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

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.

Vascular Calcification—New Insights into Its Mechanism

“…Under high-phosphate circumstances, apoptosis or necrosis of VSMCs is induced [14,68,71,72], possibly generating apoptotic bodies from VSMCs, which could serve as nidi for calcium phosphate precipitation [71,73]. Phosphate-regulated intracellular signaling includes Wnt/β-catenin, protein Vascular smooth muscle cells (VSMCs) under hyperphosphatemic conditions.…”

“…Under high-phosphate circumstances, apoptosis or necrosis of VSMCs is induced [14,68,71,72], possibly generating apoptotic bodies from VSMCs, which could serve as nidi for calcium phosphate precipitation [71,73]. Phosphate-regulated intracellular signaling includes Wnt/β-catenin, protein kinase B (PKB or Akt), nuclear factor-kappa B (NF-κB), and serum-and glucocorticoid-inducible kinase 1 (SGK1) [57,[73][74][75][76]. The role of the inflammasome is also important [77,78].…”

Signaling pathways involved in vascular smooth muscle cell calcification during hyperphosphatemia

“…Previous studies showed that high extracellular phosphate levels induce apoptosis and necrosis of VSMCs [ 1 , 2 , 16 , 46 ]. Under such circumstances, VSMCs release apoptotic bodies, which could serve as a nidus for calcium phosphate deposition [ 1 , 42 , 54 , 56 ]. In addition, apoptosis of VSMCs may lead to medial VSMC loss and degeneration as well as elastin breaks, cyst-like structures, and changes in extracellular matrix composition within the medial layer of the arteries [ 55 , 57 ], effects that may also contribute to vascular mineralization [ 2 , 7 , 43 ].…”

“…AKT (also known as protein kinase B) signaling contributes to the complex machinery underlying VSMC osteoinduction [ 56 , 100 , 101 ]. Phosphate reduces AKT phosphorylation in VSMCs [ 56 , 100 ], while both pro-calcific effects [ 101 ] and protective effects against vascular calcification [ 101 , 102 ] of AKT activation have been described. AKT and SGK1 are able to phosphorylate and inactivate glycogen synthase kinase 3 (GSK-3) [ 103 , 104 ].…”

Intracellular matrix Gla protein promotes tumor progression by activating JAK2/STAT5 signaling in gastric cancer

“…Previous studies found that activation of PI3K/AKT signaling increases MGP expression (Mirsaidi et al , 2017; Ponnusamy et al , 2018). Although the crosstalk of JAK2/STAT5 signaling and PI3K/AKT signaling has been reported (Britschgi et al , 2012; Khanna et al , 2018), the underlying mechanisms remain largely unknown.…”