Identification of mouse and human macrophages as a site of synthesis of hepatic lipase

Hepatic lipase (HL) is synthesized by the liver and is also present in steroidogenic tissues. As both a lipolytic enzyme and a ligand that facilitates the cellular uptake of lipoproteins, HL plays a major role in lipoprotein metabolism and may modulate atherogenic risk. However, HL has not been directly implicated in lesion development. In the present study we demonstrate that HL is also synthesized by mouse and human macrophages. Northern analysis and real time RT-PCR showed that HL mRNA is present in mouse peritoneal macrophages, RAW-264.7, and IC-21 cells. The levels of HL mRNA in mouse peritoneal macrophages were approximately 10-30% that of mouse liver. HL protein was identified by Western blot analyses in human monocyte-derived macrophages, THP, RAW-264.7, and mouse peritoneal macrophages following fractionation by heparin-sepharose affinity chromatography. These combined findings establish that HL is synthesized de novo by macrophages as well as liver, and raises the possibility that HL may have a direct role in the pathogenesis of atherosclerosis.