Cholesterol-Induced M4-Like Macrophages Recruit Neutrophils and Induce NETosis.
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ABSTRACT:
SUBMITTER: Maretti-Mira AC
PROVIDER: S-EPMC8126646 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The liver is the central organ for cholesterol synthesis and homeostasis. The effects of dietary cholesterol on hepatic injury, mainly of oxidized low-density lipoproteins (OxLDL), are not fully understood. Here, we show that the degree of cholesterol oxidation had different impacts on the global gene expression of human M2-like macrophages, with highly oxidized LDL causing the most dramatic changes. M2-like macrophages and Kupffer cells undergo M4-like polarization, decreasing the expression of important markers, such as IL10, MRC1, and CD163. These cells also displayed functional changes, with reduced phagocytic capacity, increased neutrophil recruitment, and more effective neutrophil extracellular traps (NETs) induction. Our findings provide a link between the accumulation of OxLDL and NASH progression, offering a new target for NAFLD treatment.
2021-05-25 | GSE160200 | GEO
Project description:Cholesterol-induced M4-like Macrophages in Non-alcoholic Steatohepatitis recruit Neutrophils and induce NETosis
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Project description:Neutrophil infiltration and subsequent extracellular trap formation (NETosis) is a contributing factor in sterile inflammation. Furthermore, neutrophil extracellular traps (NETs) are prothrombotic, as they provide a scaffold for platelets and red blood cells to attach to. In circulation, neutrophils are constantly exposed to hemodynamic forces such as shear stress, which in turn regulates many of their biological functions such as crawling and NETosis. However, the mechanisms that mediate mechanotransduction in neutrophils are not fully understood. In this study, we demonstrate that shear stress induces NETosis, dependent on the shear stress level, and increases the sensitivity of neutrophils to NETosis-inducing agents such as adenosine triphosphate and lipopolysaccharides. Furthermore, shear stress increases intracellular calcium levels in neutrophils and this process is mediated by the mechanosensitive ion channel Piezo1. Activation of Piezo1 in response to shear stress mediates calpain activity and cytoskeleton remodeling, which consequently induces NETosis. Thus, activation of Piezo1 in response to shear stress leads to a stepwise sequence of cellular events that mediates NETosis and thereby places neutrophils at the centre of localized inflammation and prothrombotic effects.
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Project description:Excessive activation of blood coagulation and neutrophil accumulation have been described in several human cancers. However, whether hypercoagulation and neutrophilia are linked and involved in cancer development is currently unknown. Here we show that spontaneous intestinal tumorigenesis correlates with the accumulation of low-density neutrophils with a pro-tumorigenic N2 phenotype and unprompted neutrophil extracellular traps (NET) formation. We find that increased circulating lipopolysaccharide induces upregulation of complement C3a receptor on neutrophils and activation of the complement cascade. This leads to NETosis, induction of coagulation and N2 polarization, which prompts tumorigenesis, showing a novel link between coagulation, neutrophilia and complement activation. Finally, in a cohort of patients with small but not large intestinal cancer, we find a correlation between neutrophilia and hypercoagulation. This study provides a mechanistic explanation for the tumour-promoting effects of hypercoagulation, which could be used as a new biomarker or as a therapeutic target.
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Project description:Wound healing is impaired in diabetes, resulting in significant morbidity and mortality. Neutrophils are the main leukocytes involved in the early phase of healing. As part of their anti-microbial defense, neutrophils form extracellular traps (NETs) by releasing decondensed chromatin lined with cytotoxic proteins. NETs, however, can also induce tissue damage. Here we show that neutrophils isolated from type 1 and type 2 diabetic humans and mice were primed to produce NETs (a process termed NETosis). Expression of peptidylarginine deiminase 4 (PAD4, encoded by Padi4 in mice), an enzyme important in chromatin decondensation, was elevated in neutrophils from individuals with diabetes. When subjected to excisional skin wounds, wild-type (WT) mice produced large quantities of NETs in wounds, but this was not observed in Padi4(-/-) mice. In diabetic mice, higher levels of citrullinated histone H3 (H3Cit, a NET marker) were found in their wounds than in normoglycemic mice and healing was delayed. Wound healing was accelerated in Padi4(-/-) mice as compared to WT mice, and it was not compromised by diabetes. DNase 1, which disrupts NETs, accelerated wound healing in diabetic and normoglycemic WT mice. Thus, NETs impair wound healing, particularly in diabetes, in which neutrophils are more susceptible to NETosis. Inhibiting NETosis or cleaving NETs may improve wound healing and reduce NET-driven chronic inflammation in diabetes.
