Roles of secretory phospholipases A2 in inflammatory diseases and trauma

Six distinct secretory small molecular weight phospholipases A2 (PLA2) have been cloned and characterized from human tissues. Two of them, pancreatic group IB PLA2 (PLA2-IB) and synovial-type group IIA PLA2 (PLA2-IIA) have been studied as to their association to various inflammatory diseases. PLA2-IB is a digestive enzyme synthesized by pancreatic acinar cells. In acute pancreatitis, which is characterized by destruction of pancreatic tissue, PLA2-IB is released into the circulation, but its role in pancreatic and other tissue damage is still hypothetical. The concentration of PLA2-IIA increases in blood plasma in generalized inflammatory response resulting from infections, chronic inflammatory diseases, acute pancreatitis, trauma and surgical operations. PLA2-IIA is synthesized in a number of gland cells and is present in cellular secretions on mucosal surfaces including Paneth cells of intestinal mucosa, prostatic gland cells and seminal plasma, and lacrimal glands and tears. PLA2-IIA is expressed in hepatoma-derived cells in vitro and hepatocytes in vivo. PLA2-IIA is regarded as an acute phase protein and seems to function as an antibacterial agent especially effective against Gram-positive bacteria. Other putative functions in the inflammatory reaction include hydrolysis of cell membrane phospholipids and release of arachidonic acid for prostanoid synthesis.