Mitochondrial dynamics and mitophagy in Parkinson's disease: A fly point of view

Elimination of damaged mitochondria during UVB-induced senescence is orchestrated by NIX-dependent mitophagy

Skin aging is the result of two types of aging, "intrinsic aging" an inevitable consequence of physiologic and genetically determined changes and "extrinsic aging," which is dependent on external factors such as exposure to sunlight, smoking, and dietary habits. UVB causes skin injury through the generation of free radicals and other oxidative byproducts, also contributing to DNA damage. Appearance and accumulation of senescent cells in the skin are considered one of the hallmarks of aging in this tissue. Mitochondria play an important role for the development of cellular senescence, in particular stress-induced senescence of human cells. However, many aspects of mitochondrial physiology relevant to cellular senescence and extrinsic skin aging remain to be unraveled. Here, we demonstrate that mitochondria damaged by UVB irradiation of human dermal fibroblasts (HDF) are eliminated by NIX-dependent mitophagy and that this process is important for cell survival under these conditions. Additionally, UVB-irradiation of human dermal fibroblasts (HDF) induces the shedding of extracellular vesicles (EVs), and this process is significantly enhanced in UVB-irradiated NIX-depleted cells. Our findings establish NIX as the main mitophagy receptor in the process of UVB-induced senescence and suggest the release of EVs as an alternative mechanism of mitochondrial quality control in HDF.

Alginate oligosaccharide-mediated butyrate-HIF-1α axis improves skin aging in mice

The "gut-skin" axis has been proved and is considered as a novel therapy for the prevention of skin aging. The antioxidant efficacy of oligomannonic acid (MAOS) make it an intriguing target for use to improve skin aging. The present study further explored whereby MAOS-mediated gut-skin axis balance prevented skin aging in mice. The data indicated the skin aging phenotypes, oxidative stress, skin mitochondrial dysfunction, and intestinal dysbiosis (especially the butyrate and HIF-1α levels decreased) in aging mice. Similarly, fecal microbiota transplantation (FMT) from aging mice rebuild the aging-like phenotypes. Further, we demonstrated MAOS-mediated colonic butyrate-HIF-1α axis homeostasis promoted the entry of butyrate into the skin, upregulated mitophagy level and ultimately improving skin aging via HDAC3/PHD/HIF-1α/mitophagy loop in skin of mice. Overall, our study offered a better insights of the effectiveness of alginate oligosaccharides (AOS), promised to become a personalized targeted therapeutic agents, on gut-skin axis disorder inducing skin aging.

Nickel induces mitochondrial damage in renal cells in vitro and in vivo through its effects on mitochondrial biogenesis, fusion, and fission

Nickel (Ni) and its compounds are common, widely distributed components of hazardous waste in the chemical industry. Excessive exposure to Ni can cause kidney damage in humans and animals. We investigated the impact of Ni on renal mitochondria using in vivo and in vitro models of Ni nephrotoxicity, and explored the Ni nephrotoxic mechanism. We showed that nickel chloride (NiCl2) damaged the renal mitochondria, causing mitochondrial swelling, breakage of the mitochondrial cristae, increased levels of mitochondrial reactive oxygen species (mt-ROS), and depolarization of the mitochondrial membrane potential (MMP). The levels of the mitochondrial respiratory chain complexes I-IV were reduced in the kidneys of mice treated with NiCl2. In addition, NiCl2 treatment inhibited mitochondrial biogenesis in renal cells by down-regulating mRNA and the protein expression of TFAM, PGC-1α, and NRF1. Moreover, NiCl2 reduced the levels of the proteins involved in mitochondrial fusion, including Mfn1 and Mfn2, while significantly augmenting the levels of the proteins Fis1 and Drip1 involved in mitochondrial fission in renal cells. Taken together, these results suggested that NiCl2 inhibited mitochondrial biogenesis, suppressed mitochondrial fusion, and promoted mitochondrial fission, resulting in mitochondrial dysfunction in renal cells, ultimately causing renal injury. This study provided novel insights into the mechanisms of nephrotoxicity of Ni and new ideas for the development of targeted treatments for Ni-induced kidney injury.

DDIT3/CHOP promotes LPS/ATP-induced pyroptosis in osteoblasts via mitophagy inhibition

Inflammatory environments can trigger endoplasmic reticulum (ER) stress and lead to pyroptosis in various tissues and cells, including liver, brain, and immune cells. As a key factor of ER stress, DNA damage-inducible transcript 3 (DDIT3)/CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is upregulated in osteoblasts during inflammatory stimulation. DDIT3/CHOP may therefore regulate osteoblast pyroptosis in inflammatory conditions. During this investigation, we found that lipopolysaccharides (LPS)/adenosine 5'-triphosphate (ATP) stimulation in vitro induced osteoblasts to undergo pyroptosis, and the expression of DDIT3/CHOP was increased during this process. The overexpression of DDIT3/CHOP further promoted osteoblast pyroptosis as evidenced by the increased expression of the inflammasome NLR family pyrin domain containing 3 (NLRP3) and ratios of caspase-1 p20/caspase-1 and cleaved gasdermin D (GSDMD)/GSDMD. To explore the specific mechanism of this effect, we found through fluorescence imaging and Western blot analysis that LPS/ATP stimulation promoted PTEN-induced kinase 1 (PINK1)/E3 ubiquitin-protein ligase parkin (Parkin)-mediated mitophagy in osteoblasts, and this alteration was suppressed by the DDIT3/CHOP overexpression, resulting in increased ratio of pyroptosis compared with the control groups. The impact of DDIT3/CHOP on pyroptosis in osteoblasts was reversed by the application of carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a specific mitophagy agonist. Therefore, our data demonstrated that DDIT3/CHOP promotes osteoblast pyroptosis by inhibiting PINK1/Parkin-mediated mitophagy in an inflammatory environment.

Ribosome Profiling and Mass Spectrometry Reveal Widespread Mitochondrial Translation Defects in a Striatal Cell Model of Huntington Disease

Huntington disease (HD) is caused by an expanded polyglutamine mutation in huntingtin (mHTT) that promotes prominent atrophy in the striatum and subsequent psychiatric, cognitive deficits, and choreiform movements. Multiple lines of evidence point to an association between HD and aberrant striatal mitochondrial functions; however, the present knowledge about whether (or how) mitochondrial mRNA translation is differentially regulated in HD remains unclear. We found that protein synthesis is diminished in HD mitochondria compared to healthy control striatal cell models. We utilized ribosome profiling (Ribo-Seq) to analyze detailed snapshots of ribosome occupancy of the mitochondrial mRNA transcripts in control and HD striatal cell models. The Ribo-Seq data revealed almost unaltered ribosome occupancy on the nuclear-encoded mitochondrial transcripts involved in oxidative phosphorylation (SDHA, Ndufv1, Timm23, Tomm5, Mrps22) in HD cells. By contrast, ribosome occupancy was dramatically increased for mitochondrially encoded oxidative phosphorylation mRNAs (mt-Nd1, mt-Nd2, mt-Nd4, mt-Nd4l, mt-Nd5, mt-Nd6, mt-Co1, mt-Cytb, and mt-ATP8). We also applied tandem mass tag-based mass spectrometry identification of mitochondrial proteins to derive correlations between ribosome occupancy and actual mature mitochondrial protein products. We found many mitochondrial transcripts with comparable or higher ribosome occupancy, but diminished mitochondrial protein products, in HD. Thus, our study provides the first evidence of a widespread dichotomous effect on ribosome occupancy and protein abundance of mitochondria-related genes in HD.

The mechanism of nickel-induced autophagy and its role in nephrotoxicity

Nickel (Ni), an environmental health hazard, is nephrotoxic to humans, but the exact mechanism is unknown. This study aims to identify whether nephrotoxicity is associated with autophagy. Here, nickel chloride (NiCl2) increased autophagy in TCMK-1 cells. NiCl2 induces autophagy through Akt and AMPK/mTOR pathways. Next, oxidative stress was investigated in NiCl2-induced autophagy. The findings demonstrated that the antioxidant (NAC) or mitochondrial targeted antioxidant (Mito-TEMPO) attenuated NiCl2-induced autophagy, reversed the influence on AMPK-mTOR and Akt pathways. Additionally, our study examined the role of autophagy in NiCl2-induced nephrotoxicity. Autophagy inhibition with 3-MA could inhibit cell viability and increase apoptosis in the TCMK-1 cells, however, autophagy promotion with rapamycin relieved cytotoxicity and decreased apoptosis. Additionally, co-treatment with Z-VAD-FMK reduced cytotoxicity, but did not affect autophagy. Besides, NiCl2 can increase the level of mitophagy in vivo and vitro. Mitophagy inhibition could inhibit cell viability and increase apoptosis in the TCMK-1 cells, whereas, promotion of mitophagy could increase cell viability and decrease apoptosis. In summary, above-mentioned results showed that NiCl2 induces autophagy in TCMK-1 cells through oxidative stress-dependent AMPK/AKT-mTOR pathway, autophagy plays a role in reducing NiCl2-induced renal toxicity, and a major mechanism in autophagy's inhibitory effect on NiCl2-induced apoptosis may be mitophagy.

Intermittent fasting promotes adipocyte mitochondrial fusion through Sirt3-mediated deacetylation of Mdh2

Fat deposition and lipid metabolism are closely related to the morphology, structure and function of mitochondria. The morphology of mitochondria between fusion and fission processes is mainly regulated by protein posttranslational modification. Intermittent fasting (IF) promotes high expression of Sirtuin 3 (Sirt3) and induces mitochondrial fusion in high-fat diet (HFD)-fed mice. However, the mechanism by which Sirt3 participates in mitochondrial protein acetylation during IF to regulate mitochondrial fusion and fission dynamics remains unclear. This article demonstrates that IF promotes mitochondrial fusion and improves mitochondrial function in HFD mouse inguinal white adipose tissue. Proteomic sequencing revealed that IF increased protein deacetylation levels in HFD mice and significantly increased Sirt3 mRNA and protein expression. After transfecting with Sirt3 overexpression or interference vectors into adipocytes, we found that Sirt3 promoted adipocyte mitochondrial fusion and improved mitochondrial function. Furthermore, Sirt3 regulates the JNK-FIS1 pathway by deacetylating malate dehydrogenase 2 (MDH2) to promote mitochondrial fusion. In summary, our study indicates that IF promotes mitochondrial fusion and improves mitochondrial function by upregulating the high expression of Sirt3 in HFD mice, promoting deacetylation of MDH2 and inhibiting the JNK-FIS1 pathway. This research provides theoretical support for studies related to energy limitation and animal lipid metabolism.

Mitochondrial dysfunction and mitophagy: crucial players in burn trauma and wound healing

Burn injuries are a significant cause of death worldwide, leading to systemic inflammation, multiple organ failure and sepsis. The progression of burn injury is explicitly correlated with mitochondrial homeostasis, which is disrupted by the hyperinflammation induced by burn injury, leading to mitochondrial dysfunction and cell death. Mitophagy plays a crucial role in maintaining cellular homeostasis by selectively removing damaged mitochondria. A growing body of evidence from various disease models suggest that pharmacological interventions targeting mitophagy could be a promising therapeutic strategy. Recent studies have shown that mitophagy plays a crucial role in wound healing and burn injury. Furthermore, chemicals targeting mitophagy have also been shown to improve wound recovery, highlighting the potential for novel therapeutic strategies based on an in-depth exploration of the molecular mechanisms regulating mitophagy and its association with skin wound healing.

Low Levels of Adenosine and GDNF Are Potential Risk Factors for Parkinson's Disease with Sleep Disorders

Sleep disturbances are the most prevalent non-motor symptoms in the preclinical stage of Parkinson's disease (PD). Adenosine, glial-derived neurotrophic factor (GDNF), and associated neurotransmitters are crucial in the control of sleep arousal. This study aimed to detect the serum levels of adenosine, GDNF, and associated neurotransmitters and explored their correlations with PD with sleep disorders. Demographic characteristics and clinical information of PD patients and healthy participants were assessed. Serum concentrations of adenosine, GDNF, and related neurotransmitters were detected by ELISA and LC-MS. The correlation between serum levels of adenosine, GDNF, and associated neurotransmitters and sleep disorders was explored using logistic regression. PD patients with sleep disorders had higher scores of HAMA, HAMD, ESS, UPDRS-III, and H-Y stage. Lower levels of adenosine, GDNF, and γ-GABA were observed in PD patients who had sleep problems. Logistic regression analysis showed adenosine and GDNF were protective factors for preventing sleep disorders. Adenosine combined with GDNF had a higher diagnostic efficiency in predicting PD with sleep disorders by ROC analysis. This study revealed low adenosine and GDNF levels may be risk factors for sleep disorders in PD. The decrease of serum adenosine and GDNF levels may contribute to the diagnosis of PD with sleep disturbances.

