Cellular proliferative effect of dexamethasone in immortalized trabecular meshwork cell (TM5) line

Dexamethasone (DEX), one of the corticosteroid hormones, is one of the most common therapeutic strategies in ophthalmological treatment. Despite its widespread use and clinical efficiency, little is known regarding the specific effects of DEX on cell growth, differentiation and cell death in human trabecular meshwork cells. The presence of the glucocorticoid receptor (GR, dexamethasone receptor) in TM-5 cell line, which was derived from the primary human trabecular meshwork cells, was verified by RT-PCR and western blot analysis. The effects of DEX on the cellular proliferation of TM5 cells were measured by a BrdU incorporation assay. Western blot analysis were used to examine the effects of DEX on the Ras/MEK/ERK signaling pathway. The total Ras, MEK1/2 and ERK1/2 protein levels as well as the levels of activated (phosphorylated) form were both significantly increased by the DEX treatment for 5 days. Both MEK1/2 and ERK1/2 were significantly activated by phosphorylation after 10 minutes. The dependence of this increased cell proliferation on GR activation by DEX and the sustained activation of ERK was examined using RU486 (a GR inhibitor) and U0126 (a MEK inhibitor). Both RU486 and U0126 prevented the induction of cell proliferation by the DEX treatment in the TM5 cells. In conclusion this study demonstrated that GR is expressed in TM5 cells. Secondly, DEX treatment for 5 days stimulates cell proliferation in TM5 cells, and that this increased proliferation effect is mediated by the Ras/MEK/ERK pathway.     

糖皮质激素通过抑制p38MAPK信号通路缓解大鼠内毒素性急性肺损伤

目的： 研究糖皮质激素对内毒素导致的急性肺损伤的影响及作用机制。方法: 成年雄性SD大鼠被随机分为6组：对照组（control 组,n=6）;LPS组（n=24）;地塞米松＋LPS组（Dex＋LPS组,n=24）;糖皮质激素受体拮抗剂RU486组（RU486组,n=6）;RU486+LPS组（n=24）以及RU486＋Dex＋LPS组（n=24）。除对照组和RU486组外,其余4组在注射LPS后1、3、6、12 h又被分为4个亚组。分别检测各组大鼠支气管肺泡灌洗液（BALF）中TNF-α和IL-6的浓度,肺组织的病理变化,以及肺组织中p38MAPK的活化状态和MKP-1的表达情况。另外又分别比较了LPS组与RU486＋LPS组、Dex＋LPS组与RU486＋Dex＋LPS组大鼠48 h的死亡率。结果: 注射LPS后,BALF中TNF-α 和IL-6的浓度明显升高（P<0.05）,HE染色显示肺组织内广泛炎症反应。而这些现象在应用RU486后变得更加严重,并且RU486＋LPS组的死亡率也明显高于LPS组(P<0.05)。地塞米松能明显缓解LPS导致的肺损伤,糖皮质激素受体(GR)参与此作用。另外,在注射LPS后,肺组织中磷酸化的p38MAPK的表达明显升高,而MKP-1的表达则明显受到抑制。地塞米松能显著降低p38MAPK的磷酸化,这一作用也是GR依赖的。结论: 糖皮质激素活化GR诱导肺组织中MKP-1的表达,进而抑制p38MAPK的活化,从而发挥其抗炎作用,缓解LPS诱导的肺损伤。     

糖皮质激素受体功能对大鼠前额叶单胺氧化酶A的影响及其交互作用

目的：通过原代培养神经元细胞,探究糖皮质激素受体（GR）功能对单胺氧化酶A （MAO A）的影响及 其可能通路。方法： 取生后48 h 内的SD大鼠前额叶,经反复消化沉淀后,对神经元进行纯化并培养,48 h 后, 分为地塞米松（DEX）组、米非司酮（mifepristone,RU486）组和对照组,分别予以GR激动剂DEX、GR抑制 剂RU486 和等体积相同溶剂干预,继续培养48 h。采用免疫细胞化学染色法检测大鼠神经细胞Sp1、Krüppel 样 转录因子-11（KLF11）和MAO A表达情况。结果： DEX 干预后,前额叶神经细胞中KLF11、Sp1 及MAO A的 表达均较对照组升高,而RU486 干预后,Sp1 和MAO A的表达较对照组降低,但KLF11 的表达无明显变化。结论： 糖皮质激素（GC）可提高前额叶区GR的表达;GC可通过激活GR,提高脑内神经细胞KLF11、Sp1 和MAO A 表达水平,Sp1 的表达和MAO A存在正相关,提示GR功能与MAO A之间可能通过KLF11、Sp1 起交互作用。     

