Dániel Érces

The anti-inflammatory effects of methane.

Objective:Gastrointestinal methane generation has been demonstrated in various stress conditions, but it is not known whether nonasphyxiating amounts have any impact on the mammalian pathophysiology. We set out to characterize the effects of exogenous methane administration on the process of inflammatory events arising after reoxygenation in a large animal model of ischemia–reperfusion. Design:A randomized, controlled in vivo animal study. Setting:A university research laboratory. Subjects:Inbred beagle dogs (12.7 6 2 kg). Interventions:Sodium pentobarbital-anesthetized animals were randomly assigned to sham-operated or ischemia–reperfusion groups, where superior mesenteric artery occlusion was maintained for 1 hr and the subsequent reperfusion was monitored for 3 hrs. For 5 mins before reperfusion, the animals were mechanically ventilated with normoxic artificial air with or without 2.5% methane. Biological responses to methane–oxygen respirations were defined in pilot rat studies and assay systems were used with xanthine oxidase and activated canine granulocytes to test the in vitro bioactivity potential of different gas concentrations. Measurements and Main Results:The macrohemodynamics and small intestinal pCO2 gap changes were recorded and peripheral blood samples were taken for plasma nitrite/nitrate and myeloperoxidase analyses. Tissue superoxide and nitrotyrosine levels and myeloperoxidase activity changes were determined in intestinal biopsy samples; structural mucosal damage was measured by hematoxylin and eosin staining. Methane inhalation did not influence the macrohemodynamics but significantly reduced the magnitude of the tissue damage and the intestinal pCO2 gap changes after reperfusion. Furthermore, the plasma and mucosal myeloperoxidase activity and the intestinal superoxide and nitrotyrosine levels were reduced, whereas the plasma nitrite/nitrate concentrations were increased. Additionally, methane effectively and specifically inhibited leukocyte activation in vitro. Conclusions:These data demonstrate the anti-inflammatory profile of methane. The study provides evidence that exogenous methane modulates leukocyte activation and affects key events of ischemia–reperfusion-induced oxidative and nitrosative stress and is therefore of potential therapeutic interest in inflammatory pathologies. (Crit Care Med 2012; 40:–1278)

N-Methyl-D-aspartate receptor antagonism decreases motility and inflammatory activation in the early phase of acute experimental colitis in the rat.

Background  Inflammatory bowel diseases are accompanied by severe motility disorders. The aim of our study was to investigate whether the blockade of peripheral N‐methyl‐D‐aspartate (NMDA)‐sensitive glutamate receptors (NMDA‐Rs) alters motility changes in chemically induced acute colitis and how this modulation is accomplished.

N-methyl-d-aspartate receptor antagonist therapy suppresses colon motility and inflammatory activation six days after the onset of experimental colitis in rats

We set out to investigate the time-dependent colon motility and inflammatory changes in a rodent model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in order to estimate the efficacy of N-methyl-D-aspartate (NMDA) receptor antagonist therapy administered 6 day after the acute inflammatory event. Anaesthetized Sprague-Dawley rats were randomized to control (n=6) or colitis groups (n=18). The endogenous NMDA receptor antagonist kynurenic acid (n=6) or the synthetic analog SZR-72 (n=6) was administered 6 day after TNBS induction. Large bowel motility parameters, macrohaemodynamics and serosal microcirculatory changes were recorded; the severity of colonic damage was monitored by using in vivo confocal laser endomicroscopy. Nitrite/nitrate and nitrotyrosine levels, and xanthine oxidoreductase and myeloperoxidase activities were determined on colon biopsies; plasma levels of TNF-α and IL-6 were compared with those under control and 1-day colitis (n=6) conditions. TNBS induction elevated the tissue inflammatory enzyme activities, proinflammatory cytokine release, and nitrite/nitrate and nitrotyrosine formation. The microscopic vascular and mucosal lesions were accompanied by significant increases in serosal microcirculation and frequent intestinal movements 6 day after colitis. The NMDA receptor antagonist treatments significantly decreased the signs of inflammatory activation and the levels of nitric oxide end-products, normalized the microcirculation and the rate of bowel movements in both NMDA receptor antagonist-treated colitis groups. Blockade of the enteric NMDA receptors 6 day after colitis induction concurrently influenced NO production-linked nitrosative stress and colon dysmotility and may therefore offer a possibility via which to inhibit the progression of inflammatory changes in the later phase of TNBS colitis.

