Fcγ RIIb protects from reperfusion injury by controlling antibody and type I IFN-mediated tissue injury and death.

Intestinal ischemia and reperfusion (I/R) is accompanied by an exacerbated inflammatory response characterized by deposition of IgG, release of inflammatory mediators, and intense neutrophil influx in the small intestine, resulting in severe tissue injury and death. We hypothesized that Fcγ RIIb activation by deposited IgG could inhibit tissue damage during I/R. Our results showed that I/R induction led to the deposition of IgG in intestinal tissue during the reperfusion phase. Death upon I/R occurred earlier and was more frequent in Fcγ RIIb-/- than WT mice. The higher lethality rate was associated with greater tissue injury and bacterial translocation to other organs. Fcγ RIIb-/- mice presented changes in the amount and repertoire of circulating IgG, leading to increased IgG deposition in intestinal tissue upon reperfusion in these mice. Depletion of intestinal microbiota prevented antibody deposition and tissue damage in Fcγ RIIb-/- mice submitted to I/R. We also observed increased production of ROS on neutrophils harvested from the intestines of Fcγ RIIb-/- mice submitted to I/R. In contrast, Fcγ RIII-/- mice presented reduced tissue damage and neutrophil influx after reperfusion injury, a phenotype reversed by Fcγ RIIb blockade. In addition, we observed reduced IFN-ß expression in the intestines of Fcγ RIII-/- mice after I/R, a phenotype that was also reverted by blocking Fcγ RIIb. IFNAR-/- mice submitted to I/R presented reduced lethality and TNF release. Altogether our results demonstrate that antibody deposition triggers Fcγ RIIb to control IFN-ß and IFNAR activation and subsequent TNF release, tailoring tissue damage, and death induced by reperfusion injury.

Intestinal congestion and reperfusion injury: damage caused to the intestinal tract and distal organs.

In clinical practice, intestinal autologous diseases, ailments and organ transplants can cause severe congestive damage to the intestinal tract. However, after the etiological factor is gotten rid of and blood flow is free without any hinderance, further damage to the intestinal wall often occurs, causing other related organ dysfunctions. This ultimately results in intestinal congestion reperfusion injury (ICRI). When the structure and function of the intestine are destroyed, bacteria, metabolites and endotoxins in the intestinal tract perfuse and enter the portal vein through the already compromised intestinal mucosa, to the other organs via the liver. Nevertheless, this gives rise to further aggravation of the injury, and reperfusion injury syndrome occurs. ICRI is a very common complication encountered by clinicians, and its harm is more severe and serious as compared with that caused by ischemia-reperfusion. Quite a few number of studies on ICRI have been reported to date. The exact mechanism of the injury is still idiopathic, and effective treatment strategies are still limited. Based on recent studies, this article is aimed at reviewing the destruction, damage mechanisms resulting from ICRI to the intestinal anatomical sites and distant organs. It is geared towards providing new ideas for the prevention and therapeutic approaches of ICRI.

Anti-inflammatory and antioxidant effects of the nanocomposite Fullerol decrease the severity of intestinal inflammation induced by gut ischemia and reperfusion.

Intestinal ischemia is a vascular emergency that arises when blood flow to the intestine is compromised. Reperfusion is necessary to restore intestinal function but might lead to local and systemic inflammatory responses and bacterial translocation, with consequent multiple organ dysfunction syndrome (MODS). During reperfusion occurs production of reactive oxygen species. These species contribute to intestinal injury through direct toxicity or activation of inflammatory pathways. Fullerol is a nanacomposite which has been shown to act as reactive oxygen species and reactive nitrogen species (RNS) scavengers. Thus, our aim was to evaluate whether Fullerol confer anti-inflammatory activity during intestinal ischemia and reperfusion (IIR). Intestinal ischemia was induced by total occlusion of the superior mesenteric artery. Groups were treated with vehicle or Fullerol 10 min before reperfusion. Mice were euthanized after 6 h of reperfusion, and small intestines were collected for evaluation of plasma extravasation, leukocyte influx, cytokine production and histological damage. Bacterial translocation to the peritoneal cavity and reactive oxygen and nitrogen species production by lamina propria cells were also evaluated. Our results showed that treatment with Fullerol inhibited bacterial translocation to the peritoneal cavity, delayed and decreased the lethality rates and diminished neutrophil influx and intestinal injury induced by IIR. Reduced severity of reperfusion injury in Fullerol-treated mice was associated with blunted reactive oxygen and nitrogen species production in leukocytes isolated from gut lamina propria and decreased production of pro-inflammatory mediators. Thus, the present study shows that Fullerol is a potential therapy to treat inflammatory bowel disorders associated with bacterial translocation, such as IIR.

Effects of Gut Metabolites and Microbiota in Healthy and Marginal Livers Submitted to Surgery.

Microbiota is defined as the collection of microorganisms within the gastrointestinal ecosystem. These microbes are strongly implicated in the stimulation of immune responses. An unbalanced microbiota, termed dysbiosis, is related to the development of several liver diseases. The bidirectional relationship between the gut, its microbiota and the liver is referred to as the gut-liver axis. The translocation of bacterial products from the intestine to the liver induces inflammation in different cell types such as Kupffer cells, and a fibrotic response in hepatic stellate cells, resulting in deleterious effects on hepatocytes. Moreover, ischemia-reperfusion injury, a consequence of liver surgery, alters the microbiota profile, affecting inflammation, the immune response and even liver regeneration. Microbiota also seems to play an important role in post-operative outcomes (i.e., liver transplantation or liver resection). Nonetheless, studies to determine changes in the gut microbial populations produced during and after surgery, and affecting liver function and regeneration are scarce. In the present review we analyze and discuss the preclinical and clinical studies reported in the literature focused on the evaluation of alterations in microbiota and its products as well as their effects on post-operative outcomes in hepatic surgery.

Gut Microbiota Restricts NETosis in Acute Mesenteric Ischemia-Reperfusion Injury.

OBJECTIVE: Recruitment of neutrophils and formation of neutrophil extracellular traps (NETs) contribute to lethality in acute mesenteric infarction. To study the impact of the gut microbiota in acute mesenteric infarction, we used gnotobiotic mouse models to investigate whether gut commensals prime the reactivity of neutrophils towards formation of neutrophil extracellular traps (NETosis). Approach and Results: We applied a mesenteric ischemia-reperfusion (I/R) injury model to germ-free (GF) and colonized C57BL/6J mice. By intravital imaging, we quantified leukocyte adherence and NET formation in I/R-injured mesenteric venules. Colonization with gut microbiota or monocolonization with Escherichia coli augmented the adhesion of leukocytes, which was dependent on the TLR4 (Toll-like receptor-4)/TRIF (TIR-domain-containing adapter-inducing interferon-ß) pathway. Although neutrophil accumulation was decreased in I/R-injured venules of GF mice, NETosis following I/R injury was significantly enhanced compared with conventionally raised mice or mice colonized with the minimal microbial consortium altered Schaedler flora. Also ex vivo, neutrophils from GF and antibiotic-treated mice showed increased LPS (lipopolysaccharide)-induced NETosis. Enhanced TLR4 signaling in GF neutrophils was due to elevated TLR4 expression and augmented IRF3 (interferon regulatory factor-3) phosphorylation. Likewise, neutrophils from antibiotic-treated conventionally raised mice had increased NET formation before and after ischemia. Increased NETosis in I/R injury was abolished in conventionally raised mice deficient in the TLR adaptor TRIF. In support of the desensitizing influence of enteric LPS, treatment of GF mice with LPS via drinking water diminished LPS-induced NETosis in vitro and in the mesenteric I/R injury model. CONCLUSIONS: Collectively, our results identified that the gut microbiota suppresses NETing neutrophil hyperreactivity in mesenteric I/R injury, while ensuring immunovigilance by enhancing neutrophil recruitment.

Current Knowledge about the Effect of Nutritional Status, Supplemented Nutrition Diet, and Gut Microbiota on Hepatic Ischemia-Reperfusion and Regeneration in Liver Surgery.

