An angiotensin-I converting enzyme inhibitor from buckwheat (Fagopyrum esculentum Moench) flour

A compound that inhibited angiotensin-I converting enzyme (ACE) activity was isolated from buckwheat powder. This compound is thought to be the hydroxy derivative of nicotianamine and its chemical structure is 2''-hydroxynicotianamine. This compound showed a very high inhibitory activity toward ACE, and the IC(50) was 0.08 microM. Only this hydroxy analog was found in buckwheat powder, at about 30 mg/100g, and no nicotianamine was detected. However, nicotianamine was detected in the buckwheat plant body. 2''-hydroxynicotianamine was also found in other polygonaceous plants.

Azelnidipine Down-Regulates Renal Angiotensin-Converting Enzyme and Mineralocorticoid Receptor mRNA in Diabetic Hypertensive Rats

Effects of a new lipophilic L-type calcium channel blocker, azelnidipine, on the expression of molecular components of the renin-angiotensin-aldosterone system (RAAS) were assessed. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of diabetes with hypertension, and their lean littermates, Long-Evans Tokushima Otsuka (LETO) rats, were treated with azelnidipine for 2 weeks. The renal cortical mineralocorticoid receptor mRNA in OLETF was higher than in LETO, but was suppressed (P<0.05) by azelnidipine. Renal cortical angiotensin-converting enzyme mRNA of OLETF was lower than that of LETO rats, and it was further suppressed by azelnidipine (P<0.05). Azelnidipine can down-regulate the gene expression of molecular components of RAAS.

Effects of calcium channel blockade on angiotensin II-induced peritubular ischemia in rats

Recent studies have indicated that derangement of peritubular capillary (PTC) circulation with consequent tubulointerstitial hypoxia plays a pivotal role in the pathogenesis of renal injury. The present study was performed to determine whether azelnidipine, a new dihydropyridine calcium channel blocker, attenuates angiotensin II (AngII)-induced peritubular ischemia in anesthetized rats. The superficial PTCs were visualized directly using an intravital fluorescence videomicroscope system, and the PTC blood flow was evaluated by analyzing the velocity of fluorescein isothiocyanate-labeled erythrocytes. Intravenous infusion of AngII (50 ng/kg/min, 10 min) significantly increased mean arterial pressure (MAP) and renal vascular resistance (RVR) (by 35 +/- 3% and 110 +/- 32%, respectively), and decreased total renal blood flow (RBF) and PTC erythrocyte velocity (by -34 +/- 4 and -37 +/- 1%, respectively). Treatment with azelnidipine (5 microg/kg/min i.v., 10 min) had no effect on basal MAP, RBF, RVR, or PTC erythrocyte velocity. However, azelnidipine markedly attenuated the AngII-induced increases in MAP (7 +/- 3%) and RVR (40 +/- 4%) and decreases in RBF (-24 +/- 1%) and PTC erythrocyte velocity (-22 +/- 1%). Similar attenuation in the AngII-induced responses of MAP, RBF, RVR, and PTC erythrocyte velocity were observed in rats treated with a higher dose of azelnidipine (20 microg/kg/min i.v., 10 min), which significantly decreased basal MAP and RVR and increased RBF and PTC erythrocyte velocity. These data suggest that calcium channel blockade attenuates AngII-induced peritubular ischemia, which may be involved in its beneficial effects on renal injury.

Functional effects of Japanese style fermented soy sauce (shoyu) and its components

The functional effects of Japanese style fermented soy sauce (shoyu) have been studied. Soy sauce promotes digestion, because the consumption of a cup of clear soup containing soy sauce enhances gastric juice secretion in humans. Soy sauce possesses antimicrobial activity against bacteria such as Staphylococcus aureus, Shigella flexneri, Vibrio cholera, Salmonella enteritidis, nonpathogenic Escherichia coli and pathogenic E. coli O157:H7. Soy sauce also contains an antihypertensive component. An angiotensin I-converting enzyme inhibitor having antihypertensive effects was found in soy sauce. The active compound was identified as nicotianamine, which comes from soybeans. Soy sauce exhibits anticarcinogenic effects. Giving diets containing soy sauce to mice inhibit benzo[a]pyrene (BP)-induced forestomach neoplasia. The anticarcinogenic compounds in soy sauce were identified. The flavor components of Japanese style fermented soy sauce, such as 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), which is a characteristic flavor component of Japanese style fermented soy sauce and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 4-hydroxy-5-methyl-3(2H)-furanone (HMF) exhibit antioxidant activities and anticarcinogenic effects on BP-induced mice forestomach neoplasia when fed following carcinogen exposure. The feeding of a diet containing 10% soy sauce to male C3H mice for 13 months also reduces the frequency and multiplicity of spontaneous liver tumors. HDMF and HEMF also exhibit anticataract effects in the spontaneous cataract rat (ICR/f rat). Fermented soy sauce contains three tartaric isoflavone derivatives called shoyuflavones. These shoyuflavones were shown to have inhibitory activities against histidine decarboxylase, which produces histamine, a mediator of inflammation, allergy and gastric acid secretion. Soy sauce also exhibits antiplatelet activity. beta-Carbolines were isolated from soy sauce as the active compounds. Soybeans and wheat, which are the main raw materials of soy sauce, are allergenic foods. However, recent studies by enzyme-linked immunosorbent assay showed the absence of soybean and wheat allergens in soy sauce.

Additive beneficial effects of the combination of a calcium channel blocker and an angiotensin blocker on a hypertensive rat-heart failure model

The present study was undertaken to examine the effects of a calcium channel blocker, azelnidipine (1 mg/kg/day), an angiotensin converting enzyme (ACE) inhibitor, temocapril (10 mg/kg/day), an angiotensin II type 1 (AT1) receptor blocker (ARB), olmesartan (5 mg/kg/day), and their combination on Dahl salt-sensitive rats (DS rats) developing heart failure with preserved systolic function. DS rats were fed a high-salt diet (8% NaCl) from 7 weeks of age and progressively developed hypertension. Although monotherapy with azelnidipine lowered the blood pressure of DS rats to a greater extent than monotherapy with temocapril or olmesartan, the three drugs had similar effects on cardiac hypertrophy, cardiac fibrosis, the expressions of brain natriuretic peptide, transforming growth factor-beta1, collagen I, collagen III and monocyte chemoattractant protein-1 mRNA (as estimated by Northern blot analysis), and cardiac diastolic dysfunction (as estimated by echocardiography). These results show that ACE and AT1 receptor, as well as hypertension, are involved in the development of heart failure with preserved systolic function in DS rats. The combination of azelnidipine with olmesartan or temocapril produced no additive hypotensive effect in DS rats and no additive effect on cardiac hypertrophy or gene expressions. However, the combination therapy prolonged the survival rate of DS rats more than azelnidipine (p <0.01) or temocapril alone (p <0.05), and this additive beneficial effect by the combination therapy was associated with a greater reduction of cardiac fibrosis, urinary albumin excretion and serum creatinine. Our results thus showed that the combination of a calcium channel blocker with an ARB or an ACE inhibitor had additive preventive effects on a rat model of hypertensive heart failure with preserved systolic function. Thus, combination therapy with these agents seems to be a useful therapeutic strategy for the prevention of hypertensive heart failure.

Effect of combination of calcium antagonist, azelnidipine, and AT1 receptor blocker, olmesartan, on atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Angiotensin II type 1 receptor blockers (ARB) are widely recognized to have a vasculoprotective effect. Accumulating data have revealed that calcium antagonists also retard atherosclerosis. We examined the possibility that combination therapy of ARB and calcium antagonists could more effectively prevent atherosclerosis than monotherapy.

METHODS AND RESULTS

We observed a marked increase in the atherosclerotic area, associated with the exaggerated expression of nicotinamide adenine dinucleotide (phosphate), reduced form [NAD(P)H] oxidase subunits (p22 and p47) and superoxide anion production, in the aorta of apolipoprotein E-deficient mice maintained on a 1.25% high-cholesterol diet for 10 weeks. A calcium antagonist, azelnidipine, at a dose of 1 mg/kg a day or an ARB, olmesartan, at a dose of 3 mg/kg a day, significantly inhibited these parameters, with no change in systolic blood pressure and the blood cholesterol level. Moreover, the co-administration of lower doses of azelnidipine (0.1 mg/kg a day) and olmesartan (1 mg/kg a day) significantly inhibited the atherosclerotic area and oxidative stress, whereas azelnidipine or olmesartan alone at these doses did not affect these parameters. Furthermore, we observed similar inhibitory effects of azelnidipine or olmesartan on angiotensin II-induced NADPH oxidase activity and Akt activity in cultured vascular smooth muscle cells.

CONCLUSION

These results suggest that the co-administration of calcium antagonists and ARB synergistically blunts oxidative stress at least partly through the inhibition of Akt activity and enhances the beneficial effects of these drugs on atherosclerosis compared with monotherapy.

Effect of Azelnidipine on Angiotensin II-Mediated Growth-Promoting Signaling in Vascular Smooth Muscle Cells

The detailed mechanism of the effects of extracellular Ca2+ entry blockade on angiotensin II (Ang II) type 1 (AT1) receptor-mediated growth-promoting signals in vascular smooth muscle cells (VSMCs) is not fully understood. Ang II stimulation caused biphasic activation of growth-promoting signals, reaching a peak at 5 to 10 min followed by a decrease and a second peak at around 2 to 4 h. Addition of PD98059 (2'-amino-3'-methoxyflavone), a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor, or AG490 [alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide], a Janus-activated kinase 2 (Jak2) inhibitor, even 4 h after Ang II treatment inhibited [3H]thymidine incorporation. The calcium channel blocker azelnidipine attenuated the later peaks of extracellular signal-regulated kinase (ERK), tyrosine kinase 2, Jak2 activation, and phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT3. Interestingly, azelnidipine increased rather than decreased the later ERK peaks in cells treated with small interfering RNA against mitogen-activated protein kinase phosphatase-1. Ang II-mediated [3H]thymidine incorporation was inhibited dose dependently by azelnidipine and also by azelnidipine, plus olmesartan, whereas olmesartan or azelnidipine alone at such lower doses did not affect [3H]thymidine incorporation. These data provide new insight into the manner in which calcium channels exert an essential action in the AT1 receptor-mediated growth-promoting actions in VSMCs.

Unique atheroprotective property of azelnidipine, a dihydropyridine-based calcium antagonist

Insulin resistance and central obesity are often associated with hypertension. The metabolic syndrome is a cluster of these common clinical disorders, and is related with an increased risk for cardiovascular diseases. A number of pro-inflammatory cytokines derived from adipose tissues have been thought to contribute to the development of insulin resistance and accelerated atherosclerosis. Among them, TNF-alpha has been most widely studied; it not only suppresses the insulin signaling, but also elicits vascular inflammation. Indeed, inhibition of TNF-alpha was found to improve insulin resistance in obese rats and reduce the progression of atherosclerosis in apolipoprotein E knockout mice, respectively. These observations demonstrate that TNF-alpha could play a central role in the pathogenesis of insulin resistance and accelerated atherosclerosis in the metabolic syndrome. Considering that the primary goals of treatment for hypertensive patients with the metabolic syndrome are prevention of the development of diabetes and cardiovascular events, anti-hypertensive drugs that have abilities to block the TNF-alpha signaling would be desirable as a first-line therapy for these patients. In the process of the search for such a unique anti-hypertensive drug, we have recently found that azelnidipine, a newly developed and commercially used long-acting dihydropyridine-based calcium antagonist (DHP), inhibited TNF-alpha-induced activator protein-1 activation and interleukin-8 expression in human umbilical vein endothelial cells by suppressing NADPH oxidase-mediated reactive oxygen species generation. The concentration of azelnidipine that was found effective in these in vitro-experiments is well within the therapeutic range. Since endothelial cells do not possess voltage-operated L-type calcium channels, these observations suggest that the beneficial effects of azelnidipine are not likely due to calcium channel blocking property, but due to its unique anti-oxidative ability. Furthermore, we have very recently found that serum levels of monocyte chemoattractant protein-1, a biomarker for subclinical atherosclerosis, were significantly decreased by the treatment of azelnidipine in patients with essential hypertension. In this paper, we would like to hypothesize that due to its unique TNF-alpha signal modulatory, anti-oxidative property, azelnidipine may be a promising DHP that targets diabetes and cardiovascular diseases in hypertensive patients with the metabolic syndrome.

Azelnidipine, a dihydropyridine-based calcium antagonist, inhibits angiotensin II-induced oxidative stress generation and downregulation of pigment epithelium-derived factor mRNA levels in microvascular endothelial cells

We have previously shown that azelnidipine, a long-acting dihydropyridine-based calcium antagonist (DHP), inhibited tumor necrosis factor-alpha-induced endothelial cell (EC) activation through its antioxidative properties. However whether azelnidipine could also block the angiotensin II (Ang II)-signaling in ECs remains to be elucidated. Since Ang II-type 1 receptor interaction could contribute to exacerbation of diabetic retinopathy by downregulating pigment epithelium-derived factor (PEDF) gene expression in ECs, we examined here whether azelnidipine inhibited the Ang II-induced reactive oxygen species (ROS) generation and subsequent PEDF gene suppression in microvascular ECs. Azelnidipine, but not nitrendipine, the other popular DHFP completely inhibited the Ang II-induced ROS generation in ECs. Furthermore, azelnidipine, but not nitrendipine, was found to partially restore decreased PEDF mRNA levels in Ang II-exposed ECs. The present study suggests that azelnidipine could inhibit the Ang II-induced decrease in PEDF mRNA levels in ECs through its antioxidative properties. Upregulation of PEDF by azelnidipine may become a therapeutic target for the treatment of diabetic retinopathy associated with hypertension.

Chronic exposure to ammonia alters the modulation of phosphorylation of microtubule-associated protein 2 by metabotropic glutamate receptors 1 and 5 in cerebellar neurons in culture

Hyperammonemia impairs signal transduction associated to glutamate receptors and phosphorylation of some neuronal proteins including microtubule-associated protein 2 (MAP-2). The aim of this work was to analyze the effects of hyperammonemia on modulation of MAP-2 phosphorylation by metabotropic glutamate receptors (mGluRs) in rat cerebellar neurons in culture. Hyperammonemia increased basal phosphorylation of MAP-2 (180%). Activation of mGluRs 1 and 5 with (S)-3,5-dihydroxyphenylglycine (DHPG) increased MAP-2 phosphorylation (170%) in control neurons but not in neurons exposed to ammonia. Activation of mGluRs 2 and 3 with (2S,3S,4S)-CCG/(2S, 1'S,2'S)-2-(carboxycyclopropyl)glycine increased slightly (25%) MAP-2 phosphorylation in neurons exposed to ammonia or not. Activation of mGluR5 with (+/-)-trans-azetidine-2,4-dicarboxylic acid increased MAP-2 phosphorylation (24%) in control neurons but decreased it by 56% in neurons exposed to ammonia. Activation of mGluR1 using 2-methyl-6-(phenylethynyl)pyridine and DHPG increased MAP-2 phosphorylation 183% in control neurons but only 89% in neurons exposed to ammonia. In control neurons mGluR1 activation greatly increases phosphorylation of MAP-2, while activation of mGluRs 5, 2 or 3 increased it slightly. Taken together, hyperammonemia reduces the increase in MAP-2 phosphorylation induced by mGluR1activation. Moreover, in neurons exposed to ammonia activation of mGluR5 reduces MAP-2 phosphorylation. These effects reflect significant alterations in signal transduction associated to mGluR1 and mGluR5 in hyperammonemia that may contribute to altered glutamatergic neurotransmission and to the neurological alterations in hyperammonemia and hepatic encephalopathy.

Effects of a New Calcium Channel Blocker, Azelnidipine, on Systemic Hemodynamics and Renal Sympathetic Nerve Activity in Spontaneously Hypertensive Rats

Antihypertensive treatment with dihydropyridine calcium channel blockers elicits sympathetic nerve activation, which may contribute to cardiovascular events. However, recent clinical studies showed that treatment with azelnidipine, a new dihydropyridine calcium channel blocker, significantly reduced blood pressure in hypertensive patients while either maintaining or actually decreasing heart rate (HR). In this study, we examined the effects of azelnidipine and amlodipine on systemic hemodynamics and renal sympathetic nerve activity (RSNA) in anesthetized spontaneously hypertensive rats (SHR). We also examined the effects of these agents on baroreflex functions by infusing phenylephrine (30 microg/kg/min, i.v.) and sodium nitroprusside (10 microg/kg/min, i.v.) into azelnidipine- or amlodipine-treated SHR. Fifty min after administration of azelnidipine (10 microg/kg/min for 10 min, i.v.), mean arterial pressure (MAP) significantly decreased from 153+/-5 to 122+/-5 mmHg; however, HR and integrated RSNA did not change significantly (from 352+/-9 to 353+/-10 beats/ min and 115+/-5% of baseline, respectively). Infusion of amlodipine (50 microg/kg/min for 10 min) elicited similar effects on MAP (from 152+/-5 to 120+/-4 mmHg). However, amlodipine significantly increased HR (from 351+/-9 to 375+/-11 beats/min) and integrated RSNA (165+/-5% of baseline). Analyses of baroreflex function curves revealed that azelnidipine-treated rats showed a smaller baroreflex function than amlodipine-treated rats (p<0.05). These data suggest that azelnidipine possesses sympathoinhibitory effects, which may be one reason why it had less pronounced effects on HR in hypertensive patients.

