Opposing roles of glucocorticoid receptor and mineralocorticoid receptor in trimethyltin-induced cytotoxicity in the mouse hippocampus

The organotin trimethyltin (TMT) is known to cause neuronal degeneration in the murine brain. Earlier studies indicate that TMT-induced neuronal degeneration is enhanced by adrenalectomy and prevented by exogenous glucocorticoid. The aim of this study was to investigate the regulation of TMT neuroxicity by corticosterone receptors including type I (mineralocorticoid receptor, MR) and type II (glucocorticoid receptor, GR) in adult mice. The systemic injection of TMT at the dose of 2.0 or 2.8 mg/kg produced a marked elevation in the level of plasma corticosterone that was both dose and time dependent. The MR agonist aldosterone had the ability to exacerbate TMT cytotoxicity in the dentate granule cell layer, whereas its antagonist spironolactone protected neurons from TMT cytotoxicity there. In contrast, the GR antagonist mifepristone exacerbated the TMT cytotoxicity. Taken together, our data suggest TMT cytotoxicity is oppositely regulated by GR and MR signals, being exacerbated by MR activation in adult mice.     

Cytosolic glucocorticoid receptor expression in the rat vestibular nucleus and hippocampus following unilateral vestibular deafferentation

It has been suggested that vestibular compensation, the process of behavioural recovery that occurs following peripheral vestibular damage, might be partially dependent on the release of glucocorticoids (GC) during the early stages of recovery from the lesion. One possibility is that glucocorticoid receptors (GRs) in the vestibular nucleus complex (VNC) might change following the lesion, altering their response to GCs. We sought to test this hypothesis by quantifying the expression of cytosolic GRs in the bilateral VNCs at 10 h, 58 h and 2 weeks following unilateral vestibular deafferentation (UVD) in rat, using western blotting. We also examined GR expression in the CA1, CA2/3 and dentate gyrus (DG) subregions of the hippocampus and measured serum corticosterone levels. Compared with sham surgery and anaesthetic controls, we found no significant changes in GR expression in the ipsilateral or contralateral VNCs at any time post-UVD. However, we did find a significant decrease in GR expression in the ipsilateral CA1 at 2 weeks post-UVD. Serum corticosterone levels were significantly lower in all groups at 58 h post-op. compared to 10 h and 2 weeks; however, there were no significant differences between the UVD and control groups at any time point. These results suggest that changes in GR expression in the VNC are unlikely to contribute to the development of vestibular compensation. However, long-term changes in GR expression in CA1 might be related to chronic deficits in hippocampal function and spatial cognition following vestibular damage.     

Glucocorticoid receptor protein expression in human hippocampus; stability with age

The glucocorticoid receptor (GR) exerts numerous functions in the body and brain. In the brain, it has been implicated, amongst others, in feedback regulation of the hypothalamic-pituitary-adrenal axis, with potential deficits during aging and in depression. GRs are abundantly expressed in the hippocampus of rodent, except for the Ammon's horn (CA) 3 subregion. In rhesus monkey however, GR protein was largely absent from all hippocampal subregions, which prompted us to investigate its distribution in human hippocampus. After validation of antibody specificity, we investigated GRα protein distribution in the postmortem hippocampus of 26 human control subjects (1–98 years of age) and quantified changes with age and sex. In contrast to monkey, abundant GR-immunoreactivity was present in nuclei of almost all neurons of the hippocampal CA subfields and dentate gyrus (DG), although neurons of the CA3 subregion displayed lower levels of immunoreactivity. Colocalization with glial fibrillary acidic protein confirmed that GR was additionally expressed in approximately 50% of the astrocytes in the CA regions, with lower levels of colocalization (approximately 20%) in the DG. With increased age, GR expression remained stable in the CA regions in both sexes, whereas a significant negative correlation was found with age only in the DG of females. Thus, in contrast to the very low levels previously reported in monkey, GR protein is prominently expressed in human hippocampus, indicating that this region can form an important target for corticosteroid effects in human.     

Colocalization of mineralocorticoid receptor and glucocorticoid receptor in the hippocampus and hypothalamus

We investigated the distribution and colocalization pattern of the two corticosteroid receptors, mineralocorticoid receptor (MR) and glucocorticoid receptor (GR), in the hippocampus and hypothalamus, the main target regions of corticosterone in the rat brain, using double immunofluorescence histochemistry in conjunction with specific polyclonal antibodies against MR and GR. In the hippocampus, MR- and GR-immunoreactivity (ir) were colocalized in CA1 and CA2 pyramidal neurons and granule cells of the dentate gyrus, while only MR-ir was seen in the CA3 pyramidal neurons. Colocalization of MR- and GR-ir was also observed in the parvocellular region, but not in the magnocellular region of the paraventricular nucleus (PVN). Subcellular distribution of MR-ir was more cytoplasmic in comparison with that of GR-ir, while the ratio of cytoplasmic to nuclear distribution of these receptors was different among the regions. After adrenalectomy (ADX), the distribution pattern of both receptors was changed to cytoplasmic, although the degree of the change of distribution was different among each region. Replacement of corticosterone after ADX recovered the distribution pattern to that of the sham-operated animals. These results suggest that the balance of MR and GR in the cell underlies the potential regulation of corticosteroid through the hippocampus and hypothalamus.     

Cannabinoid CB(1) receptor expression and affinity in the rat hippocampus following bilateral vestibular deafferentation

Numerous studies have shown that bilateral vestibular deafferentation (BVD) results in spatial memory deficits and hippocampal dysfunction in rats and humans. Since cannabinoid CB(1) receptors are well known to regulate synaptic plasticity in the hippocampus, we investigated whether BVD resulted in changes in CB(1) receptor expression and affinity in the rat hippocampus at 1, 3 and 7 days post-surgery, using a combination of Western blotting and radioligand binding. Using Western blotting, we found that CB(1) receptor expression was significantly lower in BVD animals compared to sham controls only in the CA3 area across the 3 time points (P=0.03). CB(1) receptor expression decreased significantly over time for both the BVD and sham animals (P=0.000). The radioligand binding assays showed no significant change in the IC(50) of the CB(1) receptor for the cannabinoid CB(1)/CB(2) receptor agonist, WIN55,212-2. These results suggest that the CB(1) receptor down-regulates in the CA3 region of the hippocampus following BVD, but with no changes in the affinity of the CB(1) receptor for WIN55,212-2.     

Acute stress increases neuropsin mRNA expression in the mouse hippocampus through the glucocorticoid pathway

Stress affects synaptic plasticity and may alter various types of behaviour, including anxiety or memory formation. In the present study, we examined the effects of acute stress (1 h restraint with or without tail-shock) on mRNA levels of a plasticity-related serine protease neuropsin (NP) in the hippocampus using semiquantitative RT-PCR and in situ hybridization. We found that NP mRNA expression was dramatically increased shortly after exposure to the acute restraint tail-shock stress and remained at high level for at least 24 h. The level of NP mRNA would be correlated to the elevated plasma concentration of the glucocorticoid corticosterone (CORT) and to the stress intensity. Application of CORT either onto primary cultured hippocampal neurons (5 nM) or in vivo to adrenalectomized (ADX) mice (10 mg/kg B.W., s.c.) mimicked the effect of stress and significantly elevated NP mRNA. These results suggest that the upregulation of NP mRNA after stress is CORT-dependent and point to a role for neuropsin in stress-induced neuronal plasticity.     

Chronic lithium chloride injection increases glucocorticoid receptor but not mineralocorticoid receptor mRNA expression in rat brain

Lithium has been used clinically for the treatment of bipolar disorders. However, the brain mechanisms, by which lithium acts, are still unclear. An impaired hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the pathogenesis of mood disorders. In this study, we investigated the effects of chronic lithium on the corticosteroid receptors in the brain. Male Wistar rats were injected with LiCl (1.5 mEq/kg) or saline intraperitoneally (i.p.) once a day for 14 days. Twenty-four hours after the last injection, the expressions of mRNA for glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) in the brain were determined by non-radioactive in situ hybridization. Chronic administration of LiCl increased the expression of GR mRNA in the hippocampus and paraventricular nucleus of the hypothalamus (PVN). However, no significant changes were observed in the expression of either MR mRNA in the hippocampus or GR mRNA in the locus ceruleus. Since the hippocampus and PVN mediate negative feedback regulation of the HPA axis, an increased expression of GR mRNA in these regions may normalize HPA axis activity in mood disorders. Thus, the effect of chronic lithium on GR function may be involved in its antimanic and/or prophylactic activity in bipolar disorders.     

糖皮质激素对大鼠下丘脑亨廷顿蛋白相关蛋白1表达的影响

目的 探讨外源性糖皮质激素对大鼠下丘脑亨廷顿蛋白相关蛋白1（HAP1）表达的影响。 方法 成年雄性Wistar大鼠80只,随机分为实验对照组（注射生理盐水）、皮质酮注射组、皮质酮+皮质酮受体拮抗剂(RU38486)注射组、饮用氢化可的松组。皮质酮注射［(5mg/(kg.12h)］组又分为注射持续1d、3d、5d、7d组;皮质酮+皮质酮受体拮抗剂(RU38486)注射［(10mg/(kg.12h)］组注射持续3d;饮用氢化可的松组大鼠饮用水中加氢化可的松（0.01g/L）,连续1个月。应用RT-PCR、免疫印迹法观察大鼠下丘脑HAP1表达的变化。 结果 注射皮质酮1d和3d后,下丘脑HAP1表达明显减少,其mRNA的表达明显下调,5d后HAP1开始回升,7d 后恢复到正常水平,HAP1 mRNA表达5d后明显增加,并高于正常水平;长期(一个月)饮用氢化可的松的大鼠,其下丘脑中HAP1的表达明显减少;在皮质酮注射的同时注射RU38486,可以对抗由皮质酮注射所引起的下丘脑HAP1的变化。 结论 外源性过量糖皮质激素能影响下丘脑HAP1的表达,下丘脑中的HAP1可能参与下丘脑神经元或神经内分泌细胞的功能活动。     

Determination of glucocorticoid receptors in human leukemias

Summary Determination of steroid receptors has been used to predict steroid sensitivity in various neoplasias. In an attempt to investigate its applicability in human leukemias we have studied glucocorticoid receptors in the leukemic cells from 23 patients with various hematologic neoplasias and in the lymphocytes from 18 normal donors. Specific glucocorticoid binding in intact cells was determined by a whole cell competitive binding assay. Normal lymphocytes have about 4,611 specific binding sites per cell. The blasts from 9 patients with acute myelogenous leukemias (AML) have strongly varying high levels of specific binding sites, ranging from 4,817 to 15,416 per cell. Of the 13 patients with chronic lymphocytic leukemia (CLL), 5 have received glucocorticoid treatment for years and were clinically resistant to glucocorticoid. Their lymphocytes have lower specific binding sites (range: 2,047 to 3,999) than the other CLL cases which were newly diagnosed (range: 3,734 to 11,020). Our results suggest that determination of glucocorticoid receptors might be of value in predicting clinical responsiveness in leukemias.Supported by the Tumorzentrum Heidelberg-Mannheim, and Karl- und Maria-Biesinger-Stiftung, Hirschhorn, F.R.G.     

C-Jun蛋白对糖皮质激素受体表达及转录激活能力的影响

目的观察促进与抑制c-Jun蛋白表达对糖皮质激素受体(GR)表达和转录激活能力的影响,探索c-Jun与GR功能的相互关系.方法采用基因重组技术,构建PAVU6-c Jun siRNA干涉质粒,电穿孔法分别转染U937细胞c-Jun蛋白表达真核载体与PAVU6-c Jun siRNA干涉质粒,观察c-Jun表达对GR表达和转录激活能力的影响.结果成功构建PAVU6-c JunsiRNA干涉质粒,转化U937细胞后GR的表达和转录激活活性有增强,而转染c-Jun表达载体pCMV-c JunGR的表达和转录激活活性有所减弱.结论c-Jun蛋白表达水平对GR的表达和转录激活活性有影响,抑制c-Jun蛋白表达,一定程度上可促进GR表达并增强其转录激活功能.     

