Conservation of IL-6 trans-signaling mechanisms controlling L-selectin adhesion by fever-range thermal stress

Dissecting Interleukin-6 Classic and Trans-signaling in Inflammation and Cancer

Interleukin-6 (IL-6) is a cytokine synthesized by many cells in the human body. IL-6 binds to a membrane-bound receptor (IL-6R), which is only present on hepatocytes, some epithelial cells, and some leukocytes. The complex of IL-6 and IL-6R binds to the ubiquitously expressed receptor subunit gp130, which forms a homodimer and thereby initiates intracellular signaling, e.g., the JAK/STAT and MAPK pathways. Proteases can cleave the membrane-bound IL-6R from the cell surface and generate a soluble IL-6R (sIL-6R), which retains its ability to bind IL-6. The IL-6/sIL-6R complex associates with gp130 and induces signaling even on cells which do not express the IL-6R. This paradigm has been called IL-6 trans-signaling, whereas signaling via the membrane-bound IL-6R is referred to as classic signaling. We have generated several molecular tools to differentiate between both pathways and to analyze the consequences of cellular IL-6 signaling in vivo. One of these tools is soluble gp130Fc, which selectively inhibits IL-6 trans-signaling. This protein under the WHO name Olamkicept has successfully undergone phase II clinical trials in patients with autoimmune diseases. Here, in this chapter, we describe several molecular tools to differentiate between IL-6 classic and trans-signaling and to analyze the consequences of cellular IL-6 signaling in vivo.

Temperature Plays an Essential Regulatory Role in the Tumor Immune Microenvironment

In recent years, emerging immunotherapy has been included in various malignant tumor treatment standards. Temperature has been considered to affect different pathophysiological reactions such as inflammation and cancer for a long time. However, in tumor immunology research, temperature is still rarely considered a significant variable. In this review, we discuss the effects of room temperature, body temperature, and the local tumor temperature on the tumor immune microenvironment from multiple levels and perspectives, and we discuss changes in the body's local and whole-body temperature under tumor conditions. We analyze the current use of ablation treatment-the reason for the opposite immune effect. We should pay more attention to the therapeutic potential of temperature and create a better antitumor microenvironment that can be combined with immunotherapy.

Enhancing innate immunity against virus in times of COVID-19: Trying to untangle facts from fictions

Introduction

In light of the current COVID-19 pandemic, during which the world is confronted with a new, highly contagious virus that suppresses innate immunity as one of its initial virulence mechanisms, thus escaping from first-line human defense mechanisms, enhancing innate immunity seems a good preventive strategy.

Methods

Without the intention to write an official systematic review, but more to give an overview of possible strategies, in this review article we discuss several interventions that might stimulate innate immunity and thus our defense against (viral) respiratory tract infections. Some of these interventions can also stimulate the adaptive T- and B-cell responses, but our main focus is on the innate part of immunity. We divide the reviewed interventions into: 1) lifestyle related (exercise, >7 h sleep, forest walking, meditation/mindfulness, vitamin supplementation); 2) Non-specific immune stimulants (letting fever advance, bacterial vaccines, probiotics, dialyzable leukocyte extract, pidotimod), and 3) specific vaccines with heterologous effect (BCG vaccine, mumps-measles-rubeola vaccine, etc).

Results

For each of these interventions we briefly comment on their definition, possible mechanisms and evidence of clinical efficacy or lack of it, especially focusing on respiratory tract infections, viral infections, and eventually a reduced mortality in severe respiratory infections in the intensive care unit. At the end, a summary table demonstrates the best trials supporting (or not) clinical evidence.

Conclusion

Several interventions have some degree of evidence for enhancing the innate immune response and thus conveying possible benefit, but specific trials in COVID-19 should be conducted to support solid recommendations.

Targeted Antitumor Mechanism of C-PC/CMC-CD55sp Nanospheres in HeLa Cervical Cancer Cells

