Induction of Proliferation in Isolated Guinea Pig Gastric Epithelium During Restitution After Superficial Injury

Immediate repair of the gastrointestinalepithelium after superficial injury is calledrestitution. It is based on the migration of thesurviving mucoid neck cells over the area of injury. Theinvolvement of growth factors in the process has beenrecently documented. They are known to enhance theprocess (ie, EGF, FGF, TGF-) and to activate thebasolateral Na⁺-H⁺-antiport (EGF).They may exert their effect by activating intracellular tyrosinekinases or by inducing chemotaxis. Yet, their precisemechanism of action in the process is unknown. The aimof the present study was to investigate the effect of modulation of the signal transductionpathway on the occurrence of proliferative mucoid neckand foveolar cells in guinea pig gastric epithelium.Therefore guinea pig gastric epithelium was mounted in Ussing chambers in vitro and perfused 4 hrafter superficial injury with 1.25 M NaCl. The potentialdifference over the epithelium and tissue resistancewere recorded simultaneously. The tissue was exposed either to cycloheximide, genistein, or to4-phorbol myristate 13-acetate (PMA) during the 4-hrrecovery, and the expression of proliferative cells wasassessed by staining the tissue for proliferative cells (Ki-67). The mean proliferative index oftissues subjected to NaCl injury was significantlyhigher than that of uninjured control tissues after 4 hrof restitution. Inhibition of the signaling pathway with genistein decreased the proliferative indexsignificantly, while its stimulation with phorbolmyristate increased it. Both electrophysiologic andmorphologic restitution were sensitive to genistein, but not to PMA or cycloheximide. Superficialepithelial injury results in a significantly increasedoccurrence of proliferative cells in isolated guinea piggastric epithelium. This endogenous activation of the tissue is sensitive to inhibition bytyrosine kinases and to stimulation by protein kinases.Electrophysiologic and morphologic recovery are alsoaffected by the modulation of the signaling pathway. This suggests that it is involved in theimmediate repair process.     

Heat-Shock Preconditioning Affects Restitution of Isolated Guinea Pig Gastric Mucosa by an Arachidonic Acid and Protein Synthesis Dependent Mechanism

Background: Superficial mucosal injury is repaired immediately by a process known as restitution, which is controlled by several factors and is based on cellular migration. Heat-shock preconditioning increases the tolerance of tissue to deep gastric mucosal injury via synthesis of heat-shock proteins. Despite immediate positive effects on the tissue, we have shown that heat-shock preconditioning inhibits restitution of gastric mucosa after subsequent superficial injury in correlation with Hsp70 levels. In addition to heat-shock proteins, heat preconditioning is known to affect eicosanoid pathways. In this study, we explore the role of eicosanoid pathways and protein synthesis in heat-shock-induced inhibition of restitution. Methods: Guinea pig gastric mucosa was mounted and perfused in a Ussing chamber (37°C). After heat-shock preconditioning (HS) (42°C) and normothermic recovery, a superficial injury was induced (1.25 mol/L NaCl) followed by a 3-h restitution. Transmucosal electrophysiologic resistance of the tissue (R) was recorded during the experiment. During perfusion, the mucosa was exposed to 30 μmol/L arachidonic acid as a substrate for eicosanoid pathways; 50 μmol/L quercetin to inhibit the metabolism of arachidonic acid via lipoxygenases, 50 μmol/L indomethacin to inhibit the metabolism of arachidonic acid via cyclo-oxygenases, or 150 μmol/L cycloheximide to inhibit de novo protein synthesis. After the experiment, the mucosa was prepared for morphologic analysis and Western blotting. Results: HS inhibited restitution after NaCl insult and upregulated Hsp70. Exposure of the tissue to quercetin, cycloheximide, arachidonic acid, or to indomethacin overcame the inhibitory effect of HS, which could be pronounced by simultaneous indomethacin and quercetin augmenting expression of Hsp70. Conclusion: HS preconditioning inhibits restitution by a mechanism that involves arachidonic acid metabolism and de novo protein synthesis.     

黄苔胃病患者胃粘膜凋亡基因及相关蛋白的表达

目的:探讨胃病患者黄苔与胃粘膜组织细胞凋亡之间的关系.方法:选取黄苔胃病患者62例,采用免疫组化法与63例白苔胃病患者进行对照,采用免疫组化法检测胃粘膜增殖细胞核抗原(PCNA)、p53、bcl-2、fas凋亡基因相关蛋白.结果:黄苔患者p53、fas表达均明显高于白苔患者(均P<0.05),而PCNA、bc1-2表达则与白苔患者差异均无统计学意义(均P>0.05).结论:黄苔胃病患者伴有促凋亡基因相关蛋白的过度表达,黄苔是胃内有活动性炎症的较灵敏的指标.     

Keratinocyte growth factor is an endogenous stimulant of rabbit gastric epithelial cell proliferation and migration in primary culture

Mesenchymal-epithelial interactions are important in the gastric mucosal repair. However, specific factors responsible for such interactions have not been established. In the present study, keratinocyte growth factor (KGF) significantly stimulated proliferation of gastric epithelial cells dose dependently and synergistically with hepatocyte growth factor (HGF), epidermal growth factor (EGF) and insulin. Restitution of gastric epithelial monolayers was also assessed, using a round wound restitution model. Keratinocyte growth factor facilitated the restitution of gastric epithelial cells significantly but did not have any effects on gastric fibroblasts. Keratinocyte growth factor receptor mRNA was expressed by gastric epithelial cells, indicating that these effects were elicited by the specific receptor mediated pathway. Northern blot analysis revealed the expression of KGF mRNA in gastric fibroblasts but not in gastric epithelial cells, indicating the production of KGF. These results suggest that KGF might be involved in gastric mucosal repair, through mesenchymal-epithelial interaction.