Inhibition of poly(ADP-ribose) polymerase-1 attenuates the toxicity of carbon tetrachloride

Abstract

Carbon tetrachloride (CCl(4)) is routinely used as a model compound for eliciting centrilobular hepatotoxicity. It can be bioactivated to the trichloromethyl radical, which causes extensive lipid peroxidation and ultimately cell death by necrosis. Overactivation of poly(ADP-ribose) polymerase-1 (PARP-1) can rapidly reduce the levels of β-nicotinamide adenine dinucleotide and adenosine triphosphate and ultimately promote necrosis. The aim of this study was to determine whether inhibition of PARP-1 could decrease CCl(4)-induced hepatotoxicity, as measured by degree of poly(ADP-ribosyl)ation, serum levels of lactate dehydrogenase (LDH), lipid peroxidation, and oxidative DNA damage. For this purpose, male ICR mice were administered intraperitoneally a hepatotoxic dose of CCl(4) with or without 6(5H)-phenanthridinone, a potent inhibitor of PARP-1. Animals treated with CCl(4) exhibited extensive poly(ADP-ribosyl)ation in centrilobular hepatocytes, elevated serum levels of LDH, and increased lipid peroxidation. In contrast, animals treated concomitantly with CCl(4) and 6(5H)-phenanthridinone showed significantly lower levels of poly(ADP-ribosyl)ation, serum LDH, and lipid peroxidation. No changes were observed in the levels of oxidative DNA damage regardless of treatment. These results demonstrated that the hepatotoxicity of CCl(4) is dependent on the overactivation of PARP-1 and that inhibition of this enzyme attenuates the hepatotoxicity of CCl(4).

Figure 1

Serum LDH activity for control (S, D, P) and treated (C, C + P) male ICR mice 24 h after treatment. n = 4 for PBS (S), DMSO (D), and 6(5H)-phenanthridinone (P); n =10 for CCl₄ (C) and CCl₄ plus 6(5H)-phenanthridinone (C + P). Results are expressed as the mean ± the standard deviation. *Indicates a statistically significant difference from controls (P<0.05). **Indicates a statistically significant difference between CCl₄ and CCl₄ plus 6(5H)-phenanthridinone treated animals (P<0.05).

Figure 2

Immunohistochemistry for poly(ADP-ribose) of male ICR mice treated for 24h with CCl₄. Representative photomicrograph (100×) of [A] PBS controls (S); [B] CCl₄ (C), and [C] animals co-treated with CCl₄ and 6(5H)-phenanthridinone (C + P). (See colour version of this figure online at http://www.informahealthcare.com/enz)

Figure 3

Lipid peroxidation in liver samples of male ICR mice treated with CCl₄. No statistically significant differences were detected with a P<0.05; n = 4 for PBS (S), DMSO (D), and 6(5H)-phenanthridinone (P); n = 9-10 for CCl₄ (C) and CCl₄ plus 6(5H)-phenanthridinone (C + P).

Figure 4

Oxidative DNA damage in liver samples of male ICR mice treated with CCl₄. No statistically significant differences were detected with a P<0.05; n = 4 for PBS (S), DMSO (D), and 6(5H)-phenanthridinone (P); n = 9-10 for CCl₄ (C) and CCl₄ plus 6(5H)-phenanthridinone (C + P).