The roles of sirtuins in ferroptosis

Is uric acid a true antioxidant? Identification of uric acid oxidation products and their biological effects

Uric acid (UA), the final product of purine metabolism in humans, exhibits a dual role as an anti or pro-oxidant, depending on the microenvironment. The two-electron oxidation of UA by biological oxidants can neutralize such harmful molecules. Additionally, UA chelates metals and can activate adaptive response against oxidation. However, some products of the reaction between UA and oxidants are not inert and, therefore, do not confer the anticipated antioxidant protection. A direct pro-oxidant effect is favoured in the one-electron oxidation of UA by heme-peroxidases yielding free radical intermediates that can initiate or propagate a radical-chain reaction. Additionally, an indirect pro-oxidant effect has been proposed by eliciting the expression or activation of enzymes that catalyse oxidant production, e.g. NADPH oxidase (NOX). This review brings together fundamental concepts and the molecular mechanisms of the redox reactions involving UA. The signature metabolites from these reactions are discussed to give valuable insights on whether these intermediates are being formed and what role they may play in disease pathogenesis. It proposes that, through identifying specific products, it may be possible to elucidate whether a harmful or protective action is linked to downstream bioactivities.

Mitigating seizure-induced cognitive deficits in mice induced with pentylenetetrazol by roflumilast through targeting the NLRP3 inflammasome/BDNF/SIRT3 pathway and regulating ferroptosis

AIMS

Comorbidities with epilepsy and antiseizure medications (ASMs) are currently the main challenges in treating epilepsy. The current study evaluates for the first time the neuroprotective effect of roflumilast (ROF) alone or combined with phenytoin (PHT) against pentylenetetrazol (PTZ)-induced kindling in mice. It focuses on the crosstalk between the NOD-like receptor protein 3 (NLRP3)/caspase 1/interleukin 1β (IL-1β) cascade and the brain-derived neurotrophic factor (BDNF)/sirtuin 3 (SIRT3) pathway as possible strategies to treat epilepsy.

MAIN METHODS

The kindled mouse model was induced via fifteen (35 mg/kg) intraperitoneal injections every other day. Roflumilast (0.4 mg/kg) and phenytoin (30 mg/kg) were orally administered daily from the start until the end of the experiment. Following the PTZ injection, the seizure severity score was assessed. The Morris water maze (MWM) test was performed to evaluate cognition. Histopathological examinations of hippocampi were conducted.

KEY FINDINGS

Roflumilast significantly improved neurobehavioral and histological assessments, whereas Racine scores declined. The improvement was confirmed through BDNF upregulation in contrast to NLRP3 and caspase-1 in the hippocampus, as revealed immunohistochemically. In addition, roflumilast induced a prominent elevation in gamma-aminobutyric acid (GABA), sirtuin 3 (SIRT3), and glutathione peroxidase (GPX4), whereas malondialdehyde (MDA), and arachidonic acid 15-lipoxygenase (ALOX15) expressions were downregulated.

SIGNIFICANCE

Our findings demonstrate that roflumilast conferred neuroprotective benefits against PTZ-induced kindling seizures, suggesting its potential as a novel adjuvant therapy for epilepsy-related disorders. This effect might be due to the modification of the NLRP3 inflammasome/BDNF pathway, ferroptosis, and a decrease in oxidative stress and neuroinflammation.

A comprehensive review of ferroptosis in environmental pollutants-induced chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common chronic lung disease that impacts hundreds of millions of individuals worldwide. It is principally characterized by irreversible and progressive airflow limitation. Environmental pollutants, including cigarette smoke, air pollution, occupational pollutants, remain predominant risk factors for COPD and play remarkable roles in COPD progression. Despite the availability of treatments to alleviate symptoms of COPD, it continues to exert a serious health and socioeconomic burden. Ferroptosis, a unique form of iron-dependent cell death distinguished by lipid peroxidation, is implicated in various diseases. Recent studies, utilizing COPD patients samples, animal models, and Gene Expression Omnibus (GEO) database, have revealed that ferroptosis is involved in pathogenesis of COPD. Inhibiting ferroptosis signaling pathways halts the progression of COPD. This review consolidates current insights into the mechanisms of ferroptosis in environmental pollutants-induced COPD, which might offer a novel therapeutic strategy for COPD.

Targeting sirtuins for cancer therapy: epigenetics modifications and beyond

Sirtuins (SIRTs) are well-known as nicotinic adenine dinucleotide+(NAD+)-dependent histone deacetylases, which are important epigenetic enzymes consisting of seven family members (SIRT1-7). Of note, SIRT1 and SIRT2 are distributed in the nucleus and cytoplasm, while SIRT3, SIRT4 and SIRT5 are localized in the mitochondria. SIRT6 and SIRT7 are distributed in the nucleus. SIRTs catalyze the deacetylation of various substrate proteins, thereby modulating numerous biological processes, including transcription, DNA repair and genome stability, metabolism, and signal transduction. Notably, accumulating evidence has recently underscored the multi-faceted roles of SIRTs in both the suppression and progression of various types of human cancers. Crucially, SIRTs have been emerging as promising therapeutic targets for cancer therapy. Thus, in this review, we not only present an overview of the molecular structure and function of SIRTs, but elucidate their intricate associations with oncogenesis. Additionally, we discuss the current landscape of small-molecule activators and inhibitors targeting SIRTs in the contexts of cancer and further elaborate their combination therapies, especially highlighting their prospective utility for future cancer drug development.

Overview of ferroptosis and pyroptosis in acute liver failure

In this editorial, we comment on the article by Zhou et al published in a recent issue. We specifically focus on the crucial roles of ferroptosis and pyroptosis in acute liver failure (ALF), a disease with high mortality rates. Ferroptosis is the result of increased intracellular reactive oxygen species due to iron accumulation, glutathione (GSH) depletion, and decreased GSH peroxidase 4 activity, while pyroptosis is a procedural cell death mediated by gasdermin D which initiates a sustained inflammatory process. In this review, we describe the characteristics of ferroptosis and pyroptosis, and discuss the involvement of the two cell death modes in the onset and development of ALF. Furthermore, we summarize several interfering methods from the perspective of ferroptosis and pyroptosis for the alleviation of ALF. These observations might provide new targets and a theoretical basis for the treatment of ALF, which are also crucial for improving the prognosis of patients with ALF.

The anti-atherosclerotic effect of Paeonol against the lipid accumulation in macrophage-derived foam cells by inhibiting ferroptosis via the SIRT1/NRF2/GPX4 signaling pathway

Atherosclerosis (AS) is the underlying cause of many severe vascular diseases and is primarily characterized by abnormal lipid metabolism. Paeonol (Pae), a bioactive compound derived from Paeonia Suffruticosa Andr., is recognized for its significant role in reducing lipid accumulation. Our research objective is to explore the link between lipid buildup in foam cells originating from macrophages and the process of ferroptosis, and explore the effect and mechanism of Pae on inhibiting AS by regulating ferroptosis. In our animal model, ApoE-deficient mice, which were provided with a high-fat regimen to provoke atherosclerosis, were administered Pae. The treatment was benchmarked against simvastatin and ferrostatin-1. The results showed that Pae significantly reduced aortic ferroptosis and lipid accumulation in the mice. In vitro experiments further demonstrated that Pae could decrease lipid accumulation in foam cells induced by oxidized low-density lipoprotein (LDL) and challenged with the ferroptosis inducer erastin. Crucially, the protective effect of Pae against lipid accumulation was dependent on the SIRT1/NRF2/GPX4 pathway, as SIRT1 knockdown abolished this effect. Our findings suggest that Pae may offer a novel therapeutic approach for AS by inhibiting lipid accumulation through the suppression of ferroptosis, mediated by the SIRT1/NRF2/GPX4 pathway. Such knowledge has the potential to inform the creation of novel therapeutic strategies aimed at regulating ferroptosis within the context of atherosclerosis.

NAD+ precursors promote the restoration of spermatogenesis in busulfan-treated mice through inhibiting Sirt2-regulated ferroptosis

Rationale: In recent years, nicotinamide adenine dinucleotide (NAD+) precursors (Npre) have been widely employed to ameliorate female reproductive problems in both humans and animal models. However, whether and how Npre plays a role in the male reproductive disorder has not been fully clarified. Methods: In the present study, a busulfan-induced non-obstructive azoospermic mouse model was used, and Npre was administered for five weeks following the drug injection, with the objective of reinstating spermatogenesis and fertility. Initially, we assessed the NAD+ level, germ cell types, semen parameters and sperm fertilization capability. Subsequently, testis tissues were examined through RNA sequencing analysis, ELISA, H&E, immunofluorescence, quantitative real-time PCR, and Western blotting techniques. Results: The results indicated that Npre restored normal level of NAD+ in blood and significantly alleviated the deleterious effects of busulfan (BU) on spermatogenesis, thereby partially reestablishing fertilization capacity. Transcriptome analysis, along with recovery of testicular Fe2+, GSH, NADPH, and MDA levels, impaired by BU, and the fact that Fer-1, an inhibitor of ferroptosis, restored spermatogenesis and semen parameters close to CTRL values, supported such possibility. Interestingly, the reduction in SIRT2 protein level by the specific inhibitor AGK2 attenuated the beneficial effects of Npre on spermatogenesis and ferroptosis by affecting PGC-1α and ACLY protein levels, thus suggesting how these compounds might confer spermatogenesis protection. Conclusion: Collectively, these findings indicate that NAD+ protects spermatogenesis against ferroptosis, probably through SIRT2 dependent mechanisms. This underscores the considerable potential of Npre supplementation as a feasible strategy for preserving or restoring spermatogenesis in specific conditions of male infertility and as adjuvant therapy to preserve male fertility in cancer patients receiving sterilizing treatments.

