IL-11 activates human endothelial cells to resist immune-mediated injury

Functional Expression of the Interleukin-11 Receptor α-Chain and Evidence of Antiapoptotic Effects in Human Colonic Epithelial Cells

A tissue-protective effect of interleukin-11 (IL-11) for the intestinal mucosa has been postulated from animal models of inflammatory bowel disease (IBD). Despite the fact that the clinical usefulness of the anti-inflammatory effects of this cytokine is presently investigated in patients with IBD, there are no data available regarding the target cells of IL-11 action and the mechanisms of tissue protection within the human colonic mucosa. IL-11 responsiveness is restricted to cells that express the interleukin-11 receptor alpha-chain (IL-11Ralpha) and an additional signal-transducing subunit (gp130). In this study, we identified the target cells for IL-11 within the human colon with a new IL-11Ralpha monoclonal antibody and investigated the functional expression of the receptor and downstream effects of IL-11-induced signaling. Immunohistochemistry revealed expression of the IL-11Ralpha selectively on colonic epithelial cells. HT-29 and colonic epithelial cells (CEC) constitutively expressed IL-11Ralpha mRNA and protein. Co-expression of the signal-transducing subunit gp130 was also demonstrated. IL-11 induced signaling through triggering activation of the Jak-STAT pathway without inducing anti-inflammatory or proliferative effects in colonic epithelial cells. However, IL-11 stimulation resulted in a dose-dependent tyrosine phosphorylation of Akt, a decreased activation of caspase-9, and a reduced induction of apoptosis in cultured CEC. In HLA-B27 transgenic rats treated with IL-11, a reduction of apoptotic cell numbers was found. This study demonstrates functional expression of the IL-11Ralpha restricted on CEC within the human colonic mucosa. IL-11 induced signaling through triggering activation of the Jak-STAT pathway, without inducing anti-inflammatory or proliferative effects. The beneficial effects of IL-11 therapy are likely to be mediated by CEC via activation of the Akt-survival pathway, mediating antiapoptotic effects to support mucosal integrity.

Interleukin-11 and interleukin-6 protect cultured human endothelial cells from H2O2-induced cell death

Acute lung injury is a frequent and treatment-limiting consequence of therapy with 100% oxygen. Previous studies have determined that both interleukin (IL)-6 and IL-11 are protective in oxygen toxicity. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals, and both IL-6 and IL-11 markedly diminished this cell death response. However, the mechanism(s) by which these cytokines protect cells from death is unclear. In the present study, we characterized the effects of H2O2 on subconfluent human umbilical vein endothelial cell (HUVEC) and human pulmonary microvascular endothelial cell (HPMEC) cultures. We found that preincubation of HUVEC cultures with either IL-6 or IL-11 diminished H2O2 (1.0 mM)-induced cell death. Similar effects were noted with HPMEC showing that this effect is not HUVEC-specific. The protective effects of both IL-6 and IL-11 were not associated with any changes in antioxidants and were decreased by approximately 80% in the presence of U0126, a specific inhibitor of MEK-1-dependent pathways. The cytoprotective effects of IL-11 and IL-6 were also completely eliminated in STAT3 dominant-negative transduced HUVEC cultures. These studies demonstrate that IL-6 and IL-11 both confer cytoprotective effects that diminish oxidant-mediated endothelial cell injury. They also demonstrate that this protection is mediated, at least in part, by a STAT3 and MEK-1-dependent specific signal transduction pathway(s).

Desensitization of signaling by oncostatin M in human vascular cells involves cytoplasmic Tyr residue 759 in gp130 but is not mediated by either Src homology 2 domain-containing tyrosine phosphatase 2 or suppressor of cytokine signaling 3

