n-n-n-trimethylsphingosine and Disease-Models--Animal

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

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction as well as myocardial injury. These deleterious effects are due in large part to endothelial dysfunction leading to an upregulation of cell adhesion molecules and subsequent neutrophil-induced cardiac injury. At physiologically relevant concentrations, N,N,N-trimethylsphingosine (TMS), a synthetic N-methylated sphingosine derivative, has been shown to attenuate leukocyte-endothelial cell interactions. We wanted to test the effects of TMS on neutrophil-mediated cardiac dysfunction in ischemia/reperfusion.. This study examines the effects of TMS in a neutrophil-dependent isolated perfused rat heart model of ischemia (I) (20 min) and reperfusion (R) (45 min) injury.. Administration of TMS (20 micrograms/kg) to I/R hearts perfused with PMNs improved coronary flow and preserved left ventricular developed pressure as an index of cardiac contractile function (95 +/- 5%) in comparison to those I/R hearts receiving only vehicle (60 +/- 7%) (P < 0.001). In addition, TMS significantly reduced PMN accumulation in the ischemic myocardium, as evidenced by an attenuation in cardiac myeloperoxidase activity from 1.12 +/- 0.04 in untreated hearts to 0.01 +/- 0.02 in treated hearts (P < 0.001). However, TMS did not directly stimulate nitric oxide (NO) release from rat vascular endothelium.. These results provide evidence that TMS is a potent and effective cardioprotective agent that inhibits leukocyte-endothelial cell interactions and preserves cardiac contractile function and coronary perfusion following myocardial ischemia and reperfusion.

Topics: Animals; Aorta; Disease Models, Animal; Electrodes; Endothelium, Vascular; Enzyme Inhibitors; In Vitro Techniques; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocardium; Neutrophils; Nitric Oxide; Perfusion; Peroxidase; Protein Kinase C; Rats; Rats, Sprague-Dawley; Sphingosine; Ventricular Function, Left