Endogenous cholesterol synthesis is associated with VLDL-2 apoB-100 production in healthy humans

Subjects with high plasma cholesterol levels exhibit a high production of VLDL apolipoprotein B-100 (apoB-100), suggesting that cholesterol is a mediator for VLDL production. The objective of the study was to examine whether endogenous cholesterol synthesis, reflected by the lathosterol-cholesterol ratio (L-C ratio), affects the secretory rates of different VLDL subfractions. Ten healthy subjects were studied after overnight fasting. During a 10 h primed, constant infusion of 13C-valine (15 micromol/kg/h), enrichment was determined in apoB-100 from ultracentrifugally isolated VLDL-1 and VLDL-2 by gas chromatography mass spectrometry. The synthesis rates of VLDL-1 apoB-100 and VLDL-2 apoB-100, catabolism, and transfer were estimated by compartmental analysis. Mean VLDL-1 apoB-100 pool size was 90 +/- 15 mg, and mean VLDL-2 apoB-100 pool size was 111 +/- 14 mg. Absolute synthesis rate of VLDL-1 apoB-100 was 649 +/- 127 mg/day and 353 +/- 59 mg/day for VLDL-2 apoB-100. There was a strong association between the absolute synthesis rate of VLDL-2 apoB-100 and L-C ratio (r 2 = 0.61, P < 0.01). In contrast, no correlation was observed between L-C ratio and absolute synthesis rate of VLDL-1 apoB-100 (r 2 = 0.302, P = 0.09). In conclusion, these data provide additional support for an independent regulation of VLDL-1 apoB-100 and VLDL-2 apoB-100 production.Endogenous cholesterol synthesis is correlated only with the VLDL-2 apoB-100 production.     

Role of the C-terminal 28 residues of beta2-microglobulin in amyloid fibril formation

Beta2microglobulin (beta2m) is the major protein component of the fibrillar amyloid deposits isolated from patients diagnosed with dialysis-related amyloidosis (DRA). While investigating the molecular mechanism of amyloid fibril formation by beta2m, we found that the beta2m C-terminal peptide of 28 residues (cbeta2m) itself forms amyloid fibrils. When viewed by electron microscopy, cbeta2m aggregates appear as elongated unbranched fibers, the morphology typical for amyloids. Cbeta2m fibers stain with Congo red and show apple-green birefringence in polarized light, characteristic of amyloids. The observation that the beta2m C-terminal fragment readily forms amyloid fibrils implies that beta2m amyloid fibril formation proceeds via interactions of amyloid forming segments, which become exposed when the beta2m subunit is partially unfolded.     

Ascorbic acid induces a marked conformational change in long duplex DNA.

Ascorbic acid is often regarded as an antioxidant in vivo, where it protects against cancer by scavenging DNA-damaging reactive oxygen species. However, the detailed mechanism of the action of ascorbic acid on genetic DNA is still unclear. We examined the effect of ascorbic acid on the higher-order structure of DNA through real-time observation by fluorescence microscopy. We found that ascorbic acid generates a pearling structure in single giant DNA molecules, with elongated and compact regions coexisting along a molecular chain. Results from electron microscopy and atomic force microscopy indicate that the compact regions assume a loosely packed conformation. A possible mechanism for the induction of this conformational change is discussed in relation to the interplay between the higher-order and second-order structures of DNA.     

4-Hydroxy hexenal derived from dietary n-3 polyunsaturated fatty acids induces anti-oxidative enzyme heme oxygenase-1 in multiple organs

It has recently been reported that expression of heme oxygenase-1 (HO-1) plays a protective role against many diseases. Furthermore, n-3 polyunsaturated fatty acids (PUFAs) were shown to induce HO-1 expression in several cells in vitro, and in a few cases also in vivo. However, very few reports have demonstrated that n-3 PUFAs induce HO-1 in vivo.     

Rhododendrol biosynthesis and metabolism in Acer nikoense callus

Cell suspensions derived from Acer nikoense callus, not containing (S)-rhododendrol, converted 4-(p-hydroxyphenyl)-2- butanone into (R)-, (S)-rhododendrol and their glycosides. (R)- and (S)-rhododendrol formed was only detected in the culture medium and their glycosides only in the cells. The former compound disappeared within a short time and the latter one also tended to decrease during prolonged culture. Quantitative analysis of rhododendrol glycosides in the callus showed that most of them were (S)-rhododendrol 2-O--D-glucopyranoside and its content was much lower than that of the original plants. © Rapid Science Ltd. 1998     

Multiple independent evolutionary solutions to core histone gene regulation

Background  

Core histone genes are periodically expressed along the cell cycle and peak during S phase. Core histone gene expression is deeply evolutionarily conserved from the yeast Saccharomyces cerevisiae to human.     

