Endotoxin-induced myocardial tumor necrosis factor-alpha synthesis depresses contractility of isolated rat hearts: evidence for a role of sphingosine and cyclooxygenase-2-derived thromboxane production.
BACKGROUND
Although endotoxin (lipopolysaccharides, LPS) is recognized as a mediator of septic cardiodepression, its cardiac effects are still not fully elucidated.


RESULTS
Perfusion of isolated rat hearts with LPS for 180 minutes resulted in a decline of left ventricular contractility after 90 minutes, whereas coronary perfusion pressure remained unaffected. This cardiodepression was paralleled by a release of tumor necrosis factor (TNF)-alpha into the perfusate and preceded by myocardial TNF-alpha mRNA upregulation as quantified by real-time polymerase chain reaction. The cardiodepression was abrogated when LPS was perfused with a TNF-alpha antiserum or the ceramidase inhibitor N:-oleoylethanolamine. In contrast, the cardiac release of nitric oxide (NO) was not augmented by LPS. Immunohistochemical studies of LPS-perfused hearts revealed a positive staining for the constitutive (NOSIII) but not for the inducible NO synthase (NOSII). Accordingly, NOSII mRNA levels commenced to increase only at the very end of the LPS perfusion period. Progressive liberation of thromboxane (Tx) A(2) and prostacyclin was induced by LPS together with myocardial cyclooxygenase (Cox)-2 mRNA expression. Both nonselective inhibition of Cox by indomethacin and selective inhibition of the inducible Cox-2 by NS-398 abolished prostanoid release. Interestingly, the generation of TNF-alpha and the associated cardiodepression caused by LPS were reduced by indomethacin, NS-398 and the Tx-receptor antagonist daltroban.


CONCLUSIONS
LPS depresses contractility of isolated rat hearts by inducing TNF-alpha synthesis and subsequently activating the sphingomyelinase pathway, whereas no evidence for a role of NOSII- or NOSIII-generated NO was found. Moreover, Cox-2-derived TxA(2) appears to facilitate TNF-alpha synthesis in response to LPS.
Grandel
U
U
Department of Internal Medicine, Justus-Liebig-University, Giessen, Germany.
Fink
L
L
Blum
A
A
Heep
M
M
Buerke
M
M
Kraemer
H J
HJ
Mayer
K
K
Bohle
R M
RM
Seeger
W
W
Grimminger
F
F
Sibelius
U
U
D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects; D003402:Creatine Kinase / Q000187:drug effects / Q000378:metabolism; D051546:Cyclooxygenase 2; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000378:metabolism; D004983:Ethanolamines / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D007106:Immune Sera / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology; D007770:L-Lactate Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D009578:Nitrobenzenes / Q000494:pharmacology; D009829:Oleic Acids; D010648:Phenylacetates / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013110:Sphingosine / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D013928:Thromboxane A2 / Q000378:metabolism; D013931:Thromboxanes / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D004983:Ethanolamines; D007106:Immune Sera; D007527:Isoenzymes; D008070:Lipopolysaccharides; D009578:Nitrobenzenes; D009829:Oleic Acids; D010648:Phenylacetates; D012333:RNA, Messenger; D013449:Sulfonamides; D013931:Thromboxanes; D014409:Tumor Necrosis Factor-alpha; C033595:N-oleoylethanolamine; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D009569:Nitric Oxide; D013928:Thromboxane A2; D011464:Epoprostenol; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D003402:Creatine Kinase; D013110:Sphingosine; C051762:daltroban; D007213:Indomethacin