Effects of epoxycarotenoids, beta-carotene, and retinoic acid on the differentiation and viability of the leukemia cell line NB4 in vitro.

Three all-trans epoxides of beta-carotene (beta-Car), namely, 5,6-epoxy-beta-carotene (5,6-EC), 5,8-epoxy-beta-carotene (5,8-EC) and 5,6,5',6'-diepoxy-beta-carotene (5,6,5',6'-DEC) were synthesized by treatment of beta-carotene with 3-chloroperoxybenzoic acid, were purified chromatographically, and were characterized. The relative potencies (mean +/- S.D.) of 1 microM compounds in inducing the differentiation of NB4 cells, a cell line that contains the chromosomal transposition t(15;17) characteristic of acute promyelocytic leukemia, after 4 days of incubation were: RA: 1.35 +/- 0.16, 5,6-EC: 0.29 +/- 0.01, 5,8-EC: 0.22 +/- 0.05, 5,6,5',6'-DEC: 0.11 +/- 0.02, beta C: 0.09 +/- 0.01, and the control: 0.06 +/- 0.01. The same order of potencies existed at other concentrations tested and at other incubation times. P values for the differences between the inducing activities of successive pairs of compounds at 1 microM were: RA vs. 5,6-EC, < 0.001; 5,6-EC vs. 5,8-EC, < 0.01; 5,8-EC vs. 5,6,5',6'-DEC, < 0.01; 5,6,5',6'-DEC vs. beta-Car, < 0.10; beta-Car vs. control, < 0.005. Similar P values were also obtained for studies at other concentrations and at other incubation times. The viable cell mass at 4 days was inversely proportional to the extent of differentiation (rs = -1.0). The inducing activities of all compounds were dose-dependent. Thus, the 5,6-monoepoxide of beta-carotene, which has not previously been studied as an inducer, showed higher activity in NB4 cell differentiation than the 5,8-monoepoxide, the 5,6,5',6'-diepoxide, or beta-carotene. Possible explanations of these observations are discussed.

Reduction of serum retinol levels following a single oral dose of all-trans retinoic acid in humans.

Following a single oral dose of all-trans retinoic acid (RA) (0.167 mmole) in corn oil to 6 healthy human subjects, the mean serum retinol (ROL) level fell by approximately 20% within 1 h and remained depressed for 24 h. After dosing, RA appeared in the blood within 30 min, peaked at 0.3-0.5 mumol/l, and then declined to very low concentrations after 7 h. All-trans retinoyl beta-glucuronide (RAG) appeared simultaneously with RA in the plasma, albeit more sporadically, whereas only traces of 4-oxoretinoic acid (4-oxoRA) were detected. Some possible physiologic consequences of therapeutic uses of all-trans RA are discussed.

Vitamin A and vitamin E statuses of preschool children of socioeconomically disadvantaged families living in the midwestern United States.

OBJECTIVE: To determine the vitamin A and vitamin E statuses of socioeconomically disadvantaged preschool American children. DESIGN: Cross-sectional study of preschool children from socioeconomically disadvantaged families. SETTING: Central Iowa, USA. SUBJECTS: A group of 77 apparently healthy children was studied with the following characteristics: 5 mo-6 y; 37 males, 40 females, 56 non-Hispanic Caucasians, 3 Hispanics, 18 Afro-Americans. METHODS: Modified relative dose response (MRDR) test for vitamin A status assessment; serum retinol, alpha-tocopherol, cholesterol, and carotenoids; weight for age. RESULTS: Although the mean weight for age was the 53rd percentile of the NCHS standard, a significant number of children (P = 0.006, chi(2)) were either markedly underweight or overweight. Ratios of 3,4-didehydroretinol to retinol (DR/R) were > 0.030, in 32% of the children. Mean serum retinol, alpha-tocopherol and cholesterol (+/- s.d.) were 1.09 +/- 0.23 microM/L, 16.8 +/- 6.3 microM/L and 4.01 +/- 0.8 microM/L. Three children (3.9%) showed a serum retinol value < 0.7 microM/L. One child with a serum retinol value < 0.7 microM/L and one additional child showed a ratio of alpha-tocopherol to cholesterol < 1.44 mumol/mmol. The mean alpha-tocopherol to cholesterol ratio for the group (4.31 +/- 1.71 mumol/mmol), however, was satisfactory. The only significant (P < or = 0.05) age-related changes were an increase in the serum cholesterol (P = 0.005) and decrease in the alpha-tocopherol to cholesterol ratio (P < 0.005) between the 0-2 y and the 2-4 y groups. Serum cholesterol (P = 0.0165, two-tailed) and lycopene (P = 0.004) concentrations of Afro-Americans were significantly higher than those of Caucasians. Median serum concentrations of alpha-carotene and beta-carotene were lower and, of lycopene higher than those found in children studied in a national survey. Serum carotenoid concentrations generally increased with age. CONCLUSIONS: Larger percentages of underweight and overweight children and a significant degree (32%) of inadequate vitamin A status were found in this group of socioeconomically disadvantaged children. Afro-Americans showed higher serum cholesterol and lycopene concentrations than did Caucasians, but otherwise were nutritionally similar. Age-related changes were small. Of nutritional parameters considered, the vitamin A status of socioeconomically disadvantaged segments of our population clearly needs attention.

