Effects of glutamine on the nuclear factor-kappaB signaling pathway of murine peritoneal macrophages

The aim of this study was to evaluate the effect of glutamine on the expression of proteins involved in the nuclear factor-kappaB (NF-κB) signaling pathway of murine peritoneal macrophages. Since glutamine is essential for the normal functioning of macrophages, it was hypothesized that in vitro glutamine supplementation would increase NF-κB activation. Peritoneal macrophages were pretreated with glutamine (0, 0.6, 2 and 10 mM) before incubation with lipopolysaccharide (LPS), and the effects of glutamine on the production of tumor necrosis factor-alpha and on the expression and activity of proteins involved in the NF-κB signaling pathway were studied by an enzyme linked immuno-sorbent assay, Western blotting, and an electrophoretic mobility shift assay. Glutamine treatment (2 and 10 mM) increased the activation of NF-κB in LPS-stimulated peritoneal macrophages (P < 0.05). In non-stimulated cells, glutamine treatment (2 and 10 mM) significantly reduced IκB-α protein expression (P < 0.05). Glutamine modulates NF-κB signaling pathway by reducing the level of IκB-α, leading to an increase in NF-κB within the nucleus in peritoneal macrophages.     

Promoting effect of IFN-γ on the expression of LPS-induced IL-12 p40 and p35 mRNA in murine suppressor macrophages

We detected the expression of IL-12 p40/p35 mRNA by semi-quantitative RT-PCR and silver staining, and studied the molecular interaction between the IL-12 expression and the NF-eB activation induced by LPS and IFN-γ/LPS in murine peritoneal suppressor macrophages (MPSMs). It was found that IFN-γ strongly enhanced the LPS-induced IL-12 p40 and p35 mRNA expression. Both p40 and p35 mRNA levels were approximately equal. IFN-a also greatly promoted the LPS-induced secretion of IL-12 p70 in MPSMs. The Proteasome Inhibitor I (PSI) could block the expression of IL-12 p40 and p35 mRNA, and the degradation of IκBα induced by LPS or LPS/IFN-γ. EMSA showed that LPS could augment the NF-κB binding activity to p40 promoter DNA. However, IFN-γ could neither enhance the LPS-induced NF-κB activity nor promote the degradation of IκBα. Taken together, the data suggest: (i) IFN-γ/LPS could strongly induce the expression of IL-12 p40 and p35 mRNA; both the expression levels were equal; this phenomenon coincided with the high-level secretion of IL-12 p70 induced by IFN-γ/LPS; (ii) NF-κB signal pathway is essential for IFN-γ/LPS to induce IL-12 mRNA expression; (iii) by blocking the degradation of IκB, the PSI suppresses the IL-12 p40/p35 mRNA expression induced by LPS and IFN-γ/LPS; (iv) NF-κB signal may not be involved in the mechanism by which IFN-γ enhanced the expression of the LPS-induced IL-12 p40/p35 mRNA. The first two authors contributed equally to this work.     

A lectin from <Emphasis Type="Italic">Musca domestica</Emphasis> pupae stimulates B cell proliferation and enhances IL-12 production via ERK1/2-NF-κB signaling pathways

A d-galactose-specific lectin, MW = 40 kDa, had been purified from pupae of Musca domestica (MPL). MPL significantly promoted the proliferation of B cells and enhanced the production of IL-12 in a dose-dependent manner. MPL stimulated IκB-α degradation, NF-κB translocation and ERK1/2 phosphorylation which played an upstream role for NF-кB in MPL-induced B cells. Moreover, MPL regulated cell proliferation and induced IL-12 production through ERK1/2-NF-κB signaling pathway.     

Apoptosis of Dedifferentiated Hepatoma Cells is Independent of NF-κB Activation in Response to LPS

Dedifferentiated hepatoma cells, in contrast to most other cell types including hepatoma cells, undergo apoptosis when treated with lipopolysaccharide (LPS) plus the protein synthesis inhibitor cycloheximide (CHx). We recently reported that the dedifferentiated hepatoma cells also exhibit a strong and prolonged NF-κB induction phenotype upon exposure to LPS, suggesting that NF-κB signaling may play a pro-survival role, as reported in several other cell systems. To test the role of NF-κB in preventing LPS-mediated apoptosis, we examined the dedifferentiated cell line M38. Results show that antioxidants strongly inhibited LPS + CHx-mediated cell death in the M38 cells, yet only modestly inhibited NF-κB induction. In addition, inhibition of NF-κB translocation by infection of the M38 cells with an adenoviral vector expressing an IκBα super-repressor did not result in LPS-mediated cell death. These results suggest that unlike TNFα induction, the cell survival pathway activated in response to LPS is independent of NF-κB translocation in the dedifferentiated cells. Addition of inhibitors of JNK, p38 and ERK pathways also failed to elicit LPS-mediated apoptosis similar to that observed when protein synthesis is prevented. Thus, cell survival pathways other than those involving NF-κB inducible gene expression or other well-known pathways appear to be involved in protecting the dedifferentiated hepatoma variant cells from LPS-mediated apoptosis. Importantly, this pro-apoptotic function of LPS appears to be a function of loss of hepatic gene expression, as the parental hepatoma cells resist LPS-mediated apoptosis in the presence of protein synthesis inhibitors.     

Bortezomib induces in HepG2 cells IκBα degradation mediated by caspase-8

Abstact The present paper demonstrates that the proteasome inhibitor bortezomib, which behaves as an apoptotic agent in hepatoma HepG2 cells, caused in these cells a decrease in IκBα level and a consequent increase in NF-κB activity. The effect already appeared at 4 h of treatment and preceded the onset of apoptosis which was observed at 24 h. Our results demonstrate that bortezomib-induced IκBα degradation occurred in conjunction with the activation of caspase-8; moreover, the decrease in IκBα level was prevented in a dose-dependent manner by the addition of z-IETD, a specific inhibitor of caspase-8. Bortezomib caused the same effects in non-tumor Chang liver cells, which were not susceptible to the apoptotic effect of the drug. Our results also show that other proteases, such as caspase-3 and calpains, exerted only a limited effect on IκBα degradation. These findings suggest that caspase-8 can be involved in the control of IκBα level. In addition, the activation of caspase-8 can exert, at least in the first phase of treatment with bortezomib, a protective effect in both HepG2 and Chang liver cells, favouring the activation of the survival factor NF-κB     

Genomic organization and chromosomal mapping of mouse nuclear factor kappa B 2 (NFKB2)

 NFKB2 is a member of the NFKB/Rel gene family, which is known to be a pivotal regulator of the acute phase and immune responses. NF-κB2 is initially synthesized as a ∼100 000 M _r protein which needs to be processed in order to bind DNA, either as homodimer or as heterodimer with other members of the NF-κB/Rel family. The unprocessed form of NF-κB2 acts as an IκB-like protein. Therefore, NF-κB2 has a dual function. In this report we describe the genomic structure, expression pattern, and chromosomal localization of mouse NFKB2. Genomic clones were isolated, which span the entire gene of approximately 8.5 kilobases (kb) including 1.5 kb of the promoter region. Comparison to its human and avian homologues revealed a strong evolutionary conservation of the gene structure including the exon/intron borders, sequence, and position of the nuclear localization signal, the glycine-hinge region, and the ankyrin repeats. By fluorescence in situ hybridization, mouse NFKB2 was mapped to Chromosome (Chr) MMU 19C3-D2, which is homologous to human Chr 10q24, at which position the human NFKB2 was previously located. NFKB2 is ubiquitously expressed, highest in lymph nodes and thymus, underlining its role in the immune function. Received: 14 January 1999 / Revised: 29 March 1999     

