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.

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.

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.

Neurological and histological consequences induced by in vivo cerebral oxidative stress: evidence for beneficial effects of SRT1720, a sirtuin 1 activator, and sirtuin 1-mediated neuroprotective effects of poly(ADP-ribose) polymerase inhibition

Poly(ADP-ribose)polymerase and sirtuin 1 are both NAD⁺-dependent enzymes. In vitro oxidative stress activates poly(ADP-ribose)polymerase, decreases NAD⁺ level, sirtuin 1 activity and finally leads to cell death. Poly(ADP-ribose)polymerase hyperactivation contributes to cell death. In addition, poly(ADP-ribose)polymerase inhibition restores NAD⁺ level and sirtuin 1 activity in vitro. In vitro sirtuin 1 induction protects neurons from cell loss induced by oxidative stress. In this context, the role of sirtuin 1 and its involvement in beneficial effects of poly(ADP-ribose)polymerase inhibition were evaluated in vivo in a model of cerebral oxidative stress induced by intrastriatal infusion of malonate in rat. Malonate promoted a NAD⁺ decrease that was not prevented by 3-aminobenzamide, a poly(ADP-ribose)polymerase inhibitor, at 4 and 24 hours. However, 3-aminobenzamide increased nuclear SIRT1 activity/expression ratio after oxidative stress. Malonate induced a neurological deficit associated with a striatal lesion. Both were reduced by 3-aminobenzamide and SRT1720, a sirtuin 1 activator, showing beneficial effects of poly(ADP-ribose)polymerase inhibition and sirtuin 1 activation on oxidative stress consequences. EX527, a sirtuin 1 inhibitor, given alone, modified neither the score nor the lesion, suggesting that endogenous sirtuin 1 was not activated during cerebral oxidative stress. However, its association with 3-aminobenzamide suppressed the neurological improvement and the lesion reduction induced by 3-aminobenzamide. The association of 3-aminobenzamide with SRT1720, the sirtuin 1 activator, did not lead to a better protection than 3-aminobenzamide alone. The present data represent the first demonstration that the sirtuin 1 activator SRT1720 is neuroprotective during in vivo cerebral oxidative stress. Furthermore sirtuin 1 activation is involved in the beneficial effects of poly(ADP-ribose)polymerase inhibition after in vivo cerebral oxidative stress.

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.

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.

Combination chemotherapy with 5-fluorouracil and heptaplatin as first-line treatment in patients with advanced gastric cancer

Heptaplatin is a recently developed platinum derivative. This agent has been reported to have a response rate of 17% as a single agent, and tolerable toxicity in the treatment of advanced gastric cancer. The aim of this study was to evaluate the efficacy and toxicity of a combination of 5-fluorouracil (5-FU) and heptaplatin in patients with advanced gastric cancer. Forty-seven chemotherapy-naive patients with advanced or recurred gastric cancer were recruited. 5-FU was administered over 120 hr by continuous intravenous infusion from day 1 to 5, at a daily dose of 1,000 mg/m2 and heptaplatin was administered over 1 hr by intravenous infusion on day 1 at 400 mg/m2, and this cycle was repeated every 4 weeks. The response rate was 21%, median progression-free survival was 1.9 months (95% CI, 1.6 to 2.2 months). Median overall survival was 6.2 months (95% CI, 4 to 8.4 months) and the 1-yr survival rate was 29% for all patients. The most frequent toxicity was proteinuria. Toxicities were generally mild and reversible. This study demonstrates that the combination of 5-FU/heptaplatin combination is less active but tolerated in patients with advance gastric cancer.

Development of novel 5-FU-loaded poly(methylidene malonate 2.1.2)-based microspheres for the treatment of brain cancers

In order to treat malignant brain tumors by local delivery of antineoplastic agents, the feasibility of 5-fluorouracil (5-FU)-sustained release biodegradable microspheres with a novel material, poly(methylidene malonate 2.1.2), was investigated using an emulsion/extraction method. This polymer was expected to present a slow degradation rate, thus leading to a long term local delivery system. Microparticles were successfully obtained and characterized in terms of drug loading, size, morphology and release profile. The size of the particles was between 40 and 50 microm, which was compatible with a stereotactic injection through a needle. Sufficient drug loadings were obtained (i.e. compatible with the preparation of therapeutic 5-FU doses in a minimal volume of injection), and perfectly spherical microspheres were observed. The respective influences of the polymer molecular weight, the polymer concentration, and the emulsion time on the release profiles were studied using a 2(3) factorial design. In the same objective, the solvent extraction time was extended while keeping all the previous parameters fixed at their optimal values. The in vitro study of these different parameters allowed a reduction of the initial burst release, with a percentage of 5-FU released after 24 h that was lowered from 90 to 65%, and the achievement of a long term drug delivery system, since the release was still ongoing after 43 days. Moreover, the microparticles could be gamma-sterilized (25 kGy) without modification of the release kinetics. Thus, the requested specifications to perform animal experiments were attained.

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.

In vivo quantification of localized neuronal activation and inhibition in the rat brain using a dedicated high temporal-resolution beta +-sensitive microprobe

Understanding brain disorders, the neural processes implicated in cognitive functions and their alterations in neurodegenerative pathologies, or testing new therapies for these diseases would benefit greatly from combined use of an increasing number of rodent models and neuroimaging methods specifically adapted to the rodent brain. Besides magnetic resonance (MR) imaging and functional MR, positron-emission tomography (PET) remains a unique methodology to study in vivo brain processes. However, current high spatial-resolution tomographs suffer from several technical limitations such as high cost, low sensitivity, and the need of restraining the animal during image acquisition. We have developed a beta(+)-sensitive high temporal-resolution system that overcomes these problems and allows the in vivo quantification of cerebral biochemical processes in rodents. This beta-MICROPROBE is an in situ technique involving the insertion of a fine probe into brain tissue in a way very similar to that used for microdialysis and cell electrode recordings. In this respect, it provides information on molecular interactions and pathways, which is complementary to that produced by these technologies as well as other modalities such as MR or fluorescence imaging. This study describes two experiments that provide a proof of concept to substantiate the potential of this technique and demonstrate the feasibility of quantifying brain activation or metabolic depression in individual living rats with 2-[(18)F]fluoro-2-deoxy-d-glucose and standard compartmental modeling techniques. Furthermore, it was possible to identify correctly the origin of variations in glucose consumption at the hexokinase level, which demonstrate the strength of the method and its adequacy for in vivo quantitative metabolic studies in small animals.

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.

Protection of malonate-induced GABA but not dopamine loss by GABA transporter blockade in rat striatum

Previous work has shown that overstimulation of GABA(A) receptors can potentiate neuronal cell damage during excitotoxic or metabolic stress in vitro and that GABA(A) antagonists or GABA transport blockers are neuroprotective under these situations. Malonate, a reversible succinate dehydrogenase/mitochondrial complex II inhibitor, is frequently used in animals to model cell loss in neurodegenerative diseases such as Parkinson's and Huntington's diseases. To determine if GABA transporter blockade during mitochondrial impairment can protect neurons in vivo as compared with in vitro studies, rats received a stereotaxic infusion of malonate (2 micromol) into the left striatum to induce a metabolic stress. The nonsubstrate GABA transport blocker, NO711 (20 nmol) was infused in some rats 30 min before and 3 h following malonate infusion. After 1 week, dopamine and GABA levels in the striata were measured. Malonate caused a significant loss of striatal dopamine and GABA. Blockade of the GABA transporter significantly attenuated GABA, but not dopamine loss. In contrast with several in vitro reports, GABA(A) receptors were not a downstream mediator of protection by NO711. Intrastriatal infusion of malonate (2 micromol) plus or minus the GABA(A) receptor agonist muscimol (1 micromol), the GABA(A) Cl- binding site antagonist picrotoxin (50 nmol) or the GABA(B) receptor antagonist saclofen (33 nmol) did not modify loss of striatal dopamine or GABA when examined 1 week following infusion. These data show that GABA transporter blockade during mitochondrial impairment in the striatum provides protection to GABAergic neurons. GABA transporter blockade, which is currently a pharmacological strategy for the treatment of epilepsy, may thus also be beneficial in the treatment of acute and chronic conditions involving energy inhibition such as stroke/ischemia or Huntington's disease. These findings also point to fundamental differences between immature and adult neurons in the downstream involvement of GABA receptors during metabolic insult.

A Phase I study of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane] platinum(II) in patients with advanced malignancies

BACKGROUND

A Phase I study of cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane] platinum(II) (SKI 2053R), a new platinum derivative, was performed to determine the maximum tolerated dose (MTD), the dose limiting toxicities (DLTs), and the pharmacokinetic profile of SKI 2053R in patients with advanced, refractory malignancies.

METHODS

Twenty-one patients were entered into the study. SKI 2053R was administered with an intravenous infusion over 1 hour every 4 weeks. The SKI 2053R dose was escalated from 40 mg/m(2) up to 480 mg/m(2) using a modified Fibonacci scheme. Pharmacokinetic analysis was done in all patients to determine the total and ultrafiltrable platinum concentrations in both the plasma and the urine.

RESULTS

All patients were evaluable for toxicity and response. There was no significant toxicity with dosages up to 360 mg/m(2). At 480 mg/m(2), two of three patients developed Grade 4 hepatotoxicity, Grade 3 leukopenia and thrombocytopenia, and Grade 2 azotemia and proteinuria. Other toxicity included nausea and emesis, but it was controlled with antiemetics. SKI 2053R did not cause significant neurotoxicity or mucositis. There were 4 patients with stable disease among the 21 patients. Plasma decay of the total and free platinum concentrations was best fitted by using a two-compartment, open model. The terminal plasma half-life of the total platinum after SKI 2053R administration ranged from 63.4 hours to 114.1 hours in dosages ranging from 40 mg/m(2) to 480 mg/m(2) without significant dose dependency. However, the terminal plasma half-life of the free platinum concentration showed a significant dose dependent, incremental pattern. The renal excretion of SKI 2053R measured as platinum ranged from 49% to 75% of the administered dose.

CONCLUSIONS

The MTD of SKI 2053R was 480 mg/m(2). The major DLTs were hepatotoxicity, nephrotoxicity, and myelosuppression. The recommended starting dose for a subsequent Phase II study is 360 mg/m(2) once every 4 weeks.

In situ produced 7-chlorokynurenate provides protection against quinolinate- and malonate-induced neurotoxicity in the rat striatum

Excitotoxic mechanisms may play a critical role in the pathophysiology of several neurological and psychiatric diseases. Excitatory amino acid receptor antagonists are therefore of great therapeutic interest, but untoward side effects often prevent their clinical use. Targeting the glycine coagonist site of the (NMDA) receptor may bypass these shortcomings. The present study was designed to evaluate the neuroprotective characteristics of l-4-chlorokynurenine (4-Cl-KYN), a synthetic compound which is enzymatically converted to the selective glycine/NMDA receptor antagonist 7-chlorokynurenate (7-Cl-KYNA). Using slow (2 h) intrastriatal infusions of the excitotoxins quinolinate (QUIN; 120 nmol) or malonate (6.8 micromol) as the experimental paradigm, the neuroprotective potency of 4-Cl-KYN was first compared with that of exogenous 7-Cl-KYNA, using glutamate decarboxylase activity as a lesion marker. One hundred and thirty-five nanomoles of the prodrug 4-Cl-KYN or 27 nmol 7-Cl-KYNA, the former used in a pre- and cotreatment regimen, were required to block QUIN or, less efficiently, malonate toxicity. In separate animals, the metabolic fate of this neuroprotective dose of 4-Cl-KYN was examined in vivo. In control striata, the treatment gave rise to 170 +/- 25 pmol 7-Cl-KYNA/mg protein, approximately six times less than an infusion of 27 nmol exogenous 7-Cl-KYNA, indicating greatly superior efficacy of the focally produced antagonist. Notably, the conversion of 4-Cl-KYN to 7-Cl-KYNA increased by 82% in the presence of QUIN. 4-Cl-KYN was also metabolized to 4-chloro-3-hydroxyanthranilate, an established, powerful inhibitor of QUIN synthesis. This unique pharmacological profile and the fact that the prodrug, unlike 7-Cl-KYNA, readily penetrates the blood-brain barrier suggest that 4-Cl-KYN may be exceptionally useful as an anti-excitotoxic agent.

NMDA receptors modulate dopamine loss due to energy impairment in the substantia nigra but not striatum

Defects in energy metabolism have been detected in patients with Parkinson's disease and have been proposed as a contributing factor in the disease. Previous in vitro studies showed that NMDA receptors contribute to the loss of dopamine neurons caused by the metabolic inhibitor malonate. In vivo, it is not known whether this interaction occurs through a postsynaptic action on the cell body in the substantia nigra or through a presynaptic action at the dopamine terminal in the striatum. So we could discern the anatomical level of NMDA receptor involvement, rats were infused with malonate, either into the left striatum or into the left substantia nigra. NMDA receptors were locally blocked by an intranigral or intrastriatal coinfusion of malonate plus MK-801 followed by a second infusion of MK-801 3 h later. Animals were examined at 1 week for striatal and nigral dopamine and GABA levels. Intranigral infusion of malonate (0.5 micromol) produced an approximate 50% loss of both nigral dopamine and GABA. MK-801 (0.1 micromol) provided significant protection against both nigral dopamine and GABA loss and against anterograde damage to dopamine terminals in the striatum. Intrastriatal administration of malonate (2 micromol) produced a 68 and 35% loss of striatal dopamine and GABA, respectively. In contrast to intranigral administration, intrastriatal blockade of NMDA receptors did not protect against striatal dopamine loss, although GABA loss was significantly attenuated. Core body temperature monitored several hours throughout the experiment was unchanged. Consistent with a lack of effect of NMDA antagonists on malonate-induced toxicity to dopamine neurons in striatum, intrastriatal infusion of NMDA had a pronounced effect on long-term GABA toxicity with little effect of dopamine loss. These findings are consistent with a postsynaptic action of NMDA receptors on mediating toxicity to dopamine neurons during impaired energy metabolism.

Phase II clinical trial of SKI-2053R, a new platinum analog, in the treatment of patients with advanced gastric adenocarcinoma

BACKGROUND

SKI-2053R (SK Chemicals, Kyungki-Do, South Korea) is a new platinum derivative with antitumor activity against various cell lines, including cisplatin-resistant tumor cell lines. Preclinical studies have suggested that it is less nephrotoxic than cisplatin. This study evaluated the efficacy and toxicity of SKI-2053R in the treatment of patients with advanced gastric adenocarcinoma.

METHODS

Thirty-seven patients with advanced gastric adenocarcinoma that was unresectable or metastatic were treated. No prior chemotherapy or radiotherapy was allowed. Patients received SKI-2053R 360 mg/m(2) by 1-hour infusion on Day 1. After the first cycle, subsequent doses were adjusted according to the toxicity. Courses were repeated every 28 days.

RESULTS

Thirty-five patients were evaluable for response and toxicity. Six patients achieved a major response (17%; 95% confidence interval, 8-33%); 2 were complete and 4 were partial responses. The median duration of response was 7.2 months, with a range of 1-20 months. Patients could tolerate the treatment without significant toxicity. No patients had Grade 3 or 4 toxicity. The most frequent toxicity was Grade 1 or 2 proteinuria (26% of cycles), but it was mild and transient. Leukopenia, thrombocytopenia, azotemia, nausea and vomiting, and neurotoxicity were not frequent. These low toxicity profiles indicated that the dose of SKI-2053R could be increased in future studies.

