Cntnap4 partial deficiency exacerbates α-synuclein pathology through astrocyte-microglia C3-C3aR pathway

Astrocyte-neuron communication through the complement C3-C3aR pathway in Parkinson's disease

Neuroinflammation and autoimmunity are pivotal in the pathogenesis of neurodegenerative diseases. Complement activation and involvement of astrocyte-neuron C3/C3aR pathway have been observed, yet the mechanisms influencing α-synuclein (α-syn) pathology and neurodegeneration remain unclear. In this study, elevated levels of complement C3 were detected in the plasma of α-syn PFF-induced mice and the substantia nigra of A53T transgenic mice. Colocalization of complement C3 with astrocytes was also observed. Overexpression of complement C3 exacerbated motor dysfunction, dopaminergic neuron loss, and phosphorylated α-syn expression in mice injected with α-syn preformed fibrils (α-syn PFFs). Conversely, downregulation of complement C3 protected α-syn PFF-induced mice. Molecular investigations revealed that inhibition of Toll-like receptor 2 (TLR2) or NF-κB reduced complement C3 expression in primary astrocytes following α-syn PFF treatment. Astrocyte-neuron communication via the C3/C3aR pathway influenced α-syn PFF-induced neuronal apoptosis and α-syn pathology, potentially through modulation of GSK3β. These findings underscore the critical role of astrocyte-neuron communication via the C3/C3aR pathway in PD pathogenesis, highlighting its potential as a therapeutic target.

Astroglial membrane camouflaged Ptbp1 siRNA delivery hinders glutamate homeostasis via SDH/Nrf2 pathway

Polypyrimidine tract-binding protein 1 (PTBP1) regulates numerous alternative splicing events during tumor progression and neurogenesis. Previously, PTBP1 downregulation was reported to convert astrocytes into functional neurons; however, how PTBP1 regulates astrocytic physiology remains unclear. In this study, we revealed that PTBP1 modulated glutamate uptake via ATP1a2, a member of Na+/K+-ATPases, and glutamate transporters in astrocytes. Ptbp1 knockdown altered mitochondrial function and energy metabolism, which involved PTBP1 regulating mitochondrial redox homeostasis via the succinate dehydrogenase (SDH)/Nrf2 pathway. The malfunction of glutamate transporters following Ptbp1 knockdown resulted in enhanced excitatory synaptic transmission in the cortex. Notably, we developed a biomimetic cationic triblock polypeptide system, i.e., polyethylene glycol44-polylysine30-polyleucine10 (PEG44-PLL30-PLLeu10) with astrocytic membrane coating to deliver Ptbp1 siRNA in vitro and in vivo, which approach allowed Ptbp1 siRNA to efficiently cross the blood-brain barrier and target astrocytes in the brain. Collectively, our findings suggest a framework whereby PTBP1 serves as a modulator in glutamate transport machinery, and indicate that biomimetic methodology is a promising route for in vivo siRNA delivery.

Comprehensive Analysis of Bulk RNA-Seq and Single-Cell RNA-Seq Data Unveils Sevoflurane-Induced Neurotoxicity Through SLC7A11-Associated Ferroptosis

Sevoflurane's potential impact on cognitive function and neurodevelopment, especially in susceptible populations such as infants and the elderly, has raised widespread concern. This study focuses on how sevoflurane induces ferroptosis in astrocytes and identifies solute carrier family 7 member 11 (SLC7A11) as a mediator of ferroptosis, providing new insights into sevoflurane-related neurotoxic pathways. We analysed single-cell sequencing (scRNA-seq) data from sevoflurane-exposed mice and control mice, supplemented with bulk RNA-seq data, to assess gene expression alterations. Additionally, pregnant mice were subjected to in vivo experiments, and in vitro studies using U251 astrocytoma cells were conducted to evaluate sevoflurane's neurotoxic effects on offspring, focusing on ferroptosis markers and SLC7A11 expression. Sevoflurane exposure led to learning, memory and behavioural deficits in offspring, associated with decreased SLC7A11 expression and increased signs of ferroptosis. In U251 cells, sevoflurane reduced cell viability, increased reactive oxygen species (ROS) levels and affected the expression of ferroptosis regulatory factors, supporting the hypothesis that sevoflurane induces astrocyte ferroptosis through SLC7A11 modulation. Molecular docking experiments suggest a direct interaction between sevoflurane and SLC7A11. This study provides mechanistic insights into sevoflurane-induced neurotoxicity, emphasising the importance of SLC7A11 in regulating astrocyte ferroptosis. Our findings highlight the potential for targeting ferroptosis pathways to mitigate the adverse effects of sevoflurane anaesthesia.

