Enhanced Mitophagy Activity in Prion-Infected Cultured Cells and Prion-Infected Experimental Mice via a Pink1/Parkin-Dependent Mitophagy Pathway

Mitochondrial tRNAGlu 14693A > G Mutation, an "Enhancer" to the Phenotypic Expression of Leber's Hereditary Optic Neuropathy

Leber's hereditary optic neuropathy (LHON), a maternally inherited ocular disease, is predominantly caused by mitochondrial DNA (mtDNA) mutations. Mitochondrial tRNA variants are hypothesized to amplify the pathogenic impact of three primary mutations. However, the exact mechanisms remained unclear. In the present study, the synergistic effect of the tRNAGlu 14693A > G and ND6 14484T > C mutations in three Chinese families affected by LHON is investigated. The m.14693A > G mutation nearly abolishes the pseudouridinylation at position 55 of tRNAGlu, leading to structural abnormalities, decreased stability, aberrant mitochondrial protein synthesis, and increased autophagy. In contrast, the ND6 14484T > C mutation predominantly impairs complex I function, resulting in heightened apoptosis and virtually no induction of mitochondrial autophagy compared to control cell lines. The presence of dual mutations in the same cell lines exhibited a coexistence of both upregulated cellular stress responses to mitochondrial damage, indicating a scenario of autophagy and mutation dysregulation within these dual-mutant cell lines. The data proposes a novel hypothesis that mitochondrial tRNA gene mutations generally lead to increased mitochondrial autophagy, while mutations in genes encoding mitochondrial proteins typically induce apoptosis, shedding light on the intricate interplay between different genetic factors in the manifestation of LHON.

Non-cytopathic bovine viral diarrhea virus (BVDV) inhibits innate immune responses via induction of mitophagy

Bovine viral diarrhea virus (BVDV) belongs to the genus Pestivirus within the family Flaviviridae. Mitophagy plays important roles in virus-host interactions. Here, we provide evidence that non-cytopathic (NCP) BVDV shifts the balance of mitochondrial dynamics toward fission and induces mitophagy to inhibit innate immune responses. Mechanistically, NCP BVDV triggers the translocation of dynamin-related protein (Drp1) to mitochondria and stimulates its phosphorylation at Ser616, leading to mitochondrial fission. In parallel, NCP BVDV-induced complete mitophagy via Parkin-dependent pathway contributes to eliminating damaged mitochondria to inhibit MAVS- and mtDNA-cGAS-mediated innate immunity responses, mtROS-mediated inflammatory responses and apoptosis initiation. Importantly, we demonstrate that the LIR motif of ERNS is essential for mitophagy induction. In conclusion, this study is the first to show that NCP BVDV-induced mitophagy plays a central role in promoting cell survival and inhibiting innate immune responses in vitro.

The PINK1/Parkin pathway of mitophagy exerts a protective effect during prion disease

The PINK1/Parkin pathway of mitophagy has been implicated in the pathogenesis of Parkinson's disease. In prion diseases, a transmissible neurodegenerative disease caused by the misfolded and infectious prion protein (PrPSc), expression of both PINK1 and Parkin are elevated, suggesting that PINK1/Parkin mediated mitophagy may also play a role in prion pathogenesis. Using mice in which expression of either PINK1 (PINK1KO) or Parkin (ParkinKO) has been ablated, we analyzed the potential role of PINK1 and Parkin in prion pathogenesis. Prion infected PINK1KO and ParkinKO mice succumbed to disease more rapidly (153 and 150 days, respectively) than wild-type control C57Bl/6 mice (161 days). Faster incubation times in PINK1KO and ParkinKO mice did not correlate with altered prion pathology in the brain, altered expression of proteins associated with mitochondrial dynamics, or prion-related changes in mitochondrial respiration. However, the expression level of mitochondrial respiration Complex I, a major site for the formation of reactive oxygen species (ROS), was higher in prion infected PINK1KO and ParkinKO mice when compared to prion infected control mice. Our results demonstrate a protective role for PINK1/Parkin mitophagy during prion disease, likely by helping to minimize ROS formation via Complex I, leading to slower prion disease progression.

