Zoledronic Acid Binds CYP2C8 and is Toxic to HMEC-1 Endothelial Cells and Angiogenesis
Livezey, Mara R.
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Cytochrome P450 2C8 (CYP2C8) is a heme-containing enzyme known for the oxidation of substrates such as endogenous arachidonic acid, antimalarial drugs, and antidiabetics. A recent genome-wide association study points to a relationship between increased incidence of bisphosphonate induced osteonecrosis of the jaw (BONJ) and three single nucleotide polymorphisms (SNPs) within the CYP2C8 gene. We hypothesized that CYP2C8 expression and activity in the jaw bone may be down-regulated in patients treated with the bisphosphonate zoledronic acid (ZA), a drug used to treat diseases such as osteoporosis and cancer-related metastases of the bone. The ability of ZA to bind CYP2C8 was confirmed spectrophotometrically in a purified recombinant CYP2C8 system resulting in a Ks of 4.2 μM. AutoDock simulations resulted in lowest energy binding conformations that were more favorable for ZA than clodronate. Additionally, AutoDock simulations suggest that Arg 97, Val 296 and Ala 297 (backbone carbonyl), and Thr 301 may be important for hydrogen-bonding interactions within the active site. Immortalized human microvascular endothelial cells (HMEC-1) were treated with ZA and significant cell toxicity was observed with an IC50 value of 40 μM. Modification of CYP2C8 mRNA expression was not apparent via ZA treatment and RT-PCR analysis. However, inhibition of VEGF dependent angiogenesis was confirmed by qualitative morphology comparison in the presence or absence of ZA. Together these results show that ZA does indeed bind CYP2C8 and is toxic to HMEC-1 endothelial cells and angiogenesis.