Simple-sugar meals target GLUT2 at enterocyte apical membranes to improve sugar absorption: a study in GLUT2-null mice

The physiological significance of the presence of GLUT2 at the food-facing pole of intestinal cells is addressed by a study of fructose absorption in GLUT2-null and control mice submitted to different sugar diets. Confocal microscopy localization, protein and mRNA abundance, as well as tissue and membrane vesicle uptakes of fructose were assayed. GLUT2 was located in the basolateral membrane of mice fed a meal devoid of sugar or containing complex carbohydrates. In addition, the ingestion of a simple sugar meal promoted the massive recruitment of GLUT2 to the food-facing membrane. Fructose uptake in brush-border membrane vesicles from GLUT2-null mice was half that of wild-type mice and was similar to the cytochalasin B-insensitive component, i.e. GLUT5-mediated uptake. A 5 day consumption of sugar-rich diets increased fructose uptake fivefold in wild-type tissue rings when it only doubled in GLUT2-null tissue. GLUT5 was estimated to contribute to 100 % of total uptake in wild-type mice fed low-sugar diets, falling to 60 and 40 % with glucose and fructose diets respectively; the complement was ensured by GLUT2 activity. The results indicate that basal sugar uptake is mediated by the resident food-facing SGLT1 and GLUT5 transporters, whose mRNA abundances double in long-term dietary adaptation. We also observe that a large improvement of intestinal absorption is promoted by the transient recruitment of food-facing GLUT2, induced by the ingestion of a simple-sugar meal. Thus, GLUT2 and GLUT5 could exert complementary roles in adapting the absorption capacity of the intestine to occasional or repeated loads of dietary sugars.     

Glucocorticoids modulate human gonadotrophin releasing hormone upstream promoter activity in transfected human placental cells (JEG-3)

A human gonadotrophin releasing hormone (GnRH) upstream promoter/luciferase reporter gene construct (H2 construct) was generated by inserting a 1.7 kb XbaI/AflII fragment containing the human GnRH upstream promoter region only into a promoter-less luciferase reporter vector. When JEG-3 cells were transiently transfected with this construct and treated with cortisol or its synthetic analogue dexamethasone, a stimulatory effect on the upstream promoter activity was observed. This stimulation was dependent on the cotransfection of a glucocorticoid receptor (GR) cDNA expression vector due to the low level of GR in JEG-3 cells and could be completely abolished by RU486, a glucocorticoid antagonist. Moreover, the cortisol actions could be modulated to a different extent by oestradiol. Thus, since the human placenta contains GRs and the increase in cortisol metabolism near term is regulated by oestrogen, the current findings suggest that cortisol may be physiologically involved in the regulation of GnRH gene expression in the human placenta.      

Low glucocorticoid receptor (GR), high Dig2 and low Bcl-2 expression in double positive thymocytes of BALB/c mice indicates their endogenous glucocorticoid hormone exposure

Several studies have shown that of the four major thymocyte subsets, the CD4/CD8 double positive (DP) thymocytes are the most sensitive to in vivo glucocorticoid hormone (GC)-induced apoptosis. Our aim was to analyse fine molecular differences among thymocyte subgroups that could underlie this phenomenon. Therefore, we characterised the glucocorticoid hormone receptor (GR) expression of thymocyte subgroups both at the mRNA and protein levels by real-time PCR and flow cytometry, and correlated these features to their apoptotic sensitivity. We also investigated the time-dependent effects of the GC agonist dexamethasone (DX) with or without GC antagonist (RU486) treatments on GR mRNA/protein expression. We also analysed the expression of two apoptosis-related gene products: dexamethasone-induced gene 2 (Dig2) mRNA and Bcl-2 protein. We found that DN thymocytes had the highest GR expression, followed by CD8 single positive (SP), CD4 SP and DP thymocytes in 4-week-old BALB/c mice, both at the mRNA and protein levels, respectively. In DP cells, the Dig2 expression was significanty higher, while the Bcl-2 expression was significantly lower than in DN, CD4 SP and CD8 SP thymocytes. Single high dose DX treatment caused time-dependent depletion of DP thymocytes due to their higher apoptosis rate, which could not be abolished with RU486 pretreatment. After a single high dose DX treatment, there was a transient, significant increase of the GR mRNA and protein level of unsorted thymocytes after 8 and 16 h, followed by a significant decrease at 24 h, respectively. The time-dependent GR expression changes after DX administration could not be inhibited by the GC antagonist RU486. Twenty-four hours after exposure to high dose DX the DN, CD4 SP and CD8 SP cells showed a significant decrease of GR mRNA and protein expression, whereas the DP thymocytes, showed no significant alteration of GR mRNA or protein expression. The kinetical analysis of GR expression and apoptotic marker changes upon single high dose GC analogue administration revealed a two-phase process in thymocytes: early events, within 4–8 h, include GR upregulation and early apoptosis induction, while the late events appear most prominently at 16–20 h, when the GR is already downregulated and apoptotic cell ratio reaches its peak, with marked DP cell depletion. The low GR, high Dig2 and low Bcl-2 expression, coupled with the absence of homologous downregulation of GR after exogenous GC analogue treatment, could contribute to the high GC sensitivity of DP thymocytes. The downregulated GR and Bcl-2 together with the upregulated Dig2 level in DP cells indicates the significance of intrathymic GC effects at this differentiation stage. Since GR expression changes and apoptotic events could not be completely inhibited by GC antagonist, we propose the involvement of non-genomic GR mechanisms in these processes.     

Corticosterone and dexamethasone potentiate cytotoxicity associated with oxygen-glucose deprivation in organotypic cerebellar slice cultures

Many patients display elevated levels of serum cortisol following acute ischemic stroke. Given that glucocorticoids may potentiate some forms of insult, these studies examined the effects of corticosterone or dexamethasone exposure on cytotoxicity following oxygen-glucose deprivation in the cerebellum, a brain region susceptible to stroke. In organotypic cerebellar slice cultures prepared from neonatal rat pups, 90-min of oxygen-glucose deprivation at 15 days in vitro resulted in significant cytotoxicity at 24-, 48-, and 72-h post-oxygen-glucose deprivation, as measured by uptake of propidium iodide. Exposure of cultures following oxygen-glucose deprivation to the antioxidant trolox (500 microM), but not to the glucocorticoid receptor antagonist RU486 (10 microM), completely blocked oxygen-glucose deprivation-induced cytotoxicity. Corticosterone (1 microM) or dexamethasone (10 microM) exposure alone did not significantly increase propidium iodide uptake above levels observed in control cultures. However, corticosterone or dexamethasone exposure after oxygen-glucose deprivation potentiated oxygen-glucose deprivation-mediated propidium iodide uptake at each time point. Trolox, as well as RU486, co-exposure of cultures to corticosterone or dexamethasone after oxygen-glucose deprivation abolished all cytotoxicity. In conclusion, these data demonstrated that glucocorticoid exposure modulated oxygen-glucose deprivation-mediated propidium iodide uptake, which likely involved glucocorticoid receptor activation and pro-oxidant effects.     

The steroid RU486 induces UCP1 expression in brown adipocytes

RU486 (mifepristone), a potent antagonist at progesterone and glucocorticoid receptors (PR and GR), is well known for its use in the termination of unwanted pregnancies, the potential development of oral contraceptives, treatment of certain cancers and other activities. Potentially, it could also play a role in obesity control, although the few studies that have addressed this aspect have focused mainly on its central and anti-glucocorticoid effects. We have shown previously that it could have a direct effect on brown adipocytes in culture when administered together with progesterone. The aim of the present work was to analyse the effects of RU486 on the expression of uncoupling proteins (UCPs) in brown adipocytes. In culture-grown, differentiated brown adipocytes, placed in a serum-free medium to exclude the presence of progesterone or glucocorticoids, RU486 stimulated UCP1 expression at both the mRNA and protein levels. These effects could be mediated by PR, GR or other unknown mechanisms but do not seem to be due to its anti-progestin or anti-glucocorticoid actions. The results suggest that the steroid RU486 has a direct action on adipocytes which could be useful for stimulating non-shivering BAT thermogenesis and therefore is of interest in obesity studies.     