Review of PINK1-Parkin-mediated mitochondrial autophagy in Alzheimer's disease

Mitochondrial autophagy plays an important role in maintaining the complexity of mitochondrial functions and removing damaged mitochondria, of which the PINK1-Parkin signal pathway is one of the most classical pathways. Thus, a comprehensive and in-depth interpretation of the PINK1-Parkin signal pathway might deepen our understanding on the impacts of mitochondrial autophagy. Alzheimer's disease (AD) is a classical example of neurodegenerative disease. Research on the pathogenesis and treatments of AD has been a focus of scientific research because of its complexity and the limitations of current drug therapies. It was reported that the pathogenesis of AD might be related to mitochondrial autophagy due to excessive deposition of Aβ protein and aggravation of the phosphorylation of Tau protein. Two key proteins in the PINK1-Parkin signaling pathway, PINK1 and Parkin, have important roles in the folding and accumulation of Aβ protein and the phosphorylation of Tau protein. In addition, the intermediate signal molecules in the PINK1-Parkin signal pathway also have certain effects on AD. In this paper, we first described the role of PINK1-Parkin signal pathway on mitochondrial autophagy, then discussed and analyzed the effect of the PINK1-Parkin signal pathway in AD and other metabolic diseases. Our aim was to provide a theoretical direction to further elucidate the pathogenesis of AD and highlight the key molecules related to AD that could be important targets used for AD drug development.

PHB2 Alleviates Neurotoxicity of Prion Peptide PrP106-126 via PINK1/Parkin-Dependent Mitophagy

Prion diseases are a group of neurodegenerative diseases characterized by mitochondrial dysfunction and neuronal death. Mitophagy is a selective form of macroautophagy that clears injured mitochondria. Prohibitin 2 (PHB2) has been identified as a novel inner membrane mitophagy receptor that mediates mitophagy. However, the role of PHB2 in prion diseases remains unclear. In this study, we isolated primary cortical neurons from rats and used the neurotoxic prion peptide PrP106-126 as a cell model for prion diseases. We examined the role of PHB2 in PrP106-126-induced mitophagy using Western blotting and immunofluorescence microscopy and assessed the function of PHB2 in PrP106-126-induced neuronal death using the cell viability assay and the TUNEL assay. The results showed that PrP106-126 induced mitochondrial morphological abnormalities and mitophagy in primary cortical neurons. PHB2 was found to be indispensable for PrP106-126-induced mitophagy and was involved in the accumulation of PINK1 and recruitment of Parkin to mitochondria in primary neurons. Additionally, PHB2 depletion exacerbated neuronal cell death induced by PrP106-126, whereas the overexpression of PHB2 alleviated PrP106-126 neuronal toxicity. Taken together, this study demonstrated that PHB2 is indispensable for PINK1/Parkin-mediated mitophagy in PrP106-126-treated neurons and protects neurons against the neurotoxicity of the prion peptide.

Cardiolipin externalization mediates prion protein (PrP) peptide 106-126-associated mitophagy and mitochondrial dysfunction

Proper mitochondrial performance is imperative for the maintenance of normal neuronal function to prevent the development of neurodegenerative diseases. Persistent accumulation of damaged mitochondria plays a role in prion disease pathogenesis, which involves a chain of events that culminate in the generation of reactive oxygen species and neuronal death. Our previous studies have demonstrated that PINK1/Parkin-mediated mitophagy induced by PrP^106-126 is defective and leads to an accumulation of damaged mitochondria after PrP^106-126 treatment. Externalized cardiolipin (CL), a mitochondria-specific phospholipid, has been reported to play a role in mitophagy by directly interacting with LC3II at the outer mitochondrial membrane. The involvement of CL externalization in PrP^106-126-induced mitophagy and its significance in other physiological processes of N2a cells treated with PrP^106-126 remain unknown. We demonstrate that the PrP^106-126 peptide caused a temporal course of mitophagy in N2a cells, which gradually increased and subsequently decreased. A similar trend in CL externalization to the mitochondrial surface was seen, resulting in a gradual decrease in CL content at the cellular level. Inhibition of CL externalization by knockdown of CL synthase, responsible for de novo synthesis of CL, or phospholipid scramblase-3 and NDPK-D, responsible for CL translocation to the mitochondrial surface, significantly decreased PrP^106-126-induced mitophagy in N2a cells. Meanwhile, the inhibition of CL redistribution significantly decreased PINK1 and DRP1 recruitment in PrP^106-126 treatment but had no significant decrease in Parkin recruitment. Furthermore, the inhibition of CL externalization resulted in impaired oxidative phosphorylation and severe oxidative stress, which led to mitochondrial dysfunction. Our results indicate that CL externalization induced by PrP^106-126 on N2a cells plays a positive role in the initiation of mitophagy, leading to the stabilization of mitochondrial function.

Mitophagy alleviates AIF-mediated spleen apoptosis induced by AlCl3 through Parkin stabilization in mice

Aluminium (Al) accumulates in the spleen and causes spleen apoptosis. Mitochondrial dyshomeostasis represents primary mechanisms of spleen apoptosis induced by Al. Apoptosis-inducing factor (AIF) is located in the gap of the mitochondrial membrane and can be released into the nucleus, leading to apoptosis. Phosphatase and tensin homolog (PTEN)-induced putative kinase1 (PINK1)/E3 ubiquitin ligase PARK2 (Parkin)-mediated mitophagy maintains mitochondrial homeostasis by removing damaged mitochondria, but its function in AIF-mediated spleen apoptosis induced by Al is not clear. In our study, aluminium trichloride (AlCl₃) was diluted in water for 90 d and administered to 75 male C57BL/6N mice at 0, 44.8, 59.8, 89.7, and 179.3 mg/kg body weight. AlCl₃ triggered PINK1/Parkin pathway-mediated mitophagy, induced AIF release and AIF-mediated spleen apoptosis. AlCl₃ was administered to sixty male C57BL/6N mice of wild type and Parkin knockout for 90 d at 0 and 179.3 mg/kg body weight. The results indicated that Parkin deficiency decreased mitophagy, aggravated mitochondrial damage, AIF release and AIF-mediated spleen apoptosis induced by AlCl₃. According to our results, PINK1/Parkin-mediated mitophagy and AIF-mediated spleen apoptosis are caused by AlCl₃, whereas mitophagy is protective in AIF-mediated apoptosis induced by AlCl₃.

PINK1/Parkin-mediated mitophagy in neurodegenerative diseases

Mitochondria play key roles in bioenergetics, metabolism, and signaling; therefore, stable mitochondrial function is essential for cell survival, particularly in energy-intensive neuronal cells. In neurodegenerative diseases, damaged mitochondria accumulate in neurons causing associated bioenergetics deficiency, impaired cell signaling, defective cytoplasmic calcium buffering, and other pathological changes. Mitochondrial quality control is an important mechanism to ensure the maintenance of mitochondrial health, homeostasis, and mitophagy, the latter of which is a pathway that delivers defective mitochondria to the lysosome for degradation. Defective mitophagy is thought to be responsible for the accumulation of damaged mitochondria, which leads to cellular dysfunction and/or death in neurodegenerative diseases. PINK1/Parkin mainly regulates ubiquitin-dependent mitophagy, which is crucial for many aspects of mitochondrial physiology, particularly the initiation of autophagic mechanisms. Therefore, in the present review, we summarize the current knowledge of the conventional mitophagy pathway, focusing on the molecular mechanisms underlying mitophagy dysregulation in prion disease and other age-related neurodegenerative diseases, especially in relation to the PINK1/Parkin pathway. Moreover, we list the inducers of mitophagy that possess neuroprotective effects, in addition to their mechanisms related to the PINK1/Parkin pathway. These mechanisms may provide potential interventions centered on the regulation of mitophagy and offer therapeutic strategies for the treatment of neurodegenerative diseases.

Impairment of Neuronal Mitochondrial Quality Control in Prion-Induced Neurodegeneration

