Plumieride as a novel anti-fungal and anti-inflammatory iridoid against superficial candidiasis in mice

Abstract

In the past few decades, there has been a notable rise in the occurrence of several types of candidiasis. Candida albicans is the most common cause of superficial fungal infections in humans. In this study, plumieride, one of the major iridoids from Plumeria obtusa L. leaves, was isolated and investigated for its potential against Candida albicans (CA)-induced dermatitis in mice. qRT-PCR was done to assess the impact of plumieride on the expression of the major virulence genes of CA. Five groups (n = 7) of adult male BALB/c mice were categorized into: group I: non-infected mice; group II: mice infected intradermally with 10⁷-10⁸ CFU/mL of CA; group III: CA-infected mice treated with standard fluconazole (50 mg/kg bwt.); group IV and V: CA-infected mice treated with plumieride (25- and 50 mg/kg. bwt., respectively). All the treatments were subcutaneously injected once a day for 3 days. Skin samples were collected on the 4th day post-inoculation to perform pathological, microbial, and molecular studies. The results of the in vitro study proved that plumieride has better antifungal activity than fluconazole, manifested by a wider zone of inhibition and a lower MIC. Plumieride also downregulated the expression of CA virulence genes (ALS1, Plb1, and Hyr1). CA-infected mice showed extensive dermatitis, confirmed by strong iNOS, TNF-α, IL-1β, and NF-κB genes or immune expressions. Whereas the treatment of CA-infected mice with plumieride significantly reduced the microscopic skin lesions and modulated the expression of all measured proinflammatory cytokines and inflammatory markers in a dose-dependent manner. Plumieride interfered with the expression of C. albicans virulence factors and modulated the inflammatory response in the skin of mice infected with CA.

Keywords: Candida albicans; Gene expression; Inflammation; Pathology; Plumieride.

Fig. 1

Chemical structure of plumieride

Fig. 2

(A) Agarose gel photo electrophoresis of conventional PCR on genetic material extracted from C. albicans as a molecular typing for detection of SAP4, ALS1, HWP1, ALS3, RAS1, Plb1, Plb1 and Hyr1 genes. Lane L: molecular weight marker (100–1000 BP). Lane Neg: negative control. Lane Pos.: positive control. (B) Bar chart showing the fold change of ALS1 expression upon plumieride treatment. (C) Bar chart showing the fold change of HYR1 expression upon plumieride treatment. Data was expressed as median (n = 7) and analyzed using the Mann-Whitney U test. ⁎⁎⁎ means significant difference at 0.001

Fig. 3

Photomicrograph of skin tissue sections in various groups. (A, B) Normal control group, (C - F) C. albicans-infected group, (G, H) FZ-treated group, (I) plumieride (25 mg/kg bwt.)-treated group, and (J) plumieride (50 mg/kg bwt.)-treated group. Note: Epidermis (black arrows), inflammatory cells (blue arrows), Congested BVs (yellow arrows). All figures are H&E stained except Fig. F is PAS stained for demonstration of C. albicans (circle)

Fig. 4

Photomicrograph of skin showing iNOS Immunostaining in diverse groups. (A) Normal control group, (B) C. albicans-infected group (C) FZ-treated group, (D) plumieride (25 mg/kg bwt.)-treated group, (E) plumieride (50 mg/kg bwt.)-treated group. Data represented as mean ± SEM (n = 7). Different superscript letters indicate significant difference at P ≤ 0.05

Fig. 5

Bar chart representing the transcript levels of (A) TNF-α, (B) IL-1β (C) NF-κB. Values are presented as mean ± SEM (n = 7). Different superscript letters indicate a significant difference at P ≤ 0.05