Effect of hydrocortisone and thyroxine on arylsulphatases A and B of cultured cells of neuronal and glial origin

Multihormonal control of proliferation and cytosolic glycerol phosphate dehydrogenase, lactate dehydrogenase and malic enzyme in glial cells in culture

We have examined the effect of a physiological concentration of l-triiodothyronine on the activity of cytosolic enzymes in the C6 rat glioma cell line. l-Triiodothyronine decreased glycerol phosphate dehydrogenase activity. This effect seems to be rather specific, since l-triiodothyronine did not change malic enzyme or lactate dehydrogenase activity and did not alter the amount of either cytosolic or total cell protein. Dexamethasone greatly increased glycerol phosphate dehydrogenase and l-triiodothyronine also decreased the response to the glucocorticoid. Noradrenaline or dibutyryl cyclic AMP potentiated the dexamethasone-induced specific activity of this enzyme, and l-triiodothyronine lowered the response to the combined effects of these agents. The effect of l-triiodothyronine is not restricted to the C6 cells, since it also decreased basal glycerol phosphate dehydrogenase activity in primary cultures of cells dissociated from brains of embryonic mice. The results indicate that thyroid hormones have a direct effect on the modulation of cytosolic glycerol phosphate dehydrogenase in cultured cells of glial origin.

Expression of thyroid hormone receptor isoforms in the oligodendrocyte lineage

Thyroid hormone (T3) regulates brain development and function and in particular ensures normal myelination. Animal models and in vitro systems have been employed to demonstrate the effects of T3, which acts via nuclear hormone receptors. T3 receptors (TRs) are transcription factors that activate or suppress target gene expression, such as myelin basic protein (MBP), in a hormone-dependent or -independent fashion. Two distinct genes, TR alpha and TR beta, encode several receptor isoforms with specific functions. This overview summarizes current knowledge on the cellular expression and the role of these isoforms and also examines the action of T3 on oligodendrocyte lineage cell types at defined developmental stages. Re-expression of TRs and also that of other transcription factors in oligodendrocytes may constitute some of the metabolic changes required for succesfull remyelination in the adult central nervous system after demyelinating lesions.

Hydrocortisone regulates arylsulfatase A (cerebroside-3-sulfate-3-sulfohydrolase) by decreasing the quantity of the enzyme in cultures of cells dissociated from embryonic mouse cerebra

Previous work from our laboratory (Biochem. J. 219:689-697 (1984] had shown that hydrocortisone stimulated the net accumulation of the myelin-specific sulfolipid in cultures of cells dissociated from embryonic mouse cerebra. This accumulation caused by hydrocortisone was shown to be due to a decrease of sulfolipid degradation by arylsulfatase A (ASA) and not due to a stimulation of its synthesis by a sulfotransferase. Both ASA activity and the turnover of sulfolipid were decreased by hydrocortisone to 60-62% of untreated cells. In current work the same decrease in enzyme activity was obtained and enzyme linked immunosorbent assays demonstrate that hydrocortisone decreased the number of ASA protein molecules to 61% of untreated cells [(-)hydrocortisone: 0.31 +/- 0.06 ng ASA/microgram protein; (+)hydrocortisone: 0.18 +/- 0.04 ng ASA/microgram protein]. This decrease in the number of ASA molecules correlates well with the decrease in both the enzyme activity and the sulfolipid turnover, which suggests that the major mode of inhibition of ASA activity by hydrocortisone involves a decrease in the concentration of ASA in the cells rather than some other mechanism of inhibition.

Effect of glucocorticoids on galactosylceramide sulfotransferase activity in rat brain

Previous studies have shown that glucocorticoids can induce the sulfatide-forming enzyme galactosylceramide sulfotransferase (GalCer-ST) in cultured glioblastoma cells. To investigate whether a similar process occurs in vivo, we administered corticosterone to infant and adult adrenalectomized rats and then assayed brain GalCer-ST activity and sulfatide content. Both measures were unexpectedly decreased rather than increased by hormone treatment, indicating that glucocorticoids may not regulate brain sulfatide biosynthesis in the same manner as observed in clonal cell lines.

Serum lysosomal acid hydrolase activities in Graves' disease

The activities of seven lysosomal enzymes (alpha-D-glucosidase, beta-D-galactosidase, beta-D-glucuronidase, hexosaminidase, alpha-L-fucosidase, alpha-D-mannosidase, acid phosphatases) were studied in the serum of 31 untreated patients with Graves' disease, 30 treated hyperthyroid patients whose clinical abnormalities had disappeared and whose hormones had returned to euthyroid levels, and 34 controls. The hyperthyroid state is characterized by increased serum levels of alpha-D-glucosidase, beta-D-glucuronidase, hexosaminidase and especially of alpha-L-glucosidase and alpha-D-mannosidase. In contrast, neither beta-D-galactosidase nor acid phosphatases serum levels were significantly modified. After antithyroid treatment, the activities of these enzymes returned to normal levels, except for alpha-D-mannosidase. The interpretation of these changes in serum acid hydrolases activities is controversial.

Lung development and the pulmonary surfactant system: hormonal ifluences

The effect of hormones on developmental events is not a new area of scientific investigation. However, in the last decade, the developing lung has been the focus of an increasing amount of basic and applied research. Inadequate development of the newborn's respiratory system precludes extra-uterine existence; indeed, such respiratory inadequacy has been a leading cause of death in premature infants. Tremendous strides have been made in understanding the basic cell biology of the developing lung. Much has been learned about the source, composition, and function of pulmonary surfactant, a surface-active material produced by the lung and essential to alveolar stability. Deficient stores of this material is a major etiologic factor in the respiratory distress syndrome of the newborn (RDS). This fact, coupled with observations that certain hormones can accelerate lung development and the consequent availability of adequate stores of pulmonary surfactant, has led to a large body of literaturae dealing with the effects of hormones (and other agents) on lung development. It is the purpose of this literature review (1) to discuss the various kinds of investigations which have linked surfactant synthesis to the type II pulmonary epithelial cell; and (2) to review the current status of research dealing with the effects of glucocorticoids and thyroid hormones on lung maturation.