Developmental changes in cholinephosphate cytidylyltransferase activity and microsomal phospholipid fatty acid composition in alveolar type II cells

Transcriptional regulation of lung cytidylyltransferase in developing transgenic mice

Lung development is associated with a surge in surfactant phosphatidylcholine (PC) production to prepare the newborn for extrauterine breathing. This process is associated with a marked increase in the activity of the rate-regulatory surfactant enzyme, CTP:phosphocholine cytidylyltransferase (CCTalpha). To investigate the molecular basis for developmental activation of CCTalpha, we analyzed expression of endogenous CCTalpha and a reporter gene, beta-galactosidase, in fetal, newborn, and adult promoter-reporter transgenic mice. Transgenics harboring approximately 2 kb of the CCTalpha promoter linked upstream of a beta-galactosidase reporter gene displayed relatively high expression in distal lung epithelia. Endogenous lung CCTalpha and beta-galactosidase activities, protein content, and transcript levels displayed maximal expression within the newborn period. CCTalpha and beta-galactosidase activities and enzyme levels increased with time in cultured fetal lung explants isolated from transgenics. Transfectional analysis using CCTalpha promoter-reporter constructs in developing rat type II cells revealed that a region encompassing -169/+71 contained the DNA elements required for perinatal activation. The studies demonstrate that developmental induction of surfactant phospholipid is due, at least in part, to transcriptional activation of the CCTalpha gene.

Oncogenic Ha-Ras transformation modulates the transcription of the CTP:phosphocholine cytidylyltransferase alpha gene via p42/44MAPK and transcription factor Sp3

We have shown previously that expression of the murine CTP:phosphocholine cytidylyltransferase (CT) alpha gene is regulated during cell proliferation (Golfman, L. S., Bakovic, M., and Vance, D. E. (2001) J. Biol. Chem. 276, 43688-43692). We have now characterized the role of Ha-Ras in the transcriptional regulation of the CTalpha gene. The expression of CTalpha and CTbeta2 proteins and mRNAs was stimulated in C3H10T1/2 murine fibroblasts expressing oncogenic Ha-Ras. Incubation of cells with the specific inhibitor (PD98059) of p42/44(MAPK) decreased the expression of both CT isoforms. Transfection of fibroblasts with CTalpha promoter-luciferase constructs resulted in an approximately 2-fold enhanced luciferase expression in Ha-Ras-transformed, compared with nontransformed, fibroblasts. Electromobility shift assays indicated enhanced binding of the Sp3 transcription factor to the CTalpha promoter in Ha-Ras-transformed cells. Expression of several forms of Sp3 was increased in nuclear extracts of Ha-Ras-transformed fibroblasts compared with nontransformed cells. Tyrosine phosphorylation of one Sp3 form was decreased, whereas phosphorylation of two other forms of Sp3 was increased in nuclear extracts of Ha-Ras-transformed cells. When control fibroblasts were transfected with a Sp3-expressing plasmid, an enhanced expression of CTalpha and CTbeta was observed. However, the expression of CTalpha or CTbeta was not increased in Ha-Ras-transformed cells transfected with a Sp3 plasmid presumably because expression was already maximally enhanced. The results suggest that Sp3 is a downstream effector of a Ras/p42/44(MAPK) signaling pathway which increases CTalpha gene transcription.

Melatonin: from basic research to cancer treatment clinics

Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger, an indirect antioxidant, as well as an important immunomodulatory agent. In both in vitro and in vivo investigations, melatonin protected healthy cells from radiation-induced and chemotherapeutic drug-induced toxicity. Furthermore, several clinical studies have demonstrated the potential of melatonin, either alone or in combination with traditional therapy, to yield a favorable efficacy to toxicity ratio in the treatment of human cancers. This study reviews the literature from laboratory investigations that document the antioxidant and oncostatic actions of melatonin and summarizes the evidence regarding the potential use of melatonin in cancer treatment. This study also provides rationale for the design of larger translational research-based clinical trials.

