A Pleomorphic Puzzle: Heterogeneous Pulmonary Vascular Occlusions in Patients with COVID-19

Tuberculosis (TB) remains one of the top 10 causes of death worldwide and still poses a serious challenge to public health. Recent attention to neutrophils has uncovered unexplored areas demanding further investigation. Therefore, the aim of this study was to determine neutrophil activation and circulatory neutrophil extracellular trap (NET) formation in various types of TB. Sera from TB patients (n = 91) and healthy controls (NHD; n = 38) were analyzed for NE-DNA and MPO–DNA complexes, cell-free DNA (cfDNA), and protease activity (elastase). We show that these NET parameters were increased in TB sera. Importantly, NET formation and NE activity were elevated in TB patients with extensive tissue damage when compared to those with minor damage and in patients with relapse, compared to new cases. We discuss the importance of balancing NET formation to prevent tissue damage or even relapse and argue to analyze circulating NET parameters to monitor the risk of disease relapse. To investigate the tissues for NETs and to find the source of the circulating NET degradation products, we collected sections of granulomas in lung and lymph node biopsies. Samples from other diseases with granulomas, including sarcoidosis (SARC) and apical periodontitis (AP), served as controls. Whereas NET formation characterizes the caseating granulomas, both caseating and non-caseating granulomas harbor DNA with unusual conformation. As TB is associated with hypercoagulation and thromboembolism, we further imaged the pulmonary vessels of TB patients and detected vascular occlusions with neutrophil aggregates. This highlights the dual role of neutrophils in the pathology of TB.

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Neutrophils Aggravate Inflammation and NEC-like Lesions in NEC Intestinal Organoids

Vincent,

Heuer,

Raluy

et al. 2024

Preprint

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Necrotizing enterocolitis (NEC) is a leading cause of neonatal death and long-term morbidity, involving complex pathophysiology including prematurity, abnormal bacterial colonization, and ischemia-reperfusion injury, partially mediated by neutrophils. However, development of targeted therapies for NEC is hindered by the limitations of current animal models. Thus, this study aimed to develop a human intestinal organoid model for NEC to investigate its pathophysiology, understand neutrophil involvement, and bridge animal and human research. Organoid cultures were established from human neonatal intestinal samples with NEC (n = 7) and without gut inflammation (controls, n = 7), treated with lipopolysaccharide (LPS), and/or cocultured with neutrophils. Flow cytometry quantified neutrophil survival (PI/Annexin), activation (CD11b/CD66b), and TLR-4 expression, as well as organoid TLR-4 expression and apoptosis markers. NEC status and neutrophil recruitment were analyzed using immunofluorescence. After LPS administration, NEC organoids showed significantly increased TLR-4 expression, intestinal apoptosis markers, and NEC scores compared to controls, with more pronounced differences after neutrophil addition. Neutrophil activation markers were elevated when cocultured with both NEC and control organoids, but TLR-4 expression increased only with NEC organoids. The findings suggest that epithelial cells from NEC patients have a heightened innate TLR-4 expression upon LPS stimulation, potentially contributing to NEC development. LPS stimulation resulted in more pronounced NEC-like lesions in NEC organoids, which was exacerbated by neutrophils. This model demonstrates that neutrophils might contribute to NEC manifestation and maintenance, and that NEC organoids can reflect disease aspects, potentially aiding in the development of targeted therapies.

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A Pleomorphic Puzzle: Heterogeneous Pulmonary Vascular Occlusions in Patients with COVID-19

Cited by 3 publications

References 53 publications

COVID-19 in Systemic Lupus Erythematosus patients treated with belimumab: a retrospective clinical study

COVID-19 in Systemic Lupus Erythematosus patients treated with belimumab: a retrospective clinical study

Neutrophil extracellular traps characterize caseating granulomas

Neutrophils Aggravate Inflammation and NEC-like Lesions in NEC Intestinal Organoids

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