From autophagy to mitophagy: the roles of P62 in neurodegenerative diseases

Intrinsic aerobic capacity modulates Alzheimer's disease pathological hallmarks, brain mitochondrial function and proteome during aging

Low aerobic capacity is strongly associated with all-cause mortality and risk for Alzheimer's disease (AD). Individuals with early dementia and AD have lower aerobic capacity compared to age-matched controls. The mechanism by which aerobic capacity influences AD risk is unknown but is likely mediated by sexual dimorphism and tissue-level differences in mitochondrial energetics. Here, we used rats selectively bred for large differences in intrinsic aerobic exercise capacity. Brain tissue from 18-month and 24-month-old female and male low-capacity runner (LCR) and high-capacity runner (HCR) rats were analyzed for markers of mitochondrial function and AD-associated pathologies. LCR rats, irrespective of sex, exhibited a greater increase in brain amyloid beta (Aβ42) and tau hyperphosphorylation (pTauthr181/total tau) with aging. In female LCR rats, brain mitochondrial respiration at states 3, 4, and FCCP-induced uncoupling, when stimulated with pyruvate/malate, was reduced at 18 and 24 months, leading to lower ATP-linked mitochondrial respiration compared to mitochondria from HCR rats. Male LCR rats also showed reduced complex II-stimulated mitochondrial respiration (succinate + rotenone) at 24 months compared to HCR rats. Differences in mitochondrial respiration were associated with tau hyperphosphorylation and Aβ42 alterations in both HCR and LCR strains. Proteomic analysis unveiled a distinct difference in the mitochondrial proteome, wherein female LCR rats displayed diminished mitochondrial translation and oxidative phosphorylation (OXPHOS) proteins at 18 months compared to female HCR rats. Conversely, male LCR rats exhibited increased OXPHOS protein abundance but reduced tricarboxylic acid (TCA) cycle proteins compared to male HCR rats. These findings underscore a robust association between intrinsic aerobic exercise capacity, brain mitochondrial function, and AD pathologies during aging.

Gentiana decoction inhibits liver fibrosis and the activation of hepatic stellate cells via upregulating the expression of Parkin

Liver fibrosis is a wound-healing process. It can be induced by various chronic liver diseases. Liver fibrosis is characterized by the activation of hepatic stellate cells (HSCs), a key event. However, no effective treatment strategies to cure or alleviate liver fibrosis-induced pathologic changes have yet been developed. Traditional Chinese medicine (TCM) exhibits a good anti-fibrosis action, with few side effects. Gentiana decoction, a TCM also called Longdan Xiegan Tang (LXT), is used for purging the liver in clinical settings. However, the role of LXT in preventing liver fibrosis and the underlying regulatory mechanism have not yet been investigated. This study demonstrates that LXT treatment can protect the liver from the injuries resulting from CCl4-induced liver fibrosis in mice and suppress the activation of HSCs. The mice in the LXT group exhibit litter collagen I and HSC activation marker α-smooth muscle actin (α-SMA) expression. Transcriptome sequencing of the mouse liver tissue reveals that the level of Parkin, a mitophagy marker, decreased in CCl4-induced liver fibrosis. Further study shows that the injection of Parkin-overexpression adeno-associated virus (Parkin-AAV) via the tail vein can reduce CCl4-induced liver fibrogenesis in mice. We conducted a mechanistic study also, which suggests that LXT treatment suppresses the activation of HSCs by upregulating the expression of Parkin. Hence, it can be suggested that LXT inhibits liver fibrosis by activating the Parkin signaling pathway.

Proximity labeling reveals dynamic changes in the SQSTM1 protein network

Sequestosome1 (SQSTM1) is an autophagy receptor that mediates degradation of intracellular cargo, including protein aggregates, through multiple protein interactions. These interactions form the SQSTM1 protein network, and these interactions are mediated by SQSTM1 functional interaction domains, which include LIR, PB1, UBA and KIR. Technological advances in cell biology continue to expand our knowledge of the SQSTM1 protein network and of the relationship of the actions of the SQSTM1 protein network in cellular physiology and disease states. Here we apply proximity profile labeling to investigate the SQSTM1 protein interaction network by fusing TurboID with the human protein SQSTM1 (TurboID::SQSTM1). This chimeric protein displayed well-established SQSTM1 features including production of SQSTM1 intracellular bodies, binding to known SQSTM1 interacting partners, and capture of novel SQSTM1 protein interactors. Strikingly, aggregated tau protein altered the protein interaction network of SQSTM1 to include many stress-associated proteins. We demonstrate the importance of the PB1 and/or UBA domains for binding network members, including the K18 domain of tau. Overall, our work reveals the dynamic landscape of the SQSTM1 protein network and offers a resource to study SQSTM1 function in cellular physiology and disease state.

High frequency electrical stimulation reduces α-synuclein levels and α-synuclein-mediated autophagy dysfunction

Accumulation of α-synuclein (α-Syn) has been implicated in proteasome and autophagy dysfunction in Parkinson's disease (PD). High frequency electrical stimulation (HFS) mimicking clinical parameters used for deep brain stimulation (DBS) in vitro or DBS in vivo in preclinical models of PD have been found to reduce levels of α-Syn and, in certain cases, provide possible neuroprotection. However, the mechanisms by which this reduction in α-Syn improves cellular dysfunction associated with α-Syn accumulation remains elusive. Using HFS parameters that recapitulate DBS in vitro, we found that HFS led to a reduction of mutant α-Syn and thereby limited proteasome and autophagy impairments due to α-Syn. Additionally, we observed that HFS modulates via the ATP6V0C subunit of V-ATPase and mitigates α-Syn mediated autophagic dysfunction. This study highlights a role for autophagy in reduction of α-Syn due to HFS which may prove to be a viable approach to decrease pathological protein accumulation in neurodegeneration.

Artesunate improves learning and memory impairment in rats with vascular cognitive impairment by down-regulating the level of autophagy in cerebral cortex neurons

Background

Vascular cognitive impairment (VCI) is the second leading cause of dementia. Cognitive impairment is a common consequence of VCI. However, there is no effective treatment for VCI and the underlying mechanism of its pathogenesis remains unclear. This study to investigate whether artesunate (ART) can improve the learning and memory function in rats with VCI by down-regulating he level of autophagy in cerebral cortex neurons.

Methods

The models for VCI were the rat bilateral common carotid artery occlusion (BACCO), which were randomized into three groups including the sham operation group (Sham), model + vehicle group (Model) and model + ART group (ART). Then the animal behaviors were recorded, as well as staining the results of cortical neurons. Western blot was performed to determine the protein expressions of LC3BⅡ/Ⅰ, p-AMPK, p-mTOR, and Beclin-1.

Results

Behavioral outcomes and the protein expressions in Model group were supposedly affected by the induction of autophagy in cerebral cortex neurons. Compared to the Model group, ART improved memory impairment in VCI rats. And the expression of LC3BⅡ/Ⅰ, p-AMPK/AMPK, Beclin-1 is significant decreased in the ART group, while significant increases of p-mTOR/mTOR were showed. These results suggest that ART improved learning and memory impairment in VCI rats by down-regulating the level of autophagy in cerebral cortex neurons.

Conclusion

The results suggest that autophagy occurs in cerebral cortex neurons in rats with VCI. It is speculated that ART can improve learning and memory impairment in VCI rats by down-regulating the level of autophagy in cerebral cortex neurons.

Proximity labeling reveals dynamic changes in the SQSTM1 protein network

Sequestosome1 (SQSTM1) is an autophagy receptor that mediates degradation of intracellular cargo, including protein aggregates, through multiple protein interactions. These interactions form the SQSTM1 protein network, and these interactions are mediated by SQSTM1 functional interaction domains, which include LIR, PB1, UBA and KIR. Technological advances in cell biology continue to expand our knowledge of the SQSTM1 protein network and of the relationship of the actions of the SQSTM1 protein network in cellular physiology and disease states. Here we apply proximity profile labeling to investigate the SQSTM1 protein interaction network by fusing TurboID with the human protein SQSTM1 (TurboID::SQSTM1). This chimeric protein displayed well-established SQSTM1 features including production of SQSTM1 intracellular bodies, binding to known SQSTM1 interacting partners, and capture of novel SQSTM1 protein interactors. Strikingly, aggregated tau protein altered the protein interaction network of SQSTM1 to include many stress-associated proteins. We demonstrate the importance of the PB1 and/or UBA domains for binding network members, including the K18 domain of tau. Overall, our work reveals the dynamic landscape of the SQSTM1 protein network and offers a resource to study SQSTM1 function in cellular physiology and disease state.

