Inhibitory effect of Thai propolis on human osteoclastogenesis

Effects of systemic Anatolian propolis administration on a rat-irradiated osteoradionecrosis model

OBJECTIVE

Radiotherapy after head and neck cancer is associated with the risk of osteonecrosis development. This study aims to investigate the effectiveness of systemic propolis application to prevent the disease as it has no definite treatment protocol despite the proposed treatment methods and significantly decreases individuals' quality of life.

METHODOLOGY

In total, 29 male Wistar-Albino rats were divided into control, 35 Gy irradiation (Group 1), 35 Gy irradiation+100 mg/kg/ml propolis administration (Group 2), and 35 Gy irradiation+200 mg/kg/ml propolis administration groups (Group 3). Propolis was first applied on the day after radiotherapy, except for the control group. Right first and second molars were extracted from all rats three weeks following radiotherapy. Samples were collected seven weeks after radiotherapy. Osteoblast and osteoclast counts were calculated by histomorphometric analysis. Immunohistochemical analysis determined bone morphogenic protein-2 (BMP-2) and transforming growth factor beta-3 (TGFβ-3).

RESULTS

Group comparison found non-significant differences regarding osteoblast (p=0.130) and osteoclast (p=0.063) counts. However, Group 1 showed the lowest mean osteoblast (OBL: 82.63 [±13.10]) and highest mean osteoclast counts (OCL: 12.63 [±5.55]). OBL/OCL ratio showed significant differences between groups (p=0.011). Despite the significant difference between the Control and Groups 1 (p=0.006) and 2 (p=0.029), Group 3 showed a non-significant difference (p=0.091). For BMP-2 and TGFB3, the control group showed significant differences with the other two groups (p<0.001), except for Group 3.

CONCLUSION

Anatolian propolis showed beneficial effects in a radiotherapy-mediated osteonecrosis model, highlighting its potential as a promising intervention.

An in vitro anti-inflammatory effect of Thai propolis in human dental pulp cells

OBJECTIVE

To explore the potential for development of Thai propolis extract as a pulp capping agent to suppress pulpal inflammation from dental pulp infections. This study aimed to examine the anti-inflammatory effect of the propolis extract on the arachidonic acid pathway, activated by interleukin (IL)-1β, in cultured human dental pulp cells.

METHODOLOGY

Dental pulp cells, isolated from three freshly extracted third molars, were first characterized for their mesenchymal origin and treated with 10 ng/ml of IL-1β in the presence or absence of non-toxic concentrations of the extract from 0.08 to 1.25 mg/ml, as determined by the PrestoBlue cytotoxic assay. Total RNA was harvested and analyzed for mRNA expressions of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2). Western blot hybridization was performed to investigate COX-2 protein expression. Culture supernatants were assayed for released prostaglandin E2 levels. Immunofluorescence was conducted to determine involvement of nuclear factor-kappaB (NF-kB) in the inhibitory effect of the extract.

RESULTS

Stimulation of the pulp cells with IL-1β resulted in the activation of arachidonic acid metabolism via COX-2, but not 5-LOX. Incubation with various non-toxic concentrations of the propolis extract significantly inhibited upregulated COX-2 mRNA and protein expressions upon treatment with IL-1β (p<0.05), resulting in a significant decrease in elevated PGE2 levels (p<0.05). Nuclear translocation of the p50 and the p65 subunits of NF-kB upon treatment with IL-1β was also blocked by incubation with the extract.

CONCLUSIONS

Upregulated COX-2 expression and enhanced PGE2 synthesis upon treatment with IL-1β in human dental pulp cells were suppressed by incubation with non-toxic doses of Thai propolis extract via involvement of the NF-kB activation. This extract could be therapeutically used as a pulp capping material due to its anti-inflammatory properties.

Application of Propolis in Protecting Skeletal and Periodontal Health-A Systematic Review

Chronic inflammation and oxidative stress are two major mechanisms leading to the imbalance between bone resorption and bone formation rate, and subsequently, bone loss. Thus, functional foods and dietary compounds with antioxidant and anti-inflammatory could protect skeletal health. This review aims to examine the current evidence on the skeletal protective effects of propolis, a resin produced by bees, known to possess antioxidant and anti-inflammatory activities. A literature search was performed using Pubmed, Scopus, and Web of Science to identify studies on the effects of propolis on bone health. The search string used was (i) propolis AND (ii) (bone OR osteoporosis OR osteoblasts OR osteoclasts OR osteocytes). Eighteen studies were included in the current review. The available experimental studies demonstrated that propolis could prevent bone loss due to periodontitis, dental implantitis, and diabetes in animals. Combined with synthetic and natural grafts, it could also promote fracture healing. Propolis protects bone health by inhibiting osteoclastogenesis and promoting osteoblastogenesis, partly through its antioxidant and anti-inflammatory actions. Despite the promising preclinical results, the skeletal protective effects of propolis are yet to be proven in human studies. This research gap should be bridged before nutraceuticals based on propolis with specific health claims can be developed.

The use of propolis in dentistry, oral health, and medicine: A review

BACKGROUND

Propolis is a resinous product that is collected from plants by bees to cover holes and crevices in their hives. Propolis has potent antibacterial, antiviral, anti-inflammatory, wound healing, and anticancer properties. Propolis has been used therapeutically by humans for centuries, including the treatment of dental caries and mouth infections.

HIGHLIGHT

This review article attempts to analyze the potential use of propolis in general dentistry and oral health management.

CONCLUSION

Propolis is potentially useful in dentistry and oral health management based on available in vitro, in vivo, and ex vivo studies, as well as human clinical trials.

