Mechanisms of cetylpyridinium chloride inhibition of immune cell function - People are widely exposed to high (mM) doses of the positively-charged antibacterial agent
cetylpyridinium chloride (CPC) via janitorial and personal care products and foods treated with
CPC, yet little is known about its toxicology in humans, especially below the critical micelle
concentration (~900 µM). While applied CPC is retained in the oral mucosa and is released into
saliva such that low-µM CPC continuously bathes oral cells, there is a dearth of publications on
the effects of CPC on eukaryotes. The Gosse lab has discovered that exposure to non-
cytotoxic, low-µM CPC concentrations potently inhibits signaling of mast cells, key players in the
immune and nervous systems that share core signaling elements with T cells and other cell
types. In mast cells, upon antigen crosslinking of cell surface receptors, a tyrosine
phosphorylation cascade ensues, leading to activation of PLC¿1 enzymatic cleavage of
phosphatidylinositol 4,5-bisphosphate (PIP2) and subsequent Ca2+ mobilization and
degranulation: microtubule transport of granules to the cell surface, leading to exocytosis of
bioactive substances such as histamine and serotonin. Analogous aggregation of T cell
receptors leads also to tyrosine phosphorylation, Ca2+ mobilization, and downstream T cell
function. CPC effects on both mast and T cell function will be determined. Preliminary data
have led to the hypothesis that CPC inhibits immune cell function by electrostatically interfering
with phosphorylation and PIP2, leading to displacement of PIP2-binding proteins, disrupted
nanoscale clustering of PIP2, muted release of Ca2+ from endoplasmic reticulum (ER) stores,
and, thereby, inhibited inflow of Ca2+ to the cytosol and extinguished microtubule polymerization.
CPC effects on phosphorylation will be assessed by multiple means. Confocal microscopy and
plate reader experiments will define CPC effects on sub-cellular localization and function of
PLC¿1; of PLC¿1 product inositol 1,4,5-trisphosphate which initiates release of ER Ca2+; of Ca2+
dynamics in ER, mitochondria, Golgi, and cytosol; and of key elements downstream of Ca2+
including protein kinase C, phospholipase D, and microtubules. Whether CPC directly displaces
PIP2 from its partner proteins will be measured. Super-resolution fluorescence photoactivation
localization microscopy will interrogate nanoscale CPC effects on PIP2 clusters and other
protein interactions crucial to immune function, including co-localization of Git1 regulator with
tubulin as well as PIP2 with machinery required for granule exocytosis. This research will
uncover the mechanisms underlying CPC disruption of immune cell function in order to fulfill an
urgent need by providing insights into CPC effects on environmental human health.