Apoptosis of rheumatoid synovial cells by statins through the blocking of protein geranylgeranylation: a potential therapeutic approach to rheumatoid arthritis.
OBJECTIVE
To determine whether statins induce apoptosis in rheumatoid arthritis (RA) synoviocytes.


METHODS
The effects of lipophilic and hydrophilic statins (fluvastatin and pravastatin, respectively) on the apoptosis of cultured RA synoviocytes were examined in vitro. Apoptosis was analyzed by flow cytometry after staining with JC-1 (to measure the mitochondrial transmembrane potential), active caspase 3, annexin V, and propidium iodide. Add-back experiments were conducted to determine which downstream products of the mevalonate pathway could suppress apoptosis. Modulation of various signaling pathways induced by statins, including protein prenylation, was also investigated.


RESULTS
Fluvastatin, but not pravastatin, induced apoptosis in RA synoviocytes in a concentration-dependent (1-10 microM) and time-dependent (48-96 hours) manner. Another lipophilic statin, pitavastatin, displayed almost the same effects as fluvastatin. In sharp contrast, lipophilic statins did not significantly increase apoptosis in synoviocytes from patients with osteoarthropathy. Apoptosis induced by fluvastatin was mitochondrial- and caspase 3-dependent and was abrogated by mevalonate and geranylgeranyl pyrophosphate, but not by farnesyl pyrophosphate. In addition, the geranylgeranyl transferase inhibitor GGTI-298 mimicked the effect of fluvastatin on RA synoviocytes. Treatment of RA synoviocytes with the RhoA kinase inhibitor Y-27632 caused apoptosis. Fluvastatin decreased the amount of RhoA protein in the membrane fraction, but increased the amount in the cytosolic fraction.


CONCLUSIONS
Fluvastatin induced apoptosis in RA synoviocytes through a mitochondrial- and caspase 3-dependent pathway and by the blockage of mevalonate pathways, particularly through the inhibition of protein geranylgeranylation and RhoA/RhoA kinase pathways. These findings suggest that lipophilic statins have potential as novel therapeutic agents for RA.
Nagashima
Takao
T
Jichi Medical School, Tochigi, Japan.
Okazaki
Hitoaki
H
Yudoh
Kazuo
K
Matsuno
Hiroaki
H
Minota
Seiji
S
D017209:Apoptosis / Q000187:drug effects*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D001549:Benzamides / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D000077340:Fluvastatin; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology*; D008798:Mevalonic Acid / Q000494:pharmacology; D011106:Polyisoprenyl Phosphates / Q000494:pharmacology; D017368:Protein Prenylation / Q000187:drug effects*; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
D001549:Benzamides; D004791:Enzyme Inhibitors; D005229:Fatty Acids, Monounsaturated; C102521:GGTI 298; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007211:Indoles; D011106:Polyisoprenyl Phosphates; D000077340:Fluvastatin; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid