Interleukin-18 as a drug repositioning opportunity for inflammatory bowel disease: A Mendelian randomization study

Evaluating the causal effect of circulating proteome on the risk of inflammatory bowel disease-related traits using Mendelian randomization

Objective

This study sought to identify circulating proteins causally linked to Inflammatory Bowel Disease (IBD) traits through a Mendelian Randomization (MR) analytical framework.

Methods

Using a large-scale, two-sample MR approach, we estimated the genetic links of numerous plasma proteins with IBD and its subtypes, leveraging information from the Inflammatory Bowel Disease Genetics Consortium. To assess the robustness of MR findings, methods like Bayesian colocalization, and Steiger filtering analysis, evaluation of protein-altering variants. Further insights into IBD's underlying mechanisms and therapeutic targets were gleaned from single-cell sequencing analyses, protein-protein interaction assessments, pathway enrichment analyses, and evaluation of drug targets.

Results

By cis-only MR analysis, we identified 83 protein-phenotype associations involving 27 different proteins associated with at least one IBD subtype. Among these proteins, DAG1, IL10, IL12B, IL23R, MST1, STAT3 and TNFRSF6B showed overlapping positive or negative associations in all IBD phenotypes. Extending to cis + trans MR analysis, we further identified 117 protein-feature associations, including 44 unique proteins, most of which were not detected in the cis-only analysis. In addition, by performing co-localization analysis and Steiger filtering analysis on the prioritized associations, we further confirmed the causal relationship between these proteins and the IBD phenotype and verified the exact causal direction from the protein to the IBD-related feature.

Conclusion

MR analysis facilitated the identification of numerous circulating proteins associated with IBD traits, unveiling protein-mediated mechanisms and promising therapeutic targets.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Discerning Endoscopic Severity of Inflammatory Bowel Disease by Scoping the Peripheral Blood Transcriptome

Background and Aims

Ulcerative colitis (UC) and Crohn's disease (CD) are chronic inflammatory bowel diseases (IBDs) with an incompletely understood etiology and pathogenesis. Identification of suitable drug targets and assessment of disease severity are crucial for optimal management.

Methods

Using RNA sequencing, we investigated differential gene expression in peripheral blood samples from IBD patients and non-inflamed controls, analyzed pathway enrichment, and identified genes whose expression correlated with endoscopic disease severity.

Results

Neutrophil degranulation emerged as the most significant pathway across all IBD sample types. Signaling by interleukins was prominent in patients with active intestinal inflammation but also enriched in CD and UC patients without intestinal inflammation. Nevertheless, genes correlated to endoscopic disease severity implicated the primary cilium in CD patients and translation and focal adhesion in UC patients. Moreover, several of these genes were located in genome-wide associated loci linked to IBD, cholesterol levels, blood cell counts, and levels of markers assessing liver and kidney function. These genes also suggested connections to intestinal epithelial barrier dysfunction, contemporary IBD drug treatment, and new actionable drug targets. A large number of genes associated with endoscopic disease severity corresponded to noncoding RNAs.

Conclusion

This study revealed biological pathways associated with IBD disease state and endoscopic disease severity, thus providing insights into the underlying mechanisms of IBD pathogenesis as well as identifying potential biomarkers and therapies. Peripheral blood might constitute a suitable noninvasive diagnostic sample type, in which gene expression profiles might serve as indicators of ongoing mucosal inflammation, and thus guide personalized treatment decisions.

Prioritising genetic findings for drug target identification and validation

The decreasing costs of high-throughput genetic sequencing and increasing abundance of sequenced genome data have paved the way for the use of genetic data in identifying and validating potential drug targets. However, the number of identified potential drug targets is often prohibitively large to experimentally evaluate in wet lab experiments, highlighting the need for systematic approaches for target prioritisation. In this review, we discuss principles of genetically guided drug development, specifically addressing loss-of-function analysis, colocalization and Mendelian randomisation (MR), and the contexts in which each may be most suitable. We subsequently present a range of biomedical resources which can be used to annotate and prioritise disease-associated proteins identified by these studies including 1) ontologies to map genes, proteins, and disease, 2) resources for determining the druggability of a potential target, 3) tissue and cell expression of the gene encoding the potential target, and 4) key biological pathways involving the potential target. We illustrate these concepts through a worked example, identifying a prioritised set of plasma proteins associated with non-alcoholic fatty liver disease (NAFLD). We identified five proteins with strong genetic support for involvement with NAFLD: CYB5A, NT5C, NCAN, TGFBI and DAPK2. All of the identified proteins were expressed in both liver and adipose tissues, with TGFBI and DAPK2 being potentially druggable. In conclusion, the current review provides an overview of genetic evidence for drug target identification, and how biomedical databases can be used to provide actionable prioritisation, fully informing downstream experimental validation.

Investigating the association between genetically proxied circulating levels of immune checkpoint proteins and cancer survival: protocol for a Mendelian randomisation analysis

INTRODUCTION

Compared with the traditional drug development pathway, investigating alternative uses for existing drugs (ie, drug repurposing) requires substantially less time, cost and resources. Immune checkpoint inhibitors are licensed for the treatment of certain breast, colorectal, head and neck, lung and melanoma cancers. These drugs target immune checkpoint proteins to reduce the suppression of T cell activation by cancer cells. As T cell suppression is a hallmark of cancer common across anatomical sites, we hypothesise that immune checkpoint inhibitors could be repurposed for the treatment of additional cancers beyond the ones already indicated.

METHODS AND ANALYSIS

We will use two-sample Mendelian randomisation to investigate the effect of genetically proxied levels of protein targets of two immune checkpoint inhibitors-programmed cell death protein 1 and programmed death ligand 1-on survival of seven cancer types (breast, colorectal, head and neck, lung, melanoma, ovarian and prostate). Summary genetic association data will be obtained from prior genome-wide association studies of circulating protein levels and cancer survival in populations of European ancestry. Various sensitivity analyses will be performed to examine the robustness of findings to potential violations of Mendelian randomisation assumptions, collider bias and the impact of alternative genetic instrument construction strategies. The impact of treatment history and tumour stage on the findings will also be investigated using summary-level and individual-level genetic data where available.

ETHICS AND DISSEMINATION

No separate ethics approval will be required for these analyses as we will be using data from previously published genome-wide association studies which individually gained ethical approval and participant consent. Results from analyses will be submitted as an open-access peer-reviewed publication and statistical code will be made freely available on the completion of the analysis.

Circulating levels of cytokines and risk of inflammatory bowel disease: evidence from genetic data

Background

Prior epidemiological studies have established a correlation between inflammatory cytokines and inflammatory bowel disease (IBD). However, the nature of this relationship remains uncertain. Mendelian randomization (MR) study has the advantages of avoiding confounding and reverse causality compared with traditional observational research.

Objective

We aimed to evaluate whether genetically determined circulating levels of cytokines are associated with the risk of IBD by using the MR approach.

Materials and methods

We selected genetic variants associated with circulating levels of 28 cytokines at the genome-wide significance level from a genome-wide association study (GWAS) including 8,293 individuals. Summary-level data for IBD (including Crohn's disease and ulcerative colitis) were obtained from the International Inflammatory Bowel Disease Genetics Consortium and UK Biobank. We performed the primary analysis using the inverse-variance weighted method, as well as sensitivity analyses to test the stability of our results. We subsequently replicated the results of IBD in the UK Biobank dataset. A reverse MR analysis was also conducted to evaluate the possibility of reverse causation.

Results

Genetically predicted elevated levels of interleukin-17 (IL-17) and monokine induced by interferon-gamma (MIG) were associated with an increased risk of IBD[odds ratio (OR): 1.52, 95% confidence interval (CI):1.10-2.08, P =0.010 for IL-17 and OR: 1.58, 95% CI: 1.24-2.00, P = 1.60×10-4 for MIG]. Moreover, we observed suggestive associations between β-NGF and MIP-1β with the risk of Crohn's disease (OR: 0.71, 95% CI: 0.52-0.98, P = 0.039) and ulcerative colitis (OR: 1.08, 95% CI: 1.01-1.15, P= 0.019). In the reverse MR study, there was no evidence of causal effects of IBD and these cytokines.

Conclusion

Our study suggests the potential causal associations of IL-17 and MIG with IBD. Further studies are needed to determine whether IL-17 and MIG or their downstream effectors could be useful in the management of IBD.

From target discovery to clinical drug development with human genetics

The substantial investments in human genetics and genomics made over the past three decades were anticipated to result in many innovative therapies. Here we investigate the extent to which these expectations have been met, excluding cancer treatments. In our search, we identified 40 germline genetic observations that led directly to new targets and subsequently to novel approved therapies for 36 rare and 4 common conditions. The median time between genetic target discovery and drug approval was 25 years. Most of the genetically driven therapies for rare diseases compensate for disease-causing loss-of-function mutations. The therapies approved for common conditions are all inhibitors designed to pharmacologically mimic the natural, disease-protective effects of rare loss-of-function variants. Large biobank-based genetic studies have the power to identify and validate a large number of new drug targets. Genetics can also assist in the clinical development phase of drugs-for example, by selecting individuals who are most likely to respond to investigational therapies. This approach to drug development requires investments into large, diverse cohorts of deeply phenotyped individuals with appropriate consent for genetically assisted trials. A robust framework that facilitates responsible, sustainable benefit sharing will be required to capture the full potential of human genetics and genomics and bring effective and safe innovative therapies to patients quickly.

Causal association between atopic eczema and inflammatory bowel disease: A two-sample bidirectional Mendelian randomization study of the East Asian population

Observation studies have postulated that atopic eczema is associated with a risk of inflammatory bowel disease in the East Asian population; however, this association does not obviate the biases resulting from confounding effects and reverse causation. This study aimed to determine whether this association is causal in the East Asian population using a bidirectional two-sample Mendelian randomization design. Independent genetic variants obtained from public genome-wide association studies for atopic eczema (4296 cases, 163 807 controls) were extracted to estimate the causal effects on inflammatory bowel disease (2824 cases, 3719 controls) and its two main conditions: Crohn's disease (1690 cases, 3719 controls) and ulcerative colitis (1134 cases, 3719 controls). Atopic eczema was found to be strongly associated with inflammatory bowel disease (odds ratio [95% confidence interval]: 1.520 [1.179, 1.959]; p = 0.001), but not vice versa. Subtype analyses revealed that atopic eczema is significantly associated with Crohn's disease (1.650 [1.293, 2.106]; p = 0.000) but not with ulcerative colitis. Both Crohn's disease and ulcerative colitis were found to be causally related to atopic eczema; Crohn's disease could reduce the risk of atopic eczema (0.866 [0.807, 0.930]; p = 0.000) while ulcerative colitis could increase the risk of atopic eczema (1.112 [1.021, 1.212]; p = 0.015). In conclusion, this study revealed that statistically causal relationships are present between atopic eczema and inflammatory bowel disease in the East Asian population. These findings are significant for guiding the treatment of atopic eczema and inflammatory bowel disease in clinical practice.

Caspase-8-driven apoptotic and pyroptotic crosstalk causes cell death and IL-1β release in X-linked inhibitor of apoptosis (XIAP) deficiency

Genetic lesions in X-linked inhibitor of apoptosis (XIAP) pre-dispose humans to cell death-associated inflammatory diseases, although the underlying mechanisms remain unclear. Here, we report that two patients with XIAP deficiency-associated inflammatory bowel disease display increased inflammatory IL-1β maturation as well as cell death-associated caspase-8 and Gasdermin D (GSDMD) processing in diseased tissue, which is reduced upon patient treatment. Loss of XIAP leads to caspase-8-driven cell death and bioactive IL-1β release that is only abrogated by combined deletion of the apoptotic and pyroptotic cell death machinery. Namely, extrinsic apoptotic caspase-8 promotes pyroptotic GSDMD processing that kills macrophages lacking both inflammasome and apoptosis signalling components (caspase-1, -3, -7, -11 and BID), while caspase-8 can still cause cell death in the absence of both GSDMD and GSDME when caspase-3 and caspase-7 are present. Neither caspase-3 and caspase-7-mediated activation of the pannexin-1 channel, or GSDMD loss, prevented NLRP3 inflammasome assembly and consequent caspase-1 and IL-1β maturation downstream of XIAP inhibition and caspase-8 activation, even though the pannexin-1 channel was required for NLRP3 triggering upon mitochondrial apoptosis. These findings uncouple the mechanisms of cell death and NLRP3 activation resulting from extrinsic and intrinsic apoptosis signalling, reveal how XIAP loss can co-opt dual cell death programs, and uncover strategies for targeting the cell death and inflammatory pathways that result from XIAP deficiency.

Tackling Inflammatory Bowel Diseases: Targeting Proinflammatory Cytokines and Lymphocyte Homing

Inflammatory bowel diseases (IBDs) are characterized by chronic inflammatory disorders that are a result of an abnormal immune response mediated by a cytokine storm and immune cell infiltration. Proinflammatory cytokine therapeutic agents, represented by TNF inhibitors, have developed rapidly over recent years and are promising options for treating IBD. Antagonizing interleukins, interferons, and Janus kinases have demonstrated their respective advantages in clinical trials and are candidates for anti-TNF therapeutic failure. Furthermore, the blockade of lymphocyte homing contributes to the excessive immune response in colitis and ameliorates inflammation and tissue damage. Factors such as integrins, selectins, and chemokines jointly coordinate the accumulation of immune cells in inflammatory regions. This review assembles the major targets and agents currently targeting proinflammatory cytokines and lymphatic trafficking to facilitate subsequent drug development.

Interleukin-18 cytokine in immunity, inflammation, and autoimmunity: Biological role in induction, regulation, and treatment

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine involved in host defense against infections and regulates the innate and acquired immune response. IL-18 is produced by both hematopoietic and non-hematopoietic cells, including monocytes, macrophages, keratinocytes and mesenchymal cell. IL-18 could potentially induce inflammatory and cytotoxic immune cell activities leading to autoimmunity. Its elevated levels have been reported in the blood of patients with some immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, atopic dermatitis, psoriasis, and inflammatory bowel disease. In the present review, we aimed to summarize the biological properties of IL-18 and its pathological role in different autoimmune diseases. We also reported some monoclonal antibodies and drugs targeting IL-18. Most of these monoclonal antibodies and drugs have only produced partial effectiveness or complete ineffectiveness in vitro, in vivo and human studies. The ineffectiveness of these drugs targeting IL-18 may be largely due to the loophole caused by the involvement of other cytokines and proteins in the signaling pathway of many inflammatory diseases besides the involvement of IL-18. Combination drug therapies, that focus on IL-18 inhibition, in addition to other cytokines, are highly recommended to be considered as an important area of research that needs to be explored.

Mendelian randomization study for the roles of IL-18 and IL-1 receptor antagonist in the development of inflammatory bowel disease

BACKGROUND AND AIMS

IL-1 and IL-18 play important roles in intestine barrier integrity maintenance and inflammatory response. However, their net effects on the risk of IBD are still inconclusive. Here, we used Mendelian randomization (MR) approaches to investigate the causal associations of IL-18 and IL-1Ra (receptor antagonist) on the risks of IBD and subtypes.

METHODS

For IL-18, both three-sample and two-sample MR approaches were used for the causal inferences. In three-sample MR, three single nucleotide polymorphisms (SNPs) and the effect values were extracted from two quantitative trait loci (pQTL) datasets with non-overlapping populations. In two-sample MR, we extracted genetic instruments information from the same larger pQTL dataset. For IL-1Ra, we applied the two-sample MR method with summary-statistics from the larger pQTL dataset. Summary-level results of three large IBD/CD/UC genome-wide association studies in European ancestry were employed. Inverse-variance weighted method, various sensitivity analyses and meta-analysis were performed to give causal estimates, detect heterogeneity and correct for outliers.

