(-)deprenyl increases activities of superoxide dismutase and catalase in certain brain regions in old male mice

Multidrug resistance-associated protein 2 is negatively regulated by oxidative stress in rat intestine via a posttranslational mechanism. Impact on its membrane barrier function

Oxidative stress (OS) is a key factor in the development of gastrointestinal disorders, in which the intestinal barrier is altered. However, the Multidrug resistance-associated protein 2 (Mrp2) status, an essential component of the intestinal transcellular barrier exhibiting pharmaco-toxicological relevance by limiting the orally ingested toxicants and drugs absorption, has not been investigated. We here evaluated the short-term effect of OS on Mrp2 by treatment of isolated rat intestinal sacs with tert-butyl hydroperoxide (TBH) for 30 min. OS induction by TBH (250 and 500 μM) was confirmed by increased lipid peroxidation end products, decreased reduced glutathione (GSH) content and altered antioxidant enzyme activities. Under this condition, assessment of Mrp2 distribution between brush border (BBM) and intracellular (IM) membrane fractions, showed that Mrp2 protein decreased in BBM and increased in IM, consistent with an internalization process. This was associated with decreased efflux activity and, consequently, impaired barrier function. Subsequent incubation with N-Acetyl-L-Cysteine (NAC, 1 mM) reestablished GSH content and reverted concomitantly the alteration in Mrp2 localization and function induced by TBH. Cotreatment with a specific inhibitor of classic calcium-dependent Protein Kinase C (cPKC) implicated this kinase in TBH-effects. In conclusion, we demonstrated a negative posttranslational regulation of rat intestinal Mrp2 after short-term exposition to OS, a process likely mediated by cPKC and dependent on intracellular GSH content. The concomitant impairment of the Mrp2 barrier function may have implications in xenobiotic absorption and toxicity in a variety of human diseases linked to OS, with notable consequences on the toxicity/safety of therapeutic agents.

Reversion of down-regulation of intestinal multidrug resistance-associated protein 2 in fructose-fed rats by geraniol and vitamin C: Potential role of inflammatory response and oxidative stress

Intestinal multidrug resistance-associated protein 2 is an ABC transporter that limits the absorption of xenobiotics ingested orally, thus acting as essential component of the intestinal biochemical barrier. Metabolic Syndrome (MetS) is a pathological condition characterized by dyslipidemia, hyperinsulinemia, insulin resistance, chronic inflammation, and oxidative stress (OS). In a previous study we demonstrated that MetS-like conditions induced by fructose in drinking water (10% v/v, during 21 days), significantly reduced the expression and activity of intestinal Mrp2 in rats. We here evaluated the potential beneficial effect of geraniol or vitamin C supplementation, natural compounds with anti-inflammatory and anti-oxidant properties, in reverse fructose-induced Mrp2 alterations. After MetS-like conditions were induced (21 days), animals were cotreated with geraniol or vitamin C or vehicle for another 14 days. Decreased expression of Mrp2 protein and mRNA due to fructose administration was reversed by geraniol and by vitamin C, consistent with restoration of Mrp2 activity evaluated in everted intestinal sacs. Concomitantly, increased intestinal IL-1β and IL-6 levels induced by fructose were totally and partially counterbalanced, respectively, by geraniol administration. The intestinal redox unbalance generated by fructose was improved by geraniol and vitamin C, as evidenced by decreasing lipid peroxidation products and activity of Superoxide Dismutase and by normalizing glutathione reduced/oxidized glutathione ratio. The restoration effects exhibited by geraniol and vitamin C suggest that local inflammatory response and OS generated under MetS-like conditions represent important mediators of the intestinal Mrp2 down-regulation. Additionally, both agents could be considered of potential therapeutic value to preserve Mrp2 function under MetS conditions.

Intestinal multidrug resistance-associated protein 2 is down-regulated in fructose-fed rats

Expression and activity of jejunal multidrug resistance-associated protein 2 (Mrp2) and glutathione-S-transferase (GST) were examined in fructose fed Wistar rats, an experimental model of metabolic syndrome. Animals were fed on (a) control diet or (b) control diet plus 10% w/vol fructose in the drinking water. Mrp2 and the α class of GST proteins as well as their corresponding mRNAs were decreased, suggesting a transcriptional regulation by fructose. Confocal microscopy studies reaffirmed down-regulation of Mrp2. Everted intestinal sacs were incubated with 1-chloro-2,4-dinitrobenzene in the mucosal compartment, and the glutathione-conjugated derivative, dinitrophenyl- S-glutathione (DNP-SG; model Mrp2 substrate), was measured in the same compartment to estimate Mrp2 activity. Excretion of DNP-SG was substantially decreased by fructose treatment, consistent with simultaneous down-regulation of Mrp2 and GST. In addition, the effect of fructose on intestinal barrier function exerted by Mrp2 was evaluated in vivo using valsartan, a recognized Mrp2 substrate of therapeutic use. After intraduodenal administration as a bolus, intestinal absorption of valsartan was increased in fructose-drinking animals. Fructose administration also induced oxidative stress in intestinal tissue as demonstrated by significant increases of intestinal lipid peroxidation end products and activity of the antioxidant enzyme superoxide dismutase, by a decreased GSH/GSSG ratio. Moreover, fructose treatment conduced to increased intestinal levels of the proinflammatory cytokines IL-β1 and IL-6. Collectively, our results demonstrate that metabolic syndrome-like conditions, induced by a fructose-rich diet, result in down-regulation of intestinal Mrp2 expression and activity and consequently in an impairment of its barrier function.

Design Expert(®) supported optimization and predictive analysis of selegiline nanoemulsion via the olfactory region with enhanced behavioural performance in Parkinson's disease

Selegiline is a monoamine oxidase B (MAO-B) inhibitor and is used in the treatment of Parkinson's disease. The main problem associated with its oral administration is its low oral bioavailability (10%) due to its poor aqueous solubility and extensive first pass metabolism. The aim of the present research work was to develop a nanoemulsion loaded with selegiline for direct nose-to-brain delivery for the better management of Parkinson's disease. A quality by design (QbD) approach was used in a statistical multivariate method for the preparation and optimization of nanoemulsion. In this study, four independent variables were chosen, in which two were compositions and two were process variables, while droplet size, transmittance, zeta potential and drug release were selected as response variables. The optimized formulation was assessed for efficacy in Parkinson's disease using behavioural studies, namely forced swimming, locomotor, catalepsy, muscle coordination, akinesia and bradykinesia or pole test in Wistar rats. The observed droplet size, polydispersity index (PDI), refractive index, transmittance, zeta potential and viscosity of selegiline nanoemulsion were found to be 61.43 ± 4.10 nm, 0.203 ± 0.005, 1.30 ± 0.01, 99.80 ± 0.04%, -34 mV and 31.85 ± 0.24 mPas respectively. Surface characterization studies demonstrated a spherical shape of nanoemulsion which showed 3.7 times enhancement in drug permeation as compared to drug suspension. The results of behaviour studies showed that treatment of haloperidol induced Parkinson's disease in rats with selegiline nanoemulsion (administered intranasally) showed significant improvement in behavioural activities in comparison to orally administered drug. These findings demonstrate that nanoemulsion could be a promising new drug delivery carrier for intranasal delivery of selegiline in the treatment of Parkinson's disease.

The effect of R-(-)-deprenyl administration on antioxidant enzymes in rat testis

The aim of the study was to investigate the effect of R-(-)-deprenyl administration on the activity and localization of superoxide dismutases (SODs) and catalase (CAT) in rat testis. After 30 days of intraperitoneal administration of either saline (control) or R-(-)-deprenyl dissolved in saline at concentrations of 0.0025mg/kg (low dose of deprenyl, LDD) or 0.25mg/kg (high dose of deprenyl, HDD), males were killed by thiopental, and their testes were collected. We found that deprenyl administration significantly increased the activity of antioxidant enzymes, and this effect varied by dosage. LDD caused significant elevation of all monitored enzymes, but HDD did not increase the activity of SOD2. Employing immunohistochemistry, we detected enzymes predominantly in Leydig cells (SOD1, SOD2, CAT), in late spermatids and residual bodies (SOD1, SOD2), and in primary spermatocytes (SOD2). Histopathological examination did not reveal testicular damage in experimental groups compared to control. Deprenyl proved to be a potent stimulator of antioxidant enzymes in rat testes; therefore, it could be used in the therapy of male infertility. On the other hand, it is crucial to choose a proper dose, since lower dose was more competent compared to a dosage that was one hundred times higher.

Neuroprotective multifunctional iron chelators: from redox-sensitive process to novel therapeutic opportunities

Accumulating evidence suggests that many cytotoxic signals occurring in the neurodegenerative brain can initiate neuronal death processes, including oxidative stress, inflammation, and accumulation of iron at the sites of the neuronal deterioration. Neuroprotection by iron chelators has been widely recognized with respect to their ability to prevent hydroxyl radical formation in the Fenton reaction by sequestering redox-active iron. An additional neuroprotective mechanism of iron chelators is associated with their ability to upregulate or stabilize the transcriptional activator, hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha stability within the cells is under the control of a class of iron-dependent and oxygen-sensor enzymes, HIF prolyl-4-hydroxylases (PHDs) that target HIF-1alpha for degradation. Thus, an emerging novel target for neuroprotection is associated with the HIF system to promote stabilization of HIF-1alpha and increase transcription of HIF-1-related survival genes, which have been reported to be regulated in patient's brains afflicted with diverse neurodegenerative diseases. In accordance, a new potential therapeutic strategy for neurodegenerative diseases is explored, by which iron chelators would inhibit PHDs, target the HIF-1-signaling pathway and ultimately activate HIF-1-dependent neuroprotective genes. This review discusses two interrelated approaches concerning therapy targets in neurodegeneration, sharing in common the implementation of iron chelation activity: antioxidation and HIF-1-pathway activation.

Novel mechanisms of central nervous system damage in HIV infection

Human immunodeficiency virus-1 infection of the central nervous system is an early event after primary infection, resulting in motor and cognitive defects in a significant number of individuals despite successful antiretroviral therapy. The pathology of the infected brain is characterized by enhanced leukocyte infiltration, microglial activation and nodules, aberrant expression of inflammatory factors, neuronal dysregulation and loss, and blood–brain barrier disruption. Months to years following the primary infection, these central nervous system insults result in a spectrum of motor and cognitive dysfunction, ranging from mild impairment to frank dementia. The mechanisms that mediate impairment are still not fully defined. In this review we discuss the cellular and molecular mechanisms that facilitate impairment and new data that implicate intercellular communication systems, gap junctions and tunneling nanotubes, as mediators of human immunodeficiency virus-1 toxicity and infection within the central nervous system. These data suggest potential targets for novel therapeutics.