In vitro studies had shown that C-Phycocyanin (C-PC) inhibited cervical cancer HeLa cells growth. We constructed C-PC/CMC-CD55sp nanospheres using C-PC, Carboxymethyl Chitosan (CMC), and CD55 ligand peptide (CD55sp) to allow for targeted antitumor effects against HeLa cells in vitro and in vivo. The characteristics of the nanospheres were determined using FTIR, electron microscopy, and laser particle size analysis. Flow cytometry, laser confocal microscopy and small animal imaging system showed the targeting of C-PC/CMC-CD55sp nanospheres on HeLa cells. Subsequently, the proliferation and apoptosis were analyzed by Cell Counting Kit-8 (CCK-8), flow cytometry, TUNEL assay and electron microscopy. The expression of the apoptosis-related protein was determined using western blot. The stainings of Hematoxylin and Eosin (HE) were employed to evaluate the cell condition of tumor tissue sections. The cytokines in the blood in tumor-bearing nude mice was determined using ELISA. These results showed that C-PC/CMC-CD55sp nanospheres were successfully constructed and targeted HeLa cells. The constructed nanospheres were more effective than C-PC alone in inhibiting the proliferation and inducing apoptosis in HeLa cells. We also found that C-PC/CMC-CD55sp nanospheres had a significant inhibitory effect on the expression of antiapoptotic protein Bcl-2 and a promotion on the transformation of caspase 3 to cleaved caspase 3. C-PC/CMC-CD55sp nanospheres played an important role in tumor suppression, reduced the expression TGF-β, and increased IL-6 and TNF-α. This study demonstrates that the constructed new C-PC/CMC-CD55sp nanospheres exerted targeted antitumor effects in vivo and in vitro which provided a novel idea for application of C-PC, and provided experimental basis for comprehensive targeted treatment of tumors.

Temperature as a modulator of the gut microbiome: what are the implications and opportunities for thermal medicine?

There is substantial research being conducted on the relationships between the gut microbiome, the immune response and health and disease. Environmental temperature and heat stress are known to modify the gut microbiome. Changes in core temperature have been linked, in multiple phyla, to altered microbiome composition and function. This raises the question of whether local/regional or whole body thermal therapies which target tumors in the abdomen, peritoneal cavity, or pelvis influence the gut microbiome. To date, there is little information on whether thermal therapy exerts positive or negative effects on the microbiome. This is an intriguing question since there is growing interest in the immunological impact of various thermal therapies. The goal of this brief review is to highlight research on how environmental conditions, particularly temperature (internal as well as external temperatures) influences the gut microbiome. Given the potential for temperature shifts to modulate gut microbe function and composition, it is likely that various forms of thermal therapy, including hyperthermic intraperitoneal chemotherapy (HIPEC), deep regional, and whole body hyperthermia influence the microbiome in ways that are currently not appreciated. More research is needed to determine whether thermal therapy induced changes in the microbiome occur, and whether they are beneficial or detrimental to the host. Currently, although approaches to microbiome modification such as dietary intervention, fecal transfer, probiotics and prebiotics are being developed, the potential of temperature manipulation has, as yet, not been explored. Therefore, new research could reveal whether perturbations of the microbiome composition that have negative health consequences (dysbiosis) could be an important target for treatment by thermal medicine.

Exercise as an anti-inflammatory therapy for cancer cachexia: a focus on interleukin-6 regulation

Cancer cachexia is a complicated disorder of extreme, progressive skeletal muscle wasting. It is directed by metabolic alterations and systemic inflammation dysregulation. Numerous studies have demonstrated that increased systemic inflammation promotes this type of cachexia and have suggested that cytokines are implicated in the skeletal muscle loss. Exercise is firmly established as an anti-inflammatory therapy that can attenuate or even reverse the process of muscle wasting in cancer cachexia. The interleukin IL-6 is generally considered to be a key player in the development of the microenvironment of malignancy; it promotes tumor growth and metastasis by acting as a bridge between chronic inflammation and cancerous tissue and it also induces skeletal muscle atrophy and protein breakdown. Paradoxically, a beneficial role for IL-6 has also been identified recently, and that is its status as a “founding member” of the myokine class of proteins. Skeletal muscle is an important source of circulating IL-6 in people who participate in exercise training. IL-6 acts as an anti-inflammatory myokine by inhibiting TNFα and improving glucose uptake through the stimulation of AMPK signaling. This review discusses the action of IL-6 in skeletal muscle tissue dysfunction and the role of IL-6 as an “exercise factor” that modulates the immune system. This review also sheds light on the main considerations related to the treatment of muscle wasting in cancer cachexia.

IL-6 Activities in the Tumour Microenvironment. Part 1

The predominant role of IL-6 in cancer is its key promotion of tumour growth. IL-6 binds IL-6 receptor (IL-6R) and the membrane-bound glycoprotein gp130. The complex I-6/IL-6R/gp130 starts the Janus kinases (JAKs) and signal transducer and activator of transcription 3 (STAT3) or JAK/STAT3 pathway. IL-6 R exits in two forms: a membrane-bound IL-6Rα subunit (mIL-6R) that participates in classic signalling pathway and soluble IL-6R subunit (sIL-6R) engaged in trans-signalling. The pro-tumour functions of IL-6 are associated with STAT3, a major oncogenic transcription factor that triggers up-regulation of target genes responsible for tumour cell survival. IL-6 combined with TGF-β induces proliferation of pathogenic Th17 cells. The anti-tumour function of IL-6 is the promotion of anti-tumour immunity. IL-6 trans-signaling contributed to transmigration of lymphocytes in high endothelial venules (HEV). Dendritic cell (DC) secreted IL-6 in the lymph node influences the activation, distribution and polarisation of the immune response. Elevated serum levels of IL-6 and increased expression of IL-6 in tumour tissue are negative prognostic marker for patients' survival.

Reverse Engineering the Febrile System

Fever, the elevation of core body temperature by behavioral or physiological means, is one of the most salient aspects of human sickness, yet there is debate regarding its functional role. In this paper, we demonstrate that the febrile system is an evolved adaptation shaped by natural selection to coordinate the immune system to fight pathogens. First, we show that previous arguments in favor of fever being an adaptation are epistemologically inadequate, and we describe how an adaptationist strategy addresses this issue more effectively. Second, we argue that the mechanisms producing fever provide clear indications of adaptation. Third, we demonstrate that there are many beneficial immune system responses activated during fever and that these responses are not mere byproducts of heat on chemical reactions. Rather, we show that natural selection appears to have modified several immune system effects to be coordinated by fever. Fourth, we argue that there are some adaptations that coordinate the febrile system with other important fitness components, particularly growth and reproduction. Finally, we discuss evidence that the febrile system may also have evolved an antitumor function, providing suggestions for future research into this area. This research informs the debate on the functional value of fever and antipyretic use.

Dissecting Interleukin-6 Classic- and Trans-Signaling in Inflammation and Cancer

Interleukin-6 is a cytokine synthesized by many cells in the human body. IL-6 binds to a membrane bound IL-6R, which is only present on hepatocytes, some epithelial cells and some leukocytes. The complex of IL-6 and IL-6R binds to the ubiquitously expressed receptor subunit gp130, which forms a homodimer and thereby initiates intracellular signaling via the JAK/STAT and the MAPK pathways. IL-6R expressing cells can cleave the receptor protein to generate a soluble IL-6R (sIL-6R), which can still bind IL-6 and can associate with gp130 and induce signaling even on cells, which do not express IL-6R. This paradigm has been called IL-6 trans-signaling whereas signaling via the membrane bound IL-6R is referred to as classic signaling. We have generated several molecular tools to differentiate between IL-6 classic- and trans-signaling and to analyze the consequence of cellular IL-6 signaling in vivo.

Interleukin-6 in Allogeneic Stem Cell Transplantation: Its Possible Importance for Immunoregulation and As a Therapeutic Target

Allogeneic stem cell transplantation is associated with a high risk of treatment-related mortality mainly caused by infections and graft-versus-host disease (GVHD). GVHD is characterized by severe immune dysregulation and impaired regeneration of different tissues, i.e., epithelial barriers and the liver. The balance between pro- and anti-inflammatory cytokine influences the risk of GVHD. Interleukin-6 (IL-6) is a cytokine that previously has been associated with pro-inflammatory effects. However, more recent evidence from various autoimmune diseases (e.g., inflammatory bowel disease, rheumatoid arthritis) has shown that the IL-6 activity is more complex with important effects also on tissue homeostasis, regeneration, and metabolism. This review summarizes the current understanding of how pro-inflammatory IL-6 effects exerted during the peritransplant period shapes T-cell polarization with enhancement of Th17 differentiation and suppression of regulatory T cells, and in addition we also review and discuss the results from trials exploring non-selective IL-6 inhibition in prophylaxis and treatment of GVHD. Emerging evidence suggests that the molecular strategy for targeting of IL-6-initiated intracellular signaling is important for the effect on GVHD. It will therefore be important to further characterize the role of IL-6 in the pathogenesis of GVHD to clarify whether combined IL-6 inhibition of both trans- (i.e., binding of the soluble IL-6/IL-6 receptor complex to cell surface gp130) and cis-signaling (i.e., IL-6 ligation of the IL-6 receptor/gp130 complex) or selective inhibition of trans-signaling should be tried in the prophylaxis and/or treatment of GVHD in allotransplant patients.

