Proangiogenic properties of complement protein C1q can contribute to endometriosis.

Endometriosis (EM) is defined as the engraftment and proliferation of functional endometrial-like tissue outside the uterine cavity, leading to a chronic inflammatory condition. While the precise etiology of EM remains elusive, recent studies have highlighted the crucial involvement of a dysregulated immune system. The complement system is one of the predominantly altered immune pathways in EM. Owing to its involvement in the process of angiogenesis, here, we have examined the possible role of the first recognition molecule of the complement classical pathway, C1q. C1q plays seminal roles in several physiological and pathological processes independent of complement activation, including tumor growth, placentation, wound healing, and angiogenesis. Gene expression analysis using the publicly available data revealed that C1q is expressed at higher levels in EM lesions compared to their healthy counterparts. Immunohistochemical analysis confirmed the presence of C1q protein, being localized around the blood vessels in the EM lesions. CD68+ macrophages are the likely producer of C1q in the EM lesions since cultured EM cells did not produce C1q in vitro. To explore the underlying reasons for increased C1q expression in EM, we focused on its established pro-angiogenic role. Employing various angiogenesis assays on primary endothelial endometriotic cells, such as migration, proliferation, and tube formation assays, we observed a robust proangiogenic effect induced by C1q on endothelial cells in the context of EM. C1q promoted angiogenesis in endothelial cells isolated from EM lesions (as well as healthy ovary that is also rich in C1q). Interestingly, endothelial cells from EM lesions seem to overexpress the receptor for the globular heads of C1q (gC1qR), a putative C1q receptor. Experiments with siRNA to silence gC1qR resulted in diminished capacity of C1q to perform its angiogenic functions, suggesting that C1q is likely to engage gC1qR in the pathophysiology of EM. gC1qR can be a potential therapeutic target in EM patients that will disrupt C1q-mediated proangiogenic activities in EM.

Complement C1q is involved in the activation of membrane attack complexes, regulation of bacterial infectious inflammation, and apoptosis through overexpression in primary cells of silver pomfret (Pampus argenteus) in vitro.

The complement system is pivotal in innate immune defense, with Complement 1qb (C1qb) playing a key role in recognizing immune complexes and initiating the classical pathway. In this research, we cloned the full-length cDNA of silver pomfret (Pampus argenteus) c1qb and demonstrated its role in mediating defense responses against Nocardia seriolae (N. seriolae) infection, which notably causes significant economic losses in the aquaculture industry. Our investigation revealed that N. seriolae infection led to tissue damage in fish bodies, as observed in tissue sections. Subsequent analysis of differential genes (DEGs) in the transcriptome highlighted genes linked to apoptosis and inflammation. Through experiments involving overexpression and interference of c1qb in vitro, we confirmed that c1qb could suppress N. seriolae-induced apoptosis and inflammation. Moreover, overexpression of c1qb hindered N. seriolae invasion, and the purified and replicated C1qb protein displayed antimicrobial properties. Additionally, our study unveiled that overexpression of c1qb might stimulate the expression of membrane attack complexes (MAC), potentially enhancing opsonization and antibacterial effects. In conclusion, our findings offer valuable insights into the immune antibacterial mechanisms of c1qb and contribute to the development of strategies for controlling N. seriolae.

Identification of the C1qDC gene family in grass carp (Ctenopharyngodon idellus) and the response of C1qA, C1qB, and C1qC to GCRV infection in vivo and in vitro.