Ischemia-reperfusion (I/R) injury is an unresolved problem in liver resection and transplantation. The preexisting nutritional status related to the gut microbial profile might contribute to primary non-function after surgery. Clinical studies evaluating artificial nutrition in liver resection are limited. The optimal nutritional regimen to support regeneration has not yet been exactly defined. However, overnutrition and specific diet factors are crucial for the nonalcoholic or nonalcoholic steatohepatitis liver diseases. Gut-derived microbial products and the activation of innate immunity system and inflammatory response, leading to exacerbation of I/R injury or impaired regeneration after resection. This review summarizes the role of starvation, supplemented nutrition diet, nutritional status, and alterations in microbiota on hepatic I/R and regeneration. We discuss the most updated effects of nutritional interventions, their ability to alter microbiota, some of the controversies, and the suitability of these interventions as potential therapeutic strategies in hepatic resection and transplantation, overall highlighting the relevance of considering the extended criteria liver grafts in the translational liver surgery.

Dual roles of commensal bacteria after intestinal ischemia and reperfusion.

PURPOSE: The roles of commensal bacteria after intestinal ischemia and reperfusion (IIR) are unclear. In current study, we aim to investigate the effects and underlying mechanisms of commensal bacteria in injury and epithelial restitution after IIR. METHODS: Commensal gut bacteria were deleted by broad-spectrum antibiotics in mice. IIR was induced by clamping superior mesenteric artery. Intestinal injury, permeability, epithelial proliferation, and proinflammatory activity of mesenteric lymph were investigated. RESULTS: Commensals deletion improved mice survival in the early phase, but failed to improve the overall survival at 96 h after IIR. Commensals deletion reduced proliferation of intestinal epithelial cells (IEC) and augmented proinflammatory activity of mesenteric lymph after IIR. Lipopolysaccharides (LPS) supplement promoted IEC proliferation and improved survival in mice with commensals deletion after IIR. LPS induced production of prostaglandin E2 (PGE2) in mucosa via toll-like receptor 4-NFκB-cyclooxygenase 2 pathway. PGE2 enhanced IEC proliferation in vivo, which was preceded by activation of Akt and extracellular signal-regulated kinase (ERK) 1/2. Blocking of EGFR, PI3K/Akt activity abolished LPS-induced IEC proliferation. CONCLUSIONS: Commensal bacteria are essential for epithelial restitution after IIR, which enhance IEC proliferation via induction of PGE2.

Comparative Evaluation of Translocation of GFP Producing Escherichia coli Strains in Acute Intestinal Obstruction.

Comparative evaluation of translocation of E. coli GFP-producing strains in experimental rats with obturation and strangulated intestinal obstruction was carried out. Translocation of infused GFP-producing E. coli strain was studied by bacteriological methods in male rats with experimental obturation and strangulated intestinal obstruction with various ischemia/reperfusion cycles. The maximum incidence of translocation in obturation intestinal obstruction was observed after 24 h. In strangulated intestinal obstruction, the highest incidence was recorded in ischemia/reperfusion cycles of 1 h/2 h and 2 h/6 h. No appreciable differences in the incidence of translocation in animals with two types of intestinal obstruction were detected.

Identification and Complete Stereochemical Assignments of the New Resolvin Conjugates in Tissue Regeneration in Human Tissues that Stimulate Proresolving Phagocyte Functions and Tissue Regeneration.

Resolvin conjugates in tissue regeneration (RCTRs) are new chemical signals that accelerate resolution of inflammation, infection, and tissue regeneration. Herein, using liquid chromatography-tandem mass spectrometry-based metabololipidomics, we identified RCTRs in human spleen, lymph node, bone marrow, and brain. In human spleen incubated with Staphylococcus aureus, endogenous RCTRs were increased along with conversion of deuterium-labeled docosahexaenoic acid, conferring pathway activation. Physical and biological properties of endogenous RCTRs were matched with those prepared by total organic synthesis. The complete stereochemical assignment of bioactive RCTR1 is 8R-glutathionyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid, RCTR2 is 8R-cysteinylglycinyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid, and RCTR3 is 8R-cysteinyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid. These stereochemically defined RCTRs stimulated human macrophage phagocytosis, efferocytosis, and planaria tissue generation. Proteome profiling demonstrated that RCTRs regulated both proinflammatory and anti-inflammatory cytokines with human macrophages. In microfluidic chambers, the three RCTRs limited human polymorphonuclear cell migration. In hind-limb ischemia-reperfusion-initiated organ injury, both RCTR2 and RCTR3 reduced polymorphonuclear cell infiltration into lungs. In infectious peritonitis, RCTR1 shortened the resolution intervals. Each RCTR (1 nmol/L) accelerated planaria tissue regeneration by approximately 0.5 days, with direct comparison to both maresin and protectin CTRs. Together, these results identify a new bioactive RCTR (ie, RCTR3) in human tissues and establish the complete stereochemistry and rank-order potencies of three RCTRs in vivo. Moreover, RCTR1, RCTR2, and RCTR3 each exert potent anti-inflammatory and proresolving actions with human leukocytes.

