Abstract
Purpose :
RvD2 is biosynthesized from docosahexaenoic acid (DHA) and was identified in murine self-resolving exudates during the resolution phase of self-limited acute inflammation in vivo. The resolution promoting action of RvD2 was observed in multiple organs and tissues. Histamine is an autacoid produced in the conjunctiva by mast cells in response to an allergen. All four histamine receptor subtypes, H1-4, are present on conjunctival goblet cells and with stimulation increase intracellular [Ca2+] ([Ca2+]i) and mucin secretion as a component of allergic conjunctivitis. To determine the molecular mechanism used by RvD2 to terminate the histamine-stimulated allergic response, we investigated the interaction of RvD2 with histamine and its receptors in conjunctival goblet cells.
Methods :
Goblet cells were cultured from male rat conjunctiva. Signaling pathways were studied by measuring the [Ca2+]i responses using fura 2/AM. Mucin secretion was determined using an ELLA.
Results :
Thirty-minute treatment with RvD2 (10-8M) significantly blocked the histamine (10-5M) -induced increase in [Ca2+]i and mucin secretion. Stimulation with an agonist selective for each of the four histamine receptors showed that RvD2 inhibited the [Ca2+]i increase induced by the activation of H1, H3, or H4 receptors. Blockage of the H1 receptor agonist by RvD2 was reversed by inhibiting β adrenergic receptor kinase (βARK) and protein kinase A (PKA), but not by inhibiting protein kinase C (PKC). Blockage of the H3 receptor agonist by RvD2 was only reversed by inhibiting PKA. Blockage of the H4 receptor agonist was reversed by inhibiting βARK and PKC, but not by inhibiting PKA.
Conclusions :
RvD2 counter-regulates histamine-induced [Ca2+]i increase and mucin secretion by phosphorylating and down-regulating H1, H3, and H4 receptors by activating receptor-specific protein kinases.
This is a 2021 ARVO Annual Meeting abstract.