The large clostridial toxins from Clostridium sordellii and C. difficile repress glucocorticoid receptor activity

We have previously shown that Bacillus anthracis lethal toxin represses glucocorticoid receptor (GR) transactivation. We now report that repression of GR activity also occurs with the large clostridial toxins produced by Clostridium sordellii and C. difficile. This was demonstrated using a transient transfection assay system for GR transactivation. We also report that C. sordellii lethal toxin inhibited GR function in an ex vivo assay, where toxin reduced the dexamethasone suppression of the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha). Furthermore, the glucocorticoid antagonist RU-486 in combination with C. sordellii lethal toxin additively prevented glucocorticoid suppression of TNF-alpha. These findings corroborate the fact that GR is a target for the toxin and suggest a physiological role for toxin-associated GR repression in inflammation. Finally, we show that this repression is associated with toxins that inactivate p38 mitogen-activated protein kinase (MAPK).     

Megadose glucocorticoid therapy: Investigations in rat anaphylactic shock and experimental allergic encephalomyelitis

Glucocorticoids are the most potent antiinflammatory drugs. Large doses of dexamethasone and other glucocorticoids are widely used in the clinic but the mechanism of the beneficial effects of megadoses still remains to be explained. We tested the effects of a dexamethasone (DEX) megadose therapy in a rat model of anaphylactic shock. By combining DEX with the potent glucocorticoid receptor antagonist RU 486 we looked for evidence of a non-specific action of the glucocorticoid at high doses. A dose of 10 mg/kg DEX given 2h before challenge protected the heart against the symptoms of cardiac anaphylaxis: heart rate was improved by 22%, ventricular contractility by 13% and coronary flow by 5%. Administration of 20 mg/kg RU 486, 30 min before dexamethasone, reduced the beneficial effect of DEX by about 30%, although this failed to reach statistical significance. We found no dose-response relationship for the high dexamethasone doses of 0.5–10 mg/kg. In experimental allergic encephalomyelitis (EAE) there was a surprising toxic action of DEX after daily doses of 0.25 mg/kg for 5 days, and also following single administration of 2.5 or 10 mg/kg. A single dose of 1.25 mg/kg, given on the day of immunization alone or with additional doses at weekly intervals for 3 weeks, caused a strong inhibition of the EAE. In summary we conclude that the present data of cardiac anaphylaxis hardly point to extra glucocorticoid megadose effects. The present dexamethasone effects in cardiac anaphylaxis and in EAE have to be cleared up by further experiments.

     

The progesterone antagonist RU 486. A potential new contraceptive agent

Since progesterone supports endometrial nidation of the fertilized ovum, a progesterone antagonist would theoretically block this process and thus have contraceptive potential. We have explored the ability of RU 486, a newly developed competitive progesterone antagonist, to function as a contraceptive agent. A single oral dose of 10 mg per kilogram of body weight given in the midluteal phase consistently induced menses within 72 hours in women with normal cycles and no risk of pregnancy. Bleeding was not prevented by administration of human chorionic gonadotropin in the midluteal phase. This suggested that giving a single dose of RU 486 late in the menstrual cycle might be an effective contraceptive strategy. This concept was tested in monkeys. When given to rhesus females on day 25 of the cycle, a single intramuscular dose of RU 486 (5 mg per kilogram) prevented pregnancy. The vehicle-treated control animals had a 28 percent pregnancy rate (P less than 0.05 by chi-square analysis). No side effects were noted in women or monkeys. These data suggest that a progesterone antagonist such as RU 486 has the potential to be an effective, safe, and convenient contraceptive agent. Further work will be necessary to assess the safety of long-term monthly administration and to define the optimal dose and time of administration in women.     

Relationship between glucose transporter and changes in the absorptive system in small intestinal absorptive cells during the weaning process

In the present study, we investigated the changes in the localization of the glucose transporter GLUT2 and the fructose transporter GLUT5 in small intestinal absorptive cells during postnatal development, especially during the weaning period, using immunohistochemistry and confocal laser scanning microscopy. In the jejunum, GLUT2 was observed within the apical and basolateral membrane domain of absorptive cells, especially in the middle part of the villi. In the suckling rat ileum, GLUT2 was found within the apical and basolateral membrane domain of absorptive cells, but after 18 or 19 days after birth, GLUT2 was found mainly within the apical membrane domain. GLUT5 was observed within the apical membrane domain of absorptive cells in the suckling rat jejunum. In the 18- or 19-day-old rat jejunum, GLUT5 was localized within the apical and basolateral membrane domain of absorptive cells in the lower part of the villi, but after weaning, GLUT5 was found within the apical and basolateral membrane domain of absorptive cells throughout the entire villi. In the suckling rat ileum, there was little GLUT5 in the absorptive cells. In the 18- or 19-day-old rat ileum, GLUT5 was localized within the apical membrane domain of absorptive cells in the lower part of the villi, but after weaning, GLUT5 was observed mainly within the apical membrane domain of absorptive cells throughout the entire villi. These results suggest that the localization of glucose transporters corresponds with a shift from neonatal-suckling to weaned absorptive cells during postnatal development.     

Dexamethasone enhances macrophage colony stimulating factor- and granulocyte macrophage colony stimulating factor-stimulated proliferation of bone marrow-derived macrophages

Glucocorticoids are effective repressors of the immune system. We have examined the effect of glucocorticoids on the proliferation of murine macrophages. Dexamethasone by itself did not affect proliferation of differentiated or undifferentiated bone marrow-derived macrophages (BMM) and elicited peritoneal macrophages. However, dexamethasone enhanced the proliferation induced by macrophage colony stimulating factor (M-CSF) of these cells. The effect of dexamethasone was not restricted to M-CSF-dependent proliferation. Similarly, dexamethasone enhanced granulocyte macrophage colony stimulating factor (GM-CSF)- dependent proliferation of BMM. In agreement, macrophages transfected with the glucocorticoid receptor showed an enhancement of M-CSF- dependent proliferation. The enhancement of proliferation by dexamethasone or the glucocorticoid receptor was abolished by RU 486, an antagonist of the glucocorticoid receptor. Moreover, the addition of antibodies against M-CSF inhibits the effect of dexamethasone, suggesting that dexamethasone increases the autocrine production of M- CSF. This only occurs when M-CSF or GM-CSF, which induce M-CSF, are present in the media. In tissues, dexamethasone may enhance macrophage proliferation and contribute to the resolution of the inflammatory states.      

Glucocorticoid receptor activation reduces CD11b and CD49d levels on murine eosinophils: characterization and functional relevance

In vitro incubation of mouse blood eosinophils with dexamethasone (DEX) resulted in concentration- and time-dependent reduction in CD11b and CD49d cell-surface expression as detected by flow cytometry. This inhibitory effect ranged between 20 and 40% for both integrins, and it was not related to alteration of cell survival. DEX was maximally effective at 1 microM, and it was prevented by coaddition of the glucocorticoid receptor antagonist RU486 (mifepristone; 10 microM). Budesonide, hydrocortisone, and prednisolone, but not the sex steroids testosterone and progesterone, reduced CD11b and CD49d cell-surface expression to a similar extent. Subchronic treatment of mice with 1 mg/kg DEX again reduced both CD11b and CD49d expression on circulating eosinophils, without alterations in CD11b messenger RNA expression as assessed by polymerase chain reaction analysis. In contrast, membrane but not intracellular protein expression of either CD11b or CD49d was inhibited by eosinophil incubation with DEX in vitro; thus, an interference with exportation of these adhesion molecules to the cell surface is proposed as the mechanism of action of the glucocorticoid. Finally, steroid effects on integrin expression were linked to a reduced eosinophil function as indicated by a lower degree of cell chemotaxis after incubation with DEX, an effect which was again prevented by 10 microM RU486. These observations may explain part of the therapeutic efficacy displayed by glucocorticoid hormones in the clinical control of tissue eosinophilia in allergic disease conditions.     

Inhibition of I-Ad-, but not Db-restricted peptide-induced thymic apoptosis by glucocorticoid receptor antagonist RU486 in T cell receptor transgenic mice

