Versatile attosecond beamline in a two-foci configuration for simultaneous time-resolved measurements

We present our attoline which is a versatile attosecond beamline at the Ultrafast Laser Physics Group at ETH Zurich for attosecond spectroscopy in a variety of targets. High-harmonic generation (HHG) in noble gases with an infrared (IR) driving field is employed to generate pulses in the extreme ultraviolet (XUV) spectral regime for XUV-IR cross-correlation measurements. The IR pulse driving the HHG and the pulse involved in the measurements are used in a non-collinear set-up that gives independent access to the different beams. Single attosecond pulses are generated with the polarization gating technique and temporally characterized with attosecond streaking. This attoline contains two target chambers that can be operated simultaneously. A toroidal mirror relay-images the focus from the first chamber into the second one. In the first interaction region a dedicated double-target allows for a simple change between photoelectron/photoion measurements with a time-of-flight spectrometer and transient absorption experiments. Any end station can occupy the second interaction chamber. A surface analysis chamber containing a hemispherical electron analyzer was employed to demonstrate successful operation. Simultaneous RABBITT measurements in two argon jets were recorded for this purpose.

Smoking is associated with impaired long-term glucose metabolism in patients with type 1 diabetes mellitus

BACKGROUND AND AIMS

Smoking is known to negatively influence glucose metabolism both in healthy subjects and in patients with diabetes. The aim of this study was to compare glycemic control in patients with type 1 diabetes mellitus who were smokers with those who did not smoke during a prospective long-term follow-up.

METHODS AND RESULTS

In a single center, 763 patients with type 1 diabetes mellitus were included, 160 (21.0%) of them were smokers. Patients were treated with intensive insulin therapy according to existing guidelines. Glucose control was monitored quarterly, diabetes related complications and cardiovascular risk factors were assessed at least once a year. Glucose control in smokers was significantly worse than in non-smokers at baseline and during follow-up (mean HbA1c during 5047 patient-years of follow-up 7.9 ± 1.3% in smokers and 7.3 ± 1.1% in non-smokers, p < 0.001) despite a higher insulin dosage in smokers (0.71 ± 0.30 U/kg vs. 0.65 ± 0.31 U/kg in non-smokers, p = 0.046). HDL cholesterol was lower in smokers at baseline (1.53 ± 0.45 vs. 1.68 ± 0.51 in non-smokers, p = 0.048). Diabetes related complications tended to occur with a higher frequency in smokers, with a significant difference in macroalbuminuria (9.8% vs. 4.8% in non-smokers, p = 0.047).

CONCLUSION

Smoking is associated with worse glucose control in patients with type 1 diabetes mellitus despite the same treatment strategies as in non-smokers. Hyperglycemia, therefore, may contribute to an earlier incidence of diabetes related complications in these patients, in addition to direct toxic effects of smoking.

Homoepitaxial growth of CVD diamond: effect of nitrogen contaminations on growth rates

Homoepitaxial diamond films were deposited on {100} and {111} oriented substrates using microwave plasma assisted CVD. The growth rate was measured in situ using laser interferometry. Various amounts of 15N2 were admixed to the process gas (0-50 ppm). The growth rate on {100} faces was found to increase significantly (by a factor 1.8) with increasing 15N2 content. In contrast, on { 111 } faces only a minor increase of the growth rate upon nitrogen admixture was observed. These findings are in perfect agreement with the observed influence of nitrogen contaminations on the α-parameter, as derived by the X-ray texture analysis of polycrystalline diamond films [1]

Vitamin E prevents extensive lipid peroxidation in patients with hypertension

Oxidative modification of low-density lipoprotein (LDL) increases atherogenic potential to induce the accumulation of lipids and cells in the vascular wall. Previous studies reveal that hypertensive patients have a higher susceptibility to LDL oxidation. As animal models indicate that vitamin E protects LDL from oxidation, here we study the influence of vitamin E on the resistance of LDL to oxidation (lag time) in 47 subjects (31 normotensive, 16 hypertensive) before and after oral administration of vitamin E (400 IE) daily for two months. LDL was isolated and oxidised by incubation with copper ions. The time course of oxidation was measured by continuous photometric monitoring of diene formation at 234 nm. At the beginning of this study, normotensive subjects showed a lag time of 108 +/- 26 minutes and hypertensive patients a lag time of 85 +/- 24 minutes (P<0.05). Vitamin E caused a significant increase in the lag time in both groups: normotensive subjects 128 +/- 33, hypertensives patients 114 +/- 27 minutes (P<0.01). At completion of the study, lag times in both groups were similar (P=not significant). The data presented here suggests that vitamin E protects against the increased risk of vascular disease in patients with hypertension by reducing the susceptibility to oxidative modification of LDL. Vitamin E may therefore act as an inhibitor of atherogenesis.

LDL-oxidation and -subgroups in normo- and hypertensive patients with and without a family history of hypertension

OBJECTIVES

Oxidative modification of low-density-lipoprotein (LDL) increases its atherogenic potential to induce the accumulation of lipids and cells in the vascular wall. Patients have different lipoprotein profiles according to their LDL-subgroup pattern. The subgroup of LDL, which is most susceptible to oxidation, is most likely the dense LDL3 subfraction. In order to study an assumed association between hypertension, LDL subgroup distribution and the susceptibility of LDL to oxidation, 14 normotensive patients without family histories of hypertension (NT), 13 normotensive patients with family histories of hypertension (NT-FH), 10 hypertensive patients without family histories of (HT) and 11 hypertensive patients with family histories of hypertension (HT-FH) were evaluated.

PATIENTS AND METHODS

LDL was oxidatively modified by incubation with copper ions (1.6 microM/L). The course of LDL-oxidation was measured in vitro by continuous photometric monitoring and the quantitative distribution of 3 LDL-subgroups by capillary isotachophoresis (ITP).

RESULTS

The lag-phases of NT-FH and hypertensive patients were shorter than those of the control group (NT: 116 +/- 36 minutes; NT-FH 92 +/- 32 minutes, p < 0.05; HT: 95 +/- 41 minutes; HT-FH: 76 +/- 33 minutes, p < 0.05). Compared to NT a significant difference in the relative preponderance of LDL3 subgroup was observed for HT-FH (23.5 +/- 4.6% versus NT: 19.3 +/- 6.6%), additionally, statistical analysis showed a similar trend amongst the other patient groups (NT-FH: 20.4 +/- 7.4%, HT: 21.4 +/- 4.6%).

CONCLUSIONS

The increased occurrence of the LDL3 subgroup might contribute to a higher susceptibility to LDL oxidation and therefore create an increased risk of vascular disease in the genotypic and phenotypic hypertensive patient population.

[Homocysteine: a cardiovascular risk factor?]

Elevated plasma homocysteine levels may lead to an increased risk for atherosclerosis. Besides genetic factors a deficiency of folate, vitamin B6 and/or vitamin B12 may lead to an increase in the plasma concentration of this sulfur containing amino acid. Homocysteine may enhance by several direct and/or indirect mechanisms the pathogenesis of atherosclerosis. In this review selected aspects of homocysteine in relation to clinical practice will be discussed.

Is there a role for the ob gene product leptin in essential hypertension?

In this study we wanted to evaluate the relationship between the ob gene product leptin and blood pressure, as well as plasma renin activity and plasma aldosterone levels. We studied 139 subjects with a mean+/-SD age of 50 +/-14 years and a body mass index of 26.5+/-5.3 kg/m2; 110 subjects had essential hypertension and 29 were healthy nonhypertensive controls. Blood pressure was measured in resting conditions in the morning and blood was drawn for the determination of the plasma renin activity, aldosterone, and leptin levels. The mean blood pressure of the population was 155/97 mm Hg. The relationship between these parameters was studied by univariate regression analysis according to gender and, whenever indicated, adjusted for age and body mass. The mean+/-SEM plasma leptin level in the whole population was 9.5+/-0.6 ng/mL (range, 1.1-43.3). Subjects with stage I hypertension had significantly higher plasma leptin levels than normotensive subjects. Systolic blood pressure correlated with the plasma leptin levels and the leptin levels adjusted for body weight in women (r = 0.422, P < .01) and nonhypertensive men (r = 0.644, P = .03) only. Plasma renin activity (r = 0.329, P = .03) and aldosterone levels (r = 0.342, P = .026) correlated with the leptin concentration. A significant relationship between the peripheral expression of the ob gene product leptin and systolic blood pressure was found in women and nonhypertensive men. In view of the multiple functions of leptin a causal relationship is postulated and potential mechanisms may involve modulatory effects of leptin on neuropeptide Y, angiotensinogen gene expression, the modulation of the autonomous nervous system, or effects on the pituitary adrenal axis. Direct relationships between both plasma renin activity and aldosterone levels and leptin support the potential importance of the relationship between leptin and blood pressure. Our observation may be of future importance for the understanding of the link between the increase in blood pressure and increasing body weight.

Sperm allocation in the simultaneously hermaphroditic land snail Arianta arbustorum

To test the idea that individuals of the simultaneously hermaphroditic land snail Arianta arbustorum can control the number of spermatozoa in their spermatophores, we investigated whether they differentially release sperm to virgin or nonvirgin partners with respect to the potential risk of sperm competition in a given mating. The number of sperm transferred ranged from 802 620 to 3 968 800 (X= 2 185 100; N=91), but was related neither to the mating history of the partner nor to copulation duration. This indicates that individuals of A. arbustorum are not able to adjust sperm expenditure to the mating history of the partner. Furthermore, the number of sperm transferred was correlated neither with the size of the donor nor with the size of the recipient. It has been proposed that the sexual conflict between the two genders in simultaneous hermaphrodites could be resolved by gamete trading. Theory predicts that sperm trading should occur in hermaphrodites in which the female role controls fertilization, for example in gastropods with a gametolytic gland and/or sperm storage such as A. arbustorum. To see whether sperm trading occurs, we also examined whether individuals of A. arbustorum adjust the number of sperm they release to the number they receive from their mating partner. There was a high degree of reciprocity in spermatophore transfer: in 45 of the 46 mating pairs investigated both partners delivered a spermatophore that contained spermatozoa. The numbers of sperm transferred by the two mating partners were not correlated, however. This indicates that sperm trading does not occur in this simultaneously hermaphroditic land snail. Copyright 1998 The Association for the Study of Animal Behaviour.

Can low density lipoprotein influence microvascular caliber?

The intracellular free calcium concentration ([Ca2+]i) plays an important role in the regulation of vascular tone. In vascular smooth muscle cells (VSMCs) LDL causes changes in vascular tone by increasing [Ca2+]i. Pericytes are regarded as the microvascular counterpart of VSMCs and implicated in the regulation of microvascular cell biology under normal and pathological conditions (e.g., diabetes mellitus, arterial hypertension, arteriosclerosis). For this reason pericytes and VSMCs were compared in their ability to increase [Ca2+]i after stimulation with LDL. Single VSMCs and pericytes were loaded with 2 microM of the Ca2+-sensitive dye Indo-1/AM. Fluorescence was recorded at 405 nm (Ca2+-bound) and 485 nm (Ca2+-free). Cells in suspension were loaded with 2 microM of the calcium ionophore FURA-2 AM (excitation wavelengths: 340 and 380 nm, emission 505 nm). Basal [Ca2+]i levels were significantly higher in single pericytes (165 +/- 38 nmol/L, n = 41) than in VSMCs (150 +/- 39 nmol/L, n = 40, P = 0.0038). In cell suspensions the following values were obtained: Pericytes (113 +/- 27 nmol/L, n = 36) and VSMCs (109 +/- 26 nmol/L, n = 28), which are statistically not significant. For all concentrations of LDL used (except at 1 microg/ml n-LDL), the increase above basal values was significant and both cell types showed a clear dose-dependent reaction pattern. This study shows for the first time that pericytes and VSMCs increase their [Ca2+]i in a similar way after LDL stimulation. In analogy to aortic smooth muscle cells, our results indicate that LDL mediated [Ca2+]i changes in pericytes in the microvascular bed may cause vasoconstriction leading to impairment of blood flow in the microvasculature.

Inhibitory action of silibinin on low density lipoprotein oxidation

Low density lipoprotein (LDL) oxidation and smooth muscle cell growth represent key events in atherogenesis. Any mean to reduce these two phenomena may decrease the risk of coronary artery disease and atherosclerosis in general. The effects of silibinin (CAS 22888-70-6) on LDL oxidation and proliferation of vascular smooth muscle cells were evaluated in vitro. Silibinin (50-200 mumol/l) prolonged the lag times of both LDL autooxidation and oxidation by copper by > 50%, as assessed by recordings of diene formation. However, silibinin (up to 500 mumol/l) did not interfere with LDL-stimulated radiolabeled thymidine incorporation. These findings indicate that silibinin, apart from its hepatoprotective effects, has inhibitory properties on LDL oxidation in vitro. Therefore silibinin might represent a novel tool in the prevention and therapy of atherosclerosis.

Ethanol suppresses smooth muscle cell proliferation in the postprandial state: a new antiatherosclerotic mechanism of ethanol?

Epidemiologic studies suggest that moderate amounts of ethanol may reduce cardiovascular risk. The mechanisms of the alcohol-associated risk reduction are not known exactly. Vascular smooth muscle cell proliferation represents an important phenomenon in the pathogenesis of atherosclerosis. Recently, it was suggested that metabolic changes during the postprandial phase may be important in the pathogenesis of atherosclerosis. Therefore, we evaluated the effect of postprandial plasma with and without ethanol on the proliferation of rat vascular smooth muscle cells. Identical meals containing 1 g fat/kg body wt were given with and without ethanol (38 +/- 0.5 g) to eight healthy young men. Blood was drawn hourly during an 8-h postprandial period; the plasma was separated and added to the cell cultures (0.3%, by vol). The proliferative response (DNA synthesis) of these cells was assessed by measuring the incorporation of [methyl-3H]thymidine. The maximal blood ethanol concentration of 11.5 +/- 0.6 mmol/L (mean +/- SEM) was attained within the first hour. The ingestion of the meal with ethanol led to a 20% reduction in the capacity of postprandial plasma to induce thymidine incorporation into smooth muscle cells compared with the meal without ethanol (P < 0.05). These results suggest that ethanol may reduce cardiovascular risk by modulating vascular muscle cell growth during the postprandial period. Considering the amount of time humans spend in the postprandial state during their lifetimes, these findings may be of great importance in the pathogenesis of atherosclerosis.

Single pericytes and pericytes in suspension are stimulated in a similar way by low-density lipoprotein

BACKGROUND

Pericytes are regarded as the microvascular counterpart of smooth muscle cells and implicated in the regulation of blood pressure at the microvascular level. Ca2+ plays an important role in biochemical processes involved in blood pressure regulation and can be activated by low-density lipoprotein (LDL) cholesterol.

OBJECTIVE

To determine whether stimulation either of single cells or of cells in suspension by LDL would produce any difference in the increase in cytosolic free calcium levels ([Ca2+]i).

DESIGN AND METHODS

Single pericytes were loaded with 2 micromol/l of the Ca2+-sensitive dye Indo-1/AM. The Indo-1 fluorescence was recorded at 405 nm (Ca2+-bound) and 485 nm (Ca2+-free) after stimulation with LDL. Pericytes in suspension were loaded with 2 micromol/l of the Ca2+-sensitive dye FURA-2/AM. The FURA-2 fluorescence kinetics were recorded at 340-380 nm. Ratios of fluorescence at the two wavelengths were transformed to [Ca2+]i.

RESULTS

Basal [Ca2+] levels appeared to be higher in single cells (148+/-13 nmol/l, n = 20) than they were in cells in suspension (128+/-8 nmol/l, n = 25; P= 0.0078). After stimulation with LDL the increase in [Ca2+]i in both systems was about 220% above baseline. A clear dose dependency was seen for both systems.

CONCLUSIONS

Single pericytes and pericytes in suspension increase their [Ca2+]i after stimulation with LDL dose-dependently. Even though single-cell measurements revealed some technical limitations, their responses were comparable to those obtained in a cell suspension. In analogy to aortic smooth muscle cells, our results indicate that LDL might also play a blood-pressure-regulatory role in the microvasculature.

Low-density lipoprotein-induced formation of nitric oxide by cultured vascular smooth muscle cells of the rat

There is evidence that low-density lipoprotein (LDL) plays a crucial role in atherogenesis. On the cellular level, LDL has been shown to activate a number of mechanisms involved in atherogenesis and vasoconstriction. Local immoderate vasoconstriction is physiologically antagonized by nitric oxide, which is released from the endothelium. To find out whether LDL also influences the synthesis of nitric oxide in vascular smooth muscle cells, both the conversion of arginine to citrulline and the production of nitrite were determined as a measure of nitric oxide formation. After incubation of rat vascular smooth muscle cells with native LDL (25 micrograms mL-1) for 24 h, the production of both L-[14C]-citrulline [39600 (3600) cpm mg-1 cell protein] and nitric oxide [2.95 (0.56) mumol L-1] were about twice and 1.5-fold the amount of the corresponding values in untreated cells (mean +/- SD, P < 0.05, n = 4). Oxidized LDL was less effective than the native form. The presence of the arginine analogue NG-methyl-L-arginine reduced citrulline production dose-dependently but augmented DNA synthesis, both induced by LDL. In addition, the lipoprotein caused a 1.6-fold increase in cyclic GMP production following a 24-h incubation [control = 10.9 (3.8) pmol mg-1 cell protein, P = 0.016]. The results suggest that native LDL might partly impair its atherogenic potential on the vasculature by stimulating the production by smooth muscle cells of both nitric oxide and cyclic GMP.

In vitro antioxidant activity of calcium antagonists against LDL oxidation compared with alpha-tocopherol

The dose-dependent (1, 5, 10, 50 microM) antioxidative activity of calcium antagonists (verapamil, diltiazem, nifedipine, amlodipine, isradipine or lacidipine) and alpha-tocopherol against copper-induced LDL (0.25 mg/ml) oxidation was compared by measuring the diene formation and the content of TBARS. For diltiazem no antioxidant effect could be found, whereas the other calcium antagonists and alpha-tocopherol have demonstrated antioxidant activity at least at concentrations of 10 and 50 microM: alpha-tocopherol > lacidipine > nifedipine > isradipine, verapamil, amlodipine. Additionally, alpha-tocopherol and lacidipine were able to attenuate LDL-oxidation significantly at 1 and 5 microM. These results indicate in vitro antioxidative activity of calcium antagonists especially from the dihydropyridine-type with greatest activity for the strongly lipophilic lacidipine. This might be one possible antiatherogenic mechanism of calcium antagonists, since oxidative modification enhances the atherogenic potential of LDL.

