Biomedical subjects

S Lanone

Publications and source records attributed to S Lanone.

13 recordsLinked to original sources

PubMed2002

[Diaphragmatic weakness in sepsis: the role of oxidant stress].

In sepsis contractile weakness of the diaphragm is a major cause of the onset of respiratory failure. This muscular weakness is the result of haemodynamic and metabolic disorders secondary to sepsis and also the damaging effects of inflammatory mediators, among which oxygen free radicals play a crucial role. This role is demonstrated by the protective effect of various exogenous anti-oxidants on diaphragmatic contraction. Early in the course of sepsis there is, in animal models and in man, an increased production of oxygen free radicals and nitric oxide (NO) in the diaphragm, principally within the mitochondria. The formation of peroxinitrite as the result of the action of NO on superoxide anions impairs mitochondrial respiration and consequently the energy production necessary for diaphragmatic contraction. Among the endogenous anti-oxidant systems haem oxygenase, which splits haemoglobin into bilirubin, iron and carbon monoxide, is an effective system for the protection of diaphragmatic function by limiting the damage of oxidant stress. Nevertheless a transient deficiency of local anti-oxidant defences during the early stages of sepsis, when the production of oxygen free radicals is intense, encourages the onset of contractile weakness.

Animals↗

PubMed2001

Activation of cardiac endothelium as a compensatory component in endotoxin-induced cardiomyopathy: role of endothelin, prostaglandins, and nitric oxide.

BACKGROUND: In view of growing evidence of an important endothelial paracrine regulation of cardiac function, the present study investigated the role of cardiac endothelium-derived endothelin-1 (ET-1), prostaglandins, and nitric oxide (NO) during endotoxin-induced cardiomyopathy in rabbits. METHODS AND RESULTS: Immunohistochemical studies showed a marked transient coinduction of the inducible isoforms of NO synthase (NOS-2) and cyclooxygenase (COX-2) in endocardial endothelium and coronary arteriolar endothelium of hearts 12 hours after intravenous administration of lipopolysaccharide (LPS+12h); staining for both isoforms was much weaker 24 hours later (LPS+36h). Nitrotyrosine localization was similar to that of NOS-2, suggesting a NOS-2-related endothelial formation of peroxynitrite in septic hearts. Contractile performance of papillary muscles was depressed in both LPS-treated groups. In the LPS+12h group, however, isometric twitches were significantly prolonged (482+/-14 versus 420+/-14 ms in the saline-treated group, P<0.005). This twitch prolongation was completely reversed by simultaneous administration of BQ-123 and indomethacin to block endogenous ET-1 and prostaglandins, respectively. In addition, in the LPS+12h group, myocardial inotropic responsiveness to exogenous ET-1 was enhanced (P<0.01). CONCLUSIONS: Cardiac endothelial activation and myocardial sensitization to endothelium-derived mediators may be part of an adaptive response in the early (12 hours) stages of septic cardiomyopathy.

Animals↗

PubMed2001

Interleukin-13 induces tissue fibrosis by selectively stimulating and activating transforming growth factor beta(1).

Interleukin (IL)-13 is a key mediator of tissue fibrosis caused by T helper cell type 2 inflammation. We hypothesized that the fibrogenic effects of IL-13 are mediated by transforming growth factor (TGF)-beta. To test this hypothesis we compared the regulation of TGF-beta in lungs from wild-type mice and CC10-IL-13 mice in which IL-13 overexpression causes pulmonary fibrosis. IL-13 selectively stimulated TGF-beta(1) production in transgenic animals and macrophages were the major site of TGF-beta(1) production and deposition in these tissues. IL-13 also activated TGF-beta(1) in vivo. This activation was associated with decreased levels of mRNA encoding latent TGF-beta-binding protein-1 and increased mRNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. TGF-beta(1) activation was abrogated by the plasmin/serine protease antagonist aprotinin. It was also decreased in progeny of crosses of CC10-IL-13 mice and MMP-9 null mice but was not altered in crosses with CD44 null animals. IL-13-induced fibrosis was also significantly ameliorated by treatment with the TGF-beta antagonist soluble TGFbetaR-Fc (sTGFbetaR-Fc). These studies demonstrate that IL-13 is a potent stimulator and activator of TGF-beta(1) in vivo. They also demonstrate that this activation is mediated by a plasmin/serine protease- and MMP-9-dependent and CD44-independent mechanism(s) and that the fibrogenic effects of IL-13 are mediated, in great extent, by this TGF-beta pathway.