Shifts in temperature within the physiologic range modify strand-specific expression of select human microRNAs

Previous studies have revealed that clinically relevant changes in temperature modify clinically relevant gene expression profiles through transcriptional regulation. Temperature dependence of post-transcriptional regulation, specifically, through expression of miRNAs has been less studied. We comprehensively analyzed the effect of 24 h exposure to 32°C or 39.5°C on miRNA expression profile in primary cultured human small airway epithelial cells (hSAECs) and its impact on expression of a targeted protein, protein kinase C α (PKCα). Using microarray, and solution hybridization-based nCounter assays, with confirmation by quantitative RT-PCR, we found significant temperature-dependent changes in expression level of only five mature human miRNAs, representing only 1% of detected miRNAs. Four of these five miRNAs are the less abundant passenger (star) strands. They exhibited a similar pattern of increased expression at 32°C and reduced expression at 39.5°C relative to 37°C. As PKCα mRNA has multiple potential binding sites for three of these miRNAs, we analyzed PKCα protein expression in HEK 293T cells and hSAECs. PKCα protein levels were lowest at 32°C and highest at 39.5°C and specific miRNA inhibitors reduced these effects. Finally, we analyzed cell-cycle progression in hSAECs and found 32°C cells exhibited the greatest G1 to S transition, a process known to be inhibited by PKCα, and the effect was mitigated by specific miRNA inhibitors. These results demonstrate that exposure to clinically relevant hypothermia or hyperthermia modifies expression of a narrow subset of miRNAs and impacts expression of at least one signaling protein involved in multiple important cellular processes.

Fever and the thermal regulation of immunity: the immune system feels the heat

Fever is a cardinal response to infection that has been conserved in warm-blooded and cold-blooded vertebrates for more than 600 million years of evolution. The fever response is executed by integrated physiological and neuronal circuitry and confers a survival benefit during infection. In this Review, we discuss our current understanding of how the inflammatory cues delivered by the thermal element of fever stimulate innate and adaptive immune responses. We further highlight the unexpected multiplicity of roles of the pyrogenic cytokine interleukin-6 (IL-6), both during fever induction and during the mobilization of lymphocytes to the lymphoid organs that are the staging ground for immune defence. We also discuss the emerging evidence suggesting that the adrenergic signalling pathways associated with thermogenesis shape immune cell function.

Fever, immunity, and molecular adaptations

The heat shock response (HSR) is an ancient and highly conserved process that is essential for coping with environmental stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms temporarily subject themselves to thermal stress in the face of infections. We review the phylogenetically conserved mechanisms that regulate fever and discuss the effects that febrile-range temperatures have on multiple biological processes involved in host defense and cell death and survival, including the HSR and its implications for patients with severe sepsis, trauma, and other acute systemic inflammatory states. Heat shock factor-1, a heat-induced transcriptional enhancer is not only the central regulator of the HSR but also regulates expression of pivotal cytokines and early response genes. Febrile-range temperatures exert additional immunomodulatory effects by activating mitogen-activated protein kinase cascades and accelerating apoptosis in some cell types. This results in accelerated pathogen clearance, but increased collateral tissue injury, thus the net effect of exposure to febrile range temperature depends in part on the site and nature of the pathologic process and the specific treatment provided.

The two faces of IL-6 in the tumor microenvironment

Within the tumor microenvironment, IL-6 signaling is generally considered a malevolent player, assuming a dark visage that promotes tumor progression. Chronic IL-6 signaling is linked to tumorigenesis in numerous mouse models as well as in human disease. IL-6 acts intrinsically on tumor cells through numerous downstream mediators to support cancer cell proliferation, survival, and metastatic dissemination. Moreover, IL-6 can act extrinsically on other cells within the complex tumor microenvironment to sustain a pro-tumor milieu by supporting angiogenesis and tumor evasion of immune surveillance. A lesser known role for IL-6 signaling has recently emerged in which it plays a beneficial role, presenting a fairer face that opposes tumor growth by mobilizing anti-tumor T cell immune responses to attain tumor control. Accumulating evidence establishes IL-6 as a key player in the activation, proliferation and survival of lymphocytes during active immune responses. IL-6 signaling can also resculpt the T cell immune response, shifting it from a suppressive to a responsive state that can effectively act against tumors. Finally, IL-6 plays an indispensable role in boosting T cell trafficking to lymph nodes and to tumor sites, where they have the opportunity to become activated and execute their cytotoxic effector functions, respectively. Here, we discuss the dual faces of IL-6 signaling in the tumor microenvironment; the dark face that drives malignancy, and the fairer aspect that promotes anti-tumor adaptive immunity.

