FoxO3 normalizes Smad3-induced arterial smooth muscle cell growth

Area of Science:

• Cardiovascular Biology
• Cellular Signaling
• Molecular Medicine

Background:

• Arterial smooth muscle (ASM) cell transition to a growth-promoting state is central to cardiovascular disease (CVD).
• The roles of transcription factors Smad3 and FoxO3 in ASM growth are not fully understood.
• Investigating their coordinated impact is crucial for understanding CVD pathogenesis.

Purpose of the Study:

• To determine a coordinated, phosphorylation-specific relationship between Smad3 and FoxO3 in controlling ASM cell growth.
• To test the hypothesis that FoxO3 can moderate Smad3-induced ASM cell growth.
• To explore the therapeutic potential of targeting Smad3 and FoxO3 in CVD.

Main Methods:

• Utilized a rat in vivo arterial injury model and in vitro ASM cell culture models.
• Employed adenoviral gene delivery for overexpression of Smad3 and FoxO3.
• Analyzed protein expression, phosphorylation, cellular localization, and ubiquitin ligase activity (MuRF-1).

Main Results:

• Smad3 and FoxO3 exhibit unique cellular distributions under growth conditions.
• FoxO3 overexpression reversed Smad3-induced ASM cell proliferation and Smad3 overexpression reversed FoxO3-induced cytostasis.
• FoxO3 induced MuRF-1 expression, which was reversed by Smad3 co-expression, indicating a role in regulating protein degradation.

Conclusions:

• FoxO3 can effectively reverse Smad3-mediated ASM cell growth.
• Reciprocal antagonism exists between Smad3 and FoxO3, dependent on phosphorylation and localization.
• Smad3 and FoxO3 represent potential therapeutic targets for mitigating abnormal ASM growth in cardiovascular disease.