Initial serum ferritin levels in patients with multiple trauma and the subsequent development of acute respiratory distress syndrome

Elevated ferritin, mediated by IL-18 is associated with systemic inflammation and mortality in acute respiratory distress syndrome (ARDS)

BACKGROUND

Inflammatory subphenotypes have been identified in acute respiratory distress syndrome (ARDS). Hyperferritinaemia in sepsis is associated with hyperinflammation, worse clinical outcomes, and may predict benefit with immunomodulation. Our aim was to determine if raised ferritin identified a subphenotype in patients with ARDS.

METHODS

Baseline plasma ferritin concentrations were measured in patients with ARDS from two randomised controlled trials of simvastatin (Hydroxymethylglutaryl-CoA Reductase Inhibition with Simvastatin in Acute Lung Injury to Reduce Pulmonary Dysfunction-2 (HARP-2); discovery cohort, UK) and neuromuscular blockade (ROSE; validation cohort, USA). Results were analysed using a logistic regression model with restricted cubic splines, to determine the ferritin threshold associated with 28-day mortality.

RESULTS

Ferritin was measured in 511 patients from HARP-2 (95% of patients enrolled) and 847 patients (84% of patients enrolled) from ROSE. Ferritin was consistently associated with 28-day mortality in both studies and following a meta-analysis, a log-fold increase in ferritin was associated with an OR 1.71 (95% CI 1.01 to 2.90) for 28-day mortality. Patients with ferritin >1380 ng/mL (HARP-2 28%, ROSE 24%) had a significantly higher 28-day mortality and fewer ventilator-free days in both studies. Mediation analysis, including confounders (acute physiology and chronic health evaluation-II score and ARDS aetiology) demonstrated a statistically significant contribution of interleukin (IL)-18 as an intermediate pathway between ferritin and mortality.

CONCLUSIONS

Ferritin is a clinically useful biomarker in ARDS and is associated with worse patient outcomes. These results provide support for prospective interventional trials of immunomodulatory agents targeting IL-18 in this hyperferritinaemic subgroup of patients with ARDS.

Exploratory Analysis of Image-Guided Ionizing Radiation Delivery to Induce Long-Term Iron Accumulation and Ferritin Expression in a Lung Injury Model: Preliminary Results

BACKGROUND

Radiation therapy (RT) is an integral and commonly used therapeutic modality for primary lung cancer. However, radiation-induced lung injury (RILI) limits the irradiation dose used in the lung and is a significant source of morbidity. Disruptions in iron metabolism have been linked to radiation injury, but the underlying mechanisms remain unclear.

PURPOSE

To utilize a targeted radiation delivery approach to induce RILI for the development of a model system to study the role of radiation-induced iron accumulation in RILI.

METHODS

This study utilizes a Small Animal Radiation Research Platform (SARRP) to target the right lung with a 20 Gy dose while minimizing the dose delivered to the left lung and adjacent heart. Long-term pulmonary function was performed using RespiRate-x64image analysis. Normal-appearing lung volumes were calculated using a cone beam CT (CBCT) image thresholding approach in 3D Slicer software. Quantification of iron accumulation was performed spectrophotometrically using a ferrozine-based assay as well as histologically using Prussian blue and via Western blotting for ferritin heavy chain expression.

RESULTS

Mild fibrosis was seen histologically in the irradiated lung using hematoxylin and eosin-stained fixed tissue at 9 months, as well as using a scoring system from CBCT images, the Szapiel scoring system, and the highest fibrotic area metric. In contrast, no changes in breathing rate were observed, and median survival was not achieved up to 36 weeks following irradiation, consistent with mild lung fibrosis when only one lung was targeted. Our study provided preliminary evidence on increased iron content and ferritin heavy chain expression in the irradiated lung, thus warranting further investigation.

CONCLUSIONS

A targeted lung irradiation model may be a useful approach for studying the long-term pathological effects associated with iron accumulation and RILI following ionizing radiation.

Iron Chelation as a Potential Therapeutic Approach in Acute Lung Injury

Acute lung injury (ALI) has been challenging health care systems since before the COVID-19 pandemic due to its morbidity, mortality, and length of hospital stay. In view of the complex pathogenesis of ALI, effective strategies for its prevention and treatment are still lacking. A growing body of evidence suggests that iron dysregulation is a common characteristic in many subtypes of ALI. On the one hand, iron is needed to produce reactive oxygen species (ROS) as part of the immune response to an infection; on the other hand, iron can accelerate the occurrence of ferroptosis and extend host cell damage. Iron chelation represents a novel therapeutic strategy for alleviating lung injury and improving the survival of patients with ALI. This article reviews the current knowledge of iron homeostasis, the role of iron in ALI development, and potential therapeutic targets.

Reduction in Ferritin Concentrations among Patients Consuming a Dark-Green Leafy Vegetable-Rich, Low Inflammatory Foods Everyday (LIFE) Diet

Background

Ferritin is an iron-containing protein and acute-phase reactant, which may be elevated due to systemic iron overload or inflammation. Various diseases are associated with excess iron, but therapeutic iron chelation is suboptimal. Prior studies suggest that several plant phytochemicals possess iron-chelating properties, indicating that a plant-based diet may benefit patients with iron overload.

Objectives

The aim was to investigate whether patients who consume a nutrient-dense, dark-green leafy vegetable-rich diet, called the Low Inflammatory Foods Everyday (LIFE) diet, experience reductions in ferritin concentrations.

Methods

This was a retrospective study in which patients were intensively counseled to follow the LIFE diet. Compliance was assessed by patient interviews and serum B-carotene measurements. Primary outcomes included changes in ferritin, B-carotene, and C-reactive protein (CRP). Patients with elevated CRP concentrations at baseline were excluded in order to separate the impact of inflammation from iron overload on ferritin concentrations. Premenopausal women, who lose iron from menstruation, were also excluded.

Results

Thirty-two patients met the inclusion criteria. The median follow-up was 183 d.   Following the dietary intervention, ferritin decreased (-81 μg/L, P = 0.006) and B-carotene increased (46 μg/L, P < 0.0001), whereas CRP remained unchanged (-0.02 mg/L, P = 0.86). Adherent patients had greater reductions in ferritin compared with nonadherent patients (-138 μg/L vs. 15 μg/L, P = 0.001). Among all patients, there was an inverse relation between B-carotene and ferritin (-2.02, P = 0.03).

