High glucose induces alteration of gap junction permeability and phosphorylation of connexin-43 in cultured aortic smooth muscle cells

Tatsuya Kuroki, Toyoshi Inoguchi, Fumio Umeda, Fusao Ueda, Hajime Nawata

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88 Citations (Scopus)

Abstract

Gap junction is thought to have a crucial role in maintaining tissue homeostasis. We examined the effect of a high glucose level on gap junctional intercellular communication (GJIC) activity in cultured vascular smooth muscle cells (VSMCs) using the fluorescent dye transfer method. After a 48-h incubation with 22 mmol/l glucose (high glucose level), GJIC activity of VSMCs was significantly reduced compared with incubation with 5.5 mmol/l glucose (normal glucose level) (P < 0.05). Treatment of the cells with 12-O- tetradecanoylphorbol-13-acetate (TPA; 5 x 10-8 mol/l), a protein kinase C (PKC) activator, for 1 h also reduced GJIC activity (P < 0.01). In addition, treatment of the cells with calphostin C, a specific PKC inhibitor, for 3 h completely restored the GJIC activity inhibited by the high glucose level. Western blot analysis showed that connexin 43 (Cx43), which is the major functional protein of gap junction, is present in multiphosphorylated forms: a nonphosphorylated form (P0) and phosphorylated forms (P1, P2, and P3). Incubation of VSMCs with a high glucose level significantly increased the density ratio of P3/P0 compared with a normal glucose level (P < 0.05). Similarly, treatment of the cells with TPA significantly increased the P3/P0 ratio compared with controls (P < 0.01). In addition, the increase in the P3/P0 density ratio induced by a high glucose level was restored to the control level by both staurosporine and calphostin C. These results suggest that the high glucose level induced the inhibition of GJIC activity in cultured VSMCs through excessive phosphorylation of Cx43, mediated by PKC activation. This may contribute to the development of the macroangiopathy associated with diabetes.

Original languageEnglish
Pages (from-to)931-936
Number of pages6
JournalDiabetes
Volume47
Issue number6
DOIs
Publication statusPublished - Jun 15 1998

All Science Journal Classification (ASJC) codes

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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