Btk regulates macrophage polarization in response to lipopolysaccharide.
Bacterial Lipopolysaccharide (LPS) is a strong inducer of inflammation and does so by inducing polarization of macrophages to the classic inflammatory M1 population. Given the role of Btk as a critical signal transducer downstream of TLR4, we investigated its role in M1/M2 induction. In Btk deficient (Btk (-\-)) mice we observed markedly reduced recruitment of M1 macrophages following intraperitoneal administration of LPS. Ex vivo analysis demonstrated an impaired ability of Btk(-/-) macrophages to polarize into M1 macrophages, instead showing enhanced induction of immunosuppressive M2-associated markers in response to M1 polarizing stimuli, a finding accompanied by reduced phosphorylation of STAT1 and enhanced STAT6 phosphorylation. In addition to STAT activation, M1 and M2 polarizing signals modulate the expression of inflammatory genes via differential activation of transcription factors and regulatory proteins, including NF-κB and SHIP1. In keeping with a critical role for Btk in macrophage polarization, we observed reduced levels of NF-κB p65 and Akt phosphorylation, as well as reduced induction of the M1 associated marker iNOS in Btk(-/-) macrophages in response to M1 polarizing stimuli. Additionally enhanced expression of SHIP1, a key negative regulator of macrophage polarisation, was observed in Btk(-/-) macrophages in response to M2 polarizing stimuli. Employing classic models of allergic M2 inflammation, treatment of Btk (-/-) mice with either Schistosoma mansoni eggs or chitin resulted in increased recruitment of M2 macrophages and induction of M2-associated genes. This demonstrates an enhanced M2 skew in the absence of Btk, thus promoting the development of allergic inflammation.
Molecular and Cellular Therapeutics and RCSI Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland.
Joan
J
Ní Gabhann
Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland.
Emily
E
Hams
Molecular and Cellular Therapeutics and RCSI Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland.
Siobhán
S
Smith
Molecular and Cellular Therapeutics and RCSI Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland ; School of Biological Sciences, Dublin Institute of Technology, Kevin St, Dublin, Ireland.
Claire
C
Wynne
Molecular and Cellular Therapeutics and RCSI Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland.
Jennifer C
JC
Byrne
Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland.
Kiva
K
Brennan
Centre for Infection and Immunity, School of Medicine Dentistry and Biomedical Sciences, Queen's University, Belfast, United Kingdom.
Shaun
S
Spence
Centre for Infection and Immunity, School of Medicine Dentistry and Biomedical Sciences, Queen's University, Belfast, United Kingdom.
Adrien
A
Kissenpfennig
Amgen Inc., Thousand Oaks, California, United States of America.
James A
JA
Johnston
Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland ; Institute of Molecular Medicine, St. James's Hospital, Trinity College Dublin, Dublin, Ireland ; National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland.
Padraic G
PG
Fallon
Molecular and Cellular Therapeutics and RCSI Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland.
Caroline A
CA
Jefferies
D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D016764:Cell Polarity / Q000187:drug effects*; D006967:Hypersensitivity / Q000150:complications / Q000201:enzymology / Q000473:pathology; D007249:Inflammation / Q000150:complications / Q000201:enzymology / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase