Steroid hormone catabolites activate the pyrin inflammasome through a non-canonical mechanism

The needed daily dose of colchicine in patients with Familial Mediterranean Fever may be higher in women: a study on behalf of the JIR cohort

BACKGROUND

At present, there are no data on the relationship between colchicine dose and weight in patients with Familial Mediterranean Fever (FMF). We aimed at describing the daily colchicine dose in a cohort of FMF patients.

METHODS

From 2016 to 2023, a retrospective evaluation of prospectively followed homozygous FMF patients at the French National Reference Centre was performed.

RESULTS AND CONCLUSIONS

Out of 272 patients, 149 were women (57.8%), with a mean age of 43 years old. The mean weight was 67.8 kg and body mass index 24,2 kg/m². Colchicine was taken by 96% of patients. A subgroup of 30 patients received 2.5 mg/day: they were mostly women (n = 23; 76.7%; p = 0.018), with a lower mean weight (p = 0.019); indeed, 26/30 (87%) weighed < 50 kg. Female sex correlated with higher values of daily colchicine dose (p = 0.0208); weight was not associated with colchicine dose (p = 0.4073). No toxicity has been noted in patients treated with 2.5 mg/day, including patients weighing < 50 kg, and most of these patients were women. We may speculate that the clinical picture of female patients requiring an increased dose of colchicine may be related to the hormonal background, with a possible exaggeration of pyrin activation. This is the first study to examine the question of colchicine dosage in relation to weight of FMF adult patients and to highlight a possible link with female gender. We advise clinicians to explain that colchicine treatment may be used daily up to 2.5 mg without toxicity.

A treatment algorithm for familial Mediterranean fever patients with menstruation-associated attacks

OBJECTIVES

FMF is characterized by febrile polyserositis attacks. Menstruation could be a trigger for attacks. We aimed to analyse the features of adolescent FMF patients with menstruation-associated attacks and propose a management algorithm.

METHODS

All female FMF patients who had menarche and visited the Pediatric Rheumatology Unit between January and December 2022, were included into this study. Demographics, general characteristics and the features of menstrual cycle and FMF attacks were noted.

RESULTS

A total of 151 female FMF patients were included. Thirty-five (23.2%) had menstruation-associated attacks. Fever and arthritis were less frequent during the menstruation-associated attacks than the attacks not associated with menstruation in these patients (65.7% vs 88.6%, P = 0.01 and 2.9% vs 20%, P = 0.04, respectively). Patients with menstruation-associated FMF attacks were younger at symptom onset and diagnosis (2.5 vs 5 years, P = 0.004 and 4 vs 7 years, P = 0.01; respectively), had a higher rate of dysmenorrhea (74.3% vs 38.8%, P < 0.001, respectively) and higher pre- and post-menarche attack frequency (4 vs 2 and 10 vs 0, respectively; P < 0.001 for both) than patients whose attacks were not associated with menstruation. The interventions for menstruation-associated attacks included initiating colchicine, increasing the dose of colchicine, switching from coated to compressed colchicine tablets or adding anti-interleukin 1 drugs and initiating on-demand non-steroidal anti-inflammatory drugs, on-demand glucocorticoids and on-demand anakinra. On-demand therapies were beneficial in controlling menstruation-associated attacks.

CONCLUSIONS

This is the largest cohort of adolescent FMF patients with menstruation-associated attacks. Severe FMF may cause a tendency to this association. On-demand therapies could be preferred in the management.