Renoprotective effects of azelnidipine, a dihydropyridine-based calcium antagonist in advanced glycation end product (AGE)-injected rats

Diabetic nephropathy is a leading cause of end-stage renal disease in industrialized countries. Although the molecular mechanisms for the development and progression of diabetic nephropathy are not fully understood, the formation and accumulation of advanced glycation end products (AGEs) have been considered to play a major role in the pathogenesis of diabetic nephropathy. Hypertension is also an independent risk factor for the progression of diabetic nephropathy. However, functional cross-talk between AGEs and blood pressure and their involvement in diabetic nephropathy remain to be elucidated. In this study, we examined the effects of oral administration of azelnidipine, a commercially available dihydropyridine-based calcium antagonist, on renal injury in AGE-treated rats. Administration of azelnidipine inhibited the increase of systolic and diastolic blood pressure levels and urinary N-acetyl-beta-D-glucosaminidase activity in exogenously AGE-injected rats. Furthermore, azelnidipine treatment also prevented glomerulosclerosis in AGE-treated rats. These results indicate that renal damage in AGE-injected rats could be mediated, at least in part, by the elevation of blood pressure. Our present study suggests that azelnidipine would represent a valuable drug for the treatment of diabetic nephropathy by blocking the deleterious effects of AGEs.

Characterization of the genomic structures and selective expression profiles of nine class I small heat shock protein genes clustered on two chromosomes in rice (Oryza sativa L.)

The cytosolic class I small heat shock proteins (sHSP-CI) represent the most abundant sHSP in plants. Here, we report the characterization and the expression profile of nine members of the sHSP-CI gene family in rice (Oryza sativa Tainung No.67), of which Oshsp16.9A, Oshsp16.9B, Oshsp16.9C, Oshsp16.9D and Oshsp17.9B are clustered on chromosome 1, and Oshsp17.3, Oshsp17.7, Oshsp17.9A and Oshsp18.0 are clustered on chromosome 3. Oshsp17.3 and Oshsp18.0 are linked by a 356-bp putative bi-directional promoter. Individual gene products were identified from the protein subunits of a heat shock complex (HSC) and from in vitro transcription/ translation products by two-dimensional gel electrophoreses (2-DE). All sHSP-CI genes except Oshsp17.9B were induced strongly after a 2-h heat shock treatment. The genes on chromosome 3 were induced rapidly at 32 and 41 degrees C, whereas those on chromosome 1 were induced slowly by similar conditions. Seven of these genes, except Oshsp16.9D and Oshsp17.9B, were induced by arsenite (As), but only genes on chromosome 3 were strongly induced by azetidine-2-carboxylic acid (Aze, a proline analog) and cadmium (Cd). A similar expression profile of all sHSP-CI genes at a lower level was evoked by ethanol, H2O2 and CuCl2 treatments. Transient expression assays of the promoter activity by linking to GUS reporter gene also supported the in vivo selective expression of the sHSP-CI genes by Aze treatment indicating the differential induction of rice sHSP-CI genes is most likely regulated at the transcriptional level. Only Oshsp16.9A abundantly accumulated in mature dry seed also suggested additionally prominent roles played by this HSP in development.

Nck-dependent activation of extracellular signal-regulated kinase-1 and regulation of cell survival during endoplasmic reticulum stress

In response to stress, the endoplasmic reticulum (ER) signaling machinery triggers the inhibition of protein synthesis and up-regulation of genes whose products are involved in protein folding, cell cycle exit, and/or apoptosis. We demonstrate that the misfolding agents azetidine-2-carboxylic acid (Azc) and tunicamycin initiate signaling from the ER, resulting in the activation of Jun-N-terminal kinase, p44(MAPK)/extracellular signal-regulated kinase-1 (ERK-1), and p38(MAPK) through IRE1alpha-dependent mechanisms. To characterize the ER proximal signaling events involved, immuno-isolated ER membranes from rat fibroblasts treated with ER stress inducers were used to reconstitute the activation of the stress-activated protein kinase/mitogen-activate protein kinase (MAPK) pathways in vitro. This allowed us to demonstrate a role for the SH2/SH3 domain containing adaptor Nck in ERK-1 activation after Azc treatment. We also show both in vitro and in vivo that under basal conditions ER-associated Nck represses ERK-1 activation and that upon ER stress this pool of Nck dissociates from the ER membrane to allow ERK-1 activation. Moreover, under the same conditions, Nck-null cells elicit a stronger ERK-1 activation in response to Azc stress, thus, correlating with an enhanced survival phenotype. These data delineate a novel mechanism for the regulation of ER stress signaling to the MAPK pathway and demonstrate a critical role for Nck in ER stress and cell survival.

Novel function of ascorbic acid as an angiostatic factor

Endothelial permeability is increased by vascular endothelial cell growth factor and decreased by antioxidants. Whether or not l-ascorbic acid (Asc), which decreases endothelial permeability by stimulating the endothelial barrier function, is anti-angiogenic (angiostatic) remains unknown. We examined the role of Asc on angiogenesis using two assay systems. At first, the potential role of Asc on four steps of angiogenesis was investigated in cultured bovine microvascular endothelial cells. Asc inhibited the formation of vessel-like tubular structures of endothelial cells cultured on Matrigel; however, it did not decrease the activity of plasminogen activator (PA), which creates the space into which vascular vessels extend. Furthermore, even at high concentrations, Asc did not inhibit either the proliferation or migration of endothelial cell cultures. Secondly, whether Asc inhibited in vivo angiogenesis or not was studied on chick chorioallantoic membrane (CAM) during the 4-6 days of embryogenesis when neovascularization is rapid. It also revealed that angiogenesis was dose-dependently inhibited by Asc from 0.5 micro mol/CAM with half-maximal inhibition at 2.5 micro mol/CAM. Because it was previously reported that the endothelial barrier function decreases permeability via the stimulation of collagen synthesis induced by Asc, we treated CAM with the inhibitor of collagen synthesis, l-azetidine 2-carboxylic acid (AzC). This compound partially attenuated the angiostatic function of Asc on CAM. To understand the involvement of an antioxidant activity in the angiostatic function of Asc, we further examined the effect of glutathione (GSH), which is an endogenous antioxidant, on angiogenesis in CAM and endothelial cells. GSH inhibited CAM angiogenesis, as well as the formation of vessel-like tubular structures of endothelial cell cultures on Matrigel. Both Asc and GSH inhibited hydrogen peroxide (H(2)O(2)) induced tubular morphogenesis. These findings suggest that Asc affects angiogenesis through both its antioxidant properties and the stimulation of collagen synthesis. As the angiostatic activity of Asc may be one of the many effects involved in host resistance to the growth or invasiveness of solid cancer, it may be useful as a supplementary therapy in various angiogenic diseases.

Discordance of UPR signaling by ATF6 and Ire1p-XBP1 with levels of target transcripts

Accumulation of misfolded proteins within the lumen of the mammalian endoplasmic reticulum (ER) activates the unfolded protein response (UPR). ATF6 and Ire1p are ER-associated proteins that control UPR-specific transcription systems in mammals; UPR signaling involves cleavage of ATF6 and splicing of XBP1 mRNA initiated by Ire1p. We tested the hypothesis that activation of ATF6 and/or Ire1p determines the levels of mRNAs derived from target genes encoding GRP78/BiP and EDEM. By subjecting dermal fibroblasts to multiple stresses, strong correlations were found between ATF6 activation and XBP1 splicing, and between GRP78/BiP mRNA and EDEM mRNA accumulation. Surprisingly, there was no reasonable correlation between activation of either signal transducer with accumulation of either target transcript. Thus, ATF6 and Ire1p signaling do not define the magnitude of UPR-dependent mRNA increases, even though they may be necessary for gene activation, suggesting the existence of additional stress-sensitive factors acting as "coincidence detectors" for transcript accumulation.

Azelnidipine, A Newly Developed Long-Acting Calcium Antagonist, Inhibits Tumor Necrosis Factor-α-Induced Interleukin-8 Expression in Endothelial Cells through its Anti-Oxidative Properties

Interleukin-8 (IL-8), a member of CXC chemokine family, has been found to play an important role in the pathogenesis of atherosclerosis. Tumor necrosis factor-alpha (TNF-alpha) is involved in the development and progression of atherosclerosis as well. In this study, we investigated whether and how azelnidipine, a newly developed long-acting calcium antagonist, could inhibit TNF-alpha-induced IL-8 expression in human umbilical vein endothelial cells (HUVEC). TNF-alpha significantly increased intracellular reactive oxygen species (ROS) generation in HUVEC, which was completely blocked by azelnidipine or apocynin, an inhibitor of NADPH oxidase. Azelnidipine also completely prevented TNF-alpha-induced increase in NADPH oxidase activity in HUVEC. Further, azelnidipine was found to significantly inhibit activator protein-1 (AP-1) promoter activity and IL-8 expression in TNF-alpha-exposed HUVEC. An inhibitor of AP-1, curcumin, or an anti-oxidant, N-acetylcysteine, also inhibited the TNF-alpha-induced IL-8 expression in HUVEC. These results demonstrated that azelnidipine inhibited TNF-alpha-induced IL-8 expression in HUVEC by blocking NADPH oxidase-mediated ROS generation and subsequent AP-1 activation. Our present study suggests that azelnidipine may play a protective role in the development and progression of atherosclerosis through its anti-oxidative properties.

Azelnidipine

Azelnidipine is a new dihydropyridine calcium channel antagonist with selectivity for L-type calcium channels that has recently been approved in Japan for the treatment of patients with hypertension. Results from clinical trials showed that, in 95 patients with mild-to-moderate hypertension, long-term treatment with azelnidipine effectively controls blood pressure (BP). The mean reduction from baseline in sitting systolic/diastolic BP after 1 year of treatment was 27.8/16.6 mm Hg. Among 172 patients with uncontrolled hypertension receiving non-calcium channel antagonist antihypertensive agents, the addition of azelnidipine therapy significantly reduced mean BP in a noncomparative, 1-year study (a reduction from 165.7/95.4 mm Hg at baseline to 138.2/79.9 mm Hg at study end). The antihypertensive efficacy of azelnidipine in patients with mild-to-moderate hypertension was shown to be similar to that of amlodipine or nitrendipine in randomised, double-blind studies. Azelnidipine and amlodipine controlled 24-hour BP to a similar extent. Azelnidipine is generally well tolerated; vasodilator adverse events such as as headache and hot facial flushes account for most of the adverse events. Its use is not associated with reflex tachycardia.

Antioxidant Effect of a New Calcium Antagonist, Azelnidipine, in Cultured Human Arterial Endothelial Cells

Azelnidipine is a novel dihydropyridine-type calcium antagonist with long-acting anti-hypertensive action and a low reported incidence of tachycardia. We aimed to evaluate its antioxidant activity in cultured human arterial endothelial cells under oxidative stress. Endothelial cells were exposed to 1 mM H2O2 and treated with 100 μM α-tocopherol, 1 nM, 10 nM or 100 nM azelnidipine, 100 nM nifedipine or 100 nM amlodipine. After 3 h, the cell number and level of lipid peroxidation were evaluated by measuring the total protein and 8-iso-PGF2α concentrations, respectively. The total protein concentration was similar with each treatment. Inhibition of 8-iso-PGF2α was greatest with 10 nM azelnidipine (compared with the other drugs); the difference between 10 nM and 100 nM azelnidipine was not significant. We conclude that azelnidipine has a potent antioxidative effect that could be of significant clinical benefit when combined with its long-lasting anti-hypertensive action and low incidence of tachycardia.

Activation of glutamate transporters in rods inhibits presynaptic calcium currents

We found that L-glutamate (L-Glu) inhibits L-type Ca2+currents (ICa) in rod photoreceptors. This inhibition was studied in isolated rods or rods in retinal slices from tiger salamander using perforated patch whole cell recordings and Cl−-imaging techniques. Application of L-Glu inhibitedICaby ∼20% at 0.1 mM and ∼35% at 1 mM. L-Glu also produced an inward current that reversed aroundECl. The metabotropic glutamate receptor (mGluR) agonists t-ADA (Group I), DCG-IV (Group II), and L-AP4 (Group III) had no effect onICa. However, the glutamate transport inhibitor, TBOA (0.1 mM), prevented L-Glu from inhibitingICa. D-aspartate (D-Asp), a glutamate transporter substrate, also inhibitedICawith significantly more inhibition at 1 mM than 0.1 mM. Using Cl−imaging, L-Glu (0.1–1 mM) and D-Asp (0.1–1 mM) were found to stimulate a Cl−efflux from terminals of isolated rods whereas the ionotropic glutamate receptor agonists NMDA, AMPA, and kainate and the mGluR agonist, 1S,3R-ACPD, did not. Glutamate-evoked Cl−effluxes were blocked by the glutamate transport inhibitors TBOA and DHKA. Cl−efflux inhibits Ca2+channel activity in rod terminals (Thoreson et al. (2000),Visual Neuroscience17, 197). Consistent with the possibility that glutamate-evoked Cl−efflux may play a role in the inhibition, reducing intraterminal Cl−prevented L-Glu from inhibitingICa. In summary, the results indicate that activation of glutamate transporters inhibitsICain rods possibly as a consequence of Cl−efflux. The neurotransmitter L-Glu released from rod terminals might thus provide a negative feedback signal to inhibit further L-Glu release.

Calcium channel blocker azelnidipine enhances vascular protective effects of AT1 receptor blocker olmesartan

The present studies were undertaken to investigate the potential effect of a calcium channel blocker (CCB) to enhance the inhibitory effect of an angiotensin (Ang) II type 1 (AT1) receptor blocker (ARB) on vascular injury and the cellular mechanism of the effect of CCB on vascular remodeling. In polyethylene cuff-induced vascular injury of the mouse femoral artery, proliferation of vascular smooth muscle cells (VSMCs) and neointimal formation associated with activation of extracellular signal-regulated kinase (ERK), and tyrosine-phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT3, inflammatory response assessed by monocyte chemoattractant protein-1 and tumor necrosis factor-alpha expression, as well as oxidative stress such as expression of NADH/NADPH oxidase p22(phox) subunit and superoxide production, were less in AT1a receptor null mice. Administration of nonhypotensive doses of a CCB, azelnidipine (0.5 or 1 mg/kg per day) attenuated these parameters in wild-type and AT1a receptor null mice. Coadministration of lower doses of an ARB, olmesartan (0.5 mg/kg per day), and azelnidipine (0.1 mg/kg per day), which did not affect vascular remodeling, significantly inhibited these parameters in wild-type mice. Moreover, the effective dose of azelnidipine (1 mg/kg per day) exaggerated the inhibitory action of olmesartan at effective doses of 1 or 3 mg/kg per day on VSMC proliferation in the injured arteries. These results suggest that azelnidipine could inhibit vascular injury at least partly independent of the inhibition of AT1 receptor activation and that azelnidipine could exaggerate the vascular protective effects of olmesartan, suggesting clinical possibility that the combination of CCB and ARB could be more effective in the treatment of vascular diseases.

Effects of ascorbic acid and ascorbic acid 2-phosphate, a long-acting vitamin C derivative, on the proliferation and differentiation of human osteoblast-like cells

In order to investigate the effect of ascorbic acid (AsA) and ascorbic acid 2-phosphate (Asc 2-P), a long-acting vitamin C derivative, on the growth and differentiation of human osteoblast-like cells, we supplemented the culture medium of MG-63 cells with various concentrations (0.25 to 1 mM) of these factors. Asc 2-P significantly stimulated nascent cell growth at all concentrations in the presence of fetal bovine serum (FBS). On the other hand, AsA showed a growth repressive effect depending on its concentration, and that of FBS. Asc 2-P also increased expression of osteoblast differentiation markers, such as collagen synthesis and alkaline phosphatase (ALP) activity. These stimulative activities of Asc 2-P were attenuated by inhibitors of collagen synthesis, indicating that these effects were dependent on collagen synthesis. Electron micrographs of the cells showed the formation of a three-dimensional tissue-like structure endowed with a mature extracellular matrix in the presence of Asc 2-P.

Pharmacological profiles and clinical effects of azelnidipine, a long-acting calcium channel blocker

Azelnidipine (Calblock) is a newly developed dihydropyridine-type calcium antagonist for the treatment of hypertension. In hypertensive animals, a single oral administration of azelnidipine caused a slowly developed and long-lasting hypotensive effect with a little reflex tachycardia. The extent of tachycardia was less with azelnidipine than with other agents of the same class. Long-term administrations of azelnidipine produced a stable antihypertensive effect with a slight decrease in heart rate. The hypotensive effect was preceded by an increase in plasma drug concentration and it persisted even after plasma drug concentration declined to very low levels. In the isolated arteries, the calcium blocking action developed gradually after treatment with azelnidipine and survived for a long period of time after the drug was removed from the bathing solution. These data suggest that the high affinity to vascular tissue contributes to the long-lasting hypotensive effects of this agent. The results from clinical studies in hypertensive patients indicated that once daily administration of azelnidipine achieved stable, 24-h control of blood pressure with no change or a slight decrease in heart rate. Clinical studies also showed a low incidence of adverse events such as headache, facial flush, dizziness, and palpitations. These characteristics make azelnidipine a new generation calcium antagonist that can be used for the treatment of hypertension.

