Mitochondrial reactive oxygen species generation triggers inflammatory response and tissue injury associated with hepatic ischemia-reperfusion: therapeutic potential of mitochondrially targeted antioxidants

Neutrophils and NADPH Oxidases Are Major Contributors to Mild but Not Severe Ischemic Acute Kidney Injury in Mice

Upregulation of free radical-generating NADPH oxidases (NOX), xanthine oxidoreductase (XOR), and neutrophil infiltration-induced, NOX2-mediated respiratory burst contribute to renal ischemia-reperfusion injury (IRI), but their roles may depend on the severity of IRI. We investigated the role of NOX, XOR, and neutrophils in developing IRI of various severities. C57BL/6 and Mcl-1ΔMyelo neutrophil-deficient mice were used. Oxidases were silenced by RNA interference (RNAi) or pharmacologically inhibited. Kidney function, morphology, immunohistochemistry and mRNA expression were assessed. After reperfusion, the expression of NOX enzymes and XOR increased until 6 h and from 15 h, respectively, while neutrophil infiltration was prominent from 3 h. NOX4 and XOR silencing or pharmacological XOR inhibition did not protect the kidney from IRI. Attenuation of NOX enzyme-induced oxidative stress by apocynin and neutrophil deficiency improved kidney function and ameliorated morphological damage after mild but not moderate/severe IRI. The IR-induced postischemic renal functional impairment (BUN, Lcn-2), tubular necrosis score, inflammation (TNF-α, F4/80), and decreases in the antioxidant enzyme (GPx3) mRNA expression were attenuated by both apocynin and neutrophil deficiency. Inhibition of NOX enzyme-induced oxidative stress or the lack of infiltration by NOX2-expressing neutrophils can attenuate reperfusion injury after mild but not moderate/severe renal IR.

Mitochondrial Targeted Interventions for Aging

Changes in mitochondrial function play a critical role in the basic biology of aging and age-related disease. Mitochondria are typically thought of in the context of ATP production and oxidant production. However, it is clear that the mitochondria sit at a nexus of cell signaling where they affect metabolite, redox, and energy status, which influence many factors that contribute to the biology of aging, including stress responses, proteostasis, epigenetics, and inflammation. This has led to growing interest in identifying mitochondrial targeted interventions to delay or reverse age-related decline in function and promote healthy aging. In this review, we discuss the diverse roles of mitochondria in the cell. We then highlight some of the most promising strategies and compounds to target aging mitochondria in preclinical testing. Finally, we review the strategies and compounds that have advanced to clinical trials to test their ability to improve health in older adults.

Mitochondrial quality control in liver fibrosis: Epigenetic hallmarks and therapeutic strategies

BACKGROUND AND AIM

Mitochondrial quality control (MQC) plays a significant role in the progression of liver fibrosis, with key processes such as mitochondrial fission, fusion, mitophagy and biogenesis maintaining mitochondrial homeostasis. To understand the molecular mechanisms underlying epigenetic regulation of mitochondrial quality control in liver fibrosis, with the aim of uncovering novel therapeutic targets for treating, mitigating, and potentially reversing liver fibrosis, in light of the most recent advances in this field.

METHODS

We searched PubMed, Web of Science, and Scopus for published manuscripts using terms "mitochondrial quality control" "mitochondrial fission" "mitochondrial fusion" "mitochondrial biogenesis" "mitophagy" "liver fibrosis" "epigenetic regulation" "DNA methylation" "RNA methylation" "histone modification" and "non-coding RNA". Manuscripts were collated, studied and carried forward for discussion where appropriate.

RESULTS

Mitochondrial fission, fusion, biogenesis, and mitophagy regulate the homeostasis of mitochondria, and the imbalance of mitochondrial homeostasis can induce liver fibrosis. Epigenetic regulation, including DNA methylation, RNA methylation, histone modifications, and non-coding RNAs, plays a significant role in regulating the processes of mitochondrial homeostasis.

CONCLUSION

Mitochondrial quality control and epigenetic mechanisms are intricately linked to the pathogenesis of liver fibrosis. Understanding these molecular interactions provides insight into potential therapeutic strategies. Further research is necessary to translate these findings into clinical applications, with a focus on developing epigenetic drugs to ameliorate liver fibrosis by modulating MQC and epigenetic pathways.

Mitoquinone alleviates osteoarthritis progress by activating the NRF2-Parkin axis

Osteoarthritis (OA) is a prevalent degenerative disease of the elderly. The NRF2 antioxidant system plays a critical role in maintaining redox balance. Mitoquinone (MitoQ) is a mitochondria-targeted antioxidant. This research aimed to determine whether MitoQ alleviated OA and the role of the NRF2/Parkin axis in MitoQ-mediated protective effects. In interleukin (IL)-1β-induced OA chondrocytes, MitoQ activated the NRF2 pathway, reducing extracellular matrix (ECM) degradation and inflammation. MitoQ also increased glutathione peroxidase 4 (GPX4) expression, leading to decreased levels of reactive oxygen species (ROS) and lipid ROS. Silencing NRF2 weakened MitoQ's protective effects, while knockdown of Parkin upregulated the NRF2 pathway, inhibiting OA progression. Intra-articular injection of MitoQ mitigated cartilage destruction in destabilized medial meniscus (DMM)-induced OA mice. Our study demonstrates that MitoQ maintains cartilage homeostasis in vivo and in vitro through the NRF2/Parkin axis. We supplemented the negative feedback regulation mechanism between NRF2 and Parkin. These findings highlight the therapeutic potential of MitoQ for OA treatment.

Unveiling the Crucial Roles of O2•- and ATP in Hepatic Ischemia-Reperfusion Injury Using Dual-Color/Reversible Fluorescence Imaging

Hepatic ischemia-reperfusion injury (HIRI) is mainly responsible for morbidity or death due to graft rejection after liver transplantation. During HIRI, superoxide anion (O2•-) and adenosine-5'-triphosphate (ATP) have been identified as pivotal biomarkers associated with oxidative stress and energy metabolism, respectively. However, how the temporal and spatial fluctuations of O2•- and ATP coordinate changes in HIRI and particularly how they synergistically regulate each other in the pathological mechanism of HIRI remains unclear. Herein, we rationally designed and successfully synthesized a dual-color and dual-reversible molecular fluorescent probe (UDP) for dynamic and simultaneous visualization of O2•- and ATP in real-time, and uncovered their interrelationship and synergy in HIRI. UDP featured excellent sensitivity, selectivity, and reversibility in response to O2•- and ATP, which rendered UDP suitable for detecting O2•- and ATP and generating independent responses in the blue and red fluorescence channels without spectral crosstalk. Notably, in situ imaging with UDP revealed for the first time synchronous O2•- bursts and ATP depletion in hepatocytes and mouse livers during the process of HIRI. Surprisingly, a slight increase in ATP was observed during reperfusion. More importantly, intracellular O2•-─succinate dehydrogenase (SDH)─mitochondrial (Mito) reduced nicotinamide adenine dinucleotide (NADH)─Mito ATP─intracellular ATP cascade signaling pathway in the HIRI process was unveiled which illustrated the correlation between O2•- and ATP for the first time. This research confirms the potential of UDP for the dynamic monitoring of HIRI and provides a clear illustration of HIRI pathogenesis.

Redox-crippled MitoQ potently inhibits breast cancer and glioma cell proliferation: A negative control for verifying the antioxidant mechanism of MitoQ in cancer and other oxidative pathologies

Mitochondria-targeted coenzyme Q10 (Mito-ubiquinone, Mito-quinone mesylate, or MitoQ) was shown to be an effective antimetastatic drug in patients with triple-negative breast cancer. MitoQ, sold as a nutritional supplement, prevents breast cancer recurrence. It potently inhibited tumor growth and tumor cell proliferation in preclinical xenograft models and in vitro breast cancer cells. The proposed mechanism of action involves the inhibition of reactive oxygen species by MitoQ via a redox-cycling mechanism between the oxidized form, MitoQ, and the fully reduced form, MitoQH2 (also called Mito-ubiquinol). To fully corroborate this antioxidant mechanism, we substituted the hydroquinone group (-OH) with the methoxy group (-OCH3). Unlike MitoQ, the modified form, dimethoxy MitoQ (DM-MitoQ), lacks redox-cycling between the quinone and hydroquinone forms. DM-MitoQ was not converted to MitoQ in MDA-MB-231 cells. We tested the antiproliferative effects of both MitoQ and DM-MitoQ in human breast cancer (MDA-MB-231), brain-homing cancer (MDA-MB-231BR), and glioma (U87MG) cells. Surprisingly, DM-MitoQ was slightly more potent than MitoQ (IC50 = 0.26 μM versus 0.38 μM) at inhibiting proliferation of these cells. Both MitoQ and DM-MitoQ potently inhibited mitochondrial complex I-dependent oxygen consumption (IC50 = 0.52 μM and 0.17 μM, respectively). This study also suggests that DM-MitoQ, which is a more hydrophobic analog of MitoQ (logP: 10.1 and 8.7) devoid of antioxidant function and reactive oxygen species scavenging ability, can inhibit cancer cell proliferation. We conclude that inhibition of mitochondrial oxidative phosphorylation by MitoQ is responsible for inhibition of breast cancer and glioma proliferation and metastasis. Blunting the antioxidant effect using the redox-crippled DM-MitoQ can serve as a useful negative control in corroborating the involvement of free radical-mediated processes (e.g., ferroptosis, protein oxidation/nitration) using MitoQ in other oxidative pathologies.

