Disturbance of energy and redox homeostasis and reduction of Na+,K+-ATPase activity provoked by in vivo intracerebral administration of ethylmalonic acid to young rats.

Ethylmalonic acid (EMA) accumulation occurs in various metabolic diseases with neurological manifestation, including short acyl-CoA dehydrogenase deficiency (SCADD) and ethylmalonic encephalopathy (EE). Since pathophysiological mechanisms responsible for brain damage in these disorders are still poorly understood, we investigated the ex vivo effects of acute intrastriatal administration of EMA on important parameters of energy and redox homeostasis in striatum from young rats. We evaluated CO(2) production from glucose, glucose utilization and lactate production, as well as the activities of the citric acid cycle (CAC) enzymes, the electron transfer chain (ETC) complexes II-IV (oxidative phosphorylation, OXPHOS) and synaptic Na(+),K(+)-ATPase. We also tested the effect of EMA on malondialdehyde (MDA) levels (marker of lipid oxidation) and reduced glutathione (GSH) levels. EMA significantly reduced CO(2) production, increased glucose utilization and lactate production, and reduced the activities of citrate synthase and of complexes II and II-III of the ETC, suggesting an impairment of CAC and OXPHOS. EMA injection also reduced Na(+),K(+)-ATPase activity and GSH concentrations, whereas MDA levels were increased. Furthermore, EMA-induced diminution of Na(+),K(+)-ATPase activity and reduction of GSH levels were prevented, respectively, by the antioxidants melatonin and N-acetylcysteine, indicating that reactive species were involved in these effects. Considering the importance of CAC and ETC for energy production and Na(+),K(+)-ATPase for the maintenance of the cell membrane potential, the present data indicate that EMA compromises mitochondrial homeostasis and neurotransmission in striatum. We presume that these pathomechanisms may be involved to a certain extent in the neurological damage found in patients affected by SCADD and EE.

Characterisation of liver-specific distribution of a novel 1-benzyl-4-aminoindole-based thyroid hormone receptor ß agonist, SKL-13784: comparison with GC-1.

1. SKL-13784, a novel series of 1-benzyl-4-aminoindole-based thyroid hormone receptor ß (TRß)-selective agonists, showed higher liver selectivity than GC-1 and was poorly distributed in the heart and brain. We aimed to clarify the mechanism of liver selectivity of SKL-13784 through a comparative study with GC-1. 2. Media-loss assays using fresh rat hepatocytes showed that the Oatp family may have been involved in liver uptake for both compounds and that SKL-13784 was more efficiently taken up than GC-1. 3. In addition, the media-loss assay results showed that hepatic uptake was important in eliminating both compounds in rats. 4. The low passive permeability of SKL-13784 on the parallel artificial membrane permeability assay (PAMPA) contributed to the limited distribution of SKL-13784 into extrahepatocytes. 5. Biliary extraction was a major route of SKL-13784 and GC-1 disposition. SKL-13784 was excreted into bile unchanged and in its glucuronide form, whereas almost all GC-1 in bile was in its glucuronide form. In bile duct-cannulated rats, a 4.3-fold decrease in t1/2 of SKL-13784 was observed, implicating enterohepatic biliary recirculation. 6. The selective distribution of SKL-13784 in the liver was largely due to efficient uptake via hepatic transporters.

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, ameliorates lipid metabolism and attenuates atherosclerosis in hyperlipidemic animal models.

JTT-130 was developed as an intestine-specific MTP inhibitor designed to rapidly catabolize after absorption to avoid causing hepatotoxicity due to hepatic MTP inhibition. In previous reports, we have demonstrated that JTT-130 suppresses dietary lipid absorption in the small intestine without inducing hepatic steatosis. Thus, in this report, JTT-130 was administered to hyperlipidemic animals fed a Western diet to investigate the effect of intestinal MTP inhibition on lipid metabolism and progression of atherosclerosis. JTT-130 potently lowered plasma non-high density lipoprotein-cholesterol, and elevated plasma high density lipoprotein-cholesterol (HDL-C), indicating improvement in atherogenic index in hamsters. HDL fractions obtained after two weeks treatment with JTT-130 significantly increased the efflux of cholesterol from macrophages, as an index parameter of HDL function. Furthermore, long-term treatment with JTT-130 also improved the plasma lipid profile without inducing hepatic steatosis in rabbits, resulting in the suppression of atherosclerosis formation in aortas. From these results, JTT-130 ameliorates lipid metabolism accompanied with the enhancement of the anti-atherosclerotic function of HDL, and attenuates the progression of atherosclerosis in hyperlipidemic animals. These findings indicate that intestinal MTP inhibition may be atherogenic in vivo and that JTT-130 may be a useful compound for the treatment of dyslipidemia and a potential anti-atherogenic drug.

Biochemical modulation of cell energy by 2-deoxyglucose and malonate in 7,12-dimethylbenz(a)anthracene-induced carcinogenesis in rats.

The goal of this study was to explore the impact of 2-deoxglucose or malonate individually or in combination on the level of cell energy (adenosine-5'-triphosphate) and oxidative stress in 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary proliferation in rats. A total of 60 adult female Sprague Dawley rats were randomly divided into five groups (12 rats each): group I serves as the control group. Rats in groups (II-V) were administrated intragastrically a single dose of 50 mg/kg body weight (bw) of DMBA. A day after DMBA administration, rats in group III were injected intraperitoneally (ip) with 100 mg 2-deoxyglucose (2-DG)/kg bw daily. Rats in group IV were injected ip with 10 mg sodium malonate/kg bw daily. Rats in group V were injected ip with 100 mg 2-DG/kg bw and 10 mg sodium malonate/kg bw (treatment for 90 days). The results obtained showed that DMBA induced oxidative stress by decreasing the activities of glutathione reductase (GRase) and superoxide dismutase (SOD), glutathione peroxidase (GPx) and elevating the levels of malondialdehyde (MDA) and nitric oxide (NO) in mammary tissues when compared with control. The combined treatment protected against the previous deleterious changes by a significant elevation in the activities of GRase and SOD, GPx and lowering the levels of MDA and NO more potentially when compared with individual treatment. Apoptosis, as indicated by a significant release of cytochrome c from mitochondria into the cytosol, observed in DMBA-injected rats was positively significantly correlated with the elevation of the level of NO. These data explained the possible additive effect of 2-DG and malonate by depleting the cell energy by their protective effects against the earlier stages of carcinogenesis.

Discovery of novel pyrimidine and malonamide derivatives as TGR5 agonists.

Takeda G-protein-coupled receptor 5 (TGR5) is a promising molecular target for metabolic diseases. A series of 4-(2,5-dichlorophenoxy)pyrimidine and cyclopropylmalonamide derivatives were synthesized as potent agonists of TGR5 based on a bioisosteric replacement strategy. Several compounds exhibited improved potency, compared to a reference compound with a pyridine scaffold. The pharmacokinetic profile of the representative compound 18 was considered moderate.

Chemosensitivity of resistant colon cancer cell lines to lobaplatin, heptaplatin, and dicycloplatin.

PURPOSE: Lobaplatin, heptaplatin, and dicycloplatin are three new platinum drugs. The aim of this study is to investigate the chemosensitivity of resistant colon cancer cell lines to these three drugs. METHODS: Eight resistant colon cancer cell lines (four oxaliplatin-resistant colon cancer cell lines and four irinotecan-resistant colon cancer cell lines) were cultured in 96-well plates. Lobaplatin, heptaplatin, and dicycloplatin were added in various concentrations. IC50 was determined by MTT assay and the results were confirmed by CCK-8 assay. A cell death detection ELISA assay was performed to quantitate the apoptotic index by detecting the histone-associated DNA fragments generated by the apoptotic cells. RESULTS: Lobaplatin and heptaplatin had an inhibiting effect in all resistant cell lines, dicycloplatin demonstrate only weak antitumor activity in vitro. CONCLUSIONS: We confirmed the efficacy of two platinum drugs to oxaliplatin/ irinotecan-resistant colon cancer cell lines, suggesting these two drugs could be considered for improving the control of recurrent colon cancer following initial therapy with oxaliplatin and irinotecan.

A Reproducible New Model of Focal Ischemic Injury in the Marmoset Monkey: MRI and Behavioural Follow-Up.

Ischemic stroke mostly affects the primary motor cortex and descending motor fibres, with consequent motor impairment. Pre-clinical models of stroke with reproducible and long-lasting sensorimotor deficits in higher-order animals are lacking. We describe a new method to induce focal brain damage targeting the motor cortex to study damage to the descending motor tracts in the non-human primate. Stereotaxic injection of malonate into the primary motor cortex produced a focal lesion in middle-aged marmosets (Callithrix jacchus). Assessment of sensorimotor function using a neurological scale and testing of forelimb dexterity and strength lasted a minimum of 12 weeks. Lesion evolution was followed by magnetic resonance imaging (MRI) at 24 h, 1 week, 4 and 12 weeks post-injury and before sacrifice for immunohistochemistry. Our model produced consistent lesions of the motor cortex, subcortical white matter and caudate nucleus. All animals displayed partial spontaneous recovery with long lasting motor deficits of force (54% loss) and dexterity (≈ 70% loss). Clearly visible T2 hypointensity in the white matter was observed with MRI and corresponded to areas of chronic gliosis in the internal capsule and lenticular fasciculus. We describe a straightforward procedure to reproducibly injure the motor cortex in the marmoset monkey, causing long-lasting motor deficits. The MRI signature reflects Wallerian degeneration and remote injury of corticospinal and corticopontine tracts, as well as subcortical motor loops. Our model may be suitable for the testing of therapies for post-stroke recovery, particularly in the chronic phase.

Treating photodamage of the décolletage area with a novel copper zinc malonate complex plus hydroquinone and tretinoin.

There has been a proliferation of treatments for facial rejuvenation but, curiously, the use of such treatments on other areas of the body has not been widely investigated. The clinical effects of treating photodamaged skin of the neck and anterior chest area (décolletage) with a proprietary copper zinc malonate lotion and a proprietary 4% hydroquinone cream (twice daily), plus tretinoin cream (once daily), were evaluated in 42 females in a 24-week investigator-blind randomized study. Treatment was associated with early and significant (P< or =0.05) improvements in mean scores on an overall integrated assessment of photodamage (from week 4 onward) and for multiple signs of photodamage--tactile roughness (from week 2 onward); mottled hyperpigmentation, lentigines and fine wrinkling (from week 4 onward); laxity (from week 8 onward); and crepiness and coarse wrinkling (from week 12 onward). Treatment was generally well tolerated and 94% of subjects were satisfied or very satisfied with the overall improvement in their décolletage at week 24.

Extracellular matrix in cutaneous ageing: the effects of 0.1% copper-zinc malonate-containing cream on elastin biosynthesis.

Cutaneous ageing, as visualized at the exposed areas of skin, reflects dramatic alterations in the structure and function of the extracellular matrix of connective tissues. Among them, the elastic fibre network, which is responsible for the physiological elasticity and resilience of normal skin, undergoes degradative changes leading to loss of functional elastic fibres. A potential strategy to counteract these degenerative changes entails topical application of a compound that may lead to regeneration of the elastic fibre network. In this study, we have evaluated the effects of a bi-metal, 0.1% copper-zinc malonate-containing cream that has been shown to efface wrinkles in clinical trials. An effect on elastin biosynthesis and elastic tissue accumulation in skin biopsies was observed in 21 female patients with photoaged facial skin, as measured at baseline and at 6 weeks of treatment. Histopathological evaluation revealed evidence of elastic fibre regeneration, including those extending perpendicularly towards the dermo-epidermal junction within the papillary dermis. Elastin biosynthesis, measured by semi-quantitative immunofluorescence with an antibody recognizing only the newly synthesized, uncrosslinked tropoelastin molecules, suggested statistically significant enhancement of elastin biosynthesis by the bi-metal compound when applied twice daily. Accumulation of elastic fibres was confirmed by assay of desmosine, an elastin-specific crosslink compound. These results suggest that the bi-metal, 0.1% copper-zinc malonate-containing cream has the propensity to increase elastin synthesis in human skin in vivo, and that regeneration of elastic fibres may contribute to wrinkle effacement in female patients with photoaged facial skin.

Biocompatible poly(methylidene malonate)-made materials for pharmaceutical and biomedical applications.

In the past 20 years, mainly with the sponsorship of Laboratoires UPSA (France) and, afterwards, its spin-off company Virsol (France), several authors have studied methylidene malonate-based polymers used in drug delivery approaches and in the development of novel biomaterials. The present paper aims at summing up the preparation of methylidene malonate monomers, and essentially a novel asymmetric diester structure: 1-ethoxycarbonyl-1-ethoxycarbonylmethylenoxycarbonyl ethene named methylidene malonate 2.1.2. Their polymeric and copolymeric derivatives and a few of their applications which were reported in the literature are also presented. It encompasses the manufacturing of particulate systems such as nano- and macroparticles designed for the delivery of hydrophilic or hydrophobic drugs and biomolecules. This review article also describes their use as biomaterials of interest in the fields of tissue repair, as drug reservoirs or ophthalmology, as implants. Copolymers based on these monomers offer a large range of properties and could be used as new surfactants, micellar vectors, or particulate systems for gene delivery. Therefore, this review, certainly the first dedicated exclusively to methylidene malonate-based materials, highlights the great biomedical and pharmaceutical technology potential of these new materials.

