Systematic construction of a conceptual minimal model of plasma cholesterol levels based on knockout mouse phenotypes

Elevated plasma cholesterol, a well-known risk factor for cardiovascular diseases, is the result of the activity of many genes and their encoded proteins in a complex physiological network. We aim to develop a minimal kinetic computational model for predicting plasma cholesterol levels. To define the scope of this model, it is essential to discriminate between important and less important processes influencing plasma cholesterol levels. To this end, we performed a systematic review of mouse knockout strains and used the resulting dataset, named KOMDIP, for the identification of key genes that determine plasma cholesterol levels. Based on the described phenotype of mouse knockout models, 36 of the 120 evaluated genes were marked as key genes that have a pronounced effect on the plasma cholesterol concentration. The key genes include well-known genes, e.g., Apoe and Ldlr, as well as genes hardly linked to cholesterol metabolism so far, e.g., Plagl2 and Slc37a4. Based on the catalytic function of the genes, a minimal conceptual model was defined. A comparison with nine conceptual models from literature revealed that each of the individual published models is less complete than our model. Concluding, we have developed a conceptual model that can be used to develop a physiologically based kinetic model to quantitatively predict plasma cholesterol levels.     

Involvement of androgen receptor in nitric oxide production induced by icariin in human umbilical vein endothelial cells

Icariin, a flavonoid isolated from Epimedii herba, stimulated phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177, Akt (Ser473) and ERK1/2 (Thr202/Tyr204). The icariin-induced eNOS phosphorylation was abolished by an androgen receptor (AR) antagonist, nilutamide in human umbilical vein endothelial cells (HUVECs). Furthermore, it was also reduced in the cells transfected with small interfering RNA in which the expression of AR was broken down. The icariin-induced eNOS phosphorylation was inhibited by wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor and partially attenuated by PD98059, an upstream inhibitor for ERK1/2. These data suggest that icariin stimulates release of NO by AR-dependent activation of eNOS in HUVECs. PI3K/Akt and MAPK-ERK kinase (MEK)/ERK1/2 pathways were involved in the phosphorylation of eNOS by icariin.     

Impact of mitochondriotropic quercetin derivatives on mitochondria

Mitochondria-targeted polyphenols are being developed with the intent to intervene on the levels of reactive oxygen species (ROS) in mitochondria. Polyphenols being more than just anti-oxidants, the interaction of these derivatives with the organelles needs to be characterised. We have studied the effects of two quercetin derivatives, 3-(4-O-triphenylphosphoniumbutyl)quercetin iodide (Q3BTPI) and its tetracetylated analogue (QTA3BTPI), on the inner membrane aspecific permeability, transmembrane voltage difference and respiration of isolated rat liver mitochondria. While the effects of low concentrations were too small to be reliably defined, when used in the 5-20 μM range these compounds acted as inducers of the mitochondrial permeability transition (MPT), an effect due to pro-oxidant activity. Furthermore, Q3BTPI behaved as an uncoupler of isolated mitochondria, causing depolarisation and stimulating oxygen consumption. When applied to tetramethylrhodamine methyl ester (TMRM)-loaded HepG2 or Jurkat cells uptake of the compounds was predictably associated with a loss of TMRM fluorescence, but there was no indication of MPT induction. A production of superoxide could be detected in some cells upon prolonged incubation of MitoSOX®-loaded cells with QTA3BTPI. The overall effects of these model mitochondriotropic polyphenols may thus differ considerably depending on whether their hydroxyls are protected or not and on the experimental system. In vivo assays will be needed for a definitive assessment of their bioactivities.     

Structure–activity relationship of marinostatin,a serine protease inhibitor isolated from a marine organism

A 12‐residue MST isolated from a marine organism is a potent serine protease inhibitor that has a double cyclic structure composed of two ester linkages formed between the β‐hydroxyl and β‐carboxyl groups, Thr³‐Asp⁹ and Ser⁸‐Asp¹¹. MST was synthesized by a regioselective esterification procedure employing two sets of orthogonally removable side‐chain protecting groups for the Asp and Ser/Thr residues. In the MST molecule, there were no significant changes observed in yield by changing the order of esterification. SAR study of MST revealed that the minimum required structure for expressing the inhibitory activity is the sequence (1–9) in a monocyclic structure where Pro⁷ located in the ring plays a crucial role in keeping the structural rigidity. By applying the structural motif of MST, we rationally designed protease inhibitory specificities that differ from those of the natural product. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Enhancement of Enantioselectivity in the Bacillus subtilis Protease-catalyzed Hydrolysis of N-free Amino Acid Esters using the Ester Grouping-modification Approach

