Sex differences in resilience to ferroptosis underlie sexual dimorphism in kidney injury and repair

Proprotein convertase subtilisin/kexin type 9 contributes to cisplatin-induced acute kidney injury by interacting with cyclase-associated protein 1 to promote megalin lysosomal degradation

Cisplatin-induced acute kidney injury (AKI) is associated with a considerable risk of mortality, highlighting the critical need for effective preventive and therapeutic strategies to mitigate its impact on patients' outcomes. Mounting evidence suggests that administration of the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor evolocumab significantly reduces the risk of AKI, however, the underlying mechanisms remain poorly understood. Megalin is an endocytic receptor that plays a crucial role in tubular cells. In this study, elevated PCSK9 expression, accompanied by decreased megalin expression, was observed in cellular and murine models of cisplatin-induced AKI. Further experiments revealed that PCSK9 overexpression downregulated megalin expression and promoted tubular injury. Additionally, the PCSK9 inhibitor evolocumab inhibited megalin loss and protected against increases in urinary protein levels, blood urea nitrogen, serum creatinine, and the kidney injury markers neutrophil gelatinase-associated lipocalin and kidney injury molecule 1. Mechanistically, PCSK9 binds to megalin and facilitates its lysosomal degradation through the coordinated actions of cyclase-associated protein 1 (CAP1) and human leukocyte antigen C (HLA-C). Similar to evolocumab, CAP1 deletion significantly protected against megalin loss and mitigated tubular injury both in vitro and in vivo. Collectively, these findings suggest that PCSK9 and CAP1 are potential therapeutic targets for patients with cisplatin-induced AKI.

Can ferroptosis be a target for reproductive health?

Ferroptosis has been implicated in several reproductive disorders, but the underlying mechanisms remain unknown; thus, interventions targeting this pathway are lacking. Here we summarize the emerging findings on ferroptosis in reproductive biology and corresponding disorders, and highlight perspectives and challenges on future ferroptosis research with potential clinical applications.

Multi-omic and spatial analysis of mouse kidneys highlights sex-specific differences in gene regulation across the lifespan

There is a sex bias in the incidence and progression of many kidney diseases. To better understand such sexual dimorphism, we integrated data from six platforms, characterizing 76 kidney samples from 68 mice at six developmental and adult time points, creating a molecular atlas of the mouse kidney across the lifespan for both sexes. We show that proximal tubules have the most sex-biased differentially expressed genes emerging after 3 weeks of age and are associated with hormonal regulations. We reveal potential mechanisms involving both direct and indirect regulation by androgens and estrogens. Spatial profiling identifies distinct sex-biased spatial patterns in the cortex and outer stripe of the outer medulla. Additionally, older mice exhibit more aging-related gene alterations in loops of Henle, proximal tubules and collecting ducts in a sex-dependent manner. Our results enhance the understanding of spatially resolved gene expression and hormone regulation underlying kidney sexual dimorphism across the lifespan.

Phospholipids and peroxisomes in ferroptosis: the therapeutic target of acupuncture regulating vascular cognitive impairment and dementia

Ferroptosis, since its conceptualization in 2012, has witnessed an exponential growth in research interest over recent years. It is regulated by various cellular metabolic pathways during chronic cerebral ischemia and hypoxia, including reactive oxygen species (ROS) generation, iron accumulation, abnormalities in glutathione metabolism, and disruptions in lipid and glucose metabolism. With the deepening and widespread research, ferroptosis has emerged as a critical pathway in the pathogenesis of vascular cognitive impairment and dementia (VCID). This unique cell death pathway caused by iron-dependent phospholipid peroxidation is strongly related to VICD. We examine the impact of phospholipid composition on neuronal susceptibility to ferroptosis, with a particular focus on the critical role of polyunsaturated fatty acids (PUFAs) in this process. Intriguingly, peroxisomes, as key regulators of lipid metabolism and oxidative stress, influence the susceptibility of neuronal cells to ferroptosis through the synthesis of plasmalogens and other lipid species. In this Review, we provide a critical analysis of the current molecular mechanisms and regulatory networks of acupuncture for ferroptosis, the potential functions of acupuncture in peroxisomal functions and phospholipid metabolism, and its neuroprotective effects in VCID, together with a potential for therapeutic targeting. As such, this highlights the theoretical basis for the application of acupuncture in VCID through multi-target regulation of ferroptosis. This review underscores the potential of acupuncture as a non-pharmacological therapeutic approach in VCID, offering new insights into its role in modulating ferroptosis and associated metabolic pathways for neuroprotection.

Recommendations for robust and reproducible research on ferroptosis

Ferroptosis is a necrotic, non-apoptotic cell death modality triggered by unrestrained iron-dependent lipid peroxidation. By unveiling the regulatory mechanisms of ferroptosis and its relevance to various diseases, research over the past decade has positioned ferroptosis as a promising therapeutic target. The rapid growth of this research field presents challenges, associated with potentially inadequate experimental approaches that may lead to misinterpretations in the assessment of ferroptosis. Typical examples include assessing whether an observed phenotype is indeed linked to ferroptosis, and selecting appropriate animal models and small-molecule modulators of ferroptotic cell death. This Expert Recommendation outlines state-of-the-art methods and tools to reliably study ferroptosis and increase the reproducibility and robustness of experimental results. We present highly validated compounds and animal models, and discuss their advantages and limitations. Furthermore, we provide an overview of the regulatory mechanisms and the best-studied players in ferroptosis regulation, such as GPX4, FSP1, SLC7A11 and ACSL4, discussing frequent pitfalls in experimental design and relevant guidance. These recommendations are intended for researchers at all levels, including those entering the expanding and exciting field of ferroptosis research.

Mechanisms of ferroptosis sensitization and resistance

Ferroptosis is an iron-dependent and oxidative form of non-apoptotic cell death with roles in development, homeostasis, and disease. Ferroptosis sensitivity can vary between cells, often for reasons that are not well understood. In this perspective, we describe the core ferroptosis mechanism and outline how changes in iron, redox, and lipid metabolism can alter ferroptosis sensitivity. We propose the concept of a ferroptosis sensitivity-resistance continuum to describe how different intrinsic and extrinsic factors interact to push cells toward a more ferroptosis-sensitive or ferroptosis-resistant state, with effects on development and diseases such as cancer.

Warm-ischemia and cold storage induced modulation of ferroptosis observed in human hearts donated after circulatory death and brain death

We investigated ferroptosis, a type of programmed cell death mechanism, in human hearts donated after brain death (DBD) and those donated after circulatory death (DCD), focusing on warm ischemia time (WIT) and cold storage. A total of 24 hearts were procured, with six from the DBD group and 18 from the DCD group. The DCD group was divided into three subgroups, each containing six hearts, based on different WITs of 20, 40, and 60 min. All procured hearts were placed in cold storage for up to 6 h. Left ventricular biopsies were performed at 0, 2, 4, and 6 h. We measured ferroptosis regulators [glutathione peroxidase 4 (GPX4), acyl-CoA synthetase long chain family member 4 (ACSL4), and transferrin receptor], iron content (Fe2+ and Fe3+), and lipid peroxidation (malondialdehyde, MDA) in the cardiac tissue. Modulation of ferroptosis was observed in both DBD and DCD hearts. Warm ischemia injury increased myocardial vulnerability to ferroptotic cell death. For DBD hearts, up to 6 h of cold storage increases cardiac levels of MDA, iron content, and ACSL4, thereby increasing vulnerability to ferroptotic cell death. In contrast, for DCD hearts with a WIT of 40 min or more, warm ischemia injury was identified as the primary factor contributing to increased myocardial susceptibility to ferroptotic cell death. Ferroptosis may serve as a promising target to optimize cold preservation for DBD hearts. For DCD hearts, strategies to inhibit ferroptosis should focus on the early warm ischemia phase to assess donor heart quality and suitability for transplantation.NEW & NOTEWORTHY The first human heart research explored the effects of ischemia on the myocardial ferroptotic cell death mechanism. Prolonged cold storage increases the susceptibility of DBD hearts to ferroptotic cell death. In contrast, warm ischemic injury appears to be the main factor leading to the vulnerability of DCD heart ferroptosis. Targeting ferroptosis could be beneficial in optimizing cold preservation for DBD hearts. However, for DCD hearts, interventions should focus on the early phase of warm ischemia.

Protective role of vitamin D receptor against mitochondrial calcium overload from PM2.5-Induced injury in renal tubular cells

PURPOSE

This research explores the consequences of being exposed to PM2.5 contribute to renal injury while also evaluating the protective role of Vitamin D-VDR signaling in alleviating mitochondrial calcium imbalance and oxidative stress in renal tubular cells.

METHODS

Animal models of chronic PM2.5 exposure were used to simulate environmental conditions in wild type and VDR-overexpressing mice specific to renal tubules. In parallel, HK-2 cell lines were treated with PM2.5 in vitro. Mitochondrial function, calcium concentration, and oxidative stress markers were assessed. VDR activation, achieved through genetic overexpression and paricalcitol, was induced to examine its effect on mitochondrial calcium uniporter (MCU) expression and mitochondrial calcium regulation.

RESULTS

PM2.5 exposure caused significant mitochondrial damage in renal tubular cells, including mitochondrial calcium overload, increased oxidative stress, reduced membrane potential, and diminished ATP production. Elevated MCU expressions were a key contributor to these disruptions. VDR activation effectively reversed these effects by downregulating MCU, restoring mitochondrial calcium balance, reducing oxidative stress, and improving renal function.

CONCLUSION

This study shows that activating Vitamin D-VDR signaling shields the kidneys from PM2.5-induced damage by reestablishing mitochondrial calcium balance and lowering oxidative stress via inhibition of the MCU. These results unveil a new protective role of VDR in defending against environmental pollutants and suggest that targeting the MCU could offer a potential therapeutic strategy for treating chronic kidney disease linked to pollution exposure.

Sex, Acute Kidney Injury, and Age: A Prospective Cohort Study

RATIONALE & OBJECTIVE

Animal models of kidney disease suggest a protective role for female sex hormones, but some authorities assert that female sex in humans is a risk factor for acute kidney injury (AKI). To better understand the risk of AKI, we studied the strength of association between sex and AKI incidence in hormonally distinct age groups across the life span.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

All patients hospitalized in the Montefiore Health System between October 15, 2015, and January 1, 2019, excluding those with kidney failure or obstetrics diagnoses.

EXPOSURE

Male versus female sex.

OUTCOME

AKI occurring during hospitalization based on KDIGO definitions.

ANALYTICAL APPROACH

Generalized estimating equation logistic regression adjusted for comorbidities, sociodemographic factors, and severity of illness. Analyses were stratified into 3 age categories: 6 months to≤16 years,>16 years to<55 years, and≥55 years.

RESULTS

A total of 132,667 individuals were hospitalized a total of 235,629 times. The mean age was 55.2±23.8 (SD) years. The count of hospitalizations for women was 129,912 (55%). Hospitalization count among Black and Hispanic patients was 71,834 (30.5%) and 24,199 (10.3%), respectively. AKI occurred in 53,926 (22.9%) hospitalizations. In adjusted models, there was a significant interaction between age and sex (P<0.001). Boys and men had a higher risk of AKI across all age groups, an association more pronounced in the age group>16 years to<55 years in which the odds ratio for men was 1.7 (95% CI, 1.6-1.8). This age-based pattern remained consistent across prespecified types of hospitalizations. In a sensitivity analysis, women older than 55 years who received prescriptions for estrogen had lower odds of AKI than those without prescriptions.

LIMITATIONS

Residual confounding.

CONCLUSIONS

The greatest relative risk of AKI for males occurred during ages>16 to<55 years. The lower risk among postmenopausal women receiving supplemental estrogen supports a protective role for female sex hormones.

PLAIN-LANGUAGE SUMMARY

Male sex is a risk factor for acute kidney injury (AKI) in animals, but in human studies this association is not as robust. We studied hospitalizations at a single center to examine the association of hospital-acquired AKI and sex. After controlling for various sources of potential bias and stratifying by age categories through the life course, we observed that men have a higher risk of AKI throughout life. This risk was especially high compared with women of fertile age and older women prescribed estrogen. This pattern was consistent in prespecified subgroups of hospitalizations. These results support a protective role for female sex hormones in the occurrence of hospitalized AKI.

Persistent subclinical renal injury in female rats following renal ischemia-reperfusion injury

The incidence of acute kidney injury (AKI) continues to rise in both men and women. Although creatinine levels return to normal quicker in females following AKI than in males, it remains unclear whether subclinical renal injury persists in young females post-AKI. This study tested the hypothesis that AKI results in subclinical renal injury in females despite plasma creatinine returning to sham levels. For the present study, 12-13-week-old female Sprague-Dawley (SD) rats were randomized to sham or 45-minute warm bilateral ischemia-reperfusion surgery as an experimental model of ischemic AKI. Rats were euthanized 1, 3, 7, 14, or 30 days post-AKI/sham. Plasma creatinine, cystatin C, kidney injury molecule 1 (KIM-1), and NGAL were quantified via assay kits or immunoblotting. Kidneys were processed for histological analysis to assess tubular injury and fibrosis, and for electron microscopy to examine mitochondrial morphology. Immunoblots on kidney homogenates were performed to determine oxidative stress and apoptosis. Plasma creatinine levels were increased 24 hours post-AKI but returned to sham control levels three days post-AKI. However, cystatin C, KIM-1, and NGAL were increased 30 days post-AKI compared with sham. Tubular injury, tubulointerstitial fibrosis, and mitochondrial dysfunction were all increased in 30-day post-AKI rats compared with sham. Additionally, 30-day post-AKI rats had higher p-JNK expression and lower antioxidant enzyme glutathione peroxidase and catalase levels compared with sham. AKI resulted in higher expression of cleaved caspase 3, TUNEL+ cells, and caspase 9 than sham. Despite the normalization of creatinine levels, our data support the hypothesis that subclinical renal injury persists following ischemia-reperfusion injury in young female rats.

Associations of Systemic Immune-Inflammation Index With Mortality Risk Among Adults in Diabetic Kidney Disease, NHANES 1999 to 2018

OBJECTIVES

Immune-inflammation plays a crucial role in the pathogenesis of diabetic kidney disease (DKD), but an exact assessment of indicators remains undefined. In this study we address the link between systemic immune-inflammation index (SII) and mortality risk in DKD, and we explore the effect of sex disparities.

METHODS

Data from patients with DKD from the National Health and Nutritional Examination Surveys (NHANES, 1999 to 2018) were studied and their causes of death were identified from NHANES-related files. A weighted Cox model was used to evaluate hazard ratios for all-cause, cardiovascular, and cardiocerebrovascular mortality, and these associations were visualized by smoothing curves.

RESULTS

The average SII was 634.20 (103/μL). There were 1,283 deaths recorded during 273,422 person months (396 were cardiovascular related and 461 were cardiocerebrovascular related). Higher SIIs in the fifth quintile were significantly associated with increased mortality (p<0.01). SII trends showed an increased risk of all-cause mortality of >697.0 (103/μL), cardiovascular risk of >717.8 (103/μL), and cardiocerebrovascular risk of >650.0 (103/μL). In men, mortality increased when SII reached 500 to 660 (103/μL) and 700 to 760 (103/μL) for women.

