Glycogen synthase kinase 3β promotes liver innate immune activation by restraining AMP-activated protein kinase activation

Background & Aims: Glycogen synthase kinase 3 beta (Gsk3 beta [Gsk3 beta]) is a ubiquitously expressed kinase with distinctive functions in different types of cells. Although its roles in regulating innate immune activation and ischaemia and reperfusion injuries (IRIs) have been well documented, the underlying mechanisms remain ambiguous, in part because of the lack of cell-specific tools in vivo. Methods: We created a myeloid-specific Gsk3 beta knockout (KO) strain to study the function of Gsk3 beta in macrophages in a murine liver partial warm ischaemia model. Results: Compared with controls, myeloid Gsk3 beta KO mice were protected from IRI, with diminished proinflammatory but enhanced anti-inflammatory immune responses in livers. In bone marrow-derived macrophages, Gsk3 beta deficiency resulted in an early reduction of Tnf gene transcription but sustained increase of Il10 gene transcription on Toll-like receptor 4 stimulation in vitro. These effects were associated with enhanced AMP-activated protein kinase (AMPK) activation, which led to an accelerated and higher level of induction of the novel innate immune negative regulator small heterodimer partner (SHP [Nr0b2]). The regulatory function of Gsk3 beta on AMPK activation and SHP induction was confirmed in wild-type bone marrow-derived macrophages with a Gsk3 inhibitor. Furthermore, we found that this immune regulatory mechanism was independent of Gsk3 beta Ser9 phosphorylation and the phosphoinositide 3-kinase-Akt signalling pathway. In vivo, myeloid Gsk3 beta deficiency facilitated SHP upregulation by ischaemia-reperfusion in liver macrophages. Treatment of Gsk3 beta KO mice with either AMPK inhibitor or SHP small interfering RNA before the onset of liver ischaemia restored liver proinflammatory immune activation and IRI in these otherwise protected hosts. Additionally, pharmacological activation of AMPK protected wild-type mice from liver IRI, with reduced proinflammatory immune activation. Inhibition of the AMPK-SHP pathway by liver ischaemia was demonstrated in tumour resection patients. Conclusions: Gsk3 beta promotes innate proinflammatory immune activation by restraining AMPK activation. Lay summary: Glycogen synthase kinase 3 beta promotes macrophage inflammatory activation by inhibiting the immune regulatory signalling of AMP-activated protein kinase and the induction of small heterodimer partner. Therefore, therapeutic targeting of glycogen synthase kinase 3 beta enhances innate immune regulation and protects liver from ischaemia and reperfusion injury. (C) 2018 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.