Maintenance of mitochondrial integrity in midbrain dopaminergic neurons governed by a conserved developmental transcription factor

Progressive degeneration of dopaminergic (DA) neurons in the substantia nigra is a hallmark of Parkinson’s disease (PD). Dysregulation of developmental transcription factors is implicated in dopaminergic neurodegeneration, but the underlying molecular mechanisms remain largely unknown. Drosophila Fer2 is a prime example of a developmental transcription factor required for the birth and maintenance of midbrain DA neurons. Using an approach combining ChIP-seq, RNA-seq, and genetic epistasis experiments with PD-linked genes, here we demonstrate that Fer2 controls a transcriptional network to maintain mitochondrial structure and function, and thus confers dopaminergic neuroprotection against genetic and oxidative insults. We further show that conditional ablation of Nato3, a mouse homolog of Fer2, in differentiated DA neurons causes mitochondrial abnormalities and locomotor impairments in aged mice. Our results reveal the essential and conserved role of Fer2 homologs in the mitochondrial maintenance of midbrain DA neurons, opening new perspectives for modeling and treating PD.

Mitochondrial dysfunction in dopaminergic neurons is a pathological hallmark of Parkinson’s disease. Here, the authors find a conserved mechanism by which a single transcription factor controls mitochondrial health in dopaminergic neurons during the aging process.

Oxidative Stress Is a Key Modulator in the Development of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and scientific studies consistently report that NAFLD development can be accelerated by oxidative stress. Oxidative stress can induce the progression of NAFLD to NASH by stimulating Kupffer cells, hepatic stellate cells, and hepatocytes. Therefore, studies are underway to identify the role of antioxidants in the treatment of NAFLD. In this review, we have summarized the origins of reactive oxygen species (ROS) in cells, the relationship between ROS and NAFLD, and have discussed the use of antioxidants as therapeutic agents for NAFLD.

Microtubule-Based Mitochondrial Dynamics as a Valuable Therapeutic Target in Cancer

Mitochondria constitute an ever-reorganizing dynamic network that plays a key role in several fundamental cellular functions, including the regulation of metabolism, energy production, calcium homeostasis, production of reactive oxygen species, and programmed cell death. Each of these activities can be found to be impaired in cancer cells. It has been reported that mitochondrial dynamics are actively involved in both tumorigenesis and metabolic plasticity, allowing cancer cells to adapt to unfavorable environmental conditions and, thus, contributing to tumor progression. The mitochondrial dynamics include fusion, fragmentation, intracellular trafficking responsible for redistributing the organelle within the cell, biogenesis, and mitophagy. Although the mitochondrial dynamics are driven by the cytoskeleton-particularly by the microtubules and the microtubule-associated motor proteins dynein and kinesin-the molecular mechanisms regulating these complex processes are not yet fully understood. More recently, an exchange of mitochondria between stromal and cancer cells has also been described. The advantage of mitochondrial transfer in tumor cells results in benefits to cell survival, proliferation, and spreading. Therefore, understanding the molecular mechanisms that regulate mitochondrial trafficking can potentially be important for identifying new molecular targets in cancer therapy to interfere specifically with tumor dissemination processes.

Astrocyte dysfunction in Parkinson's disease: from the perspectives of transmitted α-synuclein and genetic modulation

Parkinson's disease (PD) is a common neurodegenerative disorder that primarily affects the elderly. While the etiology of PD is likely multifactorial with the involvement of genetic, environmental, aging and other factors, α-synuclein (α-syn) pathology is a pivotal mechanism underlying the development of PD. In recent years, astrocytes have attracted considerable attention in the field. Although astrocytes perform a variety of physiological functions in the brain, they are pivotal mediators of α-syn toxicity since they internalize α-syn released from damaged neurons, and this triggers an inflammatory response, protein degradation dysfunction, mitochondrial dysfunction and endoplasmic reticulum stress. Astrocytes are indispensable coordinators in the background of several genetic mutations, including PARK7, GBA1, LRRK2, ATP13A2, PINK1, PRKN and PLA2G6. As the most abundant glial cells in the brain, functional astrocytes can be replenished and even converted to functional neurons. In this review, we discuss astrocyte dysfunction in PD with an emphasis on α-syn toxicity and genetic modulation and conclude that astrocyte replenishment is a valuable therapeutic approach in PD.

How Inflammation Pathways Contribute to Cell Death in Neuro-Muscular Disorders

Neuro-muscular disorders include a variety of diseases induced by genetic mutations resulting in muscle weakness and waste, swallowing and breathing difficulties. However, muscle alterations and nerve depletions involve specific molecular and cellular mechanisms which lead to the loss of motor-nerve or skeletal-muscle function, often due to an excessive cell death. Morphological and molecular studies demonstrated that a high number of these disorders seem characterized by an upregulated apoptosis which significantly contributes to the pathology. Cell death involvement is the consequence of some cellular processes that occur during diseases, including mitochondrial dysfunction, protein aggregation, free radical generation, excitotoxicity and inflammation. The latter represents an important mediator of disease progression, which, in the central nervous system, is known as neuroinflammation, characterized by reactive microglia and astroglia, as well the infiltration of peripheral monocytes and lymphocytes. Some of the mechanisms underlying inflammation have been linked to reactive oxygen species accumulation, which trigger mitochondrial genomic and respiratory chain instability, autophagy impairment and finally neuron or muscle cell death. This review discusses the main inflammatory pathways contributing to cell death in neuro-muscular disorders by highlighting the main mechanisms, the knowledge of which appears essential in developing therapeutic strategies to prevent the consequent neuron loss and muscle wasting.

A link between protein acetylation and mitochondrial dynamics under energy metabolism: A comprehensive overview

Cells adjust mitochondrial morphologies to coordinate between the cellular demand for energy and the availability of resources. Mitochondrial morphology is regulated by the balance between two counteracting mitochondrial processes of fusion and fission. Fission and fusion are dynamic and reversible processes that depend on the coordination of a number of proteins and are primarily regulated by posttranslational modifications. In the mitochondria, more than 20% of proteins are acetylated in proteomic surveys, partly involved in the dynamic regulation of mitochondrial fusion and fission. This article focuses on the molecular mechanism of the mitochondrial dynamics of fusion and fission, and summarizes the related mechanisms and targets of mitochondrial protein acetylation to regulate the mitochondrial dynamics of fusion and fission in energy metabolism.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Targeting cellular senescence based on interorganelle communication, multilevel proteostasis, and metabolic control

