Endotoxin-induced Shock Research Articles

Polycomb-mediated loss of microRNA let-7c determines inflammatory macrophage polarization via PAK1-dependent NF-κB pathway.

Serine/threonine kinase family members p21-activated kinases (PAKs) are important regulators of cytoskeletal remodeling and cell motility in mononuclear phagocytic system, but their role in macrophage differentiation and polarization remains obscure. We have shown here that inflammatory stimuli induced PAK1 overexpression in human and murine macrophages. Elevated expression of PAK1 contributed to macrophage M1 polarization and lipopolysaccharide (LPS)-induced endotoxin shock. We further observed that epigenetic loss of microRNA let-7c due to enhancer of zeste homolog 2 (EZH2) upregulation determined PAK1 elevation and inflammatory phenotype in M1 macrophages. EZH2/let-7c/PAK1 axis promotes macrophage M1 polarization via NIK-IKK-NF-κB signaling. Moreover, pharmacological and genetic ablation with EZH2/let-7c/PAK1 axis blunted inflammatory phenotype in M1 macrophages. Critically, either myeloid-restricted PAK1 deletion (PAK1(Lyz2cre)) or pharmacological and genetic ablation with EZH2/let-7c/PAK1 signal resulted in resistance to LPS-induced endotoxin shock via blunting macrophage M1 polarization. PAK1, therefore, is an essential controller of inflammatory macrophage polarization, regulating immune responses against pathogenic stimuli.

Protective effect of recombinant human brain natriuretic peptide on acute renal injury induced by endotoxin in canines.

The objective of this study was to evaluate the protective effect of recombinant human brain natriuretic peptide (rhBNP) on endotoxin-induced acute kidney injury (AKI) in canine model of septic shock and its potential mechanisms. Dogs with endotoxin-induced septic shock were subjected to intravenous infusion of saline solution or rhBNP at the concentrations of 5 μg/kg (low-dose intervention group) or 10 μg/kg (high-dose intervention group). At 0, 2, 4, 8, and 12 h, the systemic vascular resistance index (SVRI) as well as serum levels of high mobility group box 1 protein (HMGB-1) and creatinine were measured, and kidney tissue samples were taken for histological examination. We have found that low and high doses of rhBNP could significantly reduce kidney tissue damage, such as tubular epithelial swelling and atrophy, and interstitial cell swelling in response to LPS injection in the dog sepsis models. rhBNP administration significantly reduced SVRI and serum levels of creatinine in dogs with LPS-induced sepsis in a dose-dependent manner, and attenuated the rise in the circulating HMGB-1. In conclusion, these findings suggest that rhBNP may exert dose-dependent protective effect on kidney tissue with endotoxin-induced injury, and this effect may be associated with the changes in blood levels of HMGB-1. rhBNP may be considered as therapeutic agents for treating sepsis-induced AKI.

The orphan nuclear receptor estrogen-related receptor α negatively regulates Toll-like receptor-induced inflammation through A20 induction (IRM11P.759)

Abstract Estrogen-related receptor (ERR) α, an orphan nuclear receptor member, is a key metabolic regulator in various organs and tissues. However, its function in regulating innate immune responses has remained largely unknown. Herein we show that ERRα negatively regulates toll-like receptor (TLR)-induced inflammatory responses through induction of A20. ERRα-deficient (ERRα-/-) mice showed a higher susceptibility to endotoxin-induced septic shock, with a concurrent increase of proinflammatory responses in vivo and in vitro. Global gene expression analysis showed that ERRα regulated TLR-induced inflammation through induction of A20, a deubiquitinating enzyme in TLR signaling. Lack of ERRα in macrophages increased NF-κB signaling and IKK activation. In addition, treatment of macrophages with inverse agonist XCT-790 led to an increase of inflammatory responses induced by TLR4 stimulation. These findings identify a novel function of ERRα as an intrinsic negative regulator of inflammation through induction of A20.

