ORIGINAL ARTICLE Effect of pluronic acid F-127 on the toxicity towards eukaryotic cells of CSA-13, a cationic steroid analogue of antimicrobial peptides C. Nagant 1 , P.B. Savage 2 and J.P. Dehaye 1 1 Laboratoire de Chimie biologique et me ´ dicale et de Microbiologie pharmaceutique, Faculte ´ de Pharmacie, Universite ´ libre de Bruxelles, Brussels, Belgium 2 Department of Chemistry and Biochemistry, C100 BNSN Brigham Young University, Provo, UT, USA Introduction Cystic fibrosis (CF) is a congenital exocrinopathology provoked by the mutation of a chloride channel, the cys- tic fibrosis transmembrane regulator expressed by exo- crine glands. The mutation of this channel greatly impairs its activity and the movements of ions in exocrine cells. This accounts for the high viscosity of the pancreatic or bronchial secretions which provokes either obstructions of the pancreatic secretory ducts and pancreatic insuffi- ciency or bronchiolar obstructions and lobar atelectasis (Di Sant’Agnese 1956). The disease leads to the premature death of the patients after recurrent and intractable infections of the upper airways. Pseudomonas aeruginosa is a ubiquitous Gram-negative bacteria especially present in water and soil. It is also very often responsible for opportunistic infections in immuno- compromised patients, and this pathogen is the predomi- nant cause of fatal pulmonary infections in patients with CF (Gomez and Prince 2007). Ps. aeruginosa interacts with the highly viscous mucus of these patients and adheres to epithelial cells of their respiratory airways. This initial adhesion is followed by the secretion of exopoly- saccharides. The formation of this organic matrix is at the basis of a complex tridimensional structure, the bio- film (Høiby et al. 2010). The transfer of bacteria from planktonic conditions to a biofilm is coupled to a change in gene regulation and expression. This switch contributes to the increased resistance of these bacteria to antibiotherapy (Folsom et al. 2010). The tracheal and bronchial epithelia are constantly exposed to environmental pathogens. Colonization of the Keywords antimicrobials, cytotoxicity, HUVEC, mitochondria, pluronic acid, Pseudomonas aeruginosa. Correspondence Jean-PaulDehaye, Department of Biological and Medical Chemistry and Pharmaceutical Microbiology, Faculty of Pharmacy C.P. 205 ⁄ 3, Campus Plaine, Universite ´ libre de Bruxelles, Boulevard du Triomphe, B1050 Brussels, Belgium. E-mail: jpdehaye@gmail.com 2011 ⁄ 2203: received 4 January 2012, revised 13 March 2012 and accepted 24 March 2012 doi:10.1111/j.1365-2672.2012.05297.x Abstract Aims: CSA-13 is an antimicrobial cationic steroid with some toxicity against eukaryotic cells. The purpose of this work was to test whether pluronic acid F-127 could interfere with the toxicity of CSA-13 on human umbilical vein endothelial (HUVEC) without modifying its bactericidal activity against Pseu- domonas aeruginosa. Methods and Results: The addition of pluronic acid F-127 slightly decreased the number of dead cells after exposure to CSA-13. Pluronic acid F-127 blocked the permeabilizing effect of CSA-13 on the plasma membrane of HUVEC (uptake of ethidium bromide, release of lactate dehydrogenase) with- out modifying its toxic effect on their mitochondrial function (MTT test, uptake of tetramethyl rhodamine ethyl ester). Conclusion: Pluronic acid F-127 decreased the toxicity of CSA-13 against eukaryotic cells without completely protecting them from mitochondrial dam- age at high concentrations of the drug. Significance and Impact of the Study: This work establishes that studies on the toxic effects of synthetic antimicrobials on eukaryotic cells should not only focus on the permeability of the plasma membrane but also on the integrity of the mitochondria. Journal of Applied Microbiology ISSN 1364-5072 ª 2012 The Authors Journal of Applied Microbiology 112, 1173–1183 ª 2012 The Society for Applied Microbiology 1173