Amrani, Yassine

Introduction: Children with low Vitamin D levels are at increased risk of developing asthma. In the present study, we tested the hypothesis that the Vitamin D receptor (VDR) agonist, calcitriol, will reduce tumor necrosis factor‐α (TNF‐α)‐induced expression of chemokines in human fetal airway smooth muscle cells (fASM). Methods and Results Human fASM cells were dissociated from canalicular stage (18‐22 weeks gestation) lung tissue (de‐identified samples, in vitro use only and considered exempt by Mayo Institutional Review Board). Fetal ASM cells were pre‐treated with vehicle (0.001% DMSO) or 100 nM calcitriol for 1 h, and then exposed to 10 ng/mL TNFα for 6 or 24 h. Expression of CCL5 and CCL11 were measured by quantitative real time PCR and ELISA. Cells were transfected with VDR siRNA. Treatment with TNFα for 6 h increased mRNA expression and secretion of CCL5 and CCL11. While pre‐treatment with calcitriol reduced CCL5 and CCL11 expression in the presence of TNFα. Knockdown of the VDR expression demonstrated that calcitriol's effects are mediated through VDR. Conclusions These novel data demonstrate that calcitriol modulates cytokine enhancement of chemokines in developing ASM. Vitamin D may be a new therapeutic target in reducing inflammation in the immature airway. Supported by NIH F32 HL123075 (Britt), T32 HL105355 (Vogel), and R01s HL088029 and HL056470 (Prakash), and the Mayo Clinic Department of Anesthesiology (Pabelick, Prakash).

Asthma in the pediatric population remains a significant contributor to morbidity and increasing healthcare costs. Vitamin D3 insufficiency and deficiency have been associated with development of asthma. Recent studies in models of adult airway diseases suggest that the bioactive Vitamin D3 metabolite, calcitriol (1,25‐dihydroxyvitamin D3; 1,25(OH)2D3), modulates responses to inflammation; however, this concept has not been explored in developing airways in the context of pediatric asthma. We used human fetal airway smooth muscle (ASM) cells as a model of the early postnatal airway to explore how calcitriol modulates remodeling induced by pro‐inflammatory cytokines. Cells were pre‐treated with calcitriol and then exposed to TNFα or TGFβ for up to 72 h. Matrix metalloproteinase (MMP) activity, production of extracellular matrix (ECM), and cell proliferation were assessed. Calcitriol attenuated TNFα enhancement of MMP‐9 expression and activity. Additionally, calcitriol attenuated TNFα and TGFβ‐induced collagen III expression and deposition, and separately, inhibited proliferation of fetal ASM cells induced by either inflammatory mediator. Analysis of signaling pathways suggested that calcitriol effects in fetal ASM involve ERK signaling, but not other major inflammatory pathways. Overall, our data demonstrate that calcitriol can blunt multiple effects of TNFα and TGFβ in developing airway, and point to a potentially novel approach to alleviating structural changes in inflammatory airway diseases of childhood. J. Cell. Physiol. 230: 1189–1198, 2015. © 2014 Wiley Periodicals, Inc., A Wiley Company

Maintenance of blood oxygen saturation dictates supplemental oxygen administration to premature infants, but hyperoxia predisposes survivors to respiratory diseases such as asthma. Although much research has focused on oxygen effects on alveoli in the setting of bronchopulmonary dysplasia, the mechanisms by which oxygen affects airway structure or function relevant to asthma are still under investigation. We used isolated human fetal airway smooth muscle (fASM) cells from 18–20 postconceptual age lungs (canalicular stage) to examine oxygen effects on intracellular Ca 2+ ([Ca 2+ ] i ) and cellular proliferation. fASM cells expressed substantial smooth muscle actin and myosin and several Ca 2+ regulatory proteins but not fibroblast or epithelial markers, profiles qualitatively comparable to adult human ASM. Fluorescence Ca 2+ imaging showed robust [Ca 2+ ] i responses to 1 μM acetylcholine (ACh) and 10 μM histamine (albeit smaller and slower than adult ASM), partly sensitive to zero extracellular Ca 2+ . Compared with adult, fASM showed greater baseline proliferation. Based on this validation, we assessed fASM responses to 10% hypoxia through 90% hyperoxia and found enhanced proliferation at <60% oxygen but increased apoptosis at >60%, effects accompanied by appropriate changes in proliferative vs. apoptotic markers and enhanced mitochondrial fission at >60% oxygen. [Ca 2+ ] i responses to ACh were enhanced for <60% but blunted at >60% oxygen. These results suggest that hyperoxia has dose-dependent effects on structure and function of developing ASM, which could have consequences for airway diseases of childhood. Thus detrimental effects on ASM should be an additional consideration in assessing risks of supplemental oxygen in prematurity.

Abstract CD38/cyclic adenosine diphosphate ribose (cADPR) signaling plays an important role in the regulation of intracellular calcium responses to agonists in a variety of cells, including airway smooth muscle (ASM) cells. The present study was aimed at determining the effect of interleukin (IL)-13, a cytokine implicated in the pathogenesis of asthma, on CD38/cADPR signaling and to ascertain the contribution of CD38/cADPR signaling to IL-13–induced airway hyperresponsiveness. Human ASM cells maintained in culture were exposed to 50 ng/ml IL-13 for 22 h and levels of CD38 expression and intracellular calcium responses to agonists were measured. Treatment of human ASM cells with IL-13 resulted in increased CD38 expression as determined by real-time polymerase chain reaction, Western blot analysis, and indirect immunofluorescence. Increased CD38 expression was reflected as increased ADP-ribosyl cyclase activity in the ASM cell membranes. The net intracellular calcium responses to bradykinin, thrombin, and histamine were significantly (P ≤ 0.05) higher in cells treated with IL-13 compared with controls. Furthermore, 8-bromo-cADPR, a cADPR antagonist, attenuated IL-13–induced augmented intracellular calcium responses to agonists in human ASM cells. These findings indicate that the CD38/cADPR–dependent pathway has a major role in IL-13–induced modulation of calcium signaling in human ASM.