Biomedical subjects

Reto Asmis

Publications and source records attributed to Reto Asmis.

12 recordsLinked to original sources

PubMed2006

Positive effect of dietary soy in ESRD patients with systemic inflammation--correlation between blood levels of the soy isoflavones and the acute-phase reactants.

BACKGROUND: Inflammation is commonly associated with malnutrition and cardiovascular disease in end-stage renal failure patients. Anti-inflammatory properties of the isoflavones, a micronutrient component of soy, have been reported in several experimental models and disease conditions, but never in renal failure. We hypothesized that dietary soy isoflavones correct laboratory evidence of systemic inflammation in haemodialysis (HD) patients with underlying high blood levels of C-reactive protein (CRP). METHODS: End-stage renal disease patients on chronic HD, with elevated CRP (>10.0 mg/l) were enrolled in this pilot study. The subjects were double-blind randomly distributed with 2 : 1 ratio to receive isoflavone-containing soy-based nutritional supplements (soy group) or isoflavone-free milk protein (control group) for 8 weeks. Serum isoflavone, inflammatory markers and nutrition markers were assessed at baseline and at the end of the treatment. RESULTS: Thirty-two subjects were enrolled. Fifteen subjects in the soy group and 10 in the control group completed the study; five dropouts were due to acute illness and two due to food intolerance. After intervention, blood isoflavone levels were 5- to 10-fold higher in the soy group than in the control group [e.g. median genistein (25-75th percentile): 337.9 (175.5-1007) nM in the soy group vs 41.4 (22.9-100.4) nM in the control group; P < 0.001]. However, the isoflavone levels ranged widely in the soy group (e.g. genistein: 33-1868 nM) and, depending on the individual compound, four to seven subjects had end-of-treatment levels that were not different from baseline. Variation from baseline of the individual serum isoflavone levels (Delta-isoflavone) and CRP displayed a strong inverse correlation in the soy group (R = -0.599, P < 0.02). In addition, Delta-isoflavone correlated positively with the variation of albumin (R = 0.522, P = 0.05) and insulin-like growth factor-1 (R = 0.518, P < 0.05). Group levels of CRP were not statistically different after intervention although a trend towards lower levels was noted in the soy group [18.2 (12.7-29.1) mg/l at baseline vs 9.7 (5.2-20.7) mg/l at week 8; NS] but not in the control group [20.6 (9.2-38.5) vs 17.6 (9.1-40.7) mg/l]. CONCLUSION: These data suggest the possibility of beneficial effects of isoflavone-rich soy foods on the inflammatory and nutritional status of HD patients with underlying systemic inflammation.

Acute-Phase Proteins↗

PubMed2006

Molecular mechanism of glutathione-mediated protection from oxidized low-density lipoprotein-induced cell injury in human macrophages: role of glutathione reductase and glutaredoxin.

Macrophage death is a hallmark of advanced atherosclerotic plaque, and oxidized low-density lipoprotein (OxLDL) found in these lesions is believed to contribute to macrophage injury. However, the underlying mechanisms of this phenomenon are only poorly understood. Here we show that in human monocyte-derived macrophages, OxLDL depleted intracellular glutathione (GSH) and inhibited glutathione reductase, resulting in a marked diminution of the glutathione/glutathione disulfide ratio. In the absence of OxLDL, an 80% depletion of intracellular GSH levels did not affect cell viability, but glutathione depletion dramatically increased OxLDL-induced cell death. Conversely, supplementation of intracellular GSH stores with glutathione diethyl ester substantially diminished OxLDL toxicity. OxLDL also promoted protein-S-glutathionylation, which was increased in macrophages pretreated with the glutathione reductase inhibitor BCNU. Knockdown experiments with siRNA directed against glutathione reductase and glutaredoxin showed that both enzymes are essential for the protection of macrophages against OxLDL. Finally, the peroxyl-radical scavenger Trolox did not prevent GSH depletion but completely blocked OxLDL-induced protein-S-glutathionylation and cell death. These data suggest that OxLDL promotes ROS formation and protein-S-glutathionylation by a mechanism independent from its effect on GSH depletion. Neither mechanism was sufficient to induce macrophage injury, but when stimulated concurrently, these pathways promoted the accumulation of protein-glutathione mixed disulfides and cell death.

Cell Death↗

PubMed2006

Adriamycin promotes macrophage dysfunction in mice.

Impaired wound healing contributes to the morbidity and mortality associated with adriamycin chemotherapy. Macrophages are essential for tissue repair and loss of macrophage function leads to impaired wound healing. We recently showed that adriamycin is a potent inducer of thiol oxidation and cell injury in cultured macrophages (FASEB J. 19:1866-1868; 2005). Here we tested the hypothesis that adriamycin also promotes oxidative stress and macrophage dysfunction in vivo. We treated FVB mice twice a week either with low doses of adriamycin (4 mg/kg) or with the same volume of saline by tail vein injection for a total of 8 injections. Wound healing was significantly delayed in adriamycin-treated mice. The number of resident peritoneal macrophages was decreased by 30% and macrophage recruitment in response to thiogycolate stimulation was decreased by 46% in mice treated with adriamycin. LPS-induced TNFalpha and IL-1beta secretion from macrophages of adriamycin-treated mice was decreased by 28.7 and 29.5%, respectively, compared to macrophages isolated from saline-injected mice. Peritoneal macrophages isolated from adriamycin-treated mice also showed increased formation of reactive oxygen species and enhanced protein-S-glutathionylation. In summary, our results show that low cumulative doses of adriamycin are sufficient both to promote sustained thiol oxidative stress and macrophage dysfunction in vivo and to delay tissue repair, suggesting that macrophage dysfunction contributes to impaired wound healing associated with adriamycin chemotherapy.

Animals↗

PubMed2006

Scavenger receptor BI prevents nitric oxide-induced cytotoxicity and endotoxin-induced death.

Nitric oxide (NO)-induced oxidative stress contributes to a variety of diseases. Although numerous mechanisms have been described controlling the production of NO, the mechanisms to prevent NO-induced cytotoxicity after NO synthesis are largely unknown. Here we report that scavenger receptor BI (SR-BI) prevents NO-induced cytotoxicity. Using CHO cell lines expressing wild-type and single-site mutant SR-BI protein, we demonstrate that SR-BI prevents NO-induced cytotoxicity and that a highly conserved CXXS redox motif is required for the anti-NO cytotoxicity activity of SR-BI. Using genetically manipulated mice, we demonstrate that SR-BI-null mice have a 3- to 4-fold increase in tyrosine nitrated proteins in aorta and liver compared with wild-type littermates, indicating that expression of SR-BI prevents peroxynitrite formation in vivo. Using lipopolysacharide (LPS)-challenged mice as an in vivo model of NO-induced cytotoxicity, we found that a single dose of LPS (120,000 U/g IP) induced 90% fatality of SR-BI-null mice within 3 days, whereas all of the wild-type littermates survived (n=20), demonstrating that SR-BI is highly protective against NO cytotoxicity in vivo. Importantly, SR-BI prevents LPS-induced death without eliminating NO production, suggesting that SR-BI prevents NO-induced cytotoxicity post-NO synthesis. Our study describes a novel observation that may shed new light on the treatment of nitric oxidative stress-associated diseases, such as septic shock.

Amino Acid Sequence↗

PubMed2006

P53 status influences regulation of HSPs and ribosomal proteins by PDTC and radiation.

Pyrrolidine dithiocarbamate (PDTC) is a thiol-containing compound that can act under varying conditions as an anti-oxidant or pro-oxidant. Utilizing microarrays, we determined the effect of PDTC +/- ionizing radiation (IR) on the expression of heat shock protein (HSP) genes in isolated B6/129 wild-type (WT) and p53-/- spleen cells. Extremely significant microarrays demonstrated that PDTC, but not IR, markedly up-regulated the expression of the majority of detectable HSP genes in WT and many to a significantly greater degree in p53-/- deficient cells. Determination of the glutathione/glutathione disulfide ratio indicated that PDTC was acting as a pro-oxidant under these conditions. From these data we conclude that the clinical use of "antioxidants" with radiotherapy or chemotherapy must be very carefully based on knowledge of the p53 status of their intended normal and tumor target cells.

Animals↗

PubMed2005

A novel thiol oxidation-based mechanism for adriamycin-induced cell injury in human macrophages.

Adriamycin is a widely used antitumor antibiotic, but its use has been limited by its cytotoxicity in both cardiomyocytes and non-cardiac tissues. While adriamycin's ability to redox cycle via one-electron transfer reactions and generate ROS is thought to promote cardiotoxicity, the mechanisms involved in non-cardiac tissue injury are not clear. Here we show that prolonged exposure (48 h) of human monocyte-derived macrophages to adriamycin at concentrations as low as 1 microM promotes caspase-independent cell death. Treatment of cells with scavengers of superoxide and peroxyl radicals blocked adriamycin-induced oxidation of dichlorodihydrofluorescein (DCFH) but did not prevent macrophage injury. Macrophages treated with either adriamycin or the thiol oxidant diamide showed elevated levels of glutathione disulfide and increased protein-S-glutathionylation prior to cell injury, indicating that thiol oxidation is involved in adriamycin-induced macrophage death. Furthermore, inhibition of glutathione reductase (GR) with 1,3-bis[2-chloroethyl]-1-nitrosourea or transfection of macrophages with small inhibitory RNA (siRNA) directed against GR or glutaredoxin (Grx) potentiated adriamycin-induced macrophage injury. Thus, both GR and Grx appear to play a crucial role in protecting macrophages from adriamycin-induced cell injury. These findings suggest a new mechanism for adriamycin-induced tissue injury whereby thiol oxidation, rather than one-electron redox cycling and ROS generation, mediates adriamycin-induced cell damage.

Antineoplastic Agents, Alkylating↗

PubMed2005

Lipoprotein aggregation protects human monocyte-derived macrophages from OxLDL-induced cytotoxicity.

Oxidative modifications render low density lipoprotein cytotoxic and enhance its propensity to aggregate and fuse into particles similar to those found in atherosclerotic lesions. We showed previously that aggregation of oxidized LDL (OxLDL) promotes the transformation of human macrophages into lipid-laden foam cells (Asmis, R., and J. Jelk. 2000. Large variations in human foam cell formation in individuals. A fully autologous in vitro assay based on the quantitative analysis of cellular neutral lipids. Atherosclerosis. 148: 243-253). Here, we tested the hypothesis that aggregation of OxLDL enhances its clearance by human macrophages and thus may protect macrophages from OxLDL-induced cytotoxicity. We found that increased aggregation of OxLDL correlated with decreased macrophage injury. Using 3H-labeled and Alexa546-labeled OxLDL, we found that aggregation enhanced OxLDL uptake and increased cholesteryl ester accumulation but did not alter free cholesterol levels in macrophages. Acetylated LDL was a potent competitor of aggregated oxidized LDL (AggOxLDL) uptake, suggesting that scavenger receptor A plays an important role in the clearance of AggOxLDL. Inhibitors of actin polymerization, cytochalasin B, cytochalasin D, and latrunculin A, also prevented AggOxLDL uptake and restored OxLDL-induced cytotoxicity. This suggests that OxLDL-induced macrophage injury does not require OxLDL uptake and may occur on the cell surface. Our data demonstrate that aggregation of cytotoxic OxLDL enhances its clearance by macrophages without damage to the cells, thus allowing macrophages to avoid OxLDL-induced cell injury.

