Injured Gut Research Articles

Bloodstream Infections in Infants and Children With Congenital Heart Disease Undergoing Cardiac Surgery

Children with congenital heart disease undergoing cardiac surgery are at risk for laboratory-confirmed bloodstream infections (LCBIs). These infections can lead to morbidity, mortality, and increased health care costs. The role of mucosal barrier injury in causing LCBIs is unknown. To describe characteristics of LCBIs in patients admitted to cardiac intensive care and step-down units and to assess frequencies of National Healthcare Safety Network infection types and associations with organism classification, patient clinical factors, and infection outcomes. A retrospective cohort analysis using manual electronic medical record data abstraction included children with congenital heart disease who developed an LCBI while receiving inpatient cardiac care between August 2011 and November 2018 at one institution. Demographic, clinical, laboratory, and outcome variables were collected and analyzed with descriptive and inferential statistics. Eighty-seven patients with congenital heart disease developed 103 LCBIs during the study time frame. The most common causative microorganisms were gram-positive bacteria, including Enterococcus faecalis and Staphylococcus epidermidis. Sixty-three percent of causative organisms were characterized as originating from mucosal barrier injury, although no infections met National Healthcare Safety Network criteria for mucosal barrier injury LCBIs. Translocation of bacteria through injured gut mucosa may cause bloodstream infections in children with congenital heart disease. Further investigation is warranted to understand microbiome changes that adversely select pathogenic gut organisms. Preventive care to maintain intact gut function and a healthy microbiome should be explored for this patient population.

Designing Microfluidic Devices to Sort Haematopoietic Stem Cells Based on Their Mechanical Properties.

Aim Few haematopoietic stem cells (HSCs) injected systemically for therapeutic purposes actually reach sites of injury as the vast majority become entrapped within pulmonary capillaries. One promising approach to maintain circulating HSC numbers would be to separate subpopulations with smaller size and/or greater deformability from a heterogeneous population. This study tested whether this could be achieved using label-free microfluidic devices. Methods 2 straight (A-B) and 3 spiral (C-E) devices were fabricated with different dimensions. Cell sorting was performed at different flow rates after which cell diameter and stiffness were determined using micromanipulation. Cells isolated using the most efficient device were tested intravitally for their ability to home to the mouse injured gut. Results Only straight Device B at a high flow rate separated HSCs with different mechanical properties. Side outlets collected mostly deformable cells (nominal rupture stress/σR = 6.81 kPa; coefficient of variation/CV = 0.31) at a throughput of 2.3 × 105 cells/min. All spiral devices at high flow rates separated HSCs with different stiffness and size. Inner outlets collected mostly deformable cells in Devices C (σR = 25.06 kPa; CV = 0.26), D (σR = 22.21 kPa; CV = 0.41), and E (σR = 29.26 kPa; CV = 0.27) at throughputs of 2.3 × 105 cells/min, 1.5 × 105 cells/min, and 1.6 × 105 cells/min, respectively. Since Device C separated cells with higher efficiency and throughput, it was utilized to test the homing ability of separated cells in vivo. Significantly more deformable cells were observed trafficking through the injured gut—interestingly, increased retention was not observed. Conclusion This study applied microfluidics to separate subpopulations from one stem cell type based on their intrinsic mechanical heterogeneity. Fluid dynamics within curved devices most effectively separated HSCs. Such devices may benefit cellular therapy.

Functional Role of Microbiota‐derived Metabolites in the GPCR‐mediated Regulation of Intestinal Wound Healing and Barrier Function

The mammalian intestine houses a complex and abundant ensemble of commensal bacteria, which are in constant cross‐talk with the intestinal epithelial cells, and thereby, ensure gut homeostasis, development, permeability, and repair. Wound regeneration is a complex but coordinated cellular events to repair injured gut mucosa, which involves both cellular proliferation and migration. Gut barrier function is central to the health and is critical in a wide variety of diseases including inflammatory bowel diseases (IBD). Our recent metagenomics study discovered a consortium of novel gut mucosa‐associated proregenerative symbiotic bacteria, which preferentially enrich in and colonize the injured mucosa to augment epithelial repair. The resident microbiota of the gut is endowed with over a hundred times more genes than those in our genome. However, the microbiota's more than nine million genes, and their metabolic functions remained mostly unrecognized. We performed an unbiased screening analysis by mass spectrometry‐based metabolomic profiling of intact and wounded mucosa in germ‐free and conventional mice. Unlike the germ‐free animals, the colon of the conventional mice demonstrated increased amounts of acidic microbial metabolites, which established an extracellular pH gradient with more acidic pH at the apex of the colonic crypt. We found that the murine and human intestinal epithelial cells express the proton‐sensing G‐protein coupled‐receptor GPCR68. Intriguingly, the murine colonic contents of the conventional mouse or a specific metabolite, 2‐hydroxy‐4‐methylpentanoic acid (HMP) decreases the extracellular pH to modulate claudin‐4 dependent paracellular permeability and to regulate the proliferation of intestinal epithelial cells in a GPCR68‐dependent manner. Importantly, our findings highlighted that the HMP‐stimulated intestinal epithelial wound closure requires GPR68. Collectively, our data underscore the significance of intestinal metabolites in modulating the extracellular proton concentration in the gut mucosal microenvironment. Furthermore, our findings demonstrate that the GPCR68 functions as the sensor of microbially modulated proton gradient that is potentially involved in the maintenance of gut mucosal homeostasis, wound healing, and restoration of the intestinal barrier function.Support or Funding InformationK01DK114391 (National Institute of Diabetes and Digestive and Kidney Diseases), R01DK089763 (National Institute of Diabetes and Digestive and Kidney Diseases), R01AI064462 (National Institute of Allergy and Infectious Diseases)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Pretreatment of Mesenchymal Stem Cells Manipulates Their Vasculoprotective Potential While Not Altering Their Homing Within the Injured Gut.

Mesenchymal stem cells (MSCs) have shown therapeutic promise in many experimental and clinical models of inflammation. However, a commonly reported feature of MSC transplantation is poor homing to injured tissues. Previously, we have shown that pretreatment with cytokines/chemical factors enhances hematopoietic SC adhesion within intestinal microvasculature following ischemia‐reperfusion (IR) injury. Using intravital microscopy, the ability of similar pretreatment strategies to enhance the recruitment of murine MSCs to murine intestinal microvasculature following IR injury was investigated. Primary MSCs were isolated from bone marrow and selected on the basis of platelet‐derived growth factor receptor‐α and SC antigen‐1 positivity (PDGFRα+/Sca‐1+). MSC recruitment was similar in IR injured gut mucosa when compared with sham operated controls, with limited cell adhesion observed. MSCs appeared contorted in microvessels, suggesting physical entrapment. Although not recruited specifically by injury, MSC administration significantly reduced neutrophil recruitment and improved tissue perfusion in the severely injured jejunum. Vasculoprotective effects were not demonstrated in the lesser injured ileum. Pretreatment of MSCs with tumor necrosis factor (TNF)‐α, CXCL12, interferon (IFN)‐γ, or hydrogen peroxide did not enhance their intestinal recruitment. In fact, TNFα and IFNγ removed the previous therapeutic ability of transplanted MSCs to reduce neutrophil infiltration and improve perfusion in the jejunum. We provide direct evidence that MSCs can rapidly limit leukocyte recruitment and improve tissue perfusion following intestinal IR injury. However, this study also highlights complexities associated with strategies to improve MSC therapeutic efficacy. Future studies using cytokine/chemical pretreatments to enhance MSC recruitment/function require careful consideration and validation to ensure therapeutic function is not impeded. Stem Cells 2015;33:2785–2797

Enhancing the Adhesion of Hematopoietic Precursor Cell Integrins with Hydrogen Peroxide Increases Recruitment within Murine Gut

Hematopoietic stem cells (HSCs) migrate to injury sites and aid in tissue repair. However, clinical success is poor and is partially due to limited HSC recruitment. We hypothesized that HSC pretreatment with H2O2 would enhance their recruitment to injured gut. As HSCs are rare cells, the number of primary cells obtained from donors is often inadequate for functional experiments. To circumvent this, in this study we utilized a functionally relevant cell line, HPC-7. Anesthetized mice were subjected to intestinal ischemia-reperfusion (IR) injury, and HPC-7 recruitment was examined intravitally. Adhesion to endothelial cells (ECs), injured gut sections, and ICAM-1/VCAM-1 protein were also quantitated in vitro. H2O2 pretreatment significantly enhanced HPC-7 recruitment to injured gut in vivo. A concomitant reduction in pulmonary adhesion was also observed. Enhanced adhesion was also observed in all in vitro models. Increased clustering of α4 and β2 integrins, F-actin polymerization, and filopodia formation were observed in pretreated HPC-7s. Importantly, H2O2 did not reduce HPC-7 viability or proliferative ability. HPC-7 recruitment to injured gut can be modulated by H2O2 pretreatment. This may be through increasing the affinity or avidity of surface integrins that mediate HPC-7 homing to injured sites or through stimulating the migratory apparatus. Strategies that enhance hematopoietic stem/progenitor cell recruitment may ultimately affect their therapeutic efficacy.

Mechanisms of Adhesion and Subsequent Actions of a Haematopoietic Stem Cell Line, HPC-7, in the Injured Murine Intestinal Microcirculation In Vivo

ObjectivesAlthough haematopoietic stem cells (HSCs) migrate to injured gut, therapeutic success clinically remains poor. This has been partially attributed to limited local HSC recruitment following systemic injection. Identifying site specific adhesive mechanisms underpinning HSC-endothelial interactions may provide important information on how to enhance their recruitment and thus potentially improve therapeutic efficacy. This study determined (i) the integrins and inflammatory cyto/chemokines governing HSC adhesion to injured gut and muscle (ii) whether pre-treating HSCs with these cyto/chemokines enhanced their adhesion and (iii) whether the degree of HSC adhesion influenced their ability to modulate leukocyte recruitment.MethodsAdhesion of HPC-7, a murine HSC line, to ischaemia-reperfused (IR) injured mouse gut or cremaster muscle was monitored intravitally. Critical adhesion molecules were identified by pre-treating HPC-7 with blocking antibodies to CD18 and CD49d. To identify cyto/chemokines capable of recruiting HPC-7, adhesion was monitored following tissue exposure to TNF-α, IL-1β or CXCL12. The effects of pre-treating HPC-7 with these cyto/chemokines on surface integrin expression/clustering, adhesion to ICAM-1/VCAM-1 and recruitment in vivo was also investigated. Endogenous leukocyte adhesion following HPC-7 injection was again determined intravitally.ResultsIR injury increased HPC-7 adhesion in vivo, with intestinal adhesion dependent upon CD18 and muscle adhesion predominantly relying on CD49d. Only CXCL12 pre-treatment enhanced HPC-7 adhesion within injured gut, likely by increasing CD18 binding to ICAM-1 and/or CD18 surface clustering on HPC-7. Leukocyte adhesion was reduced at 4 hours post-reperfusion, but only when local HPC-7 adhesion was enhanced using CXCL12.ConclusionThis data provides evidence that site-specific molecular mechanisms govern HPC-7 adhesion to injured tissue. Importantly, we show that HPC-7 adhesion is a modulatable event in IR injury and further demonstrate that adhesion instigated by injury alone is not sufficient for mediating anti-inflammatory effects. Enhancing local HSC presence may therefore be essential to realising their clinical potential.

Dipeptidyl peptidase-4 expression is reduced in Crohn's disease

BackgroundDipeptidyl peptidase 4 (DP4) is a serine protease that preferentially cleaves N‐terminal dipeptides from polypeptides containing proline or alanine as the penultimate amino acid. DP4 inactivates glucagon like peptide-2 (GLP-2), a trophic peptide with cytoprotective and reparative properties in the injured gut; therefore DP4 potentially inhibits repair processes. DP4 also modulates the activity of GLP-1 and polypeptide YY (PYY) which regulate appetite and motility. No data are yet available on the tissue and plasma expression of DP4 in inflammatory bowel disease (IBD). MethodsTissue and plasma were studied from active CD and healthy controls for DP4 quantification. Experiments were also carried out in a reductionist Caco-2 cell line model of intestinal inflammation with TNFα incubation. DP4 expression was studied by tissue Western blotting and plasma enzymelinked immunosorbent assay (ELISA), in addition to quantitative polymerase chain reaction (qPCR). ResultsThere was a ~2.7-fold decrease in DP4 protein in CD tissue (p=0.05). Plasma DP4 in CD was also significantly lower than the control group. A negative correlation between plasma DP4 levels and inflammatory activity as measured by C-reactive protein was observed. In Caco-2 cells an ~18-fold increase (p<0.0001) in DP4 protein expression was seen after incubation with TNFα at a concentration of 25ng/μl for 48hours paralleled by a 2-fold increase in DP4 mRNA. DiscussionDP4 is reduced in tissue and plasma in active Crohn's disease. This is unlikely to represent simple downregulation induced by inflammation since the key proinflammatory cytokine strongly upregulated DP4 expression in Caco-2 cells. Clearly a more complex situation exists in vivo. We propose that reduced DP4 activity limits the cleavage of regulatory peptides, for example potentiating the trophic signal from GLP-2. Pharmacological DP4 inhibition may present an additional therapeutic target in IBD.

