α-synuclein promotes progression of Parkinson's disease by upregulating autophagy signaling pathway to activate NLRP3 inflammasome

Immune responses to oligomeric α-synuclein in Parkinson's disease peripheral blood mononuclear cells

Parkinson's disease displays clinical heterogeneity, presenting with motor and non-motor symptoms. Heterogeneous phenotypes, named brain-first and body-first, may reflect distinct α-synuclein pathology starting either in the central nervous system or in the periphery. The immune system plays a prominent role in the central and peripheral pathology, with misfolded α-synuclein being placed at the intersection between neurodegeneration and inflammation. Here, we characterized the inflammatory profile and immune-phenotype of peripheral blood mononuclear cells (PBMCs) from Parkinson's disease patients upon stimulation with α-synuclein monomer or oligomer, and investigated relationships of immune parameters with clinical scores of motor and non-motor symptoms. Freshly isolated PBMCs from 21 Parkinson's disease patients and 18 healthy subjects were exposed in vitro to α-synuclein species. Cytokine/chemokine release was measured in the culture supernatant by Multiplex Elisa. The immune-phenotype was studied by FACS-flow cytometry. Correlation analysis was computed between immune parameters and parkinsonian motor and non-motor scales. We found that Parkinson's disease patients exhibited a dysregulated PBMC-cytokine profile, which remained unaltered after exposure to α-synuclein species and correlated with both motor and non-motor severity, with a strong correlation observed with olfactory impairment. Exposure of PBMCs from healthy controls to α-synuclein monomer/oligomer increased the cytokine/chemokine release up to patient's values. Moreover, the PBMCs immune phenotype differed between patients and controls and revealed a prominent association of the Mos profile with olfactory impairment, and of NK profile with constipation. Results suggest that a deranged PBMC-immune profile may reflect distinct clinical subtypes and would fit with the recent classification of Parkinson's disease into peripheral-first versus brain-first phenotype.

From inflammatory signaling to neuronal damage: Exploring NLR inflammasomes in ageing neurological disorders

The persistence of neuronal degeneration and damage is a major obstacle in ageing medicine. Nucleotide-binding oligomerization domain (NOD)-like receptors detect environmental stressors and trigger the maturation and secretion of pro-inflammatory cytokines that can cause neuronal damage and accelerate cell death. NLR (NOD-like receptors) inflammasomes are protein complexes that contain NOD-like receptors. Studying the role of NLR inflammasomes in ageing-related neurological disorders can provide valuable insights into the mechanisms of neurodegeneration. This includes investigating their activation of inflammasomes, transcription, and capacity to promote or inhibit inflammatory signaling, as well as exploring strategies to regulate NLR inflammasomes levels. This review summarizes the use of NLR inflammasomes in guiding neuronal degeneration and injury during the ageing process, covering several neurological disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, stroke, and peripheral neuropathies. To improve the quality of life and slow the progression of neurological damage, NLR-based treatment strategies, including inhibitor-related therapies and physical therapy, are presented. Additionally, important connections between age-related neurological disorders and NLR inflammasomes are highlighted to guide future research and facilitate the development of new treatment options.

Mitochondrial dysfunction in chronic neuroinflammatory diseases (Review)

Chronic neuroinflammation serves a key role in the onset and progression of neurodegenerative disorders. Mitochondria serve as central regulators of neuroinflammation. In addition to providing energy to cells, mitochondria also participate in the immunoinflammatory response of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, multiple sclerosis and epilepsy, by regulating processes such as cell death and inflammasome activation. Under inflammatory conditions, mitochondrial oxidative stress, epigenetics, mitochondrial dynamics and calcium homeostasis imbalance may serve as underlying regulatory mechanisms for these diseases. Therefore, investigating mechanisms related to mitochondrial dysfunction may result in therapeutic strategies against chronic neuroinflammation and neurodegeneration. The present review summarizes the mechanisms of mitochondria in chronic neuroinflammatory diseases and the current treatment approaches that target mitochondrial dysfunction in these diseases.

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.

