophysiologic states. We speculate that treatment with CB2 receptor agonists may have potential therapeutic benefits for the treatment of cerebral vascular diseases via a mechanism that can increase cerebral blood flow.

P66shc and its role in ischemic cardiovascular diseases.

Oxidative stress caused by an imbalance in the formation and removal of reactive oxygen species (ROS) plays an important role in the development of several cardiovascular diseases. ROS originate from various cellular origins; however, the highest amount of ROS is produced by mitochondria. One of the proteins contributing to mitochondrial ROS formation is the adaptor protein p66shc, which upon cellular stresses translocates from the cytosol to the mitochondria. In the present review, we focus on the role of p66shc in longevity, in the development of cardiovascular diseases including diabetes, atherosclerosis and its risk factors, myocardial ischemia/reperfusion injury and the protection from it by ischemic preconditioning. Also, the contribution of p66shc towards cerebral pathologies and the potential of the protein as a therapeutic target for the treatment of the aforementioned diseases are discussed.

Dementia: new vistas and opportunities.

Over the past four decades, Alzheimer disease has become near synonymous with dementia and the amyloid/tau hypothesis as its dominant explanation. However, this monorail approach to etiology has failed to yield a single disease-modifying drug. Part of the explanation stems from the fact that most dementias in the elderly result from interactive Alzheimer and cerebrovascular pathologies. Stroke and dementia share the same risk factors and their control is associated with a decrease in stroke and some dementias. Additionally, intensive control of risk factors and enhancement of protective factors improve cognition. Moreover, anticoagulation of atrial fibrillation patients decreases their chance of developing dementia by 48%. Preliminary data suggest that treating blood pressure to a target of 120 mmHg systolic compared to a target of 140 mmHg decreases the chances of mild cognitive impairment by 19%. The Berlin Manifesto establishes the scientific bases of "preventing dementia by preventing stroke." Enlarging our vista of dementia to include cerebrovascular disease offers the opportunity of preventing not only stroke, but some dementias, beginning now.

Endothelial Mitochondrial Preprotein Translocase Tomm7-Rac1 Signaling Axis Dominates Cerebrovascular Network Homeostasis.

Objective- Mitochondria are the important yet most underutilized target for cardio-cerebrovascular function integrity and disorders. The Tom (translocases of outer membrane) complex are the critical determinant of mitochondrial homeostasis for making organs acclimate physiological and pathological insults; however, their roles in the vascular system remain unknown. Approach and Results- A combination of studies in the vascular-specific transgenic zebrafish and genetically engineered mice was conducted. Vascular casting and imaging, endothelial angiogenesis, and mitochondrial protein import were performed to dissect potential mechanisms. A loss-of-function genetic screening in zebrafish identified that selective inactivation of the tomm7 (translocase of outer mitochondrial membrane 7) gene, which encodes a small subunit of the Tom complex, specially impaired cerebrovascular network formation. Ablation of the ortholog Tomm7 in mice recapitulated cerebrovascular abnormalities. Restoration of the cerebrovascular anomaly by an endothelial-specific transgenesis of tomm7 further indicated a defect in endothelial function. Mechanistically, Tomm7 deficit in endothelial cells induced an increased import of Rac1 (Ras-related C3 botulinum toxin substrate 1) protein into mitochondria and facilitated the mitochondrial Rac1-coupled redox signaling, which incurred angiogenic impairment that underlies cerebrovascular network malformation. Conclusions- Tomm7 drives brain angiogenesis and cerebrovascular network formation through modulating mitochondrial Rac1 signaling within the endothelium.

High-resolution Imaging of Myeloperoxidase Activity Sensors in Human Cerebrovascular Disease.

Progress in clinical development of magnetic resonance imaging (MRI) substrate-sensors of enzymatic activity has been slow partly due to the lack of human efficacy data. We report here a strategy that may serve as a shortcut from bench to bedside. We tested ultra high-resolution 7T MRI (µMRI) of human surgical histology sections in a 3-year IRB approved, HIPAA compliant study of surgically clipped brain aneurysms. µMRI was used for assessing the efficacy of MRI substrate-sensors that detect myeloperoxidase activity in inflammation. The efficacy of Gd-5HT-DOTAGA, a novel myeloperoxidase (MPO) imaging agent synthesized by using a highly stable gadolinium (III) chelate was tested both in tissue-like phantoms and in human samples. After treating histology sections with paramagnetic MPO substrate-sensors we observed relaxation time shortening and MPO activity-dependent MR signal enhancement. An increase of normalized MR signal generated by ultra-short echo time MR sequences was corroborated by MPO activity visualization by using a fluorescent MPO substrate. The results of µMRI of MPO activity associated with aneurysmal pathology and immunohistochemistry demonstrated active involvement of neutrophils and neutrophil NETs as a result of pro-inflammatory signalling in the vascular wall and in the perivascular space of brain aneurysms.

Cytochrome P450 family 4 subfamily F member 2 (CYP4F2) rs1558139, rs2108622 polymorphisms and susceptibility to several cardiovascular and cerebrovascular diseases.

BACKGROUND: Inconsistent conclusions have been reported for the genetic relationship between CYP4F2 (Cytochrome P450 Family 4 Subfamily F Member 2) polymorphisms and the susceptibility to cardiovascular and cerebrovascular diseases. METHODS: We performed a meta-analysis to assess the potential role of rs1558139 C/T and rs2108622 G/A polymorphisms of CYP4F2 in the risks of cardiovascular and cerebrovascular diseases. The retrieval of four databases, including PubMed, Web of Science (WOS), China National Knowledge Infrastructure (CNKI) and WANFANG DATA, was conducted. Mantel-Haenszel statistics for association test, Cochran's Q statistic, sensitivity analysis for heterogeneity assessment, and Begg's/Egger's tests for publication bias evaluation were performed under allele, homozygote, heterozygote, dominant, and recessive models, respectively. RESULTS: A total of 597 articles were initially obtained by database searching, and twenty eligible articles were finally included. For rs1558139, a decreased risk of cardiovascular and cerebrovascular diseases was observed in the overall meta-analysis and in "hypertension", "population-based" and "male" subgroups under models of T vs. C, CT vs. CC, and CT + TT vs. CC [all P values in association tests < 0.05, odds ratio (OR) < 1]. For rs2108622, a decreased coronary artery disease (CAD) risk was observed in the subgroup meta-analysis based on disease type under all genetic models (all P values in association tests < 0.05, OR< 1). Begg's/Egger's tests excluded the potential publication bias, while sensitivity analysis data supported the stability of the above results. CONCLUSION: C/T genotype of CYP4AF2 rs1558139 may be linked to the decreased risk of hypertension in the male patients of Asian populations, while CYP4F2 rs2108622 is likely associated with reduced susceptibility to CAD.

ADAMTS-13 and von Willebrand factor: a dynamic duo.

von Willebrand factor (VWF) is a key player in hemostasis, acting as a carrier for factor VIII and capturing platelets at sites of vascular damage. To capture platelets, it must undergo conformational changes, both within its A1 domain and at the macromolecular level through A2 domain unfolding. Its size and this function are regulated by the metalloproteinase ADAMTS-13. Recently, it has been shown that ADAMTS-13 undergoes a conformational change upon interaction with VWF, and that this enhances its activity towards its substrate. This review summarizes recent work on these conformational transitions, describing how they are controlled. It points to their importance in hemostasis, bleeding disorders, and the developing field of therapeutic application of ADAMTS-13 as an antithrombotic agent in obstructive microvascular thrombosis and in cardiovascular disease.

G6PD plays a neuroprotective role in brain ischemia through promoting pentose phosphate pathway.

