Two forms of NF-kappa B1 (p105/p50) in murine macrophages: differential regulation by lipopolysaccharide, interleukin-2, and interferon-gamma

Differential expression of nuclear factor-kappaB mediates increased pulmonary expression of tumor necrosis factor-alpha and virus-induced asthma

Infections with respiratory pathogens such as respiratory syncytial virus and rhinovirus have been associated with the development of long-term chronic airway disease. To better understand the events responsible for this clinical outcome, a rodent model of virus-induced chronic airway disease has been characterized. Upon infection with Sendai virus (parainfluenza virus type-1), Brown Norway (BN) rats develop an asthma-like clinical syndrome, while Fischer 344 (F344) rats fully recover. Our previous studies demonstrated that after infection, tumor necrosis factor-alpha (TNF-alpha) expression is substantially higher in BN rats compared to F344 rats, and this may at least partially mediate the virus-induced airway abnormalities. To investigate the underlying mechanism(s) for the increased TNF-alpha expression, the role of nuclear factor-kappaB (NF-kappaB), an important regulator of TNF-alpha gene transcription, was examined. Supershift electrophoretic mobility shift assays (EMSAs) indicate that normal F344 rats predominantly express the p65 subunit of NF-kappaB in the lungs, and virus infection temporarily increases expression of the p50 subunit. In contrast, normal BN rats have higher expression of the p50 subunit in the pulmonary tract. Upon infection, p50-subunit expression in BN rats increases to levels higher than those observed in virus-infected F344 rats. Interestingly, treatment of infected BN rats with dexamethasone at doses known to prevent virus-induced airway abnormalities increases pulmonary expression of the p65 subunit, and decreases TNF-alpha mRNA levels in the lungs. Furthermore, direct inhibition of TNF-alpha also increases pulmonary expression of p65 in virus-infected BN, but not F344, rats. Taken together, these results suggest that differential expression of NF-kappaB subunits may play an important role in the development of post-viral chronic airway abnormalities.

Ethyl pyruvate improves survival and ameliorates distant organ injury in rats with severe acute pancreatitis

OBJECTIVE

To evaluate the effect of ethyl pyruvate (EP) in improving the survival and ameliorating distant organ damage and to investigate the role of high-mobility group box (HMGB) 1 in rats with established severe acute pancreatitis (SAP).

METHODS

Severe acute pancreatitis was induced by retrograde infusion of sodium taurodeoxycholate (5%, 1 mL/kg) into the biliopancreatic ducts in male Wistar rats. The rats were infused intravenously with EP of 40 mg/kg, 4 mg/kg, and 0.4 mg/kg initiating 12 hours, and EP of 40 mg/kg was administered beginning 2 hours before surgery (-2 hours) and 12, 24, and 36 hours after induction of SAP; then, the mortality was recorded. Serum tumor necrosis factor alpha, interleukin (IL) 6, and IL-1beta were measured using enzyme-linked immunosorbent assay. High-mobility group box 1 levels were measured using Western immunoblotting analysis.

RESULTS

Serum HMGB1 levels were increased dramatically after 12 hours, remained at high levels for 72 hours, and were significantly higher in rats with SAP than in those with mild and moderate pancreatitis (P < 0.01). Treatment with EP (40 mg/kg) conferred protection from lethality of SAP (EP survival [63%] vs vehicle survival [6.3%]; P < 0.001). No survival advantage occurred when treatment was initiated 36 hours after surgery, but administration beginning 2 hours before operation (-2 hours) and 12 and 24 hours after induction of SAP significantly increased survival. Ethyl pyruvate treatment significantly decreased serum HMGB1, tumor necrosis factor alpha, IL-1beta, and IL-6 levels and ameliorated extrapancreatic organ dysfunction in rats with SAP.

CONCLUSIONS

Ethyl pyruvate improves survival and ameliorates distant organ injury of SAP. These beneficial effects of EP are because of the modulation of HMGB1 and other inflammatory cytokine responses.

