Endothelial cell tolerance to lipopolysaccharide challenge is induced by monophosphoryl lipid A.

Stark RJ, Choi H, Koch SR, Fensterheim BA, Lamb FS, Sherwood ER
Clin Sci (Lond). 2016 130 (6): 451-61

PMID: 26669797 · PMCID: PMC4744094 · DOI:10.1042/CS20150592

Prior exposure to lipopolysaccharide (LPS) produces a reduced or "tolerant" inflammatory response to subsequent challenges with LPS, however the potent pro-inflammatory effects of LPS limit its clinical benefit. The adjuvant monophosphoryl lipid A (MPLA) is a weak toll-like receptor 4 (TLR4) agonist that induces negligible inflammation but retains potent immunomodulatory properties. We postulated that pre-treatment with MPLA would inhibit the inflammatory response of endothelial cells to secondary LPS challenge. Human umbilical vein endothelial cells (HUVECs), were exposed to MPLA (10 μg/ml), LPS (100 ng/ml) or vehicle control. HUVECs were then washed and maintained in culture for 24 h before being challenged with LPS (100 ng/ml). Supernatants were collected and examined for cytokine production in the presence or absence of siRNA inhibitors of critical TLR4 signalling proteins. Pre-treatment with MPLA attenuated interleukin (IL)-6 production to secondary LPS challenge to a similar degree as LPS. The application of myeloid differentiation primary response gene 88 (MyD88) siRNA dramatically reduced MPLA-induced tolerance while TIR-domain-containing adapter-inducing interferon-β (TRIF) siRNA had no effect. The tolerant phenotype in endothelial cells was associated with reduced IκB kinase (IKK), p38 and c-Jun N-terminal kinase (JNK) phosphorylation and enhanced IL-1 receptor associated kinase-M (IRAK-M) expression for LPS-primed HUVECs, but less so in MPLA primed cells. Instead, MPLA-primed HUVECs demonstrated enhanced p-extracellular-signal-regulated kinase (ERK) phosphorylation. In contrast with leucocytes in which tolerance is largely TRIF-dependent, MyD88 signalling mediated endotoxin tolerance in endothelial cells. Most importantly, MPLA, a vaccine adjuvant with a wide therapeutic window, induced tolerance to LPS in endothelial cells.

© 2016 Authors; published by Portland Press Limited.

MeSH Terms (11)

Adaptor Proteins, Vesicular Transport Adjuvants, Immunologic Extracellular Signal-Regulated MAP Kinases Humans Human Umbilical Vein Endothelial Cells Immune Tolerance Interleukin-1 Receptor-Associated Kinases Lipid A Lipopolysaccharides Myeloid Differentiation Factor 88 Phosphorylation

Connections (2)

This publication is referenced by other Labnodes entities: