Georg H. Waetzig

Genetic variation in DLG5 is associated with inflammatory bowel disease

Crohn disease and ulcerative colitis are two subphenotypes of inflammatory bowel disease (IBD), a complex disorder resulting from gene-environment interaction. We refined our previously defined linkage region for IBD on chromosome 10q23 and used positional cloning to identify genetic variants in DLG5 associated with IBD. DLG5 encodes a scaffolding protein involved in the maintenance of epithelial integrity. We identified two distinct haplotypes with a replicable distortion in transmission (P = 0.000023 and P = 0.004 for association with IBD, P = 0.00012 and P = 0.04 for association with Crohn disease). One of the risk-associated DLG5 haplotypes is distinguished from the common haplotype by a nonsynonymous single-nucleotide polymorphism 113G→A, resulting in the amino acid substitution R30Q in the DUF622 domain of DLG5. This mutation probably impedes scaffolding of DLG5. We stratified the study sample according to the presence of risk-associated CARD15 variants to study potential gene-gene interaction. We found a significant difference in association of the 113A DLG5 variant with Crohn disease in affected individuals carrying the risk-associated CARD15 alleles versus those carrying non-risk-associated CARD15 alleles. This is suggestive of a complex pattern of gene-gene interaction between DLG5 and CARD15, reflecting the complex nature of polygenic diseases. Further functional studies will evaluate the biological significance of DLG5 variants.

p38 Mitogen-Activated Protein Kinase Is Activated and Linked to TNF-α Signaling in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD)—Crohn’s disease and ulcerative colitis—are relapsing chronic inflammatory disorders which involve genetic, immunological, and environmental factors. The regulation of TNF-α, a key mediator in the inflammatory process in IBD, is interconnected with mitogen-activated protein kinase pathways. The aim of this study was to characterize the activity and expression of the four p38 subtypes (p38α–δ), c-Jun N-terminal kinases (JNKs), and the extracellular signal-regulated kinases (ERK)1/2 in the inflamed intestinal mucosa. Western blot analysis revealed that p38α, JNKs, and ERK1/2 were significantly activated in IBD, with p38α showing the most pronounced increase in kinase activity. Protein expression of p38 and JNK was only moderately altered in IBD patients compared with normal controls, whereas ERK1/2 protein was significantly down-regulated. Immunohistochemical analysis of inflamed mucosal biopsies localized the main expression of p38α to lamina propria macrophages and neutrophils. ELISA screening of the supernatants of Crohn’s disease mucosal biopsy cultures showed that incubation with the p38 inhibitor SB 203580 significantly reduced secretion of TNF-α. In vivo inhibition of TNF-α by a single infusion of anti-TNF-α Ab (infliximab) resulted in a highly significant transient increase of p38α activity during the first 48 h after infusion. A significant infliximab-dependent p38α activation was also observed in THP-1 myelomonocytic cells. In human monocytes, infliximab enhanced TNF-α gene expression, which could be inhibited by SB 203580. In conclusion, p38α signaling is involved in the pathophysiology of IBD.

The IL-6/sIL-6R complex as a novel target for therapeutic approaches.

IL-6 plays a pivotal role in immune responses and certain oncologic conditions. The intense investigation of its biological activity and function led to the discovery of two different IL-6-driven signalling pathways. Binding to the membrane-bound IL-6 receptor (mIL-6R, CD126) causes the recruitment of two gp130 co-receptor molecules (CD130) and the activation of intracellular signalling cascades via gp130. Although this classical pathway is mainly limited to hepatocytes, neutrophils, monocytes/macrophages and certain other leukocyte populations, which express IL-6R on their surface, an alternative mechanism has also been described. Proteolytic cleavage of the mIL-6R protein or translation from alternatively spliced mRNA leads to the generation of a soluble form of the IL-6R (sIL-6R), which is likewise able to bind to IL-6. The resulting IL-6/sIL-6R complex is also capable of binding to gp130 and inducing intracellular signalling. Through this so-called ‘trans-signalling’ mechanism, IL-6 is able to stimulate cells that lack an endogenous mIL-6R. High levels of IL-6 and sIL-6R have been reported in several chronic inflammatory and autoimmune diseases as well as in cancer. Preclinical animal disease models have provided strong evidence that specific blockade of IL-6-regulated signalling pathways represents a promising approach for the therapy of these diseases. An optimised variant of the recently described fusion protein sgp30Fc is now heading towards its clinical evaluation.

