Transcriptional profiling ofScedosporium apiospermumenzymatic antioxidant gene battery unravels the involvement of thioredoxin reductases against chemical and phagocytic cells oxidative stress

Abstract

Scedosporium species rank the second, after Aspergillus fumigatus, among the filamentous fungi colonizing the airways of patients with cystic fibrosis (CF). Development of microorganisms in the respiratory tract depends on their capacity to evade killing by the host immune system, particularly through the oxidative response of macrophages and neutrophils, with the release of reactive oxygen species (ROS) and reactive nitrogen species (RNS). This is particularly true in the airways of CF patients which display an exacerbated inflammatory reaction. To protect themselves, pathogens have developed various enzymatic antioxidant systems implicated in ROS degradation, including superoxide dismutases, catalases, cytochrome C peroxidases, chloroperoxidases and enzymes of the glutathione and thioredoxin systems, or in RNS degradation, that is, flavohemoglobins, nitrate reductases, and nitrite reductases. Here we investigated the transcriptional regulation of the enzymatic antioxidant gene battery in 24-h-old hyphae of Scedosporium apiospermum in response to oxidative stress induced chemically or by exposure to activated phagocytic cells. We showed that 21 out of the 33 genes potentially implicated in the oxidative or nitrosative stress response were overexpressed upon exposure of the fungus to various chemical oxidants, while they were only 13 in co-cultures with macrophages or neutrophils. Among them, genes encoding two thioredoxin reductases and to a lesser extent, a peroxiredoxin and one catalase were found to be overexpressed after chemical oxidative stress as well as in co-cultures. These results suggest that thioredoxin reductases, which are known to be virulence factors in other pathogenic fungi, play a key role in pathogenesis of scedosporiosis, and may be new drug targets.

Repurposing of auranofin and honokiol as antifungals against Scedosporium species and the related fungus Lomentospora prolificans

“…These drugs (auranofin, ebselen, PX-12, conoidin A, and honokiol), which have been previously reported to possess antimicrobial activity, were selected based on their known capacity to impair the cellular redox hemostasis. The selection was stemmed from very recent findings on the behavior of S. apiospermum under oxidative stress, where the genes encoding TrxRs and Prxs were not only the most upregulated among core oxidative-stress genes but also the fastest expressed upon exposure to neutrophils [11].…”

“…Afterward, hyphae were filtered on Miracloth membrane, washed once with distilled water, ground in liquid nitrogen, and kept at −20°C before RNA extraction. Total RNAs extraction and reverse transcription (RT)-quantitative PCR (qPCR) were done as described previously [11]. Primers used in qPCR experiments are listed in Supplemental table S1.…”

“…Twenty-five genes encoding oxidoreductase enzymes were studied and the actin gene was used for normalization. The relative expression of each gene was calculated from the threshold cycle (Ct) values as previously described [11].…”

“…This last property is due, at least in part, to the presence of more than 30 genes encoding putative antioxidant enzymes in S. apiospermum genome [10]. Interestingly, transcriptional analysis of the given genes following exposure of S. apiospermum to chemically-or naturally-induced oxidative stresses revealed overexpression of many of them, especially those encoding thioredoxin reductases (TrxRs) and peroxiredoxins (Prxs) [11]. The thioredoxin system is known as the key component of redox homeostasis in eukaryotes.…”

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

“…In this regard, a mechanism defense has been tested by using H2O2 with a concentration enough to affect J o u r n a l P r e -p r o o f the physiology of the algae, which revealed the presence of an extracellular antioxidant enzyme catalase whose activity can remove low concentrations of H2O2 before it can exert any negative effect, Fig. In both cases, the fungi overexpressed genes encoding two thioredoxin reductases, a peroxiredoxin and a catalase were overexpressed [224]. In the same report, the effects of two graphenebased materials (GBM), few-layer graphene (FLG) and graphene oxide (GO), were studied.…”