Inhibition of Netosis with PAD Inhibitor Attenuates Endotoxin Shock Induced Systemic Inflammation

Neutrophils play a pivotal role in innate immunity by releasing neutrophils extracellular traps (NETs). Excessive NETs are detrimental to the local tissue and further exacerbate inflammation. Protein arginine deiminases (PAD) mediate histone citrullination and NET formation that, in turn, exacerbate endotoxin shock damages. In this study, we further investigated the molecular mechanism underlying PAD and NETs in endotoxic stress in mice. The control group mice were injected with solvent, the LPS endotoxic shock group mice were intraperitoneally injected with LPS at 35 mg/kg only, while the LPS and PAD inhibitor YW3-56 treatment group mice were injected with YW3-56 at 10 mg/kg prior to the LPS injection. YW3-56 significantly prolonged the survival time of the LPS-treated mice. NETs, cfDNA, and inflammatory factors were detected by ELISA in serum, paitoneal cavity, and lung at 24 h after LPS administration. Lung injuries were detected by immunostaining, and lung tissue transcriptomes were analyzed by RNA-seq at 24 h after LPS administration. We found that YW3-56 altered neutrophil tissue homeostasis, inhibited NET formation, and significantly decreased cytokines (IL-6, TNFα and IL-1β) levels, cytokines gene expression, and lung tissue injury. In summary, NET formation inhibition offers a new avenue to manage inflammatory damages under endotoxic stress.

Understanding the role of endotoxin tolerance in chronic inflammatory conditions and periodontal disease

OBJECTIVE

This review aims to present the current understanding of endotoxin tolerance (ET) in chronic inflammatory diseases and explores the potential connection with periodontitis.

SUMMARY

Subsequent exposure to lipopolysaccharides (LPS) triggers ET, a phenomenon regulated by different mechanisms and pathways, including toll-like receptors (TLRs), nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), apoptosis of immune cells, epigenetics, and microRNAs (miRNAs). These mechanisms interconnect ET with chronic inflammatory diseases that include periodontitis. While the direct correlation between ET and periodontal destruction has not been fully elucidated, emerging reports point towards the potential tolerization of human periodontal ligament cells (hPDLCs) and gingival tissues with a significant reduction of TLR levels.

CONCLUSIONS

There is a potential link between ET and periodontal diseases. Future studies should explore the crucial role of ET in the pathogenesis of periodontal diseases as evidence of a tolerized oral mucosa may represent an intrinsic mechanism capable of regulating the oral immune response. A clear understanding of this host immune regulatory mechanism might lead to effective and more predictable therapeutic strategies to treat chronic inflammatory diseases and periodontitis. This article is protected by copyright. All rights reserved.

Atraric Acid Exhibits Anti-Inflammatory Effect in Lipopolysaccharide-Stimulated RAW264.7 Cells and Mouse Models

Lichens, composite organisms resulting from the symbiotic association between the fungi and algae, produce a variety of secondary metabolites that exhibit pharmacological activities. This study aimed to investigate the anti-inflammatory activities of the secondary metabolite atraric acid produced by Heterodermia hypoleuca. The results confirmed that atraric acid could regulate induced pro-inflammatory cytokine, nitric oxide, prostaglandin E2, induced nitric oxide synthase and cyclooxygenase-2 enzyme expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Meanwhile, atraric acid downregulated the expression of phosphorylated IκB, extracellular signal-regulated kinases (ERK) and nuclear factor kappa B (NFκB) signaling pathway to exhibit anti-inflammatory effects in LPS-stimulated RAW264.7 cells. Based on these results, the anti-inflammatory effect of atraric acid during LPS-induced endotoxin shock in a mouse model was confirmed. In the atraric acid treated-group, cytokine production was decreased in the peritoneum and serum, and each organ damaged by LPS-stimulation was recovered. These results indicate that atraric acid has an anti-inflammatory effect, which may be the underlying molecular mechanism involved in the inactivation of the ERK/NFκB signaling pathway, demonstrating its potential therapeutic value for treating inflammatory diseases.

CD163 deficiency facilitates lipopolysaccharide-induced inflammatory responses and endotoxin shock in mice

Objectives

Septic (or endotoxin) shock is a severe systemic inflammatory disease caused by bacteraemia or endotoxaemia. Although it is known that increased serum levels of CD163 are observed in septic/endotoxin shock patients, the exact function and significance of CD163 in macrophage activation remain unclear. Therefore, in the current study, we tested whether CD163 contributes to the pathogenesis of endotoxin shock in mice.

