Arrabidaea chica Verlot: in vitro evaluation of toxicity, antimicrobial and cytoprotective activities from standardized free crude extract combined with zoledronic acid, and microencapsulation studies

Abstract

The bisphosphonate related osteonecrosis of the jaw (BRONJ) is a condition associated to bisphosphonates, medicines used to treat bone disorders, as zoledronic acid. In vitro studies showed epithelial cells viability and growth can be altered by bisphosphonates, and may cause a deficient wound healing in BRONJ. Arrabidaea chica (H&B.) Verlot is a Bignoniaceae with wound healing properties, however, anthocyanidins, the main compounds of the plant extract, can be easily degraded under environmental conditions. This in vitro study aimed to evaluate the antimicrobial, citotoxic and citoprotective actions of A. chica hydroalcoholic extract (AC) in the presence of ZA therapy. Stability studies at 40 °C and 75% humidity conditions, from microencapsulated into arabic gum plus maltodextrin (1:1) and free crude extract samples were conducted. Keratinocytes (HaCaT), fibroblasts (PT64-04HF) and osteoblasts (MC3T3-E1) were submitted to 2 treatment protocols: zoledronic acid 10 µM (ZA) therapy during 24 h and then AC during 48 h and vice-versa; or co-treatment with both. Parameters as viability, apoptosis and caspase 3/7 activation were evaluated. Cancer cells (C4-2B) viability was determined after AC treatment. Streptococcus mutans were submitted to co-treatment with ZA and AC. Microcapsules containing AC were obtained after spray dryer processing, aliquoted and stored into climatic chamber for stability study according to ANVISA protocol (RE 01/2005). ANOVA and T Student test, a=0,05, were applied for statistical analysis. After 48 h, ZA treatment decreased viability of keratinocytes, fibroblasts and osteoblasts repectively by 34%, 47% and 51%. Co-treatments ZA and AC 5 µg mL-1 (82%, 83% and 55%), and ZA and AC 10 µg mL-1 (69%, 70% and 64%) increased cell viability. No apoptosis or caspase activation were detected on fibroblasts, however, caspase 3/7 was active on osteoblasts after ZA 48 h treatment. Concentrations higher than 10 µg mL-1 of AC were toxic to cancer cells and showed a decrease by 40% in cell viability, while no effect was seen with AC 5 or 10 µg mL-1. Higher ZA concentrations (50 µM) seemed to induce S. mutans growth, while AC showed no effect on bacteria. Finally, the studied core matherial (arabic gum plus matodextrin 1:1) was ineffective on protecting AC extract against degradation, since anthocyanidins concentration was reduced after 15 days incubation. Therefore, lower AC concentrations (5 and 10 µg mL-1) were promising on treating BRONJ wounds, as they were effective in protect epithelial cells against harmfull effects of ZA, without affecting cancer cells or S. mutans growth. Different types of core matherials must be evaluated for improving AC chemical stability. More studies are required to prove AC beneficial effects on treating BRONJ. (AU)