Use of a novel peptide leukotriene receptor antagonist, Ly-163443, in splanchnic artery occlusion shock

Role of poly(ADP-ribose) glycohydrolase (PARG) in shock, ischemia and reperfusion

Poly(ADP-ribosyl)ation is regulated by the synthesizing enzyme poly(ADP-ribose) polymerase-1 (PARP-1) and the degrading enzyme poly(ADP-ribose) glycohydrolase (PARG). Homeostasis of poly(ADP-ribosyl)ation has been proposed to be an important regulator for pathogenesis in multi-cellular organisms. Although the role of PARP-1 in tissue damage, inflammation and ischemia has been extensively studied, the function of PARG in various cellular processes is largely unknown. Recent studies using chemical inhibitors of PARG and genetically engineered Drosophila and mouse models that carry a disrupted PARG gene have started to shed new light on the biological function of PARG in vivo. These animal models and cells isolated from them will be useful for further validation of PARG as a potential pharmaceutical target to intervene the pathogenesis induced by acute tissue injury, ischemia and inflammation.

Peroxisome proliferator-activated receptors gamma ligands and ischemia and reperfusion injury

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR subfamily comprises of three members, PPAR-alpha, PPAR-beta and PPAR-gamma. PPAR-gamma has recently been implicated as a regulator of cellular proliferation and inflammatory responses. There is good evidence that ligands of PPAR-gamma, including certain thiazolinediones, reduce tissue injury associated with ischemia and reperfusion. The potential utility of PPAR-gamma ligands in ischemia and reperfusion will be discussed in this review.

Beneficial effects of 5-aminoisoquinolinone, a novel, potent, water-soluble, inhibitor of poly (ADP-ribose) polymerase, in a rat model of splanchnic artery occlusion and reperfusion

Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischemia-reperfusion and inflammation. Splanchnic artery occlusion and reperfusion causes an enhanced formation of reactive oxygen species which contribute to the pathophysiology of shock. The aim of the present study was to investigate the effects of 5-aminoisoquinolinone (5-AIQ), a potent water-soluble inhibitor of poly(ADP-ribose) polymerase (PARP), in the pathogenesis of splanchnic artery occlusion shock. Splanchnic artery occlusion shock was induced in rats by clamping both the superior mesenteric artery and the celiac artery for 45 min, followed thereafter by release of the clamp (reperfusion). At 60 min after reperfusion, all animals were sacrificed for histological examination and biochemical studies. Treatment of rats with 5-AIQ (3 mg/kg i.v.), attenuated the fall of mean arterial blood pressure caused by splanchnic artery occlusion shock. 5-AIQ also attenuated the ileum injury as well as the increase in the tissue levels of myeloperoxidase and malondialdehyde caused by splanchnic artery occlusion shock in the ileum. The immunohistochemical examination also demonstrated a marked increase in the immunoreactivity to PAR, nitrotyrosine, and intercellular adhesion molecule (ICAM-1) in the necrotic ileum from splanchnic artery occlusion-shocked rats. 5-AIQ treatment significantly reduced the increase of positive staining for PAR, nitrotyrosine and ICAM-I. In conclusion, these results show that 5-AIQ, a new water-soluble potent inhibitor of poly(ADP-ribose) polymerase, exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock.

Rosiglitazone and 15-deoxy-Delta12,14-prostaglandin J2, ligands of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), reduce ischaemia/reperfusion injury of the gut

