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

Polyamine-Conjugated Nitroxides Are Efficacious Inhibitors of Oxidative Reactions Catalyzed by Endothelial-Localized Myeloperoxidase

The heme enzyme myeloperoxidase (MPO) is a key mediator of endothelial dysfunction and a therapeutic target in cardiovascular disease. During inflammation, MPO released by circulating leukocytes is internalized by endothelial cells and transcytosed into the subendothelial extracellular matrix of diseased vessels. At this site, MPO mediates endothelial dysfunction by catalytically consuming nitric oxide (NO) and producing reactive oxidants, hypochlorous acid (HOCl) and the nitrogen dioxide radical (^•NO₂). Accordingly, there is interest in developing MPO inhibitors that effectively target endothelial-localized MPO. Here we studied a series of piperidine nitroxides conjugated to polyamine moieties as novel endothelial-targeted MPO inhibitors. Electron paramagnetic resonance analysis of cell lysates showed that polyamine conjugated nitroxides were efficiently internalized into endothelial cells in a heparan sulfate dependent manner. Nitroxides effectively inhibited the consumption of MPO's substrate hydrogen peroxide (H₂O₂) and formation of HOCl catalyzed by endothelial-localized MPO, with their efficacy dependent on both nitroxide and conjugated-polyamine structure. Nitroxides also differentially inhibited protein nitration catalyzed by both purified and endothelial-localized MPO, which was dependent on ^•NO₂ scavenging rather than MPO inhibition. Finally, nitroxides uniformly inhibited the catalytic consumption of NO by MPO in human plasma. These studies show for the first time that nitroxides effectively inhibit local oxidative reactions catalyzed by endothelial-localized MPO. Novel polyamine-conjugated nitroxides, ethylenediamine-TEMPO and putrescine-TEMPO, emerged as efficacious nitroxides uniquely exhibiting high endothelial cell uptake and efficient inhibition of MPO-catalyzed HOCl production, protein nitration, and NO oxidation. Polyamine-conjugated nitroxides represent a versatile class of antioxidant drugs capable of targeting endothelial-localized MPO during vascular inflammation.

Exogenous spermidine elevating cadmium tolerance in Salix matsudana involves cadmium detoxification and antioxidant defense

In this study, exogenous spermidine role on Salix matsudana tolerance to cadmium was evaluated. Spermidine and cadmium presented antagonistic effects on the biomass, copper and zinc concentrations in S. matsudana. cadmium mainly distributed in the cell wall of subcellular fraction; 46.97%-60.43% of cadmium existed in a sodium chloride-extracted form. Cadmium contents in roots, leaves, and twigs ranged from 2002.67 to 3961.00, 111.59 to 229.72, and 102.56 to 221.27 mg/kg, respectively. Spermidine application elevated cadmium concentrations in the roots, cuttings, and cell wall and the ratio of deionized water-extracted cadmium, but decreased cadmium levels in the twigs and leaves and the fractions of cadmium extracted by ethanol and sodium chloride, respectively. Putrescine and malondialdehyde were important indicators of cadmium-induced oxidative damage. Exogenous spermidine alleviated the accumulation of superoxide anion, hydrogen peroxide, malondialdehyde via promoting the levels of spermidine, soluble protein, superoxide dismutase, reductive ascorbate, glutathione reductase, and glutathione peroxidase in S. matsudana leaves under the corresponding cadmium stress. The results indicated that S. matsudana was a candidate for cadmium rhizoremediation and extraction in leaves; the spermidine application enhanced the cadmium tolerance of S. matsudana through promoting cadmium accumulation in roots, cell wall, and less bioactive chemical forms and the antioxidative ability.

Nutritional and exercise-based interventions in the treatment of amyotrophic lateral sclerosis

BACKGROUND & AIMS

Disease pathogenesis in amyotrophic lateral sclerosis (ALS) involves a number of interconnected mechanisms all resulting in the rapid deterioration of motor neurons. The main mechanisms include enhanced free radical production, protein misfolding, aberrant protein aggregation, excitotoxicity, mitochondrial dysfunction, neuroinflammation and apoptosis. The aim of this review is to assess the efficacy of using nutrition- and exercise-related interventions to improve disease outcomes in ALS.

METHODS

Studies involving nutrition or exercise in human and animal models of ALS were reviewed.

RESULTS

Treatments conducted in animal models of ALS have not consistently translated into beneficial results in clinical trials due to poor design, lack of power and short study duration, as well as differences in the genetic backgrounds, treatment dosages and disease pathology between animals and humans. However, vitamin E, folic acid, alpha lipoic acid, lyophilized red wine, coenzyme Q10, epigallocatechin gallate, Ginkgo biloba, melatonin, Cu chelators, and regular low and moderate intensity exercise, as well as treatments with catalase and l-carnitine, hold promise to mitigating the effects of ALS, whereas caloric restriction, malnutrition and high-intensity exercise are contraindicated in this disease model.