Selegiline and oxidative stress in HIV-associated cognitive impairment

OBJECTIVE

To assess the effectiveness of the selegiline transdermal system (STS) in reversing HIV-induced metabolic brain injury (as measured by proton magnetic resonance spectroscopy [MRS]) and in decreasing oxidative stress, measured by CSF protein carbonyl concentration.

METHODS

Sixty-two subjects with HIV-associated cognitive impairment were coenrolled in a 24-week placebo-controlled study (AIDS Clinical Trial Group protocol A5090) and were randomly assigned to receive STS 3 mg/24 h, STS 6 mg/24 h, or matching placebo. Cognitive performance was evaluated using the neuropsychological z score (NPZ)-8 and NPZ-6, as well as cognitive domain scores. Subjects underwent proton MRS at study entry and weeks 12 and 24. CSF protein carbonyl was measured at baseline and week 24.

RESULTS

A slight increase in N-acetyl aspartate/creatine from baseline to week 24 was found in the basal ganglia (p = 0.023) and centrum semiovale (p = 0.072) of the placebo group compared with the STS groups; however, there were no significant changes when the absolute metabolite concentrations were analyzed. The levels of choline/creatine in the midfrontal cortex were also significantly higher during the week 12 visit in the combined STS groups. This persisted to the week 24 visit (p = 0.002). Evaluation of the change in NPZ-8, NPZ-6, and cognitive domain scores from baseline to weeks 12 and 24 revealed no significant differences between treatment arms. Protein carbonyl analysis revealed no significant changes among the groups.

CONCLUSION

In this 24-week study, the selegiline transdermal system (STS) had no effect on either magnetic resonance spectroscopy (MRS) metabolites or oxidative stress, as measured by CSF protein carbonyl concentration. The lack of effect on these biomarkers is also reflected in the lack of cognitive improvement in the STS groups compared to placebo.

LEVEL OF EVIDENCE

This study provides Class II evidence that STS had no effect on either MRS metabolites or oxidative stress, as measured by CSF protein carbonyl concentration over a period of 24 weeks.

The effects of rivastigmine plus selegiline on brain acetylcholinesterase, (Na, K)-, Mg-ATPase activities, antioxidant status, and learning performance of aged rats

We investigated the effects of rivastigmine (a cholinesterase inhibitor) and selegiline ((-)deprenyl, an irreversible inhibitor of monoamineoxidase-B), alone and in combination, on brain acetylcholinesterase (AChE), (Na(+), K(+))-, Mg(2+)-ATPase activities, total antioxidant status (TAS), and learning performance, after long-term drug administration in aged male rats. The possible relationship between the biochemical and behavioral parameters was evaluated.

METHODS

Aged rats were treated (for 36 days) with rivastigmine (0.3 mg/kg rat/day ip), selegiline (0.25 mg/kg rat/day im), rivastigmine plus selegiline in the same doses and way of administration as separately. Aged and adult control groups received NaCl 0.9% 0.5 ml ip.

RESULTS

TAS was lower in aged than in adult rats, rivastigmine alone does not affect TAS, decreases AChE activity, increases (Na(+), K(+))-ATPase and Mg(2+)-ATPase activity of aged rat brain and improves cognitive performance. Selegiline alone decreases free radical production and increases AChE activity and (Na(+), K(+))-ATPase activity, improving cognitive performance as well. In the combination: rivastigmine seems to cancel selegiline action on TAS and AChE activity, while it has additive effect on (Na(+), K(+))-ATPase activity. In the case of Mg(2+)-ATPase selegiline appears to attenuate rivastigmine activity. No statistically significant difference was observed in the cognitive performance.

CONCLUSION

Reduced TAS, AChE activity and learning performance was observed in old rats. Both rivastigmine and selesiline alone improved performance, although they influenced the biochemical parameters in a different way. The combination of the two drugs did not affect learning performance.

Oxidative stress in primary culture hepatocytes isolated from partially hepatectomized rats

The aim of this study was to evaluate the influence of partial hepatectomy prior to cell isolation on hepatocytes in vitro. We characterized the possible changes of various stress oxidative parameters within the first 24 h after seeding. Male Wistar rats served as donors. Hepatocytes were isolated by collagenase digestion from either liver of simulated surgery (SH) or from liver 1 h after 70% hepatectomy (PH), and the changes in stress parameters were analyzed after 1, 3, 18, and 24 h in culture. At 24 h, only hepatocytes from PH maintained significantly increased reactive oxygen species production, oxidized glutathione percentage, and Cu/Zn superoxide dismutase and catalase activities. Our results show that hepatocytes suffer significant cell injury as a result of the isolation procedure, but primary cultured cells from SH metabolically recover from this stress after 18 h. After this time, primary culture hepatocytes primed by PH maintain their in vivo-like metabolic activities (increase in both oxidative stress and antioxidant status).

Selegiline transdermal system (STS) for HIV-associated cognitive impairment: open-label report of ACTG 5090

OBJECTIVE

To assess the long-term safety (primary aim) and efficacy (secondary aim) of the MAO-B inhibitor Selegiline Transdermal System (STS) for the treatment of HIV-associated cognitive impairment.

BACKGROUND

HIV infection is associated with increased oxidative stress. In vitro and animal studies have shown that selegiline can reduce oxidative stress levels while enhancing the synthesis of neurotrophic factors. We conducted and reported a 24-week, double-blind, placebo-controlled study with STS in HIV-infected individuals with cognitive impairment (ACTG 5090). We now report the results of the 24-week open-label follow-up.

