Lipopolysaccharide and tumor necrosis factor-alpha induce lipopolysaccharide receptor expression on bone marrow cells by different mechanisms.
Two cell types, monocytes/macrophages and neutrophilic granulocytes, play a prominent role in the pathogenic effects of endotoxins during Gram-negative infections. We previously established that nanomolar concentrations of LPS induce the expression of new specific LPS-binding sites (LpsR) in bone marrow granulocytes of LPS-responsive mice. To examine this induction process further, we asked whether it, like other LPS activities, can be mediated by TNF-alpha. We report that exogenous rTNF-alpha can induce LpsR expression in bone marrow cells (BMC) from both LPS-responsive (C3H/HeOU) and LPS-hyporesponsive (C3H/HeJ) mice. In BMC, LPS elicited a down-regulation of the TNF-alpha receptors (TNF-R) without direct binding to TNF-R. On the other hand, taxol, a microtubule stabilizer that has shown LPS mimetic activity in macrophages, was unable to elicit LpsR expression or induce TNF-R down-regulation in BMC. Thus, unlike the LPS-signaling receptor of macrophages, that of BMC is apparently not functionally associated with microtubules. The LPS-induced expression of LpsR was inhibited only partially with an anti-TNF-alpha serum, and with dexamethasone, suggesting that an autocrine activity of endogenous TNF-alpha cannot alone account for the LPS effect. Comparative analyses also indicated that dexamethasone inhibited the LPS-induced increase of LpsR, but enhanced the number of TNF-induced LpsR+ BMC. Furthermore, the synthetic lipid PPDm2 (a 1,4-bisphosphorylated and N,N-diacylated derivative of 2,3-diamino-2,3-dideoxy-D-glucose) inhibited LPS-induced, but not TNF-induced, expression of LpsR. These data show that in BMC, LPS and TNF-alpha induce LpsR expression by different mechanisms.
Chaby
R
R
Equipe Endotoxines, URA-1116 du Centre National de la Recherche Scientifique, Université de Paris-Sud, Orsay, France.
Pedron
T
T
Stütz
P L
PL
Girard
R
R
D000818:Animals; D001853:Bone Marrow / Q000378:metabolism*; D001854:Bone Marrow Cells; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation; D005260:Female; D006017:Glycolipids / Q000494:pharmacology; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011971:Receptors, Immunologic / Q000096:biosynthesis* / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D006017:Glycolipids; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D011971:Receptors, Immunologic; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone