The Machanism Of Palmitic Acid Induced Inflammation On Pancreatic Acinar Cells Via NF-κB Pathway

Background and Objective: Acute pancreatitis(AP)is an inflammatory disease mediated by damage to acinar cells and subsequent pancreatic inflammation with recruitment of leukocytes.Hypertriglyceridemia(HTG)is an independent factor in the pathogenesis of acute pancreatitis,whereas the precise mechanism has not been illustrated.This study aims to investigate the mechanism of acinar cell inflammation and its role in leucocytes recruitment in HTG-related AP.Methods: HTG rats were induced by high-fat diet(HFD)and AP model was induced by intraperitoneal injection of caerulein.Blood samples and pancreatic tissues were obtained for biochemistry and histology examination to assess the severity of pancreatitis.Palmitic acid(PA)was added to the isolated rat pancreatic acinar cells(PACs)to investigate the effect of HTG on PACs in-vitro.The infiltration of macrophages in pancreas was determined by fluorescent analysis.The effect of PA on macrophage chemotaxis was determined by the transwell system in which PACs were co-incubated with macrophages.Results: HTG aggravated pancreatic injury in caerulein-induced AP rats with more severe pancreatic histological injuries and higher plasma amylase activity.Endoplasmic reticulum(ER)stress and inflammatory responses were inducted in PACs after exposure to PA.PA-induced inflammatory responses were inhibited by pre-incubation with ER stress inhibitor 4-PBA,while induced with ER stress inducer thapsigargin stimulation alone.PA stimulation induced C/EBPβ and C/EBPα in PACs,which could be inhibited by 4-PBA pre-incubation and be induced by thapsigargin stimulation alone.Knockdown of C/EBPβ by si RNA transfection inhibited PAC inflammation and C/EBPα induction but exerted no effect on ER stress.An increase of CD68 positive macrophages in pancreas was detected in the caerulein induced AP rats and this increase was further aggravated in HTG pancreatitis ones.In a co-culture system of PACs with bone marrow derived macrophages,PA significantly induced chemotaxis of macrophages towards acinar cells.Both m RNA and protein expression levels of monocyte chemotactic protein 1(MCP-1)were elevated in the pancreas and protein level was elevated in the plasm in AP rats,and this response was further aggravated in the HTG pancreatitis ones.The expression and release of MCP-1 was also significantly elevated in PA-stimulated acinar cells.Neutralizing antibody against MCP-1 inhibited the chemotaxis of macrophages towards acinar cells.NF-κB inhibitor Bay11-7089 reduced the PA-induced MCP-1 m RNA expression level in PACs and the chemotaxis of macrophages towards acinar cells.MCP-1 also acted as a regulator of NF-κB pathway in PACs.ER stress inhibitor 4-PBA decreased the expression of MCP-1 in PACs and inhibited the chemotaxis of macrophages towards acinar cells.ER stress inducer thapsigargin induced the expression of MCP-1 in PACs and the chemotaxis of macrophages towards acinar cells.Inhibition of C/EBPβ with si RNA transfection inhibited the production and release of MCP-1 in PACs.Conclusions: HTG/PA aggravates PAC inflammation in vivo and in vitro.In PA-induced PAC injuries,ER stress induced inflammatory responses through induction of C/EBP family in which C/EBPβ was responsible for C/EBPα activation.PA induced the production and release of MCP-1 in acinar cells,which mediated the macrophage infiltration of the pancreas in rats with HTG pancreatitis.The induction of MCP-1 in PA-stimulated PACs presented a positive feedback which was associated with NF-κB activation via ER stress-C/EBPβ pathway.