Parkinson's disease: connecting mitochondria to inflammasomes

Fibrinogen exacerbates α-synuclein aggregation and mitochondrial dysfunction via alpha5beta3 integrin in Parkinson's disease

INTRODUCTION

Blood-brain barrier(BBB) disruption promotes the influx of the fibrinogen(FG); however, it remains unknown whether FG deposit contributes to neurodegeneration in Parkinson's disease(PD).

OBJECTIVES

We aimed to examine the pathophysiologic link among FG, mitochondrial dysfunction and α-synuclein(α-syn) abnormality in PD.

METHODS

First, plasma FG levels were measured in 60 healthy controls and 60 PD patients. Second, to determine whether FG contributes to PD pathogenesis, FG was injected into the substantia nigra pars compacta(SNpc) of healthy and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-treated PD mice. Meanwhile, intraperitoneal injections of batroxobin were used to deplete FG in the brain of PD mice. Mitochondrial ultrastructure in mouse models was observed by transmission electron microscopy(TEM), and mitochondrial functions in SH-SY5Y cells were examined by different assay kits and flow cytometry. The mechanisms underlying FG-induced α-syn abnormality and mitochondrial dysfunction were observed by RNA sequencing and validated in various experiments including western blot and immunostaining. Last, the endocytosis of FG in primary neurons were detected by confocal microscopy, and α-syn aggregation after FG co-incubation were evaluated by western blot, ThT-binding assay and TEM.

RESULTS

PD patients exhibited elevated levels of FG in peripheral blood compared to HCs, and there was a positive correlation between the plasma FG and PD clinical severity. Excessive FG in the SNpc of MPTP-treated mice promoted poly (ADP-ribose) (PAR) polymerase-1(PARP1) elevation, mediated by the αvβ3 integrin receptor. FG exacerbated α-syn abnormalities and mitochondrial dysfunctions via PARP1 activation. Moreover, FG entered neurons by αvβ3 integrin mediation, potentially enhancing α-syn fibrillation and toxicity. FG facilitated α-syn aggregation subsequently reduced ATP-dependent Clp protease(ClpP) level, impairing neuronal mitochondrial unfolded response and increasing mitochondrial ROS. Pharmacological depletion of FG by batroxobin ameliorated neurodegeneration in MPTP-treated mice.

CONCLUSION

Our study indicate that FG plays an essential pathological role in α-syn abnormality. FG-targeting therapy can be a promising strategy against neurodegeneration in PD.

CRM1 mediates ASC nuclear export and inflammasome activation

Inflammasomes are multiprotein complexes of the innate immune system that sense different pathogens or danger signals, and have been implicated in the pathogenesis of multiple human inflammatory diseases. The translocation of adaptor protein ASC from the nucleus to the cytosol is important for inflammasome assembly and activation, but the mechanism remains unclear. Here we show that pharmacological inhibition or genetic deletion of chromosome region maintenance 1 (CRM1) in macrophages significantly inhibits the activation of NLRP3, AIM2, NLRC4 and pyrin inflammasomes. Mechanistically, CRM1 directly binds to the PYD domain of ASC to promote its nuclear-cytosolic transport. More importantly, treatment with CRM1 inhibitor KPT-330 or deletion of CRM1 in myeloid cells attenuates the pathological symptoms of experimental autoimmune encephalomyelitis (EAE) in mice. Thus, our findings reveal that CRM1 is an essential mediator for ASC nuclear export to promote inflammasome assembly and activation, which provides a potential target for inflammasome-related diseases.

The interplay between α-synuclein aggregation and necroptosis in Parkinson's disease: a spatiotemporal perspective

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the death of dopaminergic neurons and the aggregation of alpha-synuclein (α-Syn). It presents with prominent motor symptoms, and by the time of diagnosis, a significant number of neurons have already been lost. Current medications can only alleviate symptoms but cannot halt disease progression. Studies have confirmed that both dopaminergic neuronal loss and α-Syn aggregation are associated with necroptosis mechanisms. Necroptosis, a regulated form of cell death, has been recognized as an underexplored hotspot in PD pathogenesis research. In this review, we propose a spatiotemporal model of PD progression, highlighting the interactions between α-Syn aggregation, mitochondrial dysfunction, oxidative stress, neuroinflammation and necroptosis. These processes not only drive motor symptoms but also contribute to early non-motor symptoms, offering insights into potential diagnostic markers. Finally, we touch upon the therapeutic potential of necroptosis inhibition in enhancing current PD treatments, such as L-Dopa. This review aims to provide a new perspective on the pathogenesis of PD and to identify avenues for the development of more effective therapeutic strategies.

Perfluoropentane-based oxygen-loaded nanodroplets reduce microglial activation through metabolic reprogramming

JOURNAL/nrgr/04.03/01300535-202504000-00032/figure1/v/2024-07-06T104127Z/r/image-tiff Microglia, the primary immune cells within the brain, have gained recognition as a promising therapeutic target for managing neurodegenerative diseases within the central nervous system, including Parkinson's disease. Nanoscale perfluorocarbon droplets have been reported to not only possess a high oxygen-carrying capacity, but also exhibit remarkable anti-inflammatory properties. However, the role of perfluoropentane in microglia-mediated central inflammatory reactions remains poorly understood. In this study, we developed perfluoropentane-based oxygen-loaded nanodroplets (PFP-OLNDs) and found that pretreatment with these droplets suppressed the lipopolysaccharide-induced activation of M1-type microglia in vitro and in vivo, and suppressed microglial activation in a mouse model of Parkinson's disease. Microglial suppression led to a reduction in the inflammatory response, oxidative stress, and cell migration capacity in vitro. Consequently, the neurotoxic effects were mitigated, which alleviated neuronal degeneration. Additionally, ultrahigh-performance liquid chromatography-tandem mass spectrometry showed that the anti-inflammatory effects of PFP-OLNDs mainly resulted from the modulation of microglial metabolic reprogramming. We further showed that PFP-OLNDs regulated microglial metabolic reprogramming through the AKT-mTOR-HIF-1α pathway. Collectively, our findings suggest that the novel PFP-OLNDs constructed in this study alleviate microglia-mediated central inflammatory reactions through metabolic reprogramming.

Protective role of mitophagy on microglia-mediated neuroinflammatory injury through mtDNA-STING signaling in manganese-induced parkinsonism

Manganese (Mn), the third most abundant transition metal in the earth's crust, has widespread applications in the emerging field of organometallic catalysis and traditional industries. Excessive Mn exposure causes neurological syndrome resembling Parkinson's disease (PD). The pathogenesis of PD is thought to involve microglia-mediated neuroinflammatory injury, with mitochondrial dysfunction playing a role in aberrant microglial activation. In the early stages of PD, PINK1/Parkin-mediated mitophagy contributes to the microglial inflammatory response via the cGAS/STING signaling pathway. Suppression of PINK1/Parkin-mediated mitophagy due to excessive Mn exposure exacerbates neuronal injury. Moreover, excessive Mn exposure leads to neuroinflammatory damage via the microglial cGAS-STING pathway. However, the precise role of microglial mitophagy in modulating neuroinflammation in Mn-induced parkinsonism and its underlying molecular mechanism remains unclear. Here, we observed that Mn-exposed mice exhibited neurobehavioral abnormalities and detrimental microglial activation, along with increased apoptosis of nerve cells, proinflammatory cytokines, and intracellular ROS. Furthermore, in vivo and in vitro experiments showed that excessive Mn exposure resulted in microglial mitochondrial dysfunction, manifested by increased mitochondrial ROS, decreased mitochondrial mass, and membrane potential. Additionally, with the escalating Mn dose, PINK1/Parkin-mediated mitophagy changed from activation to suppression. This was evidenced by decreased levels of LC3-II, PINK1, p-Parkin/Parkin, and increased levels of p62 protein expression level, as well as the colocalization between ATPB and LC3B due to excessive Mn exposure. Upregulation of mitophagy by urolithin A could mitigate Mn-induced mitochondrial dysfunction, as indicated by decreased mitochondrial ROS, increased mitochondrial mass, and membrane potential, along with improvements in neurobehavioral deficits and attenuated detrimental microglial activation. Using single-nucleus RNA-sequencing (snRNA-seq) analysis in the Mn-exposed mouse model, we identified the microglial cGAS-STING signaling pathway as a potential mechanism underlying Mn-induced neuroinflammation. This pathway is associated with an increase in cytosolic mtDNA levels, which activate STING signaling. These findings point to the induction of microglial mitophagy as a viable strategy to alleviate Mn-induced neuroinflammation through mtDNA-STING signaling.

Increased expression of ER stress, inflammasome activation, and mitochondrial biogenesis-related genes in peripheral blood mononuclear cells in major depressive disorder

A subset of major depressive disorder (MDD) is characterized by immune system dysfunction, but the intracellular origin of these immune changes remains unclear. Here we tested the hypothesis that abnormalities in endoplasmic reticulum (ER) stress, inflammasome activity and mitochondrial biogenesis contribute to the development of systemic inflammation in MDD. RT-qPCR was used to measure mRNA expression of key organellar genes from peripheral blood mononuclear cells (PBMCs) isolated from 186 MDD and 67 healthy control (HC) subjects. The comparative CT (2-ΔΔCT) method was applied to quantify mRNA expression using GAPDH as the reference gene. After controlling for age, sex, BMI, and medication status using linear regression models, expression of the inflammasome (NLRC4 and NLRP3) and the ER stress (XBP1u, XBP1s, and ATF4) genes was found to be significantly increased in the MDD versus the HC group. Sensitivity analyses excluding covariates yielded similar results. After excluding outliers, expression of the inflammasome genes was no longer statistically significant but expression of the ER stress genes (XBP1u, XBP1s, and ATF4) remained significant and the mitochondrial biogenesis gene, MFN2, was significantly increased in the MDD group. NLRC4 and MFN2 were positively correlated with serum C-reactive protein concentrations, while ASC trended significant. The altered expression of inflammasome activation, ER stress, and mitochondrial biogenesis pathway components suggest that dysfunction of these organelles may play a role in the pathogenesis of MDD.

Mitochondrial diseases: from molecular mechanisms to therapeutic advances

Mitochondria are essential for cellular function and viability, serving as central hubs of metabolism and signaling. They possess various metabolic and quality control mechanisms crucial for maintaining normal cellular activities. Mitochondrial genetic disorders can arise from a wide range of mutations in either mitochondrial or nuclear DNA, which encode mitochondrial proteins or other contents. These genetic defects can lead to a breakdown of mitochondrial function and metabolism, such as the collapse of oxidative phosphorylation, one of the mitochondria's most critical functions. Mitochondrial diseases, a common group of genetic disorders, are characterized by significant phenotypic and genetic heterogeneity. Clinical symptoms can manifest in various systems and organs throughout the body, with differing degrees and forms of severity. The complexity of the relationship between mitochondria and mitochondrial diseases results in an inadequate understanding of the genotype-phenotype correlation of these diseases, historically making diagnosis and treatment challenging and often leading to unsatisfactory clinical outcomes. However, recent advancements in research and technology have significantly improved our understanding and management of these conditions. Clinical translations of mitochondria-related therapies are actively progressing. This review focuses on the physiological mechanisms of mitochondria, the pathogenesis of mitochondrial diseases, and potential diagnostic and therapeutic applications. Additionally, this review discusses future perspectives on mitochondrial genetic diseases.

From mitochondrial dysfunction to neuroinflammation in Parkinson's disease: Pathogenesis and mitochondrial therapeutic approaches

Parkinson's disease (PD) is a prevalent and intricate neurological condition resulting from a combination of several factors, such as genetics, environment, and the natural process of aging. Degeneration of neurons in the substantia nigra pars compacta (SN) can cause motor and non-motor impairments in patients with PD. In PD's etiology, inflammation and mitochondrial dysfunction play significant roles in the disease's development. Studies of individuals with PD have revealed increased inflammation in various brain areas. Furthermore, mitochondrial dysfunction is an essential part of PD pathophysiology. Defects in the components of the mitochondrial nucleus, its membrane or internal signaling pathways, mitochondrial homeostasis, and morphological alterations in peripheral cells have been extensively documented in PD patients. According to these studies, neuroinflammation and mitochondrial dysfunction are closely connected as pathogenic conditions in neurodegenerative diseases like PD. Given the mitochondria's role in cellular homeostasis maintenance in response to membrane structural flaws or mutations in mitochondrial DNA, their dynamic nature may present therapeutic prospects in this area. Recent research investigates mitochondrial transplantation as a potential treatment for Parkinson's disease in damaged neurons. This review delves into the impact of inflammation and mitochondrial dysfunction on PD occurrence, treatment approaches, and the latest developments in mitochondrial transplantation, highlighting the potential consequences of these discoveries.

Heme Oxygenase-1 Overexpression Activates the IRF1/DRP1 Signaling Pathway to Promote M2-Type Polarization of Spinal Cord Microglia

Microglia-mediated neuroinflammatory responses have a critical function in the spinal cord injury (SCI) mechanism, and targeted modulation of microglia activity has emerged as a new therapeutic strategy for SCI. Heme oxygenase 1(HO-1) regulates the close dynamic crosstalk between oxidative stress and inflammatory responses. This investigation aimed to study the molecular pathways by which HO-1 regulates the inflammatory response of microglia. We cultivated primary rat spinal cord microglia and BV2 cell lines and used lipopolysaccharide (LPS) to stimulate microglia to establish an in vitro model. The adeno-associated virus (AAV) was used to induce HO-1 overexpression to observe the effects of HO-1 overexpression on microglia survival, morphological changes, microglia activation, inflammatory cytokines secretion, mitochondrial dynamics, and nucleotide-binding oligomerization domain-like receptor protein (NLRP3) inflammatory complex and nuclear factor-κB (NF-κB) signaling pathways. It was found that HO-1 overexpression was successfully induced using an AAV on microglia in vitro. HO-1 overexpression increased microglia survival and reduced microglia apoptosis in the inflammatory microenvironment. Overexpressed HO-1 inhibited microglia M1-type polarization, downregulated the NF-κB signaling pathway, inhibited NLRP3 inflammatory complex activation, and reduced the secretion of inflammatory factors. Overexpressed HO-1 maintained the stability of mitochondrial dynamics and inhibited excessive mitochondrial cleavage. Further experiments showed that overexpression of HO-1 activated the interferon regulatory factor 1 (IRF1)/dynamin-related protein 1 (DRP1) signaling pathway, thereby promoting microglia M2-type polarization and improving neuronal survival. This study demonstrates that HO-1 activates the IRF1/DRP1 axis, promoting M2 polarization in microglia and attenuating neuroinflammation by suppressing the NF-κB signaling pathway. These outcomes offer new visions and important clues for effectively managing SCI in the clinic.

Aberrant Enhanced NLRP3 Inflammasomes and Cell Pyroptosis in the Brains of Prion-Infected Rodent Models Are Largely Associated with the Proliferative Astrocytes

Neuroinflammation is a common pathological feature in a number of neurodegenerative diseases, which is mediated primarily by the activated glial cells. Nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) inflammasome-associated neuroinflammatory response is mostly considered. To investigate the situation of the NLRP3-related inflammation in prion disease, we assessed the levels of the main components of NLRP3 inflammasome and its downstream biomarkers in the scrapie-infected rodent brain tissues. The results showed that the transcriptional and expressional levels of NLRP3, caspase-1, and apoptosis-associated speck-like protein (ASC) in the brains of scrapie-infected rodents were significantly increased at terminal stage. The increased NLPR3 overlapped morphologically well with the proliferated GFAP-positive astrocytes, but little with microglia and neurons. Using the brain samples collected at the different time-points after infection, we found the NLRP3 signals increased in a time-dependent manner, which were coincidental with the increase of GFAP. Two main downstream cytokines, IL-1β and IL-18, were also upregulated in the brains of prion-infected mice. Moreover, the gasdermin D (GSDMD) levels, particularly the levels of GSDMD-NT, in the prion-infected brain tissues were remarkably increased, indicating activation of cell pyroptosis. The GSDMD not only co-localized well with the astrocytes but also with neurons at terminal stage, also showing a time-dependent increase after infection. Those data indicate that NLRP3 inflammasomes were remarkably activated in the infected brains, which is largely mediated by the proliferated astrocytes. Both astrocytes and neurons probably undergo a pyroptosis process, which may help the astrocytes to release inflammatory factors and contribute to neuron death during prion infection.

Resveratrol protects against a high-fat diet-induced neuroinflammation by suppressing mitochondrial fission via targeting SIRT1/PGC-1α

Various health issues have emerged due to consuming high-fat diets (HFD), particularly the detrimental impact they have on mitochondrial dynamics and subsequet cognition functions. Specially, mitochondrial fission can serve as an upstream signal in the regulation of cortical inflammation and neural pyroptosis. Our study was designed to verify the existence of neuroinflammation in the pathogenesis of HFD-induced cognitive dysfunction and demonstrated that resveratrol (RSV) attenuated neural deficits via regulation of cortical mitochondrial fission. A total of 50 male Sprague Dawley rats were randomly divided into five groups: control (Cont, 26 weeks on normal rodent diet); high-fat diet (HFD); dietary adjustments (HFD + ND); resveratrol intervention (HFD + R); joint intervention (HFD + ND + R) for 26 weeks. The spatial learning and memory function, spine density, NLRP3 inflammasome associated protein, mRNA and protein expression involved in mitochondrial dynamics and SIRT1/PGC-1α signaling pathway in brain were measured. Furthermore, reactive oxygen species (ROS) accumulation and resultant mitochondrial membrane potential (MMP) alteration in PC12 cells exposed to palmitic acid (PA) or Drp1 inhibitor (Mdivi-1) were detected to reflect mitochondrial function. The findings suggested that prolonged treatment of RSV improved cognitive deficits and neuronal damage induced by HFD, potentially attributed to activation of the SIRT1/PGC-1α axis. We further indicated that the activation of the NLRP3 inflammasome in PA (200 μM) treated PC12 cells could be inhibited by Mdivi-1. More importantly, Mdivi-1 (10 μM) reduced intracellular ROS levels and enhanced MMP by reversing Drp1-mediated aberrant mitochondrial fission. To summarize, those results clearly indicated that a HFD inhibited the SIRT1/PGC-1α pathway, which contributed to an imbalance in mitochondrial dynamics and the onset of NLRP3-mediated pyroptosis. This effect was mitigated by the RSV possibly through triggering the SIRT1/PGC-1α axis, prevented aberrant mitochondrial fission and thus inhibited the activation of the NLRP3 inflammatory pathway.

Yin-Yang: two sides of extracellular vesicles in inflammatory diseases

The concept of Yin-Yang, originating in ancient Chinese philosophy, symbolizes two opposing but complementary forces or principles found in all aspects of life. This concept can be quite fitting in the context of extracellular vehicles (EVs) and inflammatory diseases. Over the past decades, numerous studies have revealed that EVs can exhibit dual sides, acting as both pro- and anti-inflammatory agents, akin to the concept of Yin-Yang theory (i.e., two sides of a coin). This has enabled EVs to serve as potential indicators of pathogenesis or be manipulated for therapeutic purposes by influencing immune and inflammatory pathways. This review delves into the recent advances in understanding the Yin-Yang sides of EVs and their regulation in specific inflammatory diseases. We shed light on the current prospects of engineering EVs for treating inflammatory conditions. The Yin-Yang principle of EVs bestows upon them great potential as, therapeutic, and preventive agents for inflammatory diseases.

Hyperglycemia-induced Sirt3 downregulation increases microglial aerobic glycolysis and inflammation in diabetic neuropathic pain pathogenesis

BACKGROUND

Hyperglycemia-induced neuroinflammation significantly contributes to diabetic neuropathic pain (DNP), but the underlying mechanisms remain unclear.

OBJECTIVE

To investigate the role of Sirt3, a mitochondrial deacetylase, in hyperglycemia-induced neuroinflammation and DNP and to explore potential therapeutic interventions.

METHOD AND RESULTS

Here, we found that Sirt3 was downregulated in spinal dorsal horn (SDH) of diabetic mice by RNA-sequencing, which was further confirmed at the mRNA and protein level. Sirt3 deficiency exacerbated hyperglycemia-induced neuroinflammation and DNP by enhancing microglial aerobic glycolysis in vivo and in vitro. Overexpression of Sirt3 in microglia alleviated inflammation by reducing aerobic glycolysis. Mechanistically, high-glucose stimulation activated Akt, which phosphorylates and inactivates FoxO1. The inactivation of FoxO1 diminished the transcription of Sirt3. Besides that, we also found that hyperglycemia induced Sirt3 degradation via the mitophagy-lysosomal pathway. Blocking Akt activation by GSK69093 or metformin rescued the degradation of Sirt3 protein and transcription inhibition of Sirt3 mRNA, which substantially diminished hyperglycemia-induced inflammation. Metformin in vivo treatment alleviated neuroinflammation and diabetic neuropathic pain by rescuing hyperglycemia-induced Sirt3 downregulation.

CONCLUSION

Hyperglycemia induces metabolic reprogramming and inflammatory activation in microglia through the regulation of Sirt3 transcription and degradation. This novel mechanism identifies Sirt3 as a potential drug target for treating DNP.

LncRNA SOX21-AS1 Promotes Activation of BV2 Cells via Epigenetical Silencing of SOCS3 and Aggravates Parkinson's Disease

BACKGROUND

LncRNAs perform a crucial impact on microglia's activation in Parkinson's disease (PD). Here, our purpose was to probe the function and involved mechanism of lncRNA SOX21-AS1 on microglial activation in PD.

METHODS

Mice were treated with MPTP, and BV2 cells were treated with LPS/ATP to build PD animal and cell models. Genes' expression was measured using RT-qPCR, immunoblotting, and IHC stain. ELISA was applied for testing inflammatory factors' levels. Cell viability and apoptosis were tested using kits. RIP and RNA pull-down assay were utilized for monitoring the bond of SOX21-AS1 to EZH2, and ChIP was applied for affirming the bond between EZH2 and SOCS3's promoter.

RESULTS

The expression of SOX21-AS1 and SOCS3 was abnormal in PD cell and animal models. Inhibition of SOX21-AS1 repressed LPS/ATP-induced activation in BV2 cells and nerve damage caused by activated BV2 cells, alleviating the pathological features of PD mice. Further studies found that SOX21-AS1 epigenetically inhibited SOCS3 by recruiting EZH2 to SOCS3 promoter. SOX21-AS1 overexpression partially offset the repressive impact of SOCS3 enhancement on BV2 cell activation and the protective effect on nerve cells.

CONCLUSION

SOX21-AS1 enhances LPS/ATP-induced activation of BV2 cells and nerve damage caused by activated BV2 cells though recruiting EZH2 to SOCS3's promoter, thereby alleviating PD progression. Our research supplies new potential target for curing PD.

The P2X7 Receptor is a Master Regulator of Microparticle and Mitochondria Exchange in Mouse Microglia

Microparticles (MPs) are secreted by all cells, where they play a key role in intercellular communication, differentiation, inflammation, and cell energy transfer. P2X7 receptor (P2X7R) activation by extracellular ATP (eATP) causes a large MP release and affects their contents in a cell-specific fashion. We investigated MP release and functional impact in microglial cells from P2X7R-WT or P2X7R-KO mice, as well as mouse microglial cell lines characterized for high (N13-P2X7RHigh) or low (N13-P2X7RLow) P2X7R expression. P2X7R stimulation promoted release of a mixed MP population enriched with naked mitochondria. Released mitochondria were taken up and incorporated into the mitochondrial network of the recipient cells in a P2X7R-dependent fashion. NLRP3 and the P2X7R itself were also delivered to the recipient cells. Microparticle transfer increased the energy level of the recipient cells and conferred a pro-inflammatory phenotype. These data show that the P2X7R is a master regulator of intercellular organelle and MP trafficking in immune cells.

MiR-29a efficiently suppresses the generation of reactive oxygen species and α-synuclein in a cellular model of Parkinson's disease by potentially targeting GSK-3β

MicroRNA-29a (miR-29a) has been suggested to serve a potential protective function against Parkinson's disease (PD); however, the exact molecular mechanisms remain elusive. This study explored the protective role of miR-29a in a cellular model of PD using SH-SY5Y cell lines through iTRAQ-based quantitative proteomic and biochemistry analysis. The findings showed that using a miR-29a mimic in SH-SY5Y cells treated with 1-methyl-4-phenylpyridinium (MPP+) significantly decreased cell death and increased mitochondrial membrane potential. It also reduced mitochondrial reactive oxygen species (ROS) and the production of α-synuclein. Subsequent heatmap analysis using iTRAQ-based quantitative proteomics revealed remarkably contrasting protein expression profiles for 882 genes when comparing the groups treated with miR-29a mimic plus MPP + against the control group treated solely with MPP+. The KEGG pathway analysis of these 882 genes indicated the substantial role of miR-29a in the PD pathway (P = 1.58x10-5) and highlighted its function in mitochondrial genes. Furthermore, treatment with a miR-29a mimic in SH-SY5Y cells reduced the levels of GSK-3β, phosphorylated GSK-3β, and cleaved caspase-7 following exposure to MPP+. The miR-29a mimic also upregulated the expressions of α-synuclein clearance proteins FYCO1 and Rab7 in this cellular PD model, thereby inhibiting the production of α-synuclein. Luciferase activity analysis confirmed the specific binding of miR-29a to the 3' untranslated region (3'UTR) of GSK-3β, leading to its repression. Our findings demonstrated miR-29a's neuroprotective role in mitochondrial function and highlighted its potential to inhibit ROS and α-synuclein production, offering possible therapeutic avenues for PD treatment.

Microfluidics-enabled mesenchymal stem cell derived Neuron like cell membrane coated nanoparticles inhibit inflammation and apoptosis for Parkinson's Disease

Parkinson's disease (PD) is the second largest group of neurodegenerative diseases, and its existing drug treatments are not satisfactory. Natural cell membrane drugs are used for homologous targeting to enhance efficacy. In this study, microfluidic electroporation chip prepared mesenchymal stem cell-derived neuron-like cell membrane-coated curcumin PLGA nanoparticles (MM-Cur-NPs) was synthesized and explored therapeutic effect and mechanism in PD. MM-Cur-NPs can protect neuron from damage, restore mitochondrial membrane potential and reduce oxidative stress in vitro. In PD mice, it also can improve movement disorders and restore damaged TH neurons. MM-Cur-NPs was found to be distributed in the brain and metabolized with a delay within 24 h. After 1 h administration, MM-Cur-NPs were distributed in brain with a variety of neurotransmitters were significantly upregulated, such as dopamine. Differentially expressed genes of RNA-seq were enriched in the inflammation regulation, and it was found the up-expression of anti-inflammatory factors and inhibited pro-inflammatory factors in PD. Mechanically, MM-Cur-NPs can not only reduce neuronal apoptosis, inhibit the microglial marker IBA-1 and inflammation, but also upregulate expression of neuronal mitochondrial protein VDAC1 and restore mitochondrial membrane potential. This study proposes a therapeutic strategy provide neuroprotective effects through MM-Cur-NPs therapy for PD.

Advances in the Understanding of the Correlation Between Neuroinflammation and Microglia in Alzheimer's Disease

Alzheimer's disease (AD) is a fatal neurodegenerative disease with a subtle and progressive onset and is the most common type of dementia. However, its etiology and pathogenesis have not yet been fully elucidated. The common pathological manifestations of AD include extraneuronal β-amyloid deposition (Aβ), intraneuronal tau protein phosphorylation leading to the formation of 'neurofibrillary tangles' (NFTs), neuroinflammation, progressive loss of brain neurons/synapses, and glucose metabolism disorders. Current treatment approaches for AD primarily focus on the 'Aβ cascade hypothesis and abnormal aggregation of hyperphosphorylation of tau proteins', but have shown limited efficacy. Therefore, there is an ongoing need to identify more effective treatment targets for AD. The central nervous system (CNS) inflammatory response plays a key role in the occurrence and development of AD. Neuroinflammation is an immune response activated by glial cells in the CNS that usually occurs in response to stimuli such as nerve injury, infection and toxins or in response to autoimmunity. Neuroinflammation ranks as the third most prominent pathological feature in AD, following Aβ and NFTs. In recent years, the focus on the role of neuroinflammation and microglia in AD has increased due to the advancements in genome-wide association studies (GWAS) and sequencing technology. Furthermore, research has validated the pivotal role of microglia-mediated neuroinflammation in the progression of AD. Therefore, this article reviews the latest research progress on the role of neuroinflammation triggered by microglia in AD in recent years, aiming to provide a new theoretical basis for further exploring the role of neuroinflammation in the process of AD occurrence and development.

The septin modifier, forchlorfenuron, activates NLRP3 via a potassium-independent mitochondrial axis

The Nod-like receptor protein 3 (NLRP3) inflammasome is activated by stimuli that induce perturbations in cell homeostasis, which commonly converge on cellular potassium efflux. NLRP3 has thus emerged as a sensor for ionic flux. Here, we identify forchlorfenuron (FCF) as an inflammasome activator that triggers NLRP3 signaling independently of potassium efflux. FCF triggers the rearrangement of septins, key cytoskeletal proteins that regulate mitochondrial function. We report that FCF triggered the rearrangement of SEPT2 into tubular aggregates and stimulated SEPT2-independent NLRP3 inflammasome signaling. Similar to imiquimod, FCF induced the collapse of the mitochondrial membrane potential and mitochondrial respiration. FCF thereby joins the imidazoquinolines as a structurally distinct class of molecules that triggers NLRP3 inflammasome signaling independent of potassium efflux, likely by inducing mitochondrial damage.

Focusing on mitochondria in the brain: from biology to therapeutics

Mitochondria have multiple functions such as supplying energy, regulating the redox status, and producing proteins encoded by an independent genome. They are closely related to the physiology and pathology of many organs and tissues, among which the brain is particularly prominent. The brain demands 20% of the resting metabolic rate and holds highly active mitochondrial activities. Considerable research shows that mitochondria are closely related to brain function, while mitochondrial defects induce or exacerbate pathology in the brain. In this review, we provide comprehensive research advances of mitochondrial biology involved in brain functions, as well as the mitochondria-dependent cellular events in brain physiology and pathology. Furthermore, various perspectives are explored to better identify the mitochondrial roles in neurological diseases and the neurophenotypes of mitochondrial diseases. Finally, mitochondrial therapies are discussed. Mitochondrial-targeting therapeutics are showing great potentials in the treatment of brain diseases.

