Internal thiols and reactive oxygen species in candidacidal activity exerted by an N-terminal peptide of human lactoferrin.
We previously showed that the energized mitochondrion and extracellular ATP are essential for the candidacidal activity of the N-terminal peptide of human lactoferrin, subsequently referred to as hLF(1-11). The present study focuses on the involvement of internal thiols and reactive oxygen species (ROS) in the candidacidal activity exerted by hLF(1-11). Our results reveal that hLF(1-11) reduced the internal thiol level of Candida albicans by 20%. In agreement, N-acetyl-L-cysteine (NAC), which is a precursor of glutathione and an ROS scavenger, inhibited the candidacidal activity of hLF(1-11). In addition, azodicarboxylic acid bis(N,N-dimethylamide) (diamide), which oxidizes internal thiols, was candidacidal. Furthermore, hLF(1-11) increased the level of ROS production by C. albicans in a dose-dependent manner, and a correlation between ROS production and candidacidal activity was found. 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), which is an ROS scavenger, partially inhibited the hLF(1-11)-induced, but not the diamide-triggered, candidacidal activity. It is of interest that hLF(1-11) and diamide acted synergistically in killing C. albicans and in ROS production. In agreement, oxidized ATP, an irreversible inhibitor of extracellular ATP receptors, partially blocked the hLF(1-11)-induced, but not the diamide-triggered, candidacidal activity. Finally, the hLF(1-11)-induced activation of mitochondria was inhibited by NAC, indicating that internal thiols and ROS affect mitochondrial activity. Therefore, the candidacidal activity of hLF(1-11) involves both generation of ROS and reduction of internal thiols.
Lupetti
Antonella
A
Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
Paulusma-Annema
Akke
A
Senesi
Sonia
S
Campa
Mario
M
Van Dissel
Jaap T
JT
Nibbering
Peter H
PH
D000111:Acetylcysteine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects* / Q000378:metabolism*; D015169:Colony Count, Microbial; D003958:Diamide / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D007781:Lactoferrin / Q000494:pharmacology*; D008163:Luminescent Measurements; D008826:Microbial Sensitivity Tests; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D016166:Free Radical Scavengers; D010446:Peptide Fragments; D010455:Peptides; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; C466658:lactoferrin (1-11), human; D003958:Diamide; D000255:Adenosine Triphosphate; D007781:Lactoferrin; D000111:Acetylcysteine