In vivo role of HMGB1 in endotoxemia and bacterial infection (IRC5P.454)

Abstract High-mobility group box protein 1 is nuclear protein conserved among almost all eukaryotic cells. HMGB1 is thought to be a danger signal mediator when it is released both actively from activated immune cells and passively from dead cells into extracellular milieu upon pathogen infections or sterile inflammations. Released HMGB1 act as an inflammatory cytokine and promote inflammatory disorders. However, in vivo function of HMGB1 is still elusive since Hmgb1 gene-deficient mice are lethal. In this study, by using Hmgb1 gene conditional knockout mice which we have established recently, we examined the role of HMGB1 in innate immune responses and inflammation in vivo. We successfully generated Hmgb1fl/flLysM-Cre+ mice because it has been reported that HMGB1 is released from myeloid cells. They developed without significant anomaly and HMGB1 is deleted from macrophages. Interestingly, we observed that, in LPS induced endotoxin shock model, Hmgb1fl/flLysM-Cre+ mice became more sensitive while plasma HMGB1 level of Hmgb1fl/flLysM-Cre+ mice is comparable with wild-type control. These mice also became more susceptible to bacterial infection. In this poster session, we would like to discuss these and recent data further.

Dexmedetomidine renders a brain protection on hippocampal formation through inhibition of nNOS-NO signalling in endotoxin-induced shock rats

Background: Endotoxin shock (ES) and its severe complications, such as brain injury, remain a handicap clinically. Therefore, it is a clinical significance of developing a new drug to treat brain damage induced by ES.Aim: The present study aimed to observe the protective effect of dexmedetomidine (Dex) on hippocampal formation in endotoxin-induced shock rats and explore its possible mechanism.Methods: High and low doses of Dex were tail intravenously administered slowly. After a 5-minute interval, lipopolysaccharide was tail intravenous injected slowly to establish the ES rats. Six hours after Dex administration, these rats were immediately sacrificed. Then, the brain water content was determined. NO amounts in homogenate, cerebrospinal fluid and serum were detected by Griess Reagent assay. nNOS mRNA in hippocampal formation was measured by RT-PCR and nNOS protein was determined by Western blotting and immunohistochemistry.Results: ES rats showed that cerebral water contents were significantly increased, NO concentrations in brain tissues, serum and cerebrospinal fluid were each obviously raised and meanwhile expressions of nNOS mRNA and its protein in hippocampal formation were notably augmented. Treatment of these rats with Dex evidently decreased cerebral water contents, NO concentrations and nNOS mRNA and its protein expressions.Conclusion: These results demonstrated that Dex exerted a brain protection on hippocampal formation through inhibition of the nNOS-NO signalling in ES rats and Dex may have a favourably therapeutic value in treating brain damage in patients with endotoxin shock.

Analysis of intraosseous samples in endotoxemic shock--an experimental study in the anaesthetised pig.

Intraosseous (IO) access is used in emergency situations to allow rapid initiation of treatment. IO access is also sometimes used for blood sampling, although data on accuracy of such sampling in critical illness are limited. There is also a potential risk that bone marrow fragments in IO samples may damage laboratory equipment. It is ethically questionable to perform a simultaneous comparison between IO and arterial/venous sampling in critically ill humans. We have, thus, studied the analytical performance of IO sampling in a porcine septic shock model using a cartridge-based analyser. Eight pigs with endotoxin-induced septic shock were sampled hourly for 6 h, and analysed for blood gases, acid base status, haemoglobin, glucose and lactate using point of care instruments. Samples were taken from three IO cannulae (tibia bilaterally, one with infusion, and humerus), one arterial and one venous. An interaction test was used to assess changes in agreement between methods over time. Bland–Altman plots were constructed to study bias between methods. There were, to a varying extent, differences between IO and arterial/venous levels for all studied variables, but agreement did not change significantly during the experiment. A general finding was a large dispersion of differences between methods. IO sample values should be treated with caution in this setting but may add useful information to the clinical picture. The tibia or humerus may be used for sampling. IO infusion decreases agreement, thus sampling during infusion should be avoided.

TREM-1 Deficiency Can Attenuate Disease Severity without Affecting Pathogen Clearance

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a potent amplifier of pro-inflammatory innate immune reactions. While TREM-1-amplified responses likely aid an improved detection and elimination of pathogens, excessive production of cytokines and oxygen radicals can also severely harm the host. Studies addressing the pathogenic role of TREM-1 during endotoxin-induced shock or microbial sepsis have so far mostly relied on the administration of TREM-1 fusion proteins or peptides representing part of the extracellular domain of TREM-1. However, binding of these agents to the yet unidentified TREM-1 ligand could also impact signaling through alternative receptors. More importantly, controversial results have been obtained regarding the requirement of TREM-1 for microbial control. To unambiguously investigate the role of TREM-1 in homeostasis and disease, we have generated mice deficient in Trem1. Trem1−/− mice are viable, fertile and show no altered hematopoietic compartment. In CD4+ T cell- and dextran sodium sulfate-induced models of colitis, Trem1−/− mice displayed significantly attenuated disease that was associated with reduced inflammatory infiltrates and diminished expression of pro-inflammatory cytokines. Trem1−/− mice also exhibited reduced neutrophilic infiltration and decreased lesion size upon infection with Leishmania major. Furthermore, reduced morbidity was observed for influenza virus-infected Trem1−/− mice. Importantly, while immune-associated pathologies were significantly reduced, Trem1−/− mice were equally capable of controlling infections with L. major, influenza virus, but also Legionella pneumophila as Trem1+/+ controls. Our results not only demonstrate an unanticipated pathogenic impact of TREM-1 during a viral and parasitic infection, but also indicate that therapeutic blocking of TREM-1 in distinct inflammatory disorders holds considerable promise by blunting excessive inflammation while preserving the capacity for microbial control.

Studies onIn VivoFunction of Peroxiredoxins in Knockout Mice

appearance and fertile, however showed several pathophysiological disorders. Using the mice, we found that Prx II is an essential antioxidant enzyme that prevents oxidative stress in erythropoiesis, protects against endotoxin-induced lethal shock, regulates platelet-derived growth factor signaling and angiogenesis, inhibits cellular senescence, preserves cognitive function against age-linked hippocampal oxidative damage and exacerbates tumorigenesis in a liver cancer mouse model. The Prx I-/- mice were also healthy in appearance and fertile like Prx II -/- mice. With the mice, we found that Prx I suppresses K-ras-driven lung tumorigenesis by opposing the redox-sensitive extracellular-signal-regulated kinase/ cyclin D1 pathway and plays concerted action with sulfiredoxin in preventing against al cohol-induced oxidative injury in the mouse liver. The results obtained suggest that Prx I and II are essential antioxidant enzymes for maintaining redox homeostasis in mice.

STAT1-Deficient Mice Are Resistant to Cecal Ligation and Puncture–Induced Septic Shock

STAT1 (signal transducer and activator of transcription 1) is a member of the JAK-STAT signaling family and plays a key role in facilitating gene transcription in response to activation of the types I and II interferon (IFN) receptors. TYK2 is essential for type I, but not type II, IFN-induced STAT1 activation. Previous studies show that STAT1-deficient mice are resistant to endotoxin-induced shock. The goal of the present study was to assess the response of STAT1- and TYK2-deficient mice to septic shock caused by cecal ligation and puncture (CLP). End points included survival, core temperature, organ injury, systemic cytokine production, and bacterial clearance. Results showed that survival rates were significantly higher in STAT1 knockout (STAT1KO) mice compared with wild-type controls (80% vs. 10%). The improved survival of STAT1KO mice was associated with less hypothermia, metabolic acidosis, hypoglycemia, and hepatocellular injury. Plasma interleukin 6, MIP-2, CXCL10, and IFN-α concentrations were significantly lower in STAT1KO mice than in wild-type mice. In the absence of antibiotic treatment, blood and lung bacterial counts were significantly lower in STAT1KO mice than in controls. However, treatment with antibiotics ablated that difference. A survival advantage was not observed in TYK2-deficient mice compared with control. However, CLP-induced hypothermia and systemic interleukin 6 and CXCL10 production were significantly attenuated in TYK2-deficient mice. These results indicate that STAT1 activation is an important factor in the pathogenesis of CLP-induced septic shock and is associated with the development of systemic inflammation and organ injury. TYK2 activation also appears to contribute to CLP-induced inflammation, but to a lesser extent than STAT1.

Preventive and therapeutic effects of quercetin on lipopolysaccharide-induced oxidative stress and vascular dysfunction in mice

Quercetin, a dietary antioxidant flavonoid, possesses strong anti-inflammatory and cytoprotective activities. The effects were investigated in an animal model of lipopolysaccharide (LPS)-induced endotoxaemia and vascular dysfunction in vivo. Male ICR mice were injected with LPS (10mg/kg; i.p.). Quercetin (50 or 100mg/kg) was intragastrically administered either before or after LPS administration. Fifteen hours after LPS injection, mice were found in endotoxaemic condition, as manifested by hypotension, tachycardia, and blunted vascular responses to vasodilators and vasoconstrictor. The symptoms were accompanied by increased aortic iNOS protein expression, decreased aortic eNOS protein expression, marked suppression of cellular glutathione (GSH) redox status, enhanced aortic superoxide production, increased plasma malodialdehyde and protein carbonyl, and elevated urinary nitrate/nitrite. Treatment with quercetin either before or after LPS preserved the vascular function, as blood pressure, heart rate, vascular responsiveness were restored to near normal values, particularly when quercetin was given as a preventive regimen. The vascular protective effects were associated with upregulation of eNOS expression, reduction of oxidative stress, and maintained blood GSH redox ratio. Overall findings suggest the beneficial effect of quercetin on the prevention and restoration of a failing eNOS system and alleviation of oxidative stress and vascular dysfunction against endotoxin-induced shock in mice.

Effects of propofol with hyperthermia in a rat model of endotoxemic shock

We aimed to investigate the effects of active mild hyperthermia and the effects of active mild hyperthermia with propofol on mortality and inflammatory responses during endotoxin-induced shock in rats. Intravenous Escherichia coli endotoxin (15 mg/kg over 2 min) was injected in 48 rats. The animals were randomly allocated to one of the following four groups (n = 12 per group): normothermia group (group N), rectal temperature maintained between 36 °C and 38 °C; hyperthermia group (group H), rectal temperature was moderate and maintained between 39 °C and 40 °C; propofol with normothermia group (group PN), propofol (10 mg/kg/h) was administered, and temperature was between 36 °C and 38 °C; Propofol with hyperthermia group (group PH), propofol (10 mg/kg/h) administrated, and temperatures were maintained between 39 °C and 40 °C. The primary outcome was mortality 8 h after endotoxin injection. Secondary outcomes included changes in haemodynamics, arterial blood gases and plasma cytokine concentrations for the 8-h observation period. Mortality rates 8 h after endotoxin injection were 92%, 100%, 68% and 50% for N, H, PN and PH groups, respectively. There was no difference in hypotension, acidosis, and increase in plasma cytokine concentrations between N and H groups, but these parameters were attenuated in group PH. The mortality rates in the present study were extremely high; further hypotension and elevations in plasma pro-inflammatory and anti-inflammatory cytokine concentrations after endotoxin injection were not attenuated by mild hyperthermia between 39 °C and 40 °C, but they were attenuated by propofol with mild hyperthermia.

Arterial dP/dtmax accurately reflects left ventricular contractility during shock when adequate vascular filling is achieved

BackgroundPeak first derivative of femoral artery pressure (arterial dP/dtmax) derived from fluid-filled catheter remains questionable to assess left ventricular (LV) contractility during shock. The aim of this study was to test if arterial dP/dtmax is reliable for assessing LV contractility during various hemodynamic conditions such as endotoxin-induced shock and catecholamine infusion.MethodsVentricular pressure-volume data obtained with a conductance catheter and invasive arterial pressure obtained with a fluid-filled catheter were continuously recorded in 6 anaesthetized and mechanically ventilated pigs. After a stabilization period, endotoxin was infused to induce shock. Catecholamines were transiently administrated during shock. Arterial dP/dtmax was compared to end-systolic elastance (Ees), the gold standard method for assessing LV contractility.ResultsEndotoxin-induced shock and catecholamine infusion lead to significant variations in LV contractility. Overall, significant correlation (r = 0.51; p < 0.001) but low agreement between the two methods were observed. However, a far better correlation with a good agreement were observed when positive-pressure ventilation induced an arterial pulse pressure variation (PPV) ≤ 11% (r = 0.77; p < 0.001).ConclusionWhile arterial dP/dtmax and Ees were significantly correlated during various hemodynamic conditions, arterial dP/dtmax was more accurate for assessing LV contractility when adequate vascular filling, defined as PPV ≤ 11%, was achieved.

What Is the Role for the Inflammasome in Burn Injury and Sepsis?

