The Effects of Simvastatin on Human Airway Epithelial Cell Viability and Morphology.
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The Effects of Simvastatin on Human Airway Epithelial Cell Viability and Morphology.
Amir A. Zeki1, Saeid Ghavami2, Andrew Halayko2, Reen Wu1
1. Pulmonary, Critical Care, & Sleep Medicine, University of California, Davis School of Medicine, Sacramento, CA, United States. 2. Section of Respiratory Medicine, University of Manitoba, Winnipeg, MB, Canada.
Purpose of Study: To determine if simvastatin causes airway epithelial cytotoxicity and if this is dependent on mevalonate (MA); i.e. MA is the immediate product of HMG-CoA reductase (HMGR), the enzyme inhibited by statins.
Methods Used: The normal human bronchial epithelial cell line (HBE1), and primary normal human bronchial epithelial (NHBE) cells were used (in vitro), grown to 90% confluence, then treated with simvastatin (Sim) ± MA (2 mM) in standard serum-starved cell culture conditions. After treatment with low- (2.5, 5, 10 ?M) vs. high-dose Sim (20 ?M) for 24, 48, 72, &/or 96 hrs, we assessed for (1) cell viability using the Alamar blue & MTT assays, (2) cell death using Trypan blue exclusion & total live cell counts, & (3) cell morphological changes using light microscopy.
Summary of Results: Low-dose Sim treatment of HBE1 cells (24 & 48 hrs) did not decrease cell viability, whereas high-dose Sim treatment decreased cell viability in a MA-dependent manner without causing cell death or reduced total cell counts. High-dose Sim treatment (24 and 48 hrs), altered cell morphology (decreased cell size, development of multiple cellular projections, & reduced cell-cell contact), in a MA-dependent manner. In primary NHBE cells there was a time- & dose-dependent decrease in cell viability. After 24 hrs of Sim treatment there was no significant decline in cell viability at any statin dose. However, after 48, 72, & 96 hrs treatment, there was a dose-dependent decrease in cell viability at all statin doses (the greatest decrease at 20 ?M). Both low- & high-dose Sim treatment (40 or 96 hrs) altered cell morphology (changes in cell size and shape/volume, the development of multiple cellular projections, reduced cell-cell contact, & cellular elongation).
Conclusions: Simvastatin may be cytotoxic to human airway epithelial cells at the micromolar doses used. Although there was no detectible cell death at the time points observed, Sim reduced cell viability and altered cell morphology. Some of these statin effects were MA-dependent, indicating that HMGR inhibition mediated some of these effects. Future studies are needed to determine the optimal therapeutic statin dose that preserves cell viability and barrier integrity.
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