Mitotherapy for Fatty Liver by Intravenous Administration of Exogenous Mitochondria in Male Mice

Human umbilical cord mesenchymal stem cell-derived mitochondria (PN-101) attenuate LPS-induced inflammatory responses by inhibiting NFκB signaling pathway

Inflammation is one of the body’s natural responses to injury and illness as part of the healing process. However, persistent inflammation can lead to chronic inflammatory diseases and multi-organ failure. Altered mitochondrial function has been implicated in several acute and chronic inflammatory diseases by inducing an abnormal inflammatory response. Therefore, treating inflammatory diseases by recovering mitochondrial function may be a potential therapeutic approach. Recently, mitochondrial transplantation has been proven to be beneficial in hyperinflammatory animal models. However, it is unclear how mitochondrial transplantation attenuates inflammatory responses induced by external stimuli. Here, we isolated mitochondria from umbilical cord-derived mesenchymal stem cells, referred as to PN-101. We found that PN-101 could signifi-cantly reduce LPS-induced mortality in mice. In addition, in phorbol 12-myristate 13-acetate (PMA)-treated THP-1 macrophages, PN-101 attenuated LPS-induced increase production of pro-inflammatory cytokines. Furthermore, the anti-inflammatory effect of PN-101 was mediated by blockade of phosphorylation, nuclear translocation, and trans-activity of NFκB. Taken together, our results demonstrate that PN-101 has therapeutic potential to attenuate pathological inflammatory responses.

Mesenchymal stem cell-mediated transfer of mitochondria: mechanisms and functional impact

There is a steadily growing interest in the use of mitochondria as therapeutic agents. The use of mitochondria derived from mesenchymal stem/stromal cells (MSCs) for therapeutic purposes represents an innovative approach to treat many diseases (immune deregulation, inflammation-related disorders, wound healing, ischemic events, and aging) with an increasing amount of promising evidence, ranging from preclinical to clinical research. Furthermore, the eventual reversal, induced by the intercellular mitochondrial transfer, of the metabolic and pro-inflammatory profile, opens new avenues to the understanding of diseases' etiology, their relation to both systemic and local risk factors, and also leads to new therapeutic tools for the control of inflammatory and degenerative diseases. To this end, we illustrate in this review, the triggers and mechanisms behind the transfer of mitochondria employed by MSCs and the underlying benefits as well as the possible adverse effects of MSCs mitochondrial exchange. We relay the rationale and opportunities for the use of these organelles in the clinic as cell-based product.

Mitochondria, oxidative stress and nonalcoholic fatty liver disease: A complex relationship

According to the 'multiple-hit' hypothesis, several factors can act simultaneously in nonalcoholic fatty liver disease (NAFLD) progression. Increased nitro-oxidative (nitroso-oxidative) stress may be considered one of the main contributors involved in the development and risk of NAFLD progression to nonalcoholic steatohepatitis (NASH) characterized by inflammation and fibrosis. Moreover, it has been repeatedly postulated that mitochondrial abnormalities are closely related to the development and progression of liver steatosis and NAFLD pathogenesis. However, it is difficult to determine with certainty whether mitochondrial dysfunction or oxidative stress are primary events or a simple consequence of NAFLD development. On the one hand, increasing lipid accumulation in hepatocytes could cause a wide range of effects from mild to severe mitochondrial damage with a negative impact on cell fate. This can start the cascade of events, including an increase of cellular reactive nitrogen species (RNS) and reactive oxygen species (ROS) production that promotes disease progression from simple steatosis to more severe NAFLD stages. On the other hand, progressing mitochondrial bioenergetic catastrophe and oxidative stress manifestation could be considered accompanying events in the vast spectrum of abnormalities observed during the transition from NAFL to NASH and cirrhosis. This review updates our current understanding of NAFLD pathogenesis and clarifies whether mitochondrial dysfunction and ROS/RNS are culprits or bystanders of NAFLD progression.

Shaping of Hepatic Ischemia/Reperfusion Events: The Crucial Role of Mitochondria

Hepatic ischemia reperfusion injury (HIRI) is a major hurdle in many clinical scenarios, including liver resection and transplantation. Various studies and countless surgical events have led to the observation of a strong correlation between HIRI induced by liver transplantation and early allograft-dysfunction development. The detrimental impact of HIRI has driven the pursuit of new ways to alleviate its adverse effects. At the core of HIRI lies mitochondrial dysfunction. Various studies, from both animal models and in clinical settings, have clearly shown that mitochondrial function is severely hampered by HIRI and that its preservation or restoration is a key indicator of successful organ recovery. Several strategies have been thus implemented throughout the years, targeting mitochondrial function. This work briefly discusses some the most utilized approaches, ranging from surgical practices to pharmacological interventions and highlights how novel strategies can be investigated and implemented by intricately discussing the way mitochondrial function is affected by HIRI.

Traumatic optic neuropathy: a review of current studies

Traumatic optic neuropathy (TON) is a serious complication of craniofacial trauma that directly or indirectly damages the optic nerve and can cause severe vision loss. The incidence of TON has been gradually increasing in recent years. Research on the protection and regeneration of the optic nerve after the onset of TON is still at the level of laboratory studies and which is insufficient to support clinical treatment of TON. And, due to without clear guidelines, there is much ambiguity regarding its diagnosis and management. Clinical interventions for TON include observation only, treatment with corticosteroids alone, or optic canal (OC) decompression (with or without steroids). There is controversy in clinical practice concerning which treatment is the best. A review of available studies shows that the visual acuity of patients with TON can be significantly improved after OC decompression surgery (especially endoscopic transnasal/transseptal optic canal decompression (ETOCD)) with or without the use of corticosteroids. And new findings of laboratory studies such as mitochondrial therapy, lipid change studies, and other studies in favor of TON therapy have also been identified. In this review, we discuss the evolving perspective of surgical treatment and experimental study.

Mitochondrial Transfer in Cardiovascular Disease: From Mechanisms to Therapeutic Implications

Mitochondrial dysfunction has been proven to play a critical role in the pathogenesis of cardiovascular diseases. The phenomenon of intercellular mitochondrial transfer has been discovered in the cardiovascular system. Studies have shown that cell-to-cell mitochondrial transfer plays an essential role in regulating cardiovascular system development and maintaining normal tissue homeostasis under physiological conditions. In pathological conditions, damaged cells transfer dysfunctional mitochondria toward recipient cells to ask for help and take up exogenous functional mitochondria to alleviate injury. In this review, we summarized the mechanism of mitochondrial transfer in the cardiovascular system and outlined the fate and functional role of donor mitochondria. We also discussed the advantage and challenges of mitochondrial transfer strategies, including cell-based mitochondrial transplantation, extracellular vesicle-based mitochondrial transplantation, and naked mitochondrial transplantation, for the treatment of cardiovascular disorders. We hope this review will provide perspectives on mitochondrial-targeted therapeutics in cardiovascular diseases.

