Y. Rojanasakul et al., PROTECTION AGAINST OXIDATIVE INJURY AND PERMEABILITY ALTERATION IN CULTURED ALVEOLAR EPITHELIUM BY TRANSFERRIN-CATALASE CONJUGATE, Biochimica et biophysica acta. Molecular basis of disease, 1315(1), 1996, pp. 21-28
The successful prevention of hydrogen peroxide-induced alveolar permea
bility alterations and cell injury by transferrin-catalase conjugate i
s described in this study. Permeability alterations and cell injury we
re induced in cultured alveolar epithelial monolayers by hydrogen pero
xide. Transepithelial transport of a permeability marker, [C-14]mannit
ol, and cellular nuclear fluorescence of a membrane integrity indicato
r, propidium iodide, were used to quantitate epithelial permeability a
nd damage respectively. Hydrogen peroxide (0.1-10 mM) induced a dose-d
ependent increase in both alveolar permeability and cellular damage; h
owever, the oxidant effect on monolayer permeability did not require p
rior cell damage, Electron spin resonance measurements using the spin
trap 5,5-dimethyl-1-pyrroline-N-oxide indicated the formation of hydro
xyl radicals in hydrogen peroxide-treated cells. Chelation of the cell
ular pool of iron by deferoxamine inhibited radical formation and help
ed protect the cells from oxidative changes. Prior treatment of the ce
lls with catalase (0.1 U-10 U/ml) had minimal protective effects on ce
ll injury and permeability alterations. In contrast, transferrin-catal
ase conjugate, at the same concentration range, exhibited much improve
d protective effects on the cells in response to oxidant stress. This
enhanced protection was found to correlate well with an increase in ce
llular uptake of the enzyme conjugate via the transferrin receptor end
ocytosis pathway. Effective protection by the enzyme conjugate was sho
wn to require both the antioxidant enzyme moiety and the cognate moiet
y for the cell surface receptor. These findings indicate the potential
therapeutic merit of transferrin-catalase conjugate for the treatment
of pathological processes in the lung, whenever oxidative stress is i
nvolved.