Ultrastructural heterogeneity of the alveolar macrophages from tobacco smokers with chronic bronchitis.

Alveolar macrophages recovered by bronchoalveolar lavage from 14 heavy smokers with chronic bronchitis were assessed. Ultrastructural examination revealed marked cellular heterogeneity. Three subpopulations of alveolar macrophages were readily identifiable. These have been termed "young," "mature," and "degrading," reflecting their ultrastructural features. In addition, a majority of the cells were found to be positive by TUNEL staining, indicating DNA damage, but a very small percentage tested positive for Caspase-3, suggesting that apoptosis might not account for the DNA damage in at least some of these cells. A small percentage of proliferating cells were noted.

Modification of type I collagenous gels by alveolar epithelial cells.

Contraction of type I collagen gels is an in vitro model of tissue remodeling. In addition to fibroblasts, some epithelial cells can mediate this process. We therefore hypothesized that alveolar epithelial cells might contract extracellular matrices and have the potential to directly participate in the remodeling of the lung after alveolar injury. A549 cells were plated on top of collagen gels, and the gels were floated in culture medium. A549 cells contracted the gels in a time- and cell density-dependent manner. A549 cells, as well as human bronchial epithelial cells (HBEC) and rat alveolar epithelial cells (RalvEC) contracted collagen gels more when they were plated on top of the gel than when they were embedded inside, in contrast to human fetal lung fibroblast (HFL1), which contracted more when cast inside. The amount of hydroxyproline in the collagen gels remained unchanged throughout the contraction. Anti-beta(1) integrin antibody inhibited A549 cell-mediated contraction. Transforming growth factor beta augmented the contraction by A549 cells as well as that by HBEC and HFL1. Prostaglandin E(2) inhibited the contraction by HFL1 but did not affect the contraction by A549 cells, HBEC, or RalvEC. Cytomix (a mixture of tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma) inhibited the contraction by HFL1 but strongly enhanced the contraction by A549 cells. Cytomix also caused a morphologic change of A549 cells from a polygonal to a spindle shape. Immunocytochemistry showed that cytomix induced alpha-tubulin expression in A549 cells, whereas cytokeratin, vimentin, smooth muscle actin, beta(1) integrin, and paxillin expressions were not changed. This study thus demonstrates that alveolar epithelial cells can cause contraction of extracellular matrices and that this process is modulated by exogenous mediators, which also modify the microtubular system. Such an activity might contribute to alveolar remodeling after injury.

Biotransformation and pharmacokinetics of prodrug 9-(beta-D-1,3-dioxolan-4-yl)-2-aminopurine and its antiviral metabolite 9-(beta-D-1,3-dioxolan-4-yl)guanine in mice.

9-(beta-D-1,3-Dioxolan-4-yl)guanine (DXG) exhibits potent antiviral activity against human immunodeficiency virus type 1 (HIV-1) and hepatitis B virus (HBV) in vitro. However, since DXG possesses limited aqueous solubility, a more water soluble prodrug of DXG, 9-(beta-D-1,3-dioxolan-4-yl)-2-aminopurine (APD), was synthesized. The purpose of this study was to characterize the pharmacokinetics of APD and its antiviral metabolite DXG in mice. Female NIH-Swiss mice were administered 100 mg/kg APD intravenously or orally. Serum, brain and liver were collected at selected times following prodrug administration and concentrations of APD and DXG were determined by HPLC. APD was efficiently converted to parent nucleoside DXG following both intravenous and oral administration. Biotransformation of APD to DXG likely occurs in the liver and is mediated by xanthine oxidase. Similar pharmacokinetic profiles for DXG were observed following either route of administration in serum, liver and brain. These results demonstrate that APD appears to be a promising prodrug for the delivery of DXG.