Gene transfer of extracellular superoxide

dismutase protects against vascular

dysfunction with aging

Am J Physiol Heart Circ Physiol 290: H2600–H2605, 2006.

Kathryn A. Brown, Yi Chu,Donald D. Lund, Donald D. Heistad, and Frank M. Faraci

Speaker: 賴小婷Date:97/08/13

Introduction

Recent studies suggest that oxidative stress may increase in blood vessels during aging.

Hamilton CA. Hypertension 37: 529–534, 2001Van der Loo B,. J Exp Med 192: 1731–1744, 2000.

NO reacts with superoxide to form peroxynitrite (ONOO¯), and ONOO¯ can induce protein modifications and DNA damage

NO + O2 ． ¯ ONOO¯ DNA damage (Peroxynitrite)

O2 ． ¯ H202 H2O+O2

NO + O2 ． ¯ ONOO¯ Oxidative stress (Peroxynitrite) DNA damage (Endothelial dysfunction)

SOD Calatase

GPx

SOD

ONOO¯ can induce protein modifications and DNA damage

Three isoforms of endogenous SOD:

＊ Cytosolic CuZnSOD (SOD-1) ＊ Mitochondrial MnSOD (SOD-2) ＊ Extracellular CuZnSOD (ECSOD; SOD-3)

ECSOD is found throughout the vessel wall in many

species and is the only isoform of SOD that is located

outside of the cell, binding to cell surfaces and the

extracellular matrix via its heparin-binding domain (HBD)

Aim This study was to examine the hypothesis that

gene

transfer of ECSOD ( but not ECSOD lacking the

HBD ), reduces superoxide levels and improves

vascular function during aging in rats.

gene transfer of ECSOD Superoxide levels ↓

vascular function?

Methods

Male Fischer 344 rats ages 4–6 months (n = 23) Young

29–31 months (n =37) Old

Plasma analysis ( glucose 、 cholesterol )

Gene transfer of ECSOD and ECSOD HBD△

Thoracic aortas (95% O2-5% CO2 .37 )℃

＊ Vasomotor function (ACh 、 SNP 、 5-HT 、 PE )＊ SOD protein expression ＊ Superoxide levels (O2 ． ¯ )

ECSODHBD is identical to ECSOD except that the carboxy-terminal 13-amino-acid segment containing the HBD is deleted.

ECSOD is a homotetramericglycosylatedprotein (155 kDa)

CuZnSOD is a 32-kDahomodimer without glycosylation

(Circ Res. 2003;92:461-468.)

Results

Fig 1

* Old rats had significantly higher plasma levels of cholesterol than young rats, although the levels of cholesterol were still relatively low

There was no significant difference in body weight or plasma glucose (nonfasting) between young and old Fischer 344 rats

◎ Acetylcholine (ACh) stimulates the endothelial cells to produce a factor, NO, which penetrates into and activates the muscle cells causing relaxation

Acetylcholine

Relaxation

Vasomotor function

Fig 2

Responses to ACh were significantly improved after adenoviral-mediated gene transfer of human ECSOD

Transfection with ECSOD lacking the HBD had no significant effect on responses to ACh in vessels from old rats

ACh:Acetylcholine

＊ ACh was used to assess NO-mediated endothelial function

Fig 3

Responses to SNP were similar in aortas from young and old rats and were not altered by gene transfer of either form of ECSOD

◎ SNP (sodium nitroprusside) : activates the vessel causing relaxation

Fig 4

There were no significant differences in response to serotonin in aortas from young and old rats

◎ 5-HT (5-hydroxytryptamine 、 serotonin) : stimulates smooth muscle cell contraction

Fig 5

Gene transfer of either form of ECSOD had no significant effect on the response to phenylephrine

◎ PE (Phenylephrine): stimulates the vessel causing contraction

Fig 6

There were no significant differences in the levels of MnSOD and CuZnSOD between groups

There was a tendency for MnSOD to be increased in the old rats

Fig 7

After gene transfer of ECSOD, superoxide levels from old rats were similar to those in aorta from young rats

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Discussion

These results suggest :

1 . Vascular dysfunction associated with aging is mediated

in part by increased levels of superoxide

2. Gene transfer of ECSOD reduces vascular superoxide

and dysfunction in old rats

3 .Beneficial effects of ECSOD in old rats require the

heparin-binding domain (HBD) of ECSOD.

Endothelial dysfunction with aging appears to be related to an increase in ROS, especially superoxide .

Pacher P. Br J Pharmacol 135:, 2002Van der Loo B, J Exp Med 192:, 2000

Our laboratory has recently demonstrated that vasomotor function can be improved by gene transfer of ECSOD to blood vessels in rats with hypertension and inflammation.

Chu Y, Circ Res 92: 461–468, 2003.

ECSOD is an important determinant of NO levels by preventing destruction of NO released from the endothelium

Fukai T, Cardiovasc Res 55: 239–249, 2002.

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