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

Regulation mechanism of GPS2 on PGC-1α/Drp1-mediated mitochondrial dynamics in inflammation of acute lung injury

Acute lung injury (ALI) has been a hot topic in the field of critical care research in recent years. Mitochondrial dynamics consists of mitochondrial fusion and mitochondrial fission. Dynamin-related protein 1 (Drp1), a key molecule that regulates mitochondrial fission, is important in the oxidative stress and inflammatory response to ALI. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a core protein that mediates mitochondrial biogenesis. G-protein pathway suppressor 2 (GPS2) acts as a transcriptional cofactor with regulatory effects on nuclear-encoded mitochondrial genes. This study aimed to investigate the mechanism of PGC-1α/Drp1-mediated mitochondrial dynamics involved in ALI and to demonstrate the protective mechanism of GPS2 in regulating mitochondrial structure and function and inflammation in ALI. The ALI model was constructed using LPS-induced wild-type mice and human pulmonary microvascular endothelial cells (HPMVECs). It was found that lung injury, oxidative stress and inflammation were exacerbated in the mice ALI model and that mitochondrial structure and function were disrupted in HPMVECs. In vitro studies revealed that LPS led to the upregulated expression of Drp1 and the downregulated expression of PGC-1α and GPS2. Mitochondrial division was reduced and respiratory function was restored in Drp1 knockdown cells, which inhibited oxidative stress and inflammatory response. In addition, the overexpression of PGC-1α and GPS2 significantly inhibited the expression of Drp1, mitochondrial function was restored, and inhibited reactive oxygen species (ROS) production and inflammatory factor release. Moreover, the overexpression of GPS2 promoted the upregulated expression of PGC-1α. This mechanism was also validated in vivo, in which the low expression of GPS2 in mice resulted in the upregulated expression of Drp1 and the downregulated expression of PGC-1α, and further exacerbated LPS-induced ALI. In the present study, we also found that LPS-induced the downregulated expression of GPS2 may be associated with its increased degradation by the proteasome. Therefore, these findings revealed that GPS2 inhibited oxidative stress and inflammation by modulating PGC-1α/Drp1-mediated mitochondrial dynamics to alleviate LPS-induced ALI, which may provide a new approach to the therapeutic orientation for LPS-induced ALI.

Role of mitochondrial dysfunction and biogenesis in fibromyalgia syndrome: Molecular mechanism in central nervous system

A critical role for mitochondrial dysfunction has been shown in the pathogenesis of fibromyalgia. It is a chronic pain syndrome characterized by neuroinflammation and impaired oxidative balance in the central nervous system. Boswellia serrata (BS), a natural polyphenol, is a well-known able to influence the mitochondrial metabolism. The objective of this study was to evaluate the mitochondrial dysfunction and biogenesis in fibromyalgia and their modulation by BS. To induce the model reserpine (1 mg/Kg) was subcutaneously administered for three consecutive days and BS (100 mg/Kg) was given orally for twenty-one days. BS reduced pain like behaviors in reserpine-injected rats and the astrocytes activation in the dorsal horn of the spinal cord and prefrontal cortex that are recognized as key regions associated with the neuropathic pain. Vulnerability to neuroinflammation and impaired neuronal plasticity have been described as consequences of mitochondrial dysfunction. BS administration increased PGC-1α expression in the nucleus of spinal cord and brain tissues, promoting the expression of regulatory genes for mitochondrial biogenesis (NRF-1, Tfam and UCP2) and cellular antioxidant defence mechanisms (catalase, SOD2 and Prdx 3). According with these data BS reduced lipid peroxidation and the GSSG/GSH ratio and increased SOD activity in the same tissues. Our results also showed that BS administration mitigates cytochrome-c leakage by promoting mitochondrial function and supported the movement of PGC-1α protein into the nucleus restoring the quality control of mitochondria. Additionally, BS reduced Drp1 and Fis1, preventing both mitochondrial fission and cell death, and increased the expression of Mfn2 protein, facilitating mitochondrial fusion. Overall, our results showed important mitochondrial dysfunction in central nervous system in fibromyalgia syndrome and the role of BS in restoring mitochondrial dynamics.

Downregulation of PGC-1α during cisplatin-induced muscle atrophy in murine skeletal muscle

This study aimed to investigate the effects of cisplatin on adenosine triphosphate (ATP) levels, expressions of genes related to mitochondrial oxidative phosphorylation (OXPHOS), and the factors related to mitochondrial biosynthesis in skeletal muscle. Systemic cisplatin administration decreased skeletal muscle mass, skeletal muscle strength, and endurance. The mitochondrial DNA /nuclear DNA ratio was also reduced after treatment with cisplatin. Moreover, among the factors related to mitochondrial biogenesis and function, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was significantly downregulated in the cisplatin-treated group. Downregulation of PGC-1α in the skeletal muscle may contribute to muscle weakness during cisplatin-induced muscle atrophy.

