Hepcidin and Host Defense against Infectious Diseases

Iron Deficiency Related to Obesity

There is a direct correlation between being overweight and iron deficiency. Physiological changes occur in obese adipose cells that contribute to the development of iron deficiency (ID) and iron deficiency anemia (IDA). These changes disrupt the normal iron metabolic checks and balances. Furthermore, bariatric surgery can lead to long-term ID and IDA. Oral iron supplementation may not be effective for many of these patients. Intravenous iron infusions can significantly increase the quality of life for individuals experiencing this condition but are also associated with potentially serious complications. Adequate knowledge about intravenous (IV) iron administration can greatly increase the safety of this beneficial therapy. This review article explains the relationship between obesity, ID/IDA, bariatric surgery and the safe administration of IV iron.

Malaria blood stage infection suppresses liver stage infection via host-induced interferons but not hepcidin

Malaria-causing Plasmodium parasites first replicate as liver stages (LS), which then seed symptomatic blood stage (BS) infection. Emerging evidence suggests that these stages impact each other via perturbation of host responses, and this influences the outcome of natural infection. We sought to understand whether the parasite stage interplay would affect live-attenuated whole parasite vaccination, since the efficacy of whole parasite vaccines strongly correlates with their extend of development in the liver. We thus investigated the impact of BS infection on LS development of genetically attenuated and wildtype parasites in female rodent malaria models and observed that for both, LS infection suffered severe suppression during concurrent BS infection. Strikingly and in contrast to previously published studies, we find that the BS-induced iron-regulating hormone hepcidin is not mediating suppression of LS development. Instead, we demonstrate that BS-induced host interferons are the main mediators of LS developmental suppression. The type of interferon involved depended on the BS-causing parasite species. Our study provides important mechanistic insights into the BS-mediated suppression of LS development. This has direct implications for understanding the outcomes of live-attenuated Plasmodium parasite vaccination in malaria-endemic areas and might impact the epidemiology of natural malaria infection.

Bone marrow stromal cell-derived hepcidin has antimicrobial and immunomodulatory activities

Bone marrow stromal cells (BMSCs) have immunomodulatory activities in numerous species and have been used in clinical trials. BMSCs also make antibacterial agents. Since hepcidin is known to have antimicrobial effects in fish, we wondered if it might also be used as an antimicrobial agent by mammalian BMSCs. In the present study, we show hepcidin expression in both mouse (mBMSC) and human BMSCs (hBMSC). We observed a hBMSC hepcidin-dependent degradation of ferroportin in HEK-293 reporter cells in vitro. In human and mouse bone marrows (BM) we detected hepcidin-positive BMSCs in close proximity to hematopoietic progenitors. The conditioned culture medium of hBMSCs significantly reduced bacterial proliferation that was partially blocked by a hepcidin-neutralizing antibody. Similarly, medium in which hepcidin-deficient (Hamp-/-) mouse BMSCs had been grown was significantly less effective in reducing bacterial counts than the medium of wild-type cells. In a zymosan-induced peritonitis mouse model we found that mBMSC-derived hepcidin reduced the number of invading polymorphonuclear (PMN) cells in the peritoneal cavity. Our results show that BMSC-derived hepcidin has antimicrobial properties in vitro and also reduces inflammation in vivo. We conclude that hepcidin should be added to the expanding arsenal of agents available to BMSCs to fight infections and inflammation.

Interplay between gut microbiota and the master iron regulator, hepcidin, in the pathogenesis of liver fibrosis

INTRODUCTION

There is a proven role for hepcidin and the composition of gut microbiota and its derivatives in the pathophysiology of liver fibrosis.

AREA COVERED

This review focuses on the literature search regarding the effect of hepcidin and gut microbiota on regulating liver physiology. We presented the regulating mechanisms of hepcidin expression and discussed the possible interaction between gut microbiota and hepcidin regulation. Furthermore, we investigated the importance of the hepcidin gene in biological processes and bacterial interactions using bioinformatics analysis.

EXPERT OPINION

One of the main features of liver fibrosis is iron accumulation in hepatic cells, including hepatocytes. This accumulation can induce an oxidative stress response, inflammation, and activation of hepatic stellate cells. Hepcidin is a crucial regulator of iron by targeting ferroportin expressed on hepatocytes, macrophages, and enterocytes. Various stimuli, such as iron load and inflammatory signals, control hepcidin regulation. Furthermore, a bidirectional relationship exists between iron and the composition and metabolic activity of gut microbiota. We explored the potential of gut microbiota to influence hepcidin expression and potentially manage liver fibrosis, as the regulation of iron metabolism plays a crucial role in this context.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Revisiting geophagy: An evolved sickness behavior to microbiome-mediated gastrointestinal inflammation

Geophagy, the consumption of clay or similar substances, is known as an evolved behavior that protects vulnerable populations, such as pregnant women and children, against gastrointestinal injury. However, perplexing questions remain, like the presence of geophagy in the absence of overt gastrointestinal infection and the potential causal relationship between geophagy and iron deficiency anemia. In this review, we hypothesize that geophagy is an inflammation-mediated sickness behavior regulated via the vagus nerve. We further hypothesize that the gut microbiome plays a critical role in mediating the relationship between inflammation and geophagy. By including inflammation and the microbiome within the existing protection hypothesis, we can explain how subclinical gastrointestinal states induce geophagy. Furthermore, we can explain how gastrointestinal inflammation is responsible for both geophagy and iron-deficiency anemia, explaining why the two phenomena frequently co-occur. Ultimately, defining geophagy as a sickness behavior allows us to integrate the gut-brain axis into geophagy research.

Key players in the regulation of iron homeostasis at the host-pathogen interface

Iron plays a crucial role in the biochemistry and development of nearly all living organisms. Iron starvation of pathogens during infection is a striking feature utilized by a host to quell infection. In mammals and some other animals, iron is essentially obtained from diet and recycled from erythrocytes. Free iron is cytotoxic and is readily available to invading pathogens. During infection, most pathogens utilize host iron for their survival. Therefore, to ensure limited free iron, the host's natural system denies this metal in a process termed nutritional immunity. In this fierce battle for iron, hosts win over some pathogens, but others have evolved mechanisms to overdrive the host barriers. Production of siderophores, heme iron thievery, and direct binding of transferrin and lactoferrin to bacterial receptors are some of the pathogens' successful strategies which are highlighted in this review. The intricate interplay between hosts and pathogens in iron alteration systems is crucial for understanding host defense mechanisms and pathogen virulence. This review aims to elucidate the current understanding of host and pathogen iron alteration systems and propose future research directions to enhance our knowledge in this field.

Effect of Supplementation with Curcuma longa and Rosmarinus officinalis Extract Mixture on Acute Phase Protein, Cathelicidin, Defensin and Cytolytic Protein Gene Expression in the Livers of Young Castrated Polish White Improved Bucks

Goats are an excellent animal model for research on some physiological and pathophysiological processes in humans. The search for supplements that prevent homeostasis disorders and strengthen the immune system is necessary to reduce the risk of many diseases in both humans and animals. The aim of the study was to analyze the effect of supplementation with a mixture of dried extracts of Curcuma longa and Rosmarinus officinalis on the expression of acute-phase protein (SAA, HP, CRP, LALBA, AGP, CP, FGA, FGB, and FGG), cathelicidin (BAC5, BAC7.5, BAC3.4, MAP28, MAP34, and HEPC), beta-defensin-1 (GBD1, DEFB1), and beta-defensin-2, and cytolytic protein (LIZ and LF) genes in the livers of young castrated bucks of the Polish White Improved breed. The higher expression of LF in the control group suggests that it is important for the first line of hepatic immune defense and its expression is downregulated by the mixture of turmeric and rosemary extracts; thus, the spice-herb mixture mutes its activity. The lower expression of FGB and the higher expression of BAC5 genes in the livers of healthy, young castrated bucks who were administered the supplement suggest the silencing effects of the mixture on the acute-phase response and the stimulating effect on the antimicrobial activity of the immune system.

Inflammation alters iron distribution in bone and spleen in mice

Anemia of inflammation (or inflammation-associated anemia) decreases the quality of life in billions of patients suffering from various inflammatory diseases, such as infection, autoimmune diseases, and cancer, associated with a prolonged state of immune activation. While proper utilization of iron, a nutrient metal essential for erythropoiesis, is important for the prevention of anemia, the alteration of body iron homeostasis upon inflammation, which can contribute to the development of anemia, is not completely understood. Thus, we sought to examine temporal and spatial changes in the distribution of iron and iron-associated molecules during inflammation in mice. To induce inflammation, C57BL/6J mice were injected with turpentine oil weekly for 3 weeks, which resulted in anemia, decreased protein expression of ferroportin, a cellular iron exporter, in the spleen, duodenum, and liver, and increased iron stores in the duodenum and spleen. Tracer kinetic studies after oral administration of 59Fe revealed that more iron was found in the spleen and less in the femur bone in turpentine oil-injected mice compared to the saline-injected mice, indicating tissue-specific abnormalities in iron distribution during inflammation. However, there was no difference in the utilization of iron for red blood cell production after turpentine oil injection; instead, serum hemopexin level and lactate dehydrogenase activity were increased, suggesting increased red blood cell destruction upon inflammation. Our findings provide an improved understanding of temporal and spatial changes in the distribution and utilization of iron during inflammation.

Differential Modulation of miR-122 Transcription by TGFβ1/BMP6: Implications for Nonresolving Inflammation and Hepatocarcinogenesis

Chronic inflammation is widely recognized as a significant factor that promotes and worsens the development of malignancies, including hepatocellular carcinoma. This study aimed to explore the potential role of microRNAs in inflammation-associated nonresolving hepatocarcinogenesis. By conducting a comprehensive analysis of altered microRNAs in animal models with liver cancer of various etiologies, we identified miR-122 as the most significantly downregulated microRNA in the liver of animals with inflammation-associated liver cancer. Although previous research has indicated the importance of miR-122 in maintaining hepatocyte function, its specific role as either the trigger or the consequence of underlying diseases remains unclear. Through extensive analysis of animals and in vitro models, we have successfully demonstrated that miR-122 transcription is differentially regulated by the immunoregulatory cytokines, by the transforming growth factor-beta 1 (TGFβ1), and the bone morphogenetic protein-6 (BMP6). Furthermore, we presented convincing evidence directly linking reduced miR-122 transcription to inflammation and in chronic liver diseases. The results of this study strongly suggest that prolonged activation of pro-inflammatory signaling pathways, leading to disruption of cytokine-mediated regulation of miR-122, may significantly contribute to the onset and exacerbation of chronic liver disease.

GPX4 is a key ferroptosis biomarker and correlated with immune cell populations and immune checkpoints in childhood sepsis

Sepsis is the uncontrolled reaction of the body to infection-induced inflammation, which results in life-threatening multiple-organ dysfunction (MODS). Although the research on sepsis has advanced significantly in recent years, its pathophysiology remains entirely unknown. Ferroptosis is a new-fashioned type of programmed cell death that may have an impact on sepsis development. However, the precise mechanism still needs to be explored. In this paper, Four pediatric sepsis datasets [training datasets (GSE26378 and GSE26440) and validation datasets (GSE11755 and GSE11281)] were chosen through the GEO (Gene Expression Omnibus) database, and 63 differentially expressions of ferroptosis-relation-genes (DE-FRGs) were eventually discovered using bioinformatics investigation. Functional annotation was performed using GO and KEGG pathway enrichment analysis. Then, four Core-FRGs (FTH1, GPX4, ACSL1, and ACSL6) were extracted after the construction of the protein-protein interaction (PPI) network and the research of the MCODE module. Consequently, Hub-FRG (GPX4) was found using the validation datasets, and correlation exploration of immunity populations (neutrophils, r =  - 0.52; CD8 T-cells, r = 0.43) and immunity checkpoints (CD274, r =  - 0.42) was implemented. The usefulness of GPX4 as a marker in sepsis was assessed in a mouse model of sepsis. The findings demonstrate that GPX4 is a crucial biomarker and a new latent immunotherapy target for the prediction and therapy of pediatric sepsis.

Vitamin E Induces Liver Iron Depletion and Alters Iron Regulation in Mice

BACKGROUND

Vitamin E (vit E) is an essential nutrient that functions as a lipophilic antioxidant and is used clinically to treat nonalcoholic fatty liver disease, where it suppresses oxidative damage and impedes the progression of steatosis and fibrosis. Mice lacking a critical liver iron-trafficking protein also manifest steatosis because of iron-mediated oxidative damage and are protected from liver disease by oral vit E supplements.

OBJECTIVES

We aimed to examine the role of dietary vit E supplementation in modulating iron-sensing regulatory systems and nonheme iron levels in mouse liver.

METHODS

C57Bl/6 male mice, aged 6 wk, were fed purified diets containing normal amounts of iron and either control (45 mg/kg) or elevated (450 mg/kg) levels of 2R-α-tocopherol (vit E) for 18 d. Mouse plasma and liver were analyzed for nonheme iron, levels and activity of iron homeostatic proteins, and markers of oxidative stress. We compared means ± SD for iron and oxidative stress parameters between mice fed the control diet and those fed the vit E diet.

RESULTS

The Vit E-fed mice exhibited lower levels of liver nonheme iron (38% reduction, P < 0.0001) and ferritin (74% reduction, P < 0.01) than control-fed mice. The levels of liver mRNA for transferrin receptor 1 and divalent metal transporter 1 were reduced to 42% and 57% of the control, respectively. The mRNA levels for targets of nuclear factor erythroid 2-related factor (Nrf2), a major regulator of the oxidative stress response and iron-responsive genes, were also suppressed in vit E livers. Hepcidin, an iron regulatory hormone, levels were lower in the plasma (P < 0.05), and ferroportin (FPN), the iron exporter regulated by hepcidin, was expressed at higher levels in the liver (P < 0.05).

CONCLUSIONS

Oral vit E supplementation in mice can lead to depletion of liver iron stores by suppressing the iron- and redox-sensing transcription factor Nrf2, leading to enhanced iron efflux through liver FPN. Iron depletion may indirectly enhance the antioxidative effects of vit E.

Single-cell epitope-transcriptomics reveal lung stromal and immune cell response kinetics to nanoparticle-delivered RIG-I and TLR4 agonists

Lung-resident and circulatory lymphoid, myeloid, and stromal cells, expressing various pattern recognition receptors (PRRs), detect pathogen- and danger-associated molecular patterns (PAMPs/DAMPs), and defend against respiratory pathogens and injuries. Here, we report the early responses of murine lungs to nanoparticle-delivered PAMPs, specifically the retinoic acid-inducible gene I (RIG-I) agonist poly-U/UC (PUUC), with or without the TLR4 agonist monophosphoryl lipid A (MPLA). Using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq), we characterized the responses at 4 and 24 h after intranasal administration. Within 4 h, ribosome-associated transcripts decreased in both stromal and immune cells, followed by widespread interferon-stimulated gene (ISG) expression. Using RNA velocity, we show that lung-neutrophils dynamically regulate the synthesis of cytokines like CXCL-10, IL-1α, and IL-1β. Co-delivery of MPLA and PUUC increased chemokine synthesis and upregulated antimicrobial binding proteins targeting iron, manganese, and zinc in many cell types, including fibroblasts, endothelial cells, and epithelial cells. Overall, our results elucidate the early PAMP-induced cellular responses in the lung and demonstrate that stimulation of the RIG-I pathway, with or without TLR4 agonists, induces a ubiquitous microbial defense state in lung stromal and immune cells. Nanoparticle-delivered combination PAMPs may have applications in intranasal antiviral and antimicrobial therapies and prophylaxis.

The Role of Plasminogen Activator Inhibitor 1 in Predicting Sepsis-Associated Liver Dysfunction: An Observational Study

Sepsis-associated liver dysfunction (SALD) is associated with a poor prognosis and increased mortality in the intensive care unit. Bilirubin is one of the components of Sequential Organ Failure Assessment used in Sepsis-3 criteria. Hyperbilirubinemia is a late and non-specific symptom of liver dysfunction. This study aimed to identify plasma biomarkers that could be used for an early diagnosis of SALD. This prospective, observational study was conducted on a group of 79 patients with sepsis and septic shock treated in the ICU. Plasma biomarkers-prothrombin time, INR, antithrombin III, bilirubin, aspartate transaminase (AST), alanine transaminase, alkaline phosphatase, gamma glutamyl transferase, albumin, endothelin-1, hepcidin, plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex, and interferon-gamma inducible protein (10 kDa) were analysed. Plasma samples were obtained within 24 h after having developed sepsis/septic shock. Enrolled patients were followed for 14 days for developing SALD and 28 days for overall survival. A total of 24 patients (30.4%) developed SALD. PAI-1 with a cut-off value of 48.7 ng/mL was shown to be a predictor of SALD (AUC = 0.671, sensitivity 87.3%, and specificity 50.0%) and of 28-day survival in patients with sepsis/septic shock (p = 0.001). Measuring PAI-1 serum levels at the onset of sepsis and septic shock may be useful in predicting the development of SALD. This should be verified in multicenter prospective clinical trials.

