Browsing by Subject "neuroprotection"
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Item 17Beta-Estradiol Suppresses Hydrogen Peroxide-Induced Nuclear Factor Kappa B Activation in HT22 Cells(2008-05-01) Kim, Pil J.; Simpkins; Singh; Yang, ShaohuaKim, Pil J., 17beta-estradiol suppresses hydrogen peroxide-induced nuclear factor κappa B activation in HT22 cells. Master of Science (Biomedical Sciences), May, 2008, 78pp., 20 illustrations, 66 titles. Reactive oxygen species (ROS) are natural byproducts of normal cellular reactions. They are oxygen ions, free (non)radicals, and peroxides that are highly reactive with normal macromolecules, such as lipids, DNA, and proteins. Cells are normally able to defend against the damages of ROS via enzymes that neutralize them into water. However, when cells are not able to cope with the accumulation of ROS, distributions in signaling pathways and gene transcription will occur, which will ultimately lead to cell death. It is now widely accepted that increased oxidative stress-induced damage in the brain is a major cause of neurodegenerative diseases, such as Alzheimer’s disease (AD). Nuclear factor κappa-B (NFκB) is not only a ubiquitously expressed transcription factor but also a signaling protein that is activated by ROS-induced oxidative stress. Our laboratory has demonstrated the neuroprotective effects of 17β-estradiol (E2) are elicited via an anti-oxidant effect. The purpose of this project was to determine the role of NFκB activation in E2-mediated neuroprotection against hydrogen peroxide (H2O2)-induced oxidative stress. HT-22, a murine immortalized hippocampal neuronal cell line, was utilized to determine whether NFκB is activated by hydrogen peroxide-induced oxidative stress and whether E2 suppresses H2O2-induced NFκB activation. We observed that H2O2 activated NFκB by phosphorylation of IκBα (pIκBα), one of the NFκB inhibitor proteins, reduction of total IκBα, and induction of NFκB (p65) nuclear translocation. In contrast, E2 suppressed H2O2-induced NFκB activation by dramatic reducing pIκBα, increasing total IκBα, and inhibiting p65 nuclear translocation. Our results show that one of the mechanisms by which estrogens are neuroprotective against oxidative stress is through the attenuation of H2O2-induced NFκB activation.Item A Novel Prodrug Approach for Central Nervous System-Selective Estrogen Therapy(MDPI, 2019-11-19) Prokai-Tatrai, Katalin; Prokai, LaszloBeneficial effects of estrogens in the central nervous system (CNS) results from the synergistic combination of their well-orchestrated genomic and non-genomic actions, making them potential broad-spectrum neurotherapeutic agents. However, owing to unwanted peripheral hormonal burdens by any currently known non-invasive drug administrations, the development of estrogens as safe pharmacotherapeutic modalities cannot be realized until they are confined specifically and selectively to the site of action. We have developed small-molecule bioprecursor prodrugs carrying the para-quinol scaffold on the steroidal A-ring that are preferentially metabolized in the CNS to the corresponding estrogens. Here, we give an overview of our discovery of these prodrugs. Selected examples are shown to illustrate that, independently of the route of administrations and duration of treatments, these agents produce high concentration of estrogens only in the CNS without peripheral hormonal liability. 10beta,17beta-Dihydroxyestra-1,4-dien-3-one (DHED) has been the best-studied representative of this novel type of prodrugs for brain and retina health. Specific applications in preclinical animal models of centrally-regulated and estrogen-responsive human diseases, including neurodegeneration, menopausal symptoms, cognitive decline and depression, are discussed to demonstrate the translational potential of our prodrug approach for CNS-selective and gender-independent estrogen therapy with inherent therapeutic safety.Item Artemisinin Prevents Glutamate-Induced Neuronal Cell Death Via Akt Pathway Activation(Frontiers Media S.A., 2018-04-20) Lin, Shao-Peng; Li, Wenjun; Winters, Ali; Liu, Ran; Yang, ShaohuaArtemisinin is an anti-malarial drug that has been in use for almost half century. Recently, novel biological effects of artemisinin on cancer, inflammation-related disorders and cardiovascular disease were reported. However, neuroprotective actions of artemisinin against glutamate-induced oxidative stress have not been investigated. In the current study, we determined the effect of artemisinin against oxidative insult in HT-22 mouse hippocampal cell line. We found that pretreatment of artemisinin declined reactive oxygen species (ROS) production, attenuated the collapse of mitochondrial membrane potential induced by glutamate and rescued HT-22 cells from glutamate-induced cell death. Furthermore, our study demonstrated that artemisinin activated Akt/Bcl-2 signaling and that neuroprotective effect of artemisinin was blocked by Akt-specific inhibitor, MK2206. Taken together, our study indicated that artemisinin prevented neuronal HT-22 cell from glutamate-induced oxidative injury by activation of Akt signaling pathway.Item Cellular and Molecular Mechanisms that Distinguish the Effects of Progestorone and Medroxyprogesterone Acetate on Neuroprotection(2006-07-28) Kaur, Paramjit; Goldfarb, Ronald; Singh, Meharvan; Agarwal, NeerajKaur, Paramjit. Cellular and Molecular Mechanisms That Distinguish the Effects of Progesterone and Medroxyprogesterone Acetate on Neuroprotection., Doctor of Philosophy, (Pharmacology and Neuroscience), July, 2006, 203 pp., 5 illustrations, 20 figures and bibliography. Women have a higher prevalence for Alzheimer’s disease (AD) than men, suggesting that the precipitous decline in gonadal hormone levels following the menopause may contribute to the risk of developing AD. However, principal results from the Women’s Health Initiative concluded that women taking conjugated equine