Oceanapiside, a Marine Natural Product, Targets the Sphingolipid Pathway of Fluconazole-Resistant Candida glabrata

Abstract

Oceanapiside (OPS), a marine natural product with a novel bifunctional sphingolipid structure, is fungicidal against fluconazole-resistant Candida glabrata at 10 μg/mL (15.4 μM). The fungicidal effect was observed at 3 to 4 h after exposure to cells. Cytological and morphological studies revealed that OPS affects the budding patterns of treated yeast cells with a significant increase in the number of cells with single small buds. In addition, this budding morphology was found to be sensitive in the presence of OPS. Moreover, the number of cells with single medium-sized buds and cells with single large buds were decreased significantly, indicating that fewer cells were transformed to these budding patterns, suggestive of inhibition of polarized growth. OPS was also observed to disrupt the organized actin assembly in C. glabrata, which correlates with inhibition of budding and polarized growth. It was also demonstrated that phytosphingosine (PHS) reversed the antifungal activity of oceanapiside. We quantified the amount of long chain-bases (LCBs) and phytoceramide from the crude extracts of treated cells using LC-ESI-MS. PHS concentration was elevated in extracts of cells treated with OPS when compared with cells treated with miconazole and amphotericin B. Elevated levels of PHS in OPS-treated cells confirms that OPS affects the pathway at a step downstream of PHS synthesis. These results also demonstrated that OPS has a mechanism of action different to those of miconazole and amphotericin B and interdicts fungal sphingolipid metabolism by specifically inhibiting the step converting PHS to phytoceramide.

Oceanalin B, a Hybrid α,ω-Bifunctionalized Sphingoid Tetrahydroisoquinoline β-Glycoside from the Marine Sponge Oceanapia sp.

“…Confirm that your intended meaning is retained Confirm that your intended meaning is retained with a minimum inhibitory concentration (MIC) of 25 µg/mL, which is comparable to the activity of oceanalin A (MIC = 30 µg/mL) [4] when tested under similar conditions. Due to its similarity in the structure of oceanapiside as a α,ω-bipolar compound with sphingolipid units on the ends of the molecule, oceanalin B may target the sphingolipid pathway of C. glabrata as demonstrated by the mechanism of action of oceanapiside [11].…”

“…Some of these substances are glycosylated with a glucose or galactose residue [1][2][3][4][5][6]8]. α,ω-Bipolar sphingolipids substances exhibit antifungal [4,5,10,11], antimicrobial [1] and cytotoxic activity against mouse Ehrlich carcinoma cells [1]; DNAdamaging activity [6] and inhibition of protein kinase C activity [9]. In continuation of our search for new antifungal agents against the pathogenic fluconazole-resistant yeast Candida glabrata, we isolated oceanalin A (2) [4], a unique α,ω-bipolar compound containing isoquinoline and sphingolipid units on the ends of the molecule.…”

Marine Compounds with Anti-Candida sp. Activity: A Promised “Land” for New Antifungals

“…Probably, the inhibition of polarized growth promoted by OPS is due to the disruption of organized actin. Phytosphingosine (PHS) was able to reverse OPS activity which indicates that it blocks fungal sphingolipid metabolism by specifically inhibiting the conversion step of PHS to phytoceramide [ 58 ]. Similarly, marine polyunsaturated fatty acids inhibit biofilm formation of C. albicans and Candida dubliniensis .…”

Barringtonia asiatica Seed Extract Induces G1 Cell Cycle Arrest in Saccharomyces cerevisiae and Exhibits Cytotoxicity in A2780 Human Ovarian Cancer Cells

“…Methylene blue dye (0.1 mg/mL in 0.1 M phosphate buffer with pH 7.2) was added to the cells and incubated for 5 min at RT. Five µL of the mixture was mounted onto a glass slide and was observed under a microscope [34]. According to yeast budding patterns, the cells were classified and counted, namely unbudded cells, cells with a single small bud, cells with a single medium sized-bud, and cells with a single large bud [35].…”

“…A budding yeast experiment using methylene blue dye was performed to determine which cell cycle stage is targeted by B. asiatica seed extract. Methylene blue is a basic dye that can only penetrate nonviable cells producing blue fluorescence, while the absence of the blue coloration indicates viable cell [34]. The results showed that B. asiatica seed extracts caused a high accumulation of single dead cells at 84.3%…”