Metabotropic receptor-mediated Ca2+ signaling elevates mitochondrial Ca2+ and stimulates oxidative metabolism in hippocampal slice cultures

Metabotropic receptors modulate numerous cellular processes by intracellular Ca2+ signaling, but less is known about their role in regulating mitochondrial metabolic function within the CNS. In this study, we demonstrate in area CA3 of rat organotypic hippocampal slice cultures that glutamatergic, serotonergic, and muscarinic metabotropic receptor ligands, namely trans-azetidine-2,4-dicarboxylic acid, alpha-methyl-5-hydroxytryptamine, and carbachol, transiently increase mitochondrial Ca2+ concentration ([Ca2+]m) as recorded by changes in Rhod-2 fluorescence, stimulate mitochondrial oxidative metabolism as revealed by elevations in NAD(P)H fluorescence, and induce K+ outward currents as monitored by rapid increases in extracellular K+ concentration ([K+]o). Carbachol (1-1,000 microM) elevated NAD(P)H fluorescence by <or=14%DeltaF/F0 and increased [K+]o by <or=4.3 mM in a dose-dependent manner. Carbachol-induced responses persisted in Ca2+-free solution and blockade of ionotropic glutamatergic and nicotinic receptors. Under similar conditions caffeine, known to cause Ca2+-induced Ca2+ release (CICR), also evoked elevations in [Ca2+]m, NAD(P)H fluorescence and [K+]o that, in contrast to carbachol-induced responses, displayed oscillations. After depletion of intracellular Ca2+ stores by carbachol in Ca2+-free solution, re-application of 1.6 mM Ca2+-containing solution triggered marked elevations in [Ca2+]m, NAD(P)H fluorescence and [K+]o. These data indicate that metabotropic transmission effectively regulates mitochondrial oxidative metabolism via diverse receptor types in hippocampal cells and that inonitol 1,4,5-trisphosphate-induced Ca2+ release (IICR) or CICR or capacitative Ca2+ entry might suffice in stimulating oxidative metabolism by elevating [Ca2+]m. Thus activation of metabotropic receptors might significantly contribute to generation of ATP within neurons and glial cells.

Polymorphism of the MPR1 gene required for toxic proline analogue resistance in the Saccharomyces cerevisiae complex species

We recently discovered, on the chromosome of Saccharomyces cerevisiae sigma 1278b, novel MPR1 and MPR2 genes required for resistance to a toxic analogue of L-proline, L-azetidine-2-carboxylic acid. The MPR genes, which were absent in the S. cerevisiae genome project strain S288C, encoded a novel acetyltransferase of 229 amino acids that detoxifies the analogue by acetylating it. The MPR1 gene homologue found in Schizosaccharomyces pombe was also shown to encode a similar acetyltransferase. To further analyse the origin and the physiological role of the yeast novel gene, we report here the comparative analysis of the MPR1 gene in the S. cerevisiae complex spp. which belong to the Saccharomyces sensu stricto group. Only the type strain of S. paradoxus exhibited resistance and acetyltransferase activity to L-azetidine-2-carboxylic acid. PCR was then used to isolate the new MPR1 homologue (Spa MPR1) from S. paradoxus with the primers based on the sequence of the MPR1 gene. Gene expression and enzymatic analysis showed that the cloned Spa MPR1 gene encodes an L-azetidine-2-carboxylic acid acetyltransferase of 231 amino acids, which has 87% identity to the MPR1 protein. We also found in the protein databases that S. bayanus contains a DNA fragment that is partly homologous to the MPR1 gene. However, the gene product was considered to lose the enzymatic activity, possibly due to the gene truncation or the base substitution(s) at the important region for catalysis. Further, genomic PCR analysis showed that most of the S. cerevisiae complex spp. have the sequence highly homologous to the MPR1 gene.

Misfolded proteins are competent to mediate a subset of the responses to heat shock in Saccharomyces cerevisiae

Cells may sense heat shock via the accumulation of thermally misfolded proteins. To explore this possibility, we determined the effect of protein misfolding on gene expression in the absence of temperature changes. The imino acid analog azetidine-2-carboxylic acid (AZC) is incorporated into protein competitively with proline and causes reduced thermal stability or misfolding. We found that adding AZC to yeast at sublethal concentrations sufficient to arrest proliferation selectively induced expression of heat shock factor-regulated genes to a maximum of 27-fold and that these inductions were dependent on heat shock factor. AZC treatment also selectively repressed expression of the ribosomal protein genes, another heat shock factor-dependent process, to a maximum of 20-fold. AZC treatment thus strongly and selectively activates heat shock factor. AZC treatment causes this activation by misfolding proteins. Induction of HSP42 by AZC treatment required protein synthesis; treatment with ethanol, which can also misfold proteins, activated heat shock factor, but treatment with canavanine, an arginine analog less potent than AZC at misfolding proteins, did not. However, misfolded proteins did not strongly induce the stress response element regulon. We conclude that misfolded proteins are competent to specifically trigger activation of heat shock factor in response to heat shock.

Protein misfolding and temperature up-shift cause G1 arrest via a common mechanism dependent on heat shock factor in Saccharomycescerevisiae

Accumulation of misfolded proteins in the cell at high temperature may cause entry into a nonproliferating, heat-shocked state. The imino acid analog azetidine 2-carboxylic acid (AZC) is incorporated into cellular protein competitively with proline and can misfold proteins into which it is incorporated. AZC addition to budding yeast cells at concentrations sufficient to inhibit proliferation selectively activates heat shock factor (HSF). We find that AZC treatment fails to cause accumulation of glycogen and trehalose (Msn2/4-dependent processes) or to induce thermotolerance (a protein kinase C-dependent process). However, AZC-arrested cells can accumulate glycogen and trehalose and can acquire thermotolerance in response to a subsequent heat shock. We find that AZC treatment arrests cells in a viable state and that this arrest is reversible. We find that cells at high temperature or cells deficient in the ubiquitin-conjugating enzymes Ubc4 and Ubc5 are hypersensitive to AZC-induced proliferation arrest. We find that AZC treatment mimics temperature up-shift in arresting cells in G1 and represses expression of CLN1 and CLN2. Mutants with reduced G1 cyclin-Cdc28 activity are hypersensitive to AZC-induced proliferation arrest. Expression of the hyperstable Cln3-2 protein prevents G1 arrest upon AZC treatment and temperature up-shift. Finally, we find that the EXA3-1 mutation, encoding a defective HSF, prevents efficient G1 arrest in response to both temperature up-shift and AZC treatment. We conclude that nontoxic levels of misfolded proteins (induced by AZC treatment or by high temperature) selectively activate HSF, which is required for subsequent G1 arrest.

Saccharomyces cerevisiae sigma 1278b has novel genes of the N-acetyltransferase gene superfamily required for L-proline analogue resistance

We discovered on the chromosome of Saccharomyces cerevisiae Sigma 1278b novel genes involved in L-proline analogue L-azetidine-2-carboxylic acid resistance which are not present in the standard laboratory strains. The 5.4 kb-DNA fragment was cloned from the genomic library of the L-azetidine-2-carboxylic acid-resistant mutant derived from a cross between S. cerevisiae strains S288C and Sigma 1278b. The nucleotide sequence of a 4.5-kb segment exhibited no identity with the sequence in the genome project involving strain S288C. Deletion analysis indicated that one open reading frame encoding a predicted protein of 229 amino acids is indispensable for L-azetidine-2-carboxylic acid resistance. The protein sequence was found to be a member of the N-acetyltransferase superfamily. Genomic Southern analysis and gene disruption showed that two copies of the novel gene with one amino acid change at position 85 required for L-azetidine-2-carboxylic acid resistance were present on chromosomes X and XIV of Sigma 1278b background strains. When this novel MPR1 or MPR2 gene (sigma 1278b gene for L-proline analogue resistance) was introduced into the other S. cerevisiae strains, all of the recombinants were resistant to L-azetidine-2-carboxylic acid, indicating that both MPR1 and MPR2 are expressed and have a global function in S. cerevisiae.

Heat shock response by cells treated with azetidine-2-carboxylic acid

The purpose of this study is to reinvestigate the heat shock response in cells treated with the antimetabolite azetidine-2-carboxylic acid (azetidine), an analogue of proline. Previous studies could not clearly discriminate between the progressive thermosensitization caused by amino acid analogues and a parallel induction of thermotolerance by heat shock. Incubation of H35 cells with 2.5 mm azetidine causes an increasing thermosensitization which achieves a maximum after approximately 18-22 h. At this point, azetidine does not prevent the development of acute thermotolerance following a heat shock at 42.5 degrees C, or the simultaneous induction of chronic thermotolerance during mild hyperthermia at 38-41 degrees C. However, for both the acute and chronic heating conditions thermotolerance levels are reduced in proportion with azetidine-thermosensitization. Incorporation of azetidine causes an apparent downward temperature shift of approximately 1 degree C relative to the time-temperature relationships for normal, or following heat shocks, for thermotolerant cells. After 18 h of incubation with azetidine, protein synthesis is reduced by a factor of 4 and cells show a preferential synthesis of heat shock proteins (hsp). A heat shock then, although inducing thermotolerance, is not followed by any noticeable effect on the synthesis of hsps. It is shown that the combination of prolonged azetidine treatment and heat shock causes a persistent inhibition of protein synthesis. This is hypothesized to result in the development of hsp synthesis independent thermotolerance. Additional treatment following heat shock in azetidine-treated cells with the protein synthesis inhibitor cycloheximide does not affect the induction of thermotolerance. In contrast to the heat shock response, no thermotolerance induction is observed in azetidine-treated cells after an exposure to sodium arsenite.

