Elevated serum iron level is a predictor of prognosis in ICU patients with acute kidney injury

Deciphering the iron enigma: Navigating the complexities of iron metabolism in critical illness

Iron is a double-edged sword! Despite being essential for numerous physiological processes of the body, a dysregulated iron metabolism can result in tissue damage, exaggerated inflammatory response, and increased susceptibility to infection with certain pathogens that thrive in iron-rich environment. During sepsis, there is an alteration of iron metabolism, leading to increased transport and uptake into cells. This increase in labile iron may cause oxidative damage and cellular injury (ferroptosis) which progresses as the disease worsens. Critically ill patients are often complicated with systemic inflammation which may contribute to multiple organ dysfunction syndrome or sepsis, a common cause of mortality in intensive care unit. Originally, ferritin was known to play an important role in the hematopoietic system for its iron storage capacity. Recently, its role has emerged as a predictor of poor prognosis in chronic inflammation and critical illnesses. Apart from predicting the disease outcome, serum ferritin can potentially reflect disease activity as well.

Targeting ferroptosis by natural products in pathophysiological conditions

Ferroptosis is a form of cell death that is induced by iron-mediated accumulation of lipid peroxidation. The involvement of ferroptosis in different pathophysiological conditions has offered new perspectives on potential therapeutic interventions. Natural products, which are widely recognized for their significance in drug discovery and repurposing, have shown great promise in regulating ferroptosis by targeting various ferroptosis players. In this review, we discuss the regulatory mechanisms of ferroptosis and its implications in different pathological conditions. We dissect the interactions between natural products and ferroptosis in cancer, ischemia/reperfusion, neurodegenerative diseases, acute kidney injury, liver injury, and cardiomyopathy, with an emphasis on the relevance of ferroptosis players to disease targetability.

Iron and ferritin effects on intensive care unit mortality: A meta-analysis

BACKGROUND

The effect of serum iron or ferritin parameters on mortality among critically ill patients is not well characterized.

AIM

To determine the association between serum iron or ferritin parameters and mortality among critically ill patients.

METHODS

Web of Science, Embase, PubMed, and Cochrane Library databases were searched for studies on serum iron or ferritin parameters and mortality among critically ill patients. Two reviewers independently assessed, selected, and abstracted data from studies reporting on serum iron or ferritin parameters and mortality among critically ill patients. Data on serum iron or ferritin levels, mortality, and demographics were extracted.

RESULTS

Nineteen studies comprising 125490 patients were eligible for inclusion. We observed a slight negative effect of serum ferritin on mortality in the United States population [relative risk (RR) 1.002; 95%CI: 1.002-1.004). In patients with sepsis, serum iron had a significant negative effect on mortality (RR = 1.567; 95%CI: 1.208-1.925).

CONCLUSION

This systematic review presents evidence of a negative correlation between serum iron levels and mortality among patients with sepsis. Furthermore, it reveals a minor yet adverse impact of serum ferritin on mortality among the United States population.

Hepcidin, in contrast to heparin binding protein, does not portend acute kidney injury in patients with community acquired septic shock

BACKGROUND

Acute kidney injury (AKI) is a common and severe complication in patients treated at an Intensive Care Unit (ICU). The pathogenesis of AKI has been reported to involve hypoperfusion, diminished oxygenation, systemic inflammation, and damage by increased intracellular iron concentration. Hepcidin, a regulator of iron metabolism, has been shown to be associated with sepsis and septic shock, conditions that can result in AKI. Heparin binding protein (HBP) has been reported to be associated with sepsis and AKI. The aim of the present study was to compare serum hepcidin and heparin binding protein (HBP) levels in relation to AKI in patients admitted to the ICU.

METHODS

One hundred and forty patients with community acquired illness admitted to the ICU within 24 hours after first arrival to the hospital were included in the study. Eighty five of these patients were diagnosed with sepsis and 55 with other severe non-septic conditions. Logistic and linear regression models were created to evaluate possible correlations between circulating hepcidin and heparin-binding protein (HBP), stage 2-3 AKI, peak serum creatinine levels, and the need for renal replacement therapy (RRT).

