Activation of mitochondrial biogenesis by heme oxygenase-1-mediated NF-E2-related factor-2 induction rescues mice from lethal Staphylococcus aureus sepsis

Heme and immunity: The heme oxygenase dichotomy

Heme, an iron containing organic ring, is required for a diverse range of biological processes across all forms of life. Although this nutrient is essential, its pro-inflammatory and cytotoxic properties can lead to cellular damage. Heme oxygenase 1 (HO-1) is an endoplasmic reticulum (ER)-anchored enzyme that degrades heme, releasing equimolar amounts of carbon monoxide (CO), biliverdin (BV), and iron. The induction of HO-1 by heme presents an interesting dichotomy in the cell: CO and BV possess anti-inflammatory and antioxidant properties while free iron can be detrimental as it can generate hydroxyl radicals through the Fenton reaction. The heme/HO-1 axis is tightly regulated, and can influence cell fate, local tissue environments, and disease outcomes during pathogen infection. In this review we explore the role of heme during macrophage polarization and its ability to act as an immune activator while also examining the contribution of HO-1 and heme during infections with intracellular and extracellular pathogens. We highlight work from the emerging field of nutritional immunity of heme and iron, and how the substrates and byproducts of heme metabolism via HO-1 can be beneficial to the host or the pathogen depending on the context.

What Do We Know About Staphylococcus aureus and Oxidative Stress? Resistance, Virulence, New Targets, and Therapeutic Alternatives

Staphylococcus aureus is associated with human infections, being a resistant bacterium involved in serious infections, and its virulence and resistance are linked to oxidative stress. In this study, we review the role of oxidative stress in the pathogenesis of this bacterium and its influence on immune system evasion, antibiotic resistance, and pharmacological targeting. S. aureus infection generates an intense inflammatory response in the host, evidenced by the activation of pro-inflammatory pathways, the exacerbated production of reactive oxygen species (ROS), and cellular oxidative stress. However, the bacterium develops protective mechanisms against damage, including the production of endogenous antioxidants, the formation of biofilms, and the regulation of redox metabolism, favoring pathogenicity and drug resistance. Resistance seems to be related to alterations in redox metabolism, which influences the sensitization of the immune system. Modulation of the redox response has emerged as a promising approach for developing new antibiotics and formulating more effective combination therapies to combat resistant infections. Natural compounds, including flavonoids, terpenes, and quinones, have demonstrated antibacterial properties by inducing oxidative stress in S. aureus. In summary, the involvement of oxidative stress is complex, with an increase in ROS in the infection and a reduction in immune system evasion and resistance, which could be an interesting therapeutic target.

Compelling Evidence: A Critical Update on the Therapeutic Potential of Carbon Monoxide

Carbon monoxide (CO) is an endogenous signaling molecule. It is produced via heme degradation by heme oxygenase (HMOX), releasing stoichiometric amounts of CO, iron, and biliverdin (then bilirubin). The HMOX-CO axis has long been shown to offer beneficial effects by modulating inflammation, proliferation and cell death as they relate to tissue and organ protection. Recent years have seen a large number of studies examining CO pharmacology, its molecular targets, cellular mechanisms of action, pharmacokinetics, and detection methods using various delivery modalities including inhaled CO gas, CO solutions, and various types of CO donors. Unfortunately, one widely used donor type includes four commercially available carbonyl complexes with metal or borane, CORM-2 (Ru2+), CORM-3 (Ru2+), CORM-A1 (BH3), and CORM-401 (Mn+), which have been shown to have minimal and/or unpredictable CO production and extensive CO-independent chemical reactivity and biological activity. As a result, not all "CO biological activities" in the literature can be attributed to CO. In this review, we summarize key findings based on CO gas and CO in solution for the certainty of the active principal and to avoid data contamination resulting from the confirmed or potential reactivities and activities of the "carrier" portion of CORMs. Along a similar line, we discuss interesting potential research areas of CO in the brain including a newly proposed CO/HMOX/dopamine axis and the role of CO in cognitive stimulation and circadian rhythm. This review is critical for the future development of the CO field by steering clear of complications caused by chemically reactive donor molecules.

Serine ubiquitination of SQSTM1 regulates NFE2L2-dependent redox homeostasis

The KEAP1-NFE2L2 axis is essential for the cellular response against metabolic and oxidative stress. KEAP1 is an adaptor protein of CUL3 (cullin 3) ubiquitin ligase that controls the cellular levels of NFE2L2, a critical transcription factor of several cytoprotective genes. Oxidative stress, defective autophagy and pathogenic infections activate NFE2L2 signaling through phosphorylation of the autophagy receptor protein SQSTM1, which competes with NFE2L2 for binding to KEAP1. Here we show that phosphoribosyl-linked serine ubiquitination of SQSTM1 catalyzed by SidE effectors of Legionella pneumophila controls NFE2L2 signaling and cell metabolism upon Legionella infection. Serine ubiquitination of SQSTM1 sterically blocks its binding to KEAP1, resulting in NFE2L2 ubiquitination and degradation. This reduces NFE2L2-dependent antioxidant synthesis in the early phase of infection. Levels of serine ubiquitinated SQSTM1 diminish in the later stage of infection allowing the expression of NFE2L2-target genes; causing a differential regulation of the host metabolome and proteome in a NFE2L2-dependent manner.Abbreviation: ARE: antioxidant response element; Dup: deubiquitinase specific for phosphoribosyl-linked serine ubiquitination; ER: endoplasmic reticulum; h.p.i: hours post infection; HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha; KEAP1: kelch like ECH associated protein 1; KIR: KEAP1-interacting region; LIR: LC3-interacting region; NES: nuclear export signal; NFKB/NF-κB: nuclear factor kappa B; NLS: nuclear localization signal; NFE2L2/Nrf2: NFE2 like bZIP transcription factor 2; PB1 domain: Phox1 and Bem1 domain; PR-Ub: phosphoribosyl-linked serine ubiquitination; ROS: reactive oxygen species; SQSTM1/p62: sequestosome 1; tBHQ: tertiary butylhydroquinone; TUBE2: tandem ubiquitiin binding entity 2; UBA domain: ubiquitin-associated domain.

Combination of Low-Dose Sulforaphane and Docetaxel on Mitochondrial Function and Metabolic Reprogramming in Prostate Cancer Cell Lines

Considering the limitations of monotherapies due to chemoresistance and side effects, this research aimed to determine whether low doses of sulforaphane (SFN) combined with docetaxel (DCT) could enhance therapeutic efficacy. Prostate cancer cell lines LNCaP and PC-3 were treated with individual IC50 doses of SFN and DCT and half-reduced IC50 values for the SFN:DCT combination. Metabolic markers, including glucose consumption, lactate production, reactive oxygen species (ROS), mitochondrial mass, and caspase activity, were assessed. In LNCaP cells, the SFN:DCT combination reduced cell viability to 50%, comparable to DCT monotherapy (48%). Caspase 3 activation was also higher with SFN:DCT (2.4 ± 0.75 RFU) than DCT alone (2.1 ± 0.47 RFU), while caspase 8 activation remained comparable, indicating equivalent effectiveness at lower concentrations. In PC-3 cells, the combination induced caspase 3 activation (1.16 ± 0.0484 RFU) at levels slightly lower than DCT (1.51 ± 0.2062 RFU) but achieved greater reductions in mitochondrial mass, reflecting its ability to target metabolic vulnerabilities in aggressive phenotypes. Our findings suggest that the SFN:DCT combination is a promising strategy for early-stage prostate cancer. By achieving comparable efficacy to DCT monotherapy at low doses, the SFN:DCT combination maintains the therapeutic impact, mitigating the adverse effects of conventional DCT treatment.

The impact of glucose metabolism on inflammatory processes in sepsis-induced acute lung injury

Acute lung injury (ALI) is a prevalent and critical complication of sepsis, marked by high incidence and mortality rates, with its pathogenesis still not being fully elucidated. Recent research has revealed a significant correlation between the metabolic reprogramming of glucose and sepsis-associated ALI (S-ALI). Throughout the course of S-ALI, immune cells, including macrophages and dendritic cells, undergo metabolic shifts to accommodate the intricate demands of immune function that emerge as sepsis advances. Indeed, glucose metabolic reprogramming in S-ALI serves as a double-edged sword, fueling inflammatory immune responses in the initial stages and subsequently initiating anti-inflammatory responses as the disease evolves. In this review, we delineate the current research progress concerning the pathogenic mechanisms linked to glucose metabolic reprogramming in S-ALI, with a focus on the pertinent immune cells implicated. We encapsulate the impact of glucose metabolic reprogramming on the onset, progression, and prognosis of S-ALI. Ultimately, by examining key regulatory factors within metabolic intermediates and enzymes, We have identified potential therapeutic targets linked to metabolic reprogramming, striving to tackle the inherent challenges in diagnosing and treating Severe Acute Lung Injury (S-ALI) with greater efficacy.

