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Enhancement of Mast Cell Degranulation Mediated by Purinergic Receptor Activation and PI3K(δ)
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  • Haruhisa Nishi,
  • Francois Niyonsaba,
  • Amir Pelleg,
  • Edward Schulman
Haruhisa Nishi
Jikei University School of Medicine

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Francois Niyonsaba
Juntendo University Graduate School of Medicine,
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Amir Pelleg
Danmir Therapeutics
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Edward Schulman
Drexel University College of Medicine
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Background: Mast cells express multiple metabotropic purinergic receptor (P2YR) subtypes, however, only few studies have evaluated their role in human mast cells (HMC) allergic response as measured by degranulation resulting from FcεRI-activation. We have previously shown that extracellular nucleotides modify the FcεRI-activation-dependent degranulation in HMC derived from human lungs, but the mechanism of this action has not been fully delineated. The present study was undertaken to determine the mechanism of P2YR’s activation on HMC’s degranulation and elucidate the specific post-receptor mechanistic steps/pathways involved. Methods: Sensitized LAD2 cells, a human derived mast cell line, were subjected to a weak allergic stimulation (WAS) using a low concentration of antigen in the absence and presence of the P2Y11R agonist, ATPγS. Results: In the presence of ATPγS, WAS-induced degranulation was enhanced by 7-fold (N = 4, p < 0.01). None of the other P2YR agonists tested, including high concentrations of ATPγS (1000 μM), enhanced WAS-induced intracellular Ca2+ mobilization, which is an important component of degranulation. Both a phosphoinositide 3-kinase (PI3K) inhibitor and the relevant gene knockout decreased the ATPγS-induced enhancement s of degranulation. ATPγS’ effect was associated with enhanced phosphorylation of PI3K type δ (PI3K(δ)) and protein kinase B (Akt), but not the phosphoinositide-dependent kinase-1 (PDK-1). The effects of ATPγS were dose dependently inhibited by NF157, a P2Y11R antagonist. Conclusion: We determined for the first time that at least one subtype of P2YR, i.e., P2Y11R is linked to enhancement of allergic degranulation in HMC independent of [Ca2+]i mobilization.