Methods and results

In samples obtained from autopsy, the number of CD163‐positive macrophages was increased in the kidney, liver, heart, bone marrow and spleen of patients who had died from septic/endotoxin shock when compared to patients who had died from other causes. The animal study revealed a significantly lower survival rate in CD163‐deficient mice after lipopolysaccharide (LPS) injection. Several cytokines and oxidative stress‐related molecules were significantly elevated in the sera of LPS‐induced endotoxin shock mice models. Higher concentrations of IL‐6, TNF‐α, IL‐1β, nitrite (NO2‐) and nitrate (NO3‐) and a lower concentration of IL‐10 were observed in CD163‐deficient mice treated with LPS. Similar results were observed in CD163‐deficient LPS‐stimulated macrophages. Furthermore, in an antitype II collagen antibody‐induced arthritis (CAIA), rheumatoid arthritis model, inflammation and bone erosion scores as well as the expression of IL‐6 and IL‐1β were significantly increased in CD163‐deficient mice.

Conclusions

CD163 was suggested to be involved in the regulation of inflammatory cytokine expression in septic/endotoxin shock and CAIA.

The Caspase Inhibitor Z-VAD-FMK Alleviates Endotoxic Shock via Inducing Macrophages Necroptosis and Promoting MDSCs-Mediated Inhibition of Macrophages Activation

Macrophages play a critical role in the pathogenesis of endotoxin shock by producing excessive amounts of pro-inflammatory cytokines. A pan-caspase inhibitor, zVAD, can be used to induce necroptosis under certain stimuli. The role of zVAD in both regulating the survival and activation of macrophages, and the pathogenesis of endotoxin shock remains not entirely clear. Here, we found that treatment of mice with zVAD could significantly reduce mortality and alleviate disease after lipopolysaccharide (LPS) challenge. Notably, in LPS-challenged mice, treatment with zVAD could also reduce the percentage of peritoneal macrophages by promoting necroptosis and inhibiting pro-inflammatory responses in macrophages. In vitro studies showed that pretreatment with zVAD promoted LPS-induced nitric oxide-mediated necroptosis of bone marrow-derived macrophages (BMDMs), leading to reduced pro-inflammatory cytokine secretion. Interestingly, zVAD treatment promoted the accumulation of myeloid-derived suppressor cells (MDSCs) in a mouse model of endotoxin shock, and this process inhibited LPS-induced pro-inflammatory responses in macrophages. Based on these findings, we conclude that treatment with zVAD alleviates LPS-induced endotoxic shock by inducing macrophage necroptosis and promoting MDSC-mediated inhibition of macrophage activation. Thus, this study provides insights into the effects of zVAD treatment in inflammatory diseases, especially endotoxic shock.

Developmentally Regulated Innate Immune NFκB Signaling Mediates IL-1α Expression in the Perinatal Murine Lung

Bronchopulmonary dysplasia (BPD) is the most common morbidity complicating premature birth. Importantly, preclinical models have demonstrated that IL-1 receptor antagonism prevents the lung injury and subsequent abnormal development that typically results following perinatal exposure to inflammatory stresses. This receptor is activated by two pro-inflammatory cytokines, IL-1α and IL-1β. While many studies have linked IL-1β to BPD development, IL-1α is relatively under-studied. The objective of our study was to determine whether systemic inflammatory stress induces IL-1α expression in the neonatal lung, and if so, whether this expression is mediated by innate immune NFκB signaling. We found that endotoxemia induced IL-1α expression during the saccular stage of neonatal lung development and was not present in the other neonatal organs or the adult lung. This IL-1α expression was dependent upon sustained pulmonary NFκB activation, which was specific to the neonatal lung. Using in vivo and in vitro approaches, we found that pharmacologic and genetic inhibition of NFκB signaling attenuated IL-1α expression. These findings demonstrate that innate immune regulation of IL-1α expression is developmentally regulated and occurs via an NFκB dependent mechanism. Importantly, the specific role of developmentally regulated pulmonary IL-1α expression remains unknown. Future studies must determine the effect of attenuating innate immune IL-1α expression in the developing lung before adopting broad IL-1 receptor antagonism as an approach to prevent neonatal lung injury.

Leukadherin-1-Mediated Activation of CD11b Inhibits LPS-Induced Pro-inflammatory Response in Macrophages and Protects Mice Against Endotoxic Shock by Blocking LPS-TLR4 Interaction

Dysregulation of macrophage has been demonstrated to contribute to aberrant immune responses and inflammatory diseases. CD11b, expressed on macrophages, plays a critical role in regulating pathogen recognition, phagocytosis, and cell survival. In the present study, we explored the effect of leukadherin-1 (LA1), an agonist of CD11b, on regulating LPS-induced pro-inflammatory response in macrophages and endotoxic shock. Intriguingly, we found that LA1 could significantly reduce mortalities of mice and alleviated pathological injury of liver and lung in endotoxic shock. In vivo studies showed that LA1-induced activation of CD11b significantly inhibited the LPS-induced pro-inflammatory response in macrophages of mice. Moreover, LA1-induced activation of CD11b significantly inhibited LPS/IFN-γ-induced pro-inflammatory response in macrophages by inhibiting MAPKs and NF-κB signaling pathways in vitro. Furthermore, the mice injected with LA1-treated BMDMs showed fewer pathological lesions than those injected with vehicle-treated BMDMs in endotoxic shock. In addition, we found that activation of TLR4 by LPS could endocytose CD11b and activation of CD11b by LA1 could endocytose TLR4 in vitro and in vivo, subsequently blocking the binding of LPS with TLR4. Based on these findings, we concluded that LA1-induced activation of CD11b negatively regulates LPS-induced pro-inflammatory response in macrophages and subsequently protects mice from endotoxin shock by partially blocking LPS-TLR4 interaction. Our study provides a new insight into the role of CD11b in the pathogenesis of inflammatory diseases.

