Dysregulation of autophagy and mitochondrial function in Parkinson's disease

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.

Protective effect of phenylpropionamides in the seed of Cannabis Sativa L. on Parkinson's disease through autophagy

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. As one of the major degradation pathways, autophagy plays a pivotal role in maintaining the effective turnover of proteins and damaged organelles in cells. Lewy bodies composed of α-synuclein (α-syn) abnormally aggregated in the substantia nigra are important pathological features of PD, and autophagy dysfunction is considered to be an important factor leading to abnormal aggregation of α-syn. Phenylpropionamides (PHS) in the seed of Cannabis sativa L. have a protective effect on neuroinflammation and antioxidant activity. However, the therapeutic role of PHS in PD is unclear. In this study, the seeds of Cannabis sativa L. were extracted under reflux with 60% EtOH-H2O, and the 60% EtOH-H2O elution fraction was identified as PHS with the UPLC-QTOF-MS. The 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP)-induced PD model in C57BL/6 J mice was used for behavioral and pharmacodynamic experiments. Behavioral symptoms were improved, Nissl-stained and TH-positive neurons in the substantia nigra were significantly increased in PHS-treated MPTP-induced PD model mice. Compared with the model group, PHS treatment reduced the expression level of α-syn, and the expression of TH increased significantly by western blotting, compared with the model group, the PHS group suppressed Caspase 3 and Bax expression and promoted Bcl-2 expression and levels of p62 decreased significantly, the ratio of LC3-II/I and p-mTOR/mTOR in the PHS group had a downward trend, suggesting that the therapeutic effect of PHS on MPTP-induced PD model mice may be triggered by the regulation of autophagy.

LncRNA NR_030777 promotes mitophagy by targeting CDK1-related mitochondrial fission and ATG12 to attenuate paraquat-induced Parkinson's disease

With the evidence emerging that abnormal expression of long noncoding RNAs (lncRNAs) are involved in onset of Parkinson's disease (PD), the role of NR_030777 contributing to this disease is of great interest. We recently found that a novel lncRNA "NR_030777" demonstrates protective effects on PQ-induced neurodegeneration. However, the underlying molecular mechanisms of NR_030777 in the regulation of mitochondrial fission and mitophagy involved in PQ-induced neuronal damage remain to be explored. NR_030777 brain conditional overexpressing mice as well as in vitro primary neuronal cells from cerebral cortex and Neuro2a cells were adopted. Immunofluorescence, Immunohistochemistry, qRT-PCR and Western blotting were used to evaluate the expression levels of RNA and proteins. RNA immunoprecipitation and RNA pulldown experiment were used to evaluate the interaction of NR_030777 with its target proteins. NR_030777 and mitophagy were increased, and tyrosine hydroxylase (TH) levels recovered after NR_030777 overexpression upon PQ treatment. The overexpression and knockdown of NR_030777 unveiled that NR_030777 positively regulated mitophagy such as the upregulation of LC3B-II:I, ATG12-ATG5, p62 and NBR1. Moreover, the application of mdivi-1, a DRP-1 inhibitor, in combination with NR_030777 genetic modified cells unveiled that NR_030777 promoted DRP1-mediated mitochondrial fission and mitophagy. Furthermore, NR_030777 were directly bound to CDK1 to increase p-DRP1 levels at the Ser616 site, leading to mitochondrial fission and mitophagy. On the other hand, NR_030777 acted directly on ATG12 within the ATG12-ATG5 complex in the 800-1400 nt region to modulate the membrane formation. Accordingly, NR_030777 deficiency in neuron cells compromised cell mitophagy. Finally, the above findings were confirmed using NR_030777-overexpressing mice. NR_030777 exerted a protective effect on PQ-exposed mice by enhancing mitophagy. Our data provide the first scientific evidence for the precise invention of PQ-induced PD. Our findings further propose a breakthrough for understanding the regulatory relationship between NR_030777, CDK1, ATG12 and mitophagy in PQ-induced PD.

Neuroprotective effects of cordycepin on MPTP-induced Parkinson's disease mice via suppressing PI3K/AKT/mTOR and MAPK-mediated neuroinflammation

Parkinson's disease (PD) is a prevalent progressive and multifactorial neurodegenerative disorder. Cordycepin is known to exhibit antitumor, anti-inflammatory, antioxidative stress, and neuroprotective effects; however, few studies have explored the neuroprotective mechanism of cordycepin in PD. Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model, we investigated the impact of cordycepin on PD and its underlying molecular mechanisms. The findings indicated that cordycepin significantly mitigated MPTP-induced behavior disorder and neuroapoptosis, diminished the loss of dopaminergic neurons in the striatum-substantia nigra pathway, elevated striatal monoamine levels and its metabolites, and inhibited the polarization of microglia and the expression of pro-inflammatory factors. Subsequent proteomic and phosphoproteomic analyses revealed the involvement of the MAPK, mTOR, and PI3K/AKT signaling pathways in the protective mechanism of cordycepin. Cordycepin treatment inhibited the activation of the PI3K/AKT/mTOR signaling pathway and enhanced the expression of autophagy proteins in the striatum and substantia nigra. We also demonstrated the in vivo inhibition of the ERK/JNK signaling pathway by cordycepin treatment. In summary, our investigation reveals that cordycepin exerts neuroprotective effects against PD by promoting autophagy and suppressing neuroinflammation and neuronal apoptosis by inhibiting the PI3K/AKT/mTOR and ERK/JNK signaling pathways. This finding highlights the favorable characteristics of cordycepin in neuroprotection and provides novel molecular insights into the neuroprotective role of natural products in PD.

Mitochondrial homeostasis regulation: A promising therapeutic target for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) and the presence of Lewy bodies (LBs) or Lewy neurites (LNs) which consist of α-synuclein (α-syn) and a complex mix of other biomolecules. Mitochondrial dysfunction is widely believed to play an essential role in the pathogenesis of PD and other related neurodegenerative diseases. But mitochondrial dysfunction is subject to complex genetic regulation. There is increasing evidence that PD-related genes directly or indirectly affect mitochondrial integrity. Therefore, targeted regulation of mitochondrial function has great clinical application prospects in the treatment of PD. However, lots of PD drugs targeting mitochondria have been developed but their clinical therapeutic effects are not ideal. This review aims to reveal the role of mitochondrial dysfunction in the pathogenesis of neurodegenerative diseases based on the mitochondrial structure and function, which may highlight potential interventions and therapeutic targets for the development of PD drugs to recover mitochondrial dysfunction in neurodegenerative diseases.

Rhabdomyosarcoma: Current Therapy, Challenges, and Future Approaches to Treatment Strategies

Rhabdomyosarcoma is a rare cancer arising in skeletal muscle that typically impacts children and young adults. It is a worldwide challenge in child health as treatment outcomes for metastatic and recurrent disease still pose a major concern for both basic and clinical scientists. The treatment strategies for rhabdomyosarcoma include multi-agent chemotherapies after surgical resection with or without ionization radiotherapy. In this comprehensive review, we first provide a detailed clinical understanding of rhabdomyosarcoma including its classification and subtypes, diagnosis, and treatment strategies. Later, we focus on chemotherapy strategies for this childhood sarcoma and discuss the impact of three mechanisms that are involved in the chemotherapy response including apoptosis, macro-autophagy, and the unfolded protein response. Finally, we discuss in vivo mouse and zebrafish models and in vitro three-dimensional bioengineering models of rhabdomyosarcoma to screen future therapeutic approaches and promote muscle regeneration.

Astrocytes in Parkinson's Disease: From Role to Possible Intervention

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons. While neuronal dysfunction is central to PD, astrocytes also play important roles, both positive and negative, and such roles have not yet been fully explored. This literature review serves to highlight these roles and how the properties of astrocytes can be used to increase neuron survivability. Astrocytes normally have protective functions, such as releasing neurotrophic factors, metabolizing glutamate, transferring healthy mitochondria to neurons, or maintaining the blood-brain barrier. However, in PD, astrocytes can become dysfunctional and contribute to neurotoxicity, e.g., via impaired glutamate metabolism or the release of inflammatory cytokines. Therefore, astrocytes represent a double-edged sword. Restoring healthy astrocyte function and increasing the beneficial effects of astrocytes represents a promising therapeutic approach. Strategies such as promoting neurotrophin release, preventing harmful astrocyte reactivity, or utilizing regional astrocyte diversity may help restore neuroprotection.

The p53 tumor suppressor regulates AKR1B1 expression, a metastasis-promoting gene in breast cancer

Alteration of metabolism in cancer cells is a central aspect of the mechanisms that sustain aggressive traits. Aldo-keto reductase 1 B1 (AKR1B1) catalyzes the reduction of several aldehydes to alcohols consuming NADPH. Nevertheless, the ability of AKR1B1 to reduce different substrates renders difficult to comprehensively ascertain its biological role. Recent evidence has implicated AKR1B1 in cancer; however, the mechanisms underlying its pro-oncogenic function remain largely unknown. In this work, we report that AKR1B1 expression is controlled by the p53 tumor suppressor. We found that breast cancer patients bearing wild-type TP53 have reduced AKR1B1 expression. In cancer cell lines, p53 reduced AKR1B1 mRNA and protein levels and repressed promoter activity in luciferase assays. Furthermore, chromatin immunoprecipitation assays indicated that p53 is recruited to the AKR1B1 promoter. We also observed that AKR1B1 overexpression promoted metastasis in the 4T1 orthotopic model of triple-negative breast cancer. Proteomic analysis of 4T1 cells overexpressing AKR1B1 showed that AKR1B1 exerts a marked effect on proteins related to metabolism, with a particular impact on mitochondrial function. This work provides novel insights on the link between the p53 pathway and metabolism in cancer cells and contributes to characterizing the alterations associated to the pathologic role of AKR1B1.

Chronodisruption and Loss of Melatonin Rhythm, Associated with Alterations in Daily Motor Activity and Mitochondrial Dynamics in Parkinsonian Zebrafish, Are Corrected by Melatonin Treatment

Beyond sleep/wake, clock genes regulate the daily rhythms of melatonin production, motor activity, innate immunity, and mitochondrial dynamics, among others. All these rhythms are affected in Parkinson's disease (PD), suggesting that chronodisruption may be an early stage of the disease. The aim of this study was to evaluate the connection between clock genes and these rhythms in PD, and whether melatonin administration reestablished the normal clock function. Parkinsonism was induced with 600 μM MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in 24-120 h post fertilization (hpf) zebrafish embryos and melatonin was administered at a dose of 1 μM. Day-night melatonin rhythm disappeared in MPTP-treated embryos, which showed an advance in the activity phase in parallel with changes in the rhythm of clock genes. An alteration in the fission-to-fusion mitochondrial dynamics was also detected in parkinsonian embryos, increasing the former and leading to apoptosis. Melatonin administration to MPTP-treated embryos fully restored the circadian system, including the rhythms of clock genes, motor activity, melatonin rhythm, and mitochondrial dynamics, and decreasing apoptosis. Because clock-controlled rhythms such as sleep/wake alterations are early events in PD, the data here reported may point to chronodisruption as one initial pathophysiological event of the disease.

Co-occurring pathogenic variants in 6q27 associated with dementia spectrum disorders in a Peruvian family

Evidence suggests that there may be racial differences in risk factors associated with the development of Alzheimer's disease and related dementia (ADRD). We used whole-genome sequencing analysis and identified a novel combination of three pathogenic variants in the heterozygous state (UNC93A: rs7739897 and WDR27: rs61740334; rs3800544) in a Peruvian family with a strong clinical history of ADRD. Notably, the combination of these variants was present in two generations of affected individuals but absent in healthy members of the family. In silico and in vitro studies have provided insights into the pathogenicity of these variants. These studies predict that the loss of function of the mutant UNC93A and WDR27 proteins induced dramatic changes in the global transcriptomic signature of brain cells, including neurons, astrocytes, and especially pericytes and vascular smooth muscle cells, indicating that the combination of these three variants may affect the neurovascular unit. In addition, known key molecular pathways associated with dementia spectrum disorders were enriched in brain cells with low levels of UNC93A and WDR27. Our findings have thus identified a genetic risk factor for familial dementia in a Peruvian family with an Amerindian ancestral background.

Role of Astrocytes in Parkinson's Disease Associated with Genetic Mutations and Neurotoxicants

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons and the aggregation of Lewy bodies in the basal ganglia, resulting in movement impairment referred to as parkinsonism. However, the etiology of PD is not well known, with genetic factors accounting only for 10-15% of all PD cases. The pathogenetic mechanism of PD is not completely understood, although several mechanisms, such as oxidative stress and inflammation, have been suggested. Understanding the mechanisms of PD pathogenesis is critical for developing highly efficacious therapeutics. In the PD brain, dopaminergic neurons degenerate mainly in the basal ganglia, but recently emerging evidence has shown that astrocytes also significantly contribute to dopaminergic neuronal death. In this review, we discuss the role of astrocytes in PD pathogenesis due to mutations in α-synuclein (PARK1), DJ-1 (PARK7), parkin (PARK2), leucine-rich repeat kinase 2 (LRRK2, PARK8), and PTEN-induced kinase 1 (PINK1, PARK6). We also discuss PD experimental models using neurotoxins, such as paraquat, rotenone, 6-hydroxydopamine, and MPTP/MPP+. A more precise and comprehensive understanding of astrocytes' modulatory roles in dopaminergic neurodegeneration in PD will help develop novel strategies for effective PD therapeutics.

Is Disrupted Mitophagy a Central Player to Parkinson's Disease Pathology?

Whilst the pathophysiology at a cellular level has been defined, the cause of Parkinson's disease (PD) remains poorly understood. This neurodegenerative disorder is associated with impaired dopamine transmission in the substantia nigra, and protein accumulations known as Lewy bodies are visible in affected neurons. Cell culture models of PD have indicated impaired mitochondrial function, so the focus of this paper is on the quality control processes involved in and around mitochondria. Mitochondrial autophagy (mitophagy) is the process through which defective mitochondria are removed from the cell by internalisation into autophagosomes which fuse with a lysosome. This process involves many proteins, notably including PINK1 and parkin, both of which are known to be coded on genes associated with PD. Normally in healthy individuals, PINK1 associates with the outer mitochondrial membrane, which then recruits parkin, activating it to attach ubiquitin proteins to the mitochondrial membrane. PINK1, parkin, and ubiquitin cooperate to form a positive feedback system which accelerates the deposition of ubiquitin on dysfunctional mitochondria, resulting in mitophagy. However, in hereditary PD, the genes encoding PINK1 and parkin are mutated, resulting in proteins that are less efficient at removing poorly performing mitochondria, leaving cells more vulnerable to oxidative stress and ubiquitinated inclusion bodies, such as Lewy bodies. Current research that looks into the connection between mitophagy and PD is promising, already yielding potentially therapeutic compounds; until now, pharmacological support for the mitophagy process has not been part of the therapeutic arsenal. Continued research in this area is warranted.

Association of cerebral spinal fluid copper imbalance in amyotrophic lateral sclerosis

A plethora of environmental risk factors has been persistently implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS), including metal/metalloids. This study aimed to examine potential associations between cerebral spinal fluid (CSF) metal/metalloids and ALS risks. CSF concentrations of copper (Cu), nickel (Ni), mercury (Hg), arsenic (As), manganese (Mn), and iron (Fe) in ALS (spinal- and bulbar-onset) patients and controls were measured using inductively coupled plasma mass spectrometry (ICP-MS). Results from this study revealed marked differences between control, spinal-onset, and bulbar-onset groups. We report that Cu levels were lower in the ALS and spinal-onset groups compared to the control group. Ni level were higher in the spinal-onset group compared to the control and bulbar-onset groups. In addition, associations between CSF metal/metalloid levels with disease severity, sex, and serum triglycerides were also examined to broach the potential relevance of neurotoxic metal/metalloids in ALS disease heterogeneity.

Low skull bone density is associated with poor motor prognosis in women with Parkinson’s disease

Parkinson’s disease (PD) and osteoporosis are degenerative diseases that have shared pathomechanisms. To investigate the associations of skull bone density with nigrostriatal dopaminergic degeneration and longitudinal motor prognosis in female patients with PD. We analyzed the data of 260 drug-naïve female PD patients aged ≥50 years old who were followed-up for ≥3 years after their first visit to the clinic with baseline dopamine transporter (DAT) imaging. We measured skull bone density as a surrogate marker for systemic bone loss by calculating the Hounsfield unit (HU) in computed tomography scans. A Cox proportional hazard model was built to compare the rates of levodopa-induced dyskinesia (LID) or wearing-off according to skull HU. Longitudinal changes in levodopa-equivalent dose (LED) during a 3-year follow-up were assessed using a linear mixed model. A lower skull HU was associated with lower baseline DAT availability in striatal subregions; however, this relationship was not significant after adjusting for age, disease duration, body mass index, and white matter hyperintensities. After adjusting for confounding factors, a lower skull HU was significantly associated with an increased risk of LID development (hazard ratio = 1.660 per 1 standard deviation decrease, p = 0.007) and wearing-off (hazard ratio = 1.613, p = 0.016) in younger (<67 years) but not in older patients. Furthermore, a lower skull HU was associated with a steeper increase in LED during follow-up in younger patients only (β = –21.99, p < 0.001). This study suggests that baseline skull bone density would be closely linked to motor prognosis in drug naïve women with PD.

Calcitriol ameliorates renal injury with high-salt diet-induced hypertension by upregulating GLIS2 expression and AMPK/mTOR-regulated autophagy

The goal of the present study was to investigate the protective effect of calcitriol on high-salt diet-induced hypertension. The hypertension rat model was established by a long-term high-salt diet (8% NaCl). Rats were treated with calcitriol, losartan, or their combination. Histological staining was used to confirm renal pathology. Global transcriptome analysis of renal tissues was performed, and the mechanism of the therapeutic effect of calcitriol was analysed by functional annotation and pathway analysis of the differentially expressed genes (DEGs) as well as by Western blotting analysis. The core genes for potential therapeutic regulation were identified through the coexpression gene network. For in vitro HK-2 cell experiments, small interfering RNA (siRNA) was used to knockdown key a transcription factor (TF) Glis2 to validate the therapeutic target of calcitriol. MAPK1 and CXCL12 expression was downregulated and the apoptosis pathway was significantly enriched by calcitriol treatment. The western blotting results showed that calcitriol treatment increased AMPK phosphorylation and decreased downstream mTOR phosphorylation, which was accompanied by a decrease in autophagy protein p62 expression and an increase in LC3-II/I expression. GLIS2 was identified as a specific therapeutic target for calcitriol. GLIS2 expression was upregulated by calcitriol and confirmed by HK-2 cells in vitro. Our omics data show that calcitriol can alleviate oxidative stress and fibrosis. Moreover, calcitriol can regulate the CXCL12/ERK1/2 cascade to inhibit the inflammatory response and renal cell apoptosis and induce renal autophagy through the AMPK/mTOR pathway. Our study partially elucidate the pathogenesis and treatment mechanism underlying hypertension, and provide new insights into the treatment of hypertension.

Transcriptional analysis of peripheral memory T cells reveals Parkinson's disease-specific gene signatures

Parkinson's disease (PD) is a multi-stage neurodegenerative disorder with largely unknown etiology. Recent findings have identified PD-associated autoimmune features including roles for T cells. To further characterize the role of T cells in PD, we performed RNA sequencing on PBMC and peripheral CD4 and CD8 memory T cell subsets derived from PD patients and age-matched healthy controls. When the groups were stratified by their T cell responsiveness to alpha-synuclein (α-syn) as a proxy for an ongoing inflammatory autoimmune response, the study revealed a broad differential gene expression profile in memory T cell subsets and a specific PD associated gene signature. We identified significant enrichment of transcriptomic signatures previously associated with PD, including for oxidative stress, phosphorylation, autophagy of mitochondria, cholesterol metabolism and inflammation, and the chemokine signaling proteins CX3CR1, CCR5, and CCR1. In addition, we identified genes in these peripheral cells that have previously been shown to be involved in PD pathogenesis and expressed in neurons, such as LRRK2, LAMP3, and aquaporin. Together, these findings suggest that features of circulating T cells with α-syn-specific responses in PD patients provide insights into the interactive processes that occur during PD pathogenesis and suggest potential intervention targets.

Potential role of mitochondria-associated endoplasmic reticulum membrane proteins in diseases

Mitochondria-associated endoplasmic reticulum membranes (MAMs) are dynamic membrane coupling regions formed by the coupling of the mitochondrial outer membrane and endoplasmic reticulum (ER). MAMs are involved in the mitochondrial dynamics, mitophagy, Ca²⁺ exchange, and ER stress. A large number of studies indicate that many proteins are involved in the formation of MAMs, including dynamic-related protein 1 (Drp1), DJ-1, PTEN-induced putative kinase 1 (PINK), α-synuclein (α-syn), sigma-1 receptor (S1R), mitofusin-2 (Mfn2), presenilin-1 (PS1), protein kinase R (PKR)-like ER kinase (PERK), Parkin, Cyclophilin D (CypD), glucose-related protein 75 (Grp75), FUN14 domain containing 1 (Fundc1), vesicle-associated membrane-protein-associated protein B (VAPB), phosphofurin acidic cluster sorting protein 2 (PACS-2), ER oxidoreductin 1 (Ero1), and receptor expression-enhancing protein 1 (REEP1). These proteins play an important role in the structure and functions of the MAMs. Abnormalities in these MAM proteins further contribute to the occurrence and development of related diseases, such as neurodegenerative diseases, non-alcoholicfattyliverdisease (NALFD), type 2 diabetes mellitus (T2DM), and diabetic kidney (DN). In this review, we introduce important proteins involved in the structure and the functions of the MAMs. Furthermore, we effectively summarize major insights about these proteins that are involved in the physiopathology of several diseases through the effect on MAMs.

Pitavastatin activates mitophagy to protect EPC proliferation through a calcium-dependent CAMK1-PINK1 pathway in atherosclerotic mice

Statins play a major role in reducing circulating cholesterol levels and are widely used to prevent coronary artery disease. Although they are recently confirmed to up-regulate mitophagy, little is known about the molecular mechanisms and its effect on endothelial progenitor cell (EPC). Here, we explore the role and mechanism underlying statin (pitavastatin, PTV)-activated mitophagy in EPC proliferation. ApoE^−/− mice are fed a high-fat diet for 8 weeks to induce atherosclerosis. In these mice, EPC proliferation decreases and is accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway. PTV reverses mitophagy and reduction in proliferation. Pink1 knockout or silencing Atg7 blocks PTV-induced proliferation improvement, suggesting that mitophagy contributes to the EPC proliferation increase. PTV elicits mitochondrial calcium release into the cytoplasm and further phosphorylates CAMK1. Phosphorylated CAMK1 contributes to PINK1 phosphorylation as well as mitophagy and mitochondrial function recover in EPCs. Together, our findings describe a molecular mechanism of mitophagy activation, where mitochondrial calcium release promotes CAMK1 phosphorylation of threonine¹⁷⁷ before phosphorylation of PINK1 at serine²²⁸, which recruits PARK2 and phosphorylates its serine⁶⁵ to activate mitophagy. Our results further account for the pleiotropic effects of statins on the cardiovascular system and provide a promising and potential therapeutic target for atherosclerosis.

Endothelial progenitor cell (EPCs) proliferation decreased, accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway in atherosclerosis. Statins induce mitophagy to protect EPCs by mitochondrial calcium release and CAMK1-mediated PINK1 phosphorylation.

Autophagy-Lysosomal Pathway as Potential Therapeutic Target in Parkinson's Disease

Cellular quality control systems have gained much attention in recent decades. Among these, autophagy is a natural self-preservation mechanism that continuously eliminates toxic cellular components and acts as an anti-ageing process. It is vital for cell survival and to preserve homeostasis. Several cell-type-dependent canonical or non-canonical autophagy pathways have been reported showing varying degrees of selectivity with regard to the substrates targeted. Here, we provide an updated review of the autophagy machinery and discuss the role of various forms of autophagy in neurodegenerative diseases, with a particular focus on Parkinson's disease. We describe recent findings that have led to the proposal of therapeutic strategies targeting autophagy to alter the course of Parkinson's disease progression.

Energy, Entropy and Quantum Tunneling of Protons and Electrons in Brain Mitochondria: Relation to Mitochondrial Impairment in Aging-Related Human Brain Diseases and Therapeutic Measures

Adult human brains consume a disproportionate amount of energy substrates (2-3% of body weight; 20-25% of total glucose and oxygen). Adenosine triphosphate (ATP) is a universal energy currency in brains and is produced by oxidative phosphorylation (OXPHOS) using ATP synthase, a nano-rotor powered by the proton gradient generated from proton-coupled electron transfer (PCET) in the multi-complex electron transport chain (ETC). ETC catalysis rates are reduced in brains from humans with neurodegenerative diseases (NDDs). Declines of ETC function in NDDs may result from combinations of nitrative stress (NS)-oxidative stress (OS) damage; mitochondrial and/or nuclear genomic mutations of ETC/OXPHOS genes; epigenetic modifications of ETC/OXPHOS genes; or defects in importation or assembly of ETC/OXPHOS proteins or complexes, respectively; or alterations in mitochondrial dynamics (fusion, fission, mitophagy). Substantial free energy is gained by direct O2-mediated oxidation of NADH. Traditional ETC mechanisms require separation between O2 and electrons flowing from NADH/FADH2 through the ETC. Quantum tunneling of electrons and much larger protons may facilitate this separation. Neuronal death may be viewed as a local increase in entropy requiring constant energy input to avoid. The ATP requirement of the brain may partially be used for avoidance of local entropy increase. Mitochondrial therapeutics seeks to correct deficiencies in ETC and OXPHOS.

