Dietary iron enhances colonic inflammation and IL-6/IL-11-Stat3 signaling promoting colonic tumor development in mice.

Chronic intestinal inflammation and high dietary iron are associated with colorectal cancer development. The role of Stat3 activation in iron-induced colonic inflammation and tumorigenesis was investigated in a mouse model of inflammation-associated colorectal cancer. Mice, fed either an iron-supplemented or control diet, were treated with azoxymethane and dextran sodium sulfate (DSS). Intestinal inflammation and tumor development were assessed by endoscopy and histology, gene expression by real-time PCR, Stat3 phosphorylation by immunoblot, cytokines by ELISA and apoptosis by TUNEL assay. Colonic inflammation was more severe in mice fed an iron-supplemented compared with a control diet one week post-DSS treatment, with enhanced colonic IL-6 and IL-11 release and Stat3 phosphorylation. Both IL-6 and ferritin, the iron storage protein, co-localized with macrophages suggesting iron may act directly on IL-6 producing-macrophages. Iron increased DSS-induced colonic epithelial cell proliferation and apoptosis consistent with enhanced mucosal damage. DSS-treated mice developed anemia that was not alleviated by dietary iron supplementation. Six weeks post-DSS treatment, iron-supplemented mice developed more and larger colonic tumors compared with control mice. Intratumoral IL-6 and IL-11 expression increased in DSS-treated mice and IL-6, and possibly IL-11, were enhanced by dietary iron. Gene expression of iron importers, divalent metal transporter 1 and transferrin receptor 1, increased and iron exporter, ferroportin, decreased in colonic tumors suggesting increased iron uptake. Dietary iron and colonic inflammation synergistically activated colonic IL-6/IL-11-Stat3 signaling promoting tumorigenesis. Oral iron therapy may be detrimental in inflammatory bowel disease since it may exacerbate colonic inflammation and increase colorectal cancer risk.

An anti-inflammatory selective glucocorticoid receptor modulator preserves osteoblast differentiation.

Glucocorticoids (GCs) are in widespread use to treat inflammatory bone diseases, such as rheumatoid arthritis (RA). Their anti-inflammatory efficacy, however, is accompanied by deleterious effects on bone, leading to GC-induced osteoporosis (GIO). These effects include up-regulation of the receptor activator of NF-κB ligand/osteoprotegerin (RANKL/OPG) ratio to promote bone-resorbing osteoclasts and include inhibition of bone-forming osteoblasts. We previously identified suppression of osteoblast differentiation by the monomer glucocorticoid receptor (GR) via the inhibition of Il11 expression as a crucial mechanism for GIO. Here we show that the GR-modulating substance compound A (CpdA), which does not induce GR dimerization, still suppresses proinflammatory cytokines in fibroblast-like synovial cells from patients with RA and in osteoblasts. In contrast to the full GR agonist dexamethasone, it does not unfavorably alter the RANKL/OPG ratio and does not affect Il11 expression and subsequent STAT3 phosphorylation in these cells. Notably, while dexamethasone inhibits osteoblast differentiation, CpdA does not affect osteoblast differentiation in vitro and in vivo. We describe here for the first time that selective GR modulators can act against inflammation, while not impairing osteoblast differentiation.

Interleukin-11 stimulates proopiomelanocortin gene expression and adrenocorticotropin secretion in corticotroph cells: evidence for a redundant cytokine network in the hypothalamo-pituitary-adrenal axis.

We recently characterized leukemia inhibitory factor (LIF) as an important modulator of hypothalamo-pituitary-adrenal (HPA) axis activity. We now describe the role of interleukin (IL)-11, another member of the IL-6 cytokine family, in the neuro-immuno-endocrine modulation of the HPA axis. In murine hypothalamus, pituitary and corticotroph AtT-20 cells, IL-11 messenger RNA (mRNA) was detectable by RT-PCR only, whereas IL-11R mRNA transcripts were demonstrated by Northern blot. Using RT-PCR, IL-11 and IL-11R gene expression were also detected in normal human pituitaries, as well as in corticotropic and nonfunctioning pituitary adenomas. Incubation of AtT-20 cells for 24 h with 10(-9) M IL-11 stimulated ACTH secretion 1.4 +/- 0.1-fold (P < 0.01), whereas LIF at the same concentration caused a 1.5 +/- 0.1-fold increase (P < 0.001). POMC mRNA expression was induced by IL-11 (0.5 x 10(-9) M) and LIF (0.5 x 10(-9) M) 1.5 +/- 0.18-fold (P < 0.05) and 1.7 +/- 0.13-fold (P < 0.01), respectively. POMC promoter activity, assayed by a -706/+64 rat POMC promoter-luciferase construct, was stimulated by 0.5 x 10(-9) M IL-11 (1.9 +/- 0.06-fold; P < 0.001) and 5 mM Bu2cAMP (7.1 +/- 0.52-fold, P < 0.001), and combined treatment of IL-11 plus Bu2cAMP caused a synergistic 11.7+/-0.71-fold increase ofluciferase activity (P < 0.001 vs. Bu2cAMP alone). Gene expression of SOCS-3, an intracellular inhibitor of cytokine action, peaked as early as 60 min after incubation with IL-11 (0.5 x 10(-9) M) and was induced 3.5-fold. In comparison to mock-transfected AtT-20 cells (AtT-20M), stable overexpression of SOCS-3 (AtT-20S) resulted in significant inhibition of ACTH secretion induced by IL-11 alone (1.5 +/- 0.09 vs. 1.1 +/- 0.04-fold induction, P < 0.01) and IL-11 plus Bu2cAMP (2.1 +/- 0.21 vs. 1.5 +/- 0.06-fold, P < 0.05), but not by Bu2cAMP alone (1.5 +/- 0.12 vs. 1.4 +/- 0.06). In summary, human and murine pituitary express IL-11 and IL-11R transcripts. In murine corticotroph AtT-20 cells, IL- 11 induces POMC gene transcription and ACTH secretion. IL-11 induction of SOCS-3 indicates an intracellular negative feedback control of cytokine-induced POMC expression and ACTH secretion. Thus, IL-11 regulates the HPA axis similarly to LIF, providing further evidence for a redundant cytokine network in the neuro-immuno-endocrine regulation of the HPA axis.

