Biomedical subjects

Csaba Szabo

Publications and source records attributed to Csaba Szabo.

24 records · Page 2Linked to original sources

PubMed2003

Integrin-mediated suppression of endotoxin-induced DNA damage in lung endothelial cells is sensitive to poly(ADP-ribose) polymerase-1 gene deletion.

Endotoxin (LPS) is a cause of adult respiratory distress syndrome (ARDS), a disease which is preceded by acute lung injury involving the pulmonary endothelium. Experimentally, LPS causes acute DNA strand breakage in mouse lung endothelial cells (MLEC). Engagement of integrin cell adhesion receptors inhibits acute DNA breakage, which could be of use in reducing lung injury. Because integrins presumably inhibit DNA damage or activate repair, we hypothesized that the DNA-damage response protein, poly(ADP-ribose) polymerase-1 (PARP-1), regulates the protective action of integrins, as well as sensitivity to LPS. Therefore, the effect of LPS on MLEC cultured from wild-type and PARP-1 knockout mice was determined. Fluorescence microscopic measures were used to assess plasma membrane integrity, PARP activity, DNA strand breakage and DNA repair in attached cells. LPS caused a concentration-dependent increase in the permeability of wild-type MLEC. Engagement of beta1 integrins with an antibody protected wild-type MLEC from this LPS-induced injury. Wild-type cells treated with the PARP-inhibitor, 3-aminobenzamide, and PARP-1 knockout MLEC were also resistant. LPS caused acute DNA breakage in both wild-type and knockout MLEC, but PARP was activated only in wild-type cells. LPS-induced DNA breakage was inhibited by 3-aminobenzamide, but not by knockout. Anti-beta1 integrin antibody also inhibited the DNA breakage and PARP activation caused by LPS in wild-type MLEC. However, integrin engagement did not prevent DNA breakage in PARP-1 knockout cells, despite a similar level of beta1 integrin in wild-type and knockout cells. Thus, integrin engagement, 3-aminobenzamide, and PARP-1 deletion protected MLEC from increases in membrane permeability caused by LPS. PARP-1 deletion also impaired the ability of integrin engagement to inhibit LPS-induced DNA breakage, suggesting that knockout may affect nuclear factors necessary for integrin-mediated suppression of LPS-induced DNA breakage.

Animals↗

PubMed2002

Aerosolized linear polyethylenimine-nitric oxide/nucleophile adduct attenuates endotoxin-induced lung injury in sheep.

Pulmonary hypertension and edema are mainstays of acute lung injury (ALI). We synthesized linear polyethylenimine-nitric oxide/nucleophile adduct (DS-1), a water-soluble nitric oxide donor, and demonstrated that it is a potent relaxant of precontracted rat aortic rings without inducing desensitization. Moreover, DS-1 does not suppress the viability of human pulmonary epithelial cells in vitro. We also tested whether DS-1 counteracts ALI in endotoxemic sheep. Animals were instrumented for a chronic study. In 16 awake, spontaneously breathing sheep, Escherichia coli endotoxin (10 ng/kg/minute) was infused for 8 hours. From 2 hours of endotoxemia, sheep received either nebulized DS-1 (1 mg/kg/hour) or isotonic saline. DS-1 reduced endotoxin-induced rises in pulmonary arterial and microwedge pressures and vascular resistance index by 40-70%. In parallel, DS-1 decreased the accumulation of extravascular lung water by 60-70% and reduced the increment in right ventricle stroke work index and the falls in right ventricle ejection fraction, stroke volume, and left ventricle stroke work indices. Furthermore, DS-1 reduced venous admixture and improved arterial oxygen saturation. In four healthy animals, DS-1 alone slightly increased arterial oxygenation but had no other effects. Thus, aerosolized DS-1 attenuates endotoxin-induced ALI in sheep by reducing pulmonary hypertension and edema and improving myocardial function and gas exchange.

Acute Disease↗

PubMed2002

Myocardial protection by PJ34, a novel potent poly (ADP-ribose) synthetase inhibitor.

BACKGROUND: The activation of poly (ADP-ribose) synthetase plays an important role in the pathogenesis leading to myocardial ischemia-reperfusion injury. The aim of this study was to determine if a novel potent inhibitor of poly (ADP-ribose) synthetase, PJ34, provides myocardial protection. METHODS: Pigs were subjected to 60 minutes of regional ischemia followed by 180 minutes of reperfusion. Ten mg/kg of PJ34 (PJ34; n = 6) was administrated intravenously (treated group) from 15 to 5 minutes before reperfusion followed by 3 mg/kg/hour of PJ34 from 5 minutes before reperfusion to the end of 180 minutes reperfusion. Control pigs (n = 7) received vehicle only. Arterial and left ventricular pressure and coronary flow were monitored. RESULTS: The PJ34 showed significant reduction on infarct size (37.5%+/-4.5% and 50.5%+/-4.8% of the area at risk) for PJ34 and control pigs groups, respectively, (p < 0.05). Significant reduction in postsystolic shortening, as well as improvement on segment shortening, and positive first derivative of pressure over time (+dP/dt) maximum were also observed in PJ34 versus control pigs (p < 0.05). CONCLUSIONS: Our results suggest that PJ34 provides cardioprotection by decreasing myocardial infarct size and enhancing postischemic regional and global functional recovery.

