Protection from chlordecone-amplified carbon tetrachloride toxicity by cyanidanol: Biochemical and histological studies

Abstract

Chlordecone (CD) pretreatment is well known to greatly potentiate CCl 4 toxicity. Previous work has shown that suppression of hepatocellular regeneration permits an ordinarily limited liver injury to progress in an irreversible manner. Insufficient hepatocellular energy has been proposed as a mechanism for suppressed hepatocellular regeneration. Since cyanidanol reportedly increases cellular ATP, this compound was employed to test the above hypothesis. The present study was designed to investigate the sequential biochemical and histological changes over a time course of 120 hr after CCl 4 administration. Male Sprague-Dawley rats (125–150 g) were maintained on 10 ppm CD diet for 15 days and were challenged with either a standard protocol dose (100 μl/kg) or a low (50 μ/kg, L) dose of CCl 4. Cyanidanol pretreatment at 48, 24, and 2 hr before CCl 4 administration to rats maintained on CD diet resulted in 100 or 70% animal survival, for CCl 4 (L) or the standard dose of CCl 4, respectively. Preliminary studies indicated that neither simultaneous nor subsequent administration of cyanidanol with CCl 4 challenge affords such protection. Prior treatment with cyanidanol and a latency period were found necessary for protection. Without cyanidanol, CD + CCl 4 combination caused 50 and 100% lethality after CCl 4 (L) and the standard dose, respectively, while the same doses of CCl 4 alone did not cause lethal effects. Plasma enzymes (alanine aminotransferase, asparatate aminotransferase, sorbitol dehydrogenase) in control rats showed only moderate and transient increases after CCl 4 challenge. The combination of CD + standard dose of CCl 4 resulted in progressive and marked elevations of all three serum enzymes at all time intervals until the death of animals. Cyanidanol pretreatment resulted in significant decline in the plasma enzyme elevations at later time points. Cyanidanol pretreatment increased hepatic ATP synthesis in control or CD rats. CCl 4 administration to control rats did not alter hepatic ATP levels, while in CD-fed rats hepatic ATP levels were significantly decreased. Cyanidanol pretreatment to CD + CCl 4 combination-treated rats did not significantly prevent the decline in hepatic ATP and glycogen levels. However, in the surviving rats a recovery in these parameters was observed. Light microscopic examination of livers from animals that received CCl 4 alone revealed only marginal cellular injury, at early time points only. However, CCl 4 challenge to rats maintained on CD resulted in progressive injury, characterized by the appearance of ballooned cells, necrotic cells, and cells with lipid droplets in the liver. Cyanidanol pretreatment to these rats caused decreased vacuolation and significantly reduced the progression of liver necrosis. These results show that cyanidanol protects against an irreversibly progressive phase of liver injury and the interactive lethality of CD + CCl 4. In conclusion, the cyanidanol protection of CD-amplified CCl 4 toxicity requires a latency period and appears to be through mechanisms other than interference with the injurious events such as free radical injury, bioactivation, or covalent binding of CCl 4. These findings are consistent with the possibility that protection might be through a facilitation of cellular supply of energy.