LPS-induced biomarkers in mice: a potential model for identifying insulin sensitizers

The contribution of nutrient overload and associated inflammation to insulin resistance has highlighted several therapeutic targets including c-Jun N-terminal kinase (JNK) and S6 kinase (S6K). To investigate how a lipopolysaccharide (LPS)-mediated inflammatory response may modulate pathways implicated in insulin resistance, we characterized the LPS-induced changes in key biomarkers. Administration of 0.06-4 mg/kg LPS to C57BL/6 mice stimulated increases in plasma levels of TNFalpha, IL-12p40, IL-6 and MCP-1 and in JNK activity as measured by phosphorylated c-Jun in fat. For the first time, we show that LPS induces S6K activity by up to 6.1-fold, as measured by the phosphorylation of S6 ribosomal protein in liver, and increases by up to 1.8-fold, plasma levels of the novel pro-inflammatory cytokine osteopontin which is implicated in the pathogenesis of insulin resistance. These novel findings suggest that LPS administration may form the basis of an acute in vivo pharmacodynamic model for therapies targeting multiple pathways implicated in insulin resistance.     

Granulocyte-macrophage colony-stimulating factor (CSF) and macrophage CSF-dependent macrophage phenotypes display differences in cytokine profiles and transcription factor activities: implications for CSF blockade in inflammation

GM-CSF and M-CSF (CSF-1) can enhance macrophage lineage numbers as well as modulate their differentiation and function. Of recent potential significance for the therapy of inflammatory/autoimmune diseases, their blockade in relevant animal models leads to a reduction in disease activity. What the critical actions are of these CSFs on macrophages during inflammatory reactions are unknown. To address this issue, adherent macrophages (GM-BMM and BMM) were first derived from murine bone marrow precursors by GM-CSF and M-CSF, respectively, and stimulated in vitro with LPS to measure secreted cytokine production, as well as NF-kappaB and AP-1 activities. GM-BMM preferentially produced TNF-alpha, IL-6, IL-12p70, and IL-23 whereas, conversely, BMM generated more IL-10 and CCL2; strikingly the latter population could not produce detectable IL-12p70 and IL-23. Following LPS stimulation, GM-BMM displayed rapid IkappaBalpha degradation, RelA nuclear translocation, and NF-kappaB DNA binding relative to BMM, as well as a faster and enhanced AP-1 activation. Each macrophage population was also pretreated with the other CSF before LPS stimulation and found to adopt the phenotype of the other population to some extent as judged by cytokine production and NF-kappaB activity. Thus, GM-CSF and M-CSF demonstrate, at the level of macrophage cytokine production, different and even competing responses with implications for their respective roles in inflammation, including a possible dampening or suppressive role for M-CSF in certain circumstances.     

Up-regulation of IL-18BP,but not IL-18 mRNA in rat liver by LPS

Interleukin (IL)-18 is a pro-inflammatory cytokine that plays a critical role in inflammation leading to liver damage, through promotion of Fas-mediated apoptosis. Inhibition of IL-18 activity protects against LPS-induced lethality in mice and against liver damage induced by LPS after sensitisation of mice with Proprionibacterium acnes. A specific, potent, endogenous inhibitor of IL-18 (IL-18BP) has been identified in mice and humans, and IL-18BP mRNA is expressed constitutively in liver. The objectives of this study were to compare changes in IL-1beta and IL-18 mRNA expression in the liver of rats in response to peripheral injection of LPS, using real-time PCR, and also to investigate whether IL-18BP mRNA expression is affected by this treatment. LPS rapidly up-regulated IL-1beta mRNA expression, but IL-18 mRNA expression was unaffected by LPS treatment. Unlike IL-18, IL-18BP mRNA was up-regulated dramatically by approximately 12-fold above nai;ve levels, peaking 3 h after LPS injection. This ability of LPS to up-regulate expression of the endogenous IL-18 inhibitor may indicate a mechanism by which the inflammatory response to LPS is regulated.     

C-reactive protein mediates protection from lipopolysaccharide through interactions with Fc gamma R

C-reactive protein (CRP) is a component of the acute phase response to infection, inflammation, and trauma. A major activity of acute phase proteins is to limit the inflammatory response. It has been demonstrated that CRP protects mice from lethal doses of LPS. In the mouse, CRP binds to the regulatory receptor, FcgammaRIIb, and to the gamma-chain-associated receptor, FcgammaRI. The goal ofthis study was to determine whether FcgammaRs are necessary for the protective effect of CRP. The ability of CRP to protect mice from a lethal dose of LPS was confirmed using injections of 500 and 250 micro g of CRP at 0 and 12 h. CRP treatment of FcgammaRIIb-deficient mice increased mortality after LPS challenge and increased serum levels of TNF and IL-12 in response to LPS. CRP did not protect FcR gamma-chain-deficient mice from LPS-induced mortality. Treatment of normal mice, but not gamma-chain-deficient mice, with CRP increased IL-10 levels following LPS injection. In vitro, in the presence of LPS, CRP enhanced IL-10 synthesis and inhibited IL-12 synthesis by bone marrow macrophages from normal, but not gamma-chain-deficient mice. The protective effect of CRP appears to be mediated by binding to FcgammaRI and FcgammaRII resulting in enhanced secretion of the anti-inflammatory cytokine IL-10 and the down-regulation of IL-12. These results suggest that CRP can alter the cytokine profile of mouse macrophages by acting through FcgammaR leading to a down-regulation of the inflammatory response.     

Ethyl acetate extracts of alfalfa (Medicago sativa L.) sprouts inhibit lipopolysaccharide-induced inflammation in vitro and in vivo

This study aimed to investigate if food components that exert anti-inflammatory effects may be used for inflammatory disorders by examining alfalfa sprout ethyl acetate extract (ASEA). The cytokine profile and life span of BALB/c mice with acute inflammation after intra-peritoneal (ip) injection of 15 mg/kg BW lipopolysaccharide (LPS) were determined. The results showed that the life span of LPS-induced inflammatory mice were negatively correlated with serum levels of TNF-α, IL-6, and IL-1β at 9 hr after LPS-injection, which indicated that suppressing these cytokines in the late phase of inflammation may be beneficial for survival. The in vitro experiment then showed that ASEA significantly reduced IL-6 and IL-1β production and the NF-κB trans-activation activity of mitogen-stimulated RAW264.7 cells. To further evaluate the anti-inflammatory effects of ASEA in vivo, BALB/c mice were tube-fed with 25 mg ASEA/kg BW/day in 50 μl sunflower oil, while the control and PDTC (pyrrolidine dithiocarbamate, an anti-inflammatory agent) groups were tube-fed with 50 μl sunflower oil/day only. After one week of tube-feeding, the PDTC group was injected with 50 mg/kg BW PDTC and one hour later, all of the mice were injected with 15 mg/kg BW LPS. The results showed that the ASEA and PDTC groups had significantly lower serum TNF-α, IL-6, and IL-1β levels at 9 hr after LPS challenge, and significantly higher survival rates than the control group. This study suggests that ASEA supplementation can suppress the production of pro-inflammatory cytokines and alleviate acute inflammatory hazards.     

Interleukin-35 Inhibits Endothelial Cell Activation by Suppressing MAPK-AP-1 Pathway

