Active Species for Ce(IV)-Induced Hydrolysis of Phosphodiester Linkage in cAMP AND DNA

The hydrolysis of cyclic adenosine 3′,5′-monophosphate and 2′-deoxythymidylyl(3′-5′)2′-deoxythymidine by Ce(NH₄)₂(NO₃)₆ was kinetically studied. The rate of hydrolysis was fairly proportional to the concentration of [Ce ^IV ₂ (OH)₄]⁴⁺, showing that this is the catalytically active species. According to quantum-chemical calculation, the two Ce(IV) ions in this [Ce^IV ₂(OH)₄]⁴⁺ cluster are bridged by two OH residues. Upon the complex formation with H₂ PO₄ ^? (a model compound for the phosphodiesters), these two Ce(IV) ions bind the two oxygen atoms of the substrate and enhance the electrophilicity of the phosphorus atom. The catalytic mechanism of Ce(IV)-induced hydrolysis of phosphodiesters has been proposed on the basis these results.     

Thermophilic microspheres of peptide-like polymers and silicates formed at 250 degrees C

We examined the possibility of chemical evolution in superheated hydrothermal environments and found the formation of microspheres at 250 degrees C and above from a mixture of glycine, alanine, valine, and aspartic acid. The microspheres did not form at lower temperatures and consisted of silicates and peptide-like polymers that contained imide bonds and amino acid residues having an abundance of valine. The results show the possibility of thermophilic cellular structures, which might be adopted by the extremely thermophilic organisms, if they exist, reported by Baross and Deming.     

4-Hydroxydigitolutein,a new anthraquinone from callus tissue of Digitalis lanata

Many anthraquinone derivatives were isolated from the callus tissue of Digitalis lanata (Scrophulariaceae). Two of them were digitolutein (I) and a new anthraquinone 4-hydroxydigitolutein (II). The chemical structure of 4-hydroxydigitolutein was established to be 3-methylpurpurin 1-methyl ether by mass i.r. and NMR spectra and mixed melting point test with synthetic sample. Anthraquinone derivatives have been found for the first time in plant tissue cultures.     

Insulin-like growth factor-I stimulates diacylglycerol production via multiple pathways in Balb/c 3T3 cells

We previously reported that insulin-like growth factor-I (IGF-I) induced sustained calcium cycling across the plasma membrane in primed competent Balb/c 3T3 cells (Kojima, I., Matsunaga, H., Kurokawa, K., Ogata, E., and Nishimoto, I. (1989) J. Biol. Chem. 263, 16561-16567). The present study was conducted to examine whether IGF-I affected cellular metabolism of 1,2-diacylglycerol (1,2-DAG). In primed competent cells prelabeled with [3H]myristate, 1 nM IGF-I caused a 50% increase in [3H]DAG within 10 min. This increase in [3H]DAG was accompanied by 1) a decrease in radioactivity in the glycosylphosphatidylinositol fraction in [3H]glucosamine-labeled cells and a concomitant increase in [3H]inositol-glycan, and 2) a decrease in [3H]phosphatidylcholine and a concomitant elevation of [3H]phosphorylcholine in [3H]choline-labeled cells. When [3H]choline-labeled cells were treated with 10 nM 12-O-tetradecanoylphorbol-4-acetate (TPA), [3H]phosphatidylcholine was reduced by 50%. The TPA-induced reduction of [3H]phosphatidylcholine was completely blocked by 50 microM sphingosine and 50 microM H-7, inhibitors of protein kinase C. Both sphingosine and H-7 attenuated IGF-I-mediated reduction of [3H]phosphatidylcholine. In addition, treatment with IGF-I for 3 h or more resulted in sustained increase in 1,2-DAG mass, which was attenuated by cycloheximide. The increase in DAG mass was accompanied by enhanced incorporation of [14C]glucose into 1,2-DAG. These results indicate that, in primed competent Balb/c 3T3 cells, IGF-I stimulates 1,2-DAG production via multiple pathways and that IGF-I may induce breakdown of phosphatidylcholine by a mechanism involving protein kinase C.     

