Mitochondria-targeted antioxidant MitoQ ameliorates ischaemia-reperfusion injury in kidney transplantation models

Long-Term Functional and Structural Renoprotection After Experimental Acute Kidney Injury in Subclinical Chronic Kidney Disease In Vivo

Subclinical chronic kidney disease (sCKD) predisposes one to acute kidney injury (AKI) and chronic kidney disease (CKD). Reduced kidney functional reserve (KFR) detects sCKD in preclinical studies and predicts AKI after cardiac surgery. We evaluated renal protection in a rat model of kidney injury where ischaemia-reperfusion injury (IRI) was induced after sCKD. Dual treatment boosting nicotinamide adenine dinucleotide (NAD) by nicotinamide riboside (NR) combined with the mitochondria-targeted antioxidant SkQR1 protected the KFR and reduced structural kidney damage, including markers of vascular integrity and the relative blood volume (rBV). The dual treatment upregulated Sirt1 and Nrf2, increased the nuclear localisation of the mitochondrial biogenesis regulator PGC-1α and the mitochondrial protein marker COX4, and upregulated the antioxidant gene NOQ1. These observations suggest mitochondrial protection and modulation of the cellular redox state provided long-term structural and functional protection against kidney injury superimposed on background sCKD.

MitoQ enhances CYP19A1 expression to stimulate WNT/β-catenin signaling pathway for promoting hair growth in androgenetic alopecia

Increased sensitivity to androgens and androgen receptors is the underlying cause of androgenetic alopecia (AGA), a hereditary disease. Our study investigated the preventive effects of MitoQ on dihydrotestosterone (DHT)-induced mitochondrial dysfunction and subsequent hair loss from three perspectives: in vivo, in vitro, and network pharmacology. A mouse model of AGA was used to assess the effectiveness of MitoQ intervention. Seventy-five drug targets and 367 disease targets were identified through network pharmacology analysis. Molecular docking analysis revealed that the androgen receptor (AR) and CYP19A1, which are key targets of MitoQ, may play a role in AGA treatment. CYP19A1 expression was downregulated in lesions from patients with AGA compared to healthy scalp tissue, while AR expression was upregulated. Cellular tests of human dermal papilla cells (DPCs) treated with MitoQ revealed that the mRNA and protein expression of AR remained unchanged, but the mRNA expression of CYP19A1 was upregulated. Our experiments also confirmed that CYP19A1 overexpression prevented DHT-induced apoptosis and upregulated the expression levels of WNT3A and β-catenin, whereas increased apoptosis levels and the downregulation of WNT3A and β-catenin due to CYP19A1 knockdown were reduced by MitoQ. We verified that MitoQ enhanced hair growth in DHT-induced hair loss model mice and reversed DHT-induced apoptosis by enhancing the expression of CYP19A1 in DPCs and that MitoQ may act by mediating the WNT/β-catenin pathway. These findings indicate that MitoQ could be a promising intervention for AGA and that CYP19A1 may serve as a valuable therapeutic target for AGA.

Cardiolipin in myocardial ischaemia-reperfusion injury: From molecular mechanisms to clinical strategies

Myocardial reperfusion injury occurs when blood flow is restored after ischemia, an essential process to salvage ischemic tissue. However, this phenomenon is intricate, characterized by various harmful effects. Tissue damage in ischemia-reperfusion injury arises from various factors, including the production of reactive oxygen species, the sequestration of proinflammatory immune cells in ischemic tissues, the induction of endoplasmic reticulum stress, and the occurrence of postischemic capillary no-reflow. Secretory phospholipase A2 (sPLA2) plays a crucial role in the eicosanoid pathway by releasing free arachidonic acid from membrane phospholipids' sn-2 position. This liberated arachidonic acid serves as a substrate for various eicosanoid biosynthetic enzymes, including cyclooxygenases, lipoxygenases, and cytochromes P450, ultimately resulting in inflammation and an elevated risk of reperfusion injury. Therefore, the activation of sPLA2 directly correlates with the heightened and accelerated damage observed in myocardial ischemia-reperfusion injury (MIRI). Presently, clinical trials are in progress for medications aimed at sPLA2, presenting promising avenues for intervention. Cardiolipin (CL) plays a crucial role in maintaining mitochondrial function, and its alteration is closely linked to mitochondrial dysfunction observed in MIRI. This paper provides a critical analysis of CL modifications concerning mitochondrial dysfunction in MIRI, along with its associated molecular mechanisms. Additionally, it delves into various pharmacological approaches to prevent or alleviate MIRI, whether by directly targeting mitochondrial CL or through indirect means.

