Recent studies have suggested that exogenously administered carbon monoxide (CO) is beneficial for resolution of acute inflammation. Severe acute pancreatitis (SAP) is an inflammatory condition which leads to a systemic inflammatory response syndrome (SIRS). In this study, we investigated the role of CO liberated from carbon monoxide releasing molecule-2 (CORM-2) in rats with SAP. SAP was induced by retrograde infusion of 5% sodium taurocholate into the pancreatobiliary duct. Forty Wistar rats were randomly divided into four groups. Sham group was given normal saline after the sham operation. SAP group was treated with normal saline after the induction of SAP. CORM-2 group was injected with CORM-2 (8 mg/kg, i.v.) after the onset of SAP. iCORM-2 group was given iCORM-2 (an inactive compound used as negative control) after SAP induction. All animals were sacrificed at 12h after the operation. Eighty rats (n=20 for each group) were monitored for 7days to observe their survival rates. In another set of experiments, the former three groups received the same treatment as mentioned above. The last group was given ZnPPIX (HO-1 inhibitor) by peritoneal injection at 1h before the administration of CORM-2 (n=10 for each group). Serum levels of amylase, tumor necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), and interleukin 10 (IL-10) as well as myeloperoxidase (MPO) activity in pancreatic tissue were determined. Histological score, mRNA expression of these cytokines, heme oxygenase-1 (HO-1) expression, HO activity, and nuclear factor kappaB (NF-kappaB)-binding activity in the pancreas were also evaluated. Our results showed that compared with SAP group, CORM-2 treatment significantly reduced the serum levels of amylase, TNF-alpha, and IL-1beta, suppressed pancreatic tissue mRNA expression of TNF-alpha and IL-1beta, and decreased MPO activity in the pancreas. In contrast with the pro-inflammatory cytokines, the serum level and pancreatic tissue mRNA expression of IL-10 were markedly increased by the injection of CORM-2. The severity of pancreatic histology and survival rate were also significantly improved by the administration of CORM-2. Treatment with CORM-2 was associated with an increase in HO-1 expression at 12h after SAP induction. Pretreatment with ZnPPIX had no effect on the production and mRNA expression of these cytokines at 12h after the development of SAP with the treatment of CORM-2 as compared to CORM-2 group. Furthermore, CORM-2 treatment inhibited the activation of NF-kappaB in the pancreas. These results indicate that CORM-2-liberated CO exerts protective effects on SAP in rats, and the beneficial effects may be due to the suppression of NF-kappaB activation and subsequent regulation of NF-kappaB-dependent expression of cytokines.
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