Mitochondrial dynamics continually maintain cell survival and bioenergetics through mitochondrial quality control processes (fission, fusion, and mitophagy). Aberrant mitochondrial quality control has been implicated in the pathogenic mechanism of various human diseases, including cancer, cardiac dysfunction, and neurological disorders, such as Alzheimer’s disease, Parkinson’s disease, and prion disease. However, the mitochondrial dysfunction-mediated neuropathological mechanisms in prion disease are still uncertain. Here, we used both in vitro and in vivo scrapie-infected models to investigate the involvement of mitochondrial quality control in prion pathogenesis. We found that scrapie infection led to the induction of mitochondrial reactive oxygen species (mtROS) and the loss of mitochondrial membrane potential (ΔΨm), resulting in enhanced phosphorylation of dynamin-related protein 1 (Drp1) at Ser616 and its subsequent translocation to the mitochondria, which was followed by excessive mitophagy. We also confirmed decreased expression levels of mitochondrial oxidative phosphorylation (OXPHOS) complexes and reduced ATP production by scrapie infection. In addition, scrapie-infection-induced aberrant mitochondrial fission and mitophagy led to increased apoptotic signaling, as evidenced by caspase 3 activation and poly (ADP-ribose) polymerase cleavage. These results suggest that scrapie infection induced mitochondrial dysfunction via impaired mitochondrial quality control processes followed by neuronal cell death, which may have an important role in the neuropathogenesis of prion diseases.

Extensive Disturbances of Intracellular Components and Dysfunctions of Biological Pathways in the Brain Tissues During Prion Infection - China's Studies

The study describes some of the major findings of changes in intracellular components and biological pathways in the brain during prion infection and hypothesizes some important physiological and pathological approaches mainly based on our studies. Omics techniques analysis of messenger RNA (mRNA) and proteins were carried out in the study. Meanwhile, Western blot, immunohistochemistry, and immunofluorescence were used for protein analysis in different signaling pathways. Statistical analyses were used to describe the protein differences in signaling pathways of infected and normal samples. This report reviewed and summarized our studies on the aberrant changes in intracellular components and biological functions in the brains of prion disease (PrD). Omics analyses proposed extensive abnormal alterations of brain mRNAs transcriptions, protein expressions, and post-translational modifications. The molecular disturbances for microtubule instability and depolymerization, the dysregulations of different signals related with neuron loss and synaptic plasticity, the abnormalities of mitochondrial and endoplasmic reticulum stress, and disturbance of intracellular reactive oxygen species homeostasis during prion infection were precisely analyzed and reviewed. Aberrant disturbances of numerous biological molecules and signals in brain tissues were found during prion infection.

Activation of Innate Immunity and Autophagy in Brain Tissues with Prion Disease and Degradation of Abnormal PrPs in Cells - China's Studies

Unlike infectious diseases caused by conventional microbes, there are no detectable specific humoral or cellular immunoresponses to prion infection. However, extensive and active gliosis is observable in affected brain regions along with significant deposits of scrapie-like prion protein (PrP^Sc). Here, we summarize our studies of vibrant activation of host non-specific immune components and autophagy in the microenvironment of prion infected brains. Activation of the brain's innate immunity and autophagy upon prion infection reflect non-specific host defense systems attempt to dispose of accumulated prions. Vibrant elevation of neuroinflammation leads to neuron injury.

A new hope: Mitochondria, a critical factor in the war against prions

Prion diseases encompass a group of incurable neurodegenerative disorders that occur due to the misfolding and aggregation of infectious proteins. The most well-known prion diseases are Creutzfeldt-Jakob disease (CJD), bovine spongiform encephalopathy (also known as mad cow disease), and kuru. It is estimated that around 1-2 persons per million worldwide are affected annually by prion disorders. Infectious prion proteins propagate in the brain, clustering in the cells and rapidly inducing tissue degeneration and death. Prion disease alters cell metabolism and energy production damaging mitochondrial function and dynamics leading to a fast accumulation of damage. Dysfunction of mitochondria could be considered as an early precursor and central element in the pathogenesis of prion diseases such as in sporadic CJD. Preserving mitochondria function may help to resist the rapid spread and damage of prion proteins and even clearance. In the war against prions and other degenerative diseases, studying how to preserve the function of mitochondria by using antioxidants and even replacing them with artificial mitochondrial transfer/transplant (AMT/T) may bring a new hope and lead to an increase in patients' survival. In this perspective review, we provide key insights about the relationship between the progression of prion disease and mitochondria, in which understanding how protecting mitochondria function and viability by using antioxidants or AMT/T may help to develop novel therapeutic interventions.

