Laquinimod inhibits the expression and function of hypoxia-inducible factor-2 alpha in osteoblasts

Zhao Guang-zong; Fang Jun; Ding Gang; Zhang Long-qiang; Li Hua-zhuang; Gao Ke-hai

doi:10.3969/j.issn.2095-4344.2016.07.001

Abstract：BACKGROUND:Fractures can induce bone cel hypoxia, and remarkably reduce the oxygen tension in cels. Hypoxia-inducible factor-2α is a key oxygen-dependent transcriptional activator to regulate the body function under hypoxia and mediate the release of various inflammatory factors after fractures. <br> OBJECTIVE:To explore the role of Laquinimod in expression and function of hypoxia-inducible factor-2αin osteoblasts. <br> METHODS: Mouse osteoblasts MC3T3-E1 (clone 14) were pretreated with Laquinimod at various concentrations(10-100μmol/L) before hypoxia in the presence or absence of specific proteasome inhibitors MG132 or N-acetyl-leucyl-leucyl-norleucine. Then, the media were pre-conditioned in 1% or 21% oxygen tension for 1 to 24 hours. <br> RESULTS AND CONCLUSION: Under hypoxia, the expression of hypoxia-inducible factor-2α in osteoblasts was increased remarkably, and Laquinimod could inhibit the expression of hypoxia-inducible factor-2α and its target genes in mouse MC3T3-E1 cels. Mechanisticaly, Laquinimod promoted hypoxia-inducible factor-2α degradation in a proteasome-dependent but von Hippel-Lindau protein-independent manner. Importantly, we found that Laquinimod disrupted the interaction between hypoxia-inducible factor-2α and its chaperone heat shock protein 90, but promoted the interaction between hypoxia-inducible factor-2α and the receptor of activated protein kinase C. These findings suggest that Laquinimod may promote the degradation of hypoxia-inducible factor-2α by affecting its folding and maturation. Laquinimod is a novel inhibitor of hypoxia-inducible factor-2α by changing its functional interaction with chaperone proteins heat shock protein 90 and receptor of activated protein kinase C.