| 11 th Annual Pediatric Critical Care Colloquium |
| Session/Time | Cell Physiology/Sepsis/Sat, 8:00 - 9:30 AM |
| Title | Tyrosine Kinase Inhibition Attenuates Sepsis-induced Vasoplegia and INOS MRNA Expression in Rats But Does Not Affect NF- kappab Nuclear Translocation |
| Author | SM Klein, HR Wong, EK Dayao, GJ Hauser |
| Affiliation | Division of Pediatric Critical Care Medicine, Georgetown University Children's Medical Center, Washington, DC, and Division of Critical Care Medicine, Children's Hospital Medical Center, Cincinnati, OH |
| Introduction | Tyrosine kinase inhibition iattenuates sepsis-induced vasoplegia and INOS MRNA expression in rats but does not aftect NF-kappaB nuclear translocation. Nitric oxide (NO) is an important mediator of endotoxin (LPS)- induced hypotension. Early hypotension after endotoxin administration is thought to be related to the activation of constitutive NO synthase (CNOS) , while subsequent hypotension is mediated via expression of the inducible form of the enzyme (iNOS). Tyrosine Idnase CM) as Nvell as the transcription factor NF-kappaB participate in the induction of INOS, and TK participates in calciwn-dependent CNOS activation. The TK inhibitor AG556 improves blood pressure in septic canines and inhibits INOS MRNA expression in vitro after LPS challenge. We studied the effect of AG556 in vivo on hemodynamics, INOS MRNA expression and NF-KappaB nuclear translocation in rats challenged with LPS and on vasoplegia ex vivo in rats rendered septic by cecal ligation and puncture (CLP). |
| Method | Wistar rats were treated Nvith AG556 (2.5 mgtkg i.p.) or saline control. Sixty min later, rats were anesthetized Nvith pentobarbital, undenvent venous and arterial caiinwations, and challenged with 10mglkg i.v. of E. coli lipopolysaccharide 0127:B8 or saline. Blood pressure and heart rate were monitored for 2 h. In similar groups of rats treated Nvitli AGS56 and challenged Nvith LPS, lung and liver samples Nvere obtained 4 h after LPS. Total RNA was extracted and Northern blot analyses were carried out %vith 32P-labeled murine macrophage INOS CDNA. Nuclear translocation and binding of NF-kappaB was detected by electromobility shift assay using a radiolabeted oligonucleotide corresponding to the NF-kappaB consensus sequence. In separate experiments , AG556 or saline ivas given i.p..al the time of CLP. ContMction of mesenteric arteries Nvas measured 4 h later via a concentmtion-response ctim,e to norepinephrine in an automated myograph. |
| Result | AG556 pretreatment resulted in attenuation of early LPS-induced hypotension (at 5, 15 and 30 minutes but not at 60 and 120 minutes, p<0.05). Prior AG 556 administration inhibited CLP-induced suppression of ex vivo vascular contraction to norepinephrine (p<0.05). iNOS mRNA expression was not detectable in control rats or in rats treated with AG556 alone. LPs challenge resulted in expression of steady state iNOS mRNA in lung and liver. Prior administration of AG556 reduced LPS-mediated iNOS mRNA expression. Nuclear translocation of NF-kappaB was detected after LPS, but was not inhibited after AG556. |
| Conclusion | Administration of AG556, a TK inhibitor, prior to .LPS challenge blocked early LPS-induced hypotension in vivo (possibly via CNOS inhibition) .ind CLP-induced -vasoplegia ex vivo. AG5i6 pretreatment inhibited LPS-mediated INOS MRNA expression. However, LPS-indticed Nl---kippaB transtocition was not affected by AG556 administration. Several distinct mechanisms may be involved in the saltilary effect of TK |
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