Change in iron metabolism in rats after renal ischemia/reperfusion injury

The usefulness of initial serum ferritin level as a predictor of in-hospital mortality in STEMI

Several studies have shown that elevated serum ferritin level is associated with a higher risk of coronary artery disease. Recently, it has been shown that high serum ferritin levels in men are independently correlated with an increased risk of cardiovascular mortality. This study aimed to investigate the possible correlation between the initial serum ferritin level and in-hospital mortality in patients presenting with ST-elevation myocardial infarction (STEMI). This retrospective cohort study included 890 patients who presented with acute STEMI and underwent successful primary percutaneous coronary intervention (PPCI) according to the standard techniques during the period from 1 May 2020 to 1 May 2021. At the time of admission, an initial serum ferritin level was measured in all patients. Comparison between initial ferritin levels was made between two groups: died and survived. Propensity matching was performed to exclude confounding factors effect. Forty-one patients had in-hospital mortality. There was no significant difference between both groups regarding baseline clinical characteristics. Initial serum ferritin levels were higher in deceased patients, even after propensity matching. In conclusion, even after propensity matching, initial ferritin levels were significantly higher in patients who died after being admitted for STEMI.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

Agathis robusta Bark Extract Protects from Renal Ischemia-Reperfusion Injury: Phytochemical, In Silico and In Vivo Studies

Background: Acute kidney injury (AKI) induced by renal ischemia-reperfusion injury (RIRI) is associated with a high incidence of mortality. Existing therapies are mainly supportive, with no available nephroprotective agent. The purpose of this study is to examine the potential protective effect of Agathis robusta Bark Extract (ARBE) in RIRI. Methods: The chemical composition of ARBE was examined by LC-ESI-MS/MS. Network pharmacology was utilized to identify the RIRI molecular targets that could be aimed at by the identified major components of ARBE. Experimentally validated protein–protein interactions (PPIs) and compound-target networks were constructed using the STRING database and Cytoscape software. Molecular docking studies were employed to assess the interaction of the most relevant ARBE compounds with the hub RIRI-related targets. Furthermore, ARBE was tested in a rat model of RIRI. Results: The phytochemical analysis identified 95 components in ARBE, 37 of which were majors. Network analysis identified 312 molecular targets of RIRI that were associated with ARBE major compounds. Of these 312, the top targets in the experimentally validated PPI network were HSP90, EGFR, and P53. The most relevant compounds based on their peak area and network degree value included narcissoside, isorhamnetin-3-O-glucoside, and syringetin-3-O-glucoside, among others. Docking studies of the most relevant compounds revealed significant interactions with the top RIRI-related targets. In the in vivo RIRI experiments, pretreatment of ARBE improved kidney function and structural changes. ARBE reduced the renal expression of p-NfkB and cleaved caspase-3 by downregulating HSP90 and P53 in rats exposed to RIRI. Conclusion: Taken together, this study revealed the chemical composition of ARBE, depicted the interrelationship of the bioactive ingredients of ARBE with the RIRI-related molecular targets, and validated a nephroprotective effect of ARBE in RIRI.

Iron accumulation typifies renal cell carcinoma tumorigenesis but abates with pathological progression, sarcomatoid dedifferentiation, and metastasis

Iron is a potent catalyst of oxidative stress and cellular proliferation implicated in renal cell carcinoma (RCC) tumorigenesis, yet it also drives ferroptosis that suppresses cancer progression and represents a novel therapeutic target for advanced RCC. The von Hippel Lindau (VHL)/hypoxia-inducible factor-α (HIF-α) axis is a major regulator of cellular iron, and its inactivation underlying most clear cell (cc) RCC tumors introduces both iron dependency and ferroptosis susceptibility. Despite the central role for iron in VHL/HIF-α signaling and ferroptosis, RCC iron levels and their dynamics during RCC initiation/progression are poorly defined. Here, we conducted a large-scale investigation into the incidence and prognostic significance of total tissue iron in ccRCC and non-ccRCC patient primary tumor cancer cells, tumor microenvironment (TME), metastases and non-neoplastic kidneys. Prussian Blue staining was performed to detect non-heme iron accumulation in over 1600 needle-core sections across multiple tissue microarrays. We found that RCC had significantly higher iron staining scores compared with other solid cancers and, on average, >40 times higher than adjacent renal epithelium. RCC cell iron levels correlated positively with TME iron levels and inversely with RCC levels of the main iron uptake protein, transferrin receptor 1 (TfR1/TFRC/CD71). Intriguingly, RCC iron levels, including in the TME, decreased significantly with pathologic (size/stage/grade) progression, sarcomatoid dedifferentiation, and metastasis, particularly among patients with ccRCC, despite increasing TfR1 levels, consistent with an increasingly iron-deficient tumor state. Opposite to tumor iron changes, adjacent renal epithelial iron increased significantly with RCC/ccRCC progression, sarcomatoid dedifferentiation, and metastasis. Lower tumor iron and higher renal epithelial iron each predicted significantly shorter ccRCC patient metastasis-free survival. In conclusion, iron accumulation typifies RCC tumors but declines toward a relative iron-deficient tumor state during progression to metastasis, despite precisely opposite dynamics in adjacent renal epithelium. These findings raise questions regarding the historically presumed selective advantage for high iron during all phases of cancer evolution, suggesting instead distinct tissue-specific roles during RCC carcinogenesis and early tumorigenesis versus later progression. Future study is warranted to determine how the relative iron deficiency of advanced RCC contributes to ferroptosis resistance and/or introduces a heightened susceptibility to iron deprivation that might be therapeutically exploitable.

