Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK) Enhances Activation of STAT3/NLRC4 Inflammasome Signaling Axis through PKCδ in Astrocytes: Implications for Parkinson's Disease

Role of inflammatory cytokine in mediating the effect of plasma lipidome on epilepsy: a mediation Mendelian randomization study

Background

Epilepsy is one of the most prevalent serious brain disorders globally, impacting over 70 million individuals. Observational studies have increasingly recognized the impact of plasma lipidome on epilepsy. However, establishing a direct causal link between plasma lipidome and epilepsy remains elusive due to inherent confounders and the complexities of reverse causality. This study aims to investigate the causal relationship between specific plasma lipidome and epilepsy, along with their intermediary mediators.

Methods

We conducted a two-sample Mendelian randomization (MR) and mediation MR analysis to evaluate the causal effects of 179 plasma lipidomes and epilepsy, with a focus on the inflammatory cytokine as a potential mediator based on the genome-wide association study. The primary methodological approach utilized inverse variance weighting, complemented by a range of other estimators. A set of sensitivity analyses, including Cochran's Q test, I 2 statistics, MR-Egger intercept test, MR-PRESSO global test and leave-one-out sensitivity analyses was performed to assess the robustness, heterogeneity and horizontal pleiotropy of results.

Results

Our findings revealed a positive correlation between Phosphatidylcholine (18:1_18:1) levels with epilepsy risk (OR = 1.105, 95% CI: 1.036-1.178, p = 0.002). Notably, our mediation MR results propose Tumor necrosis factor ligand superfamily member 12 levels (TNFSF12) as a mediator of the relationship between Phosphatidylcholine (18,1_18:1) levels and epilepsy risk, explaining a mediation proportion of 4.58% [mediation effect: (b = 0.00455, 95% CI: -0.00120-0.01030), Z = 1.552].

Conclusion

Our research confirms a genetic causal relationship between Phosphatidylcholine (18:1_18:1) levels and epilepsy, emphasizing the potential mediating role of TNFSF12 and provide valuable insights for future clinical investigations into epilepsy.

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.

Sex-dimorphic neuroprotective effect of CD163 in an α-synuclein mouse model of Parkinson's disease

Alpha-synuclein (α-syn) aggregation and immune activation represent hallmark pathological events in Parkinson's disease (PD). The PD-associated immune response encompasses both brain and peripheral immune cells, although little is known about the immune proteins relevant for such a response. We propose that the upregulation of CD163 observed in blood monocytes and in the responsive microglia in PD patients is a protective mechanism in the disease. To investigate this, we used the PD model based on intrastriatal injections of murine α-syn pre-formed fibrils in CD163 knockout (KO) mice and wild-type littermates. CD163KO females revealed an impaired and differential early immune response to α-syn pathology as revealed by immunohistochemical and transcriptomic analysis. After 6 months, CD163KO females showed an exacerbated immune response and α-syn pathology, which ultimately led to dopaminergic neurodegeneration of greater magnitude. These findings support a sex-dimorphic neuroprotective role for CD163 during α-syn-induced neurodegeneration.

Systems level analysis of sex-dependent gene expression changes in Parkinson's disease

Parkinson's disease (PD) is a heterogeneous disorder, and among the factors which influence the symptom profile, biological sex has been reported to play a significant role. While males have a higher age-adjusted disease incidence and are more frequently affected by muscle rigidity, females present more often with disabling tremors. The molecular mechanisms involved in these differences are still largely unknown, and an improved understanding of the relevant factors may open new avenues for pharmacological disease modification. To help address this challenge, we conducted a meta-analysis of disease-associated molecular sex differences in brain transcriptomics data from case/control studies. Both sex-specific (alteration in only one sex) and sex-dimorphic changes (changes in both sexes, but with opposite direction) were identified. Using further systems level pathway and network analyses, coordinated sex-related alterations were studied. These analyses revealed significant disease-associated sex differences in mitochondrial pathways and highlight specific regulatory factors whose activity changes can explain downstream network alterations, propagated through gene regulatory cascades. Single-cell expression data analyses confirmed the main pathway-level changes observed in bulk transcriptomics data. Overall, our analyses revealed significant sex disparities in PD-associated transcriptomic changes, resulting in coordinated modulations of molecular processes. Among the regulatory factors involved, NR4A2 has already been reported to harbor rare mutations in familial PD and its pharmacological activation confers neuroprotective effects in toxin-induced models of Parkinsonism. Our observations suggest that NR4A2 may warrant further research as a potential adjuvant therapeutic target to address a subset of pathological molecular features of PD that display sex-associated profiles.