METHOD

Subjects received either 3 mg/24 h or 6 mg/24 h STS daily. The primary efficacy endpoint was changes in the mean of z scores of six neuropsychological tests (NPZ-6). Additional outcomes included NPZ-8 and NPZ scores by cognitive domain.

RESULTS

86 subjects were enrolled. There were few severe adverse experiences (n = 13). There was no significant change in NPZ-6 score, whereas significant changes were observed in NPZ-8 score and several cognitive domains.

CONCLUSION

Long-term use of selegiline was safe and well tolerated in this HIV cohort of HIV with cognitive impairment. Cognitive improvement may be delayed in neuroprotective trials, suggesting that trials longer than 6 months may be necessary to assess the efficacy of putative neuroprotective agents.

Involvement of reactive oxygen species on the apoptotic mechanism induced by IFN-alpha2b in rat preneoplastic liver

Interferon-alpha2b (IFN-alpha2b) is an important component in the preventive treatment of patients who have severe hepatic illness such as hepatitis B or C and hepatocarcinomas. In a previous work, using a rat liver preneoplastic model, we have demonstrated that IFN-alpha2b reduces the number and volume of altered hepatic foci (AHF) inducing apoptosis through a mechanism mediated by TGF-beta(1). In this study, the implication of hepatocytes redox status of IFN-alpha2b-treated preneoplastic liver in the TGF-beta(1)-induced apoptotic death was analyzed. Results indicate that IFN-alpha2b induces hepatocytic TGF-beta(1) production and secretion by induction of reactive oxygen species (ROS) formation through the activation of a membrane bound NADPH oxidase complex. TGF-beta(1), in turn, reduces hepatocytes antioxidant defenses and induces programmed cell death. On the other hand, it was also demonstrated that treatment of rats with IFN-alpha2b plus a ROS scavenger such as ascorbic acid, abolishes the apoptotic effect of IFN-alpha2b in rat preneoplastic livers, leading to an increase of the foci volume. In conclusion, these findings strongly suggest that ROS have a fundamental role as signaling and/or regulator molecules in the IFN-alpha2b-induced apoptosis in hepatic preneoplastic cells.

Selegiline increases heme oxygenase-1 expression and the cytotoxicity produced by dopamine treatment of neuroblastoma SK-N-SH cells

Increased dopamine catabolism may be associated with oxidative stress and neuronal cell death in Parkinson's disease. The present study was carried out to examine the effect of dopamine on the expression of heme oxygenase-1 and -2 (HO-1 and HO-2) in human neuroblastomas (SK-N-SH cell line) and the effects of selegiline and antioxidants on this expression. Cells were kept with close control of pH and were incubated with varying concentrations of dopamine (0.1-100 microM) for 24 h. HO-1 and HO-2 cDNA probes were prepared by reverse transcription-polymerase chain reaction amplification. The mRNA expression of HO-1 and HO-2 was measured by Northern blot analysis. The levels of HO-1 mRNA increased after dopamine treatment, in a dose-dependent manner, in all cell lines studied, whereas levels of the two HO-2 transcripts did not. The HO-1 and HO-2 protein expression was analyzed by Western blotting. HO-1 protein was undetectable in untreated SK-N-SH cells and increased after treatment with dopamine. In contrast, the HO-2 protein (36 kDa) was detected in untreated cells and the levels did not change as a result of treatment. Alpha-tocopherol (10-100 microM) and ascorbic acid (100 microM) did not attenuate the effects of dopamine. Selegiline (10 microM) produced significant increase (P < 0.01) in the induction of HO-1 by dopamine (more than six times the control values). The increased expression of HO-1 following dopamine treatment indicates that dopamine produces oxidative stress in this cell line.

Antioxidant protection from HIV-1 gp120-induced neuroglial toxicity

Background

The pathogenesis of HIV-1 glycoprotein 120 (gp120) associated neuroglial toxicity remains unresolved, but oxidative injury has been widely implicated as a contributing factor. In previous studies, exposure of primary human central nervous system tissue cultures to gp120 led to a simplification of neuronal dendritic elements as well as astrocytic hypertrophy and hyperplasia; neuropathological features of HIV-1-associated dementia. Gp120 and proinflammatory cytokines upregulate inducible nitric oxide synthase (iNOS), an important source of nitric oxide (NO) and nitrosative stress. Because ascorbate scavenges reactive nitrogen and oxygen species, we studied the effect of ascorbate supplementation on iNOS expression as well as the neuronal and glial structural changes associated with gp120 exposure.

Methods

Human CNS cultures were derived from 16–18 week gestation post-mortem fetal brain. Cultures were incubated with 400 μM ascorbate-2-O-phosphate (Asc-p) or vehicle for 18 hours then exposed to 1 nM gp120 for 24 hours. The expression of iNOS and neuronal (MAP2) and astrocytic (GFAP) structural proteins was examined by immunohistochemistry and immunofluorescence using confocal scanning laser microscopy (CSLM).

Results

Following gp120 exposure iNOS was markedly upregulated from undetectable levels at baseline. Double label CSLM studies revealed astrocytes to be the prime source of iNOS with rare neurons expressing iNOS. This upregulation was attenuated by the preincubation with Asc-p, which raised the intracellular concentration of ascorbate. Astrocytic hypertrophy and neuronal injury caused by gp120 were also prevented by preincubation with ascorbate.

