PubMed Health⌕ Search

Biomedical subjects

B Zingarelli

Publications and source records attributed to B Zingarelli.

At least 37 records · Page 2Linked to original sources
PubMed1998

Genetic disruption of poly (ADP-ribose) synthetase inhibits the expression of P-selectin and intercellular adhesion molecule-1 in myocardial ischemia/reperfusion injury.

The nuclear enzyme poly (ADP-ribose) synthetase (PARS) has been shown to play an important role in the pathogenesis of ischemia/reperfusion injury and circulatory shock. The aim of this study was to investigate whether PARS activity may modulate endothelial-neutrophil interaction. We present evidence that genetic disruption of PARS provides protection against myocardial ischemia and reperfusion injury by inhibiting the expression of P-selectin and intercellular adhesion molecule-1 (ICAM-1) and, consequently, by inhibiting the recruitment of neutrophils into the jeopardized tissue. Furthermore, using in vitro studies, we demonstrate that in fibroblasts lacking a functional gene for PARS, cytokine-stimulated expression of ICAM-1 is significantly reduced compared with fibroblasts from animals with a normal genotype. Similarly, in cultured human endothelial cells, oxidative- or cytokine-dependent expression of P-selectin and ICAM-1 is reduced by pharmacological inhibition of PARS by 3-aminobenzamide. These findings provide the first direct evidence that PARS activation participates in neutrophil-mediated myocardial damage by regulating the expression of P-selectin and ICAM-1 in ischemic and reperfused myocardium, and they also provide the basis for a novel therapeutic approach for the treatment of reperfusion injury.

Animals↗
PubMed1998

Protection against peroxynitrite-induced fibroblast injury and arthritis development by inhibition of poly(ADP-ribose) synthase.

Peroxynitrite, a cytotoxic oxidant formed from nitric oxide (NO) and superoxide, induces DNA strand breakage, which activates the nuclear enzyme poly(ADP-ribose) synthase (PARS; EC 2.4.2.30). The cellular function of PARS was determined in fibroblast lines from PARS knockout animals (PARS-/-) and corresponding wild-type animals (PARS+/+), with the aid of the lipophilic PARS inhibitor 5-iodo-6-amino-1,2-benzopyrone (INH2BP). We investigated the role of PARS in peroxynitrite-induced fibroblast injury in vitro and also in the development of arthritis in vivo. Exposure of embryonic fibroblasts from the PARS+/+ animals to peroxynitrite caused DNA single-stand breakage and PARS activation and caused an acute suppression of mitochondrial respiration. INH2BP protected the PARS+/+ cells against the suppression of mitochondrial respiration in response to peroxynitrite (50-100 microM). Similarly to PARS inhibition with INH2BP, the PARS-/- cells were protected against peroxynitrite-induced injury. The protection against cellular injury by PARS-/- phenotype or INH2BP waned when cells were challenged with higher concentrations of the oxidant. Inhibition of PARS by INH2BP or by PARS-/- phenotype reduced inducible nitric-oxide synthase (iNOS; EC 1.14.13.39) mRNA levels and inhibited production of NO in immunostimulated cells. INH2BP had no peroxynitrite scavenging or hydroxyl radical scavenging effects, and it exerted no additional (nonspecific) effects in the PARS-/- cells. In collagen-induced arthritis, significant staining for nitrotyrosine, a marker of peroxynitrite formation, was found in the inflamed joints. Oral treatment with INH2BP (0.5 g/kg, daily), starting at the onset of arthritis (day 25), delayed the development of the clinical signs at days 26-35 and improved histological status in the knee and paw. Our data demonstrate that deletion of PARS by genetic manipulation or pharmacological inhibition of PARS protects against oxidant-induced cellular injury in vitro and exhibits anti-inflammatory effects in vivo.

Animals↗
PubMed1998

Protective effects of 3-aminobenzamide, an inhibitor of poly (ADP-ribose) synthase in a carrageenan-induced model of local inflammation.