Targeting NLRP3 inflammasome for neurodegenerative disorders

Neuroinflammation is a key pathological feature in neurological diseases, including Alzheimer's disease (AD). The nucleotide-binding domain leucine-rich repeat-containing proteins (NLRs) belong to the pattern recognition receptors (PRRs) family that sense stress signals, which play an important role in inflammation. As a member of NLRs, the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) is predominantly expressed in microglia, the principal innate immune cells in the central nervous system (CNS). Microglia release proinflammatory cytokines to cause pyroptosis through activating NLRP3 inflammasome. The active NLRP3 inflammasome is involved in a variety of neurodegenerative diseases (NDs). Recent studies also indicate the key role of neuronal NLRP3 in the pathogenesis of neurological disorders. In this article, we reviewed the mechanisms of NLRP3 expression and activation and discussed the role of active NLRP3 inflammasome in the pathogenesis of NDs, particularly focusing on AD. The studies suggest that targeting NLRP3 inflammasome could be a novel approach for the disease modification.

The Potential of NLRP3 Inflammasome as a Therapeutic Target in Neurological Diseases

NLRP3 (NLRP3: NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome is the best-described inflammasome that plays a crucial role in the innate immune system and a wide range of diseases. The intimate association of NLRP3 with neurological disorders, including neurodegenerative diseases and strokes, further emphasizes its prominence as a clinical target for pharmacological intervention. However, after decades of exploration, the mechanism of NLRP3 activation remains indefinite. This review highlights recent advances and gaps in our insights into the regulation of NLRP3 inflammasome. Furthermore, we present several emerging pharmacological approaches of clinical translational potential targeting the NLRP3 inflammasome in neurological diseases. More importantly, despite small-molecule inhibitors of the NLRP3 inflammasome, we have focused explicitly on Chinese herbal medicine and botanical ingredients, which may be splendid therapeutics by inhibiting NLRP3 inflammasome for central nervous system disorders. We expect that we can contribute new perspectives to the treatment of neurological diseases.

A novel sorbicillinoid compound as a potent anti-inflammation agent through inducing NLRP3 protein degradation

BACKGROUND AND PURPOSE

Chronic inflammation is pathogenic and contributes to human diseases, causing a significant threat to public health. The NLR family pyrin domain-containing protein 3 (NLRP3) is the best-characterized factor regulating inflammation. Therefore, targeting NLRP3 has the potential to treat inflammatory diseases and improve human health.

EXPERIMENTAL APPROACH

Lipopolysaccharide was used to induce inflammation in cell cultures. Lipopolysaccharide/d-galactosamine and dextran sulfate sodium salt were used to induce acute liver inflammation and ulcerative colitis respectively in C57BL/6J mice. Western blotting, immunofluorescence, immunoprecipitation, quantitative PCR and enzyme-linked immunosorbent assay (ELISA) were used to evaluate the activation of the inflammatory response in cell cultures and in mice.

KEY RESULTS

JNUTS013, a novel sorbicillinoid compound recently synthesized by us, significantly inhibited inflammation both in cell cultures and in mouse models. Mechanistically, JNUTS013 induced proteasome-dependent degradation of NLRP3. Hence, it suppressed the formation of the NLRP3 inflammasome and the production of downstream inflammatory cytokines and chemokines. The inhibitory effect of JNUTS013 on NLRP3 protein expression was confirmed in mice. Importantly, JNUTS013 failed to ameliorate bowel inflammation in Nlrp3^-/- knockout mice, supporting NLRP3 as the biological target by which JNUTS013 inhibits inflammation. Further studies revealed critical chemical moieties of JNUTS013 required for inducing NLRP3 degradation.

CONCLUSION AND IMPLICATIONS

This study identifies a novel compound JNUTS013 that inhibits inflammation through inducing NLRP3 protein degradation in vitro and in vivo, which not only supports the development of JNUTS013 as an anti-inflammation agent but also creates a new way for the treatment of inflammation by chemically inducing NLRP3 degradation.

In vitro methods in autophagy research: Applications in neurodegenerative diseases and mood disorders

Background

Autophagy is a conserved physiological intracellular mechanism responsible for the degradation and recycling of cytoplasmic constituents (e.g., damaged organelles, and protein aggregates) to maintain cell homeostasis. Aberrant autophagy has been observed in neurodegenerative diseases, including Alzheimer's Disease (AD), Parkinson's Disease (PD), Amyotrophic Lateral Sclerosis (ALS), and Huntington's Disease (HD), and recently aberrant autophagy has been associated with mood disorders, such as depression. Several in vitro methods have been developed to study the complex and tightly regulated mechanisms of autophagy. In vitro methods applied to autophagy research are used to identify molecular key players involved in dysfunctional autophagy and to screen autophagy regulators with therapeutic applications in neurological diseases and mood disorders. Therefore, the aims of this narrative review are (1) to compile information on the cell-based methods used in autophagy research, (2) to discuss their application, and (3) to create a catalog of traditional and novel in vitro methods applied in neurodegenerative diseases and depression.

