Hypoferremia of inflammation: Innate host defense against infections

Interplay between iron metabolism, inflammation, and EPO-ERFE-hepcidin axis in RDEB-associated chronic anemia

ABSTRACT

Recessive dystrophic epidermolysis bullosa (RDEB) is a genodermatosis characterized by severe cutaneous and mucosal fragility, and frequently complicated by multifactorial chronic anemia that responds poorly to conventional therapies. This cross-sectional study investigates the factors contributing to anemia in RDEB by analyzing a representative cohort, that was stratified by disease severity, anemia, and iron status, to examine their hematological parameters, cytokine profile, and the erythropoietin-erythroferrone-hepcidin (EPO-ERFE-hepcidin) axis. Anemia was present in 50% of the cohort. Hemoglobin levels showed a strong negative correlation with the percentage of body surface area affected and C-reactive protein levels (CRP), identifying these as anemia risk factors in RDEB. Moderate-severe inflammation (CRP ≥ 15 mg/L) was observed in all patients with anemia, but no specific cytokine profile was linked with anemia risk because of variability in interleukin-6 (IL-6), IL-1β, IL-10, tumor necrosis factor, and interferon-γ levels. The regulation of the EPO-ERFE-hepcidin axis showed discrepancies with the patterns expected based on patients' anemia severity and iron status. According to the reticulocyte production index, an inadequate bone marrow response was observed in 90% of patients with anemia, irrespective of EPO levels. Patients with functional or true iron deficiency had higher ERFE levels, although ERFE showed no consistent correlation with EPO and was elevated in both patients with anemia and those without anemia. Elevated hepcidin was primarily linked to the highest ferritin levels, mostly in patients with a history of iron infusions and/or transfusions. These findings highlight the need for personalized, targeted approaches that address the complex interplay between inflammation and iron dysregulation, to improve anemia management in RDEB and other chronic inflammatory conditions.

Association of Stress and Inflammatory Diseases with Serum Ferritin and Iron Concentrations in Neonatal Calves

This study investigated the effects of iron supplementation and inflammatory disease on cortisol, white blood cell (WBC) count, total protein (TP), lactate, interleukin 1 β (IL1β), interleukin 6 (IL6), substance P (SP), hepcidin, haptoglobin, and ferric-reducing ability of plasma (FRAP) in calves. Correlation analyses for the aforementioned parameters with serum iron and ferritin were performed in 40 neonatal calves over the first 10 days of life. Neither iron supplementation, disease status, nor sex had statistically significant effects on the areas under the curve of ferritin, WBC, TP, IL1β, IL6, SP, hepcidin, haptoglobin, or FRAP. However, cortisol concentrations were influenced by disease development. Cortisol concentrations were higher at birth (44.1 ± 1.95 ng/mL) than on day 2 (38.8 ± 1.87 ng/mL) (p = 0.0477), and healthy animals exhibited lower cortisol concentrations than diseased calves (p = 0.0028). Correlation analyses indicated weak positive correlations between ferritin and IL1β (p = 0.0015; ρ = 0.49) and IL6 (p = 0.0011; ρ = 0.50), respectively. The clinical significance of these findings and resulting therapeutic consequences, especially with respect to iron supplementation, should be further investigated in calves and adult cattle.

Sex and Gender Differences in Iron Chelation

BACKGROUND/OBJECTIVES

In the absence of physiological mechanisms to excrete excessive iron, the administration of iron chelation therapy is necessary. Age and hormones have an impact on the absorption, distribution, metabolism, and excretion of the medications used to treat iron excess, resulting in notable sex- and gender-related variances.

METHODS

Here, we aimed to review the literature on sex and gender in iron overload assessment and treatment.

RESULTS

The development of iron chelators has shown to be a successful therapy for lowering the body's iron levels and averting the tissue damage and organ failure that follows. Numerous studies have described how individual factors can impact chelation treatment, potentially impact therapeutic response, and/or result in inadequate chelation or elevated toxicity; however, most of these data have not considered male and female patients as different groups, and particularly, the effect of hormonal variations in women have never been considered.

CONCLUSIONS

An effective iron chelation treatment should take into account sex and gender differences.

IL-6 Does Not Influence the Expression of SLC41A1 and Other Mg-Homeostatic Factors

Together with chronic inflammation, disturbed magnesium homeostasis is a factor accompanying chronic disease which thus contributes to a reduced quality of human life. In this study, our objective was to examine the possible IL-6-mediated chronic inflammation-dependent regulation of nine magnesiotropic genes encoding for constituents of magnesium homeostasis of the cell. We used three cell lines (HepG2, U-266, and PANC-1), all characterized by high expression of the IL6R gene and the presence of a membrane form of IL-6R capable of responding to human IL-6. Despite the confirmed activation of the IL-6R/JAK/STAT3 pathway after hIL-6 treatment, we observed no biologically relevant changes in the transcription intensity of the studied magnesiotropic genes. This, however, does not exclude the possibility that IL-6 can affect magnesium homeostasis at levels other than through modified transcription.

