1. Phenylephrine Enhances the Mitogenic Effect of S-Allyl-L-cysteine on Primary Cultured Hepatocytes through Protein Kinase C-Induced B-Raf Phosphorylation.
- Author
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Moteki H, Ogihara M, and Kimura M
- Subjects
- Animals, Phosphorylation drug effects, Cells, Cultured, Male, Prazosin pharmacology, Tetradecanoylphorbol Acetate pharmacology, Tetradecanoylphorbol Acetate analogs & derivatives, Mitogen-Activated Protein Kinase 1 metabolism, Maleimides pharmacology, Rats, Indoles pharmacology, Adrenergic alpha-1 Receptor Antagonists pharmacology, Drug Synergism, Rats, Sprague-Dawley, Mitogens pharmacology, Phenylephrine pharmacology, Hepatocytes drug effects, Hepatocytes metabolism, Protein Kinase C metabolism, Cysteine pharmacology, Cysteine analogs & derivatives, Cell Proliferation drug effects, Adrenergic alpha-1 Receptor Agonists pharmacology, Proto-Oncogene Proteins B-raf metabolism
- Abstract
The co-mitogenic effects of the α
1 -adrenoceptor agonist phenylephrine on S-allyl-L-cysteine (SAC)-induced hepatocyte proliferation were examined in primary cultures of adult rat hepatocytes. The combination of phenylephrine (10-10 -10-6 M) and SAC (10-6 M) exhibited a significant dose-dependent increase in the number of hepatocyte nuclei and viable cells compared to SAC alone. This combination also increased the progression of hepatocyte nuclei into the S-phase. The potentiating effect of phenylephrine on SAC-induced cell proliferation was counteracted by prazosin (an α1 -adrenergic receptor antagonist) and GF109203X (selective protein kinase C (PKC) inhibitor). In addition, PMA (direct PKC activator) potentiated the proliferative effects of SAC similarly to phenylephrine. In essence, these findings suggest that PKC activity plays a crucial role in enhancing SAC-induced cell proliferation. Moreover, the effects of phenylephrine on SAC-induced Ras activity, Raf phosphorylation, and extracellular signal-regulated kinase 2 (ERK2) phosphorylation were investigated. Phenylephrine (or PMA) in combination with SAC did not augment Ras activity, but further increased ERK2 phosphorylation and its upstream B-Raf phosphorylation. These results indicate that PKC activation, triggered by stimulating adrenergic α1 receptors, further amplifies SAC-induced cell proliferation through enhanced ERK2 phosphorylation via increased B-Raf-specific phosphorylation in primary cultured hepatocytes.- Published
- 2024
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