The complement C3a/C3aR pathway is associated with treatment resistance to gemcitabine-based neoadjuvant therapy in pancreatic cancer

Gemcitabine is a standard first-line drug for pancreatic cancer chemotherapy. Nevertheless, gemcitabine resistance is common and significantly limits its therapeutic efficacy, impeding advancements in pancreatic cancer treatment. In this study, through a comprehensive analysis of gemcitabine-resistant cell lines and patient samples, 39 gemcitabine resistance-associated risk genes were identified, and two distinct gemcitabine response-related phenotypes were delineated. Through a combination of bioinformatics analysis and in vivo and in vitro experiments, we identified the C3a/C3aR signaling pathway as a pivotal player in the development of gemcitabine resistance in pancreatic cancer. We found that activation of the C3a/C3aR signaling pathway promoted the proliferation, migration and gemcitabine resistance of pancreatic cancer cells, while the C3aR antagonist SB290157 effectively counteracted these effects by impeding the activation of the C3a/C3aR pathway. Our study reveals the fundamental role of complement C3a in the progression of pancreatic cancer, suggesting that complement C3a may serve as a promising biomarker in pancreatic cancer.

Nanotherapeutic Approaches of Interleukin-3 to Clear the α-Synuclein Pathology in Mouse Models of Parkinson's Disease

Astrocyte-microglia crosstalk is vital for neuronal survival and clearing aggregate accumulation in neurodegenerative diseases. While interleukin-3 (IL-3) has been reported to exert both protective and detrimental effects in neurodegenerative diseases, however, its role in α-synuclein pathology remains unclear. In this study, it is found that astrocytic IL-3 and microglial IL-3R are positively responsive to α-synuclein pathology in the brains of transgenic A53T Parkinson's disease (PD) mice and in an adeno-associated virus (AAV)-human α-synuclein (AAV-hα-Syn)-injected PD mouse model. Exogenous IL-3 infusion reduces behavioral abnormities and nigrostriatal α-synuclein pathology. Mechanistically, IL-3 induces microglial phagocytosis of pathological α-synuclein while simultaneously stimulating dopaminergic (DA) neurons to clear pathological α-synuclein via induction of autophagy through the IFN-β/Irgm1 pathway. Due to its limited efficiency in crossing the blood-brain barrier, a precise IL-3 delivery strategy is developed by cross-linking IL-3 and RVG29 with PEG-Linker (RVG-modified IL-3 nanogels-RVG-IL3 NGs). Intravenous administration of RVG-IL3 NGs shows efficient uptake by microglia and DA neurons within the brain. RVG-IL3 NGs ameliorate motor deficits and pathological α-synuclein by improving microglial and neuronal function in the AAV-hα-Syn mouse model of PD. Collectively, IL-3 may represent a feasible therapeutic strategy for PD.

Small Molecule Drug C381 Attenuates Brain Vascular Damage Following Repetitive Mild Traumatic Injury

Traumatic brain injury (TBI) remains a significant public health concern, with no effective therapeutic interventions to ameliorate the enduring consequences. The prevailing understanding of TBI pathophysiology indicates a central role for vascular dysfunction. Transforming growth factor-β (TGF-β) is a multifunctional cytokine crucial for vascular development. Aberrant TGF-β signaling is implicated in vascular pathologies associated with various neurological conditions. We recently developed a novel small molecule drug, C381, a TGF-β activator with the ability to restore lysosomal function. Here we used a mouse model of repetitive mild TBI (mTBI) to examine whether C381 would attenuate vascular injury. We first employed RNA-seq analysis to investigate the gene expression patterns associated with mTBI and evaluated the therapeutic potential of C381 in mitigating these changes. Our results demonstrate distinct mTBI-related gene expression signatures, prominently implicating pathways related to vascular integrity and endothelial function. Notably, treatment with C381 reversed these mTBI-induced gene expression changes. Immunohistochemical analysis further corroborated these findings, revealing that C381 treatment attenuated vascular damage in mTBI-affected brain tissue. These findings strongly support the potential clinical usefulness of C381 as a novel therapeutic intervention for mTBI.