High-Throughput Screening of an FDA-Approved Compound Library Reveals a Novel GAS6 Receptor Agonist for Therapeutic Intervention in Septic Myocardial and microvascular Injury via Modulation of Danger-Associated Molecular Patterns

PGAM5 and VDAC1 have both been reported to regulate mitophagy. However, the mechanisms by which they regulate sepsis-induced inflammatory microvascular injury remain unverified. In previous studies, we established the role of this regulatory axis in various phenotypic processes, including mitophagy, mitochondrial biogenesis, the mitochondrial unfolded protein response, and mitochondrial dynamics, while further confirming the interactive regulatory proteins within this axis. However, the validation and elucidation of these regulatory phenotypes have primarily focused on ischemic heart diseases such as ischemic myocardial injury and heart failure. Sepsis-related myocardial injury is currently recognized as a significant cardiac impairment, and although there are cardioprotective and nutritional agents available for supportive therapy, fundamental research validating the upstream targets and mechanisms of microvascular injury is still lacking. Based on our previous research, we further explored the role of mitophagy dysfunction mediated by VDAC1 and its upstream regulatory protein PGAM5 in sepsis-induced coronary microvascular injury. We also confirmed the material basis and metabolic pathway regulation targeting the PGAM5- VDAC1 interactive mechanism with relevant drugs. Our findings suggest that PGAM5-mediated mitophagy dysfunction may be a crucial factor leading to sepsis-induced microvascular injury, primarily interacting with VDAC1-mediated mitochondrial membrane dysfunction. Animal experiments revealed that cardiac-specific knockout of PGAM5 could reverse LPS-induced coronary microvascular injury and inflammatory damage, restoring cardiac ejection function and mitophagy functionality. In vitro studies also confirmed that the PGAM5-VDAC1 interaction can normalize mitophagy, restoring the normal morphology and structure of mitochondria while maintaining normal mitochondrial energy metabolism levels and respiratory chain function. Further pharmacological research indicated that the active ingredients of traditional Chinese medicine-Puerarin (TCM, a GAS6 Receptor Agonist) can target the PGAM5- VDAC1 axis to regulate mitophagy and inhibit LPS-induced necrotic apoptosis in cardiomyocytes, potentially reversing mitochondrial pathway-related cardiac injury. TCM may emerge as a prospective therapeutic agent targeting the PGAM5- VDAC1 axis.

Carbon monoxide and mitochondria: Cell energy and fate control

Carbon monoxide (CO) is a ubiquitously produced endogenous gas in mammalian cells and is involved in stress response being considered as a cytoprotective and homeostatic factor. In the present review, the underlying mechanisms of CO are discussed, in particular CO's impact on cellular metabolism affecting cell fate and function. One of the principal signaling molecules of CO is reactive oxygen species (ROS), particularly hydrogen peroxide, which is mainly generated at the mitochondrial level. Likewise, CO acts on mitochondria modulating oxidative phosphorylation and mitochondria quality control, namely mitochondrial biogenesis (mitobiogenesis) and mitophagy. Other metabolic pathways are also involved in CO's mode of action such as glycolysis and pentose phosphate pathway. The review ends with some new perspectives on CO Biology research. Carboxyhemoglobin (COHb) formation can also be implicated in the CO mode of action, as well as its potential biological role. Finally, other organelles such as peroxisomes hold the potential to be targeted and modulated by CO.

Nrf2 as a regulator of energy metabolism and mitochondrial function

Nuclear factor erythroid-2-related factor 2 (Nrf2) is essential for the control of cellular redox homeostasis. When activated, Nrf2 elicits cytoprotective effects through the expression of several genes encoding antioxidant and detoxifying enzymes. Nrf2 can also improve antioxidant defense via the pentose phosphate pathway by increasing NADPH availability to regenerate glutathione. Microarray and genome-wide localization analyses have identified many Nrf2 target genes beyond those linked to its redox-regulatory capacity. Nrf2 regulates several intermediary metabolic pathways and is involved in cancer cell metabolic reprogramming, contributing to malignant phenotypes. Nrf2 also modulates substrate utilization for mitochondrial respiration. Here we review the experimental evidence supporting the essential role of Nrf2 in the regulation of energy metabolism and mitochondrial function.

Effects of ozone exposure on lung injury, inflammation, and oxidative stress in a murine model of nonpneumonic endotoxemia

Recent studies have identified exposure to environmental levels of ozone as a risk factor for the development of acute respiratory distress syndrome (ARDS), a severe form of acute lung injury (ALI) that can develop in humans with sepsis. The aim of this study was to develop a murine model of ALI to mechanistically explore the impact of ozone exposure on ARDS development. Mice were exposed to ozone (0.8 ppm, 3 h) or air control followed 24 h later by intravenous administration of 3 mg/kg lipopolysaccharide (LPS) or PBS. Exposure of mice to ozone + LPS caused alveolar hyperplasia; increased BAL levels of albumin, IgM, phospholipids, and proinflammatory mediators including surfactant protein D and soluble receptor for advanced glycation end products were also detected in BAL, along with markers of oxidative and nitrosative stress. Administration of ozone + LPS resulted in an increase in neutrophils and anti-inflammatory macrophages in the lung, with no effects on proinflammatory macrophages. Conversely, the numbers of resident alveolar macrophages decreased after ozone + LPS; however, expression of Nos2, Arg1, Cxcl1, Cxcl2, Ccl2 by these cells increased, indicating that they are activated. These findings demonstrate that ozone sensitizes the lung to respond to endotoxin, resulting in ALI, oxidative stress, and exacerbated pulmonary inflammation, and provide support for the epidemiologic association between ozone exposure and ARDS incidence.

Therapeutic Strategies Targeting Mitochondrial Dysfunction in Sepsis-induced Cardiomyopathy

Sepsis is an increasingly worldwide problem; it is currently regarded as a complex life-threatening dysfunction of one or more organs as a result of dysregulated host immune response to infections. The heart is one of the most affected organs, as roughly 10% to 70% of sepsis cases are estimated to turn into sepsis-induced cardiomyopathy (SIC). SIC can be defined as a reversible myocardial dysfunction characterized by dilated ventricles, impaired contractility, and decreased ejection fraction. Mitochondria play a critical role in the normal functioning of cardiac tissues as the heart is highly dependent on its production of adenosine triphosphate (ATP), its damage during SIC includes morphology impairment, mitophagy, biogenesis disequilibrium, electron transport chain disturbance, molecular damage from the actions of pro-inflammatory cytokines and many other different impairments that are major contributing factors to the severity of SIC. Although mitochondria-targeted therapies usage is still inadequate in clinical settings, the preclinical study outcomes promise that the implementation of these therapies may effectively treat SIC. This review summarizes the different therapeutic strategies targeting mitochondria structure, quality, and quantity abnormalities for the treatment of SIC.

Heme oxygenase-1: A potential therapeutic target for improving skeletal muscle atrophy

Skeletal muscle atrophy is a common muscle disease that is directly caused by an imbalance in protein synthesis and degradation. At the histological level, it is mainly characterized by a reduction in muscle mass and fiber cross-sectional area (CSA). Patients with skeletal muscle atrophy present with reduced motor ability, easy fatigue, and poor life quality. Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes the degradation of heme and has attracted much attention for its anti-oxidation effects. In addition, there is growing evidence that HO-1 plays an important role in anti-inflammatory, anti-apoptosis, pro-angiogenesis, and maintaining skeletal muscle homeostasis, making it a potential therapeutic target for improving skeletal muscle atrophy. Here, we review the pathogenesis of skeletal muscle atrophy, the biology of HO-1 and its regulation, and the biological function of HO-1 in skeletal muscle homeostasis, with a specific focus on the role of HO-1 in skeletal muscle atrophy, aiming to observe the therapeutic potential of HO-1 for skeletal muscle atrophy.

