Effects of a membrane-permeable radical scavenger, Tempol, on healing of colonic anastomoses in the cecal ligation and puncture model of polymicrobial sepsis in rats

Mitochondrial dysfunction during loss of prohibitin 1 triggers Paneth cell defects and ileitis

OBJECTIVE

Although perturbations in mitochondrial function and structure have been described in the intestinal epithelium of Crohn's disease and ulcerative colitis patients, the role of epithelial mitochondrial stress in the pathophysiology of inflammatory bowel diseases (IBD) is not well elucidated. Prohibitin 1 (PHB1), a major component protein of the inner mitochondrial membrane crucial for optimal respiratory chain assembly and function, is decreased during IBD.

DESIGN

Male and female mice with inducible intestinal epithelial cell deletion of Phb1 (Phb1^iΔIEC ) or Paneth cell-specific deletion of Phb1 (Phb1^ΔPC ) and Phb1^fl/fl control mice were housed up to 20 weeks to characterise the impact of PHB1 deletion on intestinal homeostasis. To suppress mitochondrial reactive oxygen species, a mitochondrial-targeted antioxidant, Mito-Tempo, was administered. To examine epithelial cell-intrinsic responses, intestinal enteroids were generated from crypts of Phb1^iΔIEC or Phb1^ΔPC mice.

RESULTS

Phb1^iΔIEC mice exhibited spontaneous ileal inflammation that was preceded by mitochondrial dysfunction in all IECs and early abnormalities in Paneth cells. Mito-Tempo ameliorated mitochondrial dysfunction, Paneth cell abnormalities and ileitis in Phb1^iΔIEC ileum. Deletion of Phb1 specifically in Paneth cells (Phb1^ΔPC ) was sufficient to cause ileitis. Intestinal enteroids generated from crypts of Phb1^iΔIEC or Phb1^ΔPC mice exhibited decreased viability and Paneth cell defects that were improved by Mito-Tempo.

CONCLUSION

Our results identify Paneth cells as highly susceptible to mitochondrial dysfunction and central to the pathogenesis of ileitis, with translational implications for the subset of Crohn's disease patients exhibiting Paneth cell defects.

Tempol modulates the leukocyte response to inflammatory stimuli and attenuates endotoxin-induced sickness behaviour in mice

Background and aims: Lipopolysaccharide (LPS), an endotoxin, is a component of the outer membrane of Gram-negative bacteria that is able to activate the peripheral immune system, leading to changes in signalling pathways that act locally and systemically to achieve adaptive responses. Sickness behaviour is a motivational state in response to endotoxin exposure and includes depressed activity and a reduction of exploratory behaviour, potentially reorganising organism priorities to cope with infectious diseases. We hypothesised that 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) modulates the leukocyte response to endotoxins and decreases LPS-induced sickness behaviour in mice.Methods: The effects of Tempol on LPS-induced peritonitis and the respiratory burst of neutrophils primed with LPS and triggered by phorbol 12-myristate-13-acetate (PMA) were evaluated. To evaluate the effects of Tempol on sickness behaviour, the mice were submitted to an open field and forced swim tests.Results: Tempol (50-100 μM/10⁶ cells) decreased the respiratory burst of LPS-primed and PMA-stimulated neutrophils in vitro. In vivo, this nitroxide (30 and 100 mg/kg body weight) inhibited leukocyte migration to the peritoneal cavity after LPS administration in mice. Moreover, Tempol pretreatment (30 and 100 mg/kg body weight) before LPS administration also attenuated sickness behavioural changes.Conclusions: Together, these findings shed light on the mechanisms underlying the anti-inflammatory potential and confirm the therapeutic potential of nitroxides.

Gut bacteria signaling to mitochondria in intestinal inflammation and cancer

The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.

Therapeutic improvement of colonic anastomotic healing under complicated conditions: A systematic review

AIM: To identify therapeutic agents for the prophylaxis of gastrointestinal anastomotic leakage (AL) under complicated conditions.

METHODS: The PubMed and EMBASE databases were searched for English articles published between January 1975 and September 2014. Studies with the primary purpose of improving anastomotic healing in the colon or rectum under complicated preoperative and/or intraoperative conditions were included. We excluded studies investigating the adverse effects or risk assessment of an active intervention. Furthermore, investigations of biophysical materials, sealants, electrical stimulation and nutrients were excluded. The primary study outcome was biomechanical anastomotic strength or AL. The meta-analysis focused on therapeutic agents that were investigated in one animal model using the same outcome by at least three independent research groups.

RESULTS: The 65 studies included were divided into 7 different complicated animal models: Bowel ischemia, ischemia/reperfusion, bowel obstruction, obstructive jaundice, peritonitis, chemotherapy and radiotherapy. In total, 48 different therapeutic compounds were examined. The majority of investigated agents (65%) were reported as beneficial for anastomotic healing. Twelve of the agents (25%) were tested more than once in the same model, whereas 13 (27%) of the agents were tested in two or more models of complicated healing. Two therapeutic agents met our inclusion criteria for the meta-analysis. Postoperative hyperbaric oxygen therapy significantly increased anastomotic bursting pressure in ischemic colon anastomoses by a mean of 28 mmHg (95%CI: 17 to 39 mmHg, P < 0.00001). Granulocyte macrophage-colony stimulating factor failed to show a significant increase in anastomotic bursting pressure (95%CI: -20 to 21 mmHg, P = 0.97) vs controls in experimental chemotherapeutic models.

CONCLUSION: This systematic review identified potential therapeutic agents, but more studies are needed before concluding that any of these are useful for AL prophylaxis.

Hyperbaric oxygen therapy and mechanical resistence of the colonics anastomosis in rats with peritonitis

PURPOSE

To analyze the effects of hyperbaric oxygen therapy (HBO) on the mechanical resistance of anastomosis performed in rats' distal colon presenting peritonitis induced by ligature and cecal punction using the Total Energy Rupture biomechanical test (ETR).

METHODS

It was used 45 rats divided into three groups of 15 animals each. In Control Group (CG), it was performed anastomosis in distal colon without peritonitis. In Peritonitis Group (PG), it was performed anastomosis six hours after the induction of peritonitis by ligature and cecal punction. In Hyperbaric Chamber Group (HCG), it was performed six hours after the induction of peritonitis by ligature and cecal punction. The animals on CG and PG were kept at place air while the animals on HCG were placed on an experimental hyperbaric chamber in order to inhale oxygen at 100%, two absolute atmospheres, for 120 minutes, for four consecutive days. Euthanasia took place on the fifth day of the experiment. All the animals underwent to Total Energy Rupture Biomechanical Resistance test (ETR). Total Energy Rupture was defined as the necessary internal energy stored up to promote the colon rupture after an external traction force imposition.

RESULTS

The Peritonitis Group presents smaller average ETR than Control Group. There was no statistical difference between Peritonitis Group and Hyberbaric Chamber Group.

CONCLUSION

Hyperbaric oxygen therapy did not alter the mechanical resistance of anastomosis performed in distal colon of rats under the presence of peritonitis induced by ligature and cecal puncture.

Thrombospondin-1 contributes to mortality in murine sepsis through effects on innate immunity

Background

Thrombospondin-1 (TSP-1) is involved in many biological processes, including immune and tissue injury response, but its role in sepsis is unknown. Cell surface expression of TSP-1 on platelets is increased in sepsis and could activate the anti-inflammatory cytokine transforming growth factor beta (TGFβ1) affecting outcome. Because of these observations we sought to determine the importance of TSP-1 in sepsis.

Methodology/Principal Findings

We performed studies on TSP-1 null and wild type (WT) C57BL/6J mice to determine the importance of TSP-1 in sepsis. We utilized the cecal ligation puncture (CLP) and intraperitoneal E.coli injection (IP E.coli) models of peritoneal sepsis. Additionally, bone-marrow-derived macrophages (BMMs) were used to determine phagocytic activity. TSP-1−/− animals experienced lower mortality than WT mice after CLP. Tissue and peritoneal lavage TGFβ1 levels were unchanged between animals of each genotype. In addition, there is no difference between the levels of major innate cytokines between the two groups of animals. PLF from WT mice contained a greater bacterial load than TSP-1−/− mice after CLP. The survival advantage for TSP-1−/− animals persisted when IP E.coli injections were performed. TSP-1−/− BMMs had increased phagocytic capacity compared to WT.