Preservation of the viability and gene expression of human periodontal ligament cells by Thai propolis extract

BACKGROUND/AIM

Success of tooth replantation depends on the quality and quantity of periodontal ligament (PDL) cells. The aims of this study were to evaluate Thai propolis extract as a storage medium for maintaining PDL cell viability and preserving gene expressions in PDL tissues.

MATERIALS AND METHODS

PDL cells from human premolars were tested for cytotoxicity of the extract by PrestoBlue assay to determine a non-toxic concentration. Subsequently, 96 freshly extracted premolars were allocated into different treatment groups. Control groups were freshly extracted premolars or they had been stored dry for 12 hours. Experimental avulsed teeth were created by leaving them air-dried for 30 minutes immediately after extraction, then they were immersed in Thai propolis extract, HBSS or milk for 3, 6 and 12 hours. After tooth storage, the remaining PDL cells were determined for their cell viability. RNA isolated from PDL tissues of three premolars treated similarly was analysed for periostin and S100A4 expressions using RT-qPCR.

RESULTS

Thai propolis extract at 0.625 mg mL^-1 promoted the greatest PDL cell viability. Tooth storage in 0.625 mg mL^-1 Thai propolis extract, HBSS or milk showed no difference in maintaining cell viability. Periostin mRNA level was preserved by Thai propolis extract. Expression of S100A4 mRNA in PDL tissues stored in all tested media was dampened.

CONCLUSIONS

PDL cells from mock avulsed teeth stored in 0.625 mg mL^-1 Thai propolis extract for 3, 6 and 12 hours remained viable and the expression of periostin was preserved. This study suggests this extract as an alternative for a tooth storage medium for up to 12 hours. However, transporting an avulsed tooth in a storage medium for extended extra-oral time might affect the PDL cell phenotypes.

Effect of ScLL and 15d-PGJ2 on viability and cytokine release in LPS-stimulated fibroblasts: an in vitro study

This study evaluated the effect of a cyclopentenone-type PG, 15-Deoxy-Δ12,14-PG J2 (15d-PGJ2), and lectin (ScLL) on the viability of human gingival fibroblasts (HGFs), and on IL-6 and TGFβ-1 release by these fibroblasts, stimulated with lipopolysaccharide (LPS). HGFs were stimulated with LPS 10 μg/ml and treated with 15d-PGJ2 1 and 2 μg/ml, and ScLL 2 and 5 μg/ml, for 1 and 3h, and then evaluated for viability by MTT assay. Supernatant was collected to detect IL-6 and TGFβ-1 release, by ELISA. Positive control was cells kept in Dulbecco's Modified Eagle's Medium, and negative control was those kept in LPS. Data were analyzed by ANOVA and Dunnett's test (α = 0.05). No significant difference was found in viability among experimental groups at 1h (p > 0.05). Percentage of ScLL 5 µg/ml viable cells was similar to that of positive control at evaluated periods (p > 0.05), whereas the other groups had lower levels than the positive control (p < 0.05). IL-6 release was statistically higher for ScLL 5 μg/ml and 15d-PGJ2 2 µg/ml at 1h, compared with the other treated groups and positive control (p < 0.05). No significant differences were found among the groups at 3h (p > 0.05), except for ScLL 2 µg/ml and 15d-PGJ2 1 µg/ml, which showed lower IL-6 release compared with that of negative control (p < 0.05). No significant difference was found among the groups for TGFβ-1 release (p > 0.05). Results indicated that ScLL 5 μg/ml did not interfere in viability, and ScLL 2 µg/ml and 15d-PGJ2 1 µg/ml demonstrated reduced IL-6 release. Tested substances had no effect on TGFβ-1 release.

Anti-inflammatory and anti-resorptive efficacy of adrenergic blockers on late replanted rat incisors

BACKGROUND/AIM

In addition to their anti-inflammatory and anti-osteoclastogenesis properties, adrenergic blockers may also have promising anti-resorptive effects that can prevent root resorption when teeth are replanted because of avulsion. The aim of this study was to investigate the effects of phentolamine (Ph) and propranolol (Pr) in gels on the repair process of late replanted rat incisors. A further aim was to evaluate the biocompatibility of both drugs to human periodontal ligament fibroblasts (HPDLFs).

MATERIALS AND METHODS

Forty-eight maxillary right incisors were extracted from male Wistar rats, stored in paper napkins for 60 minutes, and randomly allocated to one of eight groups (n = 6). The root canal, root surface, and alveolus were treated with 0.75 µg/mL Ph gel (Ph0.75), 10 µg/mL Ph gel (Ph10), 100 µg/mL Ph gel (Ph100), 2.5 µg/mL Pr gel (Pr2.5), 10 µg/mL Pr gel (Pr10), 100 µg/mL Pr gel (Pr100), or sodium carboxymethylcellulose gel (CMC) before replantation. In the control group (CH), only the root canal was treated with calcium hydroxide paste. Thirty days following surgery, the animals were euthanized, and the right hemimaxilla was removed to perform micro-CT and histomorphometric analysis to determine osteoclastic activity. Ethanolic solutions of Ph10 and Pr10 were selected based on the in vivo study, and the viability of HPDLFs stimulated with lipopolysaccharide was determined by MTT assays.

RESULTS

The micro-CT and histomorphometric analysis revealed no significant differences among the treatments (P > .05). The presence of active osteoclasts was significantly decreased in the Ph10 and Pr10 groups (P < .05). Ph10 and Pr10 produced statistically similar cell survival rates compared to the control group (P > .05).

CONCLUSIONS

Ph10 and Pr10 significantly decreased osteoclastogenesis in delayed replanted rat teeth and were not cytotoxic toward HPDLFs.