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Anti-dsDNA antibodies bind to TLR4 and activate NLRP3 inflammasome in lupus monocytes/macrophages
Zhang et al. J Transl Med
Anti-dsDNA antibodies bind to TLR4 and activate NLRP3 inflammasome in lupus monocytes/macrophages
Hui Zhang 0
Rong Fu 0
Chaohuan Guo 0
Yuefang Huang 1
Hongyue Wang 0
Shuang Wang 0
Jijun Zhao 0
Niansheng Yang 0
0 Department of Rheumatology, First Affiliated Hospital, Sun Yat-sen University , 58 Zhongshan Road II, Guangzhou 510080 , China
1 Department of Pediatrics, First Affiliated Hospital, Sun Yat-sen University , Zhongshan Road II, Guang- zhou 510080 , China
Background: NLRP3 inflammasome has been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The activation of NLRP3 inflammasome results in the production of IL-1β and the subsequent inflammation. Anti-dsDNA antibodies (anti-dsDNA Abs) play critical roles in the development and progression of SLE. However, the mechanism of NLRP3 inflammasome activation in SLE is still not known. This study investigated the activation of NLRP3 inflammasome stimulated by anti-dsDNA Abs in monocytes/macrophages from SLE patients. Methods: Monocytes/macrophages from SLE patients or healthy controls were stimulated with anti-dsDNA Ab-positive serum or purified anti-dsDNA Abs. Activation of inflammasome was measured by flow cytometry or Western blot. Anti-dsDNA Abs isolated from active SLE patients were injected into female (NZB × NZW) F1 mice and the activation of NLRP3 inflammasome and the frequencies of Th17 and Treg were examined. Results: The activity of caspase-1 was significantly increased in active SLE patients and was correlated with serum levels of anti-dsDNA Abs and disease activities. The concentrations of IL-1β and IL-17A were also significantly higher in SLE patients compared to healthy controls. Anti-dsDNA Ab-positive serum rather than healthy serum or RF (rheumatoid factor)-positive serum stimulated the activation of caspase-1 in monocytes. Anti-dsDNA Abs bound to TLR4 on macrophages and induced the production of ROS. Mitochondria-targeting antioxidant Mito-TEMPO, IκB kinase inhibitor peptide or TLR4 siRNA inhibited the activation of NLRP3 inflammasome and the secretion of IL-1β induced by antidsDNA Abs. Injection of anti-dsDNA Abs into (NZB × NZW) F1 mice resulted in increased caspase-1 activation and production of IL-1β and IL-17A. The Th17/Treg cell ratio also significantly increased following anti-dsDNA Ab injection. Conclusions: Anti-dsDNA Abs activated NLRP3 inflammasome in monocytes/macrophages from SLE patients by binding to TLR4 and inducing the production of mitochondrial ROS.
SLE; Anti-dsDNA antibodies; NLRP3 inflammasome; TLR4; Mitochondrial ROS
Background
Systemic lupus erythematosus (SLE) is a systemic
autoimmune disease with multiple organs involvement [
1
].
Despite the advances in the treatment of SLE, the
morbidity and mortality of the disease remain high [
2
].
Dysregulation of immune system plays a critical role in the
initiation and progression of SLE. Overproduction of
cytokines and the subsequent inflammation are involved
in the pathogenesis of SLE [
3
]. IL-1β is a
proinflammatory cytokine that has been linked to SLE. It has been
demonstrated that IL-1β is elevated in the serum of SLE
patients [
3, 4
] and IL-1 receptor antagonist led to clinical
and serological improvement [5]. In addition, IL-1β−/−
and IL-1α/β−/− mice are resistant to the induction of
experimental lupus [
6
].
Inflammasomes are a family of molecular platforms
mostly expressed in the cytoplasm of monocytes/
macrophages. Inflammasomes are activated by infection
or danger signals and trigger the maturation of
proinflammatory cytokines such as IL-1β to engage in innate
immune response [
7
]. NLRP3 inflammasome is one of
the most studied members. Activation of NLRP3
inflammasome involves the recruitment of adapter protein
apoptosis-associated speck like protein (ASC) through
homotypic PYD-PYD interaction. ASC subsequently
recruits pro-caspase-1 via CARD-CARD contact in turn.
The oligomerization of NLRP3 inflammasome leads to
autocatalytic activation of caspase-1, which converts
inactive pro-IL-1 into bioactive form [
8
]. NLRP3
inflammasome can be activated by either exogenous or
endogenous stimuli [
9–11
].
Anti-double stranded DNA (anti-dsDNA) antibodies
are the hallmark antibodies of SLE [
12
]. Anti-dsDNA
antibodies are correlated with disease activity [
13
] and
involved in the pathogenesis of SLE [
14
]. Anti-dsDNA
antibodies presented in the blood before disease onset
[
15
] and administration of anti-dsDNA antibodies from
SLE patients into NZBWF1/J mice resulted in
accelerated lupus [
16
]. Data showed that anti-dsDNA
antibodies stimulated the expression and secretion of IL-1β
from mononuclear cells and monocytes [
17, 18
]. It
implies that anti-dsDNA antibodies might initiate and
promote the disease by stimulating the production of
IL-1β.
Recently, we have showed that NLRP3 inflammasome
was activated in a mouse model of SLE, and inhibition
of NLRP3 inflammsome activation resulted in (...truncated)