CONCLUSIONS

There was a significant association between higher SII and increased risk of all-cause, cardiovascular, and cardiocerebrovascular mortality in DKD patients. In addition, although men had lower SII, their mortality was higher than that of women.

Targeting allograft inflammatory factor 1 reprograms kidney macrophages to enhance repair

The role of macrophages (MΦs) remains incompletely understood in kidney injury and repair. The plasticity of MΦs offers an opportunity to polarize them toward mediating injury resolution in both native and transplanted kidneys undergoing ischemia and/or rejection. Here, we show that infiltrating kidney MΦs augmented their own allograft inflammatory factor 1 (AIF-1) expression after injury. Aif1 genetic deletion led to MΦ polarization toward a reparative phenotype while halting the development of kidney fibrosis. The enhanced repair was mediated by higher levels of antiinflammatory and proregenerative markers, leading to a reduction in cell death and an increase in proliferation of kidney tubular epithelial cells after ischemia followed by reperfusion injury (I/RI). Adoptive transfer of Aif1-/- MΦs into Aif1+/+ mice conferred protection against I/RI. Conversely, depletion of MΦs reversed the tissue-reparative effects in Aif1-/- mice. We further demonstrated increased expression of AIF-1 in human kidney biopsies from native kidneys with acute kidney injury or chronic kidney disease, as well as in biopsies from kidney allografts undergoing acute or chronic rejection. We conclude that AIF-1 is a MΦ marker of renal inflammation, and its targeting uncouples MΦ reparative functions from profibrotic functions. Thus, therapies inhibiting AIF-1 when ischemic injury is inevitable have the potential to reduce the global burden of kidney disease.

Testosterone deficiency aggravates diet-induced non-alcoholic fatty liver disease by inducing hepatocyte ferroptosis via targeting BMAL1 in mice

BACKGROUND

Testosterone deficiency is linked to an increased prevalence of non-alcoholic fatty liver disease (NAFLD), although the mechanisms underlying this association are not fully understood. Ferroptosis, a regulated cell death pathway driven by iron-dependent lipid peroxidation, has been suggested to play a role in NAFLD pathogenesis. Since testosterone deficiency is associated with lipid disorders and iron deposition, we hepothesize that ferroptosis may be involved in the pathogenesis of diet-induced NAFLD exacerbated by testosterone deficiency.

METHODS

Apolipoprotein E (APOE-/-) mice were subjected to sham surgery or bilateral castration and subsequently fed a high-fat diet for 16 weeks. Liver gene expression was analyzed using RNA sequencing. Additional assessments included blood analysis, histological staining, measurement of iron and antioxidant enzyme levels, quantitative real-time PCR, Western blotting, and electron microscopy. The effects of testosterone on ferroptosis induced by free fatty acids (FFAs) and Erastin were further investigated in HepG2 cells in vitro.

RESULTS

Testosterone deficiency resulted in increased hepatic lipid accumulation and macrovesicular steatosis in high-fat diet-fed APOE-/- mice, accompanied by hepatic inflammation, fibrosis, and elevated liver enzyme levels. Transcriptomic analysis revealed that testosterone deficiency affects ferroptosis and circadian rhythm-related signaling pathways. Castrated APOE-/- mice exhibited significantly higher hepatic iron deposition, lipid peroxidation, and expression of key ferroptosis-related proteins, along with decreased Brain and muscle ARNT-like gene 1 (BMAL1) protein expression. In vitro, testosterone treatment reduced lipid and iron accumulation and lipid peroxidation in HepG2 cells subjected to FFAs and Erastin. Moreover, BMAL1 knockdown negated the protective effects of testosterone against ferroptosis in hepatocytes.

CONCLUSION

Our study demonstrated that testosterone deficiency exacerbates NAFLD induced by a high-fat diet by promoting hepatocyte ferroptosis through modulation of the circadian protein BMAL1.

Intestinal Cyp24a1 regulates vitamin D locally independent of systemic regulation by renal Cyp24a1 in mice

Vitamin D regulates mineral homeostasis. The most biologically active form of vitamin D, 1,25-dihydroxyvitamin D (1,25D), is synthesized by CYP27B1 from 25-dihydroxyvitamin D (25D) and is inactivated by CYP24A1. Human monogenic diseases and genome-wide association studies support a critical role for CYP24A1 in regulation of mineral homeostasis, but little is known about its tissue-specific effects. Here, we describe the responses of mice with inducible global deletion, kidney-specific, and intestine-specific deletion of Cyp24a1 to dietary calcium challenge and chronic kidney disease (CKD). Global and kidney-specific Cyp24a1 deletion caused similar syndromes of systemic vitamin D intoxication: elevated circulating 1,25D, 25D, and fibroblast growth factor 23 (FGF23), activation of vitamin D target genes in the kidney and intestine, hypercalcemia, and suppressed parathyroid hormone (PTH). In contrast, mice with intestine-specific Cyp24a1 deletion demonstrated activation of vitamin D target genes exclusively in the intestine, despite no changes in systemic vitamin D levels. In response to a high calcium diet, PTH was suppressed, despite normal serum calcium. In mice with CKD, intestinal Cyp24a1 deletion decreased PTH and FGF23 without precipitating hypercalcemia. These results implicate kidney CYP24A1 in systemic vitamin D regulation while independent local effects of intestinal CYP24A1 could be targeted to treat secondary hyperparathyroidism in CKD.

JP4-039 Mitigates Cisplatin-Induced Acute Kidney Injury by Inhibiting Oxidative Stress and Blocking Apoptosis and Ferroptosis in Mice

Cisplatin is a commonly used chemotherapeutic agent in the treatment of a wide array of cancers. Due to its active transport into the kidney proximal tubule cells, cisplatin treatment can cause a buildup of this nephrotoxic compound in the kidney, resulting in acute kidney injury (AKI). About 30% of patients receiving cisplatin chemotherapy develop cisplatin-induced AKI. JP4-039 is a mitochondria-targeted reactive oxygen species (ROS) and electron scavenger. Recent studies have shown that JP4-039 mitigates a variety of genotoxic insults in preclinical studies in rodents by suppressing oxidative stress-mediated tissue damage and blocking apoptosis and ferroptosis. However, the benefits of JP4-039 treatment have not been tested in the setting of AKI. In this study, we investigated the potential renoprotective effect of JP4-039 on cisplatin-induced AKI. To address this goal, we treated mice with JP4-039 before or after cisplatin administration and analyzed them for functional and molecular changes in the kidney. JP4-039 co-administration attenuated cisplatin-induced renal dysfunction and histopathological changes. Upregulation of tubular injury markers was also suppressed by JP4-039. Mechanistically, JP4-039 suppressed lipid peroxidation, prevented tissue oxidative stress, and preserved the glutathione levels in cisplatin-injected mice. An increase in cisplatin-induced apoptosis and ferroptosis was also alleviated by the compound. Moreover, JP4-039 inhibited cytokine overproduction in cisplatin-injected mice. Together, our findings demonstrate that JP4-039 is a promising therapeutic agent against cisplatin-induced kidney injury.