The Histopathalogical Effects of Retinoic Acid on the Tissues

The aim of this study is to sum up the important information that has emerged from the last 10 years of experimental investigations over the effects of retinoic acid (RA) on embryonic structure and adult tissues. Administration of exogenous RA can affect the connective tissues including enhancement of myeloid compartment and suppression of erythroid cells and conversion of hematopoietic stem cells to erythroid progenitors. Also, it is able to induce osteogenic differentiation of stem cells derived from adipose tissues and etc. Examining the neural tissue highlighted that disruption of RA signaling in the adult leads to degeneration of motor neurons and development of some diseases. In vitro administration of All-Trans Retinoic Acid (ATRA) increased dendritic growth and synaptophysin puncta intensity and increased expressions of neuronal nuclei, neuron specific enolase, synaptophysin. RA also promotes expression of a marker of mature astrocytes. On muscular tissue, it can inhibit proliferation of smooth muscle cells (SMC) while promoting differentiation of SMC in vitro instead. The ATRA stimulates skeletal myogenesis while inhibiting cardiomyogenesis and hypertrophy and proliferation of cultured neonatal cardiomyocytes and cardiofibroblasts. In addition, differences in levels of embryonic RA may contribute to variability in great artery anomalies. In epithelial tissue, the squamous epithelium exposed to ATRA showed the columnar differentiation independent to proliferation. Also RA seems able to rescue the regeneration process of injured gut and revealing a better wound healing of the intestine undergone intra-operative radiotherapy. It can interrupt the process of progressive fibrosis, enhancements of the langerhans islets, exocrine pancreas, modulate the health of the mammary glands and repairs the lung cell. Thus, differences in levels of endogenous RA in embryonic and adult tissues may contribute to anomalies and pathogenesis of disease, furthermore RA has paradoxical effects on the parts forming the connective and muscles tissue in equal conditions.

The role of mesenteric lymph in pathogenesis of systemic inflammatory response syndrome and systemic complications following severe acute pancreatitis in rats

To observe the effect of mesenteric lymph duct ligation (MLDL) on systemic inflammatory response syndrome (SIRS) and systemic complications in severe acute pancreatitis (SAP) in rats. Twenty-four Sprague-Dawley (SD) male rats were randomly divided into sham operation group, SAP group, and SAP+MLDL group, with 8 rats in each group. Sham operation group underwent laparotomy only. SAP complicated with multiple organ injury model was reproduced by retrograde injection of sodium taurocholate into the pancreatic duct in SD rats. In SAP+MLDL group MLDL was performed before reproduction of SAP. Rats were sacrificed at 24 hours after operation. The terminal ileum were collected for examination under light microscope. The samples of pancreas, lung and liver were collected for measuring the level of myeloperoxidase (MPO). The mesenteric lymph nodes were harvested for standard bacteriologic culture. The blood levels of diamine oxidase (DAO), D-lactate, endotoxin, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were also measured. The blood levels of DAO [(0.64 + or - 0.17) kU/L vs. (0.37 + or - 0.07) kU/L], D-lactate [(8.16 + or - 1.79) ng/L vs. (3.24 + or - 1.00) ng/L], endotoxin [(0.068 + or - 0.019) kEU/L vs. (0.033 + or - 0.009) kEU/L], TNF-alpha [(65.21 + or - 13.38) ng/L vs. (22.16 + or - 5.04) ng/L] and IL-6 [(7.95 + or - 1.83) ng/L vs. (4.26 + or - 1.23) ng/L] in SAP group were increased significantly comparing with those in sham operation group (all P<0.01). The contents of pulmonary tissue [(9.07 + or - 2.52) U/g vs. (4.38 + or - 1.29) U/g], pancreatic [(5.14 + or - 1.24) U/g vs. (2.88 + or - 0.75) U/g] and liver [(6.36 + or - 1.63) U/g vs. (3.19 + or - 0.96) U/g] MPO were increased significantly in SAP group comparing with those in sham operation group (all P<0.01). The rate of bacterial translocation to mesenteric lymph nodes in SAP group was significantly higher than that of the sham operation group (75.0% vs. 0, P< 0.01). Compared to SAP group, the contents of DAO [(0.50 + or - 0.13) kU/L], D-lactate [(6.23 + or - 1.25) ng/L] , endotoxin [(0.048 + or - 0.014) kEU/L], TNF-alpha [(48.50 + or - 13.23) ng/L] and IL-6 [(6.06 + or - 1.64) ng/L] were significantly decreased in SAP+MLDL group (P<0.05 or P<0.01). The levels of pulmonary [(6.58 + or - 1.96) U/g], pancreatic [(4.01 + or - 1.05) U/g] and liver [(4.64 + or - 1.34) U/g] MPO, as well as the rate of bacterial translocation to mesenteric lymph nodes (12.5%) were significantly lower in SAP+MLDL group than those in SAP group (all P<0.05). MLDL decreases bacteria/ endotoxin translocation and reduces the systemic inflammatory response by interrupting the lymph flow from the injured gut into the bloodstream. This procedure may protect the small intestine mucosal barrier function and other organs by reducing the neutrophil aggregation and the release of cytokines.

