Hypoxia transcriptionally induces macrophage-inflammatory protein-3alpha/CCL-20 in primary human mononuclear phagocytes through nuclear factor (NF)-kappaB

Phase I/II Trial of Exportin 1 Inhibitor Selinexor plus Docetaxel in Previously Treated, Advanced KRAS-Mutant Non-Small Cell Lung Cancer

PURPOSE

Patients with Kirsten rat sarcoma viral oncogene (KRAS)-mutant non-small cell lung cancer (NSCLC) have limited therapeutic options. Based on the activity of nuclear export inhibition in preclinical models, we evaluated this strategy in previously treated, advanced KRAS-mutant NSCLC.

PATIENTS AND METHODS

The primary outcomes of this multicenter phase I/II dose-escalation trial of selinexor plus docetaxel were safety and tolerability. Selinexor was started 1 week before docetaxel to permit monotherapy pharmacodynamic assessment.

RESULTS

Among 40 enrolled patients, the median age was 66 years, 55% were female, and 85% were White. The MTD was selinexor 60 mg orally weekly plus docetaxel 75 mg/m2 every 3 weeks. The most common adverse events were nausea (73%, 8% grade ≥3), fatigue (70%, 5% grade ≥3), neutropenia (65%, 60% grade ≥3), and diarrhea (58%, 10% grade ≥3). Of 32 efficacy-evaluable patients, 7 (22%) had partial responses and 18 (56%) had stable disease. Outcomes were not associated with KRAS mutation type but were significantly better in cases with wild-type TP53 (42%), including response and disease control rates (27% and 80% vs. 9% and 27%, respectively; P = 0.03) and progression-free survival (median 7.4 vs. 1.8 months; HR, 0.2; 95% confidence interval, 0.07-0.67; P = 0.003). After selinexor initiation and prior to docetaxel administration, serum lactate dehydrogenase levels increased an average of 51 U/L in TP53-altered cases and decreased an average of 48 U/L in TP53 wild-type cases (P = 0.06).

CONCLUSIONS

Selinexor plus docetaxel was relatively well tolerated in patients with advanced KRAS-mutant NSCLC. The regimen has promising efficacy in TP53 wild-type cases, in which selinexor monotherapy may also have activity.

PD-L2 mediates tobacco smoking-induced recruitment of regulatory T cells via the RGMB/NFκB/CCL20 cascade

Programmed cell death ligand 2 (PD-L2), a ligand for the receptor programmed cell death 1 (PD-1), has an identity of 34% with its twin ligand PD-L1 and exhibits higher binding affinity with PD-1 than PD-L1. However, the role of PD-L2 in non-small cell lung cancer (NSCLC) progression, especially tobacco-induced cancer progression, has not been fully understood. Here, we found that PD-L2 promoted tumor growth in murine models with recruitment of regulatory T cells (Tregs). In patients with NSCLC, PD-L2 expression level in tumor samples was higher than in counterpart normal controls and was positively associated with patients' response to anti-PD-1 treatment. Mechanismly, PD-L2 bound its receptor Repulsive guidance molecule B (RGMB) on cancer cells and activated extracellular signal-regulated kinase (Erk) and nuclear factor κB (NFκB), leading to increased production of chemokine CCL20, which recruited Tregs and contributed to NSCLC progression. Consistently, knockdown of RGMB or NFκB p65 inhibited PD-L2-induced CCL20 production, and silencing of PD-L2 repressed Treg recruitment by NSCLC cells. Furthermore, cigarette smoke and carcinogen benzo(a)pyrene (BaP) upregulated PD-L2 in lung epithelial cells via aryl hydrocarbon receptor (AhR)-mediated transcription activation, whose deficiency markedly suppressed BaP-induced PD-L2 upregulation. These results suggest that PD-L2 mediates tobacco-induced recruitment of Tregs via the RGMB/NFκB/CCL20 cascade, and targeting this pathway might have therapeutic potentials in NSCLC.

Molecular Signature of Neuroinflammation Induced in Cytokine-Stimulated Human Cortical Spheroids

Crucial in the pathogenesis of neurodegenerative diseases is the process of neuroinflammation that is often linked to the pro-inflammatory cytokines Tumor necrosis factor alpha (TNFα) and Interleukin-1beta (IL-1β). Human cortical spheroids (hCSs) constitute a valuable tool to study the molecular mechanisms underlying neurological diseases in a complex three-dimensional context. We recently designed a protocol to generate hCSs comprising all major brain cell types. Here we stimulate these hCSs for three time periods with TNFα and with IL-1β. Transcriptomic analysis reveals that the main process induced in the TNFα- as well as in the IL-1β-stimulated hCSs is neuroinflammation. Central in the neuroinflammatory response are endothelial cells, microglia and astrocytes, and dysregulated genes encoding cytokines, chemokines and their receptors, and downstream NFκB- and STAT-pathway components. Furthermore, we observe sets of neuroinflammation-related genes that are specifically modulated in the TNFα-stimulated and in the IL-1β-stimulated hCSs. Together, our results help to molecularly understand human neuroinflammation and thus a key mechanism of neurodegeneration.

Toxicity of the iron siderophore mycobactin J in mouse macrophages: Evidence for a hypoxia response

Mycobacterium tuberculosis, the causative agent of tuberculosis, is an obligate intracellular pathogen that lives within the phagosome of macrophages. Here we demonstrate that the siderophore mycobactin J, produced by the closely related intracellular pathogen Mycobacterium paratuberculosis, is toxic to murine macrophage cells. Its median lethal dose, 10 μM, is lower than that of the iron chelators desferrioxamine B and TrenCAM, an enterobactin analog. To determine the source of this toxicity, we conducted microarray, ELISA, and metabolite profiling experiments. The primary response is hypoxia-like, which implies iron starvation as the underlying cause of the toxicity. This observation is consistent with our recent finding that mycobactin J is a stronger iron chelator than had been inferred from previous studies. Mycobactin J is known to partition into cell membranes and hydrophobic organelles indicating that enhanced membrane penetration is also a likely factor. Thus, mycobactin J is shown to be toxic, eliciting a hypoxia-like response under physiological conditions.

Hypoxia Alters the Expression of CC Chemokines and CC Chemokine Receptors in a Tumor-A Literature Review

Hypoxia, i.e., oxygen deficiency condition, is one of the most important factors promoting the growth of tumors. Since its effect on the chemokine system is crucial in understanding the changes in the recruitment of cells to a tumor niche, in this review we have gathered all the available data about the impact of hypoxia on β chemokines. In the introduction, we present the chronic (continuous, non-interrupted) and cycling (intermittent, transient) hypoxia together with the mechanisms of activation of hypoxia inducible factors (HIF-1 and HIF-2) and NF-κB. Then we describe the effect of hypoxia on the expression of chemokines with the CC motif: CCL1, CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11, CCL13, CCL15, CCL16, CCL17, CCL18, CCL19, CCL20, CCL21, CCL22, CCL24, CCL25, CCL26, CCL27, CCL28 together with CC chemokine receptors: CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10. To better understand the effect of hypoxia on neoplastic processes and changes in the expression of the described proteins, we summarize the available data in a table which shows the effect of individual chemokines on angiogenesis, lymphangiogenesis, and recruitment of eosinophils, myeloid-derived suppressor cells (MDSC), regulatory T cells (T_reg), and tumor-associated macrophages (TAM) to a tumor niche.

MTSS1 suppresses mammary tumor-initiating cells by enhancing RBCK1-mediated p65 ubiquitination

Tumor-initiating cells (TICs) are considered the culprits of cancer development and progression. Dysregulation of metastasis suppressor protein 1 (MTSS1) has been widely observed in tumor metastasis, but its functional contribution and mechanism in cancer is poorly understood. Here we report a role of MTSS1 in suppressing TICs in breast cancer. Mtss1 knockout (KO) enhances the mammary epithelial TIC subpopulation in both luminal and basal-like breast cancer mouse models. MTSS1 also suppresses tumorsphere formation in breast cancer cells. Mechanistically, MTSS1 interacts with the E3 ligase RanBP2-type and C3HC4-type zinc finger containing 1 (RBCK1) to facilitate RBCK1-mediated p65 ubiquitination and degradation, thus suppressing the NF-κB signaling pathway and tumorigenesis. In addition, actin beta-like 2 (ACTBL2) competes with RBCK1 for MTSS1 binding, leading to p65 stabilization. Importantly, MTSS1 silencing promotes patient-derived organoid formation and xenograft growth. MTSS1 downregulation in clinical tumors is also linked to worse prognosis. Overall our data reveal a new paradigm of NF-κB regulation and may have important implications in therapeutics targeting TICs.

Astrocyte-derived CCL20 reinforces HIF-1-mediated hypoxic responses in glioblastoma by stimulating the CCR6-NF-κB signaling pathway

During tumor development, stromal cells are co-opted to the tumor milieu and provide favorable conditions for the tumor. Hypoxia stimulates cancer cells to acquire a more malignant phenotype via activation of hypoxia-inducible factor 1 (HIF-1). Given that cancer cells and astrocytes in glioblastomas coexist in a hypoxic microenvironment, we examined whether astrocytes affect the adaptation of glioblastoma cells to hypoxia. Immunoblotting, reporter assays, quantitative RT-PCR, and chromatin immunoprecipitation were performed to evaluate HIF-1 signaling in glioblastoma cells. Astrocyte-derived chemokine C-C motif ligand 20 (CCL20) was identified using cytokine arrays, and its role in glioblastoma development was evaluated in orthotopic xenografts. Astrocytes augmented HIF-1α expression in glioblastoma cells under hypoxia. The expression of HIF-1 downstream genes, cancer colony formation, and Matrigel invasion of glioblastoma cells were stimulated by conditioned medium from astrocytes pre-exposed to hypoxia. CCL20 was secreted in a hypoxia-dependent manner from astrocytes and busted the hypoxic induction of HIF-1α in glioblastoma cells. Mechanistically, the CCL20/CCR6 signaling pathway upregulates HIF-1α by stimulating nuclear factor kappa B-driven transactivation of the HIF1A gene. Compared with the control tumors, CCR6-deficient glioblastoma xenografts grew more slowly, with poor vascularization, and expressed lower levels of HIF-1α and its downstream proteins. Furthermore, CCR6 expression was correlated with HIF-1α expression in GEO and TCGA datasets from human glioblastoma tissues. These results suggest that glioblastoma cells adapt well to hypoxic stress by virtue of CCL20 derived from neighboring astrocytes.

The power of bioluminescence imaging in understanding host-pathogen interactions

Infectious diseases are one of the leading causes of death worldwide. Modelling and understanding human infection is imperative to developing treatments to reduce the global burden of infectious disease. Bioluminescence imaging is a highly sensitive, non-invasive technique based on the detection of light, produced by luciferase-catalysed reactions. In the study of infectious disease, bioluminescence imaging is a well-established technique; it can be used to detect, localize and quantify specific immune cells, pathogens or immunological processes. This enables longitudinal studies in which the spectrum of the disease process and its response to therapies can be monitored. Light producing transgenic rodents are emerging as key tools in the study of host response to infection. Here, we review the strategies for identifying biological processes in vivo, including the technology of bioluminescence imaging and illustrate how this technique is shedding light on the host-pathogen relationship.

The Absence of Interferon-β Promotor Stimulator-1 (IPS-1) Predisposes to Bronchiolitis and Asthma-like Pathology in Response to Pneumoviral Infection in Mice

Respiratory syncytial virus (RSV)-bronchiolitis is a major cause of infant morbidity and mortality and a risk factor for subsequent asthma. We showed previously that toll-like receptor (TLR)7 in plasmacytoid dendritic cells (pDCs) is critical for protection against bronchiolitis and asthma in mice infected with pneumonia virus of mice (PVM), the mouse homolog of RSV. This lack of redundancy was unexpected as interferon-β promotor stimulator-1 (IPS-1) signalling, downstream of RIG-I-like receptor (RLR) and not TLR7 activation, contributes to host defence in hRSV-inoculated adult mice. To further clarify the role of IPS-1 signalling, we inoculated IPS-1^−/− and WT mice with PVM in early-life, and again in later-life, to model the association between bronchiolitis and asthma. IPS-1 deficiency predisposed to severe PVM bronchiolitis, characterised by neutrophilic inflammation and necroptotic airway epithelial cell death, high mobility group box 1 (HMGB1) and IL-33 release, and downstream type-2 inflammation. Secondary infection induced an eosinophilic asthma-like pathophysiology in IPS-1^−/− but not WT mice. Mechanistically, we identified that IPS-1 is necessary for pDC recruitment, IFN-α production and viral control. Our findings suggest that TLR7 and RLR signalling work collaboratively to optimally control the host response to pneumovirus infection thereby protecting against viral bronchiolitis and subsequent asthma.

Rhinovirus-bacteria coexposure synergistically induces CCL20 production from human bronchial epithelial cells

Exacerbations of chronic obstructive pulmonary disease are triggered by viral or bacterial pathogens, with human rhinovirus (HRV) and nontypeable Hemophilus influenzae (NTHI) among the most commonly detected pathogens. Patients who suffer from concomitant viral and bacterial infection have more severe exacerbations. The airway epithelial cell is the initial site of viral and bacterial interactions, and CCL20 is an epithelial chemokine that attracts immature dendritic cells to the airways and can act as an antimicrobial. As such, it contributes to innate and adaptive immune responses to infection. We used primary cultures of human bronchial epithelial cells and the BEAS-2B cell line to examine the effects of bacterial-viral coexposure, as well as each stimulus alone, on epithelial expression of CXCL8 and, in particular, CCL20. HRV-bacterial coexposure induced synergistic production of CXCL8 and CCL20 compared with the sum of each stimulus alone. Synergistic induction of CCL20 did not require viral replication and occurred with two different HRV serotypes that use different viral receptors. Synergy was also seen with either NTHI or Pseudomonas aeruginosa Synergistic induction of CCL20 was transcriptionally regulated. Although NF-κB was required for transcription, it did not regulate synergy, but NF-IL-6 did appear to contribute. Among MAPK inhibitors studied, neither SB203580 nor PD98059 had any effect on synergy, whereas U0126 prevented synergistic induction of CCL20 by HRV and bacteria, apparently via "off-target" effects. Thus bacterial-viral coexposure synergistically increases innate immune responses compared with individual infections. We speculate that this increased inflammatory response leads to worse clinical outcomes.

Functional promoter polymorphisms direct the expression of cystathionine gamma-lyase gene in mouse models of essential hypertension

Despite the well-known role of cystathionine γ-lyase (Cth) in cardiovascular pathophysiology, transcriptional regulation of Cth remains incompletely understood. Sequencing of the Cth promoter region in mouse models of genetic/essential hypertension (viz. Blood Pressure High [BPH], Blood Pressure Low [BPL] and Blood Pressure Normal [BPN] mice) identified several genetic variations. Transient transfections of BPH/BPL-Cth promoter-reporter plasmids into various cell types revealed higher promoter activity of BPL-Cth than that of BPH-Cth. Corroboratively, endogenous Cth mRNA levels in kidney and liver tissues were also elevated in BPL mice. Computational analysis of the polymorphic Cth promoter region predicted differential binding affinity of c-Rel, HOXA3 and IRF1 with BPL/BPH-Cth promoter domains. Over-expression of c-Rel/HOXA3/IRF1 modulated BPL/BPH-Cth promoter activities in a consistent manner. Gel shift assays using BPH/BPL-Cth-promoter oligonucleotides with/without binding sites for c-Rel/HOXA3/IRF1 displayed formation of specific complexes with c-Rel/HOXA3/IRF1; addition of antibodies to reaction mixtures resulted in supershifts/inhibition of Cth promoter-transcription factor complexes. Furthermore, chromatin immunoprecipitation (ChIP) assays proved differential binding of c-Rel, HOXA3 and IRF1 with the polymorphic promoter region of BPL/BPH-Cth. Tumor necrosis factor-α (TNF-α) reduced the activities of BPL/BPH-Cth promoters to different extents that were further declined by ectopic expression of IRF1; on the other hand, siRNA-mediated down-regulation of IRF1 rescued the TNF-α-mediated suppression of the BPL/BPH-Cth promoter activities. In corroboration, ChIP analysis revealed enhanced binding of IRF1 with BPH/BPL-Cth promoter following TNF-α treatment. BPL/BPH-Cth promoter activity was diminished upon exposure of hepatocytes and cardiomyoblasts to ischemia-like pathological condition due to reduced binding of c-Rel with BPL/BPH-Cth-promoter. Taken together, this study reveals the molecular basis for the differential expression of Cth in mouse models of essential hypertension under basal and pathophysiological conditions.

Mutually Supportive Mechanisms of Inflammation and Vascular Remodeling

Chronic inflammation is often accompanied by angiogenesis, the development of new blood vessels from existing ones. This vascular response is a response to chronic hypoxia and/or ischemia, but is also contributory to the progression of disorders including atherosclerosis, arthritis, and tumor growth. Proinflammatory and proangiogenic mediators and signaling pathways form a complex and interrelated network in these conditions, and many factors exert multiple effects. Inflammation drives angiogenesis by direct and indirect mechanisms, promoting endothelial proliferation, migration, and vessel sprouting, but also by mediating extracellular matrix remodeling and release of sequestered growth factors, and recruitment of proangiogenic leukocyte subsets. The role of inflammation in promoting angiogenesis is well documented, but by facilitating greater infiltration of leukocytes and plasma proteins into inflamed tissues, angiogenesis can also propagate chronic inflammation. This review examines the mutually supportive relationship between angiogenesis and inflammation, and considers how these interactions might be exploited to promote resolution of chronic inflammatory or angiogenic disorders.

CARMA3 Is Critical for the Initiation of Allergic Airway Inflammation

Innate immune responses to allergens by airway epithelial cells (AECs) help initiate and propagate the adaptive immune response associated with allergic airway inflammation in asthma. Activation of the transcription factor NF-κB in AECs by allergens or secondary mediators via G protein-coupled receptors (GPCRs) is an important component of this multifaceted inflammatory cascade. Members of the caspase recruitment domain family of proteins display tissue-specific expression and help mediate NF-κB activity in response to numerous stimuli. We have previously shown that caspase recruitment domain-containing membrane-associated guanylate kinase protein (CARMA)3 is specifically expressed in AECs and mediates NF-κB activation in these cells in response to stimulation with the GPCR agonist lysophosphatidic acid. In this study, we demonstrate that reduced levels of CARMA3 in normal human bronchial epithelial cells decreases the production of proasthmatic mediators in response to a panel of asthma-relevant GPCR ligands such as lysophosphatidic acid, adenosine triphosphate, and allergens that activate GPCRs such as Alternaria alternata and house dust mite. We then show that genetically modified mice with CARMA3-deficient AECs have reduced airway eosinophilia and proinflammatory cytokine production in a murine model of allergic airway inflammation. Additionally, we demonstrate that these mice have impaired dendritic cell maturation in the lung and that dendritic cells from mice with CARMA3-deficient AECs have impaired Ag processing. In conclusion, we show that AEC CARMA3 helps mediate allergic airway inflammation, and that CARMA3 is a critical signaling molecule bridging the innate and adaptive immune responses in the lung.

Tobacco smoke induces production of chemokine CCL20 to promote lung cancer

Tobacco kills nearly 6 million people each year, and 90% of the annual 1.59 million lung cancer deaths worldwide are caused by cigarette smoke. Clinically, a long latency is required for individuals to develop lung cancer since they were first exposed to smoking. In this study, we aimed to identify clinical relevant inflammatory factors that are critical for carcinogenesis by treating normal human lung epithelial cells with tobacco carcinogen nicotine-derived nitrosaminoketone (NNK) for a long period (60 days) and systematic screening in 84 cytokines/chemokines. We found that a chemokine CCL20 was significantly up-regulated by NNK, and in 78/173 (45.1%) patients the expression of CCL20 was higher in tumor samples than their adjacent normal lung tissues. Interestingly, CCL20 was up-regulated in 48/92 (52.2%) smoker and 29/78 (37.2%) nonsmoker patients (p = 0.05), and high CCL20 was associated with poor prognosis. NNK induced the production of CCL20, which promoted lung cancer cell proliferation and migration. In addition, an anti-inflammation drug, dexamethasone, inhibited NNK-induced CCL20 production and suppressed lung cancer in vitro and in vivo. These results indicate that CCL20 is crucial for tobacco smoke-caused lung cancer, and anti-CCL20 could be a rational approach to fight against this deadly disease.

