C1q Expression Research Articles

Activation of complement C1q and C3 in glomeruli might accelerate the progression of diabetic nephropathy: Evidence from transcriptomic data and renal histopathology.

ABSTRACTAims/IntroductionIt is not unclear whether the complement system is involved in the pathogenesis of diabetic nephropathy (DN). We explored the role of the complement system in glomeruli from patients with DN using integrated transcriptomic bioinformatics analysis and renal histopathology.Materials and MethodsFour datasets (GSE30528, GSE104948, GSE96804 and GSE99339) from the Gene Expression Omnibus database were integrated. We used a protein–protein interaction network and the Molecular Complex Detection App to obtain hub genes. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were carried out to identify significant pathways. We also investigated the associations of C1q and C3 deposition on renal histopathology with clinical data, pathological parameters and renal survival in DN patients.ResultsWe identified 47 up‐ and 48 downregulated genes associated with DN. C3, C1QB and C1QA were found to be complement‐related hub genes. The gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses identified complement activation and humoral immune response as the significant oncology terms, with C1QB and C3 positioned at the center of the pathway. Regarding renal histopathology, patients with both C1q and C3 deposition had more severe glomerular classes. Multivariate Cox proportional hazards regression showed that the deposition of glomerular C1q and C3 was an independent risk factor for kidney failure. Patients with high C1q, C3 or C4d expression in glomeruli were more likely to progress to kidney failure, whereas glomerular mannose‐binding lectin was rare.ConclusionsComplement activation is involved in the development of DN, and activation of the classical complement pathway in glomeruli might accelerate disease progression.

The Programming of Antioxidant Capacity, Immunity, and Lipid Metabolism in Dojo Loach (Misgurnus anguillicaudatus) Larvae Linked to Sodium Chloride and Hydrogen Peroxide Pre-treatment During Egg Hatching.

Non-nutritional stress during early life period has been reported to promote the metabolic programming in fish induced by nutritional stimulus. Sodium chloride (NaCl) and hydrogen peroxide (H2O2) have been widely applied during fish egg hatching, but the influences on health and metabolism of fish in their later life remain unknown. In the present study, H2O2 treatment at 400mg/L but not 200mg/L significantly increased the loach hatchability and decreased the egg mortality, while NaCl treatment at 1,000 and 3,000mg/L showed no significant influences on the loach hatchability nor egg mortality. Further studies indicated that 400mg/L H2O2 pre-treatment significantly enhanced the antioxidant capacity and the mRNA expression of genes involved in immune response of loach larvae, accompanied by the increased expression of genes involved in fish early development. However, the expression of most genes involved in lipid metabolism, including catabolism and anabolism of loach larvae, was significantly upregulated after 200mg/L H2O2 pre-treatment. NaCl pre-treatment also increased the expression of antioxidant enzymes; however, only the expression of C1q within the detected immune-related genes was upregulated in loach larvae. One thousand milligram per liter NaCl pre-treatment significantly increased the expression of LPL and genes involved in fish early development. Thus, our results suggested the programming roles of 400mg/L H2O2 pre-treatment during egg hatching in enhancing antioxidant capacity and immune response of fish larvae via promoting fish early development.

Effects of early pregnancy on the complement system in the ovine thymus.

The complement system is crucial for the innate immune system, and complement activation is related to abnormal pregnancy in mice and humans. It is hypothesized that the complement system participates in maternal thymic immune regulation during early pregnancy in sheep. In this study, maternal thymuses were sampled on day 16 of the estrous cycle, and days 13, 16 and 25 of gestation in sheep. Quantitative real-time PCR, Western blot and immunohistochemistry analyses were used to analyze the expression of the complement components C1q, C1r, C1s, C2, C3, C4a, C5b and C9 in the maternal thymus. The results revealed that the mRNA and protein expression of C1r, C1s, C2, C3 and C4a was inhibited by early pregnancy, and the pregnancy recognition signal induced upregulation of C1q, C5b and C9 expression at day 16 of gestation. Furthermore, C3 protein was mostly located in epithelial reticular cells and thymic corpuscles, which may be involved in immune regulation. In summary, early pregnancy inhibits the complement system in the maternal thymus, which may be essential for the maternal immune regulation and successful pregnancy in sheep.

