Heme oxygenase-1 protects against neutrophil-mediated intestinal damage by down-regulation of neutrophil p47phox and p67phox activity and O2- production in a two-hit model of alcohol intoxication and burn injury

Faecal proteomics links neutrophil degranulation with mortality in patients with alcohol-associated hepatitis

OBJECTIVE

Patients with alcohol-associated hepatitis (AH) have a high mortality. Alcohol exacerbates liver damage by inducing gut dysbiosis, bacterial translocation and inflammation, which is characterised by increased numbers of circulating and hepatic neutrophils.

DESIGN

In this study, we performed tandem mass tag (TMT) proteomics to analyse proteins in the faeces of controls (n=19), patients with alcohol-use disorder (AUD; n=20) and AH (n=80) from a multicentre cohort (InTeam). To identify protein groups that are disproportionately represented, we conducted over-representation analysis using Reactome pathway analysis and Gene Ontology to determine the proteins with the most significant impact. A faecal biomarker and its prognostic effect were validated by ELISA in faecal samples from patients with AH (n=70), who were recruited in a second and independent multicentre cohort (AlcHepNet).

RESULT

Faecal proteomic profiles were overall significantly different between controls, patients with AUD and AH (principal component analysis p=0.001, dissimilarity index calculated by the method of Bray-Curtis). Proteins that showed notable differences across all three groups and displayed a progressive increase in accordance with the severity of alcohol-associated liver disease were predominantly those located in neutrophil granules. Over-representation and Reactome analyses confirmed that differentially regulated proteins are part of granules in neutrophils and the neutrophil degranulation pathway. Myeloperoxidase (MPO), the marker protein of neutrophil granules, correlates with disease severity and predicts 60-day mortality. Using an independent validation cohort, we confirmed that faecal MPO levels can predict short-term survival at 60 days.

CONCLUSIONS

We found an increased abundance of faecal proteins linked to neutrophil degranulation in patients with AH, which is predictive of short-term survival and could serve as a prognostic non-invasive marker.

Recombinant Human Annexin A5 Alleviated Traumatic-Brain-Injury Induced Intestinal Injury by Regulating the Nrf2/HO-1/HMGB1 Pathway

Aims: Annexin A5 (ANXA5) exhibited potent antithrombotic, antiapoptotic, and anti-inflammatory properties in a previous study. The role of ANXA5 in traumatic brain injury (TBI)-induced intestinal injury is not fully known. Main methods: Recombinant human ANXA5 (50 µg/kg) or vehicle (PBS) was administered to mice via the tail vein 30 min after TBI. Mouse intestine tissue was gathered for hematoxylin and eosin staining 0.5 d, 1 d, 2 d, and 7 d after modeling. Intestinal Western blotting, immunofluorescence, TdT-mediated dUTP nick-end labeling staining, and enzyme-linked immunosorbent assays were performed 2 days after TBI. A series of kits were used to assess lipid peroxide indicators such as malonaldehyde, superoxide dismutase activity, and catalase activity. Key findings: ANXA5 treatment improved the TBI-induced intestinal mucosa injury at different timepoints and significantly increased the body weight. It significantly reduced apoptosis and matrix metalloproteinase-9 and inhibited the degradation of tight-junction-associated protein in the small intestine. ANXA5 treatment improved intestinal inflammation by regulating inflammation-associated factors. It also mitigated the lipid peroxidation products 4-HNE, 8-OHDG, and malonaldehyde, and enhanced the activity of the antioxidant enzymes, superoxide dismutase and catalase. Lastly, ANXA5 significantly enhanced nuclear factor E2-related factor 2 (Nrf2) and hemeoxygenase-1, and decreased high mobility group box 1 (HMGB1). Significance: Collectively, the results suggest that ANXA5 inhibits TBI-induced intestinal injury by restraining oxidative stress and inflammatory responses. The mechanisms involved sparking the Nrf2/hemeoxygenase-1-induced antioxidant system and suppressing the HMGB1 pathway. ANXA5 may be an attractive therapeutic candidate for protecting against TBI-induced intestinal injury.

The Effect of Paracrine Factors Released by Irradiated Peripheral Blood Mononuclear Cells on Neutrophil Extracellular Trap Formation

Neutrophil extracellular trap (NET)-formation represents an important defence mechanism for the rapid clearance of infections. However, exaggerated NET formation has been shown to negatively affect tissue-regeneration after injury. As our previous studies revealed the strong tissue-protective and regenerative properties of the secretome of stressed peripheral blood mononuclear cells (PBMCsec), we here investigated the influence of PBMCsec on the formation of NETs. The effect of PBMCsec on NET formation was assessed ex vivo in ionomycin stimulated neutrophils derived from healthy donors using flow cytometry, image stream analysis, and quantification of released extracellular DNA. The effect of PBMCsec on molecular mechanisms involved in NET formation, including Ca-flux, protein kinase C activity, reactive oxygen species production, and protein arginine deiminase 4 activity, were analysed. Our results showed that PBMCsec significantly inhibited NET formation. Investigation of the different biological substance classes found in PBMCsec revealed only a partial reduction in NET formation, suggesting a synergistic effect. Mechanistically, PBMCsec treatment did not interfere with calcium signalling and PKC-activation, but exerted anti-oxidant activity, as evidenced by reduced levels of reactive oxygen species and upregulation of heme oxygenase 1 and hypoxia inducible-factor 1 in PBMCsec-treated neutrophils. In addition, PBMCsec strongly inhibited the activation of protein arginine deiminase 4 (PAD4), ultimately leading to the inhibition of NET formation. As therapeutics antagonizing excessive NET formation are not currently available, our study provides a promising novel treatment option for a variety of conditions resulting from exaggerated NET formation.

Itaconate Suppresses Formation of Neutrophil Extracellular Traps (NETs): Involvement of Hypoxia-Inducible Factor 1α (Hif-1α) and Heme Oxygenase (HO-1)

Neutrophil extracellular traps (NETs) immobilize pathogens during early stages of systemic inflammation but as the reaction progresses they become detrimental to endothelial cells and the organ-specific cells. For this reason it would be of importance to control their formation by either physiological or pharmacological means. Endogenously, formation of NETs is under control of cellular and whole organism metabolism as shown previously in the course of bacterial systemic inflammation, obesity or the combination of the two. Numerous leukocytes are subjected to immunometabolic regulation and in macrophages exposure to lipopolysaccharide (LPS) leads to two breaks in the Krebs cycle that impact this cell functioning. As a consequence of the first break, anti-microbial itaconic acid (itaconate) is produced whereas the second break activates hypoxia-inducible factor-1α (Hif-1α). In turn, itaconate activates transcription of the anti-inflammatory nuclear factor erythroid 2-related factor 2 (Nrf2) which upregulates cyto-protective heme oxygenase (HO-1). Here we report that exogenously added derivative of the itaconic acid, 4-octyl itaconate (4-OI), diminishes formation of NETs by neutrophils of either normal (lean) or obese mice, and independently of the age of the animals or immunoaging. Elucidating the mechanism of this inhibition we unravel that although Nrf2/HO-1 expression itself is not altered by 4-OI, it is up-regulated when compared against the NET formation while Hif-1α is downregulated in 4-OI-pre-treated LPS-stimulated neutrophils in either way. We further show that blockage of Hif-1α by its specific inhibitor diminishes NET release as does inhibition by 4-OI. Also inhibition of HO-1 activity correlates with diminished LPS-induced NET release upon pre-treatment with 4-OI albeit LPS alone induced NETs are not HO-1-dependent. In summary, we unravel that 4-OI inhibits NET formation by murine neutrophils independently of their origin (health vs. metabolically challenged animals) and the age of individuals/immunosenescence via inhibition of Hif-1α and induction of HO-1.

Lycopene Inhibits IL-6 Expression by Upregulating NQO1 and HO-1 via Activation of Nrf2 in Ethanol/Lipopolysaccharide-Stimulated Pancreatic Acinar Cells

In alcoholic pancreatitis, alcohol increases gut permeability, which increases the penetration of endotoxins, such as lipopolysaccharides (LPS). LPS act as clinically significant triggers to increase pancreatic damage in alcoholic pancreatitis. Ethanol or LPS treatment increases reactive oxygen species (ROS) production in pancreatic acinar cells. ROS induce inflammatory cytokine production in pancreatic acinar cells, leading to pancreatic inflammation. The nuclear erythroid-2-related factor 2 (Nrf2) pathway is activated as a cytoprotective response to oxidative stress, and induces the expression of NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Lycopene exerts anti-inflammatory and antioxidant effects in various cells. We previously showed that lycopene inhibits NADPH oxidase to reduce ROS and IL-6 levels, and zymogene activation in ethanol or palmitoleic acid-treated pancreatic acinar cells. In this study, we examined whether lycopene inhibits IL-6 expression by activating the Nrf2/NQO1-HO-1 pathway, and reducing intracellular and mitochondrial ROS levels, in ethanol and LPS-treated pancreatic AR42J cells. Lycopene increased the phosphorylated and nuclear-translocated Nrf2 levels by decreasing the amount of Nrf2 sequestered in the cytoplasm via a complex formation with Kelch-like ECH1-associated protein 1 (Keap1). Using exogenous inhibitors targeting Nrf2 and HO-1, we showed that the upregulation of activated Nrf2 and HO-1 results in lycopene-induced suppression of IL-6 expression and ROS production. The consumption of lycopene-rich foods may prevent the development of ethanol and LPS-associated pancreatic inflammation by activating Nrf2-mediated expression of NQO1 and HO-1, thereby decreasing ROS-mediated IL-6 expression in pancreatic acinar cells.