Conclusions

Ascorbate supplementation prevents the deleterious upregulation of iNOS and associated neuronal and astrocytic protein expression and structural changes caused by gp120 in human brain cell cultures.

Neuroprotective strategies in Parkinson's disease : an update on progress

In spite of the extensive studies performed on postmortem substantia nigra from Parkinson's disease patients, the aetiology of the disease has not yet been established. Nevertheless, these studies have demonstrated that, at the time of death, a cascade of events had been initiated that may contribute to the demise of the melanin-containing nigro-striatal dopamine neurons. These events include increased levels of iron and monoamine oxidase (MAO)-B activity, oxidative stress, inflammatory processes, glutamatergic excitotoxicity, nitric oxide synthesis, abnormal protein folding and aggregation, reduced expression of trophic factors, depletion of endogenous antioxidants such as reduced glutathione, and altered calcium homeostasis. To a large extent, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) animal models of Parkinson's disease confirm these findings. Furthermore, neuroprotection can be afforded in these models with iron chelators, radical scavenger antioxidants, MAO-B inhibitors, glutamate antagonists, nitric oxide synthase inhibitors, calcium channel antagonists and trophic factors. Despite the success obtained with animal models, clinical neuroprotection is much more difficult to accomplish. Although the negative studies obtained with the MAO-B inhibitor selegiline (deprenyl) and the antioxidant tocopherol (vitamin E) may have resulted from an inappropriate choice of drug (selegiline) or an inadequate dose (tocopherol), the niggling problem that still remains is why these drugs, and others, do work in animals while they fail in the clinic. One reason for this may be related to the fact that in normal human brains the number of dopaminergic neurons falls by around 3-5% every decade, while in Parkinson's disease this decline is greater. Brain autopsy studies have shown that by the time the disease is identified, some 70-75% of the dopamine-containing neurons have been lost. More sensitive reliable methods and clinical correlative markers are required to discern between confoundable symptomatic effects versus a possible neuroprotective action of drugs, namely, the ability to delay or forestall disease progression by protecting or rescuing the remaining dopamine neurons or even restoring those that have been lost.A number of other possibilities for the clinical failure of potential neuroprotectants also exist. First, the animal models of Parkinson's disease may not be totally reflective of the disease and, therefore, the chemical pathologies established in the animal models may not cause, or contribute to, the progression of the disease clinically. Second, because of the series of events occurring in neurodegeneration and our ignorance about which of these factors constitutes the primary event in the pathogenic process, a single drug may not be adequate to induce neuroprotection and, as a consequence, use of a cocktail of drugs may be more appropriate. The latter concept receives support from recent complementary DNA (cDNA) microarray gene expression studies, which show the existence of a gene cascade of events occurring in the nigrostriatal pathway of MPTP, 6-OHDA and methamphetamine animal models of Parkinson's disease. Even with the advent of powerful new tools such as genomics, proteomics, brain imaging, gene replacement therapy and knockout animal models, the desired end result of neuroprotection is still beyond our current capability.

Selegiline attenuates cardiac oxidative stress and apoptosis in heart failure: association with improvement of cardiac function

We have shown recently that selegiline exerts a cardiac neuroprotective effect in chronic heart failure. Since selegiline has an antioxidant antiapoptotic effect, we proposed to determine whether selegiline attenuates cardiac oxidative stress and myocyte apoptosis in chronic heart failure by modulating Bcl-2 and Bax protein expression, and whether the effects are associated with the improvement of cardiac function. Rabbits with rapid cardiac pacing (360 beats/min) and sham operation without pacing were randomized to receive oral selegiline (1 mg/day) or placebo for 8 weeks. Echocardiography was used to measure left ventricular fractional shortening. After 8 weeks of treatment, animals were studied for arterial norepinephrine and left ventricular systolic function (fractional shortening and dP/dt), and were then sacrificed for measuring the stable oxidative product of myocardial mitochondrial DNA (mtDNA) 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), myocyte apoptosis by monoclonal antibody to single stranded DNA, and Bcl-2 and Bax protein expression by Western blot and immunohistochemistry. Rapid cardiac pacing increased plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, reduced Bcl-2 and the Bcl-2 to Bax ratio. These changes were associated with decreased left ventricular fractional shortening and dP/dt. Selegiline treatment in chronic heart failure animals reduced plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, prevented the changes of Bcl-2 and Bcl-2 to Bax ratio, and improved left ventricular fractional shortening and dP/dt. The findings suggest that the reduction by selegiline of myocyte apoptosis is related to the decrease of cardiac oxidative stress and the modulation of apoptotic and antiapoptotic proteins. The antioxidant antiapoptotic effects of selegiline are potentially beneficial in the improvement of cardiac function in chronic heart failure.

