Characterization of a novel brain-derived microglial cell line isolated from neonatal rat brain

We observed highly aggressively proliferating immortalized (HAPI) cells gro wing in cultures that had been enriched for microglia. The cells were initi ally obtained from mixed glial cultures prepared from 3-day-old rat brains. HAPI cells are typically round with few or no processes when cultured in 1 0% serum containing medium. As the percentage of serum in the medium is dec reased, the HAPI cells have more processes. HAPI cells stain for the isolec tin B4, OX-42, and GLUT5, which are markers for microglial cells, but the c ells do not immunolabel with A2B5, a marker of cells in the oligodendroglia l cell lineage, or with the astrocyte-specific marker, glial fibrillary aci idic protein (GFAP). In addition, HAPI cells are capable of phagocytosis. W e conclude that HAPI cells are of microglia/macrophage lineage. Exposing HA PI cells to lipopolysaccharide (LPS) induces the mRNAs for tumor necrosis f actor-alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS). LPS exp osure also induces secretion of TNF-alpha and production of nitric oxide (N O) in HAPI cells. Because activation of microglia is associated with an inc rease in iron accumulation and ferritin expression, we tested the hypothesi s that iron status affects the production of TNF-alpha and NO. Our studies demonstrate that both iron chelation and iron loading diminished the LPS-in duced effect of TNF-alpha and NO. The results of this study indicate that H API cells possess the characteristics of microglia/brain macrophages, provi ding an alternative cell culture model for the study of microglia. In addit ion, we demonstrate that the activation of microglial cells could be modifi ed by iron. GLIA 35:53-62, 2001. (C) 2001 Wiley-Liss, Inc.