Molecular Dissection of Pro-Fibrotic IL11 Signaling in Cardiac and Pulmonary Fibroblasts

Chronic Kidney Disease Diets for Kidney Failure Prevention: Insights from the IL-11 Paradigm

Nearly every fifth adult in the United States and many older adults worldwide are affected by chronic kidney disease (CKD), which can progress to kidney failure requiring invasive kidney replacement therapy. In this review, we briefly examine the pathophysiology of CKD and discuss emerging mechanisms involving the physiological resolution of kidney injury by transforming growth factor beta 1 (TGFβ1) and interleukin-11 (IL-11), as well as the pathological consequences of IL-11 overproduction, which misguides repair processes, ultimately culminating in CKD. Taking these mechanisms into account, we offer an overview of the efficacy of plant-dominant dietary patterns in preventing and managing CKD, while also addressing their limitations in terms of restoring kidney function or preventing kidney failure. In conclusion, this paper outlines novel regeneration strategies aimed at developing a reno-regenerative diet to inhibit IL-11 and promote repair mechanisms in kidneys affected by CKD.

IL11-mediated stromal cell activation may not be the master regulator of pro-fibrotic signaling downstream of TGFβ

Fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF) and systemic scleroderma (SSc), are commonly associated with high morbidity and mortality, thereby representing a significant unmet medical need. Interleukin 11 (IL11)-mediated cell activation has been identified as a central mechanism for promoting fibrosis downstream of TGFβ. IL11 signaling has recently been reported to promote fibroblast-to-myofibroblast transition, thus leading to various pro-fibrotic phenotypic changes. We confirmed increased mRNA expression of IL11 and IL11Rα in fibrotic diseases by OMICs approaches and in situ hybridization. However, the vital role of IL11 as a driver for fibrosis was not recapitulated. While induction of IL11 secretion was observed downstream of TGFβ signaling in human lung fibroblasts and epithelial cells, the cellular responses induced by IL11 was quantitatively and qualitatively inferior to that of TGFβ at the transcriptional and translational levels. IL11 blocking antibodies inhibited IL11Rα-proximal STAT3 activation but failed to block TGFβ-induced profibrotic signals. In summary, our results challenge the concept of IL11 blockade as a strategy for providing transformative treatment for fibrosis.

Roles of IL-11 in the regulation of bone metabolism

Bone metabolism is the basis for maintaining the normal physiological state of bone, and imbalance of bone metabolism can lead to a series of metabolic bone diseases. As a member of the IL-6 family, IL-11 acts primarily through the classical signaling pathway IL-11/Receptors, IL-11 (IL-11R)/Glycoprotein 130 (gp130). The regulatory role of IL-11 in bone metabolism has been found earlier, but mainly focuses on the effects on osteogenesis and osteoclasis. In recent years, more studies have focused on IL-11's roles and related mechanisms in different bone metabolism activities. IL-11 regulates osteoblasts, osteoclasts, BM stromal cells, adipose tissue-derived mesenchymal stem cells, and chondrocytes. It's involved in bone homeostasis, including osteogenesis, osteolysis, bone marrow (BM) hematopoiesis, BM adipogenesis, and bone metastasis. This review exams IL-11's role in pathology and bone tissue, the cytokines and pathways that regulate IL-11 expression, and the feedback regulations of these pathways.

Understanding interleukin 11 as a disease gene and therapeutic target

Interleukin 11 (IL11) is an elusive member of the IL6 family of cytokines. While initially thought to be a haematopoietic and cytoprotective factor, more recent data show instead that IL11 is redundant for haematopoiesis and toxic. In this review, the reasons that led to the original misunderstandings of IL11 biology, which are now understandable, are explained with particular attention on the use of recombinant human IL11 in mice and humans. Following tissue injury, as part of an evolutionary ancient homeostatic response, IL11 is secreted from damaged mammalian cells to signal via JAK/STAT3, ERK/P90RSK, LKB1/mTOR and GSK3β/SNAI1 in autocrine and paracrine. This activates a program of mesenchymal transition of epithelial, stromal, and endothelial cells to cause inflammation, fibrosis, and stalled endogenous tissue repair, leading to organ failure. The role of IL11 signalling in cell- and organ-specific pathobiology is described, the large unknowns about IL11 biology are discussed and the promise of targeting IL11 signalling as a therapeutic approach is reviewed.

Interleukin-11 and its eminent role in tissue fibrosis: a possible therapeutic target

Interleukin-11 is a cytokine from the IL-6 family of cytokines that includes IL-6 and oncostatin-M. Initially described for its role in platelet generation, it is now appreciated that this cytokine has multiple functions. Recently it has been found that IL-11 is critical in fibrosis in multiple different organ systems and systemically as in the autoimmune disease systemic sclerosis. Animal models of fibrosis have determined that animals with IL-11 receptor deletions have retarded fibrosis and that in wild-type animals IL-11 is found at the organ of fibrosis. Recent evidence suggests that IL-11 may be a master regulator of fibrosis regardless of end target organ. With the development of neutralizing antibodies targeting the cytokine in pre-clinical models this could be a possible therapeutic, in a disease in which no specific therapies exist. This review appraises the evidence of the role of IL-11 in tissue fibrosis, its signalling properties, and therapeutic targeting. The review ends with an appraisal of indications for which IL-11 modulation is targeted.

The Emerging Role of Interleukin-(IL)-11/IL-11R in Bone Metabolism and Homeostasis: From Cytokine to Osteokine

Interleukin-(IL)-11 is a cytokine involved in hematopoiesis, cancer metastasis, and inflammation. IL-11 belongs to the IL-6 cytokine family, binding to the complex of receptors glycoprotein gp130 and the ligand-specific-receptor subunits (IL-11Rα or their soluble counterpart sIL-11R). IL-11/IL-11R signaling enhances osteoblast differentiation and bone formation and mitigates osteoclast-induced bone resorption and cancer bone metastasis. Recent studies have shown that systemic and osteoblast/osteocyte-specific IL-11 deficiency leads to reduced bone mass and formation, but also adiposity, glucose intolerance, and insulin resistance. In humans, mutations of IL-11 and the receptor IL-11RA genes are associated with height reduction, osteoarthritis, and craniosynostosis. In this review, we describe the emerging role of IL-11/IL-11R signaling in bone metabolism by targeting osteoblasts, osteoclasts, osteocytes, and bone mineralization. Furthermore, IL-11 promotes osteogenesis and suppresses adipogenesis, thereby influencing the fate of osteoblast/adipocyte differentiation derived from pluripotent mesenchymal stem cells. We have newly identified IL-11 as a bone-derived cytokine that regulates bone metabolism and the link between bone and other organs. Thus, IL-11 is vital in bone homeostasis and could be considered a potential therapeutic strategy.

Structures of the interleukin 11 signalling complex reveal gp130 dynamics and the inhibitory mechanism of a cytokine variant

Interleukin (IL-)11, an IL-6 family cytokine, has pivotal roles in autoimmune diseases, fibrotic complications, and solid cancers. Despite intense therapeutic targeting efforts, structural understanding of IL-11 signalling and mechanistic insights into current inhibitors are lacking. Here we present cryo-EM and crystal structures of the human IL-11 signalling complex, including the complex containing the complete extracellular domains of the shared IL-6 family β-receptor, gp130. We show that complex formation requires conformational reorganisation of IL-11 and that the membrane-proximal domains of gp130 are dynamic. We demonstrate that the cytokine mutant, IL-11 Mutein, competitively inhibits signalling in human cell lines. Structural shifts in IL-11 Mutein underlie inhibition by altering cytokine binding interactions at all three receptor-engaging sites and abrogating the final gp130 binding step. Our results reveal the structural basis of IL-11 signalling, define the molecular mechanisms of an inhibitor, and advance understanding of gp130-containing receptor complexes, with potential applications in therapeutic development.

Pirfenidone affects human cardiac fibroblast proliferation and cell cycle activity in 2D cultures and engineered connective tissues

The anti-fibrotic drug pirfenidone (PFD) is currently in clinical testing for the treatment of heart failure with preserved ejection fraction; however, its effects on human cardiac cells have not been fully investigated. Therefore, we aimed to characterize the impact of PFD on human cardiac fibroblasts (CF) in 2D culture as well as in 3D-engineered connective tissues (ECT). We analyzed proliferation by automated cell counting and changes in signaling by immunoblotting. We generated ECT with different geometries to modify the cellular phenotype and investigated the effects of PFD on cell number and viability as well as on cell cycle activity. We further studied its effect on ECT compaction, contraction, stiffening, and strain resistance by ECT imaging, pole deflection analysis, and ultimate tensile testing. Our data demonstrate that PFD inhibits human CF proliferation in a concentration-dependent manner with an IC50 of 0.43 mg/ml and its anti-mitogenic effect was further corroborated by an inhibition of MEK1/2, ERK1/2, and riboprotein S6 (rpS6) phosphorylation. In ECT, a lower cell cycle activity was found in PFD-treated ECT and fewer cells resided in these ECT after 5 days of culture compared to the control. Moreover, ECT compaction as well as ECT contraction was impaired. Consequently, biomechanical analyses demonstrated that PFD reduced the stiffness of ECT. Taken together, our data demonstrate that the anti-fibrotic action of PFD on human CF is based on its anti-mitogenic effect in 2D cultures and ECT.

