Increased levels of the high mobility group box 1 protein sustain the inflammatory bone marrow microenvironment in patients with chronic idiopathic neutropenia via activation of toll-like receptor 4

Inflammatory abrasion of hematopoietic stem cells: a candidate clue for the post-CAR-T hematotoxicity?

Chimeric antigen receptor T-cell (CAR-T) therapy has shown remarkable effects in treating various hematological malignancies. However, hematotoxicity, specifically neutropenia, thrombocytopenia, and anemia, poses a serious threat to patient prognosis and remains a less focused adverse effect of CAR-T therapy. The mechanism underlying lasting or recurring late-phase hematotoxicity, long after the influence of lymphodepletion therapy and cytokine release syndrome (CRS), remains elusive. In this review, we summarize the current clinical studies on CAR-T late hematotoxicity to clarify its definition, incidence, characteristics, risk factors, and interventions. Owing to the effectiveness of transfusing hematopoietic stem cells (HSCs) in rescuing severe CAR-T late hematotoxicity and the unignorable role of inflammation in CAR-T therapy, this review also discusses possible mechanisms of the harmful influence of inflammation on HSCs, including inflammatory abrasion of the number and the function of HSCs. We also discuss chronic and acute inflammation. Cytokines, cellular immunity, and niche factors likely to be disturbed in CAR-T therapy are highlighted factors with possible contributions to post-CAR-T hematotoxicity.

Incidence and Prognosis of Clonal Hematopoiesis in patients with Chronic Idiopathic Neutropenia

The incidence and prognosis of clonal hematopoiesis in patients with isolated neutropenia among patients with idiopathic cytopenia of undetermined significance (ICUS), known as ICUS-N or chronic idiopathic neutropenia (CIN) patients, is poorly defined. In the present study we sought to investigate the frequency and clinical significance of mutations of genes implicated in myeloid malignancies using next generation sequencing, in CIN patients (n=185) with a long follow-up. We found that 21/185 patients (11.35%) carried totally 25 somatic mutations in 6 genes with median variant allele frequency (VAF) 12.75%. The most frequently mutated genes were DNMT3A and TET2 involving more than 80% of patients followed by IDH1/2, SRSF2 and ZRSR2. The frequency of transformation to a myeloid malignancy was low in the total group of patients (5/185 patients; 2.70%). However, from the transformed patients four belonged to the clonal (4/21; 19.05%) and one to the non-clonal (1/164; 0.61%) group, indicating that the presence of mutation(s) confers a relative risk for transformation 31.24 (P = 0.0017). The VAF of the mutant clones in the transformed patients was higher than 10% in all cases and the genes most frequently associated with malignant transformation were the SRSF2 and IDH1. No significant differences were identified between clonal and non-clonal groups in the severity of neutropenia. Patients with clonal disease were older compared to non-clonal patients. These data contribute to the better understanding of the heterogeneous entities underlying ICUS and highlight the importance of the mutation analysis for the diagnosis and prognosis of patients with unexplained neutropenias.

The relationship between idiopathic cytopenias/dysplasias of uncertain significance (ICUS/IDUS) and autoimmunity

INTRODUCTION

This review examines the several lines of evidence that support the relationship between myelodysplasia and autoimmunity, i.e. their epidemiologic association, the existence of common immune-mediated physiopathologic mechanisms, and the response to similar immunosuppressive therapies. The same relationship is reviewed here considering idiopathic cytopenia of uncertain significance (ICUS) and idiopathic dysplasia of uncertain significance (IDUS), two recently recognized provisional conditions characterized by isolated/unexplained cytopenia and/or dysplasia in <10% bone marrow cells. Areas covered: The review focuses on alterations of cytokine profiles, telomere/telomerase and toll-like receptors, and on increased myelosuppressive mediators and apoptotic markers in both myelodysplasia and autoimmunity. In addition, the presence of an autoimmune reaction directed against marrow precursors is described in refractory/relapsing autoimmune cytopenias (autoimmune hemolytic anemia, immune thrombocytopenia, chronic idiopathic neutropenia), possibly contributing to their evolution to ICUS/IDUS/bone marrow failure syndromes. Expert commentary: The increasing availability of omics methods has fuelled the discussion on the role of somatic mutations in the pathogenesis of IDUS/ICUS, clonal hematopoiesis of indeterminate potential, and clonal cytopenias of undetermined significance, and in their possible evolution. Even more attracting is the involvement of the genetic background/accumulating somatic mutations in cytopenias with autoimmune alterations.