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Project description:Neutrophils represent primary mobile phagocytes recruited to the site of infection, and their functions are essential to enhance animals' health performance. Neutrophils have an essential role in innate immunity and are able to kill the pathogens via the synthesis of neutrophil extracellular traps (NETs). The objective of the present work was the study of the in vitro NETosis of peripheral neutrophils isolated from dairy cows supplemented with olive pomace. Dairy cows (n = 16) balanced for parity (3.67 ± 1.5 for CON, 3.67 ± 1.9 for OP), milk yield (24.3 ± 4.5 kg d-1for CON and 24.9 ± 1.7 kg d-1 for OP), the number of days in milk (109 ± 83.5 for CON and 196 ± 51 for OP), and body weight (647 ± 44.3 kg for CON and 675 ± 70.7 kg for OP) were divided into two experimental groups fed with a control diet (CON) and supplemented with 6% of olive pomace (OP). Peripheral blood neutrophils were isolated and stimulated in vitro with phorbol-myristate-acetate (PMA) as a marker for activation and reactivity of the neutrophils. After isolation, both the viability and CD11b expression were analyzed by flow cytometry. Both NETosis by neutrophil elastase-DNA complex system and myeloperoxidase (MPO) activity were evaluated by ELISA. The specific antibodies against MPO and citrullination of Histone-H1 were used for investigating NETosis by immunofluorescence microscopy. The neutrophil elastase-DNA complexes produced during NETosis and MPO activity of neutrophil extracts were affected by OP supplementation. Furthermore, results from immunofluorescence analysis of NETosis depicted a similar result found by ELISA showing a higher expression of MPO and citrullination of Histone-H1 in OP than the CON neutrophils. In addition, all data showed that the OP diet resulted in a better response of neutrophils to PMA stimulation than the CON diet, which did not support the neutrophils' responses to PMA stimulation. Our results demonstrated that OP supplementation can enhance the neutrophil function in dairy cows leading to udder defense and inflammation response especially when an immunosuppression state can occur.
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Project description:BackgroundThe CANTOS trial (Canakinumab Antiinflammatory Thrombosis Outcome Study) showed that antagonism of interleukin (IL)-1β reduces coronary heart disease in patients with a previous myocardial infarction and evidence of systemic inflammation, indicating that pathways required for IL-1β secretion increase cardiovascular risk. IL-1β and IL-18 are produced via the NLRP3 inflammasome in myeloid cells in response to cholesterol accumulation, but mechanisms linking NLRP3 inflammasome activation to atherogenesis are unclear. The cholesterol transporters ATP binding cassette A1 and G1 (ABCA1/G1) mediate cholesterol efflux to high-density lipoprotein, and Abca1/g1 deficiency in myeloid cells leads to cholesterol accumulation.MethodsTo interrogate mechanisms connecting inflammasome activation with atherogenesis, we used mice with myeloid Abca1/g1 deficiency and concomitant deficiency of the inflammasome components Nlrp3 or Caspase-1/11. Bone marrow from these mice was transplanted into Ldlr-/- recipients, which were fed a Western-type diet.ResultsMyeloid Abca1/g1 deficiency increased plasma IL-18 levels in Ldlr-/- mice and induced IL-1β and IL-18 secretion in splenocytes, which was reversed by Nlrp3 or Caspase-1/11 deficiency, indicating activation of the NLRP3 inflammasome. Nlrp3 or Caspase-1/11 deficiency decreased atherosclerotic lesion size in myeloid Abca1/g1-deficient Ldlr-/- mice. Myeloid Abca1/g1 deficiency enhanced caspase-1 cleavage not only in splenic monocytes and macrophages, but also in neutrophils, and dramatically enhanced neutrophil accumulation and neutrophil extracellular trap formation in atherosclerotic plaques, with reversal by Nlrp3 or Caspase-1/11 deficiency, suggesting that inflammasome activation promotes neutrophil recruitment and neutrophil extracellular trap formation in atherosclerotic plaques. These effects appeared to be indirectly mediated by systemic inflammation leading to activation and accumulation of neutrophils in plaques. Myeloid Abca1/g1 deficiency also activated the noncanonical inflammasome, causing increased susceptibility to lipopolysaccharide-induced mortality. Patients with Tangier disease, who carry loss-of-function mutations in ABCA1 and have increased myeloid cholesterol content, showed a marked increase in plasma IL-1β and IL-18 levels.ConclusionsCholesterol accumulation in myeloid cells activates the NLRP3 inflammasome, which enhances neutrophil accumulation and neutrophil extracellular trap formation in atherosclerotic plaques. Patients with Tangier disease, who have increased myeloid cholesterol content, showed markers of inflammasome activation, suggesting human relevance.
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