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.


CONCLUSIONS
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.
Cao
Lei
L
Department of Pediatrics, Hebei Province People's Hospital, Shijiazhuang, P.R. China.
Liu
Cuiqing
C
Cai
Baoping
B
Jia
Xiqun
X
Kang
Limin
L
Speer
Christian P
CP
Sun
Bo
B
D001724:Birth Weight; D004797:Enzyme-Linked Immunosorbent Assay; D005865:Gestational Age; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007231:Infant, Newborn; D007235:Infant, Premature, Diseases / Q000378:metabolism*; D007375:Interleukin-1 / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D008070:Lipopolysaccharides / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000737:chemistry*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000032:analysis*; D012121:Respiration, Artificial; D012127:Respiratory Distress Syndrome, Newborn / Q000378:metabolism*
D020672:I-kappa B Proteins; D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha