Fibroblast-like synoviocytes orchestrate daily rhythmic inflammation in arthritis.

Rheumatoid arthritis is a chronic inflammatory disease that shows characteristic diurnal variation in symptom severity, where joint resident fibroblast-like synoviocytes (FLS) act as important mediators of arthritis pathology. We investigate the role of FLS circadian clock function in directing rhythmic joint inflammation in a murine model of inflammatory arthritis. We demonstrate FLS time-of-day-dependent gene expression is attenuated in arthritic joints, except for a subset of disease-modifying genes. The deletion of essential clock gene Bmal1 in FLS reduced susceptibility to collagen-induced arthritis but did not impact symptomatic severity in affected mice. Notably, FLS Bmal1 deletion resulted in loss of diurnal expression of disease-modulating genes across the joint, and elevated production of MMP3, a prognostic marker of joint damage in inflammatory arthritis. This work identifies the FLS circadian clock as an influential driver of daily oscillations in joint inflammation, and a potential regulator of destructive pathology in chronic inflammatory arthritis.

Superficial CD34 fibroblastic tumors and PRDM10-rearranged soft tissue neoplasm: An evolving diagnosis.

Superficial CD34 fibroblastic tumors (SCD34FT) and PRDM10-rearranged tumors (PRTs) are mesenchymal tumors that have recently received increased scientific attention due to their irrefutable similarities yet debatable relationship. A 74-year-old male presented to the dermatology clinic with a violaceous, well-defined nodule on the left medial knee of 2-year duration. Shave biopsy demonstrated spindle cells arranged in a vaguely storiform pattern forming fascicles. Immunohistochemical stains were positive for vimentin, CD68, CD10, and CD34 diffusely. ERG, S-100, HMB45, and SOX-10 were negative. Molecular studies identified a mediator complex subunit 12 (MED12)-PR/SET Domain 10 (PRDM10) gene fusion thus favoring confirming the diagnosis of a PRT. Our patient underwent wide local excision with negative margins and had no complications. This case aims to provide context for considering SCD34FT and PRT as intersecting entities and to discuss a diagnostic approach when encountering these tumors.

Frequency and features of malignant tumors clinically mimicking cutaneous cysts: A retrospective chart review.

BACKGROUND: Many cutaneous lesions are clinically suspected as "cyst"; however, following histopathological examination, are found to be more significant lesions. Here, we examine the frequency and features of malignancies with cutaneous cysts in the clinical differential. METHODS: A retrospective study of surgical pathology specimens at the James A. Haley Veterans' Hospital from January 2018 to December 2022 was conducted. Cutaneous specimens containing the clinical diagnosis of "cyst" were included. The clinicopathological features were summarized. RESULTS: Premalignant or malignant neoplasms accounted for 4.5% of all specimens submitted with cysts in the clinical differential. Most cyst-mimicking cancers were basal cell carcinoma (BCC) or squamous cell carcinoma (SCC); however, cancers with poorer prognoses, such as Merkel cell carcinoma and melanoma, also clinically masqueraded as cysts. The BCCs were predominately nodular, and the SCCs were largely well-differentiated and invasive. Many exhibited clinical signs and symptoms compatible with benign cysts, such as central punctum, pain, and rapid growth. Identified risk factors included history of prior non-melanoma skin cancer diagnosis, previous excision, and immunosuppression. CONCLUSIONS: Many lesions clinically concerning cutaneous cysts were found to be malignancies following histopathological review. Accordingly, following biopsy all cyst-like lesions should be examined microscopically, especially in certain clinical contexts in which the incidence of skin cancer is increased.

Consequences of collagen induced inflammatory arthritis on circadian regulation of the gut microbiome.

The gut microbiota is important for host health and immune system function. Moreover autoimmune diseases, such as rheumatoid arthritis, are associated with significant gut microbiota dysbiosis, although the causes and consequences of this are not fully understood. It has become clear that the composition and metabolic outputs of the microbiome exhibit robust 24 h oscillations, a result of daily variation in timing of food intake as well as rhythmic circadian clock function in the gut. Here, we report that experimental inflammatory arthritis leads to a re-organization of circadian rhythmicity in both the gut and associated microbiome. Mice with collagen induced arthritis exhibited extensive changes in rhythmic gene expression in the colon, and reduced barrier integrity. Re-modeling of the host gut circadian transcriptome was accompanied by significant alteration of the microbiota, including widespread loss of rhythmicity in symbiont species of Lactobacillus, and alteration in circulating microbial derived factors, such as tryptophan metabolites, which are associated with maintenance of barrier function and immune cell populations within the gut. These findings highlight that altered circadian rhythmicity during inflammatory disease contributes to dysregulation of gut integrity and microbiome function.

ClinCirc identifies alterations of the circadian peripheral oscillator in critical care patients.

BackgroundAssessing circadian rhythmicity from infrequently sampled data is challenging; however, these types of data are often encountered when measuring circadian transcripts in hospitalized patients.MethodsWe present ClinCirc. This method combines 2 existing mathematical methods (Lomb-Scargle periodogram and cosinor) sequentially and is designed to measure circadian oscillations from infrequently sampled clinical data. The accuracy of this method was compared against 9 other methods using simulated and frequently sampled biological data. ClinCirc was then evaluated in 13 intensive care unit (ICU) patients as well as in a separate cohort of 29 kidney-transplant recipients. Finally, the consequences of circadian alterations were investigated in a retrospective cohort of 726 kidney-transplant recipients.ResultsClinCirc had comparable performance to existing methods for analyzing simulated data or clock transcript expression of healthy volunteers. It had improved accuracy compared with the cosinor method in evaluating circadian parameters in PER2:luc cell lines. In ICU patients, it was the only method investigated to suggest that loss of circadian oscillations in the peripheral oscillator was associated with inflammation, a feature widely reported in animal models. Additionally, ClinCirc was able to detect other circadian alterations, including a phase shift following kidney transplantation that was associated with the administration of glucocorticoids. This phase shift could explain why a significant complication of kidney transplantation (delayed graft dysfunction) oscillates according to the time of day kidney transplantation is performed.ConclusionClinCirc analysis of the peripheral oscillator reveals important clinical associations in hospitalized patients.FundingUK Research and Innovation (UKRI), National Institute of Health Research (NIHR), Engineering and Physical Sciences Research Council (EPSRC), National Institute on Academic Anaesthesia (NIAA), Asthma+Lung UK, Kidneys for Life.

Chronotype in Patients With Immune-Mediated Inflammatory Disease: A Systematic Review.

Immune-mediated inflammatory diseases (IMIDs) such as rheumatoid arthritis, inflammatory bowel disease, and asthma share common pathophysiological pathways characterized by chronic inflammation and subsequent tissue damage involving multiple body sites. Circadian rhythms are 24-h body cycles that regulate immune activity and control the magnitude of immune response based on time of day. Chronotype is a person's individual circadian phase preference, ranging from morningness to eveningness, which is known to influence the risk of cardiometabolic and mental health disease. We systematically reviewed the literature to assess the association of questionnaire-based chronotype and patients with IMID. A comprehensive search of MEDLINE and Embase identified 12 studies meeting the inclusion criteria, conducted in 7 countries and covering 4 IMIDs to include 15,625 IMID patients and 410,783 healthy controls. Results showed that later chronotype may be a risk factor for worse quality of life and increased symptom burden in patients with IMIDs. In addition, chronotype may be a risk factor for IMID incidence, but the direction and magnitude of this effect were not consistent across individual IMIDs. Chronotype assessment could contribute to risk stratification in patients with IMIDs. Cross-disciplinary collaboration to understand the role of circadian rhythms and chronotype in driving common inflammatory pathways could help to improve outcomes for patients with IMIDs.

Rhythmicity of intestinal IgA responses confers oscillatory commensal microbiota mutualism.