Liver iron stores and effectors of ferroptosis are dependent on age and sex

Ferroptosis is a form of cell death characterized by a pro-oxidative cellular milieu and iron-dependent lipid peroxidation. Ferroptosis has been implicated in various forms of liver injury, in keeping with the major role of the liver in iron metabolism. Limited research has addressed potential differences in ferroptosis mediators with age and sex, especially in an in vivo model. The goal of this investigation was to evaluate hepatic labile iron and mediators of ferroptosis with ageing in both sexes. Because female animals generally display greater antioxidant defences than males, we hypothesized that females would display a phenotype resistant to ferroptosis. Here, we determined iron contents, protein expression of ferroptosis mediators and measures of oxidative injury in liver samples from 12- and 24-month-old male and female Fischer 344 rats. In comparison to males, the livers of female rats at both ages contained more non-haem iron, which was associated with greater ferritin heavy chain expression and attenuated expression of transferrin receptor-1. In female rats, the 24-month-old group had higher contents of thiobarbituric acid reactive substances compared with their 12-month-old counterparts, yet similar contents of labile iron. These results suggest a disconnect between labile iron contents and oxidative injury with age. Female animals also displayed greater expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), a modulator of ferroptosis, and greater abundance of high molecular weight 4-hydroxnonenal-modified proteins. These results demonstrate clear differences in iron and ferroptosis mediators between sexes and suggest that female rats of this strain might be more susceptible to ferroptosis.

TGFβ2-Driven Ferritin Degradation and Subsequent Ferroptosis Underlie Salivary Gland Dysfunction in Postmenopausal Conditions

Despite the high incidence of dry mouth in postmenopausal women, its underlying mechanisms and therapeutic interventions remain underexplored. Using ovariectomized (OVX) mouse models, here this study identifies ferroptosis, an iron-dependent regulated cell death, as a central mechanism driving postmenopausal salivary gland (SG) dysfunction. In the OVX-SGs, TGFβ signaling pathway is enhanced with the aberrant TGFβ2 expression in SG mesenchymal cells. Intriguingly, TGFβ2 treatment reduces iron-storing ferritin levels, leading to lipid peroxidation and ferroptotic death in SG epithelial organoids (SGOs). Mechanistically, TGFβ2 promotes the autophagy-mediated ferritin degradation, so-called ferritinophagy. A notable overexpression of the type III TGFβ receptor (TβRIII) is found in the OVX-SGs and TGFβ2-treated SGOs, while the silencing of TβRIII mitigates the ferroptosis-mediated deleterious effects of TGFβ2 on SGOs. Finally, administration of ferroptosis inhibitor, Liproxstatin-1 (Lip-1), improves saliva secretion in OVX mice. Present findings collectively suggest a link between TGFβ signaling, ferroptosis, and SG injury, offering new therapeutic avenues for postmenopausal xerostomia.

Serum apolipoprotein H determines ferroptosis resistance by modulating cellular lipid composition

Ferroptosis is a regulated cell death process dependent on iron, triggered by the accumulation of lipid peroxidation. The environmental context significantly impacts cellular sensitivities to ferroptosis. Serum, constituting the extracellular fluid composition in vivo, provides crucial environmental biomolecules. In this study, we investigated the influence of sera on ferroptosis induction, pinpointing the serum protein apolipoprotein H (APOH) as a pivotal inhibitor of ferroptosis. Moreover, we elucidated that APOH suppresses ferroptosis by activating the phosphoinositide 3-kinase (PI3K)-AKT-sterol regulatory element-binding proteins (SREBPs) pathway, thereby elevating stearoyl-CoA desaturase (SCD) levels and augmenting cellular monounsaturated fatty acid-containing phospholipids (MUFA-PLs). Furthermore, ApoHinfer, the peptide derivative of the active region of APOH, mimics its ferroptosis inhibitory activity. Our findings underscore the critical role of serum protein APOH in the inhibition of ferroptosis and indicates potential therapeutic applications in treating cancer and diseases associated with ferroptosis.

Sex Differences in Doxorubicin‐Induced Cardiotoxicity: Insights from Transcriptome Analysis

Male patients have a higher risk of cardiotoxicity following doxorubicin (DOX) treatment than female patients. However, how this difference occurs at the transcriptome level remains unclear, and the mechanisms underlying these differences are understudied. This study aimed to describe the transcriptional patterns of males and females after DOX treatment and explore the possible mechanisms of sexual differences in DOX‐induced cardiotoxicity. Following DOX treatment, male mice exhibit more severe heart damage than female mice. Transcriptome analysis of mice with and without DOX treatment showed that differentially expressed genes (DEGs) are significantly different between males and females. The majority of DEGs are sex‐specific, and more DEGs are identified in males than females. A number of genes, including the oxidation‐related genes Gdf15 and Rbm3, exhibited altered expression either in males or females. Some other genes, including the ferroptosis‐related gene Cd74, changed their expression levels in both sexes, but at different scales. Biochemical experiments suggested that cardiomyocyte oxidation and ferroptosis may contribute to the sexual dimorphism of DOX‐induced cardiotoxicity. In summary, this study shows that, after exposure to DOX, males and females respond differently regarding the expression of hundreds of genes, including Gdf15, Rbm3, and Cd74, possibly explaining the sexual differences in DOX‐induced cardiotoxicity.

Gene regulation in regeneration after acute kidney injury

Acute kidney injury (AKI) is a common condition associated with significant morbidity, mortality, and cost. Injured kidney tissue can regenerate after many forms of AKI. However, there are no treatments in routine clinical practice to encourage recovery. In part, this shortcoming is due to an incomplete understanding of the genetic mechanisms that orchestrate kidney recovery. The advent of high-throughput sequencing technologies and genetic mouse models has opened an unprecedented window into the transcriptional dynamics that accompany both successful and maladaptive repair. AKI recovery shares similar cell-state transformations with kidney development, which can suggest common mechanisms of gene regulation. Several powerful bioinformatic strategies have been developed to infer the activity of gene regulatory networks by combining multiple forms of sequencing data at single-cell resolution. These studies highlight not only shared stress responses but also key changes in gene regulatory networks controlling metabolism. Furthermore, chromatin immunoprecipitation studies in injured kidneys have revealed dynamic epigenetic modifications at enhancer elements near target genes. This review will highlight how these studies have enhanced our understanding of gene regulation in injury response and regeneration.

Association between nonalcoholic steatohepatitis and high serum ferritin levels in type 2 diabetes mellitus

OBJECTIVE

The aim of this study was to assess the role of elevated serum ferritin levels in the onset, pathological progression and prognosis of nonalcoholic fatty liver disease. Nonalcoholic fatty liver disease has been rapidly increasing worldwide. Despite extensive research on the pathogenesis of nonalcoholic fatty liver disease, a lack of sufficient clinical research on the relationship between nonalcoholic fatty liver disease and serum ferritin levels remains.

METHODS

We analysed 968 patients with type 2 diabetes mellitus who underwent liver ultrasound examination and had their serum ferritin levels measured. The presence of nonalcoholic fatty liver disease and advanced liver fibrosis was determined through abdominal ultrasound examination and the nonalcoholic fatty liver disease fibrosis score.

RESULTS

Compared to that in the non-nonalcoholic fatty liver disease group, the presence of hyperferritinemia was significantly more common in the nonalcoholic fatty liver disease group (83.3 vs. 56.3%, p=0.005). When patients with nonalcoholic fatty liver disease were stratified by the nonalcoholic fatty liver disease fibrosis score, those with advanced liver fibrosis exhibited a higher prevalence of hyperferritinemia (56.3, 78.9, and 88.9% for none, simple steatosis, and advanced fibrosis, respectively; p for trend=0.002). In multivariate logistic regression, liver fibrosis was independently associated with hyperferritinemia (odds ratio [OR] 1.45; 95% confidence interval [CI] 1.18-2.02; p=0.014), and this association remained significant in male patients after adjusting for other risk factors (OR 2.66; 95% CI 1.43-5.48; p=0.026).

