Comparison of Segmental Versus Longitudinal Intravascular Ultrasound Analysis for Pediatric Cardiac Allograft Vasculopathy.

Intravascular ultrasound (IVUS) has been routinely used in some centers to investigate cardiac allograft vasculopathy in pediatric heart transplant recipients. We present an alternative method using more sophisticated imaging software. This study presents a comparison of this method with an established standard method. All patients who had IVUS performed in 2014 were retrospectively evaluated. The standard technique consisted of analysis of 10 operator-selected segments along the vessel. Each study was re-evaluated using a longitudinal technique, taken at every third cardiac cycle, along the entire vessel. Semiautomatic edge detection software was used to detect vessel imaging planes. Measurements included outer and inner diameter, total and luminal area, maximal intimal thickness (MIT), and intimal index. Each IVUS was graded for severity using the Stanford classification. All results were given as mean ± standard deviation (SD). Groups were compared using Student t test. A P value <.05 was considered significant. There were 59 IVUS studies performed on 58 patients. There was no statistically significant difference between outer diameter, inner diameter, or total area. In the longitudinal group, there was a significantly smaller luminal area, higher MIT, and higher intimal index. Using the longitudinal technique, there was an increase in Stanford classification in 20 patients. The longitudinal technique appeared more sensitive in assessing the degree of cardiac allograft vasculopathy and may play a role in the increase in the degree of thickening seen. It may offer an alternative way of grading severity of cardiac allograft vasculopathy in pediatric heart transplant recipients.

Heart and heart-lung transplantation for idiopathic restrictive cardiomyopathy in children.

OBJECTIVE: To review the outcome of cardiac transplantation for restrictive cardiomyopathy (RCM) in children and to assess the ability of new strategies to modulate the effects of high pulmonary vascular resistance. DESIGN: Retrospective case note analysis of all patients receiving a transplant for RCM. PATIENTS: 18 children with RCM referred for transplantation assessment to Great Ormond Street Hospital, London. RESULTS: Eight boys and 10 girls were referred for assessment. Median age at presentation was 5.0 (mean (SD) 6.1 (4.0)) years. Fourteen orthotopic and two heterotopic transplantations were performed and two patients were referred for heart-lung transplantation. Mean duration from diagnosis to transplantation was 3.3 (3.0) years. Three patients with haemodynamic decompensation before transplantation had increased morbidity in the postoperative period. No patients died while awaiting a transplant. Three patients died in the first year after transplantation, one within 30 days. Five patients received pre-transplantation prostacyclin for a mean duration of 57 (18) days. Transpulmonary gradient was reduced in four of the patients. Mean transpulmonary gradient was 27 (9.8) mm Hg before and 17 (6.7) mm Hg after treatment with prostacyclin (p < 0.05). CONCLUSION: Most children with RCM require transplantation within four years of diagnosis. Referral for transplantation assessment should precede haemodynamic decompensation. Increase of pulmonary vascular resistance is a variable problem but can be modulated with pre-transplantation prostacyclin. With these strategies, orthotopic transplantation is possible in the majority of cases.

Cardiac arrests at the Cenotaph.

This report describes the case histories of three veterans who suffered cardiac arrests at the 2005 Cenotaph Remembrance Parade. All three were successfully resuscitated and admitted to the St Thomas' Hospital Coronary Care Unit. They had internal cardioverter defibrillators (ICDs) inserted and remain well. All three plan to attend Remembrance ceremonies this year. We review the evidence between emotional stress and arrhythmias and the updated National Institute for Health and Clinical Excellence (NICE) guidelines for ICDs.

Negative regulation of IL-1beta production at the level of transcription in macrophages stimulated with LPS.

