• BMB Reports
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• v.43 no.9
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• pp.629-634
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• 2010

Endotoxin including lipopolysaccharide (LPS) confers organ tolerance against subsequent challenge by ischemia and reperfusion (I/R) insult. The mechanisms underlying this powerful adaptive defense remain to be defined. Therefore, in this study we attempted to determine whether nitric oxide (NO) and its associated enzymes, inducible NOS (iNOS) and endothelial NOS (eNOS, a constitutive NOS), are associated with LPS-induced renal tolerance against I/R injury, using iNOS (iNOS knock-out) or eNOS (eNOS knock-out) gene-deleted mice. A systemic low dose of LPS pretreatment protected kidney against I/R injury. LPS treatment increased the activity and expression of iNOS, but not eNOS, in kidney tissue. LPS pretreatment in iNOS, but not eNOS, knock-out mice did not protect kidney against I/R injury. In conclusion, the kidney tolerance to I/R injury conferred by pretreatment with LPS is mediated by increased expression and activation of iNOS.

• Journal of Life Science
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• v.18 no.11
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• pp.1471-1478
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• 2008

In this study, nitric oxide (NO) production in a macrophage-lymphocyte co-culture system was used to assess the cytokine producing capability of cells during endotoxin tolerance in mice. Incubation of peritoneal macrophages with interferon-$\tau$ (IFN-$\tau$) in the presence of lipopolysaccharide (LPS) augmented NO synthesis. Exogenous tumor necrosis factor-$\alpha$(TNF-$\alpha$) could also replace LPS for the stimulation of NO production. Macrophages co-cultured with splenic lymphocytes showed augmented NO synthesis by LPS alone. However, pretreatment of mice with 2.5 mg/kg LPS completely prevented the lethality and the increase of blood TNF-$\alpha$ and IFN-$\tau$ after the second challenge with a lethal dose of LPS. In addition, when macrophages prepared from LPS-tolerant mice were co-cultured with normal splenocytes, LPS also could not induce the production of NO, even in the presence of exogenous TNF-$\alpha$. Moreover, when normal macrophages were co-cultured with splenocytes obtained from LPS-tolerant mice, stimulation with LPS could not evoke the NO production enhancement. However, this down-regulation was able to reverse by exogenous IFN-$\tau$ or concanavalin A (ConA), a stimulator of IFN-$\tau$ production. Our results indicate that not only macrophages but also lymphocytes contribute to LPS tolerance. As INF-$\tau$ can enhance the expression of TNF-$\alpha$, the decrease of INF-$\tau$synthesis from lymphocytes may orchestrate with the decrease of TNF-$\alpha$ synthesis from LPS-tolerant macrophages for the production of tolerant state and the prevention of excessive inflammation. Therefore, LPS tolerance may be exploited for prophylaxis of severe sepsis in patients at risk.

• Tuberculosis and Respiratory Diseases
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• v.44 no.3
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• pp.601-610
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• 1997

Background : Monocytes/macrophages play a central role in determining the host response during Gram-negative infection through secretion of a variety of mediators after stimulation of LPS. Even though cytokine production has been shown to play an important role in host defense during sepsis, cytokine release may also lead to tissue injury. Thus, regulation of macrophage response to LPS is critical for host survival during Gram-negative sepsis. In animals exposed to nonlethal doses of endotoxin, a characteristic hyporesponsiveness to subsequent administration of endotoxin has been observed. This phenomenon was known as 'LPS tolerance'. However, little information is available regarding the underlying mechanism of LPS tolerance. Method : Peripheral blood monocyte(PBMC) was isolated from peripheral blood of normal volunteers by adhesion purification method. To evaluate the conditions to obtain LPS tolerance, preculture was carried out with LPS at 10ng/ml for 24 hours. For stimulation, culture plates were washed two times and were stimulated with LPS at $1{\mu}g/ml$ for 4, 6 and 26 hours. To assess the underlying mechanisms of LPS tolerance, autologous serum, PMA, anti-CD14 Ab, Indomethacin or $PGF_2$ were added to preculture solution respectively. Cytokine concentrations in culture supernatants were measured using ELISA for TNF-$\alpha$ and IL-8 and mRNA of TNF-$\alpha$ and IL-8 were determined by Northern blot analysis. Results : The exposure of PBMC to low dose of LPS suppressed the cytokine production and mRNA expression of TNF-$\alpha$, but not IL-8. Anti-CD14 Ab partially recovered production of TNF-$\alpha$ which was suppressed by preculture with low dose LPS. The preculture with PMA induces LPS tolerance, as preculture with low dose LPS. Conclusion : LPS tolerance to TNF-$\alpha$ is regulated pretranslationally and is influenced by protein kinase C pathway and CD14.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.910-916
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• 2002

