Statin-induced apoptosis linked with membrane farnesylated Ras small G protein depletion, rather than geranylated Rho protein

Abstract

Rhabdomyolysis is a severe adverse effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins). This myopathy is strongly enhanced by the combination with statins and fibrates, another hypolipidaemic agent. We have evaluated the initial step of statin-induced apoptosis by the detection of membrane flip-flop using flow cytometric analysis. L6 rat myoblasts were treated with various statins (atorvastatin (3 microM), cerivastatin (3 microM), fluvastatin (3 microM), pravastatin (3 mM), or simvastatin (3 microM)) for 2, 4 or 6 h followed by reacting with FITC-conjugated annexin V for the detection of initial apoptosis signal (flip-flop). Various statin-treated myoblasts were significantly stained with FITC-annexin V at 6 h, whereas they were not detected at 2 h. Moreover, immunoblot analysis indicated that when the cells were treated with cerivastatin (3 microM), membrane-associated Ras protein was activated and detached until 6 h, resulting in cell death through the consequent activation of caspase-8. On the other hand, since cytosolic Ras activation did not activate, there is still an unknown mechanism in statin-related Ras depletion. In conclusion, statin-induced apoptosis in muscular tissue was directly initiated by the farnesyl-anchored Ras protein depletion from cell membrane with subsequent apoptosis.

Mechanism of Statin-Induced Rhabdomyolysis

“…2). One group using rat immortalized L6 myoblasts reported that the depletion of FPP is critical for myotoxicity (22), but another laboratory using the same cell line suggested that GGPP was the critical isoprenoid (12). In our hands, it was not FPP (3 mM), but GGPP (3 mM) alone, because the addition of GGPP, not FPP, in the presence of fluvastatin completely canceled the toxic effects of statins in skeletal myofibers (15,17).…”

Reduction of mitomycin C resistance in human bladder cancer T24 cells by knocking-down ras oncogene

“…Contrary to this effect, we observed ras immunoreactivity was decreased 72 h after treatment with low concentrations of MMC. This could be attributed to depletion of the protein synthesis capacity in T24 cells after 72 h [29] . These data suggest that ras siRNA would be most effective 72 h after treatment with low concentrations of MMC.…”

The Possibility of Simvastatin as a Chemotherapeutic Agent for All-trans Retinoic Acid-Resistant Promyelocytic Leukemia

“…4,19,20) These isoprenoids are used for the prenylation of ras and rho GTPases, which are involved in signal transduction, and therefore, their lack of signal transduction causes severe cell dysfunction. We have previously studied the action mechanism of statin-induced rhabdomyolysis.…”

“…Additional study revealed that apoptosis was induced by dropping ras GTPase from the cell membrane, indicating that the depletion of farnesyl pyrophosphate was essential for statin-induced apoptosis. 4) A small GTPase-related signal is fundamental for cellular function, anticipating that cerivastatin also causes cellular damage to other differentiating tissues. In fact, we examined the cytotoxic effect of statins on IM-9 lymphoblastic leukocytes in a more recent study.…”

“…As reported previously, statin-induced apoptosis in L6 myocytes was triggered by the lack of ras GTPase from the cell membrane at 6 h, and thereafter, caspase-8 was activated. 4) Figure 4 summarizes caspase activity in statin-treated HL-60 cells. As shown in Fig.…”