Emerging Roles of Complement Protein C1q in Neurodegeneration

Xixin Decoction May Treat Vascular Dementia by Modulating the NPTX2/C1q/C3 Complement Pathway

Vascular dementia (VaD) is a type of dementia that results from brain injury caused by cerebrovascular disease or vascular risk factors. Accumulating evidence from clinical studies has found that Xixin decoction can effectively improve the cognitive function of patients with VaD and improve their daily living ability. However, the pathogenesis of VaD is not fully understood, and the therapeutic mechanism of Xixin decoction is also unclear. The Morris water maze, new object recognition, transmission electron microscopy observation, Golgi staining, Nissl staining, Western blotting, and quantitative real-time polymerase chain reaction were employed to explore the therapeutic mechanism of Xixin decoction. The results showed decreased learning and cognitive abilities, hippocampal neuron damage, decreased NPTX2 protein expression, and increased expression of inflammatory factors such as C1q and C3 in the model group compared with the control group. Furthermore, compared with the model group, the above symptoms were improved after administration of Xixin decoction, and the activity of the NPTX2/C1q/C3 complement pathway was altered. In conclusion, these results suggested that Xixin decoction might treat VaD by modulating the NPTX2/C1q/C3 complement pathway.

Astrocytic Hevin/SPARCL-1 Regulates Cognitive Decline in Pathological and Normal Brain Aging

Dementia, characterized by loss of cognitive abilities in the elderly, poses a significant global health challenge. This study explores the role of astrocytes, one of most representative glial cells in the brain, in mitigating cognitive decline. Specifically, we investigated the impact of Hevin (also known as SPARC-like1/SPARCL-1), a secreted glycoprotein, on cognitive decline in both normal and pathological brain aging. By using adeno-associated viruses, we overexpressed Hevin in hippocampal astrocytes of middle-aged APP/PSEN mice, an established Alzheimer's disease (AD) model. Results demonstrated that Hevin overexpression attenuates cognitive decline, as evidenced by cognitive tests, increased pre- and postsynaptic markers colocalization, and altered expression of synaptic mediators, as revealed by proteomic profiling. Importantly, Hevin overexpression did not influence the deposition of Aβ plaques in the hippocampus, a hallmark of AD pathology. Furthermore, the study extended its findings to middle-aged wild-type animals, revealing improved cognitive performance following astrocytic Hevin overexpression. In conclusion, our results propose astrocytic Hevin as a potential therapeutic target for age-associated cognitive decline.

SIRT1-based therapy targets a gene program involved in mitochondrial turnover in a model of retinal neurodegeneration

Neurodegenerative diseases of the eye such as optic neuritis (ON) are hallmarked by retinal ganglion cell (RGC) loss and optic nerve degeneration leading to irreversible blindness. Therapeutic interventions enhancing expression or activity of SIRT1, an NAD+-dependent deacetylase, support, at least in part, survival of RGCs in the face of injury. Herein, we used mice with experimental autoimmune encephalomyelitis (EAE) which recapitulates axonal and neuronal damages characteristic of ON to identify gene regulatory networks affected by constitutive ubiquitous Sirt1 expression in SIRT1 knock-in mice and wild-type mice upon targeted adeno-associated virus (AAV)-mediated SIRT1 expression in RGCs. RNA seq data analysis showed that the most upregulated genes in EAE mouse retinas include those involved in inflammation, immune response, apoptosis, and mitochondrial turnover. The latter includes genes regulating mitophagy (e.g., Atg4), mitochondrial transport (e.g., Ipo- 6, Xpo- 6), and mitochondrial localization (e.g., Chrna4, Scn9a). The constitutive or RGC-targeted SIRT1 overexpression in EAE mice upregulated the expression of non-mitochondrial genes such as Ecel1 and downregulated the expression of mitophagy genes (e.g., Atg2b, Arifip1) which were upregulated by EAE alone. Thus, SIRT1 induces neuroprotection by, at least in part, balancing mitochondrial biogenesis and mitophagy and/or enhancing mitochondrial self-repair to preserve the bioenergetic capacity of RGCs.

Olfactory bulb microglia activation mediates neuronal pyroptosis in ozone-exposed mice with olfactory and cognitive dysfunction

In recent years, there has been a notable increase in the concentration of air pollutants in the troposphere, especially ozone. However, limited research has gone beyond examining histopathological alterations in the olfactory bulb (OB) to explore the effects of ozone exposure on olfactory and cognitive functions. In our study, we exposed nine-month-old C57BL/6 mice to ozone at a concentration of 1.0 ppm for 13 weeks to examine the effects of ozone on the OB. The results indicated that ozone exposure induces olfactory and cognitive impairments in the mice. Subsequently, microglia in the OB are activated, leading to neuroinflammation. Ozone-induced downregulation of PSD95 and Synaptophysin, which was accompanied by a decrease in dendritic length and spine density. Simultaneously, increasing in the co-labeling of C1q, Iba1, and PSD95 after ozone exposure indicated that C1q-mediated synaptic phagocytosis by microglia might play a role in synaptic damage. Furthermore, the co-labeling of GSDMD-N and NEUN results suggests that ozone exposure triggers pyroptosis in neurons. Additionally, minocycline administration can alleviate ozone-induced olfactory and cognitive impairments by suppressing microglial activation. This study illustrates that prolonged ozone exposure leads to microglial activation in the OB, causing synaptic damage, neuronal pyroptosis, and subsequent deficits in olfactory and cognitive functions.

Exploring immunotherapeutic strategies for neurodegenerative diseases: a focus on Huntington's disease and Prion diseases

Immunotherapy has emerged as a promising therapeutic approach for the treatment of neurodegenerative disorders, which are characterized by the progressive loss of neurons and impaired cognitive functions. In this review, active and passive immunotherapeutic strategies that help address the underlying pathophysiology of Huntington's disease (HD) and prion diseases by modulating the immune system are discussed. The current landscape of immunotherapeutic strategies, including monoclonal antibodies and vaccine-based approaches, to treat these diseases is highlighted, along with their potential benefits and mechanisms of action. Immunotherapy generally works by targeting disease-specific proteins, which serve as the pathological hallmarks of these diseases. Additionally, the review addresses the challenges and limitations associated with immunotherapy. For HD, immunotherapeutic approaches focus on neutralizing the toxic effects of mutant huntingtin and tau proteins, thereby reducing neurotoxicity. Immunotherapeutic approaches targeting flanking sequences, rather than the polyglutamine tract in the mutant huntingtin protein, have yielded promising outcomes for patients with HD. In prion diseases, therapies attempt to prevent or eliminate misfolded proteins that cause neurodegeneration. The major challenge in prion diseases is immune tolerance. Approaches to overcome the highly tolerogenic nature of the prion protein have been discussed. A common hurdle in delivering antibodies is the blood‒brain barrier, and strategies that can breach this barrier are being investigated. As protein aggregation and neurotoxicity are related, immunotherapeutic strategies being developed for other neurodegenerative diseases could be repurposed to target protein aggregation in HD and prion diseases. While significant advances in this field have been achieved, continued research and development are necessary to overcome the existing limitations, which will help in shaping the future of immunotherapy as a strategy for managing neurological disorders.

A Pilot Proteomic Analysis of Huntington's Disease by Functional Capacity

Background: The molecular biology of Huntington's Disease (HD) has grown substantially, with pathological considerations extending to genetic modifiers, epigenetic changes, transcriptomics, the proteome, and the metabolome. The metabolome and proteome are especially intriguing in that they most directly reflect the functional state of the cellular environment, which may involve some combination of pathology as well as compensation. Methods: We assessed CSF proteomics from eight participants by their functional severity (TFC range 3-13), with 47 proteins having a minimum r-value of 0.7 and nominal p-values < 0.05. Results: Our exploratory data reveal correlations between progression and several processes including inflammation, ECM homeostasis and NAD+ metabolism. Conclusions: Consistently identified targets that correlate with phenotype or progression may have value, if validated, as enrichment tools in clinical trials and potentially as markers of therapeutic response.

The interaction of tPA with NMDAR1 drives neuroinflammation and neurodegeneration in α-synuclein-mediated neurotoxicity

The thrombolytic protease tissue plasminogen activator (tPA) is expressed in the CNS, where it regulates diverse functions including neuronal plasticity, neuroinflammation, and blood-brain-barrier integrity. However, its role in different brain regions such as the substantia nigra (SN) is largely unexplored. In this study, we characterize tPA expression, activity, and localization in the SN using a combination of retrograde tracing and β-galactosidase tPA reporter mice. We further investigate tPA's potential role in SN pathology in an α-synuclein mouse model of Parkinson's disease (PD). To characterize the mechanism of tPA action in α-synuclein-mediated pathology in the SN and to identify possible therapeutic pathways, we performed RNA-seq analysis of the SN and used multiple transgenic mouse models. These included tPA deficient mice and two newly developed transgenic mice, a knock-in model expressing endogenous levels of proteolytically inactive tPA (tPA Ala-KI) and a second model overexpressing proteolytically inactive tPA (tPA Ala-BAC). Our findings show that striatal GABAergic neurons send tPA+ projections to dopaminergic (DA)-neurons in the SN and that tPA is released from SN-derived synaptosomes upon stimulation. We also found that tPA levels in the SN increased following α-synuclein overexpression. Importantly, tPA deficiency protects DA-neurons from degeneration, prevents behavioral deficits, and reduces microglia activation and T-cell infiltration induced by α-synuclein overexpression. RNA-seq analysis indicates that tPA in the SN is required for the upregulation of genes involved in the innate and adaptive immune responses induced by α-synuclein overexpression. Overexpression of α-synuclein in tPA Ala-KI mice, expressing only proteolytically inactive tPA, confirms that tPA-mediated neuroinflammation and neurodegeneration is independent of its proteolytic activity. Moreover, overexpression of proteolytically inactive tPA in tPA Ala-BAC mice leads to increased neuroinflammation and neurodegeneration compared to mice expressing normal levels of tPA, suggesting a tPA dose response. Finally, treatment of mice with glunomab, a neutralizing antibody that selectively blocks tPA binding to the N-methyl-D-aspartate receptor-1 (NMDAR1) without affecting NMDAR1 ion channel function, identifies the tPA interaction with NMDAR1 as necessary for tPA-mediated neuroinflammation and neurodegeneration in response to α-synuclein-mediated neurotoxicity. Thus, our data identifies a novel pathway that promotes DA-neuron degeneration and suggests a potential therapeutic intervention for PD targeting the tPA-NMDAR1 interaction.

Single-cell sequencing in diffuse large B-cell lymphoma: C1qC is a potential tumor-promoting factor

BACKGROUND

Complement component 1q (C1q) is central to the classical complement pathway. High C1q expression has been linked to poor prognosis in patients with cancer. However, the precise mechanism via which C1q contributes to diffuse large B-cell lymphoma (DLBCL) is still unknown. We aimed to explore the potential mechanism by which C1qC promoting DLBCL.

METHODS

Using multiplex immunohistochemistry (mIHC) to identify immunocyte subgroups associated with prognosis in DLBCL tissues. Constructing a risk prediction model based on immunocytes using least absolute shrinkage and selection operator (LASSO) regression. Single-cell sequencing detects the expression level of C1qC in immunocytes in the DLBCL microenvironment. Using Wb and qPCR to detect markers of M2 macrophages after knocking down C1qC, and exploring the interactions between lymphoma cells and macrophages through co-culture. Analyzing clinical data from DLBCL patients to investigate the clinical significance of C1qC+ M2 macrophages. Lastly, using bioinformatics in conjunction with mIHC to elucidate the potential pro-tumor mechanism of C1qC.

RESULTS

First, we found T cell subtypes, neutrophils, and M2 macrophages are associated with prognosis. Subsequently, the risk model identified C1qC as a differential gene relevant to DLBCL prognosis. Furthermore, single-cell sequencing suggested high C1qC expression in M2 macrophages. The expression level of CD163 is significantly lower following siC1qC. Co-culture experiments have shown that M2 macrophages can promote the proliferation of tumor cells and reduce their drug sensitivity. Furthermore, as an independent predictive indicator, high expression of C1qC+ M2 macrophages is associated with poor prognosis in patients. Finally, a positive correlation between increased C1qC expression and immune checkpoints, as well as an increase in the infiltration of regulatory T cells (Tregs) and M2 macrophages.

CONCLUSIONS

C1qC offering new insights into pathogenesis and presenting a potential therapeutic target in DLBCL.

Revolutionizing Neuroimmunology: Unraveling Immune Dynamics and Therapeutic Innovations in CNS Disorders

Neuroimmunology is reshaping the understanding of the central nervous system (CNS), revealing it as an active immune organ rather than an isolated structure. This review delves into the unprecedented discoveries transforming the field, including the emerging roles of microglia, astrocytes, and the blood-brain barrier (BBB) in orchestrating neuroimmune dynamics. Highlighting their dual roles in both repair and disease progression, we uncover how these elements contribute to the intricate pathophysiology of neurodegenerative diseases, cerebrovascular conditions, and CNS tumors. Novel insights into microglial priming, astrocytic cytokine networks, and meningeal lymphatics challenge the conventional paradigms of immune privilege, offering fresh perspectives on disease mechanisms. This work introduces groundbreaking therapeutic innovations, from precision immunotherapies to the controlled modulation of the BBB using nanotechnology and focused ultrasound. Moreover, we explore the fusion of immune modulation with neuromodulatory technologies, underscoring new frontiers for personalized medicine in previously intractable diseases. By synthesizing these advancements, we propose a transformative framework that integrates cutting-edge research with clinical translation, charting a bold path toward redefining CNS disease management in the era of precision neuroimmunology.

Nuclear alpha-synuclein accelerates cell senescence and neurodegeneration

BACKGROUND

The progression of Parkinson's disease (PD) is related to ageing. The accumulation of nuclear alpha-synuclein (α-syn) may accelerate the occurrence of neurodegenerative diseases, but its role in PD remains poorly understood.

METHODS

In the present study, α-syn expression was specifically targeted to the nucleus by constructing an adeno-associated virus (AAV) vector in which a nuclear localization sequence (NLS) was added to the α-syn coding sequence. Virus-mediated gene transfer, behavioural tests, RNA-Seq, immunohistochemistry, western blotting, and quantitative real-time PCR were then performed.

RESULTS

In vivo experiments using a mouse model showed that nuclear α-syn increased the severity of the PD-like phenotype, including the loss of dopaminergic neurons concomitant with motor impairment and the formation of α-syn inclusions. These nuclear inclusions contained α-syn species of high molecular weights and induced strong transcriptional dysregulation, especially induced high expression of p21 and senescence-associated secretory phenotype (SASP)-related genes. In addition, the transcriptional alterations induced by nuclear α-syn were associated with gliosis, inflammation, oxidative and DNA damage, and lysosomal dysfunction, and they eventually accelerated neuronal loss and neurodegeneration.

CONCLUSIONS

Our results suggest that nuclear α-syn plays a crucial role in PD pathogenesis.

Amyotrophic lateral sclerosis: exploring pathophysiology in the context of treatment

Amyotrophic lateral sclerosis (ALS) is a complex, neurodegenerative disorder in which alterations in structural, physiological, and metabolic parameters act synergistically. Over the last decade there has been a considerable focus on developing drugs to slow the progression of the disease. Despite this, only four disease-modifying therapies are approved in North America. Although additional research is required for a thorough understanding of ALS, we have accumulated a large amount of knowledge that could be better integrated into future clinical trials to accelerate drug development and provide patients with improved treatment options. It is likely that future, successful ALS treatments will take a multi-pronged therapeutic approach, targeting different pathways, akin to personalized medicine in oncology. In this review, we discuss the link between ALS pathophysiology and treatments, looking at the therapeutic failures as learning opportunities that can help us refine and optimize drug development.

Brain-derived neurotrophic factor from microglia regulates neuronal development in the medial prefrontal cortex and its associated social behavior

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45-p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.

