Molecular identification and coexpression of galanin and GalR-1 galanin receptor in the human ocular ciliary epithelium: differential modulation of their expression by the activation of alpha2- and beta2-adrenergic receptors in cultured ciliary epithelial cells.
Here we report the coexpression of the neuropeptide galanin and GalR-1 galanin receptors in the human ciliary epithelium, a bilayer of neuroepithelial cells [nonpigmented (NPE) and pigmented (PE)] with neuroendocrine functions, and in a cell line (ODM-2) derived from the NPE cells. Stimulation of ODM-2 cells with phorbol ester [phorbol 12-myristate 13-acetate (PMA)] or forskolin resulted in an up-regulation (two- to threefold) of galanin mRNA expression. Procaterol, a selective beta2-adrenergic agonist, and the catecholamine isoproterenol exerted a long-term down-regulation on galanin mRNA expression when added alone or in combination with PMA or forskolin. These actions exerted by procaterol or isoproterenol were abolished in the presence of ICI 118,551, a selective beta2-adrenergic antagonist. A radioimmunoassay for galanin peptide indicated that galanin or a galanin-like product is present in the human aqueous humor fluid and is accumulated with time in the culture medium of ODM-2 cells. It is interesting that norepinephrine, which exhibited no effect on galanin mRNA expression, induced a down-regulation in the level of galanin or galanin-like product accumulated in the medium of cultured ODM-2 cells to levels even lower than those induced by beta2-adrenergic agonists. This effect is best explained by the concomitant up-regulation (four- to fivefold) of GalR-1 galanin receptor transcripts induced through the activation of alpha2-adrenergic receptors. These findings support the view that pathways elicited by the activation of alpha2- and beta2-adrenergic receptors influence the expression of galanin and GalR-1 galanin receptors in ciliary epithelial cells.
Ortego
J
J
Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Coca-Prados
M
M
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D001082:Aqueous Humor / Q000378:metabolism; D002460:Cell Line; D002924:Ciliary Body / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D019004:Galanin / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009638:Norepinephrine / Q000494:pharmacology; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D044088:Receptors, Galanin; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D016895:Culture Media, Serum-Free; C056567:GAL protein, human; D011498:Protein Precursors; D012333:RNA, Messenger; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D044088:Receptors, Galanin; D018013:Receptors, Neuropeptide; D005576:Colforsin; C016986:apraclonidine; D019004:Galanin; D003000:Clonidine; D013755:Tetradecanoylphorbol Acetate; D009638:Norepinephrine