Genes Differentially Expressed in Conidia and Hyphae of Aspergillus fumigatus upon Exposure to Human Neutrophils

Aspergillus fumigatus is the most common etiologic agent of invasive aspergillosis in immunocompromised patients. Several studies have addressed the mechanism involved in host defense but only few have investigated the pathogen's response to attack by the host cells. To our knowledge, this is the first study that investigates the genes differentially expressed in conidia vs hyphae of A. fumigatus in response to neutrophils from healthy donors as well as from those with chronic granulomatous disease (CGD) which are defective in the production of reactive oxygen species.Transcriptional profiles of conidia and hyphae exposed to neutrophils, either from normal donors or from CGD patients, were obtained by using the genome-wide microarray. Upon exposure to either normal or CGD neutrophils, 244 genes were up-regulated in conidia but not in hyphae. Several of these genes are involved in the degradation of fatty acids, peroxisome function and the glyoxylate cycle which suggests that conidia exposed to neutrophils reprogram their metabolism to adjust to the host environment. In addition, the mRNA levels of four genes encoding proteins putatively involved in iron/copper assimilation were found to be higher in conidia and hyphae exposed to normal neutrophils compared to those exposed to CGD neutrophils. Deletants in several of the differentially expressed genes showed phenotypes related to the proposed functions, i.e. deletants of genes involved in fatty acid catabolism showed defective growth on fatty acids and the deletants of iron/copper assimilation showed higher sensitivity to the oxidative agent menadione. None of these deletants, however, showed reduced resistance to neutrophil attack.This work reveals the complex response of the fungus to leukocytes, one of the major host factors involved in antifungal defense, and identifies fungal genes that may be involved in establishing or prolonging infections in humans

Cationic type I amphiphiles as modulators of membrane curvature elastic stress in vivo

Recently we proposed that the antineoplastic properties observed in vivo for alkyl-lysophospholipid and alkylphosphocholine analogues are a direct consequence of the reduction of membrane stored elastic stress induced by these amphiphiles. Here we report similar behavior for a wide range of cationic surfactant analogues. Our systematic structure?activity studies show that the cytotoxic properties of cationic surfactants follow the same pattern of activity we observed previously for alkyl-lysophospholipid analogues, indicating a common mechanism of action that is consistent with the theory that these amphiphiles reduce membrane stored elastic stress. We note that several of the cationic surfactant compounds we have evaluated are also potent antibacterial and antifungal agents. The similarity of structure?activity relationships for cationic surfactants against microorganisms and those we have observed in eukaryotic cell lines leads us to suggest the possibility that the antibacterial and antifungal properties of cationic surfactants may also be due to modulation of membrane stored elastic stress