A cytotoxic cycle triggered by oxidant-induced DNA single strand breakage and subsequent activation of the nuclear enzyme poly (ADP-ribose) synthetase have been shown to contribute to the cellular injury during various forms of oxidant stress in vitro. The aim of the present study was to investigate the role of poly (ADP-ribose) synthetase in a model of acute local inflammation (carrageenan-induced pleurisy), where oxyradicals, nitric oxide and peroxynitrite are known to play a crucial role in the inflammatory process. The results show that the poly (ADP-ribose) synthetase inhibitor 3-aminobenzamide (given at 1-30 mg/kg) inhibits the inflammatory response (pleural exudate formation, mononuclear cell infiltration, histological injury). Moreover, 3-aminobenzamide reduces the formation of nitrotyrosine, an indicator of the formation of peroxynitrite, in the lung. The present results demonstrate that 3-aminobenzamide, presumably by inhibition of poly (ADP-ribose) synthetase, exerts potent anti-inflammatory effects. Part of the anti-inflammatory effects of 3-aminobenzamide may be related to a reduction of neutrophil recruitment into the inflammatory site.

Animals↗
PubMed1998

Evidence for in vivo peroxynitrite production in human chronic hepatitis.

During inflammation nitric oxide reacts at near diffusion limited rates with superoxide to form the strong oxidant peroxynitrite. Nitration on the ortho position is a major product of peroxynitrite attack on proteins. In the present study we investigated whether immunohistochemical detection of nitrotyrosine (footprint of peroxynitrite) can be associated with human hepatitis. Paraffin-embedded liver tissue biopsies from patients with chronic active hepatitis, chronic active hepatitis plus cirrhosis and chronic persistent hepatitis exhibit significant specific immunostaining with the antibody to nitrotyrosine. Positive staining was found in 57% and 72% of tissue specimens from patients with chronic hepatitis and cirrhosis, respectively. Immunohistochemical staining of nitrotyrosine residues was found in the hepatocytes and Kuppffer cells of the necrotic area. The presence of nitrotyrosine indicates that oxidants derived from nitric oxide such as peroxynitrite are generated in human hepatitis and may be involved in its pathogenesis.

Adult↗
PubMed1998

Role of constitutive nitric oxide synthase and peroxynitrite production in a rat model of splanchnic artery occlusion shock.

Peroxynitrite, a potent cytotoxic oxidant formed by the reaction of nitric oxide with superoxide anion, is an important mediator of reperfusion injury. In a rodent model of mesenteric ischemia and reperfusion injury we evaluated the contribution of the constitutive and/or inducible nitric oxide synthase (cNOS or iNOS) in the formation of peroxynitrite. Splanchnic artery occlusion (SAO) shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed by release of the clamps (reperfusion). A significant peroxynitrite production was found in the plasma of the splanchnic occlusion shocked rats at 60 minutes after reperfusion. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific "footprint" of peroxynitrite, in the necrotic ileum and the aorta of shocked rats. No change in plasma levels of nitrate/nitrite, tissue iNOS expression (by western blotting detection) or iNOS activity was found in the intestine at 60 minutes after reperfusion. On the contrary, activity of the cNOS was reduced (approximately 50%) in the reperfused ischemic intestinal tissue. Treatment with NG-nitro-L-arginine methyl ester, a non selective inhibitor of nitric oxide synthase (given at 3 mg/kg i.v., 5 min prior to reperfusion), significantly reduced plasma level of peroxynitrite and the immunohistochemical staining for nitrotyrosine in the ileum and aorta. Our results suggest that during splanchnic artery occlusion shock peroxynitrite formation is likely to be correlated with nitric oxide production from constitutive nitric oxide synthase activation rather than from the inducible isoform enzyme.

Analysis of Variance↗
PubMed1998

Role of peroxynitrite and poly (ADP-ribosyl) synthetase activation in cardiovascular derangement induced by zymosan in the rat.

Peritoneal administration of zymosan in the rat induced a severe inflammatory process characterised by an increase in the plasma levels of nitrite and nitrate, stable metabolites of nitric oxide (NO) and in the levels of peroxynitrite, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123, at 18 hours zymosan challenge. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific "footprint" of peroxynitrite, in the aorta of zymosan-shocked rats. In ex vivo experiments, thoracic aorta rings of zymosan-treated rats showed a reduced contraction to noradrenaline and reduced responsiveness to the relaxant effect to acetylcholine (vascular hyporeactivity and endothelial dysfunction, respectively). Treatment of zymosan-shocked rats with 3-aminobenzamide or Nicotinamide, inhibitors of poly ADP-ribosil synthetase (PARS) activity reduced the production of peroxynitrite and significantly prevented the cardiovascular dysfunction. Our data suggest that peroxynitrite and PARS activation play a role in the zymosan-induced cardiovascular derangements in the rat.