Interactions between the mammalian host and commensal microbiota are enforced through a range of immune responses that confer metabolic benefits and promote tissue health and homeostasis. Immunoglobulin A (IgA) responses directly determine the composition of commensal species that colonize the intestinal tract but require substantial metabolic resources to fuel antibody production by tissue-resident plasma cells. Here, we demonstrate that IgA responses are subject to diurnal regulation over the course of a circadian day. Specifically, the magnitude of IgA secretion, as well as the transcriptome of intestinal IgA+ plasma cells, was found to exhibit rhythmicity. Oscillatory IgA responses were found to be entrained by time of feeding and were also found to be in part coordinated by the plasma cell-intrinsic circadian clock via deletion of the master clock gene Arntl. Moreover, reciprocal interactions between the host and microbiota dictated oscillatory dynamics among the commensal microbial community and its associated transcriptional and metabolic activity in an IgA-dependent manner. Together, our findings suggest that circadian networks comprising intestinal IgA, diet, and the microbiota converge to align circadian biology in the intestinal tract and to ensure host-microbial mutualism.

Chronic inflammatory arthritis drives systemic changes in circadian energy metabolism.

Chronic inflammation underpins many human diseases. Morbidity and mortality associated with chronic inflammation are often mediated through metabolic dysfunction. Inflammatory and metabolic processes vary through circadian time, suggesting an important temporal crosstalk between these systems. Using an established mouse model of rheumatoid arthritis, we show that chronic inflammatory arthritis results in rhythmic joint inflammation and drives major changes in muscle and liver energy metabolism and rhythmic gene expression. Transcriptional and phosphoproteomic analyses revealed alterations in lipid metabolism and mitochondrial function associated with increased EGFR-JAK-STAT3 signaling. Metabolomic analyses confirmed rhythmic metabolic rewiring with impaired ß-oxidation and lipid handling and revealed a pronounced shunt toward sphingolipid and ceramide accumulation. The arthritis-related production of ceramides was most pronounced during the day, which is the time of peak inflammation and increased reliance on fatty acid oxidation. Thus, our data demonstrate that localized joint inflammation drives a time-of-day­dependent build-up of bioactive lipid species driven by rhythmic inflammation and altered EGFR-STAT signaling.

Adaptive immunity, chronic inflammation and the clock.

The adaptive arm of the immune system facilitates recognition of specific foreign pathogens and, via the action of T and B lymphocytes, induces a fine-tuned response to target the pathogen and develop immunological memory. The functionality of the adaptive immune system exhibits daily 24-h variation both in homeostatic processes (such as lymphocyte trafficking and development of T lymphocyte subsets) and in responses to challenge. Here, we discuss how the circadian clock exerts influence over the function of the adaptive immune system, considering the roles of cell intrinsic clockwork machinery and cell extrinsic rhythmic signals. Inappropriate or misguided actions of the adaptive immune system can lead to development of autoimmune diseases such as rheumatoid arthritis, ulcerative colitis and multiple sclerosis. Growing evidence indicates that disturbance of the circadian clock has negative impact on development and progression of these chronic inflammatory diseases and we examine current understanding of clock-immune interactions in the setting of these inflammatory conditions. A greater appreciation of circadian control of adaptive immunity will facilitate further understanding of mechanisms driving daily variation in disease states and drive improvements in the diagnosis and treatment of chronic inflammatory diseases.

Parasites-The importance of time.

The special edition of Parasite Immunology 'Parasites-The importance of time' embraces the intersection between three established research disciplines-parasitology, immunology, and circadian biology. Each of these research areas has a longstanding history littered with landmark discoveries with the intersect between the three bringing exciting findings and new questions and perhaps even a greater sense of awe in terms of how parasites have evolved to interact and live with their hosts.

Circadian rhythms in immunity and host-parasite interactions.

The mammalian immune system adheres to a 24 h circadian schedule, exhibiting daily rhythmic patterns in homeostatic immune processes, such as immune cell trafficking, as well as the inflammatory response to infection. These diurnal rhythms are driven by endogenous molecular clocks within immune cells which are hierarchically coordinated by a light-entrained central clock in the suprachiasmatic nucleus of the hypothalamus and responsive to local rhythmic cues including temperature, hormones and feeding time. Circadian control of immunity may enable animals to anticipate daily pathogenic threat from parasites and gate the magnitude of the immune response, potentially enhancing fitness. However, parasites also strive for optimum fitness and some may have co-evolved to benefit from host circadian timing mechanisms, possibly via the parasites' own intrinsic molecular clocks. In this review, we summarize the current knowledge surrounding the influence of the circadian clock on the mammalian immune system and the host-parasitic interaction. We also discuss the potential for chronotherapeutic strategies in the treatment of parasitic diseases.

