Glucose or diabetes activates p38 mitogen-activated protein kinase via different pathways
Masahiko Igarashi, … , Christopher J. Rhodes, George L. King
Masahiko Igarashi, … , Christopher J. Rhodes, George L. King
Published January 15, 1999
Citation Information: J Clin Invest. 1999;103(2):185-195. https://doi.org/10.1172/JCI3326.
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Article

Glucose or diabetes activates p38 mitogen-activated protein kinase via different pathways

Abstract

Hyperglycemia can cause vascular dysfunctions by multiple factors including hyperosmolarity, oxidant formation, and protein kinase C (PKC) activation. We have characterized the effect of hyperglycemia on p38 mitogen-activated protein (p38) kinase activation, which can be induced by oxidants, hyperosmolarity, and proinflammatory cytokines, leading to apoptosis, cell growth, and gene regulation. Glucose at 16.5 mM increased p38 kinase activity in a time-dependent manner compared with 5.5 mM in rat aortic smooth muscle cells (SMC). Mannitol activated p38 kinase only at or greater than 22 mM. High glucose levels and a PKC agonist activated p38 kinase, and a PKC inhibitor, GF109203X, prevented its activation. However, p38 kinase activation by mannitol or tumor necrosis factor-α was not inhibited by GF109203X. Changes in PKC isoform distribution after exposure to 16.5 mM glucose in SMC suggested that both PKC-β2 and PKC-δ isoforms were increased. Activities of p38 kinase in PKC-δ– but not PKC-β1–overexpressed SMC were increased compared with control cells. Activation of p38 kinase was also observed and characterized in various vascular cells in culture and aorta from diabetic rats. Thus, moderate hyperglycemia can activate p38 kinase by a PKC-δ isoform–dependent pathway, but glucose at extremely elevated levels can also activate p38 kinase by hyperosmolarity via a PKC-independent pathway.

Authors

Masahiko Igarashi, Hisao Wakasaki, Noriko Takahara, Hidehiro Ishii, Zhen-Y Jiang, Teruaki Yamauchi, Koji Kuboki, Matthias Meier, Christopher J. Rhodes, George L. King

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Effect of GF109203X on p38 MAP kinase activation in rat aortic SMC. Afte...
Effect of GF109203X on p38 MAP kinase activation in rat aortic SMC. After 72 h of exposure to several concentrations of glucose or mannitol, the cells were untreated, or treated with a PKC-specific inhibitor, GF109203X (GFX, 5 μM), for 30 min; then, the cells were lysed as described in Methods. (a) p38 MAP kinase activity measured by the phosphorylation of MBP using [γ-32P]ATP. The results were derived from four separate experiments. **P < 0.01 vs. 5.5 mM glucose, #P < 0.05 vs. 16.5 mM glucose, +P < 0.05 vs. 22 mM glucose. (b) Expression of p38 MAP kinase by immunoblot analysis. The samples were separated by 10% SDS-PAGE, transferred to PVDF membranes, and blocked overnight. The membranes were incubated with antiphosphospecific p38 MAP kinase and anti-p38 antibody. The arrowhead shows the phosphorylation of p38 MAP kinase. The results were derived from three separate experiments. (c) p38 MAP kinase activity by the phosphorylation of MBP using [γ-32P]ATP. The results were derived from three separate experiments, with each experiment performed in duplicate. **P < 0.01 vs. 5.5 mM glucose. Each bar represents the mean ± SEM. PVDF, polyvinyldene difluoride.