Excessive production and/or inadequate removal of ROS (reactive oxygen species), especially superoxide anion, (commonly referred to as "oxidative stress") has been implicated in the pathogenesis of many cardiovascular diseases, including hypercholesterolemia, atherosclerosis, hypertension, diabetes, and heart failure. One of the major antioxidant systems against superoxide anion is superoxide dismutase (SOD). In mammalian tissue, three isoforms of superoxide dismutase exist: the cytoplasmic SOD1 (Cu/ZnSOD, SOD1), the mitochondrial MnSOD (SOD2) and the extracellular SOD (ecSOD, SOD3). In the vessel wall, ecSOD functions as a major antioxidant enzyme in the extracellular space. During the past six years, we have demonstrated that the expression of ecSOD is subject to a substantial degree of regulation at the transcriptional and posttranscriptional levels. Furthermore, we found that ecSOD requires a copper carrier protein (copper chaperone) to obtain its full activity. Based on these, we have focused on elucidating the molecular mechanism of modulating ecSOD activity using molecular biological and gene targeting approaches to understand the role of ecSOD in cardiovascular disease. The following four areas are currently investigated in our laboratory:

1. Extracellular SOD and copper transport system

Since ecSOD is a copper-containing enzyme, its activity is not only regulated by protein expression but also by copper content within the enzyme. SOD1 obtains its catalytic copper ion through interaction with the cytosolic carrier protein termed "copper chaperone" for SOD, CCS, indicating that CCS is a central mediator for SOD1 activity. The role of copper transport system in ecSOD activity, however, has not been investigated. Recently, our laboratory provide the first evidence that ecSOD requires copper transport system to obtain its full activity. We found that copper transport system includes antioxidant-1 (pubmed) and Menkes protein (ATP7A) (FASEB J (in press)). We are currently characterizing these proteins in cardiovascular disease.



2. 2. Extracellular SOD and extracellular matrix

Although heparan sulfate proteoglycan is an important ligand for ecSOD in the extracellular matrix, little is known about other biological partners of ecSOD. Using yeast two-hybrid system, we recently discovered fibulin-5 as a novel binding protein for ecSOD. Moreover, we have demonstrated that: 1) ecSOD directly interacts with fibulin-5 in vitro and in vivo; 2) the binding site of fibulin-5 with ecSOD is the C-terminal domain of fibulin-5; 3) plasma level of ecSOD is significantly increased, while tissue-bound ecSOD in aorta is markedly decreased in fibulin-5 -/- mice. Based on these, we are currently testing hypothesis that fibulin-5 plays an important role in regulating tissue-bound ecSOD in the vasculature, which may modulate vascular extracellular redox state, thereby contributing to cardiovascular disease.



3. Extracellular SOD and hypertension

Angiotensin II-induced hypertension is dependent on the reactive oxygen species derived from NAD(P)H oxidase. We have previously demonstrated that the ecSOD plays an important compensatory role in blunting the angiotensin II-induced hypertension. We found that angiotensin II stimulates induction of ecSOD expression in cultured human vascular smooth muscle cells and mice. In collaboration with Dr. Dave Harrison, we are currently examining the role of endogenous ecSOD in regulating nitric oxide bioavailability and blood pressure using gene targeting approaches.



4. 4. Enzymatic properties of extracellular SOD
We have previously shown that both cytosolic Cu/ZnSOD and ecSOD are partially inactivated in aortas of ApoE -/- mice, in which superoxide production is increased. We also found that activity of these enzymes can be restored by elevating endogenous levels of uric acid, a potent inhibitor of peroxidase activity of both cytosolic Cu/ZnSOD and ecSOD in vivo and in vitro. Thus, levels of uric acid commonly encountered in vivo may play an important role in regulating vascular redox state by preserving the activity of these SODs. Furthermore, we demonstrated that the specific activity of ecSOD showed a linear relationship with its copper content, indicating that copper is a critical regulator of ecSOD activity. Thus, using recombinant ecSOD protein, we are currently characterizing enzymatic properties of ecSOD.

Lab Members

Our lab is currently accepting postdoctoral applications, if interested please contact Dr. Tohru Fukai.

• Qin Z, Reszka KJ, Fukai T, Weintraub N.  Extracellular superoxide dismutase in vascular biology: an update on exogenous gene transfer and endogenous regulators of ecSOD (invited review).  Transl Res 2008;151(2):68-78.
  
  
• Kim HW, Ushio-Fukai M, Lin A, Guldberg RE, Fukai T. Essential role of extracellular superoxide dismutase in neovascularization in response to hindlimb ischemia. Circ Res 2007 June 29.
  
  
• Fukai T. Extracellular SOD Inactivation in High Volume Hypertension: Role of Hydrogen Peroxide. (Editorial) Arterioscler Thromb Vasc Biol. 2007 Mar;27(3):442-4.
  
  
• Gongora MC, Qin Z, Laude K, Kim HW, McCann L, Dikalov S, Folz RJ, Fukai T, Harrison DG. The Role of Eextracellular Superoxide Dismutase in Hypertension. Hypertension 2006 ;48(3):473-81.


• Qin Z, Ito h S, Jeney V, Ushio-Fukai M, Fukai T*. Essential Role for the Menkes ATPase in Activation of Extracellular Superoxide Dismutase: Implication for Vascular Oxidative Stress. FASEB J. 2006;20(2):334-6.


• Chen Y, Hou M, Li Y, Traverse JH, Zhang P, Salvemini D, Fukai T, Bache RJ. Increased superoxide production causes coronary endothelial dysfunction and depressed oxygen consumption in the failing heart. Am J Physiol. 2005;288(1):H133-41.


• Jeney V, Itoh S, Wendt M, Gradek Q, Ushio-Fukai M, Harrison DG, Fukai T**. The Role of Antioxidant-1 in Extracellular Superoxide Dismutase Function Circ Res. 2005;96(7):723-9.


• Laude K, Cai H, Fink B, Hoch N, Weber DS, McCann L, Kojda G, Fukai T, Schmidt HH, Dikalov S, Ramasamy S, Gamez G, Griendling KK, Harrison DG. Hemodynamic and biochemical adaptations to vascular smooth muscle overexpression of p22phox in mice. Am J Physiol. 2005 Jan;288(1):H7-H12.


• Nguyen A, Ito h S, Jeney V, Yanagisawa H, Fujimoto M, Ushio-Fukai M, Fukai T*. Fibulin-5 is a Novel Binding Protein for Extracellular Superoxide Dismutase Circ Res. 2004 Nov 26;95(11):1067-74.


• Davis ME, Cai H, McCann L, Fukai T, and Harrison DG. Role of c-Src in regulation of endothelial nitric oxide synthase expression during exercise training. Am J Physiol 2003;284(4) H1449-53.


• Hink HU, Fukai T*. Extracellular Superoxide Dismutase, Uric Acid, and Atherosclerosis. (Review) Cold Spring Harb Symp Quant Biol. 2002;67:483-90.


• Fukai T* , Folz RJ, Landmesser U, Harrison DG. Extracellular superoxide dismutase and cardiovascular disease. (Review) Cardiovasc Res 2002;55(2) 239-249.


• Hink HU, Santanam N, Dikalov S, McCann L, Nguyen AD, Parthasarathy S, Harrison DG, Fukai T*. Peroxidase properties of extracellular superoxide dismutase: role of uric acid in modulating in vivo activity. Arterioscler Thromb Vasc Biol. 2002;22(9) 1402-8.


• Fukai T*, Siegfried MR, Ushio-Fukai M, Cheng Y, Kodja G, Harrison DG. Regulation of the vascular extracellular superoxide dismutase by nitric oxide and exercise training. J Clin Invest. 2000; 105:1631-1639.


• Mavromatis K, Fukai T, Tate M, Chesler N, Ku D, Galis ZS. Early effects of arterial hemodynamic conditions upon ex vivo perfused human saphenous vein. Arterioscler Thromb Vasc Biol. 2000;20:1889-1895.


• Fukai T, Siegfried MR, Ushio-Fukai M, Griendling KK, arrison DG. Modulation of extracellular superoxide dismutase expression by angiotensin II and hypertension. Circ Res 1999;85:23-28.


• Fukai T, Galis ZS, Meng XP, Parthasarathy S, Harrison.DG. Vascular expression of ecSOD in atherosclerosis. J Clin Invest. 1998;101(10):2101-2111.


• Inoue N, Ramasamy S, Fukai T, Nerem RM, Harrison DG: Shear stress modulates expression of Cu/Zn superoxide dismutase in human aortic endothelial cells. Circ Res. 1996;79(1) 32-7.


• Fukai T, Egashira K, Numaguchi K, Hata H, Takahashi T, Kasuya H, Sakata M, Shimokawa H, Takeshita A: Endothelin-1 is not involved in serotonin-induced coronary spasm in a swine model. Cardiovasc Res. 1995;30(2) 193-9.


• Tsutsui H, Ando S, Fukai T, Kuroiwa M, Egashira K, Sasaki M, Kuwabara S, Koyanagi S, Takeshita A: Detection of angina-provoking coronary stenosis by resting iodine 123 metaiodobenzylguanidine scintigraphy in patients with unstable angina pectoris. Am Heart J; 1995;129(4) 708-715.


• Fukai T, Egashira K, Numaguchi K, Hata H, Takahashi T, Kasuya H, Sakata M, Shimokawa H, Takeshita A: Endothelin-1 is not involved in serotonin-induced coronary spasm in a swine model. Cardiovasc Res. 1995;30(2) 193-9.


• Ito A, Shimokawa H, Nakaike R, Fukai T, Sakata M, Takayanagi T, Egashira K, Takeshita A: Protein kinase C is activated at the spastic site in a swine mode of coronary artery spasm. Circulation 1994;90(5) 2425-2431.


• Fukai T, Koyanagi S, Takeshita A: Role of coronary vasospasm in the pathogenesis of myocardial infarction: Study in patients with no significant coronary stenosis. Am Heart J 1993;126:1305-1311.


• Fukai T, Egashira K, Hata H, Numaguchi K, Ohara Y, Takahashi T, Tomoike H, Takeshita A: Serotonin-induced coronary spasm in a swine model. a minor role of defective endothelium-derived relaxing factor. Circulation 1993;88:1922-1930.


• Fukai T, Koyanagi S, Takeshita A: Role of coronary vasospasm in the pathogenesis of myocardial infarction: Study in patients with no significant coronary stenosis. Am Heart J 1993;126:1305-1311.