Distinct Transcriptional Profile Activated by SCYE1 Through JAK‐mediated STAT3 in Partially Activated Macrophages

Abstract

Small inducible cytokine subfamily E, member 1, SCYE1 (also known as EMAP II) is a secreted factor that is locally expressed near sites of injury, labeled as a ‘find‐me’ signal, and recruits macrophages and neutrophils. Our previous studies identified that macrophages sustained protein expression of SCYE1. The transcriptional events that occur within the recruited macrophages in response to SCYE1 are unknown. The objective was to identify the transcription factor activated in partially activated thioglycollate macrophages upon exposure to SCYE1.Partially activated murine thioglycollate‐elicited macrophages (TEPMs) were exposed to SCYE1. Following 2 hours of exposure to either vehicle or SCYE1, fractionated nuclear proteins from TEPMs were used for a luminescence based transcription factor activation screen. The acute SCYE1‐mediated transcription factor activation was assessed by immunoblotting and gene expression by quantitative PCR. Secreted cytokines were measured in supernatants of TEPMs exposed to either vehicle or SCYE1 while pre‐treated with +/− JAK1/2 inhibitor, Ruxolitinib.In this study, we identify STAT3 (Signal Transducer and Activator of Transcription 3) as the most activated transcription factor mediated by SCYE1 in a model of partially activated, recruited thioglycollate‐elicited peritoneal macrophages. The acute and dose‐dependent phosphorylation of STAT3 (Y705) occurs between 5 and 15 minutes in response to SCYE1. Its activation is SCYE1‐specific and could be prevented by inhibition of Janus Associated Kinase (JAK) 1/2.We profiled not only anti‐ and pro‐inflammatory genes but also that of STAT3 target genes upon exposure to SCYE1. STAT3 target genes Arg1 and Socs3, commonly activated in anti‐inflammatory macrophages, are maximal by 1 to 2 hours of exposure to SCYE1. Yet Il10 expression decreased by 1 hour suggesting that any persisting STAT3 activation was not due to Il10. There was also rapid increase of chemokine STAT3 target genes Ccl5 along with other genes activated that are typically found in pro‐inflammatory macrophages.Unlike activated transcription, neither secreted IL‐6 nor IL‐10 was elevated by SCYE1. Consistent with a JAK‐STAT signature, both IL‐1a and G‐CSF secretion by SCYE1 was elevated and could be prevented by JAK inhibition.Our results identify a rapid SCYE1‐mediated STAT3 activation that coincides with both pro‐ and anti‐inflammatory gene expression in partially activated macrophages.Support or Funding InformationFunding: This publication was made possible in part by 5R01HL114977 (MAS) from NIH and the Lilly Endowment, Inc. Physician Scientist Initiative (MAS).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.