TY - JOUR
T1 - Alterations in the structure, physicochemical properties, and pH of hepatocyte lysosomes in experimental iron overload
AU - Myers, Brent M.
AU - Prendergast, Franklyn G.
AU - Holman, Ralph
AU - Kuntz, Susan M.
AU - LaRusso, Nicholas F.
PY - 1991
Y1 - 1991
N2 - While hemochromatosis is characterized by sequestration of iron-protein complexes in hepatocyte lysosomes, little is known about the effects of excess iron on these organelles. Therefore, we studied the effects of experimental iron overload on hepatocyte lysosomal structure, physicochemical properties, and function in rats fed carbonyl iron. A sixfold increase (P < 0.0001) in hepatic iron and a fivefold increase in lysosomal iron (P < 0.01) was observed after iron loading; as a result, hepatocyte lysosomes became enlarged and misshapen. These lysosomes displayed increased (P < 0.0001) fragility; moreover, the fluidity of lysosomal membranes isolated from livers of iron-loaded rats was decreased (P < 0.0003) as measured by fluorescence polarization. Malondialdehyde, an end product of lipid peroxidation, was increased by 73% (P < 0.008) in lysosomal membranes isolated from livers of iron-overloaded rats. While amounts of several individual fatty acids in isolated lysosomal membranes were altered after iron overload, cholesterol/ phospholipid ratios, lipid/protein ratios, double-bond index, and total saturated and unsaturated fatty acids remained unchanged. The pH of lysosomes in hepatocytes isolated from livers of iron-loaded rats and measured by digitized video microscopy was increased (control, 4.70 ± 0.05; iron overload, 5.21 ± 0.10; P < 0.01). Our results demonstrate that experimental iron overload causes marked alterations in hepatocyte lysosomal morphology, an increase in lysosomal membrane fragility, a decrease in lysosomal membrane fluidity, and an increase in intralysosomal pH. Iron-catalyzed lipid peroxidation is likely the mechanism of these structural, physicochemical, and functional disturbances.
AB - While hemochromatosis is characterized by sequestration of iron-protein complexes in hepatocyte lysosomes, little is known about the effects of excess iron on these organelles. Therefore, we studied the effects of experimental iron overload on hepatocyte lysosomal structure, physicochemical properties, and function in rats fed carbonyl iron. A sixfold increase (P < 0.0001) in hepatic iron and a fivefold increase in lysosomal iron (P < 0.01) was observed after iron loading; as a result, hepatocyte lysosomes became enlarged and misshapen. These lysosomes displayed increased (P < 0.0001) fragility; moreover, the fluidity of lysosomal membranes isolated from livers of iron-loaded rats was decreased (P < 0.0003) as measured by fluorescence polarization. Malondialdehyde, an end product of lipid peroxidation, was increased by 73% (P < 0.008) in lysosomal membranes isolated from livers of iron-overloaded rats. While amounts of several individual fatty acids in isolated lysosomal membranes were altered after iron overload, cholesterol/ phospholipid ratios, lipid/protein ratios, double-bond index, and total saturated and unsaturated fatty acids remained unchanged. The pH of lysosomes in hepatocytes isolated from livers of iron-loaded rats and measured by digitized video microscopy was increased (control, 4.70 ± 0.05; iron overload, 5.21 ± 0.10; P < 0.01). Our results demonstrate that experimental iron overload causes marked alterations in hepatocyte lysosomal morphology, an increase in lysosomal membrane fragility, a decrease in lysosomal membrane fluidity, and an increase in intralysosomal pH. Iron-catalyzed lipid peroxidation is likely the mechanism of these structural, physicochemical, and functional disturbances.
KW - Hemochromatosis
KW - Lipid peroxidation
KW - Organelle damage
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U2 - 10.1172/JCI115423
DO - 10.1172/JCI115423
M3 - Article
C2 - 1918375
AN - SCOPUS:0025925346
SN - 0021-9738
VL - 88
SP - 1207
EP - 1215
JO - Journal of Clinical Investigation
JF - Journal of Clinical Investigation
IS - 4
ER -