Leukadherin-1-Mediated Activation of CD11b Inhibits LPS-Induced Pro-inflammatory Response in Macrophages and Protects Mice Against Endotoxic Shock by Blocking LPS-TLR4 Interaction

Dysregulation of macrophage has been demonstrated to contribute to aberrant immune responses and inflammatory diseases. CD11b, expressed on macrophages, plays a critical role in regulating pathogen recognition, phagocytosis, and cell survival. In the present study, we explored the effect of leukadherin-1 (LA1), an agonist of CD11b, on regulating LPS-induced pro-inflammatory response in macrophages and endotoxic shock. Intriguingly, we found that LA1 could significantly reduce mortalities of mice and alleviated pathological injury of liver and lung in endotoxic shock. In vivo studies showed that LA1-induced activation of CD11b significantly inhibited the LPS-induced pro-inflammatory response in macrophages of mice. Moreover, LA1-induced activation of CD11b significantly inhibited LPS/IFN-γ-induced pro-inflammatory response in macrophages by inhibiting MAPKs and NF-κB signaling pathways in vitro. Furthermore, the mice injected with LA1-treated BMDMs showed fewer pathological lesions than those injected with vehicle-treated BMDMs in endotoxic shock. In addition, we found that activation of TLR4 by LPS could endocytose CD11b and activation of CD11b by LA1 could endocytose TLR4 in vitro and in vivo, subsequently blocking the binding of LPS with TLR4. Based on these findings, we concluded that LA1-induced activation of CD11b negatively regulates LPS-induced pro-inflammatory response in macrophages and subsequently protects mice from endotoxin shock by partially blocking LPS-TLR4 interaction. Our study provides a new insight into the role of CD11b in the pathogenesis of inflammatory diseases.

The initial fall in arterial pressure evoked by endotoxin is mediated by the ventrolateral periaqueductal gray

This study tested the hypothesis that the initial fall in arterial pressure evoked by lipopolysaccharide (LPS) is mediated by the ventrolateral column of the midbrain periaqueductal gray region (vlPAG). To test this hypothesis, the local anaesthetic lidocaine (2%; 0.1 μL, 0.2 μL or 1.0 μL), the delta opioid receptor antagonist naltrindole (2 nmol) or saline was microinjected into the vlPAG of isoflurane-anaesthetized rats bilaterally and LPS (1 mg/kg) or saline was administered intravenously 2 min later. Both lidocaine and naltrindole inhibited LPS-evoked hypotension significantly but did not affect arterial pressure in saline-treated control animals. Neither lidocaine nor naltrindole altered heart rate significantly in either LPS-treated or control animals. Microinjection of lidocaine or naltrindole into the dorsolateral PAG was ineffective. These data indicate that the vlPAG plays an important role in the initiation of endotoxic hypotension and further show that delta opioid receptors in the vlPAG participate in the response.

Altered levels of soluble CD18 may associate immune mechanisms with outcome in sepsis

The pathogenesis of sepsis involves a dual inflammatory response, with a hyperinflammatory phase followed by, or in combination with, a hypoinflammatory phase. The adhesion molecules lymphocyte function-associated antigen (LFA-1) (CD11a/CD18) and macrophage-1 (Mac-1) (CD11b/CD18) support leucocyte adhesion to intercellular adhesion molecules and phagocytosis through complement opsonization, both processes relevant to the immune response during sepsis. Here, we investigate the role of soluble (s)CD18 in sepsis with emphasis on sCD18 as a mechanistic biomarker of immune reactions and outcome of sepsis. sCD18 levels were measured in 15 septic and 15 critically ill non-septic patients. Fifteen healthy volunteers served as controls. CD18 shedding from human mononuclear cells was increased in vitro by several proinflammatory mediators relevant in sepsis. sCD18 inhibited cell adhesion to the complement fragment iC3b, which is a ligand for CD11b/CD18, also known as Mac-1 or complement receptor 3. Serum sCD18 levels in sepsis non-survivors displayed two distinct peaks permitting a partitioning into two groups, namely sCD18 'high' and sCD18 'low', with median levels of sCD18 at 2158 mU/ml [interquartile range (IQR) 2093-2811 mU/ml] and 488 mU/ml (IQR 360-617 mU/ml), respectively, at the day of intensive care unit admission. Serum sCD18 levels partitioned sepsis non-survivors into one group of 'high' sCD18 and low CRP and another group with 'low' sCD18 and high C-reactive protein. Together with the mechanistic data generated in vitro, we suggest the partitioning in sCD18 to reflect a compensatory anti-inflammatory response syndrome and hyperinflammation, respectively, manifested as part of sepsis.