The Dishevelled, EGL-10 and pleckstrin (DEP) domain-containing protein DEPDC7 binds to CARMA2 and CARMA3 proteins, and regulates NF-κB activation

The molecular complexes containing BCL10, MALT1 and CARMA proteins (CBM complex) have been recently identified as a key component in the signal transduction pathways that regulate activation of Nuclear Factor kappaB (NF-κB) transcription factor. Herein we identified the DEP domain-containing protein DEPDC7 as cellular binding partners of CARMA2 and CARMA3 proteins. DEPDC7 displays a cytosolic distribution and its expression induces NF-κB activation. Conversely, shRNA-mediated abrogation of DEPDC7 results in impaired NF-κB activation following G protein-coupled receptors stimulation, or stimuli that require CARMA2 and CARMA3, but not CARMA1. Thus, this study identifies DEPDC7 as a CARMA interacting molecule, and provides evidence that DEPDC7 may be required to specifically convey on the CBM complex signals coming from activated G protein-coupled receptors.

Evaluation of cytotoxicity and immune modulatory activities of soyasaponin Ab: an in vitro and in vivo study

To improve the immune efficacy of protein subunit vaccines, novel adjuvants are needed to elicit a suitable protective immune response and to promote long term immunologic memory. In this work, soyasaponin Ab, a major constituent among group A soyasaponins in soybeans was purified and prepared from soy hypocotyls. The immunomodulatory effects of soyasaponin Ab both in vitro and in vivo were investigated, and its pro-immunomodulatory molecular mechanism was also studied. For in vitro assays, with mouse macrophage cell line RAW264.7 as the studying model, both cytotoxicity and immune stimulatory activity were investigated to evaluate the potential of soyasaponin Ab as the vaccine adjuvant. The results indicated that soyasaponin Ab could be significantly safer than Quillaja saponins (QS). Soyasaponin Ab showed no toxicities over the tested concentration ranges compared to QS. Soyasaponin Ab was proved able to promote releases of inflammatory cytokines like TNFα and IL-1β in a dose-dependent manner. Furthermore, NF-κB signalling was also activated by soyasaponin Ab effectively. In addition, with TLR4 gene expression of RAW264.7 cell inhibited by RNA interference, immune stimulatory effects by soyasaponin Ab dropped down significantly. On the other hand, the in vivo experiment results showed that anti-ovalbumin (OVA) IgG, IgG1, IgG2a, IgG2b were significantly enhanced by the soyasaponin Ab and QS groups (p<0.05 or p<0.01). The results suggested that compared to QS, soyasaponin Ab may represent a viable candidate for effective vaccine adjuvant. TLR4 receptor dependent pathway may be involved in immune stimulatory effects of soyasaponin Ab.

Mutations in BALB mitochondrial DNA induce CCL20 up-regulation promoting tumorigenic phenotypes

mtDNA mutations are common in human cancers and are thought to contribute to the process of neoplasia. We examined the role of mtDNA mutations in skin cancer by generating fibroblast cybrids harboring a mutation in the gene encoding the mitochondrial tRNA for arginine. This somatic mutation (9821insA) was previously reported in UV-induced hyperkeratotic skin tumors in hairless mice and confers specific tumorigenic phenotypes to mutant cybrids. Microarray analysis revealed and RT-PCR along with Western blot analysis confirmed the up-regulation of CCL20 and its receptor CCR6 in mtBALB haplotype containing the mt-Tr 9821insA allele compared to wild type mtB6 haplotype. Based on reported role of CCL20 in cancer progression we examined whether the hyper-proliferation and enhanced motility of mtBALB haplotype would be associated with CCL20 levels. Treatment of both genotypes with recombinant CCL20 (rmCCL20) resulted in enhanced growth and motility of mtB6 cybrids. Furthermore, the acquired somatic alteration increased the in vivo tumor growth of mtBALB cybrids through the up-regulation of CCL20 since neutralizing antibody significantly decreased in vivo tumor growth of these cells; and tumors from anti-CCL20 treated mice injected with mtBALB cybrids showed significantly decreased CCL20 levels. When rmCCL20 or mtBALB cybrids were used as chemotactic stimuli, mtB6 cybrids showed increased motility while anti-CCL20 antibody decreased the migration and in vivo tumor growth of mtBALB cybrids. Moreover, the inhibitors of MAPK signaling and NF-κB activation inhibited CCL20 expression in mtBALB cybrids and decreased their migratory capabilities. Thus, acquired mtDNA mutations may promote tumorigenic phenotypes through up-regulation of chemokine CCL20.

Vascular endothelial growth factor signaling in hypoxia and inflammation

Infection, cancer and cardiovascular diseases are the major causes for morbidity and mortality in the United States according to the Center for Disease Control. The underlying etiology that contributes to the severity of these diseases is either hypoxia induced inflammation or inflammation resulting in hypoxia. Therefore, molecular mechanisms that regulate hypoxia-induced adaptive responses in cells are important areas of investigation. Oxygen availability is sensed by molecular switches which regulate synthesis and secretion of growth factors and inflammatory mediators. As a consequence, tissue microenvironment is altered by re-programming metabolic pathways, angiogenesis, vascular permeability, pH homeostasis to facilitate tissue remodeling. Hypoxia inducible factor (HIF) is the central mediator of hypoxic response. HIF regulates several hundred genes and vascular endothelial growth factor (VEGF) is one of the primary target genes. Understanding the regulation of HIF and its influence on inflammatory response offers unique opportunities for drug development to modulate inflammation and ischemia in pathological conditions.

Syndecan-1 (CD138) modulates triple-negative breast cancer stem cell properties via regulation of LRP-6 and IL-6-mediated STAT3 signaling

Syndecan-1 (CD138), a heparan sulfate proteoglycan, acts as a coreceptor for growth factors and chemokines and is a molecular marker associated with epithelial-mesenchymal transition during development and carcinogenesis. Resistance of Syndecan-1-deficient mice to experimentally-induced tumorigenesis has been linked to altered Wnt-responsive precursor cell pools, suggesting a potential role of Syndecan-1 in breast cancer cell stem function. However, the precise molecular mechanism is still elusive. Here, we decipher the functional impact of Syndecan-1 knockdown using RNA interference on the breast cancer stem cell phenotype of human triple-negative MDA-MB-231 and hormone receptor-positive MCF-7 cells in vitro employing an analytical flow cytometric approach. Successful Syndecan-1 siRNA knockdown was confirmed by flow cytometry. Side population measurement by Hoechst dye exclusion and Aldehyde dehydrogenase-1 activity revealed that Syndecan-1 knockdown in MDA-MB-231 cells significantly reduced putative cancer stem cell pools by 60% and 27%, respectively, compared to controls. In MCF-7 cells, Syndecan-1 depletion reduced the side population by 40% and Aldehyde dehydrogenase-1 by 50%, repectively. In MDA-MB-231 cells, the CD44(+)CD24(-/low) phenotype decreased significantly by 6% upon siRNA-mediated Syndecan-1 depletion. Intriguingly, IL-6, its receptor sIL-6R, and the chemokine CCL20, implicated in regulating stemness-associated pathways, were downregulated by >40% in Syndecan-1-silenced MDA-MB-231 cells, which showed a dysregulated response to IL-6-induced shifts in E-cadherin and vimentin expression. Furthermore, activation of STAT-3 and NFkB transcription factors and expression of a coreceptor for Wnt signaling, LRP-6, were reduced by >45% in Syndecan-1-depleted cells compared to controls. At the functional level, Syndecan-1 siRNA reduced the formation of spheres and cysts in MCF-7 cells grown in suspension culture. Our study demonstrates the viability of flow cytometric approaches in analyzing cancer stem cell function. As Syndecan-1 modulates the cancer stem cell phenotype via regulation of the Wnt and IL-6/STAT3 signaling pathways, it emerges as a promising novel target for therapeutic approaches.