Enhanced and feedback-resistant gamma-glutamyl kinase activity of an Escherichia coli transformant carrying a mutated proB gene of Streptococcus thermophilus

We used a PCR-based method to generate a single base pair mutation in the proB gene of Streptococcus thermophilus, which replaced an aspartic acid with a glycine residue at position 192 of the first proline biosynthetic enzyme gamma-glutamyl kinase. This was the first identified mutation in amino acid biosynthesis in S. thermophilus to our knowledge. The mutation caused an enhanced, feedback-resistant gamma-glutamyl kinase activity and conferred an analogue-resistant phenotype to an Escherichia coli transformant containing the mutated gene.

Presynaptic group 1 metabotropic glutamate receptors may contribute to the expression of long-term potentiation in the hippocampal CA1 region

In this study, we investigated the possible contribution of presynaptic group 1 metabotropic glutamate receptor activation to changes in synaptic efficacy by means of analysis of glutamate release in hippocampal synaptosomes. Data were interpreted in the context of group 1 metabotropic glutamate receptor involvement in synaptic plasticity in the CA1 region of freely moving rats. In synaptosomes, 3,5-dihydroxyphenylglycine enhanced diacylglycerol formation and facilitated vesicular Ca(2+)-dependent glutamate release, whereas trans-azetidine-2,4-dicarboxylic acid had no effect on these processes. Trans-azetidine-2,4-dicarboxylic acid enhanced glutamate release, but in a Ca(2+)-independent manner. This effect was mimicked by the L-glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid. (R,S)-alpha-Methyl-4-carboxyphenylglycine blocked the effects of 3,5-dihydroxyphenylglycine, but not trans-azetidine-2,4-dicarboxylic acid in synaptosomes. Short-term potentiation (100 Hz, three bursts of 10 stimuli, 0.1 ms stimulus duration, 10 s interburst interval) was induced in the CA1 region in vivo. The metabotropic glutamate receptor agonist 1S,3R-aminocyclopentane-2,3-dicarboxylic acid, or the group 1 metabotropic glutamate receptor agonists, 3,5-dihydroxyphenylglycine and trans-azetidine-2,4-dicarboxylic acid, dose-dependently facilitated short-term potentiation into long-term potentiation, which lasted > 24 h. The facilitation was inhibited by the metabotropic glutamate receptor antagonist, (R,S)-alpha-methyl-4-carboxyphenylglycine, and the group 1 metabotropic glutamate receptor antagonist, (S)-4-carboxy-phenylglycine, but not by the group 2 metabotropic glutamate receptor antagonist, (R,S)-alpha-methylserine-O-phosphate monophenyl ester. L-Trans-pyrrolidine-2,4-dicarboxylic acid dose-dependently facilitated short-term potentiation into long-term potentiation, which lasted < 4 h. These data suggest that activation of group 1 metabotropic glutamate receptors results in presynaptic modulation of glutamate release. This effect may contribute to group 1 metabotropic glutamate modulation of the expression of long-term potentiation in vivo.

Differential temperature dependency of chemical stressors in HSF1-mediated stress response in mammalian cells

Expression of stress proteins is generally induced by a variety of stressors. To gain a better understanding of the sensing and induction mechanisms of stress responses, we studied the effects of culture temperature on responses to various stressors, since the induction of hsp70 in mammalian cells by heat shock is somehow modulated by culture temperature. Hsp70 was not induced by treatment with sodium arsenite, azetidine-2-carboxylic acid, or zinc sulfate at the level of heat shock factor (HSF) 1 activation in cells incubated at low temperature, although these treatments induced hsp70 in cells incubated at 37 degrees C. The repression of sodium arsenite or zinc sulfate-induced HSF1 activation by low temperature was not simply due to the inhibition of protein synthesis. On the other hand, heat shock and iodoacetamide induced HSF 1 activation in cells incubated at either temperature. Thus, there seem to be two kinds of stressors that induce HSF1 activation independently of or dependent on culture temperature. Furthermore, the reduction of glutathione level seemed to be essential for HSF1 activation by chemical stressors.

Activation of the unfolded protein response pathway induces human asparagine synthetase gene expression

The gene for the amino acid biosynthetic activity asparagine synthetase (AS) is induced by both amino acid and glucose deprivation of cells. The data reported here document that the human AS gene is induced following activation of the Unfolded Response Pathway (UPR), also known as the Endoplasmic Reticulum Stress Response (ERSR) in mammals. Increased AS transcription occurs in response to glucose deprivation, tunicamycin, or azetidine-2-carboxylate, all known to activate the UPR/ERSR pathway. Previously identified ERSR target genes contain multiple copies of a single highly conserved cis-element. In contrast, the human AS gene does not contain the ERSR element, as it has been described for other responsive genes. Instead, AS induction requires an Sp1-like sequence, a sequence previously shown to be associated with amino acid control of transcription, and possibly, a third region containing no consensus sequences for known transcription factors. Oligonucleotides covering each of these regions form DNA-protein complexes in vitro, and for some the amount of these complexes is greater when nuclear extracts from glucose-starved cells are tested. These results document that a wider range of metabolic activities are activated by the UPR/ERSR pathway than previously recognized and that genomic elements other than those already described can serve to enhance transcription of specific target genes.

Tissue culture based screening for selection of high biomass and phenolic producing clonal lines of lavender using pseudomonas and azetidine-2-carboxylate

Lavender is a good source of essential oils and phenolic metabolites for food, medicine, and cosmetic applications. Due to cross-pollination, lavender has substantial plant to plant variation and therefore a high degree of genetic inconsistency in the level of phytochemicals produced for diverse applications. Tissue culture methods, using benzyladenine-induced shoot organogenesis, were used to isolate clonal lines originating from individual heterozygous seeds among a heterogeneous seed population to exploit the genetic heterogeneity. Subsequently, in a two-step method, clonal shoots of each clonal line were evaluated for the ability to tolerate Pseudomonas inoculation and various levels (0-200 microM) of proline analogue, azetidine-2-carboxylate. On the basis of tolerance to Pseudomonas and proline analogue treatments, multiple shoot forming ability, biomass, rosmarinic acid, total phenolics, and total chlorophyll, 20 separate clonal lines were screened and isolated for further vegetative propagation and evaluation. From the clonal lines isolated, lines LH-14, LH-15, LH-17, and LH-11 showed the best potential for overexpression of phenolic metabolites in response to Pseudomonas and proline analogue.

Intracellular retention of procollagen within the endoplasmic reticulum is mediated by prolyl 4-hydroxylase

The correct folding and assembly of proteins within the endoplasmic reticulum (ER) are prerequisites for subsequent transport from this organelle to the Golgi apparatus. The mechanisms underlying the ability of the cell to recognize and retain unassembled or malfolded proteins generally require binding to molecular chaperones within the ER. One classic example of this process occurs during the biosynthesis of procollagen. Here partially folded intermediates are retained and prevented from secretion, leading to a build up of unfolded chains within the cell. The accumulation of these partially folded intermediates occurs during vitamin C deficiency due to incomplete proline hydroxylation, as vitamin C is an essential co-factor of the enzyme prolyl 4-hydroxylase. In this report we show that this retention is tightly regulated with little or no secretion occurring under conditions preventing proline hydroxylation. We studied the molecular mechanism underlying retention by determining which proteins associate with partially folded procollagen intermediates within the ER. By using a combination of cross-linking and sucrose gradient analysis, we show that the major protein binding to procollagen during its biosynthesis is prolyl 4-hydroxylase, and no binding to other ER resident proteins including Hsp47 was detected. This binding is regulated by the folding status rather than the extent of hydroxylation of the chains demonstrating that this enzyme can recognize and retain unfolded procollagen chains and can release these chains for further transport once they have folded correctly.

A new Ca-antagonist, azelnidipine, reduced blood pressure during exercise without augmentation of sympathetic nervous system in essential hypertension: a randomized, double-blind, placebo-controlled trial

This study was carried out to evaluate the effect of a new long-acting calcium-channel antagonist, azelnidipine, on hemodynamic and neural responses to exercise. Ten patients (age, 36-69 years) with mild essential hypertension were enrolled in this study. A randomized, double-blind, crossover treatment of azelnidipine at a dose of 8.0 mg once daily for 4 weeks was performed. After a 4-week placebo period, the patients exercised in a submaximal test by using an ergometer with azelnidipine or placebo treatment. The changes caused by exercise in arterial blood pressure (BP), heart rate, cardiac output (CO), and systemic vascular resistance were evaluated. In addition, the plasma norepinephrine (NE), epinephrine (E), plasma renin activity, and plasma aldosterone concentration were determined at rest, at peak exercise, and at the recovery period. Both the SBP and diastolic (D) BP were decreased at rest by azelnidipine treatment (from 158 +/- 10/97 +/- 7 to 145 +/- 14/90 +/- 9 mm Hg). Azelnidipine significantly decreased both SBP and DBP during exercise (SBP, F = 6.09, p < 0.05, Fi = 0.612, NS; DBP, F = 17.78, p < 0.001, Fi = 0.298, NS). No significant changes in the resting heart rate and CO were observed, and the exercise-induced increase of these parameters was also not affected by azelnidipine. Azelnidipine produced no significant change of the resting plasma NE and E levels and an exercise-induced increase of plasma NE. In conclusion, these results indicate that azelnidipine, different from another dihydropyridine-type calcium channel antagonists, does not produce any changes in the hemodynamic and neurohumoral response to exercise, and it may be beneficial for patients with mild essential hypertension.

