SAO Shock Research Articles

Effects of palmitoylethanolamide on intestinal injury and inflammation caused by ischemia-reperfusion in mice

Our primary aim in this study was to test the hypothesis that PEA, a member of the fatty acid ethanolamide family and an endogenous PPAR-α ligand, exerts anti-inflammatory effects on SAO shock, causing a severe form of circulatory shock and enhanced formation of ROS. SAO shock was induced by clamping the superior mesenteric artery and the celiac trunk, resulting in a total occlusion of these arteries for 30 min. After this period of occlusion, the clamps were removed. In this study, we demonstrated that the administration of PEA, 5 min before reperfusion, significantly reduced all of the parameters involved during inflammation, such as proinflammatory cytokine production (TNF-α, IL-1β), adhesion molecules (ICAM-1, P-selectin) expression, NF-κB expression, and apoptosis (Bax, Bcl-2, TUNEL assay) activation. In addition, to study whether the protective action of PEA on SAO shock is also related to the activation of PPAR-α, we have investigated the effect of PEA in PPAR-α KO mice subjected to SAO shock. Our study clearly demonstrates that PEA significantly attenuated the degree of intestinal injury and inflammation caused by I/R injury. Moreover, the positive effects of PEA were at least in part dependent on the PPAR-α pathway. The results clearly indicate that PEA exerts an anti-inflammatory effect, also in a SAO shock model, which could imply a future use of PEA in the treatment of I/R shock.

Protective effects of apocynin, an inhibitor of NADPH oxidase activity, in splanchnic artery occlusion and reperfusion

SAO shock is a severe form of circulatory shock produced by I/R of the splanchnic organs. SAO causes an enhanced formation of ROS, which contributes to the pathophysiology of shock. Apocynin is a naturally occurring, methoxy-substituted catechol, experimentally used as an inhibitor of NOX. It can decrease the production of ROS from activated neutrophils and macrophages, inhibiting the assembly of NADPH-oxidase activity. In this study, we wanted to evaluate the pharmacological action of apocynin in rats subjected to SAO shock, which was induced by clamping the superior mesenteric artery and the celiac trunk, resulting in a total occlusion of these arteries for 45 min. After this period of occlusion, the clamps were removed. Administration of apocynin i.p. (5 mg/kg i.p. 10% DMSO) 5 min before reperfusion significantly reduced the (1) histological evidence of tissue injury, (2) proinflammatory cytokine production (TNF-α, IL-1β), (3) adhesion molecules (ICAM-1, P-selectin), (4) nitrotyrosine formation, (5) NF-κB expression, and (6) apoptosis (Bax, Bcl-2, Fas-L, and TUNEL). These results could imply a future use of apocynin in the treatment of I/R shock.

GW0742, a selective PPAR-β/δ agonist, contributes to the resolution of inflammation after gut ischemia/reperfusion injury

PPARs belong to a subfamily of transcription nuclear factors. Three isoforms of PPARs have been identified: alpha, beta/delta, and gamma, encoded by different genes and distributed in various tissues. They play important roles in metabolic processes, such as regulation of glucose and lipid redistribution. They also have antiatherogenic, anti-inflammatory, as well as antihypertensive functions. There is good evidence that ligands of PPARs reduce tissue injury associated with I/R. This study investigated the effects of GW0742, a potent and selective PPAR-beta/delta agonist, on tissue injury, caused in a mouse model of SAO shock. IRI of the intestine was caused by clamping the superior mesenteric artery and the celiac trunk for 45 min, followed by release of the clamp, allowing reperfusion for 1 or 6 h. Only 10% of the SAO animals survived the entire 6-h reperfusion period. In a separate set of experiments after 60 min of reperfusion, animals were killed for histological examination and biochemical studies. Administration of GW0742 (0.1 mg/kg, i.p.), 5 min prior to reperfusion, significantly reduced the (1) mortality rate, (2) histological evidence of gut injury, (3) MPO activity, (4) proinflammatory cytokines (TNF-alpha, IL-1beta), (5) adhesion molecules (ICAM-1, P-selectin), (6) nitrotyrosine formation, (7) NF-kappaB expression, (8) PAR formation, and (9) apoptosis (Bax, Bcl-2, Fas-L, and TUNEL). Based on these findings, we propose that GW0742 would be useful in the treatment of various I/R diseases.

Liver X receptor agonist treatment reduced splanchnic ischemia and reperfusion injury

LXR is another member of the superfamily of nuclear hormone receptors that heterodimerizes with RXR and regulates the intracellular levels of cholesterol through gene induction of enzymes and proteins involved in the cholesterol metabolism and transport. LXR ligands inhibit the gene expression of proinflammatory mediators in immunostimulated macrophages; in vivo studies have shown that activation of LXR reduces the inflammatory response in a murine model of contact dermatitis and atherosclerosis. No reports have addressed a role for LXRs in pathophysiology of intestinal ischemia. The aim of this study was to investigate the effects of T0901317, a potent LXR ligand, in a mouse model of SAO shock, which was induced by clamping the superior mesenteric artery and the celiac trunk, resulting in a total occlusion of these arteries for 30 min. After this period of occlusion, the clamps were removed. Mice were killed at 60 min after reperfusion. This study provides the evidence that T0901317, LXR agonist, modulates: the development of SAO shock; the infiltration of the tissue with PMNs; the expression of TNF-alpha and IL-1beta; the nitration of tyrosine residues; NF-kappaB expression; the MAPK phosphorylation (ERK, JNK, and p38); FasL; apoptosis; Bax and Bcl-2 expression; and the degree of tissue injury caused by SAO shock. Our results imply that LXR agonists may be useful in the therapy of inflammation.

PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion

Poly (ADP-ribosyl)ation, an early post-translational modification in response to DNA damage, is catalyzed by poly (ADP-ribose) polymerase (PARP-1) and catabolized by poly(ADP-ribose) glycohydrolase (PARG). The aim of this study was to investigate the role of PARG on the modulation of the inflammatory response caused by splanchnic ischemia and reperfusion. SAO shock in rats and wild-type (WT) mice was associated with a significant neutrophil infiltration in the ileum and production of tumor necrosis factor-alpha (TNF-alpha). Reperfused ileum tissue sections from SAO-shocked WT mice and rats showed positive staining for P-selectin and ICAM-1 localized mainly in the vascular endothelial cells. Genetic disruption of the PARG gene in mice or pharmacological inhibition of PARG by PARG inhibitors significantly improved the histological status of the reperfused tissues associated with reduced expression of P-selectin and ICAM-1, neutrophil infiltration into the reperfused intestine, and TNF-alpha production. These results suggest that PARG activity modulates the inflammatory response in ischemia/reperfusion and participates in end (target) organ damage under these conditions.

Pancreatic proteases and inflammatory mediators in peritoneal fluid during splanchnic arterial occlusion and reperfusion.

Pancreatic enzymes in the ischemic intestine are involved in the production of in vivo inflammatory mediators. These mediators stimulate cells in the cardiovascular system during shock and initiate multiorgan failure. An important aspect that controls the extent of the inflammation is the dispersion of these mediators from the ischemic intestine. In the past, two pathways for dispersion of these inflammatory mediators have been identified, absorption into the intestinal venous circulation and uptake into the lymphatics. We hypothesize here that the inflammatory mediators produced by pancreatic digestive enzymes in the lumen of the intestine may also be released directly into the peritoneal space. To assess the presence of inflammatory mediators in the peritoneal cavity in response to splanchnic arterial occlusion (90 min) and reperfusion (SAO shock), we measured the ability of fluid collected from this cavity to activate naive donor granulocytes. After SAO in control rats, peritoneal lavage fluid caused activation of naive donor granulocytes when tested in vitro. In contrast, when the lumen of the small intestine was flushed with a broad-acting pancreatic enzyme inhibitor (6-amidino-2-naphtyl p-guanidinobenzoate dimethanesulfate), the fluid no longer caused leukocyte activation. Reduction of the levels of inflammatory mediators in the peritoneal fluid was associated with an attenuation in the fall of blood pressure after SAO shock. These results indicate that the inflammatory mediators, which are produced by pancreatic digestive enzymes, can be absorbed directly into the systemic circulation via a transperitoneal route and play a part in the development of multiorgan failure.

