ag-556 and Shock--Septic

We have previously shown that an increase in NO activity activated ATP-sensitive potassium channel (K(ATP)) and shortened action potential duration (APD) in an endotoxic shock model. Because the increase in NO production and the decrease of APD appear to be downstream late events in endotoxic shock, we hypothesized that a common signaling pathway might mediate these effects.. Using a guinea pig model of endotoxic shock, we investigated the effect of genistein and tyrphostin AG 556 on the cardiac action potential. Adult Hartley guinea pigs (300 to 450 gm) were randomized into 2 treatment parts. In the chronic treatment part, guinea pigs were randomized to receive daily subcutaneous injection of one of the five agents: saline, genistein, tyrphostin AG 556, daidzein, and vehicle for 10 days. In the acute treatment part, these agents were administered by intraperitoneal injection 1 hour before endotoxic shock. The animals were then anesthetized and mechanically ventilated, and underwent 6-hour endotoxic shock or sham experiment.. In the chronic treatment part, the plasma nitrate concentration, myocardial guanosine 3',5'-cyclic monophosphate (cGMP) content, and APD at 90% repolarization (APD90) of papillary muscle showed no difference in the five groups before endotoxic shock. After 6-hour endotoxic shock, the elevation of plasma nitrate concentration and myocardial cGMP content was found significant in the control, the daidzein, and the vehicle groups, but was blunted in the genistein and the tyrphostin groups. The shortening of APD90 of papillary muscle was also significant in the control, the daidzein, and the vehicle groups, but blunted in the genistein and tyrphostin groups. There were similar findings in the acute treatment part, except the weaker effect of genistein and tyrphostin.. Genistein and tyrphostin AG 556, either administered chronically or acutely, significantly attenuate the cardiac APD shortening in endotoxic shock, presumably through the decrease in the plasma nitrate and the cardiac cGMP production. It is suggested that tyrosine kinase signaling plays an important role in the modulation of APD in endotoxic shock.

Topics: Action Potentials; Animals; Cyclic GMP; Female; Genistein; Guinea Pigs; Heart; Male; Myocardium; Nitrates; Nitric Oxide; Papillary Muscles; Potassium Channels; Shock, Septic; Tyrphostins

The dependence of the critical steps in the sepsis cascade on the transcription factor NF-kappaB andation to nitric oxide (NO) production are controversial. Tyrosine kinase (TK) is involved in several of the steps, and TK inhibitors (TKI) inhibit lipopolysaccharide (LPS)-induced vascular hyporesponsiveness in septic animals. We studied the relationship of TK inhibition, hemodynamics, vascular contraction, iNOS mRNA expression and NF-kappaB translocation in anesthetized endotoxic rats. The TKI AG556 (2.5 mg/kg i.p.), given 1 h before i.v. endotoxin (LPS) resulted in attenuation of early (<60 min) and late (60-120 min) hypotension, improved contraction of mesenteric arteries to norepinephrine 4 h after LPS, and attenuated tissue iNOS mRNA expression. LPS-induced NF-kappaB translocation was unaffected. The observed dissociation between NF-kappaB translocation and the salutary effect of TKI in vivo and ex vivo and its effect on iNOS mRNA expression suggest that although NF-kappaB may be involved in the sepsis cascade, it may not be essential for some of the molecular and vascular consequences of septic shock.