The IL-1beta gene is rapidly and transiently expressed in LPS-stimulated macrophages. While several studies have addressed the molecular basis of LPS-induced transcriptional activity, the mechanisms which underlie the subsequent decrease in IL-1beta gene expression have not been as extensively examined. In this regard, we found that the characteristic decrease in IL-1beta production after LPS stimulation could be abrogated by treatment of macrophages with the protein kinase inhibitor staurosporine. This inhibitor mediated an enhancement of IL-1beta production which was first evident 8-12 h after LPS stimulation and continued at peak levels for the rest of the incubation period (24 h). IL-1beta production was correlated with the level of mRNA specific for the cytokine. Staurosporine also mediated an enhancement of LPS-induced IL-1beta promoter activity measured in RAW 264.7 cells transiently transfected with an IL-1beta reporter plasmid. This increase paralleled the enhancement of IL-1beta mRNA by staurosporine both in intensity and time after LPS stimulation, suggesting that the negative regulation of IL-1beta is exerted primarily at the level of transcription. This regulation may be at least partially due to an observed inhibition of nitric oxide production by staurosporine in LPS-activated macrophages, which was correlated with enhanced IL-1beta production. However, the intensity of the observed effects suggested that additional staurosporine-sensitive regulatory mechanisms are in operation at the level of promoter activity.

Induction of tolerance to lipopolysaccharide and mycobacterial components in Chinese hamster ovary/CD14 cells is not affected by overexpression of Toll-like receptors 2 or 4.

Down-regulation of cell surface expression of Toll-like receptor (TLR) 4 following LPS stimulation has been suggested to underlie endotoxin tolerance. In this study, we examined whether overexpression of TLR2 or TLR4 would affect the ability of cells to become tolerant to LPS or the mycobacterial components, arabinose-capped lipoarabinomannan (LAM) and soluble tuberculosis factor (STF). To this end, Chinese hamster ovary/CD14 cells stably transfected with a NF-kappaB-dependent reporter construct, endothelial leukocyte adhesion molecule CD25 (the 3E10 clone), were engineered to overexpress either human TLR2 or TLR4. Transfected TLRs exhibited proper signaling functions, as evidenced by increased LPS responsiveness of 3E10/TLR4 cells and acquisition of sensitivity to TLR2-specific ligands upon transfection of TLR2 into TLR2-negative 3E10 cells. Pretreatment of cells with LPS, LAM, or STF did not modulate TLR2 or TLR4 cell surface expression. Following LPS exposure, 3E10, 3E10/TLR2, and 3E10/TLR4 cells exhibited comparable decreases in LPS-mediated NF-kappaB activation and mitogen-activated protein (MAP) kinase phosphorylation. Likewise, LPS pretreatment profoundly inhibited LPS-induced NF-kappaB translocation in Chinese hamster ovary cells that concomitantly overexpressed human TLR4 and myeloid differentiation protein-2 (MD-2), but failed to modulate TLR4 or MD-2 cell surface expression. Pretreatment of 3E10/TLR2 cells with LAM or STF decreased their NF-kappaB responses induced by subsequent stimulation with these substances or LPS. Conversely, prior exposure of 3E10/TLR2 cells to LPS led to hyporesponsiveness to LPS, LAM, and STF, indicating that LPS and mycobacterial products induce cross-tolerance. Thus, tolerance to LPS and mycobacterial components cannot be attributed solely to a decrease in TLR/MD-2 expression levels, suggesting inhibition of expression or function of other signaling intermediates.

Different Toll-like receptor agonists induce distinct macrophage responses.

We previously reported that gram-negative bacterial lipopolysaccharide (LPS) activates cells via Toll-like receptor (TLR) 4, whereas the mycobacterial cell wall glycolipid lipoarabinomannan (LAM) activates cells via TLR2. We also identified a secreted TLR2 agonist activity in short-term culture filtrates of Mycobacterium tuberculosis bacilli, termed soluble tuberculosis factor (STF). Here we show that STF contains mannosylated phosphatidylinositol (PIM) and that purified PIM possesses TLR2 agonist activity. Stimulation of RAW 264.7 macrophages by LPS, LAM, STF, and PIM rapidly activated nuclear factor (NF)-kappaB, activator protein-1 (AP-1), and mitogen-activated protein (MAP) kinases. These TLR agonists induced similar levels of NF-kappaB and AP-1 DNA-binding activity, as well as trans-activation function. Unexpectedly, these TLR agonists induced tumor necrosis factor alpha secretion, whereas only LPS was capable of inducing interleukin-1beta and nitric oxide secretion. Thus, different TLR proteins are still capable of activating distinct cellular responses, in spite of their shared capacities to activate NF-kappaB, AP-1, and MAP kinases.

