Inhibition of STAT6 Activation by AS1517499 Inhibits Expression and Activity of PPARγ in Macrophages to Resolve Acute Inflammation in Mice.

Ye-Ji Lee,Minsuk Kim,Jihee Lee Kang,Young-Ho Ahn,Kiyoon Kim

doi:10.3390/biom12030447

Abstract

Signal transducer and activator of transcription 6 (STAT6) promotes an anti-inflammatory process by inducing the development of M2 macrophages. We investigated whether modulating STAT6 activity in macrophages using AS1517499, the specific STAT6 inhibitor, affects the restoration of homeostasis after an inflammatory insult by regulating PPARγ expression and activity. Administration of AS1517499 suppressed the enhanced STAT6 phosphorylation and nuclear translocation observed in peritoneal macrophages after zymosan injection. In addition, AS1517499 delayed resolution of acute inflammation as evidenced by enhanced secretion of pro-inflammatory cytokines, reduced secretion of anti-inflammatory cytokines in PLF and supernatants from peritoneal macrophages, and exaggerated neutrophil numbers and total protein levels in PLF. We demonstrate temporal increases in annexin A1 (AnxA1) protein and mRNA levels in peritoneal lavage fluid (PLF), peritoneal macrophages, and spleen in a murine model of zymosan-induced acute peritonitis. In vitro priming of mouse bone marrow-derived macrophages (BMDM) and peritoneal macrophages with AnxA1 induced STAT6 activation with enhanced PPARγ expression and activity. Using AS1517499, we demonstrate that inhibition of STAT6 activation delayed recovery of PPARγ expression and activity, as well as impaired efferocytosis. Taken together, these results suggest that activation of the STAT6 signaling pathway mediates PPARγ expression and activation in macrophages to resolve acute inflammation.

Highlights

Several members of the signal transducer and activator of transcription (STAT) family are involved in regulating macrophage functional status
To assess the direct effect of annexin A1 (AnxA1) on the activation of Signal transducer and activator of transcription 6 (STAT6) and PPARγ in macrophages, we investigated whether AnxA1 enhances the activation of STAT6 and PPARγ in mouse bone marrow-derived macrophages (BMDM) in vitro
We examined the role of STAT6 activation in PPARγ activation, peritoneal macrophage efferocytosis, and pro- or anti-inflammatory cytokine production during acute sterile inflammation

Summary

Introduction

Several members of the signal transducer and activator of transcription (STAT) family are involved in regulating macrophage functional status. STAT6 is the signal mediator of interleukin (IL)-4 and IL-13, promoting an anti-inflammatory process by inducing the development of T helper (Th) 2 lymphocytes and M2 type macrophages [1–5]. Activation of STAT6 is initiated by binding of IL-4 and IL-13 to their receptors, which leads to the activation of Janus tyrosine kinases (JAKs), which are associated with the cytoplasmic tails of the receptors. Macrophage M2 polarization involves tyrosine phosphorylation and activation of STAT6, which mediates the transcriptional activation of M2 macrophage-specific genes such as arginase 1 (Arg1), macrophage mannose receptor (MMR, known as Mrc1), resistin-like molecule α (Retnla, Fizz1), chitinase-like protein 3 (Chil, Ym1), and the chemokine genes.

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