Anti-Inflammatory and Pro-Resolving Actions of the N-Terminal Peptides Ac2-26, Ac2-12, and Ac9-25 of Annexin A1 on Conjunctival Goblet Cell Function

Abstract

Annexin A1 (AnxA1) is the primary mediator of the anti-inflammatory actions of glucocorticoids. AnxA1 functions as a pro-resolving mediator in cultured rat conjunctival goblet cells to ensure tissue homeostasis through stimulation of intracellular [Ca²⁺] ([Ca²⁺]_i) and mucin secretion. AnxA1 has several N-terminal peptides with anti-inflammatory properties of their own, including Ac2-26, Ac2-12, and Ac9-25. The increase in [Ca²⁺]_i caused by AnxA1 and its N-terminal peptides in goblet cells was measured to determine the formyl peptide receptors used by the compounds and the action of the peptides on histamine stimulation. Changes in [Ca²⁺]_i were determined by using a fluorescent Ca²⁺ indicator. AnxA1 and its peptides each activated formyl peptide receptors in goblet cells. AnxA1 and Ac2-26 at 10^-12 mol/L and Ac2-12 at 10^-9 mol/L inhibited the histamine-stimulated increase in [Ca²⁺]_i, as did resolvin D1 and lipoxin A₄ at 10^-12 mol/L, whereas Ac9-25 did not. AnxA1 and Ac2-26 counter-regulated the H₁ receptor through the p42/p44 mitogen-activated protein kinase/extracellular regulated kinase 1/2, β-adrenergic receptor kinase, and protein kinase C pathways, whereas Ac2-12 counter-regulated only through β-adrenergic receptor kinase. In conclusion, current data show that the N-terminal peptides Ac2-26 and Ac2-12, but not Ac9-25, share multiple functions with the full-length AnxA1 in goblet cells, including inhibition of histamine-stimulated increase in [Ca²⁺]_i and counter-regulation of the H₁ receptor. These actions suggest a potential pharmaceutical application of the AnxA1 N-terminal peptides Ac2-26 and Ac2-12 in homeostasis and ocular inflammatory diseases.