Effects of acute iron overload on Nrf2-related glutathione metabolism in rat brain

Evidence for chromium crosses blood brain barrier from the hypothalamus in chromium mice model

It has been shown that exposure to hexavalent Chromium, Cr (Ⅵ), via nasal cavity can have neurotoxicological effects and induces behavioral impairment due to the fact that blood brain barrier (BBB) does not cover olfactory bulb. But whether Cr (Ⅵ) can cross the BBB and have a toxicological effects in central nervous system (CNS) remains unclear. Therefore, we investigated the effects of Cr (Ⅵ) on mice treated with different concentrations and exposure time (14 days and 28 days) of Cr (Ⅵ) via intraperitoneal injection. Results revealed that Cr accumulated in hypothalamus (HY) in a timely dependent manner. Much more severer neuropathologies was observed in the group of mice exposed to Cr (Ⅵ) for 28 days than that for 14 days. Gliosis, neuronal morphological abnormalities, synaptic degeneration, BBB disruption and neuronal number loss were observed in HY. In terms of mechanism, the Nrf2 related antioxidant stress signaling dysfunction and activated NF-κB related inflammatory pathway were observed in HY of Cr (Ⅵ) intoxication mice. And these neuropathologies and signaling defects appeared in a timely dependent manner. Taking together, we proved that Cr (Ⅵ) can enter HY due to weaker BBB in HY and HY is the most vulnerable CNS region to Cr (Ⅵ) exposure. The concentration of Cr in HY increased along with time. The accumulated Cr in HY can cause BBB disruption, neuronal morphological abnormalities, synaptic degeneration and gliosis through Nrf2 and NF-κB signaling pathway. This finding improves our understanding of the neurological dysfunctions observed in individuals who have occupational exposure to Cr (Ⅵ), and provided potential therapeutic targets to treat neurotoxicological pathologies induced by Cr (Ⅵ).

Acetylated oligopeptide and N-acetylcysteine protect against iron overload-induced dentate gyrus hippocampal degeneration through upregulation of Nestin and Nrf2/HO-1 and downregulation of MMP-9/TIMP-1 and GFAP

Iron accumulation in the brain causes oxidative stress, blood-brain barrier (BBB) breakdown, and neurodegeneration. We examined the preventive effects of acetylated oligopeptides (AOP) from whey protein on iron-induced hippocampal damage compared to N-acetyl cysteine (NAC). This 5-week study used 40 male albino rats. At the start, all rats received 150 mg/kg/day of oral NAC for a week. The 40 animals were then randomly divided into four groups: Group I (control) received a normal diet; Group II (iron overload) received 60 mg/kg/day intraperitoneal iron dextran 5 days a week for 4 weeks; Group III (NAC group) received 150 mg/kg/day NAC and iron dextran; and Group IV (AOP group) received 150 mg/kg/day AOP and iron dextran. Enzyme-linked immunosorbent assay, spectrophotometry, and qRT-PCR were used to measure MMP-9, tissue inhibitor metalloproteinase-1 (TIMP-1), MDA, reduced glutathione (GSH) levels, and nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) gene expression. Histopathological and immunohistochemical detection of nestin, claudin, caspase, and GFAP was also done. MMP-9, TIMP-1, MDA, caspase, and GFAP rose in the iron overload group, while GSH, Nrf2, HO-1, nestin, and claudin decreased. The NAC and AOP administrations improved iron overload-induced biochemical and histological alterations. We found that AOP and NAC can protect the brain hippocampus from iron overload, improve BBB disruption, and provide neuroprotection with mostly no significant difference from healthy controls.

Molecular mechanism of paraquat-induced ferroptosis leading to pulmonary fibrosis mediated by Keap1/Nrf2 signaling pathway