Low pulse pressure and high serum complement C1q are risk factors for hemodialysis headache: A case-control study

BACKGROUND AND OBJECTIVE

Hemodialysis headache (HDH) is a common complication of dialysis that negatively affects the patient's quality of life. The etiology and triggering factors of HDH are not fully understood. This study aims to assess the prevalence and characteristics of HDH among patients undergoing hemodialysis across multiple centers in China. Furthermore, we conducted a case-control study at one hospital to identify risk factors associated with HDH.

METHODS

The study consisted of two phases including a cross-sectional observational study and a case-control study. Participants underwent neurological examinations and interviews. Demographic and medical information were collected from both medical records and patient files. Serum creatinine, uric acid, urea, estimated glomerular filtration rate (eGFR), plasma osmolarity, glucose, C1q, and a variety of electrolytes including potassium, sodium, chloride, calcium, magnesium, and phosphorus were measured before and after dialysis. Blood pressure variables including systolic blood pressure, diastolic blood pressure, pulse pressure (PP), and heart rate were monitored hourly. Serum levels of inflammatory factors, including tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-4, IL-6, and IL-10 were quantified using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

The prevalence of HDH was 37.7% (183/485). HDH was characterized by a bilateral tightening headache of moderate intensity and duration of <2 h, occurring in different locations. The case-control study included 50 patients with HDH and 84 control patients, pre-dialysis PP was found to be lower in the HDH group than in the control group (mean ± standard deviation 51.5 ± 18.2 vs. 67.9 ± 14.9, p = 0.027). Furthermore, the pre-dialysis serum complement C1q level was significantly higher for the HDH group than the control group (median and interquartile range 201.5 [179.0-231.5] vs. 189.0 [168.9-209.0], p = 0.021). Pre-dialysis PP was associated with 5.1% decreased odds of HDH (odds ratio [OR] = 0.96; 95% confidence interval [CI], 0.93-0.99, p = 0.026), body weight was associated with a 5.4% decreased risk of HDH (OR = 0.95; 95% CI, 0.91-0.99, p = 0.013), and pre-dialysis C1q levels increased the odds of HDH by 1.9% (OR = 1.02; 95% CI, 1.01-1.03, p = 0.005).

CONCLUSION

Low PP, low body weight, and high blood complement C1q may be potential risk factors associated with HDH.

New Insights into Oxidative Stress and Inflammatory Response in Neurodegenerative Diseases

Oxidative stress (OS) and inflammation are two important and well-studied pathological hallmarks of neurodegenerative diseases (NDDs). Due to elevated oxygen consumption, the high presence of easily oxidizable polyunsaturated fatty acids and the weak antioxidant defenses, the brain is particularly vulnerable to oxidative injury. Uncertainty exists over whether these deficits contribute to the development of NDDs or are solely a consequence of neuronal degeneration. Furthermore, these two pathological hallmarks are linked, and it is known that OS can affect the inflammatory response. In this review, we will overview the last findings about these two pathways in the principal NDDs. Moreover, we will focus more in depth on amyotrophic lateral sclerosis (ALS) to understand how anti-inflammatory and antioxidants drugs have been used for the treatment of this still incurable motor neuron (MN) disease. Finally, we will analyze the principal past and actual clinical trials and the future perspectives in the study of these two pathological mechanisms.

Integrative human and murine multi-omics: Highlighting shared biomarkers in the neuronal ceroid lipofuscinoses

Neuronal ceroid lipofuscinosis (NCL) is a group of neurodegenerative disorders whose molecular mechanisms remain largely unknown. Omics approaches are among the methods that generate new information on modifying factors and molecular signatures. Moreover, omics data integration can address the need to progressively expand knowledge around the disease and pinpoint specific proteins to promote as candidate biomarkers. In this work, we integrated a total of 62 proteomic and transcriptomic datasets originating from humans and mice, employing a new approach able to define dysregulated processes across species, stages and NCL forms. Moreover, we selected a pool of differentially expressed proteins and genes as species- and form-related biomarkers of disease status/progression and evaluated local and spatial differences in most affected brain regions. Our results offer promising targets for potential new therapeutic strategies and reinforce the hypothesis of a connection between NCLs and other forms of dementia, particularly Alzheimer's disease.

Complement C1q essential for aeroallergen sensitization via CSF1R+ conventional dendritic cells type 2

BACKGROUND

Dendritic cells (DCs) are heterogeneous, comprising multiple subsets with unique functional specifications. Our previous work has demonstrated that the specific conventional type 2 DC subset, CSF1R+cDC2s, plays a critical role in sensing aeroallergens.

OBJECTIVE

It remains to be understood how CSF1R+cDC2s recognize inhaled allergens. We sought to elucidate the transcriptomic programs and receptor-ligand interactions essential for function of this subset in allergen sensitization.

METHODS

We applied single-cell RNA sequencing to mouse lung DCs. Conventional DC-selective knockout mouse models were employed, and mice were subjected to inhaled allergen sensitization with multiple readouts of asthma pathology. Under the clinical arm of this work, human lung transcriptomic data were integrated with mouse data, and bronchoalveolar lavage (BAL) specimens were collected from subjects undergoing allergen provocation, with samples assayed for C1q.

RESULTS

We found that C1q is selectively enriched in lung CSF1R+cDC2s, but not in other lung cDC2 or cDC1 subsets. Depletion of C1q in conventional DCs significantly attenuates allergen sensing and features of asthma. Additionally, we found that C1q binds directly to human dust mite allergen, and the C1q receptor CD91 (LRP1) is required for lung CSF1R+cDC2s to recognize the C1q-allergen complex and induce allergic lung inflammation. Lastly, C1q is enriched in human BAL samples following subsegmental allergen challenge, and human RNA sequencing data demonstrate close homology between lung IGSF21+DCs and mouse CSF1R+cDC2s.

CONCLUSIONS

C1q is secreted from the CSF1R+cDC2 subset among conventional DCs. Our data indicate that the C1q-LRP1 axis represents a candidate for translational therapeutics in the prevention and suppression of allergic lung inflammation.

Complement C4-deficient mice have a high mortality rate during PTZ-induced epileptic seizures, which correlates with cognitive problems and the deficiency in the expression of Egr1 and other immediate early genes

Complement system plays an important role in the immune defense against pathogens; however, recent studies demonstrated an important role of complement subunits C1q, C4, and C3 in normal functions of the central nervous system (CNS) such as non-functional synapse elimination (synapse pruning), and during various neurologic pathologies. Humans have two forms of C4 protein encoded by C4A and C4B genes that share 99.5% homology, while mice have only one C4B gene that is functionally active in the complement cascade. Overexpression of the human C4A gene was shown to contribute to the development of schizophrenia by mediating extensive synapse pruning through the activation C1q-C4-C3 pathway, while C4B deficiency or low levels of C4B expression were shown to relate to the development of schizophrenia and autism spectrum disorders possibly via other mechanisms not related to synapse elimination. To investigate the potential role of C4B in neuronal functions not related to synapse pruning, we compared wildtype (WT) mice with C3- and C4B- deficient animals for their susceptibility to pentylenetetrazole (PTZ)- induced epileptic seizures. We found that C4B (but not C3)-deficient mice were highly susceptible to convulsant and subconvulsant doses of PTZ when compared to WT controls. Further gene expression analysis revealed that in contrast to WT or C3-deficient animals, C4B-deficient mice failed to upregulate expressions of multiple immediate early genes (IEGs) Egrs1-4, c-Fos, c-Jus, FosB, Npas4, and Nur77 during epileptic seizures. Moreover, C4B-deficient mice had low levels of baseline expression of Egr1 on mRNA and protein levels, which was correlated with the cognitive problems of these animals. C4-deficient animals also failed to upregulate several genes downstream of IEGs such as BDNF and pro-inflammatory cytokines IL-1β, IL-6, and TNF. Taken together, our study demonstrates a new role of C4B in the regulation of expression of IEGs and their downstream targets during CNS insults such as epileptic seizures.

C1q and central nervous system disorders

C1q is a crucial component of the complement system, which is activated through the classical pathway to perform non-specific immune functions, serving as the first line of defense against pathogens. C1q can also bind to specific receptors to carry out immune and other functions, playing a vital role in maintaining immune homeostasis and normal physiological functions. In the developing central nervous system (CNS), C1q functions in synapse formation and pruning, serving as a key player in the development and homeostasis of neuronal networks in the CNS. C1q has a close relationship with microglia and astrocytes, and under their influence, C1q may contribute to the development of CNS disorders. Furthermore, C1q can also have independent effects on neurological disorders, producing either beneficial or detrimental outcomes. Most of the evidence for these functions comes from animal models, with some also from human specimen studies. C1q is now emerging as a promising target for the treatment of a variety of diseases, and clinical trials are already underway for CNS disorders. This article highlights the role of C1q in CNS diseases, offering new directions for the diagnosis and treatment of these conditions.

Bringing synapses into focus: Recent advances in synaptic imaging and mass-spectrometry for studying synaptopathy

Synapses are integral for healthy brain function and are becoming increasingly recognized as key structures in the early stages of brain disease. Understanding the pathological processes driving synaptic dysfunction will unlock new therapeutic opportunities for some of the most devastating diseases of our time. To achieve this we need a solid repertoire of imaging and molecular tools to interrogate synaptic biology at greater resolution. Synapses have historically been examined in small numbers, using highly technical imaging modalities, or in bulk, using crude molecular approaches. However, recent advances in imaging techniques are allowing us to analyze large numbers of synapses, at single-synapse resolution. Furthermore, multiplexing is now achievable with some of these approaches, meaning we can examine multiple proteins at individual synapses in intact tissue. New molecular techniques now allow accurate quantification of proteins from isolated synapses. The development of increasingly sensitive mass-spectrometry equipment means we can now scan the synaptic molecular landscape almost in totality and see how this changes in disease. As we embrace these new technical developments, synapses will be viewed with clearer focus, and the field of synaptopathy will become richer with insightful and high-quality data. Here, we will discuss some of the ways in which synaptic interrogation is being facilitated by methodological advances, focusing on imaging, and mass spectrometry.

Neuronal glutathione loss leads to neurodegeneration involving gasdermin activation

Accumulating evidence suggests that glutathione loss is closely associated with the progression of neurodegenerative disorders. Here, we found that the neuronal conditional-knockout (KO) of glutamyl-cysteine-ligase catalytic-subunit (GCLC), a rate-limiting enzyme for glutathione synthesis, induced brain atrophy accompanied by neuronal loss and neuroinflammation. GCLC-KO mice showed activation of C1q, which triggers engulfment of neurons by microglia, and disease-associated-microglia (DAM), suggesting that activation of microglia is linked to the neuronal loss. Furthermore, gasdermins, which regulate inflammatory form of cell death, were upregulated in the brains of GCLC-KO mice, suggesting the contribution of pyroptosis to neuronal cell death in these animals. In particular, GSDME-deficiency significantly attenuated the hippocampal atrophy and changed levels of DAM markers in GCLC-KO mice. Finally, we found that the expression of GCLC was decreased around amyloid plaques in App^NL-G-F AD model mice. App^NL-G-F mouse also exhibited inflammatory events similar to GCLC-KO mouse. We propose a mechanism by which a vicious cycle of oxidative stress and neuroinflammation enhances neurodegenerative processes. Furthermore, GCLC-KO mouse will serve as a useful tool to investigate the molecular mechanisms underlying neurodegeneration and in the development of new treatment strategies to address neurodegenerative diseases.

Multi-omics analysis of magnetically levitated plasma biomolecules

We recently discovered that superparamagnetic iron oxide nanoparticles (SPIONs) can levitate plasma biomolecules in the magnetic levitation (MagLev) system and cause formation of ellipsoidal biomolecular bands. To better understand the composition of the levitated biomolecules in various bands, we comprehensively characterized them by multi-omics analyses. To probe whether the biomolecular composition of the levitated ellipsoidal bands correlates with the health of plasma donors, we used plasma from individuals who had various types of multiple sclerosis (MS), as a model disease with significant clinical importance. Our findings reveal that, while the composition of proteins does not show much variability, there are significant differences in the lipidome and metabolome profiles of each magnetically levitated ellipsoidal band. By comparing the lipidome and metabolome compositions of various plasma samples, we found that the levitated biomolecular ellipsoidal bands do contain information on the health status of the plasma donors. More specifically, we demonstrate that there are particular lipids and metabolites in various layers of each specific plasma pattern that significantly contribute to the discrimination of different MS subtypes, i.e., relapsing-remitting MS (RRMS), secondary-progressive MS (SPMS), and primary-progressive MS (PPMS). These findings will pave the way for utilization of MagLev of biomolecules in biomarker discovery for identification of diseases and discrimination of their subtypes.

Immune response in retinal degenerative diseases - Time to rethink?

Retinal degeneration comprises a group of diseases whereby either the retinal neurons or the neurovascular unit degenerates leading to the loss of visual function. Although the initial cause varies in different conditions, inflammation is known to play an important role in disease pathogenesis. Recent advances in molecular and cell biology and systems biology have yielded unexpected findings, including the heterogeneity of immune cells in the degenerative retina, bidirectional neuron-microglia cross talk, and links to the gut microbiome. Here we discuss the immune response in retinal degenerative conditions, taking into account both regional (retinal) and systemic factors. We propose to classify retinal degeneration into dry and wet forms based on whether the blood-retinal barrier (BRB) is breached and fluid is accumulated in retinal parenchyma. The dry form has a relatively intact BRB and is characterised by progressive retinal thinning. Immune response to degenerative insults is dominated by the retinal defence system, which remains to be regulated by neurons. In contrast, the wet form has retinal oedema due to BRB damaged. Inflammation is executed by infiltrating immune cells as well as the retinal defence system. The gut microbiome will have easy access to the retina in wet retinal degeneration and may affect significantly retinal immune response.

Microglia deficiency accelerates prion disease but does not enhance prion accumulation in the brain

Prion diseases are transmissible, neurodegenerative disorders associated with misfolding of the prion protein. Previous studies show that reduction of microglia accelerates central nervous system (CNS) prion disease and increases the accumulation of prions in the brain, suggesting that microglia provide neuroprotection by phagocytosing and destroying prions. In Csf1r^ΔFIRE mice, the deletion of an enhancer within Csf1r specifically blocks microglia development, however, their brains develop normally and show none of the deficits reported in other microglia-deficient models. Csf1r^ΔFIRE mice were used as a refined model in which to study the impact of microglia-deficiency on CNS prion disease. Although Csf1r^ΔFIRE mice succumbed to CNS prion disease much earlier than wild-type mice, the accumulation of prions in their brains was reduced. Instead, astrocytes displayed earlier, non-polarized reactive activation with enhanced phagocytosis of neuronal contents and unfolded protein responses. Our data suggest that rather than simply phagocytosing and destroying prions, the microglia instead provide host-protection during CNS prion disease and restrict the harmful activities of reactive astrocytes.

Association Between the C4 Binding Protein Level and White Matter Integrity in Major Depressive Disorder

OBJECTIVE

Considerable evidence suggests that neuroinflammation plays an important role in the pathophysiology of major depressive disorder (MDD). However, the relationship between serum C4 binding protein (C4BP) and white matter (WM) tract integrity in MDD has not been investigated.

METHODS

We obtained diffusion tensor images of 44 patients with MDD and 44 healthy controls and performed TRActs Constrained by UnderLying Anatomy (TRACULA) analysis to assess WM tract integrity. Serum C4-binding protein alpha chain (C4BPA) and C4- binding protein beta chain (C4BPB) levels were measured and in-between group comparisons were obtained. The correlation between serum C4BP levels and WM tract integrity was examined.

RESULTS

In comparison to healthy controls, both serum C4BPA and C4BPB were higher in MDD. Also, fractional anisotropy (FA) was increased in the left cingulum-angular bundle (CAB) in MDD, but not healthy controls (HCs). A significant correlation was found between serum C4BP and FA levels in the right cingulum-cingulate gyrus bundle (CCG) in MDD.