Structural and functional characterisation of HepTH1-5 peptide as a potential hepcidin replacement

Hepcidin is a principal regulator of iron homeostasis and its dysregulation has been recognised as a causative factor in cancers and iron disorders. The strategy of manipulating the presence of hepcidin peptide has been used for cancer treatment. However, this has demonstrated poor efficiency and has been short-lived in patients. Many studies reported using minihepcidin therapy as an alternative way to treat hepcidin dysregulation, but this was only applied to non-cancer patients. Highly conserved fish hepcidin protein, HepTH1-5, was investigated to determine its potential use in developing a hepcidin replacement for human hepcidin (Hepc25) and as a therapeutic agent by targeting the tumour suppressor protein, p53, through structure-function analysis. The authors found that HepTH1-5 is stably bound to ferroportin, compared to Hepc25, by triggering the ferroportin internalisation via Lys42 and Lys270 ubiquitination, in a similar manner to the Hepc25 activity. Moreover, the residues Ile24 and Gly24, along with copper and zinc ligands, interacted with similar residues, Lys24 and Asp1 of Hepc25, respectively, showing that those molecules are crucial to the hepcidin replacement strategy. HepTH1-5 interacts with p53 and activates its function through phosphorylation. This finding shows that HepTH1-5 might be involved in the apoptosis signalling pathway upon a DNA damage response. This study will be very helpful for understanding the mechanism of the hepcidin replacement and providing insights into the HepTH1-5 peptide as a new target for hepcidin and cancer therapeutics.Communicated by Ramaswamy H. Sarma.

Antimicrobial Resistance and Recent Alternatives to Antibiotics for the Control of Bacterial Pathogens with an Emphasis on Foodborne Pathogens

Antimicrobial resistance (AMR) is one of the most important global public health problems. The imprudent use of antibiotics in humans and animals has resulted in the emergence of antibiotic-resistant bacteria. The dissemination of these strains and their resistant determinants could endanger antibiotic efficacy. Therefore, there is an urgent need to identify and develop novel strategies to combat antibiotic resistance. This review provides insights into the evolution and the mechanisms of AMR. Additionally, it discusses alternative approaches that might be used to control AMR, including probiotics, prebiotics, antimicrobial peptides, small molecules, organic acids, essential oils, bacteriophage, fecal transplants, and nanoparticles.

The Pathogenesis of African Trypanosomiasis

African trypanosomes are bloodstream protozoan parasites that infect mammals including humans, where they cause sleeping sickness. Long-lasting infection is required to favor parasite transmission between hosts. Therefore, trypanosomes have developed strategies to continuously escape innate and adaptive responses of the immune system, while also preventing premature death of the host. The pathology linked to infection mainly results from inflammation and includes anemia and brain dysfunction in addition to loss of specificity and memory of the antibody response. The serum of humans contains an efficient trypanolytic factor, the membrane pore-forming protein apolipoprotein L1 (APOL1). In the two human-infective trypanosomes, specific parasite resistance factors inhibit APOL1 activity. In turn, many African individuals express APOL1 variants that counteract these resistance factors, enabling them to avoid sleeping sickness. However, these variants are associated with chronic kidney disease, particularly in the context of virus-induced inflammation such as coronavirus disease 2019. Vaccination perspectives are discussed.

Iron in infectious diseases friend or foe?: The role of gut microbiota

Iron is a trace element involved in metabolic functions for all organisms, from microorganisms to mammalians. Iron deficiency is a prevalent health problem that affects billions of people worldwide, and iron overload could have some hazardous effect. The complex microbial community in the human body, also called microbiota, influences the host immune defence against infections. An imbalance in gut microbiota, dysbiosis, changes the host's susceptibility to infections by regulating the immune system. In recent years, the number of studies on the relationship between infectious diseases and microbiota has increased. Gut microbiota is affected by different parameters, including mode of delivery, hygiene habits, diet, drugs, and plasma iron levels during the lifetime. Gut microbiota may influence iron levels in the body, and iron overload and deficiency can also affect gut microbiota composition. Novel researches on microbiota shed light on the fact that the bidirectional interactions between gut microbiota and iron play a role in the pathogenesis of many diseases, especially infections. A better understanding of these interactions may help us to comprehend the pathogenesis of many infectious and metabolic diseases affecting people worldwide and following the development of more effective preventive and/or therapeutic strategies. In this review, we aimed to present the iron-mediated host-gut microbiota interactions, susceptibility to bacterial infections, and iron-targeted therapy approaches for infections.

Emerging Roles of Growth Differentiation Factor 15 in Immunoregulation and Pathogenesis

Growth differentiation factor 15 (GDF-15) is a cytokine that is widely used as a biomarker for the severity of diverse disease states. It also has been shown to play a protective role after tissue injury and to promote a negative energy balance during obesity and diabetes. In addition to its metabolic effects, GDF-15 also regulates the host's immune responses to infectious and noninfectious diseases. GDF-15 can suppress a type 1 and, in contrast, promote a type 2 inflammatory response. In this brief review, we discuss how GDF-15 affects the effector function and recruitment of immune cells, the pathways that induce its expression, and the diverse mechanisms by which it is regulated during inflammation and infection. We further highlight outstanding questions that should be the focus of future investigations in this emerging field.

Genome-wide identification of antisense lncRNAs and their association with susceptibility to Flavobacterium psychrophilum in rainbow trout

Eukaryotic genomes encode long noncoding natural antisense transcripts (lncNATs) that have been increasingly recognized as regulatory members of gene expression. Recently, we identified a few antisense transcripts correlating in expression with immune-related genes. However, a systematic genome-wide analysis of lncNATs in rainbow trout is lacking. This study used 134 RNA-Seq datasets from five different projects to identify antisense transcripts. A total of 13,503 lncNATs were identified genome-wide. About 75% of lncNATs showed multiple exons compared to 36.5% of the intergenic lncRNAs. RNA-Seq datasets from resistant, control, and susceptible rainbow trout genetic lines with significant differences in survival rate following Flavobacterium psychrophilum (Fp) infection were analyzed to investigate the potential role of the lncNATs during infection. Twenty-four pairwise comparisons between the different genetic lines, infectious status, and time points revealed 581 differentially expressed (DE) lncNATs and 179 differentially used exons (DUEs). Most of the DE lncNATs strongly and positively correlated in expression with their corresponding sense transcripts across 24 RNA-Seq datasets. LncNATs complementary to genes related to immunity, muscle contraction, proteolysis, and iron/heme metabolism were DE following infection. LncNATs complementary to hemolysis-related genes were DE in the resistant fish compared to susceptible fish on day 5 post-infection, suggesting enhanced clearance of free hemoglobin (Hb) and heme and increased erythropoiesis. LncNATs complementary to hepcidin, a master negative regulator of the plasma iron concentration, were the most downregulated lncNATs on day 5 of bacterial infection in the resistant fish. Ninety-four DE lncNAT, including five complementary to hepcidin, are located within 26 QTL regions previously identified in association with bacterial cold water disease (BCWD) in rainbow trout. Collectively, lncNATs are involved in the molecular architecture of fish immunity and should be further investigated for potential applications in genomic selection and genetic manipulation in aquaculture.

Evaluation of the Relationship Between Aquaporin-1, Hepcidin, Zinc, Copper, and İron Levels and Oxidative Stress in the Serum of Critically Ill Patients with COVID-19

Our study aims to determine the relationship between hepcidin, aquaporin (AQP-1), copper (Cu), zinc (Zn), iron (Fe) levels, and oxidative stress in the sera of seriously ill COVID-19 patients with invasive mechanical ventilation. Ninety persons with and without COVID-19 were taken up and separated into two groups. The first group included seriously COVID-19 inpatients having endotracheal intubation in the intensive care unit (n = 45). The second group included individuals who had negative PCR tests and had no chronic disease (the healthy control group n = 45). AQP-1, hepcidin, Zn, Cu, Fe, total antioxidant status (TAS), and total oxidant status (TOS) were studied in the sera of both groups, and the relations of these levels with oxidative stress were determined. When the COVID-19 patient and the control groups were compared, all studied parameters were found to be statistically significant (p < 0.01). Total oxidant status (TOS), oxidative stress index (OSI), and AQP-1, hepcidin, and Cu levels were increased in patients with COVID-19 compared to healthy people. Serum TAC, Zn, and Fe levels were found to be lower in the patient group than in the control group. Significant correlations were detected between the studied parameters in COVID-19 patients. Results indicated that oxidative stress may play an important role in viral infection due to SARS-CoV-2. We think that oxidative stress parameters as well as some trace elements at the onset of COVID-19 disease will provide a better triage in terms of disease severity.

