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Microdynamics of the phospholipid bilayer in cardiomyopathic hamster heart cell membrane
H Okamoto1, H Kawaguchi, H Sano
1Department of Cardiovascular Medicine, Hokkaido University, Sapporo, Japan.
Insights
Cardiomyopathy alters heart cell membrane structure and function with age in Syrian hamsters. These changes in membrane phospholipid composition and microdynamics may contribute to cardiac dysfunction via impaired calcium handling.
Area of Science:
- Cardiovascular Biology
- Membrane Biophysics
- Biochemistry
Background:
- Cardiomyopathy is a progressive heart muscle disease.
- Intracellular calcium (Ca2+) accumulation is implicated in cardiomyopathy pathogenesis.
- Understanding cardiac membrane alterations is crucial for disease mechanism insights.
Purpose of the Study:
- To investigate age-dependent changes in cardiac membrane phospholipid bilayer microdynamics and structure in cardiomyopathic Syrian hamsters.
- To correlate these structural changes with disease progression.
- To explore the potential role of membrane alterations in cardiac dysfunction.
Main Methods:
- Preparation of cardiac membrane fractions from cardiomyopathic (BIO 14.6) and control (F1b) Syrian hamsters at 4, 18, and 31 weeks of age.
- Analysis of membrane lipid composition (cholesterol, phospholipids, fatty acids) using chromatography techniques.
- Determination of phospholipid bilayer microdynamics (viscosity, wobbling angle) via nanosecond fluorometry with diphenyl-hexatriene probe.
Main Results:
- No significant lipid composition or microdynamic differences were observed at 4 weeks.
- By 18 weeks, significant alterations in saturated and unsaturated fatty acid profiles were noted in cardiomyopathic hamsters.
- At 31 weeks, decreased phospholipids (phosphatidylinositol, phosphatidylethanolamine), reduced viscosity, and smaller wobbling angles indicated profound membrane structural changes.
Conclusions:
- Cardiac membranes in cardiomyopathic hamsters undergo significant age-dependent structural and functional alterations.
- These membrane changes, including altered lipid composition and microdynamics, may contribute to cardiac hypertrophy and dysfunction.
- Impaired Ca2+ handling due to altered membrane properties is a potential mechanism in cardiomyopathy progression.
Abstract:
To investigate the microdynamics and the structural architecture of the membrane phospholipid bilayer during the course of cardiomyopathy, membrane fractions were prepared from hearts of cardiomyopathic Syrian hamsters (BIO 14.6) aged 4, 18 and 31 weeks and compared with age-matched control hamsters (F1b). Membrane cholesterol, phospholipids and phospholipid fatty acids were measured by thin-layer chromatography, gas-liquid chromatography and high performance liquid chromatography. Microdynamics of the phospholipid bilayer were determined by a nanosecond fluorometer using pulsed excitation of a fluorescent probe, diphenyl-hexatriene. At the age of 4 weeks, there was no difference in lipid compositions and microdynamics between the BIO 14.6 and F1b. At the age of 18 weeks, saturated fatty acids, 18:0 and 22:0 increased and 20:0, 20:2 and 32:4 decreased in the BIO 14.6. At the age of 31 weeks, adding to the above changes in phospholipid fatty acids, unsaturated fatty acids 20:4 and 22:6 decreased, moreover membrane phospholipids, especially phosphatidylinositol and phosphatidylethanolamine significantly decreased. The viscosity and the wobbling angle of phospholipid molecules were decreased significantly. We have previously demonstrated that intracellular Ca2+ accumulation might be responsible for the pathogenesis of cardiomyopathy. Thus, we conclude that cardiomyopathic membrane may alter its structure and function with age. These alterations in cell membranes might be involved in the cardiac hypertrophy and dysfunction through impaired Ca2+ handling in cardiomyopathic hamsters.