Postischemic, systemic administration of polyamine-modified superoxide dismutase reduces hippocampal CA1 neurodegeneration in rat global cerebral ischemia

Oral delivery of a highly stable superoxide dismutase as a skin aging inhibitor

As an effective antioxidant enzyme, superoxide dismutase (SOD) has been widely used as a food supplement, cosmetic additive, and therapeutic agent. However, oral delivery of SOD is challenging due to its relative instability, limited bioavailability, and low absorption efficiency in the gastrointestinal (GI) tract. We addressed these issues using a highly stable superoxide dismutase (hsSOD) generated from a hot spring microbial sample. This SOD exhibited a specific activity of 5000 IU/mg while retaining its enzymatic activity under low pH environments of an artificial GI system and in the presence of surfactants and various proteolytic enzymes. The inhibitory effects of hsSOD against skin-aging was evaluated under both in vitro and in vivo experiments using fibroblast cell and D-galactose induced aging-mouse models, respectively. Effective oral delivery of hsSOD promises wide applicability in pharmaceutical and food industries.

Treating brain diseases using systemic parenterally-administered protein therapeutics: Dysfunction of the brain barriers and potential strategies

The parenteral administration of protein therapeutics is increasingly gaining importance for the treatment of human diseases. However, the presence of practically impermeable blood-brain barriers greatly restricts access of such pharmaceutics to the brain. Treating brain disorders with proteins thus remains a great challenge, and the slow clinical translation of these therapeutics may be largely ascribed to the lack of appropriate brain delivery system. Exploring new approaches to deliver proteins to the brain by circumventing physiological barriers is thus of great interest. Moreover, parallel advances in the molecular neurosciences are important for better characterizing blood-brain interfaces, particularly under different pathological conditions (e.g., stroke, multiple sclerosis, Parkinson's disease, and Alzheimer's disease). This review presents the current state of knowledge of the structure and the function of the main physiological barriers of the brain, the mechanisms of transport across these interfaces, as well as alterations to these concomitant with brain disorders. Further, the different strategies to promote protein delivery into the brain are presented, including the use of molecular Trojan horses, the formulation of nanosystems conjugated/loaded with proteins, protein-engineering technologies, the conjugation of proteins to polymers, and the modulation of intercellular junctions. Additionally, therapeutic approaches for brain diseases that do not involve targeting to the brain are presented (i.e., sink and scavenging mechanisms).

Agile delivery of protein therapeutics to CNS

A variety of therapeutic proteins have shown potential to treat central nervous system (CNS) disorders. Challenge to deliver these protein molecules to the brain is well known. Proteins administered through parenteral routes are often excluded from the brain because of their poor bioavailability and the existence of the blood-brain barrier (BBB). Barriers also exist to proteins administered through non-parenteral routes that bypass the BBB. Several strategies have shown promise in delivering proteins to the brain. This review, first, describes the physiology and pathology of the BBB that underscore the rationale and needs of each strategy to be applied. Second, major classes of protein therapeutics along with some key factors that affect their delivery outcomes are presented. Third, different routes of protein administration (parenteral, central intracerebroventricular and intraparenchymal, intranasal and intrathecal) are discussed along with key barriers to CNS delivery associated with each route. Finally, current delivery strategies involving chemical modification of proteins and use of particle-based carriers are overviewed using examples from literature and our own work. Whereas most of these studies are in the early stage, some provide proof of mechanism of increased protein delivery to the brain in relevant models of CNS diseases, while in few cases proof of concept had been attained in clinical studies. This review will be useful to broad audience of students, academicians and industry professionals who consider critical issues of protein delivery to the brain and aim developing and studying effective brain delivery systems for protein therapeutics.

Pergolide protects CA1 neurons from apoptosis in a gerbil model of global cerebral ischemia

OBJECTIVE

To investigate the effects of dopamine (DA) receptor agonists and antagonists on neuronal apoptosis in hippocampal CA1 region after forebrain ischemia/reperfusion (I/R) injury in gerbils.

METHODS

Gerbil forebrain ischemia was induced by occluding bilateral carotid arteries for 5 minutes. The open field test, hematoxylin-eosin staining and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) methods were used 1, 3 and 7 days after reperfusion. Western blot was used to examine the phosphorylation of c-Jun.

RESULTS

Pergolide could significantly reduce the habituation impairments of ischemic gerbils, increase the number of normal neurons and reduce the number of apoptotic neurons in hippocampal CA1 region after reperfusion. SKF38393, SCH23390 and spiperone had no effects on these changes in this transient I/R injury model. Furthermore, pergolide can significantly reduce the phosphorylation of c-Jun induced by transient forebrain ischemia.

Superoxide dismutase administration, a potential therapy against oxidative stress related diseases: several routes of supplementation and proposal of an original mechanism of action

Oxidative stress, involved in many diseases, is defined as an impaired balance between reactive oxygen species (ROS) production and antioxidant defences. Antioxidant enzymes such as superoxide dismutase (SOD) play a key role in diminishing oxidative stress. Thus, the removal of ROS by exogenous SODs could be an effective preventive strategy against various diseases. The poor bioavailability of exogenous SODs has been criticized. However, improvements in SOD formulation may overcome this limitation and boost interest in its therapeutic properties. Here, we provide a review of animal and human studies about SODs supplementation in order to evaluate their therapeutic value. Protective effects have been observed against irradiation, carcinogenesis, apoptosis and neurodegeneration. SODs administration has also been reported to alleviate inflammatory, infectious, respiratory, metabolic and cardiovascular diseases and genitourinary and fertility disorders, raising the question of its mechanism of action in these diverse situations. Some authors have shown an increase in endogenous antioxidant enzymes after exogenous SODs administration. The induction of endogenous antioxidant defence and, consequently, a decrease in oxidative stress, could explain all the effects observed. Further investigations need to be carried out to test the hypothesis that SODs supplementation acts by inducing an endogenous antioxidant defence.