IL-23 Promotes Neutrophil Extracellular Trap Formation and Bacterial Clearance in a Mouse Model of Alcohol and Burn Injury

Our previous studies have shown that ethanol intoxication combined with burn injury increases intestinal bacterial growth, disrupts the intestinal barrier, and enhances bacterial translocation. Additionally, studies show that Th17 effector cytokines IL-17 and IL-22, which are dependent on IL-23, play important roles in maintaining intestine mucosal barrier integrity. Recent findings suggest neutrophils are a significant source of IL-17 and IL-22. We determined the effect of ethanol and burn injury on neutrophil IL-17 and IL-22 production, as well as their ability to phagocytose and in bacterial clearance, and whether these effects are modulated by IL-23. Mice were given ethanol 4 h prior to receiving ∼12.5% total body surface area burn and were euthanized day 1 after injury. We observed that intoxication combined with burn injury significantly decreases blood neutrophil phagocytosis and bacteria killing, as well as their ability to produce IL-17 and IL-22, compared with sham vehicle mice. The treatment of neutrophils with rIL-23 significantly increases IL-22 and IL-17 release and promotes expression of IL-23R, retinoic acid-related orphan receptor γt, Lipocalin2, and Nod-like receptor 2 following ethanol and burn injury. Furthermore, IL-22- and IL-17-producing neutrophils have enhanced neutrophil extracellular trap formation and bacterial killing ability, which are dependent on IL-23. Finally, although we observed that peritoneal neutrophils harvested after casein treatment are functionally different from blood neutrophils, both blood and peritoneal neutrophils exhibited the same response to rIL-23 treatment. Together these findings suggest that IL-23 promotes neutrophil IL-22 and IL-17 production and their ability to kill bacteria following ethanol and burn injury.

Heme oxygenase-1 induction mitigates burn-associated early acute kidney injury via the TLR4 signaling pathway

OBJECTIVES

Early acute kidney injury (AKI) after burn contributes to disastrous prognoses for severely burned patients. Burn-induced renal oxidative stress and secondary proinflammatory mediator release contribute to early AKI development, and Toll-like receptor (TLR) 4 regulates inflammation. Heme oxygenase-1 (HO-1) is a stress-responsive enzyme that plays a vital role in protecting against ischemia-induced organ injury via its antioxidant properties and regulation of inflammation. We investigated the potential effect of HO-1 induction in preventing burn-induced early AKI and its related mechanism.

METHODS

A classic major-burn rat model was established using a 100 °C water bath, and hemin was injected intraperitoneally immediately after the injury to induce HO-1. Histological staining and blood tests were used to assess AKI progression based on structural changes and function. Renal levels of HO-1, oxidative stress, proinflammatory mediators and TLR4-related signals were detected using ELISA, immunostaining, qRT-PCR, and western blotting. The selective TLR4 inhibitor TAK242 and TLR4 inducer LPS were introduced to determine the roles of HO-1 in burn-related renal inflammation and the TLR4 pathway.

RESULTS

Hemin improved burn-induced renal histological damage and dysfunction, and this beneficial effect was related to reduced renal oxidative stress and the release of proinflammatory mediators, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6 and intracellular adhesion molecule-1 (ICAM-1). Hemin downregulated the expression of TLR4 and the subsequent phosphorylation of IKKα/β, IκBα, and NF-κB p65;. TAK242 exerted an effect similar to but weaker than hemin; and LPS reversed the antiinflammatory effect of hemin and the regulation of TLR4 signals. These results suggested that the TLR4 signaling pathway mediated the HO-1-facilitated regulation of renal inflammation after burn.

CONCLUSION

The present study demonstrated that HO-1 induction prevented burn-induced early AKI by targeting renal inflammation, which was mediated via regulation of the TLR4/NF-κB signaling pathway.

Heme Oxygenase-1 as a Pharmacological Target for Host-Directed Therapy to Limit Tuberculosis Associated Immunopathology

Excessive inflammation and tissue damage are pathological hallmarks of chronic pulmonary tuberculosis (TB). Despite decades of research, host regulation of these clinical consequences is poorly understood. A sustained effort has been made to understand the contribution of heme oxygenase-1 (HO-1) to this process. HO-1 is an essential cytoprotective enzyme in the host that controls inflammation and oxidative stress in many pathological conditions. While HO-1 levels are upregulated in animals and patients infected with Mycobacterium tuberculosis (Mtb), how it regulates host responses and disease pathology during TB remains unclear. This lack of clarity is due in part to contradictory studies arguing that HO-1 induction contributes to both host resistance as well as disease progression. In this review, we discuss these conflicting studies and the role of HO-1 in modulating myeloid cell functions during Mtb disease progression. We argue that HO-1 is a promising target for host-directed therapy to improve TB immunopathology.

NOX2 decoy peptides disrupt trauma-mediated neutrophil immunosuppression and protect against lethal peritonitis

Trauma and sepsis are frequent causes of immunosuppression and risk of secondary bacterial infections and mortality among critically ill patients. Reduced activity of neutrophil NADPH oxidase 2 (NOX2) and impaired bacterial killing are among the major indices of immunosuppression. We hypothesize that NOX2-decoy peptides disrupt the inhibition of neutrophil NOX2 by plasma of patients with severe trauma and immunosuppression, thereby preserving the neutrophil respiratory burst that is a central antimicrobial mechanism. We demonstrate that plasma from trauma/hemorrhage (T/H) patients, but not healthy donors (HD), significantly reduced the activity of neutrophil NOX2 and impaired bacterial killing. The inhibitory action of plasma was associated with an increase in bacterial infections among trauma survivors. High Mobility Group Box 1 (HMGB1) is a mediator of lethality in trauma and sepsis and our mechanistic studies revealed that disulfide and oxidized forms of HMGB1 bind to the gp91^phox subunit of NOX2, and thus decrease the neutrophil respiratory burst and bacterial killing. NOX2 decoy Anti-Immunosuppression (Ai) Peptides 1 and 3 effectively disrupted the immunosuppressive action of T/H plasma. HMGB1 selectively binds to Ai-Peptide 3, supporting the possibility for direct interaction between HMGB1 and the third external loop of gp91^phox. In vivo, Ai-Peptides improved survival of mice subjected to lethal peritonitis. Taken together, plasma-dependent inhibition of neutrophil NOX2 appeared to be a suitable indicator of immunosuppression in patients with severe trauma. Given that gp91^phox decoys protected the neutrophil respiratory burst, selected Ai-Peptides have therapeutic potential to reduce bacterial infections and end-organ injury associated with sepsis/trauma-induced immunosuppression.

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Plasma-induced neutrophil dysfunction is linked to immunosuppression in trauma.

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HMGB1 are among relevant mediators of neutrophil immunosuppression.

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NOX2 decoy peptides improved survival of mice with intraperitoneal infections.

FNDC5 alleviates oxidative stress and cardiomyocyte apoptosis in doxorubicin-induced cardiotoxicity via activating AKT

Oxidative stress and cardiomyocyte apoptosis play critical roles in doxorubicin (DOX)-induced cardiotoxicity. Previous studies indicated that fibronectin type III domain-containing 5 (FNDC5) and its cleaved form, irisin, could preserve mitochondrial function and attenuate oxidative damage as well as cell apoptosis, however, its role in DOX-induced cardiotoxicity remains unknown. Our present study aimed to investigate the role and underlying mechanism of FNDC5 on oxidative stress and cardiomyocyte apoptosis in DOX-induced cardiotoxicity. Cardiomyocyte-specific FNDC5 overexpression was achieved using an adeno-associated virus system, and then the mice were exposed to a single intraperitoneal injection of DOX (15 mg/kg) to generate DOX-induced cardiotoxicity. Herein, we found that FNDC5 expression was downregulated in DOX-treated murine hearts and cardiomyocytes. Fndc5 deficiency resulted in increased oxidative damage and apoptosis in H9C2 cells under basal conditions, imitating the phenotype of DOX-induced cardiomyopathy in vitro, conversely, FNDC5 overexpression or irisin treatment alleviated DOX-induced oxidative stress and cardiomyocyte apoptosis in vivo and in vitro. Mechanistically, we identified that FNDC5/Irisin activated AKT/mTOR signaling and decreased DOX-induced cardiomyocyte apoptosis, and moreover, we provided direct evidence that the anti-oxidant effect of FNDC5/Irisin was mediated by the AKT/GSK3β/FYN/Nrf2 axis in an mTOR-independent manner. And we also demonstrated that heat shock protein 20 was responsible for the activation of AKT caused by FNDC5/Irisin. In line with the data in acute model, we also found that FNDC5/Irisin exerted beneficial effects in chronic model of DOX-induced cardiotoxicity (5 mg/kg, i.p., once a week for three times, the total cumulative dose is 15 mg/kg) in mice. Based on these findings, we supposed that FNDC5/Irisin was a potential therapeutic agent against DOX-induced cardiotoxicity.

