Baicalin Ameliorates Dexamethasone-Induced Osteoporosis by Regulation of the RANK/RANKL/OPG Signaling Pathway.

BACKGROUND: Osteoporosis is a chronic bone metabolism disorder affecting millions of the world population. The RANKL/RANK/OPG signaling pathway has been confirmed to be the main regulator of osteoporosis. It is of great interest to identify appropriate therapeutic agents that can regulate the RANKL/RANK/OPG pathway. Baicalin (BA) is a well-known traditional Chinese medicine formula against various inflammatory diseases with a proven role of the RANKL/RANK/OPG pathway regulation. However, the potential effect of BA on osteoporosis and the mechanisms underlying this remain unclear. In the present study, we aimed to evaluate the efficacy of BA in the prevention of dexamethasone (DEX)-induced osteoporosis in zebrafish. METHODS: In this study, growth and development changes of zebrafish and calcein staining were assessed with a micrograph. The expression levels of RANKL and OPG and transcription factors in response to DEX induction and BA administration were evaluated by Western blotting and qRT-PCR. In addition, the intermolecular interactions of BA and RANKL were investigated by molecular docking. RESULTS: Results show that BA enhances the growth and development of dexamethasone (DEX)-induced osteoporosis in zebrafish larvae. Calcein staining and calcium and phosphorus determination revealed that BA ameliorates mineralization of DEX-induced osteoporosis zebrafish larvae. BA also regulates the expression of RANKL and OPG and hampers the changes in gene expression related to bone formation and resorption under the induction of DEX in zebrafish. It can be inferred by molecular docking that BA may interact directly with the extracellular domain of RANKL. CONCLUSION: The findings, herein, reveal that BA ameliorates DEX-induced osteoporosis by regulation of the RANK/RANKL/OPG signaling pathway.

Short-Term Curcumin Gavage Sensitizes Insulin Signaling in Dexamethasone-Treated C57BL/6 Mice.

BACKGROUND: Long-term dietary curcumin (>12 wk) improves metabolic homeostasis in obese mice by sensitizing insulin signaling and reducing hepatic gluconeogenesis. Whether these occur only secondary to its chronic anti-inflammatory and antioxidative functions is unknown. OBJECTIVE: In this study, we assessed the insulin sensitization effect of short-term curcumin gavage in a rapid dexamethasone-induced insulin resistance mouse model, in which the chronic anti-inflammatory function is eliminated. METHODS: Six-week-old male C57BL/6 mice received an intraperitoneal injection of dexamethasone (100 mg/kg body weight) or phosphate-buffered saline every day for 5 d, with or without simultaneous curcumin gavage (500 mg/kg body weight). On day 7, insulin tolerance tests were performed. After a booster dexamethasone injection and curcumin gavage on day 8, blood glucose and insulin concentrations were measured. Liver tissues were collected on day 10 for quantitative polymerase chain reaction and Western blotting to assess gluconeogenic gene expression, insulin signaling, and the expression of fibroblast growth factor 21 (FGF21). Primary hepatocytes from separate, untreated C57BL/6 mice were used for testing the in vitro effect of curcumin treatment. RESULTS: Dexamethasone injection impaired insulin tolerance (P < 0.05) and elevated ambient plasma insulin concentrations by ~2.7-fold (P < 0.01). Concomitant curcumin administration improved insulin sensitivity and reduced hepatic gluconeogenic gene expression. The insulin sensitization effect of curcumin was demonstrated by increased stimulation of S473 phosphorylation of protein kinase B (P < 0.01) in the dexamethasone-treated mouse liver, as well as the repression of glucose production in primary hepatocytes (P < 0.001). Finally, curcumin gavage increased FGF21 expression by 2.1-fold in the mouse liver (P < 0.05) and curcumin treatment increased FGF21 expression in primary hepatocytes. CONCLUSION: These observations suggest that the early beneficial effect of curcumin intervention in dexamethasone-treated mice is the sensitization of insulin signaling, involving the stimulation of FGF21 production, a known insulin sensitizer.

Folic acid attenuates dexamethasone-induced placental growth restriction.