Fusion Peptides CPU1 and CPU2 Inhibit Matrix Metalloproteinases and Protect Mice from Endotoxin Shock Within a Strict Time Window

Endotoxin shock induction in mice is a commonly used animal model to evaluate the protective effect of biologically active reagents. After an lipopolysaccharides (LPS) stimulus, matrix metalloproteinase-8 (MMP-8) and matrix metalloproteinase-9 (MMP-9) are rapidly degranulated and released by neutrophils, aside other enzymes and effector molecules. MMPs cleave extracellular matrix components and cytokines, and such processes contribute to shock syndrome development. CPU1 and CPU2 are two peptide MMP inhibitors with different in vitro IC50 values to several key enzymes, including MMP-8 and MMP-9. In vivo work confirmed that CPU1 and CPU2 protected mice from endotoxin shock after intravenous and intraperitoneal injections. Furthermore, their minimal effective dose after an intravenous injection and the maximum time interval between intraperitoneal peptide injection (150 mg/kg) and intravenous LPS injection were determined. With the use of an indirect competitive ELISA, plasma CPU1 and CPU2 concentrations in different experimental settings were measured. In addition, the acuteness of MMP-9 release in the mouse circulation after an intravenous LPS injection was confirmed with the zymography technique. Our findings reinforce previous work with other inhibitors about a strict time window within which effective MMP inhibition is needed to obtain significant survival rate improvements and also show that, with strict pharmacokinetic monitoring, potent protease inhibitors may in the future become life-savers in shock conditions.

[Protective action figurations for superoxide dismutase - chondroitin sulfate - catalase bienzyme conjugate after its medicative administration in endotoxin shock]

Previously it found that the bienzymatic conjugate superoxide dismutase-chondroitin sulfate, catalase (SOD-CHS-CAT) increased the survival rate of rats with endotoxic shock caused by the administration of lipopolysaccharide (LPS). This effect was observed both in preventive (before LPS) and therapeutic conjugate administration (after the administration of LPS). This study shows that the development of endotoxic shock is accompanied by increased levels of NO in the liver, lungs, kidneys, heart; administration of the SOD-CHS-CAT conjugate insignificantly influenced this parameter. At the same time, the changes in blood urea and creatinine suggest the protective effect of the conjugate on renal function, while diverse changes in biochemical parameters studied complicate the formation of the agreed conclusions on the state of other organs.

Caspase-11: arming the guards against bacterial infection

As a front line of defense against pathogenic microbes, our body employs a primitive, yet highly sophisticated and potent innate immune response pathway collectively referred to as the inflammasome. Innate immune cells, epithelial cells, and many other cell types are capable of detecting infection or tissue injury and mounting a coordinated molecular defense. For example, Gram-negative bacteria are specifically detected via a surveillance mechanism that involves activation of extracellular receptors such as Toll-like receptors (TLRs) followed by intracellular recognition and activation of pathways such as caspase-11 (caspase-4/5 in humans). Importantly, lipopolysaccharide (LPS), the major component of the outer membrane of Gram-negative bacteria, is a strong trigger of these pathways. Extracellular LPS primarily stimulates TLR4, which can serve as a priming signal for expression of inflammasome components. Intracellular LPS can then trigger caspase-11-dependent inflammasome activation in the cytoplasm. Here, we briefly review the burgeoning caspase-11-dependent non-canonical inflammasome field, focusing mainly on the innate sensing of LPS.

ADAM17 controls IL-6 signaling by cleavage of the murine IL-6Rα from the cell surface of leukocytes during inflammatory responses

The cytokine IL-6 is part of a regulatory signaling network that controls immune responses. IL-6 binds either to the membrane-bound IL-6 receptor-α (classic signaling) or to the soluble IL-6 receptor-α (trans-signaling) to initiate signal transduction via gp130 activation. Because classic and trans-signaling of IL-6 fulfill different tasks during immune responses, controlled shedding of the membrane-bound IL-6 receptor-α from the surface of immune cells can be considered a central regulator of IL-6 function. The results from cell culture-based experiments have implicated both a disintegrin and metalloprotease 10 and a disintegrin and metalloprotease 17 in IL-6 receptor-α shedding. However, the nature of the protease mediating IL-6 receptor-α release in vivo is not yet known. We used hypomorphic a disintegrin and metalloprotease 17 mice and conditional a disintegrin and metalloprotease 10 knock-out mice to identify the natural protease of the murine IL-6 receptor-α. Circulating homeostatic soluble IL-6 receptor-α levels are not dependent on a disintegrin and metalloprotease 10 or 17 activity. However, during Listeria monocytogenes infection, IL-6 receptor-α cleavage by the α-secretase a disintegrin and metalloprotease 17 is rapidly induced from the surface of different leukocyte populations. In contrast, CD4-Cre-driven a disintegrin and metalloprotease 10 deletion in T cells did not influence IL-6 receptor-α shedding from these cells after L. monocytogenes infection. A disintegrin and metalloprotease 17 was also required for IL-6 receptor-α ectodomain cleavage and release during endotoxemia. These results demonstrate a novel physiologic role for a disintegrin and metalloprotease 17 in regulating murine IL-6 signals during inflammatory processes.

Salt-inducible kinase 3 deficiency exacerbates lipopolysaccharide-induced endotoxin shock accompanied by increased levels of pro-inflammatory molecules in mice

Macrophages play important roles in the innate immune system during infection and systemic inflammation. When bacterial lipopolysaccharide (LPS) binds to Toll-like receptor 4 on macrophages, several signalling cascades co-operatively up-regulate gene expression of inflammatory molecules. The present study aimed to examine whether salt-inducible kinase [SIK, a member of the AMP-activated protein kinase (AMPK) family] could contribute to the regulation of immune signal not only in cultured macrophages, but also in vivo. LPS up-regulated SIK3 expression in murine RAW264.7 macrophages and exogenously over-expressed SIK3 negatively regulated the expression of inflammatory molecules [interleukin-6 (IL-6), nitric oxide (NO) and IL-12p40] in RAW264.7 macrophages. Conversely, these inflammatory molecule levels were up-regulated in SIK3-deficient thioglycollate-elicited peritoneal macrophages (TEPM), despite no impairment of the classical signalling cascades. Forced expression of SIK3 in SIK3-deficient TEPM suppressed the levels of the above-mentioned inflammatory molecules. LPS injection (10 mg/kg) led to the death of all SIK3-knockout (KO) mice within 48 hr after treatment, whereas only one mouse died in the SIK1-KO (n = 8), SIK2-KO (n = 9) and wild-type (n = 8 or 9) groups. In addition, SIK3-KO bone marrow transplantation increased LPS sensitivity of the recipient wild-type mice, which was accompanied by an increased level of circulating IL-6. These results suggest that SIK3 is a unique negative regulator that suppresses inflammatory molecule gene expression in LPS-stimulated macrophages.

Augmented inducible nitric oxide synthase expression and increased NO production reduce sepsis-induced lung injury and mortality in myeloperoxidase-null mice

The myeloperoxidase (MPO)-hydrogen peroxide-halide system is an efficient oxygen-dependent antimicrobial component of polymorphonuclear leukocyte (PMN)-mediated host defense. However, MPO deficiency results in few clinical consequences indicating the activation of compensatory mechanisms. Here, we determined possible mechanisms protecting the host using MPO(-/-) mice challenged with live gram-negative bacterium Escherichia coli. We observed that MPO(-/-) mice unexpectedly had improved survival compared with wild-type (WT) mice within 5-12 h after intraperitoneal E. coli challenge. Lungs of MPO(-/-) mice also demonstrated lower bacterial colonization and markedly attenuated increases in microvascular permeability and edema formation after E. coli challenge compared with WT. However, PMN sequestration in lungs of both groups was similar. Basal inducible nitric oxide synthase (iNOS) expression was significantly elevated in lungs and PMNs of MPO(-/-) mice, and NO production was increased two- to sixfold compared with WT. Nitrotyrosine levels doubled in lungs of WT mice within 1 h after E. coli challenge but did not change in MPO(-/-) mice. Inhibition of iNOS in MPO(-/-) mice significantly increased lung edema and reduced their survival after E. coli challenge, but iNOS inhibitor had the opposite effect in WT mice. Thus augmented iNOS expression and NO production in MPO(-/-) mice compensate for the lack of HOCl-mediated bacterial killing, and the absence of MPO-derived oxidants mitigates E. coli sepsis-induced lung inflammation and injury.

C1 inhibitor: biologic activities that are independent of protease inhibition

C1 inhibitor therapy improves outcome in several animal models of inflammatory disease. These include sepsis and Gram negative endotoxin shock, vascular leak syndromes, hyperacute transplant rejection, and ischemia-reperfusion injury. Furthermore, some data suggest a beneficial effect in human inflammatory disease. In many inflammatory conditions, complement system activation plays a role in pathogenesis. The contact system also very likely is involved in mediation of damage in inflammatory disease. Therefore, the beneficial effect of C1 inhibitor has been assumed to result from inhibition of one or both of these systems. Over the past several years, several other potential anti-inflammatory effects of C1 inhibitor have been described. These effects do not appear to require protease inhibition and depend on non-covalent interactions with other proteins, cell surfaces or lipids. In the first, C1 inhibitor binds to a variety of extracellular matrix components including type IV collagen, laminin, entactin and fibrinogen. The biologic role of these reactions is unclear, but they may serve to concentrate C1 inhibitor at extravascular inflammatory sites. The second is a non-covalent interaction with C3b that results in inhibition of formation of the alternative pathway C3 convertase, a function analogous to that of factor H. The third is an interaction with E and P selectins on endothelial cells that is mediated by the Lewis(x) tetrasaccharides that are expressed on C1 inhibitor. These interactions result in suppression of leukocyte rolling and transmigration. The fourth interaction is the binding of C1 inhibitor to Gram negative bacterial endotoxin that results in suppression of endotoxin shock by interference with the interaction of endotoxin with its receptor complex on macrophages. Lastly, C1 inhibitor binds directly to Gram negative bacteria, which leads to suppression of the development of sepsis, as demonstrated in the cecal ligation and puncture model. These observations suggest that C1 inhibitor is a multi-faceted anti-inflammatory protein that exerts its effects through a variety of mechanisms including both protease inhibition and several different non-covalent interactions that are unrelated to protease inhibition.

Activation of common antiviral pathways can potentiate inflammatory responses to septic shock

Induction of the antiviral cytokine interferon alpha/beta (IFN-alpha/beta) is common in many viral infections. The impact of ongoing antiviral responses on subsequent bacterial infection is not well understood. In human disease, bacterial superinfection complicating a viral infection can result in significant morbidity and mortality. We injected mice with polyinosinic-polycytidylic (PIC) acid, a TLR3 ligand and known IFN-alpha/beta inducer as well as nuclear factor kappaB (NF-kappaB) activator to simulate very early antiviral pathways. We then challenged mice with an in vivo septic shock model characterized by slowly evolving bacterial infection to simulate bacterial superinfection early during a viral infection. Our data demonstrated robust induction of IFN-alpha in serum within 24 h of PIC injection with IFN-alpha/beta-dependent major histocompatibility antigen class II up-regulation on peritoneal macrophages. PIC pretreatment before septic shock resulted in augmented tumor necrosis factor alpha and interleukins 6 and 10 and heightened lethality compared with septic shock alone. Intact IFN-alpha/beta signaling was necessary for augmentation of the inflammatory response to in vivo septic shock and to both TLR2 and TLR4 agonists in vitro. To assess the NF-kappaB contribution to PIC-modulated inflammatory responses to septic shock, we treated with parthenolide, an NF-kappaB inhibitor before PIC and septic shock. Parthenolide did not inhibit IFN-alpha induction by PIC. Inhibition of NF-kappaB by parthenolide did reduce IFN-alpha-mediated potentiation of the cytokine response and lethality from septic shock. Our data demonstrate that pathways activated early during many viral infections can have a detrimental impact on the outcome of subsequent bacterial infection. These pathways may be critical to understanding the heightened morbidity and mortality from bacterial superinfection after viral infection in human disease.

Increased susceptibility to LPS-induced endotoxin shock in secretory leukoprotease inhibitor (SLPI)-deficient mice

Secretory leukoprotease inhibitor (SLPI) protects tissue against the destructive action of neutrophil elastase at the site of inflammation. Recent studies on new functions of SLPI have demonstrated that SLPI may play a larger role in innate immunity than merely as a protease inhibitor. To clarify the functions of SLPI in bacterial infections, we generated SLPI-deficient mice (SLPI(-/-) mice) and analyzed their response to experimental endotoxin shock induced by lipopolysaccharide (LPS). SLPI(-/-) mice showed a higher mortality from endotoxin shock than did wild type mice. This may be explained in part by our observation that SLPI(-/-) macro-phages show higher interleukin 6 and high-mobility group (HMG)-1 production and nuclear factor kappaB activities after LPS treatment than do SLPI(+/+) macrophages. SLPI also affects B cell function. SLPI(-/-) B cells show more proliferation and IgM production after LPS treatment than SLPI(+/+) B cells. Our results suggest that SLPI attenuates excessive inflammatory responses and thus assures balanced functioning of innate immunity.

Prevention of the expression of inducible nitric oxide synthase by a novel positive inotropic agent, YS 49, in rat vascular smooth muscle and RAW 264.7 macrophages

