m-40403 and Reperfusion-Injury

Oxidative stress results from an oxidant/antioxidant imbalance: an excess of oxidants relative to the antioxidant capacity. Recent evidence strongly suggests that oxidant stress plays a major role in several aspects of ischemia and reperfusion. Immunohistochemical and biochemical evidence demonstrate the significant role of reactive oxygen species, in particular superoxide and its reaction product peroxynitrite, formed by the interaction of superoxide and nitric oxide, in endothelial and tissue injury associated with ischemia and reperfusion. Endothelial cell damage, neutrophil activation and infiltration into tissues, lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3-phosphate dehydrogenase, inhibition of membrane sodium/potassium ATPase activity, inactivation of membrane sodium channels and other oxidative protein modifications contribute to the cytotoxic effect of superoxide and peroxynitrite. In addition, superoxide and peroxynitrite trigger DNA strand breakage, with subsequent activation of the nuclear enzyme poly-ADP ribosyl synthetase, a pathway which contributes to the cellular injury in ischemia and reperfusion. In vivo, removal of superoxide (and thus of peroxynitrite) by superoxide dismutase mimetics (SODm), which mimic the catalytic activity of the human superoxide dismutase enzymes, prevent the cellular energetic failure and tissue damage associated with ischemia and reperfusion and exert an overall beneficial effect in this situation. The role(s) of superoxide and the potential utility of SODm will be discussed in this review.

Topics: Animals; Free Radical Scavengers; Humans; Manganese; Organometallic Compounds; Reperfusion Injury; Superoxide Dismutase; Superoxides

1. Splanchnic artery occlusion shock (SAO) causes an enhanced formation of reactive oxygen species (ROS), which contribute to the pathophysiology of shock. Here we have investigated the effects of M40401, a new S:,S:-dimethyl substituted biscyclohexylpyridine Mn-based superoxide dismutase mimetic (SODm, k(cat)=1.2x10(+9) M(-1) s(-1) at pH=7.4), in rats subjected to SAO shock. 2. Treatment of rats with M40401 (applied at 0.25, 2.5 or 25 microg kg(-1), 15 min prior to reperfusion), attenuated the mean arterial blood and the migration of polymorphonuclear cells (PMNs) caused by SAO-shock. M40401 also attenuated the ileum injury (histology) as well as the increase in the tissue levels of myeloperoxidase (MPO) and malondialdehyde (MDA) caused by SAO shock in the ileum. 3. Immunohistochemical analysis for nitrotyrosine revealed a positive staining in ileum from SAO-shocked rats. The degree of staining for nitrotyrosine was markedly reduced in tissue sections obtained from SAO-shocked rats which had received M40401. Reperfused ileum tissue sections from SAO-shocked rats showed positive staining for P-selectin and for anti-intercellular adhesion molecule (ICAM-1) in the vascular endothelial cells. M40401 treatment markedly reduced the intensity and degree of P-selectin and ICAM-1 in tissue sections from SAO-shocked rats. M40401 treatment significantly improved survival. 4. Additionally, the very high catalytic activity of this new mimetic (comparable to the native human Cu/Zn SOD enzyme and exceeding the activity of the human Mn SOD enzyme) translates into a very low dose ( approximately microg kg(-1)) required to afford protection in this SAO model of ischemia reperfusion injury. 5. Taken together, our results clearly demonstrate that M40401 treatment exerts a protective effect, and part of this effect may be due to inhibition of the expression of adhesion molecules and peroxynitrite-related pathways with subsequent reduction of neutrophil-mediated cellular injury.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Arterial Occlusive Diseases; Catalysis; Cytokines; Fluorescent Antibody Technique; Ileum; Leukocyte Count; Male; Malondialdehyde; Manganese; Nitrates; Nitrites; Organometallic Compounds; P-Selectin; Peroxidase; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Splanchnic Circulation; Superoxide Dismutase; Superoxides; Tyrosine

Many human diseases are associated with the overproduction of oxygen free radicals that inflict cell damage. A manganese(II) complex with a bis(cyclohexylpyridine)-substituted macrocyclic ligand (M40403) was designed to be a functional mimic of the superoxide dismutase (SOD) enzymes that normally remove these radicals. M40403 had high catalytic SOD activity and was chemically and biologically stable in vivo. Injection of M40403 into rat models of inflammation and ischemia-reperfusion injury protected the animals against tissue damage. Such mimics may result in better clinical therapies for diseases mediated by superoxide radicals.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Cytoprotection; Dinoprostone; Dose-Response Relationship, Drug; Drug Design; Drug Stability; Inflammation; Interleukin-1; L-Lactate Dehydrogenase; Male; Manganese; Molecular Mimicry; Neutrophils; Organometallic Compounds; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Splanchnic Circulation; Superoxide Dismutase; Superoxides; Time Factors; Tumor Necrosis Factor-alpha

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Computer Simulation; Drug Design; Inflammation; Intestines; Manganese; Molecular Mimicry; Organometallic Compounds; Rats; Reperfusion Injury; Superoxide Dismutase; Superoxides