Inhibition of Nuclear Factor Kappa B Prevents the Development of Experimental Periapical Lesions.

Introduction: Nuclear factor kappa B (NF-κB) is an important transcriptional regulator of angiogenesis involving B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) signaling pathways. Thus, inhibition of NF-κB may suppress the development of periapical lesions via blockage of angiogenesis. Accordingly, we examined the effects of NF-κB decoy oligodeoxynucleotide (ODN) treatment on experimentally induced periapical lesions.

Methods: Periapical lesions were induced in the mandibular first molars of 5-week-old male Wistar rats by the application of lipopolysaccharide to the pulp. NF-κB decoy ODN or NF-κB decoy scramble (control) was injected intraperitoneally every 7 days, starting 1 day before pulp exposure. After 28 days, the samples were retrieved, and digital radiographs were taken for radiomorphometry. Samples were processed for (1) immunohistochemistry of CD31, Bcl-2, and Bax; (2) laser capture microdissection to analyze Bcl-2, Bax, chemokine (C-X-C motif) ligand 1 (CXCL1), CXC receptor 2 (CXCR2), and vascular endothelial cell growth factor receptor 2 (VEGFR2) messenger RNA (mRNA) expression in CD31+ endothelial cells; (3) enzyme-linked immunosorbent assay to determine NF-κB/p65 activity; and (4) Western blotting for vascular endothelial growth factor expression.

Results: NF-κB decoy ODN treatment significantly reduced lesion size, NF-κB/p65 activity, and the density of CD31+ endothelial cells in the lesion. NF-κB decoy ODNs also down-regulated CXCL1, CXCR2, and VEGFR2 mRNAs and up-regulated Bax mRNA in endothelial cells but did not affect Bcl2 mRNA in endothelial cells. Vascular endothelial growth factor protein expression in the lesions was significantly decreased.

Conclusions: The inhibition of NF-κB activity by decoy ODN treatment suppressed the development of experimentally induced periapical lesions with a concomitant reduction in angiogenic responses in endothelial cells.