Caspase-1 inhibition alleviates acute renal injury in rats with severe acute pancreatitis.

Aim: To assess the effect of inhibition of caspase-1 on acute renal injury in rats with severe acute pancreatitis (SAP).

Methods: Forty-two Sprague-Dawley rats were randomly divided into three groups: healthy controls (HC, n = 6), SAP rats treated with saline (SAP-S, n = 18), or SAP rats treated with a caspase-1/interleukin (IL)-1β-converting-enzyme (ICE) inhibitor (SAP-I-ICE, n = 18). SAP was induced by retrograde infusion of 5% sodium taurocholate into the bile-pancreatic duct. HC rats were subjected to identical treatment and surgical procedures without sodium taurocholate. Rats received an intraperitoneal injection of isotonic saline (SAP-S) or the inhibitor (SAP-ICE-I) at 2 and 12 h after induction of acute pancreatitis. Surviving rats were sacrificed at different time points after SAP induction; all samples were obtained and stored for subsequent analyses. The levels of blood urea nitrogen (BUN) and creatinine (Cr) were measured using automatic methods, and serum IL-1β concentrations were measured by an enzyme-linked immunosorbent assay. Intrarenal expression of IL-1β, IL-18 and caspase-1 mRNAs was detected by RT-PCR. IL-1β protein expression and the pathologic changes in kidney tissues were observed by microscopy after immunohistochemical or hematoxylin and eosin staining, respectively.

Results: The serum levels of BUN and Cr in the SAP-S group were 12.48 ± 2.30 mmol/L and 82.83 ± 13.89 μmol/L at 6 h, 23.53 ± 2.58 mmol/L and 123.67 ± 17.67 μmol/L at 12 h, and 23.60 ± 3.33 mmol/L and 125.33 ± 21.09 μmol/L at 18 h, respectively. All were significantly increased compared to HC rats (P < 0.01 for all). Levels in SAP-ICE-I rats were significantly decreased compared to SAP-S rats both at 12 and 18 h (P < 0.01 for all). Serum IL-1β levels in the SAP-S group were 276.77 ± 44.92 pg/mL at 6 h, 308.99 ± 34.95 pg/mL at 12 h, and 311.60 ± 46.51 pg/mL at 18 h; all significantly higher than those in the HC and SAP-ICE-I groups (P < 0.01 for all). Intrarenal expression of IL-1β mRNA was weak in HC rats, but increased significantly in SAP-S rats (P < 0.01). ICE inhibition significantly decreased the expression of IL-1β and IL-18 mRNAs (P < 0.05 for all vs SAP-S), whereas caspase-1 mRNA expression was not significantly different. Weak IL-1β immunostaining was observed in HC animals, and marked staining was found in the SAP-S group mainly in renal tubular epithelial cells. IL-1β immunostaining was significantly descended in SAP-ICE-I rats compared to SAP-S rats (P < 0.05). Caspase-1 inhibition had no effect on the severity of kidney tissue destruction.

Conclusion: The expression of caspase-1-activated cytokines IL-1β and IL-18 plays a pivotal role in acute renal injury in rats with experimental SAP. Caspase-1 inhibition improves renal function effectively.