In vitro effect of retinoids on calcineurin activity

Calcineurin was shown previously to be inhibited by members of the tyrphostin family of tyrosine kinase inhibitors, with the most effective inhibition suggested to be caused by the presence of a conjugated side chain (Martin BL, Biochem Pharmacol 56: 483-488, 1998). Retinoids are a family of naturally occurring biomolecules having non-aromatic ring structures and conjugated side chains as substituents on the ring. Three oxidation states of the all-trans configuration of retinoids (retinol, retinal, and retinoic acid) were tested as effectors of calcineurin. Only retinoic acid was found to inhibit calcineurin effectively, with an IC(50) value of approximately 50 microM. Retinol and retinal caused less than 30% inhibition at concentrations up to 100 microM. All three retinoids caused some precipitation of reaction components: retinoic acid and retinal above 50 microM, and retinol above 250 microM. Bacterial alkaline phosphatase was not inhibited by the retinoids, indicating that metal centers alone are insufficient for significant inhibition by retinoic acid. An aromatic ring was not required for inhibition and may not provide additional inhibition, inasmuch as an aromatic analog of retinoic acid (acitretin) showed less effective inhibition. These data are consistent with the presence of conjugated, unsaturated groups enhancing the inhibition of calcineurin.

Exercise training has little effect on HDL levels and metabolism in men with initially low HDL cholesterol

Low concentrations of high-density lipoprotein cholesterol (HDL-C) are a recognized risk factor for atherosclerotic cardiovascular disease. Exercise is often recommended to increase HDL-C, but the effect of exercise training on HDL levels and metabolism in subjects with low HDL concentrations is not well defined. The present study compared the HDL response to 12 months of supervised endurance exercise training without weight loss in 17 men aged 26 49 years with initially low ( < 40 mg/dl, N=7) or normal ( > 44 mg/dl, N=10) HDL-C levels. HDL-C levels and HDL apolipoprotein metabolism were assessed while the subjects consumed controlled diets before and after the year of training. Increases in total (5.1+/-2.8 versus 1.9+/-4.2 mg/dl, P=0.08) and HDL2 (3.8+/-2.9 versus 0.4+/-1.1 mg/dl, P=0.01) cholesterol were greater in men with normal initial HDL-C levels. Catabolic rates for HDL apolipoproteins decreased 7-14% and biological half-lives increased 10-15% after exercise training in subjects with normal HDL, but were unchanged in the low HDL-C group. HDL apolipoprotein synthetic rates were not consistently affected by exercise training in either group. Postheparin lipoprotein lipase activity increased 27%, the clearance rate of intravenous triglycerides increased 14%, and apolipoprotein B levels decreased 16% with training in subjects with normal HDL-C but were unchanged in the low HDL-C group. We conclude that the ability to increase HDL-C levels through endurance exercise training is limited in subjects with low initial HDL-C, possibly because exercise training in such subjects fails to alter triglyceride metabolism.

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.

Immunotherapy of collagen-induced arthritis by a T-cell antiproliferative molecule

The present study describes a novel experimental immunotherapeutic methodology for the reduction of inflammatory synovitis that is noted in an animal model of rheumatoid arthritis. The reduction in inflammation is noted in the animals administered a contra-interleukin-2 (IL-2) cytokine secreted by a cloned T-cell line. The mechanism of reduction of inflammation by this cytokine is through the inhibition of activation and differentiation of T lymphocytes. The cytokine inhibits the in vitro mitogen activation of T-cell lymphocytes as well as antigen-specific activation of a collagen type II specific T-cell line. In addition, decreased levels of messenger RNA coding for interleukin-2 are noted in T lymphocytes and IL-2 activation of the collagen type II specific cell line is inhibited by the contra-IL-2 cytokine. This initial description of a reduction in inflammation by a contra-IL-2 lymphokine suggests that immunoregulatory biologic molecules that are antagonists to IL-2 may be useful for the experimental immunotherapy of cartilage connective tissue pathology.

A T suppressor cell cytokine regulates murine arthritis and T lymphocyte stimulation

Experimental immunotherapy of murine collagen-induced arthritis can be achieved by administration of specific T suppressor cell hybridomas. The present study examines the immunoregulation noted in this experimental immunotherapy by describing the immunomodulatory effects of a cytokine produced by a suppressor T cell line, T101N. The inhibition of the activation of splenic lymphocytes in response to T cell mitogens and the erythema and edema associated with arthritis were assayed. Mice given T101N ascites showed reduced inflammation (p less than 0.05). Lymphocytes derived from naive mice and cultured in the presence of T101N culture supernatant showed reduced response to concanavalin A. Therefore, this form of experimental immunotherapy of arthritis may be associated with cytokines secreted from T suppressor cells which modulate T cell activation.