Immunocytochemical application of monoclonal antibodies to rat liver glucocorticoid receptor

Seven per cent (10/145) of hybridomas raised against partially purified activated glucocorticoid receptor from rat liver produced monoclonal antibody to receptor. Six IgM secreting clones selected for further investigation bound equally well to activated and non-activated receptor from fresh rat liver, but significantly less well (11-25 per cent) to receptor from frozen rat liver. No interaction was found with oestrogen receptor from rat uterus but extensive cross reaction occurred with progesterone receptor. Although none of the antibodies bound to glucocorticoid receptor from human or porcine liver or lymphoid cells, several cross-reacted with mouse liver glucocorticoid receptor. Immunoelectroblotting of proteins from fresh and frozen rat liver cytosol showed the antibodies bound to 90,000 and 40,000 MW forms of receptor respectively. Immunostaining of both frozen and paraffin embedded sections of rat tissue showed that receptor is preserved during fixation and processing of tissues. Using both indirect immunoperoxidase and immunogold silver staining methods, the pattern of receptor staining observed correlates with the known glucocorticoid responsiveness of the tissues studied.     

The relationship between the expression of the glucocorticoid receptor in biopsied colonic mucosa and the glucocorticoid responsiveness of ulcerative colitis patients

The objective of this study was to clarify the relationship between the frequency of infiltrating cells expressing the glucocorticoid receptors (GR) α and β in biopsied colonic mucosa and the glucocorticoid (GC) responsiveness of ulcerative colitis (UC) patients. Active UC patients (n = 38) were divided into GC-sensitive and GC-resistant groups. GRβ⁺ cells were significantly higher in the GC-resistant group than in the GC-sensitive and control groups. GRα mRNA was expressed in all UC patients, while GRβ mRNA was expressed in only 1 patient in the GC-sensitive group (n = 6) and 7 patients in the GC-resistant group (n = 8). Double-positive cells for GRβ and CD4 or CD19 were frequently observed. The Foxp3⁺ cell count was significantly higher in the GC-sensitive group than in the GC-resistant group, but double Foxp3⁺GRβ⁺ cells were not observed. These results indicated that the sensitivity of GC therapy could probably be predicted by immunostaining biopsy specimens for GRβ and Foxp3.     

音乐对大鼠海马NMDA受体表达的作用

目的：研究音乐刺激对大鼠海马组织NMDA受体及其受体蛋白mRNA表达的影响。方法：用免疫组织化学和PCR技术,定量检测了NMDA受体蛋白和编码该受体的mRNA表达。结果：音乐刺激后,NMDA受体蛋白及其mRNA表达,在持续音乐刺激组分别高出对照组40％和58％,生后音乐组高出33％和42％,而胎期音乐组与对照组相比不显著(4％和6％)。结论：音乐刺激能显著增强大鼠海马组织NMDA受体和mRNA表达,而且其增强效应具有音乐刺激时间依赖性,且生后的作用较为明显。     

大鼠烫伤后肝胞浆糖皮质激素受体和酪氨酸转氨酶的变化

成年大鼠,雌,背部用沸水烫伤,轻烫组的烫伤面积为5.3cm直径的圆面积。烫10秒。重烫组为6.5cm直径,15秒。于烫伤后1、3、6和9小时断头处死,测定血浆皮质酮(B)、肝胞浆糖皮质激素受体(GCR)和酪氨酸转氨酶活性(TAT)。结果烫后3和6小时,尽管重烫组血浆B很高,但TAT却明显低于轻烫组(P<0.001),反映了严重烫伤组靶细胞对内源性糖皮质激素(GC)的反应性降低。烫后1、3小时重烫组GCR的结合容量(R_0)也明显低于轻烫组,提示重烫组靶细胞对GC的反应性降低至少部分地是由于GCR减少所致。对严重烫伤时靶细胞对GC的反应性降低的可能的病理和临床意义作了讨论。     

新生期大鼠接种卡介苗对空间学习能力和海马突触可塑性的影响

目的检测免疫接种卡介苗（BCG）后大鼠行为学,电生理,海马神经元树突棘的变化。为进一步研究疫苗接种对突触传递和学习记忆的影响提供依据。方法实验分为卡介组和对照组。新生Sprague-Dawley（SD）大鼠于出生24h内背部皮下接种卡介苗,对照组皮下注射等量的PBS。4周时水迷宫检测其行为学的变化,在体LTP测其电生理的变化,并使用基因枪散射DiI染料法检测海马神经元树突棘的变化。结果与其对照组相比,卡介组空间学习记忆能力明显增强：LTP结果显著优于对照组;海马神经元树突棘的密度以及蘑菇样（mushroom）增多。结论新生期成功接种疫苗可以提高大鼠突触传递的可塑性并促进其学习记忆能力。     

Corticosteroids stimulate the amphibious behavior in mudskipper: potential role of mineralocorticoid receptors in teleost fish

It has long been held that cortisol, a glucocorticoid in many vertebrates, carries out both glucocorticoid and mineralocorticoid actions in teleost fish. However, 11-deoxycorticosterone (DOC) has been identified as a specific endogenous ligand for the teleostean mineralocorticoid receptor (MR). Furthermore, the expressions of MR mRNA are modest in the osmoregulatory organs, but considerably higher in the brain of most teleosts. These recent findings suggest that the mineralocorticoid system (DOC/MR) may carry out some behavioral functions in fish. To test this possibility, we examined the effects of cortisol and DOC administration in the amphibious behavior in mudskipper (Periophthalmus modestus) in vivo. It was found that mudskippers remained in the water for an increased period of time when they were immersed into 5 μM DOC or cortisol for 8 h. Additionally, an exposure to 25 μM DOC for 4 to 8 h caused a decreased migratory frequency of mudskippers to the water, reflected a tendency to remain in the water. It was further observed that after 8 h of intracerebroventricular (ICV) injection with 0.3 pmol DOC or cortisol the staying period in the water increased in fish. The migratory frequency was decreased after ICV DOC injection which indicated that fishes stayed in the water. Concurrent ICV injections of cortisol with RU486 [a specific glucocorticoid-receptor (GR) antagonist] inhibited only the partial effects of cortisol. Together with no changes in the plasma DOC concentrations under terrestrial conditions, these results indicate the involvement of brain MRs as cortisol receptors in the preference for an aquatic habitat of mudskippers. Although the role of GR signaling cannot be excluded in the aquatic preference, our data further suggest that the MR may play an important role in the brain dependent behaviors of teleost fish.     

Effect of neonatal respiratory infection on adult BALB/c hippocampal glucocorticoid and mineralocorticoid receptors

The current study investigated the effects of neonatal infection with Chlamydia muridarum bacteria on glucocorticoid (GR) and mineralocorticoid (MR) receptors in the adult mouse hippocampus. In male adults infected at birth, circulating corticosterone was significantly increased when compared to same sex controls; while neonatal infection resulted in female adults with significantly increased GR mRNA compared to same sex controls. When comparing males and females after neonatal infection, males had significantly less GR protein than females. Interestingly, after control treatment, males had significantly more GR mRNA, MR mRNA, and GR protein with significantly lower corticosterone than females. Neonatal respiratory infection significantly impacts adult hippocampal GR and MR, and circulating corticosterone in a sex-specific manner potentially altering stress responsivity.     

大鼠海马内5-HT3受体参与神经免疫调制

目的 :探讨大鼠海马不同部位 5 HT3受体对免疫的调制作用。方法 :通过小鼠腹腔和大鼠侧脑室和海马不同结构内注射 5 HT3受体激动剂 1 phenylbiguanide(PBG)后不同时间 ,用3H TdR掺入法观察对ConA、LPS刺激的脾T和B淋巴细胞增殖效应的影响 ,并观察选择性 5 HT3受体拮抗剂托烷司琼 (tropisetron ,Trop)对PBG作用的影响。结果 :小鼠腹腔注射、大鼠侧脑室和双侧腹侧海马注射 5 HT3受体激动剂PBG后可增强ConA、LPS刺激的脾T和B淋巴细胞增殖效应 ;双侧背侧海马内注射PBG后抑制ConA刺激的脾T淋巴细胞增殖效应 ,而不影响LPS刺激的B淋巴细胞增殖效应 ;5 HT3受体激动剂对脾细胞增殖效应的影响可被同时给予的托烷司琼阻断。结论 :提示大鼠海马 5 HT3受体参与了免疫的调制并有明显的部位差异