Abstract
HMG-CoA reductase inhibitor statins are used for the treatment of hypercholesterolemia. However, statins have adverse effects on skeletal muscles with unknown mechanism. We have reported previously that fluvastatin induced vacuolation and cell death in rat skeletal myofibers by depleting geranylgeranylpyrophosphate (GGPP) and suppressing small GTPases, particularly Rab (FASEB J 21:4087–4094, 2007). Rab1 is one of the most susceptible Rab isoforms to GGPP depletion and is essential for endoplasmic reticulum (ER)-to-Golgi trafficking. Here, we explored whether Rab1 and ER-to-Golgi vesicle trafficking were affected by statins in cultured single myofibers isolated from flexor digitorum brevis muscles of adult rats. Western blot analysis revealed that Rab1A protein resided predominantly in membrane but not in cytosol in control myofibers, whereas it was opposite in fluvastatin-treated myofibers, indicating that fluvastatin inhibited Rab1A translocation from cytosol to membrane. GGPP supplementation prevented the effect of fluvastatin on Rab1A translocation. Brefeldin A, a specific suppressor of ER-to-Golgi trafficking, induced vacuolation and cell death in myofibers in a manner similar to that of fluvastatin. Although ER-to-Golgi traffic suppression induces unfolded protein response (UPR) and cell death in some cell types, neither fluvastatin nor brefeldin A up-regulated UPR in myofibers. Immunofluorescence study revealed that the distribution of an ER marker, calnexin, was restricted to the region around nucleus with fluvastatin, suggesting the inhibition of ER membrane traffic by fluvastatin. We conclude that suppression of Rab1 GTPase and the subsequent inhibition of ER-to-Golgi traffic are involved in statin-induced skeletal myotoxicity.
Footnotes
This study was supported by Grants-in-aid for Young Scientists (B) [Grants 20790210, 22790257] (to K.S.) and Grants-in-aid for Scientific Research (C) [Grant 21590288] (to J.K.) from the Japan Society for the Promotion of Science and in part by the Smoking Research Foundation [Grant KI18003] (to J.K.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.179762.
-
ABBREVIATIONS:
- GGPP
- geranylgeranylpyrophosphate
- Arf
- ADP ribosylation factor
- BFA
- brefeldin A
- CBB
- Coomassie Brilliant blue
- ER
- endoplasmic reticulum
- Flv
- fluvastatin
- FPP
- farnesylpyrophosphate
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- GRP
- glucose-regulated protein
- Oatp
- organic anion transporting polypeptide
- PBS
- phosphate-buffered saline
- Tum
- tunicamycin
- UPR
- unfolded protein response.
- Received January 21, 2011.
- Accepted April 5, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|