Spanish cohort of VEXAS syndrome: clinical manifestations, outcome of treatments and novel evidences about UBA1 mosaicism

BACKGROUND

The vacuoles, E1-enzyme, X linked, autoinflammatory and somatic (VEXAS) syndrome is an adult-onset autoinflammatory disease (AID) due to postzygotic UBA1 variants.

OBJECTIVES

To investigate the presence of VEXAS syndrome among patients with adult-onset undiagnosed AID. Additional studies evaluated the mosaicism distribution and the circulating cytokines.

METHODS

Gene analyses were performed by both Sanger and amplicon-based deep sequencing. Patients' data were collected from their medical charts. Cytokines were quantified by Luminex.

RESULTS

Genetic analyses of enrolled patients (n=42) identified 30 patients carrying UBA1 pathogenic variants, with frequencies compatible for postzygotic variants. All patients were male individuals who presented with a late-onset disease (mean 67.5 years; median 67.0 years) characterised by cutaneous lesions (90%), fever (66.7%), pulmonary manifestations (66.7%) and arthritis (53.3%). Macrocytic anaemia and increased erythrocyte sedimentation rate and ferritin were the most relevant analytical abnormalities. Glucocorticoids ameliorated the inflammatory manifestations, but most patients became glucocorticoid-dependent. Positive responses were obtained when targeting the haematopoietic component of the disease with either decitabine or allogeneic haematopoietic stem cell transplantation. Additional analyses detected the UBA1 variants in both haematopoietic and non-haematopoietic tissues. Finally, analysis of circulating cytokines did not identify inflammatory mediators of the disease.

CONCLUSION

Thirty patients with adult-onset AID were definitively diagnosed with VEXAS syndrome through genetic analyses. Despite minor interindividual differences, their main characteristics were in concordance with previous reports. We detected for the first time the UBA1 mosaicism in non-haematopoietic tissue, which questions the previous concept of myeloid-restricted mosaicism and may have conceptual consequences for the disease mechanisms.

Effect of mitral regurgitation in stroke risk in patients with nonrheumatic atrial fibrillation

Background

Atrial fibrillation (AF) carries a thrombotic risk related to blood stasis produced in left atrium. In patients with rheumatic valve disease and AF, the presence of severe mitral regurgitation (MR) has been shown to reduce the risk of atrial thrombosis and stroke. In patients without rheumatic disease, the results are controversial.

Purpose

Our objective is to analyze the association between mitral regurgitation and the incidence of stroke.

Methods

We analyzed data from the retrospective registry CardioCHUVI-AF, which includes 15,720 patients with AF (excluding mechanical prostheses or rheumatic valvular disease) in the Vigo area, from 2014 to 2018. We grouped the patients according to the MR grades: grade 0–2 (15,194 patients) and grades 3–4 (526 patients). We performed propensity score matching analysis obtaining 2 groups of 511 patients. We analyzed the association between MR and stroke with a competitive risk model, being death the competitive event.

Results

During a median follow-up of 4.90 years (IQR 2.85–4.93), 859 (5.5%) patients suffered a stroke. The stroke incidence rate was 1.30 per 100 person-years (95% CI: 1.21–1.39), with no differences between the MR groups. In the univariate analysis, no relationship was observed between the MR grades and stroke (sHR 1.12, 95% CI: 0.79–1.60, P=0.530). After the propensity score matching analysis no significant association was observed between the MR grades and stroke (sHR 0.93, 95% CI: 0.57–1.53, P=0.775) (Figure 1 and 2). This same relationship was evaluated by subgroups of interest: oral anticoagulation, prior heart failure, left ventricular ejection fraction <40%, aortic valve disease, and left atrial dilatation, with results consistent with the overall sample (Figure 2).

Conclusions

In our large registry of patients with AF, we did not find a protective effect of significant mitral regurgitation (grades 3–4) on the risk of stroke.

Funding Acknowledgement

Type of funding sources: None.