Spiral intestinal lengthening and tailoring — first in vivo study

INTRODUCTION Spiral Intestinal Lengthening and Tailoring (SILT) offers a new opportunity for the surgical treatment of short bowel syndrome. SILT requires less manipulation on the mesentery than the Bianchi procedure and does not alter the orientation of the muscle fibers like serial transverse enteroplasty (STEP). This study reports the first SILT results in a surviving animal model. MATERIAL AND METHODS Vietnamese minipigs (n=6) underwent interposition of a reversed intestinal segment to produce proximal small bowel dilation. Five weeks later the reversed segment was resected, and the wall of the dilated intestine was cut spirally at 45°-60° to its longitudinal axis. The bowel was lengthened longitudinally, and the spiral shaped intestinal wound was sutured. Five weeks later, the animals were explored, and the lengthened segments were measured. Haematoxylin and eosin, picrosirius, neuron specific enolase, S-100, C-kit, and immunohistochemistry were performed. RESULTS Mean lengthening was 74.8% ± 29.5% and mean tailoring (lumen reduction) was 56.25% ± 18.8%. No instances of necrosis, perforation, suture break down, or peritonitis were observed in 6/6 animals. Four of six animals recovered uneventfully with viable lengthened segments. Statistical analysis showed no significant difference in length (p=0,078) and width (p=0,182) after 5 weeks. Two animals developed bowel obstruction due to narrowed lumen, adhesion, and strangulation after 14 and 24 days of surgery. In both animals the lumen was tailored by more than 70% to less than 1.5 cm diameter. The mucosa and the muscle layers in the operated segment had become hypertrophic, but the orientation of the circular and longitudinal muscle fibres remained normal after the SILT procedure. There were no signs of chronic ischemia or collagen accumulation after the SILT. The myenteric and submucosal plexuses and the Cajal cell network appeared normal. CONCLUSION The bowel remained viable macroscopically and microscopically after SILT, such that SILT may be an alternative or an addition to the present technical repertoire of intestinal lengthening. However the limitations of tailoring should be kept in mind.

Kynurenines and intestinal neurotransmission: the role of N-methyl-D-aspartate receptors.

Gastrointestinal neuroprotection involves the net effect of many mechanisms which protect the enteral nervous system and its cells from death, dysfunction or degeneration. Neuroprotection is also a therapeutic strategy, aimed at slowing or halting the progression of primary neuronal loss following acute or chronic diseases. The neuroprotective properties of a compound clearly have implications for an understanding of the mechanism of dysfunctions and for therapeutic approaches in a number of gastrointestinal diseases.This paper focused on the roles of glutamate and N-methyl-d-aspartate (NMDA) receptors in the intrinsic neuronal control of gastrointestinal motility; the consequences of inflammation on gastrointestinal motility changes; and the involvement of tryptophan metabolites (especially kynurenic acid) in the regulatory function of the enteral nervous system and the modulation of the inflammatory response. Common features in the mechanisms of action, illustrative evidence from animal models, and experimental neuroprotective therapies making use of the currently available possibilities are also discussed.Overall, the evidence suggests that gastrointestinal neuroprotection against inflammation and glutamate-induced neurotoxicity may be mediated synergistically through the blockade of NMDA receptors and the inhibition of neuronal nitric oxide synthase activity and xanthine oxidoreductase-dependent superoxide production. These components are likewise significant factors in the pathomechanism of gastrointestinal inflammatory diseases and inflammation-linked motility alterations. Inhibition of the enteric NMDA receptors by kynurenic acid or its analogues may provide a novel option via which to influence intestinal hypermotility and inflammatory processes simultaneously.

Central venous oxygen saturation is a good indicator of altered oxygen balance in isovolemic anemia

Red blood cell transfusion is done primarily as a means to improve oxygen delivery (DO2). Current transfusion guidelines are based solely on hemoglobin levels, regardless of actual DO2 need. As central venous oxygen saturation (ScvO2) may reflect imbalances in DO2 and consumption (VO2) the aim of this study was to investigate the value of ScvO2 as an indicator of oxygen balance in isovolemic anemia.

Central venous oxygen saturation and carbon dioxide gap as resuscitation targets in a hemorrhagic shock

Fluid resuscitation is still a major challenge. We aimed to describe changes in central venous oxygen saturation (ScvO2) and venous‐to‐arterial carbon dioxide gap (dCO2) during an experimental stroke volume (SV) index (SVI)‐guided hemorrhage and fluid resuscitation model in pigs.

