Serum Amyloid A1: A Biomarker for Neutrophilic Airway Inflammation in Adult Asthmatic Patients

Tra Cao Thi Bich; Quang Luu Quoc; Youngwoo Choi; Eun-Mi Yang; Hoang Kim Tu Trinh; Yoo Seob Shin; Hae-Sim Park

doi:10.4168/aair.2022.14.1.40

Serum Amyloid A1: A Biomarker for Neutrophilic Airway Inflammation in Adult Asthmatic Patients

Allergy Asthma Immunol Res. 2022 Jan;14(1):40-58. doi: 10.4168/aair.2022.14.1.40.

Authors

Tra Cao Thi Bich^{1

2}, Quang Luu Quoc^{1

2}, Youngwoo Choi¹, Eun-Mi Yang¹, Hoang Kim Tu Trinh³, Yoo Seob Shin¹, Hae-Sim Park⁴

Affiliations

¹ Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, Korea.
² Department of Biomedical Science, Ajou University School of Medicine, Suwon, Korea.
³ University of Medicine and Pharmacy at Ho Chi Minh City, Vietnam.
⁴ Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, Korea. hspark@ajou.ac.kr.

Abstract

Purpose: We evaluated the role of serum amyloid A1 (SAA1) in the pathogenesis of airway inflammation according to the phenotype of asthma.

Methods: One hundred twenty-two asthmatic patients and 60 healthy control subjects (HCs) were enrolled to measure SAA1 levels. The production of SAA1 from airway epithelial cells (AECs) and its effects on macrophages and neutrophils were investigated in vitro and in vivo.

Results: The SAA1 levels were significantly higher in sera of asthmatic patients than in those of HCs (P = 0.014); among asthmatics, patients with neutrophilic asthma (NA) showed significantly higher SAA1 levels than those with non-NA (P < 0.001). In vitro, polyinosinic:polycytidylic acid (Poly I-C) treatment markedly enhanced the production of SAA1 from AECs, which was further augmented by neutrophils; SAA1 could induce the production of interleukin (IL)-6, IL-8, and S100 calcium-binding protein A9 from AECs. Additionally, SAA1 activated neutrophils and macrophages isolated from peripheral blood of asthmatics, releasing neutrophil extracellular traps (NETs) and secreting proinflammatory cytokines presenting M1 phenotype, respectively. In ovalbumin-induced asthma mice, Poly I-C treatment significantly increased SAA1 levels as well as IL-17A/interferon-gamma/IL-33 levels in bronchoalveolar lavage fluid (BALF), leading to airway hyperresponsiveness and inflammation. The highest levels of SAA1 and neutrophilia were noted in the BALF and sera of the NA mouse model, followed by the mixed granulocytic asthma (MA) model. Especially, SAA1 induced IL-17/retinoic acid receptor-related orphan receptor γt expression from activated CD4+ T lymphocytes in asthmatic mice.

Conclusions: The results show that SAA1 could induce neutrophilic airway inflammation by activating neutrophils along with NET formation, M1 macrophages, and Th2/Th17 predominant cells, contributing to the phenotype of NA or MA.

Keywords: Poly I-C; Serum amyloid A protein; asthma; biomarkers; epithelial cells; inflammation; macrophages; neutrophils; phenotype.

Abstract

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