Effectiveness of creatine monohydrate on seizures and oxidative damage induced by methylmalonate.

Methylmalonic acidemias are metabolic disorders caused by a severe deficiency of methylmalonyl CoA mutase activity, which are characterized by neurological dysfunction, including convulsions. It has been reported that methylmalonic acid (MMA) accumulation inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity and respiratory chain complexes in vitro, leading to decreased CO2 production, O2 consumption and increased lactate production. Acute intrastriatal administration of MMA also induces convulsions and reactive species production. Though creatine has been reported to decrease MMA-induced convulsions and lactate production, it is not known whether it also protects against MMA-induced oxidative damage. In the present study we investigated the effects of creatine (1.2-12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) on the convulsions, striatal content of thiobarbituric acid reactive substances (TBARS) and on protein carbonylation induced by MMA. Moreover, we investigated the effect of creatine (12 mg/kg, i.p.) on the MMA-induced striatal creatine and phosphocreatine depletion. Low doses of creatine (1.2 and 3.6 mg/kg) protected against MMA-induced oxidative damage, but did not protect against MMA-induced convulsions. A high dose of creatine (12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) protected against MMA-induced seizures (evidenced by electrographic recording), protein carbonylation and TBARS production ex vivo. Furthermore, acute creatine administration increased the striatal creatine and phosphocreatine content and protected against MMA-induced creatine and phosphocreatine depletion. Our results suggest that an increase of the striatal high-energy phosphates elicited by creatine protects not only against MMA-induced convulsions, but also against MMA-induced oxidative damage. Therefore, since NMDA antagonists are limited value in the clinics, the present results indicate that creatine may be useful as an adjuvant therapy for methylmalonic acidemic patients.

Bumadizone calcium dihydrate microspheres compressed tablets for colon targeting: formulation, optimization and in vivo evaluation in rabbits.

The objective of this study was the development of a colon-targeted microspheres which were compressed into tablets containing the non-steroidal anti-inflammatory bumadizone calcium hemihydrate. [corrected]. A 3(2) full factorial design was adopted for the evaluation of the prepared microspheres. The effect of two independent variables namely polymer type (Eudragit RS100, ethyl cellulose and cellulose acetate butyrate), and drug: polymer ratio (1:1, 9:1 and 18:1) was studied on the entrapment efficiency and in vitro drug release for 12 h. Colon targeting aims to minimize the release of the drug off target area (pH 1.2 and 6.8) and to maximize the release of the drug in target area (pH 7.4). Candidate formulae were compressed into core tablets and colon targeting was achieved using the enzyme-dependent polymer (pectin) as coat in three different concentrations 50, 75 and 90%. Candidate formula F15 (microspheres prepared using BDZ:CAB in a ratio of 18:1 and compressed into tablets using 50% pectin and 50% Avicel in the coat) was able to adequately modulate drug release avoiding drug release in the gastric ambient, and reaching the colonic targeting where 99.7% release was achieved within 12 h following zero-order model. In vivo studies showed that F15 achieved significant decrease in myeloperoxidase activity and inflammation with delayed Tmax (4 h) and lower Cmax (2700 ng/ml) when compared to marketed product.

ABCG2 transporter inhibitor restores the sensitivity of triple negative breast cancer cells to aminolevulinic acid-mediated photodynamic therapy.