[The metabolic syndrome: common etiology for distinct cardiovascular risk factors?]

Hypertension, dyslipidemias, glucose intolerance and obesity are among the most important cardiovascular risk factors. There is growing evidence for the concept of a relationship between blood pressure regulation and metabolic changes. The combination of hypertension and the metabolic changes mentioned above has been named metabolic syndrome in the literature. The central role of insulin resistance and consecutive hyperinsulinemia in the metabolic syndrome has been shown in epidemiological, clinical, genetic and animal studies. The metabolic syndrome can be demonstrated in about one half of the hypertensive population. This pathophysiological concept has to be taken into consideration in the therapy and prevention of the different cardiovascular risk factors.

Low density lipoprotein subfractions and [Ca2+]i in vascular smooth muscle cells

Several studies have established that plasma low density lipoprotein (LDL) consists of various discrete subfractions. Using a variety of techniques (analytical ultracentrifugation, equilibrium density gradient ultracentrifugation, and gradient gel electrophoresis), LDL has been fractionated into a maximum of seven subclasses that differ in particle size, density, and physiochemical composition. Recently, a predominance of smaller denser LDL particles has been associated with an increased risk of coronary artery disease. However, other lipoprotein changes, such as elevated triglycerides and lower HDL cholesterol levels, have been shown in patients with a predominance of the smaller denser LDL subfractions. Thus, it is unclear whether the enhanced atherogenic potential is induced by the LDL subfraction pattern per se or by concomitant lipoprotein changes. Because intracellular free Ca2+ is an important second messenger involved in atherogenesis and regulation of vascular tone, we studied the influence of three LDL subfractions (very light [LDL1], 1.030 to 1.033 g/mL; light [LDL2], 1.033 to 1.040 g/mL; and dense [LDL3], 1.040 to 1.045 g/mL) on [Ca2+]i in vascular smooth muscle cells (VSMCs) cultured from rat aorta. LDL subfractions were isolated by density gradient ultracentrifugation from human EDTA-plasma (n = 15). [Ca2+]i was measured by fura 2 fluorescence. Basal [Ca2+]i was 77 +/- 6 nmol/L. Stimulation of VSMCs with dense LDL3 caused a significantly (P < .05) more pronounced increase (+71 +/- 13 nmol/L) compared with LDL1 (+38 +/- 8 nmol/L) and LDL2 (+36 +/- 9 nmol/L). To further investigate the mechanisms leading to the stimulation of [Ca2+]i by LDL subfractions, we incubated VSMCs with the Ca2+ antagonists nifedipine, diltiazem, and verapamil in concentrations up to 10 mumol/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Low density lipoprotein subfractions increase thromboxane formation in endothelial cells

Correlations between dyslipidemia and high blood pressure have been shown. It is unclear whether there is a causal relationship but there are indications that blood lipids might have a direct effect on mechanisms regulating the vascular tone. As secretory products of endothelial cells (EC) have been suggested to be involved in blood pressure regulation, we studied the influence of low density lipoprotein subfractions on thromboxane (T) synthesis in human umbilical vein endothelial cells (HUVEC). LDL can be separated into at least three major subfractions. In the present study, subfractions LDL1 (d = 1.030-1.033 g/ml), LDL 2 (d = 1.033-1.040 g/ml), and LDL 3 (d = 1.040-1.045 g/ml) were obtained by density gradient ultracentrifugation. T was measured by a radioimmuno-assay. LDL subfractions induced a dose dependent (10-100 micrograms/ml) increase in T synthesis. Control T concentration was 96 +/- 12 pg/ml. LDL 3 (205 +/- 17 pg/ml, p < 0.01) and LDL 2 (194 +/- 13 pg/ml, p < 0.05) caused a significantly higher T concentration compared to the LDL 1 subfraction (152 +/- 11 pg/ml). These results indicate that LDL 2 and 3- the subfractions with the higher density-might have a more pronounced effect on T synthesis by EC than the other LDL subfractions.

Inositol Trisphosphate Metabolism in Subcellular Fractions of Barley (Hordeum vulgare L.) Mesophyll Cells

Phosphatases in cytosolic fractions, vacuoles, and vacuolar membranes from barley (Hordeum vulgare L.) leaves were found to dephosphorylate inositol 1,4,5-trisphosphate (IP3). 1,4-inositol bisphosphate (1,4-IP2) is the main product of IP3 dephosphorylation by the cytosolic fraction. The activity was strictly Mg2+ dependent. In contrast, IP3 dephosphorylation activity of both the soluble vacuolar and the tonoplast fractions was inhibited up to 50% by Mg2+. When vacuolar membranes were incubated with IP3, 1,4-IP2 was produced only under neutral and slightly alkaline conditions. Under acidic conditions, however, dephosphorylation yielded putative 4,5-inositol bisphosphate. Li+ (20 mM) and Ca2+ (100 [mu]M) strongly inhibited activity in the soluble vacuolar fraction but had only a slight effect on the activities of the cytosolic and tonoplast fractions.

Lipoproteins induce expression of the early growth response gene-1 in vascular smooth muscle cells from rat

Recently, we reported that low-density lipoprotein (LDL) induces in vascular smooth muscle cells (VSMCs) intracellular effects such as an elevation of intracellular free Ca2+ concentration ([Ca2+]i) and intracellular pH (pHi). The early growth response gene-1 (Egr-1) has been identified as a transcription factor belonging to a class of immediate-early genes expressed upon growth, and/or differentiation signals in a large variety of cells and species. Here we show that LDL induces a dose-dependent expression of the Egr-1 mRNA with a maximum at 30 min. Experiments in the presence of the dihydropyridine calcium blocker isradipine suggest that the lipoprotein-induced Egr-1 mRNA induction occurs via a Ca2+ dependent pathway. To demonstrate whether these intracellular responses are only specific to LDL we examined the effects of high- and very low density lipoprotein (HDL and VLDL) on [Ca2+]i and expression of Egr-1 mRNA. The present results show that all lipoproteins induce expression of Egr-1 mRNA and elevation in [Ca2+]i in VSMCs.

