Targeting IL-6 trans-signalling by sgp130Fc attenuates severity in SARS-CoV-2 -infected mice and reduces endotheliopathy.

BACKGROUND: SARS-CoV-2 infection is considered as a relapsing inflammatory process with a dysregulation of IL-6 signalling. Classic IL-6 signalling is thought to represent a defence mechanism against pathogens. In contrast, IL-6 trans-signalling has pro-inflammatory effects. In severe COVID-19, therapeutic strategies have focused on global inhibition of IL-6, with controversial results. We hypothesized that specific blockade of IL-6 trans-signalling could inhibit inflammatory response preserving the host defence activity inherent to IL-6 classic signalling. METHODS: To test the role of the specific IL-6 trans-signalling inhibition by sgp130Fc in short- and long-term consequences of COVID-19, we used the established K18-hACE2 transgenic mouse model. Histological as well as immunohistochemical analysis, and pro-inflammatory marker profiling were performed. To investigate IL-6 trans-signalling in human cells we used primary lung microvascular endothelial cells and fibroblasts in the presence/absence of sgp130Fc. FINDINGS: We report that targeting IL-6 trans-signalling by sgp130Fc attenuated SARS-CoV-2-related clinical symptoms and mortality. In surviving mice, the treatment caused a significant decrease in lung damage. In vitro, IL-6 trans-signalling induced strong and persisting JAK1/STAT3 activation in endothelial cells and lung fibroblasts with proinflammatory effects, which were attenuated by sgp130Fc. Our data also suggest that in those cells with scant amounts of IL-6R, the induction of gp130 and IL-6 by IL-6:sIL-6R complex sustains IL-6 trans-signalling. INTERPRETATION: IL-6 trans-signalling fosters progression of COVID-19, and suggests that specific blockade of this signalling mode could offer a promising alternative to mitigate both short- and long-term consequences without affecting the beneficial effects of IL-6 classic signalling. These results have implications for the development of new therapies of lung injury and endotheliopathy in COVID-19. FUNDING: The project was supported by ISCIII, Spain (COV-20/00792 to MB, PI23/01351 to MARH) and the European Commission-Next generation EU (European Union) (Regulation EU 2020/2094), through CSIC's Global Health Platform (PTI Salud Global, SGL2103029 to MB). PID2019-110587RB-I00 (MB) supported by MICIN/AEI/10.13039/501100011033/and PID2022-143034OB-I00 (MB) by MICIN/AEI/10.13039/501100011033/FEDER. MAR-H acknowledges support from ISCIII, Spain and the European Commission-Next generation EU (European Union), through CSIC's Global Health PTI.

Activation of gp130 signaling in T cells drives TH17-mediated multi-organ autoimmunity.

The IL-6-gp130-STAT3 signaling axis is a major regulator of inflammation. Activating mutations in the gene encoding gp130 and germline gain-of-function mutations in STAT3 (STAT3GOF) are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis. To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, the gp130-JAK-STAT3 axis was constitutively activated using a transgene, L-gp130, specifically targeted to T cells. Activating gp130 signaling in T cells in vivo resulted in fatal, early onset, multi-organ autoimmunity in mice that resembled human STAT3GOF disease. Female mice had more rapid disease progression than male mice. On a cellular level, gp130 signaling induced the activation and effector cell differentiation of T cells, promoted the expansion of T helper type 17 (TH17) cells, and impaired the activity of regulatory T cells. Transcriptomic profiling of CD4+ and CD8+ T cells from these mice revealed commonly dysregulated genes and a gene signature that, when applied to human transcriptomic data, improved the segregation of patients with transcriptionally diverse STAT3GOF mutations from healthy controls. The findings demonstrate that increased gp130-STAT3 signaling leads to TH17-driven autoimmunity that phenotypically resembles human STAT3GOF disease.

An epithelial gene signature of trans-IL-6 signaling defines a subgroup of type 2-low asthma.

BACKGROUND: Asthma is stratified into type 2-high and type 2-low inflammatory phenotypes. Limited success has been achieved in developing drugs that target type 2-low inflammation. Previous studies have linked IL-6 signaling to severe asthma. IL-6 cooperates with soluble-IL-6Rα to activate cell signaling in airway epithelium. OBJECTIVE: We sought to study the role of sIL-6Rα amplified IL-6 signaling in airway epithelium and to develop an IL-6+ sIL-6Rα gene signature that may be used to select asthma patients who potentially respond to anti-IL-6 therapy. METHODS: Human airway epithelial cells were stimulated with combinations of IL-6, sIL-6Rα, and inhibitors, sgp130 (Olamkicept), and anti-IL-6R (Tocilizumab), to assess effects on pathway activation, epithelial barrier integrity, and gene expression. A gene signature was generated to identify IL-6 high patients using bronchial biopsies and nasal brushes. RESULTS: Soluble-IL-6Rα amplified the activation of the IL-6 pathway, shown by the increase of STAT3 phosphorylation and stronger gene induction in airway epithelial cells compared to IL-6 alone. Olamkicept and Tocilizumab inhibited the effect of IL-6 + sIL-6Rα on gene expression. We developed an IL-6 + sIL-6Rα gene signature and observed enrichment of this signature in bronchial biopsies but not nasal brushes from asthma patients compared to healthy controls. An IL-6 + sIL-6Rα gene signature score was associated with lower levels of sputum eosinophils in asthma. CONCLUSION: sIL-6Rα amplifies IL-6 signaling in bronchial epithelial cells. Higher local airway IL-6 + sIL-6Rα signaling is observed in asthma patients with low sputum eosinophils.

Therapeutic blockade of ER stress and inflammation prevents NASH and progression to HCC.

The incidence of hepatocellular carcinoma (HCC) is rapidly rising largely because of increased obesity leading to nonalcoholic steatohepatitis (NASH), a known HCC risk factor. There are no approved treatments to treat NASH. Here, we first used single-nucleus RNA sequencing to characterize a mouse model that mimics human NASH-driven HCC, the MUP-uPA mouse fed a high-fat diet. Activation of endoplasmic reticulum (ER) stress and inflammation was observed in a subset of hepatocytes that was enriched in mice that progress to HCC. We next treated MUP-uPA mice with the ER stress inhibitor BGP-15 and soluble gp130Fc, a drug that blocks inflammation by preventing interleukin-6 trans-signaling. Both drugs have progressed to phase 2/3 human clinical trials for other indications. We show that this combined therapy reversed NASH and reduced NASH-driven HCC. Our data suggest that these drugs could provide a potential therapy for NASH progression to HCC.

STAT3/LKB1 controls metastatic prostate cancer by regulating mTORC1/CREB pathway.

Prostate cancer (PCa) is a common and fatal type of cancer in men. Metastatic PCa (mPCa) is a major factor contributing to its lethality, although the mechanisms remain poorly understood. PTEN is one of the most frequently deleted genes in mPCa. Here we show a frequent genomic co-deletion of PTEN and STAT3 in liquid biopsies of patients with mPCa. Loss of Stat3 in a Pten-null mouse prostate model leads to a reduction of LKB1/pAMPK with simultaneous activation of mTOR/CREB, resulting in metastatic disease. However, constitutive activation of Stat3 led to high LKB1/pAMPK levels and suppressed mTORC1/CREB pathway, preventing mPCa development. Metformin, one of the most widely prescribed therapeutics against type 2 diabetes, inhibits mTORC1 in liver and requires LKB1 to mediate glucose homeostasis. We find that metformin treatment of STAT3/AR-expressing PCa xenografts resulted in significantly reduced tumor growth accompanied by diminished mTORC1/CREB, AR and PSA levels. PCa xenografts with deletion of STAT3/AR nearly completely abrogated mTORC1/CREB inhibition mediated by metformin. Moreover, metformin treatment of PCa patients with high Gleason grade and type 2 diabetes resulted in undetectable mTORC1 levels and upregulated STAT3 expression. Furthermore, PCa patients with high CREB expression have worse clinical outcomes and a significantly increased risk of PCa relapse and metastatic recurrence. In summary, we have shown that STAT3 controls mPCa via LKB1/pAMPK/mTORC1/CREB signaling, which we have identified as a promising novel downstream target for the treatment of lethal mPCa.

EGFR stimulation enables IL-6 trans-signalling via iRhom2-dependent ADAM17 activation in mammary epithelial cells.