TIGAR-regulated pentose phosphate pathway (PPP) plays a critical role in the neuronal survival during cerebral ischemia/reperfusion. Glucose-6-phosphate dehydrogenase (G6PD) is a rate-limiting enzyme in PPP and thus, we hypothesized that it plays an essential role in anti-oxidative defense through producing NADPH. The present study investigated the regulation and the role of G6PD in ischemia/reperfusion-induced neuronal injury with in vivo and in vitro models of ischemic stroke. The results showed that the levels of G6PD mRNA and protein were increased after ischemia/reperfusion. In vivo, lentivirus-mediated G6PD overexpression in mice markedly reduced neuronal damage after ischemia/reperfusion insult, while lentivirus-mediated G6PD knockdown exacerbated it. In vitro, overexpression of G6PD in cultured primary neurons decreased neuronal injury under oxygen and glucose deprivation/reoxygenation (OGD/R) condition, whereas knockdown of G6PD aggravated it. Overexpression of G6PD increased levels of NADPH and reduced form of glutathione (rGSH), and ameliorated ROS-induced macromolecular damage. On the contrary, knockdown of G6PD executed the opposite effects in mice and in primary neurons. Supplementation of exogenous NADPH alleviated the detrimental effects of G6PD knockdown, whereas further enhanced the beneficial effects of G6PD overexpression in ischemic injury. Therefore, our results suggest that G6PD protects ischemic brain injury through increasing PPP. Thus G6PD may be considered as potential therapeutic target for treatment of ischemic brain injury.

Regulation of high glucose-induced apoptosis of brain pericytes by mitochondrial CA VA: A specific target for prevention of diabetic cerebrovascular pathology.

Events responsible for cerebrovascular disease in diabetes are not fully understood. Pericyte loss is an early event that leads to endothelial cell death, microaneurysms, and cognitive impairment. A biochemical mechanism underlying pericyte loss is rapid respiration (oxidative metabolism of glucose). This escalation in respiration results from free influx of glucose into insulin-insensitive tissues in the face of high glucose levels in the blood. Rapid respiration generates superoxide, the precursor to all reactive oxygen species (ROS), and results in pericyte death. Respiration is regulated by carbonic anhydrases (CAs) VA and VB, the two isozymes expressed in mitochondria, and their pharmacologic inhibition with topiramate reduces respiration, ROS, and pericyte death. Topiramate inhibits both isozymes; therefore, in the earlier studies, their individual roles were not discerned. In a recent genetic study, we showed that mitochondrial CA VA plays a significant role in regulation of reactive oxygen species and pericyte death. The role of CA VB was not addressed. In this report, genetic knockdown and overexpression studies confirm that mitochondrial CA VA regulates respiration in pericytes, whereas mitochondrial CA VB does not contribute significantly. Identification of mitochondrial CA VA as a sole regulator of respiration provides a specific target to develop new drugs with fewer side effects that may be better tolerated and can protect the brain from diabetic injury. Since similar events occur in the capillary beds of other insulin-insensitive tissues such as the eye and kidney, these drugs may also slow the onset and progression of diabetic disease in these tissues.

Matrix Metalloproteinase-Mediated Neuroinflammation in Vascular Cognitive Impairment of the Binswanger Type.

Vascular cognitive impairment (VCI) is a heterogeneous group of diseases linked together by cerebrovascular disease. Treatment of VCI has been hindered by the lack of a coherent pathophysiological process that could provide molecular targets. Of the several forms of VCI, the small vessel disease form is both the most prevalent and generally has a progressive course. Binswanger's disease (BD) is the small vessel form of VCI that involves extensive injury to the deep white matter. Growing evidence suggests that there is disruption of the blood-brain barrier (BBB) secondary to an inflammatory state. Matrix metalloproteinases (MMPs) are increased in the brain and CSF of patients with BD, and have been shown to disrupt the BBB in animal studies, suggesting that they may be biomarkers and therapeutic targets. Multimodal biomarkers derived from clinical, neuropsychological, imaging, and biochemical data can be used to narrow the VCI population to the progressive inflammatory form that will be optimal for treatment trials. This review describes the role of the MMPs in pathophysiology and their use as biomarkers.

NADPH oxidase 4 attenuates cerebral artery changes during the progression of Marfan syndrome.

Marfan syndrome (MFS) is a connective tissue disorder that is often associated with the fibrillin-1 (Fbn1) gene mutation and characterized by cardiovascular alterations, predominantly ascending aortic aneurysms. Although neurovascular complications are uncommon in MFS, the improvement in Marfan patients' life expectancy is revealing other secondary alterations, potentially including neurovascular disorders. However, little is known about small-vessel pathophysiology in MFS. MFS is associated with hyperactivated transforming growth factor (TGF)-ß signaling, which among numerous other downstream effectors, induces the NADPH oxidase 4 (Nox4) isoform of NADPH oxidase, a strong enzymatic source of H2O2 We hypothesized that MFS induces middle cerebral artery (MCA) alterations and that Nox4 contributes to them. MCA properties from 3-, 6-, or 9-mo-old Marfan (Fbn1(C1039G/+)) mice were compared with those from age/sex-matched wild-type littermates. At 6 mo, Marfan compared with wild-type mice developed higher MCA wall/lumen (wild-type: 0.081 ± 0.004; Marfan: 0.093 ± 0.002; 60 mmHg; P < 0.05), coupled with increased reactive oxygen species production, TGF-ß, and Nox4 expression. However, wall stiffness and myogenic autoregulation did not change. To investigate the influence of Nox4 on cerebrovascular properties, we generated Marfan mice with Nox4 deficiency (Nox4(-/-)). Strikingly, Nox4 deletion in Marfan mice aggravated MCA wall thickening (cross-sectional area; Marfan: 6,660 ± 363 µm(2); Marfan Nox4(-/-): 8,795 ± 824 µm(2); 60 mmHg; P < 0.05), accompanied by decreased TGF-ß expression and increased collagen deposition and Nox1 expression. These findings provide the first evidence that Nox4 mitigates cerebral artery structural changes in a murine model of MFS.

Endothelial nitric oxide synthase: a potential therapeutic target for cerebrovascular diseases.

Endothelial nitric oxide (NO) is a significant signaling molecule that regulates cerebral blood flow (CBF), playing a pivotal role in the prevention and treatment of cerebrovascular diseases. However, achieving the expected therapeutic efficacy is difficult using direct administration of NO donors. Therefore, endothelial nitric oxide synthase (eNOS) becomes a potential therapeutic target for cerebrovascular diseases. This review summarizes the current evidence supporting the importance of CBF to cerebrovascular function, and the roles of NO and eNOS in CBF regulation.

Rho kinase as a target for cerebral vascular disorders.

The development of novel pharmaceutical treatments for disorders of the cerebral vasculature is a serious unmet medical need. These vascular disorders are typified by a disruption in the delicate Rho signaling equilibrium within the blood vessel wall. In particular, Rho kinase overactivation in the smooth muscle and endothelial layers of the vessel wall results in cytoskeletal modifications that lead to reduced vascular integrity and abnormal vascular growth. Rho kinase is thus a promising target for the treatment of cerebral vascular disorders. Indeed, preclinical studies indicate that Rho kinase inhibition may reduce the formation/growth/rupture of both intracranial aneurysms and cerebral cavernous malformations.

Morphological changes of cerebral vessels and expression patterns of MMP-2 and MMP-9 on cerebrovascular wall of alcoholic rats.

Alcohol abuse increases the incidence of cerebral accidents, which correlates with cerebrovascular structural changes. The present study was designed to observe the cerebrovascular remodeling of drinking rats with light microscopy and transmission electron microscopy (TEM). Short-term alcohol administration induced apparent amplification of perivascular spaces around small vessels in brain tissue, while long-term administration caused pathological changes of basilar arteries (BAs), including endothelial exfoliation, inner elastic lamina (IEL) fragmentation and thickening of tunica media and adventitia. In addition, the relationship between cerebrovascular remodeling and MMP-2 and MMP-9 synthesized by endothelial cells and vascular smooth muscle cells was explored by immunohistochemistry. The two protein expression in cerebral vessels changed dynamically, peaking at 1-2 weeks after treatment, and decreasing as treatment continued. These results suggest that MMP-2 and MMP-9 may play a significant role in blood-brain barrier disruption after alcohol abuse. But the chronic changes of cerebral arteries resulted from drinking are not coincident with time course of MMP-2 and MMP-9 expression in situ.

A therapeutic approach to cerebrovascular diseases based on indole substituted hydrazides and hydrazines able to interact with human vascular adhesion protein-1, monoamine oxidases (A and B), AChE and BuChE.

