Anti-inflammatory activities of fenoterol through β-arrestin-2 and inhibition of AMPK and NF-κB activation in AICAR-induced THP-1 cells

The AMP-activated protein kinase (AMPK) pathway has been shown to be able to regulate inflammation in several cell lines. We reported that fenoterol, a beta(2)-adrenergic receptor (beta(2)-AR) agonist, inhibited lipopolysaccharide (LPS)-induced AMPK activation and inflammatory cytokine production in THP-1 cells, a monocytic cell line in previous studies. 5-amino-1-beta-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) is an agonist of AMPK. Whether AICAR induced AMPK activation and inflammatory cytokine production in THP-1 cells can be inhibited by fenoterol is unknown. In this study, we explored the mechanism of beta(2)-AR stimulation with fenoterol in AICAR-induced inflammatory cytokine secretion in THP-1 cells. We studied AMPK activation using p-AMPK and AMPK antibodies, nuclear factor-kappa B (NF-kappa B) activation and inflammatory cytokine secretion in THP-1 cells stimulated by beta(2)-AR in the presence or absence of AICAR and small interfering RNA (siRNA)-mediated knockdown of beta-arrestin-2 or AMPK alpha 1 subunit. AICAR-induced AMPK activation, NF-kappa B activation and tumor necrosis factor (TNF)-alpha release were reduced by fenoterol. In addition, siRNA-mediated knockdown of beta-arrestin-2 abolished fenoterol's inhibition of AICAR-induced AMPK activation and TNF-alpha release, thus beta-arrestin-2 mediated the anti-inflammatory effects of fenoterol in AICAR-treated THP-1 cells. Furthermore, siRNA-mediated knockdown of AMPKa1 significantly attenuated AICAR-induced NF-kappa B activation and TNF-alpha release, so AMPKa1 was a key signaling molecule involved in AICAR-induced inflammatory cytokine production. These data suggested that fenoterol inhibited AICAR-induced AMPK activation and TNF-alpha release through beta-arrestin-2 in THP-1 cells. Management especially inhibition of AMPK signaling may provide new approaches and strategies for the treatments of immune diseases including inflammatory diseases and other critical illness. Published by Elsevier Masson SAS.