Related Experiment Videos
Lipoprotein(a) induces cell growth in rat peritoneal macrophages through inhibition of transforming growth
1Department of Metabolic Medicine, Kumamoto University School of Medicine, Japan.
Abstract:
To elucidate the atherogenicity of lipoprotein(a) (Lp(a)), we examined its growth-stimulating activity in rat resident peritoneal macrophages. When macrophages were incubated with Lp(a), cell numbers were increased 1.5-fold as compared with control macrophages. Furthermore, apolipoprotein(a) (apo(a)), a plasminogen-like glycoprotein which is covalently attached to a low density lipoprotein-like particle (Lp(a)), also induced macrophage growth, while the growth-stimulating effect of Lp(a-) was negligible. These results suggest that apo(a) plays an active role in the mitogenic activity of Lp(a). Lp(a)-induced macrophage growth was inhibited by exogenously added active transforming growth factor-beta (TGF-beta) dose-dependently, and also by the addition of plasmin, which converts latent TGF-beta to an active form. Moreover, the amounts of endogenous active TGF-beta in the medium were significantly reduced by the incubation with Lp(a). It is evident from these results that Lp(a) induces macrophage growth by inhibiting TGF-beta activation. The capacity of Lp(a) to stimulate macrophage growth shown here could be novel atherogenic function of Lp(a).
Insights
Lipoprotein(a) (Lp(a)) stimulates macrophage growth, a novel atherogenic function. The apolipoprotein(a) (apo(a)) component drives this effect by inhibiting transforming growth factor-beta (TGF-beta) activation.
Area of Science:
- Cardiovascular Biology
- Atherosclerosis Research
- Cellular Immunology
Background:
- Lipoprotein(a) (Lp(a)) is implicated in atherosclerosis.
- The specific mechanisms underlying Lp(a)'s atherogenicity require further elucidation.
- Macrophage accumulation is a key feature of atherosclerotic plaque development.
Purpose of the Study:
- To investigate the atherogenic potential of Lp(a) by examining its effect on macrophage proliferation.
- To identify the specific component of Lp(a) responsible for growth stimulation.
- To explore the molecular pathways involved in Lp(a)-induced macrophage growth.
Main Methods:
- Incubation of rat resident peritoneal macrophages with purified Lp(a).
- Assessment of macrophage cell numbers and proliferation.
- Analysis of the role of apolipoprotein(a) (apo(a)) and transforming growth factor-beta (TGF-beta) signaling.
Main Results:
- Lp(a) significantly increased macrophage cell numbers by 1.5-fold.
- The growth-stimulating activity was attributed to the apolipoprotein(a) (apo(a)) component of Lp(a).
- Lp(a) inhibited TGF-beta activation, leading to increased macrophage proliferation.
Conclusions:
- Apolipoprotein(a) (apo(a)) plays a critical role in the mitogenic activity of Lp(a).
- Lp(a) promotes macrophage growth by inhibiting TGF-beta activation, representing a novel atherogenic mechanism.
- These findings highlight a new potential therapeutic target for cardiovascular disease.