Paraquat (PQ) is a widely used and highly toxic pesticide that is often actively ingested and causes pulmonary fibrosis in patients. Ferroptosis is a regulated form of non-apoptotic cell death associated with iron-dependent lipid peroxidation. Previous studies have shown that ferroptosis is involved in the occurrence and development of acute lung injury (ALI). In this study, a model rat with inflammatory response, oxidative stress, lipid peroxidation, and pulmonary fibrosis was successfully established by PQ administration. The occurrence of ferroptosis in PQ model rats was confirmed by TUNEL staining, iron ion detection, and Ferroptosis related biomarkers detection. Western blotting (WB) and real-time PCR (RT-PCR) showed that the expression of Keap1 was significantly up-regulated and the expression of Nrf2 was significantly down-regulated in the lung tissue of PQ rats. Further transcriptomics and proteomics confirmed: (1) Enrichment of molecular processes related to iron ion binding; (2) Keap1 may promote Nrf2 ubiquitination and lead to Nrf2 degradation; (3) There is functional enrichment in ferroptosis related pathways. Our results suggest that PQ can regulate Keap1/Nrf2 signaling pathway, leading to increased lipid peroxidation and abnormal iron uptake, thereby inducing iron death and exacerbating the progression of pulmonary fibrosis. Our study provides new insights into PQ-induced pulmonary fibrosis.

DNMT3A R882H mutation promotes acute leukemic cell survival by regulating glycolysis through the NRF2/NQO1 axis

BACKGROUND

Studies have confirmed that acute myeloid leukemia (AML) cells with DNA methyltransferase 3A Arg882His (DNMT3A R882H) mutation show an increased proliferation capability. However, the associated mechanism is still unclear. Glycolysis is involved in regulating malignant proliferation of cancer cell. Hence, we analyzed whether the DNMT3A R882H mutation interferes with glycolysis and thereby influences AML cell proliferation.

METHODS

We generated AML cell line carrying a DNMT3A-R882H mutation and compared it with the wild type (DNMT3A-WT) with regard to glycolysis regulation. Moreover, we analyzed the cell line's proliferation and apoptosis by a CCK-8 assay, western blotting, and flow cytometry. The role of NRF2/NQO1 signaling in regulating glycolysis was investigated by NRF2-knockdown and Brusatol (specific inhibitor of NRF2) treatment.

RESULTS

DNMT3A R882H cells had a higher glucose transport capacity compared to WT cells and their viability could be reduced by glucose deprivation. Moreover, daunorubicin had a slight inhibitory effect on glycolysis while glycolysis inhibition re-sensitized mutant cells to daunorubicin. Obviously, DNMT3A R882H mutation activated the NRF2/NQO1 pathway and enhanced the glycolytic activity in mutant cells.

CONCLUSION

Taken together, these results suggest a novel mechanism by which a DNMT3A R882H mutation promotes glycolysis via activation of NRF2/NQO1 pathway. A parallel glycolysis inhibition adds to the anticancer effects of daunorubicin which might lead to a novel therapeutic approach for the treatment of AML patients carrying a DNMT3A R882H mutation.

Transcription Factor Nrf2 and Mitochondria - Friends or Foes in the Regulation of Aging Rate

At the first sight, the transcription factor Nrf2 as a master regulator of cellular antioxidant systems, and mitochondria as the main source of reactive oxygen species (ROS), should play the opposite roles in determining the pace of aging. However, since the causes of aging cannot be confined to the oxidative stress, the role of Nrf2 role cannot be limited to the regulation of antioxidant systems, and moreover, the role of mitochondria is not confined to the ROS production. In this review, we discussed only one aspect of this problem, namely, the molecular mechanisms of interaction between Nrf2 and mitochondria that influence the rate of aging and the lifespan. Experimental data accumulated so far show that the Nrf2 activity positively affects both the mitochondrial dynamics and mitochondrial quality control. Nrf2 influences the mitochondrial function through various mechanisms, e.g., regulation of nuclear genome-encoded mitochondrial proteins and changes in the balance of ROS or other metabolites that affect the functioning of mitochondria. In turn, multiple regulatory proteins functionally associated with the mitochondria affect the Nrf2 activity and even form mutual regulatory loops with Nrf2. We believe that these loops enable the fine-tuning of the cellular redox balance and, possibly, of the cellular metabolism as a whole. It has been commonly accepted for a long time that all mitochondrial regulatory signals are mediated by the nuclear genome-encoded proteins, whereas the mitochondrial genome encodes only a few respiratory chain proteins and two ribosomal RNAs. Relatively recently, mtDNA-encoded signal peptides have been discovered. In this review, we discuss the data on their interactions with the nuclear regulatory systems, first of all, Nrf2, and their possible involvement in the regulation of the aging rate. The interactions between regulatory cascades that link the programs ensuring the maintenance of cellular homeostasis and cellular responses to the oxidative stress are a significant part of both aging and anti-aging programs. Therefore, understanding these interactions will be of great help in searching for the molecular targets to counteract aging-associated diseases and aging itself.

