Antimicrob Agents Chemother. 2012 Oct 31. [Epub ahead of print]
Caspofungin kills Candida albicans by causing both cellular apoptosis and necrosis.
Hao B, Cheng S, Clancy CJ, Nguyen MH.
University of Pittsburgh and VA Pittsburgh Health System, Pittsburgh, PA.
Caspofungin exerts candidacidal activity by inhibiting cell wall (1, 3)-β-D-glucan synthesis. We investigated the physiologic mechanisms of caspofungin-induced C. albicans cell death.
Methods. Apoptosis (programmed cell death) and necrosis were studied after exposing C. albicans SC5314 to caspofungin at 0.06, 0.125 and 0.5 μg/mL (0.5x, 1x and 4x MIC, respectively) for three hours.
Caspofungin at 0.125 and 0.5 μg/mL reduced cellular viability by >50%, as measured by colony counts and methylene blue exclusion. Apoptosis and necrosis were demonstrated by annexin-V and propidium iodine staining for phosphatidylserine externalization and loss of membrane integrity, respectively. At all concentrations ofcaspofungin, 20-25% and 5-7% of C. albicans cells exhibited early apoptosis and late apoptosis/necrosis, respectively (p=NS). Necrosis, on the other hand, was significantly greater at 0.125 (43%) and 0.5 μg/mL (48%) than 0.06 μg/mL (26%; p=0.003 and 0.003, respectively). The induction of apoptosis at concentrations ≤ MIC was corroborated by DHR-123 and DHE staining (reactive oxygen species production), JC-1 staining (mitochondrial membrane potential dissipation), and TUNEL and DAPI staining (DNA damage and nuclear fragmentation). Moreover, electron microscopy of cells exposed to 0.125 μg/mL of caspofungin showed hallmark apoptotic features like chromatin margination and condensation and nuclear blebs. Apoptosis was associated with metacaspase 1 activation, as demonstrated by D2R staining.
Caspofungin exerts activity against C. albicans by directly killing cells (resulting in necrosis) and causing others to undergo programmed cell death (apoptosis). Apoptosis is initiated at subinhibitory concentrations, suggesting that strategies to target this process may augment the benefits of antifungal agents.
[PubMed – as supplied by publisher]