Simvastatin, a 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) inhibitor, is an effective serum cholesterol-lowering agent, and also found to induce cells apoptosis by inhibiting the farnesylation or geranylgeranylation of the small GTP-binding proteins. Recent study also showed that simvastatin has anti-inflammatory properties in a murine model of allergic asthma. But the molecular basis of this anti-inflammatory activity of simvastatin has not been fully established. As asthma is characterized by chronic eosinophilic inflammation in the airways, we investigate the effect of simvastatin on eosinophil (EOS) apoptosis in asthma patients.
Peripheral blood EOS from 10 asthma patients were cultured in the presence or absence of simvastatin, together with or without mevalonate for different time. Apoptosis was monitored by annexin V / PI staining. Caspase-3 was measured by ELISA.
EOS were particularly susceptible to apoptosis after incubated with 5μM simvastatin for 6,12,24,48 hours (the rates of EOS undergoing apoptosis were: 23.20+3.19, 32.30+5.77, 41.00+6.22, 70.40+12.07% in control and 31.54+4.10, 46.58+6.73, 61.54+8.64, 85.60+14.19% in simvastatin; compared with control at the same time point: p=0.000∼0.014). EOS apoptosis occurred at doses of 1 μM and already maximal at 5μM after incubated with simvastatin for 12 hours (the rates of EOS undergoing apoptosis were: 23.90+3.32% in control, 37.40+3.31, 50.80+3.43, 53.40+3.57, 52.10+3.76% in 1,5,10,20μM simvastatin, resepectively; compared with control: p=0.000). The level of Caspase-3 in EOS were similar to the cell apoptosis (8.23+2.70 ng/ml in control, 13.60+4.03, 22.30+4.11, 23.50+4.28, 22.90+4.86 ng/ml in 1,5,10,20μM simvastatin, respectively; compared with control: p=0.000∼0.003). However, Co-incubation of simvastatin with mevalonate(the production of HMGR) completely reversed the activity of simvastatin on EOS apoptosis even when the highest simvastatin(20 μM) dose was used ( the rate of EOS undergoing apoptosis in mevalonate combined simvastatin and simvastatin alone were 25.10+3.35 and 52.10+3.76%; p=0.000).
Simvastatin induces apoptosis of EOS in asthma depending on its ability to block the synthesis of the isoprenoid intermediates, which leads to the inhibition of small GTP-binding proteins activity.
This result suggests that simvastatin may be used as anti-inflammatory medicine in asthma treatment.
F. Luo, None.