Conclusions

The LIFE diet, or similar dark-green leafy vegetable-rich, whole-food plant-based diets, may benefit patients with disorders of iron overload and iron-induced oxidative stress.

Potential Immune Indicators for Predicting the Prognosis of COVID-19 and Trauma: Similarities and Disparities

Although cellular and molecular mediators of the immune system have the potential to be prognostic indicators of disease outcomes, temporal interference between diseases might affect the immune mediators, and make them difficult to predict disease complications. Today one of the most important challenges is predicting the prognosis of COVID-19 in the context of other inflammatory diseases such as traumatic injuries. Many diseases with inflammatory properties are usually polyphasic and the kinetics of inflammatory mediators in various inflammatory diseases might be different. To find the most appropriate evaluation time of immune mediators to accurately predict COVID-19 prognosis in the trauma environment, researchers must investigate and compare cellular and molecular alterations based on their kinetics after the start of COVID-19 symptoms and traumatic injuries. The current review aimed to investigate the similarities and differences of common inflammatory mediators (C-reactive protein, procalcitonin, ferritin, and serum amyloid A), cytokine/chemokine levels (IFNs, IL-1, IL-6, TNF-α, IL-10, and IL-4), and immune cell subtypes (neutrophil, monocyte, Th1, Th2, Th17, Treg and CTL) based on the kinetics between patients with COVID-19 and trauma. The mediators may help us to accurately predict the severity of COVID-19 complications and follow up subsequent clinical interventions. These findings could potentially help in a better understanding of COVID-19 and trauma pathogenesis.

Infection-Mediated Clinical Biomarkers for a COVID-19 Electrical Biosensing Platform

The race towards the development of user-friendly, portable, fast-detection, and low-cost devices for healthcare systems has become the focus of effective screening efforts since the pandemic attack in December 2019, which is known as the coronavirus disease 2019 (COVID-19) pandemic. Currently existing techniques such as RT-PCR, antigen-antibody-based detection, and CT scans are prompt solutions for diagnosing infected patients. However, the limitations of currently available indicators have enticed researchers to search for adjunct or additional solutions for COVID-19 diagnosis. Meanwhile, identifying biomarkers or indicators is necessary for understanding the severity of the disease and aids in developing efficient drugs and vaccines. Therefore, clinical studies on infected patients revealed that infection-mediated clinical biomarkers, especially pro-inflammatory cytokines and acute phase proteins, are highly associated with COVID-19. These biomarkers are undermined or overlooked in the context of diagnosis and prognosis evaluation of infected patients. Hence, this review discusses the potential implementation of these biomarkers for COVID-19 electrical biosensing platforms. The secretion range for each biomarker is reviewed based on clinical studies. Currently available electrical biosensors comprising electrochemical and electronic biosensors associated with these biomarkers are discussed, and insights into the use of infection-mediated clinical biomarkers as prognostic and adjunct diagnostic indicators in developing an electrical-based COVID-19 biosensor are provided.

The Role of Ferroptosis in Acute Respiratory Distress Syndrome

Ferroptosis is a newly discovered type of regulated cell death that is different from apoptosis, necrosis and autophagy. Ferroptosis is characterized by iron-dependent lipid peroxidation, which induces cell death. Iron, lipid and amino acid metabolism is associated with ferroptosis. Ferroptosis is involved in the pathological development of various diseases, such as neurological diseases and cancer. Recent studies have shown that ferroptosis is also closely related to acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS), suggesting that it can be a novel therapeutic target. This article mainly introduces the metabolic mechanism related to ferroptosis and discusses its role in ALI/ARDS to provide new ideas for the treatment of these diseases.

Outcome Predictive Value of Serum Ferritin in ICU Patients with Long ICU Stay

Background and Objectives: The simplified interpretation of serum ferritin levels, according to which low ferritin levels indicate iron deficiency and high levels indicate hemochromatosis is obsolete, as in the presence of inflammation serum ferritin levels, no longer correlate with iron stores. However, further data are needed to interpret serum ferritin levels correctly in patients with ongoing inflammation. Our study aimed to assess serum iron and ferritin dynamics in patients with long ICU stay and the possible correlations with organ dysfunction progression and outcome. Materials and Methods: We conducted a prospective study in a university hospital intensive care unit (ICU) over six months. All patients with an ICU length-of-stay of more than seven days were enrolled. Collected data included: demographics, Sequential Organ Failure Assessment (SOFA) score, admission, weekly serum iron and ferritin levels, ICU length-of-stay and outcome. Interactions between organ dysfunction progression and serum iron and ferritin levels changes were investigated. Outcome predictive value of serum ferritin was assessed. Results: Seventy-two patients with a mean ICU length-of-stay of 15 (4.4) days were enrolled in the study. The average age of patients was 62 (16.8) years. There were no significant differences between survivors (39 patients, 54%) and nonsurvivors (33 patients, 46%) regarding demographics, serum iron and ferritin levels and SOFA score on ICU admission. Over time, serum iron levels remained normal or low, while serum ferritin levels statedly increased in all patients. Serum ferritin increase was higher in nonsurvivors than survivors. There was a significant positive correlation between SOFA score and serum ferritin (r = 0.7, 95%CI for r = 0.64 to 0.76, p < 0.01). The predictive outcome accuracy of serum ferritin was similar to the SOFA score. Conclusions: In patients with prolonged ICU stay, serum ferritin dynamics reflects organ dysfunction progression and parallels SOFA score in terms of outcome predictive accuracy.

Novel risk scoring system for predicting acute respiratory distress syndrome among hospitalized patients with coronavirus disease 2019 in Wuhan, China

Background

The mortality rate from acute respiratory distress syndrome (ARDS) is high among hospitalized patients with coronavirus disease 2019 (COVID-19). Hence, risk evaluation tools are required to immediately identify high-risk patients upon admission for early intervention.