Mediator caused induction of a human bradykinin B1 receptor minigene: participation of c-Jun in the process.

The bradykinin B1 receptor (BKB1R) gene is expressed in selected tissues such as lung and kidney. In these tissues it is expressed at a very low level until induced by inflammatory mediators. Our aim has been to understand the mechanism of this regulatory process. A human BKB1R minigene was constructed. It contained a 1.8 kb promoter, the entire exon I, 1.5 kb of intron I, the entire exon II and intron II, and the luciferase gene as a reporter. Transient transfection of the minigene into SV40-transformed IMR90 cells (IMRSV) resulted in a promoter activity which was activated by the mediators, lipopolysaccharide and (LPS) desArg(10)-kallidin. In contrast, these mediators did not induce the activity of the 1.8 kb promoter construct alone. Thus, motifs exclusive of the promoter such as 5'-UTR and/or intron regions are required for mediator-induced expression of this gene. Promoter activities of both the minigene and the 1.8 kb promoter construct were enhanced in a dose-dependent manner upon cotransfection with c-Jun. Furthermore, cotransfecting c-Jun with the minigene achieved the maximal promoter activity with no further increase in response to mediators. Conversely, the induction of the minigene promoter activity by mediators was abolished upon cotransfection with a dominant negative mutant of c-Jun. Other experiments suggest that multiple AP-1 sites are interactive with the c-Jun upregulation of this gene. Taken together, these results point to c-Jun as a key intermediary in the activation of the expression of this gene by mediators. However, participation of motifs outside of the promoter are necessary to obtain this inducible expression.

PU.1 and multiple IFN regulatory factor proteins synergize to mediate transcriptional activation of the human IL-1 beta gene.

Both lymphoid and myeloid cells express two related members of the IFN regulatory factor (IRF) family of transcription factors, specifically IRF-4 and IFN consensus binding protein (ICSBP or IRF-8). We previously reported that macrophages express IRF-4 and in combination with the ETS-like protein PU.1 can synergistically activate a human IL-1beta reporter gene. Here we report that this synergy is mediated by a composite PU.1/IRF element located within an upstream enhancer known to confer cytokine- and LPS-inducible expression. In macrophages, synergistic activation of IL-1beta reporter gene expression was preferentially mediated by IRF-4, whereas IRF-4 and ICSBP were equally capable of synergizing with PU.1 when coexpressed in fibroblasts. Furthermore, coexpression of IRF-1 and IRF-2 dramatically increased the capacity of both PU.1/IRF-4 and PU.1/ICSBP to induce IL-1beta reporter gene expression in fibroblasts. The additional synergy observed with IRF-1 and IRF-2 coexpression is mediated by a region of DNA distinct from either the IL-1beta enhancer or promoter. We also assessed the capacity of these transcription factors to activate endogenous IL-1beta gene when overexpressed in human embryonic kidney 293 cells. Although ectopic expression of PU.1 alone was sufficient to activate modest levels of IL-1beta transcripts, endogenous IL-1beta expression was markedly increased following coexpression of additional IRF proteins. Thus, maximal expression of both a human IL-1beta reporter gene and the endogenous IL-1beta gene was observed in cells that coexpressed PU.1, IRF-4 (or ICSBP), IRF1, and IRF2. Together, our observations suggest that these factors may function together as an enhanceosome.

Differential effects of a Toll-like receptor antagonist on Mycobacterium tuberculosis-induced macrophage responses.

