Intranasal Administration Of Poly (I:C) Modulates Cell-Associated Levels Of Tlr3 In The Lungs Of C57bl/6 Mice

Poly (I:C) (PIC) is a synthetic dsRNA analog recognized by Toll-like receptor 3 (TLR3). The functional significance of surface vs. intracellular TLR3 has not yet been determined. The goal of these studies was to evaluate the impact of intranasal PIC on TLR3 protein levels and localization in lung cell populations. PIC (50ug) was administered intranasally to C57BL/6 mice once a day for three consecutive days to induce pulmonary inflammation. Cells were disassociated from lungs and analyzed by flow cytometry to evaluate changes in cell populations and TLR3 expression. TLR3 was expressed on 27% (surface) and 60% (intracellular) of the total viable lung cell population following intranasal PIC administration. Neutrophils, macrophages, and dendritic cells were dramatically increased in the lungs of mice treated with intranasal PIC compared to saline-treated controls. Intranasal PIC increased the levels of intracellular TLR3 on macrophages, NK cells, and a CD45+ collagen-1+ fibrocyte population. In contrast, intracellular TLR3 was decreased in dendritic cells following intranasal PIC. RT-PCR of cDNA prepared from lung cells indicated increased expression of genes involved in fibrosis, neutrophil chemotaxis, and angiogenesis following intranasal PIC vs. saline controls. In summary, these results demonstrated that intranasal PIC modulated TLR3 expression in specific lung cell types.