Sigma-2 receptor antagonists rescue neuronal dysfunction induced by Parkinson's patient brain-derived α-synuclein

α‐Synuclein oligomers are thought to have a pivotal role in sporadic and familial Parkinson's disease (PD) and related α‐synucleinopathies, causing dysregulation of protein trafficking, autophagy/lysosomal function, and protein clearance, as well as synaptic function impairment underlying motor and cognitive symptoms of PD. Moreover, trans‐synaptic spread of α‐synuclein oligomers is hypothesized to mediate disease progression. Therapeutic approaches that effectively block α‐synuclein oligomer‐induced pathogenesis are urgently needed. Here, we show for the first time that α‐synuclein species isolated from human PD patient brain and recombinant α‐synuclein oligomers caused similar deficits in lipid vesicle trafficking rates in cultured rat neurons and glia, while α‐synuclein species isolated from non‐PD human control brain samples did not. Recombinant α‐synuclein oligomers also increased neuronal expression of lysosomal‐associated membrane protein‐2A (LAMP‐2A), the lysosomal receptor that has a critical role in chaperone‐mediated autophagy. Unbiased screening of several small molecule libraries (including the NIH Clinical Collection) identified sigma‐2 receptor antagonists as the most effective at blocking α‐synuclein oligomer‐induced trafficking deficits and LAMP‐2A upregulation in a dose‐dependent manner. These results indicate that antagonists of the sigma‐2 receptor complex may alleviate α‐synuclein oligomer‐induced neurotoxicity and are a novel therapeutic approach for disease modification in PD and related α‐synucleinopathies.

HMGA1 Induction of miR-103/107 Forms a Negative Feedback Loop to Regulate Autophagy in MPTP Model of Parkinson's Disease

Autophagy dysfunction has been directly linked with the onset and progression of Parkinson’s disease (PD), but the underlying mechanisms are not well understood. High-mobility group A1 (HMGA1), well-known chromatin remodeling proteins, play pivotal roles in diverse biological processes and diseases. Their function in neural cell death in PD, however, have not yet been fully elucidated. Here, we report that HMGA1 is highly induced during dopaminergic cell death in vitro and mice models of PD in vivo. Functional studies using genetic knockdown of endogenous HMGA1 show that HMGA1 signaling inhibition accelerates neural cell death, at least partially through aggravating MPP⁺-induced autophagic flux reduction resulting from partial block in autophagic flux at the terminal stages, indicating a novel potential neuroprotective role for HMGA1 in dopaminergic neurons death. MicroRNA-103/107 (miR-103/107) family, which is highly expressed in neuron, coordinately ensures proper end-stage autophagy. We further illustrate that MPP⁺/1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced HMGA1 elevation counterparts the effect of miR-103/107 downregulation by directly binding to their promoters, respectively, sustaining their expression in MPP⁺-damaged MN9D cells and modulates autophagy through CDK5R1/CDK5 signaling pathway. We also find that HMGA1 is a direct target of miR-103/107 family. Thus, our results suggest that HMGA1 forms a negative feedback loop with miR-103/107-CDK5R1/CDK5 signaling to regulate the MPP⁺/MPTP-induced autophagy impairment and neural cell death. Collectively, we identify a paradigm for compensatory neuroprotective HMGA1 signaling in dopaminergic neurons that could have important therapeutic implications for PD.

Calcitriol alleviates ethanol-induced hepatotoxicity via AMPK/mTOR-mediated autophagy

Excessive ethanol consumption causes cellular damage, leading to fetal alcohol syndrome and alcohol liver diseases, which are frequently seen with vitamin D (VD) deficiency. A great deal of progress has been achieved in the mechanisms of ethanol-induced hepatocyte damage. However, there are limited intervention means to reduce or rescue hepatocytes damage caused by ethanol. On the basis of our preliminary limited screen process, calcitriol showed a positive effect on protecting hepatocyte viability. Therefore, the molecular basis is worth elucidating. We found that calcitriol pretreatment markedly improved the cell viability, decreased cell apoptosis and oxidative stress and alleviated the abnormal mitochondrial morphology and membrane potential of hepatocytes induced by ethanol. Notably, autophagy was significantly enhanced by calcitriol, as evident by the increasing number of autophagosomes and autolysosomes, upregulated LC3B-Ⅱ and ATG5 levels, and promotion of p62 degradation. Furthermore, calcitriol pretreatment increased the colocalization of GFP-LC3-labeled autophagosomes with mitochondria, suggesting that calcitriol effectively promoted ethanol-induced mitophagy in hepatocytes. In addition, the inhibition of autophagy attenuated the protective and preventive effect of calcitriol. Furthermore, the effect of calcitriol on autophagy was regulated by AMPK/mTOR signaling, and signaling transduction was dependent on the Vitamin D receptor (VDR). In conclusion, calcitriol ameliorates ethanol-induced hepatocyte damage by enhancing autophagy. It may offer a convenient preventive and hepatoprotective mean for people on occasional social drink.

PARK7 maintains the stemness of glioblastoma stem cells by stabilizing epidermal growth factor receptor variant III

PARK7 is involved in many key cellular processes, including cell proliferation, transcriptional regulation, cellular differentiation, oxidative stress protection, and mitochondrial function maintenance. Deregulation of PARK7 has been implicated in the pathogenesis of various human diseases, including cancer. Here, we aimed to clarify the effect of PARK7 on stemness and radioresistance of glioblastoma stem cells (GSCs). Serum differentiation and magnetic cell sorting of GSCs revealed that PARK7 was preferentially expressed in GSCs rather than differentiated GSCs. Immunohistochemical staining showed enhanced expression of PARK7 in glioma tissues compared to that in normal brain tissues. shRNA-mediated knockdown of PARK7 inhibited the self-renewal activity of GSCs in vitro, as evidenced by the results of neurosphere formation, limiting dilution, and soft-agar clonogenic assays. In addition, PARK7 knockdown suppressed GSC invasion and enhanced GSC sensitivity to ionizing radiation (IR). PARK7 knockdown suppressed expression of GSC signatures including nestin, epidermal growth factor receptor variant III (EGFRvIII), SOX2, NOTCH1, and OCT4. Contrarily, overexpression of PARK7 in CD133^- non-GSCs increased self-renewal activities, migration, and IR resistance, and rescued the reduction of GSC factors under shPARK7-transfected and serum-differentiation conditions. Intriguingly, PARK7 acted as a co-chaperone of HSP90 by binding to it, protecting EGFRvIII from proteasomal degradation. Knockdown of PARK7 increased the production of reactive oxygen species, inducing partial apoptosis and enhancing IR sensitivity in GSCs. Finally, PARK7 knockdown increased mouse survival and IR sensitivity in vivo. Based on these data, we propose that PARK7 plays a pivotal role in the maintenance of stemness and therapeutic resistance in GSCs.

Emendation of autophagic dysfuction in neurological disorders: a potential therapeutic target

BACKGROUND

Neurological disorders have been continuously contributing to the global disease burden and affect millions of people worldwide. Researchers strive hard to extract out the ultimate cure and serve for the betterment of the society, and yet the treatments available provide only symptomatic relief. Aging and abnormal mutations seem to be the major culprits responsible for neurotoxicity and neuronal death. One of the major causes of these neurological disorders that has been paid utmost attention recently, is Autophagic Dysfunction.

AIM

The aim of the study was to understand the autophagic process, its impairment in neurological disorders and targeting the impairments as a therapeutic option for the said disorders.

METHODS

For the purpose of review, we carried out an extensive literature study to excerpt the series of steps involved in autophagy and to understand the mechanism of autophagic impairment occurring in a range of neurodegenerative and neuropsychiatric disorders like Parkinson, Alzheimer, Depression, Schizophrenia, Autism etc. The review also involved the exploration of certain molecules that can help in triggering the compromised autophagic members.

RESULTS

We found that, a number of genes, proteins, receptors and transcription factors interplay to bring about autophagy and plethora of neurological disorders are associated with the diminished expression of one or more autophagic member leading to inhibition of autophagy.

CONCLUSION

Autophagy is a significant process for the removal of misfolded, abnormal, damaged protein aggregates and nonfunctional cell organelles in order to suppress neurodegeneration. Therefore, triggering autophagy could serve as an important therapeutic target to treat neurological disorders.

Zebrafish as a model to study autophagy and its role in skeletal development and disease

In the last twenty years, research using zebrafish as a model organism has increased immensely. With the many advantages that zebrafish offer such as high fecundity, optical transparency, ex vivo development, and genetic tractability, they are well suited to studying developmental processes and the effect of genetic mutations. More recently, zebrafish models have been used to study autophagy. This important protein degradation pathway is needed for cell and tissue homeostasis in a variety of contexts. Correspondingly, its dysregulation has been implicated in multiple diseases including skeletal disorders. In this review, we explore how zebrafish are being used to study autophagy in the context of skeletal development and disease, and the ways these areas are intersecting to help identify potential therapeutic targets for skeletal disorders.

