HMGB1 Mediates Anemia of Inflammation in Murine Sepsis Survivors

Fine-mapping causal tissues and genes at disease-associated loci

Heritable diseases often manifest in a highly tissue-specific manner, with different disease loci mediated by genes in distinct tissues or cell types. We propose Tissue-Gene Fine-Mapping (TGFM), a fine-mapping method that infers the posterior probability (PIP) for each gene-tissue pair to mediate a disease locus by analyzing GWAS summary statistics (and in-sample LD) and leveraging eQTL data from diverse tissues to build cis-predicted expression models; TGFM also assigns PIPs to causal variants that are not mediated by gene expression in assayed genes and tissues. TGFM accounts for both co-regulation across genes and tissues and LD between SNPs (generalizing existing fine-mapping methods), and incorporates genome-wide estimates of each tissue's contribution to disease as tissue-level priors. TGFM was well-calibrated and moderately well-powered in simulations; unlike previous methods, TGFM was able to attain correct calibration by modeling uncertainty in cis-predicted expression models. We applied TGFM to 45 UK Biobank diseases/traits (average N = 316K) using eQTL data from 38 GTEx tissues. TGFM identified an average of 147 PIP > 0.5 causal genetic elements per disease/trait, of which 11% were gene-tissue pairs. Implicated gene-tissue pairs were concentrated in known disease-critical tissues, and causal genes were strongly enriched in disease-relevant gene sets. Causal gene-tissue pairs identified by TGFM recapitulated known biology (e.g., TPO-thyroid for Hypothyroidism), but also included biologically plausible novel findings (e.g., SLC20A2-artery aorta for Diastolic blood pressure). Further application of TGFM to single-cell eQTL data from 9 cell types in peripheral blood mononuclear cells (PBMC), analyzed jointly with GTEx tissues, identified 30 additional causal gene-PBMC cell type pairs at PIP > 0.5-primarily for autoimmune disease and blood cell traits, including the biologically plausible example of CD52 in classical monocyte cells for Monocyte count. In conclusion, TGFM is a robust and powerful method for fine-mapping causal tissues and genes at disease-associated loci.

[Predictive value of hemoglobin decrease for necrotizing enterocolitis in preterm infants with late-onset sepsis]

OBJECTIVES

To study the predictive value of hemoglobin (Hb) decrease for the occurrence of necrotizing enterocolitis (NEC) in preterm infants with late-onset sepsis (LOS) .

METHODS

Clinical data of 93 LOS preterm infants were collected for retrospective analysis, among which 16 infants developed NEC while 77 infants did not. Based on the decrease in Hb levels from the most recent Hb measurement before LOS occurrence to the initial Hb levels during LOS, the infants were divided into three groups: no Hb decrease (n=15), mild Hb decrease (Hb decrease <15 g/L; n=35), and severe Hb decrease (Hb decrease ≥15 g/L; n=43). Multivariate logistic regression analysis was conducted to explore the predictive factors for NEC secondary to LOS, and the value of Hb decrease in predicting NEC secondary to LOS was evaluated through receiver operating characteristic curve analysis.

RESULTS

The incidence of NEC in the severe Hb decrease group, mild Hb decrease group, and no Hb decrease group were 26%, 14%, and 0% (P<0.05), respectively. Multivariate logistic regression analysis revealed that a larger Hb decrease was an independent predictive factor for NEC in LOS preterm infants (OR=1.141, 95%CI: 1.061-1.277, P<0.001). Receiver operating characteristic curve analysis showed that the area under the curve for predicting NEC in preterm infants with LOS using Hb decrease (with a cut-off value of 20 g/L) was 0.803, with sensitivity and specificity of 0.69 and 0.78, respectively.

CONCLUSIONS

Hb decrease can serve as an indicator for prediction of NEC in preterm infants with LOS.

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.

Navigating the marrow sea towards erythromyeloblastic islands under normal and inflammatory conditions

PURPOSE OF REVIEW

Terminal erythroid differentiation occurs in specialized niches called erythroblastic islands. Since their discovery in 1958, these niches have been described as a central macrophage surrounded by differentiating erythroblasts. Here, we review the recent advances made in the characterization of these islands and the role they could play in anaemia of inflammation.

RECENT FINDINGS

The utilization of multispectral imaging flow cytometry (flow cytometry with microscopy) has enabled for a more precise characterization of the niche that revealed the presence of maturing granulocytes in close contact with the central macrophage. These erythromyeloblastic islands (EMBIs) can adapt depending on the peripheral needs. Indeed, during inflammation wherein inflammatory cytokines limit erythropoiesis and promote granulopoiesis, EMBIs present altered structures with increased maturing granulocytes and decreased erythroid precursors.

SUMMARY

Regulation of the structure and function of the EMBI in the bone marrow emerges as a potential player in the pathophysiology of acute and chronic inflammation and its associated anaemia.

Erythroblastic islands foster granulopoiesis in parallel to terminal erythropoiesis

The erythroblastic island (EBI), composed of a central macrophage surrounded by maturing erythroblasts, is the erythroid precursor niche. Despite numerous studies, its precise composition is still unclear. Using multispectral imaging flow cytometry, in vitro island reconstitution, and single-cell RNA sequencing of adult mouse bone marrow (BM) EBI-component cells enriched by gradient sedimentation, we present evidence that the CD11b+ cells present in the EBIs are neutrophil precursors specifically associated with BM EBI macrophages, indicating that erythro-(myelo)-blastic islands are a site for terminal granulopoiesis and erythropoiesis. We further demonstrate that the balance between these dominant and terminal differentiation programs is dynamically regulated within this BM niche by pathophysiological states that favor granulopoiesis during anemia of inflammation and favor erythropoiesis after erythropoietin stimulation. Finally, by molecular profiling, we reveal the heterogeneity of EBI macrophages by cellular indexing of transcriptome and epitope sequencing of mouse BM EBIs at baseline and after erythropoietin stimulation in vivo and provide a searchable online viewer of these data characterizing the macrophage subsets serving as hematopoietic niches. Taken together, our findings demonstrate that EBIs serve a dual role as niches for terminal erythropoiesis and granulopoiesis and the central macrophages adapt to optimize production of red blood cells or neutrophils.

