Pterostilbene complexed with cyclodextrin exerts antimicrobial and anti-inflammatory effects

Abstract

Resveratrol (RES) is a natural polyphenol with potential as an adjunctive therapeutic modality for periodontitis. However, its inferior pharmacokinetics and toxicity concerns about its commonly used solvent dimethyl sulfoxide (DMSO) hinder translation to clinical applicability. Our study aimed to investigate the comparative antimicrobial properties of RES and its analogues (pterostilbene [PTS], oxyresveratrol [OXY] and piceatannol [PIC]), utilizing 2-hydroxypropyl-β-cyclodextrin (HPβCD) as a solubiliser, which has a well-documented safety profile and FDA approval. These properties were investigated against Fusobacterium nucleatum, a key periodontal pathogen. PTS demonstrated the most potent antibacterial effects in HPβCD, with MIC > 60-fold lower than that of RES, OXY and PIC. In addition, PTS inhibited F. nucleatum biofilm formation. PTS exerted antimicrobial effects by eliciting leakage of cellular contents, leading to loss of bacterial cell viability. PTS also conferred immunomodulatory effects on F. nucleatum-challenged macrophages via upregulation of antioxidant pathways and inhibition of NF-κB activation. Given the superior antimicrobial potency of PTS against F. nucleatum compared to RES and other analogues, and coupled with its immunomodulatory properties, PTS complexed with HPβCD holds promise as a candidate nutraceutical for the adjunctive treatment of periodontitis.

Figure 1

Chemical structures of (a) Resveratrol (RES), (b) Piceatannol (PIC), (c) Oxyresveratrol (OXY), and (d) Pterostilbene (PTS).

Figure 2

Quantification of F. nucleatum biofilm biomass. The amount of F. nucleatum biofilm formed in the presence of PTS (complexed with HPβCD) at the indicated concentrations over 48 hours was determined by crystal violet assay, and expressed as percentage biomass of control (untreated) biofilm at 24 hours. Results are expressed as the means ± SD of triplicates from three independent experiments. ***p < 0.001 compared to control group.

Figure 3

PTS triggered leakage of cellular contents. The amounts of extracellular (a) proteins and (b) nucleic acid were measured at 0, 2, 4 and 6 hours following treatment of F. nucleatum with PTS. (c) Viability of F. nucleatum following treatment with PTS was determined by ATP assay. Results are expressed as the means ± SD of triplicates from three independent experiments. *p < 0.05, ***p < 0.001 compared to the respective control (untreated) bacteria at the respective time points.

Figure 4

Determination of non-cytotoxic concentrations of PTS. Viability of RAW 264.7 macrophages following treatment with PTS at the indicated doses was determined by MTS assay. Cell viability was expressed as percentage of the untreated control group. Results are expressed as the means ± SD of triplicates from three independent experiments. **p < 0.01, ***p < 0.001.

Figure 5

PTS elicited anti-inflammatory and antioxidant effects in macrophages. (a) Cellular NF-κB activity was determined by reporter assay. The expression of (b) IL-1β, (c) IL-6, (d) TNF-α, (e) IL-10, (f) HO-1, (g) NDQ, and (h) catalase were determined by qPCR. Results are expressed as the means ± SD of triplicates from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001.