Differential mechanisms of hepatic vascular dysregulation with mild vs
Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.AJP Gastrointestinal and Liver Physiology (Impact Factor: 3.8). 06/2008; 294(5):G1219-26. DOI: 10.1152/ajpgi.00527.2007
Endotoxemia produces hepatic vascular dysregulation resulting from inhibition of endothelin (ET)-stimulated NO production. Mechanisms include overexpression of caveolin-1 (Cav-1) and altered phosphorylation of endothelial nitric oxide (NO) synthase (NOS; eNOS) in sinusoidal endothelial cells. Since ischemia-reperfusion (I/R) also causes vascular dysregulation, we tested whether the mechanisms are the same. Rats were exposed to either mild (30 min) or moderate (60 min) hepatic ischemia in vivo followed by reperfusion (6 h). Livers were harvested and prepared into precision-cut liver slices for in vitro analysis of NOS activity and regulation. Both I/R injuries significantly abrogated both the ET-1 (1 microM) and the ET(B) receptor agonist (IRL-1620, 0.5 microM)-mediated stimulation of NOS activity. 30 min I/R resulted in overexpression of Cav-1 and loss of ET-stimulated phosphorylation of Ser1177 on eNOS, consistent with an inflammatory response. Sixty-minute I/R also resulted in loss of ET-stimulated Ser1177 phosphorylation, but Cav-1 expression was not altered. Moreover, expression of ET(B) receptors was significantly decreased. This suggests that the failure of ET to activate eNOS following 60-min I/R is associated with decreased protein expression consistent with ischemic injury. Thus hepatic vascular dysregulation following I/R is mediated by inflammatory mechanisms with mild I/R whereas ischemic mechanisms dominate following more severe I/R stress.
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ABSTRACT: It is known that some types of variable bit rate (VBR) video traffic exhibit strong long term correlations and non-stationary behavior. Estimation of an accurate amount of bandwidth to support this traffic has been a challenging task using conventional algorithmic approaches. We show that radial basis function neural networks (RBFNN) are capable of learning the non-linear multi-dimensional mapping between different video traffic patterns, quality of service (QoS) requirements and the required bandwidth to support each call. In addition, the RBFNN model adopts to new traffic scenarios and still produces accurate results. This approach bypass the modeling approach which requires detailed knowledge about the traffic statistical patterns. Our method employs “on-line” measurements of the traffic count process over a monitoring period. In order to simplify the design of the RBFNN, the input traffic is preprocessed through a lowpass filter in order to smooth all high frequency fluctuations. A large set of training data, representing different traffic patterns with different QoS requirements, was used to ensure that the RBFNN can generalize and produce accurate results when confronted with new data. The reported results prove that the neurocomputing approach is effective in achieving more accurate results than other traditional methods, based upon mathematical or simulation analysis. This is primarily due to the fact that the unique learning and adaptive capabilities of NN enable them to extract and memorize rules from previous experienceMILCOM 97 Proceedings; 12/1997
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ABSTRACT: Chronic alcohol consumption leads to inflammation and cirrhosis of the liver. In this study, we observed that liver sinusoidal endothelial cells (LSEC) derived from ethanol-fed rats showed several fold increases in the mRNA expression of endothelin-1 (ET-1), hypoxia-inducible factor-1alpha (HIF-1alpha), and inflammatory cytochemokines compared with control rat LSEC. We also observed the same results in acute ethanol-treated LSEC from control rats and human dermal microvascular endothelial cells. Ethanol-mediated ET-1 expression involved NADPH oxidase and HIF-1alpha activation. Furthermore, ethanol increased the expression of the ET-1 cognate receptor ET-BR in Kupffer cells and THP-1 monocytic cells, which also involved HIF-1alpha activation. Promoter analysis and chromatin immunoprecipitation showed that hypoxia response element sites in the proximal promoter of ET-1 and ET-BR were required for the binding of HIF-1alpha to up-regulate their expression. We showed that microRNAs, miR-199 among several microRNAs, attenuated HIF-1alpha and ET-1 expression, while anti-miR-199 reversed the effects, suggesting that ethanol-induced miR-199 down-regulation may contribute to augmented HIF-1alpha and ET-1 expression. Our studies, for the first time to our knowledge, show that ethanol-mediated ET-1 and ET-BR expression involve HIF-1alpha, independent of hypoxia. Additionally, ethanol-induced ET-1 expression in rat LSEC is regulated by miR-199, while in human endothelial cells, ET-1 expression is regulated by miR-199 and miR-155, indicating that these microRNAs may function as novel negative regulators to control ET-1 transcription and, thus, homeostatic levels of ET-1 to maintain microcirculatory tone.The Journal of Immunology 09/2009; 183(8):5232-43. DOI:10.4049/jimmunol.0901084 · 4.92 Impact Factor
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ABSTRACT: Statins are established in the prevention and therapy of chronic cardiovascular diseases because of inhibition of HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A), thus lowering blood cholesterol levels. However, their cholesterol-independent effects include regulation of Rho/Rho-kinases (ROCK) and eNOS, proteins centrally involved in various models of acute inflammation. Therefore, we tested the hypothesis that simvastatin confers protection after rat hemorrhage/resuscitation (H/R) and wanted to elucidate the mechanisms involved. Fifty-two female Lewis rats (180-250 g) were pretreated with simvastatin 5 mg/kg per day or vehicle for 6 days (i.p.). Then, rats were hemorrhaged to a mean arterial pressure of 30 +/- 2 mmHg for 60 min and resuscitated. Control group underwent surgical procedures without H/R. Two hours after resuscitation, tissues were harvested. Mortality was assessed 72 h after H/R. Simvastatin pretreatment increased survival after H/R from 20% to 80%. Serum alanine aminotransferase after H/R increased 2.2-fold in vehicle as compared with simvastatin-treated rats. Histopathological analysis revealed decreased hepatic necrosis in simvastatin-treated rats after H/R. Hepatic oxidative (4-hydroxynonenal) and nitrosative (3-nitrotyrosine) stress, inflammatory markers (serum IL-6 and hepatic infiltration with polymorphonuclear leukocytes), and actin cytoskeleton rearrangements were decreased after simvastatin pretreatment compared with vehicle-treated rats after H/R. Simvastatin increased eNOS and heme oxygenase 1 expression and eNOS activation. Expression of Rho/Rho-kinase and myosin phosphatase targeting subunit, Thr-MYPT1, a marker for Rho-kinase activity, decreased after simvastatin treatment compared with vehicle-treated rats after H/R. Simvastatin pretreatment exerts beneficial effects in this model of acute inflammation by supporting protective mechanisms that are important for hepatic microcirculation after H/R.Shock (Augusta, Ga.) 12/2009; 34(1):46-54. DOI:10.1097/SHK.0b013e3181cd8d05 · 3.05 Impact Factor
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