1,5-anhydro-D-fructose induces anti-aging effects on aging-associated brain diseases by increasing 5'-adenosine monophosphate-activated protein kinase activity via the peroxisome proliferator-activated receptor-γ co-activator-1α/brain-derived neurotrophic factor pathway

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor that serves as a cellular housekeeper; it also controls energy homeostasis and stress resistance. Thus, correct regulation of this factor can enhance health and survival. AMPK signaling may have a critical role in aging-associated brain diseases. Some in vitro studies have shown that 1,5-anhydro-D-fructose (1,5-AF) induces AMPK activation. In the present study, we experimentally evaluated the effects of 1,5-AF on aging-associated brain diseases in vivo using an animal model of acute ischemic stroke (AIS), stroke-prone spontaneously hypertensive rats (SHRSPs), and the spontaneous senescence-accelerated mouse-prone 8 (SAMP8) model. In the AIS model, intraperitoneal injection of 1,5-AF reduced cerebral infarct volume, neurological deficits, and mortality. In SHRSPs, oral administration of 1,5-AF reduced blood pressure and prolonged survival. In the SAMP8 model, oral administration of 1,5-AF alleviated aging-related decline in motor cognitive function. Although aging reduced the expression levels of peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) and brain-derived neurotrophic factor (BDNF), we found that 1,5-AF activated AMPK, which led to upregulation of the PGC-1α/BDNF pathway. Our results suggest that 1,5-AF can induce endogenous neurovascular protection, potentially preventing aging-associated brain diseases. Clinical studies are needed to determine whether 1,5-AF can prevent aging-associated brain diseases.

Peroxisom proliferator-activated receptor-γ coactivator-1α in neurodegenerative disorders: A promising therapeutic target

Neurodegenerative disorders (NDDs) are characterized by progressive loss of selectively vulnerable neuronal populations and myelin sheath, leading to behavioral and cognitive dysfunction that adversely affect the quality of life. Identifying novel therapies that attenuate the progression of NDDs would be of significance. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a widely expressed transcriptional regulator, modulates the expression of genes engaged in mitochondrial biosynthesis, metabolic regulation, and oxidative stress (OS). Emerging evidences point to the strong connection between PGC-1α and NDDs, suggesting its positive impaction on the progression of NDDs. Therefore, it is urgent to gain a deeper and broader understanding between PGC-1α and NDDs. To this end, this review presents a comprehensive overview of PGC-1α, including its basic characteristics, the post-translational modulations, as well as the interacting transcription factors. Secondly, the pathogenesis of PGC-1α in various NDDs, such as Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD) is briefly discussed. Additionally, this study summarizes the underlying mechanisms that PGC-1α is neuroprotective in NDDs via regulating neuroinflammation, OS, and mitochondrial dysfunction. Finally, we briefly outline the shortcomings of current NDDs drug therapy, and summarize the functions and potential applications of currently available PGC-1α modulators (activator or inhibitors). Generally, this review updates our insight of the important role of PGC-1α on the development of NDDs, and provides a promising therapeutic target/ drug for the treatment of NDDs.

Arsenic-Induced, Mitochondria-Mediated Apoptosis Is Associated with Decreased Peroxisome Proliferator-Activated Receptor γ Coactivator α in Rat Brains

Chronic exposure to arsenic in drinking water damages cognitive function, and nerve cell apoptosis is one of the primary characteristics. The damage to mitochondrial structure and/or function is one of the main characteristics of apoptosis. Peroxisome proliferator-activated receptor γ coactivator α (PGC-1α) is involved in the regulation of mitochondrial biogenesis, energy metabolism, and apoptosis. In this study, we aimed to study the role of PGC-1α in sodium arsenite (NaAsO₂)-induced mitochondrial apoptosis in rat hippocampal cells. We discovered that increased arsenic-induced apoptosis in rat hippocampus increased with NaAsO₂ (0, 2, 10, and 50 mg/L, orally via drinking water for 12 weeks) exposure by TUNEL assay, and the structure of mitochondria was incomplete and swollen and had increased lysosomes, lipofuscins, and nuclear membrane shrinkage observed via transmission electron microscopy. Furthermore, NaAsO₂ reduced the levels of Bcl-2 and PGC-1α and increased the levels of Bax and cytochrome C expression. Moreover, correlation analysis showed that brain arsenic content was negatively correlated with PGC-1α levels and brain ATP content; PGC-1α levels were negatively correlated with apoptosis rate; and brain ATP content was positively correlated with PGC-1α levels, but no significant correlation between ATP content and apoptosis has been observed in this study. Taken together, the results of this study indicate that NaAsO₂-induced mitochondrial pathway apoptosis is related to the reduction of PGC-1α, accompanied by ATP depletion.