RESULTS

We observed consistent positive causal effects of IL-18 on all three major outcomes using three-sample MR, with meta-analyses odds ratios (ORs) equal to 1.240 (IBD), 1.199 (CD) and 1.274 (UC) respectively. The two-sample MR demonstrated similar results. Moreover, genetically predicted IL-1Ra is inversely associated with the risk of IBD/UC/CD with ORs equal to 0.915 (IBD), 0.902 (CD) and 0.899 (UC) respectively in meta-analyses.

CONCLUSIONS

This study suggested genetically predicted IL-18 and IL-1Ra level are causally associated with an increased and decreased risk of IBD and subtypes.

Pattern Recognition Receptor Signaling and Cytokine Networks in Microbial Defenses and Regulation of Intestinal Barriers: Implications for Inflammatory Bowel Disease

Inflammatory bowel disease is characterized by defects in epithelial function and dysregulated inflammatory signaling by lamina propria mononuclear cells including macrophages and dendritic cells in response to microbiota. In this review, we focus on the role of pattern recognition receptors in the inflammatory response as well as epithelial barrier regulation. We explore cytokine networks that increase inflammation, regulate paracellular permeability, cause epithelial damage, up-regulate epithelial proliferation, and trigger restitutive processes. We focus on studies using patient samples as well as speculate on pathways that can be targeted to more holistically treat patients with inflammatory bowel disease.

Serum Analyte Profiles Associated With Crohn's Disease and Disease Location

BACKGROUND

Crohn's disease (CD) can affect any segment of the digestive tract but is most often localized in the ileal, ileocolonic, and colorectal regions of the intestines. It is believed that the chronic inflammation in CD is a result of an imbalance between the epithelial barrier, the immune system, and the intestinal microbiota. The aim of the study was to identify circulating markers associated with CD and/or disease location in CD patients.

METHODS

We tested 49 cytokines, chemokines, and growth factors in serum samples from 300 patients with CD and 300 controls. After quality control, analyte levels were tested for association with CD and disease location.

RESULTS

We identified 13 analytes that were higher in CD patients relative to healthy controls and that remained significant after conservative Bonferroni correction (P < 0.0015). In particular, CXCL9, CXCL1, and interleukin IL-6 had the greatest effect and were highly significant (P < 5 × 10-7). We also identified 9 analytes that were associated with disease location, with VEGF, IL-12p70, and IL-6 being elevated in patients with colorectal disease (P < 3 × 10-4).

CONCLUSIONS

Multiple serum analytes are elevated in CD. These implicate the involvement of multiple cell types from the immune, epithelial, and endothelial systems, suggesting that circulating analytes reflect the inflammatory processes that are ongoing within the gut. Moreover, the identification of distinct profiles according to disease location supports the existence of a biological difference between ileal and colonic CD, consistent with previous genetic and clinical observations.

Target Discovery for Drug Development Using Mendelian Randomization

Making drug development more efficient by identifying promising drug targets can contribute to resource savings. Identifying promising drug targets using human genetic approaches can remove barriers related to translation. In addition, genetic information can be used to identify potentially causal relationships between a drug target and disease. Mendelian randomization (MR) is a class of approaches used to identify causal associations between pairs of genetically predicted traits using data from human genetic studies. MR can be used to prioritize candidate drug targets by predicting disease outcomes and adverse events that could result from the manipulation of a drug target. The theory behind MR is reviewed, including a discussion of MR assumptions, different MR analytical methods, tests for violations of assumptions, and MR methods that can be robust to some violations of MR assumptions. A protocol to perform two-sample MR (2SMR) with summary genome-wide association study (GWAS) results is described. An example of 2SMR examining the causal relationship between low-density lipoprotein (LDL) and coronary artery disease (CAD) is provided as an illustration of the protocol.

