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2013 Abstracts

Measuring Cellular Ceramide Accrual using Immunofluorescence

Anindita Ravindran, University of Utah

Exercise and Sport Science

Obesity predisposes individuals with Type II Diabetes to cardiovascular complications such as impaired blood vessel function. Due to the elevation of free fatty acids (FFAs) in obese individuals, ceramide, a lipid metabolite, accumulates and might contribute to the inability of a blood vessel to constrict or relax appropriately. Vessel dysfunction is partly caused by the inability of the endothelium, the innermost protective lining of blood vessels, to synthesize and release nitric oxide (NO). Our data indicate that ceramide impairs endothelial NO synthase (eNOS), the enzyme that synthesizes NO. In order to study mechanisms by which ceramide might impair eNOS, it is important to measure cellular ceramide production in response to pharmacological and genetic manipulations. Previously we used P-32 radioactive assays to measure ceramide accumulation. However, the use of radioactivity is expensive, potentially hazardous, and waste disposal is an environmental concern. Therefore, I sought to import a less harmful, more cost effective, yet accurate technique of measuring ceramide production by immunofluorescence (IF). IF allows ceramide to be tagged with a primary antibody which can be detected by a secondary antibody conjugated with a fluorescent dye. I have observed that 250, 500, and 750 uM palmitate (pal) incubation for 3 h increases (p<0.05) endothelial cell ceramide accrual in a dose-dependent manner. Further, a FFA-independent method to alter ceramide accrual i.e., 3 h incubation of cells with N-oleoylethanolamine, also elevates (p<0.05) ceramide production. Importantly, I have shown that 500 uM palmitate-induced ceramide accrual can be prevented (p<0.05) by two structurally dissimilar inhibitors (10 uM myriocin, 1mM L-cycloserine) of the rate-limiting enzyme responsible for ceramide biosynthesis i.e., serine palmitoyl transferase (SPT). None of these inhibitors impairs cell viability. These data indicate that IF is an accurate and reproducible method whereby ceramide accrual can be quantified in endothelial cell systems.