Restoring the infected powerhouse: Mitochondrial quality control in sepsis

Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

An ischemic area-targeting, peroxynitrite-responsive, biomimetic carbon monoxide nanogenerator for preventing myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (MI/R) injury is common in patients who undergo revascularization therapy for myocardial infarction, often leading to cardiac dysfunction. Carbon monoxide (CO) has emerged as a therapeutic molecule due to its beneficial properties such as anti-inflammatory, anti-apoptotic, and mitochondrial biogenesis-promoting properties. However, its clinical application is limited due to uncontrolled release, potential toxicity, and poor targeting efficiency. To address these limitations, a peroxynitrite (ONOO^-)-triggered CO donor (PCOD585) is utilized to generate a poly (lactic-co-glycolic acid) (PLGA)-based, biomimetic CO nanogenerator (M/PCOD@PLGA) that is coated with the macrophage membrane, which could target to the ischemic area and neutralize proinflammatory cytokines. In the ischemic area, local produced ONOO^- triggers the continuous release of CO from M/PCOD@PLGA, which efficiently ameliorates MI/R injury by clearing harmful ONOO^-, attenuating the inflammatory response, inhibiting cardiomyocyte apoptosis, and promoting mitochondrial biogenesis. This study provides a novel insight into the safe therapeutic use of CO for MI/R injury by utilizing a novel CO donor combined with biomimetic technology. The M/PCOD@PLGA nanogenerator offers targeted delivery of CO to the ischemic area, minimizing potential toxicity and enhancing therapeutic efficacy.

U-Shaped Association Between Carboxyhemoglobin and Mortality in Patients With Acute Respiratory Distress Syndrome on Venovenous Extracorporeal Membrane Oxygenation

Background

Carbon monoxide (CO) is an endogenous signaling molecule that activates cytoprotective programs implicated in the resolution of acute respiratory distress syndrome (ARDS) and survival of critical illness. Because CO levels can be measured in blood as carboxyhemoglobin, we hypothesized that carboxyhemoglobin percent (COHb%) may associate with mortality.

OBJECTIVES

To examine the relationship between COHb% and outcomes in patients with ARDS requiring venovenous extracorporeal membrane oxygenation (ECMO), a condition where elevated COHb% is commonly observed.

DESIGN

Retrospective cohort study.

SETTING

Academic medical center ICU.

PATIENTS

Patients were included that had ARDS on venovenous ECMO.

MEASUREMENTS AND MAIN RESULTS

We examined the association between COHb% and mortality using a Cox proportional hazards model. Secondary outcomes including ECMO duration, ventilator weaning, and hospital and ICU length of stay were examined using both subdistribution and causal-specific hazard models for competing risks. We identified 109 consecutive patients for analysis. Mortality significantly decreased per 1 U increase in COHb% below 3.25% (hazard ratio [HR], 0.35; 95% CI, 0.15-0.80; p = 0.013) and increased per 1 U increase above 3.25% (HR, 4.7; 95% CI, 1.5-14.7; p = 0.007) reflecting a nonlinear association (p = 0.006). Each unit increase in COHb% was associated with reduced likelihood of liberation from ECMO and mechanical ventilation, and increased time to hospital and ICU discharge (all p < 0.05). COHb% was significantly associated with hemolysis but not with initiation of hemodialysis or blood transfusions.

CONCLUSIONS

In patients with ARDS on venovenous ECMO, COHb% is a novel biomarker for mortality exhibiting a U-shaped pattern. Our findings suggest that too little CO (perhaps due to impaired host signaling) or excess CO (perhaps due to hemolysis) is associated with higher mortality. Patients with low COHb% may exhibit the most benefit from future therapies targeting anti-oxidant and anti-inflammatory pathways such as low-dose inhaled CO gas.

Mitochondrial Dysfunction in Bacterial Infections

Mitochondria are critical in numerous cellular processes, including energy generation. Bacterial pathogens target host cell mitochondria through various mechanisms to disturb the host response and improve bacterial survival. We review recent advances in the understanding of how bacteria cause mitochondrial dysfunction through perturbations in mitochondrial cell-death pathways, energy production, mitochondrial dynamics, mitochondrial quality control, DNA repair, and the mitochondrial unfolded protein response. We also briefly highlight possible therapeutic approaches aimed at restoring the host mitochondrial function as a novel strategy to enhance the host response to bacterial infection.

Ferroptosis: The functions of Nrf2 in human embryonic stem cells

Human embryonic stem cells (hESCs) have the capacity of self-renewal as well as differentiation towards three germ layer derivatives which makes them as a source of therapeutic application. hESCs are tremendously prone to cell death after dissociation into single cells. Therefore, it technically hinders their applications. Our recent study has revealed that hESCs can be prone to ferroptosis which differs from those in earlier explorations reporting that cellular detachment results in a process cited as anoikis. Ferroptosis occurs via increasing intracellular iron. Therefore, this form of programmed cell death is distinct from other cell deaths in terms of biochemistry, morphology, and genetics. Ferroptosis is found by excessive iron which plays an important part role in reactive oxygen species (ROS) generation through the Fenton reaction as a cofactor. Many genes are related to ferroptosis under the control of nuclear factor erythroid 2-related factor 2 (Nrf2) which is a transcription factor regulating the expression of genes to protect cells from oxidative stress. Nrf2 was demonstrated to take a perilous role in the suppression of ferroptosis by regulating the iron, antioxidant defense enzymes, usage, and restoration of glutathione, thioredoxin, and NADPH. Mitochondrial function is another target of Nrf2 to control cell homeostasis through the modulation of ROS production. In this review, we will give a succinct overview of lipid peroxidation and discuss the major players in the ferroptotic cascade. Additionally, we discussed the important role of the Nrf2 signaling pathway in mediating lipid peroxidation and ferroptosis, with a focus on known Nrf2 target genes that inhibit these processes and their possible role in hESCs.

A small-molecule inhibitor of Keap1-Nrf2 interaction attenuates sepsis by selectively augmenting the antibacterial defence of macrophages at infection sites

BACKGROUND

Macrophages at infection sites are considered as the promising therapeutic targets to prevent sepsis development. The Nrf2/Keap1 system acts as a critical modulator of the antibacterial activity of macrophages. Recently, Keap1-Nrf2 protein-protein interaction (PPI) inhibitors have emerged as safer and stronger Nrf2 activators; however, their therapeutic potential in sepsis remains unclear. Herein, we report a unique heptamethine dye, IR-61, as a Keap1-Nrf2 PPI inhibitor that preferentially accumulates in macrophages at infection sites.

METHODS

A mouse model of acute lung bacterial infection was used to investigate the biodistribution of IR-61. SPR study and CESTA were used to detect the Keap1 binding behaviour of IR-61 in vitro and in cells. Established models of sepsis in mice were used to determine the therapeutic effect of IR-61. The relationship between Nrf2 levels and sepsis outcomes was preliminarily investigated using monocytes from human patients.

FINDINGS

Our data showed that IR-61 preferentially accumulated in macrophages at infection sites, enhanced bacterial clearance, and improved outcomes in mice with sepsis. Mechanistic studies indicated that IR-61 potentiated the antibacterial function of macrophages by activating Nrf2 via direct inhibition of the Keap1-Nrf2 interaction. Moreover, we observed that IR-61 enhanced the phagocytic ability of human macrophages, and the expression levels of Nrf2 in monocytes might be associated with the outcomes of sepsis patients.

INTERPRETATIONS

Our study demonstrates that the specific activation of Nrf2 in macrophages at infection sites is valuable for sepsis management. IR-61 may prove to be a Keap1-Nrf2 PPI inhibitor for the precise treatment of sepsis.

FUNDING

This work was supported by the National Natural Science Foundation of China (Major program 82192884), the Intramural Research Project (Grants: 2018-JCJQ-ZQ-001 and 20QNPY018), and the Chongqing National Science Foundation (CSTB2022NSCQ-MSX1222).

DJ-1 Deficiency Protects against Sepsis-Induced Myocardial Depression

Oxidative stress is considered one of the early underlying contributors of sepsis-induced myocardial depression. DJ-1, also known as PARK7, has a well-established role as an antioxidant. We have previously shown, in a clinically relevant model of polymicrobial sepsis, DJ-1 deficiency improved survival and bacterial clearance by decreasing ROS production. In the present study, we investigated the role of DJ-1 in sepsis-induced myocardial depression. Here we compared wildtype (WT) with DJ-1 deficient mice at 24 and 48 h after cecal ligation and puncture (CLP). In WT mice, DJ-1 was increased in the myocardium post-CLP. DJ-1 deficient mice, despite enhanced inflammatory and oxidative responses, had an attenuated hypertrophic phenotype, less apoptosis, improved mitochondrial function, and autophagy, that was associated with preservation of myocardial function and improved survival compared to WT mice post-CLP. Collectively, these results identify DJ-1 as a regulator of myocardial function and as such, makes it an attractive therapeutic target in the treatment of early sepsis-induced myocardial depression.

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

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

Controlled therapeutic delivery of CO from carbon monoxide-releasing molecules (CORMs)

Carbon monoxide (CO) has been regarded as a "silent killer" for its toxicity toward biological systems. However, a low concentration of endogenously produced CO has shown a number of therapeutic benefits such as anti-inflammatory, anti-proliferative, anti-apoptosis, and cytoprotective activities. Carbon monoxide-releasing molecules (CORMs) have been developed as alternatives to direct CO inhalation, which requires a specialized setting for strict dose control. CORMs are efficient CO donors, with central transition metals (such as ruthenium, iron, cobalt, and manganese) surrounded by CO as a ligand. CORMs can stably store and subsequently release their CO payload in the presence of certain triggers including solvent, light, temperature, and ligand substitution. However, CORMs require appropriate delivery strategies to improve short CO release half-life and target specificity. Herein, we highlighted the therapeutic potential of inhalation and CORMs-delivered CO. The applications of conjugate and nanocarrier systems for controlling CO release and improving therapeutic efficacy of CORMs are also described in detail. The review concludes with some of the hurdles that limit clinical translation of CORMs. Keeping in mind the tremendous potential and growing interest in CORMs, this review would be helpful for designing controlled CO release systems for clinical applications.

NRF2 and Mitochondrial Function in Cancer and Cancer Stem Cells

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

Effects of fluoride exposure on mitochondrial function: Energy metabolism, dynamics, biogenesis and mitophagy

Fluoride is ubiquitous in the environment. Furthermore, drinking water represents the main source of exposure to fluoride for humans. Interestingly, low fluoride concentrations have beneficial effects on bone and teeth development; however, chronic fluoride exposure has harmful effects on human health. Besides, preclinical studies associate fluoride toxicity with oxidative stress, inflammation, and apoptosis. On the other hand, it is well-known that mitochondria play a key role in reactive oxygen species production. By contrast, fluoride's effect on processes such as mitochondrial dynamics, biogenesis and mitophagy are little known. These processes modulate the size, content, and distribution of mitochondria and their depuration help to counter the reactive oxygen species production and cytochrome c release, thereby allowing cell survival. However, a maladaptive response could enhance fluoride-induced toxicity. The present review gives a brief account of fluoride-induced mitochondrial alterations on soft and hard tissues, including liver, reproductive organs, heart, brain, lung, kidney, bone, and tooth.

Molecular Mechanisms Underlying Intensive Care Unit-Acquired Weakness and Sarcopenia

Skeletal muscle is a highly adaptable organ, and its amount declines under catabolic conditions such as critical illness. Aging is accompanied by a gradual loss of muscle, especially when physical activity decreases. Intensive care unit-acquired weakness is a common and highly serious neuromuscular complication in critically ill patients. It is a consequence of critical illness and is characterized by a systemic inflammatory response, leading to metabolic stress, that causes the development of multiple organ dysfunction. Muscle dysfunction is an important component of this syndrome, and the degree of catabolism corresponds to the severity of the condition. The population of critically ill is aging; thus, we face another negative effect-sarcopenia-the age-related decline of skeletal muscle mass and function. Low-grade inflammation gradually accumulates over time, inhibits proteosynthesis, worsens anabolic resistance, and increases insulin resistance. The cumulative consequence is a gradual decline in muscle recovery and muscle mass. The clinical manifestation for both of the above conditions is skeletal muscle weakness, with macromolecular damage, and a common mechanism-mitochondrial dysfunction. In this review, we compare the molecular mechanisms underlying the two types of muscle atrophy, and address questions regarding possible shared molecular mechanisms, and whether critical illness accelerates the aging process.

Hepatoprotective Effect of Mitochondria-Targeted Antioxidant Mito-TEMPO against Lipopolysaccharide-Induced Liver Injury in Mouse

The liver is vulnerable to sepsis, and sepsis-induced liver injury is closely associated with poor survival of sepsis patients. Studies have found that the overproduction of reactive oxygen species (ROS) is the major cause of oxidative stress, which is the main pathogenic factor for the progression of septic liver injury. The mitochondria are a major source of ROS. Mito-TEMPO is a mitochondria-specific superoxide scavenger. The aim of this study was to investigate the effect of Mito-TEMPO on lipopolysaccharide- (LPS-) induced sepsis mice. We found that Mito-TEMPO pretreatment inhibited inflammation, attenuated LPS-induced liver injury, and enhanced the antioxidative capability in septic mice, as evidenced by the decreased MDA content and the increased SOD activity. In addition, Mito-TEMPO restored mitochondrial size and improved mitochondrial function. Finally, we found that the levels of pyroptosis-related proteins in the liver of LPS-treated mice were lower after pretreatment with Mito-TEMPO. The mechanisms could be related to Mito-TEMPO enhanced antioxidative capability and improved mitochondrial function, which reflects the ability to neutralize ROS.

Roles and Molecular Mechanisms of Physical Exercise in Sepsis Treatment

Physical exercise is a planned, purposeful action to keep a healthy lifestyle and improve physical fitness. Physical exercise has been widely used as a non-pharmacological approach to preventing and improving a wide range of diseases, including cardiovascular disease, cancer, metabolic disease, and neurodegenerative disease. However, the effects of physical exercise on sepsis have not been summarized until now. In this review, we discuss the effects of physical exercise on multiple organ functions and the short- and long-time outcomes of sepsis. Furthermore, the molecular mechanisms underlying the protective effects of physical exercise on sepsis are discussed. In conclusion, we consider that physical exercise may be a beneficial and non-pharmacological alternative for the treatment of sepsis.

Hydrogen-rich medium ameliorates lipopolysaccharides-induced mitochondrial fission and dysfunction in human umbilical vein endothelial cells (HUVECs) via up-regulating HO-1 expression

BACKGROUND

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. It has been showed that the change of mitochondrial dynamics has been proved to be one of the main causes of death in patients with severe sepsis. And hydrogen has been proved to exert its protective effects against sepsis via heme oxygenase-1 (HO-1). This study was designed to demonstrate that whether the benefit effects of hydrogen can maintain the dynamic process of mitochondrial fusion/fission to mitigate human umbilical vein endothelial cells (HUVECs) injury exposed to endotoxin through HO-1.

METHODS

HUVECs cells cultured with medium which contained Lipopolysaccharides (LPS), Saline, hydrogen, Mdivi-1 (a dynamin-related protein 1 [Drp1] inhibitor) or zinc protoporphyrin IX (Znpp) (a HO-1 inhibitor) were also used in the research. Cell death and apoptosis were assessed using FITC annexin V and PI. Mitochondria were stained with Mitotracker orange and observed by confocal microscope. Oxygen consumption rate was assessed by seahorse xf24 extracellular analyzer. Mitochondrial membrane potential monitored by JC-1 dye. The expressions of Drp1 and HO-1 were tested by Western blot. The co-localization of Drp1 and mitochondria was determined by immunofluorescence.

RESULTS

LPS caused a decrease in ATP content, mitochondrial membrane potential, and maximal respiration rate. At the same time, increased expression of Drp1 were observed in LPS-stimulated HUVECs, concomitantly with excessive mitochondrial fission. We found that hydrogen-rich medium can increase ATP content, mitochondrial membrane potential and maximal respiration rate, and decrease the expression of Drp1 in LPS-treated HUVECs. Meanwhile, hydrogen can ameliorate excessive mitochondrial fission caused by LPS. Furthermore, hydrogen-rich medium had a similar effect to Mdivi-1, a mitochondrial fission blocker. Both of them rescued the up-regulation of Drp1 and mitochondrial fission induced by LPS, then normalized mitochondrial shape after LPS stimulation. But after Znpp pretreatment, HO-1 expression was inhibited and the protective effects of hydrogen were abrogated.

CONCLUSIONS

Hydrogen-rich medium can alleviate the LPS-induced mitochondrial fusion/fission and dysfunction in HUVECs via HO-1 up-regulation.

