Robert Castro, M.D. 
Exogenous pulmonary surfactant, used for the treatment of respiratory distress syndrome in preterm infants, influences the function of inflammatory cells. Production and release of proinflammatory mediators in alveolar macrophages (AMs) are dependent on the activation of a number of signaling pathways including changes in cytosolic free Ca2+ (Δ[Ca2+]i). We have examined the effects of surfactant preparations on Ca2+ influx in the immortalized rat AM cell line, NR8383. The particulate (1-3)-b-glucan receptor agonist, zymosan (200 mg/ml), induced a gradual increase in [Ca2+]i in fura-2 loaded AMs. In the presence of exogenous surfactants standardized to similar phospholipid concentrations (0.25 mg/ml), the initial zymosan-induced Δ[Ca2+]i was significantly reduced by beractant, colfosceril, calfactant, and the primary surfactant phospholipid, dipalmitoyl phosphatidylcholine. Direct activation of PKC induced a Δ[Ca2+]i which was inhibited by 56% with beractant. All surfactants also inhibited MAPK activation with C6-ceramide. Exposure to both beractant and Ca2+ channel blocker SKF 96365 completely abolished the zymosan-stimulated Δ[Ca2+]i. These results suggest that exogenous surfactant inhibit Ca2+ influx in AMs probably through an interaction with downstream elements or Ca2+ channels.
Shamim B. Mustafa, Ph.D 
The research in my lab focuses on regulation of the amiloride-sensitive epithelial sodium channel (ENaC) by glucocorticoids and catecholamines. ENaC, consisting of three subunits (α, β, and γ) are predominantly expressed in the distal lung, salivary glands, kidney, and colon. Fluid clearance in the lung is mediated by Na+ transport via ENaC; the α-subunit being essential for Na+ transport. I am also investigating the developmental regulation of ENaC by glucocorticoids in the preterm fetal rabbit lung. During injurious scenarios distal lung alveolar epithelial cells are particularly susceptible to mechanical stretching; using a mouse lung epithelial cell line (MLE12) I am investigating the effects of stretch on α-ENaC expression, localization and signaling pathways.
Margarita M. Vasquez, M.D.
Dr. Vasquez has investigated potential signal transduction pathways regulating α-Epithelial Sodium Channel (ENaC) and serum and glucocorticoid-induced protein kinase 1 (sgk1) expression induced by cAMP in epithelial cells derived from the rat submandibular gland (SMG-C6) cell line. These cells when cultured in media in the absence of hydrocortisone exhibit minimal amiloride-sensitive Na+ transport properties and negligible expression of the a-subunit of ENaC. In addition, she has attempted to describe a potential relationship between the induction of sgk1 and expression of α-ENaC in this cell model. Her initial studies characterized the upstream pathways that are activated following stimulation with DbcAMP, including the induction of sgk1 followed by α-ENaC expression and function. These results provide additional evidence for the regulatory effects of sgk1 on α-ENaC expression. Since activation of Na+ transport properties at the time of birth is vital for fluid lung absorption, Dr. Vasquez has focused on characterizing the signaling elements regulating these mechanisms.
Fellows' Research Profiles
Timothy A. Biela, M.D.
Dr. Tim Biela is working project is to characterize the response to dexamethasone or synthetic glucocorticoids selective for transactivation on DNA-protein binding, mRNA expression and cell death. Although treatment with postnatal dexamethasone during the perinatal period does improve lung function, this therapeutic regime is felt to exert deleterious side effects on long-term brain development and function. Therefore, postnatal use in preterm infants has been now limited or discouraged. To this end Timothy has compared the effect of novel synthetic glucocorticoids which selectively initiate gene transcription (transactivation) with dexamethasone (increases and decreases gene transcription and transrepression) on the expression of epithelial sodium channels (ENaC) and glucocorticoid receptors in murine lung epithelial cells. ENaC activity, regulated by glucocorticoids, is extremely important for the clearance of lung fluid at the time of birth.
Christine E. Bishop, M.D.
Dr. Chris Bishop is examining the effects of cytokine and glucocorticoids on the MLE-12 cell glucocorticoid receptor and alpha-ENAC. She also submitted a grant utilizing a novel Multiplex Flow Cytometry system to characterize a panel of 21 cytokines and chemokines from micro tracheal aspirate samples obtained from ventilated preterm baboons cared for at the NICU Southwest Foundation of Biomedical Research in San Antonio, Texas. Levels will be correlated with the clinical courses of the preterm animals and clearance of Ureaplasma urealyticum (Uu) infections. The results from this study will elucidate the role that Uu colonization and infection may have on the pathogenesis of chronic lung disease in preterm infants. Dr. Bishop is also working on a clinical project involving hospital modeling of infant sleeping position and parents' perceptions of appropriate infant sleeping positions.