The cytokine interleukin-6 (IL-6) has considerable pro-inflammatory properties and is a driver of many physiological and pathophysiological processes. Cellular responses to IL-6 are mediated by membrane-bound or soluble forms of the IL-6 receptor (IL-6R) complexed with the signal-transducing subunit gp130. While expression of the membrane-bound IL-6R is restricted to selected cell types, soluble IL-6R (sIL-6R) enables gp130 engagement on all cells, a process termed IL-6 trans-signalling and considered to be pro-inflammatory. sIL-6R is predominantly generated through proteolytic processing by the metalloproteinase ADAM17. ADAM17 also liberates ligands of the epidermal growth factor receptor (EGFR), which is a prerequisite for EGFR activation and results in stimulation of proliferative signals. Hyperactivation of EGFR mostly due to activating mutations drives cancer development. Here, we reveal an important link between overshooting EGFR signalling and the IL-6 trans-signalling pathway. In epithelial cells, EGFR activity induces not only IL-6 expression but also the proteolytic release of sIL-6R from the cell membrane by increasing ADAM17 surface activity. We find that this derives from the transcriptional upregulation of iRhom2, a crucial regulator of ADAM17 trafficking and activation, upon EGFR engagement, which results in increased surface localization of ADAM17. Also, phosphorylation of the EGFR-downstream mediator ERK mediates ADAM17 activity via interaction with iRhom2. In sum, our study reveals an unforeseen interplay between EGFR activation and IL-6 trans-signalling, which has been shown to be fundamental in inflammation and cancer.

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.

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.

The RNA editor ADAR2 promotes immune cell trafficking by enhancing endothelial responses to interleukin-6 during sterile inflammation.

Immune cell trafficking constitutes a fundamental component of immunological response to tissue injury, but the contribution of intrinsic RNA nucleotide modifications to this response remains elusive. We report that RNA editor ADAR2 exerts a tissue- and stress-specific regulation of endothelial responses to interleukin-6 (IL-6), which tightly controls leukocyte trafficking in IL-6-inflamed and ischemic tissues. Genetic ablation of ADAR2 from vascular endothelial cells diminished myeloid cell rolling and adhesion on vascular walls and reduced immune cell infiltration within ischemic tissues. ADAR2 was required in the endothelium for the expression of the IL-6 receptor subunit, IL-6 signal transducer (IL6ST; gp130), and subsequently, for IL-6 trans-signaling responses. ADAR2-induced adenosine-to-inosine RNA editing suppressed the Drosha-dependent primary microRNA processing, thereby overwriting the default endothelial transcriptional program to safeguard gp130 expression. This work demonstrates a role for ADAR2 epitranscriptional activity as a checkpoint in IL-6 trans-signaling and immune cell trafficking to sites of tissue injury.

Constitutive Activation of gp130 in T Cells Results in Senescence and Premature Aging.

IL-6 family members contribute to host defense through the stimulation of acute-phase signaling, hematopoiesis, immune reactions, and regenerative processes. To investigate essential mechanisms that are linked toward a constitutively activated gp130 signaling, we generated and characterized a mouse model that reflects a constitutive and cytokine-independent activation of JAK/STAT3 signaling by Lgp130 in CD4- and CD8-positive T cells. Lgp130 is an engineered form of gp130 in which dimerization and activation are forced by a leucine zipper. T cell-specific Lgp130 activation resulted in massive phenotypical abnormalities, including splenomegaly, lymphadenopathy, and an upregulation of innate immune system components shown by hyperinflammatory signatures in several organs. Moreover, T cell-restricted expression of Lgp130 resulted in increased numbers of cytotoxic and regulatory T cells, especially in lymph nodes. Consistent with this, we found an elevated platelet production and increase in megakaryocytes in the spleen and bone marrow that are causative for an acute thrombocytosis accompanied by anemia. Due to a shortened life span of T cell-specific Lgp130 mice, we could also show that next to an overall increase in regulatory cell-cycle genes, an activation of p53 and increased expression of p21 provide evidence for a senescence-like phenotype. Together, these data suggest that T cell-restricted gp130 activation is not only involved in autoimmune processes but also in senescence-associated aging. Therefore, Lgp130 expression in T cells might be a suitable model to study inflammation and disease.

Cell-Autonomous Constitutive gp130 Signaling in T Cells Amplifies TH17 Cell Responses and Causes Severe Lung Inflammation.