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.

Complement activation and increased expression of Syk, mucin-1 and CaMK4 in kidneys of patients with COVID-19

Acute and chronic kidney failure is common in hospitalized patients with COVID-19, yet the mechanism of injury and predisposing factors remain poorly understood. We investigated the role of complement activation by determining the levels of deposited complement components (C1q, C3, FH, C5b-9) and immunoglobulin along with the expression levels of the injury-associated molecules spleen tyrosine kinase (Syk), mucin-1 (MUC1) and calcium/calmodulin-dependent protein kinase IV (CaMK4) in the kidney tissues of people who succumbed to COVID-19. We report increased deposition of C1q, C3, C5b-9, total immunoglobulin, and high expression levels of Syk, MUC1 and CaMK4 in the kidneys of COVID-19 patients. Our study provides strong rationale for the expansion of trials involving the use of inhibitors of these molecules, in particular C1q, C3, Syk, MUC1 and CaMK4 to treat patients with COVID-19.

Novel Monoclonal Antibodies Against Mouse C1q: Characterisation and Development of a Quantitative ELISA for Mouse C1q

Recent studies have identified roles for complement in synaptic pruning, both physiological during development and pathological in Alzheimer’s disease (AD). These reports suggest that C1q initiates complement activation on synapses and C3 fragments then tag them for removal by microglia. There is an urgent need to characterise these processes in rodent AD models; this requires the development of reagents and methods for detection and quantification of rodent C1q in fluids and pathological tissues. These will enable better evaluation of the role of C1q in disease and its value as disease biomarker. We describe the generation in C1q-deficient mice of novel monoclonal antibodies against mouse and rat C1q that enabled development of a sensitive, specific, and quantitative ELISA for mouse and rat C1q capable of measuring C1q in biological fluids and tissue extracts. Serum C1q levels were measured in wild-type (WT), C1q knockout (KO), C3 KO, C7 KO, Crry KO, and 3xTg and APPNL-G-F AD model mice through ageing. C1q levels significantly decreased in WT, APPNL-G-F, and C7 KO mice with ageing. C1q levels were reduced in APPNL-G-F compared to WT at all ages and in 3xTg at 12 months; C3 KO and C7 KO, but not Crry KO mice, also demonstrated significantly lower C1q levels compared to matched WT. In brain homogenates, C1q levels increased with age in both WT and APPNL-G-F mice. This robust and adaptable assay for quantification of mouse and rat C1q provides a vital tool for investigating the expression of C1q in rodent models of AD and other complement-driven pathologies.

Physical exercise modulates the astrocytes polarization, promotes myelin debris clearance and remyelination in chronic cerebral hypoperfusion rats

AimsWhite matter damage is the main pathological feature of chronic cerebral hypoperfusion (CCH) and glial activation is crucial in this process. Physical exercise has protective effects on CCH, but the mechanism is unclear. Therefore, this study focuses on investigating the influence of physical exercise on activated astrocytes polarization and its role in CCH. Main methodsRats were given wheel running 48 h after 2VO (2 vessel occlusion) surgery. The cognitive function was evaluated by Morris water maze and novel object recognition test. Inflammatory cytokines expressions were detected by ELISA. Astrocytes polarization was analyzed by immunofluorescence. Myelin debris clearance and remyelination were detected by immunofluorescence and transmission electron microscopy. Key findingsAstrocytes were activated and mainly switched to A1 phenotype in rats 2 and 3 months after 2VO. Myelin debris deposition and limited remyelination can be observed at the corresponding time. Whereas physical exercise can improve the cognitive function of 2VO rats, downregulate the expression of inflammatory factors IL-1α, C1q and TNF, upregulate the release of TGFβ, and promote activated astrocytes transformation from A1 to A2 phenotype. In addition, it can also enhance myelin debris removal and remyelination. SignificanceThese findings suggest that the benefits of physical exercise on white matter repair and cognition improvement may be related to its regulation of astrocytes polarization, which contributes to myelin debris clearance and effective remyelination in CCH.

Complement Initiation Varies by Sex in Intestinal Ischemia Reperfusion Injury.

Intestinal ischemia reperfusion (IR)-induced tissue injury represents an acute inflammatory response with significant morbidity and mortality. The mechanism of IR-induced injury is not fully elucidated, but recent studies suggest a critical role for complement activation and for differences between sexes. To test the hypothesis that complement initiation differs by sex in intestinal IR, we performed intestinal IR on male and female WT C57B6L/, C1q-/-, MBL-/-, or properdin (P)-/- mice. Intestinal injury, C3b and C5a production and ex vivo secretions were analyzed. Initial studies demonstrated a difference in complement mRNA and protein in male and female WT mice. In response to IR, male C1q-, MBL- and P-deficient mice sustained less injury than male WT mice. In contrast, only female MBL-/- mice sustained significantly less injury than female wildtype mice. Importantly, wildtype, C1q-/- and P-/- female mice sustained significant less injury than the corresponding male mice. In addition, both C1q and MBL expression and deposition increased in WT male mice, while only elevated MBL expression and deposition occurred in WT female mice. These data suggested that males use both C1q and MBL pathways, while females tend to depend on lectin pathway during intestinal IR. Females produced significantly less serum C5a in MBL-/- and P-/- mice. Our findings suggested that complement activation plays a critical role in intestinal IR in a sex-dependent manner.

Neuroprotective effect of mitochondrial translocator protein ligand in a mouse model of tauopathy

BackgroundThe translocator protein (TSPO) has been identified as a positron emission tomography (PET)-visible biomarker of inflammation and promising immunotherapeutic target for the treatment of Alzheimer’s disease (AD). While TSPO ligands have been shown to reduce the accumulation of the toxic Alzheimer’s beta-amyloid peptide, their effect on tau pathology has not yet been investigated. To address this, we analyzed the effects of TSPO ligand, Ro5-4864, on the progression of neuropathology in rTg4510 tau transgenic mice (TauTg).MethodsBrain atrophy, tau accumulation, and neuroinflammation were assessed longitudinally using volumetric magnetic resonance imaging, tau-PET, and TSPO-PET, respectively. In vivo neuroimaging results were confirmed by immunohistochemistry for markers of neuronal survival (NeuN), tauopathy (AT8), and inflammation (TSPO, ionized calcium-binding adaptor molecule 1 or IBA-1, and complement component 1q or C1q) in brain sections from scanned mice.ResultsTSPO ligand treatment attenuated brain atrophy and hippocampal neuronal loss in the absence of any detected effect on tau depositions. Atrophy and neuronal loss were strongly associated with in vivo inflammatory signals measured by TSPO-PET, IBA-1, and levels of C1q, a regulator of the complement cascade. In vitro studies confirmed that the TSPO ligand Ro5-4864 reduces C1q expression in a microglial cell line in response to inflammation, reduction of which has been shown in previous studies to protect synapses and neurons in models of tauopathy.ConclusionsThese findings support a protective role for TSPO ligands in tauopathy, reducing neuroinflammation, neurodegeneration, and brain atrophy.

Therapeutic Hypothermia Inhibits the Classical Complement Pathway in a Rat Model of Neonatal Hypoxic-Ischemic Encephalopathy.