Animals↗

PubMed2002

PARP as a Drug Target for the Therapy of Diabetic Cardiovascular Dysfunction.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a member of the PARP enzyme family consisting of PARP-1 and a growing family of additional, novel poly(ADP-ribosylating) enzymes. PARP-1 is one of the most abundant nuclear proteins, and it functions as a DNA nick sensor enzyme. Upon binding to DNA breaks, activated PARP cleaves NAD(+) into nicotinamide and ADP-ribose and polymerizes the latter onto nuclear acceptor proteins including histones, transcription factors and PARP itself. Overactivation of PARP in response to oxidant- and free radical-mediated excessive DNA single strand breaks promotes cell dysfunction and necrotic-type cell death in a variety of pathophysiological conditions. Emerging data indicate that high circulating glucose in diabetes mellitus is able to induce free radical and oxidant generation in the cardiovascular system with the concomitant activation of PARP. This process results in acute loss of the ability of the endothelium to release nitric oxide (endothelial dysfunction) and leads to a severe functional impairment of the heart (diabetic cardiomyopathy). Accordingly, pharmacological inhibition of PARP protects against diabetic cardiovascular dysfunction. Surprisingly, PARP inhibition not only prevents the development of diabetic endothelial dysfunction, but also restores normal vascular function in established diabetes. In addition to the direct cytotoxic pathway regulated by DNA injury and PARP activation, PARP also modulates the course of cardiovascular inflammation and injury by regulating the activation of NF-kappaB, and the expression of a number of proinflammatory genes. The research into the role of PARP in diabetic cardiovascular injury is now supported by novel tools, such as new classes of potent inhibitors of PARP, as well as genetically engineered animals lacking the gene for PARP. Inhibitors of PARP may become useful in the experimental therapy of diabetic vascular complications. (c) 2002 Prous Science. All rights reserved.

Journal Article↗

PubMed2002

The Flagellin-TLR5 Axis: Therapeutic Opportunities.

Motile bacteria synthesize large-sized surface structures known as flagella through the ordered polymerization of protein subunits. Flagellin, a protein of 40-60 kDa, is the principal constituent of the flagellum; each flagellum consists of approximately 20,000 flagellin molecules. An alignment of the amino acid sequences from different Gram-negative species shows a high degree of similarity in the amino and carboxy terminal domains. In contrast, the central hypervariable regions of these proteins are quite divergent. Recent work reveals that--in addition to playing a role in bacterial adhesion--monomeric flagellin, a protein component of flagellated bacteria, can also act as a soluble immunostimulatory and proinflammatory factor, activating the immune/inflammatory axis via the Toll-like receptor 5-nuclear factor-kappaB axis. Monocytes and macrophages, as well as intestinal and pulmonary epithelial cells, respond to monomeric flagellin at low concentrations. Administration of flagellin at doses comparable to or lower than that of bacterial lipopolysaccharide (endotoxin) can induce prominent local and systemic immune/inflammatory responses in vivo. Recognition of the flagellin-TLR5 pathway offers novel opportunities for the experimental therapy of various forms of shock, sepsis, acute respiratory distress syndrome, bacterial inflammation and infection. (c) Prous Science 2002. All rights reserved.

Journal Article↗

PubMed2000

Mitogen-activated protein kinase phosphorylation in kidneys of beta(s) sickle cell mice.

Previous studies in beta(s) sickle cell mice demonstrated renal immunostaining for nitrotyrosine, which is putative evidence of peroxynitrite (ONOO(-)) formation. ONOO(-) is known to nitrate tyrosine residues of various enzymes, thereby interfering with phosphorylation and inactivating them. The present study examined the state of phosphorylation of mitogen-activated protein (MAP) kinase signal transduction enzymes, i.e., p38, c-Jun NH(2)-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK). Western blot performed with antibodies directed against specific phosphorylated threonine/tyrosine residues of these enzymes demonstrated reduced phosphorylation of renal p38 and a trend toward reduced phosphorylation of ERK. In contrast, phosphorylation of renal JNK was markedly increased compared with normal mice. The abundance of MAP kinase phosphatase-1 (MKP-1), a key upstream enzyme that modulates phosphorylation of MAP kinases, was not different in beta(s) versus normal mice. To determine whether nitration of tyrosine by ONOO(-) was responsible for reduced phosphorylation of p38 and ERK, mercaptoethylguanidine (MEG), a compound known to reduce inducible isoform of nitric oxide synthase activity and to scavenge ONOO(-), was administered to beta(s) mice for 5 d. MEG was found to restore phosphorylation of p38 and ERK toward normal levels. These observations provide evidence that ONOO(-) (or closely related reaction products of NO) contributes to dephosphorylation of p38 and ERK, and presumably reduces activity of these enzymes. The increased phosphorylation of JNK, which suggests activation of this signaling pathway by extracellular stress signals, may play a role in apoptosis in the kidneys of these mice. The changes in phosphorylation of MAP kinase pathways found in this study could have important consequences for regulation of nuclear transcription factors, and thus renal function and pathology in sickle cell kidneys.

Analysis of Variance↗