以核受体为靶标的胆汁淤积治疗药物研究进展

胆汁淤积的治疗药物匮乏,熊去氧胆酸是目前唯一被FDA通过的治疗原发性胆汁性肝硬化的药物,但其药效却限于疾病早期,因此迫切需要开发新的胆汁淤积治疗药物。核受体能调控胆汁酸稳态,它作为胆汁淤积治疗的靶标是目前研究的热点。该综述对目前报道最多的核受体进行总结,分析其作为胆汁淤积药物治疗靶标的利弊及应用前景。

Molecular mechMolecular mechanism of glucocorticoid resistance in inflammatory bowel disease

Natural and synthetic glucocorticoids (GCs) are widely employed in a number of inflammatory, autoimmune and neoplastic diseases, and, despite the introduction of novel therapies, remain the first-line treatment for inducing remission in moderate to severe active Crohn’s disease and ulcerative colitis. Despite their extensive therapeutic use and the proven effectiveness, considerable clinical evidence of wide inter-individual differences in GC efficacy among patients has been reported, in particular when these agents are used in inflammatory diseases. In recent years, a detailed knowledge of the GC mechanism of action and of the genetic variants affecting GC activity at the molecular level has arisen from several studies. GCs interact with their cytoplasmic receptor, and are able to repress inflammatory gene expression through several distinct mechanisms. The glucocorticoid receptor (GR) is therefore crucial for the effects of these agents: mutations in the GR gene (NR3C1, nuclear receptor subfamily 3, group C, member 1) are the primary cause of a rare, inherited form of GC resistance; in addition, several polymorphisms of this gene have been described and associated with GC response and toxicity.However, the GR is not self-standing in the cell and the receptor-mediated functions are the result of a complex interplay of GR and many other cellular partners. The latter comprise several chaperonins of the large cooperative hetero-oligomeric complex that binds the hormonefree GR in the cytosol, and several factors involved in the transcriptional machinery and chromatin remodeling, that are critical for the hormonal control of target genes transcription in the nucleus. Furthermore, variants in the principal effectors of GCs (e.g. cytokines and their regulators) have also to be taken into account for a comprehensive evaluation of the variability in GC response. Polymorphisms in genes involved in the transport and/or metabolism of these hormones have also been suggested as other possible candidates of interest that could play a role in the observed inter-individual differences in efficacy and toxicity. The best-characterized example is the drug efflux pump P-glycoprotein, a membrane transporter that extrudes GCs from cells, thereby lowering their intracellular concentration. This protein is encoded by the ABCB1/ MDR1 gene; this gene presents different known polymorphic sites that can influence its expression and function. This editorial reviews the current knowledge on this topic and underlines the role of genetics in predicting GC clinical response. The ambitious goal of pharmacogenomic studies is to adapt therapies to a patient’s specific genetic background, thus improving on efficacy and safety rates.

Effect of Calpain inhibitor I on glucocorticoid receptor-dependent degradation and its transactivation ability

Objective: To investigate the effect of Calpain inhibitor I on glucocorticoid receptor-dependent proteasomal degradation and its transcriptional activity. Methods: After Raw-264.7 cells were treated with Calpain inhibitor I, dexamethasone, or both for about 12 h, the change of glucocorticoid receptor was detected by western blot analysis. COS-7 cells were transfected with PRsh-GRα expression vector and glucocorticoid-responsive receptor pMAMneo-CAT, then the effect of Calpain inhibitor I on glucocorticoid receptor transcriptional activation ability was determined by CAT activity. Results: The glucocorticoid receptor levels decreased after RAW-264.7 cells were treated with dexamethasone for 12 hours, which effect can be inhibited by Calpain inhibitor I to some extent. CAT activity assay showed that Calpain inhibitor I enhance glucocorticoid receptor transcriptional activity. Conclusion: Calpain inhibitor I can inhibit the down-regulation of dexamethasone on glucocorticoid receptor, and enhances glucocorticoid receptor transactivation ability.

Blockage of glucocorticoid receptors during memory acquisition, retrieval and reconsolidation prevents the expression of morphine-induced conditioned place preferences in mice

Association between the reward caused by consuming drugs and the context in which they are consumed is essential in the formation of morphine-induced conditioned place preference (CPP). Glucocorticoid receptor (GRs) activation in different regions of the brain affects reward-based reinforcement and memory processing. A wide array of studies have demonstrated that blockage of GRs in some brain areas can have an effect on reward-related memory; however, to date there have been no systematic studies about the involvement of glucocorticoids (GCs) in morphine-related reward memory. Here, we used the GR antagonist RU38486 to investigate how GRs blockage affects the sensitization and CPP behavior during different phases of reward memory included acquisition, retrieval and reconsolidation. Interestingly, our results showed RU38486 has the ability to impair the acquisition, retrieval and reconsolidation of reward-based memory in CPP and sensitization behavior. But RU38486 by itself cannot induce CPP or conditioned place aversion (CPA) behavior. Our data provide a much more complete picture of the potential effects that glucocorticoids have on the reward memory of different phases and inhibit the sensitization behavior.

