The mechanism of cAMP-induced glucocorticoid receptor expression. Correlation to cellular glucocorticoid response

The mechanism of regulation of glucocorticoid receptor (GR) expression by cAMP was investigated in rat hepatoma cells (HTC). Incubation of HTC cells with the cAMP-inducing agent, forskolin, caused a significant increase in the levels of both [3H]dexamethasone binding capacity and GR mRNA by about 2- to 2.4-fold within 4 h. Incubation of HTC cells with the cAMP analogue, 8-bromo-cAMP, also increased the GR mRNA level to a similar degree in a concentration-dependent manner. The increase in GR mRNA did not require ongoing translation or transcription. Determination of GR mRNA stability in 8-bromo-cAMP-induced cells showed that the message had a half-life of approximately 10 h, which is about 2.5 times longer than the GR mRNA half-life in nontreated cells (t1/2 = 4 h). These results indicate that the increased steady state level of GR mRNA induced by cAMP analogue is, at least in part, caused by increased GR mRNA stability. In both forskolin-pretreated and nontreated HTC cells, dexamethasone caused an approximately 70% down-regulation of GR protein levels. However, since forskolin induced the GR level 2- to 2.4-fold, the relative amount of GR protein remaining in cells treated with both forskolin and dexamethasone was about 2- to 2.4-fold higher compared to cells treated with dexamethasone alone. This increased GR level correlated well with the increase in inducibility of two glucocorticoid regulated genes, the endogenous tyrosine aminotransferase and the stably integrated mouse mammary tumor virus. These data suggest that relatively small changes in GR levels are reflected in parallel changes in cellular response to glucocorticoid hormones. This also implicates a limiting nature of the GR protein in determining the biological response.

[Preliminary report on the clinical application of anti-Jo-1 antibody]

Jo-1 antigen was purified from the rabbit thymus acetone powder. Using it as antigen, we found anti-Jo-1 antibody in 25% of polymyositis, 7.1% in dermatomyositis, none in other connective tissue diseases nor non-connective tissue diseases. Other antinuclear antibodies, eg anti-RNP, anti-SSA were also found in our polymyositis-dermatomyositis patients. Our study suggested, the positivity of anti-Jo 1 antibody not only confirmed the patient's diagnosis of polymyositis but also demonstrated the autoimmune pathogenesis of this disease.

A prospective, controlled, double-blind, cross-over study of tripterygium wilfodii hook F in treatment of rheumatoid arthritis

A polyglycosides of Tripterygium wilfodii hook F (TWH) preparation with a code name of T2 is used in the present double-blind, controlled, cross-over study on the treatment of 70 cases of rheumatoid arthritis (RA). An impressive curative effect of T2 is confirmed much more convincingly by the present study than that by the previously reported clinical open trials. The adverse reactions and the probable pharmacological mechanism of T2 are also discussed.

[The clinical significance of anti-RNP antibody]

67 cases of anti-RNP antibody were reported in different patients with connective tissue disease. The high titre of anti-RNP antibody not only presents in patients with mixed connective tissue disease (MCTD), but also in individual patient with systemic lupus erythematosus (SLE). Anti-RNP antibody is usually associated with clinical manifestation of raynauds phenomena, myositis, and sclerodactyly. The clinical significance of anti-RNP antibody and the diagnosis about MCTD were discussed in this article.

[Antiphospholipid antibodies: clinical significance in systemic lupus erythematosus]

A radioimmunoassay using cardiolipin as antigen and labelled SPA, anti-human IgG, anti-human IgM, anti-human IgA as second antibodies in detecting anti-cardiolipin antibody with the sera from 308 patients and 70 normal controls. Among them, 126 patients were of SLE, 27 systemic sclerosis, 40 rheumatoid arthritis, 40 Sjögren syndrome, 26 other connective tissue diseases, 7 syphilis and 32 with obstetric complications. The positive rate of anticardiolipin antibody were 42.9% (SLE), 29.7% (PSS), 20% (RA), 15% (SS), 26.9% (CTD), 85.7% (syphilis), 3.1% (obstetric complication), 0% (NC). In SLE the anticardiolipin antibody were well correlated with thrombocytopenia, cerebral lupus, thrombosis of vein and spontaneous recurrent abortion. Lupus anticoagulant (APTT) was found in 21.3% of SLE and biological false positive of VDRL test in 4.8%. Both of them correlated with the anticardiolipin antibody detected by the radioimmunoassay. The authors concluded that antiphospholipid antibodies is a group of commonly seen antibodies, which may play a rule in the pathogenesis of SLE. Further study is progressing.

[Comparative study of diagnostic criteria of rheumatoid arthritis in Chinese patients]

The ARA 1958 and 1987 revised classification criteria of RA are tested in 111 consecutive patients with RA and 54 cases of non-RA connective tissue diseases from three hospitals of tertiary level in Beijing. Comparing the two criteria, the specificity was the same as 88%, whereas the sensitivity changed from 94% of 1958 criteria to 91% of 1987 criteria. Factors affecting the sensitivity of 1987 criteria were mainly the morning stiffness which became to be more than 1 hour and increasing of number of swelling joints from one to three.

Localization of glucocorticoid receptor mRNA in the male rat brain by in situ hybridization

The localization and distribution of mRNA encoding the glucocorticoid receptor (GR) was investigated in tissue sections of the adult male rat brain by in situ hybridization and RNA blot analysis. GR mRNA levels were measured by quantitative autoradiography with 35S- and 32P-labeled RNA probes, respectively. Strong labeling was observed within the pyramidal nerve cells of the CA1 and CA2 areas of the hippocampal formation, in the granular cells of the dentate gyrus, in the parvocellular nerve cells of the paraventricular hypothalamic nucleus, and in the cells of the arcuate nucleus, especially the parvocellular part. Moderate labeling of a large number of nerve cells was observed within layers II, III, and VI of the neocortex and in many thalamic nuclei, especially the anterior and ventral nuclear groups as well as several midline nuclei. Within the cerebellar cortex, strong labeling was observed all over the granular layer. In the lower brainstem, strong labeling was found within the entire locus coeruleus and within the mesencephalic raphe nuclei rich in noradrenaline and 5-hydroxytryptamine cell bodies, respectively. A close correlation was found between the distribution of GR mRNA and the distribution of previously described GR immunoreactivity. These studies open the possibility of obtaining additional information on in vivo regulation of GR synthesis and how the brain may alter its sensitivity to circulating glucocorticoids.

Regulation of glucocorticoid receptor expression: evidence for transcriptional and posttranslational mechanisms

The mechanism of ligand-induced (homologous) down-regulation of the glucocorticoid receptor (GR) has been studied. Dexamethasone caused a down-regulation of the levels of GR mRNA and protein both in hepatoma tissue culture cells and rat liver in vivo. The decrease in the level of rat liver GR mRNA was due to a reduced transcription rate of the GR gene, as assessed by nuclear run-on transcription experiments. The half-life of GR mRNA in hepatoma tissue culture cells was determined to be approximately 4.5 h and was unaffected by dexamethasone. In addition to the transcriptional regulation of GR gene expression, a dexamethasone-dependent posttranslational modification in the rate of GR protein turnover was observed. In the absence of dexamethasone, GR protein half life was approximately 25 h whereas it decreased to approximately 11 h in the presence of hormone. Down-regulation of GR protein occurred with a 6- to 24-h delay as compared to the decline in GR mRNA. This is most likely due to the differences in half-lives of GR mRNA and protein, respectively. Our results suggest that auto-regulation of GR by its cognate ligand is complex and occurs at both transcriptional and posttranslational levels.

Regulation of gene expression of class I alcohol dehydrogenase by glucocorticoids

The effect of glucocorticoids on gene expression of rat class I alcohol dehydrogenase (ADH; alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was investigated. A cDNA clone for the beta-subunit of human ADH (ADH2) was used to analyze class I ADH mRNA levels in rat hepatoma cells, which are known to contain a functional glucocorticoid receptor. RNA gel blot analysis of total cellular RNA isolated from these cells showed hybridization of the human ADH2 cDNA probe to a single approximately equal to 1500-base RNA species. Treatment of the cells with dexamethasone (0.1 nM to 1 microM) caused a dose-dependent increase in total cellular class I ADH mRNA levels by a factor of 2-4. Maximal levels were reached within 18-24 hr of treatment. This effect was reversible following withdrawal of dexamethasone. The glucocorticoid induction of class I ADH mRNA does not seem to require ongoing protein synthesis since treatment of the cells with cycloheximide did not affect the increase in class I ADH mRNA levels by dexamethasone. The human ADH2 gene contains both upstream and within the coding region sequence motifs that display homology with response elements of genes positively regulated by glucocorticoids. These data suggest a receptor-mediated transcriptional enhancement of the ADH2 gene as the mechanism of regulation. However, analysis of RNA decay in cells treated with actinomycin D indicates that the dexamethasone-induced increase in class I ADH mRNA might, at least in part, be due to enhanced ADH mRNA stability.