We previously showed that viable Mycobacterium tuberculosis (Mtb) bacilli contain distinct ligands that activate cells via the mammalian Toll-like receptor (TLR) proteins TLR2 and TLR4. We now demonstrate that expression of a dominant negative TLR2 or TLR4 proteins in RAW 264.7 macrophages partially blocked Mtb-induced NF-kappa B activation. Coexpression of both dominant negative proteins blocked virtually all Mtb-induced NF-kappa B activation. The role of the TLR4 coreceptor MD-2 was also examined. Unlike LPS, Mtb-induced macrophage activation was not augmented by overexpression of ectopic MD-2. Moreover, cells expressing an LPS-unresponsive MD-2 mutant responded normally to Mtb. We also observed that the lipid A-like antagonist E5531 specifically inhibited TLR4-dependent Mtb-induced cellular responses. E5531 could substantially block LPS- and Mtb-induced TNF-alpha production in both RAW 264.7 cells and primary human alveolar macrophages (AM phi). E5531 inhibited Mtb-induced AM phi apoptosis in vitro, an effect that was a consequence of the inhibition of TNF-alpha production by E5531. In contrast, E5531 did not inhibit Mtb-induced NO production in RAW 264.7 cells and AM phi. Mtb-stimulated peritoneal macrophages from TLR2- and TLR4-deficient animals produced similar amounts of NO compared with control animals, demonstrating that these TLR proteins are not required for Mtb-induced NO production. Lastly, we demonstrated that a dominant negative MyD88 mutant could block Mtb-induced activation of the TNF-alpha promoter, but not the inducible NO synthase promoter, in murine macrophages. Together, these data suggest that Mtb-induced TNF-alpha production is largely dependent on TLR signaling. In contrast, Mtb-induced NO production may be either TLR independent or mediated by TLR proteins in a MyD88-independent manner.

Lipopolysaccharide binding protein potentiates airway reactivity in a murine model of allergic asthma.

The development of allergic asthma is influenced by both genetic and environmental factors. Epidemiologic data often show no clear relationship between the levels of allergen and clinical symptoms. Recent data suggest that bacterial LPS may be a risk factor related to asthma severity. Airborne LPS is typically present at levels that are insufficient to activate alveolar macrophages in the absence of the accessory molecule LPS binding protein (LBP). LBP levels are markedly elevated in bronchoalveolar lavage fluids obtained from asthmatic subjects compared with those in normal controls. We hypothesized that LBP present in the lung could augment the pulmonary inflammation and airway reactivity associated with allergic asthma by sensitizing alveolar macrophages to LPS or other bacterial products and triggering them to release proinflammatory mediators. We compared wild-type (WT) and LBP-deficient mice using a defined Ag immunization and aerosol challenge model of allergic asthma. Immunized LBP-deficient mice did not develop substantial Ag-induced airway reactivity, whereas WT mice developed marked bronchoconstriction following aerosol Ag sensitization and challenge with methacholine. Similarly, production of NO synthase 2 protein and the NO catabolite peroxynitrite was dramatically higher in the lungs of WT mice following challenge compared with that in LBP-deficient mice. Thus, NO production appears to correlate with airway reactivity. In contrast, both mice developed similar pulmonary inflammatory cell infiltrates and elevated mucin production. Thus, LBP appears to participate in the development of Ag-induced airway reactivity and peroxynitrite production, but does not seem to be required for the development of pulmonary inflammation.

Differential roles of Toll-like receptors in the elicitation of proinflammatory responses by macrophages.