Interleukin-6: from basic biology to selective blockade of pro-inflammatory activities

Cytokines receptors exist in membrane bound and soluble form. A soluble form of the human IL-6R is generated by limited proteolysis and alternative splicing. The complex of IL-6 and soluble IL-6R stimulates target cells not stimulated by IL-6 alone, since they do not express the membrane bound IL-6R. We have named this process trans-signaling. Soluble gp130 is the natural inhibitor of IL-6/soluble IL-6R complex responses. Recombinant soluble gp130 protein is a molecular tool to discriminate between gp130 responses via membrane bound and soluble IL-6R responses. Neutralizing monoclonal antibodies for global blockade of IL-6 signaling and the sgp130Fc protein for selective blockade of IL-6 trans-signaling have been used in several animal models of human diseases. Using the sgp130Fc protein or sgp130Fc transgenic mice we demonstrate in models of inflammatory bowel disease, peritonitis, rheumatoid arthritis, atherosclerosis pancreatitis, colon cancer, ovarian cancer and pancreatic cancer, that IL-6 trans-signaling via the soluble IL-6R is the crucial step in the development and the progression of the disease. Therefore, sgp130Fc is a novel therapeutic agent for the treatment of chronic inflammatory diseases and cancer and it undergoes phase I clinical trials as an anti-inflammatory drug since June 2013.

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.

Fish T cells: recent advances through genomics

This brief review is intended to provide a concise overview of the current literature concerning T cells, advances in identifying distinct T cell functional subsets, and in distinguishing effector cells from memory cells. We compare and contrast a wealth of recent progress made in T cell immunology of teleost, elasmobranch, and agnathan fish, to knowledge derived from mammalian T cell studies. From genome studies, fish clearly have most components associated with T cell function and we can speculate on the presence of putative T cell subsets, and the ability to detect their differentiation to form memory cells. Some recombinant proteins for T cell associated cytokines and antibodies for T cell surface receptors have been generated that will facilitate studying the functional roles of teleost T cells during immune responses. Although there is still a long way to go, major advances have occurred in recent years for investigating T cell responses, thus phenotypic and functional characterization is on the near horizon.

Fine-tuning immune surveillance by fever-range thermal stress

An effectively orchestrated immune response to infection and disease depends on efficient trafficking of lymphocytes across vascular beds at distinct tissue sites. Local inflammation and systemic fever increase immune surveillance to immune-relevant sites throughout the body. During the initiation phase of inflammation, this tightly regulated process improves leukocyte trafficking to the secondary lymphoid organs where they undergo activation and expansion in response to cognate antigen. In the resolution phase following the clearance of the invading pathogen, lymphocyte entry is rapidly returned to baseline conditions. Specialized blood vessels termed high endothelial venules (HEVs) have emerged as critical 'hotspots' controlling the rate of lymphocyte entry into lymphoid organs during both phases of inflammation. In this review, we will examine the remarkably tight regulation of lymphocyte trafficking across HEVs conferred by inflammatory cues associated with the thermal element of fever. These studies have revealed a novel role for interleukin-6 (IL-6) trans-signaling in eliciting systemic effects on lymphocyte trafficking patterns to fine-tune immune surveillance.

Regulation of a lymphocyte-endothelial-IL-6 trans-signaling axis by fever-range thermal stress: hot spot of immune surveillance

The pleiotropic cytokine, interleukin-6 (IL-6), has emerged in recent years as a key regulator of the transition from innate to adaptive immunity through its ability to modulate leukocyte recruitment at inflammatory sites. This review highlights a newly identified role for IL-6 trans-signaling, initiated by an agonistic complex of IL-6 and a soluble form of IL-6 receptor alpha, in heightening immune surveillance of peripheral lymphoid organs during febrile inflammatory responses. Inflammatory cues provided by the thermal component of fever trigger IL-6 trans-signaling to act at discrete levels in the multistep adhesion cascade that governs the entry of blood-borne lymphocytes across 'gatekeeper' high endothelial venules (HEVs) in lymph nodes and Peyer patches. IL-6 trans-signaling-dependent mechanisms have been elucidated during thermal stimulation of primary tethering and rolling of lymphocytes along the lumenal surface of HEVs as well as during secondary firm arrest of lymphocytes in HEVs prior to their migration into the underlying parenchyma. These mechanisms profoundly increase the probability that lymphocytes that continuously patrol the body will engage in productive encounters with target antigens sequestered within lymphoid organs. Findings that the lymphocyte-HEV-IL-6 trans-signaling biological axis functions as a thermally-sensitive alert system that promotes immune surveillance provide insight into one of the unresolved mysteries in immunology regarding the benefits of mounting a febrile reaction during inflammation.