Nitroxide-HMP-Protects Human Trophoblast HTR-8/SVneo Cells from H2O2-Induced Oxidative Stress by Reducing the HIF1A Signaling Pathway

Preeclampsia (PE) is a pregnancy-specific syndrome affecting 5-7% of patients. There is no effective treatment available. Early abnormal placental development is associated with oxidative stress (OS) and a release of reactive oxygen species (ROS) in the placenta. This phenomenon leads to downstream signaling, Hypoxia Inducible Factor 1A (HIF1A) stabilization and transcription of the anti-angiogenic factors soluble fms-like tyrosine kinase 1 (sFLT1) and soluble endoglin (sEng), which are known to cause endothelial and trophoblast dysfunction and cardinal features of PE: hypertension, proteinuria and, in severe cases, eclampsia. We tested whether 3-(Hydroxymethyl)-1-oxy-2,2,5,5-tetramethylpyrrolidine (HMP)-a nitroxide-type antioxidant molecule-can reduce placental OS and mitigate PE symptoms in vitro. We induced OS in human trophoblast (HTR-8/SVneo) cells with hydrogen peroxide (H2O2) and assessed whether modulating cell redox function with HMP reduces cell injury, mitochondrial stress and HIF1A and sFLT1 production. Pre-treatment with HMP reduced mitochondrial-derived ROS production, restored LC3B expression and reduced HIF1A and sFLT1 expression in H2O2-exposed HTR-8/SVneo trophoblast cells. HMP improved the mitochondrial electron chain enzyme activity, indicating that a reduction in OS alleviates mitochondrial stress and also reduces anti-angiogenic responses. In reducing placental trophoblast OS, HMP presents a potential novel therapeutic approach for the treatment of PE. Future investigation is warranted regarding the in vivo use of HMP.

Single-cell transcriptomic analysis uncovers diverse and dynamic senescent cell populations

Senescence is a state of enduring growth arrest triggered by sublethal cell damage. Given that senescent cells actively secrete proinflammatory and matrix-remodeling proteins, their accumulation in tissues of older persons has been linked to many diseases of aging. Despite intense interest in identifying robust markers of senescence, the highly heterogeneous and dynamic nature of the senescent phenotype has made this task difficult. Here, we set out to comprehensively analyze the senescent transcriptome of human diploid fibroblasts at the individual-cell scale by performing single-cell RNA-sequencing analysis through two approaches. First, we characterized the different cell states in cultures undergoing senescence triggered by different stresses, and found distinct cell subpopulations that expressed mRNAs encoding proteins with roles in growth arrest, survival, and the secretory phenotype. Second, we characterized the dynamic changes in the transcriptomes of cells as they developed etoposide-induced senescence; by tracking cell transitions across this process, we found two different senescence programs that developed divergently, one in which cells expressed traditional senescence markers such as p16 (CDKN2A) mRNA, and another in which cells expressed long noncoding RNAs and splicing was dysregulated. Finally, we obtained evidence that the proliferation status at the time of senescence initiation affected the path of senescence, as determined based on the expressed RNAs. We propose that a deeper understanding of the transcriptomes during the progression of different senescent cell phenotypes will help develop more effective interventions directed at this detrimental cell population.

Development of a Novel Ex Vivo Porcine Hepatic Segmental Perfusion Proof-of-Concept Model Towards More Ethical Translational Research

Introduction Ex vivo machine perfusion describes the technique where organs are continuously perfused and oxygenated extracorporeally (at physiological conditions) to maintain the organs' viability. To our knowledge, there are currently no reported studies describing ex vivo perfusion of a single hepatic segment. Here, we describe the development of a porcine ex vivo hepatic segmental perfusion model to demonstrate proof of concept and support further research into the ex vivo perfusion of the human liver using discarded tissue.  Methods Whole livers were retrieved from abattoir-derived pigs and connected to a normothermic extracorporeal perfusion circuit. Constant segmental perfusion via the common or segmental hepatic artery and portal vein with heparinised autologous blood was established. The viability of the perfused organ was assessed by monitoring perfusion pressures, flow rates and histology samples. Results Following perfusion and optimisation of the model for three hepatic segments, the third perfusion demonstrated viable hepatocytes centrally after 4 h of segmental perfusion. Conclusion Ex vivo hepatic segmental perfusion is technically challenging but its success in a porcine model and the principles learned should facilitate the development of an analogous human model using discarded tissue following formal liver resections. The model would use a healthy liver segment following a major formal resection such as a hemi-hepatectomy and ex vivo perfusion performed via a segmental hepatic artery and portal vein. If successful this model would represent a significant development and enable ethical translation research to assess the response of human livers to a variety of stressors, including toxicity and infection.

Antioxidant Mitoquinone Alleviates Chronic Pancreatitis via Anti-Fibrotic and Antioxidant Effects

Background

Chronic pancreatitis (CP) is a long-term inflammatory disease of the pancreas that can be caused by various pathogenic factors. Oxidative stress (OS), which is associated with several pancreatic diseases, can induce pancreatic stellate cell (PSC) activation, leading to pancreatic fibrosis. Given the inefficacy of existing treatments for CP, in this study, our objective was to evaluate the therapeutic effect of the antioxidant, mitoquinone (MitoQ).

Methods

First, in vivo, we established a CP mouse model via the repeated injection of cerulein. Mice in the MitoQ group simultaneously received MitoQ daily. After 4 weeks of cerulein injection, pancreatic tissues from mice were evaluated by morphological changes and the expression of fibrosis markers. Further, OS in the collected pancreatic tissue samples was evaluated by determining the level of malondialdehyde (MDA) as well as the expression levels and activities of antioxidants. Furthermore, in vitro, the effect of MitoQ on human PSCs (hPSCs) was evaluated based on PSC activation markers and fibrotic phenotypes, and OS in these treated hPSCs was evaluated by measuring reactive oxygen species (ROS), MDA, and antioxidant levels.

Results

In vivo, MitoQ alleviated pancreatic fibrosis and inhibited OS in the cerulein-induced murine CP model. In vitro, it inhibited PSC activation as well as the subsequent development of the profibrogenic phenotypes by balancing out the levels of free radicals and the intracellular antioxidant system.

Conclusion

MitoQ is a potential candidate for CP treatment.

The mitochondria-targeted antioxidant MitoQ ameliorates myocardial ischemia-reperfusion injury by enhancing PINK1/Parkin-mediated mitophagy in type 2 diabetic rats

Type 2 diabetic hearts are more vulnerable to myocardial ischemia reperfusion (MIR) injury, which involves decreased mitophagy status with unknown mechanisms. MitoQ, a mitochondria-targeted antioxidant, has been shown to have protection against ischemia reperfusion injury through upregulating mitophagy. The aim of this study was to investigate the effects of MitoQ on myocardium during MIR injury in type 2 diabetes (T2D). Herein, this study discovered that type 2 diabetic hearts with PINK1/Parkin downregulation suffered more MIR injury accompanied by reduced mitophagy. Treatment with MitoQ significantly decreased the levels of CK-MB, LDH, myocardial infarction, myocardial pathological damage, and cardiomyocytes apoptosis, while it improved cardiac function, mitophagy status, and PINK1/Parkin pathway in vivo study. Furthermore, MitoQ significantly reduced high glucose/high fat and hypoxia/reoxygenation induced injury in H9C2 cells as evidenced by reduced cardiomyocytes apoptosis and ROS production, and increased cell viability, the level of mitochondrial membrane potential, PINK1/Parkin expression. However, mitochondrial division inhibitor (mdivi-1), an inhibitor of mitophagy, reversed the improvement and protein expression levels of PINK1/Parkin pathway in vitro models. In conclusion, MIR induced more severe damage in T2D by reduction of mitophagy. MitoQ can confer cardioprotection following MIR in T2D by mitophagy up-regulation via PINK1/Parkin pathway.

Synthesis and anti-inflammatory activity of paeonol derivatives with etherized aryl urea by regulating TLR4/MyD88 signaling pathway in RAW264.7 cell

Thirty-three novel paeonol etherized aryl urea derivatives (PEUs) were synthesized via a bromination-Williamson Ether Synthesis-deprotection-nucleophilic addition reaction sequence. The structures of PEUs were characterized by LC-MS, HRMS, ¹H NMR and ¹³C NMR spectra. The levels of nitric oxide (NO), tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages were initially employed to evaluate the anti-inflammatory effects of all compounds. Remarkably, b16 exhibited a good anti-inflammatory activity at 2.5 μm which is the same as the potency of paeonol at 20 μm. The results of mechanism research displayed that the anti-inflammatory effect of b16 was ascribed to the inhibition of the TLR4/MyD88 signaling pathway and inflammatory factors. Additionally, b16 distinctly reduced the generation of free radicals in macrophages and strikingly increased the mitochondrial membrane potential. According to the structure-activity relationships (SAR) of PEUs, the incorporation of halogens on the benzene ring and the hydrogen of phenol hydroxyl substituted by aryl urea, were beneficial to enhance the anti-inflammatory activities. Molecular docking results illustrated that the binding ability of b16 to TLR4 was stronger than that of paeonol. In summary, the novel aryl urea-derivied paeonol b16 could be a new promising candidate for the treatment of inflammation-related diseases.

Effects of the methanol fraction of modified Seonghyangjeongki-san water extract on transient ischaemic brain injury in mice

CONTEXT

Recently in Korean medicine, the antioxidant and anti-inflammatory activities of Seonghyangjeongki-san (SHJKS) were reported. However, studies on the specific mechanisms of action of SHJKS for the treatment of ischaemic stroke are still lacking.

OBJECTIVE

This study investigates the mechanism of action of the water extract methanol fraction of modified SHJKS (SHJKSmex) on cerebral ischaemic injury.

MATERIALS AND METHODS

C57BL/6 male mice were orally administered SHJKSmex (30, 100, or 300 mg/kg) for 3 consecutive days (2 days, 1 day, and 1 h, respectively) before middle cerebral artery occlusion (MCAO). Twenty-four hours after MCAO, the infarct volumes were measured, brain edoema indices were calculated, and neurological deficit scores were determined. Inflammation-related substances in the ipsilateral hemisphere were determined by western blotting, dichlorofluorescin diacetate, thiobarbituric acid-reactive substances assay, and enzyme-linked immunosorbent assay.

RESULTS

SHJKSmex pre-treatment at 300 mg/kg decreased infarct volume by 87% and mean brain water content by 90% of the MCAO control group. Moreover, SHJKSmex effectively suppressed the expression of inducible nitric oxide synthase, reactive oxygen species, interleukin 1, and caspases-8 and -9 and increased the B-cell lymphoma 2/Bcl-2-associated X protein ratio (Bcl-2/Bax) in ischaemic mouse brain. The hippocampal pyramidal cell densities were significantly increased in the 300 mg/kg SHJKSmex-administered group compared to the MCAO control group.

DISCUSSION AND CONCLUSIONS

SHJKSmex protected the brain from ischaemic stroke in mice through its antioxidant, anti-inflammatory, and antiapoptotic activities. Our findings suggest that SHJKSmex is a promising therapeutic candidate for the development of a new formulation for ischaemia-induced brain damage.

MitoQ inhibits hepatic stellate cell activation and liver fibrosis by enhancing PINK1/parkin-mediated mitophagy

Mitophagy affects the activation of hepatic stellate cells (HSCs). Mitochondria-targeted ubiquinone (MitoQ) is a mitochondria-targeted antioxidant that reduces the production of intracellular reactive oxygen species (ROS). However, its relationship with mitophagy remains unclear. This study evaluated mitophagy during HSC activation and the effects of MitoQ on mitophagy in cell culture and in an animal model of the activation of HSCs. We found that MitoQ reduced the activation of HSCs and alleviated hepatic fibrosis. PINK1 (PTEN-induced putative kinase 1) is a putative serine/threonine kinase located in the mitochondria’s outer membrane. While the activation of primary HSCs or LX-2 cells was associated with reduced PINK1/parkin-mediated mitophagy, MitoQ reduced intracellular ROS levels, enhanced PINK1/parkin-mediated mitophagy, and inhibited the activation of HSCs. After knocking down the key mitophagy-related protein, PINK1, in LX-2 cells to block mitophagy, MitoQ intervention failed to inhibit HSC activation. Our results showed that MitoQ inhibited the activation of HSCs and alleviated hepatic fibrosis by enhancing PINK1/parkin-mediated mitophagy.

Role of microRNA‑218‑5p in sevoflurane‑induced protective effects in hepatic ischemia/reperfusion injury mice by regulating GAB2/PI3K/AKT pathway

Hepatic ischemia/reperfusion (I/R) injury (HIRI) often occurs following tissue resection, hemorrhagic shock or transplantation surgery. Previous investigations showed that sevoflurane (Sevo), an inhalation anesthetic, had protective properties against different organ damage in animal models including HIRI. This study is aimed to investigate the underlying mechanisms involved in the protective effects of Sevo on HIRI. The present study results showed that treatment with Sevo improved histologic damage, inflammatory response, oxidative stress and apoptosis after hepatic I/R, indicating the protective role of Sevo against liver I/R injury. Importantly, in order to determine the molecular mechanism of Sevo in HIRI, the focus of the study was on microRNA (miR) regulation. By retrieving the microarray data in the Gene Expression Omnibus dataset (GSE72315), miR-218-5p was found to be significantly downregulated by Sevo. Moreover, miR-218-5p overexpression using agomiR-218-5p reversed the protective roles of Sevo against HIRI. Furthermore, GAB2, a positive regulator of PI3K/AKT signaling pathway, was found as a target gene of miR-218-5p. It was also found that the Sevo-mediated protective effects may be dependent on the activation of GAB2/PI3K/AKT. Collectively, these data revealed that Sevo alleviated HIRI in mice by restraining apoptosis, relieving oxidative stress and inflammatory response through the miR-218-5p/GAB2/PI3K/AKT pathway, which helps in understanding the novel mechanism of the hepatic-protection of Sevo.

Integrative Analysis of the Roles of lncRNAs and mRNAs in Itaconate-Mediated Protection Against Liver Ischemia-Reperfusion Injury in Mice

Purpose

Itaconate is well known for its strong anti-inflammatory and antioxidant effect, but little is known about the potential role of long non-coding RNAs (lncRNAs) in the underlying mechanisms of hepatic ischemia-reperfusion (IR) injury. The aim of our study is to identify lncRNAs related to IR injury and itaconate-mediated protection and to demonstrate the mechanism by which itaconate acts in liver IR injury from the new perspective of lncRNAs.

Methods

4-Octyl itaconate (OI), a membrane-permeable derivative of itaconate, was used as a substitute for itaconate in our study. By using a mouse model of hepatic IR injury, serum and liver samples were collected to measure indexes of liver injury. Then, the liver samples of the mice were subjected to RNA sequencing (RNA-seq) and subsequent bioinformatics analysis.

Results

Itaconate attenuated liver IR injury. A total of 138 lncRNAs and 156 messenger RNAs (mRNAs) were markedly differentially expressed in the IR-damaged liver tissues pretreated with OI compared with the matched liver tissues treated with vehicle. Functional analysis indicated that lncRNAs may indirectly participate in the effects of itaconate. Furthermore, 41 mRNAs were examined for the protein-protein interaction (PPI) network analysis, and a key gene cluster was defined. Then, combined the coexpression analysis and the cis and trans regulatory function prediction of lncRNAs, some "candidate" lncRNA-mRNA pairs which might relate to itaconate-mediated liver protection were identified, while the relationship requires future validation.

Conclusion

Our study revealed that itaconate could protect the liver against IR injury and that lncRNAs might play a role in this process. Our study provides a novel way to investigate the mechanism by which itaconate affects hepatic IR injury and exerts its anti-inflammatory and antioxidative stress effects.

Targeting oxidative stress, a crucial challenge in renal transplantation outcome

Disorders characterized by ischemia/reperfusion (I/R) are the most common causes of debilitating diseases and death in stroke, cardiovascular ischemia, acute kidney injury or organ transplantation. In the latter example the I/R step defines both the amplitude of the damages to the graft and the functional recovery outcome. During transplantation the kidney is subjected to blood flow arrest followed by a sudden increase in oxygen supply at the time of reperfusion. This essential clinical protocol causes massive oxidative stress which is at the basis of cell death and tissue damage. The involvement of both reactive oxygen species (ROS) and nitric oxides (NO) has been shown to be a major cause of these cellular damages. In fact, in non-physiological situations, these species escape endogenous antioxidant control and dangerously accumulate in cells. In recent years, the objective has been to find clinical and pharmacological treatments to reduce or prevent the appearance of oxidative stress in ischemic pathologies. This is very relevant because, due to the increasing success of organ transplantation, clinicians are required to use limit organs, the preservation of which against oxidative stress is crucial for a better outcome. This review highlights the key actors in oxidative stress which could represent new pharmacological targets.

PGC-1α Protects against Hepatic Ischemia Reperfusion Injury by Activating PPARα and PPARγ and Regulating ROS Production

Peroxisome proliferator-activated receptors (PPARs) α and γ have been shown to be protective in hepatic ischemia/reperfusion (I/R) injury. However, the precise role of PPARγ coactivator-1α (PGC-1α), which can coactivate both of these receptors, in hepatic I/R injury, remains largely unknown. This study was designed to test our hypothesis that PGC-1α is protective during hepatic I/R injury in vitro and in vivo. Our results show that endogenous PGC-1α is basally expressed in normal livers and is moderately increased by I/R. Ectopic PGC-1α protects against hepatic I/R and hepatocyte anoxia/reoxygenation (A/R) injuries, whereas knockdown of endogenous PGC-1α aggravates such injuries, as evidenced by assessment of the levels of serum aminotransferases and inflammatory cytokines, necrosis, apoptosis, cell viability, and histological examination. The EMSA assay shows that the activation of PPARα and PPARγ is increased or decreased by the overexpression or knockdown of PGC-1α, respectively, during hepatic I/R and hepatocyte A/R injuries. In addition, the administration of specific antagonists of either PPARα (MK886) or PPARγ (GW9662) can effectively decrease the protective effect of PGC-1α against hepatic I/R and hepatocyte A/R injuries. We also demonstrate an important regulatory role of PGC-1α in reactive oxygen species (ROS) metabolism during hepatic I/R, which is correlated with the induction of ROS-detoxifying enzymes and is also dependent on the activations of PPARα and PPARγ. These data demonstrate that PGC-1α protects against hepatic I/R injury, mainly by regulating the activation of PPARα and PPARγ. Thus, PGC-1α may be a promising therapeutic target for the protection of the liver against I/R injury.

A role of connexin 43 on the drug-induced liver, kidney, and gastrointestinal tract toxicity with associated signaling pathways

Drug-induced organ toxicity/injury, especially in the liver, kidney, and gastrointestinal tract, is a systematic disorder that causes oxidative stress formation and inflammation resulting in cell death and organ failure. Current therapies target reactive oxygen species (ROS) scavenging and inhibit inflammatory factors in organ injury to restore the functions and temporary relief. Organ cell function and tissue homeostasis are maintained through gap junction intercellular communication, regulating connexin hemichannels. Mis-regulation of such connexin, especially connexin (Cx) 43, affects a comprehensive process, including cell differentiation, inflammation, and cell death. Aim to describe knowledge about the importance of connexin role and insights therapeutic targeting. Cx43 misregulation has been implicated in recent decades in various diseases. Moreover, in recent years there is increasing evidence that Cx43 is involved in the toxicity process, including hepatic, renal, and gastrointestinal disorders. Cx43 has the potential to initiate the immune system to cause cell death, which has been activated in the acceleration of apoptosis, necroptosis, and autophagy signaling pathway. So far, therapies targeting Cx43 have been under inspection and are subjected to clinical trial phases. This review elucidates the role of Cx43 in drug-induced vital organ injury, and recent reports compromise its function in the major signaling pathways.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Involvement of kindlin-2 in irisin's protection against ischaemia reperfusion-induced liver injury in high-fat diet-fed mice

Liver steatosis is associated with increased ischaemia reperfusion (I/R) injury. Our previous studies have shown that irisin, an exercise-induced hormone, mitigates I/R injury via binding to αVβ5 integrin. However, the effect of irisin on I/R injury in steatotic liver remains unknown. Kindlin-2 directly interacts with β integrin. We therefore suggest that irisin protects against I/R injury in steatotic liver via a kindlin-2 dependent mechanism. To study this, hepatic steatosis was induced in male adult mice by feeding them with a 60% high-fat diet (HFD). At 12 weeks after HFD feeding, the mice were subjected to liver ischaemia by occluding partial (70%) hepatic arterial/portal venous blood for 60 minutes, which was followed by 24 hours reperfusion. Our results showed HFD exaggerated I/R-induced liver injury. Irisin (250 μg/kg) administration at the beginning of reperfusion attenuated liver injury, improved mitochondrial function, and reduced oxidative and endoplasmic reticulum stress in HFD-fed mice. However, kindlin-2 inhibition by RNAi eliminated irisin's direct effects on cultured hepatocytes. In conclusion, irisin attenuates I/R injury in steatotic liver via a kindlin-2 dependent mechanism.

Role of NAD+-Modulated Mitochondrial Free Radical Generation in Mechanisms of Acute Brain Injury

It is commonly accepted that mitochondria represent a major source of free radicals following acute brain injury or during the progression of neurodegenerative diseases. The levels of reactive oxygen species (ROS) in cells are determined by two opposing mechanisms—the one that produces free radicals and the cellular antioxidant system that eliminates ROS. Thus, the balance between the rate of ROS production and the efficiency of the cellular detoxification process determines the levels of harmful reactive oxygen species. Consequently, increase in free radical levels can be a result of higher rates of ROS production or due to the inhibition of the enzymes that participate in the antioxidant mechanisms. The enzymes’ activity can be modulated by post-translational modifications that are commonly altered under pathologic conditions. In this review we will discuss the mechanisms of mitochondrial free radical production following ischemic insult, mechanisms that protect mitochondria against free radical damage, and the impact of post-ischemic nicotinamide adenine mononucleotide (NAD⁺) catabolism on mitochondrial protein acetylation that affects ROS generation and mitochondrial dynamics. We propose a mechanism of mitochondrial free radical generation due to a compromised mitochondrial antioxidant system caused by intra-mitochondrial NAD⁺ depletion. Finally, the interplay between different mechanisms of mitochondrial ROS generation and potential therapeutic approaches are reviewed.

Connexin 32 deficiency protects the liver against ischemia/reperfusion injury

Hepatic ischemia/reperfusion (I/R) injury is a common complication in the clinical setting. Our previous study has shown that connexin 32 (Cx32) plays a major role in renal I/R injury; however, the role of Cx32 in hepatic I/R injury remains unknown. Liver tissue and serum samples from patients undergoing orthotopic liver transplantation (OLT) were used to evaluate the function of Cx32 in OLT post-reperfusion injury. Then, partial hepatic ischemia was established in global Cx32 knockout mice and wild-type mice followed by reperfusion. Hepatic injury markers were examined. Cx32 small interfering RNA and the p53 inhibitor, pifithrin-α, tenovin-1 were used to examine the relationship between Cx32 and the p53/puma pathways in the BRL-3A and murine primary hepatocytes hypoxia/reoxygenation (H/R) model. Corresponding to liver damage, Cx32 was significantly induced both during OLT in human patients and partial hepatic I/R in mice. Cx32 KO mice exhibited less liver injury than controls. Cx32 deficiency significantly suppressed the p53/puma pathways and hepatocyte apoptosis. Similar results were observed in the BRL-3A and murine primary hepatocytes H/R model. Propofol protected against OLT post-reperfusion injury and hepatocyte apoptosis by inhibiting Cx32. In conclusion Cx32 is a novel regulator of hepatic I/R injury through the modulation of hepatocyte apoptosis and damage, largely via the p53/puma signaling pathway.

Exercise training protects the heart against ischemia-reperfusion injury: A central role for mitochondria?