HMGB1-mediated restriction of EPO signaling contributes to anemia of inflammation

Anemia of inflammation, also known as anemia of chronic disease, is refractory to erythropoietin (EPO) treatment, but the mechanisms underlying the EPO refractory state are unclear. Here, we demonstrate that high mobility group box-1 protein (HMGB1), a damage-associated molecular pattern molecule recently implicated in anemia development during sepsis, leads to reduced expansion and increased death of EPO-sensitive erythroid precursors in human models of erythropoiesis. HMGB1 significantly attenuates EPO-mediated phosphorylation of the Janus kinase 2/STAT5 and mTOR signaling pathways. Genetic ablation of receptor for advanced glycation end products, the only known HMGB1 receptor expressed by erythroid precursors, does not rescue the deleterious effects of HMGB1 on EPO signaling, either in human or murine precursors. Furthermore, surface plasmon resonance studies highlight the ability of HMGB1 to interfere with the binding between EPO and the EPOR. Administration of a monoclonal anti-HMGB1 antibody after sepsis onset in mice partially restores EPO signaling in vivo. Thus, HMGB1-mediated restriction of EPO signaling contributes to the chronic phase of anemia of inflammation.

Adrenergic Modulation of Erythropoiesis After Trauma

Severe traumatic injury results in a cascade of systemic changes which negatively affect normal erythropoiesis. Immediately after injury, acute blood loss leads to anemia, however, patients can remain anemic for as long as 6 months after injury. Research on the underlying mechanisms of such alterations of erythropoiesis after trauma has focused on the prolonged hypercatecholaminemia seen after trauma. Supraphysiologic elevation of catecholamines leads to an inhibitive effect on erythropoiesis. There is evidence to show that alleviation of the neuroendocrine stress response following trauma reduces these inhibitory effects. Both beta blockade and alpha-2 adrenergic receptor stimulation have demonstrated increased growth of hematopoietic progenitor cells as well as increased pro-erythropoietic cytokines after trauma. This review will describe prior research on the neuroendocrine stress response after trauma and its consequences on erythropoiesis, which offer insight into underlying mechanisms of prolonged anemia postinjury. We will then discuss the beneficial effects of adrenergic modulation to improve erythropoiesis following injury and propose future directions for the field.

Toll-like Receptor 4, Osteoblasts and Leukemogenesis; the Lesson from Acute Myeloid Leukemia

Toll-like receptor 4 (TLR4) is a pattern-recognizing receptor that can bind exogenous and endogenous ligands. It is expressed by acute myeloid leukemia (AML) cells, several bone marrow stromal cells, and nonleukemic cells involved in inflammation. TLR4 can bind a wide range of endogenous ligands that are present in the bone marrow microenvironment. Furthermore, the TLR4-expressing nonleukemic bone marrow cells include various mesenchymal cells, endothelial cells, differentiated myeloid cells, and inflammatory/immunocompetent cells. Osteoblasts are important stem cell supporting cells localized to the stem cell niches, and they support the proliferation and survival of primary AML cells. These supporting effects are mediated by the bidirectional crosstalk between AML cells and supportive osteoblasts through the local cytokine network. Finally, TLR4 is also important for the defense against complicating infections in neutropenic patients, and it seems to be involved in the regulation of inflammatory and immunological reactions in patients treated with allogeneic stem cell transplantation. Thus, TLR4 has direct effects on primary AML cells, and it has indirect effects on the leukemic cells through modulation of their supporting neighboring bone marrow stromal cells (i.e., modulation of stem cell niches, regulation of angiogenesis). Furthermore, in allotransplant recipients TLR4 can modulate inflammatory and potentially antileukemic immune reactivity. The use of TLR4 targeting as an antileukemic treatment will therefore depend both on the biology of the AML cells, the biological context of the AML cells, aging effects reflected both in the AML and the stromal cells and the additional antileukemic treatment combined with HSP90 inhibition.

Vagus Nerve Stimulation Reduces Indomethacin-Induced Small Bowel Inflammation

Crohn's disease is a chronic, idiopathic condition characterized by intestinal inflammation and debilitating gastrointestinal symptomatology. Previous studies of inflammatory bowel disease (IBD), primarily in colitis, have shown reduced inflammation after electrical or pharmacological activation of the vagus nerve, but the scope and kinetics of this effect are incompletely understood. To investigate this, we studied the effect of electrical vagus nerve stimulation (VNS) in a rat model of indomethacin-induced small intestinal inflammation. 1 min of VNS significantly reduced small bowel total inflammatory lesion area [(mean ± SEM) sham: 124 ± 14 mm2, VNS: 62 ± 14 mm2, p = 0.002], intestinal peroxidation and chlorination rates, and intestinal and systemic pro-inflammatory cytokine levels as compared with sham-treated animals after 24 h following indomethacin administration. It was not known whether this observed reduction of inflammation after VNS in intestinal inflammation was mediated by direct innervation of the gut or if the signals are relayed through the spleen. To investigate this, we studied the VNS effect on the small bowel lesions of splenectomized rats and splenic nerve stimulation (SNS) in intact rats. We observed that VNS reduced small bowel inflammation also in splenectomized rats but SNS alone failed to significantly reduce small bowel lesion area. Interestingly, VNS significantly reduced small bowel lesion area for 48 h when indomethacin administration was delayed. Thus, 1 min of electrical activation of the vagus nerve reduced indomethacin-induced intestinal lesion area by a spleen-independent mechanism. The surprisingly long-lasting and spleen-independent effect of VNS on the intestinal response to indomethacin challenge has important implications on our understanding of neural control of intestinal inflammation and its potential translation to improved therapies for IBD.

Circulating HMGB1 is increased in myelodysplastic syndrome but not in other bone marrow failure syndromes: proof-of-concept cross-sectional study

Background

Myelodysplastic syndrome (MDS) is associated with persistent immune activation. High mobility group box-1 (HMGB1) is a ubiquitous, functionally diverse, non-histone intranuclear protein. During acute and chronic inflammatory states, HMGB1 is actively released by inflammatory cells, further amplifying the inflammatory response. A role in MDS and other hypoplastic bone marrow (BM) disorders is incompletely understood.

Objectives

The objective of the study is to evaluate whether circulating HMGB1 is elevated in patients with MDS and other BM failure syndromes [namely, aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH)].

Design

This is a observational, cross-sectional, single-center, exploratory study.

Methods

We evaluated circulating concentrations of HMGB1, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in patients with MDS and age-matched hematologically healthy controls as well as patients with AA and PNH.

