Ut. Brunk et al., LETHAL HYDROGEN-PEROXIDE TOXICITY INVOLVES LYSOSOMAL IRON-CATALYZED REACTIONS WITH MEMBRANE DAMAGE, Redox report, 1(4), 1995, pp. 267-277
Secondary lysosomes contain low-molecular weight iron-complexes as a c
onsequence of normal autophagocytotic degradation of various metallo-p
roteins. Thus, entry of hydrogen peroxide into these organelles may in
duce iron-catalyzed oxidative reactions with ensuing damage to lysosom
al membranes and leakage of destructive contents. The amount of lysoso
mal reactive iron and the cellular capacity to degrade hydrogen peroxi
de would then be important determining factors in cellular resistance
to oxidative stress. The effects of hydrogen peroxide on cell viabilit
y and, in particular, on lysosomal membrane integrity, evaluated by ac
ridine orange, lucifer yellow, neutral red, and cathepsin D relocaliza
tion, were investigated in a model system of cultured J-774 cells. The
protective effect of the iron-chelator desferal was studied after exp
osure to the drug under ordinary culture conditions and after inhibiti
on of cellular endocytosis. Hydrogen peroxide-exposure (500 mu M in PB
S, 37 degrees C, 5-90 min) was manifested as a time-dependent decrease
in cell viability. This was preceded by a rapid reduction of the prot
on gradient across the lysosomal membranes, as judged by relocalizatio
n of acridine orange. Another early sign of damage was plasma membrane
blebbing, found on many cells within minutes after the initiation of
hydrogen peroxide-exposure. The cells also showed a partial redistribu
tion of the lysosomal markers lucifer yellow, neutral red, and catheps
in D, indicating lysosomal destabilization. The preexposure of cells t
o desferal in culture prevented all these phenomena, unless endocytoti
c uptake of the drug was prevented.