The NF-kappaB pathway

NF-kappa B as a therapeutic target in autoimmune disease

NF-kappaB transmits signals from the cell surface to the nucleus. Signaling through cell surface receptors to activate NF-kappaB and mitogen-activated protein kinases through adaptor molecules is of critical importance to survival and activation of all cells in the body, including those regulating innate and adaptive immunity. As such, NF-kappaB is a key signaling component in autoimmunity and an attractive target for autoimmune disease therapy. However, given its global importance, targeting NF-kappaB tends to be immunosuppressive. In this review, the authors discuss the roles played by NF-kappaB in autoimmunity, drugs which target it, and complexities which need to be addressed to improve the use of NF-kappaB as a target. Finally, the authors highlight some novel approaches that are likely to be important in the next generation of NF-kappaB therapies.

Enhanced Ca2+ sensitivity in hyperresponsive cultured bronchi is mediated by TNFalpha and NF-kappaB

The mechanical properties and Ca2+ sensitivity of an organ-culture model derived from guinea pig airways have been examined. The cultured explants develop airway hyperresponsiveness to pharmacological agonists after 3-day culture, when compared with fresh and ovalbumin-sensitized tissues. The reactivity of cultured explants is dependent on the presence of the epithelium. They are also sensitive to glucocorticosteroid pretreatments, which neutralize the TNFalpha antibody and NF-kappaB inhibitor. Hence, specific immunostaining of NF-kappaB subunits (p65 and p50) was increased in the nuclear extract of cultured explants. In beta-escin-permeabilized preparations, step-increases in pCa revealed enhanced Ca2+ sensitivity of the contractile apparatus in cultured explants, which was prevented by epithelium removal. Pretreatments of cultured explants with neutralizing TNFalpha antibody and NF-kappaB inhibitor consistently reduced their Ca2+ sensitivity. These findings suggest that AHR developed in this organ culture model may be triggered by an inflammatory process mediated by the TNFalpha and NF-kappaB transcription factor, which results in an increased sensitivity to [Ca2+]i.

Ethanol Extract of Inonotus obliquus Inhibits Lipopolysaccharide-Induced Inflammation in RAW 264.7 Macrophage Cells

Inonotus obliquus (Pers.:Fr.) Pil. is a white rot fungus that belongs to the family Hymenochaetaceae of Basidiomycetes. Extracts and fractions of this fungus have been known to have biological activities, including antimutagenic, anticancer, antioxidative, and immunostimulating effects. Recently, there have been reports that the anti-inflammatory and antinociceptive properties of the methanol extract of I. obliquus may be due to the inhibition of inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) expression via the down-regulation of nuclear factor kappaB (NF-kappaB) binding activity. However, the effects of I. obliquus on Akt and mitogen-activated protein kinase (MAPK) activation of inflammatory mediator production have not yet been elucidated. In the present study, a 70% ethanol extract of I. obliquus (IOE70) showed antioxidative effects. We also tested the ability of the I. obliquus extract to inhibit the inflammatory cascades in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells. The NO inhibition of IOE70 was better than that of other ethanol extracts from I. obliquus. To investigate the mechanism by which IOE 70 inhibits NO production and iNOS and COX-2 expression, we examined the activations of IkappaBalpha, Akt, and c-Jun NH(2) -terminal kinase (JNK) in LPS-activated macrophages. IOE70 markedly inhibited the phosphorylation of IkappaBalpha, Akt, and MAPKs in dose-dependent manners in LPS-activated macrophages. Taken together, these experiments demonstrated that IOE70 inhibition of LPS-induced expression of iNOS and COX-2 protein is mediated by Akt and JNK. Based on our findings, the most likely mechanism that can account for this biological effect of IOE70 involves the inhibition of NF-kappaB through the phosphatidylinositol 3-kinase/Akt/IkappaB pathway and the inhibition of JNK activation. Thus, IOE70 might have useful clinical applications in the management of inflammatory diseases and may also be useful as a medicinal food.

Toll-like receptor 4 mediates lung ischemia-reperfusion injury

BACKGROUND

We have previously reported that nuclear factor (NF)-kappaB activation and inflammatory cytokine expression were involved in the development of lung ischemia-reperfusion injury (LIRI). Because Toll-like receptor 4 (TLR4) activates NF-kappaB-dependent transcription of inflammatory cytokine genes during myocardial ischemia-reperfusion injury, we examined whether absence of TLR4 in TLR4-deficient mice protects against LIRI.

