Vitamin D Reduces Inflammation-induced Contractility and Remodeling of Asthmatic Human Airway Smooth Muscle.

BACKGROUND: Although multiple clinical studies have found an association between vitamin D (Vit D) deficiency and asthma, a recent clinical study suggested lack of therapeutic effect of Vit D supplementation. Nonetheless, the mechanisms by which Vit D influences airway structure and function in the context of inflammation and asthma remains undefined. In this regard, Vit D effects on airway smooth muscle (ASM) are important, given the role of this cell type in the hypercontractility and remodeling. We assessed the mechanisms by which Vit D modulates the enhancing effects of proinflammatory cytokines tumor necrosis factor-α (TNF-α) and IL-13 on intracellular Ca(2+) ([Ca(2+)]i) levels and remodeling in nonasthmatic versus asthmatic human ASM. METHODS: Human ASM was enzymatically isolated from surgical lung specimens of patients with clinically defined mild to moderate asthma versus no asthma. Cells were treated with 10 ng/ml TNF-α and 50 ng/ml IL-13 in the presence or absence of 100 nM calcitriol. MEASUREMENTS AND MAIN RESULTS: Interestingly, Vit D receptor (VDR) and retinoic X receptor-α levels were maintained, even increased, in subjects with asthma when treated with TNF-α and IL-13. Compared with untreated cells, calcitriol blunted the heightened effect of TNF-α on [Ca(2+)]i response to histamine in ASM. Calcitriol particularly blunted TNF-α and IL-13 effects on collagen and fibronectin deposition, especially in asthmatic ASM. Calcitriol stimulated VDR/retinoic X receptor dimerization and VDR activity even in subjects with asthma and with IL-13, highlighting retained functionality. Expression of Class I histone deacetylases 1-3 (HDAC) and overall HDAC activity were lower in IL-13-exposed ASM, but calcitriol enhanced HDAC expression/activity. CONCLUSIONS: In asthmatic ASM, Vit D functionality is maintained, allowing calcitriol to reduce the procontractile and proremodeling effects of inflammatory cytokines, particularly IL-13, which is relevant to asthma. These findings highlight a potential role for Vit D in asthma pathogenesis, particularly in the context of airway structure and functional changes early in disease.

Soluble guanylate cyclase modulators blunt hyperoxia effects on calcium responses of developing human airway smooth muscle.

Exposure to moderate hyperoxia in prematurity contributes to subsequent airway dysfunction and increases the risk of developing recurrent wheeze and asthma. The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic GMP (cGMP) axis modulates airway tone by regulating airway smooth muscle (ASM) intracellular Ca(2+) ([Ca(2+)]i) and contractility. However, the effects of hyperoxia on this axis in the context of Ca(2+)/contractility are not known. In developing human ASM, we explored the effects of novel drugs that activate sGC independent of NO on alleviating hyperoxia (50% oxygen)-induced enhancement of Ca(2+) responses to bronchoconstrictor agonists. Treatment with BAY 41-2272 (sGC stimulator) and BAY 60-2770 (sGC activator) increased cGMP levels during exposure to 50% O2. Although 50% O2 did not alter sGCα1 or sGCß1 expression, BAY 60-2770 did increase sGCß1 expression. BAY 41-2272 and BAY 60-2770 blunted Ca(2+) responses to histamine in cells exposed to 50% O2. The effects of BAY 41-2272 and BAY 60-2770 were reversed by protein kinase G inhibition. These novel data demonstrate that BAY 41-2272 and BAY 60-2770 stimulate production of cGMP and blunt hyperoxia-induced increases in Ca(2+) responses in developing ASM. Accordingly, sGC stimulators/activators may be a useful therapeutic strategy in improving bronchodilation in preterm infants.

Maternal dietary docosahexaenoic acid supplementation attenuates fetal growth restriction and enhances pulmonary function in a newborn mouse model of perinatal inflammation.

The preterm infant is often exposed to maternal and neonatal inflammatory stimuli and is born with immature lungs, resulting in a need for oxygen therapy. Nutritional intervention with docosahexaenoic acid (DHA; 6.3 g/kg of diet) has been shown to attenuate inflammation in various human diseases. Previous studies demonstrated that maternal DHA supplementation during late gestation and lactation attenuated hyperoxic lung injury in newborn mouse pups. In the present studies, we tested the hypothesis that DHA supplementation to the dam would reduce hyperoxic lung injury and growth deficits in a more severe model of systemic maternal inflammation, including lipopolysaccharide (LPS) and neonatal hyperoxia exposure. On embryonic day 16, dams were placed on DHA (6.3 g DHA/kg diet) or control diets and injected with saline or LPS. Diets were maintained through weaning. At birth, pups were placed in room air or hyperoxia for 14 d. Improvements in birth weight (P < 0.01), alveolarization (P ≤ 0.01), and pulmonary function (P ≤ 0.03) at 2 and 8 wk of age were observed in pups exposed to perinatal inflammation and born to DHA-supplemented dams compared with control diet-exposed pups. These improvements were associated with decreases in tissue macrophage numbers (P < 0.01), monocyte chemoattractant protein-1 expression (P ≤ 0.05), and decreases in soluble receptor for advanced glycation end products concentrations (P < 0.01) at 2 and 8 wk. Furthermore, DHA supplementation attenuated pulmonary fibrosis, which was associated with the reduction of matrix metalloproteinases 2, 3, and 8 (P ≤ 0.03) and collagen mRNA (P ≤ 0.05), and decreased collagen (P < 0.01) and vimentin (P ≤ 0.03) protein concentrations. In a model of severe inflammation, maternal DHA supplementation lessened inflammation and improved lung growth in the offspring. Maternal supplementation with DHA may be a therapeutic strategy to reduce neonatal inflammation.

Maternal docosahexaenoic acid supplementation decreases lung inflammation in hyperoxia-exposed newborn mice.

DHA is a long-chain fatty acid that has potent antiinflammatory properties. Whereas maternal DHA dietary supplementation has been shown to improve cognitive development in infants fed DHA-supplemented milk, the antiinflammatory effects of maternal DHA supplementation on the developing fetus and neonate have not been extensively explored. Pregnant C3H/HeN dams were fed purified control or DHA-supplemented diets (~0.25% of total fat) at embryonic d 16 and consumed these diets throughout the study. At birth, the nursing mouse pups were placed in room air (RA; 21% O(2)) or >95% O(2) (hyperoxia) for up to 7 d. These studies tested the hypothesis that maternal DHA supplementation would decrease inflammation and improve alveolarization in the lungs of newborn mouse pups exposed to hyperoxia. Survival, inflammatory responses, and lung growth were compared among control diet/RA, DHA/RA, control/O(2), and DHA/O(2) pups. There were fewer neutrophils and macrophages in lung tissues from pups nursed by DHA-supplemented dams than in those nursed by dams fed the control diet at 7 d of hyperoxia exposure (P < 0.015). Although differences due to hyperoxia exposure were observed, maternal diet did not affect keratinocyte-derived chemokine, macrophage inflammatory protein-2, IL-1ß, or TNFα mRNA levels in pup tissues. Hyperoxia also induced NF-κB activity, but maternal diet did not affect NF-κB or PPARγ activities. In mice, DHA supplementation decreases leukocyte infiltration in the offspring exposed to hyperoxia, suggesting a potential role for DHA supplementation as a therapy to reduce inflammation in preterm infants.