Transgenic mouse model harboring the transcriptional fusion ccl20-luciferase as a novel reporter of pro-inflammatory response

The chemokine CCL20, the unique ligand of CCR6 functions as an attractant of immune cells. Expression of CCL20 is induced by Toll-like Receptor (TLR) signaling or proinflammatory cytokine stimulation. However CCL20 is also constitutively produced at specific epithelial sites of mucosa. This expression profile is achieved by transcriptional regulation. In the present work we characterized regulatory features of mouse Ccl20 gene. Transcriptional fusions between the mouse Ccl20 promoter and the firefly luciferase (luc) encoding gene were constructed and assessed in in vitro and in vivo assays. We found that liver CCL20 expression and luciferase activity were upregulated by systemic administration of the TLR5 agonist flagellin. Using shRNA and dominant negative form specific for mouse TLR5, we showed that this expression was controlled by TLR5. To address in situ the regulation of gene activity, a transgenic mouse line harboring a functional Ccl20-luc fusion was generated. The luciferase expression was highly concordant with Ccl20 expression in different tissues. Our data indicate that the transgenic mouse model can be used to monitor activation of innate response in vivo.

Hypoxia: how does the monocyte-macrophage system respond to changes in oxygen availability?

Hypoxia is an important feature of inflamed tissue, such as the RA joint. Activated monocytes/macrophages and endothelial cells play a pivotal role in the pathogenesis of RA, implicated in the mechanism of inflammation and erosion. During development, myeloid progenitor cells sequentially give rise to monoblasts, promonocytes, and monocytes that are released from the bone marrow into the bloodstream. After extravasation, monocytes differentiate into long-lived, tissue-specific macrophages or DCs. The effect of different oxygen concentrations experienced by these cells during maturation represents a novel aspect of this developmental process. In inflamed joint tissue, the microvascular architecture is highly dysregulated; thus, efficiency of oxygen supply to the synovium is poor. Therefore, invading cells must adapt instantaneously to changes in the oxygen level of the microenvironment. Angiogenesis is an early event in the inflammatory joint, which is important in enabling activated monocytes to enter via endothelial cells by active recruitment to expand the synovium into a "pannus", resulting in cartilage degradation and bone destruction. The increased metabolic turnover of the expanding synovial pannus outpaces the dysfunctional vascular supply, resulting in hypoxia. The abnormal bioenergetics of the microenvironment further promotes synovial cell invasiveness. In RA, joint hypoxia represents a potential threat to cell function and survival. Notably, oxygen availability is a crucial parameter in the cellular energy metabolism, itself an important factor in determining the function of immune cells.

Identification of CD300a as a new hypoxia-inducible gene and a regulator of CCL20 and VEGF production by human monocytes and macrophages

Peripheral blood monocytes are recruited to inflammatory and tumor lesions where they undergo terminal differentiation into macrophages. Monocytes/macrophages integrate stimulatory and inhibitory signals present in the pathologic microenvironment through a defined repertoire of cell surface receptors, and deregulated expression of these molecules may result in amplification of inflammation or establishment of immune escape mechanisms. Characterization of the expression and function of these receptors is required for a better understanding of the regulation of monocyte/macrophage activity at pathologic sites. Hypoxia is a common feature of many pathological situations and an important regulator of monocyte/macrophage pro-inflammatory responses. In this study, we identify the leukocyte membrane antigen, CD300a, a member of the CD300 superfamily of immunoregulatory receptors, as a new hypoxia-inducible gene in primary human monocytes and monocyte-derived macrophages. CD300a mRNA up-regulation by hypoxia was rapid and reversible, paralleled by increased surface protein expression, and mediated by hypoxia-inducible factor-1α. CD300a induction was also triggered by the hypoxia-mimetic agent, desferrioxamine. CD300a exhibited both activating and inhibitory potential, differentially regulating CCL20 and vascular endothelial growth factor pro-inflammatory cytokine production by monocytes/macrophages upon triggering by an agonist Ab. These results suggest that CD300a induction by the hypoxic environment represents a mechanism of regulation of monocyte/macrophage pro-inflammatory responses at pathologic sites.

The serine protease plasmin triggers expression of the CC-chemokine ligand 20 in dendritic cells via Akt/NF-κB-dependent pathways

The number of dendritic cells is increased in advanced atherosclerotic lesions. In addition, plasmin, which might stimulate dendritic cells, is generated in atherosclerotic lesions. Here, we investigated cytokine and chemokine induction by plasmin in human dendritic cells. In human atherosclerotic vessel sections, plasmin colocalized with dendritic cells and the CC-chemokine ligand 20 (CCL20, MIP-3α), which is important for homing of lymphocytes and dendritic cells to sites of inflammation. Stimulation of human dendritic cells with plasmin, but not with catalytically inactivated plasmin, induced transcriptional regulation of CCL20. By contrast, proinflammatory cytokines such as TNF-α, IL-1α, and IL-1β were not induced. The plasmin-mediated CCL20 expression was preceded by activation of Akt and MAP kinases followed by activation of the transcription factor NF-κB as shown by phosphorylation of its inhibitor IκBα, by nuclear localization of p65, its phosphorylation, and binding to NF-κB consensus sequences. The plasmin-induced CCL20 expression was dependent on Akt- and ERK1/2-mediated phosphorylation of IκBα on Ser32/36 and of p65 on Ser276, whereas p38 MAPK appeared to be dispensable. Thus, plasmin triggers release of the chemokine CCL20 from dendritic cells, which might facilitate accumulation of CCR6⁺ immune cells in areas of plasmin generation such as inflamed tissues including atherosclerotic lesions.

Human monocytes and macrophages differ in their mechanisms of adaptation to hypoxia

Introduction

Inflammatory arthritis is a progressive disease with chronic inflammation of joints, which is mainly characterized by the infiltration of immune cells and synovial hyperproliferation. Monocytes migrate towards inflamed areas and differentiate into macrophages. In inflamed tissues, much lower oxygen levels (hypoxia) are present in comparison to the peripheral blood. Hence, a metabolic adaptation process must take place. Other studies suggest that Hypoxia Inducible Factor 1-alpha (HIF-1α) may regulate this process, but the mechanism involved for human monocytes is not yet clear. To address this issue, we analyzed the expression and function of HIF-1α in monocytes and macrophages, but also considered alternative pathways involving nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB).

