Lovastatin Inhibits Thrombospondin-1-Induced Smooth Muscle Cell Chemotaxis

Hypercholesterolemia exacerbates in-stent restenosis in rabbits: Studies of the mitigating effect of stent surface modification with a CD47-derived peptide

BACKGROUND AND AIMS

Hypercholesterolemia (HC) has previously been shown to augment the restenotic response in animal models and humans. However, the mechanistic aspects of in-stent restenosis (ISR) on a hypercholesterolemic background, including potential augmentation of systemic and local inflammation precipitated by HC, are not completely understood. CD47 is a transmembrane protein known to abort crucial inflammatory pathways. Our studies have examined the interrelation between HC, inflammation, and ISR and investigated the therapeutic potential of stents coated with a CD47-derived peptide (pepCD47) in the hypercholesterolemic rabbit model.

METHODS

PepCD47 was immobilized on metal foils and stents using polybisphosphonate coordination chemistry and pyridyldithio/thiol conjugation. Cytokine expression in buffy coat-derived cells cultured over bare metal (BM) and pepCD47-derivatized foils demonstrated an M2/M1 macrophage shift with pepCD47 coating. HC and normocholesterolemic (NC) rabbit cohorts underwent bilateral implantation of BM and pepCD47 stents (HC) or BM stents only (NC) in the iliac location.

RESULTS

A 40 % inhibition of cell attachment to pepCD47-modified compared to BM surfaces was observed. HC increased neointimal growth at 4 weeks post BM stenting. These untoward outcomes were mitigated in hypercholesterolemic rabbits treated with pepCD47-derivatized stents. Compared to NC animals, inflammatory cytokine immunopositivity and macrophage infiltration of peri-strut areas increased in HC animals and were attenuated in HC rabbits treated with pepCD47 stents.

CONCLUSIONS

Augmented inflammatory responses underlie severe ISR morphology in hypercholesterolemic rabbits. Blockage of initial platelet and leukocyte attachment to stent struts through CD47 functionalization of stents mitigates the pro-restenotic effects of hypercholesterolemia.

Connective tissue growth factor promotes chemotaxis of preosteoblasts through integrin α5 and Ras during tensile force-induced intramembranous osteogenesis

In vertebrates, new bone formation via intramembranous osteogenesis is a critical biological event for development, remodeling, and fracture healing of bones. Chemotaxis of osteoblast lineage cells is an essential cellular process in new bone formation. Connective tissue growth factor (CTGF) is known to exert chemotactic properties on various cells; however, details of CTGF function in the chemotaxis of osteoblast lineage cells and underlying molecular biological mechanisms have not been clarified. The aim of the present study was to evaluate the chemotactic properties of CTGF and its underlying mechanisms during active bone formation through intramembranous osteogenesis. In our mouse tensile force-induced bone formation model, preosteoblasts were aggregated at the osteogenic front of calvarial bones. CTGF was expressed at the osteogenic front, and functional inhibition of CTGF using a neutralizing antibody suppressed the aggregation of preosteoblasts. In vitro experiments using μ-slide chemotaxis chambers showed that a gradient of CTGF induced chemotaxis of preosteoblastic MC3T3-E1 cells, while a neutralizing integrin α5 antibody and a Ras inhibitor inhibited the CTGF-induced chemotaxis of MC3T3-E1 cells. These findings suggest that the CTGF-integrin α5-Ras axis is an essential molecular mechanism to promote chemotaxis of preosteoblasts during new bone formation through intramembranous osteogenesis.

Thrombospondin-5 and fluvastatin promote angiogenesis and are protective against endothelial cell apoptosis

