Abstract
Gliotoxin (GT) and fumagillin (FUM) are mycotoxins most abundantly produced by Aspergillus fumigatus during the early stages of infection to cause invasive aspergillosis (IA). Therefore, we hypothesized that GT and FUM could be the possible source of virulence factors, which we put to test adopting in vitro monoculture and the novel integrated multiple organ co-culture (IdMOC) of A549 and L132 cell. We found that (i) GT is more cytotoxic to lung epithelial cells than FUM, and (ii) GT and FUM act synergistically to inflict pathology to the lung epithelial cell. Reactive oxygen species (ROS) is the master regulator of the cytotoxicity of GT, FUM and GT + FUM. ROS may be produced as a sequel to mitochondrial damage and, thus, mitochondria are both the source of ROS and the target to ROS. GT-, FUM- and GT + FUM-induced DNA damage is mediated either by ROS-dependent mechanism or directly by the fungal toxins. In addition, GT, FUM and GT + FUM may induce protein accumulation. Further, it is speculated that GT and FUM inflict epithelial damage by neutrophil-mediated inflammation. With respect to multiple organ cytotoxicity, GT was found to be cytotoxic at IC50 concentration in the following order: renal epithelial cells < type II epithelial cells < hepatocytes < normal lung epithelial cells. Taken together, GT and FUM alone and in combination contribute to exacerbate the damage of lung epithelial cells and, thus, are involved in the progression of IA.
Highlights
Gliotoxin (GT) and fumagillin (FUM) are mycotoxins most abundantly produced by Aspergillus fumigatus during the early stages of infection to cause invasive aspergillosis (IA)
The fungal hyphae should breach the lung alveolar surface that consists of type I and type II epithelial cells in which type I cells cover 95% of the surface and engage in gas exchange whereas type II cells cover only 5% of the surface but engage crucially in the secretion of surfactant proteins and innate immune r esponse[2,19]
It is important to select such cell types to study the molecular mechanism of mycotoxins to relate with IA adopting in vitro techniques
Summary
Gliotoxin (GT) and fumagillin (FUM) are mycotoxins most abundantly produced by Aspergillus fumigatus during the early stages of infection to cause invasive aspergillosis (IA). Abbreviations DMSO Dimethyl sulfoxide FUM Fumagillin GT Gliotoxin IC50 Concentration at which 50% of cells are dead IdMOC Integrated discrete multiple organ co-culture IA Invasive aspergillosis MTT 3-4, 5-Dimethylthiazole-2-yl, 2,5-diphenyl tetrazolium bromide ROS Reactive oxygen species. Immunocompetent healthy individuals are able to deal with the fungal conidia by the several immune mechanisms that prevent the germination and growth of hyphae whereas in immunocompromised persons conidial germination and mycelial development in the lung epithelial cells can cause severe/fatal disease called Invasive Aspergillosis (IA)[1,3]. In order to fight against the first-line host innate immune response, A. fumigatus adopts a strategy that involves discharge of mycotoxins to damage the epithelial/endothelial barriers of the respiratory tract. In the light of the fact that two or more mycotoxins would interact synergistically or additively and produce more serious adverse effects than single c ompounds[6,7], it is pertinent that this issue in respect of highly virulent mycotoxins produced by A. fumigatus is worthy of being addressed
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