Michelle S M A Damen1, Jéssica Cristina Dos Santos2, Rob Hermsen3, J Adam van der Vliet4, Mihai G Netea1, Niels P Riksen1, Charles A Dinarello5, Leo A B Joosten6, Bas Heinhuis1. 1. Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Nijmegen, The Netherlands. 2. Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Nijmegen, The Netherlands; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Brazil. 3. Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands. 4. Division of Vascular and Transplant Surgery, Department of Surgery, Radboud University Medical Centre, Nijmegen, The Netherlands. 5. Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Nijmegen, The Netherlands; School of Medicine, Division of Infectious Diseases, University of Colorado Denver, Aurora, CO 80045, USA. 6. Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Nijmegen, The Netherlands. Electronic address: leo.joosten@radboudumc.nl.
Abstract
BACKGROUND AND AIMS: The role of interleukin (IL-)32 in inflammatory conditions is well-established, however, the mechanism behind its role in atherosclerosis remains unexplained. Our group reported a promoter single nucleotide polymorphism in IL-32 associated with higher high-density lipoprotein (HDL) concentrations. We hypothesize that endogenous IL-32 in liver cells, a human monocytic cell line and carotid plaque tissue, can affect atherosclerosis by regulating (HDL) cholesterol homeostasis via expression of cholesterol transporters/mediators. METHODS: Human primary liver cells were stimulated with recombinant human (rh)TNFα and poly I:C to study the expression of IL-32 and mediators in cholesterol pathways. Additionally, IL-32 was overexpressed in HepG2 cells and overexpressed and silenced in THP-1 cells to study the direct effect of IL-32 on cholesterol transporters expression and function. RESULTS: Stimulation of human primary liver cells resulted in induction of IL-32α, IL-32β and IL-32γ mRNA expression (p < 0.01). A strong correlation between the expression of IL-32γ and ABCA1, ABCG1, LXRα and apoA1 was observed (p < 0.01), and intracellular lipid concentrations were reduced in the presence of endogenous IL-32 (p < 0.05). Finally, IL32γ and ABCA1 mRNA expression was upregulated in carotid plaque tissue and when IL-32 was silenced in THP-1 cells, mRNA expression of ABCA1 was strongly reduced. CONCLUSIONS: Regulation of IL-32 in human primary liver cells, HepG2 and THP-1 cells strongly influences the mRNA expression of ABCA1, ABCG1, LXRα and apoA1 and affects intracellular lipid concentrations in the presence of endogenous IL-32. These data, for the first time, show an important role for IL32 in cholesterol homeostasis.
BACKGROUND AND AIMS: The role of interleukin (IL-)32 in inflammatory conditions is well-established, however, the mechanism behind its role in atherosclerosis remains unexplained. Our group reported a promoter single nucleotide polymorphism in IL-32 associated with higher high-density lipoprotein (HDL) concentrations. We hypothesize that endogenous IL-32 in liver cells, a human monocytic cell line and carotid plaque tissue, can affect atherosclerosis by regulating (HDL) cholesterol homeostasis via expression of cholesterol transporters/mediators. METHODS:Human primary liver cells were stimulated with recombinant human (rh)TNFα and poly I:C to study the expression of IL-32 and mediators in cholesterol pathways. Additionally, IL-32 was overexpressed in HepG2 cells and overexpressed and silenced in THP-1 cells to study the direct effect of IL-32 on cholesterol transporters expression and function. RESULTS: Stimulation of human primary liver cells resulted in induction of IL-32α, IL-32β and IL-32γ mRNA expression (p < 0.01). A strong correlation between the expression of IL-32γ and ABCA1, ABCG1, LXRα and apoA1 was observed (p < 0.01), and intracellular lipid concentrations were reduced in the presence of endogenous IL-32 (p < 0.05). Finally, IL32γ and ABCA1 mRNA expression was upregulated in carotid plaque tissue and when IL-32 was silenced in THP-1 cells, mRNA expression of ABCA1 was strongly reduced. CONCLUSIONS: Regulation of IL-32 in human primary liver cells, HepG2 and THP-1 cells strongly influences the mRNA expression of ABCA1, ABCG1, LXRα and apoA1 and affects intracellular lipid concentrations in the presence of endogenous IL-32. These data, for the first time, show an important role for IL32 in cholesterol homeostasis.
Authors: Jéssica Cristina Dos Santos; Valéria Bernadete Leite Quixabeira; Muriel Vilela Teodoro Silva; Michelle S M A Damen; Kiki Schraa; Martin Jaeger; Marije Oosting; Samuel T Keating; Miriam Leandro Dorta; Sebastião Alves Pinto; Fernanda Bugalho Duarte; Ledice Inácia de Araújo Pereira; Mihai G Netea; Fátima Ribeiro-Dias; Leo A B Joosten Journal: PLoS Negl Trop Dis Date: 2020-02-05