Glucocorticoid receptors and corticosensitivity in the human monocytic cell line CM-S: changes during phorbol ester-induced differentiation

Response of amoeboid and differentiating ramified microglia to glucocorticoids in postnatal rats: a lectin histochemical and ultrastructural study

After glucocorticoid injection(s), the number of amoeboid microglial cells (AMC) in the corpus callosum labelled by lectin was markedly reduced when compared with the corresponding control rats. In rats killed at the age of 7 days, all the labeled cells differentiated to become ramified microglia. Ultrastructurally, the AMC in glucocorticoid-injected rats were extremely vacuolated and showed increased lipid droplets. Furthermore, the cells displayed varied lectin labelling patterns especially at both the trans saccules of the Golgi apparatus and lysosomes. In differentiating ramified microglia, massive cellular debris and lectin-stained vesicles or vacuoles were observed; some of the latter appeared to fuse with the plasma membrane. The most striking feature after glucocorticoid (GCC) treatment was the complete diminution of lectin labelling at the Golgi saccules in some differentiating ramified microglia. The present results have demonstrated different effects of glucocorticoids on AMC and differentiating ramified microglia. The differential response of AMC and differentiating ramified microglia to the immunosuppressive drugs may be attributed to the fact that these cells in the postnatal brains subserve different functions or that they are at different differentiation stages. In other words, the sensitivity of microglial cells to the immunosuppressive drugs is dependent upon the stage of cell maturation/differentiation.

Type II oestrogen binding sites in acute lymphoid and myeloid leukaemias: growth inhibitory effect of oestrogen and flavonoids

The presence of oestrogen receptors (ER) and type II oestrogen binding sites (type II EBS) have been investigated by a whole cell assay in seven cases of acute lymphoid leukaemia (ALL) and 16 cases of acute myeloid leukaemia (AML). ER were detected in 6/7 ALL patients with values ranging between 133 and 2268 sites/cell and in 12/16 AML patients with values ranging between 274 and 4197 sites/cell. The apparent dissociation constant (KD) for ER was 0.6 +/- 0.3 nM (mean + SD of 20 cases). All blasts from ALL and AML patients expressed type II EBS at variable levels ranging between 3109 and 239450 sites/cell. The mean KD value for these sites was 18.3 +/- 5.6 nM (mean +/- SD of 23 cases). Specificity experiments demonstrated that type II EBS are oestrogen specific relative to the class of steroid hormones. In addition, the flavonol quercetin was able to compete for [3H]17 beta-oestradiol (E2) binding to type II EBS, the relative binding affinity (RBA) of quercetin being greater than that of diethylstillboestrol (DES). DES and quercetin exerted a dose-dependent inhibition of ALL and AML blast proliferation in the range of concentrations between 10(-8) and 10(-5) M. The RBA of DES and quercetin for type II EBS correlated well with their potency as cell growth inhibitors. Moreover, the flavonols rutin and hesperidin which compete slightly for [3H]E2 binding to type II EBS, were scarcely effective in inhibiting leukaemic cell proliferation. The inhibitory effect of DES and quercetin was not due to a non-specific cytotoxic action since after a 1 d culture period, cell viability did not vary between control and treated cells, being greater than 80%. Our results suggest that high oestrogen concentrations and the flavonol quercetin may inhibit leukaemic blast proliferation through a common mechanism involving a binding interaction with type II EBS.

Down-regulation of glucocorticoid binding sites by retinoic acid in squamous carcinoma cells resistant to the induction of keratinization by hydrocortisone

Physiologic concentrations of retinoic acid strongly inhibit the in vitro maturation of human squamous carcinoma cells in serum-free medium. Differentiation, as measured by the capacity to synthesize cornified cell envelopes, could be induced by hydrocortisone in retinoic acid-treated SqCC/Y1 and CE-81T cells. However, two other cell lines (C4-1 and A431) were less competent to spontaneously form cornified cell envelopes and resistant to the induction of envelope competence by hydrocortisone in the presence of retinoic acid. To investigate the mechanism underlying the resistance of these two lines to hydrocortisone, the characteristics of glucocorticoid receptors were analyzed. Whole cell dexamethasone binding sites ranged from 1300 to 9000 sites per cell for the four cell lines. The binding affinity for dexamethasone was similar in all four squamous carcinoma cell lines (1.32 to 4.75 nM). During retinoic acid-treatment, the binding of dexamethasone by intact SqCC/Y1 and CE-81T cells increased 1.5- to 3.0-fold over 48 h. In contrast, the number of dexamethasone binding sites were decreased by 80% in retinoic acid-treated A431 and C4-1 cells. In each case, the regulation of dexamethasone binding was dependent on the concentration of retinoic acid, with maximal effects being observed at 10(-6) M. Thus, the manner in which retinoic acid regulates the availability of dexamethasone binding sites might explain, in part, the effects of glucocorticoids on differentiation of retinoic acid-treated squamous carcinoma cell lines.