TWEAK-Fn14 Axis Induces Calcium-Associated Autophagy and Cell Death To Control Mycobacterial Survival in Macrophages

Autophagy is a natural defense mechanism that protects the host against pathogens. We previously demonstrated that mycobacterial infection upregulated tumor necrosis factor-like weak inducer of apoptosis (TWEAK) to promote autophagy and mycobacterial autophagosome maturation through activation of AMP-activated protein kinase (AMPK). Fibroblast growth factor-inducible 14 (Fn14) is the receptor of TWEAK. But the role of Fn14 in mycobacterial infection remains elusive. Herein, we observed increased expression of Fn14 in peripheral blood mononuclear cells of active tuberculosis (TB) patients. Downregulation of cellular Fn14 enhanced mycobacterial survival in macrophages. Conversely, Fn14 overexpression inhibited mycobacterial growth, suggesting that Fn14 can inhibit mycobacterial infection. The in vitro results revealed that TWEAK-promoted mycobacterial phagosome maturation is Fn14-dependent. We demonstrated that TWEAK-Fn14 signaling promotes oxidative stress to enhance the expression of stromal interaction molecule 1 (STIM1) and its activation of the Ca2+ channel ORAI1. Elevated calcium influx stimulated the activation of CaMCCK2 (calcium/calmodulin-dependent protein kinase kinase 2) and its downstream effector AMPK, thus inducing autophagy in early infection. Persistently TWEAK-Fn14 signaling caused cell death in late infection by reducing mitochondrial membrane potential, leading to mitochondrial ROS accumulation, and activating cell death-associated proteins. Genetic Fn14 deficiency or TWEAK blockers decreased oxidative stress-induced calcium influx, thus suppressing autophagy and cell death in mycobacteria-infected macrophages, and resulting in elevated mycobacterial survival. We propose that the TWEAK-Fn14 axis and calcium influx could be manipulated for anti-TB therapeutic purposes. Our results offer a new molecular machinery to understand the association between the TWEAK-Fn14 axis, calcium influx, and mycobacterial infection. IMPORTANCE Tuberculosis remains a major cause of morbidity and mortality worldwide. We previously demonstrated a relationship between TWEAK and activation of the autophagic machinery, which promotes anti-mycobacterial immunity. The TWEAK-Fn14 axis is multi-functional and involved in the pathogenesis of many diseases, thus blockade of TWEAK-Fn14 axis has been considered as a potential therapeutic target. Here, we demonstrated that the TWEAK-Fn14 axis plays a novel role in anti-mycobacterial infection by regulating calcium-associated autophagy. Persistently, TWEAK-Fn14 signaling caused cell death in late infection by reducing mitochondrial membrane potential, leading to mitochondrial ROS accumulation, and activating cell death-associated proteins. TWEAK blocker or Fn14 deficiency could suppress oxidative stress and calcium-associated autophagy, resulting in elevated mycobacterial survival. We propose that the TWEAK-Fn14 axis and calcium influx could be manipulated for anti-TB therapeutic purposes. This study offers a new molecular machinery to understand the association between the TWEAK-Fn14 axis, calcium influx, and mycobacterial infection.

Microglial AIM2 alleviates antiviral-related neuro-inflammation in mouse models of Parkinson's disease

Inflammasome involvement in Parkinson's disease (PD) has been intensively investigated. Absent in melanoma 2 (AIM2) is an essential inflammasome protein known to contribute to the development of several neurological diseases. However, a specific role for AIM2 in PD has not been reported. In this study, we investigated the effect of AIM2 in the N-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced PD model by use of various knockout and bone marrow chimeric mice. The mechanism of action for AIM2 in PD was assessed by RNA-sequencing and in vitro primary microglial transfection. Results were validated in the A30P transgenic mouse model of PD. In the MPTP mouse model, AIM2 activation was found to negatively regulate neuro-inflammation independent of the inflammasome. Microglial AIM2 deficiency exacerbated behavioral and pathological features of both MPTP-induced and transgenic PD mouse models. Mechanistically, AIM2 reduced cyclic GMP-AMP synthase (cGAS)-mediated antiviral-related inflammation by inhibition of AKT-interferon regulatory factor 3 (IRF3) phosphorylation. These results demonstrate microglial AIM2 to inhibit the antiviral-related neuro-inflammation associated with PD and provide for a foundation upon which to identify new therapeutic targets for treatment of the disease.