OBJECTIVE: Intrauterine glucocorticoid (GC) exposure is associated with disturbances in feto-placental growth. This study aimed to investigate whether folic acid supplementation can prevent dexamethasone (Dex)-induced feto-placental growth restriction. MATERIALS AND METHODS: Female C57BL/6J mice were subject to four different treatments, respectively: normal drinking water plus saline injection (NN), normal drinking water plus Dex injection (ND), drinking water supplemented with folic acid plus saline injection (FN), and drinking water supplemented with folic acid plus Dex injection (FD). Folic acid (100 µg/L) was administrated since 2 weeks before the mating and throughout pregnancy. Dex injection (100 µg/kg•d) was performed from E12.5 to E16.5. The placentas were collected at E17.5. RESULTS: The parameters including placental and fetal weight, the maximum placental diameter, volume of junctional and labyrinthine zones, and vascular density in the ND group were significantly smaller compared to the NN group. Except the maximum placental diameter, each of the above parameters in the FD group was significantly larger compared to the ND group. The levels of glucocorticoid receptor (GR) protein, and endothelial growth factor A, C (VEGFA, VEGFC) and placental growth factor (PIGF) mRNAs were significantly lower in the ND group compared to NN group. The VEGFA and PIGF mRNA level in the FD group was significantly higher than that in the ND group, as well as VEGFA and VEGFC protein level. CONCLUSIONS: Folic acid may attenuate Dex-induced restriction on placental growth by elevating the expression of VEGFA and PIGF, and further raising vascular density.

[Effects of astragalosides on PC12 cells injury and APP expression induced by dexamethasone and Abeta(25-35)].

OBJECTIVE: To study the effects of Astragaloside (AST) on PC12 cells injury and APP expression induced by dexamethasone (DEX) and beta-amyloid protein 25-35 (Abeta(25-35). METHODS: Logarithmic growth phase of the PC12 cells were seeded in culture plates. DEX 5 micromol/L and Abeta(25-35) 1 micromol/L were used to induce PC12 cells injury. MTT assay was used to detect the PC12 cells activity. RT-PCR was used to detect the APP, alpha-secretase and beta-secretase mRNA level of PC12 cells. Western bloting was used to detect APP protein expression of PC12 cells. RESULTS: MTT results showed that, DEX and Abeta(35-35) co-application could significantly decrease PC12 cells activity (P5 < 0.01). AST (10.20 mg/L) and Ginsenoside Rg1 (16 micromol/L) could increase PC12 cells activity. RT-PCR analysis showed that DEX and Abeta(25-35) co-application could significantly increase the beta-secretase mRNA levels and APP770, lower alpha-secretase mRNA levels. AST (10.20 mg/L) and Rg1 could decrease the elevated APP770, beta-secretase mRNA levels and increase the alpha-secretase mRNA level of PCl2 cells. Western bloting analysis result showed that AST (10.20 mg/L) and Rg1 could decrease the APP expression of PC12 cells induced by DEX and Abeta(25-35). CONCLUSION: AST has protective effects on PC12 cell injury induced by DEX and Abeta(25-35). The mechanism may be associated with decreasing the beta-secretase mRNA levels and APP expression, increasing the alpha-secretase mRNA levels.

Neuroprotective effects of quercetin, rutin and okra (Abelmoschus esculentus Linn.) in dexamethasone-treated mice.

The administration of dexamethasone, a synthetic glucocorticoid receptor agonist, causes neuronal death in the CA3 layer of the hippocampus, which has been associated with learning and memory impairments. This study aimed to examine the ability of okra (Abelmoschus esculentus Linn.) extract and its derivatives (quercetin and rutin) to protect neuronal function and improve learning and memory deficits in mice subjected to dexamethasone treatment. Learning and memory functions in mice were examined using the Morris water maze test. The results showed that the mice treated with dexamethasone had prolonged water maze performance latencies and shorter time spent in the target quadrant while mice pretreated with quercetin, rutin or okra extract prior to dexamethasone treatment showed shorter latencies and longer time spent in target quadrant. Morphological changes in pyramidal neurons were observed in the dexamethasone treated group. The number of CA3 hippocampal neurons was significantly lower while pretreated with quercetin, rutin or okra attenuated this change. Prolonged treatment with dexamethasone altered NMDA receptor expression in the hippocampus. Pretreatment with quercetin, rutin or okra extract prevented the reduction in NMDA receptor expression. Dentate gyrus (DG) cell proliferation was examined using the 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry technique. The number of BrdU-immunopositive cells was significantly reduced in dexamethasone-treated mice compared to control mice. Pretreatment with okra extract, either quercetin or rutin was found to restore BrdU-immunoreactivity in the dentate gyrus. These findings suggest that quercetin, rutin and okra extract treatments reversed cognitive deficits, including impaired dentate gyrus (DG) cell proliferation, and protected against morphological changes in the CA3 region in dexamethasone-treated mice. The precise mechanism of the neuroprotective effect of these plant extracts should be further investigated.