Results

We included 66 patients with MDS and 65 age-matched controls as well as 44 patients with other BM failures (AA = 27, PNH = 17). Circulating levels of HMGB1 were higher in patients with MDS [median, 4.9 ng/ml; interquartile range (IQR): 2.3-8.1] than in AA (median, 2.6 ng/ml; IQR: 1.7-3.7), PNH (median, 1.7 ng/ml; IQR: 0.9-2.5), and age-matched healthy individuals (median, 1.9 ng/ml; IQR: 0.9-2.5) (p = 0.0001). We observed higher concentrations of HMGB1 in the very low/low-risk MDS patients than in the intermediate/high/very high-risk ones (p = 0.046). Finally, in comparison with patients with AA, those with hypocellular MDS (h-MDS) had significantly higher levels of circulating HMGB1 (n = 14; median concentration, 5.6 ng/ml, IQR: 2.8-7.3; p = 0.006). We determined a circulating HMGB1 value of 4.095 ng/ml as a diagnostic cutoff differentiator between h-MDS and AA.

Conclusion

These observations indicate that circulating HMGB1 is increased in patients with MDS. HMGB1 (but not IL-1β or TNF-α) differentiated between MDS and other BM failures, suggesting that HMGB1 may be mechanistically involved in MDS and a druggable target to decrease inflammation in MDS.

Basic research and clinical progress of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE), a major cerebral complication of sepsis, occurs in 70% of patients admitted to the intensive care unit (ICU). This condition can cause serious impairment of consciousness and is associated with a high mortality rate. Thus far, several experimental screenings and radiological techniques (e.g., electroencephalography) have been used for the non-invasive assessment of the structure and function of the brain in patients with SAE. Nevertheless, the pathogenesis of SAE is complicated and remains unclear. In the present article, we reviewed the currently available literature on the epidemiology, clinical manifestations, pathology, diagnosis, and management of SAE. However, currently, there is no ideal pharmacological treatment for SAE. Treatment targeting mitochondrial dysfunction may be useful in the management of SAE.

Plasma HMGB1 levels and physical performance in ICU survivors

PURPOSE

Physical impairment after critical illness is recognized as a part of the post-intensive care syndrome (PICS). About one third of intensive care unit (ICU) survivors suffer from long-term physical disability, yet the underlying pathophysiological mechanisms remain poorly understood. The pro-inflammatory alarmin, high mobility group box 1 (HMGB1), promotes muscle dysfunction in experimental models, and HMGB1 stays elevated in some patients after ICU discharge. Accordingly, we investigated the relationship between HMGB1 plasma levels and physical performance in ICU survivors.

METHODS

Prospective cohort study of 100 ICU survivors from the general ICU at the Karolinska University Hospital, Sweden. Patients returned for follow up at 3 (58 patients) and 6 months (51 patients) after ICU discharge. Blood samples were collected, and a 6-minute walk test (6-MWT), a handgrip-strength test (HST), and a timed-stands test (TST) were performed.

RESULTS

Compared to reference values of the different physical tests, 16% of patients underperformed at all tests at 3 months and 12% at 6 months. All test results, except hand-grip strength left, improved significantly over the follow-up period (P < .05). There was no significant association between plasma HMGB1 levels at 3 and 6 months and scores on the three tests (6-MWT, TST, and HST) (P = .50-0.69).

CONCLUSION

In this follow-up study of ICU survivors, we found no significant association between plasma HMGB1 levels and physical performance. Additional follow-up studies of HMGB1 plasma levels and muscle function in ICU survivors are still warranted.

EDITORIAL COMMENT

HMGB-1, a marker of cell damage and activation, is known to increase in ICU patients. In study participants at 3- to 6-month post-ICU stay, HMGB-1 levels were still elevated, although no association to the primary outcome, physical performance, was found. Mechanisms for failure to recover physical performance post-ICU remain unclear, and investigations into cause of post-intensive care syndrome need to continue.

TRIAL REGISTRATIONS

ClinicalTrials.gov identifier NCT02914756.

Electroacupuncture reduces cold stress-induced pain through microglial inactivation and transient receptor potential V1 in mice

Background

The treatment, and efficacy thereof, is considered to be inadequate with specificity to alleviation of Fibromyalgia and its associated pain. Fibromyalgia patients suffer from chronic and persistent widespread pain and generalized tenderness. Transient receptor potential V1 (TRPV1), which is reported as a Ca²⁺ permeable ion channel that can be activated by inflammation, is reported to be involved in the development of fibromyalgia pain.

Methods

The current study explored the TRPV1 channel functions as a noxious sensory input in mice cold stress model. It remains unknown whether electroacupuncture (EA) attenuates fibromyalgia pain or affects the TRPV1 pathway.

Results

We show that cold stress increases mechanical and thermal pain (day 7: mechanical: 1.69 ± 0.41 g; thermal: 4.68 ± 0.56 s), and that EA and Trpv1 deletion counter this increase. EA and Trpv1 deletion reduced the cold stress-induced increase in inflammatory mediators and TRPV1-related molecules in the hypothalamus, periaqueductal gray (PAG), and cerebellum of mice.

Conclusions

Our results imply that EA has an analgesic effect associated with TRPV1 downregulation. We provide novel evidence that these inflammatory mediators can modulate the TRPV1 signaling pathway and suggest new potential therapeutic targets for fibromyalgia pain.

A significant decrease in hemoglobin concentrations may predict occurrence of necrotizing enterocolitis in preterm infants with late-onset sepsis

OBJECTIVE

This study aimed to examine the clinical value of a decrease in hemoglobin concentration (HC) after the onset of sepsis for predicting occurrence of necrotizing enterocolitis (NEC) in preterm infants with late-onset sepsis.

METHODS

We performed a retrospective cohort study between January 2015 and January 2020. Premature neonates (gestational age <37 weeks) with late-onset sepsis (age >3 days) were enrolled. According to the degree of reduction in HC, neonates were divided into the non-decrease group, mild decrease group, and severe decrease group. Demographic data, perinatal conditions, blood cell count analysis, blood culture, and treatment measures were compared.

RESULTS

Eighty premature infants with sepsis were studied. The mortality rate and incidence of NEC were significantly higher in the severe decrease group than in the non-decrease and mild decrease groups. Significant differences were observed in the decrease in HC, red blood cell transfusion, and ventilator application between the NEC and non-NEC groups. A significant decrease in HC was an independent risk factor for NEC in preterm infants with sepsis.

CONCLUSION

A significant decrease in HC is an independent risk factor for NEC and may predict the occurrence of NEC in preterm infants with sepsis.

The Effect and Regulatory Mechanism of High Mobility Group Box-1 Protein on Immune Cells in Inflammatory Diseases

High mobility group box-1 protein (HMGB1), a member of the high mobility group protein superfamily, is an abundant and ubiquitously expressed nuclear protein. Intracellular HMGB1 is released by immune and necrotic cells and secreted HMGB1 activates a range of immune cells, contributing to the excessive release of inflammatory cytokines and promoting processes such as cell migration and adhesion. Moreover, HMGB1 is a typical damage-associated molecular pattern molecule that participates in various inflammatory and immune responses. In these ways, it plays a critical role in the pathophysiology of inflammatory diseases. Herein, we review the effects of HMGB1 on various immune cell types and describe the molecular mechanisms by which it contributes to the development of inflammatory disorders. Finally, we address the therapeutic potential of targeting HMGB1.

Chrysophanol Exerts Anti-inflammatory Activity by Targeting Histone Deacetylase 3 Through the High Mobility Group Protein 1-Nuclear Transcription Factor-Kappa B Signaling Pathway in vivo and in vitro

Chrysophanol (Chr) is the main monomer isolated from Rheum rhabarbarum. This study aimed to identify the potential in vitro and in vivo cytoprotective effects of Chr on lipopolysaccharide (LPS)-triggered acute lung injury (ALI). We used an ALI-murine model and constructed an inflammatory macrophage in vitro cell model to determine the cellular mechanisms involved in Chr-mediated activity. To observe the vital role of histone deacetylase 3 (HDAC3) in abolishing inflammation action, HDAC3 was downregulated using small interfering RNA. Analysis of the expression of nuclear transcription factor-kappa B p65 (NF-κB p65) and molecules of its downstream signaling pathway were assessed in vitro and in lung tissue samples using the mouse model. Concentrations of tumor necrosis factor-α, interleukin-1β, high mobility group protein 1 (HMGB1), and interleukin-16 in supernatants and the bronchoalveolar lavage fluid were measured using enzyme-linked immunosorbent assay. A reporter gene assay measured HMGB1 activity, and NF-κB p65 and HMGB1 intracellular localization was determined by immunofluorescence detection on histological lung samples from Chr-treated mice. The protein interactions between HMGB1, HDAC3, and NF-κB p65 were tested by co-immunoprecipitation. Chr treatment relieved LPS-induced lung lesions. Chr also enhanced superoxide dismutase levels in ALI mice. Chr reduced the LPS-induced protein expression of NF-κB and its related pathway molecules in both in vivo and in vitro models. Moreover, Chr downregulated LPS-enhanced HMGB1 expression, acetylation, and nuclear nucleocytoplasmic translocation. However, HDAC3 knockdown substantially reduced Chr-mediated HDAC3/NF-κB expression.

Furthermore, Chr enhanced HMGB1/HDAC3/NF-κB p65 complex interaction, whereas HDAC3 knockdown reduced Chr-mediated HMGB1/HDAC3/NF-κB p65 formation. This study showed that the protective effects induced by Chr were associated with the regulation of the HMGB1/NF-κB pathway via HDAC3.

Targeting adaptor protein SLP76 of RAGE as a therapeutic approach for lethal sepsis

Accumulating evidence shows that RAGE has an important function in the pathogenesis of sepsis. However, the mechanisms by which RAGE transduces signals to downstream kinase cascades during septic shock are not clear. Here, we identify SLP76 as a binding partner for the cytosolic tail of RAGE both in vitro and in vivo and demonstrate that SLP76 binds RAGE through its sterile α motif (SAM) to mediate downstream signaling. Genetic deficiency of RAGE or SLP76 reduces AGE-induced phosphorylation of p38 MAPK, ERK1/2 and IKKα/β, as well as cytokine release. Delivery of the SAM domain into macrophages via the TAT cell-penetrating peptide blocks proinflammatory cytokine production. Furthermore, administration of TAT-SAM attenuates inflammatory cytokine release and tissue damage in mice subjected to cecal ligation and puncture (CLP) and protects these mice from the lethality of sepsis. These findings reveal an important function for SLP76 in RAGE-mediated pro-inflammatory signaling and shed light on the development of SLP76-targeted therapeutics for sepsis.

Bile is a promising gut nutrient that inhibits intestinal bacterial translocation and promotes gut motility via an interleukin-6-related pathway in an animal model of endotoxemia

OBJECTIVES

People who are critically ill have high rates of endotoxemia that can significantly decrease bile flow and increase bile cytokines, the latter of which might worsen their condition. Bile acids are nutrient-signaling hormones that have a significant impact on gut barrier function and motility, and the gut is considered the origin of systemic inflammation. Therefore, healthy exogenous bile could be a promising gut nutrient for critical illness, so the biomedical role of bile in endotoxemia was investigated in this study.

METHODS

Twelve rats were injected with lipopolysaccharide (LPS) and randomized into a group with sham operation) and a group with bile external drainage (n = 6 for each group); six rats with sham operation served as the control group. In addition, interleukin-6 (IL-6) knockout mice and macrophages were treated with LPS.

RESULTS

Compared to the control animals, the group with LPS injection and sham operation had significantly increased levels of gut permeability, gut bacterial translocation, gut mucosal tumor necrosis factor α, IL-6 transcripts, and serum tumor necrosis factor α and IL-6. Compared to group with sham operation and LPS injection, bile external drainage (in LPS-challenged rats) increased gut bacterial translocation by 10 times, and this detrimental effect was associated with prolonged intestinal transit time, increased serum IL-6 concentration, and up-regulated gut mucosal IL-6 transcripts. Moreover, bile selectively inhibited LPS-stimulated macrophages in IL-6 release, which can activate gastrointestinal submucosal neurons to promote motility. Knocking out IL-6 significantly reduced gut bacterial translocation in endotoxemic mice.

CONCLUSIONS

Bile is a promising gut nutrient that inhibits gut bacterial translocation and promotes gut motility via an IL-6-related pathway in experimental endotoxemia.

SARS-CoV-2 and interferon blockade

The response to viral infection generally includes an activation of the adaptive immune response to produce cytotoxic T cells and neutralizing antibodies. We propose that SARS-CoV-2 activates the innate immune system through the renin-angiotensin and kallikrein-bradykinin pathways, blocks interferon production and reduces an effective adaptive immune response. This model has therapeutic implications.

The performance of the alarmin HMGB1 in pediatric diseases: From lab to clinic

INTRODUCTION

The ubiquitously expressed nonhistone nuclear protein high-mobility group box protein 1 (HMGB1) has different functions related to posttranslational modifications and cellular localization. In the nucleus, HMGB1 modulates gene transcription, replication and DNA repair as well as determines chromosomal architecture. When the post-transcriptional modified HMGB1 is released into the extracellular space, it triggers several physiological and pathological responses and initiates innate immunity through interacting with its reciprocal receptors (i.e., TLR4/2 and RAGE). The effect of HMGB1-mediated inflammatory activation on different systems has received increasing attention. HMGB1 is now considered to be an alarmin and participates in multiple inflammation-related diseases. In addition, HMGB1 also affects the occurrence and progression of tumors. However, most studies involving HMGB1 have been focused on adults or mature animals. Due to differences in disease characteristics between children and adults, it is necessary to clarify the role of HMGB1 in pediatric diseases.

METHODS AND RESULTS

Through systematic database retrieval, this review aimed to first elaborate the characteristics of HMGB1 under physiological and pathological conditions and then discuss the clinical significance of HMGB1 in the pediatric diseases according to different systems.

CONCLUSIONS

HMGB1 plays an important role in a variety of pediatric diseases and may be used as a diagnostic biomarker and therapeutic target for new strategies for the prevention and treatment of pediatric diseases.

HMGB1 as a therapeutic target in disease

High-mobility group box 1 (HMGB1) was initially recognized as a ubiquitous nuclear protein involved in maintaining the nucleosome integrity and facilitating gene transcription. HMGB1 has since been reevaluated to be a prototypical damage-associated molecular pattern (DAMP) protein, and together with its exogenous counterpart, pathogen-associated molecular pattern (PAMP), completes the body's alarmin system against disturbances in homeostasis. HMGB1 can be released into the extracellular matrix (ECM) by either granulocytes or necrotic cells to serve as a chemotaxis/cytokine during infection, endotoxemia, hypoxia, ischemia-reperfusion events, and cancer. Different isoforms of HMGB1 present with distinctive physiological functions in ECM-fully-reduced HMGB1 (all thiol) acts as the initial damage signal to recruit circulating myeloid cells, disulfide HMGB1 behaves as a cytokine to activate macrophages and neutrophils, and both signals are turned off when HMGB1 is terminally oxidized into the final sulfonate form. Targeting HMGB1 constitutes a favorable therapeutic strategy for inflammation and inflammatory diseases. Antagonists such as ethyl pyruvate inhibit HMGB1 by interfering with its cytoplasmic exportation, while others such as glycyrrhizin directly bind to HMGB1 and render it unavailable for its receptors. The fact that a mixture of different HMGB1 isoforms is present in the ECM poses a challenge in pinpointing the exact role of an individual antagonist. A more discriminative probe for HMGB1 may be necessary to advance our knowledge of HMGB1, HMGB1 antagonists, and inflammatory-related diseases.

Stress erythropoiesis: definitions and models for its study

Steady-state erythropoiesis generates new erythrocytes at a constant rate, and it has enormous productive capacity. This production is balanced by the removal of senescent erythrocytes by macrophages in the spleen and liver. Erythroid homeostasis is highly regulated to maintain sufficient erythrocytes for efficient oxygen delivery to the tissues, while avoiding viscosity problems associated with overproduction. However, there are times when this constant production of erythrocytes is inhibited or is inadequate; at these times, erythroid output is increased to compensate for the loss of production. In some cases, increased steady-state erythropoiesis can offset the loss of erythrocytes but, in response to inflammation caused by infection or tissue damage, steady-state erythropoiesis is inhibited. To maintain homeostasis under these conditions, an alternative stress erythropoiesis pathway is activated. Emerging data suggest that the bone morphogenetic protein 4 (BMP4)-dependent stress erythropoiesis pathway is integrated into the inflammatory response and generates a bolus of new erythrocytes that maintain homeostasis until steady-state erythropoiesis can resume. In this perspective, we define the mechanisms that generate new erythrocytes when steady-state erythropoiesis is impaired and discuss experimental models to study human stress erythropoiesis.

Targeting Inflammation Driven by HMGB1

High mobility group box 1 (HMGB1) is a highly conserved, nuclear protein present in all cell types. It is a multi-facet protein exerting functions both inside and outside of cells. Extracellular HMGB1 has been extensively studied for its prototypical alarmin functions activating innate immunity, after being actively released from cells or passively released upon cell death. TLR4 and RAGE operate as the main HMGB1 receptors. Disulfide HMGB1 activates the TLR4 complex by binding to MD-2. The binding site is separate from that of LPS and it is now feasible to specifically interrupt HMGB1/TLR4 activation without compromising protective LPS/TLR4-dependent functions. Another important therapeutic strategy is established on the administration of HMGB1 antagonists precluding RAGE-mediated endocytosis of HMGB1 and HMGB1-bound molecules capable of activating intracellular cognate receptors. Here we summarize the role of HMGB1 in inflammation, with a focus on recent findings on its mission as a damage-associated molecular pattern molecule and as a therapeutic target in inflammatory diseases. Recently generated HMGB1-specific inhibitors for treatment of inflammatory conditions are discussed.

Narciclasine improves outcome in sepsis among neonatal rats via inhibition of calprotectin and alleviating inflammatory responses

Sepsis is associated with exacerbated inflammatory response which subsequently results in multiple organ dysfunction. Sepsis accounts for high mortality and morbidity among newborns worldwide. Narciclasine is a plant alkaloid which has shown to possess anti-inflammatory properties. In this study we investigated the effect and mechanism of action of narciclasine in neonatal sepsis rat models. The excessive release of S100A8/A9 or calprotectin in neonatal sepsis could be detrimental as it could exacerbate the inflammatory responses. We found that narciclasine significantly reduced the plasma levels of S100A8/A9 and also suppressed its expression in the liver and lung. The systemic and local bacterial load was also reduced in the narciclasine treated rats. The systemic and local production of pro-inflammatory cytokines in plasma and organs (liver and lungs) was significantly reduced in the narciclasine treated rats. The histopathological studies showed that narciclasine prevents the organ damage associated with sepsis and improved the survival of neonatal rats. Sepsis increased the phosphorylated NF-κβ p65 protein expression in the liver. Narciclasine suppressed the phosphorylation of NF-κβ p65 and the degradation of NF-κβ inhibitory protein alpha. It could also suppress the expression of adaptor proteins of the toll like receptor signaling pathway viz., myeloid differentiation factor 88 (MyD88), Interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor associated factor 6 (TRAF6). These results suggest that narciclasine protects against sepsis in neonatal rats through the inhibition of calprotectin, pro-inflammatory cytokines and suppression of NF-κβ signaling pathway.

