Activation of mitochondrial fusion provides a new treatment for mitochondria-related diseases

BGP-15 Protects Mitochondria in Acute, Acetaminophen Overdose Induced Liver Injury

Acetaminophen (APAP) induced hepatotoxicity involves activation of c-Jun amino-terminal kinase (JNK), mitochondrial damage and ER stress. BGP-15, a hydroximic acid derivative, has been reported to have hepatoprotective effects in APAP overdose induced liver damage. Effect of BGP-15 was further investigated on mitochondria in APAP-overdose induced acute liver injury in mice. We found that BGP-15 efficiently preserved mitochondrial morphology, and it caused a marked decrease in the number of damaged mitochondria. Attenuation of mitochondrial damage by BGP-15 is supported by immunohistochemistry as the TOMM20 label and the co-localized autophagy markers detected in the livers of APAP-treated mice were markedly reduced upon BGP-15 administration. This effect, along with the observed prevention of JNK activation likely contribute to the mitochondrial protective action of BGP-15.

Mitofusin2, a rising star in acute-on-chronic liver failure, triggers macroautophagy via the mTOR signalling pathway

Acute-on-chronic liver failure (ACLF) is a life-threatening syndrome with poor prognosis. Several studies have begun to prove that mitochondria play a crucial role in liver failure. Mitofusin2 (Mfn2) plays a key role in maintaining the integrity of mitochondrial morphology and function. However, the role and underlying mechanisms of Mfn2 on cell autophagy of ACLF remain unclear. Our aim was to explore the effect of Mfn2 on several biological functions involving cell autophagy in ACLF. In this study, we constructed an ACLF animal model and a hepatocyte autophagy model, using adenovirus and lentivirus to deliver Mfn2 to liver cells, in order to assess the effect of Mfn2 on autophagy and apoptosis in ACLF. Furthermore, we explored the biological mechanism of Mfn2-induced autophagy of ACLF using Western blotting, RT-PCR and electron microscopy. We found that Mfn2 significantly attenuated ACLF, characterized by ameliorated gross appearance and microscopic histopathology of liver, and reduced serum AST, ALT, and TBIL levels. Mfn2 improved the expressions of LC3-II, Atg5 and Bcl-2 and down-regulated the expression of P62 and Bax in ACLF. Like rapamycin, Mfn2 also significantly inhibited the expressions of p-PI3K, p-Akt and p-mTOR in ACLF. In conclusion, our findings suggest that Mfn2 influences multiple biological functions of ACLF via the PI3K/Akt/mTOR signalling pathway. This study will provide a reliable theoretical basis for the application of Mfn2 as an effective target for ACLF treatment, reversing or delaying the process of ACLF.

Role of PGC-1α in Mitochondrial Quality Control in Neurodegenerative Diseases

As one of the major cell organelles responsible for ATP production, it is important that neurons maintain mitochondria with structural and functional integrity; this is especially true for neurons with high metabolic requirements. When mitochondrial damage occurs, mitochondria are able to maintain a steady state of functioning through molecular and organellar quality control, thus ensuring neuronal function. And when mitochondrial quality control (MQC) fails, mitochondria mediate apoptosis. An apparently key molecule in MQC is the transcriptional coactivator peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α). Recent findings have demonstrated that upregulation of PGC-1α expression in neurons can modulate MQC to prevent mitochondrial dysfunction in certain in vivo and in vitro aging or neurodegenerative encephalopathy models, such as Huntington's disease, Alzheimer's disease, and Parkinson's disease. Because mitochondrial function and quality control disorders are the basis of pathogenesis in almost all neurodegenerative diseases (NDDs), the role of PGC-1α may make it a viable entry point for the treatment of such diseases. This review focuses on multi-level MQC in neurons, as well as the regulation of MQC by PGC-1α in these major NDDs.

Mitochondrial disorders and drugs: what every physician should know

Mitochondrial disorders are a group of metabolic conditions caused by impairment of the oxidative phosphorylation system. There is currently no clear evidence supporting any pharmacological interventions for most mitochondrial disorders, except for coenzyme Q10 deficiencies, Leber hereditary optic neuropathy, and mitochondrial neurogastrointestinal encephalomyopathy. Furthermore, some drugs may potentially have detrimental effects on mitochondrial dysfunction. Drugs known to be toxic for mitochondrial functions should be avoided whenever possible. Mitochondrial patients needing one of these treatments should be carefully monitored, clinically and by laboratory exams, including creatine kinase and lactate. In the era of molecular and ‘personalized’ medicine, many different physicians (not only neurologists) should be aware of the basic principles of mitochondrial medicine and its therapeutic implications. Multicenter collaboration is essential for the advancement of therapy for mitochondrial disorders. Whenever possible, randomized clinical trials are necessary to establish efficacy and safety of drugs. In this review we discuss in an accessible way the therapeutic approaches and perspectives in mitochondrial disorders. We will also provide an overview of the drugs that should be used with caution in these patients.

Mitochondrial dynamics and their potential as a therapeutic target

Mitochondrial dynamics shape the mitochondrial network and contribute to mitochondrial function and quality control. Mitochondrial fusion and division are integrated into diverse cellular functions and respond to changes in cell physiology. Imbalanced mitochondrial dynamics are associated with a range of diseases that are broadly characterized by impaired mitochondrial function and increased cell death. In various disease models, modulating mitochondrial fusion and division with either small molecules or genetic approaches has improved function. Although additional mechanistic understanding of mitochondrial fusion and division will be critical to inform further therapeutic approaches, mitochondrial dynamics represent a powerful therapeutic target in a wide range of human diseases.

TRPV1 and TRPA1 in Lung Inflammation and Airway Hyperresponsiveness Induced by Fine Particulate Matter (PM2.5)

Exposure to fine particulate matter (PM_2.5) has been associated with lung inflammation and airway hyperresponsiveness (AHR). Transient receptor potential (TRP) vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) both may play important roles in lung inflammation and AHR. We investigated whether PM_2.5-induced lung inflammation and AHR could be prevented by blocking TRPV1 and TRPA1 channels. Mice were injected intraperitoneally with AMG9810 (30 mg/kg, a TRPV1 antagonist) or A967079 (30 mg/kg, a TRPA1 antagonist) or their combination or vehicle (PBS) one hour before intranasal instillation of PM_2.5 (7.8 mg/kg) or vehicle (PBS) for two consecutive days, and then the mice were studied 24 h later. All pretreatments inhibited PM_2.5-induced AHR and inflammatory infiltration in the lung tissue and decreased inflammatory cytokine levels in the bronchoalveolar lavage fluid, together with oxidant levels in the lung. AMG9810 inhibited MFF expression and increased MFN2 expression while A967079 inhibited DRP1 expression and increased OPA1 expression; combined pretreatment reduced MFF and DPR1 expression and increased MFN2 and OPA1 expression. All pretreatments inhibited the activation of the TLR4/NF-κB pathway, while A967079 alone, and combined with AMG9810 also reduced the activation of the NLRP3/caspase-1 pathway. Both TRPV1 and TRPA1 channels play an important role in PM_2.5-induced lung inflammation and AHR. However, inhibition of the TRPA1 channel or combined inhibition of TRPA1 and TRPV1 channels resulted in greater inhibitory effect on PM_2.5-induced lung injury through regulating the mitochondrial fission/fusion proteins and inhibiting the TLR4/NF-κB and NLRP3/caspase-1 pathways.

Blockade of AMPA Receptor Regulates Mitochondrial Dynamics by Modulating ERK1/2 and PP1/PP2A-Mediated DRP1-S616 Phosphorylations in the Normal Rat Hippocampus

N-Methyl-D-aspartate receptor (NMDAR) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) activations induce fast and transient mitochondrial fragmentation under pathophysiological conditions. However, it is still unknown whether NMDAR or AMPAR activity contributes to mitochondrial dynamics under physiological conditions. In the present study, MK801 (a non-competitive NMDAR antagonist) did not affect mitochondrial length in hippocampal neurons as well as phosphorylation levels of dynamin-related protein 1 (DRP1)-serine (S) 616, extracellular-signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK) and AMPAR. In contrast, perampanel (a non-competitive AMPAR antagonist) elongated mitochondrial length in neurons concomitant with diminishing phosphorylations of DRP1-S616, ERK1/2, and JNK, but not p38 MAPK. Perampanel also reduced protein phosphatase (PP) 1, PP2A and PP2B phosphorylations, indicating activations of these PPs which were unaffected by MK801. U0126 (an ERK1/2 inhibitor) elongated mitochondrial length, accompanied by the reduced DRP1-S616 phosphorylation. SP600125 (a JNK inhibitor) did not influence mitochondrial length and DRP1 phosphorylations. Okadaic acid (a PP1/PP2A inhibitor) reduced mitochondrial length with the up-regulated DRP1-S616 phosphorylation, while CsA (a PP2B inhibitor) increased it with the elevated DRP1-S637 phosphorylation. Co-treatment of okadaic acid or CsA with perampanel attenuated the reductions in DRP1-S616 and -S637 phosphorylation without changing DRP1 expression level, respectively. GYKI 52466 (another non-competitive AMPAR antagonist) showed the similar effects of perampanel on phosphorylations of DRP1, ERK1/2, JNK, PPs, and GluR1 AMPAR subunits. Taken together, our findings suggest that a blockade of AMPAR may regulate the cooperation of ERK1/2- and PP1/PP2A for the modulation of DRP1 phosphorylations, which facilitate mitochondrial fusion.

Experimental diabetes mellitus exacerbates ischemia/reperfusion-induced myocardial injury by promoting mitochondrial fission: Role of down-regulation of myocardial Sirt1 and subsequent Akt/Drp1 interaction

Diabetes mellitus (DM) has a negative impact on clinical outcomes for patients with myocardial infarction. The aim of the present study was to assess whether decreased myocardial levels of Sirtuin1 (Sirt1) contribute to the increased susceptibility of the diabetic myocardium to ischemia/reperfusion (I/R) injury. In vivo, myocardial levels of Sirt1 expression and activity were decreased in mice with STZ-induced DM. Increasing Sirt1 activity prevented the DM-induced exacerbation of myocardial mitochondrial fission, apoptosis and dysfunction elicited by I/R. In vitro, anoxia/reoxygenation (A/R) challenge of cardiomyocytes (CM) that were preconditioned with high glucose (HG-CM) resulted in an exacerbation of the A/R-induced mitochondrial fission, oxidant production and CM apoptosis; effects reversed by increasing Sirt1 protein/activity. Inhibition of Drp1 prevented the exacerbated CM mitochondrial fission and oxidant production after A/R challenge of HG-CM. Decreased Sirt1 in HG-CM was associated with decreased Akt phosphorylation. Inhibition of Akt had no effect on CM Sirt1 levels, but further increased Drp1 activation. Increasing Sirt1 levels prevented the decrease in Akt phosphorylation and Drp1 activation in A/R challenged HG-CM. In conclusion: our data indicate that the increased vulnerability of the diabetic myocardium to I/R-induced apoptosis/dysfunction is attributable, in part, to decreased myocardial Sirt1 activity which leads to a decrease in Akt activation, an increase in Drp1 activity, culminating in excessive mitochondrial fission and ROS production.

Mitochondrial targeting as a novel therapy for stroke

Stroke is a main cause of mortality and morbidity worldwide. Despite the increasing development of innovative treatments for stroke, most are unsuccessful in clinical trials. In recent years, an encouraging strategy for stroke therapy has been identified in stem cells transplantation. In particular, grafting cells and their secretion products are leading with functional recovery in stroke patients by promoting the growth and function of the neurovascular unit – a communication framework between neurons, their supply microvessels along with glial cells – underlying stroke pathology and recovery. Mitochondrial dysfunction has been recently recognized as a hallmark in ischemia/reperfusion neural damage. Emerging evidence of mitochondria transfer from stem cells to ischemic-injured cells points to transfer of healthy mitochondria as a viable novel therapeutic strategy for ischemic diseases. Hence, a more in-depth understanding of the cellular and molecular mechanisms involved in mitochondrial impairment may lead to new tools for stroke treatment. In this review, we focus on the current evidence of mitochondrial dysfunction in stroke, investigating favorable approaches of healthy mitochondria transfer in ischemic neurons, and exploring the potential of mitochondria-based cellular therapy for clinical applications. This paper is a review article. Referred literature in this paper has been listed in the references section. The data sets supporting the conclusions of this article are available online by searching various databases, including PubMed.

Mitochondrial stress management: a dynamic journey

Mitochondria undergo continuous challenges in the course of their life, from their generation to their degradation. These challenges include the management of reactive oxygen species, the proper assembly of mitochondrial respiratory complexes and the need to balance potential mutations in the mitochondrial DNA. The detection of damage and the ability to keep it under control is critical to fine-tune mitochondrial function to the organismal energy needs. In this review, we will analyze the multiple mechanisms that safeguard mitochondrial function in light of in crescendo damage. This sequence of events will include initial defense against excessive reactive oxygen species production, compensation mechanisms by the unfolded protein response (UPR^mt), mitochondrial dynamics and elimination by mitophagy.

Betaine enhances the cellular survival via mitochondrial fusion and fission factors, MFN2 and DRP1

Betaine is a key metabolite of the methionine cycle and known for attenuating alcoholic steatosis in the liver. Recent studies have focused on the protection effect of betaine in mitochondrial regulation through the enhanced oxidative phosphorylation system. However, the mechanisms of its beneficial effects have not been clearly identified yet. Mitochondrial dynamics is important for the maintenance of functional mitochondria and cell homeostasis. A defective mitochondrial dynamics and oxidative phosphorylation system have been closely linked to several pathologies, raising the possibility that novel drugs targeting mitochondrial dynamics may present a therapeutic potential to restore the cellular homeostasis. In this study, we investigated betaine’s effect on mitochondrial morphology and physiology and demonstrated that betaine enhances mitochondrial function by increasing mitochondrial fusion and improves cell survival. Furthermore, it rescued the unbalance of the mitochondrial dynamics from mitochondrial oxidative phosphorylation dysfunction induced by oligomycin and rotenone. The elongation properties by betaine were accompanied by lowering DRP1 and increasing MFN2 expression. These data suggest that betaine could play an important role in remodeling mitochondrial dynamics to enhance mitochondrial function and cell viability.

Enhancing Mitochondrial Health to Treat Hypertension

PURPOSE OF REVIEW

This review summarizes literature pertaining to the dawning field of therapeutic targeting of mitochondria in hypertension and discusses the potential of these interventions to ameliorate hypertension-induced organ damage.

RECENT FINDINGS

In recent years, mitochondrial dysfunction has been reported as an important contributor to the pathogenesis of hypertension-related renal, cardiac, and vascular disease. This in turn prompted development of novel mitochondria-targeted compounds, some of which have shown promising efficacy in experimental studies and safety in clinical trials. In addition, drugs that do not directly target mitochondria have shown remarkable benefits in preserving these organelles in experimental hypertension. Enhancing mitochondrial health is emerging as a novel feasible approach to treat hypertension. Future perspectives include mechanistic experimental studies to establish a cause-effect relationship between mitochondrial dysfunction and hypertension and further clinical trials to confirm the reno-, cardio-, and vasculo-protective properties of these compounds in hypertension.

Understanding the Role of Dysfunctional and Healthy Mitochondria in Stroke Pathology and Its Treatment

Stroke remains a major cause of death and disability in the United States and around the world. Solid safety and efficacy profiles of novel stroke therapeutics have been generated in the laboratory, but most failed in clinical trials. Investigations into the pathology and treatment of the disease remain a key research endeavor in advancing scientific understanding and clinical applications. In particular, cell-based regenerative medicine, specifically stem cell transplantation, may hold promise as a stroke therapy, because grafted cells and their components may recapitulate the growth and function of the neurovascular unit, which arguably represents the alpha and omega of stroke brain pathology and recovery. Recent evidence has implicated mitochondria, organelles with a central role in energy metabolism and stress response, in stroke progression. Recognizing that stem cells offer a source of healthy mitochondria—one that is potentially transferrable into ischemic cells—may provide a new therapeutic tool. To this end, deciphering cellular and molecular processes underlying dysfunctional mitochondria may reveal innovative strategies for stroke therapy. Here, we review recent studies capturing the intimate participation of mitochondrial impairment in stroke pathology, and showcase promising methods of healthy mitochondria transfer into ischemic cells to critically evaluate the potential of mitochondria-based stem cell therapy for stroke patients.