CONCLUSIONS

Improved nutritional status is of utmost importance in mitigating the detrimental effects of ALS.

Effect of nitric oxide and putrescine on antioxidative responses under NaCl stress in chickpea plants

Chickpea plants were subjected to salt stress for 48 h with 100 mM NaCl, after 50 days of growth. Other batches of plants were simultaneously treated with 0.2 mM sodium nitroprusside (NO donor) or 0.5 mM putrescine (polyamine) to examine their antioxidant effects. Sodium chloride stress adversely affected the relative water content (RWC), electrolyte leakage and lipid peroxidation in leaves. Sodium nitroprusside and putrescine could completely ameliorate the toxic effects of salt stress on electrolyte leakage and lipid peroxidation and partially on RWC. No significant decline in chlorophyll content under salt stress as well as with other treatments was observed. Sodium chloride stress activated the antioxidant defense system by increasing the activities of peroxidase (POX), catalase (CAT) superoxide dismutase (SOD) and ascorbate peroxidase (APX). However no significant effect was observed on glutathione reductase (GR) and dehydro ascorbate reductase (DHAR) activities. Both putrescine and NO had a positive effect on antioxidant enzymes under salt stress. Putrescine was more effective in scavenging superoxide radical as it increased the SOD activity under salt stress whereas nitric oxide was effective in hydrolyzing H2O2 by increasing the activities of CAT, POX and APX under salt stress.

Covalent modifications of antitetanus F(ab')2 fragments with natural and synthetic polyamines and their effects on the antibody endocytosis in cultured HL60 cells

For antibody therapeutics to succeed when intracellular target molecules are involved, a strategy must be applied to increase the delivery of antibodies into cells to reach their targets. Antibody cationization by chemical conjugation of a polyamine could be one such strategy. Both natural polyamines with increasing net charge valencies (putrescine, PUT; spermidine, SPD; and spermine, SPM) and a synthetic polyamine (hexamethylenediamine, HMD) can be used to cationize antibodies, but no comparison of the respective effects of these polyamines on intracellular delivery of antibodies has been performed yet. This study describes the covalent modification of antitetanus F(ab') 2 with these four polyamines using different reaction conditions, and compares the effects of these modifications on antibody interaction with cultured HL60 cells. The cationized antibodies retained > or =80% of the binding activity of the unmodified F(ab') 2 with regard to tetanus toxin, as measured by an antigen-binding capture enzyme immunoassay. This same method was used to quantify the amount of cell-associated F(ab') 2 following incubation with HL60 cells. Cationization was shown to enhance cell interaction of the F(ab') 2 : the higher the number of coupled polyamine molecules, the greater the amount of antibody associated with the cells. Moreover, coupling the F(ab') 2 to the SPD and SPM polyamines had greater effect on cell interaction than coupling the F(ab') 2 to the PUT and HMD diamines. Internalization of the cationized antibodies by the HL60 cells was demonstrated by confocal microscopy. This technique also showed that SPD and SPM were more effective than PUT and HMD in terms of intracellular delivery of the F(ab') 2 . It follows from all these results that electrostatic interaction involving charge density plays a predominant role in the endocytic transport mechanism of the F(ab') 2 modified with these polyamines. However, coupling the F(ab') 2 to SPM and SPD yielded the same maximum effects in terms of cell interaction, although coupling SPM was expected to increase the antibody net charge valency more than coupling SPD. This finding suggests that the effective global charge for the cell interaction and uptake of polyamine-modified antibodies does not simply correspond to the addition of the ionizable amine functions on the coupled polyamines, and that other factors may come into play.

In vivo targeting of antibody fragments to the nervous system for Alzheimer’s disease immunotherapy and molecular imaging of amyloid plaques

Targeting therapeutic or diagnostic proteins to the nervous system is limited by the presence of the blood-brain barrier. We report that a F(ab')(2) fragment of a monoclonal antibody against fibrillar human Abeta42 that is polyamine (p)-modified has increased permeability at the blood-brain barrier, comparable binding to the antigen, and comparable in vitro binding to amyloid plaques in Alzheimer's disease (AD) transgenic mouse brain sections. Intravenous injection of the pF(ab')(2)4.1 in the AD transgenic mouse demonstrated efficient targeting to amyloid plaques throughout the brain, whereas the unmodified fragment did not. Removal of the Fc portion of this antibody derivative will minimize the inflammatory response and cerebral hemorrhaging associated with passive immunization and provide increased therapeutic potential for treating AD. Coupling contrast agents/radioisotopes might facilitate the molecular imaging of amyloid plaques with magnetic resonance imaging/positron emission tomography. The efficient delivery of immunoglobulin G fragments may also have important applications to other neurodegenerative disorders or for the generalized targeting of nervous system antigens.

