Glaucomatous optic neuropathy treatment options:the promise of novel therapeutics,techniques and tools to help preserve vision

Peripheral vision loss followed by ＂tunnel vision＂ and eventual irreversible blindness is the fate of patients afflicted by various forms of glaucoma including primary open-angle glaucoma（POAG） and normotensive glaucoma（NTG）.These complex and heterogeneous diseases are characterized by extensive death of retinal ganglion cells（RGCs） accompanied by retraction and severance of their axonal connections to the brain and thus damage to and thinning of the optic nerve.Since patients suffering from this glaucomatous optic neuropathy（GON） first notice visual impairment when they have lost 〉 40% of their RGCs,early diagnosis is the key to retard the progression of glaucoma.Elevated intraocular pressure（IOP）,low cerebrospinal and/or low intracranial fluid pressure,advancing age,and ethnicity are major risk factors associated with POAG.However,retinal vascular abnormalities and a high sensitivity of RGCs and optic nerve head components to neurotoxic,inflammatory,oxidative and mechanical insults also contribute to vision loss in POAG/GON.Current treatment modalities for POAG and NTG involve lowering IOP using topical ocular drugs,combination drug products,and surgical interventions.Two recently approved multi-pharmacophoric drugs（e.g.,rho kinase inhibitor,Netarsudil;a drug conjugate,Latanoprostene Bunod） and novel aqueous humor drainage devices（i Stent and Cy Pass） are also gaining acceptance for treating POAG/NTG.Neuroprotective and regenerative agents,coupled with electroceutical,mechanical support systems,stem cell transplantation and gene therapy are emerging therapeutics on the horizon to help combat GON.The latter techniques and approaches hope to rejuvenate RGCs and repair the optic nerve structures,thereby providing a gain of function of the visual system for the glaucoma patients.

Neuroaxonal and cellular damage/protection by prostanoid receptor ligands,fatty acid derivatives and associated enzyme inhibitors

Cellular and mitochondrial membrane phospholipids provide the substrate for synthesis and release of prostaglandins in response to certain chemical,mechanical,noxious and other stimuli.Prostaglandin D_(2),prostaglandin E_(2),prostaglandin F_(2)α,prostaglandin I_(2)and thromboxane-A_(2)interact with five major receptors(and their sub-types)to elicit specific downstream cellular and tissue actions.In general,prostaglandins have been associated with pain,inflammation,and edema when they are present at high local concentrations and involved on a chronic basis.However,in acute settings,certain endogenous and exogenous prostaglandins have beneficial effects ranging from mediating muscle contraction/relaxation,providing cellular protection,regulating sleep,and enhancing blood flow,to lowering intraocular pressure to prevent the development of glaucoma,a blinding disease.Several classes of prostaglandins are implicated(or are considered beneficial)in certain central nervous system dysfunctions(e.g.,Alzheimer’s,Parkinson’s,and Huntington’s diseases;amyotrophic lateral sclerosis and multiple sclerosis;stroke,traumatic brain injuries and pain)and in ocular disorders(e.g.,ocular hypertension and glaucoma;allergy and inflammation;edematous retinal disorders).This review endeavors to address the physiological/pathological roles of prostaglandins in the central nervous system and ocular function in health and disease,and provides insights towards the therapeutic utility of some prostaglandin agonists and antagonists,polyunsaturated fatty acids,and cyclooxygenase inhibitors.

Glutamate Impairs Mitochondria Aerobic Respiration Capacity and Enhances Glycolysis in Cultured Rat Astrocytes

Objective To study the effect of glutamate on metabolism, shifts in glycolysis and lactate release in rat astrocytes. Methods After 10 days, secondary cultured astrocytes were treated with 1 mmol/L glutamate for 1 h, and the oxygen consumption rates （OCR） and extra cellular acidification rate （ECAR） was analyzed using a Seahorse XF 24 Extracellular Flux Analyzer. Cell viability was then evaluated by MTT assay. Moreover, changes in extracellular lactate concentration induced by glutamate were tested with a lactate detection kit. Results Compared with the control group, treatment with 1 mmol/L glutamate decreased the astrocytes’ maximal respiration and spare respiratory capacity but increased their glycolytic capacity and glycolytic reserve. Further analysis found that 1-h treatment with different concentrations of glutamate （0.1-1 mmol/L） increased lactate release from astrocytes, however the cell viability was not affected by the glutamate treatment. Conclusion The current study provided direct evidence that exogenous glutamate treatment impaired the mitochondrial respiration capacity of astrocytes and enhanced aerobic glycolysis, which could be involved in glutamate injury or protection mechanisms in response to neurological disorders.

Downregulation of Aquaporin 4 Expression through Extracellular Signal-regulated Kinases1/2 Activation in Cultured Astrocytes Following Scratch-injury

Objective To investigate the role of extracellular signal-regulated kinase1/2（ERK1/2） pathway in the regulation of aquaporin 4（AQP4） expression in cultured astrocytes after scratch-injury. Methods The scratch-injury model was produced in cultured astrocytes of rat by a 10-μL plastic pipette tip. The morphological changes of astrocytes and lactate dehydrogenase（LDH） leakages were observed to assess the degree of scratch-injury. AQP4 expression was detected by immunofluorescence staining and Western blot, and phosphorylated-ERK1/2（p-ERK1/2） expression was determined by Western blot. To explore the effect of ERK1/2 pathway on AQP4 expression in scratch-injured astrocytes, 10 μmol/L U0126（ERK1/2 inhibitor） was incubated in the medium at 30 min before the scratch-injury in some groups. Results Increases in LDH leakage were observed at 1, 12, and 24 h after scratch-injury, and AQP4 expression was reduced simultaneously. Decrease in AQP4 expression was associated with a significant increase in ERK1/2 activation. Furthermore, pretreatment with U0126 blocked both ERK1/2 activation and decrease in AQP4 expression induced by scratch-injury. Conclusion These results indicate that ERK1/2 pathway down-regulates AQP4 expression in scratch-injured astrocytes, and ERK1/2 pathway might be a novel therapeutic target in reversing the effects of astrocytes that contribute to traumatic brain edema.

Basics on the use of acid-sensing ion channels' inhibitors as therapeutics

Since the discovery of acid-sensing ion channels in 1997, their importance in the health of neurons and other non-neuronal cells has gained significant importance. Acid-sensing ion channels play important roles in mediating pain sensation during diseases such as stroke, inflammation, arthritis, cancer, and recently migraine. More interestingly, acid-sensing ion channels may explain the sex differences in pain between males and females. Also, the ability of acid-sensing ion channel blockers to exert neuroprotective effects in a number of neurodegenerative diseases has added a new dimension to their therapeutic value. The current failure rate of ～45% of new drugs(due to toxicity issues) and saving of up to 7 years in the life span of drug approval makes drug repurposing a high priority. If acid-sensing ion channels' blockers undergo what is known as "drug repurposing", there is a great potential to bring them as medications with known safety profiles to new patient populations. However, the route of administration remains a big challenge due to their poor penetration of the blood brain and retinal barriers. In this review, the promise of using acid-sensing ion channel blockers as neuroprotective drugs is discussed.

Astrocytes Prevent Ethanol Induced Apoptosis of Nrf2 Depleted Neurons by Maintaining GSH Homeostasis

Glutathione (GSH), a major cellular antioxidant protects cells against oxidative stress injury. Nuclear factor erythroid 2-related factor 2 (NFE2L2/Nrf2) is a redox sensitive master regulator of battery of antioxidant enzymes including those involved in GSH antioxidant machinery. Earlier we reported that ethanol (ETOH) elicits apoptotic death of pri-mary cortical neurons (PCNs) which in partly due to depletion of intracellular GSH levels. Further a recent report from our laboratory illustrated that ETOH exacerbated the dysregulation of GSH and caspase mediated cell death of pure cortical neurons that are compromised in Nrf2 machinery (Narasimhan et al., 2011). In various experimental models of neurodegeneration, neuronal antioxidant defenses mainly GSH has been shown to be supported by astrocytes. We therefore sought to determine whether astrocytes can render protection to neurons against ETOH toxicity, particularly when the function of Nrf2 is compromised in neurons. The experimental model consisted of co-culturing PCAs with Nrf2 downregulated PCNs that were exposed with and without 4 mg/mL ETOH for 24 h. Monochlorobimane (MCB) staining followed by FACS analysis showed that astrocytes blocked ETOH induced GSH decrement in Nrf2-silenced neurons as opposed to exaggerated GSH depletion in Nrf2 downregulated PCNs alone. Similarly, the heightened activa-tion of caspase 3/7 observed in Nrf2-compromised neurons was attenuated when co-cultured with astrocytes as meas-ured by luminescence based caspase Glo assay. Furthermore, annexin-V-FITC staining followed by FACS analysis re-vealed that Nrf2 depleted neurons showed resistance to ETOH induced neuronal apoptosis when co-cultured with as-trocytes. Thus, the current study identifies ETOH induced dysregulation of GSH and associated apoptotic events ob-served in Nrf2-depleted neurons can be blocked by astrocytes. Further our results suggest that this neuroprotective ef-fect of astrocyte despite dysfunctional Nrf2 system in neurons could be compensated by astrocytic GSH supply.

Biomarkers and Depressive Symptoms in Older Women with and without Cognitive Impairment

A number of biological markers have been implicated in late life depression with inconsistent results. The present study examined the relationship between several serum based biomarkers and symptoms of depression in a sample of elderly women with AD or cognitively intact. Methods 171 females (58 with AD and 113 cognitively intact) were recruited from the Longitudinal Research Cohort of the Texas Alzheimer’s Research and Consortium (TARC). Stepwise regressions were conducted with GDS total and subscales and a panel of biomarkers (CRP, IL-10, IL-1α, TNF-α, ICAM-1, BDNF, and MIF). ApoE4 status was coded (carrier or non-carrier), and the results were analyzed by cognitive status (AD or controls). Results: None of the biomarkers significantly predicted total GDS score for AD cases, controls or sample as a whole. For the Controls, ICAM significantly predicted Dysphoria and level of Apathy. Among AD patients, MIF, ICAM, and CRP, were significantly associated with Apathy. MIF and ICAM were inversely associated with reported Apathy. CRP was positively associated with Apathy. CRP was also positively related to level of perceived Cognitive Impairment. Conclusions: The present study was one of the first to examine biomarkers related to depression symptoms in elderly women with AD and normal controls. For Controls ICAM alone predicted level of apathy. In the AD group, MIF, CRP, and ICAM were significantly associated with apathy. More research examining the relationship between biomarkers and depression is needed in older patients with and without cognitive impairment across genders.

Depressive Symptom Endorsement among Alzheimer’s Disease, Vascular Dementia and Mild Cognitive Impairment

Background: The Geriatric Depression Scale (GDS) is widely used to assess depressive symptoms in clinical and research settings. This study utilized a 4 factor solution for the 30-item GDS to explore differences in the presentation of depressive symptoms in various types of cognitive impairment. Method: Retrospective chart review was conducted on 254 consecutive cases of community dwelling elderly newly diagnosed with mild Alzheimer’s Dementia (AD) n = 122, mild Vascular Dementia (VaD) n = 71 or Amnestic Mild Cognitive Impairment (aMCI) n = 32 and Non-Amnestic MCI (nMCI) n = 29. Results: Analysis revealed no significant differences (p 05). No statistically significant differences were found between VaD and nMCI or between the MCI groups. Conclusions: Support is provided for the use of GDS subscales in a wide range of cognitively impaired elderly. This study suggests in mild dementia the number and type of depressive symptoms vary significantly between AD and VaD. There are indications that aMCI patients are similar in their symptom endorsement to AD and nMCI are similar to VaD which is consistent with some of the notions regarding likely trajectories of the respective MCI groups.

Purkinje-neuron-specific down-regulation of p38 protects motoric function from the repeated use of benzodiazepine

Benzodiazepine (BZD) is the most prescribed CNS depressant in America to treat hyper-excitatory disorders such as anxiety and insomnia. However, the chronic use of BZD often creates adverse effects including psychomotor deficit. In this study, we investigated a novel mechanism by which chronic BZD impedes motoric function in female mice. We used female mice because BZD use is much more prevalent in female than male populations. We tested the hypothesis that the accumulation of p38 (stress-activated protein) in cerebellar Purkinje neurons mediates motoric deficit induced by chronic BZD. To test this hypothesis, we generated transgenic mice that lack p38 incerebellar Purkinje neurons by crossing Pcp2 (Purkinje cell protein 2)-Cre mice with p38loxP/loxP mice. p38-knockdown mice and wild-type mice received BZD (lorazepam, 0.5 mg/kg) for 14 days. During this period, they were tested for motoric performance using Rotarod assay in which a quicker fall from rotating rod indicates poorer motoric performance. Cerebellum was then collected to detect p38 inPurkinje neurons and to measure mitochondrial respiration using immunohistochemistry and real-time XF respirometry, respectively. Compared to vehicletreated mice, BZD-treated mice showed poorer motoric performance, a higher number of Purkinje neurons containing p38, and lower mitochondrial respiration. These effects of BZD were much smaller in p38-knockdown mice. These results suggest that the excessive accumulation of p38 incerebellar Purkinje neurons contributes to motoric deficit associated with chronic BZD. They also suggest that Purkinje neuronal p38 mediates BZD-induced mitochondrial respiratory inhibition in cerebellum. Our findings may provide a new mechanistic insight into chronic BZD-induced motoric deficit.

缺血性卒中后血管新生的细胞和分子调节机制

卒中是由脑供血异常引起的急性神经功能缺损，其中缺血性卒中占60％～80％。脑组织对缺血缺氧十分敏感，卒中后缺血中心区脑细胞迅速大量死亡，及时抢救缺血半暗带区脑细胞可减轻脑损伤；卒中后期血管新生亦在为神经再生和脑组织修复创建良好环境中发挥重要作用，

大脑老化与神经再生和卒中

大脑老化是神经退行性疾病的主要诱因。而卒中不仅是老年人的神经系统常见疾病,而且也是70岁以上老年人致残和死亡的重要原因,因此,大脑老化与卒中发病息息相关。已经证实,老年卒中患者其缺血性脑组织损伤更加严重、脑梗死面积更大、缺血后的神经功能障碍也更加显著。尽管研究已证实老龄大脑的神经再生减少,但卒中可以诱导神经再生并能有效促进神经功能恢复,这就为神经再生治疗卒中开辟了良好的途径。本文重点就大脑老化及老化后神经再生、缺血性卒中作一简要综述。

血管新生与缺血性卒中的相关性研究进展

卒中后遗留的神经功能障碍的治疗一直是困扰人类的医学难题之一。最近的研究表明，脑缺血后神经元的修复不仅与各种生长因子有关，还取决于缺血区血管新生（angiogenesis）的能力。了解血管新生和卒中的关系有助于促进卒中后血管新生的研究，

雌激素与脑保护

随着社会的老龄化和其伴随的卒中发病率的不断升高,卒中已成为未来发展的重大隐患。该隐患在我国更是为长期的低生育率所加剧。卒中是继心血管病之后的第二位主要致死疾病,其致残率更是高居首位。卒中不仅仅导致运动功能的障碍,流行病学研究表明卒中后痴呆的发病率较同年龄组增加4～12倍。可以想象若一对独生子女夫妇的四位老人之一惠卒中后痴呆,对其工作的影响会有多大。不难预测,如果没有有效的治疗,卒中之隐患将极大阻碍中国未来生产力的发展。在过去十几年里,包括雌激素在内的神经保护或脑保护剂的研究受到了广泛的重视。不幸的是,所有脑保护剂的临床试验都以失败告终。临床试验的失败是否能够宣告脑保护研究的终结?我们是否能够承受放弃脑保护研究的后果?脑保护的基础研究和其临床试验的失败更确切的说应该是转化医学的失败。这其中包括临床向基础医学和基础向临床的双向转化。未来脑保护剂的研究是否成功将取决于此双向转化的成败,取决于我们临床和基础医学研究人员的密切协作。

Methylene blue protects mitochondrial respiration from ethanol withdrawal stress

Methylene blue (MB), a tricyclic phenothiazine drug, has been reported to enhance mitochondrial functions including mitochondrial respiration. By comparison, stress associated with abrupt ethanol withdrawal (EW) impedes mitochondrial functions. We investigated whether MB protects mitochondrial respiration and cell survival from EW stress through a key mitochondrial enzyme, cytochrome c oxidase (COX). We also investigated whether the MB’s protection involves the inhibition of an excitatory neurotransmitter, glutamate. Male rats were exposed to and withdrawn from ethanol-diet (7.5%, 5 weeks). MB (0.5 mg/kg, intraperitoneal) was injected for the last 5 days of ethanol-diet and on the first day of EW. Cerebellum was then harvested to measure mitochondrial respiration and COX expression using real-time XF respirometer and immunohistochemistry, respectively. Separately, HT22 cells (a murine hippocampal cell line) were exposed to and abruptly withdrawn for 4 hours from chronic ethanol (100 mM, 3 days). MB was administered during EW with or without a COX inhibitor (NaN3) or glutamate. Mitochondrial respiration, COX content, and cell viability were then assessed using real-time XF respirometer, an immunoblot method, and Calcein assay, respectively. MB attenuated the suppressing effects of EW on mitochondrial respiration, COX content, and cell survival. This protection was reduced after NaN3 or glutamate cotreatment. These results suggest that MB treatment help maintain mitochondrial respiratory and cellular integrity through COX-upregulation and glutamateinhibition upon EW stress. MB treatment may help identify mitochondrial mechanisms underlying hyperexcitatory CNS disorders.

雌激素的脑保护:从临床到基础再到临床

在过去的近二十年里，不论是在基础还是临床，雌激素作为一神经保护剂在世界范围受到广泛关注和研究。此类研究的原动力无不来自于临床流行病学的研究结果，即卒中的性别差异。应当注意的是，卒中的性别差异可受到包括生理因素和社会因素在内的众多因素的影响，并且雌激素的脑保护作用也不是可影响卒中差异的唯一生理因素。越来越多的证据显示其他性激素，包括孕激素和雄激素，都对卒中的病理生理及预后有一定影响。

运动训练和抗氧化剂补剂可提高成年雄性和雌性GFAP—APOE小鼠的认知功能(英文)

目的:本研究的目标是探讨抗氧化剂补剂和适度运动两者单独或结合对于成年小鼠认知功能的作用,以及APOE基因型和性别是否会影响由抗氧化剂补剂或适度运动引起的认知功能变化。方法:实验为期16周,将表达人APOE3或APOE4基因亚型的转基因小鼠按照性别分雌雄组,并分别给与对照标准食物(NIH-31)或抗氧化剂补充剂食物(添加1.1 2 IU/gα-醋酸生育酚、1.65 mg/g抗坏血酸),然后将动物进一步分成不运动组和每天运动组。经过8周干预后,对小鼠进行一系列功能测试,包括认知和情感功能测试。结果:基因型或干预手段对小鼠在Morris水迷宫中的学习表现没有影响。在鉴别回避的行为测试中,APOE4型小鼠在学习和鉴别的部分速度较其他对照组小鼠快。总之,运动可以改善APOE4和APOE3型小鼠主动回避任务的各方面表现,而抗氧化剂补剂只能改善APOE4型小鼠的表现。在焦虑测试中,APOE4型小鼠在开放测试区域停留时间较长,而抗氧化剂补剂会逆转这一状况。结论:运动在两种基因型和不同性别小鼠中都是改善认知功能最有效的手段,而抗氧化剂补剂只对APOE4型小鼠有效。对年轻成年小鼠而言,只有非空间学习和记忆能力得到提高。将运动和抗氧化剂补剂两种手段结合并没有使认知功能进一步提高,抗氧化剂补剂也不会抵消运动对于认知产生的益处。