Hydrophobicity of Antifungal β-Peptides Is Associated with Their Cytotoxic Effect on In Vitro Human Colon Caco-2 and Liver HepG2 Cells

Abstract

The widespread distribution of fungal infections, with their high morbidity and mortality rate, is a global public health problem. The increase in the population of immunocompromised patients combined with the selectivity of currents treatments and the emergence of drug-resistant fungal strains are among the most imperative reasons to develop novel antifungal formulations. Antimicrobial β-peptides are peptidomimetics of natural antimicrobial peptides (AMPs), which have been proposed as developmental platforms to enhance the AMPs selectivity and biostability. Their tunability allows the design of sequences with remarkable activity against a wide spectrum of microorganisms such as the human pathogenic Candida spp., both in planktonic and biofilm morphology. However, the β-peptide’s effect on surrounding host cells remains greatly understudied. Assessments have mainly relied on the extent of hemolysis that a candidate peptide is able to cause. This work investigated the in vitro cytotoxicity of various β-peptides in the Caco-2 and HepG2 mammalian cell lines. Results indicated that the cytotoxic effect of the β-peptides was influenced by cell type and was also correlated to structural features of the peptide such as hydrophobicity. We found that the selectivity of the most hydrophobic β-peptide was 2–3 times higher than that of the least hydrophobic one, for both cell types according to the selectivity index parameter (IC50/MIC). The IC50 of Caco-2 and HepG2 increased with hydrophobicity, which indicates the importance of testing putative therapeutics on different cell types. We report evidence of peptide-cell membrane interactions in Caco-2 and HepG2 using a widely studied β-peptide against C. albicans.

Synthesis, antifungal activity of caffeic acid derivative esters, and their synergism with fluconazole and nystatin against Candida spp.

“…The establishment of this concentration was essential to calculate the selectivity index (SI) (IC 50 /MIC ratio), which was used as an indicator of potential toxicity against normal cells lines at the effective therapeutic concentration for each strain. Hence, theSIindicated the relationship between drug toxicity against C. albicans and the host cells (Gullo et al, 2012;Mora-Navarro et al, 2016).…”

In vitro fungicidal effects of methylene blue at 625‐nm

“…Systemic antifungal drugs, while successful, produce side effects (even adverse effects) and drug resistance. Common side effects range from itching, burning and redness for topical agents to uncomfortable gastrointestinal issues and nephrotoxicity when oral antifungals are used . Although rare, antifungal medications can lead to liver damage .…”

“…Common side effects range from itching, burning and redness for topical agents to uncomfortable gastrointestinal issues and nephrotoxicity when oral antifungals are used. 5,6 Although rare, antifungal medications can lead to liver damage. 7 The non-uniformity of topical application of fungistatic drugs can result in low drug concentrations which foster dermatophyte resistance.…”

Advances in Development of Antimicrobial Peptidomimetics as Potential Drugs

“…Recently, cytotoxicity of various antifungal β-peptides was investigated in vitro in the Caco-2 and HepG2 mammalian cell lines [ 246 ]. In contrast to observations made for AMPs and antibacterial peptidomimetics, the most hydrophobic and relatively more hemolytic member tested (i.e., β 3 hTyr-[ACHC-β 3 hPhe-β 3 hLys] 3 -NH 2 ) was the least cytotoxic toward Caco-2 cells, while the most hydrophilic β 3 -peptide (i.e., H-[ACHC-β 3 hVal-β 3 hLys] 3 -NH 2 ) was least tolerated (IC 50 values of 53.2 and 27.3 µM, respectively).…”

“…In contrast to observations made for AMPs and antibacterial peptidomimetics, the most hydrophobic and relatively more hemolytic member tested (i.e., β 3 hTyr-[ACHC-β 3 hPhe-β 3 hLys] 3 -NH 2 ) was the least cytotoxic toward Caco-2 cells, while the most hydrophilic β 3 -peptide (i.e., H-[ACHC-β 3 hVal-β 3 hLys] 3 -NH 2 ) was least tolerated (IC 50 values of 53.2 and 27.3 µM, respectively). For HepG2 no clear trend was observed except that H-[ACHC-β 3 hVal-β 3 hLys] 3 -NH 2 despite its higher polarity affected viability most (IC 50 of 38.8 µM) [ 246 ]. Hence, the cell selectivity (ratio between IC 50 and MIC) was in the range of 2–8 for the four tested compounds also comprising H-[ACHC-β 3 hVal-β 3 hArg] 3 -NH 2 and β 3 hTyr-[β 3 hVal-β 3 hVal-β 3 hArg] 3 -NH 2 , which is considerably lower (~10- to 100-fold) than usually seen for optimized AMPs and antibacterial peptidomimetics.…”