New Diseases Linked to MEFV Variants or Pyrinopathies

Autoinflammatory diseases (AIDs) are characterized by dysregulation of innate immunity, leading to systemic inflammation. Familial Mediterranean fever (FMF) is the most common AID, associated with variants in exon 10 of MEFV. This gene codes for pyrin, a key protein in the inflammasome of the same name, involved in the innate immune response. Since the discovery of FMF, many other pathogenic variants of MEFV have been identified. These variants, apart from exon 10, are responsible for a variety of AIDs known as pyrin-associated AIDs or pyrinopathies. Variants in exon 10, 8, 5, and 3 are associated with dominant forms of FMF. Other inflammatory clinical pictures not resembling typical FMF are possible: pyrin-associated autoinflammation with neutrophilic dermatosis is characterized by febrile attacks and severe neutrophilic dermatosis associated with variants in exon 2; pyrin-associated autoinflammation with hypereosinophilia was described among patients displaying severe inflammation and hypereosinophilia-associated variants in exon 2, different from pyrin-associated autoinflammation with neutrophilic dermatosis; and pyrin-associated autoinflammation associated with neuroinflammation manifests with systemic inflammation, serositis, and neuroinflammation associated with variants in exon 9. Somatic forms of FMF have also been described. We present here a review of the literature on the various AIDs associated with pathogenic MEFV variants and propose a practical approach to the genetic diagnosis of MEFV-associated AIDs.

Investigation of dysmenorrhea in adolescent girls with familial Mediterranean fever: a comparative study with healthy controls

Perimenstrual attacks have been reported in up to 15% of patients with FMF, suggesting that menstruation may be a trigger for FMF attacks. The aim of this study was to investigate menstrual period patterns and dysmenorrhea in adolescents with FMF in comparison to their healthy peers. This cross-sectional case-control study included 73 FMF patients and 70 age- and body mass index-matched controls. A structured questionnaire was designed to assess menstrual history, the frequency and severity of dysmenorrhea, symptoms related to dysmenorrhea, and the clinical features of FMF attacks. Dysmenorrhea was present in 90.4% of patients and 95.7% of controls (p = 0.32). Pain was reported during every cycle or every two cycles by 83.3% of patients versus 65.6% of controls (p = 0.02). Fever (27.4% vs. 10.3%, p = 0.01) was significantly more frequent in patients, while musculoskeletal symptoms (46.6% vs. 66.2%, p = 0.02), fatigue (53.4% vs. 83.8%, p < 0.001), and sleep disturbances (19.2% vs. 50.7%, p < 0.001) were more common in controls. Notably, FMF patients reported heavier bleeding episodes with higher number of sanitary pads used during menstruation (p = 0.001). Menstruation-associated FMF attacks were reported by 37% of patients, with 14.8% experiencing them every cycle. Exon 10 variants were present in 86.3% of cases, with 23.3% being homozygous. The frequency and character of dysmenorrhea did not differ significantly according to genetic profiles.

CONCLUSIONS

This study is the first to investigate menstrual patterns and dysmenorrhea symptoms in adolescent FMF patients compared to their healthy peers. Dysmenorrhea is prevalent in FMF patients with distinct menstrual characteristics, including more frequent fever and heavier bleeding.

WHAT IS KNOWN

• Menstruation may trigger Familial Mediterranean Fever (FMF) attacks in a subset of patients, but the relationship between FMF and dysmenorrhea remains unclear. • Some studies suggest that inflammation associated with FMF could contribute to menstrual pain and abnormalities, but comprehensive data in adolescents are limited.

WHAT IS NEW

• This study is the first to compare menstrual patterns and dysmenorrhea characteristics between adolescent FMF patients and healthy controls, highlighting distinct menstrual symptoms in FMF patients. • FMF patients experience more frequent febrile episodes and heavier menstrual bleeding compared to their healthy peers, but dysmenorrhea characteristics are not influenced by specific MEFV gene mutations.

Serum metabolites and risk of aortic dissection: a two-sample Mendelian randomization study

Purpose

Acute aortic dissection is a serious cardiovascular emergency with a high mortality rate. Its pathogenesis is complex and remains unclear. This study aimed to assess the connection between the levels of genetically predicted circulating metabolites and the risk of aortic dissection.

Methods

A two-sample Mendelian randomization (MR) approach was employed to determine the causal relationship between genetically determined metabolites and the incidence of aortic dissection. In total, 1091 specific metabolites were identified from genome-wide association study (GWAS) data and aortic dissection involving 207,011 participants. Causal inference was performed using the inverse-variance weighted (IVW) method, supplemented by extensive sensitivity analyses to ensure the validity of the results. In addition, pathway analysis was performed using the Metaconflict 5.0 platform.

