Olecranon fractures in children and adolescents: outcomes based on fracture fixation

PURPOSE

Open reduction and internal fixation with a tension band construct is the standard treatment for displaced transverse intra-articular olecranon fractures. The purpose of this study is to describe the outcomes of tension band fixation of olecranon fractures in children, specifically assessing the need for revision fixation and hardware removal.

METHODS

Patients less than 18 years of age diagnosed with a displaced transverse intra-articular olecranon fracture and treated with tension band fixation between 2008 and 2017 were retrospectively enrolled. Operative treatment was with tension band wire (TBW) or tension band suture (TBS) constructs.

RESULTS

A total of 46 patients, 36 male and ten female with a mean age of 12.3 years (6 to 17), were included. Surgical fixation was with TBW in 17 patients and TBS in 29 patients. Revision fixation due to failure and fracture displacement was required in 6% of the TBW group and 14% of the TBS group (p = 0.19). The patients who required revision fixation in the TBS group were older (14.7 years versus 11.6 years, p = 0.05) and heavier (70.5 kg versus 48.5 kg, p = 0.05) than those in the same group who did not require revision fixation.

CONCLUSION

Paediatric olecranon fractures treated with TBW or TBS fixation unite in the majority of patients with similar need for hardware removal due to prominence and/or pain between fixation techniques. In a select group of older patients weighing greater than 50 kg, TBS constructs demonstrate increased failure rates, requiring revision fixation, and should be avoided in this population group.

LEVEL OF EVIDENCE

IV.

Ischemic stroke subtype is associated with outcome in thrombolyzed patients

OBJECTIVES

The impact of ischemic stroke subtype on clinical outcome in patients treated with intravenous tissue-type plasminogen activator (IV-tPA) is sparsely examined. We studied the association between stroke subtype and clinical outcome in magnetic resonance imaging (MRI)-evaluated patients treated with IV-tPA.

MATERIAL AND METHODS

We conducted a single-center retrospective analysis of MRI-selected stroke patients treated with IV-tPA between 2004 and 2010. The Trial of ORG 10172 in Acute Stroke Treatment criteria were used to establish the stroke subtype by 3 months. The outcomes of interest were a 3-month modified Rankin Scale score of 0-1 (favorable outcome), and early neurological improvement defined as complete remission of neurological deficit or improvement of ≥4 on the National Institute of Health Stroke Scale at 24 h. The outcomes among stroke subtypes were compared with multivariable logistic regression.

RESULTS

Among 557 patients, 202 (36%) had large vessel disease (LVD), 153 (27%) cardioembolic stroke (CE), 109 (20%) small vessel disease, and 93 (17%) were of other or undetermined etiology. Early neurological improvement was present in 313 (56.4%) patients, and 361 (64.8%) patients achieved a favorable outcome. Early neurological improvement and favorable outcome were more likely in CE patients compared with LVD patients (odds ratio (OR), 2.1 (95% confidence interval, 1.4-3.3), and 2.0 (95% confidence interval, 1.2-3.3), respectively).

CONCLUSIONS

Cardioembolic stroke patients were more likely to achieve early neurological improvement and favorable outcome compared with LVD stroke following MRI-based IV-tPA treatment. This finding may reflect a difference in the effect of IV-tPA among stroke subtypes.

Relationship of ECMO duration with outcomes after pediatric cardiac surgery: a multi-institutional analysis

BACKGROUND

There are very sparse data on the outcomes of children receiving prolonged extracorporeal membrane oxygenation (ECMO) after cardiac surgery. This study was aimed to evaluate the association of ECMO duration with outcomes in children undergoing surgery for congenital heart disease using the Pediatric Health Information System (PHIS) database.

METHODS

Patients aged ≤18 years receiving ECMO after pediatric cardiac surgery (with or without cardiopulmonary bypass) at a PHIS-participating hospital (2004-2013) were included. De-identified data obtained from retrospective, observational dataset included demographic information, baseline characteristics, pre-ECMO risk factors, operation details, patient diagnoses, and center data. Outcomes evaluated included in-hospital mortality, length of mechanical ventilation, length of ICU stay, length of hospital stay, and hospital charges. Cox proportional hazards models were fitted to study the probability of study outcomes as a function of ECMO duration.

RESULTS

Nine hundred ninety-eight patients from 37 hospitals qualified for inclusion. The median duration of ECMO run was 4 days (IQR: 1.7). After adjusting for patient and center characteristics, there was 12% increase in the odds of mortality for every 24 hours increase in ECMO duration (OR: 1.12, 95% CI: 1.07-1.18, P<0.001). Patients receiving longer duration of ECMO were associated with longer length of mechanical ventilation, longer length of ICU stay, longer length of hospital stay, and higher hospital charges.

CONCLUSION

Data from this large multicenter database suggest that longer duration of ECMO support after pediatric cardiac surgery is associated with worsening outcomes.

Deregulated expression of TANK in glioblastomas triggers pro-tumorigenic ERK1/2 and AKT signaling pathways

Signal transmission by the noncanonical IkappaB kinases (IKKs), TANK-binding kinase 1 (TBK1) and IKKɛ, requires interaction with adapter proteins such as TRAF associated NF-κB activator (TANK). Although increased expression or dysregulation of both kinases has been described for a variety of human cancers, this study shows that deregulated expression of the TANK protein is frequently occurring in glioblastomas (GBMs). The functional relevance of TANK was analyzed in a panel of GBM-derived cell lines and revealed that knockdown of TANK arrests cells in the S-phase and prohibits tumor cell migration. Deregulated TANK expression affects several signaling pathways controlling cell proliferation and the inflammatory response. Interference with stoichiometrically assembled signaling complexes by overexpression or silencing of TANK prevented constitutive interferon-regulatory factor 3 (IRF3) phosphorylation. Knockdown of TANK frequently prevents constitutive activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). TANK-mediated ERK1/2 activation is independent from the canonical MAP kinase or ERK kinase (MEK) 1/2-mediated pathway and utilizes an alternative pathway that uses a TBK1/IKKɛ/Akt signaling axis, thus identifying a novel pathway suitable to block constitutive ERK1/2 activity.

Regulation of NF-κB activity by competition between RelA acetylation and ubiquitination

The NF-κB transcription factor plays essential roles in inflammation and oncogenesis. Its ubiquitous RelA subunit is regulated by several post-translational modifications (PTMs) including phosphorylation, ubiquitination, and acetylation. Ubiquitination promotes the termination of RelA-dependent transcription, but its regulation is incompletely understood. Through mass spectrometry analysis of ubiquitinated RelA, we identified 7 lysines that were attached to degradative and non-degradative forms of polyubiquitin. Interestingly, lysines targeted for acetylation were among the residues identified as ubiquitin acceptor sites. Mutation of these particular sites resulted in decreased polyubiquitination. Acetylation and ubiquitination were found to inhibit each other consistent with their use of overlapping sites. Reconstitution of rela^−/− fibroblasts with wild-type and mutant forms of RelA revealed that modifications at these residues can play activating and inhibitory functions depending on the target gene context. Altogether, this study elucidates that ubiquitination and acetylation can modulate each other and regulate nuclear NF-κB function in a gene-specific manner.