Recipient HO-1 inducibility is essential for posttransplant hepatic HO-1 expression and graft protection: From bench-to-bedside

By documenting potent antioxidative and anti-inflammatory functions, preclinical studies encourage heme oxygenase-1 (HO-1)-inducing regimens in clinical orthotopic liver transplantation (OLT). We aimed to determine the importance of recipient-derived HO-1 in murine and human OLTs. Hepatic biopsies from 51 OLT patients were screened for HO-1 expression (Western blots) prior to put-in (basal) and post reperfusion (stressed) and correlated with the hepatocellular function. In parallel, livers from HO-1 proficient mice (WT; C57/BL6), subjected to ex vivo cold storage (18 hour), were transplanted to syngeneic myeloid HO-1 deficient (mHO-1 KO) or FLOX (control) hosts, and sampled postreperfusion (6 hour). In human OLT, posttransplant but not pretransplant HO-1 expression correlated negatively with ALT levels (P = .0178). High posttransplant but not pretransplant HO-1 expression trended with improved OLT survival. Compared with controls, livers transplanted into mHO-1 KO recipient mice had decreased HO-1 levels, exacerbated hepatic damage/frequency of TUNEL+ cells, increased mRNA levels coding for TNFα/CXCL1/CXCL2/CXCL10, higher frequency of Ly6G+/4HN+ neutrophils; and enhanced MPO activity. Peritoneal neutrophils from mHO-1 KO mice exhibited higher CellRox+ ratio and increased TNFα/CXCL1/CXCL2/CXCL10 expression. By demonstrating the importance of posttransplant recipient HO-1 phenotype in hepatic macrophage/neutrophil regulation and function, this translational study identifies recipient HO-1 inducibility as a novel biomarker of ischemic stress resistance in OLT.

Bone marrow-derived mesenchymal stromal cells ameliorate severe acute pancreatitis in rats via hemeoxygenase-1-mediated anti-oxidant and anti-inflammatory effects

BACKGROUND AND AIMS

It has been previously verified that mesenchymal stromal cells (MSCs) have a good therapeutic effect on severe acute pancreatitis (SAP) and the potential for regeneration of damaged pancreatic tissue, but the exact molecular mechanism remains unclear. In this study, we demonstrated the therapeutic effect of bone morrow MSCs (BMSCs) on SAP, probably by targeting heme oxygenase-1 (HO-1).

METHODS

Six hours after SAP induction, either phosphate-buffered saline (PBS) or BMSCs were transfused into the caudal vein of rats, zinc protoporphyrin (ZnPP) was administered intraperitoneally. Pancreatic pathological scoring, serum levels of amylase and inflammatory factors, as well as levels of reactive oxygen species (ROS), malondialdehyde (MDA) and myeloperoxidase (MPO), superoxide dismutase (SOD) and catalase (CAT) activity in the pancreas were evaluated.

RESULTS

Our data showed that BMSCs significantly reduce inflammation and oxidative stress, reduce apoptosis and promote angiogenesis of damaged pancreas. Moreover, BMSCs increased the level of HO-1 in the serum and pancreatic tissue in rats with SAP. In addition, the protective effect of BMSCs was partially neutralized by the HO-1 activity inhibitor ZnPP, suggesting a key role of HO-1 in the therapeutic effect of BMSCs on SAP.

CONCLUSIONS

BMSCs ameliorated SAP, probably by inducing expression of HO-1, which can exert anti-inflammatory and anti-oxidant effects, reduce apoptosis and promote angiogenesis.

Macrophage heme oxygenase-1-SIRT1-p53 axis regulates sterile inflammation in liver ischemia-reperfusion injury

BACKGROUND & AIMS

Hepatic ischemia-reperfusion injury (IRI), characterized by exogenous antigen-independent local inflammation and hepatocellular death, represents a risk factor for acute and chronic rejection in liver transplantation. We aimed to investigate the molecular communication involved in the mechanism of liver IRI.

METHODS

We analyzed human liver transplants, primary murine macrophage cell cultures and IR-stressed livers in myeloid-specific heme oxygenase-1 (HO-1) gene mutant mice, for anti-inflammatory and cytoprotective functions of macrophage-specific HO-1/SIRT1 (sirtuin 1)/p53 (tumor suppressor protein) signaling.

RESULTS

Decreased HO-1 expression in human post-reperfusion liver transplant biopsies correlated with a deterioration in hepatocellular function (serum ALT; p<0.05) and inferior patient survival (p<0.05). In the low HO-1 liver transplant biopsy group, SIRT1/Arf (alternative reading frame)/p53/MDM2 (murine double minute 2) expression levels decreased (p<0.05) while cleaved caspase 3 and frequency of TUNEL+cells simultaneously increased (p<0.05). Immunofluorescence showed macrophages were the principal source of HO-1 in human and mouse IR-stressed livers. In vitro macrophage cultures revealed that HO-1 induction positively regulated SIRT1 signaling, whereas SIRT1-induced Arf inhibited ubiquitinating activity of MDM2 against p53, which in turn attenuated macrophage activation. In a murine model of hepatic warm IRI, myeloid-specific HO-1 deletion lacked SIRT1/p53, exacerbated liver inflammation and IR-hepatocellular death, whereas adjunctive SIRT1 activation restored p53 signaling and rescued livers from IR-damage.

CONCLUSION

This bench-to-bedside study identifies a new class of macrophages activated via the HO-1-SIRT1-p53 signaling axis in the mechanism of hepatic sterile inflammation. This mechanism could be a target for novel therapeutic strategies in liver transplant recipients.

LAY SUMMARY

Post-transplant low macrophage HO-1 expression in human liver transplants correlates with reduced hepatocellular function and survival. HO-1 regulates macrophage activation via the SIRT1-p53 signaling network and regulates hepatocellular death in liver ischemia-reperfusion injury. Thus targeting this pathway in liver transplant recipients could be of therapeutic benefit.

Nrf2 plays a pivotal role in protection against burn trauma-induced intestinal injury and death

Nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a basic leucine zipper transcription factor that principally defends against oxidative stress and also plays a unique role in severe sepsis. However, its contribution to intestinal injury and death after burn trauma is unclear.In this study, wild-type (Nrf2+/+) and Nrf2-deficient (Nrf2-/-) mice were subjected to 15% or 30% total body surface area burn or sham injury. Survival, systemic inflammation, and gut injury were determined.Nrf2-/- mice were more susceptible to burn-induced intestinal injury, as characterized by increases in damage to the gut structure and in intestinal permeability. This exacerbation was associated with an increase in the intestinal mRNA expression of inflammatory cytokines (interleukin [IL]-6, IL-1B, monocyte chemotactic protein 1, intercellular adhesion molecule, and vascular cell adhesion molecule) and a decrease in the intestinal mRNA expression of Nrf2-regulated genes (NAD(P)H dehydrogenasequinine-1 and glutamate-cysteine ligase modifier subunit). Nrf2-deficient mice also showed a lower survival rate and higher levels of systemic cytokines (IL-6 and IL-1B) and high-mobility group protein B1 than wild-type mice. This study demonstrates for the first time that mice that lack Nrf2 are more susceptible to burn-induced intestinal injury and have more systemic inflammation and a lower survival rate.

Reprint of: Heme oxygenase 1 affects granulopoiesis in mice through control of myelocyte proliferation

Heme oxygenase-1 (HO-1) is stress-inducible, cytoprotective enzyme degrading heme to carbon monoxide (CO), biliverdin and Fe²⁺. We showed that HO-1 knock-out mice (HO-1^-/-) have a twofold higher level of granulocytes than wild type (WT) mice, despite decreased concentration of granulocyte colony-stimulating factor (G-CSF) in the blood and reduced surface expression of G-CSF receptor on the hematopoietic precursors. This suggests the effect of HO-1 on granulopoiesis. Here we aimed to determine the stage of granulopoiesis regulated by HO-1. The earliest stages of hematopoiesis were not biased toward myeloid differentiation in HO-1^-/- mice. Within committed granulocytic compartment, in WT mice, HO-1 was up-regulated starting from myelocyte stage. This was concomitant with up-regulation of miR-155, which targets Bach1, the HO-1 repressor. In HO-1^-/- mice granulopoiesis was accelerated between myelocyte and metamyelocyte stage. There was a higher fraction of proliferating myelocytes, with increased nuclear expression of pro-proliferative C/EBPβ (CCAAT/enhancer binding protein beta) protein, especially its active LAP (liver-enriched activator proteins) isoform. Also our mathematical model confirmed shortening the myelocyte cyclic-time and prolonged mitotic expansion in absence of HO-1. It seems that changes in C/EBPβ expression and activity in HO-1^-/- myelocytes can be associated with reduced level of its direct repressor miR-155 or with decreased concentration of CO, known to reduce nuclear translocation of C/EBPs. Mature HO-1^-/- granulocytes were functionally competent as determined by oxidative burst capacity. In conclusion, HO-1 influences granulopoiesis through regulation of myelocyte proliferation. It is accompanied by changes in expression of transcriptionally active C/EBPβ protein. As HO-1 expression vary in human and is up-regulated in response to chemotherapy, it can potentially influence chemotherapy-induced neutropenia.

Simvastatin nanoparticles attenuated intestinal ischemia/reperfusion injury by downregulating BMP4/COX-2 pathway in rats

The purpose of the research was to explore the therapeutic action of simvastatin-loaded poly(ethylene glycol)-b-poly(gamma-benzyl l-glutamate) (PEG-b-PBLG₅₀) on intestinal ischemia/reperfusion injury (II/RI) through downregulating bone morphogenetic protein 4 (BMP4)/cyclooxygenase-2 (COX-2) pathway as compared to free simvastatin (Sim). Sprague Dawley rats were preconditioned with 20 mg/kg Sim or simvastatin/PEG-b-PBLG₅₀ (Sim/P) compounds, and then subjected to 45 min of ischemia and 1 h of reperfusion. The blood and small intestines were collected, serum levels of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α, and nitric oxide (NO) were checked, and the dry/wet intestine ratios, superoxide dismutase activity, myeloperoxidase content, reactive oxygen species, endothelial nitric oxide synthase, protein 47 kDa phagocyte oxidase (p47phox), BMP4, COX-2, and p38 mitogen-activated protein kinase (p38MAPK) expressions were measured in intestinal tissues. Both Sim and Sim/P pretreatment reduced intestinal oxidative damnification, restricted inflammatory harm, and downregulated the BMP4 and COX-2 expressions as compared to II/RI groups, while Sim/P remarkably improved this effect.

