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Clara cell protein (CC16) is an anti-inflammatory protein and a biomarker of pulmonary epithelial cells and alveolocapillary membrane injury in adults. We investigated whether low cord blood concentrations of CC16 are associated with the development of respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD) in preterm infants and the relationship between CC16 and its pro-inflammatory counterpart, the secretory phospholipase A(2) (sPLA(2)) enzyme. CC16 concentration, sPLA(2) activity and IL-6 concentration were measured in cord blood plasma from 79 preterm infants (25 controls, 37 infants who developed RDS and 17 infants who developed BPD). After adjustment for gestational age and Apgar score at 5 min, the CC16 concentration was lower in BPD infants than in preterm controls (p<0.01). sPLA(2) activity was similar in all groups and the IL-6 concentrations were increased in both RDS and BPD infants (p<0.01 and p<0.05, respectively, vs. controls). We conclude that low cord blood CC16 concentrations in preterm infants independently predict the development of BPD. Low CC16 levels may reflect early lung injury, which contributes to the severity of RDS and progress towards BPD. Future studies are needed to assess whether the early administration of recombinant human CC16 in preterm infants with low cord blood CC16 prevents the development of BPD.

Background: The massive pulmonary neutrophil influx in respiratory distress syndrome (RDS) in preterm infants has been ascribed to the effect of leukotriene B₄ (LTB₄). Objectives: To investigate whether secretory phospholipase A₂ (sPLA₂), the rate-limiting enzyme in LTB₄ production, is present in lungs of RDS infants and stimulates neutrophil migration. Methods: sPLA₂ was measured in tracheal aspirates from 15 preterm infants with RDS. The effect of aspirates on cord blood neutrophil migration was first measured, and the contribution of sPLA₂ was assessed by addition of its endogenous inhibitor Clara cell protein (CC16) or absorption of sPLA₂ from the aspirates. The role of intracellular signal transduction activation and LTB₄ formation in sPLA₂-induced neutrophil migration was determined using purified sPLA₂, several inhibitors of signal transduction, a LTB₄ synthesis inhibitor and a LTB₄ receptor antagonist. Results: All aspirates contained sPLA₂, which significantly stimulated neutrophil migration. Addition of CC16 or absorption of sPLA₂ abolished the stimulatory effect. All inhibitors significantly reduced sPLA₂-induced neutrophil migration. Conclusions: sPLA₂ is present in tracheal aspirates of preterm infants with RDS. Human recombinant sPLA₂ and pancreatic type sPLA₂ stimulate in vitro cord blood neutrophil migration via activation of intracellular signal transduction pathways, LTB₄ production and receptor binding. We speculate that sPLA₂ contributes to pulmonary neutrophil influx in RDS. Further studies are needed to determine the potential of sPLA₂ inhibition as a treatment for RDS.

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Preliminary studies on ischemia/reperfusion injury in transplanted small bowel grafts showed that secretory phospholipase A2 (sPLA2) may play a substantial role by breaking down membrane phospholipids. This study sought to determine the normal values of sPLA2 in the rat small bowel as a function of site and length as a baseline for future studies. The entire small bowel of male Lewis rats (200 g) was flushed with normal saline to eliminate solid contents. In group 1, the entire small bowel was divided into 5-cm segments (numbered 1-9), which were snap frozen and processed the same day for sPLA2. In group 2, a 25-cm segment of bowel (corresponding to segments 2-6 in group 1) was harvested from each animal, snap frozen, and immediately processed for sPLA2. To assess the effect of bowel storage on enzyme content, group 3 and group 4 grafts were stored for 7 and 14 days, respectively, at -85 degrees C prior to processing. All samples were homogenized in buffer, extracted with H2SO4 and assayed for sPLA2 activity using [1-14C]oleate-labeled autoclaved Escherichia coli as substrate. Results were analyzed statistically by ANOVA. sPLA2 activity rose from 85.46 +/- 14.46% hydrolysis/min fraction-1 in segment 1, to 476.38 +/- 176.75% hydrolysis/min fraction-1 in segment 9. The increase was linear and statistically significant (p < .0001). There was no significant difference in enzymatic activity between groups 2, 3, and 4. Group 2 activity was 263.02 +/- 43.74% hydrolysis/min fraction-1. This value was not statistically different from the mathematically calculated mean of segments 2-6 in group 1 (237.75). The results show that (1) sPLA2 activity increases predictably with distance from the ligament of Treitz (2) storage at -85 degrees C does not affect sPLA2, activity, and (3) 25-cm grafts may be evaluated in toto with reproducible baseline enzyme activity. Given the variability of enzyme activity along the course of the rat small bowel, it is imperative that exact location be identified in any studies evaluating sPLA2 activity.