Glucocorticoid sensitivity and receptors in BALB/c T cell lymphoma lines expressing restricted patterns of Ly differentiation antigens

Lymphoid cell resistance to glucocorticoids in HIV infection

In humans infected with the HIV-1 virus there may be a disproportionate severity of signs and symptoms of illness compared to the fraction of CD4+ infected T-lymphoid cells. In part, this may be due to altered intercellular signalling systems and intracellular signal transduction. Glucocorticoids are well known for their effects on the vitality and function of lymphoid cells. Patients with HIV infections often show elevated circulating levels of cortisol, suggesting some misfunction in the regulatory systems that maintain the levels of this critical hormone. At the cellular level, it is known that both acute HIV infection and glucocorticoids can cause apoptotic cell death in thymic lymphocytes. However, chronically HIV-infected cells appear to be resistant to glucocorticoid-evoked cell death. Glucocorticoid receptor-ligand binding studies on patients' cells have shown reduced affinity between the receptor binding sites and test steroids. In vitro, chronically HIV-infected cells of the lymphoid CEM line displayed resistance to glucocorticoid-induced apoptosis. These cells showed reduced numbers of binding sites with little alteration in apparent affinity between ligand and receptor. Thus it appears that there may often be malfunction of the normal glucocorticoid response in HIV-infected cells probably due to altered interactions between the glucocorticoid receptor and its hormone. Such alterations may have clinical consequences, including the possibility of a relatively longer life span of infected CD4+ T-lymphocytes, as well as systemic effects of chronically elevated cortisol level.

Corticosterone effects on differentiation and X-ray-induced transformation of C3H/10T1/2 mouse cells

Glucocorticoid hormones have dramatic effects on cytodifferentiation and carcinogenesis in vitro and in vivo. We have investigated the effects of the endogenous rodent glucocorticoid hormone, corticosterone, on the X-irradiation-induced transformation and differentiation of C3H/10T1/2 mouse fibroblast cells in culture. Initially, we have demonstrated the presence of functional glucocorticoid receptors in these cells. We found that corticosterone has little effect on X-ray-induced transformation. However, this hormone alone was found to differentiate a high number of these fibroblastic cells to the adipogenic cell lineage. Using an antagonist to the glucocorticoid receptor, we demonstrate that the hormonal effect on differentiation is mediated by the corticosterone-receptor complex.

Cellular receptor levels and glucocorticoid responsiveness of lymphoma cells

A series of mouse lymphoma cell lines of independent origin was investigated with respect to glucocorticoid sensitivity, cellular receptor levels, and properties of receptors. The concentrations of the glucocorticoid dexamethasone required to produce comparable growth-inhibitory effects varied considerably amongst these cell lines. Also a wide range in the number of receptors per cell was found. When the receptor-steroid complexes were compared with respect to nuclear binding properties and affinities for DNA, no differences were seen. For 7 out of 10 cell lines studied we obtained a direct correlation between hormonal sensitivity and the number of cellular receptor sites divided by the dissociation constants KD for the receptor-dexamethasone complexes. This suggests that the receptor is a major quantitative determinant for steroid responsiveness. The limitations of receptor measurements for glucocorticoid therapy of lymphoid neoplastic disease are discussed.