The generality of enantioselectivity enhancement through the modification of the alcohol moiety of a substrate ester was ascertained, for in the Bacillus subtilis protease-catalyzed hydrolysis of N-unprotected amino acid esters the enantioselectivity was enhanced largely by switching the conventional methyl ester to esters with a longer alkyl chain such as the isobutyl ester (from E = 3 to E = 130–170 in the case of 4-fluorophenylalanine esters) as in the enzymatic hydrolysis mediated by Aspergillus oryzae protease. There was indeed a profound dependence of E on the nature of the ester grouping.     

Recent advances in chlorophyll biosynthesis

The importance of chlorophyll (Chl) to the process of photosynthesis is obvious, and there is clear evidence that the regulation of Chl biosynthesis has a significant role in the regulation of assembly of the photosynthetic apparatus. The understanding of Chl biosynthesis has rapidly advanced in recent years. The identification of genetic loci associated with each of the biochemical steps has been accompanied by a greater appreciation of the role of Chl biosynthesis intermediates in intracellular signaling. The purpose of this review is to provide a source of information for all the steps in Chl and bacteriochlorophyll a biosynthesis, with an emphasis on steps that are believed to be key regulation points.     

Intravenous administration of mannosylated cationic liposome/NFkappaB decoy complexes effectively prevent LPS-induced cytokine production in a murine liver failure model

The purpose of this study was to inhibit endotoxin induced cytokines production and liver injury by liver non-parenchymal cell (NPC) selective delivery of nuclear factor kappaB (NFkappaB) decoy using mannosylated cationic liposomes (Man-liposomes). In this study, we examined the distribution, inhibitory effect on cytokines production and ALT/AST of intravenously injected Man-liposome/NFkappaB decoy complex. Man-liposome/[(32)P] NFkappaB decoy complexes mostly accumulated in the liver, preferentially in NPC. In a murine lipopolysaccharide-induced liver failure model, the production of tumor necrosis factor-alpha (TNFalpha), IFNgamma, IL1-beta, ALT and AST were effectively reduced by Man-liposome complexes. However, cationic or galactosylated cationic liposome complexes could not inhibit TNFalpha production.     

Characterization of novel imidazole derivative, JM-8686, a potent inhibitor of allene oxide synthase

The inhibitory properties of a first synthetic jasmonic acid biosynthesis inhibitor, JM-8686, were investigated. Steady-state kinetic analysis indicates that the compound is a competitive inhibitor of allene oxide synthase (AOS) with a K(i) value of approximate 0.62+/-0.15 microM. Dialysis experiment indicates that AOS inactivation by JM-8686 is reversible. The optical difference spectroscopy analysis of JM-8686 and AOS interaction indicates that JM-8686 induced type II binding spectra with a K(d) value of approximate 1.6+/-0.2 microM, suggesting that JM-8686 binds to the prosthetic heme iron of AOS. Comparison of the inhibitory potency of the compound against HPL (CYP74B) from tomato revealed that JM-8686 was a highly selective inhibitor for AOS.     

Involvement of Na+/H+ exchanger in the calcium signaling in epimastigotes of Trypanosoma cruzi

We studied the effect of Na(+) extracellular on Ca(2+) mobilization from intracellular store evoked by carbachol in Trypanosoma cruzi. We report that slow component of Ca(2+) signaling evoked by agonist is dependent on extracellular Na(+) but not on InsP(3) increase. Moreover, this Ca(2+) signaling progressively increased when pH of the medium changed from 7.0 to 7.8. In addition, we found that it was regulated by PKC. The agonist was also able to induce the alkalinization of the acidic compartment, and both Ca(2+) signaling and alkalinization were inhibited by the EIPA-inhibitor of the Na(+)/H(+) exchanger. These results demonstrated the alkalinization of acidic vacuoles and PKC are involved in the triggering of the epimastigote Ca(2+) signaling.