1. The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors related to retinoid, steroid and thyroid hormone receptors. The thiazolidinedione rosiglitazone and the endogenous cyclopentenone prostaglandin (PG)D2 metabolite, 15-deoxy-Delta12,14-PGJ2 (15d-PGJ2), are two PPAR-gamma ligands, which modulate the transcription of target genes. 2. The aim of this study was to investigate the effect of rosiglitazone and 15d-PGJ2 on the tissue injury caused by ischaemia/reperfusion (I/R) of the gut. 3. I/R injury of the intestine was caused by clamping both the superior mesenteric artery and the coeliac trunk for 45 min, followed by release of the clamp allowing reperfusion for 2 or 4 h. This procedure results in splanchnic artery occlusion (SAO) shock. 4. Rats subjected to SAO developed a significant fall in mean arterial blood pressure, and only 10% of the animals survived for the entire 4 h reperfusion period. Surviving animals were killed for histological examination and biochemical studies. Rats subjected to SAO displayed a significant increase in tissue myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels, significant increases in plasma tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta levels and marked injury to the distal ileum. 5. Increased immunoreactivity to nitrotyrosine was observed in the ileum of rats subjected to SAO. Staining of sections of the ileum obtained from SAO rats with anti-intercellular adhesion molecule (ICAM-1) antibody resulted in diffuse staining. 6. Administration at 30 min prior to the onset of gut ischaemia of the two PPAR-gamma agonists (rosiglitazone (0.3 mg kg-1 i.v.) and 15d-PGJ2 (0.3 mg kg-1 i.v.)) significantly reduced the (i) fall in mean arterial blood pressure, (ii) mortality rate, (iii) infiltration of the reperfused intestine with polymorphonuclear neutrophils (MPO activity), (iv) lipid peroxidation (MDA levels), (v) production of proinflammatory cytokines (TNF-alpha and IL-1beta) and (vi) histological evidence of gut injury. Administration of rosiglitazone and 15d-PGJ2 also markedly reduced the nitrotyrosine formation and the upregulation of ICAM-1 during reperfusion. 7. In order to elucidate whether the protective effects of rosiglitazone and 15d-PGJ2 are related to the activation of the PPAR-gamma receptor, we also investigated the effect of a PPAR-gamma antagonist, bisphenol A diglycidyl ether (BADGE), on the protective effects of rosiglitazone and 15d-PGJ2. BADGE (1 mg kg-1 administered i.v. 30 min prior to the treatment of rosiglitazone or 15d-PGJ2) significantly antagonised the effect of the two PPAR-gamma agonists and thus abolished the protective effect against gut I/R. 8. These results demonstrate that the two PPAR-gamma agonists, rosiglitazone and 15d-PGJ2, significantly reduce I/R injury of the intestine.

Beneficial effects of GPI 6150, an inhibitor of poly(ADP-ribose) polymerase in a rat model of splanchnic artery occlusion and reperfusion

The aim of the present study was to investigate the effects of GPI 6150, a new poly(ADP-ribose) polymerase (PARP) inhibitor, in the pathogenesis of splanchnic artery occlusion (SAO) shock. SAO shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed by reperfusion. At 60 min after reperfusion, SAO-shocked rats developed a significant fall in mean arterial blood pressure, significant increase of tissue myeloperoxidase activity (111 +/- 4.3 U/100 mg wet tissue vs. 28 +/- 3.2 U/100 mg wet tissue of sham-operated rats), and marked histological injury to the distal ileum and a significant mortality (0% survival at 2 h after reperfusion). Immuno-histochemical examination demonstrated a marked increase in the immunoreactivity to PARP, P-selectin, and intercellular adhesion molecule (ICAM-1) in the necrotic ileum. GPI 6150 treatment significantly improved mean arterial blood pressure, prevented the infiltration of neutrophils (72 +/- 3.6 U/100 mg wet tissue) into the reperfused intestine, improved the histological status of the reperfused tissues, markedly reduced the intensity of P-selectin and ICAM-1 in tissue section from SAO-shocked rats, and improved survival. In conclusion, our study demonstrates that GPI 6150 exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock.

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.

