Detection of native, activated Notch receptors in normal human apocrine-bearing skin and in hidradenitis suppurativa

Notch signalling has generated considerable interest as a pathogenetic factor and a drug target in a range of human diseases. The gamma-secretase complex is crucial in the activation of Notch receptors by cleaving the intracellular domain allowing nuclear translocation. In recent years several mutations in gamma-secretase components have been discovered in patients with familial hidradenitis suppurativa (HS). This has led to hypotheses that impaired Notch signalling could be an important driver for HS in general, not only in the monogenic variants. However, no study has examined in situ Notch activation per se in HS, and some reports with conflicting results have instead been based on expression of Notch receptors or indirect measures of Notch target gene expression. In this study we established immunostaining protocols to identify native, activated Notch receptors in human skin tissue. The ability to detect changes in Notch activation was confirmed with an ex vivo skin organ model in which signal was reduced or obliterated in tissue exposed to a gamma-secretase inhibitor. Using these methods on skin biopsies from healthy volunteers and a general HS cohort we demonstrated for the first time the distribution of active Notch signalling in human apocrine-bearing skin. Quantification of activated NOTCH1 & NOTCH2 revealed similar levels in non-lesional and peri-lesional HS to that of healthy controls, thus ruling out a general defect in Notch activation in HS patients. We did find a variable but significant reduction of activated Notch in epidermis of lesional HS with a distribution that appeared related to the extent of surrounding tissue inflammation.

Antibody blockade of Jagged1 attenuates choroidal neovascularization

Antibody-based blocking of vascular endothelial growth factor (VEGF) reduces choroidal neovascularization (CNV) and retinal edema, rescuing vision in patients with neovascular age-related macular degeneration (nAMD). However, poor response and resistance to anti-VEGF treatment occurs. We report that targeting the Notch ligand Jagged1 by a monoclonal antibody reduces neovascular lesion size, number of activated phagocytes and inflammatory markers and vascular leakage in an experimental CNV mouse model. Additionally, we demonstrate that Jagged1 is expressed in mouse and human eyes, and that Jagged1 expression is independent of VEGF signaling in human endothelial cells. When anti-Jagged1 was combined with anti-VEGF in mice, the decrease in lesion size exceeded that of either antibody alone. The therapeutic effect was solely dependent on blocking, as engineering antibodies to abolish effector functions did not impair the therapeutic effect. Targeting of Jagged1 alone or in combination with anti-VEGF may thus be an attractive strategy to attenuate CNV-bearing diseases.

Activated, Pro-Inflammatory Th1, Th17, and Memory CD4+ T Cells and B Cells Are Involved in Delayed-Type Hypersensitivity Arthritis (DTHA) Inflammation and Paw Swelling in Mice

Delayed-type hypersensitivity arthritis (DTHA) is a recently established experimental model of rheumatoid arthritis (RA) in mice with pharmacological values. Despite an indispensable role of CD4+ T cells in inducing DTHA, a potential role for CD4+ T cell subsets is lacking. Here we have quantified CD4+ subsets during DTHA development and found that levels of activated, pro-inflammatory Th1, Th17, and memory CD4+ T cells in draining lymph nodes were increased with differential dynamic patterns after DTHA induction. Moreover, according to B-cell depletion experiments, it has been suggested that this cell type is not involved in DTHA. We show that DTHA is associated with increased levels of B cells in draining lymph nodes accompanied by increased levels of circulating IgG. Finally, using the anti-rheumatoid agents, methotrexate (MTX) and the anti-inflammatory drug dexamethasone (DEX), we show that MTX and DEX differentially suppressed DTHA-induced paw swelling and inflammation. The effects of MTX and DEX coincided with differential regulation of levels of Th1, Th17, and memory T cells as well as B cells. Our results implicate Th1, Th17, and memory T cells, together with activated B cells, to be involved and required for DTHA-induced paw swelling and inflammation.

A novel somatic mutation in GNB2 provides new insights to the pathogenesis of Sturge-weber syndrome

Sturge-Weber syndrome (SWS) is a neurocutaneous disorder characterised by vascular malformations affecting skin, eyes and leptomeninges of the brain, which can lead to glaucoma, seizures and intellectual disability. The discovery of a disease-causing somatic missense mutation in the GNAQ gene, encoding an alpha chain of heterotrimeric G-proteins, has initiated efforts to understand how G-proteins contribute to SWS pathogenesis. The mutation is predominantly detected in endothelial cells and is currently believed to affect downstream MAPK-signalling. In this study of six Norwegian patients with classical SWS, we aimed to identify somatic mutations through deep sequencing of DNA from skin biopsies. Surprisingly, one patient was negative for the GNAQ mutation, but instead harboured a somatic mutation in GNB2 (NM_005273.3:c.232A > G, p.Lys78Glu) which encodes a beta chain of the same G-protein complex. The positions of the mutant amino acids in the G-protein are essential for complex reassembly. Therefore, failure of reassembly and continuous signalling is a likely consequence of both mutations. Ectopic expression of mutant proteins in endothelial cells revealed that expression of either mutant reduced cellular proliferation, yet regulated MAPK-signalling differently, suggesting that dysregulated MAPK-signalling cannot fully explain the SWS phenotype. Instead, both mutants reduced synthesis of YAP, a transcriptional co-activator of the Hippo signalling pathway, suggesting a key role for this pathway in the vascular pathogenesis of SWS. The discovery of the GNB2 mutation sheds novel light on the pathogenesis of SWS and suggests that future research on targets of treatment should be directed towards the YAP, rather than the MAPK, signalling pathway.

Inflammatory activation of endothelial cells increases glycolysis and oxygen consumption despite inhibiting cell proliferation

Endothelial cell function and metabolism are closely linked to differential use of energy substrate sources and combustion. While endothelial cell migration is promoted by 2‐phosphofructokinase‐6/fructose‐2,6‐bisphosphatase (PFKFB3)‐driven glycolysis, proliferation also depends on fatty acid oxidation for dNTP synthesis. We show that inflammatory activation of human umbilical vein endothelial cells (HUVECs) by interleukin‐1β (IL‐1β), despite inhibiting proliferation, promotes a shift toward more metabolically active phenotype. This was reflected in increased cellular glucose uptake and consumption, which was preceded by an increase in PFKFB3 mRNA and protein expression. However, despite a modest increase in extracellular acidification rates, the increase in glycolysis did not correlate with extracellular lactate accumulation. Accordingly, IL‐1β stimulation also increased oxygen consumption rate, but without a concomitant rise in fatty acid oxidation. Together, this suggests that the IL‐1β‐stimulated energy shift is driven by shunting of glucose‐derived pyruvate into mitochondria to maintain elevated oxygen consumption in HUVECs. We also revealed a marked donor‐dependent variation in the amplitude of the metabolic response to IL‐1β and postulate that the donor‐specific response should be taken into account when considering targeting dysregulated endothelial cell metabolism.

Shifts in the Skin Microbiota after UVB Treatment in Adult Atopic Dermatitis

BACKGROUND

The pathophysiology in atopic dermatitis (AD) is not fully understood, but immune dysfunction, skin barrier defects, and alterations of the skin microbiota are thought to play important roles. AD skin is frequently colonized with Staphylococcus aureus (S. aureus) and microbial diversity on lesional skin (LS) is reduced compared to on healthy skin. Treatment with narrow-band ultraviolet B (nb-UVB) leads to clinical improvement of the eczema and reduced abundance of S. aureus. However, in-depth knowledge of the temporal dynamics of the skin microbiota in AD in response to nb-UVB treatment is lacking and could provide important clues to decipher whether the microbial changes are primary drivers of the disease, or secondary to the inflammatory process.

OBJECTIVES

To map the temporal shifts in the microbiota of the skin, nose, and throat in adult AD patients after nb-UVB treatment.

METHODS

Skin swabs were taken from lesional AD skin (n = 16) before and after 3 treatments of nb-UVB, and after 6-8 weeks of full-body treatment. We also obtained samples from non-lesional skin (NLS) and from the nose and throat. All samples were characterized by 16S rRNA gene sequencing.

RESULTS

We observed shifts towards higher diversity in the microbiota of lesional AD skin after 6-8 weeks of treatment, while the microbiota of NLS and of the nose/throat remained unchanged. After only 3 treatments with nb-UVB, there were no significant changes in the microbiota.

CONCLUSION

Nb-UVB induces changes in the skin microbiota towards higher diversity, but the microbiota of the nose and throat are not altered.

Targeting the Notch Signaling Pathway in Chronic Inflammatory Diseases

The Notch signaling pathway regulates developmental cell-fate decisions and has recently also been linked to inflammatory diseases. Although therapies targeting Notch signaling in inflammation in theory are attractive, their design and implementation have proven difficult, at least partly due to the broad involvement of Notch signaling in regenerative and homeostatic processes. In this review, we summarize the supporting role of Notch signaling in various inflammation-driven diseases, and highlight efforts to intervene with this pathway by targeting Notch ligands and/or receptors with distinct therapeutic strategies, including antibody designs. We discuss this in light of lessons learned from Notch targeting in cancer treatment. Finally, we elaborate on the impact of individual Notch members in inflammation, which may lay the foundation for development of therapeutic strategies in chronic inflammatory diseases.

Rapid systemic surge of IL-33 after severe human trauma: a prospective observational study

Background

Alarmins are considered proximal mediators of the immune response after tissue injury. Understanding their biology could pave the way for development of new therapeutic targets and biomarkers in human disease, including multiple trauma. In this study we explored high-resolution concentration kinetics of the alarmin interleukin-33 (IL-33) early after human trauma.

Methods

Plasma samples were serially collected from 136 trauma patients immediately after hospital admission, 2, 4, 6, and 8 h thereafter, and every morning in the ICU. Levels of IL-33 and its decoy receptor sST2 were measured by immunoassays.

Results

We observed a rapid and transient surge of IL-33 in a subset of critically injured patients. These patients had more widespread tissue injuries and a greater degree of early coagulopathy. IL-33 half-life (t_1/2) was 1.4 h (95% CI 1.2–1.6). sST2 displayed a distinctly different pattern with low initial levels but massive increase at later time points.

Conclusions

We describe for the first time early high-resolution IL-33 concentration kinetics in individual patients after trauma and correlate systemic IL-33 release to clinical data. These findings provide insight into a potentially important axis of danger signaling in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00288-1.

Endothelial Cells in Emerging Viral Infections

There are several reasons to consider the role of endothelial cells in COVID-19 and other emerging viral infections. First, severe cases of COVID-19 show a common breakdown of central vascular functions. Second, SARS-CoV-2 replicates in endothelial cells. Third, prior deterioration of vascular function exacerbates disease, as the most common comorbidities of COVID-19 (obesity, hypertension, and diabetes) are all associated with endothelial dysfunction. Importantly, SARS-CoV-2's ability to infect endothelium is shared by many emerging viruses, including henipaviruses, hantavirus, and highly pathogenic avian influenza virus, all specifically targeting endothelial cells. The ability to infect endothelium appears to support generalised dissemination of infection and facilitate the access to certain tissues. The disturbed vascular function observed in severe COVID-19 is also a prominent feature of many other life-threatening viral diseases, underscoring the need to understand how viruses modulate endothelial function. We here review the role of vascular endothelial cells in emerging viral infections, starting with a summary of endothelial cells as key mediators and regulators of vascular and immune responses in health and infection. Next, we discuss endotheliotropism as a possible virulence factor and detail features that regulate viruses' ability to attach to and enter endothelial cells. We move on to review how endothelial cells detect invading viruses and respond to infection, with particular focus on pathways that may influence vascular function and the host immune system. Finally, we discuss how endothelial cell function can be dysregulated in viral disease, either by viral components or as bystander victims of overshooting or detrimental inflammatory and immune responses. Many aspects of how viruses interact with the endothelium remain poorly understood. Considering the diversity of such mechanisms among different emerging viruses allows us to highlight common features that may be of general validity and point out important challenges.

Nuclear IL-33 restrains the early conversion of fibroblasts to an extracellular matrix-secreting phenotype

Interleukin (IL)-33 is a cytokine that appears to mediate fibrosis by signaling via its receptor ST2 (IL-33R/IL1RL1). It is also, however, a protein that after synthesis is sorted to the cell nucleus, where it appears to affect chromatin folding. Here we describe a novel role for nuclear IL-33 in regulating the fibroblast phenotype in murine kidney fibrosis driven by unilateral ureteral obstruction. Transcriptional profiling of IL-33-deficient kidneys 24 h after ligation revealed enhanced expression of fibrogenic genes and enrichment of gene sets involved in extracellular matrix formation and remodeling. These changes relied on intracellular effects of IL-33, because they were not reproduced by treatment with a neutralizing antibody to IL-33 that prevents IL-33R/ST2L receptor signaling nor were they observed in IL-33R/ST2-deficient kidneys. To further explore the intracellular function of IL-33, we established transcription profiles of human fibroblasts, observing that knockdown of IL-33 skewed the transcription profile from an inflammatory towards a myofibroblast phenotype, reflected in higher levels of COL3A1, COL5A1 and transgelin protein, as well as lower expression levels of IL6, CXCL8, CLL7 and CCL8. In conclusion, our findings suggest that nuclear IL-33 in fibroblasts dampens the initial profibrotic response until persistent stimuli, as enforced by UUO, can override this protective mechanism.

Exploring the potential effect of paricalcitol on markers of inflammation in de novo renal transplant recipients

Following a successful renal transplantation circulating markers of inflammation may remain elevated, and systemic inflammation is associated with worse clinical outcome in renal transplant recipients (RTRs). Vitamin D-receptor (VDR) activation is postulated to modulate inflammation and endothelial function. We aimed to explore if a synthetic vitamin D, paricalcitol, could influence systemic inflammation and immune activation in RTRs. Newly transplanted RTRs were included in an open-label randomized controlled trial on the effect of paricalcitol on top of standard care over the first post-transplant year. Fourteen pre-defined circulating biomarkers reflecting leukocyte activation, endothelial activation, fibrosis and general inflammatory burden were analyzed in 74 RTRs at 8 weeks (baseline) and 1 year post-engraftment. Mean changes in plasma biomarker concentrations were compared by t-test. The expression of genes coding for the same biomarkers were investigated in 1-year surveillance graft biopsies (n = 60). In patients treated with paricalcitol circulating osteoprotegerin levels increased by 0.19 ng/ml, compared with a 0.05 ng/ml increase in controls (p = 0.030). In graft tissue, a 21% higher median gene expression level of TNFRSF11B coding for osteoprotegerin was found in paricalcitol-treated patients compared with controls (p = 0.026). Paricalcitol treatment did not significantly affect the blood- or tissue levels of any other investigated inflammatory marker. In RTRs, paricalcitol treatment might increase both circulating and tissue levels of osteoprotegerin, a modulator of calcification, but potential anti-inflammatory treatment effects in RTRs are likely very modest. [NCT01694160 (2012/107D)]; [www.clinicaltrials.gov].

Early transcriptional changes after UVB treatment in atopic dermatitis include inverse regulation of IL-36γ and IL-37

Phototherapy with narrow-band Ultraviolet B (nb-UVB) is a major therapeutic option in atopic dermatitis (AD), yet knowledge of the early molecular responses to this treatment is lacking. The objective of this study was to map the early transcriptional changes in AD skin in response to nb-UVB treatment. Adult patients (n = 16) with AD were included in the study and scored with validated scoring tools. AD skin was irradiated with local nb-UVB on day 0, 2 and 4. Skin biopsies were taken before and after treatment (day 0 and 7) and analysed for genome-wide modulation of transcription. When examining the early response after three local UVB treatments, gene expression analysis revealed 77 significantly modulated transcripts (30 down- and 47 upregulated). Among them were transcripts related to the inflammatory response, melanin synthesis, keratinization and epidermal structure. Interestingly, the pro-inflammatory cytokine IL-36γ was reduced after treatment, while the anti-inflammatory cytokine IL-37 increased after treatment with nb-UVB. There was also a modulation of several other mediators involved in inflammation, among them defensins and S100 proteins. This is the first study of early transcriptomic changes in AD skin in response to nb-UVB. We reveal robust modulation of a small group of inflammatory and anti-inflammatory targets, including the IL-1 family members IL36γ and IL-37, which is evident before any detectable changes in skin morphology or immune cell infiltrates. These findings provide important clues to the molecular mechanisms behind the treatment response and shed light on new potential treatment targets.

Lack of interleukin-33 and its receptor does not prevent calcipotriol-induced atopic dermatitis-like inflammation in mice

Current studies addressing the influence of interleukin-33 or its receptor (IL-33R/ST2) on development of atopic dermatitis-like inflammation in mice have reported conflicting results. We compared the response in single- and double-deficient IL-33^−/−/ST2^−/− C57BL/6J BomTac mice in the well-established calcipotriol-induced model of atopic dermatitis. All genotypes (groups of up to 14 mice) developed atopic dermatitis-like inflammation yet we observed no biologically relevant difference between groups in gross anatomy or ear thickness. Moreover, histological examination of skin revealed no differences in mononuclear leukocyte and granulocyte infiltration nor Th2 cytokine levels (IL-4 and IL-13). Finally, skin CD45+ cells and CD3+ cells were found at similar densities across all groups. Our findings indicate that lack of interleukin-33 and its receptor ST2 does not prevent the development of AD-like skin inflammation.

3PO inhibits inflammatory NFκB and stress-activated kinase signaling in primary human endothelial cells independently of its target PFKFB3

Inhibition of the key glycolytic activator 6-phosphofructokinase 2/fructose-2,6-bisphosphatase-3 (PFKFB3) by 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO) strongly attenuates pathological angiogenesis in cancer and inflammation. In addition to modulating endothelial proliferation and migration, 3PO also dampens proinflammatory activation of endothelial cells and experimental inflammation in vivo, suggesting a potential for 3PO in the treatment of chronic inflammation. The aim of our study was to explore if the anti-inflammatory action of 3PO in human endothelial cells was mediated by inhibition of PFKFB3 and glycolysis and assess if other means of PFKFB3 inhibition reduced inflammatory activation in a similar manner. We found that 3PO caused a rapid and transient reduction in IL-1β- and TNF-induced phosphorylation of both IKKα/β and JNK, thus inhibiting signaling through the NFκB and the stress-activated kinase pathways. However, in contrast to 3PO-treatment, neither shRNA-mediated silencing of PFKFB3 nor treatment with the alternative PFKFB3 inhibitor 7,8-dihydroxy-3-(4-hydroxy-phenyl)-chromen-4-one (YN1) prevented cytokine-induced NFκB signaling and upregulation of the adhesion molecules VCAM-1 and E-selectin, implying off target effects of 3PO. Collectively, our results suggest that the anti-inflammatory action of 3PO in human endothelial cells is not limited to inhibition of PFKFB3 and cellular glycolysis.

HMGB1 concentration measurements in trauma patients: assessment of pre-analytical conditions and sample material

BACKGROUND

HMGB1 is a mediator of systemic inflammation in sepsis and trauma, and a promising biomarker in many diseases. There is currently no standard operating procedure for pre-analytical handling of HMGB1 samples, despite that pre-analytical conditions account for a substantial part of the overall error rate in laboratory testing. We hypothesized that the considerable variations in reported HMGB1 concentrations and kinetics in trauma patients could be partly explained by differences in pre-analytical conditions and choice of sample material.

METHODS

Trauma patients (n = 21) admitted to a Norwegian Level I trauma center were prospectively included. Blood was drawn in K2EDTA coated tubes and serum tubes. The effects of delayed centrifugation were evaluated in samples stored at room temperature for 15 min, 3, 6, 12, and 24 h respectively. Plasma samples subjected to long-term storage in - 80 °C and to repeated freeze/thaw cycles were compared with previously analyzed samples. HMGB1 concentrations in simultaneously acquired arterial and venous samples were also compared. HMGB1 was assessed by standard ELISA technique, additionally we investigated the suitability of western blot in both serum and plasma samples.

RESULTS

Arterial HMGB1 concentrations were consistently lower than venous concentrations in simultaneously obtained samples (arterial = 0.60 x venous; 95% CI 0.30-0.90). Concentrations in plasma and serum showed a strong linear correlation, however wide limits of agreement. Storage of blood samples at room temperature prior to centrifugation resulted in an exponential increase in plasma concentrations after ≈6 h. HMGB1 concentrations were fairly stable in centrifuged plasma samples subjected to long-term storage and freeze/thaw cycles. We were not able to detect HMGB1 in either serum or plasma from our trauma patients using western blotting.

CONCLUSIONS

Arterial and venous HMGB1 concentrations cannot be directly compared, and concentration values in plasma and serum must be compared with caution due to wide limits of agreement. Although HMGB1 levels in clinical samples from trauma patients are fairly stable, strict adherence to a pre-analytical protocol is advisable in order to protect sample integrity. Surprisingly, we were unable to detect HMGB1 utilizing standard western blot analysis.

Hypo-osmotic Stress Drives IL-33 Production in Human Keratinocytes-An Epidermal Homeostatic Response

Although inflammation has traditionally been considered a response to either exogenous pathogen-associated signals or endogenous signals of cell damage, other perturbations of homeostasis, generally referred to as stress, may also induce inflammation. The relationship between stress and inflammation is, however, not well defined. Here, we describe a mechanism of IL-33 induction driven by hypo-osmotic stress in human keratinocytes and also report interesting differences when comparing the responsiveness of other inflammatory mediators. The induction of IL-33 was completely dependent on EGFR and calcium signaling, and inhibition of calcium signaling not only abolished IL-33 induction but also dramatically changed the transcriptional pattern of other cytokines upon hypo-osmotic stress. IL-33 was not secreted but instead showed nuclear sequestration, conceivably acting as a failsafe mechanism whereby it is induced by potential danger but released only upon more extreme homeostatic perturbations that result in cell death. Finally, stress-induced IL-33 was also confirmed in an ex vivo human skin model, translating this mechanism to a potential tissue-relevant signal in the human epidermis. In conclusion, we describe hypo-osmotic stress as an inducer of IL-33 expression, linking cellular stress to nuclear accumulation of a strong proinflammatory cytokine.

Inhibition of Endothelial NOTCH1 Signaling Attenuates Inflammation by Reducing Cytokine-Mediated Histone Acetylation at Inflammatory Enhancers

OBJECTIVE

Endothelial upregulation of adhesion molecules serves to recruit leukocytes to inflammatory sites and appears to be promoted by NOTCH1; however, current models based on interactions between active NOTCH1 and NF-κB components cannot explain the transcriptional selectivity exerted by NOTCH1 in this context.

APPROACH AND RESULTS

Observing that Cre/Lox-induced conditional mutations of endothelial Notch modulated inflammation in murine contact hypersensitivity, we found that IL (interleukin)-1β stimulation induced rapid recruitment of RELA (v-rel avian reticuloendotheliosis viral oncogene homolog A) to genomic sites occupied by NOTCH1-RBPJ (recombination signal-binding protein for immunoglobulin kappa J region) and that NOTCH1 knockdown reduced histone H3K27 acetylation at a subset of NF-κB-directed inflammatory enhancers.

CONCLUSIONS

Our findings reveal that NOTCH1 signaling supports the expression of a subset of inflammatory genes at the enhancer level and demonstrate how key signaling pathways converge on chromatin to coordinate the transition to an infla mmatory endothelial phenotype.

Early introduction of oral paricalcitol in renal transplant recipients. An open-label randomized study

In stable renal transplant recipients with hyperparathyroidism, previous studies have indicated that vitamin D agonist treatment might have anti-proteinuric effects. Animal studies indicate possible anti-fibrotic and anti-inflammatory effects. Early introduction of paricalcitol in de novo renal transplant recipients might reduce proteinuria and prevent progressive allograft fibrosis. We performed a single-center, prospective, randomized, open-label trial investigating effects of paricalcitol 2 μg/day added to standard care. Participants were included 8 weeks after engraftment and followed for 44 weeks. Primary end point was change in spot urine albumin/creatinine ratio. Exploratory microarray analyses of kidney biopsies at study end investigated potential effects on gene expression. Secondary end points included change in glomerular filtration rate (GFR), pulse wave velocity (PWV), and endothelial function measured by peripheral arterial tonometry as reactive hyperemia index (RHI). Seventy-seven de novo transplanted kidney allograft recipients were included, 37 receiving paricalcitol. Paricalcitol treatment lowered PTH levels (P = 0.01) but did not significantly reduce albuminuria (P = 0.76), change vascular parameters (PWV; P = 0.98, RHI; P = 0.33), or influence GFR (P = 0.57). Allograft gene expression was not influenced. To summarize, in newly transplanted renal allograft recipients, paricalcitol reduced PTH and was well tolerated without negatively affecting kidney function. Paricalcitol did not significantly reduce/prevent albuminuria, improve parameters of vascular health, or influence allograft gene expression.

Endothelial IL-33 Expression Is Augmented by Adenoviral Activation of the DNA Damage Machinery

IL-33, required for viral clearance by cytotoxic T cells, is generally expressed in vascular endothelial cells in healthy human tissues. We discovered that endothelial IL-33 expression was stimulated as a response to adenoviral transduction. This response was dependent on MRE11, a sensor of DNA damage that can also be activated by adenoviral DNA, and on IRF1, a transcriptional regulator of cellular responses to viral invasion and DNA damage. Accordingly, we observed that endothelial cells responded to adenoviral DNA by phosphorylation of ATM and CHK2 and that depletion or inhibition of MRE11, but not depletion of ATM, abrogated IL-33 stimulation. In conclusion, we show that adenoviral transduction stimulates IL-33 expression in endothelial cells in a manner that is dependent on the DNA-binding protein MRE11 and the antiviral factor IRF1 but not on downstream DNA damage response signaling.

Single Nucleotide Polymorphisms and Long-Term Clinical Outcome in Renal Transplant Patients: A Validation Study

Genome-wide association studies (GWAS) are designed to investigate single nucleotide polymorphisms (SNPs) and the association with a clinical phenotype. A previous GWAS performed in 300 renal transplant recipients identified two SNPs (rs3811321 and rs6565887) associated with serum creatinine and clinical outcome. We sought to validate these findings. Genotyping of the two SNPs was performed using Taqman assays in 1638 Caucasians participating in the Assessment of LEscol in Renal Transplant (ALERT) study. Primary endpoint was death-censored graft loss, and secondary endpoint was all-cause mortality. Applying Cox regression, no crude association to graft loss was found for rs3811321 on chromosome 14 (hazard ratio [HR] 0.87, 95% CI 0.59-1.29, p = 0.50) or rs6565887 on chromosome 18 (HR 0.88, CI 0.62-1.25, p = 0.48). Multivariable adjustments did not change results, nor did evaluation of the number of risk alleles formed by the two SNPs. No association with mortality was detected. In conclusion, an impact of two SNPs on chromosomes 14 and 18 on death-censored graft survival or all-cause mortality was not confirmed. Our results emphasize the importance of validating findings from high-throughput genetics studies and call for large collaborative research initiatives in the field of transplantation outcomes.

Inhibition of the Glycolytic Activator PFKFB3 in Endothelium Induces Tumor Vessel Normalization, Impairs Metastasis, and Improves Chemotherapy

Abnormal tumor vessels promote metastasis and impair chemotherapy. Hence, tumor vessel normalization (TVN) is emerging as an anti-cancer treatment. Here, we show that tumor endothelial cells (ECs) have a hyper-glycolytic metabolism, shunting intermediates to nucleotide synthesis. EC haplo-deficiency or blockade of the glycolytic activator PFKFB3 did not affect tumor growth, but reduced cancer cell invasion, intravasation, and metastasis by normalizing tumor vessels, which improved vessel maturation and perfusion. Mechanistically, PFKFB3 inhibition tightened the vascular barrier by reducing VE-cadherin endocytosis in ECs, and rendering pericytes more quiescent and adhesive (via upregulation of N-cadherin) through glycolysis reduction; it also lowered the expression of cancer cell adhesion molecules in ECs by decreasing NF-κB signaling. PFKFB3-blockade treatment also improved chemotherapy of primary and metastatic tumors.

Adoptive Transfer of Tumor-Specific Th2 Cells Eradicates Tumors by Triggering an In Situ Inflammatory Immune Response

Adoptive cell therapy (ACT) trials to date have focused on transfer of autologous tumor-specific cytotoxic CD8⁺ T cells; however, the potential of CD4⁺ T helper (Th) cells for ACT is gaining interest. While encouraging results have been reported with IFNγ-producing Th1 cells, tumor-specific Th2 cells have been largely neglected for ACT due to their reported tumor-promoting properties. In this study, we tested the efficacy of idiotype-specific Th2 cells for the treatment of mice with MHC class II-negative myeloma. Th2 ACT efficiently eradicated subcutaneous myeloma in an antigen-specific fashion. Transferred Th2 cells persisted in vivo and conferred long-lasting immunity. Cancer eradication mediated by tumor-specific Th2 cells did not require B cells, natural killer T cells, CD8⁺ T cells, or IFNγ. Th2 ACT was also curative against B-cell lymphoma. Upon transfer, Th2 cells induced a type II inflammation at the tumor site with massive infiltration of M2-type macrophages producing arginase. In vivo blockade of arginase strongly inhibited Th2 ACT, consistent with a key role of arginase and M2 macrophages in myeloma elimination by Th2 cells. These results illustrate that cancer eradication may be achieved by induction of a tumor-specific Th2 inflammatory immune response at the tumor site. Thus, ACT with tumor-specific Th2 cells may represent a highly efficient immunotherapy protocol against cancer. Cancer Res; 76(23); 6864-76. ©2016 AACR.

Tenascins in fibrotic disorders-from bench to bedside

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in chronic inflammatory diseases, available treatment strategies are limited. Tenascins constitute a family of matricellular proteins, primarily modulating interactions of cells with other matrix components and growth factors. Data obtained from tenascin C deficient mice show important roles of this molecule in several models of fibrosis. Moreover there is growing evidence that tenascin C has a strong impact on chronic inflammation, myofibroblast differentiation and recruitment. Tenascin C as well as tenascin X has furthermore been shown to affect TGF-β activation and signaling. Taken together these data suggest that these proteins might be important factors in fibrosis development and make them attractive both as biological markers and as targets for therapeutical intervention. So far most clinical research in fibrosis has been focused on tenascin C. This review aims at summarizing our up-to-date knowledge on the involvement of tenascin C in the pathogenesis of fibrotic disorders.

The biliary epithelium presents antigens to and activates natural killer T cells

Cholangiocytes express antigen-presenting molecules, but it has been unclear whether they can present antigens. Natural killer T (NKT) cells respond to lipid antigens presented by the major histocompatibility complex class I-like molecule CD1d and are abundant in the liver. We investigated whether cholangiocytes express CD1d and present lipid antigens to NKT cells and how CD1d expression varies in healthy and diseased bile ducts. Murine and human cholangiocyte cell lines as well as human primary cholangiocytes expressed CD1d as determined by flow cytometry and western blotting. Murine cholangiocyte cell lines were able to present both exogenous and endogenous lipid antigens to invariant and noninvariant NKT cell hybridomas and primary NKT cells in a CD1d-dependent manner. A human cholangiocyte cell line, cholangiocarcinoma cell lines, and human primary cholangiocytes also presented exogenous CD1d-restricted antigens to invariant NKT cell clones. CD1d expression was down-regulated in the biliary epithelium of patients with late primary sclerosing cholangitis, primary biliary cirrhosis, and alcoholic cirrhosis compared to healthy controls.

CONCLUSIONS

Cholangiocytes express CD1d and present antigens to NKT cells and CD1d expression is down-regulated in diseased biliary epithelium, findings which show that the biliary epithelium can activate an important lymphocyte subset of the liver. This is a potentially important immune pathway in the biliary system, which may be capable of regulating inflammation in the context of biliary disease.

Oligomerized, filamentous surface presentation of RANTES/CCL5 on vascular endothelial cells

Vascular endothelial cells present luminal chemokines that arrest rolling leukocytes by activating integrins. It appears that several chemokines must form higher-order oligomers to elicit proper in vivo effects, as mutants restricted to forming dimers have lost the ability to recruit leukocytes to sites of inflammation. Here, we show for the first time that the chemokine RANTES/CCL5 binds to the surface of human endothelial cells in a regular filamentous pattern. Furthermore, the filaments bound to the surface in a heparan sulfate-dependent manner. By electron microscopy we observed labeling for RANTES on membrane projections as well as on the remaining plasma membrane. Mutant constructs of RANTES restricted either in binding to heparin, or in forming dimers or tetramers, appeared either in a granular, non-filamentous pattern or were not detectable on the cell surface. The RANTES filaments were also present after exposure to flow, suggesting that they can be present in vivo. Taken together with the lacking in vivo or in vitro effects of RANTES mutants, we suggest that the filamentous structures of RANTES may be of physiological importance in leukocyte recruitment.

Expression of the T cell-specific adapter protein in human tissues

T cell-specific adapter protein (TSAd) encoded by the SH2D2A gene is expressed in activated T cells, NK cells and endothelial cells, but its tissue expression has not yet been mapped. Here, we have defined the specificity of two commercially available anti-TSAd monoclonal reagents using peptide arrays. We found them to bind separate epitopes in the C-terminal part of TSAd. We then used immunohistochemistry to examine TSAd expression in various human lymphoid and non-lymphoid tissues. Immunostaining of adjacent tissue sections revealed that a substantial fraction of CD3-positive cells in normal lymphoid and non-lymphoid tissues expressed TSAd. In particular, essentially all intra-epithelial T cells appeared to coexpress TSAd. In addition, TSAd expression was observed in endothelial cells of dermal microvessels, while it was not detected in endothelial cells of the other tested tissues. This work provides insight into the expression pattern of TSAd in various healthy human tissues.

Generation and characterization of an immortalized human mesenchymal stromal cell line

Human mesenchymal stromal cells (hMSCs) show great potential for clinical and experimental use due to their capacity to self-renew and differentiate into multiple mesenchymal lineages. However, disadvantages of primary cultures of hMSCs are the limited in vitro lifespan, and the variable properties of cells from different donors and over time in culture. In this article, we describe the generation of a telomerase-immortalized nontumorigenic human bone marrow-derived stromal mesenchymal cell line, and its detailed characterization after long-term culturing (up to 155 population doublings). The resulting cell line, iMSC#3, maintained a fibroblast-like phenotype comparable to early passages of primary hMSCs, and showed no major differences from hMSCs regarding surface marker expression. Furthermore, iMSC#3 had a normal karyotype, and high-resolution array comparative genomic hybridization confirmed normal copy numbers. The gene expression profiles of immortalized and primary hMSCs were also similar, whereas the corresponding DNA methylation profiles were more diverse. The cells also had proliferation characteristics comparable to primary hMSCs and maintained the capacity to differentiate into osteoblasts and adipocytes. A detailed characterization of the mRNA and microRNA transcriptomes during adipocyte differentiation also showed that the iMSC#3 recapitulates this process at the molecular level. In summary, the immortalized mesenchymal cells represent a valuable model system that can be used for studies of candidate genes and their role in differentiation or oncogenic transformation, and basic studies of mesenchymal biology.

Indirect CD4+ T-cell-mediated elimination of MHC II(NEG) tumor cells is spatially restricted and fails to prevent escape of antigen-negative cells

Tumor-specific Th1 cells can activate tumor-infiltrating macrophages that eliminate MHC class II negative (MHC II(NEG)) tumor cells. Activated M1-like macrophages lack antigen (Ag) receptors, and are presumably unable to discriminate and thus kill both Ag-positive (Ag(POS)) and Ag-negative (Ag(NEG)) tumor cells (bystander killing). The lack of specificity of macrophage-mediated cytotoxicity might be of clinical importance as it could provide a means of avoiding tumor escape. Here, we have tested this idea using mixed populations of Ag(POS) and Ag(NEG) tumor cells in a TCR-transgenic model in which CD4(+) T cells recognize a secreted tumor-specific antigen. Surprisingly, while Ag(POS) tumor cells were recognized and rejected, Ag(NEG) cells grew unimpeded and formed tumors. We further demonstrated that macrophage-mediated cytotoxicity was spatially restricted to areas dominated by Ag(POS) tumor cells, sparing Ag(NEG) tumor cells in the vicinity. As a consequence, macrophage tumoricidal activity did not confer bystander killing in vivo. The present results offer novel insight into the mechanisms of indirect Th1-mediated elimination of MHC II(NEG) tumor cells.

Cellular expression of the alarmin IL-33 in acute skin inflammation (P6337)

Background: IL-33, a recently described member of the IL-1-family, is an important player in a variety of inflammatory settings and is thought to be released from damaged or necrotic cells. Little work has so far been published on the cellular expression and regulation of IL-33 in inflammatory lesions. Results: In normal mouse skin IL-33 showed a nuclear expression in non-proliferating keratinocytes (Ki67-) and periglandular myoepithelial cells. After injection with Staphylococcus aureus (6h i.d.) we observed that nuclear IL-33 disappeared from keratinocytes in the center of the lesion and instead appeared in fibroblasts at the periphery. The keratinocyte layer remained intact and expressed nuclear HMGB1, revealing no evidence of overt necrosis at this time point, thus indicating possible secretion. Wound lesions of the ear showed a similar picture at the margins. At later time points IL-33 reappeared in keratinocytes, initially in a hyperproliferative, multilayer structure in which IL33 and Ki-67 remained minimally co-localized. Similarly, in cultured human keratinocytes there was constitutive expression of nuclear IL-33 in non-proliferating cells and in contrast to endothelial cells, expression levels appeared unaffected by cell density or pro-inflammatory activation (TNF-a or IL1b) Conclusion: The regulation of IL-33 in keratinocytes appears to involve molecular signals different from the regulation seen in vascular endothelial cells and deserves further investigation.

CD4+ T cell-mediated protection against tumors: no bystander killing (P2114)

Background: MHC class II-restricted CD4+ T cells reactive against the Id peptide of MHC class II-negative MOPC315 murine myeloma cells can protect mice against injected tumors. This protection occurs via indirect recognition of secreted tumor-specific antigen, presented on MHC class II-molecules of tumor-infiltrating CD11b+ cells. Activated Id-specific Th1 cells produce IFNγ that activate macrophages which become cytotoxic to tumor cells. We wanted to assay the ability of such CD4+/M1 macrophage mediated protection to prevent the outgrowth of antigen-loss tumor variants. Methods: Id-specific TCR-transgenic SCID mice were challenged with a mixed population of Id-secreting and non-secreting MOPC315 cells, differentially labeled with fluorescent proteins. Tumor growth was monitored by in vivo imaging. Tumor-infiltrating macrophages were assayed for their ability to inhibit tumor growth. Results: In the presence of a large excess of antigen-secreting tumor cells, outgrowth of antigen loss-variants occurred with no evidence of bystander killing. A predominance of alternatively activated macrophages was seen in areas dominated by antigen loss-variants, whereas classic activation was the dominant phenotype in areas populated by regressing Id-secreting tumor cells. In vitro, growth of antigen loss-variants was completely inhibited by the provision of the tumor-specific antigen. This data suggests strict spatial requirements of antigen for effective macrophage-mediated protection.

The alarmin IL-33 is a notch target in quiescent endothelial cells

The molecular mechanisms that drive expression of the alarmin interleukin-33 (IL-33) in endothelial cells are unknown. Because nuclear IL-33 is a marker of endothelial cell quiescence (corroborated in this study by coexpression of cyclin-dependent kinase inhibitor p27(Kip1)), we hypothesized that Notch signaling might be involved in regulating IL-33 expression. Activation of Notch1 by immobilized Notch ligands was sufficient to induce nuclear IL-33 expression in cultured endothelial cells. Conversely, IL-33 expression was inhibited by the γ-secretase inhibitor DAPT or by inhibiting the function of Dll4, Jagged1, Notch1, or the canonical Notch transcription factor RBP-Jκ. Insensitivity to cycloheximide indicated that IL-33 was a direct target of Notch signaling, well in line with the identification of several conserved RBP-Jκ binding sites in the IL33 gene. The in vivo expression of Dll4 but not of Jagged1 was well correlated with expression of IL-33 in quiescent vessels, and subcutaneous injection of DAPT in healthy skin reduced IL-33 expression, indicating that Notch signaling was involved. On the other hand, loss of IL-33 during angiogenesis occurred despite sustained Dll4 and Notch1 expression, suggesting that other signals may override the IL-33-driving signal in this context. Taken together, our data demonstrate that endothelial nuclear IL-33 is induced by Notch and that Dll4 may be the dominant ligand responsible for this signaling in vivo.

Statins affect the presentation of endothelial chemokines by targeting to multivesicular bodies

Background

In addition to lowering cholesterol, statins are thought to beneficially modulate inflammation. Several chemokines including CXCL1/growth-related oncogene (GRO)-α, CXCL8/interleukin (IL)-8 and CCL2/monocyte chemoattractant protein (MCP)-1 are important in the pathogenesis of atherosclerosis and can be influenced by statin-treatment. Recently, we observed that atorvastatin­treatment alters the intracellular content and subcellular distribution of GRO-α in cultured human umbilical vein endothelial cells (HUVECs). The objective of this study was to investigate the mechanisms involved in this phenomenon.

Methodology/ Principal Findings

The effect of atorvastatin on secretion levels and subcellular distribution of GRO-α, IL-8 and MCP-1 in HUVECs activated by interleukin (IL)-1β were evaluated by ELISA, confocal microscopy and immunoelectron microscopy. Atorvastatin increased the intracellular contents of GRO-α, IL-8, and MCP-1 and induced colocalization with E-selectin in multivesicular bodies. This effect was prevented by adding the isoprenylation substrate GGPP, but not the cholesterol precursor squalene, indicating that atorvastatin exerts these effects by inhibiting isoprenylation rather than depleting the cells of cholesterol.

Conclusions/ Significance

Atorvastatin targets inflammatory chemokines to the endocytic pathway and multivesicular bodies and may contribute to explain the anti-inflammatory effect of statins at the level of endothelial cell function.

The Alarmin Interleukin-33 is a Notch Target in Quiescent Endothelial Cells (174.6)

The molecular mechanisms that induce and maintain expression of the alarming interleukin-33 (IL-33) in endothelial cells are unknown. Based on the observation that IL-33 is also a marker of endothelial cell quiescence, we hypothesized that the Notch signaling pathway might be involved in regulation of IL-33 expression. Here we show that activation of Notch1 by immobilized Notch ligands was sufficient to induce nuclear IL-33 expression in human umbilical vein endothelial cells (HUVECs). Furthermore, IL-33 expression in confluent HUVECs was inhibited by the γ-secretase inhibitor DAPT or by blocking antibodies to Dll4, Jagged1 or Notch1, as well as by knockdown of the transcription factor RBP-Jκ. In vivo, expression of Dll4 but not Jagged1 was generally observed in all segments of quiescent vessels in healthy organs in both human and rat tissue, and therefore well correlated with expression of IL-33. Moreover, subcutaneous injections of DAPT markedly reduced expression of vascular IL-33, compatible with a role for Notch signaling in driving vascular IL-33 expression in vivo. Taken together, our data demonstrate that the alarmin IL-33 is a target of Notch and serve to further establish Notch signaling in innate immune defense.

Endostatin suppresses IGF-II-mediated signaling and invasion of human extravillous trophoblasts

Endostatin, a biological active fragment of the extracellular matrix protein collagen XVIII, is known to interfere with cellular motility in the context of pathological angiogenesis. However, the physiological role of endostatin remains largely elusive. Recent evidence suggested that the inhibitor is produced in human decidual cells of early pregnancy, indicating that endostatin could be involved in diverse reproductive processes, such as implantation and/or placental differentiation. To gain more insights into the role of endostatin, we here analyzed its effects on trophoblast motility, proliferation, and signaling using purified primary trophoblasts, first-trimester villous explant cultures, and trophoblastic SGHPL-5 cells. In vitro Transwell assays demonstrated that purified endostatin inhibited both basal and IGF-II-induced migration and invasion as well as outgrowth from villous explant cultures. In contrast, basal and IGF-II-stimulated proliferation was unaffected upon addition of the inhibitor. Analyses of IGF-II-associated downstream signaling events showed that endostatin interfered with activation of various signaling kinases such as ERK1/2, protein kinase B (Akt)/mammalian target of rapamycin/p70 S6 kinase, and focal adhesion kinase. Furthermore, virus-mediated, stable gene silencing of Akt1 in SGHPL-5 cells using a micro-RNA-adapted short hairpin RNA-expressing plasmid revealed that endostatin-mediated inhibition of IGF-II-induced Akt phosphorylation was critically dependent on the expression of the particular isoform. In conclusion, the data suggest that endostatin could be a physiological inhibitor of IGF-II-dependent trophoblast cell motility by suppressing focal adhesion kinase/Akt/mammalian target of rapamycin/p70 S6 kinase signaling.