Meta-analysis of the efficacy of adjunctive NMDA receptor modulators in chronic schizophrenia

BACKGROUND

Based on the glutamatergic NMDA receptor hypofunction theory of schizophrenia, NMDA receptor modulators (NMDARMs) may have therapeutic potential in the treatment of schizophrenia.

OBJECTIVE

This meta-analysis aimed to evaluate the potential of modulators of the NMDA receptor as adjunctive therapy for schizophrenia, using the results from published trials.

DATA SOURCES

A primary electronic search for controlled clinical trials using NMDARMs in schizophrenia was conducted on the PubMed, Cochrane Library, EMBASE, CINAHL® and PsycINFO databases. A secondary manual search of references from primary publications was also performed.

STUDY SELECTION

Inclusion criteria were the application of an established method of diagnosis, randomized case assignment, comparison of NMDARM add-on therapy with placebo, and double-blind assessment of symptoms in chronic schizophrenia using standardized rating scales. Results were based on a total sample size of 1253 cases from 29 trials that fulfilled the specified criteria.

DATA EXTRACTION

Scores on rating scales or on their relevant subscales were obtained for all selected studies from published results for the minimum dataset to compute the difference between post- and pre-trial scores and their pooled standard deviation for NMDARM add-on therapy and placebo groups for negative, positive and total symptoms.

RESULTS

A negative standardized mean difference (SMD) indicates therapeutic benefit in favour of NMDARM add-on therapy and all SMD results mentioned here are statistically significant. The overall effect size for NMDARMs as a group was small for negative (SMD -0.27) and medium for total (SMD -0.40) symptoms of chronic schizophrenia. Subgroup analysis revealed medium effect sizes for D-serine and N-acetyl-cysteine (NAC) for negative (SMD -0.53 and -0.45, respectively) and total (SMD -0.40 and -0.64, respectively) symptoms, and for glycine (SMD -0.66) and sarcosine (SMD -0.41) for total symptoms. As adjuvants to non-clozapine antipsychotics, additional therapeutic benefits were observed for NMDARM as a group (SMD -0.14) and glycine (SMD -0.54) for positive symptoms; D-serine (SMD -0.54), NAC (SMD -0.45) and sarcosine (SMD -0.39) for negative symptoms; and NMDARM as a group (SMD -0.38), D-serine (SMD -0.40), glycine (SMD -1.12), NAC (SMD -0.64) and sarcosine (SMD -0.53) for total symptoms. When added to clozapine, none of the drugs demonstrated therapeutic potential, while addition of glycine (SMD +0.56) worsened positive symptoms.

CONCLUSIONS

Taking into consideration the number of trials and sample size in subgroup analyses, D-serine, NAC and sarcosine as adjuncts to non-clozapine antipsychotics have therapeutic benefit in the treatment of negative and total symptoms of chronic schizophrenia. While glycine improves positive and total symptoms as an adjuvant to non-clozapine antipsychotics, it worsens them when added to clozapine.

Review and meta-analysis of usage of ginkgo as an adjunct therapy in chronic schizophrenia

This study aimed to review the roles of antioxidants in the pathophysiology of schizophrenia, whether the properties of ginkgo can ameliorate symptoms of this illness, and evaluate available literature to test this assumption. This review is based upon published works on antioxidants and ginkgo. A primary electronic search for meta-analysis on the usage of ginkgo or its derived products in schizophrenia was conducted using Pubmed, Cochrane Library, EMBASE, CINAHL, PsycINFO and AMED. Inclusion criteria were: criteria-based diagnosis of schizophrenia, randomized case assignment, use of ginkgo as an add-on therapy, and assessment using standardized rating scales to measure the state of psychopathology for negative and total symptoms of schizophrenia. Additionally, a detailed review was undertaken to investigate if antioxidants are involved in development of psychotic symptoms in schizophrenia. The six studies that fulfilled the selection criteria were constituted of 466 cases on ginkgo and 362 cases on placebo. They all used the Scale for the Assessment of Negative Symptoms (SANS) to measure negative symptoms, and the Scale for the Assessment of Positive Symptoms (SAPS) or the Brief Psychiatric Rating Scale (BPRS) to measure total symptoms. Difference between ginkgo and control groups from their pre- and post-trial scores and its pooled standard deviation were used to compute standardized mean difference (SMD). Ginkgo as an add-on therapy to antipsychotic medication produced statistically significant moderate improvement (SMD=-0.50) in total and negative symptoms of chronic schizophrenia. Ginkgo as add-on therapy ameliorates the symptoms of chronic schizophrenia. The role of antioxidants in pathogenesis of schizophrenia has also been explored.

CNS delivery via adsorptive transcytosis

Adsorptive-mediated transcytosis (AMT) provides a means for brain delivery of medicines across the blood-brain barrier (BBB). The BBB is readily equipped for the AMT process: it provides both the potential for binding and uptake of cationic molecules to the luminal surface of endothelial cells, and then for exocytosis at the abluminal surface. The transcytotic pathways present at the BBB and its morphological and enzymatic properties provide the means for movement of the molecules through the endothelial cytoplasm. AMT-based drug delivery to the brain was performed using cationic proteins and cell-penetrating peptides (CPPs). Protein cationization using either synthetic or natural polyamines is discussed and some examples of diamine/polyamine modified proteins that cross BBB are described. Two main families of CPPs belonging to the Tat-derived peptides and Syn-B vectors have been extensively used in CPP vector-mediated strategies allowing delivery of a large variety of small molecules as well as proteins across cell membranes in vitro and the BBB in vivo. CPP strategy suffers from several limitations such as toxicity and immunogenicity--like the cationization strategy--as well as the instability of peptide vectors in biological media. The review concludes by stressing the need to improve the understanding of AMT mechanisms at BBB and the effectiveness of cationized proteins and CPP-vectorized proteins as neurotherapeutics.

MR microimaging of amyloid plaques in Alzheimer's disease transgenic mice

INTRODUCTION

Alzheimer's disease (AD) is the most prevalent neurological condition affecting industrialized nations and will rapidly become a healthcare crisis as the population ages. Currently, the post-mortem histological observation of amyloid plaques and neurofibrillary tangles is the only definitive diagnosis available for AD. A pre-mortem biological or physiological marker specific for AD used in conjunction with current neurological and memory testing could add a great deal of confidence to the diagnosis of AD and potentially allow therapeutic intervention much earlier in the disease process.

DISCUSSION AND CONCLUSION

Our group has developed MRI techniques to detect individual amyloid plaques in AD transgenic mouse brain in vivo. We are also developing contrast-enhancing agents to increase the specificity of detection of amyloid plaques. Such in vivo imaging of amyloid plaques will also allow the evaluation of anti-amyloid therapies being developed by the pharmaceutical industry in pre-clinical trials of AD transgenic mice. This short review briefly discusses our progress in these areas.

Effects of fluoxetine on ischemic cells and expressions in BDNF and some antioxidants in the gerbil hippocampal CA1 region induced by transient ischemia

Fluoxetine, a selective serotonin reuptake inhibitor, alters several physiological processes, for example, elevating intracellular cAMP level, in the hippocampus. We examined the effect of fluoxetine on ischemia-induced neuronal death, the expression of brain-derived neurotrophic factor (BDNF) and changes in some antioxidative enzymes in the hippocampal CA1 region induced by transient ischemia. In addition, we also studied the effect of fluoxetine on locomotor activity in gerbils after ischemia/reperfusion. Animals were administered with various doses of fluoxetine (10, 20, and 40 mg/kg, i.p.) once daily for 3 days before the ischemic surgery. The treatment of 10 mg/kg and 20 mg/kg fluoxetine did not show significant neuroprotective effects on CA1 pyramidal cells 4 days after ischemia/reperfusion, while the treatment with 40 mg/kg fluoxetine in ischemic animals showed about 77% neuronal survival rate compared to the control group. The treatment of 40 mg/kg fluoxetine in ischemic animals enhanced significantly BDNF, catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase-1 (SOD1) immunoreactivity in the CA1 region compared to those in the saline-treated group 4 days after ischemia/reperfusion. In addition, the treatment of fluoxetine (10, 20, 40 mg/kg) significantly inhibited post-ischemic hyperactivity. In brief, treatment with fluoxetine protects neuronal damage after transient ischemia, and the neuroprotective effect of fluoxetine in an ischemic animal model may be related with the up-regulation of BDNF, CAT, GPX, and SOD1 expression.

Astaxanthin, a carotenoid with potential in human health and nutrition

Astaxanthin (1), a red-orange carotenoid pigment, is a powerful biological antioxidant that occurs naturally in a wide variety of living organisms. The potent antioxidant property of 1 has been implicated in its various biological activities demonstrated in both experimental animals and clinical studies. Compound 1 has considerable potential and promising applications in human health and nutrition. In this review, the recent scientific literature (from 2002 to 2005) is covered on the most significant activities of 1, including its antioxidative and anti-inflammatory properties, its effects on cancer, diabetes, the immune system, and ocular health, and other related aspects. We also discuss the green microalga Haematococcus pluvialis, the richest source of natural 1, and its utilization in the promotion of human health, including the antihypertensive and neuroprotective potentials of 1, emphasizing our experimental data on the effects of dietary astaxanthin on blood pressure, stroke, and vascular dementia in animal models, is described.

Dopamine D2-like receptor agonist bromocriptine protects against ischemia/reperfusion injury in rat kidney

BACKGROUND

Dopamine, via activation of D1-like and D2-like receptors, plays an important role in the regulation of renal sodium excretion. Recently, we demonstrated that dopamine D2-like receptor agonist (bromocriptine) stimulates p44/42 mitogen-activated protein kinases (MAPKs) and Na+,K(+)ATPase (NKA) activity in proximal tubular epithelial cells. Since both these parameters are compromised in ischemia/reperfusion (I/R) injury to the kidney, we investigated whether bromocriptine protects against the injury.

METHODS

In this study we used unilateral rat model of renal I/R injury. The Sprague-Dawley rats were divided into vehicle and bromocriptine groups. The vehicle and bromocriptine group was treated with vehicle and bromocriptine (500 microg/kg intravenously), respectively, 15 minutes before the induction of unilateral ischemia followed by 24- or 48-hour reperfusion. At the end of 24 or 48 hours the animals were sacrificed to collect control and ischemic kidney cortices, in which necrosis, apoptosis, NKA activity, NKA alpha1 subunit expression, and p44/42 MAPK phosphorylation were measured.

RESULTS

We found extensive necrosis, apoptosis, and decreased NKA activity (with no change in alpha1 subunit) in the ischemic kidney cortex compared to the nonischemic cortex from the vehicle-treated rats as early as 24 hours post-reperfusion. In contrast, I/R injury-induced necrotic, apoptotic, and decrease in NKA activity were absent in the outer cortex of bromocriptine-treated rats after 24 or 48 hours. Interestingly, we detected significantly higher phosphorylation of p44/42 MAPKs in control and ischemic kidneys of bromocriptine-treated rats compared to those of vehicle-treated rats.

CONCLUSION

Therefore, bromocriptine, a D1-like receptor agonist, may protect against I/R injury to proximal tubules of the kidney, via p44/42 MAPK activation.