CONCLUSION

Identifying nonalcoholic fatty liver disease patients at a risk of developing nonalcoholic steatohepatitis and advanced fibrosis is crucial for implementing timely interventions and improving patient outcomes. This study highlights the potential utility of serum ferritin levels as a serum biomarker for identifying nonalcoholic steatohepatitis patients and those at a risk of late-stage fibrosis, particularly in male patients with nonalcoholic fatty liver disease.

The cell biology of ferroptosis

Ferroptosis is a non-apoptotic cell death mechanism characterized by iron-dependent membrane lipid peroxidation. Here, we review what is known about the cellular mechanisms mediating the execution and regulation of ferroptosis. We first consider how the accumulation of membrane lipid peroxides leads to the execution of ferroptosis by altering ion transport across the plasma membrane. We then discuss how metabolites and enzymes that are distributed in different compartments and organelles throughout the cell can regulate sensitivity to ferroptosis by impinging upon iron, lipid and redox metabolism. Indeed, metabolic pathways that reside in the mitochondria, endoplasmic reticulum, lipid droplets, peroxisomes and other organelles all contribute to the regulation of ferroptosis sensitivity. We note how the regulation of ferroptosis sensitivity by these different organelles and pathways seems to vary between different cells and death-inducing conditions. We also highlight transcriptional master regulators that integrate the functions of different pathways and organelles to modulate ferroptosis sensitivity globally. Throughout this Review, we highlight open questions and areas in which progress is needed to better understand the cell biology of ferroptosis.

Cell death‑related molecules and targets in the progression of urolithiasis (Review)

Urolithiasis is a high‑incidence disease caused by calcium oxalate (mainly), uric acid, calcium phosphate, struvite, apatite, cystine and other stones. The development of kidney stones is closely related to renal tubule cell damage and crystal adhesion and aggregation. Cell death, comprising the core steps of cell damage, can be classified into various types (i.e., apoptosis, ferroptosis, necroptosis and pyroptosis). Different crystal types, concentrations, morphologies and sizes cause tubular cell damage via the regulation of different forms of cell death. Oxidative stress caused by high oxalate or crystal concentrations is considered to be a precursor to a variety of types of cell death. In addition, complex crosstalk exists among numerous signaling pathways and their key molecules in various types of cell death. Urolithiasis is considered a metabolic disorder, and tricarboxylic acid cycle‑related molecules, such as citrate and succinate, are closely related to cell death and the inhibition of stone development. However, a literature review of the associations between kidney stone development, metabolism and various types of cell death is currently lacking, at least to the best of our knowledge. Thus, the present review summarizes the major advances in the understanding of regulated cell death and urolithiasis progression.

International consensus guidelines for the definition, detection, and interpretation of autophagy-dependent ferroptosis

Macroautophagy/autophagy is a complex degradation process with a dual role in cell death that is influenced by the cell types that are involved and the stressors they are exposed to. Ferroptosis is an iron-dependent oxidative form of cell death characterized by unrestricted lipid peroxidation in the context of heterogeneous and plastic mechanisms. Recent studies have shed light on the involvement of specific types of autophagy (e.g. ferritinophagy, lipophagy, and clockophagy) in initiating or executing ferroptotic cell death through the selective degradation of anti-injury proteins or organelles. Conversely, other forms of selective autophagy (e.g. reticulophagy and lysophagy) enhance the cellular defense against ferroptotic damage. Dysregulated autophagy-dependent ferroptosis has implications for a diverse range of pathological conditions. This review aims to present an updated definition of autophagy-dependent ferroptosis, discuss influential substrates and receptors, outline experimental methods, and propose guidelines for interpreting the results.Abbreviation: 3-MA:3-methyladenine; 4HNE: 4-hydroxynonenal; ACD: accidentalcell death; ADF: autophagy-dependentferroptosis; ARE: antioxidant response element; BH2:dihydrobiopterin; BH4: tetrahydrobiopterin; BMDMs: bonemarrow-derived macrophages; CMA: chaperone-mediated autophagy; CQ:chloroquine; DAMPs: danger/damage-associated molecular patterns; EMT,epithelial-mesenchymal transition; EPR: electronparamagnetic resonance; ER, endoplasmic reticulum; FRET: Försterresonance energy transfer; GFP: green fluorescent protein;GSH: glutathione;IF: immunofluorescence; IHC: immunohistochemistry; IOP, intraocularpressure; IRI: ischemia-reperfusion injury; LAA: linoleamide alkyne;MDA: malondialdehyde; PGSK: Phen Green™ SK;RCD: regulatedcell death; PUFAs: polyunsaturated fatty acids; RFP: red fluorescentprotein;ROS: reactive oxygen species; TBA: thiobarbituricacid; TBARS: thiobarbituric acid reactive substances; TEM:transmission electron microscopy.

Lineage tracing reveals transient phenotypic adaptation of tubular cells during acute kidney injury

Tubular injury is the hallmark of acute kidney injury (AKI) with a tremendous impact on patients and health-care systems. During injury, any differentiated proximal tubular cell (PT) may transition into a specific injured phenotype, so-called "scattered tubular cell" (STC)-phenotype. To understand the fate of this specific phenotype, we generated transgenic mice allowing inducible, reversible, and irreversible tagging of these cells in a murine AKI model, the unilateral ischemia-reperfusion injury (IRI). For lineage tracing, we analyzed the kidneys using single-cell profiling during disease development at various time points. Labeled cells, which we defined by established endogenous markers, already appeared 8 h after injury and showed a distinct expression set of genes. We show that STCs re-differentiate back into fully differentiated PTs upon the resolution of the injury. In summary, we show the dynamics of the phenotypic transition of PTs during injury, revealing a reversible transcriptional program as an adaptive response during disease.

Sex disparities in mortality and cardiovascular outcomes in chronic kidney disease

Sex (biologically determined) and gender (socially constructed) modulate manifestations and prognosis of a vast number of diseases, including cardiovascular disease (CVD) and chronic kidney disease (CKD). CVD remains the leading cause of death in CKD patients. Population-based studies indicate that women present a higher prevalence of CKD and experience less CVD than men in all CKD stages, although this is not as clear in patients on dialysis or transplantation. When compared to the general population of the same sex, CKD has a more negative impact on women on kidney replacement therapy. European women on dialysis or recipients of kidney transplants have life expectancy up to 44.8 and 19.8 years lower, respectively, than their counterparts of similar age in the general population. For men, these figures stand at 37.1 and 16.5 years, representing a 21% to 20% difference, respectively. Hormonal, genetic, societal, and cultural influences may contribute to these sex-based disparities. To gain a more comprehensive understanding of these differences and their implications for patient care, well-designed clinical trials that involve a larger representation of women and focus on sex-related variables are urgently needed. This narrative review emphasizes the importance of acknowledging the epidemiology and prognosis of sex disparities in CVD among CKD patients. Such insights can guide research into the underlying pathophysiological mechanisms, leading to optimized treatment strategies and ultimately, improved clinical outcomes.

Membrane Dynamics and Cation Handling in Ferroptosis

Ferroptosis, a regulated cell death hallmarked by excessive lipid peroxidation, is implicated in various (patho)physiological contexts. During ferroptosis, lipid peroxidation leads to a diverse change in membrane properties and the dysregulation of ion homeostasis via the cation channels, ultimately resulting in plasma membrane rupture. This review illuminates cellular membrane dynamics and cation handling in ferroptosis regulation.

Role of ferroptosis in chronic kidney disease

Chronic kidney disease (CKD) has historically been a significant global health concern, profoundly impacting both life and well-being. In the process of CKD, with the gradual loss of renal function, the incidence of various life-threatening complications, such as cardiovascular diseases, cerebrovascular accident, infection and stroke, is also increasing rapidly. Unfortunately, existing treatments exhibit limited ability to halt the progression of kidney injury in CKD, emphasizing the urgent need to delve into the precise molecular mechanisms governing the occurrence and development of CKD while identifying novel therapeutic targets. Renal fibrosis, a typical pathological feature of CKD, plays a pivotal role in disrupting normal renal structures and the loss of renal function. Ferroptosis is a recently discovered iron-dependent form of cell death characterized by lipid peroxide accumulation. Ferroptosis has emerged as a potential key player in various diseases and the initiation of organ fibrosis. Substantial evidence suggests that ferroptosis may significantly contribute to the intricate interplay between CKD and its progression. This review comprehensively outlines the intricate relationship between CKD and ferroptosis in terms of iron metabolism and lipid peroxidation, and discusses the current landscape of pharmacological research on ferroptosis, shedding light on promising avenues for intervention. It further illustrates recent breakthroughs in ferroptosis-related regulatory mechanisms implicated in the progression of CKD, thereby providing new insights for CKD treatment. Video Abstract.

A Nutrient-Deficient Microenvironment Facilitates Ferroptosis Resistance via the FAM60A-PPAR Axis in Pancreatic Ductal Adenocarcinoma

Ferroptosis, a nonapoptotic form of cell death, is an emerging potential therapeutic target for various diseases, including cancer. However, the role of ferroptosis in pancreatic cancer remains poorly understood. Pancreatic ductal adenocarcinoma (PDAC) is characterized by a poor prognosis and chemotherapy resistance, attributed to its high Kirsten rats arcomaviral oncogene homolog mutation rate and severe nutritional deficits resulting from a dense stroma. Several studies have linked rat sarcoma (RAS) mutations to ferroptosis, suggesting that inducing ferroptosis may be an effective strategy against oncogenic RAS-bearing tumors. We investigated the role of Family With Sequence Similarity 60 Member A (FAM60A) in this study, a protein closely associated with a poor prognosis and highly expressed in PDAC and tumor tissue from KrasG12D/+;Trp53R172H/+; Pdx1-Cre mice, in regulating ferroptosis, tumor growth, and gemcitabine sensitivity in vitro and in vivo. Our results demonstrate that FAM60A regulates 3 essential metabolic enzymes, ACSL1/4 and GPX4, to protect PDAC cells from ferroptosis. Furthermore, we found that YY1 transcriptionally regulates FAM60A expression by promoting its transcription, and the Hippo-YY1 pathway is restricted in the low-amino-acid milieu in the context of nutrient deprivation, leading to downstream suppression of peroxisome proliferator-activated receptor and ACSL1/4 and activation of GPX4 pathways. Importantly, FAM60A knockdown sensitized PDAC cells to gemcitabine treatment. A new understanding of FAM60A transcriptional regulation pattern in PDAC and its dual function in ferroptosis reliever and chemotherapy resistance is provided by our study. Targeting FAM60A may therefore offer a promising therapeutic approach for PDAC by simultaneously addressing 2 major features of the disease (high RAS mutation rate and tumor microenvironment nutrient deficiency) and preventing tumor cell metabolic adaptation.

Pax protein depletion in proximal tubules triggers conserved mechanisms of resistance to acute ischemic kidney injury preventing transition to chronic kidney disease

Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part, this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Identifying the molecular and genetic regulators unique to nephron segments that dictate vulnerability to injury and regenerative potential could lead to new therapeutic targets to treat ischemic kidney injury. Pax2 and Pax8 are homologous transcription factors with overlapping functions that are critical for kidney development and are re-activated in AKI. Here, we examined the role of Pax2 and Pax8 in recovery from ischemic AKI and found them upregulated after severe AKI and correlated with chronic injury. Surprisingly, proximal-tubule-selective deletion of Pax2 and Pax8 resulted in a less severe chronic injury phenotype. This effect was mediated by protection against the acute insult, similar to pre-conditioning. Prior to injury, Pax2 and Pax8 mutant mice develop a unique subpopulation of proximal tubule cells in the S3 segment that displayed features usually seen only in acute or chronic injury. The expression signature of these cells was strongly enriched with genes associated with other mechanisms of protection against ischemic AKI including caloric restriction, hypoxic pre-conditioning, and female sex. Thus, our results identified a novel role for Pax2 and Pax8 in mature proximal tubules that regulates critical genes and pathways involved in both the injury response and protection from ischemic AKI.

Integrin β1-rich extracellular vesicles of kidney recruit Fn1+ macrophages to aggravate ischemia-reperfusion-induced inflammation

Ischemia-reperfusion injury-induced (IRI-induced) acute kidney injury is accompanied by mononuclear phagocyte (MP) invasion and inflammation. However, systematic analysis of extracellular vesicle-carried (EV-carried) proteins mediating intercellular crosstalk in the IRI microenvironment is still lacking. Multiomics analysis combining single-cell RNA-Seq data of kidney and protein profiling of kidney-EV was used to elucidate the intercellular communication between proximal tubular cells (PTs) and MP. Targeted adhesion and migration of various MPs were caused by the secretion of multiple chemokines as well as integrin β1-rich EV by ischemic-damaged PTs after IRI. These recruited MPs, especially Fn1+ macrophagocyte, amplified the surviving PT's inflammatory response by secreting the inflammatory factors TNF-α, MCP-1, and thrombospondin 1 (THBS-1), which could interact with integrin β1 to promote more MP adhesion and interact with surviving PT to further promote the secretion of IL-1β. However, GW4869 reduced MP infiltration and maintained a moderate inflammatory level likely by blocking EV secretion. Our findings establish the molecular bases by which chemokines and kidney-EV mediate PT-MP crosstalk in early IRI and provide insights into systematic intercellular communication.

p53R245W Mutation Fuels Cancer Initiation and Metastases in NASH-driven Liver Tumorigenesis

Obesity is a significant global health concern. Non-alcoholic fatty liver disease and non-alcoholic steatohepatitis (NASH) are common risk factors for hepatocellular carcinoma (HCC) and are closely associated with metabolic comorbidities, including obesity and diabetes. The TP53 tumor suppressor is the most frequently mutated gene in liver cancers, with half of these alterations being missense mutations. These mutations produce highly abundant proteins in cancer cells which have both inhibitory effects on wildtype (WT) p53, and gain-of-function (GOF) activities that contribute to tumor progression. A Western diet increases p53 activity in the liver. To elucidate the functional consequences of Trp53 mutations in a NASH-driven liver tumorigenesis model, we generated somatic mouse models with Trp53 deletion or the missense hotspot mutant p53R245W only in hepatocytes and placed mice on a high-fat, choline-deficient diet. p53R245W in the presence of diet increased fatty liver, compensatory proliferation in the liver parenchyma, and enriched genes of tumor-promoting pathways such as KRAS signaling, MYC, and epithelial-mesenchymal transition when compared with controls in the premalignant liver. Moreover, p53R245W suppressed transcriptional activity of WT p53 in the liver in vivo under metabolic challenges, and shortened survival and doubling of HCC incidence as compared with control heterozygous mice. Complete loss of Trp53 also significantly accelerated liver tumor incidence and lowered time-to-tumor development compared with WT controls. p53R245W GOF properties increased carcinoma initiation, fueled mixed hepatocholangial carcinoma incidence, and tripled metastatic disease. Collectively, our in vivo studies indicate that p53R245W has stronger tumor promoting activities than Trp53 loss in the context of NASH.