Results

We found that six serum metabolites were genetically associated with an increased risk of aortic dissection, whereas eleven metabolites were associated with a decreased risk, and these associations were confirmed by rigorous sensitivity analyses. Reverse MR analysis indicated that aortic dissection could decrease the serum level of kynurenine (odds ratio (OR) = 0.9675, 95% confidence interval (CI) 0.9383-0.9976, P IVW = 0.0344). The metabolic pathways suggested that steroid hormone biosynthesis, steroidogenesis, and bile acid biosynthesis are involved in the pathogenesis of aortic dissection.

Conclusion

This MR analysis revealed a significant association between seventeen serum metabolites and the risk of aortic dissection. Further research is needed to fully elucidate the complex mechanisms underlying these associations.

Graphical Abstract

Supplementary information

The online version contains supplementary material available at 10.1007/s12055-024-01807-5.

Guards and decoys: RIPoptosome and inflammasome pathway regulators of bacterial effector-triggered immunity

Virulent microbes produce proteins that interact with host cell targets to promote pathogenesis. For example, virulent bacterial pathogens have proteins called effectors that are typically enzymes and are secreted into host cells. To detect and respond to the activities of effectors, diverse phyla of host organisms evolved effector-triggered immunity (ETI). In ETI, effectors are often sensed indirectly by detection of their virulence activities in host cells. ETI mechanisms can be complex and involve several classes of host proteins. Guards monitor the functional or physical integrity of another host protein, the guardee or decoy, and become activated to initiate an immune response when the guardee or decoy is modified or disrupted by an effector. A guardee typically has an intrinsic anti-pathogen function and is the intended target of an effector. A decoy structurally mimics a host protein that has intrinsic anti-pathogen activity and is unintentionally targeted by an effector. A decoy can be an individual protein, or a protein domain integrated into a guard. Here, we review the origins of ETI and focus on 5 mechanisms, in which the key steps of a pathway can include activation of a caspase by a RIPoptosome or inflammasome, formation of pores in the plasma membrane, release of cytokines and ending in cell death by pyroptosis. Survey of the 5 mechanisms, which have been shown to be host protective in mouse models of bacterial infection, reveal how distinct regulators of RIPoptosome or inflammasome pathways can act as guards or integrated decoys to trigger ETI. Common themes are highlighted and the limited mechanistic understanding of ETI bactericidal activity is discussed.

Inflammasome components as new therapeutic targets in inflammatory disease

Inflammation drives pathology in many human diseases for which there are no disease-modifying drugs. Inflammasomes are signalling platforms that can induce pathological inflammation and tissue damage, having potential as an exciting new class of drug targets. Small-molecule inhibitors of the NLRP3 inflammasome that are now in clinical trials have demonstrated proof of concept that inflammasomes are druggable, and so drug development programmes are now focusing on other key inflammasome molecules. In this Review, we describe the potential of inflammasome components as candidate drug targets and the novel inflammasome inhibitors that are being developed. We discuss how the signalling biology of inflammasomes offers mechanistic insights for therapeutic targeting. We also discuss the major scientific and technical challenges associated with drugging these molecules during preclinical development and clinical trials.

Pyrin-associated autoinflammation with neutrophilic dermatosis: A case report

Pyrin-associated autoinflammation with neutrophilic dermatosis (PAAND) is a rare, monogenic, autoinflammatory disorder caused by mutations in exon 2 of the MEFV gene. Characterized by neutrophilic dermatosis, recurrent fever, and arthralgia, this syndrome presents a diagnostic challenge due to its low prevalence and varied clinical manifestations. Here, we present the case of a 49-year-old Spanish male with severe hidradenitis suppurativa and pyoderma gangrenosum with a heterozygous variant (p.E244K) in the MEFV gene, consistent with PAAND syndrome. This variant has only been documented in one other case with notable similarities. Both patients share Spanish ancestry and present a severe form of hidradenitis suppurativa. Treatment of the disorder presents challenges due to its variable response to standard therapies. Anti-interleukin-1 agents, such as anakinra or anti-tumor necrosis factor (TNF)-α are the therapeutic approaches supported by the most substantial evidence. Our findings highlight the importance of genetic evaluation of MEFV mutations in individuals with neutrophilic dermatosis and systemic symptoms.

The past 25 years in paediatric rheumatology: insights from monogenic diseases

The past 25 years have seen major novel developments in the field of paediatric rheumatology. The concept of autoinflammation was introduced to this field, and medicine more broadly, with studies of familial Mediterranean fever, the most common autoinflammatory disease globally. New data on the positive evolutionary selection of familial Mediterranean fever-associated genetic variants might be pertinent to mild gain-of-function variants reported in other disease-associated genes. Genetic studies have unveiled the complexity of human heritability to inflammation and flourishing data from rare monogenic disorders have contributed to a better understanding of general disease mechanisms in paediatric rheumatic conditions. Beyond genomics, the application of other 'omics' technologies, including transcriptomics, proteomics and metabolomics, has generated an enormous dataset that can be applied to the development of new therapies and in the practice of precision medicine. Novel biomarkers for monitoring disease activity and progression have also emerged. A surge in the development of targeted biologic therapies has led to durable remission and improved prognosis for many diseases that in the past caused major complications. Last but not least, the COVID-19 pandemic has affected paediatric rheumatology practice and has sparked new investigations into the link between viral infections and unregulated inflammatory responses in children.

New and future perspectives in familial Mediterranean fever and other autoinflammatory diseases

Systemic autoinflammatory diseases are a group of disorders characterized by sterile episodes of inflammation resulting from defects in the innate immune system. In contrast to classical autoimmune diseases, where circulating autoantibodies and the adaptive immune system are involved, these conditions involve excessive presence of proinflammatory cytokines leading to inflammatory attacks. Excessive cytokine production, functional mutations in regulatory pathways, excessive interferon production, defects in the nuclear factor-kappa B signaling pathway, abnorARCHmal protein folding, and complement activation are the mechanisms leading to autoinflammatory diseases. A defect in the mTOR pathway and trained immunity are newly discovered possible causes in pathogenesis. Early onset and severe forms of classical rheumatological diseases have been more frequently associated with autoinflammatory diseases in the last decade. Therefore, monogenic autoinflammatory diseases should be considered in rheumatic diseases with family history, consanguinity, early onset, and severe disease. The combination of functional and genotyping research will help to identify unclassified patients. The optimal treatment strategy remains uncertain, functional studies such as interferon signature and cytokine profiling, may prove valuable in guiding the treatment process. Stem cell transplantation strategies in autoinflammatory diseases with partial response to biological therapies can be considered. Autoinflammatory diseases are becoming increasingly complex and are bringing new perspectives to already known rheumatic diseases. Although we have effective treatments, we are still far from personalized recommendations.

5β-Dihydrosteroids: Formation and Properties

5β-Dihydrosteroids are produced by the reduction of Δ4-3-ketosteroids catalyzed by steroid 5β-reductase (AKR1D1). By analogy with steroid 5α-reductase, genetic deficiency exists in AKR1D1 which leads to errors in newborn metabolism and in this case to bile acid deficiency. Also, like the 5α-dihydrosteroids (e.g., 5α-dihydrotestosterone), the 5β-dihydrosteroids produced by AKR1D1 are not inactive but regulate ligand access to nuclear receptors, can act as ligands for nuclear and membrane-bound receptors, and regulate ion-channel opening. For example, 5β-reduction of cortisol and cortisone yields the corresponding 5β-dihydroglucocorticoids which are inactive on the glucocorticoid receptor (GR) and provides an additional mechanism of pre-receptor regulation of ligands for the GR in liver cells. By contrast, 5β-pregnanes can act as neuroactive steroids at the GABAA and NMDA receptors and at low-voltage-activated calcium channels, act as tocolytic agents, have analgesic activity and act as ligands for PXR, while bile acids act as ligands for FXR and thereby control cholesterol homeostasis. The 5β-androstanes also have potent vasodilatory properties and work through blockade of Ca2+ channels. Thus, a preference for 5β-dihydrosteroids to work at the membrane level exists via a variety of mechanisms. This article reviews the field and identifies gaps in knowledge to be addressed in future research.

