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Biomedical subjects

Angelika M Vollmar

Publications and source records attributed to Angelika M Vollmar.

At least 19 recordsLinked to original sources
PubMed2007

Sesquiterpene lactones induce distinct forms of cell death that modulate human monocyte-derived macrophage responses.

Sesquiterpene lactones (SQTLs) are shown to possess anti-inflammatory as well as cytotoxic activity. No study, however, links both activities. We, therefore, hypothesized that SQTL-treated, dying cells might induce an anti-inflammatory response in cocultured THP-1 macrophages. Here we show that SQTLs bearing either an alpha,beta-unsaturated cyclopentenone or an alpha-methylene-gamma-lactone induce different forms of cell death. Whereas the cyclopentenone SQTL induced typical apoptosis, the alpha-methylene-gamma-lactone SQTLs-induced cell death lacked partly classical signs of apoptosis, such as DNA fragmentation. All SQTLs, however, activated caspases and the nuclear morphology of cell death was dependent on caspase activation. Most interestingly, alpha-methylene-gamma-lactone SQTLs induced a more pronounced phosphatidylserine (PS) exposure than the cyclopentenone SQTL. Especially, 7-hydroxycostunolide (HC), with an alpha-methylene-gamma-lactone substituted with a hydroxyl group, showed a striking fast and pronounced PS translocation. This result was in agreement with a strong activation of phagocytosis in cocultured THP-1 macrophages. Interestingly, HC-treated Jurkat cells led to an early (3.5 h) but transient increase in TNF-alpha levels in macrophage coculture. Release of TGF-beta remained unaffected after 18 h. We propose that this type of SQTL may influence local inflammation by transiently activating the immune system and help to clear cells by inducing a form of cell death that promotes phagocytosis.

Apoptosis↗
PubMed2007

Biologically active oxidized lipids (phytoprostanes) in the plant diet and parenteral lipid nutrition.

Phytoprostanes (PP) are autoxidation products of alpha-linolenate that are present in all plant tissues. Several classes of PP with a prostaglandin (PG) F1-, E1-, A1- and B1-like structure were identified and quantified by gas chromatography-mass spectrometry in vegetable oils and parenteral nutrition (intralipid). High levels of PP (0.09 up to 99 mg/l) were found even in apparently fresh vegetable oils. After oral consumption of olive or soybean oil, PPF1 were absorbed, found to circulate in plasma in conjugated form and excreted in free form into urine. Evidence is emerging that certain PP, such as the PPE1, may modulate the function of immune cells in a PG-like fashion. Here, we show that PPA1- and deoxy-PPJ1 display potent anti-inflammatory and apoptosis inducing activities similar to PGA1 and deoxy-PGJ2. Results of this study indicate that PP are novel, biologically active lipids in plant nutrition.

Adolescent↗
PubMed2006

MAPK phosphatase-1 represents a novel anti-inflammatory target of glucocorticoids in the human endothelium.

Glucocorticoids are well-established anti-inflammatory drugs thought to mainly act by inhibition of proinflammatory transcription factors like NF-kappaB. In recent years, however, transcription factor-independent mechanisms of glucocorticoid action have been proposed, namely the influence on MAPK pathways. Here we identify MAPK phosphatase-1 (MKP-1) as a pivotal mediator of the anti-inflammatory action of glucocorticoids in the human endothelium. We applied dexamethasone (Dex) to TNF-alpha-activated human endothelial cells and used the adhesion molecule E-selectin as inflammatory read-out parameter. Dex is known to reduce the expression of E-selectin, which is largely regulated by NF-kappaB. Here, we communicate that Dex at low concentrations (1-100 nM) markedly attenuates E-selectin expression without affecting NF-kappaB. Importantly, Dex is able to increase the expression of MKP-1, which causes an inactivation of TNF-alpha-induced p38 MAPK and mediates inhibition of E-selectin expression. In endothelial MKP-1(-/-) cells differentiated from MKP-1(-/-) embryonic stem cells and in MKP-1-silenced human endothelial cells, Dex did not inhibit TNF-alpha-evoked E-selectin expression. Thus, our findings introduce MKP-1 as a novel and crucial mediator of the anti-inflammatory action of glucocorticoids at low concentrations in the human endothelium and highlight MKP-1 as an important and promising anti-inflammatory drug target.

Animals↗
PubMed2006

Synthetic cryptolepine inhibits DNA binding of NF-kappaB.

The alkaloid cryptolepine is thought to mediate the anti-inflammatory effects of the climbing shrub, Cryptolepis sanguinoleta. The underlying mechanism of action, however, is largely unknown. In the present study, we show that the synthetic cryptolepine-hydrochloride (2.5-10microM) dose-dependently inhibits lipopolysaccharide (LPS)-induced nitric oxide production in the murine macrophage cell line RAW 264.7. We furthermore demonstrate a strong inhibition of nuclear factor (NF)-kappaB, a transcription factor primarily involved in inflammatory and immune responses, by cryptolepine (2.5-10microM) using a luciferase reporter gene assay in human HEK 293 cells. Examining the individual steps of NF-kappaB activation in the presence of cryptolepine we could exclude an inhibitory effect on degradation of IkappaB or nuclear translocation of NF-kappaB by the alkaloid. However, EMSA of nuclear extracts from LPS-activated RAW cells revealed reduced DNA binding activity of NF-kappaB by cryptolepine in vivo and in vitro. This indicates that cryptolepine may exhibit its anti-inflammatory action by blocking DNA binding of activated NF-kappaB and thus transcription of NF-kappaB-regulated proinflammatory proteins.

Alkaloids↗
PubMed2006

Atrial natriuretic peptide, a regulator of nuclear factor-kappaB activation in vivo.

Natriuretic peptides (NPs) comprise a family of vasoactive hormones that play important roles in the regulation of cardiovascular and renal homeostasis. Along this line, atrial NP (ANP) (international non-proprietary name: carperitide, HANP) is an approved drug for the treatment of acute heart failure. In recent years, evidence has been given that the NP system possesses a far broader biological spectrum than the regulation of blood pressure and volume homeostasis. In fact, a substantial amount of in vitro work indicates that ANP affects important inflammatory processes and signaling pathways. Quite surprisingly, however, no information exists on the in vivo antiinflammatory potential and signaling of ANP. We show here that pretreatment of lipopolysaccharide (Salmonella abortus equi, 2.5 mg/kg)-challenged mice with ANP (5 microg/kg iv, 15 min) rapidly inhibits nuclear factor-kappaB activation via inhibition of phosphorylation and degradation of the IkappaB-alpha protein. ANP also reduces Akt activation upon lipopolysaccharide injection. In ANP-pretreated mice, the increase of TNF-alpha serum concentration is markedly prevented; most importantly, the survival of these animals improved. These findings demonstrate both in vitro and in vivo an antiinflammatory profile of ANP that deserves to be further investigated in a therapeutic perspective.

Animals↗
PubMed2006

The marine product cephalostatin 1 activates an endoplasmic reticulum stress-specific and apoptosome-independent apoptotic signaling pathway.

Cephalostatin 1, a bis-steroidal marine natural product, has been reported to induce apoptosis without the requirement of an active caspase-8 or mitochondrial cytochrome c release and apoptosome formation. Here we show that despite the absence of these events, caspase-9 activation is essential for cephalostatin 1-induced apoptosis. Cephalostatin 1 initiates a rapid endoplasmic reticulum stress response characterized by phosphorylation of eukaryotic initiation factor-2 alpha-subunit and increased expression of the chaperone immunoglobulin heavy chain-binding protein GRP78 as well as the transcription factor C/EBP homologous protein (CHOP)/GADD153. Cephalostatin 1 activates apoptosis signal-regulating kinase 1 and c-Jun N-terminal kinase (JNK). However, this pathway does not play a major role in cephalostatin 1-induced apoptosis, as assessed by stable expression of a dominant negative apoptosis signal-regulating kinase 1. Importantly, the endoplasmic reticulum-associated caspase-4 is required and as shown by biochemical and genetic inhibition experiments, acts upstream of caspase-9 in cephalostatin-induced apoptosis.

Animals↗
PubMed2006

Evaluation of the analgesic and anti-inflammatory effects of a Brazilian green propolis.