SARS-CoV-2 accessory proteins involvement in inflammatory and profibrotic processes through IL11 signaling

SARS-CoV-2, the cause of the COVID-19 pandemic, possesses eleven accessory proteins encoded in its genome. Their roles during infection are still not completely understood. In this study, transcriptomics analysis revealed that both WNT5A and IL11 were significantly up-regulated in A549 cells expressing individual accessory proteins ORF6, ORF8, ORF9b or ORF9c from SARS-CoV-2 (Wuhan-Hu-1 isolate). IL11 is a member of the IL6 family of cytokines. IL11 signaling-related genes were also differentially expressed. Bioinformatics analysis disclosed that both WNT5A and IL11 were involved in pulmonary fibrosis idiopathic disease and functional assays confirmed their association with profibrotic cell responses. Subsequently, data comparison with lung cell lines infected with SARS-CoV-2 or lung biopsies from patients with COVID-19, evidenced altered profibrotic gene expression that matched those obtained in this study. Our results show ORF6, ORF8, ORF9b and ORF9c involvement in inflammatory and profibrotic responses. Thus, these accessory proteins could be targeted by new therapies against COVID-19 disease.

Roles and mechanism of IL-11 in vascular diseases

Vascular diseases are the leading cause of morbidity and mortality worldwide. Therefore, effective treatment strategies that can reduce the risk of vascular diseases are urgently needed. The relationship between Interleukin-11 (IL-11) and development of vascular diseases has gained increasing attention. IL-11, a target for therapeutic research, was initially thought to participate in stimulating platelet production. Additional research concluded that IL-11 is effective in treating several vascular diseases. However, the function and mechanism of IL-11 in these diseases remain unknown. This review summarizes IL-11 expression, function, and signal transduction mechanism. This study also focuses on the role of IL-11 in coronary artery disease, hypertension, pulmonary hypertension, cerebrovascular disease, aortic disease, and other vascular diseases and its potential as a therapeutic target. Consequently, this study provides new insight into the clinical diagnosis and treatment of vascular diseases.

The role of infected epithelial cells in Chlamydia-associated fibrosis

Ocular, genital, and anogenital infection by the obligate intracellular pathogen Chlamydia trachomatis have been consistently associated with scar-forming sequelae. In cases of chronic or repeated infection of the female genital tract, infection-associated fibrosis of the fallopian tubes can result in ectopic pregnancy or infertility. In light of this urgent concern to public health, the underlying mechanism of C. trachomatis-associated scarring is a topic of ongoing study. Fibrosis is understood to be an outcome of persistent injury and/or dysregulated wound healing, in which an aberrantly activated myofibroblast population mediates hypertrophic remodeling of the basement membrane via deposition of collagens and other components of the extracellular matrix, as well as induction of epithelial cell proliferation via growth factor signaling. Initial study of infection-associated immune cell recruitment and pro-inflammatory signaling have suggested the cellular paradigm of chlamydial pathogenesis, wherein inflammation-associated tissue damage and fibrosis are the indirect result of an immune response to the pathogen initiated by host epithelial cells. However, recent work has revealed more direct routes by which C. trachomatis may induce scarring, such as infection-associated induction of growth factor signaling and pro-fibrotic remodeling of the extracellular matrix. Additionally, C. trachomatis infection has been shown to induce an epithelial-to-mesenchymal transition in host epithelial cells, prompting transdifferentiation into a myofibroblast-like phenotype. In this review, we summarize the field's current understanding of Chlamydia-associated fibrosis, reviewing key new findings and identifying opportunities for further research.

IL-11 drives the phenotypic transformation of tracheal epithelial cells and fibroblasts to enhance abnormal repair after tracheal injury

Tracheal stenosis (TS) is a multifactorial and heterogeneous disease that can easily lead to respiratory failure and even death. Interleukin-11 (IL-11) has recently received increased attention as a fibrogenic factor, but its function in TS is uncertain. This study aimed to investigate the role of IL-11 in TS regulation based on clinical samples from patients with TS and a rat model of TS produced by nylon brush scraping. Using lentiviral vectors expressing shRNA (lentivirus-shRNA) targeting the IL-11 receptor (IL-11Rα), we lowered IL-11Rα levels in the rat trachea. Histological and immunostaining methods were used to evaluate the effects of IL-11Rα knockdown on tracheal injury, molecular phenotype, and fibrosis in TS rats. We show that IL-11 was significantly elevated in circulating serum and granulation tissue in patients with TS. In vitro, TGFβ1 dose-dependently stimulated IL-11 secretion from human tracheal epithelial cells (Beas-2b) and primary rat tracheal fibroblasts (PRTF). IL-11 transformed the epithelial cell phenotype to the mesenchymal cell phenotype by activating the β-catenin pathway. Furthermore, IL-11 activated the atypical ERK signaling pathway, stimulated fibroblasts proliferation, and transformed fibroblasts into alpha-smooth muscle actin (α-SMA) positive myofibroblasts. IL-11-neutralizing antibodies (IL-11NAb) or ERK inhibitors (U0126) inhibited IL-11 activity and downregulated fibrotic responses involving TGFβ/SMAD signaling. In vivo, IL-11Rα knockdown rats showed unobstructed tracheal lumen, relatively intact epithelial structure, and significantly reduced granulation tissue proliferation and collagen fiber deposition. Our findings confirm that IL-11 may be a target for future drug prevention and treatment of tracheal stenosis.

Interleukin-11 in idiopathic pulmonary fibrosis: predictive value of prognosis and acute exacerbation

Background

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease with a poor prognosis and unknown aetiology. We have recently clarified the prognostic value of the serum platelet-derived growth factor (PDGF) level in patients with IPF. Interleukin (IL)-11 is a member of the IL-6 family, and in vivo and in vitro studies have suggested that it has profibrotic effects in pulmonary fibrosis. In this study, we investigated the predictive value of the serum IL-11 level in patients with IPF for survival and occurrence of acute exacerbation (AE).

Methods

This retrospective study included 68 patients with IPF diagnosed according to the 2018 guideline. Serum PDGF levels were measured using the Bio-Plex method and serum IL-11 levels using enzyme-linked immune-sorbent assay. Cytokine production per lung volume was evaluated using the serum cytokine/percent predicted forced vital capacity (%FVC) value.

Results

Forty-six patients were male and the median age was 67 years. The serum IL-11/%FVC value was significantly correlated with the percent predicted diffusing capacity of carbon monoxide (ρ=-0.518, P<0.001) and modified Medical Research Council score for shortness of breath (mMRC) (ρ=0.335, P=0.006) by Spearman's rank correlation analysis. Multivariate Cox proportional hazard regression analysis revealed that the serum IL-11/%FVC value was a significant prognostic factor after adjustment for the serum PDGF/%FVC value and other clinical parameters including mMRC and lymphocyte percentage in bronchoalveolar lavage [hazard ratio (HR): 88.540, 95% confidence interval (CI): 1.905-4,115.686, P=0.022]. IL-11/%FVC value was also a significant predictor of AE after adjustment for age and PDGF/%FVC (HR: 1,815.443, 95% CI: 10.49-314,109.219, P=0.004).

Conclusions

The serum IL-11/%FVC value was an independent predictor of prognosis and AE occurrence in patients with IPF, and the IL-11 level appeared to show pathophysiologic value in IPF.

Extracellular stimulation of lung fibroblasts with arachidonic acid increases interleukin 11 expression through p38 and ERK signaling

Interleukin-11 (IL-11) is a pleiotropic cytokine that regulates proliferation and motility of cancer cells. Fibroblasts reside in the cancer microenvironment and are the primary source of IL-11. Activated fibroblasts, including cancer-associated fibroblasts that produce IL-11, contribute to the development and progression of cancer, and induce fibrosis associated with cancer. Changes in fatty acid composition or its metabolites, and an increase in free fatty acids have been observed in cancer. The effect of deregulated fatty acids on the development and progression of cancer is not fully understood yet. In the present study, we investigated the effects of fatty acids on mRNA expression and secretion of IL-11 in lung fibroblasts. Among the eight fatty acids added exogenously, arachidonic acid (AA) increased mRNA expression and secretion of IL-11 in lung fibroblasts in a dose-dependent manner. AA-induced upregulation of IL-11 was dependent on the activation of the p38 or ERK MAPK signaling pathways. Furthermore, prostaglandin E2, associated with elevated cyclooxygenase-2 expression, participated in the upregulation of IL-11 via its specific receptor in an autocrine/paracrine manner. These results suggest that AA may mediate IL-11 upregulation in lung fibroblasts in the cancer microenvironment, accompanied by unbalanced fatty acid composition.

