Abstract

Tuberous sclerosis complex (TSC) is a multi-systemic syndrome caused by mutations in TSC1 or TSC2 gene. In TSC2-null cells, Rheb, a member of the Ras family of GTPases, is constitutively activated. Statins inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase and block the synthesis of isoprenoid lipids with inhibition of Rheb farnesylation and RhoA geranylgeranylation. The effects of rosuvastatin on the function of human TSC2^−/− and TSC2^-/meth α-actin smooth muscle (ASM) cells have been investigated. The TSC2^−/− and TSC2^-/meth ASM cells, previously isolated in our laboratory from the renal angiomyolipoma of two TSC patients, do not express tuberin and bear loss of heterozigosity caused by a double hit on TSC2 and methylation of TSC2 promoter, respectively. Exposure to rosuvastatin affected TSC2^-/meth ASM cell growth and promoted tuberin expression by acting as a demethylating agent. This occurred without changes in interleukin release. Rosuvastatin also reduced RhoA activation in TSC2^-/meth ASM cells, and it required coadministration with the specific mTOR (mammalian target of rapamycin) inhibitor rapamycin to be effective in TSC2^−/− ASM cells. Rapamycin enhanced rosuvastatin effect in inhibiting cell proliferation in TSC2^−/− and TSC2^-/meth ASM cells. Rosuvastatin alone did not alter phosphorylation of S6 and extracellular signal-regulated kinase (ERK), and at the higher concentration, rosuvastatin and rapamycin slightly decreased ERK phosphorylation. These results suggest that rosuvastatin may potentially represent a treatment adjunct to the therapy with mTOR inhibitors now in clinical development for TSC. In particular, rosuvastatin appears useful when the disease is originated by epigenetic defects.