Chemical constituents from Macleaya cordata (Willd) R. Br. and their phenotypic functions against a Parkinson's disease patient-derived cell line

Cytological profiling (CP) assay against a human olfactory neuroshpere-derived (hONS) cell line using a library of traditional Chinese medicinal plant extracts gave indications that the ethanolic extract of Macleaya cordata (Willd) R. Br. elicited strong perturbations to various cellular components. Further chemical investigation of this extract resulted in the isolation of two new benzo[c]phenanthridine alkaloids, (6R)-10-methoxybocconoline (1) and 6-(1-hydroxyethyl)-10-methoxy-5,6-dihydrochelerythrine (2). Their planar structures were elucidated by extensive 1D and 2D NMR studies, together with MS data. The absolute configuration for position C-6 of 1 and relative configurations for position C-6 and C-1' of 2 were assigned by density functional theory (DFT) calculations of ECD and NMR data, respectively. Also isolated were fourteen known metabolites, including ten alkaloids (3-12) and four coumaroyl-containing compounds (13-16). Cytological profiling of the isolates against Parkinson's Disease (PD) patient-derived olfactory cells revealed bocconoline (3) and 6-(1-hydroxyethyl)-5,6-dihydrochelerythrine (4) significantly perturbated the features of cellular organelles including early endosomes, mitochondria and autophagosomes. Given that hONS cells from PD patients model some functional aspects of the disease, the results suggested that these phenotypic profiles may have a role in the mechanisms underlying PD and signified the efficacy of CP in finding potential chemical tools to study the biological pathways in PD.

Guilt-by-Association - Functional Insights Gained From Studying the LRRK2 Interactome

The Parkinson's disease-associated Leucine-rich repeat kinase 2 (LRRK2) is a complex multi-domain protein belonging to the Roco protein family, a unique group of G-proteins. Variants of this gene are associated with an increased risk of Parkinson's disease. Besides its well-characterized enzymatic activities, conferred by its GTPase and kinase domains, and a central dimerization domain, it contains four predicted repeat domains, which are, based on their structure, commonly involved in protein-protein interactions (PPIs). In the past decades, tremendous progress has been made in determining comprehensive interactome maps for the human proteome. Knowledge of PPIs has been instrumental in assigning functions to proteins involved in human disease and helped to understand the connectivity between different disease pathways and also significantly contributed to the functional understanding of LRRK2. In addition to an increased kinase activity observed for proteins containing PD-associated variants, various studies helped to establish LRRK2 as a large scaffold protein in the interface between cytoskeletal dynamics and the vesicular transport. This review first discusses a number of specific LRRK2-associated PPIs for which a functional consequence can at least be speculated upon, and then considers the representation of LRRK2 protein interactions in public repositories, providing an outlook on open research questions and challenges in this field.

Mitochondrial clearance and maturation of autophagosomes are compromised in LRRK2 G2019S familial Parkinson's disease patient fibroblasts

This study utilized human fibroblasts as a preclinical discovery and diagnostic platform for identification of cell biological signatures specific for the LRRK2 G2019S mutation producing Parkinson's disease (PD). Using live cell imaging with a pH-sensitive Rosella biosensor probe reflecting lysosomal breakdown of mitochondria, mitophagy rates were found to be decreased in fibroblasts carrying the LRRK2 G2019S mutation compared to cells isolated from healthy subject (HS) controls. The mutant LRRK2 increased kinase activity was reduced by pharmacological inhibition and targeted antisense oligonucleotide treatment, which normalized mitophagy rates in the G2019S cells and also increased mitophagy levels in HS cells. Detailed mechanistic analysis showed a reduction of mature autophagosomes in LRRK2 G2019S fibroblasts, which was rescued by LRRK2 specific kinase inhibition. These findings demonstrate an important role for LRRK2 protein in regulation of mitochondrial clearance by the lysosomes, which is hampered in PD with the G2019S mutation. The current results are relevant for cell phenotypic diagnostic approaches and potentially for stratification of PD patients for targeted therapy.

Nitroxide Radical-Containing Redox Nanoparticles Protect Neuroblastoma SH-SY5Y Cells against 6-Hydroxydopamine Toxicity

Parkinson's disease (PD) patients can benefit from antioxidant supplementation, and new efficient antioxidants are needed. The aim of this study was to evaluate the protective effect of selected nitroxide-containing redox nanoparticles (NRNPs) in a cellular model of PD. Antioxidant properties of NRNPs were studied in cell-free systems by protection of dihydrorhodamine 123 against oxidation by 3-morpholino-sydnonimine and protection of fluorescein against bleaching by 2,2-azobis(2-amidinopropane) hydrochloride and sodium hypochlorite. Model blood-brain barrier penetration was studied using hCMEC/D3 cells. Human neuroblastoma SH-SY5Y cells, exposed to 6-hydroxydopamine (6-OHDA), were used as an in vitro model of PD. Cells were preexposed to NRNPs or free nitroxides (TEMPO or 4-amino-TEMPO) for 2 h and treated with 6-OHDA for 1 h and 24 h. The reactive oxygen species (ROS) level was estimated with dihydroethidine 123 and Fluorimetric Mitochondrial Superoxide Activity Assay Kit. Glutathione level (GSH) was measured with ortho-phtalaldehyde, ATP by luminometry, changes in mitochondrial membrane potential with JC-1, and mitochondrial mass with 10-Nonyl-Acridine Orange. NRNP1, TEMPO, and 4-amino-TEMPO (25-150 μM) protected SH-SY5Y cells from 6-OHDA-induced viability loss; the protection was much higher for NRNP1 than for free nitroxides. NRNP1 were better antioxidants in vitro and permeated better the model BBB than free nitroxides. Exposure to 6-OHDA decreased the GSH level after 1 h and increased it considerably after 24 h (apparently a compensatory overresponse); NRNPs and free nitroxides prevented this increase. NRNP1 and free nitroxides prevented the decrease in ATP level after 1 h and increased it after 24 h. 6-OHDA increased the intracellular ROS level and mitochondrial superoxide level. Studied antioxidants mostly decreased ROS and superoxide levels. 6-OHDA decreased the mitochondrial potential and mitochondrial mass; both effects were prevented by NRNP1 and nitroxides. These results suggest that the mitochondria are the main site of 6-OHDA-induced cellular damage and demonstrate a protective effect of NRNP1 in a cellular model of PD.

Galantamine Inhibits Aβ1-42-Induced Neurotoxicity by Enhancing α7nAChR Expression as a Cargo Carrier for LC3 Binding and Aβ1-42 Engulfment During Autophagic Degradation

Despite Alzheimer's disease (AD) being the most common neurodegenerative disorder worldwide, no FDA-approved disease-modifying treatments have been approved for this condition since 2003. Neuronal-type alpha7 nicotinic acetylcholine receptors (α7nAChRs) play an essential role in cognitive functions, binding with extracellular β-amyloid (Aβ plaques) and inhibiting Aβ-induced neurotoxicity. α7nAChRs are impaired early in the course of AD; drugs targeting α7nAChRs are being hotly pursued as a treatment of AD. Encenicline, a partial selective agonist of α7nAChR and modulator of acetylcholine, failed in phase III trials because of gastrointestinal side effects. We, therefore, evaluated the efficacy of galantamine, a positive allosteric modulator at α7nAChRs and an acetylcholinesterase inhibitor, that has been used since 2000 as first-line treatment of mild-to-moderate dementia. This study highlights an important new benefit with galantamine. We found that galantamine inhibits Aβ1-42-induced apoptosis by activating the JNK signaling pathway, thus enhancing α7nAChR expression, and also inhibits the Akt pathway, which further increases autophagosome biogenesis and autophagy. These effects can be reproduced by α7nAChR overexpression in the absence of galantamine. Importantly, the α7 subunit protein sequence of α7nAChRs contains 3 LC3-interacting regions; our immunoprecipitation data show that α7 binds with the autophagosomal marker protein LC3. This is the first report to provide evidence showing that the cell surface receptor α7nAChR acts as a cargo carrier for LC3 binding for Aβ1-42 sequestration to autophagosomes, suggesting a novel mechanism for the neuroprotective efficacy of galantamine in AD.

How autophagy can restore proteostasis defects in multiple diseases?

