Elimination of cholesterol ester accumulated in foam cells by adenovirus-mediated overexpression of hormone-sensitive lipase.

Hiroaki Okazaki, Jun-ichi Osuga, Yoshiaki Tamura, Tetsuya Kitamine, Sachiko Tomita, Yoko Iizuka, Naoya Yahagi, Ken Ohashi, Kazuhisa Tsukamoto, Shun Ishibashi

Hormone-sensitive lipase (HSL) is a multifunctional enzyme that catalyzes the hydrolysis of cholesterol ester (CE) and triacylglycerol. Here we showed the nearly complete elimination of CE accumulated in THP-1 macrophage-derived foam cells by adenovirus-mediated overexpression of HSL. THP-1 cells were loaded with cholesterol ester by incubation with 100 ug/ml acetylated LDL (Ac-LDL) for 24 hours. Thereafter we infected these cells with recombinant adenovirus carrying HSL (Ad-HSL) at a dose of 100 MOI for 3 days. The cells infected with Ad-HSL showed a 127-fold increase in neutral cholesterol ester hydrolase activity compared to the Ad-LacZ infected cells which is used as a control (3.5 445.7 pmol/min/mg protein). As a result, CE contents, measured by enzymatic fluorometric assay, were markedly decreased in the Ad-HSL infected cells (120.3 } 7.0 14.1 } 9.6 nmol/mg protein), but there was no significant difference in free cholesterol content between two groups. Consistently, CE formation from 14C-oleate was significantly decreased in Ad-HSL infected cells (759.7 } 193.5 94.3 } 13.3 nmol/ mg protein). To clarfify the mechanism by which Ad-HSL eliminates CE, we first examined the uptake and degradation of 125I-AcLDL. Ad-HSL infected cells showed 50.8 % decreased degradation of 20 ug/ml 125I-AcLDL (345.4 } 21.9 169.9 } 3.5 ng/mg protein/hr). Next we examined the cholesterol efflux from cells incubated with 3H-cholesterol-loaded Ac-LDL, and revealed 2.1-fold increased rate of cholesterol efflux in Ad-HSL infected cells. In conclusion, Ad-HSL eliminates cholesterol ester almost completely from foam cell THP-1 cells, that was achieved by inhibiting lipoprotein uptake, and promoting hydrolysis and efflux. These results suggest that Ad-HSL can be used to achieve regression of atherosclerotic foam cell lesion.