estrogens combined with medroxyprogesterone acetate (MPA, tradename: Prempro) incurred more harmful than beneficial outcomes versus the placebo group (Rossouw et al., 2002). This dissertation was aimed at determining if the discrepancy between basic science reports and these clinical studies could have been due to the synthetic progestin, MPA. I hypothesized that P4 and MPA differed in their ability to protect against the excitotoxic/oxidative insult, glutamate. Further, I proposed that this difference in neuroprotective potential would be reflected in the difference in the ability of these hormones to elicit key effectors of two neuroprotection-associated signaling pathways, the ERK/MAPK and P13-Kinase pathways. Finally, studies were initiated to evaluate the potential importance of BDNF (brain-derived neurotrophic factor) in mediating the protective effects of P4. I used organotypic explants of the cerebral cortex, and found that both P4 and MPA elicit the phosphorylation of ERK and Akt, two signaling pathways implicated in neuroprotection, with maximal phosphorylation occurring at a concentration of 100 nM. Interestingly, P4 protected against glutamate- induced toxicity however, while an equimolar concentration of MPA (100nM) did not. Further, P4 resulted in an increase in BDNF, while MPA did not. Our data bring into question the relevance of using MPA as a component of hormone therapies in postmenopausal women, and instead, argue that the relevant progestin for use in treating brain-related disorders is progesterone. Collectively, the data presented here suggest that P4 is protective via multiple, and potentially related mechanism, and importantly, its neurobiology is different from the clinically used progestin, MPA.Item DELAYED NEURONAL DEATH IN SWINE FOLLOWING CARDIAC ARREST AND RESUSCITATION(2014-03) Nguyen, Anh Q.; Cherry, Brandon H.; Myoung-Gwi, Ryou; Williams, Arthur G.; Hollrah, Roger; Baker, Charla L.; Choudhury, Gourav; Olivencia-Yurvati, Albert H.; Mallet, Robert T.Purpose (a): Cardiac arrest, a leading cause of death in the U.S., kills >90% of its victims, and survivors often are disabled by permanent brain injury inflicted by ischemia-reperfusion. Purkinje cells of the cerebellum and CA1 neurons of the hippocampus are especially vulnerable to post-ischemic neuronal death. We tested the hypothesis that cardiac arrest in a swine model caused delayed neuronal death. Methods (b): Yorkshire swine (25-35 kg) were subjected to cardiac arrest-resuscitation (n = 9) or non-arrest sham (n = 5) protocols. Ventricular fibrillation was induced by electrical pacing. Precordial compressions (100/min) were given at 6-10 min arrest, and then sinus rhythm was restored with transthoracic countershocks. NaCl was infused iv at 0.1 mmol/kg/min during CPR and the first 60 min after return of spontaneous circulation (ROSC). At 7 d ROSC, brain regions were fixed in 4% paraformaldehyde and H&E stained. Results (c): More than 70% of the Purkinje cells were shrunken, lacked dendrites and displayed condensed cytoplasm at 7 d ROSC; in contrast, in shams the majority of Purkinje cells retained the characteristic thick dendrites and well-defined nuclei. Conclusions (d): Thus, cardiac arrest-resuscitation produced marked changes in cerebellar neurons evident 7d after acute insult.Item Effect of Progesterone on Calcium Signaling of Hippocampal Neurons(2006-05-01) Hwang, Ji-Yeon; Koulen; Singh, Meharvan; Yang, ShaohuaJi-yeon Hwang, Effects of Progesterone on Calcium Signaling of Hippocampal Neurons. Master of Science (Pharmacology and Neuroscience), May 2006, 74 pp., 18 Figures. Progesterone (P4) is one of the steroid hormones responsible for female sexual behavior. It has been recently show that P4 plays also multiple roles in the central nervous system (CNS) including neuroprotection. Calcium (Ca2+) is involved in numerous cellular processes in nerve cells such as neurotransmitter release and cell death. In the present studies, we present evidence that P4 increases the activity of IP3R-mediated Ca2+ release within nerve cells leading to cell survival and neuroprotection. The purpose of the present study is to identify the subcellular distribution of all IP3Rs and other signaling proteins including Akt and phosphor-Akt, in the primary hippocampal neuron and to test the hypothesis that P4 controls the gain of IP3R-mediated intracellular Ca2+ signaling in neurons. We observed that primary hippocampal neurons express predominantly IP3R type 1, 2, and 3. The cellular distribution of all IP3R isoforms as well as Akt and phospho-Akt was increased in primary hippocampal neurons by P4 treatment. In addition, phospho-Akt was translocated to nucleus in response to P4. P4-pretreated neurons showed potentiated IP3R-mediated intracellular Ca2+ responses. Acute application of P4 resulted in transient elevations of intracellular Ca2+ concentrations. Our results will contribute to establishing potential pharmacological approaches for the treatment of pathological conditions characterized by a dysregulation of cellular Ca2+ concentrations such as Alzheimer’s disease.Item ERK5/KLF4 SIGNALING IS A SHARED PATHWAY UNDERLYING THE NEUROPROTECTIVE EFFECTS OF H2O2 PRECONDITIONING AND NGF(2013-04-12) Su, ChangPurpose: Oxidative stress has long been implicated in the pathogenesis of various neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. While high levels of oxidative stress is generally associated with neuronal death, a slight rise of reactive oxygen species (ROS) levels can be protective by "preconditioning" cells to develop a resistance against subsequent challenges. However, the mechanisms underlying such a preconditioning (PC)-induced protection are still poorly understood. One clue stems from the observation that the mitogen-activated protein (MAP) kinase ERK5 is recruited both under conditions of H2O2 - induced neuronal preconditioning (PC) as well as following application of the application of the