Actins↗

PubMed2005

A novel ligand-independent apoptotic pathway induced by scavenger receptor class B, type I and suppressed by endothelial nitric-oxide synthase and high density lipoprotein.

Scavenger receptor class B, type I (SR-BI)/ApoE double null mice develop severe atherosclerosis within 4 weeks, whereas ApoE null mice take several months to develop the disease, indicating that SR-BI plays a pivotal role in atherosclerosis. Importantly, SR-BI/ApoE double null mice have lower plasma cholesterol levels than ApoE null mice, suggesting involvement of a non-lipids mechanism. In the present study, we revealed a novel ligand-independent apoptotic pathway induced by SR-BI, and regulated by endothelial nitric-oxide synthase (eNOS) and high density lipoprotein (HDL). SR-BI significantly induces apoptosis in three independent cell systems. In contrast to known ligand-dependent apoptotic pathways, SR-BI-induced apoptosis is ligand-independent. We further showed that SR-BI-induced apoptosis is suppressed by eNOS and HDL. By using a single site mutation, we demonstrated that SR-BI induces apoptosis through a highly conserved CXXS redox motif. We finally demonstrated that SR-BI-induced apoptosis is via the caspase-8 pathway. We hypothesize that in healthy cells, the SR-BI apoptotic pathway is turned off by eNOS and HDL which prevents inappropriate apoptotic damage to the vascular wall. When HDL levels are low, oxidative stress causes the relocation of eNOS away from caveolae, which turns on SR-BI-induced apoptosis and rapidly clears damaged cells to prevent further inflammatory damage to neighboring cells. The current studies offer a new paradigm in which to study the non-cholesterol effects of SR-BI, HDL, and eNOS on the development of atherosclerosis and potentially other cardiovascular diseases.

Amino Acid Motifs↗

PubMed2004

Low-density lipoprotein from apolipoprotein E-deficient mice induces macrophage lipid accumulation in a CD36 and scavenger receptor class A-dependent manner.

OBJECTIVE: To investigate the potential of circulating low-density lipoprotein (LDL), isolated from apolipoprotein E (apoE)-deficient mice (E-/-LDL) and from LDL receptor-deficient mice (Lr-/-LDL), to induce foam cell formation. METHODS AND RESULTS: Binding studies using COS-7 cells overexpressing CD36, J774 cells, and mouse peritoneal macrophages (MPMs) unexpectedly showed for the first time that E-/-LDL, which is enriched in cholesterol, is a high-affinity ligand for CD36 and exhibited greater macrophage uptake than Lr-/-LDL or normal LDL. Minimal copper-mediated oxidization of Lr-/-LDL or C57LDL in vitro resulted in increased ligand internalization, although cell uptake of these oxidized LDLs was lower than that of E-/-LDL, even at oxidation levels similar to that found in E-/-LDL. Treatment of MPMs with E-/-LDL and Lr-/-LDL (to a 2- to 3-fold lesser extent), but not normal LDL, resulted in significant cellular cholesteryl ester accumulation and foam cell formation. Experiments using MPMs lacking CD36, scavenger receptor class A (SR-A), or both, indicated a major contribution of CD36 ( approximately 50%), and to a lesser extent, SR-A (24% to 30%), to E-/-LDL uptake. CONCLUSIONS: Because of its increased state of oxidation and high cholesterol content, LDL in apoE-deficient mice acts in a proatherogenic manner, without requiring further modification in the vascular wall, to induce foam cell formation through its uptake by scavenger receptors.

Adenoviridae↗

PubMed2004

Acute hyperhomocysteinemia decreases NO bioavailability in healthy adults.

