Pathophysiology of iron overload-induced renal injury and dysfunction: Roles of renal oxidative stress and systemic inflammatory mediators

Predictive value of ferroptosis-related biomarkers for diabetic kidney disease: a prospective observational study

AIMS

To explore the predictive value of ferroptosis-related (FR) biomarkers for diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This prospective observational study enrolled patients with T2DM at the Second Hospital of Jilin University between December 2021 and March 2022. DKD was measured by the urinary albumin-to-creatinine ratio. Receiver operating characteristic curve (ROC) analysis was performed to assess the predictive value of ferroptosis-related biomarkers for DKD.The risk factors for massive proteinuria were performed by multivariable logistic regression analysis.

RESULTS

Finally, 118 patients (53.0 ± 12.2 years, 76 males) were enrolled, 52 of them without DKD (had normal proteinuria), while 66 with DKD. (Forty-one had microproteinuria, and 25 had massive proteinuria.) FR biomarkers, including acyl-CoA synthase long chain family member 4 (ACSL4), malondialdehyde (MDA), and reactive oxygen species (ROS), were significantly higher in the massive proteinuria group than in the other groups, while glutathione peroxidase 4 (GPX4) was significantly lower (all P < 0.05). The area under the ROC of the combination of GPX4, ACSL4, MDA, and ROS for predicting DKD was 0.804 (P < 0.001). Additionally, multivariate logistic regression analysis showed that the course of disease and ferritin levels were independent risk factors for massive proteinuria, while high serum iron, transferrin, and GPX4 levels were independent protective factors for massive proteinuria in patients with T2DM (all P < 0.05).

CONCLUSIONS

The GPX4, ACSL4, MDA, and ROS combination might have a good predictive value for DKD. Additionally, the course of disease, ferritin levels, serum iron, transferrin, and GPX4 were independently associated with massive proteinuria.

Association between preoperative serum myoglobin and acute kidney injury after Stanford Type A aortic dissection surgery

BACKGROUND

Acute kidney injury (AKI) is a common complication after Type A aortic dissection (TAAD) surgery, and it is associated with poor outcomes. The nephrotoxic effect of myoglobin was established, but its correlation with AKI following TAAD repair still lacks sufficient evidence. We clarified the correlation between preoperative serum myoglobin (pre-sMyo) concentrations and AKI after TAAD surgery.

METHOD

A retrospective analysis was performed on the perioperative data of 382 patients treated with TAAD surgery at Beijing Anzhen Hospital. AKI was defined and classified according to the criteria established by the Kidney Disease: Improving Global Outcomes Acute Kidney Injury Work Group. We attempted to determine the correlation between pre-sMyo concentrations and postoperative AKI.

RESULTS

The incidences of Stage 1, 2, and 3 AKI were 37.3 % (57/153), 23.5 % (36/153), and 39.2 % (60/153), respectively. The pre-sMyo concentrations of the AKI group were significantly increased than the non-AKI group [43.1 (21.4, 107.5) vs 26.4 (18.0, 37.2), P < 0.001]. Pre-sMyo concentrations have a linear correlation with preoperative renal function-related indicators. The multivariable logistic regression analysis showed that Ln (pre-sMyo) was an independent risk factor for AKI. When the pre-sMyo concentration was at the fourth quartile [109.3 (64.8, 213.4) ng/ml], the risk of developing any-stage and severe AKI was significantly increased (OR = 4.333, 95 % CI: 2.364-7.943, P < 0.001; OR = 3.862, 95 %, CI: 2.011-7.419, P < 0.001). This difference persisted after adjustment (OR = 3.830, 95 % CI: 1.848-7.936, P < 0.001; OR = 2.330, 95 % CI: 1.045-5.199, P = 0.039). Furthermore, pre-sMyo concentrations were not affected by lower limb malperfusion, myocardial malperfusion, and cardiac tamponade.

CONCLUSIONS

Increased pre-sMyo concentrations correlated with postoperative AKI in TAAD, which may increase the risk of developing any-stage AKI and severe AKI after TAAD surgery.

