Flanking sequences for the human intercellular adhesion molecule-1 NF-kappaB response element are necessary for tumor necrosis factor alpha-induced gene expression

Modulation of endothelial cell integrity and inflammatory activation by commercial lipid emulsions

Background

Thrombosis and immune dysfunction are two important complications that result from the administration of parenteral nutrition. Endothelial cells within the vasculature are crucial components necessary for maintenance of normal coagulation and immune function.

Methods

We compared the effects of three commercial lipid emulsions (LEs; Intralipid®, ClinOleic® [or Clinolipid®], and Omegaven®) differing in the levels of omega-6 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, omega-9 monounsaturated fatty acids, and saturated fatty acids upon endothelial cell fatty acid composition using Gas chromatography, endothelial cell integrity by assessing measurement of apoptosis and necrosis using flow cytometry, endothelial cell inflammatory activation by assessing the induction of ICAM-1 by lipopolysaccharide [LPS]), and transcription factor activation (phosphorylation of NF-κB) using western blot analysis.

Results

Gas chromatographic analysis confirmed cellular uptake of the fatty acids within the LEs; furthermore, these fatty acid changes reflected the composition of the oils and egg phosphatides used in the manufacturing of these emulsions. However, the kinetics of fatty acid uptake and processing differed between LEs. Fish oil LE negatively impacted cell viability by doubling the percentage of apoptotic and necrotic cell populations quantified by flow cytometry using Annexin V/Fluorescein and propidium iodide. The soybean oil LE did not alter cell viability, while the olive oil-predominate emulsion improved cell viability. All LEs were capable of suppressing LPS-induced ICAM-1 expression; however, the fish oil LE was more potent than the other emulsions. Fish oil LE supplementation of cells also suppressed LPS-induced phosphorylation of NF-κB, while the soybean oil and olive predominant LE had no effect upon NF-κB phosphorylation.

Conclusions

Lipid emulsions are readily incorporated and stored in the form of triacylglycerols. Soybean oil-based, olive oil-predominant and fish-oil based LEs differentially affected endothelial cell integrity. Importantly, these three LEs were capable of suppressing endothelial cell inflammatory response despite their fatty acid content.

Identification of an NF-κB p50/p65-responsive site in the human MIR155HG promoter

Background

MicroRNA-155 (miR-155) is the diced product of the MIR155HG gene. miR-155 regulates the expression of many immune-specific transcripts, is overexpressed in many human lymphomas, and has oncogenic activity in mouse transgenic models. MIR155HG has been proposed to be a target gene for transcription factor NF-κB largely due to the positive correlation between high nuclear NF-κB activity and increased miR-155 expression following treatment with NF-κB inducers or in subsets of hematopoietic cancers. Nevertheless, direct regulation of the human MIR155HG promoter by NF-κB has not been convincingly demonstrated previously.

Results

This report shows that induction of NF-κB activity rapidly leads to increased levels of both primary MIR155HG mRNA and mature miR-155 transcripts. We have mapped an NF-κB-responsive element to a position approximately 178 nt upstream of the MIR155HG transcription start site. The -178 site is specifically bound by the NF-κB p50/p65 heterodimer and is required for p65-induced reporter gene activation. Moreover, the levels of miR-155 in nine human B-lymphoma cell lines generally correlate with increased nuclear NF-κB proteins.

Conclusion

Overall, the identification of an NF-κB-responsive site in the MIR155HG proximal promoter suggests that MIR155HG is a direct NF-κB target gene in vivo. Understanding NF-κB-mediated regulation of miR-155 could lead to improved immune cell-related diagnostic tools and targeted therapies.

Human lactoferrin suppresses TNF-α-induced intercellular adhesion molecule-1 expression via competition with NF-κB in endothelial cells

Lactoferrin (Lf) is known to have anti-inflammatory activity, but the mechanisms of action by Lf remain to be elucidated. Here, we demonstrated that TNF-α-induced expression of intercellular adhesion molecule-1 (ICAM-1) was down-regulated by Lf in a DNA-binding dependent manner at transcriptional level in endothelial cells. Our results showed that Lf bound to a DNA region in the ICAM-1 promoter in vitro as well as in chromatin context. Lf inhibited binding of NF-κB to a proximal NF-κB site in ICAM-1 promoter. This type of repression represents an additional mechanism for the action of Lf in regulation of gene expression.

Single nucleotide changes in the human Igamma1 and Igamma4 promoters underlie different transcriptional responses to CD40

Analysis of subclass-specific germline transcription in activated peripheral B cells revealed a highly biased expression pattern of the four Igamma transcripts to signals through CD40 and IL-4. This difference was most pronounced when comparing the profile of Igamma1 and Igamma4 transcripts and was not expected given the very high degree of sequence conservation between promoters. In this report, the influence of sequence differences on the regulation of the Igamma1 and Igamma4 promoters has been investigated given the highly muted transcriptional activity of the Igamma4 promoter. Two regions were analyzed where single nucleotide differences corresponded to major changes in transcriptional activity. These regions were the previously defined CD40 response region containing three putative NF-kappaB-binding sites and the downstream 36-bp region containing CREB/activating transcription factor and kappaB6 sites. Mutation of a single nucleotide at position 6 within the Igamma4 kappaB6 site increased promoter activity to approximately 50% of the activity of the Igamma1 promoter. Furthermore, elevated promoter strength corresponded with increased binding of p50, p65, c-Rel, RelB, and p300 proteins to a level comparable with that of Igamma1. Minor nucleotide changes to both the Igamma4 CD40 response region and the 36-bp element resulted in a response undistinguishable from an Igamma1 response, suggesting cooperation between the two regulatory regions for optimal transcriptional activity. Collectively, these mutational analyses suggest that minor sequence differences contribute to the composition and affinity of transcriptional protein complexes regulating subclass-specific germline transcription, which in part impacts the overall level of class switch recombination to targeted C(H) regions.

Regulation of bacteria-induced intercellular adhesion molecule-1 by CCAAT/enhancer binding proteins

Direct interaction between bacteria and epithelial cells may initiate or amplify the airway response through induction of epithelial defense gene expression by nuclear factor-kappaB (NF-kappaB). However, multiple signaling pathways modify NF-kappaB effects to modulate gene expression. In this study, the effects of CCAAT/enhancer binding protein (C/EBP) family members on induction of the leukocyte adhesion glycoprotein intercellular adhesion molecule-1 (ICAM-1) was examined in primary cultures of human tracheobronchial epithelial cells incubated with nontypeable Haemophilus influenzae. Increased ICAM-1 gene transcription in response to H. influenzae required gene sequences located at -200 to -135 in the 5'-flanking region that contain a C/EBP-binding sequence immediately upstream of the NF-kappaB enhancer site. Constitutive C/EBPbeta was found to have an important role in epithelial cell ICAM-1 regulation, while the adjacent NF-kappaB sequence binds the RelA/p65 and NF-kappaB1/p50 members of the NF-kappaB family to induce ICAM-1 expression in response to H. influenzae. The expression of C/EBP proteins is not regulated by p38 mitogen-activated protein kinase activation, but p38 affects gene transcription by increasing the binding of TATA-binding protein to TATA-box-containing gene sequences. Epithelial cell ICAM-1 expression in response to H. influenzae was decreased by expressing dominant-negative protein or RNA interference against C/EBPbeta, confirming its role in ICAM-1 regulation. Although airway epithelial cells express multiple constitutive and inducible C/EBP family members that bind C/EBP sequences, the results indicate that C/EBPbeta plays a central role in modulation of NF-kappaB-dependent defense gene expression in human airway epithelial cells after exposure to H. influenzae.

AIDS: caused by development of resistance to drugs in a non-target intracellular parasite

The origin of acquired immune disorder syndrome (AIDS) has been the subject of substantial controversy both in the scientific community and in the popular press. The debate involves the mode of transmission of a simian virus (SIV) to humans. Both major camps in the argument presume that humans are normally free of such viruses and assume that once the simian virus was transmitted, it immediately infected some T-cells and caused the release of toxic agents that killed off bystander (uninfected) T-cells resulting in AIDS. The evolution of the Simian virus (SIV) into a human virus (HIV) is regarded as an artifact. In contrast, a fundamentally different hypothesis has been proposed [Parris GE. Med Hypotheses 2004;62(3):354–7] in which it is presumed that in hyper-endemic areas of malaria (central Africa), all primates (humans and non-human primates) have shared a retrovirus that augments their T-cell response to the malaria parasite. The virus can be called “primate T-cell retrovirus” (PTRV). Over thousands of years the virus has crossed species lines many times (with little effect) and typically adapts to the host quickly. In this model, AIDS is seen to be the result of the development of resistance of the virus (PTRV) to continuous exposure to pro-apoptotic (schizonticidal) aminoquinoline drugs used to prevent malaria. The hypothesis was originally proposed based on biochemical activities of the aminoquinolines (e.g., pamaquine (plasmoquine(TM)), primaquine and chloroquine), but recent publications demonstrated that some of these drugs definitely adversely affect HIV and other viruses and logically would cause them to evolve resistance. Review of the timeline that has been created for the evolution of HIV in humans is also shown to be qualitatively and quantitatively consistent with this hypothesis (and not with either version of the conventional hypothesis). SARS and Ebola also fit this pattern.

Persistent interleukin-1beta signaling causes long term activation of NFkappaB in a promoter-specific manner in human glial cells

Nuclear factor-kappaB (NFkappaB) is an inducible transcription factor that plays a key role in regulating the expression of a wide range of immune and inflammatory response genes. The activity of NFkappaB is controlled at multiple levels, including cytoplasmic retention with inhibitor of kappaB (IkappaB) proteins in the basal state. Persistent activation of the transcription factor is seen in numerous chronic inflammatory disease states, and we have previously demonstrated sustained activation of NFkappaB in human glial cells upon stimulation with interleukin (IL)-1beta. In these cells, NFkappaB retains DNA binding activity for up to 72 h despite the presence of resynthesized IkappaBalpha and in the absence of IkappaBbeta. Here we characterized the apparent inability of newly synthesized IkappaBalpha to terminate activation of NFkappaB in glial cells. We showed unexpectedly that newly synthesized IkappaBalpha can enter the nucleus, interact with the NFkappaB subunit p65, and export it to the cytoplasm. However, in vitro analysis of enzyme activity demonstrates that IL-1beta causes the long term activation of the IkappaB kinase complex leading to chronic phosphorylation of the newly synthesized IkappaBalpha signal response domain and persistent activation of NFkappaB. Such sustained activation of NFkappaB is dependent on the continuous presence and activity of IL-1beta. Interestingly, the sustained nature of NFkappaB activity is promoter type-specific. Chromatin immunoprecipitation studies revealed that p65 is detected at the promoters of both intercellular adhesion molecule-1 and IL-8 1 h following IL-1beta stimulation but is only found at the latter at 24 h. The functional significance of this finding is indicated by the transient induction of intercellular adhesion molecule-1 mRNA, but more sustained induction of IL-8 expression, by IL-1beta. These studies thus demonstrated that persistent IL-1 signaling causes sustained activation of NFkappaB in a promoter-specific manner in human glial cells, leading to prolonged induction of selective pro-inflammatory genes. This is likely to make a key contribution to chronic inflammatory conditions of the brain.

A c-Rel subdomain responsible for enhanced DNA-binding affinity and selective gene activation

The NF-kappaB family members p65 (RelA) and c-Rel recognize similar DNA sequences, yet the phenotypes of mutant mice suggest that these proteins regulate distinct sets of genes. Here we demonstrate that 46 unique residues within an 86-residue segment of the Rel homology region (RHR) of c-Rel are responsible for the c-Rel requirement for Il12b gene induction by lipopolysaccharide in bone marrow-derived macrophages. These same residues were responsible for the c-Rel requirement for Il12a induction in dendritic cells, and in both instances, no evidence of c-Rel-specific coactivator interactions was found. Although the residues of c-Rel and p65 that contact specific bases and the DNA backbone within nuclear factor-kappaB (NF-kappaB) recognition sequences are identical, homodimers of c-Rel and of a chimeric p65 protein containing the critical c-Rel residues bound with high affinity to a broader range of NF-kappaB recognition sequences than did wild-type p65 homodimers. These results demonstrate that the unique functions of closely related transcription factor family members can be dictated by differences in the range of DNA sequences recognized at high affinity, despite having similar binding site consensus sequences and DNA contact residues.

TNFalpha suppresses human colonic circular smooth muscle cell contractility by SP1- and NF-kappaB-mediated induction of ICAM-1

BACKGROUND & AIMS

Intercellular adhesion molecule 1 (ICAM-1) receptors are expressed at low levels on human colonic circular smooth muscle cells (HCCSMCs) and their expression is increased in patients with Crohn's disease. We investigated the roles of transcription factors Sp1 and nuclear factor kappa B (NF-kappaB) in the regulation of ICAM-1 expression on HCCSMCs and examined whether ICAM-1 expression mediates the suppression of contractility in response to TNFalpha.

METHODS

Experiments were performed on primary cultures of HCCSMCs and fresh human colonic circular muscle strips.

RESULTS

TNFalpha treatment of HCCSMCs induced rapid and prolonged accumulation of ICAM-1 messenger RNA (mRNA) and protein. NF-kappaB inhibition before, but not after, 1 hour of TNFalpha-stimulation blocked the expression of ICAM-1. TNFalpha significantly enhanced Sp1/DNA binding. Sp1 bound to the 3' flanking region of a variant kappaB site in the -192/-172 region of ICAM-1 promoter. Mutation of this region abolished the response to TNFalpha. The treatment of HCCSMCs with Sp1 antisense oligonucleotides (ODNs) blocked the expression of ICAM-1, but sense ODNs had no effect. Protein kinase C zeta (PKCzeta) inhibition before or 3 hours after stimulation with TNFalpha also blocked the expression of ICAM-1. TNFalpha treatment of circular muscle strips pretreated with ICAM-1 sense ODNs or control medium significantly reduced their response to acetylcholine, whereas pretreatment with antisense ODNs blocked this effect.

CONCLUSIONS

The expression of ICAM-1 on HCCSMCs in response to TNFalpha is regulated by transcription factors Sp1 and NF-kappaB binding independently to the -192/-172 region of the ICAM-1 promoter. The expression of ICAM-1 plays a critical role in the suppression of cell contractility in response to TNFalpha.

TNF-alpha-induced increase in intestinal epithelial tight junction permeability requires NF-kappa B activation

Crohn's disease (CD) patients have an abnormal increase in intestinal epithelial permeability. The defect in intestinal tight junction (TJ) barrier has been proposed as an important etiologic factor of CD. TNF-alpha increases intestinal TJ permeability. Because TNF-alpha levels are markedly increased in CD, TNF-alpha increase in intestinal TJ permeability could be a contributing factor of intestinal permeability defect in CD. Our purpose was to determine some of the intracellular mechanisms involved in TNF-alpha modulation of intestinal epithelial TJ permeability by using an in vitro intestinal epithelial system consisting of filter-grown Caco-2 monolayers. TNF-alpha produced a concentration- and time-dependent increase in Caco-2 TJ permeability. TNF-alpha-induced increase in Caco-2 TJ permeability correlated with Caco-2 NF-kappa B activation. Inhibition of TNF-alpha-induced NF-kappa B activation by selected NF-kappa B inhibitors, curcumin and triptolide, prevented the increase in Caco-2 TJ permeability, indicating that NF-kappa B activation was required for the TNF-alpha-induced increase in Caco-2 TJ permeability. This increase in Caco-2 TJ permeability was accompanied by down-regulation of zonula occludens (ZO)-1 proteins and alteration in junctional localization of ZO-1 proteins. TNF-alpha modulation of ZO-1 protein expression and junctional localization were also prevented by NF-kappa B inhibitors. TNF-alpha did not induce apoptosis in Caco-2 cells, suggesting that apoptosis was not the mechanism involved in TNF-alpha-induced increase in Caco-2 TJ permeability. These results demonstrate for the first time that TNF-alpha-induced increase in Caco-2 TJ permeability was mediated by NF-kappa B activation. The increase in permeability was associated with NF-kappa B-dependent downregulation of ZO-1 protein expression and alteration in junctional localization.

IL-6 induces NF-kappa B activation in the intestinal epithelia

IL-6 is a potent proinflammatory cytokine that has been shown to play an important role in the pathogenesis of inflammatory bowel disease (IBD). It is classically known to activate gene expression via the STAT-3 pathway. Given the crucial role of IL-6 in the pathogenesis of chronic intestinal inflammation, it is not known whether IL-6 activates NF-kappaB, a central mediator of intestinal inflammation. The model intestinal epithelial cell line, Caco2-BBE, was used to study IL-6 signaling and to analyze whether suppressor of cytokine signaling 3 (SOCS-3) proteins play a role in the negative regulation of IL-6 signaling. We show that IL-6 receptors are present in intestinal epithelia in a polarized fashion. Basolateral IL-6 and, to a lesser extent, apical IL-6 induces the activation of the NF-kappaB pathway. Basolateral IL-6 stimulation results in a maximal induction of NF-kappaB activation and NF-kappaB nuclear translocation at 2 h. IL-6 induces polarized expression of ICAM-1, an adhesion molecule shown to be important in the neutrophil-epithelial interactions in IBD. Using various deletion constructs of ICAM-1 promoter, we show that ICAM-1 induction by IL-6 requires the activation of NF-kappaB. We also demonstrate that overexpression of SOCS-3, a protein known to inhibit STAT activation in response to IL-6, down-regulates IL-6-induced NF-kappaB activation and ICAM-1 expression. In summary, we demonstrate the activation of NF-kappaB by IL-6 in intestinal epithelia and the down-regulation of NF-kappaB induction by SOCS-3. These data may have mechanistic and therapeutic implications in diseases such as IBD and rheumatoid arthritis in which IL-6 plays an important role in the pathogenesis.

Iron chelators inhibit VCAM-1 expression in human dermal microvascular endothelial cells

Vascular cell adhesion molecule (VCAM)-1 expression may be coupled to redox-sensitive regulatory pathways, and iron may play a role in generation of reactive oxygen species that participate in these signaling pathways. To investigate the role of iron in TNF alpha-induced VCAM-1 gene expression, human dermal microvascular endothelial cells (HDMEC) were stimulated with TNF alpha in the presence of iron chelators and examined for expression of VCAM-1. The iron chelators dipyridyl (DP) and desferoxamine (DFO) inhibited VCAM-1 protein and mRNA induction in a concentration- and time-dependent manner. The induction of VCAM-1 was not inhibited by nonmetal binding reactive oxygen species (ROS) scavengers, implying a direct effect of iron in the expression of these adhesion molecules. The effect of iron was mediated at the level of gene transcription since pretreatment with DP abrogated the TNF alpha-mediated up-regulation of VCAM-1 heterogeneous nuclear RNA. Pretreatment of HDMEC with DP prior to TNFalpha treatment had no effect on p65 nuclear localization, DNA binding, or serine phosphorylation. DP pretreatment inhibited TNF alpha- and IFN gamma-mediated interferon regulatory factor 1 (IRF-1) protein expression, although restoration of IRF-1 expression failed to reconstitute VCAM-1 expression. DP treatment also blocked VCAM-1 induction in human umbilical vein endothelium and blocked induction of a host of NF-kB activated genes in HDMEC including ICAM-1, IL-8, and tissue factor. I kappa B alpha, an NF-kappa B inducible and constitutively accessible gene not requiring chromatin remodeling for transcription, was not affected by DP treatment. These data suggest that iron plays a critical role in TNF alpha mediated VCAM-1 induction in HDMEC, and the target for iron effects may be IRF-1, NF-kappa B, and potentially chromatin remodeling.

The adhesion molecule ICAM-1 and its regulation in relation with the blood-brain barrier

The blood-brain barrier (BBB) is formed by high resistance tight junctions within the capillary endothelium perfusing the vertebrate brain. Normal BBB maintains a unique microenvironment within the central nervous system (CNS). In neurodegenerative disorders (for example multiple sclerosis, MS), the BBB becomes impaired. Perivascular cells (astrocytes, macrophages and microglial cells) and brain microvascular endothelial cells (BMEC) produce various inflammatory factors that affect the BBB permeability and the expression of adhesion molecules. Indeed, cytokines can stimulate the expression of several adhesion molecules on brain microvascular endothelial cells. Among these adhesion molecules, the intercellular adhesion molecule-1 (ICAM-1) binds to its leukocyte ligands and allows activated leukocytes entry into the CNS. This review is dealing with the expression and regulation of ICAM-1 in relation with several properties of the BBB. Particularly, the role of ICAM-1 in the control of the leukocyte traffic into the CNS, as well as in cerebral malaria and in CNS infection by viruses, is discussed.

Role of neutrophil NADPH oxidase in the mechanism of tumor necrosis factor-alpha -induced NF-kappa B activation and intercellular adhesion molecule-1 expression in endothelial cells

In this study, we explored a novel function of polymorphonuclear neutrophils (PMN) NAD(P)H oxidase in the mechanism of tumor necrosis factor-alpha (TNFalpha)-induced NF-kappaB activation and intercellular adhesion molecule-1 (ICAM-1) expression in endothelial cells. Studies were made in mice lacking the p47(phox) subunit of NAD(P)H oxidase as well as in cultured mouse lung vascular endothelial cells (MLVEC) from these mice. In response to TNFalpha challenge, NF-kappaB activation and ICAM-1 expression were significantly attenuated in lungs of p47(phox)(-/-) mice as compared with wild-type (WT) mice. The attenuated NF-kappaB activation in p47(phox)(-/-) mice was secondary to inhibition of NIK activity and subsequent IkappaBalpha degradation. Induction of neutropenia using anti-PMN serum prevented the initial TNFalpha-induced NF-kappaB activation and ICAM-1 expression in WT mice, indicating the involvement of PMN NAD(P)H oxidase in signaling these responses. Moreover, the responses were restored upon repletion with PMN obtained from WT mice but not with PMN from p47(phox)(-/-) mice. These findings were recapitulated in MLVEC co-cultured with PMN, suggesting that NF-kappaB activation and resultant ICAM-1 expression in endothelial cells occurred secondary to oxidants generated by the PMN NAD(P)H oxidase complex. The functional relevance of the PMN NAD(P)H oxidase in mediating TNFalpha-induced ICAM-1-dependent endothelial adhesivity was evident by markedly reduced adhesion of p47(phox)(-/-) PMN in co-culture experiments. Thus, oxidant signaling by the PMN NAD(P)H oxidase complex is an important determinant of TNFalpha-induced NF-kappaB activation and ICAM-1 expression in endothelial cells.

Tumor necrosis factor alpha-induced activation of downstream NF-kappaB site of the promoter mediates epithelial ICAM-1 expression and monocyte adhesion. Involvement of PKCalpha, tyrosine kinase, and IKK2, but not MAPKs, pathway

TNF-alpha induced an increase in intercellular adhesion molecule-1 (ICAM-1) expression in human A549 epithelial cells and immunofluorescence staining confirmed this result. The enhanced ICAM-1 expression was shown to increase the adhesion of U937 cells to A549 cells. Tyrosine kinase inhibitors (genistein or tyrphostin 23) or phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor (D 609) attenuated TNF-alpha-induced ICAM-1 expression. TNF-alpha produced an increase in protein kinase C (PKC) activity and this effect was inhibited by D 609. PKC inhibitors (staurosporine, Ro 31-8220, calphostin C, or Go 6976) also inhibited TNF-alpha-induced response. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a PKC activator, stimulated ICAM-1 expression, this effect was inhibited by genistein or tyrphostin 23. Treatment of cells with TNF-alpha resulted in stimulation of p44/42 MAPK, p38, and JNK. However, TNF-alpha-induced ICAM-1 expression was not affected by either MEK inhibitor, PD 98059, or p38 inhibitor, SB 203580. A cell-permeable ceramide analog, C(2) ceramide, also stimulated the activation of these three MAPKs, but had no effect on ICAM-1 expression. NF-kappaB DNA-protein binding and ICAM-1 promoter activity were enhanced by TNF-alpha and these effects were inhibited by D 609, calphostin C, or tyrphostin 23, but not by PD 98059 or SB 203580. TPA also stimulated NF-kappaB DNA-protein binding and ICAM-1 promoter activity, these effects being inhibited by genistein or tyrphostin 23. TNF-alpha- or TPA-induced ICAM-1 promoter activity was inhibited by dominant negative PKCalpha or IKK2, but not IKK1 mutant. IKK activity was stimulated by both TNF-alpha and TPA, and these effects were inhibited by Ro 31-8220 or tyrphostin 23. These data suggest that, in A549 cells, TNF-alpha activates PC-PLC to induce activation of PKCalpha and protein tyrosine kinase, resulting in the stimulation of IKK2, and NF-kappaB in the ICAM-1 promoter, then initiation of ICAM-1 expression and neutrophil adhesion. However, activation of p44/42 MAPK, p38, and JNK is not involved in this event.