Insulin-like growth factor-1 restores dexamethasone-induced heart growth arrest in rats: the role of the ubiquitin pathway.

OBJECTIVE: In skeletal muscle, glucocorticoids induce catabolism and proteolysis which is accomplished via the ubiquitin (Ub) proteolytic pathway. Cardiac muscle is a striated muscle which, compared to skeletal muscle, more abundantly expresses components of the Ub pathway, thus suggesting an important role for this pathway in heart physiology. The aim of our study was to explore the role of the Ub pathway in heart muscle physiology. DESIGN: We treated rats for three days with a pharmacologic dose of dexamethasone (DEXA) 0.5mg/100g body weight (BW). An attempt was also made to counteract the DEXA effect by co-treatment with insulin-like growth factor-1 (IGF-1; 0.35 mg/100g BW). RESULTS: DEXA treatment caused a 7.8% decrease in heart weight compared to control (p<0.05) and also increased heart tissue levels of the ubiquitin-conjugating enzyme E2 and the 20S proteasome protein. Myofibrillar proteins degraded by the ubiquitin pathway (α-actin, myoglobin, and troponin 1) were all decreased by DEXA, while ubiquitinated forms of α-actin were increased. Co-treatment with IGF-1 completely prevented DEXA-induced decrease in heart weight, an effect which was accompanied by decreased heart tissue levels of several ubiquitinated proteins including α-actin, the 20S proteasome protein, E2-14 kDa mRNA, and C-3 proteasome subunit mRNA, while the levels of non-ubiquinated α-actin, myoglobin, and troponin 1 were all partially restored. CONCLUSION: These results demonstrate that DEXA activates the ubiquitin proteolytic pathway in the heart and that IGF-1 efficiently counteracts this effect. Our findings reveal a possible mechanism for the anti-proteolytic actions of IGF-1 and its cardioprotective role involving the Ub pathway.

Effect of rifampicin on the risk of steroid-induced osteonecrosis of the femoral head.

OBJECTIVE: To investigate the effects and possible mechanism of rifampicin on steroid-induced osteonecrosis of the femoral head (ONFH). METHODS: Bone marrow stromal cells (BMSC) separated from male rats were cultured in vitro without any treatment (Group mA), exposed to dexamethasone (Group mB), treated with rifampicin (Group mC), and exposed to dexamethasone and rifampicin simultaneously (Group mD) respectively (n = 5 in each group). After 7 days, P-glycoprotein (P-gp) activity and adipogenesis of the BMSC were evaluated. In an in vivo experiment, 80 rats were randomly divided into 4 groups (n= 20 in each group). Group A received intragastric saline for 5 weeks. Group B received intragastric saline for one week, followed by subcutaneous methylprednisolone and saline for 4 weeks. Group C received intragastric rifampicin for 5 weeks. Group D received intragastric rifampicin for one week, followed by subcutaneous methylprednisolone and rifampicin for 4 weeks. At the end of the experiment, all rats underwent analysis of P-gp activity of BMSC, P-gp expression in the femoral heads, MRI and histomorphometry of the femoral heads. RESULTS: In vitro, the P-gp activity of BMSC increased and lipid accumulation decreased significantly in Group mD, compared to Group mB. In vivo, P-gp activity and P-gp expression in Group D increased compared to Group B. The mean area of MRI abnormal signal, adipocytic variables and apoptotic cells in Group D decreased, mean percentage of the whole epiphysis made up by the epiphyseal ossification center and trabecular structure variables improved compared to those in Group B. The incidence of ONFH was lower in Group D (50%) than in Group B (80%). CONCLUSION: Rifampicin may decrease the risk of steroid-induced ONFH by enhancing P-gp activity, thus preventing steroid-induced BMSC adipogenesis.

