Study on the relation among protein kinase C activity, adhesion molecules expression of irradiated vascular endothelial cells and transmigration of haemopoietic stem cells

Objective: To study the relation among protein kinase C (PKC) ,adhesion molecules expression of vascular endothelial cells irradiated by small dose of γ-rays and transmigration of haemopoietic stem cells. Methods: Human umbilical vein endothelial cells (HUVECs) were irradiated with 1-5 Gy γ-rays. The PKC activity of irradiated cells was measured by the incorporation of [γ-32P] ATP into exogenous substrate. The expression of adhesion molecules VCAM-1, PECAM-1, CD44 in irradiated HUVECs was detected by ELISA and transmigration of CD34+ haemopoietic stem cells across the irradiated HUVECs was determined by the tran swell migration assay. Results: PKC in HUVECs was activated by less than 3 Gy γ-irradiation, resulting in membranous PKC activity increasing and cytosolic PKC activity decreasing gradually. The dominant change occurred in HU-VECs irradiated by 2-3 Gy γ-rays (P<0.01). There was a decreasing trend of membranous and cytosolic activity PKC in HUVECs irradiated by more than 3 Gy γ-rays. The expressions of VACM-1, PECAM-1 and CD44 in HU-VECs irradiated by less than 3 Gy γ-rays were significantly increased compared with the results of the control group (P<0.01). The numbers of CD34+ haemopoietic stem cells migrating across the irradiated HUVECs were much higher than those in the control group (P<0.01), but monoclonal antibodies to VACM-1, PEACM-1, CD44 could depress the transmigration activity. There was a positive relation beween the PKC activity and the expression of VCAM-1, PECAM-1 and CD44 respectively. Conclusions: Optimal small dose of γ-rays could activate PKC, enhance PKC activity of irradiated vascular endothelial cells, and up-regulate the adhesion molecules expression of VACM-1, PECAM-1 and CD44, resulting in promoting the transendothelial migration of haemopoietic stem cells. (authors)