Interleukin 6 trans-signaling is a critical driver of lung allograft fibrosis

Relationship between immune cells and the development of chronic lung allograft dysfunction

A major cause of death for lung transplant recipients (LTRs) is the advent of chronic lung allograft dysfunction (CLAD), which has long plagued the long-term post-transplant prognosis and quality of survival of transplant patients. The intricacy of its pathophysiology and the irreversibility of its illness process present major obstacles to the clinical availability of medications. Immunotherapeutic medications are available, but they only aim to slow down the course of CLAD rather than having any therapeutic impact on the disease's development. For this reason, understanding the pathophysiology of CLAD is essential for both disease prevention and proven treatment. The immunological response in particular, in relation to chronic lung allograft dysfunction, has received a great deal of interest recently. Innate immune cells like natural killer cells, eosinophils, neutrophils, and mononuclear macrophages, as well as adaptive immunity cells like T and B cells, play crucial roles in this process through the release of chemokines and cytokines. The present review delves into changes and processes within the immune microenvironment, with a particular focus on the quantity, subtype, and characteristics of effector immune cells in the peripheral and transplanted lungs after lung transplantation. We incorporate and solidify the documented role of immune cells in the occurrence and development of CLAD with the advancements in recent years.

Interleukin Receptor Therapeutics Attenuate Inflammation in Canine Synovium following Cruciate Ligament Injury

OBJECTIVE

In the knee, synovial fibrosis after ligamentous injury is linked to progressive joint pain and stiffness. The objective of this study was to evaluate changes in synovial architecture, mechanical properties, and transcriptional profiles following naturally occurring cruciate ligament injury in canines and to test potential therapeutics that target drivers of synovial inflammation and fibrosis.

DESIGN

Synovia from canines with spontaneous cruciate ligament tears and from healthy knees were assessed via histology (n=10/group) and micromechanical testing (n=5/group) to identify changes in tissue architecture and stiffness. Additional samples (n=5/group) were subjected to RNA-sequencing to define the transcriptional response to injury. Finally, synovial tissue samples from injured animals (n=6 (IL1) or n=8 (IL6)/group) were assessed in vitro for response to therapeutic molecules directed against interleukin (IL) signaling (IL1 or IL6).

RESULTS

Cruciate injury resulted in increased synovial fibrosis, vascularity, inflammatory cell infiltration, and intimal hyperplasia. Additionally, the stiffness of both the intima and subintima regions were higher in diseased compared to healthy tissue. Differential gene expression analysis showed that diseased synovium had an upregulation of immune response and cell adhesion pathways and a downregulation of Rho protein transduction pathways. In vitro application of small molecule therapeutics targeting IL1 (anakinra) or IL6 (tocilizumab) dampened expression of inflammatory and matrix deposition mediators.

CONCLUSION

Spontaneous cruciate ligament injury in canines is associated with synovial inflammation and fibrosis in a relevant model for testing emerging intra-articular treatments. Small molecule therapeutics targeting IL pathways may be ideal interventions for delivery to the joint space after injury.

Decoding the hallmarks of allograft dysfunction with a comprehensive pan-organ transcriptomic atlas

The pathogenesis of allograft (dys)function has been increasingly studied using 'omics'-based technologies, but the focus on individual organs has created knowledge gaps that neither unify nor distinguish pathological mechanisms across allografts. Here we present a comprehensive study of human pan-organ allograft dysfunction, analyzing 150 datasets with more than 12,000 samples across four commonly transplanted solid organs (heart, lung, liver and kidney, n = 1,160, 1,241, 1,216 and 8,853 samples, respectively) that we leveraged to explore transcriptomic differences among allograft dysfunction (delayed graft function, acute rejection and fibrosis), tolerance and stable graft function. We identified genes that correlated robustly with allograft dysfunction across heart, lung, liver and kidney transplantation. Furthermore, we developed a transfer learning omics prediction framework that, by borrowing information across organs, demonstrated superior classifications compared to models trained on single organs. These findings were validated using a single-center prospective kidney transplant cohort study (a collective 329 samples across two timepoints), providing insights supporting the potential clinical utility of our approach. Our study establishes the capacity for machine learning models to learn across organs and presents a transcriptomic transplant resource that can be employed to develop pan-organ biomarkers of allograft dysfunction.

Potential biomarkers for immune monitoring after renal transplantation

Renal transplantation represents the foremost efficacious approach for ameliorating end-stage renal disease. Despite the current state of advanced renal transplantation techniques and the established postoperative immunosuppression strategy, a subset of patients continues to experience immune rejection during both the early and late postoperative phases, ultimately leading to graft loss. Consequently, the identification of immunobiomarkers capable of predicting the onset of immune rejection becomes imperative in order to facilitate early intervention strategies and enhance long-term prognoses. Upon reviewing the pertinent literature, we identified several indicators that could potentially serve as immune biomarkers to varying extents. These include the T1/T2 ratio, Treg/Th17 ratio, IL-10/TNF-α ratio, IL-33, IL-34, IL-6, IL-4, other cytokines, and NOX2/4.

Fibrotic progression from acute cellular rejection is dependent on secondary lymphoid organs in a mouse model of chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) remains one of the major limitations to long-term survival after lung transplantation. We modified a murine model of CLAD and transplanted left lungs from BALB/c donors into B6 recipients that were treated with intermittent cyclosporine and methylprednisolone postoperatively. In this model, the lung allograft developed acute cellular rejection on day 15 which, by day 30 after transplantation, progressed to severe pleural and peribronchovascular fibrosis, reminiscent of changes observed in restrictive allograft syndrome. Lung transplantation into splenectomized B6 alymphoplastic (aly/aly) or splenectomized B6 lymphotoxin-β receptor-deficient mice demonstrated that recipient secondary lymphoid organs, such as spleen and lymph nodes, are necessary for progression from acute cellular rejection to allograft fibrosis in this model. Our work uncovered a critical role for recipient secondary lymphoid organs in the development of CLAD after pulmonary transplantation and may provide mechanistic insights into the pathogenesis of this complication.

The Lung Microbiome Predicts Mortality and Response to Azithromycin in Lung Transplant Recipients with Chronic Rejection

Rationale: Chronic lung allograft dysfunction (CLAD) is the leading cause of death after lung transplant, and azithromycin has variable efficacy in CLAD. The lung microbiome is a risk factor for developing CLAD, but the relationship between lung dysbiosis, pulmonary inflammation, and allograft dysfunction remains poorly understood. Whether lung microbiota predict outcomes or modify treatment response after CLAD is unknown. Objectives: To determine whether lung microbiota predict post-CLAD outcomes and clinical response to azithromycin. Methods: Retrospective cohort study using acellular BAL fluid prospectively collected from recipients of lung transplant within 90 days of CLAD onset. Lung microbiota were characterized using 16S rRNA gene sequencing and droplet digital PCR. In two additional cohorts, causal relationships of dysbiosis and inflammation were evaluated by comparing lung microbiota with CLAD-associated cytokines and measuring ex vivo P. aeruginosa growth in sterilized BAL fluid. Measurements and Main Results: Patients with higher bacterial burden had shorter post-CLAD survival, independent of CLAD phenotype, azithromycin treatment, and relevant covariates. Azithromycin treatment improved survival in patients with high bacterial burden but had negligible impact on patients with low or moderate burden. Lung bacterial burden was positively associated with CLAD-associated cytokines, and ex vivo growth of P. aeruginosa was augmented in BAL fluid from transplant recipients with CLAD. Conclusions: In recipients of lung transplants with chronic rejection, increased lung bacterial burden is an independent risk factor for mortality and predicts clinical response to azithromycin. Lung bacterial dysbiosis is associated with alveolar inflammation and may be promoted by underlying lung allograft dysfunction.

Label-free SERS for rapid identification of interleukin 6 based on intrinsic SERS fingerprint of antibody‑gold nanoparticles conjugate

A label-free surface-enhanced Raman scattering (SERS) was designed for sensitive detection of interleukin-6 (IL-6). The sensing element composed of anti-IL-6 antibodies adsorbed on the surface of spherical gold nanoparticles (AuNPs) as SERS-active surface. The principle of detection was probing antibody conformational changes using its intrinsic SERS fingerprint after binding to IL-6. Comparison of SERS spectra of antibody before and after binding to IL-6 showed that secondary structure of antibody does not change upon binding to IL-6. Vibrational information from disulfide bonds ν(SS) in antibody structure indicated some changes of geometry around SS bridges as a consequence of the immunocomplex formation. Transmission electron microscopy (TEM) and UV-Vis spectroscopy were used to confirm AuNPs conjugation with antibody as well as IL-6 binding to antibody on the surface of AuNPs. The SERS-based immunoassay showed a wide linear range (2.0-1000 pg mL-1) and a high sensitivity with a limit of detection (LOD) as low as 0.91 pg mL-1 (0.04 pM) without using any extrinsic Raman label. UV-Vis spectroscopy was employed as a conventional method for IL-6 detection based on observation of any change in the position of localized surface plasmon resonance (LSPR) band of AuNPs-antibody conjugates with LOD of 10 ng mL-1.

Role of Interleukin-6 Family Cytokines in Organ Fibrosis

Background

Organ fibrosis remains an important cause of high incidence rate and mortality worldwide. The prominent role of interleukin-6 (IL-6) family members represented by IL-6 in inflammation has been extensively studied, and drugs targeting IL-6 have been used clinically. Because of the close relationship between inflammation and fibrosis, researches on the role of IL-6 family members in organ fibrosis are also gradually emerging.