Mitochondria in Focus: From Function to Therapeutic Strategies in Chronic Lung Diseases

Mitochondria are essential organelles for cell metabolism, growth, and function. Mitochondria in lung cells have important roles in regulating surfactant production, mucociliary function, mucus secretion, senescence, immunologic defense, and regeneration. Disruption in mitochondrial physiology can be the central point in several pathophysiologic pathways of chronic lung diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and asthma. In this review, we summarize how mitochondria morphology, dynamics, redox signaling, mitophagy, and interaction with the endoplasmic reticulum are involved in chronic lung diseases and highlight strategies focused on mitochondrial therapy (mito-therapy) that could be tested as a potential therapeutic target for lung diseases.

Mitochondrial Transplantation Attenuates Cerebral Ischemia-Reperfusion Injury: Possible Involvement of Mitochondrial Component Separation

Background

Mitochondrial dysfunctions play a pivotal role in cerebral ischemia-reperfusion (I/R) injury. Although mitochondrial transplantation has been recently explored for the treatment of cerebral I/R injury, the underlying mechanisms and fate of transplanted mitochondria are still poorly understood.

Methods

Mitochondrial morphology and function were assessed by fluorescent staining, electron microscopy, JC-1, PCR, mitochondrial stress testing, and metabolomics. Therapeutic effects of mitochondria were evaluated by cell viability, reactive oxygen species (ROS), and apoptosis levels in a cellular hypoxia-reoxygenation model. Rat middle cerebral artery occlusion model was applied to assess the mitochondrial therapy in vivo. Transcriptomics was performed to explore the underlying mechanisms. Mitochondrial fate tracking was implemented by a variety of fluorescent labeling methods.

Results

Neuro-2a (N2a) cell-derived mitochondria had higher mitochondrial membrane potential, more active oxidative respiration capacity, and less mitochondrial DNA copy number. Exogenous mitochondrial transplantation increased cellular viability in an oxygen-dependent manner, decreased ROS and apoptosis levels, improved neurobehavioral deficits, and reduced infarct size. Transcriptomic data showed that the differential gene enrichment pathways are associated with metabolism, especially lipid metabolism. Mitochondrial tracking indicated specific parts of the exogenous mitochondria fused with the mitochondria of the host cell, and others were incorporated into lysosomes. This process occurred at the beginning of internalization and its efficiency is related to intercellular connection.

Conclusions

Mitochondrial transplantation may attenuate cerebral I/R injury. The mechanism may be related to mitochondrial component separation, altering cellular metabolism, reducing ROS, and apoptosis in an oxygen-dependent manner. The way of isolated mitochondrial transfer into the cell may be related to intercellular connection.

Mitochondrial regulation and white adipose tissue homeostasis

The important role of mitochondria in the regulation of white adipose tissue (WAT) remodeling and energy balance is increasingly appreciated. The remarkable heterogeneity of the adipose tissue stroma provides a cellular basis to enable adipose tissue plasticity in response to various metabolic stimuli. Regulating mitochondrial function at the cellular level in adipocytes, in adipose progenitor cells (APCs), and in adipose tissue macrophages (ATMs) has a profound impact on adipose homeostasis. Moreover, mitochondria facilitate the cell-to-cell communication within WAT, as well as the crosstalk with other organs, such as the liver, the heart, and the pancreas. A better understanding of mitochondrial regulation in the diverse adipose tissue cell types allows us to develop more specific and efficient approaches to improve adipose function and achieve improvements in overall metabolic health.

Dimeric Histidine as a Novel Free Radical Scavenger Alleviates Non-Alcoholic Liver Injury

Non-alcoholic liver injury (NLI) is a common disease worldwide. Since free radical damage in the liver is a crucial initiator leading to diseases, scavenging excess free radicals has become an essential therapeutic strategy. To enhance the antioxidant capacity of histidine, we synthesized a protonated dimeric histidine, H-bihistidine, and investigated its anti-free radical potential in several free-radical-induced NLI. Results showed that H-bihistidine could strongly scavenge free radicals caused by H₂O₂, fatty acid, and CCl₄, respectively, and recover cell viability in cultured hepatocytes. In the animal model of nonalcoholic fatty liver injury caused by high-fat diet, H-bihistidine reduced the contents of transaminases and lipids in serum, eliminated the liver’s fat accumulation, and decreased the oxidative damage. Moreover, H-bihistidine could rescue CCl₄-induced liver injury and recover energy supply through scavenging free radicals. Moreover, liver fibrosis prepared by high-fat diet and CCl₄ administration was significantly alleviated after H-bihistidine treatment. This study suggests a novel nonenzymatic free radical scavenger against NLI and, potentially, other free-radical-induced diseases.

Mitochondria-Rich Fraction Isolated From Mesenchymal Stromal Cells Reduces Lung and Distal Organ Injury in Experimental Sepsis

OBJECTIVES

To ascertain whether systemic administration of mitochondria-rich fraction isolated from mesenchymal stromal cells would reduce lung, kidney, and liver injury in experimental sepsis.

DESIGN

Animal study.

SETTING

Laboratory investigation.

SUBJECTS

Sixty C57BL/6 male mice.

INTERVENTIONS

Sepsis was induced by cecal ligation and puncture; sham-operated animals were used as control. At 24 hours after surgery, cecal ligation and puncture and Sham animals were further randomized to receive saline or mitochondria-rich fraction isolated from mesenchymal stromal cells (3 × 106) IV. At 48 hours, survival, peritoneal bacterial load, lung, kidney, and liver injury were analyzed. Furthermore, the effects of mitochondria on oxygen consumption rate and reactive oxygen species production of lung epithelial and endothelial cells were evaluated in vitro.

