Effect of bowel resection on TLR signaling during intestinal adaptation in a rat model

Muscle hypertrophy and neuroplasticity in the small bowel in short bowel syndrome

Short bowel syndrome (SBS) is a severe, life-threatening condition and one of the leading causes of intestinal failure in children. Here we were interested in changes in muscle layers and especially in the myenteric plexus of the enteric nervous system (ENS) of the small bowel in the context of intestinal adaptation. Twelve rats underwent a massive resection of the small intestine to induce SBS. Sham laparotomy without small bowel transection was performed in 10 rats. Two weeks after surgery, the remaining jejunum and ileum were harvested and studied. Samples of human small bowel were obtained from patients who underwent resection of small bowel segments due to a medical indication. Morphological changes in the muscle layers and the expression of nestin, a marker for neuronal plasticity, were studied. Following SBS, muscle tissue increases significantly in both parts of the small bowel, i.e., jejunum and ileum. The leading pathophysiological mechanism of these changes is hypertrophy. Additionally, we observed an increased nestin expression in the myenteric plexus in the remaining bowel with SBS. Our human data also showed that in patients with SBS, the proportion of stem cells in the myenteric plexus had risen by more than twofold. Our findings suggest that the ENS is tightly connected to changes in intestinal muscle layers and is critically involved in the process of intestinal adaptation to SBS.

The effect of hepatocyte growth factor on intestinal adaption in an experimental model of short bowel syndrome

PURPOSE

Nowadays, the standard therapy for patients with short bowel syndrome is parenteral nutrition (PN). Various growth factors have been tested to achieve weaning from prolonged PN administration. We evaluated the effect of hepatocyte growth factor (HGF) on structural intestinal adaptation and cell proliferation in a rat model of SBS.

METHODS

Thirty Sprague-Dawley rats were divided into three groups; group A rats (sham) underwent bowel transection, group B rats underwent a 75% bowel resection, and group C rats underwent the same procedure but were treated postoperatively with HGF. Histopathologic parameters of intestinal adaptation were determined, while microarray and rt-PCR analyses of ileal RNA were also performed.

RESULTS

Treatment with HGF resulted in significant increase in body weight, while the jejunal and ileal villus height and crypt depth were increased in HGF rats (36%, p < 0.05 and 27%, p < 0.05 respectively). Enterocyte proliferation was also significantly increased in HGF rats (21% p < 0.05). Microarray and quantitative rt-PCR analyses showed that the genes hgfac, rac 1, cdc42, and akt 1 were more than twofold up-regulated after HGF treatment.

CONCLUSION

HGF emerges as a growth factor that enhances intestinal adaptation. The future use of HGF may potentially reduce the requirement for PN in SBS patients.

Self-Assembled Integrative Nutrient Carrier Platform Containing Green Tea Catechin for Short Bowel Syndrome Treatment

Extensive resection of the small intestine leads to the development of short bowel syndrome (SBS), which reduces the effective absorptive surface area of the intestine and predisposes patients to emaciation, malnutrition, and other severe symptoms. Herein, green tea catechin (-)-epigallocatechin gallate (EGCG) and ferrous ions (Fe²⁺ ) are utilized to construct a nutrient carrier platform that self-assembles with nutrients to form phenolic-based nutrient complexes (PNCs). PNCs effectively prolong the residence and absorption time of nutrients in the intestine. Further this platform is applied to integrate full nutrient formula, an enteral nutrition (EN) preparation containing a range of full nutrient components. In an SBS rat model, the prepared phenolic-based integrative nutrient complexes (PINCs) enhance nutritional status, improve anemia and immune function, as well as facilitate the growth of remaining intestinal villi and crypts, and maintain the integrity of the intestinal barrier. In addition, PINCs enable the modulation of gut microbial dysbiosis, enrich the abundance of beneficial bacteria, and have no toxic effects after the long-term ingestion. These results provide a proof of principle for the use of polyphenol-based nanocomplexes as EN preparation, offering a feasible strategy for both nutritional support and therapeutic perspectives for SBS treatment.

Distal Small Bowel Resection Yields Enhanced Intestinal and Colonic Adaptation

BACKGROUND

Murine ileocecal resection (ICR) has been used to investigate intestinal adaptation. The established model often includes the sacrifice of significant length of the proximal colon. Here, we optimized a highly selective vascular approach to the ICR, with primary jejunal-colic anastomosis yielding maximal colonic preservation.

MATERIALS AND METHODS

Forty C57BL/6 mice underwent a highly vascularly selective ICR. The terminal branches of the ileocecal artery are isolated apart from the mesenteric branches supplying the small bowel to be resected. The distal 50% of small bowel and cecum are resected; a primary jejuno-colonic anastomosis is performed. Animals were sacrificed at postoperative weeks 2 (n = 10) and 10 (n = 29). Proximal 50% small bowel resection (SBR) with jejuno-ileal anastomosis was also performed for comparison.