1 The effects of a novel positive inotropic isoquinoline compound, YS 49, on NO production and iNOS protein expression were investigated in cultured rat aortic vascular smooth muscle cells (RAVSMC) and RAW 264.7 cells exposed to lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). In addition, the effects of YS 49 on vascular hyporeactivity in vitro and ex vivo, and on survival rate (mice) and serum NOx (rat) levels, were also investigated in LPS-treated animals. 2 Pre- or co-treatment of YS 49 with LPS plus IFN-gamma, concentration-dependently reduced NO production in RAVSMC and RAW 264.7 cells (IC50 values, 22 and 30 microM, respectively). Although the inhibitory effect on NO production was reduced when YS 49 was applied 2 and 4 h after cytokine in RAW 264.7 cells, it was still statistically significant (P<0.05). 3 YS 49 reduced iNOS mRNA expression in LPS-treated rat aorta in vitro, an effect which was associated with restoration of contractility to the vasoconstrictor, phenylephrine (PE), and reduction in L-arginine-induced relaxation. 4 Serum NOx levels were significantly (P<0.01) reduced by YS 49 (5 mg kg-1, i.p.) in LPS-treated rats (10 mg kg-1, i.p.). Administration of YS 49 (10 and 20 mg kg-1) 30 min prior to LPS (10 mg kg-1) also significantly (P<0.01) increased the subsequent survival rates in mice. 5 Finally, expression of iNOS protein induced by LPS plus IFN-gamma in RAVSMC and RAW 264.7 cells was suppressed by YS 49, in a concentration-dependent manner. 6 These data strongly suggest that YS 49 suppresses iNOS gene expression induced by LPS and/or cytokines in RAVSMC and RAW 264.7 cells at the transcriptional level. YS 49 could therefore be beneficial in septic shock and other diseases associated with iNOS over-expression.

Decline in the expression of copper/zinc superoxide dismutase in the kidney of rats with endotoxic shock: effects of the superoxide anion radical scavenger, tempol, on organ injury

1. Endotoxaemia causes an enhanced formation of reactive oxygen species (ROS) which contribute to the multiple organ dysfunction syndrome (MODS) in septic shock. Here we investigate (i) the effects of endotoxin on the expression of two isoforms of superoxide dismutase (SOD), namely Cu/Zn-SOD (cytosol) and Mn-SOD (mitochondria) in the rat kidney, and (ii) the effects of the radical scavenger tempol on the MODS caused by lipopolysaccharide (LPS, E. coli, 6 mg kg(-1) i.v.) in the rat. 2. Endotoxaemia resulted in a rapid, but transient, decline in the expression of both mRNA and protein of Cu/Zn-SOD as well as an increase in the expression of the mRNA of Mn-SOD in the kidney. Endotoxaemia for 6 h also caused hypotension, acute renal dysfunction, hepatocellular injury, pancreatic injury and an increase in the plasma levels of nitrite/nitrate. 3. Pretreatment of rats with tempol (100 mg kg(-1) i.v. bolus injection, 15 min prior to LPS followed by an infusion of 30 mg kg(-1) i.v., n=9) did not affect the circulatory failure, but attenuated the renal dysfunction and the hepatocellular injury/dysfunction caused by LPS. Tempol did not affect the rise in nitrite/nitrate caused by endotoxin. 4. These results imply that an enhanced formation of ROS (including superoxide anions) in conjunction with inadequate defences against such ROS contributes to the injury and dysfunction of the kidney and the liver in endotoxic shock.

Effects of inhibitors of the activity of cyclo-oxygenase-2 on the hypotension and multiple organ dysfunction caused by endotoxin: a comparison with dexamethasone

1. Endotoxaemia is associated with the expression of the inducible isoform of cyclo-oxygenase, cyclo-oxygenase-2 (COX-2), and an overproduction of arachidonic acid (AA) metabolites. The role of the AA metabolites generated by COX-2 in the circulatory failure and multiple organ dysfunction caused by endotoxin is unclear. Dexamethasone prevents the expression of COX-2 and exerts beneficial effects in animal models of shock. 2. Here we compare the effects of two inhibitors of COX-2 activity, namely NS-398 (5 mg kg(-1), i.p., n=7) and SC-58635 (3 mg kg(-1), i.p., n=9) with those of dexamethasone (3 mg kg(-1), i.p., n=9) on the circulatory failure and organ dysfunction caused by lipopolysaccharide (LPS, E. coli, 6 mg kg(-1), i.v., n=11) in the rat. 3. Endotoxaemia for 6 h caused hypotension, acute renal dysfunction, hepatocellular injury, pancreatic injury and an increase in the plasma levels of 6-keto-PGF1alpha (indicator of the induction of COX-2) and nitrite/nitrate (indicator of the induction of iNOS). 4. Pretreatment of rats with dexamethasone attenuated the hypotension, the renal dysfunction, the hepatocellular and pancreatic injury and the induction of COX-2 and iNOS caused by LPS. In contrast, inhibition of COX-2 activity with SC-58635 or NS-398 neither attenuated the circulatory failure nor the multiple organ failure caused by endotoxin. 5. Thus, the prevention of the circulatory failure and the multiple organ injury/dysfunction caused by dexamethasone in the rat is not due to inhibition of the activity of COX-2. Our results suggest that an enhanced formation of eicosanoids by COX-2 does not contribute to the development of organ injury and/or dysfunction in rats with endotoxaemia.