Interleukin-11 Is Elevated in Patients with Atrial Fibrillation, Correlates with Serum Fibrosis Markers, and Represents a Therapeutic Target for Atrial Fibrosis

INTRODUCTION

Inflammatory cytokines are closely associated with developing cardiac fibrosis. This research aimed to explore the significant role of IL-11 in atrial fibrosis progression and potential therapeutic targets.

METHODS

207 AF patients and 160 healthy subjects were included in the case-control study. Blood samples were analyzed for the level of IL-11 by enzyme-linked immunosorbent assay (ELISA). Angiotensin II (Ang II)-treated fibrosis mouse models were generated, and expression of IL-11 mRNA and protein was detected by RT-qPCR and Western blot. IL-11 antagonist was used to evaluating atrial fibrosis-related markers.

RESULTS

The persistent atrial fibrillation patients (n = 76) had significantly larger left atrial size, higher serum levels of hypertrophic protein BNP, proinflammatory cytokine high-sensitivity C-reactive protein (hs-CRP), and interleukin-6 (IL-6) compared to paroxysmal atrial fibrillation patients (n = 131), and healthy subjects (all p < 0.05). Pearson correlation analysis revealed significant positive correlation between serum IL-11 and cardiac fibrosis markers BNP (r = 0.394, p < 0.001), CTX-I (r = 0.418, p < 0.001), PICP (r = 0.306, p < 0.001), PIIINP (r = 0.335, p < 0.001), and TGF-β1 (r = 0.273, p < 0.001). In the fibrosis mouse model, Ang II infusion significantly upregulated IL-11 mRNA and protein expression in the left atrium of mice (p < 0.05), as well as staining intensity of Masson trichrome, the intensity of α-SMA, and it increased mRNA expression of collagen I and III in atrial tissue. IL-11 antagonist treatment significantly attenuated Masson trichrome, number of α-SMA-positive myofibroblasts in atrial tissue. Also, it significantly reduced the p-ERK1/2 in atrial tissue of mice infused with Ang II (p < 0.05).

CONCLUSIONS

IL-11 is upregulated in the serum of AF patients, and IL-11 inhibitor significantly inhibited Ang II-induced atrial fibrosis, a key pathological feature of AF. Therefore, IL-11 could be a potential therapeutic target for AF.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

Targeting endogenous kidney regeneration using anti-IL11 therapy in acute and chronic models of kidney disease

The kidney has large regenerative capacity, but this is compromised when kidney damage is excessive and renal tubular epithelial cells (TECs) undergo SNAI1-driven growth arrest. Here we investigate the role of IL11 in TECs, kidney injury and renal repair. IL11 stimulation of TECs induces ERK- and p90RSK-mediated GSK3β inactivation, SNAI1 upregulation and pro-inflammatory gene expression. Mice with acute kidney injury upregulate IL11 in TECs leading to SNAI1 expression and kidney dysfunction, which is not seen in Il11 deleted mice or in mice administered a neutralizing IL11 antibody in either preemptive or treatment modes. In acute kidney injury, anti-TGFβ reduces renal fibrosis but exacerbates inflammation and tubule damage whereas anti-IL11 reduces all pathologies. Mice with TEC-specific deletion of Il11ra1 have reduced pathogenic signaling and are protected from renal injury-induced inflammation, fibrosis, and failure. In a model of chronic kidney disease, anti-IL11 therapy promotes TEC proliferation and parenchymal regeneration, reverses fibroinflammation and restores renal mass and function. These data highlight IL11-induced mesenchymal transition of injured TECs as an important renal pathology and suggest IL11 as a therapeutic target for restoring stalled endogenous regeneration in the diseased kidney.

Oxygen–Glucose Deprivation Promoted Fibroblast Senescence and Collagen Expression via IL11

Cell senescence is one of the most important forms of injury induced by cardiovascular and other ischemic diseases. Fibroblasts are important participants in tissue repair after ischemic injury and the main source of IL11 secretion. However, the roles of oxygen–glucose deprivation (OGD) and IL11 in promoting fibroblast senescence and their regulatory mechanisms remain unclear. This study selected the NIH3T3 and L929 fibroblast cell lines as research objects. We found that OGD could induce the expression of p53, P16, p21, and collagen in fibroblasts. In the condition of OGD, when IL11 intervened, fibroblasts’ senescence and collagen expression were changed. Some studies have found that changes in kynurenine (KYN) metabolism are related to aging diseases, and indoleamine 2,3-dioxygenase 1 (IDO1) is a key rate-limiting enzyme in the KYN metabolic pathway. We found that KYN secretion decreased after OGD increased fibroblast senescence, and inhibition of IL11 promoted IDO1 and increased KYN secretion. These results suggest that OGD may promote fibroblast senescence and collagen expression via IL11 inhibition of the IDO1/KYN metabolic pathway. Therefore, the revealed mechanism of OGD-promoted fibroblast senescence could provide an effective theoretical basis for the clinical treatment of aging-related ischemic diseases.

