Proteome Analysis of the Anti-inflammatory Response of Flavonoids Isolated from Korean Citrus aurantium L. in Lipopolysaccharide-Induced L6 Rat Skeletal Muscle Cells

Skeletal muscle is an important organ in our body and a dynamic composite of proteins. Citrus aurantium L. has been widely used in oriental medicine in Eastern Asia for a long time. It contains over 100 bioactive compounds and flavonoids that regulate the inflammatory response and tumorigenesis, through various mechanisms. In the present study, we investigated changes in the protein pattern using two-dimensional electrophoresis (2-DE) and matrix assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF/MS) to assess the anti-inflammatory effect of flavonoids isolated from Korean C. aurantium L. in lipopolysaccharide (LPS)-induced L6 cells. L6 skeletal muscle cells were pretreated with flavonoids for 1 h and stimulated with LPS for 24 h. Proteins from the L6 cells of the control, LPS treated and flavonoid treated groups were extracted and resolved by 2-DE using pH 4-7 IPG strips loaded with 150 mu g of protein. Forty-one differentially expressed protein spots were identified (more than two-fold was considered significant, p < 0.05), and 18 were detected by MALDI-TOF/MS. These results suggest that proteomics can be used to identify changes in the expression of marker proteins and the anti-inflammatory effect of flavonoids isolated from Korean C. aurantium L.