Summary

In this review, we systematically reviewed the role of IL-6 family members in fibrosis and their possible mechanisms. We listed the role of IL-6 family members in organ fibrosis and drew two diagrams to illustrate the downstream signal transductions of IL-6 family members. We also summarized the effect of some IL-6 family members' antagonists in a table.

Key Messages

Fibrosis contributes to organ structure damage, organ dysfunction, and eventually organ failure. Although IL-6 family cytokines have similar downstream signal pathways, different members play various roles in an organ-specific manner which might be partly due to their different target cell populations. The pathogenic role of individual member in various diseases needs to be deciphered carefully.

Intragraft immune cells: accomplices or antagonists of recipient-derived macrophages in allograft fibrosis?

Organ fibrosis caused by chronic allograft rejection is a major concern in the field of transplantation. Macrophage-to-myofibroblast transition plays a critical role in chronic allograft fibrosis. Adaptive immune cells (such as B and CD4⁺ T cells) and innate immune cells (such as neutrophils and innate lymphoid cells) participate in the occurrence of recipient-derived macrophages transformed to myofibroblasts by secreting cytokines, which eventually leads to fibrosis of the transplanted organ. This review provides an update on the latest progress in understanding the plasticity of recipient-derived macrophages in chronic allograft rejection. We discuss here the immune mechanisms of allograft fibrosis and review the reaction of immune cells in allograft. The interactions between immune cells and the process of myofibroblast formulation are being considered for the potential therapeutic targets of chronic allograft fibrosis. Therefore, research on this topic seems to provide novel clues for developing strategies for preventing and treating allograft fibrosis.

An Enhanced Dissolving Cyclosporin-A Inhalable Powder Efficiently Reduces SARS-CoV-2 Infection In Vitro

This work illustrates the development of a dry inhalation powder of cyclosporine-A for the prevention of rejection after lung transplantation and for the treatment of COVID-19. The influence of excipients on the spray-dried powder's critical quality attributes was explored. The best-performing powder in terms of dissolution time and respirability was obtained starting from a concentration of ethanol of 45% (v/v) in the feedstock solution and 20% (w/w) of mannitol. This powder showed a faster dissolution profile (Weibull dissolution time of 59.5 min) than the poorly soluble raw material (169.0 min). The powder exhibited a fine particle fraction of 66.5% and an MMAD of 2.97 µm. The inhalable powder, when tested on A549 and THP-1, did not show cytotoxic effects up to a concentration of 10 µg/mL. Furthermore, the CsA inhalation powder showed efficiency in reducing IL-6 when tested on A549/THP-1 co-culture. A reduction in the replication of SARS-CoV-2 on Vero E6 cells was observed when the CsA powder was tested adopting the post-infection or simultaneous treatment. This formulation could represent a therapeutic strategy for the prevention of lung rejection, but is also a viable approach for the inhibition of SARS-CoV-2 replication and the COVID-19 pulmonary inflammatory process.

Biomarkers for Chronic Lung Allograft Dysfunction: Ready for Prime Time?

Chronic lung allograft dysfunction (CLAD) remains a major hurdle impairing lung transplant outcome. Parallel to the better clinical identification and characterization of CLAD and CLAD phenotypes, there is an increasing urge to find adequate biomarkers that could assist in the earlier detection and differential diagnosis of CLAD phenotypes, as well as disease prognostication. The current status and state-of-the-art of biomarker research in CLAD will be discussed with a particular focus on radiological biomarkers or biomarkers found in peripheral tissue, bronchoalveolar lavage' and circulating blood' in which significant progress has been made over the last years. Ultimately, although a growing number of biomarkers are currently being embedded in the follow-up of lung transplant patients, it is clear that one size does not fit all. The future of biomarker research probably lies in the rigorous combination of clinical information with findings in tissue, bronchoalveolar lavage' or blood. Only by doing so, the ultimate goal of biomarker research can be achieved, which is the earlier identification of CLAD before its clinical manifestation. This is desperately needed to improve the prognosis of patients with CLAD after lung transplantation.

