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Retinoid-induced limb defects 2: involvement of TGF-beta 2 in retinoid-induced inhibition of limb bud development.

We previously demonstrated that retinoid-induced inhibition of chondrogenesis in the forelimb bud may be mediated by TGF-beta2 (1). The present study was conducted to examine whether TGF-beta2 is involved in the inhibition of forelimb bud development caused by all-trans-retinoic acid (RA). Expression of TGF-beta2 was examined immunohistochemically in forelimb buds of embryos 24 h after dosing to the mother on Day 12 of gestation in the rat. In the control and 50 mg/kg group, TGF-beta2 was expressed in the epithelium and prechondrogenic area around dead cells in the forelimb bud. In the 100 mg/kg group, a dose at which RA caused reduction defects of forearm bones, TGF-beta2 expression was observed in the distal margin of forelimb buds, in which no expression was observed in the control and 50 mg/kg group. Immunohistologic studies also indicated that in the 100 mg/kg group, the expression of TGF-beta2 was enhanced in forearm-bone prechondrocytes around the dead cells. In a whole embryo culture system, exposure to RA for 24 h reduced the proximodistal length and protein content in forelimb buds at concentrations of 3 microg/mL or more. The whole embryo culture system also showed that the expression of TGF-beta2 was induced at the concentration of 3 microg/mL in the same region as found in forelimb buds of embryos from dams administered a teratogenic dosage of RA in vivo. Local application of TGF-beta2 to the distal margin of the forelimb bud in Day 12 embryos reduced proximodistal growth and protein content in forelimb buds for 24 h in culture even without RA treatment. We also found that exogenous TGF-beta2 inhibited DNA synthesis of forelimb bud cells in culture in a concentration-dependent manner. Neutralization of TGF-beta2 with its antibody in the distal margin of forelimb buds partially prevented the RA-induced inhibition of forelimb bud growth in the whole embryo culture system. These results suggest that RA-induced TGF-beta2 in the distal margin of forelimb buds may be involved in RA-induced inhibition of forelimb bud growth via reduction of cell proliferation in the distal margin, and RA-induced TGF-beta2 in the prechondrogenic area may inhibit chondrogenesis in the future forearm bones, followed by reduction defects of the forearm bones.

Animals↗
PubMed1982

Affinity therapeutics. 1. Selective incorporation of 2-thiouracil derivatives in murine melanomas. Cytostatic activity of 2-thiouracil arotinoids, 2-thiouracil retinoids, arotinoids, and retinoids.

The incorporation of 2-[35S]thiouracil and two of its derivatives into murine melanomas, in vivo, was studied. It was confirmed [J. R. Whittaker, J. Biol. Chem., 246, 6217--6226 (1971)] that 2-thiouracil has a marked affinity for melanin-producing tissue and that an affinity for such tissue could be sustained by 5-substituted 2-thiouracils. A series of derivatives of arotinoids and retinoids, with or without a 2-thiouracil group as a potential carrier to obtain affinity for melanomas, was examined for cytostatic activity, in vitro. None of these showed significant activity against murine melanomas.

Animals↗
PubMed2005

Microdermabrasion followed by a 5% retinoid acid chemical peel vs. a 5% retinoid acid chemical peel for the treatment of photoaging - a pilot study.

BACKGROUND: Both retinoid acid (RA) chemical peeling and microdermabrasion are minimally invasive procedures recently developed for the treatment of photoaging. The efficacy of each procedure has been proved, but the results of the combination of these two methods have not been studied until now. OBJECTIVES: To assess and compare the efficacy of microdermabrasion followed by a 5% RA chemical peel with that of a 5% RA chemical peel alone. METHODS: Six female patients with moderate degrees of photodamage were evaluated. Three submitted to microdermabrasion followed by the application of a 5% RA chemical peel and three submitted to a 5% RA chemical peel alone. Each patient underwent three treatment sessions, with intervals of 7-10 days. Photographs were taken, and both biopsies and histological assessments were carried out, before treatment and 7 days after the final treatment session. RESULTS: In the opinion of the patients, in both groups there was improvement in the texture, pigmentation, and appearance of the treated skin, and this was confirmed with the assessment of the pre- and post-treatment photographs. The combination of microdermabrasion followed by a 5% RA peel showed slightly greater improvement in the histological alterations resulting from photoaging. Conclusion Both methods, microdermabrasion followed by a 5% RA chemical peel and a 5% RA chemical peel alone are effective in the treatment of photoaging.

Journal Article↗
PubMed1989

Cytoplasmic retinoid-binding proteins and retinoid effects on insulin release in RINm5F beta-cells.

Vitamin A (retinol) is required for insulin secretion, and retinoic acid substitutes for retinol in this function. To determine if retinol acts at the beta-cell level, we assayed beta-cells of the rat insulinoma (RINm5F) line for cytosolic retinol- and retinoic acid-binding proteins (CRBP and CRABP) by radioimmunoassay (RIA) and [3H]retinol and [3H]retinoic acid binding to cytosol extracts. Furthermore, we tested whether insulin release from cells was affected by addition of retinol or retinoic acid to culture medium. RINm5F cells were grown to near confluence before assay of CRBP and CRABP. Scatchard analysis showed the Kd for retinol to be approximately 6 nM at a level of 4.5 pmol/mg protein or 300,000 sites/cell. Sucrose density-gradient assay showed single discrete peaks migrating at 2S for both retinol and retinoic acid. RIA of whole-cell extracts showed CRBP and CRABP levels of 5.27 +/- 0.41 and 2.95 +/- 0.75 pmol/mg protein, respectively. Retinol (1.75 microM) and retinoic acid (0.175 and 1.75 microM) increased KCl-induced insulin release. Considered together, the presence of CRBP and CRABP in a beta-cell line and the increase in KCl-induced insulin release by retinol and retinoic acid are consistent with the idea that retinol has a functional role in insulin secretion and suggest a potential mechanism of action at the beta-cell level similar to that observed in other retinoid-responsive cells.

Animals↗
PubMed1981

Cellular retinoid-binding proteins in reginerating rat liver: demonstration of a novel cellular retinoid-binding protein.

Changes in the levels of liver cellular aetinol- and retinoic acid-binding proteins were studied after partial (about 70%) hepatectomy for 14 days in the rat. It was found that a novel binding protein designated F-type appears transiently in liver cytosol 3 days after the operation. The appearance of this protein coincides with the peak level of the alpha 1-fetoproteain. In contrast, cellular retinoic acid-binding protein was detected only the first day after hepatectomy, whereas no significant change was observed in the level of the cellular retinol-binding protein during the entire observation period. [3H]Retinol or [3H]retinoic acid complexed with serum retinol-binding protein injected intravenously into vitamin A-deficient rats 1 day after the hepatectomy was recovered 5 min or 20 min later bound specifically to cellular retinol- or retinoic acid-binding protein, respectively. The results presented here strongly suggest that each of the three cellular retinoid-binding proteins plays a distinct role in cell proliferation and differentiation.

Animals↗