Ba. Hart et al., INCREASED OXIDANT RESISTANCE OF ALVEOLAR MACROPHAGES ISOLATED FROM RATS REPEATEDLY EXPOSED TO CADMIUM AEROSOLS, Toxicology, 107(3), 1996, pp. 163-175
This study investigated potential mechanisms of oxidant resistance in
alveolar macrophages (AM) isolated from Lewis rats exposed repeatedly
to cadmium aerosols. Macrophages from Cd-adapted animals exhibited sig
nificantly greater resistance to oxidant-induced cytotoxicity than con
trol cells when challenged with hydrogen peroxide in vitro. Elevations
in glutathione peroxidase and glutathione reductase activities were a
ssociated with increased oxidant tolerance but catalase activity was u
nchanged. Metallothionein (MT) expression (protein and mRNA) was drama
tically up-regulated in response to in vivo Cd exposure. A study using
immunocytochemistry and in situ hybridization techniques revealed sig
nificant heterogeneity in the expression of metallothionein by AMs. Th
e percentage of AMs positive for MT (protein and mRNA) and the degree
of MT expression within individual cells increased in response to addi
tional Cd exposures. A putative state of activation was suggested by t
he differences in size and number of inclusion bodies in macrophages f
rom Cd-adapted animals and by secretion of a cytokine with interleukin
-1-like characteristics. In summary, AMs from Cd-adapted animals are d
istinguished from control cells with respect to: (1) increased oxidant
resistance, (2) secretion of cytokines, (3) elevations in enzymes ass
ociated with glutathione metabolism, and (4) up-regulation in metallot
hionein expression.