Norepinephrine provides short-term neuroprotection against Aβ1–42 by reducing oxidative stress independent of Nrf2 activation

Pathophysiological evidence correlating locus ceruleus neuron loss with increased Alzheimer's disease pathology suggests that norepinephrine (NE) is neuroprotective. Here, we evaluated the effects of NE on amyloid-β (Aβ)1-42–induced neurotoxicity and determined how NE exerts its actions in human SK-N-SH neurons. NE protected SK-N-SH cells against Aβ1-42–induced neurotoxicity only after a 4-hour treatment. The ability of NE to reduce Aβ1-42–induced neurotoxicity was independent of the adrenoceptor signaling pathway. Notably, NE downregulated Aβ1-42–mediated increases in intracellular reactive oxygen species (ROS) production. However, NE did not affect Aβ1-42–induced activation of the nuclear factor erythroid 2–related factor 2 (Nrf2) redox signaling pathway, known to be involved in oxidative stress. Among the antioxidants tested, N-acetyl cysteine and glutathione, which are not only ROS scavengers but also thiol-reducing agents, mimicked the protective effects of NE. Consistently, Kelch-like ECH-associating protein 1 inhibitors, which activated the Nrf2 pathway, failed to decrease Aβ1-42–induced ROS generation and elicited no protection against Aβ1–42. Taken together, these findings suggest that NE could exert neuroprotective function against Aβ1–42 via redox cycling and reduction of intracellular oxidative stress regardless of downstream activation of the Nrf2 pathway.     

Desensitization pattern of cardiac β-adrenoceptor subtypes by prolonged in vivo infusion of pindolol and celiprolol in rats

Summary The regulatory effects of pindolol and celiprolol on cardiac -adrenoceptor density were studied in vivo in order to assess the subtype selectivity of their partial agonistic activity (PAA). The substances were continuously administered to rats for 1 week by means of implanted osmotic minipumps. The density of -adrenoceptor subtypes were estimated from ICYP saturation binding experiments performed on cardiac ventricular plasma membranes in the presence of a highly selective antagonist (CGP 20172 A or ICI 118,551). Both antagonists were employed at concentrations as high as to block one subtype only without affecting the complementary subtype. For control purposes, rats were also treated with isoprenaline (0.4 mg/kg/h) and propranolol (0.15 mg/kg/h), or vehicle. Pindolol (0.036 mg/kg/h) and celiprolol (0.36 mg/kg/h) reduced the density of ventricular ₂-adrenoceptors by 46% and 23%, respectively, which — in the case of pindolol — was significant when compared to the non-treated controls. Both compounds, however, produced a small, but distinct increase in the number of ₁-adrenoceptors by approximately 26%. This finding is in contrast to the propranolol-induced upregulation of both ₁- and ₂-adrenoceptors by approximately 80%. Since supramaximal doses of each drug were administered, a significant smaller increase of ₁-adrenoceptors by pindolol and celiprolol —as compared to the increase produced by propranolol — can be interpreted as evidence for a PAA of pindolol and celiprolol on ₁-adrenoceptors as well. Isoprenaline as a full agonist caused a marked loss of of both -adrenoceptor subtypes. Although it exhibits equal affinity at both subtypes the decrease amounted to 80% of the ₂- but only to 54% of the ₁-adrenoceptors density. This indicates that the down-regulation of cardiac -adrenoceptors in general seems to be more pronounced at the ₂-than at the ₁-adrenoceptors population. We conclude that the subtype desensitization pattern of agents with intrinsic activity precludes the determination of subtype-selectivity, since ₁- and ₂-adrenoceptors appear to differ in their sensitivity presumably as a result of subtype specific baseline desensitization produced by endogenous catecholamines.     

Human antibody titers to Epstein–Barr Virus (EBV) gp350 correlate with neutralization of infectivity better than antibody titers to EBV gp42 using a rapid flow cytometry-based EBV neutralization assay

Measurement of neutralizing antibodies to Epstein–Barr virus (EBV) is important for evaluation of candidate vaccines. The current neutralization assay is based on antibody inhibition of EBV transformation of B cells and requires 6 weeks to perform. We developed a rapid, quantitative flow cytometry assay and show that neutralizing antibody titers measured by the new assay strongly correlate with antibody titers in the standard transformation-based assay. Antibodies to EBV gp350 and gp42 have been shown to block infection of B cells by EBV. Using new assays to quantify antibodies to these glycoproteins, we show for the first time that human plasma contains high titers of antibody to gp42; these titers correlate with neutralization of EBV infectivity or transformation. Furthermore, we show that antibody titers to EBV gp350 correlate more strongly with neutralization than antibody titers to gp42. These assays should be useful in accessing antibody responses to candidate EBV vaccines.     

Role of p21‐activated kinase in cell polarity and directional mesendoderm migration in the Xenopus gastrula

The p21 activated kinases (Paks) are prominently involved in the regulation of cell motility. Using a kinase‐dead mutant of xPak1, we show that during Xenopus gastrulation, the kinase activity of Pak1 is required upstream of Cdc42 for the establishment of cell polarity in the migrating mesendoderm. Overactivation of Pak1 function by the expression of constitutively active xPak1 compromises the maintenance of cell polarity, by indirectly inhibiting RhoA function. Inhibition of cell polarization does not affect the migration of single mesendoderm cells. However, Pak1 inhibition interferes with the guidance of mesendoderm migration by directional cues residing in the extracellular matrix of the blastocoel roof, and with mesendoderm translocation in the embryo. Developmental Dynamics 238:1709–1726, 2009. © 2009 Wiley‐Liss, Inc.     