The multiple biotoxicity integrated study in grass carp (Ctenopharyngodon idella) caused by Ochratoxin A: Oxidative damage, apoptosis and immunosuppression

Ochratoxin A (OTA) is a common hazardous food contaminant that seriously endangers human and animal health. However, limited study is focused on aquatic animal. This research investigated the multiple biotoxicity of OTA on spleen (SP) and head kidney (HK) in grass carp and its related mechanism. Our data showed that, dietary supplemented with OTA above 1209 μg/kg caused histopathological damages by decreasing the number of lymphocytes and necrotizing renal parenchymal cells. Meanwhile, OTA caused oxidative damage and reduced the isoforms mRNAs transcripts of antioxidant enzymes (e.g., GPX1, GPX4, GSTO) partly due to suppressing NF-E2-related factor 2 (Nrf2). OTA triggered apoptosis through mitochondria and death receptor pathway potentially by p38 mitogen-activated protein kinase (p38MAPK) activation. Besides, OTA exacerbated inflammation by down-regulation of anti-inflammatory factor (e.g., IL-10, IL-4) and up-regulations of pro-inflammatory factors (e.g., TNF-α, IL-6), which could be ascribed to signaling meditation of Janus kinase / signal transducer and activator of transcription (JAK/STAT). Additionally, the safe upper limits of OTA were estimated to be 677.6 and 695.08 μg/kg based on the immune-related indexes (C3 contents in the SP and LZ activities in the HK, respectively). Our study has provided a wide insight for toxicological assessment of feed pollutant in aquatic animals.

NRF2 and Mitochondrial Function in Cancer and Cancer Stem Cells

The NRF2–KEAP1 system is a fundamental component of the cellular response that controls a great variety of transcriptional targets that are mainly involved in the regulation of redox homeostasis and multiple cytoprotective mechanisms that confer adaptation to the stress conditions. The pleiotropic response orchestrated by NRF2 is particularly relevant in the context of oncogenic activation, wherein this transcription factor acts as a key driver of tumor progression and cancer cells’ resistance to treatment. For this reason, NRF2 has emerged as a promising therapeutic target in cancer cells, stimulating extensive research aimed at the identification of natural, as well as chemical, NRF2 inhibitors. Excitingly, the influence of NRF2 on cancer cells’ biology extends far beyond its mere antioxidant function and rather encompasses a functional crosstalk with the mitochondrial network that can influence crucial aspects of mitochondrial homeostasis, including biogenesis, oxidative phosphorylation, metabolic reprogramming, and mitophagy. In the present review, we summarize the current knowledge of the reciprocal interrelation between NRF2 and mitochondria, with a focus on malignant tumors and cancer stem cells.

Revealing the Effects of Endoplasmic Reticulum Stress on Ferroptosis by Two-Channel Real-Time Imaging of pH and Viscosity

Endoplasmic reticulum (ER) is sensitive to changes in the intracellular environment such as pH and viscosity, and slight changes may trigger stress response. Besides, different from apoptosis and necrosis, ferroptosis is the result of lipid peroxidation accumulation. There is evidence that ferroptosis is closely related to endoplasmic reticulum stress (ERS). However, the possible changes in the pH and viscosity of the ER during the ferroptosis process have not yet been studied. Therefore, we used a new type of ER-targeted dual-excitation fluorescent probe (DSPI-3) to investigate the possible changes of pH and viscosity of ER during the ferroptosis. The novel probe DSPI-3 exhibited a highly sensitive and selective response to pH and viscosity. During the bioimaging process, it was found that the ER acidified and viscosity increased during the ferroptosis process induced by erastin, while the cells treated with ferrostatin-1 did not alter significantly. In addition, when dithiothreitol (DTT) and erastin stimulated the cells at the same time, we discovered that ER was acidified considerably at short notice, but the pH was slightly increased in the later stage. Besides, the change of the viscosity enhanced slowly with the passage of time, and there was a noteworthy decline in the later stage, demonstrating that the DTT-induced ERS accelerated the process of ferroptosis. We hope that this unique fluorescent probe can provide an effective method for studying the relationship between ERS and ferroptosis.