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

Exploring the landscape of synthetic IL-6-type cytokines

Interleukin-6 (IL-6)-type cytokines not only have key immunomodulatory functions that affect the pathogenesis of diseases such as autoimmune diseases, chronic inflammatory conditions, and cancer, but also fulfill important homeostatic tasks. Even though the pro-inflammatory arm has hindered the development of therapeutics based on natural-like IL-6-type cytokines to date, current synthetic trends might pave the way to overcome these limitations and eventually lead to immune-inert designer cytokines to aid type 2 diabetes and brain injuries. Those synthetic biology approaches include mutations, fusion proteins, and inter-cytokine swapping, and resulted in IL-6-type cytokines with altered receptor affinities, extended target cell profiles, and targeting of non-natural cytokine receptor complexes. Here, we survey synthetic cytokine developments within the IL-6-type cytokine family and discuss potential clinical applications.

Targeting IL-6 trans-signalling: past, present and future prospects

Interleukin-6 (IL-6) is a key immunomodulatory cytokine that affects the pathogenesis of diverse diseases, including autoimmune diseases, chronic inflammatory conditions and cancer. Classical IL-6 signalling involves the binding of IL-6 to the membrane-bound IL-6 receptor α-subunit (hereafter termed 'mIL-6R') and glycoprotein 130 (gp130) signal-transducing subunit. By contrast, in IL-6 trans-signalling, complexes of IL-6 and the soluble form of IL-6 receptor (sIL-6R) signal via membrane-bound gp130. A third mode of IL-6 signalling - known as cluster signalling - involves preformed complexes of membrane-bound IL-6-mIL-6R on one cell activating gp130 subunits on target cells. Antibodies and small molecules have been developed that block all three forms of IL-6 signalling, but in the past decade, IL-6 trans-signalling has emerged as the predominant pathway by which IL-6 promotes disease pathogenesis. The first selective inhibitor of IL-6 trans-signalling, sgp130, has shown therapeutic potential in various preclinical models of disease and olamkicept, a sgp130Fc variant, had promising results in phase II clinical studies for inflammatory bowel disease. Technological developments have already led to next-generation sgp130 variants with increased affinity and selectivity towards IL-6 trans-signalling, along with indirect strategies to block IL-6 trans-signalling. Here, we summarize our current understanding of the biological outcomes of IL-6-mediated signalling and the potential for targeting this pathway in the clinic.

Heat Shock Proteins in Tooth Development and Injury Repair

Heat shock proteins (HSPs) are a class of molecular chaperones with expression increased in response to heat or other stresses. HSPs regulate cell homeostasis by modulating the folding and maturation of intracellular proteins. Tooth development is a complex process that involves many cell activities. During tooth preparation or trauma, teeth can be damaged. The damaged teeth start their repair process by remineralizing and regenerating tissue. During tooth development and injury repair, different HSPs have different expression patterns and play a special role in odontoblast differentiation and ameloblast secretion by mediating signaling pathways or participating in protein transport. This review explores the expression patterns and potential mechanisms of HSPs, particularly HSP25, HSP60 and HSP70, in tooth development and injury repair.

Cytokimera GIL-11 rescued IL-6R deficient mice from partial hepatectomy-induced death by signaling via non-natural gp130:LIFR:IL-11R complexes

All except one cytokine of the Interleukin (IL-)6 family share glycoprotein (gp) 130 as the common β receptor chain. Whereas Interleukin (IL-)11 signal via the non-signaling IL-11 receptor (IL-11R) and gp130 homodimers, leukemia inhibitory factor (LIF) recruits gp130:LIF receptor (LIFR) heterodimers. Using IL-11 as a framework, we exchange the gp130-binding site III of IL-11 with the LIFR binding site III of LIF. The resulting synthetic cytokimera GIL-11 efficiently recruits the non-natural receptor signaling complex consisting of gp130, IL-11R and LIFR resulting in signal transduction and proliferation of factor-depending Ba/F3 cells. Besides LIF and IL-11, GIL-11 does not activate receptor complexes consisting of gp130:LIFR or gp130:IL-11R, respectively. Human GIL-11 shows cross-reactivity to mouse and rescued IL-6R^-/- mice following partial hepatectomy, demonstrating gp130:IL-11R:LIFR signaling efficiently induced liver regeneration. With the development of the cytokimera GIL-11, we devise the functional assembly of the non-natural cytokine receptor complex of gp130:IL-11R:LIFR.

Secreted glucose regulated protein78 ameliorates DSS-induced mouse colitis

The secreted form of 78-kDa glucose-regulated protein (sGRP78) has been widely reported for its property in aiding resolution of inflammatory. However, little is known on its potential in the treatment of colitis. To investigate the expression pattern and functional outcome of GRP78 in ulcerative colitis, its expression was measured in human and murine colitis samples. It was found that GRP78 was spontaneously secreted to a high level in gut, which is a physiological site of immune tolerance. During the active phase of DSS-induced colitis, the sGRP78 level was significantly reduced but rebounded quickly during resolving phase, making it a potential candidate for the treatment of colitis. In the following experiments, the administration of sGRP78 was proved to decrease susceptibility to experimental colitis, as indicated by an overall improvement of intestinal symptoms, restoration of TJ integrity, decreased infiltration of immune cells and impaired production of inflammatory cytokines. And specific cleavage of endogenous sGRP78 could aggravate DSS colitis. Adoptive transfer of sGRP78-conditioned BMDMs reduced inflammation in the gut. We linked sGRP78 treatment with altered macrophage biology and skewed macrophage polarization by inhibiting the TLR4-dependent MAP-kinases and NF-κB pathways. Based on these studies, as a naturally occurring immunomodulatory molecule, sGRP78 might be an attractive novel therapeutic agent for acute intestinal inflammation.

Quorum sensing: a new perspective to reveal the interaction between gut microbiota and host

Quorum sensing (QS), a chemical communication process between bacteria, depends on the synthesis, secretion and detection of signal molecules. It can synchronize the gene expression of bacteria to promote cooperation within the population and improve competitiveness among populations. The preliminary exploration of bacterial QS has been completed under ideal and highly controllable conditions. There is an urgent need to investigate the QS of bacteria under natural conditions, especially the QS of intestinal flora, which is closely related to health. Excitingly, growing evidence has shown that QS also exists in the intestinal flora. The crosstalk of QS between gut microbiota and the host is systematically clarified in this review.

Effect of Bacillus subtilis, Enterococcus faecium, and Enterococcus faecalis supernatants on serotonin transporter expression in cells and tissues

BACKGROUND

Bacillus subtilis (B. subtilis), Enterococcus faecium (E. faecium), and Enterococcus faecalis (E. faecalis) are probiotics that are widely used in the clinical treatment of irritable bowel syndrome (IBS). Whether the supernatants of these three probiotics can improve gastrointestinal sensation and movement by regulating the serotonin transporter (SERT) expression needs to be clarified.