Effects of tyrphostins and genistein on the circulatory failure and organ dysfunction caused by endotoxin in the rat: a possible role for protein tyrosine kinase

1 Here we compared the effects of various inhibitors of the activity of protein tyrosine kinase on (i) the expression of the activity of the inducible isoform of nitric oxide (NO) synthase (iNOS) caused by endotoxin (lipopolysaccharide, LPS) in cultured macrophages, (ii) the induction of iNOS and cyclooxygenase 2 (COX-2) protein and activity in rats with endotoxaemia, and (iii) the circulatory failure and organ dysfunction caused by LPS in the anesthetized rat. 2 Activation of murine cultured macrophages with LPS (1 microgram ml-1) resulted, within 24 h, in a significant increase in nitrite (an indicator of the formation of NO) in the cell supernatant. This increase in nitrate was attenuated by the tyrphostins AG126, AG556, AG490 or AG1641 or by genistein in a dose-dependent fashion (IC50: approximately 15 microM). In contrast, tyrphostin A1 (an analogue of tyrphostin AG126) or daidzein (an analogue of genistein) had no effect on the rise in nitrite caused by LPS. 3 Administration of LPS (E. coli, 10 mg kg-1, i.v.) caused hypotension and a reduction of the pressor responses elicited by noradrenaline (NA, 1 microgram kg-1, i.v.). Pretreatment of rats with the tyrphostins AG126, AG490, AG556, AG1641 or A1 attenuated the circulatory failure caused by LPS. Although genistein attenuated the vascular hyporeactivity to NA, it did not affect the hypotension caused by LPS. Daidzein did not affect the circulatory failure caused by LPS. 4 Endotoxaemia for 360 min resulted in rises in the serum levels of (i) urea and creatinine (indicators of renal failure), (ii) alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin and gamma-glutamyl transferase (gamma GT) (indicators of liver injury/dysfunction), lipase (an indicator of pancreatic injury) as well as lactate (an indicator of tissue hypoxia). None of the tyrosine kinase inhibitors tested had a significant effect on the rise i the serum levels of urea, but the tyrphostins AG126, AG556 or A1 significantly attenuated the rises in the serum level of creatinine caused by LPS. In addition, all tyrphostins and genistein attenuated the liver injury/failure, the pancreatic injury, the hypoglycaemia and the lactic acidosis caused by LPS. In contrast, daidzein did not reduce the organ injury/dysfunction or the lactic acidosis caused by LPS. 5 Injection of LPS resulted (within 90 min) in a substantial increase in the serum level of tumor necrosis factor alpha (TNF alpha), which was attenuated by pretreatment of LPS-rats with any of the tyrphostins used. Genistein, but not daidzein, also reduced the rise in the serum levels of TNF alpha caused by LPS. Endotoxaemia for 6 h also resulted in a substantial increase in the expression of iNOS and COX-2 protein and activity in the lung, which was attenuated by pretreatment of LPS-rats with the tyrphostins AG126, AG556 or genistein, but not by daidzein. 6 Thus, tyrphostins (AG126, AG556, AG1641 or A1) and genistein, but not daidzein (inactive analogue of genistein), prevent the (i) circulatory failure, (ii) the multiple organ dysfunction (liver and pancreatic dysfunction/injury lactacidosis, hypoglycaemia), as well as (iii) the induction of iNOS and COX-2 protein and activity in rats with endotoxic shock.

The expression of tumour necrosis factor in the hypothalamus after treatment with lipopolysaccharide

To investigate the effects of tumour necrosis factor (TNF) in the hypothalamus, Wistar rats received an intravenous administration of lipopolysaccharide (LPS) at a dose of 3.0 mg/100 g. Concentrations of TNF-alpha in the cerebral liquor and blood sera rapidly increased at 30 minutes after administration of LPS, rose to the maximum level at 1 hour, and then gradually decreased. Using horse-radish peroxidase as a tracer, a transient increase in paracellular permeability throughout the tight junctions of the ependymal cell layer covering the third ventricle was observed by electron microscopy at 30 minutes and in that of the capillary endothelium at 1 hour after administration, respectively. Following LPS administration, TNF was preferentially localized by immunoelectron microscopy in the tight junctional area of the ependymal cell layer and the capillary. These data indicate that TNF, synthesized in the ependymal cell layer, induces a deterioration in the cerebrospinal fluid-brain barrier and subsequently in the blood-brain barrier. The present study suggests that oedematous changes in the hypothalamic areas determined by ultrastructural and magnetic resonance analyses were mainly due to TNF conveyed from the ependymal cell layer to the hypothalamus after administration of LPS.

Endotoxin induced changes in the pharmacokinetics of warfarin in rabbits

The action of bacterial endotoxin on the pharmacokinetics of warfarin was investigated in rabbits injected with bacterial endotoxin from E. coli. High doses of endotoxin were able to change the kinetics of warfarin in rabbits by changing its volume of distribution. It is not possible to conclude whether the changes in elimination rate of warfarin in rabbits were mediated through changes in liver blood flow or through impairment of the metabolic capacity of the liver cells.