Ischemic heart disease is one of the main causes of morbidity and mortality worldwide. Physical exercise is an effective lifestyle intervention to reduce the risk factors for cardiovascular disease and also to improve cardiac function and survival in patients with ischemic heart disease. Among the strategies that contribute to reduce heart damages during ischemia and reperfusion, regular physical exercise is efficient both in rodent experimental models and in humans. However, the cellular and molecular mechanisms of the cardioprotective effects of exercise remain unclear. During ischemia and reperfusion, mitochondria are crucial players in cell death, but also in cell survival. Although exercise training can influence mitochondrial function, the consequences on heart sensitivity to ischemic insults remain elusive. In this review, we describe the effects of physical activity on cardiac mitochondria and their potential key role in exercise-induced cardioprotection against ischemia-reperfusion damage. Based on recent scientific data, we discuss the role of different pathways that might help to explain why mitochondria are a key target of exercise-induced cardioprotection.

Implications of hydrogen sulfide in liver pathophysiology: Mechanistic insights and therapeutic potential

Background

Over the last several decades, hydrogen sulfide (H₂S) has been found to exert multiple physiological functions in mammal systems. The endogenous production of H₂S is primarily mediated by cystathione β-synthase (CBS), cystathione γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes are widely expressed in the liver tissues and regulate hepatic functions by acting on various molecular targets.

Aim of Review

In the present review, we will highlight the recent advancements in the cellular events triggered by H₂S under liver diseases. The therapeutic effects of H₂S donors on hepatic diseases will also be discussed.

Key Scientific Concepts of Review

As a critical regulator of liver functions, H₂S is critically involved in the etiology of various liver disorders, such as nonalcoholic steatohepatitis (NASH), hepatic fibrosis, hepatic ischemia/reperfusion (IR) injury, and liver cancer. Targeting H₂S-producing enzymes may be a promising strategy for managing hepatic disorders.

The mitochondria-targeted anti-oxidant MitoQ protects against intervertebral disc degeneration by ameliorating mitochondrial dysfunction and redox imbalance

Objective

Mitochondrial dysfunction, oxidative stress and nucleus pulposus (NP) cell apoptosis are important contributors to the development and pathogenesis of intervertebral disc degeneration (IDD). Here, we comprehensively evaluated the effects of mitochondrial dynamics, mitophagic flux and Nrf2 signalling on the mitochondrial quality control, ROS production and NP cell survival in in vitro and ex vivo compression models of IDD and explored the effects of the mitochondria‐targeted anti‐oxidant MitoQ and its mechanism.

Material and methods

Human NP cells were exposed to mechanical compression to mimic pathological conditions.

Results

Compression promoted oxidative stress, mitochondrial dysfunction and NP cell apoptosis. Mechanistically, compression disrupted the mitochondrial fission/fusion balance, inducing fatal fission. Concomitantly, PINK1/Parkin‐mediated mitophagy was activated, whereas mitophagic flux was blocked. Nrf2 anti‐oxidant pathway was insufficiently activated. These caused the damaged mitochondria accumulation and persistent oxidative damage. Moreover, MitoQ restored the mitochondrial dynamics balance, alleviated the impairment of mitophagosome‐lysosome fusion and lysosomal function and enhanced the Nrf2 activity. Consequently, damaged mitochondria were eliminated, redox balance was improved, and cell survival increased. Additionally, MitoQ alleviated IDD in an ex vivo rat compression model.

Conclusions

These findings suggest that comodulation of mitochondrial dynamics, mitophagic flux and Nrf2 signalling alleviates sustained mitochondrial dysfunction and oxidative stress and represents a promising therapeutic strategy for IDD; furthermore, our results provide evidence that MitoQ might serve as an effective therapeutic agent for this disorder.

Redox Control of the Immune Response in the Hepatic Progenitor Cell Niche

The liver commonly self-regenerates by a proliferation of mature cell types. Nevertheless, in case of severe or protracted damage, the organ renewal is mediated by the hepatic progenitor cells (HPCs), adult progenitors capable of differentiating toward the biliary and the hepatocyte lineages. This regeneration process is determined by the formation of a stereotypical niche surrounding the emerging progenitors. The organization of the HPC niche microenvironment is crucial to drive biliary or hepatocyte regeneration. Furthermore, this is the site of a complex immunological activity mediated by several immune and non-immune cells. Indeed, several cytokines produced by monocytes, macrophages and T-lymphocytes may promote the activation of HPCs in the niche. On the other side, HPCs may produce pro-inflammatory cytokines induced by liver inflammation. The inflamed liver is characterized by high generation of reactive oxygen and nitrogen species, which in turn lead to the oxidation of macromolecules and the alteration of signaling pathways. Reactive species and redox signaling are involved in both the immunological and the adult stem cell regeneration processes. It is then conceivable that redox balance may finely regulate the immune response in the HPC niche, modulating the regeneration process and the immune activity of HPCs. In this perspective article, we summarize the current knowledge on the role of reactive species in the regulation of hepatic immunity, suggesting future research directions for the study of redox signaling on the immunomodulatory properties of HPCs.

Use of S1QELs and S3QELs to link mitochondrial sites of superoxide and hydrogen peroxide generation to physiological and pathological outcomes

Changes in mitochondrial superoxide and hydrogen peroxide production may contribute to various pathologies, and even aging, given that over time and in certain conditions, they damage macromolecules and disrupt normal redox signalling. Mitochondria-targeted antioxidants such as mitoQ, mitoVitE, and mitoTEMPO have opened up the study of the importance of altered mitochondrial matrix superoxide/hydrogen peroxide in disease. However, the use of such tools has caveats and they are unable to distinguish precise sites of production within the reactions of substrate oxidation and the electron transport chain. S1QELs are specific small-molecule Suppressors of site IQElectron Leak and S3QELs are specific small-molecule Suppressors of site IIIQoElectron Leak; they prevent superoxide/hydrogen production at specific sites without affecting electron transport or oxidative phosphorylation. We discuss the benefits of using S1QELs and S3QELs as opposed to mitochondria-targeted antioxidants, mitochondrial poisons, and genetic manipulation. We summarise pathologies in which site IQ in mitochondrial complex I and site IIIQo in mitochondrial complex III have been implicated using S1QELs and S3QELs.

Puerarin protects against high-fat high-sucrose diet-induced non-alcoholic fatty liver disease by modulating PARP-1/PI3K/AKT signaling pathway and facilitating mitochondrial homeostasis

As yet, there was no effective pharmacological therapy approved for non-alcoholic fatty liver disease (NAFLD). Here, we aimed to evaluate the therapeutic potential of puerarin against NAFLD and explored the underlying mechanisms. C57BL/6J mice were fed with a high-fat high-sucrose (HFHS) diet with or without puerarin coadministration intragastrically. The levels of hepatocellular injury, steatosis, fibrosis, and mitochondrial and metabolism alteration were detected. First, puerarin ameliorated histopathologic abnormalities due to HFHS. We observed a marked increase in hepatic lipid content, inflammation, and fibrosis level, which were attenuated by puerarin. Possible mechanisms were related to puerarin-mediated activation of PI3K/AKT pathway and further improvement in fatty acid metabolism. Puerarin restored the NAD+ content and beneficially affected the hepatic mitochondrial function, which attenuated HFHS-induced steatosis and metabolic disturbances. Finally, hepatic PARP-1 was activated due to excessive fat intake. Puerarin attenuated the PARP-1 expression in HFHS-fed mice, and PJ34, the PARP inhibitor, could mimic these protections of puerarin. However, pharmacological inhibition of PI3K disabled the protection of puerarin or PJ34 toward NAD+ refilling and mitochondrial homeostasis. In conclusion, our findings indicated that puerarin could be a promising and practical therapeutic strategy in NAFLD through modulating PARP-1/PI3K/AKT signaling pathway and further facilitating mitochondrial function.

TNFα-Mediated Necroptosis Aggravates Ischemia-Reperfusion Injury in the Fatty Liver by Regulating the Inflammatory Response

Nonalcoholic fatty liver disease (NAFLD) is more sensitive to ischemia and reperfusion injury (IRI), while there are no effective methods to alleviate IRI. Necroptosis, also known as “programmed necrosis,” incorporates features of necrosis and apoptosis. However, the role of necroptosis in IRI of the fatty liver remains largely unexplored. In the present study, we aimed to assess whether necroptosis was activated in the fatty liver and whether such activation accelerated IRI in the fatty liver. In this study, we found that the liver IRI was enhanced in HFD-fed mice with more release of TNFα. TNFα and supernatant of macrophages could induce necroptosis of hepatocytes in vitro. Necroptosis was activated in NAFLD, leading to more severe IRI, and such necroptosis could be inhibited by TN3-19.12, the neutralizing monoclonal antibody against TNFα. Pretreatment with Nec-1 and GSK′872, two inhibitors of necroptosis, significantly reduced the liver IRI and ROS production in HFD-fed mice. Moreover, the inhibition of necroptosis could decrease ROS production of hepatocytes in vitro. Inflammatory response was activated during IRI, and necroptosis inhibitors could suppress signaling pathways of inflammation and the soakage of inflammation cells. In conclusion, TNFα-induced necroptosis played an important role during IRI in the fatty liver. Our findings demonstrated that necroptosis might be a potential target to reduce the fatty liver-associated IRI.

