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Monocytes differentiate along two alternative pathways during sterile inflammation.

ABSTRACT: During inflammation, monocytes differentiate within tissues into macrophages (mo-Mac) or dendritic cells (mo-DC). Whether these two populations derive from alternative differentiation pathways or represent different stages along a continuum remains unclear. Here, we address this question using temporal single-cell RNA sequencing in an in vitro model, allowing the simultaneous differentiation of human mo-Mac and mo-DC. We find divergent differentiation paths, with a fate decision occurring within the first 24 h and confirm this result in vivo using a mouse model of sterile peritonitis. Using a computational approach, we identify candidate transcription factors potentially involved in monocyte fate commitment. We demonstrate that IRF1 is necessary for mo-Mac differentiation, independently of its role in regulating transcription of interferon-stimulated genes. In addition, we describe the transcription factors ZNF366 and MAFF as regulators of mo-DC development. Our results indicate that mo-Macs and mo-DCs represent two alternative cell fates requiring distinct transcription factors for their differentiation.

SUBMITTER: Villar J

PROVIDER: S-EPMC10328069 | biostudies-literature | 2023 Jul

REPOSITORIES: biostudies-literature

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Monocytes differentiate along two alternative pathways during sterile inflammation.

Villar Javiera J Ouaknin Léa L Cros Adeline A Segura Elodie E

EMBO reports 20230516 7

During inflammation, monocytes differentiate within tissues into macrophages (mo-Mac) or dendritic cells (mo-DC). Whether these two populations derive from alternative differentiation pathways or represent different stages along a continuum remains unclear. Here, we address this question using temporal single-cell RNA sequencing in an in vitro model, allowing the simultaneous differentiation of human mo-Mac and mo-DC. We find divergent differentiation paths, with a fate decision occurring within ...[more]

PMID: 37191947

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Project description:Background & aimsAlthough transient bacteremia is common during dental and endoscopic procedures, infections developing during sterile diseases like acute pancreatitis (AP) can have grave consequences. We examined how impaired bacterial clearance may cause this transition.MethodsBlood samples from patients with AP, normal controls, and rodents with pancreatitis or those administered different nonesterified fatty acids (NEFAs) were analyzed for albumin-unbound NEFAs, microbiome, and inflammatory cell injury. Macrophage uptake of unbound NEFAs using a novel coumarin tracer were done and the downstream effects-NEFA-membrane phospholipid (phosphatidylcholine) interactions-were studied on isothermal titration calorimetry.ResultsPatients with infected AP had higher circulating unsaturated NEFAs; unbound NEFAs, including linoleic acid (LA) and oleic acid (OA); higher bacterial 16S DNA; mitochondrial DNA; altered β-diversity; enrichment in Pseudomonadales; and increased annexin V-positive myeloid (CD14) and CD3-positive T cells on admission. These, and increased circulating dead inflammatory cells, were also noted in rodents with unbound, unsaturated NEFAs. Isothermal titration calorimetry showed progressively stronger unbound LA interactions with aqueous media, phosphatidylcholine, cardiolipin, and albumin. Unbound NEFAs were taken into protein-free membranes, cells, and mitochondria, inducing voltage-dependent anion channel oligomerization, reducing ATP, and impairing phagocytosis. These were reversed by albumin. In vivo, unbound LA and OA increased bacterial loads and impaired phagocytosis, causing infection. LA and OA were more potent for these amphipathic interactions than the hydrophobic palmitic acid.ConclusionsRelease of stored LA and OA can increase their circulating unbound levels and cause amphipathic liponecrosis of immune cells via uptake by membrane phospholipids. This impairs bacterial clearance and causes infection during sterile inflammation.

Project description:ImportanceRandomized clinical trials are conducted to establish both drug safety and efficacy. However, evidence of adverse events associated with these drugs in the clinical practice setting can be of value at generating hypotheses regarding less common safety issues, even if causality cannot be determined.ObjectiveTo present and analyze cases of intraocular inflammation associated with faricimab therapy in patients referred to a single European institution.Design, setting, and participantsThis was a review starting in April of 2024 of an observational case series. Patients were from a single academic-based tertiary referral center in Switzerland. Included in the analysis were patients referred for intraocular inflammation soon after receiving a faricimab intravitreal injection between June 1, 2022, and March 5, 2024.ExposureFaricimab, 6 mg (0.05 mL of a 120-mg/mL solution), administrated for neovascular age-related macular degeneration or diabetic macular edema.Main outcomes and measuresThe systemic and ocular histories and imaging data available were reviewed. The following were evaluated: visual acuity measured with habitual correction using the Early Treatment of Diabetic Retinopathy Study charts before and after the event; intraocular pressure; patient symptoms; anterior, intermediate, or posterior location of the intraocular inflammation; and the presence of retinal vasculitis. Multimodal imaging including color fundus photographs, fluorescein angiograms, indocyanine green angiograms, and optical coherence tomography were reviewed.ResultsA total of 12 eyes from 7 patients (mean [SD] age, 73.3 [16.7] years; 4 female [57.1%]) over 22 months were identified as having noninfectious intraocular inflammation after intravitreal faricimab injections. Among these cases, in 2 eyes, retinal vasculitis was present together with anterior and posterior inflammation. One of the 2 eyes had an occlusive form of vasculitis of the arteries and veins, leading to subsequent macular capillary nonperfusion and clinically relevant irreversible vision deterioration from 20/80 to 20/2000. The remaining eyes were characterized by moderate anterior segment inflammation without substantial vision changes. The intraocular inflammation event occurred after a median (IQR) of 3.5 (2.0-4.3) faricimab injections. The median (IQR) interval between the last faricimab injection and the diagnosis of inflammation was 28 (24-38) days. Increased intraocular pressure of 30 mm Hg or higher was found in 3 eyes.Conclusions and relevanceThis case series highlights the occurrence of rare, but potentially severe, intraocular inflammation associated with faricimab therapy. Although these findings do not prove causality and can only generate hypotheses for future investigations, these results suggest the importance of continuous surveillance and monitoring for patients undergoing faricimab therapy to promptly identify and manage potential adverse events.

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Monocytes differentiate along two alternative pathways during sterile inflammation.

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Monocytes differentiate along two alternative pathways during sterile inflammation.

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