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The effect of all-trans-retinoic acid on the synthesis of epidermal cell-surface-associated carbohydrates.

ABSTRACT: 1. all-trans-Retinoic acid at concentrations greater than 10(-7)m stimulated the incorporation of d-[(3)H]glucosamine into 8m-urea/5% (w/v) sodium dodecyl sulphate extracts of 1m-CaCl(2)-separated epidermis from pig ear skin slices cultured for 18h. The incorporation of (35)SO(4) (2-), l-[(14)C]fucose and U-(14)C-labelled l-amino acids was not significantly affected. 2. Electrophoresis of the solubilized epidermis showed increased incorporation of d-[(3)H]glucosamine into a high-molecular-weight glycosaminoglycan-containing peak when skin slices were cultured in the presence of 10(-5)m-all-trans-retinoic acid. The labelling of other epidermal components with d-[(3)H]glucosamine, (35)SO(4) (2-), l-[(14)C]fucose and U-(14)C-labelled l-amino acids was not significantly affected by 10(-5)m-all-trans-retinoic acid. 3. Trypsinization dispersed the epidermal cells and released 75-85% of the total d-[(3)H]glucosamine-labelled material in the glycosaminoglycan peak. Thus most of this material was extracellular in both control and 10(-5)m-all-trans-retinoic acid-treated epidermis. 4. Increased labelling of extracellular epidermal glycosaminoglycans was also observed when human skin slices were treated with all-trans-retinoic acid, indicating a similar mechanism in both tissues. Increased labelling was also found when the epidermis was cultured in the absence of the dermis, suggesting a direct effect of all-trans-retinoic acid on the epidermis. 5. Increased incorporation of d-[(3)H]-glucosamine into extracellular epidermal glycosaminoglycans in 10(-5)m-all-trans-retinoic acid-treated skin slices was apparent after 4-8h in culture and continued up to 48h. all-trans-Retinoic acid (10(-5)m) did not affect the rate of degradation of this material in cultures ;chased' with 5mm-unlabelled glucosamine after 4 or 18h. 6. Cellulose acetate electrophoresis at pH7.2 revealed that hyaluronic acid was the major labelled glycosaminoglycan (80-90%) in both control and 10(-5)m-all-trans-retinoic acid-treated epidermis. 7. The labelling of epidermal plasma membranes isolated from d-[(3)H]glucosamine-labelled skin slices by sucrose density gradient centrifugation was similar in control and 10(-5)m-all-trans-retinoic acid-treated tissue. 8. The results indicate that increased synthesis of mainly extracellular glycosaminoglycans (largely hyaluronic acid) may be the first response of the epidermis to excess all-trans-retinoic acid.

SUBMITTER: King IA

PROVIDER: S-EPMC1162749 | biostudies-other | 1981 Jan

REPOSITORIES: biostudies-other

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Project description:OBJECTIVE:Caseins and fatty acids of milk are synthesized and secreted by the epithelial cells of the mammary gland. All-trans retinoic acid (ATRA), an active metabolite of vitamin A, has been shown to promote mammary development. This study was conducted to determine the effect of ATRA on casein synthesis and fatty acid composition in MAC-T cells. METHODS:MAC-T cells were allowed to differentiate for 4 d, treated with ATRA (0, 1.0, 1.5, and 2.0 μM), and incubated for 3 d. We analyzed the fatty acid composition, the mRNA expression of casein and fatty acid synthesis-related genes, and the phosphorylation of casein synthesis-related proteins of MAC-T cells by gas chromatography, quantitative polymerase chain reaction, and western blotting, respectively. RESULTS:In MAC-T cells, ATRA increased the mRNA levels of αS1-casein and β-casein, janus kinase 2 (JAK2) and E74-like factor 5 of the signal transducer and activator of transcription 5 β (STAT5-β) pathway, ribosomal protein S6 kinase beta-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 of the mammalian target of rapamycin (mTOR) pathway, inhibited the mRNA expression of phosphoinositide 3-kinase and eukaryotic initiation factor 4E of the mTOR pathway, and promoted the phosphorylation of STAT5-β and S6K1 proteins. Additionally, ATRA increased the de novo synthesis of fatty acids, reduced the content of long-chain fatty acids, the ratio of monounsaturated fatty acids to saturated fatty acids (SFA), the ratio of polyunsaturated fatty acids (PUFA) to SFA, and the ratio of ω-6 to ω-3 PUFA. The mRNA levels of acetyl-CoA carboxylase 1, fatty acid synthase, lipoprotein lipase, stearoyl-CoA desaturase, peroxisome proliferator-activated receptor gamma, and sterol regulatory element-binding protein 1 (SREBP1) were enhanced by ATRA. CONCLUSION:ATRA promotes the synthesis of casein by regulating JAK2/STAT5 pathway and downstream mTOR signaling pathway, and it improves the fatty acid composition of MAC-T cells by regulating SREBP1-related genes.

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The effect of all-trans-retinoic acid on the synthesis of epidermal cell-surface-associated carbohydrates.

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