Infection perturbs Bach2- and Bach1-dependent erythroid lineage 'choice' to cause anemia.

Elucidation of how the differentiation of hematopoietic stem and progenitor cells (HSPCs) is reconfigured in response to the environment is critical for understanding the biology and disorder of hematopoiesis. Here we found that the transcription factors (TFs) Bach2 and Bach1 promoted erythropoiesis by regulating heme metabolism in committed erythroid cells to sustain erythroblast maturation and by reinforcing erythroid commitment at the erythro-myeloid bifurcation step. Bach TFs repressed expression of the gene encoding the transcription factor C/EBPß, as well as that of its target genes encoding molecules important for myelopoiesis and inflammation; they achieved the latter by binding to their regulatory regions also bound by C/EBPß. Lipopolysaccharide diminished the expression of Bach TFs in progenitor cells and promoted myeloid differentiation. Overexpression of Bach2 in HSPCs promoted erythroid development and inhibited myelopoiesis. Knockdown of BACH1 or BACH2 in human CD34+ HSPCs impaired erythroid differentiation in vitro. Thus, Bach TFs accelerate erythroid commitment by suppressing the myeloid program at steady state. Anemia of inflammation and myelodysplastic syndrome might involve reduced activity of Bach TFs.

mTORC1-independent translation control in mammalian cells by methionine adenosyltransferase 2A and S-adenosylmethionine.

Methionine adenosyltransferase (MAT) catalyzes the synthesis of S-adenosylmethionine (SAM). As the sole methyl-donor for methylation of DNA, RNA, and proteins, SAM levels affect gene expression by changing methylation patterns. Expression of MAT2A, the catalytic subunit of isozyme MAT2, is positively correlated with proliferation of cancer cells; however, how MAT2A promotes cell proliferation is largely unknown. Given that the protein synthesis is induced in proliferating cells and that RNA and protein components of translation machinery are methylated, we tested here whether MAT2 and SAM are coupled with protein synthesis. By measuring ongoing protein translation via puromycin labeling, we revealed that MAT2A depletion or chemical inhibition reduced protein synthesis in HeLa and Hepa1 cells. Furthermore, overexpression of MAT2A enhanced protein synthesis, indicating that SAM is limiting under normal culture conditions. In addition, MAT2 inhibition did not accompany reduction in mechanistic target of rapamycin complex 1 activity but nevertheless reduced polysome formation. Polysome-bound RNA sequencing revealed that MAT2 inhibition decreased translation efficiency of some fraction of mRNAs. MAT2A was also found to interact with the proteins involved in rRNA processing and ribosome biogenesis; depletion or inhibition of MAT2 reduced 18S rRNA processing. Finally, quantitative mass spectrometry revealed that some translation factors were dynamically methylated in response to the activity of MAT2A. These observations suggest that cells possess an mTOR-independent regulatory mechanism that tunes translation in response to the levels of SAM. Such a system may acclimate cells for survival when SAM synthesis is reduced, whereas it may support proliferation when SAM is sufficient.

Ferroptosis is controlled by the coordinated transcriptional regulation of glutathione and labile iron metabolism by the transcription factor BACH1.

Ferroptosis is an iron-dependent programmed cell death event, whose regulation and physiological significance remain to be elucidated. Analyzing transcriptional responses of mouse embryonic fibroblasts exposed to the ferroptosis inducer erastin, here we found that a set of genes related to oxidative stress protection is induced upon ferroptosis. We considered that up-regulation of these genes attenuates ferroptosis induction and found that the transcription factor BTB domain and CNC homolog 1 (BACH1), a regulator in heme and iron metabolism, promotes ferroptosis by repressing the transcription of a subset of the erastin-induced protective genes. We noted that these genes are involved in the synthesis of GSH or metabolism of intracellular labile iron and include glutamate-cysteine ligase modifier subunit (Gclm), solute carrier family 7 member 11 (Slc7a11), ferritin heavy chain 1 (Fth1), ferritin light chain 1 (Ftl1), and solute carrier family 40 member 1 (Slc40a1). Ferroptosis has also been previously shown to induce cardiomyopathy, and here we observed that Bach1-/- mice are more resistant to myocardial infarction than WT mice and that the severity of ischemic injury is decreased by the iron-chelator deferasirox, which suppressed ferroptosis. Our findings suggest that BACH1 represses genes that combat labile iron-induced oxidative stress, and ferroptosis is stimulated at the transcriptional level by BACH1 upon disruption of the balance between the transcriptional induction of protective genes and accumulation of iron-mediated damage. We propose that BACH1 controls the threshold of ferroptosis induction and may represent a therapeutic target for alleviating ferroptosis-related diseases, including myocardial infarction.

Impact of subcutaneous belimumab on disease activity, patient satisfaction, and metabolic profile in long-lasting systemic lupus erythematosus.

OBJECTIVE: Atherosclerosis is a major complication of systemic lupus erythematosus (SLE) and is exacerbated by the disease itself, drug toxicity, and metabolic syndrome. Although belimumab (BEL) can ameliorate disease activity and reduce prednisolone (PSL) dose in SLE, its effect on metabolic profiles is obscure. We aimed to assess the effects of subcutaneous BEL on disease activity and metabolic profiles. METHODS: A total of 106 patients with SLE who received subcutaneous BEL were included, and 76 patients who started BEL treatment at least 1 year prior were evaluated. Clinical information, including retention rate, disease activity, renal outcome, patient satisfaction, and metabolic profiles, were retrospectively analysed. RESULTS: The retention rate of BEL was > 80% after 2 years, and ineffectiveness and pain were the major reasons for discontinuation of BEL treatment. Satisfaction with side effects was higher in the BEL group than that in the PSL group. Belimumab significantly improved disease activity, lupus nephritis, and PSL dosage, with a median reduction of 4 mg/day. These effects were observed in active disease and positive C1q-binding immune complex, and PSL reduction ≥ 5 mg was achievable in such cases. Patients with PSL reduction of ≥ 5 mg showed significantly lower blood low-density lipoprotein and triglyceride by 13 and 17 mg/dL, respectively, while those with PSL reduction of < 5 mg remained unaltered. CONCLUSION: Subcutaneous BEL was effective in improving disease activity and proteinuria in patients with chronic disease while reducing PSL. Reduction in PSL by BEL also improved lipid status, which could synergistically reduce cardiovascular risk in SLE. Key Points • Significant reduction of disease activity, proteinuria, and prednisolone was observed in patients using subcutaneous belimumab. • Patient satisfaction was higher in terms of side effects in subcutaneous belimumab compared with prednisolone. • Reduction in prednisolone by belimumab contributed to the improvement of lipid status and would reduce the cardiovascular risk.

Distinct transcriptomes and autocrine cytokines underpin maturation and survival of antibody-secreting cells in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple autoantibody types, some of which are produced by long-lived plasma cells (LLPC). Active SLE generates increased circulating antibody-secreting cells (ASC). Here, we examine the phenotypic, molecular, structural, and functional features of ASC in SLE. Relative to post-vaccination ASC in healthy controls, circulating blood ASC from patients with active SLE are enriched with newly generated mature CD19-CD138+ ASC, similar to bone marrow LLPC. ASC from patients with SLE displayed morphological features of premature maturation and a transcriptome epigenetically initiated in SLE B cells. ASC from patients with SLE exhibited elevated protein levels of CXCR4, CXCR3 and CD138, along with molecular programs that promote survival. Furthermore, they demonstrate autocrine production of APRIL and IL-10, which contributed to their prolonged in vitro survival. Our work provides insight into the mechanisms of generation, expansion, maturation and survival of SLE ASC.

SLE Antibody-Secreting Cells Are Characterized by Enhanced Peripheral Maturation and Survival Programs.

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by multiple autoantibodies, some of which are present in high titers in a sustained, B cell-independent fashion consistent with their generation from long-lived plasma cells (LLPC). Active SLE displays high numbers of circulating antibody-secreting cells (ASC). Understanding the mechanisms of generation and survival of SLE ASC would contribute important insight into disease pathogenesis and novel targeted therapies. We studied the properties of SLE ASC through a systematic analysis of their phenotypic, molecular, structural, and functional features. Our results indicate that in active SLE, relative to healthy post-immunization responses, blood ASC contain a much larger fraction of newly generated mature CD19- CD138+ ASC similar to bone marrow (BM) LLPC. SLE ASC were characterized by morphological and structural features of premature maturation. Additionally, SLE ASC express high levels of CXCR4 and CD138, and molecular programs consistent with increased longevity based on pro-survival and attenuated pro-apoptotic pathways. Notably, SLE ASC demonstrate autocrine production of APRIL and IL-10 and experience prolonged in vitro survival. Combined, our findings indicate that SLE ASC are endowed with enhanced peripheral maturation, survival and BM homing potential suggesting that these features likely underlie BM expansion of autoreactive PC.

Chronic inflammation, neutrophil activity, and autoreactivity splits long COVID.

While immunologic correlates of COVID-19 have been widely reported, their associations with post-acute sequelae of COVID-19 (PASC) remain less clear. Due to the wide array of PASC presentations, understanding if specific disease features associate with discrete immune processes and therapeutic opportunities is important. Here we profile patients in the recovery phase of COVID-19 via proteomics screening and machine learning to find signatures of ongoing antiviral B cell development, immune-mediated fibrosis, and markers of cell death in PASC patients but not in controls with uncomplicated recovery. Plasma and immune cell profiling further allow the stratification of PASC into inflammatory and non-inflammatory types. Inflammatory PASC, identifiable through a refined set of 12 blood markers, displays evidence of ongoing neutrophil activity, B cell memory alterations, and building autoreactivity more than a year post COVID-19. Our work thus helps refine PASC categorization to aid in both therapeutic targeting and epidemiological investigation of PASC.

Congenital sideroblastic anemia model due to ALAS2 mutation is susceptible to ferroptosis.

X-linked sideroblastic anemia (XLSA), the most common form of congenital sideroblastic anemia, is caused by a germline mutation in the erythroid-specific 5-aminolevulinate synthase (ALAS2) gene. In XLSA, defective heme biosynthesis leads to ring sideroblast formation because of excess mitochondrial iron accumulation. In this study, we introduced ALAS2 missense mutations on human umbilical cord blood-derived erythroblasts; hereafter, we refer to them as XLSA clones. XLSA clones that differentiated into mature erythroblasts showed an increased frequency of ring sideroblast formation with impaired hemoglobin biosynthesis. The expression profiling revealed significant enrichment of genes involved in ferroptosis, which is a form of regulated cell death induced by iron accumulation and lipid peroxidation. Notably, treatment with erastin, a ferroptosis inducer, caused a higher proportion of cell death in XLSA clones. XLSA clones exhibited significantly higher levels of intracellular lipid peroxides and enhanced expression of BACH1, a regulator of iron metabolism and potential accelerator of ferroptosis. In XLSA clones, BACH1 repressed genes involved in iron metabolism and glutathione synthesis. Collectively, defective heme biosynthesis in XLSA clones could confer enhanced BACH1 expression, leading to increased susceptibility to ferroptosis. The results of our study provide important information for the development of novel therapeutic targets for XLSA.

Lipid peroxidation and the subsequent cell death transmitting from ferroptotic cells to neighboring cells.

Ferroptosis regulated cell death due to the iron-dependent accumulation of lipid peroxide. Ferroptosis is known to constitute the pathology of ischemic diseases, neurodegenerative diseases, and steatohepatitis and also works as a suppressing mechanism against cancer. However, how ferroptotic cells affect surrounding cells remains elusive. We herein report the transfer phenomenon of lipid peroxidation and cell death from ferroptotic cells to nearby cells that are not exposed to ferroptotic inducers (FINs). While primary mouse embryonic fibroblasts (MEFs) and NIH3T3 cells contained senescence-associated ß-galactosidase (SA-ß-gal)-positive cells, they were decreased upon induction of ferroptosis with FINs. The SA-ß-gal decrease was inhibited by ferroptotic inhibitors and knockdown of Atg7, pointing to the involvement of lipid peroxidation and activated autophagosome formation during ferroptosis. A transfer of cell culture medium of cells treated with FINs, type 1 or 2, caused the reduction in SA-ß-gal-positive cells in recipient cells that had not been exposed to FINs. Real-time imaging of Kusabira Orange-marked reporter MEFs cocultured with ferroptotic cells showed the generation of lipid peroxide and deaths of the reporter cells. These results indicate that lipid peroxidation and its aftereffects propagate from ferroptotic cells to surrounding cells, even when the surrounding cells are not exposed to FINs. Ferroptotic cells are not merely dying cells but also work as signal transmitters inducing a chain of further ferroptosis.

Successful Treatment of Pulmonary Arterial Hypertension in Systemic Sclerosis with Anticentriole Antibody.

Systemic sclerosis (SSc) is characterized by skin sclerosis and multiple organ damages which may cause mortality and is usually accompanied with several specific autoantibodies, each of which is associated with characteristic complications. Among them, anticentriole antibody is recently reported to be highly associated with SSc-associated pulmonary arterial hypertension (SSc-PAH). In general, several vasodilators are used as therapeutic drugs for SSc-PAH, whereas immunosuppressive therapies are not. Here, we report the case of a 62-year-old female with anticentriole antibody-positive SSc-PAH treated with immunosuppressants and vasodilators. She presented with two-year exertional dyspnea and was diagnosed with PAH and SSc owing to the centriole staining pattern and other symptoms without digital sclerosis. Oral vasodilators were initially administered but were not sufficiently effective on dyspnea. Immunosuppressants such as prednisolone and cyclophosphamide were started. Both of them improved mean pulmonary arterial pressure and 6-minute walk distance, and the anticentriole antibody also disappeared. In this case, SSc-PAH with anticentriole antibody was properly diagnosed and immunosuppressants and vasodilators improved the hemodynamics of PAH with anticentriole antibody and stably maintained it and, in addition, reduced the titer of anticentriole antibody. This indicates that anticentriole antibody might represent a good responsive group to therapies among subgroups of patients with SSc-PAH.

Nasal Septal Perforation in Propylthiouracil-Induced Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis.

Here, we present the case of a 29-year-old woman with nasal septal perforation and positive myeloperoxidase- (MPO-) anti-neutrophil cytoplasmic antibody (ANCA). She had been diagnosed with Graves' disease and had been treated with propylthiouracil (PTU) for 14 months. A biopsy of the nasal septum revealed an infiltration of inflammatory cells, with no evidence of malignancy or granulomatous change. Because of the use of PTU, destructive nasal lesion, and positive MPO-ANCA, she was diagnosed with drug-induced ANCA-associated vasculitis (AAV) and was treated with prednisolone and methotrexate after the cessation of PTU. Although PTU is known to be the medicine that induces drug-induced AAV, the manifestation of nasal septal perforation in drug-induced AAV is poorly identified. This is the rare case of drug-induced AAV which manifested only nasal septal perforation.

Takayasu Arteritis Coexisting with Sclerosing Osteomyelitis.

We report a rare case of a 27-year-old woman with Takayasu arteritis (TAK) complicated by diffuse sclerosing osteomyelitis. She first presented with sclerosing osteomyelitis of the right mandible without evidence of arteritis in the carotid arteries. Eight months later, she complained of left neck pain, and imaging studies revealed the presence of arteritis in the left carotid artery. She was diagnosed with TAK, and immunosuppressive treatment was initiated, which was effective for both the arteritis and the osteomyelitis. Osteomyelitis is an important complication of TAK and bone scintigraphy is useful for its detection.