CONCLUSION

This study is the first to investigate the correlation between serum C4BP levels and WM tract integrity in MDD. We identified an increase in WM integrity in the left CAB region in MDD. Furthermore, serum C4BP levels were higher in MDD, and this finding correlated with increased WM integrity in the right CCG region.

Behavioral- and blood-based biomarkers for Huntington's disease: Studies on the R6/1 mouse model with prospects for early diagnosis and monitoring of the disease

Background

Objective

Methods

Results

Conclusion

•

Gender is one of the factors that determine the rate of progression of Huntington's disease symptoms.

•

A set of non-invasive biomarkers that are useful in the diagnosis and monitoring of Huntington's disease progression.

•

Hormonal profile may be a factor in the efficacy of potential therapy for Huntington's disease.

Complement Receptor 3 Pathway and NMDA Receptor 2B Subunit Involve Neuropathic Pain Associated with Spinal Cord Injury

Background

Neuropathic pain (NP) after spinal cord injury (SCI-evoked NP) is clinically challenging; the underlying mechanisms are not fully understood, leading to a lack of promising treatment options. NP occurs in only a subset of patients with SCI. The injured spinal cord exhibits a series of histopathological changes, and the complement system has been shown to play an important role in these processes. In addition, NMDA receptor subunit 2B (NR2B) is involved in the development and maintenance of NP. This preliminary study was performed to investigate the correlations of the complement receptor 3/complement component 3 (CR3/C3) pathway and NR2B with SCI-evoked NP.

Methods

A trauma-induced SCI animal model was established and SCI-evoked NP was evaluated by behavioural analysis. Transcriptome analysis was performed to identify genes in the CR3/C3 pathway related to synaptic modification, while the expression and distribution of NR2B in the injured spinal cord, and the relation to NP, were examined by immunohistochemical analysis.

Results

Nine of seventeen SCI rats (52.9%) developed NP. C3 mRNA expression was significantly decreased in SCI-evoked NP rats and significantly increased in the non-NP SCI rats. C1q mRNA and CR3 mRNA expression were significantly increased in all SCI rats, but higher levels of expression were observed in the non-NP SCI rats. NR2B mRNA expression was significantly increased in the SCI-evoked NP rats and significantly decreased in the non-NP SCI rats. In addition, significantly elevated expression of NR2B-positive cells was seen in lamina II of the superficial dorsal horn in SCI-evoked NP rats in comparison with non-NP SCI rats.

Conclusion

NP occurred in only a subset of SCI rats, and the CR3/C3 pathway and NR2B were involved in SCI-evoked NP. Further studies are required to determine the mechanisms underlying the SCI-evoked NP associated with the CR3/C3 pathway and NR2B.

Current and Possible Future Therapeutic Options for Huntington's Disease

Huntington's disease (HD) is an autosomal neurodegenerative disease that is characterized by an excessive number of CAG trinucleotide repeats within the huntingtin gene (HTT). HD patients can present with a variety of symptoms including chorea, behavioural and psychiatric abnormalities and cognitive decline. Each patient has a unique combination of symptoms, and although these can be managed using a range of medications and non-drug treatments there is currently no cure for the disease. Current therapies prescribed for HD can be categorized by the symptom they treat. These categories include chorea medication, antipsychotic medication, antidepressants, mood stabilizing medication as well as non-drug therapies. Fortunately, there are also many new HD therapeutics currently undergoing clinical trials that target the disease at its origin; lowering the levels of mutant huntingtin protein (mHTT). Currently, much attention is being directed to antisense oligonucleotide (ASO) therapies, which bind to pre-RNA or mRNA and can alter protein expression via RNA degradation, blocking translation or splice modulation. Other potential therapies in clinical development include RNA interference (RNAi) therapies, RNA targeting small molecule therapies, stem cell therapies, antibody therapies, non-RNA targeting small molecule therapies and neuroinflammation targeted therapies. Potential therapies in pre-clinical development include Zinc-Finger Protein (ZFP) therapies, transcription activator-like effector nuclease (TALEN) therapies and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system (Cas) therapies. This comprehensive review aims to discuss the efficacy of current HD treatments and explore the clinical trial progress of emerging potential HD therapeutics.

Transcriptomic Profiling of Gene Expression Associated with Granulosa Cell Tumor Development in a Mouse Model

Ovarian granulosa cell tumors (GCTs) are rare sex cord-stromal tumors, accounting for ~5% ovarian tumors. The etiology of GCTs remains poorly defined. Genetically engineered mouse models are potentially valuable for understanding the pathogenesis of GCTs. Mice harboring constitutively active TGFβ signaling (TGFBR1-CA) develop ovarian GCTs that phenocopy several hormonal and molecular characteristics of human GCTs. To determine molecular alterations in the ovary upon TGFβ signaling activation, we performed transcriptomic profiling of gene expression associated with GCT development using ovaries from 1-month-old TGFBR1-CA mice and age-matched controls. RNA-sequencing and bioinformatics analysis coupled with the validation of select target genes revealed dysregulations of multiple cellular events and signaling molecules/pathways. The differentially expressed genes are enriched not only for known GCT-related pathways and tumorigenic events but also for signaling events potentially mediated by neuroactive ligand-receptor interaction, relaxin signaling, insulin signaling, and complements in TGFBR1-CA ovaries. Additionally, a comparative analysis of our data in mice with genes dysregulated in human GCTs or granulosa cells overexpressing a mutant FOXL2, the genetic hallmark of adult GCTs, identified some common genes altered in both conditions. In summary, this study has revealed the molecular signature of ovarian GCTs in a mouse model that harbors the constitutive activation of TGFBR1. The findings may be further exploited to understand the pathogenesis of a class of poorly defined ovarian tumors.

Functional and transcriptional profiling of microglial activation during the chronic phase of TBI identifies an age-related driver of poor outcome in old mice

Elderly patients with traumatic brain injury (TBI) have greater mortality and poorer outcomes than younger individuals. The extent to which old age alters long-term recovery and chronic microglial activation after TBI is unknown, and evidence for therapeutic efficacy in aged mice is sorely lacking. The present study sought to identify potential inflammatory mechanisms underlying age-related outcomes late after TBI. Controlled cortical impact was used to induce moderate TBI in young and old male C57BL/6 mice. At 12 weeks post-injury, aged mice exhibited higher mortality, poorer functional outcomes, larger lesion volumes, and increased microglial activation. Transcriptomic analysis identified age- and TBI-specific gene changes consistent with a disease-associated microglial signature in the chronically injured brain, including those involved with complement, phagocytosis, and autophagy pathways. Dysregulation of phagocytic and autophagic function in microglia was accompanied by increased neuroinflammation in old mice. As proof-of-principle that these pathways have functional importance, we administered an autophagic enhancer, trehalose, in drinking water continuously for 8 weeks after TBI. Old mice treated with trehalose showed enhanced functional recovery and reduced microglial activation late after TBI compared to the sucrose control group. Our data indicate that microglia undergo chronic changes in autophagic regulation with both normal aging and TBI that are associated with poorer functional outcome. Enhancing autophagy may therefore be a promising clinical therapeutic strategy for TBI, especially in older patients.

Identification of Key Biomarkers and Pathways for Maintaining Cognitively Normal Brain Aging Based on Integrated Bioinformatics Analysis

Background

Given the arrival of the aging population has caused a series of social and economic problems, we aimed to explore the key genes underlying cognitively normal brain aging and its potential molecular mechanisms.

Methods

GSE11882 was downloaded from Gene Expression Omnibus (GEO). The data from different brain regions were divided into aged and young groups for analysis. Co-expressed differentially expressed genes (DEGs) were screened. Functional analysis, protein–protein interaction (PPI) network, microRNA (miRNA)-gene, and transcription factor (TF)-gene networks were performed to identify hub genes and related molecular mechanisms. AlzData database was used to elucidate the expression of DEGs and hub genes in the aging brain. Animal studies were conducted to validate the hub genes.

Results

Co-expressed DEGs contained 7 upregulated and 87 downregulated genes. The enrichment analysis indicated DEGs were mainly involved in biological processes and pathways related to immune-inflammatory responses. From the PPI network, 10 hub genes were identified: C1QC, C1QA, C1QB, CD163, FCER1G, VSIG4, CD93, CD14, VWF, and CD44. CD44 and CD93 were the most targeted DEGs in the miRNA-gene network, and TIMP1, HLA-DRA, VWF, and FGF2 were the top four targeted DEGs in the TF-gene network. In AlzData database, the levels of CD44, CD93, and CD163 in patients with Alzheimer’s disease (AD) were significantly increased than those in normal controls. Meanwhile, in the brain tissues of cognitively normal mice, the expression of CD44, CD93, and CD163 in the aged group was significantly lower than those in the young group.

Conclusion

The underlying molecular mechanisms for maintaining healthy brain aging are related to the decline of immune-inflammatory responses. CD44, CD93, and CD 163 are considered as potential biomarkers. This study provides more molecular evidence for maintaining cognitively normal brain aging.

Different Complement Activation Pathways Underly Cognitive Impairment and Type 2 Diabetes Mellitus Combined With Cognitive Impairment

Background

The immune response and the complement system are associated with cognitive impairment and diabetes mellitus, respectively. Activation of the complement system in these diseases occurs mainly through either the classical pathway or the alternative pathway. However, the specific complement proteins involved in the development of the type 2 diabetes mellitus (T2DM) and cognitive impairment are still unclear. Here, we investigated complement proteins in serum from patients with T2DM, cognitive impairment, or both T2DM and cognitive impairment.

Objective

To investigate the levels of serum immune complement proteins in patients with T2DM, cognitive impairment, or T2DM combined with cognitive impairment and the associations between these complement proteins and risk factors for T2DM or cognitive impairment.

Methods

Clinical markers were collected from blood samples of 264 participants. Luminex multiplex assays were used to detect serum complement proteins. All statistical analyses were performed using Prism or R studio.

Results

There was a difference in serum levels of the complement proteins C1q, C3, C3b, and FH between the three different groups. Hyperglycemia was significantly correlated with elevated C3b or reduced C3, C1q, and FH. In addition, hyperlipidemia was positively correlated with elevated levels of C3, C4, C1q, and FH proteins. There was an association between C1q, C3, C4, and FH and β-pancreas cell function, whereas only FH was associated with insulin resistance. Higher serum C1q was significantly associated with an increased risk of cognitive impairment.

Conclusion

Serum levels of complement proteins were closely associated with hyperglycemia and hyperlipidemia. We found that classical complement pathway activation mainly occurred in the cognitive impairment only group, whereas the alternative pathway may reflect T2DM and T2DM with cognitive impairment.

Early pregnancy regulates expression of complement components in ovine liver

Complement pathways participate in the regulation of innate immune system, and complement activation is inhibited in normal pregnancy. The liver plays key roles in the modulation of immunity and tolerance, but it is unclear that early pregnancy induces the changes in expression of complement components in the ovine maternal liver. The aim of the present study was to explore the expression of complement components in the liver using quantitative real-time polymerase chain reaction (PCR), Western blot, and immunohistochemistry. Maternal livers were collected on Day 16 of the estrous cycle and Days 13, 16, and 25 of gestation. The results indicated that early pregnancy suppressed the expression of C1q, C1r, C1s, C2, C4a, C5b, and C9 in the maternal liver, but C3 expression was increased. In addition, C3 protein was located in the endothelial cells of the proper hepatic arteries and portal veins and hepatocytes. In summary, the downregulaltion of C1q, C1r, C1s, C2, C4a, C5b, and C9 may be involved in the suppression of complement activation, and upregulation of C3 is related to the modulation of maternal immune tolerance in ovine liver.

Neuroplastic Effect of Exercise Through Astrocytes Activation and Cellular Crosstalk

Physical exercise is an effective therapy for neurorehabilitation. Exercise has been shown to induce remodeling and proliferation of astrocyte. Astrocytes potentially affect the recruitment and function of neurons; they could intensify responses of neurons and bring more neurons for the process of neuroplasticity. Interactions between astrocytes, microglia and neurons modulate neuroplasticity and, subsequently, neural circuit function. These cellular interactions promote the number and function of synapses, neurogenesis, and cerebrovascular remodeling. However, the roles and crosstalk of astrocytes with neurons and microglia and any subsequent neuroplastic effects have not been studied extensively in exercise-induced settings. This article discusses the impact of physical exercise on astrocyte proliferation and highlights the interplay between astrocytes, microglia and neurons. The crosstalk between these cells may enhance neuroplasticity, leading to the neuroplastic effects of exercise.

Complement Component C1q as a Potential Diagnostic Tool for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Subtyping

BACKGROUND

Routine blood analytics are systematically used in the clinic to diagnose disease or confirm individuals' healthy status. For myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a disease relying exclusively on clinical symptoms for its diagnosis, blood analytics only serve to rule out underlying conditions leading to exerting fatigue. However, studies evaluating complete and large blood datasets by combinatorial approaches to evidence ME/CFS condition or detect/identify case subgroups are still scarce.

METHODS

This study used unbiased hierarchical cluster analysis of a large cohort of 250 carefully phenotyped female ME/CFS cases toward exploring this possibility.

RESULTS

The results show three symptom-based clusters, classified as severe, moderate, and mild, presenting significant differences (p < 0.05) in five blood parameters. Unexpectedly the study also revealed high levels of circulating complement factor C1q in 107/250 (43%) of the participants, placing C1q as a key molecule to identify an ME/CFS subtype/subgroup with more apparent pain symptoms.

CONCLUSIONS

The results obtained have important implications for the research of ME/CFS etiology and, most likely, for the implementation of future diagnosis methods and treatments of ME/CFS in the clinic.

Complement factor C1q mediates sleep spindle loss and epileptic spikes after mild brain injury

Although traumatic brain injury (TBI) acutely disrupts the cortex, most TBI-related disabilities reflect secondary injuries that accrue over time. The thalamus is a likely site of secondary damage because of its reciprocal connections with the cortex. Using a mouse model of mild TBI (mTBI), we found a chronic increase in C1q expression specifically in the corticothalamic system. Increased C1q expression colocalized with neuron loss and chronic inflammation and correlated with disruption in sleep spindles and emergence of epileptic activities. Blocking C1q counteracted these outcomes, suggesting that C1q is a disease modifier in mTBI. Single-nucleus RNA sequencing demonstrated that microglia are a source of thalamic C1q. The corticothalamic circuit could thus be a new target for treating TBI-related disabilities.

Bispecific Tau Antibodies with Additional Binding to C1q or Alpha-Synuclein

BACKGROUND

Alzheimer's disease (AD) and other tauopathies are neurodegenerative disorders characterized by cellular accumulation of aggregated tau protein. Tau pathology within these disorders is accompanied by chronic neuroinflammation, such as activation of the classical complement pathway by complement initiation factor C1q. Additionally, about half of the AD cases present with inclusions composed of aggregated alpha-synuclein called Lewy bodies. Lewy bodies in disorders such as Parkinson's disease and Lewy body dementia also frequently occur together with tau pathology.

OBJECTIVE

Immunotherapy is currently the most promising treatment strategy for tauopathies. However, the presence of multiple pathological processes within tauopathies makes it desirable to simultaneously target more than one disease pathway.

METHODS

Herein, we have developed three bispecific antibodies based on published antibody binding region sequences. One bispecific antibody binds to tau plus alpha-synuclein and two bispecific antibodies bind to tau plus C1q.

RESULTS

Affinity of the bispecific antibodies to their targets compared to their monospecific counterparts ranged from nearly identical to one order of magnitude lower. All bispecific antibodies retained binding to aggregated protein in patient-derived brain sections. The bispecific antibodies also retained their ability to inhibit aggregation of recombinant tau, regardless of whether the tau binding sites were in IgG or scFv format. Mono- and bispecific antibodies inhibited cellular seeding induced by AD-derived pathological tau with similar efficacy. Finally, both Tau-C1q bispecific antibodies completely inhibited the classical complement pathway.

CONCLUSION

Bispecific antibodies that bind to multiple pathological targets may therefore present a promising approach to treat tauopathies and other neurodegenerative disorders.

