Effects of Baicalin on Expression of B-cellymphoma-2 (Bcl-2) and Bcl-2 Assaciated X Protein Gene (Bax) and Apoptosis Rates of Pig Kidney Proximal Tubular (LLC-PK1) Cells Subjected to Heat Stress
Abstract：The objective of this study is to explore baicalin influence B-cellymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) expression as well as apoptosis rates of heat-stressed pig kidney proximal tubular cells (LLC-PK1). Readily cultured LLC-PK1 cells were randomly divided into seven groups. The cells in groupⅠwere used as blank control cultured at 37 ℃ and cells in groupⅡwere heart-stressed at 42 ℃ for 1 h. Cells in groups Ⅲ,Ⅳ,Ⅴ,Ⅵ and Ⅶ were cultured additionally with different concentrations (0.01, 0.1, 1, 10 and 100 μg/mL) of baicalin at 42 ℃ for 1 h, respectively. Expression of Bcl-2 mRNA and Bax protein were detected with Real-time PCR and Western blot, respectively. Apoptosis rates of LLC-PK1 cells were determined with Annexin V-FITC/PI. Results showed that as compared to groupⅠ, Bcl-2 mRNA in groupⅡincreased significantly (P＜0.05), and Bax mRNA and its protein increased extremely significantly (P＜0.01), and both ratios between Bcl-2 and Bax mRNA and their proteins decreased significantly (P＜0.01), and the apoptosis rates increased extremely significantly(P＜0.01). However, there was no evident influence on Bcl-2 protein expression (P＞0.05). Compared with groupⅡ, Bcl-2 mRNA expression significantly increased in groupⅣand Ⅵ (P＜0.05) and extremely significantly in groupⅤ(P＜0.01), but not in groupⅢor Ⅶ (P＞0.05), while the Bal-2 protein expression had no difference (P＞0.05). Similarly, compared with groupⅡ, both Bax mRNA and its protein expression decreased significantly in groupsⅢ, Ⅳand Ⅶ (P＜0.05) and decreased extremely significantly in groupⅤand Ⅵ(P＜0.01). Ratios between Bcl-2 and Bax mRNA and their proteins in all groups except groupⅢ had a significant increase (P＜0.05), while the ratio between Bcl-2 and Bax protein in groupⅤ increased extremely significantly (P＜0.01). The apoptosis rates decreased extremely significantly in groupⅤ and Ⅵ (P＜0.01), and decreased significantly in group Ⅳand Ⅶ(P＜0.05). The results indicated that certain concentration (0.1~100 μg/mL) of baicalin protectsed heat-stressed LLC-PK cells by down-regulating Bax expression, increasing the ratio between Bcl-2 and Bax and decreasing apoptosis rates. This experiment reveals some heat-resistant mechanism of baicalin on LLC-PK1 cells exposed to heat stress which will provide valuable reference for its clinical application.