What Is the Role for the Inflammasome in Burn Injury and Sepsis?

Effects of acute low-dose ethanol on inflammatory reactions to endotoxin-induced shock in rats

Effects of acute low-dose ethanol on inflammatory reactions to endotoxin-induced shock in rats

Glibenclamide reduces proinflammatory cytokines in an ex vivo model of human endotoxinaemia under hypoxaemic conditions

Aims In vivo application of the K ATP-channel blocker glibenclamide can reverse endotoxin-induced hypotension, vascular hyporeactivity and shock in experimental animals. The hypothesis of the present study is, that the drug effects might not only be based on direct inhibition of K ATP-channels of vascular smooth muscle cells, but might also reflect reduction of shock-induced excess proinflammatory cytokines and procoagulatory molecules produced in the blood monocytes. Main methods Human whole blood (normoxaemic or hypoxaemic) supplemented ex vivo with 100 ng/ml LPS was used to assess glibenclamide (3–100 μM) effects on IL-1beta, IL-6, TNF-alpha, tissue factor, and plasminogen-activator-inhibitor-2 (PAI-2). Co-incubations with monocytes and erythrocytes and cytosolic calcium measurements were performed to reveal their purinergic intercellular interaction. Key findings In heparinized blood, glibenclamide reduced LPS-induced release of IL-1beta and TNF-alpha, tissue factor and PAI-2 mRNA in a concentration-dependent manner. When samples were subjected to strong hypoxemia using 95% N 2/5% CO 2, these parameters became even more sensitive to the drug. No drug effect was observable in citrated blood or in isolated monocytes. IL-1beta mRNA inhibition by glibenclamide appeared to be dependent on P2X7-receptor activation of monocytes by ATP-releasing erythrocytes during hypoxia. Cytosolic calcium values as well as the duration of calcium transients elicited by P2X7-receptor stimulation in isolated monocytes were strongly increased during hypoxia, both of which could be abolished by glibenclamide. Significance We conclude that the anti-inflammatory effect of glibenclamide is mainly based on the reduction of calcium entry by drug-induced depolarization of hypoxic monocytes. Thus, glibenclamide possesses a potentially beneficial shock-specific anti-inflammatory action.

Hyperbilirubinemia in infants with Gram-negative sepsis does not affect mortality

Background Sepsis is associated with an increased production of oxidant species and a decrease in endogenous antioxidant defenses. Mortality is high, especially when endotoxins are involved, e.g., in infants with Gram-negative sepsis. Yet, chronic as well as acute unconjugated hyperbilirubinemia has been shown to protect against endotoxin-induced shock in vivo in rats and in mice. We hypothesized that hyperbilirubinemia in infants with Gram-negative sepsis improves survival and/or mitigates the inflammatory response. Objective To assess the relationships between serum bilirubin concentrations on the one hand, and leukocyte count, C-reactive protein and survival on the other hand, in infants with Gram-negative sepsis. Methods Retrospectively, we retrieved clinical and biochemical data from infants less than 90 days of age with a blood culture-proven Gram-negative sepsis between January 1998 and December 2005. Results We identified 92 infants with Gram-negative sepsis in the indicated period. Median gestational age was 29 (24–42) weeks. 22 Patients died. Preceding sepsis, median total serum bilirubin concentrations were below 150 μmol/L. Median concentrations of conjugated bilirubin concentrations increased (+ 63%, p < 0.05), and median concentrations of unconjugated bilirubin decreased (− 36%, p < 0.05) in infants with Gram-negative sepsis. Median total bilirubin concentrations before and during sepsis were not significantly different between survivors and non-survivors. Changes in bilirubin concentrations were not significantly correlated with changes in either white blood cell count or C-reactive protein. Conclusion Present data do not support the concept that bilirubin positively affects survival or the inflammatory response in infants with Gram-negative sepsis.

640: In utero inflammation alters the cardiovascular response of adult offspring

The effect of the uterine environment on adult vascular function has been well documented. Our previous studies have shown that exposure to significant inflammation at day 16 gestation in mice alters the in vitro carotid artery vascular reactivity in the adult offspring. Our objective in this study was to test the hypothesis that exposure to inflammation in late gestation alters the adult offspring's blood pressure both during normal activity and in endotoxin-induced shock.