Conclusions

TSP-1 deficiency was protective in two murine models of peritoneal sepsis, independent of TGFβ1 activation. Our studies suggest TSP-1 expression is associated with decreased phagocytosis and possibly bacterial clearance, leading to increased peritoneal inflammation and mortality in WT mice. These data support the contention that TSP-1 should be more fully explored in the human condition.

Treatment with chlorhexidine modifies the healing of colon anastomosis in rats

PURPOSE

To investigate the effects of chlorhexidine on the healing of colon anastomosis in the presence of peritonitis.

METHODS

Peritonitis was induced in male Wistar rats by cecal ligation and puncture (CLP). The abdominal cavities of experimental animals were irrigated with warm solutions containing 0.9% saline (SAL group; n = 8) or 0.05% chlorhexidine (CHD group; n = 8), following which colon anastomosis was performed. Rats of the control group (n = 8) were submitted to colon anastomosis but not to CLP. Animals were euthanized seven days after surgery, and healing was assessed by histopathological examination and by measuring anastomotic burst pressure.

RESULTS

Post-operative survival rates were 100, 87.5 and 75% for the control, SAL, and CHD groups, respectively. The degree of inflammation was significantly lower (ρ = 0.01) in the CHD group compared with the other groups, whilst the anastomotic burst pressure within the CHD group (156.7 ± 53.2 mmHg) was lower than, but not significantly different from, those of the control and SAL groups (196.3 ± 49.8, 208.6 ± 72.7 mmHg, respectively).

CONCLUSIONS

Peritoneal irrigation with chlorhexidine solution is effective in the control of inflammation promoted by peritonitis but does not improve healing of colon anastomosis in rats.

Analysis of gelatin plasma substitutes in blood based on detection of hydroxyproline derivatives

The gelatin plasma substitute is often polydisperse and heterogenous, making it difficult to determine the elimination rate and half-life in the body. In this study, one method was developed based on quantitative determination of hydroxyproline derivatives. Two plasma substitutes were prepared by succinylation and genipin-crosslinking, respectively. After transfusion, the blood samples were hydrolyzed and derivatized, and then analyzed by HPLC. A two-phase exponential association equation was used for fitting the time-concentration curves. The results indicated that this method could be used for quantitative determination of gelatin in blood, and the pharmacokinetic parameters such as elimination rate and half-life.

A systematic review of experimental treatments for mitochondrial dysfunction in sepsis and multiple organ dysfunction syndrome

Sepsis and multiple organ dysfunction syndrome (MODS) are major causes of morbidity and mortality in the intensive care unit. Recently mitochondrial dysfunction has been proposed as a key early cellular event in critical illness. A growing body of experimental evidence suggests that mitochondrial therapies are effective in sepsis and MODS. The aim of this article is to undertake a systematic review of the current experimental evidence for the use of therapies for mitochondrial dysfunction during sepsis and MODS and to classify these mitochondrial therapies. A search of the MEDLINE and PubMed databases (1950 to July 2009) and a manual review of reference lists were conducted to find experimental studies containing data on the efficacy of mitochondrial therapies in sepsis and sepsis-related MODS. Fifty-one studies were included in this review. Five categories of mitochondrial therapies were defined-substrate provision, cofactor provision, mitochondrial antioxidants, mitochondrial reactive oxygen species scavengers, and membrane stabilizers. Administration of mitochondrial therapies during sepsis was associated with improvements in mitochondrial electron transport system function, oxidative phosphorylation, and ATP production and a reduction in cellular markers of oxidative stress. Amelioration of proinflammatory cytokines, caspase activation, and prevention of the membrane permeability transition were reported. Restoration of mitochondrial bioenergetics was associated with improvements in hemodynamic parameters, organ function, and overall survival. A substantial body of evidence from experimental studies at both the cellular and the organ level suggests a beneficial role for the administration of mitochondrial therapies in sepsis and MODS. We expect that mitochondrial therapies will have an increasingly important role in the management of sepsis and MODS. Clinical trials are now required.