Social isolation and the risk of Parkinson disease in the UK biobank study

Parkinson disease (PD) has become one of the most rapidly growing causes of disability among the older population and social isolation is a major concern in the PD community. However, the relationship between social isolation and future risk of PD remains unclear. This study included 192,340 participants aged 60 or older who were free of dementia and PD at baseline from the UK Biobank study. Social isolation was measured using a composite score derived from three questions on number in household, frequency of friend/family visits, and leisure/social activities. Incident PD cases were identified through electronic health records. Multivariable-adjusted Cox regression models were used to compute the hazard ratio (HR) and 95% confidence interval (CI). Among the 192,340 participants (mean [standard deviation] age, 64.2 [2.9] years; 103,253 [53.7%] women), 89,075 (46.3%) participants were in the least isolated group and 26,161 (13.6%) were in the most isolated group. Over a median follow-up of 12.5 years, 2048 incident PD cases were documented. Compared to the least isolated group, the multivariable-adjusted HRs (95% CIs) for PD were 1.00 (0.91-1.10) for the moderately isolated group and 1.19 (1.05-1.36) for the most isolated group (P-trend = 0.04). The observed association was independent of the genetic susceptibility to PD and consistent in subgroup analyses. Social isolation was associated with a higher risk of PD regardless of genetic risk. Our findings highlighted the importance of developing screening and intervention strategies for social isolation among older adults to reduce the risk of PD.

Inflammasomes in neurological disorders - mechanisms and therapeutic potential

Inflammasomes are molecular scaffolds that are activated by damage-associated and pathogen-associated molecular patterns and form a key element of innate immune responses. Consequently, the involvement of inflammasomes in several diseases that are characterized by inflammatory processes, such as multiple sclerosis, is widely appreciated. However, many other neurological conditions, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, stroke, epilepsy, traumatic brain injury, sepsis-associated encephalopathy and neurological sequelae of COVID-19, all involve persistent inflammation in the brain, and increasing evidence suggests that inflammasome activation contributes to disease progression in these conditions. Understanding the biology and mechanisms of inflammasome activation is, therefore, crucial for the development of inflammasome-targeted therapies for neurological conditions. In this Review, we present the current evidence for and understanding of inflammasome activation in neurological diseases and discuss current and potential interventional strategies that target inflammasome activation to mitigate its pathological consequences.

Increased expression of ER stress, inflammasome activation, and mitochondrial biogenesis-related genes in peripheral blood mononuclear cells in major depressive disorder

A subset of major depressive disorder (MDD) is characterized by immune system dysfunction, but the intracellular origin of these immune changes remains unclear. Here we tested the hypothesis that abnormalities in the endoplasmic reticulum (ER) stress, inflammasome activity and mitochondrial biogenesis contribute to the development of systemic inflammation in MDD. RT-qPCR was used to measure mRNA expression of key organellar genes from peripheral blood mononuclear cells (PBMCs) isolated from 186 MDD and 67 healthy control (HC) subjects. The comparative CT (2-ΔΔCT) method was applied to quantify mRNA expression using GAPDH as the reference gene. After controlling for age, sex, BMI, and medication status using linear regression models, expression of the inflammasome (NLRC4 and NLRP3) and the ER stress (XBP1u, XBP1s, and ATF4) genes was found to be significantly increased in the MDD versus the HC group. After excluding outliers, expression of the inflammasome genes was no longer statistically significant but expression of the ER stress genes (XBP1u, XBP1s, and ATF4) and the mitochondrial biogenesis gene, MFN2, was significantly increased in the MDD group. ASC and MFN2 were positively correlated with serum C-reactive protein concentrations. The altered expression of inflammasome activation, ER stress, and mitochondrial biogenesis pathway components suggest that dysfunction of these organelles may play a role in the pathogenesis of MDD.

Targeting CB2R in astrocytes for Parkinson's disease therapy: unraveling the Foxg1-mediated neuroprotective mechanism through autophagy-mediated NLRP3 degradation

BACKGROUND

Inflammasomes in astrocytes have been shown to play a crucial role in the pathogenesis of neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD). Cannabinoid Receptor 2(CB2R), a G protein-coupled receptor (GPCR), is considered a promising therapeutic target in inflammation-related disorders. This study aims to explore the role of CB2R in regulating NOD-like receptor family pyrin domain containing 3 (NLRP3)-mediated neuroinflammation in astrocytes.

METHODS

In an in vivo animal model, specific targeting of astrocytic CB2R was achieved by injecting CB2R-specific adenovirus (or fork head box g1(foxg1) adenovirus) to knock down CB2R or administering CB2R agonists, inhibitors, etc., in the substantia nigra pars compacta (SNc) of mice. A PD mouse model was established using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induction. Animal behavioral tests, western blot, immunofluorescence, and other experiments were performed to assess the loss of midbrain tyrosine hydroxylase (TH) neurons, activation of astrocytes, and activation of the NLRP3 pathway. Primary astrocytes were cultured in vitro, and NLRP3 inflammasomes were activated using 1-methyl-4-phenylpyridinium (MPP+) or lipopolysaccharide (LPS) and adenosine triphosphate (ATP). Western blot and ELISA experiments were conducted to assess the release of inflammatory factors. Transcriptomic sequencing and CUT&RUN techniques were employed to study the CB2R regulation of the foxg1 binding site on the autophagy molecule microtubule-associated protein 1 light chain 3 beta (MAP1LC3B).

RESULTS

Astrocytic CB2R knockdown impaired the motor abilities of MPTP-induced mice, exacerbated the loss of TH neurons, and induced activation of the NLRP3/Caspase-1/interleukin 1 (IL-1β) pathway. Activation of CB2R significantly alleviated motor impairments in mice while reducing NLRP3 deposition on astrocytes. In vitro cell experiments showed that CB2R activation attenuated the activation of the NLRP3/Caspase-1/IL-1β pathway induced by LPS + ATP or MPP+. Additionally, it inhibited the binding of foxg1 to MAP1LC3B, increased astrocytic autophagy levels, and facilitated NLRP3 degradation through the autophagy-lysosome pathway.

CONCLUSION

Activation of CB2R on astrocytes effectively mitigates NLRP3-mediated neuroinflammation and ameliorates the disease characteristics of PD in mice. CB2R represents a potential therapeutic target for treating PD.