Oncostatin M (OnM) signals through cell surface receptors, which utilize the gp130 subunit. In cultured human umbilical vein endothelial cells (HUVEC), OnM transiently elevates mRNA encoding for suppressor of cytokine signaling-3 (SOCS-3). By 1 h of OnM treatment, HUVEC become refractory to the restimulation by OnM, measured as failure to reinduce SOCS-3 mRNA. OnM-induced desensitization also prevents responses to other gp130-signaling cytokines (e.g. leukemia inhibitory factor and interleukin 11). OnM treatment does not affect gp130 expression levels and desensitizes signaling mediated by a transduced chimeric receptor containing extracellular domains of platelet-derived growth factor receptor-beta (PDGFRbeta) and the cytoplasmic region of gp130. Interestingly, a chimeric PDGFRbeta-gp130 mutant receptor, in which intracellular Tyr residue 759 of gp130 is replaced by a Phe residue, mediates prolonged signaling and is not cross-desensitized by OnM. Phospho-Tyr759 is the binding site for both SOCS-3 and for Src homology domain 2-containing tyrosine phosphatase 2 (SHP-2). In human aortic smooth muscle cells, neither prevention of SOCS-3 protein induction, using STAT3 or SOCS-3 antisense, nor prevention of SHP-2 expression, also with antisense, ablates desensitization. These data suggest that desensitization of vascular cells to OnM is mediated in trans and involves Tyr residue 759 in gp130 but is not mediated by either SOCS-3 or SHP-2, the only two proteins currently known to bind to gp130 at this site.

Interleukin-11-induced heat shock protein 25 confers intestinal epithelial-specific cytoprotection from oxidant stress

BACKGROUND & AIMS

The mechanisms of interleukin-11 (IL-11) cytoprotection in intestinal epithelial injury are largely unknown. IL-11 protects barrier integrity during oxidant stress, a common endpoint of numerous types of intestinal injury including ischemia and immune-mediated inflammation. Because heat shock proteins (hsp) are cytoprotective in intestinal epithelia, we hypothesized that IL-11-conferred cytoprotection is mediated by inducible hsps.

METHODS

IL-11 receptor (IL-11R) activation was determined using phospho-specific antibodies to STAT3. IL-11 induction of hsp72 and hsp25 was determined by immunoblot in IEC-18 crypt and young adult mouse colon colonic epithelial cells. Epithelial resistance to oxidant injury by monochloramine was determined by (51)Cr release. Stable hsp anti-sense IEC-18 cell clones were obtained by electroporation and hygromycin B selection. The IL-11 effect on hsp25 distribution was characterized by analysis of Triton x-100 insoluble fractions, 2-D isoelectric focusing gels, and confocal microscopy.

RESULTS

IL-11R signaling was detected in all cells under study. IL-11 induces hsp25 in an intestinal epithelial-specific manner that significantly preserves cellular viability in the presence of monochloramine. This effect was significantly reversed in intestinal epithelia stably expressing anti-sense to hsp25. IL-11 induced a shift of hsp25 to Triton x-100 insoluble fractions containing cytoskeletal elements, which was not associated with altered hsp25 phosphorylation. The shift was not paralleled by increased hsp25 co-localization with F-actin by confocal microscopy.

CONCLUSIONS

The induction of hsp25 by IL-11 confers epithelial-specific cytoprotection that is independent of phosphorylation-dependent co-localization of hsp25 to F-actin, thereby contributing to the protective effects of IL-11 in models of intestinal epithelial injury.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Recombinant human interleukin 11 and bacterial infection in patients with [correction of] haematological malignant disease undergoing chemotherapy: a double-blind placebo-controlled randomised trial

BACKGROUND

Bacteraemia in patients with haematological malignant disease causes substantial morbidity. Recombinant human interleukin 11 (rhIL-11) prevents gastrointestinal epithelial disintegrity and has immunomodulatory actions. Our aim was to ascertain whether or not treatment with rhIL-11 can prevent gut-associated infections.

METHODS

We did a double-blind placebo-controlled randomised trial, to which we enrolled 40 patients with haematological malignant disease who were undergoing chemotherapy. Patients received either rhIL-11 50 microg/kg (n=20) or placebo (n=20) daily by subcutaneous injection from the day before the start of chemotherapy until resolution of neutropenia or for 21 days, whichever was longer. Our primary outcome measure was a reduction in bacteraemia. Analysis was by intention to treat.

