Cytochrome P450 monooxygenase of Acanthamoeba castellanii participates in resistance to polyhexamethylene biguanide treatment.

Wei-Chen Lin,Po-Wei Wen,Min-Hsiu Shih,Chao-Li Huang,Pin-Ju Ko,Jian-Ming Huang,Fu-Chin Huang,Chun-Hsien Chen

doi:10.1051/parasite/2021074

Abstract

Acanthamoeba spp. are free-living parasites that can cause severe infections such as granulomatous amoebic encephalitis (GAE) and amoebic keratitis (AK). Polyhexamethylene biguanide (PHMB) is a topical application for AK treatment. However, PHMB is not entirely effective against all Acanthamoeba strains or isolates. The mechanisms by which Acanthamoeba protects itself against extreme drug conditions without encystation are still unknown. According to a previous study, cytochrome P450 monooxygenase (CYP450MO) plays an important role in the oxidative biotransformation of numerous drugs related to metabolism. In this study, a CYP450MO fragment was inserted into the pGAPDH-EGFP vector and transfected into Acanthamoeba castellanii. We found that CYP450MO-overexpressing Acanthamoeba had higher survival rates than those of the control cells after PHMB treatment. Moreover, we also found that encystation-related genes such as cellulose synthase I (CSI), encystation-mediating serine proteinase (EMSP), and autophagy-related protein 8 (ATG8) expression levels were not significantly different between Acanthamoeba transfected by pGAPDH-EGFP or pGAPDH-EGFP-CYP450MO. We suggest that Acanthamoeba transfected by pGAPDH-EGFP-CYP450MO may not induce encystation-related genes to resist PHMB treatment. In conclusion, these findings indicate that CYP450MO may be an additional target when PHMB is used for treatment of amoebic keratitis.

Highlights

Acanthamoeba spp. are free-living pathogenic protozoa that are distributed in several environments, including swimming lakes, pools, soil, and dust [6]
We suggest that CYP450MO in Acanthamoeba may catalyze Polyhexamethylene biguanide (PHMB) drug metabolism to enhance survival rates after PHMB treatment
Cytochrome P450 enzymes (CYP450s) are widely distributed throughout different organisms ranging from protozoa to mammals [9, 32, 40]

Summary

Introduction

Acanthamoeba spp. are free-living pathogenic protozoa that are distributed in several environments, including swimming lakes, pools, soil, and dust [6]. Acanthamoeba spp. cause severe sight-threatening infections such as granulomatous amoebic encephalitis (GAE) and amoebic keratitis (AK) [25, 37]. Acanthamoeba infects patients by causing lid edema, photophobia, epithelial defects, and ring-like stromal infiltrates through injury to the cornea [20, 24]. Patients with AK have been treated effectively over the last two decades with topical biguanides; current therapy requires surgical intervention because of the failure of medical treatment [15]. PHMB combined with H2O2 is used as an ingredient in contact lens-cleaning solutions to prevent corneal infections [30]. Corneal transplantation is another therapeutic approach when topical treatment fails. There are no clinical therapeutic approaches recommended for incorporation into standard practice

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