IL11 stimulates ERK/P90RSK to inhibit LKB1/AMPK and activate mTOR initiating a mesenchymal program in stromal, epithelial, and cancer cells

IL11 initiates fibroblast activation but also causes epithelial cell dysfunction. The mechanisms underlying these processes are not known. We report that IL11-stimulated ERK/P90RSK activity causes the phosphorylation of LKB1 at S325 and S428, leading to its inactivation. This inhibits AMPK and activates mTOR across cell types. In stromal cells, IL11-stimulated ERK activity inhibits LKB1/AMPK which is associated with mTOR activation, ⍺SMA expression, and myofibroblast transformation. In hepatocytes and epithelial cells, IL11/ERK activity inhibits LKB1/AMPK leading to mTOR activation, SNAI1 expression, and cell dysfunction. Across cells, IL11-induced phenotypes were inhibited by metformin stimulated AMPK activation. In mice, genetic or pharmacologic manipulation of IL11 activity revealed a critical role of IL11/ERK signaling for LKB1/AMPK inhibition and mTOR activation in fatty liver disease. These data identify the IL11/mTOR axis as a signaling commonality in stromal, epithelial, and cancer cells and reveal a shared IL11-driven mesenchymal program across cell types.

IL11 Stimulates IL33 Expression and Proinflammatory Fibroblast Activation across Tissues

Interleukin 11 (IL11) is upregulated in inflammatory conditions, where it is mostly believed to have anti-inflammatory activity. However, recent studies suggest instead that IL11 promotes inflammation by activating fibroblasts. Here, we assessed whether IL11 is pro- or anti-inflammatory in fibroblasts. Primary cultures of human kidney, lung or skin fibroblasts were stimulated with IL11 that resulted in the transient phosphorylation of signal transducer and activator of transcription 3 (STAT3) and the sustained activation of extracellular signal-regulated protein kinases (ERK). RNA sequencing over a time course of IL11 stimulation revealed a robust but short-lived transcriptional response that was enriched for gene set hallmarks of inflammation and characterized by the upregulation of SERPINB2, TNFRSF18, Interleukin 33 (IL33), CCL20, IL1RL1, CXCL3/5/8, ICAM1 and IL11 itself. IL33 was the most upregulated signaling factor (38-fold, p = 9.8 × 10^-5), and IL1RL1, its cognate receptor, was similarly increased (18-fold, p = 1.1 × 10^-34). In proteomic studies, IL11 triggered a proinflammatory secretome with the notable upregulation of IL8, IL6, MCP1, CCL20 and CXCL1/5/6, which are important chemotaxins for neutrophils, monocytes, and lymphocytes. IL11 induced IL33 expression across fibroblast types, and the inhibition of STAT3 but not of MEK/ERK prevented this. These data establish IL11 as pro-inflammatory with specific importance for priming the IL33 alarmin response in inflammatory fibroblasts across tissues.

Interleukin-11: A Potential Biomarker and Molecular Therapeutic Target in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) accounts for 85% of lung cancer and is a fast progressive disease when left untreated. Identification of potential biomarkers in NSCLC is an ongoing area of research that aims to detect, diagnose, and prognosticate patients early to optimize treatment. We review the role of interleukin-11 (IL11), a stromal-cell derived pleiotropic cytokine with profibrotic and cellular remodeling properties, as a potential biomarker in NSCLC. This review identifies the need for biomarkers in NSCLC, the potential sources of IL11, and summarizes the available information leveraging upon published literature, publicly available datasets, and online tools. We identify accumulating evidence suggesting IL11 to be a potential biomarker in NSCLC patients. Further in-depth studies into the pathophysiological effects of IL11 on stromal-tumor interaction in NSCLC are warranted and current available literature highlights the potential value of IL11 detection as a diagnostic and prognostic biomarker in NSCLC.

