Importance of Rac1 signaling pathway inhibition in the pleiotropic effects of HMG-CoA reductase inhibitors.
BACKGROUND
The pleiotropic effects of HMG-CoA reductase inhibitors (statins) are thought to be mediated through inhibition of small GTP-binding proteins; however, it remains to be examined whether clinical concentrations/doses of statins actually exert them.


RESULTS
In vitro studies with cultured human umbilical venous endothelial cells found that statins (atorvastatin, pitavastatin and pravastatin at 10 micromol/L) had no inhibitory effects on RhoA/Rho-kinase or Ras, but atorvastatin and pitavastatin inhibited membrane Rac1 expression. In animal studies of angiotensin II (AngII)-infused rats, atorvastatin showed only mild inhibitory effects on AngII-induced cardiovascular hypertrophy, whereas fasudil, a selective Rho-kinase inhibitor, significantly suppressed it. Statins had no inhibitory effects on RhoA/Rho-kinase, but inhibited both membrane and GTP-bound Rac1 in the heart, whereas fasudil only inhibited Rho-kinase activity. Furthermore, the combination of atorvastatin and fasudil showed more effective inhibitory effects than fasudil alone. Finally, in studies of normal healthy volunteers, clinical doses of pravastatin or atorvastatin (20 mg/day for 1 week) significantly inhibited Rac1, but not RhoA/Rho-kinase activity, in circulating leukocytes.


CONCLUSIONS
The pleiotropic effects of statins, if any, at their clinical doses are mediated predominantly through inhibition of the Rac1 signaling pathway.
Rashid
Mamunur
M
Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
Tawara
Shunsuke
S
Fukumoto
Yoshihiro
Y
Seto
Minoru
M
Yano
Kazuo
K
Shimokawa
Hiroaki
H
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000009:adverse effects / Q000031:analogs & derivatives / Q000494:pharmacology; D000328:Adult; D000804:Angiotensin II / Q000009:adverse effects; D000818:Animals; D000069059:Atorvastatin; D002478:Cells, Cultured; D018592:Cross-Over Studies; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006538:Heptanoic Acids / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D017379:Hypertrophy, Left Ventricular / Q000139:chemically induced / Q000517:prevention & control; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D017035:Pravastatin / Q000009:adverse effects / Q000494:pharmacology*; D011758:Pyrroles / Q000009:adverse effects / Q000494:pharmacology*; D011804:Quinolines / Q000009:adverse effects / Q000494:pharmacology*; D051381:Rats; D011921:Rats, Inbred WKY; D015398:Signal Transduction / Q000187:drug effects*; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011758:Pyrroles; D011804:Quinolines; D000804:Angiotensin II; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000069059:Atorvastatin; D054460:rho-Associated Kinases; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein; D017035:Pravastatin; C108475:pitavastatin; C049347:fasudil