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.

The effects of recombinant human granulocyte-colony stimulating factor on vascular dysfunction and splanchnic ischaemia-reperfusion injury.

1. The aim of our study was to investigate the effects of recombinant human granulocyte-colony stimulating factor in a rat model of splanchnic ischaemia-reperfusion injury. 2. Male anaesthetized rats were subjected to clamping of the splanchnic arteries for 45 min. This surgical procedure resulted in an irreversible state of shock (splanchnic artery occlusion shock. SAO shock). Sham operated animals were used as controls. Survival rate, serum tumour necrosis factor-alpha (TNF-alpha), neutrophil count, bone marrow myeloid precursor cells, myeloperoxidase activity (MPO; studied as a quantitative means to assess leukocyte accumulation), mean arterial blood pressure and the responsiveness of aortic rings to phenylephrine (PE, 1 nM-10 microM) were studied. 3. SAO shocked rats had a decreased survival rate (0% at 4 h of reperfusion, while sham shocked rats survived more than 4 h), increased serum levels of TNF-alpha (201 +/- 10 u ml-1; sham shocked rats = undetectable), neutropenia, enhanced MPO activity in the ileum (0.11 +/- 0.06 u x 10(-3) g-1 tissue; sham shocked rats = 0.02 +/- 0.001 u x 10(-3) g-1 tissue) and in the lung (1.5 +/- 0.2 u x 10(-3) g-1 tissue; sham shocked rats = 0.19 +/- 0.05 u x 10(-3) g-1 tissue) and unchanged bone marrow myeloid precursor cells. Furthermore aortic rings from shocked rats showed a marked hyporeactivity to PE. 4. Administration of recombinant human granulocyte colony stimulating factor (rh G-CSF; 5, 10 and 20 micrograms kg-1 5 min following the release of occlusion) increased in a dose-dependent manner survival rate (90% at 4 h of reperfusion with the dose of 20 u x 10(-3) g kg-1), reduced serum TNF-alpha (13 +/- 5 u ml-1) and MPO activity in the ileum (0.065 +/- 0.002 u x 10(-3) g-1 tissue) and in the lung (0.7 +/- 0.03 microgram kg-1 tissue), improved neutropenia and mean arterial blood pressure but did not modify bone marrow myeloid progenitor cells. Furthermore rh G-CSF, either in vivo or in vitro (200 nM for 1 h in the organ bath), restored to control values the hyporeactivity to PE. Finally rh G-CSF potently inhibited the activity of inducible nitric oxide synthase in peritoneal macrophages activated with endotoxin. 5. Our results suggest that rh G-CSF protects against splanchnic ischaemia reperfusion injury by a mechanism(s) that does not depend upon its haematopoietic effects.

Improved survival and reversal of endothelial dysfunction by the 21-aminosteroid, U-74389G in splanchnic ischaemia-reperfusion injury in the rat.

1. Anaesthetized rats subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state (splanchnic artery occlusion, SAO shock) resulting in death within 70-90 min after release of the occlusion. Sham-operated animals were used as controls. 2. Survival rate, survival time, serum tumour necrosis factor (TNF-alpha), white blood cell (WBC) count, mean arterial blood pressure (MAP), plasma malonyladehyde (MAL); myeloperoxidase activity (MPO) and the responsiveness to acetylcholine (ACh 10 nM-10 microM) of aortic rings were investigated. 3. SAO shocked rats had a decreased survival rate and survival time (74 +/- 10 min, while sham-shocked rats survived more than 4 h), reduced mean arterial blood pressure, increased serum levels of TNF-alpha (267 +/- 13 u ml-1) and plasma levels of MAL (57 +/- 7 nmol ml-1), enhanced MPO activity in the ileum (0.23 +/- 0.04 u x 10(-3) g-1 tissue) and in the lung (2.2 +/- 0.8 u x 10(-3) g-1 tissue), leukopenia and reduced responsiveness to ACh of aortic rings. 4. The 21-aminosteroid U-74389G (30 mg kg-1, i.v.) increased survival (survival time = 232 +/- 15 min), lowered the serum levels of TNF-alpha and the plasma levels of MAL, reduced leukopenia and MPO activity both in the ileum (0.021 +/- 0.004 u x 10(-3) g-1 tissue) and in the lung (0.23 +/- 0.03 u x 10(-3) g-1 tissue), improved MAP and restored the responsiveness to ACh of aortic rings. 5. Our data suggest that U-74389G is a potent lipid peroxidation inhibitor and that it has antishock and endothelial protective actions.

Splanchnic artery occlusion shock: vinblastine-induced leukopenia reduces tumour necrosis factor and thromboxane A 2 formation, and increases survival rate

This study was designed to assess the role of leukocytes in rats subjected to splanchnic artery occlusion for 45 min followed by reperfusion (SAO shock). Leukopenia was induced by an intravenous injection of vinblastine (1 mg/kg) 72 h before SAO shock. Survival rate (within 6 h), plasma levels of thromboxane B 2 (TxB 2), serum levels of tumour necrosis factor (TNF-α), and histological alteration of the intestinal tract were investigated. Control rats [white blood cells (WBC)=10362±630/mm 3] died within 2 h following ischaemia and reperfusion. Leukopenic (WBC=1263±311/mm 3) animals which underwent SAO shock survived more than 2 h and 50% of them were still alive after 6 h. Plasma TxB 2 levels significantly increased in WBC count normal rats subjected to SAO shock (8.4±2.1 ng/ml), compared to sham animals (0.4± 0.08ng/ml); however SAO shock raised TxB 2 levels significantly less (2.1±1.1 ng/ml) in leukopenic rats. Serum TNF-α, undetectable in sham-shocked rats (either with normal WBC count or without), rose up to 150±12 U/ml in shocked rate and to 45±5 U/ml ( P<0.01) in shocked animals with leukopenia. SAO shock induced a massive necrosis of the intestinal tract in rats with normal WBC count. Leukopenia prevented ileum necrosis in SAO shock. These data indicate that leukocytes play an important role in splanchnic artery occlusion and reperfusion.

Hemorheological modifications induced by lysophosphatidylcholine in rats under endotoxic or SAO shock

Hemorheological modifications induced by lysophosphatidylcholine in rats under endotoxic or SAO shock

Plasma prostaglandin F2alpha and 15-keto-F2alpha concentrations during splanchnic artery occlusion shock.

Arterial plasma concentrations of PGF2alpha and 15-keto-PGF2alpha were determined in sham shock and splanchnic artery occlusion shock dogs. Arterial PGF2alpha concentrations (expressed as percentage of control) increased significantly in the SAO group when compared to the sham group during postrelease sampling periods. Similarly, 15-keto-PGF2alpha, a major metabolite of PGF2alpha also increased significantly in arterial blood in SAO shock. Comparison of 15-keto-PGF2alpha and PGF2alpha at each sampling period suggest that the efficiency of 15-hydroxyprostaglandin dehydrogenase is not impaired during SAO shock in the dog. However, the ability of the kidney and other organs to remove 15-keto-PGF2alpha from the circulation during SAO shock does appear to be significantly reduced. Although the changes in circulating concentrations of PGF2alpha are significant, the role of the increased prostaglandin is not clearly understood. We found no basis for any toxic effect of the PGF2alpha nor of any beneficial action. Others, however, have found exogenous PGF2alpha to improve survival in circulatory shock.