METHODS

Left lungs of wild-type (C57BL/6J) mice or TLR4-null (TLR4-/-) mice were made ischemic for 60 minutes and then reperfused for 180 minutes. Response to injury was quantified by tissue myeloperoxidase activity, vascular permeability ([125I]-bovine serum albumin extravasation), and leukocyte and inflammatory mediator accumulation in bronchoalveolar lavage expression. Lung homogenates were also analyzed for activation of mitogen-activated protein kinases and nuclear translocation of the transcription factors NF-kappaB and activator protein-1.

RESULTS

After LIRI, lungs from TLR4-/- mice demonstrated a 52.4% reduction in vascular permeability (p = 0.001), a 52.6% reduction in lung myeloperoxidase activity (p = 0.006), and a marked reduction in bronchoalveolar lavage leukocyte accumulation when compared with lungs from wild-type mice. The TLR4-/- mice lungs, subjected to LIRI, also demonstrated marked reductions in amounts of several proinflammatory cytokines/chemokines in bronchoalveolar lavage samples. Phosphorylation of c-Jun NH2-terminal kinase, and activation of NF-kappaB and activator protein-1 were also significantly reduced in homogenates of lungs from TLR4-/- mice injured by ischemia and reperfusion (p < 0.05).

CONCLUSIONS

These data suggest that TLR4 plays a role in LIRI. Thus, TLR4 may be a potential therapeutic target to minimize ischemic-reperfusion-induced tissue damage and organ dysfunction.

Nickel Compounds Render Anti-apoptotic Effect to Human Bronchial Epithelial Beas-2B Cells by Induction of Cyclooxygenase-2 through an IKKβ/p65-dependent and IKKα- and p50-independent Pathway

The carcinogenicity of nickel compounds has been well documented both in vitro and in vivo; however, the molecular mechanisms by which nickel compounds cause cancers are far from understood. Because suppression of apoptosis is thought to contribute to carcinogenesis, we investigated the mechanisms implicated in nickel-induced anti-apoptotic effect in human bronchial epithelial (Beas-2B) cells. We found that exposure of Beas-2B cells to nickel compounds resulted in increased cyclooxygenase-2 (COX-2) expression and that small interfering RNA (siCOX-2) knockdown of COX-2 expression resulted in increased cell sensitivity to nickel-triggered cell apoptosis, demonstrating that COX-2 induction has an anti-apoptotic effect on Beas-2B cells. Overexpression of IKKbeta-KM, a kinase inactive mutant of IKKbeta, blocked NF-kappaB activation and COX-2 induction by nickel compounds, indicating that activated NF-kappaB may be a mediator for COX-2 induction. To further explore the contribution of the NF-kappaB pathway in COX-2 induction and in protection from nickel exposure, mouse embryonic fibroblasts deficient in IKKbeta, IKKalpha, p65, and p50 were analyzed. Loss of IKKbeta impaired COX-2 induction by nickel exposure, whereas knockout of IKKalpha had a marginal effect. Moreover, the NF-kappaB p65, and not the p50 subunit, was critical for nickel-induced COX-2 expression. In addition, a deficiency of IKKbeta or p65 rendered cells more sensitive to nickel-induced apoptosis as compared with those in wild type cells. Finally, it was shown that reactive oxygen species H(2)O(2) were involved in both NF-kappaB activation and COX-2 expression. Collectively, our results demonstrate that COX-2 induction by nickel compounds occurs via an IKKbeta/p65 NF-kappaB-dependent but IKKalpha- and p50-independent pathway and plays a crucial role in antagonizing nickel-induced cell apoptosis in Beas-2B cells.