RESULTS

During the 7-day study period, 52% of the 85 sepsis and 33% of the 55 non-sepsis patients had been diagnosed with AKI stage 2-3 already at inclusion. The need for RRT was 20% and 15%, respectively, in the groups. Hepcidin levels at admission were significantly higher in the sepsis group compared to the non-sepsis group but these levels did not significantly correlate to the development of stage 2-3 AKI in the sepsis group (p = 0.189) nor in the non-sepsis group (p = 0.910). No significant correlation between hepcidin and peak creatinine levels, nor with the need for RRT was observed. Stage 2-3 AKI correlated, as expected, significantly with HBP levels at admission in both groups (Odds Ratio 1.008 (CI 1.003-1.014, p = 0.005), the need for RRT, as well as with peak creatinine in septic patients.

CONCLUSION

Initial serum hepcidin, and HBP levels in patients admitted to the ICU are biomarkers for septic shock but in contrast to HBP, hepcidin does not portend progression of disease into AKI or a later need for RRT. Since hepcidin is a key regulator of iron metabolism our present data do not support a decisive role of initial iron levels in the progression of septic shock into AKI.

A Matched-Cohort Analysis of Outcomes in Patients with Hereditary Hemochromatosis After Anterior Cervical Discectomy and Fusion

BACKGROUND

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder. This disease affects gut iron transport, leading to iron overload, which affects immune function, coagulation mechanics, and bone health. Within the spine, HH contributes to decreased bone mineral density and accelerated intervertebral disc degeneration. The purpose of this study was to discover the differences in the rates of common 90-day postoperative complications and 1-year and 2-year surgical outcomes in patients with and without HH after anterior cervical discectomy and fusion (ACDF).

METHODS

Using the PearlDiver database, patients with active diagnoses of HH before ACDF were matched to patients without HH using a 1:5 ratio on the basis of age, sex, body mass index, and comorbidities. Postoperative complications were assessed at 90 days, and 1-year and 2-year surgical outcomes were assessed. All outcomes and complications were analyzed using multivariate logistic regression with significance achieved at P < 0.05.

RESULTS

Patients with HH had significantly higher rates of 1-year and 2-year reoperation rates compared with patients without HH (29.19% vs. 3.94% and 37.1% vs. 5.93%, respectively; P < 0.001). The rates of 90-day postoperative complications significantly increased in patients with HH including dysphagia, pneumonia, cerebrovascular accident, deep vein thrombosis, acute kidney injury, urinary tract infection, hyponatremia, surgical site infection, iatrogenic deformity, emergency department visit, and hospital readmission.

CONCLUSIONS

Patients with HH undergoing ACDF showed increased 90-day postoperative complications and significantly increased rates of 1-year and 2-year reoperation compared with patients without HH. These findings suggest that iron overload may contribute to adverse outcomes in patients with HH undergoing 1-level and 2-level ACDF.

Value of serum iron and urine neutrophil gelatinase-associated lipocalin in predicting the mortality of critically ill patients with sepsis

INTRODUCTION

We aimed to investigate the association of iron metabolism-related parameters with 60-day mortality in critically ill patients with sepsis.

METHODS

Serum or urine concentrations of iron metabolism-related parameters on intensive care unit admission were measured in a prospective cohort of 133 eligible patients with sepsis according to the Sepsis-3 criteria, and these values were compared between survivors and nonsurvivors, categorized according to their 60-day survival status. Cox regression analyses were performed to examine the association between iron parameters and 60-day mortality. Kaplan-Meier methods were used to illustrate the differences in survival between different iron parameters.

RESULTS

Of the 133 patients included in the study, 61 (45.8%) had died by day 60. After adjusting for confounding variables, higher concentrations of serum iron (cut-off 9.5 μmol/mL) and higher concentrations of urine neutrophil gelatinase-associated lipocalin (uNGAL; cut-off 169.3 ng/mL) were associated with a significantly greater risk of death in the Cox regression analysis. These two biomarkers combined with Sequential Organ Failure Assessment (SOFA) scores increased the area under the receiver operating characteristic (AUROC) curve to 0.85.

DISCUSSION

These findings suggest that higher concentrations of serum iron and uNGAL are each associated with higher 60-day mortality, and they add significant accuracy to this prediction in combination with SOFA. Abbreviations: uNGAL: urine neutrophil gelatinase-associated lipocalin; ICU: intensive care unit; SOFA: Sequential Organ Failure Assessment; APACHE II: the Acute Physiology and Chronic Health Evaluation II; ELISA: enzyme-linked immunosorbent assay; HR: hazard ratio; CIs: confidence intervals; WBC: white blood cell; TBIL: total bilirubin.

Iron as an emerging therapeutic target in critically ill patients

The multiple roles of iron in the body have been known for decades, particularly its involvement in iron overload diseases such as hemochromatosis. More recently, compelling evidence has emerged regarding the critical role of non-transferrin bound iron (NTBI), also known as catalytic iron, in the care of critically ill patients in intensive care units (ICUs). These trace amounts of iron constitute a small percentage of the serum iron, yet they are heavily implicated in the exacerbation of diseases, primarily by catalyzing the formation of reactive oxygen species, which promote oxidative stress. Additionally, catalytic iron activates macrophages and facilitates the growth of pathogens. This review aims to shed light on this underappreciated phenomenon and explore the various common sources of NTBI in ICU patients, which lead to transient iron dysregulation during acute phases of disease. Iron serves as the linchpin of a vicious cycle in many ICU pathologies that are often multifactorial. The clinical evidence showing its detrimental impact on patient outcomes will be outlined in the major ICU pathologies. Finally, different therapeutic strategies will be reviewed, including the targeting of proteins involved in iron metabolism, conventional chelation therapy, and the combination of renal replacement therapy with chelation therapy.

Targeted inhibition of CX3CL1 limits podocytes ferroptosis to ameliorate cisplatin-induced acute kidney injury

BACKGROUND

It is widely acknowledged that cisplatin-induced nephrotoxicity hinders its efficacy during clinical therapy. Effective pharmaceutical interventions for cisplatin-induced acute kidney injury (Cis-AKI) are currently lacking. Prior studies have implicated the chemokine CX3CL1 in the development of lipopolysaccharide-induced AKI; however, its specific role in Cis-AKI remains uncertain. This research aimed to comprehensively characterize the therapeutic impact and mechanism of CX3CL1 inhibition on Cis-AKI.

METHODS

This study employed an in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes. Kidney pathological changes were assessed using hematoxylin-eosin (HE) and Periodic-Schiff (PAS) staining. Transcriptome changes in mouse kidney tissue post-cisplatin treatment were analyzed through RNA sequencing (RNA-seq) datasets. Evaluation parameters included the expression of inflammatory markers, intracellular free iron levels, ferroptosis-related proteins-solute carrier family 7 member 11 (SLC7A11/XCT) and glutathione peroxidase 4 (GPX4)-as well as lipid peroxidation markers and mitochondrial function proteins. Mitochondrial morphological changes were visualized through transmission electron microscopy. The impact of CX3CL1 on the glucose-regulated protein 78/eukaryotic translation initiation factor 2A/CCAAT enhancer binding protein-homologous protein (GRP78/eIF2α/CHOP) and hypoxia-inducible factor 1-alpha/heme oxygenase-1 (HIF1A/HO-1) pathways in Cis-AKI was assessed via Western Blot and Immunofluorescence experiments, both in vivo and in vitro.

RESULTS

Kidney CX3CL1 levels were elevated following cisplatin injection in wild-type (WT) mice. Cisplatin-treated CX3CL1-Knockout mice exhibited reduced renal histological changes, lowered blood creatinine (Cre) and blood urea nitrogen (BUN) levels, and decreased expression of inflammatory mediators compared to cisplatin-treated WT mice. RNA-seq analysis revealed the modulation of markers associated with oxidative stress and lipid metabolism related to ferroptosis in the kidneys of mice with Cis-AKI. Both the in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes demonstrated that CX3CL1 inhibition could mitigate ferroptosis. This effect was characterized by alleviated intracellular iron overload, malondialdehyde (MDA) content, and reactive oxygen species (ROS) production, alongside increased glutathione/glutathione disulfide ratio, superoxide dismutase (SOD), XCT, and GPX4 activity. CX3CL1 inhibition also ameliorated mitochondrial dysfunction and upregulated expression of mitochondrial biogenesis proteins-uncoupling protein (UCP), mitofusin 2 (Mfn2), and peroxisome proliferators-activated receptor γ coactivator l-alpha (PGC1α)-both in vivo and in vitro. Furthermore, CX3CL1 inhibition attenuated cisplatin-induced endoplasmic reticulum (ER) stress in podocytes. Notably, CX3CL1 inhibition reduced cisplatin-induced expression of HIF-1α and HO-1 in vivo and in vitro.

CONCLUSION

Our findings suggest that CX3CL1 inhibition exerts therapeutic effects against Cis-AKI by suppressing podocyte ferroptosis.

Emerging significance and therapeutic targets of ferroptosis: a potential avenue for human kidney diseases

Kidney diseases remain one of the leading causes of human death and have placed a heavy burden on the medical system. Regulated cell death contributes to the pathology of a plethora of renal diseases. Recently, with in-depth studies into kidney diseases and cell death, a new iron-dependent cell death modality, known as ferroptosis, has been identified and has attracted considerable attention among researchers in the pathogenesis of kidney diseases and therapeutics to treat them. The majority of studies suggest that ferroptosis plays an important role in the pathologies of multiple kidney diseases, such as acute kidney injury (AKI), chronic kidney disease, and renal cell carcinoma. In this review, we summarize recently identified regulatory molecular mechanisms of ferroptosis, discuss ferroptosis pathways and mechanisms of action in various kidney diseases, and describe the protective effect of ferroptosis inhibitors against kidney diseases, especially AKI. By summarizing the prominent roles of ferroptosis in different kidney diseases and the progress made in studying ferroptosis, we provide new directions and strategies for future research on kidney diseases. In summary, ferroptotic factors are potential targets for therapeutic intervention to alleviate different kidney diseases, and targeting them may lead to new treatments for patients with kidney diseases.

Relationships between serum iron and liver diseases in nutrition intervention trials: A nested case-control study

BACKGROUND

Serum iron is associated with the risk of several diseases. However, limited prospective studies have been performed between serum iron and the subsequent risk of chronic liver disease (CLD) and primary liver cancer (PLC) incidence.

METHODS

We performed a nested case-control study using data from the Linxian Nutrition Intervention Trials among participants who developed PLC incidence or died from CLD over 22-years of follow-up. We calculated the odds ratios (ORs) and 95% confidence intervals (CIs) to estimate the risk of PLC incidence or CLD death in different quintile of baseline serum iron using logistic regression.

RESULTS

Individuals with serum iron in the highest quintile, compared to those in the second quintile (the reference), had an increased risk of CLD mortality (OR=2.02, 95% CI=1.27-3.27, Ptrend=0.011). The association was stronger among HCV-positive participants (Pinteraction=0.005). For PLC incidence, the risk estimates were above one, but not statistically significant (all P > 0.05).

CONCLUSIONS

A significant positive association was found between serum iron and the risk of CLD-related mortality, especially in HCV-positive subjects. Our results suggest that serum iron plays a risk role in CLD death but not in PLC incidence.

ADAMTS-13-regulated nuclear factor E2-related factor 2 signaling inhibits ferroptosis to ameliorate cisplatin-induced acute kidney injuy

ADAMTS-13 plays an important role in acute kidney injury (AKI), but the mechanism of cisplatin (CP) induced AKI remains unclear. Ferroptosis is increased in CP-induced AKI, and ADAMTS13 levels are associated with ferritin expression. In this article, we will explore the relationship between the three. After CP induction, mice were given 0.1 and 0.3 nmol/kg ADAMTS-13, and then serum creatinine (Scr) and blood urea nitrogen (BUN) were detected by the kits. The pathological changes of renal tissue were observed by staining with HE and PAS staining, and Western blot detected the expressions of KIM1 and NGAL in renal tissu. Perl's staining detected iron deposition in renal tissues, the kits detected iron levels, and western blot detected the expression of ferroptosis related proteins. Then the mechanism was further explored by adding ferroptosis inhibitors Ferrostatin 1 (Fer-1) and iron supplements Fe. The expression of Nrf2 pathway related proteins were detected by Western blot. We found that ADAMTS13 alleviated CP-induced ferroptosis in AKI mice with renal function impairment and tubular damage. Fer-1partially reversed CP-induced AKI, and Fe exacerbated this effect. ADAMTS13 alleviated CP-induced inflammatory response and oxidative stress in AKI mice, during which the Nrf2 signaling pathway was abnormal. Overall, ADAMTS-13-regulated Nrf2 signaling inhibits ferroptosis to ameliorate CP-induced AKI.