The thrombospondins (TSPs), multifunctional matricellular proteins, are known mediators of endothelial cell (EC) angiogenesis and apoptosis. TSP-1, an antiangiogenic molecule, is important in the progression of vascular disease, in part by inducing EC apoptosis. TSP-2, although less studied, also induces EC apoptosis and inhibits angiogenesis. The effects of TSP-5 are largely unexplored in ECs, but TSP-5 is believed to be protective against arterial disease. Statin drugs have been shown to have beneficial pleiotropic effects, including decreasing EC apoptosis, increasing angiogenesis, and blocking TSP signaling. We hypothesized TSP-5 will be proangiogenic and antiapoptotic, and statin pretreatment would reverse the proapoptotic and antiangiogenic phenotype of TSP-1 and TSP-2. ECs were exposed to serum-free medium, TSP-1, TSP-2, or TSP-5 with or without fluvastatin pretreatment. Quantitative real-time polymerase chain reaction was performed on 96 apoptosis and 96 angiogenesis-related genes using microfluidic card assays. Angiogenesis was measured using Matrigel assays, while apoptosis was measured by fluorescent caspase assay. TSP-5 suppressed apoptotic genes and had a mixed effect on the angiogenic genes; however, TSP-5 did not alter apoptois but was proangiogenic. Pretreatment with fluvastatin downregulated proapoptotic genes and apoptosis and upregulated proangiogenic genes and angiogenesis. Findings indicate TSP-5 and fluvastatin have a protective effect on ECs, being proangiogenic and reversing the antiangiogenic effects of TSP-1 and TSP-2. In conclusion, TSP-5 and fluvastatin may be beneficial for inducing angiogenesis in the setting of ischemia.

Statins and nitric oxide donors affect thrombospondin 1-induced chemotaxis

BACKGROUND

Thrombospondin 1 (TSP-1) induces vascular smooth muscle cell (VSMC) migration and intimal hyperplasia. Statins and nitric oxide (NO) donors decrease intimal hyperplasia. We previously showed that statins (long-term exposure) and NO donors inhibit TSP-1-induced VSMC chemotaxis.

HYPOTHESES

(1) Pretreatment with short-term statin will inhibit TSP-1-induced VSMC chemotaxis and (2) NO donors will enhance statin inhibition of TSP-1-induced or platelet-derived growth factor (PDGF)-induced VSMC chemotaxis.

METHODS

We examined these treatment effects on TSP-1-induced VSMC chemotaxis: (1) long-term (20 hours) versus short-term (20 minutes) pravastatin, (2) diethylenetriamine NONOate (DETA/NO) or S-nitroso-N-acetylpenicillamine (SNAP) in combination with pravastatin, and (3) comparison of TSP-1 to PDGF as a chemoattractant.

RESULTS

Pravastatin (long term or short term) inhibited TSP-1-induced chemotaxis. Diethylenetriamine NONOate and SNAP impeded statin inhibition of TSP-1-induced chemotaxis. Platelet-derived growth factor and TSP-1 had opposite effects on DETA/NO-pravastatin treatment.

CONCLUSION

Short-term statin pretreatment inhibited TSP-1-induced VSMC chemotaxis, suggesting a pleiotropic effect. High-dose NO reversed statin inhibition of TSP-1-induced chemotaxis, suggesting NO and statin combination therapies warrant further study.

Differential effect of nitric oxide on thrombospondin-1-, PDGF- and fibronectin-induced migration of vascular smooth muscle cells

BACKGROUND

Neointimal hyperplasia involves the migration of medial vascular smooth muscle cells (VSMCs) in response to arterial injury. Thrombospondin-1 (TSP1), platelet-derived growth factor (PDGF), and fibronectin (Fn) induce VSMC migration. Nitric oxide (NO) limits VSMC migration. The hypothesis of this study is that NO would dose dependently inhibit TSP1-induced, PDGF-induced, and Fn-induced VSMC chemotaxis.

METHODS

VSMCs were pretreated with serum free media or the NO donors diethylenetriamine NONOate or S-nitroso-N-acetyl-D,L-penicillamine. Chemotaxis to TSP1, PDGF, or Fn was determined. Analysis of variance with post hoc testing was done. P values < .05 were considered significant.

RESULTS

PDGF, TSP1, and Fn induced VSMC chemotaxis. NO donors inhibited chemotaxis of VSMCs to PDGF in a concentration-dependent manner. NO donors had a variable effect on TSP1-induced chemotaxis. NO donors did not inhibit Fn-induced chemotaxis.

CONCLUSION

The complex interactions of these proteins in vivo will need to be considered when developing NO-dependent therapies for neointimal hyperplasia.