Differential effect of dopamine catabolism and uptake inhibition on dopamine-induced calcium dysregulation and viability loss

The present study was aimed at evaluating of the effects of dopamine (DA) toxicity on PC12 cells' calcium homeostasis, cellular viability, and free radical levels. Moreover, the effect of receptor inhibition, and DA metabolism and reuptake antagonism on all parameters was also evaluated. Acute treatment with DA impaired the ability of PC12 cells to buffer excess calcium after K+-depolarization, decreased cellular viability by approximately 35%, and increased free radical levels by about 10% in a dose dependent manner. Pretreatment with both active and inactive pargyl monoamine oxidase inhibitors (MAOi) protected PC12 cells from DA toxicity on cellular viability and free radical levels, regardless of the presence or absence of their target enzymes in PC12 cells. These results suggest a lack of specific involvement of DA metabolism by MAO in dopamine's effects on cellular viability and production of free radicals. However, DA-induced dysregulation of calcium homeostasis seems to be more specifically mediated by DA metabolism by MAO. Results indicate that, in order for toxicity to occur the DA must be taken up into the cells. DA receptors do not mediate dopamine cytoxicity, and the D2 receptor plays a modest role in DA-induced calcium dysregulation and generation of free radicals. Moreover, DA-induced cell viability loss is not mediated by calcium, nor by caspase-3 enzyme, but is prevented by inhibition of mitochondrial permeability transition pores.

Oxidative stress as a mechanism for quinolinic acid-induced hippocampal damage: protection by melatonin and deprenyl

1. There are differences between the excitotoxic actions of quinolinic acid and N-methyl-D-aspartate (NMDA) which suggest that quinolinic acid may act by mechanisms additional to the activation of NMDA receptors. The present study was designed to examine the effect of a potent antioxidant, melatonin, and the potential neuroprotectant, deprenyl, as inhibitors of quinolinic acid-induced brain damage. Injections were made into the hippocampus of anaesthetized rats, which were allowed to recover before the brains were taken for histology and the counting of surviving neurones. 2. Quinolinic acid (120 nmols) induced damage to the pyramidal cell layer, which was prevented by the co-administration of melatonin (5 nmols locally plus 2x20 mg kg(-1) i.p.). This protective effect was not prevented by the melatonin receptor blocker luzindole. Neuronal damage produced by NMDA (120 nmols) was not prevented by melatonin. 3. Quinolinic acid increased the formation of lipid peroxidation products from hippocampal tissue and this effect was prevented by melatonin. 4. Deprenyl also prevented quinolinic acid-induced damage at a dose of 50 nmols but not 10 nmols plus 2x1.0 mg kg(-1) i.p. The non-selective monoamine oxidase inhibitor nialamide (10 and 50 nmols plus 2x25 mg kg(-1)) did not afford protection. 5. The results suggest that quinolinic acid-induced neuronal damage can be prevented by a receptor-independent action of melatonin and deprenyl, agents which can act as a potent free radical scavenger and can increase the activity of endogenous antioxidant enzymes respectively. This suggests that free radical formation contributes significantly to quinolinic acid-induced damage in vivo.

Chronic (-) deprenyl administration alters dendritic morphology of layer III pyramidal neurons in the prefrontal cortex of adult Bonnett monkeys

Chronic (-) deprenyl (0.2 mg/kg, b.wt; for 25 days) treatment induced alterations in the dendritic morphology of prefrontal cortical neurons in adult Bonnett monkeys were evaluated in the present study. The branching points and intersections in apical and basal dendrites were studied up to a distance of 400 and 200 micrometers, respectively, in Golgi impregnated layer III pyramidal neurons of the prefrontal cortex. Our results revealed a significant (p<0.001) increase in the number of branching points and intersections in both apical and basal dendrites in (-) deprenyl treated monkeys compared to controls. Such an enriched dendritic arborization in prefrontal cortical neurons may be responsible for the enhancement of cognitive functions in Alzheimer disease patients following (-) deprenyl treatment.

Assessing the effects of deprenyl on longevity and antioxidant defenses in different animal models

Among many pharmaceuticals that have been tested for their effects on longevities of different animal rodents, deprenyl is unique in that its effects on longevity has been tested in at least four different animal species by independent research groups and that the effect has been postulated to be due to its effect of raising such antioxidant enzyme activities as superoxide dismutase (SOD) and catalase (CAT) in selective brain regions. Thus far, in all four species of animals examined (rats, mice, hamsters, and dogs), a positive effect was demonstrated, although the extent of its effect is quite variable. Our group has examined the effect on longevities in rats and mice and on antioxidant enzymes in rats, mice, and dogs. Although in rats of both sexes, we have obtained positive effects on longevity, two studies with different doses in mice did not reveal a significantly positive effect. We have observed, however, significantly positive effects on SOD (in Cu, Zn-, and Mn-) as well as CAT (but not glutathione peroxidase) activities in the brain dopaminergic system such as in the S. nigra and striatum (but not in hippocampus) in all rats, mice, and dogs, although the effects were quite variable, depending on the doses used. In mice, however, a long-term administration (3x/w, 3 months) caused a remarkable decrease in the magnitude of activity as well as a narrowing of the effective dose range, which may explain a relatively weak effect of the drug on mouse longevity. Further, a recent study on aging beagle dogs by Ruehl et al. showed a remarkable effect on longevity, which agrees with our SOD study in dogs. Although deprenyl has been claimed to have several other effects, such as a radical scavenging effect and a neuroprotective effect, past reports on its effects on longevities and antioxidant defenses are compatible with the notion that the drug prolongs the life span of animals by reducing the oxidative damage to the brain dopaminergic system during aging. Further, our studies on F-344 rats as well as a dog study by Ruehl et al. suggest that the drug may at least partially prolong the life span of animals by enhancing immune system function and preventing tumor development in animals.