ObjectiveComplement activation is instrumental in the pathogenesis of Hypoxic-ischemic encephalopathy (HIE), a significant cause of neonatal mortality and disability worldwide. Therapeutic hypothermia (HT), the only available treatment for HIE, only modestly improves outcomes. Complement modulation as a therapeutic adjunct to HT has been considered, but is challenging due to the wide-ranging role of the complement system in neuroinflammation, homeostasis and neurogenesis in the developing brain. We sought to identify potential therapeutic targets by measuring the impact of treatment with HT on complement effector expression in neurons and glia in neonatal HIE, with particular emphasis on the interactions between microglia and C1q.MethodsThe Vannucci model was used to induce HIE in term-equivalent rat pups. At P10-12, pups were randomly assigned to three different treatment groups: Sham (control), normothermia (NT), and hypothermia (HT) treatment. Local and systemic complement expression and neuronal apoptosis were measured by ELISA, TUNEL and immunofluorescence labeling, and differences compared between groups.ResultsTreatment with HT is associated with decreased systemic and microglial expression of C1q, decreased systemic C5a levels, and decreased microglial and neuronal deposition of C3 and C9. The effect of HT on cytokines was variable with decreased expression of pro and anti-inflammatory effectors. HT treatment was associated with decreased C1q binding on cells undergoing apoptosis.ConclusionOur data demonstrate the extreme complexity of the immune response in neonatal HIE. We propose modulation of downstream effectors C3a and C5a as a therapeutic adjunct to HT to enhance neuroprotection in the developing brain.

Uromodulin aggravates renal tubulointerstitial injury through activation of the complement pathway in rats.

Uromodulin (Umod) is the most abundant constituent of urine in humans and exclusively found in the kidney tubular epithelium. However, the specific role of Umod in renal tubulointerstitial injury is yet to be understood. The present study was conducted with aim of investigating the potential therapeutic mechanism of Umod in the regulation of renal tubulointerstitial injury. Protein expression of Umod in renal tubular epithelial cells was measured with the conduction of Western blot analysis. Enzyme-linked immunosorbent assay and immunofluorescence assaywere performed to detect the complement activation products and the activation products of surface deposition. The expression of C1q, C2, C4, B factor, C3, C5, H factor, CD46, CD55, C3aR, and C5aR were determined with the use of reverse-transcription quantitative polymerase chain reactionand Western blot analyses. Subsequently, the unilateral ureteral obstruction (UUO) rat model was established. Renal tubulointerstitial injury was assessed with the application of hematoxylin-eosin staining and Masson staining in rats. UUO rats and normal rats were injected with si-NC or si-Umod and complement inhibitor. UUO rats were observed to have serious impairment of kidney tubule, renal tubular dilation, and epithelial atrophy, with downregulated Umod and activated complement pathway. Silencing of Umod resulted in the activation of complement system while promoting interstitial fibrosis in renal tubules. Moreover, addition of complement inhibitor significantly alleviated the renal tubule injury and fibrosis. Collectively, our study suggests that silencing of Umod mediates the complement pathway, exacerbating renal tubulointerstitial injury in rats, which provides insight into the development of novel therapeutic agents for renal tubulointerstitial injury.

Integrated genomic and transcriptomic analysis reveals unique characteristics of hepatic metastases and pro-metastatic role of complement C1q in pancreatic ductal adenocarcinoma

BackgroundPancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers due to its high metastasis rate in the liver. However, little is known about the molecular features of hepatic metastases due to difficulty in obtaining fresh tissues and low tumor cellularity.ResultsWe conduct exome sequencing and RNA sequencing for synchronous surgically resected primary tumors and the paired hepatic metastases from 17 hepatic oligometastatic pancreatic ductal adenocarcinoma and validate our findings in specimens from 35 of such cases. The comprehensive analysis of somatic mutations, copy number alterations, and gene expressions show high similarity between primary tumors and hepatic metastases. However, hepatic metastases also show unique characteristics, such as a higher degree of 3p21.1 loss, stronger abilities of proliferation, downregulation of epithelial to mesenchymal transition activity, and metabolic rewiring. More interesting, altered tumor microenvironments are observed in hepatic metastases, especially a higher proportion of tumor infiltrating M2 macrophage and upregulation of complement cascade. Further experiments demonstrate that expression of C1q increases in primary tumors and hepatic metastases, C1q is mainly produced by M2 macrophage, and C1q promotes migration and invasion of PDAC cells.ConclusionTaken together, we find potential factors that contribute to different stages of PDAC metastasis. Our study broadens the understanding of molecular mechanisms driving PDAC metastasis.