Prolyl hydroxylase-1 negatively regulates IkappaB kinase-beta, giving insight into hypoxia-induced NFkappaB activity

Hypoxia is a feature of the microenvironment of a growing tumor. The transcription factor NFkappaB is activated in hypoxia, an event that has significant implications for tumor progression. Here, we demonstrate that hypoxia activates NFkappaB through a pathway involving activation of IkappaB kinase-beta (IKKbeta) leading to phosphorylation-dependent degradation of IkappaBalpha and liberation of NFkappaB. Furthermore, through increasing the pool and/or activation potential of IKKbeta, hypoxia amplifies cellular sensitivity to stimulation with TNFalpha. Within its activation loop, IKKbeta contains an evolutionarily conserved LxxLAP consensus motif for hydroxylation by prolyl hydroxylases (PHDs). Mimicking hypoxia by treatment of cells with siRNA against PHD-1 or PHD-2 or the pan-prolyl hydroxylase inhibitor DMOG results in NFkappaB activation. Conversely, overexpression of PHD-1 decreases cytokine-stimulated NFkappaB reporter activity, further suggesting a repressive role for PHD-1 in controlling the activity of NFkappaB. Hypoxia increases both the expression and activity of IKKbeta, and site-directed mutagenesis of the proline residue (P191A) of the putative IKKbeta hydroxylation site results in a loss of hypoxic inducibility. Thus, we hypothesize that hypoxia releases repression of NFkappaB activity through decreased PHD-dependent hydroxylation of IKKbeta, an event that may contribute to tumor development and progression through amplification of tumorigenic signaling pathways.

PRKAR1A Inactivation Leads to Increased Proliferation and Decreased Apoptosis in Human B Lymphocytes

The multiple neoplasia syndrome Carney complex (CNC) is caused by heterozygote mutations in the gene, which codes for the RIalpha regulatory subunit (PRKAR1A) of protein kinase A. Inactivation of PRKAR1A and the additional loss of the normal allele lead to tumors in CNC patients and increased cyclic AMP signaling in their cells, but the oncogenetic mechanisms in affected tissues remain unknown. Previous studies suggested that PRKAR1A down-regulation may lead to increased mitogen-activated protein kinase (MAPK) signaling. Here, we show that, in lymphocytes with PRKAR1A-inactivating mutations, there is increased extracellular signal-regulated kinase (ERK) 1/2 and B-raf phosphorylation and MAPK/ERK kinase 1/2 and c-Myc activation, whereas c-Raf-1 is inhibited. These changes are accompanied by increased cell cycle rates and decreased apoptosis that result in an overall net gain in proliferation and survival. In conclusion, inactivation of PRKAR1A leads to widespread changes in molecular pathways that control cell cycle and apoptosis. This is the first study to show that human cells with partially inactivated RIalpha levels have increased proliferation and survival, suggesting that loss of the normal allele in these cells is not necessary for these changes to occur.

Toll-like receptors and their ligands control mesenchymal stem cell functions

Mesenchymal stem cells (MSCs) are widespread in adult organisms and may be involved in tissue maintenance and repair as well as in the regulation of hematopoiesis and immunologic responses. Thus, it is important to discover the factors controlling MSC renewal and differentiation. Here we report that adult MSCs express functional Toll-like receptors (TLRs), confirmed by the responses of MSCs to TLR ligands. Pam3Cys, a prototypic TLR-2 ligand, augmented interleukin-6 secretion by MSC, induced nuclear factor kappa B (NF-kappaB) translocation, reduced MSC basal motility, and increased MSC proliferation. The hallmark of MSC function is the capacity to differentiate into several mesodermal lineages. We show herein that Pam3Cys inhibited MSC differentiation into osteogenic, adipogenic, and chondrogenic cells while sparing their immunosuppressive effect. Our study therefore shows that a TLR ligand can antagonize MSC differentiation triggered by exogenous mediators and consequently maintains the cells in an undifferentiated and proliferating state in vitro. Moreover, MSCs derived from myeloid factor 88 (MyD88)-deficient mice lacked the capacity to differentiate effectively into osteogenic and chondrogenic cells. It appears that TLRs and their ligands can serve as regulators of MSC proliferation and differentiation and might affect the maintenance of MSC multipotency.

