COX-2 inhibition results in alterations in nuclear factor (NF)-κB activation but not cytokine production in acute pancreatitis

Acute pancreatitis is characterized by local inflammation and cytokine production, and release is thought to contribute to this process. Nuclear factor (NF)-κB activation and cytokine production are linked and inhibition of NF-κB has been shown to decrease the severity of pancreatitis. We have shown that inhibition of COX-2 ameliorates pancreatitis; however, the mechanism by which this effect occurs is unclear. Swiss Webster mice were injected intraperitoneally with either saline (control) or caerulein (CAE; 50 mg/kg) hourly for 8 hours; mice receiving CAE were further subdivided to receive saline or the cyclooxygenase-2 (COX-2) selective inhibitor (SC-58125; 10 mg, intraperitoneally) at the time of the first injection of CAE. Pancreata were harvested, histologic sections were scored, and protein was extracted to determine cytokine (interleukin [IL]-6, IL-1β) levels and NF-κB subunits by ELISA and NF-κB activation by gel shift. In addition, serum was collected for measurement of cytokines. COX-2 inhibition resulted in decreased inflammation and a decrease in NF-κB activation. IL-6 and IL-1β levels after COX-2 inhibition, however, remained elevated to levels equivalent to those of mice with histologic inflammation after CAE alone. COX-2 inhibition decreases inflammation as well as late-phase NF-κB activation but does not diminish levels of inflammatory cytokines, thus suggesting a two-phase activator of NF-κB. The attenuation of inflammation, despite unaltered cytokine levels, suggests that cytokines may not be critical for the inflammatory phase of pancreatitis.