Sesame lignans suppress age-related disorders of the kidney in mice.

OBJECTIVE: Sesamin is a functional ingredient in sesame (Sesamum indicum) seeds and has many physiological effects. This study investigated whether sesame lignans, sesamin and episesamin (1:1), can suppress age-related disorders of the kidney. MATERIALS AND METHODS: Twenty-month-old mice were divided into three groups, and each group received a regular diet (O-C), diet containing sesame lignans (O-SE), and diet containing sesame lignans and α-tocopherol (VE; O-SE+VE), respectively, for 5 months. Six-month-old young mice (Y-C) were compared to the older mice. RESULTS: Renal lipofuscin deposition was increased in the O-C group compared to that in the Y-C group and its deposition with aging was significantly decreased in both O-SE and O-SE+VE groups. Plasma blood urea nitrogen levels in the O-C group increased compared to those in the Y-C group; however, those in both O-SE and O-SE+VE groups did not differ from those in the Y-C group. The number of podocytes in the O-C group decreased compared to that in the Y-C group and this effect was attenuated in the O-SE and O-SE+VE groups. The effect was strongest in the O-SE+VE group. Histological examinations showed that glomerular hypertrophy accompanied by mesangial hyperplasia and renal tubular degeneration was less severe in the O-SE and O-SE+VE groups than in the O-C group. Moreover, age-related increases in the mRNA expression of NADPH oxidase- and inflammation-related genes, including p67phox, p40phox, TNFα, and IL-6, in the kidney were suppressed in the O-SE and O-SE+VE groups. CONCLUSIONS: Sesame lignans might be useful to suppress age-related kidney disorders, and these effects could be enhanced with VE.

Sesame lignans increase sympathetic nerve activity and blood flow in rat skeletal muscles.

Beneficial effects of sesame lignans, especially antioxidative effects, have been widely reported; however, its potential effects on autonomic nerves have not yet been investigated. Therefore, the current study aimed to investigate the effect of sesame lignans on the autonomic nervous system. The sympathetic nerve activity in rat skeletal muscle was measured using electrophysiological approaches, with blood flow determined using the laser Doppler method. Sesame lignans were administered intragastrically at 2 and 20 mg/kg, and after 60 min, the sympathetic nerve activity was observed to increase by 45.2% and 66.1%, respectively. A significant increase in blood flow (39.6%) was also observed for the 20-mg/kg dose when measured at 55 min after administration. These sympathomimetic effects were completely prevented by subdiaphragmatic vagotomy, and the increase in blood flow was eliminated in the presence of the beta2-adrenergic receptor inhibitor butoxamine. Thus, it is proposed that sesame lignans can increase the blood flow of skeletal muscle, possibly by exciting sympathetic nerve activity through the afferent vagal nerve.

Dietary arachidonic acid improves age-related excessive enhancement of the stress response.

OBJECTIVE: The aim of this study is to understand whether the responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to stress increases excessively with aging in senescence-accelerated mice-prone 10 (SAMP10) and to investigate the role of arachidonic acid (ARA) in this process. MATERIALS AND METHODS: The area under the curve of CORT concentration (CORT-AUC), an index of the HPA axis responsiveness to stress, was assessed in SAMP10 subjected to a 30-minute restraint stress up to 120 minutes after the restraint stress onset. Furthermore, the HPA axis responsiveness was evaluated in aged SAMP10 fed 0.4% ARA-containing diet (ARA group) or control diet (CON group) for 4 weeks. Three weeks later, these mice were divided into a group with a 30-minute restraint stress (CON-S or ARA-S group) and a group without restraint stress (CON-NS or ARA-NS group). Hippocampi were collected after stress release and fatty acid and glucocorticoid receptor (GR) protein levels were evaluated in the nucleus and cytosol. RESULTS: The CORT-AUC of aged SAMP10 was 21% significantly higher than that of young SAMP10. In the ARA group, hippocampal ARA was 0.5% significantly higher than that in the CON group. CORT-AUC in the ARA group was 24% significantly lower than that in the CON group. The ratio of GR protein levels in the nucleus and cytosol in the ARA-S group was 1.72 times significantly higher than that in the ARA-NS group but no difference was observed between the CON-S and CON-NS groups. CONCLUSIONS: Dietary ARA seems to suppress age-related excessive enhancement of the HPA axis responsiveness via attenuation of age-related decline in hippocampal GR translocation into the nucleus after stress loading, which may contribute to an improvement of mental health.

Sesame lignans reduce LDL oxidative susceptibility by downregulating the platelet-activating factor acetylhydrolase.

OBJECTIVE: Low-density lipoprotein (LDL) oxidative susceptibility is recognized as a risk factor for atherosclerosis. We previously reported that the ingestion of a supplement containing sesame lignans (sesamin/episesamin) for 4 weeks reduced LDL oxidative susceptibility in humans. MATERIALS AND METHODS: To elucidate the mechanisms underlying this observation, 12-week-old New Zealand White rabbits were fed a fat/cholesterol-enriched diet (100 g/day) for 6 weeks followed by oral administration of vehicle (control) or sesame lignans (50 mg/kg) for 4 weeks with the fat/cholesterol-enriched diet. RESULTS: The results showed that the ingestion of sesame lignans prolonged LDL oxidation lag time, regardless of the existence of the anti-oxidative catechol metabolite of sesamin/episesamin in LDL. Plasma platelet-activating factor acetylhydrolase (PAF-AH) activity was significantly reduced by sesame lignans. The prolongation of LDL oxidation lag time was abolished by the addition of a PAF-AH inhibitor. The expression level of pro-inflammatory cytokines and macrophage infiltration observed in the liver following the feeding of the fat/cholesterol-enriched diet were also significantly reduced by sesame lignans. CONCLUSIONS: These results indicate that sesame lignans reduce LDL oxidative susceptibility by downregulating plasma PAF-AH activity via the reduction of inflammation in the liver induced by fat/cholesterol-enriched diets.

Expression of placental leucine aminopeptidase/oxytocinase in neuronal cells and its action on neuronal peptides.

The placental leucine aminopeptidase (P-LAP)/oxytocinase whose serum level increases with gestation is thought to contribute to the maintenance of normal pregnancy. P-LAP mRNAs are expressed in various tissues other than the placenta. In this study, we identified P-LAP protein in the brain. In contrast with the placenta where a significant portion of P-LAP is released, the enzyme was localized in the membrane fraction in brain and PC12 cells and no soluble form of the enzyme was detected. When PC12 cells were differentiated into neuronal cells by nerve growth factor (NGF), a significant increase in the expression level of P-LAP in the cell was observed. As in the case of insulin treatment of 3T3-L1 adipocytes, treatment of PC12 cells with forskolin caused the translocation of the enzyme from intracellular vesicle to the cell surface plasma membrane. In addition, P-LAP was shown to degrade several bioactive neuropeptides such as Met-enkephalin and dynorphin A (1-8). These results suggest that P-LAP plays an important role in the regulation of neuronal cell function in the brain.

Characterization of recombinant human adipocyte-derived leucine aminopeptidase expressed in Chinese hamster ovary cells.

Adipocyte-derived leucine aminopeptidase (A-LAP) is a recently identified novel member of the M1 family of zinc-metallopeptidases. Transfection of the A-LAP cDNA into COS-7 cells resulted in the secretion of the enzyme. In this study, recombinant A-LAP was expressed in Chinese hamster ovary cells, purified to homogeneity and its enzymatic properties were characterized. The purified enzyme was active towards a synthetic substrate, L-leucyl-p-nitroanilide, yielding a V(max) of 3.55 micromol/min/mg and a K(m) of 1.28 mM, and was shown to be a monomeric protein with molecular mass of 120 kDa in solution. By monitoring the sequential N-terminal amino acid liberation, it was found that the enzyme hydrolyzes a variety of bioactive peptides, including angiotensin II and kallidin. Immunohistochemical analysis indicated that the enzyme is expressed in the cortex of the human kidney, where tissue kallikrein is localized. Taken together, these results indicate that A-LAP possesses a broad substrate specificity towards naturally occurring peptide hormones and suggest that it plays a role in the regulation of blood pressure through the inactivation of angiotensin II and/or the generation of bradykinin in the kidney.

Characterization of a recombinant soluble form of human placental leucine aminopeptidase/oxytocinase expressed in Chinese hamster ovary cells.

Serum levels of human placental leucine aminopeptidase/oxytocinase (P-LAP) increase with gestation. cDNA cloning of P-LAP revealed that the enzyme is a type II membrane-bound protein containing the consensus HEXXH(X)18E motif found in the M1 family of zinc-metallopeptidase proteins. In this study, a recombinant soluble form of P-LAP found in maternal serum was expressed in Chinese hamster ovary cells, purified to homogeneity and then characterized. Although N-terminal sequencing revealed a four-amino-acid deletion, the purified enzyme was active and was shown to be a zinc-containing homodimeric protein with molecular mass of 280 kDa in solution. Using artificial substrates, it was shown that the enzyme has broad specificity and is inhibited by several compounds known as aminopeptidase inhibitors. Subsequently, sequential N-terminal amino-acid liberation of several peptide hormones by the enzyme was monitored and structures of the products were determined. Among the hormones having a cysteine residue at their N-terminal end and intramolecular disulfide bonds, it was found that vasopressin and oxytocin, but not calcitonin and endothelins, were cleaved by the enzyme. Because the molecular properties of oxytocinase so far reported often conflict, our results provide an initial biochemical and enzymatic characterization of moleculary defined P-LAP/oxytocinase.

Purification, cDNA cloning, and characterization of a new serpin with megakaryocyte maturation activity.

