Browsing by Author "Shahina, Zinnat"

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Open Access
Anti-candida and Anti-virulence Activity of Essential Oils and Their Components
(Faculty of Graduate Studies and Research, University of Regina, 2021-10) Shahina, Zinnat; Dahms, Tanya; Suh, Dae-Yeon; Babu, Mohan; Cameron, Andrew; Lee, Samuel A.
Candida albicans is one of the most common fungi associated with lifethreatening infections. Treatment of the associated infections is often ineffective in the light of resistance, and so there is an urgent need to discover novel antifungals. Rather than killing the fungal cells, which requires quite high specificity and can lead to the emergence of further resistance, inhibiting growth and virulence factors in fungal cells represents a good alternative for the development of new antifungal drugs. Recently, there has been a resurged interest in essential oils and their active components, in relation to their pharmacological properties. The primary objective of this research was to evaluate the antifungal activity of cinnamon bark and rosemary essential oils, along with its major components cinnamadehyde, and 1,8-cineole, α-pinene, respectively, and two other common essential oil components, namely eugenol and citral, against C. albicans. Despite many reports on the antimicrobial activities of essential oils, the results have been diverse and the evaluation methods inconsistent. At higher essential oil concentrations, reactive oxygen species were generated, impacting a wide range of processes including cell membrane depolarization, vacuolar segregation, mitochondrial dysfunction, cell-cycle checkpoint deficiency, and mitotic catastrophe, which resulted in C. albicans death. At lower fractional MICs, essential oils had a ROS-independent response that inhibited mycelial growth and biofilm formation, which may be attributable to defects at the cell membrane. However, microtubule inhibition also plays a role in limiting hyphal growth. I explored the microtubule defects and how they relate to Kar3p, a member of the kinesin-14 family shown to be linked to microtubule stability. Interestingly, both tubulin and Kar3 protein was delocalized with essential oil components exposure at levels for which endogenous ROS levels were normal. I further demonstrate that the level of Kar3 is associated with resistance and susceptibility of C. albicans to essential oil components in both liquid and on solid growth media. All mutant strains grown on hyphae-inducing media in the presence of essential oil components exhibited an enhanced tendency to form pseudohyphal cells, a common phenotype for the homozygous and heterozygous deletion strains. Towards these ends, microtubule defects were linked with theoretical binding between essential oil components and α-tubulin and Kar3p adjacent to cofactor binding sites, consistent with experimentally observed hyphal defects and biofilm inhibition. This study for the first time uncovers a new mode of essential oilmediated microtubule defects, which does not follow the known mechanisms of conventional microtubule inhibition. The essential oil components appear to impact C. albicans eventually giving rise to psuedohyphal formation, microtubule loss, hyphal and biofilm reduction. Since those essential oil components impact multiple Candida targets, they should be less susceptible to resistance. Further, many components showed antivirulence, and may represent an effective approach for inhibiting Candida, especially in the context of physically preventing Candida from entering its host through catheters and prosthetics.
Open Access
Candida albicans Reactive Oxygen Species (ROS)-Dependent Lethality and ROS-Independent Hyphal and Biofilm Inhibition by Eugenol and Citral.
(American Society for Microbiology, 2022-11-17) Shahina, Zinnat; Ndlovu, Easter; Persaud, Omkaar; Sultana, Taranum; Dahms, Tanya E.S.
Candida albicans is part of the normal human flora but is most frequently isolated as the causative opportunistic pathogen of candidiasis. Plant-based essential oils and their components have been extensively studied as antimicrobials, but their antimicrobial impacts are poorly understood. Phenylpropenoids and monoterpenes, for example, eugenol from clove and citral from lemon grass, are potent antifungals against a wide range of pathogens. We report the cellular response of C. albicans to eugenol and citral, alone and combined, using biochemical and microscopic assays. The MICs of eugenol and citral were 1,000 and 256 μg/mL, respectively, with the two exhibiting additive effects based on a fractional inhibitory concentration index of 0.83 ± 0.14. High concentrations of eugenol caused membrane damage, oxidative stress, vacuole segregation, microtubule dysfunction and cell cycle arrest at the G1/S phase, and while citral had similar impacts, they were reactive oxygen species (ROS) independent. At sublethal concentrations (1/2 to 1/4 MIC), both oils disrupted microtubules and hyphal and biofilm formation in an ROS-independent manner. While both compounds disrupt the cell membrane, eugenol had a greater impact on membrane dysfunction. This study shows that eugenol and citral can induce vacuole and microtubule dysfunction, along with the inhibition of hyphal and biofilm formation.
Open Access
Cinnamomum zeylanicum bark essential oil induces cell wall remodelling and spindle defects in Candida albicans
(BMC, 2018-02-09) Shahina, Zinnat; El-Ganiny, Amira M.; Minion, Jessica; Whiteway, Malcolm; Sultana, Taranum; Dahms, Tanya E.S.
Cinnamon (Cinnamomum zeylanicum) bark extract exhibits potent inhibitory activity against Candida albicans but the antifungal mechanisms of this essential oil remain largely unexplored.
Open Access
Cinnamon leaf and clove essential oils are potent inhibitors of Candida albicans virulence traits.
(MDPI, 2022-10-08) Shahina, Zinnat; Molaeitabari, Ali; Sultana, Taranum; Dahms, Tanya E.S.
Plant-based essential oils are promising anti-virulence agents against the multidrug-resistant opportunistic pathogen Candida albicans. Gas chromatography–mass spectrometry of Cinnamomum zeylanicum (cinnamon) leaf and Eugenia caryophyllus (clove) flower bud essential oils revealed eugenol (73 and 75%, respectively) as their major component, with β-caryophyllene, eugenyl acetate, and α-humulene as common minor components. Cinnamon leaf and clove essential oils had minimum inhibitory concentrations of 600 and 500 µg/mL, respectively against the C. albicans RSY150 reference strain and 1000 and 750 µg/mL, respectively for the clinical reference strain ATCC 10231. The combined oils are additive (FICI = 0.72 ± 0.16) and synergistic (0.5 ± 0.0) against RSY150 and the clinical reference strain, respectively. Mycelial growth was inhibited by sublethal concentrations of either essential oil, which abolished colony growth. At half of the lowest combined lethal concentration for the two oils, the yeast-to-hyphal transition and mycelial growth was potently inhibited. Mutant strains als1Δ/Δ, als3Δ/Δ, hwp1Δ/HWP1+, and efg1Δ/Δ were sensitive to either or both oils, especially efg1Δ/Δ. In conclusion, oils of cinnamon leaf and clove and their combination significantly impact C. albicans virulence by inhibiting hyphal and mycelial growth.
Open Access
Correlative atomic force microscopy quantitative imaging- laser scanning confocal microscopy quantifies the impact of stressors on live cells in real-time
(Nature Research, 2018-05-29) Bhat, Supriya V.; Sultana, Taranum; Körnig, André; McGrath, Seamus G. K.; Shahina, Zinnat; Dahms, Tanya E.S.
There is an urgent need to assess the effect of anthropogenic chemicals on model cells prior to their release, helping to predict their potential impact on the environment and human health. Laser scanning confocal microscopy (LSCM) and atomic force microscopy (AFM) have each provided an abundance of information on cell physiology. In addition to determining surface architecture, AFM in quantitative imaging (QI) mode probes surface biochemistry and cellular mechanics using minimal applied force, while LSCM offers a window into the cell for imaging fluorescently tagged macromolecules. Correlative AFM-LSCM produces complimentary information on different cellular characteristics for a comprehensive picture of cellular behaviour. We present a correlative AFM-QI-LSCM assay for the simultaneous real-time imaging of living cells in situ, producing multiplexed data on cell morphology and mechanics, surface adhesion and ultrastructure, and real-time localization of multiple fluorescently tagged macromolecules. To demonstrate the broad applicability of this method for disparate cell types, we show altered surface properties, internal molecular arrangement and oxidative stress in model bacterial, fungal and human cells exposed to 2,4-dichlorophenoxyacetic acid. AFM-QI-LSCM is broadly applicable to a variety of cell types and can be used to assess the impact of any multitude of contaminants, alone or in combination.
Open Access
Exposure to sub-lethal 2,4-dichlorophenoxyacetic acid arrests cell division and alters cell surface properties in Escherichia coli
(Frontiers Media, 2018-02-01) Bhat, Supriya V.; Kamencic, Belma; Körnig, André; Shahina, Zinnat; Dahms, Tanya E.S.
Escherichia coli is a robust, easily adaptable and culturable bacterium in vitro, and a model bacterium for studying the impact of xenobiotics in the environment. We have used correlative atomic force – laser scanning confocal microscopy (AFM-LSCM) to characterize the mechanisms of cellular response to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). One of the most extensively used herbicides world-wide, 2,4-D is known to cause hazardous effects in diverse non-target organisms. Sub-lethal concentrations of 2,4-D caused DNA damage in E. coli WM1074 during short exposure periods which increased significantly over time. In response to 2,4-D, FtsZ and FtsA relocalized within seconds, coinciding with the complete inhibition of cell septation and cell elongation. Exposure to 2,4-D also resulted in increased activation of the SOS response. Changes to cell division were accompanied by concomitant changes to surface roughness, elasticity and adhesion in a time-dependent manner. This is the first study describing the mechanistic details of 2,4-D at sub-lethal levels in bacteria. Our study suggests that 2,4-D arrests E. coli cell division within seconds after exposure by disrupting the divisome complex, facilitated by dissipation of membrane potential. Over longer exposures, 2,4-D causes filamentation as a result of an SOS response to oxidative stress induced DNA damage.
Open Access
Key essential oil components delocalize Candida albicans Kar3p and impact microtubule structure
(Elsevier, 2023-04-03) Shahina, Zinnat; Yennamalli, Ragothaman M.; Dahms, Tanya E.S.
Treatment of Candida albicans associated infections is often ineffective in the light of resistance, with an urgent need to discover novel antimicrobials. Fungicides require high specificity and can contribute to antifungal resistance, so inhibition of fungal virulence factors is a good strategy for developing new antifungals.
Open Access
Rosemary essential oil and its components 1,8-cineole and α-pinene induce ROS-dependent lethality and ROS-independent virulence inhibition in Candida albican
(Public Library of Science, 2022-11-16) Shahina, Zinnat; Al Homsi, Raymond; Price, Jared D.W.; Whiteway, Malcolm; Sultana, Taranum; Dahms, Tanya E.S.
The essential oil from Rosmarinus officinalis L., a composite mixture of plant-derived secondary metabolites, exhibits antifungal activity against virulent candidal species. Here we report the impact of rosemary oil and two of its components, the monoterpene α-pinene and the monoterpenoid 1,8-cineole, against Candida albicans, which induce ROS-dependent cell death at high concentrations and inhibit hyphal morphogenesis and biofilm formation at lower concentrations. The minimum inhibitory concentrations (100% inhibition) for both rosemary oil and 1,8-cineole were 4500 μg/ml and 3125 μg/ml for α-pinene, with the two components exhibiting partial synergy (FICI = 0.55 ± 0.07). At MIC and 1/2 MIC, rosemary oil and its components induced a generalized cell wall stress response, causing damage to cellular and organelle membranes, along with elevated chitin production and increased cell surface adhesion and elasticity, leading to complete vacuolar segregation, mitochondrial depolarization, elevated reactive oxygen species, microtubule dysfunction, and cell cycle arrest mainly at the G1/S phase, consequently triggering cell death. Interestingly, the same oils at lower fractional MIC (1/8-1/4) inhibited virulence traits, including reduction of mycelium (up to 2-fold) and biofilm (up to 4-fold) formation, through a ROS-independent mechanism.