Vascular response is an essential pathological mechanism underlying various inflammatory diseases. This study determines whether IL-35, a novel responsive anti-inflammatory cytokine, inhibits vascular response in acute inflammation. Using a mouse model of LPS-induced acute inflammation and plasma samples from sepsis patients, we found that IL-35 was induced in the plasma of mice after LPS injection as well as in the plasma of sepsis patients. In addition, IL-35 decreased LPS-induced proinflammatory cytokines and chemokines in the plasma of mice. Furthermore, IL-35 inhibited leukocyte adhesion to the endothelium in the vessels of lung and cremaster muscle and decreased the numbers of inflammatory cells in bronchoalveolar lavage fluid. Mechanistically, IL-35 inhibited the LPS-induced up-regulation of endothelial cell (EC) adhesion molecule VCAM-1 through IL-35 receptors gp130 and IL-12Rβ2 via inhibition of the MAPK-activator protein-1 (AP-1) signaling pathway. We also found that IL-27, which shares the EBI3 subunit with IL-35, promoted LPS-induced VCAM-1 in human aortic ECs and that EBI3-deficient mice had similar vascular response to LPS when compared with that of WT mice. These results demonstrated for the first time that inflammation-induced IL-35 inhibits LPS-induced EC activation by suppressing MAPK-AP1-mediated VCAM-1 expression and attenuates LPS-induced secretion of proinflammatory cytokines/chemokines. Our results provide insight into the control of vascular inflammation by IL-35 and suggest that IL-35 is an attractive novel therapeutic reagent for sepsis and cardiovascular diseases.     

Changes of hepatic lactoferrin gene expression in two mouse models of the acute phase reaction

Lactoferrin (Ltf), an iron binding glycoprotein, is a pleiotropic molecule whose serum concentration increases under acute phase conditions. The physiological roles of this protein have been well elucidated, but the source and serum regulation of Ltf gene expression have not been investigated in detail as part of the acute phase reaction (APR). In the current work, the changes in hepatic Ltf-gene-expression during turpentine oil- (TO-) or LPS-induced APR were investigated. Ltf was upregulated at both the mRNA and protein levels in the liver of TO- and LPS-treated wild type (WT) mice. The pattern of induction however was different in both animal models indicating distinctive signalling patterns resulting in an acute phase reaction. Cytokines are the core regulators of APR. Among the major cytokines, IL-6 is an important signalling molecule, which also regulates iron homeostasis in response to an inflammatory situation. In this study, the administration of IL-6 induced Ltf gene expression in the liver of WT mice, in murine hepatocytes and in hepa 1-6 cells. Ltf-gene-expression was upregulated also in the liver of TO- and LPS-treated IL-6 knockout (KO) mice. The increase in serum Ltf after LPS injection was greater than after TO-injection both in WT and IL-6-KO mice. To evaluate the contribution of other acute phase cytokines in the regulation of Ltf-gene-expression in the liver, both in vitro and in vivo studies with IL-1β, TNF-α, or IFN-γ were performed. The results demonstrate that TNF-α and IFN-γ also upregulated Ltf-gene-expression, while IL-1β has no role in the regulation of Ltf-gene-expression.     

Il-10 is a central regulator of cyclooxygenase-2 expression and prostaglandin production

IL-10 is a potent anti-inflammatory and immune regulatory cytokine. IL-10(-/-) mice produce exaggerated amounts of inflammatory cytokines when stimulated with LPS, indicating that endogenous IL-10 is a central regulator of inflammatory cytokine production in vivo. PGs are lipid mediators that are also produced in large amounts during the inflammatory response. To study the role of IL-10 in the regulation of PG production during the acute inflammatory response, we evaluated LPS-induced cyclooxygenase (COX) expression and PG production in wild-type (wt) and IL-10(-/-) mice. LPS-induced PGE(2) production from IL-10(-/-) spleen cells was 5.6-fold greater than that from wt spleen cells. LPS stimulation resulted in the induction of COX-2 mRNA and protein in both wt and IL-10(-/-) spleen cells; however, the magnitude of increase in COX-2 mRNA was 5.5-fold greater in IL-10(-/-) mice as compared with wt mice. COX-1 protein levels were not affected by LPS stimulation in either wt or IL-10(-/-) mice. Neutralization of IFN-gamma, TNF-alpha, or IL-12 markedly decreased the induction of COX-2 in IL-10(-/-) spleen cells, suggesting that increased inflammatory cytokine production mediates much of the COX-2 induction in IL-10(-/-) mice. Treatment of IL-10(-/-) mice with low doses of LPS resulted in a marked induction of COX-2 mRNA in the spleen, whereas wt mice had minimal expression of COX-2 mRNA. These findings indicate that, in addition to IL-10's central role in the regulation of inflammatory cytokines, endogenous IL-10 is an important regulator of PG production in the response to LPS.     

TRAIL administration down-modulated the acute systemic inflammatory response induced in a mouse model by muramyldipeptide or lipopolysaccharide

The potent inducer of apoptosis TRAIL/Apo2 ligand is now under considerations in clinical trials for the treatment of different types of cancer. Since the natural history of cancer is often characterized by microbial infections, we have investigated the effect of recombinant human TRAIL in a mouse model of systemic acute inflammation of microbial origin represented by BALB/c mice treated with either bacterial muramyldipeptide (MDP) or lipopolysaccharide (LPS). When administered intraperitoneally (i.p.), these inflammatory bacterial compounds triggered a severe systemic inflammatory response within 2h, represented by body temperature elevation, increase of circulating serum amyloid-A (SAA) and of the number of leukocytes in the peritoneal cavity. Moreover, both MDP and LPS induced a significant elevation of the circulating levels of several inflammatory cytokines and chemokines. Noteworthy, pre-treatment with recombinant human TRAIL 48 and 72h before administration of either MDP or LPS, significantly counteracted all acute inflammatory responses, including the elevation of key pro-inflammatory cytokines/chemokines such as IL-1α, IL-6, G-CSF, MCP-1. These data demonstrate for the first time that TRAIL has a potent anti-inflammatory activity, which might be beneficial for the anti-tumoral activity of TRAIL.     

Pre-Weaning Growth Hormone Treatment Ameliorates Bone Marrow Macrophage Inflammation in Adult Male Rat Offspring following Maternal Undernutrition

Maternal undernutrition (UN) is associated with the development of obesity and metabolic complications in adult offspring. While the role of inflammation in obesity and related comorbidities has been well established, there is little evidence regarding the effects of maternal UN-induced programming on immune function in male adult offspring. This study examines the effects growth hormone (GH), which is known to induce anti-inflammatory effects, on maternal UN-induced bone marrow macrophage (BMM) function in adult male offspring. Sprague-Dawley rats were assigned to chow (C) or UN (50% ad libitum; UN) diet throughout gestation. Male C and UN pups received saline (CS/UNS) or GH (2.5 µg/g/d; CGH/UNGH) from day 3–21. Bone marrow hematopoietic cells were differentiated to a macrophage phenotype in the presence of M-CSF (50 ng/ml). Differentiated bone marrow macrophages (BMM) were stimulated with LPS (100 ng/ml) for 6 h. UNS-derived BMM had significantly increased secretion and expression of IL-1β and IL-6 following LPS stimulation. This was accompanied by increased expression of IL-1R1, IL-6R and TLR4. Pre-weaning GH treatment reversed this pro-inflammatory phenotype. Furthermore UNGH displayed increased expression of markers of alternative (M2) macrophage activation, mannose receptor and PPARγ. This study demonstrates that fetal UN exposure primes hematopoietic immune cells to a more potent pro-inflammatory phenotype with heightened cytokine secretion and receptor expression. Furthermore these cells are pre-disposed to pro-inflammatory M1 macrophage phenotype which has wide-reaching and important effects in terms of obesity and metabolic disease.     

Acrolein inhalation suppresses lipopolysaccharide-induced inflammatory cytokine production but does not affect acute airways neutrophilia

Acrolein is a reactive unsaturated aldehyde that is produced during endogenous oxidative processes and is a major bioactive component of environmental pollutants such as cigarette smoke. Because in vitro studies demonstrate that acrolein can inhibit neutrophil apoptosis, we evaluated the effects of in vivo acrolein exposure on acute lung inflammation induced by LPS. Male C57BL/6J mice received 300 microg/kg intratracheal LPS and were exposed to acrolein (5 parts per million, 6 h/day), either before or after LPS challenge. Exposure to acrolein either before or after LPS challenge did not significantly affect the overall extent of LPS-induced lung inflammation, or the duration of the inflammatory response, as observed from recovered lung lavage leukocytes and histology. However, exposure to acrolein after LPS instillation markedly diminished the LPS-induced production of several inflammatory cytokines, specifically TNF-alpha, IL-12, and the Th1 cytokine IFN-gamma, which was associated with reduction in NF-kappaB activation. Our data demonstrate that acrolein exposure suppresses LPS-induced Th1 cytokine responses without affecting acute neutrophilia. Disruption of cytokine signaling by acrolein may represent a mechanism by which smoking contributes to chronic disease in chronic obstructive pulmonary disease and asthma.     

Selective macrophage suppression during sepsis

Polymicrobial sepsis induces suppression of macrophage function as determined by a reduction of pro-inflammatory cytokine production upon re-exposure to lipopolysaccharide (LPS) in vitro. We examined whether macrophages were refractory to only LPS challenge or if they were immunoparalyzed and unable to respond to other stimuli such as lipoteichoic acid (LTA) or zymosan (ZYM). This study evaluated the capacity of peritoneal macrophages to produce pro-inflammatory and anti-inflammatory cytokines as well as chemokines following mild or severe sepsis induced by cecal ligation and puncture (CLP). Peritoneal macrophages were isolated 29 h after CLP and challenged with different stimuli. LPS was a more potent stimulus for cytokine induction than LTA or ZYM in both mild and severe sepsis. In mild sepsis, the macrophage cytokine response to LPS was selective and less refractory than in severe sepsis. While production of IL-6 and KC was reduced, secretion of TNF-alpha and MIP-1alpha was enhanced in those cells isolated from mice with mild sepsis. Production of IL-10 and the IL-1 receptor antagonist , MIP-2, and MCP-1 in response to LPS stimulation was equivalent to the amount produced by naive macrophages. Our results indicate that macrophages are not immunoparalyzed during sepsis and may still be induced to secrete some inflammatory mediators.     

GCN2-Dependent Metabolic Stress Is Essential for Endotoxemic Cytokine Induction and Pathology

Activated inflammatory macrophages can express indoleamine 2,3-dioxygenase (IDO) and thus actively deplete their own tryptophan supply; however, it is not clear how amino acid depletion influences macrophage behavior in inflammatory environments. In this report, we demonstrate that the stress response kinase GCN2 promotes macrophage inflammation and mortality in a mouse model of septicemia. In vitro, enzymatic amino acid consumption enhanced sensitivity of macrophages to the Toll-like receptor 4 (TLR4) ligand lipopolysaccharide (LPS) with significantly increased interleukin 6 (IL-6) production. Tryptophan withdrawal induced the stress response proteins ATF4 and CHOP/GADD153; however, LPS stimulation rapidly enhanced expression of both proteins. Moreover, LPS-driven cytokine production under amino acid-deficient conditions was dependent on GCN2, as GCN2 knockout (GCN2KO) macrophages had a significant reduction of cytokine gene expression after LPS stimulation. To test the in vivo relevance of these findings, monocytic-lineage-specific GCN2KO mice were challenged with a lethal dose of LPS intraperitoneally (i.p.). The GCN2KO mice showed reduced inflammatory responses, with decreased IL-6 and IL-12 expression correlating with significant reduction in animal mortality. Thus, the data show that amino acid depletion stress signals (via GCN2) synergize with proinflammatory signals to potently increase innate immune responsiveness.     

Expression of IL-1 beta and IL-8 by human gingival epithelial cells in response to Actinobacillus actinomycetemcomitans

The interaction between epithelial cells and microorganisms is the most important step in bacterial infections. Epithelial cells in response to exposure to pathogenic bacteria produce cytokines that initiate inflammation. However, little is known about the cytokine response of gingival epithelial cells to periodontopathogenic bacteria. Actinobacillus actinomycetemcomitans is thought to play a significant role in the initiation of periodontitis because of its bacteriological characteristics. In the present study, we investigated the cytokine induction by human gingival epithelial cells (HGEC) following exposure to A. actinomycetemcomitans in comparison with human gingival fibroblasts (HGF) in culture. Northern blot analysis showed that mRNAs of interleukin 1beta (IL-1beta) and IL-8, but not IL-6, in HGEC were induced in response to A. actinomycetemcomitans. Secretion of IL-8 by HGEC was also increased following A. actinomycetemcomitans challenge, whereas production of IL-1beta could not be detected. The levels of IL-8 and its mRNA were increased depending on the concentration of A. actinomycetemcomitans. The co-culture with HGF and A. actinomycetemcomitans resulted in an increase in the levels of IL-6 and IL-8 mRNA in HGF. However, HGF exposed to A. actinomycetemcomitans, showed no expression of IL-1beta mRNA. These findings demonstrated that HGEC and HGF stimulated with A. actinomycetemcomitans have different profiles in cytokine mRNA expression. Furthermore, A. actinomycetemcomitans may play an important role in amplifying the local immune response and in initiating inflammatory reaction through release of IL-8 from gingival epithelial cells.     

Vitamin D inhibits monocyte/macrophage proinflammatory cytokine production by targeting MAPK phosphatase-1

It is estimated that 1 billion people around the world are vitamin D deficient. Vitamin D deficiency has been linked to various inflammatory diseases. However, the mechanism by which vitamin D reduces inflammation remains poorly understood. In this study, we investigated the inhibitory effects of physiologic levels of vitamin D on LPS-stimulated inflammatory response in human blood monocytes and explored potential mechanisms of vitamin D action. We observed that two forms of the vitamin D, 1,25(OH)(2)D(3), and 25(OH)D(3), dose dependently inhibited LPS-induced p38 phosphorylation at physiologic concentrations, IL-6 and TNF-α production by human monocytes. Upon vitamin D treatment, the expression of MAPK phosphatase-1 (MKP-1) was significantly upregulated in human monocytes and murine bone marrow-derived macrophages (BMM). Increased binding of the vitamin D receptor and increased histone H4 acetylation at the identified vitamin D response element of the murine and human MKP-1 promoters were demonstrated. Moreover, in BMM from MKP1(-/-) mice, the inhibition of LPS-induced p38 phosphorylation by vitamin D was completely abolished. Vitamin D inhibition of LPS-induced IL-6 and TNF-α production by BMM from MKP-1(-/-) mice was significantly reduced as compared with wild-type mice. In conclusion, this study identified the upregulation of MKP-1 by vitamin D as a novel pathway by which vitamin D inhibits LPS-induced p38 activation and cytokine production in monocytes/macrophages.     

Glucocorticoids as cytokine inhibitors: role in neuroendocrine control and therapy of inflammatory diseases

Glucocorticoids are potent inhibitors of inflammation and endotoxic shock. This probably occurs through an inhibition of the synthesis of pro-inflammatory cytokines as well as of many of their toxic activities. Therefore, endogenous glucocorticoids (GC) might represent a major mechanism in the control of cytokine mediated pathologies. GC inhibit the synthesis of cytokines in various experimental models. Adrenalectomy or GC antagonists potentiate TNF, IL-1 and IL-6 production in LPS treated mice. GC inhibit the formation of arachidonic acid metabolites and the induction of NO synthase. They also inhibit various activities of cytokines including toxicity, haemodynamic shock and fever. Adrenalectomy sensitizes to the toxic effects of LPS, TNF and IL-1. On the other hand, GC potentiate the synthesis of several cytokine induced APP by the liver. Since many of these proteins have anti-toxic activities (antioxidant, antiprotease etc.) or bind cytokines, this might well represent a GC mediated protective feedback mechanism involving the liver. Not only do GC inhibit cytokines, but in vivo LPS and various cytokines (TNF, IL-1, IL-6) increase blood GC levels through a central mechanism involving the activation of the HPA. Thus, this neuroendocrine response to cytokines constitutes an important immunoregulatory feedback involving the brain.     

Effects of vagus nerve stimulation and vagotomy on systemic and pulmonary inflammation in a two-hit model in rats

Pulmonary inflammation contributes to ventilator-induced lung injury. Sepsis-induced pulmonary inflammation (first hit) may be potentiated by mechanical ventilation (MV, second hit). Electrical stimulation of the vagus nerve has been shown to attenuate inflammation in various animal models through the cholinergic anti-inflammatory pathway. We determined the effects of vagotomy (VGX) and vagus nerve stimulation (VNS) on systemic and pulmonary inflammation in a two-hit model. Male Sprague-Dawley rats were i.v. administered lipopolysaccharide (LPS) and subsequently underwent VGX, VNS or a sham operation. 1 hour following LPS, MV with low (8 mL/kg) or moderate (15 mL/kg) tidal volumes was initiated, or animals were left breathing spontaneously (SP). After 4 hours of MV or SP, rats were sacrificed. Cytokine and blood gas analysis was performed. MV with 15, but not 8 mL/kg, potentiated the LPS-induced pulmonary pro-inflammatory cytokine response (TNF-α, IL-6, KC: p<0.05 compared to LPS-SP), but did not affect systemic inflammation or impair oxygenation. VGX enhanced the LPS-induced pulmonary, but not systemic pro-inflammatory cytokine response in spontaneously breathing, but not in MV animals (TNF-α, IL-6, KC: p<0.05 compared to SHAM), and resulted in decreased pO(2) (p<0.05 compared to sham-operated animals). VNS did not affect any of the studied parameters in both SP and MV animals. In conclusion, MV with moderate tidal volumes potentiates the pulmonary inflammatory response elicited by systemic LPS administration. No beneficial effects of vagus nerve stimulation performed following LPS administration were found. These results questions the clinical applicability of stimulation of the cholinergic anti-inflammatory pathway in systemically inflamed patients admitted to the ICU where MV is initiated.     

Lipopolysaccharide-induced liver apoptosis is increased in interleukin-10 knockout mice

Although IL-10 down-regulates pro-inflammatory cytokine secretion by hepatic Kupffer cells, the mechanisms underlying its hepatoprotective effects are not fully clear. This study tested the hypothesis that IL-10 protects the liver against pro-inflammatory cytokines by counteracting their pro-apoptotic effects. Wild type and IL-10 knockout mice were treated with bacterial lipopolysaccharide and sacrificed 1, 4, 8, and 12 h later. Plasma ALT activity was measured as a marker of liver injury. Liver pathology and TUNEL response were assessed by histology. Plasma levels and whole liver mRNA levels were measured for TNF-alpha, IL-1 beta, TGF-beta1, IL-10, and their respective receptors. Hepatic mRNA levels were measured for several pro-apoptotic adaptors/regulators, including FasL, Fas receptor, FADD, TRADD, Bad, Bak, Bax, and Bcl-X(S), and anti-apoptotic regulators, including Bcl-w, Bcl-X(L), Bcl-2, and Bfl-1. Caspase-3 activity in the liver was determined as well as immunohistochemistry for IL-1RII, TGF-betaRII and Fas receptor. At all time points the livers from IL-10 knockout mice displayed a significantly increased number of apoptotic nuclei compared to wild type mice. Changes in plasma cytokine levels and their liver mRNA levels were consistent with suppression by IL-10 of pro-inflammatory cytokine secretion. In addition, pro-inflammatory cytokine receptor mRNA levels (TNF-alpha, TGF-beta, and IL-1 beta) were markedly up-regulated by LPS at all time points in IL-10 knockout mice as compared to wild type mice. Expression of the pro-inflammatory cytokine receptor IL-1RII was similarly increased as shown by immunostaining. The mRNA levels of a typical pro-apoptotic cytokine, TRAIL, were increased and LPS also up-regulated the mRNA expression of other apoptotic factors to a larger extent in IL-10 knockout mice than in their wild type counterparts, suggestive of an IL-10 anti-apoptotic effect. In the livers of knockout mice, markedly increased caspase-3 activity was already evident at the 1-h time point following LPS administration, while in the wild type animals this increase was delayed. Immunostaining also indicated that LPS increased hepatic expression of the pro-apoptotic receptors Fas and TGF-betaRII in IL-10 knockout mice. The data presented in this study show that: (i) IL-10 modulates not only the secretion of pro-inflammatory cytokines, but also the receptors of these cytokines, and ii) IL-10 protects the liver against LPS-induced injury at least in part by counteracting pro-inflammatory cytokine-induced liver apoptosis.     