Extracellular vesicles with diagnostic and therapeutic potential for prion diseases

Prion diseases (PrD) or transmissible spongiform encephalopathies (TSE) are invariably fatal and pathogenic neurodegenerative disorders caused by the self-propagated misfolding of cellular prion protein (PrP^C) to the neurotoxic pathogenic form (PrP^TSE) via a yet undefined but profoundly complex mechanism. Despite several decades of research on PrD, the basic understanding of where and how PrP^C is transformed to the misfolded, aggregation-prone and pathogenic PrP^TSE remains elusive. The primary clinical hallmarks of PrD include vacuolation-associated spongiform changes and PrP^TSE accumulation in neural tissue together with astrogliosis. The difficulty in unravelling the disease mechanisms has been related to the rare occurrence and long incubation period (over decades) followed by a very short clinical phase (few months). Additional challenge in unravelling the disease is implicated to the unique nature of the agent, its complexity and strain diversity, resulting in the heterogeneity of the clinical manifestations and potentially diverse disease mechanisms. Recent advances in tissue isolation and processing techniques have identified novel means of intercellular communication through extracellular vesicles (EVs) that contribute to PrP^TSE transmission in PrD. This review will comprehensively discuss PrP^TSE transmission and neurotoxicity, focusing on the role of EVs in disease progression, biomarker discovery and potential therapeutic agents for the treatment of PrD.

PINK1-parkin-mediated neuronal mitophagy deficiency in prion disease

A persistent accumulation of damaged mitochondria is part of prion disease pathogenesis. Normally, damaged mitochondria are cleared via a major pathway that involves the E3 ubiquitin ligase parkin and PTEN-induced kinase 1 (PINK1) that together initiate mitophagy, recognize and eliminate damaged mitochondria. However, the precise mechanisms underlying mitophagy in prion disease remain largely unknown. Using prion disease cell models, we observed PINK1-parkin-mediated mitophagy deficiency in which parkin depletion aggravated blocked mitochondrial colocalization with LC3-II-labeled autophagosomes, and significantly increased mitochondrial protein levels, which led to inhibited mitophagy. Parkin overexpression directly induced LC3-II colocalization with mitochondria and alleviated defective mitophagy. Moreover, parkin-mediated mitophagy was dependent on PINK1, since PINK1 depletion blocked mitochondrial Parkin recruitment and reduced optineurin and LC3-II proteins levels, thus inhibiting mitophagy. PINK1 overexpression induced parkin recruitment to the mitochondria, which then stimulated mitophagy. In addition, overexpressed parkin and PINK1 also protected neurons from apoptosis. Furthermore, we found that supplementation with two mitophagy-inducing agents, nicotinamide mononucleotide (NMN) and urolithin A (UA), significantly stimulated PINK1-parkin-mediated mitophagy. However, compared with NMN, UA could not alleviate prion-induced mitochondrial fragmentation and dysfunction, and neuronal apoptosis. These findings show that PINK1-parkin-mediated mitophagy defects lead to an accumulation of damaged mitochondria, thus suggesting that interventions that stimulate mitophagy may be potential therapeutic targets for prion diseases.

Deciphering the Protein, Modular Connections and Precision Medicine for Heart Failure With Preserved Ejection Fraction and Hypertension Based on TMT Quantitative Proteomics and Molecular Docking

Background: Exploring the potential biological relationships between heart failure with preserved ejection fraction (HFpEF) and concomitant diseases has been the focus of many studies for the establishment of personalized therapies. Hypertension (HTN) is the most common concomitant disease in HFpEF patients, but the functional connections between HFpEF and HTN are still not fully understood and effective treatment strategies are still lacking.

Methods: In this study, tandem mass tag (TMT) quantitative proteomics was used to identify disease-related proteins and construct disease-related networks. Furthermore, functional enrichment analysis of overlapping network modules was used to determine the functional similarities between HFpEF and HTN. Molecular docking and module analyses were combined to identify therapeutic targets for HFpEF and HTN.

Results: Seven common differentially expressed proteins (co-DEPs) and eight overlapping modules were identified in HFpEF and HTN. The common biological processes between HFpEF and HTN were mainly related to energy metabolism. Myocardial contraction, energy metabolism, apoptosis, oxidative stress, immune response, and cardiac hypertrophy were all closely associated with HFpEF and HTN. Epinephrine, sulfadimethoxine, chloroform, and prednisolone acetate were best matched with the co-DEPs by molecular docking analyses.

Conclusion: Myocardial contraction, energy metabolism, apoptosis, oxidative stress, immune response, and cardiac hypertrophy were the main functional connections between HFpEF and HTN. Epinephrine, sulfadimethoxine, chloroform, and prednisolone acetate could potentially be effective for the treatment of HTN and HFpEF.

Accumulation of Prion and Abnormal Prion Protein Induces Hyperphosphorylation of α-Synuclein in the Brain Tissues from Prion Diseases and in the Cultured Cells

Prion disease (PrD) and Parkinson's disease (PD) are neurodegenerative diseases characterized by aggregation of misfolded proteins in brain tissues, including protease-resistant prion protein (PrP^Sc) in PrD and α-synuclein in PD. In recent years, overlap of these two proteins has attracted increased attention, and cross-seeding of prion proteins by aggregated α-synuclein has been proposed. However, the changes in α-synuclein after prion infection are still unclear. In this study, we showed that α-synuclein expression was significantly decreased in the brains of prion-infected rodent models, in the SMB-S15 cell line, which exhibits persistent prion replication, and in the brains of humans with PrDs. Meanwhile, α-synuclein phosphorylated at serine 129(p(S129)-α-synuclein) was significantly increased in the brains of scrapie-infected mice and prion-infected SMB-S15 cells. The increased p(S129)-α-synuclein colocalized with GFAP- and NeuN-positive cells in the brains of scrapie-infected mice. p(S129)-α-synuclein was also observed in the cytoplasm of SMB-S15 and HEK-293 cells transiently expressing an abnormal form of prion protein (Cyto-PrP). Molecular interactions between PrP and α-synuclein were detected in recombinant proteins, normal and prion-infected brain tissues, and cultured cells. The increased p(S129)-α-synuclein colocalized with PrP signals from prion-infected SMB-S15 and HEK-293 cells expressing Cyto-PrP. Moreover, increased morphological colocalization of p(S129)-α-synuclein with mitochondrial markers was also detected in the two cell types. Our results indicate that prion replication and accumulation in cells and brains induce hyperphosphorylation of α-synuclein, particularly at S129, which may aggravate mitochondrial damage and facilitate α-synuclein aggregation in the central nervous system tissues from PrDs.

FOXO3a acetylation regulates PINK1, mitophagy, inflammasome activation in murine palmitate-conditioned and diabetic macrophages

Nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing 3 inflammasome and mitophagy play an important role in cytokine release and diabetes progression; however, the role of saturated fatty acid that is induced under such conditions remains little explored. Therefore, the present study evaluates mechanisms regulating mitophagy and inflammasome activation in primary murine diabetic and palmitate-conditioned wild-type (WT) peritoneal macrophages. Peritoneal macrophage, from the diabetic mice and WT mice, challenged with LPS/ATP and palmitate/LPS/ATP, respectively, showed dysfunctional mitochondria as assessed by their membrane potential, mitochondrial reactive oxygen species (mtROS) production, and mitochondrial DNA (mtDNA) release. A defective mitophagy was observed in the diabetic and palmitate-conditioned macrophages stimulated with LPS/ATP as assessed by translocation of PTEN-induced kinase 1 (PINK1)/Parkin or p62 in the mitochondrial fraction. Consequently, increased apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) oligomerization, caspase-1 activation, and IL1β secretion were observed in LPS/ATP stimulated diabetic and palmitate-conditioned macrophages. LPS/ATP induced Forkhead box O3a (FOXO3a) binding to PINK1 promoter and increased PINK1 mRNA expression in WT macrophages. However, PINK1 mRNA and protein expression were significantly decreased in diabetic and palmitate-conditioned macrophages in response to LPS/ATP. Palmitate-induced acetyl CoA promoted FOXO3a acetylation, which prevented LPS/ATP-induced FOXO3a binding to the PINK1 promoter. C646 (P300 inhibitor) and SRT1720 (SIRT1 activator) prevented FOXO3a acetylation and restored FOXO3a binding to the PINK1 promoter, PINK1 mRNA expression, and mitophagy in palmitate-conditioned macrophages treated with LPS/ATP. Also, a significant decrease in the LPS/ATP-induced mtROS production, mtDNA release, ASC oligomerization, caspase-1 activation, and IL-1β release was observed in the palmitate-conditioned macrophages. Similarly, modulation of FOXO3a acetylation also prevented LPS/ATP-induced mtDNA release and inflammasome activation in diabetic macrophages. Therefore, FOXO3a acetylation regulates PINK1-dependent mitophagy and inflammasome activation in the palmitate-conditioned and diabetic macrophages.