Photosensitizer protoporphyrin IX (PpIX) fluorescence, intracellular localization and cell response to photodynamic therapy (PDT) were analyzed in MCF10A normal breast epithelial cells and a panel of human breast cancer cells including estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2) positive and triple negative breast cancer (TNBC) cells after treatment with PpIX precursor aminolevulinic acid (ALA). Although PpIX fluorescence was heterogeneous in different cells, TNBC cells showed significantly lower PpIX level than MCF10A and ER- or HER2-positive cells. PpIX fluorescence in TNBC cells also had much less mitochondrial localization than other cells. There was an inverse correlation between PpIX fluorescence and cell viability after PDT. Breast cancer cells with the highest PpIX fluorescence were the most sensitive to ALA-PDT and TNBC cells with the lowest PpIX level were resistant to PDT. Treatment of TNBC cells with ABCG2 transporter inhibitor Ko143 significantly increased ALA-PpIX fluorescence, enhanced PpIX mitochondrial accumulation and sensitized cancer cells to ALA-PDT. Ko143 treatment had little effect on PpIX production and ALA-PDT in normal and ER- or HER2-positive cells. These results demonstrate that enhanced ABCG2 activity renders TNBC cell resistance to ALA-PDT and inhibiting ABCG2 transporter is a promising approach for targeting TNBC with ALA-based modality.

Brain and muscle redox imbalance elicited by acute ethylmalonic acid administration.

Ethylmalonic acid (EMA) accumulates in tissues and biological fluids of patients affected by short-chain acyl-CoA dehydrogenase deficiency (SCADD) and ethylmalonic encephalopathy, illnesses characterized by neurological and muscular symptoms. Considering that the mechanisms responsible for the brain and skeletal muscle damage in these diseases are poorly known, in the present work we investigated the effects of acute EMA administration on redox status parameters in cerebral cortex and skeletal muscle from 30-day-old rats. Animals received three subcutaneous injections of EMA (6 µmol/g; 90 min interval between injections) and were killed 1 h after the last administration. Control animals received saline in the same volumes. EMA administration significantly increased thiobarbituric acid-reactive substances levels in cerebral cortex and skeletal muscle, indicating increased lipid peroxidation. In addition, carbonyl content was increased in EMA-treated animal skeletal muscle when compared to the saline group. EMA administration also significantly increased 2',7'-dihydrodichlorofluorescein oxidation and superoxide production (reactive species markers), and decreased glutathione peroxidase activity in cerebral cortex, while glutathione levels were decreased only in skeletal muscle. On the other hand, respiratory chain complex I-III activity was altered by acute EMA administration neither in cerebral cortex nor in skeletal muscle. The present results show that acute EMA administration elicits oxidative stress in rat brain and skeletal muscle, suggesting that oxidative damage may be involved in the pathophysiology of the brain and muscle symptoms found in patients affected by SCADD and ethylmalonic encephalopathy.

Coenzyme Q10 in the central nervous system and its potential usefulness in the treatment of neurodegenerative diseases.

Coenzyme Q10 is an essential cofactor of the electron transport chain and is an antioxidant. We examined the effects of oral feeding with coenzyme Q10 in young animals on brain concentrations. Feeding with coenzyme Q10 at a dose of 200 mg/kg for 1-2 months in young rats resulted in significant increases in liver concentrations, however, there was no significant increase in brain concentrations of either reduced- or total coenzyme Q10 levels. Nevertheless there was a reduction in malonate-induced increases in 2,5 dihydroxybenzoic acid to salicylate, consistent with an antioxidant effect. In other studies we found that oral administration of coenzyme Q10 significantly reduced increased concentrations of lactate in the occipital cortex of Huntington's disease patients. These findings suggest that coenzyme Q10 might be useful in treating neurodegenerative diseases.

Primidone, phenobarbital, and PEMA: II. Seizure protection, neurotoxicity, and therapeutic index of varying combinations in mice.

Neurotoxicity and protection against maximal electroshock (MES) and pentylenetrazol (Metrazol) seizures were determined in mice for various combinations of primidone (PRM), phenobarbital (PB), and phenylethylmalonamide (PEMA). The results suggest that PRM and PB together are superior to either one alone in terms of spectrum of activity and relative toxicity. The protection against Metrazol and the toxicity of PB are both potentiated by PEMA at low concentrations. PEMA also potentiates the toxicity of combined PRM plus PB, without altering their protection against MES, thus lowering their therapeutic index. We conclude that PRM and PB together have an advantage over PB alone, especially when their brain concentration ratio is at or above 1 and PEMA concentrations are low. These conditions are usually not present at steady state in patients treated with PRM.

Nephrotoxicity of heptaplatin: a randomized comparison with cisplatin in advanced gastric cancer.

PURPOSE: Heptaplatin is a newly developed platinum derivative which has been reported to be less toxic than cisplatin. This study was designed to evaluate the nephrotoxicity of heptaplatin in comparison with that of cisplatin. METHODS: Previously untreated advanced gastric cancer patients with normal renal function were randomly assigned into either group I (heptaplatin 400 mg/m(2) i.v. over 1 h on day 1 plus 5-fluorouracil (5-FU) 1000 mg/m(2) per day continuous i.v. from day 1 to day 5), or group II (cisplatin 60 mg/m(2) i.v. over 1 h on day 1 plus 5-FU 1000 mg/m(2) per day continuous i.v. from day 1 to day 5), with the cycles repeated every 4 weeks. Renal function parameters before, during, and after the chemotherapy were compared between the two groups. RESULTS: A total of 99 patients were enrolled in the study, 51 in group I and 48 in group II. The 24-h proteinuria on day 5 was markedly increased in group I (95+/-108 mg/day to 9098+/-4514 mg/day, means+/-SD) in comparison with the increase observed in group II (104+/-148 mg/day to 151+/-102 mg/day), and creatinine clearance showed a greater decrease in group I (83.1+/-23.6 ml/min to 44.9+/-17.3 ml/min) than in group II (89.6+/-22.1 ml/min to 72.8+/-21.0 ml/min). The differences in these parameters between the two groups were statistically significant throughout the subsequent cycles. CONCLUSIONS: Our findings show that nephrotoxicity was more severe in patients treated with heptaplatin 400 mg/m(2) than with cisplatin 60 mg/m(2) when it was combined with 5-FU. Measures to more effectively prevent nephrotoxicity should be developed for the safe use of heptaplatin.

Damage to dopaminergic nerve terminals in mice by combined treatment of intrastriatal malonate with systemic methamphetamine or MPTP.

The mechanisms involved in methamphetamine (METH)-induced damage to nigrostriatal dopaminergic neurons in experimental animals are unknown. We have examined the possibility that perturbations in energy metabolism contribute to METH-induced toxicity by investigating the effects of systemic METH treatment in mice which received a unilateral intrastriatal infusion of malonate, a metabolic inhibitor which decreases ATP levels. Malonate (1-4 mumol) produced a dose-dependent decrease in striatal dopamine (DA). The combined treatment of intrastriatal malonate with systemic METH resulted in greater damage to dopaminergic neurons than by METH or malonate treatment alone. In parallel studies, MPTP was administered to mice which received intrastriatal infusions of saline or malonate. Similar to results obtained with METH, decreases in striatal DA content and tyrosine hydroxylase (TH) activity were greatest in MPTP-treated mice infused with malonate. The present results lend credence to the hypothesis that METH-induced increases in energy utilization create a state of metabolic stress for DA neurons which may ultimately contribute to the neurodegenerative effects of METH. Moreover, the finding that combined malonate and MPTP treatment produced greater damage than either substance alone is consistent with the hypothesis that perturbations in energy metabolism contribute to the neuronal death produced by MPP+.

Inhibition of striatal energy metabolism produces cell loss in the ipsilateral substantia nigra.

This study examined whether damage to dopamine (DA) nerve terminals via inhibition of energy metabolism in the striatum would result in the retrograde loss of cell bodies in the substantia nigra. Infusion of 2 micromol malonate into the left striatum of rats resulted in a 67% loss of striatal DA and a 40% loss of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. No change in the number of Nissl-positive-TH-negative neurons was observed. These findings demonstrate the retrograde destruction of DA cell bodies in the substantia nigra resulting from energy impairment at their terminal projection site.

Biphasic modulation by nitric oxide of caspase activation due to malonate injection in rat striatum.

The present study examined caspase activation and its modulation by nitric oxide (NO) in a model of oxidative stress induced by injection of malonate (3 micromol), a mitochondrial toxin, into rat striatum. Caspase-3-like enzymatic activity was maximal 6 h after malonate while NO production evaluated by its metabolites nitrites and nitrates was increased at 3 h. The neuronal NO-synthase inhibitor 7-nitroindazole reduced malonate induced-NO production by 50% at 25 mg/kg and enhanced by 32% caspase activation. This result suggests that a moderate production of NO potentiates caspase activation, an effect counterbalanced by NO itself at higher concentrations. Accordingly, complete inhibition of NO production by 7-nitroindazole at 50 mg/kg did not modify malonate-induced caspase activity. Thus NO production by the neuronal isoform of NO-synthase is not the major event leading to caspase activation due to malonate. However, NO seems to have pro- and anti-caspase effects that neutralize each other.