Litvak D A, Evers B M, Hwang K O, Hellmich M R, Ko T C, Townsend C M
Department of Surgery, University of Texas Medical Branch, Galveston 77555-0533, USA.
Surgery. 1998 Aug;124(2):161-9; discussion 169-70.
Intestinal mucosal turnover is a process of proliferation, differentiation, and apoptosis; the mechanisms remain largely undefined. The purpose of our study was to (1) assess the relationship between apoptosis and enterocyte differentiation and (2) determine whether the cell-cycle inhibitors, p21Waf1/Cip1 and p27Kip1, or the apoptosis inhibitors, Bcl-2 and Bcl-XL, may be involved.
Gut-derived Caco-2 cells were treated with sodium butyrate. Apoptosis was assessed by Hoechst stain, DNA laddering, and annexin V assay; differentiation was determined by alkaline phosphatase and sucrase activity. RNA and protein were analyzed for expression of p21Waf1/Cip1, p27Kip1, and members of the Bcl-2 family.
Treatment of Caco-2 cells with sodium butyrate resulted in the concomitant induction of both differentiation (increased alkaline phosphatase and sucrase activity) and apoptosis. Increased levels of p21Waf1/Cip1 and p27Kip1 mRNA and protein were detected at 24 hours, occurring before apoptosis or differentiation; decreased mRNA levels of Bcl-2 and Bcl-XL were noted at 24 hours.
Differentiation and apoptosis occurred simultaneously in Caco-2 cells, suggesting that apoptosis may be linked to enterocyte differentiation. The induction of p21Waf1/Cip1 and p27Kip1 and the down-regulation of Bcl-2 and Bcl-XL further suggest a link between the cell-cycle mechanisms regulating enterocyte differentiation and apoptosis.
肠黏膜更新是一个增殖、分化和凋亡的过程；其机制在很大程度上仍不明确。我们研究的目的是：（1）评估凋亡与肠上皮细胞分化之间的关系；（2）确定细胞周期抑制剂p21Waf1/Cip1和p27Kip1，或凋亡抑制剂Bcl-2和Bcl-XL是否参与其中。
用丁酸钠处理来源于肠道的Caco-2细胞。通过Hoechst染色、DNA梯状条带分析和膜联蛋白V测定评估凋亡；通过碱性磷酸酶和蔗糖酶活性确定分化情况。分析RNA和蛋白质中p21Waf1/Cip1、p27Kip1以及Bcl-2家族成员的表达情况。
用丁酸钠处理Caco-2细胞导致分化（碱性磷酸酶和蔗糖酶活性增加）和凋亡同时诱导发生。在24小时时检测到p21Waf1/Cip1和p27Kip1的mRNA及蛋白质水平升高，这发生在凋亡或分化之前；在24小时时注意到Bcl-2和Bcl-XL的mRNA水平降低。
Caco-2细胞中分化和凋亡同时发生，表明凋亡可能与肠上皮细胞分化有关。p21Waf1/Cip1和p27Kip1的诱导以及Bcl-2和Bcl-XL的下调进一步表明调节肠上皮细胞分化和凋亡的细胞周期机制之间存在联系。