IL-6 plays a fundamental role in T cell differentiation and is strictly controlled by surface expression and shedding of IL-6R. IL-6 also acts on other cells that might affect T cell maturation. To study the impact of cell-autonomous and uncontrolled IL-6 signaling in T cells, we generated mice with a constitutively active IL-6R gp130 chain (Lgp130) expressed either in all T cells (Lgp130 × CD4Cre mice) or inducible in CD4+ T cells (Lgp130 × CD4CreERT2 mice). Lgp130 × CD4Cre mice accumulated activated T cells, including TH17 cells, in the lung, resulting in severe inflammation. Tamoxifen treatment of Lgp130 × CD4CreERT2 mice caused Lgp130 expression in 40-50% of CD4+ T cells, but mice developed lung disease only after several months. Lgp130+ CD4+ T cells were also enriched for TH17 cells; however, there was concomitant expansion of Lgp130- regulatory T cells, which likely restricted pathologic Lgp130+ T cells. In vitro, constitutive gp130 signaling in T cells enhanced but was not sufficient for TH17 cell differentiation. Augmented TH17 cell development of Lgp130+ T cells was also observed in Lgp130 × CD4CreERT2 mice infected with Staphylococcus aureus, but gp130 activation did not interfere with formation of TH1 cells against Listeria monocytogenes. Lgp130+ CD4+ T cells acquired a memory T cell phenotype and persisted in high numbers as a polyclonal T cell population in lymphoid and peripheral tissues, but we did not observe T cell lymphoma formation. In conclusion, cell-autonomous gp130 signaling alters T cell differentiation. Although gp130 signaling is not sufficient for TH17 cell differentiation, it still promotes accumulation of activated T cells in the lung that cause tissue inflammation.

Crosstalk between microbiome, regulatory T cells and HCA2 orchestrates the inflammatory response in a murine psoriasis model.

The organ-specific microbiome plays a crucial role in tissue homeostasis, among other things by inducing regulatory T cells (Treg). This applies also to the skin and in this setting short chain fatty acids (SCFA) are relevant. It was demonstrated that topical application of SCFA controls the inflammatory response in the psoriasis-like imiquimod (IMQ)-induced murine skin inflammation model. Since SCFA signal via HCA2, a G-protein coupled receptor, and HCA2 expression is reduced in human lesional psoriatic skin, we studied the effect of HCA2 in this model. HCA2 knock-out (HCA2-KO) mice reacted to IMQ with stronger inflammation, presumably due to an impaired function of Treg. Surprisingly, injection of Treg from HCA2-KO mice even enhanced the IMQ reaction, suggesting that in the absence of HCA2 Treg switch from a suppressive into a proinflammatory type. HCA2-KO mice differed in the composition of the skin microbiome from wild type mice. Co-housing reversed the exaggerated response to IMQ and prevented the alteration of Treg, implying that the microbiome dictates the outcome of the inflammatory reaction. The switch of Treg into a proinflammatory type in HCA2-KO mice could be a downstream phenomenon. This opens the opportunity to reduce the inflammatory tendency in psoriasis by altering the skin microbiome.

The Alzheimer's disease-linked protease BACE1 modulates neuronal IL-6 signaling through shedding of the receptor gp130.

BACKGROUND: The protease BACE1 is a major drug target for Alzheimer's disease, but chronic BACE1 inhibition is associated with non-progressive cognitive worsening that may be caused by modulation of unknown physiological BACE1 substrates. METHODS: To identify in vivo-relevant BACE1 substrates, we applied pharmacoproteomics to non-human-primate cerebrospinal fluid (CSF) after acute treatment with BACE inhibitors. RESULTS: Besides SEZ6, the strongest, dose-dependent reduction was observed for the pro-inflammatory cytokine receptor gp130/IL6ST, which we establish as an in vivo BACE1 substrate. Gp130 was also reduced in human CSF from a clinical trial with a BACE inhibitor and in plasma of BACE1-deficient mice. Mechanistically, we demonstrate that BACE1 directly cleaves gp130, thereby attenuating membrane-bound gp130 and increasing soluble gp130 abundance and controlling gp130 function in neuronal IL-6 signaling and neuronal survival upon growth-factor withdrawal. CONCLUSION: BACE1 is a new modulator of gp130 function. The BACE1-cleaved, soluble gp130 may serve as a pharmacodynamic BACE1 activity marker to reduce the occurrence of side effects of chronic BACE1 inhibition in humans.

Blockade of the protease ADAM17 ameliorates experimental pancreatitis.

