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The specific glucocorticoid binding capacity in cytosols prepared from L929 mouse fibroblasts (L cells) is inactivated with a half-life of approximately 2 h at 25 degrees C. As previously published, this inactivation can be prevented with 10 mM molybdate and markedly slowed by addition of other phosphatase inhibitors such as glucose 1-phosphate and fluoride. We have now found that ATP (5 to 10 mM) also slows the rate of this inactivation. After extensively inactivating the receptor by preincubating cytosol at 25 degrees C for 4 and preventing further inactivation by addition of molybdate, addition of ATP results in reactivation of the steroid binding capacity. Maximal reactivation of 40 to 70% is achieved with 5 to 10 mM ATP. The activation is temperature-dependent and specific for ATP. ADP, GTP, CTP, and UTP do not cause activation and preliminary results indicate no effect of cyclic nucleotides in this system. If activation is prevented by addition of 10 mM EDTA to the cytosol, addition of 3 to 10 mM magnesium permits ATP-dependent activation of the binding capacity. The level of reactivation can be enhanced by addition of a heat-stable factor prepared from the same L cell supernatant. These results support the proposal that L cell glucocorticoid receptors can be activated to the glucocorticoid binding state by an ATP-dependent phosphorylation mechanism.

The results from a number of clinical and experimental studies have suggested that during endotoxemia, suppression of adrenocortical steroidogenesis may occur. We have examined the possibility that macrophages are the source of a factor that suppresses adrenocortical steroidogenesis. Resident and peptone-elicited peritoneal exudate macrophages (PEM) from C3HeB/FeJ mice were incubated for 4 hr at 37 degrees C in the presence or absence of T cell hybridoma-derived lymphokine (LK) that contained high concentrations of MAF activity (assessed by induction of nonspecific tumoricidal activity in PEM). The LK was removed by rinsing, and fresh medium was added, followed by Salmonella minnesota R595 LPS (final concentration 10 micrograms/ml). After 18 hr at 37 degrees C the PEM supernatants and control medium from flasks without cells were harvested and stored at -20 degrees C. Explanted rabbit adrenocortical cells in 96-well plates were exposed to 30 microliters of PEM supernatant or control medium and ACTH (10 or 100 mU/ml) in a final volume of 120 microliters for 3 consecutive days. The adrenocortical cell supernatants were harvested each day, followed by replenishment of medium, PEM supernatant, and ACTH. Fluorogenic steroid production in wells that received control medium or supernatants from PEM not treated with LPS was normal (0.22 microgram +/- 0.010 (SD) per 5 X 10(4) cells). However, as much as 75 to 95% suppression of steroidogenesis was observed in wells that received supernatants from PEM treated with LK and LPS, compared to 40% suppression in wells that received supernatant from PEM treated with LPS alone. Continued exposure (over 3 days) of adrenocortical cells to supernatants from LPS-treated PEM resulted in progressively decreasing response to ACTH. Comparable suppressive activity was observed in supernatants from LPS-treated bone marrow-derived macrophages. In further experiments, suppression was observed in wells that were pretreated (22 hr) with the appropriate PEM supernatant, and evidence was obtained that the suppressive activity was not due to carry-over LPS. Finally, results from control experiments demonstrated that suppressive PEM supernatants neither inactivate ACTH nor interfere with the assay of fluorogenic steroids. Thus, these results suggest that during endotoxemia, products from LPS-stimulated macrophages may suppress adrenocortical function.

Although glucocorticoids are not cytolytic for and do not inhibit the growth of the IM-9 line of cultured human lymphoblasts, these cells have a high steroid-binding capacity. We have used IM-9 cells in order to examine whether unoccupied glucocorticoid receptors are inactivated and activated in intact cells. when IM-9 cells are incubated in glucose-free medium in a nitrogen atmosphere, both their ability to bind triamcinolone acetonide and their ATP levels decline and, when glucose and oxygen are reintroduced, ATP levels and receptor activity return. The specific glucocorticoid-binding activity of cytosol prepared from cells exposed to various degrees of energy limitation is directly correlated with the ATP content. Receptor activation in intact cells is rapid and independent of protein synthesis. Cytosol prepared from inactivated cells cannot be activated by addition of ATP. The inactivation of glucocorticoid receptors that occurs when cytosol from normal IM-9 cells is incubated at 25 degrees C is inhibited by molybdate, vanadate, fluoride, ATP, and several other nucleotides. The experiments with intact human lymphoblasts suggest that assays of specific glucocorticoid-binding capacity do not necessarily reflect the cellular content of receptor protein.

Lipopolysaccharide-treated murine peritoneal exudate macrophages (PEM) release a factor or factors into the supernatant that suppress adrenocorticotropic hormone-induced steroidogenesis in explanted rabbit adrenocortical cells (J. C. Mathison et al., J. Immunol. 130:2757-2762, 1983). To determine the requirements for suppression, PEM supernatants (30 microliters) were added to explanted rabbit adrenocortical cells in a final volume of 120 microliters with 10 mU of adrenocorticotropic hormone per ml, and after 18 h at 37 degrees C, steroid concentrations were measured by a fluorometric assay. Supernatant from proteose peptone-elicited C3HeB/FeJ PEM (5 X 10(6) PEM per 3.5-cm well, 10 micrograms of Salmonella minnesota Re595 LPS per ml, 18 h) suppressed steroid production ca. 50%, and kinetic studies demonstrated that the appearance of suppressive activity in the supernatant was gradual over 4 to 18 h. Release of suppressive activity was not associated with decreased viability of the PEM (assessed by fluorescein diacetate staining and measurement of lactic dehydrogenase in the supernatant). Suppression was not observed when the PEM supernatant was diluted 10-fold before addition to the adrenocortical cells, whereas supernatant concentrated 20-fold (prepared with a 10,000-molecular-weight-cutoff filter) produced 75 to 80% suppression. The suppressive activity was stable at pH 4, pH 11, or 70 degrees C for 30 min but was inactivated at 100 degrees C (10 min). Suppressive activity was also induced in C3HeB/FeJ PEM by O111:B4 lipopolysaccharide or heat-killed Listeria monocytogenes. In contrast, PEM from C3H/HeJ mice did not produce detectable suppressive activity in response to Re595 lipopolysaccharide or heat-killed L. monocytogenes. Thus, these results provide additional support for the inducible, selective release of a macrophage product that could affect the host response to lipopolysaccharide by regulation of the adrenocortical response to adrenocorticotropic hormone.