Adherence regulates macrophage signal transduction and primes tumor necrosis factor production.
While monocyte/macrophage (Mphi) adherence to a matrix is necessary for differentiation and prolonged survival, the effect of adherence on the signaling mechanisms responsible for Mphi activation is unknown. Lipopolysaccharide (LPS) activates Mphi by signaling through members of the mitogen activated protein kinase (MAPK) family thereby inducing transcription of proinflammatory cytokines, such as TNF-alpha. Since adherence has been shown to affect different activities of various myeloid phagocytes, we investigated whether adherence affects intracellular signaling and modulates activation of the Mphi proinflammatory phenotype. We assessed the effect of adherence on activation of rabbit alveolar Mphi by measuring LPS-induced TNF-alpha mRNA and TNF-alpha secreted product in adherent versus nonadherent cells, in vitro. The effect of adherence on LPS-induced activation of MAPK was assessed by western analysis using a dual phosphospecific antibody against p38MAPK, p42,44ERK, and p54SAPK. LPS is known to induce activation of NF-kappaB and AP-1. Modulation of these two transcription factors by LPS under adherent versus nonadherent conditions was evaluated by gel-shift analyses. The results were that adherent cells treated with LPS, 10 ng/mL or 1 microg/ml, elicited a 26- and 132-fold increase, respectively, in TNF-alpha production. Nonadherent cells did not elicit significant TNF-alpha in response to LPS. Adherence alone induced significant ERK and AP-1 activation, but did not stimulate a significant TNF-alpha response and no further activation of ERK and AP-1 was observed with LPS stimulation. Adherence alone did not activate p38MAPK or NF-kappaB, but primed Mphi for an augmented response to LPS in activation of p38, NF-kappaB and in production of TNF-alpha. We conclude that adherence primes Mphi for activation and regulates MAPK signal transduction pathways.
Bauer
G J
GJ
Department of Surgery, University of Washington Medical School, Seattle, USA.
Arbabi
S
S
Garcia
I A
IA
de Hingh
I
I
Rosengart
M R
MR
Maier
R V
RV
D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion; D017931:DNA Primers / Q000235:genetics; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000502:physiology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics
D017931:DNA Primers; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases