Early alterations in neutrophil activation are associated with outcome in acute lung injury

Nuclear Factor-Kappa B Expression in Alveolar Macrophages of Mechanically Ventilated Neonates with Respiratory Distress Syndrome

BACKGROUND

Inflammatory reaction and injury in mature lungs are associated with activation of nuclear factor-kappaB (NF-kappaB) to trigger proinflammatory cytokine release. In preterm infants with immature lungs, this mechanism is not yet fully understood, therefore we investigated this mechanism in mechanically ventilated neonates with respiratory distress syndrome (RDS).

METHODS

Serial samples of the airway aspirates (AA) were obtained during mechanical ventilation from 21 preterm infants with RDS, of which 12 were survivors (birth weight 1.48 +/- 0.32 kg and gestational age 31 +/- 1.5 weeks) and 9 nonsurvivors (1.34 +/- 0.31 kg and 30 +/- 2 weeks). Seven neonates matched for age and birth weight without respiratory disorders served as controls. Alveolar macrophages (AM) of AA were isolated by differential adherence, some were cultured with lipopolysaccharide (LPS) for 1 h. Then, nuclear extracts of AM were analyzed by electrophoretic mobility shift assay for NF-kappaB expression. The NF-kappaB inhibitor (IkappaB-alpha protein) in cytoplasmic extracts was detected by Western blot, and concentrations of IL-1beta and IL-8 in AA by enzyme-linked immunosorbent assay (ELISA).

RESULTS

On day 2 NF-kappaB expression in AM was significantly increased in the survivors and nonsurvivors at 33.3 +/- 9 and 54.8 +/- 10.2 relative density units (RDU) compared to control infants (11.1 +/- 6.7; p < 0.01). Expression of IkappaB-alpha was significantly higher in controls than that in the survivors and nonsurvivors on days 2 and 4. Moreover, in the nonsurvivors of RDS, expression of NF-kappaB was decreased following LPS stimulation in vitro on day 4. IL-1beta and IL-8 levels in the AA supernatant were higher in the survivors than in controls on days 2 and 4, but lower than those of the nonsurvivors on day 2. There were close correlations between the expression of NF-kappaB and levels of IL-1beta (r = 0.78, p < 0.01), and IL-8 (r = 0.81, p < 0.01) in AA.

CONCLUSION

There were alterations in NF-kappaB activity in the AM of mechanically ventilated preterm neonates with RDS, mediated by decreased synthesis and increased degradation of IkappaB.

Variation of infected cell count in bronchoalveolar lavage and timing of ventilator-associated pneumonia

OBJECTIVES

The aim of this study was to evaluate and compare the accuracy of the percentage of infected cells (%IC) in bronchoalveolar lavage (BAL) for ventilator-associated pneumonia (VAP) diagnosis according to its onset from the initiation of mechanical ventilation.

PATIENTS

One hundred and eight patients admitted to a surgical ICU were retrospectively included (1999-2001). A total of 171 cases of VAP were diagnosed on clinical, biological, chest X-ray and BAL results (threshold >/=10(4 )cfu/ml).

RESULTS

The %IC significantly decreased with the timing of VAP diagnosis: 12.2+/-12.1% for VAP occurring less than 7 days after the initiation of mechanical ventilation, 7.4+/-9.2% for VAP occurring between 7 and 15 days and 4.8+/-6.4% for VAP after 15 days ( p=0.0002), despite the same number of elements and proportion of polymorphonuclear neutrophils in BAL. In addition, a relationship between the %IC and the pathogen responsible for VAP was observed for P. aeruginosa [higher for VAP <7 days than for VAP 7-15 days ( p=0.01) and VAP >15 days ( p=0.006)] and S. aureus [lower for VAP >15 days than VAP 7-15 days ( p=0.04) and VAP <7 days ( p=0.04)]. Furthermore, the %IC in BAL was lower in patients undergoing antimicrobial therapy than in patients without antibiotics ( p=0.04). Three factors were independently associated with the %IC: quantitative culture of BAL (beta=0.42, p<0.0001), ongoing antimicrobial therapy (beta= -0.21, p=0.003) and onset of VAP (beta= -0.17, p=0.01).

CONCLUSIONS

A relationship between the %IC in BAL, duration of ventilation, quantitative culture of BAL and ongoing antimicrobial therapy has been proved in this study. The %IC for VAP diagnosis may not be accurate in patients with ongoing antibiotics and late onset infections (>7 days).

Assessing the antioxidative status in critically ill patients

PURPOSE OF REVIEW

Oxidative stress is caused by a higher production of reactive oxygen and reactive nitrogen species or a decrease in endogenous protective antioxidative capacity. In all types of critical illness, such as sepsis, trauma, burn injury, acute pancreatitis, liver injury, severe diabetes, acute respiratory distress syndrome, AIDS and kidney failure, the occurrence of increased oxidative stress or a reduced antioxidative status is described. Whereas in the past, reactive oxygen and reactive nitrogen species were mainly known as harmful agents, recent investigations have given a new insight into the (patho)physiological importance of these substances as powerful messenger molecules involved in gene regulation, thereby enabling the synthesis of cytokines or adhesion molecules necessary for defending inflammatory processes. As shown in this review, there are numerous possibilities for the quantification of oxidative stress.

RECENT FINDINGS

Several investigations showed a close association of single or multiple parameters, such as total antioxidative capacity, lipid peroxidation, vitamins C and E, the activation of nuclear factor kappa B, and respiratory burst, with the patient's outcome. However, no recommendation for a single parameter to be measured can be given because the assays described do not allow the definition of an overall "antioxidative status" for patients.

SUMMARY

The occurrence of oxidative stress in critically ill patients is associated with a poor prognosis. The measurement of a cluster of assays representative of the quantification of reactive species or of antioxidants may improve the usefulness of therapeutic intervention and increase knowledge of pathophysiological alterations.

Immune cells: free radicals and antioxidants in sepsis

The excessive production of reactive oxygen species (ROS), associated with inflammation, leads to a condition of oxidative stress. Oxidative stress is a major contributing factor to the high mortality rates associated with several diseases such as endotoxic shock. This condition can be controlled to a certain degree by antioxidant therapies. Immune cells use ROS in order to support their functions and therefore need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive production of ROS. This review discusses the toxic effects of endotoxin, paying particular attention to immune function. It continues by analyzing the mechanism to which specific cells of the immune system recognize endotoxin, and the resulting pathways leading to nuclear factor-kappaB activation and proinflammatory gene transcription. We also focus on the involvement of reactive oxygen and nitric oxide (NO) and the protective role of antioxidants. The potential clinical use of antioxidants in the treatment of sepsis and the effects on the redox state of the immune cells are discussed.