Methods

A cohort of 220 consecutive patients with COVID-19 were included in this study. To analyze the risk factors of ARDS, data obtained from approximately 70% of the participants were randomly selected and used as training dataset to establish a logistic regression model. Meanwhile, data obtained from the remaining 30% of the participants were used as test dataset to validate the effect of the model.

Results

Lactate dehydrogenase, blood urea nitrogen, D-dimer, procalcitonin, and ferritin levels were included in the risk score system and were assigned a score of 25, 15, 34, 20, and 24, respectively. The cutoff value for the total score was > 35, with a sensitivity of 100.00% and specificity of 81.20%. The area under the receiver operating characteristic curve and the Hosmer–Lemeshow test were 0.967 (95% confidence interval [CI]: 0.925–0.989) and 0.437(P Value = 0.437). The model had excellent discrimination and calibration during internal validation.

Conclusions

The novel risk score may be a valuable risk evaluation tool for screening patients with COVID-19 who are at high risk of ARDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-020-05561-y.

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.

Serological ferritin, 100A12, procalcitonin and APACHEII score in prediction the prognosis of acute respiratory distress syndrome

Objective The aim of the present work was to investigate the prognostic value of serological ferritin, 100A12, procalcitonin (PCT) and APACHEII score in predicting death risk for patients with acute respiratory distress syndrome (ARDS).

Methods Forty eight ARDS patients were recruited from Feb. 2016 to Jan. 2019 from Lishui People’s Hospital. According to their prognosis (survival or death within 28 days), these 48 patients were further divided into the survival group (n=28) and death group (n=20). The serological levels of S100A12, PCT and ferritin of the 48 ARDS patients were examined within 24 hours after hospitalization. Demographic characteristics, serum S100A12, PCT and ferritin were compared between the two groups, and diagnostic analysis was performed to evaluate the clinical efficacy of these markers in predicting the death of ARDS patients.

Results The serum S100A12, ferritin and APACHEII scores of the death group were significantly higher than those of the survival group (p<0.05). However, serum PCT levels were not statistically different between the two groups (p>0.05). The death prediction sensitivity for serum S100A12, PCT, ferritin and APACHEII score were 65.0 (40.78-84.61)%, 60.00(36.05-80.88) %,75.0(50.90-91.34)% and 85.0(62.11-96.79)% respectively. The death prediction specificity for serum S100A12, PCT, ferritin and APACHEII score were 75.0(55.13-89.31)%, 60.00(36.05-80.88)%, 64.29(44.07-81.36)% and 82.14(63.11-93.94)%, respectively. The area under the ROC curve (AUC) for serum S100A12, PCT, ferritin and APACHEII score were 0.68(0.51-0.84), 0.63(0.46-0.79), 0.71(0.56-0.86) and 0.91(0.83-0.99) respectively.

Conclusion Serological ferritin, 100A12, PCT and APACHEII scores can be used as biomarkers to predict the death risk of ARDS patients.

Iron in Lung Pathology

The lung presents a unique challenge for iron homeostasis. The entire airway is in direct contact with the environment and its iron particulate matter and iron-utilizing microbes. However, the homeostatic and adaptive mechanisms of pulmonary iron regulation are poorly understood. This review provides an overview of systemic and local lung iron regulation, as well as the roles of iron in the development of lung infections, airway disease, and lung injury. These mechanisms provide an important foundation for the ongoing development of therapeutic applications.

Role of iron in the pathogenesis of respiratory disease

Iron is essential for many biological processes, however, too much or too little iron can result in a wide variety of pathological consequences, depending on the organ system, tissue or cell type affected. In order to reduce pathogenesis, iron levels are tightly controlled in throughout the body by regulatory systems that control iron absorption, systemic transport and cellular uptake and storage. Altered iron levels and/or dysregulated homeostasis have been associated with several lung diseases, including chronic obstructive pulmonary disease, lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis and asthma. However, the mechanisms that underpin these associations and whether iron plays a key role in the pathogenesis of lung disease are yet to be fully elucidated. Furthermore, in order to survive and replicate, pathogenic micro-organisms have evolved strategies to source host iron, including freeing iron from cells and proteins that store and transport iron. To counter these microbial strategies, mammals have evolved immune-mediated defence mechanisms that reduce iron availability to pathogens. This interplay between iron, infection and immunity has important ramifications for the pathogenesis and management of human respiratory infections and diseases. An increased understanding of the role that iron plays in the pathogenesis of lung disease and respiratory infections may help inform novel therapeutic strategies. Here we review the clinical and experimental evidence that highlights the potential importance of iron in respiratory diseases and infections.

Association of serum ferritin levels with smoking and lung function in the Korean adult population: analysis of the fourth and fifth Korean National Health and Nutrition Examination Survey

Background

Iron-catalyzed oxidative stress contributes to lung injury after exposure to various toxins, including cigarette smoke. An oxidant/antioxidant imbalance is considered to play a critical role in the pathogenesis of COPD. Ferritin is a key protein in iron homeostasis, and its capacity to oxidize and sequester the metal preventing iron prooxidant activity implicates its possible role in the alteration of antioxidant imbalance. We investigated the relationship among cigarette smoking, lung function, and serum ferritin concentration in a large cohort representative of the Korean adult population.

Materials and methods

Among 50,405 participants of the Korean National Health and Nutrition Examination Survey from 2010 to 2014, 15,239 adult subjects older than 40 years with serum ferritin levels and spirometric data were selected for this study.

Results

The mean age was 56.5 years for men (43%) and 56.9 years for women (57%). The prevalence of airway obstruction was 13.4%, which was significantly higher in men than in women, and increased in former or current smokers. The median levels of serum ferritin were highest in the airway obstruction group, followed by the restrictive pattern group, and lowest in the normal lung function group. The median ferritin levels were increased by smoking status and amounts in each spirometric subgroup. In multivariable regression analysis, serum ferritin was positively associated with forced expiratory volume in 1 second and forced expiratory volume in 1 second/forced vital capacity, whereas the smoking amount was negatively associated with the adjustment with age, sex, height, and weight.