Lysolecithin actions on vascular smooth muscle cells

Oxidation of low density lipoprotein increases its atherogenic potential. During oxidation there is an extensive conversion of lecithin to lysolecithin. In rat aortic smooth muscle cells, 2-25 micrograms/ml lysolecithin elevated cytosolic calcium concentration up to 560%. Lysolecithin (10-20 micrograms/ml) increased [3H]thymidine incorporation from 15 cpm/mg cell protein (controls) up to 189 cpm/mg cell protein. Lysolecithin (10 micrograms/ml) potentiated the PDGF-induced (50 ng/ml) [3H]thymidine incorporation up to 6.3 times. The results indicate that lysolecithin could induce mechanisms, by which oxidized low density lipoproteins could promote cell growth and thus contribute to atherosclerosis.

Oxidation of low density lipoprotein enhances its potential to increase intracellular free calcium concentration in vascular smooth muscle cells

There have been suggestions that oxidation of low density lipoproteins (LDL) might increase their atherogenic potential. Because changes in intracellular free calcium concentration [Ca2+]i have been linked to atherogenesis, we compared the influence of oxidized LDL (Ox-LDL) and native LDL (N-LDL) on [Ca2+]i in vascular smooth muscle cells cultured from rat aortas. For determination of [Ca2+]i, fura-2 fluorescence was used. LDL was isolated by ultracentrifugation from the sera of human donors (n = 17). In N-LDL, oxidation was prevented by addition of antioxidants, whereas Ox-LDL was obtained by auto-oxidation. The extent of oxidation was assessed by measurement of thiobarbituric acid-reactive substances. Addition of Ox-LDL (20 micrograms protein/ml) to the vascular smooth muscle cells induced a mean increase of 129 +/- 13% in [Ca2+]i compared with 81 +/- 7% with N-LDL (p less than 0.01). Dose-response curves from 1 to 20 micrograms/ml (six experiments) confirmed this difference within the entire dose range. These results indicate that a more pronounced increase in [Ca2+]i induced by Ox-LDL might be one of the cellular mechanisms responsible for the higher atherogenic potential of Ox-LDL compared with N-LDL, as [Ca2+]i is an important second-messenger system involved in many atherogenic processes such as hypertrophy, cell migration, and cell damage.

Oxidized low-density lipoproteins in atherogenesis: possible mechanisms of action

The increased atherogenic potential of oxidized low-density lipoprotein (ox-LDL) is well documented. In the present study, we investigated possible mechanisms of action of the difference to native LDL. In vitro oxidation of LDL was determined by measurement of thiobarbituric acid-reacting substances and absorption at 234 nm. Copper (5 mumol/L) induced significant (p less than 0.01) oxidation in vitro. Furthermore, LDL isolated from atherosclerotic patients was slightly but significantly (p less than 0.05) more oxidized than LDL from normal controls (2.81 +/- 0.08 vs. 3.21 +/- 0.16 nmol of TBARS/mg of LDL protein). Ox-LDL caused significantly (p less than 0.01) more pronounced contractions of rat aortic rings in vitro compared to nonoxidized LDL expressed as a percentage of maximal contractions induced by 40 mmol/L of KCl (29.0 +/- 5.4% vs. 61.1 +/- 7.2%). Lysolecithin, which is a principal component of ox-LDL formed during oxidation, induced a dose-dependent increase in intracellular free calcium in vascular smooth muscle cells cultured from rat aorta. Doses from 2-25 micrograms/ml were tested and caused a maximum increase of more than 500% (25 micrograms/ml). In conclusion, this study provides further evidence for a higher biological activity of ox-LDL. Lysolecithin might be one of the active components formed during oxidation of LDL.

Intracellular free calcium concentration and thromboxane A2 formation of vascular smooth muscle cells are influenced by fish oil and n-3 eicosapentaenoic acid

The effect of fish oil and n-3 eicosapentaenoic acid (EPA) on intracellular free calcium concentration ([Ca2+]i) and thromboxane B2 (TXB2) formation in resting and stimulated cultured rat vascular smooth muscle cells (VSMC) was examined. In resting control cells [Ca2+]i was 147 +/- 15 nmol l-1 (mean +/- SEM, n = 4). After pretreatment of the cells with fish oil or EPA for 24 days the resting [Ca2+]i was decreased to 126 +/- 10 nmol l-1 and 84 +/- 8 nmol-1, respectively. After stimulation of untreated control cells with either 100 nmol l-1 angiotensin II (AII), 40 micrograms ml-1 low-density lipoprotein (LDL), or 100 ng ml-1 of recombinant platelet-derived growth factor (PDGFAB), [Ca2+]i was (in nmol l-1) 306 +/- 31, 217 +/- 25 and 213 +/- 16. Treatment of cells with fish oil or EPA reduced the stimulatory effect of the agonists, and the following [Ca2+]i values (in nmol l-1) were found: 199 +/- 21, 131 +/- 10, 148 +/- 13; and 175 +/- 11, 98 +/- 12, and 103 +/- 6, respectively. PDGFAB induced a four fold increase in TXB2-generation (270 +/- 28 pg mg-1 cell protein compared with 61 +/- 8.2 pg mg-1 in unstimulated control cells) within 6 min. In cells pretreated with fish oil or EPA, TXB2-formation was reduced by 54% and 44%, respectively.

IN CONCLUSION

in rat VSMC stimulated by a variety of vasoactive agonist, fish oil and EPA can markedly attenuate intracellular mechanisms related to changes of cytosolic calcium concentration and eicosanoid production.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of vascular smooth muscle cell activity by cyclosporin A

Pretreatment of rat vascular smooth muscle cells with cyclosporin A caused concentration- and time-dependent enhancement of both angiotensin II- and platelet-derived growth factor-stimulated cellular functions, which may be related to a rise in vascular tone. In particular, cyclosporin A increased cytosolic free calcium, and augmented the agonist-induced formation of inositol polyphosphate. In addition, it markedly increased the sensitivity of the cells to platelet-derived growth factor-mediated stimulation of thymidine incorporation. The potentiation of vascular smooth muscle cell activity by cyclosporin A may be a novel mechanism by which it exerts an adverse vasoconstrictor effect.

