Inhibitory Effect Of Retinoic Acid Research Articles

The Effect of Retinoic Acid on Collagen Synthesis by Human Dermal Fibroblasts

The effect of all-trans retinoic acid (RA) on cell proliferation and protein synthesis was examined using neonatal human dermal fibroblasts in culture. Incorporation of [3H]-methylthymidine showed that cell proliferation decreased in response to increasing concentrations of RA. Analysis of proteins secreted into culture medium showed a decrease in the synthesis of both collagen and noncollagenous proteins, paralleling the effect on cell proliferation. Secreted proteins showed increased enzymatic processing of type I procollagen. The enhanced appearance of pc collagens, intermediates in the enzymatic conversion of procollagen to collagen, indicated that retinoic acid increased the activity of procollagen aminoterminal protease. Electrophoretic mobility and mannosylation of fibronectin was unchanged at RA concentrations tested. Cell morphology was unchanged at all concentrations of retinoic acid. The inhibitory effect of RA on cell proliferation is consistent with previous observations. The enhanced activity of procollagen aminoterminal protease may be important in the overall influence of RA on the elaboration of connective tissue.

Differential inhibitory effects of retinoic acid on Epstein-Barr virus induction in producer and nonproducer cell lines.

The effects of retinoic acid on Epstein-Barr virus (EBV) antigen induction by 12-O-tetradecanoyl-phorbol-13-acetate, 5-iodo-2'-deoxyuridine, and n-butyrate and by combinations of them were examined in two virus-producer and two nonproducer cell lines. Irrespective of the inducers used, the induction was markedly inhibited in the nonproducer lines and only weakly inhibited in the producer lines. The possible sites of action of retinoic acid are discussed.

Fibroblasts from humans genetically predisposed to colon cancer are abnormally resistant to vitamin A.

We report here than skin fibroblasts (SF) from patients with hereditary adenomatosis of the colon and rectum (ACR) and its Gardner syndrome (GS) variant are abnormally resistant to retinoic acid (RA). The effects by RA on the proliferation of SF was concentration dependent, exhibiting a bimodal dose-response pattern that consisted of both a stimulatory and an inhibitory component. Cell density appears to modulate both the stimulatory and inhibitory effects of RA. ACR cells were abnormally resistant to RA at all concentrations tested. Although more resistant to RA-induced cytotoxicity, ACR cells showed morphological changes on exposure to RA similar to those seen in normal cells. These differential effects by RA will be used to further identify individuals at risk of this dominant form of colon cancer.

Intervening effect of L-ascorbic acid on Epstein-Barr virus activation in human lymphoblastoid cells and its comparison with the effect of retinoic acid

L-Ascorbic acid was found to reduce the induction of Epstein-Barr virus-associated antigens in human lymphoblastoid P3HR-1 cells and Raji cells to the level of approximately 45–85% of the untreated control culture at concentrations of 100–1000 μM. When such an effect of L-ascorbic acid was compared with the inhibitory effect of retinoic acid known to occur in the same system, the intervention was weaker but its cytotoxicity was remarkably lower than the latter compound.

Effects of cell surface receptor-altering agents on the binding and biological activity of 12-O-tetradecanoylphorbol-13-acetate in isolated epidermal cells.

Isolated epidermal cells were incubated with a variety of compounds known to interfere with or alter the ultrastructure of cell surface receptors, and the ability of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) to bind to these cells and induce epidermal ornithine decarboxylase (ODC) activity was investigated. The alpha- and beta-adrenergic antagonists, phentolamine and propranolol, and the cholinergic antagonist, atropine, which competed effectively for the binding receptors of [3H]dihydro-alpha-ergocryptine, [3H]dihydroalprenolol, and [14C]acetylcholine, did not inhibit the induction of ODC activity by TPA or the specific binding of [3H]TPA to the cells. Neuraminidase treatments caused a time- and dose-related release of sialic acid from the cells and enhanced the stimulatory effect of cholera toxin on basal and TPA-induced ODC activities as much as the monosialoganglioside GM1. Neuraminidase and the other membrane-altering agents, fucosidase, galactosidase, galactose oxidase, phospholipases A2 and C, and NaIO4, were used alone and/or in various combinations in our studies. All treatments tested inhibited the specific binding of several 125I-labeled hormones and epidermal growth factor to the cells. In contrast, none of these treatments was able, in the same cell system, to affect either the binding or the biological activity of TPA. Therefore, these results suggest that the primary interaction of TPA at the plasma membrane level as well as its biological effect in the intact cell do not proceed through adrenergic or cholinergic receptors and do not require the integrity of the cell surface glycoconjugates and phospholipids. In addition, the inhibitory effect of retinoic acid on TPA-induced ODC activity remained unaffected by some of the above treatments, suggesting that retinoic acid is unlikely to interfere with TPA interactions at the plasma membrane level.

