Hyperglycemia Does Not Affect Iron Mediated Toxicity of Cultured Endothelial and Renal Tubular Epithelial Cells: Influence of L-Carnosine

Carnosine alleviates cisplatin-induced acute kidney injury by targeting Caspase-1 regulated pyroptosis

Acute kidney injury (AKI) is a syndrome characterized by rapid loss of renal excretory function. Its underlying mechanisms remain unclear. Pyroptosis, a form of programmed cell death, plays an important role in AKI. It is characterized by cell swelling and membrane rupture, triggering the release of cellular contents and activating robust inflammatory responses. Carnosine, a dipeptide with antioxidant and anti-inflammatory properties, has therapeutic effects in AKI. However, the mechanism by which carnosine treats AKI-associated pyroptosis remains unexplored. In this study, we investigated the protective effect of carnosine on renal tubule cells using in vivo and in vitro models of AKI. We found that carnosine therapy significantly alleviated altered serum biochemical markers and histopathological changes in mice with cisplatin-induced AKI. It also reduced the levels of inflammation and pyroptosis. These results were consistent with those seen in human kidney tubular epithelial cells (HK-2) treated with cisplatin. Through molecular docking and cellular thermal shift assay, we identified caspase-1 as a target of carnosine. By knocking down caspase-1 in HK-2 cells using caspase-1 siRNA, we demonstrated that carnosine did not exhibit a protective role in cisplatin-induced HK-2 cells. This study provides the first evidence that carnosine alleviates damage to kidney tubular epithelial cells by targeting caspase-1 and inhibiting pyroptosis. Therefore, carnosine holds promise as a potential therapeutic agent for AKI, with caspase-1 representing an effective therapeutic target in this pathology.

Ferulic acid protects HepG2 cells and mouse liver from iron-induced damage

Liver as iron storage organ is particularly susceptible to oxidative stress-induced injury from excess iron. Thus, antioxidant therapies are often used to reverse oxidative damage and protect cells and tissues. This study investigated the protective effects of phenolic acids; ferulic acid (FA) and its metabolite, ferulic acid 4-O-sulfate disodium salt (FAS) against oxidative stress under iron overload conditions in mouse and HepG2 cells. Cells were exposed to FA or FAS and then treated with iron-induced oxidative stress complex of 50 μmol/L FAC and 20 μmol/L of 8-hydroxyquinoline 8HQ (8HQ-FAC). Iron dextran was injected intraperitoneally on alternate days for 10 days to induce the iron overload condition in BALB/c mice. The study revealed that the phenolic acids were protective against ROS production, lipid peroxidation and antioxidant depletion in HepG2 cells and liver tissues of BALB/c mice during iron-induced oxidative stress. The protective function of phenolic acids was achieved by the transcriptional activation of nuclear factor erythroid-2-related factor 2 (Nrf2) to regulate antioxidant genes. In conclusion, the study provides evidence that FA has the potential as a therapeutic agent against iron-related diseases such as T2D.

Phenolic Acids Rescue Iron-Induced Damage in Murine Pancreatic Cells and Tissues

Iron is an essential element involved in a variety of physiological functions. However, excess iron catalyzes the generation of reactive oxygen species (ROS) via the Fenton reaction. Oxidative stress, caused by an increase in intracellular ROS production, can be a contributory factor to metabolic syndromes such as dyslipidemia, hypertension, and type 2 diabetes (T2D). Accordingly, interest has grown recently in the role and use of natural antioxidants to prevent iron-induced oxidative damage. This study investigated the protective effect of the phenolic acids; ferulic acid (FA) and its metabolite ferulic acid 4-O-sulfate disodium salt (FAS) against excess iron-related oxidative stress in murine MIN6 cells and the pancreas of BALB/c mice. Rapid iron overload was induced with 50 μmol/L ferric ammonium citrate (FAC) and 20 μmol/L 8-hydroxyquinoline (8HQ) in MIN6 cells, while iron dextran (ID) was used to facilitate iron overload in mice. Cell viability was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, ROS levels were determined by dihydrodichlorofluorescein (H2DCF) cell-permeant probe, iron levels were measured by inductively coupled plasma mass spectrometry (ICP-MS), glutathione, SOD (superoxide dismutase) and lipid peroxidation, and mRNA were assayed with commercially available kits. The phenolic acids enhanced cell viability in iron-overloaded MIN6 cells in a dose-dependent manner. Furthermore, MIN6 cells exposed to iron showed elevated levels of ROS, glutathione (GSH) depletion and lipid peroxidation (p < 0.05) compared to cells that were protected by treatment with FA or FAS. The treatment of BALB/c mice with FA or FAS following exposure to ID increased the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) gene levels in the pancreas. Consequently, levels of its downstream antioxidant genes, HO-1, NQO1, GCLC and GPX4, increased in the pancreas. In conclusion, this study shows that FA and FAS protect pancreatic cells and liver tissue from iron-induced damage via the Nrf2 antioxidant activation mechanism.

Carnosine Supplementation Enhances Post Ischemic Hind Limb Revascularization

High (millimolar) concentrations of the histidine containing dipeptide - carnosine (β-alanine-L-histidine) are present in the skeletal muscle. The dipeptide has been shown to buffer intracellular pH, chelate transition metals, and scavenge lipid peroxidation products; however, its role in protecting against tissue injury remains unclear. In this study, we tested the hypothesis that carnosine protects against post ischemia by augmenting HIF-1α angiogenic signaling by Fe2+ chelation. We found that wild type (WT) C57BL/6 mice, subjected to hind limb ischemia (HLI) and supplemented with carnosine (1g/L) in drinking water, had improved blood flow recovery and limb function, enhanced revascularization and regeneration of myocytes compared with HLI mice placed on water alone. Carnosine supplementation enhanced the bioavailability of carnosine in the ischemic limb, which was accompanied by increased expression of proton-coupled oligopeptide transporters. Consistent with our hypothesis, carnosine supplementation augmented HIF-1α and VEGF expression in the ischemic limb and the mobilization of proangiogenic Flk-1+/Sca-1+ cells into circulation. Pretreatment of murine myoblast (C2C12) cells with octyl-D-carnosine or carnosine enhanced HIF-1α protein expression, VEGF mRNA levels and VEGF release under hypoxic conditions. Similarly pretreatment of WT C57/Bl6 mice with carnosine showed enhanced blood flow in the ischemic limb following HLI surgery. In contrast, pretreatment of hypoxic C2C12 cells with methylcarcinine, a carnosine analog, lacking Fe2+ chelating capacity, had no effect on HIF-1α levels and VEGF release. Collectively, these data suggest that carnosine promotes post ischemic revascularization via augmentation of pro-angiogenic HIF-1α/VEGF signaling, possibly by Fe2+ chelation.

Curcumin and (-)- Epigallocatechin-3-Gallate Protect Murine MIN6 Pancreatic Beta-Cells Against Iron Toxicity and Erastin-Induced Ferroptosis

Ferroptosis is a form of programmed cell death that is characterized by lipid peroxidation and is inducible by iron and the accumulation of reactive oxygen species (ROS). It is triggered by erastin but inhibited by antioxidants such as α-tocopherol, β-carotene, polyphenols, and iron chelators such as deferoxamine (DFO), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). This study investigated the protective effects of two polyphenols, curcumin and (−)- epigallocatechin-3-gallate (EGCG), against iron loading and erastin-mediated ferroptosis in MIN6 cells. Cells were treated with polyphenols before exposure to iron-induced oxidative stress comprising of 20 μmol/L of 8-hydroxyquinoline (8HQ) and 50 μmol/L of ferric ammonium citrate, (FAC) (8HQ+FAC) or Fenton reaction substrate (FS) (30 μmol/L of FeSO₄ and 0.5 of mmol/L H₂O₂) and 20 μmol/L erastin. Cell viability was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, iron levels were measured by inductively-coupled plasma mass spectrometry (ICP-MS), glutathione and lipid peroxidation were assayed with commercially-available kits. Curcumin and EGCG both significantly protected pancreatic cells against iron-induced oxidative damage. Moreover, both compounds also protected against erastin-induced ferroptosis in pancreatic cells. The polyphenols enhanced cell viability in erastin-treated MIN6 cells in a dose- and time-dependent manner. Furthermore, MIN6 cells exposed to erastin alone showed elevated levels of iron, glutathione (GSH) depletion, glutathione peroxidase 4 (GPX4) degradation and lipid peroxidation (p < 0.05) compared to cells that were protected by pre-treatment with curcumin or EGCG. Taken together, the data identify curcumin and EGCG as novel ferroptosis inhibitors, which might exert their protective effects by acting as iron chelators and preventing GSH depletion, GPX4 inactivation, and lipid peroxidation in MIN6 cells. The implications of the findings on the effects of iron overload and ferroptosis represent a potential therapeutic strategy against iron-related diseases.

Carnosine supplementation reduces plasma soluble transferrin receptor in healthy overweight or obese individuals: a pilot randomised trial

Abnormalities of iron homeostasis have been linked to insulin resistance, type 2 diabetes and cardiovascular disease. Carnosine, an over-the-counter food supplement with chelating properties, has been shown to decrease serum iron and improve glucose metabolism in diabetic rodents. We have previously demonstrated that carnosine supplementation prevented worsening of glucose metabolism in healthy overweight and obese middle-aged adults. Yet, the impact of carnosine on markers of iron metabolism in humans has not been investigated. We aimed to determine whether carnosine supplementation has an effect on iron parameters in overweight and obese, otherwise healthy adults. We included 26 participants, who were randomly allocated to receive 1 g carnosine (n = 14) or identical placebo (n = 12) twice daily for 12 weeks. Iron parameters including iron, ferritin, transferrin, soluble transferrin receptor, total iron binding capacity and iron saturation were measured in serum or plasma by standard commercial assays. Carnosine supplementation decreased plasma soluble transferrin receptor compared to placebo (mean change difference ± standard error: - 0.07 ± 0.03 mg/l, p = 0.04). None of the other iron parameters were different between carnosine and placebo groups. At follow-up, soluble transferrin receptor was associated inversely with urinary carnosine concentrations and positively with serum carnosinase-1 activity (both p < 0.02). Our findings suggest that carnosine may modulate iron metabolism in high-risk groups which could ameliorate insulin resistance and prevent type 2 diabetes. Larger human clinical trials are required to confirm our results.