Phosphodiesterase Inhibition Attenuates Stored Blood-Induced Neutrophil Activation: A Novel Adjunct to Blood Transfusion

Protective effects of pentoxifylline in pulmonary inflammation are adenosine receptor A2A dependent

Pentoxifylline (PTX) has been shown to exert anti-inflammatory effects in experimental acute lung injury. However, results in humans were controversial. Recent in vitro studies suggested that the adenosine receptor A2A may be required for PTX to be effective. Therefore, we studied the association between A2A and PTX in a murine model of LPS-induced pulmonary inflammation. PTX treatment (10 mg/kg) reduced cellular influx (by 40%), microvascular permeability (30%), and the release of chemotactic cytokines into the alveolar space (TNF-α 60%, IL-6 60%, and CXCL2/3 53%, respectively). These protective effects were abolished completely in A2A(-/-) mice and in wild-type mice that had been treated with the selective A2A antagonist (1 mg/kg), but effects were not different in mice with altered adenosine levels. In vitro transmigration assays revealed a pivotal role of the endothelium in PTX-mediated PMN migration, with a reduction of 50% (2 mM PTX). This effect was also A2A dependent. Further, oxidative burst of human PMNs was A2A-dependently reduced by 53% after PTX treatment. In summary, PTX exhibits its anti-inflammatory effects in LPS-induced lung injury through an A2A-dependent pathway. These results will help to better understand previous conflicting data on PTX in inflammation and will direct further studies to consider the predominant role of A2A.

Polymorphonuclear cell priming associated with NF-kB activation in patients with severe injury is partially dependent on macrophage migration inhibitory factor

BACKGROUND

Severe trauma may induce alternations of cytokine response and polymorphonuclear cell (PMN) activity in patients. This study investigated the correlation of plasma migration inhibitory factor (MIF) level and PMN activation after severe injury, and their relationship with clinical outcomes.

STUDY DESIGN

A prospective observational study was performed at the emergency department and intensive care unit of a university hospital. Thirty-two severe blunt trauma patients (Injury Severity Score greater than 16) with systemic inflammatory response syndrome (SIRS) were enrolled. Age- and gender-matched healthy persons were the controls. Patient blood samples were obtained within 24 hours of and at 72 hours after injury. PMNs were isolated and measured for NF-kBp65 translocation and respiratory burst. Plasma MIF, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8, and IL-10 concentrations were measured. Control PMNs were incubated with patient plasma preincubated with anti-MIF antibody or anti-IL-6 antibody; cytokine blockade effects were evaluated.

RESULTS

Twelve patients developed organ failure. Compared with patients without organ failure, patients with organ failure had lower blood pressure and a higher base deficit on admission, higher NF-kBp65 translocation and respiratory burst of PMNs, and higher plasma MIF (968 ± 246 pg/mL vs 564 ± 299 pg/mL) and IL-6 (202 ± 91 pg/mL vs 119 ± 84 pg/mL) levels within 24 hours after injury. Plasma MIF had significant positive correlation with NF-kB translocation of PMNs within 24 hours of incurring trauma (R = 0.668). The presence of anti-MIF antibody in patients' plasma obtained within 24 hours, but not at 72 hours, after injury could significantly partially block the NF-kBp65 translocation and respiratory activity of PMNs in the controls.

CONCLUSIONS

An early increase of plasma MIF associates with NF-kB translocation and respiratory burst in PMNs of severe trauma patients and correlates with higher morbidity. MIF is one of the important factors responsible for early PMN activation and may provide a target of immunomodulation after injury.

Pentoxifylline modulates p47phox activation and downregulates neutrophil oxidative burst through PKA-dependent and -independent mechanisms

BACKGROUND AND AIM

Pentoxifylline (PTX) has been proven to be an inhibitor of fMLP-induced neutrophil (PMN) oxidative burst and is thought to function by increasing cAMP and Protein kinase A (PKA). We hypothesized that PTX diminishes production of the neutrophil respiratory burst by both PKA-dependent and independent mechanisms.

MATERIAL AND METHODS

Human neutrophils were isolated and stimulated with fMLP (1microM) alone or in combination with PTX (2mM). PMN activation was determined by the cytochrome C reduction method in the presence and absence of p38 MAPK (SB203580), ERK (PD98059), and PKA inhibitors (H89). Western blot analysis of Ras, Raf, p38 MAPK, ERK, and Akt was performed in PMNs exposed to fMLP and PTX. Cell membranes were fractionated to measure membrane-associated p47 phox. Treated cells were imaged using confocal microscopy to examine changes in localization of Akt and p47phox.

RESULTS

PTX produced a decrease in oxidative burst that was diminished but not abrogated by H89 exposure. The reduction in Ras, Raf, and Akt activation seen with PTX was not effected by the presence of H89. The ability of PTX to attenuate phosphorylation of p38 MAPK and ERK was significantly decreased in the presence of H89, suggesting a PKA-dependent mechanisms. Membrane fractions of neutrophils demonstrate that PTX decreased membrane-associated p47phox, thus diminishing the ability to generate oxidative burst. PTX also decreased membrane localization of Akt and p47phox by confocal microscopy.

CONCLUSIONS

PTX attenuates activation of signaling molecules involved in activation of p47phox and suppress the subsequent assembly of the NADPH machinery through both PKA-dependent and PKA-independent mechanisms.

From acute pancreatitis to end-organ injury: mechanisms of acute lung injury

BACKGROUND

Multi-organ dysfunction, and in particular lung injury, is often responsible for the unfavorable outcome of patients with severe acute pancreatitis. Understanding of the mechanisms by which local inflammation in the pancreas leads to end-organ injury is crucial for the development of new therapeutic strategies.

METHODS

A MEDLINE search was performed with the terms "acute pancreatitis," "lung injury," "inflammatory response," "SIRS," and "multi-organ dysfunction." Pertinent articles were selected for analysis.

RESULTS

Modulation of the inflammatory response using a combination of immunomodulatory agents may decrease the incidence of severe pancreatitis-related acute lung injury and acute respiratory distress syndrome.

CONCLUSION

Clinical trials are of utmost importance to establish the validity of such strategies.

Pentoxifylline attenuates stored blood-induced inflammation: A new perspective on an old problem

BACKGROUND

Blood transfusion is a risk factor for many inflammatory processes. Its supernatant fraction has been proven to activate neutrophils. We hypothesized that pentoxifylline (PTX) would attenuate stored blood-induced neutrophil activation and pro-inflammatory mediator production.

METHODS

Whole blood was incubated with HBSS, LPS (100 microg/mL), leukoreduced PRBC supernatant + LPS, or supernatant + LPS + PTX (2 mmol/L). TNF-alpha levels were measured by ELISA. MMP-9 was evaluated with zymography. Neutrophil CD66b expression was determined by flow cytometry in blood treated with HBSS, fMLP (1 micromol/L), supernatant + fMLP, or supernatant + fMLP + PTX.

RESULTS

TNF-alpha levels were elevated in both the LPS and supernatant + LPS groups (100%; P < 0.01 and 120%; P < 0.01, respectively). PTX administration resulted in a 106% decrease in TNF-alpha (P < 0.0001). MMP-9 levels were increased in all groups. Administration of PTX to the supernatant + LPS group generated a 33% decrease in MMP-9 levels, which was not statistically significant (P < 0.4). Upregulation of CD66b expression was seen in LPS and supernatant + LPS groups. Significant attenuation was seen with PTX (47%; P < 0.01).

CONCLUSIONS

PTX downregulates CD66b and TNF-alpha expression in supernatant-induced whole blood. Because blood transfusion can contribute to inflammatory injury, the adjunctive use of PTX may have therapeutic potential.