Design and chemical synthesis of a magnetic resonance contrast agent with enhanced in vitro binding, high blood-brain barrier permeability, and in vivo targeting to Alzheimer's disease amyloid plaques

Molecular imaging is an important new direction in medical diagnosis; however, its success is dependent upon molecular probes that demonstrate selective tissue targeting. We report the design and chemical synthesis of a derivative of human amyloid-beta (Abeta) peptide that is capable of selectively targeting individual amyloid plaques in the brain of Alzheimer's disease transgenic mice after being intravenously injected. This derivative is based on the sequence of the first 30 amino acid residues of Abeta with asparagyl/glutamyl-4-aminobutane residues (N-4ab/Q-4ab) substituted at unique Asp and Glu positions and with Gd-DTPA-aminohexanoic acid covalently attached at the N-terminal Asp. The Gd[N-4ab/Q-4ab]Abeta30 peptide was homogeneous as shown by high-resolution analytical techniques with a mass of +/-4385 Da determined by electrospray ionization mass spectrometry. This diamine- and gadolinium-substituted derivative of Abeta is shown to have enhanced in vitro binding to Alzheimer's disease (AD) amyloid plaques and increased in vivo permeability at the blood-brain barrier because of the unique Asp/Glu substitutions. In addition, specific in vivo targeting to AD amyloid plaques is demonstrated throughout the brain of an APP, PS1 transgenic mouse after intravenous injection. Because of the magnetic resonance (MR) imaging contrast enhancement provided by gadolinium, this derivative should enable the in vivo MR imaging of individual amyloid plaques in the brains of AD animals or patients to allow for early diagnosis and also provide a direct measure of the efficacy of anti-amyloid therapies currently being developed.

Molecular targeting of Alzheimer's amyloid plaques for contrast-enhanced magnetic resonance imaging

Smart molecular probes for both diagnostic and therapeutic purposes are expected to provide significant advances in clinical medicine and biomedical research. We describe such a probe that targets beta-amyloid plaques of Alzheimer's disease and is detectable by magnetic resonance imaging (MRI) because of contrast imparted by gadolinium labeling. Three properties essential for contrast enhancement of beta-amyloid plaques on MRI exist in this smart molecular probe, putrescine-gadolinium-amyloid-beta peptide: (1) transport across the blood-brain barrier following intravenous injection conferred by the polyamine moiety, (2) binding to plaques with molecular specificity by putrescine-amyloid-beta, and (3) magnetic resonance imaging contrast by gadolinium. MRI was performed on ex vivo tissue specimens at 7 T at a spatial resolution approximating plaque size (62.5 microm(3)), in order to prove the concept that the probe, when administered intravenously, can selectively enhance plaques. The plaque-to-background tissue contrast-to-noise ratio, which was precisely correlated with histologically stained plaques, was enhanced more than nine-fold in regions of cortex and hippocampus following intravenous administration of this probe in AD transgenic mice. Continuing engineering efforts to improve spatial resolution are underway in MRI, which may enable in vivo imaging at the resolution of individual plaques with this or similar contrast probes. This could enable early diagnosis and also provide a direct measure of the efficacy of anti-amyloid therapies currently being developed.

Targeting alzheimer amyloid plaques in vivo

The only definitive diagnosis for Alzheimer disease (AD) at present is postmortem observation of neuritic plaques and neurofibrillary tangles in brain sections. Radiolabeled amyloid-beta peptide (Abeta), which has been shown to label neuritic plaques in vitro, therefore could provide a diagnostic tool if it also labels neuritic plaques in vivo following intravenous injection. In this study, we show that the permeability of Abeta at the blood-brain barrier can be increased by at least twofold through covalent modification with the naturally occurring polyamine, putrescine. We also show that, following intravenous injection, radiolabeled, putrescine-modified Abeta labels amyloid deposits in vivo in a transgenic mouse model of AD, as well as in vitro in human AD brain sections. This technology, when applied to humans, may be used to detect plaques in vivo, allowing early diagnosis of the disease and therapeutic intervention before cognitive decline occurs.

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.

Hepatocyte-specific distribution of catalase and its inhibitory effect on hepatic ischemia/reperfusion injury in mice

To explore the possibility of using catalase for the treatment of reactive oxygen species (ROS)-mediated injuries, the pharmacokinetics of bovine liver catalase (CAT) labeled with 111In was investigated in mice. At a dose of 0.1 mg/kg, more than 70% of 111In-CAT was recovered in the liver within 10 min after intravenous injection. In addition, 111In-CAT was predominantly recovered from the parenchymal cells (PC) in the liver. Increasing the dose retarded the hepatic uptake of 111In-CAT, suggesting saturation of the uptake process. This cell-specific uptake could not be inhibited by coadministration of various compounds which are known to be taken up by liver PC, indicating that the uptake mechanism of CAT by PC is very specific to this compound. The preventive effect of CAT on a hepatic ischemia/reperfusion injury was examined in mice by measuring the GOT and GPT levels in plasma. A bolus injection of CAT at 5 min prior to the reperfusion attenuated the increase in the levels of these indicators in a dose-dependent manner. These results suggest that catalase can be used for various hepatic injuries caused by ROS.

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.