IL11 Activates Pancreatic Stellate Cells and Causes Pancreatic Inflammation, Fibrosis and Atrophy in a Mouse Model of Pancreatitis

Interleukin-11 (IL11) is important for fibrosis and inflammation, but its role in the pancreas is unclear. In pancreatitis, fibrosis, inflammation and organ dysfunction are associated with pancreatic stellate cell (PSC)-to-myofibroblast transformation. Here, we show that IL11 stimulation of PSCs, which specifically express IL11RA in the pancreas, results in transient STAT3 phosphorylation, sustained ERK activation and PSC activation. In contrast, IL6 stimulation of PSCs caused sustained STAT3 phosphorylation but did not result in ERK activation or PSC transformation. Pancreatitis factors, including TGFβ, CTGF and PDGF, induced IL11 secretion from PSCs and a neutralising IL11RA antibody prevented PSC activation by these stimuli. This revealed an important ERK-dependent role for autocrine IL11 activity in PSCs. In mice, IL11 was increased in the pancreas after pancreatic duct ligation, and in humans, IL11 and IL11RA levels were elevated in chronic pancreatitis. Following pancreatic duct ligation, administration of anti-IL11RA to mice reduced pathologic (ERK, STAT, NF-κB) signalling, pancreatic atrophy, fibrosis and pro-inflammatory cytokine (TNFα, IL6 and IL1β) levels. This is the first description of IL11-mediated activation of PSCs, and the data suggest IL11 as a stromal therapeutic target in pancreatitis.

Inhibition of IL11 Signaling Reduces Aortic Pathology in Murine Marfan Syndrome

BACKGROUND

Marfan syndrome (MFS) is associated with TGF (transforming growth factor) β-stimulated ERK (extracellular signal-regulated kinase) activity in vascular smooth muscle cells (VSMCs), which adopt a mixed synthetic/contractile phenotype. In VSMCs, TGFβ induces IL (interleukin) 11) that stimulates ERK-dependent secretion of collagens and MMPs (matrix metalloproteinases). Here, we examined the role of IL11 in the MFS aorta.

METHODS

We used echocardiography, histology, immunostaining, and biochemical methods to study aortic anatomy, physiology, and molecular endophenotypes in Fbn1^C1041G/+ mice, an established murine model of MFS (mMFS). mMFS mice were crossed to an IL11-tagged EGFP (enhanced green fluorescent protein; Il11^EGFP/+) reporter strain or to a strain deleted for the IL11 receptor (Il11ra1^-/-). In therapeutic studies, mMFS were administered an X209 (neutralizing antibody against IL11RA [IL11 receptor subunit alpha]) or IgG for 20 weeks and imaged longitudinally.

RESULTS

IL11 mRNA and protein were elevated in the aortas of mMFS mice, as compared to controls. mMFS mice crossed to Il11^EGFP/+ mice had increased IL11 expression in VSMCs, notably in the aortic root and ascending aorta. As compared to the mMFS parental strain, double mutant mMFS:Il11ra1^-/- mice had reduced aortic dilatation and exhibited lesser fibrosis, inflammation, elastin breaks, and VSMC loss, which was associated with reduced aortic COL1A1 (collagen type I alpha 1 chain), IL11, MMP2/9, and phospho-ERK expression. To explore therapeutic targeting of IL11 signaling in MFS, we administered either a neutralizing antibody against IL11RA (X209) or an IgG control. After 20 weeks of antibody administration, as compared to IgG, mMFS mice receiving X209 had reduced thoracic and abdominal aortic dilation as well as lesser fibrosis, inflammation, elastin breaks, and VSMC loss. By immunoblotting, X209 was shown to reduce aortic COL1A1, IL11, MMP2/9, and phospho-ERK expression.

CONCLUSIONS

In MFS, IL11 is upregulated in aortic VSMCs to cause ERK-related thoracic aortic dilatation, inflammation, and fibrosis. Therapeutic inhibition of IL11, imminent in clinical trials, might be considered as a new approach in MFS.

A Neutralizing IL-11 Antibody Improves Renal Function and Increases Lifespan in a Mouse Model of Alport Syndrome

BACKGROUND

Alport syndrome is a genetic disorder characterized by a defective glomerular basement membrane, tubulointerstitial fibrosis, inflammation, and progressive renal failure. IL-11 was recently implicated in fibrotic kidney disease but its role in Alport syndrome is unknown Methods: We determined IL-11 expression by molecular analyses and in an Alport syndrome mouse model. We assessed the effects of a neutralizing IL-11 antibody (X203) versus an IgG control in Col4a3-/- mice (lacking the gene encoding a type IV collagen component) on renal tubule damage, function, fibrosis, and inflammation. Effects on lifespan of X203, the IgG control, an angiotensin-converting enzyme inhibitor (ramipril), or ramipril+X203 were also studied.

