The inhibitory effect of quercetin on IL-6 production by LPS-stimulated neutrophils

Quercetin is a herbal flavonoid derived from various foods of plant origin and plays a role in anti-inflammation. Although a number of researches in the field have been done, the mechanism of anti-inflammatory effect of quercetin should be further darified. In the present study, we investigated the effects of quercetin on IL-6 production by LPS-stimulated neutrophils in human. Neutrophils were were pre-treated with quercetin at the final concentrations of ranging from 0-80 ~M for 30 rain, or not treated, and then incubated in the presence or absence of lipopolysaccharide （LPS） at a final concentration of 100 ng/ml for indicated time. The secretion level of IL-6 in the culture supernatants was assayed by ELISA, the intracellular level of IL-6 was detected by flow cytometry and the expression of IL-6 mRNA was analyzed by RT-PCR. The experiment results showed that neutrophils cultured with medium or quercetin alone did not express IL-6, but LPS （100 ng/ml） induced IL-6 expression of neutrophils. However, after pre-treatment of neutrophils with quercetin （40 ~Vl） for 30 rain, the inducible effects of LPS on the increase of IL-6 secretion, intracellular IL-6 level and IL-6 mRNA expression by neutrophils were abrogated. IL-6 is one of the important pro-inflammatory factors, especially in early phage of inflammation. Thus, our data suggested that quercetin might exert its anti-inflammatory effect through negatively modulating pro-inflammatory factors, such as IL-6. The inhibitory effects of quercetin on IL-6 production by neutrophils may provide a theoretical basis on future therapy of inflammation. Cellular ＆ Molecular Immunology. 2005;2（6）：455-460.     

Inhibition of nitric oxide synthase attenuates lipopolysaccharide-induced fever without reduction of circulating cytokines in guinea-pigs

 It was recently demonstrated that the diffusible messenger molecule nitric oxide (NO) is involved in the febrile response of rats and rabbits to exogenous or endogenous pyrogens. In this study we have investigated the effects of systemic administration of the NO-synthase inhibitor N-nitro-l-arginine-methylester (l-NAME) on abdominal temperature and on lipopolysaccharide- (LPS-) induced fever in guinea-pigs. We further studied the effects of l-NAME on the LPS-induced circulating cytokine network by measurement of tumor necrosis factor α (TNF) and interleukin-6 (IL-6) in blood plasma during the time course of fever. At a dose of 10 mg/kg, intra-arterial injection of l-NAME per se had no influence on the abdominal temperature of guinea-pigs, while administration of 50 mg/kg l-NAME evoked a pronounced fall of body temperature which lasted about 12 h. When injected simultaneously with 10 μg/kg LPS into the arterial circulation, the lower dose of l-NAME that did not decrease abdominal temperature per se caused a significant attenuation of LPS-induced fever due to suppression of the second phase of the biphasic febrile response. The LPS-induced cytokine network remained unimpaired by the treatment with l-NAME. Peak activity of TNF in plasma (measured 60 min after LPS injection) was 20,596±2368 pg/ml in control animals and 18,900±4778 pg/ml in guinea-pigs treated with l-NAME. In addition, circulating levels of IL-6 were not statistically different between both groups of animals 60 min or 180 min after administration of LPS along with l-NAME or vehicle. The results confirm that endogenous NO formation has a role in the generation of LPS-induced fever and demonstrate that the attenuation of fever by inhibition of NO-synthase is independent of the circulating LPS-induced cytokine network. Received: 28 April 1998 / Received after revision: 20 July 1998 / Accepted: 22 July 1998     

创伤性休克与全身性炎症反应

Trauma is the NO.1 cause of death in persons under the age of 45 and the No.3 cause of all deaths.Many trauma patients die of multiple organ failure(MOF),induced by systemic inflammatory re-sponse syndrome(SIRS). This paper reviesw the relations of traumatic shock with systemic inflammation.     

Respiratory syncytial virus infection in immunocompetent and immunocompromised murine

The purpose of this study is to distinguish respiratory syncytial virus ( RSV) infection and immunology between immunocompetent and immunocompromised murine and to explore immune mechanism of RSV infection. At various time points after RSV infection of BALB/c mice and nude mice, pulmonary viral titers were assayed, RSV antigen was tested by direct immune-fluorescent assay and immu nohistochemistry. Pulmonary mRNA expressions of Toll like receptor (TLR)2 and TLR4 were assayed by RT-PCR. CD4 cells and CD8 cells in peripheral blood were examined by flow cytometry and plasma total IgE was assayed by ELISA. Leukocytes in bronchoalveolar lavage fluid (BALF) and pulmonary histology were identified to reflect airway inflammation. It was found that RSV titers of both mice peaked on the 3rd day post infection with a much higher level of viral titer in nude mice than in BALB/c mice and a longer viral duration in nude mice (over 9 days post infection) than in BALB/c mice (6 days post infection). RSV infection induced higher viral antigen expression in nude mice (0.267±0.045) than in BALB/c mice (0.168±0.031). RSV infection enhanced pulmonary TLR4 expression of BALB/c mice (51.96%±11.34%) and nude mice (48.96%±12.35%) compared with each control (34.04%±10.06% and 32.37%±9.87% respectively). CD4 peripheral blood cells increased in RSV infected BALB/c mice (66.51%±2.09%) compared with the control BALB/c mice (51.63%±5.90%), and CD4 cells and CD8 cells were deficient in nude mice. RSV infection increased plasma total IgE in both mice, and BALB/c mice had a larger amount of IgE on the 7th day post infection (9.02 ng/ml±2.90 ng/ml) and on the 14th day post infection (12.76 ng/ml±4.15 ng/ml) than corresponding nude mice (3.72 ng/ml±1.06 ng/ml and 7.62 ng/ml±3.08 ng/ml respectively on the 7th and 14th day post infection). RSV infected nude mice had more severe airway inflammation than infected BALB/c mice. It is concluded that BALB/c mice and nude mice presented similar RSV infectious characteristics. However, infection of nude mice showed higher viral titer with longer duration and more severe airway inflammation, lower level of plasm total IgE and CD4 peripheral blood cells, but the similar pulmonary TLR4 expression with BALB/c mice.     

The molecular mechanism of interaction between sushi peptide and Pseudomonas endotoxin

Septic shock is caused by Gram-negative bacterial infection. Lipopolysaccharide （LPS） is the bioactive molecule present on the outer membrane of the Gram-negative bacteria. It is generally thought that LPS interacts with sensors on the host cell membrane to activate the intracellular signaling pathway resulting in the overproduction of cytokines such as TNF-α This causes inflammation and ultimately, septic shock. Lipid A is the pharmacophore of the LPS molecule. Thus, developing bio-molecules which are capable of binding LPS at high affinity, especially to the lipid A moiety is an efficient way to neutralize the LPS toxicity. Factor C, a serine protease in the horseshoe crab ameobocytes, is sensitive to trace levels of LPS. We have derived Sushi peptides from the LPS-binding domains of Factor C. Our earlier study showed that the Sushi peptides inhibit LPS-induced septic shock in mice. Here, we demonstrate that the molecular interaction between LPS and Sushi 1 peptide is supported by the hydrophobic interaction between the lipid tail of LPS and Sushi 1 peptide. Furthermore, in the presence of LPS, the peptide transitions from a random structure into an α-helical conformation and it disrupts LPS aggregates, hence, neutralizing the LPS toxicity.     

内毒素诱导p38MAPK信号转导作用的研究进展

The diseases caused by endotoxin have seriously affected human health. Previous studies have shown that p38 MAPK pathway is involved in the intracellular signal transduction induced by lipopolysaccharide (LPS), which plays an important role in the activation of inflammation-related cells to release inflammation mediator. Recently there have been some progresses in the isoforms distribution, substrate, molecular mechanism of regulating the release of inflammatory mediators, cellular specific activation and levels of p38 MAPK.     

Schistosoma japonicum infection induces macrophage polarization

The role of macrophages （MФ） as the first line of host defense is well accepted. These cells play a central role in orchestrating crucial functions during schistosomal infection. Thus, understanding the functional diversity of these cells in the process of infection as well as the mechanisms underlying these events is crucial for developing disease control strategies. In this study, we adopted a Mqb polarization recognition system. M1 macrophage was characterized by expressing CD16/32, IL-12 and iNOS. M2 macrophage was characterized by expressing CD206, IL-10 and arg-1. In vivo （mouse peritoneal macrophages of different infection stages were obtained） and in vitro （different S. japonicum antigens were used to stimulate RAW264.7） were characterized by using the above mentioned system. NCA and ACA stimulated RAW264.7 express significantly higher levels of IL-12 while significantly higher levels of IL-10 were detected after soluble egg antigen （SEA） stimulation. The results showed that dramatic changes of antigen in the microenvironment before and after egg production led to macrophage polarization. Furthermore, through TLR blocking experiments, the TLR4 signaling pathway was found to play a role in the process of macrophage polarization toward M1. Our data suggest that macrophage polarization during S. japonicum infection had significant effects on host immune responses to S. japonicum.     

MyD88/PI3-K/NF-κB pathway mediates the antagonism of lipoxin A4 on LPS-induced synthesis of interleukins in endothelial cells

In order to investigate whether lipoxin A4(LXA4) has an antagonistic effect on lipopolysaccharide (LPS)-induced synthesis of interleukin (IL)-1β, IL-6 and IL-8 in rat pulmonary microvascular endothelial cells (PMVEC) , and to explore the molecular mechanisms of signal pathway in LXA4 actions, cultured PMVEC were treated with LPS, with or without preincubation with LXA4. Proteins of IL-1β, IL-6 and IL-8 in supernatant were analyzed by enzyme-linked immunosorbent assay (ELISA) . Expressions of mRNA of IL-1β, IL-6 and IL-8 were determined by RT-PCR. Expressions of phosphorylation of phosphoinositide 3-kinase (PI3-K) and myeloid differentiation factor 88 (MyD88) were analyzed by Western blot. Activities of DNA-binding of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1) were measured by electrophoretic mobility shift assay (EMSA) . The results showed that LPS induced production of IL-1β, IL-6 and IL-8 in rat PMVEC via MyD88/PI3-K/NF-κB and AP-1 pathway-dependent signal transduction. LPS-stimulated expression of PI3-K, activities of NFκB and AP-1, secretion of protein and expression of mRNA of IL-1β, IL-6 and IL-8 but not MyD88 expression in PMVEC were inhibited by LXA4 in a dose-dependent manner. In conclusion, LXA4 inhibits synthesis of IL-1β, IL-6 and IL-8 by down-regulation of PI3-K/NF-κB and AP-1 signal pathway in PMVEC.     

Dendritic cell-derived hepcidin sequesters iron from the microbiota to promote mucosal healing

正Bleeding and altered iron distribution occur in multiple gastrointestinal diseases, but the importance and regulation of these changes remain unclear. We found that hepcidin, the master regulator of systemic iron homeostasis, is required for tissue repair in the mouse intestine after experimental damage. This effect was independent of hepatocyte-derived hepcidin or systemic iron levels. Rather, we identified conventional dendritic cells(cDCs) as a source of hepcidin that is induced by microbial stimulation     

The immune response induced by hepatitis B virus principal antigens

Hepatitis B virus （HBV） infection occurs primarily in hepatocytes in the liver with release of infectious virions and non-infectious empty surface antigen particles into the bloodstream. HBV replication is non-cytopathic. Transient infections run a course of several months, and chronic infections are often life-long. Chronic infections can lead to liver failure with cirrhosis and hepatocellniar carcinoma. It is generally accepted that neutralizing anti-HBs antibodies plays a key role in recovery from HBV infection by containing the spread of infection in the infected host and facilitating the removal and destruction of viral particles. However, the immune response initiated by the T-cell response to viral antigens is also important for viral clearance and disease pathogenesis in HBV infection. The three structural forms of the viral proteins, the HBsAg, the particulate HBcAg, and the nonparticulate HBeAg, may preferentially elicit different Th cell subsets. The different IgG subclass profiles of anti-HBs, anti-HBc, and anti-HBe in different HBV infection status were revealed. Moreover, the different IgG subclass profiles in chronic carriers did not change with different ALT and AST levels and may reflect the difference between stimulating antigens, immune response, and the stages of viral disease and provide the basis for the use of vaccines and prophylactic treatments for individuals at high risk of human HBV infection. This review elucidates the detailed understanding of the immune responses induced during transient and persistent infection, and the development of immunotherapy and immunodiagnosis in patients with HBV infection, and possible means of reducing the liver damage.     

Critical role for peripherally-derived interleukin-10 in mediating the thermoregulatory manifestations of fever and hypothermia in severe forms of lipopolysaccharide-induced inflammation

Although peripherally released interleukin (IL)-10 has a critical regulatory role in limiting fever in mild-to-moderate forms of inflammation, its role in regulating the more complex thermoregulatory manifestations of hypothermia and fever noted during severe inflammation is less clear. Using cytokine antagonism, we therefore investigated the involvement of peripherally released IL-10 in mediating hypothermia, fever and inflammation induced by intraperitoneal (IP) administration of a large dose of lipopolysaccharide (LPS). Male Wistar rats (200–250 g) were anaesthetized and implanted intra-abdominally with temperature-sensitive radiotelemeters. Rats were randomly assigned to receive IL-10 antiserum (IL-10AS) or normal sheep serum IP, 4 h before receiving an IP injection of LPS (10 mg/kg) or phosphate-buffered saline (PBS). Inflammatory responses were measured in plasma and tissue samples (spleen, liver and brain) at 90 min and 6 h after the IP injection of LPS or PBS. Administration of LPS induced an initial period of hypothermia (~90 min) after which fever developed. Pre-treating rats with IL-10AS abolished the LPS-induced increase in plasma IL-10 levels, attenuated the hypothermia and increased the amplitude of the fever. Moreover, IL-10AS pre-treatment augmented the LPS-induced increase in plasma levels of tumor necrosis factor-alpha (90 min and 6 h), IL-1β (90 min), prostaglandin E₂ (90 min) and IL-6 (6 h), in the periphery, but not the hypothalamus, over the duration of hypothermia and fever. Via its action on the synthesis of inflammatory mediators in the spleen and liver, endogenous IL-10 plays a crucial regulatory role in mediating hypothermia and fever during severe aspectic (LPS-induced) systemic inflammation.     

A crucial role for IL-6 in the CNS of rats during fever induced by the injection of live <Emphasis Type="Italic">E</Emphasis>. <Emphasis Type="Italic">coli</Emphasis>

Interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 have been established as important mediators of fever induced by lipopolysaccharide (LPS) from Gram-negative bacteria. Whether these pro-inflammatory cytokines are also important in mediating fever induced by live bacteria remains less certain. We therefore investigated the following: (1) the synthesis of TNF-α, IL-1β, and IL-6 during E. coli-induced fever and (2) the effect of blocking the action of cytokines within the brain on E. coli-induced fever. Body or tail skin temperature (bT or Tsk, respectively) was measured by biotelemetry or telethermometry, every 30 min, during 6 or 24 h. Depending on the number of colony-forming units (CFU) injected i.p., administration of E. coli induced a long-lasting increase in bT of male Wistar rats. The duration of fever did not correlate with the number of CFU found in peritoneal cavity or blood. Because 2.5 × 10⁸ CFU induced a sustained fever without inducing a state of sepsis/severe infection, this dose was used in subsequent experiments. The E. coli-induced increase in bT was preceded by a decrease in Tsk, reflecting a thermoregulatory response. TNF-α, IL-1β, and IL-6 were detected at 3 h in serum of animals injected i.p. with E. coli. In the peritoneal exudates, TNF-α, IL-1β, and IL-6 were detected at 0.5 and 3 h after E. coli administration. Moreover, both IL-1β and IL-6, but not TNF-α, were found in the cerebrospinal fluid (CSF) and hypothalamus of animals injected with E. coli. Although pre-treatment (i.c.v., 2 μl, 15 min before) with anti-IL-6 antibody (anti-IL-6, 5 μg) reduced E. coli-induced fever, pre-treatment with either IL-1 receptor antagonist (IL-1ra, 200 μg) or soluble TNF receptor I (sTNFRI, 500 ng) had no effect on the fever response. In conclusion, replicating E. coli promotes an integrated thermoregulatory response in which the central action of IL-6, but not IL-1 and TNF, appears to be important.     

Sympathetic nervous responses during cytokine-induced fever in conscious rabbits

 Sympathetic responses during fever induced by two representative endogenous pyrogens, interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα), and their effective inducer, lipopolysaccharide (LPS), were investigated in conscious rabbits. Rectal temperature, ear skin temperature as an index for the ear skin sympathetic nerve activity (ESNA), renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were recorded during fever induced by intravenous injection of these pyrogens. IL-1β (100 ng/kg) elicited a fever accompanied by a transient activation of ESNA and long-lasting increases in RSNA, MAP and HR. Subcutaneous indomethacin (20 mg/kg) significantly attenuated all the responses induced by IL-1β. TNFα (10 μg/kg) also elicited fever with increases in ESNA, RSNA and HR, while MAP was not affected. All the TNF-induced responses were totally blocked by indomethacin. LPS at two doses of 500 ng/kg and 1 μg/kg elicited fever and increased ESNA, RSNA and HR. Only the larger dose induced hypotension. The present results show in conscious rabbits exposed to thermoneutral environment that these pyrogens activate sympathetic efferents in regionally differentiated time courses. The present results also suggest that arachidonate metabolites are involved not only in the thermoregulatory vasoconstrictor response in the ear and the body temperature increase but also in simultaneously evoked renal sympathetic and haemodynamic adjustments in fever. Received: 5 June 1996 / Received after revision: 12 November 1996 / Accepted: 27 November 1996     

Participation of interleukin-1 and tumor necrosis factor in the responses of the sympathetic nervous system during lipopolysaccharide-induced fever

The regional sympathetic responses during fevers induced by an exogenous pyrogen, lipopolysaccharide, and by two endogenous pyrogens, interleukin-1 (IL-1) and tumor necrosis factor (TNF-), were compared in urethane-anesthetized rabbits. Rectal temperature (T_re), ear skin temperature (T_ear) as an index for cutaneous sympathetic activity, renal sympathetic nerve activity (RSNA) representing visceral efferents, arterial blood pressure, and heart rate were recorded during fever caused by intravenous injections of each of the three pyrogens. Lipopolysaccharide (1 g/kg i.v.) caused prolonged fever of more than 3 h duration with a tendency towards a biphasic course of temperature, whereas fevers induced by IL-1 (1 g/kg i.v.) and TNF- (10 g/kg i.v.) were monophasic with a maximum between the 45th and 60th min. Each of the three pyrogens typically induced a decrease in T_ear, indicative of cutaneous sympathetic activation, and simultaneous inhibition of RSNA during the first phase of rising T_re. RSNA tended to increase again approximately to its control level when the maximum T_re had been attained after the injection of each pyrogen. When the second rising phase of lipopolysaccharide fever started, T_ear decreased once more, but RSNA remained at its control level. Taken together with the enhancement of IL-1 and TNF production during lipopolysaccharide-induced fever, the present results suggest the participation of these endogenous pyrogens in the responses of the sympathetic nervous system during the early phase of the lipopolysaccharide induced fever.     