A cell-active inhibitor of mitogen-activated protein kinase phosphatases restores paclitaxel-induced apoptosis in dexamethasone-protected cancer cells.

Mitogen-activated protein kinase phosphatase (MKP)-1 is a dual-specificity phosphatase that negatively regulates the activity of mitogen-activated kinases and that is overexpressed in human tumors. Contemporary studies suggest that induction of MKP-1 during chemotherapy may limit the efficacy of clinically used antineoplastic agents. Thus, MKP-1 is a rational target to enhance anticancer drug activity, but suitable small-molecule inhibitors of MKP-1 are currently unavailable. Here, we have used a high-content, multiparameter fluorescence-based chemical complementation assay for MKP activity in intact mammalian cells to evaluate the cellular MKP-1 and MKP-3 inhibitory activities of four previously described, quinone-based, dual-specificity phosphatase inhibitors, that is, NSC 672121, NSC 95397, DA-3003-1 (NSC 663284), and JUN-1111. All compounds induced formation of reactive oxygen species in mammalian cells, but only one (NSC 95397) inhibited cellular MKP-1 and MKP-3 with an IC(50) of 13 mumol/L. Chemical induction of MKP-1 by dexamethasone protected cells from paclitaxel-induced apoptosis but had no effect on NSC 95397. NSC 95397 phenocopied the effects of MKP-1 small inhibitory RNA by reversing the cytoprotective effects of dexamethasone in paclitaxel-treated cells. Isobologram analysis revealed synergism between paclitaxel and NSC 95397 only in the presence of dexamethasone. The data show the power of a well-defined cellular assay for identifying cell-active inhibitors of MKPs and support the hypothesis that small-molecule inhibitors of MKP-1 may be useful as antineoplastic agents under conditions of high MKP-1 expression.

Wogonin prevents immunosuppressive action but not anti-inflammatory effect induced by glucocorticoid.

Glucocorticoid, such as dexamethasone, has anti-inflammatory and immunosuppressive action as major pharmacological effects. The latter action caused by lymphocyte apoptosis is not only a therapeutic effect but also an adverse reaction. Wogonin, a plant flavone found in Scutellaria baicalensis Georgi, inhibited dexamethasone-induced apoptotic changes, such as DNA fragmentation, nuclear condensation, phosphatidylserine translocation, and caspase activation in rat thymocytes. Since wogonin inhibited dexamethasone-induced DNA fragmentation in a noncompetitive manner, a target of this flavone is unlikely to be an antagonist of glucocorticoid receptor. Wogonin did not only act as an inhibitor of caspases, but also protected apoptosis induced by other glucocorticoids. Since wogonin reduced one of the major pharmacological effects of dexamethasone, we examined whether this flavone diminishes the anti-inflammatory action, another pharmacological effect. The anti-inflammatory action of dexamethasone was evaluated by carrageenan-induced paw edema model. Although dexamethasone significantly suppressed paw edema induced by carrageenan, wogonin had no effect on the anti-inflammatory action of dexamethasone. These results suggest that wogonin may be a useful compound to reduce the immunosuppressive side effect of glucocorticoid.

Investigation of the effect of mistletoe (Viscum album L.) extract Iscador on the proliferation and apoptosis of murine thymocytes.