Immune Activated Cellular Therapy for Drug Resistant Infections: Rationale, Mechanisms, and Implications for Veterinary Medicine

Simple Summary

Mesenchymal stromal/stem cells have intrinsic antimicrobial properties, thus making them attractive as an alternative treatment strategy in chronic, drug-resistant bacterial infections. Recent evidence has suggested that these antimicrobial effects can be significantly enhanced by immune activation just prior to injection. This review examines the potential role for cellular therapies in treatment of drug resistant infections in veterinary medicine, drawing on insights across species and discussing the therapeutic potential of this approach overall in today’s veterinary patients.

Abstract

Antimicrobial resistance and biofilm formation both present challenges to treatment of bacterial infections with conventional antibiotic therapy and serve as the impetus for development of improved therapeutic approaches. Mesenchymal stromal cell (MSC) therapy exerts an antimicrobial effect as demonstrated in multiple acute bacterial infection models. This effect can be enhanced by pre-conditioning the MSC with Toll or Nod-like receptor stimulation, termed activated cellular therapy (ACT). The purpose of this review is to summarize the current literature on mechanisms of antimicrobial activity of MSC with emphasis on enhanced effects through receptor agonism, and data supporting use of ACT in treatment of bacterial infections in veterinary species including dogs, cats, and horses with implications for further treatment applications. This review will advance the field’s understanding of the use of activated antimicrobial cellular therapy to treat infection, including mechanisms of action and potential therapeutic applications.

Liver macrophages in health and disease

Single-cell and spatial transcriptomic technologies have revealed an underappreciated heterogeneity of liver macrophages. This has led us to rethink the involvement of macrophages in liver homeostasis and disease. Identification of conserved gene signatures within these cells across species and diseases is enabling the correct identification of specific macrophage subsets and the generation of more specific tools to track and study the functions of these cells. Here, we discuss what is currently known about the definitions of these different macrophage populations, the markers that can be used to identify them, how they are wired within the liver, and their functional specializations in health and disease.

Hepcidin discriminates sepsis from other critical illness at admission to intensive care

Initial differential diagnosis and prognosis for patients admitted to intensive care with suspected sepsis remain arduous. Hepcidin has emerged as a potential biomarker for sepsis. Here we report data on the relevance of levels of hepcidin versus other biomarkers as a diagnostic and prognostic tool for sepsis. 164 adult patients admitted to the intensive care unit (ICU) within 24 h upon arrival to the hospital were included. Blood samples collected daily for seven consecutive days and hepcidin levels, heparin binding protein (HBP) levels and standard biomarkers were determined. Blood cultures were initiated at inclusion. Clinical scores were evaluated daily and mortality after 28- and 180-days was recorded. One hundred of the patients were found to fulfil the criteria for sepsis whereas 64 did not. Hepcidin levels at admission were significantly higher in the septic than in the non-septic patients. In septic patients hepcidin levels declined significantly already at 24 h followed by a steady decline. A significant negative correlation was observed between hepcidin levels and SAPS 3 in patients with sepsis. Hepcidin levels at inclusion were significantly higher among septic patients that survived 180-days and predicted mortality. Our data show that hepcidin levels are indicative of sepsis in patients admitted to the ICU and has a prognostic value for mortality.

Computational Modeling of Macrophage Iron Sequestration during Host Defense against Aspergillus

Iron is essential to the virulence of Aspergillus species, and restricting iron availability is a critical mechanism of antimicrobial host defense. Macrophages recruited to the site of infection are at the crux of this process, employing multiple intersecting mechanisms to orchestrate iron sequestration from pathogens. To gain an integrated understanding of how this is achieved in aspergillosis, we generated a transcriptomic time series of the response of human monocyte-derived macrophages to Aspergillus and used this and the available literature to construct a mechanistic computational model of iron handling of macrophages during this infection. We found an overwhelming macrophage response beginning 2 to 4 h after exposure to the fungus, which included upregulated transcription of iron import proteins transferrin receptor-1, divalent metal transporter-1, and ZIP family transporters, and downregulated transcription of the iron exporter ferroportin. The computational model, based on a discrete dynamical systems framework, consisted of 21 3-state nodes, and was validated with additional experimental data that were not used in model generation. The model accurately captures the steady state and the trajectories of most of the quantitatively measured nodes. In the experimental data, we surprisingly found that transferrin receptor-1 upregulation preceded the induction of inflammatory cytokines, a feature that deviated from model predictions. Model simulations suggested that direct induction of transferrin receptor-1 (TfR1) after fungal recognition, independent of the iron regulatory protein-labile iron pool (IRP-LIP) system, explains this finding. We anticipate that this model will contribute to a quantitative understanding of iron regulation as a fundamental host defense mechanism during aspergillosis.

IMPORTANCE Invasive pulmonary aspergillosis is a major cause of death among immunosuppressed individuals despite the best available therapy. Depriving the pathogen of iron is an essential component of host defense in this infection, but the mechanisms by which the host achieves this are complex. To understand how recruited macrophages mediate iron deprivation during the infection, we developed and validated a mechanistic computational model that integrates the available information in the field. The insights provided by this approach can help in designing iron modulation therapies as anti-fungal treatments.

Novel insights into alcoholic liver disease: Iron overload, iron sensing and hemolysis

The liver is the major target organ of continued alcohol consumption at risk and resulting alcoholic liver disease (ALD) is the most common liver disease worldwide. The underlying molecular mechanisms are still poorly understood despite decades of scientific effort limiting our abilities to identify those individuals who are at risk to develop the disease, to develop appropriate screening strategies and, in addition, to develop targeted therapeutic approaches. ALD is predestined for the newly evolving translational medicine, as conventional clinical and health care structures seem to be constrained to fully appreciate this disease. This concept paper aims at summarizing the 15 years translational experience at the Center of Alcohol Research in Heidelberg, namely based on the long-term prospective and detailed characterization of heavy drinkers with mortality data. In addition, novel experimental findings will be presented. A special focus will be the long-known hepatic iron accumulation, the somewhat overlooked role of the hematopoietic system and novel insights into iron sensing and the role of hepcidin. Our preliminary work indicates that enhanced red blood cell (RBC) turnover is critical for survival in ALD patients. RBC turnover is not primarily due to vitamin deficiency but rather to ethanol toxicity directly targeted to erythrocytes but also to the bone marrow stem cell compartment. These novel insights also help to explain long-known aspects of ALD such as mean corpuscular volume of erythrocytes (MCV) and elevated aspartate transaminase (GOT/AST) levels. This work also aims at identifying future projects, naming unresolved observations, and presenting novel hypothetical concepts still requiring future validation.

Stunting Status and Exposure to Infection and Inflammation in Early Life Shape Antibacterial Immune Cell Function Among Zimbabwean Children

Background

Children who are stunted (length-for-age Z-score<-2) are at greater risk of infectious morbidity and mortality. Previous studies suggest that stunted children have elevated inflammatory biomarkers, but no studies have characterised their capacity to respond to new infections (i.e., their immune function). We hypothesised that antibacterial immune function would differ between stunted and non-stunted children and relate to their health and environment during early life.

Methods

We enrolled a cross-sectional cohort of 113 HIV-negative children nested within a longitudinal cluster-randomised controlled trial of household-level infant and young child feeding (IYCF) and water, sanitation and hygiene (WASH) interventions in rural Zimbabwe (SHINE; Clinical trials registration: NCT01824940). Venous blood was collected at 18 months of age and cultured for 24 h without antigen or with bacterial antigens: heat-killed Salmonella typhimurium (HKST) or Escherichia coli lipopolysaccharide (LPS). TNFα, IL-6, IL-8, IL-12p70, hepcidin, soluble (s)CD163, myeloperoxidase (MPO) and IFNβ were quantified in culture supernatants by ELISA to determine antigen-specific immune function. The effect of stunting status and early-life exposures (anthropometry, inflammation at 18 months, maternal health during pregnancy, household WASH) on immune function was tested in logit and censored log-normal (tobit) regression models.