A tetrahydrophthalazine derivative 'sodium nucleinate" exerts a potent suppressive effect upon LPS-stimulated mononuclear cells in vitro and in vivo

We described the use of a new chemical substance Sodium nucleinate (SN) as an immunomodulatory substance exhibiting antiinflammatory properties. Sodium nucleinate (SN) registrated in Russian Federation as Tamerit, is 2-amino-1,2,3,4-tetrahydrophthalazine-1,4-dione sodium salt dihydrate, derivative of well known chemical substance luminol. To comprehend the mechanisms of SN immunomodulatory activity, we examined the SN modulation of the innate inflammatory cytokine response of human PBMC stimulated with LPS in vitro. Furthermore, we studied the immunomodulatory effects of SN in mice challenged with E. coli LPS in vivo to investigate a possible novel approach to therapy of excessive inflammation that interfere with the response to endotoxin and inflammatory mediators. Our results demonstrated that SN is an efficient inhibitor of sepsis development in mice model of LPS-induced sepsis. The changes induced by SN include decreased mice plasma inflammatory cytokine production. Simmilary we demonstrated a decreased TNF-alpha, IFN-gamma and IL-6 response in human LPS-stimulated PBMNCs. SN was therefore shown to be a promising inhibitor of multiple inflammatory cytokine secretion.     

Inflammatory cytokine production in interferon-gamma-primed mice, challenged with lipopolysaccharide. Inhibition by SK&F 86002 and interleukin-1 beta-converting enzyme inhibitor

Mice challenged with lipopolysaccharide (LPS) produce variable serum levels of pro-inflammatory cytokines, and particularly low levels of interleukin-1 beta (IL-1 beta). Interferon-gamma (IFN-gamma) has been shown to be an important mediator of bacteria-induced hypersensitivity to LPS in mice. In the present study, we show that mice pretreated with IFN-gamma exhibit an enhanced capacity to produce serum IL-1 beta, IL-1 alpha, tumour necrosis factor (TNF-alpha) as well as IL-6 in response to LPS. Priming with intraperitoneal (i.p.) injection of 15 mg rat recombinant IFN-gamma, 18 hours prior to the i.p. LPS (300 mg) challenge resulted in a 4-fold increase in the LPS-stimulated release of IL-1 beta and a 2- to 7-fold increase in the release of IL-1 alpha, TNF-alpha, as well as IL-6 into the serum. LPS induced a concentration-dependent increase in the release of IL-1 beta in isolated peritoneal macrophages from IFN-gamma-primed mice whereas macrophages from unprimed mice released minute amounts of IL-1 beta. In addition, nigericin markedly enhanced the release of IL-1 beta in unprimed mice but not in macrophages from IFN-gamma primed mice. The cytokine synthesis inhibitor SK&F 86002, administered per os (100 mg/kg), 1 hour prior to LPS challenge, strongly inhibited the rise in serum levels of the four cytokines. Furthermore, treatment with the IL-1 beta converting enzyme (ICE) specific reversible inhibitor YVAD-CHO resulted in a sharp dose- and time-dependent inhibition of IL-1 beta secretion in the serum, whereas the other cytokines were not affected. In conclusion, IFN-gamma priming strongly potentiates the release of proinflammatory cytokines in the serum of mice as compared to LPS stimulation alone, and provides therefore a useful way to test the in vivo potency and selectivity of cytokine synthesis inhibitors.