MEASUREMENTS AND MAIN RESULTS

In vitro exposure of lung epithelial and endothelial cells from cecal ligation and puncture animals to mitochondria-rich fraction isolated from mesenchymal stromal cells restored oxygen consumption rate and reduced total reactive oxygen species production. Infusion of exogenous mitochondria-rich fraction from mesenchymal stromal cells (mitotherapy) reduced peritoneal bacterial load, improved lung mechanics and histology, and decreased the expression of interleukin-1β, keratinocyte chemoattractant, indoleamine 2,3-dioxygenase-2, and programmed cell death protein 1 in lung tissue, while increasing keratinocyte growth factor expression and survival rate in cecal ligation and puncture-induced sepsis. Mitotherapy also reduced kidney and liver injury, plasma creatinine levels, and messenger RNA expressions of interleukin-18 in kidney, interleukin-6, indoleamine 2,3-dioxygenase-2, and programmed cell death protein 1 in liver, while increasing nuclear factor erythroid 2-related factor-2 and superoxide dismutase-2 in kidney and interleukin-10 in liver.

CONCLUSIONS

Mitotherapy decreased lung, liver, and kidney injury and increased survival rate in cecal ligation and puncture-induced sepsis.

Mitochondrial Targeting Therapy Role in Liver Transplant Preservation Lines: Mechanism and Therapeutic Strategies

The normal function of mitochondria in the hepatic parenchyma can be disrupted by ischemia/reperfusion (I/R) damage during liver transplantation. The pathology of these insults involves various cellular and molecular steps of events that have been extensively researched over decades but are yet to provide complete answers. This review discusses the brief mechanism of the pathophysiology following ischemia/reperfusion injury (IRI) and various targeting strategies that could result in improved graft function.

The traditional treatment for end-stage liver disease i.e., liver transplantation, has been complicated by I/R damage. The poor graft function or primary non-function found after liver transplantation may be due to mitochondrial dysfunction following IRI. As a result, determining the sequence of incidents that cause human hepatic mitochondrial dysfunction is crucial; it might contribute to further improvements in the outcome of liver transplantation. Early discovery of novel prognostic factors involved in IRI could serve as a primary endpoint for predicting the outcome of liver grafts as well as promoting the early implementation of novel IRI-prevention strategies. In this review, recent developments in the study of mitochondrial dysfunction and I/R damage are discussed, specifically those concerning liver transplantation. Furthermore, we also explore different pharmacological therapeutic methods that may be used and their connections to mitochondrion-related processes and goals.

Although significant progress has been made in our understanding of IRI and mitochondrial dysfunction, further research is needed to elucidate the cellular and molecular pathways underlying these processes to help identify biomarkers that can aid donor organ evaluation.

Mitochondrial dysfunction and liver disease: role, relevance, and potential for therapeutic modulation

Mitochondria are key organelles involved in energy production as well as numerous metabolic processes. There is a growing interest in the role of mitochondrial dysfunction in the pathogenesis of common chronic diseases as well as in cancer development. This review will examine the role mitochondria play in the pathophysiology of common liver diseases, including alcohol-related liver disease, non-alcoholic fatty liver disease, chronic hepatitis B and hepatocellular carcinoma. Mitochondrial dysfunction is described widely in the literature in studies examining patient tissue and in disease models. Despite significant differences in pathophysiology between chronic liver diseases, common mitochondrial defects are described, including increased mitochondrial reactive oxygen species production and impaired oxidative phosphorylation. We review the current literature on mitochondrial-targeted therapies, which have the potential to open new therapeutic avenues in the management of patients with chronic liver disease.

Mitotherapy: Unraveling a Promising Treatment for Disorders of the Central Nervous System and Other Systemic Conditions

Mitochondria are key players of aerobic respiration and the production of adenosine triphosphate and constitute the energetic core of eukaryotic cells. Furthermore, cells rely upon mitochondria homeostasis, the disruption of which is reported in pathological processes such as liver hepatotoxicity, cancer, muscular dystrophy, chronic inflammation, as well as in neurological conditions including Alzheimer’s disease, schizophrenia, depression, ischemia and glaucoma. In addition to the well-known spontaneous cell-to-cell transfer of mitochondria, a therapeutic potential of the transplant of isolated, metabolically active mitochondria has been demonstrated in several in vitro and in vivo experimental models of disease. This review explores the striking outcomes achieved by mitotherapy thus far, and the most relevant underlying data regarding isolated mitochondria transplantation, including mechanisms of mitochondria intake, the balance between administration and therapy effectiveness, the relevance of mitochondrial source and purity and the mechanisms by which mitotherapy is gaining ground as a promising therapeutic approach.

Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD.

Disturbed mitochondrial redox state and tissue energy charge in cholestasis

The liver is the primary organ affected by cholestasis. However, the brain, skeletal muscle, heart, and kidney are also severely influenced by cholestasis/cirrhosis. However, little is known about the molecular mechanisms of organ injury in cholestasis. The current study was designed to evaluate the mitochondrial glutathione redox state as a significant index in cell death. Moreover, tissue energy charge (EC) was calculated. Rats underwent bile duct ligation (BDL) and the brain, heart, liver, kidney, and skeletal muscle mitochondria were assessed at scheduled time intervals (3, 7, 14, and 28 days after BDL). A significant decrease in mitochondrial glutathione redox state and EC was detected in BDL animals. Moreover, disturbed mitochondrial indices were evident in different organs of BDL rats. These data could offer new insight into the mechanisms of organ injury and the source of oxidative stress during cholestasis and might provide novel therapeutic strategies against these complications.

Mitotherapy as a Novel Therapeutic Strategy for Mitochondrial Diseases

BACKGROUND

The mitochondrion is a multi-functional organelle that is mainly responsible for energy supply in the mammalian cells. Over 100 human diseases are attributed to mitochondrial dysfunction. Mitochondrial therapy (mitotherapy) aims to transfer functional exogenous mitochondria into mitochondria-defective cells for recovery of the cell viability and consequently, prevention of the disease progress.

OBJECTIVE

The review summarizes the evidence on exogenous mitochondria that can directly enter mammalian cells for disease therapy following local and intravenous administration, and suggests that when healthy cells donate their mitochondria to damaged cells, the mitochondrial transfer between cells serve as a new mode of cell rescue. Then the transferred mitochondria play their roles in recipient cells, including energy production and maintenance of cell function.

