MPTP, MPP+ and mitochondrial function

1-Methyl-4-phenylpyridinium (MPP+), the putative toxic metabolite of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), inhibited NAD(H)-linked mitochondrial oxidation at the level of Complex I of the electron transport system. MPTP and MPP+ inhibited aerobic glycolysis in mouse striatal slices, as measured by increased lactate production; MPTP-induced effects were prevented by inhibition of monoamine oxidase B activity. Several neurotoxic analogs of MPTP also form pyridinium metabolites via MAO; these MPP+ analogs were all inhibitors of NAD(H)-linked oxidation by isolated mitochondria. 2'-Methyl-MPTP, a more potent neurotoxin in mice than MPTP, was also more potent than MPTP in inducing lactate accumulation in mouse brain striatal slices. Overall, the studies support the hypothesis that compromise of mitochondrial oxidative capacity is an important factor in the mechanisms underlying the toxicity of MPTP and similar compounds.     

Crystallization and preliminary X-ray study of a complex between d(ATGCAT) and actinomycin D

Crystals of a 2:1 complex between the self-complementary DNA hexamer d(ATGCAT) and the antitumor drug actinomycin D have been grown from solutions of polyethylene glycol 400. The crystals are orthorhombic with space group P2(1)2(1)2(1) and a = 95.6, b = 42.7, and c = 40.8 A. A Patterson map calculated from preliminary diffractometer data as well as packing considerations suggest a model in which the actinomycin D is intercalated into a double-stranded DNA hexamer. There are four such complexes in the asymmetric unit.     

Mechanism-based inactivation of monoamine oxidases A and B by tetrahydropyridines and dihydropyridines.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its primary oxidation product, 1-methyl-4-phenyl-2,3-dihydropyridinium (MPDP+), are mechanism-based inhibitors of monoamine oxidases A and B. The pseudo-first-order rate constants for inactivation were determined for various analogues of MPTP and MPDP+ and the concentrations in all redox states were measured throughout the reaction. Disproportionation was observed for all the dihydropyridiniums, but non-enzymic oxidation was insignificant. The dihydropyridiniums were poor substrates for monoamine oxidase A and, consequently, inactivated the enzyme only slowly, despite partition coefficients lower than those for the tetrahydropyridines. For monoamine oxidase B, the dihydropyridiniums were more effective inactivators than the tetrahydropyridines. Substitutions in the aromatic ring had no major effect on the inactivation of monoamine oxidase B, but the 2'-ethyl- and 3'-chloro-substituted compounds were very poor mechanism-based inactivators of monoamine oxidase A. It is clear that both oxidation steps can generate the reactive species responsible for inactivation.     

Some observations on the effect of Daflon (micronized purified flavonoid fraction of Rutaceae aurantiae) in bancroftian filarial lymphoedema

BACKGROUND: Morbidity management is a core component of the global programme for the elimination of lymphatic filariasis. In a double-blind clinical trial, the tolerability and efficacy of Daflon (500 mg) + DEC (25 mg) or DEC (25 mg) alone, twice daily for 90 days, was studied in 26 patients with bancroftian filarial lymphoedema. RESULTS: None of the patients in either drug group reported any adverse reaction throughout the treatment period (90 days). Haematological and biochemical parameters were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 90) values. The group receiving Daflon showed significant reduction in oedema volume from day 90 (140.6 PlusMinus; 18.8 ml) to day 360 (71.8 PlusMinus; 20.7 ml) compared to the pre-treatment (day 0, 198.4 PlusMinus; 16.5 ml) value. This accounted for a 63.8% reduction in oedema volume by day 360 (considering the pre-treatment (day 0) as 100%). In the DEC group, the changes in oedema volume (between day 1 and day 360) were not significant when compared to the pre-treatment (day 0) value. The percentage reduction at day 360 was only 9%, which was not significant (P > 0.05). CONCLUSION: This study has shown that Daflon (500 mg, twice a day for 90 days) is both safe and efficacious in reducing oedema volume in bancroftian filarial lymphoedema. Further clinical trials are essential for strengthening the evidence base on the role of this drug in the morbidity management of lymphatic filariasis.     

