British journal of pharmacology
Bode, M;Diemer, JN;Luu, TV;Ehnert, N;Teigeler, T;Wiech, T;Lindenmeyer, MT;Herrnstadt, GR;Bülow, J;Huber, TB;Tomas, NM;Wenzel, UO;
PMID: 37076314 | DOI: 10.1111/bph.16097
Complement activation may drive hypertension through its effects on immunity and tissue integrity.We examined expression of C3, the central protein of the complement cascade, in hypertension.Increased C3 expression was found in kidney biopsies and microdissected glomeruli of patients with hypertensive nephropathy. Renal single cell RNA seq data from normotensive and hypertensive patients confirmed expression of C3 in different cellular compartments of the kidney. In angiotensin II (Ang II) induced hypertension renal C3 expression was upregulated. C3-/- mice revealed a significant lower albuminuria in the early phase of hypertension. However, no difference was found for blood pressure, renal injury (histology, glomerular filtration rate, inflammation) and cardiac injury (fibrosis, weight, gene expression) between C3-/- and wildtype mice after Ang II infusion. Also, in deoxycorticosterone acetate (DOCA) salt hypertension, a significantly lower albuminuria was found in the first weeks of hypertension in C3 deficient mice but no significant difference in renal and cardiac injury. Downregulation of C3 by C3 targeting GalNAc (n-acetylgalactosamine) small interfering RNA (siRNA) conjugate decreased C3 in the liver by 96% and lowered albuminuria in the early phase but showed no effect on blood pressure and endorgan damage. Inhibition of complement C5 by siRNA showed no effect on albuminuria.Increased C3 expression is found in the kidneys of hypertensive mice and men. Genetic and therapeutic knockdown of C3 improved albuminuria in the early phase of hypertension but did not ameliorate arterial blood pressure nor renal and cardiac injury.This article is protected by
Investigative Ophthalmology & Visual Science
Yang, H;Yuan, M;Gaurang, P;Sun, A;
RESULTS : In rodent eye (both rat and mouse), CFH mRNA is strongly expressed in the retinal pigment epithelium with some expression also found in inner nuclear (INL) and retinal ganglion cell (RGC) layers of the retina. C3 mRNA is expressed mainly in RGC, INL of retina, ciliary body, corneal epithelium with some expression is also found in rodent retinal pigment epithelium layer. However, in human eye, CFH and C3 mRNA are strongly expressed in the choroid. Some expression is also found in RGC, INL layer of retina, ONH, sclera, cornea endothelial and stroma; and ciliary body. There is no C3 or CFH signal detected in RPE cells.
King BC, Kulak K, Krus U, Rosberg R, Golec E, Wozniak K, Gomez MF, Zhang E, O'Connell DJ, Renström E, Blom AM.
PMID: - | DOI: 10.1016/j.cmet.2018.09.009
We show here that human pancreatic islets highly express C3, which is both secreted and present in the cytosol. Within isolated human islets, C3 expression correlates with type 2 diabetes (T2D) donor status, HbA1c, and inflammation. Islet C3 expression is also upregulated in several rodent diabetes models. C3 interacts with ATG16L1, which is essential for autophagy. Autophagy relieves cellular stresses faced by β cells during T2D and maintains cellular homeostasis. C3 knockout in clonal β cells impaired autophagy and led to increased apoptosis after exposure of cells to palmitic acid and IAPP. In the absence of C3, autophagosomes do not undergo fusion with lysosomes. Thus, C3 may be upregulated in islets during T2D as a cytoprotective factor against β cell dysfunction caused by impaired autophagy. Therefore, we revealed a previously undescribed intracellular function for C3, connecting the complement system directly to autophagy, with a broad potential importance in other diseases and cell types.
bioRxiv : the preprint server for biology
Wu, M;Zheng, W;Song, X;Bao, B;Wang, Y;Ramanan, D;Yang, D;Liu, R;Macbeth, JC;Do, EA;Andrade, WA;Yang, T;Cho, HS;Gazzaniga, FS;Ilves, M;Coronado, D;Thompson, C;Hang, S;Chiu, IM;Moffitt, JR;Hsiao, A;Mekalanos, JJ;Benoist, C;Kasper, DL;
PMID: 36778396 | DOI: 10.1101/2023.02.02.523770
Canonically, complement is a serum-based host defense system that protects against systemic microbial invasion. Little is known about the production and function of complement components on mucosal surfaces. Here we show gut complement component 3 (C3), central to complement function, is regulated by the composition of the microbiota in healthy humans and mice, leading to host-specific gut C3 levels. Stromal cells in intestinal lymphoid follicles (LFs) are the predominant source of intestinal C3. During enteric infection with Citrobacter rodentium or enterohemorrhagic Escherichia coli, luminal C3 levels increase significantly and are required for protection. C. rodentium is remarkably more invasive to the gut epithelium of C3-deficient mice than of wild-type mice. In the gut, C3-mediated phagocytosis of C. rodentium functions to clear pathogens. Our study reveals that variations in gut microbiota determine individuals†intestinal mucosal C3 levels, dominantly produced by LF stromal cells, which directly correlate with protection against enteric infection.Gut complement component 3 (C3) is induced by the microbiome in healthy humans and mice at a microbiota-specific level.Gut stromal cells located in intestinal lymphoid follicles are a major source of luminal C3 During enteric infections with Citrobacter rodentium or enterohemorrhagic Escherichia coli, gut luminal C3 levels increase and are required for protection. C. rodentium is significantly more invasive of the gut epithelium in C3-deficient mice when compared to WT mice. In the gut, C3-mediated opsonophagocytosis of C. rodentium functions to clear pathogens.
Bourel, J;Planche, V;Dubourdieu, N;Oliveira, A;Séré, A;Ducourneau, EG;Tible, M;Maitre, M;Lesté-Lasserre, T;Nadjar, A;Desmedt, A;Ciofi, P;Oliet, SH;Panatier, A;Tourdias, T;
PMID: 34673149 | DOI: 10.1016/j.nbd.2021.105533
Memory impairment is one of the disabling manifestations of multiple sclerosis (MS) possibly present from the early stages of the disease and for which there is no specific treatment. Hippocampal synaptic dysfunction and dendritic loss, associated with microglial activation, can underlie memory deficits, yet the molecular mechanisms driving such hippocampal neurodegeneration need to be elucidated. In early-stage experimental autoimmune encephalomyelitis (EAE) female mice, we assessed the expression level of molecules involved in microglia-neuron interactions within the dentate gyrus and found overexpression of genes of the complement pathway. Compared to sham immunized mice, the central element of the complement cascade, C3, showed the strongest and 10-fold upregulation, while there was no increase of downstream factors such as the terminal component C5. The combination of in situ hybridization with immunofluorescence showed that C3 transcripts were essentially produced by activated microglia. Pharmacological inhibition of C3 activity, by daily administration of rosmarinic acid, was sufficient to prevent early dendritic loss, microglia-mediated phagocytosis of synapses in the dentate gyrus, and memory impairment in EAE mice, while morphological markers of microglial activation were still observed. In line, when EAE was induced in C3 deficient mice (C3KO), dendrites and spines of the dentate gyrus as well as memory abilities were preserved. Altogether, these data highlight the central role of microglial C3 in early hippocampal neurodegeneration and memory impairment in EAE and, therefore, pave the way toward new neuroprotective strategies in MS to prevent cognitive deficit using complement inhibitors.
Fan, W;Huang, W;Chen, J;Li, N;Mao, L;Hou, S;
PMID: 35403700 | DOI: 10.1111/imm.13479
Microglia, the resident immune cells in the retina and nervous system, make irreplaceable contributions to the maintenance of normal homeostasis and immune surveillance of these systems. Recently, great progress has been made in determining the origin, distribution, features and functions of retinal microglia and in identifying their roles in retinal diseases. In the retinal microenvironment, microglia constantly monitor changes in their surroundings and maintain balanced functions by communicating with other retinal cells. When disturbed, activated microglia may kill degenerated neurons and photoreceptors through phagocytosis and exacerbate retinal injury by producing multiple proinflammatory mediators. Numerous animal studies and in situ analyses of human tissue have shown that retinal microglia are involved in multiple retinal diseases. The functions and mechanisms of activated microglia in retinal disorders are gradually being elucidated. Increasing evidence points towards the dual roles of microglia in the retina and they are regulated by many factors. How to inhibit the detrimental effects of microglia and promote beneficial effects are worth studying. This review focuses primarily on the features and functions of microglia and how they participate in retinal diseases based on existing research findings. We also discuss current opinions about microglial transdifferentiation.
The complement system drives local inflammatory tissue priming by metabolic reprogramming of synovial fibroblasts
Friščić, J;Böttcher, M;Reinwald, C;Bruns, H;Wirth, B;Popp, SJ;Walker, KI;Ackermann, JA;Chen, X;Turner, J;Zhu, H;Seyler, L;Euler, M;Kirchner, P;Krüger, R;Ekici, AB;Major, T;Aust, O;Weidner, D;Fischer, A;Andes, FT;Stanojevic, Z;Trajkovic, V;Herrmann, M;Korb-Pap, A;Wank, I;Hess, A;Winter, J;Wixler, V;Distler, J;Steiner, G;Kiener, HP;Frey, B;Kling, L;Raza, K;Frey, S;Kleyer, A;Bäuerle, T;Hughes, TR;Grüneboom, A;Steffen, U;Krönke, G;Croft, AP;Filer, A;Köhl, J;Klein, K;Buckley, CD;Schett, G;Mougiakakos, D;Hoffmann, MH;
PMID: 33761330 | DOI: 10.1016/j.immuni.2021.03.003
Arthritis typically involves recurrence and progressive worsening at specific predilection sites, but the checkpoints between remission and persistence remain unknown. Here, we defined the molecular and cellular mechanisms of this inflammation-mediated tissue priming. Re-exposure to inflammatory stimuli caused aggravated arthritis in rodent models. Tissue priming developed locally and independently of adaptive immunity. Repeatedly stimulated primed synovial fibroblasts (SFs) exhibited enhanced metabolic activity inducing functional changes with intensified migration, invasiveness and osteoclastogenesis. Meanwhile, human SF from patients with established arthritis displayed a similar primed phenotype. Transcriptomic and epigenomic analyses as well as genetic and pharmacological targeting demonstrated that inflammatory tissue priming relies on intracellular complement C3- and C3a receptor-activation and downstream mammalian target of rapamycin- and hypoxia-inducible factor 1α-mediated metabolic SF invigoration that prevents activation-induced senescence, enhances NLRP3 inflammasome activity, and in consequence sensitizes tissue for inflammation. Our study suggests possibilities for therapeutic intervention abrogating tissue priming without immunosuppression.
Clarke LE, Liddelow SA, Chakraborty C, Münch AE, Heiman M, Barres BA.
PMID: - | DOI: 10.1073/pnas.1800165115
The decline of cognitive function occurs with aging, but the mechanisms responsible are unknown. Astrocytes instruct the formation, maturation, and elimination of synapses, and impairment of these functions has been implicated in many diseases. These findings raise the question of whether astrocyte dysfunction could contribute to cognitive decline in aging. We used the Bac-Trap method to perform RNA sequencing of astrocytes from different brain regions across the lifespan of the mouse. We found that astrocytes have region-specific transcriptional identities that change with age in a region-dependent manner. We validated our findings using fluorescence in situ hybridization and quantitative PCR. Detailed analysis of the differentially expressed genes in aging revealed that aged astrocytes take on a reactive phenotype of neuroinflammatory A1-like reactive astrocytes. Hippocampal and striatal astrocytes up-regulated a greater number of reactive astrocyte genes compared with cortical astrocytes. Moreover, aged brains formed many more A1 reactive astrocytes in response to the neuroinflammation inducer lipopolysaccharide. We found that the aging-induced up-regulation of reactive astrocyte genes was significantly reduced in mice lacking the microglial-secreted cytokines (IL-1α, TNF, and C1q) known to induce A1 reactive astrocyte formation, indicating that microglia promote astrocyte activation in aging. Since A1 reactive astrocytes lose the ability to carry out their normal functions, produce complement components, and release a toxic factor which kills neurons and oligodendrocytes, the aging-induced up-regulation of reactive genes by astrocytes could contribute to the cognitive decline in vulnerable brain regions in normal aging and contribute to the greater vulnerability of the aged brain to injury.