Antisense ablation of type I metabotropic glutamate receptor mGluR1 inhibits spinal nociceptive transmission

Electrophysiological and behavioral studies point to a role of group I metabotropic glutamate receptors (mGluR1 and mGluR5) in mediating spinal nociceptive responses in rats. However, antagonists with a high degree of specificity for each of these sites are not yet available. We, therefore, examined the effects of antisense deletion of spinal mGluR1 expression in assays of behavioral analgesia and of electrophysiological responses of dorsal horn neurons. Rats treated with an mGluR1 antisense oligonucleotide reagent, delivered continuously to the intrathecal space of the lumbar spinal cord, developed marked analgesia as measured by an increase in the latency to tail-flick (55 degreesC) over a period of 4-7 d. This correlated with a selective reduction in mGluR1, but not mGluR5, immunoreactivity in the superficial dorsal horn compared with untreated control rats, in parallel with a significant reduction in the proportion of neurons activated by the mGluR group I agonist 3, 5-dihydroxyphenylglycine (DHPG), whereas the proportion of cells excited by the mGluR5 agonist, trans-azetidine-2,4-dicarboxylic acid (t-ADA) remained unaffected. In contrast, rats treated with mGluR1 sense or mismatch probes showed none of these changes compared with untreated, control rats. Furthermore, multireceptive dorsal horn neurons in mGluR1 antisense-treated rats were strongly excited by innocuous stimuli to their peripheral receptive fields, but showed severe reductions in their sustained excitatory responses to the selective C-fiber activator mustard oil and in responses to DHPG.

Effects of azelnidipine, a dihydropyridine calcium antagonist, on myocardial stunning in dogs

Effects of azelnidipine, a dihydropyridine derivative, on stunned myocardium were examined in anesthetized open-chest dogs. The left anterior descending (LAD) coronary artery was ligated for 20 min and then released for 60 min. Dimethyl sulfoxide (DMSO), the solvent of azelnidipine, or azelnidipine (0.03, 0.1 or 0.3 mg/kg) was injected i.v. 20 min before ligation. Segment shortening was determined by sonomicrometry. The levels of high-energy phosphate were measured in 60-min reperfused hearts. Azelnidipine at 0.1 and 0.3 mg/kg significantly decreased diastolic blood pressure and increased % segment shortening. The increase in % segment shortening due to azelnidipine appeared to be abolished by propranolol and atropine pretreatment. Ischemia significantly decreased % segment shortening in all groups. The % segment shortening that had been decreased by ischemia recovered during reperfusion, but did not reach its preischemic level in each group. In the 0.1 and 0.3 mg/kg of azelnidipine-treated dogs, a significant enhancement of % segment shortening recovery during reperfusion was observed, as compared with that in the DMSO-treated dogs. Azelnidipine did not affect the high-energy phosphate levels in 60-min reperfused hearts. In conclusion, azelnidipine improved the contractile dysfunction in stunned myocardium, without any preservation of high-energy phosphate.

Different contributions of GABAA and GABAC receptors to rod and cone bipolar cells in a rat retinal slice preparation

Whole cell currents were recorded from rod and cone bipolar cells in a slice preparation of the rat retina. Use of the gramicidin D perforated-patch technique prevented loss of intracellular compounds. The recorded cells were identified morphologically by injection with Lucifer yellow. During the recordings, the cells were isolated synaptically by extracellular cobalt. To distinguish the gamma-aminobutyric acid (GABA) receptors pharmacologically, the GABAA receptor antagonist, bicuculline, and the GABAC receptor antagonist, 3-aminopropyl(methyl)phosphinic acid, were used. In all bipolar cells tested, application of GABA induced postsynaptic chloride currents that hyperpolarized the cells from their resting potential of about -40 mV. GABA was applied at different concentrations to allow for the different affinity of GABA at GABAA and GABAC receptors. At a GABA concentration of 25 microM, in the case of rod bipolar cells, approximately 70% of the current was found to be mediated by GABAC receptors. In the case of cone bipolar cells, only approximately 20% of the current was mediated by GABAC receptors. Furthermore, this GABAC-mediated fraction varied among the different morphological types of cone bipolar cells, supporting the hypothesis of distinct functional roles for the different types of cone bipolar cells. There is evidence that the efficacy of GABAC receptors is modulated by glutamate through metabotropic glutamate receptors. We tested this hypothesis by applying agonists of metabotropic glutamate receptors (mGluR)1/5 to rod bipolar cells. The specific agonist (+/-)-trans-azetidine-2, 4-dicarboxylic acid and the potent mGluR agonist quisqualic acid reduced the amplitude of the GABAC responses by 10-30%. This suggests a functional role for the modulation of GABAC receptors by the metabotropic glutamate receptors mGluR1/5.

Ascorbate affects proliferation of guinea-pig vascular smooth muscle cells by direct and extracellular matrix-mediated effects

Proliferation of smooth muscle cells and deposition of extracellular matrix proteins are important events in the formation of atherosclerotic plaques. We have investigated the direct and matrix-mediated effects of ascorbate on the proliferation rate of vascular smooth muscle cells (VSMC) isolated from the guinea-pig aorta. In the presence of ascorbate, cells showed a bi-phasic growth pattern. At 125 microM ascorbate, -3H--thymidine incorporation was stimulated 25%. However, higher concentrations of ascorbate gradually decreased cell-incorporated radioactivity up to 50% at 2 mM ascorbate. These effects of ascorbate on DNA synthesis in VSMC were paralleled by the changes in cell number and were not due to ascorbate cytotoxicity. Alpha-tocopherol (0.1 mM), individually and in combinations with 1 mm ascorbate, also inhibited DNA synthesis in VSMC. Ascorbate also influenced proliferation of smooth muscle cells through matrix-mediated effect. New VSMC culture plated on extracellular matrices deposited by smooth muscle cells in the presence of 0.1-1 mM ascorbate had up to 50% lower proliferation rate than on matrices from ascorbate-deficient cells, as assessed by [3H]-thymidine incorporation. This effect was independent from alpha-tocopherol and specific inhibitors of collagen synthesis: L-azetidine-2-carboxylic acid and pyridine-2,4-dicarboxylic acid. An ascorbate-dependent matrix effect was specific for smooth muscle cells grown on VSMC and human skin fibroblast-originated matrices, but not for human vascular endothelial cells. The possible involvement of ascorbate in the regulation of smooth muscle cells proliferation by its antioxidant/pro-oxidant effects and regulation of extracellular matrix composition are discussed.

Reduced induction of HSP70 in PC12 cells during neuronal differentiation

Rat pheochromocytoma PC12 cells differentiate into nonreplicating neuronal cells with neurite extensions in response to nerve growth factor (NGF). To gain better understanding of the regulation of stress responses in neuronal cells, we examined the induction of HSP70, HSP70 mRNA, and heat shock factor 1 (HSF1) DNA-binding activity following treatment by heat shock or with sodium arsenite or amino acid analogue in PC12 cells treated with or without NGF. The induction of HSP70 and HSP70 mRNA following these stresses was diminished in the differentiated PC12 cells compared to the undifferentiated cells, whereas the HSF1 DNA-binding activity was enhanced in the differentiated PC12 cells. This phenomenon was characteristic of the differentiated neuronal cells rather than growth-arrested cells. Thus, neuronal cells appear to show an altered stress response depending on their differentiation state, and the diminished HSP70 expression in the differentiated neuronal cells may explain the sensitivity of neuronal cells to pathophysiological stressors.

Activation of phospholipases C and D by the novel metabotropic glutamate receptor agonist tADA

In hippocampal slices taken from 8-day-old rats, trans-azetidine-2,4-dicarboxylic acid (tADA), a novel glutamatergic agonist acting preferentially at class I mGluR receptors, activates phosphoinositide and phosphatidylcholine hydrolysis with widely different potencies. Inositol phosphate formation was maximally increased at 10 microM tADA (EC50: 1.2 microM), while phospholipase D activation was observed at a tADA concentration of 1 mM. This is the first report of a tADA-induced phospholipase D activity.