Conclusion

Serum ferritin levels were increased in former or current smokers and were increased with smoking amount in all subgroups of participants categorized according to spirometric results. The result was also evident in the subgroups divided by obstructive severity. While smoking amount was inversely related to lung function, higher levels of serum ferritin were associated with enhanced spirometric results in a representative sample of the general Korean adult population. Future prospective studies will be needed to clarify the causality between serum ferritin and lung functions and their role in COPD morbidity.

Biochemical and Ultrastructural Lung Damage Induced by Rhabdomyolysis in the Rat

Rhabdomyolysis-induced oxidative stress is associated with morphological and functional damage to the kidney and other organs, but applications of this model in the lung are still lacking. The aim of the present study was to determine the relationship between oxidative stress and the morphological changes occurring in the lungs of rats subjected to rhabdomyolysis. Rhabdomyolysis was induced by intramuscular glycerol injection (50% v/v, 10 ml/kg), and the control group was injected with saline vehicle. Arterial blood samples were drawn at 0, 2, 4, and 6 hrs for measurement of arterial gases, creatine kinase activity, and plasma free F2-isoprostane levels. Six hours later, the lungs were removed to determine the wet-to-dry weight ratio, reduced glutathione (GSH) and GSH disulfide (GSSG) levels, and activity of antioxidant enzymes (cataiase [CAT], superoxide dismutase [SOD], and GSH peroxidase [GSH-Px]). Protein carbonylation and lipid peroxidation were assessed in the lungs by measurement of carbonyl and malondialdehyde (MDA) production, respectively. Bronchoalveolar lavage, cell counts, and lung ultrastructural studies were also performed. Six hours after glycerol injection, arterial PO2 and PCO2 were 23% and 38% lower, respectively, and plasma free F2-isoprostane levels were 72% higher, compared with control values. In lungs, protein carbonyl and MDA production were 58% and 12% higher, respectively; the GSH:GSSG ratio and GSH-Px activity were 43% and 60% lower, respectively; and activities of CAT and SOD showed no significant differences compared with controls. Rhabdomyolysis-induced ultrastructural impairment of the lung showed Type II cell damage, extracytoplasmic lamellar bodies and lack of tubular myelin reorganization, endothelial cellular edema, and no disruption of the alveolar-capillary barrier. These results provide evidence that rhabdomyolysis could induce tissue injury associated with increased oxidative stress, suggesting the contribution of oxidative stress to the pathogenic mechanism of acute lung injury.

Proteomic study of acute respiratory distress syndrome: current knowledge and implications for drug development

The acute respiratory distress syndrome (ARDS) is a common cause of acute respiratory failure, and is associated with substantial mortality and morbidity. Dozens of clinical trials targeting ARDS have failed, with no drug specifically targeting lung injury in widespread clinical use. Thus, the need for drug development in ARDS is great. Targeted proteomic studies in ARDS have identified many key pathways in the disease, including inflammation, epithelial injury, endothelial injury or activation, and disordered coagulation and repair. Recent studies reveal the potential for proteomic changes to identify novel subphenotypes of ARDS patients who may be most likely to respond to therapy and could thus be targeted for enrollment in clinical trials. Nontargeted studies of proteomics in ARDS are just beginning and have the potential to identify novel drug targets and key pathways in the disease. Proteomics will play an important role in phenotyping of patients and developing novel therapies for ARDS in the future.

The role of iron in pulmonary pathology

Respiratory disease accounts for a large proportion of emergency admissions to hospital and diseaseassociated mortality. Genetic association studies demonstrate a link between iron metabolism and pulmonary disease phenotypes. IREB2 is a gene that produces iron regulatory protein 2 (IRP2), which has a key role in iron homeostasis. This review addresses pathways involved in iron metabolism, particularly focusing on the role of IREB2. In addition to this, environmental factors also influence phenotypic variation in respiratory disease, for example inhaled iron from cigarette smoke is deposited in the lung and causes tissue damage by altering iron homeostasis. The effects of cigarette smoke are detailed in this article, particularly in relation to lung conditions that favour the upper lobes, such as emphysema and lung cancer. Clinical applications of iron homeostasis are also discussed in this review, especially looking at the pathophysiology of chronic obstructive pulmonary disease, lung cancer, pulmonary infections and acute respiratory distress syndrome. Promising new treatments involving iron are also covered.

Impact of the serum ferritin concentration in liver transplantation

The serum ferritin (SF) concentration is a widely available and objective laboratory parameter. SF is also widely recognized as an acute-phase reactant. The purpose of the present study was to identify the chronological changes in the recipient's SF concentration during liver transplantation (LT) and to clarify factors having an effect on the recipient's intraoperative SF level. In addition, the study retrospectively evaluated the usefulness of measuring SF during LT. Ninety-eight pediatric recipients were retrospectively analyzed. The data were analyzed and compared according to the SF level in the recipient. Patients were classified into 2 groups based on the intraoperative peak SF levels of ≤ 1000 ng/mL (low-SF group) or >1000 ng/mL (high-SF group). The SF value increased dramatically after reperfusion and fell to normal levels within the early postoperative period. The warm ischemia time (WIT) was significantly longer in the high-SF group (47.0 versus 58.5 minutes; P = 0.003). In addition, a significant positive correlation was observed between the peak SF value and WIT (r = 0.35; P < 0.001). There were significant positive correlations between the peak SF value and the donors' preoperative laboratory data, including transaminases, cholinesterase, hemoglobin, transferrin saturation, and SF, of which SF showed the strongest positive correlation (r = 0.74; P < 0.001). The multivariate analysis revealed that WIT and donor's SF level were a significant risk factor for high SF level in the recipient (P = 0.007 and 0.02, respectively). In conclusion, the SF measurement can suggest the degree of ischemia/reperfusion injury (IRI). A high SF level in the donor is associated with the risk of further acute reactions, such as IRI, in the recipient.

Ceruloplasmin and Hypoferremia: Studies in Burn and Non-Burn Trauma Patients

OBJECTIVE

Normal iron handling appears to be disrupted in critically ill patients leading to hypoferremia that may contribute to systemic inflammation. Ceruloplasmin (Cp), an acute phase reactant protein that can convert ferrous iron to its less reactive ferric form facilitating binding to ferritin, has ferroxidase activity that is important to iron handling. Genetic absence of Cp decreases iron export resulting in iron accumulation in many organs. The objective of this study was to characterize iron metabolism and Cp activity in burn and non-burn trauma patients to determine if changes in Cp activity are a potential contributor to the observed hypoferremia.

MATERIAL AND METHODS

Under Brooke Army Medical Center Institutional Review Board approved protocols, serum or plasma was collected from burn and non-burn trauma patients on admission to the ICU and at times up to 14 days and measured for indices of iron status, Cp protein and oxidase activity and cytokines.

RESULTS

Burn patients showed evidence of anemia and normal or elevated ferritin levels. Plasma Cp oxidase activity in burn and trauma patients were markedly lower than controls on admission and increased to control levels by day 3, particularly in burn patients. Plasma cytokines were elevated throughout the 14 days study along with evidence of an oxidative stress. No significant differences in soluble transferrin receptor were noted among groups on admission, but levels in burn patients were lower than controls for the first 5 days after injury.

CONCLUSION

This study further established the hypoferremia and inflammation associated with burns and trauma. To our knowledge, this is the first study to show an early decrease in Cp oxidase activity in burn and non-burn trauma patients. The results support the hypothesis that transient loss of Cp activity contributes to hypoferremia and inflammation. Further studies are warranted to determine if decreased Cp activity increases the risk of iron-induced injury following therapeutic interventions such as transfusions with blood that has undergone prolonged storage in trauma resuscitation.

Serum ferritin correlates with Glasgow coma scale scores and fatal outcome after severe traumatic brain injury

OBJECTIVES

Severe traumatic brain injury (TBI) is associated with a 30-70% mortality rate. Nevertheless, in clinical practice there are no effective biomarkers for the prediction of fatal outcome following severe TBI. Therefore, the aim was to determine whether ferritin serum levels are associated with ICU mortality in patients with severe TBI.

METHODS

This prospective study enrolled 69 male patients who suffered severe TBI [Glasgow Coma Scale (GCS) 3-8 at emergency room admission]. The serum ferritin protein level was determined at ICU admission (mean 5.6 ± 2.5 hours after emergency room admission).

RESULTS

Severe TBI was associated with a 39% mortality rate. Higher serum ferritin concentrations were significantly associated with lower hospital admission GCS scores (p = 0.049). Further, there was a significant association between higher ferritin concentrations and fatal outcome (289.5 ± 27.1 µg L(-1) for survivors and 376.5 ± 31.5 µg L(-1) for non-survivors, respectively, mean ± SEM, p = 0.032).

CONCLUSIONS

Increased serum ferritin levels were associated with lower hospital admission GCS scores and predicted short-term fatal outcome following severe TBI.

Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells

"Serum ferritin" presents a paradox, as the iron storage protein ferritin is not synthesised in serum yet is to be found there. Serum ferritin is also a well known inflammatory marker, but it is unclear whether serum ferritin reflects or causes inflammation, or whether it is involved in an inflammatory cycle. We argue here that serum ferritin arises from damaged cells, and is thus a marker of cellular damage. The protein in serum ferritin is considered benign, but it has lost (i.e. dumped) most of its normal complement of iron which when unliganded is highly toxic. The facts that serum ferritin levels can correlate with both disease and with body iron stores are thus expected on simple chemical kinetic grounds. Serum ferritin levels also correlate with other phenotypic readouts such as erythrocyte morphology. Overall, this systems approach serves to explain a number of apparent paradoxes of serum ferritin, including (i) why it correlates with biomarkers of cell damage, (ii) why it correlates with biomarkers of hydroxyl radical formation (and oxidative stress) and (iii) therefore why it correlates with the presence and/or severity of numerous diseases. This leads to suggestions for how one might exploit the corollaries of the recognition that serum ferritin levels mainly represent a consequence of cell stress and damage.

The Role of Iron Metabolism in Lung Inflammation and Injury

Iron is required for many vital functions including oxygen transport and energy metabolism. Protective mechanisms maintain optimal iron concentration involving dynamic regulation of the transporters and iron storage proteins. In addition to these systemic regulatory mechanisms, the unique lung environment must provide detoxification from metal-induced oxidative stress and pathogenic infections. This review focuses on the unique role of iron metabolism in lung injury and inflammation.

Serum ferritin: Past, present and future

BACKGROUND

Serum ferritin was discovered in the 1930s, and was developed as a clinical test in the 1970s. Many diseases are associated with iron overload or iron deficiency. Serum ferritin is widely used in diagnosing and monitoring these diseases.

SCOPE OF REVIEW

In this chapter, we discuss the role of serum ferritin in physiological and pathological processes and its use as a clinical tool.

MAJOR CONCLUSIONS

Although many aspects of the fundamental biology of serum ferritin remain surprisingly unclear, a growing number of roles have been attributed to extracellular ferritin, including newly described roles in iron delivery, angiogenesis, inflammation, immunity, signaling and cancer.

GENERAL SIGNIFICANCE

Serum ferritin remains a clinically useful tool. Further studies on the biology of this protein may provide new biological insights.

Ischemia/reperfusion Lung Injury Increases Serum Ferritin and Heme Oxygenase-1 in Rats

Intestinal ischemia/reperfusion (I/R) is one of common causes of acute lung injury (ALI). Early and accurate diagnosis of patients who are like to develop serious acute respiratory distress syndrome (ARDS) would give a therapeutic advantage. Ferritin and heme oxygenase-1 (HO-1) are increased by oxidative stress and are potential candidates as a predictive biomarker of ARDS. However, the mechanisms responsible for the increases of ferritin and HO-1, and their relationship to ALI, are unclear. In order to elucidate the interactions between ferritin and HO-1, we studied the changes in ferritin and HO-1 levels in serum and bronchoalveolar lavage (BAL) fluid after intestinal I/R injury in rats. Leukocyte number and protein contents in BAL fluid were elevated following I/R, and the increases were attenuated by mepacrine pretreatment. Both serum ferritin and HO-1 concentrations were progressively elevated throughout the 3 h observation period. Mepacrine pretreatment attenuated the increase of serum and BAL fluid ferritin concentrations, but did not suppress the increase of serum HO-1. Moreover, BAL fluid HO-1 levels did not change after I/R or after mepacrine pretreated I/R compared with sham rats. Unlike ferritin, HO-1 levels are not exactly matched with the ALI. Therefore, there might be a different mechanism between the changes of ferritin and HO-1 in intestinal I/R-induced ALI model.

Secondary hemophagocytic lymphohistiocytosis and severe sepsis/ systemic inflammatory response syndrome/multiorgan dysfunction syndrome/macrophage activation syndrome share common intermediate phenotypes on a spectrum of inflammation

In an effort to attain earlier diagnoses in children with hemophagocytic lymphohistiocytosis (HLH), the International Histiocyte Society has now broadened their diagnostic criteria to no longer differentiate primary (HLH) and secondary hemophagocytic lymphohistiocytosis (SHLH). Five of the following eight diagnostic criteria needed to be met: 1) fever, 2) cytopenia of two lines, 3) hypertriglyceridemia and/or hypofibrinogenemia, 4) hyperferritinemia (>500 microg/L), 5) hemophagocytosis, 6) elevated soluble interleukin-2 receptor (CD25), 7) decreased natural killer-cell activity, and 8) splenomegaly can also commonly be found in patients with sepsis, systemic inflammatory response syndrome (SIRS), multiorgan dysfunction syndrome (MODS), and macrophage activation syndrome (MAS). Nevertheless, the therapeutic options for these are radically different. Chemotherapy and bone marrow transplant have been used for treatment of HLH/SHLH, whereas antibiotics and supportive treatment are used in severe sepsis/SIRS and MODS. MAS is treated with limited immune suppression. Outcomes are also different, SHLH has a mortality rate around 50%, whereas pediatric septic shock and MODS have a mortality of 10.3% and 18%, respectively, and severe sepsis in previously healthy children has a mortality rate of 2%. MAS has a mortality rate between 8% and 22%. Because SHLH and severe sepsis/SIRS/MODS/MAS share clinical and laboratory inflammatory phenotypes, we recommend extreme caution when considering applying HLH therapies to children with sepsis/SIRS/MODS/MAS. HLH therapies are clearly warranted for children with HLH; however, a quantitative functional estimate of cytotoxic lymphocyte function may be a more precise approach to define the overlap of these conditions, better identify these processes, and develop novel therapeutic protocols that may lead to improved treatments and outcomes.

The pathogenetic and prognostic value of biologic markers in acute lung injury

Over the past 2 decades, measurement of biomarkers in both the airspaces and plasma early in the course of acute lung injury has provided new insights into the mechanisms of lung injury. In addition, biologic markers of cell-specific injury, acute inflammation, and altered coagulation correlate with mortality from acute lung injury in several single center studies as well as in multicenter clinical trials. To date, biomarkers have been measured largely for research purposes. However, with improved understanding of their role in the pathogenesis of acute lung injury, biomarkers may play an important role in early detection of lung injury, risk stratification for clinical trials, and, ultimately, tailoring specific therapies to individual patients. This article provides a review of biologic markers in acute lung injury, with an emphasis on recent analysis of results from multicenter clinical trials.

Disruption of iron homeostasis and lung disease

As a result of a direct exchange with the external environment, the lungs are exposed to both iron and agents with a capacity to disrupt the homeostasis of this metal (e.g. particles). An increased availability of catalytically reactive iron can result from these exposures and, by generating an oxidative stress, this metal can contribute to tissue injury. By importing this Fe(3+) into cells for storage in a chemically less reactive form, the lower respiratory tract demonstrates an ability to mitigate both the oxidative stress presented by iron and its potential for tissue injury. This means that detoxification is accomplished by chemical reduction to Fe(2+) (e.g. by duodenal cytochrome b and other ferrireductases), iron import (e.g. by divalent metal transporter 1 and other transporters), and storage in ferritin. The metal can subsequently be exported from the cell (e.g. by ferroportin 1) in a less reactive state relative to that initially imported. Iron is then transported out of the lung via the mucociliary pathway or blood and lymphatic pathways to the reticuloendothelial system for long term storage. This coordinated handling of iron in the lung appears to be disrupted in several acute diseases on the lung including infections, acute respiratory distress syndrome, transfusion-related acute lung injury, and ischemia-reperfusion. Exposures to bleomycin, dusts and fibers, and paraquat similarly alter iron homeostasis in the lung to affect an oxidative stress. Finally, iron homeostasis is disrupted in numerous chronic lung diseases including pulmonary alveolar proteinosis, transplantation, cigarette smoking, and cystic fibrosis.

Pathogenesis of the systemic inflammatory syndrome and acute lung injury: role of iron mobilization and decompartmentalization

Changes in iron homeostatic responses routinely accompany infectious or proinflammatory insults. The systemic inflammatory response syndrome (SIRS) and the development of acute lung injury (ALI) feature pronounced systemic and lung-specific alterations in iron/heme mobilization and decompartmentalization; such responses may be of pathological significance for both the onset and progression of acute inflammation. The potential for excessive iron-catalyzed oxidative stress, altered proinflammatory redox signaling, and provision of iron as a microbial growth factor represent obvious adverse aspects of altered in vivo iron handling. The release of hemoglobin during hemolytic disease or surgical procedures such as those utilizing cardiopulmonary bypass procedures further impacts on iron mobilization, turnover, and storage with associated implications. Genetic predisposition may ultimately determine the extent to which SIRS and related syndromes develop in response to such changes. The design of specific therapeutic interventions based on endogenous stratagems to limit adverse aspects of altered iron handling may prove of therapeutic benefit for the treatment of SIRS and ALI.

Ferritin levels in children with severe sepsis and septic shock

AIM

To evaluate serum ferritin level in children with severe sepsis and septic shock and its association with mortality.

METHOD

A cohort study of 36 children aged 1 month-16 years with severe sepsis or septic shock requiring intensive care was conducted. Serum ferritin levels were measured at the time of diagnosis of sepsis and a ferritin index (FI=observed serum ferritin divided by the upper limit of normal ferritin for age and gender) was calculated.

