Abstract:

Objective  To investigate the inhibitory effect of rapamycin (Rapa) on the proliferation of vascular endothelial cells induced by cyclosporin A (CsA) and possible mechanisms. Methods  Human umbilical vein endothelial cells (HUVECs) that proliferated under the induction of CsA were treated by different concentrations of Rapa. The synthesis of DNA and protein was detected by ³H-TdR incorporation and ³H-leucine incorporation. The secretion of Ang Ⅱ in cytoplasm and culture medium was measured by radioimmunoassay. Western blotting was adopted to assess expressions of ribosomal protein S6 kinase (p70S6K) and ERK₂. Results  Compared with the CsA group, the synthesis of DNA and protein of vascular endothelial cells of the CsA+Rapa intervention group was significantly inhibited and AngⅡ levels in culture supernatant and protein extract significantly decreased and were dose-dependent with Rapa. Results of Western blotting showed that compared with the CsA group, the expressions of p70S6K of the CsA+Rapa (10 nmol/L) intervention group and CsA+Rapa (100 nmol/L) intervention group significantly decreased. The expression of ERK₂ of the CsA+Rapa intervention group decreased in a dose-dependent manner, but the difference was not statistically significant (P>0.05).  Conclusion  Rapa may inhibit expression of p70S6K, block PI3K-p70S6K signaling pathway, and inhibit the vascular endothelial cells stimulated by CsA from secreting AngⅡ, so as to inhibit the proliferation of vascular endothelial cells by inhibiting the expression of signal protein p70S6K. The immunosuppression therapy of Rapa combined with CsA facilitates inhibiting the proliferation of vascular endothelial cells of grafts.

Key words: rapamycin, ribosomal protein S6 kinase, cyclosporine A, angiotensin Ⅱ