Protective properties of 2-acetylcyclopentanone in a mouse model of acetaminophen hepatotoxicity.

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-p-benzoquinone 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.

Bone protective effect of simvastatin in experimental arthritis.

OBJECTIVE: Emerging evidence suggests that clinically important antiinflammatory effects of HMG-CoA reductase inhibition may extend beyond cardiovascular disease to other inflammatory disorders, such as rheumatoid arthritis (RA). Protective bone-specific anabolic and antiresorptive effects of HMG-CoA reductase inhibitors have also been evaluated in normal and osteoporotic bone. The specific effect of statins on inflammation-induced bone loss has not previously been a focus of evaluation. We investigated whether simvastatin, a potent HMG-CoA reductase inhibitor, alters bone turnover in an animal model of RA, thus preventing periarticular bone loss. METHODS: Hydrolyzed simvastatin (20 mg/kg/day) was administered subcutaneously to female Lewis rats 4 days before or 8 days after induction of arthritis by intraperitoneal injection of streptococcal cell wall or vehicle. Effects of simvastatin (vs vehicle) on periarticular bone, assessed by bone mineral density (BMD), biochemical markers of bone turnover, and joint histology, were determined. Effects on joint swelling were assessed clinically and histologically. RESULTS: Simvastatin prevented early and late joint inflammation in association with a decrease in articular macrophage influx. Simvastatin suppressed the periarticular bone destruction occurring late in the course of disease, preserving periarticular BMD and preventing increases in periarticular osteoclasts and serum pyridinoline levels in arthritic animals, while having no effect on these measures in normal animals. Osteocalcin levels, which were decreased in arthritic animals, were unaltered by statin treatment. CONCLUSION: Our results suggest that inhibition of HMG-CoA reductase may be therapeutically useful in preserving periarticular bone in RA joints via suppression of inflammation-induced bone resorption.

Parathyroid hormone-related protein induction in focal stroke: a neuroprotective vascular peptide.

Parathyroid hormone-related protein (PTHrP) is a multifunctional peptide that enhances blood flow in non-central nervous system (CNS) vascular beds by causing vasodilation. PTHrP expression is induced in non-CNS organs in response to ischemia. Experiments were therefore undertaken to determine whether PTHrP can be induced in brain in response to ischemic injury and whether PTHrP can act locally as a vasodilator in the cerebral vasculature, an effect that could be neuroprotective in the setting of stroke. PTHrP expression was examined by Northern analysis and immunohistochemical staining in male Sprague-Dawley rats subjected to permanent middle cerebral artery occlusion (MCAO). Vasodilatory effects of superfused PTHrP(1-34) on pial arterioles were determined by intravital fluorescence microscopy. Effects of PTHrP(1-34) peptide administration on MCAO infarction size reduction were assessed. PTHrP expression was induced in the ischemic hemisphere as early as 4 h after MCAO and remained elevated for up to 24 h. Increased immunoreactive PTHrP at sites of ischemic tissue injury was located in the cerebral microvessels. Superfusion with PTHrP(1-34) peptide for up to 25 min increased pial arteriolar diameter by 30% in normal animals. In animals with permanent MCAO, PTHrP(1-34) peptide treatment significantly decreased cortical infarct size (-47%). In summary, PTHrP expression increases at sites of ischemic brain injury in the cerebrovasculature. This local increase in PTHrP could be an adaptive response that enhances blood flow to the ischemic brain, thus limiting cell injury.