[Role of phospholipid transfer protein in cigarette smoke-induced apoptosis of RLE-6TN cells].

OBJECTIVE: To investigate the role of phospholipid transfer protein (PLTP) in cigarette smoke extract (CSE)-induced apoptosis of rat alveolar type II cells (RLE-6TN) in vitro. METHODS: Rat alveolar epithelial cell line RLE-6TN were transfected with a small interfering RNA (siRNA) targeting PLTP prior to exposure to different concentrations of CSE for 24 or 48 h. The morphological changes of the apoptotic cells were observed by fluorescence microscopy with Hochest staining, and the cell apoptosis rate was measured with flow cytometry. The expression level of PLTP and caspase-3 activity in the cells were examined with Western blotting. RESULTS: Exposure to CSE significantly increased the cell apoptosis rate from (1.68∓0.098)% to (18.663∓0.964)% (P<0.001). Hoechst staining revealed distinct apoptotic changes in CSE-treated cells, which showed increased PLTP expression and caspase-3 activity. PLTP knockdown with the specific siRNA partly suppressed the SCE-induced enhancement of caspase-3 activity in the cells. CONCLUSION: PLTP may play a role in CSE-induced apoptosis of rat alveolar cells in vitro.

[Inhibitory effect of trichostatin A on HepG2 cell proliferation and the mechanisms].

OBJECTIVE: To investigate the inhibitory effect of trichostatin A (TSA) on the proliferation of HepG2 cells and explore the underlying mechanism. METHODS: HepG2 cells exposed to different concentrations of TSA for 24, 48, or 72 h were examined for cell growth inhibition using a cell counting kit, changes in cell cycle distribution with flow cytometry, cell apoptosis with annexin V-FTIC/PI double staining, and cell morphology changes under inverted microscope. The expressions of beta-catenin, HDAC1, HDAC3, H3K9, cyclinD1 and Bax proteins in the exposed cells were detected by Western blotting, and the expressions of HDAC1 and HDAC3 mRNAs by quantitative fluorescent PCR. RESULTS: Exposure to TSA caused significant dose- and time-dependent inhibition of HepG2 cell proliferation (P<0.05) and resulted in increased cell percentage in G0/G1 and G2/M phases and decreased cell percentage in S phase. The apoptotic index in the control group was (6.22 ± 0.25)%, which increased to (7.17 ± 0.20)% and (18.14 ± 0.42)% after exposure to 250 and 500 nmol/L TSA, respectively. Exposure to 250 and 500 nmol/L TSA also caused cell morphology changes with numerous floating cells. The expressions of beta-catenin, H3K9 and Bax proteins were significantly increased and CyclinD1, HDAC1, and HDAC3 protein expressions decreased in TSA-treated cells, but the expressions of HDAC1 and HDAC3 mRNAs showed no significant changes. CONCLUSIONS: TSA can inhibit the proliferation of HepG2 cells and induce cell cycle arrest and apoptosis by inhibiting HDAC activity, promoting histone acetylation, and activating Wnt/beta-catenin signaling pathway.