E. Claudio et al., ACTIVATION OF MURINE MACROPHAGES BY SILICA PARTICLES IN-VITRO IS A PROCESS INDEPENDENT OF SILICA-INDUCED CELL-DEATH, American journal of respiratory cell and molecular biology, 13(5), 1995, pp. 547-554
We have tested the murine macrophagic cell line RAW 264.7 for its abil
ity to undergo activation after exposure to silica particles in vitro.
When exposed to silica under controlled conditions (each cell having
access to about 10 silica particles), RAW 264.7 cells were able to pha
gocytose the particles. Concomitantly, there was a significant increas
e in tumor necrosis factor alpha (TNF alpha) mRNA accumulation and TNF
alpha secretion. The level of TNF alpha production by RAW 264.7 cells
increased up to 5-fold 48 h after phagocytosis of silica particles wi
th very low cell toxicity. The phagocytic stimulus did not induce nitr
ic oxide production. When cells were exposed to a higher number of sil
ica particles, cell activation was attained at shorter times but a sub
stantial number of cells were damaged at 48 h. Interferon gamma (IFN g
amma) alone induced an increased production of TNF alpha in RAW 264.7
cells, not further augmented by a subsequent exposure to silica of the
IFN gamma-treated cells. Other macrophage-like cell lines as well as
primary peritoneal macrophages were able to phagocytose silica particl
es but showed different abilities to produce and secrete TNF alpha onc
e phagocytosis took place. Therefore, RAW 264.7 cells were chosen as a
model for in vitro studies of the long-term response of macrophages t
o silica.