Nrf2 Activation in Chronic Kidney Disease: Promises and Pitfalls

The nuclear factor erythroid 2-related factor 2 (Nrf2) protects the cell against oxidative damage. The Nrf2 system comprises a complex network that functions to ensure adequate responses to redox perturbations, but also metabolic demands and cellular stresses. It must be kept within a physiologic activity range. Oxidative stress and alterations in Nrf2-system activity are central for chronic-kidney-disease (CKD) progression and CKD-related morbidity. Activation of the Nrf2 system in CKD is in multiple ways related to inflammation, kidney fibrosis, and mitochondrial and metabolic effects. In human CKD, both endogenous Nrf2 activation and repression exist. The state of the Nrf2 system varies with the cause of kidney disease, comorbidities, stage of CKD, and severity of uremic toxin accumulation and inflammation. An earlier CKD stage, rapid progression of kidney disease, and inflammatory processes are associated with more robust Nrf2-system activation. Advanced CKD is associated with stronger Nrf2-system repression. Nrf2 activation is related to oxidative stress and moderate uremic toxin and nuclear factor kappa B (NF-κB) elevations. Nrf2 repression relates to high uremic toxin and NF-κB concentrations, and may be related to Kelch-like ECH-associated protein 1 (Keap1)-independent Nrf2 degradation. Furthermore, we review the effects of pharmacological Nrf2 activation by bardoxolone methyl, curcumin, and resveratrol in human CKD and outline strategies for how to adapt future Nrf2-targeted therapies to the requirements of patients with CKD.

Limited Heme Oxygenase Contribution to Modulating the Severity of Salmonella enterica serovar Typhimurium Infection

An important virulence trait of Salmonella enterica serovar Typhimurium (S. Typhimurium) is the ability to avoid the host immune response, generating systemic and persistent infections. Host cells play a crucial role in bacterial clearance by expressing the enzyme heme oxygenase 1 (Hmox1), which catalyzes the degradation of heme groups into Fe2+, biliverdin, and carbon monoxide (CO). The role of Hmox1 activity during S. Typhimurium infection is not clear and previous studies have shown contradictory results. We evaluated the effect of pharmacologic modulation of Hmox1 in a mouse model of acute and persistent S. Typhimurium infection by administering the Hmox1 activity inductor cobalt protoporphyrin-IX (CoPP) or inhibitor tin protoporphyrin-IX (SnPP) before infection. To evaluate the molecular mechanism involved, we measured the colocalization of S. Typhimurium and autophagosome and lysosomal markers in macrophages. Administering CoPP reduced the bacterial burden in organs of mice 5 days post-infection, while SnPP-treated mice showed bacterial loads similar to vehicle-treated mice. Furthermore, CoPP reduced bacterial loads when administered after infection in macrophages in vitro and in a persistent infection model of S. Typhimurium in vivo, while tin protoporphyrin-IX (SnPP) treatment resulted in a bacterial burden similar to vehicle-treated controls. However, we did not observe significant differences in co-localization of green fluorescent protein (GFP)-labeled S. Typhimurium with the autophagic vesicles marker microtubule-associated protein 1A/1B-light chain 3 (LC3) and the lysosomal marker lysosomal-associated membrane protein 1 (LAMP-1) in macrophages treated with CoPP. Our results suggest that CoPP can enhance antimicrobial activity in response to Salmonella infection, reducing bacterial dissemination and persistence in mice, in a CO and autophagy- independent manner.

Gases in Sepsis: Novel Mediators and Therapeutic Targets

Sepsis, a potentially lethal condition resulting from failure to control the initial infection, is associated with a dysregulated host defense response to pathogens and their toxins. Sepsis remains a leading cause of morbidity, mortality and disability worldwide. The pathophysiology of sepsis is very complicated and is not yet fully understood. Worse still, the development of effective therapeutic agents is still an unmet need and a great challenge. Gases, including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), are small-molecule biological mediators that are endogenously produced, mainly by enzyme-catalyzed reactions. Accumulating evidence suggests that these gaseous mediators are widely involved in the pathophysiology of sepsis. Many sepsis-associated alterations, such as the elimination of invasive pathogens, the resolution of disorganized inflammation and the preservation of the function of multiple organs and systems, are shaped by them. Increasing attention has been paid to developing therapeutic approaches targeting these molecules for sepsis/septic shock, taking advantage of the multiple actions played by NO, CO and H2S. Several preliminary studies have identified promising therapeutic strategies for gaseous-mediator-based treatments for sepsis. In this review article, we summarize the state-of-the-art knowledge on the pathophysiology of sepsis; the metabolism and physiological function of NO, CO and H2S; the crosstalk among these gaseous mediators; and their crucial effects on the development and progression of sepsis. In addition, we also briefly discuss the prospect of developing therapeutic interventions targeting these gaseous mediators for sepsis.

The Role of Iron in Staphylococcus aureus Infection and Human Disease: A Metal Tug of War at the Host—Microbe Interface

Iron deficiency anemia can be treated with oral or intravenous Fe supplementation. Such supplementation has considerable effects on the human microbiome, and on opportunistic pathogenic micro-organisms. Molecular understanding of the control and regulation of Fe availability at the host-microbe interface is crucial to interpreting the side effects of Fe supplementation. Here, we provide a concise overview of the regulation of Fe by the opportunistic pathogen Staphylococcus aureus. Ferric uptake regulator (Fur) plays a central role in controlling Fe uptake, utilization and storage in order to maintain a required value. The micro-organism has a strong preference for heme iron as an Fe source, which is enabled by the Iron-regulated surface determinant (Isd) system. The strategies it employs to overcome Fe restriction imposed by the host include: hijacking host proteins, replacing metal cofactors, and replacing functions by non-metal dependent enzymes. We propose that integrated omics approaches, which include metalloproteomics, are necessary to provide a comprehensive understanding of the metal tug of war at the host-microbe interface down to the molecular level.

Heme Oxygenase-1: An Anti-Inflammatory Effector in Cardiovascular, Lung, and Related Metabolic Disorders

The heme oxygenase (HO) enzyme system catabolizes heme to carbon monoxide (CO), ferrous iron, and biliverdin-IXα (BV), which is reduced to bilirubin-IXα (BR) by biliverdin reductase (BVR). HO activity is represented by two distinct isozymes, the inducible form, HO-1, and a constitutive form, HO-2, encoded by distinct genes (HMOX1, HMOX2, respectively). HO-1 responds to transcriptional activation in response to a wide variety of chemical and physical stimuli, including its natural substrate heme, oxidants, and phytochemical antioxidants. The expression of HO-1 is regulated by NF-E2-related factor-2 and counter-regulated by Bach-1, in a heme-sensitive manner. Additionally, HMOX1 promoter polymorphisms have been associated with human disease. The induction of HO-1 can confer protection in inflammatory conditions through removal of heme, a pro-oxidant and potential catalyst of lipid peroxidation, whereas iron released from HO activity may trigger ferritin synthesis or ferroptosis. The production of heme-derived reaction products (i.e., BV, BR) may contribute to HO-dependent cytoprotection via antioxidant and immunomodulatory effects. Additionally, BVR and BR have newly recognized roles in lipid regulation. CO may alter mitochondrial function leading to modulation of downstream signaling pathways that culminate in anti-apoptotic, anti-inflammatory, anti-proliferative and immunomodulatory effects. This review will present evidence for beneficial effects of HO-1 and its reaction products in human diseases, including cardiovascular disease (CVD), metabolic conditions, including diabetes and obesity, as well as acute and chronic diseases of the liver, kidney, or lung. Strategies targeting the HO-1 pathway, including genetic or chemical modulation of HO-1 expression, or application of BR, CO gas, or CO donor compounds show therapeutic potential in inflammatory conditions, including organ ischemia/reperfusion injury. Evidence from human studies indicate that HO-1 expression may represent a biomarker of oxidative stress in various clinical conditions, while increases in serum BR levels have been correlated inversely to risk of CVD and metabolic disease. Ongoing human clinical trials investigate the potential of CO as a therapeutic in human disease.