CONCLUSION

Mitotherapy makes the of modulation of cell survival possible, and it would be a potential therapeutic strategy for mitochondrial diseases.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

Mitochondrial transplantation therapy inhibit carbon tetrachloride-induced liver injury through scavenging free radicals and protecting hepatocytes

Carbon tetrachloride (CCl4)-induced liver injury is predominantly caused by free radicals, in which mitochondrial function of hepatocytes is impaired, accompanying with the production of ROS and decreased ATP energy supply in animals intoxicated with CCl4. Here we explored a novel therapeutic approach, mitochondrial transplantation therapy, for treating the liver injury. The results showed that mitochondria entered hepatocytes through macropinocytosis pathway, and thereby cell viability was recovered in a concentration-dependent manner. Mitochondrial therapy could increase ATP supply and reduce free radical damage. In liver injury model of mice, mitochondrial therapy significantly improved liver function and prevented tissue fibrogenesis. Transcriptomic data revealed that mitochondrial unfold protein response (UPRmt), a protective transcriptional response of mitochondria-to-nuclear retrograde signaling, would be triggered after mitochondrial administration. Then the anti-oxidant genes were up-regulated to scavenge free radicals. The mitochondrial function was rehabilitated through the transcriptional activation of respiratory chain enzyme and mitophage-associated genes. The protective response re-balanced the cellular homeostasis, and eventually enhanced stress resistance that is linked to cell survival. The efficacy of mitochondrial transplantation therapy in the animals would suggest a novel approach for treating liver injury caused by toxins.

Mitochondrial Transplantation as a Novel Therapeutic Strategy for Mitochondrial Diseases

Mitochondria are the major source of intercellular bioenergy in the form of ATP. They are necessary for cell survival and play many essential roles such as maintaining calcium homeostasis, body temperature, regulation of metabolism and apoptosis. Mitochondrial dysfunction has been observed in variety of diseases such as cardiovascular disease, aging, type 2 diabetes, cancer and degenerative brain disease. In other words, the interpretation and regulation of mitochondrial signals has the potential to be applied as a treatment for various diseases caused by mitochondrial disorders. In recent years, mitochondrial transplantation has increasingly been a topic of interest as an innovative strategy for the treatment of mitochondrial diseases by augmentation and replacement of mitochondria. In this review, we focus on diseases that are associated with mitochondrial dysfunction and highlight studies related to the rescue of tissue-specific mitochondrial disorders. We firmly believe that mitochondrial transplantation is an optimistic therapeutic approach in finding a potentially valuable treatment for a variety of mitochondrial diseases.

Mitochondrial dysfunction and mitochondrion-targeted therapeutics in liver diseases

The liver is a vital metabolic and detoxifying organ and suffers diverse endogenous or exogenous damage. Hepatocyte mitochondria experience various structural and functional defects from liver injury, bearing oxidative stress, metabolic dysregulation, and the disturbance of mitochondrial quality control (MQC) mechanisms. Mitochondrial malfunction initiates the mitochondria-mediated apoptotic pathways and the release of damage signals, aggravating liver damage and disease progression via inflammation and reparative fibrogenesis. Removal of mitochondrial impairment or the improvement of MQC mechanisms restore mitochondrial homeostasis and benefit liver health. This review discusses the association of mitochondrial disorders with hepatic pathophysiological processes and the resultant potential of mitochondrion-targeting therapeutics for hepatic disorders. The recent advances in the MQC mechanisms and the mitochondrial-derived damage-associated molecular patterns (DAMPs) in the pathology and treatment of liver disease are particularly focussed.

Mitochondrial dynamics and nonalcoholic fatty liver disease (NAFLD): new perspectives for a fairy-tale ending?

Nonalcoholic fatty liver disease (NAFLD) includes a broad spectrum of liver dysfunctions and it is predicted to become the primary cause of liver failure and hepatocellular carcinoma. Mitochondria are highly dynamic organelles involved in multiple metabolic/bioenergetic pathways in the liver. Emerging evidence outlined that hepatic mitochondria adapt in number and functionality in response to external cues, as high caloric intake and obesity, by modulating mitochondrial biogenesis, and maladaptive mitochondrial response has been described from the early stages of NAFLD. Indeed, mitochondrial plasticity is lost in progressive NAFLD and these organelles may assume an aberrant phenotype to drive or contribute to hepatocarcinogenesis. Severe alimentary regimen and physical exercise represent the cornerstone for NAFLD care, although the low patients' compliance is urging towards the discovery of novel pharmacological treatments. Mitochondrial-targeted drugs aimed to recover mitochondrial lifecycle and to modulate oxidative stress are becoming attractive molecules to be potentially introduced for NAFLD management. Although the path guiding the switch from bench to bedside remains tortuous, the study of mitochondrial dynamics is providing intriguing perspectives for future NAFLD healthcare.

Mitochondrial dysfunction in nonalcoholic fatty liver disease and alcohol related liver disease

Fatty liver disease constitutes a spectrum of liver diseases which begin with simple steatosis and may progress to advance stages of steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The two main etiologies are-alcohol related fatty liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). NAFLD is a global health epidemic strongly associated with modern dietary habits and life-style. It is the second most common cause of chronic liver disease in the US after chronic hepatitis C virus (HCV) infection. Approximately 100 million people are affected with this condition in the US alone. Excessive intakes of calories, saturated fat and refined carbohydrates, and sedentary life style have led to explosion of this health epidemic in developing nations as well. ALD is the third most common cause of chronic liver disease in the US. Even though the predominant trigger for onset of steatosis is different in these two conditions, they share common themes in progression from steatosis to the advance stages. Oxidative stress (OS) is considered a very significant contributor to hepatocyte injury in these conditions. Mitochondrial dysfunction contributes to this OS. Role of mitochondrial dysfunction in pathogenesis of fatty liver diseases is emerging but far from completely understood. A better understanding is essential for more effective preventive and therapeutic interventions. Here, we discuss the pathogenesis and therapeutic approaches of NAFLD and ALD from a mitochondrial perspective.

Protocols for Mitochondria as the Target of Pharmacological Therapy in the Context of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent metabolic chronic liver diseases in developed countries and puts the populations at risk of progression to liver necro-inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Mitochondrial dysfunction is involved in the onset of NAFLD and contributes to the progression from NAFLD to nonalcoholic steatohepatitis (NASH). Thus, liver mitochondria could become the target for treatments for improving liver function in NAFLD patients. This chapter describes the most important steps used for potential therapeutic interventions in NAFLD patients, discusses current options gathered from both experimental and clinical evidence, and presents some novel options for potentially improving mitochondrial function in NAFLD.

Mitochondrial transplant to replenish damaged mitochondria: A novel therapeutic strategy for neurodegenerative diseases?

Neurodegenerative diseases are currently some of the most debilitating and incurable illness, including highly prevalent disorders, such as Alzheimer's and Parkinson's disease. Despite impressive advances in understanding the molecular basis of neurodegenerative diseases, several clinical trials have failed in identifying drugs that successfully delay or stop disease progression. New targets are likely necessary to successfully combat these devastating diseases. In this chapter, we review the evidence indicating that impairment in the cellular energy machinery in the form of mitochondrial damage and dysfunction may be at the root of neurodegeneration. We also propose that transplant of functional isolated mitochondria may overcome the energetic damage and delay the progression of neurodegenerative diseases.

Mesenchymal Stem Cell-Mediated Mitochondrial Transfer: a Therapeutic Approach for Ischemic Stroke

Stroke is the leading cause of death and adult disability worldwide. Mitochondrial dysfunction is one of the hallmarks of stroke-induced neuronal death, and maintaining mitochondrial function is essential in cell survival and neurological progress following ischemic stroke. Stem cell-mediated mitochondrial transfer represents an emerging therapeutic approach for ischemic stroke. Accumulating evidence suggests that mesenchymal stem cells (MSCs) can directly transfer healthy mitochondria to damaged cells, and rescue mitochondrial damage-provoked tissue degeneration. This review summarizes the research on MSCs-mediated mitochondrial transfer as a therapeutic strategy against ischemic stroke.

Challenges in Promoting Mitochondrial Transplantation Therapy

Mitochondrial transplantation therapy is an innovative strategy for the treatment of mitochondrial dysfunction. The approach has been reported to be useful in the treatment of cardiac ischemic reperfusion injuries in human clinical trials and has also been shown to be useful in animal studies as a method for treating mitochondrial dysfunction in various tissues, including the heart, liver, lungs, and brain. On the other hand, there is no methodology for using preserved mitochondria. Research into the pharmaceutical formulation of mitochondria to promote mitochondrial transplantation therapy as the next step in treating many patients is urgently needed. In this review, we overview previous studies on the therapeutic effects of mitochondrial transplantation. We also discuss studies related to immune responses that occur during mitochondrial transplantation and methods for preserving mitochondria, which are key to their stability as medicines. Finally, we describe research related to mitochondrial targeting drug delivery systems (DDS) and discuss future perspectives of mitochondrial transplantation.

Inter and Intracellular mitochondrial trafficking in health and disease

Neurons and glia maintain central nervous system (CNS) homeostasis through diverse mechanisms of intra- and intercellular signaling. Some of these interactions include the exchange of soluble factors between cells via direct cell-to-cell contact for both short and long-distance transfer of biological materials. Transcellular transfer of mitochondria has emerged as a key example of this communication. This transcellular transfer of mitochondria are dynamically involved in the cellular and tissue response to CNS injury and play beneficial roles in recovery. This review highlights recent research addressing the cause and effect of intra- and intercellular mitochondrial transfer with a specific focus on the future of mitochondrial transplantation therapy. We believe that mitochondrial transfer plays a crucial role during bioenergetic crisis/deficit, but the quality, quantity and mode of mitochondrial transfer determines the protective capacity for the receiving cells. Mitochondrial transplantation is a new treatment paradigm and will overcome the major bottleneck of traditional approach of correcting mitochondria-related disorders.

Bases for Treating Skin Aging With Artificial Mitochondrial Transfer/Transplant (AMT/T)

The perception of mitochondria as only the powerhouse of the cell has dramatically changed in the last decade. It is now accepted that in addition to being essential intracellularly, mitochondria can promote cellular repair when transferred from healthy to damaged cells. The artificial mitochondria transfer/transplant (AMT/T) group of techniques emulate this naturally occurring process and have been used to develop therapies to treat a range of diseases including cardiac and neurodegenerative. Mitochondria accumulate damage with time, resulting in cellular senescence. Skin cells and its mitochondria are profoundly affected by ultraviolet radiation and other factors that induce premature and accelerated aging. In this article, we propose the basis to use AMT/T to treat skin aging by transferring healthy mitochondria to senescent cells, possibly revitalizing them. We provide insightful information about how skin structure, components, and cells could age rapidly depending on the amount of damage received. Arguments are shown in favor of the use of AMT/T to treat aging skin and its cells, among them the possibility to stop free radical production, add new genetic material, and provide an energetic boost to help cells prolong their viability over time. This article intends to present one of the many aspects in which mitochondria could be used as a universal treatment for cell and tissue damage and aging.

Mitochondrial Transfer as a Therapeutic Strategy Against Ischemic Stroke

Stroke is a debilitating disease that remains the second leading cause of death and disability worldwide. Despite accumulating knowledge of the disease pathology, treatments for stroke are limited, and clinical translation of the neuroprotective agents has not been a complete success. Accumulating evidence links mitochondrial dysfunction to brain impairments after stroke. Recent studies have implicated the important roles of healthy mitochondria in neuroprotection and neural recovery following ischemic stroke. New and convincing studies have shown that mitochondrial transfer to the damaged cells can help revive cells energetic in the recipient cells. Hence, mitochondrial transplantation has shown to replace impaired or dysfunctional mitochondria with exogenous healthy mitochondria after ischemic stroke. We highlight the potential of mitochondrial transfer by stem cells as a therapeutic strategy for the treatment of ischemic stroke. This review captures the recent advances in the mitochondrial transfer as a novel and promising treatment for ischemic stroke.

Multifaceted Roles of Mitochondrial Components and Metabolites in Metabolic Diseases and Cancer

Mitochondria are essential cellular components that ensure physiological metabolic functions. They provide energy in the form of adenosine triphosphate (ATP) through the electron transport chain (ETC). They also constitute a metabolic hub in which metabolites are used and processed, notably through the tricarboxylic acid (TCA) cycle. These newly generated metabolites have the capacity to feed other cellular metabolic pathways; modify cellular functions; and, ultimately, generate specific phenotypes. Mitochondria also provide intracellular signaling cues through reactive oxygen species (ROS) production. As expected with such a central cellular role, mitochondrial dysfunctions have been linked to many different diseases. The origins of some of these diseases could be pinpointed to specific mutations in both mitochondrial- and nuclear-encoded genes. In addition to their impressive intracellular tasks, mitochondria also provide intercellular signaling as they can be exchanged between cells, with resulting effects ranging from repair of damaged cells to strengthened progression and chemo-resistance of cancer cells. Several therapeutic options can now be envisioned to rescue mitochondria-defective cells. They include gene therapy for both mitochondrial and nuclear defective genes. Transferring exogenous mitochondria to target cells is also a whole new area of investigation. Finally, supplementing targeted metabolites, possibly through microbiota transplantation, appears as another therapeutic approach full of promises.

