| Background Stress ulcer is a common clinical complication in critically ill patients. The main pathogenesis is that stress causes neuroendocrine dysfunction, thus reduces the blood flow to the gastric mucosa leading to local hypoxia and ischemia, destructs the mucosal barrier, ultimately induces the formation of ulcers. The clinically drugs of prophylaxis and treatment of SU are acid-inhibitory drugs such as PPIs, H2RAs etc.. However, the studys of drugs about increasing gastric mucosal blood flow are rarely.Hypoxia-inducible factor 1 (HIF-1) as a nuclear transcription factor within the cell, can regulate the expression of multiple genes to play biological effect, including the angiogenesis, glucose metabolism and cell proliferation, etc.. HIF-1 is a transcription factor that contains an oxygen concentration sensor a subunit and the constitutively expressed β subunit. Stability and synthesis of HIF-1α is regulated by oxygen concentration, pH, growth factors etc.. Under stress condition, gastric mucosal local ischemia and hypoxia, thus presumably stress-induced gastric mucosal injury may increase the expression of HIF-1α, thus starts the self protection mechanism. Currently, the research of SU treatment targeted on HIF-1α is little.Insulin-like growth factor-1 (IGF-1) is a kind of growth factor with the metabolic effects of insulin-like, could promote cell growth. The study found that cultivation of gastric mucosa epithelial cells in vitro, exogenous IGF-1 promoted the cell migration, proliferation and increased expression of HIF-1α. However, the study of effects of exogenous IGF-1 on the expression of HIF-1α in gastric mucosa in vivo is rare. Phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB/Akt) pathway is an important intracellular signaling pathways, has an important role on cell proliferation, apoptosis, cancer and so on. Study has shown IGF-1 via PI3K and MAPK signaling pathways regulating expression of HIF-1α and VEGF in colon cancer cells, promoting tumor angiogenesis. This study attempts to explore whether the PI3K-Akt signaling pathway is involved in the effects of exogenous IGF-1 on the expression of HIF-1α in gastric mucosa in vivo, thus to further understand the mechanisms of protective effect on gastric mucosal of IGF-1.Objective Establishing SU rat model by water-immersion and restraint stress method, to explore the protective effect and mechanism of exogenous IGF-1 on expression of HIF-1α on gastric stress ulcer in rats, to further research the gastric mucosal protection of IGF-1.Method 1. Experiment one:Establishing SU rat model by water-immersion and restraint stress method, depending on the time of soaking,42 male Sprague-Dawley rats were randomly divided into 5 groups (n=6):0 h (Con) group,2 h (W 2) group,4 h (W 4) group,6 h (W 6) group,8 h (W 8) group. The gastric juice pH levels, gastric mucosal blood flow (GMBF), ulcer index (UI) were measured in each group of rats after stress. The gastric mucosa was observed grossly. The expression of HIF-la, vascular endothelial growth factor (VEGF) were measured by Western blot.2. Experiment two:According to different dose of exogenous IGF-1,24 male SD rats were randomly divided into 4 groups (n=6):WRS (W) group, W+IGF-125 μg/kg (WI 1) group, W+IGF-150 μg/kg (WI 2) group, W+IGF-1 100μg/kg (WI 3) group. Choose the stress point of most obvious gastric mucosal injury in experiment one as the soaking time in W group. The gastric juice pH levels,GMBF, UI was measured in rats after stress. The gastric mucosa was observed grossly. The expression of HIF-1α, VEG were measured by Western blot3. Experiment three:30 male SD rats were randomly divided into 5 groups (n=6):the normal control (Con) group, WRS (W) group, W+IGF-1 (WI) group, W+LY294002 (WL) group and W+IGF-1+LY294002 (WIL) group. The dose of IGF-1, which could obviously improve gastric mucosal injury in experiment two, will be used to WI group in this experiment. LY294002, a specific inhibitor of PI3K. The gastric juice pH levels, GMBF, UI was measured in each group of rats after stress. The gastric mucosa was observed grossly and also observed under the light microscope. Detected the expression of HIF-la, VEGF, p-Akt, t-Akt in gastric mucosa of rats in each group by Westernblot.Results:1.Experiment one:As the water immersion time extended, the gastric juice pH levels, GMBF were significantly lower, UI gradually increased (P<0.05); the expression of HIF-la, VEGF was increased (P<0.05); the indexes of W8 group reached peak. Confirmed WRS method could induce gastric mucosa injury and the expression of HIF-1α.2. Experiment two:Compared with W group, the gastric juice pH levels, GMBF were higer, UI lower in other IGF-1 groups respectively, but there was no statistically significant differences between W and WI 1 group (P>0.05), thus WI 2、WI 3 group had statistical differences respectively (P<0.05). The expression of HIF-1α, VEGF was significantly improved (P<0.05), to some extent, dependenting on the increasing of IGF-1 dose, indicating that IGF-1 could up-regulate the expression of HIF-1α to play gastric mucosal protection.3. Experiment three:Compared with W group, the gastric juice pH levels, GMBF was higer, UI was lower in WI group, results were consistent with experiment two, the expression of p-Akt was elevated, HIF-1α-. VEGF was increased obviously (P<0.05), showing that exogenous IGF-1 could up-regulate HIF-1α expression in gastric mucosal by activating PI3K/Akt signal pathway. WIL group in comparison with W group, the gastric juice pH levels, GMBF was lower, UI was higer(P<0.05), the expression of p-Akt was reduced, meanwhile HIF-1α, VEGF was decreased (P<0.05); indicating PI3K inhibitors LY294002 blocking PI3K/Akt signal pathway, could reduce the expression of HIF-1α, thus weaken the gastric mucosal protection of IGF-1.ConclusionsExogenous IGF-1 could up-regulate expression of HIF-la in SU by PI3K-Akt signaling pathway, thus increase GMBF, promote ulcer healing, play the gastric mucosal protection. |
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