Herein, we report the biological evaluation of a series of indole substituted hydrazides and hydrazines throughout the assessment of their multipotent inhibitory potency towards monoamine oxidase (MAO) A and B, semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1), and the cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Hydrazine JL72 (3-(3-hydrazinylpropyl)-1H-indole) showed a potent, reversible and non-time-dependent inhibition of MAO-A, which suggests its capacity in restoring serotoninergic neurotransmission being devoid of the side effects observed for classic MAO-A inhibitors. In addition, JL72 behaved as a moderate BuChE inhibitor. Finally, both hydrazines and hydrazides derivatives showed high affinity towards SSAO/VAP-1. Among them, JL72 behaved as a noncompetitive and the most potent inhibitor (IC50 = 0.19 ± 0.04 µM), possessing also a significant anti-inflammatory activity. The combined inhibition of SSAO/VAP-1, MAO (A and B), AChE and BuChE appear as an important therapeutic target to be considered in the treatment of cerebrovascular and neurological disorders such as Alzheimer's disease.

Neuronal nitric oxide synthase and sympathetic nerve activity in neurovascular and metabolic systems.

Nitric oxide, derived from nitric oxide synthase (NOS), plays an important role in regulating sympathetic nerve activity. Neuronal NOS (nNOS) is expressed throughout the central and peripheral nervous system. nNOS has a sympathoinhibitory effect under physiological conditions by acting on different sites of the nervous system, including the paraventricular nucleus, the nucleus of the solitary tract, the rostral ventrolateral medulla, the carotid body and nerves in the kidney. nNOS is sympathoinhibitory in a range of diseases including chronic heart failure, chronic renal failure, hypertension and diabetes. nNOS is believed to mediate sympathoinhibitory effects induced by a range of signaling pathways including those promoted by angiotensin-converting enzyme 2 over-expression; statin therapy; angiotensin II type 1 receptor blockers; exercise training; tumor necrosis factor-α blockade; superoxide dismutase mimetics; and estrogen replacement therapy. Increase in nNOS can increase sympathoinhibitory γ-aminobutyric acid activity and decrease sympathoexcitatory angiotensin II signaling and glutamate activity. nNOS may have sympathoexcitatory effects in some circumstances such as chronic heart failure induced by prolonged high salt treatment. The effectiveness of nNOS upregulation in treating sympathetic overactive conditions including chronic heart failure needs to be further investigated.

p38 MAPK: a mediator of hypoxia-induced cerebrovascular inflammation.

Vascular perturbations and hypoxia are increasingly implicated in Alzheimer's disease (AD) pathogenesis. Cerebral hypoxia induces a large number of inflammatory proteins in brain endothelial cells via signaling pathways that have not been defined. The p38 mitogen-activated protein kinase (MAPK) signaling system has been implicated in endothelial injury and inflammation. The objective of this study is to examine p38 MAPK levels in the cerebromicrovasulature in AD and AD animal models and determine the role of p38 MAPK signaling in hypoxia-mediated effects on brain endothelial cells. Western blot analysis of isolated human brain microvessels show that the phosphorylated (active) form of p38 MAPK (pp38 MAPK) is increased in vessels derived from AD brains compared to control-derived vessels. Similarly, immunofluorescent analysis reveals an increase in cerebrovascular pp38 MAPK as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in transgenic AD mice. Exposure of brain endothelial cells to hypoxia (2-6 hours) shows a time-dependent increase in pp38 MAPK. Examination of these cultures at 6 hours hypoxia shows that iNOS and COX-2 are significantly elevated and that the selective p38 MAPK inhibitor SB203580 significantly reduces the hypoxia-mediated increase in their expression. Inhibition of p38 MAPK in cultured brain endothelial cells also significantly decreases the hypoxia-induced increase in the inflammatory proteins, matrix metalloproteinase-2 and angiopoietin-2. These data demonstrate that pp38 MAPK is a key regulator of hypoxia in the cerebrovasculature and suggest that control of this signaling pathway could have therapeutic value in AD and other disorders where hypoxia is involved.