Emerging roles of SIRT1 activator, SRT2104, in disease treatment

Silent information regulator 1 (SIRT1) is a NAD+-dependent class III deacetylase that plays important roles in the pathogenesis of numerous diseases, positioning it as a prime candidate for therapeutic intervention. Among its modulators, SRT2104 emerges as the most specific small molecule activator of SIRT1, currently advancing into the clinical translation phase. The primary objective of this review is to evaluate the emerging roles of SRT2104, and to explore its potential as a therapeutic agent in various diseases. In the present review, we systematically summarized the findings from an extensive array of literature sources including the progress of its application in disease treatment and its potential molecular mechanisms by reviewing the literature published in databases such as PubMed, Web of Science, and the World Health Organization International Clinical Trials Registry Platform. We focuses on the strides made in employing SRT2104 for disease treatment, elucidating its potential molecular underpinnings based on preclinical and clinical research data. The findings reveal that SRT2104, as a potent SIRT1 activator, holds considerable therapeutic potential, particularly in modulating metabolic and longevity-related pathways. This review establishes SRT2104 as a leading SIRT1 activator with significant therapeutic promise.

Sodium-Glucose Transporter 2 (SGLT2) Inhibitors and Iron Deficiency in Heart Failure and Chronic Kidney Disease: A Literature Review

Heart failure (HF) and chronic kidney disease (CKD) are associated with high mortality. In both disorders, impaired iron homeostasis, mostly in the form of a functional iron deficiency, is a frequent co-morbidity. In HF, functional iron deficiency and management by i.v. iron supplementation have been proven to affect both prognosis and functional capacity. In the same context, iron supplementation is routine for the adequate management of renal anemia in CKD. In numerous recent studies in HF and in CKD, sodium-glucose transporter 2 (SGLT2) inhibitor treatment has been proven to significantly reduce mortality. Furthermore, the same trials showed that these drugs alleviate iron deficiency and anemia. These effects of SGLT2 inhibitors may be due to an amelioration of inflammation with reduced interleukin-6 (IL-6) and to an enhancement of autophagy with increased sirtuin 1 (SIRT1), both associated with modified production of hepcidin and enhanced ferritinophagy. However, the exact pathogenic basis of the beneficial SGLT2 inhibitor action is not fully elucidated. Nevertheless, effects on iron homeostasis might be a potential explanatory mechanism for the powerful SGLT2 inhibitors' cardiovascular and renal outcome benefits. In addition, the interaction between iron supplementation and SGLT2 inhibitors and its potential impact on prognosis remains to be clarified by future studies. This review represents a significant effort to explore the complex relationships involved, seeking to elucidate the intricate mechanisms by which SGLT2 inhibitors influence iron homeostasis.

Epigenetic modulation of ferroptosis in cancer: Identifying epigenetic targets for novel anticancer therapy

Ferroptosis is a newly recognized form of oxidative-regulated cell death resulting from iron-mediated lipid peroxidation accumulation. Radical-trapping antioxidant systems can eliminate these oxidized lipids and prevent disrupting the integrity of cell membranes. Epigenetic modifications can regulate ferroptosis by altering gene expression or cell phenotype without permanent sequence changes. These mechanisms include DNA methylation, histone modifications, RNA modifications, and noncoding RNAs. Epigenetic alterations in cancer can control the expression of ferroptosis regulators or related pathways, leading to changes in cell sensitivity to ferroptosis inducers or cancer progression. Epigenetic alterations in cancer are influenced by a wide range of cancer hallmarks, contributing to therapeutic resistance. Targeting epigenetic alterations is a promising approach to overcoming cancer resilience. However, the exact mechanisms involved in different types of cancer remain unresolved. Discovering more ferroptosis-associated epigenetic targets and interventions can help overcome current barriers in anticancer therapy. Many papers on epigenetic modifications of ferroptosis have been continuously published, making it essential to summarize the current state-of-the-art in the epigenetic regulation of ferroptosis in human cancer.

Ferroptosis in cardiac hypertrophy and heart failure

Heart failure has become a public health problem that we cannot avoid choosing to face in today's context. In the case of heart failure, pathological cardiac hypertrophy plays a major role because of its condition of absolute increase in ventricular mass under various stresses. Ferroptosis, it could be defined as regulatory mechanisms that regulate cell death in the absence of apoptosis in iron-dependent cells. This paper introduces various new research findings on the use of different regulatory mechanisms of cellular ferroptosis for the treatment of heart failure and cardiac hypertrophy, providing new therapeutic targets and research directions for clinical treatment. The role and mechanism of ferroptosis in the field of heart failure has been increasingly demonstrated, and the relationship between cardiac hypertrophy, which is one of the causes of heart failure, is also an area of research that we should focus on. In addition, the latest applications and progress of inducers and inhibitors of ferroptosis are reported in this paper, updating the breakthroughs in their fields.