Fig. 5.

Accumulation of lipids in lysosomes isolated from THP-1 macrophages incubated with aggLDL and/or VLDL. THP-1 macrophages were treated for 6 days at 37°C in RPMI containing 1% FBS and TPA (50 ng/ml) alone or with 100 μg protein/ml of aggLDL and/or VLDL. The cells were harvested following 6 day lipid accumulation and lysosomes were isolated. The lysosomal lipid levels were determined as described in Materials and Methods. A: Incubation of cells with aggLDL produced a significant increase (P < 0.05) in the total cellular cholesterol that was seen primarily as increase in CE. In contrast, incubation of cells with VLDL did not produce an increase in lysosomal sterol. Importantly, coincubation of THP-1 with both VLDL and aggLDL limited significantly reduced the amount of CE found in lysosomes. B: Incubation of THP-1 with aggLDL and VLDL together significantly increased (P < 0.05) the amount of TG accumulating within lysosomes. Values are the mean ± SEM for three experiments.