AIM

To investigate whether B. subtilis, E. faecium, and E. faecalis supernatants can upregulate SERT expression in vitro and in vivo.

METHODS

Caco-2 and HT-29 cells were stimulated with probiotic culture supernatants for 12 and 24 h, respectively. A male Sprague-Dawley rat model of post-infectious irritable bowel syndrome (PI-IBS) was established and the rats were treated with phosphate-buffered saline (group A) and three probiotics culture supernatants (groups B, C, and D) for 4 wk. The levels of SERT were detected by quantitative PCR and western blotting.

RESULTS

The levels of SERT at post-treatment 12 and 24 h were significantly elevated in Caco-2 cells treated with B. subtilis supernatant compared with those in the control group (^aP < 0.05). Those levels were markedly upregulated in Caco-2 cells stimulated with E. faecium and E. faecalis supernatants at 24 h (^aP < 0.05). In addition, SERT expression in groups B, C, and D was significantly higher than that in group A in the 2nd wk (^aP < 0.05). Increased SERT expression was only found in group D in the 3rd wk (^aP < 0.05). However, there was no significant difference in SERT expression between the groups in the last week (P > 0.05).

CONCLUSION

The supernatants of B. subtilis, E. faecium, and E. faecalis can upregulate SERT expression in intestinal epithelial cells and the intestinal tissues in the rat model of PI-IBS.

The protective effects of resveratrol on ulcerative colitis via changing the profile of Nrf2 and IL-1β protein

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) with increasing incidence and prevalence in developed countries. The presence of inflammatory cytokines is considered the main detrimental factor in severe types of IBD. The Nrf2 transcription factor plays an important role in reducing the expression of inflammatory agents such as interleukin (IL)-1β and increasing reparative factors such as IL-11. Resveratrol, a plant-derived phenolic compound, reduces the damage in chronic experimentally induced colitis. Twenty patients with UC and also 20 healthy controls were recruited in this study. The proteins expression of Nrf2 and IL-1β was assessed in colonic biopsies by Western blotting. Caco-2 cells were challenged with TNF-α (in vitro simulation of UC), in the presence or not of 190 nM (24 h) and 75 nM (48 h) Resveratrol. Then, Nrf2 and IL-1β in gene and protein expression were measured by real time-PCR and Western blotting in different treatments. Finally, IL-11 proteins expression was measured in culture supernatant by ELISA. A significant increase of IL-1β protein was detected in inflamed colonic tissues from UC patients compared with the control individuals. In Caco-2 cells challenged with TNF-α, protein expression of IL-1β and p-Nrf2 showed an increase, while gene expression of Nrf2 did not show a significant difference. After treatment with Resveratrol, both IL-1β mRNA and protein levels were reduced, while IL-11 protein levels showed any increase. The p-Nrf2 is a dominant form which is prevalent in inflamed tissues from UC patients. Resveratrol can reverse the inflammatory effects of TNF-α by reducing IL-1β and increasing IL-11 production.

The Functions and Therapeutic Potential of Heat Shock Proteins in Inflammatory Bowel Disease-An Update

Inflammatory bowel disease (IBD) is a multifactorial human intestinal disease that arises from numerous, yet incompletely defined, factors. Two main forms, Crohn's disease (CD) and ulcerative colitis (UC), lead to a chronic pathological form. Heat shock proteins (HSPs) are stress-responsive molecules involved in various pathophysiological processes. Several lines of evidence link the expression of HSPs to the development and prognosis of IBD. HSP90, HSP70 and HSP60 have been reported to contribute to IBD in different aspects. Moreover, induction and/or targeted inhibition of specific HSPs have been suggested to ameliorate the disease consequences. In the present review, we shed the light on the role of HSPs in IBD and their targeting to prevent further disease progression.

The expression analysis of Fra-1 gene and IL-11 protein in Iranian patients with ulcerative colitis

BACKGROUND

Fra-1 (fosl1) belongs to the activator protein1 (AP-1) family inducing IL-11 expression in oxidative stress condition. IL-11 plays a pivotal role in protecting epithelial barriers integrity. In this study, we investigated the Fra-1 gene expression in the inflamed mucosa of patients with ulcerative colitis (UC) as well as its relation to IL-11 expression.

MATERIALS AND METHODS

We enrolled 20 patients and 20 healthy controls with definite UC based on the clinical criteria. Fra-1 gene expression in inflamed and non-inflamed colonic biopsies was determined by real-time polymerase chain reaction (RT-PCR). The IL-11 protein concentration was measured by Enzyme-Linked Immunosorbent Assay (ELISA) method. Pearson correlation was applied to calculate the relation between Fra-1 and IL-11.

RESULTS

An increased level of Fra-1 gene expression was observed in patients with mild ulcerative colitis. The protein concentration of IL-11 was also increased in mild UC patients. Conversely, a significant decrease of IL-11 protein level was detected in severe UC patients compared to control group.

CONCLUSION

Oxidative stress in inflamed intestinal biopsies can induce fra-1 gene expression. Our findings suggest that Fra-1 transcription factor leads to the production of IL-11 protein in UC patients.

Supplemental psyllium fibre regulates the intestinal barrier and inflammation in normal and colitic mice

Our previous study demonstrated that supplemental psyllium fibre increased cytoprotective heat-shock protein (Hsp) 25 levels in the intestinal cells of mice. Here, we examined the effect of psyllium fibre on colonic gene and protein expression and faecal microbiota in normal and colitic mice to improve the understanding of the preventive role of the supplement. DNA microarray analysis revealed that a 10 % psyllium fibre diet administered for 5 d up-regulated eleven extracellular matrix (ECM)-associated genes, including collagens and fibronectins, in normal mice. Acute colitis was induced using dextran sodium sulphate (DSS) in mice that were administered a pre-feeding 5 to 10 % psyllium fibre diet for 5 d. Psyllium fibre partially ameliorated or resolved the DSS-induced colon damage and inflammation characterised by body weight loss, colon shortening, increased levels of pro-inflammatory cytokines and decreased tight junction protein expression in the colon. Analysis of faecal microbiota using denaturing gradient gel electrophoresis of the PCR-amplified 16S rRNA gene demonstrated that psyllium fibre affected the colonic microbiota. Intestinal permeability was evaluated by growing intestinal Caco-2 cell monolayers on membrane filter supports coated with or without fibronectin and collagen. Cells grown on collagen and fibronectin coating showed higher transepithelial electrical resistance, indicating a strengthening of barrier integrity. Therefore, increased Hsp25 levels and modification of colonic ECM contribute to the observed psyllium-mediated protection against DSS-induced colitis. Furthermore, ECM modification appears to play a role in the strengthening of the colon barrier. In conclusion, psyllium fibre may be useful in the prevention of intestinal inflammatory diseases.

Interleukin 11: similar or opposite roles in female reproduction and reproductive cancer?

During placental development and carcinogenesis, cell invasion and migration are critical events in establishing a self-supporting vascular supply. Interleukin (IL)-11 is a pleiotropic cytokine that affects the invasive and migratory capabilities of trophoblast cells that form the placenta during pregnancy, as well as various malignant cell types. The endometrium is the site of embryo implantation during pregnancy; conversely, endometrial carcinoma is the most common gynaecological malignancy. Here, we review what is known about the role of IL-11 in trophoblast function and in gynaecological malignancies, focusing primarily on the context of the uterine environment.

Interleukin-11 protects mouse liver from warm ischemia/reperfusion (WI/Rp) injury

BACKGROUND

IL-11 is a multifunctional cytokine that belongs to the IL-6 family. Previous studies have demonstrated that IL-11 has underlying anti-inflammatory and anti-apoptotic properties. In this study, we evaluated the potential effects of IL-11 on mouse liver WI/Rp injury.

METHODS

For in vivo experiments, mice were randomly divided into four main experimental groups (n=5 each): (1) normal group - anesthesia; (2) sham group- laparotomy; (3) I/R group- liver WI/Rp; and (4) IL-11 pretreatment (500μg/kg, tail vein injection) group- administration of RhIL-11 2h before liver WI/Rp induced in the same manner as in group 3. For in vitro experiments, cells were divided into two groups: (1) H/R group- H/R; and (2) IL-11 pretreatment group- pretreatment with RhIL-11 (2μg/mL for 12h) before the induction of H/R. For both groups, three periods of reoxygenation were examined (2h, 6h, and 12h).

RESULTS

In the in vivo experiments, IL-11 protected mouse livers from WI/Rp by reducing liver enzyme levels and cellular degeneration. In the in vitro experiments, IL-11 significantly reduced hepatocyte apoptosis. In both the in vivo and in vitro experiments, IL-11 pre-treatment significantly reduced the expression of TNF-α and IL-1β. In addition, NF-κB, a target of IL-11, was suppressed in macrophages after IL-11 pre-treatment.

CONCLUSIONS

Pre-treatment with IL-11 protects mouse livers from WI/Rp injury by suppressing NF-kB activity.

A panoramic review and in silico analysis of IL-11 structure and function

Human Interleukin (IL)-11 is a multifunctional cytokine, recognized for its thrombopoietic effects for more than two decades; clinically, IL-11 is used in the treatment of thrombocytopenia. IL-11 shares structural and functional similarities with IL-6, a related family member. In recent years, there has been a renewed interest in IL-11, because its distinct biological activities associated with cancers of epithelial origin and inflammatory disorders have been revealed. Although the crystal structure of IL-11 was resolved more than two years, a better understanding of the mechanisms of IL-11 action is required to further extend the clinical use of IL-11. This review will discuss the available structural, functional, and bioinformatics knowledge concerning IL-11 and will summarize its relationship with several diseases.

IL-11 signaling as a therapeutic target for cancer

IL-11 is a member of the IL-6 family of cytokines. While it was discovered over 20 years ago, we have very little understanding of the role of IL-11 during normal homeostasis and disease. Recently, IL-11 has gained interest for its newly recognized role in the pathogenesis of diseases that are attributed to deregulated mucosal homeostasis, including gastrointestinal cancers. IL-11 can increase the tumorigenic capacity of cells, including survival of the cell or origin, proliferation of cancerous cells and survival of metastatic cells at distant organs. Here we outline our current understanding of IL-11 biology and recent advances in our understanding of its role in cancer. We advocate that inhibition of IL-11 signaling may represent an emerging therapeutic opportunity for numerous cancers.

Gut epithelial inducible heat-shock proteins and their modulation by diet and the microbiota

The epidemic of metabolic diseases has raised questions about the interplay between the human diet and the gut and its microbiota. The gut has two vital roles: nutrient absorption and intestinal barrier function. Gut barrier defects are involved in many diseases. Excess energy intake disturbs the gut microbiota and favors body entry of microbial compounds that stimulate chronic metabolic inflammation. In this context, the natural defense mechanisms of gut epithelial cells and the potential to boost them nutritionally warrant further study. One such important defense system is the activation of inducible heat-shock proteins (iHSPs) which protect the gut epithelium against oxidative stress and inflammation. Importantly, various microbial components can induce the expression of iHSPs. This review examines gut epithelial iHSPs as the main targets of microbial signals and nutrients and presents data on diseases involving disturbances of gut epithelial iHSPs. In addition, a broad literature analysis of dietary modulation of gut epithelial iHSPs is provided. Future research aims should include the identification of gut microbes that can optimize gut-protective iHSPs and the evaluation of iHSP-mediated health benefits of nutrients and food components.

Overexpression of Hsp70 confers cytoprotection during gliadin exposure in Caco-2 cells

BACKGROUND

In Celiac disease (CD), cytoskeletal integrity of intestinal cells is disrupted by gliadin exposure. This study investigates the role of heat shock protein (Hsp)70 during cytoskeletal recovery in CD by assessing its induction and effects on junctional proteins.

METHODS

Using an in-vitro model of CD, cytoskeletal injury and recovery was assessed in gliadin-exposed Caco-2 cells by measuring cellular distribution of ezrin, E-cadherin, and Hsp70 by differential centrifugation. Effects of Hsp70 were tested by an in-vitro repair assay, based on the incubation of injured or recovered cytoskeletal cellular fractions in noncytoskeletal supernatants containing low or high levels of Hsp70, or by transient transfection of Caco-2 cells with Hsp70.

RESULTS

Cytoskeletal disruption of ezrin and E-cadherin was demonstrated in gliadin-exposed Caco-2 cells by their significant shift from the cytoskeletal pellet into the noncytoskeletal supernatant fraction. Recovery from gliadin exposure was associated with induction and cytoskeletal redistribution of Hsp70. The in-vitro repair assay delineated direct evidence for HSP-mediated repair by stabilization of junctional proteins by Hsp70. Overexpression of Hsp70 resulted in significantly increased cytoskeletal integrity.

CONCLUSION

Our results establish an essential role of HSP-mediated cytoskeletal repair in Caco-2 cells during recovery from in-vitro gliadin exposure.

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.

STAT3-Activating Cytokines: A Therapeutic Opportunity for Inflammatory Bowel Disease?

The gastrointestinal tract is lined by a single layer of epithelial cells that secrete mucus toward the lumen, which collectively separates the immune sentinels in the underlying lamina propria from the intestinal microflora to prevent aberrant immune responses. Inflammatory bowel disease (IBD) describes a group of autoimmune diseases that arise from defects in epithelial barrier function and, as a consequence, aberrant production of inflammatory cytokines. Among these, interleukin (IL)-6, IL-11, and IL-22 are elevated in human IBD patients and corresponding mouse models and, through activation of the JAK/STAT3 pathway, can both propagate and ameliorate disease. In particular, cytokine-mediated activation of STAT3 in the epithelial lining cells affords cellular protection, survival, and proliferation, thereby affording therapeutic opportunities for the prevention and treatment of colitis. In this review, we focus on recent insights gained from therapeutic modulation of the activities of IL-6, IL-11, and IL-22 in models of IBD and advocate a cautionary approach with these cytokines to minimize their tumor-promoting activities on neoplastic epithelium.

Enterococcus faecium NCIMB 10415 modulates epithelial integrity, heat shock protein, and proinflammatory cytokine response in intestinal cells

Probiotics have shown positive effects on gastrointestinal diseases; they have barrier-modulating effects and change the inflammatory response towards pathogens in studies in vitro. The aim of this investigation has been to examine the response of intestinal epithelial cells to Enterococcus faecium NCIMB 10415 (E. faecium), a probiotic positively affecting diarrhea incidence in piglets, and two pathogenic Escherichia coli (E. coli) strains, with specific focus on the probiotic modulation of the response to the pathogenic challenge. Porcine (IPEC-J2) and human (Caco-2) intestinal cells were incubated without bacteria (control), with E. faecium, with enteropathogenic (EPEC) or enterotoxigenic E. coli (ETEC) each alone or in combination with E. faecium. The ETEC strain decreased transepithelial resistance (TER) and increased IL-8 mRNA and protein expression in both cell lines compared with control cells, an effect that could be prevented by pre- and coincubation with E. faecium. Similar effects were observed for the increased expression of heat shock protein 70 in Caco-2 cells. When the cells were challenged by the EPEC strain, no such pattern of changes could be observed. The reduced decrease in TER and the reduction of the proinflammatory and stress response of enterocytes following pathogenic challenge indicate the protective effect of the probiotic.

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.

Oral interleukin 11 as a countermeasure to lethal total-body irradiation in a murine model

Countermeasures against radiation are critically needed. Ideally, these measures would be easy to store, easy to administer and have minimal toxicity. We used oral delivery of interleukin 11 (IL11) in mice exposed to lethal doses of total-body irradiation (TBI). Animals were given IL11 by gavage at various daily doses beginning 24 h after TBI, which continued for 5 days. At a TBI of 9.0 Gy, mice treated with IL11 had a 70% survival at 30 days compared with control group survival of 25% (P = 0.035). At 10.0 Gy, treated animals had 50% survival at 30 days compared with no survivors in the control group. Treated animals had significant improvement in intestinal mucosal surface area and crypt survival. In addition bacterial translocation of coliform bacteria was significantly less in the treated animals. Systemic absorption of IL11 was low in treated animals and effects on the hematopoietic cells were not seen. Serum citrulline levels rebounded significantly faster after irradiation in the IL11 treated animals, indicating quicker recovery of small intestine health. These data suggest that IL11 given orally protects the intestinal mucosa from radiation damage and that this compound is beneficial as a mitigating agent even when started 24 h after radiation exposure.

Do reciprocal interactions between cell stress proteins and cytokines create a new intra-/extra-cellular signalling nexus?

Cytokine biology began in the 1950s, and by 1988, a large number of cytokines, with a myriad of biological actions, had been discovered. In 1988, the basis of the protein chaperoning function of the heat shock, or cell stress, proteins was identified, and it was assumed that this was their major activity. However, since this time, evidence has accumulated to show that cell stress proteins are secreted by cells and can stimulate cellular cytokine synthesis with the generation of pro- and/or anti-inflammatory cytokine networks. Cell stress can also control cytokine synthesis, and cytokines are able to induce, or even inhibit, the synthesis of selected cell stress proteins and may also promote their release. How cell stress proteins control the formation of cytokines is not understood and how cytokines control cell stress protein synthesis depends on the cellular compartment experiencing stress, with cytoplasmic heat shock factor 1 (HSF1) having a variety of actions on cytokine gene transcription. The endoplasmic reticulum unfolded protein response also exhibits a complex set of behaviours in terms of control of cytokine synthesis. In addition, individual intracellular cell stress proteins, such as Hsp27 and Hsp90, have major roles in controlling cellular responses to cytokines and in controlling cytokine synthesis in response to exogenous factors. While still confusing, the literature supports the hypothesis that cell stress proteins and cytokines may generate complex intra- and extra-cellular networks, which function in the control of cells to external and internal stressors and suggests the cell stress response as a key parameter in cytokine network generation and, as a consequence, in control of immunity.

Trp53 deficiency protects against acute intestinal inflammation

The p53 protein has not only important tumor suppressor activity but also additional immunological and other functions, whose nature and extent are just beginning to be recognized. In this article, we show that p53 has a novel inflammation-promoting action in the intestinal tract, because loss of p53 or the upstream activating kinase, ATM, protects against acute intestinal inflammation in murine models. Mechanistically, deficiency in p53 leads to increased survival of epithelial cells and lamina propria macrophages, higher IL-6 expression owing to enhanced glucose-dependent NF-κB activation, and increased mucosal STAT3 activation. Blockade or loss of IL-6 signaling reverses the protective effects of p53 deficiency. Conversely, IL-6 treatment protects against acute colitis in a manner dependent on STAT3 signaling and induction of cytoprotective factors in epithelial cells. Together, these results indicate that p53 promotes inflammation in the intestinal tract through suppression of epithelium-protective factors, thus significantly expanding the spectrum of physiological and immunological p53 activities unrelated to cancer formation.

IL-11 is required for A1 adenosine receptor-mediated protection against ischemic AKI

A1 adenosine receptor activation ameliorates ischemic AKI through the induction of renal proximal tubular sphingosine kinase-1. However, systemic adverse effects may limit A1 adenosine receptor-based therapy for ischemic AKI, indicating a need to identify alternative therapeutic targets within this pathway. Here, we evaluated the function of renal proximal tubular IL-11, a clinically approved hematopoietic cytokine, in A1 adenosine receptor-mediated induction of sphingosine kinase-1 and renal protection. Treatment of human proximal tubule epithelial (HK-2) cells with a selective A1 adenosine receptor agonist, chloro-N(6)-cyclopentyladenosine (CCPA), induced the expression of IL-11 mRNA and protein in an extracellular signal-regulated kinase-dependent manner, and administration of CCPA in mice induced renal synthesis of IL-11. Pretreatment with CCPA protected against renal ischemia-reperfusion injury in wild-type mice, but not in IL-11 receptor-deficient mice. Administration of an IL-11-neutralizing antibody abolished the renal protection provided by CCPA. Similarly, CCPA did not induce renal IL-11 expression or protect against renal ischemia-reperfusion injury in mice lacking the renal proximal tubular A1 adenosine receptor. Finally, treatment with CCPA induced sphingosine kinase-1 in HK-2 cells and wild-type mice, but not in IL-11 receptor-deficient or renal proximal tubule A1 adenosine receptor-deficient mice. Taken together, these results suggest that induction of renal proximal tubule IL-11 is a critical intermediary in A1 adenosine receptor-mediated renal protection that warrants investigation as a novel therapeutic target for the treatment of ischemic AKI.