Improving mitochondrial function in preclinical models of heart failure: therapeutic targets for future clinical therapies?

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from the unsuccessful compensation of symptoms of myocardial damage. Mitochondrial dysfunction is a process that occurs because of an attempt to adapt to the disruption of metabolic and energetic pathways occurring in the myocardium. This, in turn, leads to further dysfunction in cardiomyocyte processes. Currently, many therapeutic strategies have been implemented to improve mitochondrial function, but their effectiveness varies widely.

AREAS COVERED

This review focuses on new models of therapeutic strategies targeting mitochondrial function in the treatment of heart failure.

EXPERT OPINION

Therapeutic strategies targeting mitochondria appear to be a valuable option for treating heart failure. Currently, the greatest challenge is to develop new research models that could restore the disrupted metabolic processes in mitochondria as comprehensively as possible. Only the development of therapies that focus on improving as many dysregulated mitochondrial processes as possible in patients with heart failure will be able to bring the expected clinical improvement, along with inhibition of disease progression. Combined strategies involving the reduction of the effects of oxidative stress and mitochondrial dysfunction, appear to be a promising possibility for developing new therapies for a complex and multifactorial disease such as heart failure.

von Hippel-Lindau-targeting microRNA-143-3p attenuates mitochondrial abnormality via AMPK/PGC-1α axis in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease characterized by selective loss of dopaminergic neurons. We previously found that inhibition of von Hippel-Lindau (VHL) can alleviate dopaminergic neuron degeneration in PD models via regulation of mitochondrial homeostasis, however, the disease-related alterations of VHL and the regulatory mechanisms of VHL level in PD need to be further investigated. In this study, we found that the levels of VHL were markedly increased in multiple cell models of PD and identified microRNA-143-3p (miR-143-3p) as a promising candidate for regulating VHL expression involved in PD. MiR-143-3p directly bound to the 3'untranslated region of human VHL mRNA and inhibited its translation, and exerted neuroprotective effects by improving cell viability, apoptosis and tyrosine hydroxylase abnormality. Furthermore, we demonstrated that miR-143-3p exerted neuroprotection by attenuating mitochondrial abnormality via AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) axis, and AMPK inhibitor abolished the beneficial effects of miR-143-3p on the cell model of PD. Therefore, we identify the dysregulated VHL and miR-143-3p in PD, and propose the therapeutic potential of miR-143-3p to alleviate PD by improving mitochondrial homeostasis via AMPK/PGC-1α axis.

PGC-1α Is a Master Regulator of Mitochondrial Lifecycle and ROS Stress Response

Mitochondria play a major role in ROS production and defense during their life cycle. The transcriptional activator PGC-1α is a key player in the homeostasis of energy metabolism and is therefore closely linked to mitochondrial function. PGC-1α responds to environmental and intracellular conditions and is regulated by SIRT1/3, TFAM, and AMPK, which are also important regulators of mitochondrial biogenesis and function. In this review, we highlight the functions and regulatory mechanisms of PGC-1α within this framework, with a focus on its involvement in the mitochondrial lifecycle and ROS metabolism. As an example, we show the role of PGC-1α in ROS scavenging under inflammatory conditions. Interestingly, PGC-1α and the stress response factor NF-κB, which regulates the immune response, are reciprocally regulated. During inflammation, NF-κB reduces PGC-1α expression and activity. Low PGC-1α activity leads to the downregulation of antioxidant target genes resulting in oxidative stress. Additionally, low PGC-1α levels and concomitant oxidative stress promote NF-κB activity, which exacerbates the inflammatory response.

Modified Linggui Zhugan Decoction protects against ventricular remodeling through ameliorating mitochondrial damage in post-myocardial infarction rats

Introduction

Modified Linggui Zhugan Decoction (MLZD) is a Traditional Chinese Medicine prescription developed from Linggui Zhugan Decoction (LZD) that has been used for the clinical treatment of ischemic cardiovascular diseases. However, the cardioprotective mechanism of MLZD against post-myocardial infarction (MI) ventricular remodeling remains unclear.

Methods

We explored the effects of MLZD on ventricular remodeling and their underlying mechanisms, respectively, in SD rats with MI models and in H9c2 cardiomyocytes with oxygen-glucose deprivation (OGD) models. The cardiac structure and function of rats were measured by echocardiography, HE staining, and Masson staining. Apoptosis, inflammation, mitochondrial structure and function, and sirtuin 3 (SIRT3) expression were additionally examined.