Cellular senescence, a stable cell division arrest caused by severe damage and stress, is a hallmark of aging in vertebrates including humans. With progressing age, senescent cells accumulate in a variety of mammalian tissues, where they contribute to tissue aging, identifying cellular senescence as a major target to delay or prevent aging. There is an increasing demand for the discovery of new classes of small molecules that would either avoid or postpone cellular senescence by selectively eliminating senescent cells from the body (i.e., ‘senolytics’) or inactivating/switching damage‐inducing properties of senescent cells (i.e., ‘senostatics/senomorphics’), such as the senescence‐associated secretory phenotype. Whereas compounds with senolytic or senostatic activity have already been described, their efficacy and specificity has not been fully established for clinical use yet. Here, we review mechanisms of senescence that are related to mitochondria and their interorganelle communication, and the involvement of proteostasis networks and metabolic control in the senescent phenotype. These cellular functions are associated with cellular senescence in in vitro and in vivo models but have not been fully exploited for the search of new compounds to counteract senescence yet. Therefore, we explore possibilities to target these mechanisms as new opportunities to selectively eliminate and/or disable senescent cells with the aim of tissue rejuvenation. We assume that this research will provide new compounds from the chemical space which act as mimetics of caloric restriction, modulators of calcium signaling and mitochondrial physiology, or as proteostasis optimizers, bearing the potential to counteract cellular senescence, thereby allowing healthy aging.

miR-103a-3p regulates mitophagy in Parkinson's disease through Parkin/Ambra1 signaling

Parkin is a crucial protein that promotes the clearance of damaged mitochondria via mitophagy in neuron, and parkin mutations result in autosomal-recessive Parkinson's disease (AR-PD). However, the exact mechanisms underlying the regulation of Parkin-mediated mitophagy in PD remain unclear. In this study, PD models were generated through incubation of SH-SY5Y cells with 1-methyl-4-phenylpyridinium ion (MPP⁺, 1.5 mM for 24 h) and intraperitoneal injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg for five consecutive days) in mice. A Bioinformatics database was used to identify Parkin-targeting microRNAs (miRNAs). Then, miR-103a-3p agomir, miR-103a-3p antagomir and Parkin siRNA were used to assess the effects of miR-103a-3p/Parkin/Ambra1 signaling-mediated mitophagy in PD in vitro and in vivo. The protein and mRNA levels of Parkin and Ambra1 were significantly decreased, while miR-103a-3p, which is a highly expressed miRNA in the human brain, was obviously increased in PD mouse and SH-SY5Y cell models. Moreover, miR-103a-3p suppressed Parkin expression by targeting a conserved binding site in the 3'-untranslated region (UTR) of Parkin mRNA. Importantly, miR-103a-3p inhibition resulted in neuroprotective effects and improved mitophagy in vitro and in vivo, whereas Parkin siRNA strongly abolished these effects. These findings suggested that miR-103a-3p inhibition has neuroprotective effects in PD, which may be involved in regulating mitophagy through the Parkin/Ambra1 pathway. Modulating miR-103a-3p levels may be an applicable therapeutic strategy for PD.

Deletion of Mitochondrial Uncoupling Protein 2 Exacerbates Mitochondrial Damage in Mice Subjected to Cerebral Ischemia and Reperfusion Injury under both Normo- and Hyperglycemic Conditions

Deletion of mitochondrial uncoupling protein 2 (UCP2) has been shown to aggravate ischemic damage in the brain. However, the underlying mechanisms are not fully understood. The objective of this study is to explore the impact of homozygous UCP2 deletion (UCP2^-/-) on mitochondrial fission and fusion dynamic balance in ischemic mice under normo- and hyperglycemic conditions. UCP2^-/- and wildtype mice were subjected to a 60 min middle cerebral artery occlusion (MCAO) and allowed reperfusion for 6h, 24h and 72h. Our results demonstrated that deletion of UCP2 enlarged infarct volumes and increased numbers of cell death in both normo- and hyperglycemic ischemic mice compared with their wildtype counterparts subjected to the same duration of ischemia and reperfusion. The detrimental effects of UCP deletion were associated with increased ROS production, elevated mitochondrial fission markers Drp1 and Fis1 and suppressed fusion markers Opa1 and Mfn2 in UCP2^-/- mice. Electron microscopic study demonstrated a marked mitochondrial swolling after 6h of reperfusion in UCP2^-/- mice, contrasting to a mild mitochondrial swolling in wildtype ischemic animals. It is concluded that the exacerbating effects of UCP2^-/- on ischemic outcome in both normo- and hyperglycemic animals are associated with increased ROS production, disturbed mitochondrial dynamic balance towards fission and early damage to mitochondrial ultrastructure.

Induction of Autophagy by Vasicinone Protects Neural Cells from Mitochondrial Dysfunction and Attenuates Paraquat-Mediated Parkinson's Disease Associated α-Synuclein Levels

Mitochondrial dysfunction and disturbed mitochondrial dynamics were found to be common phenomena in the pathogenesis of Parkinson's disease (PD). Vasicinone is a quinazoline alkaloid from Adhatoda vasica. Here, we investigated the autophagy/mitophagy-enhancing effect of vasicinone and explored its neuroprotective mechanism in paraquat-mimic PD modal in SH-SY5Y cells. Vasicinone rescued the paraquat-induced loss of cell viability and mitochondrial membrane potential. Subsequently, the accumulation of mitochondrial reactive oxygen species (ROS) was balanced by an increase in the expression of antioxidant enzymes. Furthermore, vasicinone restored paraquat-impaired autophagy and mitophagy regulators DJ-1, PINK-1 and Parkin in SH-SY5Y cells. The vasicinone mediated autophagy pathways were abrogated by treatment with the autophagy inhibitor 3-MA, which lead to increases α-synuclein accumulation and decreased the expression of p-ULK and ATG proteins and the autophagy marker LC3-II compared to that observed without 3-MA treatment. These results demonstrated that vasicinone exerted neuroprotective effects by upregulating autophagy and PINK-1/Parkin mediated mitophagy in SH-SY5Y cells.

Interactions of 17β-Hydroxysteroid Dehydrogenase Type 10 and Cyclophilin D in Alzheimer's Disease

The nucleus-encoded 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) regulates cyclophilin D (cypD) in the mitochondrial matrix. CypD regulates opening of mitochondrial permeability transition pores. Both mechanisms may be affected by amyloid β peptides accumulated in mitochondria in Alzheimer's disease (AD). In order to clarify changes occurring in brain mitochondria, we evaluated interactions of both mitochondrial proteins in vitro (by surface plasmon resonance biosensor) and detected levels of various complexes of 17β-HSD10 formed in vivo (by sandwich ELISA) in brain mitochondria isolated from the transgenic animal model of AD (homozygous McGill-R-Thy1-APP rats) and in cerebrospinal fluid samples of AD patients. By surface plasmon resonance biosensor, we observed the interaction of 17β-HSD10 and cypD in a direct real-time manner and determined, for the first time, the kinetic parameters of the interaction (ka 2.0 × 105 M1s-1, kd 5.8 × 104 s-1, and KD 3.5 × 10-10 M). In McGill-R-Thy1-APP rats compared to controls, levels of 17β-HSD10-cypD complexes were decreased and those of total amyloid β increased. Moreover, the levels of 17β-HSD10-cypD complexes were decreased in cerebrospinal fluid of individuals with AD (in mild cognitive impairment as well as dementia stages) or with Frontotemporal lobar degeneration (FTLD) compared to cognitively normal controls (the sensitivity of the complexes to AD dementia was 92.9%, that to FTLD 73.8%, the specificity to AD dementia equaled 91.7% in a comparison with the controls but only 26.2% with FTLD). Our results demonstrate the weakened ability of 17β-HSD10 to regulate cypD in the mitochondrial matrix probably via direct effects of amyloid β. Levels of 17β-HSD10-cypD complexes in cerebrospinal fluid seem to be the very sensitive indicator of mitochondrial dysfunction observed in neurodegeneration but unfortunately not specific to AD pathology. We do not recommend it as the new biomarker of AD.