Animals↗

PubMed2001

Sepsis is associated with reciprocal expressional modifications of constitutive nitric oxide synthase (NOS) in human skeletal muscle: down-regulation of NOS1 and up-regulation of NOS3.

OBJECTIVE: To study the expression (mRNA and protein) and activity of the constitutive isoforms of nitric oxide synthase (NOS1 and NOS3) in a skeletal muscle of septic patients. DESIGN: Prospective study. SETTING: An adult trauma/surgical intensive care unit in an urban teaching hospital. PATIENTS: Sixteen septic patients and 21 controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Samples of the rectus abdominis muscle were obtained during surgical procedure. NOS mRNA, protein, and activity were detected by reverse-transcriptase polymerase chain reaction, Western blot, and the conversion of [3H]L-arginine to [3H]L-citrulline, respectively. The main results of this study are as follows: a) Levels of NOS1 mRNA and protein were significantly higher than those of NOS3 in the rectus abdominis muscle of control patients; b) NOS1 expression was down-regulated in septic patients, whereas NOS3 was up-regulated; c) these modulations were associated with a reduction in constitutive NOS activity; and d) modifications of NOS1 and NOS3 protein expression were correlated significantly with the severity of sepsis, assessed by the Simplified Acute Physiology Score II. CONCLUSIONS: Sepsis induces reciprocal expressional modifications of NOS1 and NOS3 in human skeletal muscle, which decreases muscular constitutive NOS activity. These modifications may have implications for muscle impairment in septic patients.

Caenorhabditis elegans Proteins↗

PubMed2001

Protective role of heme oxygenases against endotoxin-induced diaphragmatic dysfunction in rats.

Reactive oxygen species are strongly implicated in diaphragmatic dysfunction during sepsis. We investigated whether the heme oxygenase (HO) pathway, which is a powerful protective cellular system, protects the diaphragm against oxidative stress and contractile failure during sepsis. A basal expression of both the inducible and constitutive HO protein isoforms (HO-1 and HO-2, respectively) was found in the diaphragm. Enhanced HO-1 expression in diaphragmatic myocytes was observed 24 h after Escherichia coli endotoxin (lipopolysaccharide, LPS) inoculation and remained elevated for at least 96 h. Enhanced HO-1 expression was also observed in the rectus abdominis and soleus muscles and in the left ventricular myocardium of endotoxemic animals. Diaphragmatic HO-2 expression was not modified by endotoxin. Diaphragmatic HO activity exhibited a biphasic time course characterized by a transient decrease during the first 12 h followed by a significant increase at 24 h, corresponding to HO-1 induction. Diaphragmatic force was significantly reduced 24 h after LPS, concomitantly with muscular oxidative stress. Administation of an inhibitor of heme oxygenase activity, zinc protoporphyrin IX (ZnPP-IX), further impaired muscular oxidative stress and contractile failure. By contrast, increased levels of HO-1 expression obtained by pretreatment of rats with hemin, a powerful inducer of HO-1, completely prevented LPS-mediated diaphragmatic oxidative stress and contractile failure. This protective effect was reversed by ZnPP-IX. These results show an important protective role for the HO pathway against sepsis-induced diaphragmatic dysfunction, which could be related to its antioxidant properties.

Animals↗

PubMed2000

Cardiac contractile impairment associated with increased phosphorylation of troponin I in endotoxemic rats.

The subcellular mechanisms underlying intrinsic myocardial depression during sepsis remain poorly defined, in particular the relative roles of altered intracellular Ca2+ transients versus changes in myofilament properties. We studied contractile function of cardiac myocytes isolated 12 h after induction of endotoxemia (5 mg/kg intravenous E. coli lipopolysaccharide [LPS]) in conscious rats. Cardiomyocytes from LPS-injected rats had depressed twitch shortening compared with control cells (4.10.2% versus 7.80.3%; P2+ transients (peak indo-1 ratio 1.130.02 versus 1.120.02; P = NS). Contractile depression was unaffected by inhibitors of nitric oxide synthase. Steady-state myofilament response to Ca2+, assessed by tetanization of intact cells over a range of [Ca2+], was reduced significantly in the LPS group (P2+ was unaffected by isoproterenol (3 nmol/L) in endotoxemic cells, whereas there was a rightward shift in control cells. A reduction in myofilament response to Ca2+ is the major determinant of intrinsic cardiac depression in systemic endotoxemia. This condition appears to be related to an increase in myocardial troponin I phosphorylation.