Animals↗
PubMed1998

Antiinflammatory effects of mercaptoethylguanidine, a combined inhibitor of nitric oxide synthase and peroxynitrite scavenger, in carrageenan-induced models of inflammation.

In vitro studies have demonstrated that mercaptoethylguanidine (MEG), a selective inhibitor of the inducible NO synthase (iNOS), is also effective as a scavenger of peroxynitrite (a potent cytotoxic oxidant produced by the reaction of NO and superoxide). In the present study, we evaluated the antiinflammatory potential of MEG treatment in two models of acute inflammation (carrageenan-induced paw edema and pleurisy), where oxyradicals, NO, and peroxynitrite play a crucial role in the inflammatory process. Our data show that MEG (given at 25 microg/paw in the paw edema model or 10 mg/kg in the pleurisy model) inhibits the inflammatory response (paw swelling, pleural exudate formation, mononuclear cell infiltration, histological injury) in both models. Furthermore, MEG reduced nitrite/nitrate concentrations in the exudate and reduced the activity of the inducible isoform of NO synthase in the lung ex vivo. MEG also reduced the appearance of nitrotyrosine immunoreactivity in the inflamed tissues. Taken together, the present results demonstrate that MEG exerts potent antiinflammatory effects. Part of these antiinflammatory effects may be related to an inhibition of the expression/activity of the inducible NO synthase, another part may be related to oxyradical and peroxynitrite scavenging.

Animals↗
PubMed1998

Effect of L-buthionine-(S,R)-sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase on peroxynitrite- and endotoxic shock-induced vascular failure.

1. Peroxynitrite, a cytotoxic oxidant formed from the reaction of nitric oxide (NO) and superoxide is a mediator of cellular injury in ischaemia/reperfusion injury, shock and inflammation. Here we investigated whether L-buthionine-(S,R)-sulphoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase, alters endothelial and vascular smooth muscle injury in response to peroxynitrite in vitro and during endotoxic shock in vivo. 2. In human umbilical vein endothelial cells and in rat aortic smooth muscle cells, BSO (1 mM, for 24 h) enhanced, whereas glutathione (3 mM) or glutathione ethyl ester (3 mM) attenuated the peroxynitrite (100-1000 microM)-induced suppression of mitochondrial respiration (measured by the conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to formazan), formation of nitrotyrosine (detected by Western blotting), protein oxidation (measured by detection of 2,4 dinitrophenylhydrazine-reactive carbonyls), and DNA single strand breakage and activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS) (measured by the incorporation of radiolabelled NAD+ into nuclear proteins and by the alkaline unwinding assay, respectively). Glutathione ethyl ester treatment reduced the BSO-induced enhancement of peroxynitrite-induced cytotoxicity. 3. In rat isolated thoracic aortic rings, BSO treatment (in vivo, at 1 g kg(-1) intraperitoneally (i.p.) for 24 h) enhanced, whereas pretreatment with glutathione (in vitro, 3 mM) attenuated the peroxynitrite-induced reduction of the contractions to noradrenaline, and the peroxynitrite-induced impairment of the endothelium-dependent relaxations to acetylcholine. 4. In BSO-pretreated rats, treatment with bacterial lipopolysaccharide (LPS, 15 mg kg(-1), i.p., for 6 h) caused a more pronounced vascular hyporeactivity and endothelial dysfunction ex vivo. BSO pretreatment also increased the degree of nitrotyrosine staining (detected by imunohistochemistry) in the aorta after LPS treatment. 5. In conclusion, our results demonstrate that L-buthionine-(S,R)-sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase enhances peroxynitrite- and endotoxic shock-induced vascular failure. Based on these findings, we suggest that endogenous glutathione plays an important protective role against peroxynitrite- and LPS-induced vascular injury.

Animals↗
PubMed1998

Peroxynitrite-mediated DNA strand breakage activates poly (ADP-ribose) synthetase and causes cellular energy depletion in carrageenan-induced pleurisy.

The aim of the present study was to investigate the role of poly (ADP-ribose) synthetase in acute local inflammation (carrageenan-induced pleurisy), where oxyradicals, nitric oxide and peroxynitrite are known to play a crucial role in the inflammatory process. DNA single-strand breakage and activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS) triggers an energy-consuming, inefficient repair cycle, which contributes to peroxynitrite-induced cellular injury. Here we investigated whether peroxynitrite production and PARS activation are involved in cytotoxicity in macrophages collected from rats subjected to carrageenan-induced pleurisy. Macrophages harvested from the pleural cavity exhibited a significant production of peroxynitrite, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123, and by nitrotyrosine Western blotting at 4 hr after carrageenan injection. Furthermore, carrageenan-induced pleurisy caused a suppression of macrophage mitochondrial respiration, DNA strand breakage, activation of PARS and reduction of NAD+ cellular levels. In vivo treatment with 3-aminobenzamide (10 mg/kg intraperitoneally, 1 hr after carrageenin injection) significantly inhibited the decrease in mitochondrial respiration and the activation of PARS and partially restored the cellular level of NAD+. In a separate group of experiments, in vivo pretreatment with NG-nitro-L-arginine methyl ester, a non-selective inhibitor of nitric oxide (NO) synthesis (10 mg/kg intraperitoneally, 15 min before carrageenan administration), reduced peroxynitrite formation and prevented the appearance of DNA damage, the decrease in mitochondrial respiration and the loss of cellular levels of NAD+. Our study suggests that formation of peroxynitrite and subsequent activation of PARS may alter macrophage function in inflammatory processes and inhibition of NO and PARS may be a novel pharmacological approach to prevent cell injury in inflammation.

Animals↗
PubMed1998

Melatonin inhibits expression of the inducible isoform of nitric oxide synthase in murine macrophages: role of inhibition of NFkappaB activation.

The role of melatonin as an immunomodulator is well established. Recent reports showed that melatonin exerts protective effects in septic and hemorrhagic shock and in inflammation. The expression of the inducible isoform of nitric oxide synthase (iNOS) makes an important contribution to the pathophysiology of shock and inflammation. We studied, in cultured murine macrophages, the role of melatonin in the regulation of the expression of iNOS and defined the mode of melatonin's action. Our results show that melatonin, at 1 microM-1 mM, decreased the production of nitrite/nitrate (the breakdown products of NO) as well as the production of 6-keto-prostaglandin F1alpha (the major stable breakdown product of prostacyclin) in macrophages stimulated with bacterial lipopolysaccharide (10 microg/ml). We observed that melatonin reduces iNOS steady-state mRNA levels and iNOS protein expression in the same concentration range (1 microM-1 mM). Melatonin, up to 10 mM, exerted only a slight direct inhibitory effect on iNOS activity. Using iNOS promoter-luciferase constructs, we found that melatonin inhibits iNOS promoter activation. Inhibition of iNOS expression was associated with inhibition of activation of the transcription factor nuclear factor kappa B (NFkappaB). We conclude that melatonin inhibits NO production in immunostimulated macrophages mainly by inhibiting the expression of iNOS. This is due to inhibition of iNOS transcription, in part through inhibition of NFkappaB activation. Inhibition of iNOS-derived NO production by melatonin may contribute to the anti-inflammatory effects of this pineal secretory product.

Animals↗
PubMed1998

Peroxynitrate-mediated DNA strand breakage activates poly(ADP-ribose) synthetase and causes cellular energy depletion in a nonseptic shock model induced by zymosan in the rat.