Lck is necessary and sufficient for Fas-ligand expression and apoptotic cell death in mature cycling T cells

Apoptotic cell death is induced in mature cycling T cells upon ligation of the Ag-specific TCR. This process is essential for the maintenance of homeostasis in the immune system, as it is capable of down-regulating ongoing immune responses. The analysis of the mechanism underlying TCR-induced programmed cell death has focused the attention of many scientists recently. In this regard, several recent reports have implicated Fas/Fas-ligand molecules as the final mediators of this process. Several other gene products have been implicated in the control of apoptosis (as Bcl-2, p53, and c-Myc); however, no information was available in the early signaling molecules that trigger this phenomena. The results presented in this work indicate that pp56(lck) src family kinase is actually required for the TCR to trigger cell death in mature cycling T cells. In fact, while inhibition of pp56(lck) expression with antisense oligonucleotides blocked TCR-induced apoptosis, pharmacologic inhibition of phosphatidylinositol 3-kinase activity had no effect. Accordingly, ligation of the Ag receptor in a cell line defective for pp56(lck) expression was unable to induce apoptosis, although it induced cellular stimulation, as measured by the expression of CD69. In addition, we show in this work that expression of constitutively active pp56(lck) mutants, but not pp59(fyn) mutants, in the absence of any other TCR-derived signal, is sufficient to induce apoptosis not only in transformed, but also in normal cycling T cells. Finally, evidence is presented indicating that a mechanism through which pp56(lck) regulates TCR-induced apoptosis in mature cycling T cells is by controlling Fas-ligand expression.

Lck is necessary and sufficient for Fas-ligand expression and apoptotic cell death in mature cycling T cells

Apoptotic cell death is induced in mature cycling T cells upon ligation of the Ag-specific TCR. This process is essential for the maintenance of homeostasis in the immune system, as it is capable of down-regulating ongoing immune responses. The analysis of the mechanism underlying TCR-induced programmed cell death has focused the attention of many scientists recently. In this regard, several recent reports have implicated Fas/Fas-ligand molecules as the final mediators of this process. Several other gene products have been implicated in the control of apoptosis (as Bcl-2, p53, and c-Myc); however, no information was available in the early signaling molecules that trigger this phenomena. The results presented in this work indicate that pp56(lck) src family kinase is actually required for the TCR to trigger cell death in mature cycling T cells. In fact, while inhibition of pp56(lck) expression with antisense oligonucleotides blocked TCR-induced apoptosis, pharmacologic inhibition of phosphatidylinositol 3-kinase activity had no effect. Accordingly, ligation of the Ag receptor in a cell line defective for pp56(lck) expression was unable to induce apoptosis, although it induced cellular stimulation, as measured by the expression of CD69. In addition, we show in this work that expression of constitutively active pp56(lck) mutants, but not pp59(fyn) mutants, in the absence of any other TCR-derived signal, is sufficient to induce apoptosis not only in transformed, but also in normal cycling T cells. Finally, evidence is presented indicating that a mechanism through which pp56(lck) regulates TCR-induced apoptosis in mature cycling T cells is by controlling Fas-ligand expression.

Role of the autophosphorylation site on the biological function of pp56lck

Src-family tyrosine kinases act as signaling molecules in a wide array of cellular activation processes. The existence of the various src-family members reflects the requirement for different cell-surface receptors to transmit cell-type specific intracellular signals. The structural basis for the functional specificity of src-kinases is being actively investigated. In the present report we have analysed the contribution of the area surrounding the autophosphorylation site (located at subdomain VII of the catalytic domain) in determining src-kinases activity and functional specificity. To this end we analysed the kinase activities of the lymphoid src-kinase pp56lck and a mutant of pp56lck in which this region has been exchanged for the corresponding area of the serine/threonine kinase c-Raf. Our studies indicate that the change at subdomain VII affected the ability of pp56lck to phosphorylate physiological substrates. Furthermore, when analysed in T cells, the mutant at subdomain VII failed to induce interleukin-2 production, a specific biological function of pp56lck. Thus, the area surrounding the autophosphorylation site of pp56lck plays a critical role in mediating its specific biological function.