Immunomodulatory drug fingolimod (FTY720) restricts the growth of opportunistic yeast Candida albicans in vitro and in a mouse candidiasis model

PLOS ONE RESEARCH ARTICLE Immunomodulatory drug fingolimod (FTY720) restricts the growth of opportunistic yeast Candida albicans in vitro and in a mouse candidiasis model Niloofar Najarzadegan1, Mahboobeh Madani1*, Masoud Etemadifar2, Nahad Sedaghat ID3,4 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Department of Microbiology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran, 2 Department of Neurosurgery, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran, 3 Alzahra Research Institute, Alzahra University Hospital, Isfahan University of Medical Sciences, Isfahan, Iran, 4 Network of Immunity in Infection, Malignancy and Autoimmunity (NIIMA), Universal Scientific, Education, and Research Network (USERN), Isfahan, Iran * Abstract OPEN ACCESS Citation: Najarzadegan N, Madani M, Etemadifar M, Sedaghat N (2022) Immunomodulatory drug fingolimod (FTY720) restricts the growth of opportunistic yeast Candida albicans in vitro and in a mouse candidiasis model. PLoS ONE 17(12): e0278488. https://doi.org/10.1371/journal. pone.0278488 Editor: Aijaz Ahmad, University of the Witwatersrand, SOUTH AFRICA Received: June 2, 2022 Accepted: November 17, 2022 Published: December 7, 2022 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0278488 Copyright: © 2022 Najarzadegan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Fingolimod (FTY720) is a drug derived from the fungicidal compound myriocin. As it was unclear whether FTY720 has antifungal effects as well, we aimed to characterize its effect on Candida albicans in vitro and in a mouse candidiasis model. First, antifungal susceptibility testing was performed in vitro. Then, a randomized, six-arm, parallel, open-label trial was conducted on 48 mice receiving oral FTY720 (0.3 mg/kg/day), intraperitoneal C. albicans inoculation, or placebo with different combinations and chorological patterns. The outcome measures of the trial included serum concentrations of interleukin-10 and interferongamma, absolute lymphocyte counts, and fungal burden values in the mice’s livers, kidneys, and vaginas. Broth microdilution assay revealed FTY720’s minimum inhibitory concentration (MIC99) to be 0.25 mg/mL for C. albicans. The infected mice treated with FTY720 showed lower fungal burden values than the ones not treated with FTY720 (p<0.05). As expected, the mice treated with FTY720 showed a less-inflammatory immune profile compared to the ones not treated with FTY720. We hypothesize that FTY720 synergizes the host’s innate immune functions by inducing the production of reactive oxygen species. Further studies are warranted to unveil the mechanistic explanations of our observations and clarify further aspects of repurposing FTY720 for clinical antifungal usage. 1. Introduction Fingolimod (FTY720) is an immunomodulatory drug currently indicated and approved by the United States Food and Drug Administration (FDA) for treatment of the relapsing forms of multiple sclerosis (MS)–an autoimmune entity involving the central nervous system. It is used off-label for progressive MS and other autoimmune neuropathies, while being evaluated for extra-nervous pathologies as well [1–3]. FTY720 is considered a prodrug of its phosphorylated PLOS ONE | https://doi.org/10.1371/journal.pone.0278488 December 7, 2022 1 / 16 PLOS ONE Funding: The author(s) received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. Characterization of the antifungal effect of fingolimod (FTY720) form fingolimod-phosphate (FTY720-P). Being a modulator of the sphingosine-1-phosphate receptors (S1PR) by structural analogy, FTY720-P induces internalization of S1PR from the surface of lymphocytes, hindering their trafficking outside the primary lymphatics and, therefore, keeping them away from inflammatory sites in end organs [4]. While being associated with beneficial outcomes and reasonable tolerability among people with immune-mediated conditions such as MS [5, 6], safety and toxicity studies have shown both dose-dependent and time-dependent adverse effects associated with FTY720 [7]. The time-dependent adverse effects have been opportunistic infections, reactivation of latent viruses, malignancies, etc.; these are mostly deemed to be due to chronic immunosuppression [7]. Among the dose-dependent adverse effects, the most common has been cardiotoxicity [5, 6]. S1PRs are highly expressed on cardiomyocytes; the initial agonistic effect of FTY720-P on S1PRs before inducing their internalization seems to be responsible for its dose-dependent cardiotoxic effects [8]. Hepatotoxic dose-dependent effects have also been reported [5–7], deemed to be associated with FTY720’s metabolic burden on the liver [9]. Other dose-dependent unwanted and toxic effects of FTY720 due to S1PR agonism, e.g., macular edema [10], unwanted loss of weight and appetite [11], etc. have been reported. FTY720 was derived from myriocin (ISP-1), which is a secondary metabolite of the entomopathogenic fungus Isaria sinclairii and a potent inhibitor of the serine palmitoyltransferase (SPT) enzyme in the de novo sphingolipid biosynthesis pathway [12]. Myriocin alters a metabolic pathway in eukaryotic cells vital for their stability and proliferation. Consistently, it has shown to have antifungal effects e.g., against Candida and Aspergillus spp. [13, 14]. While FTY720 has no activity against the SPT, emerging studies [3, 15] are pointing towards S1PR-independent anti-proliferative effects of FTY720 in its non-phosphorylated form. Meanwhile, several cases of opportunistic fungal infections are reported among people receiving FTY720 chronically [16, 17]. Although these reports describe case studies and population-based evidence is lacking in this regard, it seems unclear whether FTY720 facilitates fungal expansion in vivo by weakening the immune system, or has retained the antifungal effect of its molecular ancestor. The subject of identifying and confirming the possible antifungal properties of substances like FTY720 –which could be administered safely in humans–gains more relevance when considering the rapid emergence of serious mycosis cases resistant to our usual antifungal armamentarium. Among the candidiasis cases, resistance to drugs is classically attributed to the less prevalent infections with non-albicans species, however, recent studies are docu (...truncated)