Exploring the Anti-Infective Value of Inuloxin A Isolated from Inula viscosa against the Brain-Eating Amoeba (Naegleria fowleri) by Activation of Programmed Cell Death

Abstract

Primary amoebic meningoencephalitis (PAM), caused by the pathogenic free-living amoeba Naegleria fowleri, is a rare but fatal disease. Nowadays, no fully effective therapy is available to erradicate or prevent this disease. Natural products could constitute a promising source of useful bioactive compounds in drug discovery. The present study is a characterization of main active compounds from the ethanolic extract of Inula viscosa (Asteraceae) leaves against N. fowleri trophozoites. Four compounds (1–4) were successfully identified by spectroscopic techniques, but only inuloxin A displayed a potential antiamoebic activity with an IC50 of 21.27 μM. The specificity of this compound toward the studied strain leads us to analyze the insight into its mechanism of action by performing in vitro assays of programmed cell death markers and to discuss the structure–activity relationship (SAR). The obtained results demonstrated that inuloxin A interferes with various processes leading to membrane damage, mitochondria alteration, chromatin condensation, and ROS accumulation, which highlight features specific to apoptosis. The current findings could be a promising step for developing new effective drugs against PAM.

The therapeutic potential of novel isobenzofuranones against Naegleria fowleri

“…In previous works of our group, PCD process in Naegleria fowleri was evaluated after detection of specific metabolic events such as DNA condensation, plasmatic membrane and mitochondrial membrane damage, collapse of ATP levels and intracellular ROS generation(A. Rizo-Liendo et al, 2020 ; Zeouk et al, 2020 ). The isobenzofuranones selected in this study were able to induce all the metabolic events mentioned above hence showing signs of PCD induction (early apoptosis) leading to a safer therapy if used in the near future.…”

“…Consequently, there is a correlation between the high mortality rate data with the late diagnosis and the non-specific treatment ( Cope and Ali, 2016 ). Hence, the development of novel amoebicidal compounds (fast action, more efficiently and with low toxic effects) is an urgent need ( Zeouk et al, 2021 ).…”

Naphthyridine Derivatives Induce Programmed Cell Death in Naegleria fowleri

“…For the evaluation of programmed cell death induction by compound 3 in Naegleria fowleri, the ATCC ® 30808™ strain was used. Amoebae were incubated with the IC 90 (inhibitory concentration 90%) of the compound to later evaluate the presence of some of the PCD characteristic metabolic events [49] with different stains, following the manufacturer's instructions.…”

Natural Terpenes Inhibit the Cytopathogenicity of Naegleria fowleri Causing Primary Amoebic Meningoencephalitis in the Human Cell Line Model

“…A wide range of natural, bioactive compounds have been studied in the past few years for their antiamoebic effects and were found to show amoebicidal effects againstN. fowleri. − Terpenes also known as terpenoids are a group of naturally occurring compounds and have a wide range of biological activities such as antifungal, antimicrobial, and antiparasitic activities . Thymol is a phenol monoterpene and a major constituent ofThymus vulgaris essential oil .…”