Utilizing pathophysiological concepts of ischemia-reperfusion injury to design renoprotective strategies and therapeutic interventions for normothermic ex vivo kidney perfusion

Normothermic machine perfusion (NMP) has emerged as a promising tool for the preservation, viability assessment, and repair of deceased-donor kidneys prior to transplantation. These kidneys inevitably experience a period of ischemia during donation, which leads to ischemia-reperfusion injury when NMP is subsequently commenced. Ischemia-reperfusion injury has a major impact on the renal vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis. With an increased understanding of the underlying pathophysiological mechanisms, renoprotective strategies and therapeutic interventions can be devised to minimize additional injury during normothermic reperfusion, ensure the safe implementation of NMP, and improve kidney quality. This review discusses the pathophysiological alterations in the vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis of deceased-donor kidneys and delineates renoprotective strategies and therapeutic interventions to mitigate renal injury and improve kidney quality during NMP.

Metabolite accumulation from oral NMN supplementation drives aging-specific kidney inflammation

The mitochondrial-rich renal tubule cells are key regulators of blood homeostasis via excretion and reabsorption of metabolic waste. With age, tubules are subject to increasing mitochondrial dysfunction and declining nicotinamide adenine dinucleotide (NAD+) levels, both hampering ATP production efficiency. We tested two mitochondrial interventions in young (6-mo) and aged (26-mo) adult male mice: elamipretide (ELAM), a tetrapeptide in clinical trials that improves mitochondrial structure and function, and nicotinamide mononucleotide (NMN), an NAD+ intermediate and commercially available oral supplement. Kidneys were analyzed from young and aged mice after eight weeks of treatment with ELAM (3 mg/kg/day), NMN (300 mg/kg/day), or from aged mice treated with the two interventions combined (ELAM+NMN). We hypothesized that combining pharmacologic treatments to ameliorate mitochondrial dysfunction and boost NAD+ levels, would more effectively reduce kidney aging than either intervention alone. Unexpectedly, in aged kidneys, NMN increased expression of genetic markers of inflammation (IL-1-beta; and Ccl2) and tubule injury (Kim-1). Metabolomics of endpoint sera showed that NMN-treated aged mice had higher circulating levels of uremic toxins than either aged controls or young NMN-treated mice. ELAM+NMN-treated aged mice accumulated uremic toxins like NMN-only aged mice, but reduced IL-1-beta; and Ccl2 kidney mRNA. This suggests that pre-existing mitochondrial dysfunction in aged kidney underlies susceptibility to inflammatory signaling with NMN supplementation in aged, but not young, mice. These findings demonstrate age and tissue dependent effects on downstream metabolic accumulation from NMN and highlight the need for targeted analysis of aged kidneys to assess the safety of anti-aging supplements in older populations.

Multifaceted functions of Drp1 in hypoxia/ischemia-induced mitochondrial quality imbalance: from regulatory mechanism to targeted therapeutic strategy

Hypoxic-ischemic injury is a common pathological dysfunction in clinical settings. Mitochondria are sensitive organelles that are readily damaged following ischemia and hypoxia. Dynamin-related protein 1 (Drp1) regulates mitochondrial quality and cellular functions via its oligomeric changes and multiple modifications, which plays a role in mediating the induction of multiple organ damage during hypoxic-ischemic injury. However, there is active controversy and gaps in knowledge regarding the modification, protein interaction, and functions of Drp1, which both hinder and promote development of Drp1 as a novel therapeutic target. Here, we summarize recent findings on the oligomeric changes, modification types, and protein interactions of Drp1 in various hypoxic-ischemic diseases, as well as the Drp1-mediated regulation of mitochondrial quality and cell functions following ischemia and hypoxia. Additionally, potential clinical translation prospects for targeting Drp1 are discussed. This review provides new ideas and targets for proactive interventions on multiple organ damage induced by various hypoxic-ischemic diseases.