Degradation of IkappaBalpha in activated RAW264.7 cells is blocked by the phosphatidylinositol 3-kinase inhibitor LY294002

The mechanism by which lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) induces production of proinflammatory cytokines in murine macrophages, and the role of phosphatidylinositol 3-kinase (PI3-kinase) have not been well investigated. Activation of nuclear factor κB (NF-κB) is initiated by the phosphorylation of the inhibitory subunit, IκB, which targets IκB for degradation and leads to the release of active NF-κB. In this study we demonstrate that 2- (4-morpholinyl)-8-phenylchromone (LY294002), which inhibits PI3-kinase, specifically inhibited degradation of IκBα in RAW264.7 cells stimulated with interferon-γ (IFN-γ) plus LPS or IFN-γ plus PMA. To elucidate the importance of this activity in RAW264.7 cells, we examined tumor necrosis factor-α (TNF-α) and interleukin IL)-6 production in the activated cells. Pretreatment of the cells with LY294002 resulted in the inhibition of TNF-α and IL-6 production in RAW264.7 cells stimulated with IFN-γ plus LPS or IFN-γ plus PMA. Furthermore, LY294002 inhibited the production of nitric oxide NO) in RAW264.7 cells stimulated with IFN-γ plus LPS or IFN-γ plus PMA. LY294002 also inhibited inducible NO synthase (iNOS) mRNA expression in the activated RAW264.7 cells. In conclusion, the present results suggest that PI3-kinase is involved in the signal transduction pathway responsible for LPS- or PMA-mediated TNF-α and IL-6 production, and that LY294002 inhibits NO generation through blocking the degradation of IκBα in activated RAW264.7 cells. This revised version was published online in August 2006 with corrections to the Cover Date.     

2-phenylethynesulfonamide Prevents Induction of Pro-inflammatory Factors and Attenuates LPS-induced Liver Injury by Targeting NHE1-Hsp70 Complex in Mice

The endotoxin-mediated production of pro-inflammatory cytokines plays an important role in the pathogenesis of liver disorders. Heat shock protein (Hsp70) overexpression has established functions in lipopolysaccharide (LPS)-mediated inflammatory response. However, little is known about the role of Hsp70 activity in LPS signaling. We hypothesized that inhibition of Hsp70 substrate binding activity can ameliorate LPS-induced liver injury by decreasing induction of pro-inflammatory factors. In this study, C57/BL6 mice were injected intraperitoneally with LPS and 2-phenylethynesulfonamide (PES), an inhibitor of Hsp70 substrate binding activity. We found that i. PES prevented LPS-induced increase in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, infiltration of inflammatory cells, and liver cell apoptosis; ii. PES reduced inducible nitric oxide synthase (iNOS) protein expression as well as serum nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) content in LPS-stimulated mice; iii. PES reduced the mRNA level of iNOS, TNF-α, and IL-6 in LPS-stimulated liver. iiii. PES attenuated the degradation of inhibitor of κB-α (IκB-α) as well as the phosphorylation and nuclear translocation of nuclear factor-κB (NF-κB) in LPS-stimulated liver. Similar changes in the protein expression of inflammatory markers, IκB-α degradation, and NF-κB phosphorylation and nuclear translocation were observed in RAW 264.7 cells. Further mechanistic studies revealed that PES remarkably reduced the elevation of [Ca²⁺]_i and intracellular pH value (pH_i) in LPS-stimulated RAW 264.7 cells. Furthermore, PES significantly reduced the increase in Na⁺/H⁺ exchanger 1 (NHE1) association to Hsp70 in LPS-stimulated macrophages and liver, suggesting that NHE1-Hsp70 interaction is required for the involvement of NHE1 in the inflammation response. In conclusion, inhibition of Hsp70 substrate binding activity in vivo reduces the induction of pro-inflammatory factors and prevents LPS-induced liver injury likely by disrupting NHE1-Hsp70 interaction which consequently reduces the activation of IκB-α-NF-κB pathway in liver.     

