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Published on: June 2, 2011
Synchrotron-based X-ray fluorescence microscopy reveals accumulation of polymyxins in single human alveolar
Mohamad A K Azad1, Shuo Zhang2, Jiayao Li2
1Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, Australia.
Abstract:
Intravenous administration of the last-line polymyxins results in poor drug exposure in the lungs and potential nephrotoxicity; while inhalation therapy offers better pharmacokinetics/pharmacodynamics for pulmonary infections by delivering the antibiotic to the infection site directly. However, polymyxin inhalation therapy has not been optimized and adverse effects can occur. This study aimed to quantitatively determine the intracellular accumulation and distribution of polymyxins in single human alveolar epithelial A549 cells. Cells were treated with an iodine-labeled polymyxin probe FADDI-096 (5.0 and 10.0 μM) for 1, 4, and 24 h. Concentrations of FADDI-096 in single A549 cells were determined by synchrotron-based X-ray fluorescence microscopy. Concentration- and time-dependent accumulation of FADDI-096 within A549 cells was observed. The intracellular concentrations (mean ± SEM, n ≥ 189) of FADDI-096 were 1.58 ± 0.11, 2.25 ± 0.10, and 2.46 ± 0.07 mM following 1, 4 and 24 h of treatment at 10 μM, respectively. The corresponding intracellular concentrations following the treatment at 5 μM were 0.05 ± 0.01, 0.24 ± 0.04, and 0.25 ± 0.02 mM (n ≥ 189). FADDI-096 was mainly localized throughout the cytoplasm and nuclear region over 24 h. The intracellular zinc concentration increased in a concentration- and time-dependent manner. This is the first study to quantitatively map the accumulation of polymyxins in human alveolar epithelial cells and provides crucial insights for deciphering the mechanisms of their pulmonary toxicity. Importantly, our results may shed light on the optimization of inhaled polymyxins in patients and the development of new-generation safer polymyxins.
Insights
This study quantified polymyxin accumulation in human lung cells, revealing concentration-dependent uptake and cytoplasmic/nuclear distribution. These findings are crucial for optimizing inhaled polymyxin therapies and reducing toxicity.
Area of Science:
- Pharmacology
- Cell Biology
- Toxicology
Background:
- Intravenous polymyxins have limitations including poor lung penetration and nephrotoxicity.
- Inhaled polymyxins offer targeted delivery for pulmonary infections but require optimization to mitigate adverse effects.
Purpose of the Study:
- To quantitatively determine the intracellular accumulation and distribution of polymyxins in human alveolar epithelial cells.
- To provide insights into the mechanisms of polymyxin pulmonary toxicity and inform the optimization of inhaled therapies.
Main Methods:
- Human alveolar epithelial A549 cells were treated with an iodine-labeled polymyxin probe (FADDI-096) at varying concentrations (5.0 and 10.0 μM) and time points (1, 4, and 24 h).
- Synchrotron-based X-ray fluorescence microscopy was employed to determine intracellular concentrations of FADDI-096 in single cells.
- Intracellular zinc concentrations were also monitored.
Main Results:
- Concentration- and time-dependent intracellular accumulation of FADDI-096 was observed in A549 cells.
- FADDI-096 was primarily localized in the cytoplasm and nuclear regions over 24 hours.
- Intracellular zinc concentration increased in a concentration- and time-dependent manner.
Conclusions:
- This study provides the first quantitative map of polymyxin accumulation in human alveolar cells.
- Findings offer crucial insights into polymyxin pulmonary toxicity mechanisms.
- Results may guide the optimization of inhaled polymyxin administration and the development of safer polymyxin analogs.