RESULTS

In Col4a3 mice, as kidney failure advanced, renal IL-11 levels increased and IL-11 expression localized to tubular epithelial cells. The IL-11 receptor IL11RA is expressed in tubular epithelial cells and podocytes and is upregulated in tubular epithelial cells of Col4a3 mice. Administration of X203 reduced albuminuria, improved renal function, and preserved podocyte numbers and levels of key podocyte proteins that are reduced in Col4a3 mice; these effects were accompanied by reduced fibrosis and inflammation, attenuation of epithelial-tomesenchymal transition, and increased expression of regenerative markers. X203 attenuated pathogenic ERK and STAT3 pathways, which were activated in Col4a3 mice. Median lifespan of Col4a3 mice was prolonged 22% by ramapril, 44% with X203, and 99% with amipril+X203.

CONCLUSIONS

In an Alport syndrome mouse model, renal IL-11 is upregulated, and neutralization of IL-11 reduces epithelial-to-mesenchymal transition, fibrosis, and inflammation, while improving renal function. Anti-IL-11 combined with ACE inhibition synergistically extends lifespan. This suggests that a therapeutic approach targeting IL-11 holds promise for progressive kidney disease in Alport syndrome.

CAR T cells produced in vivo to treat cardiac injury

Fibrosis affects millions of people with cardiac disease. We developed a therapeutic approach to generate transient antifibrotic chimeric antigen receptor (CAR) T cells in vivo by delivering modified messenger RNA (mRNA) in T cell–targeted lipid nanoparticles (LNPs). The efficacy of these in vivo–reprogrammed CAR T cells was evaluated by injecting CD5-targeted LNPs into a mouse model of heart failure. Efficient delivery of modified mRNA encoding the CAR to T lymphocytes was observed, which produced transient, effective CAR T cells in vivo. Antifibrotic CAR T cells exhibited trogocytosis and retained the target antigen as they accumulated in the spleen. Treatment with modified mRNA-targeted LNPs reduced fibrosis and restored cardiac function after injury. In vivo generation of CAR T cells may hold promise as a therapeutic platform to treat various diseases.

CAR T cells produced in vivo to treat cardiac injury

Cardiac fibrosis is the stiffening and scarring of heart tissue and can be fatal. Rurik et al . designed an immunotherapy strategy to generate transient chimeric antigen receptor (CAR) T cells that can recognize the fibrotic cells in the heart (see the Perspective by Gao and Chen). By injecting CD5-targeted lipid nanoparticles containing the messenger RNA (mRNA) instructions needed to reprogram T lymphocytes, the researchers were able to generate therapeutic CAR T cells entirely inside the body. Analysis of a mouse model of heart disease revealed that the approach was successful in reducing fibrosis and restoring cardiac function. The ability to produce CAR T cells in vivo using modified mRNA may have a number of therapeutic applications. —PNK

IL-11 Is Elevated and Drives the Profibrotic Phenotype Transition of Orbital Fibroblasts in Thyroid-Associated Ophthalmopathy

Orbital fibrosis is a hallmark of tissue remodeling in thyroid-associated ophthalmopathy (TAO). Previous studies have shown that interleukin (IL)-11 plays a pivotal profibrotic role in various inflammatory and autoimmune diseases. However, the expression pattern of IL-11 in patients with TAO and whether IL-11 is mechanistically linked with pathological fibrosis remains unknown. In this study, we investigated IL-11 levels in the serum and orbital connective tissue of patients with TAO, and evaluated the correlation of these levels with the patient's clinical activity score. We also evaluated the expression pattern of IL-11Rα in orbital connective tissue. Furthermore, we elucidated the regulatory factors, profibrotic function, and downstream signaling pathways for IL-11 in TAO using in vitro studies. IL-11 levels in serum and orbital connective tissues were increased in patients with TAO, as compared with healthy controls. In addition, both levels were positively correlated with disease activity. Single-cell RNA sequencing of orbital connective tissue indicated that IL-11Rα was dominantly expressed in orbital fibroblasts (OFs). RNA sequencing of paired unstimulated and transforming growth factor (TGF)-β1-stimulated samples demonstrated that upregulation of IL-11 expression defined the dominant transcriptional response. IL-11 signaling was also confirmed to be downstream of TGF-β1 and IL-1β. Therefore, we deduced that IL-11 protein is secreted in an autocrine loop in TAO. We also indicated that IL-11 mediated the profibrotic phenotype switch by inducing the expression of myofibroblast differentiation markers, including α-smooth muscle actin and collagen type I α1, which could be abrogated by an anti-IL-11 neutralizing antibody. Furthermore, we revealed that extracellular regulated protein kinase may be a crucial factor in the pro-fibrotic, translationally specific signaling activity of IL-11. These data demonstrate that IL-11 plays a crucial role in orbital fibroblast phenotype switching and may be a potential therapeutic target candidate for the treatment of TAO.