Interleukin-11 antagonizes Fas ligand-mediated apoptosis in IEC-18 intestinal epithelial crypt cells: role of MEK and Akt-dependent signaling

Cytokines of the interleukin-6 family as emerging targets in inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease (IBD) is an umbrella term that includes different chronic inflammatory diseases of the gastrointestinal tract, most commonly Crohn's disease and ulcerative colitis. IBD affects more than 6 million people worldwide and constitutes not only a debilitating disease for the patients, but also a significant factor for society due to costs for health care and reduced working capacity. Despite the introduction of biologicals for the treatment of IBD, the identification of novel targets that could lead to novel therapeutics is still needed.

AREAS COVERED

In this review, we summarize current knowledge about the interleukin-6 family of cytokines as potential therapeutic targets for improving the therapy of patients with IBD. We discuss cytokines like IL-6 itself for which therapeutics such as inhibitory monoclonal antibodies have already entered the clinics, but also focus on other family members whose therapeutic potential has not been explored yet.

EXPERT OPINION

The different cytokines of the IL-6 family offer multiple therapeutic targets that can potentially be used to treat patients with inflammatory bowel disease, but unwanted side effects like inhibition of epithelial regeneration have to be considered.

Identification and functional characterization, including cytokine production modulation, of the novel chicken Interleukin-11

Interleukin (IL)-11 plays an important role in the immune system. However, IL-11 has not yet been characterized in avian species, including chickens. This study is the first to clone and functionally characterize chicken IL-11 (chIL-11). Multiple alignments and phylogenetic tree comparisons of chIL-11 with IL-11 proteins from other species revealed high levels of conservation and a close relationship between chicken and Japanese quail IL-11. Our results demonstrate that chIL-11 was a functional ligand of IL-11RA and IL-6ST in chicken HD11 and OU2 cell lines, as well as activated and regulated JAK-STAT, NF-κB, PI3K/AKT, and MAPK signaling pathways in chicken cell lines. In addition, chIL-11 inhibited nitric oxide production, affected proliferation of both tested cell lines, inhibited Type 1 and 17 T helper (Th) cytokine and IL-26, IL-12, and IL-17A-induced interferon-γ production, and enhanced Th2 cytokine (IL-4 and IL-10) production. Taken together, functional analysis of chIL-11 revealed it bound to IL-11RA and IL-6ST and activated the JAK-STAT, NF-κB, and MAPK signaling pathways, which resulted in modulation of Th1/Th17 and Th2 cytokine production in chicken HD11 and OU2 cell lines. Overall, this indicates chIL-11 has a role in both the innate and adaptive immune system.

Jinhong Tablet Reduces Damage of Intestinal Mucosal Barrier in Rats with Acute Biliary Infection via Bcl-2/Bax mRNA and Protein Regulation

Objective

To explore the effects and mechanism of Jinhong Tablet on intestinal mucosal barrier function and SIRS in rats with acute biliary infection.

Methods

36 SD male rats were divided into three groups: sham operation (control), acute biliary infection (ABI) model, and Jinhong Tablet (Jinhong) group. Jinhong group were force-fed with Jinhong Tablet, while the other two groups received oral saline. At days 3 and 5, morphological changes of intestinal mucosa were assessed. Serum diamine oxidase (DAO), D-lactate, and endotoxin levels were measured. And the genes bcl-2 and bax in intestinal tissues were tested by real-time PCR and Western blotting.

Results

Intestinal damage was significantly less severe in Jinhong group compared with ABI group, as indicated by Chiu's scoring, TUNEL analysis, and serum DAO, D-lactic acid, and endotoxin levels. Additionally, the expression of bax mRNA and protein was decreased and the ratio of bcl-2/bax mRNA and protein was increased compared with ABI group.

Conclusion

Jinhong Tablet had a positive intervention on acute biliary infection through improving inflammation and intestinal mucosal barrier, inhibiting excessive apoptosis of intestinal epithelial cells via bax and bcl-2 gene, and protein regulation.

IAPs protect host target tissues from graft-versus-host disease in mice

Inhibitors of apoptosis proteins (IAPs) regulate apoptosis, but little is known about the role of IAPs in the regulation of immunity. Development of IAP inhibition by second mitochondria-derived activator of caspase (SMAC) mimetics is emerging as a novel therapeutic strategy to treat malignancies. We explored the role of IAPs in allogeneic immunity with 2 distinct yet complementary strategies, namely, chemical and genetic approaches, in clinically relevant models of experimental bone marrow transplantation (BMT). The small-molecule pan-IAP inhibitor SMAC mimetic AT-406 aggravated gastrointestinal graft-versus-host disease (GVHD) in multiple models. The role of specific IAPs in various host and donor cellular compartments was explored by utilizing X-linked IAP (XIAP)- and cellular IAP (cIAP)-deficient animals as donors or recipients. Donor T cells from C57BL/6 cIAP1^-/- or XIAP^-/- animals demonstrated equivalent GVHD severity and allogeneic responses, both in vivo and in vitro, when compared with B6 wild-type (B6-WT) T cells. By contrast, when used as recipient animals, both XIAP^-/- and cIAP1^-/- animals demonstrated increased mortality from GVHD when compared with B6-WT animals. BM chimera studies revealed that cIAP and XIAP deficiency in host nonhematopoietic target cells, but not in host hematopoietic-derived cells, is critical for exacerbation of GVHD. Intestinal epithelial cells from IAP-deficient animals showed reduced levels of antiapoptotic proteins as well as autophagy-related protein LC3 after allogeneic BMT. Collectively, our data highlight a novel immune cell-independent but target tissue-intrinsic role for IAPs in the regulation of gastrointestinal damage from GVHD.

Exome Analysis of Rare and Common Variants within the NOD Signaling Pathway

Pediatric inflammatory bowel disease (pIBD) is a chronic heterogeneous disorder. This study looks at the burden of common and rare coding mutations within 41 genes comprising the NOD signaling pathway in pIBD patients. 136 pIBD and 106 control samples underwent whole-exome sequencing. We compared the burden of common, rare and private mutation between these two groups using the SKAT-O test. An independent replication cohort of 33 cases and 111 controls was used to validate significant findings. We observed variation in 40 of 41 genes comprising the NOD signaling pathway. Four genes were significantly associated with disease in the discovery cohort (BIRC2 p = 0.004, NFKB1 p =  0.005, NOD2 p = 0.029 and SUGT1 p = 0.047). Statistical significance was replicated for BIRC2 (p = 0.041) and NOD2 (p = 0.045) in an independent validation cohort. A gene based test on the combined discovery and replication cohort confirmed association for BIRC2 (p = 0.030). We successfully applied burden of mutation testing that jointly assesses common and rare variants, identifying two previously implicated genes (NFKB1 and NOD2) and confirmed a possible role in disease risk in a previously unreported gene (BIRC2). The identification of this novel gene provides a wider role for the inhibitor of apoptosis gene family in IBD pathogenesis.

IL-11 Attenuates Liver Ischemia/Reperfusion Injury (IRI) through STAT3 Signaling Pathway in Mice

Background

The protective role of IL-11, an IL-6 family cytokine, has been implicated in ischemia/reperfusion injury (IRI) in the heart and kidney, but its role has not been elucidated in liver IRI. This study was designed to evaluate the effects of IL-11 and its mechanism of action on liver IRI in a mouse model.

Methods

A partial (70%) warm liver IRI was induced by interrupting the artery/portal vein blood supply to the left/middle liver lobes. IL-11 mRNA expression of ischemic liver after reperfusion was analyzed. Signal transducer and activator of transcription 3 (STAT3) was analyzed following IL-11 treatment in vivo and in vitro. Next, IL-11 was injected intraperitoneally (ip) 1 hour before ischemia. Liver injury was assessed based on serum alanine aminotransferase levels and histopathology. Apoptosis and inflammation were also determined in the ischemic liver. To analyze the role of STAT3 in IL-11 treatment, STAT3 siRNA or non-specific (NS) siRNA was used in vitro and in vivo.