SIGNIFICANCE

Using somatic NASH-driven mouse models with p53 deletion or mutant p53R245W only in hepatocytes, we discovered that p53R245W increased carcinoma initiation, fueled hepatocholangial carcinoma incidence, and tripled metastases.

Estradiol-mediated small GTP-binding protein GDP dissociation stimulator induction contributes to sex differences in resilience to ferroptosis in takotsubo syndrome

BACKGROUND

Declining beneficial cardiovascular actions of estradiol (E2) have been associated with disproportionate susceptibility to takotsubo syndrome (TTS) in postmenopausal women. However, the underlying mechanisms between E2 and this marked disproportion remain unclear. SmgGDS (small GTP-binding protein GDP dissociation stimulator), as a key modulator of cardiovascular disease, plays protective roles in reducing oxidative stress and exerts pleiotropic effects of statins. Whether SmgGDS levels are influenced by E2 status and the effect of SmgGDS on sex differences in TTS are poorly understood.

METHODS

Clinical data were reviewed from TTS inpatients. Echocardiography, immunofluorescence, and immunohistochemistry were performed together with expression analysis to uncover phenotypic and mechanism changes in sex differences in TTS-like wild-type (WT) and SmgGDS± mice. HL-1 cardiomyocytes were used to further examine and validate molecular mechanisms.

RESULTS

In 14 TTS inpatients, TTS had a higher incidence in postmenopausal women as compared to premenopausal women and men. In murine TTS, female WT mice exhibited higher cardiac SmgGDS levels than male WT mice. Ovariectomy reduced SmgGDS expression in female WT mice similar to that observed in male mice, whereas E2 replacement in these ovariectomized (OVX) female mice reversed this effect. The physiological importance of this sex-specific E2-mediated SmgGDS response is underscored by the disparity in cardiac adaptation to isoproterenol (ISO) stimulation between both sexes of WT mice. E2-mediated SmgGDS induction conferred female protection against TTS-like acute cardiac injury involving ferritinophagy-mediated ferroptosis. No such cardioprotection was observed in male WT mice and OVX female. A causal role for SmgGDS in this sex-specific cardioprotective adaptation was indicated, inasmuch as SmgGDS deficiency abolished E2-modulated cardioprotection against ferritinophagy and aggravates TTS progression in both sexes. Consistently, knockdown of SmgGDS in HL-1 cardiomyocytes exacerbated ferroptosis in a ferritinophagy-dependent manner and abrogated the protective role of E2 against ferritinophagy. Mechanistically, our findings revealed that SmgGDS regulated E2-dependent cardioprotective effects via AMPK/mTOR signaling pathway. SmgGDS deficiency abolished E2-conferred protection against ferritinophagy through activating AMPK/mTOR pathway, while treatment with recombinant SmgGDS in HL-1 cells significantly mitigated this pathway-associated ferritinophagy activity.

CONCLUSIONS

These results demonstrate that SmgGDS is a central mediator of E2-conferred female cardioprotection against ferritinophagy-mediated ferroptosis in TTS.

Direct androgen receptor control of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility, and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA sequencing (RNA-seq) data demonstrated that sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR)-mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation, whereas analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, disease, and metabolic linkage of sexually dimorphic gene activity.

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.

Pax Protein Depletion in Proximal Tubules Triggers Conserved Mechanisms of Resistance to Acute Ischemic Kidney Injury and Prevents Transition to Chronic Kidney Disease

Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Pax2 and Pax8 are homologous transcription factors with overlapping functions that are critical for kidney development and are re-activated in AKI. In this report, we examined the role of Pax2 and Pax8 in recovery from ischemic AKI. We found that Pax2 and Pax8 are upregulated after severe AKI and correlate with chronic injury. Surprisingly, we then discovered that proximal-tubule-selective deletion of Pax2 and Pax8 resulted in a less severe chronic injury phenotype. This effect was mediated by protection against the acute insult, similar to preconditioning. Prior to injury, Pax2 and Pax8 mutant mice develop a unique subpopulation of S3 proximal tubule cells that display features usually seen only in acute or chronic injury. The expression signature of these cells was strongly enriched with genes associated with other mechanisms of protection against ischemic AKI including caloric restriction, hypoxic preconditioning, and female sex. Taken together, our results identify a novel role for Pax2 and Pax8 in mature proximal tubules that regulates critical genes and pathways involved in both injury response and protection from ischemic AKI.

TRANSLATIONAL STATEMENT

Identifying the molecular and genetic regulators unique to the nephron that dictate vulnerability to injury and regenerative potential could lead to new therapeutic targets to treat ischemic kidney injury. Pax2 and Pax8 are two homologous nephron-specific transcription factors that are critical for kidney development and physiology. Here we report that proximal-tubule-selective depletion of Pax2 and Pax8 protects against both acute and chronic injury and induces an expression profile in the S3 proximal tubule with common features shared among diverse conditions that protect against ischemia. These findings highlight a new role for Pax proteins as potential therapeutic targets to treat AKI.

Ferrostatin-1 Ameliorated Oxidative Lipid Damage in LPS-induced Acute Lung Injury

INTRODUCTION

Ferroptosis is a new type of regulated cell death that is characterized by the overwhelming iron-dependent accumulation of lethal lipid reactive oxygen species and is involved in various diseases. However, the relationship between ferroptosis and lipopolysaccharide (LPS)-induced acute lung injury (ALI) remains largely unknown.

METHODS

In this study, iron metabolism and ferroptosis-related gene mRNA levels in the lung tissues of LPS-induced ALI mice at different time points were detected. Then, the histological, cytokines production, and iron levels of LPS-induced ALI mice with or without the pretreatment of the ferroptosis inhibitor ferrostatin-1 (Fer-1) were measured after mice received the ferroptosis inhibitor ferrostatin-1 (Fer-1) intraperitoneally before LPS administration. Ferroptosis-related protein (GPX4, NRF2, and DPP4) expression was measured in the in vivo and in vitro ALI model. Finally, ROS accumulation and lipid peroxidation was measured in in vivo and in vitro study.

RESULTS

Our results showed that iron metabolism and ferroptosis-related gene mRNA demonstrated significant variation in LPS-treated pulmonary tissues. The ferroptosis inhibitor Fer-1 markedly attenuated the histologic injuries of the lung tissue and suppressed the production of cytokines in bronchoalveolar lavage fluid (BALF). Fer-1 administration reduced the levels of NRF2 and DPP4 protein induced by the LPS challenge. Furthermore, Fer-1 reversed the tendency of iron metabolism, MDA, SOD, and GSH levels induced by LPS administration in in vivo and in vitro.

CONCLUSIONS

Taken together, ferroptosis inhibition by ferrostatin-1 alleviated acute lung injury through modulating oxidative lipid damages induced by the LPS challenge.

Ferroptosis model system by the re-expression of BACH1

Ferroptosis is a regulated cell death induced by iron-dependent lipid peroxidation. The heme-responsive transcription factor BTB and CNC homology 1 (BACH1) promotes ferroptosis by repressing the transcription of genes involved in glutathione (GSH) synthesis and intracellular labile iron metabolism, which are key regulatory pathways in ferroptosis. We found that BACH1 re-expression in Bach1-/- immortalized mouse embryonic fibroblasts (iMEFs) can induce ferroptosis upon 2-mercaptoethanol removal, without any ferroptosis inducers. In these iMEFs, GSH synthesis was reduced, and intracellular labile iron levels were increased upon BACH1 re-expression. We used this system to investigate whether the major ferroptosis regulators glutathione peroxidase 4 (Gpx4) and apoptosis-inducing factor mitochondria-associated 2 (Aifm2), the gene for ferroptosis suppressor protein 1, are target genes of BACH1. Neither Gpx4 nor Aifm2 was regulated by BACH1 in the iMEFs. However, we found that BACH1 represses AIFM2 transcription in human pancreatic cancer cells. These results suggest that the ferroptosis regulators targeted by BACH1 may vary across different cell types and animal species. Furthermore, we confirmed that the ferroptosis induced by BACH1 re-expression exhibited a propagating effect. BACH1 re-expression represents a new strategy for inducing ferroptosis after GPX4 or system Xc- suppression and is expected to contribute to future ferroptosis research.