The efficiency of oxerutin on apoptosis and kidney function in rats with renal ischemia reperfusion injury

BACKGROUND

Background: Renal ischemia-reperfusion injury (RIRI) is the most frequent cause of acute renal failure in clinical conditions such as trauma and shock as well as renal surgeries. Oxerutin is a member of the flavonoid family and possesses antioxidant properties. The aim of this study was to investigate whether oxerutin has protective effects on RIRI.

METHODS

Twenty-eight male Wistar albino rats were randomly divided into three groups: sham control group (n=8), RIRI group (n=10), and RIRI + oxerutin group (n=10). RIRI was achieved by clamping the left renal artery for 30 min, followed 1-h reperfusion period. Thereafter, blood samples and left kidney tissue samples were taken for histopathological and biochemical examination. Blood urea nitrogen (BUN), urea, creatinine, and cystatin C levels, which are indicators of kidney function, as well as tumor necrosis factor-alpha, which is an indicator of inflammation were analyzed in blood samples. Total antioxidant status and total oxidant status (TOS), which are indicators of oxidative stress were analyzed on renal tissues. The apoptotic index, an indicator of kidney damage, as well as histopathological changes were evaluated on renal tissues.

RESULTS

The apoptotic index, TOS, tumor necrosis factor-alpha, BUN, and urea levels were lower in the RIRI + oxerutin group than in the RIRI group (p<0.05). The results demonstrated that the histopathological and biochemical properties of oxerutin protected rats from RIRI.

CONCLUSION

The findings obtained in this study show that prophylactic administration of oxerutin has protective effects on apoptosis and renal failure caused by RIRI. Therefore, oxerutin can be used as an effective prophylactic agent in the treatment of RIRI.

Targeting SHP2 as a therapeutic strategy for inflammatory diseases

With the change of lifestyle and the acceleration of aging process, inflammatory diseases have increasingly become one of the most vital threats to global human health. SHP2 protein is a non-receptor tyrosine phosphatase encoded by PTPN11 gene, and it is widely expressed in various tissues and cells. Numerous studies have shown that SHP2 plays important roles in the regulation of inflammatory diseases, including cancer-related inflammation, neurodegenerative diseases and metabolic diseases. In this paper, the roles of SHP2 in inflammatory diseases of various physiological systems were reviewed. At the same time, the latest SHP2 inhibitors were summarized, which will hold a promise for the therapeutic potential in future.

The effects of HIF-1α overexpression on renal injury, immune disorders and mitochondrial apoptotic pathways in renal ischemia/reperfusion rats

Background

Renal ischemia/reperfusion (RI/R) injury are a common pathogenesis of acute kidney injury, which may cause renal parenchyma damage clinically. Hypoxia-inducible factor-1α (HIF-1α) has protective effects on cells in regulating the metabolism, angiogenesis, erythropoiesis, and anti-apoptosis of RI/R injury. However, the specific mechanisms for HIF-1α on RI/R injury are still unclear. This study aims to investigate the effects of HIF-1α overexpression on renal function injury, immune disorder, and mitochondrial apoptosis in RI/R rats.

Methods

The rat model of RI/R injury was set up. The lentivirus (LV) vector of HIF-1α overexpression was constructed, and then the LV was transfected to the model rats. The rats were randomly divided into four groups: the control group, RI/R group, RI/R + LV group, and RI/R + LV-HIF-1α group for later experiments. The mRNA levels of HIF-1α were detected by RT-PCR. Proteinuria, urea nitrogen, and serum creatinine levels were detected using the relative kit. Pathological damage was detected by HE staining. Apoptosis was detected by TUNEL staining. Levels of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α) and interleukin-10 (IL-10) were detected by ELISA. Western blotting was used to detect the protein levels of HIF-1α, caspase-3, caspase-9, Bax, Bcl-2, and other proteins.