Mistletoe (Viscum album L.) extracts (ME) have been shown to exhibit a bell-shaped curve of immunological efficacy and mistletoe lectins (MLs) were found to play an important role in this phenomenon. The aim of present in vivo study was to investigate the acute- and long-term effect of a standardized ME (Iscador M special) on thymocyte subpopulations and peripheral T cells using a murine (Balb/c) model. In thymus CD4-CD8- double negative (DN), CD4+CD8+ double positive (DP), CD4+ or CD8+ single positive T cells were determined 24 h after a single injection or following a long-term treatment (twice a week for 4 weeks) with three different dilutions of ME which are corresponding to 4.5 ng/ kg, 22.5 ng/kg and 112.5 ng/kg doses of MLs. The apoptosis of the thymocytes was also tested by flow cytometry using Annexin V and propidium iodide. 24 h after a single injection of ME only the lowest dose caused in the blood samples an elevated CD4+/CD8+ ratio and in thymus an enhanced proliferation of DN thymocytes indicating a similar bell-shaped curve of immunological efficacy. After a treatment for four weeks these responses were less intensive indicating that none of the three doses are immunologically optimal. Surprisingly, both in the acute and in the long-term trial only the lower doses induced significant enhancements in the ratio of apoptotic thymocytes. In addition, ME inhibited the dexamethasone (DX)-induced reduction of DN cell count in thymus, as well as the DX-induced decrease of CD4+/CD8+ ratio and CD4+ cell level in peripheral blood. These in vivo results suggest that investigation of thymocytes in vivo can be helpful in the immunological dose-finding since standardized ME is able to modulate the proliferation and apoptosis of thymocytes with a bell-shaped curve of efficacy. In addition, ME may act lymphoprotectively during DX treatment.

Ginsenosides may reverse the dexamethasone-induced down-regulation of glucocorticoid receptor.

The effects of glucocorticoid (GC) hormones are mediated via an intracellular receptor, the glucocorticoid receptor (GR). It has been established that glucocorticoid down-regulate GR. Ginsenosides (GSS) from extract of Panax ginseng have demonstrated glucocorticoid-like activities in homeostasis and regulation of immunity, etc. We hypothesize that ginsenosides might mediate some of their actions by binding to the GR. The present study is aimed to determine whether GSS can act like a GC analog in the activation of glucocorticoid response element-luciferase activity in HL7702 cells. We found that GSS alone had no effect on the expression of reporter gene, but it enhanced dexamethasone (Dex)-induced transcription of reporter gene. To further explore the effects of GSS, we examined the influence of GSS on the gene and protein expression as well as hormone binding activity of GR by semi-quantitative RT-PCR, Western blot, and radioligand-binding assay, respectively. GSS partially reversed the Dex-induced decrease in GR expression and hormone binding activity with an optimal dose of 25 microg/ml, implicating a positive regulatory effect of GSS on GR expression and binding activity. Therefore, our result suggests that GSS may reverse partially the dexamethasone-induced down-regulation of glucocorticoid receptor.

[Effects of Huangqi on phagocytic activity of peritoneal macrophage of mice].

OBJECTIVE: To study the effects of Huangqi decoction (HQD) on phagocytic activity of peritoneal macrophage of mice. METHOD: One hundred Kunming mice, whose weight varied from 18 g to 22 g, were selected and divided into 10 groups randomly in eluding contrast group, groups conducted at different doses of HQD by ig, groups conducted in various ways of taking medicine, and groups conducted with comparative treat combining Huangqi and Dexamethasone. Mice in every group were taken medicine one time daily for 6 days. RESULT: Among the groups treated at different doses of HQD, phagocytic rate and phagocytic index of mice, which were taken HQD by ig at high, middle, and low doses, were significantly higher (P < 0.01) than that of mice in contrast group, at the same time the effect in group with high dose was the best. Among the groups treated in various ways of taking medicine, phagocytic rate of the ip group was significantly better (P < 0.01) than that of the sc group and that of the ig group respectively, but there was not significant difference (P > 0.05) of phagocytic index among them. Among the groups combining Huangqi and Dexamethasone, Huangqi could antagonize the immunosuppressive effect of Dexamethasone obviously (P < 0.01). CONCLUSION: HQD at different doses and with various ways of taking medicine could improve phagocytic activity of peritoneal macrophage of mice at different degree, and could antagonize the immunosuppressive effect of Dexamethasone.

Lipopolysaccharide evokes microaggregation reactions in hemocytes isolated from tobacco hornworms, Manduca sexta.