Dysregulated Cell-Cell Communication Characterizes Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of older adults characterized by fibrotic replacement of functional gas exchange units in the lung. The strongest risk factor for IPF is a genetic variantin the promoter region of the gel-forming mucin, MUC5B. To better understand how the MUC5B variant influences development of fibrosis, we used the NicheNet R package and leveraged publicly available single-cell RNA sequencing data to identify and evaluate how epithelia participating in gas exchange are influenced by ligands expressed in control, MUC5B variant, and fibrotic environments. We observed that loss of type-I alveolar epithelia (AECI) characterizes the single-cell RNA transcriptome in fibrotic lung and validated the pattern of AECI loss using single nuclear RNA sequencing. Examining AECI transcriptomes, we found enrichment of transcriptional signatures for IL6 and AREG, which we have previously shown to mediate aberrant epithelial fluidization in IPF and murine bleomycin models. Moreover, we found that the protease ADAM17, which is upstream of IL6 trans-signaling, was enriched in control MUC5B variant donors. We used immunofluorescence to validate a role for enhanced expression of ADAM17 among MUC5B variants, suggesting involvement in IPF pathogenesis and maintenance.

The Role of IL-6 in Fibrotic Diseases: Molecular and Cellular Mechanisms

Fibrosis is a detrimental outcome of most chronic inflammatory disorders and is defined by the buildup of excess extracellular matrix (ECM) components, which eventually leads to organ failure and death. Interleukin 6 (IL-6) is promptly produced by immune cells in response to tissue injuries and has a wide range of effects on cellular processes such as acute responses, hematopoiesis, and immune reactions. Furthermore, high levels of IL-6 have been found in a variety of chronic inflammatory disorders characterized by fibrosis, and this factor plays a significant role in fibrosis in various organs via Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) activation. Here, we review what is known about the role of IL-6 in fibrosis and why targeting IL-6 for fibrotic disease treatment makes sense.

Novel approaches for long-term lung transplant survival

Allograft failure remains a major barrier in the field of lung transplantation and results primarily from acute and chronic rejection. To date, standard-of-care immunosuppressive regimens have proven unsuccessful in achieving acceptable long-term graft and patient survival. Recent insights into the unique immunologic properties of lung allografts provide an opportunity to develop more effective immunosuppressive strategies. Here we describe advances in our understanding of the mechanisms driving lung allograft rejection and highlight recent progress in the development of novel, lung-specific strategies aimed at promoting long-term allograft survival, including tolerance.

Novel biomarkers of chronic lung allograft dysfunction: is there anything reliable?

PURPOSE OF REVIEW

Chronic lung allograft dysfunction (CLAD) remains a major barrier preventing long-term survival following lung transplantation. As our clinical knowledge regarding its definition and presentation has significantly improved over the last years, adequate biomarkers to predict development of CLAD, phenotype of CLAD or prognosis post-CLAD diagnosis are definitely needed.

RECENT FINDINGS

Radiological and physiological markers are gradually entering routine clinical practice. In-depth investigation of biological samples including broncho-alveolar lavage, biopsy and serum has generated potential biomarkers involved in fibrogenesis, airway injury and inflammation but none of these are universally accepted or implemented although progress has been made, specifically regarding donor-derived cell-free DNA and donor-specific antibodies.

SUMMARY

Although a lot of promising biomarkers have been put forward, a very limited number has made it to routine clinical practice. Nevertheless, a biomarker that leads to earlier detection or more adequate disease phenotyping would advance the field enormously.

IL-6 Directed Therapy in Transplantation

Purpose of Review

IL-6 is a pleiotropic, pro-inflammatory cytokine that plays an integral role in the development of acute and chronic rejection after solid organ transplantation. This article reviews the experimental evidence and current clinical application of IL-6/IL-6 receptor (IL-6R) signaling inhibition for the prevention and treatment of allograft injury.

Recent Findings

There exists a robust body of evidence linking IL-6 to allograft injury mediated by acute inflammation, adaptive cellular/humoral responses, innate immunity, and fibrosis. IL-6 promotes the acute phase reaction, induces B cell maturation/antibody formation, directs cytotoxic T-cell differentiation, and inhibits regulatory T-cell development. Importantly, blockade of the IL-6/IL-6R signaling pathway has been shown to mitigate its harmful effects in experimental studies, particularly in models of kidney and heart transplant rejection. Currently, available agents for IL-6 signaling inhibition include monoclonal antibodies against IL-6 or IL-6R and janus kinase inhibitors. Recent clinical trials have investigated the use of tocilizumab, an anti-IL-6R mAb, for desensitization and treatment of antibody-mediated rejection (AMR) in kidney transplant recipients, with promising initial results. Further studies are underway investigating the use of alternative agents including clazakizumab, an anti-IL-6 mAb, and application of IL-6 signaling blockade to clinical cardiac transplantation.

Summary

IL-6/IL-6R signaling inhibition provides a novel therapeutic option for the prevention and treatment of allograft injury. To date, evidence from clinical trials supports the use of IL-6 blockade for desensitization and treatment of AMR in kidney transplant recipients. Ongoing and future clinical trials will further elucidate the role of IL-6 signaling inhibition in other types of solid organ transplantation.