Fangyu Shao1, Yutong Miao1, Yan Zhang2, Lulu Han1, Xiaolong Ma1, Jiacheng Deng1, Changtao Jiang1, Wei Kong1, Qingbo Xu3, Juan Feng1, Xian Wang1. 1. Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, 38 Xueyuan Road, Beijing 100191, China. 2. Department of Cardiology, Peking University First Hospital, Beijing 100034, China. 3. Cardiovascular Division, Cardiology Department, BHF Center for Vascular Regeneration, King's College London, London, UK.
Abstract
AIMS: Overactivated B cells secrete pathological antibodies, which in turn accelerate the formation of abdominal aortic aneurysms (AAAs). Hyperhomocysteinaemia (HHcy) aggravates AAA in mice; however, the underlying mechanisms remain largely elusive. In this study, we further investigated whether homocysteine (Hcy)-activated B cells produce antigen-specific antibodies that ultimately contribute to AAA formation. METHODS AND RESULTS: ELISA assays showed that HHcy induced the secretion of anti-beta 2 glycoprotein I (anti-β2GPI) antibody from B cells both in vitro and in vivo. Mechanistically, Hcy increased the accumulation of various lipid metabolites in B cells tested by liquid chromatography-tandem mass spectrometry, which contributed to elevated anti-β2GPI IgG secretion. By using the toll-like receptor 4 (TLR4)-specific inhibitor TAK-242 or TLR4-deficient macrophages, we found that culture supernatants from Hcy-activated B cells and HHcy plasma IgG polarized inflammatory macrophages in a TLR4-dependent manner. In addition, HHcy markedly increased the incidence of elastase- and CaPO4-induced AAA in male BALB/c mice, which was prevented in μMT mice. To further determine the importance of IgG in HHcy-aggravated AAA formation, we purified plasma IgG from HHcy or control mice and then transferred the IgG into μMT mice, which were subsequently subjected to elastase- or CaPO4-induced AAA. Compared with μMT mice that received plasma IgG from control mice, μMT mice that received HHcy plasma IgG developed significantly exacerbated elastase- or CaPO4-induced AAA accompanied by increased elastin degradation, MMP2/9 expression, and anti-β2GPI IgG deposition in vascular lesions, as shown by immunofluorescence histochemical staining. CONCLUSION: Our findings reveal a novel mechanism by which Hcy-induced B cell-derived pathogenic anti-β2GPI IgG might, at least in part, contribute to HHcy-aggravated chronic vascular inflammation and AAA formation. Published on behalf of the European Society of Cardiology. All rights reserved.
AIMS: Overactivated B cells secrete pathological antibodies, which in turn accelerate the formation of abdominal aortic aneurysms (AAAs). Hyperhomocysteinaemia (HHcy) aggravates AAA in mice; however, the underlying mechanisms remain largely elusive. In this study, we further investigated whether homocysteine (Hcy)-activated B cells produce antigen-specific antibodies that ultimately contribute to AAA formation. METHODS AND RESULTS: ELISA assays showed that HHcy induced the secretion of anti-beta 2 glycoprotein I (anti-β2GPI) antibody from B cells both in vitro and in vivo. Mechanistically, Hcy increased the accumulation of various lipid metabolites in B cells tested by liquid chromatography-tandem mass spectrometry, which contributed to elevated anti-β2GPI IgG secretion. By using the toll-like receptor 4 (TLR4)-specific inhibitor TAK-242 or TLR4-deficient macrophages, we found that culture supernatants from Hcy-activated B cells and HHcy plasma IgG polarized inflammatory macrophages in a TLR4-dependent manner. In addition, HHcy markedly increased the incidence of elastase- and CaPO4-induced AAA in male BALB/c mice, which was prevented in μMT mice. To further determine the importance of IgG in HHcy-aggravated AAA formation, we purified plasma IgG from HHcy or control mice and then transferred the IgG into μMT mice, which were subsequently subjected to elastase- or CaPO4-induced AAA. Compared with μMT mice that received plasma IgG from control mice, μMT mice that received HHcy plasma IgG developed significantly exacerbated elastase- or CaPO4-induced AAA accompanied by increased elastin degradation, MMP2/9 expression, and anti-β2GPI IgG deposition in vascular lesions, as shown by immunofluorescence histochemical staining. CONCLUSION: Our findings reveal a novel mechanism by which Hcy-induced B cell-derived pathogenic anti-β2GPI IgG might, at least in part, contribute to HHcy-aggravated chronic vascular inflammation and AAA formation. Published on behalf of the European Society of Cardiology. All rights reserved.