title: Major pathways of polymyxin-induced apoptosis in rat kidney proximal tubular cells.
abstract: Identifying the pathways involved in the apoptotic cell death that is associated with polymyxin-induced nephrotoxicity is crucial for the development of strategies to ameliorate this dose-limiting side effect and for the development of novel safer polymyxins. The primary aim of this study was to identify the major pathways which lead to polymyxin-induced apoptosis in cultured rat kidney proximal tubular cells (NRK-52E). Caspase-3, -8, and -9 were activated by polymyxin B treatment in a concentration-dependent manner. Concentration- and time-dependent expression of FasL and deformation of mitochondrial morphology were revealed following polymyxin B treatment. The proportion of cells with filamentous mitochondria (regular morphology) following an 8-h treatment with 1.0 mM polymyxin B was 56.2% ± 9.7% (n = 3). This was decreased to 30.7% ± 7.5% when the polymyxin B concentration was increased to 2.0 mM. The mitochondrial membrane potential (Δψm) decreased to 14.1% ± 2.9% in the cells treated with 1.0 mM polymyxin B for 24 h (n = 3) compared to that in the untreated control group. Concomitantly, concentration- and time-dependent production of mitochondrial superoxide was also observed. This study is the first to have demonstrated that polymyxin-induced apoptosis is mediated through both the death receptor and mitochondrial pathways in cultured renal tubular cells. It provides key information not only for the amelioration of polymyxin-induced nephrotoxicity but also for the discovery of novel safer polymyxin-like antibiotics against Gram-negative "superbugs."
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia.
authors.forename: Mohammad A K
authors.initials: MA
authors.lastname: Azad
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia.
authors.forename: Jesmin
authors.initials: J
authors.lastname: Akter
authors.affiliation: Centre for Dynamic Imaging, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Rogers
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia.
authors.forename: Roger L
authors.initials: RL
authors.lastname: Nation
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia Tony.Velkov@monash.edu Colistin.Polymyxin@gmail.com.
authors.forename: Tony
authors.initials: T
authors.lastname: Velkov
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia Tony.Velkov@monash.edu Colistin.Polymyxin@gmail.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein; D007674:Kidney Diseases / Q000139:chemically induced / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011113:Polymyxins / Q000633:toxicity*; D051381:Rats; D013481:Superoxides / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D053222:Fas Ligand Protein; D011113:Polymyxins; D013481:Superoxides; D020169:Caspases