neuroprotectant, Nerve Growth Factor (NGF). This project tests the hypothesis that the ERK5-dependent signaling cascade may function as a convergence point for various protective signals to counteract oxidative stress-induced neuronal death. Methods: We used PC12 cells as our model to study the effect of oxidative stress. Activity of the ERK5 signaling pathway was enhanced by over-expression of active upstream kinease, or blocked by pharmacological inhibitors or RNAi. Cell viability was determined by Calcein Assay. Results: Over-expression of a constitutively active form of MEK5, the upstream activator of ERK5, partially rescued PC12 cells from H2O2-caused death, while inhibition of ERK5 by pharmacological inhibitors or RNAi abolished NGF or PC-induced protection.Furthermore, both NGF and PC increased the expression of the transcription factor, KLF4, which can initiate an anti-apoptotic response in various cell types. Induction of KLF4 by NGF or PC in PC12 cells is blocked by siERK5, suggesting that ERK5 is required in this process. Finally, siKLF4 can also attenuate NGF- or PC-induced neuroprotection. Conclusions: Taken together, our data suggest that ERK5/KLF4 cascade is a common signaling pathway shared by multiple mechanisms to protect neurons from oxidative stress-induced cell death. Since oxidative stress is thought to be a major player in many aging-associated diseases, KLF4 may serve as a therapeutic target, that when activated, counteracts oxidative stress under such conditions.Item Exosomes Derived From Bone Mesenchymal Stem Cells Ameliorate Early Inflammatory Responses Following Traumatic Brain Injury(Frontiers Media S.A., 2019-01-24) Ni, Haoqi; Yang, Su; Siaw-Debrah, Felix; Hu, Jiangnan; Wu, Ke; He, Zibin; Yang, Jianjing; Pan, Sishi; Lin, Xiao; Ye, Haotuo; Xu, Zhu; Wang, Fan; Jin, Kunlin; Zhuge, Qichuan; Huang, LijieTraumatic brain injury (TBI) is a leading cause of mortality and disability worldwide. Although treatment guidelines have been developed, no best treatment option or medicine for this condition exists. Recently, mesenchymal stem cells (MSCs)-derived exosomes have shown lots of promise for the treatment of brain disorders, with some results highlighting the neuroprotective effects through neurogenesis and angiogenesis after TBI. However, studies focusing on the role of exosomes in the early stages of neuroinflammation post-TBI are not sufficient. In this study, we investigated the role of bone mesenchymal stem cells (BMSCs)-exosomes in attenuating neuroinflammation at an early stage post-TBI and explored the potential regulatory neuroprotective mechanism. We administered 30 mug protein of BMSCs-exosomes or an equal volume of phosphate-buffered saline (PBS) via the retro-orbital route into C57BL/6 male mice 15 min after controlled cortical impact (CCI)-induced TBI. The results showed that the administration of BMSCs-exosomes reduced the lesion size and improved the neurobehavioral performance assessed by modified Neurological Severity Score (mNSS) and rotarod test. In addition, BMSCs-exosomes inhibited the expression of proapoptosis protein Bcl-2-associated X protein (BAX) and proinflammation cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta, while enhancing the expression of the anti-apoptosis protein B-cell lymphoma 2 (BCL-2). Furthermore, BMSCs-exosomes modulated microglia/macrophage polarization by downregulating the expression of inducible nitric oxide synthase (INOS) and upregulating the expression of clusters of differentiation 206 (CD206) and arginase-1 (Arg1). In summary, our result shows that BMSCs-exosomes serve a neuroprotective function by inhibiting early neuroinflammation in TBI mice through modulating the polarization of microglia/macrophages. Further research into this may serve as a potential therapeutic strategy for the future treatment of TBI.Item GENE DELIVERY OF GRP78/BIP PROMOTES RETINAL GANGLION CELL SURVIVAL FOLLOWING OPTIC NERVE CRUSH(2014-03) Liu, Yang; Sharma, Tasneem; Wordinger, Robert J.; Gorbatyuk, Marina S.; Clark, Abbot F.We delivered GRP78/BiP gene into the mouse eye and promoted retinal ganglion cell survival after optic nerve injury. This study suggests a potential therapeutic target for central nervous system neurodegenerative diseases such as glaucoma and optic nerve trauma. Purpose (a): Optic nerve injury triggers endoplasmic reticulum (ER) stress and activates the unfolded protein response (UPR), leading to retinal ganglion cell (RGC) degeneration. Glucose-regulated protein (GRP78/BiP) is a sensor of ER homeostasis and plays a role in ER stress alleviation. In this study, we evaluated the involvement of GRP78/BiP in RGC degeneration induced by optic nerve crush (ONC) and the neuroprotective effects of gene delivery of GRP78/BiP. Methods (b): ONC was performed unilaterally in adult BALB/cJ mice. The expression of GRP78/BiP was evaluated by real time PCR and fluorescent in situ hybridization (FISH). To evaluate the potential neuroprotective effect of BiP , an AAV2 vector harboring the human BiP gene (AAV2-hBiP) or green fluorescent protein (AAV2-GFP) (2 x 109 P) was intravitreally injected 4 weeks prior to the ONC. Seven and fourteen days after the ONC, RGC survival was determined by RBPMS immunofluorescence staining of retinal flat mounts. Retinal function was assessed using full field flash ERG. Expression of UPR related proteins was evaluated by western blotting. Results (c): Three days after ONC, GRP78/BiP expression was significantly up-regulated in RGCs (p<0.01). Intravitreal administration of AAV2-hBiP significantly reduced RGC loss at 7 and 14 days post-ONC compared to AAV2-GFP injected group (n=5, p<0.01). ERG analysis showed partial protection of pSTR amplitudes in AAV2-hBiP injected eyes (n=5, p<0.05). Retina levels of cleaved ATF6 in AAV2-hBiP injected eyes were much lower than those of AAV2-GFP injected eyes. Conclusions (d): Gene delivery of GRP78/BiP promotes RGC survival and preserves RGC function following optic nerve injury. This study suggests a potential therapeutic target for central nervous system neurodegenerative diseases.Item Humanin Attenuates NMDA-Induced Excitotoxicity by Inhibiting ROS-dependent JNK/p38 MAPK Pathway(MDPI, 2018-09-29) Yang, Xiaorong; Zhang, Hongmei; Wu, Jinzi; Yin, Litian; Yan, Liang-Jun; Zhang, CeHumanin (HN) is a novel 24-amino acid peptide that protects neurons against N-methyl-d-aspartate (NMDA)-induced toxicity. However, the contribution of the different mitogen-activated protein kinases (MAPKs) signals to HN neuroprotection against NMDA neurotoxicity remains unclear. The present study was therefore aimed to investigate neuroprotective mechanisms of HN. We analyzed intracellular Ca(2+) levels, reactive oxygen species (ROS) production, and the MAPKs signal transduction cascade using an in vitro NMDA-mediated excitotoxicity of cortical neurons model. Results showed that: (1) HN attenuated NMDA-induced neuronal insults by increasing cell viability, decreasing lactate dehydrogenase (LDH) release, and increasing cell survival; (2) HN reversed NMDA-induced increase in intracellular calcium; (3) pretreatment by HN or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM), an intracellular calcium chelator, decreased ROS generation after NMDA exposure; (4) administration of HN or N-Acetyl-l-cysteine (NAC), a ROS scavenger, inhibited NMDA-induced JNK and p38 MAPK activation. These results indicated that HN reduced intracellular elevation of Ca(2+) levels, which, in turn, inhibited ROS generation and subsequent JNK and p38 MAPK activation that are involved in promoting cell survival in NMDA-induced excitotoxicity. Therefore, the present study suggests that inhibition of ROS-dependent JNK/p38 MAPK signaling pathway serves an effective strategy for HN neuroprotection against certain neurological diseases.Item Identifying Unique Therapeutic Targets To Rescue Retinal Ganglion Cells From Degeneration After Optic Nerve Crush(2014-05-01) Sharma, Tasneem P.; Clark, Abbot F.Central nervous system (CNS) trauma and neurodegenerative disorders trigger a cascade of cellular and molecular events resulting in neuronal apoptosis and regenerative failure. The pathogenic mechanisms and gene expression changes associated with these detrimental events can be effectively studied using a rodent optic nerve crush (ONC) model. The purpose of this study was to use a mouse ONC model to: (a) evaluate changes in retina and ON gene expression, (b) identify neurodegenerative pathogenic pathways, (c) discover potential new therapeutic targets, and (d) evaluate the neuroprotective and axogenic properties of one selected therapeutic target on axotomized RGCs in vitro and the optic nerve crush (ONC) mouse model in vivo. Meta-analysis of altered gene expression (≥1.5 changes and ≤1.5 changes, p [less than] 0.05 demonstrated 29 up- and 20 downregulated retinal gene clusters and 82 up- and 42 down-regulated optic nerve clusters. Regulated gene clusters included regenerative change, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation related genes. Expression of selected genes (Vsnl1, Syt1, Synpr and Nrn1) from retinal and ON neuronal clusters was qualitatively and quantitatively examined for their relation to axonal neurodegeneration by immunohistochemistry and qRT-PCR. Axotomized RGCs treated with recombinant hNrn1 (selected target) significantly increased survival of RGCs by 29% (n=8, p [less than] 0.01) and neurite outgrowth of cultured neurons by 261% compared to controls in cultured neurons (n=5-7, p [less than] 0.05). RGC transduction with AAV2-CAG-hNRN1 prior to ONC promoted RGC survival (42%, n=5-8, p [less than] 0.05) and significantly preserved ERG RGC function by 41% until 28 dpc (n=6, p [less than] 0.05) compared to the control AAV2-CAG-GFP transduction group. These ONC induced neuronal loss and regenerative failure associated clusters can be extrapolated to changes occurring in other forms of CNS trauma or in clinical neurodegenerative pathological settings. In conclusion, this study identified potential therapeutic targets to address two key mechanisms of CNS trauma and neurodegeneration: neuronal loss and regenerative failure and presented Nrn1 as a potential therapeutic target for CNS neurodegenerative diseases.Item PROLONGED NMDA STIMULATION INDUCES NEUROPROTECTIVE PATHWAYS AND ENHANCES SURVIVABILITY OF PRIMARY RETINAL GANGLION CELLS(2014-03) Mueller, Brett H.; Park, Yong; Ma, Hai-Ying; Yorio, ThomasPurpose (a): Calcium influx through postsynaptic NMDA receptors has been shown to stimulate a number of key pro-survival genes; however, prolonged stimulation has been shown to have excitotoxic effects leading to apoptosis in neurons. Previous studies have shown a rapid dephosphorylation of CREB in primary hippocampal neurons treated for 1-2 h with100µM NMDA . It is hypothesized that the activation of CREB-specific phosphatases is one of the main pathways that cause apoptosis during NMDA excitotoxicity. The current study investigated the role of NMDA stimulation on the phosphorylation of CREB in primary RGCs, and assessed if NMDA overstimulation caused excitotoxic changes similar to those seen in primary hippocampal neurons. In addition, the occurrence of NMDA excitotoxicity in bipolar and photoreceptor cells was also investigated. Methods (b): Purification and culture of RGCs were performed by sequential immunopanning using Thy 1 antibody from P3-P7 Sprague-Dawley rats. Mixed retinal cultures that remained following isolation of RGCs from the retina were plated once the RGCs were separated and purified. Calcium imaging was used to measure the intracellular changes in calcium following treatment of cells with 100µM NMDA. Western blots were performed to determine signaling pathways linked to NMDA induced cell survival or excitotoxicity. Calcein AM and ethidium homodimer were used to quantify cell survival and cell death. Cells were also subjected to a trophic factor deprivation insult for 6 hours and 24 hours. Results (c): Treatment of primary RGCs with NMDA (100 µM) for 6h caused a greater than 2-3 fold induction of the transcription factor pCREB. MK801 (NMDA antagonist) completely abolished endogenous levels of pCREB and blocked NMDA induction of pCREB. NMDA (100 µM) treatment for 6 and 24 hrs under trophic factor deprivation, protected RGCs from trophic factor deprivation induced cellular death. The mixed retinal cultures (retinal cells without RGCs) had an opposite effect, where the levels of pCREB were diminished and the neurons died when treated with 100 µM of NMDA. Conclusions (d): The data suggests that NMDA signaling is essential for RGC survivability and blocking calcium ion influx through this receptor by the NMDA blocker, MK801 can be detrimental to RGC function and survival. These results also demonstrate that primary RGCs behave differently than other neurons in the retina, and are not susceptible to NMDA excitotoxicity.Item Proteomics-Based Retinal Target Engagement Analysis and Retina-Targeted Delivery of 17beta-Estradiol by the DHED Prodrug for Ocular Neurotherapy in Males(MDPI, 2021-09-02) Prokai-Tatrai, Katalin; Zaman, Khadiza; Nguyen, Vien; De La Cruz, Daniel L.; Prokai, LaszloWe examined the impact of 17beta-estradiol (E2) eye drops on the modulation of the proteome profile in the male rat retina. With discovery-driven proteomics, we have identified proteins that were regulated by our treatment. These proteins were assembled to several bioinformatics-based networks implicating E2's beneficial effects on the male rat retina in a broad context of ocular neuroprotection including the maintenance of retinal homeostasis, facilitation of efficient disposal of damaged proteins, and mitochondrial respiratory chain biogenesis. We have also shown for the first time that the hormone's beneficial effects on the male retina can be constrained to this target site by treatment with the bioprecursor prodrug, DHED. A large concentration of E2 was produced after DHED eye drops not only in male rat retinae but also in those of rabbits. However, DHED treatment did not increase circulating E2 levels, thereby ensuring therapeutic safety in males. Targeted proteomics focusing on selected biomarkers of E2's target engagement further confirmed the prodrug's metabolism to E2 in the male retina and indicated that the retinal impact of DHED treatment was identical to that of the direct E2 treatment. Altogether, our study shows the potential of topical DHED therapy for an efficacious and safe protection of the male retina without the unwanted hormonal side-effects associated with current estrogen therapies.Item Pyruvate Intervention for Brain Injury Inflicted by Cardiac Arrest-Resuscitation(2016-05) Nguyen, Anh Q.; Mallet, Robert T.; Olivencia-Yurvati, Albert H.; Raven, Peter B.; Yang, Shaohua; Rickards, Caroline A.Fewer than 10% of the 360,000 people who suffer out-of-hospital cardiac arrest annually in the U.S. survive to hospital discharge. Many suffer brain injuries that greatly affect their daily activities and quality of life. Despite improvements in clinical outcomes from cardiac arrest as a result of therapeutic hypothermia, survival rates are still dismal. Additional interventions to be used alone or in combination with therapeutic hypothermia could potentially save many lives. The intermediate metabolite pyruvate has been proven to be neuroprotective when given acutely. The goal of this investigation is to examine the neuroprotective capabilities and mechanisms of pyruvate in a large animal model of cardiac arrest, closed-chest cardiopulmonary resuscitation (CPR) and countershock induced defibrillation. The central hypothesis is that pyruvate therapy suppresses matrix metalloproteinase (MMP) activity and thereby preserves blood-brain barrier (BBB) integrity, increases expression and content of the cytoprotective cytokine erythropoietin (EPO), and dampens inflammation following cardiac arrest, and, thus, improves neurobehavioral recovery from cardiac arrest. Experiments were conducted in Yorkshire swine, subjected to cardiac arrest, closed-chest cardiocerebral resuscitation (CCR), defibrillation by trans-thoracic countershock, and recovery. The project was divided into two studies with different durations of cardiac arrest, producing different intensities of brain damage. In the first study, swine were subjected to 6 min of untreated cardiac arrest and 4 min of CCR, following by defibrillation and recovery of spontaneous circulation (ROSC). In the second study, untreated cardiac arrest was extended to 10 min before 4 min CCR. Animals were euthanized at 1, 4, and 72 h ROSC, and the brain was biopsied for histological and biochemical analyses. For animals in 72 h ROSC groups, neurological assessment and testing were performed at 24, 48, and 72 h ROSC. At 3 d ROSC, the number of viable cerebellar Purkinje cells fell by 30% vs. Sham control, but pyruvate infusion during CCR and the first 60 min ROSC preserved these neurons. EPO mRNA abundance was sharply increased at 4 h ROSC and in the non-arrest Sham, indicating the surgical protocol, hyperoxic ventilation and anesthesia induced neuroprotective EPO, which may have limited brain injury. There were no differences in neurological scores among Sham, CPR, and CPR+Pyruvate, prompting study of more prolonged cardiac arrest to intensify brain injury. At 4 h ROSC in 10 min untreated cardiac arrest group, cardiac arrest unexpectedly decreased hippocampal and cerebellar MMP-2 activities and cerebellar EPO content, regardless of treatment. 