Results

Compared with the control group, the mRNA and protein levels of HIF-1α in the RI/R group were increased significantly (P<0.05). Proteinuria, urea nitrogen, serum creatinine levels were increased significantly (P<0.05). The levels of IL-6, IL-1 beta, TNF-α were increased significantly (P<0.05). The ratios of cleaved caspase-3/caspase-3, cleaved caspase-9/caspase-9, and Bax/Bcl-2 were increased significantly (P<0.05). There was a significant increase in apoptosis rate and renal pathological tissue damage (P<0.05). Compared with RI/R+LV group, the mRNA and protein levels of HIF-1α in the RI/R+LV-HIF-1α group were increased significantly (P<0.05). Proteinuria, urea nitrogen, serum creatinine levels were decreased significantly (P<0.05). IL-6, IL-1 beta, TNF-α levels were significantly decreased (P<0.05). IL-10 level was significantly increased (P<0.05). The ratios of cleaved caspase-3/caspase-3, cleaved caspase-9/caspase-9, and Bax/Bcl-2 were significantly reduced (P<0.05), showing that the pathological damage degree and the apoptosis rate was significantly lower.

Conclusions

HIF-1α overexpression has protective effects on renal ischemia-reperfusion rats by improving pathological injury and immune function, reducing the release of inflammatory factors, and the expression of apoptotic proteins.

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

BACKGROUND

Accumulation of iron is associated with oxidative stress, inflammation, and regulated cell death processes that contribute to the development of acute kidney injury (AKI). We aimed to investigate the association between serum iron levels and prognosis in intensive care unit (ICU) patients with AKI.

METHODS

A total of 483 patients with AKI defined as per the Kidney Disease: Improving Global Guidelines were included in this retrospective study. The data was extracted from the single-centre Medical Information Mart for Intensive Care III database. AKI patients with serum iron parameters measured upon ICU admission were included and divided into two groups (low group and high group). The prognostic value of serum iron was analysed using univariate and multivariate Cox regression analysis.

RESULTS

The optimal cut-off value for serum iron was calculated to be 60 μg/dl. Univariable Cox regression analysis showed that serum iron levels were significantly correlated with prognosis of AKI patients. After adjusting for possible confounding variables, serum iron levels higher than 60 μg/dl were associated with increases in 28-day (hazard [HR] 1.832; P <  0.001) and 90-day (HR 1.741; P <  0.001) mortality, as per multivariable Cox regression analysis.

CONCLUSIONS

High serum iron levels were associated with increased short- and long-term mortality in ICU patients with AKI. Serum iron levels measured upon admission may be used for predicting prognosis in AKI patients.

The effect of hepcidin in rats with renal ischemia/reperfusion injury

OBJECTIVE

This study sought to investigate the effectiveness of hepcidin in renal ischemia/reperfusion injury by using a rat model of renal IRI.

METHODS

In our study, male Sprague-Dawley rats were divided into a hepcidin-treated group and a control group before establishing the animal models. According to the difference of the modelling methods (renal pedicle occlusion for 45 minutes or not) and renal reperfusion time, the rats were then respectively divided into four subgroups: sham, IRI 4 h, IRI 12 h, and IRI 24 h. After the establishment of the IRI model, the rats were killed to determine renal function, histology, iron metabolism indexes in plasma and tissues, and the expression level of hepcidin and ferroportin-1.

RESULTS

The results indicated that the levels of serum creatinine, blood urea nitrogen and serum iron, the renal iron content, and the kidney injury score were significantly decreased in the hepcidin group (P<0.05). The serum hepcidin and the splenic iron content were significantly increased while the duodenal iron content was significantly decreased in the hepcidin group (P<0.05). Hepcidin expression in the liver and ferroportin-1 expression in the kidneys were significantly decreased in the hepcidin group (P<0.05).

CONCLUSION

Hepcidin has a reno-protective effect in renal IRI by possibly promoting iron intake in the spleen, inhibiting iron absorption and exportation in the duodenum, alleviating the degree of serum iron, and reducing renal iron accumulation in the renal IRI.

miR-124/IRE-1α affects renal ischemia/reperfusion injury by regulating endoplasmic reticulum stress in renal tubular epithelial cells

