Leptin induced MCP-1 secretion is decreased by JAK-2, ERK, PI3K, and Akt inhibitors. The Sca-1+/CD45-/CD34+ cells from ob/ob mice were seeded as 1 × 106/ml/well in a 24-well culture plate and pretreated with or without 50 μM of the JAK 2 inhibitor AG490, 0.5 μM of the JAK2 inhibitor JAK inhibitor I, 10 μM of the ERK inhibitor U-0126, 200 μM of the PI3 Kinase inhibitor LY294002, and 10 μM of the Akt inhibitor Akt inhibitor IV for 1 h. After 1h pretreatment, cell culture media were removed and cells were treated with leptin (1000 ng/ml) in media containing the same concentration of inhibitor for additional 24h. The supernatants were collected and determined by MCP-1 ELISA. Data are expressed as mean ± SD. **p<0.01 compared to the value for untreated control cultures. ##p<0.01 compared to the value for cultures subjected to leptin without inhibitor pretreatment.