Proteins from the C1q domain-containing (C1qDC) family recognize self-, non-self-, and altered-self ligands and serves as an initiator molecule for the classical complement pathway as well as recognizing immune complexes. In this study, C1qDC gene family members were identified and analyzed in grass carp (Ctenopharyngodon idellus). Members of the C1q subfamily were cloned, and their response to infection with the grass carp virus was investigated. In the grass carp genome, 54 C1qDC genes and 67 isoforms have been identified. Most were located on chromosome 3, with 52 shared zebrafish homologies. Seven substantially differentially expressed C1qDC family genes were identified in the transcriptomes of cytokine-induced killer (CIK) cells infected with grass carp reovirus (GCRV), all of which exhibited sustained upregulation. The opening reading frames of grass carp C1qA, C1qB, and C1qC, belonging to the C1q subfamily, were determined to be 738, 732, and 735 base pairs, encoding 245, 243, and 244 amino acids with molecular weights of 25.81 kDa, 25.63 kDa and 26.16 kDa, respectively. Three genes were detected in the nine collected tissues, and their expression patterns were similar, with the highest expression levels observed in the spleen. In vivo after GCRV infection showed expression trends of C1qA, C1qB, and C1qC in the liver, spleen, and kidney. An N-type pattern in the liver and kidney was characterized by an initial increase followed by a decrease, with the highest expression occurring during the recovering period, and a V-type pattern in the spleen with the lowest expression levels during the death period. In vitro, after GCRV infection showed expression trends of C1qA, C1qB, and C1qC, and this gradually increased within the first 24 h, with a notable increase observed at the 24 h time point. After CIK cells incubation with purified recombinant proteins, rC1qA, rC1qB, and rC1qC for 3 h, followed by GCRV inoculation, the GCRV replication indicated that rC1qC exerted a substantial inhibitory effect on viral replication in CIK cells after 24 h of GCRV inoculation. These findings offer valuable insights into the structure, evolution, and function of the C1qDC family genes and provide a foundational understanding of the immune function of C1q in grass carp.

CTRP9 prevents atherosclerosis progression through changing autophagic status of macrophages by activating USP22 mediated-de-ubiquitination on Sirt1 in vitro.

BACKGROUND: Atherosclerosis (AS) is commonly regarded as a key driver accounted for the leading causes of morbidity and mortality among cardiovascular and cerebrovascular diseases. A growing body of evidence indicates that autophagy in macrophages involved in AS might be a potential therapeutic target. C1q/TNF-related protein 9 (CTRP9) has been proven to delay the progression of cardiovascular diseases. However, the relations between CTRP9 and Sirt1, as well as their effects on macrophages autophagy have not been fully explored. METHODS: Macrophages were differentiated from mononuclear cells collected from peripheral blood samples of healthy donors. The in vitro AS models were constructed by ox-LDL treatment. Cell viability was determined by CCK-8 assay. Immunofluorescence assay of LC3 was implemented for evaluating autophagy activity. Oil Red O staining was performed for lipid accumulation detection. ELISA, cholesterol concentration assay and cholesterol efflux analysis were conducted using commercial kits. Cycloheximide assay was implemented for revealing protein stability. RT-qPCR was used for mRNA expression detection, and western blotting was performed for protein level monitoring. RESULTS: CTRP9 attenuated impaired cell viability, autophagy inhibition and increased lipid accumulation induced by ox-LDL. Moreover, CTRP9 maintained Sirt1 protein level through enhancing its stability through de-ubiquitination, which was mediated by upregulated USP22 level. CRTP9 exerted its protective role in promoting autophagy and reducing lipid accumulation through the USP22/Sirt1 axis. CONCLUSION: Collectively, CTRP9 alleviates lipid accumulation and facilitated the macrophages autophagy by upregulating USP22 level and maintaining Sirt1 protein expression, thereby exerting a protective role in AS progression in vitro.

Immune proteins C1q and CD47 may contribute to aberrant microglia-mediated synapse loss in the aging monkey brain that is associated with cognitive impairment.

Cognitive impairment in learning, memory, and executive function occurs in normal aging even in the absence of Alzheimer's disease (AD). While neurons do not degenerate in humans or monkeys free of AD, there are structural changes including synapse loss and dendritic atrophy, especially in the dorsolateral prefrontal cortex (dlPFC), and these correlate with cognitive age-related impairment. Developmental studies revealed activity-dependent neuronal properties that lead to synapse remodeling by microglia. Microglia-mediated phagocytosis that may eliminate synapses is regulated by immune "eat me" and "don't eat me" signaling proteins in an activity-dependent manner, so that less active synapses are eliminated. Whether this process contributes to age-related synapse loss remains unknown. The present study used a rhesus monkey model of normal aging to investigate the balance between the "eat me" signal, complement component C1q, and the "don't eat me" signal, transmembrane glycoprotein CD47, relative to age-related synapse loss in dlPFC Area 46. Results showed an age-related elevation of C1q and reduction of CD47 at PSD95+ synapses that is associated with cognitive impairment. Additionally, reduced neuronal CD47 RNA expression was found, indicating that aged neurons were less able to produce the protective signal CD47. Interestingly, microglia do not show the hypertrophic morphology indicative of phagocytic activity. These findings suggest that in the aging brain, changes in the balance of immunologic proteins give microglia instructions favoring synapse elimination of less active synapses, but this may occur by a process other than classic phagocytosis such as trogocytosis.

