Integrated regulation of stress responses, autophagy and survival by altered intracellular iron stores

Sephin1 enhances integrated stress response and autophagy to alleviate myocardial ischemia-reperfusion injury in mice

OBJECTIVE

Integrated stress response (ISR) is activated to promote cell survival by maintaining the phosphorylation of eukaryotic translation initiation factor 2 (eIF2α). We investigated whether Sephin1 enhances ISR and attenuates myocardial ischemia-reperfusion (MIR) injury.

METHODS

Male C57BL/6 J mice were injected with Sephin1 (2 mg/kg,i.p.) 30 min before surgery to establish a model of MIR with 45 min ischemia and 180 min reperfusion. In vitro, the H9C2 cell line with hypoxia-reoxygenation (H/R) was used to simulate MIR. Myocardial injury was evaluated by echocardiography, histologic observation after staining with TTC and H&E and electron microscopy. ISR, autophagy and apoptosis in vivo and in vitro were evaluated by immunoblotting, immunohistochemistry, immunofluorescence, and flow cytometry, respectively. Global protein synthesis was determined using a non-radioactive SUnSET Assay based on the puromycin method. Autophinib, an autophagy-specific inhibitor, was used to investigate the correlation between autophagy and apoptosis in the presence of Sephin1.

RESULTS

In vivo, Sephin1 significantly reduced myocardial injury and improved the cardiac function in MIR mice. Sephin1 administration prolonged ISR, reduced cell apoptosis, and promoted autophagy. In vitro, Sephin1 increased the number of stress granules (SGs) and autophagic vesicles, enhanced ISR and related protein synthesis suppression, and reduced cell apoptosis. Autophinib partly reversed autophagosome formation and apoptosis in H9c2 cells.

CONCLUSIONS

Sephin1 enhances ISR and related protein synthesis suppression, ameliorates myocardial apoptosis, and promotes autophagy during MIR stress. Sephin1 could act as a noval ISR enhancer for managing acute myocardial ischemia disease.

Targeting NKAα1 to treat Parkinson's disease through inhibition of mitophagy-dependent ferroptosis

Dysfunction of the Na+/K+-ATPase (NKA) has been documented in various neurodegenerative diseases, yet the specific role of NKAα1 in Parkinson's disease (PD) remains incompletely understood. In this investigation, we utilized NKAα1 haploinsufficiency (NKAα1+/-) mice to probe the influence of NKAα1 on dopaminergic (DA) neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Our findings reveal that NKAα1+/- mice displayed a heightened loss of DA neurons and more pronounced motor dysfunction compared to the control group when exposed to MPTP. Intriguingly, this phenomenon coincided with the activation of ferroptosis and impaired mitophagy both in vivo and in vitro. To scrutinize the role and underlying mechanism of NKAα1 in PD, we employed DR-Ab, an antibody targeting the DR-region of the NKA α subunit. Our study demonstrates that the administration of DR-Ab effectively reinstated the membrane abundance of NKAα1, thereby mitigating MPTP-induced DA neuron loss and subsequent improvement in behavioral deficit. Mechanistically, DR-Ab heightened the formation of the surface NKAα1/SLC7A11 complex, inhibiting SLC7A11-dependent ferroptosis. Moreover, DR-Ab disrupted the cytosolic interaction between NKAα1 and Parkin, facilitating the translocation of Parkin to mitochondria and enhancing the process of mitophagy. In conclusion, this study establishes NKAα1 as a key regulator of ferroptosis and mitophagy, identifying its DR-region as a promising therapeutic target for PD.

