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Molecular Mechanism of Hyperglycemia‐Induced Impairment of Human Large Conductance Ca 2+ ‐activated K + (hSlo) Channel Functions
Author(s) -
Lu Tong,
He Tongrong,
Katusic Zvonimir S,
Lee HonChi
Publication year - 2006
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.20.5.a1392-c
Hyperglycemia‐induced impairment of vasodilation is associated with increase in reactive oxygen species (ROS). In this study, we hypothesized that hyperglycemia would impair hSlo channel function through ROS generation. We found that HEK293 cells expressing hSlo had 50% reduction in current density when cultured in high glucose (HG, 22 mM), compared to normal glucose (NG, 5 mM). HG slowed the channel activation and deactivation time constants by 50%, and decreased the channel equivalent charge movement and the forward rate constant at 0 mV (α 0 ). Superoxide dismutase expression was increased by 36% and catalase (CAT) expression was reduced by 45% in HEK293 cells cultured in HG, leading to a 100‐fold increase in intracellular ROS (mainly H 2 O 2 ) compared to cells in NG. Application of 0.015% H 2 O 2 mimicked the HG effects on hSlo while gene transfer of adenovirus‐CAT reversed the HG effect on hSlo. Peroxynitrite (0.1 mM) inhibited the hSlo current density as much as H 2 O 2 but did not alter the channel kinetics. hSlo with a single mutation at C911A was insensitive to HG and eliminated 80% of H 2 O 2 effects. These results suggest that misbalance of antioxidant enzymes plays critical roles in ROS generation and H 2 O 2 burst concentration could reach 10 mM range in HG. Impaired hSlo channel functions in HG are mainly through oxidation of C911. This may be one of fundamental mechanisms that contribute to the impairment of vasodilation in diabetes.