Antenatal dexamethasone administration impairs normal postnatal lung growth in rats

Revealing the clinical effect and biological mechanism of acupuncture in COPD: A review

BACKGROUND

To provide new ideas for the clinical and mechanism research of acupuncture in the treatment of chronic obstructive pulmonary disease (COPD), this study systematically reviews clinical research and the progress of basic research of acupuncture in the treatment of COPD.

METHODS

PubMed and Web of Science databases were searched using acupuncture and COPD as keywords in the last 10 years, and the included literature was determined according to exclusion criteria.

FINDINGS

Acupuncture can relieve clinical symptoms, improve exercise tolerance, anxiety, and nutritional status, as well as hemorheological changes (blood viscosity), reduce the inflammatory response, and reduce the duration and frequency of COPD in patients with COPD. Mechanistically, acupuncture inhibits M1 macrophage activity, reduces neutrophil infiltration, reduces inflammatory factor production in alveolar type II epithelial cells, inhibits mucus hypersecretion of airway epithelial cells, inhibits the development of chronic inflammation in COPD, and slows tissue structure destruction. Acupuncture may control pulmonary COPD inflammation through the vagal-cholinergic anti-inflammatory, vagal-adrenomedullary-dopamine, vagal-dual-sensory nerve fiber-pulmonary, and CNS-hypothalamus-orexin pathways. Furthermore, acupuncture can increase endogenous cortisol levels by inhibiting the HPA axis, thus improving airway antioxidant capacity and reducing airway inflammation in COPD. In conclusion, the inhibition of the chronic inflammatory response is the key mechanism of acupuncture treatment for COPD.

Inducible factors and interaction of pulmonary fibrosis induced by prenatal dexamethasone exposure in offspring rats

This study aimed to investigate the correlation between prenatal dexamethasone exposure (PDE) and susceptibility to pulmonary fibrosis in offspring. Healthy female Wistar rats were given dexamethasone (0.2 mg/kg.d) or an equal volume of normal saline subcutaneously from 9 to 20 days after conception. Some of their female offspring underwent ovariectomy (OV) at 22 weeks after birth. All animals were euthanized at 28 weeks after birth. The morphological changes related to pulmonary fibrosis and extracellular matrix-related gene expression were detected, and Two-way ANOVA analyzed the interaction between PDE and OV. The results showed that adult offspring rats in FD group (female rats with PDE treatment) had early pulmonary fibrosis changes, such as pulmonary interstitial thickening, and increased expression of type IV collagen (COL4), α -smooth muscle actin (α-SMA) and fibronectin (FN) in lung tissues compared with those in FC group (female rats with saline treatment). In addition, adult offspring rats in FDO group (female rats with PDE and OV treatment) showed signs of pulmonary fibrosis, including apparent extracellular matrix deposition, increased lung injury scores (P＜0.01, P＜0.05), and extracellular matrix related gene expression (P＜0.01, P＜0.05), compared with rats in FDS (female rats with PDE treatment alone) or rats in FCO group (female rats with OV treatment alone). Moreover, PDE and OV had an interactive effect on the development of pulmonary fibrosis in female adult offspring. This study first reported the correlation between PDE and susceptibility to pulmonary fibrosis in female offspring rats, as well as the synergistic effect of PDE and OV in this pathological event, which provided a basis for further understanding of the pathogenesis of fetal originated pulmonary fibrosis.

Antenatal corticosteriods decrease forced vital capacity in infants born fullterm

Antenatal corticosteroids (ACS) administration to pregnant women for threatened preterm labor is standard obstetric care to reduce neonatal respiratory distress syndrome and the associated respiratory morbidity. While ACS stimulates surfactant production in the fetal lung, the effects of ACS upon the subsequent growth and development of the lung are unclear. Follow-up studies outside of the neonatal period have been primarily limited to spirometry, and most subjects evaluated were born prematurely. To our knowledge, no study has assessed both airway and parenchymal function in infants or adults following ACS exposure. We hypothesized that ACS impairs lung growth and performed infant pulmonary function testing, which included spirometry, alveolar volume (VA ) and lung diffusion (DL ). As a pilot study, we limited our assessment to infants whose mothers received ACS for threatened preterm labor, but then proceeded to full term delivery. This approach evaluated a more homogenous population and eliminated the confounding effects of preterm birth. We evaluated 36 full-term infants between 4 to 12 months of age; 17 infants had ACS exposure and 19 infants had no ACS exposure. Infants exposed to ACS had a significantly lower forced vital capacity compared with non-ACS exposed infants (250 vs 313 mL; P = .0075). FEV0.5 tended to be lower for the ACS exposed group (205 vs 237 mL; P = .075). VA and DL did not differ between the two groups. These findings suggest that ACS may impair subsequent growth of the lung parenchyma.

Developmental Timing Determines the Protective Effect of Maternal Electroacupuncture on Perinatal Nicotine Exposure-Induced Offspring Lung Phenotype

Introduction. Environmental exposure of the developing offspring to cigarette smoke or nicotine is an important predisposing factor for many chronic respiratory conditions, such as asthma, emphysema, pulmonary fibrosis, and so forth, in the exposed offspring. Studies showed that electroacupuncture (EA) applied to maternal "Zusanli" (ST36) acupoints during pregnancy and lactation protects against perinatal nicotine exposure- (PNE-) induced lung damage. However, the most effective time period, that is, prenatal vs. postnatal, to attain this effect has not been determined.

OBJECTIVE

To determine the most effective developmental timing of EA's protective effect against PNE-induced lung phenotype in the exposed offspring.

METHODS

Pregnant rats were given (1) saline ("S" group); (2) nicotine ("N" group); (3) nicotine + EA, exclusively prenatally ("Pre-EA" group); (4) nicotine + EA, exclusively postnatally ("Post-EA," group); and (5) nicotine + EA, administered both prenatally and postnatally ("Pre- and Post-EA" group). Nicotine was injected once daily (1 mg/kg, 100 μl) and EA was administered to bilateral ST36 acupoints once daily during the specified time-periods. At the end of the experimental periods, key hypothalamic pituitary adrenal (HPA) axis markers in pups and dams, and lung function, morphometry, and the central molecular markers of lung development in the offspring were determined.

RESULTS

After nicotine exposure, alveolar mean linear intercept (MLI) increased, but mean alveolar number (MAN) decreased and lung PPARγ level decreased, but glucocorticoid receptor (GR) and serum corticosterone (Cort) levels increased, in line with the known PNE-induced lung phenotype. In the nicotine exposed group, maternal hypothalamic corticotropin releasing hormone (CRH) level decreased, but pituitary adrenocorticotropic hormone (ACTH) and serum Cort levels increased. In the "Pre- and Post-EA" groups, PNE-induced alterations in lung morphometry, lung development markers, and HPA axis were blocked. In the "Pre-EA" group, PNE-induced changes in lung morphometry, GR, and maternal HPA axis improved; lung PPARγ level decreased, but glucocorticoid receptor (GR) and serum corticosterone (Cort) levels increased, in line with the known PNE-induced lung phenotype. In the nicotine exposed group, maternal hypothalamic corticotropin releasing hormone (CRH) level decreased, but pituitary adrenocorticotropic hormone (ACTH) and serum Cort levels increased. In the "Pre- and Post-EA" groups, PNE-induced alterations in lung morphometry, lung development markers, and HPA axis were blocked. In the "Pre-EA" group, PNE-induced changes in lung morphometry, GR, and maternal HPA axis improved; lung PPAR.

CONCLUSIONS

Maternal EA applied to ST36 acupoints during both pre- and postnatal periods preserves offspring lung structure and function despite perinatal exposure to nicotine. EA applied during the "prenatal period" affords only limited benefits, whereas EA applied during the "postnatal period" is ineffective, suggesting that the EA's effects in modulating PNE-induced lung phenotype are limited to specific time-periods during lung development.