Regulation of translation in response to iron deficiency in human cells

Protein synthesis is a highly energy-consuming process that is downregulated in response to many environmental stresses or adverse conditions. Studies in the yeast Saccharomyces cerevisiae have shown that bulk translation is inhibited during adaptation to iron deficiency, which is consistent with its requirement for ribosome biogenesis and recycling. Although iron deficiency anemia is the most common human nutritional disorder, how iron modulates translation in mammals is poorly understood. Studies during erythropoiesis have shown that iron bioavailability is coordinated with globin synthesis via bulk translation regulation. However, little is known about the control of translation during iron limitation in other tissues. Here, we investigated how iron depletion affects protein synthesis in human osteosarcoma U-2 OS cells. By adding an extracellular iron chelator, we observed that iron deficiency limits cell proliferation, induces autophagy, and decreases the global rate of protein synthesis. Analysis of specific molecular markers indicates that the inhibition of bulk translation upon iron limitation occurs through the eukaryotic initiation factor eIF2α and mechanistic target of rapamycin (mTOR) pathways. In contrast to other environmental and nutritional stresses, iron depletion does not trigger the assembly of messenger ribonucleoprotein stress granules, which typically form upon polysome disassembly.

Endoplasmic reticulum stress: bridging inflammation and obesity-associated adipose tissue

Obesity presents a significant global health challenge, increasing the susceptibility to chronic conditions such as diabetes, cardiovascular disease, and hypertension. Within the context of obesity, lipid metabolism, adipose tissue formation, and inflammation are intricately linked to endoplasmic reticulum stress (ERS). ERS modulates metabolism, insulin signaling, inflammation, as well as cell proliferation and death through the unfolded protein response (UPR) pathway. Serving as a crucial nexus, ERS bridges the functionality of adipose tissue and the inflammatory response. In this review, we comprehensively elucidate the mechanisms by which ERS impacts adipose tissue function and inflammation in obesity, aiming to offer insights into targeting ERS for ameliorating metabolic dysregulation in obesity-associated chronic diseases such as hyperlipidemia, hypertension, fatty liver, and type 2 diabetes.

Iron overload in hypothalamic AgRP neurons contributes to obesity and related metabolic disorders

Iron overload is closely associated with metabolic dysfunction. However, the role of iron in the hypothalamus remains unclear. Here, we find that hypothalamic iron levels are increased, particularly in agouti-related peptide (AgRP)-expressing neurons in high-fat-diet-fed mice. Using pharmacological or genetic approaches, we reduce iron overload in AgRP neurons by central deferoxamine administration or transferrin receptor 1 (Tfrc) deletion, ameliorating diet-induced obesity and related metabolic dysfunction. Conversely, Tfrc-mediated iron overload in AgRP neurons leads to overeating and adiposity. Mechanistically, the reduction of iron overload in AgRP neurons inhibits AgRP neuron activity; improves insulin and leptin sensitivity; and inhibits iron-induced oxidative stress, endoplasmic reticulum stress, nuclear factor κB signaling, and suppression of cytokine signaling 3 expression. These results highlight the critical role of hypothalamic iron in obesity development and suggest targets for treating obesity and related metabolic disorders.

Flvcr1a deficiency promotes heme-based energy metabolism dysfunction in skeletal muscle

The definition of cell metabolic profile is essential to ensure skeletal muscle fiber heterogeneity and to achieve a proper equilibrium between the self-renewal and commitment of satellite stem cells. Heme sustains several biological functions, including processes profoundly implicated with cell metabolism. The skeletal muscle is a significant heme-producing body compartment, but the consequences of impaired heme homeostasis on this tissue have been poorly investigated. Here, we generate a skeletal-muscle-specific feline leukemia virus subgroup C receptor 1a (FLVCR1a) knockout mouse model and show that, by sustaining heme synthesis, FLVCR1a contributes to determine the energy phenotype in skeletal muscle cells and to modulate satellite cell differentiation and muscle regeneration.

Ferroptosis and endoplasmic reticulum stress in ischemic stroke

Ferroptosis is a form of non-apoptotic programmed cell death, and its mechanisms mainly involve the accumulation of lipid peroxides, imbalance in the amino acid antioxidant system, and disordered iron metabolism. The primary organelle responsible for coordinating external challenges and internal cell demands is the endoplasmic reticulum, and the progression of inflammatory diseases can trigger endoplasmic reticulum stress. Evidence has suggested that ferroptosis may share pathways or interact with endoplasmic reticulum stress in many diseases and plays a role in cell survival. Ferroptosis and endoplasmic reticulum stress may occur after ischemic stroke. However, there are few reports on the interactions of ferroptosis and endoplasmic reticulum stress with ischemic stroke. This review summarized the recent research on the relationships between ferroptosis and endoplasmic reticulum stress and ischemic stroke, aiming to provide a reference for developing treatments for ischemic stroke.

Chlorantraniliprole induces mitophagy, ferroptosis, and cytokine homeostasis imbalance in grass carp (Ctenopharyngodon idella) hepatocytes via the mtROS-mitochondrial fission/fusion axis

Chlorantraniliprole (CAP) is a bis-amide pesticide used for pest control mainly in agricultural production activities and rice-fish co-culture systems. CAP residues cause liver damage in non-target organism freshwater fish. However, it is unclear whether CAP-exposure-induced liver injury in fish is associated with mitochondrial dysfunction-mediated mitophagy, ferroptosis, and cytokines. Therefore, we established grass carp hepatocyte models exposed to different concentrations of CAP (20, 40, and 80 μM) in vitro. MitoSOX probe, JC-1 staining, immunofluorescence double staining, Fe2+ staining, lipid peroxidation staining, qRT-PCR, and Western blot were used to verify the physiological regulatory mechanism of CAP induced liver injury. In the present study, the CAP-treated groups exhibited down-regulation of antioxidant-related enzyme activities and accumulation of peroxides. CAP treatment induced an increase in mitochondrial reactive oxygen species (mtROS) levels and altered expression of mitochondrial fission/fusion (Drp1, Fis1, Mfn1, Mfn2, and Opa1) genes in grass carp hepatocytes. In addition, mitophagy (Parkin, Pink1, p62, LC3II/I, and Beclin-1), ferroptosis (GPX4, COX2, ACSL4, FTH, and NCOA4), and cytokine (IFN-γ, IL-18, IL-17, IL-6, IL-10, IL-1β, IL-2, and TNF-α)-related gene expression was significantly altered. Collectively, these findings suggest that CAP exposure drives mitophagy activation, ferroptosis occurrence, and cytokine homeostasis imbalance in grass carp hepatocytes by triggering mitochondrial dysfunction mediated by the mtROS-mitochondrial fission/fusion axis. This study partly explained the physiological regulation mechanism of grass carp hepatocyte injury induced by insecticide CAP from the physiological and biochemical point of view and provided a basis for evaluating the safety of CAP environmental residues to non-target organisms.

Identification of ZIP8-induced ferroptosis as a major type of cell death in monocytes under sepsis conditions

Sepsis is a heterogenous syndrome with concurrent hyperinflammation and immune suppression. A prominent feature of immunosuppression during sepsis is the dysfunction and loss of monocytes; however, the major type of cell death contributing to this depletion, as well as its underlying molecular mechanisms, are yet to be identified. In this study, we confirmed the monocyte loss in septic patients based on a pooled gene expression data of periphery leukocytes. Using the collected reference gene sets from databases and published studies, we identified ferroptosis with a greater capacity to distinguish between sepsis and control samples than other cell death types. Further investigation on the molecular drivers, by a genetic algorithm-based feature selection and a weighted gene co-expression network analysis, revealed that zrt-/irt-like protein 8 (ZIP8), encoded by SLC39A8, was closely associated with ferroptosis of monocytes during sepsis. We validated the increase of ZIP8 of monocytes with in vivo and in vitro experiments. The in vitro studies also showed that downregulation of ZIP8 alleviated the lipopolysaccharide-induced lipid peroxidation, as well as restoring the reduction of GPX4, FTH1 and xCT. These findings suggest that ferroptosis might be a key factor in the loss of monocytes during sepsis, and that the heightened expression of ZIP8 may facilitate this progression.

