Human monocyte CD14 is upregulated by lipopolysaccharide

Abstract

Membrane CD14 is involved in lipopolysaccharide (LPS)-induced monocyte activation; it binds LPS, and antibodies against CD14 block the effects of low-dose LPS. It is unknown how LPS regulates its own receptor CD14 in vitro. Therefore, we investigated the effects of LPS on CD14 mRNA and membrane and soluble CD14 (mCD14 and sCD14, respectively) in human monocytes and macrophages. No changes were observed during the first 3 h of LPS stimulation. After 6 to 15 h, LPS weakly reduced CD14 mRNA and mCD14 and transiently enhanced sCD14 release. A 2-day incubation with LPS caused increases in the levels of CD14 mRNA (2-fold), mCD14 (2-fold), sCD14 (1.5-fold), and LPS-fluorescein isothiocyanate binding (1.5-fold); a 5-h incubation with LPS was sufficient to induce the late effects on mCD14 and sCD14. The maximal effect on mCD14 and sCD14 was reached with >1 ng of LPS per ml; the proportional distribution of the two sCD14 isoforms was not modified by LPS. Besides rough and smooth LPS, lipid A, heat-killed Escherichia coli, lipoteichoic acid, and Staphylococcus aureus cell wall extract (10 g/ml) caused similar increases of mCD14. The LPS effect was blocked by polymyxin B but not by anti-tumor necrosis factor alpha, anti-interleukin-6, anti-gamma interferon, and anti-LPS-binding protein. LPS-induced tumor necrosis factor alpha production was abolished after a second 4-h challenge. In contrast, the LPS-induced increases CD14 mRNA, mCD14, and sCD14 were stronger and appeared earlier after a second LPS challenge. In conclusion, CD14 is transcriptionally upregulated by LPS and other bacterial cell wall constituents. MATERIALS AND METHODSReagents. Escherichia coli ATCC 25922 was grown overnight in Mueller-Hinton broth at 37ЊC and heat killed by 15-min boiling. LPS preparations (Salmonella enterica serovar typhimurium and LPS-FITC), lipoteichoic acid (from Enterococcus faecalis), bovine serum albumin (BSA), and laurylsarcosine were purchased from Sigma Chemical Co., (St. Louis, Mo.). E. coli Re LPS, S. enterica serovar abortusequi smooth LPS, lipid A, and Staphylococcus aureus cell wall extract were kind gifts from C. Galanos (Freiburg i.Br., Germany). Anti-tumor necrosis factor alpha (TNF-␣) monoclonal antibodies (MAbs) were donated by Knoll (Ludwigshafen, Germany), and anti-gamma interferon (IFN-␥) antibodies were donated by H. Gallati (Hoffmann-La Roche, Basel, Switzerland). Goat anti-human anti-LBP antiserum and the CD14 cDNA probe was kindly provided

Systemic inflammation in acute cardiorenal syndrome: an observational pilot study

“…In addition, the reduced ability of E. coli-induced monocyte activation among CRS patients (Groups 1 and 4) in comparison with hypertensive control patients (Groups 3 and 5) implies a higher degree of activated monocytes in vivo, as lipopolysaccharide is known to activate CD14 expression in monocytes. 28 In fact, a previous study demonstrated that an enhanced expression of the membrane-bound adhesion molecule CD11b reduces the ability for in vitro stimulation of monocytes and vice versa. 29 In our study, elevated endotoxin levels were not detected.…”

Chronic immune activation in common variable immunodeficiency (CVID) is associated with elevated serum levels of soluble CD14 and CD25 but not endotoxaemia

“…Complex interactions between LPS, CD14, myeloid differentiation-2 (MD-2) and Toll-like receptor (TLR)-4 results in an activation of the nuclear factor kappa-lightchain-enhancer of activated B cells (NFkB) signalling pathway and production of multiple inflammatory factors [24][25][26][27]. The MD-2/TLR-4/LPS complex induces shedding and secretion of soluble CD14 (sCD14) from myeloid cells [28][29][30]. Plasma or serum levels of sCD14 are generally accepted as reliable markers of bacterial translocation and endotoxaemia [24,[31][32][33][34].…”

A lipoteichoic acid fraction of Enterococcus hirae activates cultured human monocytic cells via a CD14-independent pathway to promote cytokine production, and the activity is inhibited by serum components

“…Experimental evidence ( Table 4) indicated that QM-1M stimulated THP-1 cells to produce IL-8 through a CD14-independent pathway (unlike the reference LPS), although QM-1M slightly upregulated mCD14 on THP-1 cells (Fig. 3) as suggested by Landmann et al [16]. In contrast, there are reports of CD14-dependent activities of LTA preparations [4^6].…”