FINDINGS

Significantly fewer patients who received rhIL-11 rather than placebo developed bacteraemia, particularly of gastrointestinal origin: the proportion of patients with at least one positive blood culture was 0.65 and 0.25, respectively (p=0.02). The numbers of patients (placebo vs rhIL-11) for each number of distinct isolates were: no organism isolated seven versus 15, one organism nine versus four, two organisms two versus one, three organisms one versus none, and four organisms one versus none (p=0.01), suggesting a lower bacterial load in the rhIL-11 than in the placebo group. Time to first bacteraemic event was longer in patients who received rhIL-11 (p=0.03) than in those who received placebo.

INTERPRETATION

rhIL-11 reduces the frequency and load of bacteraemia in patients with haematological malignant disease undergoing chemotherapy, possibly by gastrointestinal cytoprotective or immunological mechanisms [corrected].

Interleukin-11 attenuates human vascular smooth muscle cell proliferation

Interleukin (IL)-11 is a growth factor for megakaryocytes, osteoclasts, and intestinal mucosa. IL-11 is also an anti-inflammatory agent, mediating many of its effects by inhibition of the transcriptional activator nuclear factor (NF)-kappa B. The purposes of this study were to examine the effects of IL-11 on human vascular smooth muscle cell (VSMC) proliferation and NF-kappa B activity. VSMC were cultured from human transplant donor aortas, stimulated with basic fibroblastic growth factor (bFGF), and treated with IL-11. VSMC stimulated with bFGF demonstrated an increase in cell number by direct cell counting and mitochondrial activity. IL-11 caused a concentration-dependent decrease in bFGF-induced VSMC proliferation. Furthermore, IL-11 attenuated bFGF-induced increases in cytoplasmic and intranuclear unbound NF-kappa B p65. Similarly, IL-11 attenuated VSMC expression of two NF-kappa B-dependent cytokines, IL-8 and IL-6. Stimulated VSMC did not secrete IL-11, suggesting that endogenous IL-11 did not account for our observations. In conclusion, IL-11 inhibits human VSMC proliferation in vitro and is associated with suppression of NF-kappa B.

Activation of signal transducer and activator of transcription 1 (STAT1) is not sufficient for the induction of STAT1-dependent genes in endothelial cells. Comparison of interferon-gamma and oncostatin M

We compared human endothelial cell (EC) responses to interferon-gamma (IFN gamma) and oncostatin M (OnM), cytokines that utilize Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. Both cytokines cause phosphorylation of Tyr residue 701 and Ser residue 727 of STAT1, as shown by immunoblotting. Both activate DNA binding of STAT1 homodimers, shown by electrophoretic mobility shift assay. However, only IFN gamma increases expression of three STAT1-dependent gene products examined, namely transporter associated with antigen processing-1 (TAP1), interferon regulatory factor-1 (IRF1), and class I major histocompatibility complex (MHC) protein, as demonstrated by immunoblotting. Only IFN gamma increases TAP1 transcription assessed by reporter gene assay. OnM pretreatment or co-treatment does not inhibit IFN gamma responses. Interestingly, IFN gamma activation of STAT1 is considerably more long-lived than that produced by OnM. To determine whether duration is functionally significant, we transduced EC with a chimeric receptor containing extracellular domains of platelet-derived growth factor receptor beta and intracellular regions of gp130, the signaling subunit of the OnM receptor, mutated to prevent binding of the tyrosine phosphatase SHP-2. Addition of platelet-derived growth factor to such transduced cells produces STAT1 activation that is comparable in magnitude and duration to that caused by IFN gamma, but still fails to induce TAP1, IRF1, or class I MHC molecules. OnM also activates STAT1 but not transcription of STAT1-dependent genes in HepG2 cells. Transient transfection of HepG2 cells with a STAT-defective mouse IFN gamma receptor failed to complement the OnM STAT signal. We conclude that STAT1 activation is necessary but not sufficient for induction of transcription of IFN gamma-responsive genes. However, signals provided by IFN gamma other than STAT1 activation cannot be provided in trans to complement the response to OnM.