Neurotropic virus infection and neurodegenerative diseases: Potential roles of autophagy pathway

Neurodegenerative diseases (NDs) constitute a group of disorders characterized by the progressive deterioration of nervous system functionality. Currently, the precise etiological factors responsible for NDs remain incompletely elucidated, although it is probable that a combination of aging, genetic predisposition, and environmental stressors participate in this process. Accumulating evidence indicates that viral infections, especially neurotropic viruses, can contribute to the onset and progression of NDs. In this review, emerging evidence supporting the association between viral infection and NDs is summarized, and how the autophagy pathway mediated by viral infection can cause pathological aggregation of cellular proteins associated with various NDs is discussed. Furthermore, autophagy-related genes (ARGs) involved in Herpes simplex virus (HSV-1) infection and NDs are analyzed, and whether these genes could link HSV-1 infection to NDs is discussed. Elucidating the mechanisms underlying NDs is critical for developing targeted therapeutic approaches that prevent the onset and slow the progression of NDs.

Sinomenine exerts a neuroprotective effect on PD mouse model through inhibiting PI3K/AKT/mTOR pathway to enhance autophagy

BACKGROUND

Parkinson's disease (PD), as a chronic and progressive neurodegenerative disease, is associated with autophagy. This study focused on the regulation of sinomenine (SN) on autophagy in PD and its related mechanism.

METHODS

The PD mouse model was constructed by MPTP inducement, and the mouse motor function after modeling and SN treatment was examined by rotarod, grip strength, and foot printing tests. Tyrosine hydroxylase (TH)/LC3B-positive neurons in the substantia nigra pars compacta of mouse brains were detected by immunofluorescence. The expressions of proteins related to autophagy (Beclin1, p62, LC3-I and LC3-II) and phosphorylated phosphoinositide 3-kinase (PI3K)/AKT/mechanistic target of rapamycin kinase (mTOR) signaling pathway were measured by western blot. Rescue experiments were performed to determine the effects of MHY1485 (mTOR activator) on SN-treated PD mice.

RESULTS

SN potentiated the motor ability in PD mice, promoted the survival of dopaminergic neurons, increased the protein expression level of Beclin1, LC3-II/LC3-I ratio and LC3B-positive neurons, lowered the protein expression level of p62 and inactivated PI3K/AKT/mTOR pathway in the substantia nigra tissue of mouse brains. Moreover, MHY1485 reversed the above effects of SN on PD mice via reactivating PI3K/AKT/mTOR pathway.

CONCLUSION

SN augments the autophagy of dopaminergic neurons via inhibiting the PI3K/AKT/mTOR pathway and exerts a neuroprotective effect on PD mice.

Mitophagy in neurodegenerative disease pathogenesis

Mitochondria are critical cellular energy resources and are central to the life of the neuron. Mitophagy selectively clears damaged or dysfunctional mitochondria through autophagic machinery to maintain mitochondrial quality control and homeostasis. Mature neurons are postmitotic and consume substantial energy, thus require highly efficient mitophagy pathways to turn over damaged or dysfunctional mitochondria. Recent evidence indicates that mitophagy is pivotal to the pathogenesis of neurological diseases. However, more work is needed to study mitophagy pathway components as potential therapeutic targets. In this review, we briefly discuss the characteristics of nonselective autophagy and selective autophagy, including ERphagy, aggrephagy, and mitophagy. We then introduce the mechanisms of Parkin-dependent and Parkin-independent mitophagy pathways under physiological conditions. Next, we summarize the diverse repertoire of mitochondrial membrane receptors and phospholipids that mediate mitophagy. Importantly, we review the critical role of mitophagy in the pathogenesis of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Last, we discuss recent studies considering mitophagy as a potential therapeutic target for treating neurodegenerative diseases. Together, our review may provide novel views to better understand the roles of mitophagy in neurodegenerative disease pathogenesis.

Fragile X Messenger Ribonucleoprotein Protein and Its Multifunctionality: From Cytosol to Nucleolus and Back

Silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene and a consequent lack of FMR protein (FMRP) synthesis are associated with fragile X syndrome, one of the most common inherited intellectual disabilities. FMRP is a multifunctional protein that is involved in many cellular functions in almost all subcellular compartments under both normal and cellular stress conditions in neuronal and non-neuronal cell types. This is achieved through its trafficking signals, nuclear localization signal (NLS), nuclear export signal (NES), and nucleolar localization signal (NoLS), as well as its RNA and protein binding domains, and it is modulated by various post-translational modifications such as phosphorylation, ubiquitination, sumoylation, and methylation. This review summarizes the recent advances in understanding the interaction networks of FMRP with a special focus on FMRP stress-related functions, including stress granule formation, mitochondrion and endoplasmic reticulum plasticity, ribosome biogenesis, cell cycle control, and DNA damage response.

Natural Activators of Autophagy

Autophagy is the process by which cell contents, such as aggregated proteins, dysfunctional organelles, and cell structures are sequestered by autophagosome and delivered to lysosomes for degradation. As a process that allows the cell to get rid of non-functional components that tend to accumulate with age, autophagy has been associated with many human diseases. In this regard, the search for autophagy activators and the study of their mechanism of action is an important task for treatment of many diseases, as well as for increasing healthy life expectancy. Plants are rich sources of autophagy activators, containing large amounts of polyphenolic compounds in their composition, which can be autophagy activators in their original form, or can be metabolized by the intestinal microbiota to active compounds. This review is devoted to the plant-based autophagy activators with emphasis on the sources of their production, mechanism of action, and application in various diseases. The review also describes companies commercializing natural autophagy activators.

Neuronal Gtf2i deletion alters mitochondrial and autophagic properties

Gtf2i encodes the general transcription factor II-I (TFII-I), with peak expression during pre-natal and early post-natal brain development stages. Because these stages are critical for proper brain development, we studied at the single-cell level the consequences of Gtf2i's deletion from excitatory neurons, specifically on mitochondria. Here we show that Gtf2i's deletion resulted in abnormal morphology, disrupted mRNA related to mitochondrial fission and fusion, and altered autophagy/mitophagy protein expression. These changes align with elevated reactive oxygen species levels, illuminating Gtf2i's importance in neurons mitochondrial function. Similar mitochondrial issues were demonstrated by Gtf2i heterozygous model, mirroring the human condition in Williams syndrome (WS), and by hemizygous neuronal Gtf2i deletion model, indicating Gtf2i's dosage-sensitive role in mitochondrial regulation. Clinically relevant, we observed altered transcript levels related to mitochondria, hypoxia, and autophagy in frontal cortex tissue from WS individuals. Our study reveals mitochondrial and autophagy-related deficits shedding light on WS and other Gtf2i-related disorders.

Long-term oral tribasic copper chloride exposure impedes cognitive function and disrupts mitochondrial metabolism by inhibiting mitophagy in rats

Copper (Cu) is an essential micronutrient element that commonly acted as a feed additive and antimicrobial in agricultural production. Tribasic copper chloride (TBCC) is a relatively new dietary Cu source, and its exposure directly or indirectly affects the safety of animals and ecological environment, thus posing a potential risk to human health. Cu overexposure would produce toxic reactive oxygen species (ROS) that may have toxic effects on the host, but the mechanism of neurotoxicity remains unclear. Herein, to explore the effects of long-term TBCC-induced neurotoxicity, 150 male Sprague-Dawley rats were randomly allocated and treated with different doses of TBCC, and the cortical and hippocampus tissues were harvested at 0, 6, and 12 weeks after treatment. Morris Water Maze (MWM) test showed that excessive intake of TBCC could induce cognitive dysfunction in rats. Moreover, after treatment with 160 mg/kg Cu (276 mg/kg TBCC) for 12 weeks, pathological changes were observed in the cortex and hippocampus, and the number of Nissl bodies decreased significantly in the hippocampus. Additionally, mitochondrial structure was significantly altered and neuronal mitochondrial fusion/fission equilibrium was disrupted in 80 mg/kg and 160 mg/kg Cu groups at 12 weeks. With an increase in TBCC dose and treatment time, the number of mitophagosomes and the expression of mitophagy-related genes were significantly decreased after initially increasing. Furthermore, metformin (Met) and 3-methyladenine (3-MA) were used to regulate the level of mitophagy to further explore the mechanism of Cu-induced nerve cell injury in vitro., and it found that mitophagy activator (Met) would increase mitochondrial fission, while mitophagy inhibitors (3-MA) would aggravate mitochondrial metabolic disorders by promoting mitochondrial fusion and inhibiting mitochondrial division. These results indicate that long-term oral TBCC could impede cognitive function and disrupts mitochondrial metabolism by inhibiting mitophagy, providing an insightful perspective on the neurotoxicity of dietary TBCC.

