effect of pinocembrin on thymocyte proliferation and death

Introduction: cell volume regulation is critical for cellular proliferation and death. pinocembrin effectively suppresses the volume regulation in thymocytes under hypoosmotic stress by blocking the volume-sensitive anion channel. this study aims to evaluate the effects of this flavonoid on thymocyte proliferation and death. methods: thymocytes were cultured in rpmi-1640 medium supplemented with 10% fetal bovine serum, and the cell number was determined by cloud-based automated cell counting (corning). necrotic and apoptotic cell death were evaluated by propidium iodide- and annexin v-staining, respectively. results: pinocembrin at 10–50 μm caused suppression of primary cultured thymocyte proliferation with a half-maximal effect of 28.4 ± 0.2 μm. the cell counts did not fall below the control level at the doses of 100–150 μm. the fraction of spontaneously necrotic cells was ~26% of the total population and increased to ~51% in the presence of dexamethasone. the fraction of spontaneously apoptotic cells increased by this glucocorticoid from 3.6% to 16.7%. pinocembrin protected thymocytes from necrosis both in spontaneous and dexamethasone-induced death, reducing the fraction of necrotic cells by ~40–50% at 150 μm. pinocembrin attenuated dexamethasone-induced apoptotic death, reducing the fraction of annexin-positive cells to the control (spontaneous) level. conclusion: our results suggest that pinocembrin arrests thymocyte proliferation without essential killing. under conditions of massive death (e.g., during inflammation, when the level of glucocorticoids increases sharply both physiologically and as a result of pharmacotherapy), pinocembrin protects immuno-competent cells from necrotic and apoptotic death.