Variations in cellular sensitivity to glucocorticoids: observations and mechanisms

Effects of "systemic" budesonide concentrations on in vitro allergen-induced activation of blood mononuclear cells isolated from asthmatic patients

Blood levels of inhaled corticosteroids are significantly lower than those measured in the lung, but their concentration could still have anti-inflammatory effects. To determine whether budesonide, at concentrations similar to those obtained in blood after drug inhalation (10(-9) M), could downregulate the allergen-induced activation of mononuclear cells, we studied 21 atopic patients, sensitized to Dermatophagoides pteronyssinus (Der p). On blood mononuclear cells, isolated from these patients, incubated with Der p allergen extract and with or without budesonide, we evaluated: 1) the proliferative response of T cells; 2) the expression of two surface activation markers, the HLA-DR antigens and the interleukin (IL)-2 receptors; and 3) the release of cytokines known to modulate the allergic processes. Allergen-induced T-cell proliferation was associated with increased HLA-DR antigen and IL-2 receptor expression (P < 0.001), and with increased release of IL-2, interferon-gamma (IFN-gamma), IL-1 beta, tumor necrosis factor-alpha (TNF-alpha), and granulocyte/macrophage colony-stimulating factor (GM-CSF). The addition of budesonide at the beginning of the cell cultures induced a dose-dependent inhibition of T-cell proliferation, still significant (P < 0.05) at the lowest concentrations tested (10(-9) and 10(-10) M). A significant inhibitory effect on T-cell proliferation was also present when budesonide (10(-9) M) was added to the cell cultures 3 or 5 days after the beginning of the cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Phorbol esters potentiate glucocorticoid-induced cytotoxicity in CEM-C7 human T-leukemia cell line

Phorbol ester tumor promoter, such as 12-O-tetradecanoylphorbol-13-acetate (TPA), is synergistic with dexamethasone to cause growth inhibition of CEM-C7 human T-leukemia cell line. A specific saturable binding component which may mediate the phorbol ester effects has been identified by using [20-(3)H]phorbol 12,13-dibutyrate in a whole cell binding assay. Saturation of the specific binding occurs at a concentration (approx. 100 nM) consistent with causing maximal cytotoxicity. Scatchard analysis of the binding after 15 min at 37 degrees C demonstrates a single class of binding sites. The number is 194,000 sites per cell. Other phorbol esters are also cytotoxic to CEM-C7 cell in the presence of 30 nM dexamethasone in an approximate proportion to their activity in competing for [20-(3)H]phorbol 12,13-dibutyrate binding. Phorbol 12, 13-didecanoate, 4-O-methyl PMA, 4-beta-phorbol do not compete for specific binding. The synergism of phorbol esters and dexamethasone on CEM-C7 cells is reversible by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine(H-7). However, by treating CEM-C7 cells with TPA for 48 h there is not any increase in the affinity or levels of glucocorticoid receptor. It is tentatively concluded that phorbol esters may play an important role linked to the glucocorticoid-induced growth inhibition in CEM-C7 human T-leukemic cell.

Mechanisms of glucocorticoid action in pulmonary disease

This article reviews the multiple mechanisms by which glucocorticoids influence the pathophysiology of pulmonary disease. Particular emphasis is given to the influence of glucocorticoids on the release and action of mediators that promote inflammation and that modulate other pathophysiologic processes in the lung. The time course and mechanisms of action that contribute to glucocorticoid effects on pulmonary function are also discussed.

Reaction of human leukocytes after in vitro contact with a glucocorticoid

The used hormone prednisolone bisuccinate causes in the concentration range of 2-1,000 micrograms/ml visible changes of the cell morphology and enzymatic activity in all leukocytes. These alterations appear immediately after the application of the glucocorticoid and remain nearly constant during the time of investigation (1 h). The changes in the cell morphology and the loss of enzymatic activity increase with enhanced hormone concentration. The following reproducible morphological changes caused by the hormone comprise swelling, vacuolization and deformation of the nuclei with concomitant release of nuclei material. In addition, cloverleaf and fircone-like structures originate in connection with the formation of small bubbles.

The effects of dexamethasone on palate mesenchymal cell phospholipase activity

Corticosteroids will induce cleft palate in mice. One suggested mechanism for this effect is through inhibition of phospholipase activity. This hypothesis was tested by measuring the effects of dexamethasone, a synthetic corticosteroid, on phospholipase activity in cultures of palate mesenchymal cells. Palate mesenchymal cells were prelabeled with [3H]arachidonic acid. The cells were subsequently treated with various concentrations of dexamethasone. Concurrently, cultures of M-MSV-transformed 3T3 cells were prepared identically. After treatment, phospholipase activity was stimulated by the addition of serum or epidermal growth factor (EGF), and radioactivity released into the medium was taken as a measure of phospholipase activity. Dexamethasone (1 X 10(-5) or 1 X 10(-4) M) could inhibit serum-stimulated phospholipase activity in transformed 3T3 cells after 1 to 24 hr of treatment. However, no inhibition of activity was measured in palate mesenchymal cells following this period of treatment. Not until 120 hr of treatment with dexamethasone (1 X 10(-4) M) was any significant inhibition of serum-stimulated phospholipase activity observed in palate mesenchymal cells. When EGF was used to stimulate phospholipase activity, dexamethasone (1 X 10(-5) M) caused an increase in phospholipase activity in palate mesenchymal cells. These observations suggested that phospholipase in transformed 3T3 cells was sensitive to inhibition by dexamethasone. However, palate mesenchymal cell phospholipase is only minimally sensitive to dexamethasone, and in certain instances can be enhanced. These results cannot support the hypothesis that corticosteroids mediate their teratogenic effect via inhibition of phospholipase activity.

Glucocorticoid induced cytolysis of human normal and malignant lymphocytes

Contrary to the general concept that man is a "glucocorticoid resistant species" this work demonstrates distinct human lymphoid subsets which are readily lysed in vitro by upper physiological and pharmacological concentrations of cortisol. These populations include the thymocyte precursor cells, i.e. prothymocytes, and immunoactivated T lymphocytes. Chronic lymphocytic leukemia cells and malignant cells from part of the acute lymphoblastic leukemia patients were also found to be highly sensitive to the in vitro cortisol induced lysis. The leukemic cells from all acute and chronic myeloid leukemias and from some acute lymphoblastic leukemia patients were found to be completely resistant to cortisol-induced lysis, even at the super pharmacological levels of the hormone. The lysis of the sensitive cell populations was specifically induced by glucocorticoids but not by other steroid hormones. Studies of the cytolic process showed high-affinity binding of the cortisol molecule to specific cytoplasmic receptor, and implied induction of "autolytic protein" synthesis. It is suggested that the observed in vitro cortisol-induced lysis accounts for part of the clinical effects of glucocorticoids. Furthermore this phenomenon may reflect a normal regulatory mechanism exerted by the corticoadrenal hormones on the immune system.