Results

Children who were stunted (n = 44) had higher proportions (86.4% vs. 65.2%; 88.6% vs. 73.4%) and concentrations of LPS-specific IL-6 (geometric mean difference (95% CI): 3.46 pg/mL (1.09, 10.80), p = 0.035) and IL-8 (3.52 pg/mL (1.20, 10.38), p = 0.022) than non-stunted children (n = 69). Bacterial antigen-specific pro-inflammatory cytokine concentrations were associated with biomarkers of child enteropathy at 18 months and biomarkers of systemic inflammation and enteropathy in their mothers during pregnancy. Children exposed to the WASH intervention (n = 33) produced higher LPS- (GMD (95% CI): 10.48 pg/mL (1.84, 60.31), p = 0.008) and HKST-specific MPO (5.10 pg/mL (1.77, 14.88), p = 0.003) than children in the no WASH group (n = 80). There was no difference in antigen-specific immune function between the IYCF (n = 55) and no IYCF groups (n = 58).

Conclusions

Antibacterial immune function among 18-month-old children in a low-income setting was shaped by their stunting status and prior exposure to maternal inflammation and household WASH. Heterogeneity in immune function due to adverse exposures in early life could plausibly contribute to infection susceptibility.

Timing is everything: impact of development, ageing and circadian rhythm on macrophage functions in urinary tract infections

The bladder supports a diversity of macrophage populations with functional roles related to homeostasis and host defense, including clearance of cell debris from tissue, immune surveillance, and inflammatory responses. This review examines these roles with particular attention given to macrophage origins, differentiation, recruitment, and engagement in host defense against urinary tract infections (UTIs), where these cells recognize uropathogens through a combination of receptor-mediated responses. Time is an important variable that is often overlooked in many clinical and biological studies, including in relation to macrophages and UTIs. Given that ageing is a significant factor in urinary tract infection pathogenesis and macrophages have been shown to harbor their own circadian system, this review also explores the influence of age on macrophage functions and the role of diurnal variations in macrophage functions in host defense and inflammation during UTIs. We provide a conceptual framework for future studies that address these key knowledge gaps.

Aspergillus Utilizes Extracellular Heme as an Iron Source During Invasive Pneumonia, Driving Infection Severity

BACKGROUND

Depriving microbes of iron is critical to host defense. Hemeproteins, the largest source of iron within vertebrates, are abundant in infected tissues in aspergillosis due to hemorrhage, but Aspergillus species have been thought to lack heme import mechanisms. We hypothesized that heme provides iron to Aspergillus during invasive pneumonia, thereby worsening the outcomes of the infection.

METHODS

We assessed the effect of heme on fungal phenotype in various in vitro conditions and in a neutropenic mouse model of invasive pulmonary aspergillosis.

RESULTS

In mice with neutropenic invasive aspergillosis, we found a progressive and compartmentalized increase in lung heme iron. Fungal cells cultured under low iron conditions took up heme, resulting in increased fungal iron content, resolution of iron starvation, increased conidiation, and enhanced resistance to oxidative stress. Intrapulmonary administration of heme to mice with neutropenic invasive aspergillosis resulted in markedly increased lung fungal burden, lung injury, and mortality, whereas administration of heme analogs or heme with killed Aspergillus did not. Finally, infection caused by fungal germlings cultured in the presence of heme resulted in a more severe infection.

CONCLUSIONS

Invasive aspergillosis induces local hemolysis in infected tissues, thereby supplying heme iron to the fungus, leading to lethal infection.

Massive gene expansion of hepcidin, a host defense peptide, in gilthead seabream (Sparus aurata)

Host defense peptides (HDP) are among the most ancient immune molecules in animals and clearly reflect an ancestral evolutionary history involving pathogen-host interactions. Hepcidins are a very widespread family of HDPs among vertebrates and are especially diverse in teleosts. We have investigated the identification of new hepcidins in gilthead seabream (Sparus aurata), a fish farmed in the Mediterranean. Targeted gene predictions supported with expressed sequence tags (ESTs) derived from Hidden Markov Models were used to find the hamp genes in the seabream genome. The results revealed a massively clustered hamp duplication on chromosome 17. In fact, the seabream genome contains the largest number of hepcidin copies described in any vertebrate. The evolutionary history of hepcidins in seabream, and vertebrates generally, clearly indicates high adaptation in teleosts and novel subgroups within hepcidin type II. Furthermore, basal hepcidin gene expression analysis indicates specific-tissue expression profiles, while the presence and distribution of transcription factor binding sites (TFBS) in hamp promoters as well as their transcription profile upon bacterial challenge indicates different immune roles depending on the type of hepcidin and tissue. This massive duplication of HDP genes in a bony fish could point to a far more specific and adaptive innate immune system than assumed in the classic concept of immunity in mammals. Hence, a new world of knowledge regarding hepcidins in fish and vertebrates is being initiated.

Crosstalk between Heme Oxygenase-1 and Iron Metabolism in Macrophages: Implications for the Modulation of Inflammation and Immunity

Heme oxygenase-1 (HO-1) is an enzyme that catalyzes the degradation of heme, releasing equimolar amounts of carbon monoxide (CO), biliverdin (BV), and iron. The anti-inflammatory and antioxidant properties of HO-1 activity are conferred in part by the release of CO and BV and are extensively characterized. However, iron constitutes an important product of HO-1 activity involved in the regulation of several cellular biological processes. The macrophage-mediated recycling of heme molecules, in particular those contained in hemoglobin, constitutes the major mechanism through which living organisms acquire iron. This process is finely regulated by the activities of HO-1 and of the iron exporter protein ferroportin. The expression of both proteins can be induced or suppressed in response to pro- and anti-inflammatory stimuli in macrophages from different tissues, which alters the intracellular iron concentrations of these cells. As we discuss in this review article, changes in intracellular iron levels play important roles in the regulation of cellular oxidation reactions as well as in the transcriptional and translational regulation of the expression of proteins related to inflammation and immune responses, and therefore, iron metabolism represents a potential target for the development of novel therapeutic strategies focused on the modulation of immunity and inflammation.

Related Markers for the Precision Diagnosis of Complex Appendicitis in Children

Acute appendicitis is the most common surgical emergency in children. Despite the high incidence rate of appendicitis, it is sometimes misdiagnosed or missed. Complex appendicitis (CA) in children is characterized by a critical condition, several complications, and high mortality. Precision distinguishing between simple appendicitis and CA correctly is key to choosing appropriate treatment. A safe, cheap, rapid, extensive and accurate diagnostic marker of appendicitis will be of great significance for emergency general surgeons to treat suspected CA. Many studies have investigated possible diagnostic markers for the diagnosis of CA in children. In this study, studies related to CA in children in recent years are summarized, and the related markers and scoring system for the diagnosis of CA in children are summarized.

A Bioinformatics-Assisted Review on Iron Metabolism and Immune System to Identify Potential Biomarkers of Exercise Stress-Induced Immunosuppression

The immune function is closely related to iron (Fe) homeostasis and allostasis. The aim of this bioinformatics-assisted review was twofold; (i) to update the current knowledge of Fe metabolism and its relationship to the immune system, and (ii) to perform a prediction analysis of regulatory network hubs that might serve as potential biomarkers during stress-induced immunosuppression. Several literature and bioinformatics databases/repositories were utilized to review Fe metabolism and complement the molecular description of prioritized proteins. The Search Tool for the Retrieval of Interacting Genes (STRING) was used to build a protein-protein interactions network for subsequent network topology analysis. Importantly, Fe is a sensitive double-edged sword where two extremes of its nutritional status may have harmful effects on innate and adaptive immunity. We identified clearly connected important hubs that belong to two clusters: (i) presentation of peptide antigens to the immune system with the involvement of redox reactions of Fe, heme, and Fe trafficking/transport; and (ii) ubiquitination, endocytosis, and degradation processes of proteins related to Fe metabolism in immune cells (e.g., macrophages). The identified potential biomarkers were in agreement with the current experimental evidence, are included in several immunological/biomarkers databases, and/or are emerging genetic markers for different stressful conditions. Although further validation is warranted, this hybrid method (human-machine collaboration) to extract meaningful biological applications using available data in literature and bioinformatics tools should be highlighted.