Lycopene attenuates di(2-ethylhexyl) phthalate-induced mitophagy in spleen by regulating the sirtuin3-mediated pathway

Lycopene (Lyc) has been discussed as a potential effector in the prevention and therapy of various diseases. Di(2-ethylhexyl) phthalate (DEHP) is regarded as a universal environmental pollutant. To clarify the potential protective effect of Lyc on DEHP-induced splenic injury, 140 male mice were randomized into seven groups: control (distilled water), vehicle control (corn oil per day), Lyc (5 mg per kg BW per day), DEHP (500 or 1000 mg per kg BW per day), and DEHP combined Lyc group, respectively. All experimental animals were treated by oral gavage for 28 days. The results that showed DEHP exposure significantly up-regulated the mRNA and protein expression of the sirtuin family (except SIRT4-5), PGC-1α, OPA1, Drp1, MFN1/2, NRF1, TFAM, Parkin and PINK in DEHP-treated alone groups and the SOD2 and LC3-II protein expression were also in accordance with the above changes. These were accompanied with an increase of the number of inflammatory cells and rate of mitochondrial damage, and autophagosome formation in the spleen. Notably, Lyc supplementation facilitated all these changes to effectively return to the normal level, indicating that Lyc exerts protective effects against DEHP-induced splenic toxicity. Altogether, the protective effects of Lyc may be a strategy to ameliorate DEHP-induced spleen damage.

LDHB inhibition induces mitophagy and facilitates the progression of CSFV infection

Cellular metabolism caters to the energy and metabolite needs of cells. Although the role of the terminal metabolic enzyme LDHB (lactate dehydrogenase B) in the glycolysis pathway has been widely studied in cancer cells, its role in viral infection is relatively unknown. In this study, we found that CSFV (classical swine fever virus) infection reduces pyruvate levels while promotes lactate release in pigs and in PK-15 cells. Moreover, using a yeast two-hybrid screening system, we identified LDHB as a novel interacting partner of CSFV non-structural protein NS3. These results were confirmed via co-immunoprecipitation, glutathione S-transferase and confocal assays. Furthermore, knockdown of LDHB via interfering RNA induced mitochondrial fission and mitophagy, as detected reduced mitochondrial mass. Upon inhibition of LDHB, expression of the mitophagy proteins TOMM20 and VDAC1 decreased and the ubiquitination of MFN2, a mitochondrial fusion mediator, was promoted. In addition, a sensitive dual fluorescence reporter (mito-mRFP-EGFP) was utilized to analyze the delivery of autophagosomes to lysosomes in LDHB inhibition cells. Furthermore, LDHB inhibition promoted NFKB signaling, which was regulated by mitophagy; meanwhile, infection with CSFV negated these NFKB anti-viral responses. Inhibition of LDHB also inhibited apoptosis, providing an environment conducive to persistent viral infection. Finally, we demonstrated that LDHB inhibition promoted CSFV growth via mitophagy, whereas its overexpression decreased CSFV replication. Our data revealed a novel mechanism through which LDHB, a metabolic enzyme, mediates CSFV infection, and provides new avenues for the development of anti-viral strategies.Abbreviations: 3-MA:3-methyladenine; CCCP:carbonyl cyanide 3-chlorophenylhydrazone; CCK-8:cell counting kit-8; CSFV:classical swine fever virus; DAPI:4',6-diamidino-2-phenylindole; DMSO:dimethyl sulfoxide; EGFP:enhanced green fluorescent protein; FBS:fetal bovine serum; FITC:fluorescein isothiocyanate; GST:glutathione-S-transferase; HCV:hepatitis C virus; IFN:interferon; LDH:lactate dehydrogenase; MAP1LC3/LC3:microtubule associated protein 1 light chain 3; MFN2:mitofusin 2; MOI:multiplicity of infection; NFKB:nuclear factor kappa B subunit 1; NFKBIA:nuclear factor inhibitor alpha; NS3:nonstructural protein 3; NKIRAS2:NFKB inhibitor interacting Ras like 2; PRKN:parkin E3 ubiquitin protein ligase; PBS:phosphate-buffered saline; qRT-PCR:real-time quantitative reverse transcriptase polymerase chain reaction; RELA:RELA proto-oncogene, NF-kB subunit; shRNA: short hairpin RNA; siRNA: small interfering RNA; TCID50:50% tissue culture infectious doses; TEM:transmission electron microscopy; TNF:tumor necrosis factor; TOMM20:translocase of outer mitochondrial membrane 20; VDAC1:voltage dependent anion channel 1.