Generation of intracellular signals by low density lipoprotein is independent of the classical LDL receptor

Low density lipoprotein cholesterol (LDL) and apolipoprotein B-100 (1 to 15 micrograms/mL) had no significant influence on the inositol-1,4,5-trisphosphate (InsP3) formation in vascular smooth muscle cells and fibroblasts. Low density lipoprotein cholesterol (15 micrograms/mL) induced an elevation of intracellular Ca2+ from 85 to approximately 210 nmol/L in vascular smooth muscle cells from rat aorta in the absence or in the presence of 15 micrograms/mL monoclonal antibodies against the classical low density lipoprotein receptor or in the presence of apolipoprotein B-100. Moreover, in both human cultured fibroblasts from normocholesterolemic individuals and from patients with familial hypercholesterolemia homozygote class 1, LDL induced a dose-dependent rise of free intracellular calcium and a biphasic change of intracellular pH. Since homozygote class 1 fibroblasts are classical LDL receptor negative, and as antibodies against this receptor, as well as apolipoprotein B-100, did not attenuate the LDL-induced elevation of cytosolic calcium, we conclude that LDL might modify vascular activity via the observed intracellular changes without involving the classical low density lipoprotein receptor.

The platelet-derived growth factor isomers, PDGF-AA, PDGF-AB and PDGF-BB, induce contraction of vascular smooth muscle cells by different intracellular mechanisms

The effect of human recombinant platelet-derived growth factor (PDGF) isoforms, (r)PDGF-AA, PDGF-AB and PDGF-BB, on contractility of rat aortic rings as well as on intracellular free Ca2+ ([Ca2+]i), intracellular pHi (pHi) and thromboxane A2 (TXA2) formation in cultured vascular smooth muscle cells (VSMC) was examined. PDGF-BB behaved similar to PDGF-AB and both have features characteristic of conventional vasoconstrictor-agonists that directly increase [Ca2+]i, activate the Na+/H+ exchanger, stimulate the TXA2 formation, and induced contraction in VSMC whereas PDGF-AA induced contraction without increasing of [Ca2+]i, pHi, and TXA2 formation.

Different effects of platelet-derived growth factor isoforms on rat vascular smooth muscle cells

The response of rat aortic smooth muscle cells to all three isoforms of platelet-derived growth factor (PDGF) was studied. 5,000 binding sites/cell were estimated for rPDGF-AA (Kd 0.22 nM), 45,000 for rPDGF-AB and (Kd 0.4 nM), and 31,000 for rPDGF-BB (Kd 0.29 nM). rPDGF-AB and -BB stimulated effectively [3H]thymidine incorporation, inositol 1,4,5-trisphosphate release, diacylglycerol productions, [Ca2+]i increase, and pHi changes at concentration in the range from 3 to 10 ng/ml. The extent of DNA synthesis stimulated by rPDGF-AA varied considerably, and in all cases higher concentrations than 10 ng/ml were required. rPDGF-AA did not stimulate inositol-1,4,5-trisphosphate release, [Ca2+]i increase or pHi changes but induced the production of diacylglycerol, although with a different kinetic compared with that observed with rPDGF-AB or -BB. Apparently rPDGF-AA acts via a different mechanism, generating diacylglycerol without the release of inositol-1,4,5-trisphosphate.

Novel cellular activities for low density lipoprotein in vascular smooth muscle cells

Hyperlipidemia and hypertension play important roles in the pathogenesis of atherosclerosis. To investigate the underlying intracellular mechanisms, we studied the effect of various concentrations of low density lipoprotein from normolipidemic subjects on concentrations of free intracellular calcium, intracellular pH, DNA synthesis, and vascular tone in vascular smooth muscle cells and rings from rat aortas. Low density lipoprotein in the range of 1-15 micrograms/ml induced a dose-dependent increase of concentration of free intracellular calcium and a biphasic change of the intracellular pH. Similar concentrations of low density lipoprotein led to an enhanced DNA synthesis. Furthermore, cumulative addition of 1-15 micrograms/ml low density lipoprotein produced a dose-dependent increase in contractile tension of thoracic aortic rings from rats. The maximal low density lipoprotein-induced contractile response was approximately 70% of that induced by 40 mM KCl. These findings indicate that low concentrations of low density lipoprotein occurring, for example, in the extravascular fluid might contribute to the pathogenesis of cardiovascular diseases by enhancing cell proliferation and vasoconstriction by changing intracellular calcium and intracellular pH.

Attenuation of the low-density-lipoprotein-activated phosphoinositide signalling system by calcium blockers in human lymphocytes

1. The capacity of low-density lipoprotein-cholesterol (40 micrograms/ml) to stimulate both the phosphoinositide cycle and the dislocation of the phospholipid- and calcium-dependent protein kinase C activity from the cytosolic to the membranous compartment in human circulating lymphocytes has been studied. 2. Pretreatment of lymphocytes with pertussis toxin inhibited significantly the low-density-lipoprotein-induced formation of inositol trisphosphate. 3. The calcium-channel blockers verapamil, nifedipine and diltiazem, each in a concentration range from 1 mumol/l to 1 nmol/l, attenuated the low-density lipoprotein-induced formation of inositol trisphosphate in a dose-dependent manner. Similar results were observed when so-called non-specific calcium antagonists, such as flunarizine and molsidomine, were used. 4. The results suggest that low-density lipoprotein activates the phosphoinositide cycle in circulating lymphocytes through mechanisms sensitive to calcium blockers and pertussis toxin.

Low-density lipoprotein elevates intracellular calcium and pH in vascular smooth muscle cells and fibroblasts without mediation of LDL receptor

Low-density lipoprotein (7 micrograms/ml) induced in the absence or in the presence of 7, 35, 70 micrograms/ml monoclonal antibodies against the specific Low-density lipoprotein receptor an elevation of intracellular Ca2+ from 105 to approximately 210 nM in vascular smooth muscle cells from rat aorta. Moreover, in both human cultured fibroblasts from normocholesterolemic individuals and from patients with familial hypercholesterolemia homozygote class 1, Low-density lipoprotein (7 micrograms/ml) induced a rise of free intracellular calcium and a biphasic change of intracellular pH. Low-density lipoprotein (1,7,15,30 micrograms/ml) had no significant influence on the phosphatidylinositol-turnover in vascular smooth muscle cells and fibroblasts. Since homozygote class 1 fibroblasts lack specific Low-density lipoprotein receptors, and as antibodies against this receptor did not attenuate the Low-density lipoprotein-induced elevation of cytosolic calcium and pH, we conclude that these intracellular changes are independent from the classical Low-density lipoprotein receptor.

