Cell-autonomous regulation of complement C3 by factor H limits macrophage efferocytosis and exacerbates atherosclerosis

Target complement factor H / serum amyloid a signaling in trichloroethylene-induced immune kidney injury

The aberrant activation of the intracellular complement system is a significant characteristic of trichloroethylene (TCE) -induced immune kidney injury. However, the specific role of complement factor H (CFH) in this context remains unclear. This study investigates the involvement of CFH / serum amyloid A (SAA1) signaling in TCE-induced immune kidney injury by employing a combination of in vitro experiments and TCE-sensitized mouse model. Proteomic analyses results revealed that TCE-sensitized positive mice exhibited significantly increased expression of acute-phase reactive proteins, abnormal activation of the complement system. The treatment with TNFα and IFNγ-neutralizing antibodies reduced renal vascular endothelial cell injury and kidney damage in TCE-sensitized mice, and the combined treatment of recombinant TNFα and IFNγ reduced CFH intracellular expression but increased extracellular secretion in human renal glomerular endothelial cells (HRGECs). CFH in HRGECs notably protected endothelial barrier function when stimulated by TNFα and IFNγ. Moreover, CFH deficiency can lead to increased SAA1, which interacts with Toll-like receptor-2 (TLR2) to activate nuclear factor-kappaB (NF-κB). This study revealed that the combination of TNFα and IFNγ influences renal vascular endothelial barrier function by regulating the expression and secretion of local CFH. The downregulated intracellular CFH also associated with the inflammatory response in TCE-induced immune kidney injury by regulating the SAA1/TLR2 pathway.

High-fat diet induces pre-eclampsia through dampening cell-autonomous C3 in trophoblasts

Hyperlipidemia contributes to low-grade inflammation and abnormal immune response, which is putatively involved in the development of pre-eclampsia (PE). As components of innate immune system, complements play a critical role in regulating inflammation. However, how cell-autonomous complement changes and works in PE remains elusive. In the current study, we established L-NAME-induced mice to manifest PE-like symptoms. In presence of high-fat diet (HFD) feeding, the PE-like symptoms were considerably aggravated, as well as down-regulated complement C3 in HFD/L-NAME mice trophoblasts. To explore the effect of C3 in PE development, we generated C3 overexpression and knockdown cell (Swan.71C3 and Swan.71ΔC3) based on Swan.71, a trophoblast cell line. We found that Swan.71C3 cells display promoted proliferation, migration and invasion capability and less secretion of anti-angiogenetic cytokines, while Swan.71ΔC3 showed highly-activated NLRP3 inflammasome and pyroptosis, which was also noted in HFD/L-NAME placentas, highlighting the contributing role of inflammation to PE. Indeed, pro-inflammatory cytokines were increased in placentas from HFD/L-NAME mice. The similar trends of C3 in trophoblast from severe PE patients supported the contribution role of C3 to PE pathogenesis. Thus, our study provides evidence that cell-autonomous complement C3 regulates NLRP3 inflammasome activation upon HFD exposure, affecting trophoblast cell function in PE development.

A CD4+ T cell-intrinsic complement C5aR2-prostacyclin-IL-1R2 axis orchestrates Th1 cell contraction

T helper 1 (Th1) cell initiation pathways are well characterized; however, those regulating their contraction are less understood. Here, we define a CD4+ T cell-autonomous pathway in which complement C5 orchestrated a shift from prostaglandin E2 (PGE2) dominance to enhanced prostacyclin (PGI2) production via activation of C5a receptor 2 (C5aR2). This pivot in lipid mediators induced autocrine signaling through the PGI2 receptor and expression of the interleukin-1 (IL-1) decoy IL-1 receptor type 2 (IL-1R2), which sequestered Th1 cell-driving intrinsic IL-1β, facilitating Th1 cell contraction. Disruption of this C5aR2-PGI2-R axis was a hallmark of pathologically persistent Th1 cell activity in inflammatory conditions, including cryopyrin-associated periodic syndromes (CAPS), Crohn's disease, and rheumatoid arthritis. Rebalancing this axis through selective PGE2 synthase inhibition rectified the hyperactive Th1 cell phenotype in vitro in T cells from individuals with CAPS. Therefore, complement is a key controller of prostanoid metabolism, and the latter is an intrinsic-and potentially druggable-checkpoint for the cessation of Th1 cell effector responses.

The 4 functional segments of Factor H: Role in physiological target recognition and contribution to disease

Factor H controls proximal complement activation, and its dysfunction leads to diseases that often manifest in the kidney. Structural and functional analyses have identified 4 distinct functional segments: an N-terminal regulatory unit, a cell binding unit, a segment with combined low-affinity C3b and heparin sites, and a C-terminal recognition or sensor unit with overlapping C3b/C3d and heparin sites. Three segments are linked to diseases. The regulatory segment is affected in C3 glomerulopathy and antineutrophil cytoplasmic antibody-associated vasculitis. The second segment includes the Y402H polymorphism of age-related macular degeneration, is associated with different types of cancer, and is targeted by pathogens. The C-terminal sensor segment is involved in atypical hemolytic uremic syndrome, in FHR1:FHR3 deficient and autoantibody-positive hemolytic uremic syndrome form and is exploited by pathogens. Factor H function is modulated by Factor H like protein 1 and FHR1, 2 plasma proteins that share segments with Factor H. This interplay is critical for fine-tuning local complement. Understanding Factor H's physiological role, as well as the impact of its absence, mutations, or autoantibody targeting, provides insights into disease mechanisms and provides opportunities for therapeutic intervention by using full-length Factor H, its fragments, or complement-modulatory compounds.

