Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0243026 (sepsis)
 52,417 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To elucidate cellular mechanisms of myocardial depression in Pseudomonas sepsis the effects of sublethal concentrations of P. aeruginosa exotoxin A--a main virulence factor--were studied in cultured neonatal rat cardiomyocytes. It is known that this toxin exerts its pathogenic effect by inhibition of protein synthesis via ADP-ribosylation and thereby inactivation of elongation factor 2 (EF-2). Within 48 72 h, half maximal inhibition of protein synthesis occurs at 4-10 ng/ml. The toxin prevents the beta-adrenoceptor(AR)-mediated myosin heavy chain isozyme shift (V3/V1), while the T3-induced myosin shift is not suppressed. While beta 1-AR-downregulation by excess of norepinephrine (NE) is not affected, protein synthesis-dependent receptor upregulation in the recover period after removal of NE is completely suppressed by P. aeruginosa exotoxin A. Thus, a non-lethal, partial inhibition of global cellular protein synthesis by P. aeruginosa exotoxin A: (1) completely prevents beta 1-AR-mediated myosin isozyme shift and beta-AR upregulation: (2) sustains the cardiomyocytes in a catecholamine-refractory contractile state in the recovery period after catecholamine desensitization: (3) suggests cellular mechanisms by which P. aeruginosa exotoxin A might impair heart function in Pseudomonas sepsis: and (4) may help reveal the possible influence of endogenous inhibitors of EF-2.
 ...
PMID:Partial inhibition of protein synthesis by Pseudomonas exotoxin A deranges catecholamine sensitivity of cultured rat heart myocytes. 914 Aug 36

Diminished availability of oxygen at the cellular level might account for organ dysfunction in sepsis. Although the classical forms of tissue hypoxia due to hypoxemia, anemia, or inadequate perfusion all might be important under some conditions, it seems increasingly likely that a fourth mechanism, namely cytopathic hypoxia, might play a role as well. The term cytopathic hypoxia is used to denote diminished production of adenosine triphosphate (ATP) despite normal (or even supranormal) PO2 values in the vicinity of mitochondria within cells. At least in theory, cytopathic hypoxia could be a consequence of several different (but mutually compatible) pathogenic mechanisms, including diminished delivery of a key substrate (e.g., pyruvate) into the mitochondrial tricarboxylic acid (TCA) cycle, inhibition of key mitochondrial enzymes involved in either the TCA cycle or the electron transport chain, activation of the enzyme, poly-(ADP)-ribosylpolymerase (PARP), or collapse of the protonic gradient across the inner mitochondrial membrane leading to uncoupling of oxidation (of NADH and FADH) from phosphorylation of ADP to form ATP. Tantalizing, but limited, data support the view that cytopathic hypoxia occurs in both animals and patients with sepsis or endotoxemia.
 ...
PMID:Cytopathic hypoxia in sepsis. 924 46

Nitric oxide (NO) plays a key role in the pathophysiology of inflammation and sepsis. The regulation of the peripheral inducible NO synthase (iNOS-responsible for the massive NO synthesis in inflammation) has been extensively studied in sepsis, but little is known about the actual NO production and its dependence on the location of the primary stimulus (endotoxin, LPS). We measured the activation of the NO pathway after a central (intracerebroventricular) or systemic (intravenous) low dose of LPS (2.5 micrograms/mouse) in three ways: the accumulation of its stable end products (nitrites/nitrates) in the circulation, the induction of iNOS mRNA and the decrease in sodium nitroprusside-dependent ADP ribosylation of proteins in the liver and brain. Plasma nitrites/nitrates increased after LPS by either route. iNOS mRNA was induced in the liver after intravenous and, to a lower extent, in the brain after intracerebroventricular LPS. Ex vivo ADP ribosylation was decreased in both organs after both administration routes, although to different degrees (higher in the liver after intravenous and in the brain after intracerebroventricular administration), suggesting that NO had been produced in the periphery and in the brain after both routes of LPS administration, despite the fact that no LPS is expected to reach the brain after peripheral low-dose injection. Our data thus demonstrate a cross-talk between periphery and brain in the regulation of NO by LPS. Additionally, the possibility of iNOS-independent NO synthesis stimulated by LPS is implied by the discrepancy between the amount of local NO production suggested by ADP ribosylation and the iNOS mRNA levels.
 ...
PMID:Regional production of nitric oxide after a peripheral or central low dose of LPS in mice. 926 48

