Secretory phospholipase A2 increases SR-B1-mediated selective uptake from HDL but not biliary cholesterol secretion

High density lipoprotein cholesterol represents a major source of biliary cholesterol. Secretory phospholipase A(2) (sPLA(2)) is an acute phase enzyme mediating decreased plasma HDL cholesterol levels. Clinical studies reported a link between increased sPLA(2) expression and the presence of cholesterol gallstones. The aim of our study was to investigate whether the overexpression of human sPLA(2) in transgenic mice affects biliary cholesterol secretion and gallstone formation. Liver weight (P < 0.01) and hepatic cholesterol content (P < 0.01) were significantly increased in sPLA(2) transgenic mice compared with controls as a result of increased scavenger receptor class B type I (SR-BI)mediated hepatic selective uptake of HDL cholesterol (P < 0.01), whereas hepatic SR-BI expression remained unchanged. However, biliary cholesterol secretion as well as fecal neutral sterol and fecal bile salt excretion remained unchanged in sPLA(2) transgenic mice. Furthermore, gallstone prevalence in response to a lithogenic diet was identical in both groups.jr These data demonstrate that i) increased flux of cholesterol from HDL into the liver via SR-BI as a result of phospholipase modification of the HDL particle translates neither into increased biliary and fecal sterol output nor into increased gallstone formation, and it) increased sPLA(2) expression in patients with cholesterol gallstones might be a consequence rather than the underlying cause of the disease.