Konturek P C, Brzozowski T, Konturek S J, Pajdo R, Konturek J E, Kwiecień S, Taut A, Hahn E G
Department of Physiology, Jagiellonian University School of Medicine, Cracow, Poland.
J Physiol Pharmacol. 1999 Jun;50(2):211-25.
The maintenance of gastric mucosal integrity depends upon the interplay between epithelial cell proliferation and apoptosis (programmed cell death). The Bcl-2 family of proteins plays a central role in the regulation of apoptotic cell death by suppressing the apoptosis while some others such as Bax proteins promote this process. Stress-induced gastric ulcerations are accompanied by the fall in gastric mucosal cell proliferation but little is known about the influence of the stress on the apoptosis in gastric mucosa. In the present study, the gastric epithelial apoptosis was determined by means of expression of Bax and Bcl-2 mRNA in the gastric mucosa following acute stress. Wistar rats were exposed to mild water immersion and restraint stress (WRS) for 3.5 h and then sacrificed at 0, 2, 4, 6, 12 and 24 h after the termination of WRS. At each time interval after WRS, the gastric blood flow (GBF) and the proliferating cell nuclear antigen (PCNA) labeling were determined. The apoptosis rate in the gastric mucosa was determined by the terminal deoxynucleotidyl transferase (TDT) mediated 2-deoxyuridine 5-triphosphate (dUTP)-biotin nick end-labeling (TUNEL) staining method and the expression of Bax and Bcl-2 mRNA was analyzed by RT-PCR and southern blot hybridization. WRS produced multiple erosions accompanied by the fall in GBF and PCNA index and by a dramatic enhancement in gastric epithelial apoptosis rate reaching maximum at 4 h after exposure to WRS. Following 6 and 12 h after the end of WRS the apoptotis declined but even 24 h after WRS it failed to reach the value recorded in intact gastric mucosa. The PCNA index was still significantly inhibited at 2 h after WRS but then showed significant rise at 6 and 12 h to reach at 24 h after WRS, the level similar to that measured in intact gastric mucosa. The expression of Bax mRNA was detected in intact gastric mucosa and gradually increased in first 4 h after WRS to decline at 24 h to the level not significantly different from that observed in the intact mucosa. In contrast, the expression of Bcl-2 mRNA was almost undetectable during first 4 h but showed strong signal at 6 and 12 h to decline to the control level 24 h after WRS. We conclude that: 1. Healing of WRS lesions involves an increase in GBF and mucosal cell proliferation and 2. The enhancement in gastric epithelial apoptosis accompanies the mucosal damage induced by stress and this appears to be triggered by the shift from the cell death effector Bax to the cell death repressor Bcl-2 protein.
胃黏膜完整性的维持取决于上皮细胞增殖与凋亡（程序性细胞死亡）之间的相互作用。Bcl-2家族蛋白通过抑制凋亡在调控凋亡性细胞死亡中起核心作用，而其他一些蛋白如Bax蛋白则促进这一过程。应激诱导的胃溃疡伴随着胃黏膜细胞增殖的下降，但应激对胃黏膜凋亡的影响却知之甚少。在本研究中，通过急性应激后胃黏膜中Bax和Bcl-2 mRNA的表达来测定胃上皮细胞凋亡。将Wistar大鼠暴露于轻度水浸束缚应激（WRS）3.5小时，然后在WRS结束后的0、2、4、6、12和24小时处死。在WRS后的每个时间间隔，测定胃血流量（GBF）和增殖细胞核抗原（PCNA）标记。通过末端脱氧核苷酸转移酶（TDT）介导的2-脱氧尿苷5-三磷酸（dUTP）-生物素缺口末端标记（TUNEL）染色法测定胃黏膜中的凋亡率，并通过RT-PCR和Southern印迹杂交分析Bax和Bcl-2 mRNA的表达。WRS导致多处糜烂，同时伴有GBF和PCNA指数下降以及胃上皮细胞凋亡率显著升高，在暴露于WRS后4小时达到最大值。在WRS结束后6小时和12小时，凋亡率下降，但即使在WRS后24小时，其仍未恢复到完整胃黏膜中的记录值。WRS后2小时PCNA指数仍受到显著抑制，但随后在6小时和12小时显著升高，在WRS后24小时达到与完整胃黏膜中测量值相似的水平。在完整胃黏膜中可检测到Bax mRNA的表达，在WRS后的前4小时逐渐增加，在24小时下降至与完整黏膜中观察到的水平无显著差异。相反，Bcl-2 mRNA的表达在最初4小时几乎检测不到，但在6小时和12小时显示出强信号，在WRS后24小时下降至对照水平。我们得出以下结论：1. WRS损伤的愈合涉及GBF和黏膜细胞增殖的增加；2. 胃上皮细胞凋亡的增强伴随着应激诱导的黏膜损伤，这似乎是由细胞死亡效应因子Bax向细胞死亡抑制因子Bcl-2蛋白的转变所触发。
