[Changes of nucleolin expression and cellular localization during HUVEC apoptosis induced by hydrogen peroxide]

To investigate the expression and cellular localization of nucleolin C23 during human umbilical vein endothelial cell (HUVEC) apoptosis induced by hydrogen peroxide (H(2)O(2)).

Apoptosis of HUVEC was induced by exposure to 0.5 mmol/L H(2)O(2) for different periods and detected by flow cytometry and activity of caspase-3. The mRNA and protein expression of nucleolin were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively. The intracellular distribution of nucleolin was observed by indirect immunofluorescence.

The percentage of apoptotic cells was increased significantly after treatment with H(2)O(2) for 12, 24 and 36 hours. The activity of caspase-3 reached the peak after treatment with H(2)O(2) for 4 h. RT-PCR showed that nucleolin C23 mRNA was decreased after 2, 4, and 8 hours treatment with H(2)O(2). Western blot showed that C23 protein level was decreased after 12 hours with an additional cleft band of 80 kD appeared after 8 hours. Density analysis showed that the 80 kD cleft band increased in a time-dependent manner. Immunofluorescence analysis demonstrated that H(2)O(2)-induced C23 redistribution from the nucleus to the cytoplasm.

H(2)O(2) could induce apoptosis accompanying with C23-cleavage and C23-translocation from the nucleus to the cytoplasm.