Cellular evolution develops several conserved mechanisms by which cells can tolerate various difficult conditions and overall maintain homeostasis. Autophagy is a well-developed and evolutionarily conserved mechanism of catabolism, which endorses the degradation of foreign and endogenous materials via autolysosome. To decrease the burden of the ubiquitin-proteasome system (UPS), autophagy also promotes the selective degradation of proteins in a tightly regulated way to improve the physiological balance of cellular proteostasis that may get perturbed due to the accumulation of misfolded proteins. However, the diverse as well as selective clearance of unwanted materials and regulations of several cellular mechanisms via autophagy is still a critical mystery. Also, the failure of autophagy causes an increase in the accumulation of harmful protein aggregates that may lead to neurodegeneration. Therefore, it is necessary to address this multifactorial threat for in-depth research and develop more effective therapeutic strategies against lethal autophagy alterations. In this paper, we discuss the most relevant and recent reports on autophagy modulations and their impact on neurodegeneration and other complex disorders. We have summarized various pharmacological findings linked with the induction and suppression of autophagy mechanism and their promising preclinical and clinical applications to provide therapeutic solutions against neurodegeneration. The conclusion, key questions, and future prospectives sections summarize fundamental challenges and their possible feasible solutions linked with autophagy mechanism to potentially design an impactful therapeutic niche to treat neurodegenerative diseases and imperfect aging.

Dysregulated Interorganellar Crosstalk of Mitochondria in the Pathogenesis of Parkinson's Disease

The pathogenesis of Parkinson’s disease (PD), the second most common neurodegenerative disorder, is complex and involves the impairment of crucial intracellular physiological processes. Importantly, in addition to abnormal α-synuclein aggregation, the dysfunction of various mitochondria-dependent processes has been prominently implicated in PD pathogenesis. Besides the long-known loss of the organelles’ bioenergetics function resulting in diminished ATP synthesis, more recent studies in the field have increasingly focused on compromised mitochondrial quality control as well as impaired biochemical processes specifically localized to ER–mitochondria interfaces (such as lipid biosynthesis and calcium homeostasis). In this review, we will discuss how dysregulated mitochondrial crosstalk with other organelles contributes to PD pathogenesis.

Celastrol Inhibits Dopaminergic Neuronal Death of Parkinson's Disease through Activating Mitophagy

Parkinson’s disease (PD) is a neurodegenerative disease, which is associated with mitochondrial dysfunction and abnormal protein accumulation. No treatment can stop or slow PD. Autophagy inhibits neuronal death by removing damaged mitochondria and abnormal protein aggregations. Celastrol is a triterpene with antioxidant and anti-inflammatory effects. Up until now, no reports have shown that celastrol improves PD motor symptoms. In this study, we used PD cell and mouse models to evaluate the therapeutic efficacy and mechanism of celastrol. In the substantia nigra, we found lower levels of autophagic activity in patients with sporadic PD as compared to healthy controls. In neurons, celastrol enhances autophagy, autophagosome biogenesis (Beclin 1↑, Ambra1↑, Vps34↑, Atg7↑, Atg12↑, and LC3-II↑), and mitophagy (PINK1↑, DJ-1↑, and LRRK2↓), and these might be associated with MPAK signaling pathways. In the PD cell model, celastrol reduces MPP⁺-induced dopaminergic neuronal death, mitochondrial membrane depolarization, and ATP reduction. In the PD mouse model, celastrol suppresses motor symptoms and neurodegeneration in the substantia nigra and striatum and enhances mitophagy (PINK1↑ and DJ-1↑) in the striatum. Using MPP⁺ to induce mitochondrial damage in neurons, we found celastrol controls mitochondrial quality by sequestering impaired mitochondria into autophagosomes for degradation. This is the first report to show that celastrol exerts neuroprotection in PD by activating mitophagy to degrade impaired mitochondria and further inhibit dopaminergic neuronal apoptosis. Celastrol may help to prevent and treat PD.

Hepatic encephalopathy is linked to alterations of autophagic flux in astrocytes

Background

Hepatic encephalopathy (HE) is a severe neuropsychiatric syndrome caused by various types of liver failure resulting in hyperammonemia-induced dysfunction of astrocytes. It is unclear whether autophagy, an important pro-survival pathway, is altered in the brains of ammonia-intoxicated animals as well as in HE patients.

Methods

Using primary rat astrocytes, a co-culture model of primary mouse astrocytes and neurons, an in vivo rat HE model, and post mortem brain samples of liver cirrhosis patients with HE we analyzed whether and how hyperammonemia modulates autophagy.

Findings

We show that autophagic flux is efficiently inhibited after administration of ammonia in astrocytes. This occurs in a fast, reversible, time-, dose-, and ROS-dependent manner and is mediated by ammonia-induced changes in intralysosomal pH. Autophagic flux is also strongly inhibited in the cerebral cortex of rats after acute ammonium intoxication corroborating our results using an in vivo rat HE model. Transglutaminase 2 (TGM2), a factor promoting autophagy, is upregulated in astrocytes of in vitro- and in vivo-HE models as well as in post mortem brain samples of liver cirrhosis patients with HE, but not in patients without HE. LC3, a commonly used autophagy marker, is significantly increased in the brain of HE patients. Ammonia also modulated autophagy moderately in neuronal cells. We show that taurine, known to ameliorate several parameters caused by hyperammonemia in patients suffering from liver failure, is highly potent in reducing ammonia-induced impairment of autophagic flux. This protective effect of taurine is apparently not linked to inhibition of mTOR signaling but rather to reducing ammonia-induced ROS formation.

Interpretation

Our data support a model in which autophagy aims to counteract ammonia-induced toxicity, yet, as acidification of lysosomes is impaired, possible protective effects thereof, are hampered. We propose that modulating autophagy in astrocytes and/or neurons, e.g. by taurine, represents a novel strategy to treat liver diseases associated with HE.

Funding

Supported by the DFG, CRC974 “Communication and Systems Relevance in Liver Injury and Regeneration“, Düsseldorf (Project number 190586431) Projects A05 (DH), B04 (BG), B05 (NK), and B09 (ASR).

PU-91 drug rescues human age-related macular degeneration RPE cells; implications for AMD therapeutics

Since mitochondrial dysfunction is implicated in the pathogenesis of AMD, this study is based on the premise that repurposing of mitochondria-stabilizing FDA-approved drugs such as PU-91, might rescue AMD RPE cells from AMD mitochondria-induced damage. The PU-91 drug upregulates PGC-1α which is a critical regulator of mitochondrial biogenesis. Herein, we tested the therapeutic potential of PU-91 drug and examined the additive effects of treatment with PU-91 and esterase inhibitors i.e., EI-12 and EI-78, using the in vitro transmitochondrial AMD cell model. This model was created by fusing platelets obtained from AMD patients with Rho⁰ i.e., mitochondria-deficient, ARPE-19 cell lines. The resulting AMD RPE cell lines have identical nuclei but differ in their mitochondrial DNA content, which is derived from individual AMD patients. Briefly, we report significant improvement in cell survival, mitochondrial health, and antioxidant potential in PU-91-treated AMD RPE cells compared to their untreated counterparts. In conclusion, this study identifies PU 91 as a therapeutic candidate drug for AMD and repurposing of PU-91 will be a smoother transition from lab bench to clinic since the pharmacological profiles of PU-91 have been examined already.

Unique α-synuclein pathology within the amygdala in Lewy body dementia: implications for disease initiation and progression

The protein α-synuclein (αsyn) forms pathologic aggregates in a number of neurodegenerative diseases including Lewy body dementia (LBD) and Parkinson's disease (PD). It is unclear why diseases such as LBD may develop widespread αsyn pathology, while in Alzheimer's disease with amygdala restricted Lewy bodies (AD/ALB) the αsyn aggregates remain localized. The amygdala contains αsyn aggregates in both LBD and in AD/ALB; to understand why αsyn pathology continues to progress in LBD but not in AD/ALB, tissue from the amygdala and other regions were obtained from 14 cases of LBD, 9 cases of AD/ALB, and 4 controls for immunohistochemical and biochemical characterization. Utilizing a panel of previously characterized αsyn antibodies, numerous unique pathologies differentiating LBD and AD/ALB were revealed; particularly the presence of dense neuropil αsyn aggregates, astrocytic αsyn, and αsyn-containing dystrophic neurites within senile plaques. Within LBD, these unique pathologies were predominantly present within the amygdala. Biochemically, the amygdala in LBD prominently contained specific carboxy-truncated forms of αsyn which are highly prone to aggregate, suggesting that the amygdala may be prone to initiate development of αsyn pathology. Similar to carboxy-truncated αsyn, it was demonstrated herein that the presence of aggregation prone A53T αsyn is sufficient to drive misfolding of wild-type αsyn in human disease. Overall, this study identifies within the amygdala in LBD the presence of unique strain-like variation in αsyn pathology that may be a determinant of disease progression.

Current Progress of Mitochondrial Quality Control Pathways Underlying the Pathogenesis of Parkinson's Disease

Parkinson's disease (PD), clinically characterized by motor and nonmotor symptoms, is a common progressive and multisystem neurodegenerative disorder, which is caused by both genetic and environmental risk factors. The main pathological features of PD are the loss of dopaminergic (DA) neurons and the accumulation of alpha-synuclein (α-syn) in the residual DA neurons in the substantia nigra pars compacta (SNpc). In recent years, substantial progress has been made in discovering the genetic factors of PD. In particular, a total of 19 PD-causing genes have been unraveled, among which some members have been regarded to be related to mitochondrial dysfunction. Mitochondria are key regulators of cellular metabolic activity and are critical for many important cellular processes including energy metabolism and even cell death. Their normal function is basically maintained by the mitochondrial quality control (MQC) mechanism. Accordingly, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a kind of neurotoxin, exerts its neurotoxic effects at least partially by producing its toxic metabolite, namely, 1-methyl-4-phenylpyridine (MPP+), which in turn causes mitochondrial dysfunction by inhibiting complex I and mimicking the key features of PD pathogenesis. This review focused on three main aspects of the MQC signaling pathways, that is, mitochondrial biogenesis, mitochondrial dynamics, and mitochondrial autophagy; hence, it demonstrates in detail how genetic and environmental factors result in PD pathogenesis by interfering with MQC pathways, thereby hopefully contributing to the discovery of novel potential therapeutic targets for PD.

Sensory neuropathy and nociception in rodent models of Parkinson's disease

Parkinson's disease (PD) often manifests with prodromal pain and sensory losses whose etiologies are not well understood. Multiple genetic and toxicity-based rodent models of PD partly recapitulate the histopathology and motor function deficits. Although far less studied, there is some evidence that rodents, similar to humans, develop sensory manifestations of the disease, which may precede motor disturbances and help to elucidate the underlying mechanisms of PD-associated pain at the molecular and neuron circuit levels. The present Review summarizes nociception and other sensory functions in frequently used rodent PD models within the context of the complex phenotypes. In terms of mechanisms, it appears that the acute loss of dopaminergic neurons in systemic toxicity models (MPTP, rotenone) primarily causes nociceptive hyperexcitability, presumably owing to a loss of inhibitory control, whereas genetic models primarily result in a progressive loss of heat perception, reflecting sensory fiber neuropathies. At the molecular level, neither α-synuclein deposits alone nor failure of mitophagy alone appear to be strong enough to result in axonal or synaptic pathology of nociceptive neurons that manifest at the behavioral level, and peripheral sensory loss may mask central ‘pain’ in behavioral tests. Hence, allostatic combinations or additional challenges and novel behavioral assessments are needed to better evaluate PD-associated sensory neuropathies and pain in rodents.

Summary: Rodent models of Parkinson's disease partially develop prodromal somatosensory and olfactory dysfunctions reminiscent of sensory neuropathies in patients and reveal mechanistic insight, but data are incomplete and fragmented.

Tanshinone IIA ameliorates oxaliplatin-induced neurotoxicity via mitochondrial protection and autophagy promotion

Peripheral neurotoxicity is a common adverse reaction in cancer patients undergoing chemotherapy. The neuropathologic changes were partly associated with mitochondrial dysfunction and autophagy. Tanshinone IIA, a compound extracted from the medicinal herb Salvia miltiorrhiza, has been shown to exhibit neuroprotective effects. The present study investigated the effects of tanshinone IIA on chemotherapy-induced neurotoxicity and to study the underlying mechanism. Neuroma cell line N2a and rats were treated with oxaliplatin and/or tanshinone IIA. The effects on neurotoxicity were evaluated using cell viability assay, flow cytometry detection of apoptosis, measurement of intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (Ψm), autophagy detection, nerve function assessment, and behavior assessment. The results showed that tanshinone IIA prevented oxaliplatin-induced inhibition of cell viability and reduced apoptosis. Tanshinone IIA also prevented excessive oxidative stress, as demonstrated by decreased ROS levels and reduced Ψm loss. Lastly, treatment with tanshinone IIA promoted autophagy through the PI3K/Akt/mTOR signaling pathway. The in vivo experiment showed that tanshinone IIA ameliorated oxaliplatin-induced allodynia and sciatic nerve dysfunction. An increase in serum nerve growth factor level was observed. In conclusion, the results of the study suggested a protective role of tanshinone IIA in neurotoxicity induced by oxaliplatin via mitochondrial protection and autophagy promotion.

Mechanisms and roles of mitophagy in neurodegenerative diseases

Mitochondria are double‐membrane‐encircled organelles existing in most eukaryotic cells and playing important roles in energy production, metabolism, Ca²⁺ buffering, and cell signaling. Mitophagy is the selective degradation of mitochondria by autophagy. Mitophagy can effectively remove damaged or stressed mitochondria, which is essential for cellular health. Thanks to the implementation of genetics, cell biology, and proteomics approaches, we are beginning to understand the mechanisms of mitophagy, including the roles of ubiquitin‐dependent and receptor‐dependent signals on damaged mitochondria in triggering mitophagy. Mitochondrial dysfunction and defective mitophagy have been broadly associated with neurodegenerative diseases. This review is aimed at summarizing the mechanisms of mitophagy in higher organisms and the roles of mitophagy in the pathogenesis of neurodegenerative diseases. Although many studies have been devoted to elucidating the mitophagy process, a deeper understanding of the mechanisms leading to mitophagy defects in neurodegenerative diseases is required for the development of new therapeutic interventions, taking into account the multifactorial nature of diseases and the phenotypic heterogeneity of patients.

Pink1 regulates FKBP5 interaction with AKT/PHLPP and protects neurons from neurotoxin stress induced by MPP

Loss of function mutations in the PTEN-induced putative kinase 1 (Pink1) gene have been linked with an autosomal recessive familial form of early onset Parkinson's disease (PD). However, the underlying mechanism(s) responsible for degeneration remains elusive. Presently, using co-immunoprecipitation in HEK (Human embryonic kidney) 293 cells, we show that Pink1 endogenously interacts with FK506-binding protein 51 (FKBP51 or FKBP5), FKBP5 and directly phosphorylates FKBP5 at Serine in an in vitro kinase assay. Both FKBP5 and Pink1 have been previously associated with protein kinase B (AKT) regulation. We provide evidence using primary cortical cultured neurons from Pink1-deficient mice that Pink1 increases AKT phosphorylation at Serine 473 (Ser473) challenged by 1-methyl-4-phenylpyridinium (MPP⁺ ) and that over-expression of FKBP5 using an adeno-associated virus delivery system negatively regulates AKT phosphorylation at Ser473 in murine-cultured cortical neurons. Interestingly, FKBP5 over-expression promotes death in response to MPP⁺ in the absence of Pink1. Conversely, shRNA-mediated knockdown of FKBP5 in cultured cortical neurons is protective and this effect is reversed with inhibition of AKT signaling. In addition, shRNA down-regulation of PH domain leucine-rich repeat protein phosphatase (PHLPP) in Pink1 WT neurons increases neuronal survival, while down-regulation of PHLPP in Pink1 KO rescues neuronal death in response to MPP⁺ . Finally, using co-immunoprecipitation, we show that FKBP5 interacts with the kinase AKT and phosphatase PHLPP. This interaction is increased in the absence of Pink1, both in Mouse Embryonic Fibroblasts (MEF) and in mouse brain tissue. Expression of kinase dead Pink1 (K219M) enhances FKBP5 interaction with both AKT and PHLPP. Overall, our results suggest a testable model by which Pink1 could regulate AKT through phosphorylation of FKBP5 and interaction of AKT with PHLPP. Our results suggest a potential mechanism by which PINK1-FKBP5 pathway contributes to neuronal death in PD. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Therapeutic landscape for Batten disease: current treatments and future prospects

Batten disease (also known as neuronal ceroid lipofuscinoses) constitutes a family of devastating lysosomal storage disorders that collectively represent the most common inherited paediatric neurodegenerative disorders worldwide. Batten disease can result from mutations in 1 of 13 genes. These mutations lead to a group of diseases with loosely overlapping symptoms and pathology. Phenotypically, patients with Batten disease have visual impairment and blindness, cognitive and motor decline, seizures and premature death. Pathologically, Batten disease is characterized by lysosomal accumulation of autofluorescent storage material, glial reactivity and neuronal loss. Substantial progress has been made towards the development of effective therapies and treatments for the multiple forms of Batten disease. In 2017, cerliponase alfa (Brineura), a tripeptidyl peptidase enzyme replacement therapy, became the first globally approved treatment for CLN2 Batten disease. Here, we provide an overview of the promising therapeutic avenues for Batten disease, highlighting current FDA-approved clinical trials and prospective future treatments.