The aim of the present study was to investigate the role of poly(ADP-ribose) synthetase in a nonseptic shock model, wherein oxyradicals, nitric oxide, and peroxynitrite are known to play a crucial role in the inflammatory process. DNA single-strand breakage and activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS) triggers an energy-consuming, inefficient repair cycle, which contributes to peroxynitrite-induced cellular injury. Here we investigated whether peroxynitrite production and PARS activation are involved in cytotoxicity in macrophages collected from rats subjected to zymosan-induced shock. Macrophages harvested from the peritoneal cavity exhibited a significant production of peroxynitrite, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123. Furthermore, zymosan-induced shock caused a suppression of macrophage mitochondrial respiration, DNA strand breakage, activation of PARS, and reduction of NAD+ cellular levels. In vivo treatment with 3-aminobenzamide (10 mg/kg intraperitoneally, 1 and 6 h after zymosan injection) or nicotinamide (50 mg/kg intraperitoneally, 1 and 6 h after zymosan injection) significantly inhibited the decrease in mitochondrial respiration and the activation of PARS, and partially restored the cellular level of NAD+. In a separate group of experiments, in vivo pretreatment with NG-nitro-L-arginine methyl ester, a nonselective inhibitor of nitric oxide synthesis (10 mg/kg intraperitoneally, 15 min before zymosan administration), reduced peroxynitrite formation and prevented the appearance of DNA damage, the decrease in mitochondrial respiration, and the loss of cellular levels of NAD+. Our study suggests that formation of peroxynitrite and subsequent activation of PARS may alter macrophage function in inflammatory processes and inhibition of nitric oxide, and that PARS may be a novel pharmacological approach to prevent cell injury in inflammation.

Animals↗
PubMed1998

Protective effect of melatonin in a non-septic shock model induced by zymosan in the rat.

In vitro studies have demonstrated that melatonin is a scavenger of oxyradicals and peroxynitrite and an inhibitor of nitric oxide (NO) production. Recently, it has been proposed that zymosan, a non-bacterial agent, causes inflammation by inducing the production of various cytokines and pro-inflammatory mediators. In the present study we evaluated the effect of melatonin treatment in a non-septic shock model induced by zymosan in the rat. Administration of zymosan (500 mg/kg intraperitoneally) in the rat induced acute peritonitis, as assessed by a marked increase in the leukocyte count in the exudate, as well as by an increase in the exudate nitrate/nitrite concentration. This inflammatory process coincided with the damage of lung, small intestine, and liver, as assessed by histological examination and by increase of myeloperoxidase activity, indicative of neutrophil infiltration. Peritoneal administration of zymosan in the rat induced also an significant increase in the plasma levels of nitrite and nitrate, stable metabolites of nitric oxide (NO), and in the levels of peroxynitrite, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123, at 18 hr after zymosan challenge. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific "footprint" of peroxynitrite, in the lung of zymosan-shocked rats. Pretreatment of zymosan-shocked rats with melatonin (25 and 50 mg/kg, intraperitoneally, 5 min before zymosan) prevented in a dose dependent manner the development of peritonitis and reduced peroxynitrite formation. In addition, melatonin (50 mg/kg, intraperitoneally, 5 min before zymosan) was effective in preventing the development of organ failure since tissue injury and neutrophil infiltration, by myeloperoxidase evaluation, was reduced in lung, small intestine, and liver. Taken together, the present results demonstrate that melatonin exerts potent antiinflammatory effects.

Acute Disease↗
PubMed1998

Oxidation, tyrosine nitration and cytostasis induction in the absence of inducible nitric oxide synthase.