Endotoxin tolerance reduces the capacity of monocytes to produce proinflammatory cytokines, results in cellular immune paralysis, and down-regulates the production of helper T (Th)1 type cytokines with a shift toward a Th2 cytokine response. Prostaglandin (PG)E$_2$ in the immune system also results in macrophage inactivation and the suppression of Th1 activation and the enhancement of Th2 activation. However, the inhibitory effects of PGE$_2$ on the altered polarization of the Th cell and macrophage interleukin (IL)-6 production characterized in part by cellular immune paralysis in a state of endotoxin tolerance is unclear. This study was undertaken, using indomethacin, to investigate the role of endogenous PGE$_2$ on the Th cytokines and macrophage IL-6 production in a state of endotoxin tolerance compared to those with endotoxemia mice, wherein, in this latter case, the increased production of proinflammatory cytokines and PGE$_2$ is exhibited. Endotoxemia was induced by injection of lipopolysaccharide (LPS; 10 mg/kg in saline) i.p. once in BALB/c mice, and endotoxin tolerance was induced by pretreatment with LPS (1 mg/kg in saline) injected i.p. daily for two consecutive days and then with LPS 10 mg/kg on day 4. Splenocytes or macrophages were obtained from endotoxemia and endotoxin tolerance models pretreated with indomethacin, and then cytokine production was induced by Con A-stimulated splenocytes for the Th cytokine assays and LPS-stimulated macrophages for the IL-6 assay. Our results showed that endotoxemia led to significantly reduced IL-2 and IL-4 production, to significantly increased IL-6 production, whereas interferon $(IFN)-{\gamma}$ production was not affected. Indomethacin in the case of endotoxemia markedly attenuated $IFN-{\gamma}$ and IL-6 production and didnt reverse IL-2 and IL-4 production. Endotoxin tolerance resulted in the significantly reduced production of IL-2 and $IFN-{\gamma}$ and the significantly increased production of IL-4 and IL-6. Indomethacin in endotoxin tolerance greatly augmented IL-2 production, significantly decreased IL-4 production, and slightly attenuated IL-6 production. These findings indicate that endogenous PGE$_2$ may mediate the suppressed Th1 type immune response, with a shift toward a Th2 cytokine response in a state of endotoxin tolerance, whereas endotoxemia may be regulated differentially. Also, endogenous PGE$_2$ may mediate macrophage IL-6 production in the case of endotoxemia to a greater extent than in the case of endotoxin tolerance.

• The Plant Pathology Journal
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• v.35 no.5
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• pp.445-458
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• 2019

The lipopolysaccharide (LPS) composed of lipid A, core, and O-antigen is the fundamental constituent of the outer membrane in gram-negative bacteria. This study was conducted to investigate the roles of LPS in Burkholderia glumae, the phytopathogen causing bacterial panicle blight and seedling rot in rice. To study the roles of the core oligosaccharide (OS) and the O-antigen region, mutant strains targeting the waaC and the wbiFGHI genes were generated. The LPS profile was greatly affected by disruption of the waaC gene and slight reductions were observed in the O-antigen region following wbiFGHI deletions. The results indicated that disruption in the core OS biosynthesis-related gene, waaC, was associated with increased sensitivity to environmental stress conditions including acidic, osmotic, saline, and detergent stress, and to polymyxin B. Moreover, significant impairment in the swimming and swarming motility and attenuation of bacterial virulence to rice were also observed in the waaC-defective mutant. The motility and virulence of O-antigen mutants defective in any gene of the wbiFGHI operon, were not significantly different from the wild-type except in slight decrease in swimming and swarming motility with wbiH deletion. Altogether, the results of present study indicated that the LPS, particularly the core OS region, is required for tolerance to environmental stress and full virulence in B. glumae. To our knowledge, this is the first functional study of LPS in a plant pathogenic Burkholderia sp. and presents a step forward toward full understanding of B. glumae pathogenesis.

• Tuberculosis and Respiratory Diseases
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• v.65 no.4
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• pp.343-350
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• 2008

PD-L1 is expressed in a variety of antigen-presenting cells and provides T cell tolerance via ligation with its receptor PD-1 and B7-1 on T cells. Stimulation with lipopolysaccharide (LPS) can increase the level of PD-L1 expression in B cells and macrophages, which suggests that this molecule plays a role in the immunosuppression observed in severe sepsis. The aim of this study was to identify which of the downstream pathways of TLR4 are involved in the up-regulation of PD-L1 by LPS in macrophages. Flow cytometry was used to examine the expression of PD-L1 in RAW 264.7 macrophages stimulated with LPS. The following chemical inhibitors were used to evaluate the role of each pathway: LY294002 for PI3K/Akt, SB202190 for p38 MAPK, and U0126 for MEK. LPS induced the expression of PD-L1 in a time- and dose-dependent manner. Transfection of siRNA for TLR4 suppressed the induction of PD-L1. Pretreatment with LY294002 and SB202190 decreased the level of PD-L1 expression but U0126 did not. Overall, the PI3K/Akt and p38 MAPK pathways are involved in the up-regulation of PD-L1 expression in RAW 264.7 macrophages stimulated with LPS.

• IMMUNE NETWORK
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• v.5 no.4
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• pp.221-231
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• 2005

Background: Immune regulatory dendritic cells (DCs) play an important role in maintaining self-tolerance. Recent evidences demonstrate that DCs expressing indoleamine 2,3-dioxygenase (IDO), which is involved in tryptophan catabolism, play an important role in immunoregulation and tolerance and induce T cell apoptosis. This study was devised to examine the role of IDO in the oral tolerance induction in collagen-induced arthritis (CIA) mouse model. Methods: Beginning 2 weeks before immunization, CII was fed six times to DBA/1 mice and the effect on arthritis was assessed. In tolerized mice, $CD11c^+$ DCs were isolated and stimulated with CII, IFN-${\gamma}$, and LPS with or without IDO inhibitor, 1-methyl-DL-tryptophan (1-MT) and IDO expression by $CD11c^+$ DCs was analyzed using FACS and RT-PCR. The expression of IDO, MHC II, CD80, and CD86 by $CD11c^+$ DCs were examined using confocal microscopy. Regulatory effect of $CD11c^+$ DCs on Ag-specific T cell proliferative response to CII was examined by mixed lymphocyte reaction (MLR) with or without 1-MT. Results: The proportion of IDO-expressing $CD11c^+$ DCs was slightly higher in tolerized mice than in CIA mice and significantly increased after stimulation with CII, IFN-${\gamma}$, and LPS in an IDO-dependent manner. On confocal microscopic examination, the expression of IDO was higher and those of MHC II and CD86 were lower in CD11c + DCs from tolerized mice compared to those from CIA mice. On MLR, $CD11c^+$ DCs from tolerized mice inhibited T cell proliferative response to CII in an IDO-dependent manner. Conclusion: Enhanced IDO expression by $CD11c^+$ DCs from tolerized mice may contribute to the regulation of proliferative response of CII-reactive T cells and could be involved in the induction of oral tolerance to CII.

• Journal of Ginseng Research
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• v.32 no.4
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• pp.315-323
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• 2008

In the previous studies, we isolated the compound K rich fractions (CKRF) and showed that CKRF inhibited Toll-like receptor (TLR) 4- or TLR9-induced inflammatory signaling. To extend our previous studies,1) we investigated the molecular mechanisms of CKRF in the TLR4-associated signaling via nuclear factor (NF)-${\kappa}B$, and in vivo role of CKRF for induction of tolerance in lipopolysaccharide (LPS)-induced septic shock. In murine bone marrow-dervied macrophages, CKRF significantly inhibited the induction of mRNA expression of proinflammatory mediators such as tumor necrosis factor-${\alpha}$, interleukin-6, cyclooxygenase-2, and inducible nitric oxide synthase. In addition, CKRF significantly attenuated the transcriptional activities of TLR4/LPS-induced NF-${\kappa}B$. Nuclear translocation of NF-${\kappa}B$ in response to LPS stimulation was significantly abrogated by pre-treatment with CKRF. Furthermore, CKRF inhibited the recruitment of p65 to the interferon-sensitive response element flanking region in response to LPS. Finally, oral administration of CKRF significantly protected mice from Gram-negative bacterial LPS-induced lethal shock and inhibited systemic inflammatory cytokine levels. Together, these results demonstrate that CKRF modulates the TLR4-dependent NF-${\kappa}B$ activation, and suggest a therapeutic role for Gram-negative septic shock.

• Natural Product Sciences
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• v.13 no.4
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• pp.322-327
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• 2007

Fresh Rehmanniae radix is known as a traditional medicine with anti-inflammatory and antioxidant activities. However, whether Rehmanniae radix attenuates autoimmune inflammation in lupus models characterized by T cell-dependent autoimmune disease including overproduction of proinflammatory cytokines, loss of T cell tolerance, and B cell hyperactivity remains unclear. We investigated the effect of fresh Rehmanniae radix methanol extracts (RGMeOH) on the in vitro overproduction of proinflammatory cytokines by immune cells from pristaneinduced lupus BALB/c mice. These results showed that RGMeOH remarkably attenuated Con A-increased overproduction of proinflammatory cytokines, such as IL-2, IFN-${\gamma}$, IL-6 and IL-10 by splenocytes from pristaneinduced lupus mice. RGMeOH greatly reduced LPS-induced production of TNF-${\alpha}$ by splenic macrophages from pristane-induced lupus mice, while significantly enhanced LPS-induced production of IL-10 but did not alter IL-6 by splenic macrophages and splenocytes. These findings suggest that RGMeOH may ameliorate lupus systemic inflammatory autoimmunity via down-regulation of TNF-${\alpha}$ and T cell-dependent cytokine production.

• Journal of Life Science
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• v.25 no.12
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• pp.1425-1431
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• 2015

The lymphocyte component of the immune system is divided into B lymphocytes and T lymphocytes. B lymphocytes produce antibodies (humoral immunity) via maturation into plasma cells, and T lymphocytes kill other cells or organisms (cellular immunity). A traditional immunological paradigm is that B lymphocyte and T lymphocyte interactions are a one-way phenomenon, with T lymphocytes helping to induce the terminal differentiation of B lymphocytes into immunoglobulin class-switched plasma cells. A deficiency of T lymphocytes was reported to result in defective B lymphocyte function. However, evidence for a reciprocal interaction between B and T lymphocytes is emerging, with B lymphocytes influencing the differentiation and effector function of T lymphocytes. For example, B lymphocytes have been shown to induce direct tolerance of antigen-specific CD8⁺ T lymphocytes and induce T lymphocytes anergy via transforming growth factor-beta (TGF-β) production. The present study showed that LPS-stimulated B lymphocytes inhibited the differentiation of Th1 lymphocytes by inhibiting the production of interleukin-12 (IL-12) from dendritic cells. An interaction between the B lymphocytes and dendritic cells was not needed for this inhibition, and the B lymphocytes did not alter dendritic cell maturation. B lymphocyte-derived soluble factor (BDSF) suppressed the LPS-induced IL-12p35 transcription in the dendritic cells. Overall, these results point to a novel B lymphocyte- mediated immune suppressive mechanism. The findings cast doubt on the traditional paradigm of immunological interactions involving B lymphocyte and T lymphocyte interactions.