Methods

Pubmed and Google Scholar were used to retrieve relevant in vitro studies on autophagy mechanisms in neurological diseases and depression using a combination of search terms per mechanism and disease (e.g., "macroautophagy" and "Alzheimer's disease"). A total of 37 studies were included (14 in PD, 8 in AD, 5 in ALS, 5 in %, and 5 in depression).

Results

A repertoire of traditional and novel approaches and techniques was compiled and discussed. The methods used in autophagy research focused on the mechanisms of macroautophagy, microautophagy, and chaperone-mediated autophagy. The in vitro tools presented in this review can be applied to explore pathophysiological mechanisms at a molecular level and to screen for potential therapeutic agents and their mechanism of action, which can be of great importance to understanding disease biology and potential therapeutic options in the context of neurodegenerative disorders and depression.

Conclusion

This is the first review to compile, discuss, and provide a catalog of traditional and novel in vitro models applied to neurodegenerative disorders and depression.

Mushroom Natural Products in Neurodegenerative Disease Drug Discovery

The variety of drugs available to treat neurodegenerative diseases is limited. Most of these drug's efficacy is restricted by individual genetics and disease stages and usually do not prevent neurodegeneration acting long after irreversible damage has already occurred. Thus, drugs targeting the molecular mechanisms underlying subsequent neurodegeneration have the potential to negate symptom manifestation and subsequent neurodegeneration. Neuroinflammation is a common feature of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis, and is associated with the activation of the NLRP3 inflammasome, which in turn leads to neurodegeneration. Inflammasome activation and oligomerisation is suggested to be a major driver of disease progression occurring in microglia. With several natural products and natural product derivatives currently in clinical trials, mushrooms have been highlighted as a rich and largely untapped source of biologically active compounds in both in vitro and in vivo neurodegenerative disease models, partially supported by successful clinical trial evaluations. Additionally, novel high-throughput methods for the screening of natural product compound libraries are being developed to help accelerate the neurodegenerative disease drug discovery process, targeting neuroinflammation. However, the breadth of research relating to mushroom natural product high-throughput screening is limited, providing an exciting opportunity for further detailed investigations.

Emerging targets signaling for inflammation in Parkinson's disease drug discovery

Parkinson's disease (PD) patients not only show motor features such as bradykinesia, tremor, and rigidity but also non-motor features such as anxiety, depression, psychosis, memory loss, attention deficits, fatigue, sexual dysfunction, gastrointestinal issues, and pain. Many pharmacological treatments are available for PD patients; however, these treatments are partially or transiently effective since they only decrease the symptoms. As these therapies are unable to restore dopaminergic neurons and stop the development of Parkinson's disease, therefore, the need for an effective therapeutic approach is required. The current review summarizes novel targets for PD, that can be utilized to identify disease-modifying treatments.

Targeting Macroautophagy as a Therapeutic Opportunity to Treat Parkinson's Disease

Macroautophagy, an evolutionary conserved catabolic process in the eukaryotic cell, regulates cellular homeostasis and plays a decisive role in self-engulfing proteins, protein aggregates, dysfunctional or damaged organelles, and invading pathogens. Growing evidence from in vivo and in vitro models shows that autophagy dysfunction plays decisive role in the pathogenesis of various neurodegenerative diseases, including Parkinson's disease (PD). PD is an incurable and second most common neurodegenerative disease characterised by neurological and motor dysfunction accompanied of non-motor symptoms that can also reduce the life quality of patients. Despite the investment in research, the aetiology of the disease is still unknown and the therapies available are aimed mostly at ameliorating motor symptoms. Hence, therapeutics regulating the autophagy pathway might play an important role controlling the disease progression, reducing neuronal loss and even ameliorating non-motor symptoms. In this review, we highlight potential therapeutic opportunities involved in different targeting options like an initiation of autophagy, Leucine-rich repeat kinase 2 (LRRK2) inhibition, mitophagy, lysosomes, lipid metabolism, immune system, gene expression, biomarkers, and also non-pharmacological interventions. Thus, strategies to identify therapeutics targeting the pathways modulating autophagy might hold a future for therapy development against PD.

