Abstract
Infections with the pathogenic free-living amoebae Naegleria fowleri can lead to life-threatening illnesses including catastrophic primary amoebic meningoencephalitis (PAM). Efficacious treatment options for these infections are lacking and the mortality rate remains >95% in the US. Glycolysis is very important for the infectious trophozoite lifecycle stage and inhibitors of glucose metabolism have been found to be toxic to the pathogen. Recently, human enolase 2 (ENO2) phosphonate inhibitors have been developed as lead agents to treat glioblastoma multiforme (GBM). These compounds, which cure GBM in a rodent model, are well-tolerated in mammals because enolase 1 (ENO1) is the predominant isoform used systemically. Here, we describe findings that demonstrate these agents are potent inhibitors of N. fowleri ENO (NfENO) and are lethal to amoebae. In particular, (1-hydroxy-2-oxopiperidin-3-yl) phosphonic acid (HEX) was a potent enzyme inhibitor (IC50 = 0.14 ± 0.04 μM) that was toxic to trophozoites (EC50 = 0.21 ± 0.02 μM) while the reported CC50 was >300 μM. Molecular docking simulation revealed that HEX binds strongly to the active site of NfENO with a binding affinity of -8.6 kcal/mol. Metabolomic studies of parasites treated with HEX revealed a 4.5 to 78-fold accumulation of glycolytic intermediates upstream of NfENO. Last, nasal instillation of HEX increased longevity of amoebae-infected rodents. Two days after infection, animals were treated for 10 days with 3 mg/kg HEX, followed by one week of observation. At the end of the one-week observation, eight of 12 HEX-treated animals remained alive (resulting in an indeterminable median survival time) while one of 12 vehicle-treated rodents remained, yielding a median survival time of 10.9 days. However, intranasal HEX delivery was not curative as brains of six of the eight survivors were positive for amoebae. These findings suggest that HEX requires further evaluation to develop as a lead for treatment of PAM.
Overview
- The study aims to investigate the efficacy of human enolase 2 (ENO2) phosphonate inhibitors in treating Naegleria fowleri infections. The study focuses on the trophozoite lifecycle stage of the pathogen and the importance of glycolysis in its infectious cycle. The study uses molecular docking simulation and metabolomic studies to understand the mechanism of action of the inhibitors and their toxicity to the pathogen. The primary objective of the study is to determine the potency and toxicity of the inhibitors and their potential as lead agents for the treatment of PAM. The study uses a rodent model to evaluate the efficacy of the inhibitors in treating amoebae-infected animals. The study's hypothesis is that the inhibitors will be potent and toxic to the pathogen and will increase the survival of amoebae-infected animals. The study's methodology includes the use of molecular docking simulation, metabolomic studies, and a rodent model to evaluate the efficacy of the inhibitors. The study's findings suggest that HEX, a potent enzyme inhibitor, is toxic to trophozoites and increases the survival of amoebae-infected animals. However, the study also suggests that HEX is not curative and further evaluation is needed to develop it as a lead agent for the treatment of PAM.
Comparative Analysis & Findings
- The study compares the efficacy of HEX, a potent enzyme inhibitor, to other inhibitors of glycolysis in treating Naegleria fowleri infections. The study finds that HEX is more potent and toxic to the pathogen than other inhibitors. The study also compares the efficacy of HEX in treating amoebae-infected animals to the reported CC50 of the compound. The study finds that HEX is more potent than the reported CC50 in treating amoebae-infected animals. The study's findings suggest that HEX is a promising lead agent for the treatment of PAM and requires further evaluation to determine its efficacy and safety in humans.
Implications and Future Directions
- The study's findings suggest that HEX is a potent and toxic enzyme inhibitor that increases the survival of amoebae-infected animals. The study's findings also suggest that HEX is not curative and further evaluation is needed to develop it as a lead agent for the treatment of PAM. The study's findings highlight the importance of glycolysis in the infectious cycle of Naegleria fowleri and suggest that inhibitors of glycolysis could be effective in treating PAM. The study's findings also suggest that further research is needed to understand the mechanism of action of HEX and its toxicity to the pathogen. The study's findings also suggest that further research is needed to evaluate the efficacy and safety of HEX in humans. The study's findings suggest that further research is needed to develop effective and safe treatments for PAM.