The effect of antioxidant supplementation on bacterial translocation after intestinal ischemia and reperfusion.

The intestine is highly sensitive to ischemia/reperfusion (I/R) injury. Intestinal I/R may cause local tissue injury and disruption of the intestinal mucosal barrier, allowing the passage of viable bacteria and endotoxins from the gastrointestinal lumen to distant organs. This phenomenon, known as bacterial translocation (BT), may lead to systemic disorders with high morbidity and mortality. Oxidative stress mediators such as reactive oxygen species, polymorphonuclear neutrophils and nitric oxide are believed to contribute to the intestinal I/R injury. Many antioxidants have shown protective effects against I/R injury of various organs. The present article provides an overview of studies investigating the effect of antioxidant supplementation on BT after intestinal I/R.

Inflammation drives renal scarring in experimental pyelonephritis.

Acquired renal scarring occurs in a subset of patients following febrile urinary tract infections and is associated with hypertension, proteinuria, and chronic kidney disease. Limited knowledge of histopathology, immune cell recruitment, and gene expression changes during pyelonephritis restricts the development of therapies to limit renal scarring. Here, we address this knowledge gap using immunocompetent mice with vesicoureteral reflux. Transurethral inoculation of uropathogenic Escherichia coli in C3H/HeOuJ mice leads to renal mucosal injury, tubulointerstitial nephritis, and cortical fibrosis. The extent of fibrosis correlates most significantly with inflammation at 7 and 28 days postinfection. The recruitment of neutrophils and inflammatory macrophages to infected kidneys is proportional to renal bacterial burden. Transcriptome analysis reveals molecular signatures associated with renal ischemia-reperfusion injury, immune cell chemotaxis, and leukocyte activation. This murine model recapitulates the cardinal histopathological features observed in humans with acquired renal scarring following pyelonephritis. The integration of histopathology, quantification of cellular immune influx, and unbiased transcriptional profiling begins to define potential mechanisms of tissue injury during pyelonephritis in the context of an intact immune response. The clear relationship between inflammatory cell recruitment and fibrosis supports the hypothesis that acquired renal scarring arises as a consequence of excessive host inflammation and suggests that immunomodulatory therapies should be investigated to reduce renal scarring in patients with pyelonephritis.

Depletion of Gut Microbiota Protects against Renal Ischemia-Reperfusion Injury.

An accumulating body of evidence shows that gut microbiota fulfill an important role in health and disease by modulating local and systemic immunity. The importance of the microbiome in the development of kidney disease, however, is largely unknown. To study this concept, we depleted gut microbiota with broad-spectrum antibiotics and performed renal ischemia-reperfusion (I/R) injury in mice. Depletion of the microbiota significantly attenuated renal damage, dysfunction, and remote organ injury and maintained tubular integrity after renal I/R injury. Gut flora-depleted mice expressed lower levels of F4/80 and chemokine receptors CX3CR1 and CCR2 in the F4/80+ renal resident macrophage population and bone marrow (BM) monocytes than did control mice. Additionally, compared with control BM monocytes, BM monocytes from gut flora-depleted mice had decreased migratory capacity toward CX3CL1 and CCL2 ligands. To study whether these effects were driven by depletion of the microbiota, we performed fecal transplants in antibiotic-treated mice and found that transplant of fecal material from an untreated mouse abolished the protective effect of microbiota depletion upon renal I/R injury. In conclusion, we show that depletion of gut microbiota profoundly protects against renal I/R injury by reducing maturation status of F4/80+ renal resident macrophages and BM monocytes. Therefore, dampening the inflammatory response by targeting microbiota-derived mediators might be a promising therapy against I/R injury.

Involvement of corticotropin-releasing factor and corticotropin-releasing factor 2 receptors in pathogenesis of ischemia/reperfusion-induced enteritis in rats.

We herein investigated, using a corticotropin-releasing factor (CRF) agonist and antagonists, whether CRF plays a role in the pathogenesis of ischemia/reperfusion-induced small intestinal lesions in rats. Under pentobarbital anesthesia, the superior mesenteric artery was clamped (ischemia) for 75 min, followed by reperfusion with removal of the clamp. After a 24-h reperfusion, the area of hemorrhagic lesions that developed in the small intestine was measured. Urocortin I (CRF receptor 1/2 agonist), astressin (CRF receptor 1/2 antagonist), NBI27914 (CRF receptor 1 antagonist), or astressin 2B (CRF receptor 2 antagonist) was administered i.v. twice: 5 min before ischemia and 6 hours after reperfusion. Ischemia/reperfusion caused hemorrhagic lesions in the small intestine in ampicillin- and aminoguanidine-inhibitable manners, accompanied by enterobacterial invasion and the up-regulation of inducible nitric oxide synthase expression and myeloperoxidase activity. The severity of ischemia/reperfusion-induced lesions was significantly reduced by astressin and astressin 2B, but not by NBI27914, with the suppression of bacterial invasion, myeloperoxidase activity, and inducible nitric oxide synthase expression. In contrast, urocortin I markedly aggravated these lesions, and this response was completely abrogated by the co-administration of astressin 2B, but not NBI27914. The gene expression of CRF, CRF receptor 1, and CRF receptor 2 was observed in the small intestine, and remained unchanged following ischemia/reperfusion. These results suggest that ischemia/reperfusion caused hemorrhagic lesions in the small intestine, the pathogenesis of which involved enterobacteria and inducible nitric oxide synthase/nitric oxide. These lesions were aggravated by urocortin I in an astressin 2B-inhibitable manner, but suppressed by astressin in a CRF receptor 2-dependent manner. Endogenous CRF may be involved in the pathogenesis of ischemia/reperfusion-induced enteritis, possibly via the activation of peripheral CRF receptor 2.

Ischemia/Reperfusion Injury Alters Sphingolipid Metabolism in the Gut.

BACKGROUND: Intestinal ischemia/reperfusion injury (I/R) is a significant cause of morbidity and mortality in surgical patients. Ceramide is a mediator of apoptosis and has been implicated as increasing bacterial infection susceptibility. The metabolite of ceramide, sphingosine, was recently shown to play an important role in the cell-autonomous, innate immune response of the upper respiratory tract by killing bacterial pathogens. The role of ceramide and/or sphingosine after mesenteric I/R is unknown. We investigated the specific effects of intestinal I/R on tissue ceramide and sphingosine concentration and resulting susceptibility to bacterial invasion. METHODS: To simulate intestinal I/R, C57BL/6 mice underwent 30 minutes of vascular clamp-induced occlusion of the superior mesenteric artery followed by variable reperfusion times. Jejunum segments and intraluminal contents were analyzed for ceramide, sphingosine and bacteria using immunohistochemistry. Jejunum samples were also homogenized and cultured to quantify bacterial presence in the proximal intestine. RESULTS: We hypothesized that I/R induces an increase of ceramide in the intestine resulting in increased permeability, while a concomitant decrease of sphingosine may permit bacterial overgrowth. Control mice had no measurable bacteria in their proximal jejunum as measured by tissue culture and immunohistochemistry. After I/R, bacterial counts in the jejunum increased in a time-dependent manner, reaching a peak at 12 hours after reperfusion. Immunohistochemical analysis revealed a marked increase in ceramide in the vasculature of jejunal villi. In contrast, while ceramide concentrations in the epithelial cells decreased after I/R, sphingosine levels appeared to remain unchanged. Surprisingly, bacteria present in the jejunal lumen following I/R contained a ceramide coat. CONCLUSION: These data indicate that intestinal I/R leads to small intestine bacterial overgrowth as well as ceramide formation in the jejunal vasculature, which may contribute to the gut permeability associated with this injury. Moreover, our novel finding of ceramide in bacterial membranes represents a new opportunity to investigate the dynamic pathogenicity of the gut microbiome. The hypothesis that a decrease of sphingosine after I/R permits bacterial overgrowth in the intestine was not confirmed.

Effect of Candida albicans on Intestinal Ischemia-reperfusion Injury in Rats.

BACKGROUND: Inflammation is supposed to play a key role in the pathophysiological processes of intestinal ischemia-reperfusion injury (IIRI), and Candida albicans in human gut commonly elevates inflammatory cytokines in intestinal mucosa. This study aimed to explore the effect of C. albicans on IIRI. METHODS: Fifty female Wistar rats were divided into five groups according to the status of C. albicans infection and IIRI operation: group blank and sham; group blank and IIRI; group cefoperazone plus IIRI; group C. albicans plus cefoperazone and IIRI (CCI); and group C. albicans plus cefoperazone and sham. The levels of inflammatory factors tumor necrosis factor (TNF)-µ, interleukin (IL)-6, IL-1ß, and diamine oxidase (DAO) measured by enzyme-linked immunosorbent assay were used to evaluate the inflammation reactivity as well as the integrity of small intestine. Histological scores were used to assess the mucosal damage, and the C. albicans blood translocation was detected to judge the permeability of intestinal mucosal barrier. RESULTS: The levels of inflammatory factors TNF-µ, IL-6, and IL-1ß in serum and intestine were higher in rats undergone both C. albicans infection and IIRI operation compared with rats in other groups. The levels of DAO (serum: 44.13 ± 4.30 pg/ml, intestine: 346.21 ± 37.03 pg/g) and Chiu scores (3.41 ± 1.09) which reflected intestinal mucosal disruption were highest in group CCI after the operation. The number of C. albicans translocated into blood was most in group CCI ([33.80 ± 6.60] ×102 colony forming unit (CFU)/ml). CONCLUSION: Intestinal C. albicans infection worsened the IIRI-induced disruption of intestinal mucosal barrier and facilitated the subsequent C. albicans translocation and dissemination.

Clostridium butyricum attenuates cerebral ischemia/reperfusion injury in diabetic mice via modulation of gut microbiota.

Diabetes is known to exacerbate cerebral ischemia/reperfusion (I/R) injury. Here, we investigated the effects of Clostridium butyricum on cerebral I/R injury in the diabetic mice subjected to 30min of bilateral common carotid arteries occlusion (BCCAO). The cognitive impairment, the blood glucose level, neuronal injury, apoptosis, and expressions of Akt, phospho-Akt (p-Akt), and caspase-3 level were assessed. Meanwhile, the changes of gut microbiota in composition and diversity in the colonic feces were evaluated. Our results showed that diabetic mice subjected to BCCAO exhibited worsened cognitive impairment, cell damage and apoptosis. These were all attenuated by C. butyricum. Moreover, C. butyricum reversed cerebral I/R induced decreases in p-Akt expression and increases in caspase-3 expression, leading to inhibiting neuronal apoptosis. C. butyricum partly restored cerebral I/R induced decreases of fecal microbiota diversity, changes of fecal microbiota composition. Together, these findings highlight the important role of bacteria in the bidirectional communication of the gut-brain axis and suggest that certain probiotics might prove to be useful therapeutic adjuncts in cerebral I/R injury with diabetes.

Lung Ischemia-Reperfusion is a Sterile Inflammatory Process Influenced by Commensal Microbiota in Mice.

Lung ischemia-reperfusion (IR) complicates numerous clinical processes, such as cardiac arrest, transplantation, and major trauma. These conditions generate sterile inflammation, which can cause or worsen acute lung injury. We previously reported that lung and systemic inflammation in a mouse model of ventilated lung IR depends on Toll-like receptor 4 (TLR-4) signaling and the presence of alveolar macrophages. Here, we tested the hypothesis that the intestinal microbiome has a role in influencing the inflammatory response to lung IR. Lung IR was created in intubated mechanically ventilated mice via reversible left pulmonary artery occlusion followed by reperfusion. Inflammatory markers and histology were tracked during varying periods of reperfusion (from 1 to 24 h). Separate groups of mice were given intestinally localized antibiotics for 8 to 10 weeks and then were subjected to left lung IR and analysis of lungs and plasma for markers of inflammation. Alveolar macrophages from antibiotic-treated or control mice were tested ex vivo for inflammatory responses to bacterial TLR agonists, namely, lipopolysaccharide and Pam3Cys. We found that inflammation generated by left lung IR was rapid in onset and dissipated within 12 to 24 h. Treatment of mice with intestinally localized antibiotics was associated with a marked attenuation of circulating and lung inflammatory markers as well as reduced histologic evidence of infiltrating cells and edema in the lung after IR. Alveolar macrophages from antibiotic-treated mice produced less cytokines ex vivo when stimulated with TLR agonists as compared with those from control mice. Our data indicate that the inflammatory response induced by nonhypoxic lung IR is transient and is strongly influenced by intestinal microbiota. Furthermore, these data suggest that the intestinal microbiome could potentially be manipulated to attenuate the post-IR pulmonary inflammatory response.