Results

IL-11 mRNA expression was significantly increased after reperfusion in the ischemic liver. STAT3, as a target of IL-11, was activated in hepatocytes after IL-11 treatment in vivo and in vitro. Next, effects of IL-11/STAT3 signaling pathway were assessed in liver IRI, which showed IL-11 treatment significantly attenuated liver IRI, as evidenced by reduced hepatocellular function and hepatocellular necrosis/apoptosis. In addition, IL-11 treatment significantly inhibited the gene expressions of pro-inflammatory cytokines (TNF-α and IL-10) and chemokines (IP-10 and MCP-1). To determine the role of STAT3 in the hepatoprotective effects of IL-11, STAT3 siRNA or NS siRNA was used prior to IL-11 treatment. The results showed STAT3 knockdown abrogated the protective effects of IL-11 in vitro and in vivo.

Conclusions

This work provides first-time evidence for the protective effect of IL-11 treatment on hepatocyte in liver IRI, through the activation of the STAT3 pathway.

Inhibitors of apoptosis (IAPs) regulate intestinal immunity and inflammatory bowel disease (IBD) inflammation

The inhibitor of apoptosis (IAP) family members, notably cIAP1, cIAP2, and XIAP, are critical and universal regulators of tumor necrosis factor (TNF) mediated survival, inflammatory, and death signaling pathways. Furthermore, IAPs mediate the signaling of nucleotide-binding oligomerization domain (NOD)1/NOD2 and other intracellular NOD-like receptors in response to bacterial pathogens. These pathways are important to the pathogenesis and treatment of inflammatory bowel disease (IBD). Inactivating mutations in the X-chromosome-linked IAP (XIAP) gene causes an immunodeficiency syndrome, X-linked lymphoproliferative disease type 2 (XLP2), in which 20% of patients develop severe intestinal inflammation. In addition, 4% of males with early-onset IBD also have inactivating mutations in XIAP. Therefore, the IAPs play a greater role in gut homeostasis, immunity and IBD development than previously suspected, and may have therapeutic potential.

The protective role of interleukin-11 against neutron radiation injury in mouse intestines via MEK/ERK and PI3K/Akt dependent pathways

BACKGROUND

Neutron irradiation (IR) has been proven to cause more serious damage than gamma IR. Preventing and curing neutron IR damage remains an urgent issue.

AIMS

The objective of this study was to investigate the radioprotective effects of IL-11 against neutron IR-induced damage in small intestine of mice.

METHODS

Mice were exposed to 3-Gy neutron IR whole body and then treated with 500 μg/kg interleukin-11 (IL-11) intraperitoneally every day. Mice were observed at various time-points over 1-5 days after IR. IEC-6 cells were exposed to 4 Gy neutron IR, and 100 ng/mL rhIL-11 was added to culture medium. Cell proliferation activity was estimated by MTT assay and rates of apoptosis were estimated by flow cytometry.

RESULTS

IL-11 slightly alleviated the incidence of diarrhea in the mice and promoted intestinal epithelia regeneration. In the in vitro study, neutron IR activated extracellular signal-regulated kinase (ERK)1/2 phosphorylation in intestinal epithelial cells constitutively, which was initially suppressed and then activated later by IL-11. The MEK-specific inhibitor U0126 could antagonize the positive effect of IL-11 on cell growth. Phosphatidylinositol 3-kinase (PI3K)/Akt pathway activation was suppressed after neutron IR, but could be triggered by IL-11 to protect the cells. The PI3K inhibitor LY294002 suppressed the positive effect of IL-11 on cell growth, and antagonized the protective effect of IL-11 against cell death after neutron IR.

CONCLUSION

IL-11 increases cell proliferation after neutron IR in MEK and PI3K-dependent signaling pathways, but protects cells against death only in the PI3K-dependent signaling pathway.

The protective role of interleukin-11 against neutron radiation injury in mouse intestines via MEK/ERK and PI3K/Akt dependent pathways

BACKGROUND

Neutron irradiation (IR) has been proven to cause more serious damage than gamma IR. Preventing and curing neutron IR damage remains an urgent issue.

AIMS

The objective of this study was to investigate the radioprotective effects of IL-11 against neutron IR-induced damage in small intestine of mice.

