Changes of protein kinase regulatory pathway in inhibition of curcumin on human lens epithelial cells proliferation

Abstract

Background Our previous study showed that curcumin suppresses the proliferation of human lens epithelial cells (LECs) in vitro and has an influence on the signal transduction of cyclic adenosine monophosphate (cAMP) and cyclic guanosinc monophosphate (cGMP). Actually, the regulation for biological behavior of LECs in vivo is complex. Objective This study was to investigate the changes of signal transduction of protein kinase (PK) in inhibition of curcumin on human LECs proliferation. Methods HLE-B3 was cultured and then divided into the blank control group, recombinant human basic fibroblast growth factor (rhbFGF) group and rhbFGF+ curcumin group.rhbFGF of 10 ng/ml was added in the medium in the rhbFGF group, and 20 mg/L curcumin was added into rhbFGF-induced cell medium for 24 hours in the rhbFGF+ curcumin group.The expression rates of PKA, PKC, PKG and calmodulin (CaM) in the cells were assayed using flow cytometry. Results The expression rates of PKA protein were (46.847±1.673)%, (33.250±2.242)% and (71.645±2.432)% in the blank control group, rhbFGF group and the rhbFGF+ curcumin group, respectively, and the expression rate of PKA protein was significantly reduced in the rhbFGF group compared with the blank control group (t=11.904, P<0.01), but the expression rate of PKA protein in the rhbFGF+ curcumin group was significnatly higher than that in the rhbFGF group (t=28.430, P<0.01). In the blank control group, rhbFGF group and the rhbFGF+ curcumin group, the expression rates of PKC protein in the cells were (35.575±1.937)%, (50.652±2.068)% and (27.662±4.481)%, those of PKG protein were (63.838±0.486)%, (86.562±1.325)% and (40.733±2.175)%, while those of CaM protein were (67.408±1.391)%, (83.887±3.499)% and (53.785±1.942)%, the expression rates of PKC, PKG and CaM were significantly lower in the rhbFGF group in comparison with the blank control group (all at P<0.01), and those in the rhbFGF+ curcumin group were significantly declined in comparison with the rhbFGF group (all at P<0.01). Conclusions Suppression of curcumin on HLE-B3 proliferation probably is associated with the up-regulation of PKA expression and down-regulation of PKC, PKG and CaM expression in the cells. Key words: Curcumin; Protein kinase; Signal transduction; Lens epithelial cells