Beneficial effects of 3-aminobenzamide, an inhibitor of poly (ADP-ribose) synthetase in a rat model of splanchnic artery occlusion and reperfusion

1. Peroxynitrite, a potent cytotoxic oxidant formed by the reaction of nitric oxide with superoxide anion, and hydroxyl radical, formed in the iron-catalysed Fenton reaction, are important mediators of reperfusion injury. In in vitro studies, DNA single strand breakage, triggered by peroxynitrite or by hydroxyl radical, activates the nuclear enzyme poly (ADP-ribose) synthetase (PARS), with consequent cytotoxic effects. Using 3-aminobenzamide, an inhibitor of PARS, we investigated the role of PARS in the pathogenesis of splanchnic artery occlusion shock. 2. Splanchnic artery occlusion and reperfusion shock (SAO/R) was induced in rats by clamping both the superior mesenteric artery and the coeliac trunk for 45 min, followed by release of the clamp (reperfusion). At 60 min after reperfusion, animals were killed for histological examination and biochemical studies. 3. SAO/R rats developed a significant fall in mean arterial blood pressure, significant increase of tissue myeloperoxidase activity and marked histological injury to the distal ileum. SAO/R was also associated with a significant mortality (0% survival at 2 h after reperfusion). 4. There was a marked increase in the oxidation of dihydrorhodamine 123 to rhodamine (a marker of peroxynitrite-induced oxidative processes) in the plasma of the SAO/R rats, starting early after reperfusion, but not during ischaemia alone. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific 'footprint' of peroxynitrite, in the necrotic ileum in shocked rats, as measured at 60 min after the start of reperfusion. 5. In addition, in ex vivo studies in aortic rings from shocked rats, we found reduced contractions to noradrenaline and reduced responsiveness to a relaxant effect to acetylcholine (vascular hyporeactivity and endothelial dysfunction, respectively). 6. In a separate set of studies, using a 4000 Dalton fluorescent dextran tracer, we investigated the changes in epithelial permeability associated with SAO/R. Ten minutes of reperfusion, after 30 min of splanchnic artery ischaemia, resulted in a marked increase in epithelial permeability. 7. There was a significant increase in PARS activity in the intestinal epithelial cells, as measured 10 min after reperfusion ex vivo. 3-Aminobenzamide, a pharmacological inhibitor of PARS (applied at 10 mg kg(-1), i.v., 5 min before reperfusion, followed by an infusion of 10 mg kg(-1) h(-1)), significantly reduced ischaemia/reperfusion injury in the bowel, as evaluated by histological examination. Also it significantly improved mean arterial blood pressure, improved contractile responsiveness to noradrenaline, enhanced the endothelium-dependent relaxations and reduced the reperfusion-induced increase in epithelial permeability. 8. 3-Aminobenzamide also prevented the infiltration of neutrophils into the reperfused intestine, as evidenced by reduced myeloperoxidase activity. It improved the histological status of the reperfused tissues, reduced the production of peroxynitrite in the late phase of reperfusion and improved survival. 9. In conclusion, our study demonstrates that the PARS inhibitor 3-aminobenzamide exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock. We suggest that peroxynitrite and/or hydroxyl radical, produced during the reperfusion phase, trigger DNA strand breakage, PARS activation and subsequent cellular dysfunction. The vascular endothelium is likely to represent an important cellular site of protection by 3-aminobenzamide in SAO shock.

Platelet activating factor interaction with tumor necrosis factor and myocardial depressant factor in splanchnic artery occlusion shock

Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the celiac trunk for 45 min, developed a severe shock state (splanchnic artery occlusion shock) resulting in a fatal outcome within 75-90 min after release of the occlusion. Shocked rats, treated with an intravenous bolus of L-659,989, a specific platelet activating factor (PAF) receptor antagonist (12.5, 25 or 50 nmol/kg, 4 min after reperfusion followed, 8 min thereafter, by a continuous infusion of 125, 250 or 500 nmol/kg for 30 min), maintained post-release mean arterial blood pressure at significantly higher values than did rats receiving the vehicle. Treatment with L-659,989 significantly increased survival rate, blunted the rise in plasma myocardial depressant factor activity and lowered serum and macrophage levels of tumor necrosis factor (TNF-alpha). In addition, the drug completely restored macrophage phagocytosis, improved macrophage killing and significantly inhibited leukopenia. To investigate the interaction between PAF, TNF-alpha and myocardial depressant factor, the blood levels of these three mediators were evaluated: shocked rats exhibited increased PAF levels with a peak at 30 min. The plasma levels of PAF peaked earlier than did either serum TNF-alpha or plasma myocardial depressant factor. Both peaks occurred 75 min after the release of occlusion. The results of this study therefore suggest that PAF is a key mediator of splanchnic artery occlusion shock and plays a permissive role in inducing the release of other factors (i.e. TNF-alpha and myocardial depressant factor) that are relevant to shock.

Multiple Organ Failure Syndrome—Part I: Epidemiology, Prognosis, and Pathophysiology

The multiple organ failure syndrome (MOFS) is the leading cause of death in intensive care units. Although sepsis is an important cause of MOFS, it is clear that MOFS can occur in the absence of infection. The pathophysiology of MOFS is complex and multifactorial and includes derangements in oxygen delivery and consumption, the release of inflammatory and vasoactive mediators capable of inflicting tissue damage, and alterations in the barrier function of the intestinal mucosa. Although advances have been made in our understanding of MOFS, treatment remains nonspecific and largely supportive. Early and aggressive restoration of tissue perfusion, adequate treatment of infection, timely nutritional support, and support of individual failed organs remain the mainstay of therapy. Therapeutic agents directed against the various mediators associated with the pathophysiology of MOFS may prove useful in the future.

Hemodynamic effects of glucagon after acute mesenteric ischemia in rats

We have previously shown that iv glucagon improved survival in rats from 33 to 83% when given after, but not during, superior mesenteric artery (SMA) occlusion. This study investigated potential hemodynamic mechanisms of this effect. In Part 1, cardiac output (CO) was measured in 12 male Sprague-Dawley rats with an electromagnetic flow-probe that had been placed around the ascending aorta 5 days previously. Under pentobarbital anesthesia, the SMA was occluded for 85 min. All rats received normal saline (NS, 15 ml/kg/hr) for 1 hr before and after SMA declamping. Control rats (n = 6) received only NS. Treated rats (n = 6) received NS plus glucagon (1.6 micrograms/kg/min iv) for 1 hr postocclusion. CO decreased 50% during the first hour after SMA declamping in control rats, but only 11% in glucagon-treated rats (P less than 0.02). Systemic vascular resistance (SVR) increased by 90% in control rats by 1 hr after declamp, but only 9% in glucagon rats (P less than 0.04). Systemic blood pressure and heart rate were not different in the two groups. In Part 2, relative distribution of visceral blood flow was measured with radiolabeled microspheres injected in the aortic root before clamping, before declamping, and 1 hr postdeclamping in 10 rats (5 glucagon, 5 control) using the above protocol. After SMA clamping, the proportion of visceral blood flow distributed to the intestine fell from 45 to 20% (P less than 0.05). During reperfusion, the proportion of intestinal flow exceeded baseline (P less than 0.05), but was not different in control (64%) and glucagon-treated rats (56%).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of unsaturated fatty acids in splanchnic artery occlusion shock

Diets enriched with omega-3 unsaturated fatty acids are associated with decreased hypercholesterolemia and decreased risk of ischemic and atherosclerotic diseases. We studied the acute intravascular effects of some of these unsaturated fatty acids (i.e., eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) along with omega-6 unsaturated fatty acids, (i.e., linoleic and linolenic acid) in splanchnic artery occlusion (SAO) shock in rats. Anesthetized rats subjected to total occlusion of the celiac and superior mesenteric arteries for 40 minutes followed by reperfusion usually resulted in a fatal outcome 90-120 minutes after releasing the clamps. SAO shock rats treated with the omega-3 unsaturated fatty acid, EPA, exhibited an improved survival time and rate (p less than 0.05 from vehicle) compared to those receiving only vehicle (i.e., 50% ethanol). EPA and DHA treated SAO rats also exhibited lower plasma activities of the lysosomal protease, cathepsin D, free amino-nitrogen compounds, and the cardiotoxic peptide, myocardial depressant factor. These results indicate that omega-3 unsaturated fatty acids, especially EPA, have some acute beneficial effects in SAO shock in rats.