Hippocampal alpha-synuclein mediates depressive-like behaviors

Alpha-synuclein (α-syn) which encoded by SNCA plays a critical role in the neurotransmission, vesicle dynamics, and neuroplasticity. Alteration to SNCA expression is associated with major depressive disorder. However, the pathogenic mechanism of SNCA in depression remains unknown. Herein, we reported that SNCA was up-regulated in the peripheral blood of major depressive disorder (MDD) patients and the depressive mice. Chronic restraint stress (CRS) also up-regulated the SNCA expression in the hippocampus. Moreover, over-expression of SNCA in the hippocampus triggered spontaneous depressive-like behaviors under the non-stressed conditions in mice, and knockout of SNCA could reverse CRS-induced depressive-like behaviors. SNCA led to synapse loss and neuronal cell death in the hippocampus possibly via complement-mediated microglial engulfment and inflammation, and thus contributed to the pathogenesis of depressive disorder. Overall, hippocampal SNCA and complement system are involved in the pathogenesis of depressive disorder and it provides a new perspective for the occurrence of depressive disorder.

Inflammatory and Oxidative Pathways Are New Drug Targets in Multiple Episode Schizophrenia and Leaky Gut, Klebsiella pneumoniae, and C1q Immune Complexes Are Additional Drug Targets in First Episode Schizophrenia

Breakdown of paracellular and vascular pathways and activated neuroimmune and oxidative pathways was established in (deficit) schizophrenia. The aim of this study was to delineate (a) the differences in these pathways between stable-phase, first (FES) and multiple (MES) episode schizophrenia and (b) the pathways that determine the behavioral-cognitive-physical-psychosocial (BCPS) deterioration in FES/MES. This study included 21 FES and 58 FES patients and 40 healthy controls and measured indicants of serum C1q circulating immune complexes (CIC), leaky gut, immune activation, and oxidative stress toxicity (OSTOX). We constructed a BCPS-worsening index by extracting a latent vector from symptomatic, neurocognitive, and quality of life data. FES was associated with higher IgA CIC-C1q, IgA directed to cadherin, catenin, and plasmalemma vesicle-associated protein, and IgA/IgM to Gram-negative bacteria as compared with FES and controls. In FES patients, the BCPS-worsening score was predicted (48.7%) by IgA to Klebsiella pneumoniae and lowered paraoxonase 1 activity. In MES patients, the BCPS-worsening score was explained (42.7%) by increased tumor necrosis factor-α, OSTOX, and number of episodes. In schizophrenia, 34.0% of the variance in the BCPS-worsening score was explained by IgA to K. pneumoniae, OSTOX, and number of episodes. Increased IgA to K. pneumoniae was the single best predictor of residual psychotic symptoms in FES and MES. This study delineated different mechanistic processes in FES, including breakdown of adherens junctions, bacterial translocation, and IgA CIC-C1q formation, and MES, including immune and oxidative neurotoxic pathways. FES and MES comprise different staging subtypes, i.e., FES and MES with and without worsening.

Neuropathophysiological Mechanisms and Treatment Strategies for Post-traumatic Epilepsy

Traumatic brain injury (TBI) is a leading cause of death in young adults and a risk factor for acquired epilepsy. Severe TBI, after a period of time, causes numerous neuropsychiatric and neurodegenerative problems with varying comorbidities; and brain homeostasis may never be restored. As a consequence of disrupted equilibrium, neuropathological changes such as circuit remodeling, reorganization of neural networks, changes in structural and functional plasticity, predisposition to synchronized activity, and post-translational modification of synaptic proteins may begin to dominate the brain. These pathological changes, over the course of time, contribute to conditions like Alzheimer disease, dementia, anxiety disorders, and post-traumatic epilepsy (PTE). PTE is one of the most common, devastating complications of TBI; and of those affected by a severe TBI, more than 50% develop PTE. The etiopathology and mechanisms of PTE are either unknown or poorly understood, which makes treatment challenging. Although anti-epileptic drugs (AEDs) are used as preventive strategies to manage TBI, control acute seizures and prevent development of PTE, their efficacy in PTE remains controversial. In this review, we discuss novel mechanisms and risk factors underlying PTE. We also discuss dysfunctions of neurovascular unit, cell-specific neuroinflammatory mediators and immune response factors that are vital for epileptogenesis after TBI. Finally, we describe current and novel treatments and management strategies for preventing PTE.

Neuroimmune crosstalk and evolving pharmacotherapies in neurodegenerative diseases

Neurodegeneration is characterized by gradual onset and limited availability of specific biomarkers. Apart from various aetiologies such as infection, trauma, genetic mutation, the interaction between the immune system and CNS is widely associated with neuronal damage in neurodegenerative diseases. The immune system plays a distinct role in disease progression and cellular homeostasis. It induces cellular and humoral responses, and enables tissue repair, cellular healing and clearance of cellular detritus. Aberrant and chronic activation of the immune system can damage healthy neurons. The pro-inflammatory mediators secreted by chief innate immune components, the complement system, microglia and inflammasome can augment cytotoxicity. Furthermore, these inflammatory mediators accelerate microglial activation resulting in progressive neuronal loss. Various animal studies have been carried out to unravel the complex pathology and ascertain biomarkers for these harmful diseases, but have had limited success. The present review will provide a thorough understanding of microglial activation, complement system and inflammasome generation, which lead the healthy brain towards neurodegeneration. In addition to this, possible targets of immune components to confer a strategic treatment regime for the alleviation of neuronal damage are also summarized.

The Neuromelanin Paradox and Its Dual Role in Oxidative Stress and Neurodegeneration

Aging is associated with an increasing dysfunction of key brain homeostasis mechanisms and represents the main risk factor across most neurodegenerative disorders. However, the degree of dysregulation and the affectation of specific pathways set apart normal aging from neurodegenerative disorders. In particular, the neuronal metabolism of catecholaminergic neurotransmitters appears to be a specifically sensitive pathway that is affected in different neurodegenerations. In humans, catecholaminergic neurons are characterized by an age-related accumulation of neuromelanin (NM), rendering the soma of the neurons black. This intracellular NM appears to serve as a very efficient quencher for toxic molecules. However, when a neuron degenerates, NM is released together with its load (many undegraded cellular components, transition metals, lipids, xenobiotics) contributing to initiate and worsen an eventual immune response, exacerbating the oxidative stress, ultimately leading to the neurodegenerative process. This review focuses on the analysis of the role of NM in normal aging and neurodegeneration related to its capabilities as an antioxidant and scavenging of harmful molecules, versus its involvement in oxidative stress and aberrant immune response, depending on NM saturation state and its extracellular release.

Integrated Analysis of a Competing Endogenous RNA Network Reveals a Prognostic Signature in Kidney Renal Papillary Cell Carcinoma

The kidney renal papillary cell carcinoma (KIRP) is a relatively rare type of renal cell carcinoma (RCC). Currently, most kidney cancer studies primarily focus on RCC, and there has been no investigation to find a robust signature to predict the survival outcome of KIRP patients. In this study, we constructed a competing endogenous RNA (ceRNA) network, including 1,251 lncRNA-miRNA-mRNA interactions. Eight differentially expressed genes (IGF2BP3, PLK1, LINC00200, NCAPG, CENPF, miR-217, GAS6-As1, and LRRC4) based on the TCGA database were selected. The prognostic signature was established by combining the univariate Cox regression method and a stepwise regression method, with its predictive value validated by time-dependent receiver operating characteristic (ROC) curves. In conclusion, we identified eight prognostic signatures with using ceRNA networks. Our study provided a global view and a systematic dissection on KIRP prognosis biomarkers, and the eight identified genes might be used as new and important prognostic factors involved in KIRP pathogenesis.