The effect of vitamin E treatment on tardive dyskinesia and blood superoxide dismutase: a double-blind placebo-controlled trial

Free radicals may be involved in the pathogenesis of tardive dyskinesia (TD). Vitamin E, a free radical scavenger, has been reported to improve symptoms of TD. The present study was designed to replicate this finding in a group of Chinese patients with TD, and to examine the effect of vitamin E treatment on blood superoxide dismutase (SOD), a critical enzyme in the detoxification of free radicals. Forty-one inpatients with TD completed a double-blind, placebo-controlled, parallel-group study of vitamin E. Twenty-two of the patients were randomly assigned to receive a fixed dose of 1200 IU/d vitamin E, and 19 were assigned to a placebo for 12 weeks. Patients were assessed primarily using the Abnormal Involuntary Movement Scale (AIMS) at baseline, weeks 6 and 12. Blood SOD levels were measured by radioimmunometric assay before and after treatment. The results showed that the reduction in AIMS score from baseline was significantly higher with vitamin E treatment compared with placebo (45.9% vs. 4.3%). Blood SOD levels were significantly increased after treatment with vitamin E (P = 0.001), but no change with placebo treatment (P < 0.05). These results support earlier findings of the efficacy of vitamin E in the treatment of TD. Moreover, the efficacy of vitamin E may be due to its ability to increase SOD level, which may reduce oxidative injure in tardive dyskinesia.

The protective effect of M40401, a superoxide dismutase mimetic, on post-ischemic brain damage in Mongolian gerbils

BACKGROUND

Overproduction of free radical species has been shown to occur in brain tissues after ischemia-reperfusion injury. However, most of free radical scavengers known to antagonize oxidative damage (e.g. superoxide dismutase, catalase), are unable to protect against ischemia-reperfusion brain injury when given in vivo, an effect mainly due to their difficulty to gain access to brain tissues. Here we studied the effect of a low molecular weight superoxide dismutase mimetic (M40401) in brain damage subsequent to ischemia-reperfusion injury in Mongolian gerbils.

RESULTS

In animals undergoing ischemia-reperfusion injury, neuropathological and ultrastructural changes were monitored for 1-7 days either in the presence or in the absence of M40401 after bilateral common carotid artery occlusion (BCCO). Administration of M40401 (1-40 mg/kg, given i.p. 1 h after BCCO) protected against post-ischemic, ultrastructural and neuropathological changes occurring within the hippocampal CA1 area. The protective effect of M40401 was associated with a significant reduction of the levels of malondialdehyde (MDA; a marker of lipid peroxidation) in ischemic brain tissues after ischemia-reperfusion.

CONCLUSION

Taken together, these results demonstrate that M40401 provides protective effects when given early after the induction of ischemia-reperfusion of brain tissues and suggest the possible use of such compounds in the treatment of neurological dysfunction subsequent to cerebral flow disturbances.

Therapeutic potential of superoxide dismutase mimetics as therapeutic agents in critical care medicine

Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants, or a depletion of antioxidants. A considerable body of recent evidence suggests that oxidative stress and exaggerated production of reactive oxygen species play a major role in several aspects of septic shock and ischemia and reperfusion. Initiation of lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3-phosphate dehydrogenase, inhibition of membrane Na /K adenosine triphosphatase activity, inactivation of membrane sodium channels, and other oxidative protein modifications contribute to the cytotoxic effect of reactive oxygen species. In addition, reactive oxygen species are potent triggers of DNA strand breakage, with subsequent activation of the nuclear enzyme poly-adenosine 5'-diphosphate ribosyl synthetase, and eventual severe energy depletion of the cells. Pharmacologic evidence suggests that the peroxynitrite-poly-adenosine 5'-diphosphate ribosyl polymerase pathway contributes to the cellular injury in shock and endothelial injury. Treatment with superoxide dismutase mimetics, which selectively mimic the catalytic activity of the human superoxide dismutase enzymes, has been shown to prevent the cellular energetic failure associated with shock and ischemia-reperfusion and to prevent tissue damage associated with these conditions. In this article, we will briefly review the role of superoxide in septic shock and ischemia-reperfusion injury. We hope to present evidence to support the potential development of superoxide dismutase mimetics as novel and effective agents in the area of critical care medicine.

Polyethylene glycol-superoxide dismutase, a conjugate in search of exploitation

Without a doubt PEG-SOD has been the enzyme most studied in PEGylation. One can say that it represents the preferred model to assess chemistries for PEG activation, analytical procedures suitable for conjugate characterization, the influence of PEG size in conjugate removal from circulation and elimination of immunogenicity and antigenicity, and the effect of route of administration. The effect of PEG conjugation was studied in vitro and in vivo models in comparison with the free enzyme and the following conclusions may be drawn: (1) At the blood vessel level, PEG-SOD has been shown to provide a greater resistance to oxidant stress, to improve endothelium relaxation and inhibit lipid oxidation. (2) In the heart, PEG-SOD proved to be at least as effective as native SOD in treatment of reperfusion-induced arrhythmias and myocardial ischemia. (3) In the lung, PEG-SOD appeared to be able to reduce oxygen toxicity and E. coli-induced lung injury, but not in the treatment of lung physiopathology associated with endotoxin-induced acute respiratory failure and in the reduction of asbestos-induced cell damage. (4) On cerebral ischemia/reperfusion injuries the effect of PEG-SOD was uncertain, also due to the difficulty of cerebral cell penetration. (5) In kidney and liver ischemia both enzyme forms were found to ameliorate reperfusion damage. In view of so much positive research on PEG-SOD, it is surprising that no approved application in human therapy has been established and approved.

Amyloid beta peptide as a vaccine for Alzheimer's disease involves receptor-mediated transport at the blood-brain barrier

Much research is now focused on a potential vaccine for Alzheimer's disease (AD). Current studies involve administering the amyloid beta peptide (Abeta) in Freund's complete adjuvant, which cannot be used in humans. Our studies show that the immune complex of Abeta is taken up by a receptor-mediated process at the blood-brain barrier (BBB). The success of immunization for AD, therefore, may be critically dependent on circulating Abeta levels which are lower in AD patients compared to AD transgenic mice. Moreover, we have found that modifying the antibody with polyamine increases its BBB permeability and may provide a better approach to passive immunization for Alzheimer's disease.

