Abstract
Objective: To characterize the antifungal activity of methanolic leaf extract of Calotropis gigantea alone or in combination with amphotericin B against invasive pulmonary aspergillosis in mice.
Methods: GC/MS was used for analysis of active constituents of Calotropis gigantea extract. Spore germination assay and broth micro-dilution method were used to determine antifungal potential of Calotropis gigantea/amphotericin B against Aspergillus fumigatus. Neutropenic mice were randomly assigned into 5 groups: group 1 was neutropenic (control); group 2 was infected with Aspergillus fumigatus; group 3 was infected with Aspergillus fumigatus, and treated with Calotropis gigantea extract; group 4 was infected with Aspergillus fumigatus and treated with amphotericin B; group 5 was infected with Aspergillus fumigatus and treated with both Calotropis gigantea extract and amphotericin B. Fresh lung tissues were histopathologically examined. Fungal burden and gliotoxin concentration were evaluated in lung tissues. Catalase, superoxide dismutase, and malondialdehyde content were determined in lung tissues. Myeloperoxidase, tumor necrosis factor-alpha, interleukin-1, and interleukin-17 were also estimated by the sandwich enzyme-linked immuno-sorbent assay.
Results: Calotropis gigantea/amphotericin B had a minimum inhibitory concentration and minimum fungicidal concentration of 80 and 160 mu g/mL, respectively, for Aspergillus fumigatus. Additionally, Calotropis gigantea/amphotericin B significantly reduced lung fungal burden by 72.95% and inhibited production of gliotoxin in lung tissues from 6 320 to 1 350 mu g/g lung. Calotropis gigantea/amphotericin B reduced the oxidative stress of the lung via elevating the activity of antioxidant enzymes and decreasing the levels of lipid peroxidation. Myeloperoxidase activity and the production of pro-inflammatory cytokines were also significantly reduced. Scanning electron microscopy revealed deteriorations in the hyphae ultrastructure in Calotropis gigantea/amphotericin B treated Aspergillus fumigatus and leak of cellular components after damage of the cell wall. In vivo study revealed the suppression of lung tissue damage in mice of invasive pulmonary aspergillosis, which was improved with Calotropis gigantea/amphotericin B compared to the control group.
Conclusions: Calotropis gigantea/amphotericin B is a promising treatment to reduce lung fungal burden and to improve the drugs' therapeutic effect against invasive pulmonary aspergillosis.