Results

MLZD treatment significantly ameliorated cardiac structure and function, and thus reversed ventricular remodeling, compared with the control. Further research showed that MLZD ameliorated mitochondrial structural disruption, protected against mitochondrial dynamics disorder, restored impaired mitochondrial function, inhibited inflammation, and thus inhibited apoptosis. Moreover, the decreased expression level of SIRT3 was enhanced after MLZD treatment. The protective effects of MLZD on SIRT3 and mitochondria, nevertheless, were blocked by 3-TYP, a selective inhibitor of SIRT3.

Discussion

These findings together revealed that MLZD could improve the ventricular remodeling of MI rats by ameliorating mitochondrial damage and its associated apoptosis, which might exert protective effects by targeting SIRT3.

Marine Natural Products from the Russian Pacific as Sources of Drugs for Neurodegenerative Diseases

Neurodegenerative diseases are growing to become one of humanity's biggest health problems, given the number of individuals affected by them. They cause enough mortalities and severe economic impact to rival cancers and infections. With the current diversity of pathophysiological mechanisms involved in neurodegenerative diseases, on the one hand, and scarcity of efficient prevention and treatment strategies, on the other, all possible sources for novel drug discovery must be employed. Marine pharmacology represents a relatively uncharted territory to seek promising compounds, despite the enormous chemodiversity it offers. The current work discusses one vast marine region-the Northwestern or Russian Pacific-as the treasure chest for marine-based drug discovery targeting neurodegenerative diseases. We overview the natural products of neurological properties already discovered from its waters and survey the existing molecular and cellular targets for pharmacological modulation of the disease. We further provide a general assessment of the drug discovery potential of the Russian Pacific in case of its systematic development to tackle neurodegenerative diseases.

PGC-1α-Mediated Mitochondrial Quality Control: Molecular Mechanisms and Implications for Heart Failure

Mitochondria with structural and functional integrity are essential for maintaining mitochondrial function and cardiac homeostasis. It is involved in the pathogenesis of many diseases. Peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), acted as a transcriptional cofactor, is abundant in the heart, which modulates mitochondrial biogenesis and mitochondrial dynamics and mitophagy to sustain a steady-state of mitochondria. Cumulative evidence suggests that dysregulation of PGC-1α is closely related to the onset and progression of heart failure. PGC-1α deficient-mice can lead to worse cardiac function under pressure overload compared to sham. Here, this review mainly focuses on what is known about its regulation in mitochondrial functions, as well as its crucial role in heart failure.

p38 MAPK priming boosts VSMC proliferation and arteriogenesis by promoting PGC1α-dependent mitochondrial dynamics

Vascular smooth muscle cell (VSMC) proliferation is essential for arteriogenesis to restore blood flow after artery occlusion, but the mechanisms underlying this response remain unclear. Based on our previous findings showing increased VSMC proliferation in the neonatal aorta of mice lacking the protease MT4-MMP, we aimed at discovering new players in this process. We demonstrate that MT4-MMP absence boosted VSMC proliferation in vitro in response to PDGF-BB in a cell-autonomous manner through enhanced p38 MAPK activity. Increased phospho-p38 in basal MT4-MMP-null VSMCs augmented the rate of mitochondrial degradation by promoting mitochondrial morphological changes through the co-activator PGC1α as demonstrated in PGC1α^−/− VSMCs. We tested the in vivo implications of this pathway in a novel conditional mouse line for selective MT4-MMP deletion in VSMCs and in mice pre-treated with the p38 MAPK activator anisomycin. Priming of p38 MAPK activity in vivo by the absence of the protease MT4-MMP or by anisomycin treatment led to enhanced arteriogenesis and improved flow recovery after femoral artery occlusion. These findings may open new therapeutic opportunities for peripheral vascular diseases.

Neurodegenerative disorders associated with genes of mitochondria

Background

Over the last decade, aggregating evidences suggested that there is a causative link between mutation in gene associated with mitochondrial dysfunction and development of several neurodegenerative disorders.

Main text

Recent structural and functional studies associated with mitochondrial genes have shown that mitochondrial abnormalities possibly lead to mitochondrial dysfunction. Several studies on animal models of neurodegenerative diseases and mitochondrial genes have provided compelling evidence that mitochondria is involved in the initiation as well as progression of diseases such as Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), and Friedreich ataxia (FA).

Conclusion

In this mini-review, we have discussed the different etiologic and pathogenesis connected with the mitochondrial dysfunction and relevant neurodegenerative diseases that underlie the dominant part of mitochondrial genes in the disease development and its progress.

Serine protease HtrA2/Omi regulates adaptive mitochondrial reprogramming in the brain cortex after ischemia/reperfusion injury via UCP2-SIRT3-PGC1 axis

This study is to investigate the underlying mechanisms of mitochondrial quality control (MQC) regulated by HtrA2/Omi during ischemia/reperfusion (I/R). We utilized the mnd2 mouse model, which has a missense mutation in HtrA2/Omi, to investigate the HtrA2/Omi regulation in mitochondria after I/R injury in the cerebral cortex. Compared to homozygous (HtrA2^mnd2) mice, heterozygous (HtrA2^Hetero) mice showed aging signs at a later age, increased HtrA2/Omi expression in the brain cortex, and lesser neurodegenerative signs. The brain cortex of HtrA2^Hetero mice had increased superoxide dismutase (SOD) activity; lower levels of malondialdehyde (MDA); higher expressions of mitochondrial unfolded protein response (mtUPR)-related proteins, NADH dehydrogenase [ubiquinone] iron-sulfur protein 7 (Ndufs7), and uncoupling protein 2 (UCP2) proteins; more mitochondrial fission; higher levels of ATP and mtDNA copies; elevated sirtuin 3 (SIRT3) activity; and increased NAD⁺/NADH ratio. After 1.5 h of I/R, the brain cortex of HtrA2^Hetero mice had a larger infarction size, reduced HtrA2/Omi expression, decreased S-X-linked inhibitor of apoptosis protein (XIAP), and increased C-Caspase3 than that of wild-type animals (WT). Mitochondria from the HtrA2^Hetero brain cortex showed decreased ATP production and MQC deficiency after 1.5 h I/R. Genipin pre-treatment reduced the aforementioned I/R injury in the HtrA2^Hetero brain cortex. In conclusion, mitochondrial function is compensated in the HtrA2^Hetero brain cortex via the upregulation of the UCP2-SIRT3-PGC1 axis. Decreased HtrA2/Omi function damages mitochondrial quality in the HtrA2^Hetero mouse brain cortex, leading to more brain I/R injury. Genipin pre-treatment ameliorates brain damages via the mitochondrial UCP2-SIRT3-PGC1 axis.

Positive regulation of TFEB and mitophagy by PGC-1α to alleviate LPS-induced acute lung injury in rats

AIM OF THE STUDY

Acute lung injury (ALI) exhibits the features of noncardiogenic pulmonary edema and acute inflammatory process, and it also displays significant morbidity and mortality rates. This work focused on identifying how overexpression of PPARγ coactivator 1α (PGC-1α) positively regulated TFEB and mitophagy for resisting the lipopolysaccharide (LPS)-mediated ALI.

MATERIALS AND METHODS

The levels of autophagic proteins and inflammatory factors in LPS-induced ALI rats and primary type II alveolar epithelial cells were measured, respectively. Lung wet/dry ratios were calculated. Protein co-immunoprecipitation of PGC-1α and TFEB was detected. To explore the interaction between TFEB and PGC-1α, a luciferase reporter assay was conducted.

RESULTS

The results showed that overexpression of PGC-1α decreases IL-1 and IL-6 but increases IL-10 in LPS-mediated ALI rats and type II alveolar epithelial cells (P < 0.05). Overexpression of PGC-1α can reduce lung edema in LPS-mediated ALI rats (P < 0.05). Overexpression of PGC-1α upregulates mitophagy-related proteins, such as TFEB, LC3B, Beclin, and LAMP1, and improves mitophagy in LPS-induced ALI. Protein immunoprecipitation indicated that TFEB and PGC-1α are interacting proteins. The luciferase reporter assay demonstrated that PGC-1α positively regulated TFEB in the LPS-induced primary type II alveolar epithelial cells.

CONCLUSION

PGC-1α protects LPS-induced ALI by decreasing inflammation and alleviating lung edema. The mechanism might be positive regulation of TFEB directly and then upregulation of mitophagy in LPS-induced ALI.

The medicinal chemistry of mitochondrial dysfunction: a critical overview of efforts to modulate mitochondrial health

Mitochondria are subcellular organelles that perform a variety of critical biological functions, including ATP production and acting as hubs of immune and apoptotic signalling. Mitochondrial dysfunction has been extensively linked to the pathology of multiple neurodegenerative disorders, resulting in significant investment from the drug discovery community. Despite extensive efforts, there remains no disease modifying therapies for neurodegenerative disorders. This manuscript aims to review the compounds historically used to modulate the mitochondrial network through the lens of modern medicinal chemistry, and to offer a perspective on the evidence that relevant exposure was achieved in a representative model and that exposure was likely to result in target binding and engagement of pharmacology. We hope this manuscript will aid the community in identifying those targets and mechanisms which have been convincingly (in)validated with high quality chemical matter, and those for which an opportunity exists to explore in greater depth.

High Dietary Fat Consumption Impairs Axonal Mitochondrial Function In Vivo

Peripheral neuropathy (PN) is the most common complication of prediabetes and diabetes. PN causes severe morbidity for Type 2 diabetes (T2D) and prediabetes patients, including limb pain followed by numbness resulting from peripheral nerve damage. PN in T2D and prediabetes is associated with dyslipidemia and elevated circulating lipids; however, the molecular mechanisms underlying PN development in prediabetes and T2D are unknown. Peripheral nerve sensory neurons rely on axonal mitochondria to provide energy for nerve impulse conduction under homeostatic conditions. Models of dyslipidemia in vitro demonstrate mitochondrial dysfunction in sensory neurons exposed to elevated levels of exogenous fatty acids. Herein, we evaluated the effect of dyslipidemia on mitochondrial function and dynamics in sensory axons of the saphenous nerve of a male high-fat diet (HFD)-fed murine model of prediabetes to identify mitochondrial alterations that correlate with PN pathogenesis in vivo We found that the HFD decreased mitochondrial membrane potential (MMP) in axonal mitochondria and reduced the ability of sensory neurons to conduct at physiological frequencies. Unlike mitochondria in control axons, which dissipated their MMP in response to increased impulse frequency (from 1 to 50 Hz), HFD mitochondria dissipated less MMP in response to axonal energy demand, suggesting a lack of reserve capacity. The HFD also decreased sensory axonal Ca2+ levels and increased mitochondrial lengthening and expression of PGC1α, a master regulator of mitochondrial biogenesis. Together, these results suggest that mitochondrial dysfunction underlies an imbalance of axonal energy and Ca2+ levels and impairs impulse conduction within the saphenous nerve in prediabetic PN.SIGNIFICANCE STATEMENT Diabetes and prediabetes are leading causes of peripheral neuropathy (PN) worldwide. PN has no cure, but development in diabetes and prediabetes is associated with dyslipidemia, including elevated levels of saturated fatty acids. Saturated fatty acids impair mitochondrial dynamics and function in cultured neurons, indicating a role for mitochondrial dysfunction in PN progression; however, the effect of elevated circulating fatty acids on the peripheral nervous system in vivo is unknown. In this study, we identify early pathogenic events in sensory nerve axons of mice with high-fat diet-induced PN, including alterations in mitochondrial function, axonal conduction, and intra-axonal calcium, that provide important insight into potential PN mechanisms associated with prediabetes and dyslipidemia in vivo.

Hypoxic preconditioning combined with curcumin promotes cell survival and mitochondrial quality of bone marrow mesenchymal stem cells, and accelerates cutaneous wound healing via PGC-1α/SIRT3/HIF-1α signaling

Restrained survival and function of relocated bone marrow mesenchymal stem cells (BMSCs) is a major impediment to BMSCs-mediated tissue repair. Accumulating evidences have indicated that hypoxic preconditioning of BMSCs could enhance BMSCs' adaptability after transplantation and thus improve their therapeutic properties. Curcumin, a natural dietary product, is known to exert profound protective effects on various cellular processes. Here we showed that mild hypoxic preconditioning combined with curcumin significantly increased cell survival, enriched more cells in G2/M and S phase, and improved mitochondrial function in BMSCs. Meanwhile, hypoxic preconditioning combined with curcumin altered mitochondrial cristae shape and strongly inhibited mitochondrial cytochrome c release, which consequently suppressed an apoptosis signal as revealed by reduced caspase-3 cleavage in BMSCs. Moreover, hypoxic preconditioning remarkably promoted mitochondrial quality via increasing mitochondrial fusion and elevating the activity of oxidative phosphorylation (OXPHOS) and mitochondrial complex Ⅰ enzyme in BMSCs, which were in accordance with the up-regulated expression of OPA1, PINK1 and Parkin. At the mechanistic level, the destabilization of HIF-1α and the up-regulated expression of PGC-1α and SIRT3 synergistically contributed to the protective effects of hypoxic preconditioning combined with curcumin in BMSCs. The proteasome inhibitor MG132 stabilized HIF-1a expression, but not PGC-1α or SIRT3, and dramatically restrained BMSCs survival under hypoxia combined with curcumin condition. MG132 also increased mitochondrial superoxide and intracellular hydrogen peroxide (H₂O₂) production and caspase-3 activation in hypoxia combined with curcumin-treated BMSCs. Furthermore, knockdown of SIRT3 and PGC-1α by RNAi both led to caspase-3 activation in BMSCs after hypoxia and curcumin treatment. Notably, SIRT3 RNAi suppressed OXPHOS activity, while PGC-1α RNAi triggered mitochondrial superoxide and intracellular H₂O₂ production in hypoxia combined with curcumin-treated BMSCs. Finally, we showed that hypoxia combined with curcumin-treated BMSCs accelerated the cutaneous wound healing process in a mice wound model. Overall, this study suggests that hypoxic preconditioning combined with curcumin could serve as an attractive strategy for facilitating BMSCs-mediated tissue repair, and further sheds new light on the rich repertoire of PGC-1α/SIRT3/HIF-1α signaling involved in the regulation of mitochondrial quality and function for cellular adaption to hypoxia.

β-Asarone improves learning and memory in Aβ1-42-induced Alzheimer's disease rats by regulating PINK1-Parkin-mediated mitophagy

Alzheimer's disease (AD) is a chronic neurodegenerative disease that is characterized by the extracellular accumulation of β-amyloid (Aβ). Many studies have shown a close relationship between autophagy and the formation of Aβ. As AD develops and progresses, mitophagy diminishes insoluble Aβ, and mitochondrial dysfunction seems to be a determining factor in the pathogenesis of AD. In our previous study, we showed that β-asarone pharmacological effects in APP/PS1 transgenic mice, reducing Aβ expression. However, the specific mechanism of this effect remains unclear. In this study, AD model rats induced by intracerebroventricular injection of Aβ_1-42 were randomly divided into nine groups, and medical intervention was applied to the animals for 30 days. Subsequently, spatial learning and memory were evaluated by the water maze test. Bcl-2 levels in the hippocampus were determined by western blotting (WB). The protein expression of Aβ_1-42, Beclin-1, p62, PINK1, and Parkin was assessed by WB and immunohistochemistry (IHC). The data showed that after β-asarone treatment, the learning and memory of the AD rats were clearly improved compared with those of the model group. Moreover, β-asarone decreased Aβ_1-42, Bcl-2, and p62 levels but increased Beclin-1 levels compared with those in the model group. In addition, we treated a group of rats with CsA to inhibit mitophagy. β-Asarone increased PINK1 and Parkin expression compared with that in the model group. The results showed that β-asarone can improve the learning and memory of rats with Aβ_1-42-induced AD by effectively promoting PINK1-Parkin-mediated mitophagy. Taken together, these results suggest that β-asarone may have the capacity to become a pharmaceutical agent for the treatment of AD in the future.

Peroxisome Proliferator-Activated Receptor γ Coactivator 1α Activates Vascular Endothelial Growth Factor That Protects Against Neuronal Cell Death Following Status Epilepticus through PI3K/AKT and MEK/ERK Signaling

Status epilepticus may cause molecular and cellular events, leading to hippocampal neuronal cell death. Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is an important regulator of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2), also known as fetal liver kinase receptor 1 (Flk-1). Resveratrol is an activator of PGC-1α. It has been suggested to provide neuroprotective effects in epilepsy, stroke, and neurodegenerative diseases. In the present study, we used microinjection of kainic acid into the left hippocampal CA3 region in Sprague Dawley rats to induce bilateral prolonged seizure activity. Upregulating the PGC-1α pathway will increase VEGF/VEGFR2 (Flk-1) signaling and further activate some survival signaling that includes the mitogen activated protein kinase kinase (MEK)/mitogen activated protein kinase (ERK) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways and offer neuroprotection as a consequence of apoptosis in the hippocampal neurons following status epilepticus. Otherwise, downregulation of PGC-1α by siRNA against pgc-1α will inhibit VEGF/VEGFR2 (Flk-1) signaling and suppress pro-survival PI3K/AKT and MEK/ERK pathways that are also accompanied by hippocampal CA3 neuronal cell apoptosis. These results may indicate that the PGC-1α induced VEGF/VEGFR2 pathway may trigger the neuronal survival signaling, and the PI3K/AKT and MEK/ERK signaling pathways. Thus, the axis of PGC-1α/VEGF/VEGFR2 (Flk-1) and the triggering of downstream PI3K/AKT and MEK/ERK signaling could be considered an endogenous neuroprotective effect against apoptosis in the hippocampus following status epilepticus.

Abnormal Mitochondrial Quality Control in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer’s, Parkinson’s, Huntington’s, and amyotrophic lateral sclerosis, are characterized by a progressive loss of selective neuron subtypes in the central nervous system (CNS). Although various factors account for the initiation and development of these diseases, accumulating evidence shows that impaired mitochondrial function is a prominent and common mechanism. Mitochondria play a critical role in neurons and are involved in energy production, cellular metabolism regulation, intracellular calcium homeostasis, immune responses, and cell fate. Thus, cells in the CNS heavily rely on mitochondrial integrity. Many aspects of mitochondrial dysfunction are manifested in neurodegenerative diseases, including aberrant mitochondrial quality control (mitoQC), mitochondrial-driven inflammation, and bioenergetic defects. Herein, we briefly summarize the molecular basis of mitoQC, including mitochondrial proteostasis, biogenesis, dynamics, and organelle degradation. We also focus on the research, to date, regarding aberrant mitoQC and mitochondrial-driven inflammation in several common neurodegenerative diseases. In addition, we outline novel therapeutic strategies that target aberrant mitoQC in neurodegenerative diseases.