Hyperhomocysteinemia is associated with decreased vascular reactivity and increased cardiovascular morbidity. Oxidative stress and reduced NO bioavailability have been proposed as a mechanism for the adverse effects of chronically elevated plasma homocysteine levels. Recent studies suggest that acute elevations of plasma homocysteine may also impair endothelial function and vasodilation, however, the mechanism is not clear. In the present study, we investigated whether moderate hyperhomocysteinemia after methionine loading decreases NO bioavailability, increases oxidative stress, and impairs receptor-mediated NO-dependent venodilation in healthy adults. After oral methionine loading (0.1g/kg), mean homocysteine concentrations increased 3.2-fold, from 6.9 +/- 0.5 to 27.8 +/- 1.9 micromol/l (n = 16), whereas plasma NO(x) concentrations, an indicator of NO release, were decreased by 12% compared to placebo treatment (P = 0.005). Vitamin E levels in freshly isolated low density lipoprotein (LDL), a sensitive marker of LDL oxidation, and LDL lipid (hydro)peroxide levels were unchanged after methionine loading. Endothelium-dependent venodilation induced by bradykinin was reduced by 18% during hyperhomocysteinemia (P = 0.06). Taken together our data suggest that the reduced NO bioavailability was likely due to decreased NO synthesis and release rather than to NO destruction by oxidative stress.

Adult↗

PubMed2003

Oxidized LDL promotes peroxide-mediated mitochondrial dysfunction and cell death in human macrophages: a caspase-3-independent pathway.

Several studies suggest that macrophage death and subsequent lysis contribute to the development of advanced atherosclerotic lesions. Although oxidized LDL (OxLDL) is thought to contribute to lesion formation and induces macrophage apoptosis, the mechanisms underlying macrophage lysis have not been well defined. To determine if induction of apoptosis in human macrophages also promotes cell lysis, we studied caspase-3 activation by OxLDL and activating anti-Fas antibodies. We found that Fas-induced activation of caspase-3 does not promote macrophage lysis and caspase-3 activation is not required for OxLDL-induced macrophage lysis. OxLDL induces the formation of peroxides, but not superoxide, and decreases mitochondrial membrane potential. Scavengers of peroxyl radicals restore mitochondrial membrane potential and prevent macrophage lysis, implicating peroxyl radicals in both mitochondrial dysfunction and macrophage lysis induced by OxLDL. We conclude that macrophage death induced by OxLDL results in cell lysis, but it does not require activation of Fas or caspase-3. The full text of this article is available at http://www.circresaha.org.

Antibodies↗

PubMed2002

Fluid shear stress attenuates hydrogen peroxide-induced c-Jun NH2-terminal kinase activation via a glutathione reductase-mediated mechanism.

c-Jun NH2-terminal kinase (JNK) is activated by a number of cellular stimuli including reactive oxygen species (ROS). Previous studies have demonstrated that fluid shear stress (flow) inhibits cytokine-induced JNK activation in endothelial cells (ECs). In the present study, we show JNK activation by ROS in ECs and hypothesized that flow inhibits ROS-induced JNK activation in ECs via modulation of cellular protection systems against ROS. JNK was activated by 300 micro mol/L hydrogen peroxide (H2O2) in bovine lung microvascular ECs (BLMVECs) with a peak at 60 minutes after stimulation (6.3+/-1.2-fold increase). Preexposure of BLMVECs to physiological steady laminar flow (shear stress=12 dyne/cm2) for 10 minutes significantly decreased H2O2-induced JNK activation. Thioredoxin and glutathione are cellular antioxidants that protect cells against ROS. Flow induced a significant increase in the ratio of reduced glutathione to oxidized glutathione consistent with a 1.6-fold increase in glutathione reductase (GR) activity. Preincubation of BLMVECs with the GR inhibitor, 1,3 bis-(2 chloroethyl)-1-nitrosourea, abolished the inhibitory effect of flow. In contrast, preincubation of BLMVECs with azelaic acid, a specific inhibitor for thioredoxin reductase, did not alter the effect of flow on H2O2-induced JNK activation. Overexpression of GR mimicked the effect of flow to inhibit JNK activation. These results suggest that flow activates GR, an important regulator of the intracellular redox state of glutathione, and exerts a protective mechanism against oxidative stress in endothelial cells.

Animals↗