An Update on Autophagy in Prion Diseases

Autophagy is a dynamic intracellular mechanism involved in protein and organelle turnover through lysosomal degradation. When properly regulated, autophagy supports normal cellular and developmental processes, whereas defects in autophagic degradation have been associated with several pathologies, including prion diseases. Prion diseases, or transmissible spongiform encephalopathies (TSE), are a group of fatal neurodegenerative disorders characterized by the accumulation of the pathological misfolded isoform (PrP^Sc) of the physiological cellular prion protein (PrP^c) in the central nervous system. Autophagic vacuoles have been described in experimental models of TSE and in the natural disease in humans. The precise connection of this process with prion-related neuropathology, or even whether autophagy is completely beneficial or pathogenic during neurodegeneration, is poorly understood. Thus, the biological role of autophagy in these diseases is still open to debate. During the last years, researchers have used a wide range of morphological, genetic and biochemical methods to monitor and manipulate the autophagic pathway and thus determine the specific role of this process in TSE. It has been suggested that PrP^c could play a crucial role in modulating the autophagic pathway in neuronal cells, and the presence of abnormal autophagic activity has been frequently observed in several models of TSE both in vitro and in vivo, as well as in human prion diseases. Altogether, these findings suggest that autophagy is implicated in prion neuropathology and points to an impairment or failure of the process, potentially contributing to the pathogenesis of the disease. Additionally, autophagy is now emerging as a host defense response in controlling prion infection that plays a protective role by facilitating the clearance of aggregation-prone proteins accumulated within neurons. Since autophagy is one of the pathways of PrP^Sc degradation, and drug-induced stimulation of autophagic flux (the dynamic process of autophagic degradation activity) produces anti-prion effects, new treatments based on its activation have been tested to develop therapeutic strategies for prion diseases. In this review, we summarize previous and recent findings concerning the role of autophagy in TSE.

Endurance Exercise-Induced Autophagy/Mitophagy Coincides with a Reinforced Anabolic State and Increased Mitochondrial Turnover in the Cortex of Young Male Mouse Brain

Autophagy/mitophagy, a cellular catabolic process necessary for sustaining normal cellular function, has emerged as a potential therapeutic strategy against numerous obstinate diseases. In this regard, endurance exercise (EXE)-induced autophagy/mitophagy (EIAM) has been considered as a potential health-enriching factor in various tissues including the brain; however, underlying mechanisms of EIAM in the brain has not been fully defined yet. This study investigated the molecular signaling nexus of EIAM pathways in the cortex of the brain. C57BL/6 young male mice were randomly assigned to a control group (CON, n = 12) and an endurance exercise group (EXE, n = 12). Our data demonstrated that exercise-induced autophagy coincided with an enhanced anabolic state (p-AKT, p-mTOR, and p-p70S6K); furthermore, mitophagy concurred with enhanced mitochondrial turnover: increases in both fission (DRP1, BNIP3, and PINK1) and fusion (OPA1 and MFN2) proteins. In addition, neither oxidative stress nor sirtuins (SIRT) 1 and 3 were associated with EIAM; instead, the activation of AMPK as well as a JNK-BCL2 axis was linked to EIAM promotion. Collectively, our results demonstrated that EXE-induced anabolic enrichment did not hinder autophagy/mitophagy and that the concurrent augmentation of mitochondrial fusion and fusion process contributed to sustaining mitophagy in the cortex of the brain. Our findings suggest that the EXE-induced concomitant potentiation of the catabolic and anabolic state is a unique molecular mechanism that simultaneously contributes to recycling and rebuilding the cellular structure, leading to upholding healthy cellular environment. Thus, the current study provides a novel autophagy/mitophagy mechanism, from which groundbreaking pharmacological strategies of autophagy can be developed.