Leptin and mucosal immunity

Enhanced susceptibility to infection has long been recognized in children with congenital deficiency of leptin or its receptor. Studies in mice have demonstrated that leptin deficiency affects both the innate and acquired immune systems. Here, we review recent studies that demonstrate the impact on immunity of a common non-synonomous polymorphism of the leptin receptor. In a Bangladesh cohort of children, the presence of two copies of the ancestral Q223 allele was significantly associated with resistance to amebiasis. Children and mice with at least one copy of the leptin receptor 223R mutation were more susceptible to amebic colitis. Leptin signaling in the intestinal epithelium and downstream STAT3 (signal transducer and activator of transcription 3) and SHP2 (Src homology phosphatase 2) signaling were required for protection in the murine model of amebic colitis. Murine models have also implicated leptin in protection from other infections, including Mycobacterium tuberculosis, Klebsiella pneumoniae, and Streptococcus pneumoniae. Thus, the role of leptin signaling in infectious disease and specifically leptin-mediated protection of the intestinal epithelium will be the focus of this review.

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.

Competence and sporulation factor derived from Bacillus subtilis improves epithelial cell injury in intestinal inflammation via immunomodulation and cytoprotection

INTRODUCTION

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. These probiotic effects are considered to be displayed through the mediation of effective molecules derived from these bacteria because live bacteria as well as their conditioned media exhibit beneficial effects in many cases. However, many of the probiotic-derived molecules which mediate such benefits have so far been poorly characterized. We previously found that competence and sporulation factor (CSF) activates the Akt and p38 MAPK pathways and protects epithelial cells from oxidant stress in the mammalian intestine. The purpose of this study is to determine the CSF effect on reducing intestinal inflammation.

METHODS AND RESULTS

A protein array demonstrated that CSF induced the anti-inflammatory cytokine, IL-10, and decreased the release of pro-inflammatory mediators, IL-4, IL-6 and CXCL-1, induced by TNF-α in Caco2/bbe cells. CSF also induced the cytoprotective protein Hsp 27 in Caco2/bbe cells. The histological score of intestinal inflammation in 2% dextran sodium sulfate (DSS)-treated mice with the administration of 10 nM CSF was significantly lower than that of control mice. CSF also improved the survival rate of mice treated with a lethal concentration of DSS.

CONCLUSION

Therefore, CSF is a potentially effective treatment for intestinal inflammation.

Evaluating the role of IL-11, a novel cytokine in the IL-6 family, in a mouse model of spinal cord injury

Background

Spinal cord injury (SCI) is a devastating condition with substantial functional and social morbidity. Previous research has established that the neuroinflammatory response plays a significant role in cord damage post-SCI. However, global immunosuppressive therapies have demonstrated mixed results. As a result, more specific therapies modulating inflammation after injury are needed. In this regard, research into cytokine signaling has demonstrated that cytokines of the gp130 family including IL-6 and leukemia inhibitory factor (LIF) play key roles in mediating damage to the spinal cord. Since members of the gp130 family all share a common signal transduction pathway via the JAK/STAT system, we performed the first study of a relatively new member of the gp130 family, IL-11, in SCI.

Methods

A validated clip-compression mouse model of SCI was used to assess for temporal changes in expression of IL-11 and its receptor, IL-11Rα, post-SCI. To elucidate the role of IL-II in the pathophysiology of SCI, we compared differences in locomotor recovery (Basso Mouse Score; CatWalk), electrophysiological spinal cord signaling, histopathology, and the acute inflammatory neutrophil response in IL-11Rα knockouts with littermate wild-type C57BL/6 mice.

Results

We found an increase in gene expression of IL-11 in the spinal cord to a peak at twenty-four hours post-SCI with increases in IL-11Rα gene expression, peaking at seven days post-SCI. In spite of clear changes in the temporal expression of both IL-11 and its receptor, we found that there were no significant differences in motor function, electrophysiological signaling, histopathology, or neutrophil infiltration into the spinal cord between wild-type and knockout mice.

Conclusions

This is the first study to address IL-11 in SCI. This study provides evidence that IL-11 signaling may not play as significant a role in SCI as other gp130 cytokines, which will ideally guide future therapy design and the signaling pathways those therapies target.

Activation of IL-11/STAT3 pathway in preconditioned human skeletal myoblasts blocks apoptotic cascade under oxidant stress

AIM

To determine whether our novel approach of diazoxide-induced stem cell preconditioning might be extrapolated to human skeletal myoblasts to support their survival under lethal oxidant stress.

METHODS & RESULTS

Using an in vitro model of H(2)O(2) treatment of human skeletal myoblasts, we report the ability of diazoxide-preconditioned human skeletal myoblasts to express cytokines and growth factors, which act in an autocrine and paracrine fashion to promote their own survival. Preconditioning of skeletal myoblasts was cytoprotective and significantly reduced their apoptotic index (p < 0.05). IL-11 gene and protein expression was significantly increased in preconditioned skeletal myoblasts. Transfection of skeletal myoblasts with IL-11-specific siRNA incurred their death under oxidant stress. The cytoprotective effect of diazoxide preconditioning was blocked by Erk1/2 inhibitor PD98059 (20-100 µM), which abrogated STAT-3 phosphorylation, thus confirming a possible involvement of Erk1/2/STAT3 signaling downstream of IL-11 in cell survival. We also investigated the time course of subcellular changes and signaling pathway of skeletal myoblasts apoptosis under oxidant stress before and after preconditioning. Apoptosis was induced in skeletal myoblasts with 100-500 µM H(2)O(2) for time points ranging from 1 to 24 h. Release of lactate dehydrogenase, disruption of the mitochondrial membrane potential and cytochrome-c translocation into cytoplasm were the earliest signs of apoptosis. Total Akt protein remained unchanged whereas marked reduction in pAkt was observed in the native skeletal myoblasts. Terminal dUTP nick end-labeling and annexin-V positivity were significantly increased after 4 h. Ultra-structure studies showed condensed chromatin, shriveled nuclei and swollen mitochondria.

CONCLUSION

These data suggest that skeletal myoblasts undergo apoptosis under oxidant stress in a time-dependent manner and preconditioning of skeletal myoblasts significantly prevented their apoptosis via IL-11/STAT3 signaling.