CONCLUSIONS

SKI-2053R was active in the treatment of patients with gastric adenocarcinoma and had favorable toxicity profiles.

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.

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.

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+.

Wound healing effect of malotilate in rats

The wound healing effect of malotilate (CAS 59937-28-9, NKK-105) was investigated by using an excisional skin-wound model produced on the back of normal and healing-impaired (induced by prednisolone pretreatment) rats. The rapid decrease in the square measure of wound areas and the improvement in the histological evaluation clarified that 0.3% and 1% cream preparations of malotilate were obviously effective in accelerating spontaneous healing in the normal rats. The accelerative effect of malotilate cream preparations was likely superior to that of an ointment containing 5% deproteinized calf blood extract used as a reference agent. The same effect was also observed in the healing-impaired rats. The histological findings revealed that a thicker and more cellular granulation tissue, which in turn created an adequate bed for rapid re-epithelization, was formed in the malotilate-treated animals. Acceleration of granulation tissue formation by malotilate was also supported by the cotton pellet implantation method. It is concluded from these results that malotilate seems to be a promising agent for topical wound therapy.

Exacerbation of NMDA, AMPA, and L-glutamate excitotoxicity by the succinate dehydrogenase inhibitor malonate

We report that a subtoxic dose of the succinate dehydrogenase (SDH) inhibitor malonate greatly enhances the neurotoxicity of three different excitatory amino acid agonists: N-methyl-D-aspartate (NMDA), S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (S-AMPA), and L-glutamate. In male Sprague-Dawley rats, intrastriatal stereotaxic injection of malonate alone (0.6 mumol), NMDA alone (15 nmol), S-AMPA alone (1 nmol), or glutamate alone (0.6 mumol) produced negligible toxicity as assessed by measurement of lesion volume. Coinjection of subtoxic malonate with NMDA produced a large lesion (15.2 +/- 1.4 mm3), as did coinjection of malonate with S-AMPA (11.0 +/- 1.0 mm3) or glutamate (12.8 +/- 0.7 mm3). Administration of the noncompetitive NMDA antagonist MK-801 (5 mg/kg i.p.) completely blocked the toxicity of malonate plus NMDA (0.5 +/- 0.3 mm3). This dose of MK-801 had little effect on the lesion produced by malonate plus S-AMPA (9.0 +/- 0.7 mm3), but it attenuated the toxicity of malonate plus glutamate by approximately 40% (7.5 +/- 0.9 mm3). Coinjection of the AMPA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)-quinoxaline (NBQX; 2 nmol) had no effect on malonate plus NMDA or malonate plus glutamate toxicity (12.3 +/- 1.8 and 14.0 +/- 0.9 mm3, respectively) but greatly attenuated malonate plus S-AMPA toxicity (1.5 +/- 0.9 mm3). Combination of the two antagonists conferred no additional neuroprotection in any paradigm. These results indicate that metabolic inhibition exacerbates both NMDA receptor- and non-NMDA receptor-mediated excitotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of malonate administration on renal ammoniagenesis in intact dogs

In the dog kidney in vivo, malonate augmented ammoniagenesis from both amide and nonamide nitrogen sources, similar to previous in vitro investigations using incubating canine renal tubules. This was highly significant in alkalotic dogs, where it was accompanied by decreased renal tissue concentrations of glutamate. Changes in renal ammonia metabolism were less evident in acidotic dogs where a markedly decreased glomerular filtration rate was noted following malonate administration. Under conditions of complete ureteric obstruction which effectively abolished glomerular filtration, malonate significantly augmented ammoniagenesis above baseline in acidotic dogs. These in vivo results with malonate have similarities to those seen in dogs subjected to an acid challenge alone and suggest that the adaptation in renal ammoniagenesis under both circumstances occurs via enhanced deamination of glutamate pools.

Inhalation toxicity of methyl difluoromalonyl fluoride in rats

Methyl 2,2-difluoromalonyl fluoride (MMF) is highly toxic by inhalation producing mortality in rats exposed for 4 hours to 0.55 mg/L. Repeated inhalation exposures of rats to 0.009 mg/L produced irritation but no other signs of a toxic response. Mortality was encountered following repeated exposures to 0.066 mg/L.