45Ca uptake and the actions of Bay K 8644 on aortic strips from rabbits with perinephritis hypertension

Uptake of 45Ca was measured in rings of thoracic aorta from rabbits with hypertension, induced by cellophane perinephritis (Page hypertension: one-kidney, one wrap). Basal 45Ca uptake was increased significantly in the hypertensive group (sham: 100 +/- 3, hypertensive: 133 +/- 11 nmol/g wet weight, n = 6). 45Ca uptake was increased by KCl (30 mmol/l), norepinephrine (50 nmol/l) and Bay K 8644 (14 or 56 nmol/l) by the following amounts: 152, 15, 28 and 36%, respectively. Stimulated 45Ca uptake was less in hypertensive animals for all agonists. The augmenting effect of Bay K 8644 on 45Ca uptake, stimulated by norepinephrine or by KCl, was also reduced in hypertension. It is concluded that in hypertension there are alterations in the Ca regulatory process and in the properties of the Ca channel in arterial muscle.

A microbiologic and clinical study of placental inflammation at term

This study describes the relationships between histologically evident inflammation of the placenta, membranes, and umbilical cords, and correlates these lesions with clinical outcome and with amniotic fluid and amniotic membrane cultures in pregnancies at risk for clinical infection. The overall frequency of inflammation in 123 placentas was 85.45%. There were good interrelationships between inflammatory lesions at various sites. Membrane infiltrates of 3+ were seen in 90.9% of intra-amniotic infection cases, but in only 18.4% of asymptomatic patients (P less than .001). Conversely, 76.9% of patients with 3+ inflammation had intra-amniotic infection, whereas only 7% with lesser degrees of inflammation had intra-amniotic infection. Inflammation of any degree (1-3+) had a low specificity (28%) for febrile maternal outcome. Bacteria were recovered in 117 (95.1%) of the amniotic fluids. The grade of histologic lesions was associated with total colony count of bacteria in amniotic fluid (P less than .05) and with high-virulence bacteria in amniotic fluid (P less than .05), and Mycoplasma hominis in amniotic fluid (P less than .05). Bacteria were found in 67.6% and mycoplasmas in 18.6% of amniotic membrane cultures. Chlamydia trachomatis was not recovered in any of 35 amniotic membrane cultures. No significant correlation was seen between organisms in the amniotic membrane and histologic inflammation. Thus, positive amniotic fluid culture results are associated with histologic inflammation, and may cause the inflammatory response. A logistic regression model revealed that predictors of histologic inflammation include maternal diagnosis, amniotic fluid colony count, and M hominis in amniotic fluid.

Mechanisms of regulation of rat ovarian 7,12-dimethylbenz[a]anthracene hydroxylase

The mechanisms of regulation of ovarian 7,12-dimethylbenz[a]anthracene (DMBA) hydroxylase were investigated with respect to hormonal requirements and effects of the antiestrogen tamoxifen and known inducers of cytochrome P-450. The DMBA hydroxylase is increased endogenously about 3-fold in the proestrus phase as compared to the metestrus/diestrus phases (M. Bengtsson and J. Rydstrom, Science, 219 (1983) 1437-1438). A similar effect was caused by the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) whereas pregnant mare's serum gonadotropin (PMSG) brought about a 3-7-fold increase, suggesting that the estrus cycle-dependence of the DMBA hydroxylase was due directly or indirectly to gonadotropins. In contrast, differentiation of granulosa/theca cells to corpus luteum cells after ovulation, caused by administration of human chorionic gonadotropin (hCG), led to a marked decrease in activity. The activity was not specific for DMBA since substitution of this hydrocarbon for benzo[a]pyrene (BP) as substrate gave similar results. A possible role of estrogens in this context was investigated by the administration of tamoxifen simultaneous with gonadotropin treatment, which caused a partial inhibition of the hydroxylase activity. Both estradiol and 3-methyl-cholanthrene (MC) increased DMBA hydroxylase but the effects of these agents were not additive. In contrast, the effects of estradiol and MC were partially additive to that of gonadotropin. On the basis of these results, it is proposed that the rat ovary contains one or several aryl hydrocarbon hydroxylases located in the granulosa/theca cells which are regulated by estrogens, MC and beta-naphthoflavone (BNF) and that the role of gonadotropins is to proliferate granulosa/theca cells.