Heme oxygenase 1 affects granulopoiesis in mice through control of myelocyte proliferation

Heme oxygenase-1 (HO-1) is stress-inducible, cytoprotective enzyme degrading heme to carbon monoxide (CO), biliverdin and Fe²⁺. We showed that HO-1 knock-out mice (HO-1^-/-) have a twofold higher level of granulocytes than wild type (WT) mice, despite decreased concentration of granulocyte colony-stimulating factor (G-CSF) in the blood and reduced surface expression of G-CSF receptor on the hematopoietic precursors. This suggests the effect of HO-1 on granulopoiesis. Here we aimed to determine the stage of granulopoiesis regulated by HO-1. The earliest stages of hematopoiesis were not biased toward myeloid differentiation in HO-1^-/- mice. Within committed granulocytic compartment, in WT mice, HO-1 was up-regulated starting from myelocyte stage. This was concomitant with up-regulation of miR-155, which targets Bach1, the HO-1 repressor. In HO-1^-/- mice granulopoiesis was accelerated between myelocyte and metamyelocyte stage. There was a higher fraction of proliferating myelocytes, with increased nuclear expression of pro-proliferative C/EBPβ (CCAAT/enhancer binding protein beta) protein, especially its active LAP (liver-enriched activator proteins) isoform. Also our mathematical model confirmed shortening the myelocyte cyclic-time and prolonged mitotic expansion in absence of HO-1. It seems that changes in C/EBPβ expression and activity in HO-1^-/- myelocytes can be associated with reduced level of its direct repressor miR-155 or with decreased concentration of CO, known to reduce nuclear translocation of C/EBPs. Mature HO-1^-/- granulocytes were functionally competent as determined by oxidative burst capacity. In conclusion, HO-1 influences granulopoiesis through regulation of myelocyte proliferation. It is accompanied by changes in expression of transcriptionally active C/EBPβ protein. As HO-1 expression vary in human and is up-regulated in response to chemotherapy, it can potentially influence chemotherapy-induced neutropenia.

Burn leads to long-term elevated admissions to hospital for gastrointestinal disease in a West Australian population based study

BACKGROUND

While the most obvious impact of burn is on the skin, systemic responses also occur after burn, including intestinal inflammation. The objective of this study was to assess if burns are associated with increased long-term admissions for gastrointestinal diseases.

METHODS

A population-based longitudinal study using linked hospital morbidity and death data from Western Australia was undertaken of adults aged at least 15 years when hospitalized for a first burn (n=20,561) in 1980-2012. A frequency matched non-injury comparison cohort was randomly selected from Western Australia's birth registrations and electoral roll (n=80,960). Crude admission rates and summed days in hospital for digestive diseases were calculated. Negative binomial and Cox proportional hazards regression modeling were used to generate incidence rate ratios (IRR) and hazard ratios (HR), respectively.

RESULTS

After adjustment for demographic factors and pre-existing health status, the burn cohort had 1.54 times (95% confidence interval (CI): 1.47-1.62) as many admissions and almost three times the number of days in hospital with a digestive system diagnosis (IRR, 95% CI: 2.90, 2.60-3.25) than the uninjured cohort. Significantly elevated adjusted post-burn incident rates were identified, with the risk decreasing with increasing time: in the first month (HR, 95% CI: 3.02, 1.89-4.82), from one month to five years (HR, 95% CI: 1.42, 1.31-1.54), and from five to twenty years after burn (HR, 95% CI: 1.13, 1.06-1.20).

CONCLUSIONS

Findings of increased hospital admission rates and prolonged length of hospital stay for gastrointestinal diseases in the burn cohort provide evidence to support that burns have effects that persist long after the initial injury.

The Effects of Alcohol Intoxication and Burn Injury on the Expression of Claudins and Mucins in the Small and Large Intestines

Alcohol intoxication at the time of burn injury exacerbates postburn pathogenesis. Recent findings suggest gut barrier integrity is compromised after combined alcohol and burn insult, which could contribute to these complications. Tight junction proteins and mucins play critical roles in keeping the gut barrier intact. Therefore, the goal of this study was to examine the effects of alcohol and burn injury on claudin and mucin expression in the intestines. We also evaluated if the combined insult differentially influences their expression in the small and large intestines. Male C57BL/6 mice were given a single dose of 2.9 g/kg ethanol before an approximately 12.5% body area burn. One and three days after injury, we profiled expression of several tight junction proteins, mucin, and bacterial 16S rRNA genes in the small and large intestines, using qPCR. We observed >50% decrease in claudin-4 and claudin-8 genes in both ileal and colonic epithelial cells 1 day after injury. Claudin-2 was significantly upregulated, and occludin was downregulated in the small intestine 1 day after injury. Mucin-3 expression was substantially elevated (>50%) in the small intestine, whereas mucin-2 and mucin-4 were considerably diminished in the colon (>50%) 1 day after injury. Most of the parameters were normalized to sham levels on day 3, except for mucin-3 and claudin-8, which remained decreased in the large intestine. Neither alcohol nor burn alone resulted in changes in junction or mucin gene expression compared to shams. This was accompanied with increases in the family of Gram-negative bacteria, Enterobacteriaceae, in both the small and the large intestines 1 day after injury. These findings suggest that alcohol and burn injury disrupts the normal gut microbiota and alters tight junction and mucin expression in the small and large intestines.

Intestine immune homeostasis after alcohol and burn injury

Traumatic injury remains one of the most prevalent reasons for patients to be hospitalized. Burn injury accounts for 40,000 hospitalizations in the United States annually, resulting in a large burden on both the health and economic system and costing millions of dollars every year. The complications associated with postburn care can quickly cause life-threatening conditions including sepsis and multiple organ dysfunction and failure. In addition, alcohol intoxication at the time of burn injury has been shown to exacerbate these problems. One of the biggest reasons for the onset of these complications is the global suppression of the host immune system and increased susceptibility to infection. It has been hypothesized that infections after burn and other traumatic injury may stem from pathogenic bacteria from within the host's gastrointestinal tract. The intestine is the major reservoir of bacteria within the host, and many studies have demonstrated perturbations of the intestinal barrier after burn injury. This article reviews the findings of these studies as they pertain to changes in the intestinal immune system after alcohol and burn injury.

Higenamine regulates Nrf2-HO-1-Hmgb1 axis and attenuates intestinal ischemia-reperfusion injury in mice

INTRODUCTION

Intestinal ischemia and reperfusion (IR) syndrome is a life-threatening dilemma caused by diverse events. Higenamine (HG), an active ingredient of Aconiti Lateralis Radix Praeparata, has been traditionally used as a heart stimulant and anti-inflammatory agent in oriental countries. But the function of HG on intestine IR injury has never been investigated.

MATERIALS AND METHODS

Mice underwent a 2 cm midline laparotomy, and the superior mesenteric artery (SMA) was obstructed by micro-vascular clamp to induce intestinal ischemia.

RESULTS

In our current study, HG increases mouse intestinal epithelial (IEC-6) cell viability through induced heme oxygenase-1 (HO-1) production in vitro. In our in vivo murine intestinal IR injury model, the increased HO-1 protein level and activity, decreased intestinal injury score, Myeloperoxidase (MPO) activity, and inflammatory cytokine expression induced by HG were all abolished with additional treatment of HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX). Furthermore, HG reduced high mobility group box-1 (Hmgb1) expression in IR injury-performed intestine which was inhibited by additional administration of ZnPPIX. And HG treatment significantly decreased HO-1 expression in nuclear factor erythroid 2-related factor (Nrf-2) SiRNA-transfected cells but not in control SiRNA-transfected cells.

CONCLUSION

Our study provides evidence HG regulates Nrf2-HO-1-Hmgb1 axis and attenuates intestinal IR injury in mice.

The First Line of Defense: The Effects of Alcohol on Post-Burn Intestinal Barrier, Immune Cells, and Microbiome

Alcohol (ethanol) is one of the most globally abused substances, and is one of the leading causes of premature death in the world. As a result of its complexity and direct contact with ingested alcohol, the intestine represents the primary source from which alcohol-associated pathologies stem. The gut is the largest reservoir of bacteria in the body, and under healthy conditions, it maintains a barrier preventing bacteria from translocating out of the intestinal lumen. The intestinal barrier is compromised following alcohol exposure, which can lead to life-threatening systemic complications including sepsis and multiple organ failure. Furthermore, alcohol is a major confounding factor in pathology associated with trauma. Experimental data from both human and animal studies suggest that alcohol perturbs the intestinal barrier and its function, which is exacerbated by a "second hit" from traumatic injury. This article highlights the role of alcohol-mediated alterations of the intestinal epithelia and its defense against bacteria within the gut, and the impact of alcohol on intestinal immunity, specifically on T cells and neutrophils. Finally, it discusses how the gut microbiome both contributes to and protects the intestines from dysbiosis after alcohol exposure and trauma.

Protective role of HO-1 and carbon monoxide in ethanol-induced hepatocyte cell death and liver injury in mice

BACKGROUND & AIMS

Alcoholic liver disease is associated with inflammation and cell death. Heme oxygenase-1 (HO-1) is a stress-inducible enzyme with anti-apoptotic and anti-inflammatory properties. Here we tested the hypothesis that induction of HO-1 or treatment with a carbon monoxide releasing molecule (CORM) during chronic ethanol exposure protects and/or reverses ethanol-induced liver injury.

METHODS

Female C57BL/6J mice were allowed free access to a complete liquid diet containing ethanol or to pair-fed control diets for 25days. Mice were treated with cobalt protoporphyrin (CoPP) to induce HO-1 expression during ethanol feeding or once liver injury had been established. Mice were also treated with CORM-A1, a CO-releasing molecule (CORM), after ethanol-induced liver injury was established. The impact of HO-1 induction on ethanol-induced cell death was investigated in primary cultures of hepatocytes.

RESULTS

Induction of HO-1 during or after ethanol feeding, as well as treatment with CORM-A1, ameliorated ethanol-induced increases in AST and expression of mRNAs for inflammatory cytokines. Treatment with CoPP or CORM-A1 also reduced hepatocyte cell death, indicated by decreased accumulation of CK18 cleavage products and reduced RIP3 expression in hepatocytes. Exposure of primary hepatocyte cultures to ethanol increased their sensitivity to TNFα-induced cell death; this response was attenuated by necrostatin-1, an inhibitor of necroptosis, but not by caspase inhibitors. Induction of HO-1 with CoPP or CORM-3 treatment normalized the sensitivity of hepatocytes to TNFα-induced cell death after ethanol exposure.

CONCLUSIONS

Therapeutic strategies to increase HO-1 and/or modulate CO availability ameliorated chronic ethanol-induced liver injury in mice, at least in part by decreasing hepatocellular death.

Role of interleukin 10 in norfloxacin prevention of luminal free endotoxin translocation in mice with cirrhosis

BACKGROUND & AIMS

Bacterial endotoxin is present in patients with advanced cirrhosis and can induce an immunogenic response without an overt infection. Norfloxacin is a gram-negative bactericidal drug able to maintain low endotoxin levels and stimulate IL-10 production. We aimed at investigating the role of IL-10 in decreasing endotoxin absorption in cirrhotic mice treated with norfloxacin.

METHODS

Cirrhosis was induced by carbon tetrachloride or bile duct ligation in wild type and IL10-deficient mice with or without norfloxacin prior to an intragastrical administration of E. coli, K. pneumonia or E. faecalis. Spontaneous and induced bacterial translocation, free endotoxin and cytokine levels were evaluated in mesenteric lymph nodes. Intestinal permeability was followed by fluorimetry and barrier integrity markers were measured in disrupted intestinal samples. The inflammatory-modulating mechanism was characterized in purified intestinal mononuclear cells.

RESULTS

Norfloxacin reduced spontaneous and induced MLN positive-cultures in wild type and IL-10-deficient animals. However, reduction of free endotoxin levels was associated with norfloxacin in wild type but not in IL-10-deficient mice. Wild type but not IL-10-deficient mice treated with norfloxacin significantly normalized intestinal permeability and improved gut barrier integrity markers. The toll-like receptor 4-mediated pro-inflammatory milieu was modulated by norfloxacin in a concentration-dependent manner in cultured intestinal mononuclear cells of wild type mice but not of IL-10-deficient mice. The restoration of IL-10 levels in IL-10-deficient animals reactivated the norfloxacin effect on inflammatory-modulation, gut barrier permeability, and luminal endotoxin absorption.

CONCLUSION

Norfloxacin not only reduces gram-negative intestinal flora but also participates in an IL-10-driven modulation of gut barrier permeability, thus reducing luminal free endotoxin absorption in experimental cirrhosis.

T cell IFN-γ suppression following alcohol and burn injury is independent of miRNA155

miRNA155 has been implicated in normal T cell function and their differentiations into the Th1 subtype. We have shown that acute alcohol (ethanol) intoxication combined with burn injury suppresses T cell IFN-γ release. Herein, we examined whether the decrease in IFN-γ is resulted from altered expression of miRNA155 and transcription factors--NFAT, Tbx21, Jun and Fos--in T cells following ethanol and burn injury. Mice received ethanol (∼3 g/Kg) 4 hours prior to ∼12.5% total body surface area sham or burn injury and were sacrificed one day after injury. Splenic T cells were harvested and cultured with anti-CD3 (2 µg/ml) in the presence or absence of rIL-12 (10 ng/ml) or PMA (10 ng/ml) plus ionomycin (50 ng/ml) for 48 hours. We observed a significant decrease in miRNA155, NFAT, Tbx21, Jun and Fos expression as well as IFN-γ release in T cells cultured with anti-CD3 following ethanol and burn injury compared with shams. The co-treatment of T cells with rIL-12 prevented the decrease in IFN-γ and NFAT, Tbx21, Jun and Fos, but not miRNA155. In contrast, the co-treatment with PMA plus ionomycin normalized the expression of NFAT. It did not prevent the decrease in IFN-γ, Tbx21, Jun, Fos and miRNA155. Finally, results obtained in miRNA155-/- mice did not show any change in T cell release of IFN-γ or expression of nuclear factors compared to wildtype mice. Together, these findings suggest that while ethanol and burn injury decreases the expression of miRNA155, it may not be involved in decreased IFN-γ under those conditions.

Noninvasive measurement of intestinal inflammation after burn injury

Intestinal inflammation has been linked with multiorgan failure in patients with burn and other traumatic injuries. We hypothesized that markers of intestinal inflammation are detectible noninvasively. Fecal samples were collected from seven severely burned patients and 15 control patients for the measurement of inflammatory cytokines using a multiplex assay kit. In addition, fecal levels of myeloperoxidase (MPO) and elastase were measured using standard procedures. Compared with a control group, levels of inflammatory cytokines were significantly increased in the burn group. Interleukin (IL)-6 increased to a mean (± SEM) of 2.16 ± 0.61 to 3.81 ± 0.49 pg/mg (P < .05), as did IL-8 (3.32 ± 0.76 to 20.51 ± 6.65 pg/mg; P < .05), IL-12 (6.23±0.98 to 8.11±0.95pg/mg; P=0.01), IL-13 (3.86 ± 0.32 to 11.83 ± 1.47 pg/mg; P < .05), monocyte chemoattractant protein-1 (2.78 ± 2.61 to 6.5 ± 3.97 pg/mg; P < .05), MPO (13.41 ± 1.40 to 24.52 ± 4.31 units/mg protein; P < .05), and elastase (2.46 ± 0.38 to 5.08 ± 0.72 pg/mL; P < .05). Our results suggest that markers of intestinal inflammation are measurable by noninvasive means and are increased after burn injury compared with controls. Of note, increased IL-8 correlated with increased MPO and elastase activity, suggesting a role for neutrophil activation in burn-mediated intestinal inflammation. Thus, these inflammatory cytokine profiles may be valuable biomarkers of intestinal inflammation after burn injury.

Preventive effect of agaro-oligosaccharides on non-steroidal anti-inflammatory drug-induced small intestinal injury in mice

BACKGROUND AND AIM

Non-steroidal anti-inflammatory drugs (NSAIDs), which are commonly used in clinical medicine, cause erosion, ulcers, and bleeding in the gastrointestinal tract. No effective agent for the prevention and treatment of small intestinal injury by NSAIDs has been established. This study investigates the effects of agaro-oligosaccharides (AGOs) on NSAID-induced small intestinal injury in mice.

METHODS

Mice were treated with indomethacin, an NSAID, to induce intestinal injury. The respective degrees of mucosal injury of mice that received AGO and control mice were compared. Heme oxygenase-1 (HO-1) expression using quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemistry were measured. The expression of keratinocyte chemoattractant (KC) was measured using qRT-PCR and enzyme-linked immunosorbent assay.

RESULTS

AGO administration induced HO-1 expression in mouse small intestinal mucosa. Induction was observed mainly in F4/80 positive macrophages. The increased ulcers score, myeloperoxidase activity, and KC expression by indomethacin were inhibited by AGO administration. Conversely, HO inhibitor cancelled AGO-mediated prevention of intestinal injury. In mouse peritoneal macrophages, AGOs enhanced HO-1 expression and suppressed lipopolysaccharide-induced KC expression. Furthermore, AGOs enhanced the expressions of alternatively activated macrophage markers arginase-1, mannose receptor-1, and chitinase 3-like 3.

CONCLUSIONS

Results suggest that oral administration of AGOs prevents NSAID-induced intestinal injury.

Procalcitonin as a predictive biomarker for total body irradiation-induced bacterial load and lethality in mice

Sepsis is the leading cause of mortality in intensive care units. Early detection and intervention are critical to prevent death. The acute radiation syndrome is characterized by damage of the gastrointestinal and hematopoietic systems. Translocation of intestinal microflora combined with immune system compromise may lead to septicemia and death. This work examined the utility of procalcitonin, a clinical sepsis biomarker, in a mouse model of radiation toxicity. C57/BL6 mice were exposed to total body irradiation (TBI). Intestinal mucosal permeability was measured in vivo, and liver bacterial load and plasma levels of procalcitonin (PCT), lipopolysaccharide (LPS), and LPS-binding protein were measured at baseline and at 3.5, 7, and 10 days after TBI. The value of early PCT in predicting subsequent lethality was determined by receiver operating characteristic analysis. Four days after TBI, a dose-dependent increase in permeability of the intestinal mucosa was observed, whereas bacterial translocation was present from day 7 onward. There was a high positive correlation between bacterial translocation and all sepsis biomarkers, with PCT exhibiting the strongest correlation. Moreover, plasma PCT levels were elevated already from day 3.5 onward, whereas LPS was elevated from day 7 and LPS-binding protein only 10 days after TBI. Receiver operating characteristic analysis revealed that PCT levels measured 3.5 days after TBI predicted lethality at 10 days. These data demonstrate the value of PCT as an early biomarker in radiation-induced bacteremia for mouse studies and suggest that clinical results from other septic conditions may apply to postradiation septicemia in humans.