High Mobility Group Box-1 Promotes Inflammation-Induced Lymphangiogenesis via Toll-Like Receptor 4-Dependent Signalling Pathway

Lymphangiogenesis in inflammation has received considerable attention in recent years. Administration of modulating lymphangiogenesis provides more possibilities of treating inflammation-associated diseases. However, the main mediators and factors governing inflammation-induced lymphangiogenesis (ILA) are yet to be defined. Here, we explored the role of HMGB1-TLR4 signalling pathway in modulating inflammation-induced lymphangiogenesis and its underlying mechanisms using an ILA mouse model and 2 cell lines. Our results show that HMGB1 promoted VEGF-C-induced HDLECs proliferation in a dose-dependent manner and TLR4 mediates HMGB1-induced LECs proliferation and tube formation in vitro. And in vivo, rHMGB1 treatment significantly promoted ILA, and the promoting effects was inhibited notably when HMGB1-TLR4 was blocked. HMGB1-associated ILA is primarily dependent on TLR4 but not on TLR2. In mechanisms, the recruitment and activation of CD11b+ cells are important cellular mechanisms in HMGB1-TLR4 associated ILA, and multiple key pro-lymphangiogenesis molecules mediates HMGB1-TLR4 associated ILA, including VEGF-C/VEGFR3, inflammatory factors IL-1β and TNF-α, MMP-2 and MMP-9 and NF-κB p65. In conclusion, HMGB1-associated ILA is primarily dependent on TLR4, and CD11b+ cells and multiple molecular mechanisms mediate HMGB1-TLR4 associated ILA. Furthermore, the ILA can be effectively modulated by HMGB1-TLR4 signalling. Consequently, administration of modulating ILA through HMGB1-TLR4 pathway may provide us more possibilities of treating inflammation and lymphangiogenesis associated diseases.

Is chronic neutropenia always a benign disease? Evidences from a 5-year prospective study

AIM

To evaluate infections and oncohematologic evolution in adult patients with chronic idiopathic and autoimmune neutropenia in a prospective study.

PATIENTS AND METHODS

76 consecutive patients were enrolled from September 2008 to April 2012. Complete blood counts and clinical evaluation were performed at enrolment, at month 3, 6, and then every 6 months. Anti-neutrophil antibodies were tested by GIFT method.

RESULTS

Patients (49 chronic idiopathic- and 27 autoimmune neutropenia) were followed for a median of 5 years (range 24-84 months). At enrolment, neutropenia was mild in 44 patients (median neutrophils 1.27×10(3)/μL), moderate in 23 (median 0.8×10(3)/μL), and severe in 9 (median 0.4×10(3)/μL). Neutrophil counts showed a great inter-subject but no intra-subject variability, with lower values in autoimmune neutropenia, in males, and in MGUS cases. Over time, no grade >3 infections occurred; 13/49 chronic idiopathic and 6/27 autoimmune neutropenia patients experienced a grade 2 event, irrespective of mean and nadir neutrophil values. Bone marrow evaluation at enrolment showed reduced cellularity in 23% of cases, and dyserythropoietic features in 55%, with no definite hematologic diagnosis. During the follow-up, 5 cases were diagnosed with NK expansion, 4 with hairy cell leukemia, and 3 with myelodysplasia (1 myelomonocytic leukemia, 1 refractory cytopenia with unilineage dysplasia, and 1 multilineage dysplasia), with a median time to evolution of 30 months.

CONCLUSION

Chronic idiopathic and autoimmune neutropenia, although usually benign, deserve hematological follow-up with a bone marrow evaluation at diagnosis and a re-evaluation in the presence of worsening neutropenia, appearance of additional cytopenias, and lymphocytosis.

A Genome-wide Association Study Provides Evidence of Sex-specific Involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) With Diabetic Neuropathic Pain

Neuropathic pain is defined as pain arising as a direct consequence of a lesion or a disease affecting the somatosensory system and it affects around 1 in 4 diabetic patients in the UK. The purpose of this genome-wide association study (GWAS) was to identify genetic contributors to this disorder. Cases of neuropathic pain were defined as diabetic patients with a multiple prescription history of at least one of five drugs specifically indicated for the treatment of neuropathic pain. Controls were diabetic individuals who were not prescribed any of these drugs, nor amitriptyline, carbamazepine, or nortriptyline. Overall, 961 diabetic neuropathic pain cases and 3260 diabetic controls in the Genetics of Diabetes Audit and Research Tayside (GoDARTS) cohort were identified. We found a cluster in the Chr1p35.1 (ZSCAN20-TLR12P) with a lowest P value of 2.74 × 10(- 7) at rs71647933 in females and a cluster in the Chr8p23.1, next to HMGB1P46 with a lowest P value of 8.02 × 10(- 7) at rs6986153 in males. Sex-specific narrow sense heritability was higher in males (30.0%) than in females (14.7%). This GWAS on diabetic neuropathic pain provides evidence for the sex-specific involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) with the disorder, indicating the need for further research.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Parallels between immune driven-hematopoiesis and T cell activation: 3 signals that relay inflammatory stress to the bone marrow

Quiescence, self-renewal, lineage commitment and differentiation of hematopoietic stem cells (HSCs) towards fully mature blood cells are a complex process that involves both intrinsic and extrinsic signals. During steady-state conditions, most hematopoietic signals are provided by various resident cells inside the bone marrow (BM), which establish the HSC micro-environment. However, upon infection, the hematopoietic process is also affected by pathogens and activated immune cells, which illustrates an effective feedback mechanism to hematopoietic stem and progenitor cells (HSPCs) via immune-mediated signals. Here, we review the impact of pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), costimulatory molecules and pro-inflammatory cytokines on the quiescence, proliferation and differentiation of HSCs and more committed progenitors. As modulation of HSPC function via these immune-mediated signals holds an interesting parallel with the "three-signal-model" described for the activation and differentiation of naïve T-cells, we propose a novel "three-signal" concept for immune-driven hematopoiesis. In this model, the recognition of PAMPs and DAMPs will activate HSCs and induce proliferation, while costimulatory molecules and pro-inflammatory cytokines confer a second and third signal, respectively, which further regulate expansion, lineage commitment and differentiation of HSPCs. We review the impact of inflammatory stress on hematopoiesis along these three signals and we discuss whether they act independently from each other or that concurrence of these signals is important for an adequate response of HSPCs upon infection.

Novel insights for high mobility group box 1 protein-mediated cellular immune response in sepsis: A systemic review

BACKGROUND

High mobility group box 1 protein (HMGB1) is a highly conserved, ubiquitous protein in the nuclei and cytoplasm of nearly all cell types. HMGB1 is secreted into the extracellular milieu and acts as a proinfl ammatory cytokine. In this article we reviewed briefl y the cellular immune response mediated by HMGB1 in infl ammation and sepsis.

METHODS

This systemic review is mainly based on our own work and other related reports.

RESULTS

HMGB1 can actively affect the immune functions of many types of cells including T lymphocytes, regulatory T cells (Tregs), dendritic cells (DCs), macrophages, and natural killer cells (NK cells). Various cellular responses can be mediated by HMGB1 which binds to cell-surface receptors [e.g., the receptor for advanced glycation end products (RAGE), Toll-like receptor (TLR)2, and TLR4]. Anti-HMGB1 treatment, such as anti-HMGB1 polyclonal or monoclonal antibodies, inhibitors (e.g., ethyl pyruvate) and antagonists (e.g., A box), can protect against sepsis lethality and give a wider window for the treatment opportunity.

CONCLUSION

HMGB1 is an attractive target for the development of new therapeutic strategies in the treatment of patients with septic complications.

Genomic analysis and differential expression of HMG and S100A family in human arthritis: upregulated expression of chemokines, IL-8 and nitric oxide by HMGB1

We applied global gene expression arrays, quantitative real-time PCR, immunostaining, and functional assays to untangle the role of High Mobility Groups proteins (HMGs) in human osteoarthritis (OA)-affected cartilage. Bioinformatics analysis showed increased mRNA expression of Damage-Associated Molecular Patterns (DAMPs): HMGA, HMGB, HMGN, SRY, LEF1, HMGB1, MMPs, and HMG/RAGE-interacting molecules (spondins and S100A4, S100A10, and S100A11) in human OA-affected cartilage as compared with normal cartilage. HMGB2 was down-regulated in human OA-affected cartilage. Immunohistological staining identified HMGB1 in chondrocytes in the superficial cartilage. Cells of the deep cartilage and subchondral bone showed increased expression of HMGB1 in OA-affected cartilage. HMGB1 was expressed in the nucleus, cytosol, and extracellular milieu of chondrocytes in cartilage. Furthermore, HMGB1 was spontaneously released from human OA-affected cartilage in ex vivo conditions. The effects of recombinant HMGB1 was tested on human cartilage and chondrocytes in vitro. HMGB1 stimulated mRNA of 2 NFκB gene enhancers (NFκB1 and NFκB2), 16 CC and CXC chemokines (IL-8, CCL2, CCL20, CCL3, CCL3L1, CCL3L3, CCL4, CCL4L1, CCL4L2, CCL5, CCL8, CXCL1, CXCL10, CXCL2, CXCL3, and CXCL6) by ≥10-fold. Furthermore, HMGB1 and IL-1β and/or tumor necrosis factor α (but not HMGI/Y) also significantly induced inducible nitric oxide synthase, NO, and interleukin (IL)-8 production in human cartilage and chondrocytes. The recombinant HMGB1 utilized in this study shows properties that are similar to disulfide-HMGB1. The differential, stage and/or tissue-specific expression of HMGB1, HMGB2, and S100A in cartilage was associated with regions of pathology and/or cartilage homeostasis in human OA-affected cartilage. Noteworthy similarities in the expression of mouse and human HMGB1 and HMGB2 were conserved in normal and arthritis-affected cartilage. The multifunctional forms of HMGB1 and S100A could perpetuate damage-induced cartilage inflammation in late-stage OA-affected joints similar to sterile inflammation. The paracrine effects of HMGB1 can induce chemokines and NO that are perceived to change cartilage homeostasis in human OA-affected cartilage.

Impaired clearance of apoptotic cells leads to HMGB1 release in the bone marrow of patients with myelodysplastic syndromes and induces TLR4-mediated cytokine production

Excessive pro-inflammatory cytokine production in the bone marrow has been associated with the pathogenesis of myelodysplastic syndromes. We herein investigated the involvement of toll-like receptors and their endogenous ligands in the induction/maintenance of the inflammatory process in the marrow of patients with myelodysplastic syndromes. We evaluated the expression of toll-like receptors in marrow monocytes of patients (n=27) and healthy controls (n=25) by flow-cytometry and also assessed the activation of the respective signaling using a real-time polymerase chain reaction-based array. We measured the high mobility group box-1 protein, a toll-like receptor-4 ligand, in marrow plasma and long-term bone marrow culture supernatants by an enzyme-linked immunosorbent assay and we performed cross-over experiments using marrow plasma from patients and controls in the presence/absence of a toll-like receptor-4 inhibitor to evaluate the pro-inflammatory cytokine production by chemiluminescence. We assessed the apoptotic cell clearance capacity of patients' macrophages using a fluorescence microscopy-based assay. We found over-expression of toll-like receptor-4 in patients' marrow monocytes compared to that in controls; this over-expression was associated with up-modulation of 53 genes related to the respective signaling. Incubation of patients' monocytes with autologous, but not with normal, marrow plasma resulted in over-production of pro-inflammatory cytokines, an effect that was abrogated by the toll-like receptor-4 inhibitor suggesting that the pro-inflammatory cytokine production in myelodysplastic syndromes is largely mediated through toll-like receptor-4. The levels of high mobility group box-1 protein were increased in patients' marrow plasma and culture supernatants compared to the levels in controls. Patients' macrophages displayed an impaired capacity to engulf apoptotic cells and this defect was associated with excessive release of high mobility group box-1 protein by dying cells. A primary apoptotic cell clearance defect of marrow macrophages in myelodysplastic syndromes may contribute to the induction/maintenance of the inflammatory process through aberrant release of molecules inducing toll-like receptor-4 such as high mobility group box-1 protein.

Genetic associations in acquired immune-mediated bone marrow failure syndromes: insights in aplastic anemia and chronic idiopathic neutropenia

Increasing interest on the field of autoimmune diseases has unveiled a plethora of genetic factors that predispose to these diseases. However, in immune-mediated bone marrow failure syndromes, such as acquired aplastic anemia and chronic idiopathic neutropenia, in which the pathophysiology results from a myelosuppressive bone marrow microenvironment mainly due to the presence of activated T lymphocytes, leading to the accelerated apoptotic death of the hematopoietic stem and progenitor cells, such genetic associations have been very limited. Various alleles and haplotypes of human leucocyte antigen (HLA) molecules have been implicated in the predisposition of developing the above diseases, as well as polymorphisms of inhibitory cytokines such as interferon-γ, tumor necrosis factor-α, and transforming growth factor-β1 along with polymorphisms on molecules of the immune system including the T-bet transcription factor and signal transducers and activators of transcription. In some cases, specific polymorphisms have been implicated in the outcome of treatment on those patients.