Improved intraportal islet transplantation outcome by systemic IKK-beta inhibition: NF-κB activity in pancreatic islets depends on oxygen availability

Intraportal islet transplantation suffers from low efficiency caused by substantial islet mass loss after transplantation. How this process is regulated is still unclear. Here, we show that NF-κB activation was detectable in islet grafts shortly after transplantation of porcine islets to diabetic NMRI nu/nu mice, and systemic NF-κB inhibition in transplanted animals significantly prolonged islet graft survival. Proinflammatory cytokines alone did not cause evident cell death in pancreatic islet within 24 h, while the combination of cytokines with hypoxia resulted in a strong induction of cell death that could be blocked dose-dependently by a selective IKK-β inhibitor. Under hypoxia, NF-κB activity impaired expression of antiapoptotic gene BCL-xL, c-FLIP and survivin. NF-κB activation in isolated islets was reduced by hypoxia in a time-dependent manner, accordingly, NF-κB activation in transplanted islets diminished by time. Our data indicate that, while NF-κB has an antiapoptotic role under normoxia, low oxygen conditions decrease its activity and transform it to a proapoptotic transcription factor in pancreatic islets. We conclude that NF-κB inhibition represents a potential strategy to improve islet transplantation efficiency.

The human protein kinase HIPK2 phosphorylates and downregulates the methyl-binding transcription factor ZBTB4

HIPK2 is a eukaryotic Serine-Threonine kinase that controls cellular proliferation and survival in response to exogenous signals. Here, we show that the human transcription factor ZBTB4 is a new target of HIPK2. The two proteins interact in vitro, colocalize and associate in vivo, and HIPK2 phosphorylates several conserved residues of ZBTB4. Overexpressing HIPK2 causes the degradation of ZBTB4, whereas overexpressing a kinase-deficient mutant of HIPK2 has no effect. The chemical activation of HIPK2 also decreases the amount of ZBTB4 in cells. Conversely, the inhibition of HIPK2 by drugs or by RNA interference causes a large increase in ZBTB4 levels. This negative regulation of ZBTB4 by HIPK2 occurs under normal conditions of cell growth. In addition, the degradation is increased by DNA damage. These findings have two consequences. First, we have recently shown that ZBTB4 inhibits the transcription of p21. Therefore, the activation of p21 by HIPK2 is two-pronged: stimulation of the activator p53, and simultaneous repression of the inhibitor ZBTB4. Second, ZBTB4 is also known to bind methylated DNA and repress methylated sequences. Consequently, our findings raise the possibility that HIPK2 might influence the epigenetic regulation of gene expression at loci that remain to be identified.

PML tumor suppressor is regulated by HIPK2-mediated phosphorylation in response to DNA damage

The promyelocytic leukemia (PML) tumor suppressor protein, a central regulator of cell proliferation and apoptosis, is frequently fused to the retinoic acid receptor-alpha (RARalpha) in acute PML. Here we show the interaction of PML with another tumor suppressor protein, the serine/threonine kinase homeodomain-interacting protein kinase (HIPK2). In response to DNA damage, HIPK2 phosphorylates PML at serines 8 and 38. Although HIPK2-mediated phosphorylation of PML occurs early during the DNA damage response, the oncogenic PML-RARalpha fusion protein is phosphorylated with significantly delayed kinetics. DNA damage or HIPK2 expression leads to the stabilization of PML and PML-RARalpha proteins. The N-terminal phosphorylation sites contribute to the DNA damage-induced PML SUMOylation and are required for the ability of PML to cooperate with HIPK2 for the induction of cell death.

Controlling NF-κB activation in T cells by costimulatory receptors

Full and productive activation of T lymphocytes relies on the simultaneous delivery of T cell receptor (TCR)- and coreceptor-derived signals. In naïve T cells engagement of the TCR alone causes anergy, while TCR triggering of preactivated T cells results in activation-induced cell death. Costimulatory signals are prominently mirrored by the activation of NF-kappaB, which needs input from the TCR as well as from coreceptors in order to be fully activated and to fulfil its crucial function in the immune response. Coreceptor-generated signals tightly control the duration and amplitude of the NF-kappaB response. The activation of IkappaB kinase (IKK) complex at the contact zone between a T cell and an antigen-presenting cell offers the unique opportunity to study the spatial organization of IKK activation. Recent studies indicate that coreceptor pathways influence the threshold activities of many signalling mediators and thus act on multiple layers of the NF-kappaB pathway.

Proteins controlling the nuclear uptake of NF-kappa B, Rel and dorsal

The two DNA-binding subunits of the transcription factor NF-kappa B, the products of the rel oncogene family and the product of the developmental control gene dorsal of Drosophila are homologous within a 300 amino acid region. This sequence represents a novel DNA-binding and dimerization domain. The access of the NF-kappa B/Rel/dorsal (NRD) transcription factor family to the cell nucleus is regulated. There is now evidence that functionally and structurally related accessory proteins of NF-kappa B, Rel and dorsal control the nuclear entry as well as DNA-binding activity of the transcription factors. This review summarizes current knowledge about the nuclear-uptake regulatory proteins (NURPs) I kappa B-alpha, I kappa B-beta/pp40 and cactus.

Prohibitin and prohibitone are contained in high-molecular weight complexes and interact with alpha-actinin and annexin A2

The closely related proteins prohibitin (p32) and prohibitone (p37) are evolutionarily conserved with homologues found from cyanobacteria to man. They are thought to be exclusively mitochondrial and have been assigned many-rather different-functions, ranging from a role in lifespan, in mitochondrial inheritance and as chaperones of mitochondrial proteases in yeast. Evidence for a localisation outside of mitochondria has been brought forward in mammalian cells, where they influence cell-cycle progression and are found in association with cell surface receptors. We have employed a yeast two-hybrid screen to identify other interacting proteins and have identified alpha-actinin and annexin A2 as binding partners for prohibitin and prohibitone. Coprecipitation experiments supported the putative binding between prohibitin and prohibitone on the one hand and annexin A2 or alpha-actinin on the other hand in intact cells. Surface plasmon resonance analysis was used to determine relative affinities between prohibitin and alpha-actinin and between prohibitone and annexin A2 and alpha-actinin, respectively. We further show that prohibitin and prohibitone can also form homomeric (preferentially tetrameric) and heteromultimeric complexes, with significant affinities.

The slipping rib syndrome in children

The slipping rib syndrome is an infrequent cause of thoracic and upper abdominal pain and is thought to arise from the inadequacy or rupture of the interchondral fibrous attachments of the anterior ribs. This disruption allows the costal cartilage tips to sublux, impinging on the intercostal nerves. Children with this entity are seldom described in the literature. We present a retrospective review of 12 children and young adults with slipping rib syndrome and a systematic approach for evaluation and treatment.

Experience with an anesthesiologist interventional model for endoscopy in a pediatric hospital

BACKGROUND

Endoscopy is now a routine part of the work-up for many patients with gastrointestinal symptoms. Adults tolerate these procedures well, with either no sedation or a relatively light level. In contrast, children often require deep sedation or a general anesthetic to successfully perform these procedures. Therefore, pediatric endoscopies may require more time, personnel, and monitoring equipment to provide optimal conditions for the patient. The goals of this retrospective case series were to describe the anesthesia times and recovery duration of the different procedures, the types and amounts of medications commonly used, and the types and rates of complications experienced.

METHODS

Patients (2,306) who underwent endoscopy in the Arkansas Children's Hospital endoscopy suite during a 4-year period were identified. A random sample of 720 charts was reviewed retrospectively.

RESULTS

Patients ranged in age from younger than 1 year to 29 years. Patients most often had abdominal pain or multiple gastrointestinal symptoms. Sixty-eight percent of patients underwent esophagogastroduodenoscopies; 30% colonoscopy or a combination of the two. Ninety-five percent of patients received a propofol-based anesthetic. Midazolam, fentanyl, and alfentanil were frequently used as supplemental agents. Complications occurred infrequently and were airway related. All complications were easily treated, with no adverse sequelae.

CONCLUSIONS

This model of anesthesiologist-provided sedation/anesthesia for gastrointestinal endoscopy procedures has been extremely successful in the Arkansas Children's Hospital and has served to heighten awareness of many issues surrounding sedation and anesthesia outside of the operating room, while ensuring a high level of care is provided.

CD95-induced JNK activation signals are transmitted by the death-inducing signaling complex (DISC), but not by Daxx

Here we investigated CD95-mediated JNK activation pathways and their physiological relevance by employing a variety of cell lines with deficiencies in individual signal transmitting proteins. JNK activation was completely dependent on the activation of caspases in type I and type II cells, as revealed by the inhibitory effects of the caspase inhibitors zVAD-fmk or the cowpoxvirus-encoded CrmA protein. Jurkat cells deficient in caspase-8 or expressing a dominant negative (DN) form of FADD were unable to induce JNK in response to CD95 ligation, indicating that these death-inducing signaling complex (DISC) proteins are required for signal transmission. Activation of caspases, JNK and apoptosis occurred with a markedly slower kinetics in cells expressing a DN version of ASK1, revealing an important contribution of ASK1 for these processes. A C-terminally truncated version of Daxx impaired CD95-mediated apoptosis without affecting the JNK signal. DN forms of FADD, MKK4 and MKK7 completely inhibited CD95-mediated JNK activation but remained without impact on cell killing, indicating that JNK activation is not required for the execution process of CD95-mediated cell killing.

Protein kinase C theta cooperates with Vav1 to induce JNK activity in T-cells

Here we show that in human T-cell leukemia cells Vav1 and protein kinase C theta (PKCtheta) synergize for the activation of c-Jun N-terminal kinase (JNK) but not p38 MAP kinase. Vav1 and PKCtheta also cooperated to induce transcription of reporter genes controlled either by AP-1 binding sites or the CD28RE/AP composite element contained in the IL-2 promoter by stimulating the binding of transcription factors to these two elements. Dominant negative versions of Vav1 and PKCtheta inhibited CD3/CD28-induced activation of JNK, revealing their relative importance for this activation pathway. Gel filtration experiments revealed the existence of constitutively associated Vav1/PKCtheta heterodimers in extracts from unstimulated T-cells, whereas T-cell costimulation induced the recruitment of Vav1 into high molecular weight complexes. Several experimental approaches showed that Vav1 is located upstream from PKCtheta in the control of the pathway leading to synergistic JNK activation. Vav1-derived signals lead to the activation of JNK by at least two different pathways. The major contribution of Vav1 for the activation of JNK relies on the PKCtheta-mediated Ca(2+)-independent synergistic activation pathway, whereas JNK is also activated by a separate Ca(2+)-dependent signaling route.

The Drosophila proteins Pelle and Tube induce JNK/AP-1 activity in mammalian cells

The mammalian interleukin-1 (IL-1) signal transduction pathways display remarkable homology to the Toll signaling cascade in Drosophila. To address the question whether members of the Drosophila Toll pathway are functional in mammalian cells, inactive and constitutively active versions of the protein kinase Pelle and its regulator Tube were expressed in HeLa cells and tested for their impact on IL-1-dependent signaling events. The Drosophila proteins failed to induce the IL-1-responsive transcription factor, nuclear factor-kappaB, but selectively activated the IL-1-regulated kinase, c-Jun N-terminal kinase (JNK), thus resulting in elevated AP-1 activity. Activation of JNK/AP-1 activity was seen upon expression of a Pelle mutant lacking its C-terminal half or by a membrane-bound and multimerised Tube protein, showing the functionality of the Drosophila proteins in mammalian cells.

Pheophorbide A from Solanum diflorum interferes with NF-kappa B activation

Continuing our search for biogenic NF-kappa B inhibitors we investigated Solanum diflorum, used by the Istmo Sierra Zapotec Indians of Mexico in the treatment of inflammatory skin conditions. It became obvious very early that the active substance seems to be a degradation product of chlorophyll. Pheophorbide A was identified as one of the key compounds responsible for the NF-kappa B inhibitory activity. The compound interferes with NF-kappa B activation, was cytotoxic if exposed to light, but devoid of any cytotoxic activity in the dark.

I kappa B-independent control of NF-kappa B activity by modulatory phosphorylations

Activation of the transcription factor nuclear factor kappa B (NF-kappa B) requires its release from inhibitor of NF-kappa B (I kappa B) proteins in the cytoplasm. Much work has focussed on the identification of pathways regulating this cytosolic rate-limiting step of NF-kappa B activation. However, there is increasing evidence for another complex level of NF-kappa B activation, which involves modulatory phosphorylations of the DNA-binding subunits. These phosphorylations can control several functions of NF-kappa B, including DNA binding and transactivation properties, as well as interactions between the transcription factor and regulatory proteins. Although their overall impact on NF-kappa B function has yet to be determined, modifications of this factor will very probably provide a mechanism to fine tune NF-kappa B function.

Human homeodomain-interacting protein kinase-2 (HIPK2) is a member of the DYRK family of protein kinases and maps to chromosome 7q32-q34

Here we identified the human serine/threonine kinase HIPK2 as a novel member of the DYRK kinase subfamily. Alignment of several DYRK family proteins including the kinases minibrain, MJAK, PKY, the Dictyostelium kinase YakA and Saccharomyces YAK1 allowed the identification of several evolutionary conserved DYRK consensus motifs within the kinase domain. A lysine residue conserved between all DYRK kinase family members was found to be essential for the kinase function of HIPK2. Human HIPK2 was mapped to chromosome 7q32-q34 and murine HIPK2 to chromosome 6B, the homologue to human chromosome 7.

Enhancement of T cell receptor signaling by a mild oxidative shift in the intracellular thiol pool

Exposure of T cells to the macrophage products hydrogen peroxide (HP) or L-lactate (LAC) was previously shown to enhance IL-2 production and to modulate glutathione (GSH) status. We now found that 50 microM HP and 30 mM LAC enhanced strongly the transcription from the IL-2 promoter in Jurkat T cells after stimulation with anti-CD28 together with or without anti-CD3 but not with anti-CD3 Abs alone. Therefore, we used anti-CD3 plus anti-CD28-stimulated cells to investigate the effect of the GSH reductase inhibitor 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) on the signal cascade. BCNU enhanced the transcription to a similar extent as HP or LAC. Lowering the intracellular GSH/GSH disulfide ratio by BCNU, HP, or NO resulted in all cases in the fulminant enhancement of Jun-N-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-regulated kinase 1/2. Jun-N-terminal kinase and NF-kappaB activation was enhanced through pathways involving Rac, Vav1, PKCTheta, p56(lck), p59(fyn), and IkappaB kinases. In a cell-free system, the autophosphorylation of rFyn was stimulated by GSH disulfide but not by HP. These findings suggest that the oxidation of the cellular thiol pool may play a role as an amplifying mechanism for TCR/CD3 signals in immune responses.

Synergistic activation of NF-kappa B by functional cooperation between vav and PKCtheta in T lymphocytes

Here we identified PKCtheta as an activator of transcription factor NF-kappaB in T cells. PKCtheta-induced NF-kappaB activation was synergistically augmented by Vav. Several experimental approaches revealed that PKCtheta is located downstream from Vav in the control of the pathway leading to synergistic NF-kappaB activation. In addition to the synergistic activation cascade, Vav also triggered NF-kappaB activity on a separate route. CD3/CD28-induced activation of NF-kappaB was inhibited by dominant negative forms of Vav or PKCtheta, revealing their essential role in this activation pathway. The Vav/PKCtheta-mediated signals preferentially activated IkappaB kinase beta. Vav and PKCtheta were found to be constitutively associated in unstimulated T cells. Only the ligation of the costimulatory CD28 receptor, but not of the T cell receptor, resulted in the transient dissociation of the Vav-PKCtheta complex. In contrast, T cell receptor/CD28 costimulation resulted in faster dissociation and slower reassociation kinetics.

Inhibitory effect of NF-kappaB on 1,25-dihydroxyvitamin D(3) and retinoid X receptor function

Responsiveness to 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] may be diminished in osteoporosis and inflammatory arthritis. The inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) is produced in excess in these disorders and has been shown to decrease osteoblast transcriptional responsiveness to vitamin D and to inhibit the binding of the vitamin D receptor (VDR) and its nuclear partner the retinoid X receptor (RXR) to DNA. Previous studies have shown that a vitamin D (VDRE) or retinoid X DNA response element (RXRE) is sufficient to confer TNF-alpha inhibition of vitamin D or retinoid-stimulated transcription in the absence of known TNF-alpha-responsive DNA sequences. We tested the hypothesis that the TNF-alpha-stimulated transcription factor nuclear factor (NF)-kappaB could, in part, mediate TNF-alpha action by inhibiting the transcriptional potency of the VDR and RXR at their cognate cis regulatory sites. Osteoblastic ROS 17/2.8 cells transfected with a dose of NF-kappaB comparable to that stimulated by TNF-alpha decreased 1,25(OH)(2)D(3)-stimulated transcription. This inhibitory effect of NF-kappaB was not observed on basal transcription of a heterologous reporter in the absence of the VDRE. The effects of NF-kappaB and TNF-alpha were comparable but not additive. COS-7 cells were cotransfected with reporters under the regulation of VDRE or RXRE along with vectors expressing VDR, RXR, and NF-kappaB nuclear proteins. Reconstituted NF-kappaB and the NF-kappaB subunit p65 alone, but not p50, dose dependently suppressed basal and ligand-stimulated transcription. p65 overexpression completely abrogated enhanced VDRE-mediated transcriptional activity in response to 1,25(OH)(2)D(3). Electrophoretic mobility shift experiments did not reveal a direct effect of recombinant NF-kappaB or its individual subunits on the binding of heterodimeric VDR-RXR to DNA. These results suggest that TNF-alpha inhibition of hormone-stimulated transcriptional activation may be mediated by activation of NF-kappaB. In contrast, the inhibitory effect of TNF-alpha on binding of receptors to DNA is unlikely to be mediated by NF-kappaB and is not necessary for inhibition of transcription.

Tyrosine-phosphorylated Vav1 as a point of integration for T-cell receptor- and CD28-mediated activation of JNK, p38, and interleukin-2 transcription

In this study we identified tyrosine-phosphorylated Vav1 as an early point of integration between the signaling routes triggered by the T-cell receptor and CD28 in human T-cell leukemia cells. Costimulation resulted in a prolonged and sustained phosphorylation and membrane localization of Vav1 in comparison to T-cell receptor activation alone. T-cell stimulation induced the recruitment of Vav1 to an inducible multiprotein T-cell activation signaling complex at the plasma membrane. Vav1 activated the mitogen-activated protein kinases JNK and p38. The Vav1-mediated activation of JNK employed a pathway involving Rac, HPK1, MLK3, and MKK7. The costimulation-induced activation of p38 was inhibited by dominant negative forms of Vav1, Rac, and MKK6. Here we show that Vav1 also induces transcription factors that bind to the CD28RE/AP element contained in the interleukin-2 promoter. A detailed mutational analysis of Vav1 revealed a series of constitutively active and nonfunctional forms of Vav1. Almost all inactive versions were mutated in their Dbl homology domain and behaved as dominant negative mutants that impaired costimulation-induced activation of JNK, p38, and CD28RE/AP-dependent transcription. In contrast to NF-AT-dependent transcription, Vav1-mediated transcriptional induction of the CD28RE/AP element in the interleukin-2 promoter could only partially be inhibited by cyclosporin A, suggesting a dual role of Vav1 for controlling Ca(2+)-dependent and -independent events.

The pro- or anti-apoptotic function of NF-kappaB is determined by the nature of the apoptotic stimulus

To test whether the behaviour of transcription factor NF-kappaB as a promoter or antagonist of apoptosis depends on the apoptotic stimulus, we determined the influence of NF-kappaB on cell killing elicited by a variety of inducers within a given cell type. Inhibition of NF-kappaB by genetic and pharmacological approaches rendered HeLa cells more susceptible to TNF-alpha-induced cell killing, but protected them almost completely from H2O2- and pervanadate-induced apoptosis. TNF-alpha was unable to protect HeLa from H2O2- and pervanadate-induced apoptosis and further enhanced the cytotoxicity induced by these two adverse agents. Supernatants from HeLa cells stably overexpressing a transdominant negative form of IkappaB-alpha selectively increased the cytotoxicity of TNF-alpha for HeLa cells, suggesting that the enhanced susceptibility of these cells can be attributed to one or more secretable factors. Supershift experiments showed that the various apoptotic stimuli induced the same subset of DNA-binding subunits. Therefore, the nature of the signals elicited by the respective death inducers determines whether NF-kappaB induction leads to apoptosis or survival, suggesting that the manipulation of NF-kappaB activity may provide a new approach to adjuvant therapy in cancer treatment.

Vav synergizes with protein kinase C theta to mediate IL-4 gene expression in response to CD28 costimulation in T cells

The secretion of IL-4, which displays many important immunoregulatory functions, is restricted to cells of the Th2 subtype. In this study, we investigated the early signaling events leading to the activation of IL-4 transcription. Vav, the protein kinase C (PKC) isoform theta, and the adaptor protein SLP76 (SH2-domain-containing leukocyte protein of 76 kDa), induced transcription from the IL-4 promoter. Vav and PKC theta synergistically activated human IL-4 promoter transcription and IL-4 mRNA production and were found to be constitutively associated in vivo. CD3/CD28-induced IL-4 transcription was inhibited upon coexpression of dominant negative forms of Vav, the adaptor proteins LAT (linker for activation of T cells) and SLP76, PKC theta, and components of the pathways leading to the activation of c-Jun N-terminal kinase (mitogen-activated protein kinase kinase 7 (MKK7), mixed lineage kinase 3 (MLK3)) and NF-kappa B (I kappa B kinase alpha and I kappa B kinase beta). The Vav/PKC theta-mediated synergistic activation of IL-4 transcription was not inhibited by cyclosporin A. Three independent experimental approaches revealed that Vav/PKC theta-derived signals selectively target the P1 and positive regulatory element (PRE)-I elements contained within the human IL-4 promoter. Vav/PKC theta strongly activated a luciferase reporter construct controlled by trimerized P1 or PRE-I elements and furthermore stimulated DNA binding of nuclear proteins to the P1 and PRE-I elements. Vav/PKC theta-induced transcription from the IL-4 promoter was almost completely abrogated by mutation of either the P1 or the PRE-I element within the entire IL-4 promoter.

Mixed-lineage kinase 3 delivers CD3/CD28-derived signals into the IkappaB kinase complex

The phosphorylation of IkappaB by the multiprotein IkappaB kinase complex (IKC) precedes the activation of transcription factor NF-kappaB, a key regulator of the inflammatory response. Here we identified the mixed-lineage group kinase 3 (MLK3) as an activator of NF-kappaB. Expression of the wild-type form of this mitogen-activated protein kinase kinase kinase (MAPKKK) induced nuclear immigration, DNA binding, and transcriptional activity of NF-kappaB. MLK3 directly phosphorylated and thus activated IkappaB kinase alpha (IKKalpha) and IKKbeta, revealing its function as an IkappaB kinase kinase (IKKK). MLK3 cooperated with the other two IKKKs, MEKK1 and NF-kappaB-inducing kinase, in the induction of IKK activity. MLK3 bound to components of the IKC in vivo. This protein-protein interaction was dependent on the central leucine zipper region of MLK3. A kinase-deficient version of MLK3 strongly impaired NF-kappaB-dependent transcription induced by T-cell costimulation but not in response to tumor necrosis factor alpha or interleukin-1. Accordingly, endogenous MLK3 was phosphorylated and activated by T-cell costimulation but not by treatment of cells with tumor necrosis factor alpha or interleukin-1. A dominant negative version of MLK3 inhibited NF-kappaB- and CD28RE/AP-dependent transcription elicited by the Rho family GTPases Rac and Cdc42, thereby providing a novel link between these GTPases and the IKC.

Caspase-dependent cleavage and inactivation of the Vav1 proto-oncogene product during apoptosis prevents IL-2 transcription

Here we identify the hematopoietic proto-oncogene Vav1 as a caspase substrate during apoptosis in lymphoid cells. Cleavage of Vav1 is prevented by the caspase inhibitors zDEVD and zVAD as well as by expression of CrmA. Vav1 is cleaved in vivo at the evolutionary conserved caspase consensus cleavage site DLYD161C, generating the carboxy-terminal cleavage product Vav1p76 of intermediate stability. In vitro caspase assays reveal cleavage of Vav1 at position 161 either by apoptotic cell lysates or by recombinant caspase-3. Mutation of Asp 161 to Ala leads to the usage of the adjacent alternative cleavage sequence DQID150D. Mutation of both cleavage sites at position 150 and 161 protects Vav1 from caspase-mediated proteolysis in vitro and in vivo. The cleavage product Vav1p76 is capable of activating JNK in T-cells, but fails to induce the phosphorylation of p38/HOG1. Vav1p76 displays a diminished capacity to activate the transcription factors NF-AT, AP-1 and NF-kappaB, and thus completely fails to activate IL-2 transcription. Since Vav1 is essential for IL-2 production and plays a central role for cytoskeletal reorganization, its proteolytic inactivation during apoptosis affects multiple downstream targets.

Pain assessment and treatment in children with cognitive impairment: a survey of nurses' and physicians' beliefs

OBJECTIVE

To gather information about healthcare providers' beliefs regarding pain and its treatment in children with cognitive impairment.

DESIGN

A survey consisting of two acute pain vignettes (a child undergoing surgery and a child undergoing an outpatient medical procedure) was completed by 440 nurses and 146 physicians at Arkansas Children's Hospital. Respondents completed one of four different surveys that systematically varied the child's level of cognitive impairment (none, mild, moderate, severe) in both vignettes. Questions addressed expected pain, pain assessment methods, pharmacologic regimens, and nonpharmacologic interventions.

RESULTS

In general, provider discipline and level of cognitive impairment did not significantly influence responses about pain experience and treatment. Potent analgesia, regularly scheduled dosing, and nonpainful administration were selected most frequently. Self-report of pain, patient-controlled analgesia, and behavioral interventions requiring higher cognitive skills were selected less frequently for children with more severe cognitive impairment.

CONCLUSIONS

The presence of cognitive impairment appeared to influence provider decisions regarding the appropriateness of specific pain assessment and treatment methods requiring skills on the part of the child. Overall, healthcare provider views regarding analgesia and sedation were similar for all children, regardless of impairment. Whether these beliefs are consistent with clinical practice is yet to be documented.

The antiinflammatory sesquiterpene lactone parthenolide inhibits NF-kappa B by targeting the I kappa B kinase complex

The transcription factor NF-kappa B is a key regulator of the cellular inflammatory and immune response. Therefore, components of the NF-kappa B-activating signaling pathways are frequent targets for antiinflammatory agents. This study shows that the sesquiterpene lactone parthenolide inhibits a common step in NF-kappa B activation by preventing the TNF-alpha-induced induction of I kappa B kinase (IKK) and IKK beta, without affecting the activation of p38 and c-Jun N-terminal kinase. Parthenolide impairs NF-kappa B-dependent transcription triggered by expression of TNFR-associated factor-2, mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEKK1), and NF-kappa B-inducing kinase. This compound also prevents activation of both IKKs and DNA binding of NF-kappa B induced by MEKK and NF-kappa B-inducing kinase. Parthenolide targets a component of the I kappa B kinase complex without directly inhibiting IKK alpha, IKK beta, or MEKK1. Therefore, this sesquiterpene lactone could serve as a lead compound for the development of antiinflammatory remedies and is suitable as a molecular tool, allowing the dissection of TNF-alpha-derived signaling pathways leading to the activation of NF-kappa B, c-Jun N-terminal kinase, and p38.

Inhibition of tyrosine phosphatases induces apoptosis independent from the CD95 system

The inhibition of protein tyrosine phosphatases by pervanadate, a potent activator of B- and T-cells through the induction of tyrosine phosphorylation and downstream signaling events in different activation cascades, efficiently induced apoptosis in lymphoid cell lines. Pervanadate-elicited apoptosis could be blocked by the tyrosine kinase inhibitor herbimycin A. This apoptotic process involved the activation of caspases 3, 8 and 9, the induction of mitochondrial permeability transition, the release of cytochrome C and the fragmentation of chromosomal DNA. T-cells lacking the CD95 receptor or caspase-8 and T-cells stably overexpressing a transdominant negative form of the adaptor protein FADD were still susceptible to pervanadate-induced apoptosis, excluding the involvement of the CD95 system or other FADD-dependent death receptors. The apoptotic program initiated by the inhibition of tyrosine phosphatases did not require the presence of the tyrosine kinase p56lck or phosphatase CD45, whereas Bcl-2 overexpression protected T-cells from pervanadate-induced cytochrome C release, caspase-8 cleavage and apoptosis.

Children with cognitive impairment: parent report of pain and coping

Information about pain in children with cognitive impairment is lacking. To gather pain-relevant information in this population, parents of 145 children with borderline to profound cognitive impairment were interviewed regarding their children's pain expression, experience, treatment, and coping behavior. Descriptions of pain expression and coping behavior were associated with the level of cognitive impairment. Children with mild to moderate cognitive impairment were more likely to be described as directly communicating their pain and exhibiting procedural coping strategies similar to those observed in children without cognitive impairments. More than half of the parents reported that their children experienced pain differently than did children without cognitive impairment, with the majority perceiving decreased pain sensitivity and greater pain tolerance. Finally, one third of parents felt that their children's pain was treated differently than that of other children. Half of these parents believed that health care providers had difficulties assessing and treating their children's pain. Results contribute to the developing foundation of information about pain in this special pediatric population.

Inhibition of tyrosine phosphatases antagonizes CD95-mediated apoptosis

Ligation of the CD95 receptor resulted in a transient increase of cellular tyrosine phosphorylation. The inhibition of protein tyrosine phosphatases by pervanadate, a potent activator of B cells and T cells through the induction of tyrosine phosphorylation and downstream signaling events in the activation cascade, antagonized CD95-triggered apoptosis. Pervanadate exerted its inhibitory effect only during the early phase of apoptosis prior to the CD95-induced decrease of the mitochondrial transmembrane potential. Inhibition of tyrosine phosphatases delayed the cleavage and activation of caspase-8 and caspase-3 and antagonized the tyrosine dephosphorylation of the CD95 receptor-associated phosphoproteins p61 and p89/92. In contrast, ligation of the tumor necrosis factor (TNF) receptor resulted in a continuous tyrosine dephosphorylation of cellular proteins. Pervanadate-induced tyrosine phosphorylation increased the TNF-alpha-induced cytotoxicity and NF-kappaB activation, suggesting that it stimulates early signaling events prior to the separation of the two signaling pathways.

Efficacy of parental application of eutectic mixture of local anesthetics for intravenous insertion

OBJECTIVE

To demonstrate that parent application of eutectic mixture of local anesthetics (EMLA) results in equal reduction of the pain of intravenous (IV) placement compared with clinician application of EMLA, and to assess potential difficulties with parental application.

STUDY DESIGN

A 2 x 2 randomized block design was used, with 41 children divided into two age groups (5-12 years vs 13-18 years) and randomized to one of two experimental groups (parent-applied EMLA vs clinician-applied EMLA).

METHODS

All children were scheduled to have outpatient gastrointestinal endoscopies with IV sedation. EMLA was placed at least 60 minutes before IV insertion either by the parent or a clinician, depending on the experimental group assignment. Outcome measures were child pain ratings and observed behavioral distress ratings. Parents and children were interviewed to determine parent and child anxiety levels in anticipation of the IV insertion, previous needle stick experience, and previous difficulty coping. Feasibility outcomes included technical difficulty with application of EMLA and appearance of the EMLA cream and occlusive covering.

RESULTS

Pain ratings and behavioral distress ratings in the low to moderate range for all groups and ws and were consistent w previous empiric reports of EMLA outcome. There were no significant differences in pain or distress ratings for either the age or the experimental groups. Parent ratings of their child's previous difficulty coping was related to the level of behavioral distress exhibited before (r =.50), during (r =.32) and after (r =.44) the IV insertion. In addition, children's anxiety ratings about IV insertion seemed to differ among groups (although not statistically significant for post hoc comparisons), with the most anxiety reported by the younger children when clinicians applied the EMLA and by older children when parents applied the EMLA.

CONCLUSION

Parent application of EMLA appears to be as effective as clinician application in reducing children's pain and distress associated with IV insertion. Permitting parents to apply the EMLA at home can allow children who are having procedures on an outpatient basis to benefit from topical anesthesia without having to arrive early to the clinic or hospital. Additionally, application by parents may result in less anticipatory anxiety for younger children.

Repression of NF-kappaB impairs HeLa cell proliferation by functional interference with cell cycle checkpoint regulators

NF-kappaB is an inducible transcription factor, which is regulated by interaction with inhibitory IkappaB proteins. Previous studies linked the activity of NF-kappaB to the proliferative state of the cell. Here we have analysed the function of NF-kappaB in the cell cycle. Inhibition of NF-kappaB in HeLa cells by stable overexpression of a transdominant negative IkappaB-alpha protein reduced cell growth. A kinetic analysis of the cell cycle revealed a retarded G1/S transition. The IkappaB-alpha overexpressing cell clones showed a decreased percentage of cells in the S phase and an impaired incorporation of bromodeoxyuridine (BrdU). The amounts of cyclins A, B1, D1, D3, and E were unchanged, but the G1-specific proteins cyclin D2 and cdk2 were strongly elevated in the IkappaB-alpha overexpressing cell clones. These cell clones also displayed an increase in cyclin D1-dependent kinase activity, pointing to a cell cycle arrest at the late G1 phase. IkappaB-alpha overexpression crosstalked to cell cycle checkpoints via a reduction of transcription factor p53 and elevation of p21WAF. Surprisingly, the IkappaB-alpha overexpressing cells showed an enrichment of c-Myc in the nucleoli, although the total amount of c-Myc protein was unchanged. These experiments identify an important contribution of the NF-kappaB/IkappaB system for the growth of HeLa cells.

Hypericin as a non-antioxidant inhibitor of NF-kappa B

NF-kappa B is a transcription factor involved in immune and inflammatory responses. Here we show that micromolar concentrations of hypericin inhibited the PMA- and TNF-alpha-induced activation of NF-kappa B in HeLa and TC10 cells, respectively. In contrast, NF-kappa B activated by H2O2 was not influenced by hypericin, indicating a pathway-specificity of hypericin. Hyperforin and a Hypericum perforatum extract standardised on 0.15% hypericin and 5% hyperforin were not active at pharmacologically relevant concentrations. The PMA/TNF-alpha-induced transcription of a reporter gene, which is under the control of the NF-kappa B-dependent IL-6 promoter, was strongly reduced by preincubation with hypericin.

Hydrogen peroxide-induced apoptosis is CD95-independent, requires the release of mitochondria-derived reactive oxygen species and the activation of NF-kappaB

Reactive oxygen species (ROS) play an important role in cell death induced by many different stimuli. This study shows that hydrogen peroxide-induced apoptosis in T-cells did not require tyrosine kinase p561ck, phosphatase CD45, the CD95 receptor and its associated Caspase-8. H2O2-triggered cell death led to the induced cleavage and activation of Caspase-3. Hydrogen peroxide-treatment of T-cells resulted in the formation of mitochondrial permeability transition pores, a rapid decrease of the mitochondrial transmembrane potential delta psi(m) and the release of Cytochrome C. Inhibition of the mitochondrial permeability transition by bongkrekic acid (BA), or interference with the mitochondrial electron transport system by rotenone or menadione prevented the cytotoxic effect of H2O2. Antimycin A, a mitochondrial inhibitor that increases the release of mitochondrial ROS (MiROS), enhanced apoptosis. Overexpression of Bcl-2 and the viral anti-apoptotic proteins BHRF-1 and E1B 19K counteracted H2O2-induced apoptosis. Pharmacological and genetic inhibition of transcription factor NF-kappaB protected cells from hydrogen peroxide-elicited cell death. This detrimental effect of NF-kappaB mediating hydrogen peroxide-induced cell death presumably relies on the induced expression of death effector genes such as p53, which was NF-kappaB-dependently upregulated in the presence of H2O2.

Various glucocorticoids differ in their ability to induce gene expression, apoptosis and to repress NF-kappaB-dependent transcription

Glucocorticoids (GCs) influence a great variety of cellular functions by at least three important modes of action: the activation (or repression) of genes controlled by binding sites for the glucocorticoid receptor (GR), the induction of apoptosis in lymphocytes and the recently discovered cross-talk to other transcription factors such as NF-kappaB. In this study we systematically compared various natural and synthetic steroid hormones frequently used as therapeutic agents on their ability to mediate these three modes of action. Betamethasone, triamcinolone, dexamethasone and clobetasol turned out to be the best inducers of gene expression and apoptosis. All GCs including the antagonistic compound RU486 efficiently reduced NF-kappaB-mediated transactivation to comparable extents, suggesting that ligand-induced nuclear localization of the GR is sufficient for transrepression. Glucocorticoid treatment of cells did not result in elevated IkappaB-alpha expression, but impaired the tumor necrosis factor (TNF)-alpha-induced degradation of IkappaB-alpha without affecting DNA binding of NF-kappaB. The structural requirements for the various functions of glucocorticoids are discussed.

Co-stimulatory effect of nitric oxide on endothelial NF-kappaB implies a physiological self-amplifying mechanism

Here we investigated the effects of the second messenger molecule NO at various concentrations on the activation of transcription factor NF-kappaB, IkappaB-alpha kinase (IKK-alpha), Jun N-terminal kinase (JNK) and apoptosis in murine endothelial cells. Low concentrations of NO alone failed to activate NF-kappaB, IKK-alpha and JNK. When NF-kappaB was prestimulated by TNF-alpha or phorbol 12-myristate 13-acetate, the addition of NO at low concentrations enhanced the activation of NF-kappaB. This provides a mechanism for a self-amplifying signal in the inflammatory response, since the inducible NO synthase in endothelial cells is regulated by NF-kappaB. The co-stimulatory effect of NO on NF-kappaB activation was also evident from IKK-alpha kinase assays and reporter gene experiments in endothelial cells. High doses of NO impaired the TNF-alpha-induced DNA-binding activity of NF-kappaB. Accordingly, these high amounts of NO also repressed the TNF-alpha-induced transactivation by NF-kappaB as efficient as dexamethasone. The doses of NO required for the inhibition of NF-kappaB are not cytotoxic for the endothelial cells, enabling the establishment of an autoregulatory loop for NF-kappaB signaling.

Tumor necrosis factor-alpha-induced cell killing and activation of transcription factor NF-kappaB are uncoupled in L929 cells

The induction of transcription factor NF-kappaB has been shown to counteract tumor necrosis factor (TNF)-alpha-induced cell death in various cell types. In this study, we investigated the role of NF-kappaB for TNF-alpha-triggered cell death in the widely used mouse cell line L929 by various approaches. Inhibition of the mitochondrial permeability transition by bongkrekic acid impaired TNF-alpha-induced cell death without affecting the activity of NF-kappaB. The reduction of NF-kappaB-mediated gene expression by the synthetic steroid dexamethasone was associated with a decrease in TNF-alpha-mediated cell killing, suggesting that NF-kappaB does not protect L929 cells from TNF-alpha-induced cell death. This concept was reinforced by experiments employing L929 cell lines stably overexpressing a transdominant negative form of IkappaB-alpha. These cell lines were unable to activate NF-kappaB and to inducibly express the IL-6 gene, but they showed the same susceptibility toward TNF-alpha-mediated cell death as L929 wild-type cells.

p38 and extracellular signal-regulated kinase mitogen-activated protein kinase pathways are required for nuclear factor-kappaB p65 transactivation mediated by tumor necrosis factor

Interleukin-6 (IL-6) is a pleiotropic cytokine, which is involved in inflammatory and immune responses, acute phase reactions, and hematopoiesis. In the mouse fibrosarcoma cell line L929, the nuclear factor (NF)-kappaB plays a crucial role in IL-6 gene expression mediated by tumor necrosis factor (TNF). The levels of the activated factor do not, however, correlate with the variations of IL-6 gene transcription; therefore, other factors and/or regulatory mechanisms presumably modulate the levels of IL-6 mRNA production. Upon analysis of various deletion and point-mutated variants of the human IL-6 gene promoter coupled to a reporter gene, we screened for possible cooperating transcription factors. Even the smallest deletion variant, containing almost exclusively a NF-kappaB-responsive sequence preceding the IL-6 minimal promoter, as well as a recombinant construction containing multiple kappaB-motifs, could still be stimulated with TNF. We observed that the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 was able to repress TNF-stimulated expression of the IL-6 gene, as well as of a kappaB-dependent reporter gene construct, without affecting the levels of NF-kappaB binding to DNA. Furthermore, we clearly show that, using a nuclear Gal4 "one-hybrid" system, the MAPK inhibitors SB203580 and PD0980589 have a direct repressive effect on the transactivation potential of the p65 kappaB subunit. Therefore, we conclude that, in addition to cytoplasmic activation and DNA binding of NF-kappaB, the p38 and extracellular signal-regulated kinase MAPK pathways act as necessary cooperative mechanisms to regulate TNF-induced IL-6 gene expression by modulating the transactivation machinery.

Sesquiterpene lactones specifically inhibit activation of NF-kappa B by preventing the degradation of I kappa B-alpha and I kappa B-beta

Extracts from certain Mexican Indian medicinal plants used in traditional indigenous medicine for the treatment of inflammations contain sequiterpene lactones (SLs), which specifically inhibit the transcription factor NF-kappa B (Bork, P. M., Schmitz, M. L., Kuhnt, M., Escher, C., and Heinrich, M. (1997) FEBS Lett. 402, 85-90). Here we show that SLs prevented the activation of NF-kappa B by different stimuli such as phorbol esters, tumor necrosis factor-alpha, ligation of the T-cell receptor, and hydrogen peroxide in various cell types. Treatment of cells with SLs prevented the induced degradation of I kappa B-alpha and I kappa B-beta by all these stimuli, suggesting that they interfere with a rather common step in the activation of NF-kappa B. SLs did neither interfere with DNA binding activity of activated NF-kappa B nor with the activity of the protein tyrosine kinases p59fyn and p60arc. Micromolar amounts of SLs prevented the induced expression of the NF-kappa B target gene intracellular adhesion molecule 1. Inhibition of NF-kappa B by SLs resulted in an enhanced cell killing of murine fibroblast cells by tumor necrosis factor-alpha. SLs lacking an exomethylene group in conjugation with the lactone function displayed no inhibitory activity on NF-kappa B. The analysis of the cellular redox state by fluorescence-activated cell sorter showed that the SLs had no direct or indirect anti-oxidant properties.

Glucocorticoid-mediated repression of nuclear factor-kappaB-dependent transcription involves direct interference with transactivation

Glucocorticoids exert multiple anti-inflammatory activities, one of which is the inhibition of transcription dependent on the nuclear factor (NF)-kappaB. It has been suggested that the effect of dexamethasone (DEX), a glucocorticoid analog, is attributed to an increased production of the inhibitory IkappaB molecule, which in turn would bind and remove activated, DNA-bound NF-kappaB complexes in the cell nucleus. Upon investigating DEX-mediated repression of interleukin-6 expression induced by tumor necrosis factor, DEX treatment was found to act directly on NF-kappaB-dependent transcription, without changing the expression level of IkappaB. Neither the mRNA of IkappaB nor the protein was significantly elevated by a combined treatment with tumor necrosis factor and DEX of murine endothelial or fibroblast cells. The DNA-binding activity of induced NF-kappaB also remained unchanged after stimulation of cells with DEX. Evidence for a direct nuclear mechanism of action was obtained by analysis of cell lines stably expressing a fusion protein between the DNA-binding domain of the yeast Gal4 protein and the transactivating p65 subunit of NF-kappaB. Expression of a Gal4-dependent luciferase reporter gene activated by this nuclear fusion protein was also strongly repressed after addition of DEX. Because the DNA-binding activity of the Gal4 fusion protein was not affected by DEX, it can be concluded that the reduction of gene activation was caused by interference of the activated glucocorticoid receptor with the transactivation potential of the NF-kappaB p65 subunit.

Distinct domains of the RelA NF-kappaB subunit are required for negative cross-talk and direct interaction with the glucocorticoid receptor

The RelA subunit of NF-kappaB and the glucocorticoid receptor mutually repress each others transcriptional activity, thus providing a mechanism for immunosuppression. Deletion analysis of the glucocorticoid receptor has shown that the DNA binding domain and the ligand binding domain are essential components for repression. Here, we show by deletions and point mutations that both the Rel homology domain and the transactivation domains of RelA are required for repression of the transcriptional activity of the glucocorticoid receptor in intact cells. However, only the Rel homology domain of RelA was found to associate with the glucocorticoid receptor in vitro. RelA mutants, not able to repress glucocorticoid receptor activity, but still able to dimerize, behaved as transdominant inhibitors of the repressive activity of wild type RelA. Furthermore, we show that the 13 S E1A protein is able to interfere with the transrepressive activity of RelA. We propose that negative cross-talk between the glucocorticoid receptor and RelA is due to direct interaction via the Rel homology domain of RelA and the DNA binding domain of the glucocorticoid receptor in combination with interference by the transactivation domains of RelA with the transcriptional activity of the glucocorticoid receptor.