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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Figure 2

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(a) Time course of glucose's 16.5 mM effect on in situ PKC activity in r...
(a) Time course of glucose's 16.5 mM effect on in situ PKC activity in rat aortic SMC. After indicated time of incubation with 16.5 mM glucose, PKC activities were measured by in situ PKC assay using a PKC-specific peptide substrate, RKRTLRRL, in digitonin-permeabilized cells as described in Methods. *P < 0.05 vs. 0 h. (b) Effect of regulators of PKC on p38 MAP kinase activation. After subculturing with 5.5 mM glucose, the cells were treated or not treated with PMA (100 nM) for 15 min or DMSO, treated with a PKC-specific inhibitor, GF109203X (GFX, 5 μM) pr ethanol, for 30 min, and then lysed. p38 MAP kinase activity was quantitated by in vitro phosphorylation of MBP using [γ-32P]ATP as described in Methods. GF109203X was solubilized with DMSO and PMA with ethanol, respectively, with final concentrations of DMSO and ethanol of 0.1%. The results were derived from three separate experiments. *P < 0.05 vs. 5.5 mM glucose (–), #P < 0.05 vs. 5.5 mM glucose treated with PMA. Each bar represents the mean ± SEM. PKC, protein kinase C.