Emerging therapeutic strategies for transplantation-induced acute kidney injury: protecting the organelles and the vascular bed

INTRODUCTION

Renal ischemia-reperfusion injury (IRI) is a significant clinical challenge faced by clinicians in a broad variety of clinical settings such as perioperative and intensive care. Renal IRI induced acute kidney injury (AKI) is a global public health concern associated with high morbidity, mortality, and health-care costs. Areas covered: This paper focuses on the pathophysiology of transplantation-related AKI and recent findings on cellular stress responses at the intersection of 1. The Unfolded protein response; 2. Mitochondrial dysfunction; 3. The benefits of mineralocorticoid receptor antagonists. Lastly, perspectives are offered to the readers. Expert opinion: Renal IRI is caused by a sudden and temporary impairment of blood flow to the organ. Defining the underlying cellular cascades involved in IRI will assist us in the identification of novel interventional targets to attenuate IRI with the potential to improve transplantation outcomes. Targeting mitochondrial function and cellular bioenergetics upstream of cellular damage may offer several advantages compared to targeting downstream inflammatory and fibrosis processes. An improved understanding of the cellular pathophysiological mechanisms leading to kidney injury will hopefully offer improved targeted therapies to prevent and treat the injury in the future.

Fasting reduces oxidative stress, mitochondrial dysfunction and fibrosis induced by renal ischemia-reperfusion injury

Food deprivation protects against ischemia-reperfusion (IR) injury through unknown mechanisms. In an experimental rat model of acute IR injury, we found that preoperative fasting for 3 days protects rats from tubular damage and renal functional decline by increasing antioxidant protection independently of the NF-E2-related factor 2 (Nrf2), and by maintaining mitochondrial morphology and function. In addition, further analysis revealed that fasting protects against tubulointerstitial fibrosis. In summary, our results point out to fasting as a robust nutritional intervention to limit oxidative stress and mitochondrial dysfunction in early acute kidney injury and also to promote long-term protection against fibrosis.

Ischaemia reperfusion injury in liver transplantation: Cellular and molecular mechanisms

Liver disease causing end organ failure is a growing cause of mortality. In most cases, the only therapy is liver transplantation. However, liver transplantation is a complex undertaking and its success is dependent on a number of factors. In particular, liver transplantation is subject to the risks of ischaemia-reperfusion injury (IRI). Liver IRI has significant effects on the function of a liver after transplantation. The cellular and molecular mechanisms governing IRI in liver transplantation are numerous. They involve multiple cells types such as liver sinusoidal endothelial cells, hepatocytes, Kupffer cells, neutrophils and platelets acting via an interconnected network of molecular pathways such as activation of toll-like receptor signalling, alterations in micro-RNA expression, production of ROS, regulation of autophagy and activation of hypoxia-inducible factors. Interestingly, the cellular and molecular events in liver IRI can be correlated with clinical risk factors for IRI in liver transplantation such as donor organ steatosis, ischaemic times, donor age, and donor and recipient coagulopathy. Thus, understanding the relationship of the clinical risk factors for liver IRI to the cellular and molecular mechanisms that govern it is critical to higher levels of success after liver transplantation. This in turn will help in the discovery of therapeutics for IRI in liver transplantation - a process that will lead to improved outcomes for patients suffering from end-stage liver disease.

Role of CYP2E1 in Mitochondrial Dysfunction and Hepatic Injury by Alcohol and Non-Alcoholic Substances

Alcoholic fatty liver disease (AFLD) and non-alcoholic fatty liver disease (NAFLD) are two pathological conditions that are spreading worldwide. Both conditions are remarkably similar with regard to the pathophysiological mechanism and progression despite different causes. Oxidative stressinduced mitochondrial dysfunction through post-translational protein modifications and/or mitochondrial DNA damage has been a major risk factor in both AFLD and NAFLD development and progression. Cytochrome P450-2E1 (CYP2E1), a known important inducer of oxidative radicals in the cells, has been reported to remarkably increase in both AFLD and NAFLD. Interestingly, CYP2E1 isoforms expressed in both endoplasmic reticulum (ER) and mitochondria, likely lead to the deleterious consequences in response to alcohol or in conditions of NAFLD after exposure to high fat diet (HFD) and in obesity and diabetes. Whether CYP2E1 in both ER and mitochondria work simultaneously or sequentially in various conditions and whether mitochondrial CYP2E1 may exert more pronounced effects on mitochondrial dysfunction in AFLD and NAFLD are unclear. The aims of this review are to briefly describe the role of CYP2E1 and resultant oxidative stress in promoting mitochondrial dysfunction and the development or progression of AFLD and NAFLD, to shed a light on the function of the mitochondrial CYP2E1 as compared with the ER-associated CYP2E1. We finally discuss translational research opportunities related to this field.

The damage-associated molecular pattern HMGB1 is released early after clinical hepatic ischemia/reperfusion

OBJECTIVE AND BACKGROUND

Activation of sterile inflammation after hepatic ischemia/reperfusion (I/R) culminates in liver injury. The route to liver damage starts with mitochondrial oxidative stress and cell death during early reperfusion. The link between mitochondrial oxidative stress, damage-associate molecular pattern (DAMP) release, and sterile immune signaling is incompletely understood and lacks clinical validation. The aim of the study was to validate this relation in a clinical liver I/R cohort and to limit DAMP release using a mitochondria-targeted antioxidant in I/R-subjected mice.

METHODS

Plasma levels of the DAMPs high-mobility group box 1 (HMGB1), mitochondrial DNA, and nucleosomes were measured in 39 patients enrolled in an observational study who underwent a major liver resection with (N = 29) or without (N = 13) intraoperative liver ischemia. Circulating cytokine and neutrophil activation markers were also determined. In mice, the mitochondria-targeted antioxidant MitoQ was intravenously infused in an attempt to limit DAMP release, reduce sterile inflammation, and suppress I/R injury.

RESULTS

In patients, HMGB1 was elevated following liver resection with I/R compared to liver resection without I/R. HMGB1 levels correlated positively with ischemia duration and peak post-operative transaminase (ALT) levels. There were no differences in mitochondrial DNA, nucleosome, or cytokine levels between the two groups. In mice, MitoQ neutralized hepatic oxidative stress and decreased HMGB1 release by ±50%. MitoQ suppressed transaminase release, hepatocellular necrosis, and cytokine production. Reconstituting disulfide HMGB1 during reperfusion reversed these protective effects.

CONCLUSION

HMGB1 seems the most pertinent DAMP in clinical hepatic I/R injury. Neutralizing mitochondrial oxidative stress may limit DAMP release after hepatic I/R and reduce liver damage.

Advances in therapeutic options for portal hypertension

Portal hypertension represents one of the major clinical consequences of chronic liver disease, having a deep impact on patients' prognosis and survival. Its pathophysiology defines a pathological increase in the intrahepatic vascular resistance as the primary factor in its development, being subsequently aggravated by a paradoxical increase in portal blood inflow. Although extensive preclinical and clinical research in the field has been developed in recent decades, no effective treatment targeting its primary mechanism has been defined. The present review critically summarizes the current knowledge in portal hypertension therapeutics, focusing on those strategies driven by the disease pathophysiology and underlying cellular mechanisms.

SIRT3 a Major Player in Attenuation of Hepatic Ischemia-Reperfusion Injury by Reducing ROS via Its Downstream Mediators: SOD2, CYP-D, and HIF-1α

Reactive oxygen species (ROS) production in hepatic ischemia-reperfusion injury (IRI) is a complex process where multiple cellular and molecular pathways are involved. Few of those molecular pathways are under the direct influence of SIRT3 and its downstream mediators. SIRT3 plays a major role in the mechanism of IRI, and its activation has been shown to attenuate the deleterious effect of ROS during IRI via SOD2-, CYP-D-, and HIF-1α-mediated pathways. The objective of this review is to analyze the current knowledge on SIRT3 and its downstream mediators: SOD2, CYP-D, and HIF-1α, and their role in IRI. For the references of this review article, we have searched the bibliographic databases of PubMed, Web of Science databases, MEDLINE, and EMBASE with the headings "SIRT3," "SOD2," "CYP-D," "HIF-1α," and "liver IRI." Priority was given to recent experimental articles that provide information on ROS modulation by these proteins. All the recent advancement demonstrates that activation of SIRT3 can suppress ROS production during IRI through various pathways and few of those are via SOD2, CYP-D, and HIF-1α. This effect can improve the quality of the remnant liver following resection as well as a transplanted liver. More research is warranted to disclose its role in IRI attenuation via this pathway.