Cutting Edge: Internalization of transduced E-selectin by cultured human endothelial cells: comparison of dermal microvascular and umbilical vein cells and identification of a phosphoserine-type di-leucine motif

Persistent E-selectin expression on human dermal microvascular endothelial cells (HDMEC), believed to mediate skin-specific T cell homing, results from a slow rate of surface protein internalization after cytokine induction. Following transduction of unactivated HDMEC with E-selectin cDNA, the rate of internalization was largely independent of increasing levels of surface protein expression, leading to prolonged t(1/2) values of over 4 h, comparable to that observed following cytokine induction. In HUVEC, the rate of internalization increased with surface expression level, leading to an essentially constant t(1/2) of under 2 h. Thus, the internalization process rather than cytokine responsiveness or E-selectin structure underlies the difference in endothelial cell behavior. Mutational analysis of the cytoplasmic region demonstrated a role for a di-leucine-type motif involving I588 and L589 but not for a putative tyrosine-type motif. Control of E-selectin surface expression appears to be phosphoserine dependent, since alanine but not aspartic acid substitution for S581 slows E-selectin internalization.

Steps toward mapping the human vasculature by phage display

The molecular diversity of receptors in human blood vessels remains largely unexplored. We developed a selection method in which peptides that home to specific vascular beds are identified after administration of a peptide library. Here we report the first in vivo screening of a peptide library in a patient. We surveyed 47,160 motifs that localized to different organs. This large-scale screening indicates that the tissue distribution of circulating peptides is nonrandom. High-throughput analysis of the motifs revealed similarities to ligands for differentially expressed cell-surface proteins, and a candidate ligand-receptor pair was validated. These data represent a step toward the construction of a molecular map of human vasculature and may have broad implications for the development of targeted therapies.

IL-11: insights in asthma from overexpression transgenic modeling

The evolution of our understanding of IL-11 mirrors, in many ways, the problems that are faced by investigators in the post-genome era and the types of techniques that might need to be used to deal with these issues. IL-11 was discovered as a soluble factor in fibroblast supernatants that stimulated the proliferation of "IL-6-dependent" plasmacytoma cells. It was subsequently demonstrated to be an important stimulator of platelet reconstitution and a pleiotropic regulator of nonrespiratory tissues. In the lung, IL-11 is produced by a variety of structural cells and eosinophils in response to a variety of stimuli, including TGF-beta, major basic proteins, and viruses. IL-11 is also detected in exaggerated quantities at sites of virus infection. Its potential effector functions at these sites were defined with constitutive and inducible overexpression transgenic modeling systems which demonstrated that IL-11 causes nodular mononuclear infiltrates, airway remodeling with subepithelial fibrosis, airways obstruction, and airways hyperresponsiveness and can block alveolar development when expressed during development. In accord with these murine findings, IL-11 is selectively expressed in eosinophils and epithelial cells in patients with moderate and severe asthma where expression correlates directly with disease severity and inversely with FEV(1). Studies using transgenic mice also demonstrated that IL-11 inhibits antigen-induced tissue inflammation. Thus IL-11 might be an important regulator of inflammatory and remodeling responses in the asthmatic airway.

Profile of eicosanoids produced by human saphenous vein endothelial cells and the effect of dietary fatty acids

Human saphenous vein endothelial cells (HSVECs) derived from primary cultures of adult human veins constitute an excellent in vitro model for studying human endothelial metabolism. In this study we report the (14)C-labelled prostanoid profile of HSVECs under resting and stimulated conditions and the effect of the n-3 polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid on them. Results indicate that HSVECs while under resting conditions produce mainly prostaglandin F(2alpha)(PGF(2alpha)). After stimulation with calcium ionophore A23187, the cells were found to synthesise PGI(2), PGE(2)and PGF(2alpha) as major products and thromboxane B(2)and PGD(2)as minor products. Production of (14)C-labelled hydroxyeicosatetraenoic acids was not detected. Eicosapentaenoic acid was found to inhibit basal and stimulated prostanoid production whereas docosahexaenoic acid inhibited basal but strongly increased stimulated prostanoid production. These results may offer the basis for further studies aiming to investigate targets for pharmacological intervention in inflammatory conditions.

Interleukin-6 family cytokines: signaling and effects in human airway smooth muscle cells

Interleukin (IL)-1β induces cyclooxygenase (COX)-2 expression and prostanoid formation in cultured human airway smooth muscle (HASM) cells. In other cell types, IL-6 family cytokines induce COX-2 or augment IL-1β-induced COX-2 expression. The purpose of this study was to determine whether IL-6 family cytokines were involved in COX-2 expression in HASM cells. RT-PCR was used to demonstrate that the necessary receptor components for IL-6-type cytokine binding are expressed in HASM cells. IL-6 and oncostatin M (OSM) each caused a dose-dependent phosphorylation of signal transducer and activator of transcription-3, whereas IL-11 did not. IL-6, IL-11, and OSM alone had no effect on COX-2 expression. However, OSM caused dose-dependent augmentation of COX-2 expression and prostaglandin (PG) E2release induced by IL-1β. In contrast, IL-6 and IL-11 did not alter IL-1β-induced COX-2 expression. IL-6 did increase IL-1β-induced PGE2formation in unstimulated cells but not in cells stimulated with arachidonic acid (AA; 10−5M), suggesting that IL-6 effects were mediated at the level of AA release. Our results indicate that IL-6 and OSM are capable of inducing signaling in HASM cells. In addition, OSM and IL-1β synergistically cause COX-2 expression and PGE2release.

Interleukin-11 up-regulates survivin expression in endothelial cells through a signal transducer and activator of transcription-3 pathway

Interleukin-11 (IL-11) reduces injury both in vivo and in vitro, but the mechanisms are unknown. Stimulation of serum- and growth factor-deprived HUVEC with IL-11 increased survivin mRNA and protein expression levels in a dose-dependent manner, with maximal induction at 50 to 100 ng/ml of IL-11. Survivin mRNA expression peaked after 3 to 6 hours of IL-11 treatment and decreased by 24 hours. Survivin protein expression was maximal at 6 hours of treatment and remained elevated through 24 hours. Survivin induction may be mediated by activation of protein kinase B/Akt, but IL-11 failed to activate this pathway in HUVEC. IL-11 did activate signal transducer and activator of transcription (STAT)-3 and IL-11 failed to induce survivin expression in HUVEC transduced with a dominant-negative STAT3 mutant, whereas control-transduced HUVEC responded normally. An IL-11 transgene caused increased survivin mRNA expression in mice compared with control littermates. Intradermal injection of IL-11 (500 ng) into human skin xenografts on immunodeficient mice up-regulated survivin protein in microvascular endothelium and epithelial keratinocytes. We conclude that IL-11 induces expression of survivin, an antiapoptotic protein, in vitro and in vivo, and identify STAT3 as a critical mediator of this response.

Interleukin 11 significantly increases plasma von Willebrand factor and factor VIII in wild type and von Willebrand disease mouse models

Interleukin (IL)-11 is a cytokine with thrombopoietic activity that has been shown to increase plasma von Willebrand factor (vWf) in preliminary clinical studies. This led to further evaluation of the effect of recombinant human (rh)IL-11 on vWf and factor VIII (FVIII) secretion. In vitro, rhIL-11 did not increase vWf production by cultured endothelial cells, which suggests an indirect mechanism. Also, in vivo, plasma vWf was not elevated in mice shortly after a single intravenous (IV) bolus injection of 250 or 1000 microg/kg rhIL-11. The effect of continuous exposure to rhIL-11 was accessed by treating wild type mice for 7 consecutive days with subcutaneous 250 microg/kg/d rhIL-11. Platelet counts increased by 25% and 40% after 4 and 7 days, respectively. Plasma vWf and FVIII levels increased 2-fold after 4 and 7 days. Surprisingly, no effect of rhIL-11 on vWf or FVIII messenger RNA was observed, which suggests that the regulation by rhIL-11 occurs after transcription. No increase in soluble P-selectin was observed after rhIL-11 treatment, indicating that platelet activation is not the source of elevated vWf. Similarly to wild type mice, vWf heterozygous mice responded to rhIL-11 treatment by a significant increase in platelet counts and vWf and FVIII levels. Importantly, in vWf-deficient mice, rhIL-11 also induced a significant increase in FVIII independent of vWf and was able to reduce skin bleeding time. These results suggest that a clinical evaluation of the effects of rhIL-11-induced vWf/FVIII elevation in maintaining hemostasis in mild hemophilia A or von Willebrand disease would be worthwhile.