FTI-277 inhibits smooth muscle cell calcification by up-regulating PI3K/Akt signaling and inhibiting apoptosis.

Arvind Ponnusamy,Smeeta Sinha,Samantha J Borland,Rebecca F Taylor,Emma Pond,Gareth D Hyde,Ann E Canfield,Heather J Eyre,Nick Ashton,Colette A Inkson,Philip A Kalra,Andrew Gilmore

doi:10.1371/journal.pone.0196232

Abstract

BackgroundVascular calcification is associated with increased cardiovascular morbidity and mortality in patients with atherosclerosis, diabetes and chronic kidney disease. However, no viable treatments for this condition have been identified. This study aimed to determine whether farnesyl transferase inhibitors (FTIs) can reduce vascular calcification and the mechanism by which this reduction occurs.ResultsWe demonstrate that FTI-277 significantly inhibits phosphate-induced mineral deposition by vascular smooth muscle cells (VSMC) in vitro, prevents VSMC osteogenic differentiation, and increases mRNA expression of matrix Gla protein (MGP), an inhibitor of mineralization. FTI-277 increases Akt signaling in VSMC in short-term serum-stimulation assays and in long-term mineralization assays. In contrast, manumycin A has no effect on Akt signaling or mineralization. Co-incubation of VSMC with FTI-277 and SH6 (an Akt inhibitor) significantly reduces the inhibitory effect of FTI-277 on mineralization, demonstrating that FTI-277 inhibits calcification by activating Akt signaling. Over-expression of the constitutively active p110 sub-unit of PI3K in VSMC using adenovirus activates Akt, inhibits mineralization, suppresses VSMC differentiation and significantly enhances MGP mRNA expression. FTI-277 also inhibits phosphate-induced activation of caspase 3 and apoptosis of VSMC, and these effects are negated by co-incubation with SH6. Finally, using an ex vivo model of vascular calcification, we demonstrate that FTI-277 inhibits high phosphate-induced mineralization in aortic rings derived from rats with end-stage renal failure.ConclusionsTogether, these results demonstrate that FTI-277 inhibits VSMC mineral deposition by up-regulating PI3K/Akt signaling and preventing apoptosis, suggesting that targeting farnesylation, or Akt specifically, may have therapeutic potential for the prevention of vascular calcification.

Highlights

Vascular calcification is associated with increased cardiovascular morbidity and mortality in patients with atherosclerosis, diabetes and chronic kidney disease (CKD) [1,2,3]
We demonstrate that farnesyl transferase inhibitors (FTIs)-277 significantly inhibits phosphate-induced mineral deposition by vascular smooth muscle cells (VSMC) in vitro, prevents VSMC osteogenic differentiation, and increases mRNA expression of matrix Gla protein (MGP), an inhibitor of mineralization
These results demonstrate that FTI-277 inhibits VSMC mineral deposition by upregulating PI3K/Akt signaling and preventing apoptosis, suggesting that targeting farnesylation, or Akt may have therapeutic potential for the prevention of vascular calcification

Summary

Introduction

Vascular calcification is associated with increased cardiovascular morbidity and mortality in patients with atherosclerosis, diabetes and chronic kidney disease (CKD) [1,2,3]. It is a complex process involving aberrant mineral metabolism, dysregulation of naturally occurring inhibitors of calcification (e.g. matrix Gla protein [MGP]), osteo/chondrogenic differentiation of vascular smooth muscle cells (VSMC), VSMC apoptosis, and the release of matrix vesicles [4,5,6]. Farnesyl transferase catalyzes the transfer of a 15 carbon isoprenoid lipid from farnesyl diphosphate onto a cysteine residue in the C-terminal CAAX box of several proteins, including small GTPases (Ras, RhoB) and prelamin A. This study aimed to determine whether farnesyl transferase inhibitors (FTIs) can reduce vascular calcification and the mechanism by which this reduction occurs

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