Gut mucosal homeostasis and cellular mediators after severe thermal trauma and the effect of insulin-like growth factor-I in combination with insulin-like growth factor binding protein-3.

Increased small bowel epithelial cell apoptosis and decreased cell proliferation lead to impairment of gut mucosal integrity and function after thermal injury. Impairment of gut integrity is associated with increased bacterial translocation and incidence of sepsis. The purpose of this study was to determine whether IGF-I/IGF binding protein (IGFBP)-3 can improve small bowel homeostasis after injury and by which cellular mechanisms these changes occur and to identify changes in apoptosis-related genes after burn and the effect of bile acid on small bowel epithelial cell apoptosis after burn. Rats sustained a thermal injury and received saline or the IGF-I/IGFBP-3 complex. Serum and small intestine were taken at 1, 2, 5, and 7 d after injury and serum inflammatory cytokines and mucosal apoptosis, proliferation, villous morphology, and apoptotic and proliferative mediators were measured. Apoptosis-related gene expression and the bile acid pool were determined in separate experiments up to 6 h after burn. Gut epithelial cell apoptosis as well as apoptosis-related genes were increased after the thermal injury, whereas bile acid secretion was significantly decreased (P < 0.05). IGF-I/IGFBP-3 significantly improved villous height and cells per villous by decreasing small bowel epithelial cell apoptosis and increasing proliferation (P < 0.05). Decreased apoptosis was associated with decreased Fas, Fas-ligand, and TNF when compared with saline (P < 0.05). A severe thermal injury caused an up-regulation of apoptosis and apoptosis-related genes and down-regulation of bile acid secretion. IGF-I/IGFBP-3 decreases small bowel epithelial cell apoptosis through down-regulation of the Fas pathway, which improves gut mucosal integrity after a severe thermal injury.

The effect of hepatocyte growth factor on gut mucosal apoptosis and proliferation, and cellular mediators after severe trauma.

BACKGROUND: A severe burn injury is associated with an impairment of gut mucosal integrity and function, which is due to increases in small-bowel epithelial cell apoptosis and decreases in cell proliferation. Hepatocyte growth factor (HGF) was shown to improve regeneration in the liver, mesentery, and skin. The purpose of this study was to determine whether HGF can improve small-bowel homeostasis after injury and the cellular mechanisms by which these changes occur. METHODS: Rats were pair-fed, underwent thermal trauma, and received saline (0.9% NaCl; n = 28) or HGF (200 microg/kg iv every 12 hours, n = 28). Small intestine and serum were taken at 1, 2, 5, and 7 days after injury. Measures were mucosal apoptosis, proliferation, villous morphology, and apoptotic and proliferative mediators, such as caspase-3 and caspase-7, Fas and Fas-ligand, Bcl-2, and Bax. In addition, serum cytokines were determined. RESULTS: Gut epithelial cell apoptosis was increased in the saline and HGF groups after the thermal injury. Despite an increase in serum tumor necrosis factor-alpha and interleukin-1beta, HGF did not affect small-bowel cell apoptosis, but it improved proliferation at days 1 and 2 after injury, which was associated with increased villous height and cell per villous, compared with saline controls, P < .05. Increased mucosal cell proliferation was associated with increased Bcl-2 in the HGF group, P < .05. HGF had no effect on apoptotic mediators, such as Fas, Fas-L, or caspase-3 and caspase-7. CONCLUSIONS: HGF improves small-bowel morphology after a severe burn by increasing mucosal Bcl-2 and, concomitantly, small-bowel epithelial cell proliferation.

The effect of growth hormone on gut mucosal homeostasis and cellular mediators after severe trauma.

BACKGROUND: Gut mucosal integrity and function is impaired after severe trauma with associated increases in small bowel epithelial cell apoptosis and decreases in cell proliferation. Growth hormone improves gastrointestinal function during chemotherapy and has anabolic effects on protein synthesis. The purpose of this study was to determine whether growth hormone can improve small bowel homeostasis after injury and by which cellular mechanisms these changes occur. MATERIALS AND METHODS: Rats were pair-fed, given a thermal trauma, and received saline (n = 28) or GH (2.5 mg/kg every 24 h, n = 28). Small intestine and serum were taken at 1, 2, 5, and 7 days after injury. Measures were mucosal apoptosis, proliferation, villous morphology, apoptotic, and proliferative mediators, such as Caspases-3, -8, Fas and Fas-Ligand, Bcl-2, and Bcl-x. In addition serum cytokines were determined. RESULTS: Gut epithelial cell apoptosis and proliferation were increased in both groups after the thermal injury (P < 0.05). GH had neither an effect on small bowel epithelial cell apoptosis or proliferation, nor dependent cellular mediators after thermal injury. However, GH significantly improved villous morphology (height and cell number) when compared with controls (P < 0.05). RhGH was found to significantly increase serum TNF-alpha compared to controls (P < 0.05). CONCLUSION: Growth hormone improves small bowel homeostasis after severe trauma independent from small bowel epithelial cell apoptosis or proliferation, probably by increasing the life span.

Effects of incremental starvation on gut mucosa.

Starvation induces gut mucosal atrophy, but the effects of progressive dietary restriction are not defined. The study's purpose was to determine the effects of incremental starvation on gut epithelial cell turnover. After food intake of mice was determined, they were divided into five groups: control (ad libitum fed), 75% normal intake, 50% intake, 25% intake, and fasted. Mice were killed after 48 hours, and the proximal small bowel were assessed for weight and protein content. Histologic specimens were examined for villus morphology, apoptosis, and proliferation. After 48 hr of diet restriction, bowel weight decreased in the 50% intake, 25% intake, and fasted groups. Villus density also decreased in the fasted group. Proliferation progressively decreased in the diet-restricted groups. Apoptosis increased in the fasted group, primarily in the villus tip. In conclusion, incremental starvation produces progressive small bowel atrophy. The mechanism involves both decreased gut epithelial cell proliferation and increased apoptosis.

Effect of bombesin on gut mucosal impairment after severe burn.

Severe cutaneous bum alters gut epithelial homeostasis. In previous studies, treatment with bombesin decreased mucosal atrophy and improved maintenance of gut mucosal integrity after severe burn. Our current hypothesis is that bombesin reduces burn-induced gut impairment by decreasing gut epithelial cell death. Fifty-four adult male Fisher-344 rats were randomly assigned to three groups: control, sham burn (I), burn (II), and burn + bombesin (III). Animals in groups II and III received a 60% total body surface area full thickness scald burn, and the treatment group (III) received bombesin subcutaneously (10 microg/kg, every 8 h) beginning immediately before the experiment. The proximal small bowel was harvested at 12 and 72 h after burn with measurement of wet and dry weight, mucosal weight, and protein content, and a 1-cm length of proximal end was excised and fixed in fomalin for histological and immunohistochemical observation. Data are expressed as means +/- SEM. Statistical analysis was by done by analysis of variance (significance at P < 0.05). Bombesin treatment attenuated mucosal atrophy demonstrated by restoration of the mucosal weight, mucosal protein content, and maintenance of mucosal height and total mucosal epithelial cell count. Gut epithelial cell apoptosis was, at least in part, inhibited by bombesin compared with a significant increase of gut cell apoptosis at 12 h after burn. Gut epithelial proliferation was not affected. Bombesin diminished burn-induced gut mucosal atrophy and gut epithelial cell apoptosis, suggesting that bombesin treatment may play an important role in the recovery of gut impairment after severe burn.

Role of TNF-alpha in gut mucosal changes after severe burn.

Gut epithelial cell death by apoptosis is increased in the gut epithelium after severe burn associated with mucosal atrophy. We hypothesized that tumor necrosis factor (TNF)-alpha-TNF receptor (TNFR) interaction activates apoptosis in small bowel mucosal cells after severe burn. C57BL6 mice received a 30% total body surface area scald burn and were treated with neutralizing anti-TNF-alpha. The proximal small bowel was assessed for mucosal atrophy. Proliferation and apoptosis of mucosal cells were assessed by proliferative cell nuclear antigen-immunostaining and terminal deoxyuridine nick-end labeling assay, respectively. Mucosal height and mucosal cell number decreased after burn. Anti-TNF-alpha-treated mice showed significantly less mucosal atrophy. Proliferation of intestinal cells was not changed with burn or anti-TNF-alpha treatment. An over threefold increase in apoptotic cell number was seen after burn, which was diminished by anti-TNF-alpha treatment. Changes in gut mucosal homeostasis after severe burn are affected, in part, by the activation of apoptosis by TNF-alpha-TNFR interaction.