Pyrophosphate inhibits mineralization of osteoblast cultures by binding to mineral, up-regulating osteopontin, and inhibiting alkaline phosphatase activity

Inorganic pyrophosphate (PP(i)) produced by cells inhibits mineralization by binding to crystals. Its ubiquitous presence is thought to prevent "soft" tissues from mineralizing, whereas its degradation to P(i) in bones and teeth by tissue-nonspecific alkaline phosphatase (Tnap, Tnsalp, Alpl, Akp2) may facilitate crystal growth. Whereas the crystal binding properties of PP(i) are largely understood, less is known about its effects on osteoblast activity. We have used MC3T3-E1 osteoblast cultures to investigate the effect of PP(i) on osteoblast function and matrix mineralization. Mineralization in the cultures was dose-dependently inhibited by PP(i). This inhibition could be reversed by Tnap, but not if PP(i) was bound to mineral. PP(i) also led to increased levels of osteopontin (Opn) induced via the Erk1/2 and p38 MAPK signaling pathways. Opn regulation by PP(i) was also insensitive to foscarnet (an inhibitor of phosphate uptake) and levamisole (an inhibitor of Tnap enzymatic activity), suggesting that increased Opn levels did not result from changes in phosphate. Exogenous OPN inhibited mineralization, but dephosphorylation by Tnap reversed this effect, suggesting that OPN inhibits mineralization via its negatively charged phosphate residues and that like PP(i), hydrolysis by Tnap reduces its mineral inhibiting potency. Using enzyme kinetic studies, we have shown that PP(i) inhibits Tnap-mediated P(i) release from beta-glycerophosphate (a commonly used source of organic phosphate for culture mineralization studies) through a mixed type of inhibition. In summary, PP(i) prevents mineralization in MC3T3-E1 osteoblast cultures by at least three different mechanisms that include direct binding to growing crystals, induction of Opn expression, and inhibition of Tnap activity.     

A dual inhibitor against prolyl isomerase Pin1 and cyclophilin discovered by a novel real-time fluorescence detection method

Pin1, a peptidyl prolyl cis/trans isomerase (PPIase), is a potential target molecule for cancer, infectious disease, and Alzheimer’s disease. We established a high-throughput screening method for Pin1 inhibitors, which employs a real-time fluorescence detector. This screening method identified 66 compounds that inhibit Pin1 out of 9756 compounds from structurally diverse chemical libraries. Further evaluations of surface plasmon resonance methods and a cell proliferation assay were performed. We discovered a cell-active inhibitor, TME-001 (2-(3-chloro-4-fluoro-phenyl)-isothiazol-3-one). Surprisingly, kinetic analyses revealed that TME-001 is the first compound that exhibits dual inhibition of Pin1 (IC₅₀ = 6.1 μM) and cyclophilin, another type of PPIase, (IC₅₀ = 13.7 μM). This compound does not inhibit FKBP. This finding suggests the existence of similarities of structure and reaction mechanism between Pin1 and cyclophilin, and may lead to a more complete understanding of the active sites of PPIases.     

Hydrogen peroxide spraying alleviates drought stress in soybean plants

To ascertain the effect of exogenously applied hydrogen peroxide (H₂O₂) on drought stress, we examined whether the spraying of soybean leaves with H₂O₂ would alleviate the symptoms of drought stress. Pre-treatment by spraying leaves with H₂O₂ delayed foliar wilting caused by drought stress compared to leaves sprayed with distilled water (DW). Additionally, the relative water content of drought-stressed leaves pre-treated with H₂O₂ was higher than that of leaves pre-treated with DW. Therefore, we analyzed the effect of H₂O₂ spraying on photosynthetic parameters and on the biosynthesis of oligosaccharides related to water retention in leaves during drought stress. Under conditions of drought stress, the net photosynthetic rate and stomatal conductance of leaves pre-treated with H₂O₂ were higher than those of leaves pre-treated with DW. In contrast to DW spraying, H₂O₂ spraying immediately caused an increase in the mRNA levels of d-myo-inositol 3-phosphate synthase 2 (GmMIPS2) and galactinol synthase (GolS), which encode key enzymes for the biosynthesis of oligosaccharides known to help plants tolerate drought stress. In addition, the levels of myo-inositol and galactinol were higher in H₂O₂-treated leaves than in DW-treated leaves. These results indicated that H₂O₂ spraying enabled the soybean plant to avoid drought stress through the maintenance of leaf water content, and that this water retention was caused by the promotion of oligosaccharide biosynthesis rather than by rapid stomatal closure.