Oxidative stress and neuroAIDS: triggers, modulators and novel antioxidants

Neurological disorders represent one of the most common disturbances accompanying HIV infection. In the past few years, highly antiretroviral active therapy has significantly reduced the incidence of HIV-related diseases. However, neurological dysfunction in AIDS patients still remains an unresolved problem. Oxidative stress, which occurs in brain tissues of patients undergoing HIV infection and is implicated in cell death of both astroglia and neurones, has recently been suggested to play a role in the pathogenesis of neuroAIDS. Thus, a better understanding of the processes that trigger and modulate free radical formation in brain tissues of AIDS patients might help in a successful therapeutic approach to the neuropathogenesis of HIV infection.

Temperature and time interval for culture of postmortem neurons from adult rat cortex

For a model of neurological disease and ischemia, we extended recent work to culture adult postmortem rat brain neurons. Frontal cortex sections were removed from adult rats immediately following sacrifice and at different postmortem intervals and with the brain at either 22 degrees C or 4 degrees C. Brain could be stored four times longer at 4 degrees C between sacrifice and neuronal disaggregation to achieve the same 20% recovery of live cells from those plated compared to 22 degrees C. Each milligram of rat frontal cortex was estimated by the optical disector method to contain 160,000 neurons. When cells were isolated as rapidly as possible, 9% of the neurons originally present in the brain were viable. Various postmortem intervals from 2 to 24 hr resulted in a reduction from 6% to 3% of the cells originally present. After 5 days in culture, viable neurons were 23-42% of those isolated. Neuron-like cells that survived represented 40-75% of the viable cells, or 0.5-2.75% of those originally estimated to be present in the brain. Electrophysiology experiments show that cells isolated 0 and 24 hr postmortem had neuronal electrical properties, including an average resting membrane potential of -48 mV, voltage-sensitive currents, and action potentials. Neuron-like cells were immunoreactive for neuron-specific enolase, neurofilament 200, glutamate, MAP2, and tau after 2 weeks in culture. These experiments show that neuron-like cells can be reliably cultured from adult rat cortex up to 6 hr postmortem when stored at 22 degrees C and up to 24 hr postmortem when stored at 4 degrees C. These findings should encourage donation of human postmortem brain neurons for studies on ischemia, adult pharmacology, and neurological disease.

Targeting of superoxide dismutase and catalase to vascular endothelium

Reactive oxygen species, such as superoxide anion (O2(-)) and H2O2, cause oxidative stress in endothelial cells, a condition implicated in the pathogenesis of many cardiovascular and pulmonary diseases. Antioxidant enzymes, superoxide dismutases (SOD, converting superoxide anion into H2O2) and catalase (converting H2O2 into water), are candidate drugs for augmentation of antioxidant defenses in endothelium. However, SOD and catalase undergo fast elimination from the bloodstream, which compromises delivery and permits rather modest, if any, protection against vascular oxidative stress. Coupling of polyethylene glycol (PEG) to the enzymes and encapsulating them in liposomes increases their bioavailability and enhances their protective effect. Chemical modifications and genetic manipulations of SOD and catalase have been proposed in order to provide more effective delivery to endothelium. For example, chimeric protein constructs consisting of SOD and heparin-binding peptides have an affinity for charged components of the endothelial glycocalix. However, the problem of developing a more effective and precise delivery of the drugs to endothelial cells persists. Endothelial surface antigens may be employed to provide targeting and subcellular addressing of drugs (vascular immunotargeting strategy). Thus, SOD and catalase conjugated to antibodies directed against the constitutively expressed endothelial antigens, angiotensin-converting enzyme (ACE) and adhesion molecules (ICAM-1 or PECAM-1), bind to endothelium in intact animals after intravascular administration, accumulate in the pulmonary vasculature, enter endothelial cells and augment their antioxidant defenses. Such immunotargeting strategies may provide secondary therapeutic benefits by inhibiting the function of target antigens. For example, blocking of ICAM-1 and PECAM-1 by carrier antibodies may attenuate inflammation and leukocyte-mediated vascular damage. Additional studies in animal models of vascular oxidative stress are necessary in order to more fully characterize potential therapeutic effects and limitations of targeting of antioxidant enzymes to endothelial cells.

Delivery of antioxidant enzyme proteins to the lung

Protection of alveolar epithelial cells (alveolocytes) and vascular endothelial cells against pulmonary oxidative stress is an important problem. An inadequate delivery to the target cells limits the protective utility of the antioxidant enzymes, superoxide dismutase (SOD) and catalase. SOD and catalase modifications, such as coupling with polyethylene glycol and encapsulation in liposomes, prolong the life span of the active enzymes in vivo. The airway administration of SOD and catalase protects alveolocytes against hyperoxic oxidative stress. Although pulmonary endothelium is poorly accessible from the airways, it is accessible from circulation. However, antioxidant enzymes and their derivatives display poor targeting to pulmonary endothelium. To improve the targeting and provide intracellular delivery to endothelium, the enzymes can be conjugated with antibodies against endothelial antigens, such as angiotensin-converting enzyme and adhesion molecules [intercellular adhesion molecule-1 (ICAM-1) or platelet-endothelial cell adhesion molecule-1 (PECAM-1)]. These immunoconjugates accumulate in the pulmonary vasculature in intact animals, enter endothelium, and augment the antioxidant defenses. The immunoconjugates directed against ICAM-1 and PECAM-1 may also provide a secondary therapeutic benefit by blocking of sequestration and infiltration of leukocytes in the lungs. Further investigations are necessary to evaluate the therapeutic effectiveness of the vascular immunotargeting of antioxidant enzymes and solve technical problems associated with production of safe, clinically useful conjugates.

Disulfiram augments oxidative stress in rat brain following bilateral carotid artery occlusion

We examined the brain oxidative stress which accompanies 30 min of bilateral carotid artery ligation (BCAL) in terms of changes in brain levels of glutathione; reduced (GSH) and oxidized (GSSG) forms and the exacerbation of oxidative stress by disulfiram (DSF). These results indicate that BCAL alone decreases GSH content and limits glutathione reductase (GR) activity, and these changes were enhanced by DSF pretreatment. Similar observations were recorded with DSF alone. GR activity (74.3 +/- 4.0 micromol min(-1) mg(-1) tissue; p < 0.001) and GSH content (1.23 +/- 0.06 micromol min(-1) g(-1) tissue; p < 0.001) was attenuated in rats subjected to synergistic effect of BCAL and DSF with a concomitant increase of GSSG (0.006 +/- 0.006 micromol min(-1) g(-1) tissue; p < 0.001). Recovery of GSH/GSSG level and GR activity during reperfusion following 30 min BCAL was considerably delayed (96 h) in the BCAL and DSF group as compared to the recovery time of 24 h in the group subjected to BCAL-reperfusion alone. Perturbation of GSH/GSSG homeostasis as a result of BCAL was augmented by DSF. These findings clearly demonstrate central nervous system oxidative stress due to a BCAL-DSF synergistic effect. Based on the results obtained with this model, we conclude that DSF increases brain oxidative stress and this may be detrimental to alcoholics who might drink and develop an acetaldehyde-induced hypotension while taking DSF.

Therapeutic benefits of putrescine-modified catalase in a transgenic mouse model of familial amyotrophic lateral sclerosis

Dominant mutations in the copper/zinc superoxide dismutase (SOD1) gene have been observed in 15-20% of familial amyotrophic lateral sclerosis (FALS) cases. The mechanism by which SOD1 mutations result in motor neuron degeneration in FALS mice partly involves oxidative damage and an increased peroxidase activity of the mutant SOD1. A new therapeutic approach designed to eliminate the substrate of this peroxidase activity was examined in two lines of transgenic mice expressing the FALS-linked mutation glycine to alanine (G93A). We investigated the ability of putrescine-modified catalase (PUT-CAT), an antioxidant enzyme that removes hydrogen peroxide and has increased permeability at the blood-brain barrier, to modify the time course of the SOD1 mutation-induced motor neuron disease in these FALS mice. Continuous, subcutaneous administration of PUT-CAT significantly delayed the age at which onset of clinical disease occurred (indicated by loss of splay and/or tremors of hindlimbs) in a high-expressor line of FALS transgenic mice. Intraperitoneal injection of PUT-CAT given two times per week also significantly delayed the onset of clinical disease in a low-expressor line of FALS mice. PUT-CAT also significantly delayed the age at which clinical weakness developed (quantified by measuring the shortening of stride length) in both lines of FALS animals. No significant changes were observed in the survival times of the high-expressor FALS mice in any of the treatment groups. However, a trend toward a prolongation of survival was observed in the PUT-CAT-treated low-expressor FALS mice. These results support the role of free radical-mediated damage in the cascade of events leading to motor neurodegeneration in FALS and indicate that PUT-CAT interacts with a critical step in this cascade to delay the onset of clinical disease as well as the development of clinical weakness in FALS transgenic mice.

Plasma pharmacokinetics, nervous system biodistribution and biostability, and spinal cord permeability at the blood-brain barrier of putrescine-modified catalase in the adult rat

Free radical-mediated oxidative damage has been proposed to be an underlying mechanism in several neurodegenerative disorders. Previous investigations in our laboratory have shown that putrescine-modified catalase (PUT-CAT) has increased permeability at the blood-brain (BBB) and blood-nerve barriers with retained enzymatic activity after parenteral administration when compared to native catalase (CAT). The goals of the present study were to examine the plasma stability, spinal cord BBB permeability, nervous system biodistribution, and spinal cord enzyme activity of CAT and PUT-CAT after parenteral administration in the adult rat. TCA precipitation and chromatographic analyses revealed that CAT and PUT-CAT were found intact in the plasma and in the central nervous system (CNS) after iv, ip, or sc bolus injections. The highest percentages of intact CAT or PUT-CAT proteins were found in the plasma after iv administration, and similar percentages of intact CAT or PUT-CAT were found in the CNS following all three types of administration. Increases of 2.4- to 4.7-fold in permeability at the BBB and similar increases in the levels of intact PUT-CAT were found in different brain regions compared to the levels of CAT. A 2.4-fold higher level of intact PUT-CAT compared to that of CAT (P < 0.05) was found in the spinal cord 60 min after a sc bolus injection. CAT enzyme activity in the spinal cord was 50% higher (P < 0.05) in rats treated with PUT-CAT continuously for 1 week by subcutaneously implanted, osmotic pumps than the activity found in rats treated with PBS. These results provide evidence that intact, enzymatically active PUT-CAT is efficiently delivered to the nervous system following iv, ip, and sc administration and suggest that sc administration of PUT-CAT may be effective in treating neurodegenerative disorders in which the underlying mechanisms involve the action of free radicals and oxidative damage.

Hippocampal cell loss in transient global cerebral ischemia in rats: a critical assessment

The induction of transient global cerebral ischemia by permanent vertebral occlusion and temporary carotid ligation (four-vessel occlusion) is widely accepted as a valid tool for the study of pathogenesis and treatment of ischemia. The neural damage inflicted by this intervention is often assessed by measuring pyramidal cell loss in the CA1 hippocampal field. Nevertheless studies using this model in rats often fail to control variables that are relevant to the outcome, and/or apply biased methods to quantitate histological damage. We have applied unbiased stereological methods to estimate absolute numbers of surviving neurons in CA1 in Wistar rats subjected to either 10 or 20 min global ischemia using the Sugio et al. variant of the original four-vessel occlusion model. Animal mortality was high at both times, with neuron losses averaging 39% and 31%, respectively. Post-operative mortality was reduced substantially by using decompressive craniectomies and, even more effectively, by pre-treating the rats with low doses of phenytoin. Both maneuvers led to a severely increased CA1 neuron loss, which reached 50%, after an ischemia of 10 min. This finding strongly supports that mortality biases the sample. Other noteworthy findings that emerged from this study were a linear relationship between per-ischemic blood pressure increments and animal survival, and a negative correlation between cell survival and preferentially left-sided damage.