We hypothesized that cellular oxygen consumption is abnormal during sepsis as a result of increased oxidative stress and selective mitochondrial damage. In a rat model of sepsis (cecal ligation and puncture), we studied the respiratory characteristics of isolated hepatocytes and liver mitochondria 16 h after onset of septic injury. Endogenous respiration by isolated cells was decreased during sepsis, while cyanide-resistant (nonmitochondrial) respiration was unaffected. Maximal oxygen consumption in ADP-supplemented, permeabilized hepatocytes was decreased with succinate as the substrate, but not with malate + glutamate or TMPD + ascorbate. In contrast, maximum oxygen consumption (State 3) by isolated liver mitochondria increased up to 35% during sepsis using either succinate or malate + glutamate as substrate. The electrophoretic features and mobility of nondenatured mitochondrial respiratory complexes were similar in control and septic hepatocytes, with the exception of decreased Complex V protein in sepsis. Structural evaluation of mitochondria in fixed liver slices by electron microscopy showed mitochondrial swelling in most of the septic animals. Measurements of oxidative stress during sepsis suggested an increase in hydroxylation of salicylate by isolated hepatocytes, and mitochondrial protein carbonyl content was increased significantly. Induction of iNOS in hepatocytes after 16 h of sepsis was variable, and little release of the oxidation products of NO. was detected. These findings are interpreted to mean that hepatocytes contain a mixed population of injured and hyperfunctional mitochondria during sepsis.
 ...
PMID:Oxidative metabolism in rat hepatocytes and mitochondria during sepsis. 930

Thrombotic complications are observed in patients undergoing bone marrow transplantation despite thrombocytopenia and impaired coagulation due to liver function disturbances. Endothelial cell damage which is involved in the pathogenesis of major transplant related complications like graft-versus-host disease, veno-occlusive disease, sepsis or microangiopathy may be a contributing factor. Little is known about platelet function in bone marrow transplant recipients. In order to study functional alterations in circulating platelets we investigated unstimulated and ADP-stimulated platelets of 10 bone marrow transplant recipients ex vivo by flow cytometry in a pilot study using a panel of monoclonal antibodies to characterize changes in membrane glycoproteins. Samples were collected before and during conditioning and at three timepoints after engraftment. 10 healthy volunteers served as controls. Platelets of bone marrow transplant recipients showed partly a significant, higher expression of surface bound fibrinogen, activated fibrinogen receptor, and glycoprotein Ib as compared to controls. P-selectin, a marker of platelet degranulation was significantly elevated after ADP-induced stimulation at all timepoints compared to controls. Only marginal differences were found for GP IIb/IIIa surface expression. The data point to an increased platelet activation state in bone marrow transplant recipients which might contribute to the thrombotic phenomena observed in these patients.
 ...
PMID:Changes in platelet membrane glycoproteins before bone marrow transplantation and after engraftment--a pilot study. 975 3

These serial clinical and experimental studies were designed to clarify the pathogenesis of postburn MODS. Both animal and clinical studies were performed. In animal experiments, 46 male cross-bred dogs were cannulated with Swan-Ganz catheters and 39 of them were inflicted with 50% TBSA third degree burns (7 were used as controls). The burned dogs were randomly divided into 4 groups: immediate infusion, delayed infusion, delayed fast infusion and delayed fast infusion combined with ginsenosides. All dogs were kept under constant barbiturate sedation during the whole study period. Hemodynamics, visceral MDA, mitochondrial respiratory control rate (RCR) and ADP/O ratio, ATP, succinic dehydrogenase (SDH), organ water content as well as light and electron microscopy of visceral tissues were determined. In the clinical study, 61 patients with extensive deep burns were chosen, of which 16 sustained MODS. Plasma TXB2/6-keto-PGF1alpha ratio, TNF, SOD, MDA, circulatory platelet aggregate ratio (CPAR), PGE2, interleukin-1, total organ water content and pathological observations of visceral tissues from patients who died of MODS were carried out. Results demonstrated that ischemic-reperfusion damage due to severe shock, sepsis and inhalation injury are three main causes of postburn death. All inflammatory mediators increased markedly in both animals and patients who sustained organ damage or MODS. SDH, RCR, ADP/O and ATP decreased significantly. These findings suggested that ischemic damage and systemic inflammatory response syndrome (SIRS) initiated by mediators or cytokines might be important in the pathogenesis of postburn MODS.
 ...
PMID:Serial experimental and clinical studies on the pathogenesis of multiple organ dysfunction syndrome (MODS) in severe burns. 991 70

Endotoxemia secondary to gram-negative sepsis has been shown to inhibit endothelium-dependent vasomotion in numerous vascular beds, including guinea pig aortae and coronary arteries. We tested the hypothesis that in vivo endotoxin impairs endothelium-dependent nitric oxide-mediated relaxation responses of pulmonary arteries isolated from guinea pigs given intraperitoneal injections of Escherichia coli endotoxin lipopolysaccharide (LPS) or saline (control) 16 h before sacrifice. Pulmonary rings from the main artery and primary branches were isolated and studied in vitro using conventional isometric techniques. Interestingly, endotoxemia resulted in enhanced pulmonary artery relaxation in response to the endothelium-dependent receptor agonists acetylcholine (10(-10) -10(-5) M) and adenosine diphosphate (ADP; 10(-9) -10(-5) M), as compared with control responses (p < .05). Nitric oxide synthase inhibitors N-monomethyl-L-arginine (300 microM) and N-nitro-L-arginine methyl ester (100 microm) reduced acetylcholine- and adenosine diphosphate-mediated relaxation in both groups (p < .05); however, vasodilation responses in arteries from LPS animals remained enhanced relative to those of control arteries. In contrast to nitric oxide synthase inhibitors, the cyclooxygenase inhibitor indomethacin markedly inhibited acetylcholine- and adenosine diphosphate-mediated relaxation responses of pulmonary arteries isolated from LPS-treated animals (p < .05) but not control arteries; indomethacin effectively reversed LPS-induced enhanced vasodilation of pulmonary arteries. Relaxation responses to the receptor-independent calcium ionophore (A23187) and to the direct smooth muscle vasodilator sodium nitroprusside (+ N-nitro-L-arginine methyl ester) were not significantly altered by LPS treatment (p > .05). These data suggest that in pulmonary arteries, unlike aortae and coronary arteries isolated from the same model, in vivo LPS enhances agonist-mediated endothelium-dependent vasodilation responses to acetylcholine and adenosine diphosphate. Underlying mechanisms appear to involve increased dependency upon vasodilator prostanoids and decreased dependency on nitric oxide synthesis/release for LPS-induced alterations in pulmonary relaxation responses.
 ...
PMID:Enhanced prostanoid-mediated vasorelaxation in pulmonary arteries isolated during experimental endotoxemia. 1045 35

Contraction-induced respiratory muscle fatigue and sepsis-related reductions in respiratory muscle force-generating capacity are mediated, at least in part, by reactive oxygen species (ROS). The subcellular sources and mechanisms of generation of ROS in these conditions are incompletely understood. We postulated that the physiological changes associated with muscle contraction (i.e., increases in calcium and ADP concentration) stimulate mitochondrial generation of ROS by a phospholipase A(2) (PLA(2))-modulated process and that sepsis enhances muscle generation of ROS by upregulating PLA(2) activity. To test these hypotheses, we examined H(2)O(2) generation by diaphragm mitochondria isolated from saline-treated control and endotoxin-treated septic animals in the presence and absence of calcium and ADP; we also assessed the effect of PLA(2) inhibitors on H(2)O(2) formation. We found that 1) calcium and ADP stimulated H(2)O(2) formation by diaphragm mitochondria from both control and septic animals; 2) mitochondria from septic animals demonstrated substantially higher H(2)O(2) formation than mitochondria from control animals under basal, calcium-stimulated, and ADP-stimulated conditions; and 3) inhibitors of 14-kDa PLA(2) blocked the enhanced H(2)O(2) generation in all conditions. We also found that administration of arachidonic acid (the principal metabolic product of PLA(2) activation) increased mitochondrial H(2)O(2) formation by interacting with complex I of the electron transport chain. These data suggest that diaphragm mitochondrial ROS formation during contraction and sepsis may be critically dependent on PLA(2) activation.
 ...
PMID:PLA(2) dependence of diaphragm mitochondrial formation of reactive oxygen species. 1090 37

The most common cause of death in patients with sepsis is the multiple organ dysfunction syndrome (MODS). One important factor underlying the pathogenesis of MODS may be sepsis-induced alterations in cellular energy metabolism due to acquired intrinsic derangements in cellular respiration, a phenomenon that might be called "cytopathic hypoxia". A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome oxidase by nitric oxide, irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite, and activation of the nuclear enzyme, poly-(ADP-ribosyl)-polymerase.
 ...
PMID:Cytopathic hypoxia. A concept to explain organ dysfunction in sepsis. 1096 12

In this study we examined the role of nitric oxide (NO) from inducible nitric oxide synthase (iNOS) and adenosine triphosphate (ATP) depletion, using aminoguanidine and 3-aminobenzamide, on diaphragm contractility in a rat model of sepsis. Intraperitoneal lipopolysaccharide (LPS) injection was used to induce septicemia in rats. The LPS treatment caused a decrease in maximal absolute force produced by the diaphragm muscle stimulated at 100 HZ, and the force-frequency curves were right-shifted with a decrease in force at 2, 5 and 15 HZ. LPS administration also made the diaphragm muscle strips more fatigable than controls. The decrease in force in LPS-treated animals was not due to an induction of pathological levels of i NOS. Increased fatigability did not appear to be due to a depletion of ATP through poly-adenosine-diphosphate-ribose polymerase (PARP) activation. This study does not support the hypothesis that the decrease in diaphragm muscle force as a result of sepsis is due to an induction of pathological levels of nitric oxide or ATP depletion.
 ...
PMID:The role of nitric oxide in diaphragmatic dysfunction in endotoxemic rats. 1115 Sep 63


<< Previous 1 2 3 4 5 6 7 8 Next >>