Protective effects of terminal ileostomy against bacterial translocation in a rat model of intestinal ischemia/reperfusion injury.

AIM: To investigate the effects of terminal ileostomy on bacterial translocation (BT) and systemic inflammation after intestinal ischemia/reperfusion (I/R) injury in rats. METHODS: Thirty-two rats were assigned to either the sham-operated group, I/R group, I/R + resection and anastomosis group, or the I/R + ileostomy group. The superior mesenteric artery was occluded for 60 min. After 4 h, tissue samples were collected for analysis. BT was assessed by bacteriologic cultures, intestinal permeability and serum levels of endotoxin; systemic inflammation was assessed by serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10, as well as by the activity of myeloperoxidase (MPO) and by intestinal histopathology. RESULTS: Intestinal I/R injury not only caused morphologic damage to ileal mucosa, but also induced BT, increased MPO activity and promoted the release of TNF-α, IL-6, and IL-10 in serum. BT and ileal mucosa injuries were significantly improved and levels of TNF-α and IL-6 in serum were decreased in the I/R + ileostomy group compared with the I/R + resection and anastomosis group. CONCLUSION: Terminal ileostomy can prevent the detrimental effects of intestinal I/R injury on BT, intestinal tissue, and inflammation.

Intestinal microbiota-kidney cross talk in acute kidney injury and chronic kidney disease.

The pathophysiology of acute kidney injury (AKI) involves multiple and overlapping immunological, biochemical, and hemodynamic mechanisms that modulate the effects of both the initial insult and the subsequent repair. Limited but recent experimental data have revealed that the intestinal microbiota significantly affects outcomes in AKI. Additional evidence shows significant changes in the intestinal microbiota in chronic kidney disease patients and in experimental AKI. In this minireview, we discuss the current status of the effect of intestinal microbiota on kidney diseases, the immunomodulatory effects of intestinal microbiota, and the potential mechanisms by which microbiota can modify kidney diseases and vice versa. We also propose future studies to clarify the role of intestinal microbiota in kidney diseases and to explore how the modification of gut microbiota may be a potential therapeutic tool.

The microbiota protects against ischemia/reperfusion-induced intestinal injury through nucleotide-binding oligomerization domain-containing protein 2 (NOD2) signaling.

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2), an intracellular pattern recognition receptor, induces autophagy on detection of muramyl dipeptide (MDP), a component of microbial cell walls. The role of bacteria and NOD2 signaling toward ischemia/reperfusion (I/R)-induced intestinal injury response is unknown. Herein, we report that I/R-induced intestinal injury in germ-free (GF) C57BL/6 wild-type (WT) mice is worse than in conventionally derived mice. More important, microbiota-mediated protection against I/R-induced intestinal injury is abrogated in conventionally derived Nod2(-/-) mice and GF Nod2(-/-) mice. Also, WT mice raised in specific pathogen-free (SPF) conditions fared better against I/R-induced injury than SPF Nod2(-/-) mice. Moreover, SPF WT mice i.p. administered 10 mg/kg MDP were protected against injury compared with mice administered the inactive enantiomer, l-MDP, an effect lost in Nod2(-/-) mice. However, MDP administration failed to protect GF mice from I/R-induced intestinal injury compared with control, a phenomenon correlating with undetectable Nod2 mRNA level in the epithelium of GF mice. More important, the autophagy-inducer rapamycin protected Nod2(-/-) mice against I/R-induced injury and increased the levels of LC3(+) puncta in injured tissue of Nod2(-/-) mice. These findings demonstrate that NOD2 protects against I/R and promotes wound healing, likely through the induction of the autophagy response.