Chronic (-) deprenyl administration increases dendritic arborization in CA3 neurons of hippocampus and AChE activity in specific regions of the primate brain

The mechanism by which (-) deprenyl enhances cognitive function in Alzheimer's disease (AD) is not yet understood. (-) Deprenyl (0.2 mg/kg/day) was administered intramuscularly to adult male monkeys (n = 6) for 25 days. Control monkeys (n = 6) received physiological saline by the same route. The activity of acetylcholinesterase (AChE) in different brain regions and the dendritic arborization in CA3 pyramidal neurons of hippocampus were analysed. (-) Deprenyl-treated monkeys showed a significant increase in the AChE activity by 43% (p < 0.001) in the frontal cortex, by 39% (p < 0.025) in the motor cortex, by 66% (p < 0.001) in the hippocampus and by 26% (p < 0.05) in the striatum compared to controls. The branching points and the intersections of both apical and basal dendrites of CA3 hippocampal pyramidal neurons were also significantly increased in (-) deprenyl-treated monkeys. Enhanced AChE activity may increase dendritic arborization in the hippocampus and it may also play a role in improving cognitive functions observed in AD, following (-) deprenyl treatment.

Restoration of sympathetic noradrenergic nerve fibers in the spleen by low doses of L-deprenyl treatment in young sympathectomized and old Fischer 344 rats

It is well-established that noradrenergic (NA) nerve fibers in spleen and lymph nodes influence cell-mediated immune responses. Such responses are diminished in young animals following chemical sympathectomy and in older animals accompanying an age-related decline in NA nerve fibers in spleen and lymph nodes. The purpose of this study was to determine whether treatment with deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor, would hasten the process of splenic NA reinnervation following chemical sympathectomy in young rats and would reverse the age-related loss of sympathetic NA fibers in the spleen of old rats. To examine the effects of deprenyl in young sympathectomized rats, 3-month-old male Fischer 344 (F344) rats were treated with 6-hydroxydopamine (6-OHDA) and administered 0, 0.25, 1.0, 2.5, or 5.0 mg deprenyl/kg body weight (BW)/day intraperitoneally (i.p.) for 1, 15, or 30 days. In another study, 21-month-old male F344 rats were treated with 0, 0.25, or 1.0 mg deprenyl/kg BW/day i.p. for 9 weeks. At the end of the treatment period, spleens were removed and NA innervation was assessed by fluorescence histochemistry, immunocytochemistry, and quantitation of norepinephrine (NE) by high performance liquid chromatography with electrochemical detection (HPLC-EC). In the spleens of young sympathectomized rats, there was faint fluorescence or absence of fluorescence and tyrosine hydroxylase-positive (TH+) fibers around the central arteriole and in the periarteriolar lymphatic sheath of the white pulp one day after administration of 6-OHDA, indicating a severe loss of NA innervation compared with unlesioned control animals. Treatment of sympathectomized rats with 1.0 mg, 2.5 mg, and 5.0 mg/kg deprenyl for 30 days increased the density of NA innervation estimated by both fluorescence histochemistry and immunocytochemistry compared with vehicle-treated controls recovering spontaneously from 6-OHDA. Splenic NE concentration was increased in the hilar region of sympathectomized rats treated with 2.5 mg and 1.0 mg/kg deprenyl after 15 and 30 days, respectively, compared with untreated and vehicle-treated sympathectomized rats. The spleens of untreated and saline-treated old rats showed a reduction in the density of NA innervation in the white pulp compared with young animals. Treatment of old rats for 9 weeks with 1.0 mg/kg deprenyl induced moderate to intense fluorescent fibers and linear TH+ nerve fibers around the central arteriole and in other compartments of the white pulp, and increased splenic NE concentration in the hilar region and NE content in the whole spleen. Taken together, these results provide strong evidence for a neurorestorative property of deprenyl on sympathetic NA innervation of the spleen, which may lead to an improvement in cell-mediated immune responses.

(-)-Deprenyl attenuates spinal motor neuron degeneration and associated locomotor deficits in rats subjected to spinal cord ischemia

We have evaluated potential neuroprotection offered by (-)-deprenyl on degenerating motor neurons of the spinal cord when subjected to transient ischemia. Thirty-six healthy adult male Wistar rats were trained for a motor function test in a staircase maze and randomly but equally (n = 6) grouped into normal control, sham control, ischemia (IS), IS rats treated with vehicle (IV), and rats treated with low (0.1 mg/kg) and high (1.0 mg/kg) doses of (-)-deprenyl. (-)-Deprenyl was given intraperitoneally 30 min after the induction of ischemia and thereafter everyday for 14 days. Spinal cord ischemia was produced at the lumbar level in conscious rats by occluding the abdominal aorta just below the branching point of the left renal artery for 30 min. Analysis of the motor performance in all groups of rats revealed a significant (P < 0.001) increase in the time taken to cross the run way of the maze, in i.s. and i.v. rats compared to all other groups of rats. In addition, qualitative and quantitative examination of spinal motor neurons at the lumbar level showed a significant (P < 0.001) decrease in the number of healthy motor neurons in i.s. and i.v. rats compared to controls. Postischemic administration of (-)-deprenyl, at both doses, significantly prevented motor neuron degeneration and the associated locomotor deficits in IS rats.