Hypoxia-induced elevated NDRG1 mediates apoptosis through reprograming mitochondrial fission in HCC

Hypoxia, as a form of stress, plays a critical role in oncogenesis, including metabolic reprogramming. Mitochondrial, the centers of energy production, re-balance mitochondria dynamic to maintain cell survival during high levels of environmental stresses. NDRG1 is a hypoxia-inducible protein that is involved in various human cancers, including HCC. However, little is known about whether NDRG1 participants in the quality control of mitochondrial in times of stress. Here, we firstly showed that how NDRG1 exerted its role through mediating mitochondrial dynamic in HCC cells under hypoxia. Initially, we identified that NDRG1 expression varies with oxygen content. NDRG1 silencing notably induced cell apoptosis under hypoxia, while no obviously change of wildtype cells in hypoxia compared with that in normoxia. Further analysis revealed that NDRG1 silencing in HCC cells led to increase of pro apoptotic protein BAX and decrease in anti-apoptotic proteins Bcl-2 and Bclx, which meant mitochondrial damage were induced. In the analysis of mitochondria, we found that more released cytochrome c located in cytosolic with NDRG1 knockdown in hypoxia, which may be due to mitochondria division. And the following experiment proved that more fragmented mitochondria were presented in NDRG1 silencing cells, as well as destroyed mitochondrial membrane potential with evidence by JC-1 was verified. Moreover, these trends could be reversed by Mdivi1. Further research showed that NDRG1 silencing disrupt hypoxia-enhanced aerobic glycolysis through effectively decreased glucose uptake, lactate output and ECAR value. In sum, we provide the first direct evidence that NDRG1-driven change in mitochondrial dynamics and aerobic glycolysis maintain cells survival in HCC during hypoxia.

Organelle-specific autophagy in inflammatory diseases: a potential therapeutic target underlying the quality control of multiple organelles

The structural integrity and functional stability of organelles are prerequisites for the viability and responsiveness of cells. Dysfunction of multiple organelles is critically involved in the pathogenesis and progression of various diseases, such as chronic obstructive pulmonary disease, cardiovascular diseases, infection, and neurodegenerative diseases. In fact, those organelles synchronously present with evident structural derangement and aberrant function under exposure to different stimuli, which might accelerate the corruption of cells. Therefore, the quality control of multiple organelles is of great importance in maintaining the survival and function of cells and could be a potential therapeutic target for human diseases. Organelle-specific autophagy is one of the major subtypes of autophagy, selectively targeting different organelles for quality control. This type of autophagy includes mitophagy, pexophagy, reticulophagy (endoplasmic reticulum), ribophagy, lysophagy, and nucleophagy. These kinds of organelle-specific autophagy are reported to be beneficial for inflammatory disorders by eliminating damaged organelles and maintaining homeostasis. In this review, we summarized the recent findings and mechanisms covering different kinds of organelle-specific autophagy, as well as their involvement in various diseases, aiming to arouse concern about the significance of the quality control of multiple organelles in the treatment of inflammatory diseases.Abbreviations: ABCD3: ATP binding cassette subfamily D member 3; AD: Alzheimer disease; ALS: amyotrophic lateral sclerosis; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; ARIH1: ariadne RBR E3 ubiquitin protein ligase 1; ATF: activating transcription factor; ATG: autophagy related; ATM: ATM serine/threonine kinase; BCL2: BCL2 apoptosis regulator; BCL2L11/BIM: BCL2 like 11; BCL2L13: BCL2 like 13; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CANX: calnexin; CAT: catalase; CCPG1: cell cycle progression 1; CHDH: choline dehydrogenase; COPD: chronic obstructive pulmonary disease; CSE: cigarette smoke exposure; CTSD: cathepsin D; DDIT3/CHOP: DNA-damage inducible transcript 3; DISC1: DISC1 scaffold protein; DNM1L/DRP1: dynamin 1 like; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; EIF2S1/eIF2α: eukaryotic translation initiation factor 2 alpha kinase 3; EMD: emerin; EPAS1/HIF-2α: endothelial PAS domain protein 1; ER: endoplasmic reticulum; ERAD: ER-associated degradation; ERN1/IRE1α: endoplasmic reticulum to nucleus signaling 1; FBXO27: F-box protein 27; FKBP8: FKBP prolyl isomerase 8; FTD: frontotemporal dementia; FUNDC1: FUN14 domain containing 1; G3BP1: G3BP stress granule assembly factor 1; GBA: glucocerebrosidase beta; HIF1A/HIF1: hypoxia inducible factor 1 subunit alpha; IMM: inner mitochondrial membrane; LCLAT1/ALCAT1: lysocardiolipin acyltransferase 1; LGALS3/Gal3: galectin 3; LIR: LC3-interacting region; LMNA: lamin A/C; LMNB1: lamin B1; LPS: lipopolysaccharide; MAPK8/JNK: mitogen-activated protein kinase 8; MAMs: mitochondria-associated membranes; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MFN1: mitofusin 1; MOD: multiple organelles dysfunction; MTPAP: mitochondrial poly(A) polymerase; MUL1: mitochondrial E3 ubiquitin protein ligase 1; NBR1: NBR1 autophagy cargo receptor; NLRP3: NLR family pyrin domain containing 3; NUFIP1: nuclear FMR1 interacting protein 1; OMM: outer mitochondrial membrane; OPTN: optineurin; PD: Parkinson disease; PARL: presenilin associated rhomboid like; PEX3: peroxisomal biogenesis factor 3; PGAM5: PGAM family member 5; PHB2: prohibitin 2; PINK1: PTEN induced putative kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; RB1CC1/FIP200: RB1 inducible coiled-coil 1; RETREG1/FAM134B: reticulophagy regulator 1; RHOT1/MIRO1: ras homolog family member T1; RIPK3/RIP3: receptor interacting serine/threonine kinase 3; ROS: reactive oxygen species; RTN3: reticulon 3; SEC62: SEC62 homolog, preprotein translocation factor; SESN2: sestrin2; SIAH1: siah E3 ubiquitin protein ligase 1; SNCA: synuclein alpha; SNCAIP: synuclein alpha interacting protein; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1; TFEB: transcription factor EB; TICAM1/TRIF: toll-like receptor adaptor molecule 1; TIMM23: translocase of inner mitochondrial membrane 23; TNKS: tankyrase; TOMM: translocase of the outer mitochondrial membrane; TRIM: tripartite motif containing; UCP2: uncoupling protein 2; ULK1: unc-51 like autophagy activating kinase; UPR: unfolded protein response; USP10: ubiquitin specific peptidase 10; VCP/p97: valosin containing protein; VDAC: voltage dependent anion channels; XIAP: X-linked inhibitor of apoptosis; ZNHIT3: zinc finger HIT-type containing 3.

