Beta2-adrenergic receptor regulates Toll-like receptor-4-induced nuclear factor-kappaB activation through beta-arrestin 2.
Toll-like receptors (TLRs) play an important role in innate immunity while, beta(2)-adrenergic receptors (beta(2)AR) provide the key linkages for the sympathetic nervous system to regulate the immune system. However, their role in macrophages remains uncertain. Here, we demonstrate the cross-talk between beta(2)AR and TLR signalling pathways. Expression of beta(2)AR was down-regulated by TLR4 ligand lipopolysaccharide (LPS) stimulation. To investigate the physiological consequence of this down-regulation RAW264 cells, a macrophage cell line, were transfected with a beta(2)AR expression vector (RAWar). Both LPS-stimulated inducible nitric oxide synthase (NOS II) expression and NO production were markedly suppressed in the RAWar cells. The activation of nuclear factor-kappaB (NF-kappaB) and degradation of the inhibitor of NF-kappaB (IkappaBalpha) in response to LPS were markedly decreased in these cells. The level of beta-arrestin 2, which regulates beta(2)AR signalling, was also reduced in RAW264 cells after stimulation with LPS, but not in RAWar cells. Overexpression of beta-arrestin 2 (RAWarr2) also inhibited NO production and NOS II expression. Furthermore, we demonstrated that beta-arrestin 2 interacted with cytosolic IkappaBalpha and that the level of IkappaBalpha coimmunoprecipitated by anti-beta-arrestin 2 antibodies was decreased in the RAW264 cells but not in RAWar or RAWarr2 cells. These findings suggest that LPS-stimulated signals suppress beta(2)AR expression, leading to down-regulation of beta-arrestin 2 expression, which stabilizes cytosolic IkappaBalpha and inhibits the NF-kappaB activation essential for NOS II expression, probably to ensure rapid and sufficient production of NO in response to microbial attack.
Kizaki
Takako
T
Department of Molecular Predictive Medicine and Sport Science, Kyorin University, School of Medicine, Mitaka, Japan. kizaki@kyorin-u.ac.jp
Izawa
Tetsuya
T
Sakurai
Takuya
T
Haga
Shukoh
S
Taniguchi
Naoyuki
N
Tajiri
Hisao
H
Watanabe
Kenji
K
Day
Noorbibi K
NK
Toba
Kenji
K
Ohno
Hideki
H
D000818:Animals; D019390:Arrestins / Q000276:immunology*; D002460:Cell Line; D015536:Down-Regulation / Q000276:immunology; D024202:Electrophoretic Mobility Shift Assay; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000276:immunology*; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605258:Arrb2 protein, mouse; D019390:Arrestins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D018343:Receptors, Adrenergic, beta-2; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D052247:Nitric Oxide Synthase Type II