Transcriptomic characterization of microglia activation in a rat model of ischemic stroke

Microglia are key regulators of inflammatory response after stroke and brain injury. To better understand activation of microglia as well as their phenotypic diversity after ischemic stroke, we profiled the transcriptome of microglia after 75 min transient focal cerebral ischemia in 3-month- and 12-month-old male spontaneously hypertensive rats. Microglia were isolated from the brains by FACS sorting on days 3 and 14 after cerebral ischemia. GeneChip Rat 1.0ST microarray was used to profile the whole transcriptome of sorted microglia. We identified an evolving and complex pattern of activation from 3 to 14 days after stroke onset. M2-like patterns were extensively and persistently upregulated over time. M1-like patterns were only mildly upregulated, mostly at day 14. Younger 3-month-old brains showed a larger microglial response in both pro- and anti-inflammatory pathways, compared to older 12-month-old brains. Importantly, our data revealed that after stroke, most microglia are activated towards a wide spectrum of novel polarization states beyond the standard M1/M2 dichotomy, especially in pathways related to TLR2 and dietary fatty acid signaling. Finally, classes of transcription factors that might potentially regulate microglial activation were identified. These findings should provide a comprehensive database for dissecting microglial mechanisms and pursuing neuroinflammation targets for acute ischemic stroke.

Complement's favourite organelle-Mitochondria?

The complement system, well known for its central role in innate immunity, is currently emerging as an unexpected, cell‐autonomous, orchestrator of normal cell physiology. Specifically, an intracellularly active complement system—the complosome—controls key pathways of normal cell metabolism during immune cell homeostasis and effector function. So far, we know little about the exact structure and localization of intracellular complement components within and among cells. A common scheme, however, is that they operate in crosstalk with other intracellular immune sensors, such as inflammasomes, and that they impact on the activity of key subcellular compartments. Among cell compartments, mitochondria appear to have built a particularly early and strong relationship with the complosome and extracellularly active complement—not surprising in view of the strong impact of the complosome on metabolism. In this review, we will hence summarize the current knowledge about the close complosome–mitochondria relationship and also discuss key questions surrounding this novel research area.

The many roles of C1q

The ability of a well-known component of the complement cascade to bind to a variety of receptors has implications for signaling biology, spinal cord injury and, possibly, the evolution of the complement system.

Immuno-hematologic parameters following rodent spinal cord contusion are negatively influenced by high-fat diet consumption

Spinal cord injury (SCI) results in perturbations to the immune system leading to increased infection susceptibility. In parallel, the consumption of high-fat diets (HFD) leads to a chronic inflammation in circulation and body tissues. We investigated the impact of 16 weeks of HFD on chronically-injured rats. SCI rats under both chow and HFD showed peripheral leukocyte changes that include reduced percentages of total, helper and cytotoxic T, and natural killer cells. Expression of immune-related genes in the spleen and thymus reflected the impact of both chronic injury and diet. Changes to the immune system following SCI are adversely impacted by HFD consumption.

cGAS/STING Pathway Activation Contributes to Delayed Neurodegeneration in Neonatal Hypoxia-Ischemia Rat Model: Possible Involvement of LINE-1

cGAS is a sensor of cytosolic DNA and responds equally to exogenous and endogenous DNA. After recognition of cytosolic dsDNA or ssDNA, cGAS synthesizes the second messenger 2'3'-cGAMP, which then binds to and activates stimulator of interferon genes (STING). STING plays an essential role in responding to pathogenic DNA and self-DNA in the context of autoimmunity. In pathologic conditions, such as stroke or hypoxia-ischemia (HI), DNA can gain access into the cytoplasm of the cell and leak from the dying cells into the extracellular environment, which potentially activates cGAS/STING. Recent in vivo studies of myocardial ischemia, traumatic brain injury, and liver damage models suggest that activation of cGAS/STING is not only a side-effect of the injury, but it can also actively contribute to cell death and apoptosis. We found, for the first time, that cGAS/STING pathway becomes activated between 24 and 48 h after HI in a 10-day-old rat model. Silencing STING with siRNA resulted in decreased infarction area, reduced cortical neurodegeneration, and improved neurobehavior at 48 h, suggesting that STING can contribute to injury progression after HI. STING colocalized with lysosomal marker LAMP-1 and blocking STING reduced the expression of cathepsin B and decreased the expression of Bax and caspase 3 cleavage. We observed similar protective effects after intranasal treatment with cGAS inhibitor RU.521, which were reversed by administration of STING agonist 2'3'-cGAMP. Additionally, we showed that long interspersed element 1 (LINE-1) retrotransposon, a potential upstream activator of cGAS/STING pathway was induced at 48 h after HI, which was evidenced by increased expression of ORF1p and ORF2p proteins and increased LINE-1 DNA content in the cytosol. Blocking LINE-1 with the nucleoside analog reverse-transcriptase inhibitor (NRTI) stavudine reduced infarction area, neuronal degeneration in the cerebral cortex, and reduced the expression of Bax and cleaved caspase 3. Thus, our results identify the cGAS/STING pathway as a potential therapeutic target to inhibit delayed neuronal death after HI.

Increased serum levels of complement C1q in major depressive disorder

BACKGROUND

The complement system is involved in multiple biological processes including inflammation, synaptic pruning, and apoptosis. However, it is not well understood whether peripheral complement C1q levels are altered in major depressive disorder (MDD) patients.

OBJECTIVE

This study aimed at assessing serum levels of complement C1q in MDD patients using a cross-sectional, case-control design. Also, the correlations between complement C1q and inflammation and lipid profile in patients with MDD were also assessed.

METHODS

Serum complement C1q levels were measured by ADVIA 2400 biochemical analyzer in 160 patients with MDD diagnosed using International Classification of Diseases-10 criteria (ICD-10) and were compared with those of 159 healthy controls between January 2017 to May 2019. Then correlation analysis was carried out between the level of serum complement C1q among MDD patients with inflammation and lipid profile.

RESULTS

Serum complement C1q levels were higher in MDD patients than in controls (P < .0001) and the difference between the two groups was small (r = 0.239 [0.128 to 0.350]). We found that serum complement C1q concentrations was positively correlated with HAMD-24 score (r = 0.234, P = .003) and log hs-CRP (r = 0.334, P < .001).

CONCLUSION

We found serum complement C1q levels were significantly higher in MDD patients than in controls. The current results suggest that the dysfunction of complement C1q may be involved in the pathophysiology of MDD.

Hepcidin-to-Ferritin Ratio Is Decreased in Astrocytes With Extracellular Alpha-Synuclein and Iron Exposure

Astrocytes are the most abundant glial cells in the central nervous system (CNS). As indispensable elements of the neurovascular unit, they are involved in the inflammatory response and disease-associated processes. Alpha-synuclein (α-syn) is released into the extracellular space by neurons and can be internalized by adjacent astrocytes, which activates glial cells to induce neuroinflammation. We were interested in whether astrocyte-mediated neuroinflammation is modulated by intracellular iron status and extracellular α-syn. Our results showed that recombinant α-syn (1 μg/ml and 5 μg/ml) treatment for 24 h did not affect the expression of the iron transporters divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1), nor those of iron regulatory protein (IRP) 1 or IRP2. Several proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 exhibited up-regulated mRNA levels in 5 μg/ml α-syn-treated astrocytes. TNF-α release was increased, indicating that inflammatory responses were triggered in these cells. Pretreatment with the iron-overload reagent ferric ammonium citrate (FAC, 100 μmol/L) for 24 h had no effects on mRNA levels and release of proinflammatory cytokines. Inflammatory responses triggered by α-syn were not affected by iron overload. The iron chelator desferrioxamine (DFO, 100 μmol/L) exerted suppressive effects on TNF-α mRNA levels, although no change was observed for TNF-α release. Hepcidin mRNA levels were down-regulated significantly in astrocytes co-treated with FAC and α-syn, although independent treatment with either FAC or α-syn did not alter hepcidin levels. In contrast, hepcidin mRNA levels were up-regulated in DFO and α-syn co-treated cells. As expected, ferritin protein levels were up-regulated or down-regulated with FAC or DFO treatment, respectively. Following the up-regulation of ferritin mediated by α-syn, hepcidin-to-ferritin levels were indicative of modulatory effects in α-syn-treated astrocytes with altered iron status. Therefore, we propose that the hepcidin-to-ferritin ratio is indicative of a detrimental response in primary cultured astrocytes experiencing iron and extracellular α-syn.