Characterization of intercellular adhesion molecule-1 regulation by Epstein-Barr virus-encoded latent membrane protein-1 identifies pathways that cooperate with nuclear factor kappa B to activate transcription

The latent membrane protein-1 (LMP1) of Epstein-Barr virus induces gene transcription, phenotypic changes, and oncogenic transformation. One cellular gene induced by LMP1 is that for intercellular adhesion molecule-1 (ICAM-1), which participates in a wide range of inflammatory and immune responses. ICAM-1 may enhance the immune recognition of cells transformed by Epstein-Barr virus, and thus combat development of malignancy. Despite growing understanding of the various signaling functions of LMP1, the molecular mechanisms by which LMP1 induces ICAM-1 are not understood. Here, we demonstrate that transcriptional activation by LMP1 is absolutely dependent upon a variant NF-kappaB motif within the tumor necrosis factor alpha (TNFalpha) response element of the ICAM-1 promoter. Although the TNFalpha response element is sufficient for TNFalpha induction of the ICAM-1 promoter, LMP1 also required the cooperation of additional upstream sequences for optimal induction. Inhibitor studies of known LMP1-induced signaling pathways ruled out the involvement of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase, and the Janus-activating tyrosine kinase 3 (JAK3), and confirmed NF-kappaB as a critical factor for induction of ICAM-1. However, although constitutive activation of NF-kappaB efficiently induced promoter activity, it was not sufficient to induce either ICAM-1 mRNA or ICAM-1 protein. Using signaling defective LMP1 mutants and deacetylation inhibitors, we showed that the C-terminal activator region 1 of LMP1 delivers a new cooperating signal to induce ICAM-1 mRNA.

Protein kinase calpha but not p44/42 mitogen-activated protein kinase, p38, or c-Jun NH(2)-terminal kinase is required for intercellular adhesion molecule-1 expression mediated by interleukin-1beta: involvement of sequential activation of tyrosine kinase, nuclear factor-kappaB-inducing kinase, and IkappaB kinase 2

IL-1beta induced an increase in ICAM-1 expression in human A549 epithelial cells and immunofluorescence staining confirmed this result. Tyrosine kinase inhibitors (genistein or tyrphostin 23) or phosphatidylcholine-specific phospholipase C inhibitor (D609) attenuated IL-1beta-induced ICAM-1 expression. IL-1beta produced an increase in PKC activity and this effect was abolished by D609. PKC inhibitors (staurosporine, Ro 31-8220, calphostin C, or Go 6976) also inhibited IL-1beta-induced response. TPA, a PKC activator, stimulated ICAM-1 expression as well, this effect being inhibited by tyrosine kinase inhibitors. Treatment of cells with IL-1beta resulted in stimulation of p44/42 MAPK, p38, and JNK. However, neither the mitogen activated protein kinase kinase inhibitor PD 98059 nor the p38 inhibitor SB 203580 affected IL-1beta-induced ICAM-1 expression. NF-kappaB DNA-protein binding and ICAM-1 promoter activity were enhanced by IL-1beta and these effects were inhibited by tyrphostin 23, but not by PD 98059 or SB 203580. TPA also stimulated NF-kappaB DNA-protein binding and ICAM-1 promoter activity as well, these effects being inhibited by tyrosine kinase inhibitors. Dominant-negative PKCalpha, NIK, or IKK2, but not IKK1 mutant, inhibited IL-1beta- or TPA-induced ICAM-1 promoter activity. IKK activity was stimulated by either IL-1beta or TPA, and these effects were inhibited by Ro 31-8220 or tyrphostin 23. Taken together, IL-1beta activates phosphatidylcholine-specific phospholipase C and induces activation of PKCalpha and protein tyrosine kinase, resulting in the stimulation of NIK, IKK2, and NF-kappaB in the ICAM-1 promoter, then initiation of ICAM-1 expression. However, activation of p44/42 MAPK, p38, and JNK is not involved.

Neural regulation of endothelial cell-mediated inflammation

There is increasing evidence that the cutaneous neurosensory system can directly modulate inflammatory responses in the skin by the release of neuropeptides such as substance P (SP). Dermal microvascular endothelial cell (DMEC) cellular adhesion molecule (CAM) expression plays a key role in directing leukocyte trafficking during cutaneous inflammatory responses. In recent studies, our laboratory examined the direct effect of SP on DMEC CAM expression and function in vitro and in vivo. Our studies indicate that DMEC express high affinity functional receptors for SP. After exposure to SP, DMEC expressed significant levels of both intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), which was accompanied by increased binding to leukocytes expressing the appropriate integrin counter receptors for these CAM. We then determined the in vivo effect of released neuropeptides on DMEC CAM expression. Our results indicate that the topical cutaneous application of the neuropeptide-releasing agent capsaicin resulted in increased ICAM-1 and VCAM-1 immunostaining of microvascular cells in the skin of human volunteers. Little is known regarding the cellular regulatory events by which SP modulates DMEC CAM expression. Our studies indicate that SP-induced cellular Ca+2 signals led to the activation of the NF-kappaB pathway, resulting in nuclear translocation of p65/p50 heterodimers that bind to high-affinity tandem kappaB sites on the VCAM-1 promoter, whereas SP activation induced NF-AT activation and ICAM-1 DNA binding. Thus, these studies further support the role of the cutaneous neurologic system in modulating inflammatory processes in the skin.