Alcohol-dependent pulmonary inflammation: A role for HMGB-1

Previous studies have demonstrated that acute alcohol intoxication significantly impairs lung immune responses, which can lead to the tissue being undefended from microbial infection and resulting disease. Data suggest that acute intoxication presents an axis where simultaneously suppressing early pro-inflammatory cytokines while inducing anti-inflammatory signals contributes to alcohol-dependent immune suppression in the lung, and thus undeterred microbial replication. Interestingly, alcoholics and those with alcohol use disorder present with increased pneumonia and acute respiratory diseases (ARDs), suggesting a more active priming of inflammatory responses in the lungs. There is current research evaluating the acute effects of binge ethanol consumption on adolescents, which is of grave concern, though long-term effects of adolescent ethanol binge exposure are less studied. We hypothesize that adolescent binge drinking may prime the individual to severe pulmonary distress, when later challenged by a microbial pathogen. Herein, we evaluate a model of adolescent intermittent ethanol (AIE) exposure to investigate pulmonary pathology after microbial challenge. Ethanol was administered to adolescent mice using a binge exposure schedule, and mice were then rested to early adulthood. These mice were then challenged with a sub-lethal intranasal inoculation of Klebsiella pneumoniae and evaluated for severity of disease. We find that AIE exposure initially activates inflammatory mediators within the lung, which resolves over time. However, when challenged with a microbial pathogen after this resolution period, these animals present with more severity of inflammation, pulmonary tissue damage, and mortality when challenged with a pulmonary microbial infection. Interestingly, our data suggest a role for alcohol-dependent release of the protein HMGB-1 from host cells, for both morbidity and mortality in our model of microbial-dependent pulmonary inflammation.

The effects of propranolol and clonidine on bone marrow expression of hematopoietic cytokines following trauma and chronic stress

BACKGROUND

Attenuating post-injury neuroendocrine stress abrogates persistent injury-associated anemia. Our objective was to examine the mechanisms by which propranolol and clonidine modulate this process. We hypothesized that propranolol and clonidine would decrease bone marrow expression of high-mobility group box-1 (HMGB1) and increase expression of stem cell factor (SCF) and B-cell lymphoma-extra large (Bcl-xL).

METHODS

Male Sprague-Dawley rats were allocated to naïve control, lung contusion followed by hemorrhagic shock (LCHS), or LCHS plus daily chronic restraint stress (LCHS/CS) ±propranolol, ±clonidine. Day seven bone marrow expression of HMGB1, SCF, and Bcl-xL was assessed by polymerase chain reaction.

RESULTS

Following LCHS, HMGB1 was decreased by propranolol (49% decrease, p = 0.012) and clonidine (54% decrease, p < 0.010). SCF was decreased following LCHS/CS, and was increased by propranolol (629% increase, p < 0.001) and clonidine (468% increase, p < 0.001). Bcl-xL was decreased following LCHS/CS, and was increased by propranolol (59% increase, p = 0.006) and clonidine (77% increase, p < 0.001).

CONCLUSIONS

Following severe trauma, propranolol and clonidine abrogate persistent injury-associated anemia by modulating bone marrow cytokines, favoring effective erythropoiesis.

p38MAPK plays a pivotal role in the development of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening illness characterized by a complex pathophysiology, involving not only the respiratory system but also nonpulmonary distal organs. Although advances in the management of ARDS have led to a distinct improvement in ARDS-related mortality, ARDS is still a life-threatening respiratory condition with long-term consequences. A better understanding of the pathophysiology of this condition will allow us to create a personalized treatment strategy for improving clinical outcomes. In this article, we present a general overview p38 mitogen-activated protein kinase (p38MAPK) and recent advances in understanding its functions. We consider the potential of the pharmacological targeting of p38MAPK pathways to treat ARDS.

DAMPs and sterile inflammation in drug hepatotoxicity

Drug hepatotoxicity is the leading cause of acute liver failure (ALF) in the developed countries. The early diagnosis and treatment are still problematic, and one important reason is the lack of reliable mechanistic biomarkers and therapeutic targets; therefore, searching for new biomarkers and therapeutic targets is urgent. Drug hepatotoxicity induces severe liver cells damage and death. Dead and damaged cells release endogenous damage-associated molecular patterns (DAMPs). Increased circulating levels of DAMPs (HMGB1, histones and DNA) can reflect the severity of drug hepatotoxicity. Elevated plasma HMGB1 concentrations can serve as early and sensitive mechanistic biomarker for clinical acetaminophen hepatotoxicity. DAMPS significantly contribute to liver injury and inhibiting the release of DAMPs ameliorates experimental hepatotoxicity. In addition, HMGB1 mediates 80% of gut bacterial translocation (BT) during acetaminophen toxicity. Gut BT triggers systemic inflammation, leading to multiple organ injury and mortality. Moreover, DAMPs can trigger and extend sterile inflammation, which contributes to early phase liver injury but improves liver regeneration at the late phase of acetaminophen overdose, because anti-inflammatory treatment reduces liver injury at early phase but impairs liver regeneration at late phase of acetaminophen toxicity, whereas pro-inflammatory therapy improves late phase liver regeneration. DAMPs are promising mechanistic biomarkers and could also be the potential therapeutic targets for drug hepatotoxicity. DAMPs-triggered sterile inflammation contributes to liver injury at early phase but improves liver regeneration at later phase of acetaminophen hepatotoxicity; therefore, anti-inflammatory therapy would be beneficial at early phase but should be avoided at the late phase of acetaminophen overdose.

High mobility group box-1 (HMGB1) is increased in injured mouse spinal cord and can elicit neurotoxic inflammation

Inflammation is a ubiquitous but poorly understood consequence of spinal cord injury (SCI). The mechanisms controlling this response are unclear but culminate in the sequential activation of resident and recruited immune cells. Collectively, these cells can exert divergent effects on cell survival and tissue repair. HMGB1 is a ubiquitously expressed DNA binding protein and also a potent inflammatory stimulus. Necrotic cells release HGMB1, but HMGB1 also is actively secreted by inflammatory macrophages. A goal of this study was to quantify spatio-temporal patterns of cellular HMGB1 expression in a controlled mouse model of experimental SCI then determine the effects of HMGB1 on post-SCI neuroinflammation and recovery of function. We documented SCI-induced changes in nuclear and cytoplasmic distribution of HMGB1 in various cell types after SCI. The data reveal a time-dependent increase in HMGB1 mRNA and protein with protein reaching maximal levels 24-72 h post-injury then declining toward baseline 14-28 days post-SCI. Although most cells expressed nuclear HMGB1, reduced nuclear labeling with increased cytoplasmic expression was found in a subset of CNS macrophages suggesting that those cells begin to secrete HMGB1 at the injury site. In vitro data indicate that extracelluar HMGB1 helps promote the development of macrophages with a neurotoxic phenotype. The ability of HMGB1 to elicit neurotoxic macrophage functions was confirmed in vivo; 72 h after injecting 500 ng of recombinant HMGB1 into intact spinal cord ventral horn, inflammatory CNS macrophages co-localized with focal areas of neuronal killing. However, attempts to confer neuroprotection after SCI by blocking HMGB1 with a neutralizing antibody were unsuccessful. Collectively, these data implicate HMGB1 as a novel regulator of post-SCI inflammation and suggest that inhibition of HMGB1 could be a novel therapeutic target after SCI. Future studies will need to identify better methods to deliver optimal concentrations of HMGB1 antagonists to the injured spinal cord.

Erythropoiesis: insights into pathophysiology and treatments in 2017

Erythropoiesis is a tightly-regulated and complex process originating in the bone marrow from a multipotent stem cell and terminating in a mature, enucleated erythrocyte.Altered red cell production can result from the direct impairment of medullary erythropoiesis, as seen in the thalassemia syndromes, inherited bone marrow failure as well as in the anemia of chronic disease. Alternatively, in disorders such as sickle cell disease (SCD) as well as enzymopathies and membrane defects, medullary erythropoiesis is not, or only minimally, directly impaired. Despite these differences in pathophysiology, therapies have traditionally been non-specific, limited to symptomatic control of anemia via packed red blood cell (pRBC) transfusion, resulting in iron overload and the eventual need for iron chelation or splenectomy to reduce defective red cell destruction. Likewise, in polycythemia vera overproduction of red cells has historically been dealt with by non-specific myelosuppression or phlebotomy. With a deeper understanding of the molecular mechanisms underlying disease pathophysiology, new therapeutic targets have been identified including induction of fetal hemoglobin, interference with aberrant signaling pathways and gene therapy for definitive cure. This review, utilizing some representative disorders of erythropoiesis, will highlight novel therapeutic modalities currently in development for treatment of red cell disorders.

Bile and circulating HMGB1 contributes to systemic inflammation in obstructive jaundice

BACKGROUND

Obstructive jaundice (OJ) patients with cholangitis are prone to sepsis; however, the underlying mechanisms are still not clear and need to be clarified.

METHODS

Analyzing all available published data related to the title of this article.

RESULTS

OJ leads to absence of gut luminal bile and accumulation of hepatic and circulating bile acids. Absence of gut luminal bile deprives the gut from its antiinflammatory, endotoxin-binding, bacteriostatic, mucosal-trophic, epithelial tight-junction maintaining, and gut motility-regulating effects, leading to gut bacterial overgrowth, mucosal atrophy, mucosal tight-junction loss, and gut motility dysfunction. These alterations promote intestinal endotoxin and bacterial translocation (BT) into portal and systemic circulation. Gut BT triggers systemic inflammation, which can lead to multiple organ dysfunctions in OJ. The accumulation of hepatic and circulating bile acids kills/damages hepatocyte and Kupffer cells, and it also significantly decreases the number of liver natural killer T-cells in OJ. This results in impaired hepatic and systemic immune function, which facilitates BT. In addition, neutralizing bile HMGB1 can reverse endotoxemic bile-induced gut BT and mucosal injury in mice, suggesting that bile HMGB1 in OJ patients can be responsible for internal drainage-related clinical complications. Moreover, the elevated circulating HMGB1 level may contribute to multiple organ injuries, and it might also mediate gut BT in OJ.

CONCLUSIONS

HMGB1 may significantly contribute to systemic inflammation and multiple organ dysfunctions in OJ.

Glutathione S-Transferase Pi Prevents Sepsis-Related High Mobility Group Box-1 Protein Translocation and Release

Glutathione S-transferase Pi (GSTP) was originally identified as one of cytosolic phase II detoxification enzymes and also was considered to function via its non-catalytic, ligand-binding activity. We have reported that GSTP played an anti-inflammatory role in macrophages, suggesting that GSTP may have a protective role in inflammation. In this study, we deleted the murine Gstp gene cluster and found that GSTP significantly decreased the mortality of experimental sepsis and reduced related serum level of high mobility group box-1 protein (HMGB1). As HMGB1 is the key cytokine involved in septic death, we further studied the effect of GSTP on HMGB1 release. The results demonstrated that a classic protein kinase C (cPKC) dependent phosphorylation of cytoplasmic GSTP at Ser184 occurred in macrophages in response to lipopolysaccharide (LPS) stimulation. Phosphorylated GSTP was then translocated to the nucleus. In the nucleus, GSTP bound to HMGB1 and suppressed LPS-triggered and cPKC-mediated HMGB1 phosphorylation. Consequently, GSTP prevented the translocation of HMGB1 to cytoplasm and release. Our findings provide the new evidence that GSTP inhibited HMGB1 release via binding to HMGB1 in the nucleus independent of its transferase activity. cPKC-mediated GSTP phosphorylation was essential for GSTP to translocate from cytoplasm to nucleus. To our knowledge, we are the first to report that nuclear GSTP functions as a negative regulator to control HMGB1 release from macrophages and decreases the mortality of sepsis.

Extracellular HMGB1 as a therapeutic target in inflammatory diseases

INTRODUCTION

High-mobility group box 1 (HMGB1) is a ubiquitous nuclear protein that promotes inflammation when released extracellularly after cellular activation, stress, damage or death. HMGB1 operates as one of the most intriguing molecules in inflammatory disorders via recently elucidated signal and molecular transport mechanisms. Treatments based on antagonists specifically targeting extracellular HMGB1 have generated encouraging results in a wide number of experimental models of infectious and sterile inflammation. Clinical studies are still to come. Areas covered: We here summarize recent advances regarding pathways for extracellular HMGB1 release, receptor usage, and functional consequences of post-translational modifications. The review also addresses results of preclinical HMGB1-targeted therapy studies in multiple inflammatory conditions and outlines the current status of emerging clinical HMGB1-specific antagonists. Expert opinion: Blocking excessive amounts of extracellular HMGB1, particularly the disulfide isoform, offers an attractive clinical opportunity to ameliorate systemic inflammatory diseases. Therapeutic interventions to regulate intracellular HMGB1 biology must still await a deeper understanding of intracellular HMGB1 functions. Future work is needed to create more robust assays to evaluate functional bioactivity of HMGB1 antagonists. Forthcoming clinical studies would also greatly benefit from a development of antibody-based assays to quantify HMGB1 redox isoforms, presently assessed by mass spectrometry methods.