Actin Cytoskeleton↗

PubMed2000

Anesthetic concentrations of riluzole inhibit neuronal nitric oxide synthase activity, but not expression, in the rat hippocampus.

We hypothesized that anesthetic dose of riluzole, an inhibitor of glutamate neurotransmission, may affect the activity and/or expression of neuronal NOS (nNOS). Riluzole, N(G)-nitro-L-arginine-methyl ester (L-NAME) and 7-nitro indazole (7-NI) produced a concentration-related inhibition of nNOS activity in vitro. Riluzole competed with 7-NI for inhibition of nNOS activity, but had no effect on nNOS or endothelial NOS (eNOS) protein expression. Also, nNOS activity was significantly decreased in riluzole-anesthetized rats (40 mg kg(-1) i.p., -32+/-6% from controls, P<0.05). Therefore, blockade of nNOS activity may be involved in the anesthetic effects of riluzole in vivo.

Actins↗

PubMed2000

Muscular contractile failure in septic patients: role of the inducible nitric oxide synthase pathway.

Skeletal muscle failure is a frequent manifestation of sepsis that affects prognosis and rehabilitation by impairing respiration and ambulation. Animal studies have shown that the inducible NO synthase (NOS2) is expressed in skeletal muscles during sepsis, likely affecting muscular function, by promoting the formation of the strong oxidant peroxynitrite. In contrast, whether human skeletal muscle expresses a functional NOS2 in similar conditions is unknown. We studied NOS2 expression (mRNA and protein) and activity and its role in contractile function in samples from rectus abdominis muscle obtained during surgical procedure in 16 septic patients and in 21 controls. Peroxynitrite formation was detected by immunohistochemical detection of nitrotyrosine residues. The main results of this study are as follows: (1) A significant increase in NOS2 mRNA, protein, and activity was found in muscles from septic patients, the expression of NOS2 protein positively correlating with sepsis severity. (2) Contractile force was significantly lower in septic than in control muscles. This phenomenon was not reverted by muscle incubation ex vivo with the NOS inhibitor L-NMMA, indicating that NO was not involved in force reduction at the time of biopsy. (3) NOS2 expression in skeletal myocytes was strongly co-localized with nitrotyrosine, revealing muscular peroxynitrite generation during the septic process, before the muscle was biopsied. Exposure of control muscles to an amount of peroxynitrite similar to that generated in septic muscles during the septic process resulted in a nonreversible reduction in force generation. These results suggest that NOS2 could be involved in the decreased muscular force of septic patients via the local generation of peroxynitrite.

Adult↗

PubMed2000

[Special characteristics of the diaphragm muscle cell].

The diaphragm is the main inspiratory muscle, accounting for more than 50% of the tidal volume during quiet breathing. It works continuously, contracting rhythmically and generally at a low intensity. In this respect, it is close to the myocardium, being the only vital skeletal muscle. From a general point of view, functional and biochemical characteristics of the diaphragm are similar to those of other skeletal muscles with a similar fiber type composition. However, the diaphragm presents some specificities allowing a high supply of metabolic substrates. This could serve to preserve contractile function in different physiological and physiopathological situations. Such specificities concern muscular vascularization, the microvascular network and the content of mitochondria and myoglobin. These characteristics are detailed and compared to those of other striated muscles.

Diaphragm↗

PubMed1999

Endogenous peroxynitrite mediates mitochondrial dysfunction in rat diaphragm during endotoxemia.

It has been shown that nitric oxide (NO), synthesized by the inducible NO synthase (iNOS) expressed in the diaphragm during endotoxemia, participates in the development of muscular contractile failure. The aim of the present study was to investigate whether this deleterious action of NO was related to its effects on cellular oxidative pathways. Rats were inoculated with E. coli lipopolysaccharide (LPS) or sterile saline solution (controls) and studied at 3 and 6 h after inoculation. iNOS protein and activity could be detected in the rat diaphragm as early as 3 h after LPS, with a sustained steady-state concentration of 0.5 microM NO in the muscle associated with increased detection of hydrogen peroxide (H(2)O(2)). In vitro, the same NO concentration produced a marked increase in H(2)O(2) production by isolated control diaphragm mitochondria, thus reflecting a higher intramitochondrial concentration of nondiffusible superoxide anion (O(2)(-.)). In a similar way, whole diaphragmatic muscle and diaphragm mitochondria from endotoxemic rats showed a progressive increase in H(2)O(2) production associated with uncoupling and decreased phosphorylating capacity. Simultaneous with the maximal impairment in respiration (6 h after LPS), nitration of mitochondrial proteins (a peroxynitrite footprint) was detected and diaphragmatic force was reduced. Functional mitochondrial abnormalities, nitration of mitochondrial proteins, and the decrease in force were significantly attenuated by administration of the NOS inhibitor L-NMMA. These results show that increased and sustained NO levels lead to a consecutive formation of O(2)(-.) that reacts with NO to form peroxynitrite, which in turn impairs mitochondrial function, which probably contributes to the impairment of muscle contractility. during endotoxemia.

Animals↗

PubMed1998

Role of nitric oxide on diaphragmatic contractile failure in Escherichia coli endotoxemic rats.

Contractile dysfunction of the respiratory muscles plays an important role in the genesis of respiratory failure during sepsis. Nitric oxide (NO), a free radical that is cytotoxic and negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by a NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to investigate whether iNOS was induced in the diaphragm of Escherichia coli endotoxemic rats and whether inhibition of iNOS induction or of NOS synthesis attenuated diaphragmatic contractile dysfunction. Rats were inoculated intravenously (IV) with 10 mg/kg of E. coli endotoxin (LPS animals) or saline (C animals). Six hours after LPS inoculation animals showed a significant increase in diaphragmatic NOS activity (L-citrulline production, P < 0.005). Inducible NOS protein was detected by Western-Blot in the diaphragms of LPS animals, while it was absent in C animals. LPS animals had a significant decrease in diaphragmatic force (P < 0.0001) measured in vitro. In LPS animals, inhibition of iNOS induction with dexamethasone (4 mg/kg IV 45 min before LPS) or inhibition of NOS activity with N(G)-methyl-L-arginine (8 mg/kg IV 90 min after LPS) prevented LPS-induced diaphragmatic contractile dysfunction. We conclude that increased NOS activity due to iNOS was involved in the genesis of diaphragmatic dysfunction observed in E. coli endotoxemic rats.

Animals↗

PubMed1996

Induction of diaphragmatic nitric oxide synthase after endotoxin administration in rats: role on diaphragmatic contractile dysfunction.

Nitric oxide (NO), a free radical that is negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by an NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to examine iNOS induction in the rat diaphragm after Escherichia Coli LPS inoculation (1.6 mg/kg i.p.), and its involvement in diaphragmatic contractile dysfunction. Inducible NOS protein and activity could be detected in the diaphragm as early as 6 h after LPS inoculation. 6 and 12 h after LPS, iNOS was expressed in inflammatory cells infiltrating the perivascular spaces of the diaphragm, whereas 12 and 24 h after LPS it was expressed in skeletal muscle fibers. Inducible NOS was also expressed in the left ventricular myocardium, whereas no expression was observed in the abdominal, intercostal, and peripheral skeletal muscles. Diaphragmatic force was significantly decreased 12 and 24 h after LPS. This decrease was prevented by inhibition of iNOS induction by dexamethasone or by inhibition of iNOS activity by N(G)-methyl-L-arginine. We conclude that iNOS was induced in the diaphragm after E. Coli LPS inoculation in rats, being involved in the decreased muscular force.

Abdominal Muscles↗

PubMedDate not supplied

Peroxynitrite-mediated mitochondrial dysfunction.

Peroxynitrite anion (ONOO(-)) is a potent biological oxidant produced by the near diffusion-limited reaction of superoxide and nitric oxide. Peroxynitrite has been implicated in diverse forms of free radical-induced tissue injury. Experimental evidence showed that exogenous and endogenous peroxynitrite causes alterations of the structure and function of mitochondrial proteins, leading to mitochondrial dysfunction and cellular or organ injury. These data are discussed along with its physiopathological implications.

Energy Metabolism↗