Shih, BB;Brown, SM;Barrington, J;Lefevre, L;Mabbott, NA;Priller, J;Thompson, G;Lawrence, AB;McColl, BW;
PMID: 36120803 | DOI: 10.1002/glia.24274
Microglia play key roles in brain homeostasis as well as responses to neurodegeneration and neuroinflammatory processes caused by physical disease and psychosocial stress. The pig is a physiologically relevant model species for studying human neurological disorders, many of which are associated with microglial dysfunction. Furthermore, pigs are an important agricultural species, and there is a need to understand how microglial function affects their welfare. As a basis for improved understanding to enhance biomedical and agricultural research, we sought to characterize pig microglial identity at genome-wide scale and conduct inter-species comparisons. We isolated pig hippocampal tissue and microglia from frontal cortex, hippocampus, and cerebellum, as well as alveolar macrophages from the lungs and conducted RNA-sequencing (RNAseq). By comparing the transcriptomic profiles between microglia, macrophages, and hippocampal tissue, we derived a set of 239 highly enriched genes defining the porcine core microglial signature. We found brain regional heterogeneity based on 150 genes showing significant (adjusted p < 0.01) regional variations and that cerebellar microglia were most distinct. We compared normalized gene expression for microglia from human, mice and pigs using microglia signature gene lists derived from each species and demonstrated that a core microglial marker gene signature is conserved across species, but that species-specific expression subsets also exist. Our data provide a valuable resource defining the pig microglial transcriptome signature that validates and highlights pigs as a useful large animal species bridging between rodents and humans in which to study the role of microglia during homeostasis and disease.
Brain : a journal of neurology
Lee, MH;Perl, DP;Steiner, J;Pasternack, N;Li, W;Maric, D;Safavi, F;Horkayne-Szakaly, I;Jones, R;Stram, MN;Moncur, JT;Hefti, M;Folkerth, RD;Nath, A;
PMID: 35788639 | DOI: 10.1093/brain/awac151
The underlying mechanisms by which severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leads to acute and long-term neurological manifestations remains obscure. We aimed to characterize the neuropathological changes in patients with coronavirus disease 2019 and determine the underlying pathophysiological mechanisms. In this autopsy study of the brain, we characterized the vascular pathology, the neuroinflammatory changes and cellular and humoral immune responses by immunohistochemistry. All patients died during the first wave of the pandemic from March to July 2020. All patients were adults who died after a short duration of the infection, some had died suddenly with minimal respiratory involvement. Infection with SARS-CoV-2 was confirmed on ante-mortem or post-mortem testing. Descriptive analysis of the pathological changes and quantitative analyses of the infiltrates and vascular changes were performed. All patients had multifocal vascular damage as determined by leakage of serum proteins into the brain parenchyma. This was accompanied by widespread endothelial cell activation. Platelet aggregates and microthrombi were found adherent to the endothelial cells along vascular lumina. Immune complexes with activation of the classical complement pathway were found on the endothelial cells and platelets. Perivascular infiltrates consisted of predominantly macrophages and some CD8+ T cells. Only rare CD4+ T cells and CD20+ B cells were present. Astrogliosis was also prominent in the perivascular regions. Microglial nodules were predominant in the hindbrain, which were associated with focal neuronal loss and neuronophagia. Antibody-mediated cytotoxicity directed against the endothelial cells is the most likely initiating event that leads to vascular leakage, platelet aggregation, neuroinflammation and neuronal injury. Therapeutic modalities directed against immune complexes should be considered.