Abnormal Mitochondrial Quality Control in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer's, Parkinson's, Huntington's, and amyotrophic lateral sclerosis, are characterized by a progressive loss of selective neuron subtypes in the central nervous system (CNS). Although various factors account for the initiation and development of these diseases, accumulating evidence shows that impaired mitochondrial function is a prominent and common mechanism. Mitochondria play a critical role in neurons and are involved in energy production, cellular metabolism regulation, intracellular calcium homeostasis, immune responses, and cell fate. Thus, cells in the CNS heavily rely on mitochondrial integrity. Many aspects of mitochondrial dysfunction are manifested in neurodegenerative diseases, including aberrant mitochondrial quality control (mitoQC), mitochondrial-driven inflammation, and bioenergetic defects. Herein, we briefly summarize the molecular basis of mitoQC, including mitochondrial proteostasis, biogenesis, dynamics, and organelle degradation. We also focus on the research, to date, regarding aberrant mitoQC and mitochondrial-driven inflammation in several common neurodegenerative diseases. In addition, we outline novel therapeutic strategies that target aberrant mitoQC in neurodegenerative diseases.

Emerging role of transcription factor EB in mitochondrial quality control

Mitochondria are energy producers that play a vital role in cell survival. Mitochondrial dysfunction is involved in many diseases, including metabolic syndrome, neurodegenerative disorders, cardiomyopathies, cancer, obesity, and diabetic kidney disease, and challenges still remain in terms of treatments for these diseases. Mitochondrial quality control (MQC), which is defined as the maintenance of the quantity, morphology, and function of mitochondria, plays a pivotal role in maintaining cellular metabolic homeostasis and cell survival. Recently, growing evidence suggests that the transcription factor EB (TFEB) plays a pivotal role in MQC. Here, we systemically investigate the potential role and mechanisms of TFEB in MQC, which include the activation of mitophagy, regulation of mitochondrial biogenesis, reactive oxygen species (ROS) clearance, and the balance of mitochondria fission-fusion cycle. Importantly, we further discuss the therapeutic measures and effects aimed at TFEB on mitochondrial dysfunction-related diseases. Taken together, targeting TFEB to regulate MQC may represent an appealing therapeutic strategy for mitochondrial dysfunction related-diseases.

Mitochondrial Protection by PARP Inhibition

Inhibitors of the nuclear DNA damage sensor and signalling enzyme poly(ADP-ribose) polymerase (PARP) have recently been introduced in the therapy of cancers deficient in double-strand DNA break repair systems, and ongoing clinical trials aim to extend their use from other forms of cancer non-responsive to conventional treatments. Additionally, PARP inhibitors were suggested to be repurposed for oxidative stress-associated non-oncological diseases resulting in a devastating outcome, or requiring acute treatment. Their well-documented mitochondria- and cytoprotective effects form the basis of PARP inhibitors’ therapeutic use for non-oncological diseases, yet can limit their efficacy in the treatment of cancers. A better understanding of the processes involved in their protective effects may improve the PARP inhibitors’ therapeutic potential in the non-oncological indications. To this end, we endeavoured to summarise the basic features regarding mitochondrial structure and function, review the major PARP activation-induced cellular processes leading to mitochondrial damage, and discuss the role of PARP inhibition-mediated mitochondrial protection in several oxidative stress-associated diseases.

Regulation of Mitochondrial ATP Production: Ca2+ Signaling and Quality Control

Cardiac ATP production primarily depends on oxidative phosphorylation in mitochondria and is dynamically regulated by Ca²⁺ levels in the mitochondrial matrix as well as by cytosolic ADP. We discuss mitochondrial Ca²⁺ signaling and its dysfunction which has recently been linked to cardiac pathologies including arrhythmia and heart failure. Similar dysfunction in other excitable and long-lived cells including neurons is associated with neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Central to this new understanding is crucial Ca²⁺ regulation of both mitochondrial quality control and ATP production. Mitochondria-associated membrane (MAM) signaling from the sarcoplasmic reticulum (SR) and the endoplasmic reticulum (ER) to mitochondria is discussed. We propose future research directions that emphasize a need to define quantitatively the physiological roles of MAMs, as well as mitochondrial quality control and ATP production.