Structure-activity relationship study of the plant-derived decapeptide OSIP108 inhibiting Candida albicans biofilm formation

Intestinal Infection of Candida albicans: Preventing the Formation of Biofilm by C. albicans and Protecting the Intestinal Epithelial Barrier

The large mortality and morbidity rate of C. albicans infections is a crucial problem in medical mycology. Because the generation of biofilms and drug resistance are growing concerns, the growth of novel antifungal agents and the looking for newer objectives are necessary. In this review, inhibitors of C. albicans biofilm generation and molecular mechanisms of intestinal epithelial barrier protection are elucidated. Recent studies on various transcription elements; quorum-sensing molecules; host responses to adherence; and changes in efflux pumps, enzymes, bud to hyphal transition, and lipid profiles have increased the knowledge of the intricate mechanisms underlying biofilm resistance. In addition, the growth of novel biomaterials with anti-adhesive nature, natural products, drugs, bioactive compounds, proteins, lipids, and carbohydrates are being researched. Recently, more and more attention has been given to various metal nanoparticles that have also appeared as antibiofilm agents in C. albicans. The intestinal epithelial obstacle exerts an crucial effect on keeping intestinal homeostasis and is increasingly associated with various disorders associated with the intestine such as inflammatory bowel disease (IBD), irritable bowel syndrome, metabolic syndrome, allergies, hepatic inflammation, septic shock, etc. However, whether their involvement in the prevention of other intestinal disorders like IBD are useful in C. albicans remains unknown. Further studies must be carried out in order to validate their inhibition functions in intestinal C. albicans. This provides innovates ideas for intestinal C. albicans treatment.

Structure-activity relationship study of the antimicrobial CRAMP-derived peptide CRAMP20-33

We report here on the structure-activity relationship study of a 14 amino acid fragment of the cathelicidin-related antimicrobial peptide (CRAMP), CRAMP20-33 (KKIGQKIKNFFQKL). It showed activity against Escherichia coli and filamentous fungi with IC₅₀ values below 30 μM and 10 μM, respectively. CRAMP20-33 variants with glycine at position 23 substituted by phenylalanine, leucine or tryptophan showed 2- to 4-fold improved activity against E. coli but not against filamentous fungi. Furthermore, the most active single-substituted peptide, CRAMP20-33 G23 W (IC₅₀ = 2.3 μM against E. coli), showed broad-spectrum activity against Candida albicans, Staphylococcus epidermidis and Salmonella Typhimurium. Introduction of additional arginine substitutions in CRAMP20-33 G23 W, more specifically in CRAMP20-33 G23 W N28R or CRAMP20-33 G23 W Q31R, resulted in 3-fold increased activity against S. epidermidis (IC₅₀ = 4 μM and 4.8 μM, respectively) as compared to CRAMP20-33 G23 W (IC₅₀ = 15.1 μM) but not against the other pathogens tested. In general, double-substituted variants were non-toxic for human HepG2 cells, pointing to their therapeutic potential.

Tackling Fungal Resistance by Biofilm Inhibitors

The high incidence and mortality of invasive fungal infections and serious drug resistance have become a global public health issue. The ability of fungal cells to form biofilms is an important reason for the emergence of severe resistance to most clinically available antifungal agents. Targeting fungal biofilm formation by small molecules represents a promising new strategy for the development of novel antifungal agents. This perspective will provide a comprehensive review of fungal biofilm inhibitors. In particular, discovery strategies, chemical structures, antibiofilm/antifungal activities, and structure-activity relationship studies will be discussed. Development of inhibitors to treat biofilm-related resistant fungal infections is a new yet clinically unexploited paradigm, and there is still a long way to go to clinical application. Better understanding of fungal biofilms in combination with systematic drug discovery efforts will pave the way for potential clinical applications.

Identification of survival-promoting OSIP108 peptide variants and their internalization in human cells

The plant-derived decapeptide OSIP108 increases tolerance of yeast and human cells to apoptosis-inducing agents, such as copper and cisplatin. We performed a whole amino acid scan of OSIP108 and conducted structure-activity relationship studies on the induction of cisplatin tolerance (CT) in yeast. The use of cisplatin as apoptosis-inducing trigger in this study should be considered as a tool to better understand the survival-promoting nature of OSIP108 and not for purposes related to anti-cancer treatment. We found that charged residues (Arg, His, Lys, Glu or Asp) or a Pro on positions 4-7 improved OSIP108 activity by 10% or more. The variant OSIP108[G7P] induced the most pronounced tolerance to toxic concentrations of copper and cisplatin in yeast and/or HepG2 cells. Both OSIP108 and OSIP108[G7P] were shown to internalize equally into HeLa cells, but at a higher rate than the inactive OSIP108[E10A], suggesting that the peptides can internalize into cells and that OSIP108 activity is dependent on subsequent intracellular interactions. In conclusion, our studies demonstrated that tolerance/survival-promoting properties of OSIP108 can be significantly improved by single amino acid substitutions, and that these properties are dependent on (an) intracellular target(s), yet to be determined.