Reduced expression of interleukin-11 in bone marrow stromal cells of senescence-accelerated mice (SAMP6): relationship to osteopenia with enhanced adipogenesis.

Aging is associated with an increase in bone marrow adipose tissue and a reduction in bone turnover. The P6 strain of senescence-accelerated mice (SAM) exhibit an early decrease in bone mass with a reduction in bone remodeling. In the bone marrow, suppressed osteoblastogenesis and osteoclastogenesis with enhanced adipogenesis are observed. The present study was undertaken to clarify the mechanism of age-related changes in bone turnover using bone marrow cells from SAMP6 mice. Because interleukin (IL)-11 has been shown to potently inhibit adipogenesis and to stimulate osteoclast formation, the effect of IL-11 on the differentiation of bone marrow cells was examined. The impaired formation of both osteoblasts and osteoclasts was restored and the enhanced formation of adipocytes was suppressed by the addition of 10 pM recombinant human IL-11. Other cytokines that activate gp130 as a common signal transducer, IL-6 and leukemia inhibitory factor, did not have such effects. Sequence analysis of the entire coding region of IL-11 cDNA obtained from SAMP6 stromal cells revealed no mutations. Constitutively secreted IL-11 protein into culture media, and its mRNA expression stimulated by transforming growth factor beta were reduced in stromal cells from SAMP6 compared with those in control mice. These results demonstrate that the expression of IL-11 is reduced in bone marrow cells of SAMP6 and suggest that the reduction in IL-11 actions is involved in the impairment of both osteoblastogenesis and osteoclastogenesis in these mice. There is a possibility that alterations in IL-11 actions may be associated with the age-related impairment in bone metabolism.

Direct formation of human interleukin-11 by cis-acting system of plant virus protease in Escherichia coli.

To produce a large amount of recombinant proteins in Escherichia coli, we constructed a unique cis-acting expression system using a plant virus protease. This new expression system could directly produce recombinant proteins, that had a biologically active form. A gene of nuclear inclusion-a (NIa), which had a specific amino acid sequence, was fused with a foreign protein gene at the same protein reading frame. One of the NIa-specific cleavage amino acid sequences, Gln-Ala, was also contained at the protein-protein junction. In the case of human interleukin-11 (hIL-11), a 23-kDa specific signal band was obtained from recombinant bacteria. N-terminal sequencing of the 23-kDa protein showed that NIa specifically cleaved the fusion protein at Gln-Ala, producing Ala-hIL-11. Furthermore, we could produce the mature rhIL-11 by extending the culture time. This 23-kDa protein had the same biological activity as hIL-11 in a mouse plasmacytoma, T1165. Combined with fermentation control, we produced mature rhIL-11 in E. coli.

Update on development of interleukin-11.

This paper reviews the recent studies of interleukin-11 gene expression and regulation, receptor and signal transduction, pharmacologic effects, and preclinical and clinical studies. Interleukin-11 is expressed in cells of mesenchymal origin and gene expression can be modulated by several inflammatory cytokines and agonists. The signaling pathways involved in cytokine induction of interleukin-11 gene expression vary between cell types. In vitro and in vivo studies reveal that interleukin-11 displays a wide spectrum of bioactivities including responses in hematopoietic and nonhematopoietic cells. Preclinical studies in animal models suggest that interleukin-11 may be useful in acceleration of the recoveries of both hematopoietic cells and gastrointestinal mucosal cells after cytoablative therapies. Several clinical studies have demonstrated interleukin-11 to be well tolerated and suggest interleukin-11 is a promising cytokine to prevent both neutropenia and thrombocytopenia in patients with cancer who are receiving chemotherapy.

The biology of interleukin 11.

Interleukin 11 (IL-11) is a multifunctional cytokine which may play a role in regulating the growth and development of cells in both the hematopoietic and lymphoid systems. IL-11 activity was originally detected in the conditioned medium of a primate bone marrow stromal cell line, and the human cDNA was cloned from a human fetal lung fibroblast cell line. The purified protein shows multifunctional activity, influencing lymphohematopoietic stem cell proliferation and differentiation, megakaryocyte progenitor cell proliferation and differentiation, erythroid progenitor cell proliferation, B lymphocyte maturation, activation of hepatocyte acute phase protein synthesis, and adipogenesis. At the molecular level, IL-11 is unique, containing no asparagine-linked glycosylation sites and no cysteine residues. The IL-11 receptor belongs to a family of cytokine receptors which includes the receptors for IL-6, leukemia inhibitory factor (LIF), oncostatin M (OSM), and ciliary neurotrophic factor (CNTF), which are all capable of interacting with the signal transducing receptor gp130 after ligand binding. IL-11 has demonstrated activity in preclinical models for the treatment of thrombocytopenia and, in some cases, neutropenia; studies are underway to confirm its usefulness in the clinic for treatment of myelosuppression associated with cancer chemotherapy and bone marrow transplantation.