Down-regulation of calreticulin promotes apoptosis in hepatic stellate cells

Abstract

Objective To investigate the effect of calreticulin (CALR) down-regulation on apoptosis and endoplasmic reticulum stress (ERS) pathway in hepatic stellate cells (HSCs). Methods Small interfering RNA (siRNA) of CALR was transfected into HSC via liposome, and pro-fibrosis factor, namely transforming growth factor-β1 (TGF-β1) was subsequently added in 24 h later. Another 24 h later, the morphology of HSCs was observed under an inverted microscope, cell apoptosis was detected by TUNEL assay, intracellular Ca2+ level was tested with a laser confocal microscope, and the expression levels of CALR, GRP78, Caspase-12 and Caspase-3 were determined using Western blotting. Results As compared with the control and negative-siRNA group, the apoptotic rate was significantly higher (P < 0.05), and the concentration of Ca2+ and protein levels of GRP78, Caspase-12 and Caspase-3 were all increased (P < 0.05) in the CALR-siRNA group. However, TGF-β1 treatment for 24 h decreased the number of apoptotic cells, concentration of Ca2+ and expression levels of above proteins when compared with the CALR-siRNA group. Conclusion Down-regulation of CALR promotes apoptosis of HSCs, which may be related to the imbalance of intracellular Ca2+ homeostasis and activation of the ERS pathway.

Keywords

• hepatic stellate cells
• calreticulin
• apoptosis
• endoplasmic reticulum stress