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

Abstract

Aim: To examine the influence of dexamethasone on pancreatitis-associated protein (PAP) gene expression using both in vitro and in vivo models of acute pancreatitis 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 PAP I, 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 PAP I, II and III genes in AR42J cells at 24 h (P < 0.05 for all comparisons). In vivo, pancreas mRNA levels of PAP I, II or III increased by 2.6-fold, 1.9-fold, and 1.3-fold respectively after dexamethasone treatment, compared with saline treated animals. 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 of dexamethasone may be via upregulating PAP gene expression during injury.

Figure 1

PAP expression was upregulated by treatment of dexame-thasone and IL-6. AR42J cells were treated with indicated dose of dexamethasone (Dex) and IL-6. PAPI and II mRNA levels were determined by real-time quantitative RT-PCR analysis, using PAPI, or II-specific TaqMan primers and probe. Amount of mRNA in each group was normalized to β-actin. Results are presented as fold change in PAP I or II mRNA in treated cells relative to the levels observed in untreated/control cells and similar results were obtained with PAPIII (data not shown). Bars represent mean ± SD from 3 independent experiments (^aP < 0.05 vs untreated/control cells, ANOVA, Tukey). Insert shows representative amplification plots.

Figure 2

PAP expression was upregulated by treatment of dexamethasone and IL-6: In vitro, dexamethasone (Dex) and IL-6 induced a marked transcription of PAP I, II and III genes in AR42J cells at 24 h when compared with untreated (control) cells. Data represent fold change of untreated/unstimulated cells as determined by real-time PCR analysis (see materials and methods). Bars represent mean ± SD from 3 independent experiments (^aP < 0.05 vs controls, ANOVA, Tukey).

Figure 3

PAP expression is upregulated by dexamethasone: Rats (8/group) were treated with daily saline (white bars) or dexamethasone (grey bars) prior to pancreatitis induction. Pancreata were harvested 24 h after pancreatitis induction and PAP levels were determined by real time PCR and presented as fold change (normalized to β-actin) as described in materials and methods, and described in text as a ratio of PAP mRNA from NaT treated/saline treated pancreas mRNA (^aP < 0.05 vs saline treated controls, Student’s t-test).

Figure 4

Dexamethasone treatment decreased pancreatitis severity in vivo. Rats were treated with saline (S) or dexamethasone (D) for 4 d prior to pancreatitis induction with sodium taurocholate (NaT). Pancreata were harvested 24 h after pancreatitis induction and severity of pancreatitis was based on serum amylase (U/L), pancreatic wet weight (mg/g BW), and histopathological score. The bars represent the mean ± SD (n = 8, ^aP < 0.05 vs the saline-treated control group).