AP39, a Modulator of Mitochondrial Bioenergetics, Reduces Antiangiogenic Response and Oxidative Stress in Hypoxia-Exposed Trophoblasts: Relevance for Preeclampsia Pathogenesis

Although the cause of preeclampsia, a pregnancy complication with significant maternal and neonatal morbidity, has not been fully characterized, placental ischemia attributable to impaired spiral artery remodeling and abnormal secretion of antiangiogenic factors are thought to be important in the pathogenesis of the disease. Placental ischemia could impair trophoblast mitochondrial function and energy production, leading to the release of reactive oxygen species (ROS). ROS have been shown to stabilize hypoxia-inducible factor (HIF)-1α, which, in turn, may induce transcription of antiangiogenic factors, soluble fms-like tyrosine kinase 1 (sFLT1), and soluble endoglin in trophoblasts. Herein, we tested whether the angiogenic imbalance and oxidative stress in the preeclamptic placenta may be prevented by improving mitochondrial function. First, to evaluate the cause-effect relationship between mitochondrial function and sFLT1 production, a human trophoblast primary cell culture model was established in which hypoxia induced mitochondrial ROS production and concurrent sFLT1 increase. Second, treatment with AP39, a novel mitochondria-targeted hydrogen sulfide donor, prevented ROS production, reduced HIF-1α protein levels, and diminished sFLT1 production. Finally, AP39, a modulator of mitochondrial bioenergetics enhanced cytochrome c oxidase activity, reversed oxidative stress and antiangiogenic response in hypoxic trophoblasts. These results suggest that placental hypoxia induces ROS production, HIF-1α stabilization, and sFLT1 up-regulation; these pathophysiological alterations can be attenuated by mitochondrial-targeted antioxidants.

Nicotinamide mononucleotide preserves mitochondrial function and increases survival in hemorrhagic shock

Hemorrhagic shock depletes nicotinamide adenine dinucleotide (NAD) and causes metabolic derangements that, in severe cases, cannot be overcome, even after restoration of blood volume and pressure. However, current strategies to treat acute blood loss do not target cellular metabolism. We hypothesized that supplemental nicotinamide mononucleotide (NMN), the immediate biosynthetic precursor to NAD, would support cellular energetics and enhance physiologic resilience to hemorrhagic shock. In a rodent model of decompensated hemorrhagic shock, rats receiving NMN displayed significantly reduced lactic acidosis and serum IL-6 levels, two strong predictors of mortality in human patients. In both livers and kidneys, NMN increased NAD levels and prevented mitochondrial dysfunction. Moreover, NMN preserved mitochondrial function in isolated hepatocytes cocultured with proinflammatory cytokines, indicating a cell-autonomous protective effect that is independent from the reduction in circulating IL-6. In kidneys, but not in livers, NMN was sufficient to prevent ATP loss following shock and resuscitation. Overall, NMN increased the time animals could sustain severe shock before requiring resuscitation by nearly 25% and significantly improved survival after resuscitation (P = 0.018), whether NMN was given as a pretreatment or only as an adjunct during resuscitation. Thus, we demonstrate that NMN substantially mitigates inflammation, improves cellular metabolism, and promotes survival following hemorrhagic shock.

Resolvin D1 attenuates liver ischaemia/reperfusion injury through modulating thioredoxin 2-mediated mitochondrial quality control

BACKGROUND AND PURPOSE

Liver ischaemia and reperfusion (IR) injury is a sterile inflammatory response involving production of ROS. Mitochondrial homeostasis is maintained by mitochondrial quality control (QC). Thioredoxin (TRX) 2 is a key mitochondrial redox-sensitive protein. Resolvin D1 (RvD1), a specialized pro-resolving lipid mediator, exerts anti-inflammatory and antioxidant activities. We investigated mechanisms of RvD1 protection against IR-induced oxidative damage to the liver, focusing on TRX2-mediated mitochondrial QC.

EXPERIMENTAL APPROACH

Mice underwent partial warm IR. RvD1 was administered 1 h before ischaemia and immediately prior to reperfusion. Human liver carcinoma HepG2 cells were exposed to hypoxia/reoxygenation and transfected with TRX2 siRNA. Immunohistochemistry, Western blotting and enzyme assays were used to follow changes in mitochondrial structure and function.

KEY RESULTS

RvD1 attenuated hepatocellular damage following IR, assessed by serum aminotransferase activities and histology. RvD1 reduced mitochondrial swelling, lipid peroxidation and glutamate dehydrogenase release. Impaired activities of mitochondrial complexes I and III were restored by RvD1. RvD1 enhanced expression of the mitophagy-related protein, Parkin and inhibited accumulation of PTEN-induced putative kinase 1. RvD1 restored levels of mitochondrial biogenesis proteins including PPARγ coactivator 1α, nuclear respiratory factor 1 and mitochondrial transcription factor A and mtDNA level. RvD1 attenuated the increase in levels of the mitochondrial fission-related protein, dynamin-related protein 1. IR reduced TRX2 levels while increasing TRX2 association with TRX-interacting protein. RvD1 attenuated these changes. The regulatory effects of RvD1 on mitochondrial QC were abolished by TRX2 knockdown.

CONCLUSIONS AND IMPLICATIONS

We suggest that RvD1 ameliorated IR-induced hepatocellular damage by regulating TRX2-mediated mitochondrial QC.

Oxidative and ER stress-dependent ASK1 activation in steatotic hepatocytes and Kupffer cells sensitizes mice fatty liver to ischemia/reperfusion injury

Steatosis intensifies hepatic ischemia/reperfusion (I/R) injury increasing hepatocyte damage and hepatic inflammation. This study evaluates if this process is associated to a differential response of steatotic hepatocytes (HP) and Kupffer cells (KC) to I/R injury and investigates the molecular mechanisms involved. Control or steatotic (treated with 50 μmol palmitic acid, PA) mouse HP or KC were exposed to hypoxia/reoxygenation (H/R). C57BL/6 mice fed 9 week with control or High Fat diet underwent to partial hepatic IR. PA increased H/R damage of HP and further activated the ASK1-JNK axis stimulated by ER stress during H/R. PA also induced the production of oxidant species (OS), and OS prevention nullified the capacity of PA to increase H/R damage and ASK1/JNK stimulation. ASK1 inhibition prevented JNK activation and entirely protected HP damage. In KC, PA directly activated ER stress, ASK1 and p38 MAPK and increased H/R damage. However, in contrast to HP, ASK1 inhibition further increased H/R damage by preventing p38 MAPK activation. In mice liver, steatosis induced the expression of activated ASK1 in only KC, whereas I/R exposure of steatotic liver activated ASK1 expression also in HP. "In vivo", ASK1 inhibition prevented ASK1, JNK and p38 MAPK activation and protected I/R damage and expression of inflammatory markers.

CONCLUSIONS

Lipids-induced ASK1 stimulation differentially affects HP and KC by promoting cytotoxic or protective signals. ASK1 increases H/R damage of HP by stimulating JNK and protects KC activating p38MAPK. These data support the potentiality of the therapeutic employment of ASK1 inhibitors that can antagonize the damaging effects of I/R upon fatty liver surgery by the contextual reduction of HP death and of KC-mediated reactions.

Effects of pretreatment with methanol extract of Peucedani Radix on transient ischemic brain injury in mice

BACKGROUND

Stroke is the second most common cause of death and may result in various disabilities; thus, identification of neuroprotective therapeutic agents is important. Peucedani Radix (PR), the root of Angelica decursiva, is a well-known remedy for damp and phlegm in Korean medicine and has also been shown to exert antioxidant and anti-inflammatory activities. This study was performed to investigate the mechanism underlying the anti-inflammatory effect of methanol extract of PR (PRex) on cerebral ischemic injury.

METHODS

C57BL/6 male mice were orally administered PRex (20, 60, or 200 mg/kg) at 2 days, 1 day, and 1 h prior to middle cerebral artery occlusion (MCAO). Twenty-four hours after MCAO, the infarct volume was measured and the neurological deficit score was assessed. The inflammatory-related substances in the ipsilateral hemisphere were determined by western blotting, DCFH-DA assay, TBARS assay, and ELISA.

