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Analysis of Cellular Responses to Imiquimod in Taste Cells
Author(s) -
Huang Anthony Y,
Wu Sandy Y
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.740.12
Subject(s) - taste , taste bud , taste receptor , imiquimod , microbiology and biotechnology , immune system , biology , receptor , thapsigargin , intracellular , endocrinology , neuroscience , immunology , biochemistry
Evidence accumulated over the past decade has highlighted the presence of various molecules involved in innate immune responses in taste buds, suggesting that defense responses may regulate their structures and functions. We hypothesized that taste cells directly respond to pathogens with implications for taste sensations. Using calcium imaging, we examined what effect imiquimod, a Toll‐like receptor 7 (TLR7) agonist, exerts on taste bud functions. Our results indicated that up to 72% of Presynaptic (Type III) taste cells responded to 100 μM imiquimod with an increase in intracellular Ca 2+ . Immunohistochemistry revealed that taste bud cells express TLR7, mainly on Presynaptic (Type III) cells of mouse vallate taste buds. In addition, a minority of Receptor (Type II) taste cells (15%) showed imiquimod‐elicited Ca 2+ transients. We demonstrated that this effect of imiquimod was prevented by thapsigargin, a SER Ca 2+ ‐ATPase inhibitor, as well as by U73122, a phospholipase C (PLC) inhibitor, suggesting that Ca 2+ mobilization was dependent on internal Ca 2+ store release. Moreover, using cellular biosensor cells, applying imiquimod evoked taste buds to release serotonin (5‐HT), which then subsequently provides negative feedback onto Receptor (Type II) cells to reduce taste‐evoked ATP secretion. Altogether, these results provide the evidence supporting the hypothesis that there is a specific subset of taste cells equipped with diverse intracellular mechanisms that respond to imiquimod. The findings are also consistent with a role of imiquimod as an immune response modifier, which shapes peripheral taste responses via the serotonergic signaling pathways. Support or Funding Information Supported by SIUSOM Research Seed Grant (AYH).Micrograph of a biosensor cell abutted against an isolated taste bud in a living preparation. A Nomarski optics image and a fluorescence microscopy image were merged.