Characterization of the human intestinal CD98 promoter and its regulation by interferon-gamma

Growing evidence that epithelial CD98 plays an important role in intestinal inflammation focused our interest to investigate the transcriptional regulation of CD98. Our mouse-based in vivo and in vitro experiments revealed that epithelial colonic CD98 mRNA expression was transcriptionally increased in intestinal inflammation. We then isolated and characterized a 5'-flanking fragment containing the promoter region required for CD98 gene transcription. Primer extension and rapid amplification of 5'-cDNA ends were used to map a transcriptional initiation site 129 bp upstream from the translational start codon (ATG). Direct sequencing of the 5'-flanking region revealed the presence of four GC-rich stimulating protein (Sp)1 binding domains, one NF-kappaB binding domain, and no TATA box. Binding of Sp1 [Sp1(-874), SP1(-386), Sp1(-187), and Sp1(-177)] and NF-kappaB [NF-kappaB(-213)] to the promoter was confirmed by EMSA and supershift assays. Furthermore, chromatin immunoprecipitation experiments showed the in vivo DNA-Sp1 and DNA-NF-kappaB interactions under basal and IFN-gamma-stimulated conditions. Reporter genes driven by serially truncated and site-mutated CD98 promoters were used to examine basal and IFN-gamma-responsive transcription in transiently transfected Caco2-BBE cells. Our results revealed that Sp1(-187), Sp1(-177), and the NF-kappaB binding site were essential for basal and IFN-gamma-stimulated CD98 promoter activities, whereas Sp1(-874) and Sp1(-386) were not. The results from additional site-mutated CD98 promoters suggested that Sp1(-187), Sp1(-177), and the NF-kappaB site may cooperate in mediating basal and IFN-gamma-stimulated CD98 promoter activities. Finally, we demonstrated that a reduction of Sp1 or NF-kappaB expression reduced CD98 protein expression in unstimulated and IFN-gamma-stimulated Caco2-BBE cells. Collectively, these findings indicate that the Sp1 and NF-kappaB transcription factors are likely to play a significant role in IFN-gamma-mediated transcriptional regulation of CD98 in the intestinal epithelium, providing new insights into the regulation of CD98 expression in intestinal inflammation.

Ethyl pyruvate prevents lethality in mice with established lethal sepsis and systemic inflammation

Sepsis, a potentially fatal clinical syndrome, is mediated by an early (e.g., tumor necrosis factor and IL-1) and late [e.g., high mobility group B-1 (HMGB1)] proinflammatory cytokine response to infection. Specifically targeting early mediators has not been effective clinically, in part because peak mediator activity often has passed before therapy can be initiated. Late-acting downstream effectors, such as HMGB1, that mediate sepsis lethality may be more relevant therapeutic targets. Ethyl pyruvate (EP) recently was identified as an experimental therapeutic that significantly protects against lethal hemorrhagic shock. Here, we report that EP attenuates lethal systemic inflammation caused by either endotoxemia or sepsis even if treatment begins after the early tumor necrosis factor response. Treatment with EP initiated 24 h after cecal puncture significantly increased survival (vehicle survival = 30% vs. EP survival = 88%, P < 0.005). EP treatment significantly reduced circulating levels of HMGB1 in animals with established endotoxemia or sepsis. In macrophage cultures, EP specifically inhibited activation of p38 mitogen-activated protein kinase and NF-kappaB, two signaling pathways that are critical for cytokine release. This report describes a new strategy to pharmacologically inhibit HMGB1 release with a small molecule that is effective at clinically achievable concentrations. EP now warrants further evaluation as an experimental "rescue" therapeutic for sepsis and other potentially fatal systemic inflammatory disorders.

Aberrant production of IL-12 by macrophages from several autoimmune-prone mouse strains is characterized by intrinsic and unique patterns of NF-kappa B expression and binding to the IL-12 p40 promoter

Intrinsic defects in macrophage (M(phi)) cytokine production characterize many autoimmune-prone mouse strains. Aberrant levels of IL-12, for example, are produced by M(phi) isolated from young mice prone to lupus (MRL and NZB/W) and diabetes (nonobese diabetic (NOD)) well before the appearance of disease signs. Evaluation of the possible mechanism(s) underlying the abnormal regulation of IL-12 in these strains revealed novel patterns of Rel family protein binding to the unique p40 NF-kappaB site in the IL-12 p40 promoter, whereas binding patterns to Ets and CCAAT enhancer binding protein/beta sites were normal. In particular, the heightened production of IL-12 by NOD M(phi) is associated with elevated levels of the trans-activating p50/c-Rel (p65) complex compared with the nonfunctional p50/p50 dimer. Conversely, the dramatically impaired production of IL-12 by both NZB/W and MRL/+ M(phi) is associated with a predominance of p50/p50 and reduced p50/c-Rel(p65) binding. Mechanistically, the unique pattern seen in the lupus strains reflects elevated p50 and reduced c-Rel nuclear protein levels. In NOD extracts, the level of c-Rel is elevated compared with that in lupus strains, but not when compared with that in normal A/J. However, the extent of c-Rel tyrosine phosphorylation noted in NOD extracts is more than double that seen in any other strain. Levels of p65 were similar in all strains tested. These findings reveal that a common mechanism, involving dysregulation of c-Rel and p50, may be used to determine the aberrant IL-12 levels that have the potential to predispose specific mouse strains to systemic or organ-specific autoimmunity.

Endotoxin clearance and its relation to hepatic and renal disturbances in rats with liver cirrhosis

BACKGROUND/AIMS

Little is known about endotoxin clearance and secretion of cytokines from macrophages in liver cirrhosis. The aims of this study were to investigate the relationship of endotoxin clearance and release of tumor necrosis factor alpha by various macrophages to hepatic and renal disturbances in liver cirrhosis.

METHODS

Male Sprague-Dawley rats were given 0.04% thioacetamide orally for 6 or 12 months. The organ distribution of infused [3H]-endotoxin (10 microg/kg b.w.) was analyzed at 30 min or at 24 h. Uptake of [3H]-endotoxin and secretion of tumor necrosis factor alpha by Kupffer cells, splenic macrophages and peripheral blood monocytes (1 x 10(4) cells/ml) from cirrhotic and control rats were determined.

RESULTS

In cirrhotic rats, more endotoxin was left in the body and more endotoxin accumulated in the spleen and kidney, and thus was related to elevation of serum total bilirubin, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, creatinine and tumor necrosis factor alpha. Endotoxin uptake and tumor necrosis factor alpha release by the Kupffer cells were decreased and those by the splenic macrophages and peripheral blood monocytes were increased in cirrhotic rats.

CONCLUSIONS

In liver cirrhosis, impaired clearance of endotoxin together with increased secretion of tumor necrosis factor alpha by extrahepatic macrophages may play an important role in the progression of hepatic and renal disturbances.

Hematotoxicity of the chinese herbal medicine Tripterygium wilfordii hook f in CD34-positive human bone marrow cells

T2, a chloroform/methanol extract of the herb Tripterygium wilfordii Hook f, has been used in China for the treatment of autoimmune and inflammatory diseases for many years. Recent experimental evidence has confirmed that T2 has potent anti-inflammatory and immunosuppressive activity, and a United States Food and Drug Administration-approved clinical trial is currently exploring the efficacy of T2 in the treatment of rheumatoid arthritis. Despite the potential therapeutic benefits of T2, there is ample documentation that T2 is toxic, targeting, among other things, the hematopoietic system, and its use has resulted in cases of leukopenia, thrombocytopenia, and aplastic anemia. This investigation was undertaken to characterize the in vitro effects of T2 on primary human CD34-positive (CD34+) bone marrow cells. Our results demonstrate that T2 has a potent inhibitory effect on the clonogenic response of human bone marrow cells to exogenously added hematopoietic growth factors. The inhibition of colony formation by T2 is not the result of direct cytotoxicity or increased apoptosis and indicates a functional suppression of hematopoiesis. Additional experiments demonstrate that T2 also alters transcriptional regulation in bone marrow cells by inhibiting nuclear factor-kappaB. This transcription factor is found in CD34+ bone marrow cells and has been recently shown to be a requirement for colony formation. These results demonstrate that therapeutic concentrations of T2 exert a significant hematotoxic effect by inhibiting growth factor response in CD34+ bone marrow cells and suggest that inhibition of nuclear factor-kappaB may play a role in the blood dyscrasias encountered with the use of this drug.

IL-12 Is Dysregulated in Macrophages from IRF-1 and IRF-2 Knockout Mice

Macrophages derived from IFN-regulatory factor-1 (IRF-1) and IRF-2 knockout (−/−) and wild-type (+/+) mice were utilized to examine the role of these transcription factors in the regulation of IL-12 mRNA and protein expression. Induction of IL-12 p40 mRNA by LPS was markedly diminished in both IRF-1−/− and IRF-2−/− macrophages. In contrast, IRF-1−/−, but not IRF-2−/−, macrophages exhibited impaired LPS-induced IL-12 p35 mRNA expression. The ability of IFN-γ to augment LPS-induced IL-12 p40 mRNA further when both stimuli were present simultaneously was significantly diminished in both IRF-1−/− and IRF-2−/− macrophages, with the most profound impairment observed for IRF-1−/− macrophages. Reductions in IL-12 mRNA expression after stimulation with LPS or LPS plus IFN-γ were accompanied by substantial reductions in IL-12 p40 and IL-12 p70 protein in both IRF-1−/− and IRF-2−/− macrophages. Priming IRF-1−/− and IRF-2−/− macrophages with IFN-γ for 24 h before LPS treatment partially restored impaired IL-12 mRNA and protein production in both IRF-1−/− and IRF-2−/− macrophages. Depressed IL-12 levels were paralleled by significant reductions in IFN-γ mRNA expression in IRF-1−/− and IRF-2−/− macrophages. These results indicate that both IRF-1 and IRF-2 are critical transcription factors in the regulation of macrophage IL-12 and consequently IFN-γ production.

An Essential Role for NF-κB in Human CD34+ Bone Marrow Cell Survival

The transcription factor, NF-κB, is important for T-cell activation, B-cell maturation, and human immunodeficiency virus transcription and plays a role in alternatively mediating and protecting against apoptosis in a variety of cell types. However, a role for NF-κB in human CD34+ bone marrow cells has not been described. We provide evidence here that virtually all human CD34+ bone marrow cells express NF-κB that can be activated by exposure to phorbol 12-myristate 13-acetate and a variety of cytokines, eg, tumor necrosis factor , interleukin-3, and granulocyte-macrophage colony-stimulating factor. In addition, we demonstrate that NF-κB may be required for human CD34+bone marrow cell clonogenic function and survival. These results offer insight into a new role for NF-κB in maintaining survival and function in hematopoietic stem and progenitor cells and suggest that proposed strategies involving inhibition of NF-κB activation as an adjunct to cancer chemotherapy should be approached with caution.

Cytokine induction of iNOS and sPLA2 in immortalized astrocytes (DITNC): response to genistein and pyrrolidine dithiocarbamate

Using an immortalized astrocyte cell line (DITNC), we showed that lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta) but not interferon-alpha (IFN-alpha) could individually induce secretory phospholipase A2 (sPLA2) mRNA and enzymatic activity. However, induction of inducible nitric oxide synthase (iNOS) mRNA and NO production by cytokines required the presence of IFN-gamma. Using a three-cytokine mixture (TNF-alpha, IL-1beta, and IFN-gamma) that could maximally induce both iNOS and sPLA2, the increase in these mRNA species reached a maximum by 4-8 h, followed by a decline up to 48 h. L-N6-(1-Iminoethyl)lysine acetate (L-NIL) inhibited cytokine-induced NO production with IC50 of 25 microM, but this compound did not affect iNOS mRNA. Furthermore, L-NIL exerted no effect on sPLA2 mRNA or sPLA2 activity. Pyrrolidine dithiocarbamate (PDTC), an inhibitor for NF-kappaB, was more effective in inhibiting iNOS mRNA and NO production than for sPLA2. Surprisingly, genistein inhibited both NO production and sPLA2 activity with IC50 of 72 microM and 88 microM, respectively. On the other hand, daidzein, a genistein analog lacking tyrosine kinase inhibitor activity, was not effective in inhibition of NO production at 250 microM. These results demonstrate distinct pathways for induction of iNOS and sPLA2 in DITNC cells by cytokines and shed new insight on transcriptional regulation for these two mRNA species.

Tumor necrosis factor alpha transcription in macrophages is attenuated by an autocrine factor that preferentially induces NF-kappaB p50

Macrophages are a major source of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), which are expressed during conditions of inflammation, infection, or injury. We identified an activity secreted by a macrophage tumor cell line that negatively regulates bacterial lipopolysaccharide (LPS)-induced expression of TNF-alpha. This activity, termed TNF-alpha-inhibiting factor (TIF), suppressed the induction of TNF-alpha expression in macrophages, whereas induction of three other proinflammatory cytokines (interleukin-1beta [IL-1beta], IL-6, and monocyte chemoattractant protein 1) was accelerated or enhanced. A similar or identical inhibitory activity was secreted by IC-21 macrophages following LPS stimulation. Inhibition of TNF-alpha expression by macrophage conditioned medium was associated with selective induction of the NF-kappaB p50 subunit. Hyperinduction of p50 occurred with delayed kinetics in LPS-stimulated macrophages but not in fibroblasts. Overexpression of p50 blocked LPS-induced transcription from a TNF-alpha promoter reporter construct, showing that this transcription factor is an inhibitor of the TNF-alpha gene. Repression of the TNF-alpha promoter by TIF required a distal region that includes three NF-kappaB binding sites with preferential affinity for p50 homodimers. Thus, the selective repression of the TNF-alpha promoter by TIF may be explained by the specific binding of inhibitory p50 homodimers. We propose that TIF serves as a negative autocrine signal to attenuate TNF-alpha expression in activated macrophages. TIF is distinct from the known TNF-alpha-inhibiting factors IL-4, IL-10, and transforming growth factor beta and may represent a novel cytokine.