RESULTS

PRex pretreatment significantly decreased the infarct volume at 24 h after MCAO. Moreover, PRex effectively suppressed the expression of iNOS, ROS, MDA, and pro-inflammatory cytokines, such as IL-1β and TNF-α, in brain tissue of mice with MCAO-induced brain injury.

CONCLUSIONS

PRex protected neurons from ischemic brain injury in mice through its antioxidant and anti-inflammatory activities. Our results suggested that PR could be a promising candidate in the therapy of ischemia-induced brain damage.

Cannabidiol attenuates alcohol-induced liver steatosis, metabolic dysregulation, inflammation and neutrophil-mediated injury

Cannabidiol (CBD) is a non-psychoactive component of marijuana, which has anti-inflammatory effects. It has also been approved by FDA for various orphan diseases for exploratory trials. Herein, we investigated the effects of CBD on liver injury induced by chronic plus binge alcohol feeding in mice. CBD or vehicle was administered daily throughout the alcohol feeding study. At the conclusion of the feeding protocol, serums samples, livers or isolated neutrophils were utilized for molecular biology, biochemistry and pathology analysis. CBD significantly attenuated the alcohol feeding-induced serum transaminase elevations, hepatic inflammation (mRNA expressions of TNFα, MCP1, IL1β, MIP2 and E-Selectin, and neutrophil accumulation), oxidative/nitrative stress (lipid peroxidation, 3-nitrotyrosine formation, and expression of reactive oxygen species generating enzyme NOX2). CBD treatment also attenuated the respiratory burst of neutrophils isolated from chronic plus binge alcohol fed mice or from human blood, and decreased the alcohol-induced increased liver triglyceride and fat droplet accumulation. Furthermore, CBD improved alcohol-induced hepatic metabolic dysregulation and steatosis by restoring changes in hepatic mRNA or protein expression of ACC-1, FASN, PPARα, MCAD, ADIPOR-1, and mCPT-1. Thus, CBD may have therapeutic potential in the treatment of alcoholic liver diseases associated with inflammation, oxidative stress and steatosis, which deserves exploration in human trials.

IDH2 deficiency increases the liver susceptibility to ischemia-reperfusion injury via increased mitochondrial oxidative injury

Mitochondrial NADP⁺-dependent isocitrate dehydrogenase 2 (IDH2) is a major producer of mitochondrial NADPH, required for glutathione (GSH)-associated mitochondrial antioxidant systems including glutathione peroxidase (GPx) and glutathione reductase (GR). Here, we investigated the role of IDH2 in hepatic ischemia-reperfusion (HIR)-associated mitochondrial injury using Idh2-knockout (Idh2^-/-) mice and wild-type (Idh2^+/+) littermates. Mice were subjected to either 60min of partial liver ischemia or sham-operation. Some mice were administered with 2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride (mito-TEMPO, a mitochondria-targeting antioxidant). HIR induced severe histological and functional damages of liver in both Idh2^+/+ mice and Idh2^-/- mice and those damages were more severe in Idh2^-/- mice than in wild-type littermates. HIR induces dysfunction of IDH2, leading to the decreases of NADPH level and mitochondrial GR and GPx functions, consequently resulting in mitochondrial and cellular oxidative injury as reflected by mitochondrial cristae loss, mitochondrial fragmentation, shift in mitochondrial fission, cytochrome c release, and cell death. These HIR-induced changes were greater in Idh2^-/- mice than wild-type mice. The mito-TEMPO supplement significantly attenuated the aforementioned changes, and these attenuations were much greater in Idh2^-/- mice when compared with wild-type littermates. Taken together, results have demonstrated that HIR impairs in the IDH2-NADPH-GSH mitochondrial antioxidant system, resulting in increased mitochondrial oxidative damage and dysfunction, suggesting that IDH2 plays a critical role in mitochondrial redox balance and HIR-induced impairment of IDH2 function is associated with the pathogenesis of ischemia-reperfusion-induced liver failure.

The Protective Effects of Fasciotomy on Reperfusion Injury of Skeletal Muscle of Rabbits

The authors aim to investigate protective effects of fasciotomy against ischemia reperfusion injury of skeletal muscle in rabbit and to compare the treatment effects of prereperfusion + fasciotomy and fasciotomy + postreperfusion against ischemia reperfusion injury of skeletal muscle. 24 healthy male Japanese white rabbits were randomly divided into 3 groups, and 4 hours' ischemia was established in these rabbits through surgery. Six hours' reperfusion was performed in group A; reperfusion + postfasciotomy was performed in group B; and prefasciotomy + reperfusion was performed in group C. Result showed that prefasciotomy and postfasciotomy could protect skeletal muscle against ischemia reperfusion injury, reduced MDA (malondialdehyde) expression, MPO (myeloperoxidase) expression, and apoptosis of muscle in the reperfused areas, increased Bcl-2 expression, and decreased Bax expression. The MDA and MPO levels in group B and group C were significantly lower than those in group A, and MDA and MPO levels in group C were significantly lower than those in group B. Prefasciotomy and postfasciotomy could protect against ischemia reperfusion injury in skeletal muscle. The protective effects of prefasciotomy against ischemia reperfusion injury are better than postfasciotomy.

Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

Mitochondria are recognized as one of the most important targets for new drug design in cancer, cardiovascular, and neurological diseases. Currently, the most effective way to deliver drugs specifically to mitochondria is by covalent linking a lipophilic cation such as an alkyltriphenylphosphonium moiety to a pharmacophore of interest. Other delocalized lipophilic cations, such as rhodamine, natural and synthetic mitochondria-targeting peptides, and nanoparticle vehicles, have also been used for mitochondrial delivery of small molecules. Depending on the approach used, and the cell and mitochondrial membrane potentials, more than 1000-fold higher mitochondrial concentration can be achieved. Mitochondrial targeting has been developed to study mitochondrial physiology and dysfunction and the interaction between mitochondria and other subcellular organelles and for treatment of a variety of diseases such as neurodegeneration and cancer. In this Review, we discuss efforts to target small-molecule compounds to mitochondria for probing mitochondria function, as diagnostic tools and potential therapeutics. We describe the physicochemical basis for mitochondrial accumulation of lipophilic cations, synthetic chemistry strategies to target compounds to mitochondria, mitochondrial probes, and sensors, and examples of mitochondrial targeting of bioactive compounds. Finally, we review published attempts to apply mitochondria-targeted agents for the treatment of cancer and neurodegenerative diseases.

Propofol post-conditioning alleviates hepatic ischaemia reperfusion injury via BRG1-mediated Nrf2/HO-1 transcriptional activation in human and mice

To explore the effects of propofol post-conditioning (PPC) on hepatic ischaemia/reperfusion injury (HIRI) and the potential mechanisms that might be involved in the interaction of Brahma-related gene1(BRG1) and Nuclear-related factor 2(Nrf2). Patients were randomized into PPC(n = 16) and non-PPC(NPC)( n = 21) groups. Propofol(2 mg/kg) was infused within 10 min. of the onset of liver reperfusion during liver transplantation in the PPC group. Liver function tests, as well as Brg1, Nrf2, Heme oxygenase-1(HO-1) and NADPH:quinone oxidoreductase1(NQO1) expression levels were evaluated. CMV-Brg1 mice were designed to investigate the role of Brg1 overexpression during HIRI. Brg1 and Nrf2 siRNA were used to examine the relationship between Brg1 and Nrf2/HO-1 pathways in propofol-mediated effects in a human hepatocyte(L02) hypoxia/reoxygenation(H/R) model. In patients, PPC attenuated both donor liver pathological and function injury, and reducing oxidative stress markers, compared to the NPC group, 24 hrs after surgery. PPC increased liver Brg1, Nrf2, HO-1 and NQO1 expression. In mice, PPC reduced HIRI by decreasing liver oxidative stress and activating Nrf2/HO-1 pathway, accompanied by up-regulation of BRG1 expression. BRG1 overexpression activated Nrf2/HO-1 transcription in CMV-BRG1 mice during HIRI. In vitro, PPC significantly elevated expression of Nrf2, HO-1 and NQO1, resulting in a reduction of cell DCFH-DA and 8-isoprostane levels and decreased lactate dehydrogenase levels, leading to an overall increase in cell viability. Moreover, the protective effects of propofol were partially abrogated in Nrf2-knock-down or BRG1-knock-down hepatocytes. Nrf2-knock-down drastically reduced protein expression of HO-1 and NQO1, while Brg1-knock-down decreased HO-1 expression. Propofol post-conditioning alleviates HIRI through BRG1-mediated Nrf2/HO-1 transcriptional activation.