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Age-associated oxidative damage in microsomal and plasma membrane lipids of rat hepatocytes
1Hokkaido Institute of Public Health, Kitaku, Sapporo, Japan.
Abstract:
Phosphatidylcholine hydroperoxide (PC-OOH) and phosphatidylethanolamine hydroperoxide (PE-OOH) concentrations were determined in microsomes and plasma membranes prepared from 2- and 17-month-old male Sprague-Dawley rat hepatocytes, to verify the dissimilarity of age dependency of lipid peroxidation in organelle membranes. The hydroperoxides were directly measured by chemiluminescence detection-high-performance liquid chromatography (CL-HPLC), and 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl) phosphatidylcholine (PLPC-OOH) and 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl) phosphatidylethanolamine (PLPE-OOH) were enzymatically synthesized and utilized as standards for the calibration. Baseline concentrations of hydroperoxides (PC-OOH + PE-OOH) of the 17-month-old rats were 46 pmol per mg protein in microsomes (2.7 times higher than the 2-month-old rats) and 306 pmol per mg protein in plasma membranes (9.9 times higher than the 2-month-old rats). Both microsomal and plasma membrane lipids were severely peroxidized and converted to phospholipid hydroperoxides by NADPH-dependent lipid peroxidation in vitro, but the age-dependency was only observed in the plasma membranes. These results demonstrate that substantial oxidative damage to membrane phospholipids occurs with ageing both in microsomes and plasma membranes, but is more prevalent in plasma membranes in rat hepatocytes.
Insights
Oxidative damage to membrane phospholipids increases with age in rat hepatocytes. This lipid peroxidation is more pronounced in plasma membranes than in microsomes, indicating a greater age-dependent impact on cellular membranes.
Area of Science:
- Biochemistry
- Cell Biology
- Gerontology
Background:
- Lipid peroxidation is a key indicator of oxidative stress and cellular aging.
- Different cellular membranes may exhibit varying susceptibility to oxidative damage over time.
Purpose of the Study:
- To investigate the age-dependent changes in lipid peroxidation in rat hepatocyte microsomes and plasma membranes.
- To compare the accumulation of phosphatidylcholine hydroperoxide (PC-OOH) and phosphatidylethanolamine hydroperoxide (PE-OOH) in different membrane types.
Main Methods:
- Quantification of PC-OOH and PE-OOH using chemiluminescence detection-high-performance liquid chromatography (CL-HPLC).
- Enzymatic synthesis of specific phospholipid hydroperoxide standards (PLPC-OOH, PLPE-OOH) for accurate calibration.
- Preparation of microsomes and plasma membranes from hepatocytes of young (2-month-old) and aged (17-month-old) rats.
Main Results:
- Aged rats (17-month-old) showed significantly higher hydroperoxide concentrations in both microsomes (2.7-fold increase) and plasma membranes (9.9-fold increase) compared to young rats (2-month-old).
- While both membrane types showed increased lipid peroxidation in vitro, the age-dependency of hydroperoxide accumulation was more pronounced in plasma membranes.
- Baseline hydroperoxide levels in plasma membranes of aged rats were substantially higher than in microsomes.
Conclusions:
- Significant oxidative damage to membrane phospholipids occurs with aging in rat hepatocytes.
- Plasma membranes exhibit a greater age-dependent increase in phospholipid hydroperoxides compared to microsomal membranes.
- These findings highlight the differential susceptibility of cellular membranes to age-related oxidative stress.