Pharmacology for Preterm Labor

Preterm birth occurs with 10% of deliveries and yet accounts for more than 85% of perinatal morbidity and mortality. Management of preterm labor prior to delivery includes a multipronged pharmacologic approach targeting utilization of reproductive hormones for continuation of pregnancy, advancement of fetal lung maturity, and the decrease of uterine contractility (tocolysis). This article will review and compare guidelines on pharmacologic management of preterm labor as recommended by the American College of Obstetricians and Gynecologists and the European Association of Perinatal Medicine. The classifications of drugs discussed include exogenous progesterone, corticosteroids, and tocolytics (β-adrenergic agonists, magnesium sulfate, calcium channel blockers, prostaglandin inhibitors, nitrates, and oxytocin receptor blockers). For each of these drug classes, the following information will be presented: mechanism of action, maternal/fetal side effects, and nursing implications.

Protective effect of electro-acupuncture at maternal different points on perinatal nicotine exposure-induced pulmonary dysplasia in offspring based on HPA axis and signal transduction pathway

Perinatal nicotine exposure can not only lead to lung dysplasia in offspring, but also cause epigenetic changes and induce transgenerational asthma. Previous studies have shown that electro-acupuncture (EA) applied to "Zusanli" (ST 36) can improve the lung morphology and correct abnormal expression of lung development-related protein in perinatal nicotine exposure offspring. However, it is still unclear whether ST 36 has a specific therapeutic effect and how maternal acupuncture can protect the offspring from pulmonary dysplasia. In this study, we compared the different effect of ST 36 and "Fenglong" (ST 40), which belong to the same meridian, in terms of lung pulmonary function and morphology, PPARγ, β-catenin, GR levels in the lung tissues and CORT in the serum of perinatal nicotine exposure offspring, and explored the mechanism of acupuncture based on the maternal hypothalamus-pituitary-adrenal (HPA) axis. It is shown that EA applied to ST 36 could restore the normal function of maternal HPA axis and alleviate maternal glucocorticoid overexposure in offspring, thereby it can up-regulate the PTHrP/PPARγ and down-regulate the Wnt/β-catenin signaling pathways, and protects perinatal nicotine exposure-induced pulmonary dysplasia in offspring. Its effect is better than that of ST 40. These results are of great significance in preventing perinatal nicotine exposure-induced pulmonary dysplasia in offspring.

Evolving neonatal steroid prescription habits and patient outcomes

AIM

Indications for post-natal steroids among preterm infants are evolving. The objective of this study was to compare steroid use in 2 cohorts 5 years apart and to document the short- and long-term outcomes of our most recent cohort.

METHODS

Retrospective chart review of infants born under 28 weeks of gestational age for two cohorts (January 2002-August 2003 and July 2008-March 2010).

RESULTS

Two hundred and fourteen infants were included. More infants received steroids in the later cohort (20% vs 35%, p = 0.021) but survival rates did not improve. There was a shift towards hydrocortisone use (<7% vs 76%) and pulmonary indications (36% vs 61% of courses; p = 0.021). Patients died later (8 days vs 30 days; p = 0.02), with a strong correlation between time of death and total dose of steroids (r = 0.91; p = 0.01). Neurodevelopmental outcomes for patients who received steroids for pulmonary indications were inferior to those for the rest of the cohort (severe adverse outcome 26% vs 4.8%, p = 0.03).

CONCLUSION

The improvement in short-term respiratory status of ill preterm patients was offset by a disturbing increase in age at death and no improvement in survival rates.