Regulation of heme oxygenase expression by alcohol, hypoxia and oxidative stress

AIM: To study the effect of both acute and chronic alcohol exposure on heme oxygenases (HOs) in the brain, liver and duodenum.

METHODS: Wild-type C57BL/6 mice, heterozygous Sod2 knockout mice, which exhibit attenuated manganese superoxide dismutase activity, and liver-specific ARNT knockout mice were used to investigate the role of alcohol-induced oxidative stress and hypoxia. For acute alcohol exposure, ethanol was administered in the drinking water for 1 wk. Mice were pair-fed with regular or ethanol-containing Lieber De Carli liquid diets for 4 wk for chronic alcohol studies. HO expression was analyzed by real-time quantitative polymerase chain reaction and Western blotting.

RESULTS: Chronic alcohol exposure downregulated HO-1 expression in the brain but upregulated it in the duodenum of wild-type mice. It did not alter liver HO-1 expression, nor HO-2 expression in the brain, liver or duodenum. In contrast, acute alcohol exposure decreased both liver HO-1 and HO-2 expression, and HO-2 expression in the duodenum of wild-type mice. The decrease in liver HO-1 expression was abolished in ARNT^+/- mice. Sod2^+/- mice with acute alcohol exposure did not exhibit any changes in liver HO-1 and HO-2 expression or in brain HO-2 expression. However, alcohol inhibited brain HO-1 and duodenal HO-2 but increased duodenal HO-1 expression in Sod2^+/- mice. Collectively, these findings indicate that acute and chronic alcohol exposure regulates HO expression in a tissue-specific manner. Chronic alcohol exposure alters brain and duodenal, but not liver HO expression. However, acute alcohol exposure inhibits liver HO-1 and HO-2, and also duodenal HO-2 expression.

CONCLUSION: The inhibition of liver HO expression by acute alcohol-induced hypoxia may play a role in the early phases of alcoholic liver disease progression.

Malaria impairs resistance to Salmonella through heme- and heme oxygenase-dependent dysfunctional granulocyte mobilization

In sub-Saharan Africa, invasive non-Typhoid Salmonella (NTS) is a common and often fatal complication of Plasmodium falciparum infection. Induction of heme oxygenase-1 (HO-1) mediates tolerance to the cytotoxic effects of heme during malarial hemolysis but might impair resistance to NTS by limiting production of bactericidal reactive oxygen species. We show that co-infection of mice with Plasmodium yoelii 17XNL (Py17XNL) and S. typhimurium causes acute, fatal bacteremia with increased bacterial load; features reproduced by phenylhydrazine hemolysis or hemin administration. S. typhimurium localized predominantly in granulocytes. Py17XNL, phenylhydrazine and hemin caused premature mobilization of granulocytes from bone marrow with a quantitative defect in the oxidative burst. Inhibition of HO by tin protoporphyrin abrogated the impairment of resistance to S. typhimurium by hemolysis. Thus a mechanism of tolerance to one infection, malaria, impairs resistance to another, NTS. Furthermore, HO inhibitors may be useful adjunctive therapy for NTS infection in the context of hemolysis.

Inflammatory response in multiple organs in a mouse model of acute alcohol intoxication and burn injury

This study characterized the inflammatory response after burn injury and determined whether ethanol (EtOH) intoxication at the time of burn injury influences this response. To accomplish this, male mice were gavaged with EtOH (2.9 g/kg) 4 hours before 12 to 15% TBSA sham or burn injury. Mice were killed on day 1 after injury; blood, small intestine, lung, and liver were collected to measure interleukin (IL)-6, IL-10, IL-18, and Monocyte chemotactic protein-1 (MCP-1) levels. In addition, neutrophil infiltration, myeloperoxidase activity, and edema formation were also measured in the small intestine, lung, and liver. There was no difference in the inflammatory markers in the small intestine, lung, and liver in mice receiving either sham or burn injury alone except IL-6 that was increased in all four tissue compartments after burn injury alone. However, when compared with EtOH or burn injury alone, EtOH combined with burn injury resulted in a significant increase in cytokines, neutrophil infiltration, myeloperoxidase activity, and edema in the small intestine, liver, and lung tissue. Furthermore, a significant increase in IL-6 and MCP-1 was observed in circulation after EtOH intoxication and burn injury compared with either EtOH intoxication or burn injury alone; no other cytokines were detected in circulation. These findings suggest that acute EtOH intoxication exacerbates the inflammatory response after burn injury.

Translocation of heme oxygenase-1 to mitochondria is a novel cytoprotective mechanism against non-steroidal anti-inflammatory drug-induced mitochondrial oxidative stress, apoptosis, and gastric mucosal injury

The mechanism of action of heme oxygenase-1 (HO-1) in mitochondrial oxidative stress (MOS)-mediated apoptotic tissue injury was investigated. MOS-mediated gastric mucosal apoptosis and injury were introduced in rat by indomethacin, a non-steroidal anti-inflammatory drug. Here, we report that HO-1 was not only induced but also translocated to mitochondria during gastric mucosal injury to favor repair mechanisms. Furthermore, mitochondrial translocation of HO-1 resulted in the prevention of MOS and mitochondrial pathology as evident from the restoration of the complex I-driven mitochondrial respiratory control ratio and transmembrane potential. Mitochondrial translocation of HO-1 also resulted in time-dependent inhibition of apoptosis. We searched for the plausible mechanisms responsible for HO-1 induction and mitochondrial localization. Free heme, the substrate for HO-1, was increased inside mitochondria during gastric injury, and mitochondrial entry of HO-1 decreased intramitochondrial free heme content, suggesting that a purpose of mitochondrial translocation of HO-1 is to detoxify accumulated heme. Heme may activate nuclear translocation of NF-E2-related factor 2 to induce HO-1 through reactive oxygen species generation. Electrophoretic mobility shift assay and chromatin immunoprecipitation studies indicated nuclear translocation of NF-E2-related factor 2 and its binding to HO-1 promoter to induce HO-1 expression during gastric injury. Inhibition of HO-1 by zinc protoporphyrin aggravated the mucosal injury and delayed healing. Zinc protoporphyrin further reduced the respiratory control ratio and transmembrane potential and enhanced MOS and apoptosis. In contrast, induction of HO-1 by cobalt protoporphyrin reduced MOS, corrected mitochondrial dysfunctions, and prevented apoptosis and gastric injury. Thus, induction and mitochondrial localization of HO-1 are a novel cytoprotective mechanism against MOS-mediated apoptotic tissue injury.

Alteration in intestine tight junction protein phosphorylation and apoptosis is associated with increase in IL-18 levels following alcohol intoxication and burn injury

Intestinal mucosal barrier is the first line of defense against bacteria and their products originating from the intestinal lumen. We have shown a role for IL-18 in impaired gut barrier function following acute alcohol (EtOH) intoxication combined with burn injury. To further delineate the mechanism, this study examined whether IL-18 alters intestine tight junction proteins or induces mucosal apoptosis under these conditions. To accomplish this, rats were gavaged with EtOH (3.2g/kg) prior to ~12.5% total body surface area burn or sham injury. One day after injury, EtOH combined with burn injury resulted in a significant decrease in total occludin protein and its phosphorylation in small intestine compared to either EtOH or burn injury alone. There was no change in claudin-1 protein content but its phosphorylation on tyrosine was decreased following EtOH and burn injury. This was accompanied with an increase in mucosal apoptosis (p<0.05). The treatment of rats with anti-IL-18 antibody at the time of burn injury prevented intestine apoptosis and normalized tight junction proteins following EtOH and burn injury. Altogether, these findings suggest that IL-18 modulates tight junction proteins and cause apoptosis leading to impaired intestinal mucosal integrity following EtOH intoxication combined with burn injury.

PPARγ stabilizes HO-1 mRNA in monocytes/macrophages which affects IFN-β expression

NADPH oxidase activation in either RAW264.7 cells or peritoneal macrophages (PM) derived from PPARγ wild-type mice increased reactive oxygen species (ROS) formation, caused PPARγ activation, heme oxygenase-1 (HO-1) induction, and concomitant IFN-β expression. In macrophages transduced with a dominant negative (d/n) mutant of PPARγ (RAW264.7 AF2) as well as PPARγ negative PM derived from Mac-PPARγ-KO mice, NADPH oxidase-dependent IFN-β expression was attenuated. As the underlying mechanism, we noted decreased HO-1 mRNA stability in RAW264.7 AF2 cells as well as PPARγ negative PM, compared to either parent RAW264.7 cells or wild-type PM. Assuming mRNA stabilization of HO-1 by PPARγ we transfected macrophages with a HO-1 3'-UTR reporter construct. The PPARγ agonist rosiglitazone significantly up-regulated luciferase expression in RAW264.7 cells, while it remained unaltered in RAW264.7 AF2 macrophages. Deletion of each of two AU-rich elements in the 3'-UTR HO-1 decreased luciferase activity in RAW264.7 cells. Using LPS as a NADPH oxidase activator, PM from Mac-PPARγ-KO mice showed a decreased HO-1 mRNA half-life in vitro and in vivo compared to PPARγ wild-type mice. These data identified a so far unappreciated role of PPARγ in stabilizing HO-1 mRNA, thus, contributing to the expression of the HO-1 target gene IFN-β.

