Lipoxin A4 Counter-regulates Histamine-stimulated Glycoconjugate Secretion in Conjunctival Goblet Cells

Abstract

Conjunctival goblet cells synthesize and secrete mucins which play an important role in protecting the ocular surface. Pro-resolution mediators, such as lipoxin A4 (LXA4), are produced during inflammation returning the tissue to homeostasis and are also produced in non-inflamed tissues. The purpose of this study was to determine the actions of LXA4 on cultured human conjunctival goblet cell mucin secretion and increase in intracellular [Ca2+] ([Ca2+]i) and on histamine-stimulated responses. LXA4 increased mucin secretion and [Ca2+]i, and activated ERK1/2 in human goblet cells. Addition of LXA4 before resolvin D1 (RvD1) decreased RvD1 responses though RvD1 did not block LXA4 responses. LXA4 inhibited histamine-stimulated increases in mucin secretion, [Ca2+]i, and ERK1/2 activation through activation of β-adrenergic receptor kinase 1. We conclude that conjunctival goblet cells respond to LXA4 through the ALX/FPR2 receptor to maintain homeostasis of the ocular surface and regulate histamine responses and could provide a new therapeutic approach for allergic conjunctivitis and dry eye diseases.

Resolvin D1 Increases Mucin Secretion in Cultured Rat Conjunctival Goblet Cells via Multiple Signaling Pathways

“…Goblet cells from rats were grown in organ culture as described previously. 6 , 15 , 22 – 24 The conjunctival explants were grown in 6-well plates containing RPMI 1640 medium supplemented with 10% FBS, 2-mM glutamine, and 100-μg/mL penicillin-streptomycin. The explant was removed before trypsinization of the cells for first passage.…”

“…Cultured cells were identified by evaluating staining with the lectin UEA-1, which detects goblet cell secretory product, and the antibody to cytokeratin 7, which detects goblet cell bodies, to ensure that goblet cells predominated. 6 , 15 , 16 , 22 – 25 …”

Identification and structure elucidation of the pro‐resolving mediators provides novel leads for resolution pharmacology

“…Of note, ALX receptor activation by its pro‐resolving ligands leads to distinct downstream signalling pathways that are cell specific. For example, LXA 4 increases intracellular calcium levels in conjunctival goblet cells via the ALX receptor (Hodges et al ., ); whereas activation of this receptor by LXA 4 does not elicit a calcium response in human neutrophils (Fiore and Serhan, ). Studies conducted by Cooray and colleagues demonstrate that the ALX receptor on cell membranes is expressed as a homo‐ or heterodimer with the formyl peptide receptor FPR1 or FPR3 (the two other family members) and operates in a ligand‐biased fashion.…”

The role of pro-resolving lipid mediators in ocular diseases

“…In vitro models that recapitulate goblet cell responses in DED and allergic conjunctivitis have demonstrated that RvD1 and RvE1 can block inflammatory eicosanoids or histamine activation of ERK and intracellular Ca 2+ mobilization in goblet cells [27, 50]. LXA 4 has unique actions on isolated conjunctival goblet cells as it can stimulate mucin secretion via activation of phospholipases, ERK and downstream protein kinases [51]. The in vivo expression, endogenous formation, and therapeutic actions of SPM have not been determined in the healthy or inflamed conjunctiva or animal models of conjunctivitis.…”