Current Neurovascular Research (v.9, #1)
Editor's Perspective (Throwing Caution to the Wnts) by Kenneth Maiese (i-ii).
The brain is dependent upon multiple cell types for protection that include neurons, inflammatory microglia, astrocytes, endothelial cells and pericytes. Each of these cell types form vital components for areas of the brain that determine cognition as well as emotion. Furthermore, the various cell types of the brain must work in an integrated fashion to not only assist with common function but also protect the brain on a larger scale. For example, pericytes are an important component to the neurovascular unit that consists of neurons, cerebral endothelial cells, and astrocytes. Pericytes assist with the maintenance of the blood-brain barrier, help maintain the survival of endothelial cells during toxic insults, and can promote endothelial cell growth during angiogenesis. Pericytes themselves also can differentiate into mesenchymal stem cells and smooth muscle cells. If one looks further at the cellular level in this neurovascular unit, multiple pathways can control survival as well as regenerative processes. One interesting pathway involves the Wnt proteins that are secreted cysteine-rich glycosylated proteins that can control proliferation, differentiation, and survival in several cellular populations that include neurons, endothelial cells, and inflammatory cells such as microglia. Wnt proteins also regulate the differentiation of pericytes, endothelial cells, and the progression of angiogenesis. In addition, Wnt proteins oversee inflammatory cell control and the regulation of endovascular injury. The Wnt pathway can ultimately determine the integrity of the neurovascular unit since activated immune cells can lead to the phagocytic removal of both neurons and vascular cells. It is clear that the different cell types and complex pathways of the brain must form an integrated network to protect and foster the function of the brain. In this issue of Current Neurovascular Research, our papers highlight several novel aspects of this vital network. Arimura and co-authors show that platelet derived growth factor receptor is expressed in pericytes during cerebral ischemic injury and that platelet derived growth factor itself in pericytes prevents apoptotic responses, suggesting that pericytes rely upon platelet derived growth factor signaling to provide protection for the brain. In the paper by Marie-Francoise Ritz et al., the authors tie the effects of hypertension to injury responses in the cortex of the brain. In addition to expected blood flow changes with hypertension, the study demonstrates that hypertension also alters gene expression in the brain that can lead to cerebral vessel disease through the up-regulation of genetic pathways involving energy and lipid metabolism, ischemia, and oxidative stress. In the next paper of this issue, Wang and co-authors elucidate new roles for Wnt signaling in hippoacampal neurons through the Wnt1 inducible signaling pathway protein 1 (WISP1). WISP1 governs a specific set of unique interconnected pathways that are not usually considered part of the Wnt signaling family that involve PI 3-K, Akt1, Bad, GSK-3β, Bim, Bax, and Bcl-xL to control mitochondrial membrane permeability, caspase activation, and neuron apoptotic injury during oxidant stress. In the work by Xi et al., they demonstrate for us the role of flavonoids to block endothelial cell degeneration associated with β-amyloid and to protect components of the neurovascular unit through signaling of the NF-E2- related factor 2 pathway. Lin and Feng take a more clinical perspective in their work in patients hospitalized with intracranial hemorrhage and show a racial disparity among risk factors in younger African Americans for recurrent stoke, myocardial infarction, and death due to vascular complications. This work points to the need for improved treatment and understanding of the cellular pathology in various patient populations that suffer from intracerebral hemorrhage. In the work by Steckert et al., they show that protein kinase C may not only play an important role during bipolar disorder, since inhibition of the protein kinase C pathway can reduce hyperactivity, but also that protein kinase C may ameliorate oxidative damage that may be a component of bipolar disorder. Studies by Bulku et al. focus upon curcumin, a popular coloring and flavor agent that has recently been demonstrated to have protective properties for the brain. The authors' current work now shows that curcumin may offer more global protection in the body to indirectly protect the brain through the prevention of drug-induced hepatic injury through anti-apoptotic gene expression. Our final article by Argandona et al. provides a welcome overview of the “neuroglialvascular” unit addressing areas that involve brain development as well as environmental enrichment and physical exercise. The thought provoking studies in this issue of Current Neurovascular Research emphasize some of the complexity and the commonality of the pathways that determine the protection of the brain and the richness of the neurovascular unit. However, given the many unknowns that continue to exist, such as why an individual may experience a different and severe response to a nervous system insult in comparison to another individual that suffers minimal deficits, we must quickly move ahead and “throw caution to the Wnts” in our pursuit to develop new treatment strategies for many nervous system disorders that are without effective therapies.
PDGF Receptor β Signaling in Pericytes Following Ischemic Brain Injury by Koichi Arimura (1-9).
Platelet derived growth factor (PDGF)-B plays a neuroprotective role in brain damages, including ischemic stroke. It has been suggested recently that PDGF receptor β (PDGFRβ) expressed in brain pericytes as well as in neurons and astrocytes may mediate the neuroprotective role of PDGF-B. The aims of this study were to elucidate the roles of PDGFRβ signaling in brain pericytes after ischemic stroke. In a rat middle cerebral artery occlusion (MCAO) model, PDGFRβ expression was induced specifically in the pericytes in peri-infarct areas and its level was gradually increased. PDGF-B induced marked phosphorylation of Akt in cultured brain pericytes. Consistently, PDGF-B was upregulated in endothelial cells in per-infarct areas and Akt was strongly phosphorylated in the PDGFRβ-expressing pericytes in periinfarct areas after MCAO. In the cultured pericytes, PDGF-B induced cell growth and anti-apoptotic responses through Akt. Furthermore, PDGF-B significantly increased the expression of nerve growth factor (NGF) and neurotrophin-3 (NT- 3) through Akt in the pericytes. Thus, the PDGFRβ-Akt signaling in brain pericytes may play various important roles leading to neuroprotection after ischemic stroke.
Gene Expression Suggests Spontaneously Hypertensive Rats May Have Altered Metabolism and Reduced Hypoxic Tolerance by Marie-Francoise Ritz (10-19).
Cerebral small vessel disease (SVD) is an important cause of stroke, cognitive decline and vascular dementia (VaD). It is associated with diffuse white matter abnormalities and small deep cerebral ischemic infarcts. The molecular mechanisms involved in the development and progression of SVD are unclear. As hypertension is a major risk factor for developing SVD, Spontaneously Hypertensive Rats (SHR) are considered an appropriate experimental model for SVD. Prior work suggested an imbalance between the number of blood microvessels and astrocytes at the level of the neurovascular unit in 2-month-old SHR, leading to neuronal hypoxia in the brain of 9-month-old animals. To identify genes and pathways involved in the development of SVD, we compared the gene expression profile in the cortex of 2 and 9-month-old of SHR with age-matched normotensive Wistar Kyoto (WKY) rats using microarray-based technology. The results revealed significant differences in expression of genes involved in energy and lipid metabolisms, mitochondrial functions, oxidative stress and ischemic responses between both groups. These results strongly suggest that SHR suffer from chronic hypoxia, and therefore are unable to tolerate ischemia-like conditions, and are more vulnerable to highenergy needs than WKY. This molecular analysis gives new insights about pathways accounting for the development of SVD.
Wnt1 Inducible Signaling Pathway Protein 1 (WISP1) Blocks Neurodegeneration through Phosphoinositide 3 Kinase/Akt1 and Apoptotic Mitochondrial Signaling Involving Bad, Bax, Bim, and Bcl-xL by Shaohui Wang (20-31).
Wnt1 inducible signaling pathway protein 1 (WISP1) is a member of the CCN family of proteins that determine cell growth, cell differentiation, immune system activation, and cell survival in tissues ranging from the cardiovascular-pulmonary system to the reproductive system. Yet, little is known of the role of WISP1 as a neuroprotective entity in the nervous system. Here we demonstrate that WISP1 is present in primary hippocampal neurons during oxidant stress with oxygen-glucose deprivation (OGD). WISP1 expression is significantly enhanced during OGD exposure by the cysteine-rich glycosylated protein Wnt1. Similar to the neuroprotective capabilities known for Wnt1 and its signaling pathways, WISP1 averts neuronal cell injury and apoptotic degeneration during oxidative stress exposure. WISP1 requires activation of phosphoinositide 3-kinase (PI 3-K) and Akt1 pathways to promote neuronal cell survival, since blockade of these pathways abrogates cellular protection. Furthermore, WISP1 through PI 3-K and Akt1 phosphorylates Bad and GSK-3β, minimizes expression of the Bim/Bax complex while increasing the expression of BclxL/ Bax complex, and prevents mitochondrial membrane permeability, cytochrome c release, and caspase 3 activation in the presence of oxidant stress. These studies provide novel considerations for the development of WISP1 as an effective and robust therapeutic target not only for neurodegenerative disorders, but also for disease entities throughout the body.
Flavonoids Protect Cerebrovascular Endothelial Cells through Nrf2 and PI3K from β-Amyloid Peptide-Induced Oxidative Damage by Yuan-Di Xi (32-41).
β-amyloid peptides (Aβ ) induced cerebrovascular dysfunction has been recognized as a vital factor involved in the pathogenesis of neurodegeneration. Genistein, a flavonoid, has antioxidative properties to prevent neurodegeneration induced by β-amyloid peptides. In this study, we were investigating whether genistein could antagonize oxidative damage induced by β-amyloid peptide 25-35 (Aβ25-35) in bEND.3 cells, and also identifying the potential neuroprotective targets of genistein. Vitamin E was used as the positive control. The bEND.3 cells were pre-incubated with/out genistein or vitamin E for 2 h followed by the incubation with 25 μM A 25-35 for another 24 h. The reactive oxygen species (ROS), nitrotyrosine, cell redox state, mRNA or protein expressions of the factors on Nrf2 signaling pathway were measured after Aβ25-35 treatment. The results showed that genistein alleviated the increase of ROS and nitrotyrosine production induced by Aβ25-35, and maintained bEND.3 cell redox state by increasing GSH level and GSH/GSSG. Genistein could reverse the down-regulation of total protein and mRNA expression of NF-E2-related factor 2 (Nrf2), nuclear Nrf2, -γ glutamylcysteine synthetase (γ-GCS), phosphatidylinositol 3-kinase (PI3K) induced by Aβ25-35; while PI3K inhibitor LY294002 could attenuate the activation effects of genistein on Nrf2, especially for the promotion of nuclear translocation. These results suggested that genistein could protect cerebrovascular endothelial cells from Aβ25-35-induced oxidative damage. The potential mechanisms might be associated with the activation of Nrf2 signaling pathway by modulating PI3K activity.
Assessment of Short- and Long-Term Outcomes of Patients Hospitalized With Intracerebral Hemorrhage by Chih-Ming Lin (42-46).
The aim of this study was to assess short- and long-term outcomes of patients hospitalized with intracerebral hemorrhage (ICH) in South Carolina. Patients with a primary diagnosis of ICH (ICD-9-CM code 431) discharged during 2002 were identified in the South Carolina hospital discharge database. Kaplan-Meier estimates of recurrent stroke, myocardial infarct, vascular death, all-cause death, and composite events were calculated at 1 month, 6 months, and 1, 2, 3, and 4 years. Age- and race-specific survival curves were plotted. A total of 893 patients were discharged during 2002. Most were Caucasian (CA) (61.4%), followed by African American (AA) (37.4%). The mean age of patients in the AA group was 12 years younger than that of the CA group; of those in the AA group, 63.8% were < 65 years of age, and of those in the CA group, 27.4% were > 65 years of age. Kaplan-Meier estimates of cumulative risk increased with time over the 4-year period after discharge, and the risk of all-cause death was high (∼40%-60%). Survival curves showed that the composite risk of recurrent stroke, myocardial infarct, or vascular death was higher for AA patients < 65 years of age compared to similarly aged CA patients, whereas the risk was higher for CA patients > 65 years of age compared to similar age AA patients. The racial disparity in short- and long-term outcomes for ICH patients < 65 years of age in South Carolina highlights the need for improvements in stroke prevention, particularly among the AA population.
Protein Kinase C and Oxidative Stress in an Animal Model of Mania by Amanda Valnier Steckert (47-57).
