Fig 1.
The structure of KPA.
Table 1.
The MICs values of KPA against different Candida species.
Fig 2.
The time-killing curves of KPA and AMB against wild type C. albicans strain SC5314.
Data represent mean values and error bars show standard deviations.
Fig 3.
Effect of KPA on intracellular ROS accumulation.
(A) The relative fluorescence intensity of treated cells stained by DCFH-DA was measured by a BioTek Synergy2 spectrofluorophotometer. Data represent mean values and error bars show standard deviations. * means statistically significant difference (P < 0.05). (B) The fluorescence microscopic observation of C. albicans SC5314 with different treatments stained with DCFH-DA. Bar, 50μm.
Fig 4.
Effect of KPA on the mitochondrial function.
(A) The fluorescence microscopic observation of C. albicans SC5314 with different treatments stained with Rh123. Bar, 50μm. (B) Change in relative fluorescence intensity of treated SC5314 cells was monitored by spectrofluorophotometry. (C) Intracellular ATP was extracted from cells treated with KPA or not and determined using an ATP assay kit. Each column in (B) and (C) represents the mean values of each group, and error bars show standard deviations. * means statistically significant difference (P < 0.05).
Fig 5.
Effect of different antioxidant Tu, VC and VE on the fungicidal activity of KPA.
SC5314, pretreated with or without Tu (A), VC (B) or VE (B) was exposed to 16 μg/mL of KPA for 3 h at 30°C. The number of viable cells was then determined by colony counting method. The bars indicate standard deviations. * means statistically significant difference (P < 0.05).
Fig 6.
Effect of KPA on the cell membrane of C. albicans.
(A) Effect of KPA on the intracellular trehalose content. (B) Effect of KPA on the extracellular trehalose content. (C) Effect of KPA on the change of membrane permeabilization by PI staining. (D) Effect of KPA on the ergosterol content. Data in (A), (B), (C) and (D) represent mean values, and bars are standard deviations. * means statistically significant difference (P < 0.05). The ultrastructure of KPA-treated C. albicans cells was shown in (E) and (F). As indicated by the white arrow in (E) and (F), comparing with control cells in (E), cell membrane destruction and disintegration were observed in KPA-treated cells. Bars, 500nm.
Fig 7.
The action model of KPA in C. albicans.
KPA stimulated mitochondria to generate more ROS. Excessive ROS in turn damage the function of mitochondria. The cellular membrane permeability barrier can be broken by the elevated ROS or KPA directly. Mitochondria dysfunction, ROS accumulation and membrane destruction all contribute to C. albicans cell death.