Retinoids and cultured human fibroblasts: Effects on cell growth and presence of cellular retinoic acid-binding protein

We have examined the effects of retinoids on growth of cultured human skin fibroblasts from four individuals. Retinoic acid and retinol both produce a dose-dependent inhibition of growth in the four strains examined; retinoic acid was more potent than retinol in this respect. The growth inhibitory effect of retinoic acid is characterized by a decrease in the exponential growth rate, which is reversible upon removal of retinoic acid from the growth medium; the final saturation density, however, is not modified by retinoic acid treatment. No alterations of cell morphology, viability, or adhesiveness to substratum are induced by the retinoid concentrations utilized. The inhibitory effect of 10 −6 M retinoic acid on cell growth is not affected by the concentration of fetal calf serum (FCS) in the medium. In all four human fibroblast strains examined, specific binding of [ 3H]retinoic acid to cytosol is present as determined by sucrose-density gradient centrifugation. Despite the effects of retinol on fibroblast growth, no cytoplasmic binding of [ 3H]retinol could be demonstrated in these cells.

Characterization of the Inhibitory Effects of Retinoids on the In Vitro Growth of Two Malignant Murine Melanomas2

The in vitro proliferation of murine melanoma cell lines S91 and B16 was inhibited by retinoic acid and retinyl acetate. The inhibitory effects were dependent on retinoid concentration and increased from 55 and 30% at 10(-9) M retinoic acid to 85 and 82% at 10(-5) M retinoic acid for S91 and B16 melanoma cells, respectively. S91 melanoma cells were more sensitive than B16 melanoma cells to inhibition by either retinoid, and both cell lines were more sensitive to retinoic acid than to retinyl acetate. When exposed to 10(-5) M retinoic acid, the two cell types grew at the same rate as did control cells for 48 hours, whereupon the growth rates of retinoid-treated cells decreased. After 6 days, the number of cells in control cultures increased 140 times (S91 melanoma cells) and 265 times (B16 melanoma cells), whereas retinoic acid-treated cells increased only 14 times (S91 melanoma cells) and 40 times (B16 melanoma cells). The degree of growth inhibition by retinoic acid was not dependent on initial cell density. Cortisone and hydrocortisone failed to prevent or reduce the inhibitory effect of retinoic acid; the release of lysosomal acid phosphatase was not increased and the intracellular level of 3',5'-cyclic AMP in cells grown for 5 days in the presence of 10(-5) M retinoic acid was not elevated. Viability of S91 and B16 cells after 8 days' exposure to 10(-5) M retinoic acid was similar to that in control cultures. The reduced growth rate of retinoic acid-treated cells reversed to the control rate 48-72 hours after removal of retinoic acid from the growth medium.

Inhibitory effects of retinoic acid or retinyl acetate on the growth of untransformed, transformed, and tumor cells in vitro.

Inhibitory effects of retinoic acid or retinyl acetate on the growth of untransformed, transformed, and tumor cells in vitro.

Inhibition of Interferon Action by Vitamin A

Simultaneous treatment of mouse cells with interferon and vitamin A (retinoic acid) resulted in an inhibition of interferon action. Increasing concentrations of calf serum decreased the inhibitory effect of retinoic acid on interferon action. Treatment of interferon with retinoic acid prior to the assay for interferon activity also resulted in a loss of interferon activity. Since the residual retinoic acid present after dilution of the interferon for assay was not sufficient to interfere with the assay, it is presumed that interferon and retinoic acid must interact in some fashion to inhibit interferon activity. Calf serum prevented the apparent interaction of retinoic acid and interferon. The loss of interferon activity which resulted from treatment of interferon with retinoic acid was dependent on temperature and time of incubation. Retinyl acetate (acetate ester of vitamin A) and retinal (vitamin A adehyde) only slightly inhibited interferon activity, while retinoic acid (vitamin A acid) and retinol (vitamin A alcohol) were similarly effective at inhibiting interferon activity. Another fat soluble vitamin, vitamin K1, did not inhibit interferon activity.