n-n-n-trimethylsphingosine and Reperfusion-Injury

Topics: Apoptosis; Cell Division; Cell Membrane; Hydrogen Bonding; Inflammation; Neoplasm Metastasis; Neoplasms; Platelet Activation; Protein Kinase C; Reperfusion Injury; Signal Transduction; Sphingolipids; Sphingosine

N,N,N-trimethylsphingosine chloride (TMS), a stable N-methylated synthetic sphingolipid analog, has been shown to modulate protein kinase C (PKC) activity and exert a number of important biological effects, including inhibition of tumor cell growth and metastasis, inhibition of leukocyte migration and respiratory burst, and inhibition of platelet aggregation. We hypothesized that TMS would be cytoprotective in clinically relevant in vivo murine models of myocardial and hepatic ischemia-reperfusion (I/R) injury. Wild-type, obese (ob/ob), and diabetic (db/db) mice were subjected to 30 min of left coronary artery occlusion followed by 24 h of reperfusion in the myocardial I/R model. In additional studies, mice were subjected to 45 min of hepatic artery occlusion followed by 5 h of reperfusion. TMS was administered intravenously at the onset of ischemia. Myocardial infarct size, cardiac function, and serum liver enzymes were measured to assess the extent of tissue injury. TMS attenuated myocardial infarct size by 66% in the wild type and by 36% in the ob/ob mice. Furthermore, TMS reduced serum alanine transaminase levels by 43% in wild-type mice. These benefits did not extend to the ob/ob mice following hepatic I/R or to the db/db mice following both myocardial and hepatic I/R. A likely mechanism is the failure of TMS to inhibit PKC-delta translocation in the diseased heart. These data suggest that although TMS is cytoprotective following I/R in normal animals, the cytoprotective actions of TMS are largely attenuated in obese and diabetic animals.

Topics: Animals; Blood Glucose; Body Weight; Cytoprotection; Diabetes Mellitus, Type 2; Disease Models, Animal; Dose-Response Relationship, Drug; Liver; Mice; Mice, Inbred C57BL; Mice, Obese; Mitochondria, Heart; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Obesity; Protective Agents; Protein Kinase C-delta; Protein Kinase Inhibitors; Protein Transport; Reperfusion Injury; Sphingosine; Time Factors; Ventricular Function, Left

Polymorphonuclear leukocytes (PMNs) play an important role in myocardial ischemia/reperfusion (MI/R) injury. We examined the cardioprotective effects of N,N,N-trimethylsphingosine (TMS) in a murine model of MI (20 min) and R (24 h) injury in vivo, focusing on leukocyte-endothelial interactions. TMS is a synthetic N-methylated sphingosine derivative that has protein kinase C inhibitory activity and has been shown to prevent leukocyte activation. TMS (18 microgram/kg), administered intravenously 1 min prior to reperfusion, significantly attenuated myocardial necrotic injury assessed by myocardial creatine kinase loss compared with MI/R rats receiving only vehicle (P<0.001). Cardiac myeloperoxidase activity, an index of PMN accumulation in the ischemic myocardium, was also significantly attenuated by TMS compared with rats receiving vehicle (P<0.001). We further examined whether TMS can attenuate leukocyte-endothelial interaction by intravital microscopy. TMS significantly attenuated NG-nitro-L-arginine-methyl ester (L-NAME)-stimulated PMN rolling and adherence to the rat microvascular endothelium. This action of TMS appears to be mediated by reduction of P-selectin expression because immunohistochemical analysis demonstrated that TMS significantly attenuated endothelial P-selectin expression in the L-NAME-superfused rat mesenteric microvasculature. Similarly, TMS markedly attenuated rapid P-selectin expression in rat platelets stimulated with either thrombin or L-NAME assessed by flow cytometry. In conclusion, TMS seems to be an effective cardioprotective agent by inhibiting early leukocyte-endothelial interaction, thus preventing leukocyte accumulation in the ischemic reperfused myocardium.

Topics: Animals; Blood Platelets; Creatine Kinase; Endothelium, Vascular; Male; Microcirculation; Myocardial Infarction; Myocardium; Neutrophils; P-Selectin; Peroxidase; Platelet Aggregation Inhibitors; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sphingosine