LOX-1, mtDNA damage, and NLRP3 inflammasome activation in macrophages: implications in atherogenesis.
OBJECTIVE
Lectin-like ox-LDL scavenger receptor-1 (LOX-1) and mitochondrial DNA (mtDNA) damage play a key role in a variety of cardiovascular diseases, including atherosclerosis, hypertension, and inflammation. We posited that damaged mtDNA could trigger autophagy and NLRP3 inflammasome activation, and LOX-1 may play a critical role in this process.


RESULTS
In order to examine this hypothesis, cultured human THP-1 macrophages exposed to lipopolysaccharide (LPS) were applied to study the link between LOX-1, mtDNA damage, autophagy, and NLRP3 inflammasome expression. Our data showed that LPS markedly induced LOX-1 expression, reactive oxygen species (ROS) generation, autophagy, mtDNA damage, and NLRP3 inflammasome. LOX-1 inhibition with a binding antibody or siRNA inhibited ROS generation, autophagy and mtDNA damage, and a decreased expression of NLRP3 inflammasome. To study the LOX-1-NLRP3 inflammasome signalling, we performed studies using ROS inhibitors and an autophagy inducer, and found that both decreased the expression of NLRP3. On the other hand, autophagy inhibitor enhanced the expression of NLRP3 inflammasome. Knockdown of DNase II inhibited autophagy and NLRP3 inflammasome, providing further support for our hypothesis. Finally, we confirmed the relationship between LOX-1, ROS, mtDNA damage, autophagy, and NLRP3 inflammasome activation in primary macrophages.


CONCLUSIONS
This study based on THP-1 macrophages and primary macrophages indicates that LOX-1-mediated autophagy and mtDNA damage play an essential role in NLRP3 inflammasome activation in inflammatory disease states.
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China School of Food and Biological Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, PR China.
Zufeng
Z
Ding
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China mehtajl@uams.edu sliu2@uams.edu.
Shijie
S
Liu
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Xianwei
X
Wang
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Yao
Y
Dai
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Magomed
M
Khaidakov
Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China.
Xiaoyan
X
Deng
Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China.
Yubo
Y
Fan
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
David
D
Xiang
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA mehtajl@uams.edu sliu2@uams.edu.
Jawahar L
JL
Mehta
D050197:Atherosclerosis / Q000378:metabolism*; D001343:Autophagy / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004272:DNA, Mitochondrial / Q000378:metabolism*; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D017382:Reactive Oxygen Species / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D002352:Carrier Proteins; D004272:DNA, Mitochondrial; D058847:Inflammasomes; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C495137:OLR1 protein, human; D017382:Reactive Oxygen Species; D051127:Scavenger Receptors, Class E
Autophagy; LOX-1; Mitochondrial DNA; NLRP3; ROS