Differential effects of olanzapine on the gene expression of superoxide dismutase and the low affinity nerve growth factor receptor

Neuroanatomical studies of schizophrenia suggest that progressive neuropathological changes (such as neuronal atrophy and/or cell death) occur over the lifetime course of the disease. Early intervention with atypical neuroleptics has been shown to prevent progression of at least some symptoms, although the mechanisms by which neuroleptics may do this remain unknown. In this study, PC12 cells were used to determine the effects of the new atypical antipsychotic olanzapine on the gene expression of superoxide dismutase (SOD1) and the low affinity nerve growth factor receptor (p75). The results show that olanzapine increases SOD1 at concentrations of 10 and 100 microM after 48 hr of incubation in PC12 cultures. The treatment decreases p75 gene expression at concentrations 100 microM after 48 hr of incubation. Since both the upregulation of SOD1 mRNA and the antisense blockade of p75 mRNA have been associated with reduced cell death, our results suggest that olanzapine has neuroprotective potential and thus may be useful in preventing further neurodegeneration accompanying schizophrenia.

Neuroprotective efficacy of combination therapy with two different antioxidants in rats subjected to transient focal ischemia

The vascular endothelium and parenchyma of the brain have both potential pathways to generate free radicals under pathological conditions. We evaluated the neuroprotective efficacy of two different antioxidants, a microvascularly acting 21-aminosteroid (U-74389G) and a brain-penetrating pyrrolopyrimidine (U-101033E) alone and in combination. Forty Sprague-Dawley rats were randomly assigned to one of four treatment groups: (1) vehicle-treated controls, (2) U-74389G, (3) U-101033E, (4) U-74389G+U-101033E. Drugs were administered in a dosage of 3x3 mg/kg i.v. before, during, and after ischemia. All animals were subjected to 90 min of middle cerebral artery occlusion. Local cortical blood flow (LCBF) was continuously recorded by bilateral laser Doppler flowmetry. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed after 7 days. There were no significant differences in LCBF among groups. U-101033E improved neurological function from postoperative day 4 to 7, while U-74389G did not improve neurological recovery. Animals treated with both drugs showed significantly less deficits from postoperative day 1 to 7. U-101033E and combination therapy reduced total infarct volume by 53% and 54% (P<0.05). U-74389G non-significantly reduced total infarct volume by 25%. Cortical infarct volume was significantly reduced in all treatment groups but only U-101033E and combination therapy protected the basal ganglia from infarction. In conclusion, brain-penetrating antioxidants have superior neuroprotective properties compared to microvascularly acting agents. Combination therapy, affording antioxidation plus radical scavenging in blood vessels and brain parenchyma, might yield the highest degree of neuronal protection from peroxidative damage. The neuroprotective efficacy seems to be independent of CBF.

Influence of the antioxidant quercetin in vivo on the level of nitric oxide determined by electron paramagnetic resonance in rat brain during global ischemia and reperfusion

We characterized the changes in nitric oxide (NO) levels in the brain during global forebrain ischemia and reperfusion and tested the ability of the natural flavonoid, quercetin, and a synthetic flavonoid, FB277, to increase the amount of available NO by elimination of the superoxide radicals produced during reperfusion. In Sprague-Dawley rats, we used a four-vessel occlusion model of forebrain ischemia (15 min) and reperfusion (30 min). Brain NO was measured on samples of cerebral cortex and cerebellum ex vivo by electron paramagnetic resonance (EPR) spectroscopy. The spin trap used was diethyldithiocarbamate sodium salt (DETC) associated with ferrous citrate. The complex Fe(DETC)2NO was detected at 77 K as a triplet signal at g = 2.035. Groups of animals were treated with quercetin or FB277 (3-morpholinomethyl-3',4',5,7tetramethoxyflavone) or polyethylene glycol-conjugated superoxide dismutase (PEG-SOD). In control (intact anesthetized animals), the signal was about 3 times greater in the cortex than in the cerebellum. During ischemia, the signal rose to 110% in cortex (NS) and 283% in cerebellum (P < 0.05). In reperfusion, it fell again to 91% of control in cerebellum (NS) and 35% in cortex (P < 0.05). Treatment by quercetin (5 mg/kg i.v.) of intact and ischemia-reperfusion groups did not significantly change the signal amplitude in the cerebellum, but did double it in the cortex (to 76% of control) for the ischemia-reperfusion group (P < 0.05). In contrast, FB277 (3.75 mg/kg i.v.) did not increase the signal in the cortex during ischemia-reperfusion, but did do so in the cerebellum (to 152% of control, P < 0.05). The results obtained for PEG-SOD (10,000 U/kg i.v.) were similar to those for FB277. In separate in vitro measurements, we found that quercetin but not FB277 efficiently scavenged superoxide. We hypothesize that quercetin but not FB277 scavenged superoxide anions released in the cortex during reperfusion, thus diminishing the amount of NO removed by the formation of peroxynitrite. The lack of effect of PEG-SOD may be related to the need for chronic treatment to obtain protection.

The antioxidant defences of brain mitochondria during short-term forebrain ischemia and recirculation in the rat

This study evaluated changes in the antioxidant defences of mitochondria induced by 30 min of forebrain ischemia and recirculation up to 24 h in rats. Following treatment, mitochondria were isolated from two brain subregions: the dorsolateral striatum, an area in which there is loss of most neurons, and the paramedian cortex in which most neurons are resistant to damage. During ischemia and the first few hours of recirculation, the mitochondrial defences were largely preserved based on measurements of the activities of the enzymes, superoxide dismutase, glutathione peroxidase and glutathione reductase, as well as the response of the mitochondria to a subsequent exposure to H2O2 in vitro. However, some moderate changes were detected, particularly in the mitochondria from the dorsolateral striatum. A decrease of 30% in the activity of superoxide dismutase was seen at the conclusion of the ischemic period and a small increase in susceptibility to changes induced by H2O2 was detected during early recirculation. This latter change preceded and possibly contributed to the development of an impairment of respiratory function detected in mitochondria from the dorsolateral striatum at 3 h of recirculation. At 24 h of recirculation, larger changes were seen in the activities of all three of the enzymes in mitochondria from the dorsolateral striatum but not the paramedian cortex that was associated with progression to advanced neuronal damage in the former subregion.