LPS suppresses expression of asialoglycoprotein-binding protein through TLR4 in thioglycolate-elicited peritoneal macrophages

Macrophages are known to express various types of endocytosis receptors that mediate the removal of foreign pathogens. Macrophage asialoglycoprotein-binding protein (M-ASGP-BP) is a Gal/GalNAc-specific lectin, which functions as an endocytosis receptor. We found here that LPS is able to down-regulate the mRNA expression of M-ASGP-BP in a time-dependent manner using thioglycolate-elicited rat and mouse peritoneal macrophages. However, LPS does not modulate the mRNA expression of M-ASGP-BP from macrophages of C3H/HeN mice, which have a point mutation of TLR4, the primary LPS receptor. Furthermore, an inhibitor of NF-κB was observed to efficiently block the suppressive effect of LPS on M-ASGP-BP as well as to inhibit the phosphorylated IκB. These results demonstrate that the mRNA expression of M-ASGP-BP is down-regulated by the LPS-mediated TLR4 pathway involving NF-κB activation, suggesting that engagement of M-ASGP-BP by LPS may yield a negative signal that interferes with the LPS-induced positive signals mediated by proinflammatory cytokines.     

H<Subscript>2</Subscript> inhibits TNF-α-induced lectin-like oxidized LDL receptor-1 expression by inhibiting nuclear factor κB activation in endothelial cells

H₂ is a therapeutic antioxidant that can reduce oxidative stress. Oxidized low-density lipoprotein, which plays roles in atherosclerosis, may promote endothelial dysfunction by binding the cell-surface receptor LOX-1. LOX-1 expression can be upregulated by various stimuli, including TNF-α. Thus, we aimed to examine whether the upregulation of LOX-1 by different stimuli could be blocked by H₂ in endothelial cells. H₂ significantly abolished the upregulation of LOX-1 by different stimuli, including TNF-α, at the protein and mRNA levels. The TNF-α-induced upregulation of LOX-1 was also attenuated by the NF-κB inhibitor N-acetyl-l-cysteine. H₂ inhibited the TNF-α-induced activation of NF-κB and the phosphorylation of IκB-α. Furthermore, H₂ inhibited the expression of LOX-1 and the activation of NF-κB in apolipoprotein E knockout mice, an animal model of atherosclerosis. Thus, H₂ probably inhibits cytokine-induced LOX-1 gene expression by suppressing NF-κB activation.     

Lipopolysaccharide pretreatment protects against ischemia/reperfusion injury via increase of HSP70 and inhibition of NF-κB

It has been reported that pretreatment of rats with lipopolysaccharide (LPS) increases myocardial functional recovery in ischemia/reperfusion (I/R) hearts. However, the mechanisms by which LPS induces cardioprotection against I/R injury have not been fully elucidated. In this study, we pretreated rats with LPS (1.0 mg/kg) 24 h before they were subjected to I/R injury, and then examined the roles of heat shock protein-70 (HSP70) and nucleus factor-κB (NF-κB) in LPS-induced cardioprotection. We observed that pretreatment with low-dose LPS resulted in significantly increased levels of HSP70 in the myocardium, which could dramatically inhibit NF-κB translocation and reduce degradation of inhibitory κB. Inhibition of NF-κB, in turn, attenuated release of inflammatory cytokines (tumor necrosis factor-α, interleukin (IL)-1β, and IL-6) and reduced apoptosis of myocardium and infarct area following I/R injury. Moreover, HSP70 could ameliorate oxidative stress following I/R injury. To further investigate whether increase of HSP70 might be responsible for protection of the myocardium against I/R injury, we co-administered the HSP70 inhibitor, quercetin, with LPS before I/R injury. We found that LPS-induced cardioprotection was attenuated by co-administration with quercetin. Herein, we concluded that increased levels of HSP70 through LPS pretreatment led to inhibition of NF-κB activity in the myocardium after I/R injury. Our results indicated that LPS-induced cardioprotection was mediated partly through inhibition of NF-κB via increase of HSP70, and LPS pretreatment could provide a means of reducing myocardial I/R injury.     

