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Interaction of various lipoproteins from normal and dyslipoproteinemic plasma with mouse peritoneal macrophages
M Rotheneder1, F Krempler, G M Kostner
1Institute of Medical Biochemistry, University of Graz, Austria.
Abstract:
In this study we tried to elucidate the atherogenicity of various plasma lipoproteins with respect to their capability of foam cell formation. Mouse peritoneal macrophages (MPM) were incubated with increasing amounts of lipoproteins and the incorporation of 14C oleate into the cholesteryl ester fraction was followed. The results may be summarized as follows: freshly isolated Lp(a) behaves very similar to normal LDL causing no or little increase in CE formation in MPM. Lp(a) treated with dextran sulfate as well as with antibodies to Apo-a, strongly interact with scavenger receptors causing massive accumulation of CE in MPM. The abnormal lipoproteins from patients suffering from liver disease, LP-X, HDL-E cause no increase in CE formation of MPM. They behave very similar to artificial PL/FC liposomes. If on the other hand these abnormal lipoproteins are mixed with Ac-LDL, a synergistic effect was observed causing an approx. 30 per cent increase in CE-formation as compared to Ac-LDL alone. This was caused by a net transfer of FC from abnormal lipoproteins to Ac-LDL alone. This was caused by a net transfer of FC from abnormal lipoproteins to Ac-LDL. It is concluded that the lipoproteins studied in this report by itself exert no atherogenic function in MPM. They may, however, aggravate the atherogenicity of other processes known to be involved in the development of vascular diseases.
Insights
Modified Lp(a) and abnormal lipoproteins can promote foam cell formation in macrophages, indicating potential roles in vascular disease development. However, unmodified lipoproteins do not appear atherogenic on their own.
Area of Science:
- Biochemistry
- Cardiovascular Biology
- Cell Biology
Background:
- Atherosclerosis is a complex vascular disease characterized by lipid accumulation in macrophages, forming foam cells.
- Plasma lipoproteins play a critical role in lipid transport and are implicated in atherogenesis.
- Understanding the atherogenic potential of specific lipoprotein subclasses is crucial for disease prevention and treatment.
Purpose of the Study:
- To investigate the atherogenicity of various plasma lipoproteins, focusing on their capacity for foam cell formation in macrophages.
- To determine how modified lipoproteins, such as Lp(a) and abnormal lipoproteins from liver disease patients, influence cholesterol ester accumulation in macrophages.
Main Methods:
- Mouse peritoneal macrophages (MPM) were incubated with different lipoproteins.
- Incorporation of 14C oleate into the cholesteryl ester (CE) fraction of MPM was measured to assess foam cell formation.
- Lipoproteins were modified using dextran sulfate or antibodies to Apo-a, or derived from patients with liver disease (LP-X, HDL-E).
Main Results:
- Freshly isolated Lp(a) and normal LDL showed minimal induction of CE formation in MPM.
- Modified Lp(a) (treated with dextran sulfate or anti-Apo-a antibodies) strongly induced CE accumulation in MPM via scavenger receptor interaction.
- Abnormal lipoproteins (LP-X, HDL-E) from liver disease patients did not increase CE formation in MPM but showed synergistic effects when combined with Ac-LDL, involving cholesterol transfer.
- This synergy resulted in an approximate 30% increase in CE formation compared to Ac-LDL alone.
Conclusions:
- The studied lipoproteins, in their native forms, do not independently exhibit atherogenic function in macrophages.
- Modified Lp(a) and abnormal lipoproteins can contribute to atherogenesis by promoting foam cell formation.
- These lipoproteins may exacerbate the atherogenicity of other factors involved in vascular disease development.