title: Important cellular targets for antimicrobial photodynamic therapy.
abstract: The persistent problem of antibiotic resistance has created a strong demand for new methods for therapy and disinfection. Photodynamic inactivation (PDI) of microbes has demonstrated promising results for eradication of antibiotic-resistant strains. PDI is based on the use of a photosensitive compound (photosensitizer, PS), which upon illumination with visible light generates reactive species capable of damaging and killing microorganisms. Since photogenerated reactive species are short lived, damage is limited to close proximity of the PS. It is reasonable to expect that the larger the number of damaged targets is and the greater their variety is, the higher the efficiency of PDI is and the lower the chances for development of resistance are. Exact molecular mechanisms and specific targets whose damage is essential for microbial inactivation have not been unequivocally established. Two main cellular components, DNA and plasma membrane, are regarded as the most important PDI targets. Using Zn porphyrin-based PSs and Escherichia coli as a model Gram-negative microorganism, we demonstrate that efficient photoinactivation of bacteria can be achieved without detectable DNA modification. Among the cellular components which are modified early during illumination and constitute key PDI targets are cytosolic enzymes, membrane-bound protein complexes, and the plasma membrane. As a result, membrane barrier function is lost, and energy and reducing equivalent production is disrupted, which in turn compromises cell defense mechanisms, thus augmenting the photoinduced oxidative injury. In conclusion, high PDI antimicrobial effectiveness does not necessarily require impairment of a specific critical cellular component and can be achieved by inducing damage to multiple cellular targets.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Kuwait University, P. O. Box 24923, Safat, 13110, Kuwait.
authors.forename: Mariam M
authors.initials: MM
authors.lastname: Awad
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Artak
authors.initials: A
authors.lastname: Tovmasyan
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Kuwait University, P. O. Box 24923, Safat, 13110, Kuwait.
authors.forename: James D
authors.initials: JD
authors.lastname: Craik
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Ines
authors.initials: I
authors.lastname: Batinic-Haberle
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Kuwait University, P. O. Box 24923, Safat, 13110, Kuwait. lbenov@hsc.edu.kw.
authors.forename: Ludmil T
authors.initials: LT
authors.lastname: Benov
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects*; D004249:DNA Damage / Q000187:drug effects*; D004269:DNA, Bacterial / Q000187:drug effects; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects*; D008027:Light; D008665:Metalloporphyrins / Q000494:pharmacology*; D050296:Microbial Viability / Q000187:drug effects*; D010084:Oxidation-Reduction; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D008665:Metalloporphyrins; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; C017802:zinc hematoporphyrin
keywords: Antimicrobial; Gram-negative; Photodynamic inactivation; Singlet oxygen