Dopamine D2 receptor agonists protect against ischaemia-induced hippocampal neurodegeneration in global cerebral ischaemia

To characterise the role played by dopamine receptors in ischaemic brain damage, we have evaluated the effects of pergolide, bromocriptine and lisuride (dopamine D2 receptor agonists), haloperidol (a dopamine D2 receptor antagonist), 2,3,4,5-tetrahydro-7,8,dihydroxy-1-phenyl-1H-3-benzazepine (SKF 38393; a dopamine D1 receptor agonist) and (R)-(+)-8-chloro 2,3,4,5-tetra-hydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol (SCH 23390; a dopamine D1 receptor antagonist) in the gerbil model of global cerebral ischaemia. Ischaemia was induced by 5 min of bilateral carotid artery occlusion under halothane anaesthesia. Sham operated animals were used as controls. Pergolide (0.5 or 1.0 mg/kg i.p), bromocriptine (0.5 or 1.0 mg/kg i.p.), lisuride (0.5 or 1.0 mg/kg i.p.), SCH 23390 (0.1 or 1.0 mg/kg i.p.), haloperidol (0.5, 1.0 or 2 mg/kg i.p.) and SKF 38393 (1.0 or 2 mg/kg i.p.) were administered 1 h before occlusion. Five-minute-occluded animals had extensive damage in the CA1 region of the hippocampus 5 days after surgery. Pergolide 0.5 and 1.0 mg/kg i.p. provided significant (P < 0.05 and P < 0.01, respectively) neuroprotection against the ischaemia-induced hippocampal damage. Bromocriptine and lisuride also provided significant (P < 0.05) neuroprotection, but only at the higher 1.0 mg/kg dose. In contrast, the dopamine D2 receptor antagonist (haloperidol), the dopamine D1 receptor agonist (SKF 38393) and the dopamine D1 receptor antagonist (SCH 23390) failed to provide any neuroprotection in the model. These results support studies indicating that dopamine is important in ischaemic situations. The results also indicate that dopamine D2 receptor agonists are neuroprotective against ischaemia-induced brain injury and may play a role in neurodegenerative disorders.

Transient increase of manganese-superoxide dismutase in remote brain areas after focal photothrombotic cortical lesion

BACKGROUND AND PURPOSE

Free radicals including superoxide are responsible for postlesional cytotoxicity. In contrast to the constitutive CuZn-superoxide dismutases (SODs), manganese-superoxide dismutase (Mn-SOD) is inducible and has the potential to protect neurons by its superoxide dismutating activity. Therefore, we studied the presence and the regional changes in Mn-SOD within the brain after focal cortical ischemia.

METHODS

Focal cortical photothrombotic lesions were produced in the hindlimb region of rat brains. Animals were anesthetized and transcardially perfused with Zamboni's fixative. Mn-SOD was immunohistochemically localized using an antiserum against rat-Mn-SOD. Changes in Mn-SOD immunoreactivity were quantified by image analysis.

RESULTS

Focal photothrombosis caused a perilesional increase in Mn-SOD after 24 hours, followed by a further significant increase at 48 hours in perilesional cortex, ipsilateral corpus callosum, hippocampus, and thalamus, as well as in a homotopic cortical area within the nonlesioned hemisphere. At day 2, Mn-SOD was present in neurons and astrocytes. Up to day 7, Mn-SOD increased in the entire ipsilateral and contralateral cortex but remained higher elevated in the ipsilateral hippocampus and thalamus. Thereafter, Mn-SOD decreased globally but remained elevated in some cortical neurons up to day 60.

CONCLUSIONS

The early transient increase of Mn-SOD in distinct brain regions, which are functionally connected via afferents and efferents, suggests that these regions are affected by the injury. It suggests that Mn-SOD protects the cells in these regions from superoxide-induced damage and therefore may limit the retrograde and anterograde spread of neurotoxicity.

Putrescine-modified catalase with preserved enzymatic activity exhibits increased permeability at the blood-nerve and blood-brain barriers

Much evidence exists in support of the hypothesis that free radicals contribute to the pathogenesis of several neurodegenerative disorders and that mechanisms of free radical generation occur both intracellularly and extracellularly. Previous studies in this laboratory have shown that covalent modification of growth factors and antioxidant enzymes with the naturally occurring polyamine, putrescine, increases their permeability at the blood-nerve and blood-brain barriers (BNB and BBB), but does not significantly inhibit bioactivity. Furthermore, putrescine-modified superoxide dismutase (SOD) was shown to reduce neurodegeneration in a rat model of global cerebral ischemia. The purpose of the present study was to modify the antioxidant enzyme, catalase (CAT), with putrescine (PUT) at carboxylic acid groups whose ionization, and hence reactivity, was controlled with pH and investigate the effects on permeability and enzymatic activity. Modification of CAT with PUT increased its permeability 2-3-fold and preserved 67% of its enzymatic activity compared to native CAT and 137% compared to lyophilized CAT. The results of this study indicate that modification of CAT with putrescine increases its permeability while preserving enzymatic activity. PUT-SOD administered in combination with PUT-CAT may eliminate both the superoxide radical and the H2O2 produced from the dismutation of superoxide, respectively, and thus prevent the formation of hydroxyl radicals. This combination may exhibit increased neuroprotective effects, compared to native enzymes, following systemic administration for the treatment of free radical associated neurodegenerative disorders.