Curcumin modulates SDF-1α/CXCR4-induced migration of human retinal endothelial cells (HRECs)

PURPOSE. The stromal-derived factor (SDF)-1 alpha and the CXC receptor (CXCR)-4 jointly regulate the trafficking of various cell types and play a pivotal role in cell migration, proliferation, and survival. The purpose of this study was to assess whether curcumin inhibits human retinal endothelial cell (HREC) migration by interfering with SDF-1 alpha/CXCR4 signaling. METHODS. Primary HREC culture was established and maintained in endothelial growth medium. The viability and proliferation of HRECs were assessed by MTT and thymidine uptake assays, respectively. The effect of SDF-1 alpha-induced HREC migration ( chemotaxis) in the presence and absence of curcumin was determined using the Boyden chamber migration assay. Intracellular Ca(2+) concentration was measured by fluorometric analysis. Immunofluorescence and Western blot analyses were performed to quantify CXCR4, phosphorylated AKT, and PI3- kinase expression levels. RESULTS. HREC migration increased in a dose-dependent manner (1, 10, 50, and 100 ng/mL; P < 0.001) in SDF-1 alpha-treated cells. In contrast, AMD3100, an inhibitor of CXCR4 effectively inhibited HREC migration dose dependently. HREC migration was decreased when the cells were exposed to EGTA, a chelator of Ca(2+). Curcumin also blocked Ca(2+) influx, an important signal for HREC migration. In addition, curcumin significantly (P < 0.001) decreased SDF-1 alpha-induced HRECs migration and downregulated SDF-1 alpha-induced expression of CXCR4, phospho-AKT, phospho-phosphatidylinositol-3-kinase ( PI3- K), and eNOS. CONCLUSIONS. This study indicates that curcumin has an inhibitory effect on SDF-1 alpha-induced HREC migration. The plausible mechanism of action could be upstream blockage of Ca(2+) influx and the downstream reduction of PI3-K/AKT signals.