Enhancing Tendon Regeneration: Investigating the Impact of Topography on the Secretome of Adipose-Derived Stem Cells

Tendons are vital for maintaining integrity and movement, but current treatment options are insufficient for their regeneration after injuries. Previous studies have shown that the secretome from mesenchymal stem cells (MSCs) promoted tendon regeneration. However, limited studies have explored the impact of the physical microenvironment on the secretome's efficacy of MSCs. In this study, it is shown that the topographic orientation regulates the secretome of human adipose-derived stem cells (ADSCs) and promotes tendon regeneration. Conditioned medium (CM) is collected from ADSCs cultured on the scaffolds with different topography. The results show that CM generated from aligned structure group has a potent effect in promoting cell migration and proliferation, tenogenic differentiation, macrophage polarization toward M2 phenotype, tendon structure and mechanical function recovery. Proteomic analysis revealed that the aligned structure can up-regulate the secretion of Extracellular matrix (ECM) proteins while down-regulate proinflammatory factors. This modulation activates the MAPK, GPCR and Integrin signaling pathways which may account for the enhanced effect on tendon regeneration. This study offers a promising and safer non-cell-based treatment option for tendon repair.

Huoxue Tongluo tablet enhances atherosclerosis efferocytosis by promoting the differentiation of Trem2+ macrophages via PPARγ signaling pathway

BACKGROUND

Atherosclerosis (AS) serves as the primary pathological basis for various cardiovascular and cerebrovascular diseases. Impaired efferocytosis by macrophages within AS plaques exacerbates lipid metabolism disorders and inflammatory responses. Huoxue Tongluo Tablet (HXTL), a traditional Chinese medicine formula, has shown efficacy in treating AS and modulating macrophage function. However, its underlying mechanisms remain unclear. It is hypothesized that HXTL ameliorates AS by enhancing macrophage efferocytosis.

PURPOSE

To assess the efficacy and mechanisms of HXTL in treating AS at the single-cell level.

METHODS

Ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) was used to analyze the constituents of HXTL. HXTL was administered to ApoE⁻/⁻ mice maintained on a high-fat diet. The progression of AS was evaluated by measuring atherosclerotic plaque area, necrotic core formation, collagen depletion, lipid accumulation, lipid profiles, pro-inflammatory mediators, and oxidative stress markers. Transcriptomic analysis was performed to explore the mechanisms underlying the therapeutic effects of HXTL on AS. Efferocytosis-related marker expression was evaluated using immunohistochemistry and quantitative PCR (qPCR), and the efferocytosis index was determined by the co-localization of apoptotic cells and macrophages. Efferocytosis inhibition was induced using Cytochalasin D. Single-cell sequencing was utilized to investigate alterations in Trem2⁺ macrophages following HXTL treatment. Trem2 expression was accessed by immunohistochemistry and qPCR, while flow cytometry and immunofluorescence staining confirmed the changes in Trem2⁺ macrophages. Bioinformatic analyses were conducted to investigate the mechanism through which HXTL enhances efferocytosis by regulating Trem2⁺ macrophage subsets. Western blotting and qPCR were used to assess the expression levels of PPARγ signaling, and the regulatory role of PPARγ signaling in macrophage subpopulation generation and efferocytosis function was accessed using GW9662.

RESULTS

UPLC-MS/MS analysis identified 99 major components in HXTL. In vivo, medium and high doses of HXTL significantly reduced atherosclerotic plaque area, improved lipid profiles, decreased pro-inflammatory mediators and reactive oxygen species (ROS), and enhanced the efferocytosis function. Inhibition of efferocytosis reversed these beneficial effects. Single-cell sequencing and in vivo validation revealed that HXTL upregulated Trem2⁺ macrophages and efferocytosis-related genes. Bioinformatics and in vivo experiments demonstrated that HXTL activated PPARγ signaling, and inhibition of PPARγ signaling negated the pro-efferocytosis effects and the upregulation of Trem2⁺ macrophage upregulation induced by HXTL.

CONCLUSIONS

HXTL activates the PPARγ pathway, upregulates Trem2⁺ macrophages, and enhances macrophage efferocytosis, thereby ameliorating AS. This study is the first to demonstrate the regulatory effects of HXTL on macrophage subpopulations and its pro-efferocytosis activity.

Microenvironments‐Targeted Nanomaterials for Atherosclerosis Therapy

Atherosclerosis significantly contributes to cardiovascular disease. Traditional treatments for atherosclerosis, such as pharmacological interventions and surgical procedures, have demonstrated limited efficacy and often yield unsatisfactory results. Consequently, safe and effective therapeutic strategies are urgently needed. The atherosclerotic microenvironments, characterized by inflammation driven by foam cells, damaged endothelial cells, recruited leukocytes, lipoproteins, and inflammatory mediators, play a key role in disease progression. By leveraging the biological components and physicochemical properties of these microenvironments, researchers have developed microenvironments‐targeted nanomaterials as a promising approach to treat atherosclerosis. These nanomaterials aim to address and eliminate inflammatory processes. Their functions include repairing endothelial damage, reducing lipoprotein accumulation, inhibiting leukocyte chemotaxis, suppressing foam cell formation, delaying plaque rupture, and preventing thrombosis within the plaque. This review highlights the therapeutic mechanisms and effects of nanomaterials targeting key processes in atherosclerotic microenvironments. Finally, the challenges and prospects of nanomaterial‐based therapies for atherosclerosis are discussed to inspire the development of nanomaterials that modulate atherosclerotic microenvironments, potentially leading to promising clinical applications.

