Abstract
BACKGROUND: Trichophyton rubrum is the main etiological agent of skin and nail infections worldwide. Because of its keratinolytic activity and anthropophilic nature, infection models based on the addition of protein substrates have been employed to assess transcriptional profiles and to elucidate aspects related to host-pathogen interactions. Chalcones are widespread compounds with pronounced activity against dermatophytes. The toxicity of trans-chalcone towards T. rubrum is not fully understood but seems to rely on diverse cellular targets. Within this context, a better understanding of the mode of action of trans-chalcone may help identify new strategies of antifungal therapy and reveal new chemotherapeutic targets. This work aimed to assess the transcriptional profile of T. rubrum grown on different protein sources (keratin or elastin) to mimic natural infection sites and exposed to trans-chalcone in order to elucidate the mechanisms underlying the antifungal activity of trans-chalcone. RESULTS: Overall, the use of different protein sources caused only slight differences in the transcriptional profile of T. rubrum. The main differences were the modulation of proteases and lipases in gene categories when T. rubrum was grown on keratin and elastin, respectively. In addition, some genes encoding heat shock proteins were up-regulated during the growth of T. rubrum on keratin. The transcriptional profile of T. rubrum exposed to trans-chalcone included four main categories: fatty acid and lipid metabolism, overall stress response, cell wall integrity pathway, and alternative energy metabolism. Consistently, T. rubrum Mapk was strongly activated during the first hours of trans-chalcone exposure. Noteworthy, trans-chalcone inhibited genes involved in keratin degradation. The results also showed effects of trans-chalcone on fatty acid synthesis and metabolic pathways involved in acetyl-CoA supply. CONCLUSION: Our results suggest that the mode of action of trans-chalcone is related to pronounced changes in fungal metabolism, including an imbalance between fatty acid synthesis and degradation that interferes with cell membrane and cell wall integrity. In addition, this compound exerts activity against important virulence factors. Taken together, trans-chalcone acts on targets related to dermatophyte physiology and the infection process.