Prospective evaluation of surfactant composition in bronchoalveolar lavage fluid of infants with congenital diaphragmatic hernia and of age-matched controls

OBJECTIVES

Infants with congenital diaphragmatic hernia may have biochemically immature lungs. However, normal lecithin/sphingomyelin ratios and phosphatidylglycerol concentrations have been reported in the amniotic fluid of congenital diaphragmatic hernia patients. We hypothesized that if the lungs of congenital diaphragmatic hernia patients are surfactant deficient, that this condition would be reflected in an altered surfactant composition in the bronchoalveolar lavage fluid compared with that composition in age-matched controls.

DESIGN

Prospective, controlled study.

SETTING

Surgical intensive care unit in a Level III pediatric university hospital.

PATIENTS

Four groups were studied: two groups of congenital diaphragmatic hernia patients (conventionally ventilated, n = 13; treated with extracorporeal membrane oxygenation, n = 5); and two control groups (conventionally ventilated, n = 13; extracorporeal membrane oxygenation, n = 6).

INTERVENTIONS

Bronchoalveolar lavage, using a blind, standardized technique, was performed in conventionally ventilated congenital diaphragmatic hernia patients, extracorporeal membrane oxygenation-treated congenital diaphragmatic hernia patients, age-matched conventionally ventilated controls without pulmonary abnormalities, and extracorporeal membrane oxygenation-treated infants without congenital diaphragmatic hernia.

MEASUREMENTS AND MAIN RESULTS

The concentrations of different surfactant phospholipids and the fatty acid composition of phosphatidylcholine in bronchoalveolar lavage fluid were measured. No significant differences between the concentrations of phosphatidylcholine and phosphatidylglycerol, and the lecithin/sphingomyelin ratios, were found between the four groups. The fatty acid composition of phosphatidylcholine in conventionally ventilated patients showed a median percentage of palmitic acid within the normal range for age in both groups: 68% in congenital diaphragmatic hernia patients and 73% in controls (p < .001).

CONCLUSIONS

Our findings indicate that the concentrations of different phospholipids are similar in congenital diaphragmatic hernia patients and controls without congenital diaphragmatic hernia. A primary surfactant deficiency is unlikely in infants with congenital diaphragmatic hernia. However, secondary surfactant deficiency after respiratory failure may be involved.

Oleic acid stimulates rapid translocation of cholinephosphate cytidylyltransferase in type II cells

Activity of cholinephosphate cytidylyltransferase, the rate-limiting enzyme in phosphatidylcholine synthesis, increases rapidly in the lung after birth predominantly due to an increase in membrane-associated activity. Although there is strong evidence that enzyme translocation is a major regulatory mechanism in other cells, this mechanism has not been conclusively demonstrated in intact alveolar type II cells. In this study, we show that oleic acid stimulates rapid translocation of cytidylyltransferase activity and protein from cytosol to microsomes in both primary cultured fetal and adult type II cells and MLE12 cells, a cell line derived from murine distal respiratory epithelial cells. Shifts in subcellular distribution occurred within 5 min of exposure to 200 microM oleic acid. The magnitude of the increases in microsomal enzyme activity and immunoreactive protein levels was several-fold greater in d21 fetal cells than adult type II cells. Oleic acid-induced translocation was confirmed in in vitro translocation experiments. After incubating MLE12 cell postmitochondrial supernatants at 37 degrees C with oleic acid and separation of enzyme isoforms on glycerol density gradients, enzyme activity was decreased in gradient fractions corresponding to both cytosolic isoforms and microsomal activity increased 7.9-fold compared to the distribution of enzyme activity in postmitochondrial supernatants incubated at 4 degrees C without oleic acid. The increase in microsomal activity was associated with an increased incorporation of [14C]oleic acid in the membrane free fatty acid fraction. Developmental changes in type II cell membrane lipid composition may induce the rapid translocation/activation of cytidylyltransferase in the lung after birth.