ABSTRACT
While angiotensin II (ang II) has been implicated in the pathogenesis of cardiac cachexia (CC), the molecules that mediate ang II's wasting effect have not been identified. It is known TNF-α level is increased in patients with CC, and TNF-α release is triggered by ang II. We therefore hypothesized that ang II induced muscle wasting is mediated by TNF-α. Ang II infusion led to skeletal muscle wasting in wild type (WT) but not in TNF alpha type 1 receptor knockout (TNFR1KO) mice, suggesting that ang II induced muscle loss is mediated by TNF-α through its type 1 receptor. Microarray analysis identified cholesterol 25-hydroxylase (Ch25h) as the down stream target of TNF-α. Intraperitoneal injection of 25-hydroxycholesterol (25-OHC), the product of Ch25h, resulted in muscle loss in C57BL/6 mice, accompanied by increased expression of atrogin-1, MuRF1 and suppression of IGF-1/Akt signaling pathway. The identification of 25-OHC as an inducer of muscle wasting has implications for the development of specific treatment strategies in preventing muscle loss.
Subject(s)
Glycogen Synthase Kinase 3 beta/metabolism , Muscle, Skeletal/metabolism , Muscular Atrophy/metabolism , Signal Transduction , Angiotensin II , Animals , Blotting, Western , Cell Line , Cells, Cultured , Gene Expression Profiling/methods , Glycogen Synthase Kinase 3 beta/antagonists & inhibitors , Hydroxycholesterols , Insulin-Like Growth Factor I/genetics , Insulin-Like Growth Factor I/metabolism , Male , Mice, Inbred C57BL , Mice, Knockout , Muscle Proteins/genetics , Muscle Proteins/metabolism , Muscle, Skeletal/drug effects , Muscle, Skeletal/pathology , Muscular Atrophy/chemically induced , Muscular Atrophy/prevention & control , Myoblasts/cytology , Myoblasts/metabolism , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Receptors, Tumor Necrosis Factor, Type I/genetics , Receptors, Tumor Necrosis Factor, Type I/metabolism , Reverse Transcriptase Polymerase Chain Reaction , SKP Cullin F-Box Protein Ligases/genetics , SKP Cullin F-Box Protein Ligases/metabolism , Steroid Hydroxylases/genetics , Steroid Hydroxylases/metabolism , Thiadiazoles/pharmacology , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/metabolismABSTRACT
The aim of this study was to identify biomarkers for gastric cancer (GC) by iTRAQ. Using proteins extracted from a panel of 4 pairs of gastric adenocarcinoma samples (stage III-IV, Her-2 negative), we identified 10 up regulated and 9 down regulated proteins in all four pairs of GC samples compared to adjacent normal gastric tissue. The up regulated proteins are mainly involved in cell motility, while the down regulated proteins are mitochondrial enzymes involved in energy metabolism. The expression of three up regulated proteins (ANXA1, NNMT, fibulin-5) and one of the down regulated proteins (UQCRC1) was validated by Western Blot in 97 GC samples. ANXA1 was up regulated in 61.36% of stage I/II GC samples compared to matched adjacent normal gastric tissue, and its expression increased further in stage III/IV samples. Knockdown of ANXA1 by siRNA significantly inhibited GC cell migration and invasion, whereas over expression of ANXA1 promoted migration and invasion. We found decreased expression of UQCRC1 in all stages of GC samples. Our data suggest that increased cell motility and decreased mitochondrial energy metabolism are important hallmarks during the development of GC.