The histone methyltransferase Ezh2 restrains macrophage inflammatory responses.

Robust inflammatory responses are critical to survival following respiratory infection, with current attention focused on the clinical consequences of the Coronavirus pandemic. Epigenetic factors are increasingly recognized as important determinants of immune responses, and EZH2 is a prominent target due to the availability of highly specific and efficacious antagonists. However, very little is known about the role of EZH2 in the myeloid lineage. Here, we show EZH2 acts in macrophages to limit inflammatory responses to activation, and in neutrophils for chemotaxis. Selective genetic deletion in macrophages results in a remarkable gain in protection from infection with the prevalent lung pathogen, pneumococcus. In contrast, neutrophils lacking EZH2 showed impaired mobility in response to chemotactic signals, and resulted in increased susceptibility to pneumococcus. In summary, EZH2 shows complex, and divergent roles in different myeloid lineages, likely contributing to the earlier conflicting reports. Compounds targeting EZH2 are likely to impair mucosal immunity; however, they may prove useful for conditions driven by pulmonary neutrophil influx, such as adult respiratory distress syndrome.

Changes in Circadian Rhythms Dysregulate Inflammation in Ageing: Focus on Leukocyte Trafficking.

Leukocyte trafficking shows strong diurnal rhythmicity and is tightly regulated by circadian rhythms. As we age, leukocyte trafficking becomes dysregulated, contributing to the increased systemic, low-grade, chronic inflammation observed in older adults. Ageing is also associated with diminished circadian outputs and a dysregulation of the circadian rhythm. Despite this, there is little evidence to show the direct impact of age-associated dampening of circadian rhythms on the dysregulation of leukocyte trafficking. Here, we review the core mammalian circadian clock machinery and discuss the changes that occur in this biological system in ageing. In particular, we focus on the changes that occur to leukocyte trafficking rhythmicity with increasing age and consider how this impacts inflammation and the development of immune-mediated inflammatory disorders (IMIDs). We aim to encourage future ageing biology research to include a circadian approach in order to fully elucidate whether age-related circadian changes occur as a by-product of healthy ageing, or if they play a significant role in the development of IMIDs.

Combination versus monotherapy as definitive treatment for Pseudomonas aeruginosa bacteraemia: a multicentre retrospective observational cohort study.

BACKGROUND: Pseudomonas aeruginosa bacteraemia is a common and serious infection. No consensus exists regarding whether definitive combination therapy is superior to monotherapy. We aimed to evaluate the impact of combination therapy on mortality. METHODS: This was a multicentre retrospective study (nine countries, 25 centres), including 1277 patients with P. aeruginosa bacteraemia during 2009-15. We evaluated the association between ß-lactam plus aminoglycoside or quinolone combination therapy versus ß-lactam monotherapy and mortality. The primary outcome was 30 day all-cause mortality. Univariate and multivariate Cox regression analyses were conducted, introducing combination as a time-dependent variable. Propensity score was conducted to adjust for confounding for choosing combination therapy over monotherapy. RESULTS: Of 1119 patients included, 843 received definitive monotherapy and 276 received combination therapy (59% aminoglycoside and 41% quinolone). Mortality at 30 days was 16.9% (189/1119) and was similar between combination (45/276; 16.3%) and monotherapy (144/843; 17.1%) groups (P = 0.765). In multivariate Cox regression, combination therapy was not associated with reduced mortality (HR 0.98, 95% CI 0.64-1.53). No advantage in terms of clinical failure, microbiological failure or recurrent/persistent bacteraemia was demonstrated using combination therapy. Likewise, adverse events and resistance development were similar for the two regimens. CONCLUSIONS: In this retrospective cohort, no mortality advantage was demonstrated using combination therapy over monotherapy for P. aeruginosa bacteraemia. Combination therapy did not improve clinical or microbiological failure rates, nor affect adverse events or resistance development. Our finding of no benefit with combination therapy needs confirmation in well-designed randomized controlled trials.

