Cellular apoptosis: An alternative mechanism of action for caspofungin against Candida glabrata

Abstract

Background and Purpose: Although the mechanism of action for echinocandins is
known, the physiological mechanisms by which these antifungal agents cause cell death
via the classical apoptotic pathways are not well-defined yet. Regarding this, the present
study aimed to evaluate the mechanisms of caspofungin-induced Candida glabrata cell
death.
Materials and Methods: For the purpose of the study, the minimum inhibitory
concentration (MIC) of caspofungin against C. glabrata (ATCC 90030) was determined
using the broth microdilution reference method (CLSI M27-A2 and M27-S4). The
annexin V and propidium iodide staining was performed to determine the way through
which caspofungin acts against C. glabrata (i.e., through the induction of apoptosis
and/or necrosis). Additionally, the possible effect of caspofungin on inducing the
expression of two apoptotic genes, namely MCA1 and NUC, was studied using the realtime polymerase chain reaction assay.
Results: According to the obtained MIC value (0.5 µg/mL), C. glabrata, exposed to
0.25, 0.5, and 1 µg/mL of caspofungin, exhibited the features of late apoptosis/necrosis
after 18 h of incubation. Furthermore, the use of 0.25, 0.5, and 1 µg/ml caspofungin
induced apoptosis (early/late) in 14.67%, 17.04%, and 15.89% of the cells, respectively.
The results showed a significant difference between the percentages of early-apoptotic
cells at the three concentrations (P<0.05). In addition, the rate of necrosis was
significantly greater than that of apoptosis in response to caspofungin. Accordingly,
necrosis occurred in 71.26%, 71.26%, and 61.26% of the cells at the caspofungin
concentrations of 0.25, 0.5, and 1 µg/mL, respectively (P<0.05). The analysis of the data
in the REST software demonstrated a significant increase in the expression of MCA1 and
NUC1 genes (P<0.05).
Conclusion: As the findings of the present study indicated, caspofungin promoted both
necrosis and apoptosis of C. glabrata cells at concentrations higher than or equal to the
MIC value.