Inside job: Roles of intracellular C3

Our understanding of the complement system continues to grow beyond that of a liver-derived systemically operative mechanism of pathogen clearance to a central orchestrator of single-cell behavior and tissue biology. These expanded activities reflect the extrahepatic and local production of complement by many, if not most, cells, and the unexpected recent finding that complement also serves important physiological intracellular roles. The complement core component C3 has emerged as a particularly critical player in basic cell functions. Here, we provide an overview of the currently known forms and functions of intracellular C3 and the mechanisms that control it. We also discuss 2 emerging concepts as potential key areas for future exploration: intracellular C3 as a second layer of pathogen defense at host-environmental interfaces and "C3 licensing." We conclude by suggesting that the potential clinical implications surrounding perturbations in intracellular C3 activities should be explored better.

Immune checkpoint inhibitor induces cardiac injury by impairing efferocytosis of macrophages via MerTK cleavage

Cancer immunotherapy is a well-established therapeutic approach for various types of cancer. However, its clinical utility is usually limited by cardiovascular adverse events. Immune Checkpoint Inhibitors (ICIs) can induce diverse forms of cardiotoxicity, with myocarditis being the most fatal complication. The underlying mechanism of its occurrence remains elusive. Therefore, this study aims to elucidate the impact of programmed death-1 (PD-1) inhibitor on myocarditis development in mice. Myeloid-epithelial-reproductive tyrosine kinase (MerTK) receptors, located on the surface of macrophages, play a pivotal role in phagocytic regulation. We established a mouse model of autoimmune myocarditis by injecting 6-week-old normal male BALB/c mice with PD-1 inhibitor and cardiac troponin I peptide fragments, which resulted in elevated levels of serum soluble MerTK (SolMer) and reduced numbers of MerTK-CD68 double-positive macrophages, accompanied by cardiac injury in mice. In vitro, PD-1 inhibitor promotes a disintegrin and metalloproteinase17 (ADAM17)-mediated shed of the MerTK, forming SolMer, through MKK3/P38 MAPK pathway, leading to downregulation of MerTK expression on the macrophage surface. This results in the inhibition of efferocytosis and impairment of tissue repair function, ultimately contributing to myocarditis development. TAPI-0 inhibited the activity of ADAM17, while SB203580 inhibited the phosphorylation of P38 MAPK. Both inhibitors effectively restored the inhibition of efferocytosis induced by the PD-1 inhibitor. In vitro, when the PD-1 receptor on the surface of RAW264.7 macrophages was knocked down and then stimulated with a PD-1 inhibitor, no further significant alterations in the pathway were elicited. In conclusion, the PD-1 inhibitor induces the shedding of MerTK in macrophages by binding to the PD-1 receptor on the surface of macrophages and activating the MKK3/P38 MAPK/ADAM17 pathway, leading to impaired efferocytosis. Elucidation of this molecular mechanism holds promise for improved prognosis and therapeutic strategies in cancer patients.

A New Insight on Atherosclerosis Mechanism and Lipid-Lowering Drugs

Atherosclerosis (AS) is a chronic vascular disease primarily affecting large and medium-sized arteries, involving complex pathological mechanisms such as inflammatory responses, lipid metabolism disorders and vascular plaque formation. In recent years, several emerging research hotspots have appeared in the field of atherosclerosis, including gut microbiota, pyroptosis, ferroptosis, autophagy, cuproptosis, exosomes and non-coding RNA. Traditional lipid-lowering drugs play a crucial role in the treatment of AS but are not able to significantly reverse the pathological changes. This article aims to summarize the latest research progress in the pathogenesis of AS and the diagnosis and treatment of the disease by comprehensively analyzing relevant literature mainly from the past five years. Additionally, the mechanisms of action and research advances of statins, cholesterol absorption inhibitors, fibrates and novel lipid-lowering drugs are reviewed to provide new insights into the diagnosis and treatment of AS.

Effects of Brown Algae (Laminaria japonica) Extract on Growth Performance, Immune Function and Intestinal Health of Largemouth Bass (Micropterus salmoides)

This study used largemouth bass (initial average weight: 33.33 ± 1.8 g) to explore the effects of adding different brown algae extracts to feed on the fish's growth, immunity and intestinal health. Six groups were set up: a control (Group A), 0.1% sodium alginate (Group B), 0.1% oligotriosaccharide I (Group C), 0.1% oligotriosaccharide II (Group D), 0.2% brown algae powder (Group E) and 0.2% brown algae powder enzymatic product (Group F), with three replicates of 35 fish each, and a 56-day feeding experiment. Results: Compared to Group A, Groups C, D and F had a higher specific growth rate and lower feed coefficient (p < 0.05). Group D had enhanced serum SOD activity; Group F had increased antioxidant enzyme activity and decreased MDA content (p < 0.05). All experimental groups had higher serum LZM levels (p < 0.05), with no IgM difference (p > 0.05). In the intestine, treatment groups had higher α-amylase activity (p < 0.05) and no lipase difference (p > 0.05), and Groups C, D and F had higher trypsin activity (p < 0.05). Group F had the tallest villi, Group B had the thickest muscular layer (p < 0.05), and villus width was similar among groups (p > 0.05). The experimental groups had fewer intestinal pathogenic bacteria, and Group F had improved intestinal microorganism diversity and richness (p < 0.05). In conclusion, adding 0.1% oligotriosaccharide and 0.2% brown algae powder enzymatic product to feed can promote largemouth bass growth, antioxidant capacity and immunity. The 0.2% brown algae powder enzymatic product is better for intestinal development and flora improvement.