Increased pyroptosis activation in white matter microglia is associated with neuronal loss in ALS motor cortex

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of motor neurons in the motor cortex, brainstem, and spinal cord. Although ALS is considered a motor neuron disorder, neuroinflammation also plays an important role. Recent evidence in ALS disease models indicates activation of the inflammasome and subsequent initiation of pyroptosis, an inflammatory type of cell death. In this study, we determined the expression and distribution of the inflammasome and pyroptosis effector proteins in post-mortem brain and spinal cord from ALS patients (n = 25) and controls (n = 19), as well as in symptomatic and asymptomatic TDP-43^A315T transgenic and wild-type mice. Furthermore, we evaluated its correlation with the presence of TDP-43 pathological proteins and neuronal loss. Expression of the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, pyroptosis effector protein cleaved Gasdermin D (GSDMD), and IL-18 was detected in microglia in human ALS motor cortex and spinal cord, indicative of canonical inflammasome-triggered pyroptosis activation. The number of cleaved GSDMD-positive precentral white matter microglia was increased compared to controls and correlated with a decreased neuronal density in human ALS motor cortex. Neither of this was observed in the spinal cord. Similar results were obtained in TDP-43^A315T mice, where microglial pyroptosis activation was significantly increased in the motor cortex upon symptom onset, and correlated with neuronal loss. There was no significant correlation with the presence of TDP-43 pathological proteins both in human and mouse tissue. Our findings emphasize the importance of microglial NLRP3 inflammasome-mediated pyroptosis activation for neuronal degeneration in ALS and pave the way for new therapeutic strategies counteracting motor neuron degeneration in ALS by inhibiting microglial inflammasome/pyroptosis activation.

The NLRP3 Inflammasome Pathway: A Review of Mechanisms and Inhibitors for the Treatment of Inflammatory Diseases

The NLRP3 inflammasome is a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Upon activation by PAMPs and DAMPs, NLRP3 oligomerizes and activates caspase-1 which initiates the processing and release of pro-inflammatory cytokines IL-1β and IL-18. NLRP3 is the most extensively studied inflammasome to date due to its array of activators and aberrant activation in several inflammatory diseases. Studies using small molecules and biologics targeting the NLRP3 inflammasome pathway have shown positive outcomes in treating various disease pathologies by blocking chronic inflammation. In this review, we discuss the recent advances in understanding the NLRP3 mechanism, its role in disease pathology, and provide a broad review of therapeutics discovered to target the NLRP3 pathway and their challenges.

Neurodegeneration and Neuroinflammation in Parkinson's Disease: a Self-Sustained Loop

Purpose of Review

Neuroinflammation plays a significant role in Parkinson’s disease (PD) etiology along with mitochondrial dysfunction and impaired proteostasis. In this context, mechanisms related to immune response can act as modifiers at different steps of the neurodegenerative process and justify the growing interest in anti-inflammatory agents as potential disease-modifying treatments in PD. The discovery of inherited gene mutations in PD has allowed researchers to develop cellular and animal models to study the mechanisms of the underlying biology, but the original cause of neuroinflammation in PD is still debated to date.

Recent Findings

Cell autonomous alterations in neuronal cells, including mitochondrial damage and protein aggregation, could play a role, but recent findings also highlighted the importance of intercellular communication at both local and systemic level. This has given rise to debate about the role of non-neuronal cells in PD and reignited intense research into the gut-brain axis and other non-neuronal interactions in the development of the disease. Whatever the original trigger of neuroinflammation in PD, what appears quite clear is that the aberrant activation of glial cells and other components of the immune system creates a vicious circle in which neurodegeneration and neuroinflammation nourish each other.

Summary

In this review, we will provide an up-to-date summary of the main cellular alterations underlying neuroinflammation in PD, including those induced by environmental factors (e.g. the gut microbiome) and those related to the genetic background of affected patients. Starting from the lesson provided by familial forms of PD, we will discuss pathophysiological mechanisms linked to inflammation that could also play a role in idiopathic forms. Finally, we will comment on the potential clinical translatability of immunobiomarkers identified in PD patient cohorts and provide an update on current therapeutic strategies aimed at overcoming or preventing inflammation in PD.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

Evidence of Inflammation in Parkinson’s Disease and Its Contribution to Synucleinopathy

Accumulation of alpha-synuclein (αSyn) protein in neurons is a renowned pathological hallmark of Parkinson’s disease (PD). In addition, accumulating evidence indicates that activated inflammatory responses are involved in the pathogenesis of PD. Thus, achieving a better understanding of the interaction between inflammation and synucleinopathy in relation to the PD process will facilitate the development of promising disease-modifying therapies. In this review, the evidence of inflammation in PD is discussed, and human, animal, and laboratory studies relevant to the relationship between inflammation and αSyn are explored as well as new therapeutic targets associated with this relationship.