Phamacological activities of a standard ethanol extract G1 from Brazilian green propolis, typified as BRP1, was evaluated in mouse models of pain and inflammation. Intraperitoneal injection ( I. P.) of G1 inhibited acetic acid-induced abdominal constrictions with an ID (50) = 0.75 +/- 0.05 mg/kg, and in the formalin test the ID (50) values were 0.85 +/- 0.07 mg/kg and 13.88 +/- 1.12 mg/kg, respectively, for the neurogenic and inflammatory phases. The extract was ineffective when assessed in the hot-plate assay. In serotonin-induced paw edema, G1 led to a maximal inhibition (MI) of 51.6 % after 120 min when administered I. P. and of 36 % after 15 min by the oral route ( O. R.). When the inflammatory agent was complete Freund's adjuvant, inhibition of paw edema was also observed after administration of the extract by both routes. In the capsaicin-induced ear edema the ID (50) values were 1.09 +/- 0.08 mg/kg ( I. P.) and 10.00 +/- 0.90 mg/kg ( O. R.). In the acute carrageenan-induced inflammatory reaction induced by carrageenan, G1 reduced the number of neutrophils in the peritoneal cavity with IC (50) values of 0.72 +/- 0.08 mg/kg and 4.17 +/- 0.50 mg/kg, by I. P. or O. R. administration, with a preferential migration of polymorphonuclear neutrophils. IN VITRO, G1 decreased nitric oxide production in LPS-stimulated RAW 264.7 cells (IC (50) = 41.60 microg/mL), and also the luciferase activity in TNF-alpha-stimulated HEK 293 cells transfected with NF-kappaB-luciferase reporter gene driven by the nuclear factor kappaB (NF-kappaB) (IC (50) = 200 microg/mL). This extract, which at low concentrations induces anti-inflammatory and analgesic effects in mouse models, presents a high content of flavonoids, known to inhibit inducible NOS (iNOS) activity. These data taken together led us to reinforce the hypothesis in the literature that the anti-inflammatory effect of propolis may be a due to inhibition of iNOS gene expression, through interference with NF-kappaB sites in the iNOS promoter.

Analgesics↗
PubMed2006

Nuclear factor-kappa B-independent anti-inflammatory action of salicylate in human endothelial cells: induction of heme oxygenase-1 by the c-jun N-terminal kinase/activator protein-1 pathway.

In contrast to aspirin, salicylate, its active metabolite, possesses profound anti-inflammatory properties without blocking cyclooxygenase. Inhibition of the transcription factor nuclear factor-kappaB (NF-kappaB) has been discussed to play a role in the anti-inflammatory profile of salicylate. However, NF-kappaB-independent effects of salicylate have been assumed but have up to now been poorly investigated. Therefore, the aim of the present study was to investigate NF-kappaB-independent anti-inflammatory mechanisms of salicylate in human umbilical vein endothelial cells using interleukin-4 (IL-4) as NF-kappaB-independent proinflammatory stimulus and P-selectin as inflammatory read-out parameter. Using quantitative real-time reverse transcription-polymerase chain reaction, we found that salicylate decreases IL-4-induced P-selectin expression. As judged by Western blot analysis, salicylate increased endothelial heme oxygenase-1 (HO-1) protein levels. Using both the HO-1 inhibitor tin(II) protoporphyrin IX and HO-1 antisense oligonucleotides, we causally linked the induction of HO-1 to the decrease of P-selectin. Moreover, we were interested in the signaling mechanisms leading to the up-regulation of HO-1 by salicylate. c-Jun NH2-terminal kinase (JNK) was found to be activated by salicylate, and we could causally link this activation to the induction of HO-1 by using the JNK inhibitor 1,9-pyrazoloanthrone. By applying activator protein-1 (AP-1) decoys, it was shown that the transcription factor AP-1 is crucially involved in the up-regulation of HO-1 downstream of JNK. In summary, our study introduces HO-1 as novel NF-kappaB-independent anti-inflammatory target of salicylate in human endothelial cells. Moreover, we elucidated the JNK/AP-1 pathway as crucial for the induction of HO-1 by salicylate.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

PI 3-kinase pathway is responsible for antiapoptotic effects of atrial natriuretic peptide in rat liver transplantation.

