Transient High Pressure in Pancreatic Ducts Promotes Inflammation and Alters Tight Junctions via Calcineurin Signaling in Mice.

Abstract

Pancreatitis after endoscopic retrograde cholangiopancreatography (PEP) is thought to be provoked by pancreatic ductal hypertension, via unknown mechanisms. We investigated the effects of hydrostatic pressures on the development of pancreatitis in mice. We performed studies with Swiss Webster mice, B6129 mice (controls), and B6129 mice with disruption of the protein phosphatase 3, catalytic subunit, βisoform gene (Cnab^-/- mice). Acute pancreatitis was induced in mice by retrograde biliopancreatic ductal or intraductal infusion of saline with a constant hydrostatic pressure while the proximal common bile duct was clamped -these mice were used as a model of PEP. Some mice were given pancreatic infusions of adeno-associated virus 6-nuclear factor of activated T-cells-luciferase to monitor calcineurin activity or the calcineurin inhibitor FK506. Blood samples and pancreas were collected at 6 and 24 hours and analyzed by enzyme-linked immunosorbent assay, histology, immunohistochemistry, or fluorescence microscopy. Ca²⁺ signaling and mitochondrial permeability were measured in pancreatic acinar cells isolated 15 minutes after PEP induction. Ca²⁺-activated phosphatase calcineurin within the pancreas was tracked in vivo over 24 hours. Intraductal pressures of up to 130 mm Hg were observed in the previously reported model of PEP; we found that application of hydrostatic pressures of 100 and 150 mm Hg for 10 minutes consistently induced pancreatitis. Pancreatic tissues had markers of inflammation (increased levels of interleukin [IL] 6, IL1B, and tumor necrosis factor), activation of signal transducer and activator of transcription 3, increased serum amylase and IL6, and loss of tight junction integrity. Transiently high pressures dysregulated Ca²⁺ processing (reduced Ca²⁺ oscillations and an increased peak plateau Ca²⁺ signal) and reduced the mitochondrial membrane potential. We observed activation of pancreatic calcineurin in the pancreas in mice. Cnab^-/- mice, which lack the catalytic subunit of calcineurin, and mice given FK506 did not develop pressure-induced pancreatic inflammation, edema, or loss of tight junction integrity. Transient high ductal pressure produces pancreatic inflammation and loss of tight junction integrity in a mouse model of PEP. These processes require calcineurin signaling. Calcineurin inhibitors might be used to prevent acute pancreatitis that results from obstruction.