Responses of multifunctional immune complement component 1q (C1q) and apoptosis-related genes in Macrophthalmus japonicus tissues and human cells following exposure to environmental pollutants.

Apoptosis is a key defense process for multiple immune system functions, playing a central role in maintaining homeostasis and cell development. The purpose of this study was to evaluate the effects of environmental pollutant exposure on immune-related apoptotic pathways in crab tissues and human cells. To do this, we characterized the multifunctional immune complement component 1q (C1q) gene and analyzed C1q expression in Macrophthalmus japonicus crabs after exposure to di(2-ethylhexyl) phthalate (DEHP) or hexabromocyclododecanes (HBCDs). Moreover, the responses of apoptotic signal-related genes were observed in M. japonicus tissues and human cell lines (HEK293T and HCT116). C1q gene expression was downregulated in the gills and hepatopancreas of M. japonicus after exposure to DEHP or HBCD. Pollutant exposure also increased antioxidant enzyme activities and altered transcription of 15 apoptotic signaling genes in M. japonicus. However, patterns in apoptotic signaling in response to these pollutants differed in human cells. HBCD exposure generated an apoptotic signal (cleaved caspase-3) and inhibited cell growth in both cell lines, whereas DEHP exposure did not produce such a response. These results suggest that exposure to environmental pollutants induced different levels of immune-related apoptosis depending on the cell or tissue type and that this induction of apoptotic signaling may trigger an initiation of carcinogenesis in M. japonicus and in humans as consumers.

Influence of complement protein C1q or complement receptor C5aR1 on gut microbiota composition in wildtype and Alzheimer's mouse models.

The contribution of the gut microbiome to neuroinflammation, cognition, and Alzheimer's disease progression has been highlighted over the past few years. Additionally, inhibition of various components of the complement system has repeatedly been demonstrated to reduce neuroinflammation and improve cognitive performance in AD mouse models. Whether the deletion of these complement components is associated with distinct microbiome composition, which could impact neuroinflammation and cognitive performance in mouse models has not yet been examined. Here, we provide a comprehensive analysis of conditional and constitutive knockouts, pharmacological inhibitors, and various housing paradigms for the animal models and wild-type controls at various ages. We aimed to determine the impact of C1q or C5aR1 inhibition on the microbiome in the Arctic and Tg2576 mouse models of AD, which develop amyloid plaques at different ages and locations. Analysis of fecal samples from WT and Arctic mice following global deletion of C1q demonstrated significant alterations to the microbiomes of Arctic but not WT mice, with substantial differences in abundances of Erysipelotrichales, Clostridiales and Alistipes. While no differences in microbiome diversity were detected between cohoused wildtype and Arctic mice with or without the constitutive deletion of the downstream complement receptor, C5aR1, a difference was detected between the C5aR1 sufficient (WT and Arctic) and deficient (C5ar1KO and ArcticC5aR1KO) mice, when the mice were housed segregated by C5aR1 genotype. However, cohousing of C5aR1 sufficient and deficient wildtype and Arctic mice resulted in a convergence of the microbiomes and equalized abundances of each identified order and genus across all genotypes. Similarly, pharmacologic treatment with the C5aR1 antagonist, PMX205, beginning at the onset of beta-amyloid plaque deposition in the Arctic and Tg2576 mice, demonstrated no impact of C5aR1 inhibition on the microbiome. This study demonstrates the importance of C1q in microbiota homeostasis in neurodegenerative disease. In addition, while demonstrating that constitutive deletion of C5aR1 can significantly alter the composition of the fecal microbiome, these differences are not present when C5aR1-deficient mice are cohoused with C5aR1-sufficient animals with or without the AD phenotype and suggests limited if any contribution of the microbiome to the previously observed prevention of cognitive and neuronal loss in the C5aR1-deficient AD models.

TREM2 receptor protects against complement-mediated synaptic loss by binding to complement C1q during neurodegeneration.

