As a common disorder, chronic kidney disease (CKD) poses a great threat to human health. Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a complication of CKD characterized by disturbances in the levels of calcium, phosphorus, parathyroid hormone (PTH), and vitamin D; abnormal bone formation affecting the mineralization and linear growth of bone; and vascular and soft tissue calcification. PTH reflects the function of the parathyroid gland and also takes part in the metabolism of minerals. The accurate measurement of PTH plays a vital role in the clinical diagnosis, treatment, and prognosis of patients with secondary hyperparathyroidism (SHPT). Previous studies have shown that there are different fragments of PTH in the body's circulation, causing antagonistic effects on bone and the kidney. Here we review the metabolism of PTH fragments; the progress being made in PTH measurement assays; the effects of PTH fragments on bone, kidney, and the cardiovascular system in CKD; and the predictive value of PTH measurement in assessing the effectiveness of parathyroidectomy (PTX). We hope that this review will help to clarify the value of accurate PTH measurements in CKD-MBD and promote the further development of multidisciplinary diagnosis and treatment.
Age-associated B cells (ABCs) accumulate after infection, during aging, and in systemic autoimmunity, contributing to pathogenesis in the latter1. To date, their precise ontogeny and whether they represent a B cell subset distinct from the other major effector subsets - plasma cells and memory B cells - remain unknown. We asked whether ABC formation requires the expression of a unique transcription factor. Here, we used single-cell RNA sequencing to identify differentially-expressed transcription factors shared by ABCs from both lupus patient and lupus-prone mice. Using an arrayed CRISPR screen, we show Zeb2 is essential for ABC differentiation in vitro. Selective deficiency of Zeb2 in B cells also leads to impaired ABC formation in vivo. Zeb2 drove ABC specification by directly binding the promoters of ABC signature genes including Itgax and Itgam encoding for CD11c and CD11b respectively. Zeb2 also targeted molecules involved in cytokine receptor signaling via the JAK/STAT pathway including Il21r and Socs5. Administration of the approved JAK/STAT inhibitor tofacitinib effectively ameliorated ABC accumulation in mice and patients with autoimmunity. This study reveals ABCs represent a distinct B cell subset dependent on Zeb2 expression, and provides a rationale for the use of JAK/STAT inhibitors to treat ABC-mediated autoimmune diseases.
Objective Disruption of B cell homeostasis and subsequent dominance of effector B cell subsets are critical for the development of systemic lupus erythematosus (SLE). Revealing the key intrinsic regulators involved in the homeostatic control of B cells has important therapeutic value for SLE. This study was undertaken to determine the regulatory role of the transcription factor Pbx1 in B cell homeostasis and lupus pathogenesis. Methods We constructed mice with B cell–specific deletion of Pbx1. T cell–dependent and T cell–independent humoral responses were induced by intraperitoneal injection of nitrophenyl‐containing hapten (NP) conjugated to keyhole limpet hemocyanin or NP‐Ficoll. The regulatory effects of Pbx1 on autoimmunity were observed in a Bm12‐induced lupus murine model. We investigated mechanisms of Pbx1 using RNA sequencing, the cleavage under targets and tagmentation assay, and chromatin immunoprecipitation–quantitative polymerase chain reaction assay. We transduced B cells from SLE patients with plasmids that overexpressed PBX1 to explore the in vitro therapeutic efficacy of PBX1. Results Pbx1 was specifically down‐regulated in autoimmune B cells and negatively correlated with disease activity. The deficiency of Pbx1 in B cells resulted in excessive humoral responses following immunization. In the Bm12‐induced lupus model, mice with B cell–specific Pbx1 deficiency displayed enhancements in germinal center responses, plasma cell differentiation, and autoantibody production. Pbx1‐deficient B cells had increased survival and proliferative advantages after activation. Pbx1 regulated genetic programs by directly targeting critical components of the proliferation and apoptosis pathways. In SLE patients, PBX1 expression was negatively correlated with effector B cell expansion; when PBX1 expression was enforced, the survival and proliferative capacity of SLE B cells were attenuated. Conclusion Our study reveals the regulatory function and mechanism of Pbx1 in adjusting B cell homeostasis and highlights Pbx1 as a therapeutic target in SLE.
Objective. Emerging evidence indicates that a distinct CD11c+T-bet+ B cell subset, termed age/autoimmuneassociated B cells (ABCs), is the major pathogenic autoantibody producer in lupus. Human lupus is associated with significant metabolic alterations, but how ABCs orchestrate their typical transcription factors and metabolic programs to meet specific functional requirements is unclear. We undertook this study to characterize the metabolism of ABCs and to identify the regulators of their metabolic pathways in an effort to develop new therapies for ABC-mediated autoimmunity.Methods. We developed a T-bet-tdTomato reporter mouse strain to trace live T-bet+ B cells and adoptively transferred CD4+ T cells from bm12 mice to induce lupus. We next sorted CD11c+tdTomato+ B cells and conducted RNA sequencing and an extracellular flux assay. A metabolic restriction to constrain ABC formation was tested in human and mouse B cells. We used a bm12-induced lupus mouse model to conduct the metabolic intervention.Results. ABCs exhibited a hypermetabolic state with enhanced glycolytic capacity. The increased glycolytic rate in ABCs was promoted by interferon-γ (IFNγ) signaling. T-bet, a downstream transcription factor of IFNγ, regulated the gene program of the glycolysis pathway in ABCs by repressing the expression of Bcl6. Functionally, glycolysis restriction could impair ABC formation. The engagement of glycolysis promoted survival and terminal differentiation of antibody-secreting cells. Administration of a glycolysis inhibitor ameliorated ABC accumulation and autoantibody production in the lupus-induced bm12 mouse model. Conclusion.T-bet can couple immune signals and metabolic programming to establish pathogenic ABC formation and functional capacities. Modulation of ABCs favored a metabolic program that could be a novel therapeutic approach for lupus.
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