The Impact of NLRP3 Inflammasome on Osteoblasts and Osteogenic Differentiation: A Literature Review

Osteoblasts (OBs), which are a crucial type of bone cells, derive from bone marrow mesenchymal stem cells (MSCs). Accumulating evidence suggests inflammatory cytokines can inhibit the differentiation and proliferation of OBs, as well as interfere with their ability to synthesize bone matrix, under inflammatory conditions. NLRP3 inflammasome is closely associated with cellular pyroptosis, which can lead to excessive release of pro-inflammatory cytokines, causing tissue damage and inflammatory responses, however, the comprehensive roles of NLRP3 inflammasome in OBs and their differentiation have not been fully elucidated, making targeting NLRP3 inflammasome approaches to treat diseases related to OBs uncertain. In this review, we provide a summary of NLRP3 inflammasome activation and its impact on OBs. We highlight the significant roles of NLRP3 inflammasome in regulating OBs differentiation and function. Furthermore, current available strategies to affect OBs function and osteogenic differentiation targeting NLRP3 inflammasome are listed and analyzed. Finally, through the prospective discussion, we seek to provide novel insights into the crucial role of NLRP3 inflammasome in diseases related to OBs and offer valuable information for devising treatment strategies.

l-Theanine Prevents Colonic Damage via NF-κB/MAPK Signaling Pathways Induced by a High-Fat Diet in Rats

SCOPE

l-Theanine (l-Thea) is an amino acid which is naturally present in tea leaves. It has been associated with possible health advantages, including obesity prevention, but the underlying molecular mechanisms have not been elucidated.

METHODS AND RESULTS

A multiomics approach is utilized to examine the mechanism by which l-Thea exerts its antiobesity effects. This study reveals that l-Thea administration significantly ameliorates high-fat diet (HFD)-induced obesity in rats by improving body weight and hyperlipidemia. l-Thea mitigates HFD-induced inflammation and reverses hepatic and colonic damage, and intestinal barrier. This research verifies that the preventive effect of l-Thea on obesity in rats induced by an HFD with colitis is accomplished by suppressing the phosphorylation of important proteins in the NF-κB/mitogen-activated protein kinase (MAPK) pathways. Metabolome analysis reveals that l-Thea regulates HFD-induced metabolic disorders, specifically through modulation of steroid hormone biosynthesis. Microbiome analysis reveals that l-Thea mitigates HFD-induced dysbiosis by increasing the relative abundance of obesity-associated probiotic bacteria, including Blautia coccoides and Lactobacillus murinus, while simultaneously suppressing the abundance of pathogenic bacteria.

CONCLUSIONS

l-Thea alleviates colitis generated by an HFD by restoring the integrity of the intestinal barrier, suppressing inflammation through regulation of MAPK/NF-κB signaling pathways, and enhancing microbial metabolism in colon.

Cellular models in autoinflammatory disease research

Systemic autoinflammatory diseases are a heterogeneous group of rare genetic disorders caused by dysregulation of the innate immune system. Understanding the complex mechanisms underlying these conditions is critical for developing effective treatments. Cellular models are essential for identifying new conditions and studying their pathogenesis. Traditionally, these studies have used primary cells and cell lines of disease-relevant cell types, although newer induced pluripotent stem cell (iPSC)-based models might have unique advantages. In this review, we discuss the three cellular models used in autoinflammatory disease research, their strengths and weaknesses, and their applications to inform future research in the field.

