Anti-Trypanosoma activity of some natural stilbenoids and synthetic related heterocyclic compounds

We report the anti-Chagasic activity of the natural dihydrostilbenoid isonotholaenic acid and several simple derivatives, as well as that of some representative compounds of related synthetic series, with basic structures of benzalphthalides, dihydrostilbamides, isoindoles, phthalazin-1-ones, imidazo[2,1-a]isoindoles and pyrimido[2,1-a]isoindoles. The evaluation was performed in vitro on cultures of epimastigote and trypomastigote forms of Trypanosoma cruzi. Some of the tested compounds resulted to be as potent as benznidazole (epimastigotes), and others were shown to be more active than gentian violet (trypomastigotes), used as reference drugs.     

Nucleolar Organizer ultrastructure in Allium cepa

The Nuoleolar Organizer Region (NOR) was studied in Allium cepa. The cells analyzed were: meristematic root tip cells, cells from the layers of the anther (exothecium, intermediate layer cells, endothecium and tapetum) and meiocytes from preleptotene to diptotene. Conventional electron microscope techniques and serial section were used in the study. Ultracytochemical tests, using preferential techniques for nucleic acids were also applied. The results show that: a) Although the NOR may have a very variable form in the different cells analyzed, in each case its fine structure is similar, being constituted of chromatin differentiated in high and low density zones. b) In each case, its cytochemical characteristics are similar; highly positively to EDTA (preferential stain for RNP) being observed in the low density zones. As scattered chromatin these would constitute the active regions of the NOR. c) In certain cases a clear relationship is seen between NOR volume and the size of the nucleolus. d) The chromatin associated to the NOR always appears as very dense zones. e) The NOR-Nucleolus relationships are established exclusively with the latter's fibrillar pars. f) The nucleolar segregation phenomenon takes place sometimes as a result of a NOR contraction and in other cases depends on the position of the NOR in relation to the nucleolus. g) In preleptotene, the NOR shows its characteristic morphology and is positive to EDTA, while from zygotene to diplotene the structure of the NOR presents no differences from the rest of the chromatin and only the lateral elements of the synaptonemal complex or its remnants are positive to EDTA. h) The synaptonemal complex runs through the NOR with no differentiation and on occasions its lateral elements show associations with the nucleolus.     

Influence of heart failure on nucleolar organization and protein expression in human hearts

We investigate for the first time the influence of heart failure (HF) on nucleolar organization and proteins in patients with ischemic (ICM) or dilated cardiomyopathy (DCM). A total of 71 human hearts from ICM (n=38) and DCM (n=27) patients, undergoing heart transplantation and control donors (n=6), were analysed by western-blotting, RT-PCR and cell biology methods. When we compared protein levels according to HF etiology, nucleolin was increased in both ICM (117%, p<0.05) and DCM (141%, p<0.01). Moreover, mRNA expression were also upregulated in ICM (1.46-fold, p<0.05) and DCM (1.70-fold, p<0.05. Immunofluorescence studies showed that the highest intensity of nucleolin was into nucleolus (p<0.0001), and it was increased in pathological hearts (p<0.0001). Ultrastructure analysis by electron microscopy showed an increase in the nucleus and nucleolus size in ICM (17%, p<0.05 and 131%, p<0.001) and DCM (56%, p<0.01 and 69%, p<0.01). Nucleolar organization was influenced by HF irrespective of etiology, increasing fibrillar centers (p<0.001), perinucleolar chromatin (p<0.01) and dense fibrillar components (p<0.01). Finally, left ventricular function parameters were related with nucleolin levels in ischemic hearts (p<0.0001). The present study demonstrates that HF influences on morphology and organization of nucleolar components, revealing changes in the expression and in the levels of nucleolin protein.     

Influence of ovariectomy on cardiac oxidative stress in a renovascular hypertension model

The aim of this study was to evaluate the potential influence of endogenous ovarian hormones on cardiac oxidative stress in renovascular hypertension. Female Wistar rats (N = 10 per group) were divided among 4 groups: (i) normotensive control; (ii) hypertensive control; (iii) normotensive ovariectomized; and (iv) hypertensive ovariectomized rats. To induce hypertension, 2-kidney 1-clip (2K1C) Goldblatt's method was followed. Blood pressure (BP) was enhanced (25%) in 2K1C and it was not further altered in hypertensive ovariectomized animals. Lipid peroxidation (measured by thiobarbituric acid reactive substances; TBARS) increased in heart homogenates after ovariectomy (253%) and was additionally augmented when associated with hypertension (by 28%). Superoxide dismutase and catalase activities were similar in both hypertensive groups. Hypertension enhanced glutathione peroxidase activity (75%), but the association with ovariectomy prevented this change. Total radical trapping antioxidant potential (TRAP) decreased in hypertensive rats (34%) and was recovered when associated with ovariectomy. However, this adaptation seems not to be sufficient to avoid the increased oxidative damage in ovariectomized hypertensive animals. These results suggest a protective role for physiological ovarian hormones in the cardiac oxidative stress induced by 2K1C hypertension.     

Repeated treatment with the kappa opioid receptor agonist U69593 reverses enhanced K+ induced dopamine release in the nucleus accumbens, but not the expression of locomotor sensitization in amphetamine-sensitized rats

The effects after the acute activation of the kappa opioid receptor (KOR) can be distinguished from the effect after repeated administration of KOR agonist. Here, we report the effect of repeated administration of U69593 during abstinence after amphetamine-induced locomotor sensitization. Rats were injected once daily with amphetamine for five consecutive days. From day 6 to 9, rats that developed locomotor sensitization, received once daily injection of U69593 or vehicle. On day 10, all rats were injected with a challenging dose of amphetamine and locomotor activity was measured to assess the expression of sensitization. Microdialysis studies were carried out to assess dopamine extracellular levels in NAc. Rats that develop and express horizontal locomotor sensitization to amphetamine show increased dopamine release in the NAc induced by high K(+). The repeated treatment with U69593 reverses the sensitized depolarization-stimulated dopamine release in the NAc, but not the expression of locomotor sensitization induced by amphetamine. Thus, repeated activation of KORs during early amphetamine withdrawal dissociates the behavioral responses and the neurochemical responses that accompany the expression of sensitization to amphetamine.     

Cells lacking Rieske iron-sulfur protein have a reactive oxygen species-associated decrease in respiratory complexes I and IV

Mitochondrial respiratory complexes of the electron transport chain (CI, CIII, and CIV) can be assembled into larger structures forming supercomplexes. We analyzed the assembly/stability of respiratory complexes in mouse lung fibroblasts lacking the Rieske iron-sulfur protein (RISP knockout [KO]cells), one of the catalytic subunits of CIII. In the absence of RISP, most of the remaining CIII subunits were able to assemble into a large precomplex that lacked enzymatic activity. CI, CIV, and supercomplexes were decreased in the RISP-deficient cells. Reintroduction of RISP into KO cells restored CIII activity and increased the levels of active CI, CIV, and supercomplexes. We found that hypoxia (1% O(2)) resulted in increased levels of CI, CIV, and supercomplex assembly in RISP KO cells. In addition, treatment of control cells with different oxidative phosphorylation (OXPHOS) inhibitors showed that compounds known to generate reactive oxygen species (ROS) (e.g., antimycin A and oligomycin) had a negative impact on CI and supercomplex levels. Accordingly, a superoxide dismutase (SOD) mimetic compound and SOD2 overexpression provided a partial increase in supercomplex levels in the RISP KO cells. Our data suggest that the stability of CI, CIV, and supercomplexes is regulated by ROS in the context of defective oxidative phosphorylation.     

Structure of minimal tetratricopeptide repeat domain protein Tah1 reveals mechanism of its interaction with Pih1 and Hsp90

Tah1 and Pih1 are novel Hsp90 interactors. Tah1 acts as a cofactor of Hsp90 to stabilize Pih1. In yeast, Hsp90, Tah1, and Pih1 were found to form a complex that is required for ribosomal RNA processing through their effect on box C/D small nucleolar ribonucleoprotein assembly. Tah1 is a minimal tetratricopeptide repeat protein of 111 amino acid residues that binds to the C terminus of the Hsp90 molecular chaperone, whereas Pih1 consists of 344 residues of unknown fold. The NMR structure of Tah1 has been solved, and this structure shows the presence of two tetratricopeptide repeat motifs followed by a C helix and an unstructured region. The binding of Tah1 to Hsp90 is mediated by the EEVD C-terminal residues of Hsp90, which bind to a positively charged channel formed by Tah1. Five highly conserved residues, which form a two-carboxylate clamp that tightly interacts with the ultimate Asp-0 residue of the bound peptide, are also present in Tah1. Tah1 was found to bind to the C terminus of Pih1 through the C helix and the unstructured region. The C terminus of Pih1 destabilizes the protein in vitro and in vivo, whereas the binding of Tah1 to Pih1 allows for the formation of a stable complex. Based on our data, a model for an Hsp90-Tah1-Pih1 ternary complex is proposed.     

Identification of ETP-46321, a potent and orally bioavailable PI3K α, δ inhibitor

Phosphoinositide-3-kinase (PI3K) is an important target for cancer therapeutics due to the deregulation of this signaling pathway in a wide variety of human cancers. Herein, we describe the optimization of imidazo [1,2-a] pyrazines, which allow us to identify compound 14 (ETP-46321), with potent biochemical and cellular activity and good pharmacokinetic properties (PK) after oral dosing. ETP-46321 PK/PD studies showed time dependent downregulation of AKT(Ser473) phosphorylation, which correlates with compound levels in tumor tissue and demonstrating to be efficacious in a GEMM mouse tumor model driven by a K-Ras(G12V) oncogenic mutation. Treatment with ETP-46321 resulted in significant tumor growth inhibition.     

Rapid identification of ETP-46992, orally bioavailable PI3K inhibitor, selective versus mTOR

Phosphoinositide-3-kinases (PI3K) are a family of lipid kinases mediating numerous cell processes such as proliferation, migration and differentiation. PI3K is an important target for cancer therapeutics due to the deregulation of this signaling pathway in a wide variety of human cancers. Herein, we describe the rapid identification of ETP-46992, within 2-aminocarbonyl imidazo [1,2-a] pyrazine series, with suitable pharmacokinetic (PK) properties that allows the establishment of mechanism of action and efficacy in vivo studies. ETP-46992 showed tumor growth inhibition in a GEMM mouse tumor model driven by a K-Ras(G12V) oncogenic mutation and in tumor xenograft models with PI3K pathway deregulated (BT474).