Transsignaling of Interleukin-6 Crucially Contributes to Atherosclerosis in Mice

Objective—Transsignaling of interleukin (IL)-6 is a central pathway in the pathogenesis of disorders associated with chronic inflammation, such as Crohn disease, rheumatoid arthritis, and inflammatory colon cancer. Notably, IL-6 also represents an independent risk factor for coronary artery disease (CAD) in humans and is crucially involved in vascular inflammatory processes. Methods and Results—In the present study, we showed that treatment with a fusion protein of the natural IL-6 transsignaling inhibitor soluble glycoprotein 130 (sgp130) and IgG1-Fc (sgp130Fc) dramatically reduced atherosclerosis in hypercholesterolemic Ldlr−/− mice without affecting weight gain and serum lipid levels. Moreover, sgp130Fc treatment even led to a significant regression of advanced atherosclerosis. Mechanistically, endothelial activation and intimal smooth muscle cell infiltration were decreased in sgp130Fc-treated mice, resulting in a marked reduction of monocyte recruitment and subsequent atherosclerotic plaque progression. Of note, patients with CAD exhibited significantly lower plasma levels of endogenous sgp130, suggesting that a compromised counterbalancing of IL-6 transsignaling may contribute to atherogenesis in humans. Conclusion—These data clarify, for the first time, the critical involvement of, in particular, the transsignaling of IL-6 in CAD and warrant further investigation of sgp130Fc as a novel therapeutic for the treatment of CAD and related diseases.

Inhibition of Classic Signaling Is a Novel Function of Soluble Glycoprotein 130 (sgp130), Which Is Controlled by the Ratio of Interleukin 6 and Soluble Interleukin 6 Receptor

Background: IL-6 trans-signaling plays a critical role in chronic inflammation and cancer. Results: The trans-signaling inhibitor sgp130(Fc) also inhibits classic signaling depending on IL-6/sIL-6R ratios. Conclusion: The additional function of sgp130(Fc) suggests that in vivo only low therapeutic concentrations guarantee blockade of trans-signaling but not classic signaling. Significance: The demonstration that the trans-signaling inhibitor can also inhibit classic signaling is central for the field of IL-6 biology. IL-6 trans-signaling via the soluble IL-6 receptor (sIL-6R) plays a critical role in chronic inflammation and cancer. Soluble gp130 (sgp130) specifically inhibits IL-6 trans-signaling but was described to not interfere with classic signaling via the membrane-bound IL-6R. Physiological and most pathophysiological conditions are characterized by a molar excess of serum sIL-6R over IL-6 characterized by free IL-6 and IL-6 found in IL-6·sIL-6R complexes allowing both classic and trans-signaling. Surprisingly, under these conditions, sgp130 was able to trap all free IL-6 molecules in IL-6·sIL-6R·sgp130 complexes, resulting in inhibition of classic signaling. Because a significant fraction of IL-6 molecules did not form complexes with sIL-6R, our results demonstrate that compared with the anti-IL-6R antibody tocilizumab or the anti-trans-signaling monoclonal antibody 25F10, much lower concentrations of the dimeric sgp130Fc were sufficient to block trans-signaling. In vivo, sgp130Fc blocked IL-6 signaling in the colon but not in liver and lung, indicating that the colon is a prominent target of IL-6 trans-signaling. Our results point to a so far unanticipated role of sgp130 in the blockade of classic signaling and indicate that in vivo only low therapeutic concentrations of sgp130Fc guarantee blockade of IL-6 trans-signaling without affecting IL-6 classic signaling.