The Interplay Between Immunity, Inflammation and Endothelial Dysfunction

The endothelium is pivotal in multiple physiological processes, such as maintaining vascular homeostasis, metabolism, platelet function, and oxidative stress. Emerging evidence in the past decade highlighted the immunomodulatory function of endothelium, serving as a link between innate, adaptive immunity and inflammation. This review examines the regulation of the immune-inflammatory axis by the endothelium, discusses physiological immune functions, and explores pathophysiological processes leading to endothelial dysfunction in various metabolic disturbances, including hyperglycemia, obesity, hypertension, and dyslipidaemia. The final section focuses on the novel, repurposed, and emerging therapeutic targets that address the immune-inflammatory axis in endothelial dysfunction.

Macrophages Unmasked: Their Pivotal Role in Driving Atherosclerosis in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that significantly increases the risk of cardiovascular diseases, particularly atherosclerosis (AS). Understanding the shared pathogenic mechanisms underlying SLE and AS is crucial for developing effective therapeutic strategies. Macrophages, as pivotal immune cells, play a critical role in the initiation and progression of atherosclerotic plaques within the context of SLE. This review delves into the molecular and cellular mechanisms governing macrophage activation and differentiation in response to SLE-related inflammatory mediators, highlighting their roles in lipid metabolism, plaque stability, and immune regulation. Additionally, we discussed the current treatment modalities for SLE and their impact on macrophage functionality, exploring these effects for atherosclerotic progression. By elucidating the intricate relationship between macrophages, SLE pathophysiology, and AS progression, this review underscores the need for a multidisciplinary approach in managing SLE and its cardiovascular complications, aiming to improve patient survival and quality of life through tailored therapeutic interventions addressing both autoimmune and cardiovascular pathologies.

Complement factor H drives idiopathic pulmonary fibrosis by autocrine C3 regulation, suppressing macrophage phagocytosis and enhancing fibrotic progression

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease with limited therapeutic options. In this study, we identified Complement Factor H (CFH) as a critical regulator in the pathogenesis of IPF, contributing to fibrotic progression through autocrine regulation of complement component C3 and suppression of macrophage phagocytosis. Transcriptomic analysis of IPF lung tissues revealed upregulation of CFH and enrichment of pro-fibrotic pathways, including M2 macrophage infiltration. Weighted Gene Co-expression Network Analysis (WGCNA) and machine learning further validated CFH as a key gene associated with macrophage polarization and fibrotic remodeling. Functional studies demonstrated that CFH deficiency in mouse models attenuated bleomycin-induced pulmonary fibrosis, as evidenced by reduced collagen deposition, improved lung function, and decreased macrophage infiltration. Mechanistically, CFH deficiency enhanced macrophage efferocytosis and autophagy, reducing macrophage-mediated inflammation and fibrosis. Moreover, siRNA-loaded liposomes targeting CFH mitigated pulmonary fibrosis in vivo, further supporting the therapeutic potential of CFH modulation. These findings highlight CFH as a promising therapeutic target for IPF and underscore the importance of complement regulation in macrophage-driven fibrosis.

Efferocytosis: the resolution of inflammation in cardiovascular and cerebrovascular disease

Cardiovascular and cerebrovascular diseases have surpassed cancer as significant global health challenges, which mainly include atherosclerosis, myocardial infarction, hemorrhagic stroke and ischemia stroke. The inflammatory response immediately following these diseases profoundly impacts patient prognosis and recovery. Efficient resolution of inflammation is crucial not only for halting the inflammatory process but also for restoring tissue homeostasis. Efferocytosis, the phagocytic clearance of dying cells by phagocytes, especially microglia and macrophages, plays a critical role in this resolution process. Upon tissue injury, phagocytes are recruited to the site of damage where they engulf and clear dying cells through efferocytosis. Efferocytosis suppresses the secretion of pro-inflammatory cytokines, stimulates the production of anti-inflammatory cytokines, modulates the phenotype of microglia and macrophages, accelerates the resolution of inflammation, and promotes tissue repair. It involves three main stages: recognition, engulfment, and degradation of dying cells. Optimal removal of apoptotic cargo by phagocytes requires finely tuned machinery and associated modifications. Key molecules in efferocytosis, such as 'Find-me signals', 'Eat-me signals', and 'Don't eat-me signals', have been shown to enhance efferocytosis following cardiovascular and cerebrovascular diseases. Moreover, various additional molecules, pathways, and mitochondrial metabolic processes have been identified to enhance prognosis and outcomes via efferocytosis in diverse experimental models. Impaired efferocytosis can lead to inflammation-associated pathologies and prolonged recovery periods. Therefore, this review consolidates current understanding of efferocytosis mechanisms and its application in cardiovascular and cerebrovascular diseases, proposing future research directions.

The complement system in lipid-mediated pathologies

The complement system, a coordinator and facilitator of the innate immune response, plays an essential role in maintaining host homeostasis. It promotes clearance of pathogen- and danger-associated molecular patterns, regulates adaptive immunity, and can modify various metabolic processes such as energy expenditure, lipid metabolism, and glucose homeostasis. In this review, we will focus on the intricate interplay between complement components and lipid metabolism. More precisely, we will display how alterations in the activation and regulation of the complement system affect pathological outcome in lipid-associated diseases, such as atherosclerosis, obesity, metabolic syndrome, age-related macular degeneration, and metabolic dysfunction-associated steatotic liver disease. In addition to that, we will present and evaluate underlying complement-mediated physiological mechanisms, observed both in vitro and in vivo. Our manuscript will demonstrate the clinical significance of the complement system as a bridging figure between innate immunity and lipid homeostasis.

Canonical and non-canonical roles of complement in atherosclerosis

Cardiovascular diseases are the leading cause of death globally, and atherosclerosis is the major contributor to the development and progression of cardiovascular diseases. Immune responses have a central role in the pathogenesis of atherosclerosis, with the complement system being an acknowledged contributor. Chronic activation of liver-derived and serum-circulating canonical complement sustains endothelial inflammation and innate immune cell activation, and deposition of complement activation fragments on inflamed endothelial cells is a hallmark of atherosclerotic plaques. However, increasing evidence indicates that liver-independent, cell-autonomous and non-canonical complement activities are underappreciated contributors to atherosclerosis. Furthermore, complement activation can also have atheroprotective properties. These specific detrimental or beneficial contributions of the complement system to the pathogenesis of atherosclerosis are dictated by the location of complement activation and engagement of its canonical versus non-canonical functions in a temporal fashion during atherosclerosis progression. In this Review, we summarize the classical and the emerging non-classical roles of the complement system in the pathogenesis of atherosclerosis and discuss potential strategies for therapeutic modulation of complement for the prevention and treatment of atherosclerotic cardiovascular disease.

Leonurine improves atherosclerosis by activating foam cell autophagy and metabolic remodeling via METTL3-mediated AKT1S1 mRNA stability modulation

BACKGROUND

Atherosclerosis (AS) is the most prevalent cardiovascular disease and remains the major contributor to death and mortality globally. Leonurine (LEO) is a unique alkaloid compound with protective effects on the cardiovascular system. However, the exact mechanisms underlying its cardiovascular-protecting action are still not fully elucidated. The methyltransferase 3 (METTL3), the catalytic core of the N6-methyladenosine modification (m6A) methyltransferase complex, has been shown to inhibit autophagy and exacerbate the process of AS via regulation of m6A modification of mRNA.

PURPOSE

We aimed to determine whether the inhibited effect of LEO on AS is related to METTL3-mediated AKT1S1 stability.

METHODS

The apolipoprotein E (ApoE) knockout mice was subjected to a high-fat diet (HFD), and THP-1 derived macrophages was exposed to oxidized low-density lipoprotein (ox-LDL), to establish the animal and cellular models of AS, respectively.

RESULTS

We found that LEO effectively improved AS and reduced the plaque area and inflammation via diminishing macrophage lipid accumulation and remodeling the lipid metabolism profile. LEO activated ox-LDL-induced macrophage autophagy, enhancing lipid metabolism decrease, according to the lipidomic and molecular biology analyses. Additionally, LEO caused a marked increase in autophagy marker levels in mouse models with advanced AS. Furthermore, we found that LEO reactivated autophagy and reversed lipid accumulation by suppressing METTL3 expression. The m6A-seq from ox-LDL-induced macrophages showed that a total of five autophagy-related mRNA transcripts (AKT1S1, AKT1, RB1CC1, CFLAR, and MTMR4) were altered, and AKT1S1 was significantly upregulated by LEO. Mechanistically, LEO-mediated regulation of METTL3 decreased AKT1S1 expression by attenuating its mRNA stability. Silencing AKT1S1 inhibited LEO-METTL3 axis-mediated autophagy and enhanced lipid accumulation in ox-LDL-induced macrophages.

CONCLUSION

The study first revealed that LEO exerts anti-atherosclerotic effect by activating METTL3-mediated macrophage autophagy in vivo and in vitro. The mechanism of LEO was further found to be the enhancement of METTL3-mediated AKT1S1 stability to activate autophagy thereby reducing lipid accumulation. This study provides a new perspective of natural medicines on the treatment of AS via an epigenetic manner.

Autoimmune diseases and atherosclerotic cardiovascular disease

Autoimmune diseases are associated with a dramatically increased risk of atherosclerotic cardiovascular disease and its clinical manifestations. The increased risk is consistent with the notion that atherogenesis is modulated by both protective and disease-promoting immune mechanisms. Notably, traditional cardiovascular risk factors such as dyslipidaemia and hypertension alone do not explain the increased risk of cardiovascular disease associated with autoimmune diseases. Several mechanisms have been implicated in mediating the autoimmunity-associated cardiovascular risk, either directly or by modulating the effect of other risk factors in a complex interplay. Aberrant leukocyte function and pro-inflammatory cytokines are central to both disease entities, resulting in vascular dysfunction, impaired resolution of inflammation and promotion of chronic inflammation. Similarly, loss of tolerance to self-antigens and the generation of autoantibodies are key features of autoimmunity but are also implicated in the maladaptive inflammatory response during atherosclerotic cardiovascular disease. Therefore, immunomodulatory therapies are potential efficacious interventions to directly reduce the risk of cardiovascular disease, and biomarkers of autoimmune disease activity could be relevant tools to stratify patients with autoimmunity according to their cardiovascular risk. In this Review, we discuss the pathophysiological aspects of the increased cardiovascular risk associated with autoimmunity and highlight the many open questions that need to be answered to develop novel therapies that specifically address this unmet clinical need.