Local Treatment of Hydrogen-Rich Saline Promotes Wound Healing In Vivo by Inhibiting Oxidative Stress via Nrf-2/HO-1 Pathway

Wound healing is a complex dynamic process involving a large number of biological events. Excessive oxidative stress is a key factor delaying wound healing. Hydrogen is an antioxidant, anti-inflammatory, and antiapoptotic medical gas with safety, effectiveness, and penetrability. However, the effects of local treatment of hydrogen on wound healing and its potential mechanisms remain unclear. In this study, Kunming (KM) mice were used to set up a wound model. All the mice were randomly divided into the control, the local treatment with saline group, the local treatment with the hydrogen-rich saline group, and the intraperitoneal injection of the hydrogen-rich saline group. To evaluate the impact of hydrogen-rich saline on wound healing, we assessed the wound healing rate, wound closure time, histomorphology, oxidative stress indicators, inflammatory cytokines, the apoptosis index, and the expression of the nuclear factor-erythroid-related factor 2(Nrf-2). Furthermore, the immortalized nontumorigenic human epidermal (HaCaT) cells were chosen to investigate the therapeutic effects of hydrogen-rich medium on oxidative stress and its underlying mechanisms. The results showed that local treatment of hydrogen-rich saline shortened wound closure time and reduced the level of proinflammatory cytokines and lipid peroxidation. Meanwhile, it decreased the cell apoptosis index and increased the Nrf-2 expression. Besides, hydrogen-rich medium relieved the oxidative stress via the activation of the Nrf-2/heme oxygenase-1 (HO-1) pathway. In conclusion, local treatment of hydrogen-rich saline exhibits the healing-promoting function through antioxidant, anti-inflammatory, and antiapoptotic effects. Hydrogen relieves the oxidative stress in the wound microenvironment via Nrf-2/HO-1 signaling pathway. This study may offer a new strategy to promote wound healing and a new perspective to illustrate the mechanism of wound healing.

Dexmedetomidine modulates mitochondrial dynamics to protect against endotoxin-induced lung injury via the protein kinase C-ɑ/heme oxygenase-1 signaling pathway

BACKGROUND

Endotoxin-induced acute lung injury (ALI) has a high mortality rate, and there are limited effective treatment options available. The aim of the present study was to identify if dexmedetomidine could regulate mitochondrial fusion and fission through the protein kinase C (PKC)-α/heme oxygenase (HO)-1 pathway to protect against endotoxin-induced ALI.

MATERIALS AND METHODS

Dexmedetomidine was administered by intraperitoneal injection once daily for 3 days prior to induction of lung injury to mice. Mice in the PKC-α inhibitor group received dexmedetomidine by intraperitoneal injection 1 h after each chelerythrine injection, and lipopolysaccharide was injected 1 h after the last dose of dexmedetomidine. The lung wet/dry weight ratio, oxidative stress, inflammatory response, and expression levels of PKC-α, Nrf2, HO-1, Mfn1, Mfn2, OPA1, Drp1, and Fis1 were determined.

RESULTS

Dexmedetomidine administration attenuated lung oxidative stress, decreased inflammatory cytokines secretion, and downregulated the expression levels of Drp1 and Fis1. Moreover, dexmedetomidine increased levels of Mfn1, Mfn2, and OPA1, and alleviated endotoxin-induced lung injury. Administration of chelerythrine partially reversed the pneumoprotective effects of dexmedetomidine.

CONCLUSIONS

Dexmedetomidine may activate the PKC-ɑ/HO-1 pathway to increase the expression of Mfn1, Mfn2, and OPA1, while decreasing Drp1 and Fis1 expression, thereby reduce endotoxin-induced acute lung injury.

miR-221-5p-Mediated Downregulation of JNK2 Aggravates Acute Lung Injury

Sepsis and acute lung injury (ALI) are linked to mitochondrial dysfunction; however, the underlying mechanism remains elusive. We previously reported that c-Jun N-terminal protein kinase 2 (JNK2) promotes stress-induced mitophagy by targeting small mitochondrial alternative reading frame (smARF) for ubiquitin-mediated proteasomal degradation, thereby preventing mitochondrial dysfunction and restraining inflammasome activation. Here we report that loss of JNK2 exacerbates lung inflammation and injury during sepsis and ALI in mice. JNK2 is downregulated in mice with endotoxic shock or ALI, concomitantly correlated inversely with disease severity. Small RNA sequencing revealed that miR-221-5p, which contains seed sequence matching to JNK2 mRNA 3’ untranslated region (3’UTR), is upregulated in response to lipopolysaccharide, with dynamically inverse correlation with JNK2 mRNA levels. miR-221-5p targets the 3’UTR of JNK2 mRNA leading to its downregulation. Accordingly, miR-221-5p exacerbates lung inflammation and injury during sepsis in mice by targeting JNK2. Importantly, in patients with pneumonia in medical intensive care unit, JNK2 mRNA levels in alveolar macrophages flow sorted from non-bronchoscopic broncholaveolar lavage (BAL) fluid were inversely correlated strongly and significantly with the percentage of neutrophils, neutrophil and white blood cell counts in BAL fluid. Our data suggest that miR-221-5p targets JNK2 and thereby aggravates lung inflammation and injury during sepsis.

Nrf2 Activation Attenuates Chronic Constriction Injury-Induced Neuropathic Pain via Induction of PGC-1α-Mediated Mitochondrial Biogenesis in the Spinal Cord

BACKGROUND

Neuropathic pain is a debilitating disease with few effective treatments. Emerging evidence indicates the involvement of mitochondrial dysfunction and oxidative stress in neuropathic pain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a potent regulator of the antioxidant response system. In this study, we investigated whether RTA-408 (RTA, a novel synthetic triterpenoid under clinical investigation) could activate Nrf2 and promote mitochondrial biogenesis (MB) to reverse neuropathic pain and the underlying mechanisms.

METHODS

Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve. Pain behaviors were measured via the von Frey test and Hargreaves plantar test. The L4-6 spinal cord was collected to examine the activation of Nrf2 and MB.

RESULTS

RTA-408 treatment significantly reversed mechanical allodynia and thermal hyperalgesia in CCI mice in a dose-dependent manner. Furthermore, RTA-408 increased the activity of Nrf2 and significantly restored MB that was impaired in CCI mice in an Nrf2-dependent manner. Peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α) is the key regulator of MB. We found that the PGC-1α activator also induced a potent analgesic effect in CCI mice. Moreover, the antinociceptive effect of RTA-408 was reversed by the preinjection of the PGC-1α inhibitor.

CONCLUSIONS

Nrf2 activation attenuates chronic constriction injury-induced neuropathic pain via induction of PGC-1α-mediated mitochondrial biogenesis in the spinal cord. Our results indicate that Nrf2 may be a potential therapeutic strategy to ameliorate neuropathic pain and many other disorders with oxidative stress and mitochondrial dysfunction.

Simvastatin affects the PPARα signaling pathway and causes oxidative stress and embryonic development interference in Mugilogobius abei

Simvastatin (SV) is a common hypolipidemic drug in clinical medicine that can reduce endogenous cholesterol biosynthesis by inhibiting hydroxyl-methyl-glutaryl coenzyme A reductase. SV took a large market share in the lipid-lowering drugs and it is frequently detected in various water bodies due to its increasing consumption in past years. In the present investigation, we selected a native fish species in the Pearl River Basin in China, Mugilogobius abei (M. abei), to study the effects of SV on non-target aquatic organisms. Results showed that a significant decrease in the volume of adipocytes under SV exposure were observed on oil red O section, and the expression of HMG-CoAR decreased significantly. The mRNA and protein expression of PPARα were significantly up-regulated, the expressions of other genes related to lipid metabolism were up-regulated to varying degrees as well. There was a positive correlation between the concentrations of SV and the protein expressions of plasma phospholipid transfer protein (PLTP) and cholesterolester transfer protein (CETP). In addition, the frozen sections showed that SV led to ROS accumulation in liver in a time and concentration dependent manner. The mRNA and protein expressions of Nrf2 were significantly up-regulated after 24 hours of SV exposure. Some biomarkers associated with antioxidant such as Trx2, TrxR and MDA content were positively correlated with the exposure concentration and time, while the content of GSH decreased sharply. It is noteworthy that the environmentally relevant concentration (0.5 μg/L) of SV exposure caused delayed embryonic development and deformations, decreased hatching rates. We conclude that SV promotes fat metabolism, gives rise to oxidative stress and has significant toxicity on embryo development in M. abei.