Contribution of Mitochondrial Dysfunction Combined with NLRP3 Inflammasome Activation in Selected Neurodegenerative Diseases

Alzheimer's disease and Parkinson's disease are the most common forms of neurodegenerative illnesses. It has been widely accepted that neuroinflammation is the key pathogenic mechanism in neurodegeneration. Both mitochondrial dysfunction and enhanced NLRP3 (nucleotide-binding oligomerization domain (NOD)-like receptor protein 3) inflammasome complex activity have a crucial role in inducing and sustaining neuroinflammation. In addition, mitochondrial-related inflammatory factors could drive the formation of inflammasome complexes, which are responsible for the activation, maturation, and release of pro-inflammatory cytokines, including interleukin-1β (IL-1β) and interleukin-18 (IL-18). The present review includes a broadened approach to the role of mitochondrial dysfunction resulting in abnormal NLRP3 activation in selected neurodegenerative diseases. Moreover, we also discuss the potential mitochondria-focused treatments that could influence the NLRP3 complex.

Mechanistic Insight from Preclinical Models of Parkinson's Disease Could Help Redirect Clinical Trial Efforts in GDNF Therapy

Parkinson’s disease (PD) is characterized by four pathognomonic hallmarks: (1) motor and non-motor deficits; (2) neuroinflammation and oxidative stress; (3) pathological aggregates of the α-synuclein (α-syn) protein; (4) neurodegeneration of the nigrostriatal system. Recent evidence sustains that the aggregation of pathological α-syn occurs in the early stages of the disease, becoming the first trigger of neuroinflammation and subsequent neurodegeneration. Thus, a therapeutic line aims at striking back α-synucleinopathy and neuroinflammation to impede neurodegeneration. Another therapeutic line is restoring the compromised dopaminergic system using neurotrophic factors, particularly the glial cell-derived neurotrophic factor (GDNF). Preclinical studies with GDNF have provided encouraging results but often lack evaluation of anti-α-syn and anti-inflammatory effects. In contrast, clinical trials have yielded imprecise results and have reported the emergence of severe side effects. Here, we analyze the discrepancy between preclinical and clinical outcomes, review the mechanisms of the aggregation of pathological α-syn, including neuroinflammation, and evaluate the neurorestorative properties of GDNF, emphasizing its anti-α-syn and anti-inflammatory effects in preclinical and clinical trials.

Modulating neuroinflammation in neurodegeneration-related dementia: can microglial toll-like receptors pull the plug?

Neurodegeneration-associated dementia disorders (NADDs), namely Alzheimer and Parkinson diseases, are developed by a significant portion of the elderly population globally. Extensive research has provided critical insights into the molecular basis of the pathological advancements of these diseases, but an efficient curative therapy seems elusive. A common attribute of NADDs is neuroinflammation due to a chronic inflammatory response within the central nervous system (CNS), which is primarily modulated by microglia. This response within the CNS is positively regulated by cytokines, chemokines, secondary messengers or cyclic nucleotides, and free radicals. Microglia mediated immune activation is regulated by a positive feedback loop in NADDs. The present review focuses on evaluating the crosstalk between inflammatory mediators and microglia, which aggravates both the clinical progression and extent of NADDs by forming a persistent chronic inflammatory milieu within the CNS. We also discuss the role of the human gut microbiota and its effect on NADDs as well as the suitability of targeting toll-like receptors for an immunotherapeutic intervention targeting the deflation of an inflamed milieu within the CNS.

Ulinastatin inhibits NLRP3-induced apoptosis in a PD cell model

Background

Emerging evidence suggests that inflammation induced by the inflammasome plays a crucial role in the course of Parkinson’s disease (PD). Ulinastatin (UTI) has shown significant anti-inflammatory effects. However, few studies have examined whether UTI protects neurons through its anti-inflammatory effects in PD. The purpose of this study is to determine whether UTI exerts neuroprotection in a PD cell model and to explore the mechanisms.

Methods

SH-SY5Y cells and nerve growth factor (NGF)-treated PC12 cells were used to establish MPP⁺ induced PD cell models. Cells were pre-treated with UTI, then cell viabilities were detected using the MTT assay. Lactate dehydrogenase (LDH) release was detected using the LDH release assay kit. Inflammatory factors such as IL-1β, IL-6, and TNF-α were detected using ELISA. The expression levels of TH, NLRP3, caspase-1, ASC, IL-1β, and IL-18 were measured using western blotting, and DA release was detected using HPLC. A NLRP3 activator Nigericin was used to verify the effect of NLRP3 in the neuroprotective mechanism of UTI.