Complement in Renal Disease as a Potential Contributor to Arterial Hypertension

Objective: Complement deposition is prevalent in kidney biopsies of patients with arterial hypertension and hypertensive nephropathy, but an association of hypertension and complement deposition or involvement of complement in the pathogenesis of hypertensive nephropathy has not been shown to date. Methods: In this study, we analyzed complement C1q and C3c deposition in a rat model of overload and hypertension by subtotal nephrectomy (SNX) and in archival human renal biopsies from 217 patients with known hypertension and 91 control patients with no history of hypertension using semiquantitative scoring of C1q and C3c immunohistochemistry and correlation with parameters of renal function. To address whether complement was only passively deposited or actively expressed by renal cells, C1q and C3 mRNA expression were additionally analyzed. Results: Glomerular C1q and C3c complement deposition were significantly higher in kidneys of hypertensive SNX rats and hypertensive compared to nonhypertensive patients. Mean arterial blood pressure (BP) in SNX rats correlated well with the amount of glomerular C1q and C3c deposition and with left ventricular weight, as an indirect parameter of high BP. Quantitative mRNA analysis showed that C3 was not only deposited but also actively produced by glomerular cells of hypertensive SNX rats and in human renal biopsies. Of note, in patients CKD-stage correlated significantly with the intensity of glomerular C3c staining, but not with that of C1q. Conclusion: Renal complement deposition correlated with experimental hypertension as well as the presence of hypertension in a variety of renal diseases. To answer the question, if and how exactly renal complement is causative for the pathogenesis of arterial hypertension in men, further studies are needed.

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.

The complement system in primary Sjögren's syndrome: the expression of certain cascade and regulatory proteins in labial salivary glands - observational study.

IntroductionThe complement cascade and regulatory proteins are involved in the pathogenesis of the Sjögren’s syndrome and other autoimmune diseases. The complement activation via the alternative pathway was recognized as a major pathogenic mechanism in autoimmune conditions. The aim of this study was to assess expression of complement cascade components and regulatory proteins in minor salivary glands in patients with primary Sjögren’s syndrome (pSS).Materials and methodsThe expression of C1q and C5b-9 – membrane attack complex and regulatory proteins such as: membrane cofactor protein (MCP), decay-accelerating factor (DAF) and protectin were examined using immunochemistry method in specimens from biopsy of minor salivary glands in pSS patients. The biopsy material was obtained from 20 pSS patients, 5 patients with non-specific sialadenitis and from 5 patients with suspicion of dryness syndrome without sialadenitis confirmation.ResultsNone of the examined samples showed the expression of C1q or the effector C5b-9. Membrane cofactor protein expression was lower in pSS group than in both non-specific sialadenitis and noninflamed salivary glands. The inflammatory cells in pSS samples partially expressed MCP. There were differences in the sites and intensity of membrane protectin expression exclusively on the luminal surfaces in pSS; on the luminal and, partially, antiluminal surface in non-specific inflammation, and on the entire cell surface in unaffected salivary glands. There were no DAF expression in salivary gland tissue in biopsy specimens in all studied subjects.ConclusionsThe study demonstrated the absence of complement-cascade proteins (C1q, MAC) in the salivary glands of pSS patients, which may indicated a lack of local complement activation via the classical pathway and the observed gland tissue damage being due to a mechanism other than MAC-induced cytolysis. The differences in the expression of complement regulatory proteins between pSS, non-specific sialadenitis, and normal salivary glands may indicate that alternative functions of these regulatory proteins may be of greater significance in pSS. Low MCP expression in pSS in comparison with non-specific sialadenitis and normal salivary glands, may suggest altered modulation of cell-mediated immunity in pSS. The differences in the location and intensity of protectin (CD59) expression indicates a possibility of reducing the proinflammatory effect of protectin in pSS.