Protective effect of malotilate (diisopropyl 1,3-dithiol-2-ylidenemalonate) on carbon tetrachloride-induced liver injury in mice and rats

The protective effect of malotilate was studied on the liver injury induced by carbon tetrachloride (CCl4) in mice and rats. Plasma GOT and GPT activities were used as indices for the liver injury, and the liver was histopathologically examined. A remarkable suppressing effect on the liver injury was observed when malotilate was orally given 6 hr prior to oral administration of CCl4 in mice and 3, 6 or 12 hr in rats. Malotilate was also effective in preventing the liver injury caused by intraperitoneal injection of CCl4, indicating that the protective effect is not derived from the decreased CCl4 absorption. The liver injury was suppressed even when malotilate was given 12 or 24 hr prior to oral administration of CCl4 in mice and 24, 48 or 72 hr in rats. It may be the characteristic of malotilate that the protective effect lasts for a long period. It is supposed that the effect is due not only to the inhibition of the metabolic activation of CCl4 but also the other action(s) of malotilate.

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.

[Comparison of bumadizone-, phenylbutazone- and oxyphenbutazone-plasma levels after a single oral dose of phenylbutazone and of bumadizone, respectively (author's transl)]

Bumadizone-calcium-semihydrate and phenylbutazone were given orally to two groups (I and II) consisting of 6 persons each; plasma levels of bumadizone, phenylbutazone and oxyphenbutazone were determined over a period of 384 h. For bumadizone a plasma half-life of 6.9 h was found, maximum plasma levels were reached after 1-6 h varying from 27 to 46 microgram/ml. Phenylbutazone- and oxyphenbutazone-AUC-values were compared between the two groups.

Anti-alcohol action of hepaticoactivator (NKK-105) on motoricity and EEG in experimental animals and man

The effects of a hepaticoactivator, diisopropyl 1, 3-dithiol-2-ylidene malonate (NKK-105), on motoricity and EEG were observed int he rat, mouse, cat and man. NKK-105 suppressed the effects of ethanol (1,000-3,000 mg/kg, p.o., in mice and rats), e.g. the blood alcohol concentration of NKK-105 treated subjects was significantly lower than that of untreated controls. NKK-105, in 100-300 mg/kg p.o. doses, significantly extended the clinging time on a glass rod, and the swimming time. Results indicate that NKK-105 inhibits the effects of alcohol, possibly by hepatic action, and to a lesser extent (neuro) motor activity, by reducing temulence. NKK-105 clearly exhibited anti-alcohol action (metabolic facilitory action) on EEG activity in experiments on cats and man. Almost complete blocking of alcohol action occurred in acute and chronic cats after NKK-105 (100 mg/kg, p.o., or 5-10 mg/kg , i.v.) treatment. It especially inhibited increased amplitude and/or increased slow components in cat neocortex recordings. Most human subjects showed similar results. It is concluded that the anti-alcohol action of NKK-105 seen in the EEG seems to be primarily a liver function, and secondarily a (neuro) motor function.

[Experiences with a new antiphlogistic and analgetic drug ("Eumotol") in orthopaedic and accident surgery patients (author's transl)]

The Bumadizon-Ca ("Eumotol") which does not contain any hormones or steroid bodies was applicated in 130 orthopaedic and accident surgical patients as an antiphologistic an analgesic drug. In over 90 percent of these cases we could state a good antiphologistic and following analgesic effect. Even when applicated for longer terms there were no allergic, toxic or some what disturbing secondary effects. The compatibility of this drug proved generally to be good. In five cases only with gastritis and peptic ulcer we had to stop the application."Eumotol" is strictly forbidden to be applicated in patients with hypersensitivity against pyrzol bodies and in cases of leukopenia. When a decreased function of kidneys and liver is evident the drug should be only given under certain precantionary measures.