CpG DNA-mediated immune response in pulmonary endothelial cells

Abstract

In this study, we show that both mouse and rat lung EC display constitutive expression of TLR9 mRNA. Exposure to CpG DNA induced a potent proinflammatory response as manifested by an increased expression of IL-8 and ICAM-1 in mouse pulmonary EC. The proinflammatary response was sensitive to chloroquine, consistent with a role of endosomal contribution. A role for p38 MAPK and NF-B pathway was apparent as the response was sensitive to inhibitors of p38 MAPK and NF-B but was not affected by inhibitors of ERK1/2. A synergistic effect of CpG DNA and LPS on the inflammatory response is consistent with multiple TLR interaction in EC. This study suggests a possible role for CpG DNA-mediated EC immune response in the host defense system. It also has important implications in plasmid DNA-mediated pulmonary endothelium gene transfer. CpG motif; lung THE VASCULAR ENDOTHELIUM SERVES as the key barrier between the intravascular compartment and extravascular tissues and plays a critical role in a large number of physiological and pathological processes (8,19). As a critical part of inflammation, endothelial cells (EC) can recognize the molecular patterns commonly associated with many microbial agents and subsequently initiate the transcription of inflammatory genes (23,29). Specific conserved components of microbes include lipopolysaccharides (LPS) from gram-negative bacteria, CpG DNA, and flagellin (11,21,22). A large body of evidence has shown that LPS is highly proinflammatory and elicits a wide array of immune responses in EC (1, 10). Little information is available on the direct biological effect of bacterial CpG DNA on the vascular EC.Unlike LPS, which is recognized by Toll-like receptor (TLR) 4, CpG DNA is recognized by TLR9 (14). The signaling of these two receptors, however, shares similar downstream pathways, including activation of kinases like the stress kinases c-Jun NH 2 -terminal kinase, p38, and the IB kinase (IKK) complex (25). A number of studies have shown that CpG DNA has strong stimulatory effects on murine and human lymphocytes in vitro and murine lymphocytes in vivo (5, 13, 18). These stimulatory effects include triggering B cell proliferation, resistance to apoptosis, and release of IL-6 and IL-12; natural killer cell secretion of IFN-␥ and increased lytic activity; and monocyte/macrophage secretion of IFN-␣/␤, IL-6, IL-12, granulocyte-monocyte colony-stimulating factor, chemokines, and TNF-␣. A recent study has shown that human colonic epithelial cells can also respond to CpG DNA via upregulation of IL-8, suggesting a new mechanism for the epithelial defense system against microbial agents (2). The purpose of the current study was to determine the CpGmediated inflammatory responses in pulmonary EC.In the present study, we provide evidence to demonstrate for the first time that mouse and rat EC constitutively express TLR9 mRNA. Exposure to CpG DNA induced a potent proinflammatory response as manifested by an increased expression of IL-8 and ICAM-1 in EC. We further show that LPS and CpG DNA have a syne...

Immune Regulation by Microvascular Endothelial Cells: Directing Innate and Adaptive Immunity, Coagulation, and Inflammation

“…In contrast, TLR9 is spontaneously expressed by mouse and rat lung ECs, and exposure to CpG DNA induces an inflammatory response manifested by IL-8 and ICAM-1 induction through p38 MAPK-and NF-Bmediated pathways (35).…”

The role of pattern recognition receptors in the innate recognition ofCandida albicans

“…89,90 Human umbilical vein endothelial cells (HUVECs) express TLR3 and TLR9. [91][92][93] Human dermal microvascular endothelial cells express MR. 94 Besides, Galection-3 was detected on cultured endothelial cells. 95 The expression of Dectin-1 on endothelial cells is controversial.…”

Toll-like receptor 9 (TLR9) agonists in the treatment of cancer

“…Cellular activation is reported to induce TLR9 expression in additional cell types, including human neutrophils (Hayashi et al, 2003), monocytes and monocyte-derived cells (Saikh et al, 2004;Siren et al, 2005) and CD4 T cells (Gelman et al, 2006), but the biologic role for this is less well understood. TLR9 expression has also been reported in some nonimmune cells, including pulmonary epithelial cells and lung cancers (Li et al, 2004;Platz et al, 2004;Droemann et al, 2005), keratinocytes (Lebre et al, 2007) and intestinal epithelium (Pedersen et al, 2005;Lee et al, 2006). TLR9 recognizes and is activated by unmethylated cytosine-phosphate-guanine (CpG) dinucleotides, which are relatively common in bacterial and viral DNA but are suppressed and methylated in vertebrate DNA (Krieg, 2004).…”