Glucocorticoid exposure and tissue gene expression of 11beta HSD-1, 11beta HSD-2, and glucocorticoid receptor in a porcine model of differential fetal growth

Glucocorticoids play a critical role in fetal development, but inappropriate exposure is associated with reduced fetal growth. We investigated cortisol exposure and supply in a porcine model of differential fetal growth. This model compares the smallest fetus of a litter with an average-sized sibling at three stages of gestation. At day 45, small fetuses had reduced plasma cortisol (16.8 +/- 3.4 ng/ml) relative to average fetuses (34.4 +/- 3.4 ng/ml, P < 0.001). At day 65 levels had reduced in small and average fetuses to similar concentrations (5.7 +/- 1.0 vs 4.8 +/- 0.5 ng/ml, P = 0.128). By day 100, elevated levels were found in small fetuses (10.7 +/- 1.5 vs 7.6 +/- 0.7 ng/ml, P < 0.001). Maternal plasma cortisol was unchanged over gestation (day 45, 56.7 +/- 21.6 ng/ml; day 65, 57.8 +/- 14.4 ng/ml; day 100, 55.7 +/- 6.5 ng/ml). We examined the cause of altered cortisol by investigating the fetal hypothalamic-pituitary-adrenal axis through the measurement of adrenocorticotropic hormone and assessing exposure to maternal cortisol by quantifying placental 11beta-hydroxysteroid dehydrogenase-isoform 2 (11beta HSD-2) gene expression. These data suggest that altered cortisol supply was of fetal origin. We examined organ glucocorticoid (GC) metabolism by the measurement of GC receptor (GR) and 11beta-hydroxysteroid dehydrogenase-isoform 1 (11beta HSD-1) gene expression. We found that fetal organs have different temporal patterns of 11beta HSD-1 and GR expression, with the liver particularly sensitive to cortisol in late gestation. This study examines GC exposure in naturally occurring differential growth and simultaneously explores tissue GC sensitivity and handling, at three key stages of gestation.

Antenatal steroids and risk of bronchopulmonary dysplasia: a lack of effect or a case of over-adjustment?

Although antenatal steroids reduce risk factors for bronchopulmonary dysplasia (BPD) in preterm infants, their effect on BPD is conflicting. We hypothesised that the lack of protective effect found in some studies could derive from over-adjustment during analysis, caused by controlling for factors intermediate in the causal pathway between treatment and outcome. We prospectively studied a cohort of infants 23-32 weeks gestation <1500 g, admitted to 10 tertiary-level neonatal units in Lombardy (Italy) in 1999-2002; 1118 neonates out of 1314 survived to 36 weeks; 15.9% developed BPD (oxygen requirement at 36 weeks); 82% were treated with steroids. In univariable analysis, steroids were not significantly protective against BPD; some intermediate factors (mechanical ventilation, greater severity of illness as measured by Clinical Risk Index for Babies score, patent ductus arteriosus) were significantly positively associated with (i.e. were risk factors for) BPD (OR = 11.0, 1.55, 4.42, respectively, all P < 0.001), and negatively associated with (i.e. prevented by) steroids (OR = 0.58, 0.92, and 0.58, respectively, all P < 0.01). In multiple logistic regression models using propensity scores, without the above-mentioned intermediate risk factors, steroid-treated infants had a lower risk of BPD (OR 0.59 [95% CI 0.36, 0.97], P = 0.036); male sex (OR = 2.08), late-onset sepsis (OR = 4.26), and birthweight (OR = 0.63 for 100 g increase) were also associated with BPD, all P < 0.001. When intermediate risk factors for BPD were also added to the model, the effect of steroids disappeared; ventilation (OR = 3.03), increased illness severity (OR = 1.11), and patent ductus arteriosus (OR = 1.90) were significant risk factors. This study suggests that including variables that are potential mediators in the causal chain can obscure the ability to detect a protective effect of treatment. We observed such a phenomenon in our analyses of the relationship between antenatal steroids and BPD, suggesting that steroid effect is partly mediated through a reduction in the classical risk factors.

Retinoic acid combined with vitamin A synergizes to increase retinyl ester storage in the lungs of newborn and dexamethasone-treated neonatal rats

BACKGROUND

Retinyl esters (REs), the major storage form of vitamin A (retinol), provide substrates for the production of bioactive retinoids, including retinoic acid (RA), which are known to promote lung development and maturation. We previously showed that the nutrient-metabolite combination VARA (molar ratio 10 vitamin A to 1 RA), synergistically increased REs in the lungs of 1-week-old rats, compared to vitamin A or RA alone.

OBJECTIVES

To test the hypotheses, first, that VARA is more effective in increasing lung RE than is vitamin A in newborn rats prior to alveolarization, and, second, that the effect of VARA is maintained during concurrent treatment with the glucocorticoid, dexamethasone (Dex).

METHODS

Newborn rats were treated with VARA, vitamin A alone, or oil (C) on postnatal days (P) 1-3, and RE in the lungs was quantified on P4, and again on P8 to assess retention. Additionally, neonatal rats were treated on P5-7 with VARA with and without Dex, and the lung and liver REs were quantified on P8.

RESULTS AND CONCLUSIONS

Lung RE was nearly 8-fold higher in VARA compared to vitamin A-treated rats on P4 (p < 0.01) and 2.5-fold higher on P8. In neonates co-treated with Dex and VARA on P5-7, the elevation in lung RE on P8 by VARA was not antagonized by Dex, although Dex reduced growth. Lung morphology and development were not significantly altered. The VARA combination may significantly increase lung RE content even during concurrent Dex therapy. Because lung retinoids are important for lung maturation and repair, increasing lung RE may possibly have clinical benefit.

A rat model for arrest of alveolarization induced by antenatal endotoxin administration

A possible association between intrauterine inflammation and impairments of lung development has been suggested. The purpose of this study is to determine the influence of a potent proinflammatory agent, intra-amniotic lipopolysaccharide (LPS), on lung development. At 21 d gestation, an intra-amniotic injection of 1 microg LPS was administered to two subgroups of WKAH rats. One subgroup received only LPS and the other received LPS plus a fetal intraperitoneal dose of 0.25 microg granulocyte-colony stimulating factor (hrG-CSF) to produce peripheral blood neutrophilia. A third subgroup received hrG-CSF only, and a control group received maternal intraamniotic and fetal intraperitoneal normal saline. All pups were delivered by cesarean section at 22 d (term, 22.5 d) and maintained under identical conditions. Left upper lungs were obtained for morphometric analysis at 1, 3, 7, 14, 21, 45, and 60 d of age. Morphometric analysis indicated that changes in alveolar surface density (Sv), average alveolar radius (r), and numerical density of alveoli (nv) all showed that there were fewer and larger alveoli in rat lungs that had been exposed to LPS, but not to hrG-CSF alone or saline. LPS-exposed alveoli showed fewer secondary septa, suggesting an arrest of alveolarization. No destructive changes were observed in any alveoli. We concluded that these changes could be caused purely by intra-amniotic LPS. These abnormalities closely mimic those of new bronchopulmonary dysplasia. The LPS damage model may be applicable to further studies of the pathophysiology of new BPD.

The long-term effects of perinatal glucocorticoid exposure on the host defence system of the respiratory tract

Glucocorticoids are used to mature the fetal lung at times of threatened premature delivery. These drugs modify leukocyte profiles when administered in adulthood, but their effects on the mature host defence system following administration during the perinatal period are incompletely understood. In this study, the long-term effects of perinatal dexamethasone exposure on rodent host defence cells in the pulmonary airspaces, the perivascular compartment of the lung, and the blood were investigated. Rats were treated prenatally (gestational days 16-19) or neonatally (postnatal days 1-7) by inclusion of dexamethasone in the mothers' drinking water (1 microg/ml). The pups were then allowed to develop to adulthood (P60-80), at which time respiratory tissues were collected for light and electron microscopy and bronchoalveolar lavage (BAL), and blood for cell count and fluorescent activated cell-sorting (FACS) analysis. Prenatal treatment had no effect on any parameter examined. Following neonatal dexamethasone exposure, light microscopy of the lung tissue revealed a significant reduction in the number of cells in the perivascular space in both the central and the peripheral regions of the adult lung, but no differences in the number of cells in the airspaces. Neonatal dexamethasone exposure was also characterized by a significant reduction in the total number of white cells in the peripheral blood in adulthood and in particular, the number of lymphocytes relative to neutrophils was significantly reduced at maturity in these animals. The results show that neonatal, but not prenatal, dexamethasone exposure significantly alters the distribution of host defence cells in the blood and lung at maturity compared with control animals. The early neonatal period is characterized by the stress hyporesponsive period in the rat, when endogenous glucocorticoid levels are very low. Therefore, exogenous glucocorticoids administered during this time are likely to have marked "programming" effects on glucocorticoid-sensitive tissues.

Asthma research: the real action is in children

Many adult diseases have their roots in infancy or even prenatally. If events that initiate these diseases, as opposed to those that propagate the disease state, are to be understood, then the difficult area of how ethically to research problems in infancy must be tackled. Furthermore, the predisposition to archetypally 'pure' adult problems such as chronic obstructive pulmonary disease, may lie antenatally, the effects being masked until the lung starts to age. An additional factor is that the success of paediatricians, for example in ensuring the survival of extremely premature, low birth weight infants leads to adult survivors with potentially a whole new morbidity. The first prerequisite to making progress is a sound understanding of the development of the normal lung and how adverse environmental and genetic influences, such as exposure to environmental tobacco smoke and maternal atopy, respectively, may affect growth. This paper focuses on three key areas: the implications of different pre-school wheezing phenotypes for adult disease; the importance of very early life events in cystic fibrosis; and the long term consequences of chronic lung disease of prematurity. Finally, the ethical principles that must underpin future research in pre-school children is discussed, as well as the means we might use to further our understanding of the relevant early disease processes.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Dexamethasone-Induced Prenatal Alveolar Wall Thinning Is Associated with a Decrease in EIIIA+ Fibronectin Isoform in the Fetal Rat Lung

BACKGROUND

Glucocorticoid hormones play an important role in architectural and biochemical lung maturation. Although much of the molecular mechanism of their action in the lung is not fully understood, glucocorticoids directly or indirectly regulate lung maturation. Indirect effects of glucocorticoids may involve the modulation of cell-cell or cell-matrix interactions. Fibronectin (FN) is the major constituent of the pulmonary extracellular matrix and exists in multiple isoforms arising from alternative RNA splicing. EIIIA is the major alternatively spliced segment, and its expression is regulated in a spatiotemporal and oncodevelopmental manner.

OBJECTIVES

The present study focuses on the regulation of EIIIA-containing FN isoforms (referred to as EIIIA+ FN) by glucocorticoids in the developing lung.

METHODS

Dexamethasone (DEX) or saline was injected daily into pregnant rats from day 15 of gestation (term = day 22) until 24 h before sacrifice. The expression of EIIIA+ FN and proliferating cell nuclear antigen (PCNA), a biochemical marker for cell proliferation, was investigated in the fetal rat lung.

RESULTS

At day 20 of gestation (the canalicular stage), the DEX-treated lung showed a significant decrease in weight and saccular septal wall thickness, while the messenger RNA expression of the surfactant protein SP-B was increased in the DEX-treated lung, as compared with the control lung. The expression of EIIIA+ FN and PCNA around the distal airspaces was less extensive in the DEX-treated lung than in the control lung at day 20 of gestation.

CONCLUSIONS

Given the finding in vitro that EIIIA+ FN regulated the cell cycle, our results suggest that the change of EIIIA+ FN expression in the DEX-treated lung affected pulmonary cell proliferation.