Triggering receptor expressed on myeloid cells 2 (TREM2) is strongly linked to Alzheimer's disease (AD) risk, but its functions are not fully understood. Here, we found that TREM2 specifically attenuated the activation of classical complement cascade via high-affinity binding to its initiator C1q. In the human AD brains, the formation of TREM2-C1q complexes was detected, and the increased density of the complexes was associated with lower deposition of C3 but higher amounts of synaptic proteins. In mice expressing mutant human tau, Trem2 haploinsufficiency increased complement-mediated microglial engulfment of synapses and accelerated synaptic loss. Administration of a 41-amino-acid TREM2 peptide, which we identified to be responsible for TREM2 binding to C1q, rescued synaptic impairments in AD mouse models. We thus demonstrate a critical role for microglial TREM2 in restricting complement-mediated synaptic elimination during neurodegeneration, providing mechanistic insights into the protective roles of TREM2 against AD pathogenesis.

Long-term voluntary exercise inhibited AGE/RAGE and microglial activation and reduced the loss of dendritic spines in the hippocampi of APP/PS1 transgenic mice.

Alzheimer's disease (AD) is closely related to hippocampal synapse loss, which can be alleviated by running exercise. However, further studies are needed to determine whether running exercise reduces synapse loss in the hippocampus in an AD model by regulating microglia. Ten-month-old male wild-type mice and APP/PS1 mice were randomly divided into control and running groups. All mice in the running groups were subjected to voluntary running exercise for four months. After the behavioral tests, immunohistochemistry, stereological methods, immunofluorescence staining, 3D reconstruction, western blotting and RNA-Seq were performed. Running exercise improved the spatial learning and memory abilities of APP/PS1 mice and increased the total number of dendritic spines, the levels of the PSD-95 and Synapsin Ia/b proteins, the colocalization of PSD-95 and neuronal dendrites (MAP-2) and the number of PSD-95-contacting astrocytes (GFAP) in the hippocampi of APP/PS1 mice. Moreover, running exercise reduced the relative expression of CD68 and Iba-1, the number of Iba-1+ microglia and the colocalization of PSD-95 and Iba-1+ microglia in the hippocampi of APP/PS1 mice. The RNA-Seq results showed that some differentially expressed genes (DEGs) related to the complement system (Cd59b, Serping1, Cfh, A2m, and Trem2) were upregulated in the hippocampi of APP/PS1 mice, while running exercise downregulated the C3 gene. At the protein level, running exercise also reduced the expression of advanced glycation end products (AGEs), receptor for advanced glycation end products (RAGE), C1q and C3 in the hippocampus and AGEs and RAGE in hippocampal microglia in APP/PS1 mice. Furthermore, the Col6a3, Scn5a, Cxcl5, Tdg and Clec4n genes were upregulated in the hippocampi of APP/PS1 mice but downregulated after running, and these genes were associated with the C3 and RAGE genes according to protein-protein interaction (PPI) analysis. These findings indicate that long-term voluntary exercise might protect hippocampal synapses and affect the function and activation of microglia, the AGE/RAGE signaling pathway in microglia and the C1q/C3 complement system in the hippocampus in APP/PS1 mice, and these effects may be related to the Col6a3, Scn5a, Cxcl5, Tdg and Clec4n genes. The current results provide an important basis for identifying targets for the prevention and treatment of AD.

Effect of avian influenza virus subtype H9N2 on the expression of complement-associated genes in chicken erythrocytes.

1. The H9N2 subtype avian influenza virus can infect both chickens and humans. Previous studies have reported a role for erythrocytes in immunity. However, the role of H9N2 against chicken erythrocytes and the presence of complement-related genes in erythrocytes has not been studied. This research investigated the effect of H9N2 on complement-associated gene expression in chicken erythrocytes.2. The expression of complement-associated genes (C1s, C1q, C2, C3, C3ar1, C4, C4a, C5, C5ar1, C7, CD93 and CFD) was detected by reverse transcription-polymerase chain reaction (RT-PCR). Quantitative Real-Time PCR (qRT-PCR) was used to analyse the differential expression of complement-associated genes in chicken erythrocytes at 0 h, 2 h, 6 h and 10 h after the interaction between H9N2 virus and chicken erythrocytes in vitro and 3, 7 and 14 d after H9N2 virus nasal infection of chicks.3. Expression levels of C1q, C4, C1s, C2, C3, C5, C7 and CD93 were significantly up-regulated at 2 h and significantly down-regulated at 10 h. Gene expression levels of C1q, C3ar1, C4a, CFD and C5ar1 were seen to be different at each time point. The expression levels of C1q, C4, C1s, C2, C3, C5, C7, CFD, C3ar1, C4a and C5ar1 were significantly up-regulated at 7 d and the gene expression of levels of C3, CD93 and C5ar1 were seen to be different at each time point.4. The results confirmed that all the complement-associated genes were expressed in chicken erythrocytes and showed the H9N2 virus interaction with chicken erythrocytes and subsequent regulation of chicken erythrocyte complement-associated genes expression. This study reported, for the first time, the relationship between H9N2 and complement system of chicken erythrocytes, which will provide a foundation for further research into the prevention and control of H9N2 infection.

The neuronal pentraxin Nptx2 regulates complement activity and restrains microglia-mediated synapse loss in neurodegeneration.

Complement overactivation mediates microglial synapse elimination in neurological diseases such as Alzheimer's disease (AD) and frontotemporal dementia (FTD), but how complement activity is regulated in the brain remains largely unknown. We identified that the secreted neuronal pentraxin Nptx2 binds complement C1q and thereby regulates its activity in the brain. Nptx2-deficient mice show increased complement activity, C1q-dependent microglial synapse engulfment, and loss of excitatory synapses. In a neuroinflammation culture model and in aged TauP301S mice, adeno-associated virus (AAV)-mediated neuronal overexpression of Nptx2 was sufficient to restrain complement activity and ameliorate microglia-mediated synapse loss. Analysis of human cerebrospinal fluid (CSF) samples from a genetic FTD cohort revealed reduced concentrations of Nptx2 and Nptx2-C1q protein complexes in symptomatic patients, which correlated with elevated C1q and activated C3. Together, these results show that Nptx2 regulates complement activity and microglial synapse elimination in the brain and that diminished Nptx2 concentrations might exacerbate complement-mediated neurodegeneration in patients with FTD.

Gene polymorphisms within regions of complement component C1q in HIV associated preeclampsia.

OBJECTIVE: This study investigates the association of C1q gene (rs292001 and rs294183) polymorphisms in HIV infected and uninfected preeclamptic women of African ancestry. MATERIALS AND METHODS: The study population consisted of 325 pregnant women of African ancestry grouped into 145 normotensive pregnant women (72 HIV uninfected normotensive, 73 HIV infected normotensive) and 180 preeclamptic pregnant women (103 HIV uninfected preeclamptics, 77 HIV infected preeclamptics). Preeclamptic pregnant women were further sub-grouped into 79 early-onset preeclampsia (EOPE) (40 HIV uninfected EOPE, 39 HIV infected EOPE) and 101 late-onset preeclampsia (LOPE) (63 HIV uninfected LOPE, 38 HIV infected LOPE). Genotyping of complement C1q gene polymorphisms (rs292001 and rs294183) was detected using a TaqMan® SNP Genotyping assay from purified DNA. RESULTS: No significant differences in allelic and genotype frequencies of rs292001 and rs294183 between preeclamptic and normotensive women were observed. Likewise, there were no significant differences in allelic and genotype frequencies between HIV infected normotensive vs HIV infected preeclampsia and HIV uninfected normotensive vs HIV uninfected preeclampsia for both SNPs. However, the odds ratio of preeclamptic women having the GA genotype was 1:2. CONCLUSION: We demonstrate that SNPs of the C1q gene (rs292001 and rs294183) are not associated with the pathogenesis of PE development in women of African ancestry. The role ofC1qrs292001 heterozygous GA is highlighted (with and without HIV infection) may affect susceptibility to PE development. Notably, this dysregulation may affect C1q translation and protein output thus influencing the downstream role of the complement system and functional immunology in HIV infection comorbid with PE.

The complement system and human autoimmune diseases.

Genetic deficiencies of early components of the classical complement activation pathway (especially C1q, r, s, and C4) are the strongest monogenic causal factors for the prototypic autoimmune disease systemic lupus erythematosus (SLE), but their prevalence is extremely rare. In contrast, isotype genetic deficiency of C4A and acquired deficiency of C1q by autoantibodies are frequent among patients with SLE. Here we review the genetic basis of complement deficiencies in autoimmune disease, discuss the complex genetic diversity seen in complement C4 and its association with autoimmune disease, provide guidance as to when clinicians should suspect and test for complement deficiencies, and outline the current understanding of the mechanisms relating complement deficiencies to autoimmunity. We focus primarily on SLE, as the role of complement in SLE is well-established, but will also discuss other informative diseases such as inflammatory arthritis and myositis.

An integrative analysis of single-cell and bulk transcriptome and bidirectional mendelian randomization analysis identified C1Q as a novel stimulated risk gene for Atherosclerosis.

Background: The role of complement component 1q (C1Q) related genes on human atherosclerotic plaques (HAP) is less known. Our aim is to establish C1Q associated hub genes using single-cell RNA sequencing (scRNA-seq) and bulk RNA analysis to diagnose and predict HAP patients more effectively and investigate the association between C1Q and HAP (ischemic stroke) using bidirectional Mendelian randomization (MR) analysis. Methods: HAP scRNA-seq and bulk-RNA data were download from the Gene Expression Omnibus (GEO) database. The C1Q-related hub genes was screened using the GBM, LASSO and XGBoost algorithms. We built machine learning models to diagnose and distinguish between types of atherosclerosis using generalized linear models and receiver operating characteristics (ROC) analyses. Further, we scored the HALLMARK_COMPLEMENT signaling pathway using ssGSEA and confirmed hub gene expression through qRT-PCR in RAW264.7 macrophages and apoE-/- mice. Furthermore, the risk association between C1Q and HAP was assessed through bidirectional MR analysis, with C1Q as exposure and ischemic stroke (IS, large artery atherosclerosis) as outcomes. Inverse variance weighting (IVW) was used as the main method. Results: We utilized scRNA-seq dataset (GSE159677) to identify 24 cell clusters and 12 cell types, and revealed seven C1Q associated DEGs in both the scRNA-seq and GEO datasets. We then used GBM, LASSO and XGBoost to select C1QA and C1QC from the seven DEGs. Our findings indicated that both training and validation cohorts had satisfactory diagnostic accuracy for identifying patients with HPAs. Additionally, we confirmed SPI1 as a potential TF responsible for regulating the two hub genes in HAP. Our analysis further revealed that the HALLMARK_COMPLEMENT signaling pathway was correlated and activated with C1QA and C1QC. We confirmed high expression levels of C1QA, C1QC and SPI1 in ox-LDL-treated RAW264.7 macrophages and apoE-/- mice using qPCR. The results of MR indicated that there was a positive association between the genetic risk of C1Q and IS, as evidenced by an odds ratio (OR) of 1.118 (95%CI: 1.013-1.234, P = 0.027). Conclusion: The authors have effectively developed and validated a novel diagnostic signature comprising two genes for HAP, while MR analysis has provided evidence supporting a favorable association of C1Q on IS.

Complement C1s deficiency in a male Caucasian patient with systemic lupus erythematosus: a case report.

Deficiencies of the early complement components of the classical pathway (CP) are well-documented in association with systemic lupus erythematosus (SLE) or SLE-like syndromes and severe pyogenic infections. Among these, complete C1s deficiency has been reported in nine cases so far. Here, we describe a 34-year-old male patient who presented with severe, recurrent infections since childhood, including meningitides with pneumococci and meningococci, erysipelas, subcutaneous abscess, and recurrent infections of the upper airways. The patient also exhibited adult-onset SLE, meeting 7/11 of the ACR criteria and 34 of the 2019 EULAR/ACR classification criteria, along with class IV-G (A) proliferative lupus nephritis (LN). A screening of the complement cascade showed immeasurably low CH50, while the alternative pathway (AP) function was normal. Subsequent determination of complement components revealed undetectable C1s with low levels of C1r and C1q, normal C3, and slightly elevated C4 and C2 concentrations. The patient had no anti-C1q antibodies. Renal biopsy showed class IV-G (A) LN with complement C1q positivity along the glomerular basement membranes (GBMs) and weak deposition of IgG, IgM, and complement C3 and C4 in the mesangium and GBM. In an ELISA-based functional assay determining C4d deposition, the patient's absent complement activity was fully restored by adding C1s. The genome of the patient was analyzed by whole genome sequencing showing two truncating variants in the C1S gene. One mutation was located at nucleotide 514 in exon 5, caused by a nucleotide substitution from G to T, resulting in a nonsense mutation from Gly172 (p.Gly172*). The other mutation was located at nucleotide 750 in exon 7, where C was replaced by a G, resulting in a nonsense mutation from Tyr250 (p.Tyr250*). Both mutations create a premature stop codon and have not previously been reported in the literature. These genetic findings, combined with the absence of C1s in the circulation, strongly suggest a compound heterozygote C1s deficiency in our patient, without additional defect within the complement cascade. As in a previous C1s deficiency case, the patient responded well to rituximab. The present case highlights unanswered questions regarding the CP's role in SLE etiopathogenesis.