Glucagon-like Peptide-2 Does Not Modify the Growth or Survival of Murine or Human Intestinal Tumor Cells

Glucagon-like peptide-2 (GLP-2) secreted from enteroendocrine cells exerts proabsorptive, regenerative, and cytoprotective actions in the normal and injured gut epithelium. Hence, sustained GLP-2 receptor (GLP-2R) activation represents a strategy under investigation for the prevention and treatment of chemotherapy-induced mucositis. Nevertheless, the consequences of increased GLP-2R signaling for the growth and survival of intestinal tumor cells remain poorly understood. We studied the proliferative and cytoprotective actions of GLP-2 in human colon cancer cells stably transfected with the GLP-2R and in nude mice harboring GLP-2R(+) human colon cancer cells. The importance of the GLP-2R for tumor growth was also examined in Apc(Min/+) mice chronically treated with exogenous GLP-2 and in Apc(Min/+):Glp2r(-/-) mice. GLP-2 increased cyclic AMP accumulation and produced cell-specific activation of growth and survival pathways in DLD-1, SW480, and HT29 cells. However, GLP-2 did not stimulate cell growth or attenuate cycloheximide-, LY294002-, indomethacin-, or chemotherapy-induced cytotoxicity in vitro. Moreover, chronic GLP-2 administration had no effect on the growth of human colon cancer cell xenografts in nude mice in vivo. Daily GLP-2 treatment for 7 weeks increased growth of normal gut mucosa but did not increase the number or size of polyps in Apc(Min/+) mice, and genetic disruption of the Glp2r gene in Apc(Min/+) mice did not modify polyp size or number. Taken together, although GLP-2R activation engages signaling pathways promoting cell proliferation and cytoprotection in the normal gut epithelium, sustained direct or indirect modulation of GLP-2R signaling does not modify intestinal tumor cell growth or survival.

Mesenteric Lymph Duct Ligation Attenuates Lung Injury and Neutrophil Activation After Intraperitoneal Injection of Endotoxin in Rats

