Effect of phospholipase A2 silencing on acute experimental pancreatitis.

BACKGROUND AND OBJECTIVES The group II phospholipase A2 (PLA2 II) in blood has been reported to increase in acute pancreatitis and to reflect the severity of pancreatitis. Here we investigated the effect of inhibition of PLA2 using siRNA gene knockdown in vitro and in an in vivo model of experimental pancreatitis. MATERIALS AND METHODS Pancreatic acinar cell line AR42J in vitro was cultured with lysophosphatidylcholine (lyso-PC) (50 uM) to induce expression of PLA2 with subsequent transfection of siRNA into stimulated AR42J cells. Acute pancreatitis in vivo was induced in Sprague Dawley rats by retrograde infusion of 4% sodium taurocholate (NaT) into the pancreatic duct. PLA2 II -specific siRNA was subsequently administrated, subcapsularly, after infusion of NaT. Controls included administration of scrambled siRNA (SC-RNA) or vehicle alone. After 24hr, pancreata were harvested and assessed for worsening pancreatitis by histopathology; The serum levels of PLA2 II and inflammatory mediators were analyzed. In both models endogenous PLA2 II gene expression was assessed at 24 hrs using real time RT-PCR. RESULTS In vitro, PLA2 II protein and mRNA levels were reduced in cells treated with PLA2-II siRNA when compared with control treatment. In vivo, induction of pancreatitis was confirmed by histopathology, inflammatory mediators such as the tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6 and IL-8. PLA2 expression were reduced 69% in siRNA treated rats, compared with controls. Serum inflammatory mediators levels decreased after administration of siRNA compared with vehicle control (p < 0.05,respectively). CONCLUSIONS siRNA mediated gene knockdown of PLA2-II appeared to relieve pancreatitis severity. PLA2-II may serve as a novel and effective therapeutic target for acute pancreatitis.