Alteration of embryonic AT2-R and inflammatory cytokines gene expression induced by prenatal exposure to lipopolysaccharide affects renal development

Prenatal exposure to LPS(lipopolysaccharide) results in renal damage in offspring rats, but the mechanism is unknown. The present study was to explore the role of angiotensin II and inflammation in the development of renal damage induced by prenatal exposure to LPS. The pregnant rats were randomly divided into two groups, i.e., control group, LPS group. The rats in the two groups were administered intraperitoneally with vehicle or 0.79 mg/kg LPS on 8th, 10th and 12th day during gestation. The mRNA expression of angiotensinogen, renin, AT₁-R, AT₂-R, TNF-α and IL-6 in embryos were assessed. Renal Ang II-positive cells, monocytes/macrophages, lymphocytes, collagen I and TUNEL-positive cells were identified by immunohistochemical staining in newborn and 7-week-old offspring rats. The number of glomeruli and creatinine clearance rate were determined in offspring at 7 weeks of age. The results showed that prenatal LPS decreased AT₂-R mRNA expression but increased TNF-α and IL-6 mRNA expression in embryos. Prenatal LPS decreased renal angiotensin II-positive cells in newborn offspring rats, while these increased in 7-week-old offspring rats. Prenatal LPS decreased glomerular number and creatinine clearance rate but increased renal infiltrating monocytes/macrophages and lymphocytes at 7 weeks of age. Prenatal LPS also increased TUNEL-positive cells and collagen I expressions in newborn rats and 7-week-old offspring rats.ConclusionAlteration of embryonic AT₂-R and inflammatory cytokines gene expression induced by prenatal exposure to lipopolysaccharide affects renal development.     

Febrile response induced by cecal ligation and puncture (CLP) in rats: involvement of prostaglandin E<Subscript>2</Subscript> and cytokines

The purpose of the present study was to better understand the events involved in the febrile response induced by cecal ligation and puncture (CLP), a complex infectious process. To this end, we conducted in vivo experiments in rats examining (1) fever development, (2) bacterial number in the infection focus and in blood, (3) peripheral and hypothalamic synthesis of cytokines, (4) hypothalamic and cerebrospinal fluid (CSF) synthesis of prostaglandin E₂ (PGE₂), (5) the effect of anti-IL-6 antibody on fever, and (6) the effect of celecoxib on fever and hypothalamic synthesis of PGE₂ after CLP induction. We found that CLP promotes fever and animal death depending on the number of punctures. The peak of CLP-induced fever overlapped with the maximal increase in the number of bacteria in the infectious focus and blood, which occurred at 6 and 12 h. The peak of the febrile response also coincided with increased amounts of interleukin (IL)-1β, IL-6 and IL-10 in the peritoneal exudate and serum; IL-6 in the hypothalamus and PGE₂ in the CSF and predominantly in the hypothalamus. Moreover, intracerebroventricularly injected anti-IL-6 antibody reduced the febrile response while celecoxib reduced the fever and PGE₂ amount in the hypothalamus induced by CLP. Tumor necrosis factor (TNF)-α peaked at 3 h at all sites studied. Conversely, IL-10 concentration decreased in the hypothalamus. These findings show that the peak of CLP-induced fever is accompanied by an increase of bacteria in peritoneal fluid (local infection) and blood; local synthesis of pyrogenic (IL-1β, IL-6) and antipyretic (IL-10) cytokines and central production of IL-6 and PGE₂, suggesting that these last are the central mediators of this response.     

Neougonin A Inhibits Lipopolysaccharide-Induced Inflammatory Responses via Downregulation of the NF-kB Signaling Pathway in RAW 264.7 Macrophages