The pyrin inflammasome, a leading actor in pediatric autoinflammatory diseases

The activation of the pyrin inflammasome represents a highly intriguing mechanism employed by the innate immune system to effectively counteract pathogenic agents. Despite its key role in innate immunity, pyrin has also garnered significant attention due to its association with a range of autoinflammatory diseases (AIDs) including familial Mediterranean fever caused by disruption of the MEFV gene, or in other genes involved in its complex regulation mechanisms. Pyrin activation is strictly dependent on homeostasis-altering molecular processes, mostly consisting of the disruption of the small Ras Homolog Family Member A (RhoA) GTPases by pathogen toxins. The downstream pathways are regulated by the phosphorylation of specific pyrin residues by the kinases PKN1/2 and the binding of the chaperone 14-3-3. Furthermore, a key role in pyrin activation is played by the cytoskeleton and gasdermin D, which is responsible for membrane pores in the context of pyroptosis. In addition, recent evidence has highlighted the role of steroid hormone catabolites and alarmins S100A8/A9 and S100A12 in pyrin-dependent inflammation. The aim of this article is to offer a comprehensive overview of the most recent evidence on the pyrin inflammasome and its molecular pathways to better understand the pathogenesis behind the significant group of pyrin-related AIDs.

Recent Insights in Pyrin Inflammasome Activation: Identifying Potential Novel Therapeutic Approaches in Pyrin-Associated Autoinflammatory Syndromes

Pyrin is a cytosolic protein encoded by the MEFV gene, predominantly expressed in innate immune cells. Upon activation, it forms an inflammasome, a multimolecular complex that enables the activation and secretion of IL-1β and IL-18. In addition, the Pyrin inflammasome activates Gasdermin D leading to pyroptosis, a highly pro-inflammatory cell death. Four autoinflammatory syndromes are associated with Pyrin inflammasome dysregulation: familial Mediterranean fever, hyper IgD syndrome/mevalonate kinase deficiency, pyrin-associated autoinflammation with neutrophilic dermatosis, and pyogenic arthritis, pyoderma gangrenosum, and acne syndrome. In this review, we discuss recent advances in understanding the molecular mechanisms regulating the two-step model of Pyrin inflammasome activation. Based on these insights, we discuss current pharmacological options and identify a series of existing molecules with therapeutic potential for the treatment of pyrin-associated autoinflammatory syndromes.

Mutations in the B30.2 and the central helical scaffold domains of pyrin differentially affect inflammasome activation

Familial Mediterranean Fever (FMF) is the most common monogenic autoinflammatory disorder. FMF is caused by mutations in the MEFV gene, encoding pyrin, an inflammasome sensor. The best characterized pathogenic mutations associated with FMF cluster in exon 10. Yet, mutations have been described along the whole MEFV coding sequence. Exon 10 encodes the B30.2 domain of the pyrin protein, but the function of this human-specific domain remains unclear. Pyrin is an inflammasome sensor detecting RhoA GTPase inhibition following exposure to bacterial toxins such as TcdA. Here, we demonstrate that the B30.2 domain is dispensable for pyrin inflammasome activation in response to this toxin. Deletion of the B30.2 domain mimics the most typical FMF-associated mutation and confers spontaneous inflammasome activation in response to pyrin dephosphorylation. Our results indicate that the B30.2 domain is a negative regulator of the pyrin inflammasome that acts independently from and downstream of pyrin dephosphorylation. In addition, we identify the central helical scaffold (CHS) domain of pyrin, which lies immediately upstream of the B30.2 domain as a second regulatory domain. Mutations affecting the CHS domain mimic pathogenic mutations in the B30.2 domain and render the pyrin inflammasome activation under the sole control of the dephosphorylation. In addition, specific mutations in the CHS domain strongly increase the cell susceptibility to steroid catabolites, recently described to activate pyrin, in both a cell line model and in monocytes from genotype-selected FMF patients. Taken together, our work reveals the existence of two distinct regulatory regions at the C-terminus of the pyrin protein, that act in a distinct manner to regulate positively or negatively inflammasome activation. Furthermore, our results indicate that different mutations in pyrin regulatory domains have different functional impacts on the pyrin inflammasome which could contribute to the diversity of pyrin-associated autoinflammatory diseases.