Crucial role of autophagy in propofol-treated neurological diseases: a comprehensive review

Neurological disorders are the leading cause of disability and death globally. Currently, there is a significant concern about the therapeutic strategies that can offer reliable and cost-effective treatment for neurological diseases. Propofol is a widely used general intravenous anesthetic in the clinic. Emerging studies demonstrate that propofol exerts neuroprotective effects on neurological diseases and disorders, while its underlying pathogenic mechanism is not well understood. Autophagy, an important process of cell turnover in eukaryotes, has been suggested to involve in the neuroprotective properties developed by propofol. In this narrative review, we summarized the current evidence on the roles of autophagy in propofol-associated neurological diseases. This study highlighted the effect of propofol on the nervous system and the crucial roles of autophagy. According to the 21 included studies, we found that propofol was a double-edged sword for neurological disorders. Several eligible studies reported that propofol caused neuronal cell damage by regulating autophagy, leading to cognitive dysfunction and other neurological diseases, especially high concentration and dose of propofol. However, some of them have shown that in the model of existing nervous system diseases (e.g., cerebral ischemia-reperfusion injury, electroconvulsive therapy injury, cobalt chloride-induced injury, TNF-α-induced injury, and sleep deprivation-induced injury), propofol might play a neuroprotective role by regulating autophagy, thus improving the degree of nerve damage. Autophagy plays a pivotal role in the neurological system by regulating oxidative stress, inflammatory response, calcium release, and other mechanisms, which may be associated with the interaction of a variety of related proteins and signal cascades. With extensive in-depth research in the future, the autophagic mechanism mediated by propofol will be fully understood, which may facilitate the feasibility of propofol in the prevention and treatment of neurological disorders.

Ultrastructural features mirror metabolic derangement in human endothelial cells exposed to high glucose

High glucose-induced endothelial dysfunction is the early event that initiates diabetes-induced vascular disease. Here we employed Cryo Soft X-ray Tomography to obtain three-dimensional maps of high D-glucose-treated endothelial cells and their controls at nanometric spatial resolution. We then correlated ultrastructural differences with metabolic rewiring. While the total mitochondrial mass does not change, high D-glucose promotes mitochondrial fragmentation, as confirmed by the modulation of fission-fusion markers, and dysfunction, as demonstrated by the drop of membrane potential, the decreased oxygen consumption and the increased production of reactive oxygen species. The 3D ultrastructural analysis also indicates the accumulation of lipid droplets in cells cultured in high D-glucose. Indeed, because of the decrease of fatty acid β-oxidation induced by high D-glucose concentration, triglycerides are esterified into fatty acids and then stored into lipid droplets. We propose that the increase of lipid droplets represents an adaptive mechanism to cope with the overload of glucose and associated oxidative stress and metabolic dysregulation.

Staphylococcus aureus extracellular vesicles induce apoptosis and restrain mitophagy-mediated degradation of damaged mitochondria

Extracellular vesicles (EVs) are nano-sized bilayer EVs with various components. EV secretion in pathogenic Gram-positive bacteria is a universal feature that can cause disease and damage the targeted host. In this study, we isolated and purified Staphylococcus aureus (S. aureus) EVs, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyzed Ev's protein composition. After that, the pathway of EVs internalized into MAC-T cells was evaluated. Moreover, the activation of mitogen-activated protein kinase (MAPK) and the nuclear factor κB (NF-κB) pathway was measured by Western blot. Meanwhile, Western blot and confocal microscopy detected mitochondrial damage, apoptosis, and Parkin-mediated mitophagy. Results showed that purified S. aureus EVs exhibited a typical cup-shaped structure and internalized into MAC-T cells by lipid raft-mediated endocytic pathway. S. aureus EVs caused mitochondrial damage and apoptosis in MAC-T cells. However, degradation of the damaged mitochondria was impeded due to the Parkin-mediated mitophagy pathway being restrained by the disruption of the acidic environment of lysosomes by S. aureus EVs. Hence, our study reveals the role of S. aureus EVs in immune stimulation, disruption of mitochondria, and lysosomal acidic environment in bovine mammary epithelial cells. These findings help us understand the role of EVs in the pathogenic mechanism of S. aureus.

Loss of insulin signaling in astrocytes exacerbates Alzheimer-like phenotypes in a 5xFAD mouse model

Brain insulin signaling controls peripheral energy metabolism and plays a key role in the regulation of mood and cognition. Epidemiological studies have indicated a strong connection between type 2 diabetes (T2D) and neurodegenerative disorders, especially Alzheimer's disease (AD), linked via dysregulation of insulin signaling, i.e., insulin resistance. While most studies have focused on neurons, here, we aim to understand the role of insulin signaling in astrocytes, a glial cell type highly implicated in AD pathology and AD progression. To this end, we created a mouse model by crossing 5xFAD transgenic mice, a well-recognized AD mouse model that expresses five familial AD mutations, with mice carrying a selective, inducible insulin receptor (IR) knockout in astrocytes (iGIRKO). We show that by age 6 mo, iGIRKO/5xFAD mice exhibited greater alterations in nesting, Y-maze performance, and fear response than those of mice with the 5xFAD transgenes alone. This was associated with increased Tau (T231) phosphorylation, increased Aβ plaque size, and increased association of astrocytes with plaques in the cerebral cortex as assessed using tissue CLARITY of the brain in the iGIRKO/5xFAD mice. Mechanistically, in vitro knockout of IR in primary astrocytes resulted in loss of insulin signaling, reduced ATP production and glycolic capacity, and impaired Aβ uptake both in the basal and insulin-stimulated states. Thus, insulin signaling in astrocytes plays an important role in the control of Aβ uptake, thereby contributing to AD pathology, and highlighting the potential importance of targeting insulin signaling in astrocytes as a site for therapeutics for patients with T2D and AD.

Dietary rutin improves breast meat quality in heat-stressed broilers and protects mitochondria from oxidative attack via the AMPK/PINK1-Parkin pathway

BACKGROUND

This study was conducted to investigate the effect of dietary rutin on the meat quality, antioxidant status and mitochondrial structure and function in the breast muscle of heat-stressed broilers. A total of 192 male broilers were randomly assigned into three groups and treated with normal control (CON), heat stress (34 °C, HS), and HS with 500 mg kg^-1 rutin supplementation (HS + Rutin), respectively.

RESULTS

Dietary rutin significantly reversed HS-induced decrease in body weight, average daily feed intake, average daily gain, and feed efficiency. Rutin supplementation attenuated HS-induced impaired meat quality by decreasing the lightness, drip loss at 24 and 48 h, the peak time of free water (T₂₂ ) and the peak area ratio of free water (P₂₂ ), and increasing the pH_24h and peak area ratio of immobilized water (P₂₁ ). Rutin supplementation promoted superoxide dismutase, glutathione peroxidase activities and total antioxidant capacity, and decreased malondialdehyde levels compared with the HS group. Moreover, rutin attenuated HS-induced mitochondrial damage by increasing the mitochondrial DNA copy number and improving mitochondrial morphology. Dietary rutin significantly increased mitochondrial biogenesis-related mRNA (proliferator-activated γ receptor coactivator-1α [PGC-1α], nuclear respiratory factor 1 [NRF1], and mitochondrial transcription factor A [TFAM]) expression via the AMP-activated protein kinase (AMPK) signaling pathway. HS significantly increased mitophagy-related genes and proteins (Parkin, PTEN-induced putative kinase 1 [PINK1], microtubule associated protein light chain 3-II [LC3-II]) expression, and dietary rutin significantly reversed these alterations.

CONCLUSION

Dietary rutin attenuated the HS-induced decline in meat quality and antioxidant capacity of broilers, which may be related to inhibition of the AMPK/PINK1-Parkin signaling pathway to attenuate mitochondrial damage. © 2023 Society of Chemical Industry.

