Dexamethasone mediates protection against acute pancreatitis via upregulation of pancreatitis-associated proteins

AIM: To examine the influence of dexamethasone on pancreatitis-associated protein (PAP) gene expression using both in vitro and in vivo models of acute pancreati- tis and to study how PAP gene expression correlates with severity of pancreatitis. METHODS: In vitro, IL-6 stimulated pancreas acinar AR42J cells were cultured with increasing concentrations of dexamethasone and assayed for PAP expression (RT-PCR). In vivo , pancreatitis was induced in rats by retrograde injection of 40 g/L taurocholate into the pancreatic duct. Animals were pretreated with dexamethasone (2 mg/kg) daily or saline for 4 d. Pancreata and serum were harvested after 24 h and gene expression levels of PAPⅠ, Ⅱ and Ⅲ were measured by RT-PCR. Severity of pancreatitis was based on serum amylase, pancreatic wet weight, and histopathological score. RESULTS: In vitro, dexamethasone and IL-6 induced a marked transcription of PAPⅠ, Ⅱ and Ⅲ genes in AR42J cells at 24 h (P < 0.05 for all comparisons). In vivo, pancreas mRNA levels of PAPⅠ, Ⅱ or Ⅲ increased by 2.6-fold, 1.9-fold, and 1.3-fold respectively after dexa- methasone treatment, compared with saline treated ani- mals. Serum amylase levels and edema were significantly lower in the dexamethasone group compared with the saline group. Histopathologic evaluation revealed less inflammation and necrosis in pancreata obtained from dexamethasone treated animals (P < 0.05). CONCLUSION: Dexamethasone significantly decreases the severity of pancreatitis. The protective mechanism ofdexamethasone may be via upregulating PAP gene ex- pression during injury.

Pancreatic regenerating protein (regⅠ) and regⅠreceptor mRNA are upregulated in rat pancreas after induction of acute pancreatitis

AIM: Pancreatic regenerating protein (regⅠ) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal andβ-cells. This suggests that regⅠand its receptor may play a role in recovery after pancreatic injury. We hypothesized that regⅠand its receptor are induced in acute pancreatitis. METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 hours after injection and from normal controls (4 rats/group). RegⅠreceptor mRNA, serum regⅠprotein, and tissue regⅠprotein levels were determined by Northern analysis, enzyme-linked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in regⅠand its receptor. RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no statistically significant change in serum regⅠconcentrations from controls. However, Western blot demonstrated increased tissue levels of regⅠat 24 and 36 h. This increase was localized primarily to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in regⅠreceptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells. CONCLUSION: Acute pancreatitis results in increased tissue regⅠprotein levels localized to the acinar and ductal cells, and a parallel threefold induction of regⅠreceptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg I and its receptor may be important for recovery from acute pancreatitis.

Acute pancreatitis in aging animals:Loss of pancreatitis-associated protein protection?

AIM:To investigate the effect of age on severity of acute pancreatitis(AP) using biochemical markers,histology and expression of the protective pancreatitisassociated proteins(PAPs).METHODS:AP was induced via intraductal injection of 4% sodium taurocholate in young and old rats.Sera and pancreata were assayed at 24 h for the parameters listed above;we also employed a novel molecular technique to assess bacterial infiltration using polymerase chain reaction to measure bacterial genomic ribosomal RNA.RESULTS:At 24 h after induction of AP,the pancreata of older animals had less edema(mean ± SE histologic score of young vs old:3.11 ± 0.16 vs 2.50 ±-0.11,P < 0.05),decreased local inflammatory response(histologic score of stromal infiltrate:3.11 ± 0.27 vs 2.00 ± 0.17,P < 0.05) and increased bacterial infiltration(174% ± 52% increase from sham vs 377% ± 4%,P < 0.05).A decreased expression of PAP1 and PAP2 was demonstrated by Western blotting analysis and immunohistochemical staining.There were no differences in serum amylase and lipase activity,or tissue myeloperoxidase or monocyte chemotactic protein-1 levels.However,in the most-aged group,serum C-reactive protein levels were higher(young vs old:0.249 ± 0.04 mg/dL vs 2.45 ± 0.68 mg/dL,P < 0.05).CONCLUSION:In older animals,there is depressed PAP expression related to a blunted inflammatory response in AP which is associated with worsened bacterial infiltration and higher C-reactive protein level;this may explain the more aggressive clinical course.