Combinatory effects of Dipterocarpus alatus twig emulgel: Wound-restoring, antibacterial, and anti-inflammatory activities against methicillin-resistant Staphylococcus aureus- infected mouse superficial wounds

Abstract

Dipterocarpus alatus has been used for the treatment of infectious skin diseases and ulcerative wounds in Thai traditional medicine. A major pathogen in human superficial skin infections is methicillin-resistant Staphylococcus aureus (MRSA). This study determined the wound healing, antibacterial, and anti-inflammatory activities of D. alatus twig emulgel against MRSA-infected mouse superficial skin wounds. Ethyl acetate-methanol crude extract of D. alatus twig was incorporated into emulgel at concentrations of 20 and 40 mg/g (D20 and D40) and its activity was compared to tetracycline emulgel (160 μg/g, Tetra). MRSA-infected superficial wounds demonstrated decreased skin barrier strength, increased transepidermal water loss (TEWL), and mast cell accumulation. Expression of toll-like receptor 2 (TLR-2), NF-κβ, TNFα, IL-1β, IL-6 and IL-10 genes were induced after MRSA infection. Daily application of 100 μL of D20 or D40 for 9 days restored skin barrier strength and TEWL while reducing mast cell and MRSA numbers compared to the non-treated group (MRSA-NT). The wounds treated with D20 and D40 were entirely healed on day 9. Expression of TLR-2 and cytokine-related genes NF-κβ, TNFα, IL-1β, IL-6 and IL-10 were normalized by treatment with either D20 or D40. Therefore, emulgel containing 20 to 40 mg/g ethyl acetate-methanol crude D. alatus twig extract is a good candidate for development as a topical formulation for MRSA-infected ulcerated wounds.

Keywords: Cytokine; Dipterocarpus alatus; MRSA; Resin tree; Superficial infection; Tape stripping; Toll-like receptor 2.

Fig. 1

The wound appearance on the mouse skin.

Fig. 2

The skin barrier strength and transepidermal water loss (TEWL) value of the wounds. *p < 0.05 VS Control on the same day (n = 5).

Fig. 3

The number of mast cells and toluidine blue O staining histology of the wounds. A) *p < 0.05 VS Control on the same day (n = 5). B) The red arrows indicate mast cells (violet dot) and the scale bar is 50 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

The effects of D. alatus twig emulgel on the mRNA expression of A) toll-like receptor 2 (TLR-2) and pro-inflammatory cytokines: B) NF-κB, C) TNF-α, D) IL-1β, E) IL-6, and F) IL-10. *p < 0.05 VS Control on the same day (n = 5); ^#p < 0.05 VS MRSA-NT on the same day (n = 5).