Quercetin as a Lyn kinase inhibitor inhibits IgE-mediated allergic conjunctivitis

Background: Allergic conjunctivitis (AC) resulting from conjunctival reactive inflammation is a common ocular surface disease. Quercetin is known for its anti-allergic properties but its effects on conjunctivitis are less well understood.

Purpose: In this study, we evaluated the anti-allergic effects of quercetin in animal models of conjunctivitis, and explored its molecular mechanism(s) of action in cultured human mast cells (MCs).

Key results: Quercetin inhibited the ovalbumin (OVA) induced expression of IgE, HA, IL-4, TNF-α and substance-P in the peripheral blood of AC mouse models. Quercetin also attenuated OVA induced MC degranulation, eosinophil number, substance P concentrations, and mRNA IL-4/TNF-α expression in the conjunctival tissue of AC models. In vitro analysis showed that quercetin reduced DNP-HSA/IgE induced calcium (Ca2+) influx, and suppressed degranulation and chemokine release in LAD2 cells (human primary mast cell). Quercetin also inhibited DNP-HSA/IgE induced Lyn/PLCγ/IP3R-Ca2+ activation, Lyn/ERK1/2 signaling, and Lyn/NF-κB activation in LAD2 cells, all of which promote inflammation. When added alone, quercetin had no effect on PLCγ1 phosphorylation or expression, but potently inhibited Lyn and phosphorylation-Lyn. Quercetin (200 μM) and Lyn inhibitors (Bafetinib, 10 μM) inhibit the activity of Lyn kinase, and quercetin can reduce the activation of Lyn kinase by Lyn agonist (Tolimidone, 10 μM). These data can be preliminarily determined that quercetin can inhibit allergic conjunctivitis as a Lyn kinase inhibitor.

Conclusions and implications: This study illustrated the use of quercetin for the treatment of allergic conjunctivitis, which might act through its ability to inhibit Lyn/PLCγ/IP3R-Ca²⁺, Lyn/ERK1/2, and Lyn/NF-κB signaling. The inhibition of Lyn likely represents a major mechanism by which quercetin dampens the inflammatory response in AC disease models.