Virtual Screening of Alkaloid and Terpenoid Inhibitors of SMT Expressed in Naegleria sp

The pathogenic form of thermophilic Naegleria sp. i.e., Naegleria fowleri, also known as brain eating amoeba, causes primary amoebic encephalitis (PAM) with a >97% fatality rate. To date, there are no specific drugs identified to treat this disease specifically. The present antimicrobial combinatorial chemotherapy is hard on many patients, especially children. Interestingly, Naegleria fowleri has complex lipid biosynthesis pathways like other protists and also has a strong preference to utilize absorbed host lipids for generating energy. The ergosterol biosynthesis pathway provides a unique drug target opportunity, as some of the key enzymes involved in this pathway are absent in humans. Sterol 24-C Methyltransferase (SMT) is one such enzyme that is not found in humans. To select novel inhibitors for this enzyme, alkaloids and terpenoids inhibitors were screened and tested against two isozymes of SMT identified in N. gruberi (non-pathogenic) as well as its homolog found in yeast, i.e., ERG6. Five natural product derived inhibitors i.e., Cyclopamine, Chelerythrine, Berberine, Tanshinone 2A, and Catharanthine have been identified as potential drug candidates based on multiple criteria including binding affinity, ADME scores, absorption, and, most importantly, its ability to cross the blood brain barrier. This study provides multiple leads for future drug exploration against Naegleria fowleri.

Naegleria fowleri: Diagnosis, Pathophysiology of Brain Inflammation, and Antimicrobial Treatments

Primary amoebic meningoencephalitis (PAM) is a very rare disease with a high mortality rate. PAM is caused by Naegleria fowleri, an amoeba which resides in freshwater lakes and ponds and can survive in inadequately chlorinated pools ( Lopez, C.; Budge, P.; Chen, J., et al. Primary amebic meningoencephalitis: a case report and literature review . Pediatr. Emerg. Care 2012 , 28 , 272 - 276 ). In the past 50 years, there have been over 130 cases of Naegleria induced PAM in the United States with only three known survivors; one survivor was diagnosed and treated at Arkansas Children's Hospital. Successful treatment of PAM started with a rapid diagnosis, extensive antimicrobial therapy including an investigational medication miltefosine, supportive care, an intraventricular shunt, and hypothermia. These treatments address different aspects of the disease process. Increased understanding of the diagnosis and treatment of PAM is important especially for patients who present with meningitis-like findings during the summer months.