Nuclear factor erythroid 2-related factor 2 protects bovine mammary epithelial cells against free fatty acid-induced mitochondrial dysfunction in vitro

Bovine mammary epithelial cells undergo an increase in metabolic rate, mitochondrial dysfunction, and oxidative stress after calving. Nuclear factor erythroid 2-related factor 2 (NFE2L2), a master regulator of cellular redox homeostasis, plays crucial roles in the regulation of mitochondrial function. The objective of this study was to investigate the role of NFE2L2 on mitochondrial function in bovine mammary epithelial cells under hyperlipidemic conditions. Three experiments were conducted as follows: (1) the immortalized bovine mammary epithelial cell line MAC-T was treated with various concentrations of free fatty acids (FFA; 0, 0.6, 1.2, or 2.4 mM) for 24 h to induce stress; (2) MAC-T cells were transfected with small interfering RNA targeting NFE2L2 (si-NFE2L2) and scrambled nontarget negative control (si-Control) for 48 h; and (3) MAC-T cells were pretreated with 10 μM sulforaphane (SFN), an activator of NFE2L2, for 24 h followed by treatment with 1.2 mM FFA for an additional 24 h. Results indicated that exogenous FFA challenge induced linear and quadratic increases in concentrations of mitochondrial reactive oxygen species (ROS). Compared with 0 mM FFA, mitochondrial membrane potential, mRNA abundance of oxidative phosphorylation complexes (CO I-V), protein abundance of nuclear respiratory factor 1 (NRF1), peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), mitochondrial transcription factor A (TFAM), and NFE2L2 along with the contents of ATP, mitochondrial DNA (mtDNA), and total mitochondria were greater in the MAC-T challenged with 0.6 mM FFA group, but lower in the 1.2 and 2.4 mM FFA cultures. Knockdown of NFE2L2 via small interfering RNA led to greater mitochondrial ROS content and lower mitochondrial membrane potential along with contents of ATP, mtDNA, and total mitochondria. The SFN pretreatment upregulated protein abundance of NFE2L2 and attenuated the downregulation of NFE2L2 induced by FFA. Pretreatment with SFN attenuated the downregulation induced by FFA of PGC-1α, NRF1, and TFAM protein abundance along with contents of mtDNA and total mitochondria. Furthermore, SFN pretreatment attenuated the upregulation of mitochondrial ROS content, the downregulation of mitochondrial membrane potential, and the decreases in ATP, mtDNA, and mitochondrial content induced by FFA. Overall, data indicated that FFA inhibit NFE2L2, resulting in mitochondrial dysfunction and ROS production in bovine mammary epithelial cells. Thus, NFE2L2 may be a promising therapeutic target against metabolic challenge-driven mitochondrial dysfunction and oxidative stress in bovine mammary epithelial cells.

Metabolic Reprogramming and Host Tolerance: A Novel Concept to Understand Sepsis-Associated AKI

Acute kidney injury (AKI) is a frequent complication of sepsis that increases mortality and the risk of progression to chronic kidney disease. However, the mechanisms leading to sepsis-associated AKI are still poorly understood. The recognition that sepsis induces organ dysfunction in the absence of overt necrosis or apoptosis has led to the consideration that tubular epithelial cells (TEC) may deploy defense mechanisms to survive the insult. This concept dovetails well with the notion that the defense against infection does not only depend on the capacity of the immune system to limit the microbial load (known as resistance), but also on the capacity of cells and tissues to limit tissue injury (known as tolerance). In this review, we discuss the importance of TEC metabolic reprogramming as a defense strategy during sepsis, and how this cellular response is likely to operate through a tolerance mechanism. We discuss the fundamental role of specific regulatory nodes and of mitochondria in orchestrating this response, and how this opens avenues for the exploration of targeted therapeutic strategies to prevent or treat sepsis-associated AKI.

Association between protoporphyrin IX and sarcopenia: a cross sectional study

Background

According to the European Working Group on Sarcopenia in Older People (EWGSOP), the diagnosis of sarcopenia primarily focused on low muscle strength with the detection of low muscle quality and quantity as confirming index. Many studies had identified mitochondrial dysfunction as one of the multifactorial etiologies of sarcopenia. Yet, no study had investigated the role of biosynthetic pathway intermediate, which was found in mitochondria, in the development of sarcopenia. This study aimed to examine the association between protoporphyrin IX (PPIX) and components of sarcopenia.

Method

The present study enrolled 1172 participants without anemia between 1999 to 2002 from the National Health and Nutrition Examination Survey (NHANES) database. We employed the multivariable-logistic regression model to examine the relationship between PPIX and sarcopenia. Covariate adjustments were designated to each of the three models for further analysis of the relationship.

Results

In the unadjusted model, PPIX was significantly associated with sarcopenia (OR = 3.910, 95% CI = 2.375, 6.439, P value < 0.001). The significance persisted after covariate adjustments as observed in the fully adjusted model (OR = 2.537, 95% CI = 1.419, 4.537, P value = 0.002).

Conclusions

The findings of this study suggested statistically significant association between PPIX and sarcopenia. Our study disclosed the potential of PPIX as a valuable indicator of sarcopenia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02331-6.

Pentoxifylline Enhances Antioxidative Capability and Promotes Mitochondrial Biogenesis in D-Galactose-Induced Aging Mice by Increasing Nrf2 and PGC-1α through the cAMP-CREB Pathway

Aging is a complex phenomenon associated with oxidative stress and mitochondrial dysfunction. The objective of this study was to investigate the potential ameliorative effects of the phosphodiesterase inhibitor pentoxifylline (PTX) on the aging process and its underlying mechanisms. We treated D-galactose- (D-gal-) induced aging mice with PTX and measured the changes in behavior, degree of oxidative damage, and mitochondrial ultrastructure and content as well as the expression of nuclear factor erythroid 2-related factor 2- (Nrf2-) mediated antioxidant genes and peroxisome proliferator-activated receptor-gamma coactivator 1-alpha- (PGC-1α-) dependent mitochondrial biogenesis genes. The results demonstrated that PTX improved cognitive deficits, reduced oxidative damage, ameliorated abnormal mitochondrial ultrastructure, increased mitochondrial content and Nrf2 activation, and upregulated antioxidant and mitochondrial biogenesis gene expression in the hippocampus of wild-type aging mice. However, the above antiaging effects of PTX were obviously decreased in the brains of Nrf2-deficient D-gal-induced aging mice. Moreover, in hydrogen peroxide-treated SH-SY5Y cells, we found that cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) and Nrf2/PGC-1α act in a linear way by CREB siRNA transfection. Thus, PTX administration improved the aging-related decline in brain function by enhancing antioxidative capability and promoting mitochondrial biogenesis, which might depend on increasing Nrf2 and PGC-1α by activating the cAMP-CREB pathway.

Hydrogen Sulfide Metabolite, Sodium Thiosulfate: Clinical Applications and Underlying Molecular Mechanisms

Thiosulfate in the form of sodium thiosulfate (STS) is a major oxidation product of hydrogen sulfide (H2S), an endogenous signaling molecule and the third member of the gasotransmitter family. STS is currently used in the clinical treatment of acute cyanide poisoning, cisplatin toxicities in cancer therapy, and calciphylaxis in dialysis patients. Burgeoning evidence show that STS has antioxidant and anti-inflammatory properties, making it a potential therapeutic candidate molecule that can target multiple molecular pathways in various diseases and drug-induced toxicities. This review discusses the biochemical and molecular pathways in the generation of STS from H2S, its clinical usefulness, and potential clinical applications, as well as the molecular mechanisms underlying these clinical applications and a future perspective in kidney transplantation.

Prognostic Significance of the Fission1/Parkin Ratio for Sepsis: A Prospective Cohort Study

Introduction: Fission1 (Fis1) and parkin are key proteins related to mitochondrial fission and mitophagy, respectively. This study aimed to assess the prognostic value of the Fis1/parkin ratio as a biomarker in patients with sepsis.

Methods: Consecutive patients with sepsis (n = 133) or simple infection (n = 24) were enrolled within 24 h of arrival at the intensive care unit (ICU). Serum levels of Fis1, parkin, mitofusin2 (Mfn2), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) were measured by enzyme-linked immunosorbent assay (ELISA) upon ICU admission. Clinical parameters and standard laboratory test data were also collected. All patients received follow-up for at least 28 days.