Methods

Isolated human CD14⁺ monocytes were incubated under normoxia and hypoxia conditions with or without phorbol 12-myristate 13-acetate (PMA) stimulation, respectively. Nuclear and cytosolic fractions were prepared in order to detect HIF-1α and NFκB by immunoblot. For the experiments with macrophages, primary human monocytes were differentiated into human monocyte derived macrophages (hMDM) using human macrophage colony-stimulating factor (hM-CSF). The effects of normoxia and hypoxia on gene expression were compared between monocytes and hMDMs using quantitative PCR (quantitative polymerase chain reaction).

Results

We demonstrate, using primary human monocytes and hMDM, that the localization of transcription factor HIF-1α during the differentiation process is shifted from the cytosol (in monocytes) into the nucleus (in macrophages), apparently as an adaptation to a low oxygen environment. For this localization change, protein kinase C alpha/beta 1 (PKC-α/β₁ ) plays an important role. In monocytes, it is NFκB1, and not HIF-1α, which is of central importance for the expression of hypoxia-adjusted genes.

Conclusions

These data demonstrate that during differentiation of monocytes into macrophages, crucial cellular adaptation mechanisms are decisively changed.

Dendritic cell reprogramming by the hypoxic environment

Myeloid dendritic cells (DCs) are professional antigen-presenting cells central to the orchestration of innate and acquired immunity and the maintenance of self-tolerance. The local microenvironment contributes to the regulation of DC development and functions, and deregulated DC responses may result in amplification of inflammation, loss of tolerance, or establishment of immune escape mechanisms. DC generation from monocytic precursors recruited at sites of inflammation, tissue damage, or neoplasia occurs under condition of low partial oxygen pressure (pO(2), hypoxia). We reviewed the literature addressing the phenotypic and functional changes triggered by hypoxia in monocyte-derived immature (i) and mature (m) DCs. The discussion will revolve around in vitro studies of gene expression profile, which give a comprehensive representation of the complexity of response of these cells to low pO(2). The gene expression pattern of hypoxic DC will be discussed to address the question of the relationship with a specific maturation stage. We will summarize data relative to the regulation of the chemotactic network, which points to a role for hypoxia in promoting a migratory phenotype in iDCs and a highly proinflammatory state in mDCs. Current knowledge of the strict regulatory control exerted by hypoxia on the expression of immune-related cell surface receptors will also be addressed, with a particular focus on a newly identified marker of hypoxic DCs endowed with proinflammatory properties. Furthermore, we discuss the literature on the transcription mechanisms underlying hypoxia-regulated gene expression in DCs, which support a major role for the HIF/HRE pathway. Finally, recent advances shedding light on the in vivo influence of the local hypoxic microenvironment on DCs infiltrating the inflamed joints of juvenile idiopathic arthritis patients are outlined.

IL-15 protects NKT cells from inhibition by tumor-associated macrophages and enhances antimetastatic activity

Vα24-invariant NKT cells inhibit tumor growth by targeting tumor-associated macrophages (TAMs). Tumor progression therefore requires that TAMs evade NKT cell activity through yet-unknown mechanisms. Here we report that a subset of cells in neuroblastoma (NB) cell lines and primary tumors expresses membrane-bound TNF-α (mbTNF-α). These proinflammatory tumor cells induced production of the chemokine CCL20 from TAMs via activation of the NF-κB signaling pathway, an effect that was amplified in hypoxia. Flow cytometry analyses of human primary NB tumors revealed selective accumulation of CCL20 in TAMs. Neutralization of the chemokine inhibited in vitro migration of NKT cells toward tumor-conditioned hypoxic monocytes and localization of NKT cells to NB grafts in mice. We also found that hypoxia impaired NKT cell viability and function. Thus, CCL20-producing TAMs served as a hypoxic trap for tumor-infiltrating NKT cells. IL-15 protected antigen-activated NKT cells from hypoxia, and transgenic expression of IL-15 in adoptively transferred NKT cells dramatically enhanced their antimetastatic activity in mice. Thus, tumor-induced chemokine production in hypoxic TAMs and consequent chemoattraction and inhibition of NKT cells represents a mechanism of immune escape that can be reversed by adoptive immunotherapy with IL-15-transduced NKT cells.

The hypoxic environment reprograms the cytokine/chemokine expression profile of human mature dendritic cells

Myeloid dendritic cells (DCs) are professional antigen-presenting cells critical for the orchestration of immunity and maintenance of self-tolerance. DC development and functions are tightly regulated by a complex network of inhibitory and activating signals present in the tissue microenvironment, and dysregulated DC responses may result in amplification of inflammation, loss of tolerance, or establishment of immune escape mechanisms. Generation of mature (m)DCs from monocytic precursors recruited at pathological sites occurs under condition of low partial oxygen pressure (pO(2)). However, the way in which the hypoxic microenvironment modulates the functions of these cells is still not clear. We demonstrate that chronic hypoxia (4 days, 1% O(2)) promotes the onset of a highly proinflammatory gene expression profile in mDCs generated from primary human monocytes, characterized by the modulation of a significant cluster of genes coding for proinflammatory chemokines/cytokines and/or their receptors. Within the chemokine system, strong upregulation of genes encoding proteins chemotactic for neutrophils, such as CXCL2, CXCL3, CXCL5, CXCL6, and CXCL8, and for activated/memory T lymphocytes, monocytes, and immature (i) DCs, e.g. CCL20, CCL3 and CCL5, was observed, concomitant with decreased expression of genes coding for naive/resting T cells chemoattractants, CCL18 and CCL23. Other hypoxia-inducible genes coded for cytokines with a primary role in inflammation and angiogenesis, including osteopontin, vascular endothelial growth factor, and IL-1β. mRNA modulation was paralleled by protein secretion. These results suggest that conditions of reduced O(2) availability reprograms mDCs toward a proinflammatory direction by tuning the cytokine/chemokine repertoire, thus affecting their ability to regulate leukocyte trafficking and activation at pathological sites, with potential implications for the pathogenesis of chronic inflammatory diseases.

Regulation of CCL20 expression in astrocytes by IL-6 and IL-17

Astrocytes have an important role in the regulation of inflammation within the central nervous system (CNS). In neuroinflammatory conditions such as multiple sclerosis, numerous cytokines and chemokines are elevated including IL-6, IL-17, and CCL20. IL-17 enhances IL-6 signaling and subsequent IL-6 expression in astrocytes. CCL20 is a CC motif chemokine that functions as a chemoattractant to facilitate the recruitment of CCR6-expressing cells, including Th17 cells. In this study, we examined the role of IL-6 and IL-17 on CCL20 production in primary murine astrocytes. IL-6 in combination with the IL-6 soluble receptor (sIL-6R) stimulated CCL20 expression in part through STAT3 activation, whereas IL-17 alone had no effect. However, the combination of IL-6, sIL-6R, and IL-17 led to a robust increase in CCL20 production. IL-17 increased the activation-associated phosphorylation of NF-κB, and inhibition of the NF-κB pathway significantly inhibited the enhancement of CCL20 expression by IL-17. In addition, chromatin immunoprecipitation revealed that stimulation of primary astrocytes with IL-6 plus the sIL-6R induced STAT3 binding to the CCL20 promoter. Combined stimulation with IL-6, sIL-6R, and IL-17 increased the recruitment of phosphorylated NF-κB to the CCL20 promoter, increased binding of coactivators such as p300 and CBP, and enhanced H3 and H4 histone acetylation, consistent with a transcriptionally active gene. The astrocyte-produced CCL20 increased T cell migration as determined by transwell migration assay. Collectively, these results suggest that astrocytes, in response to IL-6, sIL-6R, and IL-17, may shift chemokine production to that favoring T cell recruitment to the CNS.