Acute and chronic pancreatitis, the latter associated with fibrosis, are multifactorial inflammatory disorders and leading causes of gastrointestinal disease-related hospitalization. Despite the global health burden of pancreatitis, currently, there are no effective therapeutic agents. In this regard, the protease A Disintegrin And Metalloproteinase 17 (ADAM17) mediates inflammatory responses through shedding of bioactive inflammatory cytokines and mediators, including tumor necrosis factor α (TNFα) and the soluble interleukin (IL)-6 receptor (sIL-6R), the latter of which drives proinflammatory IL-6 trans-signaling. However, the role of ADAM17 in pancreatitis is unclear. To address this, Adam17ex/ex mice-which are homozygous for the hypomorphic Adam17ex allele resulting in marked reduction in ADAM17 expression-and their wild-type (WT) littermates were exposed to the cerulein-induced acute pancreatitis model, and acute (1-wk) and chronic (20-wk) pancreatitis models induced by the cigarette smoke carcinogen nicotine-derived nitrosamine ketone (NNK). Our data reveal that ADAM17 expression was up-regulated in pancreatic tissues of animal models of pancreatitis. Moreover, the genetic (Adam17ex/ex mice) and therapeutic (ADAM17 prodomain inhibitor [A17pro]) targeting of ADAM17 ameliorated experimental pancreatitis, which was associated with a reduction in the IL-6 trans-signaling/STAT3 axis. This led to reduced inflammatory cell infiltration, including T cells and neutrophils, as well as necrosis and fibrosis in the pancreas. Furthermore, up-regulation of the ADAM17/IL-6 trans-signaling/STAT3 axis was a feature of pancreatitis patients. Collectively, our findings indicate that the ADAM17 protease plays a pivotal role in the pathogenesis of pancreatitis, which could pave the way for devising novel therapeutic options to be deployed against this disease.

Tetraspanin 8 Subfamily Members Regulate Substrate-Specificity of a Disintegrin and Metalloprotease 17.

Ectodomain shedding is an irreversible process to regulate inter- and intracellular signaling. Members of the a disintegrin and metalloprotease (ADAM) family are major mediators of ectodomain shedding. ADAM17 is involved in the processing of multiple substrates including tumor necrosis factor (TNF) α and EGF receptor ligands. Substrates of ADAM17 are selectively processed depending on stimulus and cellular context. However, it still remains largely elusive how substrate selectivity of ADAM17 is regulated. Tetraspanins (Tspan) are multi-membrane-passing proteins that are involved in the organization of plasma membrane micro-domains and diverse biological processes. Closely related members of the Tspan8 subfamily, including CD9, CD81 and Tspan8, are associated with cancer and metastasis. Here, we show that Tspan8 subfamily members use different strategies to regulate ADAM17 substrate selectivity. We demonstrate that in particular Tspan8 associates with both ADAM17 and TNF α and promotes ADAM17-mediated TNF α release through recruitment of ADAM17 into Tspan-enriched micro-domains. Yet, processing of other ADAM17 substrates is not altered by Tspan8. We, therefore, propose that Tspan8 contributes to tumorigenesis through enhanced ADAM17-mediated TNF α release and a resulting increase in tissue inflammation.

Combined hepatocellular-cholangiocarcinoma derives from liver progenitor cells and depends on senescence and IL-6 trans-signaling.

BACKGROUND & AIMS: Primary liver cancers include hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (CCA) and combined HCC-CCA tumors (cHCC-CCA). It has been suggested, but not unequivocally proven, that hepatic progenitor cells (HPCs) can contribute to hepatocarcinogenesis. We aimed to determine whether HPCs contribute to HCC, cHCC-CCA or both types of tumors. METHODS: To trace progenitor cells during hepatocarcinogenesis, we generated Mdr2-KO mice that harbor a yellow fluorescent protein (YFP) reporter gene driven by the Foxl1 promoter which is expressed specifically in progenitor cells. These mice (Mdr2-KOFoxl1-CRE;RosaYFP) develop chronic inflammation and HCCs by the age of 14-16 months, followed by cHCC-CCA tumors at the age of 18 months. RESULTS: In this Mdr2-KOFoxl1-CRE;RosaYFP mouse model, liver progenitor cells are the source of cHCC-CCA tumors, but not the source of HCC. Ablating the progenitors, caused reduction of cHCC-CCA tumors but did not affect HCCs. RNA-sequencing revealed enrichment of the IL-6 signaling pathway in cHCC-CCA tumors compared to HCC tumors. Single-cell RNA-sequencing (scRNA-seq) analysis revealed that IL-6 is expressed by immune and parenchymal cells during senescence, and that IL-6 is part of the senescence-associated secretory phenotype. Administration of an anti-IL-6 antibody to Mdr2-KOFoxl1-CRE;RosaYFP mice inhibited the development of cHCC-CCA tumors. Blocking IL-6 trans-signaling led to a decrease in the number and size of cHCC-CCA tumors, indicating their dependence on this pathway. Furthermore, the administration of a senolytic agent inhibited IL-6 and the development of cHCC-CCA tumors. CONCLUSION: Our results demonstrate that cHCC-CCA, but not HCC tumors, originate from HPCs, and that IL-6, which derives in part from cells in senescence, plays an important role in this process via IL-6 trans-signaling. These findings could be applied to develop new therapeutic approaches for cHCC-CCA tumors. LAY SUMMARY: Combined hepatocellular carcinoma-cholangiocarcinoma is the third most prevalent type of primary liver cancer (i.e. a cancer that originates in the liver). Herein, we show that this type of cancer originates in stem cells in the liver and that it depends on inflammatory signaling. Specifically, we identify a cytokine called IL-6 that appears to be important in the development of these tumors. Our results could be used for the development of novel treatments for these aggressive tumors.

Cross-talk between IL-6 trans-signaling and AIM2 inflammasome/IL-1ß axes bridge innate immunity and epithelial apoptosis to promote emphysema.

Pulmonary emphysema is associated with dysregulated innate immune responses that promote chronic pulmonary inflammation and alveolar apoptosis, culminating in lung destruction. However, the molecular regulators of innate immunity that promote emphysema are ill-defined. Here, we investigated whether innate immune inflammasome complexes, comprising the adaptor ASC, Caspase-1 and specific pattern recognition receptors (PRRs), promote the pathogenesis of emphysema. In the lungs of emphysematous patients, as well as spontaneous gp130F/F and cigarette smoke (CS)-induced mouse models of emphysema, the expression (messenger RNA and protein) and activation of ASC, Caspase-1, and the inflammasome-associated PRR and DNA sensor AIM2 were up-regulated. AIM2 up-regulation in emphysema coincided with the biased production of the mature downstream inflammasome effector cytokine IL-1ß but not IL-18. These observations were supported by the genetic blockade of ASC, AIM2, and the IL-1 receptor and therapy with AIM2 antagonistic suppressor oligonucleotides, which ameliorated emphysema in gp130F/F mice by preventing elevated alveolar cell apoptosis. The functional requirement for AIM2 in driving apoptosis in the lung epithelium was independent of its expression in hematopoietic-derived immune cells and the recruitment of infiltrating immune cells in the lung. Genetic and inhibitor-based blockade of AIM2 also protected CS-exposed mice from pulmonary alveolar cell apoptosis. Intriguingly, IL-6 trans-signaling via the soluble IL-6 receptor, facilitated by elevated levels of IL-6, acted upstream of the AIM2 inflammasome to augment AIM2 expression in emphysema. Collectively, we reveal cross-talk between the AIM2 inflammasome/IL-1ß and IL-6 trans-signaling axes for potential exploitation as a therapeutic strategy for emphysema.

Single-cell transcriptomics reveals a senescence-associated IL-6/CCR6 axis driving radiodermatitis.

Irradiation-induced alopecia and dermatitis (IRIAD) are two of the most visually recognized complications of radiotherapy, of which the molecular and cellular basis remains largely unclear. By combining scRNA-seq analysis of whole skin-derived irradiated cells with genetic ablation and molecular inhibition studies, we show that senescence-associated IL-6 and IL-1 signaling, together with IL-17 upregulation and CCR6+ -mediated immune cell migration, are crucial drivers of IRIAD. Bioinformatics analysis colocalized irradiation-induced IL-6 signaling with senescence pathway upregulation largely within epidermal hair follicles, basal keratinocytes, and dermal fibroblasts. Loss of cytokine signaling by genetic ablation in IL-6-/- or IL-1R-/- mice, or by molecular blockade, strongly ameliorated IRIAD, as did deficiency of CCL20/CCR6-mediated immune cell migration in CCR6-/- mice. Moreover, IL-6 deficiency strongly reduced IL-17, IL-22, CCL20, and CCR6 upregulation, whereas CCR6 deficiency reciprocally diminished IL-6, IL-17, CCL3, and MHC upregulation, suggesting that proximity-dependent cellular cross talk promotes IRIAD. Therapeutically, topical application of Janus kinase blockers or inhibition of T-cell activation by cyclosporine effectively reduced IRIAD, suggesting the potential of targeted approaches for the treatment of dermal side effects in radiotherapy patients.

Case Report: Arterial Wall Inflammation in Atherosclerotic Cardiovascular Disease is Reduced by Olamkicept (sgp130Fc).

Inflammation is a strong driver of atherosclerotic cardiovascular disease (ASCVD). There is a large unmet need for therapies that prevent or reduce excessive inflammation while avoiding systemic immunosuppression. We showed previously that selective inhibition of pro-inflammatory interleukin-6 (IL-6) trans-signalling by the fusion protein olamkicept (sgp130Fc) prevented and reduced experimental murine atherosclerosis in low-density lipoprotein receptor-deficient (Ldlr -/-) mice on a high-fat, high-cholesterol diet independently of low-density lipoprotein (LDL) cholesterol metabolism. Therefore, we allowed compassionate use of olamkicept (600 mg intravenously biweekly for 10 weeks) in a patient with very-high-risk ASCVD. Despite optimal LDL cholesterol under maximum tolerated lipid-lowering treatment, the patient had a remaining very high risk for future cardiovascular events related to significant arterial wall inflammation with lipoprotein (a) [Lp(a)]-cholesterol as the main contributor. 18Fluorodeoxyglucose positron emission tomography/computed tomography (18FDG PET/CT) measurements were performed before and after the treatment period. Olamkicept reduced arterial wall inflammation in this patient without interfering with lipoprotein metabolism. No clinical or laboratory side effects were observed during or after treatment with olamkicept. Our findings in this patient matched the results from our mechanistic study in Ldlr -/- mice, which were extended by additional analyses on vascular inflammation. Olamkicept may be a promising option for treating ASCVD independently of LDL cholesterol metabolism. A Phase II trial of olamkicept in ASCVD is currently being prepared.

IL-6 Responsiveness of CD4+ and CD8+ T Cells after Allogeneic Stem Cell Transplantation Differs between Patients and Is Associated with Previous Acute Graft versus Host Disease and Pretransplant Antithymocyte Globulin Therapy.

Graft-versus-host disease (GVHD), one of the most common and serious complications after allogeneic stem cell transplantation, is mediated by allocative T cells. IL-6 mediates both pro- and anti-inflammatory effects and modulates T cell response through classical signaling and trans-signaling. We investigated the effects on the mTOR and JAK/STAT pathways after various types of IL-6 signaling for circulating T cells were derived from 31 allotransplant recipients 90 days post-transplant. Cells were stimulated with IL-6 alone, hyper-IL-6 (trans-signaling), IL-6+IL-6 receptor (IL-6R; classical + trans-signaling) and IL-6+IL-6R+soluble gp130-Fc (classical signaling), and flow cytometry was used to investigate the effects on phosphorylation of AKT (Thr308), mTOR (Ser2442), STAT3 (Ser727) and STAT3 (Tyr705). CD3+CD4+ and CD3+C8+ T cells responded to classical and trans IL-6 stimulation with increased STAT3 (Tyr705) phosphorylation; these responses were generally stronger for CD3+CD4+ cells. STAT3 (Tyr705) responses were stronger for patients with previous acute GVHD; CD3+CD4+ cells from GVHD patients showed an additional STAT3 (Ser727) response, whereas patients without acute GVHD showed additional mTOR (Ser2448) responses. Furthermore, treatment with antithymocyte globulin as a part of GVHD prophylaxis was associated with generally weaker STAT3 (Tyr705) responses and altered STAT3 (Ser727) responsiveness of CD3+CD4+ cells together with increased mTOR (Ser2448) responses for the CD3+CD8+ cells. Thus, early post-transplant CD3+CD4+ and CD3+ CD8+ T cell subsets differ in their IL-6 responsiveness; this responsiveness is modulated by antithymocyte globulin and differs between patients with and without previous acute GVHD. These observations suggest that allotransplant recipients will be heterogeneous with regard to the effects of post-transplant IL-6 targeting.