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Regulation of membrane phospholipid metabolism in heart cell culture
M M Freyss-Beguin1, E M Millanvoye-Van Brussel, J M Simon
1Laboratoire de Pharmacologie, URA CNRS 1482, Faculté de Médecine, Necker-Enfants Malades, Paris, France.
Abstract:
We have isolated, from newborn rats, heart cultures enriched in contractile muscle cells (M) and cultures of fibroblast-like cells (F). M cultures respond to simulated ischemia by an arrest of beating activity, by a decrease in beta oxydation rate, ATP and phosphocreatine content and by a loss of membrane phospholipids associated with neutral lipids accumulation. F cells in contrast do not respond to oxygen deprivation. Firstly, we observed that cocultures of M and F cells respond to oxygen deprivation by an arrest of beating activity and a decrease in cellular ATP content, but failed to exhibit any significant loss of membrane phospholipids. Secondly, we demonstrated that culture medium conditioned by F cells is able to inhibit the reaction of M cells to simulated ischemia thus suggesting that fibroblasts produce a diffusible factor able to block phospholipase activation. Heat treatment and trypsinisation failed to abolish this activity, indicating that the phospholipase inhibitory factor is probably not a polypeptide.
Insights
Fibroblast cells protect heart muscle cells from simulated ischemia by releasing a factor that inhibits phospholipase activation, preventing cell damage during oxygen deprivation.
Area of Science:
- Cardiovascular Biology
- Cellular Physiology
- Biochemistry
Background:
- Heart muscle cells (M) undergo significant metabolic and structural changes during simulated ischemia.
- Fibroblast-like cells (F) do not exhibit sensitivity to oxygen deprivation.
- Understanding cell-cell interactions is crucial for cardiac protection.
Purpose of the Study:
- To investigate the protective effect of fibroblasts on heart muscle cells during simulated ischemia.
- To identify the mechanism by which fibroblasts modulate the response of heart muscle cells to ischemic stress.
Main Methods:
- Isolation and culture of rat neonatal heart muscle cells (M) and fibroblasts (F).
- Co-culture experiments to assess M cell response to oxygen deprivation in the presence of F cells.
- Analysis of conditioned medium from F cells for protective properties against ischemia-induced damage in M cells.
- Biochemical assays to measure ATP content, beta-oxidation, and phospholipid loss.
Main Results:
- M cells showed decreased beating, ATP, phosphocreatine, and phospholipid loss under ischemia.
- Co-culturing M and F cells prevented phospholipid loss in M cells during ischemia.
- Medium conditioned by F cells inhibited ischemia-induced M cell responses, including phospholipid loss.
- The protective factor from F cells was heat-stable and trypsin-resistant, suggesting it is not a polypeptide.
Conclusions:
- Fibroblasts secrete a diffusible factor that protects heart muscle cells from ischemic injury.
- This factor appears to inhibit phospholipase activation, preserving membrane integrity.
- Fibroblast-conditioned medium offers a potential therapeutic strategy for mitigating cardiac damage during ischemia.