Dexamethasone selectively regulates the activity of enzymatic markers of cerebral endothelial cell lines

Summary Two endothelial cell lines were derived from grafts of the central nervous system using retrovirus mediated gene transfer to introduce the polyoma middle-T oncogene into fetal rat brain endothelial cells and transplantation of these cells into adult rat brain. In this report, we further characterize these cells and the effect of dexamethasone on the expression of specific enzymatic markers. These cells take up acetylated low density lipoprotein, leucine, and glucose, and express Factor VIII-related antigen, angiotensin converting enzyme, alkaline phosphatase, gamma-glutamyltranspeptidase, and as yet undescribed aminopeptidase A and B-like enzymes. When grown on semi-permeable membranes, these transformed cells do not spontaneously retain small hydrophilic molecules. In culture, one of the lines (EC 193) forms a confluent monolayer of spindle-shaped cells homogenously expressing gamma-glutamyltranspeptidase at a level comparable to primary cells. The other cell line (EC 219) grows as clusters of elongated cells, and gamma-glutamyltranspeptidase activity is expressed mainly in cells forming the clusters. This clustered pattern changes to a confluent one after culture on type-I collagen. Dexamethasone increases angiotensin-converting enzyme activity, and decreases the expression of gamma-glutamyltranspeptidase and aminopeptidase A, whereas the aminopeptidase B activity is little modified. Inhibition of aminopeptidase A activity by amastatin, potentiates angiotensin II effects on DNA synthesis. These results indicate that retrovirally transformed brain endothelial cells are a useful model for studying the blood-brain barrier in vitro and that dexamethasone, an agent with the potential to reduce brain edema, directly affects some blood-brain barrier properties in these endothelial cell lines.     

Developmental Expression of Nicein Adhesion Protein (Laminin-5) Subunits Suggests Multiple Morphogenic Roles

Nicein/kalinin (laminin-5) is a heterotrimeric laminin-like adhesion protein, which is secreted at the basement membrane of subsets of epithelia and is involved in the etiology of junctional epidermolysis bullosa, a severe human blistering disease characterized by disadhesion of epidermis from dermis.

cDNA clones encoding the three chains of mouse nicein and antibodies specific to each polypeptide were used to examine the expression of the protein in the developing mouse embryo from 10.5 day post coitum to 7 days after birth. At various stages of development, co-expression of the three chains of nicein was observed in amnion, skin, and in epithelia of respiratory, urinary and digestive systems. High level expression of nicein was seen in enamel-secreting ameloblasts in developing teeth. Cell-specific distribution of nicein was also detected in other specialized tissues representative of the three primary embryonic germ layers with prominent secretory or protective functions. Differential and focal expression of nicein subunits was observed in the choroid plexus and the floor plate of the neural tube. Messenger for the heavy chain of nicein was detected in the floor plate, where mouse s-laminin messengers were also found. This suggests that nicein genes may play a role in the migration and polarization of motor neurons in the developing spinal cord.     

Cells and prions: A license to replicate

Prion diseases are neurodegenerative, infectious disorders characterized by the aggregation of a misfolded isoform of the cellular prion protein (PrP^C). The infectious agent - termed prion - is mainly composed of misfolded PrP^Sc. In addition to the central nervous system prions can colonize secondary lymphoid organs and inflammatory foci. Follicular dendritic cells are important extraneural sites of prion replication. However, recent data point to a broader range of cell types that can replicate prions. Here, we review the state of the art in regards to peripheral prion replication, neuroinvasion and the determinants of prion replication competence.