Internal Thiols and Reactive Oxygen Species in Candidacidal Activity Exerted by an N-Terminal Peptide of Human Lactoferrin

Abstract

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,Ndimethylamide) (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.

Antimicrobial Activity of Lactoferrin-Related Peptides and Applications in Human and Veterinary Medicine

“…Another study demonstrated the involvement of fungal endogenous thiols and reactive oxygen species (ROS) in the candidacidal activity exerted by hLf (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In this study, hLf(1-11) caused a decrease in the internal thiol levels of Candida albicans by 20% and an increase in the level of its production of ROS in a dose-dependent manner; a correlation between ROS production and candidacidal activity was also found [51].…”

One of Two Human Lactoferrin Variants Exhibits Increased Antibacterial and Transcriptional Activation Activities and Is Associated with Localized Juvenile Periodontitis

“…Each lobe is capable of binding one Fe 3ϩ ion together with one CO 3 2Ϫ ion in a deep intralobe cleft that contains a nonheme iron-binding site (1). The noniron-dependent activities of human lactoferrin have been shown to be mediated by a 47-residue peptide (corresponding to residues 1 to 47 of the mature human lactoferrin protein) that is released upon cleavage of human lactoferrin with pepsin (5,6,8,27,28,35,46). These residues form a ␤-␣-␤ unit located on the exposed surface of the human lactoferrin protein that is distinct from the iron-binding region.…”

Trehalose Is an Important Mediator of Cap1p Oxidative Stress Response in Candida albicans

“…3) Moreover, ROS generation is involved in the mechanisms of many antifungal agents. [4][5][6] Oxidative stress could therefore be a frequent challenge for C. albicans to survive and cause diseases in its host.…”