Small bowel segment reversal induces intestinal hyperplasia but reduces whole-body growth in massive bowel resected rats

Guanylyl cyclase-G modulates jejunal apoptosis and inflammation in mice with intestinal ischemia and reperfusion

Background

Membrane bound guanylyl cyclase-G (mGC-G), a novel form of GC mediates ischemia and reperfusion (IR)-induced renal injury. We investigated the roles of mGC-G in intestinal IR-induced jejunal damage, inflammation, and apoptosis.

Materials and methods

Male C57BL/6 wild-type (WT) and mGC-G gene knockout (KO) mice were treated with a sham operation or 45 min of superior mesenteric arterial obstruction followed by 3, 6, 12, or 24 h of reperfusion.

Results

Sham-operated KO mice had significantly lower plasma nitrate and nitrite (NOx) levels and jejunal villus height, crypt depth, and protein expression of phosphorylated-nuclear factor-kappa-B (NF-κB), phosphorylated-c-Jun N-terminal kinases (JNK) 2/3, phosphorylated-p38, and B-cell lymphoma-2 (Bcl-2). They had significantly greater jejunal interleukin-6 mRNA, cytochrome c protein, and apoptotic index compared with sham-operated WT mice. Intestinal IR significantly decreased plasma NOx in WT mice and increased plasma NOx in KO mice. The jejunal apoptotic index and caspase 3 activities were significantly increased, and nuclear phosphorylated-NF-κB and phosphorylated-p38 protein were significantly decreased in WT, but not KO mice with intestinal IR. After reperfusion, KO mice had an earlier decrease in jejunal cyclic GMP, and WT mice had an earlier increase in jejunal proliferation and a later increase in cytosol inhibitor of kappa-B-alpha. Intestinal IR induced greater increases in plasma and jejunal interleukin-6 protein in WT mice and a greater increase in jejunal interleukin-6 mRNA in KO mice.

Conclusions

mGC-G is involved in the maintenance of jejunal integrity and intestinal IR-induced inflammation and apoptosis. These results suggest that targeting cGMP pathway might be a potential strategy to alleviate IR-induced jejunal damages.

Oral antibiotics attenuate bowel segment reversal-induced systemic inflammatory response and body weight loss in massively bowel-resected rats

BACKGROUND

Using a massively bowel-resected rat model, our previous study demonstrated that small bowel segment reversal stimulates jejunal hyperplasia but may also increase the possibility of bacterial translocation and the elevation of circulating white blood cells and serum interleukin-6 that may reduce the whole-body anabolism. The aim of this study is to investigate whether oral antibiotics might attenuate the inflammatory responses and might therefore facilitate the beneficial effects of bowel segment reversal.

METHODS

Male Wistar rats (approximately 270 g) underwent a 70% small bowel resection with (REV group) or without (CON group) a 3-cm small bowel segment reversal, or underwent a sham operation (SHAM group). After surgeries, half of the animals in the REV group were given oral clindamycin plus amoxicillin (50 plus 50 mg/kg/d, ANT group) for 3 weeks.

RESULTS

Oral antibiotics administration significantly attenuated the decreases in feeding efficiency (g of body weight/100 kcal diet) and increases in the circulation of white blood cells, serum nitric oxide, and interleukin-6 (1-way ANOVA, p < .05), which are associated with bowel segment reversal. In addition, antibiotics significantly increased serum concentrations of insulin-like growth factor-I, significantly decreased the total numbers of bacteria in the intestine, and tended to reduce the extent of jejunal hyperplasia in rats with bowel segment reversal.

CONCLUSIONS

Our results suggest that oral antibiotics may be used as an adjuvant to attenuate the inflammatory responses and to enhance the anabolic responses in massively bowel-resected patients with bowel segment reversal.

Enterocyte apoptosis after enterectomy in mice is activated independent of the extrinsic death receptor pathway

Intestinal adaptation following small bowel resection (SBR) is associated with greater rates of enterocyte apoptosis by unknown mechanism(s). Because postresection adaptation is associated with increased translocation of luminal bacteria, we sought to characterize the role for the extrinsic, death receptor pathway for the activation of enterocyte apoptosis after massive SBR. We first performed SBR or sham operations in mice, and the temporal expression of caspases 8, 9, and 3, death receptors tumor necrosis factor receptor-1 (TNFR1) and Fas and corresponding ligands (TNF and Fas ligand) was determined in the remnant intestine at various postoperative time points. Ileal TNFR1 and Fas expression were then measured after SBR in the setting of increased (waved-2 mice) or decreased (exogenous EGF administration) apoptosis. Finally, intestinal adaptation and apoptosis were recorded in the remnant ileum after SBR in TNFR1-null and Fas-null mice. The expression of death receptor family proteins and caspases demonstrated only modest changes after SBR and did not correlate with the histological appearance of apoptosis. In the setting of accelerated apoptosis, TNFR1 and Fas expression were paradoxically decreased. Apoptotic and adaptive responses were preserved in both TNFR1-null and Fas-null mice. These results suggest that the mechanism for increased enterocyte apoptosis following massive SBR does not appear to involve the extrinsic, death receptor-mediated pathway.

Surgery of the small intestine

The small intestine is the portal of entry of virtually all nutrients and is also the site of diverse inflammatory and neoplastic diseases. This field has recently attracted intense excitement as a result of novel clinical and experimental techniques, combined modality therapies, and basic science applications. This review will highlight important clinical advances in surgery for Crohn disease, short bowel syndrome, transplantation, trauma, and polyposis. Promising experimental approaches, novel methods of clinical assessment, and multimodality treatment will also be considered.

SYSTEMIC AND LOCAL SECRETIONS OF CYTOKINES AND NITRIC OXIDE IN MASSIVE BOWEL RESECTED RATS WITH OR WITHOUT SMALL BOWEL SEGMENT REVERSAL

Our previous study suggested that small bowel segment reversal stimulates jejunal hyperplasia, but that the elevated serum interleukin (IL-)6 eliminates whole-body anabolism in massive bowel resected rats. The aim of this study was to investigate systemic and local secretions of cytokines and nitric oxide (NO) in relation to whole-body and tissue responses in rats that underwent massive bowel resection with small bowel segment reversal. Seventy percent small bowel resection was performed in Wistar rats with (REV) or without (CON) a 5 cm reversed small bowel segment. Sham operation (SHAM) was performed on a third group of rats. Twelve days after surgery the REV group had significantly lower weight gain and greater serum levels of NO, IL-2 and IL-6 than the CON and SHAM groups. The weights of the livers in the REV and CON groups were significantly heavier, but these groups had lower levels of protein, tumour-necrosis factor-alpha, IL-2 and IL-6 than the SHAM group. The cecum weights of the REV group were significantly higher with increased protein and NO levels, but decreased IL-6 levels compared with the CON and SHAM groups. In the proximal small intestine the REV group had significantly increased protein levels and mucosal dry weights, but decreased interferon-gamma and IL-2 compared with the CON and SHAM groups. Our results suggested that cytokines and NO may have endocrine and paracrine/autocrine actions in regulating whole-body and tissue responses.