Tumour-suppressive microRNA-224 inhibits cancer cell migration and invasion via targeting oncogenic TPD52 in prostate cancer

Our recent study of the microRNA expression signature of prostate cancer (PCa) revealed that microRNA-224 (miR-224) is significantly downregulated in PCa tissues. Here, we found that restoration of miR-224 significantly inhibits PCa cell migration and invasion. Additionally, we found that oncogenic TPD52 is a direct target of miR-224 regulation. Silencing of the TPD52 gene significantly inhibits cancer cell migration and invasion. Moreover, TPD52 expression is upregulated in cancer tissues and negatively correlates with miR-224 expression. We conclude that loss of tumour-suppressive miR-224 enhances cancer cell migration and invasion in PCa through direct regulation of oncogenic TPD52.     

Elevated mitochondrial biogenesis in skeletal muscle is associated with testosterone-induced body weight loss in male mice

Androgen reduces fat mass, although the underlying mechanisms are unknown. Here, we examined the effect of testosterone on heat production and mitochondrial biogenesis. Testosterone-treated mice exhibited elevated heat production. Treatment with testosterone increased the expression level of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), ATP5B and Cox4 in skeletal muscle, but not that in brown adipose tissue and liver. mRNA levels of genes involved in mitochondrial biogenesis were elevated in skeletal muscle isolated from testosterone-treated male mice, but were down-regulated in androgen receptor deficient mice. These results demonstrated that the testosterone-induced increase in energy expenditure is derived from elevated mitochondrial biogenesis in skeletal muscle.     

Rod Visual Pigment Optimizes Active State to Achieve Efficient G Protein Activation as Compared with Cone Visual Pigments

Most vertebrate retinas contain two types of photoreceptor cells, rods and cones, which show different photoresponses to mediate scotopic and photopic vision, respectively. These cells contain different types of visual pigments, rhodopsin and cone visual pigments, respectively, but little is known about the molecular properties of cone visual pigments under physiological conditions, making it difficult to link the molecular properties of rhodopsin and cone visual pigments with the differences in photoresponse between rods and cones. Here we prepared bovine and mouse rhodopsin (bvRh and mRh) and chicken and mouse green-sensitive cone visual pigments (cG and mG) embedded in nanodiscs and applied time-resolved fluorescence spectroscopy to compare their G_t activation efficiencies. Rhodopsin exhibited greater G_t activation efficiencies than cone visual pigments. Especially, the G_t activation efficiency of mRh was about 2.5-fold greater than that of mG at 37 °C, which is consistent with our previous electrophysiological data of knock-in mice. Although the active state (Meta-II) was in equilibrium with inactive states (Meta-I and Meta-III), quantitative determination of Meta-II in the equilibrium showed that the G_t activation efficiency per Meta-II of bvRh was also greater than those of cG and mG. These results indicated that efficient G_t activation by rhodopsin, resulting from an optimized active state of rhodopsin, is one of the causes of the high amplification efficiency of rods.     

Neovessel formation promotes liver fibrosis via providing latent transforming growth factor-β

Aim

Hepatic fibrosis and angiogenesis occur in parallel during the progression of liver disease. Fibrosis promotes angiogenesis via inducing vascular endothelial growth factor (VEGF) from the activated hepatic stellate cells (HSCs). In turn, increased neovessel formation causes fibrosis, although the underlying molecular mechanism remains undetermined. In the current study, we aimed to address a role of endothelial cells (ECs) as a source of latent transforming growth factor (TGF)-β, the precursor of the most fibrogenic cytokine TGF-β.

Methods

After recombinant VEGF was administered to mice via the tail vein, hepatic angiogenesis and fibrogenesis were evaluated using immunohistochemical and biochemical analyses in addition to investigation of TGF-β activation using primary cultured HSCs and liver sinusoidal ECs (LSECs).

Results

In addition to increased hepatic levels of CD31 expression, VEGF-treated mice showed increased α-smooth muscle actin (α-SMA) expression, hepatic contents of hydroxyproline, and latency associated protein degradation products, which reflects cell surface activation of TGF-β via plasma kallikrein (PLK). Liberating the PLK-urokinase plasminogen activator receptor complex from the HSC surface by cleaving a tethering phosphatidylinositol linker with its specific phospholipase C inhibited the activating latent TGF-β present in LSEC conditioned medium and subsequent HSC activation.

Conclusion

Neovessel formation (angiogenesis) accelerates liver fibrosis at least in part via provision of latent TGF-β that activated on the surface of HSCs by PLK, thereby resultant active TGF-β stimulates the activation of HSCs.