Marwan Dib

The effect of intestinal ischemia and reperfusion injury on ICAM-1 expression, endothelial barrier function, neutrophil tissue influx, and protease inhibitor levels in rats.

Multiple organ dysfunction syndrome (MODS) is mediated by complex mechanisms in which interactions between activated leukocytes and endothelial cells play a central role. ICAM-1 (intercellular adhesion molecule-1) mediates firm adhesion and transendothelial migration of activated leukocytes from postcapillary venules into the tissue. The present study evaluated the ICAM-1 expression in various organs after 40 min of intestinal ischemia and 1, 3, 6, 12 h of reperfusion (I/R) in the rat, using a dual monoclonal antibody technique (n = 36). Endothelial barrier permeability, using the vascular leakage of radiolabeled human serum albumin was also assessed (n = 12). Neutrophil sequestration in the lungs was quantitated by myeloperoxidase activity and plasma protease inhibitor levels were measured with electroimmunoassay. Significant regional differences were found in ICAM-1 expression between organs, both constitutively and after I/R-injury. The highest constitutive levels were observed in the liver and lungs, followed by the kidneys. The constitutive ICAM-1 expression in the intestines and in the heart was about 1/20 compared with that found in the liver and lungs. The brain and muscle had levels of about 1/150 of that in the liver and lungs. After intestinal I/R, significant increases (17–45%) were found in the lungs, intestines, brain, heart, and muscle. Albumin leakage index (ALI) in all examined organs and myeloperoxidase activity in the lungs increased after I/R-injury. Serum levels of albumin and most protease inhibitors decreased significantly after I/R challenge. Intestinal I/R results in an increase of systemic ICAM-1 expression with marked organ variability. The upregulation of ICAM-1 could represent a crucial step in the adherence- and migration process of activated leukocytes and potentially in the development of tissue injury.

Mast Cells Contribute to Early Pancreatitis-Induced Systemic Endothelial Barrier Dysfunction

Background: Activated mast cells can produce and release a number of inflammatory mediators involved in the pathophysiological process of acute conditions. The aim of the study was to evaluate the effect of mast cell stimulation on the early development of multiple organ dysfunction (MODS) in acute pancreatitis (AP). Methods: AP was induced by the intraductal infusion of 5% sodium taurodeoxycholate in the rat. Tissue endothelial barrier dysfunction (TEBD) was measured by plasma exudation of radiolabeled albumin. Activation of mast cells was estimated by measuring the release of histamine. Mast cell stimulation was achieved with compound 48/80 (C48/80) administered intravenously (i.v.) or intraperitoneally (i.p.) in different doses either as pretreatment (30 min prior to induction of AP) or treatment immediately after induction of AP. Results: Administration of C48/80 both i.p. and i.v. demonstrated the same effects. A single pretreatment dose of C48/80 (0.5 mg/kg) significantly reduced AP-induced TEBD in the pancreas and gut. Administration of C48/80 immediately after sham operation or induction of AP resulted in a significant increase in pancreatic and intestinal TEBD (p < 0.05 vs. AP+saline). Plasma levels of histamine increased with increasing doses of C48/80. Conclusion: The results imply that mast cell activation could be involved in the initiation of AP and the early phase of AP-induced MODS. Mechanisms seem to be complex and are still to be elucidated.

Alterations of adhesion molecule expression and inflammatory mediators in acute lung injury induced by septic and non-septic challenges.

The lung is frequently the first failing organ during the sequential development of multiple organ dysfunction under both septic or non-septic conditions. The present study compared polymorphisms of tumor necrosis factor (TNFα), monocyte chemoattractant protein-1 (MCP-1), and adhesion molecule (AM) expression on circulating, recruited, and migrating leukocytes in the development of lung injury after induction of acute pancreatitis (AP) or abdominal sepsis by cecal ligation and puncture (CLP). Pulmonary alveolar barrier and endothelial barrier permeability dysfunction were measured. The expression of AMs (CD11b, CD11b/c, CD31, CD54 and CD62L) on leukocytes isolated from blood, lung tissue, and bronchoalveolar space were measured by flowcytometry. Plasma exudation to the interstitial tissue and the bronchoalveolar space significantly increased 1 and 3 hours after induction of pancreatitis and to the bronchoalveolar space from 6 hours after sepsis. Bronchoalveolar levels of MCP-1 significantly increased earlier than plasma exudation to the alveoli in both pancreatitis and sepsis. Alterations in expression of adhesion molecules on bronchoalveolar lavage (BAL) leukocytes can represent a marker reflecting leukocyte activation in the lung tissue, since both BAL and lung tissue leukocytes showed similar patterns of changes. Expression of adhesion molecules on circulating leukocytes increased 1 hour after induction of pancreatitis. Activating phenotypes of circulating, lung tissue and bronchoalveolar leukocytes may thus be responsible for the-development and severity of secondary lung injury.

Acute phase response in acute pancreatitis: a comparison with abdominal sepsis.

Background: Increased knowledge on the underlying pathophysiological mechanisms in acute pancreatitis (AP) and abdominal sepsis (AS) is essential, not least for the development of novel ways of treatment. The present study aims at determining dynamic changes in the systemic inflammatory response in AP and AS. Methods: AP was induced by the intraductal injection of sodium taurodeoxycholate in the rat, while AS was induced by caecal ligation and puncture. The animals were killed 1, 3, 6 and 9 h after challenge. Plasma exudation of radiolabelled albumin, myeloperoxidase (MPO), TNF‐α, MCP‐1, superoxide and hydrogen peroxide was measured. Results: Leakage index of human serum albumin showed a significant increase early (1 h) after induction of AP and later (9 h) in AS compared to controls (P < 0.05). Hydrogen peroxide generation by circulating monocytes/macrophages was high early (1 h) in AP and after 3 and 6 h in AS. Superoxide generation increased by time after both challenges. MPO activity increased significantly, starting at 3 h in both AP and AS (P < 0.05). TNF‐α increased significantly at 6 and 9 h in both models. Conclusion: Our results indicate differences in the release of systemic inflammatory mediators and cellular response in AP and AS. However, potential similarities in end‐effect, such as the development of remote organ injury (lungs), may exist as implied by the MPO results. Further investigations of the mechanisms are crucial.