Ethanol-induced DNA damage and repair-related molecules in human intestinal epithelial Caco-2 cells

The acute administration of ethanol to intestinal epithelial cells causes increased intestinal permeability and the translocation of endotoxins. The changes caused by ethanol in intestinal cells may be related to oxidative stress and DNA damage. However, DNA damage and repair-related molecules which act against stresses, including ethanol, have not been fully investigated in intestinal cells. Heat shock proteins (Hsps) are involved in the recovery and protection from cell damage and may be associated with DNA repair. Therefore, the aim of our study was to investigate cytotoxicity, DNA damage and the expression of DNA repair-related molecules, antioxidant proteins and Hsps in intestinal cells exposed to ethanol. Human intestinal Caco-2 cells were incubated with 1-8% ethanol for 1 h. Cell viability and DNA damage were determined using the MTT and comet assays, respectively. We measured DNA repair-related molecules, including DNA polymerase β, apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1), growth arrest and DNA damage 45α (GADD45α) and proliferating cell nuclear antigen (PCNA), in Caco-2 cells using western blot analysis. We also measured glutathione peroxidase-1 (GPx-1), peroxiredoxin-1 (PRX-1), superoxide dismutase-2 (SOD-2), Hsp10, Hsp27, Hsp60, heat shock cognate (Hsc)70, Hsp70 and Hsp90. The viability of the Caco-2 cells exposed to ethanol decreased at concentrations ≥ 7% (P<0.05). The Olive tail moment, indicating DNA damage, increased dose dependently in ≥ 3% ethanol (P<0.05). Among the DNA repair proteins, the expression of PCNA and APE/Ref-1 increased significantly at 1% ethanol. Antioxidant enzymes, including GPx-1, PRX-1 and SOD-2, had an increased expression at 1% ethanol. Hsp10, Hsp27 and Hsp70 expression also increased significantly at 1% ethanol. In conclusion, the expression of DNA repair molecules, antioxidants and Hsps increased in intestinal Caco-2 cells exposed to low concentrations of ethanol. In particular, PCNA, APE/Ref-1, Hsp10, Hsp27 and Hsp70 were sensitive to low ethanol concentrations, indicating that they may be useful in evaluating the DNA repair and cytoprotective effects of the drug against stress in intestinal cells.

Glutamine therapy improves outcome of in vitro and in vivo experimental colitis models

BACKGROUND

Pharmacologic doses of glutamine (GLN) can improve clinical outcome following acute illness and injury. Recent studies indicate enhanced heat shock protein (HSP) expression is a key mechanism underlying GLN's protection. However, such a link has not yet been tested in chronic inflammatory states, such as experimental inflammatory bowel disease (IBD).

METHODS

Experimental colitis was induced in Sprague-Dawley rats via oral 5% dextran sulfate sodium (DSS) for 7 days. GLN (0.75 g/kg/d) or sham was administered to rats by oral gavage during 7-day DSS treatment. In vitro inflammatory injury was studied using YAMC colonic epithelial cells treated with varying concentrations of GLN and cytokines (tumor necrosis factor-α/interferon-γ).

RESULTS

Pharmacologic dose, bolus GLN attenuated DSS-induced colitis in vivo with decreased area under curve for bleeding (8.06 ± 0.87 vs 10.38 ± 0.79, P < .05) and diarrhea (6.97 ± 0.46 vs 8.53 ± 0.39, P < .05). This was associated with enhanced HSP25 and HSP70 in colonic mucosa. In vitro, GLN enhanced cell survival and reduced proapoptotic caspase3 and poly(ADP-ribose) polymerase cleavage postcytokine injury. Cytokine-induced inducible nitric oxide synthase expression and nuclear translocation of nuclear factor-κB p65 subunit were markedly attenuated at GLN concentrations above 0.5 mmol/L. GLN increased cellular HSP25 and HSP70 in a dose-dependent manner.

CONCLUSIONS

These data demonstrate the therapeutic potential of GLN as a "pharmacologically acting nutrient" in the setting of experimental IBD. GLN sufficiency is crucial for the colonic epithelium to mount a cell-protective, antiapoptotic, and anti-inflammatory response against inflammatory injury. The enhanced HSP expression observed following GLN treatment may be responsible for this protective effect.

Bovine lactoferrin induces interleukin-11 production in a hepatitis mouse model and human intestinal myofibroblasts

PURPOSE

Orally administered bovine lactoferrin (bLF) exerts an anti-inflammatory effect on hepatitis and colitis animal models. To investigate the mechanism underlying the action of bLF, we explored the expression of inflammation-related factors in the intestine of a hepatitis mouse model after the oral administration of bLF and in several human intestinal cell lines treated with bLF.

METHODS

The effects of bLF on the expression of interleukin-11 (IL-11) and bone morphogenetic protein 2 (BMP2) in the intestinal mucosa of a hepatitis mouse model as well as in cell cultures of human intestinal epithelial cells, myofibroblasts, and monocytes were examined using the real-time reverse transcription polymerase chain reaction. Epithelial cells and myofibroblasts were also cocultured using transwells. bLF transport, and IL-11 and BMP2 induction, as well as the interactions between the two cell types, were then analyzed after bLF treatment.

RESULTS

In vivo, oral bLF administration increased the production of IL-11 and BMP2 in intestinal specimens. In vitro, bLF only stimulated the production of IL-11 in human intestinal myofibroblasts; i.e., it had no effect on BMP2 production in any cell type. In the transwell cocultures, bLF passed through the epithelium and directly stimulated IL-11 production in the myofibroblasts on the basolateral side. The IL-11 produced in the myofibroblasts subsequently acted protectively on the epithelial cells of the coculture.

CONCLUSIONS

bLF upregulated the activity of anti-inflammatory factors, such as IL-11, in the intestine of a hepatitis mouse model and human intestinal myofibroblasts.

Regional differences in colonic mucosa-associated microbiota determine the physiological expression of host heat shock proteins

Cytoprotective heat shock proteins (Hsps) are critical for intestinal homeostasis and are known to be decreased in inflammatory bowel diseases. Signals responsible for maintenance of Hsp expression are incompletely understood. In this study, we find that Hsp25/27 and Hsp70 protein expressions are differentially regulated along the longitudinal length of the large intestine, being highest in the proximal colon and decreasing to the distal colon. This longitudinal gradient was similar in both conventionally colonized mouse colon as well as biopsies of human proximal and distal colon but was abolished in the colon of germ-free mice, suggesting a role of intestinal microbiota in the Hsp regional expression. Correspondingly, analysis of 16S ribosomal RNA genes of bacteria from each colonic segment indicated increased bacterial richness and diversity in the proximal colon. The mechanism of regulation is transcriptional, as Hsp70 mRNA followed a similar pattern to Hsp70 protein expression. Lysates of mucosa-associated bacteria from the proximal colon stimulated greater Hsp25 and Hsp70 mRNA transcription and subsequent protein expression in intestinal epithelial cells than did lysates from distal colon. In addition, transrectal administration of cecal contents stimulated Hsp25 and Hsp70 expression in the distal colon. Thus host-microbial interactions resulting in differential Hsp expression may have significant implications for the maintenance of intestinal homeostasis and possibly for development of inflammatory diseases of the bowel.

From the gut to the peripheral tissues: the multiple effects of butyrate

Butyrate is a natural substance present in biological liquids and tissues. The present paper aims to give an update on the biological role of butyrate in mammals, when it is naturally produced by the gastrointestinal microbiota or orally ingested as a feed additive. Recent data concerning butyrate production delivery as well as absorption by the colonocytes are reported. Butyrate cannot be detected in the peripheral blood, which indicates fast metabolism in the gut wall and/or in the liver. In physiological conditions, the increase in performance in animals could be explained by the increased nutrient digestibility, the stimulation of the digestive enzyme secretions, a modification of intestinal luminal microbiota and an improvement of the epithelial integrity and defence systems. In the digestive tract, butyrate can act directly (upper gastrointestinal tract or hindgut) or indirectly (small intestine) on tissue development and repair. Direct trophic effects have been demonstrated mainly by cell proliferation studies, indicating a faster renewal of necrotic areas. Indirect actions of butyrate are believed to involve the hormono-neuro-immuno system. Butyrate has also been implicated in down-regulation of bacteria virulence, both by direct effects on virulence gene expression and by acting on cell proliferation of the host cells. In animal production, butyrate is a helpful feed additive, especially when ingested soon after birth, as it enhances performance and controls gut health disorders caused by bacterial pathogens. Such effects could be considered for new applications in human nutrition.

Interleukin-11 reduces TLR4-induced colitis in TLR2-deficient mice and restores intestinal STAT3 signaling

BACKGROUND & AIMS

The roles of intestinal Toll-like receptors (TLR) in the pathogenesis of colitis are not known. TLR2 and TLR4 appear to protect against dextran sodium sulfate-induced colitis by promoting mucosal integrity, but it is not clear whether this method of protection occurs in other models of colitis. We investigated the roles of TLR2 and TLR4 and the cell types that express these receptors during infectious colitis.

METHODS

We generated chimeric mice with TLR2(-/-) or TLR4(-/-) bone marrow and infected them with the bacterial pathogen Citrobacter rodentium. We assessed their susceptibility to colitis and the mechanisms of TLR-mediated mucosal integrity.

RESULTS

TLR2-expressing tissue resident cells prevented lethal colitis, whereas TLR4-dependent inflammatory responses of hematopoietic cells mediated intestinal damage. TLR2 expression protected against intestinal damage by maintaining epithelial barrier function and inducing expression of interleukin (IL)-11 from tissue resident cells in the muscularis mucosae, concurrent with epithelial activation of the transcription factor STAT3. Addition of exogenous IL-11 protected against the lethal colitis in TLR2-deficient mice via STAT3 activation in intestinal epithelial cells.

CONCLUSIONS

TLR2-dependent cytoprotective responses from tissue resident cells maintain mucosal integrity against the ultimately lethal TLR4-dependent inflammatory responses of hematopoietic cells. Whereas TLR2 protects against various noxious agents, the role of TLR4 during colitis can be either protective or damaging, depending on the stimulus. Therefore, therapeutics that reduce innate immunity (TLR2 signaling in particular) may not be beneficial to patients with colitis; they could worsen symptoms. Therapies that stimulate cytoprotective responses, like IL-11, could have benefits for patients with colitis.

More than a sidekick: the IL-6 family cytokine IL-11 links inflammation to cancer

IL-11, a member of the IL-6 family of cytokines, exerts pleiotropic activities by stimulating hemopoiesis and thrombopoiesis, regulating macrophage differentiation, and conferring mucosal protection in the intestine. These effects are mediated by a multimeric complex comprising the ligand-binding IL-11Rα and the ubiquitously expressed gp130R β-subunit, which together, trigger intracellular signaling and engagement of Stat3. In turn, activated Stat3 promotes cell survival and proliferation as well as immune responses associated with inflammatory diseases and tumor progression. IL-6 and IL-11 compete for interaction with gp130, resulting in tissue-specific functions depending on the expression patterns of their respective α-subunit receptors. Although traditionally, IL-6 has been associated with aberrant Stat3 activation and associated pathologies, here, we discuss newly emerging roles for IL-11 in linking inflammation to cancer progression. We propose that in light of the recurrence of persistent STAT3 activation and elevated IL-11 expression in inflammation-associated gastrointestinal cancers in humans, inhibition of Stat3 or pharmacologically, more amenable upstream molecules such as IL-11 may represent novel, therapeutic targets.

How bacteria-induced apoptosis of intestinal epithelial cells contributes to mucosal inflammation

The life cycle of an intestinal epithelial cell is terminated by apoptosis and/or cell shedding. Apoptotic deletion of epithelial cells from the intact intestinal mucosa is not accompanied by detectable inflammatory response or loss of barrier function. But increased permeability of the epithelial barrier and increased apoptotic rates of epithelial cells have been reported for patients suffering from inflammatory bowel disease. Microbiota can both induce or inhibit apoptosis of intestinal epithelial cells thus contribute to mucosal inflammation or support epithelial integrity respectively. Bacteria-mediated cytokine secretion and altered cell signalling are central to epithelial injury. Tumor necrosis factor (TNF) secreted after exposure to invasive bacteria induces both apoptosis and cell shedding. TNF is the major target gene of the transcription factor nuclear factor-kappa B with both pro- and anti-apoptotic effects. Autophagy promotes both cell survival and “autophagic” cell death. If autophagy is directed against microbes it is termed xenophagy. Inhibition of xenophagy has been shown to decrease cell survival. Endoplasmic reticulum (ER) stress causes misfolded proteins to accumulate in the ER lumen. It was suggested that ER stress and autophagy may interact within intestinal epithelial cells. Apoptosis in response to infection may be well proposed by the host to delete infected epithelial cells or could be a strategy of microbial pathogens to escape from exhausted cells to invade deeper mucosal layers for a prolonged bacterial colonization.

Novel perspectives in probiotic treatment: the efficacy and unveiled mechanisms of the physiological functions

Probiotics are defined as "live microorganisms which confer a health benefit on the host" when administered in adequate amounts, and have potential effects for maintaining intestinal development, nutrition, and treating intestinal inflammations, functional disorders, and other extra-intestinal diseases. Although the benefits of probiotics for human health were first noted over 100 years ago, the analysis of probiotic functions began in earnest only 20 years ago. Probiotics, such as some strains of Lactobacillus, Bifidobacterium, Escherichia coli, and Bacillus subtilis, inhibit the growth of pathogenic bacteria, induce competitive effects for the adherent of pathogenic bacteria and their toxins to intestinal epithelia, induce cytoprotective heat shock proteins, enhance the intestinal barrier function, and modulate the host immune responses. The crosstalk between the host and the probiotics appears to be mediated by bacteria-derived effectors, which can be sensed with multiple systems, including the Toll-like receptors and cell membrane transporters. Future analyses will identify more probiotic-derived effectors, the recognition mechanisms of these effectors, and the subsequent changes of the intestinal epithelia and immune cells for each probiotic treatment. For clinical use, a procedure that objectively evaluates the ability of each probiotic effect will help establish a standard for choosing the most valuable strain and its proper dose for each individual patient.

