cgp-20376 and amoscanate

Alterations in the fine structures of female Brugia spp. and Litomosoides carinii were investigated after in vivo treatment with curative doses of 4 compounds: CGP 20376 [2-tert-butyl-benzothiazole-5-methoxy-6-dithiocarbamic-S-(2- carboxyethyl)-ester], CGP 21833 (2-tert-butyl-benzothiazole-5-methyl-6- N-methylamino-piperazinylthiocarbonylamide), CGP 6140 [4-Nitro-4'-(N-methyl-piperazinylthiocarbonylamido)-diphenylamine] and amoscanate (4-isothiocyanato-4'-nitrodiphenylamine). All compounds caused early alterations in the somatic muscle cells. These alterations usually appeared within 24 h after treatment; they occurred later only after treatment of L. carinii with amoscanate. In Brugia spp., swelling of the muscle cells occurred in which the glycogen deposits considerably increased in size. The electron density of the cytoplasm surrounding the myofilaments in the fibrillar portion of the muscle cells increased, and light zones appeared between the fibrils. The muscle cell mitochondria swelled, particularly their inner matrix, which became more electron-lucent, with some dense spots. In L. carinii the muscle cells were not increased in size, but their mitochondria were considerably swollen before disintegration; this was followed by disintegration of the myofilaments and vacuolization of the cytoplasm. Vacuolization before mitochondrial swelling was observed only after treatment with CGP 6140. Other tissues of this species were not altered before the 2nd day after treatment. In Brugia spp., electron-lucent appeared in the hypodermis either simultaneously with the alterations in the muscle cells or a few hours later. At 24 h after treatment with amoscanate, blebs were formed on the luminal side of the intestinal membrane.

Topics: Aniline Compounds; Animals; Anthelmintics; Benzothiazoles; Brugia; Diphenylamine; Elephantiasis, Filarial; Female; Filariasis; Filaricides; Filarioidea; Isothiocyanates; Microscopy, Electron; Muridae; Piperazines; Thiazoles; Thiocyanates

It is suggested that the recently developed benzothiazole and amoscanate derivatives with antifilarial activity exert their action in vitro by an inhibition of mitochondrial-derived respiration. It was confirmed that the drugs CGP 20376, 21835, 20308, 21306, and 6140 cause a rapid immobilization in vitro of the adult filarial worm, Litomosoides carinii, the time required being similar to rotenone at the same concentration. The other drugs investigated, CGPs 20309, 21833, 24589, 23518, and 13231, were also effective; however, they required much longer incubation times. Submitochondrial particles (SMP) were prepared from Ascaris muscle and rat liver. The concentration of drug causing 50% inhibition of respiration (IC50) was calculated. It was found that the drugs most rapidly inhibiting respiration have IC50s for NADH oxidase of less than 25 microM in both Ascaris and rat liver SMP. This effect on SMP respiration could be overcome by using succinate as a substrate, indicating the site of inhibition to be within complex I of the mitochondrial respiratory chain. Further experiments showed that whereas the respiratory chain's NADH:ferricyanide reductase was unaffected by these drugs, there were pronounced effects on both Ascaris and rat liver NADH:quinone reductase activity. This suggests that the inhibition within complex I occurs after the flavoprotein dehydrogenase, but before the site of the quinone reduction. The other compounds examined, which had a slower effect on motility, also showed inhibition of the NADH oxidase, but not to as great an extent as the aforementioned compounds. The compounds most active against motility were also most effective at inhibiting respiration in intact adult L. carinii. Analysis of the aerobic end products produced by L. carinii showed that acetate production was greatly reduced even in the presence of low concentrations of the drugs. There was also a slight decrease in lactate production. However, a direct effect on the glycolytic pathway was ruled out by two observations. One, that the production of lactate from cell-free extracts of L. carinii is unaffected by the presence of the drugs, and secondly, that a protozoan, Giardia lamblia, reliant on glycolysis for energy production, can survive for long periods of time in the presence of high concentrations of the drugs. A correlation can be observed between the time for immobilization of the filarial worm and the strength of inhibition of mitochondrial respiration. Therefor

Topics: Anaerobiosis; Aniline Compounds; Animals; Anthelmintics; Benzothiazoles; Diphenylamine; Energy Metabolism; Female; Filaricides; Filarioidea; Hydrogen-Ion Concentration; Isothiocyanates; Movement; Oxygen Consumption; Piperazines; Rotenone; Thiazoles; Thiocyanates; Time Factors

The drug response of Dipetalonema viteae and B. pahangi under various culture conditions have been evaluated. B. pahangi female worms proved to be more susceptible to CGP 6140 (4-nitro-4'-(N-methyl)piperazinyl thiocarbonylido-diphenylamine), CGP 20376 (N-(2-tert-butyl-5-methoxy-benzothiazol-6-yl)dithiocarbonic acid 5-(1-carboxyethyl)-ether) and amoscanate when glucose availability was restricted. This increased potency may be related to effects on glycogen metabolism by CGP 20376 and amoscanate. Using the parameters of parasite motility, survival, glucose consumption and microfilarial output, Eagles Minimum Essential Medium supplemented with 10% inactivated foetal calf serum plus either a 95% air:5% CO2 or a 95% N2:5% CO2 gas phase was shown to be highly suitable for short term maintenance (5 days). Examination of 12 drugs selected on their in vivo activity against B. pahangi and D. viteae demonstrated little difference between the drug susceptibilities of male and female worms. However, there were intrinsic differences between worm species. The relationship between these disparate susceptibilities and the reported in vivo efficacies of these drugs and the importance of selecting appropriate conditions for in vitro drug assays are discussed. Ivermectin at 10(-5) M caused a rapid flaccid paralysis and a complete suppression of microfilarial output by D. viteae. Despite continued paralysis of the worms they continued to utilise as much glucose as untreated worms over a 4 day period.

Topics: Animals; Anthelmintics; Brugia; Dipetalonema; Diphenylamine; Female; Filaricides; Glucose; Isothiocyanates; Ivermectin; Male; Piperazines; Thiazoles; Thiocyanates