Results: Patients with sepsis presented with significantly decreased serum levels of parkin, Mfn2, and PGC-1α, but an increased serum Fis1 level and Fis1/parkin, Fis1/Mfn2, and Fis1/PGC-1α ratios at ICU admission. Relative to patients with simple infections, the ratios were remarkably elevated in septic patients—particularly septic shock patients. The area under the receiver operating characteristic (ROC) curve of the Fis1/parkin ratio was greater than that of Fis1, parkin, Mfn2, and PGC-1α levels as well as that of the Fis1/Mfn2 and Fis1/PGC-1α ratios for prediction of 28-day mortality due to sepsis. All of the ratios were significantly higher in non-survivors than survivors at the 28-day follow-up examination. Fis1/parkin ratio was found to be an independent predictor of 28-day mortality in patients with sepsis.

Conclusions: The Fis1/parkin ratio is valuable for risk stratification in patients with sepsis and is associated with poor clinical outcomes for sepsis in the ICU.

Upregulated-gene expression of pro-inflammatory cytokines, oxidative stress and apoptotic markers through inflammatory, oxidative and apoptosis mediated signaling pathways in Bovine Pneumonia

Pneumonia is the acute inflammation of lung tissue and is multi-factorial in etiology. Staphylococcus aureus (S. aureus) is a harmful pathogen present as a normal flora of skin and nares of dairy cattle. In bovine pneumonia, S. aureus triggers to activates Toll-Like Receptors (TLRs), that further elicits the activation of the inflammation via NF-κB pathway, oxidative stress and apoptotic pathways. In the current study, pathogen-associated gene expression of the pro-inflammatory cytokines, oxidative stress and apoptotic markers in the lung tissue of cattle was explored in bovine pneumonia. Fifty lung samples collected from abattoir located in Wuhan city, Hubei, China. Histopathologically, thickening of alveolar wall, accumulation of inflammatory cells and neutrophils in perivascular space, hyperemia, hemorrhages and edema were observed in infected lungs as compared to non-infected lung samples. Furthermore, molecular identification and characterization were carried by amplification of S. aureus-specific nuc gene (270 base pairs) from the infected and non-infected lung samples to identify the S. aureus. Moreover, qPCR results displayed that relative mRNA levels of TLR2, TLR4, pro-inflammatory gene (IL-1β, IL-6 and TNF-α) and apoptosis-associated genes (Bax, caspase-3 and caspase-9) were up-regulated except Bcl-2, which is antiapoptotic in nature, and oxidative stress related genes (Nrf2, NQO1, HO-1 and GCLC) which was down-regulated in infected pulmonary group. The relative protein expression of NF-κB, mitochondria-mediated apoptosis gene was up-regulated while Bcl-2 and Nrf2 pathway genes were downregulated in infected cattle lungs. Our findings revealed that genes expression levels of inflammatory mediators, oxidative stress and apoptosis were associated with host immunogenic regulatory mechanisms in the lung tissue during infection. Conclusively, the present study provides insights of active immune response via TLRs-mediated inflammatory, oxidative damage, and apoptotic paradox.

Intermittent hypoxia preconditioning protects WRL68 cells against oxidative injury: Involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1

The protective effect of intermittent hypoxia (IH) preconditioning against oxidative injury in hepatic cells was investigated and the involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1 (NRF-1) was evaluated. The results showed that IH preconditioning protected HepG2 cells against oxygen and glucose deprivation/reperfusion (OGD/Rep)-induced injury and protected WRL68 cells against H₂O₂ or AMA-induced oxidative injury. IH preconditioning up-regulated the protein level of NRF-1, PINK1, Parkin, and LC3 II, promoted the recruitment of the cytosolic Parkin, indicating the initiation of the PINK1/Parkin-mediated mitophagy in WRL68 cells. When NRF-1 was down-regulated by NRF-1 specific shRNA, the protein level of PINK1 and Parkin as well as the mitophagy level were significantly decreased. After IH preconditioning, the protein level of PINK1 and the recruitment of Parkin in CCCP-treated group were significantly higher than that of the control group, indicating the increased mitophagy capacity. And the increased mitophagy capacity induced by IH preconditioning was also reduced by down-regulation of NRF-1. Furthermore, the protective effect of IH preconditioning against H₂O₂-induced oxidative injury in WRL68 cells was inhibited when NRF-1 or PINK1 was down-regulated by specific shRNA. Mitochondrial ROS generation may be responsible for the increased expression of NRF-1 induced by IH preconditioning. In conclusion, the PINK1/Parkin-mediated mitophagy regulated by NRF-1 was involved in IH preconditioning-induced protective effect against oxidative cellular injury in hepatic cells.

Dihydromyricetin improves mitochondrial outcomes in the liver of alcohol-fed mice via the AMPK/Sirt-1/PGC-1α signaling axis

Alcoholic liver disease (ALD), due to the multifactorial damage associated with alcohol (ethanol) consumption and metabolism, is one of the most prevalent liver diseases in the United States. The liver is the primary site of ethanol metabolism and is subsequently injured due to the production of reactive oxygen species (ROS), acetaldehyde, and metabolic stress. Building evidence suggests that dihydromyricetin (DHM), a bioactive flavonoid isolated from Hovenia dulcis, provides hepatoprotection by enhancing ethanol metabolism in the liver by maintaining hepatocellular bioenergetics, reductions of oxidative stress, and activating lipid oxidation pathways. The present study investigates the utility of DHM on hepatic mitochondrial biogenesis via activation of the AMP-activated protein kinase (AMPK)/Sirtuin (Sirt)-1/PPARG coactivator 1 (PGC)-1α signaling pathway. We utilized a forced drinking ad libitum study that chronically fed 30% ethanol to male C57BL/6J mice over 8 weeks and induced ALD pathology. We found that chronic ethanol feeding resulted in the suppression of AMPK activation and cytoplasmic Sirt-1 and mitochondrial Sirt-3 expression, effects that were reversed with daily DHM administration (5 mg/kg; intraperitoneally [i.p.]). Chronic ethanol feeding also resulted in hepatic hyperacetylation of PGC-1α, which was improved with DHM administration and its mediated increase of Sirt-1 activity. Furthermore, ethanol-fed mice were found to have increased expression of mitochondrial transcription factor A (TFAM), reduced mitochondrial content as assessed by mitochondrial DNA to nuclear DNA ratios, and significantly lower levels of hepatic ATP. In contrast, DHM administration significantly increased TFAM expression, hepatic ATP concentrations, and induced mitochondrial expression of respiratory complex III and V. In total, this work demonstrates a novel mechanism of DHM that improves hepatic bioenergetics, metabolic signaling, and mitochondrial viability, thus adding to the evidence supporting the use of DHM for treatment of ALD and other metabolic disorders.

Mitochondrial Regulation of Macrophage Response Against Pathogens

Innate immune cells play the first line of defense against pathogens. Phagocytosis or invasion by pathogens can affect mitochondrial metabolism in macrophages by diverse mechanisms and shape the macrophage response (proinflammatory vs. immunomodulatory) against pathogens. Besides β-nicotinamide adenine dinucleotide 2'-phosphate, reduced (NADPH) oxidase, mitochondrial electron transport chain complexes release superoxide for direct killing of the pathogen. Mitochondria that are injured are removed by mitophagy, and this process can be critical for regulating macrophage activation. For example, impaired mitophagy can result in cytosolic leakage of mitochondrial DNA (mtDNA) that can lead to activation of cGAS-STING signaling pathway of macrophage proinflammatory response. In this review, we will discuss how metabolism, mtDNA, mitophagy, and cGAS-STING pathway shape the macrophage response to infectious agents.

Intercellular mitochondrial transfer as a means of tissue revitalization

As the crucial powerhouse for cell metabolism and tissue survival, the mitochondrion frequently undergoes morphological or positional changes when responding to various stresses and energy demands. In addition to intracellular changes, mitochondria can also be transferred intercellularly. Besides restoring stressed cells and damaged tissues due to mitochondrial dysfunction, the intercellular mitochondrial transfer also occurs under physiological conditions. In this review, the phenomenon of mitochondrial transfer is described according to its function under both physiological and pathological conditions, including tissue homeostasis, damaged tissue repair, tumor progression, and immunoregulation. Then, the mechanisms that contribute to this process are summarized, such as the trigger factors and transfer routes. Furthermore, various perspectives are explored to better understand the mysteries of cell-cell mitochondrial trafficking. In addition, potential therapeutic strategies for mitochondria-targeted application to rescue tissue damage and degeneration, as well as the inhibition of tumor progression, are discussed.