Potential therapeutic targets to prevent organ damage in chronic pulmonary sarcoidosis

INTRODUCTION

Sarcoidosis is a granulomatous inflammatory disease with high chances of reduced quality of life, irreversible organ damage, and reduced life expectancy when vital organs are involved. Any organ system can be affected, and the lungs are most often affected. There is no preventive strategy as the exact etiology is unknown, and complex immunogenetic and environmental factors determine disease susceptibility and phenotype. Present-day treatment options originated from clinical practice and are effective in many patients. However, a substantial percentage of patients suffer from unacceptable side effects or still develop refractory, threatening pulmonary or extrapulmonary disease.

AREAS COVERED

As non-caseating granulomas, the pathological hallmark of disease, are assigned to divergent activation and regulation of the immune system, targets in relation to the possible triggers of granuloma formation and their sequelae were searched and reviewed.

EXPERT OPINION

:The immunopathogenesis underlying sarcoidosis has been a dynamic field of study. Several recent new insights give way to promising new therapeutic targets, such as certain antigenic triggers (e.g. from Aspergillus nidulans), mTOR, JAK-STAT and PPARγ pathways, the NRP2 receptor and MMP-12, which await further exploration. Clinical and trigger related phenotyping, and molecular endotyping in sarcoidosis will likely hold the key for precision medicine in the future.

Interleukin-18 and COVID-19

Vulnerability to coronavirus disease (COVID)-19 varies due to differences in interferon gamma (IFNγ) immunity. We investigated whether a key modifiable interferon precursor, interleukin-18, was related to COVID-19, overall and by severity, using Mendelian randomisation. We used four established genome-wide significant genetic predictors of interleukin-18 applied to the most recent genome-wide association study of COVID-19 (June 2021) to obtain Mendelian randomisation inverse variance weighted estimates by severity, i.e. any (cases = 112 612, non-cases = 2 474 079), hospitalised (cases = 24 274, non-cases = 2 061 529) and very severe (cases = 8779, non-cases = 1 001 875) COVID-19. To be comprehensive, we also conducted an exploratory analysis for IFNγ and two related cytokines with less well-established genetic predictors, i.e. interleukin-12 and interleukin-23. Genetically predicted interleukin-18 was associated with lower risk of any COVID-19 (odds ratio (OR) 0.96 per standard deviation, 95% confidence interval (0.94–0.99, P-value 0.004)) and of very severe COVID-19 (OR 0.88, 95% CI 0.78–0.999, P-value 0.048). Sensitivity analysis and a more liberal genetic instrument selection gave largely similar results. Few genome-wide significant genetic predictors were available for IFNγ, interleukin-12 or interleukin-23, and no associations with COVID-19 were evident. Interleukin-18 could be a modifiable target to prevent COVID-19 and should be further explored in an experimental design.

Genetic Evidence on the Association of Interleukin (IL)-1-Mediated Chronic Inflammation with Airflow Obstruction: A Mendelian Randomization Study

Preclinical studies suggest interleukin (IL)-1α/β is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, recent trials of anti-IL-1 therapies showed limited benefit for COPD. To clarify, we primarily examined total and direct effects of IL-1 and its receptors/coreceptors/receptor antagonists (IL-1/IL-1Rs) on airflow obstruction (AO) using Mendelian randomization (MR), and secondarily explored reverse causation using bidirectional MR. We selected independent cis protein quantitative trait loci (cis-pQTLs) as genetic instruments for IL-1/IL-1Rs from two proteomic genome-wide association studies (n = 11,594) of European ancestry (mean age ∼47 years). We applied those cis-pQTLs to the International COPD Genetics Consortium (n = 15,256 cases, 47,936 controls) of ∼81.9% European descent (∼57 years). No IL-1/IL-1Rs were significantly associated with AO after correction for multiple testing. However, a higher genetically predicted IL-1 receptor antagonist (IL-1Ra) was nominally associated with a 20% reduction in AO risk using univariable MR, with a larger direct effect (∼31%, i.e. not via IL-1α/β) using multivariable MR. Furthermore, higher total IL-18 binding protein (IL-18BP) was nominally associated with lower AO. Nominal total effects were also noted for higher IL-1α with lower AO and higher IL-1R1 with higher AO. Higher IL-1Ra and IL-18BP might have a role in preventing AO, but need to be contextualized.Supplemental data for this article is available online at https://doi.org/10.1080/15412555.2021.1955848 .

