Loss of intestinal barrier function after burn injury allows movement of intraluminal contents across the mucosa, which can lead to the development of distant organ injury and multiple organ failure. Tight junction function is highly regulated by membrane-associated proteins including occludin and zonula occludens protein 1 (ZO-1), which can be modulated by systemic inflammation. We hypothesized that (1) burn injury leads to gut barrier injury, and (2) phosphodiesterase inhibition will attenuate these burn-induced changes. Male balb/c mice undergoing a 30% steam burn were randomized to resuscitation with normal saline or normal saline + pentoxifylline (PTX; 12.5 mg/kg). Intestinal injury was assessed by histological diagnosis and TNF-α levels using enzyme-linked immunosorbent assay. Intestinal permeability was assessed by measuring the plasma concentration of fluorescein isothiocyanate–dextran after intraluminal injection in the distal ileum. Occludin and ZO-1 levels were analyzed by immunoblotting and immunohistochemistry. Thirty percent total body surface area (TBSA) burn results in a significant increase in intestinal permeability. Treatment with PTX after burn attenuates intestinal permeability to sham levels. Burn injury resulted in a marked decrease in the levels of tight junction proteins occludin and ZO-1 at 6 and 24 h. The use of PTX after burn significantly decreases the breakdown of occludin and ZO-1. Pentoxifylline also attenuates the burn-induced increase in plasma and intestinal TNF-α. Confocal microscopy demonstrates that PTX attenuates the burn-induced reorganization of occludin and ZO-1 away from the tight junction. Pentoxifylline attenuates burn-induced intestinal permeability and decreases the breakdown and reorganization of intestinal occludin and ZO-1. Therefore, phosphodiesterase inhibition may be a useful adjunct strategy in the attenuation of burn-induced gut barrier injury.

Deree J, Martins JO, Melbostad H, Loomis WH, Coimbra R. Insights into the regulation of TNF-α production in human mononuclear cells: the effects of non-specific phosphodiesterase inhibition. Clinics. 2008;63:321-8. OBJECTIVE:The objective of this study was to determine the effect of nonspecific phosphodiesterase inhibition on transcription factor activation and tumor necrosis factor-alpha (TNF-α) production in lipopolysaccharide (LPS)-stimulated human mononuclear cells. INTRODUCTION:The production of TNF-α following LPS stimulation is one of the key steps in bacterial sepsis and inflammation. The mechanism by which phosphodiesterase inhibition alters TNF-α production in the presence of LPS remains unclear. METHODS: Human mononuclear cells were stimulated with LPS (1 µg/mL), in the presence and absence of Pentoxifylline (PTX; 20 mM), a nonspecific phosphodiesterase inhibitor. Western blotting of phosphorylated cytoplasmic I-κBα, nuclear factor-κB p65 (NF-κB), and nuclear cAMP-response element binding protein (CREB) was performed. DNA binding of NF-κB and CREB was verified by electrophoretic mobility shift assay. TNF-α levels were determined in the supernatant of stimulated cells in the presence and absence Protein kinase A inhibition by an enzyme-linked immunosorbent assay (ELISA). RESULTS: PTX was demonstrated to significantly reduce cytoplasmic I-κBα phosphorylation, nuclear p65 phosphorylation, and the DNA binding activity of NF-κB. In contrast, PTX markedly enhanced the phosphorylation and DNA binding activity of CREB. Cells concomitantly treated with PTX and LPS secreted similar levels of TNF-α in the presence and absence Protein kinase A inhibition. DISCUSSION: The increased level of cAMP that results from phosphodiesterase inhibition affects cytoplasmic and nuclear events, resulting in the attenuation of NF-κB and the activation of CREB transcriptional DNA binding through pathways that are partially Protein kinase A-independent. CONCLUSION: PTX-mediated phosphodiesterase inhibition occurs partially through a Protein kinase A-independent pathway and may serve as a useful tool in the attenuation of LPS-induced inflammation.

No abstract

Despite advances in fluid resuscitation, operative strategy, and transport during the past 20 years, the mortality of traumatic injury to the abdominal aorta remains high. Shock, acidosis, suprarenal aortic injury, and a lack of retroperitoneal tamponade all independently contribute to mortality and should raise the suspicion for a potentially lethal aortic injury in a severely injured patient. Rapid identification and resuscitation in the operating room may therefore be the only factors to improve current survival rates in such devastating injuries.