A Cecropin-4 Derived Peptide C18 Inhibits Candida albicans by Disturbing Mitochondrial Function

Abstract

Global burden of fungal infections and related health risk has accelerated at an incredible pace, and multidrug resistance emergency aggravates the need for the development of new effective strategies. Candida albicans is clinically the most ubiquitous pathogenic fungus that leads to high incidence and mortality in immunocompromised patients. Antimicrobial peptides (AMPs), in this context, represent promising alternatives having potential to be exploited for improving human health. In our previous studies, a Cecropin-4-derived peptide named C18 was found to possess a broader antibacterial spectrum after modification and exhibit significant antifungal activity against C. albicans. In this study, C18 shows antifungal activity against C. albicans or non-albicans Candida species with a minimum inhibitory concentration (MIC) at 4∼32 μg/ml, and clinical isolates of fluconazole (FLZ)-resistance C. tropicalis were highly susceptible to C18 with MIC = 4∼32 μg/ml. Additionally, C18 is superior to FLZ for killing planktonic C. albicans from inhibitory and killing kinetic curves. Moreover, C18 could attenuate the virulence of C. albicans, which includes damaging the cell structure, retarding hyphae transition, and inhibiting biofilm formation. Intriguingly, in the Galleria mellonella model with C. albicans infection, C18 could improve the survival rate of G. mellonella larvae to 70% and reduce C. albicans load from 5.01 × 107 to 5.62 × 104 CFU. For mechanistic action of C18, the level of reactive oxygen species (ROS) generation and cytosolic Ca2 + increased in the presence of C18, which is closely associated with mitochondrial dysfunction. Meanwhile, mitochondrial membrane potential (△Ψm) loss and ATP depletion of C. albicans occurred with the treatment of C18. We hypothesized that C18 might inhibit C. albicans via triggering mitochondrial dysfunction driven by ROS generation and Ca2 + accumulation. Our observation provides a basis for future research to explore the antifungal strategies and presents C18 as an attractive therapeutic candidate to be developed to treat candidiasis.

Cecropin D-derived synthetic peptides in the fight against Candida albicans cell filamentation and biofilm formation

“…The untreated cells had a smooth surface and normal shape, whereas treatment with peptides at fungicidal concentration in HEPES/glucose buffer resulted in damage of the cell surface with leakage of intracellular content, marked with arrows on the figures. Similar observations were shown in a recent work, in which C. albicans cells were treated with the cecropin 4-derived peptide C18 (Sun et al, 2022). The cells treated with ΔM4 showed also a rough surface.…”

“…A noticeable inhibition of fungal cell filamentation was observed at a concentration of the peptides lower than fungicidal, and it was manifested by the formation of shorter hyphae and decreased expression of genes encoding proteins characteristic for the filamentous form of C. albicans cells (Hwp1, Hyr1, and Als3). A recent study demonstrated a similar effect on C. albicans by the cecropin-derived peptide C18 (Sun et al, 2022). It should be noted that the arresting of fungal cells in the form of blastospores may facilitate their elimination, even at lower peptide concentration.…”

“…It has been found that AMPs may use two or more mechanisms to penetrate membranes that depend on the polar and non-polar distribution of amino acids; however, other characteristics such as net charge, amphipathicity, hydrophobicity, percentage of α-helix structure may be important for interaction with the cell wall (Madani et al, 2011). Recent reports have demonstrated the effect of cecropinderived amphipathic positive peptides on antifungal activity against C. albicans (Peng et al, 2022;Sun et al, 2022). These studies, however, focused on the antifungal activity of peptides that differ in amino acid sequence, charge, and hydrophobicity from the peptides tested in this study.…”

The Antimicrobial Peptide AMP-17 Derived from Musca domestica Inhibits Biofilm Formation and Eradicates Mature Biofilm in Candida albicans

“…Recently, antimicrobial peptides (AMPs) have garnered attention for their broad-spectrum antimicrobial activities against bacteria, fungi, and some enveloped viruses [ 9 , 10 , 11 , 12 ], as well as their strong antibiofilm ability [ 13 ]. AMPs are natural, small, and highly conserved effector molecules that play a key role in innate immunity, with the antimicrobial mode of action mainly focused on the integrity of microbial wall cells by pore formation or related activities.…”

Cec4-Derived Peptide Inhibits Planktonic and Biofilm-Associated Methicillin Resistant Staphylococcus epidermidis

“…Since the narrow antimicrobial spectrum of Cec4 and its long sequence increased the cost of synthesis, it has been modified to obtain a series of derived peptides with a broader antimicrobial spectrum and smaller molecular weight. Among them, C18 (16 amino acids) has been confirmed to have good antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans , which also has a certain therapeutic effect against infection in vivo ( 19 , 20 ). Meanwhile, we also found that C9, which has only one amino acid substituted compared with C18, showed good antibacterial activity against S. epidermidis , with an MIC value of 8 μg/mL, which was more than 16 times higher than that of Cec4 (>128 μg/mL).…”