Inflammatory bowel disease-associated interleukin-33 is preferentially expressed in ulceration-associated myofibroblasts

Interleukin-33 (IL-33) is a novel member of the interleukin-1 family that induces mucosal pathology in vivo and may drive fibrosis development and angiogenesis. To address its potential role in inflammatory bowel disease, we explored its tissue expression in biopsy specimens from untreated ulcerative colitis patients, observing a 2.6-fold up-regulation of IL-33 mRNA levels, compared to controls. Immunohistochemical analyses of surgical specimens showed that a prominent source of IL-33 in ulcerative colitis lesions were ulceration-associated myofibroblasts that co-expressed the fibroblast marker heat shock protein 47, platelet-derived growth factor receptor (PDGFR)β, and, in part, the myofibroblast marker α-smooth muscle actin (SMA). In contrast, IL-33-positive myofibroblasts were almost absent near the deep fissures seen in Crohn's disease. A screen of known and putative activators of IL-33 in cultured fibroblasts revealed that the Toll-like receptor-3 agonist poly (I:C) was among the strongest inducers of IL-33 and that it synergized with transforming growth factor-β, a combination also known to boost myofibroblast differentiation. Experimental wound healing in rat skin revealed that the de novo induction of IL-33 in pericytes and the possible activation of scattered, tissue-resident IL-33(+)PDGFRβ(+)αSMA(-) fibroblast-like cells were early events that preceded the later appearance of IL-33(+)PDGFRβ(+)αSMA(+) cells. In conclusion, our data point to a novel role for IL-33 in mucosal healing and wound repair and to an interesting difference between ulcerative colitis and Crohn's disease.

Genome-wide transcription profile of endothelial cells after cardiac transplantation in the rat

Transcriptome analyses of organ transplants have until now usually focused on whole tissue samples containing activation profiles from different cell populations. Here, we enriched endothelial cells from rat cardiac allografts and isografts, establishing their activation profile at baseline and on days 2, 3 and 4 after transplantation. Modulated transcripts were assigned to three categories based on their regulation profile in allografts and isografts. Categories A and B contained the majority of transcripts and showed similar regulation in both graft types, appearing to represent responses to surgical trauma. By contrast, category C contained transcripts that were partly allograft-specific and to a large extent associated with interferon-gamma-responsiveness. Several transcripts were verified by immunohistochemical analysis of graft lesions, among them the matricellular protein periostin, which was one of the most highly upregulated transcripts but has not been associated with transplantation previously. In conclusion, the majority of the differentially expressed genes in graft endothelial cells are affected by the transplantation procedure whereas relatively few are associated with allograft rejection.

The murine IL-8 homologues KC, MIP-2, and LIX are found in endothelial cytoplasmic granules but not in Weibel-Palade bodies

Rapid translocation of P-selectin from WPB to the surface of endothelial cells is crucial for early neutrophil recruitment to acute inflammatory lesions. Likewise, the chemokine CXCL8/IL-8 is sorted to WPB in human endothelial cells, but little is known about its functional importance in lack of a suitable animal model. Here, we explored the distribution of the functional IL-8 homologues CXCL1/KC, CXCL2/MIP-2, and CXCL5-6/LIX in resting and inflamed murine vessels by confocal microscopy and paired immunostaining with markers of WPB, discovering that these chemokines did not localize to WPB but displayed a granular pattern in a subset of vessels in healthy skin compatible with sorting to the type 2 endothelial compartment for regulated secretion. Moreover, all chemokines colocalized with VWF and P-selectin in platelets, suggesting that their storage in platelet alpha-granules might represent an alternative source of rapidly available, neutrophil-recruiting chemokines. In conclusion, WPB appear not to be involved in regulated secretion of chemokines in the mouse, and instead, the possible existence of type 2 granules and the role of platelets in rapid leukocyte adhesion deserve further attention.

Family-with-sequence-similarity-46, member A (Fam46a) gene is expressed in developing tooth buds

OBJECTIVE

In search for possible novel genes that may be involved in tooth development, we analysed the genome-wide transcriptome of developing mandibular tooth germs of mouse during embryonic and early life and selected family-with-sequence-similarity-46, member A (Fam46a) gene for further expression analysis.

METHODS

We applied microarray, quantitative real time polymerase chain reaction and in situ hybridisation methods for the expression study of the mouse Fam46a gene.

RESULTS

We found the family-with-sequence-similarity-46, member A (Fam46a) gene to be highly expressed and further verify its temporo-spatial expression in the mouse tooth.

CONCLUSION

We have shown that Fam46a is expressed in ameloblasts' nuclei of tooth germs and hypothesise that it might act together with morphogenetic factors important for the formation of enamel in mouse tooth.

Molecular requirements for sorting of the chemokine interleukin-8/CXCL8 to endothelial Weibel-Palade bodies

Sorting of proteins to Weibel-Palade bodies (WPB) of endothelial cells allows rapid regulated secretion of leukocyte-recruiting P-selectin and chemokines as well as procoagulant von Willebrand factor (VWF). Here we show by domain swap studies that the exposed aspartic acid in loop 2 (Ser(44)-Asp(45)-Gly(46)) of the CXC chemokine interleukin (IL)-8 is crucial for targeting to WPB. Loop 2 also governs sorting of chemokines to alpha-granules of platelets, but the fingerprint of the loop 2 of these chemokines differs from that of IL-8. On the other hand, loop 2 of IL-8 closely resembles a surface-exposed sequence of the VWF propeptide, the region of VWF that directs sorting of the protein to WPB. We conclude that loop 2 of IL-8 constitutes a critical signal for sorting to WPB and propose a general role for this loop in the sorting of chemokines to compartments of regulated secretion.

Interleukin-33 - cytokine of dual function or novel alarmin?

Cytokines are thought to exert biological effects through their specific cell surface membrane receptors but increasing evidence suggests that some also function within the nucleus. Here, we review current knowledge of such cytokines, including the novel interleukin (IL)-1 family member IL-33. Its extracellular function has attracted much recent attention as a ligand for the Th2-associated ST2 receptor, but the discoveries of its nuclear functions and modes of secretion are only just beginning to surface. We review the currently available data on IL-33 regulation, nuclear function and release and discuss them in the context of other intranuclear cytokines and the prototype alarmin HMGB1, considering to what extent IL-33 can be seen as a novel member of the alarmin family.

Nuclear interleukin-33 is generally expressed in resting endothelium but rapidly lost upon angiogenic or proinflammatory activation

Interleukin (IL)-33 is a novel member of the IL-1 family of cytokines that promotes Th2 responses in lymphocytes as well as the activation of both mast cells and eosinophils via the ST2 receptor. Additionally, IL-33 has been proposed to act as a chromatin-associated transcriptional regulator in both endothelial cells of high endothelial venules and chronically inflamed vessels. Here we show that nuclear IL-33 is expressed in blood vessels of healthy tissues but down-regulated at the earliest onset of angiogenesis during wound healing; in addition, it is almost undetectable in human tumor vessels. Accordingly, IL-33 is induced when cultured endothelial cells reach confluence and stop proliferating but is lost when these cells begin to migrate. However, IL-33 expression was not induced by inhibiting cell cycle progression in subconfluent cultures and was not prevented by antibody-mediated inhibition of VE-cadherin. Conversely, IL-33 knockdown did not induce detectable changes in either expression levels or the cellular distribution of either VE-cadherin or CD31. However, activation of endothelial cell cultures with either tumor necrosis factor-alpha or vascular endothelial growth factor and subcutaneous injection of these cytokines led to a down-regulation of vascular IL-33, a response consistent with both its rapid down-regulation in wound healing and loss in tumor endothelium. In conclusion, we speculate that the proposed transcriptional repressor function of IL-33 may be involved in the control of endothelial cell activation.

Cytokine secretion depends on Galalpha(1,3)Gal expression in a pig-to-human whole blood model

Transplants from alpha1,3-galactosyltransferase (Gal) gene-knockout pigs to nonhuman primates are largely protected from hyperacute but not acute humoral xenograft rejection. The present study investigates the role of Gal in cytokine responses using a novel pig-to-human whole blood in vitro model, developed for species-specific analysis of porcine and human cytokines. Porcine (n = 7) and human (n = 27) cytokines were measured using ELISA or multiplex technology, respectively. Porcine aortic endothelial cells from control (Gal(+/+)) and Gal-deficient (Gal(-/-)) pigs were incubated with human lepirudin anticoagulated whole blood from healthy donors. E-selectin expression was measured by flow cytometry. The C3 inhibitor compstatin and a C5aR antagonist were used to study the role of complement. Cytokine species specificity was documented, enabling detection of 2 of 7 porcine cytokines and 13 of 27 human cytokines in one single sample. Gal(+/+) porcine aortic endothelial cells incubated with human whole blood showed a marked complement C5b-9 dependent up-regulation of E-selectin and secretion of porcine IL-6 and IL-8. In contrast, Gal(-/-) cells responded with E-selectin and cytokine expression which was so weak that the role of complement could not be determined. Human IL-6, IL-8, IFN-gamma, MIP-1alpha, MIP-1beta, eotaxin, and RANTES were detected in the Gal(+/+) system, but virtually no responses were seen in the Gal(-/-) system (p = 0.03). The increase in human cytokine release was largely complement dependent and, in contrast to the porcine response, mediated through C5a. Species-specific analysis of cytokine release revealed a marked, complement-dependent response when Gal(+/+) pig cells were incubated with human whole blood, compared with Gal(-/-) cells which induced virtually no cytokine release.

A potential role of the CXC chemokine GROalpha in atherosclerosis and plaque destabilization: downregulatory effects of statins

OBJECTIVE

We examined the role of the CXCR2 ligand growth-related oncogene (GRO) alpha in human atherosclerosis.

METHODS AND RESULTS

GROalpha levels were examined by enzyme immunoassay, real-time quantitative RT-PCR, and cDNA microarrays. The in vitro effect of statins on GROalpha was examined in endothelial cells and THP-1 macrophages. Our main findings were: (1) GROalpha was among the 10 most differentially expressed transcripts comparing peripheral blood mononuclear cells (PBMCs) from patients with coronary artery disease (CAD) and healthy controls. (2) Both patients with stable (n=41) and particularly those with unstable (n=47) angina had increased plasma levels of GROalpha comparing controls (n=20). (3) We found increased expression of GROalpha within symptomatic carotid plaques, located to macrophages and endothelial cells. (4) GROalpha enhanced the release of matrix metalloproteinases in vascular smooth muscle cells, and increased the binding of acetylated LDL in macrophages. (5) Atorvastatin downregulated GROalpha levels as shown both in vitro in endothelial cells and macrophages and in vivo in PBMCs from CAD patients. (6) The effect on GROalpha in endothelial cells involved increased storage and reduced secretion of GROalpha.

CONCLUSIONS

GROalpha could be involved in atherogenesis and plaque destabilization, potentially contributing to inflammation, matrix degradation, and lipid accumulation within the atherosclerotic lesion.

The HUVEC/Matrigel assay: an in vivo assay of human angiogenesis suitable for drug validation

The future ability to manipulate the growth of new blood vessels (angiogenesis) holds great promise for treating ischemic disease and cancer. Several models of human in vivo angiogenesis have been described, but they seem to depend on transgenic support and have not been validated in a therapeutic context. Here, we describe an in vivo assay that mimics human angiogenesis in which native human umbilical vein-derived endothelial cells are suspended in a liquid laminin/collagen gel (Matrigel), injected into immunodeficient mice, and develop into mature, functional vessels that vascularize the Matrigel plug in the course of 30 d. Moreover, we demonstrate how to target this process therapeutically by sustained delivery of the angiogenesis inhibitor endostatin from subcutaneously implanted microosmotic pumps.

Human complement-activating immunoglobulin (Ig)G3 antibodies are essential for porcine endothelial cell activation

BACKGROUND

Complement-activating naturally occurring anti-porcine endothelial cell antibodies (Abs) are responsible for hyperacute rejection in porcine-to-primate transplantation, whereas the role of complement in acute vascular rejection, characterized by type II endothelial cell activation, is less well understood. We previously demonstrated a correlation between porcine type II endothelial cell activation, as detected by E-selectin expression, and human immunoglobulin (Ig)G3 anti-Gal alpha1-3Gal (Gal) Abs, which was not seen for IgG1, IgG2 or IgG4. The present study was undertaken to investigate whether there is a causal relationship between human anti-porcine IgG3 Abs and porcine endothelial cell activation.

METHODS

IgG3 was isolated employing a Protein A column to 98.3% purity. Porcine endothelial cells were incubated with isolated human IgG3 or the combination of IgG1, IgG2 and IgG4. E-selectin expression and complement activation were investigated by flow cytometry and Western blotting, respectively.

RESULTS

Purified IgG3, in contrast to the other IgG subclasses, induced a substantial increase in E-selectin expression. This activation was accompanied by complement activation as detected by C3 cleavage, and was abolished by heat inactivation or by adding the complement inhibitor FUT-175. Depletion of anti-Gal Abs reduced E-selectin expression by 60%, consistent with the presence of complement-activating anti-porcine non-Gal Abs of the IgG3 subclass.

CONCLUSIONS

Collectively, these data strengthen the hypothesis that human anti-porcine endothelial cell Abs of the IgG3 subclass are essential for endothelial cell activation in porcine-to-human species grafts and demonstrate such activation to be partly independent of Gal epitopes.

Coy decoy with a new ploy: interceptor controls the levels of homeostatic chemokines

A new subfamily of chemokine receptors is emerging that do not signal along classical G-protein-mediated pathways. Instead, these "silent" receptors efficiently internalize their cognate chemokine ligands, hence their suggested name, "chemokine interceptors", for internalizing receptors. Two of these interceptors, DARC and D6, possess intriguing patterns of tissue expression and are believed to be involved in controlling the local levels of proinflammatory chemokines. In this issue of the European Journal of Immunology, the biochemical properties of a third silent chemokine receptor, CCX-CKR, have been characterized and it is suggested that it may act as a scavenger for homeostatic chemokines, pointing to a broad and significant role for this group of chemokine binding molecules in chemokine biology.