A new member of the serine protease inhibitor (serpin) superfamily with megakaryocyte maturation activity was purified, and its cDNA was cloned and characterized. The predicted amino acid sequence consisting of 380 residues was unique and was 38% identical to the serpin plasminogen activator inhibitor type 2 (PAI-2). The recombinant factor expressed in Chinese hamster ovary cells showed species-specific activity on the induction of megakaryocyte maturation in vitro. When injected into mice, the factor indeed elicited an increase in the number of platelets in plasma. The sequence alignment indicated that the factor possessed a lysine residue at the P1 position, suggesting that it might function as an inhibitor of Lys-specific proteases. Although we could not show any inhibitory activities toward several known Lys-specific proteases, we detected the activity toward protease activity present in the culture supernatant of COLO 201 cells. These results suggested that the protein might influence the maturation of megakaryocytes via action as a serpin.

Human placental leucine aminopeptidase/oxytocinase. A new member of type II membrane-spanning zinc metallopeptidase family.

The serum level of placental leucine aminopeptidase (P-LAP) increases during pregnancy. P-LAP degrades several peptide hormones such as oxytocin and vasopresin, suggesting a role in maintaining homeostasis during pregnancy. In the study reported here, we have isolated a cDNA clone with 4084 base pairs encoding P-LAP from a human placental cDNA library. The amino acid sequence deduced from the cDNA contained all of the sequences of the peptide fragments obtained by digestion of the purified protein with trypsin. The predicted P-LAP contains the HEXXH consensus sequence of zinc metallopeptidases, indicating that the enzyme belongs to this family, which includes aminopeptidase N and aminopeptidase A. The deduced sequence also contains a hydrophobic region near the N terminus, suggesting that the enzyme is a type II integral membrane protein. Northern blot analysis revealed that P-LAP was expressed in several tissues, some of which expressed two forms of mRNAs. These results suggest that the enzyme is synthesized as an integral membrane protein and is released into blood under some physiological conditions.

Expression of Saccharomyces adenylate kinase gene in Candida boidinii under the regulation of its alcohol oxidase promoter.

The methylotrophic yeast, Candida boidinii, was investigated as a new efficient host for heterologous gene expression. The Saccharomyces cerevisiae adenylate kinase gene (ADK1) was used as the first example for heterologous enzyme production in C. boidinii. C. boidinii cells were transformed with plasmids harboring the S. cerevisiae ADK1 gene under the alcohol oxidase (C. boidinii AOD1) promoter. The chromosome-integrant strains produced adenylate kinase protein corresponding to 22%-28% of the total soluble proteins in an enzymatically active form. When the three-copy integrative transformant was grown for 60 h on methanol-glycerol medium in a 1.5-l jar fermentor, adenylate kinase was produced intracellularly with a yield of up to 2 milligrams culture medium. As the expression of the S. cerevisiae ADK1 in C. boidinii was under similar regulation to that of the C. boidinii AOD1, the previously cloned 1.7-kb AOD1 promoter fragment was proved to harbor sufficient cis elements for AOD1 regulation and found to be an efficient promoter for heterologous gene expression.

Comparative analysis of functional and structural features in the primase-dependent priming signals, G sites, from phages and plasmids.

The primase-dependent priming signals, G sites, are directly recognized by the Escherichia coli primase (dnaG gene product) and conduct the synthesis of primer RNAs. In nucleotide sequence and secondary structure, there is no striking resemblance between the phage- and plasmid-derived G sites, except for the limited sequence homology near the start position of primer RNA synthesis. In this study, we analyzed the structure and function of a G site of plasmid R100, G site (R100), and discovered the necessity of the coexistence of two domains (domains I and III), which contains blocks A, B, and C, which are nucleotide sequences highly conserved among the plasmid-derived G sites. However, neither the internal region, domain II, between domains I and III nor the potential secondary structure proposed by Bahk et al. (J. D. Bahk, N. Kioka, H. Sakai, and T. Komano, Plasmid 20:266-270, 1988) is essential for single-stranded DNA initiation activity. Furthermore, chimeric G sites constructed between a G site of phage G4, G site(G4), and G site(R100) maintained significant single-stranded DNA initiation activities. These results strongly suggest that phage- and plasmid-derived G sites have functionally equivalent domains. The primase-dependent priming mechanisms of phage- and plasmid-derived G sites are discussed.

High-level ATP production by a genetically-engineered Candida yeast.

Previous studies of ATP production with the methylotrophic yeast, Candida boidinii, suggested that the phosphorylation of AMP catalyzed by adenylate kinase (ADK) was rate-limiting. To investigate whether the enhancement of ADK activity in C. boidinii cells would improve ATP productivity, the Saccharomyces cerevisiae ADK1 gene encoding ADK was expressed in C. boidinii under the C. boidinii AOD1 promoter. Methanol-induced transformants had 10,000-fold enhanced levels of ADK activity and produced 23-fold more ATP from adenosine when compared to the control, parent strain. In a pH-controlled reaction system with successive adenosine-feeding, the ATP concentration in the reaction mixture reached 230 mM (117 g/l) over 45 hours, and was easily purified with an overall yield of 78 percent.