Neuronal nitric oxide synthase negatively regulates xanthine oxidoreductase inhibition of cardiac excitation-contraction coupling

Shakil A. Khan, Kwangho Lee, Khalid M. Minhas, Daniel R. Gonzalez, Shubha V.Y. Raju, Ankit D. Tejani, Dechun Li, Dan E. Berkowitz, Joshua M. Hare

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177 Scopus citations


Although interactions between superoxide (O°2-) and nitric oxide underlie many physiologic and pathophysiologic processes, regulation of this crosstalk at the enzymatic level is poorly understood. Here, we demonstrate that xanthine oxidoreductase (XOR), a prototypic superoxide O°2--producing enzyme, and neuronal nitric oxide synthase (NOS1) coimmunoprecipitate and colocalize in the sarcoplasmic reticulum of cardiac myocytes. Deficiency of NOS1 (but not endothelial NOS, NOS3) leads to profound increases in XOR-mediated O°2- production, which in turn depresses myocardial excitation-contraction coupling in a manner reversible by XOR inhibition with allopurinol. These data demonstrate a unique interaction between a nitric oxide and an O°2-- generating enzyme that accounts for crosstalk between these signaling pathways; these findings demonstrate a direct antioxidant mechanism for NOS1 and have pathophysiologic implications for the growing number of disease states in which increased XOR activity plays a role.

Original languageEnglish (US)
Pages (from-to)15944-15948
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number45
StatePublished - Nov 9 2004
Externally publishedYes


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