Acute kidney injury (AKI) refers to a clinical syndrome that occurs as a result of a rapid decline in renal function caused by multiple factors. Renal ischemia/reperfusion (I/R) injury is one of the main causes of AKI and has a high incidence and mortality. However, the specific pathogenesis of renal I/R injury is still unclear. In recent years, a major breakthrough has been made in the study of endoplasmic reticulum stress (ERS)-mediated apoptosis in I/R injury. It has been reported that miRNAs play protective roles in ischemic/reperfused organs, but the molecular mechanisms have not been investigated deeply. In this study, the renal I/R mouse model was used to explore the roles of miR-124 in ERS and in renal I/R injury. The western blot results showed that the expression levels of ERS-related proteins IRE-1α, XBP-1, and glucose-regulated protein 78 (GRP78) were significantly increased in the I/R model group when compared with those in the control group. Meanwhile, qPCR results showed that miR-124 expression was decreased in the I/R injury model, and overexpression of miR-124 using miR-124 mimics effectively reduced the expression of ERS-related proteins and alleviated renal I/R injury. In addition, luciferase reporter assay was performed, and the results showed that IRE-1α and miR-124 may have direct interaction. In conclusion, our data indicated that miR-124 was a negative regulator of ERS via binding to IRE-1α, ultimately conferring its protective effect on the kidney, which demonstrates the regulatory mechanism of miR-124 in renal I/R injury and provides new ideas and methods for the prevention and treatment of renal I/R injury.

The multifaceted role of iron in renal health and disease

Iron is an essential element that is indispensable for life. The delicate physiological body iron balance is maintained by both systemic and cellular regulatory mechanisms. The iron-regulatory hormone hepcidin assures maintenance of adequate systemic iron levels and is regulated by circulating and stored iron levels, inflammation and erythropoiesis. The kidney has an important role in preventing iron loss from the body by means of reabsorption. Cellular iron levels are dependent on iron import, storage, utilization and export, which are mainly regulated by the iron response element-iron regulatory protein (IRE-IRP) system. In the kidney, iron transport mechanisms independent of the IRE-IRP system have been identified, suggesting additional mechanisms for iron handling in this organ. Yet, knowledge gaps on renal iron handling remain in terms of redundancy in transport mechanisms, the roles of the different tubular segments and related regulatory processes. Disturbances in cellular and systemic iron balance are recognized as causes and consequences of kidney injury. Consequently, iron metabolism has become a focus for novel therapeutic interventions for acute kidney injury and chronic kidney disease, which has fuelled interest in the molecular mechanisms of renal iron handling and renal injury, as well as the complex dynamics between systemic and local cellular iron regulation.

Hydrogen Gas Alleviates Chronic Intermittent Hypoxia-Induced Renal Injury through Reducing Iron Overload

Iron-induced oxidative stress has been found to be a central player in the pathogenesis of kidney injury. Recent studies have indicated H₂ can be used as a novel antioxidant to protect cells. The present study was designed to investigate the protective effects of H₂ against chronic intermittent hypoxia (CIH)-induced renal injury and its correlation mechanism involved in iron metabolism. We found that CIH-induced renal iron overloaded along with increased apoptosis and oxidative stress. Iron accumulates mainly occurred in the proximal tubule epithelial cells of rats as showed by Perl’s stain. Moreover, we found that CIH could promote renal transferrin receptor and divalent metal transporter-1 expression, inhibit ceruloplasmin expression. Renal injury, apoptosis and oxidative stress induced by CIH were strikingly attenuated in H₂ treated rats. In conclusion, hydrogen may attenuate CIH-induced renal injury at least partially via inhibiting renal iron overload.

Acute and Chronic Iron Overloading Differentially Modulates the Expression of Cellular Iron-homeostatic Molecules in Normal Rat Kidney

Little is known about the renal responses to acute iron overloading. This study measured the renal tubular expression of transferrin receptor-1 (TfR1), cubilin/megalin receptors, hepcidin, ferroportin, and ferritin chains following subacute intoxication of 40 male Wistar rats with a single oral dose of ferrous iron (300 mg/kg). The animals were randomly subdivided into 4 equal subgroups at the time of necropsy (1, 2, 4, and 8 hr). The results were compared with the controls ( n=15) and with the chronic group ( n=15), which received iron for 4 weeks (75 mg/kg/day; 5 days/week). Although both toxicity models inhibited TfR1, they upregulated the cubilin/megalin receptors and hepcidin, and triggered iron deposition in tubular cells. The ferritin heavy-chain and ferroportin were downregulated in the 2-hr and 4-hr acute subgroups, whereas chronic toxicity promoted their expression, compared with controls. Moreover, the 4-hr and 8-hr subgroups had higher intracellular Fe⁺² and marked cell apoptosis compared with the chronic group. In conclusion, the kidney appears to sustain iron reabsorption in both intoxication models. However, the cellular iron storage and exporter proteins were differentially expressed in both models, and their inhibition post-acute toxicity might contribute toward the intracellular accumulation of Fe⁺², oxidative stress, and ferroptosis.