Lewy Body-like Pathology and Loss of Dopaminergic Neurons in Midbrain Organoids Derived from Familial Parkinson's Disease Patient

Progressive accumulation of α-Synuclein (αSyn) in Lewy bodies (LBs) and loss of dopaminergic (DA) neurons are the hallmark pathological features of Parkinson's disease (PD). Although currently available in vitro and in vivo models have provided crucial information about PD pathogenesis, the mechanistic link between the progressive accumulation of αSyn into LBs and the loss of DA neurons is still unclear. To address this, it is critical to model LB formation and DA neuron loss, the two key neuropathological aspects of PD, in a relevant in vitro system. In this study, we developed a human midbrain-like organoid (hMBO) model of PD. We demonstrated that hMBOs generated from induced pluripotent stem cells (hiPSCs), derived from a familial PD (fPD) patient carrying αSyn gene (SNCA) triplication accumulate pathological αSyn over time. These cytoplasmic inclusions spatially and morphologically resembled diverse stages of LB formation and were composed of key markers of LBs. Importantly, the progressive accumulation of pathological αSyn was paralleled by the loss of DA neurons and elevated apoptosis. The model developed in this study will complement the existing in vitro models of PD and will provide a unique platform to study the spatiotemporal events governing LB formation and their relation with neurodegeneration. Furthermore, this model will also be beneficial for in vitro screening and the development of therapeutic compounds.

Sodium Para-Aminosalicylic Acid Modulates Autophagy to Lessen Lead-Induced Neurodegeneration in Rat Cortex

Lead (Pb) is a common heavy metal contaminant in the environment, and it may perturb autophagy and cause neurodegeneration. Although sodium para-aminosalicylic (PAS-Na) has been shown to protect the brain from lead-induced toxicity, the mechanisms associated with its efficacy have yet to be fully understood. In this study, we evaluated the efficacy of PAS-Na in attenuating the neurotoxic effects of lead, as well as the specific mechanisms that mediate such protection. Lead exposure resulted in weight loss and injury to the liver and kidney, and PAS-Na had a protective effect against this damage. Both short-term and subchronic lead exposure impaired learning ability, and this effect was reversed by PAS-Na intervention. Lead exposure also perturbed autophagic processes through the modulation of autophagy-related factors. Short-term lead exposure downregulated LC3 and beclin1 and upregulated the expression of p62; subchronic lead exposure upregulated the expression of LC3, beclin1, and P62. It follows that PAS-Na had an antagonistic effect on the activation of the above autophagy-related factors. Overall, our novel findings suggest that PAS-Na can protect the rat cortex from lead-induced toxicity by regulating autophagic processes. (1) Short-term lead exposure inhibits autophagy, whereas subchronic lead exposure promotes autophagy. (2) PAS-NA ameliorated the abnormal process of lead-induced autophagy, which had a protective effect on the cerebral cortex.

Ciliatoside A, isolated from Peristrophe japonica, inhibits HBsAg expression and cccDNA transcription by inducing autophagy

Hepatitis B surface antigen (HBsAg) loss and seroconversion are considered as an end point of a functional cure. Therefore, it is crucial to find new agents which could efficiently decrease HBsAg. Traditional herbal plants have been considered as an important source of new hepatitis B drugs development for their extensive use in antimicrobial and anti-inflammation. In this study, Peristrophe japonica, which could remarkably reduce HBsAg in the supernatant of HepG2.2.15 cells, was screened out for further extraction. Here, an active ethyl acetate fraction of Peristrophe japonica containing 34 sub-fractions was extracted. Subsequently, the monomeric compound Ciliatoside A was isolated and identified as a potential antiviral reagent with low cytotoxicity from Fraction 30. Ciliatoside A exhibited strong inhibition on intracellular and circulating HBsAg and HBV RNAs in HBV-infected cells and an HBV recombinant-cccDNA mouse model. The mechanistic study revealed that Ciliatoside A exhibited a potent anti-HBV effect through inducing autophagy-lysosomal pathway to autophagic degradation of HBc by activating AMPK-ULK1 axis and inhibiting mTOR activation. In summary, we have identified a novel antiviral compound Ciliatoside A isolated from Peristrophe japonica. This study may provide important direction and new ideas for the discovery of hepatitis B cure drugs.

Age-Related Decline in Nrf2/ARE Signaling Is Associated with the Mitochondrial DNA Damage and Cognitive Impairments

In this research, we compared the cognitive parameters of 2-, 7-, and 15-month-old mice, changes in mitochondrial DNA (mtDNA) integrity and expression of genes involved in the nuclear erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. We showed an age-related decrease in the Nfe2l2 expression in the cerebral cortex, not in the hippocampus. At the same time, we find an increase in the mtDNA copy number in the cerebral cortex, despite the lack of an increase in gene expression, which is involved in the mitochondrial biogenesis regulation. We suppose that increase in mtDNA content is associated with mitophagy downregulation. We supposed that mitophagy downregulation may be associated with an age-related increase in the mtDNA damage. In the hippocampus, we found a decrease in the Bdnf expression, which is involved in the pathways, which play an essential role in regulating long-term memory formation. We showed a deficit of working and reference memory in 15-month-old-mice in the water Morris maze, and a decrease in the exploratory behavior in the open field test. Cognitive impairments in 15-month-old mice correlated with a decrease in Bdnf expression in the hippocampus, Nfe2l2 expression, and an increase in the number of mtDNA damage in the cerebral cortex. Thus, these signaling pathways may be perspective targets for pharmacological intervention to maintain mitochondrial quality control, neuronal plasticity, and prevent the development of age-related cognitive impairment.

Arsenic Induces M2 Macrophage Polarization and Shifts M1/M2 Cytokine Production via Mitophagy

Arsenic is an environmental factor associated with epithelial-mesenchymal transition (EMT). Since macrophages play a crucial role in regulating EMT, we studied the effects of arsenic on macrophage polarization. We first determined the arsenic concentrations to be used by cell viability assays in conjunction with previous studies. In our results, arsenic treatment increased the alternatively activated (M2) macrophage markers, including arginase 1 (ARG-1) gene expression, chemokine (C-C motif) ligand 16 (CCL16), transforming growth factor-β1 (TGF-β1), and the cluster of differentiation 206 (CD206) surface marker. Arsenic-treated macrophages promoted A549 lung epithelial cell invasion and migration in a cell co-culture model and a 3D gel cell co-culture model, confirming that arsenic treatment promoted EMT in lung epithelial cells. We confirmed that arsenic induced autophagy/mitophagy by microtubule-associated protein 1 light-chain 3-II (LC3 II) and phosphor-Parkin (p-Parkin) protein markers. The autophagy inhibitor chloroquine (CQ) recovered the expression of the inducible nitric oxide synthase (iNOS) gene in arsenic-treated M1 macrophages, which represents a confirmation that arsenic indeed induced the repolarization of classically activated (M1) macrophage to M2 macrophages through the autophagy/mitophagy pathway. Next, we verified that arsenic increased M2 cell markers in mouse blood and lungs. This study suggests that mitophagy is involved in the arsenic-induced M1 macrophage switch to an M2-like phenotype.

Cinnamaldehyde regulates mitochondrial quality against hydrogen peroxide induced apoptosis in mouse lung mesenchymal stem cells via the PINK1/Parkin signaling pathway

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal respiratory disease without effective treatments. Mitochondrial dysfunction weakens the ability of mesenchymal stem cells (MSCs) to repair the distal lung epithelium, which is a probable pathogenesis of IPF. In previous research, we found that cinnamaldehyde (CA) can maintain the mitochondrial morphology of MSCs.

Methods

This present study evaluated the effect and mechanism of CA on murine lung MSCs using the hydrogen peroxide model. Antioxidant effects and mitochondrial function were determined using flow cytometry. The mRNA levels of mitochondrial dynamics and the expressions of autophagy-related proteins were also detected.

Results

CA can increase the levels of SOD, MMP and ATP, decrease the rate of ROS and apoptosis, and restore the mitochondrial structure. CA can also improve the mRNA expression of MFN1, MFN2, FIS1, DRP1, OPA1, and PGC-1α, increase the expression of LC3 II and p62 and promote the PINK1/Parkin signaling pathway. Our results demonstrated that CA can control mitochondrial quality and avoid apoptosis, which may be associated with the regulation of the PINK1/Parkin signaling pathway.

Role of mitophagy in the neurodegenerative diseases and its pharmacological advances: A review

Neurodegenerative diseases are a class of incurable and debilitating diseases characterized by progressive degeneration and death of cells in the central nervous system. They have multiple underlying mechanisms; however, they all share common degenerative features, such as mitochondrial dysfunction. According to recent studies, neurodegenerative diseases are associated with the accumulation of dysfunctional mitochondria. Selective autophagy of mitochondria, called mitophagy, can specifically degrade excess or dysfunctional mitochondria within cells. In this review, we highlight recent findings on the role of mitophagy in neurodegenerative disorders. Multiple studies were collected, including those related to the importance of mitochondria, the mechanism of mitophagy in protecting mitochondrial health, and canonical and non-canonical pathways in mitophagy. This review elucidated the important function of mitophagy in neurodegenerative diseases, discussed the research progress of mitophagy in neurodegenerative diseases, and summarized the role of mitophagy-related proteins in neurological diseases. In addition, we also highlight pharmacological advances in neurodegeneration.

Targeting of the Mitochondrial TET1 Protein by Pyrrolo[3,2-b]pyrrole Chelators

Targeting of epigenetic mechanisms, such as the hydroxymethylation of DNA, has been intensively studied, with respect to the treatment of many serious pathologies, including oncological disorders. Recent studies demonstrated that promising therapeutic strategies could potentially be based on the inhibition of the TET1 protein (ten-eleven translocation methylcytosine dioxygenase 1) by specific iron chelators. Therefore, in the present work, we prepared a series of pyrrolopyrrole derivatives with hydrazide (1) or hydrazone (2–6) iron-binding groups. As a result, we determined that the basic pyrrolo[3,2-b]pyrrole derivative 1 was a strong inhibitor of the TET1 protein (IC₅₀ = 1.33 μM), supported by microscale thermophoresis and molecular docking. Pyrrolo[3,2-b]pyrroles 2–6, bearing substituted 2-hydroxybenzylidene moieties, displayed no significant inhibitory activity. In addition, in vitro studies demonstrated that derivative 1 exhibits potent anticancer activity and an exclusive mitochondrial localization, confirmed by Pearson’s correlation coefficient of 0.92.

Zhen-Wu-Tang Induced Mitophagy to Protect Mitochondrial Function in Chronic Glomerulonephritis via PI3K/AKT/mTOR and AMPK Pathways

Chronic glomerulonephritis (CGN) is one of the major causes of end-stage kidney disease. Zhen-wu-tang (ZWT), as a famous Chinese herbal prescription, is widely used in China for CGN therapy in clinic. However, the mechanism of ZWT in CGN has not been fully understood. The present study explored the therapeutic effect and the underlying mechanism of ZWT on mitochondrial function in cationic bovine serum albumin (C-BSA)-induced CGN model rats and tumor necrosis factor (TNF-α)-damaged mouse podocytes. The renal functions were measured by serum creatinine (Scr) and blood urea nitrogen (BUN). Renal pathological changes and ultrastructure of kidney tissues were evaluated by periodic acid-Schiff (PAS) staining and transmission electron microscopy. The levels of antioxidases, including mitochondrial catalase (CAT), superoxide dismutase 2 (SOD2), and peroxiredoxin 3 (PRDX3), in CGN rats were examined by real-time PCR. The mitochondrial functions of podocytes were measured by ATP concentration, mitochondrial membrane potential (MMP), and mitochondrial ROS (mtROS). For mitophagy level detection, the expressions of mitophagy-related proteins, including LC3, p62, heat shock protein 60 (HSP60), and translocase of outer mitochondrial membrane 20 (TOMM20), were measured by Western blot, as the colocation of LC3 and mitochondrial marker COX IV were evaluated by immunofluorescence. Our results manifested that ZWT ameliorated CGN model rats by a remarkable decrease in Scr and BUN, inhibition of mesangial matrix proliferation, protection against foot processes fusion, and basement membrane thickening. More importantly, ZWT protected against mitochondrial dysfunction by increasing the expressions of CAT, SOD2, and PRDX3 in CGN model rats, increased ATP content and MMP in podocytes, and decreased excessive mtROS. Furthermore, ZWT induced mitophagy in CGN through increasing the expression of LC3, and decreasing p62, HSP60, TOMM20, and ZWT also enhanced the colocation of LC3 to the mitochondria. We found that ZWT inhibited the PI3K/AKT/mTOR pathway, which could be disturbed by PI3K inhibitor LY294002 and agonist insulin-like growth factor 1. Moreover, ZWT reversed the inhibition of the AMPK pathway in CGN. Overall, ZWT ameliorated renal mitochondrial dysfunction probably by inducing mitophagy via the PI3K/AKT/mTOR and AMPK pathways.

BAG2 prevents Tau hyperphosphorylation and increases p62/SQSTM1 in cell models of neurodegeneration

BACKGROUND

Protein aggregates are pathological hallmarks of many neurodegenerative diseases, however the physiopathological role of these aggregates is not fully understood. Protein quality control has a pivotal role for protein homeostasis and depends on specific chaperones. The co-chaperone BAG2 can target phosphorylated Tau for degradation by an ubiquitin-independent pathway, although its possible role in autophagy was not yet elucidated. In view of this, the aim of the present study was to investigate the association among protein aggregation, autophagy and BAG2 levels in cultured cells from hippocampus and locus coeruleus as well as in SH-SY5Y cell line upon different protein aggregation scenarios induced by rotenone, which is a flavonoid used as pesticide and triggers neurodegeneration.

METHODS AND RESULTS

The present study showed that rotenone exposure at 0.3 nM for 48 h impaired autophagy prior to Tau phosphorylation at Ser199/202 in hippocampus but not in locus coeruleus cells, suggesting that distinct neuron cells respond differently to rotenone toxicity. Rotenone induced Tau phosphorylation at Ser199/202, together with a decrease in the endogenous BAG2 protein levels in SH-SY5Y and hippocampus cell culture, which indicates that rotenone and Tau hyperphosphorylation can affect this co-chaperone. Finally, it has been shown that BAG2 overexpression, increased p62/SQSTM1 levels in cells from hippocampus and locus coeruleus, stimulated LC3II recycling as well as prevented the raise of phosphorylated Tau at Ser199/202 in hippocampus.

CONCLUSIONS

Results demonstrate a possible role for BAG2 in degradation pathways of specific substrates and its importance for the study of cellular aspects of neurodegenerative diseases.

Expression Pattern of p62 in Primary Age-Related Tauopathy: Staging of p62 in PART

The present study analyzed the distribution pattern of p62 immunoreactivity in brains of primary age-related tauopathy (PART) and Braak NFT matched pre-AD and Alzheimer’s disease (AD) patients using immunohistochemistry in combination with semi-quantitative evaluation. In PART and AD brains, p62 was found positive in seven regions, including the neocortex, thalamus, basal ganglia, hippocampus, brainstem, cerebellar dentate nucleus, and the cervical spinal cord. There was a positive correlation between the Braak NFT stage and the distribution of p62 expression. Six stages of expression of p62 were proposed from the present study. Expression of p62 in the hippocampus of PART and AD was classified stage I, the brainstem stage II, the thalamus stage I _I _I, the basal ganglia stage IV, the neocortex stage V, the cerebellum and the cervical spinal cord stage VI. The hippocampus was the site initially affected by p62, especially the CA1 and the subiculum. They might be the earliest accumulation site of p62.

The different autophagy degradation pathways and neurodegeneration

The term autophagy encompasses different pathways that route cytoplasmic material to lysosomes for degradation and includes macroautophagy, chaperone-mediated autophagy, and microautophagy. Since these pathways are crucial for degradation of aggregate-prone proteins and dysfunctional organelles such as mitochondria, they help to maintain cellular homeostasis. As post-mitotic neurons cannot dilute unwanted protein and organelle accumulation by cell division, the nervous system is particularly dependent on autophagic pathways. This dependence may be a vulnerability as people age and these processes become less effective in the brain. Here, we will review how the different autophagic pathways may protect against neurodegeneration, giving examples of both polygenic and monogenic diseases. We have considered how autophagy may have roles in normal CNS functions and the relationships between these degradative pathways and different types of programmed cell death. Finally, we will provide an overview of recently described strategies for upregulating autophagic pathways for therapeutic purposes.

Multiplexed Delivery of Synthetic (Un)Conjugatable Ubiquitin and SUMO2 Enables Simultaneous Monitoring of their Localization and Function in Live Cells

Ubiquitin (Ub) and its related small Ub like modifier (SUMO) are among the most influential protein post‐translational modifications in eukaryotes. Unfortunately, visualizing these modifications in live cells is a challenging task. Chemical protein synthesis offers great opportunities in studying and further understanding Ub and SUMO biology. Nevertheless, the low cell permeability of proteins limits these studies mainly for in vitro applications. Here, we introduce a multiplexed protein cell delivery approach, termed MBL (multiplexed bead loading), for simultaneous loading of up to four differentially labeled proteins with organic fluorophores. We applied MBL to visualize ubiquitination and SUMOylation events in live and untransfected cells without fluorescent protein tags or perturbation to their endogenous levels. Our study reveals unprecedented involvements of Ub and SUMO2 in lysosomes depending on conjugation states. We envision that this approach will improve our understanding of dynamic cellular processes such as formation and disassembly of membraneless organelles.