Elevated levels of IL-18 associated with schizophrenia and first episode psychosis: A systematic review and meta-analysis

AIM

To determine whether interleukin 18 (IL-18) is elevated in the blood of schizophrenia (SCZ) and first episode psychosis patients, as well as investigate whether this potential relationship is causal.

METHOD

We conducted a systematic review and meta-analysis of IL-18 levels in the blood of SCZ patients, comprising of both chronic and first episode psychosis (FEP) cohorts. To investigate causality, we undertook the two-sample Mendelian randomization (MR) study.

RESULTS

A total of eight studies were included in our meta-analysis, our results did indeed show an association between elevated levels of IL-18 and SCZ compared to healthy controls (Z = 3.50, P = .0005). This association remained significant in subsequent subgroup analyses for chronic (Z = 3.15, P = .002) and achieved borderline significance in FEP (Z = 1.93, P = .05) SCZ. Our MR analysis failed to detect any causal relationship between IL-18 levels and SCZ.

CONCLUSION

The results of our study demonstrate that even though IL-18 levels are elevated in SCZ patients, IL-18 levels do not seem to cause of the disorder itself. Our findings suggest that IL-18 may have utility as a biomarker of SCZ and aid in research into the early intervention of the disease.

Telomere dysfunction instigates inflammation in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory condition driven by diverse genetic and nongenetic programs that converge to disrupt immune homeostasis in the intestine. We have reported that, in murine intestinal epithelium with telomere dysfunction, DNA damage-induced activation of ataxia-telangiectasia mutated (ATM) results in ATM-mediated phosphorylation and activation of the YAP1 transcriptional coactivator, which in turn up-regulates pro-IL-18, a pivotal immune regulator in IBD pathogenesis. Moreover, individuals with germline defects in telomere maintenance genes experience increased occurrence of intestinal inflammation and show activation of the ATM/YAP1/pro-IL-18 pathway in the intestinal epithelium. Here, we sought to determine the relevance of the ATM/YAP1/pro-IL-18 pathway as a potential driver of IBD, particularly older-onset IBD. Analysis of intestinal biopsy specimens and organoids from older-onset IBD patients documented the presence of telomere dysfunction and activation of the ATM/YAP1/precursor of interleukin 18 (pro-IL-18) pathway in the intestinal epithelium. Employing intestinal organoids from healthy individuals, we demonstrated that experimental induction of telomere dysfunction activates this inflammatory pathway. In organoid models from ulcerative colitis and Crohn's disease patients, pharmacological interventions of telomerase reactivation, suppression of DNA damage signaling, or YAP1 inhibition reduced pro-IL-18 production. Together, these findings support a model wherein telomere dysfunction in the intestinal epithelium can initiate the inflammatory process in IBD, pointing to therapeutic interventions for this disease.

Telomere Dysfunction as an Initiator of Inflammation: Clues to an Age-Old Mystery

Inflammatory Bowel Disease (IBD) is a challenging medical condition that is driven by various genetic and environmental factors. Therapeutic opportunities for this disease remain limited due to the lack of in-depth understanding of the pathogenetic mechanisms and actionable targets driving the disease. Analysis of telomere dysfunctional mice and patients with genetic defects in telomere maintenance unexpectedly revealed phenotypes mirroring those observed in IBD. Molecular characterization of this model identified a pathway driven by telomere DNA damage-mediated activation of the ATM/cABL/YAP1 pathway, which directly regulates genes central to IBD pathogenesis and amenable to therapeutic intervention. This review summarizes the evidence correlating telomere dysfunction with IBD and colitis-associated cancer and proposes therapeutic opportunities for such inflammatory conditions targeting this newly identified pathway.

Non-pharmacological Strategies Against Systemic Inflammation: Molecular Basis and Clinical Evidence

Systemic inflammation is a common denominator to a variety of cardiovascular (CV) and non-CV diseases and relative risk factors, including hypertension and its control, metabolic diseases, rheumatic disorders, and those affecting the gastrointestinal tract. Besides medications, a non-pharmacological approach encompassing lifestyle changes and other complementary measures is mentioned in several updated guidelines on the management of these conditions. We performed an updated narrative review on the mechanisms behind the systemic impact of inflammation and the role of non-pharmacological, complementary measures centered on lowering systemic phlogosis for preserving or restoring a good global health. The central role of genetics in shaping the immune response is discussed in conjunction with that of the microbiome, highlighting the interdependence and mutual influences between the human genome and microbial integrity, diversity, and functions. Several plausible strategies to modulate inflammation and restore balanced crosstalk between the human genome and the microbiome are then recapitulated, including dietary measures, active lifestyle, and other potential approaches to manipulate the resident microbial community. To date, evidence from high-quality human studies is sparse to allow the unconditioned inclusion of understudied, though plausible solutions against inflammation into public health strategies for global wellness. This gap claims further focused, well-designed research targeted at unravelling the mechanisms behind future personalized medicine.

COVID-19 stokes inflammasomes

The poor success rate of treating patients with aggressive sepsis in SARS-CoV-2 infections has highlighted again the challenges of managing systemic inflammatory conditions. In this issue of JEM, Rodrigues et al. (https://doi.org/10.1084/jem.20201707) discuss the role of inflammasome activation in COVID-19 disease severity, opening new possibilities for therapeutic management of sepsis syndromes.

Experimental and Clinical Evidence of Endothelial Dysfunction in Inflammatory Bowel Disease

The endothelium has a crucial role in proper hemodynamics. Inflammatory bowel disease (IBD) is mainly a chronic inflammatory condition of the gastrointestinal tract. However, considerable evidence points to high cardiovascular risk in patients with IBD. This review positions the basic mechanisms of endothelial dysfunction in the IBD setting (both clinical and experimental). Furthermore, we review the main effects of drugs used to treat IBD in endothelial (dys)function. Moreover, we leave challenging points for enlarging the therapeutic arsenal for IBD with new or repurposed drugs that target endothelial dysfunction besides inflammation.

The evaluation of cytokines to help establish diagnosis and guide treatment of autoinflammatory and autoimmune diseases

Our knowledge of the role of cytokines in pathologic conditions has increased considerably with the emergence of molecular and genetic studies, particularly in the case of autoinflammatory monogenic diseases. Many rare disorders, considered orphan until recently, are directly related to abnormal gene regulation, and the treatment with biologic agents (biologics) targeting cytokine receptors, intracellular signaling or specific cytokines improve the symptoms of an increasing number of chronic inflammatory diseases. As it is currently impossible to systematically conduct genetic studies for all patients with autoinflammatory and autoimmune diseases, the evaluation of cytokines can be seen as a simple, less time consuming, and less expensive alternative. This approach could be especially useful when the diagnosis of syndromes of diseases of unknown etiology remains problematic. The evaluation of cytokines could also help avoid the current trial-and-error approach, which has the disadvantages of exposing patients to ineffective drugs with possible unnecessary side effects and permanent organ damages. In this review, we discuss the various possibilities, as well as the limitations of evaluating the cytokine profiles of patients suffering from autoinflammatory and autoimmune diseases, with methods such as direct detection of cytokines in the plasma/serum or following ex vivo stimulation of PBMCs leading to the production of their cytokine secretome. The patients' secretome, combined with biomarkers ranging from genetic and epigenetic analyses to immunologic biomarkers, may help not only the diagnosis but also guide the choice of biologics for more efficient and rapid treatments.