The present study aims to investigate the effects of protein kinase C using the inhibitor Tamoxifen (TMX) on oxidative stress in a rat animal model of mania induced by d-amphetamine (d-AMPH). In the reversal model, d-AMPH or saline (Sal) were administered to rats for 14 days, and between days 8-14, rats were treated with TMX or Sal. In the prevention model, rats were pretreated with TMX or Sal, and between days 8-14, d-AMPH or Sal were administrated. In both experiments locomotor activity and risk-taking behavior were assessed by open-field test and oxidative stress was measured in prefrontal, amygdala, hippocampus and striatum. The results showed that TMX reversed and prevented d- AMPH-induced behavioral effects. In addition, the d-AMPH administration induced oxidative damage in both structures tested in two models. The TMX was able to reverse and prevent this impairment, however in a way dependent of cerebral area and technique evaluated. These findings reinforce the hypothesis that PKC play an important role in the pathophysiology of BD and the need for the study of inhibitors of PKC as a possible target for treatment the BD.
Curcumin Exposure Modulates Multiple Pro-Apoptotic and Anti-Apoptotic Signaling Pathways to Antagonize Acetaminophen-Induced Toxicity by Elida Bulku (58-71).
Curcumin (CUR; diferuloylmethane), a rhizome extract of Curcuma Longa L. is commonly used as a food coloring and flavoring agent. Although oriental and Ayurvedic medicines have traditionally used CUR in the treatment of diseases, conventional medicine has just begun to recognize its potential therapeutic value. Numerous recent studies have demonstrated the ability of CUR to halt or prevent certain types of cancer, decrease inflammation, and improve cardiovascular health. However, very few studies have examined its ability to protect against drug-induced organ injury. This study explored whether CUR pre-exposure has the potential to prevent acetaminophen (APAP)-induced: (i) hepatotoxicity, (ii) genomic injury, (iii) oxidative stress in the liver, and (iv) apoptotic and necrotic cell deaths in the liver in vivo. Additional goals were to investigate the interplay of pro- and anti-apoptotic genes and their ultimate impact on various forms of cell death. In order to study the CUR-APAP interaction, male B6C3F1 mice were gavaged with CUR (17 mg/kg/day, p.o.) for 12 days followed by a single APAP exposure (400 mg/kg, ip). Four groups of animals (control, CUR, APAP, CUR+APAP) were sacrificed 24 h after APAP exposure. The results indicated that APAP-induced liver injury associated events as serum ALT (80-fold), lipid peroxidation (357%) and DNA fragmentation (469%) were markedly reduced to 3-fold, 134% and 162%, respectively, in the CUR+APAP group. The APAP-induced increase in expression of pro-apoptotic genes (Bax, caspase-3) decreased while expression of anti-apoptotic genes (Bcl-XL) increased in CUR preexposed mouse livers, and these changes were mirrored in the pattern of apoptotic and necrotic cell deaths. Levels of DNA damage sensor P53 and its counterpart Mdm2 were also analyzed during this interaction. Based on the available literature, and these results, it seems likely that CUR may impart global protection in vivo against drug-induced liver injury by opposing several crucial events instrumental to both apoptosis and necrosis.
Vascular Endothelial Growth Factor: Adaptive Changes in the Neuroglialvascular Unit by Enrike G. Argandona (72-81).
Brain postnatal development is modulated by adaptation and experience. Experience-mediated changes increase neuronal activity leading to increased metabolic demands that involve adaptive changes including ones at the microvascular network. Therefore, vascular environment plays a key role in central nervous system (CNS) development and function in health and disease. Trophic factors are crucial in CNS development and cell survival in adults. They participate in protection and proliferation of neuronal, glial and endothelial cells. Among the most important molecules are: the proangiogenic vascular endothelial growth factor (VEGF), the neurotrophin brain derived neurotrophic factor (BDNF), insulin growth factor (IGF-I) and the glycoprotein erythropoietin (EPO). We propose the term angioglioneurins to define molecules acting on the three components of the neurogliovascular unit. We have previously reported the effects of environmental modifications on the three components of the neurogliovascular unit during the postnatal development. We have also described the main role played by VEGF in the experience-induced postnatal changes. Angioglioneurin administration, alone or in combination with other neuroprotective strategies such as environmental enrichment, has been proposed as a non-invasive therapeutic strategy against several CNS diseases.