Myocyte TLR4 enhances enteric and systemic inflammation driving late murine endotoxic ileus.
Myocytes are nonhemopoietic in origin and functionally essential in generating gastrointestinal motility. In endotoxemia, a rapid-onset nonhemopoietic mechanism potently triggers early ileus in a Toll-like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (MyD88)-dependent manner. Moreover, synergistically with hemopoietic cells, nonhemopoietic cells escalate late ileus via an IL-6 receptor-dependent inflammation-driven pathway. We therefore specifically investigated the role of myocytes in TLR4-triggered inflammation and ileus. TLR4(+/+), TLR4(-/-), bmTLR4(+/+)/TLR4(-/-) chimera, SM22-Cre(-/-)TLR4(flox/flox), and selective myocyte TLR4-deficient (SM22-Cre(+/-)TLR4(flox/flox)) mice were injected intraperitoneally with purified lipopolysaccharide. SM22-driven Cre recombinase activity was selectively detected in cardiac, gastrointestinal, skeletal, and vascular myocytes, of small-sized vessels in a two-color fluorescent Cre reporter mouse. In contrast to nonhemopoietic TLR4 deficiency, deletion of myocyte TLR4 signaling prevented neither endotoxin-induced suppression of spontaneous jejunal contractility in vitro nor early ileus in vivo at 6 h. Circulating plasma colony-stimulating factor 3 was greatly elevated during endotoxemia, independent of myocyte TLR4 signaling or time. TLR4 activation of myocytes contributed significantly to an early enteric IL-6 mRNA induction and systemic IL-6 release, as well as to a late increase in circulating chemokine (C-X-C motif) ligand 1 (CXCL1) and IL-17. Consequently, inhibition of myocyte TLR4 signaling allowed functional recovery of motility by preventing inflammation-driven late ileus at 24 h. Direct TLR4 activation of myocytes is not responsible for nonhemopoietic-mediated early ileus. However, myocytes are proinflammatory cells that potently drive enteric and systemic inflammation, subsequently fueling late mediator-triggered ileus. Specifically, the myocyte TLR4-dependent inflammatory signature of elevated plasma IL-6, CXCL1, and IL-17 is strongly associated with late rodent ileus.
Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Surgery, Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany; and.
Bettina M
BM
Buchholz
Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania;
Richard A
RA
Shapiro
Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania;
Yoram
Y
Vodovotz
Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania;
Timothy R
TR
Billiar
Division of Pediatric Surgery, Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
Chhinder P
CP
Sodhi
Division of Pediatric Surgery, Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
David J
DJ
Hackam
Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Physiology and Pharmacology, Liberty University College of Osteopathic Medicine, Lynchburg, Virginia ajmbauer@liberty.edu.
Anthony J
AJ
Bauer
D000818:Animals; D018925:Chemokines / Q000276:immunology*; D007079:Ileitis / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology*; D045823:Ileus / Q000276:immunology* / Q000473:pathology*; D007155:Immunologic Factors / Q000276:immunology; D008070:Lipopolysaccharides; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D032342:Muscle Cells / Q000276:immunology* / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000276:immunology*
D018925:Chemokines; D007155:Immunologic Factors; D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4
Cre reporter IRG mouse; gastrointestinal motility; lipopolysaccharide