Transcriptome Profiling of Atlantic Salmon (Salmo salar) Parr With Higher and Lower Pathogen Loads Following Piscirickettsia salmonis Infection

Salmonid rickettsial septicemia (SRS), caused by Piscirickettsia salmonis, is one of the most devastating diseases of salmonids. However, the transcriptomic responses of Atlantic salmon (Salmon salar) in freshwater to an EM-90-like isolate have not been explored. Here, we infected Atlantic salmon parr with an EM-90-like isolate and conducted time-course qPCR analyses of pathogen load and four biomarkers (campb, hampa, il8a, tlr5a) of innate immunity on the head kidney samples. Transcript expression of three of these genes (except hampa), as well as pathogen level, peaked at 21 days post-injection (DPI). Multivariate analyses of infected individuals at 21 DPI revealed two infection phenotypes [lower (L-SRS) and higher (H-SRS) infection level]. Five fish from each group (Control, L-SRS, and H-SRS) were selected for transcriptome profiling using a 44K salmonid microarray platform. We identified 1,636 and 3,076 differentially expressed probes (DEPs) in the L-SRS and H-SRS groups compared with the control group, respectively (FDR = 1%). Gene ontology term enrichment analyses of SRS-responsive genes revealed the activation of a large number of innate (e.g. “phagocytosis”, “defense response to bacterium”, “inflammatory response”) and adaptive (e.g. “regulation of T cell activation”, “antigen processing and presentation of exogenous antigen”) immune processes, while a small number of general physiological processes (e.g. “apoptotic process”, development and metabolism relevant) was enriched. Transcriptome results were confirmed by qPCR analyses of 42 microarray-identified transcripts. Furthermore, the comparison of individuals with differing levels of infection (H-SRS vs. L-SRS) generated insights into the biological processes possibly involved in disease resistance or susceptibility. This study demonstrated a low mortality (~30%) EM-90-like infection model and broadened the current understanding of molecular pathways underlying P. salmonis-triggered responses of Atlantic salmon, identifying biomarkers that may assist to diagnose and combat this pathogen.

The human symbiont Bacteroides thetaiotaomicron promotes diet-induced obesity by regulating host lipid metabolism

The gut microbiome plays an important role in lipid metabolism. Consumption of a high-fat diet (HFD) alters the bacterial communities in the gut, leading to metabolic disorders. Several bacterial species have been associated with diet-induced obesity, nonalcoholic fatty liver disease, and metabolic syndrome. However, the mechanisms underlying the control of lipid metabolism by symbiotic bacteria remain elusive. Here, we show that the human symbiont Bacteroides thetaiotaomicron aggravates metabolic disorders by promoting lipid digestion and absorption. Administration of B. thetaiotaomicron to HFD-fed mice promoted weight gain, elevated fasting glucose levels, and impaired glucose tolerance. Furthermore, B. thetaiotaomicron treatment upregulated the gene expression of the fatty acid transporter and increased fatty acid accumulation in the liver. B. thetaiotaomicron inhibits expression of the gene encoding a lipoprotein lipase inhibitor, angiopoietin-like protein 4 (ANGPTL4), thereby increasing lipase activity in the small intestine. In particular, we found that B. thetaiotaomicron induced the expression of hepcidin, the master regulator of iron metabolism and an antimicrobial peptide, in the liver. Hepcidin treatment resulted in a decrease in ANGPTL4 expression in Caco-2 cells, whereas treatment with an iron chelator restored ANGPTL4 expression in hepcidin-treated cells. These results indicate that B. thetaiotaomicron-mediated regulation of iron storage in intestinal epithelial cells may contribute to increased fat deposition and impaired glucose tolerance in HFD-fed mice.

Comparative Analysis of Salmon Cell Lines and Zebrafish Primary Cell Cultures Infection with the Fish Pathogen Piscirickettsia salmonis

Piscirickettsia salmonis is the etiologic agent of piscirickettsiosis, a disease that causes significant losses in the salmon farming industry. In order to unveil the pathogenic mechanisms of P. salmonis, appropriate molecular and cellular studies in multiple cell lines with different origins need to be conducted. Toward that end, we established a cell viability assay that is suitable for high-throughput analysis using the alamarBlue reagent to follow the distinct stages of the bacterial infection cycle. Changes in host cell viability can be easily detected using either an absorbance- or fluorescence-based plate reader. Our method accurately tracked the infection cycle across two different Atlantic salmon-derived cell lines, with macrophage and epithelial cell properties, and zebrafish primary cell cultures. Analyses were also carried out to quantify intracellular bacterial replication in combination with fluorescence microscopy to visualize P. salmonis and cellular structures in fixed cells. In addition, dual gene expression analysis showed that the pro-inflammatory cytokines IL-6, IL-12, and TNFα were upregulated, while the cytokines IL1b and IFNγ were downregulated in the three cell culture types. The expression of the P. salmonis metal uptake and heme acquisition genes, together with the toxin and effector genes ospD3, ymt, pipB2 and pepO, were upregulated at the early and late stages of infection regardless of the cell culture type. On the other hand, Dot/Icm secretion system genes as well as stationary state and nutrient scarcity-related genes were upregulated only at the late stage of P. salmonis intracellular infection. We propose that these genes encoding putative P. salmonis virulence factors and immune-related proteins could be suitable biomarkers of P. salmonis infection. The infection protocol and cell viability assay described here provide a reliable method to compare the molecular and cellular changes induced by P. salmonis in other cell lines and has the potential to be used for high-throughput screenings of novel antimicrobials targeting this important fish intracellular pathogen.

Immunotherapy for cancer: effects of iron oxide nanoparticles on polarization of tumor-associated macrophages

Cancer immunotherapy is the most promising trend in oncology, focusing on helping or activating the patient's immune system to identify and fight against cancer. In the last decade, interest in metabolic reprogramming of tumor-associated macrophages from M2-like phenotype (promoting tumor progression) to M1-like phenotypes (suppressing tumor growth) as a therapeutic strategy against cancer has increased considerably. Iron metabolism has been standing out as a target for the reprogramming of tumor-associated macrophages to M1-like phenotype with therapeutic purposes against cancer. Due to the importance of the iron levels in macrophage polarization states, iron oxide nanoparticles can be used to change the activation state of tumor-associated macrophages for a tumor suppressor phenotype and as an anti-tumor strategy.

Systemic effects of IL-6 blockade in rheumatoid arthritis beyond the joints

Interleukin (IL)-6 is produced locally in response to an inflammatory stimulus, and is able to induce systemic manifestations at distance from the site of inflammation. Its unique signaling mechanism, including classical and trans-signaling pathways, leads to a major expansion in the number of cell types responding to IL-6. This pleiotropic cytokine is a key factor in the pathogenesis of rheumatoid arthritis (RA) and is involved in many extra-articular manifestations that accompany the disease. Thus, IL-6 blockade is associated with various biological effects beyond the joints. In this review, the systemic effects of IL-6 in RA comorbidities and the consequences of its blockade will be discussed, including anemia of chronic disease, cardiovascular risks, bone and muscle functions, and neuro-psychological manifestations.

Tofacitinib Suppresses IL-10/IL-10R Signaling and Modulates Host Defense Responses in Human Macrophages

Jak inhibitors are increasingly used in dermatology. Despite broad inhibitory effects on cytokine signaling cascades, they only modestly increase the risk for infectious diseases. To address the molecular mechanisms underlying this unexpected clinical observation, we investigated how tofacintib (tofa), a first-in-class Jak inhibitor, regulates host defense responses in toll-like receptor 4-activated human macrophages. Specifically, we asked whether tofa inhibits anti-inflammatory IL-10 signaling, thereby counteracting the downregulation of inflammatory, host-protective pathways. We found that tofa blocked macrophage responses to IL-10 at the level of signal transducer and activator of transcription 3 phosphorylation. Furthermore, toll-like receptor 4-induced, autocrine/paracrine IL-10/IL-10R activation promoted the expression of hepcidin, the master regulator of iron metabolism, resulting in intracellular iron sequestration. In contrast, autocrine/paracrine IL-10/IL-10R activation repressed the expression of cathelicidin antimicrobial peptide as well as antigen-presenting molecules, thus together, inducing a pathogen-favoring environment. Although tofa further repressed cathelicidin, it prevented the induction of intracellular HAMP and restored the expression of antigen-presentation molecules in toll-like receptor 4-activated macrophages. Our study supports the concept that induction of IL-10/IL-10R signaling drives a complex immune evasion strategy of intracellular microbes. Moreover, we conclude that tofa has diverging effects on macrophage host response pathways, and we identify the toll-like receptor 4-IL-10-signal transducer and activator of transcription 3-HAMP axis as a potential therapeutic target to counteract immune evasion.

Adjunct n-3 Long-Chain Polyunsaturated Fatty Acid Treatment in Tuberculosis Reduces Inflammation and Improves Anemia of Infection More in C3HeB/FeJ Mice With Low n-3 Fatty Acid Status Than Sufficient n-3 Fatty Acid Status

Populations at risk for tuberculosis (TB) may have a low n-3 polyunsaturated fatty acid (PUFA) status. Our research previously showed that post-infection supplementation of n-3 long-chain PUFA (LCPUFA) in TB without TB medication was beneficial in n-3 PUFA sufficient but not in low-status C3HeB/FeJ mice. In this study, we investigated the effect of n-3 LCPUFA adjunct to TB medication in TB mice with a low compared to a sufficient n-3 PUFA status. Mice were conditioned on an n-3 PUFA-deficient (n-3FAD) or n-3 PUFA-sufficient (n-3FAS) diet for 6 weeks before TB infection. Post-infection at 2 weeks, both groups were switched to an n-3 LCPUFA [eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA)] supplemented diet and euthanized at 4- and 14- days post-treatment. Iron and anemia status, bacterial loads, lung pathology, lung cytokines/chemokines, and lung lipid mediators were measured. Following 14 days of treatment, hemoglobin (Hb) was higher in the n-3FAD than the untreated n-3FAS group (p = 0.022), whereas the n-3FAS (drug) treated control and n-3FAS groups were not. Pro-inflammatory lung cytokines; interleukin-6 (IL-6) (p = 0.011), IL-1α (p = 0.039), MCP1 (p = 0.003), MIP1- α (p = 0.043), and RANTES (p = 0.034); were lower, and the anti-inflammatory cytokine IL-4 (p = 0.002) and growth factor GMCSF (p = 0.007) were higher in the n-3FAD compared with the n-3FAS mice after 14 days. These results suggest that n-3 LCPUFA therapy in TB-infected mice, in combination with TB medication, may improve anemia of infection more in low n-3 fatty acid status than sufficient status mice. Furthermore, the low n-3 fatty acid status TB mice supplemented with n-3 LCPUFA showed comparatively lower cytokine-mediated inflammation despite presenting with lower pro-resolving lipid mediators.

Mechanics Insights of Alpha-Lipoic Acid against Cardiovascular Diseases during COVID-19 Infection

Coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in late December 2019. Since then, COVID-19 has spread rapidly worldwide and was declared a global pandemic on 20 March 2020. Cardiovascular complications are rapidly emerging as a major peril in COVID-19 in addition to respiratory disease. The mechanisms underlying the excessive effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on patients with cardiovascular comorbidities remain only partly understood. SARS-CoV-2 infection is caused by binding of the viral surface spike (S) protein to the human angiotensin-converting enzyme 2 (ACE2), followed by the activation of the S protein by transmembrane protease serine 2 (TMPRSS2). ACE2 is expressed in the lung (mainly in type II alveolar cells), heart, blood vessels, small intestine, etc., and appears to be the predominant portal to the cellular entry of the virus. Based on current information, most people infected with SARS-CoV-2 virus have a good prognosis, while a few patients reach critical condition, especially the elderly and those with chronic underlying diseases. The "cytokine storm" observed in patients with severe COVID-19 contributes to the destruction of the endothelium, leading to "acute respiratory distress syndrome" (ARDS), multiorgan failure, and death. At the origin of the general proinflammatory state may be the SARS-CoV-2-mediated redox status in endothelial cells via the upregulation of ACE/Ang II/AT1 receptors pathway or the increased mitochondrial reactive oxygen species (mtROS) production. Furthermore, this vicious circle between oxidative stress (OS) and inflammation induces endothelial dysfunction, endothelial senescence, high risk of thrombosis and coagulopathy. The microvascular dysfunction and the formation of microthrombi in a way differentiate the SARS-CoV-2 infection from the other respiratory diseases and bring it closer to cardiovascular diseases like myocardial infarction and stroke. Due the role played by OS in the evolution of viral infection and in the development of COVID-19 complications, the use of antioxidants as adjuvant therapy seems appropriate in this new pathology. Alpha-lipoic acid (ALA) could be a promising candidate that, through its wide tissue distribution and versatile antioxidant properties, interferes with several signaling pathways. Thus, ALA improves endothelial function by restoring the endothelial nitric oxide synthase activity and presents an anti-inflammatory effect dependent or independent of its antioxidant properties. By improving mitochondrial function, it can sustain the tissues' homeostasis in critical situation and by enhancing the reduced glutathione it could indirectly strengthen the immune system. This complex analysis could open a new therapeutic perspective for ALA in COVID-19 infection.

History of anemia and long-term mortality due to infection: a cohort study with 12 years follow-up in South Korea

BACKGROUND

Anemia, which is a condition with reduced healthy red blood cells, is reported to be closely related to the development of infectious diseases. We aimed to investigate the association between history of anemia and 12-year mortality rate due to infections, and compare it with that among non-anemic individuals.

METHODS

Data from the National Health Insurance Service Health Screening Cohort were used in this population-based cohort study. Adults who underwent standardized medical examination between and 2002-2003 were included, and the mortality rate due to infection between 2004 and 2015 was analyzed. Individuals were considered to have a history of anemia if the serum hemoglobin level in 2002-2003 was < 12 g/dL for women and < 13 g/dL for men. The severity of anemia at that time was categorized as mild (12 g/dL > hemoglobin ≥11 g/dL in women and 13 g/dL > hemoglobin ≥11 g/dL in men), moderate (hemoglobin 8-10.9 g/dL), or severe (hemoglobin < 8 g/dL). Propensity score (PS) matching and Cox regression analysis were used as statistical methods.

RESULTS

Overall, 512,905 individuals were included in this study. The mean age of the participants was 54.5 years old (range: 40-98), and 49,042 (9.6%) individuals were classified in the anemic group, which comprised of 36,383 (7.1%), 11,787 (2.3%), and 872 (0.2%) participants in the mild, moderate, and severe sub-groups, respectively. After PS matching, 49,039 individuals in each group were included in the analysis. The risk of mortality due to infection in the anemic group was 1.77-fold higher (hazard ratio [HR]: 1.77, 95% confidence interval [CI]: 1.52-2.60; P < 0.001) than that in the non-anemic group. In the subgroup analysis, the mild and moderate anemia groups had 1.38-fold (HR: 1.38, 95% CI: 1.23 to 1.55; P < 0.001) and 2.02-fold (HR: 2.02, 95% CI: 1.62 to 2.50; P < 0.001) risk of mortality due to infection compared to that of the non-anemic group, respectively. The severe anemia group did not have a significantly different risk of mortality due to infection (P = 0.448).

CONCLUSIONS

History of anemia was associated with increased mortality rate due to infection at 12-year follow-up.

The critical roles of iron during the journey from fetus to adolescent: Developmental aspects of iron homeostasis

Iron is indispensable for human life. However, it is also potentially toxic, since it catalyzes the formation of harmful oxidative radicals in unbound form and may facilitate pathogen growth. Therefore, iron homeostasis needs to be tightly regulated. Rapid growth and development require large amounts of iron, while (especially young) children are vulnerable to infections with iron-dependent pathogens due to an immature immune system. Moreover, unbalanced iron status early in life may have effects on the nervous system, immune system and gut microbiota that persist into adulthood. In this narrative review, we assess the critical roles of iron for growth and development and elaborate how the body adapts to physiologically high iron demands during the journey from fetus to adolescent. As a first step towards the development of clinical guidelines for the management of iron disorders in children, we summarize the unmet needs regarding the developmental aspects of iron homeostasis.

Serum Hepcidin-25 and Risk of Mortality in Patients on Peritoneal Dialysis

Background: Increased serum hepcidin-25 level is associated with excess mortality in hemodialysis patients. However, there is a dearth of published information about its predictive effect for survival in patients on peritoneal dialysis (PD). The purpose of this study is to evaluate the association of serum hepcidin-25 with the risk of mortality in PD patients. Methods: Serum hepcidin-25 level was measured using an enzyme-linked immunosorbent assay in a prospective cohort study of PD patients with stored serum samples at baseline. Multivariate linear regression model was used to determine clinical characteristics associated with serum hepcidin-25 concentration. We evaluated the relationship between serum hepcidin-25 and all-cause mortality using a Cox proportional hazards model and the relationship between hepcidin-25 and cardiovascular (CV) and infection-related deaths using competing-risks regression models. Results: In total, 513 PD patients were included in this study. The median serum hepcidin-25 level was 40.9 (17.9-85.9) ng/mL. Body mass index and serum ferritin were positively correlated with serum hepcidin-25 levels. During a median follow-up period of 64.1 months, 122 (24%) patients died, including 61 (50%) CV deaths and 32 (26%) infection-related deaths. In multivariable analysis, patients with the highest tertile of serum hepcidin-25 had a greater risk of all-cause [adjusted hazard ratio (aHR) 1.85, 95% confidence interval (95%CI), 1.14 to 3.00, P = 0.013] and infection-related mortality (adjusted subdistribution hazard ratio [aSHR], 2.61; 95%CI, 1.01 to 6.76, P = 0.049) when compared with those in the second tertile. However, no significant relationship was observed between serum hepcidin-25 and CV mortality. Conclusions: Higher baseline serum hepcidin-25 level was associated with increased risk for all-cause and infection-related mortality in PD patients.