Tau protein, phosphorylated tau protein, and beta-amyloid 42 levels in patients with neurodegenerative diseases complicated by cognitive deficits A non-randomized, concurrent, case-control investigation

BACKGROUND： The differential diagnosis of many neurodegenerative disorders depends primarily on clinical symptoms together with imaging methods. Recently, increased importance has been placed on the use of biomarkers for diagnosing various neurodegenerative disorders. OBJECTIVE： To assess the feasibility of tau-protein, phosphorylated tau-protein, beta-amyloid 42 （Aβ42）, and 14-3-3 protein as biomarkers for diagnosing several neurodegenerative diseases complicated by cognitive deficits. DESIGN, TIME AND SETTING： A non-randomized, concurrent, case-control investigation was performed in three medical centers in the Czech Republic （Department of Neurology at the University Hospital in Hradec Kralove, Department of Neurology at the 2rd Medical Faculty, and the University Hospital Motol） between October 2000 and November 2006. PARTICIPANTS： Eighteen patients with probable AIzheimer＇s disease, 4 patients with Creutzfeldt-Jakob disease, 10 patients with frontotemporal dementia, 9 patients with clinically isolated syndrome suggestive of multiple sclerosis, and 7 patients with multiple sclerosis, as well as 38 race-, nationality-, and age-matched cognitively intact controls, were included in the study. Diagnoses were established based on the following criteria： the criteria for Alzheimer＇s disease proposed by the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer＇s Disease and Related Disorders Association, WHO criteria for Creutzfeldt-Jakob disease, Neary criteria for frontotemporal dementia, and McDonald＇s criteria for multiple sclerosis. All included patients were confirmed to suffer from various degrees of dementia. METHODS： Enzyme-linked immunosorbent assay was used to measure concentrations of tau-protein, phosphorylated tau-protein, and Aβ42 in cerebrospinal fluid （CSF） samples collected by standard lumbar puncture from each patient. Moreover, 14-3-3 protein was assessed by Western blot in CSF of Creutzfeldt-Jakob disease patients. Cognitive status was assessed using the Mini Mental Scale Examination （MMSE） in all subjects. MAIN OUTCOME MEASURES： Establishment of biomarkers with greatest specificity and sensitivity for the investigated disorders according to Receiver Operating Characteristic curves, which were based on values from patients and controls; correlation between concentrations of given biomarkers and demographic parameters, diagnosis, duration of disease, and level of cognitive deficit. RESULTS： Increased concentrations of total tau protein and phosphorylated tau protein, and decreased levels of Aβ42, in CSF of Alzheimer＇s disease patients reached the required sensitivity/specificity ratio of 80% or greater. A marked elevation in CSF concentrations of total tau protein showed even greater sensitivity than 14-3-3 protein in Creutzfeldt-Jakob disease. There was no association between selected biomarkers and frontotemporal dementia or multiple sclerosis. Phosphorylated tau-protein was the only biomarker that noticeably correlated with MMSE scores for Alzheimer＇s disease.CONCLUSION： Levels of total tau protein, phosphorylated tau protein, and A!342 in the CSF could differentiate patients with Alzheimer＇s disease and Creutzfeldt-Jakob disease from healthy controls and patients with other neurodegenerative disorders. The diversity of absolute values demonstrates the necessity to establish a specific standard for each laboratory.     

Cdc42蛋白与细胞迁移、极化以及细胞骨架调节的关系

Cdc42蛋白在细胞骨架动态变化调节中发挥着重要的作用,而细胞骨架的变化影响细胞的各种功能,突出影响到细胞迁移与细胞极化。Cdc42蛋白对细胞骨架动态变化的调节是一个复杂的信号传递过程,涉及到Rho家族蛋白介导的信号通路以及其他多条信号通路间的相互作用。     

Cdc42参与脐带间充质干细胞向炎性因子的趋化

背景：间充质干细胞移植后的归巢能力关系到细胞移植的疗效,研究其趋化和迁移的调控将有助于提高间充质干细胞临床应用的价值。目的：观察Cdc42在人脐带间充质干细胞定向迁移中的作用。方法：首先以组织块法分离培养人脐带间充质干细胞,与炎性因子肿瘤坏死因子α、白细胞介素1β、转化生长因子β共培养后Western检测Cdc42表达变化。化学合成Cdc42的干扰RNA,转染细胞后分别采用Transwell和Matrigel胶观察细胞迁移和黏附能力。应用Western检测Cdc42下游靶分子ERK1/2的变化。结果与结论：与炎性因子共培养后的人脐带间充质干细胞中Cdc42表达明显增加,接近无因子对照组的2倍水平。siRNA下调Cdc42的表达能够显著抑制人脐带间充质干细胞的迁移和黏附,且其下游信号分子ERK1/2的表达以及磷酸化水平均相应受到抑制。提示体外培养环境下Cdc42参与了人脐带间充质干细胞的趋化过程。