Background: In periodontal disease, interleukin-1beta (IL-1β) is responsible for the matrix breakdown through excessive production of degrading enzymes by periodontal ligament fibroblasts and osteoblasts. Transforming growth factor-beta (TGF-β) plays an important role in tissue regeneration as one of the factors capable of counteracting IL-1β effects. In this study, we investigated the in vitro effect of avocado and soya unsaponifiables (ASU) on the expression of TGF-β1, TGF-β2, and bone morphogenetic protein-2 (BMP-2) by human periodontal ligament (HPL) and human alveolar bone (HAB) cells in the presence of IL-1β.

Methods: HPL and HAB cells were incubated for 48 hours with ASU (10 μg/ml) in the presence or absence of IL-1β (10 ng/ml). The steady-state levels of TGF-β1, TGF-β2, and BMP-2 mRNAs were determined by Northern blot or reverse transcription-polymerase chain reaction (RT-PCR). The amounts of TGF-β1 and TGF-β2 proteins were measured by enzyme-linked immunosorbent assay (ELISA).

Results: The data indicated that IL-1β strongly decreases the expression of TGF-β1 and TGF-β2 by HPL cells. ASU were capable of opposing the cytokine effect. In HAB cells, TGF-β1 and BMP-2 mRNA levels were downregulated by the cytokine. ASU were found to reverse the IL-1β–inhibiting effect. In contrast, the cytokine stimulated the production of TGF-β2 in alveolar bone cells, with no significant effect of ASU.

Conclusions: The results indicate that the IL-1β–driven erosive effect in periodontitis could be enhanced by a decreased expression of members of the TGF-β family. The ASU stimulation of TGF-β1, TGF-β2, and BMP-2 expression may explain their promoting effects in the treatment of periodontal disorders, at least partly. These findings support the hypothesis that ASU could exert a preventive action on the deleterious effects exerted by IL-1β in periodontal diseases.