Arctic spring: the arrival biology of migrant birds

On arrival in the Arctic, migrant birds must adjust their physiology and behavior to unpredictable snow cover, weather, food sources and predator pressure. In other words they must be resistant to environmental perturbations (stress) so that they can migrate to their tundra nesting areas and settle on territories as soon as possible. They can then begin breeding as soon as when environmental conditions become favorable. They do this partly by using micro-habitats such as areas where snow depth is low, and patches of tundra that melt out rapidly (especially near willows Salix sp). Ground temperatures increase dramatically within hours after exposure to sun; and invertebrate activity begins simultaneously. Wind speeds are attenuated almost completely within 10 cm of the ground in willows and tussock tundra. The combination of these conditions provides an ideal refuge, especially for passerine migrants in early spring. However, if conditions worsen, the birds can leave. There are adjustments of the adrenocortical responses to stress because arctic conditions in spring are potentially severe, at least compared with wintering grounds to the south. Secretion of corticosterone in response to acute stress is enhanced at arrival in males, accompanied by a decrease in sensitivity to negative feedback and a change in responsiveness of the adrenal cortex cells to adrenocorticotropin. There is also an increase in levels of corticosterone-binding globulin (CBG) so that the actions of corticosterone are buffered according to the severity of environmental conditions. Regulation at the level of genomic receptors, particularly the low affinity glucocorticosteroid-like receptor for corticosterone in brain and liver, may be important; and non-genomic actions of corticosterone may play a major role too. In other words, the hormone-behavior system associated with arrival biology is highly flexible.

Glucocorticoid receptor and heat shock protein 90 in peripheral blood mononuclear cells from asthmatics

Objective To investigate the expression of glucocerticoid receptor (GR) and heat shock protein 90(HSP90) mRNA in peripheral blood mononuclear cells (PBMCs) from steroid-sensitive (SS), steroiddependent (SD) and steroid-resistant (SR) asthmatics patients, and to evaluate the role of GR and HSP90in the pathogenesis of SR.Methods Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the expressions of GR and HSP90 mRNA in PBMC stimulated with IL-2 and/or IL-4 from 10 normal volunteers,10 SS, 5 SD and 6 SR patients.Results The expressions of GR and HSP90 mRNA were the highest in PBMC from SR patients (0.730±0.171 and 1.122±0.165, respectively) compared with the normals (P＜0.05). The second was from SS patients (0.359±0.350 and 0.885±0.250, respectively). The lowest was from the SD patients (0.017±0.008 and 0.078 ± 0.039, respectively). The ratio of HSP90/GR in SR was significantly lower than that in the others, and it suggested that the expression of HSP90 mRNA was not sufficient in this group of patients. When PBMC from SS, SD and SR was incubated with IL-2 or IL-4 alone, no changes in GR and HSP90 mRNA expression were observed. While incubated with combination of IL-2 and IL-4, a significantly higher expression of GR mRNA was observed in all asthmatics, and a significantly higher expression of HSP90 mRNA was observed only in SS and SD patients.Conclusion The lowering of HSP90/GR ratio may be one of the causes of SR. IL-2 and IL-4 may play roles in the imbalance of HSP90/GR.

Effect of moxibustion at Shenshu(BL 23) on the ethology,corticosterone and glucocorticoid receptor in aging rats

Objective：To observe the effect of moxibustion on learning and memory abilities,corticosterone and glucocorticoid receptor（GR） in subacute aging rats.Methods：Twenty four Sprague-Dawley（SD） rats were randomly divided into a normal group,a model group and a moxibustion group,8 rats in each group.Rats in the model group and the moxibustion group were subcutaneously injected with 25% D-galactose [125 mg/（kg·bw）] for 40 d continuous;rats in the normal group were injected with saline at the same position for 40 d continuous.Rats in the moxibustion group were given mild moxibustion at bilateral Shenshu（BL 23） at the same time of modeling;rats in the normal group and the model group were only identically grabbed without moxibustion for 40 d.The learning and memory abilities of rats were observed using the Morris water maze at the end of the experiment.Abdominal aorta blood and thymus were collected after water maze experiment.Enzyme-linked immunosorbent assay（ELISA） was used to detect serum corticosterone level,and immunohistochemical method was used to detect the expression of thymus GR.Results：Compared with the normal group,rats in the model group showed that a significantly longer escape latency time（P〈0.01） on the third and the fourth days;number of times crossing the platform in 70 s significantly reduced（P〈0.01）;activity times in the fourth quadrant significantly decreased（P〈0.05）;serum corticosterone levels increased（P〈0.01）;thymus GR expression decreased（P〈0.05）.Compared with the model group,rats in the moxibustion group showed that the escape latency times were significantly shorter on the third,the fourth and the fifth days（P〈0.01,P〈0.05）;number of times crossing the platform in 70 s significantly increased（P〈0.05）;activity times in the fourth quadrant significantly increased（P〈0.05）;serum corticosterone levels decreased（P〈0.05）;thymus GR expression increased（P〈0.05）.Conclusion：Moxibustion could improve the learning and memory abilities of subacute aging rats,down-regulate serum corticosterone levels,and increase thymus GR content.

Expression of glucocorticoid receptor isoforms in cutaneous hemangiomas and vascular malformations

Background Hemangiomas are the most common tumors in children. Some hemangiomas may require intervention because of their location, size, behavior, or potential for important complications. Pharmacological therapy with glucocorticoids is the mainstay treatment, but there is no consensus on therapeutic regimens or candidate selection, therapeutic efficacy vaires, and the mechanism mediating the beneficial effects of glucocorticoids remains unclear. This study was performed to investigate the expression patterns of the glucocorticoid receptor (GR) and its α isoform (GRα) in cutaneous hemangiomas and vascular malformations.Methods SP immunohistochemical technique was used to examine the expression of GR(e-20) (GR) and GR (p-20) (GRα) on vascular endothelial cells in 80 specimens that included 33 proliferating hemangiomas, 32 involuting hemangiomas, 7 vascular malformations as well as 8 normal skin tissues, all obtained from infants and children. GR and GRα expression in prepared tissue slides were examined using automated computer-assisted microscopic analysis. Mean gray scale values were compared among the various tumor types.Results The mean gray scale values of GR were 127.0±6.4 and 121.4±6.6 in hemangiomas and vascular malformations respectively, but this difference was not statistically significant ( P =0.104). However, these values were all markedly higher than that of normal skin, which was only 108.6±6.8 ( P =0.001 and P =0.000 for comparison with hemangiomas and vascular malformations respectively). The gray scale of GR in proliferation and involuting hemangiomas were 127.9±4.8 and 126.0±5.8 respectively, but this difference was not significant ( P =0.146). However, GRα expression in hemangiomas, vascular malformations and normal skin declined gradually in stepwise fashion (127.3±5.4, 120.4±6.1 and 109.9±5.3 respectively; P <0.001). GRα expression was higher in proliferating hemangiomas than in involuting hemangiomas (127.2±6.3 and 122.5±6.3; P =0.004).Conclusions GR and GRα are strongly expressed in hemangiomas and vascular malformations. The expression of GRα is closely related to the phase of the hemangioma. Determination of GR and GRα may be a positive significance to understand the information of hemangiomas and vascular malformations and may further help determining proper strategies of steroid therapy for hemangiomas and vascular malformations.

Single nucleotide polymorphisms in the human corticosteroid-binding globulin promoter alter transcriptional activity

Corticosteroid-binding globulin(CBG) is a high-affinity plasma protein that transports glucocorticoids and progesterone.Others and we have reported non-synonymous single nucleotide polymorphisms(SNPs) that influence CBG production or steroid-binding activity.However,no promoter polymorphisms affecting the transcription of human CBG gene(Cbg) have been reported.In the present study we investigated function implications of six promoter SNPs,including 26 C/G,54 C/T,144 G/C,161 A/G,205 C/A,and 443/444 AG/,five of which are located within the first 205 base pairs of 5'-flanking region and close to the highly conserved footprinted elements,TATA-box,or CCAAT-box.Luciferase reporter assays demonstrated that basal activity of the promoter carrying 54 T or 161 G was significantly enhanced.The first three polymorphisms,26 C/G,54 C/T,and 144 G/C located close to the putative hepatic nuclear factor(HNF) 1 binding elements,altered the transactivation effect of HNF1.We also found a negative promoter response to dexamethasone-activated glucocorticoid receptor(GR),although none of the SNPs affected its transrepression function.Our results suggest that human Cbg 26 C/G,54 C/T,144 G/C,and 161 A/G promoter polymorphisms alter transcriptional activity,and further studies are awaited to explore their association with physiological and pathological conditions.