Effects of acute microinjections of the thyroid hormone derivative 3-iodothyronamine to the preoptic region of adult male rats on sleep,thermoregulation and motor activity

The decarboxylated thyroid hormone derivative 3-iodothyronamine (T1AM) has been reported as having behavioral and physiological consequences distinct from those of thyroid hormones. Here, we investigate the effects of T1AM on EEG-defined sleep after acute administration to the preoptic region of adult male rats. Our laboratory recently demonstrated a decrease in EEG-defined sleep after administration of 3,3′,5-triiodo-l-thyronine (T3) to the same brain region. After injection of T1AM or vehicle solution, EEG, EMG, activity, and core body temperature were recorded for 24 h. Sleep parameters were determined from EEG and EMG data. Earlier investigations found contrasting systemic effects of T3 and T1AM, such as decreased heart rate and body temperature after intraperitoneal T1AM injection. However, nREM sleep was decreased in the present study after injections of 1 or 3 μg T1AM, but not after 0.3 or 10 μg, closely mimicking the previously reported effects of T3 administration to the preoptic region. The biphasic dose–response observed after either T1AM or T3 administration seems to indicate shared mechanisms and/or functions of sleep regulation in the preoptic region. Consistent with systemic administration of T1AM, however, microinjection of T1AM decreased body temperature. The current study is the first to show modulation of sleep by T1AM, and suggests that T1AM and T3 have both shared and independent effects in the adult mammalian brain.     

MDR1 mRNA expression and MDR1 gene variants as predictors of response to chemotherapy in patients with acute myeloid leukaemia: a meta-analysis

Abstract

Data from 30 pharmacogenomic studies that investigated MDR1 mRNA expression or gene variants (C3435T, G2677TA, C1236T) and response to therapy in acute myeloid leukaemia (AML) were synthesized. Anthracycline-based regimens were mainly used. MDR1 mRNA overexpression was associated with poor response to therapy [odds ratio (OR)?=?2.49 95% confidence interval (CI) 1.38–4.50]. The gene variants were not associated with response to treatment; the generalized ORs, a genetic model-free approach, for the variants C3435T, G2677TA and C1236T were OR_G?=?0.86 (95% CI 0.55–1.37), OR_G?=?0.97 (95% CI 0.58–1.64) and OR_G?=?1.17 (95% CI 0.75--1.83), respectively. There is indication that MDR1 mRNA expression may be considered as a potential marker for response to chemotherapy in AML patients.     

Identification of a region critical for proteolysis of the human growth hormone receptor.

Release of soluble growth hormone binding protein (GHBP) corresponding to the extracellular domain of the GH receptor (GHR) occurs via distinct mechanisms depending on species. In human, proteolysis of full length GHR results in liberation of GHBP into the extracellular medium. A putative protease responsive for GHR cleavage has been identified, however, the residues involved are still unknown. In this study, using the mutational approach to the extracellular domain of the human GHR, we demonstrated that deletion of three residues located close to the transmembrane domain abolishes constitutive GHBP shedding without change in cellular GH binding. Deletion also significantly decreased the phorbol 12-myristate 13-acetate (PMA)-induced release of GHBP and the accumulation of membrane-anchored remnant proteins. Taken together, these results suggest that integrity of the juxtamembrane region of GHR is necessary for its biochemical cleavage and that a common mechanism is involved in constitutive and PMA-induced shedding.     

Impact of stress hormone on adipogenesis in the 3T3-L1 adipocytes

Stress hormone is known to play a vital role in lipolysis and adipogenesis in fat cells. The present study was carried out to evaluate the effect of epinephrine on adipogenesis in the 3T3-L1 cells. The investigation on adipogenesis was done in both mono and co-cultured 3T3-L1 cells. 3T3-L1 preadipocytes and C2C12 cells were grown independently on transwell plates and transferred to differentiation medium. Following differentiation, C2C12 cells transferred to 3T3-L1 plate and treated with medium containing 10 μg/ml of epinephrine. Adipogenic markers such as fatty acid binding protein 4, peroxisome proliferator activating receptor, CCAAT/enhancer-binding protein, adiponectin, lipoprotein lipase and fatty acid synthase mRNA expressions were evaluated in the 3T3-L1 cells. Epinephrine treatment reduced adipogenesis, evidenced by reducing adipogenic marker mRNA expression in the 3T3-L1 cells. In addition, glycerol accumulation and oil red-O staining supported the reduced rate of adipogenesis. Taking all together, it is concluded that the stress hormone, epinephrine reduces the rate of adipogenesis in the mono and co-cultured 3T3-L1 cells. In addition, the rate of adipogenesis is much reduced in the co-cultured 3T3-L1 cells compared monocultured 3T3-L1 cells.     

Polymorphism C3435T of the MDR1 gene in Central Americans and Spaniards

The human multidrug resistance gene (MDR1) encodes for P-glycoprotein (P-gp) which is a transmembrane transporter protein that acts as an efflux pump for a number of lypophilic compounds. It plays a protective role for cells against DNA damage. The wobble C3435T polymorphism at exon 26 has been associated with different expression levels and activity. Differences in allele frequency of the C3435T polymorphism have been demonstrated between distinct ethnic groups. In our study we examined these polymorphisms in 433 healthy individuals. From these, 229 were Central American mestizos from Nicaragua (n = 117) and El Salvador (n = 112) to be compared with a group of 204 North Spaniards, with the aim of detecting potential genotypic differences between these populations. The genotypes were determined by PCR-RFLP. The frequencies of the C allele were very similar among Central Americans (0.53) and Spaniards (0.52), which is consistent with the ethnic origin of Central American individuals (Amerindians and European Caucasians). In comparison to other previously studied populations, the C allele frequency in Central Americans was significantly lower than that found in African populations and higher than that observed in the Indian and Southwest Asian populations. These data may be relevant for dose recommendation of P-gp substrate drugs and also for studies of allele disease association in the Central American population.     

Structural rearrangements in the thyroid hormone receptor hinge domain and their putative role in the receptor function

The thyroid hormone receptor (TR) D-domain links the ligand-binding domain (LBD, EF-domain) to the DNA-binding domain (DBD, C-domain), but its structure, and even its existence as a functional unit, are controversial. The D domain is poorly conserved throughout the nuclear receptor family and was originally proposed to comprise an unfolded hinge that facilitates rotation between the LBD and the DBD. Previous TR LBD structures, however, have indicated that the true unstructured region is three to six amino acid residues long and that the D-domain N terminus folds into a short amphipathic alpha-helix (H0) contiguous with the DBD and that the C terminus of the D-domain comprises H1 and H2 of the LBD. Here, we solve structures of TR-LBDs in different crystal forms and show that the N terminus of the TRalpha D-domain can adopt two structures; it can either fold into an amphipathic helix that resembles TRbeta H0 or form an unstructured loop. H0 formation requires contacts with the AF-2 coactivator-binding groove of the neighboring TR LBD, which binds H0 sequences that resemble coactivator LXXLL motifs. Structural analysis of a liganded TR LBD with small angle X-ray scattering (SAXS) suggests that AF-2/H0 interactions mediate dimerization of this protein in solution. We propose that the TR D-domain has the potential to form functionally important extensions of the DBD and LBD or unfold to permit TRs to adapt to different DNA response elements. We also show that mutations of the D domain LXXLL-like motif indeed selectively inhibit TR interactions with an inverted palindromic response element (F2) in vitro and TR activity at this response element in cell-based transfection experiments.     

Synthesis and SAR investigations of novel 2-arylbenzimidazole derivatives as melanin-concentrating hormone receptor 1 (MCH-R1) antagonists

Compounds containing 2-arybenzimidazole ring systems linked to arylpiperidines were synthesized and evaluated as MCH-R1 antagonists. The results of structure-activity relationship studies led to the identification of compound 4c as a potent MCH-R1 antagonist (IC₅₀ = 1 nM). This compound also has good metabolic stability, and favorable pharmacokinetic and brain penetration properties. However 4c was found to be potent inhibitor of the hERG potassium channel.     

Functional role of the cis-acting elements in human monocyte chemotactic protein-1 gene in the regulation of its expression by phorbol ester in human glioblastoma cells

The monocyte chemotactic protein-1 (MCP-1) is a 76 amino acid protein that specifically attracts monocytes. The expression of MCP-1 gene can be induced by lipopolysaccharides (LPS), phorbol esters (TPA) and several cytokines. However, how they regulate MCP-1 gene expression is not known. We tested whether the two putative TPA-responsive elements (TREs) and one B enhancer-like region found in the MCP-1 promoter region, are involved in this regulation of MCP-1 gene expression. The 5 untranslated region of MCP-1 gene was linked to chloramphenicol acetyl transferase (CAT) reporter gene and transfected into human glioblastoma cells in which endogenous MCP gene expression was found to be stimulated by TPA and tumor necrosis factor- (TNF-). The 128 bp 5-flanking region containing one TRE was adequate for basal promoter activity but the presence of both TREs in the MCP-1 promoter region were needed to give TPA responsive enhancement (2.5 fold) of expression of the marker gene. Mutations in either of the TRE's could abolish the TPA induction of CAT expression. Replacement of the B enhancer-like element with a TRE-like sequence caused a 10-fold enhancement of CAT expression by TPA treatment. Random mutation of B enhancer-like element did not affect CAT expression or its TPA induction. None of the MCP promoter constructs showed significant increase in CAT expression by treatment with tumor necrosis factor- (TNF-). This result suggested that the TNF regulation of MCP-1 gene involves other parts of the gene besides the proximal 5 flanking region. (Mol Cell Biochem141: 121–128, 1994)     

Thyroid hormone responsive genes in the murine hepatocyte cell line AML 12

Thyroid hormone (T3) plays an important role in gene regulation in the liver. Previous studies have been done in complex systems such as animal models, or in transformed malignant hepatic cell lines in which thyroid hormone receptor (TR) was over-expressed by co-transfection. Therefore, the aim of this study was to characterize T3-responsive genes in a simple system, by using a non-transformed hepatic cell line that is able to express sufficient amounts of endogenous TRs. For this purpose we used the murine non-transformed hepatocyte cell line AML 12. We performed analyses using a cDNA microarray containing 15,000 murine genes. We found 12 genes to be up-regulated and 5 genes to be down-regulated in the presence of T3. For some of the genes not previously known to be regulated by T3, we confirmed the regulation by T3 using real-time PCR. Our data in AML 12 cells provide a simple and physiologically relevant system to study T3 action, without the influence of neoplastic transformation or artificial TR over-expression. Furthermore, our data describe novel T3 responsive genes and provide insight into the role of T3 in important processes such as cholesterol metabolism, bile acid secretion, oncogenesis, among others, that can be tested in future experiments in vivo.