Interleukin-10-mediated heme oxygenase 1-induced underlying mechanism in inflammatory down-regulation by norfloxacin in cirrhosis

Patients with cirrhosis receiving norfloxacin show a restored inflammatory balance that likely prevents clinical complications derived from an excessive proinflammatory response to bacterial product challenges. This study sought to investigate associated inflammatory control mechanisms established in patients with cirrhosis receiving norfloxacin. A total of 62 patients with cirrhosis and ascites in different clinical conditions were considered. Blood samples were collected and intracellular and serum norfloxacin were measured. Inflammatory mediators were evaluated at messenger RNA and protein levels. Neutrophils from all patients were cultured with lipopolysaccharide (LPS) and anti-interleukin-10 (anti-IL-10) monoclonal antibody in different conditions. IL-10 and heme oxygenase-1 (HO-1) were up-regulated in patients receiving norfloxacin and correlated with norfloxacin in a concentration-dependent manner, whereas proinflammatory inducible nitric oxide synthase, cyclooxygenase-2, and nuclear factor-κB behaved inversely. Higher IL-10 levels correlated with lower white blood cell count and higher mean arterial pressure. No correlations were found between IL-10 and disease clinical scores or liver function markers in blood. Neutrophilic in vitro assays showed that the effect of LPS on proinflammatory mediator levels in the presence of norfloxacin was abrogated by significantly increasing IL-10 and HO-1 expression. After stimulation with LPS plus anti-IL-10, proinflammatory mediators were dramatically increased in patients receiving norfloxacin, and increasing intracellular norfloxacin concentrations did not decrease the expression levels of these proinflammatory molecules. Unblocking IL-10 restored proinflammatory mediator and HO-1 expression to previously observed levels in response to LPS stimulation.

CONCLUSION

Although the described association does not necessarily mean causality, an IL-10-mediated HO-1-induced anti-inflammatory mechanism is present in patients with cirrhosis receiving norfloxacin, that is directly associated with cell-modulating events in these patients.

Heme oxygenase-1: a novel therapeutic target for gastrointestinal diseases

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in the catabolism of heme, followed by production of biliverdin, free iron and carbon monoxide (CO). HO-1 is a stress-responsive protein induced by various oxidative agents. Recent studies demonstrate that the expression of HO-1 in response to different inflammatory mediators may contribute to the resolution of inflammation and has protective effects in several organs against oxidative injury. Although the mechanism underlying the anti-inflammatory actions of HO-1 remains poorly defined, both CO and biliverdin/bilirubin have been implicated in this response. In the gastrointestinal tract, HO-1 is shown to be transcriptionally induced in response to oxidative stress, preconditioning and acute inflammation. Recent studies suggest that the induction of HO-1 expression plays a critical protective role in intestinal damage models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid, and dextran sulfate sodium, indicating that activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in the gastrointestinal tract. In addition, CO derived from HO-1 is shown to be involved in the regulation in gastro-intestinal motility. These in vitro and in vivo data suggest that HO-1 may be a novel therapeutic target in patients with gastrointestinal diseases.

The role of heme oxygenase and carbon monoxide in inflammatory bowel disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease, is a chronic and recurrent inflammatory disorder of the intestinal tract. Since the precise pathogenesis of IBD remains unclear, it is important to investigate the pathogenesis of IBD and to evaluate new anti-inflammatory strategies. Recent evidence suggests that heme oxygenase-1 (HO-1) plays a critical protective role during the development of intestinal inflammation. In fact, it has been demonstrated that the activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in various animal intestinal injury models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid or dextran sulfate sodium. In addition, carbon monoxide (CO) derived from HO-1 has been shown to be involved in the regulation of intestinal inflammation. Furthermore, administration of a low concentration of exogenous CO has a protective effect against intestinal inflammation. These data suggest that HO-1 and CO may be novel therapeutic molecules for patients with gastrointestinal inflammatory diseases. In this review, we present what is currently known regarding the role of HO-1 and CO in intestinal inflammation.

Heme oxygenase-1 is induced in peripheral blood mononuclear cells of patients with acute pancreatitis: a potential therapeutic target

Heme oxygenase-1 (HO-1) induction by hemin or Panhematin protects against experimental pancreatitis. As a preclinical first step toward determining whether HO-1 upregulation is a viable target in acute pancreatitis (AP) patients, we tested the hypothesis that HO-1 expression in peripheral blood mononuclear cell (PBMC) subsets of hospitalized patients with mild AP is upregulated then normalizes upon recovery and that cells from AP patients have the potential to upregulate their HO-1 ex vivo if exposed to Panhematin. PBMCs were isolated on days 1 and 3 of hospitalization from the blood of 18 AP patients, and PMBC HO-1 levels were compared with PMBCs of 15 hospitalized controls (HC) and 7 volunteer healthy controls (VC). On day 1 of hospitalization, AP patients compared with VCs had higher HO-1 expression in monocytes and neutrophils. Notably, AP monocyte HO-1 levels decreased significantly upon recovery. Panhematin induced HO-1 in ex vivo cultured AP PBMCs more readily than in HC or VC PBMCs. Furthermore, PBMCs from acutely ill AP patients on day 1 were more responsive to HO-1 induction compared with day 3 upon recovery. Similarly, mouse splenocytes had enhanced HO-1 inducibility as their pancreatitis progressed from mild to severe. In conclusion, AP leads to reversible PBMC HO-1 upregulation that is associated with clinical improvement and involves primarily monocytes. Leukocytes from AP patients or mice with AP are primed for HO-1 induction by Panhematin, which suggests that Panhematin could offer a therapeutic benefit.

Heme oxygenase-1 is induced in peripheral blood mononuclear cells of patients with acute pancreatitis: a potential therapeutic target

Heme oxygenase-1 (HO-1) induction by hemin or Panhematin protects against experimental pancreatitis. As a preclinical first step toward determining whether HO-1 upregulation is a viable target in acute pancreatitis (AP) patients, we tested the hypothesis that HO-1 expression in peripheral blood mononuclear cell (PBMC) subsets of hospitalized patients with mild AP is upregulated then normalizes upon recovery and that cells from AP patients have the potential to upregulate their HO-1 ex vivo if exposed to Panhematin. PBMCs were isolated on days 1 and 3 of hospitalization from the blood of 18 AP patients, and PMBC HO-1 levels were compared with PMBCs of 15 hospitalized controls (HC) and 7 volunteer healthy controls (VC). On day 1 of hospitalization, AP patients compared with VCs had higher HO-1 expression in monocytes and neutrophils. Notably, AP monocyte HO-1 levels decreased significantly upon recovery. Panhematin induced HO-1 in ex vivo cultured AP PBMCs more readily than in HC or VC PBMCs. Furthermore, PBMCs from acutely ill AP patients on day 1 were more responsive to HO-1 induction compared with day 3 upon recovery. Similarly, mouse splenocytes had enhanced HO-1 inducibility as their pancreatitis progressed from mild to severe. In conclusion, AP leads to reversible PBMC HO-1 upregulation that is associated with clinical improvement and involves primarily monocytes. Leukocytes from AP patients or mice with AP are primed for HO-1 induction by Panhematin, which suggests that Panhematin could offer a therapeutic benefit.

Ischemic postconditioning attenuates lung reperfusion injury and reduces systemic proinflammatory cytokine release via heme oxygenase 1

OBJECTIVE

Systemic inflammatory response following ischemia-reperfusion injury (IRI) to a specific organ may cause injuries in multiple remote organs. The emergence of ischemic postconditioning (IPO) provides a potential method for experimentally and clinically attenuating various types of organ postischemic injuries. We have shown that IPO can attenuate lung IRI by up-regulating the protein expression of heme oxygenase-1(HO-1). This study tested the hypothesis that IPO attenuates systemic inflammatory responses following lung IRI by activating HO-1.

METHODS

Anaesthetized and mechanically ventilated adult Sprague-Dawley rats were randomly assigned to one of the following groups (n = 8 each): the sham-operated control group, the ischemia-reperfusion (IR) group (40 min of left-lung ischemia and 120 min of reperfusion), the IPO group (three successive cycles of 30-s reperfusion per 30-s occlusion before restoring full perfusion), and the zinc protoporphyrin IX (ZnP) plus IPO group (ZnP, an inhibitor of HO-1, was injected intraperitoneally at 20 mg/kg 24 h prior to the experiment, and the rest of the procedures were similar to that of the IPO group). Lung injury was assessed by arterial blood gas analysis, wet-to-dry lung weight ratio and tissue histologic and biochemical changes. The lung tissue and plasma levels of lipid peroxidation were determined by measuring the contents of malondialdehyde (MDA) production. Protein expression of HO-1 was determined by Western blotting. Pulmonary neutrophil was counted. Lung tissue myeloperoxidase (MPO) activity as well as plasma levels of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukines 6 and 8 (IL-6, IL-8) were determined by spectrophotography.

RESULTS

Lung ischemia-reperfusion led to severe lung pathologic morphologic changes and increased pulmonary MDA production, neutrophil count, and MPO activity and reduced arterial oxygen partial pressure (all P < 0.05 IR versus sham), accompanied with a compensatory increase in HO-1 protein and activity. Plasma levels of TNF-α, IL-6, and IL-8 were increased in the IR group (all P < 0.05 versus sham). IPO attenuated or prevented all the above changes, except that it further increased lung HO-1 activity. Treatment with ZnP abolished all the protective effects of postconditioning.