High expression of PLA2G2A in fibroblasts plays a crucial role in the early progression of carotid atherosclerosis

BACKGROUND

In mouse models of atherosclerosis, knockout of the PLA2G2A gene has been shown to reduce the volume of atherosclerotic plaques. Clinical trials have demonstrated the potential of using the sPLA2 inhibitor Varespladib in combination with statins to reduce lipid levels. However, this approach has not yielded the expected results in reducing the risk of cardiovascular events. Therefore, it is necessary to further investigate the mechanisms of PLA2G2A.

METHODS

Single-cell transcriptome data from two sets of carotid plaques, combined with clinical patient information. were used to describe the expression characteristics of PLA2G2A in carotid plaques at different stages. In order to explore the mechanisms of PLA2G2A, we conducted enrichment analysis, cell-cell communication analysis and single-cell regulatory network inference and clustering analyses. We validated the above findings at the cellular level.

RESULTS

Our findings indicate that PLA2G2A is primarily expressed in vascular fibroblasts and shows significant cell interactions with macrophages in the early-stage, especially in complement and inflammation-related pathways. We also found that serum sPLA2 levels have stronger diagnostic value in patients with mild carotid artery stenosis. Subsequent comparisons of single-cell transcriptomic data from early and late-stage carotid artery plaques corroborated these findings and predicted transcription factors that might regulate the progression of early carotid atherosclerosis (CA) and the expression of PLA2G2A.

CONCLUSIONS

Our study discovered and validated that PLA2G2A is highly expressed by vascular fibroblasts and promotes plaque progression through the activation of macrophage complement and coagulation cascade pathways in the early-stage of CA.

The mechanisms underlying acute myocardial infarction in chronic kidney disease patients undergoing hemodialysis

Cardiovascular disease (CVD) is a leading cause of death in chronic kidney disease (CKD). Hemodialysis is one of the main treatments for patients with end-stage kidney disease. Epidemiological data has shown that acute myocardial infarction (AMI) accounts for the main reason for death in patients with CKD under hemodialysis therapy. Immune dysfunction and changes in metabolism (including a high level of inflammatory cytokines, a disorder of lipid and mineral ion homeostasis, accumulation of uremic toxins et al.) during CKD can deteriorate stability of atherosclerotic plaque and promote vascular calcification, which are exactly the pathophysiological mechanisms underlying the occurrence of AMI. Meanwhile, the hemodialysis itself also has adverse effects on lipoprotein, the immune system and hemodynamics, which contribute to the high incidence of AMI in these patients. This review aims to summarize the mechanisms and further promising methods of prevention and treatment of AMI in CKD patients undergoing hemodialysis, which can provide an excellent paradigm for exploring the crosstalk between the kidney and cardiovascular system.

Intracellular complement and immunometabolism: The advantages of compartmentalization

The complement system is a proteolytic cascade triggered by pathogen and danger-associated molecular patterns, with resultant outcomes of inflammation, cellular activation, and opsonization of material for removal by phagocytosis. While first discovered as an activity in serum, it is now recognized that complement components play important roles at local and individual cell-intrinsic levels. In particular, apart from the extracellular serum activities of complement, it is now believed that complement also acts intracellularly, as part of a cellular signal transduction cascade that can stimulate cellular survival and activation, and individual immune cell phenotypes, via effects on cellular metabolism. This review will describe what is currently known about how complement functions in intracellular signal transduction, and outline the functional advantages of a compartmentalized and intracellular complement system.

Local complement activation and modulation in mucosal immunity

The complement system is an evolutionarily conserved arm of innate immunity, which forms one of the first lines of host response to pathogens and assists in the clearance of debris. A deficiency in key activators/amplifiers of the cascade results in recurrent infection, whereas a deficiency in regulating the cascade predisposes to accelerated organ failure, as observed in colitis and transplant rejection. Given that there are over 60 proteins in this system, it has become an attractive target for immunotherapeutics, many of which are United States Food and Drug Administration-approved or in multiple phase 2/3 clinical trials. Moreover, there have been key advances in the last few years in the understanding of how the complement system operates locally in tissues, independent of its activities in circulation. In this review, we will put into perspective the abovementioned discoveries to optimally modulate the spatiotemporal nature of complement activation and regulation at mucosal surfaces.

The complement system in neurodegenerative and inflammatory diseases of the central nervous system

Neurodegenerative and neuroinflammatory diseases, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis, affect millions of people globally. As aging is a major risk factor for neurodegenerative diseases, the continuous increase in the elderly population across Western societies is also associated with a rising prevalence of these debilitating conditions. The complement system, a crucial component of the innate immune response, has gained increasing attention for its multifaceted involvement in the normal development of the central nervous system (CNS) and the brain but also as a pathogenic driver in several neuroinflammatory disease states. Although complement is generally understood as a liver-derived and blood or interstitial fluid operative system protecting against bloodborne pathogens or threats, recent research, particularly on the role of complement in the healthy and diseased CNS, has demonstrated the importance of locally produced and activated complement components. Here, we provide a succinct overview over the known beneficial and pathological roles of complement in the CNS with focus on local sources of complement, including a discussion on the potential importance of the recently discovered intracellularly active complement system for CNS biology and on infection-triggered neurodegeneration.