Hydroxychloroquine antiparkinsonian potential: Nurr1 modulation versus autophagy inhibition

The nuclear orphan receptor (Nurr1) has recently received a perceivable solicitude as a target for the therapeutic intervention against PD. Meanwhile, the dysregulation of autophagy, along with other processes is believed to contribute massively to PD pathophysiology. Hydroxychloroquine, a hydroxy derivative of chloroquine, is an antimalarial agent which is also used as an anti-rheumatic drug. The neuroprotective potential of hydroxychloroquine and chloroquine remained controversial until recently a study showed that chloroquine exhibited an antiparkinsonian activity through Nurr1 modulation. The aim of this work is to identify whether the less toxic derivative, hydroxychloroquine, could show a similar pattern. In rat rotenone model, hydroxychloroquine effectively boosted Nurr-1 expression, exhibited an anti-inflammatory effect as verified by hindering certain pro-inflammatory cytokines and successfully reduced GSK-3β activity. Consequently, an increase in the striatal tyrosine hydroxylase content, as well as improved locomotion and muscle coordination was shown. However, this improvement was opposed by hydroxychloroquine induced autophagic inhibition as manifested by enhancing both LC3-II and P62 levels possibly through the prominent decline in sirtuin 1 level and elevated apoptotic biomarkers. In conclusion, hydroxychloroquine successfully ameliorated PD motor dysfunction in spite of the fact that both autophagy and apoptosis were deregulated through Nurr1 modulation.

Killing Two Angry Birds with One Stone: Autophagy Activation by Inhibiting Calpains in Neurodegenerative Diseases and Beyond

Proteolytic machineries execute vital cellular functions and their disturbances are implicated in diverse medical conditions, including neurodegenerative diseases. Interestingly, calpains, a class of Ca²⁺-dependent regulatory proteases, can modulate the degradational system of autophagy by cleaving proteins involved in this pathway. Moreover, both machineries are common players in many molecular pathomechanisms and have been targeted individually or together, as a therapeutic strategy in experimental setups. In this review, we briefly introduce calpains and autophagy, with their roles in health and disease, and focus on their direct pathologically relevant interplay in neurodegeneration and beyond. The modulation of calpain activity may comprise a promising treatment approach to attenuate the deregulation of these two essential mechanisms.

Are Proteinopathy and Oxidative Stress Two Sides of the Same Coin?

Parkinson's disease, like other neurodegenerative diseases, exhibits two common features: Proteinopathy and oxidative stress, leading to protein aggregation and mitochondrial damage respectively. Because both protein aggregates and dysfunctional mitochondria are eliminated by autophagy, we suggest that inadequate clearance may couple the two phenomena. If a neuron's autophagy machinery is overwhelmed, whether by excessive oxidative stress or by excessive protein aggregation, protein aggregates and dysfunctional mitochondria will both accumulate. Parkinson's disease may provide a unique window into this because there is evidence that both sides contribute. Mutations amplifying the aggregation of α-synuclein are associated with Parkinson's disease. Likewise, mutations in Parkin and PINK1, proteins involved in mitophagy, suggest that impaired mitochondrial clearance is also a contributing factor. Many have suggested that dopamine oxidation products lead to oxidative stress accounting for the dopaminergic selectivity of the disease. We have presented evidence for the specific involvement of hypochlorite-oxidized cysteinyl-dopamine (HOCD), a redox-cycling benzothiazine derivative. While toxins like 6-hydroxydopamine and 1-methyl-4-phenyl pyridinium (MPP+) have been used to study mitochondrial involvement in Parkinson's disease, HOCD may provide a more physiologically relevant approach. Understanding the role of mitochondrial dysfunction and oxidative stress in Parkinson's disease and their relation to α-synuclein proteinopathy is important to gain a full picture of the cause, especially for the great majority of cases which are idiopathic.

Analysis of macroautophagy related proteins in G2019S LRRK2 Parkinson's disease brains with Lewy body pathology

LRRK2, the gene encoding the multidomain kinase Leucine-Rich Repeat Kinase 2 (LRRK2), has been linked to familial and sporadic forms of Parkinson's disease (PD), as well as cancer, leprosy and Crohn's disease, establishing it as a target for discovery therapeutics. LRRK2 has been associated with a range of cellular processes, however its physiological and pathological functions remain unclear. The most prevalent LRRK2 mutations in PD have been shown to affect macroautophagy in various cellular models while a role in autophagy signalling has been recapitulated in vivo. Dysregulation of autophagy has been implicated in PD pathology, and this raises the possibility that differential autophagic activity is relevant to disease progression in PD patients carrying LRRK2 mutations. To examine the relevance of LRRK2 to the regulation of macroautophagy in a disease setting we examined the levels of autophagic markers in the basal ganglia of G2019S LRRK2 PD post-mortem tissue, in comparison to pathology-matched idiopathic PD (iPD), using immunoblotting (IB). Significantly lower levels of p62 and LAMP1 were observed in G2019S LRRK2 PD compared to iPD cases. Similarly, an increase in ULK1 was observed in iPD but was not reflected in G2019S LRRK2 PD cases. Furthermore, examination of p62 by immunohistochemistry (IH) recapitulated a distinct signature for G2019S PD. IH of LAMP1, LC3 and ULK1 broadly correlated with the IB results. Our data from a small but pathologically well-characterized cases highlights a divergence of G2019S PD carriers in terms of autophagic response in alpha-synuclein pathology affected brain regions compared to iPD.

Association of GALC, ZNF184, IL1R2 and ELOVL7 With Parkinson's Disease in Southern Chinese

Study Objectives: The aim of the study was to investigate the relationship between 22 single nucleotide polymorphisms (SNPs) and Parkinson’s disease (PD) in the Chinese population.

Methods: A total of 250 PD patients and 240 healthy controls were recruited. The SNaPshot technique and the polymer chain reaction were used to detect 22 SNPs.

Results: rs8005172 of GALC, rs9468199 of ZNF184 and rs34043159 of IL1R2, were associated with PD (rs8005172: p = 0.009, OR = 0.69, allele model, p = 0.010, additive model, p = 0.015, OR = 2.17, dominant model; p = 0.020, OR = 2.11, dominant model after adjustment; p = 0.036, OR = 1.47, recessive model after adjustment; rs9468199: p = 0.008, OR = 1.52, allele model, p = 0.008, additive model, p = 0.007, OR = 0.22, recessive model, p = 0.005, OR = 0.20, recessive model after adjustment; rs34043159: p = 0.034, OR = 1.31, allele model, p = 0.036, additive model).

Conclusion: Our study revealed that GALC, ZNF184, and IL1R2 were associated with PD in the southern Chinese population. GALC was also associated with LOPD. ELOVL7 and ZNF184 were associated with EOPD. In addition, trends of association to PD, between SATB1, NMD3, and FGF20, were also found.

Statement of Significance: Genetic play an important role in the pathogenesis factors of Parkinson’s disease (PD). We found that GALC, ZNF184, and IL1R2 were associated with PD. GALC was also associated with late onset of PD, while ELOVL7 and ZNF184 were associated with early onset PD. This study is the first to find an association between GALC, ZNF184, and rs2280104 with PD.

Neuroprotective Effects of Betulin in Pharmacological and Transgenic Caenorhabditis elegans Models of Parkinson's Disease

Parkinson’s disease (PD) is the second most common degenerative disorder of the central nervous system in the elderly. It is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta, as well as by motor dysfunction. Although the causes of PD are not well understood, aggregation of α-synuclein (α-syn) in neurons contributes to this disease. Current therapeutics for PD provides satisfactory symptom relief but not a cure. Treatment strategies include attempts to identify new drugs that will prevent or arrest the progressive course of PD by correcting disease-specific pathogenic process. Betulin is derived from the bark of birch trees and possesses anticancer, antimicrobial, and anti-inflammatory properties. The aim of the present study was to evaluate the potential for betulin to ameliorate PD features in Caenorhabditis elegans (C. elegans) models. We demonstrated that betulin diminished α-syn accumulation in the transgenic C. elegans model. Betulin also reduced 6-hydroxydopamine-induced dopaminergic neuron degeneration, reduced food-sensing behavioral abnormalities, and reversed life-span decreases in a pharmacological C. elegans model. Moreover, we found that the enhancement of proteasomes activity by promoting rpn1 expression and downregulation of the apoptosis pathway gene, egl-1, may be the molecular mechanism for betulin-mediated protection against PD pathology. Together, these findings support betulin as a possible treatment for PD and encourage further investigations of betulin as an antineurodegenerative agent.