Modulation of host mitochondrial dynamics during bacterial infection

Mitochondria is a dynamic organelle of the cell that can regulate and maintain cellular ATP level, ROS production, calcium signaling and immune response. In order to retain their shape and distribution, mitochondria go through coordinated cycles of fission and fusion. Further, dysfunctional mitochondria are selectively eliminated from the cell via mitophagy to synchronize mitochondrial quality control and cellular homeostasis. In addition, mitochondria when in close proximity with the endoplasmic reticulum can alter the signaling pathways and some recent findings also reveal a direct correlation between the mitochondrial localization in the cell to the immune response elicited against the invading pathogen. These modulations in the mitochondrial network are collectively termed as 'mitochondrial dynamics'. Diverse bacteria, virus and parasitic pathogens upon infecting a cell can alter the host mitochondrial dynamics in favor of their multiplication and this in turn can be a major determinant of the disease outcome. Pharmacological perturbations in these pathways thus could lead to generation of additional therapeutic opportunities. This review will focus on the pathogenic modulation of the host mitochondrial dynamics, specifically during the bacterial infections and describes how dysregulated mitochondrial dynamics facilitates the pathogen's ability to establish efficient infection.

Interplay between NADH oxidation by complex I, glutathione redox state and sirtuin-3, and its role in the development of insulin resistance

Metabolic diseases are characterized by high NADH/NAD⁺ ratios due to excessive electron supply, causing defective mitochondrial function and impaired sirtuin-3 (SIRT-3) activity, the latter driving to oxidative stress and altered fatty acid β-oxidation. NADH is oxidized by the complex I in the electron transport chain, thereby factors inhibiting complex I like acetylation, cardiolipin peroxidation, and glutathionylation by low GSH/GSSG ratios affects SIRT3 function by increasing the NADH/NAD⁺ ratio. In this review, we summarized the evidence supporting a role of the above events in the development of insulin resistance, which is relevant in the pathogenesis of obesity and diabetes. We propose that maintenance of proper NADH/NAD⁺ and GSH/GSSG ratios are central to ameliorate insulin resistance, as alterations in these redox couples lead to complex I dysfunction, disruption of SIRT-3 activity, ROS production and impaired β-oxidation, the latter two being key effectors of insulin resistance.

Deregulated Mitochondrial DNA in Diseases

Mitochondria play various important roles in energy production, metabolism, and apoptosis. Mitochondrial dysfunction caused by alterations in mitochondrial DNA (mtDNA) can lead to the initiation and progression of cancers and other diseases. These alterations include mutations and copy number variations. Especially, the mutations in D-loop, MT-ND1, and MT-ND5 affect mitochondrial functions and are widely detected in various cancers. Meanwhile, several other mutations have been correlated with muscular and neuronal diseases, especially MT-TL1 is deeply related. These pieces of evidence indicated mtDNA alterations in diseases show potential as a novel therapeutic target. mtDNA repair enzymes are the target for delaying or stalling the mtDNA damage-induced cancer progression and metastasis. Moreover, some mutations reveal a prognosis ability of the drug resistance. Current efforts aim to develop mitochondrial transplantation technique as a direct cure for deregulated mitochondria-associated diseases. This review summarizes the implications of mitochondrial dysfunction in cancers and other pathologies; and discusses the relevance of mitochondria-targeted therapies, along with their contribution as potential biomarkers.

Improvement of cognitive and motor performance with mitotherapy in aged mice

Changes in mitochondrial structure and function are mostly responsible for aging and age-related features. Whether healthy mitochondria could prevent aging is, however, unclear. Here we intravenously injected the mitochondria isolated from young mice into aged mice and investigated the mitotherapy on biochemistry metabolism and animal behaviors. The results showed that heterozygous mitochondrial DNA (mtDNA) of both aged and young mouse coexisted in tissues of aged mice after mitochondrial administration, and meanwhile, ATP content in tissues increased while reactive oxygen species (ROS) level reduced. Besides, the mitotherapy significantly improved cognitive and motor performance of aged mice. Our study, at the first report in aged animals, not only provides a useful approach to study mitochondrial function associated with aging, but also a new insight into anti-aging through mitotherapy.

Neuroprotection from optic nerve injury and modulation of oxidative metabolism by transplantation of active mitochondria to the retina

Mitochondrial dysfunctions are linked to a series of neurodegenerative human conditions, including Parkinson's disease, schizophrenia, optic neuropathies, and glaucoma. Recently, a series of studies have pointed mitotherapy - exogenous mitochondria transplant - as a promising way to attenuate the progression of neurologic disorders; however, the neuroprotective and pro-regenerative potentials of isolated mitochondria in vivo have not yet been elucidated. In this present work, we tested the effects of transplants of active (as well-coupled organelles were named), liver-isolated mitochondria on the survival of retinal ganglion cells and axonal outgrowth after optic nerve crush. Our data show that intravitreally transplanted, full active mitochondria incorporate into the retina, improve its oxidative metabolism and electrophysiological activity at 1 day after transplantation. Moreover, mitotherapy increases cell survival in the ganglion cell layer at 14 days, and leads to a higher number of axons extending beyond the injury site at 28 days; effects that are dependent on the organelles' structural integrity. Together, our findings support mitotherapy as a promising approach for future therapeutic interventions upon central nervous system damage.

Physical exercise and liver "fitness": Role of mitochondrial function and epigenetics-related mechanisms in non-alcoholic fatty liver disease

BACKGROUND

Modern lifestyles, especially high-caloric intake and physical inactivity, contribute to the increased prevalence of non-alcoholic fatty liver disease (NAFLD), which becomes a significant health problem worldwide. Lifestyle changes, however, affect not only parental generation, but also their offspring, reinforcing the need for efficient preventive approaches to deal with this disease. This transgenerational influence of phenotypes dependent on parents (particularly maternal) behaviours may open additional research avenues. Despite persistent attempts to design an effective pharmacological therapy against NAFLD, physical activity, as a non-pharmacological approach, emerges as an exciting strategy.

SCOPE OF REVIEW

Here we briefly review the effect of physical exercise on liver mitochondria adaptations in NAFLD, highlighting the importance of mitochondrial metabolism and transgenerational and epigenetic mechanisms in liver diseases.

MAJOR CONCLUSIONS

A deeper look into cellular mechanisms sheds a light on possible effects of physical activity in the prevention and treatment of NAFLD through modulation of function and structure of particular organelles, namely mitochondria. Additionally, despite of increasing evidence regarding the contribution of epigenetic mechanisms in the pathogenesis of different diseases, the role of microRNAs, DNA methylation, and histone modification in NAFLD pathogenesis still needs to be elucidated.

Fat and Sugar-A Dangerous Duet. A Comparative Review on Metabolic Remodeling in Rodent Models of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a common disease in Western society and ranges from steatosis to steatohepatitis to end-stage liver disease such as cirrhosis and hepatocellular carcinoma. The molecular mechanisms that are involved in the progression of steatosis to more severe liver damage in patients are not fully understood. A deeper investigation of NAFLD pathogenesis is possible due to the many different animal models developed recently. In this review, we present a comparative overview of the most common dietary NAFLD rodent models with respect to their metabolic phenotype and morphological manifestation. Moreover, we describe similarities and controversies concerning the effect of NAFLD-inducing diets on mitochondria as well as mitochondria-derived oxidative stress in the progression of NAFLD.

Healthy mitochondria inhibit the metastatic melanoma in lungs

Tumor mitochondria alter their functions to reprogram cell metabolism and then allow tumor cells to rapidly proliferate in the hypoxic and acidic microenvironment. However, roles of normal mitochondria played in tumor progression are still unclear. Here we investigate the normal mitochondrial effect on abnormal metabolism of tumors, and to clarify why the mitochondria have to undergo functional changes in the tumor growth. The mitochondria isolated from healthy mouse livers were intravenously injected into melanoma model mice with lung metastasis, then the tumor growth, animal survival and associated metabolic changes were studied. The results reveal that the mitochondria significantly retard tumor growth and increase survival days of animals. The anti-tumor effect of the mitochondria is related to interfering the tumor cell metabolisms, such as reducing glycolysis and producing an oxidative intracellular environment, all of which are not suitable for tumor cell proliferation. In addition, the mitochondria increases cell apoptosis, necrosis, and mitophagy. These effects are more efficient with the mitochondria isolated from young mouse livers than those from aged mice. Our study not only provides a valuable approach to invest mitochondrial function associated with tumor growth but also offer new insight into tumor therapy through interfering the tumor cell metabolism by healthy mitochondria.

Mesenchymal Stem Cells in the Adult Human Liver: Hype or Hope?

Chronic liver diseases constitute a significant economic, social, and biomedical burden. Among commonly adopted approaches, only organ transplantation can radically help patients with end-stage liver pathologies. Cell therapy with hepatocytes as a treatment for chronic liver disease has demonstrated promising results. However, quality human hepatocytes are in short supply. Stem/progenitor cells capable of differentiating into functionally active hepatocytes provide an attractive alternative approach to cell therapy for liver diseases, as well as to liver-tissue engineering, drug screening, and basic research. The application of methods generally used to isolate mesenchymal stem cells (MSCs) and maintain them in culture to human liver tissue provides cells, designated here as liver MSCs. They have much in common with MSCs from other tissues, but differ in two aspects-expression of a range of hepatocyte-specific genes and, possibly, inherent commitment to hepatogenic differentiation. The aim of this review is to analyze data regarding liver MSCs, probably another type of liver stem/progenitor cells different from hepatic stellate cells or so-called hepatic progenitor cells. The review presents an analysis of the phenotypic characteristics of liver MSCs, their differentiation and therapeutic potential, methods for isolating these cells from human liver, and discusses issues of their origin and heterogeneity. Human liver MSCs are a fascinating object of fundamental research with a potential for important practical applications.

Mitochondrial transplantation attenuates lipopolysaccharide- induced depression-like behaviors

The dysfunction of mitochondria plays important roles in the development of depression. Interestingly, increasing numbers of evidence show the therapeutic benefits of mitochondria transfer. Therefore, we hypothesized that injection of exogenous mitochondria would contribute to ameliorate depressive-like symptoms. In this study, the antidepressant-like effect of intravenous isolated mitochondria was evaluated on a lipopolysaccharide (LPS)- induced model of depression. The depressive-like behaviors were assessed using forced swim test (FST), tail suspension test (TST) and sucrose preference test. Besides, the neurogenesis, expression of brain-derived neurotrophic factor (BDNF), glial activation, neuroinflammation, oxidative stress and ATP production were determined in the hippocampus. The results showed that treatment of isolated mitochondria decreased the immobility time of mice in the FST and TST, and attenuated the decrease in sucrose preference test. Moreover, isolated mitochondria significantly reduced the activation of astrocyte and microglia as well as neuroinflammation (i.e. 1 L-1β, TNF-α and COX-2), increased BDNF expression and neurogenesis, restored the dysfunction of ATP production and oxidative stress in inflammation- induced depression. Taken together, the data suggested for the first time that injection of isolated mitochondria ameliorated LPS- induced depressive-like behaviors. The new discovery for the present study provides that mitochondrial transplantation might act as a new therapeutic strategy for MDD.

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.

Current progress of mitochondrial transplantation that promotes neuronal regeneration

Background

Mitochondria are the major source of intracellular adenosine triphosphate (ATP) and play an essential role in a plethora of physiological functions, including the regulation of metabolism and the maintenance of cellular homeostasis. Mutations of mitochondrial DNA, proteins and impaired mitochondrial function have been implicated in the neurodegenerative diseases, stroke and injury of the central nervous system (CNS). The dynamic feature of mitochondrial fusion, fission, trafficking and turnover have also been documented in these diseases.

Perspectives

A major bottleneck of traditional approach to correct mitochondria-related disorders is the difficulty of drugs or gene targeting agents to arrive at specific sub-compartments of mitochondria. Moreover, the diverse nature of mitochondrial mutations among patients makes it impossible to develop one drug for one disease. To this end, mitochondrial transplantation presents a new paradigm of therapeutic intervention that benefits neuronal survival and regeneration for neurodegenerative diseases, stroke, and CNS injury. Supplement of healthy mitochondria to damaged neurons has been reported to promote neuronal viability, activity and neurite re-growth. In this review, we provide an overview of the recent advance and development on mitochondrial therapy.

Conclusion

Key parameters for the success of mitochondrial transplantation depend on the source and quality of isolated mitochondria, delivery protocol, and cellular uptake of supplemented mitochondria. To expedite clinical application of the mitochondrial transplantation, current isolation protocol needs optimization to obtain high percentage of functional mitochondria, isolated mitochondria may be packaged by biomaterials for successful delivery to brain allowing for efficient neuronal uptake.

Potential Clinical Risk of Inflammation and Toxicity from Rare-Earth Nanoparticles in Mice

Background:

Nanotechnology is emerging as a promising tool to perform noninvasive therapy and optical imaging. However, nanomedicine may pose a potential risk of toxicity during in vivo applications. In this study, we aimed to investigate the potential toxicity of rare-earth nanoparticles (RENPs) using mice as models.

Methods:

We synthesized RENPs through a typical co-precipitation method. Institute of Cancer Research (ICR) mice were randomly divided into seven groups including a control group and six experimental groups (10 mice per group). ICR mice were intravenously injected with bare RENPs at a daily dose of 0, 0.5, 1.0, and 1.5 mg/kg for 7 days. To evaluate the toxicity of these nanoparticles in mice, magnetic resonance imaging (MRI) was performed to assess their uptake in mice. In addition, hematological and biochemical analyses were conducted to evaluate any impairment in the organ functions of ICR mice. The analysis of variance (ANOVA) followed by a one-way ANOVA test was used in this study. A repeated measures' analysis was used to determine any significant differences in white blood cell (WBC), alanine aminotransferase (ALT), and creatinine (CREA) levels at different evaluation times in each group.

Results:

We demonstrated the successful synthesis of two different sizes (10 nm and 100 nm) of RENPs. Their physical properties were characterized by transmission electron microscopy and a 980 nm laser diode. Results of MRI study revealed the distribution and circulation of the RENPs in the liver. In addition, the hematological analysis found an increase of WBCs to (8.69 ± 0.85) × 10⁹/L at the 28^th day, which is indicative of inflammation in the mouse treated with 1.5 mg/kg NaYbF₄:Er nanoparticles. Furthermore, the biochemical analysis indicated increased levels of ALT ([64.20 ± 15.50] U/L) and CREA ([27.80 ± 3.56] μmol/L) at the 28^th day, particularly those injected with 1.5 mg/kg NaYbF₄:Er nanoparticles. These results suggested the physiological and pathological damage caused by these nanoparticles to the organs and tissues of mice, especially to liver and kidney.

Conclusion:

The use of bare RENPs may cause possible hepatotoxicity and nephritictoxicity in mice.

Targeting mitochondria to oppose the progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a condition characterized by the excessive accumulation of triglycerides in hepatocytes. NAFLD is the most frequent chronic liver disease in developed countries, and is often associated with metabolic disorders such as obesity and type 2 diabetes. NAFLD definition encompasses a spectrum of chronic liver abnormalities, ranging from simple steatosis (NAFL), to steatohepatitis (NASH), significant liver fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD, therefore, represents a global public health issue. Mitochondrial dysfunction occurs in NAFLD, and contributes to the progression to the necro-inflammatory and fibrotic form (NASH). Disrupted mitochondrial function is associated with a decrease in the energy levels and impaired redox balance, and negatively affects cell survival by altering overall metabolism and subcellular trafficking. Such events reduce the tolerance of hepatocytes towards damaging hits, and favour the injurious effects of extra-cellular factors. Here, we discuss the role of mitochondria in NAFLD and focus on potential therapeutic approaches aimed at preserving mitochondrial function.

Computational Modeling of Oxidative Stress in Fatty Livers Elucidates the Underlying Mechanism of the Increased Susceptibility to Ischemia/Reperfusion Injury

QUESTION

Donor liver organs with moderate to high fat content (i.e. steatosis) suffer from an enhanced susceptibility to ischemia/reperfusion injury (IRI) during liver transplantation. Responsible for the cellular injury is an increased level of oxidative stress, however the underlying mechanistic network is still not fully understood.

METHOD

We developed a phenomenological mathematical model of key processes of hepatic lipid metabolism linked to pathways of oxidative stress. The model allows the simulation of hypoxia (i.e. ischemia-like conditions) and reoxygenation (i.e. reperfusion-like conditions) for various degrees of steatosis and predicts the level of hepatic lipid peroxidation (LPO) as a marker of cell damage caused by oxidative stress.

RESULTS & CONCLUSIONS

Our modeling results show that the underlying feedback loop between the formation of reactive oxygen species (ROS) and LPO leads to bistable systems behavior. Here, the first stable state corresponds to a low basal level of ROS production. The system is directed to this state for healthy, non-steatotic livers. The second stable state corresponds to a high level of oxidative stress with an enhanced formation of ROS and LPO. This state is reached, if steatotic livers with a high fat content undergo a hypoxic phase. Theoretically, our proposed mechanistic network would support the prediction of the maximal tolerable ischemia time for steatotic livers: Exceeding this limit during the transplantation process would lead to severe IRI and a considerable increased risk for liver failure.

Frataxin-Mediated PINK1-Parkin-Dependent Mitophagy in Hepatic Steatosis: The Protective Effects of Quercetin

SCOPE

Naturally occurring quercetin has been found to induce mitophagy and prevent nonalcoholic fatty liver disease (NAFLD). However, it still remains elusive whether frataxin upregulation by quercetin contributes to the beneficial effect through mitophagy or not.

METHODS AND RESULTS

Adult male C57BL/J mice were fed a high-fat diet (HFD, 60% of energy from fat) with quercetin (100 mg kg-1 body weight) or not for 10 weeks. Quercetin alleviated HFD-induced histopathological changes, disorders of lipid metabolism, and mitochondrial damage. Moreover, quercetin blocked mitophagy suppression by HFD based on the increased LC3II, PTEN-induced putative kinase 1 (PINK1) and Beclin1 expressions, as well as decreased p62 levels. Quercetin also improved the Parkin translocation to mitochondria confirmed by immunofluorescence. Specifically, frataxin was lowered in the liver of HFD-fed mice or HepG2 cell incubated with oleate/palmitate but restored by quercetin, and quercetin's regulation of frataxin may depend on p53. Furthermore, lentivirus-mediated stable knockdown of frataxin in HepG2 inhibited PINK1-Parkin-associated mitophagy and resulted in lipid accumulation. Frataxin was further decreased by free fatty acids in knockdown cells concomitantly with depressed PINK1-Parkin-associated mitophagy, which was partially normalized by quercetin.

CONCLUSION

Quercetin alleviated hepatic steatosis by enhancing frataxin-mediated PINK1/Parkin-dependent mitophagy, highlighting a promising preventive strategy and mechanism for NAFLD by quercetin.