RNAseq of INOCA patients identifies innate, invariant, and acquired immune changes: potential autoimmune microvascular dysfunction

Background

Ischemia with non-obstructive coronary arteries (INOCA) is a major clinical entity that involves potentially 20%-30% of patients with chest pain. INOCA is typically attributed either to coronary microvascular disease and/or vasospasm, but is likely distinct from classical coronary artery disease (CAD).

Objectives

To gain insights into the etiology of INOCA and CAD, RNA sequencing of whole blood from patients undergoing both stress testing and elective invasive coronary angiography (ICA) was conducted.

Methods

Stress testing and ICA of 177 patients identified 40 patients (23%) with INOCA compared to 39 controls (stress-, ICA-). ICA+ patients divided into 38 stress- and 60 stress+. RNAseq was performed by Illumina with ribosomal RNA depletion. Transcriptome changes were analyzed by DeSeq2 and curated by manual and automated methods.

Results

Differentially expressed genes for INOCA were associated with elevated levels of transcripts related to mucosal-associated invariant T (MAIT) cells, plasmacytoid dendritic cells (pcDC), and memory B cells, and were associated with autoimmune diseases such as rheumatoid arthritis. Decreased transcripts were associated with neutrophils, but neutrophil transcripts, per se, were not less abundant in INOCA. CAD transcripts were more related to T cell functions.

Conclusions

Elevated transcripts related to pcDC, MAIT, and memory B cells suggest an autoimmune component to INOCA. Reduced neutrophil transcripts are likely attributed to chronic activation leading to increased translation and degradation. Thus, INOCA could result from stimulation of B cell, pcDC, invariant T cell, and neutrophil activation that compromises cardiac microvascular function.

Formation of Multinucleated Giant Cells after Experimental Intracerebral Hemorrhage: Characteristics and Role of Complement C3

Hematoma clearance is critical for mitigating intracerebral hemorrhage (ICH)-induced brain injury. Multinucleated giant cells (MGCs), a type of phagocyte, and the complement system may play a pivotal role in hematoma resolution, but whether the complement system regulates MGC formation after ICH remains unclear. The current study investigated the following: (1) the characteristics of MGC formation after ICH, (2) whether it was impacted by complement C3 deficiency in mice and (3) whether it also influenced hematoma degradation (hemosiderin formation). Young and aged male mice, young female mice and C3-deficient and -sufficient mice received a 30 μL injection of autologous whole blood into the right basal ganglia. Brain histology and immunohistochemistry were used to examine MGC formation on days 3 and 7. Hemosiderin deposition was examined by autofluorescence on day 28. Following ICH, MGCs were predominantly located in the peri-hematoma region exhibiting multiple nuclei and containing red blood cells or their metabolites. Aging was associated with a decrease in MGC formation after ICH, while sex showed no discernible effect. C3 deficiency reduced MGC formation and reduced hemosiderin formation. Peri-hematomal MGCs may play an important role in hematoma resolution. Understanding how aging and complement C3 impact MGCs may provide important insights into how to regulate hematoma resolution.

Moss-produced human complement factor H with modified glycans has an extended half-life and improved biological activity

Most drugs that target the complement system are designed to inhibit the complement pathway at either the proximal or terminal levels. The use of a natural complement regulator such as factor H (FH) could provide a superior treatment option by restoring the balance of an overactive complement system while preserving its normal physiological functions. Until now, the systemic treatment of complement-associated disorders with FH has been deemed unfeasible, primarily due to high production costs, risks related to FH purified from donors' blood, and the challenging expression of recombinant FH in different host systems. We recently demonstrated that a moss-based expression system can produce high yields of properly folded, fully functional, recombinant FH. However, the half-life of the initial variant (CPV-101) was relatively short. Here we show that the same polypeptide with modified glycosylation (CPV-104) achieves a pharmacokinetic profile comparable to that of native FH derived from human serum. The treatment of FH-deficient mice with CPV-104 significantly improved important efficacy parameters such as the normalization of serum C3 levels and the rapid degradation of C3 deposits in the kidney compared to treatment with CPV-101. Furthermore, CPV-104 showed comparable functionality to serum-derived FH in vitro, as well as similar performance in ex vivo assays involving samples from patients with atypical hemolytic uremic syndrome, C3 glomerulopathy and paroxysomal nocturnal hematuria. CPV-104 - the human FH analog expressed in moss - will therefore allow the treatment of complement-associated human diseases by rebalancing instead of inhibiting the complement cascade.

The clinical role of combined circulating complement C1q and AIP for CAD with LDL-C level below 1.8mmol/L

BACKGROUND

In the past few years, circulating complement C1q involvement in atherosclerosis has garnered growing research interest in addition to the emerging recognition of the novel lipid marker named atherogenic index of plasma (AIP). Nevertheless, among patients experiencing low-density lipoprotein cholesterol (LDL-C) levels less than 1.8mmol/L, the interplay between C1q combined with the AIP for coronary artery disease (CAD) is ambiguous.

METHODS

Patients were stratified into a non-CAD and CAD group according to their coronary angiography. The association between C1q in conjunction with the AIP and CAD was explored using restricted cubic spline analyses and logistic regression models. To assess how it predicted, a receiver operating characteristic analysis was undertaken.

