Inhibition of prostate growth and inflammation by the vitamin D receptor agonist BXL-628 (elocalcitol)

The prostate is a target organ of vitamin D receptor (VDR) agonists and represents an extra-renal site of 1,25-dihydroxyvitamin D₃ synthesis, but its capacity to respond to VDR agonists has, so far, been almost exclusively probed for the treatment of prostate cancer. We have analyzed the capacity of VDR agonists to treat benign prostatic hyperplasia (BPH), a complex syndrome characterized by a static component related to prostate overgrowth, a dynamic one responsible for urinary irritative symptoms, and an inflammatory component. Preclinical data demonstrate that VDR agonists, and notably BXL-628 (elocalcitol), reduce the static component of BPH by inhibiting the activity of intra-prostatic growth factors downstream of the androgen receptor, and the dynamic component by targeting bladder cells. In addition, BXL-628 inhibits production of proinflammatory cytokines and chemokines by human BPH cells. These data have led to a proof-of-concept clinical study that has successfully shown arrest of prostate growth in BPH patients treated with BXL-628, with excellent safety. We have documented the anti-inflammatory effects of BXL-628 also in animal models of autoimmune prostatitis, observing a significant reduction of intra-prostatic cell infiltrate following administration of this VDR agonist, at normocalcemic doses, in mice with already established disease. These data extend the potential use of VDR agonists to novel indications that represent important unmet medical needs, and provide a sound rationale for further clinical testing.     

Synthesis, resolution, stereochemistry, and molecular modeling of (R)- and (S)-2-acetyl-1-(4'-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline AMPAR antagonists

Recently we identified (R,S)-2-acetyl-1-(4'-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (6) as a potent non-competitive AMPA receptor antagonist able to prevent epileptic seizures. We report here the optimized synthesis of compound 6, its resolution by chiral preparative HPLC, and the absolute configuration of (R)-enantiomer established by X-ray diffractometry. The biological tests of the single enantiomers revealed that higher anticonvulsant and antagonistic effects reside in (R)-enantiomer as also suggested by molecular modeling studies.     

Crystal structures of human and murine deoxyribonucleotidases: insights into recognition of substrates and nucleotide analogues

Cytosolic 5'(3')-deoxyribonucleotidase (cdN) and mitochondrial 5'(3')-deoxyribonucleotidase (mdN) catalyze the dephosphorylation of deoxyribonucleoside monophosphates and regulate dTTP formation in cytosol and mitochondria, protecting DNA replication from imbalanced precursor pools. They can also interfere with the phosphorylation-dependent activation of nucleoside analogues used in anticancer and antiviral treatment. To understand the relatively narrow substrate specificity of these two enzymes and their ability to use nucleotide analogues as substrates, we determined the crystal structures of human cdN in complex with deoxyuridine, murine cdN in complex with dUMP and dGMP, and human mdN in complex with the nucleotide analogues AZTMP and BVdUMP. Our results show that the active site residues Leu45 and Tyr65 in cdN form a more favorable binding surface for purine nucleotides than the corresponding Trp75 and Trp76 in mdN, explaining why cdN has higher activity for purine nucleotides than does mdN. The molecular interactions of mdN with AZTMP and BVdUMP indicate why these nucleotide analogues are poorer substrates as compared with the physiological substrate, and they provide a structural rationale for the design of drugs that are less prone to inactivation by the deoxyribonucleotidases. We suggest that introduction of substituents in the 3'-position may result in nucleoside analogues with increased resistance to dephosphorylation.     