Regulation of NF-kappaB activity and keratinocyte differentiation by the RIP4 protein: implications for cutaneous wound repair

Receptor-interacting proteins (RIPs) are important regulators of cell proliferation and differentiation. As RIP4 is a crucial modulator of epidermal differentiation, we analyzed the expression of different rip genes in healing skin wounds. Rip4 expression was strongly downregulated in keratinocytes of the hyperproliferative epithelium at the wound edge early after injury and only returned to basal levels after completion of wound repair. Rip3 expression was strongly induced as early as 1 day after wounding. In contrast, rip and rip2 expression remained unaltered. To determine the factors that regulate rip4 gene expression in keratinocytes, human HaCaT keratinocytes were used as a model system. We found that scratch wounding as well as treatment with whole serum, phorbol esters, the growth/differentiation factors epidermal growth factor, transforming growth factor-beta, and activin A, or the proinflammatory cytokines tumor necrosis factor-alpha and IL-1beta strongly suppressed rip4 expression in these cells. In contrast, the steroid dexamethasone and all-trans retinoic acid slightly stimulated rip4 expression. Suppression of rip4 expression in keratinocytes using small interfering RNA technology reduced the activation of NF-kappaB, and enhanced the expression of epidermal differentiation markers in these cells. These data suggest important and unique functions of different RIP proteins in keratinocytes of normal and wounded skin.

Ca2+- and protein kinase C-dependent signaling pathway for nuclear factor-kappaB activation, inducible nitric-oxide synthase expression, and tumor necrosis factor-alpha production in lipopolysaccharide-stimulated rat peritoneal macrophages

Lipopolysaccharide (LPS)-activated macrophages are pivotal in innate immunity. With LPS treatment, extracellular signals are transduced into macrophages via Toll-like receptor 4 and induce inflammatory mediator production by activating signaling pathways, including the nuclear factor-kappaB (NF-kappaB) pathway and the mitogen-activated protein kinase (MAPK) pathway. However, the mechanisms by which the intracellular free Ca2+ concentration ([Ca2+]i) increases and protein kinase C (PKC) is activated remain unclear. Therefore, we investigated the signaling pathway for Ca2+- and PKC-dependent NF-kappaB activation, inducible nitric-oxide synthase expression, and tumor necrosis factor-alpha (TNF-alpha) production in LPS-stimulated rat peritoneal macrophages. The results demonstrated that the LPS-induced transient [Ca2+]i increase is due to Ca2+ release and influx. Extracellular and intracellular Ca2+ chelators inhibited phosphorylation of PKCalpha and PKCbeta. A PKCbeta-specific and a general PKC inhibitor blunted phosphorylation of serine in mitogen-activated/extracellular signal-regulated kinase kinase kinase (MEKK) 1. Moreover, a MEKK inhibitor reduced activation of inhibitorykappaB kinase and NF-kappaB. Upstream of the [Ca2+]i increase, a protein-tyrosine kinase inhibitor reduced phosphorylation of phospholipase C (PLC) gamma. Furthermore, a PLC inhibitor eliminated the transient [Ca2+]i increase and decreased the amount of activated PKC. Therefore, these results revealed the following roles of Ca2+ and PKC in the signaling pathway for NF-kappaB activation in LPS-stimulated macrophages. After LPS treatment, protein-tyrosine kinase mediates PLCgamma1/2 phosphorylation, which is followed by a [Ca2+]i increase. Several PKCs are activated, and PKCbeta regulates phosphorylation of serine in MEKK1. Moreover, MEKKs regulate inhibitory kappaB kinase activation. Sequentially, NF-kappaB is activated, and inducible nitric-oxide synthase and tumor necrosis factor-alpha production is promoted.

Differentiation-induced cleavage of Cutl1/CDP generates a novel dominant-negative isoform that regulates mammary gene expression

Cutl1/CCAAT displacement protein (CDP) is a transcriptional repressor of mouse mammary tumor virus (MMTV), a betaretrovirus that is a paradigm for mammary-specific gene regulation. Virgin mammary glands have high levels of full-length CDP (200 kDa) that binds to negative regulatory elements (NREs) to repress MMTV transcription. During late pregnancy, full-length CDP levels decline, and a 150-kDa form of CDP (CDP150) appears concomitantly with a decline in DNA-binding activity for the MMTV NREs and an increase in viral transcripts. Developmental regulation of CDP was recapitulated in the normal mammary epithelial line, SCp2. Western blotting of tissue and SCp2 nuclear extracts confirmed that CDP150 lacks the C terminus. Transfection of tagged full-length and mutant cDNAs into SCp2 cells and use of a cysteine protease inhibitor demonstrated that CDP is proteolytically processed within the homeodomain to remove the C terminus during differentiation. Mixing of virgin and lactating mammary extracts or transfection of mutant CDP cDNAs missing the homeodomain into cells containing full-length CDP also abrogated NRE binding. Loss of DNA binding correlated with increased expression of MMTV and other mammary-specific genes, indicating that CDP150 is a developmentally induced dominant-negative protein. Thus, a novel posttranslational process controls Cutl1/CDP activity and gene expression in the mammary gland.