RESULTS

The entire colon (with exception of the cecum) was preserved in 100% of animals. Ninety-seven percent of animals survived to postoperative week 10, and all exhibited structural adaptation in the remnant small intestine epithelium. Crypts deepened by 175%, and villi lengthened by 106%, versus 39% and 29% in the proximal SBR cohort, respectively. Colonic proliferation, structural adaptation, and functional adaptation (measured by p-histone 3, luminal-facing apical crypt border size, and sucrase isomaltase, respectively) were increased in ICR compared with proximal SBR.

CONCLUSIONS

Highly selective isolation of the cecal vasculature allows for greater colon preservation and yields enhanced remnant intestine epithelial adaptation. ICR is also associated with greater colonic adaptation and unique plasticity toward an intestinal phenotype. These findings underscore major differences between resection sites and offer insights into the critical adaptive mechanisms in response to massive intestinal loss.

The influence on oxidative stress markers, inflammatory factors and intestinal injury-related molecules in Wahui pigeon induced by lipopolysaccharide

Introduction

The intestinal structure is the foundation for various activities and functions in poultry. An important question concerns the changes in the intestinal status under endotoxin stimulation. This study aimed to investigate the mechanism of intestinal injury induced by lipopolysaccharide (LPS) in Wahui pigeons.

Methods

Thirty-six 28-day-old healthy Wahui pigeons were randomly divided into two groups. The experimental group was injected with LPS (100 μg/kg) once per day for five days, and the control group was treated with the same amount of sterile saline. Blood and the ileum were collected from pigeons on the first, third, and fifth days of the experiment and used for oxidative stress assessment, inflammatory factor detection, histopathological examination, and positive cell localization. In addition, intestinal injury indices and mRNA expression levels (tight junction proteins, inflammatory cytokines, and factors related to autophagy and apoptosis) were evaluated.

Results

Villi in the ileum were shorter in the LPS group than in the control group, and D-lactic acid levels in the serum were significantly increased. Glutathione and catalase levels significantly decreased, but the malondialdehyde content in the serum increased. TNF-α and IL-10 were detected at higher levels in the serum, with stronger positive signals and higher mRNA expression levels, in the LPS group than in the control group. In addition, the levels of TLR4, MyD88, NF-κB, and HMGB1 in the inflammatory signaling pathway were also upregulated. Finally, the mRNA expression of Claudin3, Occludin, and ZO-1 was significantly decreased; however, that of Beclin1 and Atg5 was increased in the LPS group.

Conclusion

Ileal pathological changes and oxidative stress were caused by LPS challenge; it is proposed that this triggering regulates the inflammatory response, causing excessive autophagy and apoptosis, promoting intestinal permeability, and leading to intestinal injury in Wahui pigeons.

Compromised duodenal mucosal integrity in children with short bowel syndrome after adaptation to enteral autonomy

BACKGROUND

Intestinal adaptation has been extensively studied experimentally, but very limited data is available on human subjects. In this study we assessed intestinal adaption in humans with short bowel syndrome (SBS).

METHODS

We comparatively evaluated mucosal hyperplasia, inflammation, barrier function and nutrient transport using histology, immunohistochemistry and qPCR for selected 52 key genes in duodenal biopsies obtained from children with SBS after weaning off parenteral nutrition (n = 33), and matched controls without intestinal pathology (n = 12). Small bowel dilatation was assessed from contrast small bowel series.

RESULTS

Duodenal mucosa of SBS children showed increased histologic inflammation of lamina propria (p = 0.033) and mucosal mRNA expression of tumor necrosis factor (p = 0.027), transforming growth factor (TGF)-β2 (p = 0.006) and caveolin-1 (CAV1; p = 0.001). Villus height, crypt depth, enterocyte proliferation, apoptosis and expression of proliferation and nutrient transport genes remained unchanged. Pathologic small bowel dilatation reduced crypt depth (p = 0.045) and downregulated mRNA expression of interleukin (IL)-6 by three-fold (p = 0.008), while correlating negatively with IL6 (r = -0.609, p = 0.004). Loss of ileocecal valve (ICV) upregulated mRNA expression of toll-like receptor 4 (TLR4), TGF-β1, CAV1, several apoptosis regulating genes, and mRNA expression of zonulin (p < 0.05 for all).