The role of mitochondrial dynamics in disease

Mitochondria are multifaceted and dynamic organelles regulating various important cellular processes from signal transduction to determining cell fate. As dynamic properties of mitochondria, fusion and fission accompanied with mitophagy, undergo constant changes in number and morphology to sustain mitochondrial homeostasis in response to cell context changes. Thus, the dysregulation of mitochondrial dynamics and mitophagy is unsurprisingly related with various diseases, but the unclear underlying mechanism hinders their clinical application. In this review, we summarize the recent developments in the molecular mechanism of mitochondrial dynamics and mitophagy, particularly the different roles of key components in mitochondrial dynamics in different context. We also summarize the roles of mitochondrial dynamics and target treatment in diseases related to the cardiovascular system, nervous system, respiratory system, and tumor cell metabolism demanding high-energy. In these diseases, it is common that excessive mitochondrial fission is dominant and accompanied by impaired fusion and mitophagy. But there have been many conflicting findings about them recently, which are specifically highlighted in this view. We look forward that these findings will help broaden our understanding of the roles of the mitochondrial dynamics in diseases and will be beneficial to the discovery of novel selective therapeutic targets.

Research progress in the molecular mechanism of ferroptosis in Parkinson's disease and regulation by natural plant products

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder of the central nervous system after Alzheimer's disease. The current understanding of PD focuses mainly on the loss of dopamine neurons in the substantia nigra region of the midbrain, which is attributed to factors such as oxidative stress, alpha-synuclein aggregation, neuroinflammation, and mitochondrial dysfunction. These factors together contribute to the PD phenotype. Recent studies on PD pathology have introduced a new form of cell death known as ferroptosis. Pathological changes closely linked with ferroptosis have been seen in the brain tissues of PD patients, including alterations in iron metabolism, lipid peroxidation, and increased levels of reactive oxygen species. Preclinical research has demonstrated the neuroprotective qualities of certain iron chelators, antioxidants, Fer-1, and conditioners in Parkinson's disease. Natural plant products have shown significant potential in balancing ferroptosis-related factors and adjusting their expression levels. Therefore, it is vital to understand the mechanisms by which natural plant products inhibit ferroptosis and relieve PD symptoms. This review provides a comprehensive look at ferroptosis, its role in PD pathology, and the mechanisms underlying the therapeutic effects of natural plant products focused on ferroptosis. The insights from this review can serve as useful references for future research on novel ferroptosis inhibitors and lead compounds for PD treatment.

Role of mitophagy in ocular neurodegeneration

Neurons in the central nervous system are among the most metabolically active cells in the body, characterized by high oxygen consumption utilizing glucose both aerobically and anaerobically. Neurons have an abundance of mitochondria which generate adequate ATP to keep up with the high metabolic demand. One consequence of the oxidative phosphorylation mechanism of ATP synthesis, is the generation of reactive oxygen species which produces cellular injury as well as damage to mitochondria. Mitochondria respond to injury by fusion which serves to ameliorate the damage through genetic complementation. Mitochondria also undergo fission to meet an increased energy demand. Loss of mitochondria is also compensated by increased biogenesis to generate new mitochondria. Damaged mitochondria are removed by mitophagy, an autophagic process, in which damaged mitochondria are surrounded by a membrane to form an autophagosome which ultimately fuses with the lysosome resulting in degradation of faulty mitochondria. Dysregulation of mitophagy has been reported in several central nervous system disorders, including, Alzheimer's disease and Parkinson's disease. Recent studies point to aberrant mitophagy in ocular neurodegenerative disorders which could be an important contributor to the disease etiology/pathology. This review article highlights some of the recent findings that point to dysregulation of mitophagy and it's underlying mechanisms in ocular neurodegenerative diseases, including, glaucoma, age-related macular degeneration and diabetic retinopathy.

Cell-Type-Specific Mitochondrial Quality Control in the Brain: A Plausible Mechanism of Neurodegeneration

Neurodegeneration is an age-dependent progressive phenomenon with no defined cause. Aging is the main risk factor for neurodegenerative diseases. During aging, activated microglia undergo phenotypic alterations that can lead to neuroinflammation, which is a well-accepted event in the pathogenesis of neurodegenerative diseases. Several common mechanisms are shared by genetically or pathologically distinct neurodegenerative diseases, such as excitotoxicity, mitochondrial deficits and oxidative stress, protein misfolding and translational dysfunction, autophagy and microglia activation. Progressive loss of the neuronal population due to increased oxidative stress leads to neurodegenerative diseases, mostly due to the accumulation of dysfunctional mitochondria. Mitochondrial dysfunction and excessive neuroinflammatory responses are both sufficient to induce pathology in age-dependent neurodegeneration. Therefore, mitochondrial quality control is a key determinant for the health and survival of neuronal cells in the brain. Research has been primarily focused to demonstrate the significance of neuronal mitochondrial health, despite the important contributions of non-neuronal cells that constitute a significant portion of the brain volume. Moreover, mitochondrial morphology and function are distinctly diverse in different tissues; however, little is known about their molecular diversity among cell types. Mitochondrial dynamics and quality in different cell types markedly decide the fate of overall brain health; therefore, it is not justifiable to overlook non-neuronal cells and their significant and active contribution in facilitating overall neuronal health. In this review article, we aim to discuss the mitochondrial quality control of different cell types in the brain and how important and remarkable the diversity and highly synchronized connecting property of non-neuronal cells are in keeping the neurons healthy to control neurodegeneration.

Metabolic reprogramming and polarization of microglia in Parkinson's disease: Role of inflammasome and iron

Parkinson's disease (PD) is a slowly progressive neurodegenerative disease characterized by α-synuclein aggregation and dopaminergic neuronal death. Recent evidence suggests that neuroinflammation is an early event in the pathogenesis of PD. Microglia are resident immune cells in the central nervous system that can be activated into either pro-inflammatory M1 or anti-inflammatory M2 phenotypes as found in peripheral macrophages. To exert their immune functions, microglia respond to various stimuli, resulting in the flexible regulation of their metabolic pathways. Inflammasomes activation in microglia induces metabolic shift from oxidative phosphorylation to glycolysis, and leads to the polarization of microglia to pro-inflammatory M1 phenotype, finally causing neuroinflammation and neurodegeneration. In addition, iron accumulation induces microglia take an inflammatory and glycolytic phenotype. M2 phenotype microglia is more sensitive to ferroptosis, inhibition of which can attenuate neuroinflammation. Therefore, this review highlights the interplay between microglial polarization and metabolic reprogramming of microglia. Moreover, it will interpret how inflammasomes and iron regulate microglial metabolism and phenotypic shifts, which provides a promising therapeutic target to modulate neuroinflammation and neurodegeneration in PD and other neurodegenerative diseases.

Pterostilbene attenuates microglial inflammation and brain injury after intracerebral hemorrhage in an OPA1-dependent manner

Microglial activation and subsequent inflammatory responses are critical processes in aggravating secondary brain injury after intracerebral hemorrhage (ICH). Pterostilbene (3', 5'-dimethoxy-resveratrol) features antioxidant and anti-inflammation properties and has been proven neuroprotective. In this study, we aimed to explore whether Pterostilbene could attenuate neuroinflammation after experimental ICH, as well as underlying molecular mechanisms. Here, a collagenase-induced ICH in mice was followed by intraperitoneal injection of Pterostilbene (10 mg/kg) or vehicle once daily. PTE-treated mice performed significantly better than vehicle-treated controls in the neurological behavior test after ICH. Furthermore, our results showed that Pterostilbene reduced lesion volume and neural apoptosis, and alleviated blood-brain barrier (BBB) damage and brain edema. RNA sequencing and subsequent experiments showed that ICH-induced neuroinflammation and microglial proinflammatory activities were markedly suppressed by Pterostilbene treatment. With regard to the mechanisms, we identified that the anti-inflammatory effects of Pterostilbene relied on remodeling mitochondrial dynamics in microglia. Concretely, Pterostilbene reversed the downregulation of OPA1, promoted mitochondrial fusion, restored normal mitochondrial morphology, and reduced mitochondrial fragmentation and superoxide in microglia after OxyHb treatment. Moreover, conditionally deleting microglial OPA1 in mice largely countered the effects of Pterostilbene on alleviating microglial inflammation, BBB damage, brain edema and neurological impairment following ICH. In summary, we provided the first evidence that Pterostilbene is a promising agent for alleviating neuroinflammation and brain injury after ICH in mice, and uncovered a novel regulatory relationship between Pterostilbene and OPA1-mediated mitochondrial fusion.

Is Drp1 a link between mitochondrial dysfunction and inflammation in Alzheimer's disease?

Recent advances highlight that inflammation is critical to Alzheimer Disease (AD) pathogenesis. Indeed, several diseases characterized by inflammation are considered risk factors for AD, such as type 2 diabetes, obesity, hypertension, and traumatic brain injury. Moreover, allelic variations in genes involved in the inflammatory cascade are risk factors for AD. AD is also characterized by mitochondrial dysfunction, which affects the energy homeostasis of the brain. The role of mitochondrial dysfunction has been characterized mostly in neuronal cells. However, recent data are demonstrating that mitochondrial dysfunction occurs also in inflammatory cells, promoting inflammation and the secretion of pro-inflammatory cytokines, which in turn induce neurodegeneration. In this review, we summarize the recent finding supporting the hypothesis of the inflammatory-amyloid cascade in AD. Moreover, we describe the recent data that demonstrate the link between altered mitochondrial dysfunction and the inflammatory cascade. We focus in summarizing the role of Drp1, which is involved in mitochondrial fission, showing that altered Drp1 activation affects the mitochondrial homeostasis and leads to the activation of the NLRP3 inflammasome, promoting the inflammatory cascade, which in turn aggravates Amyloid beta (Ab) deposition and tau-induced neurodegeneration, showing the relevance of this pro-inflammatory pathway as an early event in AD.

The role of mitochondrial dynamics in cerebral ischemia-reperfusion injury

Stroke is one of the leading causes of death and long-term disability worldwide. More than 80 % of strokes are ischemic, caused by an occlusion of cerebral arteries. Without question, restoration of blood supply as soon as possible is the first therapeutic strategy. Nonetheless paradoxically, reperfusion can further aggravate the injury through a series of reactions known as cerebral ischemia-reperfusion injury (CIRI). Mitochondria play a vital role in promoting nerve survival and neurological function recovery and mitochondrial dysfunction is considered one of the characteristics of CIRI. Neurons often die due to oxidative stress and an imbalance in energy metabolism following CIRI, and there is a strong association with mitochondrial dysfunction. Altered mitochondrial dynamics is the first reaction of mitochondrial stress. Mitochondrial dynamics refers to the maintenance of the integrity, distribution, and size of mitochondria as well as their ability to resist external stimuli through a continuous cycle of mitochondrial fission and fusion. Therefore, improving mitochondrial dynamics is a vital means of treating CIRI. This review discusses the relationship between mitochondria and CIRI and emphasizes improving mitochondrial dynamics as a potential therapeutic approach to improve the prognosis of CIRI.

The Interplay between α-Synuclein and Microglia in α-Synucleinopathies

Synucleinopathies are a set of devastating neurodegenerative diseases that share a pathologic accumulation of the protein α-synuclein (α-syn). This accumulation causes neuronal death resulting in irreversible dementia, deteriorating motor symptoms, and devastating cognitive decline. While the etiology of these conditions remains largely unknown, microglia, the resident immune cells of the central nervous system (CNS), have been consistently implicated in the pathogenesis of synucleinopathies. Microglia are generally believed to be neuroprotective in the early stages of α-syn accumulation and contribute to further neurodegeneration in chronic disease states. While the molecular mechanisms by which microglia achieve this role are still being investigated, here we highlight the major findings to date. In this review, we describe how structural varieties of inherently disordered α-syn result in varied microglial receptor-mediated interactions. We also summarize which microglial receptors enable cellular recognition and uptake of α-syn. Lastly, we review the downstream effects of α-syn processing within microglia, including spread to other brain regions resulting in neuroinflammation and neurodegeneration in chronic disease states. Understanding the mechanism of microglial interactions with α-syn is vital to conceptualizing molecular targets for novel therapeutic interventions. In addition, given the significant diversity in the pathophysiology of synucleinopathies, such molecular interactions are vital in gauging all potential pathways of neurodegeneration in the disease state.