Topics: Animals; Blood Pressure; Cell Nucleus; Endotoxins; Enzyme Inhibitors; Escherichia coli; Hemodynamics; In Vitro Techniques; Lipopolysaccharides; Male; Mesenteric Arteries; Muscle, Smooth, Vascular; NF-kappa B; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Norepinephrine; Protein Transport; Protein-Tyrosine Kinases; Rats; Rats, Wistar; RNA, Messenger; Shock, Septic; Splanchnic Circulation; Transcription, Genetic; Tyrphostins; Vasoconstriction

The effects of tyrphostin AG-556 (TYR), a tyrosine kinase inhibitor, were evaluated on shock induced by lipopolysaccharide (LPS) or group B streptococcus (GBS) in rats. Mortality and mean survival time were monitored. Plasma 6-keto prostaglandin F1alpha (6-keto PGF1alpha) was also measured at four hours after LPS injection. The effects of TYR on the production of 6-keto PGF1alpha thromboxane B2(TXB2) and nitrite (NO) from LPS or GBS stimulated in vitro peritoneal rat macrophage were also examined. Salmonella enteritidis LPS (12 mg/kg, i.v. ) (n=6) produced severe shock (100% mortality). Simultaneous treatment with TYR (n=6) significantly (p < 0.01) extended mean survival time and 33% of rats survived. Plasma 6-keto PGF1alpha concentrations were increased in LPS controls, whereas TYR (5 mg/kg) significantly (p < 0.05) decreased the production. Animals treated with GBS/D-galactosamine (n=9) also exhibited shock with 100% lethality and TYR again prolonged survival time (p < 0.05) with 55% of the animals surviving. To evaluate direct effects of TYR on mediator production induced by LPS or GBS, rat macrophages were stimulated with heat-killed GBS or LPS with or without TYR. Supernatants were collected at 24 h for determination of TXB2, 6-keto PGF1alpha and NO. All mediators measured were significantly increased (p < 0.05) with LPS or GBS. TYR inhibited (p < 0.05) the production of all mediators from macrophages induced by LPS or GBS. The decrease in eicosanoids was associated with a reduction of the content of cyclooxygenase-2 (COX-2) as determined by western blotting. Collectively, these results suggest that TYR ameliorates toxic shock induced by LPS or gram positive bacteria. This protection is associated with suppression of macrophage mediator production.

Topics: 6-Ketoprostaglandin F1 alpha; Analysis of Variance; Animals; Cyclooxygenase 2; Endotoxins; Gram-Positive Bacteria; Isoenzymes; Lipopolysaccharides; Macrophages, Peritoneal; Male; Nitrites; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Long-Evans; Shock, Septic; Streptococcus; Thromboxane B2; Tyrphostins

Tyrosine kinase-dependent cell signaling is postulated to be a pivotal control point in inflammatory responses initiated by bacterial products and TNF. Using a canine model of gram-negative septic shock, we investigated the effect of tyrosine kinase inhibitors (tyrphostins) on survival. Animals were infected intraperitoneally with Escherichia coli 0111: B4, and then, in a randomized, blinded fashion, were treated immediately with one of two tyrphostins, AG 556 (n = 40) or AG 126 (n = 10), or with control (n = 50), and followed for 28 d or until death. All animals received supplemental oxygen, fluids, and antibiotics. Tyrphostin AG 556 improved survival times when compared to controls (P = 0.05). During the first 48 h after infection, AG 556 also improved mean arterial pressure, left ventricular ejection fraction, cardiac output, oxygen delivery, and alveolar-arterial oxygen gradient compared to controls (all P < or = 0.05). These improvements in organ injury were significantly predictive of survival. Treatment with AG 556 had no effect on clearance of endotoxin or bacteria from the blood (both P = NS); however, AG 556 did significantly lower serum TNF levels (P = 0.03). These data are consistent with the conclusion that AG 556 prevented cytokine-induced multiorgan failure and death during septic shock by inhibiting cell-signaling pathways without impairing host defenses as determined by clearance of bacteria and endotoxin.

Topics: Animals; Benzylidene Compounds; Disease Models, Animal; Dogs; Enzyme Inhibitors; Escherichia coli Infections; gamma-Glutamyltransferase; Heart; In Vitro Techniques; Lung; Multiple Organ Failure; Nitriles; Peritonitis; Phenols; Protein-Tyrosine Kinases; Shock, Septic; Signal Transduction; Tumor Necrosis Factor-alpha; Tyrphostins