CONCLUSION

Postconditioning attenuated pulmonary neutrophil accumulation and activation and lung IRI and reduced systemic inflammatory responses by activating HO-1.

Interleukin-18 delays neutrophil apoptosis following alcohol intoxication and burn injury

Studies have shown that burn patients who are intoxicated at the time of injury are more susceptible to infection and have a higher incidence of mortality. A major cause of death in burn and trauma patients regardless of their alcohol (EtOH) exposure is multiple organ dysfunction, which is driven in part by the systemic inflammatory response and activated neutrophils. Neutrophils are short lived and undergo apoptosis to maintain homeostasis and resolution of inflammation. A delay in apoptosis of neutrophils is one important mechanism which allows for their prolonged presence and the release of potentially harmful enzymes. The purpose of this study was to examine whether EtOH intoxication combined with burn injury influences neutrophil apoptosis and whether IL-18 plays any role in this setting. To accomplish this investigation, rats were gavaged with EtOH (3.2 g/kg) 4 h before being subjected to sham or burn injury of ~12.5% of the total body surface area, and then killed on d 1 after injury. Peripheral blood neutrophils were isolated and lysed. The lysates were analyzed for pro- and antiapoptotic proteins. We found that EtOH combined with burn injury prolonged neutrophil survival. This prolonged neutrophil survival was accompanied by a decrease in the levels of the neutrophil proapoptotic protein Bax, and an increase in antiapoptotic proteins Mcl-1 and Bcl-xl. Administration of IL-18 antibody following burn injury normalized the levels of Bax, Mcl-1 and Bcl-xl. The decrease in caspase-3 and DNA fragmentation observed following EtOH and burn injury was also normalized in rats treated with anti-IL-18 antibody. These findings suggest that IL-18 delays neutrophil apoptosis following EtOH and burn injury by modulating the pro- and antiapoptotic proteins.

NADPH oxidase-dependent reactive oxygen species mediate amplified TLR4 signaling and sepsis-induced mortality in Nrf2-deficient mice

Sepsis syndrome is characterized by a dysregulated inflammatory response to infection. NADPH oxidase-dependent reactive oxygen species (ROS) play significant roles in the pathophysiology of sepsis. We previously showed that disruption of Nrf2, a master regulator of antioxidant defenses, caused a dysregulation of innate immune response that resulted in greater mortality in a polymicrobial sepsis and LPS shock model; however, the underlying mechanisms are unclear. In the current study, compared with wild-type (Nrf2(+/+)) macrophages, we observed greater protein kinase C-induced NADPH oxidase-dependent ROS generation in Nrf2-disrupted (Nrf2(-/-)) macrophages that was modulated by glutathione levels. To address the NADPH oxidase-mediated hyperinflammatory response and sepsis-induced lung injury and mortality in Nrf2(-/-) mice, we used double knockout mice lacking Nrf2 and NADPH oxidase subunit, gp91(phox) (Nrf2(-/-)//gp91(phox-/-)). Compared with Nrf2(+/+) macrophages, LPS induced greater activation of TLR4 as evident by TLR4 surface trafficking and downstream recruitment of MyD88 and Toll/IL-1R domain-containing adaptor in Nrf2(-/-) macrophages that was diminished by ablation of gp91(phox). Similarly, phosphorylation of IkappaB and IFN regulatory factor 3 as well as cytokine expression was markedly higher in Nrf2(-/-) macrophages; whereas, it was similar in Nrf2(+/+) and Nrf2(-/-)//gp91(phox-/-). In vivo studies showed greater LPS-induced pulmonary inflammation in Nrf2(-/-) mice that was significantly reduced by ablation of gp91(phox). Furthermore, LPS shock and polymicrobial sepsis induced early and greater mortality in Nrf2(-/-) mice; whereas, Nrf2(-/-)//gp91(phox-/-) showed prolonged survival. Together, these results demonstrate that Nrf2 is essential for the regulation of NADPH oxidase-dependent ROS-mediated TLR4 activation and lethal innate immune response in sepsis.

Melatonin plays a protective role in postburn rodent gut pathophysiology

Melatonin is a possible protective agent in postburn gut pathophysiological dynamics. We investigated the role of endogenously-produced versus exogenously-administered melatonin in a major thermal injury rat model with well-characterized gut inflammatory complications. Our rationale is that understanding in vivo melatonin mechanisms in control and inflamed tissues will improve our understanding of its potential as a safe anti-inflammatory/antioxidant therapeutic alternative. Towards this end, we tested the hypothesis that the gut is both a source and a target for melatonin and that mesenteric melatonin plays an anti-inflammatory role following major thermal injury in rats with 3^rd degree hot water scald over 30% TBSA. Our methods for assessing the gut as a source of melatonin included plasma melatonin ELISA measurements in systemic and mesenteric circulation as well as rtPCR measurement of jejunum and terminal ileum expression of the melatonin synthesizing enzymes arylalkylamine N-acetyltransferase (AA-NAT) and 5-hydroxyindole-O-methyltransferase (HIOMT) in sham versus day-3 postburn rats. Our melatonin ELISA results revealed that mesenteric circulation has much higher melatonin than systemic circulation and that both mesenteric and systemic melatonin levels are increased three days following major thermal injury. Our rtPCR results complemented the ELISA data in showing that the melatonin synthesizing enzymes AA-NAT and HIOMT are expressed in the ileum and jejunum and that this expression is increased three days following major thermal injury. Interestingly, the rtPCR data also revealed negative feedback by melatonin as exogenous melatonin supplementation at a dose of 7.43 mg (32 μmole/kg), but not 1.86 mg/kg (8 μmole/kg) drastically suppressed AA-NAT mRNA expression. Our methods also included an assessment of the gut as a target for melatonin utilizing computerized immunohistochemical measurements to quantify the effects of exogenous melatonin supplementation on postburn gut mucosa barrier inflammatory profiles. Here, our results revealed that daily postburn intraperitoneal melatonin administration at a dose of 1.86 mg/kg (8 μmole/kg) significantly suppressed both neutrophil infiltration and tyrosine nitrosylation as revealed by Gr-1 and nitrotyrosine immunohistochemistry, respectively. In conclusion, our results provide support for high mesenteric melatonin levels and dynamic de novo gut melatonin production, both of which increase endogenously in response to major thermal injury, but appear to fall short of abrogating the excessive postburn hyper-inflammation. Moreover, supplementation by exogenous melatonin significantly suppresses gut inflammation, thus confirming that melatonin is protective against postburn inflammation.

Anti-inflammatory pathways and alcoholic liver disease: Role of an adiponectin/interleukin-10/heme oxygenase-1 pathway

The development of alcoholic liver disease (ALD) is a complex process involving both the parenchymal and non-parenchymal cells in the liver. Enhanced inflammation in the liver during ethanol exposure is an important contributor to injury. Kupffer cells, the resident macrophages in liver, are particularly critical to the onset of ethanol-induced liver injury. Chronic ethanol exposure sensitizes Kupffer cells to activation by lipopolysaccharide via Toll-like receptor 4. This sensitization enhances production of inflammatory mediators, such as tumor necrosis factor-α and reactive oxygen species, that contribute to hepatocyte dysfunction, necrosis, apoptosis, and fibrosis. Impaired resolution of the inflammatory process probably also contributes to ALD. The resolution of inflammation is an active, highly coordinated response that can potentially be manipulated via therapeutic interventions to treat chronic inflammatory diseases. Recent studies have identified an adiponectin/interleukin-10/heme oxygenase-1 (HO-1) pathway that is profoundly effective in dampening the enhanced activation of innate immune responses in primary cultures of Kupffer cells, as well as in an in vivo mouse model of chronic ethanol feeding. Importantly, induction of HO-1 also reduces ethanol-induced hepatocellular apoptosis in this in vivo model. Based on these data, we hypothesize that the development of therapeutic agents to regulate HO-1 and its downstream targets could be useful in enhancing the resolution of inflammation during ALD and preventing progression of early stages of liver injury.

Neutrophil-derived circulating free DNA (cf-DNA/NETs), a potential prognostic marker for mortality in patients with severe burn injury

The predictive value of circulating free DNA/neutrophil extracellular traps (cf-DNA/NETs) has recently been shown in patients with major trauma for sepsis, multiple organ failure, and mortality. Here we report on the predictive potential of cf-DNA/NETs for mortality in patients with severe burn injury. In a prospective study 32 patients with severe burn injury were included. Blood samples were sequentially obtained on day 1, 3, 5, and 7 after admission. cf-DNA/NETs was directly quantified from plasma by means of rapid fluorescence assay. Time kinetics of cf-DNA/NETs were correlated with clinical data, C-reactive protein (CRP), procalcitonin (PCT), and interleukin (IL)-6. Furthermore sensitivity, specificity, and positive and negative predictive value, as well as receiver operation characteristic (ROC) curves were calculated. Seven patients died within the first month after burn injury. cf-DNA/NETs values from these patients were significantly increased already on day 1 and 3 after admission compared with patients who survived (p < 0.01). In contrast, PCT levels of nonsurvivors were significantly elevated on day 3 and 5 (p < 0.01), while CRP and IL-6 did not show any significant difference between survivors and nonsurvivors. At a cutoff of 255 ng/ml, cf-DNA/NETs had sensitivity of 0.8 and specificity of 0.74. ROC revealed largest areas under the curve (AUC) for cf-DNA/NETs on day 1 (0.851) and 3 (0.883) after admission. For all values between day 1 and 7, AUC was 0.815. cf-DNA/NETs seems to be a rapid, valuable marker for prediction of mortality in burn patients. A larger confirmation trial ought to be carried out.