From Physiology to Pathology: The Role of Mitochondria in Acute Kidney Injuries and Chronic Kidney Diseases

Background

Renal diseases remain an increasing public health issue affecting millions of people. The kidney is a highly energetic organ that is rich in mitochondria. Numerous studies have demonstrated the important role of mitochondria in maintaining normal kidney function and in the pathogenesis of various renal diseases, including acute kidney injuries (AKIs) and chronic kidney diseases (CKDs).

Summary

Under physiological conditions, fine-tuning mitochondrial energy balance, mitochondrial dynamics (fission and fusion processes), mitophagy, and biogenesis maintain mitochondrial fitness. While under AKI and CKD conditions, disruption of mitochondrial energy metabolism leads to increased oxidative stress. In addition, mitochondrial dynamics shift to excessive mitochondrial fission, mitochondrial autophagy is impaired, and mitochondrial biogenesis is also compromised. These mitochondrial injuries regulate renal cellular functions either directly or indirectly. Mitochondria-targeted approaches, containing genetic (microRNAs) and pharmaceutical methods (mitochondria-targeting antioxidants, mitochondrial permeability pore inhibitors, mitochondrial fission inhibitors, and biogenesis activators), are emerging as important therapeutic strategies for AKIs and CKDs.

Key Messages

Mitochondria play a critical role in the pathogenesis of AKIs and CKDs. This review provides an updated overview of mitochondrial homeostasis under physiological conditions and the involvement of mitochondrial dysfunction in renal diseases. Finally, we summarize the current status of mitochondria-targeted strategies in attenuating renal diseases.

Mitoquinone Alleviates Donation after Cardiac Death Kidney Injury during Hypothermic Machine Perfusion in Rat Model

Transplanted organs are subjected to harmful conditions through stopping blood flow, hypothermic storage of the graft, and subsequent reperfusion. In particular, kidneys donated from patients after cardiac arrest (DCD) are classified as more vulnerable to ischemia-reperfusion injury (IRI). Hypothermic machine perfusion is proposed as a solution for better kidney storage before transplantation, and it is a good platform for additional graft treatment. Antioxidants have gained interest in regenerative medicine due to their ability to scavenge reactive oxygen species (ROS), which play a key role in IRI. We evaluated the effect of Mitoquinone (MitoQ), a strong mitochondria-targeted antioxidant, administered directly to the perfusing buffer. Rat kidneys were isolated, randomly classified into one of the following groups, donation after brainstem death (DBD), DCD, and DCD with MitoQ, and perfused for 22 hours with a hypothermic machine perfusion system. Subsequently, we detected levels of kidney injury (KIM-1) and oxidative stress (ROS/RNS, cytochrome C oxidase, and mitochondrial integrity) markers. We compared the activation of the apoptosis pathway (caspase 3 and 9), the concentration of phosphorylated Akt (pAkt), and the pAkt/total Akt ratio. MitoQ reduces KIM-1 concentration, total ROS/RNS, and the level of caspases. We observed a decrease in pAkt and the pAkt/total Akt ratio after drug administration. The length of warm ischemia time negatively impacts the graft condition. However, MitoQ added to the perfusing system as an 'on pump' therapy mitigates injury to the kidney before transplantation by inhibiting apoptosis and reducing ROS/RNS levels. We propose MitoQ as a potential drug for DCD graft preconditioning.

Oxidative stress in intervertebral disc degeneration: Molecular mechanisms, pathogenesis and treatment

Low back pain (LBP) is a leading cause of labour loss and disability worldwide, and it also imposes a severe economic burden on patients and society. Among symptomatic LBP, approximately 40% is caused by intervertebral disc degeneration (IDD). IDD is the pathological basis of many spinal degenerative diseases such as disc herniation and spinal stenosis. Currently, the therapeutic approaches for IDD mainly include conservative treatment and surgical treatment, neither of which can solve the problem from the root by terminating the degenerative process of the intervertebral disc (IVD). Therefore, further exploring the pathogenic mechanisms of IDD and adopting targeted therapeutic strategies is one of the current research hotspots. Among the complex pathophysiological processes and pathogenic mechanisms of IDD, oxidative stress is considered as the main pathogenic factor. The delicate balance between reactive oxygen species (ROS) and antioxidants is essential for maintaining the normal function and survival of IVD cells. Excessive ROS levels can cause damage to macromolecules such as nucleic acids, lipids, and proteins of cells, affect normal cellular activities and functions, and ultimately lead to cell senescence or death. This review discusses the potential role of oxidative stress in IDD to further understand the pathophysiological processes and pathogenic mechanisms of IDD and provides potential therapeutic strategies for the treatment of IDD.

Mitochondrial iron regulation as an emerging target in ischemia/reperfusion injury during kidney transplantation

The injury caused by ischemia and subsequent reperfusion (I/R) is inevitable during kidney transplantation and its current management remains unsatisfactory. Iron is considered to play a remarkable pathologic role in the initiation or progression of tissue damage induced by I/R, whereas the effects of iron-related therapy remain controversial owing to the complicated nature of iron's involvement in multiple biological processes. A significant portion of the cellular iron is located in the mitochondria, which exerts a central role in the development and progression of I/R injury. Recent studies of iron regulation associated with mitochondrial function represents a unique opportunity to improve our knowledge on the pathophysiology of I/R injury. However, the molecular mechanisms linking mitochondria to the iron homeostasis remain unclear. In this review, we provide a comprehensive analysis of the alterations to iron metabolism in I/R injury during kidney transplantation, analyze the current understanding of mitochondrial regulation of iron homeostasis and discussed its potential application in I/R injury. The elucidation of regulatory mechanisms regulating mitochondrial iron homeostasis will offer valuable insights into potential therapeutic targets for alleviating I/R injury with the ultimate aim of improving kidney graft outcomes, with potential implications that could also extend to acute kidney injury or other I/R injuries.

How to Best Protect Kidneys for Transplantation-Mechanistic Target

The increasing number of patients on the kidney transplant waiting list underlines the need to expand the donor pool and improve kidney graft utilization. By protecting kidney grafts adequately from the initial ischemic and subsequent reperfusion injury occurring during transplantation, both the number and quality of kidney grafts could be improved. The last few years have seen the emergence of many new technologies to abrogate ischemia-reperfusion (I/R) injury, including dynamic organ preservation through machine perfusion and organ reconditioning therapies. Although machine perfusion is gradually making the transition to clinical practice, reconditioning therapies have not yet progressed from the experimental setting, pointing towards a translational gap. In this review, we discuss the current knowledge on the biological processes implicated in I/R injury and explore the strategies and interventions that are being proposed to either prevent I/R injury, treat its deleterious consequences, or support the reparative response of the kidney. Prospects to improve the clinical translation of these therapies are discussed with a particular focus on the need to address multiple aspects of I/R injury to achieve robust and long-lasting protective effects on the kidney graft.

The Effects of Antioxidant Nutraceuticals on Cellular Sulfur Metabolism and Signaling