Soluble tumor necrosis factor (TNF) receptor-1 induces apoptosis via reverse TNF signaling and autocrine transforming growth factor-β1

The pro‐inflammatory cytokine tumor necrosis factor‐α (TNF‐α) plays a central role in inflammatory disorders. Transmembrane TNF‐α and its two receptors are cleaved by the proteinase TNF‐α converting enzyme (TACE), resulting in appreciable serum levels of soluble TNF‐α and soluble TNF‐α receptors (sTNFR1 and ‐2). The only known functions of sTNFR1 are to antagonize and buffer circulating TNF‐α. Here, we present evidence that sTNFR1 exerts immunoregulatory functions by induction of apoptosis in monocytes through reverse signaling via transmembrane TNF‐α. sTNFR1‐induced apoptosis is independent of death receptor pathways but depends on autocrine transforming growth factor (TGF)‐β1 signaling through the mitogen‐activated protein kinase p38α. This novel mechanism has implications for understanding the physiological role of sTNFR1 and for TNF‐α‐blocking therapies of autoimmune diseases.

Selective blockade of interleukin-6 trans-signaling improves survival in a murine polymicrobial sepsis model*

Objective: The pleiotropic cytokine interleukin (IL)-6 seems to play a pivotal role in sepsis, but contradictory findings in animal models impede a rationale for therapies directed against IL-6. IL-6 signals by two mechanisms via the ubiquitous transmembrane glycoprotein 130 (gp130): “classic” signaling using membrane-bound IL-6 receptor (IL-6R) and trans-signaling using soluble IL-6R (sIL-6R). Trans-signaling is selectively inhibited by soluble gp130 (sgp130). The aim of this study was to systematically compare complete blockade of IL-6 signaling (using a neutralizing anti-IL-6 antibody) and selective blockade of IL-6 trans-signaling (using a fusion protein of sgp130 and the crystallizable fragment of immunoglobulin G1, sgp130Fc) in a standardized cecal ligation and puncture (CLP) sepsis model. Design: Animal study. Setting: Animal laboratory. Subjects: C57BL/6J mice. Interventions: We performed a 96-hr dose-response study and a 24-hr study to investigate short-term mechanisms. In the 96-hr study, CLP was performed in 120 randomized mice (20 mice received vehicle, 10 mice per dose group). Mice were treated with equimolar doses of sgp130Fc (0.01/0.1/1/10 mg/kg) or anti-IL-6 (0.008/0.08/0.8/8 mg/kg) 24 hrs before CLP. Two additional groups received 0.5 mg/kg sgp130Fc 24 hrs before or 1 mg/kg sgp130Fc 24 hrs after CLP. Survival and activity scores were obtained daily until 96 hrs after CLP. In the 24-hr study, mice were randomized into four groups with 10 animals each (sham/vehicle, CLP/vehicle, CLP/anti-IL-6 [0.8 mg/kg], and CLP/sgp130Fc [1 mg/kg]) and killed after 24 hrs. Measurements and Main Results: In contrast to anti-IL-6, pretreatment with sgp130Fc significantly and dose-dependently increased survival from 45% to 100%. In addition, 1 mg/kg sgp130Fc administered 24 hrs after CLP increased survival from 45% to 80%. Mechanistically, sgp130Fc efficacy was reflected by complete prevention of epithelial cell apoptosis in the jejunum after CLP, which was not achieved with anti-IL-6. Conclusion: Selective inhibition of IL-6 trans-signaling by sgp130Fc has considerable potential for the treatment of sepsis and related disorders.

Hitting a complex target: an update on interleukin-6 trans-signalling

Introduction: Interleukin-6 (IL-6) is a key target in inflammation and cancer. Selective inhibition of IL-6 trans-signalling could provide the same or even higher therapeutic efficacy with a better side effect profile than complete IL-6 inhibition. Animal studies with IL-6 inhibitors show that the classic IL-6 signalling pathway via the membrane-bound IL-6 receptor (IL-6R) has important physiological functions, whereas blocking the trans-signalling pathway via the soluble IL-6R (sIL-6R) is sufficient to prevent or treat IL-6-driven diseases. Due to the success of the anti-IL-6R antibody tocilizumab and difficulties of constructing selective trans-signalling inhibitors, most drug candidates in clinical development target IL-6 or IL-6R and, thus, both IL-6 pathways. By contrast, the fusion protein sgp130Fc selectively targets IL-6/sIL-6R trans-signalling by utilising the soluble gp130 receptor as the natural inhibitor of trans-signalling. Areas covered: The authors summarise recent developments in the field with a focus on animal studies highlighting the mechanistic differences between classic and trans-signalling and their therapeutic implications. Expert opinion: Characterising disease mechanisms in terms of the employed IL-6 pathways will help to select the right therapeutic IL-6 inhibitor in the future. The trans-signalling inhibitor sgp130Fc is about to enter the clinic and holds promise for a clinically different profile in comparison with complete IL-6 inhibitors.

An Interleukin-6 Receptor-dependent Molecular Switch Mediates Signal Transduction of the IL-27 Cytokine Subunit p28 (IL-30) via a gp130 Protein Receptor Homodimer

Background: Anti-inflammatory signaling of IL-27, p28, and EBI3 is mediated by gp130 and Wsx-1. Results: Signaling of p28 via IL-6R is mediated by a gp130 homodimer. Conclusion: Signaling of p28 via IL-6R is likely not anti-inflammatory. Significance: We identify the signal receptor complex of p28/IL-6R. IL-27 consists of the cytokine subunit p28 and the non-signaling α-receptor EBI3. p28 was shown to additionally act via the non-signaling membrane-bound IL-6 α-receptor (IL-6R) as an agonistic cytokine but also as a gp130 β-receptor antagonist, leading to inhibition of IL-6 signaling. Here, we developed a strategy for bacterial expression, purification, and refolding of murine p28. We show that p28 did not interfere with IL-6- or IL-27-induced signaling, indicating that p28 has no antagonistic properties. Moreover, we demonstrate that murine p28 acts as an agonistic cytokine via the murine and human IL-6R, indicating that p28 exhibits no species specificity. p28 was able to induce p28-trans-signaling via the soluble IL-6R (sIL-6R), a characteristic property that was initially described for trans-signaling of IL-6 via the sIL-6R. Of notice, p28/sIL-6R trans-signaling was inhibited by the IL-6 trans-signaling antagonist, soluble gp130. At higher concentrations, p28 but not IL-6 was able to induce signaling even in the absence of IL-6R or EBI3. Although IL-27 signals via a heterodimer of the β-receptor chains gp130 and Wsx-1, p28/IL-6R specifically recruits two gp130 β-receptor chains for signal transduction. The binding of p28 to a gp130/Wsx-1 heterodimer or a gp130 homodimer is highly selective and controlled by a novel molecular switch induced by EBI3 or IL-6R, respectively.

Localization of hydrogen peroxide during the defence response of Arabidopsis thaliana against the plant-parasitic nematode Heterodera glycines

Hydrogen peroxide (H 2 O 2 ) production during the infection of Arabidopsis thaliana by the soybean cyst nematode Heterodera glycines was detected histochemically by the reaction of H 2 O 2 with cerium chloride producing four different patterns of electron-dense precipitates of cerium perhydroxides. As A. thaliana is not a regular host of H. glycines , the defence response is considerable, but does not completely inhibit the development of the nematode. H 2 O 2 was produced not only by cells mechanically damaged during invasion and feeding site induction by the nematode, but also by cells surrounding developing syncytia and cells which were neither in contact with the nematode nor with the syncytium. Die Lokalisation von Peroxid wahrend der Abwehrreaktion von Arabidopsis thaliana gegen den pflanzenparasitaren Nematoden Heterodera glycines - Die Bildung von Wasserstoffperoxid (H 2 O 2 ) im Rahmen der Infektion von Arabidopsis thaliana durch den Sojabohnen-Zystennematoden Heterodera glycines wurde histochemisch durch die Reaktion von H 2 O 2 mit Cerchlorid nachgewiesen, wobei vier verschiedene Muster elektronendichter Prazipitate von Cerperhydroxiden gebildet wurden. Da A. thaliana kein regularer Wirt von H. glycine s ist, kommt es zu einer betrachtlichen Abwehrreaktion, die jedoch die Entwicklung des Nematoden nicht vollstandig verhindert. H 2 O 2 wurde nicht nur von Zellen produziert, die im Laufe des Eindringens und der Induktion des Nahrzellensystems durch den Nematoden mechanisch beschadigt worden waren, sondern auch von Zellen, die sich entwickelnde Syncytien umgaben und von Zellen, die weder mit dem Nematoden noch mit dem Syncytium in Kontakt standen.