Complement 3a induces the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms during the development and progression of Alzheimer's disease

As a central molecule in complement system (CS), complement (C) 3 is upregulated in the patients and animal models of Alzheimer's disease (AD). C3 will metabolize to iC3b and C3a. iC3b is responsible for clearing β-amyloid protein (Aβ). In this scenario, C3 exerts neuroprotective effects against the disease via iC3b. However, C3a will inhibit microglia to clear the Aβ, leading to the deposition of Aβ and impair the functions of synapses. To their effects on AD, activation of C3a and C3a receptor (C3aR) will impair the mitochondria, leading to the release of reactive oxygen species (ROS), which activates the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasomes. The overloading of NLRP3 inflammasomes activate microglia, leading to the formation of inflammatory environment. The inflammatory environment will facilitate the deposition of Aβ and abnormal synapse pruning, which results in the progression of AD. Therefore, the current review will decipher the mechanisms of C3a inducing the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms, which facilitates the understanding the AD.

Short-chain fatty acids suppresses astrocyte activation by amplifying Trp-AhR-AQP4 signaling in experimental autoimmune encephalomyelitis mice

The function of astrocytes in response to gut microbiota-derived signals has an important role in the pathophysiological processes of central nervous system (CNS) diseases. However, the specific effects of microbiota-derived metabolites on astrocyte activation have not been elucidated yet. Experimental autoimmune encephalomyelitis (EAE) was induced in female C57BL/6 mice as a classical MS model. The alterations of gut microbiota and the levels of short-chain fatty acids (SCFAs) were assessed after EAE induction. We observed that EAE mice exhibit low levels of Allobaculum, Clostridium_IV, Clostridium_XlVb, Lactobacillus genera, and microbial-derived SCFAs metabolites. SCFAs supplementation suppressed astrocyte activation by increasing the level of tryptophan (Trp)-derived AhR ligands that activating the AhR. The beneficial effects of SCFAs supplementation on the clinical scores, histopathological alterations, and the blood brain barrier (BBB)-glymphatic function were abolished by intracisterna magna injection of AAV-GFAP-shAhR. Moreover, SCFAs supplementation suppressed the loss of AQP4 polarity within astrocytes in an AhR-dependent manner. Together, SCFAs potentially suppresses astrocyte activation by amplifying Trp-AhR-AQP4 signaling in EAE mice. Our study demonstrates that SCFAs supplementation may serve as a viable therapy for inflammatory disorders of the CNS.

Usp14 deficiency removes α-synuclein by regulating S100A8/A9 in Parkinson's disease

Ubiquitin-proteasome system dysfunction triggers α-synuclein aggregation, a hallmark of neurodegenerative diseases, such as Parkinson's disease (PD). However, the crosstalk between deubiquitinating enzyme (DUBs) and α-synuclein pathology remains unclear. In this study, we observed a decrease in the level of ubiquitin-specific protease 14 (USP14), a DUB, in the cerebrospinal fluid (CSF) of PD patients, particularly females. Moreover, CSF USP14 exhibited a dual correlation with α-synuclein in male and female PD patients. To investigate the impact of USP14 deficiency, we crossed USP14 heterozygous mouse (USP14+/-) with transgenic A53T PD mouse (A53T-Tg) or injected adeno-associated virus (AAV) carrying human α-synuclein (AAV-hα-Syn) in USP14+/- mice. We found that Usp14 deficiency improved the behavioral abnormities and pathological α-synuclein deposition in female A53T-Tg or AAV-hα-Syn mice. Additionally, Usp14 inactivation attenuates the pro-inflammatory response in female AAV-hα-Syn mice, whereas Usp14 inactivation demonstrated opposite effects in male AAV-hα-Syn mice. Mechanistically, the heterodimeric protein S100A8/A9 may be the downstream target of Usp14 deficiency in female mouse models of α-synucleinopathies. Furthermore, upregulated S100A8/A9 was responsible for α-synuclein degradation by autophagy and the suppression of the pro-inflammatory response in microglia after Usp14 knockdown. Consequently, our study suggests that USP14 could serve as a novel therapeutic target in PD.

