Complement component C5a mediates hemorrhage-induced intestinal damage.
ABSTRACT Complement has been implicated in the pathogenesis of intestinal damage and inflammation in multiple animal models. Although the exact mechanism is unknown, inhibition of complement prevents hemodynamic alterations in hemorrhage.
C57Bl/6, complement 5 deficient (C5-/-) and sufficient (C5+/+) mice were subjected to 25% blood loss. In some cases, C57Bl/6 mice were treated with C5a receptor antagonist (C5aRa) post-hemorrhage. Intestinal injury, leukotriene B4, and myeloperoxidase production were assessed for each treatment group of mice.
Mice subjected to significant blood loss without major trauma develop intestinal inflammation and tissue damage within 2 hours. We report here that complement 5 (C5) deficient mice are protected from intestinal tissue damage when subjected to hemorrhage (injury score = 0.36 compared with wildtype hemorrhaged animal injury score = 2.89; P < 0.05). We present evidence that C5a represents the effector molecule because C57Bl/6 mice treated with a C5a receptor antagonist displayed limited intestinal injury (injury score = 0.88), leukotriene B4 (13.16 pg/mg tissue), and myeloperoxidase (115.6 pg/mg tissue) production compared with hemorrhaged C57Bl/6 mice (P < 0.05).
Complement activation is important in the development of hemorrhage-induced tissue injury and C5a generation is critical for tissue inflammation and damage. Thus, therapeutics targeting C5a may be useful therapeutics for hemorrhage-associated injury.
Article: A novel role of complement: mice deficient in the fifth component of complement (C5) exhibit impaired liver regeneration.[show abstract] [hide abstract]
ABSTRACT: Components of innate immunity have recently been implicated in the regulation of developmental processes. Most strikingly, complement factors appear to be involved in limb regeneration in certain urodele species. Prompted by these observations and anticipating a conserved role of complement in mammalian regeneration, we have now investigated the involvement of complement component C5 in liver regeneration, using a murine model of CCl(4)-induced liver toxicity and mice genetically deficient in C5. C5-deficient mice showed severely defective liver regeneration and persistent parenchymal necrosis after exposure to CCl(4.) In addition, these mice showed a marked delay in the re-entry of hepatocytes into the cell cycle (S phase) and diminished mitotic activity, as demonstrated, respectively, by the absence of 5-bromo-2'-deoxyuridine incorporation in hepatocytes, and the rare occurrence of mitoses in the liver parenchyma. Reconstitution of C5-deficient mice with murine C5 or C5a significantly restored hepatocyte regeneration after toxic injury. Furthermore, blockade of the C5a receptor (C5aR) abrogated the ability of hepatocytes to proliferate in response to liver injury, providing a mechanism by which C5 exerts its function, and establishing a critical role for C5aR signaling in the early events leading to hepatocyte proliferation. These results support a novel role for C5 in liver regeneration and strongly implicate the complement system as an important immunoregulatory component of hepatic homeostasis.The Journal of Immunology 03/2001; 166(4):2479-86. · 5.79 Impact Factor
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ABSTRACT: In a porcine hemorrhagic shock model we aimed to determine: (a) whether blood flow to the intestine and kidney was more reduced than cardiac output; (b) whether parameters of anaerobic metabolism correlated with regional blood flow; and (c) whether metabolic parameters in intestine, kidney and skeletal muscles detected a compromised metabolic state at an earlier stage than did systemic parameters. In an animal research laboratory at a university hospital six domestic pigs were subjected to volume-controlled hemorrhage. Every 30 min samples of blood were withdrawn. Systemic and regional hemodynamic parameters and tissue levels of PCO2 were monitored. Whole body and organ-specific oxygen consumption (VO2) and veno-arterial (VA) differences of lactate, glucose, potassium (K+), PCO2, H+ and base excess (BE) were calculated every 30 min. With progressive hemorrhage, intestinal blood flow decreased to the same extent as cardiac output, whereas the reduction in renal blood flow was more pronounced. We found a concomitant reduction in VO2 (onset of supply dependent metabolism) in intestine, kidney and skeletal muscles. In muscular tissue PCO2 increased to levels three times higher than baseline, while renal and intestinal PCO2 increased eightfold. Supply dependency was associated with a concomitant increase in VA CO2 and VA H+. Also, VA lactate increased, mostly in intestine and least in skeletal muscle. Intestinal and renal VA K+ increased, while muscular VA K+ decreased. Arterial lactate and H+ increased considerably, whereas arterial BE decreased. With progressive hemorrhage, renal blood flow, but not intestinal and skeletal muscle blood flow, was reduced more than cardiac output. Supply dependent oxygen metabolism (VO2) and organ acidosis occurred simultaneously in the three organs, despite differences in blood flow reductions. Organ ischemia coincided with a pronounced change in arterial lactate and systemic acid base parameters.Acta Anaesthesiologica Scandinavica 08/2003; 47(6):675-86. · 2.19 Impact Factor
Article: Glycolytic inhibition: effects on diastolic relaxation and intracellular calcium handling in hypertrophied rat ventricular myocytes.[show abstract] [hide abstract]
ABSTRACT: We tested the hypothesis that glycolytic inhibition by 2-deoxyglucose causes greater impairment of diastolic relaxation and intracellular calcium handling in well-oxygenated hypertrophied adult rat myocytes compared with control myocytes. We simultaneously measured cell motion and intracellular free calcium concentration ([Ca2+]i) with indo-1 in isolated paced myocytes from aortic-banded rats and sham-operated rats. There was no difference in either the end-diastolic or peak-systolic [Ca2+]i between control and hypertrophied myocytes (97 +/- 18 vs. 105 +/- 15 nM, 467 +/- 92 vs. 556 +/- 67 nM, respectively). Myocytes were first superfused with oxygenated Hepes-buffered solution containing 1.2 mM CaCl2, 5.6 mM glucose, and 5 mM acetate, and paced at 3 Hz at 36 degrees C. Exposure to 20 mM 2-deoxyglucose as substitution of glucose for 15 min caused an upward shift of end-diastolic cell position in both control (n = 5) and hypertrophied myocytes (n = 10) (P < 0.001 vs. baseline), indicating an impaired extent of relaxation. Hypertrophied myocytes, however, showed a greater upward shift in end-diastolic cell position and slowing of relaxation compared with control myocytes (delta 144 +/- 28 vs. 55 +/- 15% of baseline diastolic position, P < 0.02). Exposure to 2-deoxyglucose increased end-diastolic [Ca2+]i in both groups (P < 0.001 vs. baseline), but there was no difference between hypertrophied and control myocytes (218 +/- 38 vs. 183 +/- 29 nM, respectively). The effects of 2-deoxyglucose were corroborated in isolated oxygenated perfused hearts in which glycolytic inhibition which caused severe elevation of isovolumic diastolic pressure and prolongation of relaxation in the hypertrophied hearts compared with controls. In summary, the inhibition of the glycolytic pathway impairs diastolic relaxation to a greater extent in hypertrophied myocytes than in control myocytes even in well-oxygenated conditions. The severe impairment of diastolic relaxation induced by 2-deoxyglucose in hypertrophied myocytes compared with control myocytes cannot be explained by greater diastolic Ca2+ overload, which implicates an increase in myofilament Ca(2+)-responsiveness as a possible mechanism.Journal of Clinical Investigation 06/1995; 95(6):2766-76. · 15.39 Impact Factor