Peroxidase-catalyzed generation of catechin oligomers that inhibit glucosyltransferase from Streptococcus sobrinus

Abstract Oolong tea extract (OTE) and the purified polymeric polyphenols from OTE have been found to inhibit glucosyltransferase (GTase) of mutans streptococci. In view of the partial fermentation characteristic of oolong tea, we describe here an in vitro model reaction system to produce partially fermented products of d-(+)-catechin or green tea extract (GTE) using horseradish peroxidase. A dimeric catechin molecule was identified as dehydro-dicatechin A by instrumental analyses. The molecular size of some oligomeric catechins was estimated by the elution profile with HPLC. These catechin oligomers markedly inhibited GTase from Streptococcus sobrinus 6715. As the degree of polymerization of catechin or GTE increased, GTase was inhibited more effectively. These results suggest that polymeric polyphenols found in OTE are synthesized by partial fermentation due to oxidases/peroxidases present in tea leaves.     

Altered prostatic epithelial proliferation and apoptosis, prostatic development, and serum testosterone in mice lacking cyclin-dependent kinase inhibitors

Normal prostatic development and some prostatic diseases involve altered expression of the cell-cycle regulators p27 and p21 (also known as CDKN1B and CDKN1A, respectively). To determine the role of these proteins in the prostate, we examined prostatic phenotype and development in mice lacking p27 and/or p21. In p27-knockout (p27KO) mice, epithelial proliferation was increased 2- and 3.8-fold in the ventral and dorsolateral prostate, respectively, versus wild-type (WT) mice, although prostatic weights were not different. Epithelial apoptosis was increased in p27KO mice and may account for the lack of a concurrent increase in weight. Testosterone deficiency observed in this group was not the cause of this increase, because vehicle- and testosterone-treated p27KO mice had similar percentages of apoptotic cells. Also observed was a trend toward a decreased functional epithelial cytodifferentiation, indicating a potential role of p27 in this process. Conversely, dorsolateral prostate and seminal vesicle (SV) of p21-knockout (p21KO) mice, and all prostatic lobes and SV of p21/p27 double-knockout mice, weighed significantly less compared to the WT mice, and their epithelial proliferation was normal. Decreased testosterone concentrations may contribute to the decreased prostatic weights. However, other factors may be involved, because testosterone replacement only partially restored prostatic weights. We conclude that loss of p27 increases prostatic epithelial proliferation and alters differentiation but does not result in prostatic hyperplasia because of increased epithelial cell loss. The p21KO mice showed phenotypes distinctly different from those of p27KO mice, suggesting nonredundant roles of p21 and p27 in prostatic development. Loss of p27 or of both p21 and p27 results in serum testosterone deficiency, complicating analysis of the prostatic effects of these cell-cycle regulators.     

Temperature dependence of the Langmuir monolayer packing of mycolic acids from Mycobacterium tuberculosis

Phase diagrams of the Langmuir monolayer of dicyclopropyl alpha mycolic acid (alpha-MA), cyclopropyl methoxy mycolic acid (MeO-MA), and cyclopropyl ketomycolic acids (Keto-MA) from Mycobacterium tuberculosis were obtained by thermodynamic analysis of the surface pressure (pi) vs. average molecular area (A) isotherms at temperatures in the range of 10-46 degrees C. The Langmuir monolayers of MAs were shown to exhibit various phases depending on the temperature (T) and the pi values. In the Langmuir monolayer of Keto-MA, the carbonyl group in the meromycolate chain apparently touches the water surface to give the molecule a W-shape in all the temperatures and surface pressures studied. Keto-MA formed a rigid solid condensed film, with four hydrocarbon chains packing together, not observed in the others. In contrast, the monolayer films of alpha-and MeO-MAs having no such highly hydrophilic intra-chain groups in the meromycolate chain were mostly in liquid condensed phase. This novel insight into the packing of mycolic acids opens up new avenues for the study of the role of mycolic acids in the mycobacterial cell envelopes and pathogenic processes.     

Acrolein induces Hsp72 via both PKCdelta/JNK and calcium signaling pathways in human umbilical vein endothelial cells

Acrolein is a highly electrophilic alpha,beta-unsaturated aldehydes to which humans are exposed in a variety of environment situations and is also a product of lipid peroxidation. Increased levels of unsaturated aldehydes play an important role in the pathogenesis of a number of human diseases such as Alzheimer's disease, atherosclerosis and diabetes. A number of studies have reported that acrolein evokes downstream signaling via an elevation in cellular oxidative stress. Here, we report that low concentrations of acrolein induce Hsp72 in human umbilical vein endothelial cells (HUVEC) and that both the PKCdelta/JNK pathway and calcium pathway were involved in the induction. The findings confirm that the production of reactive oxygen species (ROS) is not directly involved in the pathway. The induction of Hsp72 was not observed in other cells such as smooth muscle cells (SMC) or COS-1 cells. The results suggest that HUVEC have a unique defense system against cell damage by acrolein in which Hsp72 is induced via activation of both the PKCd/JNK and the calcium pathway.     

Structure and function of phosphatidylserine-specific phospholipase A1

Phospholipase A1 (PLA1) is an enzyme that hydrolyzes the sn-1 fatty acids from phospholipids and produces 2-acyl-lysophospholipids. Although PLA1 activities are detected in many tissues and cell lines, a limited number of PLA1s have been purified and cloned so far. These include phosphatidylserine (PS)-specific PLA1 (PS-PLA1) from rat platelets, PLA1 from vespid venom, and phosphatidic acid (PA)-preferential PLA1 (PA-PLA1). Structurally, the former two PLA1s belong to the lipase family, where they form a subfamily among the lipase family. An alignment of the PLA1s with other members of the lipase family revealed two molecular characteristics of PLA1: the presence of extremely short lids and deleted beta9 loops. The two surface loops have been implicated in the ligand recognition in human pancreatic lipase (PL) and guinea pig PL-related protein 2. Under physiological conditions, accessibility of PS-PLA1 to its substrate is limited as it is a secreted enzyme and PS is normally located in the inner leaflet of the lipid bilayer. However, PS-PLA1 efficiently hydrolyzes PS exposed on the surface of cells such as apoptotic cells and activated platelets, and produces 2-acyl-lysophosphatidylserine (lysoPS), which is a lipid mediator for mast cells, T cells and neural cells. Identification of PS-PLA1 reveals the presence of PLA1 subfamily within the lipase family and suggests that PLA1 has a role in the production of lysophospholipid mediators.     

Ammonia production from amino acids and urea in the caecal contents of the chicken

1. Ammonia production from urea and amino acids in the caecal contents of the chicken was evaluated using 15N-labeled nitrogenous compounds. 2. About 43% of each of urea nitrogen and glutamine amide nitrogen was converted to ammonia nitrogen, but only 25% of epsilon-nitrogen of the added arginine, a precursor of urea, was found in ammonia. 3. Amino nitrogen of the separately added glutamic acid and glycine to be converted to ammonia was 19-20% of their added amounts, whereas that of alpha-alanine was 11%. 4. It is concluded that dietary and urinary amino acids and urea which find their ways into the caeca are useful nitrogen sources for ammonia production by microflora in the caeca of the chicken.