Results

We observed decreased cell viability, increased apoptosis, and increased inflammatory factors such as IL-1β, IL-6, and TNF-α in the MPP⁺ induced PD model. We also found decreased DA secretion and TH expression, as well as increased NLRP3, caspase-1, ASC, IL-1α, and IL-18 expression in the MPP⁺ induced PD model. These changes were significantly attenuated by UTI pre-treatment in a dose dependent manner. NLRP3 activator Nigericin markedly increased LDH release, accelerated apoptosis, increased inflammation levels and decreased DA secretion and TH expression, suggesting that Nigericin eliminated the neuroprotective effect of UTI on MPP⁺ treated cells.

Conclusions

Our data demonstrated that UTI pre-treatment performed a neuroprotective role in the MPP⁺ induced PD cell models by inhibiting the NLRP3 pathway.

Immunomodulatory Effects of Dopamine in Inflammatory Diseases

Dopamine (DA) receptor, a significant G protein-coupled receptor, is classified into two families: D1-like (D1 and D5) and D2-like (D2, D3, and D4) receptor families, with further formation of homodimers, heteromers, and receptor mosaic. Increasing evidence suggests that the immune system can be affected by the nervous system and neurotransmitters, such as dopamine. Recently, the role of the DA receptor in inflammation has been widely studied, mainly focusing on NLRP3 inflammasome, NF-κB pathway, and immune cells. This article provides a brief review of the structures, functions, and signaling pathways of DA receptors and their relationships with inflammation. With detailed descriptions of their roles in Parkinson disease, inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis, this article provides a theoretical basis for drug development targeting DA receptors in inflammatory diseases.

Inhibition of long non-coding RNA HOXA11-AS against neuroinflammation in Parkinson's disease model via targeting miR-124-3p mediated FSTL1/NF-κB axis

Background: Studies have revealed that lncRNA HOXA11-AS contributes to regulating inflammation, while the role of HOXA11-AS in Parkinson’s disease (PD) remains unclear.

Methods: Both in vivo and in vitro PD models were induced. Gain- or loss-assays of HOXA11-AS and miR-124-3p were conducted. The neurological functions, dopaminergic neurons damage, microglia activation of PD mice were measured. Afterwards, the expressions of inflammatory factors were examined with RT-PCR. Western blot was employed to detect the level of FSTL1, NF-κB and NLRP3 inflammasome. Meanwhile, bioinformatics analysis and dual-luciferase reporter assay were utilized to confirm the targeting relationships among miR-124-3p, HOXA11-AS and FSTL1.

Results: HOXA11-AS promoted MPTP-mediated SH-SY5Y neuronal injury and LPS-induced microglia activation, while miR-124-3p had the opposite effects. Additionally, miR-124-3p was the target of HOXA11-AS and FSTL1. HOXA11-AS overexpression enhanced the expression of inflammatory factors and FSTL1, NF-κB and NLRP3 inflammasome, while inhibiting NF-κB weakened HOXA11-AS-mediated neuronal damage and microglia activation. Moreover, HOXA11-AS1 downregulation ameliorated MPTP-induced neurological damages and neuroinflammation in mice.

Conclusion: Inhibition of HOXA11-AS protects mice against PD through repressing neuroinflammation and neuronal apoptosis through miR-124-3p-FSTL1-NF-κB axis.

Neurodegenerative Disease and the NLRP3 Inflammasome

The prevalence of neurodegenerative disease has increased significantly in recent years, and with a rapidly aging global population, this trend is expected to continue. These diseases are characterised by a progressive neuronal loss in the brain or peripheral nervous system, and generally involve protein aggregation, as well as metabolic abnormalities and immune dysregulation. Although the vast majority of neurodegeneration is idiopathic, there are many known genetic and environmental triggers. In the past decade, research exploring low-grade systemic inflammation and its impact on the development and progression of neurodegenerative disease has increased. A particular research focus has been whether systemic inflammation arises only as a secondary effect of disease or is also a cause of pathology. The inflammasomes, and more specifically the NLRP3 inflammasome, a crucial component of the innate immune system, is usually activated in response to infection or tissue damage. Dysregulation of the NLRP3 inflammasome has been implicated in the progression of several neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and prion diseases. This review aims to summarise current literature on the role of the NLRP3 inflammasome in the pathogenesis of neurodegenerative diseases, and recent work investigating NLRP3 inflammasome inhibition as a potential future therapy.

Artemisinin attenuated oxidative stress and apoptosis by inhibiting autophagy in MPP+-treated SH-SY5Y cells

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. The oxidative stress is an important component of the pathogenesis of PD. Artemisinin (ART) has antioxidant and neuroprotective effects. The purpose of this study is to explore the neuroprotective effect of ART on 1-methyl-4-phenyliodine iodide (MPP ⁺)-treated SH-SY5Y cells and underlying mechanism.

METHODS

We used MPP⁺-treated SH-SY5Y cells to study the neuroprotective effect of ART. Cell viability was measured by MTT assay after incubating the cells with MPP⁺ and/or ART for 24 h. DCFH-DA was used to detect the level of intracellular reactive oxygen species (ROS), and WST-8 was used to detect the level of superoxide dismutase (SOD). The level of intracellular reduced glutathione (GSH) was detected with 5,5΄-dithiobis-(2-nitrobenzoic acid), and the level of malondialdehyde (MDA) was assessed based on the reaction of MDA and thiobarbituric acid. A mitochondrial membrane potential detection kit (JC-1) was used to detect changes in the mitochondrial membrane potential (MMP), and an Annexin V-FITC cell apoptosis kit was used to detect cell apoptosis. The expression levels of caspase-3, cleaved caspase-3 and the autophagy-related proteins LC3, beclin-1, and p62 were detected by Western blotting. In addition, to verify the change in autophagy, we used immunofluorescence to detect the expression of LC3 and p62.

RESULTS

No significant cytotoxicity was observed at ART concentrations up to 40 μM. ART could significantly increase the viability of SH-SY5Y cells treated with MPP⁺ and reduce oxidative stress damage and apoptosis. In addition, the Western blotting and immunofluorescence results showed that MPP⁺ treatment could increase the protein expression of beclin1 and LC3II/LC3I and decrease the protein expression of p62, indicating that MPP⁺ treatment could induce autophagy. Simultaneous treatment with ART and MPP⁺ could decrease the protein expression of beclin1 and LC3II/LC3I and increase the protein expression of p62, indicating that ART could decrease the level of autophagy induced by MPP⁺.

CONCLUSION

Our results indicate that ART has a protective effect on MPP⁺-treated SH-SY5Y cells by the antioxidant, antiapoptotic activities and inhibition of autophagy. Our findings may provide new hope for the prevention and treatment of PD.

Pivotal Role of Fyn Kinase in Parkinson's Disease and Levodopa-Induced Dyskinesia: a Novel Therapeutic Target?

The exact etiology of Parkinson's disease (PD) remains obscure, although many cellular mechanisms including α-synuclein aggregation, oxidative damage, excessive neuroinflammation, and dopaminergic neuronal apoptosis are implicated in its pathogenesis. There is still no disease-modifying treatment for PD and the gold standard therapy, chronic use of levodopa is usually accompanied by severe side effects, mainly levodopa-induced dyskinesia (LID). Hence, the elucidation of the precise underlying molecular mechanisms is of paramount importance. Fyn is a tyrosine phospho-transferase of the Src family nonreceptor kinases that is highly implicated in immune regulation, cell proliferation and normal brain development. Accumulating preclinical evidence highlights the emerging role of Fyn in key aspects of PD and LID pathogenesis: it may regulate α-synuclein phosphorylation, oxidative stress-induced dopaminergic neuronal death, enhanced neuroinflammation and glutamate excitotoxicity by mediating key signaling pathways, such as BDNF/TrkB, PKCδ, MAPK, AMPK, NF-κB, Nrf2, and NMDAR axes. These findings suggest that therapeutic targeting of Fyn or Fyn-related pathways may represent a novel approach in PD treatment. Saracatinib, a nonselective Fyn inhibitor, has already been tested in clinical trials for Alzheimer's disease, and novel selective Fyn inhibitors are under investigation. In this comprehensive review, we discuss recent evidence on the role of Fyn in the pathogenesis of PD and LID and provide insights on additional Fyn-related molecular mechanisms to be explored in PD and LID pathology that could aid in the development of future Fyn-targeted therapeutic approaches.

