Inflamation Leads to an Increase of Cholesterol's Chemical Potential in Plasma Membranes of Cultured Cells

Abstract

Our laboratory has developed a method to measure the chemical potential of cholesterol in cell membranes. We have begun to use the procedure to explore the consequences of cell inflammation on chemical potential. The chemical potential of membrane cholesterol in non-inflamed primary dermal human fibroblasts is ≈ −2.3 kBT relative to crystalline cholesterol. Treating these cells with tumor necrosis factor (TNF-α) for 72 hr results in an increase of the chemical potential. This increase occurs in a dose-dependent manner: modest for 10 ng/ml TNF-α, about 0.8 kBT greater for 20 ng/ml, and only slightly greater for 40 ng/ml. Simultaneous treatment with TNF-α and 50 nM of the anti-inflammatory agent dexamethasone abolishes the increase in the chemical potential of cholesterol caused by TNF-α alone. Using 5 ng/ml of interleukin-1β, instead of TNF-α, as a pro-inflammatory agent also resulted in a rise of chemical potential. But the effect was less than that induced by TNF-α; the increase was ≈ 0.5 kBT. These results indicate a possible causative relation between cell inflammation and the chemical potential of plasma membrane cholesterol. Supported by R01 GM101539.