Mucormycosis is commonly present in recipients of hematopoietic stem cell/solid organ transplants as well as patients with haematological malignancies, diabetes mellitus, burns, trauma and low birth weight.[1-3] Rhizopus spp. is most commonly the root of invasive mucormycosis.[2, 4] The lung is easily infected because the respiratory tract is the most frequent entry route of sporangiospores. When entering the body, the spores first challenge the innate immune cells (phagocytes, neutrophils). One of the early host responses after a fungal attack is the production of high levels of reactive oxygen species (ROS; including hydrogen

peroxide [H2O2] and hydroxyl radicals).[5] Vincristine clinical trial This so-called oxidative burst might induce apoptosis of the pathogen. This apoptotic-like phenotype has been observed in yeast and Aspergillus fumigatus.[6, 7] Experimental data indicate that an apoptotic pathway is induced by a host–pathogen interaction. Moreover,

amphotericin B (AmB), the most selleck screening library active anti-Mucorales agent, has also been seen as a strong trigger for inducing cell death in the opportunistic pathogen A. fumigatus.[7] In this paper, we tried to study whether the apoptotic-like phenotype can be observed in Rhizopus arrhizus induced by H2O2 and AmB. Rhizopus arrhizus was provided by the Fungal Genetic Stock Center (Kansas, MO, USA). H2O2 (30%, m/v; Beijing Chemical works, Beijing, China) diluted in water and AmB (Sigma-Aldrich Co., St. Louis, MO, USA) dissolved in dimethyl sulfoxide were stored at 4 and Chloroambucil −80 °C, respectively. Media used in this study included potato dextrose agar (PDA) and Yeast peptone glucose medium (YPG, a rich medium containing 0.3% yeast extract, 1% peptone and 2% glucose, PH4.5). Rhizopus arrhizus isolates were grown on PDA for 5 days at 28 °C. Freshly harvested

sporangiospores (2.5 × 104 spores ml−1) were inoculated into 100 ml flasks containing 30 ml of YPG liquid medium at 30 °C with constant shaking (200 rpm). Various concentrations of H2O2 (0–25 mmol l−1) and AmB (0–8 μg ml−1) from stock solution were added to YPG at the time of spore inoculation (0 h). The growth assay was performed in 96-well plates at 30 °C using microplate reader at OD450 (Model 550, Bio-RAD, Hercules, California, USA). Viability was assessed using the XTT method (XTT, 100 μg ml−1, menadione, 25 μmol l−1) after inoculation.[8, 9] Genomic DNA was extracted from mycelia of the exponential phase after exposure to different concentrations of H2O2 (0, 1.2, 3.6 and 6.0 μmol l−1) and AmB (0, 0.25, 0.5 and 1 μg ml−1) in phosphate-buffered saline (PBS; pH 7.4) for up to 3 h. DNA was examined on a 1.5% (w/v) agarose gel in TAE buffer and visualised after ethidium bromide staining. Rhizopus arrhizus cells (2.