Crosstalk between neuroinflammation and oxidative stress in epilepsy

The roles of both neuroinflammation and oxidative stress in the pathophysiology of epilepsy have begun to receive considerable attention in recent years. However, these concepts are predominantly studied as separate entities despite the evidence that neuroinflammatory and redox-based signaling cascades have significant crosstalk. Oxidative post-translational modifications have been demonstrated to directly influence the function of key neuroinflammatory mediators. Neuroinflammation can further be controlled on the transcriptional level as the transcriptional regulators NF-KB and nrf2 are activated by reactive oxygen species. Further, neuroinflammation can induce the increased expression and activity of NADPH oxidase, leading to a highly oxidative environment. These factors additionally influence mitochondria function and the metabolic status of neurons and glia, which are already metabolically stressed in epilepsy. Given the implication of this relationship to disease pathology, this review explores the numerous mechanisms by which neuroinflammation and oxidative stress influence one another in the context of epilepsy. We further examine the efficacy of treatments targeting oxidative stress and redox regulation in animal and human epilepsies in the literature that warrant further investigation. Treatment approaches aimed at rectifying oxidative stress and aberrant redox signaling may enable control of neuroinflammation and improve patient outcomes.

Aprepitant attenuates NLRC4-dependent neuronal pyroptosis via NK1R/PKCδ pathway in a mouse model of intracerebral hemorrhage

BACKGROUND

Pyroptosis is a programmed cell death mediated by inflammasomes. Previous studies have reported that inhibition of neurokinin receptor 1 (NK1R) exerted neuroprotection in several neurological diseases. Herein, we have investigated the role of NK1R receptor inhibition using Aprepitant to attenuate NLRC4-dependent neuronal pyroptosis after intracerebral hemorrhage (ICH), as well as the underlying mechanism.

METHODS

A total of 182 CD-1 mice were used. ICH was induced by injection of autologous blood into the right basal ganglia. Aprepitant, a selective antagonist of NK1R, was injected intraperitoneally at 1 h after ICH. To explore the underlying mechanism, NK1R agonist, GR73632, and protein kinase C delta (PKCδ) agonist, phorbol 12-myristate 13-acetate (PMA), were injected intracerebroventricularly at 1 h after ICH induction, and small interfering ribonucleic acid (siRNA) for NLRC4 was administered via intracerebroventricular injection at 48 h before ICH induction, respectively. Neurobehavioral tests, western blot, and immunofluorescence staining were performed.

RESULTS

The expression of endogenous NK1R and NLRC 4 were gradually increased after ICH. NK1R was expressed on neurons. Aprepitant significantly improved the short- and long-term neurobehavioral deficits after ICH, which was accompanied with decreased neuronal pyroptosis, as well as decreased expression of NLRC4, Cleaved-caspase-1, GSDMD (gasdermin D), IL-1β, and IL-18. Activation of NK1R or PKCδ abolished these neuroprotective effects of Aprepitant after ICH. Similarly, knocking down NLRC4 using siRNA produced similar neuroprotective effects.

CONCLUSION

Aprepitant suppressed NLRC4-dependent neuronal pyroptosis and improved neurological function, possibly mediated by inhibition of NK1R/PKCδ signaling pathways after ICH. The NK1R may be a promising therapeutic target for the treatment of ICH.

Parthenolide ameliorates neurological deficits and neuroinflammation in mice with traumatic brain injury by suppressing STAT3/NF-κB and inflammasome activation

BACKGROUND

Traumatic brain injury (TBI) triggers a set of complex inflammation that results in secondary injury. Parthenolide (PTN) is a sesquiterpene lactone extracted from the herb Tanacetum parthenium (Feverfew) and has potent anti-inflammatory, anti-apoptosis and anti-oxidative stress effects in the central nervous system (CNS)-related diseases. This study focuses on investigating the potential neuroprotective effect of PTN on TBI and the related mechanism.

