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(Circulation Research. 2006;99:78.)
© 2006 American Heart Association, Inc.

Integrative Physiology

eNOS Gene Therapy Exacerbates Hepatic Ischemia-Reperfusion Injury in Diabetes

A Role for eNOS Uncoupling

John W. Elrod, Mark R. Duranski, Will Langston, James J.M. Greer, Ling Tao, Tammy R. Dugas, Christopher G. Kevil, Hunter C. Champion, David J. Lefer

From the Departments of Medicine (J.W.E., M.R.D., D.J.L.) and Pathology (J.W.E., D.J.L.), Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY; Department of Molecular and Cellular Physiology (W.L., J.J.M.G.); Department of Pharmacology, Toxicology and Neuroscience (T.R.D.); and Department of Pathology (C.G.K.), Louisiana State University Health Sciences Center, Shreveport; Department of Emergency Medicine (L.T.), Thomas Jefferson University, Philadelphia, Pa; and Department of Cardiology (H.C.C.), Johns Hopkins Hospital, Baltimore, Md.

Correspondence to David J. Lefer, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461. E-mail dlefer{at}aecom.yu.edu

Previous studies indicate that endothelial nitric oxide synthase (eNOS) function is impaired in diabetes as a result of increased vascular generation of reactive oxygen species. We hypothesized that eNOS gene therapy would augment NO· bioavailability and protect against hepatic ischemia-reperfusion (I-R) injury in type 2 diabetes mellitus. We developed a transgenic (Tg) diabetic mouse in which eNOS is systemically overexpressed. We also examined the effects of hepatic eNOS adenovirus therapy in diabetic mice. Diabetic (db/db) and nondiabetic mice were subjected to hepatic I-R injury. In nondiabetic mice, genetic overexpression of eNOS (both eNOS-Tg and eNOS adenovirus) resulted in hepatoprotection. In contrast, hepatic I-R injury was significantly increased in the db/db eNOS-Tg mouse, as serum alanine aminotransaminase (ALT) levels were increased by 3.3-fold compared with diabetic controls. Similarly, eNOS adenovirus treatment resulted in a 3.2-fold increase in serum ALT levels as compared with diabetic controls. We determined that hepatic eNOS was dysfunctional in the db/db mouse and increased genetic expression of eNOS resulted in greater production of peroxynitrite. Treatment with the eNOS cofactor tetrahydrobiopterin (BH₄) or the BH₄ precursor sepiapterin resulted in a significant decrease in serum ALT levels following I-R injury. We present clear examples of the protective and injurious nature of NO· therapy in I-R. Our data indicate that eNOS exists in an "uncoupled" state in the setting of diabetes and that "recoupling" of the eNOS enzyme with cofactor therapy is beneficial.

Key Words: diabetes mellitus • tetrahydrobiopterin • eNOS phosphorylation • sepiapterin • peroxynitrite

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