A novel inducible complement C3 conditional knockout mouse model: Generation and characterization

AbstractBackgroundThe classical complement pathway is a complex process involved in the elimination of dead cells, debris, and pathogens, and as well as brain wiring during development. Complement protein C3 is an innate immune molecule central in the complement pathway. It participates in removing pathogens and eliminating synapses, and is elevated with aging and neurodegenerative diseases, including Alzheimer’s Disease. Previously, we showed that lifelong, germline C3‐deficiency protected aged male wild‐type and APPswe/PS1dE9 mice against hippocampal neuronal dysfunction and cognitive decline, despite increasing the Aβ plaque load. However, it remains unknown whether suppressing complement C3 signaling during early stages of AD pathogenesis, when relevant therapeutic interventions might be considered, would confer neuroprotection.MethodTo address this question, we generated the first‐ever C3 floxed (C3fl/fl) mouse line, and then crossed the C3fl/fl mice with an inducible, global Cre line (Rosa26‐Cre‐ERT2+/‐) for 2 generations to generate novel inducible C3 conditional knockout C3fl/fl; Rosa26‐Cre‐ERT2+/‐ mice. Mice aged 2‐3 months received intraperitoneal injections of either corn oil or tamoxifen (75 mg/kg) once a day for 5 consecutive days. We analyzed the C3 serum levels at 7, 14, 30, 60, and 90 days post‐tamoxifen treatment. We also analyzed the mRNA expression of complement C1q and C3 in the brain and liver 60 days following tamoxifen treatment.ResultC3fl/fl;Rosa26‐cre‐ERT2+/‐ mice had a significant 70% reduction in serum C3 levels compared to controls, which was consistent at all timepoints analyzed. We also showed that C3 expression in the liver, the main source of complement proteins, as well as in the brain was reduced, demonstrating effective recombinase activity in these organs. Intriguingly, C1q mRNA expression was increased in the brain and liver following tamoxifen treatment; further studies are underway.ConclusionIn conclusion, we present a novel mouse model in which tamoxifen treatment resulted in sustained lowering of C3 in the serum, liver, and brain. We will next cross this model with AD‐like mouse models of amyloidosis and tau pathology to evaluate whether global C3 lowering in early stages AD pathogenesis is protective and if so, our data would support targeting complement as a therapy for AD.

C5a complement and cytokine signaling mediate the pronociceptive effects of complex regional pain syndrome patient IgM in fracture mice.

It has been proposed that complex regional pain syndrome (CRPS) is a posttraumatic autoimmune disease. Previously, we observed that B cells contribute to CRPS-like changes in a mouse tibia fracture model, and that early (<12 months duration) CRPS patient IgM antibodies have pronociceptive effects in the skin and spinal cord of muMT fracture mice lacking B cells. The current study evaluated the pronociceptive effects of intraplantar or intrathecal injections of early CRPS IgM (5 µg) in muMT fracture mice. Skin and lumbar spinal cord were collected for immunohistochemistry and polymerase chain reaction analyses. Wild-type mice exhibited postfracture increases in complement component C5a and its receptor expression in skin and spinal cord, predominantly on dermal macrophages and spinal microglia. Intraplantar IgM injection caused nociceptive sensitization in muMT fracture mice with increased complement component C1q and inflammatory cytokine expression, and these IgM effects were blocked by a C5a receptor antagonist (PMX53) or a global cytokine inhibitor (pentoxifylline). Intrathecal IgM injection also had pronociceptive effects with increased spinal cytokine expression, effects that were blocked by PMX53 or pentoxifylline treatment. Intrathecal injection of chronic (>12 months duration) CRPS patient IgM (but not IgG) caused nociceptive sensitization in muMT fracture mice, but intraplantar injection of chronic CRPS IgM or IgG had no effect. We postulate that CRPS IgM antibodies bind to neoantigens in the fracture limb skin and corresponding spinal cord to activate C5a complement signaling in macrophages and microglia, evoking proinflammatory cytokine expression contributing to nociceptive sensitization in the injured limb.