Exenatide increases CTRP3 gene expression in adipose cells by inhibiting adipogenesis and induces apoptosis.

Considering the rapidly increasing prevalence of obesity worldwide, the number of weight control drugs is very few. Incretin-based therapies are currently being developed to achieve weight control, and Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RA) are used in incretin-based therapies. This study aimed to investigate the cytotoxicity of exenatide, a GLP-1A, on 3T3-L1 adipocytes and the effect of exenatide on the expression of adipogenesis-related genes, insulin and glucose levels, and apoptosis. Cytotoxic activity of exenatide on 3T3-L1 adipocytes was determined by MTT method. Gene expression levels were determined by qPCR. Apoptosis studies were performed on the Muse Cell Analyzer. C1q/TNF-related protein-3 (CTRP3) expression levels were found to be higher in exenatide treated adipocyte cells than in control cells (p < 0.001). Adipocyte cells treated with exenatide were found to have lower PPAR-γ gene expression levels when compared to control adipocyte cells (p < 0.001). Intracellular insulin (p < 0.001) and glucose levels were higher in 3T3-L1 adipocytes treated with exenatide compared to control adipocyte cells. Total apoptosis increased approximately 1.5 times as a result of exenatide administration. The increase in CTRP3 gene expression, which is thought to be a new biomarker for obesity, and the decrease in PPAR-γ gene expression indicate that exenatide is a promising new pharmacotherapeutic agent in the treatment of obesity by regulating the expression of genes related to adipogenesis and lipogenesis and inducing apoptosis.

Risk variants of obesity associated genes demonstrate BMI raising effect in a large cohort.

Obesity is highly polygenic disease where several genetic variants have been reportedly associated with obesity in different ethnicities of the world. In the current study, we identified the obesity risk or protective association and BMI raising effect of the minor allele of adiponectin, C1Q and collagen domain containing (ADIPOQ), cholesteryl ester transfer protein (CEPT), FTO alpha-ketoglutarate dependent dioxygenase (FTO), leptin (LEP), and leptin receptor (LEPR) genes in a large cohort stratified into four BMI-based body weight categories i.e., normal weight, lean, over-weight, and obese. Based on selected candidate genetic markers, the genotyping of all study subjects was performed by PCR assays, and genotypes and allele frequencies were calculated. The minor allele frequencies (MAFs) of all genetic markers were computed for total and BMI-based body weight categories and compared with MAFs of global and South Asian (SAS) populations. Genetic associations of variants with obesity risk were calculated and BMI raising effect per copy of the minor allele were estimated. The genetic variants with higher MAFs in obese BMI group were; rs2241766 (G = 0.43), rs17817449 (G = 0.54), rs9939609 (A = 0.51), rs1421085 (C = 0.53), rs1558902 (A = 0.63), and rs1137101 (G = 0.64) respectively. All these variants were significantly associated with obesity (OR = 1.03-4.42) and showed a high BMI raising effect (ß = 0.239-0.31 Kg/m2) per copy of the risk allele. In contrast, the MAFs of three variants were higher in lean-normal BMI groups; rs3764261 A = 0.38, rs9941349 T = 0.43, and rs7799039 G = 0.40-0.43). These variants showed obesity protective associations (OR = 0.68-0.76), and a BMI lowering effect per copy of the protective allele (ß = -0.103-0.155 Kg/m2). The rs3764261 variant also showed significant and positive association with lean body mass (OR = 2.38, CI = 1.30-4.34). Overall, we report six genetic variants of ADIPOQ, FTO and LEPR genes as obesity-risk markers and a CETP gene variant as lean mass/obesity protective marker in studied Pakistani cohort.

Neutrophil heterogeneity in complement C1q expression associated with sepsis mortality.

Sepsis is a life-threatening systemic inflammatory condition causing approximately 11 million annual deaths worldwide. Although key hyperinflammation-based organ dysfunctions that drive disease pathology have been recognized, our understanding of the factors that predispose patients to septic mortality is limited. Due to the lack of reliable prognostic measures, the development of appropriate clinical management that improves patient survival remains challenging. Here, we discovered that a subpopulation of CD49chigh neutrophils with dramatic upregulation of the complement component 1q (C1q) gene expression arises during severe sepsis. We further found that deceased septic patients failed to maintain C1q protein expression in their neutrophils, whereas septic survivors expressed higher levels of C1q. In mouse sepsis models, blocking C1q with neutralizing antibodies or conditionally knocking out C1q in neutrophils led to a significant increase in septic mortality. Apoptotic neutrophils release C1q to control their own clearance in critically injured organs during sepsis; thus, treatment of septic mice with C1q drastically increased survival. These results suggest that neutrophil C1q is a reliable prognostic biomarker of septic mortality and a potential novel therapeutic target for the treatment of sepsis.

Terminal complement pathway activation drives synaptic loss in Alzheimer's disease models.

Complement is involved in developmental synaptic pruning and pathological synapse loss in Alzheimer's disease. It is posited that C1 binding initiates complement activation on synapses; C3 fragments then tag them for microglial phagocytosis. However, the precise mechanisms of complement-mediated synaptic loss remain unclear, and the role of the lytic membrane attack complex (MAC) is unexplored. We here address several knowledge gaps: (i) is complement activated through to MAC at the synapse? (ii) does MAC contribute to synaptic loss? (iii) can MAC inhibition prevent synaptic loss? Novel methods were developed and optimised to quantify C1q, C3 fragments and MAC in total and regional brain homogenates and synaptoneurosomes from WT and AppNL-G-F Alzheimer's disease model mouse brains at 3, 6, 9 and 12 months of age. The impact on synapse loss of systemic treatment with a MAC blocking antibody and gene knockout of a MAC component was assessed in Alzheimer's disease model mice. A significant increase in C1q, C3 fragments and MAC was observed in AppNL-G-F mice compared to controls, increasing with age and severity. Administration of anti-C7 antibody to AppNL-G-F mice modulated synapse loss, reflected by the density of dendritic spines in the vicinity of plaques. Constitutive knockout of C6 significantly reduced synapse loss in 3xTg-AD mice. We demonstrate that complement dysregulation occurs in Alzheimer's disease mice involving the activation (C1q; C3b/iC3b) and terminal (MAC) pathways in brain areas associated with pathology. Inhibition or ablation of MAC formation reduced synapse loss in two Alzheimer's disease mouse models, demonstrating that MAC formation is a driver of synapse loss. We suggest that MAC directly damages synapses, analogous to neuromuscular junction destruction in myasthenia gravis.

The Contribution of Complement Protein C1q in COVID-19 and HIV Infection Comorbid with Preeclampsia: A Review.

Dysregulation in component 1q (C1q) levels is associated with weak placental development in preeclampsia (PE). Human immunodeficiency virus infection (HIV-1) triggers the C1q complex, resulting in opsonization of healthy host cells, contributing to their removal, and augmented progression of HIV disease. In coronavirus disease 2019 (COVID-19)-infected patients, the deposition of C1q activates the complement. Considering the paucity of data, this review highlights a significant gap in the potential of C1q in the immunocompromised state of preeclamptic HIV-infected women and COVID-19 infection. In PE, C1q is downregulated; while in antiretroviral treatment-treated HIV/COVID-19 infected patients, C1q is upregulated. It is plausible that C1q is augmented in the triad and may exacerbate severity of disease. This thereby provides a foundation for future intended research which involves the investigation of single nucleotide polymorphism expression of the C1q gene, specifically in these diseases.