Influence of an iron dextran injection in various diseases on hematological blood parameters, including serum ferritin, neonatal dairy calves

BACKGROUND

Feeding milk substitutes with low iron content or whole milk without iron supplementation is considered a major factor in developing iron-deficiency anemia in neonatal dairy calves. Young calves are often supplemented with iron dextran injections on the first day of life to prevent anemia. However, the effects of preventive treatment and the presence of disease on serum iron (Fe) concentrations, serum ferritin levels, and hematological blood parameters during the early neonatal stages have not been examined in detail. Therefore, we examined and evaluated the effects of iron dextran injections and health status on the development of hematocrit (Ht), red blood cells (RBC), hemoglobin concentration (Hb), erythrocyte indices (mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration), Fe, and serum ferritin concentrations in dairy calves within the first 10 days of life. The suitability of serum ferritin as a reliable indicator of anemia in very young calves was evaluated by correlating ferritin concentrations with known laboratory diagnostic parameters of anemia.

RESULTS

Iron supplementation significantly increased Fe levels (P = 0.048) but did not affect serum ferritin levels in neonatal calves. Fe concentrations were significantly lower in diseased than healthy calves (P = 0.0417). Iron supplementation significantly affected the health status, as observed in Ht (Ptreat=0.0057; Phealth=0.0097), RBC (Ptreat=0.0342; Phealth=0.0243), and Hb (Ptreat=0.0170; Phealth=0.0168). Serum ferritin levels did not significantly correlate with Fe levels. Both groups showed marked differences in ferritin levels, with the highest levels measured on day 2. Fe concentrations showed weak negative correlations with Hb and Ht levels on day 3 (ρ=-0.45; P = 0.0034 and ρ=-0.045; P = 0.0032, respectively). RBC count showed strong positive correlations with Hb and Ht levels (ρ = 0.91 and ρ = 0.93; P < 0.001).

CONCLUSION

Iron dextran injections increased Fe concentrations but reduced Ht level, RBC count, and Hb level. The presence of diseases led to a reduction in Fe and higher values of Ht, RBC, and Hb in moderate disease than in severe disease. Due to physiological fluctuations during the first 3 days of life, serum ferritin level seems unuseful for evaluating iron storage before day 4 of life.

Associations Between Genetically Predicted Iron Status and Cardiovascular Disease Risk: A Mendelian Randomization Study

BACKGROUND

Mendelian randomization (MR) studies suggest a causal effect of iron status on cardiovascular disease (CVD) risk, but it is unknown if these associations are confounded by pleiotropic effects of the instrumental variables on CVD risk factors. We aimed to investigate the effect of iron status on CVD risk controlling for CVD risk factors.

METHODS AND RESULTS

Iron biomarker instrumental variables (total iron-binding capacity [n=208 422], transferrin saturation [n=198 516], serum iron [n=236 612], ferritin [n=257 953]) were selected from a European genome-wide association study meta-analysis. We performed 2-sample univariate MR of each iron trait on CVD outcomes (all-cause ischemic stroke, cardioembolic ischemic stroke, large-artery ischemic stroke, small-vessel ischemic stroke, and coronary heart disease) from MEGASTROKE (n=440 328) and CARDIoGRAMplusC4D (Coronary Artery Disease Genome Wide Replication and Meta-Analysis Plus the Coronary Artery Disease Genetics) (n=183 305). We then implemented multivariate MR conditioning on 7 CVD risk factors from independent European samples to evaluate their potential confounding or mediating effects on the observed iron-CVD associations. With univariate MR analyses, we found higher genetically predicted iron status to be associated with a greater risk of cardioembolic ischemic stroke (transferrin saturation: odds ratio, 1.17 [95% CI, 1.03-1.33]; serum iron: odds ratio, 1.21 [95% CI, 1.02-1.44]; total iron-binding capacity: odds ratio, 0.81 [95% CI, 0.69-0.94]). The detrimental effects of iron status on cardioembolic ischemic stroke risk remained unaffected when adjusting for CVD risk factors (all P<0.05). Additionally, we found diastolic blood pressure to mediate between 7.1 and 8.8% of the total effect of iron status on cardioembolic ischemic stroke incidence. Univariate MR initially suggested a protective effect of iron status on large-artery stroke and coronary heart disease, but controlling for CVD factors using multivariate MR substantially diminished these associations (all P>0.05).

CONCLUSIONS

Higher iron status was associated with a greater risk of cardioembolic ischemic stroke independent of CVD risk factors, and this effect was partly mediated by diastolic blood pressure. These findings support a role of iron status as a modifiable risk factor for cardioembolic ischemic stroke.

Associations between genetically predicted iron status and cardiovascular disease risk: A Mendelian randomization study

Background

Mendelian randomization (MR) studies suggest a causal effect of iron (Fe) status on cardiovascular disease (CVD) risk, but it is unknown if these associations are confounded by pleiotropic effects of the instrumental variables (IV) on CVD risk factors. We aimed to investigate the effect of Fe status on CVD risk controlling for CVD risk factors.

Methods

Fe biomarker IVs (total Fe binding capacity (TIBC, n=208,422), transferrin saturation (TSAT, n=198,516), serum Fe (SI, n=236,612), ferritin (n=257,953)) were selected from a European GWAS meta-analysis. We performed two-sample univariate (UV) MR of each Fe trait on CVD outcomes (all-cause ischemic stroke (IS), cardioembolic IS (CES), large artery IS (LAS), small vessel IS (SVS), and coronary heart disease (CHD)) from MEGASTROKE (n=440,328) and CARDIoGRAMplusC4D (n=183,305). We then implemented multivariate (MV) MR conditioning on six CVD risk factors from independent European samples to evaluate their potential confounding and/or mediating effects on the observed Fe-CVD associations.

Results

With UVMR analyses, we found higher genetically predicted Fe status to be associated with a greater risk of CES (TSAT: OR 1.17 [95%CI 1.03, 1.33], SI: OR 1.21 [ 95%CI 1.02, 1.44]; TIBC: OR 0.81 [95%CI 0.69, 0.94]). The detrimental effects of Fe status on CES risk remained unaffected when adjusting for CVD risk factors (all P<0.05). Additionally, we found diastolic blood pressure (DBP) to mediate between 7.1-8.8% of the total effect of Fe status on CES incidence. While UVMR initially suggested a protective effect of Fe status on LAS and CHD, MVMR analyses factoring CVD risk factors revealed a complete annulment of this perceived protective effect (all P>0.05).

Discussion

Higher Fe status was associated with a greater risk of CES independent of CVD risk factors, and this effect was partly mediated by DBP. These findings support a role of Fe status as a modifiable risk factor for CES.

The effect of iron therapy on oxidative stress and intestinal microbiota in inflammatory bowel diseases: A review on the conundrum

One in five patients with Inflammatory Bowel Disease (IBD) suffers from anemia, most frequently caused by iron deficiency. Anemia and iron deficiency are associated with worse disease outcomes, reduced quality of life, decreased economic participation, and increased healthcare costs. International guidelines and consensus-based recommendations have emphasized the importance of treating anemia and iron deficiency. In this review, we draw attention to the rarely discussed effects of iron deficiency and iron therapy on the redox status, the intestinal microbiota, and the potential interplay between them, focusing on the clinical implications for patients with IBD. Current data are scarce, inconsistent, and do not provide definitive answers. Nevertheless, it is imperative to rule out infections and discern iron deficiency anemia from other types of anemia to prevent untargeted oral or intravenous iron supplementation and potential side effects, including oxidative stress. Further research is necessary to establish the clinical significance of changes in the redox status and the intestinal microbiota following iron supplementation.

Weak response of bovine hepcidin induction to iron through decreased expression of Smad4

Hepcidin negatively regulates systemic iron levels by inhibiting iron entry into the circulation. Hepcidin production is increased in response to an increase in systemic iron via the activation of the bone morphogenetic protein (BMP) pathway. Regulation of hepcidin expression by iron status has been proposed on the basis of evidence mainly from rodents and humans. We evaluated the effect of iron administration on plasma hepcidin concentrations in calves and the expression of bovine hepcidin by the BMP pathway in a cell culture study. Hematocrit as well as levels of blood hemoglobin and plasma iron were lower than the reference level in calves aged 1-4 weeks. Although intramuscular administration of iron increased iron-related parameters, plasma hepcidin concentrations were unaffected. Treatment with BMP6 increased hepcidin expression in human liver-derived cells but not in bovine liver-derived cells. A luciferase-based reporter assay revealed that Smad4 was required for hepcidin reporter transcription induced by Smad1. The reporter activity of hepcidin was lower in the cells transfected with bovine Smad4 than in those transfected with murine Smad4. The lower expression levels of bovine Smad4 were responsible for the lower activity of the hepcidin reporter, which might be due to the instability of bovine Smad4 mRNA. In fact, the endogenous Smad4 protein levels were lower in bovine cells than in human and murine cells. Smad4 also confers TGF-β/activin-mediated signaling. Induction of TGF-β-responsive genes was also lower after treatment with TGF-β1 in bovine hepatocytes than in human hepatoma cells. We revealed the unique regulation of bovine hepcidin expression and the characteristic TGF-β family signaling mediated by bovine Smad4. The present study suggests that knowledge of the regulatory expression of hepcidin as well as TGF-β family signaling obtained in murine and human cells is not always applicable to bovine cells.