CCL20 is increased in hypercholesterolemic subjects and is upregulated by LDL in vascular smooth muscle cells: role of NF-κB

OBJECTIVE

Our aim was to analyze the regulation of CC Chemokine ligand 20 (CCL20) by LDL in human vascular smooth muscle cells (VSMC).

METHODS AND RESULTS

In asymptomatic subjects, circulating CCL20 levels were higher in patients with hypercholesterolemia (18.5±3.2 versus 9.1±1.3 pg/mL; P<0.01). LDL induced the expression of CCL20 in VSMC in a dose- and time-dependent manner. Increased levels of CCL20 secreted by LDL-treated VSMC significantly induced human lymphocyte migration, an effect reduced by CCL20 silencing. The upregulation of CCL20 by LDL was dependent on the activation of kinase signaling pathways and NF-κB. By site-directed mutagenesis, electrophoretic mobility shift assay, and chromatin immunoprecipitation, we identified a NF-κB site (-80/-71) in CCL20 promoter critical for LDL responsiveness. Lysophosphatidic acid mimicked the upregulation of CCL20 induced by LDL, and minimal oxidation of LDL increased the ability of LDL to induce CCL20 through a mechanism that involves lysophosphatidic acid receptors. CCL20 was overexpressed in atherosclerotic lesions from coronary artery patients, colocalizing with VSMC. CCL20 was detected in conditioned media from healthy human aorta and its levels were significantly higher in secretomes from carotid endarterectomy specimens.

CONCLUSION

This study identifies CCL20 in atherosclerotic lesions and recognizes this chemokine as a mediator highly sensitive to the inflammatory response elicited by LDL.

Gene expression profiling provides insights into pathways of oxaliplatin-related sinusoidal obstruction syndrome in humans

Sinusoidal obstruction syndrome (SOS; formerly veno-occlusive disease) is a well-established complication of hematopoietic stem cell transplantation, pyrrolizidine alkaloid intoxication, and widely used chemotherapeutic agents such as oxaliplatin. It is associated with substantial morbidity and mortality. Pathogenesis of SOS in humans is poorly understood. To explore its molecular mechanisms, we used Affymetrix U133 Plus 2.0 microarrays to investigate the gene expression profile of 11 human livers with oxaliplatin-related SOS and compared it to 12 matched controls. Hierarchical clustering analysis showed that profiles from SOS and controls formed distinct clusters. To identify functional networks and gene ontologies, data were analyzed by the Ingenuity Pathway Analysis Tool. A total of 913 genes were differentially expressed in SOS: 613 being upregulated and 300 downregulated. Reverse transcriptase-PCR results showed excellent concordance with microarray data. Pathway analysis showed major gene upregulation in six pathways in SOS compared with controls: acute phase response (notably interleukin 6), coagulation system (Serpine1, THBD, and VWF), hepatic fibrosis/hepatic stellate cell activation (COL3a1, COL3a2, PDGF-A, TIMP1, and MMP2), and oxidative stress. Angiogenic factors (VEGF-C) and hypoxic factors (HIF1A) were upregulated. The most significant increase was seen in CCL20 mRNA. In conclusion, oxaliplatin-related SOS can be readily distinguished according to morphologic characteristics but also by a molecular signature. Global gene analysis provides new insights into mechanisms underlying chemotherapy-related hepatotoxicity in humans and potential targets relating to its diagnosis, prevention, and treatment. Activation of VEGF and coagulation (vWF) pathways could partially explain at a molecular level the clinical observations that bevacizumab and aspirin have a preventive effect in SOS.

Anti-tumor potential of type-I NKT cells against CD1d-positive and CD1d-negative tumors in humans

Vα24-invariant natural killer T cells (NKTs) are strictly CD1d-restricted, and CD1d expression has been found in several types of leukemia and lymphoma as well as in brain tumors suggesting that these malignancies could be targeted for direct NKT-cell cytotoxicity. Several studies have revealed strong positive associations between the numbers of tumor-infiltrating or circulating NKTs with improved disease outcome in patients with diverse types of CD1d-negative solid tumors. The mechanism by which NKTs mediate anti-tumor activity against CD1d-negative tumors has long remained enigmatic. Recent evidence indicates that NKTs can suppress tumor growth indirectly by targeting CD1d-positive elements of tumor-supportive stroma such as tumor-associated macrophages. This review summarizes the current knowledge about the mechanisms that regulate NKT-cell localization to the tumor site and their interaction with the tumor microenvironment. The discussed strategies for pharmacologic modulation and genetic engineering of NKTs may lead to development of effective and broadly applicable immunotherapies of cancer.

OX40 induces CCL20 expression in the context of antigen stimulation: an expanding role of co-stimulatory molecules in chemotaxis

OX40 is an inducible co-stimulatory molecule expressed by activated T cells. It plays an important role in the activation and proliferation of T lymphocytes. Recently, some co-stimulatory molecules have been shown to direct leukocyte trafficking. Chemotaxis is essential for achieving an effective immune response. CCL20 is an important chemoattractant produced by activated T cells. In this study, using DO11.10 mice whose transgenic T cell receptor specifically recognizes ovalbumin, we demonstrate that ovalbumin induces OX40 expression in CD4+ lymphocytes. Further stimulation of OX40 by OX40 activating antibody up-regulates CCL20 production. Both NF-kappaB dependent and independent signaling pathways are implicated in the induction of CCL20 by OX40. Finally, we primed the DO11.10 splenocytes with or without OX40 activating antibody in the presence of ovalbumin. Intranasal administration of the cell lysates derived from the cells with OX40 stimulation results in more severe leukocyte infiltration in the lung of DO11.10 mice, which is substantially attenuated by CCL20 blocking antibody. Taken together, this study has shown that activation of OX40 induces CCL20 expression in the presence of antigen stimulation. Thus, our results broaden the role of OX40 in chemotaxis, and reveal a novel effect of co-stimulatory molecules in orchestrating both T cell up-regulation and migration.

