Role of Nitric Oxide and Interleukin-8 in premature infants with acute and chronic lung diseases

• Main Authors: Hsin Chun Huang, 黃新純
• Other Authors: K. D. Yang
• Format: Others
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/21524771973968894591

博士 === 長庚大學 === 臨床醫學研究所 === 100 === Many studies have shown that reduced ability of neonatal vs. adult immune cells to produce cytokines. The higher inflammatory morbidities with respiratory distress and sepsis in neonates are related to deficiencies of humoral and cellular immunity. To find out whether the initial nitric oxide (NO) release in the bronchoalveolar space played a critical role for the early respiratory distress syndrome (RDS) and the later development of chronic lung disease (CLD) was due to alteration of pro- and anti-inflammatory cytokines production associate with declining of NO production, we investigated IL-8, IL-10, TNF-α and NO levels from premature infants’ bronchoalveolar lavage (BAL) fluid and blood. It was found that levels of IL-8, but not TNF-α or IL-10, in initial BAL fluid were significantly correlated to neutrophils in the BAL and inversely correlated to the gestational age of prematurity. Levels of NO2-, not IL-8, in BAL on the first day of life decreased significantly after survanta treatment. Elevation of IL-8, not NO2- levels in BAL on the first day of life was correlated to the development of CLD. To explore the mechanism of high proinflammatory cytokine production found in BAL, further study was carried out by stimulation of neonatal and adult whole blood with endotoxin. It shows that neonatal cord blood leukocytes released significantly higher IL-8, but lower TNF-α levels after stimulated by endotoxin. The augmented IL-8 mRNA expression in cord blood was inhibited by actinomycin D (Act D), but enhanced by cycloheximide (CHX), implying that IL-8 production was controlled by de novo transcriptional induction as well as post-transcriptional (PT) regulation. Studies revealed microRNA involved in the mechanism of post-transcriptional regulation. To explore whether microRNA was involved in the post-transcriptional regulation of the augmentation of proinflammatory cytokine production, monocytes from cord and adult blood were stimulated with endotoxin. It reveals that neonatal monocytes produced significantly higher TNF-α mRNA and protein than adult ones. In order to examine whether miRNA was involved in the PT regulation, differential displays of miRNA array between neonatal and adult mononuclear cells were performed, along with the discovery of hsa-miR-103, hsa-miR-125b, hsa-miR-130a, hsa-miR-454-3p and hsa-miR-542-3p, showing more than 2-fold decrease or increase after LPS treatment for 4 h. The functional validation identified that miR-125b significantly decreased in association with higher TNF-α expression by neonatal monocytes after LPS stimulation. Transfection of miR-125b precursor into neonatal monocytes significantly repressed the TNF-α mRNA and protein expression, suggesting that miR-125b negatively regulates TNF-α expression in neonatal monocytes. Modulation of miRNA expression may be used to regulate TNF-α production in newborns with altered proinflammatory reactions. In conclusion, the augmented IL-8 production in BAL and blood of premature infants related to alteration of the IL-8 post-transcriptional cascade. Neonatal monocytes expressed significantly higher TNF-α mRNA and protein after LPS stimulation. miR-125b involved in the post-transcriptional regulation of LPS-induced augmented TNF-α production in neonatal monocytes.