Thymocytes differentiate by positive and negative selection of immature CD4⁺ CD8⁺ T cells. Negative selection occurs by default or by high-affinity recognition of peptides bound to proteins encoded by the major histocompatibility complex (MHC). MHC class I molecules are expressed on many different cell types, although at different levels, whereas MHC class II molecules are selectively expressed on thymic epithelial cells (TEC) and dendritic cells (DC). We investigated the role of the glucocorticoid receptor (GR) in thymic negative selection using the receptor antagonist RU486. Glucocorticoids (GC) are known to be potent inducers of apoptosis in CD4⁺ CD8⁺ thymocytes, and we have earlier shown that anti-CD3-induced thymic apoptosis can be blocked by RU486 in vivo. We now show that anti-CD3 induces thymic apoptosis in mice that have been adrenalectomized (ADX), and that RU486 inhibits anti-CD3 antibody-mediated thymocyte killing in newborn thymic organ cultures. Thymocyte apoptosis induced by ovalbumin peptide OVA323–339 treatment of mice transgenic for the DO11.10T cell receptor (TCR), which recognizes this peptide in the context of I-A^d, was found to be inhibited by RU486. These mice responded to peptide treatment by an extensive activation of the peripheral immune system, which became lethal in 60% of the mice when accompanied by simultaneous RU486 treatment. In contrast, RU486 had no effect on thymic apoptosis induced by the influenza A nucleoprotein NP366–374 peptide, recognized in context of D^b, in F5 TCR transgenic mice. We interpret the results to demonstrate that different deletion systems operate in the thymus. We propose that endogenous GC may be important for negative selection by default and by high-affinity recognition of endogenous MHC-presented peptides on TEC.     

Progesterone Suppression of Pregnancy Lymphocytes Is not Mediated by Glucocorticoid Effect

ABSTRACT: This study investigated whether the suppressive effect of progesterone on pregnancy lymphocytes is mediated by specific progesterone receptors. The effects of a competitive progesterone antagonist (RU486) and a specific glucocorticoid receptor blocker (RU43044) were tested on the release of a blocking factor by progesterone-treated pregnancy lymphocytes. RU 486 tested at an equal concentration as progesterone significantly inhibited the production of the blocking factor, while RU 43044 was without effect. These data suggest that in pregnancy, lymphocyte progesterone acts on specific progesterone receptors and glucocorticoid binding sites are not involved.     

Characterization of human trophoblast as a mineralocorticoid target tissue

In mineralocorticoid target tissues, 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) confers mineralocorticoid receptor selectivity by metabolizing hormonally active cortisol to inactive cortisone, allowing aldosterone access to the receptor. This enzyme is also expressed in high abundance in fetal tissues, particularly in placental trophoblast, where a role has been proposed in regulating fetal growth and development by protecting the fetus from maternal hypercortisolaemia and modulating local glucocorticoid receptor (GR), rather than mineralocorticoid receptor-mediated responses. As such the placenta has not been considered a mineralocorticoid target tissue. We have used conventional RT-PCR and real-time quantitative RT-PCR to demonstrate that primary cultures of term human cytotrophoblast express the mineralocorticoid-responsive genes Na/K-ATPase (alpha1 and beta1 subunits), epithelial sodium channel (ENaC, alpha and gamma subunits) and the serum and glucocorticoid-inducible kinase (SGK). SGK expression was found to be rapidly and strongly induced by corticosteroids (24- and 38-fold by 10(-7) mol/l aldosterone and 10(-7) mol/l dexamethasone respectively after 1 h). Dexamethasone-, but not aldosterone-stimulated SGK induction was inhibited by GR antagonist (RU38486), confirming the presence of a functional mineralocorticoid receptor and suggesting that placental trophoblast expresses a functional mineralocorticoid receptor, which is in part responsible for the corticosteroid regulation of SGK expression. Placental 11beta-HSD2 may protect the MR in a fashion analogous to classical mineralocorticoid tissues to modulate trophoblast sodium transport.     

地塞米松对人卵巢癌HO-8910细胞ERK和p38活性的快速作用

目的:观察人工合成糖皮质激素地塞米松 (Dex)对人卵巢癌细胞系HO-8910中丝裂原激活的蛋白激酶 (MAPK)家族成员ERK1/2和p38活性的影响。方法:Westernblot测定ERK和p38活性。结果:10^-7mol/LDex在 5min内即可引起ERK1和ERK2活性下降,30min作用最明显,分别比对照降低 41%和 54 % (均P <0.01);之后回升,4h后活性达对照水平;该作用具有激素浓度 (10^-10-10^-6 mol/L)依赖性。Dex还可在 5min内增加p38活性,15min作用最显著,比对照增加 84% (P <0.01),1h后达对照水平。这些作用不能被糖皮质激素受体 (GR)拮抗剂RU486所阻断。结论:Dex能够以GR非依赖性方式,快速抑制HO-8910细胞ERK1/2活性和促进p38活性,可能参与其抑制细胞增殖作用.