Clinical features and risk factors of renal dysfunctions in thalassemic patients

INTRODUCTION

Chronic anemia, iron overload, and iron chelation therapy are the main contributing factors for renal complications in thalassemia, e.g., nephrolithiasis, glomerular disease, and renal tubular dysfunction. The prevalence and associated factors for developing renal dysfunctions in Thai patients with thalassemia, however, remained limited. This study aimed to determine the prevalence and risk factors of renal dysfunctions in patients with thalassemia.

METHODS

A cross-sectional study was conducted on adult patients with thalassemia disease at Srinagarind Hospital, Khon Kaen University, Thailand. All patients were evaluated for complete blood count, blood chemistry, urinalysis, and urine biochemistry. Renal tubular dysfunction was defined as existing in at least one of the following parameters including; proteinuria, hypercalciuria, hypouricemia with uricosuria, or hypophosphatemia with phosphaturia. Logistic regression analysis was used to identify associated factors for renal dysfunctions.

RESULTS

Of 105 patients, renal tubular dysfunction was found in 60 patients (57.1%). In multivariate analysis of the clinical risk factors for renal tubular dysfunction in thalassemia patients, age per 10 year increase (adjusted odds ratio [AOR] = 1.4, 95% CI: 1.0-2.0, p value 0.01) and Hb E/beta-thalassemia (AOR = 3.6, 95% CI: 1.3-10.3, p value 0.01) were statistically proven to be associated with renal tubular dysfunction. Hyperuricosuria was a significantly associated factor for microhematuria. (AOR = 2.9, 95% CI: 1.1-8.0, p value 0.03).

CONCLUSIONS

Renal dysfunctions are prevalent in thalassemia patients, with older age and Hb E/beta-thalassemia genotype as significant risk factors for renal tubular dysfunction. Hyperuricosuria is a risk factor for microhematuria. Renal dysfunctions should be recognized and monitored in aging patients with Hb E/beta-thalassemia.

Evaluating renal iron overload in diabetes mellitus by blood oxygen level-dependent magnetic resonance imaging: a longitudinal experimental study

BACKGROUND

Iron overload plays a critical role in the pathogenesis of diabetic nephropathy. Non-invasive evaluation of renal iron overload in diabetes in the management and intervention of diabetic nephropathy is of great significance. This study aimed to explore the feasibility of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in evaluating renal iron overload in diabetes using a rabbit model.

METHODS

The rabbits were randomly divided into control, iron-overload (I), diabetes (D), and diabetes with iron-overload (DI) groups (each n = 19). The diabetes models were generated by injecting intravenous alloxan solution, and the iron-overload models were generated by injecting intramuscular iron-dextran. BOLD MRI was performed immediately (week 0) and at week 4, 8, and 12 following modeling. The differences in renal cortex (CR2*) and outer medulla R2* (MR2*) and the ratio of MR2*-CR2* (MCR) across the different time points were compared.

RESULTS

Iron was first deposited in glomeruli in the I group and in proximal tubular cells in renal cortex in the D group. In the DI group, there was iron deposition in both glomeruli and proximal tubular cells at week 4, and the accumulation increased subsequently. The degree of kidney injury and iron overload was more severe in the DI group than those in the I and D groups at week 12. At week 8 and 12, the CR2* and MR2* in the DI group were higher than those in the I and D groups (all P < 0.05). The MCR in the I, D, and DI groups decreased from week 0 to 4 (all P < 0.001), and that in the I group increased from week 8 to 12 (P = 0.034). CR2* and MR2* values displayed different trends from week 0-12. Dynamic MCR curves in the D and DI groups were different from that in the I group.

CONCLUSION

It presents interactions between diabetes and iron overload in kidney injury, and BOLD MRI can be used to evaluate renal iron overload in diabetes.

High Dietary Organic Iron Supplementation Decreases Growth Performance and Induces Oxidative Stress in Broilers

Although Iron (Fe) is an essential nutrient that plays a vital role in respiratory processes, excessive Fe in the diet can affect the health of broilers. We investigated the effects of diet supplemented with high levels of iron chelates with lysine and glutamic acid (Fe−LG) on the growth performance, serum biochemical parameters, antioxidant status, and duodenal mRNA expression of Fe transporters in broilers. A total of 800 1-day-old male Arbor Acres broilers were assigned to 5 groups, with 8 replicates each. Broilers were fed a corn−soybean meal basal diet or basal diets supplemented with 40, 80, 400, or 800 mg Fe/kg as Fe−LG for 6 weeks. The body weight (BW) was increased in the 80 mg Fe/kg treatment group, but decreased in the 800 mg Fe/kg treatment group on day 21. During days 1−21, compared with the control group, the supplementation of the 80 mg Fe/kg increased the average daily gain (ADG) and average daily feed intake (ADFI); however, the supplementation of the 800 mg Fe/kg group decreased the ADG and increased the FCR in broilers (p < 0.05). The heart, liver, spleen, and kidney indices were reduced in the 800 mg Fe/kg treatment group (p < 0.05). The supplementation of the 800 mg Fe/kg group increased the serum aspartate aminotransferase activity and the levels of creatinine and urea nitrogen on day 42 (p < 0.05). The broilers had considerably low liver total superoxide dismutase activity and total antioxidant capacity in the 800 mg Fe/kg treatment group (p < 0.05). Serum and liver Fe concentrations were elevated in the 400 and 800 mg Fe/kg treatment groups, but were not affected in the 40 and 80 mg Fe/kg treatment groups. The duodenal Fe transporters divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) were downregulated in the Fe−LG treatment groups (p < 0.05). We conclude that a high dietary supplement of 800 mg Fe/kg in broilers leads to detrimental health effects, causing kidney function injury and liver oxidative stress.

Post-treatment With Irisin Attenuates Acute Kidney Injury in Sepsis Mice Through Anti-Ferroptosis via the SIRT1/Nrf2 Pathway

Kidney is one of the most vulnerable organs in sepsis, resulting in sepsis-associated acute kidney injury (SA-AKI), which brings about not only morbidity but also mortality of sepsis. Ferroptosis is a new kind of death type of cells elicited by iron-dependent lipid peroxidation, which participates in pathogenesis of sepsis. The aim of this study was to verify the occurrence of ferroptosis in the SA-AKI pathogenesis and demonstrate that post-treatment with irisin could restrain ferroptosis and alleviate SA-AKI via activating the SIRT1/Nrf2 signaling pathway. We established a SA-AKI model by cecal ligation and puncture (CLP) operation and an in vitro model in LPS-induced HK2 cells, respectively. Our result exhibited that irisin inhibited the level of ferroptosis and ameliorated kidney injury in CLP mice, as evidenced by reducing the ROS production, iron content, and MDA level and increasing the GSH level, as well as the alteration of ferroptosis-related protein (GPX4 and ACSL4) expressions in renal, which was consistent with the ferroptosis inhibitor ferrostatin-1 (Fer-1). Additionally, we consistently observed that irisin inhibited ROS accumulation, iron production, and ameliorated mitochondrial dysfunction in LPS-stimulated HK-2 cells. Furthermore, our result also revealed that irisin could activate SIRT1/Nrf2 signaling pathways both in vivo and vitro. However, the beneficial effects of irisin were weakened by EX527 (an inhibitor of SIRT1) in vivo and by SIRT1 siRNA in vitro. In conclusion, irisin could protect against SA-AKI through ferroptotic resistance via activating the SIRT1/Nrf2 signaling pathway.

From Biology to Clinical Practice: Iron Chelation Therapy With Deferasirox

Iron chelation therapy (ICT) has become a mainstay in heavily transfused hematological patients, with the aim to reduce iron overload (IOL) and prevent organ damage. This therapeutic approach is already widely used in thalassemic patients and in low-risk Myelodysplastic Syndrome (MDS) patients. More recently, ICT has been proposed for high-risk MDS, especially when an allogeneic bone marrow transplantation has been planned. Furthermore, other hematological and hereditary disorders, characterized by considerable transfusion support to manage anemia, could benefit from this therapy. Meanwhile, data accumulated on how iron toxicity could exacerbate anemia and other clinical comorbidities due to oxidative stress radical oxygen species (ROS) mediated by free iron species. Taking all into consideration, together with the availability of approved oral iron chelators, we envision a larger use of ICT in the near future. The aim of this review is to better identify those non-thalassemic patients who can benefit from ICT and give practical tips for management of this therapeutic strategy.

