LSC Abstract – Toll-like receptor 10: Expression and functional role in LPS mediated inflammation

Abstract

Toll-like receptor-10 (TLR10) is a member of innate immune receptors that recognize pathogen-associated molecules and play critical roles in host defense. However, there is very little known about TLR10. We examined TLR10 expression in normal and inflamed lungs from chickens and humans. Immunohistochemistry showed TLR10 in vascular endothelium in human and chicken lungs. Immunohistochemistry and Western blots showed an increase in TLR10 protein in lungs of chicken infected with E. coli or Fowl Adenovirus. Human neutrophils challenged with E. coli lipopolysaccharide (LPS) showed decreased total TLR10 protein and surface expression in 90 minutes. Confocal microscopy showed cytosolic and nuclear distribution of TLR10 in normal neutrophils. In the LPS-activated neutrophils, TLR10 colocalized with flotallin-1, a lipid raft marker, and EEA-1, an early endosomal marker, to suggest the cycling to endocytic compartments. Because LPS signals via TLR4, we examined and found that TLR10 colocalization with TLR4 increased up to 60 minutes followed by a decrease. TLR4 neutralization reduced cytoplasmic localization of TLR10. To determine the role of reactive oxygen species in TLR4-mediated regulation of TLR10 expression, we depleted ROS using FCCP in LPS-treated neutrophils, which led to decreased TLR10 expression and p65 nuclear translocation. Finally, we explored the role of TLR10 in neutrophil chemotaxis. Single cell imaging of live LPS-activated human neutrophils showed the translocation of TLR10 to the leading edge. siRNA-mediated silencing of TLR10 in HL-60 cell line reduced their chemotaxis towards fMLF.