Novel strategies to increase Sirtuin-1 activity in aortic aneurysm

BACKGROUND: Sirtuin-1 (SirT1), an NAD+-dependent deacetylase, is associated with cellular protective effects and beneficial metabolic processes that mimic caloric restriction, increasing cellular stress resistance. Recent studies have shown that SirT1 anti-inflammatory and anti-oxidant effects on the aortic wall are involved in preventing vascular diseases, such as aortic aneurysm (AA) and dissection. We demonstrated that SirT1 in vascular smooth muscle (VSM), the major component of large arteries, is indispensable in maintaining vascular wall homeostasis to prevent the development of aortic dissection after angiotensin II infusion, and arterial stiffness induced by high-fat high-sucrose diet. These beneficial effects of SirT1 were associated with decreases in metalloproteinase (MMPs) activity, especially MMP2 and MMP9. MMPs are extracellular matrix-degrading enzymes able to degrade elastin, a process known to be involved in the development of aortic dilatations (aneurysms) and dissections. Therefore, finding ways to increase SirT1 activity in the aortic wall has the potential of inhibiting MMP and elastin degradation, thereby preventing aortic aneurysm/dissections. Unfortunately, small molecules and polyphenolic compounds currently available to activate SirT1 lack specificity. Therefore, novel strategies to activate SirT1 are needed. Dr. Seta’s work previously showed that SirT1 activity can be inhibited by oxidative stress whereas mutating oxidation-sensitive cysteines on SirT1 (3M SirT1) or overexpressing glutaredoxin-1 (Glrx), an enzyme that prevents oxidative modifications on SirT1, was able to restore SirT1 activity in liver cells. OBJECTIVES: The goal of this study is to enhance SirT1 activity in aortas and VSM cells in a mouse model of AA (hypomorphic fibrillin-1 mice, Fbn1mgR/mgR). This thesis will determine whether, in aortas and VSM cells of Fbn1mgR/mgR mice, (1) SirT1 activity is affected by reversible oxidative post-translation modifications (OPTM); (2) there is an association between OPTM of SirT1 and MMPs activity; and (3) overexpressing a redox-resistant SirT1 mutant (3M SirT1) or glutaredoxin-1 (Glrx) with an adeno-associated virus (AAV), decreases MMP activity. METHODS: Levels of acetylated p53 (ac-p53), a SirT1 deacetylation target, were measured by Western Blot in aortas and VSM cells from Fbn1mgR/mgR mice and WT littermates, as an index of SirT1 activity. Released MMPs activity was determined by in-gel zymography in conditioned medium of aortas and VSM cells from WT and Fbn1mgR/mgR mice, before and after incubation with an AAV overexpressing 3M SirT1 or Glrx. Biotin switch assay was performed to measure SirT1 reversible oxidation. RESULTS: OPTM of SirT1 cysteines, specifically S-glutathionylation, were increased while SirT1 activity was decreased in aortas and VSM cells from WT and Fbn1mgR/mgR mice. SirT1 activity impairment was associated with increased MMP2/9 activity. Importantly, overexpression of an oxidation-resistant SirT1 mutant (3M SirT1) or glutaredoxin-1(Glrx), a thioltransferase that selectively removes S-glutathionylation from proteins, inhibited increased MMP2/9 activation in Fbn1mgR/mgR VSM cells. CONCLUSIONS: Preserving SirT1 activity in the aortic wall by preventing oxidative modifications on SirT1, may be a novel therapeutic strategy to prevent AA in individuals with Marfan syndrome and possibly other forms of AA.

Author dc:creator

• Liu, Hanxiao

Advisors dc:contributor.advisor

• Seta, Francesca
• Das, Sai Krupa

• Nutrition
• Aortic aneurysm
• Marfan syndrome
• Matrix metalloproteinase
• Oxidative post-translational modifications
• S-glutathionylation
• Sirtuin-1

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2144/45596

OAI identifier oai:identifier

oai:open.bu.edu:2144/45596