Effects of maternal undernutrition during late gestation on the lung surfactant system and morphometry in rats

Intrauterine growth restriction (IUGR) is associated with reduced lung function during infancy and throughout adulthood. We investigated the effects of maternal undernutrition (50% rations of the control food intake) during the last week of gestation on the pulmonary surfactant system and lung morphometry in postnatal rats. IUGR rats exhibited a significantly lower body weight, lower lung weight, lower lung/body weight ratio, lower lung volume, and lower lung volume/body weight ratio on some postnatal days. IUGR rats had a significantly lower lung saturated phosphatidylcholine and lower plasma corticosterone levels on postnatal d 1 only, and values were comparable between control and IUGR rats in the ensuing weeks. Lung surfactant protein (SP)-A, SP-B, SP-C, and SP-D mRNA expressions were similar between control and IUGR rats. Volume fractions of the alveolar airspace were significantly lower in IUGR rats on postnatal d 7, 14, and 42. Alveolar surface areas were significantly lower in IUGR rats during the study period. The alveolar surface area/body weight ratio reached a peak on postnatal d 7, and values were significantly lower in IUGR rats on postnatal d 1, 14, 28, and 42. We conclude that maternal undernutrition during late gestation decreases lung surfactant lipid levels in the immediate postnatal period and alters the development of lung structure during the postnatal period. Alteration of lung surfactant and structure may be important in the pathogenesis of impaired pulmonary function in IUGR infants and children.

Early postnatal dexamethasone influences matrix metalloproteinase-2 and -9, and their tissue inhibitors in the developing rat lung

In order to test the hypothesis that early postnatal exposure to dexamethasone (Dex) influences matrix metalloproteinases (MMP)-2 and -9, as well as their tissue inhibitors (TIMP-1 and -2) in the developing rat lung, newborn rats (3 litters/group) were treated with low Dex (0.1 mg/kg/day, IM), high Dex (0.5 mg/kg/day), or equivalent volumes of saline at 5 days postnatal age (P5), P6, and P7. Lung weight and lung MMP and TIMP levels were determined at sacrifice (7 days postinjection, P14; at weaning, P21; and at adolescence, P45, n = 10/group and time). Dex did not adversely affect lung weight or lung MMP-2 levels, which peaked in all groups at P21 and then fell by P45. In contrast, Dex decreased TIMP-2 at all time intervals, but achieved statistical significance only at P45. An imbalance in MMP-2/TIMP-2 ratio was noted at P21, with elevations occurring in the low and high Dex-treated groups. Lung MMP-9 levels remained comparable with controls during low Dex treatment. However, high Dex exposure resulted in elevated lung MMP-9 levels at P21 and P45. Lung TIMP-1 levels increased only with high Dex exposure at P14 and P21, whereas the lung MMP-9/TIMP-1 ratio was elevated at P21 in the high Dex group, and at P45 in both Dex-treated groups. These data provide evidence that early postnatal dexamethasone results in an imbalance between gelatinase-A and -B, and their tissue inhibitors in the developing rat lung. These changes may be responsible, in part, for some of the known maturational effects of steroids on lung structure in the newborn.

Human SP-A 3'-UTR variants mediate differential gene expression in basal levels and in response to dexamethasone

Human surfactant protein A (SP-A) is encoded by two genes (SP-A1, SP-A2), and each is identified with several alleles. SP-A is involved in normal lung function, innate immunity, inflammatory processes, and is regulated by glucocorticoids. We investigated the role of 3'-untranslated region (UTR) of 10 SP-A variants on gene expression using transient transfection of 3'-UTR constructs in the human lung adenocarcinoma cell line NCI-H441. We found: 1) both basal mRNA and protein levels of the reporter gene of SP-A 3'-UTR constructs are significantly (P < 0.01) reduced compared with controls (vector pGL3 and surfactant protein B pGL3) and that differences exist among alleles; and 2) after dexamethasone (Dex) treatment (100 nM for 16 h), mRNA was reduced (31-51%). Seven alleles showed a significant decrease (P < 0.05) in mRNA, and three did not. Reporter activity was also decreased, from 17% (1A(1)) to 38% (1A), with six alleles showing a significant decrease. The data indicate that the 3'-UTR of SP-As play a differential role in SP-A basal expression and in response to Dex. Therefore, a careful consideration of individual use of steroid treatment may be considered.