Sex difference in the association between blood alcohol concentration and serum ferritin

Introduction

The sex difference in alcohol use disorder (AUD) is ingrained in distinctive neurobiological responses between men and women, which necessitates further investigation for a more tailored management.

Methods

Minding the findings of iron dysregulation in AUD and the sex difference in iron homeostasis in multiple physiological and pathological settings, we examined the sex difference in the association between serum ferritin and blood alcohol concentration (BAC) in intoxicated males (n = 125) and females (n = 59). We included patients with both serum ferritin tested of any value and a BAC above the level of detection during the same hospital admission period. We investigated sex difference in the relationship between BAC, serum ferritin and liver enzymes in intoxicated critically ill and noncritically ill patients.

Results

We found a negative association between serum ferritin and BAC in critically ill, intoxicated females [R2 = 0.44, F(1,14) = 11.02, p = 0.005], with much attenuated serum ferritin in females compared to their male counterparts (194.5 ± 280.4 vs. 806.3 ± 3405.7 ng/L, p = 0.002). We found a positive association between serum ferritin and liver enzymes [alanine transaminase (ALT) and aspartate transferase (AST)] in critically ill intoxicated females [ALT: R2 = 0.48, F(1,10) = 9.1, p = 0.013; AST: R2 = 0.68, F(1,10) = 21.2, p = 0.001] and in noncritically ill intoxicated males [ALT: R2 = 0.1, F(1,83) = 9.4, p = 0.003; AST: R2 = 0.1, F(1,78) = 10.5, p = 0.002]. The effect of BAC on serum ferritin was not mediated by ALT [indirect effect: (B = 0.13, p = 0.1)]. We also found a significant effect of sex, anemia, intensive care unit (ICU) admission and mortality on serum ferritin.

Discussion

Our results suggest that high BAC in intoxicated female patients is associated with attenuated serum ferritin levels, questioning the role of low serum ferritin in female vulnerability to alcohol.

The Road from AKI to CKD: Molecular Mechanisms and Therapeutic Targets of Ferroptosis

Acute kidney injury (AKI) is a prevalent pathological condition that is characterized by a precipitous decline in renal function. In recent years, a growing body of studies have demonstrated that renal maladaptation following AKI results in chronic kidney disease (CKD). Therefore, targeting the transition of AKI to CKD displays excellent therapeutic potential. However, the mechanism of AKI to CKD is mediated by multifactor, and there is still a lack of effective treatments. Ferroptosis, a novel nonapoptotic form of cell death, is believed to have a role in the AKI to CKD progression. In this study, we retrospectively examined the history and characteristics of ferroptosis, summarized ferroptosis's research progress in AKI and CKD, and discussed how ferroptosis participates in regulating the pathological mechanism in the progression of AKI to CKD. Furthermore, we highlighted the limitations of present research and projected the future evolution of ferroptosis. We hope this work will provide clues for further studies of ferroptosis in AKI to CKD and contribute to the study of effective therapeutic targets to prevent the progression of kidney diseases.

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.

Direct androgen receptor regulation of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA-seq data demonstrated sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR) mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation while analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, and disease and metabolic linkage, of sexually dimorphic gene activity.

Natural Flavonoids and Ferroptosis: Potential Therapeutic Opportunities for Human Diseases

Flavonoids are a class of bioactive phytochemicals containing a core 2-phenylchromone skeleton and are widely found in fruits, vegetables, and herbs. Such natural compounds have gained significant attention due to their various health benefits. Ferroptosis is a recently discovered unique iron-dependent mode of cell death. Unlike traditional regulated cell death (RCD), ferroptosis is associated with excessive lipid peroxidation on cellular membranes. Accumulating evidence suggests that this form of RCD is involved in a variety of physiological and pathological processes. Notably, multiple flavonoids have been shown to be effective in preventing and treating diverse human diseases by regulating ferroptosis. In this review, we introduce the key molecular mechanisms of ferroptosis, including iron metabolism, lipid metabolism, and several major antioxidant systems. Additionally, we summarize the promising flavonoids targeting ferroptosis, which provides novel ideas for the management of diseases such as cancer, acute liver injury, neurodegenerative diseases, and ischemia/reperfusion (I/R) injury.

Iron and Cancer: A Special Issue

Iron is an essential element for all organisms, and iron-containing proteins play critical roles in cellular functions [...]

Nupr1 deficiency downregulates HtrA1, enhances SMAD1 signaling, and suppresses age-related bone loss in male mice

Nuclear protein 1 (NUPR1) is a stress-induced protein activated by various stresses, such as inflammation and oxidative stress. We previously reported that Nupr1 deficiency increased bone volume by enhancing bone formation in 11-week-old mice. Analysis of differentially expressed genes between wild-type (WT) and Nupr1-knockout (Nupr1-KO) osteocytes revealed that high temperature requirement A 1 (HTRA1), a serine protease implicated in osteogenesis and transforming growth factor-β signaling was markedly downregulated in Nupr1-KO osteocytes. Nupr1 deficiency also markedly reduced HtrA1 expression, but enhanced SMAD1 signaling in in vitro-cultured primary osteoblasts. In contrast, Nupr1 overexpression enhanced HtrA1 expression in osteoblasts, suggesting that Nupr1 regulates HtrA1 expression, thereby suppressing osteoblastogenesis. Since HtrA1 is also involved in cellular senescence and age-related diseases, we analyzed aging-related bone loss in Nupr1-KO mice. Significant spine trabecular bone loss was noted in WT male and female mice during 6-19 months of age, whereas aging-related trabecular bone loss was attenuated, especially in Nupr1-KO male mice. Moreover, cellular senescence-related markers were upregulated in the osteocytes of 6-19-month-old WT male mice but markedly downregulated in the osteocytes of 19-month-old Nupr1-KO male mice. Oxidative stress-induced cellular senescence stimulated Nupr1 and HtrA1 expression in in vitro-cultured primary osteoblasts, and Nupr1 overexpression enhanced p16^ink4a expression in osteoblasts. Finally, NUPR1 expression in osteocytes isolated from the bones of patients with osteoarthritis was correlated with age. Collectively, these results indicate that Nupr1 regulates HtrA1-mediated osteoblast differentiation and senescence. Our findings unveil a novel Nupr1/HtrA1 axis, which may play pivotal roles in bone formation and age-related bone loss.

Targeting NRF2 to promote epithelial repair

The transcription factor NRF2 is well known as a master regulator of the cellular stress response. As such, activation of NRF2 has gained widespread attention for its potential to prevent tissue injury, but also as a possible therapeutic approach to promote repair processes. While NRF2 activation affects most or even all cell types, its effect on epithelial cells during repair processes has been particularly well studied. In response to tissue injury, these cells proliferate, migrate and/or spread to effectively repair the damage. In this review, we discuss how NRF2 governs repair of epithelial tissues, and we highlight the increasing number of NRF2 targets with diverse roles in regulating epithelial repair.