title: Photochemotherapeutic strategy against Acanthamoeba infections.
abstract: Acanthamoeba is a protist pathogen that can cause serious human infections, including blinding keratitis and a granulomatous amoebic encephalitis that almost always results in death. The current treatment for these infections includes a mixture of drugs, and even then, a recurrence can occur. Photochemotherapy has shown promise in the treatment of Acanthamoeba infections; however, the selective targeting of pathogenic Acanthamoeba has remained a major concern. The mannose-binding protein is an important adhesin expressed on the surface membranes of pathogenic Acanthamoeba organisms. To specifically target Acanthamoeba, the overall aim of this study was to synthesize a photosensitizing compound (porphyrin) conjugated with mannose and test its efficacy in vitro. The synthesis of mannose-conjugated porphyrin was achieved by mixing benzaldehyde and pyrrole, yielding tetraphenylporphyrin. Tetraphenylporphyrin was then converted into mono-nitrophenylporphyrin by selectively nitrating the para position of the phenyl rings, as confirmed by nuclear magnetic resonance (NMR) spectroscopy. The mono-nitrophenylporphyrin was reduced to mono-aminophenylporphyrin in the presence of tin dichloride and confirmed by a peak at m/z 629. Finally, mono-aminoporphyrin was conjugated with mannose, resulting in the formation of an imine bond. Mannose-conjugated porphyrin was confirmed through spectroscopic analysis and showed that it absorbed light of wavelengths ranging from 425 to 475 nm. To determine the antiacanthamoebic effects of the derived product, amoebae were incubated with mannose-conjugated porphyrin for 1 h and washed 3 times to remove extracellular compound. Next, the amoebae were exposed to light of the appropriate wavelength for 1 h. The results revealed that mannose-conjugated porphyrin produced potent trophicidal effects and blocked excystation. In contrast, Acanthamoeba castellanii incubated with mannose alone and porphyrin alone did not exhibit an antiamoebic effect. Consistently, pretreatment with mannose-conjugated porphyrin reduced the A. castellanii-mediated host cell cytotoxicity from 97% to 4.9%. In contrast, treatment with porphyrin, mannose, or solvent alone had no protective effects on the host cells. These data suggest that mannose-conjugated porphyrin has application for the targeted photodynamic therapy of Acanthamoeba infections and may serve as a model in the development of therapeutic interventions against other eukaryotic infections.
authors.affiliation: Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, Pakistan.
authors.forename: Yousuf
authors.initials: Y
authors.lastname: Aqeel
authors.affiliation: Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, Pakistan.
authors.forename: Ruqaiyyah
authors.initials: R
authors.lastname: Siddiqui
authors.affiliation: International Center for Chemical and Biological Sciences, H. E. J. Research Institute of Chemistry, University of Karachi, Karachi, Pakistan.
authors.forename: Ayaz
authors.initials: A
authors.lastname: Anwar
authors.affiliation: International Center for Chemical and Biological Sciences, H. E. J. Research Institute of Chemistry, University of Karachi, Karachi, Pakistan.
authors.forename: Muhammad Raza
authors.initials: MR
authors.lastname: Shah
authors.affiliation: Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, Pakistan.
authors.forename: Shahrukh
authors.initials: S
authors.lastname: Khoja
authors.affiliation: Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, Pakistan naveed5438@gmail.com.
authors.forename: Naveed Ahmed
authors.initials: NA
authors.lastname: Khan
mesh_terms: D048248:Acanthamoeba castellanii / Q000187:drug effects*; D000981:Antiprotozoal Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D001547:Benzaldehydes / Q000737:chemistry; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry
chemical_list: D000981:Antiprotozoal Agents; D001547:Benzaldehydes; D011166:Porphyrins; D011758:Pyrroles; C409084:tetraphenylporphyrin; D008358:Mannose; C032175:benzaldehyde