Central venous-to-arterial CO2 gap is a useful parameter in monitoring hypovolemia-caused altered oxygen balance: Animal study

Monitoring hypovolemia is an everyday challenge in critical care, with no consensus on the best indicator or what is the clinically relevant level of hypovolemia. The aim of this experiment was to determine how central venous oxygen saturation (ScvO2) and central venous-to-arterial carbon dioxide difference (CO2 gap) reflect hypovolemia-caused changes in the balance of oxygen delivery and consumption. Anesthetized, ventilated Vietnamese minipigs (n = 10) were given a bolus followed by a continuous infusion of furosemide. At baseline and then in five stages hemodynamic, microcirculatory measurements and blood gas analysis were performed. Oxygen extraction increased significantly, which was accompanied by a significant drop in ScvO2 and a significant increase in CO2 gap. There was a significant negative correlation between oxygen extraction and ScvO2 and significant positive correlation between oxygen extraction and CO2 gap. Taking ScvO2 < 73% and CO2 gap >6 mmHg values together to predict an oxygen extraction >30%, the positive predictive value is 100%; negative predicted value is 72%. Microcirculatory parameters, capillary perfusion rate and red blood cell velocity, decreased significantly over time. Similar changes were not observed in the sham group. Our data suggest that ScvO2 < 73% and CO2 gap >6 mmHg can be complementary tools in detecting hypovolemia-caused imbalance of oxygen extraction.

Dietary phosphatidylcholine supplementation attenuates inflammatory mucosal damage in a rat model of experimental colitis

ABSTRACT This study was designed to follow the time course of inflammatory activation in a rodent model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)–induced colitis. We hypothesized that oral phosphatidylcholine (PC) pretreatment regimens may influence leukocyte-mediated microcirculatory reactions in this condition. In series I, Wistar rats were monitored 1 day after colitis induction (n = 24), and in series II (n = 24) on day 6 following a TNBS enema. The PC-pretreated animals received a 2% PC-enriched diet for 6 days before the TNBS enema (series I), or for 3 days before and 3 days after TNBS treatment (series II). The macrohemodynamics, serosal microcirculation (visualized by intravital videomicroscopy), colonic xanthine oxidoreductase, myeloperoxidase and nitric oxide end products, and changes in proinflammatory cytokine levels in plasma were measured. The mucosal structural injury was monitored in vivo by means of confocal laser scanning endomicroscopy. The TNBS enema induced a systemic hyperdynamic circulatory reaction with increased serosal capillary blood flow and significantly elevated colonic inflammatory enzyme activities, levels of nitric oxide production, and cytokine concentrations. Acute colitis caused disruption of the capillary network, whereas the morphologic damage was less severe in series II. The PC pretreatment protocols led to significant decreases in the serosal hyperemic reaction, the cytokine levels, and the inflammatory enzyme activities. The objective signs of tissue damage were reduced in both series, and the number of mucus-producing goblet cells in the resolving phase of colitis was increased. Dietary PC efficiently decreases the cytokine-mediated progression of inflammatory events and preserves the microvascular structure in the large intestine.

C5a inhibitor protects against ischemia/reperfusion injury in rat small intestine

Acute mesenteric ischemia (AMI) is caused by considerable intestinal injury, which is associated with intestinal ischemia followed by reperfusion. To elucidate the mechanisms of ischemia/reperfusion injuries, a C5a inhibitory peptide termed AcPepA was used to examine the role of C5a anaphylatoxin, induction of inflammatory cells, and cell proliferation of the intestinal epithelial cells in an experimental AMI model. In this rat model, the superior mesenteric artery was occluded and subsequently reperfused (Induce‐I/R). Other groups were treated with AcPepA before ischemia or reperfusion. Induce‐I/R induced injuries in the intestine and AcPepA significantly decreased the proportion of severely injured villi. Induce‐I/R induced secondary receptor for C5a‐positive polymorphonuclear leukocytes in the vessels and CD204‐positive macrophages near the injured site; this was correlated with hypoxia‐induced factor 1‐alpha‐positive cells. Induction of these inflammatory cells was attenuated by AcPepA. In addition, AcPepA increased proliferation of epithelial cells in the villi, possibly preventing further damage. Therefore, Induce‐I/R activates C5a followed by the accumulation of polymorphonuclear leukocyte and hypoxia‐induced factor 1‐alpha‐producing macrophages, leading to villus injury. AcPepA, a C5a inhibitory peptide, blocks the deleterious effects of C5a, indicating it has a therapeutic effect on the inflammatory consequences of experimental AMI.