Significance: Nutraceuticals are ingested for health benefits, in addition to their general nutritional value. These dietary supplements have become increasingly popular since the late 20th century and they are a rapidly expanding global industry approaching a half-trillion U.S. dollars annually. Many nutraceuticals are promulgated as potent antioxidants. Recent Advances: Experimental support for the efficacy of nutraceuticals has lagged behind anecdotal exuberance. However, accumulating epidemiological evidence and recent, well-controlled clinical trials are beginning to support earlier animal and in vitro studies. Although still somewhat limited, encouraging results have been suggested in essentially all organ systems and against a wide range of pathophysiological conditions. Critical Issues: Health benefits of "antioxidant" nutraceuticals are largely attributed to their ability to scavenge oxidants. This has been criticized based on several factors, including limited bioavailability, short tissue retention time, and the preponderance of endogenous antioxidants. Recent attention has turned to nutraceutical activation of downstream antioxidant systems, especially the Keap1/Nrf2 (Kelch like ECH associated protein 1/nuclear factor erythroid 2-related factor 2) axis. The question now becomes, how do nutraceuticals activate this axis? Future Directions: Reactive sulfur species (RSS), including hydrogen sulfide (H2S) and its metabolites, are potent activators of the Keap1/Nrf2 axis and avid scavengers of reactive oxygen species. Evidence is beginning to accumulate that a variety of nutraceuticals increase cellular RSS by directly providing RSS in the diet, or through a number of catalytic mechanisms that increase endogenous RSS production. We propose that nutraceutical-specific targeting of RSS metabolism will lead to the design and development of even more efficacious antioxidant therapeutic strategies. Antioxid. Redox Signal. 38, 68-94.

Mitochondria-Targeted Antioxidant Mitoquinone Maintains Mitochondrial Homeostasis through the Sirt3-Dependent Pathway to Mitigate Oxidative Damage Caused by Renal Ischemia/Reperfusion

Mitochondrial dysfunction is a critical factor contributing to oxidative stress and apoptosis in ischemia-reperfusion (I/R) diseases. Mitoquinone (MitoQ) is a mitochondria-targeted antioxidant whose potent anti-I/R injury capacity has been demonstrated in organs such as the heart and the intestine. In the present study, we explored the role of MitoQ in maintaining mitochondrial homeostasis and attenuating oxidative damage in renal I/R injury. We discovered that the decreased renal function and pathological damage caused by renal I/R injury were significantly ameliorated by MitoQ. MitoQ markedly reversed mitochondrial damage after I/R injury and inhibited renal reactive oxygen species production. In vitro, hypoxia/reoxygenation resulted in increased mitochondrial fission and decreased mitochondrial fusion in human renal tubular epithelial cells (HK-2), which were partially prevented by MitoQ. MitoQ treatment inhibited oxidative stress and reduced apoptosis in HK-2 cells by restoring mitochondrial membrane potential, promoting ATP production, and facilitating mitochondrial fusion. Deeply, renal I/R injury led to a decreased expression of sirtuin-3 (Sirt3), which was recovered by MitoQ. Moreover, the inhibition of Sirt3 partially eliminated the protective effect of MitoQ on mitochondria and increased oxidative damage. Overall, our data demonstrate a mitochondrial protective effect of MitoQ, which raises the possibility of MitoQ as a novel therapy for renal I/R.

Antioxidant mitoquinone ameliorates EtOH-LPS induced lung injury by inhibiting mitophagy and NLRP3 inflammasome activation

Chronic ethanol abuse is a systemic disorder and a risk factor for acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). However, the mechanisms involved are unknown. One explanation is that ethanol produces damaging reactive oxygen species (ROS) and disturbs the balance of mitochondria within the lungs to promote a pro-injury environment. We hypothesized that targeting an antioxidant to the mitochondria would prevent oxidative damage and attenuate EtOH-LPS-induced lung injury. To test this, we investigated the effects of mitochondria-targeted ubiquinone, Mitoquinone (MitoQ) on ethanol-sensitized lung injury induced by LPS. Lung inflammation, ROS, mitochondria function, and mitophagy were assessed. We demonstrated that chronic ethanol feeding sensitized the lung to LPS-induced lung injury with significantly increased reactive oxygen species ROS level and mitochondrial injury as well as lung cellular NLRP3 inflammasome activation. These deleterious effects were attenuated by MitoQ administration in mice. The protective effects of MitoQ are associated with decreased cellular mitophagy and NLRP3 inflammasome activation in vivo and in vitro. Taken together, our results demonstrated that ethanol aggravated LPS-induced lung injury, and antioxidant MitoQ protects from EtOH-LPS-induced lung injury, probably through reducing mitophagy and protecting mitochondria, followed by NLRP3 inflammasome activation. These results will provide the prevention and treatment of ethanol intake effects with new ideas.

