Protective Properties of 2-Acetylcyclopentanone in a Mouse Model of Acetaminophen Hepatotoxicity

Abstract

Our previous research showed that enolates formed from 1,3-dicarbonyl compounds, such as 2-acetylcyclopentanone (2-ACP), could provide protection in cell culture models from electrophile-or oxidative stress-induced toxicity. In the present study, we evaluated the protective abilities of 2-ACP in a mouse model of acetaminophen (APAP) hepatotoxicity. Results show that oral APAP overdose (500 mg/kg) was nearly 90% lethal within 72 hours and that the resulting hepatotoxicity was associated with substantial changes in plasma liver enzyme activities, histopathological indices, and markers of hepatocyte oxidative stress. 2-ACP administered intraperitoneally 20 minutes before APAP completely prevented lethality over a 7-day observation period. This effect was dose-dependent (0.80-2.40 mmol/kg) and was correlated with normalization of measured parameters. Nearly complete protection was afforded when 2-ACP was administered 20 minutes post-APAP, but not 60 minutes after intoxication. Although intraperitoneal administration of N-acetylcysteine (NAC) was not effective over a broad dose range (2.40-7.20 mmol/kg), temporal studies indicated that intraperitoneal NAC was hepatoprotective when injected 60 minutes after APAP intoxication. Because of a loss of function in stomach acid, oral administration of 2-ACP was associated with modest APAP protection. In contrast, NAC administered orally provided dose-dependent (0.80-2.40 mmol/kg) protection against APAP hepatotoxicity. In chemico studies and quantum mechanical calculations indicated that 2-ACP acted as a surrogate nucleophilic target for the reactive electrophilic APAP metabolite N-acetyl-pbenzoquinone imine. Our findings suggest that 2-ACP or a derivative might be useful in treating acquired toxicities associated with electrophilic drugs and metabolites or environmental toxicants.

Enolate-Forming Phloretin Pharmacophores: Hepatoprotection in an Experimental Model of Drug-Induced Toxicity

“…APAP and all experimental compounds were administered in phosphatebuffered polyethylene glycol. Previous studies demonstrated that this vehicle did not affect the experimental outcome (Zhang et al, 2013). As a general protocol, groups of mice (n 5 10-15) were pretreated by intraperitoneal injection (10 ml/kg; THA, 0.2-0.8 mmol/kg; PG, 0.4-2.4 mmol/kg) or oral administration (6 ml/kg; THA, 0.8-2.4 mmol/kg; PG, 0.8 and 2.4 mmol/kg) of putative hepatoprotectant followed 20 minutes later by oral (4 ml/kg) APAP (500 mg/kg).…”

“…A separate group of animals were given vehicle by intraperitoneal injection or oral administration followed 20 minutes later by oral APAP. To define the temporal limitations of hepatoprotection, groups of mice were treated with oral APAP (500 mg/kg) followed Enolate-Forming Compounds Prevent Acetaminophen Toxicity 60 minutes later by intraperitoneal or oral administration of putative protectant (Zhang et al, 2013). Control mice received an intraperitoneal/ oral sequence of vehicle injections.…”

“…An assessment of general toxicity was conducted at 2-day intervals over a 7-day postintoxication period. Specifically, animals were weighed and assessed by a blinded observer for changes in grooming, nest building, open field behavior, recumbency, and gait (Zhang et al, 2013). Kaplan-Meier survival curves were used to illustrate the cumulative percent daily lethality of mice in different experimental groups and were generated in Prism 6.0 software (GraphPad Software Inc., La Jolla, CA; see Zhang et al, 2013 with 25 mM HEPES, heat-inactivated horse serum, 10 IU/ml heparin, and 500 IU/ml penicillin G at 37°C in a humidified atmosphere of 95% O 2 /5% CO 2 .…”

“…1A) prevented lethality in a mouse model of APAP overdose. This protection was associated with inhibition of APAP-induced derangement of histologic (e.g., hepatocyte necrosis) and biochemical (e.g., GSH depletion; plasma appearance of liver enzymes) indices of hepatotoxicity (Zhang et al, 2013). 2-ACP is a 1,3-dicarbonyl (b-diketone) compound that can ionize in solution (Table 1) to form a nucleophilic enolate that binds and thereby detoxifies pathogenic electrophiles (e.g., NAPQI, 4-hydroxy-2-nonenal).…”

“…2-ACP is a 1,3-dicarbonyl (b-diketone) compound that can ionize in solution (Table 1) to form a nucleophilic enolate that binds and thereby detoxifies pathogenic electrophiles (e.g., NAPQI, 4-hydroxy-2-nonenal). The enolate can also chelate metal ions such as those involved in free-radical generating Fenton chemistry (LoPachin et al, 2011;Zhang et al, 2013). That enolate-forming 1,3-dicarbonyl compounds might be cytoprotective stems from the recognition that the central bridge of curcumin contains a 1,3-dicarbonyl group (Fig.…”