RESULTS

The median age (range) of the children was 6 (2-100) months. Ferritin was <200 ng/mL in 13 children, 200-500 ng/mL in 11 children and >500 ng/mL in 12 children. The mortality associated with these groups was 23%, 9% and 58%, respectively. A ferritin>500 ng/mL was associated with a 3.2 (1.3-7.9) relative risk of death (p=0.01). FI of 1.7 was the best cutoff value for identifying those who died. In a logistic regression analysis, ferritin level and PRISM were independently associated with mortality.

CONCLUSIONS

Ferritin is raised in children with septic shock and high ferritin level is associated with poorer outcome.

Serum biomarkers in acute respiratory distress syndrome an ailing prognosticator

The use of biomarkers in medicine lies in their ability to detect disease and support diagnostic and therapeutic decisions. New research and novel understanding of the molecular basis of the disease reveals an abundance of exciting new biomarkers who present a promise for use in the everyday clinical practice. The past fifteen years have seen the emergence of numerous clinical applications of several new molecules as biologic markers in the research field relevant to acute respiratory distress syndrome (translational research). The scope of this review is to summarize the current state of knowledge about serum biomarkers in acute lung injury and acute respiratory distress syndrome and their potential value as prognostic tools and present some of the future perspectives and challenges.

Serum ferritin elevation and acute lung injury in rats subjected to hemorrhage: reduction by mepacrine treatment

Ferritin regulates iron levels and, for unknown reasons, serum ferritin concentrations are increased in patients at risk for and with acute lung injury (ALI) and multiple organ failure. Uncomplexed iron could exacerbate the toxicity of the increased oxidative stress that occurs in patients with ALI and multiple organ failure and thereby contribute to disease. In the present investigation, the authors found that serum and lung lavage ferritin concentrations increased in hemorrhaged rats that develop ALI as manifested by increased lung inflammation (increased lung lavage leukocyte counts and lung myeloperoxidase activities) and increased lung leak (increased lung lavage protein concentrations). Treatment with mepacrine, a phospholipase A2 inhibitor, attenuated the increases in serum and lung lavage ferritin concentrations, lung inflammation, and lung leak that occur in rats subjected to hemorrhage. The findings show that serum and lung ferritin levels increase and may play a role in the development of acute lung injury caused by hemorrhage.

Serum ferritin increases in hemorrhaged rats that develop acute lung injury: effect of an iron-deficient diet

For unknown reasons, serum ferritin levels increase in patients at risk for and with acute lung injury (ALI). To improve understanding of the relationship between serum ferritin alterations and the development of ALI, we investigated the effect of iron deficiency on the serum ferritin response of rats subjected to hemorrhage. We found that rats fed an iron-deficient diet for 6 weeks had decreased hemoglobin, hematocrit, liver total iron, liver total iron-binding capacity, and liver ferritin concentrations but the same serum ferritin concentrations as rats fed a control diet. Following hemorrhage, serum ferritin concentrations increased rapidly and progressively in rats fed a control diet. Along with increases in serum ferritin concentrations, control diet rats subjected to hemorrhage also had increased lung lavage leukocyte numbers, lung myeloperoxidase activities (lung inflammation), and lung lavage protein concentrations (lung leak) compared to control diet fed rats subjected to sham treatment. By comparison, the serum ferritin concentrations, lung inflammation, and lung leak of hemorrhaged rats fed an iron-deficient diet were decreased compared to hemorrhaged rats fed a control diet. These findings indicate that serum ferritin concentrations increase and acute lung injury develops following hemorrhage in rats fed a control, but not an iron-deficient, diet. A relatively brief exposure to an iron-deficient diet reduces hemorrhage-induced ALI.

Iron and iron-related proteins in the lower respiratory tract of patients with acute respiratory distress syndrome

OBJECTIVE

An increased oxidative stress in the lower respiratory tract of individuals with acute respiratory distress syndrome is considered to be one mechanism of lung injury in these patients. Cell and tissue damage resulting from an oxidative stress can ultimately be the consequence of a disruption of normal iron metabolism and an increased availability of catalytically active metal. Using bronchoalveolar lavage fluid, we quantified concentrations of iron and iron-related proteins in the lower respiratory tract in patients with acute respiratory distress syndrome and healthy volunteers.

DESIGN

A clinical study to quantify iron and iron-related proteins in the lower respiratory tract in patients with acute respiratory distress syndrome and healthy volunteers.

PATIENTS

We studied 14 patients with acute respiratory distress syndrome and 28 healthy volunteers.

MAIN RESULTS

Comparable to previous investigation, protein, albumin, and cytokine concentrations in the bronchoalveolar lavage fluid were significantly increased in acute respiratory distress syndrome patients. The concentrations of total and nonheme iron were also increased in the lavage fluid of patients. Concentrations of hemoglobin, haptoglobin, transferrin, transferrin receptor, lactoferrin, and ferritin in the bronchoalveolar lavage fluid were all significantly increased in acute respiratory distress syndrome patients.

CONCLUSIONS

We conclude that bronchoalveolar lavage fluid indices reflect a disruption of normal iron metabolism in the lungs of acute respiratory distress syndrome patients. Increased concentrations of available iron in acute respiratory distress syndrome may participate in catalyzing oxidant generation destructive to the tissues of the lower respiratory tract. However, increased metal availability is also likely to elicit an increased expression of transferrin receptor, lactoferrin, and ferritin in the lower respiratory tract which will function to diminish this oxidative stress.

Iron and the redox status of the lungs

Iron is an element essential for the survival of most aerobic organisms. However, when its availability is not adequately controlled, iron, can catalyze the formation of a range of aggressive and damaging reactive oxygen species, and act as a microbial growth promoter. Depending on the concentrations formed such species can cause molecular damage or influence redox signaling mechanisms. This review describes recent knowledge concerning iron metabolism in the lung, during both health and disease. In the lower part of the lung a small redox active pool of iron is required for reasons that are at present unclear, but may be related to antimicrobial functions. When the concentration of iron is increased in the lung (usually because of environmental exposure), iron is deleterious and contributes to a range of chronic and acute respiratory diseases. Moreover, aberrant regulation of iron metabolism, and/or deficient antioxidant protection, is also associated with acute lung diseases, such as the acute respiratory distress syndrome (ARDS). Iron, with the consequent production of reactive oxygen species (ROS), microbial growth promotion, and adverse signaling is strongly implicated as a major contributor to the pathogenesis of numerous disease processes involving the lung. Heme oxgenase, an enzyme that produces reactive iron from heme catabolism, is also briefly discussed in relation to lung disease.