Characterisation of NF-kappa B complexes in Theileria parva-transformedT cells

Transformation of T cells by the intracellular parasite Theileria parva is accompanied by constitutive I-kappa B degradation and NF-kappa B activation, a process which is essential to prevent the spontaneous apoptosis of these parasite-transformed cells. NF-kappa B-mediated responses are regulated by selective combinations of NF-kappa B proteins as homo- or heterodimers and by distinct kappa B motifs. We characterised the NF-kappa B complexes induced by T. parva infection in TpM(803) T cells. By western blot, we demonstrated that all members of the NF-kappa B/Rel family of proteins translocate to the nucleus of infected cells. Using two different kappa B oligonucleotides (kappa B-1 and kappa B-2), both containing the decameric consensus kappa B motif (GGGACTTTCC), clearly distinct patterns of DNA binding activities could be demonstrated in electrophoretic mobility shift assays. Supershift analysis and UV cross-linking assays showed that complexes binding to kappa B-1 consisted of p50, p65 and RelB homo and/or heterodimers. We could also detect an association of ATF-2 and c-Fos with one of the complexes. The HIV-derived kappa B-2 oligo only bound p50 and p65. Additionally, several agents known to inhibit a wide range of NF-kappa B activation pathways had no inhibitory effect on the activation of NF-kappa B DNA binding in TpM(803) T cells.

Substance P Activates Coincident NF-AT- and NF-κB-Dependent Adhesion Molecule Gene Expression in Microvascular Endothelial Cells Through Intracellular Calcium Mobilization

Upon stimulation, cutaneous sensory nerves release neuropeptides such as substance P (SP), which modulate responses in the skin by activating a number of target cells via neurokinin receptors. We have demonstrated that SP preferentially binds to the NK-1R on human dermal microvascular cells, resulting in increased intracellular Ca2+ and induction of ICAM-1 and VCAM-1 expression. In the current studies, we identify specific elements in the regulatory regions of ICAM-1 and VCAM-1 genes as necessary and sufficient for SP-dependent transcriptional activation. SP treatment of human dermal microvascular endothelial cells leads to coincident activation and binding of the transcription factor NF-AT to the −191/−170 region of the ICAM-1 gene (a region bound by activated p65/p65 homodimers in response to TNF-α), and NF-κB (p65/p50) to tandem NF-κB binding sites at −76/−52 of the VCAM-1 gene. The SP-elicited intracellular Ca2+ signal was required for activation and subsequent binding of both NF-AT and NF-κB. The transacting factor induction by SP was specific, since a selective NK-1R antagonist blocked SP activation and subsequent NF-AT and NF-κB activation and binding. These data demonstrate coincident activation of NF-AT and NF-κB via SP-induced intracellular Ca2+ mobilization and indicate a crucial role for neuropeptides in modulating localized cutaneous inflammatory responses.

Critical flanking sequences of PU.1 binding sites in myeloid-specific promoters

The myeloid-specific transcription factor PU.1 is essential for expression of p47(phox), a component of the superoxide-forming phagocyte NADPH oxidase. The consensus PU.1 binding sequence (GAGGAA) is located on the non-coding strand from position -40 to -45 relative to the transcriptional start site of the p47phox promoter. A promoter construct extending to -46 was sufficient to drive tissue-specific expression of the luciferase reporter gene, but extension of the promoter from -46 to -48 resulted in a significant increase in reporter expression. Mutations of the nucleotides G at -46 and/or T at -47 reduced both reporter expression and PU.1 binding, whereas mutations at -48 had no effect. The PU.1 binding avidity of these sequences correlated closely with their capacity to dictate reporter gene transcription. In parallel studies on the functional PU.1 site in the promoter of CD18, mutations of nucleotides G and T at positions -76 and -77 (corresponding to -46 and -47, respectively, of the p47phox promoter) reduced PU.1 binding and nearly abolished the contribution of this element to promoter activity. We conclude that the immediate flanking nucleotides of the PU.1 consensus motif have significant effects on PU.1 binding avidity and activity and that this region is the dominant cis element regulating p47phox expression.

Adenovirus-mediated overexpression of c-Jun and c-Fos induces intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 in human endothelial cells

As distal targets and mediators of signal transduction pathways, activator protein-1 (AP-1), c-Jun, and c-Fos are among the primary regulators of genes involved in cell function, proliferation, and differentiation. By using adenovirus-mediated gene transfer, we show that overexpression of AP-1 proteins directly causes coinduction of gene expression of an adhesion molecule, intercellular adhesion molecule-1 (ICAM-1), and a chemokine, monocyte chemoattractant protein-1 (MCP-1), in human vascular endothelial cells (ECs). The AP-1-induced gene expression occurs through a mechanism independent of nuclear factor-kappaB. Because the induced expression of ICAM-1 and MCP-1 in ECs has been implicated in endothelial activation and a number of important vascular disorders, it is suggested that AP-1 activation may play an important role in the pathogeneses of inflammation, angiogenesis, and atherogenesis.

IL-4 Preferentially Activates a Novel STAT6 Isoform in Mast Cells

IL-4 is a pleiotropic cytokine that signals through STAT6 to direct the transactivation of multiple gene targets. In this study, we demonstrate that mast cells express a distinct STAT6 isoform. This “mast cell STAT” is a product of the STAT6 gene, but is only 65 kDa in size and appears to lack the defined C-terminal transactivation domain. Despite the presence of the conventional 94-kDa STAT6 molecule, it is the smaller isoform that associates with a consensus STAT6 binding site in extracts from IL-4-treated mast cells. This is the first evidence that STAT6 isoforms can be preferentially activated and bind to DNA in a cell-specific manner. These results imply that an additional level of specificity in the IL-4R signaling mechanism exists and may partially explain the diverse effects that IL-4 exerts on different cell types.

Genomic organization, sequence analysis and transcriptional regulation of the human MCP-4 chemokine gene (SCYA13) in dermal fibroblasts: a comparison to other eosinophilic beta-chemokines

The eosinophil chemotactic beta-chemokine MCP-4 is assumed to be involved in the accumulation of eosinophils characteristic for eosinophilic inflammatory diseases. We here describe the genomic organisation (3 exons of 138, 115 and 578 bp, 2 introns of 867 and 437 bp and 1.4 kb of regulatory sequences from the immediate 5' upstream region), sequence (genomic and transcribed) and mRNA expression of the human MCP-4 gene in dermal fibroblasts. Among the promoter elements potentially regulating MCP-4 gene expression and/or mediating the effects of anti-inflammatory drugs we identified consensus sequences known to interact with nuclear factors like NF-IL6, AP-2, a NF-kappaB like consensus sequence, gamma-interferon- response and YY-1 elements as well as glucocorticoid response elements. Like MCP-3, MCP-4 mRNA expression in dermal fibroblasts is upregulated by TNF-alpha, IL-1alpha, IFN-gamma or IL-4 and differs from RANTES and eotaxin mRNA expression in its response to IFN-gamma and/or IL-4.

New Insights into the Role of Nuclear Factor-κB, a Ubiquitous Transcription Factor in the Initiation of Diseases

Nuclear factor-κB (NF-κB) is a ubiquitous transcription factor that governs the expression of genes encoding cytokines, chemokines, growth factors, cell adhesion molecules, and some acute phase proteins in health and in various disease states. NF-κB is activated by several agents, including cytokines, oxidant free radicals, inhaled particles, ultraviolet irradiation, and bacterial or viral products. Inappropriate activation of NF-κB has been linked to inflammatory events associated with autoimmune arthritis, asthma, septic shock, lung fibrosis, glomerulonephritis, atherosclerosis, and AIDS. In contrast, complete and persistent inhibition of NF-κB has been linked directly to apoptosis, inappropriate immune cell development, and delayed cell growth. Therefore, development of modulatory strategies targeting this transcription factor may provide a novel therapeutic tool for the treatment or prevention of various diseases.

Neuropeptide regulation of human dermal microvascular endothelial cell ICAM-1 expression and function

There is increasing evidence that sensory nerves may participate in cutaneous inflammatory responses by the release of neuropeptides such as substance P (SP). We examined the direct effect of SP on human dermal microvascular endothelial cell (HDMEC) intercellular adhesion molecule 1 (ICAM-1) expression and function. Our results indicated that, although cultured HDMEC expressed mRNA for neurokinin receptors 1, 2, and 3 (NK-1R, NK-2R, and NK-3R), SP initiated a rapid increase in HDMEC intracellular Ca2+ levels, primarily by the activation of NK-1R. Immunohistochemistry studies likewise demonstrated that HDMEC predominantly expressed NK-1R. The addition of SP to HDMEC resulted in a rapid increase in cellular ICAM-1 mRNA levels, followed by a fivefold increase in ICAM-1 cell surface expression. This functionally resulted in a threefold increase in 51Cr-labeled binding of J-Y lymphoblastoid cells to HDMEC. In vivo studies demonstrated a marked increase in microvascular ICAM-1 immunostaining 24 and 48 h after application of capsaicin to the skin. These results indicate that neuropeptides such as SP are capable of directly activating HDMEC to express increased levels of functional ICAM-1 and further support the role of the cutaneous neurological system in modulating inflammatory processes in the skin.

Chronic blockade of NO synthase activity induces a proinflammatory phenotype in the arterial wall: prevention by angiotensin II antagonism

Chronic blockade of NO production induces hypertension and early occlusive and fibrotic end-stage organ damage owing to vascular lesions in the brain, kidney, and heart. In this study, we evaluated the inflammatory phenotypic changes induced in the arterial wall by chronic N(G)-nitro-L-arginine methyl ester (L-NAME) administration and the effect of an angiotensin II receptor (AT1) antagonist, irbesartan, on these changes. For this purpose, 2 groups of rats received L-NAME in the drinking water (50 mg x kg(-1) x d(-1)) for 2 months. One group received no other treatment and the other was treated with irbesartan (10 mg x kg(-1) x d(-1)). A third group (controls) received neither L-NAME nor irbesartan. After 8 weeks, plasma, aortas, and left ventricles were sampled from all 3 groups. Expression of inducible NO synthase (iNOS) was evaluated at both the mRNA (quantitative reverse transcription-polymerase chain reaction) and the protein (Western blot and immunohistochemistry) level in the aorta. Expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) was evaluated by reverse transcription-polymerase chain reaction, Western immunoblotting, and immunohistochemistry; inflammatory cell infiltration by immunohistochemistry; and fibrosis by Sirius red staining. Chronic L-NAME administration induced the expression of iNOS in the aorta, which was localized in smooth muscle cells as shown by immunohistochemistry and NADPH diaphorase activity. ICAM-1 and VCAM-1 expression was also increased in aortas of L-NAME-treated rats. These phenotypic changes of the vascular wall were associated with inflammatory cell infiltration and fibrosis in the heart. All of these pathological phenomena were prevented by the angiotensin II antagonist irbesartan. The proinflammatory phenotypic changes of the vascular wall induced by blockade of NOS activity could be involved in the interaction between endothelial dysfunction and the development of arteriosclerosis.