Imaging stressed organellesviasugar-conjugated color-switchable pH sensors

Sugar-conjugated pH sensors discriminate stressed lysosomes in different cell starvation conditionsviared-to-green fluorescence switch.

Fermented Korean Red Ginseng Extract Enriched in Rd and Rg3 Protects against Non-Alcoholic Fatty Liver Disease through Regulation of mTORC1

The fermentation of Korean red ginseng (RG) increases the bioavailability and efficacy of RG, which has a protective role in various diseases. However, the ginsenoside-specific molecular mechanism of the fermented RG with Cordyceps militaris (CRG) has not been elucidated in non-alcoholic fatty liver disease (NAFLD). A mouse model of NAFLD was induced by a fast-food diet (FFD) and treated with CRG (100 or 300 mg/kg) for the last 8 weeks. CRG-mediated signaling was assessed in the liver cells isolated from mice. CRG administration significantly reduced the FFD-induced steatosis, liver injury, and inflammation, indicating that CRG confers protective effects against NAFLD. Of note, an extract of CRG contains a significantly increased amount of ginsenosides (Rd and Rg3) after bioconversion compared with that of conventional RG. Moreover, in vitro treatment with Rd or Rg3 produced anti-steatotic effects in primary hepatocytes. Mechanistically, CRG protected palmitate-induced activation of mTORC1 and subsequent inhibition of mitophagy and PPARα signaling. Similar to that noted in hepatocytes, CRG exerted anti-inflammatory activity through mTORC1 inhibition-mediated M2 polarization. In conclusion, CRG inhibits lipid-mediated pathologic activation of mTORC1 in hepatocytes and macrophages, which in turn prevents NAFLD development. Thus, the administration of CRG may be an alternative for the prevention of NAFLD.

The Mitochondrion as an Emerging Therapeutic Target in Cancer

Mitochondria have emerged as important pharmacological targets because of their key role in cellular proliferation and death. In tumor tissues, mitochondria can switch metabolic phenotypes to meet the challenges of high energy demand and macromolecular synthesis. Furthermore, mitochondria can engage in crosstalk with the tumor microenvironment, and signals from cancer-associated fibroblasts can impinge on mitochondria. Cancer cells can also acquire a hybrid phenotype in which both glycolysis and oxidative phosphorylation (OXPHOS) can be utilized. This hybrid phenotype can facilitate metabolic plasticity of cancer cells more specifically in metastasis and therapy-resistance. In light of the metabolic heterogeneity and plasticity of cancer cells that had until recently remained unappreciated, strategies targeting cancer metabolic dependency appear to be promising in the development of novel and effective cancer therapeutics.

Reversible induction of mitophagy by an optogenetic bimodular system

Autophagy-mediated degradation of mitochondria (mitophagy) is a key process in cellular quality control. Although mitophagy impairment is involved in several patho-physiological conditions, valuable methods to induce mitophagy with low toxicity in vivo are still lacking. Herein, we describe a new optogenetic tool to stimulate mitophagy, based on light-dependent recruitment of pro-autophagy protein AMBRA1 to mitochondrial surface. Upon illumination, AMBRA1-RFP-sspB is efficiently relocated from the cytosol to mitochondria, where it reversibly mediates mito-aggresome formation and reduction of mitochondrial mass. Finally, as a proof of concept of the biomedical relevance of this method, we induced mitophagy in an in vitro model of neurotoxicity, fully preventing cell death, as well as in human T lymphocytes and in zebrafish in vivo. Given the unique features of this tool, we think it may turn out to be very useful for a wide range of both therapeutic and research applications.

Autophagic degradation of mitochondria (mitophagy) is a key quality control mechanism in cellular homeostasis, and its misregulation is involved in neurodegenerative diseases. Here the authors develop an optogenetic system for reversible induction of mitophagy and validate its use in cell culture and zebrafish embryos.

Induced pluripotent stem cell-based modeling of mutant LRRK2-associated Parkinson's disease

Recent advances in cell reprogramming have enabled assessment of disease-related cellular traits in patient-derived somatic cells, thus providing a versatile platform for disease modeling and drug development. Given the limited access to vital human brain cells, this technology is especially relevant for neurodegenerative disorders such as Parkinson's disease (PD) as a tool to decipher underlying pathomechanisms. Importantly, recent progress in genome-editing technologies has provided an ability to analyze isogenic induced pluripotent stem cell (iPSC) pairs that differ only in a single genetic change, thus allowing a thorough assessment of the molecular and cellular phenotypes that result from monogenetic risk factors. In this review, we summarize the current state of iPSC-based modeling of PD with a focus on leucine-rich repeat kinase 2 (LRRK2), one of the most prominent monogenetic risk factors for PD linked to both familial and idiopathic forms. The LRRK2 protein is a primarily cytosolic multi-domain protein contributing to regulation of several pathways including autophagy, mitochondrial function, vesicle transport, nuclear architecture and cell morphology. We summarize iPSC-based studies that contributed to improving our understanding of the function of LRRK2 and its variants in the context of PD etiopathology. These data, along with results obtained in our own studies, underscore the multifaceted role of LRRK2 in regulating cellular homeostasis on several levels, including proteostasis, mitochondrial dynamics and regulation of the cytoskeleton. Finally, we expound advantages and limitations of reprogramming technologies for disease modeling and drug development and provide an outlook on future challenges and expectations offered by this exciting technology.

LC3-II may mediate ATR-induced mitophagy in dopaminergic neurons through SQSTM1/p62 pathway

Atrazine (2-chloro-4-ethylamino-6-isopropylamine-1,3,5-triazine; ATR) has been demonstrated to regulate autophagy- and apoptosis-related proteins in doparminergic neuronal damage. In our study, we investigated the role of LC3-II in ATR-induced degeneration of dopaminergic neurons. In vivo dopaminergic neuron degeneration model was set up with ATR treatment and confirmed by the behavioral responses and pathological analysis. Dopaminergic neuron cells were transfected with LC3-II siRNA and treated with ATR to observe cell survival and reactive oxygen species release. The process of mitochondrial autophagy and the neurotoxic effects of mitochondrial autophagy were detected by immunofluorescence assay, immunohistochemical analysis, real-time PCR, and western blot analysis. Results showed that after ATR treatment, the grip strength of Wistar rats was significantly decreased, and behavioral signs of anxiety were clearly observed. The mRNA and protein levels of tyrosine hydroxylase, LC3-II, PINK1, and Parkin were significantly decreased in ATR-induced rat dopaminergic neurons and PC-12 cells, while the mRNA expression and protein levels of SQSTM1/p62 and Parl were increased. Exposure to ATR also led to accumulation of autophagic lysosomes and autophagic bodies along with significantly decreased levels of dopaminergic neurons and alterations in mitochondrial homeostasis, which was reversed by LC3-II siRNA. Our results suggest that ATR affects the mitochondria-mediated dopaminergic neuronal death, which may be mediated by LC3-II and other autophagy markers in vivo and in vitro through SQSTM1/p62 signaling pathway.

Cargo recognition and degradation by selective autophagy

Macroautophagy, initially described as a non-selective nutrient recycling process, is essential for the removal of multiple cellular components. In the past three decades, selective autophagy has been characterized as a highly regulated and specific degradation pathway for removal of unwanted cytosolic components and damaged and/or superfluous organelles. Here, we discuss different types of selective autophagy, emphasizing the role of ligand receptors and scaffold proteins in providing cargo specificity, and highlight unanswered questions in the field.

Differential effects of reticulophagy and mitophagy on nonalcoholic fatty liver disease

Autophagy affects the pathological progression of non-alcoholic fatty liver disease (NAFLD); however, the precise role of autophagy in NAFLD remains unclear. In this study, we want to identify the role of autophagy including reticulophagy and mitophagy in NAFLD pathogenesis. When HepG2 cells were treated with 400 μM oleic acid (OA), increased reticulophagy was induced 8 h after treatment, which correlated with an anti-apoptotic response as shown by the activation of the PI3K/AKT pathway, an increase in BCL-2 expression, and the downregulation of OA-induced lipotoxicity. When treated with OA for 24 h, DRAM expression-dependent mitophagy resulted in increased apoptosis in HepG2 cells. Inhibition of reticulophagy aggravated and increased lipotoxicity-induced apoptosis 8 h after treatment; however, the inhibition of mitophagy decreased hepatocyte apoptosis after 24 h of OA treatment. Results from the analysis of patient liver samples showed that autophagic flux increased in patients with mild or severe NAFL. PI3K/AKT phosphorylation was observed only in samples from patients with low-grade steatosis, whereas DRAM expression was increased in samples from patients with high-grade steatosis. Together, our results demonstrate that reticulophagy and mitophagy are independent, sequential events that influence NAFLD progression, which opens new avenues for investigating new therapeutics in NAFLD.

Searching for Correlations Between the Development of Neurodegenerative Hallmarks: Targeting Huntingtin as a Contributing Factor

This paper aims to study four general hallmarks of neurodegeneration and the correlations between them, with emphasis on the huntingtin (htt) interactions contributing to their prevention or promotion in its wild-type and mutated forms. Most of the neurodegenerative diseases share same or similar cell dysfunctions and huntingtin seems to associate in an polyglutamine-length dependent manner with components of the mechanisms that can go impaired. Therefore, the protein is proposed as contributing factor to the development of selective neurodegeneration.

Therapeutic effects of baicalein on rotenone-induced Parkinson's disease through protecting mitochondrial function and biogenesis

Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson’s disease (PD) for several decades, and disturbed mitochondrial biogenesis (mitobiogenesis) was recently found to be a common phenomenon in PD. Baicalein, a major bioactive flavone of Scutellaria baicalensis Georgi, exerted neuroprotective effects in several experimental PD models. However, the effects of baicalein in rotenone-induced PD rats and the possible mechanisms remain poorly understood. In this study, we evaluated the therapeutic effects of baicalein and explored its mechanism of action in rotenone-induced PD models. The results indicated that behavioural impairments and the depletion of dopaminergic neurons induced by rotenone were attenuated by baicalein. Furthermore, in rotenone-induced parkinsonian rats, baicalein treatment effectively restored mitochondrial function and improved mitobiogenesis, as determined by measuring the mitochondrial density and key regulators involved in mitobiogenesis. Additionally, we confirmed that baicalein enhanced mitobiogenesis through the cAMP-responsive element binding protein (CREB) and glycogen synthase kinase-3β (GSK-3β) pathways in rotenone-treated SH-SY5Y cells. Moreover, we demonstrated that the cytoprotective effects of baicalein could be attenuated by the mitobiogenesis inhibitor chloramphenicol as well as CREB siRNA transfection. Overall, our results suggested that baicalein partially enhanced mitobiogenesis to restore mitochondrial function, thus exerting therapeutic effects in rotenone-induced PD models.

Drosophila PINK1 and parkin loss-of-function mutants display a range of non-motor Parkinson's disease phenotypes

Parkinson's disease (PD) is more commonly associated with its motor symptoms and the related degeneration of dopamine (DA) neurons. However, it is becoming increasingly clear that PD patients also display a wide range of non-motor symptoms, including memory deficits and disruptions of their sleep-wake cycles. These have a large impact on their quality of life, and often precede the onset of motor symptoms, but their etiology is poorly understood. The fruit fly Drosophila has already been successfully used to model PD, and has been used extensively to study relevant non-motor behaviours in other contexts, but little attention has yet been paid to modelling non-motor symptoms of PD in this genetically tractable organism. We examined memory performance and circadian rhythms in flies with loss-of-function mutations in two PD genes: PINK1 and parkin. We found learning and memory abnormalities in both mutant genotypes, as well as a weakening of circadian rhythms that is underpinned by electrophysiological changes in clock neurons. Our study paves the way for further work that may help us understand the mechanisms underlying these neglected aspects of PD, thus identifying new targets for treatments to address these non-motor problems specifically and perhaps even to halt disease progression in its prodromal phase.

Overexpression of Buffy enhances the loss of parkin and suppresses the loss of Pink1 phenotypes in Drosophila

Mutations in parkin (PARK2) and Pink1 (PARK6) are responsible for autosomal recessive forms of early onset Parkinson's disease (PD). Attributed to the failure of neurons to clear dysfunctional mitochondria, loss of gene expression leads to loss of nigrostriatal neurons. The Pink1/parkin pathway plays a role in the quality control mechanism aimed at eliminating defective mitochondria, and the failure of this mechanism results in a reduced lifespan and impaired locomotor ability, among other phenotypes. Inhibition of parkin or Pink1 through the induction of stable RNAi transgene in the Ddc-Gal4-expressing neurons results in such phenotypes to model PD. To further evaluate the effects of the overexpression of the Bcl-2 homologue Buffy, we analysed lifespan and climbing ability in both parkin-RNAi- and Pink1-RNAi-expressing flies. In addition, the effect of Buffy overexpression upon parkin-induced developmental eye defects was examined through GMR-Gal4-dependent expression. Curiously, Buffy overexpression produced very different effects: the parkin-induced phenotypes were enhanced, whereas the Pink1-enhanced phenotypes were suppressed. Interestingly, the overexpression of Buffy along with the inhibition of parkin in the neuron-rich eye results in the suppression of the developmental eye defects.

MKK3 influences mitophagy and is involved in cigarette smoke-induced inflammation

Cigarette smoking is the primary risk factor for COPD which is characterized by excessive inflammation and airflow obstruction of the lung. While inflammation is causally related to initiation and progression of COPD, the mitochondrial mechanisms that underlie the associated inflammatory responses are poorly understood. In this context, we have studied the role played by Mitogen activated protein (MAP) kinase kinase 3 (MKK3), a dual-specificity protein kinase, in cigarette smoke induced-inflammation and mitochondrial dysfunction. Serum pro-inflammatory cytokines were significantly elevated in WT but not in MKK3-/- mice exposed to Cigarette smoke (CS) for 2 months. To study the cellular mechanisms of inflammation, bone marrow derived macrophages (BMDMs), wild type (WT) and MKK3-/-, were exposed to cigarette smoke extract (CSE) and inflammatory cytokine production and mitochondrial function assessed. The levels of IL-1β, IL-6, and TNFα were increased along with higher reactive oxygen species (ROS) and P-NFκB after CSE treatment in WT but not in MKK3-/- BMDMs. CSE treatment adversely affected basal mitochondrial respiration, ATP production, maximum respiratory capacity, and spare respiratory capacity in WT BMDMs only. Mitophagy, clearance of dysfunctional mitochondria, was up regulated in CS exposed WT mice lung tissue and CSE exposed WT BMDMs, respectively. The proteomic analysis of BMDMs by iTRAQ (isobaric tags for relative and absolute quantitation) showed up regulation of mitochondrial dysfunction associated proteins in WT and higher OXPHOS (Oxidative phosphorylation) and IL-10 signaling proteins in MKK3-/- BMDMs after CSE exposure, confirming the critical role of mitochondrial homeostasis. Interestingly, we found increased levels of p-MKK3 by immunohistochemistry in COPD patient lung tissues that could be responsible for insufficient mitophagy and disease progression. This study identifies MKK3 as a negative regulator of mitochondrial function and inflammatory responses to CS and suggests that MKK3 could be a therapeutic target.

Resveratrol attenuates MPP+-induced mitochondrial dysfunction and cell apoptosis via AKT/GSK-3β pathway in SN4741 cells

Oxidative stress and mitochondrial dysfunction play crucial role in the dopaminergic neurons death, which is the pathological feature of Parkinson's disease (PD). Resveratrol (Res), a polyphenol derived from grapes and blueberries, has been reported to reduce oxidative stress injury and to restore mitochondrial function. In this study, we aimed to explore the underlying molecular mechanism of the beneficial effects of Res against MPP+- induced mitochondrial dysfunction and cell apoptosis in SN4741 cells. The data showed that Res significantly alleviated MPP+- induce cytotoxicity and restored MPP+- induced mitochondrial dysfunction in SN4741 cells. Moreover, Res rescued MPP+- induced a decline on the level of p-AKT, p-GSK-3βand the ratio of Bcl-2/Bax, and an elevation on the expression of Bax and caspase-3, 9. However, inhibition GSK-3β activity clearly abolished the protective effects of Res. Taken together, these results suggest that Res attenuates MPP+- induced mitochondrial dysfunction and cell apoptosis, and these protections may be achieved through AKT/GSK-3β pathway. These also indicate that Res could be a promising therapeutic agent for PD.

Elevated Hapln2 Expression Contributes to Protein Aggregation and Neurodegeneration in an Animal Model of Parkinson's Disease

Parkinson's disease (PD), the second most common age-associated progressive neurodegenerative disorder, is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SN). The pathogenesis of PD and the mechanisms underlying the degeneration of DA neurons are still not fully understood. Our previous quantitative proteomics study revealed that hyaluronan and proteoglycan binding link protein 2 (Hapln2) is one of differentially expressed proteins in the substantia nigra tissues from PD patients and healthy control subjects. However, the potential role of Hapln2 in PD pathogenesis remains elusive. In the present study, we characterized the expression pattern of Hapln2. In situ hybridization revealed that Hapln2 mRNA was widely expressed in adult rat brain with high abundance in the substantia nigra. Immunoblotting showed that expression levels of Hapln2 were markedly upregulated in the substantia nigra of either human subjects with Parkinson's disease compared with healthy control. Likewise, there were profound increases in Hapln2 expression in neurotoxin 6-hydroxydopamine-treated rat. Overexpression of Hapln2 in vitro increased vulnerability of MES23.5 cells, a dopaminergic cell line, to 6-hydroxydopamine. Moreover, Hapln2 overexpression led to the formation of cytoplasmic aggregates which were co-localized with ubiquitin and E3 ligases including Parkin, Gp78, and Hrd1 in vitro. Endogenous α-synuclein was also localized in Hapln2-containing aggregates and ablation of Hapln2 led to a marked decrease of α-synuclein in insoluble fraction compared with control. Thus, Hapln2 is identified as a novel factor contributing to neurodegeneration in PD. Our data provides new insights into the cellular mechanism underlying the pathogenesis in PD.

Regulators of mitochondrial dynamics in cancer

Mitochondrial dynamics encompasses processes associated with mitochondrial fission and fusion, affecting their number, degree of biogenesis, and the induction of mitophagy. These activities determine the balance between mitochondrial energy production and cell death programs. Processes governing mitochondrial dynamics are tightly controlled in physiological conditions and are often deregulated in cancer. Mitochondrial protein homeostasis, transcriptional regulation, and post-translational modification are among processes that govern the control of mitochondrial dynamics. Cancer cells alter mitochondrial dynamics to resist apoptosis and adjust their bioenergetic and biosynthetic needs to support tumor initiating and transformation properties including proliferation, migration, and therapeutic resistance. This review focuses on key regulators of mitochondrial dynamics and their role in cancer.