BACKGROUND: Mammalian Toll-like receptor (TLR) proteins are pattern recognition receptors for a diverse array of bacterial and viral products. Gram negative bacterial lipopolysaccharide (LPS) activates cells through TLR4, whereas the mycobacterial cell wall glycolipids, lipoarabinomannan (LAM) and mannosylated phosphatidylinositol (PIM), activate cells through TLR2. Furthermore, short term culture filtrates of M. tuberculosis bacilli contain a TLR2 agonist activity, termed soluble tuberculosis factor (STF), that appears to be PIM. It was recently shown that stimulation of RAW264.7 murine macrophages by LPS, LAM, STF, and PIM rapidly activated NF-kappaB, AP1, and MAP kinases. RESULTS: This study shows that signalling by TLR2 and TLR4 also activates the protein kinase Akt, a downstream target of phosphatidylinositol-3'-kinase (PI-3-K). This finding suggests that activation of PI-3-K represents an additional signalling pathway induced by engagement of TLR2 and TLR4. Subsequently, the functional responses induced by the different TLR agonists were compared. LPS, the mycobacterial glycolipids, and the OspC lipoprotein (a TLR2 agonist) all induced macrophages to secrete tumour necrosis factor alpha (TNFalpha), whereas only LPS could induce nitric oxide (NO) secretion. Human alveolar macrophages also exhibited a distinct pattern of cellular response after stimulation with TLR2 and TLR4 agonists. Specifically, LPS induced TNFalpha, MIP-1beta, and RANTES production in these cells, whereas the TLR2 agonists induced only MIP-1beta production. CONCLUSION: Together, these data show that different TLR proteins mediate the activation of distinct cellular responses, despite their shared ability to activate NF-kappaB, AP1, MAP kinases, and PI-3-K.

Transcriptional regulation of the human interleukin 1beta gene by fibronectin: role of protein kinase C and activator protein 1 (AP-1).

Interleukin 1beta (IL-1beta) is a multifunctional polypeptide considered a key cytokine during inflammation. Fibronectin (FN), a matrix glycoprotein highly expressed in injured tissues, can induce expression of IL-1beta in human blood monocytic cells. Herein, we explore the intracellular signals and transcriptional mechanisms responsible for IL-1beta induction by FN using human promonocytic U937 cells transfected with the human IL-1beta promoter connected to a reporter gene. Exposure of transfected U937s to FN resulted in increased expression of the full-length IL-1beta promoter. This effect, mediated via the alpha5beta1 integrin, was associated with activation of mitogen-activated protein kinases (MAPKs) and was abolished by pre-treatment of cells with Calphostin C, a specific inhibitor of protein kinase C (PKC) activation. Deletion analysis and co-transfection studies using consensus activator protein 1 (AP-1) oligonucleotides suggested that an AP-1 site present in the 5' end of the IL-1beta promoter was involved in the FN-induced response. Finally, electrophoretic mobility shift assays showed that FN induced binding of AP-1, but not NF-kappaB. Together, these experiments demonstrate that FN binding to the alpha5beta1 integrin activates MAPK-dependent signal pathways, and results in the transcription of the IL-1beta promoter in U937 cells by activating PKC and inducing AP-1.

Interleukin-1/Toll receptor family members: receptor structure and signal transduction pathways.

Interleukin-1 (IL-1) is a central mediator of the inflammatory response. It plays a role in both systemic and local immune responses to invading microbes. There are two receptors (IL-1RI and IL-1RII) that mediate the cellular responses. These receptors belong to a family of receptors based on homologous receptor structure within the intracellular signaling domain. Other family members include the Drosophila protein Toll, the recently discovered mammalian Toll-like receptors (TLR), and the IL-18 receptor. Engagement of these receptors by their diverse ligands results in activation of very similar signal transduction cascades through use of common signaling intermediates. These signal transduction cascades lead to the activation of cellular responses that are known to regulate the innate immune response. Therefore, elucidating the function and redundancy of this receptor family is essential to the understanding of the innate immune response. This review examines each member of this receptor family and emphasizes similarities and potential differences in both receptor structure and signal transduction pathways to further the understanding of this complex receptor family.

A lipopolysaccharide-specific enhancer complex involving Ets, Elk-1, Sp1, and CREB binding protein and p300 is recruited to the tumor necrosis factor alpha promoter in vivo.

The tumor necrosis factor alpha (TNF-alpha) gene is rapidly activated by lipopolysaccharide (LPS). Here, we show that extracellular signal-regulated kinase (ERK) kinase activity but not calcineurin phosphatase activity is required for LPS-stimulated TNF-alpha gene expression. In LPS-stimulated macrophages, the ERK substrates Ets and Elk-1 bind to the TNF-alpha promoter in vivo. Strikingly, Ets and Elk-1 bind to two TNF-alpha nuclear factor of activated T cells (NFAT)-binding sites, which are required for calcineurin and NFAT-dependent TNF-alpha gene expression in lymphocytes. The transcription factors ATF-2, c-jun, Egr-1, and Sp1 are also inducibly recruited to the TNF-alpha promoter in vivo, and the binding sites for each of these activators are required for LPS-stimulated TNF-alpha gene expression. Furthermore, assembly of the LPS-stimulated TNF-alpha enhancer complex is dependent upon the coactivator proteins CREB binding protein and p300. The finding that a distinct set of transcription factors associates with a fixed set of binding sites on the TNF-alpha promoter in response to LPS stimulation lends new insights into the mechanisms by which complex patterns of gene regulation are achieved.

Activation of TNF-alpha transcription utilizes distinct MAP kinase pathways in different macrophage populations.

Stimulation of macrophages by lipopolysaccharide (LPS) leads to the rapid activation of MAP kinases (MAPK) and the subsequent induction of cytokine gene expression. We sought to determine whether LPS-inducible cytokine genes were differentially regulated in macrophages derived from different tissues. Our studies revealed that PD98059, an inhibitor of the extracellular-regulated kinase (ERK) pathway, blocked LPS-induced activation of tumor necrosis factor alpha (TNF-alpha) gene expression in a murine cell line derived from alveolar macrophages but not in a nonpulmonary macrophage cell line. These findings were confirmed using primary murine alveolar and peritoneal macrophages. This suggests that the TNF-alpha promoter contains MAPK-dependent and -independent regulatory elements that are used in a cell type-specific manner. We also found that differences in MAPK-regulated signaling were not mediated by NF-KB, LITAF, Egr-1, CREB, or ATF2/ c-Jun. Together, these studies demonstrate that transcriptional activation of the TNF-alpha gene requires the ERK signaling cascade in selected macrophage populations.

The biology of Toll-like receptors.

In 1997, a human homologue of the Drosophila Toll protein was described, a protein later to be designated Toll-like receptor 4 (TLR4). Since that time, additional human and murine TLR proteins have been identified. Mammalian TLR proteins appear to represent a conserved family of innate immune recognition receptors. These receptors are coupled to a signaling pathway that is conserved in mammals, insects, and plants, resulting in the activation of genes that mediate innate immune defenses. Numerous studies have now identified a wide variety of chemically-diverse bacterial products that serve as putative ligands for TLR proteins. More recent studies have identified the first endogenous protein ligands for TLR proteins. TLR signaling represents a key feature of innate immune response to pathogen invasion.

Toll-like receptor 4 imparts ligand-specific recognition of bacterial lipopolysaccharide.

Lipopolysaccharide (LPS) is the main inducer of shock and death in Gram-negative sepsis. Recent evidence suggests that LPS-induced signal transduction begins with CD14-mediated activation of 1 or more Toll-like receptors (TLRs). The lipid A analogues lipid IVa and Rhodobacter sphaeroides lipid A (RSLA) exhibit an uncommon species-specific pharmacology. Both compounds inhibit the effects of LPS in human cells but display LPS-mimetic activity in hamster cells. We transfected human TLR4 or human TLR2 into hamster fibroblasts to determine if either of these LPS signal transducers is responsible for the species-specific pharmacology. RSLA and lipid IVa strongly induced NF-kappaB activity and IL-6 release in Chinese hamster ovary fibroblasts expressing CD14 (CHO/CD14), but these compounds antagonized LPS antagonists in CHO/CD14 fibroblasts that overexpressed human TLR4. No such antagonism occurred in cells overexpressing human TLR2. We cloned TLR4 from hamster macrophages and found that human THP-1 cells expressing the hamster TLR4 responded to lipid IVa as an LPS mimetic, as if they were hamster in origin. Hence, cells heterologously overexpressing TLR4 from different species acquired a pharmacological phenotype with respect to recognition of lipid A substructures that corresponded to the species from which the TLR4 transgene originated. These data suggest that TLR4 is the central lipid A-recognition protein in the LPS receptor complex.