Neougonin A is a prenylated flavonoid isolated from the whole plants of Helminthostachys zeylanica (Ophioglossaceae), which was usually used as traditional Chinese herbal medicine for the treatment of fever and inflammation. In this study, the pharmacological effects and underlying molecular mechanisms of neougonin A on lipopolysaccharide (LPS)-induced inflammatory responses were investigated. We observed that neougonin A reduced the production of inflammatory mediators (TNFα, PGE₂, NO, IL-1β, and IL-6; P?<?0.001) and inflammation-related proteins (iNOS and COX-2) induced by LPS in murine macrophage RAW 264.7 cells. Furthermore, Western blot and immunofluorescence analysis indicated that neougonin A could inhibit the phosphorylation of IkBα and block the translocation of NF-kB/p65 into the nucleus even at 1.25 μM (P?<?0.05), but have no effect on JNK, ERK1/2, and p38MAPK phosphorylation. It was suggested that the anti-inflammatory actions of neougonin A might be due to the downregulation of TNFα, IL-1β, IL-6, NO, and PGE₂ via the suppression of NF-kB signal transduction pathway.     

Afferent nerves are involved in the febrile response to injection of LPS into artificial subcutaneous chambers in guinea pigs

In guinea pigs, fever was induced by injections of 100 or 10 microgram/kg lipopolysaccharide (LPS) into artificial subcutaneous chambers and analysed under the influence of the local anesthetic, ropivacaine (ROPI), which was administered into the chamber at a dose of 10 mg/kg 30 min prior to LPS. In response to injections of 100 microgram/kg LPS into the subcutaneous chambers, fever was not modified by pretreatment with ROPI. High amounts of bioactive tumor necrosis factor (TNF) alpha and interleukin-6 (IL-6) were measured in the lavage of the chambers after administration of LPS. Comparatively low concentrations of both cytokines (0.5-4% of the concentrations in the lavage fluid) were detected in blood plasma simultaneously. In response to injections of 10 microgram/kg LPS into the subcutaneous chambers, fever was significantly reduced by pretreatment with ROPI to about 60% of the febrile response of control animals. Levels of TNF and IL-6 were lower in response to the reduced dose of LPS. TNF in plasma was even below the limit of detection. The suppression of fever by the local anesthetic was not observed when ROPI was subcutaneously injected into the contralateral site of the chamber position so that a systemic effect of ROPI in the reduction of fever can be excluded.The results indicate a participation of afferent neural signals in the manifestation of fever. This effect becomes obvious only if the dose of the applied inflammatory stimulus (LPS) is not high enough to activate a systemic generalised inflammatory response.     

The effect of interleukin 6 deficiency on myocardial signal transduction pathways activation induced by bacterial lipopolysaccharide in young and old mice

PurposeExaggerated release of proinflammatory mediators during sepsis contributes to inadequate vasodilatation and depressed myocardial contractility, which lead to development of shock and circulatory collapse. The aim of the study was to evaluate the effect of IL-6 and aging on activation of intracellular signaling pathways in the myocardium induced by bacterial lipopolysaccharide (LPS) administration.Material/methodsLPS was injected intraperitoneally to male 3- and 24-month old mice with systemic IL-6 gene knock-out (IL-6KO) and the reference strain (WT). LPS was given intraperitoneally in single low (0.1 mg/kg) or high (10 mg/kg) dose, or in two doses (0.1 + 10 mg/kg) with 24-h delay. The expression and phosphorylation of STAT3, ERK1/2, Akt1/2/3 proteins in the left ventricular myocardium was evaluated after 24 h using Western blotting.ResultsLow LPS dose induced higher STAT3 phosphorylation only in old IL-6KO mice, not affecting ERK1/2 and Akt1/2/3 phosphorylation in any group. High LPS dose upregulated STAT3 phosphorylation similarly in all groups, reduced ERK1/2 expression in young WT mice and upregulated Akt1/2/3 expression and phosphorylation in young IL-6KO mice. Pretreatment with low LPS dose attenuated phosphorylation of STAT3 in both old groups and phosphorylation of Akt1/2/3 in young IL-6KO group. Two-dose approach also significantly potentiated ERK1/2 phosphorylation in both old groups.ConclusionsObtained results show that IL-6 deficiency alters the activity of intracellular signaling pathways: JAK/STAT in old and Akt in young LPS-treated mice. This may indicate that lack of IL-6 attenuates Akt-related cytoprotective effect of pretreatment with low LPS dose in young but not in aged animals.