METHODS

Mice were exposed to 3-Gy neutron IR whole body and then treated with 500 μg/kg interleukin-11 (IL-11) intraperitoneally every day. Mice were observed at various time-points over 1-5 days after IR. IEC-6 cells were exposed to 4 Gy neutron IR, and 100 ng/mL rhIL-11 was added to culture medium. Cell proliferation activity was estimated by MTT assay and rates of apoptosis were estimated by flow cytometry.

RESULTS

IL-11 slightly alleviated the incidence of diarrhea in the mice and promoted intestinal epithelia regeneration. In the in vitro study, neutron IR activated extracellular signal-regulated kinase (ERK)1/2 phosphorylation in intestinal epithelial cells constitutively, which was initially suppressed and then activated later by IL-11. The MEK-specific inhibitor U0126 could antagonize the positive effect of IL-11 on cell growth. Phosphatidylinositol 3-kinase (PI3K)/Akt pathway activation was suppressed after neutron IR, but could be triggered by IL-11 to protect the cells. The PI3K inhibitor LY294002 suppressed the positive effect of IL-11 on cell growth, and antagonized the protective effect of IL-11 against cell death after neutron IR.

CONCLUSION

IL-11 increases cell proliferation after neutron IR in MEK and PI3K-dependent signaling pathways, but protects cells against death only in the PI3K-dependent signaling pathway.

Critical role of interleukin-11 in isoflurane-mediated protection against ischemic acute kidney injury in mice

BACKGROUND

Isoflurane releases renal tubular transforming growth factor-β1 (TGF-β1) and protects against ischemic acute kidney injury. Recent studies suggest that TGF-β1 can induce a cytoprotective cytokine interleukin (IL)-11. In this study, the authors tested the hypothesis that isoflurane protects against ischemic acute kidney injury by direct induction of renal tubular IL-11 synthesis.

METHODS

Human kidney proximal tubule cells were treated with 1.25-2.5% isoflurane or carrier gas (room air + 5% carbon dioxide) for 0-16 h. The authors also anesthetized C57BL/6 mice with 1.2% isoflurane or with equianesthetic dose of pentobarbital for 4 h. In addition, the authors subjected IL-11 receptor (IL-11R) wild-type, IL-11R-deficient, or IL-11 neutralized mice to 30-min renal ischemia followed by reperfusion under 4 h of anesthesia with pentobarbital or isoflurane (1.2%).

RESULTS

Isoflurane increased IL-11 synthesis in human (approximately 300-500% increase, N = 6) and mouse (23 ± 4 [mean ± SD] fold over carrier gas group, N = 4) proximal tubule cells that were attenuated by a TGF-β1-neutralizing antibody. Mice anesthetized with isoflurane showed significantly increased kidney IL-11 messenger RNA (13.8 ± 2 fold over carrier gas group, N = 4) and protein (31 ± 9 vs. 18 ± 2 pg/mg protein or approximately 80% increase, N = 4) expression compared with pentobarbital-anesthetized mice, and this increase was also attenuated by a TGF-β1-neutralizing antibody. Furthermore, isoflurane-mediated renal protection in IL-11R wild-type mice was absent in IL-11R-deficient mice or in IL-11R wild-type mice treated with IL-11-neutralizing antibody (N = 4-6).

CONCLUSION

In this study, the authors suggest that isoflurane induces renal tubular IL-11 via TGF-β1 signaling to protect against ischemic acute kidney injury.

