The herbal medicine Sairei-to inhibits proliferation of rat mesangial cells.
BACKGROUND
The herbal medicine Sairei-to is efficacious in renal diseases where mesangial proliferation is a key event. We examined whether Sairei-to inhibits proliferation of cultured rat mesangial cells and investigated its mechanism of action.


METHODS
The effect of Sairei-to on [(3)H]-thymidine incorporation stimulated by serum was assessed. Cell cycle was analyzed by flowcytometry. Extracellular signal-regulated kinase (ERK) activity was determined by immunecomplex kinase assay. Tyrosine phosphorylation of cellular proteins, and phosphorylation of ERK and Raf-1 were analyzed by immunoblot. Cyclic AMP was measured by radioimmunoassay.


RESULTS
Incubation of mesangial cells for 18 h with water-soluble but not insoluble fraction of Sairei-to inhibited serum-stimulated [(3)H]-thymidine incorporation. In subsequent experiments, water-soluble fraction, at a dose required for a half-maximal response (2 mg/ml), was used. Sairei-to inhibited S-phase entry stimulated by serum. Serum-induced tyrosine phosphorylation of p44 and p42 ERK was inhibited by Sairei-to, but that of other cellular proteins was not affected. Suppression of serum-stimulated ERK activation by Sairei-to was confirmed by immunecomplex kinase assay. Activation of Raf-1, an upstream activator of ERK, was also attenuated by Sairei-to. Incubation of cells with Sairei-to significantly increased the generation of cAMP.


CONCLUSIONS
Sairei-to inhibits serum-induced DNA synthesis of rat mesangial cells by suppressing Raf-1/ERK cascade probably via cAMP.
Awazu
Midori
M
Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan. awazu@sc.itc.kieo.ac.jp
Fujita
Hisayo
H
Omori
Sayu
S
Hida
Mariko
M
D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D016196:S Phase / Q000187:drug effects; D013936:Thymidine / Q000493:pharmacokinetics; D014316:Tritium; D014443:Tyrosine / Q000378:metabolism
D001798:Blood Proteins; D004365:Drugs, Chinese Herbal; C080903:sairei-to; D014316:Tritium; D014443:Tyrosine; D000242:Cyclic AMP; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D013936:Thymidine