In a Mouse Model of Sepsis, Hepcidin Ablation Ameliorates Anemia More Effectively than Iron and Erythropoietin Treatment

Anemia Recovery After Lung Contusion, Hemorrhagic Shock, and Chronic Stress Is Gender-Specific in a Rat Model

Background: Severe trauma and hemorrhagic shock lead to persistent anemia. Although biologic gender is known to modulate inflammatory responses after critical illness, the impact of gender on anemia recovery after injury remains unknown. The aim of this study was to identify gender-specific differences in anemia recovery after critical illness. Materials and Methods: Male and proestrus female Sprague-Dawley rats (n = 8-9 per group) were subjected to lung contusion and hemorrhagic shock (LCHS) or LCHS with daily chronic stress (LCHS/CS) compared with naïve. Hematologic data, bone marrow progenitor growth, and bone marrow and liver gene transcription were analyzed on day seven. Significance was defined as p < 0.05. Results: Males lost substantial weight after LCHS and LCHS/CS compared with naïve males, while female LCHS rats did not compared with naive counterparts. Male LCHS rats had a drastic decrease in hemoglobin from naïve males. Male LCHS/CS rats had reduced colony-forming units-granulocyte, -erythrocyte, -monocyte, -megakaryocyte (CFU-GEMM) and burst-forming unit-erythroid (BFU-E) when compared with female counterparts. Naïve, LCHS, and LCHS/CS males had lower serum iron than their respective female counterparts. Liver transcription of BMP4 and BMP6 was elevated after LCHS and LCHS/CS in males compared with females. The LCHS/CS males had decreased expression of bone marrow pro-erythroid factors compared with LCHS/CS females. Conclusions: After trauma with or without chronic stress, male rats demonstrated increased weight loss, substantial decrease in hemoglobin level, dysregulated iron metabolism, substantial suppression of bone marrow erythroid progenitor growth, and no change in transcription of pro-erythroid factors. These findings confirm that gender is an important variable that impacts anemia recovery and bone marrow dysfunction after traumatic injury and shock in this rat model.

Intravenous iron to treat anaemia following critical care: a multicentre feasibility randomised trial

BACKGROUND

Anaemia is common and associated with poor outcomes in survivors of critical illness. However, the optimal treatment strategy is unclear.

METHODS

We conducted a multicentre, feasibility RCT to compare either a single dose of ferric carboxymaltose 1000 mg i.v. or usual care in patients being discharged from the ICU with moderate or severe anaemia (haemoglobin ≤100 g L^-1). We collected data on feasibility (recruitment, randomisation, follow-up), biological efficacy, and clinical outcomes.

RESULTS

Ninety-eight participants were randomly allocated (49 in each arm). The overall recruitment rate was 34% with 6.5 participants recruited on average per month. Forty-seven of 49 (96%) participants received the intervention. Patient-reported outcome measures were available for 79/93 (85%) survivors at 90 days. Intravenous iron resulted in a higher mean (standard deviation [sd]) haemoglobin at 28 days (119.8 [13.3] vs 106.7 [14.9] g L^-1) and 90 days (130.5 [15.1] vs 122.7 [17.3] g L^-1), adjusted mean difference (10.98 g L^-1; 95% confidence interval [CI], 4.96-17.01; P<0.001) over 90 days after randomisation. Infection rates were similar in both groups. Hospital readmissions at 90 days post-ICU discharge were lower in the i.v. iron group (7/40 vs 15/39; risk ratio=0.46; 95% CI, 0.21-0.99; P=0.037). The median (inter-quartile range) post-ICU hospital stay was shorter in the i.v. iron group but did not reach statistical significance (5.0 [3.0-13.0] vs 9.0 [5.0-16.0] days, P=0.15).

CONCLUSION

A large, multicentre RCT of i.v. iron to treat anaemia in survivors of critical illness appears feasible and is necessary to determine the effects on patient-centred outcomes.

CLINICAL TRIAL REGISTRATION

ISRCTN13721808 (www.isrctn.com).

Pharmacological Targeting of BMP6-SMAD Mediated Hepcidin Expression Does Not Improve the Outcome of Systemic Infections With Intra-Or Extracellular Gram-Negative Bacteria in Mice

Introduction

Hepcidin is the systemic master regulator of iron metabolism as it degrades the cellular iron exporter ferroportin. In bacterial infections, hepcidin is upregulated to limit circulating iron for pathogens, thereby increasing iron retention in macrophages. This mechanism withholds iron from extracellular bacteria but could be of disadvantage in infections with intracellular bacteria. We aimed to understand the role of hepcidin in infections with intra- or extracellular bacteria using different hepcidin inhibitors.

Methods

For the experiments LDN-193189 and oversulfated heparins were used, which interact with the BMP6-SMAD pathway thereby inhibiting hepcidin expression. We infected male C57BL/6N mice with either the intracellular bacterium Salmonella Typhimurium or the extracellular bacterium Escherichia coli and treated these mice with the different hepcidin inhibitors.

Results

Both inhibitors effectively reduced hepcidin levels in vitro under steady state conditions and upon stimulation with the inflammatory signals interleukin-6 or lipopolysaccharide. The inhibitors also reduced hepcidin levels and increased circulating iron concentration in uninfected mice. However, both compounds failed to decrease liver- and circulating hepcidin levels in infected mice and did not affect ferroportin expression in the spleen or impact on serum iron levels. Accordingly, both BMP-SMAD signaling inhibitors did not influence bacterial numbers in different organs in the course of E.coli or S.Tm sepsis.

Conclusion

These data indicate that targeting the BMP receptor or the BMP-SMAD pathway is not sufficient to suppress hepcidin expression in the course of infection with both intra- or extracellular bacteria. This suggests that upon pharmacological inhibition of the central SMAD-BMP pathways during infection, other signaling cascades are compensatorily induced to ensure sufficient hepcidin formation and iron restriction to circulating microbes.

Airway Epithelial Hepcidin Coordinates Lung Macrophages and Immunity Against Bacterial Pneumonia

BACKGROUND

Hepcidin is a liver-derived master regulator of iron metabolism through its molecular target ferroportin, the only known mammalian iron exporter. Accumulated evidence has shown the important roles of hepatic hepcidin in host defense and infections. Hepcidin is also expressed by airway epithelial cells. However, the function of epithelial hepcidin during bacterial pneumonia remains unknown.

METHODS

Pneumonia was induced in hepcidin-1-deficient and wild-type mice using the most common bacterial agents, and the effects of hepcidin on survival, bacterial burden, iron status, and macrophage phagocytosis after bacterial pneumonia were assessed.

RESULTS

Hepcidin levels decreased in airway epithelium during common pneumonia, while lung macrophage-derived ferroportin levels and pulmonary iron concentrations increased. Lack of hepcidin in the airway epithelium worsened the outcomes of pneumonia. Manipulation of hepcidin level in the airway epithelium in mice with macrophage-specific ferroportin deletion did not affect the progress of pneumonia. Increased pulmonary iron concentration not only facilitated bacterial growth but also led to the defective phagocytic function of lung macrophages via activation of RhoA GTPase through oxidation of RhoGDI. Furthermore, enhancing the hepcidin level in the airway epithelium rescued mice from lethal bacterial pneumonia.

CONCLUSIONS

These findings identify an uncharacterized important role of airway epithelial hepcidin in protection against bacterial pneumonia and provide the basis for novel alternative therapeutic strategies for combatting bacterial pneumonia in future translational research.

Prolonged Chronic Stress and Persistent Iron Dysregulation Prevent Anemia Recovery Following Trauma

Introduction Following major trauma, persistent injury-associated anemia is associated with organ failure, increased length of stay and mortality. We hypothesize that prolonged adrenergic stimulation following trauma is directly responsible for persistent iron dysfunction that impairs anemia recovery. Materials and Methods Naïve rodents, lung contusion and hemorrhagic shock followed by daily handling for 13 d (LCHS), LCHS followed by 6 d of restraint stress and 7 d of daily handling (LCHS/CS-7) and LCHS/CS followed by 13 d of restraint stress with day and/or night disruption (LCHS/CS-14) were sacrificed on day 14. Hemoglobin, plasma, urine, bone marrow/liver inflammatory and erythropoietic markers were analyzed. Results LCHS/CS-14 led to a significant decline in weight gain and persistently elevated plasma and urine inflammatory markers. Liver IL-6, IL-1β and hepcidin expression were significantly increased following LCHS/CS-14. LCHS/CS-14 also had impaired anemia recovery with reduced plasma transferrin and erythropoietin receptor expression. Conclusion Prolonged chronic stress following trauma/hemorrhagic shock led to sustained inflammation with increased expression of IL-1β, IL-6 and hepcidin with decreased iron availability for uptake into erythroid progenitor cells and a lack of anemia recovery.

Saccharated ferric oxide attenuates haematopoietic response induced by epoetin beta pegol in patients undergoing haemodialysis

Background

Decreased erythropoietin levels and impaired iron metabolism due to excessive hepcidin levels are responsible for renal anaemia in patients undergoing haemodialysis. Recently, erythroferrone (ERFE) has been identified as a factor that regulates hepcidin. In addition, fibroblast growth factor 23 (FGF23), which has been recognized as a phosphorus-regulating hormone, appears to be involved in haematopoietic regulation. Clarification of the detailed mechanism of haematopoiesis could lead to the improvement of renal anaemia treatment.

Methods

Epoetin beta pegol (CERA) was administered to patients undergoing haemodialysis at week 0, and the same amount of CERA with saccharated ferric oxide (SFO) was administered at week 4. The changes in haematopoiesis-related biomarkers, including ERFE, intact FGF23 (iFGF23), C-terminal FGF23 (cFGF23), and inflammatory markers, were examined.

Results

Administration of CERA increased ERFE levels, decreased hepcidin levels, and stimulated iron usage for haematopoiesis, leading to an increase in reticulocytes (Ret) and haemoglobin (Hb). Simultaneous administration of SFO with CERA (CERA + SFO) significantly attenuated the responses of ERFE, Ret, and Hb compared with CERA alone. Although iFGF23 levels were not affected by either CERA or CERA + SFO, cFGF23 was significantly elevated from baseline after CERA. Since cFGF23 levels were not affected by CERA + SFO, cFGF23 levels after CERA + SFO were significantly lower than those after CERA alone. The ratio of iFGF23 to cFGF23 (i/cFGF23 ratio) was significantly higher after CERA + SFO than that after CERA alone. In addition, high-sensitivity C-reactive protein (hsCRP) levels were significantly higher after CERA + SFO than after CERA alone.

Conclusion

Administration of SFO suppressed haematopoietic responses induced by CERA. Elevation of i/cFGF23 ratio and hsCRP could account for the inhibitory effects of SFO on haematopoiesis.

Trial registration

This study was registered with the University Hospital Medical Information Network (ID UMIN000016552).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02320-2.

A fully human anti-BMP6 antibody reduces the need for erythropoietin in rodent models of the anemia of chronic disease

Recombinant erythropoietin (EPO) and iron substitution are a standard of care for treatment of anemias associated with chronic inflammation, including anemia of chronic kidney disease. A black box warning for EPO therapy and concerns about negative side effects related to high-dose iron supplementation as well as the significant proportion of patients becoming EPO resistant over time explains the medical need to define novel strategies to ameliorate anemia of chronic disease (ACD). As hepcidin is central to the iron-restrictive phenotype in ACD, therapeutic approaches targeting hepcidin were recently developed. We herein report the therapeutic effects of a fully human anti-BMP6 antibody (KY1070) either as monotherapy or in combination with Darbepoetin alfa on iron metabolism and anemia resolution in 2 different, well-established, and clinically relevant rodent models of ACD. In addition to counteracting hepcidin-driven iron limitation for erythropoiesis, we found that the combination of KY1070 and recombinant human EPO improved the erythroid response compared with either monotherapy in a qualitative and quantitative manner. Consequently, the combination of KY1070 and Darbepoetin alfa resulted in an EPO-sparing effect. Moreover, we found that suppression of hepcidin via KY1070 modulates ferroportin expression on erythroid precursor cells, thereby lowering potentially toxic-free intracellular iron levels and by accelerating erythroid output as reflected by increased maturation of erythrocyte progenitors. In summary, we conclude that treatment of ACD, as a highly complex disease, becomes more effective by a multifactorial therapeutic approach upon mobilization of endogenous iron deposits and stimulation of erythropoiesis.

Iron homeostasis and disorders revisited in the sepsis

Sepsis is a life-threatening condition caused by a dysregulated host-response to inflammation, although it currently lacks a fully elucidated pathobiology. Iron is a crucial trace element that is essential for fundamental processes in both humans and bacteria. During sepsis, iron metabolism is altered, including increased iron transport and uptake into cells and decreased iron export. The intracellular sequestration of iron limits its availability to circulating pathogens, which serves as a conservative strategy against the pathogens. Although iron retention has been showed to have protective protect effects, an increase in labile iron may cause oxidative injury and cell death (e.g., pyroptosis, ferroptosis) as the condition progresses. Moreover, iron disorders are substantial and correlate with the severity of sepsis. This also suggests that iron may be useful as a diagnostic marker for evaluating the severity and predicting the outcome of the disease. Further knowledge about these disorders could help in evaluating how drugs targeting iron homeostasis can be optimally applied to improve the treatment of patients with sepsis. Here, we present a comprehensive review of recent advances in the understanding of iron metabolism, focusing on the regulatory mechanisms and iron-mediated injury in sepsis.

Transfusion in critical care: Past, present and future

Anaemia and coagulopathy are common in critically ill patients and are associated with poor outcomes, including increased risk of mortality, myocardial infarction, failure to be liberated from mechanical ventilation and poor physical recovery. Transfusion of blood and blood products remains the corner stone of anaemia and coagulopathy treatment in critical care. However, determining when the benefits of transfusion outweigh the risks of anaemia may be challenging in some critically ill patients. Therefore, the European Society of Intensive Care Medicine prioritised the development of a clinical practice guideline to address anaemia and coagulopathy in non-bleeding critically ill patients. The aims of this article are to: (1) review the evolution of transfusion practice in critical care and the direction for future developments in this important area of transfusion medicine and (2) to provide a brief synopsis of the guideline development process and recommendations in a format designed for busy clinicians and blood bank staff. These clinical practice guidelines provide recommendations to clinicians on how best to manage non-bleeding critically ill patients at the bedside. More research is needed on alternative transfusion targets, use of transfusions in special populations (e.g., acute neurological injury, acute coronary syndromes), use of anaemia prevention strategies and point-of-care interventions to guide transfusion strategies.

Iron overload causes a mild and transient increase in acute lung injury

Recent studies have demonstrated a strong link between acute respiratory distress syndrome (ARDS) and the levels of iron and iron-related proteins in the lungs. However, the role of iron overload in ARDS development has yet to be characterized. In this study, we compared the highly iron-overloaded hepcidin knockout mice (HKO) to their iron-sufficient wild-type (WT) littermates in a model of sterile acute lung injury (ALI) induced by treatment with oropharyngeal (OP) LPS. There were no major differences in systemic inflammatory response or airway neutrophil infiltration between the two groups at the time of maximal injury (days 2 and 3) or during the recovery phase (day 7). Hepcidin knockout mice had transiently increased bronchoalveolar lavage fluid (BALF) protein and MPO activity in the lung and BALF on day 3, indicating worse vascular leakage and increased neutrophil activity, respectively. The increased ALI severity in iron-overloaded mice may be a result of increased apoptosis of lung tissue, as evidenced by an increase in cleaved capsase-3 protein in lung homogenates from HKO mice versus WT mice on day 3. Altogether, our data suggest that even severe iron overload has a relatively minor and transient effect in LPS-induced ALI.

Misdistribution of iron and oxidative stress in chronic kidney disease

Chronic kidney disease (CKD) patients have an extremely high risk of developing cardiovascular diseases (CVD) compared to the general population. Systemic inflammation associated with oxidative stress could be an important determinant of morbidity and mortality associated with CVD. We suspected that dysregulation of iron metabolism should be considered in these patients. Anemia is prevalent in CKD patients and is often treated with erythropoiesis-stimulating agents (ESAs) and iron. In addition, iron administration sometimes causes iron overdose. Excessive iron in the cytosol and mitochondria can accelerate the formation of a highly toxic reactive oxygen species, hydroxyl radicals, which damage lipids, proteins, and DNA. In this review, we propose the following four major reasons for oxidative stress in CKD patients: 1) iron is sequestered in cells by proinflammatory cytokines and hepcidin; 2) the reduction in frataxin increases "free" iron in mitochondria; 3) the accumulation of 5-aminolevulinic acid, a heme precursor, has toxic effects on iron and mitochondrial metabolism; and 4) the elevated levels of the metabolic hormone, leptin, promote hepatic hepcidin production. Although an efficient therapy for preventing oxidative stress in these patients has not yet been well defined, we propose that ESAs for renal anemia may ameliorate these causes of oxidative stress. Further clinical trials are necessary to clarify the effectiveness of ESAs on oxidative stress in CKD patients.

Decreased total iron binding capacity upon intensive care unit admission predicts red blood cell transfusion in critically ill patients

Introduction

Red blood cell (RBC) transfusion is associated with poor clinical outcome in critically ill patients. We investigated the predictive value of biomarkers on intensive care units (ICU) admission for RBC transfusion within 28 days.

Methods

Critically ill patients (n = 175) who admitted to our ICU with organ dysfunction and an expected stay of ≥ 48 hours, without hemorrhage, were prospectively studied (derivation cohort, n = 121; validation cohort, n = 54). Serum levels of 12 biomarkers (hemoglobin, creatinine, albumin, interleukin-6 [IL-6], erythropoietin, Fe, total iron binding capacity [TIBC], transferrin, ferritin, transferrin saturation, folate, and vitamin B12) were measured upon ICU admission, days 7, 14, 21 and 28.

Results

Among the 12 biomarkers measured upon ICU admission, levels of hemoglobin, albumin, IL-6, TIBC, transferrin and ferritin were statistically different between transfusion and non-transfusion group. Of 6 biomarkers, TIBC upon ICU admission had the highest area under the curve value (0.835 [95% confidence interval] = 0.765–0.906) for predicting RBC transfusion (cut-off value = 234.5 μg/dL; sensitivity = 0.906, specificity = 0.632). This result was confirmed in validation cohort, whose sensitivity and specificity were 0.888 and 0.694, respectively. Measurement of these biomarkers every seven days revealed that albumin, TIBC and transferrin were statistically different between groups throughout hospitalization until 28 days. In validation cohort, patients in the transfusion group had significantly higher serum hepcidin levels than those in the non-transfusion group (P = 0.004). In addition, joint analysis across derivation and validation cohorts revealed that the serum IL-6 levels were higher in the transfusion group (P = 0.0014).

Conclusion

Decreased TIBC upon ICU admission has high predictive value for RBC transfusion unrelated to hemorrhage within 28 days.

What is the effect of perioperative intravenous iron therapy in patients undergoing non-elective surgery? A systematic review with meta-analysis and trial sequential analysis

Background

Guidelines to treat anaemia with intravenous (IV) iron have focused on elective surgical patients with little attention paid to those undergoing non-elective/emergency surgery. Whilst these patients may experience poor outcomes because of their presenting illness, observational data suggests that untreated anaemia may also be a contributing factor to poor outcomes. We conducted a systematic review to investigate the safety and efficacy of IV iron in patients undergoing non-elective surgery.

Methods

We followed a pre-defined review protocol and included randomised controlled trials (RCTs) in patients undergoing non-elective surgery who received IV iron. Primary outcomes were all-cause infection and mean difference in haemoglobin (Hb) at follow-up. Secondary outcomes included transfusion requirements, hospital length of stay (LOS), health-related quality of life (HRQoL), mortality and adverse events.

Results

Three RCTs (605 participants) were included in this systematic review of which two, in both hip fracture (HF) patients, provided data for meta-analysis. Both of these RCTs were at low risk of bias. We found no evidence of a difference in the risk of infection (RR 0.99, 95% CI 0.55 to 1.80, I ² = 9%) or in the Hb concentration at 'short-term' (≤ 7 days) follow-up (mean difference - 0.32 g/L, 95% CI - 3.28 to 2.64, I ² = 37%). IV iron did not reduce the risk of requiring a blood transfusion (RR 0.90, 95% CI 0.73 to 1.11, p = 0.46, I ² = 0%), and we observed no difference in mortality, LOS or adverse events. One RCT reported on HRQoL and found no difference between treatment arms.

Conclusion

We found no conclusive evidence of an effect of IV iron on clinically important outcomes in patients undergoing non-elective surgery. Further adequately powered trials to evaluate its benefit in emergency surgical specialties with a high burden of anaemia are warranted.

Trial registration

This systematic review was registered on PROSPERO (CRD42018096288).