Interleukin-11 protects against renal ischemia and reperfusion injury

Renal ischemia reperfusion (IR) injury causes renal tubular necrosis, apoptosis, and inflammation leading to acute and chronic kidney dysfunction. IL-11 is a multifunctional hematopoietic cytokine clinically approved to treat chemotherapy-induced thrombocytopenia. Recent studies suggest that IL-11 also has potent antiapoptotic and antinecrotic properties. In this study, we tested the hypothesis that exogenous IL-11 protects against renal IR injury and determined the mechanisms involved in renal protection. Pretreatment with human recombinant IL-11 (HR IL-11) or with long-acting site-specific polyethylene glycol (PEG)-conjugated human IL-11 analog (PEGylated IL-11) produced partial but significant protection against renal IR injury in mice. In addition, HR IL-11 or PEGylated IL-11 given 30-60 min after IR also provided renal protection in mice. Significant reductions in renal tubular necrosis and neutrophil infiltration as well as tubular apoptosis were observed in mice treated with HR IL-11 or PEGylated IL-11. Furthermore, HR IL-11 or PEGylated IL-11 decreased both necrosis and apoptosis in human proximal tubule (HK-2) cells in culture. Mechanistically, IL-11 increased nuclear translocation of hypoxia-inducible factor-1α (HIF-1α) and induced sphingosine kinase-1 (SK1) expression and activity in HK-2 cells. Moreover, selective HIF-1α inhibitors blocked IL-11-mediated induction of SK1 in HK-2 cells. Finally, HR IL-11 or PEGylated IL-11 failed to protect against renal IR injury in SK1-deficient mice. Together, our data show powerful renal protective effects of exogenous IL-11 against IR injury by reducing necrosis, inflammation, and apoptosis through induction of SK1 via HIF-1α.

Pathogenesis of and unifying hypothesis for idiopathic pouchitis

Ileal pouch-anal anastomosis is the procedure of choice in the surgical management of refractory ulcerative colitis. Pouchitis affects up to 60% of patients following ileal pouch-anal anastomosis for ulcerative colitis. It overlaps significantly with ulcerative colitis such that improvements in our understanding of one will impact considerably on the other. The symptoms are distressing and impinge significantly on patients' quality of life. Despite 30 years of scientific and clinical investigation, the pathogenesis of pouchitis is unknown; however, recent advances in molecular and cell biology make a synergistic hypothesis possible. This hypothesis links interaction between epithelial metaplasia, changes in luminal bacteria (in particular sulfate-reducing bacteria), and altered mucosal immunity. Specifically, colonic metaplasia supports colonization by sulfate-reducing bacteria that produce hydrogen sulfide. This causes mucosal depletion and subsequent inflammation. Although in most cases antibiotics lead to bacterial clearance and symptom resolution, immunogenetic subpopulations can develop a chronic refractory variant of pouchitis. The aims of this paper are to discuss proposed pathogenic mechanisms and to describe a novel mechanism that combines many hypotheses and explains several aspects of pouchitis. The implications for the management of both pouchitis and ulcerative colitis are discussed.

Annexin A1 regulates intestinal mucosal injury, inflammation, and repair

During mucosal inflammation, a complex array of proinflammatory and protective mechanisms regulates inflammation and severity of injury. Secretion of anti-inflammatory mediators is a mechanism that is critical in controlling inflammatory responses and promoting epithelial restitution and barrier recovery. AnxA1 is a potent anti-inflammatory protein that has been implicated to play a critical immune regulatory role in models of inflammation. Although AnxA1 has been shown to be secreted in intestinal mucosal tissues during inflammation, its potential role in modulating the injury/inflammatory response is not understood. In this study, we demonstrate that AnxA1-deficient animals exhibit increased susceptibility to dextran sulfate sodium (DSS)-induced colitis with greater clinical morbidity and histopathologic mucosal injury. Furthermore, impaired recovery following withdrawal of DSS administration was observed in AnxA1 (-/-) animals compared with wild-type (WT) control mice that was independent of inflammatory cell infiltration. Since AnxA1 exerts its anti-inflammatory properties through stimulation of ALX/FPRL-1, we explored the role of this receptor-ligand interaction in regulating DSS-induced colitis. Interestingly, treatment with an ALX/FPRL-1 agonist, 15-epi-lipoxin A4 reversed the enhanced sensitivity of AnxA1 (-/-) mice to DSS colitis. In contrast, 15-epi-lipoxin A4 did not significantly improve the severity of disease in WT animals. Additionally, differential expression of ALX/FPLR-1 in control and DSS-treated WT and AnxA1-deficient animals suggested a potential role for AnxA1 in regulating ALX/FPRL-1 expression under pathophysiological conditions. Together, these results support a role of endogenous AnxA1 in the protective and reparative properties of the intestinal mucosal epithelium.