Insect cellular immune reactions to bacterial infection include nodule formation. Eicosanoids mediate several cellular actions in the nodulation process, including formation of hemocyte microaggregates, an early step. In previous work, we reported that isolated hemocytes produce and secrete eicosanoids that influence hemocyte behavior in response to bacterial challenge. We also reported that microaggregate formation in response to challenge was mediated by prostaglandins (PGs), but not by products of the lipoxygenase (LOX) pathways. In this paper we describe experiments designed to test the idea that exposing isolated hemocytes to lipopolysaccharide (LPS) evokes formation of hemocyte microaggregates and this cellular action is mediated by PGs. Results show that isolated hemocyte preparations challenged with LPS formed more hemocyte microaggregates than unchallenged preparations (6.9x10(3) microaggregates/ml hemolymph vs. 2.5x10(3) microaggregates/ml hemolymph). LPS challenge stimulated formation of hemocyte microaggregates in a dose dependent manner. Experimental groups pretreated with cyclooxygenase inhibitors produced fewer hemocyte microaggregates in response to LPS challenge than untreated control groups. The formation of hemocyte microaggregates was not influenced by LOX inhibitors. Furthermore, the influence of dexamethasone was reversed by supplementing the experimental groups with the eicosanoid precursor fatty acid molecule, arachidonic acid and PGH(2). Palmitic acid, which is not substrate for eicosanoid biosynthesis, did not reverse the effects of dexamethasone on the formation of microaggregates. The LOX product 5(S)hydroperoxyeicosa-6E,8Z,11Z,14Z-tetraenoic acid also did not reverse the effects of dexamethasone. These results are consistent with similar investigations performed with bacterial suspensions. We infer that isolated hemocyte preparations recognize and react to LPS by forming microaggregates and this reaction is mediated by PGs, but not products of the LOX pathway.

Oxidant-mediated mitochondrial injury in eosinophil apoptosis: enhancement by glucocorticoids and inhibition by granulocyte-macrophage colony-stimulating factor.

The mainstay of asthma therapy, glucocorticosteroids (GCs) have among their therapeutic effects the inhibition of inflammatory cytokine production and induction of eosinophil apoptosis. In the absence of prosurvival cytokines (e.g., GM-CSF), eosinophils appear to be short-lived, undergoing apoptosis over 96 h in vitro. In a dose-dependent manner, GC further enhances apoptosis, while prosurvival cytokines inhibit apoptosis and antagonize the effect of GC. The mechanisms of eosinophil apoptosis, its enhancement by GC, and antagonism of GC by GM-CSF are not well-understood. As demonstrated in this study, baseline apoptosis of eosinophils resulted from oxidant-mediated mitochondrial injury that was significantly enhanced by GC. Mitochondrial injury was detected by early and progressive loss of mitochondrial membrane potential and the antioxidant protein, Mn superoxide dismutase (SOD). Also observed was the activation/translocation of the proapoptotic protein, Bax, to mitochondria. Underscoring the role of oxidants was the inhibition of mitochondrial changes and apoptosis with culture in hypoxia, or pretreatment with a flavoprotein inhibitor or a SOD mimic. GCs demonstrated early (40 min) and late (16 h) activation of proapoptotic c-Jun NH2-terminal kinase (JNK) and decreased the antiapoptotic protein X-linked inhibitor of apoptosis, a recently demonstrated inhibitor of JNK activation. Similarly, inhibition of JNK prevented GC-enhanced mitochondrial injury and apoptosis. Importantly, GM-CSF prevented GC-induced loss of X-linked inhibitor of apoptosis protein, late activation of JNK, and mitochondrial injury even in the face of unchanged oxidant production, loss of MnSOD, and early JNK activation. These data demonstrate that oxidant-induced mitochondrial injury is pivotal in eosinophil apoptosis, and is enhanced by GC-induced prolonged JNK activation that is in turn inhibited by GM-CSF.

Protection of peritoneal macrophages by granulocyte/macrophage colony-stimulating factor (GM-CSF) against dexamethasone suppression of killing of Aspergillus, and the effect of human GM-CSF.