Study on Modified Shengmai Yin Injection for Prevention and Treatment of Brain Impairment in Endotoxin Shock Rats

To examine the effects of modified Shenmai Yin on invigorating vital energy, promoting blood flow, and protection against neural impairment in an endotoxin-induced shock rat model. Ninety-six SD rats were randomly divided into four groups: sham operation (saline 20 ml/kg), shock model (lipopolysaccharide, LPS, 8 mg/kg), Reformed Shengmai Yin (Pulse-activating Decoction) (LPS 8 mg/kg + reformed Shengmai Yin Injection 10 ml/kg), and dexamethasone (LPS 8 mg/kg + dexamethasone 5 mg/kg) groups. Each group was subdivided into 1 h, 2 h, 3 h, and 6 h time points for observation. The carotid artery was separated and connected with a biological functional system to monitor mean arterial pressure (MAP). Brain water levels, malonaldehyde (MDA) content, and superoxide dismutase (SOD) activity were also determined. In the shock model group, MAP was progressively decreased after injection of LPS, brain water and MDA contents were increased, brain SOD activity was decreased, and capillary vessel edema in brain tissue was also observed. All these parameters were improved significantly in both treatment groups, although the effects were more marked with Shengmai Yin than with dexamethasone. Modified Shengmai Yin exhibits strong anti-shock and neuroprotective effects against Endotoxin-induced shock.

The roots of Nardostachys jatamansi inhibits lipopolysaccharide-induced endotoxin shock

Nardostachys jatamansi (NJ) has been used in the treatment of inflammatory diseases. However, it is not clear how NJ produces anti-inflammatory effects. In the present study, using an experimental model of lipopolysaccharide (LPS)-induced endotoxin shock, the protective effects and mechanisms of action of NJ were investigated. The water extract of roots of NJ was administrated to mice orally (1, 5, and 10mg/kg) 1h after or before LPS challenge. The administration of NJ inhibited LPS-induced endotoxin shock and the production of inflammatory mediators, such as interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-α/β. Murine peritoneal macrophages were used to determine the production of inflammatory mediators. In peritoneal macrophages, NJ also inhibited LPS-induced production of inflammatory mediators, such as IL-1β, IL-6, TNF-α, and IFN-α/β. In addition, NJ reduced the activation of mitogen-activated protein kinases (MAPKs) and the level of expression of interferon regulatory factor (IRF)-1 and IRF-7 mRNA. Furthermore, post-treatment with NJ reduced LPS-induced endotoxin shock and the production of inflammatory mediators. These results suggest that NJ inhibits endotoxin shock by inhibiting the production of IL-1β, IL-6, TNF-α, and IFN-α/β through the inhibition of MAPKs activation and IRF induction.

Distinct Roles of Hepatocyte- and Myeloid Cell-Derived IL-1 Receptor Antagonist during Endotoxemia and Sterile Inflammation in Mice

IL-1R antagonist (IL-1Ra) is a natural inhibitor of the pleiotropic proinflammatory activities of IL-1. Although several reports described the effects of complete IL-1Ra deficiency, no study has examined the consequences of cell type-specific IL-1Ra inactivation during systemic inflammation. Previous in vitro data demonstrated high IL-1Ra production by hepatocytes and myeloid cells after endotoxin stimulation. In addition, hepatocyte IL-1Ra production is regulated as an acute-phase protein in vitro. In this study, we analyzed the production and functional role of hepatocyte- and myeloid cell-derived IL-1Ra during endotoxin-induced septic shock and acute IL-1beta-induced sterile inflammation. Using conditional IL-1Ra knockout mice, we showed that hepatocytes and myeloid cells are the two major cellular sources of circulating IL-1Ra in response to LPS. Interestingly, IL-1Ra production by myeloid cells, but not hepatocytes, is critical for survival during endotoxemia. Furthermore, we provide the first in vivo evidence demonstrating that IL-1Ra is produced as an acute-phase protein by hepatocytes during IL-1beta-induced inflammation and that hepatocyte-derived IL-1Ra functions as an endogenous negative feedback downregulating the proinflammatory effects of IL-1. Taken together, our observations define distinct roles for two major cellular sources of IL-1Ra in response to different types of systemic inflammatory stimuli in vivo.