METHODS

Bv2 microglia, primary microglia were stimulated by LPS, and HT22 neuron cells were stimulated by OGD/R, and they were treated with different doses of PTN. The expression profiles of pro-inflammatory cytokines, proteins, oxidative stress mediators, STAT3/NF-κB pathway, inflammasomes were detected. Forty male/female C57BL/6 mice were randomly divided into the sham, PTN, TBI, and TBI + PTN groups (10 mice per group). A mouse TBI model was set up with a controlled cortical impact (CCI) device. The modified nerve severity score (mNSS) was implemented to check short-term neurological impairment in mice, and the mice's memory and learning were assessed by the Morris water maze test. The water content in the mice's brains was measured by the dry-wet method. Hematoxylin-eosin (H&E) staining, Nissl staining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay were applied for neuronal apoptosis.

RESULTS

PTN dramatically alleviated LPS-induced inflammation in microglia, and OGD-mediated neuronal apoptosis and oxidative stress. In addition, PTN repressed LPS- or OGD-modulated STAT3/NF-κB and NLR family pyrin domain containing 1 (NLRP1), NLRP3, NLR family CARD domain containing 4 (NLRC4) inflammasomes activation. Administering the STAT3 inhibitor Stattic or NF-κB inhibitor Bay 11-7082 attenuated PTN-mediated effects. In vivo, PTN treatment relieved neural function deficits, brain edema and neuron apoptosis and improved the memory and learning function of TBI mice. Additionally, PTN impeded microglial activation and reduced the production of pro-inflammatory cytokines in brain lesions of TBI mice. Furthermore, PTN hindered STAT3/NF-κB and inflammasome activation.

CONCLUSION

PTN can curb microglial activation and neuron apoptosis by dampening the STAT3/NF-κB pathway, thus exerting neuroprotective effects in TBI mice.

Bone Marrow Stem Cell-Exo-Derived TSG-6 Attenuates 1-Methyl-4-Phenylpyridinium+-Induced Neurotoxicity via the STAT3/miR-7/NEDD4/LRRK2 Axis

Bone marrow mesenchymal stem cell-derived exosome (BMSCs-Exo)-derived TNF-stimulated gene-6 (TSG-6) has anti-inflammatory and antioxidative stress-related properties that may be beneficial in the treatment of Parkinson disease (PD) patients. To elucidate the mechanisms involved, we analyzed the effects of BMSCs-Exo-derived TSG-6 on in vitro models of PD induced with 1-methyl-4-phenylpyridinium (MPP+). TSG-6 was abundant in BMSCs-Exo and it attenuated MPP+-induced neurotoxicity. Moreover, BMSCs-Exo reversed the MPP+-induced toxicity accelerated by neural precursor cells expressed developmentally downregulated 4 (NEDD4) knockdown or miR-7 mimics. Further analysis indicated that NEDD4 combined with leucine-rich repeat kinase 2 (LRRK2) to accelerate ubiquitin degradation of LRRK2. Signal transducer and activator of transcription 3 (STAT3) bound to the miR-7 promoter and miR-7 targeted NEDD4. These data indicate that BMSCs-Exo-derived TSG-6 attenuated neurotoxicity via the STAT3-miR-7-NEDD4 axis. Our results define the specific mechanisms for BMSCs-Exo-derived TSG-6 regulation of MPP+-induced neurotoxicity that are relevant to understanding PD pathogenesis and developing therapies for PD patients.

Glial Cells and Brain Diseases: Inflammasomes as Relevant Pathological Entities

Inflammation mediated by the innate immune system is a physiopathological response to diverse detrimental circumstances such as microbe infections or tissular damage. The molecular events that underlie this response involve the assembly of multiprotein complexes known as inflammasomes. These assemblages are essentially formed by a stressor-sensing protein, an adapter protein and a non-apoptotic caspase (1 or 11). The coordinated aggregation of these components mediates the processing and release of pro-inflammatory interleukins (IL-β and IL-18) and cellular death by pyroptosis induction. The inflammatory response is essential for the defense of the organism; for example, it triggers tissue repair and the destruction of pathogen microbe infections. However, when inflammation is activated chronically, it promotes diverse pathologies in the lung, liver, brain and other organs. The nervous system is one of the main tissues where the inflammatory process has been characterized, and its implications in health and disease are starting to be understood. Thus, the regulation of inflammasomes in specific cellular types of the central nervous system needs to be thoroughly understood to innovate treatments for diverse pathologies. In this review, the presence and participation of inflammasomes in pathological conditions in different types of glial cells will be discussed.