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

In silico analysis suggests disruption of interactions between HAMP from hepatocytes and SLC40A1 from macrophages in hepatocellular carcinoma

BACKGROUND

Identification of factors associated with proliferation in the hepatocellular carcinoma (HCC) microenvironment aids in understanding the mechanisms of disease progression and provides druggable targets. Gene expression profiles of individual cells in HCC and para-carcinoma tissues can be effectively obtained using the single-cell RNA sequencing (scRNA-Seq) technique. Here, we aimed to identify proliferative hepatocytes from HCC and para-carcinoma tissues, detect differentially expressed genes between the two types of proliferative hepatocytes, and investigate their potential roles in aberrant proliferation.

RESULTS

Two respective gene signatures for proliferative cells and hepatocytes were established and used to identify proliferative hepatocytes from HCC and para-carcinoma tissues based on scRNA-Seq data. Gene expression profiles between the two types of proliferative hepatocytes were compared. Overall, 40 genes were upregulated in proliferative hepatocytes from para-carcinoma tissue, whereas no upregulated genes were detected in those from HCC tissue. Twelve of the genes, including HAMP, were specifically expressed in the liver tissue. Based on previous reports, we found that HAMP modulates cell proliferation through interaction with its receptor SLC40A1. Comprehensive analysis of cells in HCC and para-carcinoma tissues revealed that: (1) HAMP is specifically expressed in hepatocytes and significantly downregulated in malignant hepatocytes; (2) a subset of macrophages expressing SLC40A1 and genes reacting to various infections is present in para-carcinoma but not in HCC tissue. We independently validated the findings with scRNA-Seq and large-scale tissue bulk RNA-Seq/microarray analyses.

CONCLUSION

HAMP was significantly downregulated in malignant hepatocytes. In addition, a subset of macrophages expressing SLC40A1 and genes reacting to various infections was absent in HCC tissue. These findings support the involvement of HAMP-SLC40A1 signaling in aberrant hepatocyte proliferation in the HCC microenvironment. The collective data from our in silico analysis provide novel insights into the mechanisms underlying HCC progression and require further validation with wet laboratory experiments.

Iron sucrose ('RBT-3') activates the hepatic and renal HAMP1 gene, evoking renal hepcidin loading and resistance to cisplatin nephrotoxicity

BACKGROUND

Iron sucrose (FeS) administration induces a state of renal preconditioning, protecting against selected forms of acute kidney injury (AKI). Recent evidence suggests that recombinant hepcidin also mitigates acute renal damage. Hence the goals of this study were to determine whether a new proprietary FeS formulation ('RBT-3') can acutely activate the hepcidin (HAMP1) gene in humans, raising plasma and renal hepcidin concentrations; assess whether the kidney participates in this posited RBT-3-hepcidin generation response; test whether RBT-3 can mitigate a clinically relevant AKI model (experimental cisplatin toxicity) and explore whether mechanisms in addition to hepcidin generation are operative in RBT-3's cytoprotective effects.

METHODS

Healthy human volunteers (n = 9) and subjects with Stages 3-4 CKD (n = 9) received 120, 240 or 360 mg of RBT-3 (intravenously over 2 h). Plasma and urine samples were collected and assayed for hepcidin levels (0-72 h post-RBT-3 injection). In complementary mouse experiments, RBT-3 effects on hepatic versus renal hepcidin (HAMP1) messenger RNA (mRNA) and protein levels were compared. RBT-3's impact on the mouse Nrf2 pathway and on experimental cisplatin nephrotoxicity was assessed. Direct effects of exogenous hepcidin on in vivo and in vitro (HK-2 cells) cisplatin toxicity were also tested.

RESULTS

RBT-3 induced rapid, dose-dependent and comparable plasma hepcidin increases in both healthy volunteers and chronic kidney disease subjects (∼15 times baseline within 24 h). Human kidney hepcidin exposure was confirmed by 4-fold urinary hepcidin increases. RBT-3 up-regulated mouse hepcidin mRNA, but much more so in kidney (>25 times) versus liver (∼2 times). RBT-3 also activated kidney Nrf2 [increased Nrf2 nuclear binding; increased Nrf2-responsive gene mRNAs: heme oxygenase-1, sulfiredoxin-1, glutamate-cysteine ligase catalytic subunit and NAD(P)H quinone dehydrogenase 1]. RBT-3 preconditioning (18 h time lapse) markedly attenuated experimental cisplatin nephrotoxicity (∼50% blood urea nitrogen/creatinine decrements), in part by reducing renal cisplatin uptake by 40%. Exogenous hepcidin (without RBT-3) treatment conferred protection against mild in vivo (but not in vitro) cisplatin toxicity.

CONCLUSIONS

RBT-3 acutely and dramatically up-regulates cytoprotective hepcidin production, increasing renal hepcidin levels. However, additional cytoprotective mechanisms are activated by RBT-3 (e.g. Nrf2 activation; reduced cisplatin uptake). Thus RBT-3-induced preconditioning likely confers renal resistance to cisplatin via an interplay of multiple cytoprotective activities.

Hepcidin and Ferritin Predict Microbial Etiology in Community-Acquired Pneumonia

Background

Iron is crucial for survival and growth of microbes. Consequently, limiting iron availability is a human antimicrobial defense mechanism. We explored iron and iron-related proteins as potential biomarkers in community-acquired pneumonia and hypothesized that infection-induced changes in these potential biomarkers differ between groups of pathogens and could predict microbial etiology.

Methods

Blood samples from a prospective cohort of 267 patients with community-acquired pneumonia were analyzed for hepcidin, ferritin, iron, transferrin, and soluble transferrin receptor at admission, clinical stabilization, and a 6-week follow-up. A total of 111 patients with an established microbiological diagnosis confined to 1 microbial group (atypical bacterial, typical bacterial, or viral) were included in predictive analyses.

Results

High admission levels of ferritin predicted atypical bacterial versus typical bacterial etiology (odds ratio [OR], 2.26; 95% confidence interval [CI], 1.18–4.32; P = .014). Furthermore, hepcidin and ferritin predicted atypical bacterial versus viral etiology (hepcidin: OR = 3.12, 95% CI = 1.34–7.28, P = .008; ferritin: OR = 2.38, 95% CI = 1.28–4.45, P = .006). The findings were independent of C-reactive protein and procalcitonin.

Conclusions

Hepcidin and ferritin are potential biomarkers of microbial etiology in community-acquired pneumonia.

Uncovering the Hidden Credentials of Brucella Virulence

Bacteria in the genus Brucella are important human and veterinary pathogens. The abortion and infertility they cause in food animals produce economic hardships in areas where the disease has not been controlled, and human brucellosis is one of the world's most common zoonoses. Brucella strains have also been isolated from wildlife, but we know much less about the pathobiology and epidemiology of these infections than we do about brucellosis in domestic animals. The brucellae maintain predominantly an intracellular lifestyle in their mammalian hosts, and their ability to subvert the host immune response and survive and replicate in macrophages and placental trophoblasts underlies their success as pathogens. We are just beginning to understand how these bacteria evolved from a progenitor alphaproteobacterium with an environmental niche and diverged to become highly host-adapted and host-specific pathogens. Two important virulence determinants played critical roles in this evolution: (i) a type IV secretion system that secretes effector molecules into the host cell cytoplasm that direct the intracellular trafficking of the brucellae and modulate host immune responses and (ii) a lipopolysaccharide moiety which poorly stimulates host inflammatory responses. This review highlights what we presently know about how these and other virulence determinants contribute to Brucella pathogenesis. Gaining a better understanding of how the brucellae produce disease will provide us with information that can be used to design better strategies for preventing brucellosis in animals and for preventing and treating this disease in humans.