Impact of detubulation on force and kinetics of cardiac muscle contraction

Action potential–driven Ca²⁺ currents from the transverse tubules (t-tubules) trigger synchronous Ca²⁺ release from the sarcoplasmic reticulum of cardiomyocytes. Loss of t-tubules has been reported in cardiac diseases, including heart failure, but the effect of uncoupling t-tubules from the sarcolemma on cardiac muscle mechanics remains largely unknown. We dissected intact rat right ventricular trabeculae and compared force, sarcomere length, and intracellular Ca²⁺ in control trabeculae with trabeculae in which the t-tubules were uncoupled from the plasma membrane by formamide-induced osmotic shock (detubulation). We verified disconnection of a consistent fraction of t-tubules from the sarcolemma by two-photon fluorescence imaging of FM4-64–labeled membranes and by the absence of tubular action potential, which was recorded by random access multiphoton microscopy in combination with a voltage-sensitive dye (Di-4-AN(F)EPPTEA). Detubulation reduced the amplitude and prolonged the duration of Ca²⁺ transients, leading to slower kinetics of force generation and relaxation and reduced twitch tension (1 Hz, 30°C, 1.5 mM [Ca²⁺]_o). No mechanical changes were observed in rat left atrial trabeculae after formamide shock, consistent with the lack of t-tubules in rodent atrial myocytes. Detubulation diminished the rate-dependent increase of Ca²⁺-transient amplitude and twitch force. However, maximal twitch tension at high [Ca²⁺]_o or in post-rest potentiated beats was unaffected, although contraction kinetics were slower. The ryanodine receptor (RyR)2 Ca-sensitizing agent caffeine (200 µM), which increases the velocity of transverse Ca²⁺ release propagation in detubulated cardiomyocytes, rescued the depressed contractile force and the slower twitch kinetics of detubulated trabeculae, with negligible effects in controls. We conclude that partial loss of t-tubules leads to myocardial contractile abnormalities that can be rescued by enhancing and accelerating the propagation of Ca²⁺-induced Ca²⁺ release to orphan RyR2 clusters.     

The HIV Matrix Protein p17 Promotes the Activation of Human Hepatic Stellate Cells through Interactions with CXCR2 and Syndecan-2

Background

The human immunodeficiency virus type 1 (HIV-1) p17 is a matrix protein involved in virus life''s cycle. CXCR2 and Syndecan-2, the two major coreceptors for the p17 protein, are expressed in hepatic stellate cells (HSCs), a key cell type involved in matrix deposition in liver fibrotic disorders.

Aim

In this report we have investigated the in vitro impact of p17 on HSCs transdifferentiation and function and underlying signaling pathways involved in these processes.

Methods

LX-2 cells, a human HSC line, and primary HSC were challenged with p17 and expressions of fibrogenic markers and of p17 receptors were assessed by qRT-PCR and Western blot. Downstream intracellular signaling pathways were evaluated with qRT-PCR and Western blot as well as after pre-treatment with specific pathway inhibitors.

Results

Exposure of LX2 cells to p17 increases their contractile force, reshapes the cytoskeleton fibers and upregulates the expression of transdifferentiation markers including αSMA, COL1α1 and endothelin-1 through the activation of Jak/STAT and Rho signaling pathways. These effects are lost in HSCs pre-incubated with a serum from HIV positive person who underwent a vaccination with a p17 peptide. Confocal laser microscopy studies demonstrates that CXCR2 and syndecan-2 co-associate at the plasma membrane after exposure to p17. Immunostaining of HIV/HCV liver biopsies from co-infected patients reveals that the progression of liver fibrosis correlates with a reduced expression of CXCR2.

Conclusions

The HIV matrix protein p17 is pro-fibrogenic through its interactions both with CXCR2 and syndecan-2 on activated HSCs.     

From a 2DE-Gel Spot to Protein Function: Lesson Learned From HS1 in Chronic Lymphocytic Leukemia

The identification of molecules involved in tumor initiation and progression is fundamental for understanding disease’s biology and, as a consequence, for the clinical management of patients. In the present work we will describe an optimized proteomic approach for the identification of molecules involved in the progression of Chronic Lymphocytic Leukemia (CLL). In detail, leukemic cell lysates are resolved by 2-dimensional Electrophoresis (2DE) and visualized as “spots” on the 2DE gels. Comparative analysis of proteomic maps allows the identification of differentially expressed proteins (in terms of abundance and post-translational modifications) that are picked, isolated and identified by Mass Spectrometry (MS). The biological function of the identified candidates can be tested by different assays (i.e. migration, adhesion and F-actin polymerization), that we have optimized for primary leukemic cells.     

Iron overload enhances the development of experimental liver cirrhosis in mice

The role of iron in initiating liver fibrosis in iron overload diseases is not clearly established. Partly, this is due to the lack of suitable animal models that can produce the full liver pathology seen in genetic hemochromatosis. Recent advances in this field have demonstrated that iron may be interacting with other potential liver-damaging agents. The aim of this study was to investigate if feeding with carbonyl iron (CI) facilitates the development of carbon tetrachloride (CCl4)-induced liver fibrosis in the mouse. Mice were given a diet containing 3% CI and treated with CCl4 intraperitoneally twice weekly and 5% alcohol added to the drinking water for 12 weeks. Hepatic iron content increased 15- and 22-fold in animals receiving CI and CI + CCl4. At histological examination, iron-laden hepatocytes were found in CI treated animals, whereas these were absent in animals not exposed to CI. Mice receiving iron-enriched diet alone showed a mild fibrosis. Conversely, a marked collagen deposition was observed in CCl4 and CI + CCl4 groups. In particular, in this latter group, there was evidence of liver cirrhosis. Biochemical evaluation of collagen content substantiated histologic analysis. These results demonstrate that the addition of iron facilitates the development of cirrhosis in animals exposed to subtoxic doses of CCl4. This model may be useful in exploring the pathogenesis of liver cirrhosis. Moreover, its use in genetically altered mouse strains might provide new insight on the role of iron in fibrosis.     

Hydrophobicity and conformational change as mechanistic determinants for nonspecific modulators of amyloid β self-assembly

The link between many neurodegenerative disorders, including Alzheimer's and Parkinson's diseases, and the aberrant folding and aggregation of proteins has prompted a comprehensive search for small organic molecules that have the potential to inhibit such processes. Although many compounds have been reported to affect the formation of amyloid fibrils and/or other types of protein aggregates, the mechanisms by which they act are not well understood. A large number of compounds appear to act in a nonspecific way affecting several different amyloidogenic proteins. We describe here a detailed study of the mechanism of action of one representative compound, lacmoid, in the context of the inhibition of the aggregation of the amyloid β-peptide (Aβ) associated with Alzheimer's disease. We show that lacmoid binds Aβ(1-40) in a surfactant-like manner and counteracts the formation of all types of Aβ(1-40) and Aβ(1-42) aggregates. On the basis of these and previous findings, we are able to rationalize the molecular mechanisms of action of nonspecific modulators of protein self-assembly in terms of hydrophobic attraction and the conformational preferences of the polypeptide.     

Evidence that AMP-activated protein kinase can negatively modulate Ornithine decarboxylase activity in cardiac myoblasts

The responses of AMP-activated protein kinase (AMPK) and Ornithine decarboxylase (ODC) to isoproterenol have been examined in H9c2 cardiomyoblasts, AMPK represents the link between cell growth and energy availability whereas ODC, the key enzyme in polyamine biosynthesis, is essential for all growth processes and it is thought to have a role in the development of cardiac hypertrophy. Isoproterenol rapidly induced ODC activity in H9c2 cardiomyoblasts by promoting the synthesis of the enzyme protein and this effect was counteracted by inhibitors of the PI3K/Akt pathway. The increase in enzyme activity became significant between 15 and 30min after the treatment. At the same time, isoproterenol stimulated the phosphorylation of AMPKα catalytic subunits (Thr172), that was associated to an increase in acetyl coenzyme A carboxylase (Ser72) phosphorylation. Downregulation of both α1 and α2 isoforms of the AMPK catalytic subunit by siRNA to knockdown AMPK enzymatic activity, led to superinduction of ODC in isoproterenol-treated cardiomyoblasts. Downregulation of AMPKα increased ODC activity even in cells treated with other adrenergic agonists and in control cells. Analogue results were obtained in SH-SY5Y neuroblastoma cells transfected with a shRNA construct against AMPKα. In conclusion, isoproterenol quickly activates in H9c2 cardiomyoblasts two events that seem to contrast one another. The first one, an increase in ODC activity, is linked to cell growth, whereas the second, AMPK activation, is a homeostatic mechanism that negatively modulates the first. The modulation of ODC activity by AMPK represents a mechanism that may contribute to control cell growth processes.