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Inhibiting nucleolin reduces inflammation induced by mitochondrial DNA in cardiomyocytes exposed to hypoxia and reoxygenation.

ABSTRACT: BACKGROUND AND PURPOSE:Cellular debris causes sterile inflammation after myocardial infarction. Mitochondria constitute about 30 percent of the human heart. Mitochondrial DNA (mtDNA) is a damage-associated-molecular-pattern that induce injurious sterile inflammation. Little is known about mtDNA's inflammatory signalling pathways in cardiomyocytes and how mtDNA is internalized to associate with its putative receptor, toll-like receptor 9 (TLR9). EXPERIMENTAL APPROACH:We hypothesized that mtDNA can be internalized in cardiomyocytes and induce an inflammatory response. Adult mouse cardiomyocytes were exposed to hypoxia-reoxygenation and extracellular DNA. Microscale thermophoresis was used to demonstrate binding between nucleolin and DNA. KEY RESULTS:Expression of the pro-inflammatory cytokines IL-1? and TNF? were upregulated by mtDNA, but not by nuclear DNA (nDNA), in cardiomyocytes exposed to hypoxia-reoxygenation. Blocking the RNA/DNA binding protein nucleolin with midkine reduced expression of IL-1?/TNF? and the nucleolin inhibitor AS1411 reduced interleukin-6 release in adult mouse cardiomyocytes. mtDNA bound 10-fold stronger than nDNA to nucleolin. In HEK293-NF-?B reporter cells, mtDNA induced NF-?B activity in normoxia, while CpG-DNA and hypoxia-reoxygenation, synergistically induced TLR9-dependent NF-?B activity. Protein expression of nucleolin was found in the plasma membrane of cardiomyocytes and inhibition of nucleolin with midkine inhibited cellular uptake of CpG-DNA. Inhibition of endocytosis did not reduce CpG-DNA uptake in cardiomyocytes. CONCLUSION AND IMPLICATIONS:mtDNA, but not nDNA, induce an inflammatory response in mouse cardiomyocytes during hypoxia-reoxygenation. In cardiomyocytes, nucleolin is expressed on the membrane and blocking nucleolin reduce inflammation. Nucleolin might be a therapeutic target to prevent uptake of immunogenic DNA and reduce inflammation. LINKED ARTICLES:This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

SUBMITTER: Mariero LH

PROVIDER: S-EPMC6887679 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Inhibiting nucleolin reduces inflammation induced by mitochondrial DNA in cardiomyocytes exposed to hypoxia and reoxygenation.

Mariero Lars Henrik LH Torp May-Kristin MK Heiestad Christina Mathisen CM Baysa Anton A Li Yuchuan Y Valen Guro G Vaage Jarle J Stensløkken Kåre-Olav KO

British journal of pharmacology 20191027 22

<h4>Background and purpose</h4>Cellular debris causes sterile inflammation after myocardial infarction. Mitochondria constitute about 30 percent of the human heart. Mitochondrial DNA (mtDNA) is a damage-associated-molecular-pattern that induce injurious sterile inflammation. Little is known about mtDNA's inflammatory signalling pathways in cardiomyocytes and how mtDNA is internalized to associate with its putative receptor, toll-like receptor 9 (TLR9).<h4>Experimental approach</h4>We hypothesize ...[more]

PMID: 31412132

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Inhibiting nucleolin reduces inflammation induced by mitochondrial DNA in cardiomyocytes exposed to hypoxia and reoxygenation.

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Inhibiting nucleolin reduces inflammation induced by mitochondrial DNA in cardiomyocytes exposed to hypoxia and reoxygenation.

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