Effect of low-density lipoprotein on intracellular calcium, intracellular pH and DNA synthesis in cultured vascular smooth muscle cells

Low-density lipoprotein has proliferative effects on vascular smooth muscle cells and thus may play a role in the pathogenesis of atherosclerosis and hypertension. In order to investigate the underlying mechanisms, we studied the influence of low-density lipoprotein on intracellular free calcium, intracellular pH and the rate of DNA synthesis in cultured vascular smooth muscle cells of the rat aorta. The low-density lipoprotein (1-30 micrograms/ml) caused a dose-dependent increase in intracellular calcium and affected the intracellular pH accordingly. In addition, a marked low-density lipoprotein-induced increase in 3H-thymidine incorporation into DNA was observed. It is concluded that low-density lipoprotein, apart from its classical role as a cholesterol-transporting vehicle, enhances cellular processes leading to cell proliferation.

Cortisol-stimulated phosphoinositide metabolism in vascular smooth muscle cells: a role for glucocorticoids in blood pressure control?

Physiological concentrations of cortisol (0.02-5.0 micrograms/ml) stimulate the phosphoinositide breakdown in cultured smooth muscle cells from rat aorta. After a 15-min stimulation of the cells with various concentrations of cortisol, the inositol-1,4,5-triphosphate concentrations showed a dose-dependent increase. This phenomenon was qualitatively similar but quantitatively more sensitive in smooth muscle cells from spontaneously hypertensive rats (SHR) than in vascular smooth muscle cells from normotensive animals. When the antihormone RU 486 was added before the vascular smooth muscle cells were stimulated with cortisol, the inositol-1,4,5-triphosphate production was reduced to 50%.

Vasoconstriction: a novel activity for low density lipoprotein

Low density lipoprotein plays an important role in the pathogenesis of atherosclerosis. Cumulative addition of 1-30 micrograms/ml of LDL from normolipidemic subjects produced a dose-dependent increase in contractile tension of thoracic aortic rings from rats. The maximal LDL-induced contractile response was approximately 30% of that induced by 1 microM norepinephrine. Similar concentrations of LDL induced a dose-dependent transient increase of the concentration of intracellular free calcium, and a biphasic change of the intracellular pH in cultured rat vascular smooth muscle cells. We conclude that low density lipoprotein occurring for example in the extravascular fluid can mediate vasoconstriction by changes in cytosolic calcium and intracellular pH.

Fish oil affects phosphoinositide turnover and thromboxane A metabolism in cultured vascular muscle cells

Fish oil has been reported as having beneficial effects on cardiovascular diseases. Elevated serum lipoproteins, prostaglandins and intracellular free calcium concentrations [( Ca2+]i) of the vasculature and thus the phosphoinositide (PI) turnover may be involved in the pathogenesis of these disorders. Therefore, the effect of fish oil on the potency of both low-density lipoprotein (LDL) and angiotensin II (AII) to stimulate the PI turnover in cultured rat vascular smooth muscle cells (VSMC) has been studied. Furthermore, a possible link between PI turnover activity and thromboxane A2 (TXA2) metabolism in these cells has been investigated. In VSMC cultured for up to 7 weeks with either fish oil or n-3 eicosapentaenoic acid (EPA) a decrease to 5-48% of the LDL-induced inositol trisphosphate (IP3) formation (= 100%) was found. A similar range of decreased IP3 synthesis was observed, when AII was used instead of LDL. Both LDL- and AII-stimulated TXA2 synthesis was suppressed concomitantly within the range 34-60%. Blockade of VSMC TXA2 biosynthesis with either indomethacin or TXA2 synthetase blocker (SQ-80338) inhibited LDL-induced formation of IP3 in a dose-dependent manner. Similar results were obtained, when TXA2 receptor coupling antagonists (SQ-27427 or BM-13177) were used. However, blockers of TXA2 synthesis and of TXA2 receptor binding failed to affect AII-induced formation of IP3.

The phosphoinositide turnover of vascular smooth muscle cells is influenced by fish oil

As the phosphoinositide cycle and high serum levels of low-density lipoprotein cholesterol may be involved in the pathogenesis of both hypertension and atherosclerosis, the effect of fish oil on low-density lipoprotein stimulation of phosphoinositide metabolism was studied in cultured rat vascular smooth muscle cells. Low-density lipoprotein-stimulated synthesis of inositol trisphosphate decreased to 5-48% of control values in vascular smooth muscle cells treated for 4 weeks with either fish oil or n-3 eicosapentaenoic acid (EPA), the active ingredient of fish oil. In addition, low-density lipoprotein-induced biosynthesis of thromboxane A2 was reduced by 50% in vascular smooth muscle cells precultured with either fish oil or EPA. Thus, our results may explain the mechanisms by which fish oil exerts its beneficial effects on both atherosclerosis and hypertension.

Stimulation of the phosphoinositide signalling system as a possible mechanism for glucocorticoid action in blood pressure control

Cortisol stimulates the phosphoinositide signalling system in smooth muscle cells of the rat aorta. After stimulation of the cells with cortisol, epinephrine or both compounds, inositol-1,4,5-trisphosphate concentrations were analysed by standardized ion-exchange chromatography procedure. A 15-min stimulation with physiological concentrations of cortisol (0.02-5.0 microgram/ml) led to a dose-dependent increase of the inositol trisphosphate concentrations (up to 500%) and also to a translocation of the calcium- and lipid-dependent protein kinase C activity from the cytosolic to the membranous compartment. Incubation of smooth muscle cells with epinephrine (10(-9) to -5 mol/l) did not lead to an increase in the inositol trisphosphate concentrations. However, after pre-incubation with an average dose of cortisol (0.2 microgram/ml) the inositol trisphosphate response was potentiated by 10(-7) mol/l epinephrine. Our results suggest that stimulation of the phosphoinositide system is a still unknown mechanism of glucocorticoid action in smooth muscle cells, which could influence intracellular free calcium and thus vascular reactivity and blood pressure.

Rapid activation of human platelets by low concentrations of low-density lipoprotein via phosphatidylinositol cycle

The interaction of low-density lipoprotein (LDL) with the human platelet was investigated with regard to saturable high-affinity binding, shape change, cytosolic free Ca2+ concentration, phosphatidylinositol (PtdIns) turnover, and thromboxane B2 biosynthesis. The experiments show that LDL, at a concentration approximately 100 times lower than in plasma, causes platelet activation concomitantly with stimulation of the PtdIns cycle and thromboxane B2 formation, similarly to other activators of platelets. The effects of LDL were inhibited by high-density lipoprotein. The results suggest that activation of platelets by low concentrations of LDL may play a role in pathophysiological conditions and that platelet can serve as a model for studying the influence of LDL on various target cells.

Low density lipoprotein causes general cellular activation with increased phosphatidylinositol turnover and lipoprotein catabolism

Low density lipoprotein (LDL), at concentrations high enough for receptor binding but not high enough to saturate the receptor, induces activation of phosphatidylinositol (PtdIns) turnover in a variety of cell types with various biological functions. Using both biochemical and electron microscopic studies, we have shown that blood platelets take up and degrade LDL in a manner reminiscent of phagocytic cell types. The activation of both PtdIns turnover and LDL metabolism is inhibited by high density lipoprotein. Thus, LDL at hormonal concentrations causes general cellular activation. Since all cell types studied responded to LDL with increased PtdIns turnover and uptake of LDL cholesterol, the PtdIns cycle may also be involved in the cellular regulation of LDL cholesterol metabolism.

Enalapril as a first-step agent in essential hypertension: a comparative study with atenolol

The aim of the present double-blind crossover study was to compare the antihypertensive efficacy and tolerability of enalapril and atenolol in 48 patients with mild to moderate essential hypertension. After a 2-week wash-out period, treatment was started with either enalapril 20 mg or atenolol 50 mg daily. In patients with a diastolic blood pressure value of more than 90 mmHg after 2 weeks of therapy, doses were doubled. After 4 weeks of therapy, cases were classified as responders (diastolic blood pressure less than or equal to 95 mmHg) or non-responders (diastolic blood pressure greater than 95 mmHg) and after a 2-week wash-out phase switched over to the alternative drug for another 4-week therapy period. Both substances significantly lowered mean systolic and diastolic blood pressure to a comparable degree. After 2 weeks, 57% of patients under enalapril and 59% under atenolol shared a satisfactory response, which did not change at the higher dose levels. After 4 weeks of therapy the incidence of side effects was slightly, but insignificantly, higher on atenolol than on enalapril. Thus, our results show that both agents seem equally qualified as first-step drugs in the treatment of mild to moderate essential hypertension.

Effect of atrial natriuretic polypeptide on angiotensin II-induced increase of cytosolic free calcium in cultured smooth muscle cells

We investigated the effects of angiotensin II (ANG II) and synthetic atrial natriuretic polypeptide (ANP) on cytosolic free calcium concentration [( Ca2+]i) of cultured rat vascular smooth muscle cells. Incubation with ANP alone showed little or no change in [Ca2+]i, whereas ANG II alone increased [Ca2+]i in a dose-dependent manner up to 164%, compared with basal levels of 253 +/- 17 nmol/l (mean +/- s.e.m.). Simultaneous addition of 10 nmol/l ANG II and varying concentrations of ANP produced a reduction in the ANG II-induced increase in [Ca2+]i. These data suggest that the vasorelaxant effect of ANP is at least partly mediated by changes in [Ca2+]i.

High density lipoproteins--modulators of the calcium channel?

It has recently been shown that human red blood cells possess a voltage-independent calcium channel which can be influenced by in vitro modification of the membraneous cholesterol content. To determine whether there is also a link between plasma lipids and the calcium influx through this channel under in vivo conditions, the calcium influx was measured in red blood cells from 51 male donors (aged 41 +/- 5 years). The influx through the channel was defined as the nitrendipine (15 mumol/l)-inhibitable part of 45Ca2+ influx. The Ca(2+)-ejecting ATPase was inhibited by vanadate. The results demonstrate a strong inverse relationship (r = -0.81; P < 0.001) between the plasma concentration of high density lipoproteins (HDL) and 45Ca2+ influx. No significant correlation was found between 45Ca2+ influx and triglycerides, low density lipoproteins (LDL), very low density lipoproteins (VLDL), total plasma cholesterol or extracellular electrolytes (K+, Na+, Ca2+, Mg2+). The results indicate that HDL are involved in the modulation of the calcium channel and provide a link between the cellular cholesterol turnover and the calcium influx in the pathogenesis of atherosclerosis and hypertension.

Stereospecific modulation of the calcium channel in human erythrocytes by cholesterol and its oxidized derivatives

To study the effect of cholesterol and its pathophysiologically important oxidized derivatives (OSC) on the calcium entry channel, the human red blood cell was used as a model system. The calcium ejecting adenosinetriphosphatase (ATPase) was inhibited by vanadate. The cells were loaded with OSC at concentrations between 1.25 X 10(-5) and 25 X 10(-5) mol/l. 22-Hydroxycholesterol, cholestan-3 beta,5 alpha,6 beta-triol, 5 alpha-cholestan-3 beta-ol,3 beta,5 alpha-dihydroxycholestan-6-one and 3 beta-hydroxy-5 alpha-cholestan-7-one stimulated 45Ca2+ influx by up to almost 90%, whereas 25-hydroxycholesterol, 7 beta-hydroxycholesterol, 20 alpha-hydroxycholesterol and 7-oxocholesterol inhibited influx by up to 75%. Both stimulation and inhibition were dependent on the amount of OSC incorporated into the membrane. More than 90% of the total modification of calcium influx by OSC was accounted for by an influence on the nitrendipine-inhibitable part of influx. Enrichment of cholesterol in the membrane greatly stimulated, and cholesterol depletion inhibited, Ca2+ influx. These results demonstrate that cholesterol and its oxidized derivatives are able to modulate the calcium channel in human red blood cells in a highly stereospecific manner.