Magnesium promotes vascularization and osseointegration in diabetic states

Diabetes has long been considered a risk factor in implant therapy and impaired wound healing in soft and hard oral tissues. Magnesium has been proved to promote bone healing under normal conditions. Here, we elucidate the mechanism by which Mg2+ promotes angiogenesis and osseointegration in diabetic status. We generated a diabetic mice model and demonstrated the alveolar bone healing was compromised, with significantly decreased angiogenesis. We then developed Mg-coating implants with hydrothermal synthesis. These implants successfully improved the vascularization and osseointegration in diabetic status. Mechanically, Mg2+ promoted the degradation of Kelch-like ECH-associated protein 1 (Keap1) and the nucleation of nuclear factor erythroid 2-related factor 2 (Nrf2) by up-regulating the expression of sestrin 2 (SESN2) in endothelial cells, thus reducing the elevated levels of oxidative stress in mitochondria and relieving endothelial cell dysfunction under hyperglycemia. Altogether, our data suggested that Mg2+ promoted angiogenesis and osseointegration in diabetic mice by regulating endothelial mitochondrial metabolism.

Mitochondrial-Oriented Injectable Hydrogel Microspheres Maintain Homeostasis of Chondrocyte Metabolism to Promote Subcellular Therapy in Osteoarthritis

Subcellular mitochondria serve as sensors for energy metabolism and redox balance, and the dynamic regulation of functional and dysfunctional mitochondria plays a crucial role in determining cells' fate. Selective removal of dysfunctional mitochondria at the subcellular level can provide chondrocytes with energy to prevent degeneration, thereby treating osteoarthritis. Herein, to achieve an ideal subcellular therapy, cartilage affinity peptide (WYRGRL)-decorated liposomes loaded with mitophagy activator (urolithin A) were integrated into hyaluronic acid methacrylate hydrogel microspheres through microfluidic technology, named HM@WY-Lip/UA, that could efficiently target chondrocytes and selectively remove subcellular dysfunctional mitochondria. As a result, this system demonstrated an advantage in mitochondria function restoration, reactive oxygen species scavenging, cell survival rescue, and chondrocyte homeostasis maintenance through increasing mitophagy. In a rat post-traumatic osteoarthritis model, the intra-articular injection of HM@WY-Lip/UA ameliorated cartilage matrix degradation, osteophyte formation, and subchondral bone sclerosis at 8 weeks. Overall, this study indicated that HM@WY-Lip/UA provided a protective effect on cartilage degeneration in an efficacious and clinically relevant manner, and a mitochondrial-oriented strategy has great potential in the subcellular therapy of osteoarthritis.

Research Progress on the Effect of Autophagy and Exosomes on Liver Fibrosis

Chronic liver disease is a known risk factor for the development of liver cancer, and the development of microRNA (miRNA) liver therapies has been hampered by the difficulty of delivering miRNA to damaged tissues. In recent years, numerous studies have shown that hepatic stellate cell (HSC) autophagy and exosomes play an important role in maintaining liver homeostasis and ameliorating liver fibrosis. In addition, the interaction between HSC autophagy and exosomes also affects the progression of liver fibrosis. In this paper, we review the research progress of mesenchymal stem cell-derived exosomes (MSC-EVs) loaded with specific miRNA and autophagy, and their related signaling pathways in liver fibrosis, which will provide a more reliable basis for the use of MSC-EVs for therapeutic delivery of miRNAs targeting the chronic liver disease.

Sodium Sulfite-Triggered Hepatocyte Ferroptosis via mtROS/Lysosomal Membrane Permeabilization-Mediated Lysosome Iron Efflux