Utility of flow cytometry and gene rearrangement analysis in tissue and blood of patients with suspected cutaneous T­cell lymphoma.

Cutaneous T­cell lymphoma (CTCL) is difficult to diagnose at an early stage. Current diagnostic tools include clinical examination, histomorphologic analysis, immunohistochemistry, flow cytometry of peripheral blood and/or lesional tissue, and evaluation of T­cell receptor (TCR) clonality by gene rearrangement analysis (TCRGR). Advances in genomic sequencing, including high­throughput sequencing (HTS), can be used to identify specific clones of rearranged TCR genes. Even with all of these tools, CTCL can take as long as a decade to definitively diagnose, potentially delaying treatment options and causing patient anxiety. This study aimed to evaluate the performance of the various ancillary testing modalities used to diagnose early­stage CTCL. In a subset of patients the performance of HTS was compared to flow cytometry and conventional TCRGR analysis via polymerase chain reaction (PCR). Fifty­five patients, with a total of 68 skin biopsies and peripheral blood draws, were evaluated using flow cytometry, PCR­TCRGR, and HTS­TCRGR to determine the sensitivity and specificity of each ancillary test. In tissue biopsies, flow cytometry (64%), PCR (71%) and HTS (69%) shared similar sensitivities; flow cytometry had the highest specificity (93%), followed by HTS (86%) and PCR (76.9%). However, flow cytometry and PCR had insufficient DNA quantities in 29 and 15% of the specimens, respectively. Peripheral blood testing was less sensitive than tissue testing (flow cytometry 14%, PCR 41%, HTS 33%); in peripheral blood, HTS was the most specific test (flow cytometry, 70%; PCR, 62.5%; and HTS, 100%). HTS is a highly specific molecular test for identifying CTCL in peripheral blood and skin biopsy specimens; however, our findings suggest a need for a continued search for more sensitive tests for early­stage CTCL.

Circadian Host-Microbiome Interactions in Immunity.

The gut microbiome plays a critical role in regulating host immunity and can no longer be regarded as a bystander in human health and disease. In recent years, circadian (24 h) oscillations have been identified in the composition of the microbiota, its biophysical localization within the intestinal tract and its metabolic outputs. The gut microbiome and its key metabolic outputs, such as short chain fatty acids and tryptophan metabolites contribute to maintenance of intestinal immunity by promoting barrier function, regulating the host mucosal immune system and maintaining the function of gut-associated immune cell populations. Loss of rhythmic host-microbiome interactions disrupts host immunity and increases risk of inflammation and metabolic complications. Here we review factors that drive circadian variation in the microbiome, including meal timing, dietary composition and host circadian clocks. We also consider how host-microbiome interactions impact the core molecular clock and its rhythmic outputs in addition to the potential impact of this relationship on circadian control of immunity.

Circadian asthma airway responses are gated by REV-ERBα.

BACKGROUND: The circadian clock powerfully regulates inflammation and the clock protein REV-ERBα is known to play a key role as a repressor of the inflammatory response. Asthma is an inflammatory disease of the airways with a strong time of day rhythm. Airway hyper-responsiveness (AHR) is a dominant feature of asthma; however, it is not known if this is under clock control. OBJECTIVES: To determine if allergy-mediated AHR is gated by the clock protein REV-ERBα. METHODS: After exposure to the intra-nasal house dust mite (HDM) allergen challenge model at either dawn or dusk, AHR to methacholine was measured invasively in mice. MAIN RESULTS: Wild-type (WT) mice show markedly different time of day AHR responses (maximal at dusk/start of the active phase), both in vivo and ex vivo, in precision cut lung slices. Time of day effects on AHR were abolished in mice lacking the clock gene Rev-erbα, indicating that such effects on asthma response are likely to be mediated via the circadian clock. We suggest that muscarinic receptors one (Chrm 1) and three (Chrm 3) may play a role in this pathway. CONCLUSIONS: We identify a novel circuit regulating a core process in asthma, potentially involving circadian control of muscarinic receptor expression, in a REV-ERBα dependent fashion. CLINICAL IMPLICATION: These insights suggest the importance of considering the timing of drug administration in clinic trials and in clinical practice (chronotherapy).