The release of injurious factors into the mesenteric lymph from the ischemic intestine has been shown to contribute to lung injury and systemic inflammation after shock and trauma. Since endotoxemia is also associated with gut injury, we tested the hypothesis that mesenteric lymph contributes to the lung injury seen in endotoxemia and that the ligation of the mesenteric lymph duct will attenuate this injury. To test this hypothesis, male Sprague-Dawley rats were given intraperitoneal injections (i.p.) of lipopolysaccharide (LPS) (10 mg/kg) with or without mesenteric lymph duct ligation (LDL). At 6 hours after injection of LPS, gut and lung injury, lung permeability, and neutrophil CD11b expression were measured. Lung permeability was quantified by calculating the percentage of Evan's Blue dye and the total protein concentration in the bronchoalveolar lavage fluid (BALF) when compared with the plasma and gut and lung injury were assessed morphologically. LDL attenuated LPS- induced lung injury, lung permeability, and rat PMN CD11b expression but not villous injury. The magnitude of lung permeability as measured by Evan's Blue was approximately twofold greater in the LPS rats when compared with the LPS-treated rats with LDL. The expression of CD11b was greater in the LPS rats when compared with LPS rats with LDL or to sham controls (582 +/- 106 vs. 364 +/- 29 vs. 224 +/- 12 mean fluorescence intensity p < 0.001). Based on the attenuation of lung injury and CD11b expression, these results suggest that LPS-induced lung injury and neutrophil activation is partially mediated through the release of factors from the injured gut into mesenteric lymph.

Protease protects from snakes and sepsis

High blood pressure, sepsis, and snake bites might all be cured by the same antidote, according to Schneider et al. (page 2629). Figure 1 Without the mast cell protease Mc-cpa, most mice die within an hour of being injected with ET-1. High blood pressure and septic shock are both enhanced by a 21–amino acid peptide called ET-1. This peptide is secreted by blood vessel cells that have been activated by inflammatory cytokines. ET-1 triggers the contraction of smooth muscle cells that are wrapped around blood vessels, causing blood to flow through the squeezed vessels at a higher pressure. This contraction prevents blood from getting to its target tissues, leading to sepsis-associated organ malfunction. ET-1 is structurally similar to a snake venom toxin called sarafotoxin. This toxin is lethal to mice that lack a type of immune cell called mast cells. These mice also die when sepsis-causing bacteria enter the abdominal cavity from an injured gut. How mast cells protect against sepsis and snake venom, however, was unclear. They express both ET-1 receptors and degradative enzymes that normally destroy pathogens. The authors thus imagined that the mast cells might trap ET-1 (and the toxin) and then degrade it. They focused on mast cells' most abundant defensive protease, Mc-cpa. The team now shows that Mc-cpa is indeed the weapon of choice against ET-1 and the toxin. Mice that lack mast cells died within hours after injection with ET-1. Mc-cpa protected mice by snipping and thus disarming the dangerous peptides. Mice that secreted inactive Mc-cpa were as susceptible to sepsis and snake venom as mice that lacked mast cells. ET-1 is needed for mast cell activation, but its subsequent degradation might limit its long-term destructive effects.

Mesenteric lymph duct ligation decreases red blood cell alterations caused by acute pancreatitis

Background Both experimental and clinical studies have shown that acute pancreatitis (AP) causes a significant decrease in red blood cell (RBC) deformability. The mechanisms by which AP induces RBC injury are unknown. The purpose of this study was to test the hypothesis that factors carried in the mesenteric lymph after an attack of AP significantly contribute to the RBC injury observed in AP. Methods RBC deformability was determined by means of laser-assisted ektacytometry in mesenteric lymph duct–ligated and non-ligated rats subjected to AP and in sham-operated animals. Results AP was associated with significant alterations of RBC deformability indices, namely the elongation index and half maximal RBC elongation. Pancreatitis-induced RBC deformability changes were partially prevented by mesenteric lymph duct ligation. Conclusions Mesenteric lymph in AP contains factors that cause RBC damage, which is manifested by decreased deformability. Interruption of the lymph flow from the injured gut into the bloodstream decreases these RBC alterations.

LYMPHATIC SYSTEM AS A PATH UNDERLYING THE SPREAD OF LUNG AND GUT INJURY AFTER INTESTINAL ISCHEMIA/REPERFUSION IN RATS

We investigated in rats the influence of the lymphatic system and of tumor necrosis factor (TNF) on the lung inflammation resulting from intestinal ischemia/reperfusion (I/R) performed by 45-min occlusion of the superior mesenteric artery followed by 2 h of reperfusion. A group of rats had the thoracic lymph duct ligated before I/R. In lungs, intestinal I/R evoked a significant neutrophil recruitment, and enhanced microvascular permeability, in addition to generation of TNF in serum. In the gut, there was lowered lactate dehydrogenase (LDH) activity and increased microvascular permeability. Upon lymph duct ligation, I/R rats had a significant reduction of pulmonary neutrophil recruitment and plasma extravasation, in addition to high amounts of TNF in the lymph, contrasting with undetectable levels in the serum. In addition, LDH gut levels in these animals were close to basal values; there was also some (yet significant) reduction of microvascular permeability, suggesting that the ligation of the lymphatic duct exerted some degree of protection against the intestinal injury caused by I/R. In I/R rats, the treatment with pentoxifylline (PTX) reduced TNF in serum and blunted other lung alterations. The gut alterations caused by intestinal I/R were largely blocked by PTX. On the other hand, in I/R rats with lymph duct ligation, PTX exacerbated the reduction of pulmonary neutrophil recruitment, but did not affect pulmonary and intestinal microvascular permeabilities. Similarly, intestinal LDH activity and serum TNF levels were unaffected. Overall, our data show that the pulmonary and gut injuries induced by intestinal I/R are partially dependent on TNF, which is conceivably generated in the injured gut tissue due to intestinal I/R and carried by the lymphatic system. Thus, the mesenteric lymphatic drainage seems to play a role as a path modulator of the pulmonary and intestinal dysfunctions that follow a gut trauma.

The contribution of radiation-induced injury to the gastrointestinal tract in the development of multi-organ dysfunction syndrome or failure

Severe damage to the gastrointestinal tract (GIT), such as loss of the gastrointestinal mucosa and haemorrhage, following accidental overexposure to ionising radiation appears to be a determinant feature in patient mortality. Injury to the GIT may be direct, as this tissue is particularly radiation sensitive, as well as indirect as a result of radiation burns and bone marrow aplasia. Similar to other severe trauma situations such as thermal burns, radiation exposure results in reduced intestinal barrier integrity, which initiates and/or perpetuates inflammatory–anti-inflammatory mediator release. This may result in damage to distant organs. In this context, the injured gut may be considered as a “key player” or “motor” in the development of multiple organ dysfunction syndrome or failure. Of note is that radiation exposure elicits similar GIT injury of both mucosal and vascular elements, in contrast to other severe physical insults. Common factors are the intestinal inflammatory response and loss of barrie...

Role of bombesin on gut mucosal growth.

The authors examined the effects of exogenous bombesin (BBS) on gut mucosal growth in chow-fed rats and the mucosal regeneration after gut atrophy brought about by feeding an elemental diet and after intestinal injury produced by methotrexate (MTX). Bombesin is one of many gastrointestinal peptides implicated in the regulation of gut mucosal growth. Although BBS is known to stimulate growth of normal pancreatic tissue, the trophic effect of BBS on gut mucosa is less clear and its exact role in gut mucosal regeneration and repair is not known. Rats were fed a regular chow diet (control) or an elemental diet plus either saline or BBS (10 micrograms/kg). In another experiment, rats fed a chow diet and treated with saline or BBS were given MTX (20 micrograms/kg) or a single intraperitoneal injection. In all experiments, small and large bowel mucosa and pancreas were removed and analyzed for BBS-mediated proliferation. Bombesin produced significant mucosal proliferation of the small bowel at day 14, but not at day 7, in rats fed regular chow. In contrast, BBS treatment for 7 days produced significant proliferation in both the atrophic and injured gut mucosa of rats given elemental diet or MTX. Bombesin may be an important enterotrophic factor for normal mucosal proliferation and may be clinically beneficial as an agent to restore or maintain gut mucosa during periods of atrophy or injury.

Endotoxinemia and thrombocytopenia during neonatal necrotizing enterocolitis.

Thrombocytopenia frequently complicates neonatal necrotizing enterocolitis (NEC) and has been postulated to result from absorption of bacterial endotoxins from the injured gut. The authors tested blood obtained during 47 episodes of NEC for endotoxin-like activity (ELA), using a Limulus amoebocyte lysate assay and found 23 patients (49%) had positive results. Concentrations of ELA in plasma ranged from 0.26 to 300 ng/mL of Escherichia coli equivalent activity, with a geometric mean of 1.1 ng/mL. Serial platelet measurements were available from 40 infants, 11 (28%) of whom had nadir counts below 100,000/mm3 following NEC onset. Nine of 19 infants (47%) with ELA in plasma and only 2 of 21 without (9.5%, P less than 0.05) developed thrombocytopenia, suggesting that endotoxinemia may indeed contribute to platelet depletion during NEC.