In silico and in vivo protective effect of Morus nigra leaves on oxidative damage induced by iron overload

Morus nigra L. is a plant popularly known as 'amoreira preta', very used in folk medicine. Iron overload (hemochromatosis) is a clinical condition that causes damage to various tissues due to oxidative stress. Therapy to control iron overload is still unsatisfactory. The protective effect on oxidative stress induced by iron overload was verified. Phytochemical characterization was evaluated by UHPLC-MS/MS. The in silico toxicity predictions of the main phytochemicals were performed via computer simulation. To induce iron overload, the animals received iron dextran (50 mg/kg/day). The test groups received doses of 500 and 1000 mg/kg of M. nigra extract for six weeks. Body weight, organosomatic index, serum iron, hepatic markers, cytokines, interfering factors in iron metabolism, enzymatic and histopathological evaluations were analyzed. Vanillic acid, caffeic acid, 6-hydroxycoumarin, p-coumaric acid, ferulic acid, rutin, quercitrin, resveratrol, apigenin and kaempferol were identified in the extract. In addition, in silico toxic predictions showed that the main compounds presented a low probability of toxic risk. The extract of M. nigra showed to control the mediators of inflammation and to reduce iron overload in several tissues. Our findings illustrate a novel therapeutic action of M. nigra leaves on hemochromatosis caused by iron overload.

Susceptibility-weighted Imaging for Renal Iron Overload Assessment: A Pilot Study

Purpose: To explore the feasibility of susceptibility-weighted imaging (SWI) for evaluating renal iron overload.

Methods: Twenty-eight rabbits were randomly assigned into control (n = 14) and iron (n = 14) group. In the 0th week, the study group was injected with iron dextran. Both groups underwent SWI examination at the 0th, 8th, and 12th week. The signal intensity (SI) of cortex and medulla was assessed. Angle radian value (ARV) calculated with phase image was taken as the quantitative value for cortical and medullary iron deposition. After the 12th week, the left kidneys of rabbits were removed for pathology. The difference in the ARV among three groups was analyzed using Kruskal–Wallis test. The difference of the iron content between two groups was analyzed through independent sample t-test.

Results: In the iron group: at the 12th week, eight rabbits were found to have decreased SI of only cortex, and the other six rabbits had decreased SI of cortex and medulla by the same degree; the ARV of cortex at the 8th and 12th week was significantly higher than that of the 0th week (P < 0.05); the ARV of the six rabbits’ medulla at the 12th week was significantly higher than that of the 0th week, 8th week, and the other eight rabbits at the 12th week (P < 0.05); at the 12th week, eight rabbits (iron group) were found to have many irons only deposit in the cortex, and the others were found to have many irons deposit in both cortex and medulla; the iron content of cortex and six rabbits’ medulla in the iron group was significantly higher than that of the control (P < 0.05).

Conclusion: The ARV of SWI can be used to quantitatively assess the excess iron deposition in the kidneys. Excessive iron deposition mainly occurs in the cortex or medulla and causes their SWI SI to decrease.

Epigenetic Regulation and Nonepigenetic Mechanisms of Ferroptosis Drive Emerging Nanotherapeutics in Tumor

Currently, traditional cancer therapy still falls far short of expectations. However, a variety of invasive cancers that are resistant to chemotherapy (such as platinum drugs, one of the most applied antineoplastics in clinic) and targeted agents are susceptible to ferroptosis. Ferroptosis is a form of cell death that is driven by cell metabolism and iron-dependent lipid peroxidation. Ferroptosis inducers can eliminate the drug resistance of tumor cells in the mesenchymal state, effectively inhibit the drug resistance of acquired tumor cells, and optimize cancer efficacy. Research based on the epigenetic mechanism of ferroptosis is still in the stage of screening and verifying the regulatory effect, and there is no complete regulatory mechanism network. In this review, we expound on the epigenetic regulation and nonepigenetic mechanisms of ferroptosis and review the epigenetic-based mechanisms of tumor therapy potential and emerging nonepigenetic-based therapies (nanotherapeutics).

Health examination results and work environment factors affecting urinary 8-hydroxy-2'-deoxyguanosine levels

OBJECTIVE

Oxidative stress is considered to cause lifestyle-related diseases, including cancer. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) is widely analyzed as an oxidative stress marker. We extensively scrutinized the relationships between 8-OHdG levels and lifestyle choices as carcinogenic factors.

METHODS

In this study, we investigated health examination results and working conditions affecting urinary 8-OHdG levels in 503 male workers.

RESULTS

The urinary 8-OHdG level was positively associated with high blood sugar and leanness in smokers. In addition, urinary 8-OHdG tended to increase with organic solvent or hydrochloric acid exposure, as well as long working hours. On the other hand, the urinary 8-OHdG level was negatively associated with high plasma LDL-cholesterol levels in non-smokers and anemia.

CONCLUSION

According to the results, anemia decreased the oxidative stress, regardless of smoking status, while leanness or high blood sugar increased the oxidative stress in smokers, and the presence of plasma cholesterol contributed to the lower oxidative stress in non-smokers. Certain types of occupational exposure may cause oxidative stress. The measurement of urinary 8-OHdG at annual health checks may be a useful biomarker for preventing lifestyle- and work-related diseases.

Iron, ferroptosis, and new insights for prevention in acute kidney injury

Acute kidney injury (AKI) is a very common condition with high morbidity and mortality, which can be seen in 5-7% of all hospitalized patients and in up to 57% of all intensive care unit admissions. Despite recent advances in clinical care, the prevalence of AKI has been shown to increase with virtually no change in mortality. AKI is a complex syndrome occurring in a variety of clinical settings. Early detection is crucial to prevent irreversible loss of renal function. The pathogenesis of AKI is highly multifactorial and complex, including vasoconstriction, reactive oxygen species formation, cell death, abnormal immune modulators and growth factors. Emerging evidence from both human and animal studies suggests that dysregulation of iron metabolism may play a potentially important role in AKI. Therefore, targeting the iron homeostasis may provide a new therapeutic intervention for AKI. New therapeutic strategies including iron chelation therapy, targeting iron metabolism related proteins and direct inhibitors of ferroptosis are imperative to improve the outcomes of patients. Taking into consideration the complexity of AKI, one intervention may not be enough for therapeutic success. Future preclinical studies in animal disease models followed by well-designed clinical trials should be conducted to extend findings from animal AKI models to humans.

Neutrophils from hereditary hemochromatosis patients are protected from iron excess and are primed

Iron is required for the oxidative response of neutrophils to allow the production of reactive oxygen species (ROS). However, neutrophil function may be severely altered in conditions of iron overload, as observed in chronically transfused patients. Therefore, a tight regulation of neutrophil iron homeostasis seems to be critical for avoiding iron toxicity. Hepcidin is the key iron regulator in organisms; however, no studies have investigated its role in maintaining neutrophil iron homeostasis or characterized neutrophil function in patients with hereditary hemochromatosis (HH), a common iron overload genetic disorder that results from a defect in hepcidin production. To explore these issues, we studied 2 mouse models of iron overload: an experimentally induced iron overload model (EIO), in which hepcidin is increased, and a genetic HH model of iron overload with a deletion of hepatic hepcidin. We found that iron-dependent increase of hepatic hepcidin results in neutrophil intracellular iron trapping and consecutive defects in oxidative burst activity. In contrast, in both HH mouse models and HH patients, the lack of hepcidin expression protects neutrophils from toxic iron accumulation. Moreover, systemic iron overload correlated with a surprising neutrophil priming and resulted in a more powerful oxidative burst. Indeed, important factors in neutrophil priming and activation, such as tumor necrosis factor α (TNF-α), VCAM-1, and ICAM-1 are increased in the plasma of HH patients and are associated with an increase in HH neutrophil phagocytosis capacity and a decrease in L-selectin surface expression. This is the first study to characterize neutrophil iron homeostasis and associated functions in patients with HH.