Farver, Carol

Abstract Airway smooth muscle (ASM) regulation of airway structure and contractility is critical in fetal/neonatal physiology in health and disease. Fetal lungs experience higher Ca 2+ environment that may impact extracellular Ca 2+ ([Ca 2+ ] o ) sensing receptor (CaSR). Well‐known in the parathyroid gland, CaSR is also expressed in late embryonic lung mesenchyme. Using cells from 18‐22 week human fetal lungs, we tested the hypothesis that CaSR regulates intracellular Ca 2+ ([Ca 2+ ] i ) in fetal ASM (fASM). Compared with adult ASM, CaSR expression was higher in fASM, while fluorescence Ca 2+ imaging showed that [Ca 2+ ] i was more sensitive to altered [Ca 2+ ] o . The fASM [Ca 2+ ] i responses to histamine were also more sensitive to [Ca 2+ ] o (0–2 mM) compared with an adult, enhanced by calcimimetic R568 but blunted by calcilytic NPS2143. [Ca 2+ ] i was enhanced by endogenous CaSR agonist spermine (again higher sensitivity compared with adult). Inhibition of phospholipase C (U73122; siRNA) or inositol 1,4,5‐triphosphate receptor (Xestospongin C) blunted [Ca 2+ ] o sensitivity and R568 effects. NPS2143 potentiated U73122 effects. Store‐operated Ca 2+ entry was potentiated by R568. Traction force microscopy showed responsiveness of fASM cellular contractility to [Ca 2+ ] o and NPS2143. Separately, fASM proliferation showed sensitivity to [Ca 2+ ] o and NPS2143. These results demonstrate functional CaSR in developing ASM that modulates airway contractility and proliferation.

Wheezing is a major long-term respiratory morbidity in preterm infants with and without bronchopulmonary dysplasia. We hypothesized that mild vs. severe hyperoxic exposure in neonatal mice differentially affects airway smooth muscle hypertrophy and resultant airway reactivity. Newborn mice were exposed to 7 days of mild (40% oxygen) or severe (70% oxygen) hyperoxia vs. room air controls. Respiratory system resistance (Rrs), compliance (Crs), and airway reactivity were measured 14 days after oxygen exposure ended under ketamine/xylazine anesthesia. Baseline Rrs increased and Crs decreased in both treatment groups. Methacholine challenge dose dependently increased Rrs and decreased Crs in 40% oxygen-exposed mice, whereas Rrs and Crs responses were similar between 70% oxygen-exposed and normoxic controls. Airway smooth muscle thickness was increased in 40%- but not 70%-exposed mice, whereas collagen increased and both alveolar number and radial alveolar counts decreased after 40% and 70% oxygen. These data indicate that severity of hyperoxia may differentially affect structural and functional changes in the developing mouse airway that contribute to longer-term hyperreactivity. These findings may be important to our understanding of the complex role of neonatal supplemental oxygen therapy in postnatal development of airway responsiveness.

Abstract A variety of melanoma antigen A (MAGE-A) genes are commonly detected in non–small cell lung cancers. Their biological function is not well characterized but may involve the regulation of apoptosis and cell cycle progression. We hypothesized that MAGE-A4 is involved in the regulation of apoptosis. To investigate this, expression of MAGE-A was evaluated. MAGE-A4 was expressed in 48% of non–small cell lung carcinomas. Ninety percent of lung carcinomas expressing MAGE-A4 were classified as squamous cell carcinomas and 10% were adenocarcinomas. Tumor-free surrounding lung tissue was negative for MAGE-A4. A molecular clone of MAGE-A4 derived from human lung cancer was stably expressed in human embryonic kidney cells (293 cells) to evaluate effects on cell death. Overexpression of MAGE-A4 increased apoptosis as measured by the apoptotic index (P < 0.0001) and caspase-3 activity (P < 0.002). Exposure to 25 μmol/L etoposide, a chemotherapeutic agent, increased the apoptotic effect (P < 0.0001). Furthermore, we show that MAGE-A4 silencing using a small interfering RNA approach results in decreased caspase-3 activity in the squamous cell lung cancer cell line H1703 by 58% (P = 0.0027) and by 24% (P = 0.028) in 293/MAGE-A4 cells. These findings suggest that MAGE-A4 expression may promote tumor cell death, sensitize malignancies to apoptotic stimuli, such as chemotherapeutic agents, and therefore may represent a tumor suppressor protein. (Cancer Res 2006; 66(9): 4693-700)