Effects of amniotic membrane on the healing of primary colonic anastomoses in the cecal ligation and puncture model of secondary peritonitis in rats

PURPOSE

We aimed to investigate the effects of amniotic membrane on primary colonic anastomoses in a rat peritonitis model.

MATERIALS AND METHODS

Fifty female Sprague Dawley rats were used in the study. Bacterial peritonitis was induced in all rats by performing a cecal ligation and puncture. Ten rats served as controls for the bursting pressure measurement, while the other 40 animals were divided into two groups (the anastomosis group (P) or the amniotic membrane group (PA)), and all of them underwent colonic anastomosis. The latter group had amniotic membrane covering their anastomoses. Half of the PA and P groups were sacrificed on the third postoperative day (PA3, P3), and the other half on the seventh postoperative day (PA7, P7).

RESULTS

The bursting pressures were significantly higher in groups PA3 and PA7 compared with P3 (p < 0.01) and P7 (p < 0.05), respectively. Inflammatory cell infiltration and adhesion scores were significantly lower in groups PA3 and PA7 compared with groups P3 (p < 0.001, p < 0.01, respectively) and P7 (p < 0.001, p < 0.05, respectively). Neoangiogenesis, fibroblast activity, collagen deposition, and hydroxyproline concentrations were significantly higher in groups with amniotic membrane than in groups without amniotic membrane (p < 0.05, for all comparisons).

CONCLUSION

This study showed that the covering of colonic anastomoses with amniotic membrane significantly prevented the delaying effect of intraperitoneal sepsis and provided a safer and stronger anastomosis than suture and that this was the case for both the early and late phases of anastomotic healing in the colon.

Tempol reduces bacterial translocation after ischemia/reperfusion injury in a rat model of superior mesenteric artery occlusion

PURPOSE

We investigated whether Tempol, a water-soluble antioxidant, prevents the harmful effects of superior mesenteric ischemia/reperfusion on intestinal tissues in rats.

METHODS

The rats were divided into three groups of 10. In group 1, the superior mesenteric artery (SMA) was isolated but not occluded, and in groups 2 and 3 the superior mesenteric artery was occluded for 60 min. After that, the clamp was removed and reperfusion began. In group 3, 5 min before the start of reperfusion, a bolus dose of 30 mg/kg Tempol was administered intravenously and continued at a dose of 30 mg/kg for 60 min. All animals were euthanized after 24 h and tissue samples were collected for analysis.

RESULTS

There was a significant increase in myeloperoxidase activity, malondialdehyde levels, and the incidence of bacterial translocation in group 2, with a decrease in glutathione levels. These parameters were found to be normalized in group 3. The intestinal mucosal injury score in group 2 was significantly higher than those in groups 1 and 3.

CONCLUSION

Tempol prevents bacterial translocation while precluding the harmful effects of ischemia/reperfusion injury on intestinal tissues in a rat model of superior mesenteric artery occlusion.

The effects of intraperitoneal sildenafil administration on healing of left colonic anastomoses and intra-abdominal adhesion formation in the presence of intra-abdominal infection

PURPOSE

The objective of this pilot study was to establish an animal model for intra-abdominal infection and to examine the effect of sildenafil on anastomotic healing of the left colon and intra-abdominal adhesion formation.

METHODS

Fourteen Winstar rats underwent colonic transsection and primary anastomosis after performing intra-abdominal infection. Rats were divided into two groups: Group 1 (n = 7): intra-abdominal infection, resection, and anastomoses; Group 2 (n = 7): intra-abdominal infection, resection, anastomoses, and sildenafil. Anastomotic bursting pressures, hydroxyproline levels, histopathologic grading, and abdominal adhesions were accessed on the postoperative Day 7.

RESULTS

Anastomotic healing was found to be improved in terms of a bursting pressure (P = 0.02). Histopathological examination revealed an increase in angiogenesis (P = 0.007). Moreover, intra-abdominal adhesions were significantly less in rats given sildenafil (P = 0.03).

CONCLUSION

Sildenafil may improve anastomotic healing of the left colon and diminishes peritoneal adhesion formation in the presense of abdominal infection.