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O‐GlcNAcase Exacerbates Post‐Hypoxic Cardiac Myocyte Death
Author(s) -
Ngoh Gladys Afor,
Watson Lewis J.,
Jones Steven P.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1376-c
Subject(s) - hypoxia (environmental) , myocyte , mitochondrion , membrane potential , inner mitochondrial membrane , medicine , endocrinology , chemistry , biology , pharmacology , microbiology and biotechnology , biochemistry , oxygen , organic chemistry
We have recently found that hypoxia‐reoxygenation reduces global levels of a cytoprotective metabolic signal ( O ‐linked β‐N‐acetylglucosamine, i.e. O ‐GlcNAc). Such observations may indicate a net increase in O ‐GlcNAcase (GCA, removes O ‐GlcNAc) activity. Because O ‐GlcNAc exerts protective effects on the myocardium, we hypothesized that gene transfer of GCA further reduces O ‐GlcNAc levels and sensitizes cardiac myocytes to post‐hypoxic injury. Isolated cardiac myocytes (n=4–5/group) were infected with adenovirus overexpressing GCA (AdGCA), or treated with GCA inhibitors, and subjected to hypoxia and reoxygenation. Whole cell lysates were immunoblotted for O ‐GlcNAc levels, cell injury assessed via post‐hypoxic LDH release, and post‐hypoxic loss of mitochondrial membrane potential evaluated with tetramethylrhodamine methyl ester (TMRM). Overexpression of GCA significantly reduced (p<0.05) O ‐GlcNAc levels, exacerbated post‐hypoxic LDH release, and favored the loss of mitochondrial membrane potential. GCA inhibition (via PUGNAc, streptozotocin, or alloxan) significantly enhanced (p<0.05) O ‐GlcNAc levels, reduced post‐hypoxic LDH release, and preserved mitochondrial potential. We conclude that hypoxia favors the net loss of the O ‐GlcNAc post‐translational modification reflected by the hypoxia‐sensitizing effects of GCA in cardiac myocytes. Funded by NIH (HL0833220) and AHA (0535270N).