Chronic effect of insulin on monoamine oxidase and antioxidant enzyme activities in the rat brainstem

It was shown that hydrogen peroxide (H2O2) is a possible intracellular second messenger in specific insulin action. Because its concentration in the cell depends on the activity of both antioxidant enzymes and monoamine oxidase (MAO), we studied the influence of different insulin doses (0.4 and 4.0 IU/kg body mass, i.p., daily injected over 3 days) on the activity of MAO, types A and B, copper zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), and catalase in the rat brainstem. Chronic insulin treatment significantly increased Vmax of MAO-A and B activities (P < 0.05, P < 0.025, respectively) independent of the dose applied. CuZnSOD activity was also increased (P < 0.025), but only when higher dose of hormone was injected. However, insulin had the opposite effect on MnSOD and catalase causing a decrease in their activities (P < 0.005). The observed changes in the activities of the enzymes studied are possible compensations that potentially maintain an optimal H2O2 level in the brainstem, which might be important for insulin action.

Long term treatment with (-)deprenyl reduces the optimal dose as well as the effective dose range for increasing antioxidant enzyme activities in old mouse brain

C57BL mice of the male sex received different doses of (-)deprenyl (0.25, 0.5, 1.0 mg/kg per injection 3 times a week, s.c.) for 3 months beginning at the age of 26 months. At the age of 29 months, animals were sacrificed and superoxide dismutase (SOD) and catalase (CAT) activities were examined in several brain regions. The dose of 0.5 mg/kg (3 times a week) was most effective in increasing SOD and CAT activities in S. nigra, striatum and cerebral cortex but not in hippocampus or cerebellum. The dose of 0.25 mg/kg was also effective in increasing enzyme activities, but the effect was much lower than the dose of 0.5 mg/kg. The magnitudes of increase in enzyme activities with the dose of 0.5 mg/kg, however, were generally much lower than respective values we previously found in animals treated with (-)deprenyl for only 3 weeks. The highest dose of 1.0 mg/kg had negligible effect. Enzyme activities in all groups of animals that were examined 2 weeks after the last (-)deprenyl dose were practically the same as respective control values. Together with the results from our previous study with short term (-)deprenyl treatment in old mice, these results replicate our previous findings in old female rats. We showed that longer term treatment with (-)deprenyl reduces the optimal dose for increasing antioxidant enzyme activities by a factor of 5 to 10. The present study further indicates that longer term treatment with (-)deprenyl also reduces the effective dose range of (-)deprenyl as well as the magnitude of increase of enzyme activities. If the effect of (-)deprenyl for increasing these antioxidant enzyme activities in selective brain regions is causally related to its effect of increasing average life expectancies of animals, the selection of a proper dose of the drug may be a critical factor for life span studies in which the drug, is administered for more than one year.

(-)-Deprenyl reduces neuronal apoptosis and facilitates neuronal outgrowth by altering protein synthesis without inhibiting monoamine oxidase

(-)-Deprenyl stereospecifically reduces neuronal death even after neurons have sustained seemingly lethal damage at concentrations too small to cause monoamine oxidase-B (MAO-B) inhibition. (-)-Deprenyl can also influence the process growth of some glial and neuronal populations and can reduce the concentrations of oxidative radicals in damaged cells at concentrations too small to inhibit MAO. In accord with the earlier work of others, we showed that (-)-deprenyl alters the expression of a number mRNAs or proteins in nerve and glial cells and that the alterations in gene expression/protein synthesis are the result of a selective action on transcription. The alterations in gene expression/protein synthesis are accompanied by a decrease in DNA fragmentation characteristic of apoptosis and the death of responsive cells. The onco-proteins Bcl-2 and Bax and the scavenger proteins Cu/Zn superoxide dismutase (SOD1) and Mn superoxide dismutase (SOD2) are among the 40-50 proteins whose synthesis is altered by (-)-deprenyl. Since mitochondrial ATP production depends on mitochondrial membrane potential (MMP) and mitochondrial failure has been shown to be one of the earliest events in apoptosis, we used confocal laser imaging techniques in living cells to show that the transcriptional changes induced by (-)-deprenyl are accompanied by a maintenance of mitochondrial membrane potential, a decrease in intramitochondrial calcium and a decrease in cytoplasmic oxidative radical levels. We therefore propose that (-)-deprenyl acts on gene expression to maintain mitochondrial function and to decrease cytoplasmic oxidative radical levels and thereby to reduce apoptosis. An understanding of the molecular steps by which (-)-deprenyl selectively alters transcription may contribute to the development of new therapies for neurodegenerative diseases.

Neuronal protective and rescue effects of deprenyl against MPP+ dopaminergic toxicity

Intranigral infusion of 1-Methyl-4-phenylpyridinium ion (MPP+, 2.1-16.8 nmol) dose-dependently injured nigral neurons as reflected by reduced dopamine levels in the ipsilateral striatum four days after the infusion of this toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Coadministration of deprenyl (4.2 nmol) with MPP+ into the substantia nigra protected against MPP(+)-induced moderate (20-50%) but not severe (over 70%) nigral injury as reflected in striatal dopamine reductions. However, supplementary treatment with deprenyl (0.25 mg/kg, s.c., twice daily for 4 days) after intranigral infusion of MPP+ significantly rescued nigral neurons from more severe damage caused by a higher MPP+ does (8.4 nmol) manifested by a lesser striatal dopamine decrease (-31%) compared to the non-deprenyl treated group (-70%). Thus, in addition to the blockade of bioactivation of MPTP, deprenyl can protect and/or rescue nigral neurons from MPP(+)-induced dopaminergic neurotoxicity. These in vivo data add further evidence to suggest that deprenyl, a putative and clinically unproven neuroprotective agent, may be of value in slowing the progressive nigral degeneration in "early" Parkinson's disease, but may prove to be less so in its terminal stages.