A placebo-controlled comparison of effects of repetitive doses of betamethasone and dexamethasone on lung maturation and lung, liver, and body weights of mouse pups

The aim of this study was to compare in vivo effects of single and repetitive doses of betamethasone (BETA) and dexamethasone (DEX) administered to pregnant mice on lung maturation and lung, liver, and body weights (LLBW) of their pups. One hundred and eighty gravid Swiss albino mice were randomly assigned to 1 of 6 groups (n = 30) and administered either BETA, DEX, or saline as a single dose at 14 d gestation or repetitive doses twice daily at 14 and 15 d gestation. All the study groups were then divided into three sets (n = 10). The mice in the second sets were redivided into three subsets randomly (including four, three, and three mice). All gestations in the first sets were terminated at 16.5 d gestation to observe the neonatal breathing pattern (scale to 0-5; 5 is unlabored breathing) of male and female pups whereas other sets had normal delivery. The pups in first, second, and third sets were killed for evaluation in the first set after the evaluation of breathing pattern, in the subsets of second set on postnatal d 1, 3, and 5, and in the third set on postnatal d 90. We recorded maternal body weights at 0 and 16.5 d gestation, and LLBW, the lung/body weight ratio of pups, sex, and the amount of live and dead births per litter. Pups exposed to BETA and DEX had significantly lower maternal weight compared with the saline groups. The death litter size was significantly higher in pups exposed to repetitive doses of DEX than the other treatments. Sex had no significant effect on breathing score and LLBW. Pups exposed to repetitive doses of BETA and DEX presented a higher breathing score than the other groups. The breathing score was significantly higher with BETA than DEX after their repetitive use. The LLBW were significantly less in the treatment groups, especially in the group exposed to repetitive doses of DEX. In conclusion, repetitive doses of BETA and DEX lead to increased fetal lung maturation, but this may be at the expense of fetal and neonatal growth. DEX is less potent in accelerating lung maturation than BETA but it causes more reduction in fetal and neonatal growth.

Early postnatal dexamethasone decreases hepatocyte growth factor in tracheal aspirate fluid from premature infants

OBJECTIVE

To evaluate in preterm infants the effect of dexamethasone on hepatocyte growth factor (HGF), an epithelial cell mitogen, and on vascular endothelial growth factor (VEGF), an endothelial cell mitogen, in tracheal aspirate fluid (TAF).

METHODS

Thirty preterm infants (birth weight: 1000-1500 g) with respiratory distress syndrome were randomized to receive dexamethasone or to serve as control subjects. Dexamethasone was started at the age of 12 to 24 hours at a dose of 0.5 mg/kg/d for 2 days and 0.25 mg/kg/d for the subsequent 2 days. HGF and VEGF levels were examined from TAF samples during the first postnatal week. For eliminating the effect of dilution, the concentration of the secretory component of immunoglobulin A was determined. Student t test, 1-way analysis of variance, chi2, and simple regression analysis were used for statistical analysis.

RESULTS

Mean HGF concentrations were similar in the dexamethasone and control groups on days 1 to 2, but the dexamethasone group had a lower mean HGF concentration on days 3 to 4 and 5 to 7. In contrast, no differences existed in mean VEGF levels between the dexamethasone and control groups.

CONCLUSIONS

In preterm infants who received early postnatal dexamethasone, reduced levels of HGF were seen in tracheal aspirates. This reduction may participate in the suppressive effects of dexamethasone on lung development.