The mevalonate cascade as a target to suppress extracellular matrix synthesis by human airway smooth muscle.

Abstract

Smooth muscle cells promote fibroproliferative airway remodeling in asthma, and transforming growth factor β1 (TGFβ1) is a key inductive signal. Statins are widely used to treat hyperlipidemia. Growing evidence indicates they also exert a positive impact on lung health, but the underlying mechanisms are unclear. We assessed the effects of 3-hydroxy-3-methlyglutaryl-coenzyme A (HMG-CoA) reductase inhibition with simvastatin on the fibrotic function of primary cultured human airway smooth muscle cells. Simvastatin blocked de novo cholesterol synthesis, but total myocyte cholesterol content was unaffected. Simvastatin also abrogated TGFβ1-induced collagen I and fibronectin expression, and prevented collagen I secretion. The depletion of mevalonate cascade intermediates downstream from HMG-CoA underpinned the effects of simvastatin, because co-incubation with mevalonate, geranylgeranylpyrophosphate, or farnesylpyrophosphate prevented the inhibition of matrix protein expression. We also showed that human airway myocytes express both geranylgeranyl transferase 1 (GGT1) and farnesyltransferase (FT), and the inhibition of GGT1 (GGTI inhibitor-286, 10 μM), but not FT (FTI inhibitor-277, 10 μM), mirrored the suppressive effects of simvastatin on collagen I and fibronectin expression and collagen I secretion. Moreover, simvastatin and GGTI-286 both prevented TGFβ1-induced membrane association of RhoA, a downstream target of GGT1. Our findings suggest that simvastatin and GGTI-286 inhibit synthesis and secretion of extracellular matrix proteins by human airway smooth muscle cells by suppressing GGT1-mediated posttranslational modification of signaling molecules such as RhoA. These findings reveal mechanisms related to evidence for the positive impact of statins on pulmonary health.

• Authors: Dedmer Schaafsma, Gordon Dueck, Saeid Ghavami, Andrea Kroeker, Mark M Mutawe, Kristin Hauff, Fred Y Xu, Karol D McNeill, Helmut Unruh, Grant M Hatch, Andrew J Halayko
• Journal: American journal of respiratory cell and molecular biology (Am J Respir Cell Mol Biol) Vol. 44 Issue 3 Pg. 394-403 (Mar 2011) ISSN: 1535-4989 [Electronic] United States
• PMID: 20463291 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Collagen Type I
• GGTI 286
• Transforming Growth Factor beta1
• Collagen
• Simvastatin
• Alkyl and Aryl Transferases
• geranylgeranyltransferase type-I
• Farnesyltranstransferase
• Leucine
• Mevalonic Acid

Topics

• Alkyl and Aryl Transferases (metabolism)
• Collagen (metabolism)
• Collagen Type I (metabolism)
• Extracellular Matrix (metabolism)
• Farnesyltranstransferase (metabolism)
• Gene Expression Regulation
• Humans
• Leucine (analogs & derivatives, pharmacology)
• Mevalonic Acid (metabolism)
• Models, Biological
• Protein Processing, Post-Translational
• Reverse Transcriptase Polymerase Chain Reaction
• Simvastatin (pharmacology)
• Trachea (metabolism)
• Transforming Growth Factor beta1 (metabolism)