MMP-9 in B-cell chronic lymphocytic leukemia is up-regulated by alpha4beta1 integrin or CXCR4 engagement via distinct signaling pathways, localizes to podosomes, and is involved in cell invasion and migration

B-cell chronic lymphocytic leukemia (B-CLL) progression is determined by malignant cell extravasation and lymphoid tissue infiltration. We have studied the role and regulation of matrix metalloproteinase-9 (MMP-9) in B-CLL cell migration and invasion. Adhesion of B-CLL cells to the fibronectin fragment FN-H89, VCAM-1, or TNF-alpha-activated human umbilical vein endothelial cells (HUVECs) up-regulated MMP-9 production, measured by gelatin zymography. This effect was mediated by alpha4beta1 integrin and required PI3-K/Akt signaling. The chemokine CXCL12 also up-regulated MMP-9, independently of alpha4beta1 and involving ERK1/2 but not Akt activity. Accordingly, alpha4beta1 engagement activated the PI3-K/Akt/NF-kappaB pathway, while CXCL12/CXCR4 interaction activated ERK1/2/c-Fos signaling. Anti-MMP-9 antibodies, the MMP-9 inhibitor TIMP-1, or transfection with 3 different MMP-9 siRNAs significantly blocked migration through Matrigel or HUVECs. Cell-associated MMP-9 was mainly at the membrane and contained the proactive and mature forms. Moreover, B-CLL cells formed podosomes upon adhesion to FN-H89, VCAM-1, or fibronectin; MMP-9 localized to podosomes in a PI3-K-dependent manner and degraded a fibronectin/gelatin matrix. Our results are the first to show that MMP-9 is physiologically regulated by alpha4beta1 integrin and CXCL12 and plays a key role in cell invasion and transendothelial migration, thus contributing to B-CLL progression. MMP-9 could therefore constitute a target for treatment of this malignancy.

Keratin 17 modulates hair follicle cycling in a TNFalpha-dependent fashion

Mammalian hair follicles cycle between stages of rapid growth (anagen) and metabolic quiescence (telogen) throughout life. Transition from anagen to telogen involves an intermediate stage, catagen, consisting of a swift, apoptosis-driven involution of the lower half of the follicle. How catagen is coordinated, and spares the progenitor cells needed for anagen re-entry, is poorly understood. Keratin 17 (K17)-null mice develop alopecia in the first week post-birth, correlating with hair shaft fragility and untimely apoptosis in the hair bulb. Here we show that this abnormal apoptosis reflects premature entry into catagen. Of the proapoptotic challenges tested, K17-null skin keratinocytes in primary culture are selectively more sensitive to TNFalpha. K17 interacts with TNF receptor 1 (TNFR1)-associated death domain protein (TRADD), a death adaptor essential for TNFR1-dependent signal relay, suggesting a functional link between this keratin and TNFalpha signaling. The activity of NF-kappaB, a downstream target of TNFalpha, is increased in K17-null skin. We also find that TNFalpha is required for a timely anagen-catagen transition in mouse pelage follicles, and that its ablation partially rescues the hair cycling defect of K17-null mice. These findings identify K17 and TNFalpha as two novel and interdependent regulators of hair cycling.

Protein phosphatase 6 subunit with conserved Sit4-associated protein domain targets IkappaBepsilon

Protein Ser/Thr phosphatases compose a PPP family that includes type-2 PP2A, PP4, and PP6, each with essential functions. The human PP6 gene rescues sit4(ts) mutants of Saccharomyces cerevisiae, and Sit4 phosphatase function depends on multiple Sit4-associated protein (SAP) subunits. We report here finding a SAPS sequence domain encoded in only a single gene each in Schizosaccharomyces pombe, Caenorhabditis elegans, and Drosophila but in three distinct open reading frames in Xenopus, Mus musculus, and Homo sapiens. The SAPS proteins are more divergent in sequence than PP6. Northern hybridization showed differential distribution of the human SAPS-related mRNA in multiple human tissues, named as PP6R1, PP6R2, and PP6R3. Antibodies were generated, distribution of endogenous PP6, PP6R1, PP6R2, and PP6R3 proteins was examined by immunoblotting, and the abundance of mRNA and protein in various tissues did not match. FLAG-tagged PP6R1 and PP6R2 expressed in HEK293 cells co-precipitated endogenous PP6, but not PP2A or PP4, showing specificity for recognition of phosphatases. The SAPS domain of PP6R1 alone was sufficient for association with PP6, and this predicts that conserved sequence motifs in the SAPS domain accounts for the specificity. FLAG-PP6R1 and FLAG-PP6R2 co-precipitated HA-IkappaBepsilon. Knockdown of PP6 or PP6R1 but not PP6R3 with siRNA significantly enhanced degradation of endogenous IkappaBepsilon in response to tumor necrosis factor-alpha. The results show SAPS domain subunits recruit substrates such as IkappaBepsilon as one way to determine specific functions for PP6.

Targeting signal transduction as a strategy to treat inflammatory diseases

Inflammatory diseases are a major burden on humanity, despite recent successes with biopharmaceuticals. Lack of responsiveness and resistance to these drugs, delivery problems and cost of manufacture of biopharmaceuticals mean that the search for new anti-inflammatory agents continues. Progress in our understanding of inflammatory signalling pathways has identified new targets, notably in pathways involving NF-kappaB, p38 MAP kinase, T lymphocyte activation and JAK/STAT. Other targets such as transcription factor complexes and components of pathways activated by TNF, Toll-like receptors and Nod-like receptors also present possibilities, and might show efficacy without being limited by effects on host defence. The challenge is to place a value on one target relative to another, and to devise strategies to modulate them.

Cell signaling pathways engaged by KSHV

Kaposi's sarcoma herpesvirus (KSHV) is the eighth human herpesvirus discovered in 1994 from Kaposi's sarcoma lesion of an AIDS patient. The strong molecular and epidemiological links associating KSHV with Kaposi's sarcoma and certain lymphoproliferative disorders indicate that KSHV is required for the development of these malignancies. Although KSHV is equipped to manipulate and deregulate several cellular signaling pathways, it is not yet understood how this leads to cell transformation. Profound understanding of the interplay of viral and cellular factors in KSHV-infected cells will provide valuable information on the mechanisms of viral tumorigenesis and enable development of efficient targeted therapies for virus-induced cancers. This review focuses on the cellular signaling pathways that KSHV gene products impinge on and discusses their putative contribution to tumorigenesis.

Acute exercise stimulates macrophage function: possible role of NF-κB pathways

Moderate physical activity when performed on a regular basis presents a number of benefits to the whole organism, especially regarding immune system function, such as augmenting resistance to infections and to cancer growth. Although glutamine production by active muscle cells as well as neuroendocrine alterations mediated by the chronic adaptation to exercise may play a role, the entire mechanism by which exercise makes the immune system aware of challenges remains mostly uncovered. This is particularly true for the effects of an acute exercise session on immune function. In this work, circulating monocytes/macrophages from sedentary rats submitted to an acute (1 h) swimming session were tested for the ability of phagocytosing zymosan particles, phorbol myristate acetate (PMA)-induced hydrogen peroxide production, nitric oxide (NO) release (assessed by nitrate and nitrite production) and the expression of NO synthases (NOS-1, NOS-2 and NOS-3). The results showed that an exercise bout induced a 2.4-fold rise in macrophage phagocytic capacity (p = 0.0041), a 9.6-fold elevation in PMA-induced hydrogen peroxide release into the incubation media (1-h, p = 0.0022) and a 95.5%-augmentation in nitrite basal production (1-h incubation; p = 0.0220), which was associated with a marked expression of NOS-2 (the inducible NOS isoform; p = 0.0319), but not in other NOS gene products. Although NOS-2 expression is nuclear factor-kappaB (NF-kappaB)-dependent, no systemic oxidative stress was found, as inferred from the data of plasma TBARS and glutathione disulphide (GSSG) to glutathione (GSH) ratio in circulating blood erythrocytes which remained constant after the acute exercise. Also, no stressful situation seemed to be faced by monocytes/macrophages, since the expression of the 70-kDa heat shock protein (HSP70) remained unchanged. We conclude that NF-kappaB-dependent induction of NOS-2 and macrophage activation must be related to local factor(s) produced in the surroundings of monocytes/macrophages.