Direct intracardiac injection of umbilical cord-derived stromal cells and umbilical cord blood-derived endothelial cells for the treatment of ischemic cardiomyopathy

The development of new therapeutic strategies is necessary to reduce the worldwide social and economic impact of cardiovascular disease, which produces high rates of morbidity and mortality. A therapeutic option that has emerged in the last decade is cell therapy. The aim of this study was to compare the effect of transplanting human umbilical cord-derived stromal cells (UCSCs), human umbilical cord blood-derived endothelial cells (UCBECs) or a combination of these two cell types for the treatment of ischemic cardiomyopathy (IC) in a Wistar rat model. IC was induced by left coronary artery ligation, and baseline echocardiography was performed seven days later. Animals with a left ventricular ejection fraction (LVEF) of ≤40% were selected for the study. On the ninth day after IC was induced, the animals were randomized into the following experimental groups: UCSCs, UCBECs, UCSCs plus UCBECs, or vehicle (control). Thirty days after treatment, an echocardiographic analysis was performed, followed by euthanasia. The animals in all of the cell therapy groups, regardless of the cell type transplanted, had less collagen deposition in their heart tissue and demonstrated a significant improvement in myocardial function after IC. Furthermore, there was a trend of increasing numbers of blood vessels in the infarcted area. The median value of LVEF increased by 7.19% to 11.77%, whereas the control group decreased by 0.24%. These results suggest that UCSCs and UCBECs are promising cells for cellular cardiomyoplasty and can be an effective therapy for improving cardiac function following IC.     

Effects of 1-Methyl-4-Phenyl-1,2,5,6-Tetrahydropyridine and Related Compounds on the Uptake of [3H]3,4-Dihydroxyphenylethylamine and [3H]5-Hydroxytryptamine in Neostriatal Synaptosomal Preparations

1-Methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) is known to cause a destruction of the dopaminergic nigrostriatal pathway in certain animal species including mice. MPTP and some structurally related analogs were tested in vitro for their capacity to inhibit the uptake of [3H]3,4-dihydroxyphenylethylamine-([3H]DA), [3H]5-hydroxytryptamine ([3H]5-HT), and [3H]gamma-aminobutyric acid [( 3H]GABA) in mouse neostriatal synaptosomal preparations. MPTP was a very potent inhibitor of [3H]5-HT uptake (IC50 value 0.14 microM), a moderate inhibitor of [3H]DA uptake (IC50 value 2.6 microM), and a very weak inhibitor of [3H]GABA uptake (no significant inhibition observed at 10 microM MPTP). In other experiments, MPTP caused some release of previously accumulated [3H]DA and [3H]5-HT, but in each case MPTP was considerably better as an uptake inhibitor than as a releasing agent. The 4-electron oxidation product of MPTP, i.e., 1-methyl-4-phenyl-pyridinium iodide (MPP+), was a very potent inhibitor of [3H]DA uptake (IC50 value 0.45 microM) and of [3H]5-HT uptake (IC50 value 0.78 microM) but MPP+ was a very weak inhibitor of [3H]GABA uptake. These data may have relevance to the neurotoxic actions of MPTP.     

Evaluation of the Biological Activity of Several Analogs of the Dopaminergic Neurotoxin 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine

Several analogs of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were synthesized and screened for their capacity to be oxidized by monoamine oxidase (MAO-A or MAO-B) and their capacity to produce nigrostriatal dopaminergic neurotoxicity in mice. All of the compounds were relatively weak substrates for MAO-A but many of the compounds were found to be good substrates for MAO-B. Only three of the compounds, in addition to MPTP itself, were found to be neurotoxic. These were 1-methyl-4-cyclohexyl-1,2,3,6-tetrahydropyridine, 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine and 1-methyl-4-(3'-methoxyphenyl)-1,2,3,6-tetrahydropyridine. All three of these neurotoxic compounds were found to be substrates for MAO-B; in contrast no compound was found to be neurotoxic that was not oxidized by MAO-B. The capacity of the compounds studied to be oxidized by MAO-B appears to be an important aspect of the neurotoxic process.     

A new class of powerful inhibitors of monamine oxidase A

It is well established that 1-methyl-4-phenylpyridinium (MPP), the neurotoxic bioactivation product of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and most of its analogs are good competitive inhibitors of monoamine oxidase A, with Ki values in the micromolar range, but they inhibit monoamine oxidase B only at much higher concentrations. We report here the finding that alkyl derivatives of MPP+ substituted at the 4' position of the aromatic ring are considerably more effective reversible inhibitors of the A type enzyme, with Ki values in the nanomolar range (0.075-1.6 microM). They inhibit the B type enzyme only at 2 to 3 orders of magnitude higher concentrations (32-374 microM).