Cortistatin as a Novel Multimodal Therapy for the Treatment of Parkinson's Disease

Parkinson's disease (PD) is a complex disorder characterized by the impairment of the dopaminergic nigrostriatal system. PD has duplicated its global burden in the last few years, becoming the leading neurological disability worldwide. Therefore, there is an urgent need to develop innovative approaches that target multifactorial underlying causes to potentially prevent or limit disease progression. Accumulating evidence suggests that neuroinflammatory responses may play a pivotal role in the neurodegenerative processes that occur during the development of PD. Cortistatin is a neuropeptide that has shown potent anti-inflammatory and immunoregulatory effects in preclinical models of autoimmune and neuroinflammatory disorders. The goal of this study was to explore the therapeutic potential of cortistatin in a well-established preclinical mouse model of PD induced by acute exposure to the neurotoxin 1-methil-4-phenyl1-1,2,3,6-tetrahydropyridine (MPTP). We observed that treatment with cortistatin mitigated the MPTP-induced loss of dopaminergic neurons in the substantia nigra and their connections to the striatum. Consequently, cortistatin administration improved the locomotor activity of animals intoxicated with MPTP. In addition, cortistatin diminished the presence and activation of glial cells in the affected brain regions of MPTP-treated mice, reduced the production of immune mediators, and promoted the expression of neurotrophic factors in the striatum. In an in vitro model of PD, treatment with cortistatin also demonstrated a reduction in the cell death of dopaminergic neurons that were exposed to the neurotoxin. Taken together, these findings suggest that cortistatin could emerge as a promising new therapeutic agent that combines anti-inflammatory and neuroprotective properties to regulate the progression of PD at multiple levels.

Ferroptosis in Parkinson's disease: Molecular mechanisms and therapeutic potential

Parkinson's Disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN), leading to motor and non-motor symptoms. While the exact mechanisms remain complex and multifaceted, several molecular pathways have been implicated in PD pathology, including accumulation of misfolded proteins, impaired mitochondrial function, oxidative stress, inflammation, elevated iron levels, etc. Overall, PD's molecular mechanisms involve a complex interplay between genetic, environmental, and cellular factors that disrupt cellular homeostasis, and ultimately lead to the degeneration of dopaminergic neurons. Recently, emerging evidence highlights ferroptosis, an iron-dependent non-apoptotic cell death process, as a pivotal player in the advancement of PD. Notably, oligomeric α-synuclein (α-syn) generates reactive oxygen species (ROS) and lipid peroxides within cellular membranes, potentially triggering ferroptosis. The loss of dopamine, a hallmark of PD, could predispose neurons to ferroptotic vulnerability. This unique form of cell demise unveils fresh insights into PD pathogenesis, necessitating an exploration of the molecular intricacies connecting ferroptosis and PD progression. In this review, the molecular and regulatory mechanisms of ferroptosis and their connection with the pathological processes of PD have been systematically summarized. Furthermore, the features of ferroptosis in PD animal models and clinical trials targeting ferroptosis as a therapeutic approach in PD patients' management are scrutinized.

Dietary intake of α-ketoglutarate ameliorates α-synuclein pathology in mouse models of Parkinson's disease

Parkinson's disease (PD) is a progressive movement disorder characterized by dopaminergic (DA) neuron degeneration and the existence of Lewy bodies formed by misfolded α-synuclein. Emerging evidence supports the benefits of dietary interventions in PD due to their safety and practicality. Previously, dietary intake of α-ketoglutarate (AKG) was proved to extend the lifespan of various species and protect mice from frailty. However, the mechanism of dietary AKG's effects in PD remains undetermined. In the present study, we report that an AKG-based diet significantly ameliorated α-synuclein pathology, and rescued DA neuron degeneration and impaired DA synapses in adeno-associated virus (AAV)-loaded human α-synuclein mice and transgenic A53T α-synuclein (A53T α-Syn) mice. Moreover, AKG diet increased nigral docosahexaenoic acid (DHA) levels and DHA supplementation reproduced the anti-α-synuclein effects in the PD mouse model. Our study reveals that AKG and DHA induced microglia to phagocytose and degrade α-synuclein via promoting C1q and suppressed pro-inflammatory reactions. Furthermore, results indicate that modulating gut polyunsaturated fatty acid metabolism and microbiota Lachnospiraceae_NK4A136_group in the gut-brain axis may underlie AKG's benefits in treating α-synucleinopathy in mice. Together, our findings propose that dietary intake of AKG is a feasible and promising therapeutic approach for PD.