Targeting PLD2 in adipocytes augments adaptive thermogenesis by improving mitochondrial quality and quantity in mice

Phospholipase D (PLD)2 via its enzymatic activity regulates cell proliferation and migration and thus is implicated in cancer. However, the role of PLD2 in obesity and type 2 diabetes has not previously been investigated. Here, we show that during diet-induced thermogenesis and obesity, levels of PLD2 but not PLD1 in adipose tissue are inversely related with uncoupling protein 1, a key thermogenic protein. We demonstrate that the thermogenic program in adipose tissue is significantly augmented in mice with adipocyte-specific Pld2 deletion or treated with a PLD2-specific inhibitor and that these mice are resistant to high fat diet–induced obesity, glucose intolerance, and insulin resistance. Mechanistically, we show that Pld2 deletion in adipose tissue or PLD2 pharmacoinhibition acts via p62 to improve mitochondrial quality and quantity in adipocytes. Thus, PLD2 inhibition is an attractive therapeutic approach for obesity and type 2 diabetes by resolving defects in diet-induced thermogenesis.

Arsenic causes mitochondrial biogenesis obstacles by inhibiting the AMPK/PGC-1α signaling pathway and also induces apoptosis and dysregulated mitophagy in the duck liver

Arsenic is a dangerous metalloid-material which is known to cause liver injury in many animals and humans. However, little is known about the underlying mechanism of arsenic-induced hepatotoxicity in poultry. This study was executed to systematically investigate the potential role of mitochondrial biogenesis, mitophagy and apoptosis in duck hepatotoxicity caused by arsenic. Results showed that the body weight and liver coefficient of duck had distinct changed after arsenic-exposure, and the arsenic content in serum and liver also increased significantly in a dose-dependent manner. Meanwhile, histopathological examination and metabolomics results showed that arsenic-exposure caused severe steatosis and metabolism disorder in liver tissues. Furthermore, arsenic-exposure significantly inhibited AMPK/PGC-1α-mediated mitochondrial biogenesis, determined by the ultrastructure observation and down-regulation of p-AMPKα/AMPKα, PGC-1α, NRF1, NRF2, TFAM, TFB1M, TFB2M and COX-Ⅳ expression levels. Besides, arsenic-treatment obviously increased the levels of mitophagy (PINK1, Parkin, LC3, P62) and pro-apoptotic (Caspase-3, Caspase-9, Cleaved Caspase-3, Cytc, Bax, P53) indexes, and simultaneously resulted in reductions in anti-apoptosis index (Bcl-2). Overall, our findings provided evidences that arsenic-induced duck hepatotoxicity may be caused by a combination of impaired mitochondrial biosynthesis, mitophagy, and mitochondrial-dependent apoptosis. To our knowledge, this is the first report to systematically investigate the potential mechanism of arsenic-induced hepatotoxicity in poultry.

Does Data-Independent Acquisition Data Contain Hidden Gems? A Case Study Related to Alzheimer's Disease

One of the potential benefits of using data-independent acquisition (DIA) proteomics protocols is that information not originally targeted by the study may be present and discovered by subsequent analysis. Herein, we reanalyzed DIA data originally recorded for global proteomic analysis to look for isomerized peptides, which occur as a result of spontaneous chemical modifications to long-lived proteins. Examination of a large set of human brain samples revealed a striking relationship between Alzheimer's disease (AD) status and isomerization of aspartic acid in a peptide from tau. Relative to controls, a surprising increase in isomer abundance was found in both autosomal dominant and sporadic AD samples. To explore potential mechanisms that might account for these observations, quantitative analysis of proteins related to isomerization repair and autophagy was performed. Differences consistent with reduced autophagic flux in AD-related samples relative to controls were found for numerous proteins, including most notably p62, a recognized indicator of autophagic inhibition. These results suggest, but do not conclusively demonstrate, that lower autophagic flux may be strongly associated with loss of function in AD brains. This study illustrates that DIA data may contain unforeseen results of interest and may be particularly useful for pilot studies investigating new research directions. In this case, a promising target for future investigations into the therapy and prevention of AD has been identified.

Discovery of bletillain, an unusual benzyl polymer with significant autophagy-inducing effects in A549 lung cancer cells through the Akt/GSK-3β/β-catenin signaling pathway

Lung cancer is one of the most malignant tumors with the highest mortality and morbidity. The tubers of Bletilla striata are known as "an excellent medicine for lung diseases" in traditional Chinese medicine. This study performed a targeted study to explore compounds with anti-lung cancer activity and the molecular mechanisms using A549 cells. Eighteen bibenzyl derivatives, including four new compounds (13, 14, 16, and 18), were isolated from the tubers of B. striata. Analysis of the structure-activity relationship indicated that the cytotoxicity of the bibenzyls against A549 cells increased gradually as the number of the benzyl groups in the structures increased. Bletillain (18), an unusual benzyl polymer, was found to be the most active compound. Further flow cytometric analysis, dual-luciferase assays, real-time PCR assays, and western blot assays revealed that bletillain induced autophagy in A549 cells by regulating the Akt/GSK-3β/β-catenin signaling pathway. Beclin 1, LC3, and p62 are downstream autophagy factors of Akt, and Beclin 1 was the key autophagy factor. These results suggested that bibenzyls of B. striata play important roles in the treatment of lung cancer and provided scientific evidence illustrating why the tubers of B. striata are a suitable medicine for the treatment of lung cancer in traditional Chinese medicine.

P62 accumulates through neuroanatomical circuits in response to tauopathy propagation

In Alzheimer's disease and related tauopathies, trans-synaptic transfer and accumulation of pathological tau from donor to recipient neurons is thought to contribute to disease progression, but the underlying mechanisms are poorly understood. Using complementary in vivo and in vitro models, we examined the relationship between these two processes and neuronal clearance. Accumulation of p62 (a marker of defective protein clearance) correlated with pathological tau accumulation in two mouse models of tauopathy spread; Entorhinal Cortex-tau (EC-Tau) mice where tau pathology progresses in time from EC to other brain regions, and PS19 mice injected with tau seeds. In both models and in several brain regions, p62 colocalized with human tau in a pathological conformation (MC1 antibody). In EC-Tau mice, p62 accumulated before overt tau pathology had developed and was associated with the presence of aggregation-competent tau seeds identified using a FRET-based assay. Furthermore, p62 accumulated in the cytoplasm of neurons in the dentate gyrus of EC-Tau mice prior to the appearance of MC1 positive tauopathy. However, MC1 positive tau was shown to be present at the synapse and to colocalize with p62 as shown by immuno electron microscopy. In vitro, p62 colocalized with tau inclusions in two primary cortical neuron models of tau pathology. In a three-chamber microfluidic device containing neurons overexpressing fluorescent tau, seeding of tau in the donor chamber led to tau pathology spread and p62 accumulation in both the donor and the recipient chamber. Overall, these data are in accordance with the hypothesis that the accumulation and trans-synaptic spread of pathological tau disrupts clearance mechanisms, preceding the appearance of obvious tau aggregation. A vicious cycle of tau accumulation and clearance deficit would be expected to feed-forward and exacerbate disease progression across neuronal circuits in human tauopathies.

Prompt Graft Cooling Enhances Cardioprotection during Heart Transplantation Procedures through the Regulation of Mitophagy

A complete and prompt cardiac arrest using a cold cardioplegic solution is routinely used in heart transplantation to protect the graft function. However, warm ischemic time is still inevitable during the procedure to isolate donor hearts in the clinical setting. Our knowledge of the mechanism changes prevented by cold storage, and how warm ischemia damages donor hearts, is extremely poor. The potential consequences of this inevitable warm ischemic time to grafts, and the underlying potential protective mechanism of prompt graft cooling, have been studied in order to explore an advanced graft protection strategy. To this end, a surgical procedure, including 10-15 min warm ischemic time during procurement, was performed in mouse models to mimic the clinical situation (Group I), and compared to a group of mice that had the procurement performed with prompt cooling procedures (Group II). The myocardial morphologic changes (including ultrastructure) were then assessed by electron and optical microscopy after 6 h of cold preservation. Furthermore, syngeneic heart transplantation was performed after 6 h of cold preservation to measure the graft heart function. An electron microscopy showed extensive damage, including hypercontracted myofibers with contraction bands, and damaged mitochondria that released mitochondrial contents in Group I mice, while similar patterns of damage were not observed in the mice from Group II. The results from both the electron microscopy and immunoblotting verified that cardiac mitophagy (protective mitochondrial autophagy) was present in the mice from Group II, but was absent in the mice from Group I. Moreover, the mice from Group II demonstrated faster rebeating times and higher beating scores, as compared to the mice from Group I. The pressure catheter system results indicated that the graft heart function was significantly more improved in the mice from Group II than in those from Group I, as demonstrated by the left ventricle systolic pressure (31.96 ± 6.54 vs. 26.12 ± 8.87 mmHg), the +dp/dt (815.6 ± 215.4 vs. 693.9 ± 153.8 mmHg/s), and the -dp/dt: (492.4 ± 92.98 vs. 418.5 ± 118.9 mmHg/s). In conclusion, the warm ischemic time during the procedure impaired the graft function and destroyed the activation of mitophagy. Thus, appropriate mitophagy activation has emerged as a promising therapeutic target that may be essential for graft protection and functional improvement during heart transplantation.

Age-related mitochondrial alterations in brain and skeletal muscle of the YAC128 model of Huntington disease

Mitochondrial dysfunction and bioenergetics failure are common pathological hallmarks in Huntington's disease (HD) and aging. In the present study, we used the YAC128 murine model of HD to examine the effects of mutant huntingtin on mitochondrial parameters related to aging in brain and skeletal muscle. We have conducted a cross-sectional natural history study of mitochondrial DNA changes in the YAC128 mouse. Here, we first show that the mitochondrial volume fraction appears to increase in the axons and dendrite regions adjacent to the striatal neuron cell bodies in old mice. Mitochondrial DNA copy number (mtDNAcn) was used as a proxy measure for mitochondrial biogenesis and function. We observed that the mtDNAcn changes significantly with age and genotype in a tissue-specific manner. We found a positive correlation between aging and the mtDNAcn in striatum and skeletal muscle but not in cortex. Notably, the YAC128 mice had lower mtDNAcn in cortex and skeletal muscle. We further show that mtDNA deletions are present in striatal and skeletal muscle tissue in both young and aged YAC128 and WT mice. Tracking gene expression levels cross-sectionally in mice allowed us to identify contributions of age and genotype to transcriptional variance in mitochondria-related genes. These findings provide insights into the role of mitochondrial dynamics in HD pathogenesis in both brain and skeletal muscle, and suggest that mtDNAcn in skeletal muscle tissue may be a potential biomarker that should be investigated further in human HD.

Azidothymidine Downregulates Insulin-Like Growth Factor-1 Induced Lipogenesis by Suppressing Mitochondrial Biogenesis and Mitophagy in Immortalized Human Sebocytes

Background

Increased sebum secretion is considered the main causative factor in the pathogenesis of acne. There is an unmet pharmacological need for a novel drug that can control sebum production with a favorable adverse effect profile.

Objective

To investigate the effect of azidothymidine on lipid synthesis in sebocytes and to identify the underlying mechanism of the inhibitory effect of azidothymidine on insulinlike growth factor (IGF)-1-induced lipid synthesis in sebocytes.

Methods

Immortalized human sebocytes were used for the analysis. Thin-layer chromatography (TLC) and Oil Red O staining were performed to evaluate lipid synthesis in the sebocytes. The differentiation, lipid synthesis, mitochondrial biogenesis, and mitophagy in sebocytes were investigated.

Results

TLC and Oil Red O staining revealed that azidothymidine reduced IGF-1 induced lipid synthesis in the immortalized human sebocytes. Azidothymidine also reduced IGF-1-induced expression of transcriptional factors and enzymes involved in sebocyte differentiation and lipid synthesis, respectively. Moreover, we found that IGF-1 upregulated the levels of peroxisome proliferator-activated receptorgamma coactivator-1α, LC-3B, p62, and Parkin, major regulators of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. In contrast, azidothymidine inhibited IGF-1 induced mitochondrial biogenesis and mitophagy in the sebocytes.

Conclusion

These results suggest that azidothymidine downregulates IGF-1-induced lipogenesis by dysregulating the quality of mitochondria through suppression of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. Our study provides early evidence that azidothymidine may be an effective candidate for a new pharmacological agent for controlling lipogenesis in sebocytes.

RETRACTED: MicroRNA-16-5p/BTG2 axis affects neurological function, autophagy and apoptosis of hippocampal neurons in Alzheimer's disease

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief as there are concerns about the reliability of the results. Concerns have been raised about the western blot bands in Figures 6 B + D having the same eyebrow shaped phenotype as found in many other publications as detailed here (https://pubpeer.com/publications/B32F93859FBAA13471ED0FFCA5BCB6). The journal requested the corresponding author to comment on these concerns and send the raw data, however the author was not able to provide uncropped images of the original gels. The Editor-in-Chief therefore no longer has confidence in the data and conclusions of this study.

Korean red ginseng decreases 1-methyl-4-phenylpyridinium-induced mitophagy in SH-SY5Y cells

OBJECTIVE

Mitophagy is known to contribute towards progression of Parkinson's disease. Korean red ginseng (KRG) is a widely used medicinal herb in East Asia, and recent studies have reported that KRG prevents 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced cell death. This study was undertaken to investigate whether KRG suppresses MPP⁺-induced apoptosis and mitophagy.

METHODS

SH-SY5Y cells were incubated with KRG for 24 h, and subsequently exposed to MPP⁺. The MPP⁺-induced cell death was confirmed with the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay. Changes in the structure and function of mitochondria were confirmed using mitotracker, MitoSOX red mitochondrial superoxide indicator, parkin, and phosphatase and tensin homolog deleted on chromosome ten-induced putative kinase 1 (PINK1) immunofluorescent staining. Western blotting was performed to evaluate the expression of apoptosis-related factors in whole cells, including Bax, Bcl-2 and cleaved caspase-3, and mitophagy-related factors in the mitochondrial fraction, including cytochrome c, parkin, PINK1, translocase of the outer membrane 20 (TOM20), p62 and Beclin 1.

RESULTS

MPP⁺ induced cell death by cytochrome c release and caspase-3 activation; however, this effect was suppressed by KRG's regulation of the expressions of Bcl-2 and Bax. Moreover, MPP⁺ exposure increased the mitochondrial expressions of parkin, PINK1, Beclin 1 and p62, and decreased TOM20, cytochrome c and Bcl-2 expressions. These MPP⁺-induced changes in the mitochondrial fraction were attenuated by treatment with KRG.

CONCLUSION

KRG effectively prevents MPP⁺-induced SH-SY5Y cell death by regulating cytochrome c release from mitochondria and PINK1/parkin-mediated mitophagy, through regulation of the Bcl-2 family.

Selenium triggers Nrf2-AMPK crosstalk to alleviate cadmium-induced autophagy in rabbit cerebrum

Cadmium (Cd) is a toxic heavy metal that accumulates in the brain and causes a series of histopathological changes. Selenium (Se) exerts a crucial function in protecting damage caused by toxic heavy metals, but its potential mechanism is rarely studied. The main purpose of this study is to explore the protective effects of Se on Cd-induced oxidative stress and autophagy in rabbit cerebrum. Forty rabbits were randomly divided into four groups and treated as follows: Control group, Cd (1 mg/kg⋅BW) group, Se (0.5 mg/kg⋅BW) group and Cd (1 mg/kg⋅BW)+Se (0.5 mg/kg⋅BW) group, with 30 days feeding management. Our results suggested that Se treatment significantly suppressed the Cd-induced degenerative changes including cell necrosis, vacuolization, and atrophic neurons. In addition, Se decreased the contents of MDA and H₂O₂ and increased the activities of CAT, SOD, GST, GSH and GSH-Px, alleviating the imbalance of the redox system induced by Cd. Furthermore, Cd caused the up-regulation of the mRNA levels of autophagy-related genes (ATG3, ATG5, ATG7, ATG12 and p62), AMPK (Prkaa1, Prkaa2, Prkab1, Prkab2, Prkag2, Prkag3) and Nrf2 (Nrf2, HO-1 and NQO1) signaling pathway, and the expression levels of LC3II/LC3I, p-AMPK/AMPK, Beclin-1, Nrf2 and HO-1 proteins, which were alleviated by Se, indicated that Se inhibited Cd-induced autophagy and Nrf2 signaling pathway activation. In conclusion, our study found that Se antagonized Cd-induced oxidative stress and autophagy in the brain by generating crosstalk between AMPK and Nrf2 signaling pathway.