The Dichotomous Role of Inflammation in the CNS: A Mitochondrial Point of View

Innate immune response is one of our primary defenses against pathogens infection, although, if dysregulated, it represents the leading cause of chronic tissue inflammation. This dualism is even more present in the central nervous system, where neuroinflammation is both important for the activation of reparatory mechanisms and, at the same time, leads to the release of detrimental factors that induce neurons loss. Key players in modulating the neuroinflammatory response are mitochondria. Indeed, they are responsible for a variety of cell mechanisms that control tissue homeostasis, such as autophagy, apoptosis, energy production, and also inflammation. Accordingly, it is widely recognized that mitochondria exert a pivotal role in the development of neurodegenerative diseases, such as multiple sclerosis, Parkinson's and Alzheimer's diseases, as well as in acute brain damage, such in ischemic stroke and epileptic seizures. In this review, we will describe the role of mitochondria molecular signaling in regulating neuroinflammation in central nervous system (CNS) diseases, by focusing on pattern recognition receptors (PRRs) signaling, reactive oxygen species (ROS) production, and mitophagy, giving a hint on the possible therapeutic approaches targeting mitochondrial pathways involved in inflammation.

Proteostasis Disturbances and Inflammation in Neurodegenerative Diseases

Protein homeostasis (proteostasis) disturbances and inflammation are evident in normal aging and some age-related neurodegenerative diseases. While the proteostasis network maintains the integrity of intracellular and extracellular functional proteins, inflammation is a biological response to harmful stimuli. Cellular stress conditions can cause protein damage, thus exacerbating protein misfolding and leading to an eventual overload of the degradation system. The regulation of proteostasis network is particularly important in postmitotic neurons due to their limited regenerative capacity. Therefore, maintaining balanced protein synthesis, handling unfolding, refolding, and degrading misfolded proteins are essential to preserve all cellular functions in the central nervous sysytem. Failing proteostasis may trigger inflammatory responses in glial cells, and the consequent release of inflammatory mediators may lead to disturbances in proteostasis. Here, we review the mechanisms of proteostasis and inflammatory response, emphasizing their role in the pathological hallmarks of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Furthermore, we discuss the interplay between proteostatic stress and excessive immune response that activates inflammation and leads to dysfunctional proteostasis.

Key Mechanisms and Potential Targets of the NLRP3 Inflammasome in Neurodegenerative Diseases

Neurodegenerative diseases are neuronal disorders characterized by the loss of a large number of neurons in the human brain. Innate immunity-mediated neuroinflammation actively contributes to the onset and progression of neurodegenerative diseases. Inflammasomes are involved in the progression of the innate immune response and are responsible for the maturation of caspase-1 and inflammatory cytokines during neuroinflammation. The nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome, which is one of the most intensively investigated inflammasomes, has been reported to play a key role in neurodegenerative diseases. Here, we reviewed the mechanisms, role, and latest developments regarding the NLRP3 inflammasome with respect to three neurodegenerative diseases: Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS). Patient and animal model studies have found that abnormal protein aggregation of Aβ, synuclein, or copper–zinc superoxide dismutase-1 (SOD1), which are the main proteins expressed in the three diseases, respectively, can activate microglial cells, induce increased interleukin-1β (IL-1β) release, and activate the NLRP3 pathway, leading to neurodegeneration. In contrast, a deficiency of the components of the NLRP3 pathway may inhibit Aβ, synuclein, or SOD1-induced microglial activation. These studies indicate a positive correlation between NLRP3 levels and abnormal protein aggregation. However, in the case of ALS, not only microglia but also astrocytes express increased NLRP3 levels and contribute to activation of the NLRP3 pathway. In addition, in this review article, we also focus on the therapeutic implications of targeting novel inhibitors of the NLRP3 inflammasome or of novel drugs that mediate the NLRP3 pathway, which could play a role via NLRP3 in the treatment of neurodegenerative diseases.

Cellular Models and Assays to Study NLRP3 Inflammasome Biology

The NLRP3 inflammasome is a multi-protein complex that initiates innate immunity responses when exposed to a wide range of stimuli, including pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). Inflammasome activation leads to the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 and to pyroptotic cell death. Over-activation of NLRP3 inflammasome has been associated with several chronic inflammatory diseases. A deep knowledge of NLRP3 inflammasome biology is required to better exploit its potential as therapeutic target and for the development of new selective drugs. To this purpose, in the past few years, several tools have been developed for the biological characterization of the multimeric inflammasome complex, the identification of the upstream signaling cascade leading to inflammasome activation, and the downstream effects triggered by NLRP3 activation. In this review, we will report cellular models and cellular, biochemical, and biophysical assays that are currently available for studying inflammasome biology. A special focus will be on those models/assays that have been used to identify NLRP3 inhibitors and their mechanism of action.