Sodium sulfite is a widely used preservative in the food industry. Ferroptosis has been a newly discovered form of iron-dependent oxidative cell death in recent years. However, the potential connection between sodium sulfite and ferroptosis has not been explored. In our study, we observed the abnormal expression of ferroptosis marker protein in vivo, suggesting that sodium sulfite caused ferroptosis in vivo. Next, our study revealed that sodium sulfite caused the overproduction of mitochondrial reactive oxygen species (mtROS) in the AML-12 cells. It is well established that reactive oxygen species (ROS) can induce lysosomal membrane permeabilization. After lysosomal membrane permeabilization occurs, the outflow of Fe2+ in lysosomes triggers the Fenton reaction and subsequently results in the increase of intracellular ROS level, which is closely related to ferroptosis. As speculated, acridine orange (AO) staining and LysoTracker red staining showed that sodium sulfite-induced lysosomal membrane permeabilization could be alleviated by mtROS scavenger TEMPO. In addition, TEMPO, lysosomal stabilizer mannose, and lysosomal iron chelator deferoxamine (DFO) inhibited sodium sulfite-induced ferroptosis. Overall, the results showed that sodium sulfite induced lysosomal iron efflux through the mtROS-lysosomal membrane permeabilization pathway and eventually led to ferroptosis. Our study might provide a new mechanism for the hepatotoxicity of sodium sulfite and a theoretical basis for the risk assessment of sodium sulfite as a food additive.

Differences in hepatocellular iron metabolism underlie sexual dimorphism in hepatocyte ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Why Is Iron Deficiency/Anemia Linked to Alzheimer's Disease and Its Comorbidities, and How Is It Prevented?

Impaired iron metabolism has been increasingly observed in many diseases, but a deeper, mechanistic understanding of the cellular impact of altered iron metabolism is still lacking. In addition, deficits in neuronal energy metabolism due to reduced glucose import were described for Alzheimer's disease (AD) and its comorbidities like obesity, depression, cardiovascular disease, and type 2 diabetes mellitus. The aim of this review is to present the molecular link between both observations. Insufficient cellular glucose uptake triggers increased ferritin expression, leading to depletion of the cellular free iron pool and stabilization of the hypoxia-induced factor (HIF) 1α. This transcription factor induces the expression of the glucose transporters (Glut) 1 and 3 and shifts the cellular metabolism towards glycolysis. If this first line of defense is not adequate for sufficient glucose supply, further reduction of the intracellular iron pool affects the enzymes of the mitochondrial electron transport chain and activates the AMP-activated kinase (AMPK). This enzyme triggers the translocation of Glut4 to the plasma membrane as well as the autophagic recycling of cell components in order to mobilize energy resources. Moreover, AMPK activates the autophagic process of ferritinophagy, which provides free iron urgently needed as a cofactor for the synthesis of heme- and iron-sulfur proteins. Excessive activation of this pathway ends in ferroptosis, a special iron-dependent form of cell death, while hampered AMPK activation steadily reduces the iron pools, leading to hypoferremia with iron sequestration in the spleen and liver. Long-lasting iron depletion affects erythropoiesis and results in anemia of chronic disease, a common condition in patients with AD and its comorbidities. Instead of iron supplementation, drugs, diet, or phytochemicals that improve energy supply and cellular glucose uptake should be administered to counteract hypoferremia and anemia of chronic disease.

Interferon-γ induces salivary gland epithelial cell ferroptosis in Sjogren's syndrome via JAK/STAT1-mediated inhibition of system Xc. Free Radic Biol Med 2023;205:116-128. [PMID: 37286044 DOI: 10.1016/j.freeradbiomed.2023.05.027]

The elevated level of interferon-γ (IFN-γ) in Sjogren's syndrome (SS) triggers salivary gland epithelial cells (SGEC) death. However, the underlying mechanisms of IFN-γ-induced SGEC death modes are still not fully elucidated. We found that IFN-γ triggers SGEC ferroptosis via Janus kinase/signal transducer and activator of transcription 1 (JAK/STAT1)-mediated inhibition of cystine-glutamate exchanger (System Xc-). Transcriptome analysis revealed that ferroptosis-related markers are differentially expressed in SS human and mouse salivary glands with distinct upregulation of IFN-γ and downregulation of glutathione peroxidase 4 (GPX4) and aquaporin 5 (AQP5). Inducing ferroptosis or IFN-γ treatment in the Institute of cancer research (ICR) mice aggravated and inhibition of ferroptosis or IFN-γ signaling in SS model non-obese diabetic (NOD) mice alleviated ferroptosis in the salivary gland and SS symptoms. IFN-γ activated STAT1 phosphorylation and downregulated system Xc- components solute carrier family 3 member 2 (SLC3A2), glutathione, and GPX4 thereby triggering ferroptosis in SGEC. JAK or STAT1 inhibition in SGEC rescued IFN-γ-downregulated SLC3A2 and GPX4 as well as IFN-γ-induced cell death. Our results indicate the role of ferroptosis in SS-related death of SGEC and SS pathogenicity.

Differences in Hepatocellular Iron Metabolism Underlie Sexual Dimorphism in Hepatocyte Ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe 2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe 2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Harnessing the Potential of Non-Apoptotic Cell Death Processes in the Treatment of Drug-Resistant Melanoma

Melanoma is a highly malignant skin cancer that is known for its resistance to treatments. In recent years, there has been significant progress in the study of non-apoptotic cell death, such as pyroptosis, ferroptosis, necroptosis, and cuproptosis. This review provides an overview of the mechanisms and signaling pathways involved in non-apoptotic cell death in melanoma. This article explores the interplay between various forms of cell death, including pyroptosis, necroptosis, ferroptosis, and cuproptosis, as well as apoptosis and autophagy. Importantly, we discuss how these non-apoptotic cell deaths could be targeted as a promising therapeutic strategy for the treatment of drug-resistant melanoma. This review provides a comprehensive overview of non-apoptotic processes and gathers recent experimental evidence that will guide future research and eventually the creation of treatment strategies to combat drug resistance in melanoma.

Liver specific disruption of Glutaredoxin 3 leads to iron accumulation and impaired cellular iron homeostasis

The role mammalian glutaredoxin 3 (Grx3) plays in iron homeostasis is poorly understood. Here we report the generation and characterization of a Grx3 liver-specific knockout (LKO) mouse strain. Grx3 LKO and WT mice had similar growth however, the LKO mice had elevated iron concentration and ROS production leading to impaired liver function and altered cytosolic and nuclear Fe-S cluster assembly. The expression of hepatic FTH1 and other iron homeostasis genes appeared to correlate with the elevation in iron concentration. Interestingly, this increase in hepatic FTH1 showed an inverse correlation with the abundance of autophagy pathway proteins. These findings suggest a crucial role for Grx3 in regulating hepatocyte iron homeostasis by controlling cellular storage protein turnover and recycling via the autophagy pathway.

Cross-talk between autophagy and ferroptosis contributes to the liver injury induced by fluoride via the mtROS-dependent pathway

Fluoride can induce hepatotoxicity, but the mechanisms responsible are yet to be investigated. This study sought to investigate the role and mechanism of mitochondrial reactive oxygen species (mtROS), autophagy, and ferroptosis in fluoride-induced hepatic injury with a focus on the role of mtROS-mediated cross-talk between autophagy and ferroptosis. To this end, an in vivo Sprague-Dawley rat model and in vitro BRL3A cells were exposed to sodium fluoride (NaF). The results revealed that NaF exposure diminished the mitochondrial membrane potential, increased mtROS production and TOMM20 expression, and induced autophagic flux blockage and ferroptosis in vivo and in vitro. Furthermore, the autophagy activator (RAPA) enhanced GPX4 expression while inhibiting ACSL4 expression, reduced the accumulation of ferrous ions in BRL3A cells, and restored lipid peroxidation levels, thus inhibiting ferroptosis. Fer-1, a ferritinase inhibitor, downregulated the expression of LC3-II and p62, increased the number of autolysosomes while decreasing the number of autophagosomes, and alleviated the blockage of autophagic flux by improving autophagic degradation. These results suggest the occurrence of a cross-talk between autophagy and ferroptosis. The mtROS inhibitor (Mito-TEMPO) could alleviate autophagic flux blockage and inhibit ferroptosis in NaF-induced liver injury. In addition, the cross-talk between NaF-induced autophagy and ferroptosis was dependent on the mtROS pathway.