Murine peritoneal macrophages in vitro could kill Aspergillus fumigatus conidia, and this activity could be suppressed with dexamethasone. Treatment with granulocyte/macrophage colony-stimulating factor (GM-CSF) alone did not boost killing, but GM-CSF treatment concurrently with dexamethasone reversed the dexamethasone suppression. Both recombinant human and recombinant murine GM-CSF were equivalent in this activity, even though the human reagent reportedly does not stimulate differentiation of murine stem cells. Recombinant human GM-CSF could also reverse dexamethasone suppression of bronchoalveolar macrophage conidiacidal activity. Sequential studies with peritoneal macrophages indicated that recombinant human GM-CSF pretreatment also blocked dexamethasone suppression, but the GM-CSF treatment given after dexamethasone did not block the suppressive effect. Recombinant human GM-CSF did not boost spleen cell proliferation to a mitogenic stimulus, and did not reverse dexamethasone suppression of proliferation. These studies suggest GM-CSF treatment prior to and concurrent with steroid immunosuppression may ameliorate the steroid effect on tissue macrophage antifungal activity, but does not affect steroid suppression of T-cell immunity.

Immunological properties of dehydroepiandrosterone, its conjugates, and metabolites.

The immunological response to the administration of various C-19 steroids has been of increasing interest. Although the action of dehydroepiandrosterone has been studied, the responses to its metabolites have not been explored. In the present study the ability of dehydroepiandrosterone, its conjugates, and metabolites to oppose the anti-inflammatory action of glucocorticoids on the inflammatory response to 2,4-dinitrochlorobenzene in the sensitized mouse was examined. A clear difference was seen between the antiglucocorticoid activity of dehydroepiandrosterone, its conjugates, and its 5 beta-metabolites on the one hand and the planar 5 alpha- and delta 4-metabolites, which were devoid of antiglucocorticoid activity. The mechanism of this antiglucocorticoid activity remains to be established.

Antidepressants inhibit the glucocorticoid stimulation of thyrotropin releasing hormone expression in cultured hypothalamic neurons.

BACKGROUND: The pituitary thyroid axis is frequently effected in human depression possibly due to alteration in hypothalamic thyrotropin releasing hormone (TRH) secretion. Since clinical recovery is associated with normalization of thyroid function, the direct effect of antidepressants on TRH expression in a well established fetal rat hypothalamic neuronal culture system was investigated. METHODS: Fetal rat hypothalamic neurons (day 17) in culture were treated with different concentrations of antidepressants with or without glucocorticoids for 7 days following which TRH content was measured by radioimmunoassay (RIA). RESULTS: The results showed that Imipramine (IMIP), a tricyclic antidepressant (TCA), decreased the TRH content in a dose-dependent manner (from 80.7 +/- 4.9, at 10(-9) mol/L, to 14.1 +/- 0.6, at 10(-5) mol/L, fmol/well; P < 0.05). Desipramine (DESI), another tricyclic antidepressant, also decreased the TRH content (from 63.6 +/- 2.5, at 10(-9) mol/L, to 12.6 +/- 0.4, at 10(-5) mol/L, fmol/well; P < 0.05). Sertraline (SERT) and Fluoxetine (FLUO), serotonin selective reuptake inhibitors (SSRI), also decreased TRH content in a dose dependent manner (from 83.9 +/- 7.9, at 10(-10) mol/L, to 7.6 +/- 0.4, at 10(-5) mol/L, and from 41.66 +/- 2.5, at 10(-8) mol/L, to 17.54 +/- 0.92, at 10(-6) mol/L, fmol/well, respectively; both P < 0.05). We then tested the effect of these antidepressants on the Dex stimulation of TRH content. IMIP, DESIP and FLUO at 10(-6) mol/L reduced the TRH response to glucocorticoid stimulation (36.4 +/- 4.0, 56.6 +/- 2.4, 23.75 +/- 4.0, respectively vs 107 +/- 7.5 fmol/well; P < 0.05). CONCLUSION: This raises the possibility that the enhanced thyroid function in depression, which we postulate, may result in part from glucocorticoid stimulation of TRH gene expression, can be reversed by antidepressants through a direct effect on the TRH neuron. However, other mechanisms may need to be invoked in addition since basal TRH content was also reduced.

Effect of L-NAME, a specific nitric oxide synthase inhibitor, on corticotropin-releasing hormone-elicited ACTH and corticosterone secretion.

This study was designed to determine the role of endogenous nitric oxide (NO) in the corticotropin-releasing hormone (CRH)-induced ACTH and corticosterone secretion, as well as possible involvement of hypothalamic dopamine and noradrenaline in that secretion in conscious rats. CRH given i.p. stimulated dose-dependently the pituitary-adrenocortical activity measured 1 h later. Dexamethasone (0.2 mg/kg i.p.) injected 1 h before CRH (1 microg/kg i.p.) totally abolished the CRH-elicited ACTH and corticosterone secretion, indicating a predominantly pituitary site of CRH-evoked stimulation. L-arginine (120 mg/kg i.p.) and N(omega)-nitro-L-arginine methyl ester (L-NAME 5-10 mg/kg i.p.) did not markedly affect the basal plasma ACTH and corticosterone levels. L-NAME given 15 min before CRH markedly, but not significantly, augmented the CRH-induced ACTH response, and enhanced more potently and significantly the corticosterone response. Pretreatment with L-arginine, a substrate for NOS, slightly diminished the CRH-induced ACTH response and considerably reduced the corticosterone response. L-arginine also significantly reversed the L-NAME-evoked increase in the CRH-induced ACTH and corticosterone secretion. L-NAME did not markedly alter the CRH-induced hypothalamic dopamine and noradrenaline levels, while L-arginine significantly increased noradrenaline level. However, those alterations were not directly correlated with the observed changes in ACTH and corticosterone secretion. These results indicate that in conscious rats NO plays a marked inhibitory role in the CRH-induced ACTH secretion and inhibits more potently corticosterone secretion. Hypothalamic dopamine and noradrenaline do not seem to be directly involved in the observed alterations in ACTH and corticosterone secretion.

Protection against hypoxic-ischemic damage with corticosterone and dexamethasone: inhibition of effect by a glucocorticoid antagonist RU38486.

We investigated whether the neuroprotection provided by dexamethasone against neonatal hypoxic-ischemic damage can be inhibited by a glucocorticoid antagonist and whether corticosterone, the endogenous glucocorticoid in the rat, also provides protection. Rats (6 days old) were treated with either vehicle (0.1 ml/10 g), corticosterone (3.5-80 mg/kg, s.c.) or dexamethasone alone or in combination with RU38486 (20-80 mg/kg, s.c.) 15 min prior to dexamethasone (0.1 mg/kg, i.p.). At 7 days of age, cerebral hypoxia-ischemia was produced by right carotid artery ligation under anesthesia and subsequent exposure to 2 h of hypoxia. Damage was quantified from brains perfusion-fixed and processed 2 days later. The reduction in somatic growth, thymus weight and the relatively elevated blood glucose levels at the end of hypoxia-ischemia were inhibited by RU38486. The protective effect of dexamethasone was also prevented by RU38486 (P < 0.001). Similar to pre-treatment with dexamethasone, administration of corticosterone (40-80 mg/kg) markedly reduced the extent of infarction compared to vehicle-treated controls (P < 0.0001). Thus, the endogenous glucocorticoid in the rat also provides protection against hypoxic-ischemic damage. RU38486 inhibits the beneficial effects of dexamethasone demonstrating that the neuroprotection observed with dexamethasone is a glucocorticoid receptor-mediated effect.

Interactions between growth hormone and dexamethasone in skeletal growth and bone structure of the young mouse.

The present study investigated the interactions of growth hormone (GH) and glucocorticoid on skeletal growth and bone structure in young mice. The purpose of this study was to examine the possible prevention by GH of the damage inflicted by dexamethasone (Dex) at sites of skeletal growth and ossification. Dex (1 mg/kg) with or without rat GH (rGH) or bovine GH (bGH), 1 mg/kg, was given for 4 weeks, from age 3-7 weeks, to female ICR mice. Tibiae, humerus, and vertebrae were analyzed morphometrically and biochemically. Growth, as determined by the mouse weight, tibial length, and humerus protein content was found to be compromised by dexamethasone. This was prevented by rGH or bGH. The epiphyseal growth plate width, trabecular bone volume, cortical bone width, mineral bone content, and alkaline and acid phosphatase activity were decreased by dexamethasone. These were prevented by rGH or by bGH. The findings of the present study suggest that in the mouse, GH can decrease or even avoid some of the pathological features in growing bones inflicted by high-dose glucocorticoid treatment.