72 h survival rate fell from 100% in study one (6 min pretreatment arrest) to only 2 of 6 pigs in study two (10 min pretreatment arrest), which wide disparity in neurological function among the 2 survivors. Collectively, these results indicate the prolonging pre-intervention arrest from 6 to 10 min sharply intensified brain injury, depleted cytoprotective EPO, and inactivated oxyradical-sensitive enzymes. Pyruvate treatment did not exert favorable effects on these variables, indicating that pyruvate may have had limited ability to traverse the blood brain barrier and protect the brain parenchyma in this large animal model of cardiac arrest and CCR.Item ROLE OF C/EBP HOMOLOGOUS PROTEIN (CHOP) IN THE SURVIVAL OF RETINAL GANGLION CELLS AFTER RETINAL ISCHEMIA/REPERFUSION INJURY(2014-03) Nashine, Sonali; Kim, Byung-Jin; Clark, Abbot F.; Pang, Iok-HouGlaucoma is one of the leading causes of blindness and visual impairment, affecting 70 million people worldwide. A major characteristic of this disease is the irreversible death of retinal ganglion cells (RGCs), retinal neurons that transmit visual information from the eye to the brain. There is an unmet need to develop novel therapeutic strategies for glaucoma. One of the major causes of glaucoma is increased pressure inside the eye i.e., increased intraocular pressure. Increased IOP leads to obstruction of the central retinal artery. Obstruction of this artery leads to insufficient blood supply to the eye, which in turn prevents adequate supply of oxygen and nutrients to the eye, causing ischemia. All these events result in improper folding of proteins in the endoplasmic reticulum (ER). Unfolded or misfolded proteins in the ER lead to ER stress which is one of the major pathways of RGC death. C/EBP Homologous protein (CHOP) is a player in this pathway of cell death. We are studying the mechanisms of RGC death in mice. Our mouse model is called the ischemia/reperfusion (I/R) model. In this model, IOP is increased above the normal level for an hour. This prevents blood supply to the eye and leads to ischemia. After an hour, IOP is brought back to normal and blood supply is restored i.e., reperfusion, which causes considerable damage to the eye. Damage caused to the eye in this model simulates the mechanism of RGC death caused in glaucoma. The goal of our project is to investigate if the presence of CHOP in mice causes RGC death after ischemia/reperfusion injury. If it does, then we would study if the absence of CHOP in mice helps in the survival of RGCs. If absence of CHOP in mice is found to protect retinal ganglion cells, then results of the proposed study could lead to the development of a novel therapy for glaucoma. Purpose (a): Retinal ischemia/reperfusion (I/R) causes apoptotic death of retinal ganglion cells (RGC). CHOP is a pro-apoptotic protein and a unfolded protein response (UPR) marker that plays a role in ER-stress mediated apoptotic cell death. The purpose of this study was to investigate the role of CHOP in mouse RGC survival following retinal I/R injury. Methods (b): Retinal I/R was induced in adult C57BL/6J (WT) and CHOP-/- mice by cannulation of the anterior chamber of the left eye with a needle connected to a reservoir of saline. Intraocular pressure was increased to 120 mmHg for 60 min, after which the needle was withdrawn to restore retinal circulation. Uninjured right eyes served as controls. Expression of CHOP protein and other UPR markers (p-eIF2α and BiP) in WT mice post-I/R was studied using Western blot and immunohistochemistry. To compare RGC survival between WT and CHOP-/- mice, retinal flat mount staining with RGC marker, Brn3a was performed. Scotopic threshold response electroretinography (STR-ERG) was performed at 0.03 mcd.s/m2 light intensity to evaluate retinal function. Results (c): CHOP protein was up-regulated by 30 % in I/R injured eyes (1.30 ± 0.11 arbitrary units (a.u.)) compared to control eyes (1 ± 0.07 a.u.) in WT mice three days after I/R injury (p < 0.05). Protein levels of p-eIF2α and BiP also increased by 19% (I/R: 1.19 ± 0.15 a.u., Control: 1 ± 0.06 a.u.) and 11% (I/R: 1.11 ± 0.02 a.u., Control: 1 ± 0.03 a.u.) respectively (both p < 0.05). Co-localization of CHOP and Brn3a confirmed the up-regulation of CHOP specifically in the RGCs. In the uninjured control eyes, CHOP knockout did not affect baseline RGC density or STR-ERG amplitude. I/R injury decreased RGC densities and STR-ERG amplitudes in both WT and CHOP-/- mice. However, survival of RGCs in I/R-injured CHOP-/- mouse eyes (3337.1 ± 316.4 RGC/mm2) was 48% higher (p < 0.05) than that of I/R-injured WT mouse eyes (2248.7 ± 225.9 RGC/mm2) three days after I/R injury. STR-ERG amplitudes were 83 % higher in CHOP-/- I/R eyes (18.6 ± 1.1 μV) compared to WT I/R eyes (10.1 ± 0.9 μV) (p < 0.05). Conclusions (d): Absence of CHOP partially protects against the loss of RGCs and reduction in retinal function (STR-ERG) after I/R injury. These results indicate that CHOP and thus ER-stress play an important role in RGC apoptosis in retinal I/R injury.Item Role of Nonfeminizing Estrogen Analogues in Neuroprotection of Rat Retinal Ganglion Cells Against Glutamate-Induced Cytotoxicity(2007-05-01) Kumar, Domalapalli Maneesh; Agarwal, Neeraj; Gracy, Robert; Garner, MargaretKumar, Domalapalli Maneesh, Role of Nonfeminizing Estrogen Analogues in Neuroprotection of Rat Retinal Ganglion Cells against Glutamate-Induced Cytotoxicity, Doctor of Philosophy (Cell Biology and Genetics), May, 2007, 210 pp., 3 tables, 23 figures, bibliography, 427 titles. Retinal ganglion cell death has been determined to be the final common pathway in glaucoma. Continuous loss of retinal ganglion cells results in irreversible progressive visual field deterioration that culminates in blindness. No effective therapy is currently available to reverse retinal ganglion cell loss. Therefore, preventing the loss of retinal ganglion cells is a logical approach to maintaining vision in effected individuals. Of the methods of investigation, in vivo models of ganglion cell death provide a physiological system in which to study neuroprotective drugs and their effects, but these systems are inefficient for initial screening studies. We have addressed this by utilizing the RGC-5 clonal rat retinal ganglion cell line. Glutamate treatment of RGC-5 cells induces apoptotic death which can be attenuated by pretreatment with the anti-oxidants N-acetyl cysteine and thiourea, implicating oxidative stress as a major component of glutamate’s cytotoxicity. Also antioxidants, estrogens have been demonstrated to be potent neuroprotectants in a variety of in vitro and in vivo models of neurodegeneration. Estrogens’ antioxidant capacity has been attributed to the ability of the phenolic A ring to quench and resonance stabilize oxidative free radicals. It is also known that the estrogen A ring is responsible for binding of these hormones to estrogen receptors, producing feminizing phenotypes. The feminizing effects of estrogens narrow or preclude their use as neuroprotectants in males, and in females that may be predisposed to their deleterious effects. To address these shortcomings we screened 13, non-feminizing, non-receptor binding estrogen analogues in our glutamate-induced RGC-5 model of oxidative stress-induced cell death. The most effective of these drugs was ZYC-3. ZYC-3 was synthesized by the addition of an adamantly group to the C2 position on the A ring of estrone. This modification produced a neuroprotective compound with potency and efficacy at least equal to the prototypical estrogen, 17β-estradiol, but with no appreciable binding affinity for estrogens receptors α or β. Our preliminary findings suggest that ZYC-3 enhances glutathione synthesis and blocks mitochondrial apoptotic pathways. However, as a novel drug we are naïve to its effects on cellular physiology and as to how it affords neuroprotection. Understanding how this drug regulates cellular destructive and protective mechanisms could lead to further innovations in drug design and in methods to prevent retinal ganglion cell degeneration. In vivo studies of this drug may then form the bridge to a better clinical approach to managing ocular disorders in which ganglion cell loss is the culprit for vision loss. Although promising, evidence supporting the application of estrogen analogues in models of ocular neurodegenerative diseases are nearly non-existent. It is our objective to study the neuroprotective effects of ZYC-3 in glaucomatous models with the goal of maintaining retinal ganglion cell viability and preventing vision loss.Item Sigma-1 Receptor Signaling in the Eye(2008-03-12) Tchedre, Kissaou T.; Yorio, Thomas; Singh, Meharvan; Machu, TinaSIGMA-1 Receptor Signaling in the Eye Kissaou T. Tchedre, Department of Biomedical Sciences, University of North Texas Health Science Center Fort Worth, TX 76107. SUMMARY The sigma-1 receptor is a discovered transmembrane protein that mediates the regulation of ion channels. Sigma-1 receptor ligands have exhibited a wide variety of actions in the central nervous system including attenuation of the neuronal death associated with glutamate excitotoxicity both in vitro and in vivo. Although the sigma-1 receptor was cloned almost a decade ago, the molecular mechanism of the neuroprotective effect remains to be elucidated. In the current proposal it was hypothesized that activation of sigma-1 receptors promotes retinal ganglion cells survival by decreased calcium signaling pathways and factors linked to cell death. We showed by the ratiometric calcium imaging and patch clamp techniques that sigma-1 receptor activation could inhibit both calcium influx and intracellular calcium mobilization. The results showed that sigma-1 receptor overexpressing RGC-5 cells also had a lower glutamate-induced intracellular calcium mobilization compared to non-overexpressing RGC-5 cells. The survival assay data showed that the sigma-1 receptor agonist, (+)-SKF10047 protected RGC-5 cells showed a significant resistance to glutamate-induced apoptosis compared to the control RGC-5 cells. The sigma-1 receptor neuroprotective mechanism also included the down regulation of Bax, and caveolin-1 protein expression levels and inhibited caspase-3 activation. We also demonstrated for the first time using a co-immunoprecipitation technique, the association between L-type calcium channels and sigma-1 receptors. Thus sigma-1 receptor ligands may indirectly influence the voltage-gated calcium channels by interacting with the sigma-1 receptor associated voltage-gated calcium channel complex. In conclusion, activation of sigma-1 receptors can regulate calcium homeostasis and signaling in retinal ganglion cells. Activation of sigma-1 receptors regulate intracellular calcium levels and pro-apoptotic gene expression to promote retinal ganglion cell survival. Sigma-1 receptor ligands may be neuroprotective and targets for potential glaucoma therapeutics.Item SIGMA-1 RECEPTOR STIMULATION PROTECTS PURIFIED RETINAL GANGLION CELLS FROM ISCHEMIC INSULT THROUGH THE PHOSPHORYLATION OF EXTRACELLULAR SIGNAL REGULATED KINASE 1/2(2014-03) Mueller, Brett H.; Park, Yong; Ma, Hai-Ying; Yorio, ThomasPurpose (a): Sigma-1 receptor activation and mitogen-activated protein kinases (MAPKs) have been shown to have neuroprotective roles in protecting retinal ganglion cells (RGCs) from cell death. The purpose of this study was to determine if sigma-1 receptor stimulation with pentazocine could promote neuroprotection under conditions of ischemia through the phosphorylation of extracellular signal regulated kinase (pERK)1/2. Methods (b): Primary RGCs were isolated from P3-P7 Sprague-Dawley rats and purified by sequential immunopanning using a Thy 1.1 antibody. RGCs were cultured for 7 days before subjecting the cells to an ischemic insult (0.5% oxygen in glucose-free medium) for 6 hours. During the ischemic insult, RGCs were treated with pentazocine (sigma-1 receptor agonist) with or without BD1047 (sigma-1 receptor antagonist). In other experiments primary RGCs were treated with pentazocine, in the presence or absence of PD98059 (ERK1/2 inhibitor). Cell survival/death was assessed by staining with the calcein-AM/ethidium homodimer reagent. Levels of pERK1/2, total ERK1/2, and beta tubulin expression were determined with immunoblotting and immunofluorescence. Results (c): RGCs subjected to an ischemic insult demonstrated more than a 40% increase in cell death, compared to untreated controls. RGCs maintained under ischemia also showed a 50% decrease in expression of pERK1/2 (p<0.05). Cell death was attenuated when RGCs were treated with pentazocine under ischemic conditions and levels of pERK1/2 were increased more than 60% (p<0.05), compared to untreated RGCs subjected to ischemia. Treatment with BD1047 abrogated the pentazocine neuroprotection effects, and also attenuated the increase in levels of pERK1/2 (p<0.05). Finally, treatment with PD98059 also reversed the pentazocine mediated neuroprotective effects on RGCs, and abolished the expression of pERK1/2 (p<0.05). Conclusions (d): These results establish a direct relationship between sigma-1 receptor stimulation and neuroprotective effects under ischemia through the involvement of the MAPK/ERK1/2 pathway in purified RGCs. These findings support a role for sigma receptor agonists as potential neuroprotective agents.Item The endothelin receptor antagonist macitentan ameliorates endothelin-mediated vasoconstriction and promotes the survival of retinal ganglion cells in rats(Frontiers Media S.A., 2023-01-01) Kodati, Bindu; Zhang, Wei; He, Shaoqing; Pham, Jennifer H.; Beall, Kallen J.; Swanger, Zoe E.; Krishnamoorthy, Vignesh R.; Harris, Payton E.; Hall, Trent; Tran, Ashley V.; Chaphalkar, Renuka M.; Chavala, Sai H.; Stankowska, Dorota L.; Krishnamoorthy, Raghu R.Glaucoma is a chronic and progressive eye disease, commonly associated with elevated intraocular pressure (IOP) and characterized by optic nerve degeneration, cupping of the optic disc, and loss of retinal ganglion cells (RGCs). The pathological changes in glaucoma are triggered by multiple mechanisms and both mechanical effects and vascular factors are thought to contribute to the etiology of glaucoma. Various studies have shown that endothelin-1 (ET-1), a vasoactive peptide, acting through its G protein coupled receptors, ET(A) and ET(B), plays a pathophysiologic role in glaucoma. However, the mechanisms by which ET-1 contribute to neurodegeneration remain to be completely understood. Our laboratory and others demonstrated that macitentan (MAC), a pan endothelin receptor antagonist, has neuroprotective effects in rodent models of IOP elevation. The current study aimed to determine if oral administration of a dual endothelin antagonist, macitentan, could promote neuroprotection in an acute model of intravitreal administration of ET-1. We demonstrate that vasoconstriction following the intravitreal administration of ET-1 was attenuated by dietary administration of the ET(A)/ET(B) dual receptor antagonist, macitentan (5 mg/kg body weight) in retired breeder Brown Norway rats. ET-1 intravitreal injection produced a 40% loss of RGCs, which was significantly lower in macitentan-treated rats. We also evaluated the expression levels of glial fibrillary acidic protein (GFAP) at 24 h and 7 days post intravitreal administration of ET-1 in Brown Norway rats as well as following ET-1 treatment in cultured human optic nerve head astrocytes. We observed that at the 24 h time point the expression levels of GFAP was upregulated (indicative of glial activation) following intravitreal ET-1 administration in both retina and optic nerve head regions. However, following macitentan administration for 7 days after intravitreal ET-1 administration, we observed an upregulation of GFAP expression, compared to untreated rats injected intravitreally with ET-1 alone. Macitentan treatment in ET-1 administered rats showed protection of RGC somas but was not able to preserve axonal integrity and functionality. The endothelin receptor antagonist, macitentan, has neuroprotective effects in the retinas of Brown Norway rats acting through different mechanisms, including enhancement of RGC survival and reduction of ET-1 mediated vasoconstriction.Item The Neuroprotective Efficacy of Antioxidants Against In Vitro Models of Oxidative Stress and Their Theoretical Application Via Intravitreal Injection Encapsulated in Nanoparticles(2010-05-01) Ondricek, Amber J.; Jamboor VishwanathaThe purpose of this study was to explore the possibility of utilizing antioxidants to mitigate oxidative stress induced apoptosis related to neurodegenerative diseases such as glaucoma. Our hypothesis is that in diseases related to an imbalanced redox status, whatever the primary cause may be, the loss of function may be prevented by antioxidants at the level of alleviating oxidative burden and preventing apoptotic signaling events. Application of these antioxidants to the site of injury can be improved using nanoparticle delivery methods. We have done work to characterize a model of mitochondrial associated oxidative stress induced cell death and obtained neuroprotective profiles on a group of antioxidants using this model. We have found that estrogens and phytoestrogens, as well as thiol containing antioxidants, function well as neuroprotectants in our in vitro model. Nanoparticle delivery of these models is a promising intervention and we therefore did work to optimize the characteristics of encapsulating one of these antioxidants, N-acetyl cysteine, in Poly(lactic-coglycolic acid) nanoparticles, which can be localized to the retina. Intravitreal injection of these particles is the preferred delivery route to retinal cells and has not been fully explored. We provide evidence to suggest that the intravitreal injection of nanoparticles is not detrimental to an animal’s vision. Taken together, the results of our experiments suggest that antioxidants remain a promising intervention in diseases related to mitochondrial associated oxidative stress, and that these drugs, when encapsulated in nanoparticles, can be delivered to the retina via intravitreal injection without deleterious side effects.