AIM: To investigate the in vivo effect of atrial natriuretic peptide (ANP) and its signaling pathway during orthotopic rat liver transplantation. METHODS: Rats were infused with NaCl, ANP (5 microg/kg), wortmannin (WM, 16 microg/kg), or a combination of both for 20 min. Livers were stored in UW solution (4 degrees C) for 24 h, transplanted and reperfused. Apoptosis was examined by caspase-3 activity and TUNEL staining. Phosphorylation of Akt and Bad was visualized by Western blotting and phospho-Akt-localization by confocal microscopy. RESULTS: ANP-pretreatment decreased caspase-3 activity and TUNEL-positive cells after cold ischemia, indicating antiapoptotic effects of ANP in vivo. The antiapoptotic signaling of ANP was most likely caused by phosphorylation of Akt and Bad, since pretreatment with PI 3-kinase inhibitor WM abrogated the ANP-induced reduction of caspase-3 activity. Interestingly, analysis of liver tissue by confocal microscopy showed translocation of phosphorylated Akt to the plasma membrane of hepatocytes evoked by ANP. CONCLUSION: ANP activates the PI-3-kinase pathway in the liver in vivo leading to phosphorylation of Bad, an event triggering antiapoptotic signaling cascade in ischemic liver.

Animals↗
PubMed2005

Hepatocyte cytoskeleton during ischemia and reperfusion--influence of ANP-mediated p38 MAPK activation.

AIM: To determine functional consequences of this activation, whereby we focused on a potential regulation of the hepatocyte cytoskeleton during ischemia and reperfusion. METHODS: For in vivo experiments, animals received ANP (5 microg/kg) intravenously. In a different experimental setting, isolated rat livers were perfused with KH-buffer+/-ANP (200 nmol/L) +/-SB203580 (2 micromol/L). Livers were then kept under ischemic conditions for 24 h, and either transplanted or reperfused. Actin, Hsp27, and phosphorylated Hsp27 were determined by Western blotting, p38 MAPK activity by in vitro phosphorylation assay. F-actin distribution was determined by confocal microscopy. RESULTS: We first confirmed that ANP preconditioning leads to an activation of p38 MAPK and observed alterations of the cytoskeleton in hepatocytes of ANP-preconditioned organs. ANP induced an increase of hepatic F-actin after ischemia, which could be prevented by the p38 MAPK inhibitor SB203580 but had no effect on bile flow. After ischemia untreated livers showed a translocation of Hsp27 towards the cytoskeleton and an increase in total Hsp27, whereas ANP preconditioning prohibited translocation but caused an augmentation of Hsp27 phosphorylation. This effect is also mediated via p38 MAPK, since it was abrogated by the p38 MAPK inhibitor SB203580. CONCLUSION: This study reveals that ANP-mediated p38 MAPK activation leads to changes in hepatocyte cytoskeleton involving an elevation of phosphorylated Hsp27 and thereby for the first time shows functional consequences of ANP-induced hepatic p38 MAPK activation.

Animals↗
PubMed2005

Resveratrol inhibits angiotensin II- and epidermal growth factor-mediated Akt activation: role of Gab1 and Shp2.

trans-Resveratrol (RV), a polyphenolic stilbene derivative found in grape skin and other food products, has been proposed to exert beneficial effects in cardiovascular disease. Our group has shown previously that RV inhibits angiotensin II (Ang II)-induced Akt activation and, consequently, vascular smooth muscle cell (VSMC) hypertrophy. In this work, to identify the molecular target of RV, we investigated the impact of RV on early signaling cascades in rat aortic VSMCs triggered by Ang II and epidermal growth factor (EGF). We show that RV does not influence Ang II-mediated transactivation of EGF-receptor but potently inhibits EGF-induced phosphorylation of Akt kinase, suggesting that RV acts downstream of EGF-receptor transactivation in VSMCs. Recent evidence indicates that the adapter molecule Gab1, together with the protein tyrosine phosphatase Shp2, is critically involved in regulating the strength and duration of phosphatidylinositol-3-kinase (PI3K) and Akt activation upon EGF stimulation in fibroblasts. Our results show that stimulation of VSMCs with EGF as well as Ang II leads to a rapid tyrosine phosphorylation of Gab1 and its association with the p85 subunit of PI3K. RV attenuates these processes. Experiments performed in Shp2-deficient fibroblasts revealed that RV does not inhibit EGF-stimulated Akt activation in these cells, suggesting that Shp2 is necessary for the inhibitory effect of RV on the PI3K/Akt pathway. Furthermore, RV treatment activates Shp2. We therefore propose that RV blocks Akt activation in Ang II- and EGF-stimulated VSMCs by activating Shp2, thus preventing interaction between Gab1 and PI3K that is necessary for further signal transduction.