RESULTS

A total of 7270 patients comprised 1476 non-CAD patients and 5794 patients diagnosed with CAD were analyzed. A comparison of the two groups showed that the C1q levels were notably higher compared to the CAD group, while AIP exhibited an inverse trend. Across quartiles of C1q, the AIP demonstrated a decline with increasing C1q levels, and significant differences were observed between the groups. A correlation analysis underscored a notable negative correlation between the two variables. Univariate and multivariate logistic regression analyses revealed significant associations between CAD and the C1q quartile groups/AIP. Furthermore, compared with the Q4 group, a decrease in the C1q levels corresponded to an escalation in CAD risk, with the odds ratio rising from 1.661 to 2.314.

CONCLUSIONS

In conclusion, there appears to be a notable positive correlation between the combination of C1q with the AIP and CAD.

Cordyceps militaris Extract and Cordycepin Alleviate Oxidative Stress, Modulate Gut Microbiota and Ameliorate Intestinal Damage in LPS-Induced Piglets

Cordycepin is considered a major bioactive component in Cordyceps militaris extract. This study was performed to evaluate the ameliorative effect of Cordyceps militaris extract (CME) and cordycepin (CPN) supplementation on intestinal damage in LPS-challenged piglets. The results showed that CPN or CME supplementation significantly increased the villus height (p < 0.01) and villus height/crypt depth ratio (p < 0.05) in the jejunum and ileum of piglets with LPS-induced intestinal inflammation. Meanwhile, CPN or CME supplementation alleviated oxidative stress and inflammatory responses by reducing the levels of MDA (p < 0.05) and pro-inflammatory cytokines in the serum. Additionally, supplementation with CPN or CME modulated the structure of the intestinal microbiota by enriching short-chain fatty acid-producing bacteria, and increased the level of butyrate (p < 0.05). The RNA-seq results demonstrated that CME or CPN altered the complement and coagulation-cascade-related genes (p < 0.05), including upregulating gene KLKB1 while downregulating the genes CFD, F2RL2, CFB, C4BPA, F7, C4BPB, CFH, C3 and PROS1, which regulate the complement activation involved in inflammatory and immune responses. Correlation analysis further demonstrated the potential relation between the gut microbiota and intestinal inflammation, oxidative stress, and butyrate in piglets. In conclusion, CPN or CME supplementation might inhibit LPS-induced inflammation and oxidative stress by modulating the intestinal microbiota and its metabolite butyrate in piglets.

The Role of Macrophage Efferocytosis in the Pathogenesis of Apical Periodontitis

Macrophages (Mφs) play a crucial role in the homeostasis of the periapical immune micro-environment caused by bacterial infection. Mφ efferocytosis has been demonstrated to promote the resolution of multiple infected diseases via accelerating Mφ polarization into M2 type. However, the Mφ efferocytosis-apical periodontitis (AP) relationship has not been elucidated yet. This study aimed to explore the role of Mφ efferocytosis in the pathogenesis of AP. Clinical specimens were collected to determine the involvement of Mφ efferocytosis in the periapical region via immunohistochemical and immunofluorescence staining. For a further understanding of the moderator effect of Mφ efferocytosis in the pathogenesis of AP, both an in vitro AP model and in vivo AP model were treated with ARA290, a Mφ efferocytosis agonist. Histological staining, micro-ct, flow cytometry, RT-PCR and Western blot analysis were performed to detect the inflammatory status, alveolar bone loss and related markers in AP models. The data showed that Mφ efferocytosis is observed in the periapical tissues and enhancing the Mφ efferocytosis ability could effectively promote AP resolution via facilitating M2 Mφ polarization. Collectively, our study demonstrates the functional importance of Mφ efferocytosis in AP pathology and highlights that accelerating Mφ efferocytosis via ARA290 could serve as an adjuvant therapeutic strategy for AP.

TREM2 protects from atherosclerosis by limiting necrotic core formation

Atherosclerosis is a chronic disease of the vascular wall driven by lipid accumulation and inflammation in the intimal layer of arteries, and its main complications, myocardial infarction and stroke, are the leading cause of mortality worldwide [1], [2]. Recent studies have identified Triggering receptor expressed on myeloid cells 2 (TREM2), a lipid-sensing receptor regulating myeloid cell functions [3], to be highly expressed in macrophage foam cells in experimental and human atherosclerosis [4]. However, the role of TREM2 in atherosclerosis is not fully known. Here, we show that hematopoietic or global TREM2 deficiency increased, whereas TREM2 agonism decreased necrotic core formation in early atherosclerosis. We demonstrate that TREM2 is essential for the efferocytosis capacities of macrophages, and to the survival of lipid-laden macrophages, indicating a crucial role of TREM2 in maintaining the balance between foam cell death and clearance of dead cells in atherosclerotic lesions, thereby controlling plaque necrosis.

Activation of the complement system by nanoparticles and strategies for complement inhibition

The complement system is a multicomponent and multifunctional arm of the innate immune system. Complement contributes to non-specific host defence and maintains homeostasis through multifaceted processes and pathways, including crosstalk with the adaptive immune system, the contact (coagulation) and the kinin systems, and alarmin high-mobility group box 1. Complement is also present intracellularly, orchestrating a wide range of housekeeping and physiological processes in both immune and nonimmune cells, thus showing its more sophisticated roles beyond innate immunity, but its roles are still controversial. Particulate drug carriers and nanopharmaceuticals typically present architectures and surface patterns that trigger complement system in different ways, resulting in both beneficial and adverse responses depending on the extent of complement activation and regulation as well as pathophysiological circumstances. Here we consider the role of complement system and complement regulations in host defence and evaluate the mechanisms by which nanoparticles trigger and modulate complement responses. Effective strategies for the prevention of nanoparticle-mediated complement activation are introduced and discussed.