Relationships between diabetic nephropathy and insulin resistance, inflammation, Trx, Txnip, CysC and serum complement levels.

To investigate the relationships between diabetic nephropathy (DN) and insulin resistance, inflammation, thioredoxin (Trx), thioredoxin-interacting protein (Txnip), Cystatin C (CysC) and serum complement levels. A total of 119 patients with type 2 diabetes mellitus (T2DM) treated in the Endocrinology Department of our hospital from January 2017 to December 2017 were enrolled as the experiment group, while 30 healthy volunteers were selected as the control group. The expression levels of inflammatory factors, Trx, Txnip, CysC and serum complements in every subject were detected. In addition, the type 2 diabetic nephropathy rat model was established via high-fat diet and injection of low-dose streptozotocin. Blood glucose, insulin resistance indexes and 24h-urinary albumin excretion were measured, and the histomorphological characteristics of the kidney in animals were observed. In clinical subjects, Trx level was notably lower in the simple DM group, early DN group and clinical DN group in comparison with that in the control group. The levels of Txnip and CysC in the simple DM group, early DN group and clinical DN group were remarkably higher than those in the control group. Moreover, the expression levels of TNF-α and IL-6 in the clinical DN group were significantly elevated compared with those in the simple DM group and early DN group. In addition, C1q expression in the clinical DN group was higher than that in the simple DM group and early DN group. In model rats, HOMA-IR was distinctly higher in the DM group and DN group than that in the control group. The ratio of kidney weight to body weight (KW/BW) was evidently higher in the DN group in comparison with that in the control group and DM group. Insulin resistance, inflammatory factors, and levels of Trx, Txnip, CysC and serum complement C1q are related to the progression of DM.

Loss of TDP-43 in astrocytes leads to motor deficits by triggering A1-like reactive phenotype and triglial dysfunction

Patients with amyotrophic lateral sclerosis (ALS) can have abnormal TDP-43 aggregates in the nucleus and cytosol of their surviving neurons and glia. Although accumulating evidence indicates that astroglial dysfunction contributes to motor neuron degeneration in ALS, the normal function of TDP-43 in astrocytes are largely unknown, and the role of astroglial TDP-43 loss to ALS pathobiology remains to be clarified. Herein, we show that TDP-43-deleted astrocytes exhibit a cell-autonomous increase in GFAP immunoreactivity without affecting astrocyte or microglia proliferation. At the transcriptomic level, TDP-43-deleted astrocytes resemble A1-reactive astrocytes and induce microglia to increase C1q expression. These astrocytic changes do not cause loss of motor neurons in the spinal cord or denervation at the neuromuscular junction. In contrast, there is a selective reduction of mature oligodendrocytes, but not oligodendrocyte precursor cells, suggesting triglial dysfunction mediated by TDP-43 loss in astrocytes. Moreover, mice with astroglial TDP-43 deletion develop motor, but not sensory, deficits. Taken together, our results demonstrate that TDP-43 is required to maintain the protective functions of astrocytes relevant to the development of motor deficits in mice.

C1q Regulates Horizontal Cell Neurite Confinement in the Outer Retina.

During development, neurons generate excess processes which are then eliminated in concert with circuit maturation. C1q is the initiating protein in the complement cascade and has been implicated in this process, but whether C1q-mediated elimination is targeted to particular neural compartments is unclear. Using the murine retina, we identify C1q as a specific regulator of horizontal cell neurite confinement. Subsets of horizontal cell dendritic and axonal neurites extend into the outer retina suggesting that complement achieves both cellular and subcellular selectivity. These alterations emerge as outer retina synapses become mature. C1q expression is restricted to retina microglia, and the loss of C1q results in decreased microglia activation. This pathway appears independent of the C3a receptor (C3aR) and complement receptor 3 (CR3), as horizontal cells are normal when either protein is absent. Together, these data identify a new role for C1q in cell and neurite-specific confinement and implicate microglia-mediated phagocytosis in this process.