Objective      To explore the roles of protein kinase D (PKD) and sphingosine kinase 2 (SphK2) in sodium butyrate-induced apoptosis of human liver cancer HepG2 cells.       Method      Using flow cytometry

the percentage of apoptotic HepG2 cells was examined after treatment with sodium butyrate of different concentrations. The effects of down-regulation and over-expression of SphK2 or PKD on sodium butyrate-induced apoptosis were analyzed. With Western blotting

the changes in the activated (phosphorylated) forms of SphK2 or PKD induced by sodium butyrate with or without interfer

ence of the other enzyme were detected.       Results      Sodium butyrate induced apoptosis of HepG2 cells significantly (

P

0.01) in a concentration-dependent manner. After the down-regulation of PKD or SphK2

the sodium butyrate-induced apoptosis was obviously potentiated

as compared to the non-interfered control cells (

P

0.01). On the contrary

the apoptosis of the cells with PKD or SphK2 overexpressed was significantly prohibited

in comparison with the vehicle plasmid-transfectedcells (

P

0.01). Moreover

the interference of SphK2 did not affect activation of PKD by sodium butyrate (

P

0.01)

while PKD down-regulation resulted in the absence of SphK2 activation (

P

0.01).       Conclusion      Both SphK2 and PKD negatively regulate apoptosis of HepG2 cells induced by sodium butyrate.