Comparative embryolethality and teratogenicity of the all-trans isomers of retinoic acid, 3,4-didehydroretinyl acetate, and retinyl acetate in pregnant rats.

The teratogenic potencies of the all-trans isomers of retinoic acid (RA), 3,4-didehydroretinyl acetate (A2), and retinyl acetate (A1) were compared. Groups of eight timed-pregnant Sprague-Dawley rats were administered single equimolar doses (3.5-352 mumol/kg BW) of the retinoids orally in oil on day 8.5 of pregnancy, and dams and fetuses were sacrificed on day 19. The relative teratogenicity and embryolethality of the three tested retinoids were: RA > A2 > A1. The no-effect level of RA and A2 was 3.5 mumol/kg BW and of A1 was 35 mumol/kg BW. Whereas the adverse effects of RA and A1 were dose dependent, A2 showed biphasic effects, with a peak of embryolethality at 35 mumol/kg BW. Dams also exhibited weight loss and other toxic manifestations from doses of A2 and Ra > or = 35 mumol/kg BW. In dosed dams, (1) Liver concentrations of A1 and A2 increased with the doses of A1 and A2, respectively, (2) RA had little effect on liver A1 except for an increase at the highest toxic dose, and (3) A2 showed a sparing effect on liver A1. RA, although not detected in fetuses from dams treated with A1, was present in significant concentrations (0.5-4.1 nmol/g liver) in fetuses from dams treated with A2. The biphasic change in embryolethality with the dose of A2 correlates with this enhanced concentration of fetal RA. We hypothesize that the actual teratogen in the fetuses of A2-dosed dams is RA. A2 might induce this biphasic effect by inhibiting the catabolism of RA at lower doses and its formation at higher doses.

Suppression of hepatic prostaglandin F2 alpha in rats by dietary alpha-tocopherol acetate is independent of total hepatic alpha-tocopherol.

Groups of eight weanling female F344/N rats were fed semipurified diets that supplied 0, 50, 500, 5000, or 15,000 mg alpha-tocopherol acetate/kg diet, with and without 0.05% phenobarbital (PB) for 9 weeks. Both plasma and hepatic alpha-tocopherol levels, measured by HPLC, strongly correlated with alpha-tocopherol intake (r greater than 0.73, p less than 0.0001). Phenobarbital both depleted hepatic alpha-tocopherol and increased plasma alpha-tocopherol significantly. Although treatment with PB for 9 weeks significantly increased GST activity, PB did not affect hepatic prostaglandin (PG)F2 alpha status, as determined by radioimmunoassay. PGF2 alpha was significantly greater (by 52%) in rats fed no alpha-tocopherol than in rats fed 15,000 mg alpha-tocopherol acetate/kg diet. Hepatic PGF2 alpha status was correlated inversely but weakly with dietary alpha-tocopherol (r = -0.24, p less than 0.05). Hepatic PGF2 alpha status was not correlated with hepatic or plasma alpha-tocopherol status. This finding suggests either that there is a small depletion-resistant subcellular alpha-tocopherol pool which regulates PGF2 alpha production or that alpha-tocopherol alters PGF2 alpha production in vivo by an indirect mechanism.