Isolation and characterisation of a cDNA encoding rat mitochondrial GrpE, a stress-inducible nucleotide-exchange factor of ubiquitous appearance in mammalian organs

In contrast to the E. coli chaperones DnaK, GroEL and GroES, cDNAs encoding mitochondrial homologues of DnaJ and GrpE from higher eukaryotes have yet to be reported. Based on peptide sequences, we have isolated a cDNA encoding a 217 residue nuclear encoded precursor of rat mitochondrial GrpE (mt-GrpE) including a typical mitochondrial presequence of 27 residues. Western blotting revealed that the 21 kDa GrpE homologue is present exclusively in the mitochondrial fraction where it comprises only approximately 0.03% of the total soluble protein, while Northern blotting showed that the mt-GrpE transcript is present in most if not all organs. By contrast to other mitochondrial chaperones, the levels of mt-GrpE and its transcript in cultured cells are only marginally increased in response to the proline analog L-azetidine 2-carboxylic acid but not by heat shock. Furthermore, members of the GrpE family exhibit a much lower degree of sequence identity than do the well studied members of the Hsp70, Hsp60 and Hsp10 families.

Metabotropic glutamate receptor subtype agonists facilitate long-term potentiation within a distinct time window in the dentate gyrus in vivo

Trans-azetidine-2,4-dicarboxylic acid (ADA) is a putative selective agonist of group 1 metabotropic glutamate receptors. It has been shown previously that application of ADA prior to a short-term potentiation-inducing high-frequency tetanus facilitates long-term potentiation in vivo. In order to examine the role of metabotropic glutamate receptors in this response, we studied the effect of ADA in the dentate gyrus of the rat when applied after high-frequency tetanus to the perforant path. A comparison was made with the effects of the metabotropic glutamate receptor group 1 agonist 3,5-dihydroxyphenylglycine. Drugs were applied via a cannula implanted in the lateral cerebral ventricle. Both population spike amplitude and field excitatory postsynaptic potential were measured. Weak tetanization produced a short-term potentiation of field excitatory postsynaptic potential and population spike which decayed to baseline values by 90 min, and was unaffected by vehicle injections. Application of ADA (20 mM/5 microliters) or 3,5-dihydroxyphenylglycine (4mM/5 microliters) 5 min after high-frequency tetanus facilitated short-term potentiation into a long-term potentiation which lasted over 24 h. (R,S)-alpha-Methyl-4-carboxyphenylglycine (200 mM/5 microliters), a metabotropic glutamate receptor antagonist, when applied prior to high-frequency tetanus and ADA or 3,5-dihydroxyphenylglycine, completely inhibited this effect. ADA applied 10,15,20 and 25 min after high-frequency tetanus also facilitated short-term potentiation into long-term potentiation, but the magnitude of long-term potentiation was smaller than than produced by ADA given 5 min after tetanus. Similar effects were seen with 3,5-dihydroxyphenylglycine applied 25 min after high-frequency tetanus. When (R,S)-alpha-methyl-4-carboxyphenylglycine was applied prior to high-frequency tetanus and ADA or 3,5-dihydroxyphenylglycine applied 30 min after high-frequency tetanus, or after short-term potentiation decay, elicited no facilitation of long-term potentiation. These results indicate that a distinct time window for the enhancement by ADA and 3,5-dihydroxyphenylglycine of short-term potentiation into long-term potentiation occurs in the dentate gyrus in vivo. This suggests that metabotropic glutamate receptor activation in long-term potentiation occurs within a finite period of time and may be mediated by group 1 metabotropic glutamate receptors. Furthermore, it suggests that metabotropic glutamate receptor modulation of N-methyl-D-aspartate receptors does not account for the role of metabotropic glutamate receptors in long-term potentiation.

Physiological and pharmacological profile of trans-azetidine-2,4-dicarboxylic acid: metabotropic glutamate receptor agonism and effects on long-term potentiation

In this study, we biochemically analysed the effects of the novel metabotropic glutamate receptor agonist trans-azetidine-2,4-dicarboxylic acid and examined its role in hippocampal long-term potentiation. In cell lines expressing metabotropic receptor 1 or 5 subtypes, the compound stimulated phosphoinositide hydrolysis with EC50 values of 189.4 +/- 6.4 and 32.2 +/- 8.3 microM, respectively. In hippocampal slices, trans-azetidine-2,4-dicarboxylic acid also increased phosphoinositide hydrolysis, yet failed to show any effect on forskolin-stimulated formation of cyclic AMP, even if 1 mM azetidine was applied. Since trans-azetidine-2,4-dicarboxylic acid (20 mM in 5 microliters) injected cerebroventricularly prolongs long-term potentiation induced by weak tetanization, a possible interaction with N-methyl-D-aspartate receptors was investigated using patch-clamp techniques. Neither facilitation of N-methyl-D-aspartate (500 microM) currents nor induction of non-specific currents was observed in the presence of 50 and 500 microM azetidine. Strong tetanus-induced long-term potentiation in the dentate gyrus of freely moving rats was not influenced by azetidine. In combination with the antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine (200 mM in 5 microliters), however, the potentiation was attenuated and returned to baseline within 90 min. Blockade of N-methyl-D-aspartate receptors using 2-amino-5-phosphonopentanoate (20 mM in 5 microliters) prevented the potentiation in controls, but not in the azetidine group, where normal potentiation was observed for both the population spike amplitude and the excitatory postsynaptic potential. These data suggest that (i) trans-azetidine-2,4- dicarboxylic acid is an agonist at glutamate metabotropic receptors; (ii) a facilitation of induction and maintenance of long-term potentiation via N-methyl-D-aspartate receptors seems unlikely; and (iii) pharmacological activation of metabotropic receptors prior to tetanization appears to bypass the N-methyl-D-aspartate receptor dependence of the potentiation. In conclusion, a role for metabotropic glutamate receptors in both short-term and long-term potentiation is indicated by these data.

Sensitivity of Escherichia coli to proline analogues during osmotic stress and anaerobiosis

The sensitivity of wild-type Escherichia coli K-12 to a series of proline analogues was determined in cultures containing increasing concentrations of NaCl under both aerobic and anaerobic conditions. The bacteria were most sensitive to L-azetidine-2-carboxylate and L-thiazolidine-4-carboxylate. The minimum inhibitory concentrations for these compounds decreased progressively during osmotic stress, but the bacteria were much more sensitive to these proline analogues under aerobic conditions than during anaerobiosis. The reduced sensitivity under anaerobic conditions did not reflect degradation of the compounds in the culture medium. Since both urine and medullary renal tissue contain relatively low oxygen concentrations, these results raise doubts about the potential use of proline or glycine betaine analogues in treating urinary tract infections.

Differentiation and cell surface expression of transforming growth factor-beta receptors are regulated by interaction with matrix collagen in murine osteoblastic cells

Although transforming growth factor (TGF)-beta enhances bone formation, it inhibits the differentiation of osteoblasts. To clarify the regulatory mechanism of osteoblastic differentiation and TGF-beta actions, the relationship among differentiation, TGF-beta actions, and matrix protein synthesis was examined using murine osteoblast-like MC3T3-E1 cells. Alkaline phosphatase (ALP) activity continued to increase during long-term cultures, and the increase was closely associated with a reduction in cell surface TGF-beta receptors competent to bind TGF-beta. Both the stimulation of proteoglycan synthesis and the inhibition of ALP activity by TGF-beta were also suppressed. Collagen synthesis inhibitors and an anti-alpha2beta1 integrin blocking antibody blocked the changes in ALP activity and TGF-beta receptors, and a DGEA peptide that interferes binding of collagen to alpha2beta1 integrin also blocked the increase in ALP activity. Furthermore, when MC3T3-E1 cells were cultured on extracellular matrix layers obtained from these cells, all the differentiation-associated changes could be observed without collagen production, and the extracellular matrix-induced differentiation was also blocked by an anti-alpha2beta1 integrin antibody. These results demonstrate that the interaction of cell surface alpha2beta1 integrin with matrix collagen synthesized by osteoblasts themselves is involved in the osteoblastic differentiation and the reduction in cell surface receptors and actions of TGF-beta. It is suggested that matrix collagen synthesized under the stimulation by TGF-beta plays an important role in the regulation of osteoblastic differentiation and TGF-beta actions by differentiation-associated down-regulation of TGF-beta receptors.

Class I metabotropic glutamate receptor agonists do not facilitate the induction of long-term potentiation in the dentate gyrus of the rat in vitro

The possibility that activation of class I (phospholipase C-coupled) metabotropic glutamate receptors (mGluRs) can facilitate the induction of long-term potentiation (LTP) was investigated in the dentate gyrus of rat hippocampal slices. In the presence of picrotoxin, a weak tetanus led to a short-term potentiation (STP) lasting 10-15 min. Application of the class I mGluR agonists trans-azetidine-2,4-dicarboxylic acid (tADA, 100 microM) or 3,5-dihydroxyphenylglycine (DHPG, 100 microM) for 15 or 30 min before the weak tetanus did not affect baseline synaptic transmission or the magnitude of the subsequent potentiation. DHPG (70 microM) did, however, reduce accommodation of neuronal firing in response to depolarizing current injection. These results suggest that at the medial perforant path-granule cell synapse, class I mGluR activation by exogenous agonist application does not facilitate the induction of LTP.