Stress granule formation mediates the inhibition of colonic Hsp70 translation by interferon-gamma and tumor necrosis factor-alpha

Mucosal inflammation, through cytokines such as interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), has many effects on the intestinal epithelium, including selective translational inhibition of the cytoprotective protein heat shock protein 70 (Hsp70). To further elucidate the mechanisms underlying this effect, we examined the role of stress granules in mediating the actions of these proinflammatory cytokines. Using conditionally immortalized young adult mouse colonic epithelial cells, we demonstrate that IFN-gamma and TNF-alpha, which upregulate eukaryotic initiation factor-alpha (eIF-2alpha) phosphorylation and reduce Hsp70 translation, significantly enhance stress granule formation in heat-shocked intestinal epithelial cells. The IFN-gamma and TNF-alpha effects in upregulation of stress granule formation and downregulation of Hsp70 were eIF-2alpha dependent, and the effect could be negated by blocking eIF-2alpha phosphorylation with use of an RNA-dependent protein kinase inhibitor. Correspondingly, IFN-gamma and TNF-alpha increased binding of cytoplasmic proteins to the 3'-untranslated region of Hsp70 mRNA, suggesting specific recruitment of Hsp70 to stress granules as the mechanism of IFN-gamma and TNF-alpha inhibition of Hsp70 translation. We thus report a novel linkage between inflammatory cytokine production, stress granule formation, and Hsp70 translation inhibition, providing additional insights into the response of intestinal epithelial cells to inflammatory stress.

Inflammation-induced, 3'UTR-dependent translational inhibition of Hsp70 mRNA impairs intestinal homeostasis

Although the inducible heat shock protein 70 (Hsp70) is essential for maintaining intestinal homeostasis in colitis, it is translationally downregulated in inflamed colonic mucosa, paradoxically rendering the gut more susceptible to injury. We examined the basis for this process by analyzing the role of untranslated regions (UTR) of Hsp70 mRNA in inflammation-associated downregulation in vitro and in vivo. Using luciferase-reporter assays in young adult mouse intestinal epithelial cells, we determined that cytokine-induced translational inhibition of Hsp70 mRNA was mediated by the 3'UTR, but not 5'UTR. In vivo, dextran sodium sulfate (DSS) colitis was induced in wild-type (WT) and villin-promoter regulated "UTR-less" Hsp70 transgenic (TG) mice, the latter exhibiting intestinal epithelial-specific transgene expression. Progressive downregulation of colonic Hsp70 protein expression was observed in WT, but not in TG, mice with increasing severity of mucosal inflammation, confirming the essential role of the 3'UTR in mediating inflammation-associated downregulation of Hsp70. Hsp70 TG mice demonstrated significantly lower endoscopic and histological inflammation scores in DSS-induced colitis than WT. In conclusion, downregulation of Hsp70 expression in inflamed mucosa is mediated by translational inhibition requiring the 3'UTR, resulting in increased mucosal injury. By forcing intestinal epithelial-specific Hsp70 expression in vivo, the severity of experimentally induced colitis was significantly reduced.

Oral administration of heat-killed Lactobacillus brevis SBC8803 ameliorates alcoholic liver disease in ethanol-containing diet-fed C57BL/6N mice

We examined the effect of heat-killed Lactobacillus brevis (L. brevis) SBC8803 on the development of alcoholic liver disease using ethanol-containing diet-fed mice. Heat-killed L. brevis was orally administered at a dose of 100 or 500 mg/kg once a day for 35 days. Alcoholic liver injury was examined by measuring the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in a serum, and the alcoholic fatty liver was assessed from the content of triglyceride (TG) and total cholesterol in the liver. Quantitative RT-PCR was used to examine mRNA expression of tumor necrosis factor (TNF)-alpha, sterol regulatory element-binding protein (SREBP)-1, SREBP-2, and peroxisome proliferator-activated receptor alpha (PPARalpha) in the liver, as well as E-cadherin, Zonula occludens 1 (ZO-1), and heat shock protein (Hsp) 25 in the small intestine. Oral administration of L. brevis significantly inhibited an increase in the level of serum ALT and AST, as well as the content of TG and total cholesterol in the liver caused by ethanol intake. L. brevis supplementation suppressed the overexpression of TNF-alpha, SREBP-1, and SREBP-2 mRNA in the liver induced by ethanol intake and up-regulated the expression of Hsp25 mRNA in the small intestine. These results suggest that L. brevis ameliorated the ethanol-induced liver injury and the fatty liver by suppressing the up-regulation of TNF-alpha and SREBPs in the liver. We speculate that the inhibition of TNF-alpha and SREBPs up-regulation by L. brevis is due to the inhibition of gut-derived endotoxin migration into the liver through the enhancement of intestinal barrier function by the induction of cytoprotective Hsps.

Flagellin is required for salmonella-induced expression of heat shock protein Hsp25 in intestinal epithelium

Flagellin is a bacterial protein responsible for activation of Toll-like receptor 5 (TLR5), which we hypothesize is involved in Salmonella's induction of cytoprotective heat shock proteins in intestinal epithelial cells. Flagellin induces the cytoprotective heat shock protein Hsp25 in different intestinal epithelial cell lines and in mouse intestine. Flagellin induces Hsp25 expression in a time-dependent manner in vitro. This effect is transcriptional, as confirmed by luciferase reporter assays and actinomycin D treatment. In addition, Hsp25 induction requires p38 MAPK activation and is only observed when flagellin is added to the basolateral side of polarized intestinal epithelial cells, consistent with the known location of TLR5. Flagellin-mediated Hsp25 induction is associated with increased protective effects against oxidant stress, an effect that is at least partially mediated by p38 MAPK. Use of small interfering RNA against Hsp25 demonstrates that flagellin-mediated protection against oxidant stress is to some degree mediated through Hsp25 induction. This suggests that, by protecting against oxidant injury, the induction of Hsp25 expression by flagellin may contribute to intestinal homeostasis. In a coculture cell model and in a mouse model of Salmonella enterica Serovar Typhimurium infection, not only does infection with wild-type and a flagellin-deletion mutant strain of Salmonella show that flagellin induces Hsp25 in vivo, but it also demonstrates that in the case of live Salmonella infection, flagellin serves as a major stimulus for the induction of Hsp25 expression. These data provide evidence that flagellin is required for Salmonella-mediated induction of Hsp25 expression in intestinal epithelium.