Whole Cigarette Smoke Condensates Induce Accumulation of Amyloid Beta Precursor Protein with Oxidative Stress in Murine Astrocytes

Although cigarette smoking has been postulated to be a potential risk factor for Alzheimer's disease (AD), the toxic mechanism is still unclear. Additionally, astrocytes have been identified as a potential target, given they play multiple roles in maintaining normal brain function. In this study, we explored the toxic mechanism of whole cigarette smoke condensates (WCSC) using murine astrocytes. Cell proliferation, the percentage of cells in the G2/M phase, and LDH concentrations in the cell supernatants were all reduced in WCSC-treated cells. In addition, oxidative stress was induced, together with shortening of processes, structural damage of organelles, disturbances in mitochondrial function, blockage of autophagic signals, accumulation of amyloid β precursor protein, and loss of chemotactic functions. Based on these results, we hypothesize that dysfunction of astrocytes may contribute to the occurrence of cigarette-smoking-induced AD.

Do naturally occurring antioxidants protect against neurodegeneration of the dopaminergic system? A systematic revision in animal models of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by a significant decrease in dopamine levels, caused by progressive degeneration of the dopaminergic neurons in the nigrostriatal pathway. Multiple mechanisms have been implicated in its pathogenesis, including oxidative stress, neuroinflammation, protein aggregation, mitochondrial dysfunction, insufficient support for neurotrophic factors and cell apoptosis. The absence of treatments capable of slowing or stopping the progression of PD has increased the interest in the natural antioxidant substances present in the diet, since they have multiple beneficial properties and it is possible that they can influence the mechanisms responsible for the dysfunction and death of dopaminergic neurons. Thus, the purpose of this systematic review is to analyze the results obtained in a set of studies carried out in the last years, which describe the neuroprotective, antioxidant and regenerative functions of some naturally occurring antioxidants in experimental models of PD. The results show that the exogenous no enzymatic antioxidants can significantly modify the biochemical and behavioral mechanisms that contribute to the pathophysiology of Parkinsonism in experimental animals. Therefore, it is possible that they may contribute to effective neuroprotection by providing a significant improvement in neuropathological markers. In conclusion, the results of this review suggest that exogenous antioxidants can be promising therapeutic candidates for the prevention and treatment of PD.

ONX0912, a selective oral proteasome inhibitor, triggering mitochondrial apoptosis and mitophagy in liver cancer

Proteasome inhibitors represent effective anti-tumor drugs. ONX0912 is a novel oral proteasome inhibitor that selectively targets the chymotrypsin-like activity of 20S proteasome subunits β5 and LMP7 （Low molecular mass polypeptide-7）. It has been shown to be effective in hematologic malignancies. However, its anti-tumor effect in solid tumors remains unclear. Here, we discovered that ONX0912 suppressed the expansion of liver cancer cells. ONX0912 treatment led to an increased level of mitochondrial membrane potential collapse and mitochondrial ROS in tumor cells in a concentration- and exposure time-dependent manner, indicating ONX0912 triggers apoptosis through the intrinsic mitochondrial pathway. ONX0912 also induced mitophagy by activating Parkin/Pink pathway. Silencing mitophagy receptor protein, p62, aggravated the ONX0912-mediated apoptosis, which implied a new mechanism for the conversion between autophagy and apoptosis. Furthermore, we found that the ONX0912 target protein, LMP7 was overexpressed in liver cancer tissues compared to their adjacent tissues and increased level of LMP7 predicted worse clinical characteristics and poorer prognosis. In conclusion, we demonstrated that ONX0912 suppressed liver cancer cell expansion by inducing apoptosis and mitophagy. Our data also revealed ONX0912 as a potential clinical therapeutic drug for liver cancer therapy, and inhibition of mitophagy may sensitize the anti-tumor effect of ONX0912.

Role of neddylation in neurological development and diseases

Neddylation, a posttranslational protein modification, refers to the specific conjugation of NEDD8 to substrates, which is of great significance to various biological processes. Besides members of the cullin protein family, other key proteins can act as a substrate for neddylation modification, which remarkably influences neurodevelopment and neurodegenerative diseases. Normal levels of protein neddylation contribute to nerve growth, synapse strength, neurotransmission, and synaptic plasticity, whereas overactivation of protein neddylation pathways lead to apoptosis, autophagy of neurons, and tumorigenesis. Furthermore, impaired neddylation causes neurodegenerative diseases. These facts suggest that neddylation may be a target for treatment of these diseases. This review focuses on the current understanding of neddylation function in neurodevelopment as well as neurodegenerative diseases. Meanwhile, the recent view that different level of neddylation pathway may contribute to the opposing disease progression, such as neoplasms and Alzheimer's disease, is discussed. The review also discusses neddylation inhibitors, which are currently being tested in clinical trials. However, potential drawbacks of these drugs are noted, which may benefit the development of new pharmaceutical strategies in the treatment of nervous system diseases.

Downregulation of metabotropic glutamate receptor 5 alleviates central sensitization by activating autophagy via inhibiting mTOR pathway in a rat model of chronic migraine

Central sensitization is one of the important pathological mechanisms of chronic migraine (CM). Metabolic glutamate receptor 5 (mGluR5) mediates pain by activating various intracellular pathways. However, whether mGluR5 contributes to central sensitization in CM and the exact mechanism remains unclear. Male rats were used to establish a CM model by repeated infusions of inflammatory soup (IS) for 7 days to stimulate the activation of the dural nociceptor. The mechanical and thermal thresholds were used to evaluate allodynia, and central sensitization was assessed by measuring calcitonin gene-related peptide (CGRP) and substance P (SP). Microtubule associated protein 1 light chain 3 (LC3) and p62/SQSTM1 were used to assess autophagy. We found that the expression of mGluR5 in the trigeminal nucleus caudalis (TNC) of CM rats was significantly increased. In addition, the downregulation of mGluR5 activated autophagy by inhibiting the mTOR pathway. Moreover, the activation of autophagy alleviated allodynia and central sensitization in CM rats. This study identified a novel strategy for the treatment of CM; the downregulation of mGluR5 in a rat model of CM decreased the expression of the inflammatory factor interleukin-1 beta (IL-1β) and the central sensitization-associated proteins CGRP and SP by activating autophagy via inhibiting the mTOR pathway.

Mitophagy and the Brain

Stress mechanisms have long been associated with neuronal loss and neurodegenerative diseases. The origin of cell stress and neuronal loss likely stems from multiple pathways. These include (but are not limited to) bioenergetic failure, neuroinflammation, and loss of proteostasis. Cells have adapted compensatory mechanisms to overcome stress and circumvent death. One mechanism is mitophagy. Mitophagy is a form of macroautophagy, were mitochondria and their contents are ubiquitinated, engulfed, and removed through lysosome degradation. Recent studies have implicated mitophagy dysregulation in several neurodegenerative diseases and clinical trials are underway which target mitophagy pathways. Here we review mitophagy pathways, the role of mitophagy in neurodegeneration, potential therapeutics, and the need for further study.

DJ-1 Regulates Microglial Polarization Through P62-Mediated TRAF6/IRF5 Signaling in Cerebral Ischemia-Reperfusion

The polarization of microglia/macrophage, the resident immune cells in the brain, plays an important role in the injury and repair associated with ischemia-reperfusion (I/R). Previous studies have shown that DJ-1 has a protective effect in cerebral I/R. We found that DJ-1 regulates the polarization of microglial cells/macrophages after cerebral I/R and explored the mechanism by which DJ-1 mediates microglial/macrophage polarization in cerebral I/R. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen and glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral I/R in vivo and in vitro, respectively. DJ-1 siRNA and the DJ-1-based polypeptide ND13 were used to produce an effect on DJ-1, and the P62-specific inhibitor XRK3F2 was used to block the effect of P62. Enhancing the expression of DJ-1 induced anti-inflammatory (M2) polarization of microglia/macrophage, and the expression of the anti-inflammatory factors IL-10 and IL-4 increased. Interference with DJ-1 expression induced pro-inflammatory (M1) polarization of microglia/macrophage, and the expression of the proinflammatory factors TNF-α and IL-1β increased. DJ-1 inhibited the expression of P62, impeded the interaction between P62 and TRAF6, and blocked nuclear entry of IRF5. In subsequent experiments, XRK3F2 synergistically promoted the effect of DJ-1 on microglial/macrophage polarization, further attenuating the interaction between P62 and TRAF6.