Tubular Mitochondrial Dysfunction, Oxidative Stress, and Progression of Chronic Kidney Disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected conditions, and CKD is projected to become the fifth leading global cause of death by 2040. New therapeutic approaches are needed. Mitochondrial dysfunction and oxidative stress have emerged as drivers of kidney injury in acute and chronic settings, promoting the AKI-to-CKD transition. In this work, we review the role of mitochondrial dysfunction and oxidative stress in AKI and CKD progression and discuss novel therapeutic approaches. Specifically, evidence for mitochondrial dysfunction in diverse models of AKI (nephrotoxicity, cytokine storm, and ischemia-reperfusion injury) and CKD (diabetic kidney disease, glomerulopathies) is discussed; the clinical implications of novel information on the key role of mitochondria-related transcriptional regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha, transcription factor EB (PGC-1α, TFEB), and carnitine palmitoyl-transferase 1A (CPT1A) in kidney disease are addressed; the current status of the clinical development of therapeutic approaches targeting mitochondria are updated; and barriers to the clinical development of mitochondria-targeted interventions are discussed, including the lack of clinical diagnostic tests that allow us to categorize the baseline renal mitochondrial dysfunction/mitochondrial oxidative stress and to monitor its response to therapeutic intervention. Finally, key milestones for further research are proposed.

PO2 21% oxygenated hypothermic machine perfusion in kidney transplantation: Any clinical benefit?

BACKGROUND

In deceased donor kidney transplantation (KT), the use of hypothermic machine perfusion (HMP) has been acquiring the status of best practice in the pre-transplant management of kidney grafts. Two types of HMP are currently available, oxygenated HMP and non-oxygenated HMP. However, data on the real clinical impact of oxygenation on KT outcome are still heterogeneous.

METHODS

Retrospective study on a cohort of 103 patients transplanted with a single kidney graft that was managed either with end-ischemic oxygenated (O₂ group, Waves Machine, n = 51, 49.5%) or non-oxygenated HMP (no-O₂ group, Life Port Kidney Transporter Machine, n = 52, 50.5%), during the period January 2016-December 2020. Oxygenation was performed at pO₂ 21%.

RESULTS

The median cold ischemia time was 29 h:40 min [IQR 26 h:55 min-31 h:10 min] and the prevalence of grafts from extended criteria donors (ECD) was 46.7%, with a median kidney donor profile index (KDPI) of 72 [41-94]. The study groups were homogeneous in terms of recipient characteristics, ischemia times and donor characteristics. O₂ and no-O₂ groups showed comparable outcomes in terms of delayed graft function (O₂ vs no-O₂, 21.5% vs 25%, p = 0.58), vascular (0.2% vs 0.2%, p > 0.99) and urologic (13.7% vs 11.5%, p = 0.77) complications, and episodes of graft rejection (11.7% vs 7.7%, p = 0.52). At 1 year follow up, even creatinine serum levels were comparable between the groups (1.27 mg/dL [1.09 and 1.67] vs 1.4 mg/dL [1.9-1.78], p = 0.319), with similar post-transplant trend (p = 0.870). No significant benefit was either observed in ECD or KDPI > 60 subgroups, respectively.

CONCLUSIONS

Oxygenation at pO₂ 21% during HMP seems not to significantly enhance the KT outcomes in terms of postoperative complications or graft function.

Progress and challenges for the machine learning-based design of fit-for-purpose monoclonal antibodies

Although the therapeutic efficacy and commercial success of monoclonal antibodies (mAbs) are tremendous, the design and discovery of new candidates remain a time and cost-intensive endeavor. In this regard, progress in the generation of data describing antigen binding and developability, computational methodology, and artificial intelligence may pave the way for a new era of in silico on-demand immunotherapeutics design and discovery. Here, we argue that the main necessary machine learning (ML) components for an in silico mAb sequence generator are: understanding of the rules of mAb-antigen binding, capacity to modularly combine mAb design parameters, and algorithms for unconstrained parameter-driven in silico mAb sequence synthesis. We review the current progress toward the realization of these necessary components and discuss the challenges that must be overcome to allow the on-demand ML-based discovery and design of fit-for-purpose mAb therapeutic candidates.