Shock/sepsis/trauma/critical care
Pentoxifylline Attenuates Lung Injury and Modulates Transcription Factor Activity in Hemorrhagic Shock

https://doi.org/10.1016/j.jss.2007.03.083Get rights and content

Background

Evidence exists that resuscitation with Ringer’s lactate (RL) contributes to postshock inflammation and lung injury. We hypothesized that the anti-inflammatory agent pentoxifylline (PTX) attenuates postresuscitative lung injury through modulation of transcription factors after hemorrhagic shock.

Methods

Male Sprague Dawley rats underwent a 1 h period of hypotension and resuscitation with RL (32 mL/kg) or RL + PTX (25 mg/kg). Lung sections were graded for histological injury and myeloperoxidase content. Cytokine-induced neutrophil chemoattractant concentration was determined by enzyme immunoassay. Matrix metalloproteinase-2 and -9 (MMP) activity was evaluated by zymography. Heme oxygenase-1, nuclear factor kappa B (NF-κB) p65 nuclear translocation, and cytoplasmic I-κB phosphorylation were assessed by Western blot. NF-κB and cAMP response element binding protein (CREB) DNA binding were determined by light shift chemiluminescent electrophoretic mobility shift assay.

Results

RL resuscitation led to statistically significant increases in all parameters of lung injury when compared with the negative control. The addition of PTX significantly decreased histology lung injury, myeloperoxidase content, cytokine-induced neutrophil chemoattractant by 48% (P < 0.05), heme oxygenase-1 expression by 50% (P < 0.05), MMP-2 activity by 70% (P < 0.05), MMP-9 activity by 44% (P < 0.05), cytoplasmic I-κB phosphorylation by 66% (P < 0.01), nuclear NF-κB p65 phosphorylation by 51% (P < 0.05), and NF-κB DNA binding by 42% (P < 0.05). In contrast, PTX increased CREB DNA binding by 69% when compared with RL alone (P < 0.04).

Conclusions

The addition of PTX to conventional RL infusion after shock significantly reduced histological lung injury and pulmonary neutrophil activity when compared to treatment with RL alone. The administration of PTX was also associated with diminished NF-κB and enhanced CREB activation. Therefore, the administration of PTX may serve as a novel therapeutic adjunct after hemorrhagic shock.

Introduction

Hemorrhagic shock is a major cause of death during the initial phases of trauma. For those who survive, the duration and depth of ischemia and subsequent reperfusion have been linked to the development of acute lung injury (ALI) and multisystem organ failure [1]. ALI and its most severe form, acute respiratory distress syndrome (ARDS), are characterized by disruption of the pulmonary endothelial barrier, which leads to interstitial edema, reduced lung compliance, and persistent hypoxia [2]. There is much evidence to suggest that the host’s own neutrophil population plays a central role in the development of ALI and ARDS. More specifically, migration in response to chemokines such as interleukin-8 (IL-8), degranulation of proteolytic enzymes, and generation of the respiratory burst have all been recognized as critical neutrophil functions leading to resuscitation-induced lung injury [3, 4].

The rapid production of local chemokines and cytokines, including IL-8, after ischemia and reperfusion is preceded by and dependent on an increase in the corresponding mRNA transcripts and is a direct consequence of the initiation of proinflammatory gene transcription [5, 6]. The 5′ region of these particular genes have been shown to contain promoter regions that can bind transcriptional factors such as nuclear factor-kappa B (NF-κB) and cyclic-3′,5′-adenosine monophosphate (cAMP) response element binding protein (CREB), which are capable of modulating proinflammatory gene transcription in a positive or negative manner [7]. Therefore, strategies aimed at the modulation of neutrophil or transcriptional factor activation may reduce the incidence and severity of lung injury after shock.

The present standard of care for the treatment of hemorrhagic shock involves the intravenous infusion of large amounts crystalloids. However, there is recent evidence suggesting that the choice of postshock resuscitation strategy can also modulate the inflammatory response. Therefore, in terms of inflammation, the type of fluid used to restore perfusion may be just as important as restoring perfusion itself. Racemic Ringer’s lactate (RL), the current clinical resuscitative fluid, has been shown to contribute to lung injury by augmenting neutrophil oxidative burst, adhesion molecule expression, endothelial dysfunction, and cellular apoptosis in animal models of ischemia-reperfusion [8, 9, 10, 11].

Pentoxifylline (1-[5-oxohexyl]-3,7-dimethylxanthine; PTX), a methylxanthine derivative and nonspecific phosphodiesterase inhibitor, has been clinically used in the treatment of intermittent claudication in patients with peripheral and cerebrovascular atherosclerotic disease [12]. Through its hemorheologic properties, PTX enhances the deformability of red blood cells and as a result improves microvascular blood flow. Recently, studies examining the effects of PTX have been focused on its role as an immune modulator. In prospective, randomized, double-blind, placebo-controlled trials, the administration of PTX reduced mortality in neonatal sepsis and acute alcoholic hepatitis [13, 14]. PTX has been also shown to attenuate a variety proinflammatory neutrophil functions which are important in the development and propagation of host organ injury such as degranulation, adherence, and generation of the respiratory burst in animal models of ischemia-reperfusion and endotoxemia [15, 16, 17, 18, 19]. Since PTX alone is not capable of volume expansion, its role as an adjunct to standard RL resuscitation is an attractive resuscitation alternative. In this series, we hypothesized that the combination of RL and PTX attenuates posthemorrhagic shock resuscitation-induced lung injury through the modulation of neutrophil function and pulmonary transcription factor activation when compared to classic RL resuscitation in vivo.

Section snippets

Materials and Methods

The experiment was approved by the University of California Animal Subjects Committee and was in accordance with guidelines established by the National Institutes of Health.

Histological Lung Injury

Lung specimens from those animals treated with standard RL resuscitation developed significant histological changes including cellular infiltration, edema, and alveolar-capillary membrane thickening (Fig. 1). In contrast, the addition of PTX to RL infusion after shock attenuated the severity of this injury to a level observed in the sham animals. The severity scores for interstitial inflammation, neutrophil infiltration, and congestion were all markedly higher in the RL group (11.4 ± 2) than

Discussion

Despite marked improvements in hospital care over the past four decades, the mortality rate for ALI and ARDS in trauma patients remains near 40% [27]. To date, no pharmacologic therapy has demonstrated a survival benefit in multicenter trials. Recently, conventional fluid resuscitation with RL has been shown to contribute to neutrophil activation and end organ injury [8, 9, 10, 11]. Consequently, there has been increased interest in alternative strategies or pharmacologic adjuncts that can be

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