3T3 Cells↗
PubMed2005

The role of atrial natriuretic peptide in the immune system.

Atrial natriuretic peptide (ANP) is a hormone predominately produced by the heart atria which regulates the water and salt balance as well as blood pressure homeostasis. Being expressed in various parts of the immune system a link of the peptide to the immune system has been proposed. In fact, this review focus on effects of ANP in the immune system and reports about the role of the peptide in innate immune functions as well as in the adaptive immune response.

Animals↗
PubMed2005

Cephalostatin 1 inactivates Bcl-2 by hyperphosphorylation independent of M-phase arrest and DNA damage.

Cephalostatin 1 is a marine product that induces a novel cytochrome c-independent apoptotic pathway in Jurkat leukemia T cells (Cancer Res 63:8869-8876, 2003). Here, we show that overexpression of the antiapoptotic protein Bcl-2 protects cells only partially against cephalostatin 1-induced apoptosis. The mechanism of Bcl-2 inactivation by cephalostatin 1 is based on hyperphosphorylation of Bcl-2 on Thr69 and Ser87 because Jurkat cells overexpressing a Bcl-2 protein with mutations on both phosphorylation sites were completely protected against cephalostatin 1. In search of the kinase responsible for Bcl-2 phosphorylation, c-Jun NH2-terminal kinase (JNK) was found to be activated by cephalostatin 1. Reduction of Bcl-2 phosphorylation by the specific JNK inhibitor (anthra(1,3-cd)pyrazol-6(2H)-one) SP600125 suggested a crucial role for JNK in this process. JNK activation was not a consequence of DNA damage, a known stimulus of JNK, because cephalostatin 1 did not induce DNA lesions as shown by the comet assay. Arrest in M-phase is also demonstrated to be associated with JNK activation. However, cephalostatin 1 does not evoke an arrest in M-phase as shown by flow cytometry. Together, cephalostatin 1 is shown to induce JNK activation with subsequent Bcl-2 phosphorylation and inactivation. Reported triggers, such as the induction of an M-phase arrest or DNA damage are not involved in this process, suggesting a novel mechanism for cephalostatin 1-mediated Bcl-2 hyperphosphorylation.

Cell Division↗
PubMed2005

The soy isoflavone genistein induces a late but sustained activation of the endothelial nitric oxide-synthase system in vitro.

Cardiovascular diseases are known as the major causes of death or disability in western countries. Decreased bioavailability of endothelial derived nitric oxide (NO) is recognized as an important promoter in cardiovascular disease. In vivo studies suggest that phytoestrogens, especially isoflavones from soy, enhance endothelium-dependent vasoreactivity. We hypothesized that isoflavones may affect the expression of endothelial-type nitric oxide synthase (eNOS) and thereby NO formation in vitro. Human EA.hy926 endothelial cells were treated with the soybean isoflavones biochanin A and formononetin and with their metabolites genistein and daidzein. eNOS promoter activity was examined by a luciferase reporter gene assay (20 h). Active eNOS was detected by quantifying conversion of L-arginine to L-citrulline and by measuring NO released from endothelial cells using the fluorescent probe DAF-2 (20-96 h).eNOS promoter activity increased in response to isoflavone treatment (20 h). NO and L-citrulline production by EA.hy926 cells rose up to 1.7-fold of control levels after stimulation with genistein for 48-96 h. From these results, we conclude that the suggested positive effects of soy isoflavones on vascular reactivity may be indeed mediated via a long-term effect on the eNOS system.

Arginine↗
PubMed2005

Metalloporphyrins inactivate caspase-3 and -8.

Activation of caspases represents one of the earliest biochemical indicators for apoptotic cell death. Therefore, measurement of caspase activity is a widely used and generally accepted method to determine apoptosis in a wide range of in vivo and in vitro settings. Numerous publications characterize the role of the heme-catabolizing enzyme heme oxygenase-1 (HO-1) in regulating apoptotic processes. Different metalloporphyrins representing inducers and inhibitors of this enzyme are often used, followed by assessment of apoptotic cell death. In the present work, we found that caspase-3-like activity, as well as activity of caspase-8 measured in either Fas (CD95) ligand-treated Jurkat T-lymphocytes or by the use of recombinant caspase-3 or -8, was inhibited by different metalloporphyrins (cobalt(III) protoporphyrin IX, tin and zinc(II) protoporphyrin-IX). Moreover, employing the mouse model of Fas-induced liver apoptosis these properties of porphyrins could also be demonstrated in vivo. The metalloporphyrins were shown to inhibit caspase-3-mediated PARP cleavage. Molecular modeling studies demonstrated that porphyrins can occupy the active site of caspase-3 in an energetically favorable manner and in a binding mode similar to that of known inhibitors. The data shown here introduce metalloporphyrins as direct inhibitors of caspase activity. This finding points to the need for careful employment of metalloporphyrins as modulators of HO-1.

Animals↗
PubMed2005

Vasoprotective actions of the atrial natriuretic peptide.

The Natriuretic Peptide (NP) family, especially its best-characterized member Atrial Natriuretic Peptide (ANP), plays an important role in the regulation of blood pressure homeostasis and salt and water balance. Besides their action in cardiovascular physiology, NPs have been described as anti-inflammatory regulators of macrophage function: they have been reported to inhibit the induction of inflammatory mediators, such as iNOS, COX-2, and TNF-alpha. In the following review we will focus on a rather novel aspect of NP action: NPs, especially ANP, will be presented as vasoprotective agents. We will specifically focus on ANP's interaction with the complex intracellular signalling networks responsible for proliferation, vascular permeability, attraction and adhesion of leukocytes, and the induction of cytoprotective proteins. We will also discuss the critical mediator systems involved in mediating ANP's beneficial actions. Recently, ANP as well as BNP, another member of the NP family, have been introduced as cardiovascular therapeutics. In this context, we will highlight the physiological and pharmacological relevance of NPs, particularly ANP, as endogenous vasoprotective agents.

Animals↗
PubMed2004

Atrial natriuretic peptide induces mitogen-activated protein kinase phosphatase-1 in human endothelial cells via Rac1 and NAD(P)H oxidase/Nox2-activation.

The cardiovascular hormone atrial natriuretic peptide (ANP) exerts anti-inflammatory effects on tumor necrosis factor-alpha-activated endothelial cells by inducing mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1). The underlying mechanisms are as yet unknown. We aimed to elucidate the signaling pathways leading to an induction of MKP-1 by ANP in primary human endothelial cells. By using antioxidants, generation of reactive oxygen species (ROS) was shown to be crucially involved in MKP-1 upregulation. ANP was found to increase ROS formation in cultured cells as well as in the endothelium of intact rat lung vessels. We applied NAD(P)H oxidase (Nox) inhibitors (apocynin and gp91ds-tat) and revealed this enzyme complex to be crucial for superoxide generation and MKP-1 expression. Moreover, by performing Nox2/4 antisense experiments, we identified Nox2 as the critically involved Nox homologue. Pull-down assays and confocal microscopy showed that ANP activates the small Rho-GTPase Rac1. Transfection of a dominant-negative (RacN17) and constitutively active Rac1 mutant (RacV12) indicated that ANP-induced superoxide generation and MKP-1 expression are mediated via Rac1 activation. ANP-evoked production of superoxide was found to activate c-Jun N-terminal kinase (JNK). Using specific inhibitors, we linked ANP-induced JNK activation to MKP-1 expression and excluded an involvement of protein kinase C, extracellular signal-regulated kinase, and p38 MAPK. MKP-1 induction was shown to depend on activation of the transcription factor activator protein-1 (AP-1) by using electrophoretic mobility shift assay and AP-1 decoys. In summary, our work provides insights into the mechanisms by which ANP induces MKP-1 and shows that ANP is a novel endogenous activator of endothelial Rac1 and Nox/Nox2.

Acetophenones↗