Therapeutic application of caspase 1/interleukin-1beta-converting enzyme inhibitor decreases the death rate in severe acute experimental pancreatitis

Abstract

Objective: To assess the effect of therapeutic inhibition of interleukin 1beta-converting enzyme (ICE) in an experimental model of severe acute pancreatitis (SAP).

Summary background data: Several lines of evidence suggest that cytokines activated by ICE play an instrumental role in the course of acute pancreatitis. Recent studies have shown that pharmacologic or genetic blockade of ICE significantly ameliorates the overall severity of and the death rate in SAP.

Methods: Severe acute pancreatitis was induced by infusion of 5% sodium taurocholate in Wistar rats. A new, highly selective, irreversible inhibitor of ICE was intraperitoneally applied at a dosage of 0.25 mg every 12 hours. Control animals in group 1 received treatment with saline; in group 2 rats, ICE inhibition was started 6 hours after the onset of pancreatitis; and in group 3 rats, ICE inhibition was started 12 hours after the onset of pancreatitis. After a 7-day observation period, surviving rats were killed and blood, plasma, pancreas, lung, and liver were used for subsequent analysis.

Results: Inhibition of ICE decreased the 7-day death rate from 87.5% to 38.9% irrespective whether treatment was started 6 hours or 12 hours after induction of SAP. Morphometric analysis revealed a significant reduction of acinar cell necrosis in both treated groups, whereas pancreatitis-associated pulmonary and hepatic damage was uniformly low and not influenced by ICE inhibition. Tissue myeloperoxidase concentrations were dramatically decreased in the pancreas and the lung after either regimen of ICE inhibitor treatment. In contrast to lung and liver, marked upregulation of interleukin 1beta, tumor necrosis factor alpha, and ICE mRNA was observed in the pancreas, with levels of interleukin 1beta and tumor necrosis factor alpha being reduced in ICE-inhibited animals. Compared with nontreated rats, plasma amylase levels were higher in both treatment groups, whereas lipase and hematocrit showed no difference. Changes of the differential white blood count including neutrophils, lymphocytes, and monocytes were attenuated in both groups after ICE inhibitor treatment.

Conclusions: Pharmacologic inhibition of ICE significantly improves the overall severity of and the death rate in SAP. A substantial reduction of neutrophil-mediated tissue injury in pancreas and lung seems to contribute to the beneficial effects of this approach. Moreover, ICE inhibition is still effective after a therapeutic window of 12 hours. Based on the current findings, future studies on the clinical application of ICE-inhibiting substances in acute pancreatitis seem to be promising.

Figure 1. Morphometric assessment of the extent of acinar cell necrosis (% of total pancreatic parenchyma), pancreatic parenchyma undergoing ductal transformation (% of total pancreatic parenchyma), and remaining healthy pancreatic tissue in rats given saline (SAP-S) and interleukin-1β-converting enzyme inhibitor (SAP-ICE-I) (mean ± SEM). Healthy controls (HC) showed no morphologic changes. The extent of necrosis was significantly reduced in both treated groups (SAP-S vs. SAP-ICE-I 6 hours, P < .05; SAP-S vs. SAP-ICE-I 12 hours, P < .01), along with a significantly higher percentage of remaining viable pancreatic parenchyma in both treated groups (SAP-S vs. SAP-ICE-I 6 hours and SAP-ICE-I 12 hours, P < .02). Ductal transformation was not altered by ICE inhibition.

Figure 2. Morphologic scoring of pulmonary damage in rats given saline (SAP-S) and interleukin-1β-converting enzyme inhibitor (SAP-ICE-I) (mean ± SEM). In healthy controls (HC), moderate structural damage and inflammation were present that were not different from both treated and nontreated rats with pancreatitis.

Figure 3. Tissue myeloperoxidase (MPO) concentrations in rats given saline (SAP-S) and interleukin-1β-converting enzyme inhibitor (SAP-ICE-I) (mean ± SEM). Treatment with the ICE inhibitor significantly reduced MPO levels as an indirect marker of neutrophil tissue infiltration in pancreas (SAP-S vs. SAP-ICE-I 6 hours, P < .05; SAP-S vs. SAP-ICE-I 12 hours, P < .01) and lung (SAP-S vs. SAP-ICE-I 6 hours, P < .05; SAP-S vs. SAP-ICE-I 12 hours, P < .01), whereas MPO concentrations remained within normal limits in the liver in all groups.

Figure 4. (A) Intrapancreatic, (B) intrapulmonary, and (C) intrahepatic mRNA expression of interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), and interleukin-1β-converting enzyme (ICE) in nontreated rats (SAP-S) and rats treated with the ICE inhibitor (SAP-ICE-I) during taurocholate-induced severe acute pancreatitis. β-actin was used as internal standard. HC, healthy controls.