Ferritin and desferrioxamine attenuate xanthine oxidase-dependent leak in isolated perfused rat lungs

Iron, through its participation in reactions that generate reactive oxygen species, may contribute to the oxidative lung injury observed in patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). A number of investigators have shown that the endogenous iron storage protein ferritin increases in the blood of patients with and at-risk for ALI and ARDS, but the significance of these increases are not known. In the present investigation, we measured lung tissue levels of thiobarbituric acid reactive substances (TBARS) and lung leak in isolated rat lungs perfused with xanthine oxidase (XO) and purine, an enzymatic system which generates reactive oxygen species. We found that adding ferritin (100 ng/mL) or desferrioxamine (DFO, 10 mM), an iron chelator, to the vascular perfusate solution decreased oxidant-induced leak in isolated rat lungs perfused with XO and purine. Addition of ferritin or DFO also decreased TBARS in isolated rat lungs perfused with XO and purine; neither ferritin nor DFO, however, decreased XO activity in vitro. Our results suggest that oxidative lung leak may be altered by the availability of reactive iron and that ferritin may contribute to protection against oxidative lung injury.

Humoral markers of severity and prognosis of critical illness

Despite the considerable advances made in understanding the pathophysiology of systemic inflammation during critical illness, clinical progress has been elusive as it remains a very deadly condition. Cortisol and thyroid hormone levels can be as predictive of outcome as the commonly used severity parameters (i.e. APACHE). Indeed, levels of endocrine humoral substances such as arachidonic acids, nitric oxide, endothelin, calcitonin precursors, leptin and adenosine correlate with the severity and outcome of critical illness. Furthermore, calcitonin precursors represent a potentially new hormokine paradigm, being transcriptionally activated in all cells in response to infection. The cytokines are immune markers that often correlate with severity and outcome, but their release is transient. In contrast, the so-called acute phase proteins, such as C-reactive protein and serum amyloid A, are highly sensitive to inflammatory activity and can be important markers of severity and outcome. Leukocyte esterase, adhesion molecules, platelet activating factor and activated protein C are additional humoral immune markers; the replacement of the latter has been shown to be a promising therapeutic option. Natriuretic peptides are neurocrine humoral markers that have important cardiovascular implications. The level of macrophage migrating inhibitory factor, released by the pituitary, is elevated in sepsis and counteracts glucocorticoid action. Cellular markers to severe stress include the enhanced expression of protective substances in the form of heat shock proteins. High mobility group-1 is a DNA-binding protein and a late mediator of the inflammatory response. Apoptotic markers such as the soluble fas ligand are also elevated in inflammation. In summary, during critical illness, the endocrine, immune and nervous systems elaborate a multitude of humoral markers, the roles of which merit further scrutiny in order to improve therapeutic outcome.

Role of monocyte L-selectin in the development of post-traumatic organ failure

The vascular leucocyte adhesion molecule, L-selectin, plays an important early role in monocyte trafficking at sites of inflammation, a process which leads to the development of inflammatory organ failure. In this prospective observational study, we investigate whether early numerical and functional changes in circulating monocytes, expression of monocyte L-selectin (CD62L) and monocyte:neutrophil L-selectin ratios are related to the subsequent development of post-traumatic organ failure (OF) and multiple organ dysfunction syndrome (MODS). Monocyte counts and cell surface L-selectin were measured by an automated cell counter and flow cytometry, respectively. Of 164 trauma patients admitted to a university emergency department resuscitation room, 64 had multiple injuries, 51 developed OF, 20 developed MODS and 21 died. Early monocyte counts in patients with multiple injuries were lower in those who developed MODS (0.44 x 10(9)/l) compared with those who did not (0.60 x 10(9)/l; P=0.024). Monocyte L-selectin mean channel fluorescence increased with injury severity and was highest in those who developed MODS (P=0.033). In the sub-group of patients with multiple injuries, L-selectin mean channel fluorescence was also greater in those patients who developed MODS compared with patients who did not develop MODS (P=0.042). The monocyte to neutrophil count ratio also decreased with injury severity (P=0.006). Using optimal cut off values for L-selectin mean channel, fluorescence, the positive and negative predictive values for OF was 43.5 and 91.4%, respectively and for MODS it was 25.4 and 92.9%, respectively. Alterations in early circulating monocyte counts and L-selectin expression after injury are related to the development of post-traumatic organ failure and suggest an area in the inflammatory pathway that may be influenced by L-selectin blockade.

Elevated plasma surfactant protein-B predicts development of acute respiratory distress syndrome in patients with acute respiratory failure

Surfactant protein-B is a lung specific protein secreted into the air spaces by pulmonary epithelial type II cells that leaks into the bloodstream in increased amounts in patients with ARDS. To test whether elevated plasma levels of surfactant protein-B would predict the development of ARDS in patients with acute hypoxemic respiratory failure, plasma and lung injury scores were collected at study entry and daily thereafter for 3 d from 54 patients admitted to our intensive care unit. ARDS was defined as a new bilateral infiltrate on chest radiograph and a lung injury score > or = 2.5. Twenty patients developed ARDS, of whom seven died. Although the initial lung injury score was not predictive of ARDS, the initial plasma surfactant protein-B was predictive (area under the curve = 0.77 [0.63 to 0.90], nonparametric receiver-operating characteristic analysis). In this cohort, plasma surfactant protein-B was particularly predictive of ARDS when applied to patients suffering a direct lung insult (area under the curve = 0.87 [0.72 to 1.02]), with a sensitivity of 85% (95% CI: 55 to 98%) and specificity of 78% (40 to 97%) at a cutoff of 4,994 ng/ml.