Inhibition by tunicamycin of mucin synthesis, not morphological changes, in epidermis during retinol-induced mucous metaplasia of chick embryonic cultured skin.
BACKGROUND
Our previous studies have shown that epidermal mucous metaplasia of chick embryonic skin can be induced by culture in medium containing 20 microM retinol for only 8 hr and then in a chemically defined medium without retinol for 2 days and that retinol primarily affects the dermal cells, which then transform the epithelial cells into mucus-secreting cells.


METHODS
Tarsometatarsal skin of 13-day-old chick embryo was cultured with 20 microM retinol for 1 day and then without the vitamin but with 0.1 microgram/ml tunicamycin for 5 days. Effect of tunicamycin on epidermal mucous metaplasia was studied biochemically and morphologically.


RESULTS
Tunicamycin, which prevents the formation of N-glycans and inhibits maturation or morphological organization of various epithelial cells, irreversibly inhibited the synthesis of sulfated glycoproteins (O-glycans, mucin) in the epidermis only when applied to retinol-pretreated skin. Microvilli on the surface of the cells were well developed, but mucous granules surrounded by a limiting membrane were not observed in the upper cell layer of the epidermis, and many vesicles without electron-dense materials (mucin) and dilated rough endoplasmic reticulum were seen in the intermediate cell layers of the epidermis. When recombinants of 13-day-old normal epidermis and cultured dermis, which had been treated with retinol for 24 hr and with only tunicamycin for 2 days, were cultured without the antibiotic for 5 days, epidermal mucous metaplasia was induced.


CONCLUSIONS
These results suggest that tunicamycin did not prevent morphological changes induced by retinol but inhibited mucin synthesis by a direct action on the epidermis of retinol-pretreated skin. Because in some cell-line mucin precursors contain high mannose N-linked oligosaccharides side chains, tunicamycin may have inhibited mucin synthesis. Interaction between epidermal basal cells and retinol-pretreated dermal fibroblasts is prerequisite for epidermal mucous metaplasia. Thus, the present study suggests that N-linked protein glycosylation is not required for this interaction.
Obinata
A
A
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
Akimoto
Y
Y
Kawamata
T
T
Shimizu
S
S
Hirano
H
H
D000818:Animals; D002642:Chick Embryo / Q000033:anatomy & histology / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D004586:Electrophoresis; D004817:Epidermis / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D006023:Glycoproteins / Q000037:antagonists & inhibitors; D006854:Hydrocortisone / Q000494:pharmacology; D007633:Keratins / Q000378:metabolism; D008679:Metaplasia; D009077:Mucins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D009093:Mucus / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012867:Skin / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D014415:Tunicamycin / Q000494:pharmacology*; D014801:Vitamin A / Q000494:pharmacology*
D006023:Glycoproteins; D009077:Mucins; D011506:Proteins; D014415:Tunicamycin; D014801:Vitamin A; D007633:Keratins; D006854:Hydrocortisone