CONCLUSIONS

Despite successful adaptation to enteral autonomy, duodenal mucosa of SBS children displayed histologic and molecular signs of abnormal inflammation and regulation of epithelial permeability, whereas no structural or molecular signs of adaptive hyperplasia or enhanced nutrient transport were observed. Excessive dilatation of the remaining small bowel paralleled impaired duodenal crypt homeostasis, while absence of ICV modified regulation of mucosal inflammation, regeneration and permeability.

LEVEL OF EVIDENCE

II.

TRAF6 Contributes to CFA-Induced Spinal Microglial Activation and Chronic Inflammatory Pain in Mice

Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been reported to be expressed in spinal astrocytes and is involved in neuropathic pain. In this study, we investigated the role and mechanism of TRAF6 in complete Freund's adjuvant (CFA)-evoked chronic inflammatory hypersensitivity and the effect of docosahexaenoic acid (DHA) on TRAF6 expression and inflammatory pain. We found that TRAF6 was dominantly increased in microglia at the spinal level after intraplantar injection of CFA. Intrathecal TRAF6 siRNA alleviated CFA-triggered allodynia and reversed the upregulation of IBA-1 (microglia marker). In addition, intrathecal administration of DHA inhibited CFA-induced upregulation of TRAF6 and IBA-1 in the spinal cord and attenuated CFA-evoked mechanical allodynia. Furthermore, DHA prevented lipopolysaccharide (LPS)-caused increase of TRAF6 and IBA-1 in both BV2 cell line and primary cultured microglia. Finally, intrathecal DHA reduced LPS-induced upregulation of spinal TRAF6 and IBA-1, and alleviated LPS-induced mechanical allodynia. Our findings indicate that TRAF6 contributes to pain hypersensitivity via regulating microglial activation in the spinal dorsal horn. Direct inhibition of TRAF6 by siRNA or indirect inhibition by DHA may have therapeutic effects on chronic inflammatory pain.

Broad-spectrum antibiotics alter the microbiome, increase intestinal fxr, and decrease hepatic steatosis in zebrafish short bowel syndrome

Short bowel syndrome (SBS) is associated with changes in the intestinal microbiome and marked local and systemic inflammation. There is also a late complication of SBS, intestinal failure associated liver disease (IFALD) in which hepatic steatosis progresses to cirrhosis. Most patients with SBS arrive at massive intestinal resection after a contaminating intraabdominal catastrophe and have a history of exposure to broad-spectrum antibiotics. We therefore investigated whether the administration of broad-spectrum antibiotics in conjunction with SBS in zebrafish (ZF) would replicate these systemic effects observed in humans to identify potentially druggable targets to aid in the management of SBS and resulting IFALD. In zebrafish with SBS, broad-spectrum antibiotics altered the microbiome, decreased inflammation, and reduced the development of hepatic steatosis. After two weeks of broad-spectrum antibiotics, these fish exhibited decreased alpha diversity, with less variation in microbial community composition between SBS and sham fish. Additionally, administration of broad-spectrum antibiotics was associated with decreased expression of intestinal toll-like receptor 4 (tlr4), increased expression of the intestinal gene encoding the Farnesoid X receptor (fxr), decreased expression of downstream hepatic cyp7a1, and decreased development of hepatic steatosis. SBS in zebrafish reproducibly results in increased epithelial surface area as occurs in human patients who demonstrate intestinal adaptation, but antibiotic administration in zebrafish with SBS reduced these gains with increased cell death in the intervillus pocket that contains stem/progenitor cells. These alternate states in SBS zebrafish might direct the development of future human therapies.NEW & NOTEWORTHY In a zebrafish model that replicates a common clinical scenario, systemic effects of the administration of broad-spectrum antibiotics in a zebrafish model of SBS identified two alternate states that led to the establishment of fat accumulation in the liver or its absence. Broad-spectrum antibiotics given to zebrafish with SBS over 2 wk altered the intestinal microbiome, decreased intestinal and hepatic inflammation, and decreased hepatic steatosis.

The Protective Mechanism of CAY10683 on Intestinal Mucosal Barrier in Acute Liver Failure through LPS/TLR4/MyD88 Pathway

The purpose of this study was to investigate the protective mechanism of HDAC2 inhibitor CAY10683 on intestinal mucosal barrier in acute liver failure (ALF). In order to establish ALF-induced intestinal epithelial barrier disruption models, D-galactosamine/LPS and LPS were, respectively, used with rats and NCM460 cell and then administrated with CAY10683. Transepithelial electrical resistance (TEER) was measured to detect the permeability of cells. Real-time PCR and Western blotting were employed to detect the key mRNA and protein levels. The intestinal epithelial tissue pathology was detected. After interfering with CAY10683, the mRNA and protein levels of TLR4, MyD88, TRIF, and TRAF6 were decreased compared with model group (P < 0.05), whereas the levels of ZO-1 and occluding were elevated (P < 0.05). The permeability was elevated in CAY10683-interfered groups, when compared with model group (P < 0.05). And the degree of intestinal epithelial tissue pathological damage in CAY10683 group was significantly reduced. Moreover, CAY10683 significantly decreased the TLR4 staining in animal tissue. The HDAC2 inhibitor CAY10683 could promote the damage of intestinal mucosal barrier in ALF through inhibiting LPS/TLR4/MyD88 pathway.

Host-Gut Microbiota Crosstalk in Intestinal Adaptation

Short-bowel syndrome represents the most common cause of intestinal failure and occurs when the remaining intestine cannot support fluid and nutrient needs to sustain adequate physiology and development without the use of supplemental parenteral nutrition. After intestinal loss or damage, the remnant bowel undergoes multifactorial compensatory processes, termed adaptation, which are largely driven by intraluminal nutrient exposure. Previous studies have provided insight into the biological processes and mediators after resection, however, there still remains a gap in the knowledge of more comprehensive mechanisms that drive the adaptive responses in these patients. Recent data support the microbiota as a key mediator of gut homeostasis and a potential driver of metabolism and immunomodulation after intestinal loss. In this review, we summarize the emerging ideas related to host-microbiota interactions in the intestinal adaptation processes.

Toll-like receptor 4 is critical for the development of resection-associated hepatic steatosis

BACKGROUND

A significant number of children with short bowel syndrome experience intestinal failure-associated liver disease. We recently demonstrated accelerated hepatic steatosis after 50% small bowel resection (SBR) in mice. Since SBR is associated with alterations in the gut microbiome, the purpose of this study was to determine whether TLR4 signaling is critical to the development of resection-associated hepatic steatosis.

METHODS

Male C57BL6 (control) and TLR4-knockout (KO) mice underwent 50% proximal SBR. Liver sections were analyzed to obtain the percent lipid content, and Ileal sections were assessed for morphological adaptation. Intestinal TLR4 mRNA expression was measured at 7days and 10weeks.

RESULTS

Compared to controls, TLR4 KO mice demonstrated similar weight gain and morphological adaptation after SBR. Hepatic steatosis was decreased 32-fold in the absence of TLR4. Intestinal TLR4 mRNA expression was significantly elevated 7days after SBR. We also found that TLR4 expression in the intestine was 20-fold higher in whole bowel sections compared with isolated enterocytes.

CONCLUSIONS

TLR4 signaling is critical for the development of resection-associated steatosis, but not involved in intestinal adaptation after massive SBR. Further studies are needed to delineate the mechanism for TLR4 signaling in the genesis of resection-associated liver injury.

LEVEL OF EVIDENCE

Animal study, not clinical.

Short bowel syndrome results in increased gene expression associated with proliferation, inflammation, bile acid synthesis and immune system activation: RNA sequencing a zebrafish SBS model

Background

Much of the morbidity associated with short bowel syndrome (SBS) is attributed to effects of decreased enteral nutrition and administration of total parenteral nutrition (TPN). We hypothesized that acute SBS alone has significant effects on gene expression beyond epithelial proliferation, and tested this in a zebrafish SBS model.

Methods

In a model of SBS in zebrafish (laparotomy, proximal stoma, distal ligation, n = 29) or sham (laparotomy alone, n = 28) surgery, RNA-Seq was performed after 2 weeks. The proximal intestine was harvested and RNA isolated. The three samples from each group with the highest amount of RNA were spiked with external RNA controls consortium (ERCC) controls, sequenced and aligned to reference genome with gene ontology (GO) enrichment analysis performed. Gene expression of ctnnb1, ccnb1, ccnd1, cyp7a1a, dkk3, ifng1-2, igf2a, il1b, lef1, nos2b, saa1, stat3, tnfa and wnt5a were confirmed to be elevated in SBS by RT-qPCR.

Results

RNA-seq analysis identified 1346 significantly upregulated genes and 678 significantly downregulated genes in SBS zebrafish intestine compared to sham with Ingenuity analysis. The upregulated genes were involved in cell proliferation, acute phase response signaling, innate and adaptive immunity, bile acid regulation, production of nitric oxide and reactive oxygen species, cellular barrier and coagulation. The downregulated genes were involved in folate synthesis, gluconeogenesis, glycogenolysis, fatty-acid oxidation and activation and drug and steroid metabolism. RT-qPCR confirmed gene expression differences from RNA-Sequencing.

Conclusion

Changes of gene expression after 2 weeks of SBS indicate complex and extensive alterations of multiple pathways, some previously implicated as effects of TPN. The systemic sequelae of SBS alone are significant and indicate multiple targets for investigating future therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3433-4) contains supplementary material, which is available to authorized users.