Biomedical subjects

Andras Kapus

Publications and source records attributed to Andras Kapus.

21 records · Page 2Linked to original sources

PubMed2002

Regulation of Toll-like receptor 4 expression in the lung following hemorrhagic shock and lipopolysaccharide.

The Toll-like receptor 4 (TLR4) has recently been shown to function as the major upstream sensor for LPS. In this study, a rodent model of lung injury following resuscitated hemorrhagic shock was used to examine the regulation of TLR4 gene and protein expression in vivo and in vitro. Intratracheal LPS alone induced a rapid reduction in whole lung TLR4 mRNA, an effect which is also observed in recovered alveolar macrophages. This effect appeared to be due to a lowering of TLR4 mRNA stability by approximately 69%. By contrast, while shock/resuscitation alone had no effect on TLR4 mRNA levels, it markedly altered the response to LPS. Specifically, antecedent shock prevented the LPS-induced reduction in TLR4 mRNA levels. This reversal was explained by the ability of prior resuscitated shock both to prevent the destabilization of TLR4 mRNA by LPS and also to augment LPS-stimulated TLR4 gene transcription compared with LPS alone. Oxidant stress related to shock/resuscitation appeared to contribute to the regulation of TLR4 mRNA, because supplementation of the resuscitation fluid with the antioxidant N-acetylcysteine reversed the ability of shock/resuscitation to preserve TLR4 mRNA levels following LPS. TLR4 protein levels in whole lung mirrored the changes seen for TLR4 mRNA. Considered in aggregate, these data suggest that levels of tlr4 expression are controlled both transcriptionally as well as posttranscriptionally through altered mRNA stability and that antecedent shock/resuscitation, a form of global ischemia/reperfusion, might influence regulation of this gene.

Animals↗

PubMed2002

Impaired activation of mitogen-activated protein kinases after hemorrhagic shock.

BACKGROUND: Patients sustaining major trauma are at risk of developing organ dysfunction. We have previously shown that resuscitated hemorrhagic shock primes for increased lung injury in response to lippolysaccharide (LPS), in part by preventing upregulation of the counterinflammatory cytokine IL-10. Because the mitogen-activated protein kinase (MAPK) family is known to participate in LPS signaling, we hypothesized that altered upstream signaling through these kinases might contribute to impaired LPS-simulated IL-10 release after shock and resuscitation. METHODS: Rats were bled to a mean arterial pressure of 40 mm Hg and maintained for 1 hour, then resuscitated. Alveolar macrophages were retrieved at the end of resuscitation and exposed to LPS (0.5 microg/mL). Western blotting for p38, extracellular-regulated protein kinase, and c-Jun NH2-terminal kinase was performed on whole cell lysates. In some studies, the alveolar macrophages were preincubated with the p38 inhibitor or the extracellular-regulated protein kinase inhibitor before LPS stimulation. IL-10 levels were measured by enzyme-linked immunosorbent assay. RESULTS: LPS caused an early activation in all members of the MAPK family, whereas antecedent shock both delayed and attenuated the LPS induction. To discern whether this reduction in LPS-stimulated MAPK activation after shock might contribute to reduced IL-10, specific inhibitors were used. Inhibition of p38 MAPK completely inhibited LPS-induced IL-10 production, whereas blockade of extracellular-regulated protein kinase pathway had no effect. CONCLUSIONS: Shock resuscitation impairs LPS-induced activation of the members of the MAPK family. For the critical counterinflammatory cytokine IL-10, inhibition of p38 activation appears to contribute to the reduced levels of this cytokine in response to LPS. This study provides in vitro evidence for altered signaling through p38 MAPK, as a mechanism leading to failed upregulation of a counterinflammatory cytokine, and thus the propagation of an unrestrained proinflammatory state. Restoration of normal signaling may represent an effective strategy to reverse this effect.

Animals↗

PubMed2002

25% Albumin modulates adhesive interactions between neutrophils and the endothelium following shock/resuscitation.

BACKGROUND: Polymorphonuclear neutrophil (PMN) sequestration in the lung is a hallmark of acute respiratory distress syndrome (ARDS). We have shown that 25% Albumin (A25) resuscitation attenuates lung injury after hemorrhagic shock and lipopolysaccharide (LPS) exposure by reducing lung leukosequestration. We hypothesize that this protective property is mediated by alteration of neutrophil-endothelial cell adhesive interactions. MATERIALS AND METHODS: A 2-hit rodent model of shock resuscitation was used. CD11b and L-selectin were measured using flow cytometry in rat and human neutrophils ex vivo. Intercellular adhesion molecule-1 (ICAM-1) levels were measured by Northern blot and immunohistochemistry. RESULTS: Resuscitation with A25 attenuated the increase in PMN CD11b expression in Ringer's lactate (RL) resuscitated animals at end resuscitation and at 4-hour post-LPS. While PMN L-selectin levels remained stable in RL treated animals, A25 resuscitation resulted in a significant decrease in surface L-selectin expression at 4-hour post-LPS. ICAM-1 lung endothelial cell mRNA, was increased in RL resuscitated animals, however reduced with A25 use by 51%. The LPS induced ICAM-1 endothelial cell protein expression was also prevented with A25 resuscitation. Antioxidant property of albumin was shown to play a critical role in altering CD11b expression. CONCLUSIONS: The A25 exerts its lung-protective activity at various levels including altering the interaction between neutrophils and endothelial cells via suppressed expression of adhesion molecules. These findings suggest a novel role for A25 as an anti-inflammatory agent in PMN-mediated diseases such as ARDS.

Albumins↗