Fenoterol, a beta(2)-adrenoceptor agonist, inhibits LPS-induced membrane-bound CD14, TLR4/CD14 complex, and inflammatory cytokines production through beta-arrestin-2 in THP-1 cell line.
OBJECTIVE
To investigate the molecular mechanism and signaling pathway by which fenoterol, a beta(2)-adrenergic receptor (beta(2)-AR) agonist, produces anti-inflammatory effects.


METHODS
THP-1, a monocytic cell line, was used to explore the mechanism of beta(2)-AR stimulation in LPS-induced secretion of inflammatory cytokines and changes of toll-like receptors (TLRs). We labeled TLR4 and CD14 using monoclonal anti-TLR4 PE-conjugated and anti-CD14 FITC-conjugated antibodies in THP-1 cells stimulated by beta(2)-AR in the presence or absence of lipopolysaccharide (LPS) and small, interfering RNA (siRNA)-mediated knockdown of beta-arrestin-2, and then analyzed their changes in distribution by flow cytometry, Western blotting and confocal analysis.


RESULTS
LPS-induced membrane-bound CD14, TLR4/CD14 complex levels and elevation of inflammatory cytokines were all significantly reduced by pre-incubation of fenoterol (P<0.05). However, the total level of CD14 and TLR4 was not significantly changed. Interestingly, confocal microscopy revealed redistribution of CD14 and TLR4/CD14 complex under beta(2)-AR stimulation. Furthermore, siRNA-mediated knockdown of beta-arrestin-2 eliminated the anti-inflammatory effects and redistribution of CD14 and TLR4/CD14 complex stimulated by beta(2)-AR.


CONCLUSIONS
beta(2)-AR agonist exerts its anti-inflammatory effects by down-regulating TLR signaling in THP-1 cells, potentially resulting from beta-arrestin-2 mediated redistribution of CD14 and TLR14/CD14 complex.
Wang
Wei
W
Department of Respiratory Medicine, Peking University Third Hospital, Beijing, China.
Xu
Ming
M
Zhang
You-yi
YY
He
Bei
B
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D019390:Arrestins / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D016207:Cytokines / Q000187:drug effects* / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005280:Fenoterol / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D007249:Inflammation / Q000188:drug therapy / Q000276:immunology; D018836:Inflammation Mediators / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides; D018613:Microscopy, Confocal; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000187:drug effects / Q000378:metabolism; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605254:ARRB2 protein, human; D000318:Adrenergic beta-Agonists; D019390:Arrestins; D016207:Cytokines; D018836:Inflammation Mediators; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D005280:Fenoterol