In the present study, we evaluated the impact of the lack of the gene for inducible nitric oxide synthase (iNOS) on oxidation, tyrosine nitration and cytotoxicity reactions triggered by immunostimulation. In mice injected with E. coli endotoxin (bacterial lipopolysaccharide, LPS, 50 mg/kg i.p.), there was a significant increase in the degree of oxidation of dihydrorhodamine 123 to rhodamine 123. This response was attenuated by inhibition of NO biosynthesis with NG-methyl-L-arginine (L-NMA, 30 mg/kg i.p.). In mice lacking functional iNOS gene (iNOS knock-out mice), the degree of the LPS-induced, L-NMA inhibitable increase in dihydrorhodamine oxidation was decreased, but not completely abolished. LPS stimulation induced a marked increase in the immunoreactivity for nitrotyrosine (an indicator of peroxynitrite formation), as measured in the aorta and lung. An L-NMA inhibitable increase in nitrotyrosine staining induced by LPS was also observed in the tissues of the iNOS knockout animals. LPS treatment induced the appearance of DNA single strand breakage and a suppression of mitochondrial respiration in peritoneal macrophages ex vivo. A significant degree of LPS-induced DNA single strand breakage and suppression of mitochondrial respiration was still observed in the peritoneal macrophages obtained from the iNOS knockout animals. Macrophages from wild-type mice stimulated with LPS and interferon-gamma suppressed the proliferation of various target cells (P815 mastocytoma, L929 fibrosarcoma and embryonic lung fibroblast cell line): this effect was abolished by in vitro treatment with L-NMA (1 mM). Macrophages from the iNOS knockout animals exhibited a reduced degree of target cell cytostatic activity. The remainder of the cytostasis in iNOS knockout macrophages was abolished by preventing cell contact and neutralizing tumor necrosis factor á. The present results demonstrate that the lack of iNOS gene does not fully abolish oxidation, tyrosine nitration and cytostatic activity in response to immunostimulation. The current findings may have implications for the development of NO-based approaches for the experimental therapy of inflammation.

Animals↗
PubMed1998

Endotoxin tolerance alters macrophage membrane regulatory G proteins.

Administration of sublethal doses of endotoxin (LPS) or tumor necrosis factor-alpha (TNF alpha) renders rats tolerant to supralethal doses of LPS. Peritoneal macrophages from tolerant rats are refractory to LPS induced arachidonic acid (AA) metabolism and cytokine production in vivo, and exhibit reduced membrane GTPase activity and GTP gamma S binding. Since LPS stimulated AA metabolism is mediated by Gi alpha proteins, we sought to determine whether Gi alpha and/or other G proteins are reduced in LPS tolerance. Rats were rendered tolerant by two daily sublethal doses of Salmonella enteritidis LPS, 100 micrograms/kg and 500 micrograms/kg administered intraperitoneally. Animals were allowed to rest for 72 hours. Alternatively, tolerance to LPS was induced by sublethal administration of human recombinant TNF alpha (10 micrograms/kg) intraperitoneally 24 hrs before the experiments. Macrophage membrane G protein content was determined by immunoblot analysis with specific antisera to Gi1,2 alpha, Gi3 alpha, Gs alpha and the G protein beta subunits (G beta). Membrane G proteins were differentially decreased in tolerant macrophages. In macrophages from rats rendered tolerant by sublethal doses of LPS, Gi3 alpha was reduced the most to 48 +/- 8% of control (n = 3, P < 0.05) and this reduction was significant compared to those of other G proteins. Gi1,2 alpha and G beta were reduced to 73 +/- 5% (n = 3, P < 0.05) and 65 +/- 4% (n = 3, P < 0.05) of control respectively. Gs alpha(L) and Gs alpha(H) were also reduced to 61 +/- 5% (n = 3, P < 0.05) and 68 +/- 3% (n = 3, P < 0.05) of control, respectively. In contrast, only Gi3 alpha was reduced in macrophage membranes from rats pretreated with TNF alpha. Gi3 alpha was reduced to 57 +/- 11% of control (n = 4, P < 0.05) whereas Gi1,2 alpha and G beta were not significantly affected. These results demonstrate selective changes in tolerant macrophage membrane G proteins and suggest a potential role for Gi3 alpha in mediating LPS tolerance. The molecular mechanisms underlying these changes and their significance in LPS tolerance merit further investigation.

Animals↗
PubMed1998

Mercaptoethylguanidine, a combined inhibitor of nitric oxide synthase and peroxynitrite scavenger, reduces trinitrobenzene sulfonic acid-induced colonic damage in rats.

The effect of mercaptoethylguanidine (MEG), a selective inhibitor of the inducible nitric oxide synthase and peroxynitrite scavenger, was evaluated in a rat model of colonic injury. A single intracolonic administration of trinitrobenzene sulfonic acid (TNBS, 20 mg/kg) dissolved in ethanol induced a severe colitis in male rats. Rats experienced bloody diarrhea and a significant loss of body weight. At 4 days after TNBS administration, the colon damage was characterized by areas of mucosal necrosis. Activity of myeloperoxidase, a marker of neutrophil infiltration, and levels of the 6-keto-prostaglandin F1alpha, were also markedly increased, whereas colonic ATP levels were reduced into the damaged tissue. Immunohistochemistry for the inducible nitric oxide synthase and nitrotyrosine, an index of nitrosative stress, showed an intense staining in the inflamed colon. Treatment with MEG (10 mg/kg i.v. b. i.d.) significantly reduced the appearance of diarrhea and the loss of body weight. This was associated with a remarkable amelioration of the disruption of the colonic architecture and suppression of the energetic failure, as well as a significant reduction of colonic myeloperoxidase activity and 6-keto-prostaglandin F1alpha levels. MEG also reduced the appearance of iNOS and nitrotyrosine immunoreactivity in the colon. The results of this study suggested that administration of MEG may be beneficial for the treatment of inflammatory bowel diseases.

Animals↗
PubMed1997

Lipocortin 1 protects against splanchnic artery occlusion and reperfusion injury by affecting neutrophil migration.

Splanchnic artery occlusion and reperfusion (SAO/R) shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed by release of the clamp (60-min reperfusion). Following this reperfusion period, rats developed a fall in mean arterial blood pressure, associated with a significant increase in tissue myeloperoxidase (MPO) activity in the intestine and a marked histologic injury to the distal ileum. Treatment of rats with a lipocortin-1 (LC1)-derived N-terminal peptide, peptide Ac(2-26), dose-dependently (0.125-0.5 mg/kg s.c.) reduced the progressive fall in blood pressure and prevented the infiltration of neutrophils into the reperfused intestine (reduced MPO activity). The LC1 peptide also reduced the degree of ischemia/reperfusion injury in the bowel as evaluated by histologic examination. The glucocorticoid dexamethasone (0.1 mg/kg s.c., -1 h) also produced a marked improvement in SAO/R shock (i.e., maintained mean arterial blood pressure and reduced tissue MPO activity), and this was reversed by pretreatment with two different antisera raised against the LC1 pharmacophore. Peptide Ac(2-26) (0.5 mg/kg s.c., -30 min) reduced (>60%) the extent of IL-1beta-induced cell emigration and significantly attenuated (approximately 45%) the number of adherent leukocytes in the rat mesenteric vascular bed, as assessed by video microscopy. These results suggest that LC1 inhibits neutrophil migration and accumulation into reperfused tissues, thereby ameliorating the outcome of SAO/R shock.

Amino Acid Sequence↗
PubMed1997

Amelioration by mercaptoethylguanidine of the vascular and energetic failure in haemorrhagic shock in the anesthetised rat.

The effects of mercaptoethylguanidine, a dual inhibitor of the inducible nitric oxide (NO) synthase and cyclooxygenase with scavenging effect on peroxynitrite, was studied on the delayed vascular decompensation and cellular energetic failure in a rat model of haemorrhagic shock. Shock was induced by bleeding of the animals to a mean arterial blood pressure of 50 mmHg. At 3 h, animals were resuscitated with Ringers-lactate and monitored for a subsequent 3 h period. In the treated group mercaptoethylguanidine (10 mg/kg/i.v. bolus, followed by 10 mg/kg/i.v. infusion) was administered from the beginning of the resuscitation. Haemorrhagic shock resulted in the upregulation of both the constitutive and the inducible NO synthase, as measured in the lung. In shocked rats mercaptoethylguanidine prevented the increase in plasma nitrite/nitrate and 6-keto-prostaglandin F1alpha levels, ameliorated the decrease in mean arterial blood pressure, and inhibited the development of vascular hyporeactivity of the thoracic aorta ex vivo. A significant nitrotyrosine staining, an indicator of peroxynitrite formation, was found in thoracic aortic rings from shocked animals, which was prevented by mercaptoethylguanidine treatment. In ex vivo experiments in peritoneal macrophages obtained from shocked rats, treatment with mercaptoethylguanidine prevented the reduction in the intracellular NAD+ content, ameliorated the suppression of mitochondrial respiration and reduced the development of DNA single strand breaks. Our data suggest that mercaptoethylguanidine may be an useful tool for the experimental therapy of haemorrhagic shock.

6-Ketoprostaglandin F1 alpha↗