The l1-l2 regularization framework unmasks the hypoxia signature hidden in the transcriptome of a set of heterogeneous neuroblastoma cell lines

Background

Gene expression signatures are clusters of genes discriminating different statuses of the cells and their definition is critical for understanding the molecular bases of diseases. The identification of a gene signature is complicated by the high dimensional nature of the data and by the genetic heterogeneity of the responding cells. The l₁-l₂ regularization is an embedded feature selection technique that fulfills all the desirable properties of a variable selection algorithm and has the potential to generate a specific signature even in biologically complex settings. We studied the application of this algorithm to detect the signature characterizing the transcriptional response of neuroblastoma tumor cell lines to hypoxia, a condition of low oxygen tension that occurs in the tumor microenvironment.

Results

We determined the gene expression profile of 9 neuroblastoma cell lines cultured under normoxic and hypoxic conditions. We studied a heterogeneous set of neuroblastoma cell lines to mimic the in vivo situation and to test the robustness and validity of the l₁-l₂ regularization with double optimization. Analysis by hierarchical, spectral, and k-means clustering or supervised approach based on t-test analysis divided the cell lines on the bases of genetic differences. However, the disturbance of this strong transcriptional response completely masked the detection of the more subtle response to hypoxia. Different results were obtained when we applied the l₁-l₂ regularization framework. The algorithm distinguished the normoxic and hypoxic statuses defining signatures comprising 3 to 38 probesets, with a leave-one-out error of 17%. A consensus hypoxia signature was established setting the frequency score at 50% and the correlation parameter ε equal to 100. This signature is composed by 11 probesets representing 8 well characterized genes known to be modulated by hypoxia.

Conclusion

We demonstrate that l₁-l₂ regularization outperforms more conventional approaches allowing the identification and definition of a gene expression signature under complex experimental conditions. The l₁-l₂ regularization and the cross validation generates an unbiased and objective output with a low classification error. We feel that the application of this algorithm to tumor biology will be instrumental to analyze gene expression signatures hidden in the transcriptome that, like hypoxia, may be major determinant of the course of the disease.

Hypoxia-inducible factors 1 and 2 are important transcriptional effectors in primary macrophages experiencing hypoxia

Ischemia exists in many diseased tissues, including arthritic joints, atherosclerotic plaques, and malignant tumors. Macrophages accumulate in these sites and up-regulate hypoxia-inducible transcription factors (HIFs) 1 and 2 in response to the hypoxia present. Here we show that the gene expression profile in primary human and murine macrophages changes markedly when they are exposed to hypoxia for 18 hours. For example, they were seen to up-regulate the cell surface receptors, CXCR4 and GLUT1, and the potent, tumor-promoting cytokines, vascular endothelial growth factor A, interleukin (IL)-1beta and IL-8, adrenomedullin, CXCR4, and angiopoietin-2. Hypoxia also stimulated their expression and/or phosphorylation of various proteins in the nuclear factor-kappaB (NF-kappaB) signaling pathway. We then used both genetic and pharmacologic methods to manipulate the levels of HIFs-1alpha and 2alpha or NF-kappaB in primary macrophages to elucidate their role in the hypoxic induction of many of these key genes. These studies showed that both HIF-1 and -2, but not NF-kappaB, are important transcriptional effectors regulating the responses of macrophages to such a period of hypoxia. Further studies using experimental mouse models are now warranted to investigate the role of such macrophage responses in the progression of various diseased tissues, such as malignant tumors.

Hypoxia or in situ normoxia: The stem cell paradigm

Although O(2) concentrations are considerably lowered in vivo, depending on the tissue and cell population in question (some cells need almost anoxic environment for their maintenance) the cell and tissue cultures are usually performed at atmospheric O(2) concentration (20-21%). As an instructive example, the relationship between stem cells and micro-environmental/culture oxygenation has been recapitulated. The basic principle of stem cell biology, "the generation-age hypothesis," and hypoxic metabolic properties of stem cells are considered in the context of the oxygen-dependent evolution of life and its transposition to ontogenesis and development. A hypothesis relating the self-renewal with the anaerobic and hypoxic metabolic properties of stem cells and the actual O(2) availability is elaborated ("oxygen stem cell paradigm"). Many examples demonstrated that the cellular response is substantially different at atmospheric O(2) concentration when compared to lower O(2) concentrations which better approximate the physiologic situation. These lower O(2) concentrations, traditionally called "hypoxia" represent, in fact, an in situ normoxia, and should be used in experimentation to get an insight of the real cell/cytokine physiology. The revision of our knowledge on cell/cytokine physiology, which has been acquired ex vivo at non physiological atmospheric (20-21%) O(2) concentrations representing a hyperoxic state for most primate cells, has thus become imperious.

Effects of hypoxia on transcription factor expression in human monocytes and macrophages

The presence of multiple areas of hypoxia (low oxygen tension) is a hallmark feature of human and experimental tumours. Monocytes are continually recruited into tumours where they differentiate into tumour-associated macrophages (TAM) and often accumulate in hypoxic and/or necrotic areas. A number of recent studies have shown that macrophages respond to hypoxia by up-regulating transcription factors such as HIF-1alpha and HIF-2alpha, which in turn up-regulate the expression of a broad array of mitogenic, pro-invasive, pro-angiogenic and pro-metastatic genes. Here we show that primary human macrophages but not monocytes rapidly up-regulate HIF-1alpha and HIF-2alpha proteins upon exposure to hypoxia, and that these proteins then translocate to the nucleus. We also demonstrate differences in the temporal expression and responses to re-oxygenation for HIF-1alpha and HIF-2alpha in macrophages. Here we found that, compared to HIF-1alpha, HIF-2alpha expression was prolonged and persisted with re-oxygenation. ATF-4 and Egr-1 were also found to be hypoxia-responsive transcription factors in macrophages but not monocytes, but only early after exposure to hypoxia. Taken together, these findings indicate that a number of transcription factors work together in a tightly regulated fashion to control macrophage activities in ischaemic areas of diseased tissues.

CARMA3 mediates lysophosphatidic acid-stimulated cytokine secretion by bronchial epithelial cells

NF-kappaB activation in bronchial epithelial cells is important for the development of allergic airway inflammation, and may control the expression of critical mediators of allergic inflammation such as thymic stromal lymphopoietin (TSLP) and the chemokine CCL20. Members of the caspase recruitment domain (CARD) family of proteins are differentially expressed in tissue and help mediate NF-kappaB activity in response to numerous stimuli. Here we demonstrate that CARMA3 (CARD10) is specifically expressed in human airway epithelial cells, and that expression of CARMA3 in these cells leads to activation of NF-kappaB. CARMA3 has recently been shown to mediate NF-kappaB activation in embryonic fibroblasts after stimulation with lysophosphatidic acid (LPA), a bioactive lipid-mediator that is elevated in the lungs of individuals with asthma. Consistent with this, we demonstrate that stimulation of airway epithelial cells with LPA leads to increased expression of TSLP and CCL20. We then show that inhibition of CARMA3 activity in airway epithelial cells reduces LPA-mediated NF-kappaB activity and the production of TSLP and CCL20. In conclusion, these data demonstrate that LPA stimulates TSLP and CCL20 expression in bronchial epithelial cells via CARMA3-mediated NF-kappaB activation.