TNF-like weak inducer of apoptosis / nuclear factor κB axis feedback loop promotes spinal cord injury by inducing astrocyte activation

Non-canonical signaling pathways have been proved to act as potent sites of astrocytes osmotic expanding or proliferation, which promotes the regeneration of axons in areas with non-neural spinal cord injury (SCI). However, the relevant signal pathway that induces autophagic cell death in astrocytes and its function relative to the TNF-like weak inducer of apoptosis/nuclear factor κB (TWEAK/NF-κB) axis remains elusive. The SCI model was established by vertically striking the spinal cord according to Allen’s model. Astrocytes and neuronal cells were prepared from spinal cells extracted from spinal cord tissues of SCI or normal C57BL/6 newborn mice. After co-culturing astrocytes and neurons, cell viability and autophagy were determined by CCK-8, transmission electron microscopy (TEM), and western blot. The expression of TWEAK, NF-κB and inflammatory cytokines was confirmed by qRT-PCR, western blot, Immunofluorescence and ELISA assay. Chromatin immunoprecipitation (CHIP) was used to evaluate the interaction between TWEAK and NF-κB. Our results demonstrated that knockdown of TWEAK and NF-κB inhibited secretion of high levels of TNF-α/IL-1β, partially counteracted by adding Rap. TWEAK/NF-κB was the positive correlation feedback loop regulating the proliferation and autophagy of astrocytes involved in SCI. Moreover, restraining the excess growth of astrocytes was beneficial to the growth of neurons. Collectively, our findings illustrated that the TWEAK/NF-κB pathway might act as a positive modulator of SCI by inducing astrocyte activation, shedding new insights for SCI treatment.

PKC Delta Activation Promotes Endoplasmic Reticulum Stress (ERS) and NLR Family Pyrin Domain-Containing 3 (NLRP3) Inflammasome Activation Subsequent to Asynuclein-Induced Microglial Activation: Involvement of Thioredoxin-Interacting Protein (TXNIP)/Thioredoxin (Trx) Redoxisome Pathway

A classical hallmark of Parkinson's disease (PD) pathogenesis is the accumulation of misfolded alpha-synuclein (αSyn) within Lewy bodies and Lewy neurites, although its role in microglial dysfunction and resultant dopaminergic (DAergic) neurotoxicity is still elusive. Previously, we identified that protein kinase C delta (PKCδ) is activated in post mortem PD brains and experimental Parkinsonism and that it participates in reactive microgliosis; however, the relationship between PKCδ activation, endoplasmic reticulum stress (ERS) and the reactive microglial activation state in the context of α-synucleinopathy is largely unknown. Herein, we show that oxidative stress, mitochondrial dysfunction, NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, and PKCδ activation increased concomitantly with ERS markers, including the activating transcription factor 4 (ATF-4), serine/threonine-protein kinase/endoribonuclease inositol-requiring enzyme 1α (p-IRE1α), p-eukaryotic initiation factor 2 (eIF2α) as well as increased generation of neurotoxic cytokines, including IL-1β in aggregated αSyn_agg-stimulated primary microglia. Importantly, in mouse primary microglia-treated with αSyn_agg we observed increased expression of Thioredoxin-interacting protein (TXNIP), an endogenous inhibitor of the thioredoxin (Trx) pathway, a major antioxidant protein system. Additionally, αSyn_agg promoted interaction between NLRP3 and TXNIP in these cells. In vitro knockdown of PKCδ using siRNA reduced ERS and led to reduced expression of TXNIP and the NLRP3 activation response in αSyn_agg-stimulated mouse microglial cells (MMCs). Additionally, attenuation of mitochondrial reactive oxygen species (mitoROS) via mito-apocynin and amelioration of ERS via the eIF2α inhibitor salubrinal (SAL) reduced the induction of the ERS/TXNIP/NLRP3 signaling axis, suggesting that mitochondrial dysfunction and ERS may act in concert to promote the αSyn_agg-induced microglial activation response. Likewise, knockdown of TXNIP by siRNA attenuated the αSyn_agg-induced NLRP3 inflammasome activation response. Finally, unilateral injection of αSyn preformed fibrils (αSyn_PFF) into the striatum of wild-type mice induced a significant increase in the expression of nigral p-PKCδ, ERS markers, and upregulation of the TXNIP/NLRP3 inflammasome signaling axis prior to delayed loss of TH⁺ neurons. Together, our results suggest that inhibition of ERS and its downstream signaling mediators TXNIP and NLRP3 might represent novel therapeutic avenues for ameliorating microglia-mediated neuroinflammation in PD and other synucleinopathies.