Pre-B cell leukemia transcription factor 3 induces inflammatory responses in human umbilical vein endothelial cells and murine sepsis via acting a competing endogenous RNA for high mobility group box 1 protein

The present study investigated the roles of pre-B cell leukemia transcription factor 3 (PBX3) in sepsis. Reverse transcription-quantitative polymerase chain reaction and western blot analysis indicated that overexpression of the PBX 3′-untranslated region (UTR) promoted high mobility group box 1 (HMGB1) protein expression in human umbilical vein endothelial cells (HUVECs) (P<0.01). Furthermore, post-treatment of PBX3 small interfering (si)RNA suppressed lipopolysaccharide (LPS)-mediated HMGB1 release and attenuated HMGB1-mediated hyperpermeability and leukocyte migration in HUVECs and septic mice (P<0.01). Additionally, post-injection of PBX3 siRNA also induced the downregulation of cecal ligation and puncture-induced HMGB1 release, production of IL-6 and mortality (P<0.01). Mechanistically, the 3′UTRs of PBX3 and HMGB1 were identified to harbor six common micro (mi)RNA binding sites, and PBX 3′UTR increased HMGB1 expression in a 3′UTR- and miRNA-dependent manner. Notably, the coding sequence of PBX3 did not increase HMGB1 expression in HUVECs. Collectively, the present study indicates that PBX 3′UTR may induce inflammatory responses and sepsis via acting as a competing endogenous RNA for HMGB1.

Persistent injury-associated anemia: the role of the bone marrow microenvironment

BACKGROUND

The regulation of erythropoiesis involves hematopoietic progenitor cells, bone marrow stroma, and the microenvironment. Following severe injury, a hypercatecholamine state develops that is associated with increased mobilization of hematopoietic progenitor cells to peripheral blood and decreased growth of bone marrow erythroid progenitor cells that manifests clinically as a persistent injury-associated anemia. Changes within the bone marrow microenvironment influence the development of erythroid progenitor cells. Therefore, we sought to determine the effects of lung contusion, hemorrhagic shock, and chronic stress on the hematopoietic cytokine response.

MATERIALS AND METHODS

Bone marrow was obtained from male Sprague-Dawley rats (n = 6/group) killed 7 d after lung contusion followed by hemorrhagic shock (LCHS) or LCHS followed by daily chronic restraint stress (LCHS/CS). End point polymerase chain reaction was performed for interleukin-1β, interleukin-10, stem cell factor, transforming growth factor-β, high-mobility group box-1 (HMGB-1), and B-cell lymphoma-extra large.

RESULTS

Seven days following LCHS and LCHS/CS, bone marrow expression of prohematopoietic cytokines (interleukin-1β, interleukin-10, stem cell factor, and transforming growth factor-β) was significantly decreased, and bone marrow expression of HMGB-1 was significantly increased. B-cell lymphoma-extra large bone marrow expression was not affected by LCHS or LCHS/CS (naïve: 44 ± 12, LCHS: 44 ± 12, LCHS/CS: 37 ± 1, all P > 0.05).

CONCLUSIONS

The bone marrow microenvironment was significantly altered following severe trauma in a rodent model. Prohematopoietic cytokines were downregulated, and the proinflammatory cytokine HMGB-1 had increased bone marrow expression. Modulation of the bone marrow microenvironment may represent a therapeutic strategy following severe trauma to alleviate persistent injury-associated anemia.

HMGB1 and Extracellular Histones Significantly Contribute to Systemic Inflammation and Multiple Organ Failure in Acute Liver Failure

Acute liver failure (ALF) is the culmination of severe liver cell injury from a variety of causes. ALF occurs when the extent of hepatocyte death exceeds the hepatic regenerative capacity. ALF has a high mortality that is associated with multiple organ failure (MOF) and sepsis; however, the underlying mechanisms are still not clear. Emerging evidence shows that ALF patients/animals have high concentrations of circulating HMGB1, which can contribute to multiple organ injuries and mediate gut bacterial translocation (BT). BT triggers/induces systemic inflammatory responses syndrome (SIRS), which can lead to MOF in ALF. Blockade of HMGB1 significantly decreases BT and improves hepatocyte regeneration in experimental acute fatal liver injury. Therefore, HMGB1 seems to be an important factor that links BT and systemic inflammation in ALF. ALF patients/animals also have high levels of circulating histones, which might be the major mediators of systemic inflammation in patients with ALF. Extracellular histones kill endothelial cells and elicit immunostimulatory effect to induce multiple organ injuries. Neutralization of histones can attenuate acute liver, lung, and brain injuries. In conclusion, HMGB1 and histones play a significant role in inducing systemic inflammation and MOF in ALF.

Anemia of Inflammation: A Review

Impaired iron homeostasis and the suppressive effects of proinflammatory cytokines on erythropoiesis, together with alterations of the erythrocyte membrane that impair its survival, cause anemia of inflammation. Recent epidemiologic studies have connected inflammatory anemia with critical illness, obesity, aging, kidney failure, cancer, chronic infection, and autoimmune disease. The proinflammatory cytokine, interleukin-6, the iron regulatory hormone, hepcidin, and the iron exporter, ferroportin, interact to cause iron sequestration in the setting of inflammation. Although severe anemia is associated with adverse outcomes in critical illness, experimental models suggest that iron sequestration is part of a natural defense against pathogens.

Systemic HMGB1 Neutralization Prevents Postoperative Neurocognitive Dysfunction in Aged Rats

Postoperative neurocognitive disorders are common complications in elderly patients following surgery or critical illness. High mobility group box 1 protein (HMGB1) is rapidly released after tissue trauma and critically involved in response to sterile injury. Herein, we assessed the role of HMGB1 after liver surgery in aged rats and explored the therapeutic potential of a neutralizing anti-HMGB1 monoclonal antibody in a clinically relevant model of postoperative neurocognitive disorders. Nineteen to twenty-two months Sprague-Dawley rats were randomly assigned as: (1) control with saline; (2) surgery, a partial hepatolobectomy under sevoflurane anesthesia and analgesia, + immunoglobulin G as control antibody; (3) surgery + anti-HMGB1. A separate cohort of animals was used to detect His-tagged HMGB1 in the brain. Systemic anti-HMGB1 antibody treatment exerted neuroprotective effects preventing postoperative memory deficits and anxiety in aged rats by preventing surgery-induced reduction of phosphorylated cyclic AMP response element-binding protein in the hippocampus. Although no evident changes in the intracellular distribution of HMGB1 in hippocampal cells were noted after surgery, HMGB1 levels were elevated on day 3 in rat plasma samples. Experiments with tagged HMGB1 further revealed a critical role of systemic HMGB1 to enable an access to the brain and causing microglial activation. Overall, these data demonstrate a pivotal role for systemic HMGB1 in mediating postoperative neuroinflammation. This may have direct implications for common postoperative complications like delirium and postoperative cognitive dysfunction.