<Emphasis Type="Italic">S</Emphasis>-Propargyl-cysteine (SPRC) attenuated lipopolysaccharide-induced inflammatory response in H9c2 cells involved in a hydrogen sulfide-dependent mechanism

The present study attempts to investigate the effects of S-propargyl-cysteine (SPRC), a sulfur-containing amino acid, on lipopolysaccharide (LPS)-induced inflammatory response in H9c2 cardiac myocytes. We found that SPRC prevented nuclear factor-κB (NF-κB) activation assessed by NF-κB p65 phosphorylation and IκBα degradation, suppressed LPS-induced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and intracellular reactive oxygen species (ROS) production. Furthermore, incubation of H9c2 cells with SPRC induced phosphorylation of Akt in a time- and concentration-dependent manner. In addition, SPRC attenuated LPS-induced mRNA and protein expression of tumor necrosis factor-α (TNF-α), and mRNA expression of intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS). The effects of SPRC were abolished by cystathionine γ-lyase [CSE-an enzyme that synthesizes hydrogen sulfide (H₂S)] inhibitor, dl-propargylglycine (PAG), SPRC-induced Akt phosphorylation and TNF-α release was also abolished by the phosphoinositide 3-kinase (PI3K) inhibitor LY294002. Furthermore, SPRC also increased LPS-induced down-regulation expression of CSE and H₂S level in H9c2 cells. PAG abolished SPRC-induced up-regulation of H₂S level. Therefore, we concluded that SPRC produced an anti-inflammatory effect in LPS-stimulated H9c2 cells partly through the CSE/H₂S pathway by impairing IκBα/NF-κB signaling and by activating PI3K/Akt signaling pathway.     

Nuclear factor inducing kinase: A key regulator in osteopontin- induced MAPK/IκB kinase dependent NF-κB-mediated promatrix metalloproteinase-9 activation

Osteopontin (OPN) is a secreted, non-collagenous, sialic-acid rich, glycosylated adhesive phospho- protein. Several highly metastatic transformed cells synthesized a higher level of OPN compared with non-tumorigenic cells. We have recently reported that OPN induces nuclear factor-κB (NF-κB)-mediated promatrix metalloproteinase-2 activation through IκBα/IKK signaling pathways. However, the molecular mechanism(s) by which OPN regulates pro-matrix metalloproteinase-9 (pro-MMP-9) activation and involvement of upstream kinases in regulation of these processes that ultimately control cell motility and tumor growth in murine melanoma cells are not well defined. Here we report that OPN induces αvβ3 integrin-mediated phosphorylation and activation of nuclear factor inducing kinase (NIK) and enhances the interaction between phosphorylated NIK and IκBα kinase α/β (IKKα/β) in B16F10 cells. Moreover, NIK is involved in OPN-induced phosphorylations of MEK-1 and ERK1/2 in these cells. OPN induces NIK-dependent NF-κB activation through ERK/IKKα/β-mediated pathways. Furthermore, OPN enhances NIK-regulated urokinase-type plasminogen activator (uPA) secretion, uPA-dependent pro-MMP-9 activation, and cell motility. Pretreatment of cells with anti-MMP-2 antibody along with anti-MMP-9 antibody drastically inhibited the OPN-induced cell migration and chemoinvasion, whereas cells pretreated with anti-MMP-2 antibody had no effect on OPN-induced pro-MMP-9 activation suggesting that OPN induces pro-MMP-2 and pro-MMP-9 activations through two distinct pathways. Taken together, NIK acts as crucial regulator in OPN-induced MAPK/IKK-mediated NF-κB-dependent uPA secretion and MMP-9 activation thereby controlling melanoma cell motility and chemoinvasion. An erratum to this article is available at .